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July 20

Sildenafyl Citrate

What (if anything) would happen if a woman takes a Viagra tablet? —Preceding unsigned comment added by 99.240.186.7 (talk) 01:45, 20 July 2008 (UTC)

Sildenafil#Other uses might be of some interest. --Tango (talk) 02:11, 20 July 2008 (UTC)

I would expect it to have a similar effect on the analagous structure in the female anatomy (you can decide whether to take clitorally all the things I say). StuRat (talk) 20:21, 20 July 2008 (UTC)

GROAN, that's a horrible pun! Exxolon (talk) 20:14, 21 July 2008 (UTC)

gas flaring

what is the natural consequence of gas flaring on both plants and inhabitants41.219.197.37 (talk) 09:10, 20 July 2008 (UTC)

See Environmental issues in the Niger Delta#Natural_gas_flaring. --Bowlhover (talk) 09:35, 20 July 2008 (UTC)

Universe Expansion

Is the universe's expansion speeding up or slowing down? I always thought it was slowing down but now someone has confidently asserted to me the opposite. I have looked at the wiki page on Expansion of the Universe but I don't think it says there (a lot of it was quite technical).

Thanks! 91.84.178.119 (talk) 12:05, 20 July 2008 (UTC)

The universe's expansion is currently accelerating, as far as we can tell, something thought due to dark energy.--Fangz (talk) 13:15, 20 July 2008 (UTC)

Thanks a lot, that's perfect.91.84.178.119 (talk) 13:40, 20 July 2008 (UTC)

Salt in medicine

Is salt (Natrium cloride) ever used for the treatment of any disease? (Like for example low blood pressure). —Preceding unsigned comment added by Mr.K. (talk • contribs) 12:45, 20 July 2008 (UTC)

Hyponatremia would be the obvious one. DMacks (talk) 13:40, 20 July 2008 (UTC)

For future reference, "natrium" is called Sodium in English. --Tango (talk) 17:18, 20 July 2008 (UTC)

And yes, it is used to raise blood pressure in patients with dangerously low levels, either as an IV or given orally (say as a broth). Low blood pressure is a common result of dialysis, for example, and this is a common treatment. StuRat (talk) 20:10, 20 July 2008 (UTC)

For more, see Saline (medicine). --Shaggorama (talk) 14:47, 21 July 2008 (UTC)

Olive oil in medicine

Is any serious study about the medicine use of olive oil in the treatment of any disease (like depression, for example)? —Preceding unsigned comment added by Mr.K. (talk • contribs) 12:47, 20 July 2008 (UTC)

There are some unsourced medical uses mentioned at Olive oil#Medicinal use. Zain Ebrahim (talk) 12:55, 20 July 2008 (UTC)

One of the main components of olive oil comprises the majority of Lorenzo's oil, a substance which is used in conjunction with a controlled diet to treat adrenoleukodystrophy. The oil is still being evaluated by the FDA, but it's discovery was impressive and effective enough to merit the production of an academy award nominated film. --Shaggorama (talk) 06:09, 21 July 2008 (UTC)

Disadvantages of cholesterol drugs

What could possibly be the disadvantages of taking cholesterol reducing drugs? —Preceding unsigned comment added by 89.242.157.92 (talk) 12:49, 20 July 2008 (UTC)

Most drugs have side effects. It might be a good idea to look at the article for the specific drug you are interested in. Or consulting a doctor, if this relates to a specific medical concern.--Fangz (talk) 13:17, 20 July 2008 (UTC)

You may also want to read Statins. While not without side-effects you'll probably come across a lot of talk discussing statins as a sort of wonder drug given their general relatively high safety while having a relatively high success in lowering cholesterol. One concern, as is not uncommon in treating any condition diet related is that it's generally far better to modify/improve one's diet rather then to go on drugs, not just to avoid side effects of drugs, but also because of the other likely benefits of an improved diet Nil Einne (talk) 18:10, 20 July 2008 (UTC)

Yes, the lack of a good diet is a concern. I'd even go further and argue that some people may allow their diets to significantly worsen if they think some "miracle drug" will solve all their health problems for them. StuRat (talk) 20:02, 20 July 2008 (UTC)

asteroid - earth impact

How precisely can we detect in advance menacing asteroids that might crash on earth? How do the predictions improve as the object approaches? At what moment are we able to pinpoint an area where it will crash? Is there a range of speeds asteroids find themselves in, do different speeds change the force or probability of an impact? Could one bounce off the atmosphere if it arrived a low angle? I read Asteroid impact but couldn't find the answers. Thank you. 190.190.224.115 (talk) 14:10, 20 July 2008 (UTC)

Different speeds, angles, locations, and the impactor's composition greatly affect the damage - see http://www.lpl.arizona.edu/impacteffects/ -- Finlay McWalter | Talk 16:05, 20 July 2008 (UTC)

Using radar, we can get extremely precise measurements, often a long time in advance. I think the asteroid needs to be quite close to get such measurements, but there are often close approaches to Earth before the one that could result in a collision, so we can take the measurements then and project the path forwards. Where it will hit depends on the exact time of the collision. Working out the thin path that the asteroid could hit is quite easy, since it just depends on the direction the asteroid is coming from, working out where on that path it will hit requires exact timing, and that requires much more accurate measurements. We would probably still get that some time in advance. I would expect asteroids can bounce off the atmosphere, although I'm not sure it's very likely - there's probably a very narrow range between where it becomes shallow enough to bounce and where it misses entirely. --Tango (talk) 17:28, 20 July 2008 (UTC)

The difficulty isn't just in taking precise measurements of location, direction, and velocity, but is complicated by the fact that asteroids can change direction. This change, while slight, can significantly affect whether one will hit the Earth several passes later. Changes in direction are often due to interaction with other objects, but not always in a predictable manner. For example, while passing a planet or the Sun, tidal forces or sunlight can melt ices, which can then be vented. Those can change both the mass and trajectory slightly. StuRat (talk) 19:58, 20 July 2008 (UTC)

Midget sub in Birkenhead

Please see this request for info. — RHaworth (Talk | contribs) 15:41, 20 July 2008 (UTC)

Can someone help me in my own noble pursuit of all the world's (scientific) knowledge?

What would be the proper order to read your science articles so I can become a scientific personality with a steel trap mind? I mean someone says " .... my milkman, 1846, berylium, and the tenth law of thermodynamics?" I would immediately reply "My good man, your statement about the nonexistant 10th law of thermodynamics strikes I, a well known intellectual powerhouse in the esteemed scientific community, as peplexing and oddly prophetic. For it has been determined, by a barrage of outside the box labrotory research, that the math, using a newly, sometimes controversial property discovered by a still top secret learning facility, is indeed correct. Your milkman will discover 6 more laws of thermodynamics! ]:)

It would sound rediculous to the layman, but that's just the point, I want to be resprected by scientists, not necessarily people in general. --Hey, I'm Just Curious (talk) 19:03, 20 July 2008 (UTC)

You can read them in any order. Science does not have a starting point. You study. If you find something that you do not understand, you study that. If that leads to something you do not understand, you study that. You continue until you understand the first thing you were reading. As for being respected... you will need a PhD. Make a list of the top 100 scientists of all time. You will have a handful that lived before the invention of the PhD (so they don't have one). You will have a couple that didn't get a PhD for one reason or another. Then, the majority will have a PhD. Why? If you are too stuck up or lazy to get a PhD, why should all those who got theirs want to spend their time listening to you? -- kainaw™ 19:34, 20 July 2008 (UTC)

PhD is certainly the qualifier. All those man-hours put into achieving a doctorate, shows that you are a dedicated scientist in your field, and worth listening to. No one would care about what Miss Teen South Carolina thinks of blackholes or general relativity, but lots of people listen when Carl Sagan or Michio Kaku talk about them, because they know what they are talking about. ScienceApe (talk) 20:38, 20 July 2008 (UTC)

I don't think that's true at all. A PhD is nearly a requirement if you want a career in academia, but respect in academia is almost entirely a function of what you publish. Anyone who does look at your educational history will be more interested in the schools—a BA from Berkeley is worth a lot more than a PhD from Columbia Pacific University. I think professional astronomers appreciate Sagan's popularization of astronomy, but I don't think they'd rate his scientific work as especially memorable. Kaku I think is little short of a crackpot. Jack Sarfatti is an outright crackpot, and he has a PhD in theoretical physics from UC Riverside. There's a popular perception that anyone who can get a PhD must know what they're talking about, but sadly it isn't true. Anyone can get a PhD if they try hard enough; most people are just smart enough not to bother. -- BenRG (talk) 12:37, 21 July 2008 (UTC)

It strikes me that brushing up on grammar would enhance your intellectual powerhouse reputation (even among scientists). Clarityfiend (talk) 21:50, 20 July 2008 (UTC)

If you want my, totally biased advice: a great way to get a very generalist understanding of science is not to study science itself, but to study the history of science. If you read through the article on History of physics and took the time to look into the sub-articles linked to there, you'd have a great, great understanding of physics for practical, conversational purposes. Could you set up an experiment yourself? No. That takes formal training for the most part. Could you carry on a conversation about the relevance of the expanding universe? Yes indeed. Could you probably find yourself with a lot to say on the topic of string theory, relativity, and the philosophical implications of quantum mechanics? Yes you could—and frankly, if you aren't actually going to be whipping out your calculator right there, I'm not sure trying to parse through all the equations is going to get you very far anyway. Just my two cents. --98.217.8.46 (talk) 00:29, 21 July 2008 (UTC)

Having a PhD is not a requirement for being smart, or a good scientist. To be a good scientist, it is all about the mindset and philosophy you are in. A PhD is merely a good sign of one. Freeman Dyson is a famous physicist and Planck Medal winner who hates PhDs. Just wanted to get that in there. Mac Davis (talk) 03:43, 21 July 2008 (UTC)

You're only going to read (with dedication) if you're interested, and you'll talk more about subjects you're interested in as well. I'd suggest focusing your study on areas that fascinate you and follow tangents as they arise. You might also want to start brushing up on lay-science magazines; it sounds like you're interested in physics, so I'd suggest something like Scientific American or Popular Mechanics. --Shaggorama (talk) 06:24, 21 July 2008 (UTC)

I for one don't like popular science magazines at all. They just leave you "OK, black holes are like vacuum cleaners of space, but how does it really work.". Reading Wikipedia, for example, is much better. —Bromskloss (talk) 15:02, 21 July 2008 (UTC)

Don't forget to regularly read the Wikipedia Science reference desk (like you are now), I learn lots of new things everyday in just a 5 minute visit to this place. --Mark PEA (talk) 15:12, 21 July 2008 (UTC)

How does the odor of rotten food make us gag?

I suppose the "why" is a survival mechanism, so that we won't ingest foods that have been taken over by possibly noxious or even toxic bacteria. (Please correct me if I'm wrong.) What I don't understand is how this works. I had to get within arm's length of some overage potatoes today, last week it was a (refrigerated) leftover portion of baked tilapia. My few experiences with natto also made me gag almost to the point of retching. The pharyngeal reflex page wasn't much help, though I've also had this difficulty when clenching my teeth around those cardboard-covered dental X-ray film holders. Advice on avoiding this reaction would be helpful, but I'll settle for understanding it better. -- Thanks, Deborahjay (talk) 19:30, 20 July 2008 (UTC)

Yes, evolution is certainly why. As for how, I don't think it's anything mysterious. Your nose detects various chemicals in the smell and sends the signals to the part of your brain that analyzes the info. It compares it to a list of chemical combinations it recognizes as "rotten food" and sends the appropriate response to your body. That list of chemical combinations recognized as rotten food is somewhat interesting, though. It's partly inherited, but also partly learned. If you've ever eaten a food that had gone bad and then made you violently ill, let's say eggs, that may very well cause all eggs, fresh or not, to be recognized, from then on, as "rotten food". StuRat (talk) 19:49, 20 July 2008 (UTC)

The "how" is a involuntary muscle spasm and an emotional reaction. As with many involuntary reactions you can learn to suppress it, if you for some reason have a need. Garbage men learn that trick fairly quickly, I'd bet. ---J.S (T/C/WRE) 00:09, 21 July 2008 (UTC)

Actually despite what StuRat might think, the mechanism behind the gag reflex in response to certain odors is mysterious. The reason is that it appears to be largely innate, and not learned. That means that there is some genetically hard-wired neural network that encodes the odor-to-behavioral response. This type of innate response to odors is not unusual in animals, but they typically detect such odors with their vomeronasal organ which projects neurons directly to regions of the brain that mediate innate responses. The problem is, humans do not have a vomeronasal organ. Which means we detect the odors through or main olfactory system or one of the mysterious olfactory sub-system such as the septal organ or the Grüneberg ganglion (these are so mysterious, in fact, we don't have an article on them). Yet the neurons in the these systems project to cortical regions and don't appear to mediate innate responses. So the answer is that no-one really knows how certain smells appear to be innately aversive in humans. Rockpocket 01:42, 21 July 2008 (UTC)

This isn't sourced, but I don't think I agree that it's not learned. Have you seen game shows like Fear Factor where the contestants have to eat century egg? I enjoy an occasional one "fresh" (haha, fresh century egg) out of the shell, as do many Chinese, but the people on the shows always gag. So in some ways, it has to be at least partially learned. --Wirbelwindヴィルヴェルヴィント (talk) 14:54, 21 July 2008 (UTC)

Like anything in the nature vs nurture debate, the truth is likely to lie somewhere between. Also, like I said before, it's possible to "learn" to suppress some types of involuntary reactions. ---J.S (T/C/WRE) 18:05, 21 July 2008 (UTC)

Blowing up nuclear powered vehicles

Lets say a nuclear powered vehicle like an aircraft carrier or a nuclear sub is attacked and destroyed with conventional weapons. Would the vehicle explode in a nuclear explosion, or would the explosion be no different than a similar conventional vehicle blowing up? Would there be radioactive contamination? ScienceApe (talk) 20:33, 20 July 2008 (UTC)

It's very hard to start a nuclear explosion (fission or fusion), and virtually impossible to do so with reactor that is designed specifically to avoid that occurrence. You'd get somthing like a dirty bomb, just dispersing all that nuclear material as a contaminant not trigger any further nuclear reaction. DMacks (talk) 20:36, 20 July 2008 (UTC)

(ec) There would certainly not be a nuclear explosion -- the fuels in such a vehicle are not weapons-grade in the first place, and even if they were, making a nuclear explosion is difficult; it requires very fussy design. Not gonna happen by accident. Radioactive contamination is certainly plausible -- I don't know what if any steps have been taken to prevent that in a war scenario and would be interested in finding out from someone who know --Trovatore (talk) 20:37, 20 July 2008 (UTC)

Actually US nuclear subs run on 93% enriched uranium, I do believe (and this article seems to claim such as well). It's not uncommon for small propulsion reactors to run on HEU—you get a lot more energy out of a lot less material that way (most research reactors used to run on HEU until somebody figured out that was a very bad idea). But no, you wouldn't get a real nuclear explosion, even with that fact being true, though you could get secondary explosions—e.g. inadvertent generation of hydrogen gas, that mixes with oxygen, that ignites, and spreads a lot of nasty stuff all over the place. You could imagine the fuel melting and forming a critical mass or two on the bottom of the reactor, which would result in neutron fluxes and maybe very tiny explosions but that's about it. --98.217.8.46 (talk) 21:40, 20 July 2008 (UTC)

If the reactor were a pure fusion reactor using maybe inertial confinement fusion, (I realize they aren't practical at the moment but for argument's sake) would the radioactive contamination be far less severe? ScienceApe (talk) 20:42, 20 July 2008 (UTC)

Yes. ICF contamination is just from the material holding the reactor together, mostly. An actual fission reactor is constantly producing highly radioactive substances in great quantity. ICF has very mild contamination risk compared to fission. --98.217.8.46 (talk) 21:40, 20 July 2008 (UTC)

I question the "great quantities" part. Certainly the quantity is less than or equal to the mass of nuclear fuel lost during the reaction, which is quite low. StuRat (talk) 03:39, 21 July 2008 (UTC)

Yes, but the reaction products typically have much shorter half-lives, and therefore are much more radioactive, than the fuel. So while the quantity might not be large as measured in kilograms, it's a lot as measured in curies (or, more modernly, Bequerelsoops, I guess it's becquerels, but who really knows what those are?). --Trovatore (talk) 03:51, 21 July 2008 (UTC)

And I was referring to it relative to the ICF as well. A fission reactor contains far greater quantities of far nastier poisons than something that is only getting somewhat irradiated by a bunch of neutrons would. I am not trying to be anti-fission here, just pointing out that the production of rather nasty waste is an inevitable side-effect. ICF will irradiate its containment structure with neutrons which should induce some radioactivity but it's not going to be anything as bad as actual fission products. --98.217.8.46 (talk) 17:08, 21 July 2008 (UTC)

Depending on the details of the attack, it's quite possible that the reactor would survive intact (probably not watertight, but recoverable intact). Large metal objects have survived remarkably close to nuclear explosions. If the explosion was some distance away from the vessel, and ideally with the large bulk of the vessel between it and the reactor, then you might well expect the reactor (which is very heavily constructed indeed) to be ejected intact and deposited on the sea floor as a (warped, leaky) whole. -- Finlay McWalter | Talk 20:53, 20 July 2008 (UTC)

It might also depend on the specifics of the reactor. I recall a number of scares (though only over contamination rather than nuclear explosion) involving nuclear reactors on submarines during the cold war. (E.g. Soviet submarine K-19) What almost happened by accident can happen also by malice. See [1] for a list of such accidents.--Fangz (talk) 22:37, 21 July 2008 (UTC)

Seagull dawn chorus of squawks

Why do they make so much noise as soon as it starts getting light in the morning? I looked out of my window today after they woke me up and saw them just flying around squawking loudly at each other. —Preceding unsigned comment added by 90.242.57.76 (talk) 20:51, 20 July 2008 (UTC)

Our dawn chorus article says that songbirds start to sing at dawn, often for territorial reasons. Less melodious, but the seagulls are doing the same. If you're in the UK/Europe, the seagulls have young in their nests at the moment so the parents are defensive. Watch out, because they sometimes circle and threaten to dive-bomb you. Itsmejudith (talk) 22:34, 20 July 2008 (UTC)

There is a Herring Gull nest on my roof this year. When it gets to about 4am, the chick is all "cheep! cheep! cheep! cheep! cheep!" whilst the mother (or father) gabbles/clucks away softly. It goes on all day - unless the chick is napping. The early-morning squawking gulls may also be on the look out for anything edible that has found its way onto the street overnight. When a gull spies food, it generally loudly announces the fact - which starts off a chain reaction of squawking amongst any other nearby gulls. --Kurt Shaped Box (talk) 23:26, 20 July 2008 (UTC)

Why would they announce it, knowing that this causes all the other gulls to try to steal their food ? Not the brightest, are they ? StuRat (talk) 15:34, 21 July 2008 (UTC)

I don't know for certain - but I suspect that any gull discovered feeding at a significant find without first notifying the rest of the flock will be on the receiving end of some heavy 'social pressure'. OTOH, the gull that spots the food might merely be giving a (fruitless) warning to the rest of the flock to stay away from his find... --Kurt Shaped Box (talk) 16:30, 21 July 2008 (UTC)

Or it may be that the script writers for the film Finding Nemo actually translated gull-speak correctly. They're all sqwawking "mine!" "mine!" "mine!" ~Amatulić (talk) 20:15, 21 July 2008 (UTC)

July 21

Iron magnet

Where can I buy a 10kg, magnetized chunk of iron? Thanks, *Max* (talk) 01:26, 21 July 2008 (UTC).

Why not magnetize iron with a strong rare earth magnet or by making it an electromagnet? --Bowlhover (talk) 10:02, 21 July 2008 (UTC)

Yeah its going to be much easier to magnetise a large lump of iron your self rather than obtaqin one. Just wind lots of wire round the iron and pass electric current thro it from a car battery say. —Preceding unsigned comment added by 86.130.138.231 (talk) 14:28, 21 July 2008 (UTC)

That said, you want to take safety precautions like making sure not to short the battery. Theres about a thousand different things that could go wrong in this process. If you are not an expert, please make sure to consult with one before doing anything crazy. In particular, do NOT short the battery in order to get current through the wire. EagleFalconn (talk) 14:56, 21 July 2008 (UTC)

It's not that likely that someone will be selling one. Firstly for magnets other things often get used in preference including ferrite (iron oxide).

Buying 10 kg of iron is relatively simple though. Was there any particular shape. If you just want a magnet with iron and other things in that should be possible, though 10kg is a big magnet.87.102.86.73 (talk) 19:05, 21 July 2008 (UTC)

meh, a car battery isn't going to do much harm. Shorting circuits is generally a bad idea, but car batteries don't have enough juice to really do damage. Plasticup ^T/C 19:11, 21 July 2008 (UTC)

• That's dangerously wrong. The amount of energy in a car battery is up in the megajoules, which is plenty to start a fire or make a small object dangerously hot. See http: //www.popularmechanics.com/automotive/how_to/4213127.html for an example. --Anonymous, 22:06 UTC, July 21, 2008.

I know how to magnetize it, but where can I get 10 kg of iron? *Max* (talk) 21:24, 21 July 2008 (UTC).

Check your phone book for local businesses that do custom metal work. You can get solid square bars of metal in any size you need. ---J.S (T/C/WRE) 21:32, 21 July 2008 (UTC)

An educational supply business may be able to sell such a magnet. Back in school I remember a U shaped magnet that was pretty strong. When you dropped an aluminum plate between the poles it would only fall about 1 mm per second due to eddy current damping. Graeme Bartlett (talk) 01:46, 22 July 2008 (UTC)

Consider hiring someone to magnetize a hunk of iron of the specified mass using an electromagnet. That is how magnets are created in recent centuries. Edison (talk) 04:30, 22 July 2008 (UTC)

To make a powerful electromagnet, you should use a U shape or a disc shape, so that both poles can be applied to the thing you wish to lift, or to the area where you want the powerful magnetic field. The density of Iron is 7.874 g·cm⁻³, so you need a volume of 1270 cm³. If you could find iron bars for sale, you could take three pieces to form the core into a U shape, and bolt them together, allowing three coils to be slipped over the core on the two legs and the top. Any length of core which is not being magnetized by a coil will decrease the pull of the magnet. What you are likely to find comercially available today is not Wrought iron such as Michael Faraday used to create the first strong electromagnets in the 1830's, but Carbon steel. You should review the magnetic properties of the various forms of iron, because they differ in the intensity of magnetization the accept and retain. soft iron, like a nail, quickly loses its magnetisation, while "hard" ferrous materials retain their magnetisation better. If you are building an electromagnet, you need a material which becomes demagnetised when the current is switched off. If you wish to magnetize the iron and create a permanent magnet then a "hard" ferrous material or modern rare earth magnetic materials would create a strong, long lasting magnet. If you just literally want a 10kg chunk of magnetized iron or steel, you might buy a big sledgehammer and magnetize it with a coil which can be slipped aroung the head of the sledge after the handle is removed. A sashweight is another big hunk of iron which could be easily magnetized, but a bar magnet will not be as strong as a pot or U magnet. You could also take an old transformer remove part of the core, and use the rest as an excellent electromagnet, but a weaker permanent magnet, due to the type of iron used. A machine shop might have scrap pieces of iron bar or rod they would sell at a bargain price. An ag=ngle or I beam would be undesirable since a coil would not fit well around it. Edison (talk) 16:50, 23 July 2008 (UTC)

Microwave oven

Can someone explain briefly (without too much technical or scientific lingo) why you can't place metal / aluminum foil / etc. in a microwave oven ... and what exactly would happen if you do? Also ... why is it that food tastes "different" when cooked in a microwave oven versus a conventional oven? Thanks. (Joseph A. Spadaro (talk) 02:48, 21 July 2008 (UTC))

See Microwave_oven#Dangers for the answer to your first question. The short-short version is that a piece of metal will act like an antenna, converting the microwaves into electricity. Depending on the shape, size, etc of the metal, that can cause various problems. Metal twist-ties often catch on fire, for example. APL (talk) 03:19, 21 July 2008 (UTC)

Fixed link. StuRat (talk) 03:26, 21 July 2008 (UTC)

That's interesting. Hmmmmmm. Do we have any technology that takes advantage of this phenomena of metal turning microwaves into electricity? ScienceApe (talk) 03:37, 21 July 2008 (UTC)

Sort of. Obviously making microwaves then converting them back to electricity would use more energy than it would produce. However, special metallic foils are used under food to absorb microwaves and turn them into heat, to toast the food from underneath. StuRat (talk) 03:45, 21 July 2008 (UTC)

There are also various plans (and when I say plans, I mean vague ideas that may or may not have had a 1/10,000 scale prototype made so far) to do things like power spacecraft with microwave lasers, or use microwaves to "transmit" electricity without wires - see microwave power transmission. Confusing Manifestation(Say hi!) 04:16, 21 July 2008 (UTC)

See also wireless energy transfer and solar power satellite.

But a simpler answer to the question of whether we have technology taking advantage of this effect is the antenna used by every radio receiver, every TV set not connected to a cable system, every satellite dish, and so on. Without it, radio and TV broadcasting would be impossible. --Anonymous, 04:21 UTC, July 21, 2008.

A more obscure application of the fact that microwaves heat metal is hobbyist metalworking (see http://home.c2i.net/metaphor/mvpage.html). --Bowlhover (talk) 07:19, 22 July 2008 (UTC)

We don't have an article on it, but microwave sintering is a way to custom-form metal parts from metal powder and microwaves. --Carnildo (talk) 23:57, 21 July 2008 (UTC)

As for why foods taste different, there are many reasons. One is that the air doesn't heat up in a microwave oven like in a regular oven. This means the surface of bread doesn't dry out, for example. That's good if the bread was stale already but not so good if it was soggy. Another diff is that foods often cook for different lengths of time. Longer times allow flavors to blend more. StuRat (talk) 03:31, 21 July 2008 (UTC)

There are some interesting experiments with microwave ovens which I have seen on You Tube that take advantage of the fact that when a match is lit and covered with a glass inside a microwave the burning gases act like a conductor. Placed in a microwave oven the microwaves then react with burning gasses to form a plasma in a very spectacular fashion. -- adaptron (talk) 07:28, 21 July 2008 (UTC)

See Ball_lightning#Laboratory_experiments subtitle 'Home microwave oven experiments' for more on this. --Ayacop (talk) 07:59, 21 July 2008 (UTC)

One of the reasons why food tastes different is the lack of 'browning' - microwave ovens use a lot of quite low energy waves - (lower energy than that given off by a heat lamp) - but uses massive ammounts of them - it's a bit like cooking with massive amounts of tepid water (very poor analogy) - because the energy is low it does not cause burning/browning - a bit like steam cooking.

High energy cooking such as using a pan, or oven causes more chemical reactions to occur eg see Caramelization, also maybe look at Maillard_reaction - these reactions cause a change in constitution that gives a different taste.

87.102.86.73 (talk) 09:10, 21 July 2008 (UTC)

Here is an article detailing the reason microwaved foods taste different. According the to webpage, the temperatures and cooking times involved in microwaving are insufficient for the Millard reaction to occur. Because of this, foods cooked in conventional ovens have greater quantities of volatiles associated with pleasant flavours and less undesirable substances. --Bowlhover (talk) 07:19, 22 July 2008 (UTC)

Will doing that match thing damage the microwave? 61.69.141.209 (talk) 10:36, 21 July 2008 (UTC)

Yes, according to the WP link I gave above. Don't try this at home. --Ayacop (talk) 10:39, 21 July 2008 (UTC)

Apparently, the "plasma" also releases not-too-healthy gases, like NOx, which can be really bad to breathe in. -- Aeluwas (talk) 11:54, 21 July 2008 (UTC)

Wind vortex experiment

Does any article describe or point to a reference of an experiment in which a large diameter axial fan was setup in the vertical and turned at high speed for the purpose of generating a vortex to serve as a typhoon or a hurricane "seed"? -- adaptron (talk) 07:21, 21 July 2008 (UTC)

Well, a hurricane is out of the question. Their spin is a consequence of the Coriolis effect, not a requirement for formation -- much less issues of scale. A vertical fan is also the wrong method of formation for a tornado, which originate from horizontally-inclined mesocyclones. Of course, the incorrectness of the approach doesn't preclude somebody from conducting an experiment anyway. 199.209.144.218 (talk) 12:43, 21 July 2008 (UTC)

Skin Bleaching

Started to read a new trend of anal bleaching but was not able to locate any legitimate medical articles on the procedure and the safety of this. Does anyone have any info or links for me? I don't know exactly what chemicals are used or any long term effects of this? .....you can start laughing now..... --JennaHunter (talk) 13:15, 21 July 2008 (UTC)

I would certainly expect it to be painful and result in swelling. I'd expect that fasting before the procedure might be in order to reduce the...err..."use" of the area following the procedure. Perhaps only bleaching a bit at a time might be safer, but whole area bleaching is probably done, too. StuRat (talk) 13:37, 21 July 2008 (UTC)

I've heard of people on the radio talk about adult entertainers getting it done, but other than that, I know nothing about it. --Wirbelwindヴィルヴェルヴィント (talk) 14:40, 21 July 2008 (UTC)

err....are you sure they're bleaching skin and not hair? --Shaggorama (talk) 14:42, 21 July 2008 (UTC)

Definitely. Last week there was a report in German TV about a shop in China that offers the service. Of course, their formula is kept secret. --Ayacop (talk) 07:51, 22 July 2008 (UTC)

There's an article for anal bleaching, but it's just a stub. APL (talk) 14:54, 21 July 2008 (UTC)

How about a tattoo instead. I suggest one on your butt cheeks that says "If you're close enough to see the color of my anal sphincter, you're too damn close !". StuRat (talk) 21:30, 21 July 2008 (UTC)

Or "almost close enough", of course, depending on your proclivities. -- Captain Disdain (talk) 08:24, 22 July 2008 (UTC)

Shallow seas

How deep do a scientist consider shallow seas to be? —Preceding unsigned comment added by 68.11.112.100 (talk) 15:18, 21 July 2008 (UTC)

Depends on the context. If your talking about a global-view, then anything anything above the contentnal shelf... ~300feet. If your talking about a local ecological view then either (1.) anything above the thermocline (~30-50 feet) or (2.) anything in the zone where sun-light is a major factor (~150feet). Of inteses might be: Intertidal zone, Littoral zone and surf zone. 63.80.111.2 (talk) 17:30, 21 July 2008 (UTC)

General usage amongst geologists interested in modern and ancient sedimentary environments is that waters are shallow up to about 100m, but it doesn't seem to be something that is rigorously defined. Mostly shallow water is used for areas of the continental shelf as opposed to the continental slope or abyssal plain. Oceanographers may well take a different view. Mikenorton (talk) 17:38, 21 July 2008 (UTC)

Stability of bikes with different wheel-sizes

My father and one of his oldest friends have been debating an issue of physics ever since they where in their early teens. They both got bikes when they were 13 or 14 and they (naturally) started arguing which one was better. My father's bike had bigger wheels, so he argued that it's more stable. Since the wheel is bigger, the gyroscopic effect of the spinning should be bigger, my father thought. His friend, as young boys are want to do, passionately disagreed. He argued that if the bikes are travelling at the same speed, his wheels will spin faster, thus eliminating any advantage my fathers bike might have had. it's now 35 years later, and the issue still haven't been settled.

He asked me, and I told him only the very basic stuff I know, that the gyroscopic effect depends on the angular momentum of the wheel, which does increase with the size of the wheel. However, I haven't studied physics for years and years, and I can't even come close to figuring out whether the faster rotation of the smaller wheel will be enough to outweigh the longer radius of the larger wheel. I suspect this comes down to an issue of mass, since the larger wheel presumably have more mass, it will win out. But what if the two wheel had the same mass (the smaller one is denser, or something)?

Can you fine folks please settle this long-running dispute? 83.188.199.140 (talk) 16:32, 21 July 2008 (UTC)

I don't think gyroscopes have anything to do with it. See http://www2.eng.cam.ac.uk/~hemh/gyrobike.htm . 91.143.188.103 (talk) 16:52, 21 July 2008 (UTC)

I'd say the larger wheeled bike would have a greater rotational inertia, since that's related to the square of the radius, not just the radius. That, in turn should provide more gyroscopic effect. However, I disagree that the gyroscopic effect is all good. While it helps maintain stability while going straight, this also makes turns more difficult, requiring you to slow down more to turn. StuRat (talk) 16:57, 21 July 2008 (UTC)

We have an article on Bicycle and motorcycle dynamics. -- Coneslayer (talk) 17:36, 21 July 2008 (UTC)

The moment of inertia, according to StuRat, varies according to r² - since the angular velocity in this circumstance varies according to 1/r, the larger wheeled bike will "win". --Random832 (contribs) 18:44, 21 July 2008 (UTC)

The larger-wheeled bike will be more gyro-stablilized. That doesn't mean it will be more stable -- gyro-stabilization is a fairly negligible contributor to keeping the bike upright. The more important number to look at is something called trail -- see the article Coneslayer pointed to. --Trovatore (talk) 20:50, 21 July 2008 (UTC)

A minor point to consider: IMO the moment of inertia should vary as r³, since we can probably assume the mass is concentrated at the circumference and the mass per unit length of the circumference is the same for both sizes of wheel. Therefore, m will vary linearly with r, so mr² will behave, to within the approximations, like r³, so the larger wheel wins by more. —Preceding unsigned comment added by 91.143.188.103 (talk) 15:43, 22 July 2008 (UTC)

If having bigger wheels is what makes a bike better, how come penny-farthings are so rare? — DanielLC 16:13, 22 July 2008 (UTC)

They've got other problems. --Carnildo (talk) 20:41, 22 July 2008 (UTC)

POPCORN EFFECTS ON INDIVIDUALS WITH TYPE 2 DIABETES, INSULIN DEPENDENT?

HELLO;

I'VE CANNOT FIND YES OR NO ANSWERS AS TO, HOW POPCORN EFFECTS TYPE 2 DIEBETICS. IS IT HEALTHY? —Preceding unsigned comment added by 68.10.6.240 (talk) 16:48, 21 July 2008 (UTC)

[Discussion removed]

Please do not ask for medical advice on the reference desk; consider talking to your doctor. --Random832 (contribs) 17:13, 24 July 2008 (UTC)

Fan blades and turbine blades

Why are fan blades and wind turbine blades generally very different shapes? Fan blades (such as from a desk fan) are frequently much larger and more "dish" shaped that turbine blades, which are usually thinner and more wing-like.

I would have thought that if both designs were aimed at maximizing efficiency, where efficiency is either most wind per Watt or most Watts per wind, that the two blades would look quite similar. No? — Sam 17:20, 21 July 2008 (UTC)

They are used in different ways. See turbine for more details about why they are shaped the way they are. Also, when your dealing with a desk-fan, the efficiency is much less important then a turbine. ---J.S (T/C/WRE) 17:33, 21 July 2008 (UTC)

There are two issues with "efficiency". In one case (a desk fan), the most efficient fan is the one which can be produced in mass quantities, very cheaply, and complete the job of moving enough air to make the user feel good. In a wind turbine, the most efficient turbine is the one which moves the most amount of air using the least amount of power (or produces the most amount power given some standard amount of wind). As such, a desk fan usually has blades that are cheaply cut out of sheet metal and cheaply formed into a scoop on a mechanical press. A turbine will use much better materials and designs. -- kainaw™ 17:37, 21 July 2008 (UTC)

Seeing as no one has explicity said it - a fan blade and a turbine blade that operate under the same conditions should/could be exactly the same shape.

Turbine blades may be thin because they operate under extreme conditions and so need to be flaw free.. making a continuous fan shape flaw free is harder than making a lot of smaller blades flaw free.

Also using a lot of blades allows the depth of the fan to be reduced - a continuous blade would have more depth - this may be important in enclosed things.

Interestingly the turbines in water generation plants are much more like fans than their counterparts in gas turbines/jet engines eg see Francis turbine, here you might be able to guess why a single piece turbine is favourable (or just easier) over a multibladed one. I particularily like these images: (Note however that this type of turbine does have linear flow, it's centrifugal..)87.102.86.73 (talk) 18:51, 21 July 2008 (UTC)

Note that the OP is asking specifically about wind turbines, not turbines in general. -- Coneslayer (talk) 18:58, 21 July 2008 (UTC)

Oh in that case one of the factors is also that in a fan the air is started from almost zero velocity, and it doesn't have to surive high winds.. Also such a fan could not have the pitch of the blades easily altered. For a wind turbine the opposite is true - the air/wind can be many speeds and so it is useful if the pitch of the blades can be altered - this is easier with narrow blades, it is still possible with thicker blades - but these will also cause more force on the turbine support in high wind - there's a safe limit at how much sideways force can be put up with on the turbine support.

I think it's easier to see why a typical fan would be totallly unsuitable for high winds, rather than explaining exactly why the wind turbines have blades of a certain dimension.87.102.86.73 (talk) 19:11, 21 July 2008 (UTC)

Fan blades are not the shape they are just because the shape is cheap to make. Aerodynamic studies in the 1930s, for starters, led to redesign to reduce the noise they made. The basic shape of the individual blades was altered and noise was reduced. I am sure that the science of fan making has continued apace to get the most air moved as quietly as possible for the least energy charge, beside the cost of fabrication. Edison (talk) 19:12, 21 July 2008 (UTC)

Also the long thin shape of wind turbine blades is less succeptable to cross winds than and smaller thicker design. And house fans need to be compact, so a long thin design is impractable.87.102.86.73 (talk) 19:41, 21 July 2008 (UTC)

Thank you all very much for the great answers! Here's what I'm taking away, correct me if I've misunderstood: Under the exact same conditions, what would be efficient for a fan would also be efficient for a wind turbine. However, 1) The conditions are not the same, and 2) efficiency is not the only factor, and is of much lower importance for desk fans than for turbines. — Sam 20:10, 22 July 2008 (UTC) —Preceding unsigned comment added by 63.138.152.238 (talk)

Recycling, is it a stupid thing to do?

I recently watched an episode of bullshit on recycling and they said it was more expensive and also more environmentally destructive, do you have any data about it? 88.203.106.28 (talk) 19:56, 21 July 2008 (UTC)

Did you look at the recycling article? It would be interesting to know what examples were given in the show you saw. Recycling#Criticism offers some examples of dubious benefits.

It's cost effective and more environmentally friendly to recycle aluminum cans to obtain aluminum than to mine and smelt aluminum ore to get the same material. Same is true for paper; in fact paper mills recycle their own cuttings when trimming the sheets to size, because it's already paper, not wood pulp that needs mashing and bleaching. The list goes on; it's easier to get glass from other glass than to process raw sand to get glass. Generally, if you need a material and must either make it from raw materials (including the effort needed to mine the raw materials), it's environmentally and financially sound to get what you want from materials that have already been made.

Mind you, there are misguided environmental practices out there. Making ethanol from corn comes to mind as a particularly wasteful practice that consumes more energy than it produces. But that isn't really a recycling issue. ~Amatulić (talk) 20:04, 21 July 2008 (UTC)

Ethanol fuel energy balance shows disagreement. PrimeHunter (talk) 20:44, 21 July 2008 (UTC)

Yes, although the studies showing greater than 1:1 efficiency seem to rely on accounting tricks. Nevertheless, perhaps I should have said instead that corn is one of the least efficient sources of ethanol compared to other sources. ~Amatulić (talk) 21:30, 21 July 2008 (UTC)

My favorite criticism is that corn-based ethanol policies are mass-murdering with intent that borders on genocide. But hey, that's just me. I'll get off this soap box now. Plasticup ^T/C 16:33, 22 July 2008 (UTC)

I'd say it would depend on what is being recycled and how. Probably the most efficient recycling is composting rotten food to make good soil. All that is required here is to separate out the rotten food, dump it in a pit, and leave it to rot. There are some other things that can be done to speed up the process, like introducing bacteria, worms, and water, stirring the contents periodically, and venting off gases to keep it cool. Since the methane recovered also has value, this can all be done quite cheaply. The least efficienct recycling may be on small electronic devices which must be manually broken down into different components and separated, at great cost, only to produce tiny quantities of reusable material. StuRat (talk) 21:21, 21 July 2008 (UTC)

Of the 3Rs of environmentalism recycling is the least desirable. Reduce, Reuse and THEN Recycle. ---J.S (T/C/WRE) 21:27, 21 July 2008 (UTC)

I've read that recycling glass actually does not work out to have an environmental benefit. I can't back that up with science or citations, but I find it plausible. Apparently you need the same amount of energy to remelt glass as you do to make it. Then you have to add in sorting out the trash that comes in with the recycling and the fuel for the truck that drives around to every house picking it up. Of course this neglects that fact that recycling diverts glass from landfills. ike9898 (talk) 22:06, 21 July 2008 (UTC)

Hmm, Glass recycling contradicts that, as do the sources it uses, and stuff like [2]. So well, meh. But it certainly can be the case that recycling can be uneconomic. I hear plastics recycling is supposed more dubious, though again I can't back that up with science or citations, but I find it plausible. ;) --Fangz (talk) 22:30, 21 July 2008 (UTC)

It does depend. Recycling glass in the process-engineering sense of recycling is a pretty fantastic thing to do, and one of the best examples is milk bottles if you've got a milkman. The bottles go round and round the system with only a little cleaning required, and this is efficient in terms of energy and raw materials, as well as avoiding sending waste to increasingly unavailable landfill. This is called 'reuse' in lay-speak. Generally 'reusing' things in this way is very good. If the glass has been seperated by colour, and you have someone willing to use the product, then melting broken glass down and making it into new things is also pretty good, but not nearly as good as just using jars and bottles again as jars and bottles. This is reusing the glass, but is referred to as 'recycling' in lay-speak. Not nearly so good is if you've been given a load of different types and colours of glass, some of it broken, and told to deal with it cheaply in a way that doesn't involve landfill. So you crush it down into aggragate and try to sell it to be used as decorative covering for the ground. This takes something which a lot of energy has gone into making into jars and bottles and turns out glass gravel. So these things all depend. 79.66.124.253 (talk) 17:17, 22 July 2008 (UTC)

Isn't that list supposed to be read in order anyway? Reduce THEN reuse THEN recycle. In other words you reduce usage whenever you can, what you can't you try to reuse and if you really can't reuse it then recycle it. Nil Einne (talk) 21:09, 26 July 2008 (UTC)

I wonder if instead of newspapers and bottles, it wouldn't be better to have curb-side recycling of items like batteries, and electronics, and fluorescent light bulbs. ie: Things are laden with chemicals we'd rather not have in landfills. APL (talk) 02:31, 22 July 2008 (UTC)

Here in Bermuda we aren't big enough to support our own recycling plant. We have to ship our recyclables across the Atlantic Ocean to foreign recycling plants. I really have to question whether it is worth it. Plasticup ^T/C 16:35, 22 July 2008 (UTC)

When figuring out the economic cost-benefit ratios of recycling one should remember to take into account the long-term costs involved with raw material extraction (mining, logging, etc). The costs involved are not only the short-term direct cost to the company doing the extraction, but long-term environmental costs. The latter costs are often ignored in cost-benefit calculations, but over time can, in many cases, grow to large amounts, and frequently after the company that did the extraction and environmental damage no longer exists or is bankrupt, leaving the costs to be paid for by the public. Aluminum is a great example. The cost of cleaning up bankrupt aluminum smelter sites in the US, paid for by taxpayers, is enormous. So don't forget to add such things to the cost side of calculation. Pfly (talk) 07:15, 23 July 2008 (UTC)

Lifecycle assessment is something we need an article on. Maybe next week... Another thing that's important to bear in mind is what you do with something if you don't recycle it. Certainly in the UK we are physically running out of landfill, so you have to find something to do with your waste. 79.66.124.253 (talk) 19:26, 23 July 2008 (UTC)

Usually, the way things work is that transporters use waste for recycling to take up empty cargo space on the return leg of their voyages. So it's usually not as bad as you think.--Fangz (talk) 18:10, 25 July 2008 (UTC)

Sugar water wine

Is it true that one can make wine out of refined sugar and water? I'm not supposing that the result would be any good, I'm just wondering if it would be wine.

Duomillia (talk) 20:30, 21 July 2008 (UTC)

In my view, no, because it's not made from fruit. (I don't consider sake to be wine, either.) But it's all in how you use the word, I suppose. --Trovatore (talk) 20:32, 21 July 2008 (UTC)

Not just those two things, no. There needs to be some yeast or other microbes to digest the sugar, and they will need more than just sugar and water to live on, as they can't grow and reproduce without a few other things. Then there is always the question of whether an alcoholic beverage qualifies as "wine" or not. StuRat (talk) 21:11, 21 July 2008 (UTC)

I assume the OP assumed the use of yeast. The answer is yes, you can make a semblace of "wine" from sugar water and yeast. Try it. That's basically how rum starts out. Or mead in the case of fermenting honey and water. In most western countries it wouldn't qualify as a "wine" but in other countries such as China, the term "wine" has much broader application, and your fermented sugar water would qualify. ~Amatulić (talk) 21:17, 21 July 2008 (UTC)

If it was relatively pure sugar and water, the yeast would peter out very quickly. They certainly need a nitrogen source and some trace minerals. There would be a little of these carried over in the yeast innoculum, but not enough. ike9898 (talk) 22:02, 21 July 2008 (UTC)

Perhaps not enough to ferment the wine to completion, but enough to make an unstable, low alcohol sugary wine, yes. If the use of the word "wine" is not legally regulated in your jurisdiction to require the use of grapes (EU). Rmhermen (talk) 23:00, 21 July 2008 (UTC)

There's a traditional Finnish alcoholic beverage called kilju that's made with sugar, water and yeast, manufactured mostly by teenagers (in secret, naturally) and serious-minded career drinkers conscious of the constant economic pressures they face. Copious vomiting and crapping yourself are only some of the benefits bestowed by this wonderful drink that is usually miraculously foul-tasting. I heartily recommend it to any and all who feel that there just isn't enough embarrassment and diarrhea in their lives. -- Captain Disdain (talk) 08:21, 22 July 2008 (UTC)

I remember something very similar though I couldn't possibly describe as 'wine'.87.102.86.73 (talk) 08:51, 22 July 2008 (UTC)

If it is of interest, we have an article on non-grape based wine. Plasticup ^T/C 16:28, 22 July 2008 (UTC)

Another question about wind farms

Current wind farms show a very small percentage (1%?) of the rotational area being used to generate energy at any time - is there a reason for this? (is noise a factor?)87.102.86.73 (talk) 20:59, 21 July 2008 (UTC)

Seems to me like 1% is about the ratio of blade area to rotational disc area. In that case, you may as well ask why airplane propellers use such a small fraction of the disc area for thrust? The answer is likely the same: the additional mass and drag from adding more blades has diminishing returns after a point. It's the aspect ratio of the blade that matters to get the most thrust for the least mass and drag. ~Amatulić (talk) 21:22, 21 July 2008 (UTC)

Lets play a mind-game... imagine the uselessness of a 100% ratio? ---J.S (T/C/WRE) 21:30, 21 July 2008 (UTC)

Depends on the application; a fanjet's thrust turbine uses 100% of the disc it occupies (i.e. when looking directly at the disc, there are almost no open spaces between the blades). Apparently a higher ratio can be efficient, and the efficiency may depend on the air speed required. Wind turbines and most airplane propellers are comparitively low speed, so mass and drag become important factors. ~Amatulić (talk) 21:33, 21 July 2008 (UTC)

J.S. : Ok, I'll play your mind game. Here is a photograph of a propeller that uses all 100% of it's circular disk area. [3] While far from ideal for this application, surely you're not suggesting that it would be worthless for power generation in a strong enough wind? APL (talk) 02:26, 22 July 2008 (UTC)

Similar to a thread above - don't confuse pushing air (or water in re the propeller) with drawing power from air. The two are not symmetrical operations. In the case of the pictured propeller, the Reynolds number will be dramatically different between air and water, so even operation as a propeller could not be expected as equivalent.

And in any case, I think (see thread approx. 1 month ago) that the primary consideration for space-filling on a wind turbine is the strength and cost of the bearings that have to support the load of the blades, and secondarily turbulence effects between the blades. Franamax (talk) 05:50, 22 July 2008 (UTC)

Plus cost of material used. And it would affect birds more than now. --Ayacop (talk) 07:42, 22 July 2008 (UTC)

We do of course have an article on this: Wind turbine design. See the Blade count section. --Heron (talk) 19:06, 22 July 2008 (UTC)

Thank you87.102.86.73 (talk)

Resolved

Charcoal

Can any organism use charcoal as a carbon or energy source? Assuming the answer is no, why not? ike9898 (talk) 21:58, 21 July 2008 (UTC)

Is there a natural source of it? That would be the first hurdle. --Tango (talk) 22:26, 21 July 2008 (UTC)

Cellular stuff usually involves absorbing something into the cell by osmosis. The insolubility of base carbon is likely unhelpful for that.--Fangz (talk) 22:49, 21 July 2008 (UTC)

Burned forests/shrub lands are an excellent source of charcoal. Certain plants are well adapted to growing post forest fire. Slash and burn agriculture is a perfect example of how charcoal can be used to enrich soils (though unusually done in an environmentally unfriendly manner). I can't think of anything of the top of my head that uses charcoal/hydrocarbons as a primary energy source, though if there are any, they would probably be one of those extremophile-bacteria types. 71.77.4.75 (talk) 01:29, 22 July 2008 (UTC)

Does charred wood from a forest fire count as charcoal? The key feature with producing charcoal is that it's done in the absence of oxygen. I would expect there's plenty of oxygen available during a forest fire, although I don't know for sure. --Tango (talk) 01:48, 22 July 2008 (UTC)

Yes, there would be a vast natural source of charcoal - forest fires. Within the fire zone and at the unburnt depth of any tree in the fire, there will be high heat and zero oxygen. Terra preta soil is enriched in charcoal (manmade) and provides high fertility, however the charcoal itself doesn't actually provide a source of either carbon or energy (since the carbon levels persist). Rather the charcoal provides a useful medium for growth of beneficial micro-organisms. Per Fangz, the problem would seem to be the insolubility of carbon in charcoal form. This is perhaps mirrored in the wide use that humans make of charcoal to filter everyting else, it is fairly inert. I don't know of any life form that can directly metabolize charcoal. Franamax (talk) 02:01, 22 July 2008 (UTC)

If you google for coal eating bacteria you'll get a lot of hits, I also remember an article where it was found that abandoned coal mines surprisingly released methane constantly due to those archaea. Of course, they would be able to digest charcoal, too, wouldn't they? --Ayacop (talk) 07:35, 22 July 2008 (UTC)

I am an organism, and I occasionally use charcoal to prepare my food. The process occurs outside of my body, but is that relevant? Plasticup ^T/C 13:00, 22 July 2008 (UTC)

Cute, but I don't think that's what the OP is looking for. Technically, most of us use carbon as an "energy source" beyond our gas grills: think power plants. I think the OP wants to know what organisms break down elemental carbon as food. I think Ayacop got it with bacteria and archaea. --Shaggorama (talk) 14:35, 22 July 2008 (UTC)

Just to clarify, coal and charcoal are more than just carbon. Reading this news release tells me the bacteria are processing the complex molecules in coal, and not the carbon. In fact the (rather non-scientific) article implies they use oil as their nutrient source, and break down impurities as a side effect.-84user (talk) 15:29, 22 July 2008 (UTC)

OP here. It seems to me that insolubility is an unsatisfying answer. Some fungi do very well on insoluble cellulose; they enzymatically break it into soluble pieces. On a different subject, I think that microorganisms that can use petroleum as an energy source are known. Can anyone say anything about the carbon containing molecules in charcoal that would be relevant to their non-bioavailability? Thx ike9898 (talk) 17:32, 22 July 2008 (UTC)

But the ubiquity of cellulose in e.g. plant cell walls means there are strong evolutionary pressures to adapt methods of breaking it down. Carbon in charcoal, which I think is mostly in the form of graphite, is not so common. So the ability to break it down should be rare. Though as others have said, probably some bacteria do have that capability.--Fangz (talk) 23:30, 22 July 2008 (UTC)

July 22

vapour adsorption refrigeration system

i want detailed information regarding this non cinventional refrigeration system —Preceding unsigned comment added by 117.98.108.28 (talk) 01:19, 22 July 2008 (UTC)

Try googling "vapor adsorption refrigerator." I found this PDF which seems rather detailed [4] 71.77.4.75 (talk) 01:33, 22 July 2008 (UTC)

We have an article on this: Absorption refrigerator.

Atlant (talk) 12:56, 22 July 2008 (UTC)

The brightest question on the science desk!

One of the joys of having a young child is attempting to field their damnably simple questions. I've gone through the blue sky, the twinkling stars, how tires get made, and what that bug was doing to that other bug, but I'm stumped tonight. What is the most "apparently bright" thing to be seen in the world? We were experimenting with a magnifying glass on a clear sunny day and the question came up if the sun was the brightest thing in the world (yeah, I know, but if it's in the sky, it's part of the world as far as she's concerned...). Now, I don't want to get into quasars and absolute magnitude because that's not what she's looking for. Is there any light she could experience that is brighter than the sun on a clear day? Searches online come up with some interesting homemade flashlights, but they don't specify how bright they are compared to the sun. Matt Deres (talk) 01:26, 22 July 2008 (UTC)

The initial flash of light from a nuclear explosion? You may not want to *actually* show her that one, though... :) --Kurt Shaped Box (talk) 01:35, 22 July 2008 (UTC)

Since people sometimes use welder's helments to view solar eclipses, I'd guess a welding arc and the sun have similar brightness (not that I'd make any recommendations about how to view an eclipse, I'm no expert.) In both cases, UV light is a significant aspect of the problem. --Gerry Ashton (talk) 01:42, 22 July 2008 (UTC)

Some types of arc welding are a good deal brighter than the sun. But that probably doesn't help you, you're not likely to buy an arc welder just for this, and it's not really safe to 'experience' up close anyway.

I think there are some lights designed for film-making that are available pretty cheap that are brighter than the sun at close range. Actually, I'll bet that at close range many photographic flashes appear brighter than the sun. A photographic flash would at least have the virtue be easy and relatively safe to demonstrate. Might be seen as a cop-out, though. APL (talk) 02:20, 22 July 2008 (UTC)

Er, using common sense when it comes to "close range", of course. APL (talk) 02:32, 22 July 2008 (UTC)-

I'd go with a really powerful laser. The amount of light produced isn't all that much, certainly less than a nuclear flash, but if you point it straight at her eye, I imagine far more light would hit her retina than from a nuclear flash. I wouldn't demonstrate that one either, though! --Tango (talk) 01:45, 22 July 2008 (UTC)

Apparent brightness varies dramatically with distance. While our distance to the Sun won't vary all that much, I'd expect any rather bright light to appear brighter than the Sun if you put your eyeball right up to it (not recommended for those who wish to keep their vision). Some particularly bright lights would be search lights. A specific case is the spotlights pointing upwards from the Luxor casino in Las Vegas, which are bright enough to see from 275 miles away. I'd expect that your eyeball would explode from the heat if you put it right up to those lights. StuRat (talk) 01:47, 22 July 2008 (UTC)

Actually, apparent brightness does not vary at all with distance; see my post below. --Bowlhover (talk) 05:45, 22 July 2008 (UTC)

Apparent bightness/apparent luminosity sure does vary with distance, perhaps you were thinking of absolute brightness/absolute luminosity ? The reasons why apparent brightness decreases with distance are that the light spreads out, so that less of it hits your eye at larger distances, and that dust and other particles absorb more light the farther it travels. StuRat (talk) 14:27, 22 July 2008 (UTC)

I was referring to surface brightness, which is what most people mean when they discuss the brightness of a emitter or reflector. --Bowlhover (talk) 08:12, 24 July 2008 (UTC)

Ok, that concept is that the brightness of any given apparent area stays the same, regardless of distance. However, as the total apparent area increases, the total apparent brightness of an object increases (when the distance is reduced). They also seem to have assumed there are no particles to absorb the light, which is a valid approximation in some regions in space, but never valid when looking through the atmosphere (the more atmosphere you look through, the more light will be blocked). So, in short, this method doesn't apply to the question, which was about the total apparent brightness of objects on Earth. StuRat (talk) 13:10, 24 July 2008 (UTC)

All the examples above will suffice as more "apparently bright". Are you just talking visually bright? You might explain spectrum and point out how the sun can burn every part of your body within about 15 minutes - that's pretty hard to beat.

And when you're talking about what's brighter - I hope and am absolutely sure you've explained that we never, never look right at the sun to see how bright it is. The brightness of the sun itself is already past the scale where you only see how bright it is once, so that's the very most important lesson. I'm sure you've explained that, it's worth saying again!

And that said, as far as a light source where you can see ambient light, unlike a laser (any of which can also easily destroy your vision if viewed directly, but cast no ambient light) - an arc-welding flare is a good demonstration of a very bright light cast all around (again, never look at the arc!) and is impressive indoors; a film-projector bulb; a spotlight. Now take anyone of those, look near them in broad daylight - do you see a difference? Likely not. The sun pretty much rules them all.signed byFranamax (talk) 02:56, 22 July 2008 (UTC)

When we were kids, and there were no adults around, we regularly competed to see who could stare at the sun for longest. I have never had any resulting eye problems - I'm already in old age - and wonder whether there is some protective mechanism at work? I think the taboo is wrapped up in a myth that deserves closer scrutiny. 196.2.124.253 (talk) 19:56, 28 July 2008 (UTC)

Lightning flash possibly? I know from experience that burning magnesium wire outdoors (so my eyes were already light adjusted) can be bright enough that I can't look at it directly. 71.77.4.75 (talk) 02:33, 22 July 2008 (UTC)

Those are both good, but if we agree that the sun is bright enough that we can't look at it directly, I interpret this question as "what makes other things look brighter than they do in broad daylight?" Perhaps the best test of this then would be - will this other light source cast a shadow behind something in broad daylight? So if I shine the searchlight or burn the magnesium on one side of a car, without (!) looking at the light source, but just looking at the car, at noon on a clear day, will I see a shadow being cast? Is that a realistic criterion? Franamax (talk) 03:07, 22 July 2008 (UTC)

That makes sense but again distance seems to make it more complicated. I don't remember the shadows clearly but I am pretty sure the light from the burning magnesium was powerful enough at close range to overpower a shadow cast by the sun in broad daylight. I tried to find some videos of burning magnesium in broad daylight. Here is a video of a small ribbon burning (it's enough to cause the auto brightness-senser of the camera to dim). Here is a contains-mild-swearing video of a bunch of adventurous gentlemen burning quite a bit of magnesium in an outdoor oven in midday. 71.77.4.75 (talk) 03:32, 22 July 2008 (UTC)

My thing is not "does it fill in the sun-shadow?", it's more like "does it cast a shadow the other way?" - but we may be talking about the same thing. There's no indication of that in the video by the league of gentleman adventurers, but they missed out on the fact that piping a feed of pure oxygen into the centre of their little pyro-fest would have dramatically enhanced it. If they'd used a little pure O2 in fact, they might have been able to incorporate ambulances into the footage :)

You're right about distance, as are all the above - but the OP is looking for answers for his little girl, and has ruled out distance via quasars not being applicable (and I'd say gamma ray bursters anyway). However I'd say Mg in O2, arc welding and possibly plasma torch welding would be the most accessible real-life demonstrations of comparable light sources. Now compare that with the fact that from 93 million miles away it takes the Sun a half hour to send you to bed feeling bad all over. (Leaving aside nuclear devices, which are best left unexplained until after the talk about sex - at least you can give a realistic reason for the purpose of sex) Franamax (talk) 05:20, 22 July 2008 (UTC)

I don't understand the need to be secretive about the purpose of nuclear weapons. People sometimes don't like each other and they fight to kill. I certainly knew that years before I was taught the details of sex. --Bowlhover (talk) 06:52, 22 July 2008 (UTC)

Just on the surface, that's a difficult subject for a child - 'cause the natural next question is "will someone try to kill me?". But you miss the major benefit of nuclear weapons - it's not to kill, it's to cause massive numbers of hideously wounded casualties, which tie down the resources of the defending power. Sit your young child down and read her Hiroshima by John Hersey. Explain to her how a fallout cloud would make her own hair fall out and how long it would take 'til she started vomiting and trace out on her face where the flesh would be melted to the bone. Were you taught those details when you were seven years old? Franamax (talk) 07:22, 22 July 2008 (UTC)

I never claimed that every single detail about nuclear weapons should be taught to a seven-year-old. In fact, most educated adults don't know how long it would take for nuclear bombs to cause vomiting or exactly where a person's flesh would be melted to the bone. Telling a child that nuclear weapons are used for war, or even that they waste the enemy's resources by killing civilians, requires none of the details you mention. And come on, "will someone try to kill me?" Any form of crime is more of a disconcerting topic than war unless the child's country happens to be in a nuclear war, and you can't possibly say parents don't or shouldn't inform children about crime.

Besides, the major benefit of nuclear weapons isn't forcing the enemy to provide disaster relief. It's either intimidation, or destruction of the enemy's military, economy, AND civilian population, with a focus on the first. --Bowlhover (talk) 08:24, 22 July 2008 (UTC)

Just a note for any casual readers: Do not ever look directly at the Sun; do not ever look directly at a welding arc or plasma arc; do not ever look directly at a projection bulb, especially through a focussing lens; do not ever look at the direct output of a laser of any type; do not ever look at burning magnesium metal. Doing any of these for any significant length of time can cause permanent damage to your vision. In some cases, this can be as little as 1/10th of a second (in some cases less). Use appropriate eye protection. Read instructions, ask experts, take precautions. Don't try to experiment because of something you read on Wikipedia - please! Franamax (talk) 05:33, 22 July 2008 (UTC)

Note that looking at the Sun without optical aid rarely causes permanent eye damage (see Sun#Observation and_eye damage). Burning magnesium is, as I showed below, 1/29th as bright; it is also much smaller than the Sun in angular size. Since burning the metal is a common high school experiment and was done without goggles in my former school, I would be surprised if it's dangerous. --Bowlhover (talk) 06:52, 22 July 2008 (UTC)

It is dangerous, which is why you're told not to look at it directly. The thing is, looking at the sun or a magnesium flare will damage just a part of your retina each time, causing a small permenant area of blindness. Over time you can acquire more of these until it becomes noticable. Don't look directly at the sun, and don't look directly at burning magnesium. 79.66.124.253 (talk) 17:00, 22 July 2008 (UTC)

The brightest light source on Earth or elsewhere is the laser described here, which can output 10^22 watts per square centimetre for a tenth of a trillionth of a second.

The "brightness" of an object, by the most common understanding of the word, is the amount of light emitted per unit of angular area. As distance from a light source increases, both the light's intensity and the source's angular area decrease with the square of the distance. The result is that brightness, termed surface brightness in astronomy, does not depend on the amount of space between the source and the observer. The shadow test is thus inaccurate because it measures irradiation, not the power of light in one unit of angular area.

Burning magnesium is significantly dimmer than the surface of the Sun. According to its article, magnesium's combustion temperature is 2500 K. A calculation using the Stefan-Boltzmann law reveals the Sun's photosphere, at 5778 K, to be 29 times as bright. --Bowlhover (talk) 05:45, 22 July 2008 (UTC)

Part of the lessons of live, i think she was asking for this [5]. Mion (talk) 08:47, 22 July 2008 (UTC)

I guess the article discusss it but looking at the sun directly is usually does not cause permanent damage but can be particularly dangerous during an eclipse where the lack of ambient light means the pupil may not dilate sufficiently. It's also likely to be very dangerous if you have just be given something to dilate the pupil (causing mydriasis), e.g. as part of an eye test or have taken some drug (this includes atropine and amphetamines) or have a disease (e.g. Argyll Robertson pupils, Marcus Gunn pupil, Adie syndrome) or whatever resulting in the condition. All in all, while most people are probably not going to suffer damage from looking at the sun, it's still an incredibly bad idea IMHO. (Note that the reason looking at the sun is not usually dangerous is not because it isn't bright enough to cause damage, it most definitely is, but because your pupils constrict in the bright daylight so don't allow enough light in to cause permanent damage. Also bear in mind that your unlikely to know your eyes are being damaged until it's way too late.) As for burning magnesium, I don't know that much but our own article Magnesium says it's dangerous. My guess is that it can be dangerous particularly if you are close to it, it's a significant amount and lasts a long time. From what I can recall when I was in school, this tended to be a short experiment (under 10 seconds), was usually done by the teahcer (i.e. you were probably resonably far away) and wasn't a great quantity (=smallish flame) likely greatly reducing the risk of harm. I don't see the fact that it's 1/29 as bright as the sun if true as significant as I mentioned already the sun is already way bright enough to damage your eyes. Also from what I can tell the amount of UV light is important too. Nil Einne (talk) 13:29, 22 July 2008 (UTC)

Wow, lots of replies! Thanks guys. Nothing like a six year old's question to get the smart folks thinking. There's a couple of really good suggestions here. The 'cast a shadow' thing sounds like a good one to try, at least to explore the topic (which is probably more important than the answer, even there even is one). The one problem is that I'm not sure it's actually correct. Lots of things can cast opposing shadows on a clear day, even regular flashlights. Maybe I should ignore my own restriction above and try explaining the difference between apparent and absolute magnitude, etc. Less viscerally satisfying, but still good to know. And as for the questions above, she's already aware of her mortality and we've already stayed up a few nights having very impromptu discussions about it. We haven't talked about nuclear war, but she knows about soldiers and war, etc. at least in general, historical sort of sense (Remembrance Day and all). We haven't had an in-depth sex talk yet, but she knows mom and dad somehow put her together inside mom ;-). I try to answer questions on the level they're asked, but I've always felt that if she wants to know, it's my duty to inform her, even if its unpleasant or uncomfortable. Matt Deres (talk) 10:55, 22 July 2008 (UTC)

Going the other way, you can use the shadow trick to show that an incandescent light bulb is less bright than the sun. On a clear day, you can see the shadow of the filament of a (clear) incandescent light bulb even when the bulb is lit. (But a laser still has higher intensity than unfocused sunlght.) Your daughter is already aware that focused sunlight is more intense ("brighter") than unfocused sunlight. -Arch dude (talk) 13:07, 22 July 2008 (UTC)

I have no source for this, but I'd suggest the experience of a strobe light in the dark being the brightest light you could let your daughter safely experience. The contrast from low light to intense flash can be blinding: let her eyes adjust to the dark and give a sudden strobe flash, see what happens. The brightest man made light I can think of (short of a nuke) is the arc on a plasma torch, which can cause severe damage to the retina. --Shaggorama (talk) 14:31, 22 July 2008 (UTC)

Hi. As an aside question, how bright would say, the Hiroshima bomb be in apparent magnitude from say 10km? Thanks. ~AH1^(TCU) 18:34, 22 July 2008 (UTC)

Far too bright. The Trinity test was described as "lighting up the sky like the sun" from a distance of 150 miles. --Carnildo (talk) 21:26, 22 July 2008 (UTC)

Still, you'd probably be close enough to test for yourself whether you really *can* see the bone structure of your hands through your flesh in the light of the flash. In the seconds before your eyes stopped working permanently. --Kurt Shaped Box (talk) 21:32, 22 July 2008 (UTC)

So, how did a butterfly end up being named 'Common Gull'?

Cepora nerissa, FWIW. What's the deal with that, huh? --Kurt Shaped Box (talk) 02:28, 22 July 2008 (UTC)

Quite a few of the butterflies in the genus Cepora seem to include "gull" as part of their common name. [6] I bet the word "Gull" is being used in another sense, perhaps an obsolete definition, place name, or proper name. I tried looking up "cepora" and "nerissa" in latin and greek but came up blank. I thought of the word "Gules" used in heraldry for red but the butterflies of the genus seem to be mostly yellow or white. That still doesn't exclude the possibility of "Gull" being a corruption from another language. I'll think about it some more... 71.77.4.75 (talk) 02:56, 22 July 2008 (UTC)

I got a potential origin idea. From what I can make of using online translators, the word "gul" in Hindi either is or is the first syllable of the word for rose or flower (gulAba?). Someone fluent in Hindi please check me on this. These butterflies seem to be common in India so the connection between the Indian word for flower/rose and the butterfly makes a bit of sense. 71.77.4.75 (talk) 03:08, 22 July 2008 (UTC)

You might have more luck on the language desk, but among the several meanings of gull in the OED is an obsolete adjective meaning "yellow, pale", from the Old Norse (gul-r), Swedish and Danish (gul).--Shantavira|^{feed me} 06:33, 22 July 2008 (UTC)

Do We Reduced Brain Power (Energy Save Mode like a laptop)

When I was struggling to get to sleep last night a thought occured to me. My laptop has 'energy save' mode - and in order to maximise battery-life it does a variety of things, one of which is 'turn-off' some of the processing power (perhaps by only using one of the 'cores') - this prolongs battery-life and allows functioning it a less energy intensive rate. My question is this...Does the human-brain do this ever? Given a time of low-food intake would the brain start 'shutting down' non-essential processing so as to reduce energy use. Would your IQ drop if sufficiently starved of energy (not to the point of no energy of course)? And does the act of thinking consume much more energy than not thinking? E.g. If I sit trying to work out a complicated calculation in my head does it consume more energy than just sitting idly doing nothing? Sorry if this is a daft question but I was struggling to sleep and it then (of course) consumed my thoughts for a while. The thing i'm thinking is they say hunger affects concentration - is this because the brain is working in 'best battery performance' rather than 'best performance' mode (to use my laptop's setting selections)? 194.221.133.226 (talk) 08:07, 22 July 2008 (UTC)

Not knowing exactly how much calories is used by the brain I recall there is no Save Mode for brain activity---it's just that your consciousness varies. We know now better than the Hubbard propaganda that suggested the amount of activity coincides with consciousness or even IQ. Also, the brain gets always the most blood, i.e., when your brain starves the other organs were already starving for some time. Of course I'm simplifying with this but that's the picture. --Ayacop (talk) 09:15, 22 July 2008 (UTC)

Everything you said was correct. The brain does conserve energy during times of starvation (which can include diets), it does use a substantial part of the energy your body uses, and it does use more during mentally challenging activities (like spelling, in my case). StuRat (talk) 13:49, 22 July 2008 (UTC)

Also note that the "nonessential functions" the brain shuts down are sometimes essential after all, such as when operating a vehicle or heavy machinery, where "brain fog" can be fatal. StuRat (talk) 13:53, 22 July 2008 (UTC)

See also Hypoglycemia#Neuroglycopenic_manifestations. --Mark PEA (talk) 14:06, 22 July 2008 (UTC)

I've seen a ref (can't find it now) to the effect that intense mental activity actually increases the carbs burned by the body. I wonder if thermal imaging would show the brain running hotter when doing complicated calculations or memorization, recall, puzzle solving, and such pursuits, compared to just sitting and not thinking about much in particular or in light sleep? Edison (talk) 23:57, 22 July 2008 (UTC)

Not thermal imaging, no, because blood quickly removes the excess heat generated. However, there is a process where radioactive glucose is given to the patient and the more radioactive portions of the brain show where increased brain activity uses more glucose. (I don't think I'll be personally volunteering to have my brain irradiated, however.) StuRat (talk) 07:05, 23 July 2008 (UTC)

When performing a task, more calories are used by people who are less trained or have lower IQs, implying conscious thinking consumes energy. [7] As for energy save mode, metabolism is reduced during starvation, according to this extremely detailed study. --Bowlhover (talk) 08:31, 24 July 2008 (UTC)

I'd conclude from that that learning is what uses the most energy, specifically forming new neural pathways. The "experts" already know how to perform the task, so don't learn anything new by doing so. Those with lower IQ's may learn it, but soon forget and must therefore relearn each time. StuRat (talk) 13:37, 24 July 2008 (UTC)

Doesn't follow. Consider the opposite scenario where pathbuilding cost is much lower than the cost to travel even one 'hop' or a section of path, but costs nonzero time. It need not be that the pathbuilding is expensive: just that the routes *before the direct paths exist* involve more hops, and so are inefficient. DewiMorgan (talk) 16:56, 26 July 2008 (UTC)

Boiling Water at a different tempreture to its boiling point.

Is it possible to boil water at a tempreture of 60 degrees Celcius and if so,why?137.158.152.207 (talk) 08:43, 22 July 2008 (UTC) kirsty

Since I assume this is a homework question, read your textbook or handouts, and if necessary, Boiling_point#Saturation temperature and pressure. If you still don't understand, feel free to ask again and we'll explain. --Bowlhover (talk) 08:55, 22 July 2008 (UTC)

A look at phase diagrams may also be of interest. — Lomn 13:11, 22 July 2008 (UTC)

You can even boil water at room temp by putting it in a sealed syringe and pulling back on the plunger to lower the pressure. StuRat (talk) 13:44, 22 July 2008 (UTC)

I've never seen this demonstration, but I just found this video. It's pretty cool. [8] —Preceding unsigned comment added by APL (talk • contribs) 16:54, 22 July 2008 (UTC)

Is it definitely boiling, as opposed to just having air forced through it (from around the plunger, into the syringe)? --Allen (talk) 17:08, 22 July 2008 (UTC)

Never mind; apparently this works when the syringe is pointed down as well [9]. --Allen (talk) 17:19, 22 July 2008 (UTC)

Also look at how much gas volume is present when the plunger is pushed back in compared to how much gas bubbled when it was pulled back. DMacks (talk) 18:24, 22 July 2008 (UTC)

Good point. So why doesn't the water bubble due to air being forced through it? --Allen (talk) 03:37, 23 July 2008 (UTC)

Er? My observation suggests that air isn't being forced through it (i.e., it's actually boiling). DMacks (talk) 03:54, 23 July 2008 (UTC)

I'm just figuring that a good deal of air has to be getting around the syringe; otherwise they'd be creating a near-perfect vacuum in there, which I'd think one wouldn't be able to pull against so easily. --Allen (talk) 11:49, 23 July 2008 (UTC)

Normal air pressure is around 15 PSI, which would mean only 15 pounds to pull a one inch cross-sectional area syringe (a huge syringe) against a pure vacuum. StuRat (talk) 15:13, 23 July 2008 (UTC)

When the syringe barrel is pushed up, look at how much/little gas space there is: that's exactly how much air has leaked in during the experiment. Note that you cannot (even with a high-vacuum pump) get anything close to a "perfect" vacuum here. You will always have the vapor pressure of the water: as you try to reduce the pressure below the vapor pressure of water, the water vaporizes to keep the pressure at that point. That's exactly what boiling is:) DMacks (talk) 12:51, 23 July 2008 (UTC)

Good points again, both of you. Thanks. --Allen (talk) 15:39, 23 July 2008 (UTC)

You can apply a vacuum pump to a properly constructed container with room temperature water in it and the water boils when the pressure gets low enough. You can even make ice this way. But the oil will need to be changed afterwards. In the 1960's a man testing a prototype American space suit was exposed to near-vacuum in a vacuum chamber when an air hose came loose, and he said the last thing he remembered before blacking out was the strange sensation of the saliva on his tongue boiling. He survived when the chamber was quickly repressurized.(edited to re-add the text the browser windo ate. It oftern happens that I insert text, everything looks fine in the edit window, then when I hit save some of it disappears). Edison (talk) 20:29, 22 July 2008 (UTC)

Edison, your edit seems to be missing some text but I know what your talking about, it can be found in the articleHuman_adaptation_to_space#Unprotected effects. Jdrewitt (talk) 21:50, 22 July 2008 (UTC)

Yes, the article you cited describes the incident. I recently saw a documentary on TV which had the original film or video and audio of the incident. Edison (talk) 23:55, 22 July 2008 (UTC)

We got to see a demonstration of this in my chemistry class. He put a bell jar over a beaker of water and pumped out the air, and the water boiled. It wasn't as cool as the burning methane bubbles, but it was pretty cool. Black Carrot (talk) 05:34, 24 July 2008 (UTC)

Named storm in Atlantic crossing over into Pacific

I am wondering if (a) has the following happened, and (b) if so, how the storm naming has been handled.

Presume a named Tropical Storm or Hurricane has formed in the Atlantic Ocean and is either large enough in either strength or size to cross over the relatively small land mass of Central America and either stay a TS or re-form back into a TS once in the waters of the Pacific Ocean -- would it be given a new name? Thanks. --Jordan 1972 (talk) 18:11, 22 July 2008 (UTC)

Hi. Yes, it has happened. See List of Atlantic hurricanes#Atlantic-Eastern Pacific crossover storms. Sometimes they lose their old name if the old system dissapated, as with Hurricane Dean or Tropical Storm Arthur (2008), but sometimes hyphenation is the answer, for example Hurricane Fifi-Orlene. Thanks. ~AH1^(TCU) 18:29, 22 July 2008 (UTC)

Some say that Hurricane Hattie and Tropical Storms Simone, and Inga were all the same storm that moved from the Atlantic to the Pacific and back to the Atlantic. [10] In 1961 they didn't have the fancy sateliite images that we would like to confirm it, but it is possible. Our article on Hurricane Hattie-Simone is rather confused about the issue, and there don't seem to be any reliable sources confirming that the storm maintained its circulation. The WP:WikiProject Tropical cyclones is actually discussing that storm right now. Plasticup ^T/C 19:42, 24 July 2008 (UTC)

Aphasia only when alone? Or just refusing to talk to oneself?

If a person wants to say a sentence, but can't get the words out, when alone, but can when there is another person providing a stimulus, would this be aphasia, or would it just be a mental block against talking to oneself? In looking at the article on aphasia, it sounds like the disorder is mroe than just the ability to get words out, but on the other hand, intrapersonal communication implies that everyone talks to themselves - or at least has the physical capability to.

So, I guess what I'm getting at is, is aphasia only consistent speechlessness? Or, does there have to be more of a general language problem? Is it possible for a person to develop such a persistent mental block agsinst talking to oneself that they can't speak unless someone else is int he room? (It's just nice to know that it is normal to talk to myself :-) 209.244.187.155 (talk) 18:34, 22 July 2008 (UTC)

According to the article, aphasia is caused by brain damage, so it likely to be consistent. There are other conditions which may be relevant - for example there are children that will only talk to close family and friends and will go completely silent in public. I don't know what that's called, though. What you describe seems to be the opposite of that. --Tango (talk) 20:23, 22 July 2008 (UTC)

Reply to Tango: Selective mutism. --Mark PEA (talk) 23:07, 22 July 2008 (UTC)

Sorry, but we cannot speculate about medical diagnoses here at the Reference Desk, per the guidelines posted at the top of the page. You might wish to discuss this with your physician. Edison (talk) 20:25, 22 July 2008 (UTC)

Find me Alexander Selkirk's physician and I'll ask him. :-) I had read where this real life castaway, who inspired somewhat the story of Robinson Crusoe, had mostly lost the ability to speak after being stranded for 4 years with no human companionship, and wondered if this would have been possible because he simply didn't exercise that while alone. That's where this question came from.

Although, ironically, I found the man's name in the Crusoe article, and read that a fall from a cliff is mentioned (fromt he talk section), which implies if he did lose it, it may have been because of a physical injury after all, and not because of some inhibition agains ttalking to himself that had grown into an inhibition agaisnt speaking, period, unless in the presence of others.

I thought my query would be a little less convoluted without throwing the stuff about Selkirk in there, and Crusoe - especially since I mention I can talk to myself so don't have this problem - but I guess not. And who knows, maybe what I read about Selkirk having lost the ability to speak was wrong, anyway.

Though, now that I look at your answer, Edison, you probably *did* understand it wasn't my problem and that I can talk to myselrf (and do). And, I can understand, perhaps it is best you don't speculate on anyone's medical condition. I imagine the condition of someone 300 years ago would lead to a much higher degree of speculation than you'd ever want to do Wikipedia, even without the legal ramifications. :-)

(And, I should add, now looking at the article on Selkirk that is cited, what I'd heard about his losing his ability to talk may have been quite incorrect anyway.)209.244.30.221 (talk) 21:18, 22 July 2008 (UTC)

Rodent identification

I'm trying to figure out what rodent I just saw in our garage. It was likely a chipmunk, but it looked too large to be so (though the light was off, so it's difficult to tell). Does anyone know how I can find out what rodent species are native to Manitoba? 24.76.161.28 (talk) 19:39, 22 July 2008 (UTC)

http://canadianbiodiversity.mcgill.ca/english/species/mammals/rodentia.htm is a list of rodents found in Canada. Note that clicking on the name of a species usually gives you its distribution map. --Bowlhover (talk) 20:36, 22 July 2008 (UTC)

Heat and tiredness

Why does hot weather and high humidity always tire me out and make me irratable? —Preceding unsigned comment added by 79.76.157.37 (talk) 23:34, 22 July 2008 (UTC)

See Humidity#Effects on human body. PrimeHunter (talk) 23:46, 22 July 2008 (UTC)

I believe this is a protective mechanism. Your body detects that it's overheating, and lowers your metabolic rate to limit heat production to fight this. Lowering your metabolic rate will result in you being sluggish and tired. StuRat (talk) 06:52, 23 July 2008 (UTC)

Shouldn't it rather sweat than make tired? --Ayacop (talk) 16:14, 23 July 2008 (UTC)

Hi. No, that doesn't work when it's humid, as shown by the above link. Sweating usually cools you down by evaporating, but when it's that humid, the sweat can't eveporate, so it just sits there, making you feel hotter. Hope this helps. Thanks. ~AH1^(TCU) 16:34, 23 July 2008 (UTC)

You'll also sweat. Our bodies have multiple cooling methods. In an "emergency situation", it will use every mechanism at it's disposal to cool you down quickly. StuRat (talk) 01:26, 24 July 2008 (UTC)

July 23

Theory of subspace model

Search for help on theory of subspace model!

'System identification: theory for the user'(2nd edition, 1999) had introduced such theory about subspace model in section 10.4. However, I cannot get that book. If possiable, please help me in finding some materials about that. Your kind help will be appreciated sincerely. —Preceding unsigned comment added by Cjt1982818 (talk • contribs) 01:44, 23 July 2008 (UTC)

In the case of system identification, I'm guessing that a "subspace model" would refer to Dimensionality reduction. One example is Principal components analysis which projects experimental data onto a subspace of the "parameter space", making for simpler analysis. EverGreg (talk) 09:43, 23 July 2008 (UTC)

hamburger

Ground beef is called hamburger. What do you call ground horse meat, ground ham and all of the other ground meats? -- adaptron (talk) 04:19, 23 July 2008 (UTC)

Just ground meat or mince (outside North America). 81.174.226.229 (talk) 09:03, 23 July 2008 (UTC)

Isn't 'hamburger something to do with the German city/town of Hamburg? If I wasn't at work i'd research and get a definitive answer - as it stands I hope one of the two articles references it... 194.221.133.226 (talk) 09:28, 23 July 2008 (UTC)

Just checked the Hamburg article - it is to do with the place - see the 'cuisine' section (http://en.wikipedia.org/wiki/Hamburg#Cuisine) 194.221.133.226 (talk) 09:29, 23 July 2008 (UTC)

This is also mentioned in the article Hamburger, which you have already linked to, under Definition. Jdrewitt (talk) 11:59, 23 July 2008 (UTC)

Not everyone calls ground beef hamburger, though, as it can be used for other purposes, especially meatloaf and meatballs. --Russoc4 (talk) 13:09, 23 July 2008 (UTC)

I'd go further and ask: does anyone call ground/minced beef "Hamburger"? Fribbler (talk) 13:12, 23 July 2008 (UTC)

My mom calls it "hamburg" (Western Pennsylvania, USA). -- Coneslayer (talk) 13:13, 23 July 2008 (UTC)

I've never even known it could be a synonym. A hamburger for me is most likely the premade burger or perhaps the pattie but defintely not ground/mince meat. BTW, is ground ham actually common? Ground pork is but I've never heard of ground ham. Nil Einne (talk) 13:38, 23 July 2008 (UTC)

Presumably the people who named Hamburger Helper? AlmostReadytoFly (talk) 13:50, 23 July 2008 (UTC)

I believe they call it either hamburg or hamburger in Maine. Not in NY/NJ/CT though.--Russoc4 (talk) 13:56, 23 July 2008 (UTC)

"Hamburger" has no etymological connection to "ham". It was originally a "hamburger steak", i.e. a steak made the way people in Hamburg make them. Similarly a "frankfurter" is a sausage of the kind they make in Frankfurt. I suppose "hamburger" can then by extension mean meat sold as suitable for making a hamburger. Minced (ground) pork is called "sausagemeat" in the UK; if you wanted to make sausages at home it would be the thing to choose. Itsmejudith (talk) 14:00, 23 July 2008 (UTC)

Pork mince is available labelled as such in every supermarket I've seen. Sausagemeat contains other ingredients such as rusk. It's not easy to link products, but you can browse here to see. AlmostReadytoFly (talk) 14:08, 23 July 2008 (UTC)

"Two great nations separated by a common language?" It's hard to imagine sausage made of rusk. On the U.S. side of the pond it is "ground beef" in the store, and might become a hamburger, meatloaf, meatballs, sloppy joe, tacos, or lasagna. One would not list "hamburger" as an ingredient in any of these foods. The repeated findings of E coli or other pathogens in groundbeef made in giant meat processing plants, where intestine contents from one processing mishap may be mixed in with hundreds of other cows in a given serving of ground beef, makes me avoid steak tartare, which was quite tasty back in the day of beef being locally ground. Ive never heard "minced" applied to meat. "Mincemeat" in the U.S usually contains no meat, except perhaps for fat. Edison (talk) 16:20, 23 July 2008 (UTC)

Mincemeat in the UK no longer contains meat either (though it used to), but minced meat does since mincing = grinding AlmostReadytoFly (talk) 07:54, 24 July 2008 (UTC)

N.B. In case it wasn't obvious, I was refering to adaptron who asked about ground ham whice I've never heard of before Nil Einne (talk) 17:11, 23 July 2008 (UTC)

Unindent. Google finds thousands of entries for "ground ham". The few I checked were recipes using both ground ham and ground pork. Perhaps people grind their own ham at home - I can't remember ever seeing ground ham in the meat section. Although there is deviled ham. Rmhermen (talk) 18:05, 23 July 2008 (UTC)

Apparently it's used industrially [11] Nil Einne (talk) 18:46, 23 July 2008 (UTC)

And in ham salad (ground at home, in my experience). -- Coneslayer (talk) 19:02, 23 July 2008 (UTC)

Actually, AlmostReadyToFly, to me mincing certainly does not = grinding. In my idiolect, 'grinding' is pulverisation by crushing or friction, and not by cutting or tearing; something squashy like meat cannot be ground. I am of course aware that Americans talk of 'ground beef' but to me it can only be 'minced'. --ColinFine (talk) 18:52, 26 July 2008 (UTC)

science

What is the graph called that has all the scientific symbols on it?— —Preceding unsigned comment added by 203.202.70.133 (talk) 05:12, 23 July 2008 (UTC)

You'll have to be much more specific than that. What do the scientific symbols look like? Can you post a sample of the graph? What's the title? Where did you see it? --Bowlhover (talk) 05:43, 23 July 2008 (UTC)

(Winging it here) Periodic table? --Kurt Shaped Box (talk) 06:55, 23 July 2008 (UTC)

That was gonna be my guess also. I don't know why, but many of my students call any sort of organized display of information a "graph". DMacks (talk) 07:04, 23 July 2008 (UTC)

They're certainly graphics. I imagine many people either confuse the two words or treat them as synonyms. -- BenRG (talk) 10:51, 23 July 2008 (UTC)

Technically they're right to call it a graph (ie not incorrect).. if the answer was the periodic table..?87.102.86.73 (talk) 12:18, 23 July 2008 (UTC)

I suppose it's a bit like how if all you knew were horses, you'd refer to a Frisian cow as 'a fat, funny-shaped, black and white horse'. Or something. :) --Kurt Shaped Box (talk) 18:08, 23 July 2008 (UTC)

repetitive behavior

Is there any disorder besides autism or other disorders in the autism spectrum (like Asperger syndrome where the affected person exhibits a pattern of repetitive behavior, specially repetitive verbal behavior? —Preceding unsigned comment added by Mr.K. (talk • contribs) 09:30, 23 July 2008 (UTC)

OCD? Usually not verbal, though. -- Aeluwas (talk) 09:34, 23 July 2008 (UTC)

(ec) Schizophrenia can involve stereotyped speech patterns, as can Tourette Syndrome. Also see Echolalia for one specific type of verbal repetition. 12:53, 23 July 2008 (UTC)

Tourette syndrome? -- Coneslayer (talk) 12:51, 23 July 2008 (UTC)

Then there are those who repeatedly ask the same questions here, I wonder what medical disorder they have ? StuRat (talk) 15:06, 23 July 2008 (UTC)

(from Forgetfulness#Organic_causes - Alzheimer's, Amnesia, Dementia ?)87.102.86.73 (talk) 15:57, 23 July 2008 (UTC)

Concusion, and if you want to call it a condition, Nagging. --Shaggorama (talk) 06:23, 24 July 2008 (UTC)

Methotrexate in use for RA

Can it please be explained to me why Methotrexate is used alongside Folic Acid. My boyfriend has been prescribed 5mg of Methotrexate once per week, with 5mg of Folice Acid every other day of the week. How does the Folic Acid react with Methotrexate. What exactly does it do to help RA? thank you

Dawn Gardiner 88.109.199.248 (talk) 09:46, 23 July 2008 (UTC)

For those (like me) who couldn't guess what "RA" might be, it's rheumatoid arthritis. --Sean 13:07, 23 July 2008 (UTC)

Methotrexate is an antifolate drug. (I recommend reading these links) Reducing the amount of available folic acid is beneficial to patients with autoimmune diseases such as RA. However, we don't want to eliminate all folic acid as it is needed for cell division. So a supplement is given. This is a bit of a rushed introduction to a relatively complex topic but I hope it helps! Fribbler (talk) 14:06, 23 July 2008 (UTC)

Folic acid (or folinic acid) is commonly given with methotrexate to decrease methotrexate's gastrointestinal side effects. As Fribbler described above, one of methotrexate's actions is to impair the synthesis of folic acid, an important vitamin in DNA synthesis and cell division. The gastrointestinal side effects presumably result from methotrexate inhibiting cell division in the GI system, leading to irritation, burning, etc. Adding folic acid back into the system restores the ability of the stomach and intestines to regenerate cells efficiently, thus improving the side effect profile of the drug. --David Iberri (talk) 02:50, 26 July 2008 (UTC)

mostly water

Since the human body is made mostly of water, is it possible for one to melt, and how would this be achieved? 'cause I know this one girl and I swear when ever she phones me or touches me I start to melt. —Preceding unsigned comment added by 193.115.175.247 (talk) 12:28, 23 July 2008 (UTC)

You know that ice (solid water) melts at 0 °C and that your body is much warmer than that. Therefore, any water in your body is already "melted". Physically anyway:) DMacks (talk) 12:48, 23 July 2008 (UTC)

(Insert voice of favorite American sitcom dad.) Awww, how cute. You're not melting; I think you've got puppy love. Known in American slang as a "crush" nowadays. Probably among your first; or, at least you feel different about this girl than any other you've felt; hence you're unsure what that feeling of "melting" is.

While we can't give medical advice, I will say this - if my theory is correct, then the first thing you should do is ask how she feels when she talks to you. It's okay if one feels something and the other doesn't right away, because those feelings aren't what's going to last; feelings come and go. Keep maintaining the friendship, and remember that that friendship should be the key to your relationship. Find out what she likes, and do fun stuff together. Maybe it'll last,a nd maybe it won't. But, I know one thing. That feeling can be pretty intense. But, it's fun, too. Just don't go too fast with any girl, okay? The key to a girl you like is, would you still like her if you were both really old, bald, and incontinent. but, it's okay to have fun and think about this situation now; because those feelings are real. It's part of gorwing up.

Boy, that *did* sound like a sitcom, huh? :-) Yes, that's the way I talk, too.

Oh, and to the original question, for something to melt it has to be at a very high heating point. So, for skin and bones to literally melt, you'd have to be in a blast furnace or something. Yes, the body is mostly water, but the part that isn't is very solid and rugged.Somebody or his brother (talk) 12:56, 23 July 2008 (UTC)

P.S.: Feel free to show her this response if you struggle for a topic of conversation, or how to approach your puppy love. It may help you talk about and emphasize the friendship part and also be good for a laugh, perhaps. Good luck.Somebody or his brother (talk) 13:20, 23 July 2008 (UTC)

Rather, the proteins will denaturate on heating which won't make you very attractive. --Ayacop (talk) 16:09, 23 July 2008 (UTC)

The fat will melt. Wick effect has some interesting if potentially grusome discussion of the potential effects of such Nil Einne (talk) 16:47, 23 July 2008 (UTC)

It might be best to avoid being quite so poetic until after the first date - this isn't the renaissance, you might just scare her off! If the first date goes well, though, then go for it! --Tango (talk) 21:35, 23 July 2008 (UTC)

The human body is made mostly of water in the same general way as a water balloon is. Ever seen a water balloon melt? — DanielLC 17:10, 23 July 2008 (UTC)

"When your heart's on fire, you must realize, smoke gets in your eyes." Itsmejudith (talk) 17:11, 23 July 2008 (UTC)

Yes. Just this morning I took a water balloon out from the freezer and watched it melt. Nil Einne (talk) 18:44, 23 July 2008 (UTC)

Wht did you put a water balloon into your freezer, may I ask? --Bowlhover (talk) 01:49, 24 July 2008 (UTC)

Nil, clearly that was an ice balloon that melted into a water balloon. :) — Scientizzle 18:50, 23 July 2008 (UTC)

By the way, when all the water is removed, the human body turns into a cuboctahedron made of some sort of crumbly foam rubber or something. Then the aliens take over your ship and try to fly it back to their own galaxy. --Trovatore (talk) 02:01, 24 July 2008 (UTC)

Not so! You turn into a small pile of white powder, but adding water will make you OK again. And I have a reference to prove it! [12] 17:31, 26 July 2008 (UTC) —Preceding unsigned comment added by DewiMorgan (talk • contribs)

When in doubt, always seduce the best-looking alien. And speak ... quickly with ... odd pauses. Franamax (talk) 17:44, 26 July 2008 (UTC)

biochar

Is there a Wikipedia article or other online reference that shows the yield of biochar, bio-oil and syngas from various types of municipal organic waste such as sludge and bio-mass? —Preceding unsigned comment added by Adaptron (talk • contribs) 15:59, 23 July 2008 (UTC)

The relevant articles are gasification and pyrolysis though I can't find any figures there - it probably also depends on the exact process used - which you could be more specific about.

I'd recommend trying searching for 'waste gasification' or 'waste pyrolysis' as a start.87.102.86.73 (talk) 16:44, 23 July 2008 (UTC)

Temperature scales

What temperature scales other than Fahrenheit were in common use in what countries before adoption of celsius? --Random832 (contribs) 16:10, 23 July 2008 (UTC)

The Réaumur scale. Itsmejudith (talk) 16:17, 23 July 2008 (UTC)

I guess this isn't what you mean but Centigrade. You might also be interested in Temperature conversion Nil Einne (talk) 16:41, 23 July 2008 (UTC)

No temperature scale was in widespread use before the seventeenth century, but according to the thermometer article:

"In 1665 Christian Huygens suggested using the melting and boiling points of water as standards, and in 1694 Carlo Renaldini proposed using them as fixed points on a universal scale. In 1701 Isaac Newton proposed a scale of 12 degrees between the melting point of ice and body temperature. Finally in 1724 Daniel Gabriel Fahrenheit produced a temperature scale which now (slightly adjusted) bears his name."

A more detailed history can be found here. As for the countries that adopted these scales, the Delisle scale was used in Russia from 1738 on and the Reaumur scale was widely used in Europe, particularly in France, Germany, and Russia. --Bowlhover (talk) 22:12, 23 July 2008 (UTC)

physiology of respiratory system

How long humans can stay under water holding their breath? How long perl-collectors in Tahiti can hold their breath under water? What is the world record of holding the breath? Dimitar (medical student) —Preceding unsigned comment added by Velimir14 (talk • contribs) 16:40, 23 July 2008 (UTC)

According to this article the world record is 10 minutes 12 seconds. -- Mad031683 (talk) 17:10, 23 July 2008 (UTC)

Hi. Remember however, that techniques such as hyperventilation before diving can cause drowning, see shallow water blackout. Thanks. ~AH1^(TCU) 22:19, 23 July 2008 (UTC)

According to this Reuters article, the record for underwater breath holding, set by David Blaine, is 17 minutes and 4 seconds. The average time is 1 minute, according to http://www.news.harvard.edu/gazette/2005/10.13/01-divers.html. --Bowlhover (talk) 01:40, 24 July 2008 (UTC)

Water turns cloudy after boiling

Please help solve this mystery: water from a water filter turns slightly cloudy after boiling. The water is somewhat high in dissolved minerals. The filter is supposed to reduce a variety contaminants in the water, including lead. Before boiling, the filtered water is clear.

(Edited to add:) A simple experiment reveals that water from the source turns cloudy after boiling, filtered or not. —Preceding unsigned comment added by 96.245.76.192 (talk) 17:44, 23 July 2008 (UTC)

Could this not merely be lots and lots of tiny air bubbles? I know that the water from my hot tap sometimes comes out milky-white due to this. If I put some in a glass and leave it to settle, I can see the bubbles (quite slowly) rising to the top, with the water below clearing. --Kurt Shaped Box (talk) 18:44, 23 July 2008 (UTC)

I'm aware of that possibility, but this is not a case of it. Water from the tap is initially clear. It only turns slightly cloudy after boiling. Giving things time to settle doesn't change the cloudiness. --96.245.76.192 (talk) 23:31, 23 July 2008 (UTC)

Could it be water hardness coming out as a fine suspension after boiling - some sorts of hard water do this. Also are you sure it's not your heating device - have you tried boiling in a different thing - eg a very clean pan or dish?87.102.86.73 (talk) 19:05, 23 July 2008 (UTC)

Not likely to be the "heating device"—the cloudiness is observed after the water has been boiled in a glass kettle, which seems clean. Your hardness explanation seems more plausible. --96.245.76.192 (talk) 23:31, 23 July 2008 (UTC)

Sounds like carbonate hardness. If you have high levels of carbonate minerals in your water, boiling the water causes a portion of them to precipitate. My guess is that your water comes from a limestone aquifer. -- 128.104.112.147 (talk) 21:14, 23 July 2008 (UTC)

That seems plausible. So the cloudiness is dissolved calcium bicarbonate turning into calcium carbonate? --96.245.76.192 (talk) 23:31, 23 July 2008 (UTC)

Yes exactly, and if you live in a hard water area it's probably the answer. Wait a minute - your filter should remove this I think?87.102.86.73 (talk) 00:07, 24 July 2008 (UTC)

Salmons - polyphyletic or paraphyletic?

Given that the common name "salmon" does not correspond exactly with any taxonomical group, and that some "salmon" species are closer to trouts than to other "salmons", should the term "salmon" be considered as:

• a) a paraphyletic grouping
• b) a polyphiletic grouping
• c) a vernacular name with no corresponding taxonomical group (or groups)

Which of these would fit best? Thanks. Leptictidium (mt) 19:32, 23 July 2008 (UTC)

I believe that C is correct. "A" might be correct if it was determined that the common ancestor to the group was a salmon and that trout form a monophyetic group that could be pruned from the tree (see paraphyly). "B" would only be correct if the term salmon included multiple monophyletic groups separated by other groups and I don't think that's the case (hence my qualifier at the beginning). Matt Deres (talk) 20:01, 23 July 2008 (UTC)

[edit conflict] I'd say C. To determine whether the group was paraphyletic or polyphyletic, you'd have to know whether the most recent common ancestor of all salmon was called a salmon. My guess would be that we don't know exactly what fish that was, and that we certainly haven't thought to decide whether it was a "salmon" or a "trout". --Allen (talk) 20:08, 23 July 2008 (UTC)

I don't think that really makes sense <quote> It was shown, however, that the inclusion of ancestors in the classification leads to unavoidable logical inconsistencies</quote>

You should ignore that inconsistency.87.102.86.73 (talk) 20:22, 23 July 2008 (UTC)

(edit conflict) A:

I'd assume 'A' in the absense of contrary data.

In the absence of contrary data I'd assume salmon ie Salmonidae subfamily Salmoninae to be paraphyletic

Assuming all 'salmon' (Salmonidae) Salmoninae have a common ancestor (why not?) (additional - common ancestor should not have any descendants outside salmoninae prefereably) then the salmon are paraphyletic, if you describe a group 'salmon' minus trout etc then that group would be monophyletic - but there is no name for such a grouping currently.

In phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all the descendants of that ancestor.

B is wrong because all salmon are found in the same subfamily - if there were 'salmon' in a different family as well then B would be right.

C is wrong because all salmon are found in the group Salmoninae therefor there is a corresponding taxo-group (that is fairly narrow in its spread). —Preceding unsigned comment added by 87.102.86.73 (talk) 20:19, 23 July 2008 (UTC)

CORRECTION B could be right as well if the subfamilies Oncorhynchus and Salmo each have a common ancestor, and there is a common ancestor of the common ancestors which has descendants outside these two subfamilies..

How are we supposed to know? is there any 'educational material' associated with this question which may contain answers to this problem?

The question is unanswerable as is.87.102.86.73 (talk) 20:45, 23 July 2008 (UTC)

I don't follow you. What doesn't make sense? What are you quoting from? Why would I want to ignore an inconsistency? What do you mean by asking whether two groups have a common ancestor? (Any two cellular life forms on Earth have a common ancestor.) It seems like you might be assuming that "salmon" = Salmonidae, but I think the OP was referring to fish called salmon, not all members of Salmonidae. --Allen (talk) 22:12, 23 July 2008 (UTC)

Oops sorry - mistake I've corrected that (see above)

As to the other bit - what I'm saying is that the question doesn't give enough information for us to decide? even though it says

Quote: some "salmon" species are closer to trouts than to other "salmons"

I can't read enough into that to make a decision either way. I quoted from the articles Paraphyly and Paraphyly as well for the second quote. You might want to ignore an inconsistency if it's of the kind described by yourself above, since the question is not of an (possibly extinct) ancestors 'name'.

The paraphyly/polyphyly question is answer by finding the ancestors (A and B) of both groups (that's two ancestors) and seeing if those two ancestors are either

One or the other is an ancestor of the other (A of B , or , B of A), or their common ancestor (C) has no descendants (along a branch not going through A or B) that are separate from the two groups

Or that the two ancestors of the two branches of 'salmon' (A and B again) have an ancestor themselves (C) that has descendants that have evolved into a set of species going through a branch not including A or B.

Did I get that right after the correction to the name? Maybe I'm not reading enough into the statement at the beginning - if so what is it?87.102.86.73 (talk) 22:59, 23 July 2008 (UTC)

(obviously common ancestor means 'most recent common ancestor')87.102.86.73 (talk) 23:41, 23 July 2008 (UTC)

My interpretation was that the OP, by the word "salmon", meant neither Salmonidae nor Salmoninae. Rather, they just meant all those species that have the English word "salmon" in their common name. E.g. Chinook salmon would be a "salmon", while Biwa trout would be a "trout", even though they're both in the same genus of Salmoninae. That's why I said the answer was C: the common word "salmon" does not correspond to any taxonomic group. --Allen (talk) 23:48, 23 July 2008 (UTC)

I made that assumption too. I suppose it must be C then since I can't show either A or B from the info given, and it states something very similar in the question - I must have been trying to be 'too clever' - C.87.102.86.73 (talk) 07:17, 24 July 2008 (UTC)

I still don't see how C follows though: "Salmon" could have (from the information given) corresponded to say, a family of 'salmon' and another sub-family of 'salmon' (not closely related or necessarily in the same order etc),but with a 'sister' group consisting of 'trout' in the same family. This would have made C wrong as it did say 'corresponding group or groups'. Thank god it's not my exam.!87.102.86.73 (talk) 07:22, 24 July 2008 (UTC)

As far as I can see you'd need a time machine to answer this, or more information.87.102.86.73 (talk) 23:43, 23 July 2008 (UTC)

Nuclear Physics

Kindly please answer me why don't Bosons obey the 'Pauli Exclusion Principle'?Asim Chatterjee (talk) 20:04, 23 July 2008 (UTC)

Did you read the Pauli Exclusion Principle article? DMacks (talk) 20:08, 23 July 2008 (UTC)

Yes —Preceding unsigned comment added by Asim Chatterjee (talk • contribs) 20:10, 23 July 2008 (UTC)

Did its many paragraphs explaining the answer to your question in several different ways not suffice? DMacks (talk) 20:14, 23 July 2008 (UTC)

HEY! It didn't explain why - It just said they don't obey..87.102.86.73 (talk) 20:25, 23 July 2008 (UTC)

Sorry but it did not.I'll be immensely thankful to anyone who would like explain to me the answer in brief. —Preceding unsigned comment added by Asim Chatterjee (talk • contribs) 20:18, 23 July 2008 (UTC)

It is not perfectly explained therein. —Preceding unsigned comment added by Asim Chatterjee (talk • contribs) 20:51, 23 July 2008 (UTC)

In brief, the exclusion principle is a result of particles having anti-symmetric wave-functions. That means only fermions, not bosons, are subject to it.

Let's look at the PEP article: "According to the spin-statistics theorem, particles with integer spin occupy symmetric quantum states, and particles with half-integer spin occupy antisymmetric states". The math in the "Connection to quantum state symmetry" section starts from the antisymmetry property and leads to exclusion. You asked about bosons, which by definition are integer-spin particles, and therefore have symmetric wavefunctions. I'll try the same math, but with a symmetric wave-function: if there is symmetry, A(x,y) = A(y,x), which does not lead to a conclusion of A(x,x)=0. Therefore, there can be a non-zero chance that two such particles could both be in state x. DMacks (talk) 20:56, 23 July 2008 (UTC)

So why are The wave functions of a system of identical half-integer-spin .. (are)... anti-symmetric under exchange - what does this mean, are the 'particles' (fermions) distinguishable then? Is there a simple way to understand this?87.102.86.73 (talk) 21:05, 23 July 2008 (UTC) fuck it - i remembered I don't care87.102.86.73 (talk) 21:09, 23 July 2008 (UTC)

I'm not a quantum physicist, but I'll give you a stab at it, given my The Elegant Universe/A Brief History of Time/etc. inspired understanding. (With the hope that more knowledgeable people will correct/expand upon my misstatements.) The key point is that, if they have the same quantum numbers, particles are indistinguishable. An electron is an electron is an electron, and a photon is a photon is a photon (assuming identical energy, momentum, etc.). Given this, when you do all the fancy quantum mechanical calculations you have to take into account the possibility of exchange. That is, if we have electron 'A' over here and electron 'B' over there (metaphorically speaking), we have to write all the equations such that the equations still work if we'd have electron 'B' over here and electron 'A' over there (since the electrons aren't carrying little 'A' and 'B' labels). So why does this matter? Well, since electrons are Fermions, and thus carry spin 1/2, their wavefunctions are anti-symmetrical. This means that you can't write quantum mechanical equations where two electrons have the same quantum state - if you did, you'd find out that once you include the exchange terms, the terms cancel out and your probability density goes to zero, violating a whole slew of conservation laws. Bosons, on the other hand, have symmetric wavefunctions, on account of having integer spins. This means that the probability densities don't cancel when you include all the exchange terms, leaving you with a non-zero (i.e. possible) probability density. This means that almost an infinite number of bosons can have identical quantum numbers. (The articles Bose–Einstein statistics and Fermi–Dirac statistics may help to clarify.) So the surprising result is not that Bosons don't obey the exclusion principle, but that the equations for Fermions work out such that they do. (Again, not an expert - please correct where needed.) -- 128.104.112.147 (talk) 21:09, 23 July 2008 (UTC)

Yes -you didn't explain anything - ie you didn't answer the question at all- you just restated the result, and quoted some books. That is not an explanation.

Your explanation "..the terms cancel out and your probability density goes to zero..." may well be true when the two particles have spin +1/2 and -1/2 but what about the same situation with particles spin +1 and -1 ... as far as I can see the situation is the same.. maybe there is an explanation for this?87.102.86.73 (talk) —Preceding undated comment was added at 21:18, 23 July 2008 (UTC)

So what do I read to find out why W(x,y)=-W(y,x) (W represents wavefunction?) for fermions (I see that this can explain the exclusion principle).87.102.86.73 (talk) 21:37, 23 July 2008 (UTC)

That's the definition of antisymmetry. The spin statistics theorem article is pretty technical, but it links this site that might be more understandable.

It's just a technical way of saying that the wave-function (the mathematical description of a thing) of a half-integer-spin particle is antisymmetric ("half integer spin means that the phase change for a 360 degree rotation is -1") whereas an integer-spin particle's is symmetric ("[i]nteger spin means that the phase change for a 360 degree rotation is 1").

Consider the difference between a half-wave and a full-wave of the sine function: going from the start to the end of each of these shapes begins at zero and ends at zero and both start out by going "up" (increasing y values). However, one comes back to zero by going down whereas the other comes back to zero by going up. You wind up back where you started, but in one case you're now there going the same way you started and the other you're now going in the opposite direction from how you started. Thus, the symmetry of these two cases is different. These two cases are similar to integer vs half-integer spins: the number of half-waves corresponding to the particle.

Now, if two things are symmetric, you can exchange them easily, like the you and your reflection in a mirror (you and your reflection could swap places and nobody could detect that). If two things are anti-symmetric, the mirror image is not the same (it's the opposite, like a trick mirror or a simple microscope). You and the image are now distinguishable because you go in opposite ways (move a microscope slide to the left, and you see the image through the eyepiece move right, etc.).

Two things that are antisymmetric are always distinguishable (they never exist in completely the same state) because something about them is noticeably different. Two things that are completely the not distinguishable are symmetric (could be secretly swapped for one another).

So there we have it: antisymmetry implies distinguishability, which is the Pauli Exclusion Principle. Multiple bosons indeed can exist in identical states (Bose–Einstein condensates). DMacks (talk) 21:40, 23 July 2008 (UTC)

When you quote "..half integer spin means that the phase change for a 360 degree rotation is -1 .. [i]nteger spin means that the phase change for a 360 degree rotation is 1..." is that any more than restatement of

W(x,y)=-W(y,x) for half integer spin

W(x,y)=W(y,x) for integer spin

?

Also "360 rotation" - what is that - is it another way of saying swapping, or is there more to it? If so where can I read about the properties of things that change on undergoing a "360 rotation" and why they do it. Specifically those whose 'phase' changes sign upon 360 rotation (since the other seems trivial)? 87.102.86.73 (talk) 22:02, 23 July 2008 (UTC)

I thank you both whole-heartedly for helping me.Dmacks, I'll be ever grateful to you for answering me.Now it does not appear to me tough indeed to find out the reason.Thank you once again.117.201.97.128 (talk) 05:54, 24 July 2008 (UTC)

Thanks to yuu both.Both of you have done an immense favour to me.117.201.97.128 (talk) 05:56, 24 July 2008 (UTC)

is cortisone synthetic cortisol?

Is cortisone a patented form of cortisol? I understand the drug companies pushed cortisone because of that, is that true? Thanks Mathityahu (talk) 20:08, 23 July 2008 (UTC)

No. see cortisone and cortisol - the chemical structures and formulae are different.87.102.86.73 (talk) 20:28, 23 July 2008 (UTC)

I assume by 'patented' you mean 'trade name for' - perhaps you didn't - if so please expand.87.102.86.73 (talk) 20:29, 23 July 2008 (UTC)

You may be confusing cortisone with hydrocortisone; the latter is the name commonly given to synthetic cortisol. --David Iberri (talk) 02:40, 26 July 2008 (UTC)

July 24

Arctic flora?

Is rock samphire found anywhere in the Canadian Arctic, e.g. Nunavut?

Also, is there an English umbrella term or descriptor for plants like rock samphire and purple saxifrage, i.e. plants whose roots seem to grow through rock?

--Sonjaaa (talk) 04:29, 24 July 2008 (UTC)

Here[13] talks about survival food in parts of Canada including Nunavut. Part 2, found they are "seaside plants" (somewhere said related to carrots but can't find it again). Rock samphire includes culinary uses and it was known as "Crest Marine". Some common names could turn up here[14]. Julia Rossi (talk) 06:46, 24 July 2008 (UTC)

Sunglasses

When I wear my sunglasses, I notice two interesting effects. The first is that when I look at either the sky or my laptop screen, tipping my head to the side makes it brighter or darker. I know why that is--because my lenses are polarized, only waves at a certain angle get through. The second effect, though, is a mystery. Certain screens (calculators, parking meters, some cell phones, some iPods, etc.) appear all rainbow-y and the rear window of my car appears to be covered in dark splotches (not the other windows, though). I don't see how this could be a result of the polarization (though it may be and I'm just missing something), but I don't know what other property of my sunglasses could alter light in such strange ways. Explanations? Cherry Red Toenails (talk) 05:40, 24 July 2008 (UTC)

Read Polarized light#Polarization effects in everyday life. The effect you saw in your rear window should be present in all windows except the front windshield (polarized light reveals the stress pattern in tempered glass). Perhaps you're not looking at the proper angle. --Shaggorama (talk) 06:15, 24 July 2008 (UTC)

This is somewhat off the topic, but polarization + tipping your head while looking at your laptop and the sky, made me think of Haidinger's brush. Jkasd 06:32, 24 July 2008 (UTC)

As for the screens; LCD screens use polarized light as part of how they work. See Liquid crystal display. --Random832 (contribs) 13:15, 24 July 2008 (UTC)

Nano water

There is some product on the market called "nano water",claiming that it is made of "smaller water molecules" which can be more easily absorbed by human body. Well, aren't all molecules of some kind have excatly the same size? How come nano tech can change this without changing the chemical property of water?--218.103.243.132 (talk) 07:25, 24 July 2008 (UTC)

Bunk. Pure bunk. Don't even think of spending your hard-earned money even just to try it out. Have a read of this - more than you probably ever wanted to know about pseudoscientific water-related products. --Kurt Shaped Box (talk) 07:58, 24 July 2008 (UTC)

How would being more easily absorbed be beneficial anyhow? --Bowlhover (talk) 08:10, 24 July 2008 (UTC)

O₂ enriched water, tachion absorbing mouse pads, the pyramide effect and many other things are invented to earn money not to have an effect. If the water molecules would be 10% smaller than usual you would die very soon, because the folding of proteins is vitaly conected to hydrogen bridge bonds mediated by water molecules and the equilibrium constants for all reactions including this water would be significantly different. You have a similar effect if you drink heavy water upto a certain percentage no big problem, but than......--Stone (talk) 08:47, 24 July 2008 (UTC)

To be completely fair, from what I can find online, they're not saying they restructure or alter the molecules, but rather are [supposedly] breaking up "clusters" of molecules. --Random832 (contribs) 13:24, 24 July 2008 (UTC)

Nano water is one of the most shameful marketing idea. They just flush water pass through strong magnetic, neodymium type. The water will be ionized a little, which can reduce some scale problem in the hard water. Or some even believe the germs can be killed by that ions. And the ions in the water may make someone feel refreshment like some electric fan claimed the anion wind blow. But to say changing molecular shape of water is no science intelligent wording. And H2O is smallest unit of water which has been nano unit already. Always remind yourself one thing when talking about nano technology, most of them is related to solid matter, liquid may be emulsion only.......NINJAW —Preceding unsigned comment added by 124.120.205.180 (talk) 17:05, 24 July 2008 (UTC)

You may be interested in Penta Water. 81.132.215.251 (talk) 20:26, 24 July 2008 (UTC)

Can hydrogen peroxide destroy a man?

The other week someone told me of an industrial accident that one of their friends had witnessed a few years ago. Supposedly, a man at wherever this was meant to have happened was sprayed from head to toe with concentrated hydrogen peroxide from a leaky thingamajig. Within seconds, he 'simultaneously ignited, dissolved and exploded', leaving only his boots, a few unidentifiable chunks of flesh/bone and a pool of sizzling goop behind.

Tall tale, or a possible, genuine risk when handling H2O2? --Kurt Shaped Box (talk) 08:14, 24 July 2008 (UTC)

If you jump into a tank of H₂O₂ the organics are converted to CO₂ and the carbonate of the bones and all inorganic salts are oxidized but most of them are not very volatile, so you will have a layer of salts on the bttom of the container. This will take a little while to disolve the whole man, and the iron salts catalyse the destruction of H₂O₂. This is basically a good thing for a mythbusters test, because theoretically it is possible.--Stone (talk) 08:21, 24 July 2008 (UTC)

Thew youtube video Wasserstoffperoxid in Schweineblut gives a impression on how H₂O₂ reacts with the blood of a pig.--Stone (talk) 08:33, 24 July 2008 (UTC)

The hydrogen peroxide you buy in a drug store is only 3% concentration, and can still bubble when applied to a wound, so it's easy to see how 100% concentration would dissolve flesh entirely. StuRat (talk) 11:59, 24 July 2008 (UTC)

I'm skeptical about the speed of the process. Also don't forget that it's probably just the oxygen bubbling out of the H2O2 on the wound (catalyzed by substances on the wound) not the products of dissolving the body. Finally, expect bones to not react at all with H2O2. --Ayacop (talk) 14:13, 24 July 2008 (UTC)

Ayacop beat me to it. H2O2 sizzles on a wound because of the catalytic effect of hemoglobin, which is the same reason H2O2 is used in forensics to find blood. And the visible bubbles isn't any evidence of solvency as StuRat suggested, the H2O2 is just being broken down into water and oxygen gas. On unbroken skin, store concentration H2O2 does zilch. I can believe getting burns from the stuff though if a high concentration was sprayed on you: H2O2 is relatively unstable, so if a high concentration was sprayed out at a high pressure, O2 might rapidly evolve and if there was an ignition source nearby, could cause a fire. If the H2O2 was on someone, then the fire could be localized to the surface of their body. I vote for calling mythbusters. --Shaggorama (talk) 14:22, 24 July 2008 (UTC)

Not quite zilch (3% H2O2 on unbroken skin); if you get it on your skin and leave it there you're likely to get a little white spot, sort of a burn I guess you'd say, but it doesn't usually hurt. With 30% the burn looks the same, but does hurt. --Trovatore (talk) 17:58, 24 July 2008 (UTC)

I once soaked my feet in some 3% H₂0₂, and I only felt a slight tingle at first. Then a type of slow burn set in, and they were in pain for days afterwards. The stuff's a lot nastier than it would seem. StuRat (talk) 02:59, 25 July 2008 (UTC)

I agree with the above. Oxygen fires can be pretty nasty things. shoy (reactions) 16:05, 24 July 2008 (UTC)

Why would it leave his boots, but not his skin, which are both made of the same stuff? Also, anything you hear that your friend's friend saw is probably wrong. — DanielLC 15:08, 24 July 2008 (UTC)

Concentration of H2O2 in industrial application is about 35%only, there is a note that if more than 65%concentration will be dangerous for fire and explosion matter (but never found in industry). It also dosed with some kind of retarder to slow down its O2 releasing. To activate it, staffs in factory may adjust pH. U can see details of danger from website link below:

http://www.h2o2.com/intro/MSDS_35_Arkema.pdf

If someone got spraying of concentrated H2O2 (which available in the market) on him, the problems occured with him will be as below cautions:-

DANGER!CAUSES EYE BURNS. MAY CAUSE BLINDNESS.CAUSES SKIN BURNS.CAUSES RESPIRATORY TRACT BURNS.HARMFUL IF SWALLOWED.STRONG OXIDIZER.

Something, which may cause body dissolving, should be strong acid or base most likely...........NINJAW —Preceding unsigned comment added by 124.120.205.180 (talk) 16:49, 24 July 2008 (UTC)

Can someone search the MythBusters forum? When I get back to a computer with Flash I plan on submitting this. Those guys are geeky enough that they might like the Wikipedia angle. Plasticup ^T/C 17:51, 24 July 2008 (UTC)

ANNOUNCEMENT: I now have further clarification from my associate. The substance in question was apparently High test peroxide for military use and the accident occurred while the stuff was being transferred from a tanker. --Kurt Shaped Box (talk) 00:19, 25 July 2008 (UTC)

Helicopter: blades vs. turbine

Why do all helicopter (at least the ones that I have seen so far) have blades? Couldn"t we build a helicopter with a turbine in the middle? (and perhaps some other minor turbines for controlling the balance). —Preceding unsigned comment added by Mr.K. (talk • contribs) 10:32, 24 July 2008 (UTC)

Are you talking about blowing the air through the center of the helicopter instead of around the sides ? If so, that sounds like a less useful design in that the space for passengers and cargo would be reduced and in a weird hollow cylinder shape. You could also put two turbines on opposite sides, mounted on wings, to get something like the V-22 Osprey. StuRat (talk) 11:46, 24 July 2008 (UTC)

I think he means that blades vs turbine so to say V-22 Osprey vs Dornier Do 31. And he is right if you substitute the blades by a jet engine and make them turnable you get a Vertical Take-Off and Landing aircraft. I do not recognize any jet engine driven Helicopter which neglegted the posibility to turn the exhaust of the jet around to convert itself to a jet airplane.--Stone (talk) 12:22, 24 July 2008 (UTC)

Ultimately, the "why" is a matter of efficiency. As noted near the top of our helicopter article, "The lift from the rotor also allows the helicopter to hover... more efficiently than other forms of vertical takeoff and landing (VTOL) aircraft." The advantages posed by VTOL turbines do not offset this fundamental deficiency for the roles that helicopters fill. There was a related discussion about why we don't make similar aircraft designs some time ago. — Lomn 13:59, 24 July 2008 (UTC)

Lunar Landing Research Vehicle sounds like an example of what you're talking about. There are a number of problems with this arrangement, the big ones being safety (a helicopter can autorotate if the engine fails, while an LLRV can't) and fuel consumption (the LLRV can fly for ten minutes on a thousand pounds of fuel). --Carnildo (talk) 22:04, 24 July 2008 (UTC)

The efficiency problem is due to the size of the turbofans. They are naturally smaller than a big rotor, and a big rotor is more efficient. The turbofans do have advantages over rotors though. They have a higher thrust to weight ratio than a rotor of the same size. They can be vectored easily so they can turn the VTOL into a jet airplane which means much higher velocities compared to helicopters. Since the fans can be vectored, it also means greater manuverability than either a helicopter or airplane. Eliminates the exposed rotor which can accidentally strike something when landing. It means you can land in less open areas than a helicopter. You basically get the best of both airplanes and helicopters, and even some additional advantages depending on the design. But until there are some major innovatinos in energy sources, main rotors will be used because fuel efficiency is a priority. ScienceApe (talk) 19:34, 25 July 2008 (UTC)

Several dozen at least ?

how many atoms are there in the universe? —Preceding unsigned comment added by 218.186.12.11 (talk) 12:58, 24 July 2008 (UTC)

You may be interested in Observable_universe#Matter_content. -- Coneslayer (talk) 13:25, 24 July 2008 (UTC)

Hi. On the other hand, if you want to know how many elements there are in the universe, see periodic table, but note that only 94 are found to be naturally occuring, of which 10 occur only from radioactive decay, and 118 in total if you count the synthetic elements up to ununoctium, some of the higher elements have never been sucesfully produced, and more than that if the purely theoretical elements (beyond ununoctium) are counted. Thanks. ~AH1^(TCU) 18:20, 24 July 2008 (UTC)

Whew AH, thanks indeed!  ;-) -hydnjo talk 02:36, 25 July 2008 (UTC)

Seeing colours where there are none

Sometimes when I stare at objects which have a high degree of repetitiveness I will soon start to see a rainbow of sparkling colours. This quickly gives me a headache. The objects involved are almost always white. A good example would be a very fine white mesh net. Or a piece of paper with many alternating thin black on white stripes. Is there a name for this optical illusion? PvT (talk) 14:28, 24 July 2008 (UTC)

It may be related to Fechner color; that requires motion, but perhaps the natural motions of your head are enough. -- Coneslayer (talk) 14:30, 24 July 2008 (UTC)

I don't think fechner colors explains this, although i'm not sure what does. My guesses are more along the lines of lateral inhibition, in which case you should take a look at the grid illusion and mach bands articles. You might also want to read McCollough effect. Another idea I had is that you might be staring so fixedly as to effectively kill the capacity of your eyes' saccadic motion to copmensate for hyperpolarization of cone cells. --Shaggorama (talk) 15:47, 24 July 2008 (UTC)

Well one thing is for sure that figure in the top right of the McCollough effect article sure induces rainbow fireworks in my brain. It almost becomes wavelike and the aftereffect lasts quite long. PvT (talk) 19:52, 24 July 2008 (UTC)

Quasers

According to the latest developments in the field of Radioastronomy, Quasers have been discovered. But along with their discovery, a question arises in my mind. It is well-known that light emitted from them is a bit reddish in colour. There can be two possible reasons for this, namely:-\ 1)The Doppler Effect 2)The Einstein-Shift Principle But if the first concept is right, then the Quasers must be very far away. Hence they are not present in our locality. This proves 'Steady-State Theory' wrong. But if the second concept is correct, then light from Quasers appear to be reddish because of being released from very powerful gravitational fields. This on the other side proves the Steady-State Theory right. Which is the more probable cause of this event, the Doppler effect or the Einstein-Shift? —Preceding unsigned comment added by Asim Chatterjee (talk • contribs) 14:42, 24 July 2008 (UTC)

You may want to read quasar (note spelling). Their discovery is hardly a new development, and it is well-established by this point that their redshift is cosmological in origin. -- Coneslayer (talk) 14:52, 24 July 2008 (UTC)

The lack of quasars "locally" is because their formation is a less common phenomenon than other stellar processes. In any given region of space, the chance of finding a quasar is low. Superpositioned with the weak anthropic principle, it's even less likely to have intelligent-life-sustaining planets near them. I don't see how the absence of a quasar "in our locality" proves or disproves a steady-state universe hypothesis. Nimur (talk) 15:05, 24 July 2008 (UTC)

The OP is saying that the existence of a cosmological redshift is incompatible with a steady-state theory of the universe. This is true, but it's also old news, and nobody has believed in a steady-state universe for decades. But in response to your statement, note also that the peak of quasar activity was a long time ago, at redshift 2.5–3. They really are much less common in the modern era (which is synonymous with the local universe, due to the finite speed of light) than they used to be. -- Coneslayer (talk) 15:15, 24 July 2008 (UTC)

You'll have redshift in any expanding universe and you can have an expanding steady state universe, it just requires the constant creation of matter (to fill in the gaps, so to speak). The lack of nearby quasars could disprove steady state if it was due to quasars only existing in the early universe (when we look far away we see the universe as it was long ago) - the early universe being different from the current universe is the exact opposite of what steady state is all about. I'm not sure that is the case with quasars, though, although I'm sure it has been theorised at some point. --Tango (talk) 01:41, 25 July 2008 (UTC)

I took "steady state universe" to mean non-expanding, as in Einstein's universe. Apparently, that's not what it means—I apologize for mixing up the names of discredited theories. Anyway, as I wrote above, the quasar population absolutely shows time evolution; there were more of them, and they were more luminous, at earlier redshifts. This has been known for decades, and is not merely something that people have theorized about. My PhD thesis involved measuring the faint end of the QSO luminosity function at redshift 3, so this is a topic with which I have some familiarity. -- Coneslayer (talk) 02:10, 25 July 2008 (UTC)

Building projects

Are systems engineers involved in large scale building projects along with civil engineers? If so, what do they do in such projects? Clover345 (talk) 17:46, 24 July 2008 (UTC)

Ah another Systems engineering question.. The answer is yes, thought they may not call themselves/be called 'systems engineers'.

More likely is this in large/very large projects such as building the channel tunnel or making a airport terminal, but also in design of warehousing etc - in fact anywhere where the building/construction is built for a specific purpose and needs to be designed to operate efficiently when built and also when the project is complex and requires a lot of management to be done safely/on time/etc...

So they may be managers or designers or both.87.102.86.73 (talk) 18:02, 24 July 2008 (UTC)

I find it difficult to understand the concept of systems engineering. To me it seems simply to be project management, which is an already well established field. Many engineers claim they have never heard of such a field as systems engineering. Clover345 (talk) 18:47, 24 July 2008 (UTC)

No, project management (as typically intended) is quite distinct. Management is the high-level application of administrative skills to a given project. Systems engineering is better described as the high-level application of technical skills. That said, I find that it's often an appendage of another engineering discipline. SE on a large construction project is likely better filled by someone with a civil or industrial engineering background as opposed to an electrical or computer engineering background. SE on a highly electronic project would reverse the preference. In any event the systems engineer is likely to be treating many highly-technical portions of the program, themselves complex programs in their own right, as something approaching black boxes that must themselves be engineered to function together. — Lomn 19:18, 24 July 2008 (UTC)

Yes, and No. I tend to feel that 'systems engineering' is/was just a new buzzword. It does include project management, as well as ... well , basically everything else. (I bit like how 'bin men' or 'garbage collectors' are now called 'waste management logistics operatives'.) - now everyone is a systems engineer.

Oh and a systems engineer could also be a 'designer' or just a truck driver .. at the basic level getting your truck into a depot without blocking all deliveries for the rest of the day or running anyone over, or not demolishing one of the supporting structures of the delivery bay can be described as a 'successful systems engineering procedure'.. (I might be exaggerating)

You could describe 'systems engineering' as a field of bullshit, nevertheless it is being beginning to be taught at some levels as a concept - so I might as well be respectful.87.102.86.73 (talk) 21:17, 24 July 2008 (UTC)

The above wasn't intended to be overly negative, systems engineering does give a framework to systematically study the behavior of complex multi-part things, especially useful to spot potential problems that might (in a less systematic study) only become apparent 'in the field' - nevertheless it does tend to result in a hell of a lot of paperwork, eg Systems_engineering_process,System of systems,System of systems engineering,Enterprise systems engineering, Systems thinking etc etc. which makes many people sigh at the vast number of fields that now have 'system' inserted into their name..87.102.86.73 (talk) 11:52, 25 July 2008 (UTC)

Pre Bigbang Theory

In the Pre Bigbang theory, it has been said that at the beggining of the creation of the Universe,only one superforce was there, which later split up into two forms i.e the Electronuclear force and the Gravitational Interaction. But the Electronuclear force also split up to form Electroweak force and Strong Interaction, the former of which further fragmented to generate Electromagnetic Force and the Weak Interaction. But even the Theory of Relativity can not answer what was before 10^-43 seconds of creations of the Universe, as we then need to face the Unexplainable Singularity. It is also said by Stefen W. Hawking that Bigbang will be followed by Bigcrunch, which will be the contraction of the universe to an unimaginably dense and small ball of energy floating in space. But this process will start only when the value of Ά (the Relative Density of the Universe) exceeds 1. But at the end of this process of contraction, will all the forces meet up to form the Cosmic Superforce again? And if they combine, will the unification of the forces take place just before 10^-43 seconds of the Bigcrunch? —Preceding unsigned comment added by Asim Chatterjee (talk • contribs) 19:04, 24 July 2008 (UTC)

Yes. I mean, you are missing some details and assuming certain theories to be true, but if there is a Big Crunch the Universe will experience conditions similar to those 10^-43 seconds after the Big Bang. Plasticup ^T/C 19:26, 24 July 2008 (UTC)

As noted at our Big Bang article, generally-accepted scientific theory does not reach as far as the singularity, much less prior to it. No real consensus about a theory of everything and a resultant "superforce" exists. As for Stephen Hawking's putative support of a Big Crunch, I find little evidence -- the Big Crunch is thought unlikely based on present understanding, though virtually all cosmologists acknowledge it as a possibility. Given all of this, no meaningful answer can be given to your questions. We don't know (or have significant confidence in a guess) if your scenario will occur at all, much less whether it will play out as you've indicated.

ec with User:Plasticup -- As noted at Big Crunch, a crunch is not a "bang-in-reverse". Additionally, even if final conditions closely resemble the initial conditions of the Bang, we don't know if said initial conditions are what Asim suggests above. — Lomn 19:32, 24 July 2008 (UTC)

Apothecary symbols

I am reading some early 19th century apothecary recipes and am stuck on one of the symbols. There are two consecutive underlined letter a's followed by the sign for one ounce. What do the underlined a's stand for? —Preceding unsigned comment added by Wityoungbod (talk • contribs) 19:28, 24 July 2008 (UTC)

Could it be referring to an Apothecaries' system Ounce. The symbol doesn't look the same, but I suspect things weren't particularly standard at the time Nil Einne (talk) 21:16, 24 July 2008 (UTC)

An image would help - or a link to the book? - could those a's be two s instead ? meaning half?87.102.86.73 (talk) 11:00, 25 July 2008 (UTC)

Is there any drug that does this?

Is there any drug that produces a feeling anything like orgasm or 'sexual pleasure'? 199.133.19.254 (talk) 19:50, 24 July 2008 (UTC)

Normally only orgasm is the result of genital excitement. However, there are many drugs that produce euphoria, but taking them would probably be illegal as you can't go to the doctor and say you want medicine for "euphoria". Such illegal drugs include opiates, amphetamines, cocaine, methamphetamine and MDMA (see Euphoria_(emotion)). 81.132.215.251 (talk) 20:22, 24 July 2008 (UTC)

Sure. Some anti-depressants, at least, have been known to produce spontaneous orgasms in women. There may well be other drugs that have similar effects, though I can't think of any off the top of my head. Also note that numerous recreational -- both legal and illegal -- drugs have an effect of increasing sexual desire and/or making sex more pleasurable; while they don't really produce orgasms in themselves, a bit of physical stimulation can go a long way while under their influence. -- Captain Disdain (talk) 20:32, 24 July 2008 (UTC)

Aphrodisiacs. Surprisingly, despite the commercials, Viagra has no effect on the brain. --Bowlhover (talk) 20:36, 24 July 2008 (UTC)

Clomipramine#Side_effects. --Allen (talk) 21:53, 24 July 2008 (UTC)

You don't need drugs to do this. Self hypnosis can make you fell exactly the way you want to feel. But I'm not sure it can induce orgasm. Any way, the feeling you get is better than orgasm and lasts longer! —Preceding unsigned comment added by 79.76.239.220 (talk) 02:35, 25 July 2008 (UTC)

July 25

Intellegent design...

Just looking at the human body alone, how much of it has evolved and how much was designed?I'm assuming the more complex organs like the eye and the brain were designed, and simpler ones like finger nails and the nose evolved naturally.... but I just dont get how a simple life form can have coplex organs like the aforementioned eye before the foot has had the time to evolve, or is it a case that an organism evolves to a certain level and then carefully designed components are added at different stages... I'm probably missing something obvious but your help would be appriciated, :)165.228.176.26 (talk) 06:49, 25 July 2008 (UTC)

As far as I can tell, you're the first to come up with the idea that some components are evolved and others designed. I think everyone else pretty much says either it's all evolved, or all designed. The empirical evidence supports the former view, with the latter simply being a strongly-held religious belief. - Nunh-huh 06:56, 25 July 2008 (UTC)

Well, fish have eyes (What do you call a fish with no eyes? a fsh), but they haven't evolved feet. Current consensus on the Timeline of evolution has it that animals in general have been around for much much longer than those with mammal-like feet. You don't exactly start from nothing and try to achieve feet and eyes at the same time.

Even if the eye couldn't evolve in the time for feet to evolve, would that matter? You would have blind things walking around for a while, while eyes gradually evolved. (N.B. This is not how it happened)

You might be interested in evolution of the eye, which explains how such a complex organ could evolve. The short answer is "from simpler ones", and this applies to all of the other organs too. AlmostReadytoFly (talk) 08:21, 25 July 2008 (UTC)

The problem of how the eye could develop through evolution is debated and explained by many evolutionary biologists, so there should be several texts on this online in addition to wikipedia, if you'r interested. The basic approach is to show that each step towards an eye increases evolutionary fitness. then one document through fossils or contemporary simple organisms that the intermediate steps indeed happened.

For instance, just being able to distinguish light from dark or the general direction of light would be an advantage for an organism and is indeed found in many of today's microscopic creatures.

As an apropos, Nunh-huh is wrong to say that you'r alone with the evolution+creation idea. Some creationists accept evolution-like phenomena within a species but denies that new species are ever created from old ones. EverGreg (talk) 08:30, 25 July 2008 (UTC)

Of course, that's not at all what I said. -Nunh-huh 09:17, 25 July 2008 (UTC)

Just greated an acount:) I was just using the foot as an example of something of a body part simple enough as to not necessatate design... I'll try to rephrase the question, basically I understand that parts of us evolve naturally but other parts are for to complex not to have had a designer, I'm just wondering at what stage the designed components were added? For example, back when we were just a basic blob of flesh eyes wouldn't have been much use without a brain to process the information, they would have been largely pointlessHypervalve (talk) 08:45, 25 July 2008 (UTC)

Well, first of all, a foot is a pretty complex body part. You've got circulation that brings in oxygen to the muscles, you've got the muscles themselves which make it move, you've got bones that support the foot (and the rest of the body) and cartilage that ties them together and allows them to move, you've got tendon that connects the muscles to the bones, you've got (in the cases of humans and many other, but not all species) toes that help with balancing yourself, you've got a lot of useful nerve endings that help you feel your way when you're barefoot, you've got skin that keeps out germs and regulates your body temperature by sweating... I mean, there's a lot of stuff down there that works together. It's not at all "simple". An eye does a lot of cool stuff too, but they're not that different in terms of complexity. It's not as if some simple organism in the primordial slime suddenly grew up, noticed that it had feet and then started walking around on land (presumably bumping into things a lot if it didn't have eyes yet). It doesn't work that way.

Secondly, I don't think we know exactly at what stage the various components were "added". We weren't around to observe, after all, though we can certainly make some educated guesses. You should bear in mind, though, that none of this happened overnight, and a lot of it happened "simultaneously", if you can use such a term when discussing events that took millions and millions of years. -- Captain Disdain (talk) 09:11, 25 July 2008 (UTC)

I'd recommend perusal of Evolutionary developmental biology, not just evolution. A very enlightening book 'Endless forms most beautiful' is referenced there. You'll be lead to understand homeoboxes, why they are important for development of limbs etc. and how and when they evolved (which can be measured exactly). None of these facts can be explained by intelligent design. --Ayacop (talk) 09:13, 25 July 2008 (UTC)

Is it the same as saying the body is a self-designing organism? Julia Rossi (talk) 09:38, 25 July 2008 (UTC)

As the body is 'just' the means of the DNA to survive, I'd rather say 'the DNA designs itself and the body to cope with and survive in the changing environment'. However, the process is influenced by random events (changing environment, mutation), and if you want to see this, too, as design, then there is no single design but the two mentioned, survival and chance (the latter of which you may want to connect to a god of your liking). --Ayacop (talk) 09:58, 25 July 2008 (UTC)

Hi, you wrote: "basically I understand that parts of us evolve naturally but other parts are for to complex not to have had a designer", which is based on the idea of irreducible complexity. This idea is not one which is accepted by most scientists working in the field of evolution. They would probably state "All parts of us evolved and continue to evolve naturally". AlmostReadytoFly (talk) 09:48, 25 July 2008 (UTC)

Evolving anatomical structures such as eyes, brains and feet is child's play compared to the biochemical processes such as the metabolic pathways, DNA replication and photosynthesis. The first half of the timeline of evolution is taken up with evolving these well adapted fundamental mechanisms. This is where the true complexity and wonder of life lies - compared to these processes, eyes, brains and feet are just the blinkenlights. Gandalf61 (talk) 09:42, 25 July 2008 (UTC)

Hi, you wrote: "parts are far too complex not to have had a designer", which leaves you with 3 choices for how such a designer was created:

1. He evolved from simpler forms
2. Another designer designed him
3. He's always been here

I suspect you might choose #3, but if you can accept that, why not just accept the simpler idea that eyes and feet have always been here? That's certainly more believable, since we can at least all agree that they're here now. --Sean 12:59, 25 July 2008 (UTC)

As has been pointed out above, all parts of the human body, and every living organism, has evolved, and has not been "designed" in any way or part. A good introduction to this topic if you're happy to read a book is The Blind Watchmaker which explains how the eye may have piecemeal evolved. The book may be tainted in your eyes by the author "coming out" as an atheist and practically starting the neo-atheist movement, but long before all that happened, and still, this book was considered a great neo-darwinistic introduction to evolutionary thinking. —Pengo 12:29, 26 July 2008 (UTC)

Evolution of dogs

Since many dog owners prefer dogs that react to them, including when they talk to their pets, or dogs that are more intelligent than their peers, is it too crazy to suppose than someday dogs will evolve into speaking beings?Mr.K. (talk) 08:45, 25 July 2008 (UTC)

Of course not -- provided that when you say "some day" you mean that you'd be willing to wait millions of years. (I'm sure you could shave some time off that figure by aggressively breeding for intelligence, which of course didn't happen to humans in nature.) There's no reason to believe that they couldn't evolve that way. Then again, that doesn't mean that they necessarily would. Intelligence is by no means a guaranteed result of evolution. But is it too crazy to think it might happen? Nah. (Oh, and speaking would also require some considerable changes in the shapes of their mouths, of course, but what the hell, that wouldn't be impossible either.) -- Captain Disdain (talk) 08:56, 25 July 2008 (UTC)

What about greyhounds? Since they're aggressively bred for speed is it reasonable to assume that on a long enough time line the would be able to travel at a rate approaching the speed of light? Hypervalve (talk) 09:00, 25 July 2008 (UTC)

Traveling at a rate approaching the speed of light is not possible on earth. Speaking mammals, on the other hand, do exit. Mr.K. (talk) 09:22, 25 July 2008 (UTC)

...but "thinking mammals" is an open-ended research problem ;-) --Stephan Schulz (talk)

Excuse me while I pull myself together after taking that the dogs are more intelligent that the owners' peers, but dogs do speak -- it's that we can't understand them. The question of whether they learn sign language like lab chimps, or articulate verbally so they sound like Prince Charles is another issue... I personally haven't learned to do either. Julia Rossi (talk) 09:30, 25 July 2008 (UTC)

Uh, no. No. There are all sorts of problems here. If we did have a super-evolved and super-fast greyhound that could go that fast, it would need tremendous amounts of energy in order to reach and maintain such a speed... and I don't mean an extra helping of Alpo, either. The dog would also pretty much explode right away; at speeds like that, hitting the atmosphere would be like hitting a wall. The dog would be a spectacular ball of fire that would cause horrible destruction. The sonic booms, from breaking the sound barrier, alone would wreak havoc. At those speeds, the kinetic energy from each paw hitting the ground alone would destroy both the dog and the ground. I mean, overall, the energies involved in something like that would be utterly ridiculous. (Let me put it this way: a Greyhound jumping up and running full tilt to the door to do some energetic barking when the doorbell rings would make Hiroshima look like a walk in the park...) -- Captain Disdain (talk) 09:39, 25 July 2008 (UTC)

So, if we scale things back a bit - would breeding a greyhound or whippet that could run faster than the speed of sound be in any way feasible in the extreme long term? --Kurt Shaped Box (talk) 09:57, 25 July 2008 (UTC)

Well -- if you'll allow me to wax pedantic for a moment -- in that case you wouldn't scale things back a bit, you would scale things back a lot. It's comparable the difference between a single drop of water and the Atlantic, kinda. But to answer the question... uh, I dunno. I don't think so. I can think of all sorts of problems with that, one of the key ones being the greyhound's method of propulsion -- that is to say, running. Running isn't terribly efficient at high speeds. A supersonic jet fighter has a jet engine, which doesn't require any friction with the ground; it just sucks in air and spits it out. Running, on the other hand, does; the dog needs to constantly be able to hit the ground with its legs in order to maintain or increase speed. There comes a point where it's no longer a question of whether the dog can move its legs fast enough, but whether any such movement is enough to counter air resistance instead of, say, just propelling the dog into the air. (This would be comparable to what can happen to high-powered F1 boats, for example.) I guess, if the dog were to evolve some kind of claws or something that could grab the ground and keep it anchored, that would help. Also, the mechanical stress of pumping its legs that fast would be tremendous; I think more likely than not, it'd start damaging itself pretty quickly, if not immediately. And, of course, that air resistance is no joke at those speeds: pushing through the sound barrier can be pretty harsh on the body. But, you know, given enough time? I guess a dog might -- I don't really believe this could happen, you understand, but hypothetically speaking, might -- evolve muscles and joints and bone and the claws and whatnot that could somehow support this sort of activity so the animal wouldn't just shake itself apart. (The paws would take an incredible beating. Each step would send a powerful physical shock through the animal's body; I'd guess it'd get a series of concussions when running. And the physical stress directed at an object moving that fast through the air is tremendous anyway. Falling in mid-run would be like being pummeled by fifty sledgehammers... but, you know, for the sake of argument, let's assume that somehow this amazing dog can take all this.)

But even then, there's the question of energy for this kind of activity: that dog would have to have an incredibly efficient metabolism. Kibbles and bits wouldn't do the trick; it'd be burning some serious calories at those speeds, tens of thousands of them at the very least, so it would have to eat something that contained pretty serious energy -- I don't think there would be nothing in nature to fulfill that need. (And it couldn't just make up for it by having a large stomach and eating more; it'd be crucial for the dog to be as streamlined as possible.) I mean, I guess it could have some sort of a hyper metabolism and the ability to effectively store energy for future use and depend entirely on some sort of human-created ridiculously high-energy meals, but... also, the dog would have to breathe, which is just about impossible at those speeds, and in any case the demand for oxygen would be incredible when the body is working that hard, much greater than lungs could be expected to efficiently provide, and...

...nah. I really don't think so. -- Captain Disdain (talk) 10:52, 25 July 2008 (UTC)

Man. That was a good answer. :) --Kurt Shaped Box (talk) 23:24, 25 July 2008 (UTC)

I'd expect the max speed a highly evolved dog could reach to be on order with that of a highly evolved cat, namely the cheetah, which reaches 75 mph/120 kph. That's only around a tenth of the speed of sound, however. As for intelligence, I see no inherent reason why dogs couldn't eventually evolve the same intelligence and talking abilities as people, but we are talking millions of years here, even with selective breeding, as entirly new structures (like vocal cords) need to develop. Its not just a matter of varying the size and shape of the existing range of structures, which is all dog breeding so far has accomplished. However, we might be able to speed this up using recombinant DNA technology, and end up with The Island of Dr. Moreau. StuRat (talk) 16:01, 25 July 2008 (UTC)

It's not just that, it's unlikely we're even trying to make talking dogs, whatever features are being selected for it's unlikely to be those which could eventually lead to vocal chords capable of human like speech Nil Einne (talk) 17:33, 25 July 2008 (UTC)

A highly evolved dog (millions of years of successful adaptation) named Laika achieved earth orbit in 1957. Does that count as "faster than the speed of sound?" Or did you mean "without human intervention?" A dog which went over a cliff under its own power might also exceed the hypothesized 75 mph, especially if it adopted a streamlined Underdog flight posture during the fall. Edison (talk) 16:27, 25 July 2008 (UTC)

Well, going by this logic, you might put a small radio in the dog's mouth and claim that it talks, but it's pretty obvious that it's really got nothing to do with the dog's evolution. =) -- Captain Disdain (talk) 18:50, 25 July 2008 (UTC)

Yes. Dogs may some day evolve speech. But it seems unlikely to happen in our life time, if at all. While there is evolutionary pressure for dogs to be able to communicate with humans, the type of communication will likely stay non-grammatical (you could argue that there is already 'verbal' communication between humans and dogs). What has happened already is that dogs have become very good at reading human emotions and faces -- better so than even chimps (our closest relatives in the animal world). What will happen in the future is always speculation of course -- but if dogs do start to talk, will they still want to be mere pets? —Pengo 12:38, 26 July 2008 (UTC)

The mechanics of graden furniture (AKA "garden furniture")

I'm visiting my folks at their summer-place this week, and me and my dad (well, mostly him, I'm basically the muscle of this operation) are making a large table for the garden out of concrete. It's going to be a slab that's 220cm x 90cm big, resting on three pillars in an isoceles triangle, with two pillars at the corners on one of the 90cm side and the other about 120 cm's into the table (see diagram). The slab weighs about 182 kg. This design is for two reasons, the first being that it is going to make the slab very stable. If there was four pillars and one was slightly shorter, the table might wobble depending on where the weight is (the slab is just going to be laid on top of the pillars, not screwed to it or anything). Second, my father wants to acheieve an effect that makes it appear like the table is "floating". I had some doubts about this design, mostly because I figured that if you put enough weight on one of the corners, the hole thing would flip over and fall off. To back up my assertion, I wanted to calculate how much weight would make the table flip over. And that's where I need you guys' help :)

Here's a diagram of the table, on a coordinate system with (0,0) at the bottom left corner of the table. The green squares are the pillars (which are 10cm x 10cm).

So, here's the problem: how much weight can you put on the bottom right corner (at (220,0), in other words) before the whole table flips over? I'm not really very good at this, but I tried calculating it and I got about 35 kgs (which, if true, is far to little, and I'll have to dig up one of the pillars and move it :( ). I would really appriciate if I could get someone to verify that I'm using the right method and that my calculations are correct.

The way I did it was to figure the table as just one big lever, with the red line as the fulcrum. Then I used the lever principle to figure out how much each part of the table pushes down, and how much force at the bottom right corner would make that side "heavier". The red line meets the edge of the table at approximately (0,0) and (220,65). I figured out the center of gravity for both parts of the table, which I got to be (89,58) and (149,22). To get the distance between the centers of gravity and the fulcrum-line, I used this neat formula. The distances are about 30cm and 20cm respectively (30.16 and 20.36 to be specific). The product between the distance and the weight (in newtons) of the top part of the table is 34050.64 Nm and the bottom part is 12989.68 Nm, according to my calculations (this is where the lever principle comes in). That means that the top part is 21060.96 Nm "heavier" than the bottom part. Since the distance from the bottom right corner to the red line is 62.2cm (again, using the formula mentioned above), to flip the table over it, you would have to apply 21060.96/62.2 = 338.6 newtons of force, or about 35 kilogram in earth gravity.

As I said, I really just want someone to tell me that this is the right way to do it. If someone could check on the actual calculations, I'd be hugely grateful, but that isn't necessary. Just a confirmation of the method would make me a very grateful man. Or not so much, if I have to spend most of the afternoon digging the damn thing up :) ADFSGL (talk) 11:28, 25 July 2008 (UTC)

Small correction: replace all occurances of Nm with Newton-centimetres :) —Preceding unsigned comment added by ADFSGL (talk • contribs) 12:11, 25 July 2008 (UTC)

I can't resist linking this dolmen.

I haven't checked it - but you could just use the centre of gravity for the whole table at (110,45) which should give you exactly the same result. Your reasoning seems correct otherwise.

I'd guess that 35kg is borderline unsafe.. (if I sat on the corner..)

if you want to have 4 legs - I recommend using lead/rubber/plastic spacers between table and legs to prevent wobbling - anything that can deform under weight - lead is a particularly good choice as it doesn't look out of place with concrete - just use some roofing lead folded over...87.102.86.73 (talk) 12:17, 25 July 2008 (UTC)

Out of curiosity, is there some reason to have the slab of concrete just be there instead of anchoring it to the pillars with... uh, crap, my vocabulary fails me here. I don't know what they're called, but one of those steel plate things, bent at a 90 degree angle? A couple of those would probably be quite enough to keep the slab from flipping even if someone were to sit on the other edge or something. -- Captain Disdain (talk) 12:44, 25 July 2008 (UTC)

Because the table isn't all that thick, only 4 or 5 cm. You could screw it down, but my father intends it to stay there for 15-20 years, and he doesn't want cracks to be formed. And 182 kg is a lot, so if you can eliminate the flipping risk, it'll stay there forever. ADFSGL (talk) 12:58, 25 July 2008 (UTC)

Well, you could probably get around the cracks by simply inserting steel rods or something into the concrete before it hardens and then hooking the metal plate thing into them, for example. That'd probably be easier on the concrete than drilling holes into it. (Well, maybe not; your father may well be more familiar with concrete than I am. It wouldn't take that.) In any case, if he's not willing to anchor it, you're probably going to just have to move that pillar. Or put some kind of a counter weight on top of the slab, but that'd take up table space and look less than charming. Another option that occurs: perhaps you could hook some kind of a weighted clamp on the other end of the table; done right, it would probably be pretty hard to spot. Still, not exactly the most elegant solution imaginable... -- Captain Disdain (talk) 14:10, 25 July 2008 (UTC)

In case you need a nudge towards being extra-cautious, here's a video demonstrating that concrete is heavy. --Sean 13:13, 25 July 2008 (UTC)

Hmmm ... 220 cm x 90cm x 5cm - I make that about 0.1 m³. Unless you are using pumice to make lightweight concrete, your weight calculations are on the low side - should be more like 230 to 240 kg [15]. That improves your stability, but unless you are an Olympic weightlifer, you will need a block and tackle or similar. Gandalf61 (talk) 13:28, 25 July 2008 (UTC)

I just checked with my dear old father, and he measured the thing to be 220cm x 90cm x 4cm. According to the manufacturer, the concrete has a density of 2300 kg/m^3, thus 182.16 kg. It's not lightweight concrete, but it is extremely fine-grained (the most fine-grained we could find). We did a test-table, and not only is it in a very nice eggshell-white, it's smooth as a cue-ball. ADFSGL (talk) 13:36, 25 July 2008 (UTC)

And you're right, there's no way we can lift it on our own, but we have recruited a merry band of assorted neighbours and relatives to lift it when it is dry enough tomorrow. We're going to be around six people. ADFSGL (talk) 13:38, 25 July 2008 (UTC)

I see I'm about to ask an entirely theoretical question: how come concrete? I've seen attractive cast-aluminum outdoor furniture. It doesn't rust, it's easy to move, and it doesn't look like it came from Joe Stalin's House of Outdoor Design. OtherDave (talk) 13:42, 25 July 2008 (UTC)

I had the same doubts as you, but it's actually very nice. The concrete isn't rough building-concrete, it's extremely smooth and very white, much prettier than metal. It's almost like marble, only not glossy and slightly more gray. It's also (very!) sturdy, it's not rickety or anything. It feels much more like a real table. ADFSGL (talk) 13:52, 25 July 2008 (UTC)

...unless it falls on you. A la the stability issue, why not replace that one pillar in the middle of the table with two pillars spread slightly apart? They don't have to be all the way to the edge, but spreading them a little will shift your fulcrum further from the center of gravity. Plasticup ^T/C 14:10, 25 July 2008 (UTC)

The design proposed seems unsafe to me, because it will cause the concrete beyond the pillars to be under a bending and sheering load, and concrete is quite weak under that type of load. Since concrete is best under compression, it would be better to use it, say, for the pillars themselves, and use some other material for the table surface. Also note that square, non-attached pillars will tend to concentrate forces on the table at the corners of the pillars, causing crack propagation and eventual fracture. Circular pillars would be better. If your dad insists on going with a concrete table surface, I suggest a thick steel "tray" (coated with weather-proofing material) underneath the concrete, capable of supporting the concrete and anything on the table, along with circular pillars. Here's a pic of a cantilevered concrete diving platform, which is similar to your table: [16]. Note the tapered side supports and lack of a center pillar (to prevent force concentratations). You can't see it, but I believe this design uses steel-reinforced concrete, with rebar inside the concrete. StuRat (talk) 15:25, 25 July 2008 (UTC)

Had you condsidered casting 'dumbell' shaped legs for a more organic feel:Organic architecture

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87.102.86.73 (talk) 19:56, 25 July 2008 (UTC)

Just to be clear: if I'm not paying for the table, your dad can make it out of whatever he likes. The sturdy part I had no doubt about. OtherDave (talk) 01:42, 26 July 2008 (UTC)

I am not a structural engineer, but I rather share StuRat's concern about the bending strength of the concrete. Actually, you didn't specify whether you put any rebar in it; I'd suggest you do, but that may be too late if, as you imply, it's already cast and curing. Even with rebar, I think something like circular steel plates at the tops of the legs would be useful to spread the load, and coincidentally to expand the support a bit around the middle leg. I'd also be worried about the tabletop possibly sliding off the legs when pushed if it isn't attached to them, especially when the "floating" end is loaded (which reduces the load, and thus the friction, on the corner legs). —Ilmari Karonen (talk) 13:39, 26 July 2008 (UTC)

The concrete is indeed full of rebar, for exactly this reason. Anyway, I dug up the pillar (it's a wood pillar that's screwed to a cement plinth dug down about half a meter, btw) and moved it to about 35 cm from the edge of the table. We assembled the neighborhood strong-men and we lifted it on. It's steady as a rock now, nothing short of a 8.0 earthquake is going to move it, and there's absolutely no chance of sliding. It's just far to heavy for that. Anyway, thanks everyone for all your helpful tips and nice conversation! Me and pops are grateful. Here's a picture of the finished table:

It's slightly wet because we're using soap to create a smooth surface. Oh, and in the image, it looks like right pillar is a crooked, but that's 100% illusion, it's completely straight, so don't worry :) Cheers! ADFSGL (talk) 14:33, 26 July 2008 (UTC)

Your argument that it won't slide at all due to the weight isn't correct. I'd expect it to move over time, so you will have to occasionally reposition it. After all, glaciers and continents are a lot more massive, yet still slide over time. Incidentally, this table would represent an extreme risk to anyone sitting there during an earthquake, so I hope you're in a geologically stable area. StuRat (talk) 15:27, 26 July 2008 (UTC)

High Fructose corn syrup

I have been reading quite a few health articles about the ill affects of high fructose corn syrup (or corn syrup) and the bodies inability to process it. High Fructose Corn Syrup is an extremely sweet and cheap sugar altenative but it has very bad effects on the human body. It has been looked at quite a few times but always from the perspective of a user. Is there any other studies that have fully looked at the ill affects caused by corn syrup.

P.S It is used in almost everything we eat since the 1980s and the obesity rate has risen 37% since.

Rocco F Gervasi

Well, okay. Did you have a question about it, or...? -- Captain Disdain (talk) 14:00, 25 July 2008 (UTC)

Oh, geez, I must be going blind or something; I somehow completely missed the last sentence there. I'm sorry. -- Captain Disdain (talk) 14:01, 25 July 2008 (UTC)

I need a clarification myself. It sounds like you want to know about studies of the bad effects of corn syrup, but "not from the user perspective", which I suppose means "not from the consumer perspective". What perspective do you want ? Are you talking about people who come in contact with it during processing ? As far as I know, it doesn't cause any negative health consequences from touching it or inhaling fumes, if that's what you're after. Here's the Material Safety Data Sheet for corn syrup solids (powder): [17]. It looks like the two dangers identified are getting it in your eyes and a corn syrup dust and air mixture being explosive. StuRat (talk) 14:47, 25 July 2008 (UTC)

"User" could very well refer to the industrial users (the food companies). -- Coneslayer (talk) 14:50, 25 July 2008 (UTC)

Now I'm thinking you meant to ask "rather than look at nonrigorous studies by consumer organizations, I'd like to see some hard scientific data on the health consequences of consuming corn syrup, particularly it's relationship to obesity". Is this what you're asking ? If so, I'll let others answer, but would like to comment that having cheap, sweet goods available, in and of itself, may tend to cause obesity. StuRat (talk) 14:59, 25 July 2008 (UTC)

Not just that but there are many other things that happened in the 1980s, e.g. I was born then. I don't think anyone is going to say I'm the cause of the rising obesity rate. Nil Einne (talk) 17:29, 25 July 2008 (UTC)

• Well, I start with a search for HFCS negative effects, and the first thing that comes up is "The Negative Effects of High Fructose Corn Syrup on the Human Body". Google is your friend! --jpgordon^∇∆∇∆ 14:55, 25 July 2008 (UTC)

• Doesn't turning corn into syrup start with a smelly fermentation process, which is quite noticeable when driving by one of the factories? Could such manufacturing externalities have "ill effects" on neighbors? Edison (talk) 16:11, 25 July 2008 (UTC)

If you are looking for academic studies rather than general health articles you could also try a search at pubmed. "High fructose corn syrup" gave 97 hits, including this overview editorial from the American Journal of Clinical Nutrition which might be a good place to start. best luck, WikiJedits (talk) 20:09, 25 July 2008 (UTC)

For the record, Australia has similar rates of obesity to the US, but high fructose corn syrup is hardly used here. Personally I blame cars (lack of exercise) and the meat-sweet diet of the Western world. —Pengo 12:44, 26 July 2008 (UTC)

Antimatter and matter

Why isn't there a perfect symmetry between antimatter and matter in the universe if they were formed from energy? Particles and antiparticles are produced in pairs, aren't they? —Preceding unsigned comment added by 116.68.79.122 (talk) 15:18, 25 July 2008 (UTC)

You are talking about CP-violation. As for why is exists, that is one of the biggest questions in particle physics. Hopefully the Large Hadron Collider will shed some light on that for us. Plasticup ^T/C 15:22, 25 July 2008 (UTC)

(edit conflict) Our relevant article is baryogenesis (and see also baryon asymmetry, CP violation). The question you ask is among the most important unsolved problems in physics. -- Coneslayer (talk) 15:25, 25 July 2008 (UTC)

Although the matter and antimatter are opposite to each other, but they actually do not follow the similar processes of integration and fragmentation.

To examplify, let us take the example of Proton and antiproton. Proton disintegrated to form electron and antineutrino during bigbang. But there can never be the breakdown of Antiproton to Positon and neutrino. Hence, there is no perfect symmetry between antimatter and matter. You may read the Book 'A brief History of Time by Stephen W. Hawking' as it provides a vivid description of answer of your questions.Asim Chatterjee (talk) 19:42, 25 July 2008 (UTC)

What in the world are you talking about? There is no evidence for proton decay, and there is also no proof that antiproton decay is impossible. I'm pretty sure they're on equal footing at the moment. Anyway, what you say would predict an imbalance towards more antiprotons and fewer protons, which is the opposite of what we observe! —Keenan Pepper 19:55, 25 July 2008 (UTC)

Pepper, you must know it that the total energy of the universe is zero. And according to the latest developments in quarks and quantum mechanics, proton decay can obviously take place. It has been shown in Fermi Lab that as a result of collison of proton and antiproton, top quark is evolved, which has anatural capacity to breakdown protons(and not antiprotons). But the idea of Roger Penrose regarding this is that the rate of antiproton decay, if it takes place at all, is obviously not comparable to that of proton decay. If you take into account the second step ionization equation of 'Saha Equation', you will no doubt find a possiblity leading to my statement being correct. Although we may see the positive universe, but it arose from a negative C-field as predicted by Hoyle. Even the General Theory of Relativity supports this statement.117.201.97.131 (talk) 21:04, 25 July 2008 (UTC)

Last I heard, there was no empirical evidence that proton decay could occur. Could you provide a link to something discussing these developments? --Tango (talk) 21:13, 25 July 2008 (UTC)

I'm sorry, I can't as I am not yet too much familier with Internet because of being a new user. But you may consult the Book 'Meghnad Saha & Developments in Science'. There, in the middle of the third chapter, a set of ionization equations are there, derived from Dirac Equation which will help you to understand proton-decay.117.201.97.131 (talk) 21:24, 25 July 2008 (UTC)

Sign of the wavefunction

Hi! When I was learning atomic structure, the diagrams of orbitals had '+' or '-' signs marked on it(For eg., each lobe of a p-orbital had '+' on one lobe and '-' on the other). My teacher mentioned something about it relating to the wavefunction and addition/ subtraction interference or something like that, but I didn't get the point completely(I'm only in high school) I believe the wavefunction is a complex no., the square of whose magnitude gave the probability density. I don't understand what the sign means. Does it imply that the value of the wavefunction in one region is the conjugate of another?? Can anyone explain to me?? 116.68.79.122 (talk) 15:29, 25 July 2008 (UTC) A 15-year-old.

It's the sign of the real part of the wavefunction. (or if the wavefunction is not complex - just the sign)87.102.86.73 (talk) 15:44, 25 July 2008 (UTC)

" Does it imply that the value of the wavefunction in one region is the conjugate of another?? " - no, don't think that..87.102.86.73 (talk) 16:05, 25 July 2008 (UTC)

In general, the wavefunction is complex, but in the case of atomic orbitals, the eigenfunctions of the hamiltonian all happen to be real (or more correctly, you can multiply them by some complex constant to make them real). (I'm sure there's a good reason for this, but for now you can think of it as a mathematical accident.) The sign is simply the sign of the (real) wavefunction. 128.165.101.105 (talk) 19:51, 25 July 2008 (UTC)

Neonatal Circumcision as a preventative measure against HIV...

Does neonatal circumcision help prevent the possibility of contracting HIV? Unfortunetly much of the research on the subject is highly biased either in favor for or against circumcision. I understand there is much debate on the subject and a list of medical journals or articles explaining the medical aspect of the procedure as a preventative measure without bias would be greatly appreciated. 65.9.252.237 (talk) 17:46, 25 July 2008 (UTC)

I don't know about neonatal circumcision specifically, but I remember reading a study conducted by a UN group that ended early because the results were so heavily in favor of circumcision reducing HIV transmition that they deemed it unethical to continue keeping a control group of uncircumcised men. Plasticup ^T/C 17:56, 25 July 2008 (UTC)

Does it really matter? I never understood what the point of the study was. Just wearing a condom or even better, not having sex with HIV infected women seems to be a better option than circumcision. The simplest solution is always the best solution. ScienceApe (talk) 18:57, 25 July 2008 (UTC)

The studies are all a little dicey as circumsized/uncircumsized men tend to represent different cultural samples and all this so take some salt, but yeah, circumcision reduces the transmition rate of HIV. It also reduces the occurances of trench foot in your penis if you're drafted to fight in World War I. WilyD 19:08, 25 July 2008 (UTC)

To be specific about the question though, neonatal circumcision is not shown to affect HIV transmission rates. Being circumcised has been shown effective in some populations where the males are non-monogamous and unprotected during sex (per ScienceApe) - neither of these criteria apply to a 4-year-old boy. The difference between circumcision and neonatal circumcision is that the neonate is not given a choice. Franamax (talk) 19:38, 25 July 2008 (UTC)

Err, as long as it's not so recent that you're not completely healed, the exact time of circumcision doesn't matter. It's probably not effective against many methods of HIV transmission, such as blood transfusions and sharing needles. WilyD 16:37, 26 July 2008 (UTC)

Catalyst?

In the reaction '2SO₂+O₂=2SO₃', the required conditions are 1:Presence of 450^oC temperature and 2:A catalyst Now this catalyst can be either Vanadium Pentoxide or Platinum in general. But among these two, which catalyst pprovides a better speed of reaction?Asim Chatterjee (talk) 19:33, 25 July 2008 (UTC)

According to Contact process platinum is the better catalyst.87.102.86.73 (talk) 20:14, 25 July 2008 (UTC)

Yes, I think platinum is much more expensive, so why would anyone use it unless it worked better? —Keenan Pepper 20:48, 25 July 2008 (UTC)

It is, they don't, it does... but the platinum is more easily poisoned according to reports. Otherwise they would use it if it allows the reaction to occur at a lower temperature (which is almost the same as having faster reaction rates - one follows the other..)87.102.86.73 (talk) 21:04, 25 July 2008 (UTC)

You are most welcome for having me helped,User-87.102.86.73.You are truely among the most brilliant persons I've ever talked to.Thank you. —Preceding unsigned comment added by 117.201.97.131 (talk) 21:19, 25 July 2008 (UTC)

Thank you very much, but please don't thank me, thank those who wrote the articles and did the research in the first place, and of course thank wikipedia..87.102.86.73 (talk) 21:23, 25 July 2008 (UTC)

Yeah, I'll surely do the same.But I can't ignore your efforts. I shall be ever grateful to Wikipedia.117.201.97.131 (talk) 21:27, 25 July 2008 (UTC)

Collisional quenching rate constants for some excited states of N₂ and N₂⁺ in helium

I don't really expect this to be answered here, but I figure it's worth a shot. The RD has surprised me before!

I'm interested in the C³Π_u state of the N₂ molecule, and the B²Σ_u⁺ state of the N₂⁺ molecular ion. I need to know the reaction rate constants for the collisional quenching reactions of these species when they collide with ground-state helium atoms. If experimental data are not available, I need some theory that will allow me to estimate these rate constants to at least order-of-magnitude accuracy. All responses appreciated. —Keenan Pepper 20:07, 25 July 2008 (UTC)

This pdf http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19740002549_1974002549.pdf mentions in the references "reaction rates for collisional de-excitation of B²Σ⁺_u states of N₂⁺..." see Ref 4. but doesn't mention what in.. The article itself also mentions measurements in helium, but I didn't read it all to check it..87.102.86.73 (talk) 21:01, 25 July 2008 (UTC)

Insect Survival

How long can insects survive in a vacuum? Does their exoskeleton help protect them? Just curious. Horselover Frost (talk) 22:03, 25 July 2008 (UTC)

You'll find several papers with Google Scholar and the keywords insects vacuum. However, you'll need a library visit if you want to know the complete picture, as some abstracts aren't online. What I could gather was that insect eggs aren't affected by low pressure plus low temperatures, but are vulnerable with longer exposure or higher temperature (Mbata et al., Mortality of Eggs of Stored-Product Insects Held Under Vacuum: Effects of Pressure, Temperature, and Exposure Time) and that At 50±5 mmHg, the egg stage was the most resistant in all three species, times needed to obtain 99% mortality being 45, 49 and 22 h, respectively. (Finkelman et al., Effect of low pressures on the survival of three cocoa pests at 30°C) which would give an upper bound to the answer to your first question. --Ayacop (talk) 05:57, 26 July 2008 (UTC)

Shark vs. Crocodile. Who is stronger?

In a confrontation between both. 190.49.102.65 (talk) 22:04, 25 July 2008 (UTC)

Well ignoring the fact that a shark is a blue water animal while the crocodile is a brown water animal... Actually it's almost impossible to answer because the environment would dictate who would win. A shark is not "designed" to swim in shallow brown water, where a croc lurks. Likewise, a croc can't swim forever, and would drown in open blue water. So in brown water, the croc, in blue water, the shark. Probably. ScienceApe (talk) 22:17, 25 July 2008 (UTC)

Animal Face-Off says it all - shark is the winner.87.102.86.73 (talk) 22:33, 25 July 2008 (UTC)

Those face-offs are pretty ridiculous. Incidentally they also said a lion would win in a fight against a tiger. This match-up has actually occurred a few times in captivity, and the tiger almost always wins. ScienceApe (talk) 00:47, 26 July 2008 (UTC)

Which would seem obvious from their respective sizes (tigers are HUGE). --Ayacop (talk) 06:02, 26 July 2008 (UTC)

Electronic interference on airplanes

Hello. Does leaving on your "portable electronic devices" prior to take off/landing on an airplane really have any interfering effect in the cockpit? It just seems to me that even if everyone on a plane had a CD player with headsets on, there could not possibly be enough interference to inhibit cockpit communication with the airport, or to distort the autopilot. Also, would cell phones in operation during flight cause a technical problem either? I've seen a stewardess use a credit-card scanner during flight that sends a signal to accept the charge, which to me would seem to have the same interfering effect as a cell phone, yet the scanner is allowed to be used. It makes me think that cell phones are prohibited just for the sake of passenger comfort (no one wants to sit next to someone who yells on their cell phone the whole flight). Comments? Answers? Thanks!--El aprendelenguas (talk) 22:05, 25 July 2008 (UTC)

On more thing: After the plane has landed, why is it okay to use cell phones at that point but "all other electronic devices should remain off"? Thanks!--El aprendelenguas (talk) 22:12, 25 July 2008 (UTC)

See Mobile_phones_on_aircraft#Current_status. The gist of it is the FCC forbids the use of cell phones on planes in flight (based on some evidence that they can interfere with navigational equipment), while the use of cell phones on the ground is up to the FAA, who may permit or forbid cell phone use as they see fit. Horselover Frost (talk) 22:22, 25 July 2008 (UTC)

Mythbusters aired an episode where it tested the claim. The answer was no, it doesn't effect the airplane's electronics, they just ask people to turn them off just to be safe, because there might one day be an electronic device that might have unforeseen effects on instrumentation. ScienceApe (talk) 22:25, 25 July 2008 (UTC)

The UK Civil Aviation Authority did a study in 2003 that determined that interference from cell phones may disrupt the functioning of the electric compass used in airplanes. (study and results here) Horselover Frost (talk) 22:36, 25 July 2008 (UTC)

The irony is that the alternative, the in-flight entertainment system, has already caused at least one crash, while there's no record of CD players, cell phones, etc., causing a crash. Therefore, I'd prefer if they kept all that unneeded hidden wiring off the plane and let people use their own, much safer, devices. StuRat (talk) 23:28, 25 July 2008 (UTC)

Personally I'm glad from a personal standpoint that cell phones aren't operated on planes. Businessmen on planes are irritating enough ("So I SAID to the GUY, buy LOW, sell HIGH, ya'know what I'm SAYIN'?") without being able to communicate with people outside of their seats. But the other electronics—totally silly to have them switched off for takeoff and landing, but whatever. --98.217.8.46 (talk) 03:27, 26 July 2008 (UTC)

(As an aside, this is my favorite comic on the subject.) --98.217.8.46 (talk) 03:27, 26 July 2008 (UTC)

I liked the Simpson's episode where the stewardess made Bart turn off his game. Then the plane's engines quit and it went into a dive. Next the stewardess said "turn it back on !", and the problem was fixed once Bart did. StuRat (talk) 04:44, 26 July 2008 (UTC)

EMP against guns

If an E-bomb or EMP weapon was used against soldiers armed with guns, would it ignite the smokeless powder, and cause the guns to explode? ScienceApe (talk) 22:23, 25 July 2008 (UTC)

Do you mean conventional mechanical guns, or electrically operated guns? Horselover Frost (talk) 22:28, 25 July 2008 (UTC)

Mechanical guns like M16 or AK47. ScienceApe (talk) 00:44, 26 July 2008 (UTC)

Then no, or at least it didn't happen when the U.S. Military tested EMFCGs back in the late 70s. And I don't see how it could happen, since the effects of an electromagnetic pulse on a conventional firearm would be roughly the same as a shock from static electricity. Horselover Frost (talk) 04:21, 26 July 2008 (UTC)

Possibly not - if the gun is metal and the cartridges inside the gun the metal of the gun might absorb most of the EMP.87.102.86.73 (talk) 22:35, 25 July 2008 (UTC)

Metal doesn't absorb though, it's a conductor. ScienceApe (talk) 00:45, 26 July 2008 (UTC)

A conductor will reflect em radiation —Preceding unsigned comment added by 79.76.216.89 (talk) 02:03, 26 July 2008 (UTC)

Also, if you try to argue that it may conduct or reflect and, as a result, produce heat... The heat of the Mojave (and Iraqi) desert hasn't caused round to explode. -- kainaw™ 18:15, 26 July 2008 (UTC)

Why do some birds have long tails?

Why exactly is it that some bird species have evolved long tails whilst other species in the same family with broadly similar behaviour have not?

Compare the European Magpie and the Carrion Crow, or the Peach-faced Lovebird and the Budgerigar, for example. What exactly are the benefits to a bird of having a long tail anyway? --Kurt Shaped Box (talk) 23:30, 25 July 2008 (UTC)

Good question. A common answer to "what is a long tail good for?" is either "balance" or "showing off". The latter normally implies a pronounced sexual dimorphism, which for the birds you mention is not the case; so balance (in flight, perched, or on the ground) would be the first thing that comes to mind. However, I have found this abstract, which suggests that the long tail serves for the potential mates as an indicator of overall physical condition of the bird (and therefore its reproductive potential). The suggestion is very interesting, but not necessarily correct. Another thing that can not be ruled out is that a long tail is meant to confuse predators, either by increasing the perceived size of the bird or by moving the potential point of attack away from the vital areas. The tail is graded, so it is not very bulky for its length; but a magpie really looks bigger than it really is: a typical magpie weights 200-240 gram, a typical carrion crow about 500. Hope this helps (I doubt it though...). Best regards, --Dr Dima (talk) 01:13, 26 July 2008 (UTC)

July 26

Brain development

Which is better for improving your brain, listening to music or watching TV? —Preceding unsigned comment added by 79.76.216.89 (talk) 02:00, 26 July 2008 (UTC)

I'd say it depends on the shows. Listening to Howard Stern has got to be worse for your brain than watching Charlie Rose, while listening to NPR has got to be better for your brain than watching Jerry Springer. StuRat (talk) 04:24, 26 July 2008 (UTC)

Reading, playing games, problem solving, doing puzzles, exercising and eating well are better than music or tv. That said, music is better than tv because it takes more imagination to experience it. -LambaJan (talk) 04:45, 26 July 2008 (UTC)

"I like radio better than TV...because the pictures are better." StuRat (talk) 04:50, 26 July 2008 (UTC)

Treated or untreated lumber?

Is it possible to tell, based on visual inspection, whether an existing wood structure was built with treated or untreated lumber? If so, how do you do it? —Preceding unsigned comment added by 71.162.242.76 (talk) 02:23, 26 July 2008 (UTC)

Treated wood often has a stamp indicating what kind of treatment it's had. Also, older treatment methods tended to turn the wood green. Also, if the structure's been there for a while, and it's touching the ground, and there's no rot where it's touching the ground, and it's not cedar or one of the other naturally resistant species, it's a good bet that it's treated. --Sean 69.134.125.191 (talk) 04:23, 26 July 2008 (UTC)

Anti-Light

Is it possible for there to be anti-light which when shined on a surface gives the opposite colors to what light would have given? —Preceding unsigned comment added by Jamesernator (talk • contribs) 02:27, 26 July 2008 (UTC)

Mmm, I'm thinking no. Think about how "light" works—"white light" is a broad spectrum of frequencies, most of which are absorbed by the surface you are shining them on except for a few that scatter off and produce what we consider to be the "color" of something. (This is a very rough approximation, I know.) So what you're asking for is a way to shine frequencies of light at something in a way that will instead reflect back different frequencies than they normally would. If something appears red, it's because it absorbs all frequencies except red. So how are you going to make that possible reflect back green? It's not going to happen. It doesn't have to do with the light. (If you shined light at it that didn't contain any red, you'd get something that looked blackish and washed out, like what happens when you drive through tunnels with very narrow frequency lighting and all the cars look greyish.) --98.217.8.46 (talk) 03:23, 26 July 2008 (UTC)

What is the opposite of red? Colors don't have opposites. Plasticup ^T/C 03:41, 26 July 2008 (UTC)

Yes they do (after a fashion). Cyan (a combination of blue and green) is the opposite of red. Since people percieve color using three kinds of color receptors in their eyes that roughly correspond to red, blue, and green, then every color can be approximately represented as a combination of red, blue, and green where each component has an intensity between 0 (absent) and 1 (fully saturated). This RGB color scale thus gives rise to natural opposites, where if a color has RGB components (r,g,b) then it's complement is the color represented by (1-r,1-g,1-b). Dragons flight (talk) 05:01, 26 July 2008 (UTC)

Right, but the RGB scale is more an artifact of our vision hardware than the physical aspects of the colors themselves, I do believe. There's no physical reason that a 700nm frequency is the "opposite" of 500nm (or thereabouts). As far as physics is concerned they are just lines on a scale, if that. --98.217.8.46 (talk) 05:42, 26 July 2008 (UTC)

Of course there are opposite colors: if you shine a white light on a surface that absorbes everything but colors in the red spectrum, then the surface will be red. However, if you shine a white light on a surface that does the opposite, it reflects everything except colors in the red spectrum, then you get cyan. They are opposite, complementary colors. Mix them together, and you get black, white or some sort of gray. See also Negative (photography). As for the original question, no, there is no such light. Shine a cyan light on a red surface, and the surface is going to appear black. It's never going to emit cyan because the surface absorbes those wave lengths. An even more clear example is black: a black shirt is going to stay black, no matter how much light you shine on it. It's never going to appear white under any sorts of light. ADFSGL (talk) 14:52, 26 July 2008 (UTC)

A question on civilization and cooling

How could a pre-electricity, pre-electronics people from the desert adapt their empire to stay cool in rain-forest climes? Could they build windmill fans, or would water mills or water-based turbines work without electricity? Would windmills work even if they didn't have a constant flow of wind going for them? Wiwaxia (talk) 08:12, 26 July 2008 (UTC)

I'm not sure I understand the question. Should the windmill fan create electricity or create wind? If a wind is going, you don't need a fan. Historically, there are some techniques for cooling, the most widely used ones probably evaporative cooling (humans have that build-in ;-) and manually operated fans (e.g. the slave with the palm frond). Good building construction helps (use of thermal mass and good ventilation), and so do lifestyle change. See Siesta. --Stephan Schulz (talk) 08:37, 26 July 2008 (UTC)

Bedouins wear white for a reason. --antilived^{T | C | G} 12:11, 26 July 2008 (UTC)

Rain forests tend to be quite humid, so evaporative cooling doesn't work well, and sweating therefore doesn't cool people down much. It tends to be cooler under the tree canopy just because no sunlight makes it near the ground, however. People in rain forests typically wore minimal clothing, perhaps just a loin cloth, as sunburns aren't an issue and overheating can be. As mentioned previously, resting during the hottest parts of the day can help, as can using a hand fan or taking a swim. StuRat (talk) 13:34, 26 July 2008 (UTC)

Rashes from insect bites

Insect bites sometimes produce rashes that last several days. I'm talking about the kind that is red, raised, itchy, and lumpy(?). Physiologically, what's happening at the affected sites that makes them "lumpy"? —Preceding unsigned comment added by 71.162.242.76 (talk) 13:10, 26 July 2008 (UTC)

I think it's a histamine reaction. That article may help. --Tango (talk) 17:06, 26 July 2008 (UTC)

Most of it is already answered by Tango, but I want to add something. Some insects also have greater adenine concentration. They produce a mixture of citric acid (note the formulae HOOCCH₂COHCOOHCH₂COOH) and histamine. The -COOH carboxyl group, being acidic, facilitates the action of histamine reaction. You can jump to the link for more information. Thank you, for asking such an interesting question.117.201.96.242 (talk) 19:08, 26 July 2008 (UTC)

Getting Punched in the Stomach And Its Effects On The Digestive System

When a person gets hit in the stomach, what are the effects of the force of the body blow to the stomach on the digestive system? Ericthebrainiac (talk) 15:19, 26 July 2008 (UTC)

biology

Who coined the term tissue? ```` —Preceding unsigned comment added by 61.1.236.70 (talk) 16:31, 26 July 2008 (UTC)

It's an old word, apparently originating from the Middle English word "tissu", meaning "a rich kind of cloth", according to the American Heritage Dictionary. Nobody just suddenly looked at tissue and decided to call it "tissue" out of the blue. -- Captain Disdain (talk) 16:51, 26 July 2008 (UTC)

bacteria longevity

How long would (harmful) bacteria live on a dry smooth surface, such as a plate? A women's mag I like recently had a rant about bacteria collecting on dishcloths. But if I wash a plate, let it dry in the rack overnight, and use it for breakfast or lunch the next day, does anything harmful from the dishcloth still remain? I did read the bacteria article, but couldn't find the answer. Thank you.64.231.9.30 (talk) 17:21, 26 July 2008 (UTC)

The answer is "it depends". Clean, dry surfaces like porcelain or glass are not friendly for bacteria. So while your plate may have some bacteria, the chance that there are enough to cause trouble is minimal. More importantly, fear of harmful bacteria is often much out of proportion (very much aided by advertising from detergent companies with disinfectants to sell). A normal household is never sterile, and probably never will be. Normal hygiene is sufficient in nearly all cases, and overly aggressive use of disinfectants is likely to be worse that the occasional microorganism. Just wash your utensils, hands, and towels occasionally (especially after handling risky food like chicken). --Stephan Schulz (talk) 17:58, 26 July 2008 (UTC)

Thanks!64.231.9.30 (talk) 18:24, 26 July 2008 (UTC)