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August 21

Dog mess vaporization using liquid oxygen?

Could dog mess be instantly vaporised by a device attached to its back that mixed the offending material with liquid oxygen? Would an aluminum/iron powder reaction improve the process, and could the thermal energy power a sterling generator to run portable devices? I thought I'd better ask before I try this out. Trevor Loughlin (talk) 02:03, 21 August 2009 (UTC)

This sounds like a way to blow up your dog. How are you going to collect the excreta and contain the combustion process? --FOo (talk) 02:09, 21 August 2009 (UTC)

How are you going to explain to your dog you are the alpha male? Bus stop (talk) 02:12, 21 August 2009 (UTC)

Urinate in the places that your dog likes to urinate? --Kurt Shaped Box (talk) 02:15, 21 August 2009 (UTC)

Might leave the pavement slightly scorched/pitted afterwards too. Or blister the paintwork on nearby buildings/parked cars (if not directly set them alight). You might not be the most popular person amongst your neighbours for a time. --Kurt Shaped Box (talk) 02:15, 21 August 2009 (UTC)

Aluminum/iron powder reaction? What are you trying to do, use thermite to get rid of dog poo? bibliomaniac15 02:27, 21 August 2009 (UTC)

Does Trevor kill weeds in his garden with napalm and brush his teeth with sodium hydroxide, do you reckon? --Kurt Shaped Box (talk) 03:04, 21 August 2009 (UTC)

I don't have a dog, nor am I a dog lover. I would be using Thermite AND liquid oxygen.The device would be like a calorimeter with an automatic lid closing motor, so the dog would not be blown up.80.2.202.175 (talk) 02:57, 21 August 2009 (UTC)

Thermite AND liquid oxygen would be a PERFECT recipe for starting a major firestorm. And a "calorimeter with an automatic lid closing motor" won't help either -- unless it's made out of tungsten, it would simply melt from the heat. Don't even THINK of trying this at home, OK? 98.234.126.251 (talk) 03:10, 21 August 2009 (UTC)

If dog poo were collected and accelerated into a trajectory which carried it to the Sun, that would dispose of it conclusively, though at a higher cost than the proposed method. It might also be composted, along with lawn clippings, as discussed in an earlier thread, at a lower cost. Edison (talk) 03:36, 21 August 2009 (UTC)

The oxygen alone with some accelerant will suffice. Usually a bomb-type calorimeter is started with a nichrome wire and a bit of thread if the sample will combust on its own. Otherwise a tablet of Picric acid is added to the sample cup. You would need a fairly large "bomb" and a fair amount of accelerant to combust wet dog poo. --BenBurch (talk) 19:12, 21 August 2009 (UTC)

Just remember to train the dog to run under a tank before going potty. 152.16.59.102 (talk) 04:42, 22 August 2009 (UTC)

Reacting the dog extremely rapidly with oxygen would also negate the need for any future use of the method. Just freezing with liquid oxygen would do the job nicely too. Graeme Bartlett (talk) 09:58, 24 August 2009 (UTC)

If by "dog mess" you mean explodingdog, your techniques might not work so well. ;-) ~AH1^(TCU) 12:08, 24 August 2009 (UTC)

Why not just pick it up and put in bin?

Digital physics and the bugs

Has digital physics yet addressed the problem of, if the universe is a computer or the output of a computer, how to thoroughly test it for bugs that might be exploited to violate the laws of physics? NeonMerlin 03:58, 21 August 2009 (UTC)

I hang around with a lot of physicists, and I have never heard any of them ever use the term "digital physics." Briefly scanning the article's sources, I can't see any reference that specifically mentions "digital physics" either. A Google Scholar search finds a very small set of papers, mostly not referring to the topic in that article. I think this article may be guilty of coining a neologism - as far as I can tell, there isn't actually community of physicists who consider this a "branch" of physics. As such, in response to your question - no, I don't think that any such scheme has been thought out. I think what's really at issue here is the debate between determinism and non-determinism, as well as the complexity of the system; calling the universe a "computer" and assuming there are inputs and outputs is a philosophical leap, to say the least. "Bugs", as you call them, would seem to be inconsistencies in the laws of physics - which have not really been observed. Whether such inconsistencies, if they exist, are "part of a plan" or "errors in design", is a purely philosophical, unfalsifiable concept. Nimur (talk) 06:33, 21 August 2009 (UTC)

You meant "Simulated reality" not "digital physics" right? "Digital physics" does not specifically require a universe computer.

Specifically see Simulated_reality#Scientific_and_technological_approaches some science-fiction/scientist thinkers have examine briefly these ideas.83.100.250.79 (talk) 10:03, 21 August 2009 (UTC)

The laws of physics are a description of how the universe behaves. If a law is violated you don't say that the universe violated the laws of physics, you say that you had the wrong laws. The only difference between a bug and a feature is whether the behavior is intended or not, so the idea of a bug in the laws of physics presumes an intent that differs from the reality. You'd have to say whose intent you're talking about and how we'd know what it was. -- BenRG (talk) 11:29, 21 August 2009 (UTC)

Don't take the computer metaphor TOO literally. If you do, you fundamentally miss the point of using it in the first place (which may or may not be helpful anyway). Saying "can we test for bugs" makes about as much sense as saying "maybe we can upgrade the graphics card." --98.217.14.211 (talk) 12:48, 21 August 2009 (UTC)

I assumed the question idea was the direct "we are in a computer" concept - as described in the every popular Brain in a vat page.83.100.250.79 (talk) 13:55, 21 August 2009 (UTC)

THAT would be nice. Things have been looking pretty pixelated around here for far too long.... — Sam 63.138.152.155 (talk) 13:40, 21 August 2009 (UTC)

It's OK, God has ordered us a quad core with dual-SLI 8800 cards. SteveBaker (talk) 14:45, 21 August 2009 (UTC)

I found a glitch. --Sean 14:43, 21 August 2009 (UTC)

The idea that we are all "inside The Matrix" is a perfectly valid one - and not at all new.

The weirdnesses we find when we try to probe to smaller and smaller and larger and larger scales of our "matrix" could quite easily reflect the limits of the resolution and capacity of the underlying simulation - the limits of the speed of light and our inability to see back before some particular time in the past are exactly the kind of arbitary limitations we'd impose in a real simulation. Indeed, there is reason to suppose that we'd eventually build really big computer games (think "Second life" or "World of Warcraft" - only much bigger) and that the AI's living inside it would wonder whether the fact that the ground is made up of tiny green squares and that time appears to be quantized into 1/60th second chunks was somehow indicative of the fact that they are living in a computer. Now consider that every civilisation that reaches that stage of technology probably runs dozens or even thousands of such synthetic universes. What are the odds that we're living in the real universe? Thousands to one against, perhaps?

There is no concievable test we could perform to prove that - we dismiss some insanely wierd quantum phenomena as "the way the universe runs" - when perhaps it's really just the precision with which the computer running our universe is able to store the positions and momenta of particles.

14:45, 21 August 2009 (UTC)

Somebody just sent me this link yesterday on the simulation argument[1]. I haven't read it yet, but it might be good. Like the brain in a vat, the universe as a computer simulation or merely a thought someone's mind is a purely philosophical concept. Wouldn't the only way to test this hypothesis except for leaving this simulation and observing it from the outside? Mac Davis (talk) 16:58, 21 August 2009 (UTC)

I think that it might be possible to hypothesize the kinds of error you'd expect from a simulation. Furthermore, I think that's exactly what we ARE seeing.

• Quantization and round-off errors at the finest scales of things would be something to look out for...and indeed, we've noted that things like mass, length, time, etc are indeed quantized...exactly as they would be if you stored them in a computer.
• Things like the Heisenberg uncertainty principle could be examples of finite arithmetic precision in whatever computer is running our universe.
• Having randomness at the smallest scales of the universe allows the simulation to run very approximately at that level - which would represent a huge saving in computer power.
• I could also imagine the finite speed of light and the limitation on not being able to travel faster than light would be the kinds of thing that a universe-simulation programmer might add in order to keep things within reasonable bounds. If humanity can't travel beyond it's own solar system, you don't have to simulate anything beyond a lightyear or so in any kind of detail.
• You don't want infinities cropping up in your simulation - so black holes have to be decently cloaked in event horizons to make that work.
• All of the physical constants in the universe seem to be set up just perfectly such that life can develop - in our naturalistic view of the universe, this is a big mystery - but that's exactly the kind of thing that a simulation designer would have tweaked to make things come out the way he wants.
• We can see that the universe started with the big bang - very little "data" was needed to start the simulation running...again, that's exactly the way you'd want to start things working.

We can't prove that this is a true hypothesis - but circumstantial evidence is all around us.

SteveBaker (talk) 18:55, 21 August 2009 (UTC)

The laws of physics do not suggest a design intended to reduce computational effort. Quite the opposite, in fact. The most obvious example is that computing the behavior of a quantum system appears to require exponentially more work than computing the behavior of a classical system. Like most conjectures in complexity theory that hasn't been proven, but no one can find a subexponential algorithm. If you want a cheap universe you should just make it discrete in a classical way. The uncertainty principle doesn't help, it makes things incomprehensibly worse. None of your other bullet points make sense either. -- BenRG (talk) 15:32, 23 August 2009 (UTC)

Yeah - is that some philosophical rumination, Steve, or are those ideas supported by any theory or prior research? I think we might have to flag it as ... Nimur (talk) 05:29, 24 August 2009 (UTC)

Ob.xkcd SteveBaker (talk) 18:57, 21 August 2009 (UTC)

what are the different types of leaves?

www.botanical-online.com/hojastiposangles.htm#peciolades3 —Preceding unsigned comment added by Shy222s (talk • contribs) 05:18, 21 August 2009 (UTC)

As with most things, there are numerous methods of classification for leaves. You can speak of layout, such as palmate vs. pinnate, and the go onto compound vs. simple formations of the above. You can speak of standard leaf morphology (which has a palisade mesophyll on the upper surface with a spongy mesophyll on the lower surface) vs. nonstandard morphology, such as eucalyptus, which possesses palisade mesophyll on both surfaces to allow for increased photosynthesis. You can speak of real leaves vs. modified leaves, such as cactus spines. I'm sure there are others, but that's a start. I'm no botanist, though. DRosenbach ^{(Talk | Contribs)} 13:36, 21 August 2009 (UTC)

Leaf gets into quite a bit of detail on the subject. Dcoetzee 18:38, 21 August 2009 (UTC)

Gallbladder-Thickening of the gallbladder wall

During an ultrsound for gallstones, a thickening of my gallbladder wall was detected. Does thickening equal cancer? I have an appointment with a surgeon but I was hoping for a head's up. Are there a list of possibilities to what "thickening" means? If so, please let me know.

Needsanswer (talk) 05:34, 21 August 2009 (UTC)

I think the whole point is that it takes a doctor to interpret the results of your ultrasound. One of the reasons we do not give medical advice on ref desk. Sorry and best of luck. Vespine (talk) 06:18, 21 August 2009 (UTC)

As Vespine pointed out, we won't diagnose anything. But if you're interested in background knowledge, we have an article on gallbladder, gallbladder cancer, which links to Gallbladder and Bile Duct Cancer from Johns Hopkins University. Neither their description of symptoms nor their ultrasound overview explicitly mention wall-thickening. Remember - internet-based sources, even from reputable research hospitals, are not a substitute for a professional medical opinion. Nimur (talk) 06:37, 21 August 2009 (UTC)

My advice would be to not look up a list of potential causes. Differential diagnoses without any other information are totally useless. Imagine the differential diagnosis of "Fatigue", ranging from the most common (overexertion) to the rarest (Cancer of the absolutely-everywhere); not only will there be two thousand unrelated causes inbetween but which of the two aforementioned diagnoses will stick in your mind? - Fribbler (talk) 09:39, 21 August 2009 (UTC)

I removed some medical advice from here. (See talk page for details..) -- Captain Disdain (talk) 09:08, 21 August 2009 (UTC)

See here. No, thickening does not equal cancer. A thickened gallbladder wall is a very, very common finding on ultrasound, and the most common cause is a polyp. Gallbladder cancer is rare. Polyps are common. Good luck with your surgeon. - Nunh-huh 10:00, 21 August 2009 (UTC)

How fast are we really, really moving?

Lots of time travel talk around here lately.

The big time travel issue that's always ignored is that moving through time would also require moving through space - at least if you wanted to end up in the same location and not inside a mountain, asteroid, nebula, etc.

So, here's my big question:

If one was able to "slip out" of space for exactly one second, with zero velocity (as opposed to the inherent velocity we have now), how far would he be from his original location when he "returned?"

I'm thinking this involves all sorts of interesting velocities - Earth orbit, Solar System movement in the Milky Way, galactic expansion...

Science RefDesk is the Best RefDesk! 218.25.32.210 (talk) 08:00, 21 August 2009 (UTC)

"with zero velocity" compared to what? I know you mean "well, duh, not moving", but what is the inertial frame of reference? What is the stationary (or other fixed coordinate system) point to which you would like to be not-moving? DMacks (talk) 08:10, 21 August 2009 (UTC)

One of the fundamental principles of General Relativity is that your question is meaningless. There is no absolute reference frame. --Carnildo (talk) 08:20, 21 August 2009 (UTC)

Not just general relativity, there is no absolute reference frame in classical mechanics either.83.100.250.79 (talk) 12:20, 21 August 2009 (UTC)

To give essentially the same answer with a slightly different spin - we know from special relativity and general relativity that space and time are not independent, but are intimately connected in spacetime. Your time axis and my time axis are not necessarily aligned, and the difference becomes obvious if we are moving at high speed relative to one another, or at different places in a strong gravitational field. Therefore to "slip out" of space you must "slip out" of spacetime, in which case you have also "slipped out" of time too. Gandalf61 (talk) 09:27, 21 August 2009 (UTC)

The closest we get to an absolute reference frame is the CMB rest frame, and the local group of galaxies are moving at 627 ± 22 km/s relative to that. The Earth's movement will vary over time since it depends on whether the various sources of motion are in the same direction or not and those directions change over the course on an orbit. --Tango (talk) 11:07, 21 August 2009 (UTC)

Indeed - but that doesn't make the question any more meaningful. There is absolutely no standard reference frame by which your time travelling machine can be stationary with respect to...however, since time travel isn't possible - it requires magic. It's truly impossible to describe the problems of a magical time-travel machine because Gandalf, Merlin and Dumbledore wave their wands and make it come out alright in the end. If you imagine a magical space-travel machine (a 'teleporter') - it could have the exact same problem. Your starship is in orbit around some planet - the 'away team' zap down to the planet and suddenly find themselves sliding sideways over the ground at 10,000 mph or so! You teleport yourself to the nearest star - but discover that it's moved over the four years the light from it took to reach us and (presumably) the four years our teleporter took to get us there.

We can't reason about that though because making logical conclusions from impossible technology is...impossible. What happens if you try to cut a mirror in half using a light sabre? Silly question - meaningless answer. (Which isn't going to stop someone from trying to answer it...right...below...this...line: SteveBaker (talk) 13:53, 21 August 2009 (UTC)

I just want to point out that Gandalf would wave a staff, not a wand, as Galdalf prefers to handle something with more length and girth. Googlemeister (talk) 14:31, 21 August 2009 (UTC)

Sorry, for a minute I thought you were talking about Sir Ian McKellen and his penchant for lengthy, girthy rods, not Gandalf... Coreycubed (talk) 14:44, 21 August 2009 (UTC)

I used to have a staff but they all quit. These days you just can't get the minions ... Gandalf61 (talk) 15:43, 21 August 2009 (UTC)

I think that might have been the joke... --Tango (talk) 16:49, 21 August 2009 (UTC)

Just because Gandalf's wand isn't mentioned in any of the Middle Earth books doesn't mean he doesn't have one. I'm sure he has lots of things that weren't mentioned explicitly. For the record, it's sparkly and has a large golden star on the end. :-P SteveBaker (talk) 18:24, 21 August 2009 (UTC)

I'm sitting here holding tightly to my chair and my keyboard, because I have realized that both are moving East at several hundred miles per hour! (due to the Earth's rotation and my latitude). If I use my time travel gizmo to move back an hour and undo an unfortunate Wikipedia edit, I have to allow for that rotation as well as the orbit of the Earth around the Sun and the movement of the solar system. It looks like a time travellor needs a gadget which allows for time and relative dimensions in space. Edison (talk) 15:25, 21 August 2009 (UTC)

What you don't seem to understand is that Extragalactic cosmic ray that just zipped past your ear happens to be dead stationary at the exact center of the universe...so you are actually moving at 99.9% of the speed of light...I hope you have a firm grip on that chair! SteveBaker (talk) 18:24, 21 August 2009 (UTC)

Blasphemy. I have it on the authority of Anaximander that the Earth is in the centre of the infinite "in the same place because of its indifference". Aristotle and Tolemy agree that this is the way it is so we have an overwhelming consensus here. Cuddlyable3 (talk) 05:27, 22 August 2009 (UTC)

The correct spelling is "Ptolemy", not "Tolemy". 98.234.126.251 (talk) 08:15, 22 August 2009 (UTC)

Nope. It's Κλαύδιος Πτολεμαίος . -Arch dude (talk) 13:52, 22 August 2009 (UTC)

My ptypo. Sorry. Cuddlyable3 (talk) 22:08, 22 August 2009 (UTC)

We are all traveling thro time at the speed of light. If we travel in distance, our speed thro time diminishes.(hence strange time effects). Minowski space-time continuum

Electrical fuses on the European continent

Electrical plugs in the UK often contain small fuses however, unless I am mistaken, European plugs do not, and domestic installations appear to rely on the fuse boxes/switches at the point of entrance of the electrical supply. Does this make the European standard less safe than in the UK, where I think both are usually used at the same time? ----Seans Potato Business 10:14, 21 August 2009 (UTC)

This seems to be a result of the ring main system, which is used in the UK, where the ring (one originally, but nowadays more) has to supply ALL power points / all devices with electrical power. All (or most) of mainland Europe uses a radial cabling architecture with the associated pros and cons. --Cookatoo.ergo.ZooM (talk) 12:05, 21 August 2009 (UTC)

Does that mean, then, that the consumer unit in such a star-wired scheme has a fuse per outlet (and thus has several times more fuses than its ring-main counterpart)? -- Finlay McWalter • Talk 12:11, 21 August 2009 (UTC)

A star-wired scheme has one fuse per line (or whatever that is called in electricianese) plus one main fuse. Each of these lines supplies a specific area (a number of power points and the light fixtures) of the apartment / house. As a result you can easily disable one of these lines (by disabling the fuse) and run an extension from the next room to supply light or to operate power tools. There exist specific regulations as to the permissible loads. There are also power points with a built in fuse on the market. --Cookatoo.ergo.ZooM (talk) 12:35, 21 August 2009 (UTC)

Is there then, one line per room or thereabouts, for example a UK house might have ~8 fuses per fuse box (2 downstairs 1 for plugs,1 for lighting), ditto upstairs, plus circuits for kitchen,garage,bathroom,central heating, but with such a method I think about 20 might be needed - is this the case?83.100.250.79 (talk) 13:02, 21 August 2009 (UTC)

In the US, we use the radial system and appliance cords generally do not have integral fuses. See Distribution board for a typical electrical service entrance. -Arch dude (talk) 13:58, 21 August 2009 (UTC)

The article on the ring circuit say that pre-WW2 in UK there was typically one outlet per fused circuit, and the ring circuit was developed during the postwar housing rebuild. One outlet per circuit is a quirk, from the time that one outlet per room was considered adequate wiring. Wiring in the U.S. always was radial and provided numerous outlets per fused radial circuit. The ring design requires 5-6 as much testing time (per the article) and I expect that when someone buys a house and seeks to add wiring to existing circuits, there is a high likelihood of dangerous mistakes, such as cross connections between two rings, making the fusing too high. There is also apparently a danger of cable overloads if heavy loads are connected near one end of the ring. It would not be too bad to install and test on a new installation, where the walls are open and the cables can be visually traced. but revisions would be a nightmare, unless accurate wiring diagrams are available or the electrician has Xray vision. It sounds expensive, due to the complexity of installation testing and the large number of fuses required. An advantage is its selectivity, so that one bad appliance only cuts off its own power. The outles having shutters which cut off the access to the hot and neutral holes until the ground hole is plugged would keep kids from sticking things into sockets and getting zapped. In the U.S. code requires number 10 wire (5.26 mm² for 30 amperes, but the ring bus article says the UK gets by with just 2.5mm², the equivalent of between 13 and 14 gauge wire. The U.S. would consider #14 wire only good for 15 amps. Like your wires toasty, eh? Edison (talk) 13:54, 21 August 2009 (UTC)

But 15 amps at U.K. voltage 240V delivers the same power as 30 amps at U.S. voltage 120V so what's the difference ? Cuddlyable3 (talk) 15:10, 21 August 2009 (UTC)

Wires overheat strictly based on amperes of current, and not based on the power carried, which is a function of voltage.Edison (talk) 15:18, 21 August 2009 (UTC)

So for the same power carried - which overheats first?83.100.250.79 (talk) 15:22, 21 August 2009 (UTC)

For the same power carried the wires on the smaller voltage and higher current (US in that case) will overheat faster. That's why high voltage transmission lines are high voltage (and low current). That way they reduce losses on the transmission lines. Dauto (talk) 15:30, 21 August 2009 (UTC)

Yes, but the US wires are thicker to compensate - that's what I meant. Do they work out the same?83.100.250.79 (talk) 15:51, 21 August 2009 (UTC)

Edison's rhetorical "Like your wires toasty, eh?" could distract us. Nobody wants their wires toasty except in the special case of an apparatus dedicated to partial oxidation of edible planar segments of wheat derived consumables. It has not been shown that U.K. supply wires heat any more than U.S. supply wires when delivering the same powers. In fact the ring main wiring in U.K. houses provides two parallel routes to each socket, doubling the effective wire cross section for a single load. There is no such advantage with star (radial) wiring in the U.S. Regrettably electrical development in the U.S. is sometimes influenced by Edison's eccentric notions. Cuddlyable3 (talk) 04:43, 22 August 2009 (UTC)

The distribution of lines in the star system varies depending on many things. For example, in my apartment, the kitchen has two lines each powering three outlets, plus dedicated lines for the dishwasher, the stove, and the garbage disposal. On the other hand, there's just a single line for the entry hall, living room, and bedroom, powering a dozen outlets and three light fixtures. --Carnildo (talk) 23:29, 21 August 2009 (UTC)

Another problem is that if a broken wire or loose connection causes the loop to open at one end, the other end has to carry all the load. This open circuit would not be detectable until an overload caused wires to heat up and other failures. The only test would be current measurements at each end of the loop at the source. Edison (talk) 15:18, 21 August 2009 (UTC)

Yes the US method is far better.83.100.250.79 (talk) 15:22, 21 August 2009 (UTC)

The loop system would be safe if the breaker had current sensors on each of the outgoing phase and neutral wires and tripped if flow stopped on one. This would obviously run the cost way up. Verifying the ground (earth) connections are intact going both ways would be more complicated, since they are supposed to be non-current carrying in normal operation. Edison (talk) 15:28, 21 August 2009 (UTC)

"would be safe" - there's no real sane reason do make a ring system in a house - except as some sort of copper saving measure (which I'm not 100% convinced it does effectively - considering the longer runs), everything else about it adds up to more ways to go wrong, more work, and more difficult to detect faults.

Maybe there is an example where a ring system makes sense for reasons other than saving a bit of copper and being able to bodge electrically unsafe circuits (by modern standards)?83.100.250.79 (talk) 15:58, 21 August 2009 (UTC)

What Edison cites as "another problem" can alternatively be viewed as an advantage that makes it easy to test the integrity of a ring main. At the incoming supply point temporarily break the connection to first one side of the ring, then the other. If one appliance plugged anywhere in the house keeps working in both tests then the ring is o.k. The copper saving by ring wiring may be uncertain but it has another advantage that it serves many household appliances of widely differing powers using only one standard cable size. Cuddlyable3 (talk) 05:08, 22 August 2009 (UTC)

Although I'm not a fan of ring systems - you missed one probably negligible advantage - that is - the resistance of the wire to any point on the ring is the less dependent on distance...83.100.250.79 (talk) 10:25, 22 August 2009 (UTC)

Sexuality: nurture or nature?

Are people really born with their sexual preferences? Apparently, it became politically correct to consider homosexuals as born that way and not some kind of mental illness, but is it true?--Quest09 (talk) 10:29, 21 August 2009 (UTC)

That sounds like a false dichotomy. Whether homosexuals are born that way or not is independent of whether or not it is mental illness (which is purely a question of definition). We don't really know the causes of homosexuality. Homosexuality#Etiology has a discussion of the question, though. --Tango (talk) 10:53, 21 August 2009 (UTC)

Indeed, all features of living things are a combination of both "nature and nurture". Some twin studies that I read, demonstrated approx. 30% genetic contribution to homosexuality but there are other factors explained via the link above. Regardless of whether one is born a certain way, if that condition doesn't harm others and involves more distress to "treat" than to simply accept (like trying to "treat" someone's distaste for Marmite), then it's clear to me that the individuals in question are better left to live their lives with equal rights and acceptance. ----Seans Potato Business 11:25, 21 August 2009 (UTC)

Note that "being born with a given orientation" != "genetically disposed towards a given orientation", since there are pre-natal non-genetic influences. As an extreme example, the sex (not just the orientation) of many oviparous animals is heavily influenced by temperature during the brooding period. --Stephan Schulz (talk) 12:17, 21 August 2009 (UTC)

There is a third element beyond nature and nurture: a random element. Even identical twins raised in the same environment don't turn out exactly the same, and this is due to this random element. For another example, identical twins raised in the same environment don't have identical patterns of freckles, since the location of each freckle is random. StuRat (talk) 12:30, 21 August 2009 (UTC)

This also raises the issue of the "hidden question" that always accompanies such inqueries; as though it were OK to discriminate against homosexuals if it were something entirely up to their choice. It's like saying "If they weren't born this way, but instead chose to be gay, I should be able to treat them badly". You aren't. It actually doesn't matter one way or the other why one or another person is gay, one should treat all people with respect and dignity. The fact is that the "reason" why certain people have certain sexual orientations is likely to be widely variable. --Jayron32 13:03, 21 August 2009 (UTC)

Nice point, Jayron! DRosenbach ^{(Talk | Contribs)} 13:39, 21 August 2009 (UTC)

But identical twins are never raised in the exact same environment, because their parents may treat them differently and they will experience some different things. EamonnPKeane (talk) 14:05, 29 August 2009 (UTC)

Some things (like eye color) are 100% genetically determined. Other things (like which accent you speak English with) are 100% nurture. Many things are a mixture of both - and many genetic things are the consequence of so many genes interacting that it becomes almost impossible to isolate (and thereby prove) a genetic basis for that trait. Homosexuality is tough to determine. Naive evolutionary logic would suggest that there is zero genetic basis for the trait because the drastically reduced chance of homosexuals reproducing and passing this hypothetical 'gay gene' onto the next generation would eliminate the gene in a very short amount of time. However, the world is more complex than that. If a large number of interacting genes were to produce the trait and all of them were separately highly valuable - then they could all be present in the population and vital to the survival of the species, even though they produce the occasional individual who would have a strong preference to NOT reproduce. That's the kind of thing that makes this such a complicated question. Consider, for example, the gene that produces sickle-cell anemia. If you carry two copies of this gene, you're in a lot of trouble. Most such people die at a young age without lots of modern medical help. How come the gene is still around? Well, it turns out that if you only inherit one copy of the gene, you have virtual immunity to malaria. That's such an amazingly useful thing that the gene is quite prevelant in places where malaria has historically been rampant. SteveBaker (talk) 13:10, 21 August 2009 (UTC)

I'm so glad you picked "speaking accent" as an example for 100% nurture. Check outForeign Accent Syndrome for a sort-of-exception. jeffjon (talk) 13:56, 21 August 2009 (UTC)

That's all very exciting - but Foreign Accent Syndrome isn't genetic either, it's to do with brain injury - which is most certainly nurture. SteveBaker (talk) 18:12, 21 August 2009 (UTC)

Note that your sickle-cell anemia example implies that for a gene with an obvious tendency to limit reproduction, it must also have some advantage to continue to be so widespread. There may be advantages to a group to have certain non-reproducing members, such as with worker ants. Also, since heterosexuality and homosexuality aren't absolutes, but rather a continuum, perhaps having slight homosexual tendencies might allow an individual to get along better with those of their gender without preventing them from reproducing. This seems to be the case for bonobos, for example. StuRat (talk) 22:24, 21 August 2009 (UTC)

Using a transistor as a relay/switch

Hi all,

I have a light bulb attached to a battery, and I have a small microcontroller I want to use to turn the light bulb on and off. Normally I think that this would be something that would be done with a relay, but unfortunately all I have is some NPN-type transistors. Is it possible to mimic the effects of a relay using one or more transistors?

Thanks! — Sam 166.131.64.248 (talk) 13:22, 21 August 2009 (UTC)

What current and what voltage are specified for the bulb, what is the battery voltage, and what is the current rating of the transistor (model number, manufacturer?). What are the output specs for the microcontroller (manufacturer, model), such as the amount of current and the on off voltage? Please understand that we or Wikipedia can accept no liability for any direct or consequential damage if you follow information provided here (frying the microcontroller, or the lightbulb coming on at the wrong time, failing to come on, or burning out, fire, etc. Edison (talk) 13:33, 21 August 2009 (UTC)

The bulb is actually a tiny little bulb and is being supplied with 3V. The microcontroller can actually supply up to 5V, but I want to keep the two circuits separate. — Sam 63.138.152.155 (talk) 13:41, 21 August 2009 (UTC)

See Solid state relay for the product that does this. But yes, for a small DC voltage and current, you can just use an appropriate transistor. -Arch dude (talk) 13:46, 21 August 2009 (UTC)

Also, go acquire a copy of The Art of Electronics. You will save a lot of time. -Arch dude (talk) 13:48, 21 August 2009 (UTC)

Ok, both of those are fine, but any advice how I can actually use the transistor to do this? Is an NPN an "appropriate" transistor? I'm happy to learn more, but I working with what I have at the moment, and can't get new supplies for now. Thanks! — Sam 63.138.152.155 (talk) 14:26, 21 August 2009 (UTC)

Yes, I believe an NPN transistor is correct since that's what they use to control motors with arduinos (see here, specifically a TIP120). However, I'm not sure I understand why you need the transistor at all if your microcontroller can supply enough voltage and current for the bulb. Can you not just power the controller with the batteries and run the bulb off the output pins? TastyCakes (talk) 14:35, 21 August 2009 (UTC)

Sorry, I think this link gives a more thorough description of how you'd use a transistor to do what you want to do. Also I just read that you want to keep the two separate, so disregard my question above. TastyCakes (talk) 14:37, 21 August 2009 (UTC)

You need to check the data sheet to determine if the microcontroller can safely source or sink enough current to light the bulb. Many times, microcontrollers can safely sink much higher current than they can source. This means it is best to connect the first lead from lightbulb to positive voltage (from the battery); the second lead of the lightbulb connects to the microcontroller; and the software ties that output with negative logic (1 keeps the voltage high and the bulb is off; and 0 keeps the voltage low and the bulb lights; current actually flows into the microcontroller). In general, this is a bad idea - you should use a buffer amplifier to keep the digital low-power items away from the higher-current needs of the light. You can build a buffer amplifier using one transistor; or you can get an elaborate design going; or you can buy a specialized IC which already does this. It depends on your needs and enthusiasm-level. Nimur (talk) 15:36, 21 August 2009 (UTC)

Since we really don't want you to fry your microcontroller please be aware of the risk inherent in connecting a microcontroller output directly to a lamp that is supplied by a different supply than the microcontroller. Sooner or later the microcontroller supply will be turned off and what happens then depends on the microcontroller chip. Current may flow from the bulb and through an unintended path on the chip. The chip may not survive that treatment. (I learned this the hard way when I used to connect the printer port on a PC to external circuit projects.) A safe choice is to connect an output of the microcontroller via a resistor 10 kilohm to the base of your NPN transistor, emitter to 0V ground, and bulb between its own 3V supply and the collector. Then a '1' (high) from the microcontroller will light the bulb. The transistor works like a relay but without moving parts or sound and it needs less drive current. A difference is that the output at the collector is not isolated like a relay contact would be, but that is not an issue here. Cuddlyable3 (talk) 04:07, 22 August 2009 (UTC)

(outdent) Cuddlyable has provided a good example of a one-transistor (BJT) buffer-amplifier. We have a section, Buffer_amplifier#Single-transistor_circuits in our article. Nimur (talk) 05:01, 22 August 2009 (UTC)

Nimur that section shows common-collector voltage follower buffers. I described a common-emitter saturated switch like this. Cuddlyable3 (talk) 21:50, 22 August 2009 (UTC)

Well, let's add it to the article then! Nimur (talk) 22:09, 22 August 2009 (UTC)

rectifier

what will be the output of half wave rectifier at 10HZ,50HZ,50KHZ & WHY we get no output at higer voltage?? —Preceding unsigned comment added by 117.200.60.207 (talk) 15:23, 21 August 2009 (UTC)

You get the same ouput at each frequency - only one sign of the AC input is let through, there's a image at Rectifier#Half-wave_rectification83.100.250.79 (talk) 15:26, 21 August 2009 (UTC)

As far as I know the output is the same at high voltage, unless the voltage is so high as to break the rectifier - which would probably cause AC output. (In semiconductor rectifiers the "breakdown voltage" is important)83.100.250.79 (talk) 15:28, 21 August 2009 (UTC)

Perhaps the OP means a rectifier with filter where the output will depend on the input frequency f. The simplest filter is a reservoir capacitor which may give these results when there is some load (resistance) on the output: High f: pure DC output. Medium f: DC output that contains ripple at frequency f. Low f: half-waves at frequency f i.e. the capacitor is ineffective. Cuddlyable3 (talk) 03:40, 22 August 2009 (UTC)

Well, at a higher voltage, the voltage may be larger than the diode's reverse breakdown voltage. So any charge stored on a capacitor after the diode would simply feed backwards through the diode on the other half of the AC cycle, which would probably result in a busted diode, and some smoke. Ilikefood (talk) 20:58, 25 August 2009 (UTC)

Home three phase supply

The article Distribution board seems to say that USA houses have 3 phase supply (in the UK only 2 single phase) Do other countries get 3 phase supply in the home?83.100.250.79 (talk) 15:24, 21 August 2009 (UTC)

With rare exceptions, US homes have a single-phase 220VAC supply. The distribution panel provides 110VAC branch circuits for the typical sockets all over the house, and 220VAC branch circuits for the major appliances, which use physically different types of sockets. The 220VAC is provided on two poles that are 180 degrees out of phase with each other: each varies by 110VAC with respect to "neutral". The 110VAC branches each use one pole and neutral. The 220VAC branches use both poles and do not use neutral (sort of.) The distribution panel is constructed so that you can add a two 110VAC breakers in adjacent slots, or add a single 220VAC breaker in two slots. Industries and large buildings generally have a 3-phase distribution panel. These panels can still supply single-phase 110VAC and 220VAC branch circuits, but they can also supply 208VAC three-phase circuits. -Arch dude (talk) 20:14, 21 August 2009 (UTC)

If there is a neutral, and two lives +110, and -110 I assume - isn't that not single phase (two phase? was that a typo?) (though not true 120degree three phase)

So domestic houses don't have true 3 phase 120V (that's the one with the 208V 'spiker'?)

So the +120,neutral,-120 (@180degrees) are what comes into a domestic house - that's just three taps from a single winding of a transformer - with neutral being tapped inbetween the two 120's?

So three power wires enter a US house?

Are all these things I've said above correct? (or have I missed it)83.100.250.79 (talk) 20:28, 21 August 2009 (UTC)

No. First, there are only two "live" wires, not three. the thirs wire is grounded at the pole and at the house. When the wires are overhead instead of underground, you see a bare steel cable with two insulated wires wrapped around it. The bare cable servers as ground/neutral and is also the weight-bearing part. The two power wires are not plus and minus: they are both 110VAC, so each of them varies from +110 to -110 sixty times per second with respect to neutral. Since they are 180 degrees out of phase, one of them varies from +220 to -220 with respect to the other one. -Arch dude (talk) 00:16, 22 August 2009 (UTC)

The U.S. uses two systems; a Split-phase electric power system for residential customers, featuring the three wires you describe (two "hot" wires 180deg out of phase @120V and a midpoint neutral wire) and true Three-phase electric power in a "Delta" configuration which features the same three wires as the split-phase system along with the fourth "208V" high leg on a 4th wire. The 4th leg is out of phase midway between the other two legs to provide 240V with either of them. The advantage of this system is that it can be used to supply both residential (using only 3 of the wires, skipping the 208 V supply) and heavy industrial (using all 4 wires) applications. There are also apparently evenly distributed 3-phase systems that feature 4 wires, 3 120V wires which are 120deg out of phase and a neutral wire. I don't feel like working out the trigonometry right now, but this will produce considerably less than 240V when two "hot" wires are used, rather than if you used the 2x120 + 208 system. --Jayron32 23:33, 21 August 2009 (UTC)

The three-phase system Jayron is talking about is described at High leg delta. -- 128.104.112.102 (talk) 00:06, 22 August 2009 (UTC)

(ec) Basically right. Our article calls the US -110/+110 V system split phase (as distinct from two phase). On most of the electric poles at the residential street level in the US, there are three live conductors, distributing three phase power. Still out in the street, one of those phases is tapped to a transformer (usually one per block or so) to create the 110/220V split phase. The +110/-110 conductors (with the neutral) are run to each house on the block to run the 110V circuits and a few 220V circuits (water heater, clothes dryer, etc.) Often to save on the cost of copper, transformers closest to the substation will be fed from one phase, which gets dropped from the poles, the middle transformers take from the next phase, and the most distant electrical poles only have a single remaining live conductor. This is all for residential usage. The large commercial and industrial buildings I've seen take the three phase in directly (to run their heavy-duty motors/pumps/air conditioners/etc.). -- 128.104.112.102 (talk) 23:54, 21 August 2009 (UTC)

The technical term for what's available in the US is Split-phase electric power. --Carnildo (talk) 23:35, 21 August 2009 (UTC)

ok thanks - I understand the difference between 2 phase and split phase now.83.100.250.79 (talk) 09:50, 22 August 2009 (UTC)

Resolved

Eating after a Work out

Hi, How long should i Wait to Eat after doing Cardio exercise? Thanks 82.194.62.200 (talk) 16:21, 21 August 2009 (UTC)

It depends on how hard you work out, what you eat, and how sensitive your stomach is. Most people can handle a granola bar right away even after running a couple of miles at top speed. You might want to give your metabolism an hour to settle down before eating a steak, though. Looie496 (talk) 16:36, 21 August 2009 (UTC)

This isn't completely related but is it true that food goes down the wrong intestine if you exercise after eating? Spiderone (talk) 16:39, 21 August 2009 (UTC)

No. What does "the wrong intestine" mean, anyway? Aaadddaaammm (talk) 16:45, 21 August 2009 (UTC)

Aren't your intestines in series? Anyway, I think for cardio exercise varies from person to person and is at least partly a matter of preference. On long distance runs and triathlons and such, people quite often eat during the race, but some find it harder to digest than others. I've never heard of a time limit after, unlike with weight lifting when it's commonly suggested to eat protein within an hour of finishing, when muscles are supposedly more open to absorbing it. TastyCakes (talk) 16:47, 21 August 2009 (UTC)

If you put it into your mouth and swallow it, it should go through the small intestine first (there are some who have had their small intestine removed, but it is not standard). Googlemeister (talk) 16:49, 21 August 2009 (UTC)

I generally can't run less than an hour or two after eating, and don't feel much like eating after running. But that could just be me; I think (as above contributors have noted) that it varies from person to person. My average run is 4-7 miles (6.4-11.2 km-ish), if that helps. Awickert (talk) 20:27, 21 August 2009 (UTC)

How do you digest food without a small intestine? As you sure you don't mean they have part of their small intestine removed? --Tango (talk) 20:47, 21 August 2009 (UTC)

Can't remember what it's called, but there's a type of surgery occasionally performed whereby the small intestine is removed; if I remember rightly, the patient has to carry around some sort of bag (which is attached to the digestive system) that contains some sort of mechanism to digest the food. Ideas, anyone, on what this is called? Nyttend (talk) 02:15, 24 August 2009 (UTC)

Colostomy_bag?12.34.246.72 (talk) 19:15, 25 August 2009 (UTC)

Thick eyebrows?

On my Chinese side there are a few people with thick eyebrows. I was wondering, is this a Mediterranean thing or a Chinese thing? I say this because I believe there might be Portuguese ancestry via Macau on my Chinese side. Spiderone (talk) 16:50, 21 August 2009 (UTC)

In general, I would expect the Portuguese to have thicker eyebrows than the Chinese. StuRat (talk) 22:29, 22 August 2009 (UTC)

Chinese people are still pretty capable of having thick bushy eyebrows. Take Zhang Fei, for example. bibliomaniac15 03:59, 23 August 2009 (UTC)

Do we reliably know the thickness of the eyebrows of a man who died in 221 AD ? StuRat (talk) 09:30, 23 August 2009 (UTC)

Why is a thunderstorm blue?

I thought I was seeing blue sky but soon realized that was actually a thunderstorm. Normally they are darker, but still blue.Vchimpanzee · talk · contributions · 16:52, 21 August 2009 (UTC)

Maybe for the same reason the sky is blue. Mac Davis (talk) 17:01, 21 August 2009 (UTC)

Like this one perhaps?

I doubt it. The sky is blue because it's scattering light according to Raleigh scattering - but that sort of scatter only applies to things much smaller than a water droplet. If the storm is scattering light at all, it'll be due to Mie scattering - which is responsible for the look of fog and thin clouds. But for thick clouds like thunderstorms, there is essentially no light transmitted through the cloud - so it's all about reflected light - not scattered light. I presume that the remainder of the sky was so intensely blue that the blue light from the sky was being reflected by the storm cloud. That would require that the sun was somehow not visible (like it had just set - or was behind another cloud or something). Dark-ish blue clouds are often visible when the sun is hidden like that (see photo at right for example). SteveBaker (talk) 18:06, 21 August 2009 (UTC)

The cloud looked like the blue part in that photo.Vchimpanzee · talk · contributions · 19:23, 21 August 2009 (UTC)

"That's Rayleigh!"

• Raleigh scattering - 472,000 ghits
• Rayleigh scattering - 417,000 ghits

The mob have spoken, learn to live with it. SteveBaker (talk) 02:20, 22 August 2009 (UTC)

Nice try, but you're counting all the people discussing scattering grandma's ashes in Raleigh, North Carolina. With quotes it's:

• "Raleigh scattering" - 14,000 ghits
• "Rayleigh scattering" - 417,000 ghits

--Sean 12:24, 22 August 2009 (UTC)

So you're saying that scattering grandma's ashes isn't what makes stormclouds look blue?! SteveBaker (talk) 20:57, 23 August 2009 (UTC)

Because thick clouds in general tend to appear blue;

see ^[2] , especially Figure 5. For some reason we just don't tend to notice it. 69.140.12.180 (talk) 03:01, 22 August 2009 (UTC)Nightvid

Voltage between outlet and ground

I have one of those power adapters that transform 120 V AC to a number of DC voltages (I can choose which voltage I want). When I measure the AC voltage between one of the terminals and a cold water pipe, I got 4 volts yesterday and 2 volts today. Why is the voltage not 0? —Preceding unsigned comment added by 99.237.234.104 (talk) 18:45, 21 August 2009 (UTC)

You are probably measuring the neutral wire versus the cold water pipe. The neutral wire is the wire at zero volts in reference to the "hot" wire, however this may be at a slightly different voltage than say, the water pipe. The water pipe should be at the same voltage as the "third" plug on your three pronged outlet, which is defined as "ground". Ideally ground and neutral should be at the same voltage, but for various reasons may be slightly different. --Jayron32 23:18, 21 August 2009 (UTC)

I was measuring the voltage between the direct-current output terminals of one of these adapters (but with adjustable output voltage):

http://bluewatersecurityprofessionals.com/Magellan_Roadmate_110V_Power_Adapter.jpg

and the cold water pipe. Both terminals, not just one of them, are at an AC voltage of 2 volts with respect to the water pipe. Interestingly, the voltage decreases very slightly as the output voltage of the adapter is increased. Out of curiosity, I also measured the voltage between the neutral and ground wires. The difference was tiny, about 0.4 volts. --99.237.234.104 (talk) 01:32, 22 August 2009 (UTC)

The OP is probably using a sensitive (high resistance) voltmeter which responds to leakage current through the adaptor. That can be proven by connecting a resistor of, say, 100 ohms across the voltmeter terminals: the indicated voltage would fall to zero. In contrast the voltage difference between neutral and ground, though small, has a very low resistance source and the 100 ohm resistor will not change the indicated voltage. In other words, the adaptor leakage is a constant-current source and the neutral-ground difference is a constant-voltage source. Cuddlyable3 (talk) 03:15, 22 August 2009 (UTC)

I tried both a 5 kilo-ohm resistor and a short circuit, but the first had no effect at all (even though my multimeter's resistance is 1.1 mega-ohms when measuring voltage) and the second decreased the voltage by only 0.1 volts. This multimeter is quite enigmatic.

Another mystery: when I touched the two leads of the multimeter, one with each hand, it registered about 0.03 volts. This was well above the multimeter's detection limit of 0.001 volts. I switched the leads so that each lead was now touching the other hand; same reading, and not the expected -0.03 volts. I oriented the leads in different directions; same reading. Whenever I took my hand off, the voltage reading instantly dropped to 0. I'm starting to wonder whether anything is wrong with my multimeter. --99.237.234.104 (talk) 12:14, 22 August 2009 (UTC)

(I hope the OP can find a 100 ohm resistor.) A high resistance voltmeter with long test leads is susceptible to stray mains radiation so biological potentials can be measured reliably only inside a Faraday cage or outdoors far from any cables. When you short circuit the test leads they make an inductive loop that can pick up the few millivolts you are seeing. FWIW if your hands really deliver 0.03V you can hold hands in a chain of about 100 friends and together make a LED shine brightly. Useful to know. Cuddlyable3 (talk) 21:31, 22 August 2009 (UTC)

Look at the AC plug on your adaptor. Note that you can plug it in either way. The adaptor does not know and does not care which of the two prongs is live and which is neutral. The adaptor acts as an isolation transformer. The adaptor's outputs are not referenced to the AC neutral, but to each other. You should expect the cold water pipe's voltage to be about half way between the "ground" output and the "+DC" output, the exact voltage will depend on accidental very high resistence paths inside the adaptor and will be different depending on which way the plug is plugged in. If you now short the DC ground output to the cold water pipe, the groud voltage will equal the water pipe voltage and the +DC will be as expected. You can get teh same effect with a resistor instead of a short, as long as the resistor is considerably smaller than the (very high) accidental internal resistance path in the adaptor. -Arch dude (talk) 13:40, 22 August 2009 (UTC)

Supersymmetry and Noether's theorem

I recently saw Steven Weinberg talking about symmetry and physics[3]. One theme in the talk was the duality between symmetries and conservation laws as shown by Noether's theorem. He then went on to talk about Supersymmetry and various challenges it poses. The thought occurred to me is there a conservation law which corresponds to supersymmetry? --Salix (talk): 19:36, 21 August 2009 (UTC)

Supercharge. Dauto (talk) 04:21, 22 August 2009 (UTC)

Nuclear power advances and the environment

How much less environmental impact per megawatt do modern nuclear power plants have compared to older ones? NeonMerlin 19:37, 21 August 2009 (UTC)

Basically unchanged, I'd think. Barring Chernobyl-type incidents (even the Three Mile Island accident is credited with only one or two probable cancer deaths), nuclear power plants themselves don't really produce an environmental impact by operating. I'd expect the potential impact of used fuel doesn't vary much, either. — Lomn 19:58, 21 August 2009 (UTC)

I think that the bigger issue is finding appropriate geologically-inactive and politically-tolerable places to put the nuclear waste. I don't know if this portion has improved at all or not. Awickert (talk) 20:23, 21 August 2009 (UTC)

There is usually Thermal pollution. APL (talk) 20:40, 21 August 2009 (UTC)

That's true; but probably, newer power plants release cooler water, thanks to the now-mandatory enormous cooling towers which have become the iconic symbols of nuclear power plants. It's hard to quantify "environmental impact per megawatt" (it's hard to quantify environmental impact in general). But since modern plants generally can produce more power than older ones, with effectively the same "environmental footprint", it's probably fair to say that there is less impact per megawatt. A more precise question, for example, might ask if modern plants have less thermal pollution per megawatt, which can be easily defined and numerically compared to older plants. Nimur (talk) 21:29, 21 August 2009 (UTC)

Why are they throwing away valuable energy into the air? They better be sucking every last drop of heat out of that water Matrioshka-style and turning it into useful energy til the outlet's 1 degree above ambient. Sagittarian Milky Way (talk) 22:57, 21 August 2009 (UTC)

I don't know, but I assume it has to be cost effectivness. At some point the cost of increasing efficiency will exceed the cost of the uranium it would save. APL (talk) 23:59, 21 August 2009 (UTC)

Indeed. If it were efficient to do that, they would. It's an obvious thing and nuclear engineers are a bright bunch. Using the excess hot water to heat nearby homes is quite good, I know some power plants (I think nuclear, although it might be fossil fuels, the principle is the same) do that. --Tango (talk) 00:04, 22 August 2009 (UTC)

Especially for the dollars of electricity they can liberate per kg, the fuel itself ain't expensive. The stuff they have to build to use it is expensive. They can't put windmill(s) near the top or throughout the tower (or do they do that that already)? Compared to the cost of the core, tower(s), scontainment bldg., or many safety systems can that really cost that much? They could slowly save money for the next who knows how many years, or sell the extra electric directly. Can't their habitable areas be inside the plumbing for non-radioactive coolant(s) (because of hollow walls) and they would turn a mixing valve to the non-heating pipeline when it's not cold outdoors? There's got to be something. The cost of extra features is sunk but the revenue from the 21st century's energy prices could always rise. It's sweltering in here, I thought I told Homer Simpson to turn the tertiary light-water nonemergency coolant valve two-and-a-half knobs and a smidge to the right after the warm front passed Sagittarian Milky Way (talk) 01:27, 22 August 2009 (UTC)

It's not just a matter of economics. Per second law of thermodynamics, the maximum possible efficiency is given by (T2 -T1)/T2 * 100% which means that at least T1/T2 * 100% of the energy must be wasted as heat. Where T1 is the environment temperature and T2 is the temperature inside the reactor (both measured in Kelvins). Dauto (talk) 04:34, 22 August 2009 (UTC)

So for example if the reactor core temperature is 800 K (which is actually quite a bit higher than that in most PWR-type nuclear reactors) and the outside temperature is 300 K (as on a warm summer day), the maximum efficiency of the reactor would be no more than 62.5 %, and you can't get more energy than that out of the nuclear fuel no matter how you try. 98.234.126.251 (talk) 04:55, 22 August 2009 (UTC)

That's right. Dauto (talk) 05:00, 22 August 2009 (UTC)

Well, yah, and a car engine should work better if nonessential surfaces touched Plutonian air.. I don't see why thermodynamics would prevent putting turbines inside venturis everywhere in the lower cooling loops. Maybe it could even be rational to load the last loop up with so much intermittant heat/pressure extractor that pressure would build up and release like a truck exhaust. Yes, I know there's a point to stop, eventually heat will even conduct out the pipes faster than the inlet can build it up. A few degrees is still enough to power a village or small town. Sagittarian Milky Way (talk) 08:24, 22 August 2009 (UTC)

See heat engine#efficiency. The second law of thermodynamics limits the efficiency to a maximum as I described above. There is always going to be a sizable fraction of heat wasted (That means it cannot be transformed into usable work, but it could be used for other things such as heat near by houses during winter)I don't see what putonian air's got to do with anuthing. Dauto (talk) 14:31, 22 August 2009 (UTC)

Cause the heat sink on Pluto is colder. Never mind. We seem to disagree on what we call waste heat. Consider a hypothetical heat engine that would take a 310K input and have 302K output on a 300K day, producing electricity equivalent to sucking 7K of the heat out, I would call that very efficient, and producing almost no waste heat, while you would call that very inefficient, and producing loads of waste heat. Comparing it with another engine turning 16K inflow into 8K outflow making 4K's worth electric in 4K ambient we would disagree which is more effiecient and which makes less waste heat. (all other things being equal) For engine purposes I don't even count the heat below the ambient as even existing to think about. That's like a hydroelectric turbine and what's below it's potential energy drop. But the lower gravity gradient is still there.. Sagittarian Milky Way (talk) 17:58, 22 August 2009 (UTC)

You're confusing heat (which is what I was talking about) with temperature and internal energy. Efficiency is defined here by the fraction of the energy provided by burning the fuel that eventually gets transformed into useful work. It's got nothing to do with the internal energy that you say should not be taken into consideration just as potential energy below the drop in a hydroelectric doesn't get counted. You are right that this internal energy shouldn't be counted for the definition of efficiency. Guess what, it is not counted so you don't really have a point here. Dauto (talk) 04:29, 23 August 2009 (UTC)

You're right. I have no point. Sagittarian Milky Way (talk) 03:59, 24 August 2009 (UTC)

The important point is the KIND of pollution they generate. The nuclear waste containment issue is not by any means beyond our technical ability to fix. It simply requires the political will to pick some nasty corner of the planet to dump all that stuff. The contrast is with CO2 pollution which is essentially impossible to fix...we have zero effective techniques to deal with it and we're pretty much out of ideas. If we put as much research effort into containing and dealing with nuclear waste as we put into trying to make "clean coal" work (which is a total joke) - we'd have the problem nailed by now. The problem is that whatever place you choose, a case can be made for not putting the waste there...but no matter how poorly you choose, the worst case scenario is that some small part of the planet gets trashed. That's better than what we're doing right now - which is to trash the ENTIRE planet. Even in the worst case scenario (Chernobyl) - there were 56 direct deaths and perhaps a few thousand people who'll die younger than they should. Compare that to a big tsunami or an earthquake - it's not that big a deal. a 40x40mile region is more or less uninhabitable - but it's turned into a wildlife haven with all manner of rare and endangered species thriving there...and (let's face it), it would be a REALLY good place to dump nuclear waste. Compare it to (for example) the Aberfan disaster in which a heap of tailings from a coal mine slipped, engulfed a school and killed 120 school kids - or the Val di Stava Dam collapse when a 'tailings' dam broke and killed 250 people. The 4000 miners who go to an early grave every year in the US due to black lung disease is very comparable to the number who contracted cancer as a result of Chernobyl. We could have a Chernobyl-scale accident every year and still produce less death, disease and devastation than the coal industry. SteveBaker (talk) 23:02, 21 August 2009 (UTC)

Why didn't anyone else think of that? We should leave our nuclear waste in Chernobyl! Better yet, breed it first (with sufficient safeguards to avoid hurting homeland security), then dump that waste. The less tons of nuclear waste being transported intercontinentally the better. Less opportunity for an accident. Sagittarian Milky Way (talk) 23:56, 21 August 2009 (UTC)

Note : While Chernobyl is home to some rare wildlife that is thriving, a lot of other wildlife does poorly there. APL (talk) 03:56, 22 August 2009 (UTC)

Why hasn't anyone brought up nuclear reprocessing yet? Done properly, it could reduce the amount of nuclear waste by as much as 88% while simultaneously increasing the amount of energy we could extract from the same amount of uranium by several times. 98.234.126.251 (talk) 04:30, 22 August 2009 (UTC)

Because a) reprocessing produces plutonium, which, being chemically different from uranium, is very easy to enrich to weapon grade material and b) reprocessing also has non-trivial contamination issues. But the major point is a) - any solution that you would not trust to run in Nigeria, or Iran, or Venezuela, is not going to do much good for the envirjonment - it just means that oil will be burned elsewhere. --Stephan Schulz (talk) 20:07, 22 August 2009 (UTC)

So what? If we meet all of OUR electricity demand with nuclear power, that would STILL make for a sizable decrease in pollution of OUR air and water (it would eliminate mercury pollution near our coal-fired electrical powerplants, for instance). As for the Iranians and the Venezuelans burning oil, well, why would that be our concern? I mean, (1) their energy production is MUCH lower than ours anyway, so less pollution will be generated in absolute terms, and (2) if THEY suffer from smog on a regional level, why would that be an issue for the US, eh? 98.234.126.251 (talk) 22:20, 22 August 2009 (UTC)

Who is WE? First, promoting an energy economy that only (maybe) works for developed, stable, friendly nations, and tell the rest of the world to run on dried camel dung is politically infeasible and morally bankrupt. Secondly, many of our major environmental concerns are global in scope, and many of the ones that are local are also treatable locally (in your example with decent scrubbers). But thirdly, you imply a wrong dichotomy. It's not clean nuclear vs. dirty coal, it's sustainable, clean, renewable vs. dangerous, dirty, expensive, and resource-limited. Nuclear has some advantages, especially in the short term, but is not sustainable without proliferation, and it's not now and never has been economically competitive if all costs are internalized. R&D has been massively subsidized, risks not ensured on the free market, and accruals for nuclear waste disposal are entirely insufficient. --Stephan Schulz (talk) 10:04, 23 August 2009 (UTC)

The US, India and China are the three biggest CO2 producers - with Russia and Europe (as a whole) contributing also. All of those places could usefully sustain nuclear power stations - all of them are already nuclear weapon owners and all four are pretty stable governmentally - so we don't have to worry too much about proliferation issues. We don't need the dubious, unstable countries of the world to use nuclear. They can either buy electricity produced by their neighbours, switch to wind/solar/etc - or even, just go on polluting. They aren't a big enough part of the problem here. Nuclear power probably isn't sustainable because natural uranium isn't a renewable resource. However, it is the one, single, sure-fired way to solve the CO2 problem. A massive program for constructing modern, relatively safe reactors could dramatically ramp up the amount of electrical power produced - and kill the use of coal and gas. Really cheap, (relatively) clean electricity allows us to switch transportation fleets over to electric power and thereby cut the use of oil to a minimum. That would give us the breathing space we so desperately need to figure out how to cut back our energy needs and to get hydroelectric/tidal/wind/wave/solar/biofuel/geothermal types of power sources up and running. The trouble is that nuclear power has fallen so far out of favor and piled up such a weight of legislation, NIMBY, and general public distrust that it's going to take major political willpower to make it happen. Also, pretty much everyone who ever designed or oversaw the construction of a working nuclear power plant is now in retirement! (Outside of France, where - for some wierd reason - nuclear power never got really unpopular.) Nuclear power's problems are indeed fairly severe - but we are at the point where drastic solutions are needed - and there are no really pleasant solutions left. Nuclear is probably the least unpleasant at this juncture. SteveBaker (talk) 20:49, 23 August 2009 (UTC)

Stephan Shultz, if you wanna have any credibility in energy-related discussions, you should know that the so-called "renewable energy" is a scam that was intended for no other purpose than to make some folks a lot of money (at public expense) without doing anything to meet our energy needs! Just look at most mainstream energy studies, they all agree that "renewable energy" cannot meet more than a tiny fraction of our energy demand (25% at the VERY MOST)! To advocate that we should change to using "renewable energy" exclusively is tantamount to advocating that we should GIVE UP OUR AMERICAN WAY OF LIFE AND GO BACK TO A PRE-INDUSTRIAL, LATE 18TH CENTURY EXISTENCE -- IF WE DO THAT, ELECTRICITY WILL BECOME SO EXPENSIVE THAT MOST OF OUR PEOPLE WILL HAVE TO DO WITHOUT! That said, the ONLY non-fossil-fuel-based energy source that can meet (ALMOST) ALL our energy demand is nuclear energy ("almost" because it's not practical for transportation, for reasons that have nothing to do with availability). And also, according to Scientific American, nuclear energy IS economically competitive with natural gas when you take economies of scale into account -- and now that SAFE, ECONOMICAL "fourth-generation" nuclear reactors are on the verge of commercialization, we can very well expect nuclear energy to become competitive with coal as well. ("Renewable energy", on the other hand, is MUCH more expensive per kilowatt than either coal or nuclear -- even in terms of production costs ALONE, and without taking into account the intrinsic supply limitations.)

And IMHO, if all the third-world nations end up running on dried camel dung, well, WHY WOULD WE GIVE A DAM? Why is THEIR welfare any of OUR concern, anyway? We should be concerned about meeting OUR energy needs, and let those people figure out how to meet THEIR energy needs on their own. Wasting OUR resources on solving THEIR problems (and getting NOTHING from them in return for our troubles except hatred, envy, and the occasional car bomb) will get us NOWHERE.

Furthermore, your claim that clean energy would "do no good unless we can get everyone to use it because the oil will just get burned somewhere else" is ABSOLUTELY COUNTERFACTUAL and doesn't even make ANY LOGICAL SENSE -- even if only the developed, stable, civilized nations like the US, Europe and China change from mainly coal to mainly nuclear power, that would STILL make a BIG dent in the amount of pollution generated worldwide (as SteveBaker correctly pointed out in the post above). But from someone who's too ignorant in economics and energy policy to even understand how a $150 per barrel carbon tax can hurt our economy, well, what sort of logic can we expect?

In short, the statements you made in your post are completely inaccurate, counterfactual, illogical, anti-American, and probably politically motivated in the first place. 98.234.126.251 (talk) 23:24, 23 August 2009 (UTC)

Seems like nuclear is the only way. We have too little time left to act. Someone should make a commercial a la T. Boone Pickens "Oil is not the answer. Some sort of inertial, laser; magnetic thermonuclear or other fusion is the answer. Nuclear power plants is the bridge."</endhumor>

That's right, we gotta change our electricity production from fossil fuels to nuclear power, and get started today. I'm not too sure about fusion power, though -- so far, nobody ever achieved a fusion reaction that lasted more than thirty seconds or so, or produced more energy than was used to initiate and sustain it in the first place. Perhaps that might change eventually, but so far it don't look like it's gonna happen anytime soon. (BTW, why don't you sign your posts?) 98.234.126.251 (talk) 08:57, 24 August 2009 (UTC)

My bad, that was me. Fusion is very weak. The nuclei make tremendous energy (for a particle) when they fuse, but it is so hard and rare for them to join because nuclei don't like to be near each other. Despite, what 10-15 million K, plasma densities many times that of water and billions of psi the core of the Sun still makes only 35 watts per cubic meter. That's 20 times weaker than the human body! Yet, supergiant stars produce 1,000,000 sunpower! from only 1 and 1/2 orders of magnitude higher temperature and 100 times the mass. An order or magnitude cooler and lighter and it becomes a millisunpower or even a microsunpower, till fusion finally stops. The scientists seem to recognize this by making their reactions much hotter than the core of the Sun, but so thin, the heat density is more like coffee, and like you said, it's still not enough. Those things are so expensive already but the only solution seems to be.. MAKE IT HOTTER! (And/or denser! And/or bigger!) Develop more powerful lasers? Larger tokamaks? Who knows, it might be ~ a century until most energy is made by fusion power. Maybe it will never be figured out. One thing's for sure, we were/are being led astry by clean coal/drill baby drill/corn/natural gas cars/slightly smaller large vehicles.. Sagittarian Milky Way (talk) 23:34, 24 August 2009 (UTC)

Well said, Sagittarian Milky Way. Yeah, by some estimates, it'll be more than 50 years before a sustained, controlled fusion reaction is even experimentally demonstrated, let alone commercialized. That said, fission power is the next best thing for the production of electricity, and it will certainly be a major part of our energy policy for the 21st century. I disagree with you about clean coal, though -- coal-to-liquids is certanly useful for transportation (to replace foreign oil and thus achieve energy independence), and can be coupled if necessary with carbon sequestration to alleviate global warming concerns. (Nuclear power is not practical for transportation, for understandable reasons.) So, what I believe we should be trying to achieve is to use nuclear power wherever possible (i.e. to generate all of our electricity), and use coal-to-liquids (possibly with CO2 sequestration) where liquid fuels are required (i.e. for transportation). Corn ethanol (and biofuels in general) won't be economical and won't fulfill our demand for liquid fuels to any extent (and foreign oil promotes terrorism and will run out soon anyway), so we'll need coal-to-liquids to take care of that. 98.234.126.251 (talk) 00:04, 25 August 2009 (UTC)

Seems bass-ackwards (and barely above sweeping it under the rug) to me. What about running ships and planes with natural gas? We've got plenty of gas. Since there's almost 4 hydrogens for every carbon, it's just about the closest thing to burning not-carbon as is there is commonly on this Earth. And electric cars? Build 1 or more maglevs on very populated corridors as a fast, convenient alternative for distances that are both short for a plane trip and long for a car trip? Possibly it's even be worth the extra transmission losses building nuclear power plants far away from people just so they can even get built without everyone complaining. Sagittarian Milky Way (talk) 06:07, 25 August 2009 (UTC)

Yeah, we got plenty of natural gas, but it's in high demand as it is, so it's still much more scarce than coal. Besides, there might also be safety concerns with natural gas that there aren't with liquid fuels (like, for instance, what if some air finds its way into the fuel tanks). Electric cars might be efficient and non-polluting, but the problem is, right now they have nowhere like the performance, range or payload that they need in order to truly replace gasoline-powered cars. Maybe that could change in the near future, but until then, they'll remain on the margin. (And besides, electric 18-wheeler big rigs are nowhere on the horizon right now.) Maglevs might be a good option for distances of 100-500 miles, but high-speed trains are better -- almost as fast, but a lot easier to build. As for building nuclear plants far away from people: great idea, but unfortunately you weren't the first to think of it. 98.234.126.251 (talk) 08:03, 25 August 2009 (UTC)

But isn't alot of the demand for heating and electricity? If we get people to switch to nuclear-fired electric heating and loghts we might not need alot of the gas we use now. Once we do that, would the shortage really be that bad, considering we have enough gas for almost/about a century right now?

That looks scary. The tanks are under pressure, they must have to be ruggedized and tough. Our article on liquefied natural gas shows that LNG ships have traveled over a hundred million miles and 35 years without a single man lost or accident on board. Only 3 explosions have occured in total, the earliest in 1944. What about the 1996 fuel tank explosion/airliner destruction? Flour silos explode too. I hope we would do this with the utmost of safety precautions. <h>Make them bulletproof and put DragonSkin armor on them, lol.</endhumor>

Maybe carbon could be scrubbed from ships?

Read the Tesla Roadster article, then the Tesla Model S article, then Tesla BlueStar. If you read them in order, I bet it will completely change your opinions on electric cars.

You're right, HSR is better, maybe I was just jealous of the Chinese. I read that the fares might never pay it back. But if it helps their national pride, so be it..

No, I'm not the first person to think of it, but why should I be? They still didn't listen to them as the nuclear plant I know is surrounded by about 10 thousand suburban residents within a mile, some of them right across a street from the fence. Doesn't Augusta, GA have something military nuclear across a river from it? I don't know about other states, but maybe some did isolate them out there. Sagittarian Milky Way (talk) 16:02, 25 August 2009 (UTC)

"If we get people to switch to nuclear-fired electric heating and loghts we might not need alot of the gas we use now." -- You got a point there, Sagittatian: if we do that, then natural gas might become economically feasible for transportation. Unfortunately, nobody has actually crunched the numbers on that yet (to the best of my knowledge), and I can't crunch the numbers myself because I'm not an economist, but a petroleum chemist.

"Maybe carbon could be scrubbed from ships?" -- Maybe, and then again, maybe not. I really don't know if anyone's done any research on that yet.

"Read the Tesla Roadster article, then the Tesla Model S article, then Tesla BlueStar. If you read them in order, I bet it will completely change your opinions on electric cars." -- I'm perfectly familiar with Tesla electric cars: they got good performance all right, but they still got only about a 150-200 mile range, compared to 400+ miles for your typical gasoline-powered car (quite aside from the fact that they're way too expensive for most people). 98.234.126.251 (talk) 23:54, 25 August 2009 (UTC)

(antiindent) The point was, the profit from the $110K 2008-2010 cars will be used to fund the $50K 2011 cars (they're already making profit), whose profit will be used to fund the $20-30K 2012 cars. Did 1993 computers drop in price this fast? There is virtually no maintainance, you get a $6K tax refund, and it costs $10 to $30 per 1,000 miles to "fill up the tank". $1250 in "gas money" a decade if your utility gives you a discount for electricity at night. The idea of the gas station being able to swap your drawn battery with a full one in 5 minutes is already in the works. There isn't even a radiator, the 150 lb motor is so noninefficient it can be air-cooled. Electric cars seem more far along than all the other technologies we mentioned so far, which are acheingly long. And you car drivers are so spoiled. Only 240 miles range, oh boohoo. You know what?, I never rode in a passenger car till I was almost 10 and I was wondering why it TOOK SO LONG! We did have to refuel, finally. If we can't even make this tiny sacrifice for our country of having to go to the gas station a little more often and/or cutting it a little closer than what can we do? It's actually 244 miles. Closer than 244 miles of me is Boston, Philadelphia, Baltimore, Washington, Manhattan, Gettysburg, my state capital, Erie Canal, Appalachians, Atlantic City, where all your credit card bills go, Canada (almost), a subway that runs over the ocean, and a slave port (the one in Roots). And random strange metropolitan areas. All within 1 fillup. Battery-tech will slowly improve, why should there be any laws of physics limiting batteries range compared to gas? It's all chemical energy. Exotic lower mass compounds like alcohol, nitromethane are even less energy dense, but their octane number is like 116, or 136 or something, so they're actually more powerful than gasoline, just because their able to be squeezed more w/o knocking, which is why they're used in drag racing, so gasoline is not near the limits for chemical energy density or gas tank range either. Before when they were less fuel efficient they only went 300 miles. Model S will be a 5.7s 0-60 high-end sedan, the BlueStar will be a sedan. Sagittarian Milky Way (talk) 02:18, 26 August 2009 (UTC)

Tesla cars are still much too expensive for most people, which is why they're not all that popular. I don't really have anything against electric cars per se (well, I won't when they get the same performance for the same price as gasoline cars), but right now plug-in hybrid cars are a much better choice than all-electric. 98.234.126.251 (talk) 03:01, 26 August 2009 (UTC)

The plug-in hybrid isn't available yet, either. (though very soon) An electric car almost as good as the Chevy Volt will be available only two years later (Tesla BlueStar) for a similar price (though still a little bit expensive). As of right now, there is no car that a normal human being can buy that can be plugged into anything. But prices will go down so fast it's like almost not the future the day when regular people will be able to afford one because the powers of mass production will be able to lower the costs more. Electric motors are very simple compared to gasoline engines, if enough people buy them they should even get cheaper than regular cars. Oh, and see a Killacycle video on Youtube, it's cool. It reaches 168 mph in 1/4 mile. Sagittarian Milky Way (talk) 04:15, 26 August 2009 (UTC)

Good, let's hope that this happens soon. 98.234.126.251 (talk) 04:33, 26 August 2009 (UTC)

Let's hope so. Sagittarian Milky Way (talk) 04:42, 26 August 2009 (UTC)

• so-called "renewable energy" is a scam that was intended for no other purpose than to make some folks a lot of money (at public expense) without doing anything to meet our energy needs! - No, from Renewable energy: "In 2006, about 18% of global final energy consumption came from renewables," - and wind power is growing 30% per year. Hence it does have purpose - it produces energy and cuts down reliance on non-renewable sources.
• Just look at most mainstream energy studies, they all agree that "renewable energy" cannot meet more than a tiny fraction of our energy demand (25% at the VERY MOST)! - It's certainly going to be difficult-to-impossible for renewables to completely fill the gap. However, with energy savings and judicious use of nuclear - we could maybe cut the use of CO2-producing energy production to the degree necessary to save the planet...maybe.
• To advocate that we should change to using "renewable energy" exclusively is tantamount to advocating that we should GIVE UP OUR AMERICAN WAY OF LIFE AND GO BACK TO A PRE-INDUSTRIAL, LATE 18TH CENTURY EXISTENCE -- IF WE DO THAT, ELECTRICITY WILL BECOME SO EXPENSIVE THAT MOST OF OUR PEOPLE WILL HAVE TO DO WITHOUT! - Well, not everyone is an American - and some believe that Americans will indeed have to give up at least some of their energy wasting ways. I don't think that going back to pre-industrial existance is possible with the scale of population we have now - but something has to change or we will have a planet we can't live on anymore. But very few people expect to be able to switch to 100% renewable energy production anytime soon. The goal is to cut it drastically to give ourselves time to come up with a better answer. Right now, it's a matter of mid-term survival.
• That said, the ONLY non-fossil-fuel-based energy source that can meet (ALMOST) ALL our energy demand is nuclear energy ("almost" because it's not practical for transportation, for reasons that have nothing to do with availability). - That's certainly nonsense. If we switch to electric cars & trucks (probably via plug-in hybrids) - we can indeed run our cars from nuclear-produced electricity. This is perhaps the easiest to imagine part of the puzzle.
• And also, according to Scientific American, nuclear energy IS economically competitive with natural gas when you take economies of scale into account -- and now that SAFE, ECONOMICAL "fourth-generation" nuclear reactors are on the verge of commercialization, we can very well expect nuclear energy to become competitive with coal as well. - Nuclear reactors might be technically ready for commercialization - but the current legislative barriers (in the US at least), together with the NIMBY problem, makes it VERY tough to get these things onto the generation grid quickly.
• ("Renewable energy", on the other hand, is MUCH more expensive per kilowatt than either coal or nuclear -- even in terms of production costs ALONE, and without taking into account the intrinsic supply limitations.) - That's only true if you let coal pollute the world "for free". If we charged the coal power plants with the cost of cleaning up the CO2 they produce - they'd be bankrupt overnight. Coal is only cheap compared to renewables when the 'value' of destroying the planet is $0. Nuclear might also suffer the same problem - but as I said above, the cost of dealing with nuclear waste is mostly the political decision to do it. It's not inherently costly. Anyway - when you count the FULL costs, renewables win every time. That's why we need some kind of carbon tax - to represent the costs to the entire planet fairly.
• And IMHO, if all the third-world nations end up running on dried camel dung, well, WHY WOULD WE GIVE A DAM? Why is THEIR welfare any of OUR concern, anyway? - Because we have to live on the same planet as them. If China and India don't do something just as dramatic as is advocated for the USA and Europe (although Europe is WAY ahead on this) - since we're all living on the exact same planet, we all get our cities flooded - we all get bizarre weather patterns - we all lose our biodiversity. You can't put up big walls around your particular corner of the planet and say "We're alright!" - that's just stupidly naive.
• We should be concerned about meeting OUR energy needs, and let those people figure out how to meet THEIR energy needs on their own. Wasting OUR resources on solving THEIR problems (and getting NOTHING from them in return for our troubles except hatred, envy, and the occasional car bomb) will get us NOWHERE. - See above.
• Furthermore, your claim that clean energy would "do no good unless we can get everyone to use it because the oil will just get burned somewhere else" is ABSOLUTELY COUNTERFACTUAL and doesn't even make ANY LOGICAL SENSE -- even if only the developed, stable, civilized nations like the US, Europe and China change from mainly coal to mainly nuclear power, that would STILL make a BIG dent in the amount of pollution generated worldwide (as SteveBaker correctly pointed out in the post above). - It's a matter of degree. If the big three polluters (US, India, China) were to make (say) an 80% cut in their CO2 emissions - then maybe we'd have bought enough time to gradually bring the rest of the world into the fold and have a relatively 'soft-landing'. However, if the big three only make a 20% cut - then we need everyone else to join in too. What's actually happening is that everyone is mostly talking about making a zero percent cut - fighting to avoid increasing out output anywhere higher than it is now. That's nowhere near enough!
• But from someone who's too ignorant in economics and energy policy to even understand how a $150 per barrel carbon tax can hurt our economy, well, what sort of logic can we expect? - This isn't only about economics. Without a carbon tax, the CO2 levels will continue to rise, global temperatures will rise, the ocean levels will rise and the three biggest cities in the USA will be under 20 meters of ocean. Since almost all of our productive farmland is below 20meters above sea level, food supplies in the US will become exceedingly scarce. The dent this will make in our economy will make a $150 per barrel carbon tax look like quite a good deal. The trick for the US is to become a major supplier of zero-CO2 power generation systems to the world. The US needs to turn those empty car factories into windmill plants - or nuclear power plant component makers - or electric car factories. To leverage the much-touted skills at science and technology to become world leaders in this technology. As the realisation that we really are in deep-doo-doo finally settles into the brains of people like yourself (and the Chinese and Indians) - this technology will be in high demand - and the US needs to be there ready to push the stuff and make a killing. However, that requires brains and a 'buy-in' to the problem...and sadly people like the person I'm replying to here are major roadblocks to doing that.
• In short, the statements you made in your post are completely inaccurate, counterfactual, illogical, anti-American, and probably politically motivated in the first place. - Um...actually...judging to my responses above, I think those remarks are REALLY SERIOUSLY misdirected.

SteveBaker (talk) 01:28, 24 August 2009 (UTC)

(outdent) One additional issue I didn't think about was contamination of groundwater due to in situ uranium mining, in which chemicals are pumped into the ground to leech uranium out of the ground. The plus of the technique is that there is no big hole; the minus is where some of the leeching agent gets. Awickert (talk) 01:46, 24 August 2009 (UTC)

"It's certainly going to be difficult-to-impossible for renewables to completely fill the gap." -- That's exactly the point I was making, renewables cannot provide more than a small fraction of the USA's energy needs. Nuclear power, however, CAN supply the ENTIRE nation's electricity needs, leaving transportation as the ONLY consumer of fossil fuels. That's why nuclear power is BETTER for the US than renewables and should be pursued aggressively, not "judiciously" as you seem to advocate here. The goal is to replace ALL the coal-powered electric plants with nuclear electric plants, that will solve the pollution problem even without wasting our taxpayer money on renewables, which are (at best) a very partial solution, and (at worst) a shameless scam pushed upon us by certain interested parties.

"Well, not everyone is an American - and some believe that Americans will indeed have to give up at least some of their energy wasting ways." -- Seriously, do you and Stephan Schulz work for the UN or something? I thought a Texan would know better than to advocate such blatant anti-Americanism which is otherwise seen only in third-world nations and in the UN general assembly. We're (and according to the opinion polls, most Americans will agree with me here) NOT giving up our way of life because some third-world chumps want us to -- end of discussion!

"If we switch to electric cars & trucks (probably via plug-in hybrids) - we can indeed run our cars from nuclear-produced electricity. This is perhaps the easiest to imagine part of the puzzle." -- We've already discussed this before, but I'll say this again until you finally get it: It's not just about the cars and trucks, it's also about the ships and planes. So until you come up with some way to run a jumbo-jet on electricity, we'll need fossil fuels to run this part of our economy (which will still be less than 30% of our fossil fuel use now).

"Nuclear reactors might be technically ready for commercialization - but the current legislative barriers (in the US at least), together with the NIMBY problem, makes it VERY tough to get these things onto the generation grid quickly." -- As you yourself said before, this is a matter of political will.

"when you count the FULL costs, renewables win every time." -- That does not account for the fact that renewables CANNOT meet ALL our energy needs, as you yourself have admitted more than once. Yeah, I'm all for phasing out coal-powered electrical plants -- but replacing them with NUCLEAR POWER, not renewables, since nuclear power will be produce much less pollution, but (UNLIKE renewables) can meet ALL our electricity demand WITHOUT requiring us to give up our American way of life.

"Because we have to live on the same planet as them. If China and India don't do something just as dramatic as is advocated for the USA and Europe (although Europe is WAY ahead on this) - since we're all living on the exact same planet, we all get our cities flooded - we all get bizarre weather patterns - we all lose our biodiversity." -- Perhaps I should have been more clear from the start in defining "us" and "them". For the record, I do NOT oppose having the Chinese and the Indians use nuclear technology (in any event, they already have access to it); what I do oppose is sharing this technology with every Tom, Dick and Harry in the world when many of them (like Iran, for instance) would gladly use it to make an atom bomb with which to destroy New York City (or LA, or any other suitable American city). Nuclear technology should be restricted to those nations that already have it and/or can be trusted with it, BY ANY MEANS NECESSARY is what I'm saying -- the rest of the world can get along as best they can WITHOUT access to nuclear power.

"It's a matter of degree. If the big three polluters (US, India, China) were to make (say) an 80% cut in their CO2 emissions - then maybe we'd have bought enough time to gradually bring the rest of the world into the fold and have a relatively 'soft-landing'. However, if the big three only make a 20% cut - then we need everyone else to join in too." -- The scenario that I'm discussing would involve having the big three replace about 50% or so of their fossil fuels with nuclear power.

"Without a carbon tax, the CO2 levels will continue to rise, global temperatures will rise, the ocean levels will rise and the three biggest cities in the USA will be under 20 meters of ocean." -- Didn't we discuss it all before? #1, this assertion presumes that the warming trend observed in recent years is due to the so-called "greenhouse effect", whereas quite a number of scientific studies point to an increase in solar radiation as a major contributor, if not the sole cause, of the warming trend (which, by the way, may have reversed for the past 3 years). #2, a carbon tax of $150 per barrel will CRIPPLE our nation's transportation system, as I have already proved to you before. #3, as I've already said, even if the "greenhouse effect" hypothesis is correct (which I strongly doubt), a MUCH better way to deal with the problem is to subsidize nuclear reactor construction for electricity generation -- that can STILL cut our CO2 emissions by 70+% (assuming that ALL our electricity is produced from nuclear power), while still allowing the transportation system to operate normally, and having a much lower economic cost than a carbon tax. Your statement that it's a choice between "$150/barrel carbon tax" and "let the cities get flooded" is a false dilemma, and as such, is complete nonsense.

"However, that requires brains and a 'buy-in' to the problem...and sadly people like the person I'm replying to here are major roadblocks to doing that." -- You're DEAD WRONG here, mister: for the record, I have ALWAYS advocated aggressively expanding nuclear power generation to meet our electricity demand, for many different reasons. What I oppose, and ALWAYS will, are stupid, brainless, half-baked, anti-American ideas like an across-the-board $150/barrel carbon tax that would cripple transportation, or a complete reliance on renewables (which would require us to cut back our energy consumption by 75 OR MORE PERCENT -- and consequently LEAVE AT LEAST THREE-QUARTERS OF THE AMERICAN PEOPLE IN THE DARK WITH NO ELECTRICITY). Your accusations, besides being a personal attack, just DON'T MAKE ANY SENSE!!!

98.234.126.251 (talk) 05:04, 24 August 2009 (UTC)

Oh, the man from the "I spell in caps and use a lot of exclamation points, therefore I'm right" fraction is back. Just apart from the many factual errors in your comments: I under understand that the categorical imperative is a mouthful. But I thought the Golden rule was universally recognized and even taught explicitly in US schools? --Stephan Schulz (talk) 07:30, 24 August 2009 (UTC)

What "factual errors" are you talking about here? I challenge you to identify every single one of them and present undisputed information to the contrary (which I don't remember you ever doing thus far). And what, may I ask, does the categorical imperative have to do with nuclear technology? 98.234.126.251 (talk) 08:47, 24 August 2009 (UTC)

Give it a minute. --Stephan Schulz (talk) 09:09, 24 August 2009 (UTC)

Every single one of them? Poor Schulz. It'll take you much longer than a minute. - Drew Smith What I've done 09:33, 24 August 2009 (UTC)

Sorry, miss-understanding. I was asking 98 to take a minute of thought to figure out what the categorical imperative and the Golden Rule have to do with energy policy. --Stephan Schulz (talk) 12:17, 24 August 2009 (UTC)

I was asking for your response. Frankly, these kinds of philosophical questions are not my concern -- my only ethical concerns are that I must do and stand for those things that are in my country's interest. That's called loyalty to one's country (or patriotism, for short), for those of you who are unaware of this concept. (I hate to admit this, but I haven't always said or done what was best for my country -- but I'm trying as best I can.) 98.234.126.251 (talk) 12:36, 24 August 2009 (UTC)

Drew, if you wanna take this challenge too, go right ahead. I seriously think, though, that the majority of your (and Schulz's) time will be occupied not with identifying whatever "factual errors" might be there, but with searching all over the whole wide world for even a tidbit of reliable info that contradicts my statements. 98.234.126.251 (talk) 11:56, 24 August 2009 (UTC)

Speaking of factual errors, I found one in SteveBaker's last post that I had overlooked until now. Remember, Steve said that "almost all our productive farmland is below 20 meters" and will therefore be flooded in his nightmare global-warming scenario? Well, (quite apart from the fact that the 20-meter figure is very doubtful to say the least -- and Steve never provided any hard evidence for it), I've just visited the USGS website and took a look at the map of elevations in the US -- and guess what, it turns out that although parts of Louisiana and Arkansas are below 75 meters elevation (the map only shows elevations in 75-meter increments), most of the Great Plains (which is where most of our farmland is) is actually above 75 meters. Steve -- I just proved you wrong on this count, you might as well admit it. 98.234.126.251 (talk) 09:48, 24 August 2009 (UTC)

Also, regarding SteveBaker's claim that "when you count the full costs, renewables win every time" -- you (all) might wanna take a look at the September 2006 issue of Scientific American, it's got a nice histogram (bar graph, for the uninitiated) that compares the production costs of different kinds of energy (I believe it's on page 96). Anyway, that graph shows solar power is the MOST expensive to produce, while nuclear is only slightly more expensive than coal. (I know, and freely admit, that this graph shows the production costs of hydrogen from different sources rather than electricity; but then again, the costs of producing electricity from those sources are prob'ly not too far off from these numbers, are they?) 98.234.126.251 (talk) 11:22, 24 August 2009 (UTC)

It's on page 98, sorry... 98.234.126.251 (talk) 11:27, 24 August 2009 (UTC)

TO give a more precise figure for the cost of nuclear power vs. coal: the very same magazine (Scientific American, September '06) gives the price of electricity produced from coal as 4.2 cents per kilowatt-hour; electricity from nuclear power is currently priced at 6.7 cents per kilowatt-hour, but can be brought down to 4.2 cents per kilowatt-hour simply by design and construction improvements to nuclear reactor plants, without the need for any major technological breakthrough (according to a 2003 MIT study). 98.234.126.251 (talk) 11:39, 24 August 2009 (UTC)

Looking at the graphs on causes of warming, anthropogenic causes have contributed more to global warming than solar activity has for the past 30 years or so; also see Attribution of global warming. As for the climate cooling for the past 3 years, that's also wrong. Arctic sea ice reached its dramatic minimum in 2007; methane was found to be releasing from subsea permafrost in 2008. And in 2009, the Chacaltaya glacier disappeared, a large portion of the Wilkins Ice Shelf shattered, and in July the global ocean temperatures reached a record high for that month, breaking the old record set back in 1998 (which some skeptics say was the warmest year on record, it wasn't!). This is all while solar activity has been at a drastic minimum for those very three years you claimed. Nuclear may be a good solution, but in some areas wind and solar or geothermal are viable alternatives! As for the Great Plains, one study points out that a farther 1°C (1.8°F) of global warming could turn much of the Great Plains and American Midwest into semi-desert, starting with the Sand Hills area. As for oil, read oil depletion and peak oil, it'll run out in a few decades at this rate. "We", if by this case you mean the Americans, should care about what happens in other countries, because climate change is likely to trigger political instability, and the hatreds of terrorism could be directed at what is seen as the main contributor of this warming, namely the US. What we need to solve any global issue is cooperation. Many American cities are indeed quite close to sea level, and will be affected by sea level rise. 98, it seems that you are taking every opportunity to attack what you dismiss as anti-American or what you think to be "right", trying to make all other arguments worthless by pointing out every possible inaccuracy. If that is the case, you probably belong on Conservapaedia, not the Wikipedia refdesk. Or perhaps LiveScience, where other users will actually agree with you. You have done this to many posts recently and caused the subject of the conversation to stray away from what the initial OP asked, which is what we are actually supposed to answer. ~AH1^(TCU) 11:55, 24 August 2009 (UTC)

Solar power a "viable alternative" to nuclear? I don't think so -- just look at the production costs of solar power vs. nuclear power, and you'll see the difference. Not to mention that solar power can NEVER provide more than 10% or so of the USA's electricity demand -- to try to produce ALL our electricity from solar power would require more solar panel area than we got land! Whereas, nuclear power CAN provide all our electricity (albeit at considerable cost in capital investment, it is true). As for global warming -- assuming that it's indeed caused by CO2 emissions, then nuclear power is just the solution that we need, because it's the only non-fossil-fuel source of energy that can provide ALL our electricity, whereas renewables can only provide a small fraction (and that could reduce CO2 emissions by as much as three quarters eventually, which would solve the global warming problem and all its consequences just fine -- once again, ASSUMING THAT there's a casual link between CO2 emissions and global warming). And as for terrorism, that's a whole separate topic altogether, and has absolutely nothing to do with global warming -- to say that it does is the same as saying that black cats bring bad luck. And regarding your statement that my posts have caused the subject to stray away from the original question: I don't remember exactly what was said by whom in earlier posts, but if you check this current thread, you'll see that it was Stephan Schulz who first brought up politics, not me (I was just suggesting that reprocessing could be a good way to deal with nuclear waste, and Schulz responded with the politically charged and factually dubious statement that "any solution that you would not trust to run in Nigeria, or Iran, or Venezuela, is not going to do much good for the environment - it just means that oil will be burned elsewhere".). 98.234.126.251 (talk) 12:24, 24 August 2009 (UTC)

"... to produce ALL our electricity from solar power would require more solar panel area than we got land". Complete nonsense. Not even close. Nellis Solar Power Plant produces 25 million kWh of electricity annually and occupies an area of 0.6 km². So to produce the whole electricity consumption of the US, 4 trillion kWh, would require about 100,000 km² of solar power plants, or about 10% of the area of the Great Plains. That's big, but it's certainly not "more area than we got land". Gandalf61 (talk) 13:09, 24 August 2009 (UTC)

Indeed -- and how much does the electricity cost to produce? Besides, Nellis is in the desert (I've been there), so it receives much more solar radiation per unit area than most other areas of the US (even the Great Plains). To try to extrapolate the energy density at Nellis to the rest of the US (as you seem to be doing) would lead to a vastly exaggerated estimate for the amount of solar power that can be produced per unit area. 98.234.126.251 (talk) 23:42, 24 August 2009 (UTC)

And, 98, you need to keep in mind that this is not an all-American website. This simply isn't the place to share your American patriotism, or to start debates. Besides, not even all Americans are so defensive of their country on the Internet as to attack all opposing opinions, as illustrated perfectly by Steve over there. ~AH1^(TCU) 00:06, 25 August 2009 (UTC)

Why is it always that it's OK to advocate left-wing politics (like the carbon tax) on Wikipedia, but it's not OK to oppose them in the same place? Are we talking about a double standard here, or what? It's just like you lefties always do -- you welcome all political opinions as long as they agree with your worldview, but when someone disagrees with you, you just shout'em down, or get all defensive and say "this isn't a place for political debates", or try to twist their statements to make it look like they mean something else. And besides, why shouldn't I be defensive of my country when there's a big, wide and hostile world out there with so many people who hate America and would gladly hurt it if they could? As for this not being an all-American website -- yeah, I see that the "one-world mafia" is really out in force here, and American patriots are very much in the minority. (Well, maybe there are a few who are just not sharing their patriotism for fear of being shouted down or personally attacked.) 98.234.126.251 (talk) 01:01, 25 August 2009 (UTC)

AEB1

Schulz and Gandalf, I'm still standing by for your refutation of my arguments in favor of nuclear power vs. renewables. Are you having a hard time finding the figures you're looking for? 98.234.126.251 (talk) 01:17, 25 August 2009 (UTC)

Most people look at global warming from a scientific perspective, but right now it's frankly safe to say that there will be some degree of geopolitical impact as the planet warms, chiefly from increased stress on water, food, and resources. You seem to be advocating yourself to be a rightist, and therefore are perhaps more likely to perceive Wikipedia as leftist, liberal and even anti-American (this is because Wikipedians on average are less conservative than the average American). In that case, I again recommend Conservapaedia or LiveScience. We're not advocating the carbon tax for the USA. Besides, this question wasn't about the United States in the first place, but nuclear power in general, which does have its advantages, but the main issue is what to do with all the radioactive waste. As a non-renewable resource, uranium supplies can still run out. ~AH1^(TCU) 03:45, 25 August 2009 (UTC)

Go easy on him, he's the only reasonable reasonable rightist I've seen. Don't want to scare him off.. Sagittarian Milky Way (talk) 03:59, 25 August 2009 (UTC)

Schulz, Gandalf, AH1 (especially Schulz): If you're claiming to not advocate a carbon tax, then how do you explain Schulz's strident (and illogical) arguments in favor of a carbon tax in the discussion on coal liquefaction just a couple weeks ago? Have you forgot so soon, huh? Well I haven't, and I will use his previous statements against him if he starts pushing politics again. And as for uranium supplies running out: scientists estimate that they'll last for at least several hundred years even if the industrial nations generate all their electricity from nuclear power. And besides, we can always use breeder reactors to produce more nuclear fuel artificially.

Also, Schulz, you have claimed that my previous statements contain "many factual errors", but you still haven't pointed out any specific ones (aside from my assertion that global warming is caused by solar activity -- well, I might be wrong on that, but it's not really relevant to whether nuclear power is better than renewables), much less refuted them, even though it's been almost 24 hours since you made the claim. Therefore, I strongly suspect that you couldn't really find any "factual errors" in my statements that are contradicted by reliable information. And you still haven't explained what does the categorical imperative have to do with energy policy. But hey, I can wait a while longer while you search for the info. 98.234.126.251 (talk) 07:43, 25 August 2009 (UTC)

• "... to produce ALL our electricity from solar power would require more solar panel area than we got land" is a specific factual error. Even if an average solar power plant is only 10% as efficient as Nellis, total area required to equal current US electricity production is still only 1 million km². I don't know what you are hoping to achieve here, but I suggest you take your bad-tempered rants, taunts and claims of infallibility somewhere else. Gandalf61 (talk) 10:10, 25 August 2009 (UTC)
• I do advocate a carbon tax - or rather, I advocate any system in which a reasonable value is put onto the use of a limited shared resource (like our atmosphere), so that the free market optimization does not lead to the well-understood tragedy of the commons. A carbon tax is one possible implementation. I've never claimed anything else. So far, you have not brought up any source, just a nebulous claim about "most mainstream energy studies" that allegedly "all" claim that renewables can at most provide "a tiny fraction (25% at the VERY MOST)" of "our" energy demand. Well, apart from the fact that the combination of "most" and "all" is a nice bit of rhetoric, the claimed fact is, from a scientific perspective, plain wrong. Iceland has one of the highest primary energy consumptions per capita - even higher than the US - and they manage to provide the vast majority of their energy from renewables. Nearly 100% of electricity and heating are hydro and geo already, and they are actively attracing energy-intensive industries to use their surplus capacity. They are aso moving into hydrogen for transportation.[4][5]. Denmark, a high-consumption northern European country is already providing 20% of its electricity via wind power right now. Gandalf already pointed out your obvious error about solar panel areas. Your claims of "proof" of anything only hold if you think that "proof" and "bland assertion" are the same. And your "America first" kind of patriotism is short-sighted and naive to the extreme. The current "American way of life" is not sustainable in the long term - and neither is the European way of life. If you deny this, you ignore basic scientific facts because they are politically inconvenient. The alternative is not going back to a pre-industrial level, but to move on to more resource-efficient ways living. The earlier we start, the softer the transition and the less disruption to our life styles. --Stephan Schulz (talk) 11:14, 25 August 2009 (UTC)

Technically, geothermal is not a renewable energy source. Those Icelanders are gonna be so screwed in another billion years or so. :) Franamax (talk) 17:28, 25 August 2009 (UTC)

Technically technically, solar is not renewable, either. We're all gonna be so screwed in another 4 billion years or so. ;-) --Stephan Schulz (talk) 17:38, 25 August 2009 (UTC)

Well I dunno about that. It was God wut made the Sun, it was scientists wut made those supposed radioactive elements generating the heat and them as wut invented the gravity story explaining primordial heat. Who would you rather trust? Luckily, so long as there is politics we will still have hot air moving around, so I guess windpower wins in the end! :) Franamax (talk) 20:21, 25 August 2009 (UTC)

I'm always surprised at how vehemently a carbon tax gets opposed. Certainly it will shift economic activity, but in the way people do best, by giving them an incentive to avoid paying taxes. It gives certainty for business planning, it encourages conservation first, and the tax revenues can be used to reduce other forms of taxation and to give every person a rebate representing a "right" to emit a certain base amount of carbon. There's nothing like a tax to get people's minds focussed on how to avoid having to pay it. Franamax (talk) 17:36, 25 August 2009 (UTC)

98.234.126.251, I take you are a supporter of nuclear power. The problem with nuclear power is that it is also non-renewable, so it might buy us a couple of decades but that's it. Eventually we will have to rely on renewable resources, not because it's politically correct, but simply because we will have no other choice. It seems reasonable to me that it is better to be prepared for the inevitable than wait for the shortages to become severe before taking action. Governments do know that and one of the things they will do to force society to take the necessary steps to be prepared will be instating a carbon tax. Deal with it. Dauto (talk) 19:13, 25 August 2009 (UTC)

Actually, if we could successfully complete the nuclear fuel-cycle, it would indeed solve a lot of problems. I have no source, but I think it's something like 3% of the available energy that gets extracted from fissile uranium before the fuel is poisoned. After that, it's just junk. Nuclear as it stands right now conveniently ignores an externality, disposing of the spent fuel and decomissioning reactors (plus the accident insurance issue, which we haven't had to face for 20 years, TG). Dramatically expanding nuclear power output will only expand the conundrum of safe disposal, and with all due respect to SB, deciding today on a "safe storage" method to help us bridge the gap is a disservice to our descendants one thousand years from now - are we really that smart?

I do agree that we somehow need to bridge the gap, but first of all we need to concentrate on reduction of energy use. Just because I have a windmill out back, that doesn't mean I should leave the air-conditioner running all day when I'm not even in the house. There is vast opportunity in replacing inefficient electric motors in factories which are held back by depreciation schedules and discounted-cost calculations monitored by the accounting department. Industrial plants and power-stations release their excess heat and CO2 without even trying to make use of it. What is required is a fundamental shift in attitude so that energy release is seen as an important thing, which should be minimized. I've been in an apartment building in Paris where the lights only come on when you open your door or get off the elevator, and stay on long enough for you to get to your unit and open the door. That's good, why do you care if the lights are on once you're inside the door?

What I'm getting at here is that there is no one simple answer. It's not solar or any other renewable, it's not nuclear, it's not "clean coal". It's a mix of all of them and the best way to get there is to use the power of human ingenuity. And the best way to harness that power is by creating incentives. Since energy is a fungible commodity, a simple carbon tax (which I support) may not be enough. Ref to SS's (questionable) comment above about nuclear reprocessing being infeasible since "we" can't "trust" other countries. Whilst true, it's not a reason to not explore the possibilities. Nor are the potential of nuclear power or renewable sources sufficient to give the answer. We need a mix, and we need incentives - hence my support for not only a carbon tax to recognize the externality of AGW, but an energy tax in general to recognize depletion of planetary resources. We need to recognize both the cost of producing energy and of consuming energy, and yes that will require a fundamental attitude shift which may indeed threaten the "American way of life", which seems to involve keeping restaurants so cold that you shiver while you eat. (I'm Canadian, it happens here too). End of rant. Franamax (talk) 21:19, 25 August 2009 (UTC)

""... to produce ALL our electricity from solar power would require more solar panel area than we got land" is a specific factual error. Even if an average solar power plant is only 10% as efficient as Nellis, total area required to equal current US electricity production is still only 1 million km2." -- "Only" 1 million km2?! That's the entire area of the Great Plains, as you yourself have admitted! Are you seriously proposing that we cover the entire area of our most productive farmland with solar panels?! Besides, this still conveniently ignores the much higher production cost of solar power vs. nuclear power (and I'm talking like 20-25 cents per kilowatt of solar vs. 5-6 cents per kilowatt of nuclear -- see the difference?)

"Iceland has one of the highest primary energy consumptions per capita - even higher than the US - and they manage to provide the vast majority of their energy from renewables." -- This completely ignores the fact that Iceland got a much lower population than the US, so the total energy consumption is a lot lower. Same for Denmark. Your misrepresentation of statistics won't do you much good -- I've got a lot of experience in detecting and exposing such manipulation.

"The current "American way of life" is not sustainable in the long term - and neither is the European way of life." -- You got any figures to back it up, or is this another of your unproved (and questionable) assertions? Surely we can meet our electricity demand for the next several centuries with nuclear power -- is that not "long-term" enough for you?

"I'm always surprised at how vehemently a carbon tax gets opposed. Certainly it will shift economic activity, but in the way people do best, by giving them an incentive to avoid paying taxes." -- Schulz, didn't I already prove to you that some industries (such as the airlines, for example, or the steel industry) CANNOT "avoid" a carbon tax because their business activity intrinsically results in CO2 emissions? That will mean that they get taxed disproportionately, to the detriment of the economy in general. (If the Waxman-Markey bill passes, then in a couple years you'll see what I'm talking about.)

"The problem with nuclear power is that it is also non-renewable, so it might buy us a couple of decades but that's it. Eventually we will have to rely on renewable resources, not because it's politically correct, but simply because we will have no other choice." -- Wrong again, uranium reserves will last for at least several hundred years even if the developed nations rely exclusively on nuclear power for electricity. And besides, with breeder reactors we can generate more nuclear fuel than we use -- so in that case, we can rely on nuclear power for thousands of years without the fear of running out. Your statement that it will "buy us a couple of decades but that's it" is DEAD WRONG and amounts to nothing but SHAMELESS DEMAGOGUERY. And relying on renewables will greatly increase the cost of electricity, to the detriment of everyone who uses it (including all our industries, and especially the high-tech industries). Do you really want that kind of future for America, when nuclear power can easily provide enough power for every American without contributing to CO2 emissions? Or do you have a vested interest in promoting renewables to the exclusion of nuclear power, Dauto? 98.234.126.251 (talk) 00:45, 26 August 2009 (UTC)

Umm, 98.234, has anyone warned you yet about soapboxing? When you type in capital letters "DEAD WRONG" and "SHAMELESS DEMAGOGUERY", that's a pretty good indication that you're standing on a box in Hyde Park. We don't do that here, and if you persist, it's a blockable offense.

As regards factual errors, please reserve your vitriol on the "surprised at how vehemently a carbon tax gets opposed" comment for just me. What on earth did Stephan Schulz have to do with my edit? Please read the thread more carefully before you comment.

On the economic issues around a carbon tax, well yes of course the costs would fall more disproportionately on large consumers of energy, that's the whole point. D'uhh. But think through your basic economics (which you accuse SS of ignoring). When a good or service increases in cost, the demand for that good or service decreases and generally the profitability of the business will decline - so yes, coal plants and truck fleets will have more expensive and thus less desirable output. Conversely, when a good or service attains a price advantage, demand for it will increase and profit opportunity will also increase - so energy retrofitters who know how to insulate your building and recycle your waste heat will do more business; rail will proportionately do better than long-distance trucking; truck fleets will focus more on emission-efficiency by using smaller vans and shorter-range deliveries; ships and airplanes will be at more of a disadvantage in a carbon-taxed regime, ships because they currently benefit from a no-fuel-tax regime and they're allowed to burn bunker oil, the worst of the dirtiest most-awful fuel on the planet, airlines because they also get off with zero-tax between countries and because they're a vastly inefficient form of transport. Even there, the incentives form to put those big sails onto cargo ships and explore more efficient forms of air transport. And yes, there are prototypes of electric-powered ships and aircraft, tell ya what: you deliver one source to support your more wild claims, I'll put forth one of my own...

Yes, of course, any notion of accounting for external costs has grave implications for the existing way of doing things. The key is to do it in a measured and predictable way. A carbon tax (and more generally, an energy intensity tax) will certainly be disruptive to the "American way". But I find it quite frankly laughable that you would see that as a threat. The US started off with an economic model based on colonialist trade patterns and rebounded quite smartly when independence went and ruined it. Losing a war with Canada didn't set you back (OK, maybe not the best example). Fighting a civil war over the issue of OMG-we-need-slaves-or-the-economy-won't-work was pretty messy, but didn't sink the country. Electrification came and was embraced, telegraph/Telex/telephone/Fax/email all went pretty well. Shouting/heliography/radio/television/satellties seemed to work OK. Every one of these required wrenching transformations in economic terms amd more importantly, changes in attitude. Why you would react in almost hysterical terms to this particular change is beyond me. Are you saying that the American people have lost their ability to adapt and grow? Franamax (talk) 03:05, 26 August 2009 (UTC)

"Umm, 98.234, has anyone warned you yet about soapboxing?" -- Tell the same to SteveBaker and Stephan Schulz, they're pushing politics as much as I am. Or is it only soapboxing when you advocate right-wing politics? BTW, as despicable as I find some of your posts, I haven't yet threatened to get you people blocked, or otherwise to take away your freedom of expression (unlike you). Or do you think that only liberal points of view are protected by the First Amendment, and that it's OK to "dispute" other points of view by threatening to silence the speaker? Man, what a double standard!

"airlines because they also get off with zero-tax between countries and because they're a vastly inefficient form of transport." -- They're also the fastest form of transportation for trips of more than 500 miles, so "inefficiency" is irrelevant here. Really, would you rather spend several hours flying coast-to-coast in a jet plane, or spend 3 DAYS or more traveling by train? In other words, we here in America need air transportation because of the vast distances involved. Maybe over in Europe you people can do without air transportation, but that's up to you -- as for us, we'll keep our jetliners come hell or high water, because we truly cannot afford to go back to just rail transportation even if we wanted to.

"And yes, there are prototypes of electric-powered ships and aircraft" -- OK, show me a picture of an electric-powered jumbo jet prototype, and then maybe I'll believe you.

"you deliver one source to support your more wild claims, I'll put forth one of my own..." -- Actually, I have provided sources for some of my claims, in case you haven't noticed. Tell me exactly which claims you want sources for, and I'll give you the sources, or take my claims back if I can't.

"Electrification came and was embraced, telegraph/Telex/telephone/Fax/email all went pretty well. " -- There's an important difference here, in case you didn't notice: electrification was a new technology that gave American companies a competitive advantage, whereas a carbon tax is an economic burden that will place American companies at a competitive disadvantage. You see the difference here? 98.234.126.251 (talk) 03:41, 26 August 2009 (UTC)

On the first point, soapboxing, since you seem to have a stable IP address I was planning a mea culpa on your talk page since I could accuse myself of the same thing - plus an invitation that if you would register an account, we could more easily talk to you. Too late now. Yes, we are all guilty of expounding our viewpoints to some degree, but I think yours is egregegious. When you need to GET YOUR POINT ACROSS IN CAPITALS, you're no longer making an effective point, that's all. I personally try to stick to points which I can find a ref for quickly, or make clear that I am speculating. SB can stand on as big a soapbox as he wants, since it pretty much always conceals an armaments factory which spews forth weapons of undeniable truth. But hey, mount the ponies and ride up the hill if you feel the need. Remember to wave your flag. SS, I do agree that the first comment was unfortunate, i.e. there's no reason at all that we in Canada shouldn't pursue our own nuclear-fuel reprocessing strategy - but that doesn't make him an overall politico-buffoon. Possibly you've only just arrived here. We try to talk reasonably and back our statements with citable and reliable sources. We're not a general forum for venting opiion. (And BTW, there's no First Amendment rights here on private property - but if you see your actual government doing you wrong, let me know and I'll help you however I can. If you think Wikipedia has screwed you over, tough luck, you bought the wrong can of sardines)

I'm confused about the "over in Europe you people can do without" remark. Would it help if I spelt it CANADIAN? That's where I live, it's the big blank space up top of the weather report. We're facing our own challenges too. Geez, whatever happened to "world's longest undefended border"? It's fun to go from closest friend to potential enemy within 10 years. But that's Fox News for you.

Air transport of course is useful where it's appropriate. There's the rub - airlines get to buy their fuel tax-free, which no other transport mode does. So it's not a level playing field. Adjust the pricing to reflect the external costs of CO2 and I'm right with you. But you will find that a lot of air travel can be replaced by trains. A TGV-style corridor between Houston, Austin, DFW and San Antonio would wipe SW Airlines right off the map (keeping in mind that the SWA chairman was quoted as "we don't compete with airlines, we compete with buses").

Keep the order straight, I asked you for a new source. Produce one and I'll do the same.

On the last point, I think you need to go back and review how competitive advantage works. The same dynamic comes into play regardless of the source of the external costs - the organization or individual works to minimize the costs. If a business is faced with an increase in raw material prices, or energy taxes, they don't just throw up their hands if it's taxation, they go about maximizing profit under the circumstances. That's the genius of the open marketplace, it always maximizes overall value when there's open competition. Put simply, any and every change in technology and society is a challenge. The US managed to survive all of them, including the "temporary" income tax introduced during WW1. I really don't understand your fear. Actually, living in Canada, I'm more afraid that you guys will get there first. We were a shameful third at sustainable fission reactions and we can't sell our superior and safe CANDU reactors. And we're way behind on many other next-gen techologies too. Thanks for the reminder to write my government reps about this and talk to you 20 years from now! Franamax (talk) 05:41, 26 August 2009 (UTC)

"On the first point, soapboxing, since you seem to have a stable IP address I was planning a mea culpa on your talk page since I could accuse myself of the same thing" -- OK, no hard feelings, these kinds of politically charged topics do tend to cause heated debate.

"I personally try to stick to points which I can find a ref for quickly, or make clear that I am speculating." -- That's the difference in style between us, I often quote statistics from memory but can't quite remember the name of the source where I got it from (but I usually can find the source if asked). So just because I don't give the name of the source right away, doesn't mean that the info is unsourced or otherwise unreliable, as you're about to find out.

"SB can stand on as big a soapbox as he wants, since it pretty much always conceals an armaments factory which spews forth weapons of undeniable truth." -- Not always: I've proved him wrong once, on the clathrate gun hypothesis, when he was saying "the clathrates are already melting, disaster is just around the corner" and I showed him evidence that most clathrates won't melt for at least a thousand years. And even in the current discussion, I disproved his claim that the Great Plains will end up under the ocean because of global warming -- and all I had to do was to look at a map of elevations. So his "armament factory" is not quite so invincible after all...

"SS, I do agree that the first comment was unfortunate, i.e. there's no reason at all that we in Canada shouldn't pursue our own nuclear-fuel reprocessing strategy - but that doesn't make him an overall politico-buffoon." -- In an earlier debate, he called America a "terrorist nation" for bombing Afghanistan, claimed that our support of the Contras in Nicaragua somehow justified 9/11, and compared the War on Terror to "doing a magic dance to keep the lions away" -- if that's not being a "politico-buffoon", then I don't know what is.

"I'm confused about the "over in Europe you people can do without" remark. Would it help if I spelt it CANADIAN?" -- That remark wasn't directed at you personally, but at the other parties to the debate, most of whom appear to be European. But since you're Canadian, may I ask why are you so much against air transport? From what I know, air transport is even more of a necessity in Canada than it is here in the USA.

"Geez, whatever happened to "world's longest undefended border"? It's fun to go from closest friend to potential enemy within 10 years." -- I never said anything to that effect, and I don't think it's relevant to the debate at all.

"Adjust the pricing to reflect the external costs of CO2 and I'm right with you." -- I guess I should've clarified from the start that it's not so much the idea of a carbon tax per se that I oppose, but a carbon tax AT THE LEVELS THAT SOME OF THE OTHER CONTRIBUTORS HERE ARE PROPOSING (i.e. $150 PER BARREL) -- a carbon tax OF THAT LEVEL would of course be COMPLETELY UNACCEPTABLE. A tax of, say, $10 (or even $20) per barrel, might be OK, though.

"But you will find that a lot of air travel can be replaced by trains." -- Original research: I've plotted the travel time vs. distance for each mode of transportation using Graphical Analysis (using the scheduled average speeds for each mode, and making some assumptions about waiting time at the station / airport), and the results that came out were that train travel can be faster than plane travel for trips of up to 500 miles, but plane travel is definitely faster for longer trips. Yeah, fast trains do have a place in the transportation system; however, many of the transportation routes in the US (and Canada, too) are much longer than 500 miles, so air travel will always remain a necessity for those routes.

"A TGV-style corridor between Houston, Austin, DFW and San Antonio would wipe SW Airlines right off the map" -- SWA serves many other routes besides the ones you mentioned, many of them longer than 500 miles.

"Keep the order straight, I asked you for a new source. Produce one and I'll do the same." -- You didn't tell me which of my claims you want sourced. But here we go: my claim that nuclear power can provide all our electricity for "thousands of years" is based on figures from Megawatts + Megatons: The Future of Nuclear Power and Nuclear Weapons by Garwin and Charpak, which states that with the use of breeder reactors and nuclear reprocessing, 320,000 QUADS of electricity can be generated from nuclear power in total, whereas the annual consumption of electricity by the whole wide world (I'm not talking about just the US now) was about 106 quads a year in '96. Do the math, and you'll come out with an answer of about 3,000 years. Your ball now, Franamax.

"On the last point, I think you need to go back and review how competitive advantage works." -- You should keep in mind that an increase in external costs for American businesses (but not Chinese ones, for instance) will make American goods more expensive, and thus less able to compete on the international market, compared to Chinese goods. That's the rub here -- the nation that "blinks first" and implements a carbon tax without waiting for the others to do the same, gives up at least some of its competitive advantage.

"I really don't understand your fear." -- As I should've made clear before, it's not a carbon tax per se that I fear, but a $150/BARREL carbon tax that SteveBaker proposes and Stephan Schulz tirelessly advocates. If you crunch the numbers and see how much economic damage such a confiscatory tax on anything would do, I can bet you'll be pretty scared too. 98.234.126.251 (talk) 09:15, 26 August 2009 (UTC)

AEB2

Your memory is severely faulty. I have not advocated any particular level of tax. I have said that the (nearly) US$150,- per barrel price we had back in 2008 very quickly lead to interest in energy efficiency and alternative sources. I think a tax that pegs the price at or near that level would possibly be a good thing, as it increases stability of the price and reduces the influence of speculative fluctuations. But even that is not a tax of US$150,- per barrel. I don't think I have ever called "America" or even the US "a terrorist nation". I've certainly never "claimed that our support of the Contras in Nicaragua somehow justified 9/11" and I strongly request that you either back that with a source or retract it. You seem to have a very black and white, us vs. them view of the world. That is not a useful model, and it helps neither in understanding nor in solving problems. --Stephan Schulz (talk) 10:16, 26 August 2009 (UTC)

OK, Schulz, I found the thread you asked for when you requested that I either "back it up with a source" as to the claims you made about the support of Contras justifying 9/11 and all, or take it back; it was actually from about a month ago. Read it and weep, everyone:

And if they be "harmless farmers", then WHAT THE HELL ARE THEY DOING SHELTERING TWO TERRORISTS IN THEIR VILLAGE?! WHY DON'T THEY KICK THOSE TWO CHARACTERS OUT?! Remember, IF YOU KNOWINGLY SHELTER A TERRORIST IN YOUR HOME (VILLAGE, WHATEVER), THEN YOU'RE JUST AS GUILTY AS THE TERRORIST AND YOU BECOME A LEGITIMATE TARGET YOURSELF! Besides, as I already said, WINNING THE WAR ON TERROR IS NOT ABOUT GETTING THEM TO LIKE US (WHICH THEY NEVER WILL), BUT ABOUT MAKING THEM FEAR US. 98.234.126.251 (talk) 07:44, 24 July 2009 (UTC)

Well, first off, the "terrorists" may not be terrorists, or the villagers may not know that they are terrorists, or they may be forced to shelter them, or they may not consider them terrorists. Given that the US is sheltering any number of people others can rightfully call "terrorists", does that excuse 9/11? If not, why not? And why does the same argument not apply to some village in Afghanistan? --Stephan Schulz (talk) 14:17, 24 July 2009 (UTC) (Emphasis mine)

And then again near the end of the thread:

...Why do you think we haven't been attacked here in America for these past almost 8 years? Well I'll tell you why: because the terrorists are too busy trying to save their filthy asses over in Afghanistan to have time to prepare the next attack here in America. For the record, the War on Terror has already killed most all of Al-Qaida's top generals, so for the time being all they can do is make uncoordinated localized attacks on our soldiers and kill a few at a time at the most -- and as long as we continue pounding them over there, they won't have the time or the resources to come over here and kill hundreds of our people. It's a basic principle of strategy: keep attacking the enemy whenever you can, and the enemy won't have time or resources to regroup launch a major attack. If you don't know that, I recommend you read up on Clausewitz before you go discussing strategy with anyone anywhere. 98.234.126.251 (talk) 00:19, 26 July 2009 (UTC)

Re. 98: Right. I do a little magic dance around the campfire every night. I've not been eaten by lions since I started doing that, so magic works. Why again, has the US not been subject to serious Islamic terror for the 200 years before 9/11?.. --Stephan Schulz (talk) 07:52, 26 July 2009 (UTC) (Emphasis mine, once again.)

So, at the very least, I've just quoted you saying that our support for "people whom others can rightfully call 'terrorists'" justifies 9/11 and that our bombing of Afghanistan is on the same level as the terrorists' attack on the WTC, and that the War on Terror is like "doing a magic dance around the campfire each night to keep the lions away". (BTW, in the first quote, the word "terrorists" in the phrase "others can rightfully call terrorists" links to the article on the Contras -- so I've just proved that you consider the US support for the contras as a justification for 9/11). Schulz, do you see how you've made an ass of yourself? 98.234.126.251 (talk) 04:35, 28 August 2009 (UTC)

Ummm...apparently its not your memory, its your reading ability. What you quote there is a classical Reductio ad absurdum. Your claim that some so-called terrorist hiding among villagers justifies indiscriminate bombing of that village is as absurd as the claim that the sheltering of terrorists by the US justifies 9/11. The basic principle of such an argument is the reduction to the (obviously) absurd, in this case the claim that sheltering contras justifies 9/11. Note that this is the exact opposite of what you claim - I'm not justifying 9/11, I'm using the example to demonstrate that indiscriminate bombing with disproportionate levels of so-called "collateral damage" is just as unacceptable. I strongly suspect you differ, but for me the life of an Afghan peasant has the same value - no more and no less - as that of a New York banker - and yes, even if that peasant (or that banker) burns 3 US flags per day. --Stephan Schulz (talk) 09:11, 28 August 2009 (UTC)

98.234.126.251, You are right that breeders and reprocessing could potentially increase the amount of nuclear energy avaible by a factor may be as high as a hundred fold turning the couple of decades I talked about into a millenium or so. But not without a price increase in the energy production, and since you were shooting down solar power for being expensive I thought that was also excluded. I would like to point out that different people can have different opinitions and still be polite. There was no reason for you to shout at me and call me demagogue. I find your style very abnoxious and I won't waste anymore spit with you. Dauto (talk) 15:48, 26 August 2009 (UTC)

OK, so no-one is actually proposing a $150/barrel tax (here in BC, the carbon tax will end up around $11/barrel, give or take depending on whether 7.2 cents/litre on gasoline is representative of the total mix of carbons in a barrel of oil). But just for fun, lets crunch those numbers. A barrel of oil is 440kg CO2, so the tax will be $340/tonne. $150/b x 20 million bpd means tax revenue from oil aoine will be $1 trillion/yr. Now if all carbon-equivalent emissions were taxed at the same rate, which from out article is ~7.1 Gtonne/yr, that's $2.4 trillion. So basically, the entire US federal government is paid for. That means no federal income tax on either people or business, no capital gains tax, no nothing. Now think about how comparative advantage (sorry, this is what I meant in the first place, I screwed up when I called it "competitive" advnatage) works: even if every single thing the US produces is more expensive than what the rest of the world produces, there will still be something that the US can specialize in and make money on. But it won't go that far. The US will instantly become the preferred location for every single business in the world that has relatively low carbon-intensity. Every single bank, insurer, software firm, law firm, engineering company, architecture firm, educational institute - every single one of them from around the globe will set up a US business. Nuclear reactors would pop up on every street corner, renewable power would sweep the country (though the energy-intensive components would be made offshore). Obviously the economic changes would be incredibly wrenching, which is why no-one would seriously propose such a level of taxation. But in our just-for-fun scenario, the US would gain an incredible comparative advantage in a huge range of economic activity, so much in fact that every country in the world would have no choice but to also "blink" and follow suit. In practice, that vast revenue stream would be shared out among state and local governments too, so there would be some tiny level of ongoing federal tax, and there would likely be offsetting import duties and export rebates (which would then be equally exploited for their economic value). Now imagine that release of pollutants that more directly harm human health were taxed in the same way (and here import duties would be essential). You would basically have a situation where the only time you were taxed was when you were doing harm to others. If you live clean and green, you pay nothing!!! Nada. Zero. Obviously that's a Utopian scenario, not everyone can be an outdoors hairdresser with a garden, but the point is that any particular level of taxation doesn't erase competitive advantage, it just shifts it around in the economy. That's the beauty of taxing undesirable activity. But no-one here is advocating such a radical shift. Franamax (talk) 01:42, 27 August 2009 (UTC)

98.234 posting from a public library: Schulz, you should recall the previous discussion about reprocessing from a couple of weeks ago (sorry, I don't remember the exact date or the section title, but I can look it up later today), where I advocated an embargo on nuclear technology to terrorist nations to prevent nuclear proliferation; during that discussion, I said some pretty nasty (but well-deserved to say the least) things about Islam, and you got into the act along with several other users, and it essentially turned into a big shouting match. It was during that discussion that you made all three of the comments that I allege you made, and I can quote them when I look up that thread, just wait a few hours.

Dauto, I already quoted figures from an MIT study that said that the cost of nuclear energy can be lowered to 4.2 cents per kilowatt (same as coal power) with state-of-the-art technology (including breeders, which would also extend the supply of nuclear energy for 3000 years). OK, maybe I should've been a bit more civil as far as your statements are concerned, but your assertion that "nuclear power will only last for a couple decades" is obviously BS, and when I see obvious BS quoted as if it were scientific fact, I tend to lose my patience (as many of the rest of you do).

And Franamax, a nation like the USA cannot live on financial and educational firms alone, without domestic industry to provide consumer goods for the people. We simply cannot afford to depend completely on foreign nations to produce our cars, fridges, furniture, electronics, etc., etc., etc... for our people, because of obvious geopolitical implications -- i.e., other nations would then be able to easily blackmail us into submission simply by embargoing trade with us. Your basic fallacy is to presume that "we're all brothers" and can live in peace forever. Franamax, most other nations hate and envy us for being so successful, (well, maybe Canada and a few others are exceptions), they all got a big chip on their shoulder, and they wouldn't hesitate to hurt us if they could, even if that means setting aside their own self-interest. And nuclear reactors will only pop up on every corner if we retain the industrial capability to manufacture them, or else the foreign nations will rip us off money-wise on reactor components and make it much more expensive to build them, thus keeping us from fulfilling our energy needs. (As for renewable power, I already demonstrated that it won't "sweep the country" because of production costs alone, 20-25 cents for solar vs. 5-7 cents for nuclear, keep it in mind.) And finally, it's impossible to live a modern lifestyle and be perfectly "clean and green" -- for one thing, it will mean no steel (hence no appliances of any kind), no aluminum (hence no cars, no planes), no copper (hence no electrical equipment), no plastics of any kind, no synthetic fibers (which are essential for many applications). Manufacturing these items INTRINSICALLY results in a certain amount of pollution, and implementing a carbon tax won't stop the pollution while still getting us these things we need for a modern lifestyle -- it will just "shift" the pollution (and the manufacturing) offshore (thus draining our economy and making us vulnerable to trade embargoes) while keeping it at the same level, and make these items more expensive and harder to get. 146.74.230.104 (talk) 23:24, 27 August 2009 (UTC)

Umm, "most other nations hate and envy us for being so successful" - I could hazard a guess as to which news channel you watch on cable. That was what I meant when I asked you to provide sources. Care to back that up?

And in case you're really worried about how "foreign nations will rip us off money-wise on reactor components", well hello, Canada speaking, only the US' single-largest trading partner, not that that counts for anything in the "they're all enemies" milieu. But even setting aside our well-developed and intrinsically-safe nuclear technology, I can't even begin to describe what's wrong with your contention that rip-offs happen in an open bidding process. You're actually describing corruption on a truly massive scale. Do you really have that advanced of a battlefield mentality that you think only a "few" other nations are friends of the US? I mean wow, just wow...

And just to clarify, no-one is suggesting that we should no longer use any plastic or steel, just that such use should reflect the true costs to all of society. So yes, in that sense, we are all "brothers", at least until we get us another planet. I do share your concerns about de-industrialization and having a level playing field, but your notion that the status quo muct be defended at all costs (even though that status quo has changed radically in the US over the last 30 years, with much/most new prosperity having been created in places other than assembly lines) - well, it's rather bizarre. Franamax (talk) 00:39, 28 August 2009 (UTC)

Pretty much all the first-tier (in industrialization) countries are allies, with very similar standard of living: the US, Western Europe, Japan, S. Korea, Canada, Australia, New Zealand, a few small others, with most of the population in NATO so on a planetary problem, they should be considered collectively.

Would it be practical to tax carbon based on the actual additional damage caused? The first parasustanible ton of American carbon this year would not do as much harm as the 6,800,000,000th. This would be slightly less unappealing to businesses than a flat tax. It would take only 1% of GDP to do all the things needed to build theinfrastructure and things to prevent global warming from happening – a 5 to 20% cut. Interestingly, if this completely came from carbon taxes, it would not drastically change the price of energy as 98 feared. Sagittarian Milky Way (talk) 01:19, 28 August 2009 (UTC)

Franamax, I didn't say that Canada is an enemy of the US, I said "most nations hate us", not "all nations hate us". You're putting words in my mouth in order to make a straw-man argument. And when you say that I got a "battlefield mentality", I might respond by saying that you got a "one-world mentality", and with just as much reason. But as for other nations -- well, the Islamic nations all hate us just for being infidels, and you can take that to the bank. The folks in Africa and South America envy us because we're so prosperous and they're dirt-poor, so they would just love to see America brought down to their level (or at least humiliated in some way). The Russians have been brainwashed to hate us for almost three generations, so no wonder we're not popular in that part of the world. The Chinese don't hate us especially as far as I'm aware, but they see us as their biggest rival and would love to screw us over given half a chance. And Western Europe our "allies", you say? All I can say is, they all got a chip on their shoulder bigger than their feet because they used to be the most powerful in the world and now we've taken their place. No, they're not actually gonna do anything to hurt us directly because their own self-interest is at stake, but well I've been following public opinion polls in Europe, and I can see that the Europeans don't like us at all. Just tune in to BBC, for instance, and you can see how much schadenfreude they spew forth whenever the USA gets into a little bit of difficulty. No, to regard Western Europe as loyal, steadfast allies would be supremely naive -- they're only our allies because they depend on us for trade and for defense. Which brings me to my second point: When you deny that rip-offs happen in an open bidding process, you neglect that it's only a truly "open bidding process" if American manufacturers (of nuclear reactors, in this case) are equally represented at the bidding table with all the rest of'em. Whereas, if the US throws away its manufacturing capacity by taxing it to extinction, then it's no longer an open bidding process, but a process where only foreign firms are represented -- and they can then screw us over as much as they like, and we can't do a thing about it. And while it may be true that "most prosperity has been created in places other than assembly lines" (well, I'm not too sure about "most"), that does not contradict the fact that we need to retain our domestic industrial capacity, for geopolitical reasons if nothing else. Implementing a carbon tax (well, above a certain level anyway) could jeopardize that -- it would be an incentive for our industrial firms to outsource more, to the detriment of our economy. (A supreme irony of this is that a high carbon tax might even keep American factories out of the bidding for making nuclear reactors -- the very nuclear reactors that we'll need in order to reduce CO2 emissions in the first place.) 98.234.126.251 (talk) 05:36, 28 August 2009 (UTC)

Is there any evolutionary reason for natural disaster movies being so cool to watch?

Seems strange when the hominids that enjoyed the spectacle instead of going into survival mode would've been the ones most likely to die. Maybe the savanna is a relatively docile place (except the dangerous animals, which yes, might be horror/hunting/Gladiator/even running back in American football, but not natural disasters), and humans have not had enough time in more dangerous areas to adapt? The Rift Valley had earthquakes, but in the absence of overhead death traps even a 9 earthquake can be neutralized by lying prone on asphalt (see Banda Aceh). Sagittarian Milky Way (talk) 22:15, 21 August 2009 (UTC)

Disaster movies can combine aspects of both the horror genre and that of camp movies, and their effectiveness has been been studied in literary and film criticism. See for example:

• Disaster movies: the cinema of catastrophe By Stephen Keane
• The pleasures of horror by Matt Hills
• Dying for a Laugh: Disaster Movies and the Camp Imagination by Ken Feil
• The Imagination of disaster and Notes on "Camp" by Susan Sontag

None of these address the evolutionary aspect directly, but hopefully will still be of interest. Abecedare (talk) 23:19, 21 August 2009 (UTC)

Just an idea, backed up by absolutely no scientific anything: perhaps people have an instinct to pay attention to peoples' stories of natural disasters so as to learn how to avoid/survive them if they ever get into that situation. Of course, the best way to survive a natural disaster usually has the first step of "Throw the movie away and forget about it". --Falconus^{p t c} 00:02, 22 August 2009 (UTC)

There may of course be no evolutionary association. It is a mistake to believe that all behaviour or physical characteristics are related to success or failure of past or future evolution. 86.4.181.14 (talk) 07:13, 22 August 2009 (UTC)

Any "exciting" activity will lead to release of endorphins and related compounds, and creates a pleasurable sensation. Some of these exciting activities (such as running from a sabre tooth tiger) are accompanied by fear. However fear is generally an unpleasant sensation. It is a survival trait to lead individuals to remove themselves from potentially harmful situations. In our modern culture, we have increased the number of activities that lead to endorphin release without the accompanying fear, such as sports, action movies, computer games, dancing, etc.. Some people choose activities with a higher level of risk such as freefalling or bungie jumping, thus possibly generating higher levels of endorphins ("adrenaline junkies"). Axl ¤ [Talk] 10:46, 22 August 2009 (UTC)

I guess I have a less cynical attitude about this than most people. I agree with Falconus: we are programmed to find depictions of terrible things interesting because if something terrible happens to us (which is far from impossible), we will have at least a little bit of knowledge to guide our reactions. It seems odd to me that people think we ought to be interested in abstract artistic stuff with no practical relevance, and that it is somehow shameful to be interested in depictions of situations that we might actually find ourselves in, i.e. soap operas, reality shows, shows like Cops, etc. Looie496 (talk) 19:20, 22 August 2009 (UTC)

And seeing a mile-wide tornado approaching an underpass, shooting a human out of it like a cannon and he goes flying up in the air and dodges a cow and smashes a flowerpot and something metal flies by going arrAAnk and then he drops out of the airstream and runs one thousand five hundred feet in the air and starts falling and the camera follows him all the way down like the Pearl Harbor bomb and the last frame shows dandelion fluff and goes THOOSH! as the screen goes black is supposed to help you survive how? :) Sagittarian Milky Way (talk) 20:11, 22 August 2009 (UTC)

I agree with the previous posters who said that watching people who are in actual life-threatening situations was useful, in the past, as it helped us learn how to survive in similar situations. Unfortunately, the farther you get from the actual event, such as a retelling, then a fictionalized account, then outright fiction, the less useful it is. We seem to lack the ability to discern useful, true accounts of life-threatening situations from the fake crap we see in the movies. Thus we remain convinced that if any bad guys ever chase us in a car they will suddenly flip over as if they went up a ramp, then their car will explode mid-air, as if it had been filled with dynamite. StuRat (talk) 22:21, 22 August 2009 (UTC)

It's easier to manipulate feelings when more is at stake. So a mediocre disaster movie may be more watchable than a mediocre non-disaster film. 67.243.4.208 (talk) 21:51, 23 August 2009 (UTC)

Energy drink studies vs. just sugar and caffeine?

Have any double-blind studies on the effects of energy drinks given sugar and caffeine to the control group, to test the value of the other active ingredients? NeonMerlin 23:03, 21 August 2009 (UTC)

No. Nor have any beer companies sponsored controlled studies to see whether giving the equivalent amount of ethanol to a couple of beers results in having a better party. alteripse (talk) 02:00, 22 August 2009 (UTC)

I think he means, have they tried testing taurine, ginseng, etc. No need to be snide because of an honest question. --HitmanNumber86 (talk) 04:12, 22 August 2009 (UTC)

I think a certain amount of snideness is justified. Energy drink makers have no motivation to do those tests because they have a damn good idea what the outcome would be. Looie496 (talk) 19:09, 22 August 2009 (UTC)

"Energy drinks" are all pretty much scams to get you to pay good money to drink unhealthy products, by making you think they are somehow good for you. As such, the makers don't want to pay for any scientific tests of any of the claims they make, as that may result in them being proven to be false. And, since nobody else is willing to put up money to test their highly dubious claims, they don't get tested. StuRat (talk) 22:09, 22 August 2009 (UTC)

You're darn right, StuRat. You want energy, drink coffee or black tea -- you'll get every bit as much "bang" but it'll cost you a lot fewer bucks. 98.234.126.251 (talk) 22:24, 22 August 2009 (UTC)

Really? In here price per mg of caffeine seems to be similar between coffee and energy drinks (unless you brew it yourself café tea is just way too expensive for its caffeine content). --antilived^{T | C | G} 04:47, 23 August 2009 (UTC)

Yeah, I brew my own tea and coffee -- it ain't that hard at all (especially if you got a coffee machine in your kitchen). Also I live in America, so the prices are different from those in New Zealand. (P.S.: It would really be appreciated if, when you're talking about prices in New Zealand, you actually say "in New Zealand" instead of "in here" -- other people will know what you're talking about without having to click on the link to find out.) 98.234.126.251 (talk) 00:13, 24 August 2009 (UTC)

Some of it is probably the placebo effect. John Riemann Soong (talk) 05:12, 23 August 2009 (UTC)

What I mean is whether ginseng, guarana, taurine and etc. have been tested against a backdrop of caffeine and sugar, which might for all we know change their effects due to interactions. NeonMerlin 06:59, 23 August 2009 (UTC)

OK, now this is a different problem. Those are "natural products", meaning they can't be patented. Therefore, there's no profit motive to justify a company spending the levels of money necessary to prove or disprove their effectiveness, alone or in combination. I've often thought that we should have government grants to universities to study such natural products. I would guess that most are useless, but that there's an occasional gem in there that actually does at least some of what is claimed. It sure would be nice if we could find those items. StuRat (talk) 14:04, 23 August 2009 (UTC)

Sure, it would be nice to see universities doing some research that had immediate relevance to the students. NeonMerlin 16:29, 23 August 2009 (UTC)

Drunk-happy or drunk-angry?

Some people become aggressive when drunk, others euphoric. What determines which occurs? Personality traits, for example? Long-term alcohol misuse? Side note: The euphoria is 'paid for' by some depression when the alcohol wears off, pushing people to drink again. 78.146.187.7 (talk) 23:13, 21 August 2009 (UTC)

Excuse my French, but when it comes to alcohol, drunkenness, and personal behavior, I think the appropriate answer is simply Shit Happens. Chalk it up to different personalities, but essentially it's going to depend on their mood before, while, and after drinking, what is going on in their personal life, what the circumstances of the drinking are (drinking alone may be inherently depressive, while drinking at a frat party inherently "euphoric"), and all sorts of other things. Some people get angry, some get tired, some get hungry, and some vary. ~ Amory (user • talk • contribs) 23:55, 21 August 2009 (UTC)

Essentially alcohol disinhibits the individual. We therefore see an exaggeration of whatever emotions the drunkard is feeling. The circumstances of the drinking will affect the emotions as much as the feelings of the sot. I cannot subscribe to the idea that euphoria has to be 'paid for' by later depression. Generally the depression is felt as a result of the physical after effects of the alcohol - the hangover, but not all topers suffer this. 86.4.181.14 (talk) 07:08, 22 August 2009 (UTC)

I don't know if this is OR or what, but historically in the Black Country (where I grew up), there were pubs that brewed their own beer. Some of the beers became known as "singing beer" while other beers became known as "fighting beer" for their effects on the consumers. Now whether this was due to the ingredients, change in water, or the physiology of the consumers, I really don't know and I suspect we can never find out now. The only referenced source I can come up with for this is by someone called Trevor Raybould, who used to lecture at Wolverhampton Polytechnic and who published articles in the Black Countryman, date probably 1980s.--TammyMoet (talk) 09:36, 22 August 2009 (UTC)

Nit pick: drunkard: (somewhat derogatory) A person who is habitually drunk. A kinder (more accurate) term would be drunk person, IMO. Aaadddaaammm (talk) 17:23, 22 August 2009 (UTC)

That sounds silly, but somebody should have branded the beers thusly. "Give me a fighting beer!" Tempshill (talk) 04:06, 23 August 2009 (UTC)

Kate Fox says in Watching the English: The Hidden Rules of English Behaviour":

"the effects of alcohol on behaviour are determined by social and cultural rules and norms, not by chemical actions of alcohol... In some societies ... drinking is associated with aggression, violence and anti-social behaviour, while in others ... drinking behavour is largely peaceful and harmonious. ... This basic fact has been proved time and again, not just in qualitative cross-cultural research but in carefully controlled proper scientific experiments - double-blind, placebos and all. To put it simply, the experiments show that when people think they are drinking alcohol, they behave according to their cultural beliefs about the behavioural effects of alcohol." (emphasis added)

. Unfortunately, the book contains no references, and my desultory attempts to find sources have been unsuccessful. I would be delighted if anybody can point me at these studies. --ColinFine (talk) 17:54, 23 August 2009 (UTC)

It's unsurprising. Alcohol is a psychoactive drug; and the effects of a psychoactive drug are determined in part by set and setting: the mindset with which you approach the drug experience; and the social and sensory context in which you partake of it. The fact that most drinkers do not themselves regard an evening at the pub as a "drug experience" is simply naïveté. --FOo (talk) 08:06, 25 August 2009 (UTC)

Tammy, my first thought on that would be that the happy and mad beers are more likely reflective of the owners of the pubs. I've done some OR of my own and I could point you to two bars right now, one where almost everyone is happy, another where it would be very easy to get into a fight. The difference is that the management of one "encourages" trouble-makers to go elsewhere, and the other doesn't care as long as they pay. Over time, the fighters end up where they can get into fights. Franamax (talk) 17:44, 25 August 2009 (UTC)

August 22

Tropical Cyclone Crossing the Equator

Track map of all known tropical cyclones to crossover Central America. –Juliancolton | ^Talk 02:01, 22 August 2009 (UTC)

I understand that winds almost never blow across the equator, and to my knowledge no hurricane has ever crossed the equator, but pretending that a hurricane did end up travelling across the equator, what would happen? Would it destroy itself in an attempt to spin the other way, or would it keep spinning the same way?

Also, on a semi-related note, why do hurricanes not cross Central America and keep going? Also, to my knowledge that has never happened, and I can't think of a good reason why.

Thanks,

Falconus^{p t c} 00:06, 22 August 2009 (UTC)

On the first point, winds certainly do blow across the equator. The trade winds from the northern and southern hemispheres meet at the Intertropical Convergence Zone, which moves around; thus they blow across the equator if the zone isn't on the side of it that they start from.

If you google on "hurricane" and "crossing the equator" you will find some sites that say it isn't likely to happen because they don't form near the equator in the first place, and hasn't ever been known to happen. But if it did happen, the storm would probably be able to preserve its original rotation.

Finally, hurricanes do cross Central America occasionally. The convention is that when this happens they get a new name. See Hurricane Cesar-Douglas for one example. --Anonymous, 01:55 UTC, August 22, 2009.

Yeah - the coriolis effect is not very strong near to the equator (which may be a part of the reason hurricanes don't form there to start with). Mathematically, the "coriolis coefficient" is proportional to the sine of your latitude. At the equator (zero degrees latitude) - the sine of zero is zero - so there is no coriolis force whatever. As hurricanes move towards the equator the coriolis force gradually decreases. If one ever did cross the equator, the coriolis force counteracting its rotation would get gradually stronger the further it went - eventually (presumably) disrupting the storm and causing it to fizzle out. But it would have to move a long way past the equator for that to happen. SteveBaker (talk) 02:11, 22 August 2009 (UTC)

Ah, alright. That all makes sense. Thank you, Falconus^{p t c} 04:50, 22 August 2009 (UTC)

Global Tropical Cyclone Tracks between 1985 and 2005, indicating the areas where tropical cyclones usually develop

It just does not happen. See Tropical_cyclogenesis#Unusual_areas_of_formation, which includes a global track picture. If somehow it did happen, the storm's rotation would slow and then cease as it neared the equator, and then restart in the opposite direction. Apparently there have been two storms that did get close to the equator. Remember that the atmosphere is a gas. A hurricane does not have rotational inertia in the same sense that a spinning top has roatational inertia. gass molecules can push on each other, put they cannot pull on each other. The corriolis effect is the only thing that causes the circular motion. -Arch dude (talk) 13:02, 22 August 2009 (UTC)

Once a storm got going, its intrinsic tendency to amplify its spin rate would probably allow it to survive crossing the equator; see this link for a somewhat authoritative explanation. And you can look at this pdf for an account of an exceptional typhoon that formed less than 2 degrees from the equator in 2001. Looie496 (talk) 19:05, 22 August 2009 (UTC)

Agreed. The coriolis effect is extremely tiny, and just enough to get a bit of rotation in a tropical depression. Once started, however, the energy from the rising steam off the water and the cold air dropping from the stratosphere into the eye greatly magnifies the rotational energy. I believe there are even rare cases where a hurricane or cyclone rotates the opposite direction it should, due to some local wind condition where it formed which was stronger than the coriolis effect. StuRat (talk) 21:50, 22 August 2009 (UTC)

Do you have a citation for this? Alternatively, can you describe a physical reason for this effect? I cannot think of any effect that would result in an "intrinsic tendency to amplify its spin rate." I think that the hurricane amplifies the latidudinal relative velocity differences as it pulls each packet of air radially toward itself. The hurricane's heat engine does not impart any rotation, instead the pre-existing horizontal velocity differences remain constant as each air packet moves toward the eye. -Arch dude (talk) 23:14, 22 August 2009 (UTC)

LOL@latiDudinal, is that really cool latitudes ? The concept is that, as the steam rises off the water and into higher altitudes, it creates a low-pressure area at the surface. This causes air to rush in from outside the hurricane, which has a tendency to compact the storm. As the rotational center of gravity of any rotating body is moved in towards the center, the rotational speed must increase to conserve rotational momentum. The low pressure in the center of the hurricane eventually leads cold air to be drawn down from the stratosphere in the center to form the eye, pushing the hurricane away from the center. This results in the highest rotational velocity (and therefore winds) at the eye wall. StuRat (talk) 09:10, 23 August 2009 (UTC)

Then you agree that the rotation at the eye is "merely" the concentrated rotation of the more distant atmosphere in general: your description is the same as mine. But the large-scale (i.e., Hurricane-scale) angular momentum of the atmosphere is completely dominated by the coriolis effect. So I ask again: what would cause a hurricane to carry the "wrong" rotation across the equator? I do not believe this will occur. -Arch dude (talk) 12:09, 23 August 2009 (UTC)

No, there's also something else going on that increases the rotation speed. The energy of rising heat is redirected into rotation, much like water going down the drain is redirected into rotation. The coriolis effect gets the rotation started and the previous effect I mentioned concentrates this rotation, but, once established, this redirected energy is the real powerhouse of rotation. And I didn't say that hurricanes are carried the wrong direction across the equator, my point was only that, if the steering winds pointed one that way, it could probably survive, with only a slight weakening from the coriolis effect (now rotating in the opposite direction). However, the steering winds just don't seem to point that way, and the cross-equator winds we do get just aren't strong enough to move a hurricane. StuRat (talk) 13:56, 23 August 2009 (UTC)

You may be miss-remembering the fact that tornados ocasionally (roughly 1 out 1000) spin the "wrong" way and thinking that this also applies to hurricanes. But the coriolis force is an essential part of a hurricane dynamics and there can be no hurricanes spinning the wrong way. In a hurricane coriolis and Pressure Gradient Force (PGF) always opose each other on a quisi-equilibrium. Unlike a hurricane, in a tornado the coriolis plays very little role on the dynamics which is an quasi-equilibrium between centripetal force and the PGF matching more closely your description of rotational movement getting concentrated by the tightening of the storm due to air lift at its center. Dauto (talk) 15:28, 23 August 2009 (UTC)

The story I heard was about reverse-spin "cyclones", but some in the US do mistakenly call tornadoes by that name, so I suppose they might have meant that. However, I still maintain that the sum of the rotational energy in a hurricane does not all come from the coriolis effect. If the coriolis effect were that great, then all storms would have rotation, but they don't if they lack another rotational energy source (or an energy source which can be redirected into rotation). StuRat (talk) 23:36, 23 August 2009 (UTC)

Two points: First Point: Being always perpendicular to the velocity means that the coriolis force does no work and cannot provide any energy at all to the hurricane. The energy is provided by the PGF. What the coriolis force does is to deflect the radial movement created by the PGF creating a circular movement. Second Point: All Tropical Storms, Cyclones, Typhoons, and Hurricanes DO HAVE rotation. In those storms the coriolis force is about as strong as the PGF and they are in a quasi-equilibrium. Dauto (talk) 05:22, 24 August 2009 (UTC)

To your first point, since the pressure-gradient force is itself created by rising steam off the water, as I described earlier, then the rotation is due to this heat engine, so we appear to be in agreement. As for your second point, yes, many storms have rotation, but not all. Specifically, those lacking the heat engine I described tend to also lack rotation. This is common over land, where most storms lack rotation, but can also occur over water during some tropical depressions, etc. StuRat (talk) 14:09, 24 August 2009 (UTC)

The question is about tropical cyclones. They all do rotate, they all do rotate the 'right' direction, they never rotate the 'wrong' direction and they cannot possibly rotate the 'wrong' direction and still be tropical cyclones, because there would not be any quasi-equilibrium between the PGF and the coriolis force. Dauto (talk) 15:39, 24 August 2009 (UTC)

And I'm not arguing with you about any of that, am I ? My comment that "not all storms rotate" was to illustrate that the coriolis effect can't be the sole cause of all storm rotation, because, if it was, all storms would rotate (except those on the equator). I don't go as far as you in saying the coriolis effect "cannot provide any energy at all to the hurricane", however. StuRat (talk) 22:11, 24 August 2009 (UTC)

As to the point of the coriolis force being in a different direction than the storm rotation, forces are frequently redirected, as in the case of sailboats redirecting the force of the wind to go in just about any direction they wish. StuRat (talk) 16:26, 26 August 2009 (UTC)

Actually the Coriolis effect is velocity-dependent too .... and remember, upper-level winds are really really really strong. John Riemann Soong (talk) 05:34, 23 August 2009 (UTC)

For the record, the tropical cyclone that (recently) formed closest to the equator was Tropical Storm Vamei. ~AH1^(TCU) 11:17, 24 August 2009 (UTC)

Microsleep and discontinuity

Why doesn't the brain notice a discontinuity upon waking from microsleep, as it would when watching a scratched DVD that suddenly jumped forward a few seconds? NeonMerlin 03:36, 22 August 2009 (UTC)

Why do you think the brain does not notice discontinuity? If you've ever dozed off, your personal reaction may vary; but the waking-up part is often jarring, even disproportionately so compared to the amount of time that was actually slept through. Nimur (talk) 05:09, 22 August 2009 (UTC)

...I'm exactly the opposite to what Nimur describes. When I doze off, I drift back into consciousness without ever knowing I was asleep (until I notice the clock says it's an hour and a half after my appointment). So I, too, am curious as to why this is...Although I've never microslept. Vimescarrot (talk) 18:18, 22 August 2009 (UTC)

The brain is tuned to attend to things that have implications for behavior, meaning mainly things in the external world. There are loads of discontinuities happening all the time that we never notice unless we attend to them, for example blinking and rapid (saccadic) eye movements. Also, I think that the event Nimur describes is not actually related to waking from sleep -- many people have a tendency to drift into half-sleep and then abruptly jerk into full wakefulness. These events are sometimes called hypnic jerks, and their causes and function (if any) are not well understood. Looie496 (talk) 18:45, 22 August 2009 (UTC)

If nothing much has changed while you were asleep (at least, nothing your brain considered worth paying attention to), then there is no discontinuity to notice. --Tango (talk) 19:46, 23 August 2009 (UTC)

Naga Fireballs

Is there any scientific answer for this the Naga fireballs. I mean it seems interesting that no one has apparently bothered to even look into them, or is it just soldiers firing stuff? —Preceding unsigned comment added by 58.111.132.76 (talk) 07:14, 22 August 2009 (UTC)

It's not clear that they have ever even been observed; so it's hard to have a scientific explanation of them. Like many "fringe" areas, the scientific community can't make any kind of explanation until there is good recorded observational evidence; and that kind of evidence usually comes only from well-funded scientific study by properly trained specialists. The result is a positive-feedback loop - minimal evidence, so minimal investigations, so even less evidence ... . If an amateur video existed, and the phenomenon is shown to be more than a local legend, it'll probably be looked into. Unfortunately, this is what we have - and the only thing unexplained in that video is, "why did he videotape an empty, dark sky?" Nimur (talk) 07:21, 22 August 2009 (UTC)

Are you sure it's not clear they've ever been observed? Our article suggests they're well-known:

The number of fireballs is variable, being reported at between tens and thousands per night.

The fireballs have been seen for centuries and are most often reported around the night of Wan Awk Pansa — the end of the Buddhist rains retreat — in October, although displays have also been reported in March, April, May, June, and September.

The fireballs are even being promoted as a tourist attraction: Previously known as the ghost fireballs, the event has now had its name changed and is being promoted as a festival to attract tourists. I get the impression that unlike the Ness or the Sasquatch, anybody who wants to see these fireballs can easily do so. --99.237.234.104 (talk) 12:25, 22 August 2009 (UTC)

Though it is striking how few pictures of them are on the internet. Seems like there are about three that get repeated everywhere. For a tourist phenom, you'd expect a lot more tourist photos. --98.217.14.211 (talk) 14:00, 22 August 2009 (UTC)

There are also purported photographs of Bigfoot; I'm still skeptical that a Great Forest Ape has ever actually been observed in the Pacific northwest. Evidence of extraordinary claims needs to be extraordinarily convincing. Nimur (talk) 15:19, 22 August 2009 (UTC)

There's also this less-than-convincing musical number. Nimur (talk) 07:28, 22 August 2009 (UTC)

Experiment variables

I'm considering doing an experiment. I plan to test two different cars (a heavy one and a light one) on three different surfaces (bitumen, gravel, dirt) with three different speeds (20km/h, 40km/h, 60km/h). The idea is to contrast the performance braking distance of the two cars with respect to the speed and surface variables. My question is whether one could reasonably draw a meaningful conclusion from such an experiment. Are there too many variables for anything of substance to be derived? Would any conclusion made be non-rigourous and inherently iffy? Should I perhaps consider operating with only a single variable, and axe two of the others? —Anonymous Dissident^Talk 08:02, 22 August 2009 (UTC)

• You need to define performance in order to design a meaningful test. Once the test is performed you could rigorously say that car A is better than car B, provided the data supported that conclusion. You could not imply that light cars are better than heavy ones for example. Noodle snacks (talk) 08:55, 22 August 2009 (UTC)

"performance" is an error on my part. I mean to contrast braking distance. —Anonymous Dissident^Talk 09:10, 22 August 2009 (UTC)

That sounds like a reasonable experiment. There are a few confounding variables you can consider: are the brake systems equivalent on the different vehicles (probably not). Are they reasonably equal in age? The brake pads wear out, so even testing the same car with new vs. old brake pads would result in different braking distances. How will you account for variations by the driver? Do you have a plan to slam the brakes to maximum (this can be dangerous, especially on gravel)? If not, how will you ensure consistency in the experiment? Nimur (talk) 09:17, 22 August 2009 (UTC)

Brakes will be slammed to a maximum. WRT to the other factors, you're completely right – they'd be entirely necessary to consider for something professional. But this is just an amateur experiment, and I'll just be counting such factors as the driver's variations as negligible. Nonetheless, I have an interest in drawing some kind of conclusion about the experiment – maybe something along the lines of how the lighter car's results contrast with the heavier car's and why. Thanks for the input. —Anonymous Dissident^Talk 09:42, 22 August 2009 (UTC)

Slamming on brakes is a good way to go off the road, so you might consider doing this stuff in parking lots. --Sean 12:28, 22 August 2009 (UTC)

Do both cars have anti-lock brakes? Will this be on or off? Or will you conduct experiments with on and off? Exxolon (talk) 15:13, 22 August 2009 (UTC)

And the key is to be careful about extrapolating your results. You definitely can't use this experiment to say "light cars are better than heavy cars in breaking on gravel". You also can't really say "this model is better than this model", if you want to be really rigorous, you are only allowed to say "this particular car is better than this particular car (in these particular conditions)". That's fine though, it's still a conclusion. Aaadddaaammm (talk) 17:17, 22 August 2009 (UTC)

Better yet, you could test the same car with different braking methods (anti-lock engaged vs. non-engaged; pumping the brakes vs. slamming, etc. etc.) on different surfaces. By using ONE car, and testing the methods, you can control for all of the hidden variables mentioned above. That may be a far more controlable experiment. If you are attempting to make a meaningful conclusion about car weight vs. braking distance, two cars is FAR too small a sample size, you'd have to use literally hundreds of cars, and plot some sort of graph of weight vs. stopping distance, and also try to do a proper statistical analysis to confirm the validity of the results. --Jayron32 17:32, 22 August 2009 (UTC)

Having run an experimental laboratory myself, here are my main suggestions. First, the most critical thing, you need to find drivers who are blind to the purpose of the experiment, so that you can be sure their expectations don't influence the results. Second, you need to randomize the order of tests, so that changes in conditions don't alter the results. Third, you need sufficient sampling of each condition, I would guess 5 trials for each would be enough. Whether you can handle the number of variables you mentioned is a function of whether you have enough resources to do multiple trials for each combination. Looie496 (talk) 18:34, 22 August 2009 (UTC)

(20km/h, 20km/h, 60km/h) is only 2 different speeds. Cuddlyable3 (talk) 20:23, 22 August 2009 (UTC)

Being a psychic, I've read the OP's mind and determined that they meant to say 40km/h for the middle speed. :-) StuRat (talk) 21:39, 22 August 2009 (UTC)

Scientifically, the problem is that the two cars you're using don't differ only in their weight. There are guaranteed to be lots of other differences (different sized brake disks, different brake pad materials, different braking forces, better tires, different ABS strategies, different drag coefficients, different power-assisted braking designs...heck different seats and brake-pedal-travel could make a difference). So if (say) the heavier car takes a shorter distance to come to a stop - all you can really say is that this model of car stops better than that model of car. You can't make any conclusions about the weight alone because it might be that the bigger car has bigger brake disks and that could be the reason for the difference.

What I think you need to do is to stick with just one car - and alter the weight it carries. Try it with just the driver, with one, two, three and four passengers (weigh them!) - load the thing down with sandbags or other weights. Plot a graph of weight versus stopping distance. If you have another car, then you can try the same experiment and see if the curve you get is similar in shape. If you can show that all kinds of car show the same shape of weight-versus-stopping-distance then perhaps you have learned something that's generally applicable. Of course, even that isn't 100% rigorous because the distribution of that weight (all at the front, all at the back, divided 50/50, etc) could also make a difference. In the end, the depth of your experimentation depends on the importance of the results for whatever practical purpose they are intended. If it's for something like a high-school science fair - then the experiment I describe ought to be enough to get you good marks. If you are going to use the results to design the next Ford super-monster-Uber-wagon...you're going to need to do a lot more work! One word of warning...doing this on gravel, or with ABS disabled, can cause you to fish-tail and even skid/spin-out. Be really careful about what's to either side of the car when you do this. SteveBaker (talk) 20:20, 23 August 2009 (UTC)

I ended up doing the experiment. I decided to use only one vehicle with different speeds on different surfaces. I figured that making any generalisations about one type of car vs. another was unwise with so few samples on hand, and that a conclusion about something meaningful could be more readily drawn with just two variables. It certainly made my job easier – 27 tests (3 for each speed to calculate a rough average) take much less time than 54. I didn't have any problem with skidding on the gravel – as it happened, the gravel consistently had the shortest braking distance. Is it possible the gravel had the opposite effect to what might have been expected, and actually retarded the speed faster rather than skidding it? How does the result of gravel's having the shortest braking distance fit in with the typical traction of such a surface? Is it possible the result can best be explained by some flaw in the test or by human factors? An interesting thing was that even though the gravel had a shorter braking distance than the bitumen, the gravel's braking time was longer. Thanks all for chipping in. —Anonymous Dissident^Talk 14:35, 24 August 2009 (UTC)

With gravel, you probably expected it to reduce friction by rolling between the tires and ground, but they may have actually dug into both the tires and the ground. However, smaller abrasives, like rock salt, definitely do increase braking distances by rolling between the tires and road. StuRat (talk) 22:03, 24 August 2009 (UTC)

At slower speeds, the gravel may actually pile up in front of a locked wheel and make a wedge-like thing that would stop the car quicker. It's a complicated business though. Certainly cornering on gravel is much tougher than on tarmac or concrete...not good. (And I speak from bitter experience!) SteveBaker (talk) 22:49, 24 August 2009 (UTC)

Oxidant Scavenging Systems

Hello, will someone kindly explain, how oxidant scavenging systems may be useful in cancer therapy? Many Thanks,in advance. —Preceding unsigned comment added by 59.93.214.236 (talk) 15:19, 22 August 2009 (UTC)

I assume you mean antioxidants ?83.100.250.79 (talk) 15:46, 22 August 2009 (UTC)

Perhaps they aren't useful. See http://arstechnica.com/science/news/2009/08/duplicitous-antioxidants-tumor-suppression-and-promotion.ars

For a fuller picture I recommend searching for "antioxidant" + tumor/cancer therapy etc.83.100.250.79 (talk) 15:46, 22 August 2009 (UTC)

Neanderthals

In the local train station, there's a display on evolution. It includes a model of a Neanderthal in what appears to be a crude shelter made of mammoth ribs or tusks or something. Did Neanderthals really make buildings out of mammoth bones? Aaadddaaammm (talk) 17:13, 22 August 2009 (UTC)

Mammoth bone houses are well known, and Neanderthals are contemporary with mammoth, I can't find anything as yet to prove what type of human lived in mammoth bone houses. I'm sure some archaeologist has examined mammoth bone houses in detail, and pinned them on a specific culture.. someone else will know..83.100.250.79 (talk) 17:51, 22 August 2009 (UTC)

Such dwellings have been found, amongst other places, in the Ukraine and Russia. Particularly in areas of poor forestation (the ice age had turned large areas into tundra / steppe), the bones were a valuable means of building shelter. Ivory was used for arrow heads and carved into artifacts. As to the name of the associated culture, it would depend on the "sophistication" of he stone tools unearthed on these sites. Micoquian or Mousterian may be options, but an anthroplogist will know better. --Cookatoo.ergo.ZooM (talk) 20:17, 22 August 2009 (UTC)

There's also the option of examining butchery marks on the bones, which to someone with a microscope and expertise reveals the type of knife tool used to carve up the mammoth - as I understand it Neanderthals used the simplest type of flint tool. I'm sure someone will have researched this - though if the research has been published in cyrillic text this may prevent a google search bringing in its usual rewards.83.100.250.79 (talk) 20:34, 22 August 2009 (UTC)

Wow OK I was sure this model just came from someone who'd watched too much The Flintstones. Thanks for educating me! Aaadddaaammm (talk) 20:36, 22 August 2009 (UTC)

Mammoth bone deposits and subsistence practices during Mid-Upper Palaeolithic in Central Europe: three cases from Moravia and Poland (which is unfortunately not free) seems to discuss the use of mammoth remains as a living-structure. It's not clear whether the humans were Homo sapiens or Neanderthals. Nimur (talk) 22:01, 22 August 2009 (UTC)

Tiny flies in the kitchen

My kitchen is full of tiny little flies. They are concentrated near the sink and the window above it. I know this is pretty common because I have some friends who have them too, but mine are getting out of hand.

I keep it very clean, and there is little to no food lying around exposed. There's nothing clogging the sink drains, no other obvious source.

1) What are these things called? (I live in the northeastern USA so they aren't "exotic"). People call them "fruit flies" but are they really?

2) How do I get rid of them? What am I missing?

Gohome00 (talk) 21:47, 22 August 2009 (UTC)

I'm pretty sure this has been asked before. They're likely Drosophila species, frequently Drosophila melanogaster. They way I deal with them in my kitchen is to put some wine vinegar diluted 50% in water in a small glass (although straight vinegar should work; they seem to prefer non-white vinegars. you can also use some old wine or beer). Cover the cup with plastic wrap and poke some smallish holes (roughly the size of the flies or a bit larger). The flies are attracted to the vinegar and crawl through the holes and get trapped. Then they have unfortunate swimming accidents and drown. Two such traps are usually good. Also I suggest ensuring that you have rinsed out any beverage containers or cans that contained fruit that you have in your kitchen. Beer bottles with a small amount of beer (or "empty" wine bottles) are like buffets to the fruit flies. Oh, and feel free to kill any that you can clap your hands on. I find that wet hands seem to be more effective at getting them. Good luck! -- Flyguy649 ^talk 23:58, 22 August 2009 (UTC)

Spanish flying insects

For several years we have seen what appears to be a "moth"like insect whilst on holiday in Southern Spain. Closer inspection when the insect lands on a flower reveals a birdlike face with a long probe that appears to be extracting nectar. Does anyone know what these insects are?Huscroft (talk) 21:54, 22 August 2009 (UTC)

Hmm. Feeds on nectar, has a bird-like face, about the size of a big flying insect – sounds a lot like a hummingbird, except that hummingbirds aren’t found in Spain. Red Act (talk) 22:25, 22 August 2009 (UTC)

Perhaps it’s the hummingbird hawk-moth, which is found in Spain? Red Act (talk) 22:32, 22 August 2009 (UTC)

August 23

A moth I saw when I was a kid...

The critter was about an inch long, with a bulky abdomen, coloured reddish-orange on top and light grey beneath - it was also rather 'furry looking'. However, by far the most striking characteristic of the moth was that its head and 'snout' closely resembled that of a Red Fox (but smaller, obviously). It even had the pointed 'ears'.

I was actually about to squash the thing - but ended up running away scared (hey, I was only about 6 years old at the time!) after seeing its unusual and striking face. This was more than 20 years ago now and I can't really give you any more specific details (other than that I lived in NW England at the time).

So, going on what little I've told you - does anyone have any suggestions as to what species I might've seen? --Kurt Shaped Box (talk) 02:01, 23 August 2009 (UTC)

The Smerinthus cerisyi [6] looks like it has the face of a red fox on it. Could that have been it? Red Act (talk) 04:13, 23 August 2009 (UTC)

Na. It definitely didn't have large antennae like that. Just to clarify, the moth I saw didn't have faux foxlike eyes and features on its wings - it's actual (real) head and face looked like that of a fox... --Kurt Shaped Box (talk) 23:44, 23 August 2009 (UTC)

Chinese Egrets! -- Where to report rare bird sightings for East Asia?

Out birdwatching here in NE China this morning I'm 98% sure I came across a small group of Egretta eulophotes (aka Chinese / Swinhoe's Egret).

Because they're a rare bird to begin with (est. ~3000 remaining) and I spotted them outside their common range, I'd like to report the sighting.

I managed to take poor but evidence-worthy photographs by using my binoculars as a crude lens for my digital camera. Does anyone know who I should contact about this? The Audubon Society is largely absent from China, as far as I know...

image collage link (125kb jpg version) - http://www.drewsjournal.com/JUNK/Egretta-eulophotes.jpg

image collage link (1.5mb PNG32 version)- http://www.drewsjournal.com/JUNK/Egretta-eulophotes.png

38.100.141.141 (talk) 02:03, 23 August 2009 (UTC)

You could directly email the authors of this paper (or similar scholarly papers on Chinese Egret conservation). [7] [8] [9]. These papers list a correspondance author (with email contact), who are presumably Chinese egret specialists. It's likely that the author is intersted in the breeding range of this bird; and may know more specifically about who in the community you could contact. You could also try contacting one of the editors for the respective journals. Nimur (talk) 03:29, 23 August 2009 (UTC)

Healing machines

I have this memory, either from my own imagination or something I read in the distant past, of a machine that had some type of bionic ability to heal and repair itself. FYI, this was a shaceship hull. This was not done by robots according to programming, nor guided by an artificial intelligence, but rather the nature of the material itself. The hull was like a living non-sentient creature, but definitely had been engineered. Does this concept have a name that I could research more? Thanks - Draeco (talk) 02:36, 23 August 2009 (UTC)

A lot of rubbers and polymers ("plastics") have been engineered to self-seal holes and punctures. We have an article on tires that do this. Similar material has been worked on for aircraft fuselages and fuel-tanks: self-sealing fuel tank. Nimur (talk) 03:22, 23 August 2009 (UTC)

There was talk that the Transhab would be made of self-healing materials, but I can't find any references that its prototypes actually were. Perhaps that was one of the many parts of the Transhab concept that didn't pan out. (Though it might still be a good idea.) APL (talk) 04:13, 23 August 2009 (UTC)

You might be remembering Vorlon ships from Babylon 5. See Vorlon#Spacecraft. 67.122.211.205 (talk) 05:54, 23 August 2009 (UTC)

Lots of science fiction in the past ten years has used the concept of "nanomachines" as a means of introducing self healing ships and/or self healing bodies. The Old Man's War series by John Scalzi makes heavy use of this idea, as does lots of recent sci-fi. --Jayron32 06:02, 23 August 2009 (UTC)

Another sci-fi example is the ship in the Farscape series. StuRat (talk) 08:42, 23 August 2009 (UTC)

Though Leviathans like Moya were sentient. -- 128.104.112.102 (talk) 17:09, 23 August 2009 (UTC)

That true. Are we excluding the bodies of sentient beings from the list of self-healing materials ? StuRat (talk) 15:21, 25 August 2009 (UTC)

Not necessarily, although the OP mentioned that the example being sought "was like a living non-sentient creature" (emphasis added), so I thought it was worth mentioning. -- 128.104.112.102 (talk) 21:58, 25 August 2009 (UTC)

"self healing material" seems to be the right search term, nothing more technical than that. See also Self-healing material.83.100.250.79 (talk) 12:32, 23 August 2009 (UTC)

I recall reading a science fiction book where the ship's hulls were a crystal of some sort where kinetic energy caused them to repair. It reminded me of Piezoelectricity. -- JSBillings 01:25, 24 August 2009 (UTC)

Motor learning and tools

Is there an article specifically about the phenomenon of motor learning with tools? Actually I'm thinking about the phenomenon where, with experience, most car drivers seem to drive as though the car were an extension of their body; a sudden need to swerve or brake is in fact reflexive; and control of the steering and speed are pretty much automatic (and are even conducted during those periods of time where you zone out and then "snap out of it" a few miles later, having driven on automatic pilot that whole time). Our motor learning article is surprisingly brief. Tempshill (talk) 04:05, 23 August 2009 (UTC)

Crooks and Gibson (1938) - A Theoretical Field-Analysis of Automobile-Driving - "Steering, according to this hypothesis, is a perceptually governed series of reactions by the driver of such a sort as to keep the car headed into the middle of the field of safe travel." There's no shortage of modern studies, either. Models of driving behavior: a review of their evolution (1994) - "More recent models have incorporated a hierarchical control structure, which assumes concurrent activity at strategic, maneuvering, and operational levels of control. At the same time, automaticity has emerged as a central construct in cognitive psychology. All activities are assumed to combine fast, automatic components with slower, more deliberate, controlled processing." Nimur (talk) 04:13, 23 August 2009 (UTC)

Those look excellent though I don't have access to read anything beyond the synopses. I guess I should ask whether there's a Wikipedia article about same. Tempshill (talk) 04:32, 23 August 2009 (UTC)

Exercise making someone more drunk?

As I read the "Does exercise make people less drunk?" question from several days ago, I was curious — is the following story I've heard plausible, or was it a hoax? According to a story that I've heard, part of the Lost Sea Cave in Tennessee was used as a speakeasy during Prohibition in the USA, and because the modern tunnel wasn't yet constructed, the patrons could only access the cave by a (still usable) steep rock staircase. Some patrons would consume large amounts of alcohol without becoming tipsy, but as they attempted to leave, the decreasing air pressure as they climbed to a higher altitude (I really don't know how tall the stair is, but my memory from ten years ago says perhaps over 100 feet) would somehow make them more drunk, and a few consequently fell back down the stairs. Nyttend (talk) 04:21, 23 August 2009 (UTC)

Change in air pressure during a 100ft ascent is negligible so that theory is probably rubbish. What is more likely is that alcohol absorption is a gradual process - this especially true if you had food beforehand. This, coupled with the increased circulation and thus absorption from exercising and maybe a bit of liquid lost due to sweat can increase blood alcohol concentration quite quickly (but then this is purely speculation). --antilived^{T | C | G} 10:23, 23 August 2009 (UTC)

Yes, it's not plausible that altitude would have any effect here. One of the things that alcohol most seriously impairs is the ability to balance, but it is also impaired by fatigue -- so, combine the two, and ... Looie496 (talk) 15:53, 23 August 2009 (UTC)

At higher altitudes, however, the change in air pressure would have a significant effect. That's why pilots are strictly forbidden from drinking while on duty -- even if you take just one drink at sea level and then climb to 8,000 feet, it can have the same effect as having three or four. So a pilot who's just slightly buzzed when first getting into the cockpit would be passing-out drunk by the time the plane reaches 8,000 feet.

That said, an ascent of 100 feet would not have a significant effect on how drunk you get. What prob'ly happened was that the physical exertion involved in climbing the stairs would increase the rate of circulation, which in turn would speed up alcohol absorption -- plus loss of water due to sweating, which increases the BAC significantly -- plus the effect of fatigue adding to the effect of alcohol on the brain -- and there you have it. 98.234.126.251 (talk) 23:44, 23 August 2009 (UTC)

Known precision of the nuclear force binding energy constant

Richard Dawkins, discussing the fine tuned universe in The God Delusion, writes, "Martin Rees, in Just Six Numbers, lists six fundamental constants, which are believed to hold all around the universe." Dawkins continues

An example of Rees's six numbers is the magnitude of the so-called 'strong' force, the force that binds the components of an atomic nucleus: the nuclear force that has to be overcome when one 'splits' the atom. It is measured as E, the proportion of the mass of a hydrogen nucleus that is converted to energy when hydrogen fuses to form helium. The value of this number in our universe is 0.007, and it looks as though it had to be very close to this value in order for any chemistry (which is a prerequisite for life) to exist.

This caught my eye because

1. hey, it is a dimensionless constant!
2. it exactly equals the fine structure constant (when you only consider a single significant figure).

Wikipedia discusses it in Proton–proton chain reaction#Energy release and in Dimensionless physical constant#Martin Rees's Six Numbers, but in both cases only gives a single significant figure. (Rees's book is only available via snippet view at Google Books, so I don't know if he discusses the value further.) How precisely is this constant known?

(N.B. this is a question only about the value and definition of a physical constant, and not an invitation to discuss cosmogeny.) -- Thinking of England (talk) 04:43, 23 August 2009 (UTC)

Just compare the mass of 4 protons with the mass of a alpha particle. A more precise value is 0.0068500 Dauto (talk) 06:40, 23 August 2009 (UTC)

Above I forgot to include the energy realeased from two electrons that get coverted to the much lighter neutrinos. When that is included you get the figure 0.0071224. Dauto (talk) 06:58, 23 August 2009 (UTC)

OK, I was being dense and thinking there was more to the definition than what was given in Dimensionless physical constant#Martin Rees's Six Numbers. So if we take the mass of the alpha particle, proton, and electron as m_α = 4.001506179 u, m_p = 1.007276466 u, and m_e = 0.000548580 u, then ε = 1 - m_α / (4 m_p + 2 m_e) = 0.007120446 which is reassuringly distinct from α = 0.007297352 (and from 0.007000000 -- I'll change the "ε=0.007" in Dimensionless physical constant#Martin Rees's Six Numbers to "ε≈0.007". D=3 I can accept, but I was troubled by ε being singled out of the five remaining constants for an equal sign.) Thanks. -- Thinking of England (talk) 07:49, 23 August 2009 (UTC)

software programming

what is difference between java & Asp.net —Preceding unsigned comment added by 58.68.8.187 (talk) 07:20, 23 August 2009 (UTC)

We have articles on Java (software platform) and ASP.NET, which may be of help. --Cookatoo.ergo.ZooM (talk) 08:20, 23 August 2009 (UTC)

if you require more explanation you should ask the question on the computing desk ! 83.100.250.79 (talk) 12:29, 23 August 2009 (UTC)

Streamlines and streaklines

Hi,

I've had a look through the article and my textbook, but still not sure on the difference and why they only coincide when flow is steady. Because if the streamline is calculated instantaneously, wouldn't it take into account the unsteady nature of the flow and hence end up being the same as the streakline?

Is the difference that a streakline takes into account the "history" of the flow whereas the streamline doesn't? For example, say the flow flow is unsteady, and initially it could be described as a straight line (ie the streamline was linear). But then at t₁ the streamline became parabolic. Then at t₂ it became linear again. Would the consequent streakline be a straight line followed by a parabolic section followed by a straight line?

Thanks, --Fir0002 11:56, 23 August 2009 (UTC)

Steamline is given as a snapshot of the flow (synchronous), so every point of the flow line represents a different fluid element. A streakline follows a fluid element and plots its path. Two different things. For instance, you could have all the fluid elements following similar tracks. It is possible that at some given time all of them would be moving along the same direction (say northward), but then as each element follows its track at a latter time they could be all moving eastwards. At any given time the streamlines would all be straight lines since all the fluid elements are moving towards the same direction, but the streaklines would all be curved since each element is changing the direction of its motion. Dauto (talk) 16:52, 23 August 2009 (UTC)

OK I think you're basically agreeing with my second paragraph. The streamline is the mathematical model of the flow at any point in time. The streakline is a "recording" of the path a particle takes in a given timeframe. But just so I have this clear I'd like to know what would happen in this example.. We're looking at unsteady flow. At t₀ the streamline is a straight line due north. At t₁ the flow changes and now the streamline is a straight line due east. The flow changes again at t₂ and thereafter the streamline is again a straight line due north. The streakline over that period would look something like this, correct? --Fir0002 11:06, 25 August 2009 (UTC)

Yes, that's correct. And the streamlines would all be straight lines for any given time, so they do look very different from the streaklines. Dauto (talk) 17:33, 25 August 2009 (UTC)

How to cross a river safely while hiking - portable boat?

What would be the best practical solution to being able to cross small placid rivers say 20 or 30 feet wide while hiking? Constraints include that a raft cannot be made as the materials are not available. Swimming is unsuitable as I'd get wet and cold, especially in non-summer seasons. Any portable boat would need to be light enough and compact enough to be carried. Surely inventors have considered this problem though the centuries. I'm looking for a genuine solution that I can either buy or make fairly easily. 78.149.186.253 (talk) 13:05, 23 August 2009 (UTC)

How about one of those swimming pool floating/lounge chairs that comes in (and thus is able to fit in) a remarkably small cardboard box? 69.140.12.180 (talk) 13:43, 23 August 2009 (UTC)Nightvid

...or an inflatable raft. DRosenbach ^{(Talk | Contribs)} 13:44, 23 August 2009 (UTC)

No serious hiker would carry a heavy boat through an entire hike to cross such a small stream. You just wade across. If the current is too strong you may have to use ropes for safety. 75.41.110.200 (talk) 13:47, 23 August 2009 (UTC)

A "Serious" hiker would take local conditions into account before making a decision. He already said he's hiking in "non-summer". He could be trying to cross a ten foot deep river in below-freezing weather for all you know. APL (talk) 05:05, 24 August 2009 (UTC)

The navigable rivers I have in mind are too deep to wade, with lots of water-weeds to get dangerously entangled in. Plus I'd rather not get wet and cold. 78.149.186.253 (talk) 14:14, 23 August 2009 (UTC)

I think you'll have to be prepared to get a bit wet. You can buy a floating backpack (Google it) which acts as a flotation device, even when fully laden. Just get undressed and throw your clothes into it, swim across, then dry yourself and get dressed. I saw one featured on TV a few weeks ago but I can't find a link to the exact brand at the moment.--Shantavira|^{feed me} 14:37, 23 August 2009 (UTC)

It sounds like what you're looking for is the smallest Packraft you can find. I've never used one myself so I can't vouch for any particular kind.

Incidentally, if you're hiking in a group only one person has to get wet. You can set up a simple rope bridge pretty quickly if there are trees nearby. APL (talk) 15:31, 23 August 2009 (UTC)

Wow, check out this one [10]. I wouldn't have thought they could make a boat this tiny still be useful. I've carried tents heavier than this boat. Bit pricey, though. Perhaps something like this[11]. I imagine you'd make your life a lot easier if you also packed a small bicycle pump.APL (talk) 15:43, 23 August 2009 (UTC)

The "standard" solution to this problem is to find a downed tree that lies across the stream. Where are you going to be hiking, where you find small placid rivers 20 to 30 feet across that are too deep to wade? Looie496 (talk) 17:42, 23 August 2009 (UTC)

Where are you that you have 20 to 30 feet wide rivers that are shallow enough to wade? 78.147.147.139 (talk) 19:58, 26 August 2009 (UTC)

A Klepper canoe might be useful. 98.234.126.251 (talk) 23:49, 23 August 2009 (UTC)

Or, for a small river, two people crossing arm-in-arm may make it easier. Warning. Having to cross a small river, many people look for a spot where the flow is weaker and the water is less deep, which in principle is not a bad idea. Such a point is often found in the outer side of a bend (a convexity of the river): but the opposite side, the inner side of the bend (the concavity of the river), is, for the same reasons, the spot where the flow is stronger and the water is deeper. In panic, they try to go ahead and reach the bank, making the situation worse. --pma (talk) 18:31, 25 August 2009 (UTC)

I think you are mistaken - the current is more intense on the outside bend. 78.146.255.137 (talk) 21:34, 27 August 2009 (UTC)

I think the weight-cost of carrying around the necessary scuba gear and air tanks would make that method impractical. 78.147.147.139 (talk) 19:58, 26 August 2009 (UTC)

'Level' as a point or a span

A periodontal colleague of mine insists that her goal is to "reduce clinical attachment level." Now, clinical attachment level being the level on a tooth at which the gingiva attaches, with periodontal disease resulting in loss of attachment over time so that the gingiva attaches to the tooth at a progressively more apical (towards the tip of the root) location along the surface of the root with time, a periodontist attempts to get the gingiva to stop receding (at least) and gain attachment, thereby reducing the net loss of attachment over time. I insist that my colleague is confusing CAL, because it can stand for both clinical attachment level and clinical attachment loss, but she insists that they are synonymous, so that when an initial examination reveals 7 mm of attachment loss and post-operative results exhibit only 5 mm of attachment loss, she has "reduced the clinical attachment level." I tell her she may have reduced the net loss, but the level is the spot of attachment, not the displacement span between initial level prior to disease and the current level after disease/therapy. DRosenbach ^{(Talk | Contribs)} 14:54, 23 August 2009 (UTC)

Have you a question? Cuddlyable3 (talk) 19:56, 23 August 2009 (UTC)

Haha...yes. Can level refer to a displacement between levels, or is it strictly a fixed point, based on the above soliloqy? DRosenbach ^{(Talk | Contribs)} 21:50, 23 August 2009 (UTC)

From my understanding of your description, the clinical attachment level would have "risen by 2 mm" after the surgery, whilst the clinical attachment loss would have been "reduced by 2 mm". "Level", as you point out correctly, is the "plane" of the gum´s surface surrounding the tooth, whilst "loss" (or, possibly, "gain", if such a periodontal phenomenon exists) is the distance by which this level decreases (or increases). I must add, however, that the semantics of clinical terminology are not necessarily identical to the meaning of the words in colloquial English. --Cookatoo.ergo.ZooM (talk) 22:10, 23 August 2009 (UTC)

Southwest Pacific islands

Okay, this may be patently obvious, but I don't know what I should call it, plate tectonics, or shallow seas or a subducted Atlantis or... anyway, look at a map or globe, there are random islands in the middle of all oceans, but the only really big concentration is in the southwest Pacific. It's not where two plates meet, and they're not big or spectacular in terms of the ring of fire, but there sure are a bunch of them. Any answers as to why the islands are clustered there, and not in other corners of the Pacific or in the Atlantic or Indian? Chris (クリス • フィッチュ) (talk) 16:38, 23 August 2009 (UTC)

Actually most of those islands you are talking about are located at where the australian plate meets the pacific plate. So your statement that " It's not where two plates meet" is not accurate. Most of the islands that are not located at plate boundaries, such as the Hawaiian islands, are caused by hot spots. Dauto (talk) 17:07, 23 August 2009 (UTC)

Also see Zealandia (continent) which is a microcontinent split off the Australian continent, dozens of millions of years ago, that includes quite a few of the islands. Graeme Bartlett (talk) 22:24, 23 August 2009 (UTC)

History of mind uploading

Right now I'm involved with an on going debate over some OR in the quantum mysticism article. In the process an interesting question was raised "is there an example of the idea of duplicating or copying consciousness before 1957-1962 in either philosophy of sci-fi?" I found these two "early" examples but I assume they are not the first.

• Clarke, Arthur C. (1956). City and the Stars, The. Spectra. ISBN 0553288539.
• Neumann, John Von (2000). The computer and the brain. Yale University Press. ISBN 9780300084733. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help) which was also prepared in 1956 and first published in 1958.

My question is: what is the first example of the idea of Mind uploading.--OMCV (talk) 16:42, 23 August 2009 (UTC)

Hmm. The concept of moving a mind to a different physical "body" is probably older than civilization, but the concept of doing so by copying data might not be much older than the sources you mention. If Asimov had been familiar with such an idea, he probably would have written about "uploading" human minds to the positronic brains of his robots, but I don't recall such a theme in any of his stories. Looie496 (talk) 18:36, 23 August 2009 (UTC)

The djinni was loaded mind-and-body into the lamp of Aladdin in ancient arabic folklore. I might use the expression "download" rather than "upload". Cuddlyable3 (talk) 19:51, 23 August 2009 (UTC)

November 1956: The Last Question (a short story by Isaac Asimov) talks about the minds of all of humanity becoming a part of "Multivac" - a gigantic artificial intelligence. SteveBaker (talk) 19:53, 23 August 2009 (UTC)

Thanks for the comments, I'm going to have to read The Last Question soon.--OMCV (talk) 02:18, 24 August 2009 (UTC)

In defiance of copyright, the story is hosted by the Multivax website; that site also has other derivative and original commentary related to the story. Nimur (talk) 08:07, 24 August 2009 (UTC)

Please note that I didn't say it was a good story! (But at least it's short). SteveBaker (talk) 22:44, 24 August 2009 (UTC)

Three questions about potato

1. Does a potato have a skin, or is the surface of a potato just dried and oxidised potato matter due to exposure (as found in onions)

2. It is said that the 'stolon' from which a potato grows is a sort of enlarged lateral root. I have seen the root vessels in primary root crops such as carrot, but not in a potato. Is there a root system to be seen inside a potato when cut? (It seems uniform) - A picture?

3. Does the potato grow from the outside surface, or something else?83.100.250.79 (talk) 19:15, 23 August 2009 (UTC)

My understanding is that potato skin is a kind of cork-type tissue made of suberin. --Sean 21:26, 23 August 2009 (UTC)

Decaying stew

Potato, carrot, onion, parsnip, swede, gravy, and beef.

How often can I reheat this daily before it becomes dangerous or inedible, and why will it become so? Vimescarrot (talk) 19:20, 23 August 2009 (UTC)

If you heat it to boiling, I don't see why you couldn't keep doing it indefinitely. The vegetable matter will gradually turn to goo, but there shouldn't be any harmful consequences unless you take it to absurd extremes, and even then I don't see what the harmful consequences would be. Looie496 (talk) 19:26, 23 August 2009 (UTC)

If you heat it to boiling frequently enough, it will last forever. See Perpetual stew. Red Act (talk) 22:00, 23 August 2009 (UTC)

Hiroo Onoda claimed to have killed a cow about once or twice a year; and preserved it by boiling a beef stew once a day, every day, until the meat ran out a few weeks later. This is debatably quite unhealthy; but he was in a survival situation. "If we left the carcass as it was, the rain and the crows would reduce it to a skeleton, but the remains would tell the enemy where we were. After we cut the cow up, therefore, we moved the carcass along a mountain road to as distant a point as possible... For the first three days, we would have fresh meat, broiled or stewed, two times a day. Presumably because of the meat's high calorie content, as I ate, my body temperature climbed until I felt hot to the soles of my feet. It was hard to breathe... On the fourth day, we piled up as much meat as possible in a pot and boiled it. By heating this up once every day and a half or two days after that, we kept it from spoiling, and the flavor held up for a week or ten days. While we were eating the boiled meat, we dried what was left for future consumption. We called this dried meat 'smoked beef.' ... From one cow, we could make about 250 slices of smoked beef. By eating only one slice a day, we could make the meat last for about four months." (No Surrender, chapter "Jungle Life", 1974). His biggest complaint was the flavor - the gruelish soup was very unappealing, but by adding some "magic medicine" (a tiny amount of briney sea-water for salt), he and his comrades found it palatable. Nimur (talk) 22:19, 23 August 2009 (UTC)

This is great! I KNEW about the perpetual stew and master stock idea, but for some reason i let my fiance convince me that you shouldn't reheat soup more then once. We always fridge our soup and only reheat the portion we need, but sometimes we waste some if we reheat too much.. Now I'll know better.Vespine (talk) 02:37, 24 August 2009 (UTC)

Are going to listen to your fiance or to some random anonymous internault? Dauto (talk) 04:45, 24 August 2009 (UTC)

FWIW, I have often (during the last 30 years) kept such a stew going for weeks to months with no ill effects. If you're willing to trust random internet advice, some tips are:

1. use a saucepan or pot with a closely fitting lid, and big enough to initially make a volume more than twice what you're going to eat in one sitting;
2. once you've ladled out a serving, replace the lid and don't lift it until the next time you start to heat (to minimise incoming bacteria/mould spores);
3. keep the outside of the pot, and the inside surfaces above stew-height, as clean as possible;
4. try to reboil no less frequently than every other day, but don't worry about any minor surface scum/growth, which the boiling will neutralize;
5. bring to the boil slowly with stirring and bottom scraping (to avoid a burnt bottom layer) and then simmer for at least 20 minutes;
6. during each reboil, add further washed raw vegetables, diced or sliced small, equal to the volume you ate last time in the order of their need for cooking, thus ensuring the presence of non-gooey components;
7. avoid over-dryness by adding water and/or soup when necessary (canned cream of tomato makes an excellent base stock);
8. thicken up with gravy powder or instant soup powder when necessary and if available; add pre-cooked meat such as mince or canned (and diced) meatballs from time to time;
9. use pre-cooked canned vegetables such as baked beans, chopped tomatoes or sweetcorn if and as convenient;
10. don't add all the new ingredients in one go, so as to avoid cooling too far below simmering level.

It's not Cordon Bleu, but it works for me. Note that the above assumes only one or two consumers, eating together; for a large enough household, instead of periodic reboiling it might be more convenient and more hygenic to keep the pot/cauldron simmering continually. 87.81.230.195 (talk) 12:47, 24 August 2009 (UTC)

"...don't worry about any minor surface scum/growth" ? Ewww ! If you see mold on it, toss it out. Molds can release toxins that aren't neutralized by boiling. Another hint: don't use any cream soups or milk, as that will tend to cause scorching at the bottom and/or boiling over. To end up with a reasonable amount of sodium, combine fresh veggies (containing little or no salt) with soups, canned vegetables, etc. (which often have way too much salt). You can also put something spicy in, like salsa, instead of making it salty. And, if you serve with salty crackers, then the stew doesn't need to be as salty. StuRat (talk) 21:46, 24 August 2009 (UTC)

I'm curious Stu. You aren't advocating less salt in the diet, since you're eating salty crackers with it, just less salt in the stew. Any reason why or is it just personal preference? I think one of the benefits of the salty stew is that it would probably have an added preservative effect. Vespine (talk) 22:56, 24 August 2009 (UTC)

I do advocate less salt in the diet. The point of adding salty crackers is that you can make the stew with a low level of sodium, which some members of the household will eat directly. For those who like saltier foods, they can add crackers. Of course, they could also add salt to their individual bowls of stew, but then you'd first have to listen to their complaints that the stew is "bland" (that is, lacks sodium). If they add crackers before even tasting it, they may never make such negative comments at all. StuRat (talk) 15:18, 25 August 2009 (UTC)

Why on Earth would you make this a regular habit? 67.243.4.208 (talk) 16:40, 24 August 2009 (UTC)

Because it's easier to make stew once, and reheat it, than to make stew twice. Thanks for all the answers, guys! Much appreciated. Vimescarrot (talk) 18:12, 24 August 2009 (UTC)

Also note that softening up of the stew contents over days isn't necessarily bad. Some items may be too hard to eat at first, but eventually become soft enough to eat. After several days I can eat a chicken back, discs and all, for example, and get my calcium for the day. StuRat (talk) 17:38, 25 August 2009 (UTC)

Turkey thing

What do you call the floppy thing that hangs down from the beak of a turkey? --✶♏‭ݣ 23:28, 23 August 2009 (UTC)

Wattle (anatomy). --Tagishsimon (talk) 23:29, 23 August 2009 (UTC)

Thanks!! --✶♏‭ݣ 23:32, 23 August 2009 (UTC)

The wattle hangs from under the chin. The snood hangs over from on top of the beak. Here's an impressive one. --Sean 12:55, 24 August 2009 (UTC)

Hmm, now I am curious. Does anybody know what purpose these growths serve? Are they sexual characteristics or something different? Maelin (Talk | Contribs) 03:36, 25 August 2009 (UTC)

I think they serve to attract females. FWiW 98.234.126.251 (talk) 08:21, 25 August 2009 (UTC)

Am pretty sure that the turkey in the photo IS a female. Googlemeister (talk) 14:30, 25 August 2009 (UTC)

Both males and females have wattles, but generally speaking, the male wattles are bigger. (Sort of like breasts in humans, only the other way around.) FWiW 98.234.126.251 (talk) 03:53, 26 August 2009 (UTC)

August 24

Digging yourself out of a hole

If I was in a hole that was say, 10ft deep and 4ft wide and only had a shovel could I dig myself out? I've been thinking about this for ages and everyone I ask has a different opinion! Has anyone ever done it? Thanks Smartse (talk) 03:09, 24 August 2009 (UTC)

You could dig away at the walls to continually add dirt to the floor, thereby making the pit more shallow as you dig, until you could climb out. DRosenbach ^{(Talk | Contribs)} 03:16, 24 August 2009 (UTC)

I can't think of why you "couldn't" dig your self out? The hole is 4 foot wide, that's pretty narrow, i imagine it would be difficult to manipulate a shovel which is probably at least 4 foot long, but you don't need to have the shovel horizontal. As the above says, scrape away at the sides to fill the hole up with dirt and eventually just climb out, might not be "easy" but i don't see anything impossible about it. It's not like picking yourself up by the shoe laces. Being 10 foot deep i suppose you should also worry about caving the hole in around you if you dig away at one side too much, which would be bad. Vespine (talk) 04:24, 24 August 2009 (UTC)

Caving in would be the problem, all right. If you could reach the top of the hole with the shovel there would be no problem: widen the hole at the top so that earth falls to the bottom, and then stand on this earth. But in a 10-foot hole you can't reach the top, so the best you can do is excavate the sides to get earth to stand on. But then this creates an overhang, which may be unstable. It depends very much on the characteristics of the earth that the hole is in, but since the problem is hypothetical in the first place, we don't know about that. You might be able to excavate the sides of the hole enough without collapsing the ground above you, or you might not.

It's also possible with a hole only 10 feet deep that even if you did cause a cave-in, it still might not keep you from getting out, because the amount of earth that spills into the hole might not be enough to hurt you. If you can extract yourself (and the shovel) from the collapsed earth and stand on top of it, you now have a shallower hole -- repeat the process and you're out.

--Anonymous, 05:01 UTC, August 24, 2009.

"But in a 10-foot hole you can't reach the top..." -- If you're 6 feet tall and got a 4-foot-long shovel, then yes you can. 98.234.126.251 (talk) 05:12, 24 August 2009 (UTC)

Hmm, good point. I wasn't thinking of the shovel as being usable that far overhead, but even if you can't quite reach the top, you can get near enough that a cave-in of the earth above where you're digging would not release enough earth to bury you. So unless you or the shovel are very short, the answer is yes, you should be able to dig out by working on the walls as high as you can reach. --Anon, 16:18 UTC, August 24, 2009.

A 4ft shovel seems pretty long and remember that your shoulder is ~1ft below your head. Smartse (talk) 19:52, 24 August 2009 (UTC)

Yes, "your shoulder is ~1ft below your head", but why would you have to hold the shovel from shoulder height (i.e., not exteding arms above level)? I can reach my hands over a foot above the top of my head. DMacks (talk) 20:00, 24 August 2009 (UTC)

(After e/c)x2

IF you were careful, I don't see why not. Your goal would be to 1) Remove dirt from the sides of the hole and place it under your feet at the bottom of the hole. and 2) Make the sides of the hole less steep. With a full length shovel you could reach the rim of the hole, so you could widen the hole gradually all the way from the top. (Don't try to "tunnel"; It'll cave-in.) Eventually you'd wind up with a nice cone-shaped hole about half as deep as the original hole. At that point you could just walk out. APL (talk) 05:03, 24 August 2009 (UTC)

You would want strategic digging for controlled cave-ins, to create the sloped, cone-like walls that APL is mentioning. This would require some careful planning and estimation. A catastropic cave-in could easily release enough material to smother you. By studying the way the wall reacts to your digging, I think you could carefully arrange for controlled slides. You'd get pretty dirty, though - even if not you weren't buried, debris from these cave-ins would definitely get on you. Here's a book, partially available online: Rock slope engineering. Chapter 12 has some theory overview on stability considerations for different shaped rock or sediment walls. For a more basic introduction, you can read Angle of repose - this is the maximum stable angle that a particular mix of dirt/rock prefers to take. You want to work the wall of your hole towards that angle - it's currently in an unstable state (assuming it's got "vertical" walls). We also have an article on geotechnical engineering, which has some content related to sediment stability. Nimur (talk) 05:39, 24 August 2009 (UTC)

Seems to me there's a middle position where you'd be standing in hole with a diamond-shaped or kite-shaped cross-section, maybe ten feet across at its widest point, with a large amount of earth about to fall on you. (Also, if instead of instead of aiming at building a slope, you tried the simpler method of removing earth from the sides and flattening it out under your feet, and assuming no cave-ins, there's a Zeno's arrow or limit type of situation where although you keep raising yourself higher the rate of ascent slows down due to the widening of the hole, and you never mathematically reach the top.) 213.122.42.252 (talk) 00:03, 25 August 2009 (UTC)

You don't have to "mathematically" reach the top -- the point of the whole exercise is to get yourself to where you can climb out of the hole with no further assistance. 98.234.126.251 (talk) 00:15, 25 August 2009 (UTC)

Yes, because people have a height. Just as well, really. Tell you what though, if you were a small person with a short shovel then getting out of the hole might take an awkwardly long time, what with progress slowing down as the hole gets wider. 213.122.42.252 (talk) 00:23, 25 August 2009 (UTC)

Why dig? With a four-foot diameter hole you can walk out. Put your back to one side of the hole, lean forward and place your hands on the other side of the hole. Now walk up. 152.16.59.102 (talk) 05:53, 24 August 2009 (UTC)

Climbing_technique#Chimneying requires fairly strong material--gotta be able to hold you up, not just its own weight against a cave-in or other slide. On the other hand, the lateral force as one presses against the dirt. DMacks (talk) 06:15, 24 August 2009 (UTC)

With the exception of extremely sandy soil or swampland, the chimneying technique should work just about anywhere. I've dug enough foxholes in my life to be certain that the tightly-packed dirt just under the surface would support the average person's weight. It is nothing like the loose topsoil at the surface. 152.16.59.102 (talk) 06:46, 24 August 2009 (UTC)

It's also possible to dig even deeper on half of the hole and use that material to build steps up on the other half of the hole. That might buy you 2 to 3 feet that would go a long way towards reaching the top and start widening it to fill the bottom. Dauto (talk) 06:04, 24 August 2009 (UTC)

If it's a good sturdy shovel you might be able to hold it overhead (at, say, 7 feet from the bottom), wedge it between the walls, and then climb onto it and out. But that would be riskier than digging, so use it as a last resort. --Sean 13:37, 24 August 2009 (UTC)

Thanks for the answers! Unfortunately I have kind of lost an argument but at least I know now. It seems as though it definitely does depend on the size hole then as if it where deeper than 10ft you wouldn't be able to reach the top. Can anyone find information on whether anyone has actually managed to do it or will I have to test the theory myself one day? Smartse (talk) 19:52, 24 August 2009 (UTC)

I would not advise you go try this in a personal experiment. Dry soil generally has a density of about 100lb/ft^3. a small slide could easily have over a ton of soil and you could get buried alive. Googlemeister (talk) 20:39, 24 August 2009 (UTC)

Yes, people digging even shallow ditches sometimes get buried alive. If alone they're probably done for. Even with helpers, digging them up (at least enough so they can breathe) before they suffocate is a challenge. StuRat (talk) 21:30, 24 August 2009 (UTC)

I'm not stupid! Don't worry I'm nowhere near a hole at the moment, I just wondered if anyone has actually done it. The theory sounds very convincing but if no one has done it should I really believe the answers? Are you sure about that density too - that is pretty heavy soil where you live. Smartse (talk) 22:13, 24 August 2009 (UTC)

Water weighs roughly 64lb/ft^3 and the soil article reports that it varies between one and two times the density of water, so a density of 1.5gm/cm^3 doesn't sounds particularly heavy. -- Thinking of England (talk) 11:00, 25 August 2009 (UTC)

Responders seem to assume that the OP finds themself in a hole extending downwards in earth that can be shovelled aside but there are other possibilities. If thinking about the situation has been obsessive then it seems to be more a problem in psychology than earth moving. Being buried alive is said to be one of the most widespread of human fears. Cuddlyable3 (talk) 00:43, 25 August 2009 (UTC)

Alternatively, if the hole has a diameter some amount less than the length of your shovel and the hole is less than two body lengths high, you can raise the shovel up to shoulder height, dig the spade end horizontally into the dirt and create a nearly horizontal bar across the hole. Climb up onto that, and climb out. Mac Davis (talk) 14:48, 25 August 2009 (UTC)

extraction of MGO/CACO3 from DOLOMITE/CALCITE

is it possible to extract MGO from DOLOMITE ,CACO3 from CALCITE on a comercial basis ? GRIPTOR (talk) 08:10, 24 August 2009 (UTC)

FYI, calcite is CaCO₃. As for extracting MgO from dolomite: yeah, you could do it easy enough; the only hard part would be separating it from the calcium. You could do it (for instance) by dissolving the dolomite in acid and selectively precipitating either the calcium or the magnesium to separate the two. 98.234.126.251 (talk) 09:07, 24 August 2009 (UTC)

You could calcine the dolomite to turn it to magnesium oxide and calcium oxide. On solution with water, the calcium oxide is more soluble. Alternatively if you dissolve in hydrochloric acid to form magnesium chloride, you can precipitate the magnesium hydroxide by treating it with lime. By heating the magnesium hydroxide you can get back the Magnesium oxide. However this last method would not be economical due to the cost of the acid. You can get magnesium chloride from sea water more cheaply. you may wish to read this: [12]. There could still be impurities such as iron and nickel oxides. Graeme Bartlett (talk) 12:39, 25 August 2009 (UTC)

Calculating cumulative U-values

I have two units of insulation; one being 100mm with a U-value of 0.494 W/m2K and another, on top, 200mm thick with a value of 0.140 W/m2K. I'm not sure how to calculate the cumulative U-value. I assumed I could take the reciprocal of both, add them together (to get 9.16) then take the reciprocal of this value to obtain a cumulative U-value. Is this correct? —Preceding unsigned comment added by 157.203.42.175 (talk) 09:10, 24 August 2009 (UTC)

That sounds to be the right method. If you used the R values you would just add. Graeme Bartlett (talk) 09:27, 24 August 2009 (UTC)

Bouncing X-rays

It is my understanding that x-rays either penetrate or are absorbed, but do not bounce. Is that an oversimplification, or perhaps not even true -- the article makes no mention as far as I can see. My point is that there are these dental assistants who insist on closing the door to the operatory when exposing patients to x-rays, even when the cone is clearly pointing in a direction such that the doorway is in no way in the beam from the machine. DRosenbach ^{(Talk | Contribs)} 13:53, 24 August 2009 (UTC)

To some extend they do bounce back. Otherwise [| X-Ray diffraction] would not be possible. The only part about which one could argue would be how harmful those backscattered rays would be. --91.6.61.154 (talk) 14:06, 24 August 2009 (UTC)

(edit conflict).Mostly they do not bounce - however they can be 'reflected' - using diffraction (an array of silicon crystals is sometimes used to focus x-rays) - that is irrelevant here. I would expect that the assistants are just being over cautious - closing the door may partially prevent some body innadvertantly wandering in when the x-rays are being used, or perhaps to give the patient a little 'privacy' when they are undergoing what is technically an invasive procedure.

On absorbtion of x-rays secondary emission often occurs - a less energetic ray (or particle) can be emitted randomly from the thing it absorbed - this is scattering.

It's mostly likely psychology rather than science.83.100.250.79 (talk) 14:08, 24 August 2009 (UTC)

X-rays can also be reflected by metallic surfaces if they are incident at a very shallow grazing angle. This type of reflection is used in X-ray telescopes. See this page for some diagrams. -- Coneslayer (talk) 14:20, 24 August 2009 (UTC)

Thanx for your answers -- I did forget to mention backscatter potential in the question -- but I was sort of hoping for someone to confirm that it is psychology rather than probably psychology before I go around telling everyone that they're being silly. In principle, I'm against the propagation of ignorance and it really gets me when the assistants threaten to "tell on the students and the residents" when they fail to close the door, thus exposing everyone in the hall and causing undue cases of extra cancer. Can I think of x-rays as billiard balls and the operatory as a pool table, and make sure that as long as the x-rays won't bounce to the door in one bounce, I'll be OK. I mean, certainly after hitting 2 or more walls, the intensity of the rays has dissipated to below even measurable magnitudes -- and that would be even when the wall is metal. DRosenbach ^{(Talk | Contribs)} 14:21, 24 August 2009 (UTC)

Your x-ray lab will have safe operating rules. Do these specify whether the door must be closed? AlmostReadytoFly (talk) 14:36, 24 August 2009 (UTC)

That's just it -- school regulations are based on ignorance, or at least that's what I'm trying to establish. I'm interested in science, not bureaucracy. DRosenbach ^{(Talk | Contribs)} 15:10, 24 August 2009 (UTC)

I don't think it's possible to say beyond a doubt there's no risk since as has been mentioned, there's likely some risk and a large number of variables. Assessing that risk is probably the job of an actuary who may be able to make a resonable assessment, particularly if you limit the variables (e.g. for a specific location) but that's likely a costly process. It's far easier to presume the risk is non negible and take precautions which don't have much of a negative effect then run the risk that something does go wrong and the legal and financial consequences thereof (particularly in the US). This isn't so much bureaucracy as following the cheapest and easiest pathway and there are parallels in many areas of OSH as well as in other areas of life, e.g. mobile phone use in aeroplanes. There are likely also some other concerns that haven't been mentioned, e.g. while I presume there are warning lights when the X-ray is in use, a closed door adds an extra precaution against someone walking in by accident or another e.g. it may be comforting to the people being X-rayed. BTW the psychology element is also not irrelevant since even ifan actuary does decide the risk is less then 1 in 1 trillion, people are notoriously bad at understanding risks and many may still be worried so those writing the rules would likely think it wise give those who worry piece of mind given the small cost to everyone involved. In any case, while you're obviously welcome to challenge any inaccurate claims it seems to me as long as the rules are there, those who agree to follow the rules (and I'm sure anyone working or studying there must have to agree) should follow them, regardless of the reasons for following them. If you can come up with conclusive evidence the risk is too low to be of concern, you're far better off taking that to management and convincing them to change the rules rather then ignoring the rules and expecting everyone else to not care. Nil Einne (talk) 15:43, 24 August 2009 (UTC)

There may also be regulatory issues that the place needs to comply with. APL (talk) 15:53, 24 August 2009 (UTC)

Doors do not stop Xrays very well. Doors however stop people and closing doors is a way of stopping random innocents walking through them and into the path of the beam. Random innocents includes people who cannot read, who are walking backwards pulling a trolley etc etc. Unless the door is lead I think the reason for shutting the door is most likely to be people. As for the Xrays, at the point of generation they are probably going in all directions (from a high energy or radioactive source) so there will be a few heading for the door. --BozMo talk 16:05, 24 August 2009 (UTC)

Just a note, BozMo: there is nothing magical about lead, as though this was x-ray vision. Aluminum attenuates x-ray beams, as does concrete. Lead just does attenuates very well even at minimal thicknesses, and so was used a lot early on. I'm in NJ, and I know the state just modified regulations for dental offices such that lead lines walls are no longer necessary for newly fabricated offices -- double sheet rock is now sufficient (I believe up to 7 feet or so). DRosenbach ^{(Talk | Contribs)} 18:39, 24 August 2009 (UTC)

Yes, x-rays can (and do) bounce. Generally the scattered intensity will be very low relatively to the strength of the primary beam, but cumulative exposure may be significant. A number of processes can contribute to x-ray scattering, but at the moderate energies used for medical x-rays I believe that Compton scattering] is the predominant process. (To be sure, check a copy of Eric Hall's Radiobiology for the Radiologist or similar.) Except under the very specific conditions described above (very shallow grazing incidence, or Bragg reflection from a crystalline material) it is unlikely that 'specular', highly-peaked reflections will be the major contributor to off-beam exposure. In other words, the 'bouncing billiard ball' model isn't going to work for you unless you mean to assume that the balls can bounce at any arbitrary angle off of any surface. (Even then, there will be a very small additional amount of scatter simply during passage through open air.)

Oftentimes, radiation protection practices follow the ALARA ('as low as reasonably achievable') principle. As it is virtually impossible to make firm statements about what minimum dose of ionizing radiation is absolutely harmless, we try to take whatever steps are available to us to reasonably reduce exposure. Sealing the x-ray room in the bottom of an abandoned mine would minimize public radiation exposure, but be prohibitively costly and offer only a small reduction in dose. Closing the door to the room offers a probably-comparable protection, but at virtually zero cost — so it is required.

The rules are usually designed to consider 'worst-case' scenarios, in addition to normal operations. What happens if a resident is just testing the machine (or is teaching students) and happens to have the cone pointed at a weird angle? What happens if someone moves or replaces some of the furniture in the room, so that the scattering geometry becomes more favorable? What happens if the cleaning lady, receptionist, lost patient, or a new dentist on staff assumes that it's okay to enter the room since the door is wide open? If you only leave the door open when you're sure that the beam isn't pointed at the door, are you certain that you've remembered to close it every single other time? If there are a few situations where leaving the door open might be dangerous, but none where it would be harmful to have it closed, then it may be reasonable to require that the door be closed at all times. TenOfAllTrades(talk) 16:50, 24 August 2009 (UTC)

Incidentally, the best person to discuss your specific situation with will be your facility's designated Radiation Safety Officer. The exact title differs somewhat by jurisdiction, but there ought to be a specific responsible individual tasked with organizing radiation safety courses, filling out radiation-related paperwork, and all that. Any information that we provide here may or may not apply to your situation; we also cannot comment on specific regulatory requirements in your jurisdiction. Your RSO should be able to tell you how specific local safety requirements were established. TenOfAllTrades(talk) 16:55, 24 August 2009 (UTC)

I'm very impressed with everyone's contribution. Thank you to all and to all a thank you! DRosenbach ^{(Talk | Contribs)} 18:39, 24 August 2009 (UTC)

I'm really surprised that what *I* think is the most important reason for protecting the staff didn't get mentioned until the last response. In fact, I'd say that cumulative exposure may be significant is a significant understatement :-).

A few shots of dental-grade radiation aren't going to do much damage to anybody; a twice-a-year set plus a full-mouth reference set every 2-3 years for the past 50 years doesn't seem to have hurt me (as near as I can tell). On the other hand, catching a few loose rays 4-6 times a day, five days a week, is an entirely different story.

--DaHorsesMouth (talk) 23:04, 24 August 2009 (UTC)

Cumulative exposure is for sure paramount -- but my question is sort of similar to "is standing 100 feet away any better than standing 20 feet away." In the same vein, if no radiation can be detected past the 180 degrees in which the cone exists, why develop methods of precaution that are based on ignorance? DRosenbach ^{(Talk | Contribs)} 03:31, 25 August 2009 (UTC)

Well, sure, the amount of radiation is an inverse-range-squared thing - so at 100 feet, you're getting 1/25th (4%) of the dosage that you would at 20 feet...and 1/10,000th the dosage the patient is getting at 1 foot. But cumulative effects matter - so doing it 10 times a day for 200 days a year gets you 2000 times the dose you'd have gotten from a single shot. The trouble is that the whole thing is statistical. You can get a fatal cancer from one single event where you were standing 100 feet away behind a foot of lead - or you could get X-rayed once a day for your entire life and never suffer at all...but the odds of either of those extremes happening are very small. Since there is no 'safe' dose - the only thing you can do is to minimise the exposure to everyone and calculate the risk/benefit ratio. SteveBaker (talk) 15:54, 25 August 2009 (UTC)

It looks like the OP needs data on the actual stray radiation. The operatory is obviously equipped with X-ray sensitive film and means of developing it. I suppose one could fix pieces of film close to the generator, on the door and midway and compare the results after varied prolonged exposures. Cuddlyable3 (talk) 00:24, 25 August 2009 (UTC)

It's not my room, so I don't know how well the films will remain when I'm not physically monitoring them, but it's an idea. DRosenbach ^{(Talk | Contribs)} 03:31, 25 August 2009 (UTC)

Everyone who uses the facility on a regular basis should also wear a Film badge dosimeter and have it checked regularly. SteveBaker (talk) 15:57, 25 August 2009 (UTC)

spontaneous endothermic solvation

If some solvation reactions are endothermic (e.g. dissolving NaCl in water) ... why do they spontaneously occur? Or does the entropy term become significant in solvation reactions? John Riemann Soong (talk) 18:53, 24 August 2009 (UTC)

Bingo; you hit the nail on the head. Roughly speaking, as long as the change in the Gibbs free energy (ΔG) is negative, a reaction proceeds spontaneously. Dissolution of a crystalline solid in water is always going to be associated with a big increase in entropy, so the reaction is pushed towards dissolution. TenOfAllTrades(talk) 19:26, 24 August 2009 (UTC)

Why is the entropy term so significant here? I do notice however, a few things... extra fine sugar is more soluble than if you just dissolved regular coarse sugar.... why would the solubility change here? Also, when solubility is like 20 times greater at 100 C than at 20 C for some substances, is this great solubility change generally applicable only for endothermic solvation? (That is, the heat supplies energy for the solvation?) Does stirring or agitation supply any activation energy for the solvation? John Riemann Soong (talk) 12:44, 25 August 2009 (UTC)

Extra fine sugar has a higher surface area, due to the smaller grains - that's why it dissolves faster, I'm not sure that it is more soluble - though maybe you are making a supersaturated solution? which is easier with finer grains for the same reason.

Changes in solubity with temperature - temperature increases favour dissolving (reaction) in an endothermic reaction see [13] also Le Chatelier's principle. Additionally if the entropy increases for a reaction an increase in temperature will tend to make the reaction go further (ie more soluble)

Stirring supplies heat and work to the mixture - which helps the dissolution, very strong stirring could help break up the solid to help it dissolve, it doesn't really supply activation energy - but does help speed up equilibrium by mixing. In an un stirred mixture of sugar or salt in water the solid crystals will become surrounded by a concentrated solution of the same substance - which prevents further dissolution - in this case the dissolving is limited by diffusion of the stronger solution around the crystals into the whole of the liquid. Stirring overcomes this slow diffusion limiting step by constantly diluting the liquid around the crystals. 83.100.250.79 (talk) 14:01, 25 August 2009 (UTC)

Alright, that means the (metastable) solubility won't actually decrease after lowering the solution back to RT, right? Actually I've been suspecting this for some time -- I would would dissolve a heck a lot of sugar into hot boiling water, bring it back to RT (to make custard) and wonder why I didn't observe any sugar dropping out of solution. (Yet however, if I do this for hot tea or coffee, I will notice sugar inevitably dropping out of solution as the tea/coffee cools.) For a while I had this impression that increased temperature created greater interstitial gaps between solvent molecules or some other structural effect (thermal expansion) happened at high temperatures and this led to increased solubility. John Riemann Soong (talk) 15:13, 25 August 2009 (UTC)

Nope, increased temperature doesn't create "interstitial gaps" (at least not to any appreciable extent), what it does is (in lay terms) make the solvated molecules bounce around more and thus make them less likely to stick together and fall out of solution. What you were doing in the custard example was to create a supersaturated solution of sugar -- the sugar concentration was actually more than the solubility limit, but there was nothing there to induce crystallization. Whereas in tea or coffee, you got a whole bunch of other compounds floating around, and some of them may lower the solubility of sugar and/or promote crystallization. 98.234.126.251 (talk) 04:59, 26 August 2009 (UTC)

Custard may stabilise a supersaturated solution, it may bind to either salt or sugar (via donor, or hydrogen bonds). Also it may serve to trap very small crystals of sugar that have come out of solution - in fact the custard may contain a fine suspension of sugar/salt stabilised by the custard which prevents it from crystallising out in the normal way.83.100.250.79 (talk) 12:53, 26 August 2009 (UTC)

Hmmm, later I mix in eggs and milk, and don't notice any sugar dropping out of solution either ... but then again it might be suspended in proteins, albumen and milk fat as the mixture thickens. Basically, what I'm wondering is whether the main mechanism of the added heat is to supply the free energy required for endothermic solvation, or whether it's a kinetic effect...that is, when you lower it to RT, it takes a while for the free energy of the solvated molecules to "decay" and reverse the reaction. John Riemann Soong (talk) 15:53, 26 August 2009 (UTC)

You may wonder, but I doubt anyone knows, it may be both... Note we don't know how much custard, sugar etc you are using, and even if we did, we would probably have very much difficulty finding thermodynamic data to answer your question conclusively...83.100.250.79 (talk) 19:22, 26 August 2009 (UTC)

Also, do we observe the opposite effect -- that temperature increase decreases solubility of say, HCl in water? John Riemann Soong (talk) 17:39, 25 August 2009 (UTC)

That's because HCl is a gas, and therefore comes out of solution at increased temperatures. 98.234.126.251 (talk) 04:50, 26 August 2009 (UTC)

But HCl completely dissociates in water ... how would one distinguish between heat reversing an exothermic reaction and increased vapor pressure of the solutes? John Riemann Soong (talk) 15:53, 26 August 2009 (UTC)

HCl is a special case since it is a gas , and can evaporate, heating it up tends to make it boil off (despite the dissociation) - the effect is common to all dissolved gases. Effectively distillation of the HCl is competing.83.100.250.79 (talk) 21:37, 26 August 2009 (UTC)

According to [14] soldium sulphate is an example of something that decreases in solubility with temperature. See Sodium sulphate

Na2SO4 solubility curve

In general such behaviour is rare, due to the almost guaranteed increase in entropy on dissolution.

Also see my question below Wikipedia:Reference_desk#Sodium Sulphate solubity 83.100.250.79 (talk) 21:32, 26 August 2009 (UTC)

fm transmitter using crystal oscilator119.152.15.223 (talk) 18:56, 24 August 2009 (UTC)

HY AGAIN ITS KIND OF A SILLY QUESTION BUT I CANT HELP CAN I MAKE FM TRANSMITTER USING CRYSTAL(ONE USED IN CONTROLLERS) ONLY AND NO INDUCTOR? ALSO I URGENTLY NEED A FREE FM TRANSMITTER DESIGN BOOK(UPDATED AND UPTODATE)THAT WOULD MAKE ME DESIGN A CIRCUIT MYSELF .....I HAVE TRIED WEBSITES BUT THEY CONTAIN RANDOM MATERIALS...PLZ HELP ME!!!— Preceding unsigned comment added by 119.152.15.223 (talk • contribs)

Please do not post in all caps, because it is the web equivalent of shouting, and please sign your posts with four tildes ~~~~. Were you planning on using integrated circuits, transistors, or tubes in your transmitter in addition to the crystal? What do you have against inductors, which for radio purposes can be made with a bit of wire? Edison (talk) 19:01, 24 August 2009 (UTC)

While crystals make a good oscillator, they usually need some capacitors at the output taps to tune the resonance. Also, the signals tend to be really weak, so you'll probably want an amplifier as well. You can get away without an inductor, (at least, a lumped-element version) - but it depends on your signal quality needs. The biggest question is, do you have test equipment? It's going to be hard to verify that you're actually oscillating, especially if you're playing games with passive tanks and no amplifier, unless you have a pretty good oscilloscope or a spectrum analyzer. As far as free circuit designs, have you looked on the web? I just searched Google, and found a single-transistor VCO (varactor, not crystal) which might suit your needs. What are you looking for? Do you have a frequency range in mind? Do you want tunability? How accurate are your frequency requirements? What are your power, noise, and bandwidth requirements? Do you want to build it entirely from discrete components? You should think about these questions before you dive into the electronics project. If you don't know the answers to these questions (in fact, if you don't know what they mean), you might consider scaling back your design quite significantly - building a wireless transmitter from scratch can be a pretty heavy-duty and difficult hobby project. You might want to think about buying a commercially-available, off-the-shelf TR unit. Here are over 1,000 available types from Digikey. I found some as low as $1 and $2 US. There is no way you can beat those prices if you're building out of discrete components. Nimur (talk) 21:02, 24 August 2009 (UTC)

Here is a cheap ready-made FM transmitter. If you are thinking of making a Voltage-controlled crystal oscillator they can in principle generate an FM signal but its frequency can deviate too little from the nominal crystal frequency to be much use, and the centre frequency is fixed. A crystal oscillator without an inductor must operate at a fundamental crystal frequency e.g. 1 to 20 MHz because a tuned circuit with an inductor would be needed to select a higher harmonic frequency. Perhaps you should forget about using a crystal and instead make, say, a simple LC oscillator, establish that it produces a signal (how? ideally using a spectrum analyzer or an oscilloscope, or you may detect some interference on a nearby radio) to which you add varicap diodes so the frequency can be modulated. That is like the bottom circuit at the reference that Nimur provided except you disconnect from ground the 1µF capacitor shown at the terminal labelled PLL IN (optional) and instead feed your audio signal to the lower end of the capacitor. Cuddlyable3 (talk) 00:07, 25 August 2009 (UTC)

siphon question

I know you can siphon liquid from one container to another, can you do the same thing with gas (the state of matter, not the fuel)? I imagine that the cohesion of the liquid droplets from hydrostatic forces is contributing, but is there a similar driver in a gas such as steam? Googlemeister (talk) 20:32, 24 August 2009 (UTC)

To a first approximation, there is no attractive forces between gas molecules, see Kinetic Molecular Theory and Ideal gas. However under certain extreme conditions this approximation breaks down measurably, see Van der Waals equation. I don't, however, think that under normal conditions a syphon will work for a gas any faster than normal diffusion would. --Jayron32 20:40, 24 August 2009 (UTC)

I would think it might work if you had a very heavy gas (much heavier than the surrounding environment). Just as in a liquid siphon tube, you'd need to avoid getting air bubbles in the tube. This might be tougher than with a liquid, though, as you'd need both ends of the tube to be fully submerged in the heavy gas at all times. Lifting even the downstream end out of the heavier gas briefly would likely fill it with air and break the siphon. StuRat (talk) 21:18, 24 August 2009 (UTC)

I think it'll work just fine with a gas. Pick a heavier than air gas and pretend it's water. It doesn't require "cohesiveness" or whatever. The pressure in one end of the siphon tube is higher than the other...gas flows from high to low pressure. The gas doesn't "know" that it's in a siphon tube...it could be in a pressurized natural gas pipeline goind over a hill or something. Also, being very much lighter than most liquids, the siphon tube could be very tall before it would cavitate (Mercury: 0.7 meters or so, Water: 10-ish meters, CO2: A kilometer or so maybe?)...presumably, you could even use a lighter gas - two inverted fish-bowls full of helium with a U-shaped tube between them should allow helium to flow from the lower bowl to the higher one. SteveBaker (talk) 22:35, 24 August 2009 (UTC)

Sulfur hexafluoride is a gas that is sometimes used for these kinds of experiments because it is non flammable and non toxic and very heavy for a gas. You can find vidoes online of an experiment of a paper boat floating in a fish tank half full of SHF. It looks just about how you'd expect it to look if it was floating on water, except the tank looks empty. I agree with what Stu has said about the both ends needing to be submerged. With a liquid, the liquid density is sufficient to stop air climbing up the hose and breakind the syphon, but with gas, the density isn't there and I think air would get into the end of the hose. Vespine (talk) 22:51, 24 August 2009 (UTC)

Our siphon article asserts that it works exactly because of the cohesiveness, and not because of the pressure difference between the source and the sink. --Sean 23:52, 24 August 2009 (UTC)

No, it doesn’t. The opening sentence says “…the flow being driven only by the difference in hydrostatic pressure…”, and Siphon#Explanation using Bernoulli's equation involves only pressure. “Cohesiveness”, i.e., tensile strength, is only mentioned in the Siphon#Vacuum siphons section as being a secondary effect, that can overcome the normal height limit imposed by purely pressure considerations. Red Act (talk) 00:46, 25 August 2009 (UTC)

Yes, it does:

Liquids can rise over the crest of a siphon because gravity pulls on the greater weight of the liquid in the longer outlet leg ... A common misunderstanding of siphons is that atmospheric pressure is pushing the liquid over the barrier. This is easily disproved by noting that atmospheric pressure pushes equally on the surface of the liquid at both the inlet and outlet of the siphon. Thus atmospheric pressure contributes no net force on the liquid in either flow direction.

Emphasis mine, but obviously if there's pulling going on it needs cohesion. They go on to give an analogy about trains where the train couplings represent the liquid's cohesiveness. I believe the difference in hydrostatic pressure they're referring to is the low pressure caused by the pulling/evacuation, not the difference in air pressure at the surface of the two reservoirs, which would cause pushing, and is lower on the high reservoir in any case. --Sean 12:54, 25 August 2009 (UTC)

The difference in pressure is due to the downstream tube having more length pointing downward, which means more gas and mass being pulled downwards by gravity. So, if a gas siphon wouldn't work, as you claim, what do you say would happen ? Would you get a vacuum in the tube ? Would the tube remain filled with gas but just refuse to flow ? StuRat (talk) 15:02, 25 August 2009 (UTC)

It’s not true that “if there’s pulling going on it needs cohesion”, when it’s gravity that’s doing the pulling. If you drop an object in a vacuum chamber, gravity will “pull” it toward the earth, even though there’s no material providing cohesion in between the object and the Earth.

Yes, it’s true that atmospheric pressure isn’t what causes the net force on the liquid. There is, however, a difference in hydrostatic pressure between the source and the sink, due to the greater weight of the liquid in the longer outlet leg. Namely, the difference in pressure due to the weight of the liquid is $\rho gh_{c}$, where $\rho$ is the density of the liquid, $g$ is the gravitational acceleration, and $h_{c}$ is as on the diagram in the siphon article.

The cohesion of the liquid is only important in that it prevents the liquid from changing to a very low density state, not because the cohesion is what conveys the force in the siphon (or not mainly, anyway). The main thing that conveys the force is the pressure. The couplings on the train analogy really just confuse the issue, and make for somewhat of a bad analogy. A better analogy would be to discard the couplings between the cars, letting the cars just push against each other but never pull, and put an engine on both sides of the train, pushing inward, to represent the air pressure on both ends of the siphon. The two engines push inward with equal force, so provide no net force on the train. But the extra weight of the cars on the longer side of the hill overcome some of the force provided by the lower engine, so the net force on the train is toward the lower side. But there is no net flow at all if the upper engine doesn’t provide enough force to push the trains on its side of the hill to the top, which is analogous to the maximum height of the siphon being when the atmospheric pressure just balances the pressure $\rho gh_{b}$ Red Act (talk) 15:29, 25 August 2009 (UTC)

P.S. Some actual numbers may be useful here to show that it’s pressure, not cohesion, that’s of primary importance in a siphon (unless the siphon is extremely thin, such that capillary action dominates). According to the surface energy article, the energy of cohesion per unit area of a substance is twice the substance’s surface energy per unit area. That article lists the surface energy per area of water as being 0.072 J/m², which means that water’s energy of cohesion per area is 0.144 J/m². 0.144 J/m² is only enough to lift water by about 3.8mm. Think about a water droplet forming. The droplet can only get about 3.8mm high before gravity overpowers the cohesion of the water, and the droplet falls away. In contrast, one atmosphere (unit) is enough to lift water by about 1033cm. So one atmosphere of pressure is about 2700 times as strong as the water’s cohesion. That’s why when showing the calculation for the maximum height of a siphon, the siphon article just takes atmospheric pressure into consideration, and completely neglects the effect of the liquid’s cohesion. Red Act (talk) 17:46, 25 August 2009 (UTC)

Thanks for those numbers, they really help to settle the argument. StuRat (talk) 15:23, 27 August 2009 (UTC)

Dr Jeffrey Arnett's theory of Emerging adulthood

How well accepted is this theory in the scientific community? It seems that this theory focuses only on opinions of perceptions of people in that age group. Also does this theory not contradict the concept of adolescence (the transitional phase between childhood and adulthood)? It seems to me that this proposed stage is a transitional stage between a transitional stage and the resulting stage. His theory seems to propose that Emerging adulthood is a transitional stage from adolescence to adulthood. It also seems that this proposed stage of emerging adulthood is longer than adolescence itself. 86.140.47.91 (talk) 23:12, 24 August 2009 (UTC)

Here's how to figure out how much attention the idea is getting: go to Google Scholar, and search for "Jeffrey Arnett Emerging adulthood". Look at the top entry, and you see "Cited by 1226". That means that the paper has been cited by 1226 academic publications, a huge number. The idea may or may not be widely accepted, but it's definitely getting a lot of attention. You can click on the "cited by" link to get a list of the papers that cite it, in order of "google weight". Looie496 (talk) 02:28, 25 August 2009 (UTC)

August 25

Immunity to disease/infection/etc

As far as I understand it, your body keeps a sort of inventory of diseases that you've been sick from (colds, flus, etc) so that it can fight it off again the next time it shows up. Some are only kept in this inventory for so long, right? Why do some stay in this inventory while others do not? Dismas|^(talk) 00:38, 25 August 2009 (UTC)

Right? Not sure. If you're wondering why we can catch colds repeatedly, "At least 99 serotypes of rhinoviruses affecting humans have been sequenced." That is to say, there's a lot of potential for catching a superficially different cold. 213.122.42.252 (talk) 01:09, 25 August 2009 (UTC)

There are actually about 120 types of rhinovirus, the agent behind the common cold -- that gives you just enough for about 2 colds a year for 60 years. That's what the microbio professor said in dental school. As far as antibodies go (they are the entities your B lymphocytes produce to "remember" the various foreign antigens that present themselves to your immune system), they will last forever. That doesn't necessarily mean that the actual immunoglobulin protein particle lasts for 20, 30, 40 or 80 years, but rather, a circulating bunch of these guys will be produced by your memory cells (a type of mature B cell, as mentioned above) at all times, to combat any antigen (i.e. new foreign attack) that presents itself. I'm no immunologist, so I'm unsure exactly why boosters and other advanced techniques are necessary -- I think boosters serve to add to your body's protective potential, so that a defensive strike will happen faster and more strongly than otherwise. You can check out the above linked articles for more info. DRosenbach ^{(Talk | Contribs)} 01:55, 25 August 2009 (UTC)

Immunologic memory, the ability to respond to antigens previously encountered, persists for variable lengths of time depending on many factors, including the type and intensity of the initial stimulus (e.g. infection versus vaccination), the condition of the host (e.g. healthy versus immunosuppressed), the type and intensity of the initial immune response, and any re-exposure that might boost the initial response. Contrary to what DRosenbach said, B cells certainly don't live forever. The plasma cells (which are generally not considered B cells, because they lack many important characteristics of B cells) that produce most of our antibodies may live for decades, but even they slowly decay. Some T cell responses are so intense that they seem to last indefinitely, but most of them can be shown to wane, too. So, designing a vaccine, or understanding why some infections can be repeated in the same host, depends on a lot of nuanced conditions. --Scray (talk) 03:01, 25 August 2009 (UTC)

Contrary to what Scray said, I did not say that B cells live forever. What I did say was "As far as antibodies go (they are the entities your B lymphocytes produce to "remember" the various foreign antigens that present themselves to your immune system), they will last forever. And then I qualified that by stating I am not referring to actual proteins enjoying an existence of 60-100 years, but rather a cumulative, overlapping sort of "you will be covered for life" concept. DRosenbach ^{(Talk | Contribs)} 03:34, 25 August 2009 (UTC)

Sort of like saying "Sir, your circulatory system will last your entire life," even though blood cells die off after 3 months, endothelial cells die off after a few weeks/months, etc. It's the overlap -- like shingles. DRosenbach ^{(Talk | Contribs)} 03:44, 25 August 2009 (UTC)

Your use of the term "shingles" in this context is highly relevant (inadvertently, perhaps), since shingles (the medical condition) is due to waning immunity to a virus. --Scray (talk) 03:38, 28 August 2009 (UTC)

No, antibody responses wane over a period of years, and B cell clones are unique, not interchangeable like roofing shingles are. For example, the third injection of Hepatitis B vaccine results in greater durability (duration) of antibody titers, but they still wane over time. Antibody and cellular immune responses to Hepatitis C virus dropped below detectable levels two decades after accidental infection (PMID 10802716). --Scray (talk) 03:52, 26 August 2009 (UTC)

(EC) For things like the flu the virus mutates fast enough that resistance quickly diminishes since there will be new strains your body can't effectively recognise. This is one of the reasons why Influenza vaccines are only considered effective for about a year. The article provides some detail on this, as well as how the strains are chosen each year. Nil Einne (talk) 03:04, 25 August 2009 (UTC)

Inaccuracy of Significant figures

In chemistry class today, we were doing some practice problems on the use of significant figures, and on one of the problems to have the right number of significant figures, you had to lop off an entire 500,000 from the answer. To me, this makes the answer very inaccurate, and it made me wonder: when exactness is sometimes the matter between life and death, or the success of, say, a mission to Mars rides on accurate calculations, what is the point of significant figures? Also, are there any examples of times when using significant figures could cause fatalities that might be prevented by the non-use of significant figures, or even times when this has actually happened? Ks0stm ^(T•C) 02:08, 25 August 2009 (UTC)

In real life you would not "lop off an entire 500,000" unless the measure was so imprecise that the 500,000 was far less than the expected error. The point of significant figures (your teacher should be telling you this) is to avoid giving a false impression of the accuracy of the measurement. Suppose I estimate the height of a building by dropping a rock from the top and timing how long it takes to hit the ground. Suppose the time is about 3 seconds -- I do a calculation using the Earth's gravitational constant, and get a height of 144 feet. But if I give 144 ft as the answer, I'm misleading you, because that 3 second value really just means anything between 2.5 and 3.5 seconds. I will give you a more accurate impression of what I actually know if I say "around 150 feet, probably". Looie496 (talk) 02:18, 25 August 2009 (UTC)

500,000 may be well below the ability to measure accurately if you were, say, calculating the age of a star. If you can only estimate the age of a star to within, say, 50 million years one way or the other, and result which pretends to have an accuracy down to 500,000 years is bullshit. That's the point of significant figures; if the you are writing a non-zero digit in that place, what you are saying is "I know that this number really is THIS NUMBER". If you cannot say that for certain, than regardless of what your calculator tells you, you shouldn't write it down.

Look at it this way. Say I have a scale that measures to 0.01 grams accurately. Lets say that I measure exactly 50.00 grams of a sample, and then lets say that I want to divide my sample into seven equal portions. So I get out my calculator, and divide 50.00 by 7 and get 7.1428571428571428571428571428571. So, why do I not indicate that every sample is exactly 7.1428571428571428571428571428571 grams? Because everything after 7.14... is bullshit; because my measuring device cannot measure that small. Anything after the 0.00 mark is not significant. THAT is what significant digits means; its the fact that our numbers are limited by the precision and accuracy of our best measurements, and doing a simple mathematical operation cannot change how precise your numbers are. --Jayron32 03:01, 25 August 2009 (UTC)

Reminds me of the old joke : A tour guide is showing off some dinosaur bones and a student asks how old the bones are. The guide replies "One hundred million and three years.", The student is astonished. "How can you know the age of the bones with such amazing precision?", he asks. "Easy," replies the guide, "When I started working here they told me that it was one hundred million years old, and that was three years ago!" APL (talk) 03:24, 25 August 2009 (UTC)

But 7.14 * 7 = 49.98, and your scale is accurate enough that you know for a fact this is the wrong figure ... and so is 7.15 (which gives 50.05). So, 7.143 then. 213.122.42.252 (talk) 03:19, 25 August 2009 (UTC)

True, but which of your seven samples contains the extra bits that add up to the .02 loss? You cannot be certain; that's the inaccuracy of this. You know that a few of your samples will be VERY slightly heavy or VERY slightly light of the 7.14 figure; but you just cannot tell which ones are off and by how much, you just know its not enough to change the numbers on the scale. --Jayron32 15:31, 25 August 2009 (UTC)

I think part of the confusion relates to what we're discussing here. If you start off with 50.00g and have some magical (okay there are few situations where magic isn't required) way of dividing it by 7 then you end up with samples that you can say are 7.143g. IRL, there's no magic so commonly if you have 50 g and want to divide it by 7 what you would do would be to take 7 samples that are 7.14g using the scale Nil Einne (talk) 18:13, 25 August 2009 (UTC)

Note also that that in any scientific work where the amount of expected error is important, people don't rely on just quoting things to the appropriate number of significant figures -- those are just a rough indication of the expected error. If 3 seconds really meant that you were confident it was be between 2.5 and 3.5, you'd write "3 s ±0.5 s". Now 2.5, 3.0, and 3.5 seconds correspond to heights of 101, 145, and 197 feet (rounded to the nearest foot, but using a more accurate gravity value than Looie). Then the answer might be written as "149 ft ±44 ft"; here 149 was obtained by splitting the difference between the high and low numbers. But if it was felt that exactly 3 seconds was the most likely value, then the result might be written as "145 ft +52 ft -44 ft", showing specifically the expected error amount on the high side and the low side. --Anonymous, 03:08 UTC, August 25, 2009.

+/- factors are usually based on confidence intervals based on the number in the sample size; a single measurement does not really have a confidence interval, so in the case of a single measurement, such +/- factors are not usually reported. If you make 100 repetative measurements, the +/- factor would be different than 1000 repetative measurements, and the +/- reported should reflect that, based on the standard deviation from the mean value. With a stand-alone measurement, such statistical analysis is meaningless. However, stand-alone measurements are still limited by the precision of the measuring devices, and so still have significant digits... --Jayron32 03:16, 25 August 2009 (UTC)

The precision of the measuring device still may be such that a confidence interval is appropriate. If you can read it to within a quarter of whatever the appropriate unit is, then it's perfectly reasonable to record a reading as "42.25 ±0.25", and this is more useful than just writing it down with either 2 or 3 significant digits. (Of course, if you are recording a series of measurements, you won't repeat the ±0.25 on each one.) --Anon, 09:03 UTC, August 25, 2009.

(After edit conflict : Sig figs are not used for serious calculations in the scientific world. They're better than just punching numbers into your calculator blindly, but ideally you should be calculating the margin of error of your measurements, and then calculating the min value and the max value through your entire set of calculations. Surprisingly, sometime the answer you'd get by using significant figures is OUTSIDE the properly calculated min/max. In the "real world" significant figures are mostly just used for back-of-the-envelope type calculations. Great for quickly working something out on the whiteboard, but bad for sending someone to Mars. APL (talk) 03:21, 25 August 2009 (UTC)

The height of Mt. Everest was in the 1950s stated as "29,00229,003" feet. The actual best measurement, from a careful 1855 survey, was 29,000 +/- 3 feet, but for a century they expressed the height as "29,003 feet" to clarify that it was not "29,000 +/- 1000 500 feet." Strangely there have been several careful height measurements in the past few decades which give inconsistent heights which differ by more than their stated uncertainties. If I recall correctly, numerous physical constants such as the speed of light have been stated over the years with values which differ more than their stated uncertainties. The older measurements should have had stated uncertainties broad enough to encompass the more recent and more exact figures. But scientists like to claim their results are more precise than they really are. A lot of time in college science and engineering labs was wasted trying to measure things with greater accuracy than the crummy instruments permitted. Points were taken off if the "correct" result was not obtained,regardless of the fact that, say, a 3 mm high sine wave on an oscilloscope cannot be measured with high accuracy. Edison (talk) 04:10, 25 August 2009 (UTC)

The second question by the OP is the wrong way round. There are sure to be examples where the non-use of significant figures caused accidents that could have been avoided by proper use of significant figures. An example might be a diver who relies to the last second of his calculated air supply capacity 47.123 minutes when the calculation uses the oxygen tank pressure measured by a gauge that is accurate to only 5%. Cuddlyable3 (talk) 08:16, 25 August 2009 (UTC)

Adding a decimal point at the end of a number means it is ± 5, so "29,000." would be one way to specify it, although the actual error is ±2. The more difficult problem is how to specify 29,000 ±50 using significant digits. I've never much cared for significant digits, myself, and think ± values make a lot more sense. StuRat (talk) 14:34, 25 August 2009 (UTC)

You wouldn't be annoyed to see a paper give a value of 2528.41567 ± 108.64372? Looie496 (talk) 18:42, 25 August 2009 (UTC)

Haha. What about 2528.41567 ± (108.64372 ± 5.72318)? Dauto (talk) 20:03, 25 August 2009 (UTC)

It wouldn't annoy me in any case where that accuracy might be helpful. If they are giving the weight, in pounds, of a particular model of car, then that would be rather silly, yes. StuRat (talk) 15:46, 26 August 2009 (UTC)

Why old colour televisions with Cathode Ray tube show reddish colour when swithched on?

Yesterday when i was seeing television suddenly power went off and again came back suddenly. My television with cathode ray tube showed reddish effect.Why? —Preceding unsigned comment added by Sdbhadra (talk • contribs) 06:23, 25 August 2009 (UTC)

Could this be a phase error resulting in misalignment of the beam (e.g. hitting the wrong element of an aperture grille?) It seems plausible that on cold-start, temperature or voltage some other parameter is out of the steady-state value, resulting in a small phase-error in the timing of the raster-scan beam. Nimur (talk) 06:33, 25 August 2009 (UTC)

Colour TV CRTs have 3 beams for red, green and blue. Alignment of the beams is adjusted by "purity" magnets on the neck of the CRT; it is not a matter of signal timing. The overall colour cast of the picture is depends on the beam currents which are trimmed by 6 separate electrical controls i.e. one for each beam, bright and dark. The OP's reddish effect could be due to upset of these controls or uneven wear of the CRT guns. Cuddlyable3 (talk) 08:04, 25 August 2009 (UTC)

Most old TVs had manual adjustment knobs to correct for these problems. Usually, these were located under a panel or around in back of the TV. Look for a removable panel of some sort; you should find knobs that will allow for color, brightness, and contrast correction. --Jayron32 15:27, 25 August 2009 (UTC)

Is the issue transient (it came back reddish and then eventually equilibrated back to normal) or is it permanently changed after this event? DMacks (talk) 22:28, 25 August 2009 (UTC)

Jump the Moon

If I jump when the moon is directly overhead how much longer do I spend in the air? What about when it is on the horizon or directly underneath me? TheFutureAwaits (talk) 10:19, 25 August 2009 (UTC)

(all units below are in metric/SI units)

As an estimate, the acceleration due to gravity is 9.8m/s2 (I assume an average) , the moon weighs ~7.4x10^22 kg, and is at a distance of ~380x10^6 m

F=GM1M2/r^2

So acceleration on a mass =

a= F/M1=GM2/r^2 

which is (G=6.7x10^−11) :

6.7x10^-11 x 7.4x10^22 / 3.8x10^8 x 3.8x10^8
3.4 x 10^11 x 10^-16
3.4 x 10^-5

or 0.000034 m/s2 (no attempt made to avoid compound rounding errors)

Acceleration is a vector, so it can be added and subtracted to the mean acceleration

Giving an estimate of the min and max accelerations due to gravity of

9.8+/- 0.000034

As you can see the change is so small that it's not really work calculating the difference in times for the jumps.

Jump starts with velocity V , the time to accheive velocity -v (ignoring losses this is the velocity on landing) = 2v=0.5at^2

or t^2 = 4v/a

time = 2 sqrt(v/a)

Can you take it from there?83.100.250.79 (talk) 11:35, 25 August 2009 (UTC)

Interesting, what about the Sun? It's much heavier but also much further away. I wonder if athletes gain a performance advantage during the day versus at night? TheFutureAwaits (talk) 13:06, 25 August 2009 (UTC)

Actually I just tried the math with the sun's values and because the magnitude drops with the square of distance it's even less of an impact. TheFutureAwaits (talk) 13:17, 25 August 2009 (UTC)

Could a two body system exist where the phase of one would singnificantly affect the length of a person's jump? Say two large planets closely orbiting each other? TheFutureAwaits (talk) 13:17, 25 August 2009 (UTC)

I assume it COULD, but both planets would probably be terribly ripped apart due to the gravitational effects (see Jupiters Moon IO, or take the effect the moon has on the oceans and multiply it by 10,000. Chris M. (talk) 14:24, 25 August 2009 (UTC)

Plugging the moon's Roche limit (9496 km) into 79's math will give you ~0.054 m/s² of vert, so still not much. --Sean 15:08, 25 August 2009 (UTC)

That's because 79's math is wrong. He used the moon's bare gravitational atraction which falls with the square of the distance. He should have used the moon's tidal force which fall's with the cube of the distance. Dauto (talk) 16:58, 25 August 2009 (UTC)

The Earth (and anything on it) and Moon are in free fall with respect to each other, so they are weightless. I don't think the gravitational force of the Moon will have any impact at all. The tidal force on the other hand will, but the effect will be negligible compared to things like variations in the Earth's gravity in different places, atmospheric effects, etc.. --Tango (talk) 17:56, 25 August 2009 (UTC)

To expand on what Dauto and Tango said, the Earth is already experiencing acceleration due to gravity from the moon (or sun). Standing on Earth, the apparent gravitational acceleration caused by the moon (or sun) is the difference between the total acceleration due to gravity acting on the Earth (which is equivalent to the acceleration experienced at the center of the Earth) and the acceleration due to gravity acting on you (which is the acceleration experienced on the surface). This is the tidal force. Let R be the center to center distance, r the radius of Earth and M the mass of the moon (or sun), then the apparent acceleration to someone standing on the surface of the Earth directly under or directly away from the moon (or sun) is GM/(R±r)² - GM/R² or roughly 2GMr/R³ (in magnitude) if we take r << R which is the case here. For the moon that comes out to like 1.14×10^-6m/s² and for the sun 5.06×10^-7m/s². Rckrone (talk) 18:24, 25 August 2009 (UTC)

Which is about one ten millionth the Earth's surface gravitational acceleration. Variation between different locations on Earth is on the order of a few hundredths. --Tango (talk) 20:53, 25 August 2009 (UTC)

As to whether two bodies could exist where the phase of one (by which I assume you mean it's current location in the orbit) would significantly affect the gravity of the other, this would result in dual tidal locking, where one side of each body is always facing the other. Our Moon is already tidally locked to the Earth, but the Earth is not tidally locked to the Moon. I suppose if two such bodies had just come into proximity with one another (due to some interaction with a third, massive body, perhaps), then your scenario would present itself (along with massive quakes and/or tides) for a few million years before the two bodies became mutually tidally locked. StuRat (talk) 15:19, 27 August 2009 (UTC)

220v /230v/240v

Dear engineers ,

1. I have a query on line voltages . Pls reply the impact of using a 220v ballast in a 230v or 240v supply or vice versa especially in strret lighting using 400w/ 1000w sodium lamp .

2. also pls advise the impact if can use a 50 Hz ballast on a 60 hz circuit .

Thanks . —Preceding unsigned comment added by Npc123 (talk • contribs) 12:09, 25 August 2009 (UTC)

Answering question 1) The tolerances just aren't that tight. Read our article on Mains electricity, the section titled "Voltage levels" states that the voltage will vary by as much as 10% from the mean; so that a 230 V power supply really means anything from 210-250 or so. The fact is, the tolerances on what you are plugging in should allow for this; a light bulb will not explode over a 10% spike increase in voltage. It's just not that finicky. --Jayron32 15:25, 25 August 2009 (UTC)

I would expect 10% voltage variation to have an effect on bulb/ballast efficiency and lifetime. Edison (talk) 17:07, 25 August 2009 (UTC)

So exactly what effect would it have Edison? —Preceding unsigned comment added by 79.75.6.246 (talk) 23:12, 26 August 2009 (UTC)

Potential gain of irreversible, unidirectional, negative value time travel

If it is taken as a given that an average adult member of a civilized nation in 2009 has been transported back 200 years completely naked and without his time machine -- what would be the potential gain for the past civilization as it makes it ways towards the time period of the time traveler, if the average adult may know lots about the end products of technological advancement but not really so much about how to get there from scratch? Maybe he would know that penicillin kills bacteria and that it comes from bread mold, and I suppose that would give scientists a big head start. But to advance the people effectively, would saying things like "cathode ray tube" or "internal combustion engine" lead past scientists to anything if the time traveler can't explain anything about them? DRosenbach ^{(Talk | Contribs)} 12:21, 25 August 2009 (UTC)

The article on John Titor may be a start. --Cookatoo.ergo.ZooM (talk) 12:36, 25 August 2009 (UTC)

A Connecticut Yankee in King Arthur's Court would probably also be a good read. -- 128.104.112.102 (talk) 16:36, 25 August 2009 (UTC)

Does he have to be completely naked?  :) --Sean 12:57, 25 August 2009 (UTC)

Well, I added that in mid-writing so exclude the overwhelming benefit his clothes would play, as any one can describe seams, collars, textiles and buttons, but they would likely not be able to direct anyone on how to develop a bobbin, sewing machine, etc. based purely on knowledge without a physical example. His or her nudity was not a requirement as much as a lack of clothes. :) DRosenbach ^{(Talk | Contribs)} 13:40, 25 August 2009 (UTC)

I don't think you read my link, which would help more than buttons. --Sean 14:36, 25 August 2009 (UTC)

Haha -- you're right. I was in the middle of something and I thought it was a link to an article on nudity. :) DRosenbach ^{(Talk | Contribs)} 16:00, 25 August 2009 (UTC)

I think a person of modest intelligence could make an immense difference if he/she were believed and could manage to talk to the right people. However, arriving in a town, stark naked and babbling about time travel and the future could easily get you tossed into the nearest insane asylem with no chance of passing on any ideas whatever. Simple things like "Most diseases are caused by tiny animals that are too small to see" sounds like the babbling of a raving lunatic - but if described along with "Put some lenses together into a tube and you can see them" might help. But I think you'd want to be very careful about what things you described and in what order. 200 years ago, it would have been tough to manufacture many of the things you could describe. Even if you're a car mechanic who can explain every tiny detail about how a car works - that's of zero use if they can't make sufficiently accurate machine parts in a repeatable fashion.

The John Titor link above is a pretty good example of that. If Titor were indeed who he said he was - then pretty much everyone who mattered (including ALL of us here) would have dismissed him as a hoaxer or a loonie. SteveBaker (talk) 13:54, 25 August 2009 (UTC)

Indeed. The Victorians already knew plenty of basic science and had lots of vision and ideas. What they lacked was the technology to put some of those ideas into practice. The internal combustion engine was invented by François Isaac de Rivaz in 1806 but took 60 years before it could be produced in any numbers. The incandescent light bulb was invented in 1802, but not perfected until 75 years later. The electrical telegraph, invented in 1809, only went into commercial use in 1837. A Jacquard loom (invented 1801) embodies many of the concepts behind a modern computer, but the available technology could not be scaled up to produce mechanical computers. Gandalf61 (talk) 14:52, 25 August 2009 (UTC)

A couple more — diethyl ether and nitrous oxide (laughing gas) were both known before 1800, but didn't come into use as surgical anesthetics until the 1840s. (Unfortunately, the germ theory of disease and the idea of sterile surgical instruments didn't get kicked off until much later.) Really, though, we're well into the what-if games of science fiction. The problems of conveying scientific and engineering principles, along with the construction of the necessary infrastructure for technological development, are a staple of the time-travel genre. I recently read R.A. Lafferty's short story Rainbird, in which the protagonist is an early nineteenth-century inventor who repeatedly sends himself back in time (his final project is a time machine) to advise his younger self on what order he will need to invent things. If you're interested in knowing what the people of that era would understand, our articles here on Wikipedia can give you all manner of dates and places. TenOfAllTrades(talk) 15:10, 25 August 2009 (UTC)

The traveller would do well to gain the favor of someone with the resources to develop the things he has in his head and who is already an experimentalist. If you went back 200 years to London, you might swim to the docks and say you fell off a boat and had to shed your clothes to swim. Now clothed, go to the Royal Institution and volunteer to sweep up and assist for little or no pay, and gain the attention of Humphry Davy, who was at the forefront of electricity , physics and chemistry. You will be there 3 years before Michael Faraday would arrive in our timeline, and achieve about the same thing. But you can suggest many fruitful things to Davy, anticipating the discoveries Faraday would have made together with Davy a few years later, but you are in an alternative universe, so Faraday can go on to do other things. With a nudge, there could have been photography by 1810, telegraphy, telephones, phonographs and widespread use of practical generators powered by steam engines running incandescent electric lights and motors by 1820, radio, Xrays petroleum refining and internal combustion engines by 1830, airplanes, machineguns and practical submarines by 1840, and unfortunately nukes by 1900. Of course several other countries could have similarly been a fruitful field for introduction of science and technology. But you would get farther explaining an uptime gadget to an experimentalist with a scientific bent and resources than just going to a banker or politician with words. Depending on the era, one could have approached Franklin, Jefferson, Fulton, Joseph Henry, Volta, Westinghouse, Edison, or other experimentalists. Tesla (a hundred year ago) would likely not have been perturbed at all by a strange visitor with odd ideas. Get one uptime gadget working and making money or achieving fame for the patron, then work on the next one. Once you have made a name, there is less need for the downtime experimentalist. The bankroll is needed to pay the machinists, chemists, and glassblowers, as well as to pay for expeditions to remote lands to get minerals or biologicals needed for uptime gadgets, and a lot of time would be needed to get from the basic idea to a working gadget. Getting from the idea to the practical invention ate up an amazing amount of money. It would be very hard for the stranded uptimer to get the resources needed to make a working doodad, when by definition he starts with no resources and a presumption he has a screw loose. Edison (talk) 15:11, 25 August 2009 (UTC)

How did you estimate those dates, Edison? Sagittarian Milky Way (talk) 16:42, 27 August 2009 (UTC)

There are many, many examples of the abject failure of forward-thinkers (who might as well have been time travellers for all the good it did them): Babbage's Analytical engine would have been a perfectly useable computer - it would have propelled people forward into thinking of better ways to build such things, resulting (perhaps) in a much earlier arrival of modern computers and electronics onto the scene - and introduced the powerful idea of software as a way of formalizing algorithms in the same way that mathematics formalizes algebra, arithmetic, etc. Sadly, the guy with all the bright ideas was a terrible implementer and project manager and just awful at getting funding and such. If you tried to explain any of that stuff without those skills, your work would be a soon-forgotten novelty too. I was reading a book by the guy who made the replica of the (much simpler) Difference engine - and he showed conclusively that the machine could have been built with the available metalworking technology fairly easily. He also pointed out that none of the early developers of "modern" electronic computers had any idea of Babbages' earliers work...it was that completely forgotten!

The more I consider this question, the more I'm convinced that the problem would be entirely one of "getting the message across".

I'm reminded of an old Sci-Fi story (sorry - I forget who it was by or what it was called). A guy invents a one-time-use time-machine that can take him back by up to 500 years, keep him there for exactly 10 minutes and then bring him back to the present with no possibility of it ever working again - or ever being rebuilt (yeah - that's a bit contrived...but let's go with it). Knowing that he has only one shot at "fixing" history, he studies hard to see how to improve the lot of humanity and decides that taking a simple pocket calculator back in time and giving it to Sir Isaac Newton would relieve him of doing tedious calculations and enable him to get much more productive work done before he went "off the rails" and started flailing around with alchemy, crazy religious ideas, etc. The idea is that this one small act would improve the lot of man more than anything else he could come up with. What happens is that he materializes back in Newton's study with an impressive bang and a cloud of smoke - with one of those old red-LED calculators in hand. He shows it to Newton, and in an attempt to demonstrate its power, punches in '123+543' at random, hits '='...and the machine displays '666' in fiery red letters - thereby convincing Newton that this is the work of the devil and propelling him into his crazy religious ideas, alchemy, etc - exactly as per historical record. Such are the perils of this kind of endeavor!

SteveBaker (talk) 15:37, 25 August 2009 (UTC)

What was poor Newton going to do when the batteries ran out? Googlemeister (talk) 17:47, 25 August 2009 (UTC)

What if you gave Newton an iPhone, with the most useful parts of Wikipedia on it in screenshots and saved photos? You have 5 hours to use this, then it will be lost forever. ftocks fettings fafari flide to unlocke Sagittarian Milky Way (talk) 15:39, 26 August 2009 (UTC)

This must be a weird sticking point for SciFi writers. I've never read the story you just mentioned, but I'm sure that I've read a couple of other stories about time travelers or scientists with past-viewers that don't quite work right accidentally nudging Newton into insanity and/or occult research. APL (talk) 16:29, 25 August 2009 (UTC)

If you gave Newton a calculator, it's quite possible that he would not have gone on to invent integral calculus. Symbolic integration was invented to solve a class of physics problems that are very tedious to solve by successive additions (or as we call it today, numeric integration). --Carnildo (talk) 23:13, 25 August 2009 (UTC)

I would argue that what we should actually do is work for social progress (such as democracy), and not scientific progress. Otherwise, we might end up with Nazis who had nuclear weapons. It might even be good to retard scientific progress, in certain areas, if possible (tell the scientist about quantum mechanics, guaranteeing that they would all end up in insane asylums). :-) StuRat (talk) 15:43, 25 August 2009 (UTC)

"Otherwise, we might end up with Nazis who had nuclear weapons." -- As in the movie Philadelphia Experiment II? 98.234.126.251 (talk) 05:10, 26 August 2009 (UTC)

Yes, among many other sci-fi stories with a similar theme. StuRat (talk) 13:40, 27 August 2009 (UTC)

200 years ago would not put you before the invention of the internal combustion engine. But it would put you before it was easy to buy gasoline.

Instead of randomly giving scientists a head-start on things that you know for sure are going to be invented anyway, why not try to manipulate the order that things become practical and see if you can change which technologies go "mainstream".

My first thought was that perhaps you could reduce modern-day dependency on fossil fuels, but I'm not sure how. APL (talk) 16:06, 25 August 2009 (UTC)

You could do that by not helping with internal combustion engines but instead help with hydro-electric and windmill power generation (in particular, with the invention of the dynamo). I don't think solar cells were possible then, but passive solar heating certainly was. StuRat (talk) 16:32, 25 August 2009 (UTC)

I thought useful penicillin was first found on a moldy melon. Bread mold might turn out to be ergot, with hilarious results. 81.131.32.223 (talk) 17:23, 25 August 2009 (UTC)

I sit corrected. DRosenbach ^{(Talk | Contribs)} 21:30, 25 August 2009 (UTC)

As our articles Penicillin and Discovery of penicillin note, while the strain of Penicillium mold that was used for the first mass production of penicillin was indeed isolated from a moldy cantaloupe, penicillin itself (the identical chemical structure) was isolated prior to that from airborne contamination (Flemming's work). And while we can't be sure penicillin was the curative agent, traditional folk remedies used moldy bread, moldy oilcakes, and even warm soil to treat infections. So penicillin is found in bread mold - though, as you correctly point out, not all bread molds contain penicillin. -- 128.104.112.102 (talk) 21:51, 25 August 2009 (UTC)

I would just like to poke my head in to point out that the history of technology is very firm in showing that it is not just ideas that makes things work, but the creation of an infrastructure and overall context that is receptive to the idea. Thomas Edison gets a lot of credit for the light bulb; he ought to get more for developing the infrastructure of modern electricity. All the light bulbs in the world are useless if you don't have a system for powering them, and that doesn't come easy. As a lot of failed technologists have discovered, a good idea, by itself, doesn't do much, no matter how right it is. In medicine this is especially clear—even when it was rather conclusively demonstrated that cholera was a water-based illness, it took some many decades before physicians actually believed that was the case to the point that they would actually act on it. They stubbornly clung to their previous notions (that it was miasmatic, and was related to moral squalor) in part because that was the context of their medical worldview and their professional role ("don't drink the water" was not something that got them very much). (There is more detail on the cholera example in Rosenberg's The Cholera Years.) Over time, the incredibly simple explanation did, in fact, win out, and now it looks as terribly obvious as germ theory and so much else. But it took a lot of time, because people are rather stubborn lots... even being completely and demonstrably correct does not mean you will, in your lifetime, be recognized for it. --68.50.54.144 (talk) 23:30, 25 August 2009 (UTC)

Even the end of Cholera in London was by accident; the end of Cholera there is widely credited to the development of the London sewerage system, however the sewerage system was built under the mistaken belief that the smell of the sewerage caused cholera; by diverting sewerage from water supplies, the system largely helped clean up Cholera, but not for the expressed reason it was built. The history of science is filled with examples of people who got the right results for the wrong reasons. --Jayron32 23:44, 25 August 2009 (UTC)

Is that correct ? I thought John Snow conclusively demonstrated that cholera outbreaks were due to polluted water sources in his investigation of the 1854 Broad Street cholera outbreak. Bazalgette's London sewerage system was commissioned in 1858. Gandalf61 (talk) 13:41, 26 August 2009 (UTC)

Method of exhaustion may be seen as a form of calculus available 2 millenia early. Leonardo da Vinci's workshop with modern materials may have been a marvel unfathomable. However, without machines that make machines making machines, modern high technology is difficult. Mine some palladium if you please. Manufacture a 45 nm CPU (let alone the rest of the machine so you have something useful). One's knowledge of future events would be compromised by utilization of said knowledge (pardon the cartoons, but this exact premise is used in Beast Wars - the entire history of the future (up to a point many millions of years removed) is recorded on two disks... but one change and the rest would become fiction; unless you prefer your time travel Back to the Future style anthropomorphic). Also, Lord Kelvin - I can't seem to find the incident where later in life, he refused to amend his perceptions, holding back science (as it were) a few months. 69.255.26.5 (talk) 05:09, 26 August 2009 (UTC)

Your best bet would probably be social change. You could predict the downfall of Napoleon and his failed invasion of Russia. You could also predict his return to Paris for another go. That should buy you some credibility, and you could perhaps try to avoid some major mistakes made in the past. The problem is though, that then humanity would not learn from those mistakes (assuming humanity ever learns from its mistakes). Googlemeister (talk) 13:43, 26 August 2009 (UTC)

The problem is that predicting those things might prevent Napoleon from invading Russia, refuting the prediction. What you could do is claim to be a time traveller, write an encrypted message, and say that the key will be provided on a certain day. When the message is decoded on that day, its predictions would hopefully turn out to be right. --99.237.234.104 (talk) 14:15, 26 August 2009 (UTC)

The earlier in time you go, the more out of place you'd look if you weren't white. In addition, your English would get more and more strange to their ears, and theirs to yours. Would they stone a yellow human who appeared before they'd heard stories of them thirdhand or something through the Silk Road? Sagittarian Milky Way (talk) 14:00, 27 August 2009 (UTC)

I'm not at all sure this is true. Letting aside that there are places on Earth other than England, and letting aside that if you go back far enough you won't find white people anywhere, there's still a chance that you could parley your strange appearance into an explanation for your otherworldly knowledge but lack of status. APL (talk) 15:10, 27 August 2009 (UTC)

I was just saying if you were a race they'd never heard of before, death could be enough of a possibility to affect your destination for irreversible naked time travel. Spending the rest of your life running from and thsn hiding from humans in the woods and having to learn how to make fire does not sound funner than helping Davy. Even if you die, you might live awhile. Magellan lived for awhile but Medieval deformed babies were thrown down wells immediately. Either it'd be very good for your goal or very bad, possibly depending on local mythology and legend. It's hard to imagine they'd be indifferent. With the language, you'd be very disadvantaged until you could learn Middle English or Gutenburg's German or whatever. This would be important for time tourism but moot for this purpose though, as these problems wouldn't exist in the locations and time periods most interesting for seeing the effects of your knowledge flourish in the remainder of your lifetime. Sagittarian Milky Way (talk) 16:42, 27 August 2009 (UTC)

human hermaphrodites

can a human hermaphrodite give birth or impregnat a woman ? —Preceding unsigned comment added by 123.208.128.220 (talk) 12:58, 25 August 2009 (UTC)

There are a broad range of conditions that fall under that term, with different impacts on fertility. See intersexuality for the details. --Sean 13:03, 25 August 2009 (UTC)

Recoil in a vortex launcher

Hi guys

Question: If i have an explosion driven vortex launcher and I shoot it at an object, what will happen due to recoil would it be tgus

Since the area of effect on the launcher in the explosion chamber is small in diametre (about 4 inches) and the area the vortex effects is larger (around 2 foot) the target will be moved further backwards than the launcher, since larger area and less force are better for moving objects and even though the launcher feels more kinetic energy it is over a much small serface area. (for example like a sail on a large ship. 100 psi focussed on 1 foot of the ship would not be as good for moving the ship as 0.3 psi focused on the 30 feet sail?

Thanks

Robin —Preceding unsigned comment added by 79.68.243.180 (talk) 19:57, 25 August 2009 (UTC)

How much farther back is the ship and how heavy is the ship? Dogposter 21:28, 25 August 2009 (UTC)

Who was "Lawrence" that named lots of southern African species in the early 20th century?

A person (presumably male) with the name (presumably surname) "Lawrence" seems to have done a lot of taxonomic work identifying species (e.g. spiders and lizards) in southern Africa (especially Nambia, Botswana and South Africa) around the 1920s. See for example 8 separate species on the List of Salticidae species K-M.

However I can't find who he was. Wikispecies article species:Lawrence is about George Newbold Lawrence an American ornithologist who lived from 1806 - 1895 and so isn't the right person. Thryduulf (talk) 22:36, 25 August 2009 (UTC)

Seems to be an R. F. Lawrence, if this then this google searches are anything to go by. --Tagishsimon (talk) 22:41, 25 August 2009 (UTC)

And here's an obituary. --Tagishsimon (talk) 22:44, 25 August 2009 (UTC)

August 26

Leaf Color

I want to know why most plant leaves are green. I know that is it because of the pigments in the leave reflecting green light, but what I want to know is why that holds true for most all plants. Why is the green wave lenght of light something that needs to be reflected by the plant? Why not blue? Is there something about the middle of the visible spectrum that makes it disadvantagous to absorb? Does it have have to do with the amount of energy in that part of the spectrum?--98.240.70.102 (talk) 00:08, 26 August 2009 (UTC)

Chlorophyll is one of the main chemicals involved in absorbing light energy to begin the process of photosynthesis. If you use the search box at the top of this ref-desk page to look for "chlorophyll", you can find several previous discussions about its color. DMacks (talk) 00:24, 26 August 2009 (UTC)

(e/c) Its not so much that green light needs to be reflected, the reason most plants look green is a consequence of what wavelengths of lights need to be absorbed (and, as you said, the non-absorbed part of the light spectrum is what gives plants their colour).

Different wavelengths of light require different accessory pigments to be effective for photosynthesis. In green plants are green because for chlorophylls and carotenoids mainly absorb violet-blue and red light. Its difficult to know why green plants evolved their particular system to take advantages of the blue/red light, but it is clear these spectra are extremely effective in producing energy in the ecological niche green plants find themselves in. That is not always the case, though, in red algae, for example, the spectrum is different due to phycobilins, which absorb blue-green light. This allows algae to grow in deeper waters that filter out the longer wavelengths used by green plants. Again, their colour is a by product of the most effective absorption spectra for their niche. Rockpocket 00:33, 26 August 2009 (UTC)

For what it is worth, some researchers (PMID 17407409) have proposed that there is logic in why green plants do not absorb green light. The propose that the absorbance peaks are determined by three factors:

(1) the wavelength of peak incident photon flux; (2) the longest available wavelength for core antenna or reaction center pigments; and (3) the shortest wavelengths within an atmospheric window for accessory pigments.

Personally, I don't fully understand these three factors, but I thought I would throw them out there... Rockpocket 00:48, 26 August 2009 (UTC)

Really, red or blue plants would be even better. The Sun makes more green and yellow light than any other colors. Possibly no other photosynthetic chemicals were suitable? Is it albedo? Wavelength diffraction/scattering thing with some size scale of the cell? It's suprising. If this happened (red plants), and sentients evolved to have red blood, green wouldn't be especially calming and our instinctive color for danger and calming might be conflicted. Thank goodness the Borg didn't design plants or they'd be black from UV to IR and have gears. Sagittarian Milky Way (talk) 06:42, 26 August 2009 (UTC)

I'm pretty sure this has been discussed before and so should be somewhere in the archives Nil Einne (talk) 08:50, 27 August 2009 (UTC)

I thought this little black snake was harmless, can someone help ID it?

What type of Black Snake is this, I can't make a positive id

What type of Black Snake is this, I can't make a positive id

I was handingling this little black snake on a beach in southern BC and I thought it was a garter snake and I considered it harmless, but now that I am zooming in on the photo off camera it doesn't look so much like a garter snake anymore and I since I can't really identify it I was wondering if anyone recognized it or could make an id on it, as I would like to know if I almost got myself bit by a poisonous snake? GabrielVelasquez (talk) 03:32, 26 August 2009 (UTC)

• There are relatively few species of non-rattlesnake, non-coral snake (both of which are easily and instantly recognizable) in North America. So barring it being a Cottonmouth or a Copperhead (which it isn't), it isn't poisonous. (Hooray.) It looks like a racer to me, or even a garter. (Note that I guessed that BC meant either British Columbia or Baja California, so if either of those are wrong, you'd better make it more clear which BC you meant!) --68.50.54.144 (talk) 04:14, 26 August 2009 (UTC)

Sorry, British Columbia the Province in Canada, I have never been to Mexico.

It turns out that garter snakes do actually produce some poison, but not enough to be dangerous to people. See garter snake#Venom. --Anonymous, 04:22 UTC, August 26, 2009.

To a first approximation (as in: Don't Bet Your Life on it) all Snake venom which are harmful to humans have two prominent fangs, and snakes with just teeth and no fangs aren't lethal. But usually if you're close enough to see the fangs, you're too close for comfort. -- 128.104.112.102 (talk) 16:58, 26 August 2009 (UTC)

Despite what this article says, I believe quick way to check if a snake is venomous -- check the underside of the tail (posterior to the anal slit). Non-venomous snakes underbellies feature single scales that extend from left to right up until the anus but two adjacent scales posterior to the anal slit. Venomous snakes continue the single scale feature.[15] DRosenbach ^{(Talk | Contribs)} 22:06, 26 August 2009 (UTC)

Um, but then you're picking up a potentially venomous snake. (Also, the article's mentioning of stripes as a criteria really ought to say, "unless it is a coral snake") --68.50.54.144 (talk) 04:46, 27 August 2009 (UTC)

Are coral snakes the only venomous snakes which can't be identified about the scale thing? I have no idea. [16] does give the thing DRosenbach mentioned, although it notes it's useful for when the snake is dead (although do note even a dead snake must be handled with care), as do a number of other sources. But I noticed one thing; all of them are American including DRosenbach's one. Other sources such as our article which Rosenbach mentioned and [17] all say there is no single method when you are referring to diverse geographical locations. While the original question is referring to North America, DRosenbach's claim lacked any qualification (other then I believe) and you should be very careful when making a point blank statement of that sort. Does your method work throughout Asia? What about Australia? Africa? I don't know but it's entirely possible the answer is no. BTW, even if the method does always work in identifying venomous snakes, it may not be any use if all the snakes in the area have that feature including non-venomous ones as in that case you're going to be thinking all snakes are venomous (which is not a bad thing in any case, but clearly defeats the purpose). P.S. I found [18] which may be of interest Nil Einne (talk) 05:57, 27 August 2009 (UTC)

Would it be possible to run a power plant with dissimilar metals?

You see nuclear plants, but they take so long to build. You always hear that solar panel electricity costs too much money (but they're very useful for portable or low power and remote things) What could be something we could do right now and will be finished quicker, so it will tide us over and help a few percent and not cost as much money?

If you lay an enormous area of continous copper plates on a desert and paint them black maybe cover it with glass plates (finally the greenhouse effect will help us), place a similar zinc plate next to it, join them with power lines, and connect the other two ends to the power grid would any electricity flow? Or would that work only with expensive doped semiconductors? Would a conductive bath replacing the short wire help? Or use more traditional methods of temperature gradient exploitation with pipes and turbines and stuff except imstead of having to continously make the gradient with fuels we just do something as simple as change the thermal properties? Desert caves could be the cool end. The temperature just a little inside a cave is constantly similar to the average annual temperature, which is not hot. I've never heard of "caval energy" before. Edit: Or nearby high altitude mountains. Or find an already naturally dark desert and do.. something.

They can print solar panels now. On plastic film like an inkjet printer. So what about pouring them? Some sort of viscous liquid that would be dropped from planes or helicopters over a large square area of desert, left to dry set freeze cool down or whatever until it builds up a layer, and then do it all over again with the other pourable substances: the insulator, maybe a protectant and base layer, and of course the opposite semiconductor (p and n), then after that's done, we just build power lines connect it to the grid, and use it forever? If exploitation of artificially-created albedo (and thernal mass etc.) asymmetry is done on a truely massive scale, maybe we should be careful not to negatively impact local or even global climate, but even the entire global heating and precipitation from heat-island effect from partly changing the color of 0.01 of all land plus all the energy use is positively miniscule, and local precipitational changes are small, so it might be benign? Either that or find some ways to make solar panels less like microchips and more like roadwork. I'm all out of ideas now. Sagittarian Milky Way (talk) 06:05, 26 August 2009 (UTC)

Wikipedia is not a suitable forum for discussing original proposals for machines and such, so we can't go into detail here, but other forums on the internet are great for this kind of discussion. As for the question in your title, you have to consider that these metals are not found in their pure form in nature. It takes energy to extract them and purify them. So even if electricity did flow, you would probably spend more energy building this contraption than you would get out of it. And you'd be left with a lot of waste when the battery ran down. When it comes to using thermal gradients, you may enjoy reading up on our articles on geothermal energy and Heat pumps. EverGreg (talk) 08:48, 26 August 2009 (UTC)

FWiW, as far as I can remember, your proposal for covering the desert with copper and zinc plates is similar to one of Nikita Khruschev's pet projects, to surround all the steelmaking furnaces and whatnot with layers of semiconductor thermocouples to use the waste heat for electricity production. Well, it turned out that the amount of energy produced in this way would be negligible, more energy would be spent manufacturing and installing the thermocouples than they would produce, and in any case it was more economical to surround the furnaces with water jackets and tap the steam from the jacket to run a power turbine. So, sorry to shoot down your proposal, but it just won't work. 98.234.126.251 (talk) 09:55, 26 August 2009 (UTC)

Hmm, it would appear dissimilar metals are not needed for the thermoelectric effect. Hey, if it won't work, it won't work. There's always the black pipe and turbine method.. Sagittarian Milky Way (talk) 11:46, 26 August 2009 (UTC)

There is great potential to harvest solar energy in the desert, with photovoltaic panels, or with solar reflector arrays focussed on a boiler to make steam. For a building, solar heat can be collected with a home built or commercially made collector with glass over a black-painted sheet of metal. This can heat air, or it can heat liquid flowing through metal tubes connected to the metal plate inside the well insulated collector panel. I don't see any merit in the idea of having dissimilar panels in the desert. They would been to be connected by electrolyte to act as a simple primary battery. Just as in the early 19th century, the zinc plate basically is burned up in the process, and zinc costs far more than fossil fuel, even allowing for the high efficiency of battery versus engine. Electricity could have been economically important by the 1840's if anyone had realized that a motor could be used as a generator, and powered by falling water of a steam engine instead of batteries. There will likely be great advances in lowering the cost of making semiconductor photovoltaic panels. I particularly like the idea of "solar shingles" so the entire south-facing (in the northern hemisphere) roof half would be a solar collector, perhaps with the roof (where feasible) built at an angle equal to the latitude to maximize efficiency. The solar energy striking a collector is about a kilowatt per square meter at peak intensity. Such solar shingles should be lower cost and more durable than solar collectors now for sale. Another fruitful area for research is better storage batteries. In 1908, electric cars were commonly available which had a 100 mile all-electric range. A century later, car companies promise us that in just a few years we will be able to buy electric cars with--ready for this A 100 MILE RANGE! Of course today's cars go 70 miles per hour, and the 1908 cars went only about 15 miles per hour, but that just means that your days driving is over in about 2 hours. Edison (talk) 16:28, 26 August 2009 (UTC)

All those damn cul-de-sacs! Causing millions of solarly disadvantaged roofses to have random azimuths which would otherwise have the common N-S!

Doesn't the photoelectric effect only work with blue photons and higher? Why are solar panels usually deep blue then? Is this why they're so inefficient? I'm suprised they can even print (and eventually paint) solar panels cause usually when you think of semiconductors you think 99.9999... pure silicon doped with 1 atom in 10000 of gallium or something like that. This raw stuff looks like inky goop. Sagittarian Milky Way (talk) 17:06, 26 August 2009 (UTC)

Doesn't having an irradiance comparison between Earth and New Extrasolar Planets make sense?

New planets that are being found are being referred to as being in or out of their parent star's "Habitable zone,"
Which basically refers to the distance range that water would be liquid.
But the concept is being used to insinuate more than water being present, it is used to suggest these systems could have life.
That is easy to accept if you ignore all the other factors involved in the process, and believe Water=Life.
As there are many factors other than irradiances that would keep H₂O from being liquid,(Mass/cohesion, Abundance of elements/Metalicity, Excessive X-rays/M-type star, Amount of CO₂) it is a little deceptive and irresponsible to make the suggestion to people that a planet may have life because it is X distance from its star. The idea of a habitable planet is flawed as it is, but I would like to know if anyone can find fault with the Solar Constant comparison between Earth and other planets?
Simply as a comparison of heat, a more direct comparison, no insuations, as heat does not itself equal life.
(note: Irradiance, Insolation, and Solar Constant are synonymous.)

Basic Insolation Figures Chart

Planet Distance	Insolation (W/m2)	% of Earth's.
55 Cnc f Apastron Flux	380.136	27.74%
Mars' Aphelion Flux	494.00	36.06%
55 Cnc f Average Flux	547.395	39.99%
Mars' Average Flux	590.589	43.11%
Mars' Perihelion Flux	718.545	52.45%
55 Cnc f Periastron Flux	855.305	62.4%
HD 108874 b Apastron Flux	1234.655	90.12%
Earth's Aphelion Flux	1,321.544	96.74%
Earth's Average Flux	1,366.079	100.00%
HD 108874 b Average Flux	1413.557	103.18%
Earth's Perihelion Flux	1,412.903	103.43%
HD 108874 b Periastron Flux	1634.359	119.30%
Venus' Aphelion Flux	2,585.411	188.72%
Venus' Average Flux	2,620.693	191.30%
Venus' Perihelion Flux	2,656.70	193.93%
Gliese 581 c Apastron Flux	3,619.829	264.97%
Gliese 581 c Average Flux	4,870.841	356.56%
Gliese 581 c Periastron Flux	6,903.119	505.32%

GabrielVelasquez (talk) 07:52, 26 August 2009 (UTC)

I agree with the OP that Habitable zone is little more than a hopeful categorisation. It means a range where water existing in liquid form is not strongly ruled out but not that it does occur or even necessarily would be liquid. As our article says, the zone may be further restricted by galactic location. I don't understand the OP's line of questioning. I find no fault with the Insolation comparison chart for 3 local planets though one might need to look into the sources to find whether precision of 7 significant figures is justifiable. However to the lead question, having an irradiance comparison between Earth and Extrasolar Planets makes no sense as long as we lack data to create one, and no numerical criteria are in evidence for using it to set further limits to planetary habitability.Cuddlyable3 (talk) 08:32, 26 August 2009 (UTC)

Remember also that the local solar constant is not the only possible source of heat with which to keep water liquid (a basic but not necessarily valid assumption underlying some definitions of a "zone of life") Contributory factors, difficult or impossible to quantify from interstellar distances, include nuclear fission energy released from transuranics in the candidate body's core, and tidal heat generation caused by any orbital eccentricity around its parent primary, whether a star or a larger planet. In our own Solar system, several satellites of the gas/ice giants are well outside the Solar Constant-based "habitable zone", but nevertheless may have subsurface liquid water, even oceans, due to such factors.

Some of Gabriel's not entirely clear question (which seems a little contradictory since the basic "possibility of liquid water" calculations are just initial extrapolations from the calculated insolations he espouses) implies he is aware of such factors, but merely because they cannot be certainly measured does not make it valid to ignore them entirely and revert to a single-dimension comparison between Earth and extra-solar planets; this latter is in itself inadequate because other factors like the candidate's size (not to mention composition) are crucial - consider that the rather diminutive terrestrial planet Mars is by most criteria just outside the crude "zone of life", but if Mars were Earth-sized it would probably be just within it.

I disagree with Gabriel's proposition that "it is a little deceptive and irresponsible to make the suggestion to people that a planet may have life because it is X distance from its star . . . ." Saying that, according to the criterion in question, something may be possible is not a claim that it necessarily or even probably exists. Moreover, while the possibility is is intellectually interesting and may have philosophical or even religious implications for some people, it is of little importance in most people's day-to-day lives. 87.81.230.195 (talk) 12:49, 26 August 2009 (UTC)

If you want liquid water, you are also going to need an atmosphere probably at least equivalent to earth at 25,000 ft or lower, or all your water might boil away. Googlemeister (talk) 13:27, 26 August 2009 (UTC)

And as it boils it would be building a (water) atmosphere, so no problem there. Dauto (talk) 15:31, 26 August 2009 (UTC)

That is going to depend on the gravity of the planet as a small planet might not be able to prevent that vapor from escaping. Also if its sun had a high level of solar wind, that might continuously erode the atmosphere as fast as it is built. I would imagine that a planet we have discovered would be fairly large, so gravity might not be too big an issue, but solar wind we probably can not determine from here. Googlemeister (talk) 19:27, 26 August 2009 (UTC)

Even harder to determine would be the absence/presence and strength of any planetary magnetosphere, and the consequent protection from the solar wind it might afford. Mars seems to have suffered from the multiple effects of an over-wimpy gravitational field, a lack of magnetic field-generating molten-mantle convection currents, a lack of plate tectonic movement and subduction to recycle back into its atmosphere gases and water chemically bonded to its rocks, and (more speculatively) a lack of life to beef up its water cycle and facititate said tectonics (according to the extended Gaia theory).87.81.230.195 (talk) 14:33, 27 August 2009 (UTC)

to Cuddlyable3 (talk)'s point:
In a lot of cases the Radius and Effective temperature of a parent star is known, or can be calculated using the formulas at the Luminosity article. The formula that calculates luminosity from Radius and Temperature and the formaula that calculates luminosity from distance and insolation are obviously Equal for the Sun and Earth data. and basic algebra yields:

• $L=4\pi R^{2}\sigma T^{4}\,$ ...and
• $L=4\pi d^{2}\ f\,$ ...therefore,
• $4\pi R^{2}\sigma T^{4}\ =4\pi d^{2}\ f\,$ ... and
• $R^{2}\sigma T^{4}\ =d^{2}\ f\,$
• $\ f\ =(R^{2}\sigma T^{4}\,)/d^{2}$
  

...All I'm saying is it is not unknown.

code for Earth at Perihelion: $f_{p}={\frac {((6.955\times 10^{8})^{2})\times (5.67051\times 10^{-8})\times (5778^{4})}{((1-(1\times 0.016710219))\times 149597876600)^{2}}}=1,412.903\ W/m^{2}$

code for Gliese 581 c at Periastron: $f_{p}={\frac {((0.38\times 6.955\times 10^{8})^{2})\times (5.67051\times 10^{-8})\times (3480^{4})}{((0.073-(0.073\times 0.16))\times 149597876600)^{2}}}=6.9\times 10^{3}\ W/m^{2}$

Having said that I am not saying this should go directly into an article.
But I do remember reading a debate where it was pointed out that using known data with known formulas is not synthesis.
In a lot of cases scientists are going as far as to speculate on on effective temperature and surface temperatures, using this albedo or that emissivity,
but on the other hand if the algebra is correct then the insolation is closer to fact. Definitely less misleading than saying there may be life on Gliese 581 c:
(see Than, Ker (2007-04-24). "Major Discovery: New Planet Could Harbor Water and Life". www.space.com [19] )

${\frac {Gl\ 581\ c\ Periastron\ Insolation}{Earth's\ Solar\ Constant}}=$ ${\frac {6.9\times 10^{3}\ W/m^{2}}{1,366.079\ W/m^{2}}}=505\%$

GabrielVelasquez (talk) 07:40, 27 August 2009 (UTC)

I apologise for sounding so negative with my words "makes no sense". I do not mean that such a comparison using present estimates cannot be calculated. I do mean that it is not convicing that this gives such an improved criteria for habitability of planets that the water-as-liquid estimation must be discarded. If the OP's challenge is Find fault with this insolation calculation or confess that your ideas of habitable planets are flawed, deceptive and irresponsible, then I don't see that ever being resolved short of an interaction with lifeforms on Gliese 581 c. Cuddlyable3 (talk) 08:44, 27 August 2009 (UTC)

Makeshift optical telescope

I've got a handful of different kinds of lenses and I'm trying to figure out a way to combine them into some sort of telescope. I don't need anything permanent, I'm not actually going to use it for anything, I'd just like to see how far I can see while keeping it in focus.

The different sorts of lenses I have:

- From my Nikon DSLR: 18-55mm 1:3.5-5.6G 55-200mm 1:4-5.6G (both are obviously complex lenses, I don't really know what that means towards putting them together with other lenses)

- Single simple lens (was junk), says 70-210mm 1:4-5.6 on it, but I think it might just be the top taken off of a larger photographic lens. either way, the single lens is convex on the outside and concave on the inside. According to the wiki page on lenses I think it's "negative miniscus" i.e. the concave lens is more extreme than the convex. Held close to my face it will slightly magnify my hand at a distance under 3 cm or so, and then it will only focus again if it's more than 20cm or so from my face.

- A pair of typical 7x35 binoculars (says 525 ft. at 1000yds.)

- A small fish-eye lens meant for a camcorder.

I know it's kind of a random assemblage of lenses, but I really don't know very much at all about optics, and even less about the math, so can anyone see any possible configuration that might give me a little more zoom than just the binoculars (at the moment, the most powerful of the lenses)? Thanks in advance! 210.254.117.186 (talk) 08:07, 26 August 2009 (UTC)

Good luck experimenting. I think you use the word "zoom" (variable focal length) when you really want just a fixed telephoto result. Wikipedia has articles on optics that can help. For cameras: Teleconverter and Tele extender. For Optical telescopes: Refracting telescope and Amateur telescope making. A problem you will encounter with telescopes is stable mounting. I think your Nikon 55-200mm lens with a teleconverter has possibilities. Cuddlyable3 (talk) 09:04, 26 August 2009 (UTC)

I concur with Cuddlyable3. Any telephoto camera lens is essentially a miniature telescope sans eyepiece, and can be used as the main or Objective lens (the big one at the front) of a telescope arrangement, but you will need to add an eyepiece or Ocular lens (the little one at the back you look through) whose qualities are more critical; obtaining actual telescope oculars should be both easy and relatively cheap given the number of small commercial telescopes around.

Your 3 main problems are to 1. mount the telephoto lens firmly, preferably on the biggest, heaviest moveable-head tripod you can find; 2. make a means of firmly attaching, and easily detaching, your ocular(s), exactly aligned with the optical axis of the main lens; and 3. incorporate a means of moving the ocular(s) back and forward to focus the arrangement - some sort of push-pull arrangement using nested tubes will be probably be much easier than more elaborate screw or rack & pinion mechanisms (though you could cannibalise a cheap microscope for the latter). Your resulting device will probably have a small field of view, making it quite difficult to find a target in the night sky, so you may need to add a pointing aid, which can be merely a slender open-ended tube fixed parallel to the lens body, through which you sight.

I myself once made a serviceable small telescope using an old theodolite tripod, a 600mm "mirror telephoto" camera lens (essentially identical to a small Catadioptric telescope) and an assortment of old eyepieces borrowed from my local Astronomy Club, plus various bits of camera mount conversions, plastic and/or cardboard tubes, etc. Good luck and have fun.87.81.230.195 (talk) 12:07, 26 August 2009 (UTC)

Thanks for the tips. Would the eyepiece from a crappy "toy" telescope work? I can get one of those easily, and hey the cheaper the better. And is there any system for testing out the "oculars" I have that I might be able to find something that actually magnifies quicker than just placing them all randomly? The main problem I can see just arranging them myself is that the field of view I get is almost always incredibly small, even as small as a dot in the near distance. 210.254.117.186 (talk) 12:54, 26 August 2009 (UTC)

A toy telescope eyepiece should certainly work (as might a toy microscope eyepiece), but the quality of image you will get in terms of general clarity (arising from the glass/plastic quality), resolution (fineness of detail), degree of aberration (distortions of the image) and width of field of view will doubtless be less than with higher quality telescope or microscope eyepieces (the latter are very similar in general design and quality to telescope eyepieces, and amateur astronomers sometimes use them).

As to magnification, bear in mind that this is not purely a function of the eyepiece alone, it arises from the combination of the eyepiece with the main lens: specifically M = F/f where M is the magnification, F is the focal length of the main lens, and f that of the eyepiece. For example, a telescope eyepiece of 10mm focal length (not untypical) combined with my telephoto lens of 600mm focal length would give a magnification of 60 times, but with your zoom lens racked out to 210mm the same eyepiece would give a magnification of only 21 times.

The apparent field of view you get depends more on the detailed design of the eyepiece - there are many different ones and new improvements are invented from time to time. In your actual situation, you can only see what different eyepieces you can actually get hold of and try them out to see what works best with whatever objective lens(es) you choose to use.

Depending on how far you want to get into this, you might benefit from getting hold of a relevant basic reference book, either new, second-hand or via a public library. A couple of venerable tomes from my own shelves are James Muirden's Beginner's Guide to Astronomical Telescope Making, Pelham Books 1975, ISBN 0 7207 0822 2, and J. B. Sidgewick's Amateur Astronomer's Handbook 4th Ed, Pelham Books 1979, ISBN 0 7207 1164 9, but there are many others with similar information. 87.81.230.195 (talk) 21:58, 26 August 2009 (UTC)

My understanding of a telescope is you need an object lens of long focal length to create an enlarged virtual image, then a lens of much smaller focal length to look through and magnify that image. Do not aim it at the sun, because it will start a fire or instantly blind you. If you have 2 lenses, check their focal lengths by forming an image from a distant light (do not set something on fire with a sun image). Then place the lens of longer focal length at the end of a stick or in a tube with duct tape (or precision machined holders). Aim it at the object you wish to observe and note where on the stick it forms a real image by holding a piece of paper parallel to the lens and moving it back and forth. Place your shorter focal length lens on the other side of that real image and remove the piece of paper on which the image from the object lens appeared. Adjust the spacing according to the lens formula or empirically. Look through your telescope and enjoy the world made closer. A fine adjustment method for the eyepiece lens is highly desirable. Cardboard or PVC tubes to exclude extraneous light, painted black inside to decrease reflections, are helpful. A larger object lens collects more light. Edison (talk) 03:05, 28 August 2009 (UTC)

Did Indians discovery Laws of Motion centuries before Kepler?

As a retired computer scientist, I've dabbled at reading some anthropological topics, including history of science, historical linguistics, and prehistoric discovery via Y-chromosome typing.

By coincidence(?) three of these topics had subtopics pointing to India. I'll ask a question about one, and make comments about the other two. The reason for combining three unrelated topics into one will become apparent.

1. History of laws of celestial motion.

The Laws of Motion of Kepler and Newton are a major triumph of Western civilization, and often treated as the single greatest discovery that ushered in Modern Science. Yet we see in Wikipedia and other websites that Indian astronomers, notably Aryabhatta and Bhaskara, had developed similar methods.

Is this true? I don't see a similar claim made in a 16-year old print encyclopedia. I'd hate to think that the claims of jingoists (associated with any country), abetted by tools like Wikipedia, could distort records of the history of science!

Assuming the claims about ancient Hindu astronomy are true, can anyone point to me on-line documents based on pre-Keplerian writings? In relevant Wikipedia pages I see no sources cited (except other source-free webpages). The matter affects me personally, as my own page recites these (unsourced?) claims.

  http://james.fabpedigree.com/mathmen.htm

2. Homeland of the Indo-European speakers

This age-old riddle was solved several years ago (at least by any "preponderance of evidence" standard), but some academic Indian writers continue to insist that the language originated in South Asia. Of these "Indocentric theorists", Harvard's eminent Professor of Sanskrit, Michael Witzel, writes:

"The revisionist and autochthonous project, then, should not be regarded as scholarly in the usual post-enlightenment sense of the word, but as an apologetic, ultimately religious undertaking ... [and such writings] should be regarded and used, not as scholarly contributions, but as objects for the study of the traditional mind."

3. Homeland of the R1a Y-chromosome Haplogroup

The most ancient Ydna Haplogroups of India (C5, H and L) are hardly found outside South Asia; this confirms that there has been no major post-paleolithic migration from India. The strong presence of R1a among Slavs and Hindu Brahmins confirms an "Aryan migration" from Central to South Asia (although the details are a mystery). Yet even this is denied by South Asian jingoists; nonsensical "theories" and faulty studies have polluted the relevant Wikipedia pages. Indian genetic studies suffer severe flaws which can be explained only as deliberate obfuscation of caste-haplogroup correlations. I have a page which discusses this:

  http://james.fabpedigree.com/hindu.htm

Summary. There is no need to debate the conclusions I offer in 2. and 3. As time permits, I will make corrections to the relevant Wikipedia pages. But I wonder if "Indian science" is like the caricature Americans used to have of "Soviet science."

Are the claims about the celestial motion knowledge of Aryabhatta and Bhaskara valid? Or do they suffer from jingoist misinterpretations similar to those of Indian genetic and linguistic "science"? —Preceding unsigned comment added by Jamesdowallen (talk • contribs) 08:40, 26 August 2009 (UTC)

• I would not call the website you have linked a reliable source as it does not appear to have the hallmarks of reliability (editorial control independent of the author; peer review), so making the claims you are making based SOLELY on the text of that website in an actual Wikipedia article would be a bad idea. If you have reliable sources which show independent confirmation of these claims, you may have something, but that website does not appear to be it. --Jayron32 12:51, 26 August 2009 (UTC)

Just a note... It is actually his own website, not just some website that he found. So, he is using his own writings to justify his point. -- kainaw™ 12:57, 26 August 2009 (UTC)

No, he made it clear that it's his own website: "The matter affects me personally, as my own page recites these (unsourced?) claims. http://james.fabpedigree.com/mathmen.htm" --99.237.234.104 (talk) 13:25, 26 August 2009 (UTC)

If you wish to comment on specific Wikipedia articles, it would be a big help if you mentioned the names of those articles. As far as I can see, our articles on Aryabhata and Bhāskara II do not claim that either of them discovered Kepler's laws of planetary motion. Both of these Indian astronomers may have postulated heliocentric systems, but that is a different matter. Gandalf61 (talk) 13:10, 26 August 2009 (UTC)

Hi, James again. First, my "complaint" wasn't "against" Wikipedia specifically -- I'm asking for knowledge, not Wiki editing. One claim is that Aryabhatta wrote orbits were ellipses. By itself this is only half of one of Kepler's Laws and of interest only if we can understand *how* Aryabhatta came to the conclusion. Brahmagupta is said to have discovered the law of universal gravitation; again it would be nice to read something close to contemporary. (Both these claims, by the way, are clearly made on the Wikipedia pages cited in preceding paragraph.) The claim that Bhaskara had equations of celestial motion as good as 18th-century Europe may not appear directly in Wikipedia, but is made elsewhere on 'Net. Again, my concern is NOT accuracy of Wikipedia itself, but rather: Are the claims true? Are there on-line translations of early (i.e. pre-Kepler) Indian writing to help one judge the claims? (My own pages are, of course, irrelevant to the question. I wouldn't have mentioned them if I'd anticiapted it wou lead to the confused tangential comments above.) Jamesdowallen (talk) 07:49, 27 August 2009 (UTC)

Cracking joints

Does any animal besides some H. sapiens do this habitually? -GTBacchus^(talk) 09:32, 26 August 2009 (UTC)

Most hedgehogs that I've had will stretch to the point of popping a few joints when they wake up. Since hedgehogs are at the very early part of mammal evolution and humans are at the very late part, I believe it is safe to assume that other animals in between do the same thing. -- kainaw™ 12:59, 26 August 2009 (UTC)

Hedgehogs are at the very early part of mammal evolution ? I would think that honor would go to the monotremes, like the platypus. StuRat (talk) 14:56, 26 August 2009 (UTC)

Hedgehogs have a smooth brain - which is a characteristic of early mammal evolution. I don't believe many mammals still have smooth brains. I don't what the wrinkles in the average brain are called, so it is difficult to look it up and see where in mammal evolution that trait falls. -- kainaw™ 16:08, 26 August 2009 (UTC)

Sulcus (anatomy)? Or Sulcus (neuroanatomy). Bus stop (talk) 16:17, 26 August 2009 (UTC)

Actually lots of mammals have smooth brains. Convolutions are more a function of body size than anything else -- so rats, mice, shrews, bats, and other very small mammals all have smooth brains. Looie496 (talk) 17:13, 26 August 2009 (UTC)

Thanks. I've only studied hedgehogs and mistakenly thought that their smooth brain was not so common a feature. -- kainaw™ 17:44, 26 August 2009 (UTC)

I think Kainaw is referring to a view (which AFAIK used to be the established one for most of 20th century, but not anymore) that order Insectivora - now defunct - contained the "basal" placental mammals, least changed for the last 100 My. As of now, AFAIK, the hedgehogs and gymnures are placed in Erinaceomorpha (Gregory, 1910), an order of their own. There are modern genetic studies attempting to figure out the proper cladistics and taxonomy of placental mammals. Still, I'd wait another 10-20 years for a new established view to emerge. But strictly speaking no, hedgehogs are not representative of the earliest part of evolution of mammals (or even placental mammals). --Dr Dima (talk) 16:36, 26 August 2009 (UTC)

The echidna, a monotreme, is sometimes called a hedgehog because it looks a lot like one -- however its evolutionary descent is quite different from that of true hedgehogs, which belong to Laurasiatheria. Looie496 (talk) 17:08, 26 August 2009 (UTC)

Hedgehogs are at exactly the same time of mammal evolution as humans. Specifically, the mammals around in the year 2009. — DanielLC 03:43, 27 August 2009 (UTC)

DanielLC, I think what kainaw means is that hedgehog species evolved a long time ago (maybe 15 million years) and have not evolved much since. Humans evolved between 250,000 and 400,000 years ago. Axl ¤ [Talk] 09:19, 27 August 2009 (UTC)

Well, we're getting into deep issues here. At a molecular-genetic level, hedgehogs have probably changed just about as much as humans over the same time scale. At the level of visible bodily form, hedgehogs look a lot more like their ancestors than humans do, but which is the correct level to look at, the molecular or the macroscopic? Most modern biologists seem to go with DanielLC in thinking the molecular level is more important; I personally am not quite convinced. Looie496 (talk) 16:09, 27 August 2009 (UTC)

Scientists do look at the molecular-genetic level. What changes have happened to hedgehogs in that time, I don't know, but such studies are done. --Tango (talk) 18:00, 27 August 2009 (UTC)

movement of knee

Hi if someone were to be standing up and then lift one of their knees off the ground towards their chest is this flexion of the hip? Is this also flexion of of the knee? Thanks RichYPE (talk) 12:42, 26 August 2009 (UTC)

Yes, both (as long as you're not trying to keep your leg straight). Fribbler (talk) 12:44, 26 August 2009 (UTC)

Thanks a lot! RichYPE (talk) 19:48, 26 August 2009 (UTC)

Consider this image of reference desker user:Fribbler on the way to a WP meeting to discuss this very question. Image:Ministry of Silly Walks.jpg --Cookatoo.ergo.ZooM (talk) 06:55, 27 August 2009 (UTC)

Doubling your gas mileage

I saw this cool video on YouTube on how to double your gas mileage. http://www.youtube.com/watch?v=UHAUsGlfbx8&feature=channel

I just wanted to do a reality check with some people here. Are these tips effective and safe? ScienceApe (talk) 15:06, 26 August 2009 (UTC)

Most of the stuff is common sense (proper inflation, correct spark, no excess junk, don't run the A/C), and he claims a modest improvement on them (which means he had a badly maintained car with lots of crap in the trunk before). But the biggest improvement he reports is due to adding acetone. Snopes says these claims are "false" and Mythbusters says they're "busted". Moreover, the Car Talk says it's "worse than useless", in that it also destroys o-rings in your fuel system. Heck, whenever someone tries to justify their claim with a conspiracy theory like "what the car companies don't want you to hear" that should set major alarm bells ringing. -- Finlay McWalter • Talk 15:16, 26 August 2009 (UTC)

Agree. Also see Acetone#Domestic_and_other_niche_uses and the linked sources. --Stephan Schulz (talk) 15:18, 26 August 2009 (UTC)

The thing about switching to synthetic oil is questionable. There's plenty of online postings that claim you get up to a 4% improvement (and plenty that claim less, or none at all), I've not found a single reliable source that supports any of these claims. Worse, the Wikipedia article synthetic oil#Advantages says it helps gas mileage, but doesn't cite any source at all. There are other reasons you might choose to run synthetic oil, but there doesn't seem to be real evidence that it'll help gas mileage (never mind that it'd be cost-effective). -- Finlay McWalter • Talk 15:36, 26 August 2009 (UTC)

You may wish to read Hypermiling, which runs the gamut from sensible maintenance to "strategies" of suicidal stupidity. -- Finlay McWalter • Talk 15:40, 26 August 2009 (UTC)

Far from trying to cover it up, car companies would be delighted if this were true. They make far more profit on their low mileage SUVs than they do on their fuel efficient models. An invention like this would increase demand for SUVs and so contribute to their profits. Wikiant (talk) 16:20, 26 August 2009 (UTC)

Yep - you can be sure that there aren't secrets that the car company doesn't want you to know. Good gas consumption is a HUGE selling point! Why on earth would they hide a simple, effective trick from you? In fact, with most cars, you'll find many of these tips right there in the owner's manual. My MINI Cooper'S manual says that correct tire inflation, minimal A/C usage, keeping the windows closed over 30mph, keeping your car regularly serviced (ie good oil, good spark, tight belts, etc) trying to keep the engine RPM within the 2000 to 3000 range and not using the "Sport" button will all improve your gas mileage...and that's true. All of those things work. Many of the other suggestions (acetone?! Eeek!) are either dangerous, counter-productive (because the car's computer will be confused) or damaging to the engine. The hyper-milers are a weird bunch...some of the things they claim, simply don't work. Other things (like putting the car into neutral and coasting whenever possible - or disconnecting the power steering pump) are downright dangerous. SteveBaker (talk) 17:11, 26 August 2009 (UTC)

Agreed, Steve. It's only really the maintenance-free, everlasting car that the car companies are suppressing the patents on. It's Big Oil that's keeping down the really cool fuel efficiency stuff - the water-powered car or the 10,000MPG engine, for example (much in the same way that the battery companies don't want us to know about the universal battery charger that can reliably recharge all types of disposable alkaline cells)... :) --Kurt Shaped Box (talk) 04:10, 27 August 2009 (UTC)

But bare in mind that the car companies, and specifically GM, do engage in conspiracies against the public interest. My first example is in the middle of the last century, when GM systematically bought up cheap and efficient public transportation systems in cities across the US and then destroyed them, to increase reliance on vehicles they produced. My second example is in the 1990's, where they worked to undermine California's mandate to create electric vehicles (see the movie Who Killed the Electric Car?). StuRat (talk) 12:48, 27 August 2009 (UTC)

When you say "you can be sure that there aren't secrets that the car company doesn't want you to know.", you're specifically talking about gas mileage, right? I can't imagine a vast multinational corporation that doesn't have at least some secrets. APL (talk) 14:02, 27 August 2009 (UTC)

Yeah - of course - we were talking in the context of fuel economy. They might well hide crappy fuel economy from you - but good fuel economy is something they want to talk about very much! SteveBaker (talk) 00:10, 28 August 2009 (UTC)

I'm not so sure that oil companies would necessarily want to hide fuel-saving technology. The big threat to oil companies isn't low gas prices. It is gas prices so high that it becomes worth while to develop alternate fuel sources. For the record, gas prices (as a % of median income) have been falling (on average) since the 1960s. For a gallon of gas to cost the same, in percentage of median income, as it did in 1960, the price would have to be around $4.75 per gallon. Wikiant (talk) 01:16, 28 August 2009 (UTC)

Addition Reaction of Alkynes to Alkenes

Hello. Which geometric isomer is favoured when halogens react with alkynes to form alkenes? For example, does 1-butyne react with Br₂ to yield 1,2-dibromo-trans-1-butene? Does the hydrogenation of haloalkynes differ? For example, does 1-bromopropyne react with H₂ to form 1-bromo-trans-1-propene hypothetically? Thanks in advance. --Mayfare (talk) 15:46, 26 August 2009 (UTC)

I found two sources which contain generic answers:

[20]

[21]

There's a slightly higher level analysis here [22]

For hydrogenation it depends (I think on the process and catalyst) - however when the alkyne is absorbed on a solid catalyst it is usually to expect cis addition of H2, but there are plenty of ways this can not be the case.

83.100.250.79 (talk) 23:15, 26 August 2009 (UTC)

In my experience, hydrogen-transfer hydrogenation of haloalkynes does not have noticeably different cis/trans due to the halide. DMacks (talk) 00:30, 27 August 2009 (UTC)

Exotic Matter

My understanding is if we could replicate exotic matter which negated the attraction of mass (gravity) then we could practically move a bus into earth orbit using a model rocket engine since it would be essentially massless.

So then why don't we have scientists at NASA working around the clock determining how to make this stuff? Even if we don't know exactly where to start if we know the characteristics of the final product we should be able to invent a variety of testable methods. Is this being pursued at all? TheFutureAwaits (talk) 16:23, 26 August 2009 (UTC)

It's probably being pursued by someone somewhere on a creatively written grant. However, there is no reason to believe it actually exists. There are a great many forms of magic that would be amazing if they were only non-fictional; thankfully, NASA isn't working around the clock on any of them. 24.159.32.213 (talk) 16:37, 26 August 2009 (UTC)

I always thought that the lack of a consumer Star Trek Transporter shows that capitalism doesn't work. Similarly the lack of an immortality pill on the market... --Stephan Schulz (talk) 16:45, 26 August 2009 (UTC)

We have the technology to make a wired transporter anyways. But if you want to do it, set some time aside since the computers would take years to finish the scan before transmitting, and you better not change anything during the scan. Googlemeister (talk) 17:56, 26 August 2009 (UTC)

And for chrissakes don't forget the Heisenberg compensators. (I was privately betting myself $5 that this wouldn't be a redlink - and I won!) How do they work? "Very well indeed". SteveBaker (talk) 20:37, 26 August 2009 (UTC)

No, the lack of a transporter likely shows that capitalism does work. Given the number of breakthroughs required, at the moment, the present discounted value of the expected future profits are less than the present discounted value of the expected costs. Capitalism is working by not diverting scarce resources to something whose cost exceeds its payoff. Wikiant (talk) 20:40, 26 August 2009 (UTC)

Um, I'm pretty sure Stephan was joking... Nil Einne (talk) 08:34, 27 August 2009 (UTC)

The lack of any serious consideration of transporters is simply that the underlying physics prohibits it. Until/unless there is some very fundamental change in our understanding of the universe, you can't even consider making such things. Ditto with what our OP is asking. Until some very basic physics says that the most basic part of the mechanism could even theoretically work - there is absolutely no point in spending money on how to build one! The kinds of physics that might one day make either of these things conceivable is being done...but not with the intent of producing teleporters or intertia-less drives. SteveBaker (talk) 22:11, 26 August 2009 (UTC)

I don't see anything in the laws of physics that prevents transporting a human being. It's simply a matter of quickly scanning a person down to the individual atoms, sending that information to a remote site, then quickly reassembling those atoms in that specific order at the new location from a stockpile of the various elements there. This is certainly currently well beyond our capabilities in every step, but nothing we can't one day hope to achieve. StuRat (talk) 12:37, 27 August 2009 (UTC)

The Heisenberg uncertainty principle puts a limit on how accurately you can perform that scan. Whether that level of accuracy would be sufficient or not, I don't know. --Tango (talk) 16:10, 27 August 2009 (UTC)

That limits us to not being able to know the exact position of an electron (if, indeed it has an exact position), but shouldn't make it impossible to determine the identity of a specific atom. I believe we can already do that, for a few atoms at a time, especially if we don't care if we destroy the organism attached to those atoms, in the scanning process. We just need a way to do it for all the atoms in the body, very quickly. StuRat (talk) 19:27, 27 August 2009 (UTC)

Identifying an atom is relatively easy, but you can't know its exact position and momentum at the same time. I'm not sure how precisely that information would be required, but that is the main issue with transporters. --Tango (talk) 19:34, 27 August 2009 (UTC)

See AEGIS for a possible test to see if antimatter is such an exotic matter. In any case, it would be cheaper to move the entire population of the Earth to Mars with conventional methods than it would be to create enough exotic matter to move anything visible to the naked eye into space. Also, antimatter has an annoying tendency to annihilate itself when it touches matter, so it would be particularly impractical. By the way, this wouldn't make it massless for the purposes of faster-than-light travel. You don't seem to have made that mistake, but I feel I should point it out anyway. — DanielLC 03:39, 27 August 2009 (UTC)

Nobody actually expects AEGIS to show any significant difference between matter and antimatter, do they? It's just a test to double check something that everyone is pretty certain is true - such tests are very important in science, of course. There is no way to know what the cost of producing exotic matter will be until we know how to do it (if it is even possible). It might turn out to be really easy once we know how. --Tango (talk) 16:09, 27 August 2009 (UTC)

For it's worth CP violation produced some interesting results showing that antimatter is definately different to matter in some ways. Whether this applies to yuor statement I'm not sure. Elocute (talk) 20:09, 27 August 2009 (UTC)

Fusion

I checked out this section on nuclear fusion, http://en.wikipedia.org/wiki/Nuclear_fusion#Important_reactions but it didn't list fusion between two plain old hydrogen atoms to produce helium. Why is this? ScienceApe (talk) 16:49, 26 August 2009 (UTC)

Plain old hydrogen contains no neutrons, and helium without neutrons is unstable. You need at least one; ordinary helium has two. Looie496 (talk) 16:57, 26 August 2009 (UTC)

See diproton for more info. Looie496 (talk) 16:59, 26 August 2009 (UTC)

What about plain old hydrogen fused with deuterium to produce Helium3? ScienceApe (talk) 18:55, 26 August 2009 (UTC)

As the page you linked to says, if there is only one product it is difficult (if not impossible) to conserve both energy and momentum. The momentum of the sole product would need to equal the total momentum of the two reactants as would the energy, but energy and momentum are closely related so it probably won't be possible to get them both right. --Tango (talk) 19:17, 26 August 2009 (UTC)

I'm not sure I understand. Are you saying that the conservation of energy won't allow for that fusion event to take place? ScienceApe (talk) 04:32, 27 August 2009 (UTC)

It would make it very unlikely to take place. It could only take place if the initial momentum and energy was such that it could all be given to a single particle. I'm not sure if that is ever possible (I would need pen and paper to work that out, and I don't have any), it certainly isn't likely. --Tango (talk) 16:12, 27 August 2009 (UTC)

Tango is right that a reaction with just one product would be unlikely because of energy conservation. But nothing keeps it from sheding the extra energy as a photon (a second product) as you can see for instance in the article Proton–proton chain reaction. Dauto (talk) 02:06, 28 August 2009 (UTC)

drifting

Approximately how long does it take for something to drift from South America to Cape Hope? Just need a ballpark, 2 months about right? Googlemeister (talk) 17:37, 26 August 2009 (UTC)

1-3 mph is ballpark. Did you drop the engagement ring? Sagittarian Milky Way (talk) 19:31, 26 August 2009 (UTC)

Message in a bottle. Googlemeister (talk) 19:34, 26 August 2009 (UTC)

Yeah, I know. I threw one once. It washed back in seconds. Sagittarian Milky Way (talk) 19:54, 26 August 2009 (UTC)

Did it still have the same note? APL (talk) 20:00, 26 August 2009 (UTC)

Well, duh. Yes. If it was a different bottle now that'd be a coincidence.. Sagittarian Milky Way (talk) 20:12, 26 August 2009 (UTC)

Ah - but if it was the same bottle but a different message - it would be a conversation! SteveBaker (talk) 20:35, 26 August 2009 (UTC)

I was typing up a long detailed message in my other office, but had to run and shut off the computer without sending. Very briefly, you are going the wrong way. Chances are you will drift to the Indian Ocean, missing Africa all together. If you do hit Africa, it will be a long trip anywhere from about 1,000 to 2,000 miles (it is a circular current. The inside is shorter than the outside.) Your speed will be, on average, less than a knot. So, you are looking at a mile an hour (as Sagittarian Milky Way noted). Best luck will be about 40 days. Real experience will likely be much longer. Now, if you asked about going from Africa to South America (which is what I asked a long ago), you will get a completely different answer. -- kainaw™ 20:34, 26 August 2009 (UTC)

Human Genetic Trait Pairings

What are some Human unusual genetic trait pairings? I mean, for instance, if you have Human genetic trait 'A' most likely you have Human genetic trait 'B'. I think there is one pairing that I am familiar with and that is if you have unattached earlobes, you most likely are right handed. But that can be wrong. --Reticuli88 (talk) 20:25, 26 August 2009 (UTC)

Maybe take a look at epistasis. You may be right, but if you're wrong, does that make it left? DRosenbach ^{(Talk | Contribs)} 22:10, 26 August 2009 (UTC)

The OP may be referring to genetic linkage and/or linkage disequilibrium. Genes that are located physically close to each other on a chromosome will be paired (to some extent), since the probability of them splitting up during meiosis gets smaller the closer they are. Thus, historically, Charcot-Marie-Tooth disease was known to be paired with specific Duffy antigen alleles, it turned out the genes responsible are relatively near each other.

You might also be asking about different phenotypes resultant from the same genes. For example, red hair is a genetic trait paired (at a high frequency) with pale skin and freckling. This is because loss of function alleles of the MC1R gene is largely responsible for all three phenotypes. I'm not familiar with the data the suggests that handedness is linked to ear lobes, though. Rockpocket 06:18, 27 August 2009 (UTC)

you are right, Rockpocket --64.148.9.225 (talk) 11:22, 27 August 2009 (UTC)

One well-known linkage is the "ginger" genes, which provide for both red hair and uneven skin pigmentation (which means both freckles and a tendency towards getting sunburns). StuRat (talk) 12:27, 27 August 2009 (UTC)

As stated above, that should be gene (singular). The same gene is (largely) responsible for both phenotypes. Rockpocket 17:37, 27 August 2009 (UTC)

And of course don't forget the old malaria vs sickle cell anemia story. Aaadddaaammm (talk) 19:33, 27 August 2009 (UTC)

Dulce Base/Nightmare Hall/Underground Tunnels

I read some supposed UFO conspiracy reports online about how there are vast networks of underground tunnels all around the world that, for instance, one can travel from Wyoming to Italy in a matter of hours or something crazy like that. If that were remotely true, wouldn't something or someone pick up on some vibrations, noise, etc? Is it technologically possible to create something underground where it can be virtually undetected by the human population? --Reticuli88 (talk) 20:37, 26 August 2009 (UTC)

There are a couple of different concepts here: can you detect the construction (yes if you want to); and is anyone trying to (probably not). Seismologists might be keeping an ear out for such noise, but they have a lot of data to look at and might not be very interested. But the trouble with such conspiracy theories is that they're quick to dragoon whatever resources are required to make the conspiracy so: we presume that the national geological services of the major nations will ibein on the act. There are very many other practical objections to the existence of such infrastructure. I'm reasonably confident that our lizard-like overlords probably take British or American Airways like the rest of us. --Tagishsimon (talk) 21:03, 26 August 2009 (UTC)

There have been proposals for such things - but certainly they couldn't be constructed without someone noticing. Forget noise and vibration just consider the size of the hole: From Wyoming to Italy is about 8,000 km. If the tunnel was big enough to get some kind of a super-sonic high-speed train into it, it would need to be (let's say) 3meters in diameter. That's 200,000,000 cubic meters of dirt. About ten million truckloads. Where the heck do you think you're going to hide ten million truckloads of dirt and rock - and how are you going to prevent even one of the 10,000 truck drivers from blabbing something about it to the press? How would the spectacular cost of this get covered up? Why on earth would anyone want it anyway? If you are some kind of high-up world leader, get someone to strap you into an SR-71 Blackbird and at Mach 3.2 (about 4,000 kph) and you'll make the trip in almost exactly 2 hours. This is so unreasonable as to be hardly worth consideration! SteveBaker (talk) 22:05, 26 August 2009 (UTC)

"Where the heck do you think you're going to hide ten million truckloads of dirt and rock?" Come on, the aliens would just use their anti matter ray to shoot a hole all the way through. Just focus it to 3m and aim through the end points, simple ;) Vespine (talk) 22:23, 26 August 2009 (UTC)

I'm sorry - how foolish of me not to have considered that! So I guess these tunnels are there to relieve the wear and tear on their (evidently faster than light) flying saucers due to shipping people from Wyoming to their research center in Italy where they can 'probe' them. The solution is obvious when you approach this with a mind that's clear of all of these rigid preconceptions. SteveBaker (talk) 12:07, 27 August 2009 (UTC)

200,000,000 cubic meters of rock, at a density of about 2.5 g/cm², equates to 500,000,000,000 kg. Ignoring where you're going to get the 500,000,000,000 kg of antimatter from, the 1 trillion kg of mass would convert to 9×10²⁸Joules, or, at the sun's output of 3.846×10²⁶ W, equals about 3.9 minutes of total solar output. Or, for just the amount of sunlight striking the entire earth (1.740×10¹⁷ W), 16,400 years of total solar input to the earth. I'd imagine you'd detect the digging by the fact that your eyeballs had been boiled. Besides, if Hollywood movies taught us anything, you dispose of the dirt by shaking it out of your trouser cuffs on the baseball field. Just look for an infield in Wyoming that's 265 km higher than the surrounding area. -- 128.104.112.102 (talk) 17:05, 27 August 2009 (UTC)

That's the vactrain idea; right now it exists only in some very preliminary paper studies, and in the minds of conspiracy theorists. The prevailing conspiracy theory (if such thing can be said to exist) does indeed claim a vast underground network of such tunnels, centered at Area 51 and connecting military bases and government buildings around the US. Of course, like all conspiracy theories, absence of evidence is taken (by such folks) to be ironclad evidence of a cover-up, and whether the cost, noise, vibration, or excavation-effects of such a monumental undertaking would be evident isn't important - The Conspiracy has eyes and arms everywhere, and those who can see can soon be disposed of. Steve asks "Why on earth would anyone want it anyway?" - the answer is simple - the reptilian humanoids who really control the US government need it to travel around - presumably from the big flat rocks they have in Nevada (to keep warm) to the hatch they have under the Resolute desk, so as to order their puppet B.O. around, and then back to Nevada for a hearty dinner of gerbils a-la-mode. -- Finlay McWalter • Talk 23:53, 26 August 2009 (UTC)

Reality check: smuggler tunnels under the Palestine-Egypt border certainly exist and have been kept secret for a while. Unreality check: there is alleged to be an entrance between the paws of the Sphinx to an Underworld. Cuddlyable3 (talk) 09:11, 27 August 2009 (UTC)

An actual smuggler tunnel in Rafa, Egypt

Our Smuggling tunnel article has some surprising stories to tell of tunnels from Canada and Mexico into the USA - as well as details of the Gaza strip tunnels to which you refer. Gaza Strip smuggling tunnels has more info about the Egypt/Palestine tunnels. However: in the former article - talking about a tunnel between Canada and the USA: "Authorities were alerted when a neighbour noticed the large-scale construction work being undertaken ... On inspection, it was apparent that tons of construction material was entering, and piles of dirt were coming out." - and this was for a relatively short tunnel by UFO-nut standards. However, the Gaza-strip tunnels only have to be secret at one end - removing excavated material at the non-secret end is fairly trivial. The problem with alien/UFO tunnels is that (like the Canada/US tunnel) both ends have to remain secret. SteveBaker (talk) 12:07, 27 August 2009 (UTC)

Sodium Sulphate solubility

See Sodium sulfate specifically the solubility curve, can anyone explain the 'knee' in the graph? Specifically does anyone know (or want to guess) 'exactly' what the species are that predominate before and after the knee.. please..expert attention only..ie no Yahoo! answers.. 83.100.250.79 (talk) 21:55, 26 August 2009 (UTC)

The paragraph adjacent to the graph in that article has specific information about the weird shape. DMacks (talk) 22:25, 26 August 2009 (UTC)

This (?):

This nonconformity can be explained in terms of hydration, since 32.4 °C corresponds with the temperature at which the crystalline decahydrate (Glauber's salt) changes to give a sulfate liquid phase and an anhydrous solid phase.

Does that mean that the decahydrate is dissolving without dissociation ie as an ion pair surrounded by lots of H2O, or as clusters of (Na2SO4.nH2O)_m with a surface covered in -OH's ? (A bit like a sugar or polyol dissolving)

..And that these clusters break down above 35C

I didn't expect the decahydrate to survive per se on dissolution.

Is this a well known thing - I don't recognise the process I described above from any text book. Or is something else happening?83.100.250.79 (talk) 22:35, 26 August 2009 (UTC)

Or is all the above wrong? (the behaviour can be explained by the solid phase change of Glauber's salt)

Is it known what glauber's salt dissolves as ie as fully dissociated ions, or as the species I described above? I was thinking melting point depression - but that might not work -ie there might be the same number of species on dissolution despite being different species. Plus the glauber's salt would just come out of solution anyway. Vapor pressure I woundn't expect to work easily because the two components of the solution both have quite high vapour pressures..?

What to do?83.100.250.79 (talk) 23:53, 26 August 2009 (UTC)

Cerium Sulphate solubility

(edited once) Also the solubility behaviour of Cerium (3) sulphate with temperature - it decreases apparently? How can this be explained - anyone know? Specifically an theoretical model that explains this behaviour (it seems a no brainer that entropy will increase on dissolution - yet it appears that may be wrong?) Can it be that the high charge of Ce3+ induces medium range order into the solvent - decreasing entropy- anyone know about this sort of thing? 83.100.250.79 (talk) 21:34, 26 August 2009 (UTC)

Maxwwell's Demon

In the thought experiment, known as Maxwell's demon, there exists a hypothetical "demon" that guards a trapdoor between two containers filled with gases at equal temperatures. By allowing fast molecules through the trapdoor in only one direction and only slow molecules in the other direction, the demon raises the temperature of one gas and lowers the temperature of the other, apparently violating the Second Law of Thermodynamics.

I know this is only a thought experiment but even so shouldn't there exist a degree of reality if the results are to be taken seriously? I don't understand how this should work if the temperature of the gas is the same in both containers the speed of the molecules would also be the same? OK there is bound to be one molecules speed that would be faster or slower but then the experiment could not have started with both containers of equal temperatures?

I'm not an expert in these things so keep it light if that's possible

Thanks —Preceding unsigned comment added by Makemineateaplease (talk • contribs) 21:48, 26 August 2009 (UTC)

Saying that the temperatures are the same only means that the average speeds are the same. There is always a range of speeds. Imagine you have a pool table with a few dozen balls on it, and you shake the table: would you expect all the balls, as they bounce back and forth, to always move at exactly the same speed as each other? — Preceding unsigned comment added by Looie496 (talk • contribs)

Temperature is a statistical result for a large number of molecules, and there are lots of faster- and slower-than-average molecules. In fact, virtually none of them are actually the average value. Rather, there is a Maxwell–Boltzmann distribution (yup, same "Maxwell" guy:) of values (the math can be pretty dense, but the graph in that section is a good executive summary of the result that relates to your question). DMacks (talk) 21:59, 26 August 2009 (UTC)

Good one. Thank you. —Preceding unsigned comment added by Makemineateaplease (talk • contribs) 22:19, 26 August 2009 (UTC)

Incidentally, Maxwell's deamon only seems to break the 2nd law when you think about it at a superficial level. In reality, it can be shown that the energy it has to expend to measure the speed of the atoms and the effort to open and shut the trap-door cause it to consume more energy than it creates - hence it no more violates the 2nd law than does your refrigerator. SteveBaker (talk) 11:54, 27 August 2009 (UTC)

The 2nd law is how you show that. --Tango (talk) 16:15, 27 August 2009 (UTC)

That argument always seemed like begging the question to me: "A:Does the 2nd law *always* hold? ... how about a situation like Maxwell's demon? B:No. Maxwell's demon can't work because it violates the 2nd law." - Great, we can prove that the second law isn't broken by Maxwell's demon if we assume that the second law is valid when analyzing Maxwell's demon. -- 128.104.112.102 (talk) 16:47, 27 August 2009 (UTC)

You can't show by direct empirical observation that there is no possible way to implement Maxwell's Demon. The only way is to show that it violates a law that we have lots of empirical evidence for. --Tango (talk) 17:57, 27 August 2009 (UTC)

Tango and 128 were right and Steve was wrong, or at least misleading. The historical sequence is:

1. (1824) I have invented the 2nd law of thermodynamics: here it is. Can you falsify it?
2. (1867) I have invented Maxwell's demon. I can't build one, but there seems no reason it would be impossible, and it falsifies the 2nd law. Can you falsify my claim?
3. (1929) Yes! The demon must consume energy, so if it is possible to build one, the law can still be correct if Steve's statement about energy is also right. Therefore the 2nd law is not falsified.

Today we believe that the 2nd law is true, so from that point of view we can use it to prove things about Maxwell's demon, but only from that point of view. --Anonymous, 22:38 UTC, August 27, 2009.

If Wikipedia has multiple server sites, where is the real encyclopedia image (the one that gets edited) currently?

One can imagine all kinds of possible weird speed of light-related edits due to c, the speed of light in fiber optic cable, the different server continents, near-simultaneous edits to the same section of the same article, and the already irrational nature of relativity. What if the 3,000,000th article was created by two different people in two different continents, had the same name, but different text, the first bits arrived in Florida within 3 milliseconds of each other, and then the server synchronized. The later article had a closer sending PC, but longer fiber-optic path. The first PC to send bits had slower internet access so it wasn't finished till the other already did. The PCs were very near one other server site, and far from the other. One article version consisted of only a curse word repeated and was speedy deleted by a bot in milliseconds. Then the other was only barely above auto-bot deletion and deleted by a human doing recent changes patrol. Both PCs sent the edits in the form of a fast radio signal to their own fast private servers very close, but only to some of the Wikiservers. They automatically decoded them and made the same edits on local PCs held by fellow paradox creating comrades with senses of humor. And as we all know, if they do this fast enough, these will affect the servers before the ones on the Internet, because electromagnetic waves travel 200 million miles an hour faster through atmosphere than through glass fibers. They also did this with geostationary satellite internet connections. Another unrelated article arrived at Florida in the intervening time. Or maybe it was two other copies of 3,000,000A and B but they were encyclopedic ones. Okay, I'll stop now. Sagittarian Milky Way (talk) 22:21, 26 August 2009 (UTC)

I think I drifted off half way through. You measure the thing at one place (e.g. the nominated master database) based on one event (e.g. the completion of a database append operation). You do not concern yourself too much with the manifold other ways of considering the matter lest you go mad and start posting completely inarticulate queries about the issue. --Tagishsimon (talk) 22:34, 26 August 2009 (UTC)

If there are/is more than one 'main version' then I think they must converse changes to one another - otherwise there would be serious issues when editing, which I believe Sag..MilkyWay is talking about. Often I see a delay when submitting... An auxillary question would be - if there is/are more than one main server - how much bandwidth do they use on average.?83.100.250.79 (talk) 22:41, 26 August 2009 (UTC)

You might read federated database. That article explains the methodology of the computer system architecture that Wikipedia (and in fact, most other large data processing systems) use. The distribution of data over many different computers follows deterministic algorithms for resolving conflicts. Somewhere, somehow, there is a serialization process which maps the parallel processing task (executed on many computers, possibly geographically dispersed) into a serial-order-equivalent task - this is a basic tenet of modern parallel computing algorithms. You might also want to read Help:Edit conflict, which describes the result when two "simultaneous" edits cannot be automatically resolved by the algorithm. One or both edits fails to commit to the database, and it is up to the humans to either retry or abandon the edit(s). You might also be interested in data hazard, which formally defines (from the standpoint of computer science) the situation you have described. The computer can easily recognize that you have performed a "Write After Write" hazard - and it may choose from a wide variety of recovery methods to properly handle this. (Most commonly, the second write will be rolled back). Note that in the formal definitions of data management, a "delete" is the same as a "write", as they both involve a committed modification of data. Nimur (talk) 22:46, 26 August 2009 (UTC)

Okay, conflicting parts simply don't become part of the database, then. It always boils down to an edit conflict. It is just funny if it could be possible to have slightly disparate versions floating around, and there really is no absolute time frame of reference in relativity and then the servers have to synchronize. How often do they sync? I've seen changes to widely used templates that took 20 minutes to cascade down, maybe this is unrelated to synchronize frequency? Sligthly drunk. Usually this is a thing for the Internet Oracle, but I really wanted to know. Sagittarian Milky Way (talk) 23:27, 26 August 2009 (UTC)

There's only one server, but that's masked by degrees of caching. The database server has several read-only slaves, which try to replicate it in real time, but sometimes there's a lag (it's rarely more than 30 seconds). Then there's memcached caching, which caches pre-rendered(to HTML) fragments of articles. And then (mostly for signed-out visitors) there's squid webcaches in front of the web servers. So for editors there's a single definitive copy of the encyclopedia, but for visitors it's always a delayed (and often version-skewed) copy; visitors overwhelmingly don't know and don't care that they're lot looking at the absolute latest thing, but obviously for editors that's imperative. -- Finlay McWalter • Talk 23:37, 26 August 2009 (UTC)

And then there are templates, update to which must be applied to each instance of use of the template (that is not subst'd into the page); the amount of time to do the updates will depend in large part on the number of articles using the template, and the size of the job queue. Slightly drunk. Excellent. --Tagishsimon (talk) 23:49, 26 August 2009 (UTC)

The other issue is that the conversion of pages from the internal Wiki markup language to HTML+JavaScript is cached so that the task doesn't have to be repeated over and over when the same page is viewed by many people in quick succession. That process can sometimes lag the edit queue - so you make a change - and it's accepted without an edit conflict - but it takes a few seconds for that to be reflected on the viewable page. SteveBaker (talk) 11:50, 27 August 2009 (UTC)

August 27

Canine kidney failure

I just heard a story on the television about an old dog that died of kidney failure while locked in a car during 90+ºF heat. I can understand a dog dying after several hours in such a situation, but kidney failure? Unless the dog already had nephrological issues, how would the heat kill it in that way before killing it in some other way? Nyttend (talk) 03:26, 27 August 2009 (UTC)

A quick google search shows up a bunch of links, especially this one. Essentially, the extreme over-heating is going to cause massive tissue damage, and tissues that are most active (liver, brain) are going to go first. Kidneys are pretty active, and rely on very specific chemical reactions and fluid balances to function properly. In the heat the concentration of specific molecules in the blood would've been changed drastically, and could easily affect kidney function. If the kidneys hadn't failed something else probably would've soon. I can even imagine that since the brain and liver get so much blood compared to other portions of the body, they might survive (albeit completely irreparably damaged) long enough to make the cause of death the kidneys. ~ Amory (user • talk • contribs) 05:43, 27 August 2009 (UTC)

I cannot see how a dog can die from kidney failure after such a short time with out previous aetiology. Dying from kidney failure is not a sudden death but is caused by the accumulation of fluids and waste products over an extended period of days rather than hours. It is of course quite possible that this dog did have previous kidney problems and the extreme heating was the final straw. From my veterinary experience I would suggest that the dogs brain became overheated, it was not able to oxygenate properly and this caused heat prostration and death. 86.4.181.14 (talk) 07:25, 27 August 2009 (UTC)

Hmm Nyttend are you sure the storysaid the dog died of kidney failure while locked in the car? dogs.suite101.com/article.cfm/dogs_and_heat_stroke (spam blacklisted) and [23] and Amory's ref all note that kidney failure is something that dogs should be monitored for after suffering heatstroke so it's entirely plausible the dog died from kidney failure primarily as the result of being locked in the car even if it didn't die while in the car Nil Einne (talk) 08:31, 27 August 2009 (UTC)

Kidney failure is indeed the most likely mode of death. In the extreme heat, the dog attempts homeostasis of temperature by sweating and panting. This leads to dehydration and hypovolaemia. Axl ¤ [Talk] 10:47, 27 August 2009 (UTC)

It appears that the dog died hours later; here is the story from a newspaper website. I thought that the TV broadcast said in the car, but either it was wrong or (more likely) I remembered it wrongly. Nyttend (talk) 17:06, 27 August 2009 (UTC)

A380 and An-124

According to List of large aircraft An-124 is bigger than A380. According to articles, A380 is longer, has bigger wingspan, bigger max takeoff weight and so on, so how can an-124 be bigger? —Preceding unsigned comment added by 195.255.135.235 (talk) 08:39, 27 August 2009 (UTC)

A380? An-124 eats them for breakfast! --antilived^{T | C | G} 08:48, 27 August 2009 (UTC)

You should probably bring this up on the Talk: page of List of large aircraft. If you're sure of your facts, you can Be Bold and just go fix it yourself. SteveBaker (talk) 11:41, 27 August 2009 (UTC)

A380 is fairly new. Could be that no one has gotten around to updating that list. Also, not sure but are there any specific criteria defining "large"?

Looking at our article Antonov An-124, it seems that the An-124 was the largest production aircraft in the world at the time that it was introduced. It may also be the second-largest mass-produced aircraft (after the A380). Note that the Antonov An-225 is larger than both, but only one was ever completed. (Our article indicates that a second mothballed airframe is being refurbished, and is due to fly in 2010.) If someone wants to update our last, they should go ahead. TenOfAllTrades(talk) 14:03, 27 August 2009 (UTC)

I think you missread the article. It actually claims that the Antonov An-225 is the largest airplane, while A380 is the second largest. The An-124 is one line above the An-225 which may explain the mistake. 71.203.58.148 (talk) 01:13, 28 August 2009 (UTC)

Re-OP: Is it true that using known data with known formulas is not synthesis?

New planets that are being found are being referred to as being in or out of their parent star's "Habitable zone," Which basically refers to the distance range that water would be liquid. But the concept is being used to insinuate more than water being present, it is used to suggest these systems could have life.
That is easy to accept if you ignore all the other factors involved in the process, and believe Water=Life. As there are many factors other than irradiances that would keep H₂O from being liquid,(Mass/cohesion, Abundance of elements/Metalicity, Excessive X-rays/M-type star, Amount of CO₂) it is a little deceptive and irresponsible to make the suggestion to people that a planet may have life because it is X distance from its star. The idea of a habitable zone planet is flawed as it is, but I think a "Solar Constant" comparison between Earth and other planets is of value in-of-itself. Simply as a comparison of heat, a more direct comparison even than mass (less insuating than a mass), as heat does not itself equal life. In other words less speculative. (note: Irradiance, Insolation, and Solar Constant are synonymous.)

Basic Insolation Figures Chart

Planet Distance	Insolation (W/m2)	% of Earth's.
55 Cnc f Apastron Flux	380.136	27.74%
Mars' Aphelion Flux	494.00	36.06%
55 Cnc f Average Flux	547.395	39.99%
Mars' Average Flux	590.589	43.11%
Mars' Perihelion Flux	718.545	52.45%
55 Cnc f Periastron Flux	855.305	62.4%
HD 108874 b Apastron Flux	1234.655	90.12%
Earth's Aphelion Flux	1,321.544	96.74%
Earth's Average Flux	1,366.079	100.00%
HD 108874 b Average Flux	1413.557	103.18%
Earth's Perihelion Flux	1,412.903	103.43%
HD 108874 b Periastron Flux	1634.359	119.30%
Venus' Aphelion Flux	2,585.411	188.72%
Venus' Average Flux	2,620.693	191.30%
Venus' Perihelion Flux	2,656.70	193.93%
Gliese 581 c Apastron Flux	3,619.829	264.97%
Gliese 581 c Average Flux	4,870.841	356.56%
Gliese 581 c Periastron Flux	6,903.119	505.32%

In a lot of cases the Radius and Effective temperature of a parent star is known, or can be calculated using the formulas at the Luminosity article. The formula that calculates luminosity from Radius and Temperature and the formaula that calculates luminosity from distance and insolation are obviously Equal for the Sun and Earth data. and basic algebra yields:

• $L=4\pi R^{2}\sigma T^{4}\,$ ...and
• $L=4\pi d^{2}\ f\,$ ...therefore,
• $4\pi R^{2}\sigma T^{4}\ =4\pi d^{2}\ f\,$ ... and
• $R^{2}\sigma T^{4}\ =d^{2}\ f\,$
• $\ f\ =(R^{2}\sigma T^{4}\,)/d^{2}$
  

code for Earth at Perihelion: $f_{p}={\frac {((6.955\times 10^{8})^{2})\times (5.67051\times 10^{-8})\times (5778^{4})}{((1-(1\times 0.016710219))\times 149597876600)^{2}}}=1,412.903\ W/m^{2}$

code for Gliese 581 c at Periastron: $f_{p}={\frac {((0.38\times 6.955\times 10^{8})^{2})\times (5.67051\times 10^{-8})\times (3480^{4})}{((0.073-(0.073\times 0.16))\times 149597876600)^{2}}}=6.9\times 10^{3}\ W/m^{2}$

Having said that I am not saying this should go directly into an article.
But I do remember reading a debate where it was pointed out that using known data with known formulas is not synthesis.
In a lot of cases scientists are going as far as to speculate on on effective temperature and surface temperatures, using this albedo or that emissivity,
but on the other hand if the algebra is correct then the insolation is closer to fact. Definitely less misleading than saying there may be life on Gliese 581 c:
(see Than, Ker (2007-04-24). "Major Discovery: New Planet Could Harbor Water and Life". www.space.com [24] )

${\frac {Gl\ 581\ c\ Periastron\ Insolation}{Earth's\ Solar\ Constant}}=$ ${\frac {6.9\times 10^{3}\ W/m^{2}}{1,366.079\ W/m^{2}}}=505\%$

A few published formulas for comparison

$\sigma \cdot T_{\mathrm {p} }^{4}={\frac {\sigma \cdot T_{\ast }^{4}}{4\pi \cdot d^{2}}}\cdot {\frac {4\pi \cdot R_{\ast }^{2}}{4\pi \cdot R_{\mathrm {p} }^{2}}}\cdot \pi \cdot R_{\mathrm {p} }^{2}(1-A_{\mathrm {p} })$

$T_{\mathrm {p} }=T_{\ast }\left[\left({\frac {R_{\ast }}{d}}\right)^{2}{\frac {1-A_{\mathrm {p} }}{4}}\right]^{\frac {1}{4}}$

These and other formulas have been published and used by scientist to suggest surface effective temperatures of terrestrial extrasolar planets. Would it be incorrect to use the same formulas for other extra solar planets where scientists have not bothered to publish these figures because (I suspect) they are not as reputation enhancing. Similarly, No one is likely to use these same formulas published by scientists to calculate the effective surface temperature of a extrasolar Gas Giant, but this overlooks potential habitable moons of the same Gas Giants. I know the difference between published speculation and unpublished fact, and I perfer the later and would like to know if I am alone in this or is it true that using known data with known formulas is not synthesis? GabrielVelasquez (talk) 07:40, 27 August 2009 (UTC)

It's starting to sound like you're asking us a question about the application of Wikipedia policy. Your best bet is to bring the matter up on the talk page of the article in question, or to file a request for comment to bring in outside editors. TenOfAllTrades(talk) 12:14, 27 August 2009 (UTC)

Yes Wikipedia:Synthesis redirects to Wikipedia:No original research, if your question is about policy probably that talk page, the help desk etc maybe a good place to ask. However I see no reason not to deal with it here as it seems easy to answer.

However. Without reading your entire question fully, it seems you are simply asking

"it is true that using known data with known formulas is not synthesis?"

I'm afraid the answer is "it is synthesis", technically. No question about it. Only in the most trivial cases can there be a get out clause eg covert degrees to fahrenheit.

83.100.250.79 (talk) 13:32, 27 August 2009 (UTC)

I think the rule of thumb is that if anybody expresses a "reasonable doubt" about what you're doing, then it is synthesis. Given the complexity of your presentation, I think it would be reasonable for people to express doubts about whether you got all the factors right. Looie496 (talk) 16:01, 27 August 2009 (UTC)

I've got to disagree with that - calculations producing unpublished results is always synthesis (excluding an absolutely known proceedure such as found in pure mathematics), whether or not there is any disagreement about the results. In the case of the above equations it would be bordering on original research.

Presenting a single example as a demonstration of the formula would probably be acceptable, generating an entire table would not.83.100.250.79 (talk) 17:16, 27 August 2009 (UTC)

This is a principle that sounds good but leads to absurdities -- for example, is it synthesis to say Jupiter is over twice as far from the Sun as Earth, giving a table of distances as reference? Looie496 (talk) 17:34, 27 August 2009 (UTC)

That doesn't require an equation - I (and the question poster) was talking about deriving new figures from published data and equations. In your example the tables of distance already exist. 83.100.250.79 (talk) 18:39, 27 August 2009 (UTC)

You may be conflating synthesis with analysis.83.100.250.79 (talk) 19:14, 27 August 2009 (UTC)

Working out whether a planet is in the "habitable zone" is relatively easy, working out all the other things you mention are much harder. That is why the habitable zone is used as a rule of thumb to give an idea of how to prioritise further investigations. Also, it is worth remembering that whenever we say "life" in this context we mean "life as we know it". There could be life built around very different principles than that on Earth that could exist in very different environments. (Work on other kinds of life has shown that our kind seems to work best out of all the kinds we have considered, but that doesn't rule out other kinds either being less efficient that ours or of a kind we haven't considered.) --Tango (talk) 16:22, 27 August 2009 (UTC)

To cut a long story short we have an article Synthesis, the first paragraph explains what it is. 83.100.250.79 (talk) 19:14, 27 August 2009 (UTC)

It's very simple. $1/planetAU^{2}*luminosity$ is the insolation the planet gets compared to Earth. If you want W/m² multiply that by Earth's value. Luminosity in solar units is found in the article of every planet's parent star so you don't have to originally recalculate it every time. (because the luminosity does not eminate from a single point, if the apparent angular size of the star at the planet is really large this might cause some problem, however if you have to worry about that – that planet ain't habitable.)

And albedo with the greenhouse effect are really important. Without one, Venus gets 2x insolation and is 2x as reflective, so it would be frigid! Sagittarian Milky Way (talk) 19:36, 27 August 2009 (UTC)

One of the crucial elements that you are forgetting is that known formula is subject to scientific dispute. Empirical formulas have limited applicability to problems. The job of an experimental scientist is to perform original research in deciding which formulation is relevant to a particular problem. When you make the claim that it is a "known formula", you are asserting a scientific truth, without attribution to a reliable source, that this is the correct equation that should be applied to this problem. Whether the result of that formula is trivial computation or not, you have still synthesized the scientific claim that this formulation should be used. That is the realm of research science; encyclopedias should serve to document what other scientists have agreed is the best formulation to apply. Nimur (talk) 22:00, 27 August 2009 (UTC)

Reference Desk Organization

Is there a better way we could set up the reference desk pages? I've noticed several annoyances.

1. I can not track responses to a particular question. 2. When someone replies to someone else's response while there are multiple further responses it's very difficult to determine this has occurred with out rereading every post every time. This is a bit difficult to explain but it looks like this:

- Question 7 pm

- Reply 1 8 pm
  - Reply to Reply 1 9 pm
- Reply 2 8:30 pm
- Reply 3 10 pm
etc...

How can I tell there's been a reply to reply 1 without reading everything over again?

3. Topics remain on the reference page for quite some time but almost all the replies occur for questions asked in the past 2 days. Is there a way to reorder the format to encourage discussion of unanswered, older questions?

Finally, while there may be some back discussion page I believe it is the community's interest to have this posted for everyone's consideration as most people who use the reference desk read this page.

Your thoughts? TheFutureAwaits (talk) 10:35, 27 August 2009 (UTC)

{{Unanswered}}

I found this just today ironically, and removed mine minutes before you posted your question. It only indirectly addresses your issue, but I thought you would find interesting anyway. GabrielVelasquez (talk) 10:41, 27 August 2009 (UTC)

This type of question (and subsequent response) do not belong here. Discussions about the RD itself belong on the RD Talk: page which you can reach by clicking the "discussion" tab at the top of this page. SteveBaker (talk) 11:39, 27 August 2009 (UTC)

The formatting you describe sounds like it follows the guidelines at Wikipedia:Talk page, which you can discuss at Wikipedia talk:Talk page AlmostReadytoFly (talk) 12:17, 27 August 2009 (UTC)

Yes but the problem is no one looks at those pages (looking at the history there were 7-10 edits a day on the discussion page versus hundreds for the actual desk). I'm trying to get feedback from the general users of this page on whether they agree with my points and if there are ways we could improve it. If I posted this on the discussion page it would be largely ignored.

Also I consider this a serious issue that merits discussion on the main page since the page in its current form has some fundamental flaws. I wouldn't post criticisms within an actual article but given the reference desk is all about asking questions and I'm trying to get feedback I think it merits real consideration. TheFutureAwaits (talk) 13:41, 27 August 2009 (UTC)

Few edits doesn't mean no one watches the page. The vast majority of active contributors to the RD, and even a few who don't contribute to the RD much anymore are active on the talk page (I know because I've seen them!). Also you appear to have missed the whole religion desk controversy which was hardly lacking in edits. And BTW, by posting this on the science desk (although it has little to do with science) you're missing all those who don't check out the Science desk. Also this question will disappear from here in about 7 days and as you yourself have claimed will be way up at the top in a few days and likely missed by many. If you expect a major change like this to occur in 7 days, you're seriously mistaken. BTW, while you may be right that your discussion will be largely ignored on the talk page (because part of what your discussing is part of wider policy which many people agree with and the other part doesn't really have a solution) as has already been demonstrated your discussion is going to be even more ignored here. Finally this is not the main page, but the place for asking factual questions. We have a dedicate page for discussing ways to improve the reference desk which for the many reasons I've already mentioned is a far better place to discuss this. Nil Einne (talk) 19:15, 27 August 2009 (UTC)

P.S. I commented out the template as this issue has been resolved Nil Einne (talk) 19:18, 27 August 2009 (UTC)

Repeated static shocks.

Is there any known health issue surrounding repeated static shocks to some particular part of the body (the tip of a finger, for example)? Suppose someone gets 'zapped' by their car door handle several times a day - every single day for many years? SteveBaker (talk) 11:45, 27 August 2009 (UTC)

(Not a complete answer) I used to work in a job where I had to wrap large pallets with industrial cling film - the process was semi automatic - the pallet went on a sort of turntable - like a huge record player... Anyway the unrolling of the 'cling film' produced massive amounts of static electricity (near van der graff levels) - I was constantly being zapped on the forearms (like 5 times second for ~5 hrs a day)- for a few months. I'm still alive!

More reliably I don't remember being given any health and safety warnings or instructions - so I guess it's not considered a risk - that was more than 10 years ago. I would guess that if there is any doubt then the Health and Safety Executive (UK) or the equivalent organisation in another country will have info on it. So that would be a place to look. thanks for listening83.100.250.79 (talk) 13:21, 27 August 2009 (UTC)

Apparently the International Electro Technical Commission (what? no article?) states that a single transient or capacitive discharge, as is the case with static electricity, requires energy in excess of 5 Joules (5000mJ) to produce a direct serious risk to health. As for long term effects, according to the Oregon Occupational Safety and Health Administration, "There are no specific standards for static electricity" which likely means there is no data on adverse effects. Rockpocket 17:32, 27 August 2009 (UTC)

Try International Electrotechnical Commission. --Heron (talk) 20:25, 27 August 2009 (UTC)

Ah, Damn you, Heron! ;) Rockpocket 00:54, 28 August 2009 (UTC)

Sorted. --Tagishsimon (talk) 01:00, 28 August 2009 (UTC)

OT but maybe wear gloves when handling your MINI? Perhaps one of these? P.S. Happy belated MINIversary Nil Einne (talk) 18:44, 27 August 2009 (UTC)

It's not a MINI problem - my car is very well-behaved static-electricity-wise. The problem is at work where they replaced the front doors to our office suite with sexxy glass doors with big steel handles - and everyone is getting zapped by them. But it's not really a problem - that just triggered my curiosity. P.S It's not really a "belated" MINIversary - we're celebrating the whole year long! If you're in the Austin/Round Rock, Texas area next month, come along to the Texas "All British Car Day". SteveBaker (talk) 00:04, 28 August 2009 (UTC)

There are sprays (or even some clothes dryer antistatic sheets) which can provide a subtle conductive path to drain off the charge. Edison (talk) 02:54, 28 August 2009 (UTC)

I'd ask the company to have that door checked very thoroughly. It could very likely be that an electric door lock has some creeping current or a short to the door handle. 71.236.26.74 (talk) 04:08, 28 August 2009 (UTC)

When do Baby's start going to the toilet?

According to my mother, when i was born the nurse held me and the first thing i did was to urinate on her! this got me wondering.. when do baby's start peeing and pooing? Does this first occur in the womb or what? 80.47.174.113 (talk) 13:12, 27 August 2009 (UTC)

Amniotic fluid is predominantly fetal urine. For 'number two', see meconium. TenOfAllTrades(talk) 13:52, 27 August 2009 (UTC)

What? I've been soaking in my own urine for the first 9 months of my life?!? Why isn't this little factoid more well known? --antilived^{T | C | G} 19:05, 27 August 2009 (UTC)

Do babies keep their mouths shut for 9 months, or just cough up a lot of piss when they are born? I see various flaws with this set up.83.100.250.79 (talk) —Preceding undated comment added 19:19, 27 August 2009 (UTC).

They swallow the amniotic fluid during gestation. Amniotic fluid is actually over 98% water, with the remainder consisting of fetal cells, urea, creatinine, bile, hormones and various elecrolytes. It circulates through the the stomach and lungs of the fetus and turns over quite rapidly. Rockpocket 19:24, 27 August 2009 (UTC)

Well, technically, fresh urine is sterile and not really bad for you at all. It's only if it is left in air that bacteria gets into it and spoils it. Aren't there people who even claim that drinking it has health benfits? That's something I'm not willing to google from work ;) Vespine (talk) 23:54, 27 August 2009 (UTC)

No need, the 'paedia has it covered: Urophagia and Urine therapy Rockpocket 01:14, 28 August 2009 (UTC)

Brand new babies do not smell like pee. I call BS on this. Edison (talk) 02:52, 28 August 2009 (UTC)

Choking

If you accidently choked by drinking large amounts of water, from a glass of water, but was able to recover say 10 minutes without blacking out, what happens to the liquid in your lungs? Does it get absorbed into the body somehow? And why when you really choke on something, and after 3 minutes of having a coughing fit and able to recover, does it seem impossible to keep your eyes open? --Reticuli88 (talk) 13:34, 27 August 2009 (UTC)

When you cough, you are moving liquid/mucous up into your throat. If you accidentally inhaled liquid into your lungs, unless there is a lot of it you would cough it into your throat and swallow it without noticing. If there was a lot you would cough it into your mouth most likely. As far as keeping your eyes open after a coughing fit, I have never had that problem myself so I am not sure. The Seeker 4 Talk 16:24, 27 August 2009 (UTC)

Sorry to be a pest on this spelling peeve, but I think a lot of folks just don't know this: mucous is an adjective, as in the phrase mucous membrane. The word you want is mucus, with no o. Same remarks apply to callus (a bit of thickened skin) and callous (an adjective, usually metaphorical). --Trovatore (talk) 22:18, 27 August 2009 (UTC)

I was recently watching a show we have about surf life savers and they rescued a girl who had nearly drowned. Even though she hadn't blacked out and appeared fine after coughing up some water they kept her under observation for a while because they claimed you can still suffer Secondary drowning. Vespine (talk) 00:06, 28 August 2009 (UTC)

How long till unmanned plants stop?

For a thing I am writing, I'd need to know the following. If the whole humanity were to disappear suddenly, how long would power plants work? Are there systems that would shut them down immediately? Would some of them keep working for hours/days? And what is the answer for other infrastructures (water and gas networks, say)? And am I right in thinking that communication and GPS satellites would keep working for a while, or is there some kind of necessary remote maintenance? Thanks, [[::User:Goochelaar|Goochelaar]] ([[::User talk:Goochelaar|talk]]) 14:04, 27 August 2009 (UTC)

See this article by the Straight Dope : "When the zombies take over, how long till the electricity fails?" It's an interesting read. (It is, however, North America specific.)APL (talk) 14:09, 27 August 2009 (UTC)

Hydroelectric, wind and solar plants would run a long time. Coal plants would run out of fuel fairly quickly (less then 48 hours) unless something happened to put them into automatic shutdown sooner. Not sure on nuclear, but if your power runs too long and people suddenly disappeared, then a large amount of fires might break out quickly from people who had food cooking on their stove and such. Googlemeister (talk) 15:05, 27 August 2009 (UTC)

The thrust of the article I linked seemed to be that unless specific steps were taken to allow things to fail gracefully, the whole system would come down almost immediately. Many power-plants would hit minor, routine difficulties and without operator intervention would be automatically shut down, this would screw up the whole grid, and that would in turn screw up even those power plants that would otherwise last a long time. APL (talk) 16:23, 27 August 2009 (UTC)

Having been involved in grid operation, I doubt that everything would immediately shut down. The grid would sectionalize, but it is full of automatic systems which are programmed to keep alive or reliven every section that is capable of withstanding system voltage. Hydro generation could go on a very long time. Solar and wind systems could automatically remain alive or resynchronize to a grid. Some such systems are designed to operate independently of the grid. Edison (talk) 02:51, 28 August 2009 (UTC)

Using antennas

I have a circuit which generates some sine wave. I have to transmit this signal by some antenna. May be I will use a loop antenna. Can anybody please tell me how to do that ? —Preceding unsigned comment added by 218.248.80.114 (talk) 15:24, 27 August 2009 (UTC)

Connecting the antenna to the circuit's output tap is the best way to couple the circuit oscillation into a propagating radio wave. In fact, the circuit is transmitting already - just weakly. The antenna will help match the impedance of the circuit to the surrounding air, and may provide directionality for the transmission. What frequency is the sine wave? What power is output (you might want or need a power amplifier). What do you plan to do to detect the signal? If you can answer these, you can narrow down your options significantly; otherwise your question is so broad that it's basically unanswerable. Nimur (talk) 15:49, 27 August 2009 (UTC)

Well the signal is probably 10 Mhz. The signal is to be recieved in a room 32 x 20 feet with recieving antennas at the corners. The reception antenna will be dipole type. Reception circuit is to be designed too. —Preceding unsigned comment added by 218.248.80.114 (talk) 16:19, 27 August 2009 (UTC)

HF is a tough spectrum. You either need large antennas (e.g. 10 meters), or fancy tricks you can't afford. However, you can get away with a crummy dipole whip antenna if you spend a little more effort on your power amplifier at the transmitter, and getting your receiver properly tuned (a nice low noise amplifier will help there, also). Are you simply transmitting a continous tone, or do you have any information modulated on this 10MHz signal? Are you trying to do position sensing? If so, you'll need some clock synchronization (there are a lot of ways to do this). Nimur (talk) 17:11, 27 August 2009 (UTC)

Well in that case i can in go to lower frequencies in the khz range. I will be sending a continuous tone and for position sensing of the sender by the receiver. Main consideration is to make the render antenna small and have low power consumption. Thanks.

Lower frequency will make it worse! You'll need an antenna thousands of meters long if you want to transmit effectively at VLF - and it's not very easy to build one. Nimur (talk) 18:39, 27 August 2009 (UTC)

Well then I will go for any higher frequencies that can be generated by an antenna the size of a cellphone (maybe loop type). And at the same time be received by a high gain low bandwidth antenna. —Preceding unsigned comment added by 218.248.80.114 (talk) 19:11, 27 August 2009 (UTC)

You could experiment with a VCR RF output, which is a TV transmitter, coupled to a dipole, and dipole receivers. In the US, the VHF band is presently vacant in many locations due to the changeover to digital, so interference might be minimal. US VCRs have RF output typically on Channel 3 (72-78 MHZ) and Channel 4 (78--104 MHZ). There are in the US readily available transmitters to send IPOD or cassette audio to car radios via FM at both the lower(circa 88 MHZ) and upper ends (circa 108 MHZ) of the US FM band. Similar gadgets are probably available in many countries, with suitable changes to the channel frequencies. Back in 1892-1908, US inventor Nathan Stubblefield broadcast voice and music at base band frequencies (no high frequency radio waves) using loop antennas and induction. Edison (talk) 02:45, 28 August 2009 (UTC)

Local anaesthetics

I'm curious as to what local anaesthetic I'm likely to receive when I have my tooth removed. I'm told I may need an incision, too, so it's being done at the hospital. Is there a most likely candidate for this? Vimescarrot (talk) 15:51, 27 August 2009 (UTC)

See Dental anesthesia. Probably lidocaine. Good luck with it; hope it goes well. --Tagishsimon (talk) 15:59, 27 August 2009 (UTC)

Frequently dentists use a topical anesthetic to numb the gums prior to using an injected anesthetic. The two may or may not use the same active ingredients. -- 128.104.112.102 (talk) 16:34, 27 August 2009 (UTC)

Thanks. Vimescarrot (talk) 23:11, 27 August 2009 (UTC)

Via study and practice of Eastern Religions, might it be possible to transcend dental medications? Edison (talk) 02:47, 28 August 2009 (UTC)

White noise generator

Would one of these transmitting in the range of 800-2500 MHz have any effect on nearby mobile phones, or could they filter out everything but their own signal? If such a device was able to interfere with mobiles, what sort of power would it need? This is not expressing an intention to do something illegal, just curiosity at the practicality of a method of alleviating a common social problem.→86.132.239.98 (talk) 16:10, 27 August 2009 (UTC)

It depends on the strength of the signal - it's worth noting that white noise will be the simplest to filter out - a psuedo digital signal would probably intefere worse at lower signal strengths.83.100.250.79 (talk) 17:10, 27 August 2009 (UTC)

We have discussed cell phone jammers many times previously. There are commercially available cell-phone jammers; however, these rarely work by "jamming" (e.g. saturating the front-end amplifiers with a powerful interference signal). A white-noise generator might actually have a chance; but it's unlikely you can put enough power into 2 octaves of frequency-spectrum unless you have a very large power source. Instead, a commercial jammer is more properly described as a form of electronic countermeasure, and operates by transmitting a digital interferance (as 83.100 has pointed out above). In reality, mobile radiotelephones are extremely resilient to such jamming; they operate on a lot of bands with a lot of channel options and digital encoding schemes designed to tune out interference; and if you make a jammer that is even moderately powerful, you will certainly attract the attention of the phone company and the FCC (if you're in the US). It's much easier to block signal reception (with large concrete walls, for example) than to try to actively jam the signal. Nimur (talk) 17:17, 27 August 2009 (UTC)

Wouldn't small metal walls be better than large concrete ones? --Tango (talk) 17:51, 27 August 2009 (UTC)

The "Faraday cage" effect is just... it's just a bad, terrible, completely inapplicable approximation for almost any such physical context. We've discussed "faraday cages" with regard to microwaves, elevators, skyscrapers; ... the wavenlengths involved in mobile telephony are long enough that thin metal walls are pretty transparent. Tree leaves are a better "faraday cage" than a sheet of copper [25] [26] [27] (at least, at UHF and similar mobile-telephone bands). Try standing in an elevator and making a cellular telephone call - chances are, you'll have fantastic signal strength. Then try it in a basement - chances are, you'll have no signal strength (even just three or four feet underground). Nimur (talk) 18:36, 27 August 2009 (UTC)

Bear in mind, you are three or four feet underground vertically. The cell tower won't be directly above you, so will have to go through quite a lot of ground to reach you. --Tango (talk) 19:37, 27 August 2009 (UTC)

Thanks to diffraction, though, the radio wave can bend around corners [28]. The signal does not need to be line-of-sight. I suspect the lack of signal in the basement is more due to the presence of a building structure over you, rather than the ground surrounding you. Nimur (talk) 22:04, 27 August 2009 (UTC)

You must have a better phone than mine. Mine never works in elevators. APL (talk) 21:01, 27 August 2009 (UTC)

Visual acuity

Does a person with a visual acuity of 6/7.5 or 6/9 need glasses? 86.166.47.99 (talk) 16:49, 27 August 2009 (UTC)

Need glasses for what? To see? No. To see better? Yes.

You would have to consult with a optometrist and discuss your needs. However, both are probably sufficient to drive in the UK without requiring corrective lenses (In the United Kingdom, the legal standard of vision for driving is roughly equivalent to 6/10, though this not precise). Rockpocket 17:20, 27 August 2009 (UTC)

There is a lot more to consider than just visual acuity. My visual acuity is 6/5 (that is, better than "normal"), but I still have glasses that I wear for close up work (I should be wearing them now... oops!) to correct an astigmatism. --Tango (talk) 17:48, 27 August 2009 (UTC)

Whatever happened to "20/20?" Edison (talk) 02:35, 28 August 2009 (UTC)

6 meters is approximately 20 feet. Both are the standard distance for measuring vision. See Snellen chart. -- Tcncv (talk) 03:19, 28 August 2009 (UTC)

electrical technology

can you suggest two procedure for the determination of thevenin resistance. —Preceding unsigned comment added by 203.110.246.230 (talk) 17:14, 27 August 2009 (UTC)

Yes, certainly. Edison (talk) 02:33, 28 August 2009 (UTC)

Amazingly, two methods are provided in our article, titled Thévenin's theorem. You can also read Norton's theorem, which is closely related.

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Nimur (talk) 17:19, 27 August 2009 (UTC)

Sterilization of Psylocibe spores

Hello, my question is how can psylocibe spores be killed 100%(true heat, and if what temperature?) or are there any other safe methods?TY —Preceding unsigned comment added by 89.122.224.95 (talk) 20:12, 27 August 2009 (UTC)

? What do you mean "safe methods" and why would you want to? Are you trying to torch your neighbor's magic mushroom patch? In that case you'd have to destroy the Mycelium. 71.236.26.74 (talk) 03:55, 28 August 2009 (UTC)

Gravity waves

What is the fundamental difference between gravitational waves and the varying gravitational field that is produced by any moving mass (such as the earth orbiting the sun)? (I assume there is one because gravity waves are apparently extremely difficult to detect and yet variations in the gravitational field emanating from the moving Earth, say, as it appears to a fixed observer, would seem to be trivial to detect.)

A Gravitational wave is a fluctuation in the curvature of spacetime that propagates as a wave, traveling outward from the source. In contrast, if you're in a spaceship passing by the earth, the changes in spacetime curvature that you experience are just due to your motion relative to the earth. In other words, if you stay at a fixed location relative to the Earth, your spaceship will not experience any changes in spacetime curvature (changes in gravity).

Technically, for an isolated system to be a source of a gravitational wave, the third time derivative of the quadrupole moment of the system's stress-energy tensor must be nonzero. This will not be the case for a spherical object like the Earth or the sun that's just sitting there (or equivalently, moving at a constant speed), even if the object is spinning.

Two objects orbiting each other, such as the Earth-sun system, does radiate gravitational waves, resulting in the Earth slowly getting closer to the sun over time. However, the gravitational waves radiated by the Earth-sun system are only enough to stretch or squeeze a ring of particles by just 1 part in 10²⁶, which is much smaller than the 1 part in 10²¹ that can be detected by LIGO. Red Act (talk) 23:45, 27 August 2009 (UTC)

Thank you for your reply, Red Act. Let me be a bit more specific. Let's say I'm at some distance away from the solar system, and I have a very sensitive way of measuring the strength of the gravitational field. As the earth orbits the sun, I'll see a wave-like fluctuation in gravitational field strength (all other things being equal), with a period of one year, simply because of the relative change in the configuration of the two bodies, and this will emanate away from the solar system at the speed of light. Is that correct? But the thing that confuses me is whether this is the gravitational radiation that you refer to, or whether it's a completely different effect. 86.133.242.249 (talk) 00:59, 28 August 2009 (UTC).

I think that is the gravitational wave, if I understand your use of terminology. The fluctuations in the net observed gravitational field, due to the motion of a distant source (mass), propagate with a fixed speed and represent energy movement (at least, so goes the gravitational wave hypothesis). This phenomenon is a gravitational wave; it is not entirely clear what mechanism allows such a fluctuation in observed net gravitational force to exist. Some hypotheses include the graviton, a proposed particle which "carries" these energy fluctuations per wave particle duality; but they have as-yet never been definitely measured in an unambiguous way. Another problem is that such a mechanism implies that other wave phenomena, attributable to the higher order moments of the system's stress-energy tensor, are possible. This implies things like [[like polarization of the gravitational wave, (though these implications have not yet been observed). One of the key problems is that such energy propagation must satisfy conservation of energy - which means that simply by moving, a mass is radiating energy in the form of gravity waves; yet, with no fixed frame of reference, a particle can be said to be moving; and so we need a more elaborate method (such as general relativity) to describe the relationship between the induced gravitational wave and the particles' state description. Also, note that the term "Gravity wave" is not synonymous with gravitational wave - the first is a classical effect that is well-documented and observed in Earth's ocean surface, mesosphere, and elsewhere; the latter is the relativistic physics hypothetical phenomenon. Nimur (talk) 01:16, 28 August 2009 (UTC)

Thanks Nimur. If a gravitational wave is, as you say "fluctuations in the net observed gravitational field, due to the motion of a distant source (mass)", then I guess my question is: Why are the things so hard to detect? Couldn't an experiment be set up on earth using a rotating dumbbell apparatus with a very sensitive gravimeter nearby? And why are they necessarily waves? Wouldn't a mass in non-periodic motion generate a non-wavelike fluctuation? And finally, I thought that there was still some doubt about whether gravitational waves actually exist. It seems self-evident that the movement of a mass would affect the gravitational field at some remote location. How could it be any other way? I think some of my questions might betray some fundamental lack of understanding on my part. 86.133.242.249 (talk) 01:46, 28 August 2009 (UTC).

They are difficult to detect because they are very weak. The concepts involved in detecting them are very simple - you have two rods at right angles to each other and measure them continuously to see if they change length - but the amount they will change length by is extremely small. "Wave" in physics means anything that propagates, it doesn't have to be periodic. There isn't much doubt - gravitational waves are an obvious consequence of a finite speed of gravity. The only real doubt is whether we will be able to detect them. If they aren't there at all then the whole of general relativity goes up in smoke, which would be very surprising because it has made lots of very accurate predictions. Pre-general relativity the speed of gravity was assumed to be infinite, if there aren't any gravitational waves we would need to go back to that assumption. (And find other explanations for things like inspiraling pulsars.) --Tango (talk) 02:18, 28 August 2009 (UTC)

Thank you Tango. I'm sorry to labour this, but it's been confusing me for ages. I think my mistake was in assuming that any detection of a change in gravitational field due to a moving mass (which sounds easy) would be evidence of gravitational waves (i.e. some sort of "propagation" of gravity). From what you say this is wrong for two reasons: first, this would not (by itself) show that the speed of propagation is finite; second, it would not tell anything about the relativistic model of gravitation as a distortion of spacetime, which is the model in which the concept of gravitational waves is couched. Is this more or less correct? 86.133.242.249 (talk) 02:37, 28 August 2009 (UTC).

You may be assuming that you would measure the change in the field by measuring the field itself at different times and comparing them, that won't work - the obvious way of measuring a field is to measure the force is induces, but with gravity the force on your test mass will be the same as the force on your detector (since you are in free fall with respect to anything other than the Earth) so you won't detect anything at all. You have to measure the change directly by measuring the tidal forces, that is what the two rods at right angles I mentioned are doing. Those tidal forces are very weak since to get large changes in gravity you need fast moving, heavy objects that are close by, and there aren't any. We have to make do with fast moving, heavy objects that are far away. It should also be pointed out that movement isn't actually enough, you need acceleration. Somebody else will have to explain why, though, because I'm a little confused by that (I know it must be true because emitting gravitational waves costs energy so can't depend on motion, which is relative to the frame of reference, but can't work out how it works...). --Tango (talk) 03:03, 28 August 2009 (UTC)

invisibility

if a suit emmits a spectrum of light which can't be seen by the human eye i.e. infra red or ultra violet will it be invisible or will it produce a wave like affect or distorted image.--Meloxicam (talk) 01:48, 28 August 2009 (UTC)

It won't make any difference at all. It would still block the visible light from behind it and would probably reflect visible light from in front of it as well. What is happening in parts of the spectrum we can't see is pretty much completely irrelevant for determining what we will see. --Tango (talk) 01:59, 28 August 2009 (UTC)

A suit emitting IR might, like a red hot stove, produce distortion of light waves passing near it, by heating of the air. A suit emitting UV migh cause other objects in the scene to fluoresce, just like a black light bulb. Parts of the spectrum we cannot see can have visible effects. Edison (talk) 02:32, 28 August 2009 (UTC)

"IR" and "heat" are not the same thing. All objects at any temperature emit EM radiation, objects are every day temperatures happen to emit IR. It isn't IR that distorts light near hot objects, it is the hot air caused by the actual heat of the object. Any frequency of EM radiation will heat up anything that absorbs it, what matters is just the total energy being emitted, not the frequency (although the frequency will affect how much it is absorbed). A suit will only cause heat distortions if it is very hot. I don't think the OP intended the suit to emit the radiation by being at the appropriate temperature (which, for UV, would be thousands of degrees C), it would just use bulbs (which may involve a filament at that temperature, of course). --Tango (talk) 02:50, 28 August 2009 (UTC)

Gravitational wave triangulation

LIGO says:

These sites are separated by 3,002 kilometers (1,865 miles). Since gravitational waves are expected to travel at the speed of light, this distance corresponds to a difference in gravitational wave arrival times of up to ten milliseconds. Through the use of triangulation, the difference in arrival times can determine the source of the wave in the sky.

How can a single piece of information (the difference between two times) determine the source of the wave? You need three pieces of information to determine a position in 3D space (hence the name). I can imagine two pieces of information being useful since the universe is fairly sparsely populated so there is likely to be very few potential sources along the line (or curve) that you can narrow the source down to, but there being only one source on an entire plane (or surface) seems unlikely to me. --Tango (talk) 01:57, 28 August 2009 (UTC)

Relatively local area network

Can I join the wireless home network of my friend who lives on a nearby street about 800 meters away? (Uh, half a mile, isn't it.) I asked this question in an electronics shop and the man said no, not unless I built a tall tower to provide line of sight over the intervening houses for the radio signal. Is there no better way? 81.131.51.80 (talk) 02:31, 28 August 2009 (UTC)

I don't think you need a tower, just an aerial on the roof of each house with some appropriate kind of booster. The Computing desk might be a better place to find out what you need to boost the signal. --Tango (talk) 02:42, 28 August 2009 (UTC)

OK, but just to squeeze every drop of science out of the question while I'm here - would this work even if I can't see his roof from my roof due to other people's roofs being in the way? I think the signal would have to go through about six of the things.81.131.51.80 (talk) 02:45, 28 August 2009 (UTC)

Yes. The signal will spread out from his house (or yours for the return journey) and then diffract around the roofs. Those roofs may weaken the signal, but shouldn't block it entirely. --Tango (talk) 03:06, 28 August 2009 (UTC)

In fact, for that reason, an aerial on the roof isn't strictly necessary at all, the aerial could be inside, but you'll get better signal strength with it on the roof. --Tango (talk) 03:07, 28 August 2009 (UTC)

Thanks! That was what I was hoping, having seen diffraction mentioned further up the page, but I wasn't sure if it would work over such large obstacles so many times in a row. (If I imagine water waves instead of radio waves, it seems less extraordinary.) 81.131.51.80 (talk) 03:16, 28 August 2009 (UTC)

Diffraction happens most when the wavelength and the size of the object being diffracted around are comparable. The wavelength for wireless networks is (I believe) on the scale of millimetres, the roofs are on the scale of metres, that is close enough to get significant diffraction. (You won't, however, get much diffraction of visible light (which is on the scale of 100s of nanometres), which is why you can't see the sun when it goes beneath the skyline.) I rather suspect I am oversimplifying the situation here (optics isn't really my area), but I think the general idea is right and that is all you need. --Tango (talk) 03:30, 28 August 2009 (UTC)

Ha, I like the relaxed notion of "comparable". In most situations I encounter, millimeters are not comparable with meters, but I'll take your word for it. I just went and looked up radio waves and saw that amateur radio wavelengths can be exactly house-sized, so I thought maybe that would be good to aim for, but perhaps converting LAN data to ham radio is not a practical idea, I couldn't say, I know nothing. Leaving it at the same frequency is undoubted cheaper, anyway. 81.131.51.80 (talk) 03:58, 28 August 2009 (UTC)