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June 2

What are the "tubes" on USB and similar cables?

My wife asked me about this last night. My guess is that it's some sort of inductance coil to reduce RF interference, but I realized that I don't know for sure. Now I'd like to know. Donald Hosek (talk) 01:20, 2 June 2009 (UTC)

A ferrite ring. It stops common mode signals traveling on the cable, and your guess is correct. They may be required to meet an EMI standard, or electromagnetic compatibility to stop the device beding disrupted by a strong nearby signal, such as a mobile phone. Graeme Bartlett (talk) 01:33, 2 June 2009 (UTC)

I fixed your redlink to common mode - hope you don't mind SpinningSpark 18:14, 2 June 2009 (UTC)

Thanks, the red link was a prompt for someone to write an article. I have now made a disamig page as there are two quite distinct meanings and four articles. Graeme Bartlett (talk) 06:20, 3 June 2009 (UTC)

Coughing and sneezing while unconscious

Can humans cough or sneeze while they are unconscious? -- Beland (talk) 05:05, 2 June 2009 (UTC)

It depends on the level of unconsciousness. Look at the Glasgow Coma Scale and you will see that in lighter states of unconsciousness the patient may be able to obey verbal commands. It seems possible that in this condition they would cough and sneeze. Richard Avery (talk) 07:18, 2 June 2009 (UTC)

Cough is a reflex, not requiring any cognitive input. Even in deep coma people will cough with irritation of the trachea (I've seen this many times). I don't know whether the same is true of sneezing, but I would guess that the right irritant could induce a sneeze in an unconscious person. --Scray (talk) 09:48, 2 June 2009 (UTC)

So what would be the purpose of endotracheal suction of saliva and secretions if the unconscious patient is able to cough? 86.4.190.83 (talk) 13:08, 2 June 2009 (UTC)

They may reflexively cough, but still not with enough vigor to clear their own air passages. Like blinking, there are likely both reflexive and voluntary components to coughing, and unconsciousness may hinder the clearing process without completely eliminate the cough reflex. Additionally, as Richard Avery has noted, there are different severities of unconsciousenss, and every patient is in a way unique; one patient may be able to clear his own air passages unconsciously, and another may not. --Jayron32.talk.contribs 13:31, 2 June 2009 (UTC)

Interesting. Has anyone ever seen anyone sneeze while they are unconscious? -- Beland (talk) 15:17, 2 June 2009 (UTC)

GPS in plane

Is current plane doesn't equip with GPS? Or within the black box that can survive crash? With current technology, is it possible to equip life vest with GPS? Thanks for the answer. roscoe_x (talk) 05:14, 2 June 2009 (UTC)

Many commercial aircraft are equiped with GPS: GPS_navigation_device#Commercial_Aviation. Smaller and older aircraft often do not have GPS. The GPS is not part of the black box (flight data recorder), but the data from the GPS is required to be stored on the flight data recorder (see [1] item 39). Yes, it is possible to equip lift vests with GPS. Sancho

Also it would be possible to equip each life vest with a satellite distress beacon. Of course it's not going to happen on a commercial airliner because it is not required by law and it would increase ticket prices by tens of cents. --203.22.236.14 (talk) 07:43, 2 June 2009 (UTC)

I think the op is slightly confused with how GPS works. GPS is passive. A GPS reciver doesn't transmit anything, just recives information from satalites to work out its location, meaning a life vest equipped with GPS wouldn't be much use other than to tell the wearer where they are. As far as I know you cannot be tracked via GPS. Gunrun (talk) 10:47, 2 June 2009 (UTC)

Quite so, GPS is passive (but a nearby GPS receiver could be detected due to it's internal amplification of the GPS signal). But I believe the OP's real question is "That AirFrance plane seems hard to find, couldn't it have some device to make it easy to find?" That device would be something like GPS+distress beacon and yes, it's very possible. Actually, I'm surprised that aeroplanes don't constantly upload all data that would be stored in the blackbox via the satellite phone network. --Polysylabic Pseudonym (talk) 11:03, 2 June 2009 (UTC)

From what i've found there are regulatory rules around carrying distress signals. Virtually all commercial planes must carry some - automated and manual. There are even life-rafts for planes that have them built into them. Not sure about life-jackets commercial wise but they exist. My understanding of the Air France disappearance was that the plane was flying over a part of the world that gets very limited coverage in terms of Radar / satellite and that was what has caused the difficulty of finding. 194.221.133.226 (talk) 11:12, 2 June 2009 (UTC)

Yes - as others have pointed out - you have to combine a GPS unit with some kind of a transmitter in order for someone else to find out where that unit is. However, in the case of the Air France disaster, the plane probably crashed somewhere in the mid-Atlantic - perhaps 800 miles from the nearest land. Being that far from civilisation means that there is certainly no cellphone coverage and you'd need a pretty powerful transmitter to reach anywhere useful. Just about the only practical technology would be a satellite phone. But you can't put all of that technology into something like a life vest because it's simply too expensive. There are something like 50,000 large passenger aircraft in the world - that's probably five million life vests - of which perhaps a few dozen ever get used for their intended purpose! Adding a satellite phone to each one...with a battery that's kept constantly charged - and replaced when it breaks...a phone that'll survive the worst a plane crash can do...that's an expensive thing - many hundreds of dollars each, certainly. You'd perhaps need to spend several billion dollars to add such a feature to the world's airliners...and quite frankly - it's a total waste of money because airline life vests are so very rarely used.

In the case of the Air France disaster - it appears that the aircraft was in mid-Atlantic, so it would have been flying at perhaps 30,000 feet. Whatever happened was so fast that a mayday signal couldn't be gotten out - and involved a sudden loss of cabin pressure and electricity. Basically - that means an explosion or catastrophic structural failure of some kind - and crash from 30,000 feet. Nobody is going to survive that. Having a way to find a few lifejackets floating out from the wreckage afterwards cannot possibly justify the cost.

The aircraft's own flight recorder does have various transmitters to aid in finding it later - but that assumes that the thing survived the initial disaster - and a fall from 30,000' and a good soaking in salt water afterwards. Those things are tough - but they aren't invincible. Finding the one from flight 447 in a search area of perhaps half a million square miles is going to be very hard indeed...it's probably impossible.

SteveBaker (talk) 12:27, 2 June 2009 (UTC)

Steve, an EPIRB radio beacon transmits via Satellite. Also the phones I was talking about were satellite phones which likewise have global coverage. I'm pretty sure there's global coverage. It should be fairly trivial to install at least one EPIRB in a location on an aeroplane where it will in any disaster end up separated from the wreckage and floating (radio isn't much good under hundreds of metres of water). Come to think of it, all of the black box data -- were it not automatically transmitted during flight over the satellite phone network -- could be easily stored on a small solid state memory device attached to such a beacon to make that also easy to find. --Polysylabic Pseudonym (talk) 12:47, 2 June 2009 (UTC)

"...is it possible to equip life vest with GPS?" Sure, here's one such set up. Many are carried on military and general aviation aircraft. Polysylabic Pseudonym above has linked to the two relevant articles.—eric 13:24, 2 June 2009 (UTC)

And the ugly truth of telecommunications finally comes out! Instantaneous, point-to-point radio contact is much less seamless than it appears to the untrained eye. Just because you can whip out your mobile phone and dial a long-distance number without interference from every other mobile phone on the street doesn't mean an airplane can do the same! Our radio systems, in general, are horribly short-range. While it is true that we do have some technologies for long-range transmissions, the amazing web of instantaneous digital connectivity to every other part of the world is only made possible because in most of our daily life, we are never more than one mile from the nearest cell tower, not more than 100 feet from the nearest 802.11 access point. This allows us to use high-frequency, wide-band shared channels. But these channels are not very good for long-range transmissions. Although it appears to be "point-to-point", it's a really complex set of relaying to get your off of the shared radio channel as proximally as possible. So, when you make a "wire-free" long distance call from your mobile phone to your friend in Angola, the wireless hop is not actually all that far. A series of base-stations route you to a cable (optical fiber) network, and the signal travels by wire for a very very large portion of its journey. It crosses the ocean by submarine communications cable, hits a couple more optical cable routers, and finally gets sent out to a field transmitter which is not more than a few thousand meters from the intended recipient.

An aircraft which is 3000 kilometers from the nearest base station has surprisingly few options for telecommunication, and they are not all that high-tech. On board, there is a suite of radios, ranging from VHF and UHF digital radios to very "1950s" style HF (shortwave) radios with ranges of around a few hundred kilometers. While in flight, the aircraft will often fly "convoy-style", maintaining communication to the ground by proxy over an HF channel to another aircraft a few hundred kilometers away. This radio signal is very low-bandwidth and not exactly reliable. (This has caused problems before). Unfortunately, the sort of nifty broad-band technologies we've grown very accustomed to are based on much higher frequency signals which have much shorter range. Trying to transmit a VHF radio or a 2.4 GHz microwave "mobile-phone" over a thousand kilometers is just not practical.

Maintaining a bidirectional satellite-based communication link during the entire flight would be really quite challenging, although not impossible. Therein lies the "ten extra cents per seat" which was casually described above. Now, here comes another ugly truth about satellites - they're not really global in coverage! To receive effective satellite service, a location must have one or more satellites above the horizon and in view of the transceiver. To save power and decrease launch costs, these communication satellites are NOT in a geostationary orbit - rather, they fly in constellations in predetermined orbits. These orbits do not necessarily provide full coverage for the entire planet (at least not out to "five nines" or 24-hours, 7-days-a-week). (Which telecommunication company wants to pay huge sums of money to provide fantastic satellite reception to the middle of the ocean? The number of subscribers out there is a little low). So, even satellite-based schemes might not provide a 100% uptime on the communication link.

In summary, the transoceanic airplane provides an interesting insight into our communication infrastructure. When isolated from the enormous network of ground relays, optical cables, and effective satellite coverage, the only viable solutions are pretty old-fashioned shortwave radios. Because of fundamental bandwidth limitations, these links are not suitable for an "always-on", constant monitor of the aircraft's position - imagine what would happen if every aircraft on the planet started broadcasting wideband digital updates over globally-ranged transmissions at 9 MHz - there's a shared channel, and it'd get used up pretty darn quick. (If you can't imagine, let me present an analogy - the idea is that you want every individual on a football field to yell all their conversations loud enough so that every other person can hear them, even on the other side of the field. But everyone will be yelling at the same time, and constantly hearing all the chatter from every other person - it destroys any hope for effective communication). Nimur (talk) 15:30, 2 June 2009 (UTC)

Awesome explanations! So there is no satellite that covers the crash area of AF447? If there was one, could it have located the wreck by simply looking? Without a 2-way radio communication. Satellite imagery says there are satellites that can distinguish objects on the ground at least 50 cm apart. Jay (talk) 10:03, 3 June 2009 (UTC)

No - you really don't understand the immensity of the task. They have actually found some wreckage now - just a few small parts. But the search area was immense - thousands to hundreds of thousands of square miles...they got lucky because another aircraft spotted burning wreckage on the ocean while it was still dark and that stood out fairly clearly. You don't take satellite photos at night. Suppose you take a photo (even from some super-high rez military spy satellite) with enough resolution that you can spot wreckage. 50cm resolution isn't enough - let's suppose it needs 20cm resolution to see a floating life vest that's maybe 40cm across for what it is. OK so on your (roughly) 1000x1000 resolution computer screen, you can start looking at the photos this satellite produced - right? You're looking for that life vest. But at 20cm resolution, each 1000x1000 pixel photo covers just 200x200 meters of the ocean. To look for wreckage over just one square kilometer, you'd have to carefully inspect 25 photographs looking for a TINY orange spec just a couple of pixels across that's just barely a smudge on your screen. To search 100,000 square kilometers, you have to look CAREFULLY through 2.5 million photographs of dull, boring ocean! Do have any conception about how impossible that is?!! SteveBaker (talk) 13:34, 3 June 2009 (UTC)

I didn't think of the human angle to it after the satellite had done its job. Also, I missed out that night could be a hindrance, though I did consider cloud cover. But shouldn't the task be fairly straightforward for a digital image processing software - to detect an orange, or yellow or red dot within a limited-coloured canvas of ocean? Jay (talk) 14:30, 3 June 2009 (UTC)

That's assuming you actually got a photo that shows the orange life vest. Any number of things could obscure it, or they might not be wearing a vest at all (holding onto debris, for instance). — The Hand That Feeds You:^Bite 20:14, 3 June 2009 (UTC)

"[Sarkozy] said France has asked for help from U.S. satellite equipment to locate the plane." (http://www.wral.com/news/national_world/world/story/5254928/). Would be interesting to see what the US provided. Jay (talk) 03:47, 4 June 2009 (UTC)

Commercial aircraft are equipped with ACARS, which can send low-volume data. The system uses VHF radio when in line of sight of a fixed tower (essentially when over land) SATCOM (Inmarsat) when over ocean except at high latitude, and HF when over the poles. The ACARS unit aboard the aircraft is used, among other things, to send critical maintenance information (engine performing out of specification) and takeoff and landing information. This info is gathered automatically using the datalink that connects the various computers aboard the aircraft. The datalink always has location and time infor from the aircraft navigation system, which generally uses GPS plus an inertial navigator, at least. There is nothing to prevent the ACARS from sending the aircraft's location if something bad happens, but this is has not been done because this was not one of the goals of the ACARS system. Flight 447 sent out several maintenance alerts, presumably via Inmarsat, and could easily have sent a location message if anyone had thought to add this function. This is trivially easy to see -- in retrospect. -Arch dude (talk) 18:45, 2 June 2009 (UTC)

Update: The ACARS messages do in fact contain the location information. The last flight 447 message had location information to 3 decimal places (about 100 meters.) The problem, apparently, is that this classified as "maintenance data" not "critical flight data," so it (apparently) was not conveyed to the SAR crews. I suspect that this will change in th future. -Arch dude (talk) 22:01, 2 June 2009 (UTC)

I am puzzled that it is not required for all planes to continuously send out its location, say once a minute. If something suddenly happens to a plane and communication is cut off then there is not time to only then send a message. A simple flight number and GPS location (which includes altitude) once a minute is not a lot to ask for. That's maybe 30 bytes of data per plane per minute. I'm sure the cost is negligible for hooking into something like Irridium or Globalstar - and besides you probably get great reception from 10km up. Is there any downside to this? 196.210.200.167 (talk) 19:29, 4 June 2009 (UTC) Eon

Evolution denial & genetic engineering

Do evolution denialists usually take a stand on genetic engineering? If yes, for or against? --KnightMove (talk) 09:58, 2 June 2009 (UTC)

Since almost all of them are religious fundamentalists - it's probably safe to say that most of them are against genetic engineering...although logically, they should probably conclude that it simply doesn't work and is therefore harmless...but logic isn't generally their strong point. SteveBaker (talk) 12:03, 2 June 2009 (UTC)

Actually, Steve, you'd be surprised at how some of the even Young Earthers manage to weave modern genetics into their story. The Answers in Genesis people are the best in this respect, going to great lengths to appear biologically sophisticated.) I think they would probably argue that no new species would be created by such genetic engineering, though of course you can make changes to a species (in the same way you can breed dogs to superficially look different, but they are still dogs. (I don't agree with this, but that's likely their argument.) Answers in Genesis has a LOT to say about genetics in general, about stem cells, and about cloning, but I don't see anything about genetic engineering. I'm not sure they would disagree with it if it were just being used for medical activities, but I'm just speculating. --98.217.14.211 (talk) 12:33, 2 June 2009 (UTC)

Re it's probably safe to say that most of them are against genetic engineering: I find that hard to believe considering that half of Iowa is under GM corn with no signs of the Creationists making any fuss. --Sean 13:22, 2 June 2009 (UTC)

Surely evolution and genetics are logically and conceptually independent of one another ? You could (hypothetically) have evolution without genetics or genetic inheritance without evolution. Darwin, Wallace and Huxley formulated evolution without knowing anything about genetics - indeed, Darwin proposed the entirely incorrect idea of gemmules. When Mendel discovered the laws of genetics he knew nothing of evolution. It is only the joining of the two strands of thought in the modern evolutionary synthesis that makes us think they are inextricably intertwined. Gandalf61 (talk) 15:22, 2 June 2009 (UTC)

You're perfectly right, but evolution deniers usually believe in God as the only ruler of life, which plausibly might make them disregard genetic engineering. Whether this really is the case, was my concern. --KnightMove (talk) 19:35, 2 June 2009 (UTC)

Could you have genetic inheritance without evolution? The only way I can see this working is with no copying errors and asexual reproduction. I'm no biologist though; any thoughts? (Oops, this may be derailing. Should I start a new question?) 80.41.123.51 (talk) 20:02, 2 June 2009 (UTC)

They don't deny the possibility of birth defects; some even say that (some) existing species are corrupted varieties of those that existed in Eden. —Tamfang (talk) 16:58, 4 June 2009 (UTC)

It doesn't automatically follow that individuals who dispute evolution on a religious basis are against genetic engineering. Its a little more complex than that. There are practical examples of genetic mutation and by implication, microevolution, that makes it very difficult for scientifically educated anti-evolutionists to dispute the genetic basis of phenotypic inheritance (though millions of uneducated ones do so quite vehemently). Since genetic engineering (at our current level of sophistication) really impacts at this level, is entirely possible to come up with a rationale whereby one can resolve an anti-evolution, pro-GM stance.

For example, a report issued by the National Council of Churches of Christ takes such a positive stance toward GM. The report sees us continuing God's work in genetic engineering: "Dominion carries with it a concept of custody, of stewardship, of being responsible for, of caring for all creation." They believe the Scripture "exalts the idea that men and women are coming into the full exercise of their given powers of co-creation." In other words, they see GM as a fulfillment of our "dominion over the fishes of the sea, and the fowls of the air, and the beasts." (Genesis 1:26).

However, while accepting microevolution one may still reject macroevolution and the common descent, instead believing the range of species today derive from baraminologic "kinds". They key distinction, in their minds, is the genetic "missing link" between micro- and macroevolution, which allows them to accept the former while disputing the latter. Rockpocket 01:09, 3 June 2009 (UTC)

Except that there's really no difference between micro and macro evolution. — The Hand That Feeds You:^Bite 20:19, 3 June 2009 (UTC)

Other then you can observe micro in real time. Macro has to have ancient remains to back it up. 65.121.141.34 (talk) 20:28, 3 June 2009 (UTC)

Output per man per shift

"output per man per shift" in any massproduction manufacturing industry?

Sathyavolu sar (talk) 14:36, 2 June 2009 (UTC)

This question is a double-post. A few answers were provided here. We can't answer your question any better unless you elaborate on what you mean by "output." Output can be measured a lot of ways. If you have a specific industry in mind, then it should be easy - count the number of widgets built, on average, during one shift. Different companies might have dramatically different productivity, but in a commodity industry those sorts of variations either equalize or one company goes bankrupt. The most uniform system for comparing different industries is to measure the value of the items produced, in dollars (or other currency). I would imagine that the output per man per shift is on the same order of magnitude as the wage paid to that man per shift (unless there is a severe case of worker exploitation, with the profits of the output being disproportionately allocated elsewhere). Nimur (talk) 15:38, 2 June 2009 (UTC)

Depending on the what you seek to do with the answer, output-per-worker may not be the correct measure. For example, if you want to know by how much output increases when a plant employs an additional worker, you want the marginal-worker-output, not the average-worker-output. Wikiant (talk) 15:46, 2 June 2009 (UTC)

In fact, we have an article on that, Marginal product of labor. Nimur (talk) 15:58, 2 June 2009 (UTC)

what is the name of the little crab animals that live in the sand that you see when a wave uncovers them

what is the name of the little crab animals that live in the sand that you see when a wave uncovers them. we saw them when we were at Daytona beach. thay look like tiny shells after a wave washes over them then they burrow themselves back into the sand —Preceding unsigned comment added by 72.65.6.228 (talk) 15:13, 2 June 2009 (UTC)

Emerita (genus)? Talitridae? Bus stop (talk)

Sandhoppers maybe? Check out Amphipoda, the family to which the already mentioned Talitridae belong. If you could specify a size it may be Emerita, again mentioned above, however I get the feeling that you mean something smaller. Hope this helps. 144.32.155.203 (talk) 15:56, 2 June 2009 (UTC)

Besides all of the above, you could also include the Uca genus or Fiddler crab. There are likely dozens of genera and hundreds of species of crabs that exhibit this behavior. --Jayron32.talk.contribs 03:47, 3 June 2009 (UTC)

Or better yet, the Ocypode genus, aka Ghost crab aka Sand crabs. These are often tiny (like, corn-kernel-sized) and make those tiny little holes in the sand at the beach. --Jayron32.talk.contribs 03:49, 3 June 2009 (UTC)

Judging by the location and personal experience, Emerita (genus) is definitely my pick. Sifaka ^talk 05:35, 3 June 2009 (UTC)

Missiles

Missile Technology involves which branches of engineering in actual sense????It may look naive but this doubt has been pounding me from a long time!!!! Does Mechanical Engineering play a significant role in this technology???? —Preceding unsigned comment added by 121.246.174.130 (talk) 16:52, 2 June 2009 (UTC)

Mechanical engineering, aerospace engineering, and electrical engineering are the primary contributing disciplines, with a significant amount of computer science, mathematics, chemical engineering, and other fields. It helps to break down the "missile technology" into some constituent elements, such as propulsion, structure, guidance/control, logistics, and so forth. Take a look at this FAQ from Lockheed Martin - they want "Aerospace Engineering, Business, Computer Engineering, Computer Science, Electrical Engineering, Finance, Human Resources, Math, Mechanical Engineering, Nuclear Engineering, Physics, Supply Chain Management, and Systems Engineering." It's worth noting that "missile" is an extremely broad term - an ICBM is designed and built with a host of different technologies than, say, a TOW missile. Nimur (talk) 17:03, 2 June 2009 (UTC)

A missle, like any other manufactured object, requires many disiplines to come together correctly. Mechanical Engineering plays an important role in keeping the missle in one piece while it reaches the target. On top of that, modern missles are most often computer guided, so programmers and computer engineers will need to have a role in building a missle. There are "rocket scientists" who may work on propulsion as well as the fields listed by the poster above. If you are studying to be part of the mechanical engineering field you should have no trouble finding a job anywhere that you find manufatured goods (and often beyond that). 206.131.39.6 (talk) 17:21, 2 June 2009 (UTC)

What do flu virus names mean?

For instance, H1N1 or H5N1. What is the H and the N? What are the numbers? Do these names apply only to influenza A viruses or are they given to B and C viruses as well?

-- Lesath (talk) 16:59, 2 June 2009 (UTC)

Have you seen H1N1#Nomenclature? "Influenza A virus strains are categorized according to two proteins found on the surface of the virus: hemagglutinin (H) and neuraminidase (N)." The numbers represent variations of these proteins. Nimur (talk) 17:16, 2 June 2009 (UTC)

LOL, each genotype has its own page? In any case, wouldn't a nomenclature discussion be better on a more general page or is this repeated on H5N1 too?

Nerdseeksblonde (talk) 15:38, 8 June 2009 (UTC)

Organometallic Compound

Why sodium ethoxide is not a oganomeallic compoun?Supriyochowdhury (talk) 18:11, 2 June 2009 (UTC)

For a compound to be considered organometallic, there must be a bond between a metal and a carbon atom that posses mainly covalent character. Sodium ethoxide contains a mostly ionic interaction between a sodium (Na⁺) ion and an ethoxide ion (EtO^-). I hope this helps. —Preceding unsigned comment added by 144.32.155.203 (talk) 18:19, 2 June 2009 (UTC)

Exactly. here there is a bond between sodium and oxygen, not carbon. Rkr1991 (talk) 07:56, 3 June 2009 (UTC)

Bees

Hi, i am doing a project on bees at school and i have a few questions.... I am trying to understand why bees bother collecting pollen and nectar from plants? what's motivates them? also why do they bother making honey? again what's in it for them? it seems to me like they are working all their lives, while other animals are busy just pleasing themselves? 80.47.194.97 (talk) 18:13, 2 June 2009 (UTC)

A good place to start would be on our article on the European honey bee which is quite detailed on many of these matters. It specifically talks about what bees do with pollen and nectar and honey. From that article, you can follow blue links to other articles which contain even more information. Honey is a good read as well. --Jayron32.talk.contribs 18:38, 2 June 2009 (UTC)

Briefly summarized, the bees are motivated by nectar, not pollen. However, the flowering plants benefit when bees spread pollen. You might also want to read about pollination, which also discusses the coevolution of bees and flowering plants. Nimur (talk) 18:54, 2 June 2009 (UTC)

They collect the pollen in their pollen baskets and feed it to the baby bees. Bees are built out of pollen and run on nectar (and in the case of honey bees, on honey when they can't get the nectar). 213.122.59.67 (talk) 20:17, 2 June 2009 (UTC)

I don't think it's scientifically accurate to say bees are built out of pollen. Nimur (talk) 21:37, 2 June 2009 (UTC)

Pollen is important for bees too. Pollen baskets evolved to help the bee, not the flower. As our honey bee article notes, pollen is a good source of protein for developing bees. (Nectar and thus honey are low in protein.) -- 128.104.112.106 (talk) 20:16, 2 June 2009 (UTC)

Resonance and Delocalisation

All the important properties of some covalent speices can not be explained by representing single Lewis dot structure or by showing a single structure bbased on theory of hibridisation .Again unusual stability of some covalent speices can not be explained by considaring bond energies and bond length predicted by V.B.T. after that a new thought resonance arise which can explained above property quit sucssessfully. Tell me that how it fulfill these blanck. What is the requirement of the theory of "resonance and delocalisation"?Rikichowdhury (talk) 18:36, 2 June 2009 (UTC)

Resonance is an artifact of an insufficient model. There is no "fliping" between structures or back-and-forth shuffling of electrons in real molecules. The electrons are stable and no different than in molecules whose Lewis dot diagrams do not show resonance. Resonance is a heuristic invented to fit the real behavior of molecules to the Lewis model, especially where the Lewis model cannot accurately represent the actual bonding in the molecule. Valence Bond Theory and the Lewis model cannot, for example, handle fractional bond order. Other theories, developed simultaneously to VBT, such as Molecular orbital theory do a fantastic job of handling fractional bond orders, and there is no need to introduce resonance into molecular orbital theory. However, MOT has its own shortcomings, such as its inability to deal with molecular geometry in a convenient method. Thus VBT or VSEPR theory handles geometry very well, but does not handle bond order well. MOT is complimentary because it handles bond order very well, but not geometry. Of course, real molecules are not identical to either model, and no single model can fully capture reality, but these two work well together in explaining much of molecular behavior. Delocalization is a slightly different issue; it is a real event which occurs in situations where bonding electrons are not "localized" between two atoms, but instead are shared equally among a group of atoms. Two classic examples are the "Three-center two-electron bonding" in diborane and the cyclic delocalized pi-system in aromatic hydrocarbons. --Jayron32.talk.contribs 18:48, 2 June 2009 (UTC)

Grignard Reagents

Would there be a reaction between a grignard reagent and a carboxylic acid, I have drawn a few (probably flawed) mechanisms which would suggest a ketone and water as the products, in addition to HOMgX. This just seems unlikely, it doesnt sit right as it involves OH^- as a leaving group and I felt that as a small ion it would be a poor leaving group. Am I missing some fairly basic organic chemistry?
This would be so much easier to post if I knew how to insert chemical structures in here. —Preceding unsigned comment added by 144.32.155.203 (talk) 18:43, 2 June 2009 (UTC)

The first reaction between a grignard reagent and a carboxylic acid is an acid-base reaction: the carbanion is a wickedly-strong base, removes H+ from the acid to give the carboxylate anion. Later (i.e., if there is still more grignard present), another carbanion can attack the carbonyl (just like for ketones and aldehydes). This tetrahedral (4 sigma bonds) intermediate can collapse to reform the carbonyl and eject an oxygen, but IIRC often does not for magnesium-based reagents. The reaction probably just stops at this stage. When you add water after the reaction is done, you protonate the oxygen anion, and this structure (looks something like a hemiacetal collapses to form a carbonyl. Nucleophilic reactions at carboxyl are not simple replacement of the singly-bonded piece, but rather are reactions of the carbonyl itself. That is, the loss of hydroxyl you propose is not direct. The reason that its instability isn't a problem (if it were to occur by that type of mechanism) is that you aren't just "creating unstable hydroxyl from nothing": the starting material is also an anion. You have to look at the overall reaction, and see that the result is more stable, even though it may have lots of instability. DMacks (talk) 18:59, 2 June 2009 (UTC)

If a grignard reagent gets anywhere near an active hydrogen containing compound (that is even a weak acid), then the immediate product is the corresponding alkane and water. Rkr1991 (talk) 07:54, 3 June 2009 (UTC)

Water? DMacks (talk) 08:00, 3 June 2009 (UTC)

about water quality.

sanitization process and chemicals using in water treatment plants. The concentration and duration period also want to know. —Preceding unsigned comment added by 94.97.53.246 (talk) 19:28, 2 June 2009 (UTC)

See Water purification. 78.144.244.22 (talk) 22:21, 2 June 2009 (UTC)

Cactus Question

I recently impulse purchased this cactus, which may have been poorly cared for in the past. I was just wondering what species it might be, and also what are the brown fuzzy things on it, circling the top of the plant?

Brown Spots Close: http://commons.wikimedia.org/wiki/File:CactusBrownSpots.jpg Full Cactus: http://commons.wikimedia.org/wiki/File:FullCactusWindow.jpg —Preceding unsigned comment added by Mattman723 (talk • contribs) 19:50, 2 June 2009 (UTC)

It looks like a barrel cactus to me, though I'm quite ignorant on such things. --Sean 21:17, 2 June 2009 (UTC)

Well it doesn't have notches that deep, so I doubt it. M@$+@ Ju ~ ♠ 23:18, 2 June 2009 (UTC)

Here is a cactus ID site [2]. The ring of "brown fuzzy things" may be flower buds, but possibly abhorted. Richard Avery (talk) 06:10, 3 June 2009 (UTC)

Here is a "ID request" forum on that site. It might help if you took a better picture, as the detail is in shadow in the window shot. You could also look through all the globose cacti here. --Sean 12:45, 3 June 2009 (UTC)

Does this article sound feasible at all?

This thing Does it defy the laws of physics? --71.234.104.243 (talk) 20:31, 2 June 2009 (UTC)

This invention is not new. It has been 'discovered' many times, but it violates the laws of physics and no one claiming discovery of such a machine has ever successfully demonstrated it. *Max* (talk) 21:37, 2 June 2009 (UTC).

Per Max, any perpetual motion machine of the first kind must violate the law of conservation of energy. Unique arrangements of magnets have been popular among perpetual motion aficionados for years; unsurprisingly, not one such invention has ever been successful. TenOfAllTrades(talk) 21:40, 2 June 2009 (UTC)

Here is the patent application: [3]. (Hmmm - he lives on "Asylum street" - what are the odds?) This is certainly recommended reading for enthusiastic "nut-job" spotters such as myself. (I'm DEFINITELY going to have to figure out a way for someone to pay me a dollar every time someone confuses "force" with "energy".) The Chicago Tribune article says he spins the wheel and it spins for a while and then stops...this is pretty much exactly what you'd expect any claim of a perpetual motion machine to do - so there is no surprise there. On my home Wiki, I have a "You know you are a crank when..." checklist for exactly this kind of occasions: [4]...let's see how this guy does...hmmm...so far only a rather disappointing 3 out of a possible 8 points - but I've decided to award him a bonus point for using his magnets "in cold fusion mode" - which is certainly a novel and exciting breakthrough in perpetual motion machine design. He has "neutron barrier planes" AND "atomic holes" - and it somehow involves the synergy of the entire universe as a part of it's operating mechanism - which is all really quite remarkable for a machine comprising a dozen magnets nailed onto a wheel. It's comforting to know that this wonder of mechanical genius operates equally well in clockwise AND anticlockwise rotations. But I trust that if he gets his patent, he'll be claiming that it proves that his machine works - and if he doesn't get it, he'll claim it's "big oil" putting him down...so we can look forward to plenty more fun in the future. SteveBaker (talk) 22:56, 2 June 2009 (UTC)

I think I have stumbled across a free energy system. I take TIME, and convert it to electricity. You see, I put in some TIME at another place from my home. They in turn give me a slip of paper periodically. In turn, I give this slip of paper to a a person in another building. Following the paper trail, another company sends me a slip of paper in the mail, to which I attach yet another slip of paper and mail back. As a result, I plug into the wall and get electricity! BRILLIANT! :) Arakunem^Talk 23:08, 2 June 2009 (UTC)

Does he get any extra points for "rolling stator magnetic field in the fourth dimension" (beyond the existing point for a reference to magnetism)? I think he should do. --Tango (talk) 01:01, 3 June 2009 (UTC)

Well, perhaps a half point. He might mean time (4th dimension?) in which case this is just a fancy way of saying "it's moving", for which no bonus is possible. A true crazed nut-job wouldn't be satisfied with a mere 4th dimension - it would have to be the 11th or something. To be honest, I'm bitterly disappointed that he's not yet announced that he intends to fit this to his car. Proper perpetual motion machine designers no sooner have an idea for their machine than they're out there pulling the motor out of their 1986 Acura to make way for it. But he's just getting into the role - and he's already comparing himself favorably to Edison...that's a promising start. SteveBaker (talk) 02:20, 3 June 2009 (UTC)

I just ... don't understand. The man has built a prototype. Doesn't he spin it and ... see that it does not continue spinning? Doesn't he see that his prototype is incapable of powering anything? I can understand if he is put off by complex mathematical theories or well-established scientific explanations, because those require either a certain level of comprehension or a blind trust in "smarter" scientists who DO understand. (I mean, I can write out some Maxwell equations and take a Cauchy integral and prove beyond any reasonable doubt that there is no way to have a "continuous never ending force-field" around a closed contour... but that requires knowledge of some higher math!) So my (dis)proof of the concepts in the machine might be worthless to the man. But ... he has built this machine! Can't he see that it doesn't actually work? When he tries to power it up, and it doesn't power up, you don't need any theoretical knowledge to verify that behavior. Why in the heck doesn't he accept empirical evidence? Nimur (talk) 03:24, 3 June 2009 (UTC)

And then he says it doesn't work because the magnets need to be more precision-machined and precisely aligned! That would mean... he would have to have an analytic, mathematical description of where to place the magnets and how to shape them (so that he could give the schematic to a machinist). So, he will have to measure, "by observations of the universe and reason itself," the force induced by each magnet (sort of like experimentally rederiving the Biot-Savart law?) And then he will need to calculate the fluxes and field lines and all that (sort of like, solving some Maxwell equations?) If he actually put in the proper scientific rigor into these measurements and calculations, he would rederive all of electromagnetism, and see for himself that his plan doesn't work. That's experimental physics, but he's apparently two hundred years behind on his reading, because it has been done and confirmed observationally a hundred thousand times by high school physics students. It's very frustrating to see how far these cranks can get, because most of the people who look at their work don't know enough to debunk it. Nimur (talk) 03:38, 3 June 2009 (UTC)

As my "You know you are a crank when..." page points out - 99% of cranks are not just ill educated in the sciences - but actually proud of the fact because (they generally claim) their thinking isn't restricted by the limited world-view of the people who went before them. Sadly, this neglects the solid fact that real earth-shattering advances are always made by building on the work of those who came before. Because they don't know all of this really well known science, they are doomed to repeat the mistakes of others. This failure to understand the difference between a force and energy has resulted in this guy wasting (probably) years of his life - paying a small fortune to patent lawyers and making himself look like a complete idiot to the majority of the people he's trying to impress.

It's not just knowledge though and education though. Even if he's unaware of the laws of thermodynamics - and cannot calculate all of those complicated interactions between magnetic fields (I'm quite sure I couldn't do that) - even if you know nothing of that...using the very basics of the scientific method would tell him he's going nowhere with this: He spins the wheel - it spins for a while, then gradually comes to a stop. He claims that this is just because he doesn't have the magnets quite perfectly set up and machined. But it would take him only minutes to try a 'control' experiment in the time-honored scientific tradition. First give your wheel a push of a known amount (maybe wrap a known length of string around the axle and hang a weight on the end to make it spin at a known rate) - and just measure the amount of time the machine takes to come to a stop. Then replace the magnets with bits of non-magnetic material weighing the same amount - which ought to nullify whatever effect you think you have invented. Now give the wheel the same initial push and time how long it takes to stop in that case. Do the experiment 100 times and average the results.

We all know that if he did that super-simple experiment, he'd discover that his complicated system of magnets has NO effect whatever. Not just that his magnetic motor isn't quite able to overcome friction - he'd find that the wheel would spin for exactly the same amount of time whether the things around the edge are magnets or not. At this point, a rational person would have to concede that they were wrong and go back to the drawing board. THAT is what makes someone a scientist - not the years of training and brain full of laws and equations. Although those kinds of things definitely help you to say "Hmmm - I think I'll try to invent a perpetual motion machine today...oh...but wait...those darned laws of thermodynamics again. OK then - back to making a better mousetrap." - but they aren't NECESSARY to being a scientist. SteveBaker (talk) 13:20, 3 June 2009 (UTC)

Nimur, Perpetual motion enthusiasts are convinced that if they can only "balance" out the forces that are working to slow down their machine. A non-working prototype that "isn't quite balanced" will still be taken as a proof of concept by these people, because they take it as given that they can "balance" the forces in such a way that they get free energy, in their mind the only part of the design that needs testing is everything else.

Of course, to a rational outside observer that's completely backwards. I don't need proof that you can spin some magnets around in a circle. What I need proof of is that you can "balance out" the laws of thermodynamics. APL (talk) 13:44, 3 June 2009 (UTC)

As long as his hydrocoptic marsel vanes are properly fitted to the ambifacient lunar wane shaft, I can't see why it wouldn't work. --Sean 12:56, 3 June 2009 (UTC)

vapourised alcohol after flaming sambuca?

Hi a friend of mine after having downing a shot of flaming sambuca always inverts the shot glass. He then proceeds to lift up the glass marginally (enough to get a straw under), and then inhales. He says that by doing so he is breathing in vapourised alcohol. He claims these actions help one get drunk faster. I thought wouldn't the gases in the glass just be normal gases found in air with perhaps a bit more carbon dioxide? Would there be any vapourised alcohol? Presumeably a little - but I believe alcohol (in this case just talking about ethanol, obviously) is not very well absorbed when inhaled anyway; so I think that these actions wouldn't help him get drunk more quickly. Am I right? Any thoughts on the matter would be much appreiciated! Thanks RichYPE (talk) 20:58, 2 June 2009 (UTC)

The dude wants to get drunk on Sambuca??? That should be your first clue as to how seriously to take his ideas on the subject. --Trovatore (talk) 21:03, 2 June 2009 (UTC)

Sambuca isn't good for anything else... --Tango (talk) 21:07, 2 June 2009 (UTC)

Sure it is. You put it in coffee. Or you drink it in small quantities to appreciate the taste. But drink enough of it to get drunk? What, you're out of Listerine? --Trovatore (talk) 22:36, 2 June 2009 (UTC)

...and here I should probably point out that neither I nor the Wikimedia Foundation advocates drinking Listerine.... --Trovatore (talk) 22:39, 2 June 2009 (UTC)

Inhaling alcohol vapour would probably get it into your blood pretty quickly, but I can't see why there would be more than trace amounts under the shot glass in those circumstances. --Tango (talk) 21:07, 2 June 2009 (UTC)

Vaporized ethanol can certainly get one drunk...it's used in alcohol research quite often and there are vaporizers on the market (of varying legality). It's a rapid onset of intoxication if the vapor is of sufficient quantity, and it's well absorbed. A just-consumed shot glass always has remnants of the prior contents sticking to the sides, so there would be, presumably, some modest amount of ethanol vapor in the trapped space of an inverted shotglass...but probably not much. I'd guess that the effect of the shot itself would be of a considerably greater get-ya-drunk magnitude than a a little extra vapor...consider this: if your friend had had taken a deep breath over the full (pre-lit) shot, he probably would have gotten a similar amount of ethanol vapor exposure, and trying to become inebriated that way would likely have taken a looong time. — Scientizzle 21:09, 2 June 2009 (UTC)

Back-of-the-envelope calculation: Assume a shot glass volume of 50 mL (about 1.7 ounces). Assume further an in-glass gas temperature of 25 degrees Celsius (77 Fahrenheit). If the glass were entirely filled by ethanol vapor (no air, no water vapor, no other volatiles), there would be just under a tenth of a gram of ethanol present. That works out to a little over 0.1 mL (0.004 fluid ounces) of liquid alcohol, or less than one-hundredth of a shot. Those numbers are pretty generous assumptions, too — if the gas is hotter, it will be less dense and contain less alcohol; there's also little likelihood that other gases (including air and water vapor) will not be present to dilute the alcohol. The stuff he's inhaling might have an interesting taste, but it's not going to do a damn thing for his (in)sobriety. TenOfAllTrades(talk) 21:20, 2 June 2009 (UTC)

Those are good calculations. Furthermore, obviously the absolute maximum amount of ethanol vapor that would be possible to inhale is limited by the amount of liquid left in the glass following shot consumption. Considering the poster's friend is clearly out to get hammered, it's doubtful that there'd be more than a few mL total (of a 42% EtOH fluid) left over for straw-vacuum removal. The contribution of this extra step should have minimal effects on insobriety and will likely leave your counter sticky with Sambuca. — Scientizzle 22:35, 2 June 2009 (UTC)

There's a whole lot of mythology and urban legends surrounding alcohol, like most other mild-altering substances. Since feeling drunk is very subjective, it's easy for people to believe all sorts of unreasonable things about what makes them more or less drunk. Pretty much any high schooler will tell you that, for example, drinking beer through a straw gets you drunk faster. It's complete bullshit, but it's often repeated and widely believed. Friday (talk) 21:13, 2 June 2009 (UTC)

To be honest - if you really wanted to get drunk faster (why is that a good idea?) then not setting light to the sambuca in the first place would really be the best idea! What's burning isn't really the little coffee bean in there - it's the alcohol. By burning it off, you're lowering the amount of alcohol you drink. SteveBaker (talk) 12:58, 3 June 2009 (UTC)

Here is an article about some folks trying to open an alcohol vapor bar, with mixed results. --Sean 13:00, 3 June 2009 (UTC)

wow thanks to everyone who helped! Thanks especially to tenofalltrades for the calculation. I shall inform my friend of the error of his ways! Cheers RichYPE (talk) 19:23, 3 June 2009 (UTC)

Phosphorus in Evolution

In evolution of complex organisms from small and primitive ones, how and why was the Phosphorus taken as a candidate to be a part of almost all life in such a vital form, such as in DNA, ATP, Lipid layer etc, even so when it is not available in atmosphere, only present in soil, and that too almost always in complex phosphate ion forms because of its high reactivity? We (organisms in general) are slowly running out of easily accessible phosphorus. If we really run out, what will be the course of evolution from there on? - DSachan (talk) 21:49, 2 June 2009 (UTC)

Why are we running out of phosphorus? How does it get lost (or made inaccessible)? --Tango (talk) 22:33, 2 June 2009 (UTC)

Phosphorus mentions that "In 2007, at the current rate of consumption, the supply of phosphorus was estimated to run out in 345 years." This is for industrial production of phosphorus compounds, which would presumably include fertilizer. I guess that's the question; what does that mean for everything that needs it to live? Someguy1221 (talk) 23:36, 2 June 2009 (UTC)

Actually, I read something (I think) in a recent issue of Scientific American in an editorial which claimed that the current existing phosphate mines will be tapped out in 40 years or so, and they warned of an impending "phosphorus famine". However, I am not sure if they took into account anticipated untapped phosphorus sources. --Jayron32.talk.contribs 23:59, 2 June 2009 (UTC)

Surely that is phosphorous that we are using for industrial/agricultural purposes, most phosphorous will be in some kind of cycle. Organisms die and decompose, the phosphorous gets back into the soil, gets absorbed by plants, the plant gets eaten, whatever ate the plant gets eaten, so and so on until it ends up in an organism that decomposes and it gets back into the soil. I guess it is possible it is gradually getting leached into the oceans, but that's never going to happen on a scale of 40 years. --Tango (talk) 00:54, 3 June 2009 (UTC)

Oh, the phosphorus isn't going anywhere. However, phosphorus deposits in concentrations we need to use to make all the fertilizer to grow all of the food we do now IS, and that seems to be the big problem. Phosphorus basically allows us to grow much higher calories/acre in terms of food production than would be possible without it. The question comes what will happen when all usable phosphate mines pan out. If we have no sources of phosphate fertilizer, what will happen to our farming practices. Its a genuine problem; I am not sure I trust the 40 year figure, but fertilizer phosphorus is a finite resource, and its a problem that we will likely run into some day in the future. --Jayron32.talk.contribs 03:07, 3 June 2009 (UTC)

It's an interesting question, but it isn't the one the OP asked. --Tango (talk) 13:10, 3 June 2009 (UTC)

If you have access to the journal Science, there's the classic article "Why nature chose phosphates." Westheimer, F.H. (1987) Science. 235(4793):1173-8. [5] If you don't have journal access, you'll probably be able to find a pdf copy or two floating around on the internet if you search on the article title.-- 128.104.112.106 (talk) 14:49, 3 June 2009 (UTC)

It has been suggested that life began either inside the earth or at the ocean floor, so the atmosphere may have been largely irrelevant. Also, see Abiogenesis#Polyphosphates. --JWSurf (talk) 15:02, 3 June 2009 (UTC)

overpressure wave calculation

Hi When you calculate the pressure produced by the blast wave from an explosion, when it is an overpressure shockwave, that means it is over regular atmospherice pressure. Does this mean that objects struck by the wave feel 14.7 psi (atmospheric) plus whatever psi the shockwave is ? for example if the shockwave is 3 psi, does this mean it is subjected to 17.7 psi, or would that object already be experiencing atmospheric pressure, like we do everyday, and only experience 3 psi of pressure? I ask because different sites say different things. Thank you

Robert —Preceding unsigned comment added by 79.67.192.228 (talk) 22:06, 2 June 2009 (UTC)

It's called "over"-pressure for a reason! It's the pressure over and above atmospheric pressure. So, yeah - if the air pressure today is 14.7psi and I set off a stick of dynamite that produces 3psi of overpressure - then (say) a brick wall nearby has 17.7 psi pushing on one side of it - and only 14.7 psi pushing on the other side. It might seem at first sight that a mere 3 psi was nothing much - but if you have a 10' x 6' wall in a room then that's 10x6x12x12=8640 square inches - which is 25920 pounds of force - something like 13 tons. SteveBaker (talk) 23:29, 2 June 2009 (UTC)

If you aren't familiar with pressure measurements here's some context. Weather patterns can regularly cause a 1% variation in atmospheric pressure, and really awful hurricanes can maybe cause a 3% variation (underpressure). The worst storm underpressure ever registered about a 13% under-pressure. A shockwave with 3 psi overpressure is about 20% overpressure (twice as bad as a hurricane!), and though it isn't sustained, it's localized - as Steve Baker pointed out above, it can create some pretty nasty forces on anything it hits. (Straightforward multiplication of the shockwave overpressure peak times the area gives you a good estimate, but not an exact value, of the net force on the wall - there are transient time effects and a host of complex fluid-flow issues as well). Nimur (talk) 03:47, 3 June 2009 (UTC)

global warming potential

how can a GWP value decrease if the gas is in the air for a longer amount of years.? Global warming potential thanks, -Bill —Preceding unsigned comment added by 173.30.14.113 (talk) 23:27, 2 June 2009 (UTC)

I think you've somewhat misunderstood. The amount of a gas typically decreases over the years - it's broken down in one way or another. So the amount of damage you do by putting (say) a ton of Methane into the upper atmosphere gets less and less as that gas breaks down over the years. SteveBaker (talk) 23:32, 2 June 2009 (UTC)

but why after 500 years does the total potential of methane summed over the 500 yrs equal 7.2 and over all 20 yrs it's so much higher at 72? —Preceding unsigned comment added by 173.30.14.113 (talk) 01:11, 3 June 2009 (UTC)

The GWP is how much worse that gas is than CO2, it depends on the timescale because different gasses break down or are removed from the atmosphere at different rates. The GWP of methane decreases over time, which means it must be breaking down or being removed faster than CO2. --Tango (talk) 01:20, 3 June 2009 (UTC)

Indeed. GWP compares the effect of an instantaneous release of a given GHG to an instantaneous release of the same amount of CO₂ over a given number of years. CO₂ is relatively slowly removed from the atmosphere - it's lifetime is hundreds of years (albeit its not quite so simple). Methane (CH₄)is, molecule for molecule, a stronger GHG than CO₂. But it breaks down over only a few years into CO2 and water (and the water is removed from the atmosphere nearly instantaneously). So over time, the GWP of methane approches that of CO2. One important take-home is that a naked GWP value is useless - you always need to know the time frame over which it is computed. If none is specified, often but not universally 100 years is assumed. See Global warming potential#Importance_of_time_horizon. --Stephan Schulz (talk) 09:51, 3 June 2009 (UTC)

Ultimate Fate of Mankind

Has anyone ever done a survey of what the general populace believes the ultimate future of humanity is? For example, 40% say we'll colonize the universe, 40% say we'll blow ourselves up, 20% believe some deity will end it all, something along those lines? TheFutureAwaits (talk) 23:28, 2 June 2009 (UTC)

I imagine such a survey would depend very much on when you did it (during the cold war I expect a very large proportion expected use to blow ourselves up, probably fewer do now, although maybe a few more since North Korea started making significant progress with its nuclear program), and the populace you targeted (basically, the more religious people you ask, the more people are going to give a religious response). It would be interesting to find out, though (I don't know if such surveys have been done). It's not really what we're here for, but we could hold a mini-survey of ref deskers (whose opinions are far more interesting that the general populace!). Personally, I think the two most likely ultimate fates are colonising the solar system and then getting wiped out when the sun dies (that gives us few billion years - one billion on Earth, but we could move further out, although our population may need to dramatically reduce), or colonising the galaxy (I very much doubt we'll ever leave the galaxy, the distances involved are just too vast and faster-than-light travel is just too unlikely) and getting wiped out when the galaxy runs out of stuff to make new stars out of and the old ones all die (which gives us about 100 trillion years). I know this is far longer than other animal species have generally lasted, but intelligence means we adapt to new environments without evolving physiologically (so staying the same species), other species have had to become new species in order to deal with new environments. --Tango (talk) 23:42, 2 June 2009 (UTC)

Everything must have an end, so one day humans will no longer exist. 78.151.147.255 (talk) 00:16, 3 June 2009 (UTC)

Why must everything have an end? --Tango (talk) 00:50, 3 June 2009 (UTC)

Humanity will replace itself within the next 20 years. See Technological singularity. -Arch dude (talk) 01:31, 3 June 2009 (UTC)

I'm not at all convinced. I haven't even seen a reliable quantification of human mental capacity, so how could anyone possibly make such a prediction? --Tango (talk) 01:44, 3 June 2009 (UTC)

Twenty Years? Care to ... make a wager on that? APL (talk) 13:51, 3 June 2009 (UTC)

Sheesh, you know, it would be nice if the Refdesk regulars would try to answer the OP's question while citing some sources, so the OP can do some research on his or her own, instead of spouting opinions without any citations. He didn't want our opinions; he wanted to know about everyone's opinions. OP, I found this link on Google Books that says that a 1995 Gallup poll conducted in the US said that 61% of the adults and 71% of the teenagers agreed that "the world will come to an end or be destroyed". In a separate study, a sample of 17,000 high school seniors (meaning 17 or 18 years old), "more than one-third" agreed with the statement, "Nuclear or biological annihilation will probably be the fate of all mankind within my generation." As you can probably guess, the book itself is called "The End of the World As We Know It", so it doesn't dwell on the other options that people chose; but you can presumably track down the footnotes in the book or use search engines to find these polls (and hopefully followup polls to indicate trends). Tempshill (talk) 02:23, 3 June 2009 (UTC)

According to Christianity in the United States, about 76% of the US population is Christian, and 40% of the Christians are evangelical. The bulk of these profess literal belief in the bible, and therefore believe that the rapture will occur "soon." That pretty much does it for mankind. -Arch dude (talk) 03:48, 3 June 2009 (UTC)

As always, it's going to depend on what you define as the "ultimate fate." For example, if humans don't extinguish themselves, but gradually evolve, there will be some point when we are, beyond any reasonable doubt, decisively not human (unless we genetically stagnate indefinitely). So, would that be the end of humanity? You have to precisely define all the other terms as well: "human", "civilization", "ultimate", etc... Nimur (talk) 03:53, 3 June 2009 (UTC)

Our OP isn't interested in what WE thing the end of humanity will be - but what the population in general believes. The trouble is that most of the general public are very susceptible to suggestion. If you ask "What do you think the chances of us blowing ourselves up with nuclear weapons is?" you'll get some highish number. If you ask "Will we get wiped out by a massive meteor strike like the Dinosaurs?" you'll get another high number. You can keep this up indefinitely and the probabilities will soon add up to more than 100%! But if you go and ask "Do you think humanity will get off the earth and live on other planets?" which would preclude any abrupt, disaster-type ending - then they also pick a highish number. People don't think these things through very carefully and they are terrible at understanding probabilities. So this kind of survey depends very sensitively on the questions you ask. SteveBaker (talk) 12:54, 3 June 2009 (UTC)

Steve, again, some source citations would be useful for our OP instead of just ragging on some of his possible assumptions. Tempshill (talk) 20:26, 3 June 2009 (UTC)

While I agree the way you word the question will have a big influence, as is well established in the public polling arena [6] and most people don't think much before answering, I don't think your example demonstrates that well. I can easily see someone saying yes to multiple questions of yours even with great thought because none of them specified it as what you believe is most likely. There's no reason why you can't believe all of those have a good enough chance of happening to say yes. And someone may say no or maybe even though they think one of those is the most likely fate simply because they think the chance for all is relatively low. Nil Einne (talk) 17:13, 8 June 2009 (UTC)

June 3

Earth is seriously moving away from sun?

Is earth seriously moving away from sun? I saw it was update like last night earth moving 20 centimeters apart each year they said because sun is losing solar winds and masses. Is it just earth or this is also happening to venus, mars, and others? If sun is losing mass now, then sun will just lose more and more, I don't think sun will gain mass back again.--69.229.240.187 (talk) 00:25, 3 June 2009 (UTC)

Yes. Tidal forces and loss of solar mass both result in the Earth receding slightly from the Sun. Without checking numbers, I'd expect tidal forces to be the dominant mechanism. The same effect occurs at varying rates on all other bodies orbiting the Sun. The Sun can gain mass (any time a long-period comet crashes into it, for instance) but is a net loser of mass. — Lomn 00:46, 3 June 2009 (UTC)

It is true, but it is a negligible amount. Our measurements of the distance from the Earth to the Sun are only accurate to a few metres (according to Astronomical unit), so a change of 20 centimetres isn't even measurable. It is happening to all planets, though. When the sun nears the end of its life it will throw off its outer layers, dramatically reducing its mass, and then the Earth will move significantly further away, but that won't happen for billions of years. --Tango (talk) 00:49, 3 June 2009 (UTC)

• Does all planets including Mercury and Venus? Venus have backwar orbit, so I always thought Venus will just end up like Triton vs.Neptune or Phobos vs. Mars. But how is Mercury moving farther when it is so close to sun?--69.229.240.187 (talk) 00:58, 3 June 2009 (UTC)

• I honestly can't dig anymore. I couldn't find the source said all the planets is now moving out. Formation and evolution of the solar system don't give us enough informations though.--69.229.240.187 (talk) 02:31, 3 June 2009 (UTC)

• • Venus does NOT have a backwards orbit. It has a backwards rotation, which means that it turns through a day in the opposite direction as the other planets do (or if you prefer, it is upside-down. Same difference). It turns so slowly, however, that a venusian "day" is longer than a venusian "year". And it orbits in the same direction as all of the other planets. However, as noted, the sun is losing mass via mass-energy conversion, which means that as the mass decreases, its gravity decreases over time. Since the force of gravity is decreasing, ALL objects gravitationally bound to the sun will drift farther away. It doesn't matter if we are talking about Mercury or the Oort cloud. Less mass = less gravity. Less gravity = larger orbits. Its that simple. --Jayron32.talk.contribs 03:02, 3 June 2009 (UTC)

Even if it was a retrograde orbit (which is not the case), it would still move out to a larger radius if the sun's mass decreased. Nimur (talk) 03:55, 3 June 2009 (UTC)

For perspective, at a rate of 20 cm / yr, the Earth's orbit would take 7.5 billion years to change 1% in radius. In other words, the current rate of expansion is utterly negligible for any practical purpose. Dragons flight (talk) 03:58, 3 June 2009 (UTC)

• If Dragon Flights is talking about in 7.5 billion years. It is still the same game as usual. Nothing have changed. Earth survival or not is still an even money (50/50). Mercury is going to go definitely. Venus' odd to doom is obviously better than a 50/50, Mars could be a doom one but highly unlikely. When sun expands, then it's surface area will increase drastically, then sun's mass and gravity will probably climb. This is possibly another story.--69.229.240.187 (talk) 04:26, 3 June 2009 (UTC)

Surface area expands OK, but why would mass/gravity climb? It will only decrease. - manya (talk) 04:54, 3 June 2009 (UTC)

We don't even know if earth will still exist at that time or not. It got to be some theory to make earth getting engulf, it's still a 50/50 odds.--69.229.240.187 (talk) 05:00, 3 June 2009 (UTC)

69': You have the ending of the sun all wrong. When it runs out of hydrogen and starts running on helium, it suddenly starts generating a LOT more energy (but not for very long) it blows off an immense amount of material - which is certainly enough to kill everything on earth, blow away it's atmosphere and oceans and generally trash the place. Once that's happened, both the mass and gravity of the sun are a lot less and the gravity can no longer stop the sun from expanding due to photon pressure from all the energy it's putting out - THAT'S why it expands. It doesn't gain mass or gravity - quite the opposite in fact!

You have to think of stars as fighting a continual battle between their immense gravity trying to collapse them into something much smaller and more exotic (like a black hole or a neutron star) and the photon pressure from the energy they put out that's trying to inflate them. If the gravity loses the battle, the star grows to a larger, dimmer red giant - if gravity wins, it shrinks to a white dwarf, a neutron star or a black hole depending on how much gravity there is. Ironically - the bigger the star is, the smaller it ends up being! The Sun - being relatively tiny gets bigger - but NOT heavier. SteveBaker (talk) 12:47, 3 June 2009 (UTC)

As the core fills up with heavier and heavier atoms it becomes denser and so so the pressure at the core increases (due to the stronger gravity) and the fusion rate increases. The sun expands because it is producing so much more energy. the expansion reduces the pressure in the core and slows down the rate of fusion. its a feedback process. (disclamer:I am not an expert) just-emery (talk) 20:04, 3 June 2009 (UTC)

I'm not getting the whole thing wrong just mass and gravity. I didn't know that in past, but I got it now. Yes, when sun gets bigger, it's mass and gravity plummets quickly, mass and gravity just dives way down. I got weight-size thing upside down. Yes I know neutron star and black hole comes from high mass star not sun since our sun is average mass star. yes, I know once sun runs out of hydrogen, earth ocean and life will run out first, earth will become a hell instantly until earth atmosphere runs out earth is a char garbage. But have you seen Formation and evolution of the Solar System#Future yet. They siad because of tidal interaction, earth will get destroy at end of sun's peak size, when mass and gravity drops suddenly. Studys 6 month ago hadn't change yet. Yes, if earth survives, then earth is a trash hell black-out scorchland with nothing on it. Maybe earth will be gone, destroy by sun. With tidal interaction between sun and earth I don't know what it is about.--69.229.240.187 (talk) 22:37, 3 June 2009 (UTC)

Actually what is a tidal force thing when sun gets to peak of it's diameter about? how can tidal force happen when gravity and mass drops.--69.229.240.187 (talk) 00:32, 4 June 2009 (UTC)

All the informations is on this site and source on Formation and evolution of the Solar System#Notes and references numbers 86-89, if my questions is clear fully.--69.229.240.187 (talk) 02:24, 4 June 2009 (UTC)

I haven't read all those posts yet, but the Earth really is moving away from the Sun, and it's not due to nuclear fusion: http://www.skyandtelescope.com/news/46618862.html. That article suggests tidal interactions between Earth and the Sun. Sky and Telescope is a reputable amateur astronomy magazine, but I don't know how scientifically reliable that specific article is. --Bowlhover (talk) 10:54, 4 June 2009 (UTC)

Main factor of earth moving away from sun is lost of mass.It is not only earth but all planets maybe moons vs. planets (Titan and Saturn) is also moving away so is Galilean moons vs Jupiter. Fron Section 15 they said because of tidal bulge. Earth is both moving farther and closer to sun. Is tidal bulge. Net solution is when sun gets old, hydrogen starts to deplete, then with less gravitational pull, then all planets and moons moves farther out. Tidal bulge is probably a friction, slows down earth's orbit, but I don't know how drag of sun and earth shrinking orbit works is my question.--69.229.240.187 (talk) 22:32, 4 June 2009 (UTC)

MM Experiment

When Michelson and Morley did their experiment they were looking for variations in the brightness of the light right? I was under the impresssions that the split beams were recombined into a eyepiece. As they rotated the apparatus they were looking for variations in the brightness of the light right? Because they knew they couldn't make the arms exactly the same length apart. They weren't looking for actual fringe shift, just the effect. —Preceding unsigned comment added by 24.171.145.63 (talk) 00:53, 3 June 2009 (UTC)

Basically you are correct. They could not measure the exact length of each arm with sufficient accuracy with any instrument at their disposal, but by looking at the interference pattern, you can obseerve changes in the difference between the lengths. Whe I set up an interformeter I used a laser, so I had a nice long coherence length to work with. With a laser, you start with two paths that ate roughly the same length. as you vary one length by one wavelength, you cah observe the pattern shift through an entire cycle. I used a mirror mounted to a piezoleletric actuator to vary the length through several wavelengths and observed the repeating cyclic pattern. When using a white light as Michelson did, you need to get the paths a lot closer to the same length to start with. -Arch dude (talk) 01:28, 3 June 2009 (UTC)

Just one more quick question:

http://spiff.rit.edu/classes/phys314/images/mm/mm3_rot.jpg On pg. 336 it says (little below the middle), that if the whole apparatus is turned through 90 degrees the fringe shift would double. Why? —Preceding unsigned comment added by 24.171.145.63 (talk) 04:34, 3 June 2009 (UTC)

That's what would happen if the speed of light *did* depend on motion through the "luminiferous aether". In actual fact, it doesn't, so there is no change. --Tango (talk) 14:56, 3 June 2009 (UTC)

Smallest number of neutrons

What is the smallest number of neutrons to start the formation of a Black Hole?

---- Taxa (talk) 01:04, 3 June 2009 (UTC)

Neutrons do not form black holes. Generally, they are formed by collapsed stars, as such they are called Stellar black holes (there are other types of black holes, but when most people talk about black holes, they mean stellar black holes). According to our article, which I link, there are several factors besides the mass of a star which will lead to it forming a black hole, but the threshold limit seems to be roughly 20 solar masses. That is, stars which are larger than 20x the size of our sun will generally form black holes upon their death, while stars smaller than that will not. --Jayron32.talk.contribs 02:57, 3 June 2009 (UTC)

Neutrons typically form neutron stars, which can not collapse to small enough size to form a black hole. This is because the Pauli Exclusion Principle forbids two neutrons from occupying the same spatial location with the same quantum state. This quantum-mechanical explanation can be "summarized": even though they have no electric charge, neutrons will repel each other if they get squished close enough together via a repulsive nuclear "force" (in truth, this is not a repulsive force because it can't be written as the gradient of an energy potential, which is why the quantum mechanical explanation is "better", but you can sort of conceptualize the idea). NeutronsPure neutrons can't get close enough together for gravity to dominate (which is required for black hole formation) - they must start off with other particle types present, or accrete extra mass in order to form a black hole. Nimur (talk) 04:02, 3 June 2009 (UTC)

Actually the degeneracy pressure can be expressed as a gradient of a potential in the mesoscopic limit. It's still not a force in the everyday understanding of the word as applied to isolated nucleons, but the potential formulation is plenty useful. For example, the Tolman–Oppenheimer–Volkoff limit describes the point at which degeneracy pressure is no longer able to counter gravity and a neutron star would inevitably become a black hole. According to the article it is between 1.5 and 3 solar masses (with uncertainties due to limited understanding of the behavior of nuclear matter at extreme density). So a neutron star can have at most something less than 3 solar masses, which translates to ~4×10⁵⁷ neutrons. Dragons flight (talk) 04:30, 3 June 2009 (UTC)

Of course all this applies for a neutron star under only gravitational contraction. If some other force compresses it, it should be able to go black earlier. Romulan force fields come to mind, but more realistically: What if two minimum mass neutron star smash into each other? Gamma ray burst? --Stephan Schulz (talk) 13:19, 3 June 2009 (UTC)

If you're asking how big a neutron star has to be before its gravitational force is too large for it to keep form collapsing into a black hole, I have no idea. If you're asking for the smallest number required for a black hole to be physically possible, regardless of what forces them together, the answer is a Planck mass divided by the mass of a proton which is 2.1764411×10^-8 kg / 1.672621637×10⁻²⁷ kg = 3.6403606×10¹⁹ neutrons. I think it's actually somewhat less than that, as the energy required to force the neutrons together would raise the mass. Also, the black hole would evaporate almost instantly. — DanielLC 21:45, 3 June 2009 (UTC)

Why does a black hole need to be at least the Planck mass? I believe a smaller black hole would have a Schwarschild radius of less than the Planck length, which is a somewhat meaningless concept, but does that mean the black hole can't exist, rather than just that our theory of black holes breaks down? --Tango (talk) 22:03, 3 June 2009 (UTC)

The latter. We don't have an accepted theory that can understand gravity at such small scales, so whether a black hole could have less than a Planck mass of material or be less than a Planck length in size is unknown. General relativity would no longer be an adequate theory to describe such objects. Dragons flight (talk) 08:28, 4 June 2009 (UTC)

But could you (hypothetically) take a single neutron and accelerate it until its mass exceeded the Planck mass, thus creating a black hole from one neutron (plus a lot of energy) ? Gandalf61 (talk) 15:59, 4 June 2009 (UTC)

The energy used to accelerate a particle does not help creating a black whole, after all there will always be a coordinate system in which the particle is at rest. Dauto (talk) 18:18, 4 June 2009 (UTC)

Okay, how about colliding two neutrons travelling in opposite directions at near light speed - maybe in a galaxy-sized LHC ? Could that (hypothetically) generate a high enough energy density to create a quantum black hole ? Gandalf61 (talk) 12:45, 5 June 2009 (UTC)

I think the problem lies in the definition of what a "black hole" is. A single point-sized particle (a neutron, for example) is a black hole according to some definitions. (Mathematically, there is some distance that lies outside the (zero) size of the particle at which it's gravity becomes so strong that light cannot escape.) Does that make it a black hole? Well, maybe, maybe not. You certainly can't get close enough to a neutron to be 'sucked in' as you would with a black hole created by a collapsing star. I think the problem here is not what nature does or does not do - but merely that we've decided to attach a name to a somewhat flawed definition. SteveBaker (talk) 17:26, 4 June 2009 (UTC)

If a neutron is a black whole, than the no hair theorem is not valid. Dauto (talk) 18:18, 4 June 2009 (UTC)

How to cure fungal plant pathogens

My Mango tree with leaf spots.

My Mango tree has some kind of fungus which is causing it's leafs to produce spots. I think it might be Cercospora capsici but I am not sure since there are many different kinds of plant fungus that might have similar outcomes.

I would like to know what I can do to get rid of the infestation and also how I can prevent it in the future. I have added a photo of the actual plant in question to better illustrate the problem. Joel M. (talk) 02:46, 3 June 2009 (UTC)

Sorry for the lack of responses - have you tried contacting a "master gardener"? Where I live, the local university seems to loan them out to public places like shopping malls and tree nurseries, where they run a (physical) reference desk of their own for a few hours a weekend. (Photo moved) Tempshill (talk) 20:30, 3 June 2009 (UTC)

Fungicide has a couple of natural things you can try that aren't that difficult to find. (If you can't find them at your local grocery store, health food store, drug store or pharmacy, try ordering online) I'm not sure how specific you'll have to target your fungus. Most fungicides seem to be pretty broad spectrum.71.236.26.74 (talk) 15:22, 4 June 2009 (UTC)

Understanding another part of the MM experiment

Scrap my old questions; I get them now. Anyway- I hope this doesn't go against your reference desk policy since this isn't homework that I'm not trying on. here on page 340, first line, it says something along the lines of the width of the fringes varied from 40-60 divisions (im interpreting it to mean there were between 40 and 60 fringes). It than says the average is 50 and says one division means.02 wavelength. Where did this last statement come from?

One divided by 50 is 0.02. They are taking the reciprocal. The "divisions" are not number of fringes - it's the width of each fringe, measured in "Divisions of the screw head" instead of "millimeters" or "centimeters". I don't know why they use such arbitrary units - it's just like the number of marks on a ruler or optical viewer or other measurement device, and needs some conversion to standard units. Nimur (talk) 15:55, 3 June 2009 (UTC)

Lens and mirror placed in water

We have been given following question in summer assignment:-
"A concave mirror and a convex lens are placed in water. What change, if any, do you expect in their focal length"
Since f = 1/R and curvature of lens and mirror won't change if placed in water, am I correct in assuming that focal length won't change? --shanu 05:36, 3 June 2009 (UTC)

For a reflective system, the main concern is the geometry of the surface; but for a refractive system, I think you need to consider the refractive index when calculating the focal length. DMacks (talk) 05:51, 3 June 2009 (UTC)

Take a look art the articles on mirror and refraction. A key point in the mirror article is that "a beam of light reflects off a mirror at an angle of reflection that is equal to its angle of incidence." A key point in the refraction article is "refraction occurs when light waves travel from a medium with a given refractive index to a medium with another." You may need to read more of the refraction article to better understand what this saying. Once you have a better understanding of the two principles, you can revisit the question of what effect water immersion has. A couple of related questions that may test your understanding: (1) When swimming, if you open your eyes underwater, can you see as well as above water? Why? (2) If you wear goggles or a face mask, does this change your vision? Why? (Hint: What shape is the outer surface of the face mask?). Feel free to ask follow-up questions after you've had a look. -- Tcncv (talk) 06:00, 3 June 2009 (UTC)

The question is discussed here. Cuddlyable3 (talk) 09:14, 3 June 2009 (UTC)

The key here is in the precise definition of refractive index. Since this is borderline homework - I'll point you to the "Definition" section of Refractive index - read it carefully. SteveBaker (talk) 12:35, 3 June 2009 (UTC)

Thanks for your help. By the way does it also mean that R = 2f won't work for lens in water? And also since thin lens formula will change, microscopes will be affected when placed in water.--shanu 05:21, 4 June 2009 (UTC) —Preceding unsigned comment added by Rohit..god does not exist (talk • contribs)

That should also help. Dauto (talk) 15:36, 3 June 2009 (UTC)

Thanks for your help. By the way does it also mean that R = 2f won't work for lens in water? And also since thin lens formula will change, microscopes will be affected when placed in water.--shanu 05:23, 4 June 2009 (UTC) —Preceding unsigned comment added by Rohit..god does not exist (talk • contribs)

For an importatn application, see Immersion lithography.-Arch dude (talk) 08:11, 4 June 2009 (UTC)

Sperm Count

Good day,

I was wondering - what is the time frame for the sperm count to reach its maximum ounce the person has ejaculated ? ( how long will it take from a count of 0 to reach 20 000 000)

Thank you

Marcello —Preceding unsigned comment added by Saladza (talk • contribs) 07:21, 3 June 2009 (UTC)

If I understand your question correctly, I do not believe it's normal for the sperm count to reach zero even after multiple ejaculations in a short space of time. If a sperm count is zero, that would likely indicate fertility problems like azoospermia or perhaps that the person has had a vasectomy. In fact according to our article "How long the man has abstained prior to providing the sample for analysis affects the results. Longer periods of abstinence correlate with poorer results - one study found that men with repeated normal results produced abnormal samples if they abstained for more than 10 days. It is recommended not to abstain for more than one or two days before providing the semen sample for analysis" although it's not clear if this includes sperm count or other factors like motility and morphology. Note that sperm counts are only really meaningful in when measuring them from ejaculations. Nil Einne (talk) 07:45, 3 June 2009 (UTC)

Three Step Process Of Lethal Injection

Why is it that we have a three step process for lethal injection, while pets only have one simple injection when they are getting put down? Wouldn't it be better just to use the one? It'd be cheaper and wouldn't last as long, and there have been no known accounts of pets still being alive and conscious yet paralysed when the final injection stops the heart and collapses the lungs (obviously because there is only one injection that kills them outright). Why not just do it like that? --KageTora - (영호 (影虎)) (talk) 10:52, 3 June 2009 (UTC)

You are evidently talking about the US procedure. There has been much debate about this - our article Lethal injection covers this in some detail. The idea is to use the first shot to briefly aneasthetise the victim - the second to relax the muscles so there is no embarrassing thrashing around - and the third to stop the heart. There is much controversy over this because there is a belief that the first injection might not work - or might not work for more than a couple of seconds - resulting in the victim being conscious but unable to move or speak (because of the muscle relaxant) while a painful heart attack ensues from the third injection...also the possibility of surviving the heart attack and then slowly suffocating while the muscle relaxant prevents breathing. For smaller animals (cats, dogs, etc) a single massive shot of barbiturates causes unconsciousness and then both heart stopping and a cessation of breathing in about 30 seconds. The problem is (as our Animal euthanasia article indicates), this doesn't work well on large animals because the barbiturate dose required is too high. I can only presume that humans fall into the "large animals" category...hence the controversial three-step process. SteveBaker (talk) 12:29, 3 June 2009 (UTC)

• Please avoid attempting a debate here by using loaded words like "victim". --Anonymous, 03:45 UTC, June 4, 2009.

Please avoid being uneducated in the use of the English language...pick up a dictionary sometime. From Wiktionary, meaning (2) for the word "victim" is: "Anyone who is physically harmed by another."...being killed by the state executioner certainly counts as being "physically harmed". I chose that word with great care. I you choose to pick a different, and perhaps more 'loaded' meaning - that's a debate of your own making! SteveBaker (talk) 15:39, 4 June 2009 (UTC)

To the talk page, please. --Anon, 08:00 UTC, June 5, 2009.

Also, a different ethical standard is clearly being applied to animal euthanasia than to human euthanasia (which is used more sparingly). It seems to follow that the procedures would reflect that difference in ethical concerns. Nimur (talk) 16:00, 3 June 2009 (UTC)

Having used barbiturates to anesthetize animals for surgery, I can tell you that they are pretty tricky. Even huge doses with small animals don't lead to quick death with 100% reliability -- once in a hundred times the animal continues to breathe at a very slow rate for quite a while. Barbiturates don't actually stop the heart, by the way -- so suppression of breathing is the way they kill. Looie496 (talk) 18:45, 3 June 2009 (UTC)

Animal euthanasia says there is cardiac arrest - is it incorrect? SteveBaker (talk) 20:03, 3 June 2009 (UTC)

Cardiac arrest is inevitable in a lethal injection, but barbiturates do not cause this directly, like potassium chloride does. cyclosarin (talk) 02:45, 8 June 2009 (UTC)

Pushing a helicopter

Suppose there's a helicopter (something small like a Bell 206, not a Chinook) hovering a few feet off the ground. Would it be possible for a human standing on the ground to push/pull the helicopter enough to move it, in any direction, without the aid of any other equipment? — Matt Eason ^{(Talk • Contribs)} 11:06, 3 June 2009 (UTC)

Well, there is no friction and very little air resistance involved - so all you've got to do is overcome the inertia - which is considerable. The classic Bell 212 helicopter weighs in at 3000 to 5000kg depending on fuel and passenger load (actually, technically, what we care about here is the mass not the weight - but it's still 3000 to 5000kg) so it would take quite a bit of effort to get it moving at any kind of speed - and quite a bit more to stop it: Force = Mass x Acceleration - so with a normal kind of force and a big mass, you don't get much acceleration. However even the smallest push would impart some acceleration and if you continue to push, the speed will gradually get faster and faster until you couldn't keep up with it anymore - so technically, in the purest theoretical sense - yes, you could push the helicopter around with no particular problem.

However, a helicopter doesn't just hover in one place passively. If the ground beneath has even a slight slope or unevenness - or there is any kind of wind - or a vertical surface is within maybe 50' in any direction - or if the helicopter isn't set up just perfectly - then without the pilot actively working to keep the helicopter still - it would drift off and spin all over the place at accelerations much greater than you could overcome with your puny muscles! So realistically, the pilot (or perhaps some autopilot hovering aid) is actively and continually making tiny adjustments to keep the helicopter still - and those adjustments would easily counter your puny efforts to move it. If he stops making the adjustments - then the helicopter is going to drift and you're not going to be able to stop it or make a significant difference.

So I'm pretty sure that the theoretical answer is "Yes" and the practical answer is at best "No" and at worst "Not a sufficiently precise question to yield a meaningful response"! SteveBaker (talk) 12:19, 3 June 2009 (UTC)

Very interesting - thanks Steve — Matt Eason ^{(Talk • Contribs)} 12:30, 3 June 2009 (UTC)

Here is a guy doing the fairly common stunt of pulling a train with his teeth. They claim 300 tonnes in this case, and the situation seems analogous to Steve's theoretical perfectly tuned helicopter, with far greater mass. --Sean 13:10, 3 June 2009 (UTC)

The practicality of this can be changed to a similar problem: Can the kick of shooting a gun move a helicopter? Humans are capable of countering the kick of large rifles. However, it was noted during Vietnam that firing rifles that were bolted down to the helicopter would cause it to rock enough to notice. So, humans can push with more force than the kick of the rifle and the kick of the rifle is enough force to cause the helicopter to rock. So, it is feasible that a human would have enough pushing force to cause a helicopter to noticeably move. -- kainaw™ 13:54, 3 June 2009 (UTC)

"Humans are capable of countering the kick of large rifles." But a human probably cannot counter the kick of a .50 caliber machine gun fired rapidly - it's sort of a totally different animal. Even small machine gun like a Squad automatic weapon requires a bipod or a tripod to keep it from blowing back out of control. A large gun such as a GAU-19 (standard fare on a Black Hawk) is going to impart tens or hundreds of kilogram-meters per second of momentum (according to our article, 500 pounds force sustained). I doubt any human sustain such a push. Nimur (talk) 16:06, 3 June 2009 (UTC)

There is no doubt about that. As TotoBaggins points out, humans can move trains that are far heavier than a helicopter. The only problem is the one Steve points out about the natural movement of the helicopter due to the difficulties of keeping it steady are going to be greater than the movement a human could produce. --Tango (talk) 15:37, 3 June 2009 (UTC)

You would probably be pushing below the center of mass, causing the helicopter to pitch or roll a little depending on where you push. I'm not sure which net effect this would have without corrections by the helicopter. PrimeHunter (talk) 16:04, 3 June 2009 (UTC)

OK - I'm going to have to explain helicopter aerodynamics...bear with me! A civilian helicopter - or a heavy-lift military one - would have rotors that bend upwards a little (it's called the "coneing angle"). If you think about the helicoptors rotors - instead of being a couple of separate blades that are sweeping around really fast - imagine them as if they made a solid disk...that's kinda what it looks like. So that when the weight of the helicopter's body is supported by the rotors - the rotor disk is pulled down into a cone (with the point of the cone pointing downwards). Now, when the helicopter rolls (or pitches) that tilts that cone - right? So one side of the rotor disk/cone is now more horizontal and the other side is more steeply tilted upwards. As the rotors travel around the surface of the cone - the one that's moving more horizontally to the ground pushes down the air directly towards the ground - getting the maximum possible upward push - but the rotor that's on the opposite side is nowhere near horizontal - its at some angle to the ground - so the air it pushes goes out at an angle. This does two things. Firstly, it means that when you push on the skids at the bottom of the helicopter - the steeper blade (which is on the far side of the helicopter) pushes the air slightly away from you - which makes the helicopter try to push back against you. But because that air isn't being pushed as hard against the ground as on the blade that's nearest to you - the far side of the helicopter loses a bit of lift - and the side that's nearest to you gains a bit...for as long as you push. This tends to make the helicopter level back out again. So the effect of this coning angle thing - is to give the aircraft some inherent stability...if you make it roll - it tries to roll back to the level position again. That's actually the only thing that makes the helicopter flyable...it would be impossible to have good enough reaction time if it didn't do that. So the fact that you are pushing below the center of gravity turns out not to matter very much! The other thing that helps with stability is that the center of gravity is about halfway up the helicopter - where the engine, gearbox and fueltank probably are. However, the lift from the rotors pulls upwards from the top of the 'mast' - so (in physics 101 terms) you have a 'moment' - you have gravity acting on the center of gravity and the lift acting on the top of the mast. So long as those two forces are in a straight line - nothing much happens. But if the helicopter rolls (or pitches) the two forces are no longer in a straight line - which imparts a rotation - which in turn tries to keep the helicopter level. It's as if the body of the chopper was a plumb-bob hanging under the rotor disk. Anyway - I didn't want to complicate the earlier discussion with all of this complicated stuff. Suffice to say - this ISN'T the reason you couldn't (in theory) push a hovering helicopter. SteveBaker (talk) 19:58, 3 June 2009 (UTC)

Is it possible that the "pushing back against you" bit you mention would be strong enough to actually result in the helicopter moving towards you when you pushed it away from you? That would be a rather interesting bit of trivia. --Tango (talk) 22:00, 3 June 2009 (UTC)

I don't see how. But helicopters are complicated machines - all sorts of bizarre gyroscopic effects - and the way the tail-rotor figures into things...it's tough to reason all of the forces out. SteveBaker (talk) 22:50, 3 June 2009 (UTC)

It's irrelevant to the original question, but it might be worth noting that the effect Steve describes in relation to coning has an analog on some airplanes. Rather than both wings being in a single plane, they may be tilted slightly to form a gentle V-shape, called "dihedral", and this contributes to the airplane's stability in the same way that Steve describes. On the other hand, on fighter aircraft where a bit of instability is desired so the plane is more maneuverable, the tilt may be reversed, which is called "anhedral". See dihedral (aircraft).

One other point. Steve mentioned the helicopter pushing the air "against the ground". Either an airplane or a helicopter makes its lift by pushing air toward the ground, i.e. down. Newton's third law and all that. However, if the vehicle is near enough the ground that the air is pushed substantially against the ground, it gets more lift, as the ground bounces it back up: see ground effect in aircraft.

--Anonymous, 04:02 UTC, June 4, 2009.

"… the wing keeps the airplane up by pushing the air down" eh? True but useless. An aerodynamic force on a body moving through a fluid is accompanied by an equal and opposite force on the fluid, but one does not "make" the other. A body which pushes air down generates lift—a body which generates lift pushes air down.—eric 06:43, 4 June 2009 (UTC)

(Actually - I said it pushes the air "towards" the ground - not "against" it - I picked my words carefully.) I assume that if you're pushing against a helicopter - that it's close enough to the ground for "ground effect" to matter. That greatly increases the amount of lift the helicopter has - but it doesn't change the 'coning angle' effect - which is indeed similar to the effect of dihedral on a fixed-wing aircraft - except that in the case of the helicopter it helps pitch stability as well as roll.

Eric's criticism is technically valid but I can't agree that the original statement was useless - it enabled both he and I (and hopefully, the OP) to perfectly well understand what was being described...and I think it's a clearer statement to the layman. We have to tailor our ref desk responses to a typical layperson - because we can't make assumptions about their scientific background. Saying that pushing the air down keeps the plane up is a perfectly valid statement - it merely fails to explain the REASON why pushing air down keeps the plane up. But then we also say that gasoline propels your car along the road without going into the details of the fluid dynamics, chemistry, thermodynamics and mechanics that makes that happen. Nit picking is unnecessary here - so long as the meaning is clear. 15:32, 4 June 2009 (UTC)

The lice were in Anonymous' hair, not yours. You were explaining dihedral, he was directly discussing lift, and based on his response i suspected did not fully understand your shorthand. Apologies if this was an incorrect assumption.—eric 16:23, 4 June 2009 (UTC)

I think there's been some misreading here. I was the one that mentioned dihedral (for airplanes); Steve was talking about coning (of a helicopter rotor) and I pointed out, as a point of interest, that the principle can extend to airplanes. As to the other point about "against the ground", if Steve would kindly reexamine his carefully worded posting, he will find the phrase in it. --Anon, 17:17 UTC, June 4, 2009.

Monitoring blood glucose levels

A friend of mine is diabetic and she usually tests herself once before a meal and two hours afterwards. I was curious why she has to wait two hours. After a meal, does blood sugar slowly climb to its maximum point after two hours? Or does it quickly surge high and then comes back to a "normal" level over a two hour period. Why not test one hour after eating? or three? --68.92.139.62 (talk) 12:38, 3 June 2009 (UTC)

It depends to some extent on what she's eating. If it is high in sugar then it will increase her blood sugar level pretty quickly. If it more complex carbohydrates, or mostly protein, say, then it takes longer to digest. You may find glycemic index interesting. --Tango (talk) 12:51, 3 June 2009 (UTC)

The timing of glucose testing in diabetes management mostly has to do with the medication regimen the patient is taking. In patients who take insulin, there are different formulations that have short-term (i.e. within a couple hours) and long-term (i.e. over the course of 24 hours) effects. See insulin therapy for details. Every patient will have a different regimen, depending on their own situation. One typical regimen is to take long-term insulin to maintain blood sugar throughout the day, coupled with short-term insulin doses corresponding to each meal to cope with the influx of glucose that happens after eating. The "fasting" blood test (before the meal) is meant to verify that the long-term insulin dose is correct. The 2-hour "post-prandial" blood test checks that the insulin that was taken with the meal was appropriate. You can see from the glycemic index article that in normal individuals, the blood glucose should be about back to normal by 120 minutes = 2 hours. This is the result of the pancreas releasing a burst of insulin, which is what is being simulated by the dose of insulin at mealtime. This, along with the usual time of action of the short-term insulin, is why 2 hours is a good time for a post-prandial check. Often, the patient will be given instructions about what to do if the post-prandial glucose level is too high (take some more insulin) or too low (eat something). The doctor managing the diabetes treatment will look at the test records to make sure that the dosage regimen is appropriate. --- Medical geneticist (talk) 13:33, 3 June 2009 (UTC)

Very interesting. Now my friend doesn't take insulin. It's all diet controlled. --70.167.58.6 (talk) 23:17, 4 June 2009 (UTC)

Energy of a point charge

I have read that that the self energy of a point charge, that is, the energy required to assemble a point charge, is infinite, and i am still struggling to come to terms with it. Does it mean that there cannot exist any point charges in the universe, or does it mean that it is just an embarrassing result of classical electrodynamics? I mean, you can say even the fundamental units of charge, the electron and the proton, are not point charges, but i am asking in principle. Also, we have found that even these fundamental entities are made of quarks, and quarks are made up of what not i don't know, but is there a limit? Say we somehow find the structure of a quark, and find its made up of little xions, and now we start to analyze these xions-its back to square one... is there a limit to exploring the structure of matter? And going by this notion that there can be no point charges, will we ever be able to find an end to this non stop search inside an atom ? Rkr1991 (talk) 12:52, 3 June 2009 (UTC)

The energy required to reduce the separation between two like charges increases as they get closer together. Roughly speaking, the energy for the last bit involves dividing by zero, which gives you infinity (the more precise answer involves improper integrals). We often think about fundamental particles as being point particles, but that's really just because we don't really know what they are, talking about sizes at that scale is largely meaningless because of quantum mechanical effects. So we have to make exceptions for fundamental particles, but any charge made up of more than one such particle can't have zero size. --Tango (talk) 14:39, 3 June 2009 (UTC)

You can't get around this problem by supposing that point charges exist a priori, because even an always-present point charge has an electric field, and the energy in the field (½ ∫ E²) equals the energy required to assemble the point charge from infinity. The field energy shows up as inertial and gravitational mass of the particle. This is a classical result, but in quantum field theory the problem gets worse, not better. The workaround is renormalization, which amounts to treating the particles as though they had a small but nonzero size, or introducing some other small-scale cutoff with a similar effect. Fortunately the predictions of the Standard Model are independent of the cutoff scale as long as it's small enough (the Standard Model is renormalizable). This is understood to mean that the Standard Model is just a large-scale approximation to the real physics, which presumably avoids the infinity in some unknown way, possibly by being discrete or (as in string theory) by distributing the charge over a 1-D structure instead of concentrating it in a point. This is a lot like the use of calculus to model systems that we know are discrete, like fluids or biological populations. -- BenRG (talk) 16:00, 3 June 2009 (UTC)

A finite amount of charge in a one dimensional string would also have infinite amount of energy in its field unless it was infinitely long. the idea that the mass of an electron comes from its electric field through self induction has long be abandoned. just-emery (talk) 20:12, 3 June 2009 (UTC)

BenRG, sure you must be aware that what you described (the introduction of a small arbitrary size) is not the renormalization itself but an essential housekeeping step - the regularization - that must be taken before the renormalization proper can be performed. There are several different ways to regularize the formally divergent integrals that show up in the solutions. Not all of those regularization schemes are based in the introduction of a cutoff. The renormalization itself is done by carefully subtracting the physically unorbservable (and often formally divergent) part of those integrals and keeping only the physically relevant terms. All point particles self energies gets taken care of that way. Dauto (talk) 21:25, 3 June 2009 (UTC)

Well i am able to understand and few points but unable to certain others (having had no formal education in QM), so i can only ask where this leaves us. Does it mean we shouldn't ask questions like what is the energy of a point charge, or that QM has somehow overcome this problem and say this much Joules is the energy of the point charge, or that we are still in the dark and don't know what to make of things ? Can there exeist any point charges in the universe, or is that forbidden ?Rkr1991 (talk) 05:00, 4 June 2009 (UTC)

A little bit of each. Firt: yes, you probabily shouldn't be asking that question because a point particle is a theoretical construct any ways which may not be a valid description of nature, second: yes, QFT solves the problem but it does so by sweeping it under the rug, and third: yes, we are somewhat still in the dark since we don't have a final theory yet. Dauto (talk) 17:52, 4 June 2009 (UTC)

Is it possible to set your own innards on fire?

Is it really possible to set your own innards on fire if you're chainsmoking while drinking your Neutral grain spirit (Everclear and similar) straight? --90.240.197.75 (talk) 14:46, 3 June 2009 (UTC)

The autoignition temperature of ethanol is 425°C ([7]). I doubt the smoke from a cigarette could get it up to that temperature, although I can't find a source for the temperature of cigarette smoke... --Tango (talk) 15:34, 3 June 2009 (UTC)

I'm trying to imagine where the oxygen to maintain the combustion would come from. I guess you'd have to keep taking deep breaths, but then ... Richard Avery (talk) 15:56, 3 June 2009 (UTC)

Did you swallow the booze and then swallow the cig, otherwise I can't imagine smoking gets temps that high inside a person. I am skeptical. 65.121.141.34 (talk) 16:04, 3 June 2009 (UTC)

It may be feasible to, with a combination of a lit cigarette and alcohol vapors, set your face and/or inside of your mouth on fire. But there is no way I could imagine that any such combination could burn your internal organs like lungs or GI-tract. --Jayron32.talk.contribs 18:13, 3 June 2009 (UTC)

I could sorta kinda imagine your breath catching fire (although it seems unlikely) - but not your throat or stomach - there is just not enough oxygen down there to sustain anything like that. SteveBaker (talk) 19:40, 3 June 2009 (UTC)

Sure, an accelerant and central nervous system depressant (Everclear), ignition source (cigarette), make it an obese person who maybe does not wash their clothes very often, and you've all the makings of a case of spontaneous human combustion.—eric 23:30, 3 June 2009 (UTC)

Was anyone else reminded of Helpless (Buffy the Vampire Slayer)? —Tamfang (talk) 18:49, 4 June 2009 (UTC)

What is VCR doing to my TV signal?

I have a coaxial cable from the aerial going into the VCR input socket, and another short coaxial cable connecting from the VCR output socket to the TV. I've noticed that when the VCR is completely unplugged from the power, rather than being just on standby, then the TV signal almost disapears with a very bad very noisy picture quality. So my question, please, is what is the VCR doing to my TV signal? I thought the input and output sockets on the VCR were just passively connected, but apparantly not. 89.243.113.64 (talk) 20:36, 3 June 2009 (UTC)

Almost exactly the same question was asked further up: Wikipedia:Reference_desk/Science#Poor_TV_picture_improves_a_lot_when_VCR_on. See if that answer is any help. --Tango (talk) 20:51, 3 June 2009 (UTC)

I've already seen that thanks. This is a different question about the same items. 89.243.74.161 (talk) 08:53, 4 June 2009 (UTC)

If the only connection between the VCR and the TV is a coaxial cable, that single cable carries either the off-air signal from the aerial OR the video from the VCR in the form of a modulated r.f. signal. The choice is made by an active switch circuit in the VCR. Without power the switch circuit can't pass either signal. Cuddlyable3 (talk) 10:13, 4 June 2009 (UTC)

The VCRs I've owned have passed the input coaxial signal to the output coax when powered off. -- Coneslayer (talk) 17:16, 4 June 2009 (UTC)

You're right the question is largely unrelated but as mentioned in the above question, VCRs do amplify the antenna signal. This is done I believe because otherwise the VCR would antenuate the signal, as it is using it. This amplification is active as long as the VCR is on, regardless of whether it is in standby or fully on. As mentioned above, most VCRs are also capable of adding a additional signal on a selectable channel to the feed so that you can receive the VCR on your TV if your TV has no other inputs. Nil Einne (talk) 00:03, 5 June 2009 (UTC)

I would expect the input to output of a VCR to include a powered buffer amplifier. (The phrase "common collector" comes to mind, or some reason). Edison (talk) 04:57, 5 June 2009 (UTC)

Is there any connection?

Is there any correlation between people who have Irritable Bowel Syndrome and Panic Attacks? —Preceding unsigned comment added by 86.167.247.150 (talk) 21:23, 3 June 2009 (UTC)

I am not a medical practitioner and this is merely an observation from articles I read on Wikipedia. I seems that selective serotonin re-uptake inhibitors are listed as possible treatments for both conditions. I can imagine how frequent panic attacks could result from low serotonin levels and the same could possibly be true for IBS. If you added obsessive compulsive disorder to that list then it would definitely have my vote. But again, I'm not an expert or a professional and you should probably ignore me.

It's unlikely that you'd get an official answer here as that would violate the terms of this page. 196.210.200.167 (talk) 16:32, 4 June 2009 (UTC) Eon

A brief search of medical journals suggests that there is definitely a statistical correlation between IBS and panic disorder. Additionally, the two occur more frequently in females, have similar age of onset and can be precipitated by stress. People with IBS have a higher prevalence of several psychiatric conditions and people with PD may also experience IBS-like symptoms during attacks. Finally, both seem to respond to similar treatment. - cyclosarin (talk) 08:12, 7 June 2009 (UTC)

Space inside a Black Hole

It appears then there are other requirements to form a Black Hole besides minimum number of neutrons. Is there a complete and ordered list of requirements, in addition to minimum number of neutrons, necessary to form a Black Hole? Also can a Black Hole be described (or defined) as matter in space which contains no space? ---- Taxa (talk) 21:57, 3 June 2009 (UTC)

There is only one requirement for a black hole - that the matter in question be contained within a ball of radius smaller than the Schwarzschild radius corresponding to the mass of the matter. (Actually, that's for a non-charged, non-rotating black hole. Without those assumptions you need a slightly more complicated formula, but the principle is the same.) --Tango (talk) 23:19, 3 June 2009 (UTC)

Applications of invisible light frequencies

I need a summer project for school. I have understood that variable lighting is a problem in computer vision, my just physics is not quite strong enough to tell if there are light frequecies that are not so dependent on sun's position on the sky or nearby lamps as visible light and cheap to generate/capture in good quality. I have feeling the answer is no, but it would be better to know for sure. Anyone have any idea? --194.197.235.28 (talk) 23:02, 3 June 2009 (UTC)

Actually this is quite commonly used in image processing. For example, a lot of toll-booths have a camera to catch the license plate of anyone who does not pay the toll. To cope with varying light conditions, the cameras are often sensitive only to infrared light, and the area is illuminated by an infrared bulb. This reduces interference from other sources of light and provides a controlled, constant illumination for the Optical Character Recognition program which will identify the vehicle. One reason this method is easy is because a lot of digital CCD cameras are already sensitive to infrared, so visible light can be filtered out (or left in as supplemental illumination). You might find Infrared photography interesting as well. We also have Thermographic camera, which describes passive infrared photography (using infrared cameras without an illuminating infrared lightbulb). These are commonly used as a type of night vision (not to be confused with low-light amplification). Thermographic infrared images make it very easy to spot vehicles, trucks, humans, and other hot objects, and are also often used in automatic image-processing (for example, automatic aim correction on a combat helicopter). Nimur (talk) 02:41, 4 June 2009 (UTC)

It's important to note that, while both called "infra-red", the light used by thermographic cameras and the light used by standard IR night vision cameras is very different. The latter uses "near infra-red", that is, light with wavelengths just slightly longer than that of visible red light. Thermal cameras use more distant infra-red. IR spans about 3 orders of magnitude compared to less than one spanned by visible light. There is a far greater difference between near and far IR than between violet and red visible light. If it were up to me, I would give near and far infra-red different names (with the boundary corresponding to 100°C). --Tango (talk) 02:21, 5 June 2009 (UTC)

It's not the frequency of the light - after all, the computer's camera only really sees red, green and blue - and some computer vision is done in black and white just because it's easier and the color doesn't really help much. No - the problem is uneven lighting - where some things in the scene are lit by brighter light than others - or when the lights flicker or change brightness while the computer is gathering imagery - or when the light is strongly directional producing super-bright highlights and deep shadows. You really start to appreciate how amazingly adaptable human vision is. SteveBaker (talk) 02:43, 4 June 2009 (UTC)

Right - the point of using active infrared illumination is to control the illumination environment. We could probably also control the visible-light environment too - but in the case of covert military or traffic cameras, flashing visible light around the imaging target is not an option. Using "invisible" infrared allows the operator to produce uniform illumination for the computer-vision system, without directly affecting the human-perceptible parts of the environment. Also, sometimes infrared just has better signal-to-noise qualities - I used a (mostly) infrared beacon for my robotic target-tracker project last year. Nimur (talk) 02:49, 4 June 2009 (UTC)

That answered my question perfectly. Thank you. --194.197.235.28 (talk) 15:17, 4 June 2009 (UTC)

June 4

NDE recovery, fiction vs real life

I've seen it a hundred times on the tube: someone is found completely inert, often in water, and there's a moment of suspense – is the character pining for the fiords? – while CPR is attempted; then the rescuee noisily resumes breathing, and immediately is fully awake (though disoriented).

Does that really happen? —Tamfang (talk) 00:20, 4 June 2009 (UTC)

While it's possible for a victim to regain consciousness, any good CPR will break ribs. Going from unresponsive to verbal (making sounds without any meaning) is probably the best you can hope for. Certainly most CPR will not result in a save, and you can ask anyone in the field. M@$+[[@]] Ju ~ ♠ 00:33, 4 June 2009 (UTC)

In that situation, would the heart necessarily have stopped? If all that is required is mouth-to-mouth then I think full conciousness can return pretty quickly. CPR is normally just to keep the person alive until someone with a defibrillator gets there (and even then, your chances aren't anywhere near as good as TV hospital dramas would have you believe). --Tango (talk) 01:39, 4 June 2009 (UTC)

Isn't it the case that in Real Life, the vast majority of 'flatlines' still result in death, despite the best efforts of everyone? EDIT: Also, that a defibrillator is useless in this situation, despite what TV tells us? --Kurt Shaped Box (talk) 02:45, 4 June 2009 (UTC)

Properly done CPR need not break ribs. Edison (talk) 02:58, 4 June 2009 (UTC)

I have no idea if this is actually true but I remember reading one of those 'true medical confessions!' books ages ago in which an anonymous MD stated that it was not unknown for doctors to deliberately break the patients ribs by performing rough CPR on a patient that they already knew was toast - if the relatives were watching. The thinking being that they'd see that and be assured that absolutely everything that could've be done had been done in an attempt to save the patient... --Kurt Shaped Box (talk) 03:06, 4 June 2009 (UTC)

That is correct; the ever-popular 'flatline' (beeeeeeeeeeeeeeeeeep) in televised medical dramas is not a shockable rhythm. (See asystole). Cardiac arrests can be divided into two broad groups: those which still include some mechanical action by the heart (ventricular tachycardia, atrial fibrillation), and those which don't (asystole, pulseless electrical activity). The former are susceptible to defibrillation and have a much higher survival rate. The latter aren't shockable, and have a very poor prognosis.

Our article on cardiac arrest notes an overall survival rate of about 15% for in-hospital arrests. (Out of hospital rates are lower.) Patients with shockable rhythms fare about ten times better than those with asystole. TenOfAllTrades(talk) 13:48, 4 June 2009 (UTC)

There are many studies of near drowning events, unfortunately i don't have access to any that would answer your question. 100% of victims will survive in the short term (otherwise it's a drowning and not a near drowning). Approximately 80% will survive beyond 24 hours, perhaps with some degree of neurological deficit. Many children with cyanosis or hypoxia following recovery resume breathing after clearing the airway and one or two rescue breaths, and are conscious and alert immediately thereafter.

If the victim is in arrest the prognosis is much poorer, hypoxia has been prolonged and the brain is now ischemic. CPR alone will probably not result in a return of spontaneous circulation, let alone regaining consciousness, defibrillation and/or drugs are required. One thing to note tho is that even professional healthcare providers have a poor success rate at finding a carotid pulse during a suspected arrest event. The following scenario most likely could happen: an apneic victim is removed from the water, rescuers begin CPR but fail to note the presence of a pulse. The victim resumes breathing and shortly regains consciousness. Chest compressions were performed but were not required.—eric 15:37, 4 June 2009 (UTC)

To clarify, my question is not about the odds of survival after (near)drowning or heart attack or whatever, but about the TV cliché of sudden recovery of full consciousness. —Tamfang (talk) 19:02, 4 June 2009 (UTC)

Penile's Erectiom Angel

plz answeer, how can i measure my Penile's Erection angle ? —Preceding unsigned comment added by Greatfencer (talk • contribs) 01:11, 4 June 2009 (UTC)

I suppose a mirror might help. —Tamfang (talk) 02:33, 4 June 2009 (UTC)

Protractor? --Kurt Shaped Box (talk) 02:43, 4 June 2009 (UTC)

Of course, the angle of the dangle is inversely proportional to the heat of the beat... --Jayron32.talk.contribs 02:50, 4 June 2009 (UTC)

(EC)Use your goniometer. If you do not have one handy, the angle of the dangle has been said to be inversely proportionate to the heat of the meat, so a Meat thermometer might allow an accurate indirect measurement. Other anatomical surrogate measurements are mentioned in the work cited. Edison (talk) 02:54, 4 June 2009 (UTC)

The word "goniometer" does not mean "a thing to measure gonads," just as "episcotister" is not a device to test episcopals. Edison (talk) 04:54, 5 June 2009 (UTC)

(EC)How's about making an appointment for a visit to your local hospital's Penile tumescence lab? For some reason, the hospital seen on House M.D. would appear to have more than one. --Kurt Shaped Box (talk) 03:00, 4 June 2009 (UTC)

Employ the service of a fluffer who charges by the degree and read the invoice. Cuddlyable3 (talk) 09:53, 4 June 2009 (UTC)

<applause> —Tamfang (talk) 19:14, 4 June 2009 (UTC)

Drop a barometer from the top to determine the height, and use trigonometry. I am assuming that you know, or can measure, the length. -- Coneslayer (talk) 13:08, 4 June 2009 (UTC)

<applause> —Tamfang (talk) 19:14, 4 June 2009 (UTC)

Take the barometer to a fluffer and say "I'll give you this really nice barometer if you'll measure the angle". SteveBaker (talk) 23:45, 4 June 2009 (UTC)

I think that when dealing with an erection angel I wouldn't worry about her measurements. APL (talk) 03:49, 5 June 2009 (UTC)

Does an erection angel work for a sex goddess? --Jayron32.talk.contribs 04:21, 5 June 2009 (UTC)

<sigh> Okay. What you need is a protractor. That's a half-circle (usually plastic) with marks or scratches indicating the various angles. Stand upright (yeah, erect) and place the center of the flat edge of the protractor against the side of your erect penis, so that the protractor is straight up and down. It will probably be easier to take a measurement from your belly downwards rather than from your balls upwards. HTH. Matt Deres (talk) 23:58, 5 June 2009 (UTC)

Hmmm - perhaps an inclinometer - it measures your inclination. SteveBaker (talk) 03:19, 6 June 2009 (UTC)

I'm not sure why anyone would care about the angle . . . as long as the wee fella is stiff the angle really does not matter . . .

It's one half of a Parabola, anyway, thus a conic section. Edison (talk) 05:26, 10 June 2009 (UTC)

global warming and human water retention

06:34, 4 June 2009 (UTC)Paul fitts (talk)What year did the true science of global warming start? what was the Earth's population at that time? What is the percentage of the human body that is made of water? If you had a 3ft cube of ice, and you melted it...how much water would that be in gallons??

the main reason for my questions.....it doesn't really apprear that sea levels are rising, so if ice caps and glaciers are "melting", and the water levels aren't really rising.....wouldn't it stand to reason that, that the "melted" water has to go somewhere, why not human water retention to make up 3+ billion more we've created over ther last 30 years???

Paul Fitts

The Tuvaluans beg to differ. According to this Reuters article, their whole country could disappear under the waves in 30-50 years. Another factor (which I was reminded of by An Inconvenient Truth) is that if the glaciers are in the water, their melting won't raise the water level. It's when the land-based ice melts that we have to worry. Clarityfiend (talk) 07:29, 4 June 2009 (UTC)

We have, of course, and article at Current sea level rise. Sea level is rising several mm per year. I'm too lazy to work in feet and gallons (which gallons, anyways?), but one cubic meter of ice has 1000 l and will melt into very roughly 900 l of water. --Stephan Schulz (talk) 07:36, 4 June 2009 (UTC)

Google can convert between units, put in something like "3 cubic feet in gallons". After that go outside and watch some grass carefully for a few hours. Did you see it grow? Dmcq (talk) 08:00, 4 June 2009 (UTC)

To put this in context - sea levels are rising a few millimeters each year - but each millimeter of rise represents 360,000,000,000 cubic meters of water. There are about 7 billion people - even if each of us was retaining a cubic meter of water (not even close!) we'd represent only about 0.02 millimeters of ocean depth. No - the reason the rate seems low is that 360,000,000,000 cubic meters means that it takes an awful lot of water to raise all of the oceans in the world by one millimeter. But while a few millimeters may not sound much - over 100 years, that's enough to drown quite a few coastal cities. Sadly, the evidence is that the rate of increase is going up year on year - so we could easily have a dozen or more meters of ocean level rise during the lifetimes of our children - of the younger Ref.Desk denizens. SteveBaker (talk) 15:00, 4 June 2009 (UTC)

Why are washers so called?

It was one of those idle, late night conversations in the tour van on the way home from a gig ... which led precisely nowhere. My theory is that the bigger examples are called penny washers because they are the size of pre-decimal pennies, but what about smaller varieties, and where does 'washer' come from? Any ideas please? Turbotechie (talk) 07:58, 4 June 2009 (UTC)

According to [8] (80% down the page) the origin of the term "washer" for that piece of metal is unknown, though it has had that meaning for at least 400 years and perhaps as many as 650 years. Dragons flight (talk) 08:23, 4 June 2009 (UTC)

Outside a hardware store hung the alarming sign "Nut screws washer and bolts". Cuddlyable3 (talk) 09:42, 4 June 2009 (UTC)

Not forgetting there was a launderette next door Mikenorton (talk) 10:01, 4 June 2009 (UTC)

You are right that penny washers are named for the old pennies, and often they are a similar size, but the term can actually be applied to any size washer. It is a washer with a disproportionately small centre-hole. SpinningSpark 16:34, 4 June 2009 (UTC)

Just for my own education, do you have a source I can read up on SSpark? I would frame it the other way, since washers are designed for the inserted item, so rather than "disproportionately small centre-hole", I would say "disproportionately large outside-diameter". In my very limited engineering experience in a very specialized field, we termed these "standard" and "frictional" washers, where "frictional" were the big ones, designed to offer a larger weight-bearing surface, as opposed to the I/D / O/D sizes needed to transfer load from a bolt head to a typical clearance hole. Franamax (talk) 23:42, 4 June 2009 (UTC)

Do facial products work?

Is there any scientific evidence that any face creams, anti wrinkle creams, eye treatments etc are any better than just splashing water on your face or is it really just hype? Kirk Uk —Preceding unsigned comment added by 87.82.79.175 (talk) 09:26, 4 June 2009 (UTC)

All 3 are better than water at generating profit for someone. Medical eye treatments have to be certified as safe. Cuddlyable3 (talk) 09:46, 4 June 2009 (UTC)

Many of the anti-wrinkle creams are proven to give a temporary lift and do so by using proven science, similarly darkness-removal creams can be proven to remove the appearance of darkness by masking/covering it. You may notice that in adverts of these types the claims are always quite vague (to paraphrase Charlie Brooker)...terms such as "98% of respondents agree", "help reduce appearance of", "helps fight" are all very 'vague' and undetailed - throw in a few random science-sounding (merged with natural-sounding) words and you've got something that says nothing when reviewed by a legal team but can suggest 'proof' to the average consumer. 194.221.133.226 (talk) 10:22, 4 June 2009 (UTC)

In the UK, they have to say "improves the appearance of wrinkles" rather than "removes wrinkles" on the ads now. There was one company a couple of years back that got absolutely castigated for making completely false claims about the abilities of their product (Google for 'Boxwellox'). Not quite as bad as the toothpaste that claimed to be able to split water molecules, producing free oxygen for a deeper clean - but still... --Kurt Shaped Box (talk) 10:47, 4 June 2009 (UTC)

Sunscreen definitely helps us against wrinkles. It can be scientifically tested that protecting your face against UV rays will make you look younger than you are. For example, faces of truck drivers that have been laterally exposed to sun light have been analyzed, and the half exposed to sun light looked older than the other half.--Mr.K. (talk) 10:57, 4 June 2009 (UTC)

It helps preventively against wrinkles, by the way. --Mr.K. (talk) 12:01, 4 June 2009 (UTC)

The big hype of these things in the UK ended quite a few years ago when the manufacturers were faced with either having to downsize their claims - or be treated as medical/pharmacuticals. The fair trade people argued that if they ACTUALLY reduced wrinkles, then these creams must be penetrating the skin and acting on the tissues beneath - which would require them to be classified as drugs. If all they do is fill in the wrinkles - or change their color/reflectivity to make them temporarily less noticable - then that's OK, it's just a cosmetic effect. I don't understand why that's not also the case in the USA. Certainly the claims they make are ridiculously impossible - and if they were possible, these cosmetics would certainly have to be seriously tested because they could have any number of dangerous side-effects. To the extent that they block sunlight, they might work...but their effects are essentially just changes in appearance. SteveBaker (talk) 14:52, 4 June 2009 (UTC)

Well, they also work as well as any other Moisturizer; that is by providing a barrier against evaporation, they cause the underlying skin to retain more moisture. Higher moisture content equals plumper epithelial cells, and plumper cells equals less wrinkles. Of course, a $5.00 bottle of any decent mositurizing lotion will do that; dropping $40.00 on a small 4 ounce tub of the same stuff mixed with a little make-up to cover over dark patches seems excessive to me... But then again, I'm not an aging woman trying to recapture my lost youth, what do I know. --Jayron32.talk.contribs 17:34, 4 June 2009 (UTC)

Hey, wait, here's [9] a SCIENTIFIC assessment of a particular facial product sold by that 'well known high street chemist'. Whether you are impressed by the fact that 43% of the meagre sample thought their skin had improved is up to you. 23% of the placebo sample thought their skin had improved. Richard Avery (talk) 17:38, 4 June 2009 (UTC)

A study involving 50 people; I assume half received the placebo and half the cream? That means of 25 receiving the placebo, 6 liked it, and of 25 receiving the cream, 12 liked it? I wouldn't call such small sample size "statistically significant". The error bars on a sample size of 25 would probably be bigger than the difference between the samples. Heck, I could flip a coin 25 times and get the same results. Additionally, as the sample did not compare the expensive treatment to a cheap one, only to a placebo, it only addresses the possibility that the expensive cream is better than nothing but not neccessarily better than cheaper alternatives. What you have here is a clear example of How to Lie with Statistics. --Jayron32.talk.contribs 17:45, 4 June 2009 (UTC)

Ah! "Buy our amazing anti-wrinkle cream - it has a one in five chance of being better than smearing lard on your face." SteveBaker (talk) 19:51, 4 June 2009 (UTC)

But lard has the advantage of making you smell like pie crust and biscuits. Who wouldn't want to smell fresh-baked pie crust all day? --Jayron32.talk.contribs 20:44, 4 June 2009 (UTC)

If I did it right, that's a 99.9999999635% significance level. If I did it wrong, it's even higher. This should be a two-tailed T-test (try saying that ten times fast), right? There may be problems with that study, but sample size isn't one of them. — DanielLC 16:48, 5 June 2009 (UTC)

According to the Mayo Clinic, "Research suggests that some wrinkle creams contain ingredients that may improve wrinkles. But many of these ingredients haven't undergone scientific research to prove this benefit. If you're looking for a face-lift in a bottle, you probably won't find it in over-the-counter (nonprescription) wrinkle creams. But they may slightly improve the appearance of your skin, depending on how long you use the product and the amount and type of the active ingredient in the wrinkle cream."[10] A Quest For Knowledge (talk) 17:58, 4 June 2009 (UTC)

(EC)::There is Absorption (skin). If any of the products achieve that the questions become: Do you want the substance that gets absorbed in your system? and Does your body do anything with the absorbed substance in the layers of skin that is beneficial or does the absorbed substance just accumulate or get transported away? There are some things like Botox which is a neurotoxin and Silicone or animal derived Collagen that can be injected into the skin. Since they work "internally" they get treated as medical/pharmacutical. Nevertheless they have come under criticism because the two questions above didn't come up with consistent answers when asked by different reviewers. The cosmetics industry is trying to stay away form the cost of having to get their products subjected to licensing for pharmaceuticals (see Cosmeceutical). So they have to come up with things that do not "affect the structure or function of the human body". The reputable ones also try to make sure that their products do not contain known toxins or substances that cause harm in the short term (long term use sometimes reveals things that didn't show up in testing.) Probably more driven by their desire to avoid costly product liability suits than anything else. Adding Surfactants like soap to water makes it a more efficient detergent. It also removes the protective layer of lipids covering the skin and knocks ph of the acid mantle out of whack. To counterbalance that you can apply oils to your skin after washing. Since using pure oils would give you an unpleasant and impractical film of oil on your skin what we use are emulsions. (Also see Cold cream). Since those are prone to Rancidification and microbial growth you'll not only find emulsifiers and stabilizers but also preservatives in those. (Sometimes cleverly marketed as new Vitamin ingredient) In a further step the cosmetics industry then created Moisturizers. Splashing water on your face would not have the same effect, rather the opposite actually. It would rinse away some more oils exposing cells to evaporation and upset the hydrostatic balance causing further drying. It works through constricting fine blood vessels in the skin. AFAIK interest in reducing wrinkles has only gained momentum throughout the past 70 years or so. That along with our increasing knowledge of biochemical processes in the human body has led to many theories being put forward and being rebuked in that respect. The focus used to be the moisture contents of the stratum corneum. Now things like electrolyte balance, Free radicals, cell aging and nerve stimulation, among others, are under study. Some of those studies are either financed by the cosmetics industry through grants, or done in their labs. Study results from company owned labs are rarely published. (If one of their labs found the holy grail in anti-wrinkle treatment I bet they'd gladly spin off a subsidiary and go through the pharmaceutical trials.;-) Facial products work in the regard that they don't leave greasy marks on your clothes or things you touch, don't spoil fast, smell pleasant and supply lipids to your skin. A cooling effect while the continuous phase of the emulsion evaporates is also well established. Product differentiation has companies add various ingredients that at best can provide better product performance and at least not cause any harm. You'd have to research each labeled ingredient separately to get an idea. It is very likely though that lots of substances aren't listed or any research studies are under lock and key at the company. 71.236.26.74 (talk) 00:04, 5 June 2009 (UTC)

To DanielLC, your analysis of the Boots anti-wrinkle cream data is not correct. The data uses discrete variables, not continuous variables. There are two categories of subjects: those with placebo, and those with the new cream. There are two categories of outcome: improvement, or no improvement. We need a chi-square test. The article indicates a total of 60 people in the trial. Let's assume that 30 people were in each group.

Observed values

Cream type	Improvement	No Improvement	Total
New cream	13	17	30
Placebo	7	23	30
Total	20	40	60

Expected values

Cream type	Improvement	No Improvement	Total
New cream	10	20	30
Placebo	10	20	30
Total	20	40	60

Running a chi-square test (without Yates correction) gives a probability of 0.10

This is not statistically significant (by usual criteria). Axl ¤ [Talk] 20:36, 7 June 2009 (UTC)

Although this uses a discrete distribution, it can be approximated as normal distribution. I suggest we move this to the math desk and ask them what test to use. — DanielLC 22:17, 10 June 2009 (UTC)

Feel free to ask at the maths desk, although I am not particularly interested in their opinion. Perhaps you would consider showing your working to demonstrate your conclusion? Thanks. Axl ¤ [Talk] 16:19, 11 June 2009 (UTC)

What happens to toxic sewage sludge?

About 40 - 60% (depending on whether you are in the EU or USA) of treated sewage sludge (biosolids) is reused as agricultural fertilizer. From what I can see on the article on biosolids, the main reason some biosolids cannot be used as fertilizer is that they have a heavy metal and toxic substance content that is too high. Is this true? If so, what happens to this waste? Is it incinerated, landfilled etc? —Preceding unsigned comment added by 157.203.42.175 (talk) 13:23, 4 June 2009 (UTC)

According to this parliamentary note [11], in the UK 62% is applied to agricultural land, 19% is incinerated, 11% is being used in land reclamation with the remainder going to landfill or composting. It also discusses the use of sludge to generate energy from biogas through anaerobic digestion. The report does not mention toxicity as a problem, apart from the issue of Endocrine-Disrupting Chemicals. Mikenorton (talk) 14:11, 4 June 2009 (UTC)

Sludge has some information. 71.236.26.74 (talk) 04:10, 5 June 2009 (UTC)

Frozen peas float when cooked

When you put frozen peas in a saucepan of cold water they sink to the bottom. When the water is heated up the peas float to the surface. But as ice is lighter than water, and frozen peas must contain some ice, I would expect the opposite to happen, i.e. they would start off floating then sink when heated. What is going on here? Lonegroover (talk) 14:45, 4 June 2009 (UTC)

Peas contain lots of stuff besides just water, so maybe enough to overcome the buoyancy from decrease in density of the water being frozen. Do the peas remain the same size, or do they expand when they thaw/heat? Does this happen only if the water gets hot, or can you reproduce it with room-temp water (to exclude nucleated steam giving the lift)? DMacks (talk) 14:53, 4 June 2009 (UTC)

Don't forget that water is densest at about 4C. My guess (and it really is just speculation) would be the following:

Water, in a saucepan at about 10 degrees C, combined with peas at about -18C. Peas initially float in cold water before sinking so clearly the water is denser for a short period. Presumably due to the low temperature of the peas? I would assume that the peas rapidly warm due to their high surface area to volume ratio. As such, the water within the peas would be denser than the water in the pan. Peas have other constituent components, but I would suggest the density of the water in the peas outweighs and (lower) density from the solid matter of the pea. The overall density of the pea should approach the point where they are denser than the surrounding water - this shouldn't be too difficult, the water will be getting colder from the peas but also warmer from the heat input.

I would imagine that the peas remain denser (colder) than the surrounding water for a while - since the source of heat would warm the water first, then the peas When the water boils, the peas could reach a temperature equilibrium with the water (since the water cannot get hotter, regardless of heat input, without turning to steam), or at least become warm enough such that the weighted average of the density of the pea (i.e. the solid matter and water contained within the pea) could overcome the density of the hot/boiling water. —Preceding unsigned comment added by 157.203.42.175 (talk) 15:07, 4 June 2009 (UTC)

The obvious answer is thermal expansion of the peas. Assume the peas have a density near water, but slightly more dense. This is because they are mostly water, but with some solid materials. As the peas heat, their radius expands by some small amount - but their volume increases according to (radius³), so their density will decrease inversely to that. Although water does change its density slightly, it's generally a good assumption that it is an incompressible fluid. Its density should not change significantly between room temperature and near-boiling. (Our article gives about a 5% change, but I don't know if I trust the source data). But, the water inside the peas will also expand - and so the only relevant volume change is the thermal expansion of the solid materials in the pea. Nimur (talk) 14:44, 5 June 2009 (UTC)

What happens if I drink five-year-old soda?

Not fridged, the 12-pack wasn't even opened. Just curious. I think I'll throw it out anyway. 67.243.7.41 (talk) 15:34, 4 June 2009 (UTC)

OR having tried it once. It won't be toxic, but it may be unpalatable as the bubbles will be gone and it may be a bit sludgy on the bottom of the can. 65.121.141.34 (talk) 16:23, 4 June 2009 (UTC)

This is not medical advice BUT: you might gain super powers. It's a possibility. Consider your future life as Soda Man, and whether or not you are willing to take on that responsibility. --98.217.14.211 (talk) 16:55, 4 June 2009 (UTC)

Throwing it away it probably wise. I doubt there will be anything harmful about it, but it probably won't taste very nice (depending on how it was stored). It is possible the seal has been broken somehow which might have allowed something harmful to get in, so probably not worth the risk. --Tango (talk) 18:38, 4 June 2009 (UTC)

Sugar soda may retain its flavor longer than artificially sweetened soda. I once had some old pop sweetened with Nutrasweet and all sweetness was gone. It tasted like unsweetened Coke with pineapple juice added. Heat speeds the breakdown of Nutrasweet. There is always a possibility that over time there could be greater leaching of metal or plastic from the can into the drink. If it is sealed, how would any carbon dioxide escape to make it flat? Edison (talk) 18:42, 4 June 2009 (UTC)

Major OR here, but I had some cans of orange soda that actually started leaking through the bottom of the cans after eight or nine years. They were unopened and keep in a closet. The soda actually caused corrosion and leaked out. cheers, 10draftsdeep (talk) 19:38, 4 June 2009 (UTC)

If its in a can, the soda may have eroded away enough of the can to impart a metallic taste. Don't know if its toxic though. Livewireo (talk) 21:22, 4 June 2009 (UTC)

Most modern cans have a coating of plastic on the inside I do believe. If the (presumably) citric acid in the orange soda and/or the carbonic acid in any soda has gotten through to the metal of the outside of the can, it's likely also dissolved the plastic coating on the way. This would presumably include any phthalate and/or bisphenol components of the coating plastic. Luckily, most plastic compositions are considered trade secrets, and there is intense dispute over the bio-effects of various plastic additives (softeners, etc.) which may or may not be in the plastic anyway (trade secret!) - so we can just dismiss the whole thing as "no definite evidence". Franamax (talk) 23:33, 4 June 2009 (UTC)

Check this out: Benzene in soft drinks, then check the label of your soda can. It won't kill you (immediately) but it's not healthy either. Also "a soft drink such as a cola has a pH of 2.7-3.0 compared to battery acid which is 1.0". That and the other ingredients, plus the can should make for an interesting environment for many chemical reactions and interesting compounds to form over time. 71.236.26.74 (talk) 00:26, 5 June 2009 (UTC)

Of course, you do realize that a pH of 3.0 is 1% as acidic as a pH of 1.0. Thus, soda has about 1% of the acid concentration of battery acid. Of course, the liquid in your stomach is pH of around 2 or so, which means that the soda is only 10% as acidic as your own gastric juices, or if you prefer, your gastric juices are 10 times as acidic as soda. Welcome to the wonderful world of logarithms. --Jayron32.talk.contribs 04:17, 5 June 2009 (UTC)

That's one of the reason I put that quote from an ooold paper in quotation marks. Your stomach is however a pretty good example of an environment that has interesting chemical reactions happening. 71.236.26.74 (talk) 06:00, 5 June 2009 (UTC)

Note that you generally don't want to drink any non-diet soda with a broken seal that's older than a few days - once it gets exposed to the environment I would expect the bacteria to come in and party on the sugar. A diet soda on the other hand might be fine for a longer period of time. I'm not sure. Dcoetzee 06:39, 5 June 2009 (UTC)

Nope Aspartame is less stable that sugar and gets broken down after a while. The interesting thing is what reaction products you're going to get. 71.236.26.74 (talk) 07:28, 5 June 2009 (UTC)

Capturing a warm bath's heat

It's winter in the southern hemisphere and a nice way to heat up is by taking a warm bath. I couldn't help thinking though of all the energy that gets lost when the warm water flows out the drain after a bath. Given that:

• a kilocalorie is the amount of energy it takes to heat a liter of water by 1 degree Celsius
• lets assume my bathtub holds 150 liters of water
• it's about 17 degrees in my apartment, the water after I'm done bathing is 40 degrees Celsius, a 23 degree difference

I asked Google: "(150 * 23) * kilocalories in kilowatt hours" and got "(150 * 23) * kilocalories = 4.00966667 kilowatt hours"

That's 4 kilowatt hours of energy down the drain! That's like a 1000 watt heater staying on for 4 hours. so this makes me ask, does it make sense to keep the water in the bathtub until it has cooled down so that my place will heat up a bit? One concern is evaporation that might cause the humidity to rise and thus the energy is kept as latent heat rather than actual. In that case, is there something simple one can do to prevent evaporation?

196.210.200.167 (talk) 16:14, 4 June 2009 (UTC) Eon

Any added humidity will make you feel warmer, which is just as good, isn't it? --Sean 18:25, 4 June 2009 (UTC)

I'm not sure. The formulas are given in Fahrenheit, but I suspect at 17 degrees a higher humidity might even make you feel colder. Seems counter intuitive though that just leaving the water in the bathtub can make such a huge difference. 196.210.200.167 (talk) 19:39, 4 June 2009 (UTC) Eon

A lid on the bath would prevent evaporation. --Tango (talk) 18:36, 4 June 2009 (UTC)

I don't see why leaving the water in the bath until it's cooled right down wouldn't work. The humidity might be a problem for your bathroom - but you'll certainly have a slightly lower heating bill if you do this. It's not a bad idea actually. SteveBaker (talk) 19:44, 4 June 2009 (UTC)

According to my electric bill, 4kWh is worth almost 35c, though I would imagine that it would not apply the heat evenly throughout your dwelling (unless you have incredible outer wall insulation)65.121.141.34 (talk) 19:53, 4 June 2009 (UTC)

Don't have the time to google for it, but there is a product that recovers heat from water and air leaving the house through bathroom vents and plumbing. Can't recall what it was called. (I think "this old house" had one in one of their shows)71.236.26.74 (talk) 00:31, 5 June 2009 (UTC)o.k. found a couple of pages [12] [13], Matt's comment here [14], [15] Ugh, should have known and we do have a page Waste Heat Recovery Unit - 71.236.26.74 (talk) 03:59, 5 June 2009 (UTC)

My contingency plan for what to do in the event of a prolonged power failure in winter includes leaving the hot (and a bit of cold) water trickling into bathtubs and sinks, to keep the pipes and drains from freezing and to heat the house from the water heater. This assumes the overflow can remove the water with the drain plugged. A diverter to direct the hot water to the far end of the tub might be useful. One would get tired of a batch mode of filling the tub and then draining it after an hour, repeated 24x per day. Fireplace and kitchen range (hob) or oven could also be used to advantage, but with suitable care for carbon monoxide. Edison (talk) 04:49, 5 June 2009 (UTC)

gravitational equations

Is/are the equation/equations for gravity at the center of a Black Hole the same as the equation/equations for gravity in unoccupied (empty) space? ---- Taxa (talk) 17:20, 4 June 2009 (UTC)

At the very centre of a black hole, the singularity, the laws of physics break down (ie. we don't really know what happens), so there are no equations. In an appropriate coordinate system (eg. Kruskal–Szekeres coordinates) you can use the same equations to describe everywhere except the singularity, though. --Tango (talk) 18:47, 4 June 2009 (UTC)

The singularity at the very center of a black hole does things to the equations that physics depends on that are essentially the same as dividing by zero on your pocket calculator. There is no meaningful answer. But a billionth of a trillionth of a gnat's eyebrow from the center, the laws of physics should be pretty well-behaved. The equations are exactly the same - but because these are rather extreme circumstances, you have to use the full relativistic forms of these equations, not the 'low speed/low gravity' approximations that we all learned in high school. SteveBaker (talk) 19:41, 4 June 2009 (UTC)

Eyebrows?

What is the length of a gnat's eyebrow in Planck lengths? Does anyone know? --Tango (talk) 02:08, 5 June 2009 (UTC)

Well, the photo at right claims to be 100x magnification. But (...pet hate...) I'm viewing this simultaneously on a 14" monitor and an 81" plasma screen...so it's a bit hard to measure exactly! SteveBaker (talk) 04:04, 5 June 2009 (UTC)

It's a featured picture as well, I'm surprised nobody caught that... --Tango (talk) 12:29, 5 June 2009 (UTC)

DO GRAVITATIONAL ENERGY OF EARTH REDUCE BY TIME?

Earth keeps the moon in it's gravity spending it's energy .From where do earth gain this energy? If earth do not gain energy,then is it's gravitational energy reducing by time?Surabhi12 (talk) 18:06, 4 June 2009 (UTC)

The earth does not spend energy in order to keep its moon. Dauto (talk) 18:19, 4 June 2009 (UTC)

Well, not in classical physics. But in relativistic physics, the circling moon will cause gravitational waves, which will carry away some of the potential energy of the Earth-Moon system. The effect is very small, and, at the moment, entirely overshadowed by the tidal transfer of rotational momentum from the Earth to the Moon. See Gravitational wave#Power_radiated_by_Orbiting_Bodies. --Stephan Schulz (talk) 18:26, 4 June 2009 (UTC)

The moon is falling towards the Earth, but luckily it keeps missing, just like cannonball "C" shown in the picture. It doesn't take any energy for this to happen. See orbit. --Sean 18:31, 4 June 2009 (UTC)

And the Earth is falling towards the moon, but luckily the moon keeps moving out of the way ;) Gandalf61 (talk) 12:30, 5 June 2009 (UTC)

Somebody owes me a dollar. (I've decided that I'm charging the universe a dollar every time someone confuses a 'force' (gravity in this case) with 'energy' - I plan to earn enough money from this confusion to replenish my poor 401K). The force and energy are very different things. When you stick a fridge magnet onto your fridge, the magnet exerts a force on the metal. But so long as the magnet doesn't move - it doesn't take any energy whatever for it to just hang there...magnets don't "run down". It's the same with the moon. The gravity pull between earth and moon is just a force. So long as the two bodies don't get closer or further apart - there is no energy transaction involved. Forces don't "run down" - they just are. If you hang something from the ceiling with a rope - the rope exerts a force...the rope doesn't "run down". Now, if something were to pull the moon further from the earth - that 'something' would have to expend some energy to do it...if the moon (for some reason) were to fall closer to the earth - then it would actually gain energy (kinetic energy initially - then one hell of a lot of heat energy when it kersplatted into the middle of the pacific ocean!). SteveBaker (talk) 19:35, 4 June 2009 (UTC)

Would another explanation be that the Earth is neither exerting a force nor expending energy, it is simply warping space-time such that the shortest path for the Moon to travel through the geodesic happens to be a circle? Just asking... Franamax (talk) 20:07, 4 June 2009 (UTC)

Now now, don't confuse a good discussion with a simple, elegent and correct answer. No one needs that now! --Jayron32.talk.contribs 20:34, 4 June 2009 (UTC)

Yes, but relativity gives people headaches! That, and the concepts Steve is talking about apply to all forces, even ones that can't be easily dismissed as mere geometry. --Tango (talk)

I'll give you a dollar. Remind me if see you - bring change! --Tango (talk) 02:07, 5 June 2009 (UTC)

Oooh! Thank-you! Actually - with the number of people making this error - I'm pretty sure I can still turn a profit at one Zimbabwean dollar per confused OP.  :-) SteveBaker (talk) 03:58, 5 June 2009 (UTC)

Single Zimbabwean dollars are now so rare that, pervesely, they are probably now valuable to collectors. SpinningSpark 13:48, 5 June 2009 (UTC)

and another piece of trivia (I can't leave this one alone) is according to this the $US is now worth more than a mole of the original $ZW. That must be a first for a currency. SpinningSpark 14:17, 5 June 2009 (UTC)

problem of race

Imagine:

A car travels 10km in an hour 
A bus travels 20km in an hour  
both have a race
Car is ahead of bus at point A.
By the time bus moves to the point A,car must have move little ahead say to point b.
By the time bus moves to the point b,car must have move little ahead again say to point c.
By the time bus moves to the point c,car must have move little ahead say to point d.
This continues .........
Thus car has to become the winner.
IS THIS POSSIBLE?  —Preceding unsigned comment added by Surabhi12 (talk • contribs) 18:30, 4 June 2009 (UTC) 

See Zeno's paradoxes. Short answer - it takes an infinite number of steps for the bus to overtake the car but because each of those steps takes sufficiently less time than the one before the total amount of time required to overtake is finite. See convergent series for the maths behind that. --Tango (talk) 18:35, 4 June 2009 (UTC)

Another way to look at this is that suppose the car starts off with a lead of (say) 10km. We know that using 'sensible' math, that the bus will travel at a distance D in time T=D/20 hours and the car at time T=(D-10)/10 hours. When the bus overtakes the car, they are at the same distance at the same time - so we can solve the simultaneous equations and calculate T as 1 hour. The bus catches the car after 1 hour - then zooms right past it. No problem, no controversy, no paradox.

But the crazy Zeno's paradox way says: The time it takes the bus to reach A is 1/2 hour. By that time, the car has travelled 5km to point B. 15 minutes later, the bus reaches B and the car has gone on another 2.5km to C. 7.5 minutes later, the bus reaches C...so Zeno tells us where the bus and the car are after 30+15+7.5+3.75+1.875+... minutes. Mathematically, that infinite series adds up to 59.999... minutes. And the distance that the car and bus have travelled in that time is 19.999...km from the start. Well, that's all very interesting and exciting - but by refusing to every allow the 'victim' of the paradox to just go ahead and ask where the vehicles are after a longer amount of time, he arbitarily forces us to look only at times before the two vehicles actually meet. If you limit your calculations to only times before the vehicles meet - you're obviously never going to find the time when they do actually meet. It's not a paradox - it's a dumb way of stopping the person from answering a ridiculously simple question!

But why doe Xeno insist on calculating all of these intermediate positions and stubbornly refuse to calculate where they are after exactly one hour? Because he's some stupid philosopher trying to make a name for himself by inventing a "paradox". This is why philosophers are a waste of quarks. We have a perfectly simple, completely understood problem with a VERY simple, non-paradoxical conclusion...but NO...the dumb-as-a-bag-of-hammers philosopher has to insist on never calculating the answer but instead answering an infinite series of questions that we don't need to know the answer to.

It's really no different to me saying "What is 2+2?" - but instead of just going ahead and counting it out on your fingers, I arbitarily insist that you first calculate a totally unrelated sum: 1+0.5+0.25+0.125+... which (if you try to do it the hard way) will take you an infinite amount of time - and thereby cunningly prevent you from calculating 2+2. Why the heck would you ever want to do it like that? It's obviously a stupid and unnecessary way to answer my question. So - please treat anything any philosopher says much as you would a comedian. Amusing, possibly mildly entertaining - but in no way relating to reality. SteveBaker (talk) 19:22, 4 June 2009 (UTC)

Well that and your number series will only equal 2 when you are done. 65.121.141.34 (talk) 19:49, 4 June 2009 (UTC)

I disagree - I think it is instructive to consider the "paradox" and realize that it is solved by convergence. The obvious logical solution allows the student to intuitively grasp the otherwise abstract idea that adding an infinite number of elements can still lead to a finite solution. This does have practical consequences in the study of advanced science and physics - it's an effective way to consider the parity between discrete and continuous number representations, or quantized vs. continuous physical models. Nimur (talk) 23:19, 4 June 2009 (UTC)

Perhaps the solution is to tell the philosopher you think he's wrong and ask him to write out the whole series just to be sure... Franamax (talk) 20:10, 4 June 2009 (UTC)

It is a little unfair to say philosophers are a waste of quarks in reference to ancient Greek philosophers. I agree modern ones are a waste of quarks, but in ancient times "philosophy" was a far broader subject since other things didn't exist yet. It included mathematics and what would now fall under science (but I'm not willing to call what they did science, since it didn't follow the scientific method). It easy for us now to laugh at them not understanding these simple concepts, but they are only simple to us because someone else has explained them to us. The ancient Greeks (and philosophers for quite a while after them) had some very odd ideas about infinity (as do most people today who don't have formal training in mathematics). The reason Zeno's problem seemed paradoxical to them was because they didn't think it was possible to do an infinite number of things (the idea that they got easier and easier so the total amount of resources required remained finite wasn't known to them). You may find Supertask interesting. --Tango (talk) 02:03, 5 June 2009 (UTC)

I am reminded of a quote attributed to Johannes Keppler, though it may be apocryphal. I will paraphrase. Basically, Keppler was lecturing on the organization of the solar system, and one of his students asked something like: "Weren't people 100 years ago rather stupid, I mean, they thought the earth was the center of the Universe, and that everything revolved around us. Doesn't that that make those people rather unintelligent." To which Keppler replied something like "If they were right, and the sun DID revolve around the Earth, would the sky look any different?" which makes the point that its easy given the sum of all human knowledge of today to riducule the past thinkers as somehow stupider than us; but we have the benefit of the incremental progress we have made towards understanding the universe, a process they themselves were a part of. One could just as easily have commented that Newton was an idiot for not taking into account relativistice effects of near-light-speed travel, or that proponents of phlogiston theory were stupid when they thought heat was a substance. 100 years from now people will think we are stupid because some "scientific fact" we are certain is right turns out to be inaccurate in some way. Xeno's ideas look stupid because he didn't have the 2000 years of mathematical thought already spelled out when he devised his paradoxes. However, the basic concept that infinity is a special idea that DOES need its own set of rules to deal with was a unheardof idea at Xeno's time. The fact that anyone was thinking about the infinite several hundreds of years B.C. is pretty prescient if you ask me. --Jayron32.talk.contribs 02:52, 5 June 2009 (UTC)

I'd just like to point out that 59.999...=60. You could have just said the infinite series just adds up to an hour. Also, this paradox was formulated before infinite series (it isn't just what you get when you add all the values together), so you could only get something below 60, but arbitrarily close to it. — DanielLC 16:16, 5 June 2009 (UTC)

That's true - but it doesn't get Zeno off the hook. If we ask when does the hare/Achilles/bus pass the tortoise/car? Or better still we can be REALLY clear and ask: "When is Achilles ten feet ahead of the tortoise?" Then Zeno is arguing that they just meet at T=59.999...=60 - but he's not letting you find out whether the hare ever PASSES the tortoise. So this rather wonderful mathematical result doesn't help us out much! SteveBaker (talk) 02:59, 6 June 2009 (UTC)

Of course, Zeno wasn't actually trying to find out whether or when Achilles passed the Tortoise; everyday observation made it obvious that moving things routinely passed other things. Rather, as Nimur alluded to, he was examining philosophical postulates made by others and using this paradox (alongside several others) to demonstrate their invalidity (much as Ernst Schrödinger didn't really believe a cat could be simultaneously alive and dead, his gedankenexperiment was meant to demonstrate that the concept of quantum superposition was absurd).

In Zeno's time, some philosophers had postulated that space was (S), others that it was not (s), infinitely divisible; ditto for time (T, t), giving 4 possible combinations (ST, St, sT, st). Zeno constructed a paradox for each of the four scenarios, apparently showing that each was demonstrably untrue (although the st case apparently is true). Perhaps if he'd had Leibnitz's and Newton's benefit of a more manipulable number system, he'd have managed to come up with calculus a couple of millennia earlier. 87.81.230.195 (talk) 16:38, 6 June 2009 (UTC)

Labour and multiple births

Given that Twins, and higher number births, are individuals, do mothers ever experience a sort of delayed labor, in which the second child is born at a vastly different time or even date then their sibling? For example, Paul and John are twins, Paul is born first, and John is born 2 days later, after the mother reentered labor.--Honeymane_{Heghlu meH QaQ jajvam} 19:31, 4 June 2009 (UTC)

When someone finds a good source on the range, with some statistics, please add the data to the Multiple birth and Twin articles, which should discuss this, but currently lack any data (or even a mention). Tempshill (talk) 19:53, 4 June 2009 (UTC)

If anyone wants to ask at the WP:Library for the fulltexts, here are two sources: "Management of Delayed-Interval Delivery in Multiple Gestations", S. Cristinelli et al., Fetal Diagnosis & Therapy, Jul/Aug 2005, Vol. 20, Issue 4, pp.285-290. (AN 18247478) [16] and "Delayed delivery of multiple gestations: Maternal and neonatal outcomes", M. Kalchbrenner et al., American Journal of Obstetrics & Gynecology, 179(5), pp1145-1149, Nov. 1998. [17]. According to the abstracts: in 6 cases studied, the delivery interval is 2:93 (median 7) days; the literature (148 cases from 1979-2001) supports 2:153 (median 31) days; and for 7 cases studied, a difference of 32.6 days. I'm rather startled at some of these numbers for delay in delivery, obviously some of the first-borns were very premature. However the absolute numbers indicate that this amount of delay is very rare. As for minor delays (<2 days), I didn't find much. I've fired off a query to my sister. Franamax (talk) 20:39, 4 June 2009 (UTC)

Oohh, jackpot! "Twin-to-twin delivery time interval:...", W. Stein et al., Acta Obstetricia et Gynecologica, 2008; 87: 346�353. [18] 4,110 "normal" deliveries, mean interval = 13.5 min (SD 17.1); 75.8% within 15 min, 16.4% within 16-30 min, 4.3% within 31-45 min, 1.7% within 46-60 min, 1.8% > 60 min. Now those are statistics! :) If anyone wants to try writing this up, I have some of the fulltexts and we can put up one of those "Refdesk significantly improved an article" thingies! Franamax (talk) 21:05, 4 June 2009 (UTC)

Those statistics with a median of several days are meaningless - the sample has clearly been chosen to be made up of cases with a large delay (since that is what they were studying). The rest of their results may well be interesting, but the length of the delays isn't since they were specially chosen. (The medians are probably only given in order to describe the sample chosen, not to imply anything about delayed births.) --Tango (talk) 01:54, 5 June 2009 (UTC)

Franamax, this is outstanding! I added a new "Delivery interval" section to Twin, let me know what you think. The section needs the discussion of the extremely long intervals and could use discussion (beyond the stats) of the very unusual situation where labor begins and then ends, and then a month later begins again. Thanks! Tempshill (talk) 05:47, 5 June 2009 (UTC)

Looks good, I'll work a little more on those anomalous cases where labour ceases and the delay runs to several days. I also had found this in Google Books (Multiple Pregnancy, Blickstein, Keith & Keith), which gets right into the details. Another successful RefDesk collaboration! :) Franamax (talk) 07:10, 5 June 2009 (UTC)

Thanks guys!--Honeymane_{Heghlu meH QaQ jajvam} 00:58, 6 June 2009 (UTC)

This time gap had puzzled me in the article on the Chukwu octuplets -- one of the babies was born days before the others. I don't get it. Once the amniotic sac has been breached, the rest of the fetuses are left high and dry. (So to speak.) I'm guessing, but the sequence might be: woman goes into premature labour, rushed to hospital, one baby is already in the birth canal, it comes out and is handed over to neonatologist, contraction-inhibiting drugs are immediately administered to the woman, bed rest in hospital, lots of monitoring, try to give the other bun(s) as much more time in the oven as possible. Something along those lines? BrainyBabe (talk) 20:27, 7 June 2009 (UTC)

helium balloon

If one were to take a balloon that was made of a material that could stretch an infinite amount while maintaining its structure, and filled it with enough helium for it to rise quickly, would it make it into space (assuming temperature also does not effect the structure of the helium compartment)? It is going far slower then the speed needed for orbit, but helium does escape from our atmosphere.65.121.141.34 (talk) 19:58, 4 June 2009 (UTC)

If we're going to invent materials which cannot possibly exist, why not just cast a magic spell on the balloon and teleport it to space? But seriously, the ballon would rise to a point where its density matched that of the atmosphere. For your theoretical infinitely strecthy balloon, since the volume could be infinitely large, the density could be infinitely small, which means the balloon would keep drifting up. I just have a hard time picturing a helium balloon being infinitely stretchy. --Jayron32.talk.contribs 20:41, 4 June 2009 (UTC)

As I understand the way you've stated the material, the answer is maybe space, and maybe escape. It's important to remember that escape velocity is relevant only to a specific impulse of thrust. Anything that continues thrusting as it rises need not reach escape velocity as defined at the surface in order to reach escape velocity. Anyway, the balloon matches the pressure of the atmosphere and will continue to rise (and expand) until it reaches an altitude where its density is the also same as the surrounding atmosphere. This may well be higher than 100 km, which is the usual qualification for reaching "space". This further may be high enough for the solar wind to thrust it away from Earth, thus maybe escaping. In the absence of solar wind, though (and possibly in spite of it), the balloon reaches stable equilibrium -- were it to rise, it would be more dense than the surrounding atmosphere and thus sink. Were it to sink, it would be less dense and thus rise. Since it's still in the atmosphere and its movements dictated by the atmosphere, I wouldn't characterize this as an orbit and I wouldn't expect the balloon to be in free fall. — Lomn 20:50, 4 June 2009 (UTC)

I was going to mention how the balloon material would have a density greater than that of helium, thus we could calculate the weight of the balloon at Earth surface and add in the weight of helium it encloses and make a definite calculation of the equilibrium point where the overall density of the balloon-helium system was equal to that of the atmosphere. But of course, since it's infinitely stretchy, we can fill the balloon with all the helium on Earth before we release it, so yes, the average density approaches that of helium alone. Without some constraints, this really can't be calculated... Franamax (talk) 22:23, 4 June 2009 (UTC)

And below a critical density, the atmosphere will behave sufficiently like a vacuum or a sparse plasma. Once the balloon is in the ionosphere or thermosphere, buoyancy will be an insignificant force, and thermal interactions will become insignificant (although, a balloon of near-infinite volume might have sufficient number of thermal collisions to break down our cold plasma assumptions...) Nimur (talk) 23:24, 4 June 2009 (UTC)

You didn't give us enough information to answer your question. Tell us what's the mass of the ballon, what's the mass of the helium inside and what is the tension on the baloon's rubber, and than we may be able to give you a reasonable answer. Dauto (talk) 00:59, 5 June 2009 (UTC)

The atmosphere has no end, so I guess the simplest answer is that it will continue to rise and expand until interactions with the rest of the solar system become more significant than interactions with the Earth (which basically means it has escaped the Earth). At some point, either bouyancy would cease to be significant or you would reach a point where the atmosphere gives way to the Interplanetary medium, which I believe is mostly (ionised) hydrogen, so is less dense than helium at equal pressure (to the extent that pressure is well defined in such circumstances). However, your assumptions are clearly impossible, so the only entirely accurate answer is "anything could happen". (See Vacuous truth.) --Tango (talk) 01:46, 5 June 2009 (UTC)

Actually, the atmosphere has an ill-defined end; it gets infinitessimally thinner as you keep going out from the earth. This does NOT mean that it has no end; to assume it never ends is to make the same error that is made in Xeno's paradoxes. (See discussion elsewhere at the ref desk on this). Eventually, the matter density of the atmosphere fades to match the average matter density of the rest of the so-called "empty space" of the rest of the solar system. At that point, we can say that the atmosphere has ended, since it has become indistinguishable from space. That line can be clearly drawn around the earth, so there is no point in saying it "never" ends. The atmosphere is a physical example of a convergent infinite series, and the operative part here is "convergent". The limit where the diminishing atmosphere converges with the rest of space we can say the atmosphere ends. --Jayron32.talk.contribs 03:06, 5 June 2009 (UTC)

By "has no end" I meant it never becomes a true vacuum, which is what would be required for this idealised balloon to stop rising and float on top of the atmosphere. I talked about the atmosphere giving way to the interplanetary medium, so I think it is quite clear that I understand what is going on... --Tango (talk) 03:10, 5 June 2009 (UTC)

Well, lets call it a misunderstanding over the use of imprecise language. It would be easy to assume that, when you say it "has no end" that the it continues on forever. It doesn't really, its just that you have to define what you mean by "end". --Jayron32.talk.contribs 03:32, 5 June 2009 (UTC)

Falling for infinitly long.

Since I was learning about terminal velocity I was wondering that would it be physically possible for an object to have a terminal velocity greater than c. If it were a point object such that A was very small, falling through an low density fluid with a low drag coefficient, and a great enough mass. If this were possible (albeit physically it would take a long time to attain it; imagine it falling through an infintly long tube), would that mean that as v--> c, the mass would go to zero. Such that its K(e) would never exceed E=mc². Or would the mass remain the same given that E²=(mc²)²+(pc)². Using the second equation E could increase without bound? I would imagine a vacuum would have a drag coefficient of zero, this would make terminal velocity infinite, although a perfect vaccum is impossible. —Preceding unsigned comment added by 24.171.145.63 (talk) 21:16, 4 June 2009 (UTC)

The short answer is "no". I think we have an article, relativistic addition of velocities or some such? If not, it should redirect somewhere.

Things are a bit more complicated if you consider the large-scale geometry of the universe -- see observable universe. One way of expressing the edge of the observable universe is that it's where galaxies are moving away from us faster than c. --Trovatore (talk) 21:20, 4 June 2009 (UTC)

Velocity_addition_formula#Special_Theory_of_Relativity. --Tango (talk) 01:38, 5 June 2009 (UTC)

Off topic, but the volume beyond which the recession speed exceeds c is called the Hubble volume and is smaller than the visible universe. The recession speed at the edge of the visible universe is around 3.3c. -- BenRG (talk) 17:12, 6 June 2009 (UTC)

Why would the mass go to zero? Rest mass is always the same, irrespective of velocity. Relativistic mass increases as velocity increases. The total energy of a moving object is the sum of the rest energy, mc² (where m is the rest mass), and the kinetic energy (for small velocities that's mv²/2, for velocities near the speed of light you need to use relativity). The rest energy is constant, the kinetic energy increases with velocity (and increases without bound, even though the velocity is bounded above by the speed of light). --Tango (talk) 01:38, 5 June 2009 (UTC)

A structural designation

When listing or describing archictectural structures what does HEW (insert number here) mean e.g. HEW 365, which is for the Gasworks Railway Tunnel around Kings Cross in London? Simply south (talk) 22:20, 4 June 2009 (UTC)

I think it is the Panel for Historical Engineering Works designation; and think said panel is part of or connected with the Institution of Civil Engineers. See, for instance, the introduction to London and the Thames Valley, by Denis Smith, Institution of Civil Engineers (Great Britain), and then note that the book lists HEW numbers against each structure described. --Tagishsimon (talk) 22:33, 4 June 2009 (UTC)

See also ICE overview of PHEW and a PHEW database with a crappy user interface --Tagishsimon (talk) 22:36, 4 June 2009 (UTC)

Thank you for that. Simply south (talk) 23:17, 4 June 2009 (UTC)

Understand weak interaction and beta decay

I tried long to understand how a force could result in β decay.

As for my knowledge I usually think of a force as a vectors (or a vector field if we speak of fields): electric force between 2 charges as 2 vectors with the same direction, the same for gravitational force, and I think I could do the same for strong force. But when I read of weak force and its role in β decay, first I see only feynman diagrams, which I understand, but I cannot fit them with my idea of vectors. Second I see only one particle interacts with this force, when for all of the other forces there are at least 2 particles, or a field and a particle.

I conclude saying that I think I understand the basic mechanism of β^- decay. So, said in really raw words: a neutron emits (on its own or there is a reason?) a W^- boson, which "extracts" one unit of negative electric charge from the neutron, and the neutron is transformed in a proton. Then the W^- boson decays in an electron and an electron antineutrino.

Could someone help me and clean my doubts?

ColOfAbRiX (talk) 23:56, 4 June 2009 (UTC)

You said you see only one particle interacting in the beta decay, but when you gave us an example of beta decay you mentioned a neutron, a proton, a W-, an electron and an anti-neutrino. I count five different particles. Even if we exclude the W which plays the role of the "force" here, you still have four interacting particles. Forget about vectors, they won't help you here. You should think of "forces" as interactions between different fields ()The vertices of the Feynman diagrams. Dauto (talk) 01:19, 5 June 2009 (UTC)

June 5

Distribution of stellar classes

According to the table in Harvard spectral classification, stars of spectral class M comprise over ~76% of all main sequence stars while Sun-like stars in spectral class G comprise ~7.6% of all main sequence stars. This suggests to me that class M stars outnumber class G stars by a ratio of 10:1. My own OR suggests that is roughly true within 20 light years of the Sun, but is that ratio maintained throughout the Milky Way galaxy? Presumably similar ratios can be calculated for other spectral classes as well - I am particularly interested if some parts of the Galaxy are lacking in stars a particular spectral class. Astronaut (talk) 00:10, 5 June 2009 (UTC)

I think the ratio is maintained on a large scale (presumably universally, although I'm not sure how much evidence there is to support that). I'm not sure about the distribution of different spectral classes throughout the galaxy, but there are certainly differences in the metallicity of stars in different areas (that article explains it fully). --Tango (talk) 01:32, 5 June 2009 (UTC)

I saw the metallicity article, but I'm not convinced there is a strong link between metallicity and spectral class, and anyway I'm really only interested in stars in the Milky Way disc. The kind of thing I'm trying to find out is if, for example, we observed that the population density of O and B class stars in the spiral arms was typically double that in the regions between the spiral arms, could we assume the same was true of the population density of G, K and M class stars, even though we cannot observe them directly? In other words, can I use the distribution of bright stars that can be observed at great distances, to reliably infer the existance of a much larger population of dim stars at these great distances? Astronaut (talk) 04:39, 5 June 2009 (UTC)

I don't think you can do that because the O class stars are short lived (less than 10 million years) and won't have enough time to move very far from the star nursery where they are born, while smaller stars can live much longer and will have a more uniforme spacial distribution. Dauto (talk) 06:43, 5 June 2009 (UTC)

One factor in variation of star population is related to the size of the galactic body they are in. Globular clusters are known to lose stars through a process analogous to (and actually called by some) "evaporation". The lighter stars in the cluster are the most "volatile" since they will gain the highest velocities in energy exchange interactions with other stars. Globular clusters thus tend to have a relative poverty of K and M-type stars since these will be the first to achieve escape velocities. SpinningSpark 13:08, 5 June 2009 (UTC)

Two important keywords for this type of question are the initial mass function (IMF) and the star formation history, and it's the latter that chiefly determines the current distribution of stellar types in a given stellar population. Starting from the IMF, an assumption about the star formation history and using stellar evolution models, one can try to model the stellar populations in various environments of the Milky Way, but also in other galaxies. Obviously, while in the Milky Way one can make a tally of individual stars, in other galaxies one only has a limited amount of information, like the colours of galaxies or integrated spectra. What a population of stars in a given area looks like at a given point in time thus depends on both the IMF and the star formation history. From modelling this sort of information one can then try to reconstruct these two factors. I'm far from being an expert in this, but my impression is that the IMF is fairly universal. There are indeed different versions that have been tried and which vary in particular at the low mass end, i.e. at late spectral types, but that controversy seems to be due more to our ignorance rather than variation in different environments. The star formation history is much more variable. Early-type stars, O and B, say, are very short-lived and can only exist in environments where stars are currently being formed. If you switch off star formation (e.g. by removing cold gas) these stars will disappear very quickly and you'll be left with a population that is dominated by late-type stars, main-sequence stars dominating by number, and red giants dominating the light output. The neighbourhood of the sun is in the disk of the Milky Way which is still forming stars, hence we might expect some early-type stars (typically forming OB associations). The bulge forms much less stars and is therefore dominated by later-type stars. The extreme cases would be "red and dead" elliptical galaxies. --Wrongfilter (talk) 16:24, 5 June 2009 (UTC)

Q about lovebirds

Is it true that it's impossible to keep one lovebird as a pet? Is it also true that if you have two lovebirds and one of them dies, then the other one will become depressed, stop eating and die soon after? Thanks. --84.67.12.110 (talk) 00:13, 5 June 2009 (UTC)

I've looked around and read a bunch of likely pages - and I can't find anyone that says this is true. However, it's clear that they are extremely active, intelligent, social birds and might get depressed because they don't have anything to keep them amused when their mate dies. I suspect that the myth of one bird dying and it's mate dying "of a broken heart" soon after has it's roots in the fact that if you buy two birds of the same age on the same day - keep them in the same cage and feed them the same food - then the odds are pretty good that whatever kills one of them will soon kill the other...especially if it's a bit depressed because it's bored. This would seem a lot like death from a broken heart - but in all likelyhood it's probably just that whatever killed the first one also kills the second. As for keeping just one of them - according to most of the sites I've read, it'll do OK PROVIDING you give it tons and tons of attention and keep it busy and interested in life. Having two of them relieves you of some of this huge commitment in that (to some extent) they'll keep each other amused when you aren't around. SteveBaker (talk) 03:50, 5 June 2009 (UTC)

This song recounts a field observation of catabythismus incidental to amorous dysfunction by Petroica macrocephala, the Miromiro or New Zealand Tit, a bird of the Petroicidae (Australasian robin) family colloquially known as a tom-tit. Cuddlyable3 (talk) 08:39, 5 June 2009 (UTC)

largest possible Black Hole

Is there a radius at which the density of a Black Hole is so low that it is no longer a Black Hole? --71.100.6.71 (talk) 02:50, 5 June 2009 (UTC)

No. You are correct that the density of a black hole (ie. the average density within the event horizon as viewed from a distance) decreases as the black hole grows, but there is no minimum density required to remain a black hole. --Tango (talk) 03:15, 5 June 2009 (UTC)

Density of Supermassive black holes can be surprisingly low. You will not even notice you entered it. You will just be unable to get out. --131.188.3.20 (talk) 12:51, 7 June 2009 (UTC)

zinc cloride

why zinc cloride is not weighed while it is still hot? —Preceding unsigned comment added by 115.134.149.71 (talk) 03:51, 5 June 2009 (UTC)

Nothing should be weighed while its temperature is different from the ambient temperature. If the substance it hotter than the air it will generate convection currents which can easily disrupt a sensitive balance and give an inaccurate reading. If you are going to weigh something, let it cool to room temperature so that such convection currents do not screw with the balance. Of course, you already knew all of this, because you paid attention when your chemistry teacher explained all of this to you. Right? --Jayron32.talk.contribs 04:02, 5 June 2009 (UTC)

Lame flight data recorders

The flight data recorders presently in use on jumbo jets send out a beacon signal detectable to a reported one mile, but the planes may crash in ocean depths of up to 4 miles, such as the recent Air France jet crash. Would the acoustic beacon power have to increase as the square or the cube to be detectable at 4 times the present distance, so there would be a great likelihood of recovery? This could mean 16 times the radiated acoustic signal or 64 times, respectively. News articles also say the batteries will fail after 30 days of beeping. Why couldn't the flight data recorder have a transponder which sends out a very powerful signal only when a powerful search ship probe signal triggers it, meaning it could still be found long after the crash? Edison (talk) 05:26, 5 June 2009 (UTC)

I think the deal with FDRs is that they are built to an old standard, and the standard has never been updated, because having one standard is preferable in most cases than having 100 different types of FDRs. If they are all identical, then one always knows what to look for. Actually, the better standard would seem to instead broadcast the information via a digital data stream over a satelite system. The problem is that the FDR is attached to the plane. If the flight data information were stored outside the plane, it would greatly reduce the need to recover the box. The black box could still exist as a backup. Of course, the technology exists to do exactly that; the problem would be retrofitting the worlds airplane fleet and relevent ground locations with the system, it would be a daunting task. But the technology certainly exists to devise a better system. --Jayron32.talk.contribs 05:33, 5 June 2009 (UTC)

I don't know how much data they record, but surely it's enough to make every plane in the air constantly streaming it over expensive satellite bandwidth impractical. --Sean 14:11, 5 June 2009 (UTC)

Also, couldn't bad weather (like the recent Air France crash occurred in) interrupt the signal? TastyCakes (talk) 14:25, 5 June 2009 (UTC)

In an simple isotropic medium it would generally be distance squared, but there is a correction for scattering so it is really more like $P\varpropto {e^{-r \over \lambda } \over r^{2}}$, where λ is about 1 km in the ocean. Which means that at 4 km you get about 1/300th the power as at 1 km. A further effect is the diffraction around the sofar channel in the ocean, which makes it nearly impossible for deep accoustic signals to ever reach the surface anyway, so even with a more powerful transmitter you'd still have to dangle a deep hydrophone to hear it. Dragons flight (talk) 16:44, 5 June 2009 (UTC)

Transmitting 4 miles would require more like 2000 times the power as transmitting 1 mile, given the formula above. Dragons flight (talk) 17:04, 5 June 2009 (UTC)

The Mary Sears was unable to locate the black boxes from Adam Air Flight 574 using hull mounted sonar. After returning to port and equiping a Towed Pinger Locator she detected both at a depth of 1700m. According to Jane's a TPL can detect the signal from a max depth of 20,000 ft.—eric 19:31, 5 June 2009 (UTC)

According to the Adam Air accident report they were found at 2000 and 1900 meters, and the Mary Sears was required to pass within 500m of a beacon to locate them.—eric 20:08, 5 June 2009 (UTC)

Radiocarbon and DNA evidence on Voynich Manuscript

Has the Voynich Manuscript been subjected to radiometric dating to determine the age of its materials, or to DNA testing to determine the region of their origin? NeonMerlin 05:41, 5 June 2009 (UTC)

According to this Yale journal (scroll down to "Shelf Life"), dated February 2009, "two outside specialists are analyzing the pigments in its ink and carbon dating a tiny sample of its vellum." I haven't come across any reports of their findings, though. Deor (talk) 15:02, 5 June 2009 (UTC)

Is it a coincidence that this question came today? Jørgen (talk) 17:02, 5 June 2009 (UTC)

My guess is that Merlin's inquiry was sparked after reading Mr. Munroe's comic this morning, and not by chance. 17:07, 5 June 2009 (UTC)

Electrical power usage of computer

Hi, in this green age I guess it's relevant to ask this question. I've always been told to leave my computer on all the time, as repeated on/off switching could not only damage the switch, it causes electrical spikes which could damage the motherboard(?) over time. However, now my latest concern is that leaving it on consumes at least 600W per hour (that is the size of the power supply unit with the fan). Is this true? When the computer goes into power saving mode (turn off monitor and hard disk) - how much less does it use? Would it use even less if I tell the computer to hibernate during times of no usage? Sandman30s (talk) 09:24, 5 June 2009 (UTC)

While there is certainly some increased wear and tear from turning it on and off, I don't think it is much to worry about. If you're just stepping away for 10 minutes it probably isn't worth turning it off, but if it is going to be several hours it would be good to. It's difficult to say how much power it uses at different times, it varies from computer to computer, but the 600W figure would be a maximum (plus whatever your monitor uses and any other equipment that has its own mains plug), it won't use that all the time. You can get a power meter that goes inbetween the plug and the mains socket that will tell you exactly what it is using, I think most high street electrical stores will have them. Hibernation is actually the same as turning it off completely, the only difference is that it saves its current state to the hard drive so it can load back to the same point when it turn it back on. It will probably still use some power when switched off unless you unplug it or switch it off at the mains (see Wall wart). Leaving it on standby will use a significant amount of power. --Tango (talk) 12:37, 5 June 2009 (UTC)

Thanks, I think I'll do some tests with a power meter. Sandman30s (talk) 13:27, 5 June 2009 (UTC)

Also, note that in the winter, if you heat your house with electrical heating, you can just leave your computer on as all "wasted" energy contributes to heating your house anyway. (and conversely, if you use AC in the summer, you waste "double" the energy by leaving the computer on (I'd think?)) Jørgen (talk) 13:54, 5 June 2009 (UTC)

Both of your estimates are accurate - in data centers, it is estimated that total electric bills are equal to 2 times the power consumption of the electronics - this is a very common rule of thumb for estimating costs. This means that for each watt of useful electronics, an extra watt is necessary for air conditioners. It's hard to grasp this heating/air-conditioning concept intuitively - you "know" your computer is warm, but it's not that big... If you have the chance to visit a server-room, get permission to walk BEHIND one of the rack cabinets - behind a rack of 40 high-performance systems - you'll be blasted by the hot-air fan output which might reach a hundred kilowatts - it's like a furnace! Nimur (talk) 14:53, 5 June 2009 (UTC)

Thanks for the info! This should mean that environmentally friendly data centers should be placed in the basements of large offices / residential buildings in cold areas, so that the excess heat can be used to heat the building. I think I've read some articles on large data processing centers being located in places where hydro power is prevalent, or where there is a river available for cooling, both of which would be fine, but I think that placing them in cold areas - pumping cold air in (in some controlled process, of course) to cool the components and using the excess heat for heating - would be an even better approach? Now, I know the logistics of this might be hard, but I'm sort of surprised that no fringe-targeted "environmentally friendly cluster" has marketed this yet. (Oh, and sorry for hijacking the question) Jørgen (talk) 15:08, 5 June 2009 (UTC)

The use of cold, outside air as a source of cooling for data centers is already an accepted solution in some areas. Care must be taken that outside air does not introduce fine particulates that might damage equipment, and the temperature and humidity of incoming air must be tuned; these challenges and concerns have delayed the adoption of so-called air-side economizers or outside air economizers. Nevertheless, some more recent studies (by Intel and some electrical utilities; linked from our articles) have allayed fears over these risks. Here's an article about a Canadian firm that gets about 65% of their data center cooling from outside air: [19]. TenOfAllTrades(talk) 16:51, 5 June 2009 (UTC)

Thanks! Good to see that good ideas are put to use. Jørgen (talk) 17:00, 5 June 2009 (UTC)

In this interview with an IT manager working at the South Pole, he says that at their old data center somebody had just cut a hole in the wall to cool everything inside. Tempshill (talk) 17:33, 5 June 2009 (UTC)

Actually that's only likely the case if you have central heating and heat your house 24/7 to a constant temperature. In fact even then I'm not convinced it's going to be equal unless every space and passive part in your house is at a constant temperature which I would expect unlikely. Also if you are using a heat pump then even if it is really the case, you're still going to usually spend more energy then you would have otherwise because of the better coefficient of performance for the heat generated (may be a bit confusing in the context because not all of the energy input is going to make heat but even that which is, can basically be considered akin to an electrical heater). At least though computers are usually on the ground, not near the ceiling like those who try to argue about lights. Also it is unlikely all energy input ends up as heat, even when idle. Computers do do processing etc and some of the wasted energy would likely be in sound, perhaps em etc which is not going to end up as heat (at least not in your house). If you are using a modern computer with Cool'n'quiet, Speedstep or a similar power saving technology and an efficient PSU, I would say you would still often use at least 100W when idle and even presuming 80% ends up as heat (which I expect is a bit high), and all that heat is useful for you (which as I've explained I think is unlikely) that's still 20W. Over 90 days that's 43.2kWh. That's easily a few dollars/pounds/Euros/whatevers (depending on energy costs in your area) and equivalent to leaving a 1000W heater on in the middle of nowhere for 43.2 hours for no purpose. Of course in practice your computer is not going to be off 24/7 either but it's entirely resonable to turn off your computer if you're not going to need it for an hour or more. If you need a fast start, you could always enable some standy mode. Ultimately, it's always to let specialised equipment do what they were designed to do. Don't use a computer or a light as your heater (well heat lights are designed to generate heat and light but that's a different issue altogether). Use a heater. Yes it does mean the wasted energy calculation is not as simple as it seems but it doesn't mean you shouldn't consider wasted energy because it's all just heat and you want heat. The heat has to be in the right place and the right time otherwise it's still wasted. Nil Einne (talk) 07:54, 7 June 2009 (UTC)

As I mentioned above, it makes sense to turn off your computer but it's highly unlikely your computer uses 600W even at full load. Firstly power supplies for computers are always more then the computer ever needs. If it's a professional designed computer, e.g. from Dell etc, then the power supply maximum output would be closer to the maximum expected requirement but still higher. If it's a noname or assembled by a friend then there's a good chance the power supply is way more then the computer ever needs (this isn't a good thing but it's common). Commonly people add up the maximum possible draw of every component in the computer, except that this situation usually never actually occurs in practice. Secondly most cheap, no name power supplies are rated much higher then they can actually reliably supply. In other words, even if you power supply is rated 600W, it will often not be able to reliably draw close to that before having major problems. Thirdly as I have already hinted at, this is as maximum load. If you have a modern CPU and a modern GPU and even to some extent a modern motherboard, these are designed so they will draw a lot less when idle or close to idle (old ones to but not to such an extent). With CPUs, make sure the powersaving technology (probably SpeedStep for Intel and Cool'n'quiet for AMD) is probably enabled and working. With GPUs try and get an updated driver from the manufacturer (Nvidia or AMD/ATI) and look for any powersaving options. Note that if you have an IGP these don't use much but there may sitll be some power saving options. If everything is set up right, I would expect even for quite a good computer, you can expect it to use about 100W or so when idle (a very rough estimate) and 200-300W at maximum load. Even with something like SLI/Crossfire and quad core 500W would be a high maximum. In other words, the power used is likely less then you may think (but it doesn't mean it makes sense to waste it). As has already been mentioned if you're really interested, you can buy a power meter, and plug your computer into this and see how much it draws. (This is the only reliable way to work out how much a computer uses, anyone who tries to estimate it by adding up components is coming up with a highly speculatory number, and if looking at reviews, I would ignore such figures and may be even the whole review.) The only other thing I can say is you may want to consider a new PSU. As I've stated, it's likely more then you need. If it's some no name POS (as I've suggested if it's a decent branded computer, e.g. Dell, HP-Compaq etc then the PSU is probably an okay one), this is highly problematic because many crappy PSUs are extremely inefficient particularly at low loads which is probably the case for you presuming your computer is idle most of the time (browsing the internet, running Office is usually close to idle). A high quality good brand PSU, which meets the 80 Plus Certification would likely save quite a bit of energy. Plus cheap POS PSUs are notorious for dying and taking some of the components with them so it may save you some headaches there too. It may cost a bit, but I would look into whether you really need a 600W PSU. As I've said, ignore anyone who tells you to add up the maximum theoretical load of each component. A good place to start would be this SilentPC article (sadly a bit outdated) and the forums. Obviously if you get a power meter, then you will have a rather accurate idea of how much your PCs draws and while you'd want some headroom, I wouldn't give it too much. This is one of the examples where bigger is not necessarily better. (This isn't perhaps quite as much an issue nowadays as it was before the 80 Plus days but it's still the case that you don't really want to be only using a tiny percentage of your PSUs maximum most of the time.) Nil Einne (talk) 08:28, 7 June 2009 (UTC)

Leaving your computer on while you don't even use it 75% of the time probably won't save energy compared to turning it off. Computers usually have a program where you can shut it off either without pressing the power button, or it will say that it's safe to turn off your computer. I even turn off my computer straight with the power button every time, and with no ill effects. ~AH1^(TCU) 19:48, 7 June 2009 (UTC)

Also, some computers will consume several watts of power while they are turned off. ~AH1^(TCU) 19:49, 7 June 2009 (UTC)

Satellite photos of London from today (5th June 2009)

Hi,

Is there any way of getting these? I realise live satellite feeds probably aren't available but what about very quickly archived pictures? --Rixxin (talk) 11:26, 5 June 2009 (UTC)

Photos from weather satellites, maybe. What kind of resolution are you looking for? --Tango (talk) 13:28, 5 June 2009 (UTC)

Honestly? This is sure gonna sound lame. I was interested to see if there was a big 'ol dark cloud over The Palace of Westminster today, 'cos it sure felt like there should be!--Rixxin (talk) 16:43, 5 June 2009 (UTC)

Well, there was a big dark cloud over the whole of England, pretty much... See here for visible light satellite images of London and the South East of England over today (one per hour). I can't find a close up of Westminster, but the weather was pretty consistent so it doesn't really matter. --Tango (talk) 18:51, 5 June 2009 (UTC)

The day will undoubtedly come when we will be able to view any part of the earth in real time, and zoom in on places of interest. Wars could be watched as they took place. Imagine what it would have been like to watch the D-Day invasion in real time.. – GlowWorm. —Preceding unsigned comment added by 98.21.107.157 (talk) 18:44, 5 June 2009 (UTC)

Actually, you could have watched it in real-time, with the right equipment. --98.217.14.211 (talk) 19:57, 5 June 2009 (UTC)

It's very unlikely that such a thing would ever happen, however such a nice idea it may be. Think about it. If satellite pictures of battles were freely available on the internet as the battles were taking place, they would be available to both sides and would present serious problems (and of course, advantages) to both sides. --KageTora - (영호 (影虎)) (talk) 19:11, 5 June 2009 (UTC)

You would need millions of satellites, and much more bandwith the entire Internet has today.. --131.188.3.20 (talk) 22:34, 5 June 2009 (UTC)

Half a century ago it would have sounded ridiculous that everyone was walking around with their own personal mobile phone. You could not build enough transmitters, and where would all the bandwidth come from? Technology will continue to improve apace and if you cannot think of a fundamental theoretical reason to stop such things happening, then they probably will if people want them to. SpinningSpark 00:04, 6 June 2009 (UTC)

Indeed. If you are willing to wait 50 years, almost anything is possible unless it is explicitly impossible (and maybe even then!). I believe three satellites in geostationary orbit with cameras with amazing resolution could cover most of the Earth, all it needs is for someone to invent the cameras and that could easy happen in the next 50 years. --Tango (talk) 00:08, 6 June 2009 (UTC)

It's not the satellites or the cameras - providing whole-earth, realtime coverage (as we've discussed recently) requires insane amounts of hardware - but it's not disallowed by the laws of physics. HOWEVER - what is disallowed is the bandwidth you need to get all of that data back down to earth. 500 million square kilometers - 500 trillion square meters. 50 quadrillion pixels. About 500 quadrillion bits with lossy data compression. For a 'realtime' update - you need to send that between maybe 10 and 60 times a second. So 5 quintillion bits per second. That's a truly outrageous amount of data - it would fill a million hard disk drives every second. It's more data than is available on the whole of the internet...every second. This is not merely an engineering difficulty - it's a serious "fundamental laws of physics" kind of a problem. If we had a million satellites - all with tight-beam laser links to the ground so they didn't interfere with each other - then it would be pretty much impossible - but to do it with three satellites! That's just impossible. SteveBaker (talk) 02:52, 6 June 2009 (UTC)

a) What law of physics are you suggesting is being violated? b) you're making the same mistake you made last time - there is no need to transmit all the data, just the data that someone wants to receive and c) you are making meaningless comparisons - what do hard drives have to do with anything? No-one is asking you to store the data. Really, Steve, you should know better than to cavalierly claim something is physically impossible. --Tango (talk) 12:29, 6 June 2009 (UTC)

Nanotechnology could be a way to do it. Millions of tiny satellites could be put into orbit. Each satellite would consist of a group of molecules forming a camera and a radio transmitter having a broad beam, Each satellite would be solar powered, with a rechargeable battery for nights. Each camera would be aimed at a certain place on the earth and thus would need only a narrow transmitting bandwidth. The camera would be kept in its earth-aim by viewing certain stars and automatically making aim correction using solar power. The viewer on earth would select the radio frequency of the satellite aimed at the part of the world he is interested in. He would do this by selecting a square on a grid map on his monitor. He could enlarge the picture received, or combine the adjacent pictures of several satellites to cover a larger area. The satellites would not have to be in geocentric orbits, thus preventing overcrowding of that orbit, and permitting good near-polar coverage by using polar orbits with some satellites. Automatic switching would transfer reception from satellite to satellite to maintain the selected view of the earth as the satellites move. Automatic viewing-angle correction would also take place to provide an overhead view or angle view. The satellites could be manufactured cheaply by the millions in a nanofactory. They would be so small and light that they could be put into orbit and replaced at low cost. – GlowWorm.

Steve is being a bit negative here. Updates 60 times a second are not necessary for still pictures to be considered real-time, that's only necessary if you want video. One a minute might do, which would take three or four orders of magnitude off Steve's figures. Even if the aggregate data rate really is ~10¹⁸ b/s, each individual user does not want all of that at the same time on one channel, nor is each individual satellite supplying all of that on one channel. This is what networks are for, they are composed of many channels. As for the number of hard drives required to store the data, well you only need them for the data you want to store, you don't have to store any of it if you don't want to. SpinningSpark 12:27, 6 June 2009 (UTC)

Hm, what about not archiving everything, just send the data on demand. For example, for a city of 1000 you don't need 499500 phone cables just to connect them with each other, because they will never use the system all at the same time, talking to everyone at the same time. In fact, around 30 or so lines are enough to assure a 99.9% service. Not every person on Earth will look at the video at the same time, and even if they did, they won't see the whole surface of the Earth at the same time. Even so, we will require a ridiculous amount of satellites, bandwidth and storage space by today's standards, but significantly less than the numbers discussed so far. --131.188.3.21 (talk) 15:02, 6 June 2009 (UTC)

The MODIS Rapid Response website provides "near real time" (perhaps a pass per day or so) satellite coverage of most of the planet. The website is here. It takes some work to find what you want, and odds are good it will be cloudy. The images are fairly raw with edge distortion and the like, and the maximum resolution is 250 m per pixel. Still, the OP didn't specify the resolution required, and these are near daily images, so... Pfly (talk) 08:51, 7 June 2009 (UTC)

Yes - but that's hardly what the OP is asking for. Photos of "London" would be little more than a grey blur with a pixellated river running through it. 250m resolution means that streets and buildings cannot be seen - perhaps the larger parks could be - but there would be very little point in updating those pictures that frequently since nothing much changes at that scale from day to day - or even month to month!

This is London at 25meters per pixel:

But this is all you see at 250meters per pixel:

Pretty much a grey/green blur with a suggestion of a river.

SteveBaker (talk) 18:01, 7 June 2009 (UTC)

Also, the USGS Global Visualization Viewer gets you images from different satellites near specific geographical coordinates. However, it's unlikely to allow you to see images in much resolution, although it does usually have recent (few months to weeks) images, depending on cloud cover. ~AH1^(TCU) 19:42, 7 June 2009 (UTC)

Is it really true that Planes which cruise at high altitude get hit by lightning?

Hi All,

I just keep wondering if the latest French Aeroplane's accident is really due to lightning. As I understand, at the hights of over 28k feet, there are no rainbearing clouds, in fact (again within my limited knowledge)these clouds are much below. As such there shouldn't be lightning too. Am I correct in my understanding? Would appreciate if people could enlighten me on the same.

Warm Regards, Rainlover_9 Rainlover 9 (talk) 14:22, 5 June 2009 (UTC)

See upper-atmospheric lightning. Gandalf61 (talk) 14:26, 5 June 2009 (UTC)

Planes DO get hit by lightning - but not "Upper Atmospheric Lightning)!! Upper-atmospheric lightning is WAY above where a plane flies. A plane will fly at about 35,000 feet - only about 10 km above the ground. The phenomena referenced in upper-atmospheric lightning are more appropriately called "Transient Luminous Events" because they are neither lightning, nor do they take place in the "atmosphere" (largely being above the stratosphere and in the lower boundary layers of the ionosphere). There is no way even a military aircraft would fly at those altitudes (80 or 100 km above the ground). Airplanes can and do get hit by tropospheric lightning when they fly close to or through a storm - and some cumulonimbus clouds might have storm tops as high as 60,000 feet above ground. It is this type of lightning - typically a cloud-to-cloud strike - that results in the occasional airplane strike. Nimur (talk) 14:59, 5 June 2009 (UTC)

I have seen a photo of lightning striking up from a cloud as well, so that could be a possibility. Also, an airplane flying along might build up its own static charge, and may become a lightning target by itself, similar to how lightning will go from cloud to cloud. 65.121.141.34 (talk) 15:03, 5 June 2009 (UTC)

As I understand it, lightning has been ruled out as a cause. Planes, in theory, should be safe from lightning for the same reason cars are safe from lightning: the metal skin conducts the charge safely around the passengers and sensitive electronics. This is not always the case, as I know lightning has brought down planes in the past, but I'm fairly certain that all modern planes have protection against lightning. (ref: http://blog.seattlepi.com/aerospace/archives/169983.asp) -RunningOnBrains^{(talk page)} 18:15, 6 June 2009 (UTC)

I don't think lightning has been ruled out entirely, but it is pretty clear that more than one thing went wrong. These kinds of accidents always have a sequence of causes. There are all kinds of safety features on modern places so they can survive pretty much anything that can happen, but sometimes they can't survive multiple such things happening at once. --Tango (talk) 18:33, 6 June 2009 (UTC)

The deadliest plane crash caused by lightning was LANSA Flight 508, with 91 deaths. Planes today have better safety features, but that does not completely prevent them from being downed by lightning. Some features include needle-like structures on the back of the wings and tail to repel the static charge away from the aircraft. ~AH1^(TCU) 19:38, 7 June 2009 (UTC)

Is 2 + 2 = 4 in other universes

Hello, while wandering about on the Internet I came across this interesting question on Yahoo Answers:

"Is 2 + 2 = 4 in other universes? Assuming that parallel universes exist, would their mathematics be the same as ours? I.e. could there be a universe in which, for example, 2 + 2 = 5?"

People may be interested in the answers posted: http://au.answers.yahoo.com/question/index;_ylt=AvNVaIojr7pEw1Bn_IyyzxoJ5wt.;_ylv=3?qid=20090603213159AAKkQK1

Since the theory of multiple universes was derived using the maths that we understand, then it follows that the maths on parallel universes MUST be the same. Otherwise, it would make the theory inconsistent. That's my guess, I was just wondering what others might think about this.

203.206.250.131 (talk) 14:29, 5 June 2009 (UTC)

Unless they use different numbers, then it's probaly going to be the same. If you have 2 things and add 2 more it's going to be 4 everytime. --Abce2|AccessDenied 14:31, 5 June 2009 (UTC)

Actually I would disagree and say there definitely could be universes where 2+2=5 or even 2=3. The whole idea behind a theorectical multiverse is there are an infinite number of universes in which the laws of physics, logic and math can be different. Time could run backwards, accelerate, or not exist at all. Keep in mind math has never been proven to be (maybe once we get a grand unification theory it will be)the basis of reality but simply a representation which we've created. But either way, even with a G.U.T. this would only prove math is immutable in OUR universe, others could be entirely different. TheFutureAwaits (talk) 14:56, 5 June 2009 (UTC)

A better way to phrase this question is, "Suppose a hypothetical universe existed where 2+2 != 4. What would be the consequences?" I do not think there are any verifiable consequences of such a statement, so it is a non-scientific question. I think I'll leave my response at that, and we can just wait for SteveBaker to show up and remind everyone that needless philosophizing is wasting quarks... Nimur (talk) 15:03, 5 June 2009 (UTC)

(ec)Personally i think maths evolved from what you see. If you have two balls and someone else gives you two more balls, you find out that you have four balls. This process is called addition. So, maybe, just maybe, there might be a universe where if you have two balls already and i give you two more, another one automatically materializes and you get 5. This is a physical law in the universe that whenever you give two more balls, an additional one should materialize. In this particular universe, i am inclined to believe that 2+2 will indeed be 5, and hence all our mathematics breaks down. So, if there can be universes with different physical laws, this might well be possible, so i think it cannot be said with certainty that 2+2 is always 4. It can just as well be any other number, though it is hard to visualize in this example how it can be a fraction(half a ball? pi times a ball?) I am assuming decimal systems used in all universes. Rkr1991 (talk) 15:09, 5 June 2009 (UTC)

It depends on your definitions of 2, +, = and 4. If you define them the same way as we define them, which is not dependant on the universe, then you'll get the same answers. However, life in other universes may well define them differently if different definitions are useful for them. Mathematics and universes are separate things linked by models. We model parts of the universe on mathematical things. To use Rkr1991's example, balls are well modelled in our universe by natural numbers, they might not be well modelled by natural numbers in other universes. That doesn't mean natural numbers are any different, just that they wouldn't be used. There are all kinds of possible number systems in mathematics but we generally only use the ones which are useful for describing our universe. --Tango (talk) 15:20, 5 June 2009 (UTC)

I disagree with Tango. Even if you define 2, +, = and 4 exactly the same way in our system, the problem posed in my example remains unresolved. As i said earlier, i think maths was derived from what we observe, not hard solid facts. Maths and our universe cannot be separated, and it cannot exist independently. So if we see 2 balls and 2 balls make 5 balls in a universe, then i think our maths indeed breaks down there. Rkr1991 (talk) 15:38, 5 June 2009 (UTC)

I agree with Tango. If we see 2 balls and 2 balls make 5 balls, we will reasonably deduce that our definitions of 2, +, = and 4 are no longer useful, and we will redefine one of them. But unless we do that, if instead we keep 2 defined (as is most common) as the set {{}, {{}}} and + through Peano arithmetic, 2 + 2 cannot suddenly become 5. It's not like mathematics defines 2 + 2 as "the number of physical objects in the collection resulting from putting two physical objects together with two other physical objects". Correspondence with that physical result is of course the reason for our definitions (that's why Peano chose the axioms he did, etc), but it is not the definition. —JAO • T • C 15:54, 5 June 2009 (UTC)

Our definitions of arithmetic are axiomatic, not empirical. Observations don't come into it other than to determine whether those definitions are useful. --Tango (talk) 16:29, 5 June 2009 (UTC)

Um, no. The formal axioms of arithmetic are chosen because they're true, not the other way around. How we come to know this truth, and whether that can be called "empirical", is a difficult question. But you can't seriously maintain that there's no notion of the truth of a statement like 2+2=4 apart from its provability in a formal system, when discussing provability in that system requires understanding the truth or falsity of more complicated statements. --Trovatore (talk) 16:48, 6 June 2009 (UTC)

We use those particular axioms for things like counting everyday items because they are useful axioms for doing that - they accurately model the real world (you can call that "truth" if you like, I prefer to avoid the word because it has so many different meanings). We could still consider the axioms in some universe where they didn't accurately model the real world, but it would be a largely academic exercise. If we chose to carry out that exercise, though, we would still get 2+2=4. --Tango (talk) 03:07, 7 June 2009 (UTC)

We use those axioms because they're true. They accurately describe the behavior of the mathematical objects they are intended to describe, which are part of the "real world", yes, but not the physical world.

The claim in your penultimate sentence relies essentially on the existence of real, though abstract, mathematical objects, which are the same in the hypothesized other universe. If you don't have those objects, you have no way of even formulating what it would mean to "carry out that exercise" in that other universe. --Trovatore (talk) 06:27, 7 June 2009 (UTC)

It occurs to me that I should say a little more here, to head off a possible misunderstanding of my point. My point is that the axioms themselves are abstract mathematical objects, and the syntactic manipulations of them by which one codes proofs are more complicated relationships between those abstract objects, than the relationship between the abstract objects 2 and 4.

If you don't accept abstract objects of even this simplicity, then you have no grounds whatsoever to claim that it's even meaningful to discuss "carrying out the exercise" in a hypothetical universe in which the physical objects may bear no relationship whatsoever to those we're used to. Hope that makes my point clearer, or at least not less clear. --Trovatore (talk) 06:32, 7 June 2009 (UTC)

I'm afraid you have a misunderstanding of how mathematical logic works. There is no single mathematical object called "2". Anything which satisfies the axioms for being "2" can be consider to be "2". The axioms come first, then you find a model which satisfies those axioms. The most common model for the natural numbers is to let zero be the empty set ($\emptyset$) and then the successor of each number is the set containing all the numbers that come before it, so 2 would be "$\{\emptyset ,\{\emptyset \}\}$", but there are various other models you could use all of which have an object that can legitimately be called "2". The axioms were chosen because they accurately model the way items in the real world behave (there is an obvious real world concept of there being none of something, so we need a zero, then you can always place another item in a group and get a new number of items, so every number needs a successor, etc. See Peano axioms for details). --Tango (talk) 16:11, 7 June 2009 (UTC)

My Ph.D. is in mathematical logic, which of course does not in itself refute your claim that I misunderstand it (in fact, I would even agree that it is practically guaranteed that I misunderstand it), but at least recognize that such misunderstandings as I have are not ones uninformed by knowledge of the currently-understood alternatives.

There are two separate points to be addressed here — structuralism versus unique representation on one axis, and axiomatics versus realism on the other. The bit about "no single mathematical object called 2" addresses only the structuralism-related part, and that part I'm not interested in arguing. Sure, any object could be thought of as "2", if it bears the correct relationship to other objects thought of as other naturals. But that is not the same as saying the naturals are characterized by axioms, only that they are characterized by the relationship to other objects. These cannot be captured by (first-order) axioms.

The claim about axiomatics being primary in arithmetic, though, is simply false. Just plain not true. This is easily seen — the ancients had no axioms for the naturals at all, but they still knew what they were. --Trovatore (talk) 20:58, 7 June 2009 (UTC)

(e/c) Math was originally derived from experimentation, but this is no longer the case. A mathematical theory is made by a group of axioms and is supposed to be interesting. People will find parallels between the mathematical theory and the universe, and use that to make scientific theories. You could have a universe where the strength of gravity is not inversely proportional to the square of the distance, but that just means gravity will be modeled with different mathematics. All that being said, there could be universes where it's possible to build a hypercomputer, and it would be possible to do more sophisticated math. It's not that they'd get different theorems for the same theory (2+2=4 would still be true), it's that they'd be able to use axiom schemas that we cannot. For example, they might be able to find out if every even number above four is the sum of two odd primes by checking every case, something physically impossible in our universe. — DanielLC 16:03, 5 June 2009 (UTC)

I would like to point out that there are things that appear axiomatic that are in fact dependent on unstated assumptions. Euclid teaches, and people agreed for quite some time, that the interior angles of a triangle always add up to 180º. That's been a basic theorem of geometry for hundreds of years, and is as easy to demonstrate as 2+2=4. Of course, unstated is that only works if you are talking about a triangle on a 2-D plane—if you are sketching the triangle on a 3-D surface, it isn't true at all. A triangle on a sphere can have interior angles that add up to more than 180º. There's an unstated limiting factor in Euclidean geometry—that it only applies to 2-D surfaces—that becomes clear if you actually start, say, drawing large triangles on the ground (and you happen to live on a sphere).

I don't know enough about number theory to say whether there could be something analogous with arithmetic, but it's worth considering. --98.217.14.211 (talk) 17:21, 5 June 2009 (UTC)

No good mathematician would leave those assumptions unstated, at least in formal work. Everything in mathematics is based on assumptions. Results are always of the form "A implies B" never simply "B". One of the key things that is drilled into any mathematics student, however, is to always state your assumptions. --Tango (talk) 18:01, 5 June 2009 (UTC)

If 2+2 *always* equalled 5, then the alternate universe's laws of mathematics would likely look a lot like ours (though perhaps a bit more cumbersome). However, consider a universe in which 2+2 sometimes was 4, sometimes 3, sometimes 5, etc. In a sense, we live in such a universe now. The math we use to deal with this is statistics. Two random variables, when added together, can give you different answers each time you observe them. Wikiant (talk) 18:06, 5 June 2009 (UTC)

In which case they wouldn't model items as numbers but rather as random variables. Mathematics includes all kinds of tools, you need to use the right one for the right job. Just because one tool isn't right for a particular job doesn't mean that it is wrong mathematically. --Tango (talk) 18:10, 5 June 2009 (UTC)

I would like to leap to the defence of Euclid on this one. Euclid realised perfectly well that the angles in a triangle summing to 180º was not axiomatic but was dependant on the parallel postulate and clearly states this as a postulate in his Elements (postulate 5). It was later mathematicians who through the centuries refused to believe that the parallel postulate could not somehow be proved from other basic postulates. It was only finally admitted that Euclid was right when Einstein discovered that the universe was not, in fact, Euclidean and that other geometries were possible in the real world as well as in the minds of mathematicians. SpinningSpark 23:06, 5 June 2009 (UTC)

Einstein used non-Euclidean geometry, he didn't invent it. The geometry Einstein used was mostly constructed by Bernhard Riemann, I believe, although several people had done work on the subject before him. Non-Euclidean geometry was known to be relevant to the real world before Einstein came on the scene - we live on the surface of a sphere, which in non-Euclidean. It doesn't matter anyway, you don't need a real world application to prove that the parallel postulate is independent of the preceding four. --Tango (talk) 12:08, 6 June 2009 (UTC)

I didn't say Einstein invented non-Euclidean geometry, I quite agree, it was around long before that. What his work did do was put an end to the cottage industry of trying to prove the parallel postulate, which at one time occupied the place that attempts to invent a perpetual motion machine occupy now. Very little of the mathematics of relativity are due to Einstein himself, but relativity established once and for all that as well as being unprovable, the parallel postulate was not even true in the real universe (at least on a large scale). SpinningSpark 14:21, 6 June 2009 (UTC)

The discovery of non-Euclidean geometries put an end to attempts (by legitimate mathematicians) to prove the 5th postulate from the other 4. The real world has nothing to do with mathematics. --Tango (talk) 14:28, 6 June 2009 (UTC)

Ooooh, well that would depend when you date the discovery of non-euclidean geometries. Some would credit it to Omar Khayyam, in which case do the attempted proofs of Giordano Vitale (1680), Girolamo Saccheri (1773) and Adrien-Marie Legendre (1794) render them not legitimate mathematicians? I think not, and if you define the beginning of non-Euclidean geometry as the point at which attempts to prove the 5th postulate ceased, well then you have a circular argument. SpinningSpark 15:12, 6 June 2009 (UTC)

I believe Khayyam contributed some of the initial ideas, but he didn't have a rigorous model which obeyed the first four axioms but not the fifth, which is what was required to prove the fifth was independent. I've not studied the history of non-Euclidean geometry in depth, so I'm not sure exactly who had the first such rigorous proof, but I do know if was a long time before Einstein. --Tango (talk) 15:55, 6 June 2009 (UTC)

We like to think of these discoveries as a sudden revelation and credit them to some one genius in particular. The reality is that it is a gradual process to which many contribute. As Wittgenstein said, the real change in beliefs comes not at the point of this or that discovery but at the point of a paridgm shift. It is made clear in this book for instance, that Saccheri would have been credited with the discovery of non-Euclidean geometry if only he had not continued to publish "proofs" of the 5th postulate. This is an untenable logical position, he discovered non-Euclidean geometry, according to the author, but his discovery is invalidated by his later work. If all his later work was destroyed so we did not know of it, he would be the discoverer, so if I mentally imagine I have not read of his later works he becomes the discover? In any case, as I have already said, I do not dispute this all happened long before Einstein, my point is that it was Einstein that triggered the paradigm shift in belief, and this was because Einsteins work related to the real universe, which is where reality comes in to it. This makes no difference at all to the mathematics, but it does change quite radically the way people are thinking. SpinningSpark 18:36, 6 June 2009 (UTC)

Yes, there is some confusion over exactly when the first rigorous proof was accepted by the mathematical community, but it was certainly a long time before Einstein. Einstein's discovery that Riemannian geometry was a good model for the universe has nothing to do with mathematics. Mathematicians make decisions based on logic, not empiricism. And, as I've already said, there were aspects of real life that have been modelled on non-Euclidean geometry before Einstein, such as the surface of the Earth. --Tango (talk) 01:19, 7 June 2009 (UTC)

Are we really debating this? If I have two apples on a table, and place two more apples on the same table, I now have four apples on the table. If I lived in a universe where an extra apple materialized merely because I placed two groups of two next to each other, such a universe would violate the principle of causality so as to be entirely unexplainable at any level. Seriously, why is this even being debated to this level? --Jayron32.talk.contribs 19:00, 5 June 2009 (UTC)

Your example only violates causality if it is true that 2+2=4. So, your argument boils down to the circular "2+2 must equal 4 because if it didn't, 2+2 wouldn't equal 4." For a possible counter-example, consider this universe wherein subatomic particles and anti-particles spontaneously emerge. This could be interpreted to suggest that 0+0=2. Wikiant (talk) 21:05, 5 June 2009 (UTC)

Why should another universe obey our universe's laws of causality? It isn't difficult to imagine a universe with two timelike dimensions, which would have very different principles of causality. (I think I read a paper once about such a universe and the conclusion was that complex life almost certainly couldn't evolve in it, but that's not important.) --Tango (talk) 21:15, 5 June 2009 (UTC)

This reminds me of David Deutsch's concept of "cantgotu" environments in The Fabric of Reality, but I can't remember what if anything he said about the idea of 2+2 not equaling 4. He deals with this general kind of idea, though. 213.122.1.200 (talk) 22:01, 5 June 2009 (UTC)

No, no, no. You can't use things popping into existance or whatever to envisage a scenario when 2+2 doesn't equal 4. In our universe, 0.9 times the speed of light plus 0.9 times the speed of light equals 1.8 times the speed of light (yes, it really does). However, if you're travelling at 0.9 times the speed of light relative to me and you toss a ball out in front of you at 0.9 times the speed of light, it won't be moving at 1.8 times the speed of light relative to me - it'll be more like 0.99. That's not because 0.9+0.9 doesn't equal 1.8 - it's because the arithmetic operator '+' doesn't apply to speeds as we humans always thought it did. This really shouldn't be a surprise, the '+' operator doesn't apply to a while lot of things!

So if two subatomic particles pop out of nowhere, that doesn't prove that 0+0=2 - it proves that the total number of particles in some volume of space is not a constant - so addition is (again) not an appropriate operation to apply to them.

The point is that things like '+', '2', '=' and '4' are symbols that stand for concepts that have definitions that humans have applied to them. Our definition says that 2+2=4 - not because that necessarily represents something "real" but because that's what we've defined those symbols to mean.

Suppose I were to define the symbol '#' to mean "the sum of two numbers - except when there is a full moon, when it's the product of two numbers" - then 2#2=4 happens to be a true statement...but 3#3=6 isn't always true and 7#9=5 is never true. There isn't any deep inner meaning in what I just said - it's just words and definitions. There is probably no physical property of our universe for which the '#' operator is applicable - but my definition is still a perfectly reasonable one and 2#2=4 no matter what. Perhaps in another universe, placing apples on tables follows the '#' operator - but the '+' operator is kinda useless and considered weird to the people who live there, (who are constantly checking their almanacs to see when the next full moon will be!)

So this universe does whatever it does - the other universe does whatever it does - and whether our definitions for the symbols '2', '+', '=' and '4' are applicable to apples placed on tables in that other universe (or to the way speeds are combined) is a matter that we can't answer. But our definitions still apply - you can't invalidate something that's axiomatic in the system of mathematics you choose to use.

Hence, the answer is a clear "yes" - 2+2=4 everywhere - because we happen to have defined it that way. SteveBaker (talk) 22:27, 5 June 2009 (UTC)

I'm going to expand upon what's been said above, because hopefully it'll sort out some confusion. Back off a bit - say we're in a parallel universe which doesn't have the same laws of math. First let's start with a quantity. Names are arbitrary, so let's call it "@". That's going to be boring by itself, so we'll make another quantity, and we'll call it "!". Independent quantities by themselves aren't interesting, so let's add an operation: "%". How does this operation behave? It might be nice to have an identity, that is, if we 'percent' a quantity with the identity, we get the other number back. It's arbitrary which one we choose, as they are the same, so let's pick '@'. So we have '@ % @' => '@' and '! % @' => '!'. Okay, but now what about '! % !'? Well, we could say that '! % !' => '@', or even '! % !' => '!', but we can also introduce a new symbol, so let's do that and call it '&'. So '&' is defined as '! % !'. Now what is '& % !'? Keeping it open ended we define it to be '$'. And '$ % !' => '#'. Now, let's figure out what '& % &' is. Since '&' is the same as '! % !'; we see that '& % &' is '(! % !) % (! % !)'. If we say that order in which we 'percent' doesn't matter (associative property), we can rewrite that as '((! % !) % !) % !', or '(& % !) % !' or '$ % !', which we defined earlier as '#'. As long as '! % !' => '&', '& % !' => '$', '$ % !' => '#', and the '%' operation has the associative property, '& % &' => '#'. Hopefully you can see where I'm going with this; the names I gave them were arbitrary. I could have easily have said 0 instead of @, 1 for !, 2/&, 3/$, 4/# and +/%, and you have your situation. If we have defined 1+1=2, 2+1=3, 3+1=4, and addition as associative, then 2+2=4. If 2+2=5, then either 3+1=5, 1+1≠2, or addition is not associative. We certainly could call 3+1, '5' if we wanted, but it would behave exactly the same way 4 does now. It would be the equivalent of writing 'IV' instead of '4' - the name changes, but the properties stay the same. Conversely, with addition being non-associative, why call it "addition"? Associativity is part of what defines addition - if you change that, you have something else.

"Non-standard" arithmetic are used all the time, however. That case earlier, where '!%!'=>'@' (er, 1+1=0)? That's modulo 2 arithmetic. We also have the case where '!%!'=>'!', except we call that multiplication, and we substitute 1 for @ and 0 for ! instead of vice-versa. We also frequently encounter physical situations where 2+2≠4. Take, for example, adding two liters of water to two liters of sand. 2+2≠4 in that case. Mix 2 cups vinegar to 2 cups baking soda, and the result takes up much more than 4 cups. Physical reality doesn't have to match with abstract mathematical constructs - however, instead of redefining 2+2=3 because the sand and water don't measure 4 liters afterward, or saying that 2+2=8 because of the carbon dioxide gas evolved with baking soda and water, we leave mathematics as a "pure" ideal, with 2+2=4, and realize normal addition doesn't apply to those situations. Likewise, the fact that interior angles of a triangle don't add up to 180 on the surface of the earth didn't invalidate Euclidean geometry - it still exists theoretically, we just realize that when doing surveying, we need to use a non-Euclidean geometry. -- 128.104.112.106 (talk) 01:28, 6 June 2009 (UTC)

Physicist Max Tegmark has proposed a Mathematical universe hypothesis which proposes that every mathematical structure exists physically in some universe. But from a mathematical point of view, it seems to go a bit overboard (ask in the math RD for more explanation). Note, non-standard arithmetic (in mathematical logic) means something different than what 128.104.112.106 seems to think. 207.241.239.70 (talk) 03:41, 6 June 2009 (UTC)

I believe the anon put "non-standard" in quotes in order to clarify that they weren't using it in the technical sense but just in the dictionary sense. --Tango (talk) 12:14, 6 June 2009 (UTC)

I thing I can clarify this by answering a similar question: Is there are universe in which you cannot cut a ball into five pieces and reassemble them into two balls identical to the first? Of course there is. You can't do that in this universe. It's not that the math is wrong. It's simply that our universe isn't set theory. It has parallels with it, but if you want to make a perfect model of our universe, it's going to be a bit more complex than that. 67.182.169.172 (talk) 17:21, 6 June 2009 (UTC)

That depends on your definition of "is"... but we are well into the realms of philosophy there, and we know how Steve feels about that! --Tango (talk) 18:31, 6 June 2009 (UTC)

Peacock and Peahen

Somebody told me that Peahen gets her eggs fertilized by orally shallowing the semen of the peacock.Is it true? —Preceding unsigned comment added by 202.70.74.155 (talk) 15:32, 5 June 2009 (UTC)

No. --Stephan Schulz (talk) 16:11, 5 June 2009 (UTC)

Fowlatio? Edison (talk) 01:59, 6 June 2009 (UTC)

Egg protein

Since eating raw eggs is not better than eating cooked eggs, what way should i cook them so that minimum protein is lost in the process of coooking (i.e. boil, fry etc.)? —Preceding unsigned comment added by 116.71.42.218 (talk) 18:00, 5 June 2009 (UTC)

This is a confusing question! If raw is not better than cooked, then why are you concerned about loss during cooking? As for outright loss during cooking, everything is still there except for maybe some small amounts that get stuck to the pan or leached out into the grease or other cooking medium, so something like hard-boiled would keep everything still in there. DMacks (talk) 18:04, 5 June 2009 (UTC)

The only protein loss during cooking would be the little bits that brown along where the egg meets the pan (see Maillard reaction). These are likely so small as to be insignificant, so you would be safe frying the eggs. As far as I am concerned, hard boiled eggs serve little purpose except perhaps to make deviled eggs or egg salad. I find them pretty bland and unpalatable. But if your concern is making sure you get every molecule of protein out that was there originally, taste be damned, then go with the hard-boiled method. --Jayron32.talk.contribs 18:28, 5 June 2009 (UTC)

Cooking will denature protein, but you will not lose the protein (specifically the amino acids). -- kainaw™ 18:33, 5 June 2009 (UTC)

To DMacks: I asked a question a couple of weeks back if raw eggs have any advantage over cooked ones and I was told no. And so if I work out and want max protein from the eggs I should hard boil them? I dont care about taste. —Preceding unsigned comment added by 116.71.59.87 (talk) 19:45, 5 June 2009 (UTC)

Kainaw already answered the above question, didn't he? Tempshill (talk) 22:10, 5 June 2009 (UTC)

exit polls

Has anyone actually got any for the Euro elections? —Preceding unsigned comment added by 86.128.217.5 (talk) 22:43, 5 June 2009 (UTC)

I'm guessing you're interested in UK results: European Parliament election, 2009 (United Kingdom) should gradually accumulate that information - our editors usually get results up within minutes of it being announced...for an encyclopedia, we make a better news site than most proper news sites! There seem to be some results and recent polls there - but you'll probably want to hit reload every now and again. On the remote off-chance that it's not the slowly unfolding spectacular train wreck in the UK that you're interested in, there are links for results in the other countries at European Parliament election, 2009. My brother in law (Tony Goldson) just got elected to the Suffolk County Council with a landslide result - but no sign of that result here! SteveBaker (talk) 02:40, 6 June 2009 (UTC)

They are avoiding publishing any results (which seems to include exit polls) until Sunday evening to avoid influencing the votes in other countries (the Netherlands, for the second time in a row, has chosen not to do this, and may end up in a bit of trouble over it...). --Tango (talk) 13:17, 6 June 2009 (UTC)

Just out of interest, who is the "they" who are avoiding publishing, what, if anything, is enforcing this, and under what statutes, European or Dutch, may the Netherlands end up in trouble? Tonywalton ^Talk 22:35, 6 June 2009 (UTC)

You're not supposed to ask questions I don't know the answers too... There are some kind of European laws about how these elections are supposed to take place. Of course, the Netherlands is a sovereign country, so there isn't a great deal anyone can do about it, but they'll get told off by the European Commission and that sort of thing. I don't know if those laws apply to the media (who handle the exit polls), but I would guess it's just a gentleman's agreement that stops the exit polls being published. --Tango (talk) 23:27, 6 June 2009 (UTC)

So what's the point of the exit polls? Axl ¤ [Talk] 18:16, 7 June 2009 (UTC)

They are quicker, so you can get results out straight away once the embargo is removed, rather than having to wait for the count to finish. I'm not sure there were any exit polls in the UK, though. --Tango (talk) 00:51, 8 June 2009 (UTC)

work

Why would work be defined as a scalar rather than a vector? —Preceding unsigned comment added by 70.52.45.55 (talk) 23:29, 5 June 2009 (UTC)

Work done is synonymous with energy. The energy required to do something is equal to the sum of the energies required to do each part, they don't cancel out. --Tango (talk) 23:39, 5 June 2009 (UTC)

It does seem weird - if your "work done" is pushing a block up an inclined plane or something you kinda feel like it ought to be a vector...but remember that you could be doing work to increase the air pressure in a balloon - what would the direction be in that case? Suppose it was electrical work - charging a battery or something - again, no direction. SteveBaker (talk) 02:22, 6 June 2009 (UTC)

Lets just assume Work to be a vector. Say you're pushing a block of wood up an inclined plane. But the catch us that you're not applying the force along the inclined plane. Say you're applying the force directly horizontally, but the block still moves up. SO now, what would be the direction of your work? Would it be along the inclined plane, where the block actually moves, or horizontally, in the direction where you actually pushed? If we assign a direction for Work, it results in more confusions, and essentially loss of physical significance as being equivalent to Energy. So, it is best to keep Work as a Scalar. Rkr1991 (talk) 04:26, 6 June 2009 (UTC)

Or as one of my college professors would put it: "Because that's the way the math works out". Work defined is the dot product of two vectors, which always results in a scalar. -RunningOnBrains^{(talk page)} 18:20, 6 June 2009 (UTC)

Yes, but that just changes the question to "why is it defined as the scalar product?". --Tango (talk) 18:29, 6 June 2009 (UTC)

If work (and by extension, energy) was a vector, there'd be no law of conservation of energy. When you fire a gun, more energy goes with the bullet than the gun, so there would be energy in the direction of the bullet. If you used the same gunpowder in a grenade, the energy would move in all directions and cancel itself out. Thus, more energy is extracted from the gunpowder one way than another way. Also, heat involves particles moving in all directions, so it would have zero energy. That would mean that anything that turns energy to heat destroys energy. — DanielLC 15:36, 7 June 2009 (UTC)

June 6

Jellyfish as pets.

An IP recently asked me if Jellyfish could be kept in a houshold aquarium. I told him/her basically that I didn't know for sure. I offered some in depth, but basic, guidance on how to do it, while reinforcing that I think it is a very bad idea to try. The whole reply can be seen at my talk page. After replying, I realised that while I may not have the answers, someone else might. Basically I have to questions:

• Can jellyfish be kept in a household aquarium?

• Was my reply right, wrong, or a little of both?

Thanks for any guidance on this.Drew Smith What I've done 05:58, 6 June 2009 (UTC)

Perhaps this web site can help.--Lenticel ^(talk) 06:13, 6 June 2009 (UTC)

I recently was at an event where someone was selling jellyfish kits for several hundred dollars each. I'll offer some observations from what I saw. This doesn't mean that his "kit" was actually a good idea or the optimal solution. He also seemed to be offering only one species of jelly, so these observations may not apply generally.

1. The largest tank on display was not huge, perhaps only 80 gallons and held three large jellies and basically nothing else. No scenery, no reefs, no other fish, nada. Maybe this was an open water species and preferred that; I don't know.
2. The smallest tank was perhaps 15 gallons and held one small jelly, and nothing else.
3. The "ground" in his tanks seemed to be made of rounded plastic stones roughly the size of a thumb but somewhat fatter.
4. Most of his tanks were vertically oriented, i.e. they were taller than they were wide. At the largest scale this was perhaps 3:1. All of the tanks were rounded and had no sharp corners on their vertical face.
5. All of his tanks had heavy duty aerators. Noticeably stronger than I have ever seen on aquariums of similar size. These were mostly enclosed, presumably to prevent the jelly from swimming over the air flow.
6. The type of jelly in question had very short tentacles.

I wasn't interested enough to ask about care and feeding, so I don't know anything about the water quality or nutritional requirements. I did see some sort of food packs though, so presumably they can eat things other than live/recently caught food. Hope this helps. Dragons flight (talk) 06:47, 6 June 2009 (UTC)

This helps, in that keeping jellies as pets is more common than I thought. On the other hand I have never seen a "kit" that actually keeps its intended inhabitants alive for even a fraction of its lifespan. Goldfish can live up to forty years in the wild, and seldom live more than a few months in "kits".Drew Smith What I've done 09:21, 6 June 2009 (UTC)

Physical strength requirements of Formula 1

Not sure if this is more suited to the Entertainment or Science section, so please feel free to move it

During today's qualifying for the Turkish GP a commentator stated that 10kg of weight would add 0.3 seconds per lap. Obviously that is quite a lot of time (adding about 21 seconds in a 70 lap race). This has made be wonder about the impact of keeping down a driver's weight and the trade offs that might entail. As an example, according to this page Jenson button weighs about 68kg, whereas I weigh about 95kg (I shouldn't, but I do!). At 0.3 seconds per 10kg per lap, I would, with the same driving skill, be 0.81 seconds slower per lap, or 56.7 seconds slower for a 70 lap race. So it would seem that, no matter how skillful, somebody weighing 95kg could never be successful in F1. This makes me wonder why successful F1 drivers do not tend to weigh even less. The jockey Willie Carson, seems to have weighed about 49kg, which would give him roughly a 0.6 second per lap advantage, or 42 seconds per race - presumably a woman would have even greater potential weight wise. Obviously skill is the overriding factor, but I cannot see why a woman, or a much lighter male would not be capabale of the same level of skill. So, I wonder if it is about the physical demands of F1. Is it that a degree of strength is required, that would override the weight advantage of a woman or a lighter male? I would have thought that riding a horse required greater strength than driving a Formula 1 car, and that jockeys must have a very good strength to weight ratio, but obviously there are other factors at play here, because Formula 1 is not full of drivers with the stature of jockeys. I would appreciate any thoughts on this. Thanks Chuny Beetroot (talk) 12:30, 6 June 2009 (UTC)

You do need to be very physically fit to withstand the g-forces. I'm not sure how strong jockeys need to be, but probably not as strong as a F1 driver - I can't see why they would need much strength. --Tango (talk) 13:08, 6 June 2009 (UTC)

Formula1.com says "cars must weigh at least 605kg (including the driver), but traditionally teams build the car to be considerably lighter and then use up 70 kg of ballast to bring it up to weight." So that means the weight of the driver is mostly irrelevant (all it does is given the team less ballast to move around to change the balance of the car for specific tracks). This reply (I don't know how reliable it is) claims quite a diversity in F1 driver heights (and surely weights, as the tall ones listed aren't beanpoles and the shorter ones noticeably chunky). That said, this article claims KERS promotes smaller drivers. 87.112.85.8 (talk) 13:59, 6 June 2009 (UTC)

On the official Formula 1 site the Toyota team doctor says, among other things, There is no other sport in the world which compares to the demands Formula One puts on the heart. SpinningSpark 14:07, 6 June 2009 (UTC)

Higgs boson

Might one find one or more Higgs bosons at the center of a Black Hole? ---- Taxa (talk) 12:52, 6 June 2009 (UTC)

If our theories are correct, there are Higgs bosons everywhere, they are just difficult to see. We can't say what is at the centre of a black hole, it is a singularity, which is scientist-speak for "we haven't got a clue". --Tango (talk) 13:12, 6 June 2009 (UTC)

My thinking is somewhat askew from the thinking of others. I was trained specifically to think outside the box. I have no problem, for instance, with 10/zero(0)=10. Its logical to me that when you divide by zero nothing happens. I apply the same logic to the center of a Black Hole and to a Higgs boson . It may not be possible for anyone other than myself to consider that not having a clue is not an acceptable answer unless you explain why you do not have a clue. ---- Taxa (talk) 13:42, 6 June 2009 (UTC)

I'm afraid that isn't "thinking outside the box", that is just being wrong. If 10/0=10 then we can multiply both sides by zero and get 10=10*0, but anything times zero is zero, so you have 10=0, a contradiction. Thinking which is unconventional can be a good thing, but it still has to be logically consistent. We don't have a clue about what happens at the centre of a black hole because the mathematical model we use to describe black holes breaks down at the centre and gives a result that doesn't make sense (ie. various infinite physical values, which aren't consistent with how those values are defined). Hopefully someone will come up with a theory that can explain the centre of a black hole, but they haven't yet. If you have a theory which explains black holes in terms of Higgs bosons, feel free to write it up and submit it to a peer reviewed journal, but I doubt it will be accepted because I suspect you don't actually understand what a Higgs boson is (I'm not clear on the details myself, but I fail to see any way that their presence in black holes could resolve the singularity, if they exist they will be there because they are everywhere, that doesn't help anything). --Tango (talk) 14:17, 6 June 2009 (UTC)

Not quite. The problem is that you are still thinking inside the box. You still see the division sign (/) as operational. By outside the box I no longer see the division sign as operational when a zero value is below it. What you see is that 10 is the result of an arithmetic operation. What I see is that no arithmetic can or has taken place. Its as if I were screening the values with an "if, then" statement and if the value under the division sign is zero then no arithmetical operation can take place. You see the division sign instead as an arithmetical operator that is turned on not matter what the values are because you are still thinking inside the box. You are unable to recognize that the division sign itself, its use or operation is not always valid, that there is a chink in the division sign. -- Taxa (talk) 19:23, 6 June 2009 (UTC)

If you open your mind to much... [20]. What you do by "thinking outside the box" is redefining the / sign to mean something different from what it usually means. I can just as well claim that 2+2 = 5 (by redefining "=" to mean "bigger than" and "+" to mean concatenation of the decimal representations of the arguments. --Stephan Schulz (talk) 19:36, 6 June 2009 (UTC)

Taxa, you said "Its logical to me that when you divide by zero nothing happens." so don't come now with "By outside the box I no longer see the division sign as operational when a zero value is below it." Divide by zero means divide by zero. It is by definition operational. you cannot arbitrarily redefine the meaning of words like division and call if "thinking outside of the box". That's no different than saying that instead of deviding by rezo I will replace it with my favorite color, 10/0=blue=humpty dumpty=dejavu. Even when thinking outside of the box things still must make sense, otherwise it's just plain rubish. Dauto (talk) 19:49, 6 June 2009 (UTC)

Have you observed that 2+2=5? My observation of the function of the division sign is based upon empirical evidence that the division sign is not operational dependent upon the value which is below the division sign or in other words that the division sign is turned off or no longer functional dependent entirely upon the value of the divisor. -- Taxa (talk) 19:58, 6 June 2009 (UTC)

Mathematics is not an empirical subject. You can't "observe" 2, it is an abstract concept. You can define the "/" symbol in a different way to me if you like, but don't expect anyone else to use your definition because it isn't useful. Division is useful because it obeys certain rules (like a/b=c => a=bc) that let us work with it in useful ways, if you redefine it in a way that means those rules no longer hold, then it isn't useful any more. This isn't about being open minded, it is about pragmatism. There are all kinds of mathematical objects that can be defined (infinitely many, in fact, but don't ask me which infinity), some of them are useful, so get used, most aren't useful, though, so, for the most part, get ignored (pure mathematicians play around with things that aren't necessarily useful to the real world (until a scientist comes along and finds a use for them - scientists are amazingly good at that), but they are generally useful to something, even if they are just ascetically pleasing for are useful for making mathematicians happy). --Tango (talk) 20:12, 6 June 2009 (UTC)

My great great grandfather found that he could use a simple pan to fry fish, pan for gold, keep the rain off his head. Unfortunately he learned the hard way that his pan could not stop a bullet. Thanks to empirical evidence that his most valued multipurpose tool could not serve to save his life in the capacity of armor I now know that it is a function the pan is incapable of performing and not one which I would want to try. The division sign is merely a tool and its inability to function when the divisor is equal to zero is quite enough for me to reach the conclusion the division sign is not capable of this function. -- Taxa (talk) 21:08, 6 June 2009 (UTC)

Hmmm... there are some things best not tested by direct empirical observation! I don't see the relevance of that anecdote, though... We know the division operator isn't capable of functioning when the second parameter is zero, that's why we just say you can't do that. You're saying that it can function and functions as the identity, which isn't consistent with the rest of its behaviour. --Tango (talk) 22:07, 6 June 2009 (UTC)

No you have it right now. "...the division operator isn't capable of functioning when the second parameter is zero..." What many people do not realize is that it is the function of the division sign that is the problem rather than the value of zero. -- Taxa (talk) 22:47, 6 June 2009 (UTC)

When did I have it wrong? Could you give an example of someone that doesn't realise that? I'm not sure it is appropriate to distinguish between a problem with one or the other, rather than saying it a problem with how they interact, but if you had to choose one or the other then the problem would be with division, simply because you define zero first. --Tango (talk) 23:12, 6 June 2009 (UTC)

By accepting that the function of division breaks down when zero is the divisor then you can accept 10/0=10. If you insist that the function of division does not break down then you will argue that 10 divided by zero can not equal 10 because 10 times zero does not equal 10. -- Taxa (talk) 23:31, 6 June 2009 (UTC)

When you accept that you can't use the regular definition of division to handle division by zero you have a choice. You can leave it undefined, or you can arbitrarily define it to equal something. Either gives you a valid mathematical function, but the former turns out to be more useful. You can define 10/0=10 if you want to, but there is just no reason to do so. It doesn't help you in solving any problems, which is what maths is all about. --Tango (talk) 01:04, 7 June 2009 (UTC)

When I am writing a workaround to deal with some practical division by zero problem in C, I find that MAX_INT (or something similar, the largest allowable value) is more commonly a useful answer than "nothing happens". Sometimes MAX_INT but keeping the sign of the number being divided. Sometimes applying a sign to the number from some other variable. Other times "nothing happens" might suit me, or zero. So if you're going to argue from practicality, there isn't a definite answer to be found there either. 81.131.14.50 (talk) 00:53, 7 June 2009 (UTC)

Taxa, I think that rather than thinking outside a box, you may be still trapped inside one. When we learn mathematics, it is usually as an "operation" - an action. You start with two apples, you add three apples, and the result is five apples. That's the thought process you're applying when you state 10/0 = 10. "You start with 10, you divide by 0, which doesn't change anything, so you're left with what you started with, which is 10." When you really get into mathematics, however, you need to break out of this action-oriented box, and view mathematics as relationships, rather than actions. It's no longer "10 divided by 5 is 2", but also "5, when divided into 10 is 2", and "2 is related to 10 by the division with 5". It's this relationship view which fuels Tango's assertion that 10/0 = 10 implies 10 = 10*0. The relationship of 10, 5, and 2 in "10/5 = 2" is the same as the relationship of 10, 5 and 2 in "10 = 2*5", because of the relationship between division and multiplication. You could break that relationship, but then it's no longer multiplication and division, and furthermore, as Dauto mentions, you could just as easily say that "10/0 = blue" or "10/0 = a cup of weak tea" as "10/0 = 10", because the power, nay, the whole point of division as a concept is its relationship to multiplication and other mathematical constructs. Part of that relationship is that "X/Y = Z" implies that "X = Z*Y". You certainly are free to come up with a mathematical operation where "10 op 5 = 2" and "10 op 0 = 10". It wouldn't be division, though. (Mathematicians make up new mathematical operations all the time, though they usually call them functions. And again, although functions are usually taught as actions, they're more appropriately viewed as a relationship, as a mapping of a set of numbers onto another set of numbers.) -- 128.104.112.106 (talk) 00:27, 7 June 2009 (UTC)

I don't think using the apple analogy is fair when dividing by zero, as even dividing by fractions is counter-intuitive (10 apples divided by 0.5 people leads to 20 apples each). However, I would like to ask how this would apply to molecules, i.e. with the law of mass action, specifically chemical equilibria? For example, let's say we have HCl + H₂O → H₃O⁺ + Cl^-, the HCl has fully dissociated (in this case there is one of each molecule, not one mole of each molecule). Thus the acid dissociation constant would be: K_A = [H₃O⁺][Cl^-]⁄[H₂O][HCl], which leads to 1*1 / 0*0. How is this solved? (Sorry if this is too off-topic and should be a new thread). --Mark PEA (talk) 16:46, 7 June 2009 (UTC)

The raction can temporarily reverse itself. [H₂O] and [HCl] should be seen as the (non-zero) probabilities that at any given time there will be a H₂O and/or a HCl present. Dauto (talk) 22:37, 7 June 2009 (UTC)

Okay so I should have stated that I'm assuming that after the reaction, the two products will never collide again (I tried to state it by saying there was only one of each molecule). I guess you will argue that on the reactants side there was only two molecules, so if they are capable of colliding why not the products, let's assume there is something surrounding the molecules which will attract their charge (effectively "solvate" but in a heterogeneous situation, maybe some complex situation à la Maxwell's demon). Anyway 128.104's response below answers my question. --Mark PEA (talk) 23:09, 7 June 2009 (UTC)

I used the operation on apples not to show intuitiveness, but to demonstrate how mathematics is usually taught. Your example of 10/0.5 = 20 uses the same "action oriented" viewpoint, illogical as the situation may be. "You start with 10 apples, divide them between 0.5 people, which results in 20 apples per person." The illogicality only points further to the fact that division has a broader life as a relational statement, rather than a procedural one. It's illogical because "dividing between 0.5 people" makes no physical sense. On the other hand, with division as a relationship, sense is restored "if there are 10 apples for every 0.5 people, then there is 20 apples for every 1 person." For your second point, you can only calculate equilibrium constants if the system is in equilibrium - you can't say that one hydronium and one chloride ion are "in equilibrium" with HCl and water. This is a similar situation to the original question! The fact that you are dividing by zero indicates that you've extended the mathematical models further than they are valid. If you just have two molecules, you can't derive an equilibrium constant, because it is not in equilibrium. Likewise, we can't say what happens at the singularity in the middle of a black hole, because our current models all break down. On the other hand, if we're happy saying (1*1)/(0*0) = 1, then we get a K_A = 1 for HCl, which will result in no end of trouble when you're back to dealing with liter solutions of HCl, as the true value is closer to 10 ^-7. -- 128.104.112.106 (talk) 22:31, 7 June 2009 (UTC)

Yes, sorry, my question really was... If we discover an acid that fully dissociates, what is its K_A value? (because you can't divide by zero) I guess you just don't give it one, or I am effectively asking what the K_A of a proton is. I completely agree on your final point that 1/0 doesn't = 1, or any x/0=x, it was the reason why I brought up equilibrium constants. --Mark PEA (talk) 23:09, 7 June 2009 (UTC)

I think you (Tango) must have meant gravitational singularity but you linked to the dab page by mistake. As a mathematician, do you also think that mathematicians speaking of a mathematical singularity is also to be interpreted as "haven't got a clue"? SpinningSpark 13:57, 6 June 2009 (UTC)

Not by mistake, just by laziness! In mathematics, singularities are well defined places where something goes wrong and are well understood. In physics, a singularity is somewhere where our mathematical model indicates there is a mathematical singularity, which generally means our model is flawed. --Tango (talk) 14:17, 6 June 2009 (UTC)

The mathspeak for "haven't a clue" is indeterminate. Dmcq (talk) 14:36, 6 June 2009 (UTC)

Not really, an indeterminate isn't something we don't know the value of, it's something that doesn't have a well defined value. I think "conjecture" would be the closest mathematicians have (basically it means "guess"). --Tango (talk) 15:07, 6 June 2009 (UTC)

See also independence (mathematical logic). A conjecture at least might be provable from existing axioms if someone clever enough comes along. Something independent can't be proved without new axioms. The continuum hypothesis was a conjecture for a long time, but proved independent in the 1960's, putting it closer to "haven't a clue" (or maybe "meaningless") territory. 67.122.209.126 (talk) 18:12, 6 June 2009 (UTC)

Something which has been proven independent of an axiom system isn't something we don't know about. We know everything there is know, the result is just neither "true" or "false". I think conjecture is the better analogy. Conjectures could, in time, but proven or disproven (or proven independent), just as gaps in scientific theories could, in time, be filled. --Tango (talk) 18:29, 6 June 2009 (UTC)

I was thinking of imdeterminate as in indeterminate form. the limit of x/sin(x) as x goes to zero gives the indeterminate form 0/0. In this case one can find the value 1 by other means but anything is possible. But yes conjecture is very good. And independent and undecidable and uncomputable and incomplete too... I think maths is well on the way in developing a theory of types of "haven't the foggiest". Soon we'll have terms like meta-controversial for instance and know exactly what they mean. :) Dmcq (talk) 20:12, 6 June 2009 (UTC)

0/0 is indeterminate, which doesn't mean we don't know what it equals, it means it doesn't equal anything. $\lim _{x\to 0}{\frac {x}{\sin(x)}}$ isn't indeterminate, it is simply "1". If you solve it and get an indeterminate form as the answer that just means you've done it wrong and need to find a method which actually works. --Tango (talk) 20:16, 6 June 2009 (UTC)

Pssst, you mean as it goes to 0. Dragons flight (talk) 20:52, 6 June 2009 (UTC)

I was just testing to see if you were paying attention! (Fixed now.) --Tango (talk) 21:08, 6 June 2009 (UTC)

Electrical arc

Is an Electric arc related to electrical ionisation as described here [21]. Thank you. Clover345 (talk) 17:16, 6 June 2009 (UTC)

Yes. --Dr Dima (talk) 21:17, 6 June 2009 (UTC)

Unknown garden plants for identification

Can anyone help me identify these please, all found in an english garden? This rather elegant garden plant http://i599.photobucket.com/albums/tt74/liverpoollarry/unknownplant1.jpg also had a more or less flat group of flowers above the frame. Photo taken a few weeks ago.

The small plant above the ruler in this scan http://i599.photobucket.com/albums/tt74/liverpoollarry/unknownplants2.jpg is part of a rockery-type plant, probably perennial, that I saw growing in low spreading mats with numerous flowers, and also growing out of cracks in the side of walls. When fresh the ends of the petals on the flower bend out more. It may be a Camanula or Bellflower, but they differ considerably in appearance and I want to try to identify its species or variety.

The plant beneath the ruler may be just a weed - but lots of them have suddenly appeared grouped together. Thanks. 84.13.50.195 (talk) 18:32, 6 June 2009 (UTC)

The first plant is an Aquilegia. --TammyMoet (talk) 19:38, 6 June 2009 (UTC)

The second plants: Campanula is latin for Bellflower. I'd say it's one of the Campanula family. The plant below the ruler is one of the Vetches, hard to say which - could be a Black Medick or a Hop Trefoil. It's a weed! --TammyMoet (talk) 19:43, 6 June 2009 (UTC)

Thanks. After searching around some more I think the middle one is probably Campanula portenschlagiana, variety Hoffman’s Blue, common name Dalmation bellflower. The final one seems to be, as you say, Hop Trefoil, Trifolium campestre. 78.149.117.117 (talk) 20:06, 6 June 2009 (UTC)

what kinds of companies use corporate astrologers?

Googling "corporate astrologer" (in quotes) shows some 22,000 results. So my question is about what kinds of companies use these servicse? Do any very large companies (market cap in the billions) use services like this? 94.27.141.190 (talk) 18:50, 6 June 2009 (UTC)

If they do, I doubt they would admit to it! --Tango (talk) 18:59, 6 June 2009 (UTC)

While only superficially comparable with astrology the article on Feng_shui cites sources that mention Donald Trump, Walt Disney, Singapore Polytechnic and the New York College of Health Professions inter alia as taking the subject seriously. Cuddlyable3 (talk) 19:06, 6 June 2009 (UTC)

Feng shui — as a decorating style — will generally produce an appealing aesthetic though, so even if you don't care for the mystical underpinnings, you might still choose to consult a feng shui designer. Dragons flight (talk) 19:59, 6 June 2009 (UTC)

I'm kind of skeptical about this, if only because if you ask ten feng shui "experts", you're likely to get ten different aesthetics. (Bullshit!, as I recall, demonstrated this rather well.) I'd say the appeal of the final aesthetic depends more on the decoration sense of the individuals in question than the principles of feng shui. -- Captain Disdain (talk) 07:34, 7 June 2009 (UTC)

This is more trivia than an answer to this question, but I'm sure I read somewhere about Microsoft and Apple competing in who had "the best" corporate astrologer. Tbh I think its no more than a psycological effect, but no one asked for my opinion.Alaphent (talk) 19:50, 6 June 2009 (UTC)

Microsoft and Apple! Couldn't have asked for a better response. Cite, please! 94.27.141.190 (talk) 19:52, 6 June 2009 (UTC)

Like I say, trivia only. It was read in on an online economics magazine, I've forgotten which, but it may have even been tongue in cheek. Sorry.... Alaphent (talk) 20:53, 6 June 2009 (UTC)

My guess is that only companies that sell horoscopes, or have some motive for promoting astrology, would pay for astrology services, since there's no credible scientific basis for the "predictive" results generated. Perhaps it's useful public relations in some segments, but that's marketing and not Science. --Scray (talk) 20:58, 6 June 2009 (UTC)

It is always good to cite sources on the refdesk. The above answer thinks too highly of people using logic, as can be illustrated by feng shui and Nancy Reagan#Influence in the White House. I have no sources to cite on corporate astrologers, but I am not going to sit and speculate on the refdesk that corporations make decisions based on "Science". Tempshill (talk) 23:44, 6 June 2009 (UTC)

There's also a huge gap between corporate decisions and individual decisions made by people on corporate boards. It's possible that someone is able to make his/her way into a position of power and decision-making - such as a CEO or president - and once there, make decisions based on astrology or coin-toss or any other technique. However, I suspect that such decisions would be worse than informed, scientific decisions, and would thus yield in undesired results. The corporation would quickly decide to remove such an individual, who is free to believe what they want as long as they don't do it with shareholders' money. Nimur (talk) 04:46, 7 June 2009 (UTC)

I notice that all the corporate astrologers on the first page are based in India. This seems excessive, even considering the possibility that India is renowned in corporate circles the world over for producing the best astrologers. So perhaps the answer is Indian ones. 81.131.14.50 (talk) 00:03, 7 June 2009 (UTC)

I'm from India, and yes, you'll stumble upon an astrologer here whenever you trip. But most of these men like to advertise themselves as corporate astrologers. True, no company is started here without a bhoomi pooja under some astrologers and swamis, and yes, there are a couple of high profile people who give their ""expert guidance" to companies for large sums, but nevertheless, you don't see many companies recruiting astrologers for their services. Say if they're going to start a new business, they might consult a family astrologer, or when they are about to open a new building, they might ask when is the "good time". But i'm very doubtful about corporate astrologers. Rkr1991 (talk) 04:02, 7 June 2009 (UTC)

The Mouse vs. Elephant Effect

I was watching a nature show, and a cheetah cub—the fearsome little devil—made a playful charge at a herd of wildebeest—which resulted in all of these 300+ pound animals fitted with horns making a run for it. I see this kind of embarrassing herd behavior all the time on nature shows. Obviously in some instances herd behavior has evolutionary advantages. But, when legions of gargantuan animals flee from some dogs—is this an example of a maladaptive behavior resulting from individuals evolving at the cost of the herd? i.e. it seems like it would make more sense for the prey to band together and confront the outmatched predator.

Alfonse Stompanato (talk) 21:54, 6 June 2009 (UTC)

Running away is generally the best way to avoid coming off worse in a fight. Is there any real disadvantage to running away? --Tango (talk) 22:03, 6 June 2009 (UTC)

Yes, there is, but it's a small disadvantage really. You can't feed when you are running away, and you spend some energy on running away, too. You are right, it is still much better than to risk injury or death. That is actually the reason why mammalian sensory system is "tuned" to make much more False Positives than False Negatives on identification of predators or of threats in general. If you make a False Positive, you stop grazing for five minutes, and then resume. If you make a False Negative, your brain stem is in someone else's stomach. --Dr Dima (talk) 22:36, 6 June 2009 (UTC)

But wouldn't a cooperative defense be so effective as to both conserve energy and prevent one of the herd from being picked off? The herd runs—and the young ones get taken out. I have actually seen some footage of aggressive behavior coming from water buffalo—they encircled their young, stood their ground, and actually gored some lion cubs that the pride hid in the tall grass (the herd stumbled upon the pride in this case). But, I guess my problem is that flight seems over represented in situations where the prey is greater than the predator in both size and number. Alfonse Stompanato (talk) 01:01, 7 June 2009 (UTC)

Yes Alfonse, you are right. Cooperation works better than "every one save yourself", but cooperation requires coordenated actions which require comunication. That's alot to ask from volution. Meanwhile the one wilderbeast that thinks twice before running is the one that ends up eaten. Just because a behaviour is more eficient doesn't mean that evolution will find its way there. Nevertheless some species do evolve cooperation as a defense. Dauto (talk) 03:36, 7 June 2009 (UTC)

It is faster to run, without thinking, than to take the time necessary to evaluate the situation, and perhaps conclude that flight is not necessary. There also may be advantages to running, such as exercise, and being physically prepared for the next time -- when flight may actually be very necessary. Also, the animals fleeing may be doing more than meets the eye. It may be akin to a training exercise, in which they practice their scattering techniques, and develop group dynamics that will be protective of the youngest or even the weakest. Bus stop (talk) 03:47, 7 June 2009 (UTC)

I'm pretty sure cheetahs raise their young as with most mammals. I'm guessing then if there was a cheetah cub, there would normally be cheetah parent/s close by. I don't know the details of what you were watching, perhaps the cheetah cub was being raised by humans or whatever but clearly it's unresonable to expect wildebeast to be able to appreciate such differences when such a thing is extremely abnormal. In other words, while it may seem odd for wildebeast to run away from a cheetah cub because of the risks from the cub, running away from a cheetah cub because cheetah cub usually means cheetah parent/s are close by makes far more sense Nil Einne (talk) 07:24, 7 June 2009 (UTC)

The cheetah can outrun the wildebeest but must select a young or ill animal for attack and is quickly exhausted. The defensive strategy of the wildebeest includes stampeding as a herd. This puts a predator in danger of being trampled and keeps young animals inaccessible, and it is a well adapted behaviour. It makes better sense than banding together against predator(s) that could then gather and harry the herd indefinitely. What the OP calls a playful charge by a cheetah cub is a serious activity by which it learns how to get close to a herd and how the herd reacts when spooked. A cub is likely to get closer to the herd than an adult so the alarm to the herd is correspondingly greater. BTW Mice do not prey on elephants and a mouse vs. elephant effect is unsourced. Cuddlyable3 (talk) 09:17, 7 June 2009 (UTC)

It's a matter of evolution: Suppose you are one of the Wildebeast - and suppose that the herd's instinctive strategy is to stand their ground and try to defeat the cheetah. By standing your ground - you run a small risk that the cheetah will kill you before the rest of the herd manage to bring it down. So a slightly better strategy for you, personally - would be to run away while the rest of the herd deals with the cheetah. This produces a small evolutionary benefit for those who possess the "run away" gene. Over hundreds or thousands of generations, evolution would ensure that sooner or later, the gene for the instinct to stand-your-ground would be out-evolved by the gene for running-away. Hence, Wildebeast evolve to run away. More notably, consider the opposite position: Suppose the whole herd has the gene for running-away (as real Wildebeast do)...what happens to the individual who gets the mutated "stand-your-ground" gene? Sadly, he dies the very first time a cheetah feels hungry. There is no way for that gene to get passed on. SteveBaker (talk) 01:26, 8 June 2009 (UTC)

See African Buffalo for an example of an animal that (sometimes) doesn't run. They aren't built for speed as wildebeest are. You can now argue whether wildebeest evolved to outrun cheetah or whether they survived because they could outrun them. Animals that flee from predators in a herd or flock have a higher survival rate than those that don't all act together, because most predators track motion and when there's too much going on they can get confused and become unable to track one individual. (Imagine you're in a crowd of waiters carrying trays of food and just when you've made up your mind to try some chocolate cake there's a juicy steak coming past. :-) Deciding "why" in animal behavior can usually be argued with some clever reason, but the likelihood of that being the actual cause is rather dubious. 71.236.26.74 (talk) 14:27, 8 June 2009 (UTC)

what would convince you of my ability to remote view?

I'm reading this article on "remote viewing" and I just wonder based on it why research universities the world over didn't either refute or verify the "paranormal" effect beyond a shadow of a doubt as soon as they learned Stanford was doing it? It is so easy to verify, isn't it? I mean, what would convince you of my ability to remote view? Isn't it enough if we pick a dictionary of ten thousand objects that are easy to draw (different colors, etc, to bring it up to 10k), you roll some dice and draw the one that comes up, while I tune into what you're drawing from thousands of miles away? I should get it right one time in ten thousand, getting it right 20% of the time should cinch the thing, shouldn't it? If not, what would convince you of my ability to remote view? —Preceding unsigned comment added by 94.27.141.190 (talk) 22:54, 6 June 2009 (UTC)

"Research universities" typically have serious research to do. But the James Randi Educational Foundation has debunked claims of PSI powers for ages - in fact, they will pay you ONE MILLION DOLLAR if you can prove, under reasonable experimental conditions, that you have any kind of paranormal abilities. --Stephan Schulz (talk) 23:06, 6 June 2009 (UTC)

Stanford is a very serious research University! My quesiton is why don't Princeton, Harvard, Yale, MIT, Columbia, and Brown -- the other research Universities of the same calibre...there aren't that many of them! -- try to either definitively verify or refute the claims?

Sometimes they do. There isn't much point, though. The people making the claims never accept the results and people that would accept the results don't believe the claims in the first place. Unless there is some evidence to support the claims, there is no reason to refute them - you can't spend limited research funding refuting every random thing somebody claims. There have been studies done on various types of ESP, etc., and the results have always been the same. There is no reason to suspect the results of a new study would be any different and there are better things to spend the time and money on. --

Tango (talk) 01:12, 7 June 2009 (UTC) The onus is on the OP to define in advance what remote viewing ability s/he claims to have. After that we would need to agree on a test that A) the parties are willing and able (practically and economically) to carry out, B) can give a result with high statistical confidence and C) includes precautions to eliminate unintended influences. "Beyond a shadow of a doubt" is a subjective not an objective measure, and it may reflect ignorance as readily as evidence. If I roll ordinary 6-sided dice the OP should be able to guess the result 16-2/3% of the time. Getting that right 20% of the time doesn't cinch anything. Cuddlyable3 (talk) 08:36, 7 June 2009 (UTC)

What am I currently consuming? I'll give you a hint: it's not a crustacean. -- Consumed Crustacean (talk) 23:11, 6 June 2009 (UTC)

Very funny. I'm no medium. 94.27.141.190 (talk) 23:54, 6 June 2009 (UTC)

By the way if I told you "a starbucks coffee" with lots of whipped cream and chocolate shavings and other assorted crap, and it turned out to be wrong, that would not be very good evidence that against "remote viewing". I want to know why research universities don't refute or verify the claims of Stanford (isn't it an ivy leage school?) in a scientifically conclusive way? —Preceding unsigned comment added by 94.27.141.190 (talk) 23:57, 6 June 2009 (UTC)

Actually, we're quite proud of the fact that Stanford is NOT an Ivy League school. We're a bunch of west-coast types - we're much too scruffy to fit in at a place like Harvard. (I have personally been told that I was not permitted to enter the Harvard library!) Though we don't have four hundred years of legacy, our fine institution is perfectly content to have a particle accelerator, a functioning radar telescope, and a Republican Think Tank six blocks away from an enchanted broccoli forest commune. Take that, east-coast intellectual types! And yes, it is very important to point out that our sister institution, SRI International, was responsible for the research into parapsychology; this research took place after the two institutions diverged. Nimur (talk) 01:11, 7 June 2009 (UTC)

The assertion that it hasn't been refuted is most likely wrong. This kind of crap has been proven to be exactly that over and over again, and yet people either come up with excuses that conveniently explain why it didn't work or simply ignore it. I mean, take homeopathy, for example -- there's no shortage of research that clearly shows it doesn't work, but that doesn't keep people from insisting that it does. The problem here is that people who want to believe in this kind of stuff really aren't swayed by reasonable arguments or scientific proof. One reason why universities don't waste time on researching this stuff is that there's no reason to assume it works, and plenty of evidence to indicate that it doesn't. If a really, really convincing remote viewer suddenly popped up, I'm sure that would be a different story. As it is, though, most scientists prefer to work on things that aren't completely ridiculous. (Or which, at least, are of interest to them, which may not be the same thing...) -- Captain Disdain (talk) 00:23, 7 June 2009 (UTC)

Stanford Research Institute is not Stanford University It is an independent research group. As for the 1970's work on ESP, methodological failures can produce amazing results. There is a long and well documented history of poor methodology at various labs producing amazing ESP results. The article SRI International says "A lengthy exchange ensued, with the external researchers finally concluding that the failure of Puthoff and Targ to address their concerns meant that the claim of remote viewing "can no longer be regarded as falling within the scientific domain." Edison (talk) 01:02, 7 June 2009 (UTC)

Stargate Project appears to have some related information, too. Tempshill (talk) 01:04, 7 June 2009 (UTC)

Edison is right on on this. SRI is a well-known case of physicists being hood-winked, and is not really part of Stanford University. Randi got involved with SRI started appering to be taken in by people like Uri Geller if I recall. --98.217.14.211 (talk) 02:21, 7 June 2009 (UTC)

Here is their paper, Information transmission under conditions of sensory shielding, published in the journal Nature in 1974. Nimur (talk) 03:43, 7 June 2009 (UTC)

I can recall a story in Snake Oil Science about the SRI. The anecdote was something about how the fellow in charge of some line of research (on remote viewing IIRC) presented that he had higher-than-chance results. When pressed, he admitted that there were some trials that didn't have that result, but because the people involved must have been intentionally screwing up the test, he stashed the data away and didn't count it. -- Consumed Crustacean (talk) 04:28, 7 June 2009 (UTC)

In direct response to the original question, "what would convince...", I think the starting point is to define remote viewing. In the paper I linked above, it was not really clear what "counted" as a successful remote viewing. For example, although I'm located in California, I can close my eyes and visualize a major landmark, say Eiffel Tower, in my mind. I can describe a lot of things about it. Because I'm pretty good with time-zones, I can guess the time of day, and because I check the international weather forecasts reasonably often, I can even tell you what kind of day it is in Paris. Have I "remotely viewed" anything? What level of correct information is necessary to count as a remote view? What level of incorrect information is necessary to throw out the "viewing" as unsuccessful? What information is necessarily provided or withheld? If you can develop a systematic framework for these questions, then you can run a double-blind experiment to test whether or not you have satisfied those criteria. What is fundamentally the limiting case is that you will not succeed at any such experiment if the criteria are sufficiently well defined. That is why the 1974 Uri Gellar research is discredited. The experimenters jumped right in and started counting P-norms, decibels of EEG attenuation, and so forth - without even defining what counted as a successful "view"! They did go to great lengths to preclude the possibility of Mr. Gellar knowing what the drawing should have been. But they forgot to define a valid judging criteria for the post-experiment comparison. So, they ended up with a bunch of line drawings, and they had some that really do look stunningly similar to the "target" image - but they never really stated "how similar" is an acceptable drawing. Even worse are the "descriptions of remote places" trials. In these experiments, the subject describes a remote place. Later, judges decide if the description matched the remote place. But the judgement criteria is not spelled out in gory scientific detail. If these details were present and explained in the experimental setup, the experiments would be repeatable and could be subject to scientific testing. As they stand right now, the experiments are subjective and not scientific. Nimur (talk) 05:41, 7 June 2009 (UTC)

The onus is on the OP to define in advance what remote viewing ability s/he claims to have. After that we would need to agree on a test that A) the parties are willing and able (practically and economically) to carry out, B) can give a result with high statistical confidence and C) includes precautions to eliminate unintended influences. "Beyond a shadow of a doubt" is a subjective not an objective measure of confidence, and it may reflect ignorance as readily as evidence. If I roll ordinary 6-sided dice the OP should be able to guess the result 16-2/3% of the time. Getting that right 20% of the time doesn't cinch anything. Cuddlyable3 (talk) 08:36, 7 June 2009 (UTC)

There are several things that have to be nailed down - but I think the OP's original statement would work pretty well. We have two identical books of (say) one hundred very diverse pictures, which are numbered - we agree that someone a suitable distance away uses a random number generator to pick a picture from the book and at 12 noon, GMT concentrates on it or stares at it or whatever the remote viewer claims is necessary. Meanwhile, the viewer has been kept alone in a windowless room with a clock from before the time that the random numbers were generated until they asserts that they have 'picked up the image', sketched what they saw and (since interpretation of that image is iffy) - we'll stipulate that the viewer must then look through their copy of the book and nominate between one and three photos that match what they saw. Once they have listed between one and three numbers, these will be communicated to the experimenters and that round of the experiment is over. The experiment will be repeated ten times. The results are then assessed with standard statistical tools to determine the probability of this happening by chance - and only if the result is that there is a less than 0.1% percent chance of this happening by chance alone do we give this effect any credance. I'm pretty sure that if someone were to agree to terms like this then the Randi institute folks would be happy to test that person and award them a million dollars for passing the test. SteveBaker (talk) 17:40, 7 June 2009 (UTC)

Incidentally, that would require them to get at least 4 out of 10 correct (assuming I can do basic probability, which is a big assumption... it took me two attempts!). --Tango (talk) 18:26, 7 June 2009 (UTC)

Actually, I'm not much of a statistician, but I'm not sure one set of 10 would be enough (unless they are claiming 100% reliability, which they rarely do, they just claim to be better than random chance). I think you need to do several sets of 10 and then do some fancy statistical analysis. Do we have a statistician in the room? --Tango (talk) 18:30, 7 June 2009 (UTC)

Imagine if Maxwell's Equations only worked "better than random chance." You'd pick up your mobile telephone, and 3 out of 10 times, its batteries would undergo the statistical thermodynamic processes necessary for chemically induced voltage. Electrons would statistically drift down the conductors with a 1 in 5 outcome; and they would flow into a transistor amplifier and 1 out of 6 times, amplification would occur... more electrons would flow into an antenna and induce an electromagnetic perturbation on the surrounding air... depending on convection patterns, the air near the antenna would perturb the dielectric constant 1 in 2 times, allowing effective coupling between the antenna and the radio channel... oh wait, these things are already statistical. Using statistics is perfectly fine to describe physical laws, if there is a physical law to describe. We're able to build machines and cope with statistical chances because when we scale up the size, the law of large numbers kicks in and we have a nearly deterministic system. Scientists are perfectly happy to use statistics, but we don't like making crap up. That's why we don't believe in psychokinesis or remote viewing. Nimur (talk) 19:09, 7 June 2009 (UTC)

1 in 2 times allowing effective coupling between the antenna and the radio channel...:: You just described AT&T cell service! —Preceding unsigned comment added by 94.27.225.206 (talk) 20:48, 7 June 2009 (UTC)

June 7

bound photons

Spontaneous emission of bound photons from relativistic free electrons. What is a "bound photon"? Please provide an answer that can be understood by a biologist. --JWSchmidt (talk) 01:57, 7 June 2009 (UTC)

From a really quick glance at the referenced paper it looks like the "bound photon" is a photon in one of the cavity modes, that is, a photon emitted in a discrete rather than a continuous spectrum. Cavity modes must obey the boundary conditions imposed by the cavity walls, and therefore may not, generally speaking, have just any wavelength (and any energy), but only one of the discrete -- but infinite -- list of allowed wavelengths (and thus allowed energies). Generally, a particle is said to be bound when it cannot escape to infinity in any direction. An energy spectrum of such particle is discrete, at least as long as the potential it is bound in is not changing too fast or the lifetime of the particle is not too short. --Dr Dima (talk) 02:25, 7 June 2009 (UTC)

Thanks. Cavity quantum electrodynamics talks about cavity photons functioning as part of a quantum computer. Would such photons be "bound photons"? --JWSchmidt (talk) 02:45, 7 June 2009 (UTC)

Yes, I think they would be. --Dr Dima (talk) 03:56, 8 June 2009 (UTC)

Many-worlds Question

Is it possible that beings from another universe can come into ours and interact with us? Or if quantum immortality is true, then won't a person visit us, or has already visited us (even me personally)? —Preceding unsigned comment added by 66.66.149.43 (talk) 04:41, 7 June 2009 (UTC)

No. Nimur (talk) 05:00, 7 June 2009 (UTC)

There is nothing in physics which would prevent this from happening, because what you are describing is beyond the purview of physics (which only deals with our universe, even if other universes exist). It is on the same level as asking "is it possible that God exists?" Of course it's possible, but physics has nothing to say on the matter.-RunningOnBrains^{(talk page)} 05:07, 7 June 2009 (UTC)

Mind me asking what the heck is quntum imortality? Dauto (talk) 06:19, 7 June 2009 (UTC)

Why not read our article Quantum immortality? Nil Einne (talk) 08:36, 7 June 2009 (UTC)

"Quantum immortality" is an incorrect and backwards reading of the anthropic principle. Its premise is something like this - "if a being is conscious, then all previous incidents which might have rendered it no longer conscious did not occur." For some reason, which is the really illogical part, it then concludes, "no future event will occur that will render this being unconscious (dead)." Somehow, this is linked into the idea of a quantum non-deterministic universe, by way of superposition of all possible outcomes of every possible event - and self-selection (by anthropic principle) of only those events which maintain the being as conscious (living). This doesn't really have anything to do with "quantum" anything. I'm not even really sure why this theory gets propagated - it's sort of a half-baked, nonsensical idea. But, like perpetual motion, immortality seems to spark some kind of fury in non-scientists, who hope to cherry-pick the parts of science that will somehow support their wishful thinking. Nimur (talk) 14:41, 7 June 2009 (UTC)

I think you are the one misreading it. The theory is more like: If the "many worlds" interpretation of quantum mechanics is true - then every quantum-mechanical event that can turn out in more than one way results in multiple universes in each of which the event happens differently. Since all events are ultimately quantum mechanical in nature - there is a universe in which you personally died because you were killed in a car wreck that you narrowly avoided in this universe. There is another in which you died due to a childhood disease. There are in fact an infinite number of universes in which every possible fate that could befall you has indeed befallen you.

Now - marry that (highly theoretical, and possibly dubious) hypothesis with the "anthropic principle". The 'strong' anthropic principle says that the universe is conducive to your existance BECAUSE if it was not, you would not be here to observe it. So, (for instance) it has been remarked that if the earth did not have a large moon - or if the charge on the electron differed by 1% or if water didn't expand a little as it froze - then life on Earth would be impossible. Why are we so amazingly lucky in all these respects? Well, the anthropic principle points out that in all existances in which there is intelligent life that is able to observe these conditions - the conditions must be conducive to that life.

OK - so put the many worlds and anthropic principles together - and you say that since (by definition) the only universes in this infinite number of universes in which you are able to note that you are still alive are the ones where you happened (by sheer chance) to have had all of the prior quantum events come out in favor of you living. Taken to an extreme - you cannot die because there will always be a universe in which by an AMAZING sequence of lucky breaks and one in a quadrillion chances - you happen to survive. Hence, you PERSONALLY will be immortal - although those around you will not (although they'll all be immortal in some other universe).

However, those who think this is "wishful thinking" need to carefully consider what this really implies. Suppose you are really sick - something painful and incurable. With this combination of hypotheses, you can't die. No matter what - you'll be in a universe where (though in continuous and nearly unbearable pain) - you can't commit suicide. You put a gun to your head and pull the trigger to try to end your misery...the gun will jam - or a freak gust of wind will blow the gun out of your hand. No matter what you do, there is no way out. Given you'll live forever - it's certain that you'll lose limbs, become blind and deaf - be in continuous anguish...for all eternity. If ever there was something close to old-testament hell - then Quantum Immortality is it.

(Going off-topic here.) Steve, I thought you said you worked your way through the whole Bible once? Where exactly did you find this "old-testament Hell"? There are a few lines in the Book of Daniel, but other than that Hell seems to be almost entirely a new-testament concept, as far as I can tell. The OT God might have done a bit of smiting, but once the smitten were dead, the narrative appeared to stop. --Trovatore (talk) 21:11, 7 June 2009 (UTC)

I sure hope there is an error in the theory somewhere!

SteveBaker (talk) 17:10, 7 June 2009 (UTC)

Also, not every divergence into "many worlds" will result in an explicit separation between "living" and "dead" - there are hundreds of trillions of quantum "decision points" which occur all the time, and most of them have no impact on whether or not you will be conscious and alive at the next "time step." (Think about every photon of sunlight colliding with every molecule of nitrogen on its way down to earth - most of the time, whichever way the stuff scatters out, you live anyway). But, the many-worlds interpretation suggests that the universe necessarily schisms at each of those. So, there should be exponentially increasing numbers of universes, most of them pretty similar, with an exponentially schisming "thread" of consciousness. Which one is the "real" you? This whole infinite-universe-schisming methodology is sort of silly, especially since it yields absolutely nothing predictive or otherwise scientifically helpful in understanding our universe. Nimur (talk) 18:30, 7 June 2009 (UTC)

And it also does not follow from logic or basic understanding of quantum mechanics. Quantum mechanics describes statistical probabilities for certain state transitions, rather than deterministic behavior. However, the common interpretation that there is a "small but nonzero chance" that anything can happen is simply incorrect. There is a probability density function for any physical observable, and that probability can and is often zero for certain outcomes. So, "immortality" implies that at no time will you ever encounter any situation which has a "dead-end" on the constantly schisming set of outcomes - which is sort of silly also, given that we observe living creatures dying all the time. Changing the quantum state of a bunch of atoms must still follow rules. Nimur (talk) 18:36, 7 June 2009 (UTC)

I think you really need to start by defining "universe". I would (roughly) define "universe" to mean a collection of causally connected things (you may not have everything causally connected to everything else, but there needs to be at least a connection via other things). By that definition, any being that can enter our universe is part of our universe. So, by definition, the answer to your question is "no". --Tango (talk) 16:17, 7 June 2009 (UTC)

Thanks for the explanations. I can't help but think that calling that wishful thinking is too generous. Hogwash comes to my mind. Dauto (talk) 22:29, 7 June 2009 (UTC)

OK, great points all around first of all. To me, quantum immortality makes sense. But because I can personally theoretically live forever, then that means that everything works like that, right? Since everything is made up of quantum particles then everything should have "quantum immortality" in the sense that anything can happen to it, it's just that in this universe we're observing it doesn't. But wouldn't it follow that if anything is possible then wouldn't someone from another universe be able to travel to this universe and say "hey! I'm from another universe!"? Because it's a possibility. So if the theory is true, then how come this hasn't happened OR is it completely probable that it can happen, it just hasn't happened yet? —Preceding unsigned comment added by 66.66.149.43 (talk) 00:22, 8 June 2009 (UTC)

A possible answer is that it is physically impossible to travel between universes. Everything which can physically happen, in some universe somewhere, does; but not anything else. A more gratifying answer is that it is physically impossible unless a time machine exists at the destination. (That is to say an inter-universe travel machine, universes and moments in time being the same thing.) 213.122.32.39 (talk) 03:52, 8 June 2009 (UTC)

Another thought which just occurred to me is that the emergence of a traveler into just one universe, and not any of the very similar alternate versions of that universe, is by definition an extremely unlikely event. ("The same across universes" is the definition of likely.) So if time machines have perfect accuracy, then you'd pretty much never see anybody arrive, just because of probability. Then again I suppose you have to multiply that tiny probability by the number of possible visitors, which is very large since it includes everybody in all possible futures (even though most of them wouldn't want to come here), so in conclusion, meh. 213.122.32.39 (talk) 04:22, 8 June 2009 (UTC)

Speeding up formal education

What research has been done into increasing the rate at which students can complete their formal education (e.g. decreasing sleep and leisure requirements to allow a greater course load, increasing retention from lectures, increasing comprehension-adjusted reading speed, increasing learning ROI on practical exercises)? Is this likely to become more of a priority if the demand for highly skilled workers continues to increase? NeonMerlin 04:42, 7 June 2009 (UTC)

I think a lot of research has been done on time-to-productivity. In my fields, there is an always-raging debate between the need for advanced degrees versus simple bachelors' degrees - in other words, which is more productive, two years of on-the-job training, or two years of post-graduate study towards a Master's Degree ( ... or six years of post-graduate training for a Ph.D.)? There's a lot of academic debate about this as well. Most academic research into education is not about "speedup" as much as it is about improved retention and comprehension. There's a lot of research on "force-multipliers" - such as using technology to allow one teacher to impact more students. I think this is the most practical framework you will find for "speeding up" formal education. Also, the military has developed a huge body of rapid training - take a look at AKO or NKO. I hear that the language courses for many overseas deployments claim to teach "basic fluency" from zero prior knowledge in the span of six or eight weeks (though this may be a dubious claim). Nimur (talk) 04:59, 7 June 2009 (UTC)

Magnetic force based "black holes"

Is there a "Black hole" based on the force of magnetism rather than gravity? -- Taxa (talk) 04:58, 7 June 2009 (UTC)

No. Nimur (talk) 04:59, 7 June 2009 (UTC)

Black holes form by a runaway collapse of matter, i.e. increasing density causes further increase in density ad infinitum. Since there is no phenomenon in physics by which a magnetic field could intensify itself, a "magentic hole" is impossible. -RunningOnBrains^{(talk page)} 05:03, 7 June 2009 (UTC)

but the magnetic force is much stronger than the gravitational force (brian greene: "a puny magnet can pick up a paper clip, overcoming all of the massive Earth's gravity" [paraphrased]. In fact gravity is some e-42 as strong as magnetic force!).

So it is a valid question, could we collapse a black hole by magnetic compression? 79.122.74.190 (talk) 07:35, 7 June 2009 (UTC)

No, as Runningforbrains said, the issue is not the strength of the force, but the feedback loop that is set up. Gravity results in an increase in density, causing increase in gravity. There is no mechanism by which the magnetic force could alter its magnetic domain and cause an increase in force, without the external application of energy.YobMod 08:16, 7 June 2009 (UTC)

My question is whether a traditional, gravity-based black hole, could be created through the initial compression of the proper mass down to the proper size not due to Gravity, but through a magnetic force? The point is that without the magnetic compression, the mass would not be critical enough (small enough volume) to turn into a black hole, but with the magnetic compression, the mass becomes small enough to pass the critical point and become a blcak hole. Would this be possible? 79.122.44.114 (talk) 10:23, 7 June 2009 (UTC)

Sure. It doesn't matter how the necessary density is achieved, just that you get enough mass into a sufficiently small volume. Some physics models predict the possibility that we will even be able to create micro black holes using the Large Hadron Collider. (In the LHC, very large amounts of energy – effectively mass, by E=mc² – get packed into a very tiny space when highly energetic particles collide. There's an outside chance that sufficient density can be achieved to make tiny, temporary black holes in this way.) TenOfAllTrades(talk) 15:38, 7 June 2009 (UTC)

Why would the black holes from the LHC be temporary? Once they are formed, doesn't anything that come within their event horizon just increase their mass (remaining in a point volume), making them ever bigger and bigger black holes? If not, then what's to stop whatever process would end these black holes from ending (on a larger scale) normal black holes? Thanks! 94.27.225.206 (talk) 15:53, 7 June 2009 (UTC)

See Hawking radiation. In theory, the smaller the black hole, the shorter its lifespan. A black hole created by the LHC would likely evaporate before it even gobbled up a single atom. This is why actual physicists are not concerned by the possibility of mini-black holes, even if a few botanists and biochemists are. -RunningOnBrains^{(talk page)} 16:29, 7 June 2009 (UTC)

The magnetic force is not stronger than the gravitational force. They have different units. It's like saying a pound is heavier than a foot is long. The closest you could get is using Planck units, in which case the gravity and the electromagnetic force both have a strength of one. — DanielLC 15:29, 7 June 2009 (UTC)

Daniel, you should be more careful with what you say. I can't think of a single way in which your statement that the electromagnetic force may have a strength of one would make any sense. The most natural way to measure the strength of the electromagnetic force is through its coupling constant which is adimensional. Dauto (talk) 17:53, 7 June 2009 (UTC)

Muscles + Oxygen = Energy

Would any of you know of an exercise or a few types of exercises to make your muscles require less oxygen?

Sleep. Cuddlyable3 (talk) 09:58, 7 June 2009 (UTC)

I don't think there's anything that makes them require less oxygen, but I know anaerobic exercise makes it so you can get oxygen there faster. — DanielLC 15:24, 7 June 2009 (UTC)

Intelligence as absence of stupidity

It is often said that "intelligence has its limits, but stupidity knows no bounds." This suggests that intelligence is merely the absence of stupidity, just as cold and darkness are the absence of light and heat (hence there is a minimum possible temperature but no maximum possible temperature), and that as a perfect vacuum would be perfectly dark, so too would it be perfectly intelligent. Is there a theoretical elementary particle that carries stupidity? Is it possible that some or all Standard Model particles carry it? NeonMerlin 07:07, 7 June 2009 (UTC)

Um what? Particles carrying stupidity??? Intelligence is present in a vacuum??? How do you even define intelligence and stupidity let alone carry them in particles or observe them in vacuum? I think your confusing a cute, quaint or fun comment with some sort of deep scientific statement. I doubt even many philosophers will make such a suggestion Nil Einne (talk) 07:14, 7 June 2009 (UTC)

It's also said, among other things, that a stich in time saves nine, but to hear that and start wondering what kind of a garment the stitches are on is to miss the point of the proverb. These aren't some kind of universal and literal hard facts, you know. -- Captain Disdain (talk) 07:28, 7 June 2009 (UTC)

Sayings do hold deep truths but may have to be slightly adjusted to be exactly right. For instance one can't have one's cake and eat it, unless one does them in that order (and I'm not going to think of the other alternative). A bird in the hand is worth two in the bush, unless you're talking about women. If pigs could fly a lot of biology and physics would have to be rethought but I'm sure we'll manage it one day with genetic engineering. I think in this case the saying is referring to the fact that for instance an intelligent person would say something intelligent and then stop whereas an idiot could go on wittering for ever. And furthermore.... :) Dmcq (talk) 07:49, 7 June 2009 (UTC)

It simply means that stupidity is not a conserved quantity. SpinningSpark 09:26, 7 June 2009 (UTC)

Intelligence is an attribute that can be defined and tested in various ways. There is no consensus on its limits. The word stupidity is not as suggested the opposite of intelligence but a disparaging term for negligent thinking. Persons that have high intelligence by some criteria, e.g. IQ score, are not immune to stupid actions. The OP offers hypotheses about a particle nature of stupidity that fail the scientific method because they lack falsifiability or a useful prediction. Cuddlyable3 (talk) 09:53, 7 June 2009 (UTC)

I'm sure I saw an advertisement that said there was a clever-dumb balance so it must be a conserved quantity. Advertisements are covered by the advertising standards agency and must be truthful. Dmcq (talk) 14:23, 7 June 2009 (UTC)

I presume you are referring to the toothless Advertising Standards Authority (United Kingdom) created by the advertising industry themselves whose idea of "self-regulation" is the occasional meaningless ticking off. If you believe anything they say . . . Stupidity behaves rather more like the (unconserved) entropy equation;

$\Delta S=\int {\frac {-dQ}{T}}$

Where Q is intelligent actions and T is the "intelligence temperature" - average intelligence per individual. SpinningSpark 13:18, 8 June 2009 (UTC)

Does anyone else see how ironic this question is? --Shaggorama (talk) 22:52, 7 June 2009 (UTC)

Heat death, temperature and entropy

The article about Heat death says "The heat death is a possible final state of the universe", and that is a state in which "it has reached maximum entropy" and 'In a "heat death", the temperature of the entire universe would be very close to absolute zero'. The article about entropy says "When heat is added to a system at high temperature, the increase in entropy is small. When heat is added to a system at low temperature, the increase in entropy is great". So In heat death, the entropy becomes maximum and temperature is the lowest, but if heat is added to a system (I think that means a rise in temperature), the entropy increases. Then what is the high entropy in the heat death comprised of? I have been guessing that high entropy usually means high temperture. Like sushi (talk) 10:37, 7 June 2009 (UTC)

You can think of it this way: when you transfer some heat from a high-temperature system to a low-temperature system, the high-temperature system loses a relatively small amount of entropy while the low-temperature system gains a relatively large amount, so overall entropy increases. The entropy is (locally) maximum when the temperatures are equal. Adding heat would increase the entropy, but the heat has to come from somewhere (first law). If the whole universe is at the same temperature then the loss in entropy where the heat was removed would exceed the gain in entropy where it was added, which is forbidden by the second law. -- BenRG (talk) 14:20, 7 June 2009 (UTC)

Wet matches

I left a box of matches outside last night and they got soaked in the rain. When I try to strike them, the head of the match just crumbles into a wet mush. If I leave them and the box out in the sun today, might they dry out and be useable again? Frank Bruno's Laugh (talk) 11:18, 7 June 2009 (UTC)

Sure, why not. Try it and let us know tomorrow. Avoid the temptation of putting them in the oven on a low setting though (for obvious reasons!) 94.27.225.206 (talk) 12:41, 7 June 2009 (UTC)

Yep, that worked fine. The charcoal that go wet is still a bit mushy! :) I did consider putting the matches in the electric oven on a low setting (starting with one), thinking that it wouldn't have been hot enough to ignite them, but I guess that wouldn't have been a good idea? Might it work with the charcoal? Frank Bruno's Laugh (talk) 15:01, 7 June 2009 (UTC)

I'd be surprised if they still worked. In my experience regular matches don't have a lot of tolerance for weird environments (and degrade rather quickly with age or humidity). That being said, matches are pretty cheap, so it's not exactly the end of the world. --98.217.14.211 (talk) 14:59, 7 June 2009 (UTC)

They actually seem in pretty good shape, so I guess I got lucky (they did get a real soaking) Frank Bruno's Laugh (talk) 15:05, 7 June 2009 (UTC)

If you're taking some matches somewhere they run the risk of getting wet (e.g. a camping trip), a tip I once read is to dip them in melted candle wax. I can't say I've ever tried it, and I imagine a cheap lighter would be a better bet. 87.81.230.195 (talk) 23:58, 7 June 2009 (UTC)

Yes, yes. Before use, just melt the wax off with a lighter. 79.122.119.18 (talk) 06:21, 8 June 2009 (UTC)

I see what you did there. Tempshill (talk) 17:41, 8 June 2009 (UTC)

I have dipped old-style kitchen matches (the old-fashioned strike-anywhere kind) into wax and that made them completely waterproof and they would still light just fine without having to melt the wax away or anything. I haven't tried it with safety matches. 207.241.239.70 (talk) 19:12, 8 June 2009 (UTC)

Human blood

What are the risks with drinking (fresh) human blood? Vimescarrot (talk) 14:01, 7 June 2009 (UTC)

Oh, and the possible (dietary) health benefits? Vimescarrot (talk) 14:07, 7 June 2009 (UTC)

Maybe I'm stating the obvious but a dietary benefit would be increased iron intake. I'm guessing that there are no immunoreactive issues as the antigens should be metabolized and/or not absorbed by the gastrointestinal tract. --Mark PEA (talk) 15:32, 7 June 2009 (UTC)

There are obvious risks of the transmission of disease. I think that's probably about it. You could overdose on iron (and maybe other constituents) if you drank too much of it, but that basic principle applies to anything. --Tango (talk) 16:35, 7 June 2009 (UTC)

There's also likely a risk of criminal charges, depending on who's blood it was and how you acquired it :-D -RunningOnBrains^{(talk page)} 17:03, 7 June 2009 (UTC)

You're not planning to eat your bone tumor, are you? Nimur (talk) 18:20, 7 June 2009 (UTC)

Sorry, but I must note that this line made me laugh for no less than 20 seconds. Tempshill (talk) 04:29, 8 June 2009 (UTC)

Bone tumours aren't made of blood. On a slightly related note...What about the, uhh...various components of what comes out of a female during menstruation? (I'm given to understand that it isn't just blood...) Is that any more risky? Also, what about eating a tumourous bone? That last one is just for laughs, really. The first one, I'm specifically thinking of oral sex. Vimescarrot (talk) 19:16, 7 June 2009 (UTC)

What are you, 12? Menstrual fluid doesn't get ingested during oral sex, mmmmkay? 94.27.225.206 (talk) 20:12, 7 June 2009 (UTC)

I see no reason why that isn't possible. Vimescarrot (talk) 20:33, 7 June 2009 (UTC)

If you give oral sex to a woman that is menstruating, I would expect some of the menstrual fluid to be ingested. --Tango (talk) 21:04, 7 June 2009 (UTC)

The amount would be so small though, would it really matter? —Preceding unsigned comment added by 82.43.88.87 (talk) 22:26, 7 June 2009 (UTC)

That's exactly what I'm asking. Vimescarrot (talk) 22:34, 7 June 2009 (UTC)

According to a (purportedly non-fiction) book I read some years ago, committing cunnilingus on a menstruating woman (with or without her consent) was an act for which US Hell's Angels could earn a Red Wings badge, or Black Wings if she were black. I mention this purely in the spirit of encyclopaedic completeness, not because I endorse the custom or attitudes involved in any way. 87.81.230.195 (talk) 23:55, 7 June 2009 (UTC)

This is a reference desk. Is it too much to ask for a few references, especially when dealing with matters of health? According to Aidsmap, a project of NAM (National AIDS Manual, UK registered charity, founded 1987):

The levels of HIV in vaginal fluid vary. They are likely to be highest around the time of menstruation (having your period), when HIV-bearing cells shed from the cervix are most likely to be found in vaginal fluid, along with blood. Oral sex will therefore be more risky around the time of menstruation. Factsheet here

According to The Body, a service of Body Health Resources Corporation:

It is important that you do not perform unprotected oral sex on a woman when she is menstruating (blood has a much higher concentration of HIV), and if you are experiencing any problems with your oral health (sores, abrasions, inflammation). If you would like to decrease the risk of transmission even further, you can use a latex barrier--like a dental dam or a condom cut into a square--between your partner's vagina and your mouth. Explanation here

Sources please! BrainyBabe (talk) 12:06, 8 June 2009 (UTC)

vampirism? —Preceding unsigned comment added by 82.43.88.87 (talk) 19:59, 7 June 2009 (UTC)

Not exactly human blood but animal blood (eg. pig blood) is a delicacy in Southern China; very smooth and tender, with a jello-like texture and a bit of iron after-taste. --antilived^{T | C | G} 23:06, 7 June 2009 (UTC)

I believe there is less risk from animal blood than human blood, since the diseases present in animal blood are less likely to be infectious to humans. --Tango (talk) 00:45, 8 June 2009 (UTC)

I seem to remember reading of a nomad culture where cattle are regularly bled for drinking; but maybe that was fictional. —Tamfang (talk) 04:43, 8 June 2009 (UTC)

The Maasai of East Africa certainly do that - they mix cow urine into a mixture of cow blood and milk to make it clot. According to our article, these days they only do this on ceremonial occasions or when someone is sick. When we lived in Kenya in the early 1970's, my parents bought a rather beautiful beaded gourd from a Maasai tribesman - sadly, they assumed it was a tourist trinket when in fact it was all-too authentic and still contained the guy's lunch! Despite a lot of cleaning, and soaking the insides with bleach, the...erm..."distinctive" odor of the thing never quite went away! SteveBaker (talk) 10:53, 8 June 2009 (UTC)

Well, since we are digressing, see Blood as food (alas, not a great article). Note that the consumption of raw duck and chicken blood in dishes that are delicacies in Vietnam is one of the few ways in which humans can catch so-called "bird flu" (H5N1) from birds, see BBC article. BrainyBabe (talk) 08:11, 8 June 2009 (UTC)

I believe there is less risk from animal blood than human blood, since the diseases present in animal blood are less likely to be infectious to humans. That is a rather risky belief given the number of counterexamples of diseases transferred from animals. BTW. Off hand I could probably come up with a shorter list that can not be transferred than ones that can. Just for tip of the iceberg examples see Rabies, Trichinella, Apicomplexa, vCJD, Cryptosporidiosis. Some of these get most commonly transferred by other means than consumption of blood, but that doesn't mean it can't be transmitted that way. Even intestinal parasites are often present in an infected individual's blood. Some allergologists think that humans need a certain exposure to parasites and infectious agents to prevent allergies. If only 1 in X gets infected it that figure won't make you happy if you turn out to be the one. 71.236.26.74 (talk) 15:59, 8 June 2009 (UTC)

See selection bias. Most diseases cannot be transferred from one species to another. The only animal diseases you have probably heard of (unless you are a vet) are ones that can be transferred to humans since those are the ones that make the news (or ones your pets have caught, I suppose). There is certainly some risk, but it is far lower than the risk of drinking human blood. Pretty much any human disease can be transferred by drinking human blood (the risk is rather low for some since stomach acid, etc., are quite good at killing ingested contagions, but there is still a significant risk). --Tango (talk) 16:54, 8 June 2009 (UTC)

We have an article, Zoonosis, but it doesn't seem to make comparisons to human-to-human infections. --Tango (talk) 16:58, 8 June 2009 (UTC)

Interesting discussion is interesting! I love digression - it's a great way to learn. Vimescarrot (talk) 17:14, 8 June 2009 (UTC)

Surgical memento

If surgeons are removing something from you, are you allowed to keep it? Vimescarrot (talk) 14:03, 7 June 2009 (UTC)

Let me guess. No? Bus stop (talk) 14:06, 7 June 2009 (UTC)

Why not? And if that's a guess, why would you think that? Vimescarrot (talk) 14:08, 7 June 2009 (UTC)

I don't know. I'm just joking. I really don't know. But since intuitively I would assume one should have the right to take possession of a part of one's body that has been surgically removed from one's body, it probably is the case that it is the opposite. There is probably some reason why removed body parts become the property of the medical facility in which the surgery took place. But I really don't know. Bus stop (talk) 14:51, 7 June 2009 (UTC)

Human tissue is generally classified as biohazardous material, and has to be properly disposed of in a high temperature medical incinerator. So the hospital isn't allowed just to give you a decaying necrotic kidney home in a plastic bag. They'll give you an inanimate calculus like a gallstone, because there's no risk of disease. In theory they could preserve stuff in formaldehyde, but there are considerable additional compliance costs to do with human anatomy regulations and biomedical waste; it's not the hospital's core business, so they're unlikely to want to do all that stuff. Hopper Mine (talk) 15:45, 7 June 2009 (UTC)

Is bone an "inanimate calculus"? Vimescarrot (talk) 15:57, 7 June 2009 (UTC)

Very much not; it's a complex matrix full of living cells (it couldn't very well get cancer if it was inanimate). It is possible for a lab to sterilise bone (this is done to cadaverous bone allowing it to be safe for transplant), leaving only the inorganic hydroxylapatite matrix, but this is an involved and expensive process - it's not something they'd do for souvenirs. Hopper Mine (talk) 17:57, 7 June 2009 (UTC)

I guess it depends on what they are removing. My friend kept his gall bladder stones, but some things might be toxic?91.111.74.247 (talk) 14:55, 7 June 2009 (UTC)

A bone tumour. Vimescarrot (talk) 15:01, 7 June 2009 (UTC)

note that this is by the OP. So, OP, why would you want to keep a bone tumor??? 94.27.225.206 (talk) 15:47, 7 June 2009 (UTC)

Well, why do people keep teeth? Vimescarrot (talk) 15:55, 7 June 2009 (UTC)

To get money from the tooth fairies, obviously. Now, everyone knows that the bone cancer fairies are just a myth. Frank Bruno's Laugh (talk) 18:51, 7 June 2009 (UTC)

Good thing I don't have bone cancer, then...Vimescarrot (talk) 19:13, 7 June 2009 (UTC)

This may be of some help to you. Frank Bruno's Laugh (talk) 15:10, 7 June 2009 (UTC)

Maybe the OP was talking about surgeons removing a foreign object. If it's not dangerous, I see no reason why you couldn't have it. Of course, if it was a bullet, knife, or some other weapon, they might be obliged by law to hand it over to the police for forensic investigation. Astronaut (talk) 17:35, 7 June 2009 (UTC)

-just re-read that ... a bone tumour? Are you serious? Astronaut (talk) 17:36, 7 June 2009 (UTC)

Why would I not be serious? Vimescarrot (talk) 17:47, 7 June 2009 (UTC)

A cancer is no more hazardous to others than regular tissue of the same type (barring use in transplants, obviously, and maybe cancers associated with viruses). It's just a minor programming error, not some primal nuncio of feculence; it's not contagious. That said, all living human tissue is thick with a wide range of pathogens, and it's all considered hazardous for good reason. Hopper Mine (talk) 18:05, 7 June 2009 (UTC)

If you're just thinking "ew gross", it's surprisingly common for people to feel sentimentally attached to what is, after all, part of themselves. This is true even for tumours; some people seem to think "that's the little bastard that caused me so much trouble", and want to keep it as a trophy. Hopper Mine (talk) 18:14, 7 June 2009 (UTC)

It sounds like Hopper and Frank answered my question, although if anyone disagree they're welcome to say so. Thanks. Vimescarrot (talk) 19:13, 7 June 2009 (UTC)

Famous persons could sell their excised body parts for considerable sums. These would pass from hand to hand as collector's items or investments. Soft tissue would be in a sealed glass tube. There would be a registry of ownership to ensure against fraud. If authenticity is still questioned, DNA tests could be made. – GlowWorm. —Preceding unsigned comment added by 98.21.108.254 (talk) 03:39, 8 June 2009 (UTC)

In some cases where something is removed the surgeon may actually be required by the insurance company to keep what was removed or even send it (preserved) to the insurance company as proof the surgery was actually conducted. I don't know how common that requirement is. Someguy1221 (talk) 03:47, 8 June 2009 (UTC)

— all due respect, but I think you must have just made that up. I imagine an insurance adjuster in his cubicle taking 50 FedEx shipments per day that are all dripping pus and blood. Tempshill (talk) 04:27, 8 June 2009 (UTC)

Just last week, my wife came home from the hospital with two screws that were removed from her leg. (They had, of course, been installed in a previous surgery.) The screws were clean and shiny, and had been autoclaved after removal. -- Coneslayer (talk) 16:23, 8 June 2009 (UTC)

Inertia on the bus(non-technical explanation preferred)

When riding the bus, passengers experience inertia when it accelerates(they move backwards relative to the bus) and when it decelerates(they keep moving forwards). However, why does there seem to be less inertia(and consequently less risk of getting tossed around and crashing into things/people) when you're seated than when you're standing? I don't have much background in physics, so I'd like a non-technical answer. 69.224.113.202 (talk) 18:15, 7 June 2009 (UTC)

You have exactly the same inertia, whether you are seated or standing, because inertia only depends on your mass. While standing, though, your center of mass is higher, and you are generally in a less stable position, so you might feel the sways and even stumble around a bit as the bus accelerates. This is strictly due to how stable your stance is, not how much inertia you have. Nimur (talk) 18:18, 7 June 2009 (UTC)

To expand a little on what Nimur said: when you're sitting down and typically leaning back against the seat, that's a very stable position. Not only are you braced against the seat, your butt and the backs of your thighs against the seat afford you plenty of friction that tends to hold you on the seat, especially if the seat is made of something relatively coarse, like fabric, instead of a more slippery material. If I tried to yank you away from the seat, I'd probably have to use quite a bit of force. But if I wanted to do the same to you when you're standing, it'd be a lot easier, because not only would your center of mass be higher so it'd be much easier to tip you over, there wouldn't be a lot of friction to hold you in place. Unless you were prepared for me and had strongly braced yourself, I could probably yank you off your feet without any real trouble. Another way to look at this might be to imagine a rolled-up carpet in a bus. If you stand it up, it tips over very easily, but if you lay it down, it'll most likely pretty much stay put. If the roll starts to tip over, you're going to have to use quite a bit of strength to get it back upright, because at that point you'll be working against its own mass. That's what happens when you stand up and have to work to stay on your feet: once your balance starts to go, it's your own mass that's making you fall down, more than anything else. You need to work to re-balance the load that consists of your body. -- Captain Disdain (talk) 23:33, 7 June 2009 (UTC)

Similarly, notice that when you're standing, you get thrown around most if you don't use a handhold, less if you hold on with one hand, still less if you hold on with two. The force on you is the same, but the more you're braced, the more easily you can resist it. Sitting down braces you even more, and sitting down with a hand against the seat in front (if possible) does still better. --Anonymous, 3:55 UTC, June 8, 2009.

When a person is standing in a bus, the body's center of mass is at the end of a longer leverage arm than when the person is seated. Specifically, the axis of turning is at the feet rather than the buttocks. Thus when seated, the center of mass is only slightly above the center of turning.
Also, when a bus is decelerating, the abdominal muscles of a seated person resist the inertial effect rather than the weaker ankle muscles of a standing person. Specifically, when a person is seated, holding the abdominal muscles and knees rigid and bracing the feet on the floor opposes the turning inertia of the upper part of the body. When the bus is accelerating, the person is simply pressed back in his seat. Furthermore, the mass of the legs of a seated person is below the axis of turning, reducing the body mass above that point.
All this assumes there is no slippage on the seat or floor. Inertia thus results in a turning effect. - GloWorm. —Preceding unsigned comment added by 98.21.108.254 (talk) 03:59, 8 June 2009 (UTC)

Twins conceived on successive months

Further to the excellent sourced answer above, about the time between the delivery of twins (or other multiple births), I remembered a friend-of-a-friend story. It seemed improbable, but then, so did the idea of delivering one baby and then keeping the other in utero for more than a few minutes. Here is the idea -- twins are born: one is substantially bigger than the other, and hits all the developmental milestones a full month or more before the tinier sibling. What is the probability of the bigger being conceived one month, and the smaller the next, because ovulation for some strange reason was not suppressed? In other words, not "can you get pregnant if you do it standing up?" but "can you get pregnant if you are already pregnant?". BrainyBabe (talk) 20:19, 7 June 2009 (UTC)

I don't know the answer, but I think it is quite unlikely to happen - you don't just need ovulation to take place, but the embryo to successfully implant in the uterus lining. I know some contraceptive pills don't reliably prevent ovulation, but do prevent implantation, so I would imagine pregnancy could be similar (although ovulation is even more unlikely when pregnant than when on the mini-pill). --Tango (talk) 21:02, 7 June 2009 (UTC)

This being an encyclopedia, we have an article on this rare phenomenon: see superfetation. --Cookatoo.ergo.ZooM (talk) 21:03, 7 June 2009 (UTC)

Well, I knew it was quite unlikely to happen; I wanted to know if it was impossible. I am grateful for the pointer to the article, which I never would have found on my own! BrainyBabe (talk) 08:17, 8 June 2009 (UTC)

Submersed in Water

Is there a length of time after which it would become dangerous for a person to remain in water? Assuming access to a toilet and the water is freshly running would a person eventually get sick? I'm thinking there is some sort of limit as your fingers prune after too long. The Aquatic ape hypothesis, which albeit mostly unsupported, provides some possible insight, but I can't seem to find conclusive proof of a danger from extended exposure. TheFutureAwaits (talk) 21:15, 7 June 2009 (UTC)

Incidentally, why do fingers prune? And why don't toes prune? Does pruning take place in other land-dwelling animals after prolonged water exposure? —Preceding unsigned comment added by 98.21.108.254 (talk) 02:42, 8 June 2009 (UTC)

Toes do prune. Try it and see. As for the causes there is a section dedicated to this. Sifaka ^talk 03:13, 8 June 2009 (UTC)

OK. Toes prune too. It's been a long time since I took a bag lunch and spent the whole day at the swimming pool with my pals. (What fun we had !) - GlowWorm.

The need to urinate

Why is it that if I already need to urinate, the closer i get to a toilet the worse it gets? Like, for instance, if I'm driving home I may notice that I need to urinate, but have no trouble getting it, but once I get to the door of my house I start dancing around, and then it rapidly accelerates into a mad dash to the bathroom! Is it psychological? positional? --96.231.171.95 (talk) 22:46, 7 June 2009 (UTC)

If it's any comfort, I experience the very same thing. I've always assumed that it's an example of Pavlovian conditioning, and it's interesting that this still works even when one is consciously aware of it. 87.81.230.195 (talk) 23:42, 7 June 2009 (UTC)

Yep, it happens frequently enough to wonder just how Pablovian could it be if we are so concious of it happening and still can't control it? hydnjo (talk) 00:47, 8 June 2009 (UTC)

If this were an instance of conditioning, then we would expect the urge to pee to arise whenever a suitably coniditioned individual was near a bathroom, but this is clearly not the case. --Shaggorama (talk) 04:06, 8 June 2009 (UTC)

Something autonomic, I bet. Getting out of the car means you relax, relaxation makes you liable to pee. Once you've actually released the flood gates it's difficult to stop mid-flow, so I guess there's some kind of preparatory stage, a pre-pee process if you will, which is likewise difficult to stop. 213.122.32.39 (talk) 05:08, 8 June 2009 (UTC)

I suspect it's just that you have mentally 'released', you've made it to your goal (home) and then like 213.122 says once you've released it becomes much harder to stop so makes it more rushed to get there. I know that's how I explain it to myself. 194.221.133.226 (talk) 07:44, 8 June 2009 (UTC)

I think it's definitely psychological. If you suddenly get distracted by something that's important enough, the sensation will cease -- or at least that's how it goes for me. Sure, it takes a moment, but I've had a phone call knock me out of that "I gotta go right now" mode, for example. -- Captain Disdain (talk) 08:39, 8 June 2009 (UTC)

electrical generator

How does a generator work?

In particularly, I'm wondering how a wind turbine generates electricity? —Preceding unsigned comment added by 69.144.23.204 (talk) 23:23, 7 June 2009 (UTC)

See Electrical generator or more specifically, Electromagnetic induction. In short, voltage is produced across a conductor situated in a changing magnetic field or a conductor moving through a stationary magnetic field. -- Tcncv (talk) 00:00, 8 June 2009 (UTC)

As for wind turbine specifics, you may find the Wind turbine design article worth reading as well and many of the other articles linked from the "Wind Power" navigation box at the botton of that page. The conversion of wind energy to rotating mechanical energy and the conversion of rotating mechanical energy to electrical energy are best though of as two separate processes. -- Tcncv (talk) 00:15, 8 June 2009 (UTC)

In brief - when a magnetic field is moved past a wire, it generates a tiny amount of electricity. Spinning a magnet inside coils of wire (or spinning coils of wire inside some magnets) makes the magnetic field move past LOTS of wires - which makes a useful amount of electricity. The wind spins a shaft which spins the magnet (or the coil). It's basically an electric motor working 'backwards' - instead of putting electricity in and getting mechanical rotation out - you put mechanical rotation in and get electricity out. You can prove this yourself: If you take a small battery-operated electric motor (eg from a kid's toy) and connect a flashlight bulb across its terminals - you can spin the motor with your fingers and light the bulb. If you connect some fan blades to your motor and let the wind make it spin - then you've made your own personal wind turbine! SteveBaker (talk) 01:08, 8 June 2009 (UTC)

June 8

Plant without soil

I have this plant in my garden which grows on a rock. It does not touch any soil which I can see and I can move the whole rock (about 1 metre wide and long) with the plant on it anywhere. The plant grows on one face of the rock, about 1 metre long and has big leaves about 30 cm long. What kind of plant is this and how does it live without soil?

Thanks in advance, 220.244.76.121 (talk) 02:40, 8 June 2009 (UTC)

Some species of air plant maybe? SpinningSpark 03:12, 8 June 2009 (UTC)

Plants living on a rock or rocks are called lithophytes. Lithophytic plants are way too numerous to list. Can you post a picture of the plant somewhere? That would be the best. Telling us what part of the world you are living in would also help. --Dr Dima (talk) 03:38, 8 June 2009 (UTC)

Having said what I said, it may actually be a good idea if we at least start a list of lithophytic plants. The problem is, there are plants like Capparis sp. or Hyoscyamus sp. that thrive in cracks of a rock or in a crevice of a stone wall, but are far more often found in regular soil; and there are plants like some species of Laelia that are almost obligate lithophytes. Should we come up with a criterion, or just bundle them and let the reader read? --Dr Dima (talk) 03:48, 8 June 2009 (UTC)

Even trees can grow without soil. Here is one I photographed in Scotland. Plants only need air, water, and a tiny amount of nutrient. See hydroponics.--Shantavira|^{feed me}

Alternative earphones with remote and microphone for iPod touch

moved to WP:RD/C#Alternative earphones with remote and microphone for iPod touch Nil Einne (talk) 17:01, 8 June 2009 (UTC)

Which vegetable oil is most healthy for vegetarians?

I'm looking for answers based on scientific evidence rather than something resulting from opinions formed from advertising or habitual use (eg olive oil). These two tables http://www.vaughns-1-pagers.com/food/vegetable-oils.htm http://www.annecollins.com/dietary-fat/omega-3-efa-6-chart.htm give lists of consituents of the oil, since I could not find a similar table on Wikipedia.

Canola oil is another name for rapeseed oil. I see that the amount of Omega3 in Canola oil differs considerably between the two tables - the small print in one of them says the amount listed is reduced during processing. I'm also wondering how much Omega3 there is in supermarket-bought 100% walnut oil, probably formed from hot-pressing, since neither of the labels on bottles from two different supermarkets mention it - yet I would have thought this would be a selling-point.

Fat summary: saturated fats - bad, should be avoided as far as possible. Transfats - very bad but not found in *liquid" vegetable oils. Monounsaturated - good, reduce bad cholesterol. Polyunsaturates - not so good as they reduce good cholesterol. But Omega3, which is a kind of polyunstaturated fat, is on the other hand good for you and said to be insufficient in peoples diets.

So given the above, which vegetable oil is best? Expense is not an issue. It may be that a blend of oils, determined by linear programming might be optimal. 78.149.143.187 (talk) 11:54, 8 June 2009 (UTC)

The question is clearly expressed, but I am not sure if the title is supposed to add an element to the mix. Is there a reason to believe that the healthiest oil for vegetarians would not also be the healthiest for omnivores? Also, the healthiest oil on strictly nutritional grounds may not be commercially available. Are you looking for something you can purchase and consume now, or a project to research? For example, argan oil and babassu oil are cultivated, and acorn oil to a lesser extent. You may care to investigate Sclerocarya birrea (S. caffra), aka the marula. BrainyBabe (talk) 12:21, 8 June 2009 (UTC)

We even have an article: Marula oil. BrainyBabe (talk) 12:28, 8 June 2009 (UTC)

I am looking for something available from supermarkets or health food shops. I do not know if the best oil for vegetarians would be the same as that for omnivores. Marula oil, at least, seems to have a lot of saturated fat in it. 89.242.81.255 (talk) 14:41, 8 June 2009 (UTC)

I don't think you can come up with a clear answer to this, since as with so many things when it comes to diet, there is still a fair amount of dispute. How can you come up with a 'best' when you aren't sure what's better? For example there is some evidence olive oil is good for you olive oil#nutrition but how good and why? As the phenolic compounds (and vitamins), which may be partially the cause of olive oil's alleged healthy properties, break down significantly in 12 months [22] the oil may be good in 2-3 months, not so good or at least no different if it's 12 months old. How significant the omega 3 to omega 6 ratio is another thing that remains unclear [23]. Another issue particularly since you talked about unusual oils. If these are organic or other speciality products, they may lack added antioxidants etc which despite the beliefs of those who think everything should be natural could be beneficial. Also, virgin olive oil and other oils with a low smoke point may not actually be a good oil for high temperature cooking (particularly anything over 200 degrees C) such as deep frying or perhaps traditional Asian style stir frying and high temperature roasting/baking due to the low smoke point [24]. Indeed this very high temperature cooking particularly deep frying is one area (IMHO) where the science is particularly unclear due to the complexity of what is formed, what breaks down, oxidises, etc [25] [26] [27]. Some of the beneficial compounds in olive oil may also decrease relatively rapidly for example [28]. And oils high in polyunsaturated fatty acids are prone to oxidation [29] [30] so it's possible an oil high in saturated fats may in fact be better then an oil high in PUFA for high temperature deep frying perhaps even if you only use the oil once. Remember that even if if the quantities formed are small, depending on how bad these are it could still be worse. This may be more of an issue in a restaurant etc but it does depend how often you reuse the oil (if at all), how long you deep fry for and temperatures. Home cooking is more likely to lack a temperature controlled deep fryer, filtering to remove crumbs and the deep fryer may be uncovered all of which are likely to be bad. And interesting enough, repeated heating and cooling of the oil may make things worse since the lower temperatures are apparently quite bad when it comes to oxidation [31]. Another factor, if you are referring to deep frying or any other case where you reuse the oil because of the oxidation, formation of potential carcinogens and other issues associated with repeated use, while you've said expense is not an issue, if using a more expensive oil means you will re-use it (more?), then it's potentially better for you to use the cheaper oil but refresh your oil more often. Of course since deep frying is not particularly healthy, it may just not do it, and things may not be so complicated. But then again, a perhaps interesting issue is the answer may even depend on the person. If you have a family background with a lot cases of cancer then you potentially should be more worried about carcinogens then if you have a family background with a lot of cases of coronary heart diease. One final thing that's worth remembering is where the money is coming from for research etc. General speaking, this has been primarily from developed Western countries and not uncommonly the oil producers from them (canola, soya). (There have been some attempts by developing countries to reverse this trend, particularly palm oil producers but I think the balance is still far in the other side.) This doesn't mean the research is all biased but on the other hand it seems likely someone will avoid funding any research which they expect will be unfavourable to them but fund those that they expect will be favourable. And less common oils, even ones which are perhaps gaining in popularity like rice bran oil (which may have had some use in several Asian countries for a while) are still I think not that well studied (and it's worth asking whether the reason they are gaining in popularity is because of the alleged health benefits or the research showing the health benefits started to show up when producers (rice bran would normally be a waste product) were looking for ways to make more money. (I used rice bran oil myself BTW.) For even less common ones like marula oil and acorn oil, who the heck knows? Has there even been any research in to it? (Natural products are such a complicated mixture and our knowledge still limited enough that you can't say product A has X,Y,Z which we think is good whereas product B has only X & Y so A must be better since what about the quantities and H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W which we don't know enough about?) P.S. It may be worth remembering that it was only in 1988 that we began to recognise the harm of trans fats and several years later before it became clear they were indeed bad, worse then saturated fats. It's definitely possible that there's some other hidden danger that we're not yet, or only beginning to become area of. N.B. As an aside there's some dispute whether trans fats naturally present in some animal products like milk are as bad as those formed via hydrogenation, the evidence isn't strong either way whether because of their relatively low consumption and a lack of research or because they aren't actually as bad is unclear Nil Einne (talk) 16:47, 8 June 2009 (UTC)

You may wish to tryhempseed oil, which according to our article is extremely high in EFA's. However it is not suitable for high temperature frying. --TammyMoet (talk) 18:09, 8 June 2009 (UTC)

Does cooking linseed make its oil accessable?

The Omega3 oil found in linseed, also called flax seeds, is believed to be beneficial. While flax oil is available it is expensive and tastes bitter in my experience. Flaxseed is much cheaper and tastes OK. But I understand that if you eat it raw it just goes straight through you without any of the oils inside the seed being digested, due to the seed-coat protecting them. To be digested it should be ground before eating - which is inconvenient to do.

My question is, does boiling linseed for 15 or 20 minutes (by adding to pasta or rice etc) rupture the seed coat and make the oils inside available to be digested? 78.149.143.187 (talk) 12:08, 8 June 2009 (UTC)

Yes it ruptures the seed coat. Whether it affects the quality of the oil is another question, as something boiled is not coldpressed. One simple way of ingesting raw linseed oil is to take a spoonful of linseed and chew it for 30 seconds, then swallow with a little water. I do not find the taste bitter. No need for coffee or spice grinders, etc. BrainyBabe (talk) 12:24, 8 June 2009 (UTC)

How do you know it ruptures the seed-coat please? 89.242.81.255 (talk) 14:51, 8 June 2009 (UTC)

Because if you chew with normal vigour for 30 seconds, not bite and gulp in two seconds but masticate with your molars for half a minute, the linseed becomes a paste. Try it yourself. Spit it out and look. Poke it with your finger. Can you see any intact seeds? Some might call that original research, frowned on here, but I would call it the empirical method. "Suck it and see", as they say, or in this case, spit it and see. This method is simple, free, requires no equipment, and does not depend on another level of processing (to gelcap form) with its own issues of stability, etc. Also, he enzymes in saliva help the process of digestion begin correctly; see that article. BrainyBabe (talk) 18:00, 8 June 2009 (UTC)

FWIW, you can also get cold-pressed lin/flaxseed oil in gelcap form. No taste at all there. --Kurt Shaped Box (talk) 12:31, 8 June 2009 (UTC)

What you want out of your linseed oil (most likely) are polyunsaturated fatty acids. Heating oil will turn those into ordinary fatty acids at temperatures ard. 195 F- 265 F. In addition flaxseed oil also has it's Smoke point at the upper end of that range. Labels like "cold extracted" or "cold-pressed" make a lot of sense for your salad oil. For cooking oil it's less useful and can even be bad. For frying you have to keep and eye on the smoke point and Trans fat. (P.S.: For more info see Nil's detailed post above.) 71.236.26.74 (talk) 16:52, 8 June 2009 (UTC)

Death by hypodermic to the heart?

My roommate and I noticed that "The Rock" was showing again yesterday. This inspired the conversation that led to me posting the following. Towards the end of the movie Nicolas Cage's character injects an antidote he desperately needs directly into his heart. One of us believes that this scene is realistic, at least in principle, believing that if the antidote had the proper effect quickly enough and if he had a high enough pain threshold, then the character should be ambulatory rather soon and functioning at nearly his normal level. The other of us believes that the process of injecting anything directly into the heart would lead to death rather quickly, given the required injury to the heart itself. I tried Googling this issue without much luck. Any thoughts, anyone? —Preceding unsigned comment added by 68.37.188.33 (talk) 15:01, 8 June 2009 (UTC)

Hopefully someone with more medical knowledge will reply in detail. but intracardiac injections are real. I think they're only used in extreme emergencies because of the obvious danger to the heart itself and the coronary artery. APL (talk) 15:10, 8 June 2009 (UTC)

Am personally skeptical that it would work like that, but its a great movie anyway. 65.121.141.34 (talk) 16:37, 8 June 2009 (UTC)

heat into electricity

is there something maybe like a solar panel which can convert relatively large amounts of heat say a 10000 joules possessed by its surrounding air at a 1000 kelvin within a few seconds or even a few milliseconds? --harish (talk) 15:04, 8 June 2009 (UTC)

In principle this is just a heat engine - you pump a working fluid through a heat exchanger so it absorbs heat and maybe undergoes a phase change as well. Then you pass the hot fluid through a turbine which extracts work from it. While driving the turbine, the fluid expands and cools, so you pump it round again. In practice, 1000K is a high working temperature - for comparison, the superheated steam in a fossil fuel power plant has a maximum temperature of about 800K. So you probably need to borrow technology from the nuclear industry which is designed for higher working temperatures - maybe advanced gas-cooled reactor or very high temperature reactor technology. If you want to increase the power of your heat engine then you increase the surface area of your heat exchanger and pump fluid through at a faster rate. Gandalf61 (talk) 15:56, 8 June 2009 (UTC)

There is also the thermoelectric effect, which has some similarities to the photoelectric effect, but it is even less efficient in practice. Nimur (talk) 17:00, 8 June 2009 (UTC)

You really need a temperature DIFFERENCE in order to extract some energy. So if all of the machine's surrounding air is at 1000K, you've got to find a way of connecting the thing to something at much lower temperature. If you can do that then using some substance that is a gas at 1000K but a liquid at the lower temperature (water might be a reasonable choice) then water is flashed into steam by your 1000K heat source - is used to drive a turbine - the outlet from which is passed through cooling coils in the cold part of the system to condense back into water and continue around to the hot side again. A steam engine would work - so would a stirling engine...there are many possibilities...although it's hard to imagine anything that could do that within seconds. But if the entire machine is immersed in 1000K temperatures - there is nothing you can do to extract energy because that would violate the laws of thermodynamics. SteveBaker (talk) 18:40, 8 June 2009 (UTC)

It depends on exactly how you interpret the question - if it is one batch of hot stuff containing 10kJ being converted at once, then a few seconds is probably unrealistic, if it is a continuous process converting 10kJ per second, that is perfectly achievable. A typical fossil fuel power plant generates far more than 10kW. --Tango (talk) 18:56, 8 June 2009 (UTC)

How far do iron ore Lake Freighters travel from Minnesota or Northern Michigan, through the Soo Locks & past

the Mackinac Bridge then south on Lake Michigan to the steel mills in Gary, Indiana? —Preceding unsigned comment added by 72.204.36.33 (talk) 15:52, 8 June 2009 (UTC)

porcupines

Are porcupine quills coated with venom or bacteria to cause infection? The article did not seem ot mention this one way or another. 65.121.141.34 (talk) 18:57, 8 June 2009 (UTC)

No, they are not. They are modified hairs - nothing more. The keratin makes them stiff. You may be thinking of hedgehogs. Many breeds of hedgehogs perform a ritual commonly called "anointing". They spread various chemicals (which may contain poisons) on their quills. Some people think that they do it increase the odds of infection in a predator. Others think it is just for camouflage. -- kainaw™ 19:03, 8 June 2009 (UTC)