Wikipedia:Reference desk/Archives/Science/2007 May 20

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May 20

Evolutionary purpose of anal sex

Surprisingly, neither our articles on anal sex nor anus answer this; is there any reason humans have evolved to gain pleasure from anal sex? Besides the fact that the anus does play a role in life (people actually need it), it's function in anal sex is different from the "main" function. Did evolution cause the second function to appear, because it was an advantage to gain pleasure from anal sex, or is it actually a coincidence that we are able to have anal sex? Also, did the penis also evolve to be able to be inserted into the rectum or is it, again, a mere coincidence that it is? A.Z. 00:06, 20 May 2007 (UTC)

That's a really disturbing question, but I'll try to answer it. Anal sex might be practiced by gay couples, probably because men don't have vaginas (unless their transgender). Now I'm not a biologist, but I would probably think that an organ in the excretory/reproductive system (the penis) might have evolved separately from an organ in the digestive system (the anus)--Ed ^{¿Cómo estás?} 00:14, 20 May 2007 (UTC)

It's not just a gay thing, btw. Plenty of heterosexuals practice it too, silly people. What's the evolutionary reason for sneezing feeling good? It's gonna happen no matter whether you want it to or not. What's the evolutionary reason for inedible flowers smelling nice to humans? What's the evolutionary reason for any number of things? Like the law, the rule is not "that which is not explicitly designed must be painful". - CHAIRBOY (☎) 00:18, 20 May 2007 (UTC)

In evolutionary terms, there are often happy accidents. It is an accident that the lumen of the colon is separated by a relatively thin membrane from reproductive organs that contain tissues lined with many nerve-endings. There is also a problem with this anatomy, this small separation can lead to what is referred in medicine as a vaginal-anal fistula if there is necrosis in this area.--InitialMan(adam) 02:11, 20 May 2007 (UTC)

Did the nose evolve to wear spectacles for the eyes? Just because the anatomy is in close proximity and has beneficial relationship, doesn't mean it evolved that that way. There is no selective processes by which would afford an evolutionary edge to the scenarios in your question.

I admit that, before I read the answers above, I was more inclined to believe that there was an evolutionary cause for anal sex feeling good, but I guess I can cope, after all, with the idea that it was just an accident. However, I think an at least credible theory could be devised to explain how the apparently accidental anatomical particularity could give us an edge. A.Z. 00:52, 20 May 2007 (UTC)

Um, see Occam's_Razor.--InitialMan(adam) 02:11, 20 May 2007 (UTC)

Not everything has an evolutionary benefit - in this case it seems counter-productive from a reproductive point of view - so one might expect it ought to be selected against. But genetics and evolution isn't everything. We didn't evolve the ability to make digital watches...humans do many things that our genes didn't prepare us for. SteveBaker 01:53, 20 May 2007 (UTC)

So far, everyone had merely said that there is no evidence that the development of the ability to derive pleasure from anal sex had an evolutionary purpose, but no-one had argued that it could actually be counter-productive. Why would you say that the said ability would be counter-productive from a reproductive point of view? And, by that, do you mean that the development of such an ability during the course of evolution would be counter-productive to passing on our genes? If yes, how so? A.Z. 02:21, 20 May 2007 (UTC)

Okay this isnt a debate, but... the problem with that logic is you haven't considered that chordata which mammals are a part of, have evolved from a long line of proto organisms. See mesoderm and remember that the ectoderm and mesoderm are important in blastogenesis(fetal development). These are evolutionary reasons for why they are located in close proximity.--InitialMan(adam) 02:25, 20 May 2007 (UTC)

That seems to be a good point. I don't know a lot about proto organisms, unfortunately, but, if I understand it correctly, what you're saying is that our anuses and sex organs have been close to one another since ever, for some reason that I don't understand (that they are important in blastogenesis), since we were proto organisms, and still proto organisms did not have anal sex. A.Z. 02:58, 20 May 2007 (UTC)

Ok, the thing is that you really can't produce a child through anal sex unless the semen somehow enters the vagina via the perineum. True, performing anal sex is counterproductive towards procreation, probably because it's a waste of the male's sperm. Since the sperm can't do anything in the anus, it's probably best for the male to actually make use of his sperm by having regular sex.--Ed ^{¿Cómo estás?} 02:32, 20 May 2007 (UTC)

A consequence of your logic is that every specimen that can't reproduce for one reason or the other is bad for the species and therefore the genes that made that specimen have the feature that made them not be able to reproduce would not be passed on. Therefore, there would be no reason for female human beings to live for more than 40 years, since they cannot reproduce after that age, and they would just eat everyone's food, and produce less food since they're old, living a life devoid of purpose (from an evolutionary perspective).

However, grandmothers are necessary to take care of their grandchildren, and therefore people that didn't die just after having children survived and passed on their genes, and people that just had their children and died right after that didn't pass on their genes, because the children (and the genes) would die without anyone to take care of them.

Having white or black skin also doesn't directly help you making kids, but it allows you to survive in Europe and in Africa, so you can actually live and then have the kids. Some thing like that can be true with anal sex. A.Z. 02:40, 20 May 2007 (UTC)

I haven't read what other people have said about it, but here's my two cents:

1. Freud described the different great pleasures of different ages. There is an "anal" stage. I've seen "taking a really good shit" as sometimes being quite pleasureful. There must be a pleasure in doing it, otherwise, some people would be inclined not to do it at all!
2. It's a coincidence of people taking advantage of their bodies. While anal sex almost never feels as good as say, vaginal sex, manual, or oral for the recipient, man or woman, the nerves are there so that you don't mess around in there. If there was something acidic, something puncturing, or something too hot touching your intestinal walls, that probably isn't good. The more sensitive something is, normally the better you need to take care of it, really.

There you go, rectal pleasure and pain, and people just are smart enough to take advantage of their bodies, as in masturbation. It's like asking "what is the evolutionary purpose of pleasure from listening to music? We didn't evolve to like loud music in headphones, for instance, but we took advantage of our bodies in this case as well. I forgot what else I was going to say. [Mac Δαvιs] ❖ 02:59, 20 May 2007 (UTC)

Interesting. I guess people are also smart enought to take advantage of opposable thumbs to get food, in many different ways. Yet, getting food is not something nearly as unimportant to our survival as you seem to be implying that anal sex and masturbation are. Could we have survived at all without masturbation? A.Z. 03:10, 20 May 2007 (UTC)

Well, maybe we could. But the article on non-human animal sexual behavior states that "Georgetown University professor Janet Mann has specifically theorised that homosexual behaviour, at least in dolphins, is an evolutionary advantage that minimises intraspecies aggression, especially among males." We are not talking about homosexuality here; we are talking about anal sex, but that is one example of an apparently unimportant behavior of an animal that one could say to be derived from the fact that the animals are just smart enough to take advantage of their bodies (by having sex even though it's not for procreation). Nonetheless, it could give dolphins an evolutionary advantage, for the reason stated above. Maybe we took advantage of anal sex in a way that it gave us an evolutionary advantage as well, and people who felt more pleasure with anal sex survived more, and people that felt less pleasure died instead... A.Z. 04:49, 20 May 2007 (UTC)

I believe if you go back far enough in the evolutionary timeline, the cloaca served as the anus, bladder outlet, and reproductive canal. Once they separated, the "pleasure nerves" apparently split up, as well, with some going to the anus. As for why they remained there after millions of years, I guess you'd need to go with the theory that nonreproductive sex serves to reduce aggression within a population, as in the dolphin example above and the somewhat closer to home bonobo example. StuRat 05:05, 20 May 2007 (UTC)

Well, finally! Someone saying that there could be an evolutionary purpose after all! So, once the anus and reproductive canal split up, evolution would have made the nerves in the anus just disappear, because they were devoid of purpose. However, they remained there, and those nerves don't necessarily participate in vaginal intercourse at all. So, the reason why they remained there could be because engaging in anal sex gave us an evolutionary advantage!

But, aren't there any other reasons why it would be an advantage, besides reducing aggression within a population? Not that that's not a good reason. I'm just wondering. A.Z. 05:21, 20 May 2007 (UTC)

Evolution doesn't make anything "just disappear, because they were devoid of purpose." Firstly, there may be plenty of purposes for something, we may just not appreciate them fully. Even if if there isn't a purpose, there may be a very good reason they are there (for example, as a consequence of a developmental mechanism that is essential for something else). Finally, even if there isn't a purpose or reason for something anymore, for it to be lost by evolution it would most likely require selection against it. Rockpocket 07:17, 20 May 2007 (UTC)

Agree with most of what you say here, but not quite with the final sentence. If there's no longer a selection pressure 'for' something, it can be lost randomly without necessarily being selected 'against'. See for example genetic drift. --jjron 07:49, 20 May 2007 (UTC)

Incidently, putting pressure on the ventral wall of the rectum will stimulate the (male) prostate gland, this happens during anal sex. The prostate plays an essential role in male orgasm, therefore part of the pleasure from anal sex (in males) may simply be an artifact of prostate stimulation. Secondly, there appears to be an element of pleasure derived from having a full bowel (just as there is from having a full stomach). Therefore the feeling of pressue during anal sex may be pleasureable for that reason. Rockpocket 07:40, 20 May 2007 (UTC)

"There is no evidence that same-sex sexual acts per se are under direct [evolutionary] selective pressure any more than is masturbation, anal sex, bestiality, pedophilia, vaginal entry from the front or rear, or any other sexual practice. Sexual desire, arousal, orgasm (especially in men), and male ejaculation, all basic human capacities, are selectively maintained through production of offspring. But these capacities are not specific to reproduction . . . [The strong human] sex drive, maintained by its guarantee of reproduction, is available for elaboration in socially condoned, prohibited, or ignored forms for social, emotional, and physiological satisfaction. . . . It is a common "Darwinian" fallacy to assume that all components of a behavioral act are under equal selective pressure. This leads to treating behavioral acts as discrete adaptive units when in fact they usually have both adaptive and nonadaptive or neutral components. Language, for example, aids in survival and reproduction, but not all linguistic acts provide direct reproductive gain. There is no direct selection for, nor are there genes for, the creation of poetry. The direct, genetically inherited components of homosexuality are those listed above, common to all sex acts."

—Jeffrey M. Dickemann, commentary on "The Evolution of Human Homosexual Behavior" by R. C. Kirkpatrick, from Current Anthropology, Vol. 41 No. 3, June 2000. From "Gay Gene" Critique Quotes, echoing some of the statements made above. ---Sluzzelin talk 08:07, 20 May 2007 (UTC)

Excellent answer, Sluzzelin, and bonus points for the childish amusement to be drawn from finding a Mr Dickemann commenting on homosexual behavior. Rockpocket 08:21, 20 May 2007 (UTC)

I find it astonishing that someone dismisses so easily the possibility that there is a genetic component of homosexuality besides those common to all sex acts, and that this component could have given animals an evolutionary advantage and could have been selected to stay with us. I don't think there is any proven explanation of how psychological development could lead an otherwise straight male (as the author says that we are when we are born) to feel no attraction for females at all and to start directing all that strong sex drive towards other men. Having anal sex and masturbating do not require that one shifts one's entire idea of what is attractive the way that becoming homosexual as one grows up would.

Anyway, Sluzzelin, we are not talking about whether homosexuality has a genetic component in the first place. The question is about anal sex. We all seem to agree with the author that the desire to have anal sex wasn't selected through evolution: this desire is the same primitive sexual desire that we all have. As Mac Davis said, animals are smart enough to take advantage of their bodies, and so they took advantage of the fact that they could have anal sex. What I did want to find out is whether the physiological characteristics that make anal sex feel good (not that make us want to have anal sex) remained with us because having anal sex gives us an evolutionary advantage or are with us because of other reasons unrelated to the fact that we have anal sex. A.Z. 16:51, 20 May 2007 (UTC)

A couple more comments:

1) I don't agree that there must be selection against a feature for it to disappear over time, the mere absence of selection for it will eventually lead the trait to disappear due to genetic drift. A common example is that formerly sighted animals which live in complete darkness appear to lose their eyesight. There is no reason why eyesight would be harmful to them, it simply isn't necessary any more.

2) A more general explanation for nonreproductive sex is that it serves a social bonding purpose. Thus, like grooming each other or eating together, it helps to ensure to cohesion of a group. As mentioned previously, this tends to be used more in some species than others. StuRat 00:59, 21 May 2007 (UTC)

While it is true that many men and women, whatever their sexuality, do find receptive penetrative anal sex pleasurable, a person reading the above thread might gain the impression that this is true for all homosexual men. It is not. Many gay men refrain from receptive anal sex; there are numerous reasons, one of which is that they find being penetrated intensely uncomfortable, even painful. It is possible to train oneself to relax so that it becomes less uncomfortable, but for many men it never leaves the discomfort zone even if they are happy to accommodate their partner's wishes. I'm sure this is true for many women as well. For some uncircumcised men, even being the penetrator can cause pain when the foreskin is forced backwards during sex. The majority of gay men who engage in anal sex on a regular basis like to be either the "top" (penetrator) or the "bottom" (penetratee). Relatively few are "versatile" (like it both ways). JackofOz 01:28, 21 May 2007 (UTC)

Identification

I found this in the upper track of the sliding door when I moved into my apartment. It is on the southside of the building, in Houston, TX. Anybody have any idea what it is? I have no clue...

anonymous6494 02:22, 20 May 2007 (UTC)

Guess: A dry rot fungus ? ---Sluzzelin talk 02:51, 20 May 2007 (UTC)

I think some paper wasp nests look something like that (they are better disguised when on the side of a tree). I would guess, if it is a wasp nest, that the openings are between the two layers. See this pic of a paper wasp nest built on top of bird house (halfway down the page), it looks a lot like yours: [1]. (I wouldn't want to be the bird that flew into that nest !) StuRat 04:48, 20 May 2007 (UTC)

Looks a bit like a very untidy house martin nest. Not sure if you get those in Texas, but it could be an old bird's nest of some sort. It seems to be made of mud and twigs, although that could be just me misinterpreting the photo. How big is it? --YFB ¿ 05:04, 20 May 2007 (UTC)

You can get an idea of the size by the screen mesh in the lower right. It's about two inches long, and maybe an inch wide and an inch deep. anonymous6494 05:25, 20 May 2007 (UTC)

Since I didn't know what the pitch of the mesh was, I couldn't tell much from that! :-) But at 2 inches that seems far too small to be a bird's nest. No idea what it is. --YFB ¿ 05:27, 20 May 2007 (UTC)

I agree with StuRat, it looks like a wasp nest to me too. I live a long way from Houston (in Australia), but have found wasp nests around my place that look very similar. Pretty sure the ones around my place are European wasps nests. (BTW, re Sluzzelin, I don't think it would be a fungus growing on metal). --jjron 06:01, 20 May 2007 (UTC)

Question: have you tried breaking it open to see what it looks like inside? That could give you the answer. If it has a cellular/honeycomb type structure, it'd almost certainly be a wasp nest. --jjron 06:16, 20 May 2007 (UTC)

If you get stung on the nose by a wasp when breaking it open, you can be reasonably sure it was a wasp nest. If you want to avoid that, try breaking it off on a cold day when they will be dormant, or soak it with wasp spray first. StuRat 00:40, 21 May 2007 (UTC)

Re-re: yep, seems a bit unlikely now. :-) ---Sluzzelin talk 08:14, 20 May 2007 (UTC)

Mud dauber wasp?

Atlant 13:01, 21 May 2007 (UTC)

I had considered that possibility, but their nests tend to be individual "potlike" structures, as shown in these excellent pics: [2]. StuRat 07:36, 22 May 2007 (UTC)

Red something syndrome

There's this syndrome I'm trying to think of. It has red in it and has to do with... something? It's a hereditary syndrome and very rare. Red rag or red fiber or red strings or somethings syndrome. What is it? People that have it tend to be short I think because... I don't remember. Help? [Mac Δαvιs] ❖ 04:00, 20 May 2007 (UTC)

Red man syndrome? — Kieff | Talk 04:10, 20 May 2007 (UTC)

Are you thinking of the mitochondrial myopathies - maybe myoclonus epilepsy (which is associated with ragged-red muscle fibers)? -- MarcoTolo 04:14, 20 May 2007 (UTC)

Whoops - here's a link. -- MarcoTolo 04:15, 20 May 2007 (UTC)

How about Rett syndrome? People with it can be short. --Joelmills 04:16, 20 May 2007 (UTC)

What about redshirt syndrome? --Cody.Pope 11:15, 20 May 2007 (UTC)

It was ragged-red fibers that I was thinking of, thanks :) MERRF syndrome. [Mac Δαvιs] ❖ 04:24, 21 May 2007 (UTC)

energy loss = mass loss

Hi,
We're doing Einstein's special relativity in Physics at school now, and we watched a film called "E=mc^2 Einstein's Big Idea" (something like that anyway). And one of the things that was said was that if for example Paris was burnt to the ground and you had a dome over it and retained all the gases etc - if you measured all the mass it would identical to what Paris was before you burnt it. Seem logical enough. But then, taking the example perhaps too far, I thought that this wasn't true since heat and light energy would be lost, and hence because of the interchangeability between mass and energy according to e=mc^2 then a small amount of the matter will be lost. My physics teacher disagrees because it is only chemical reactions which are taking place and hence no mass is lost. Which is true? Thanks, --Fir0002 09:55, 20 May 2007 (UTC)

I'm not entirely positive, but I believe you are right. Though the conservation of mass rule does generally apply, I think that bond energy makes compounds lighter than the sum of their parts. When the bonds are broken this mass is expressed as energy in the form of light/heat. So if the this dome retained all the "energy" as well, then you'd still have a balanced equation, but if the dome let out heat/light then there would be mass loss. It depends on how closed the system really is. In the end though, this mas loss is so minimal it doesn't matter. --Cody.Pope 10:28, 20 May 2007 (UTC)

If any energy is radiated away from the system e.g. heat and light, as the above poster says, then mass will be lost. But the amount of mass lost is likely to be only a small proportion of the total mass of the system, as is E=mc^2, then m = E/c^2. With E in Joules, c in meters per second, then you need ~9 x 10¹³ Joules of energy radiated to lose just 1 gram - that's approximately the same as the energy released in the Hiroshima and Nagasaki atomic bombs - equivalent to around 20 kilotons of TNT. So yes, burning an entire large city will end up releasing mass if there is energy lost from the system, but you need to release a lot of energy to get measurable mass loss. Compared to the overall mass of Paris, the mass lost would be negligible.Richard B 10:50, 20 May 2007 (UTC)

Thanks for that! Yeah I understand about the miniscule amounts we'd be talking about - but it was just a Gedanken experiment where it was just a question of whether mass could be lost even in a chemical reaction. Yay I was right! --Fir0002 12:55, 20 May 2007 (UTC)

Einstein was able to show mass and energy were related with Special_relativity using an absolute velocity ~3x10ˆ8 which is independent of inertial reference frame relative to any observer. One consequence shows an equivalent between mass and energy. A fire is an oxidation reduction reaction which is exothermic in nature. Regardless of infra red electromagnetic radiation, other wavelengths of visible and lower wavelength radiation undoubtedly was produced in this reaction. Electromagnetic radiation can get transferred through convection, conduction and irradiation. Therefore, if the surface was an ideal insulator and had a surface that reflected all wavelengths of electromagnetic radiation, this would demonstrate special relativity fairly well.--InitialMan(adam) 13:04, 20 May 2007 (UTC)

How about a flashlight in a dome with those properties going the speed of light? According to your science teacher's logic, a chemical half cell is a chemical reaction as well, yet it is producing visible light EMR. The battery is losing some mass on a small scale, I believe. Yet the mass/energy would still stay in the dome while the light would be going no faster than 3x10ˆ8m/s

In an educational film? Was it old? Maybe that film is the root cause for this stupid myth.

I'd just like to point out that the battery is not losing mass. If you are referring perhaps to the metal rod at the anode gradually decaying as it get oxidized, then you already know that it is being oxidized into an ion which passes into the solution, so its mass is not lost. The lost electrons are transferred to the cathode, so their mass is not lose either. —LestatdeLioncourt 08:23, 22 May 2007 (UTC)

No, I know the film he's talking about. Here [3] is a link to it. It's 2005. BTW the part he's talking about is in the part of the film about Antoine Lavoisier and his original statement of the law of conservation of mass. --jjron 04:38, 21 May 2007 (UTC)

What about shockwaves? Does the "dome" extend underground?--0rrAvenger 01:01, 22 May 2007 (UTC)

Siphon

Does a siphon work in a vacuum? Actually that's just an excuse to ask someone who knows about these things to take a look at the article, as I'm sure it needs work but I don't think I'm up to it. It seems to me that a simple siphon will still work in a vacuum as it is more dependent on gravity than air pressure. (Surely someone has tried it.) Also soda-siphon bottles aren't really siphons, are they? And is a sink trap an inverted siphon? I don't think so...--Shantavira|^{feed me} 13:13, 20 May 2007 (UTC)

Siphon

No, it wouldn't work. The air pressure is what makes the fluid in the upper reservoir flow upward through the tube. —Bromskloss 13:36, 20 May 2007 (UTC)

Siphon cannot work in vacuum because no material remains liquid in vacuum (except possibly Helium; but liquid Helium is a different story anyway). Any material at zero pressure is either solid, or gas, or a mixture of solid and gas; the gas being (formally speaking) infinitely dilute in absence of containing wall, which is the case here. The solid-liquid-gas triple point pressure is the minimal pressure at which liquid can exist in thermodynamic equilibrium. Lower the pressure, and the liquid will boil out. At atmospheric pressure the proximity of the triple point is not an issue, since most "siphonable" liquids have triple-point pressure orders of magnitude below 1 atm. However, at sufficiently low pressure the weight of the liquid in the "down" part of tube will produce a certain pressure drop, causing the liquid to boil in the upper part of the tube and thus breaking the flow. Now, as far as fixing our siphon article is concerned, I have no books here, and I would really hate to add stuff with no refs. I may get to it later (no promise) , but definitely not before the next weekend. Best regards, Dr_Dima.

So if we imagine a really big tank of liquid - so while the surface of it is boiling off into the vacuum, the rest is still comfortably liquid a foot or two beneath the surface - and presuming that the siphon tube is full of liquid and immersed deeply enough - then the air pressure that would have been pressing down on the upper container is absent - but so is the air pressure on the bottom container (or the end of the siphon tube if it's not submerged). So the lack of air pressure should completely cancel out - and so long as there is enough liquid that it can siphon before it boils away - I can't see any reason why it would matter that it's happening in a vacuum. SteveBaker 15:06, 20 May 2007 (UTC)

If at no point the siphon is above the surface of the liquid in the big tank then - yes - it will work. However, that would be a simple pipe, not a true siphon. In other words, when the surface pressure (in the upper vessel) equals to the triple-point pressure, the pressure of the liquid in the siphon above that level would be lower than the triple-point pressure, and liquid in that part of the siphon will boil. What can save the day, however, is a phenomenon called metastability. That is, even when the gas phase (or solid-gas mixture) has lower Helmholtz free energy than the liquid phase, which is exactly the case below the triple-point pressure, the boiling may be delayed somewhat, see superheating. Relying on metastability is basically the same as taking chances: it may boil or it may not. So it is not a good idea for space applications ... Best regards, Dr_Dima.

Let's eliminate the gas boiling problem by adding a plate to cover the liquid on each cylinder. The plates in the two cylinders are of exactly equal weight and (since this is a thought experiment) the plates can move without friction and float in contact with the liquid.Now what happens? My guess is that liquid flows from the top cylinder tot he bottom one, but I don't know the mechanism. -Arch dude 20:31, 20 May 2007 (UTC)

Ah - OK. I think I've got it. I've changed my mind - it won't work in a vacuum. The maximum height of the siphon tube above the surface of the upper container is determined by the air pressure - for water, on a normal day at sea level, your siphon tube can't rise more than about 32 feet above the tank. The reason for that is that the air pressing down on the surface of the water weighs as much as water that's 32 feet deep. The water in the siphon tube can't tell whether it's immersed in 32 feet of water - or an equivelent weight of air. As the air pressure drops - the height of the pipe above the surface of the liquid decreases until in a perfect vacuum, the siphon tube has to be level with the surface of the liquid - at which point it's not a siphon anymore - it's just a hose sticking out of the side of the container. SteveBaker 21:01, 20 May 2007 (UTC)

If you do this experiment under low pressure conditions (which eliminates the problem of boiling), the fluid will just run out of the siphon at both ends and leave the top part evacuated.

Almost. Under reduced pressure (but not a hard vacuum), the siphon would still work so long as the siphon tube doesn't rise too high above the two containers. But if it is too high and if both ends of the siphon tube are submerged - then the liquid would be some way up the tube with the top part of the loop being full of vapor from the liquid. In effect, the siphon tube is behaving like a Barometer tube. SteveBaker 12:31, 21 May 2007 (UTC)

identifying a bird

Due to the likelihood that my previous post might not be seen anymore (earlier post), I'm beginning a new thread here. This is the bird that I'm talking about. The parental bird has come back (thank god) and has resumed feeding it. Can someone help me to identify this bird?--Ed ^{¿Cómo estás?} 15:00, 20 May 2007 (UTC)

looks like a dove. What part of the world do you live in? Dr_Dima

Chicago suburbs--Ed ^{¿Cómo estás?} 15:54, 20 May 2007 (UTC)

It's a mourning dove. --YFB ¿ 16:01, 20 May 2007 (UTC)

Yep. Dr_Dima

Doves grow up really quickly. A.Z. 16:27, 20 May 2007 (UTC)

Why is it mourning? Who died?

According to the article: "The "mourning" part of its common name comes from its call." SteveBaker 20:13, 20 May 2007 (UTC)

{{spoiler}}

Civility? Clarityfiend 18:23, 20 May 2007 (UTC)

{{endspoiler}}

Should there also be Tailfin warnings, or do too few cars have them to justify a template? Edison 15:14, 21 May 2007 (UTC)

Absolute Error

If one has two values, a=30±0.5 and b=28±0.5, and calculates a value z=a-b, what is the absolute error in z?

As I understand it, there are two avenues of approach.

(1) One could first find the percentage error of a and b, and add them, then convert this back to an absolute error? So error in a=1.67% and error in b=1.79%, thus error in z=3.46% Hence one can find absolute error in z as being .0346 × 2 = ±0.0692. Thus z=2±0.0692.

(2) Or is it true to say that one could simply add the absolute errors of a and b to get the absolute error in z? If absolute error is defined as maximum deviation from a value, is it true to say that z=2±1?

I think that (1) seems to be too much of a small error, and (2) seems better, but surely there is only 1 right answer-which is it?

Thanks! --Fadders 15:13, 20 May 2007 (UTC)

I was going to refer you to our Error analysis article, but it doesn't say much.

But it does refer to our Errors and residuals in statistics article, which... also doesn't say much.

But it does refer to our Propagation of uncertainty article, which says quite a bit, although it's heavy on the math.

But between the three of those, you might find some pointers to your answer.

(One thing I do know is that the proper method for combining the two errors will depend on whether the values are independent or not. So there's not "one right answer".) —Steve Summit (talk) 16:23, 20 May 2007 (UTC)

Well, just think about it - if the true values for your variables are a=30+0.5 and b=28-0.5 - then your estimate for z would be off by +1, if a=30-0.5 and b=28+0.5 then z would be off -1.0 - so adding your errors will give you the worst case. But if you are measuring a and b with the same instrument and the error is because it's mis-calibrated or something (so the actual errors in a and b are not independent) then the expected error in z might actually be zero because the error in a and b neatly cancel out. In the real world, some part of the error will likely be independent and some part not. Basically - you've got to know more about the nature of the sources of your errors. SteveBaker 20:50, 20 May 2007 (UTC)

Last question (not about starch)

All I need now is a link to a websight where I can find a list of beta sources. I would particularly like a list of sources of just beta radiation, and with a long halflife. I tried searching the internet and found a lot of adverts and junk. Can anyone here give me some advice as to what I should do?

Also can a beta partical be said to have an electrostatic charge or have I accidentally borrowed this word from another sort of physics?

Yet another last question- how could I go about making an electron travel in a certain direction using magnets?

I think this is basically what a Cathode ray tube does :) I'm not sure exactly how, but if you read the article you may find it somewhere in there :( HS7 16:30, 20 May 2007 (UTC)

Red article, not got a clue. Would just having the source in a solenoid work? It doesn't have to be too accurate.

Hello. Really need help here

Answer to question regarding moving an electron in a certain direction with magnets. A magnet has magnetic_field lines, B^→ that originate at south poles and terminate at the north pole of the permanent magnet. These ferrous magnets will repel an electron with the N-pole and attract it with the S-Pole depending on the orientation the magnet is held toward a beam. With other electromagnets, the right hand rule comes into effect when predicting the direction of the field related to the polarity of current. ferrous magnets are simple. An electron gun can be used to fire a beam of electrons at a phosphorescently coated screen, however unlike a CRT, the device in my physics lab had an open area which when exposed to magnets, let us demonstrate this phenomena you describe. (Anyone know what this setup is called specifically?)--InitialMan(adam) 18:40, 20 May 2007 (UTC)

Re. the two first questions: our article Common beta emitters might be a reasonable place to start. For more information, try the links at the end of the article Radioactivity. The word 'electrostatic' implies electrical charge that is static, i.e. not moving, such as static electricity. A beta particle carries electrical charge, not electrostatic charge. --NorwegianBlue ^talk 18:48, 20 May 2007 (UTC)

Very last question. If I wanted to measure how much radiation passed through something would I be measuring its permeability or permittivity? Or something else?

That's it now, I've finished. Thanks for all the help with my homework, if it wasn't for you, I might have had to do some work. ;)172.189.71.94 09:41, 21 May 2007 (UTC)

Electrical source

Hi. I've been wondering about many possible sources of electricity, and I have ideas that may work. However, I want to know which do work and which don't. Please indicate if they have already been used as a source of electricity, if they have already been planned as a source, if it is already being used in a different way, if it has been used in many different ways, if it is likely, unlikely, near impossible, too hard to control, too rare to harness, too expensive, too unpredictable, generates too little power, requires more power than it produces, etc. Here is the list:

• lightning
• aurorae
• heat from combustion
• energy from explosives
• human power
• animal power
• chemical reactions
• electrons from matter
• recycled electricity
• continuously rotating magnets
• supercompressed superheated water
• supercompressed air
• energy from pressurised air leaking into a vaccuum
• short wavelength radiation to strip off electrons
• bacteria
• concentrated radio waves
• controlled nuclear explosion
• controlled antimatter annilation
• energy from meteoroids
• moonlight
• gravity
• the strong and weak forces
• colliding atomic particles

So, which are possible? Thanks. -- AstroHurricane001^(T+C+U) 19:10, 20 May 2007 (UTC)

One creates difference in electric potential in a conductor through electromagnetic induction. This process turns mechanical energy into electric energy. Therefore, anything you can attach two magnets to and have them spin near a wire is capable of creating AC electricity suitable for transmission down long lengths of copper wire.--InitialMan(adam) 19:24, 20 May 2007 (UTC)

The trouble with moonlight is that it is almost entirely visible light - solar panels require either the high energy of ultraviolet or the radiant heat of infrared. Also, attempting to extract energy from particles colliding seems to violate the Second law of thermodynamics, unless you are constantly adding more heat to the mixture, in which case it simply becomes an inefficient generator (it would be easier to heat those particles, cause them to enter the gas-phase, and use them to drive a turbine). Laïka 19:37, 20 May 2007 (UTC)

If you're talking about PV cells (as opposed to purely thermal solar energy collection methods), this is not entirely true. Assuming we're talking about the cheap vanilla (poly-)crystalline silicon cells, the peak internal quantum efficiency will be with photons near the band gap energy (1.12 eV), which corresponds to the near-infrared wavelength of ~1100 nm. However, higher photons with energy greater than the band gap energy may still be collected and converted into electrical energy (though the collection probability falls off quickly from the band gap energy). So really, most of the visible spectrum down to the energy of NIR can be effectively converted by cheap solar cells, which is pretty good at airmass 1.5. Once you get to the energy levels of deep violets and ultraviolets, silicon no longer provides very efficient photovoltaic conversion since the absorption coefficient for these short wavelengths is usually so high that photons don't make it to the active region (or within one diffusion length of) before being absorbed, meaning they do not contribute to electrical photocurrent. -- mattb 22:32, 21 May 2007 (UTC)

In theory, you could power something with bacteria, provided bacteria were only part of the process: pump sugar solution into a tank of bacteria, and ferment it to ethanol/methanol, which are both good fuels for vehicles. Laïka 19:39, 20 May 2007 (UTC)

He clearly asked about electricity and then referred to power as a measure of electrical output, I think. Could run generator with the ethanol. There are also ways to use photoelectric effect as was mentioned earlier.InitialMan(adam) 19:45, 20 May 2007 (UTC)

Here's your list (slightly rearranged) with my comments:

• lightning

Suggested, but never implemented.[4] —Keenan Pepper 20:45, 20 May 2007 (UTC)

• aurorae

Same deal.[5] —Keenan Pepper 20:45, 20 May 2007 (UTC)

• energy from meteoroids

Not steady or reliable (and not very big energy sources at that).

• heat from combustion

We use it all the time, of course.

Can you give me a few examples (not too many) of how we use combustion for electricity? Thanks. -- AstroHurricane001^(T+C+U) 22:01, 20 May 2007 (UTC)

I'm sure you can think of some examples (not too many) yourself! How many methods of electrical generation do you know of? How many of them involve burning something? --Steve Summit (talk) 02:06, 21 May 2007 (UTC)

• energy from explosives

Not so different from "heat from combustion" (remembering, though, that in either case, you need a source of fuel/explosives).

• controlled nuclear explosion

Not so different from the nuclear power we already use today. (Again, though, you need a source of nuclear fuel.)

• human power

Works great on small scales; here's a radio with a crank: [6] —Keenan Pepper 20:45, 20 May 2007 (UTC)

Yes, but what if people volunteered to get a paid job where they use their energy to generate electricity for a town, etc? Thanks. -- AstroHurricane001^(T+C+U) 22:01, 20 May 2007 (UTC)

As I said below, humans can't provide the vast quantities of power we need for modern industrial society.

In fact, let's ignore "industrial" society, and look for a moment at the power required by just an ordinary house. According to this web page, the average household in the United States consumes power at the rate of about 1000 watts. (Stated another way, the average household uses 1 kilowatt-hour of energy per hour. Stated another way, this is like having 10 hundred-watt light bulbs burning.)

But according to our article on Horsepower, an average human can only do about 0.1 horsepower of work for sustained periods. There are 746 watts in a horsepower, so an average human can only put out about 75 watts -- not even enough to keep one of those hundred-watt lightbulbs lit. So this average household would have to have 1000 ÷ 75 = 13 (and a bit) people in it, working all the time, just to provide that one household's electricity needs. And there wouldn't be any left over for streetlights, or for the electricity used by city hall, or the electricity used to pump the city's water, or the electricity used to run the steel mills to make metal things out of, etc.

(Now, my analysis here isn't really fair, because you didn't say you wanted to generate all the electricity we need from people, but rather just some, from as many people as volunteer. But I think you can see that a few people, generating electricity just some of the time, aren't going to put much of a dent in a large city's electricity needs. And if you're thinking of paying these people, you have to compare what you'd pay them to the amount you'd spend on other sources of energy. I think electricity tends to cost 10-15¢/kWh these days, at least in the U.S. It'll take 1000 ÷ 75 = 13.3 hours for one person to generate 1 kWh of energy, so if you don't want to pay them more than conventioanlly-generated electricity would cost, you can't pay them more than about 1¢/hour. And you also have to think about the cost of the food they're eating, and the energy cost of transporting the food to them, and the energy cost of transporting water to them to replace the water they'll lose due to perspiration while generating electricity, and...) --Steve Summit (talk) 02:03, 21 May 2007 (UTC)

• animal power

Both work fine and have been used historically, but don't provide the vast quantities of power we need for modern industrial processes. Also, they require food.

Further to Keenan's comment: part of me desperately wants every stairmaster, treadmill, elliptical trainer, and rowing ergometer in every gym and health club connected to a generator feeding back into the electrical grid, instead of dissipating the "excess" energy as heat (which, if in the summertime, we may well have to expend extra real energy on air conditioning to remove). But it's not clear it'd make any significant difference... --Steve Summit (talk) 21:20, 20 May 2007 (UTC)

• chemical reactions

Combustion is of course a chemical reaction. There are plenty of chemical reactions that can be used to produce electricity -- but once again, the problem (if you want to make the process economical) is finding the reactants in quantity and for less money than the generated electricity is worth.

• recycled electricity

There's no such thing.

Really? Isn't it possible to use the leftover electricity (because appliances also send electricity back to the socket) from home use, then combining this energy from many homes, to be stepped back up to powerline voltage, then sent back into homes? Thanks. -- AstroHurricane001^(T+C+U) 22:01, 20 May 2007 (UTC)

Yes, really, there is no such thing as "recycled" electricity.

You can think of a flow of electricity as a flow of water, but what's interesting is not the water itself, it's the water pressure. Electrons aren't valuable in and of themselves; there are billions of them in every gram of matter you own. Electricity isn't just a bunch of electrons; it's a flow of electrons (a current) under pressure (a voltage).

Imagine that in your house you used pressurized water for energy, instead of electricity. Whenever you wanted to do something, you'd turn on a faucet, and the water would run a little waterwheel and do a little work. Then the water would run down the drain. (This would obviously be better for running motors than creating light or heat, or making your television or computer work.)

Now, you could say, the sewer in the street contains all the "leftover" water from all the houses on the street, so can't we recycle it somehow? Well, no, because it's not under pressure any more. Unless you pressurize it again, you can't get any more useful work out of it. But pressurizing it would require more energy. You could recycle it right away as plain water for washing or making cement or something, but not as pressurized water for powering machines with.

When you turn on an electric appliance, yes, the electrons flow into your house, through the appliance, and back out of your house. But the energy flow is one-way: from the power company, to your house. (And actually, since it's alternating current, the electrons aren't even really flowing into, through, and back out of your house, they're basically just sitting there vibrating back and forth. But this doesn't change the fact that the energy flow is one-way.) --Steve Summit (talk) 22:42, 20 May 2007 (UTC)

Just a side comment here. You might imagine that when Steve writes "Imagine that in your house you used pressurized water for energy, instead of electricity", he's describing an imaginary system of power transmission. Not so; hydraulic networks were available in some cities, notably in London, as an alternative to electricity 100+ years ago. However, the power was intended for big industrial-type machines, not for household appliances. And of course it couldn't provide light; but people could burn gas for that. --Anonymous, May 21, 2007, 03:15 (UTC).

• continuously rotating magnets

What rotates the magnets? If a turbine, then this is in effect how our generators (either water- or steam-powered) already work. Otherwise, you might be talking about perpetual motion, which of course doesn't work at all.

I was thinking if the magnets were given a little "push" (which would be quite big since they would have to be quite large) to make the magnets rotate. I was thinking of a hollow cylindrical magnet with alternating polarities across its length, with NSNSNS consecutively, etc, fixed to a kind of axle, but still able to rotate, around another non-hollow cylindrical magnet, with similar consecutively alternating poles all around, also fixed to an axle and able to rotate, and the "push" should send the magnets into motion, with poles constantly attacting and repelling, pushing the magnets around, to generate magnetoelectricity (aka electromagnetism), quite similar to the way bullet trains work, so is it possible? Thanks. -- AstroHurricane001^(T+C+U) 22:01, 20 May 2007 (UTC)

No. You are basically talking about a perpetual motion machine, and as I said, those don't work. --Steve Summit (talk) 22:50, 20 May 2007 (UTC)

• supercompressed superheated water
• supercompressed air

Sure -- but what energy do you use to do the supercompressing and superheating?

Other electricity, of course, which is why I wanted to know whether it will generate more power than it uses or not. Thanks. -- AstroHurricane001^(T+C+U) 22:01, 20 May 2007 (UTC)

It never generates more power than it uses. No matter what "it" is. Besides TANSTAAFL and the perpetual motion article, you might want to read our articles on the second law of thermodynamics (specifically, the Perpetual motion of the second kind section) and conservation of energy. --Steve Summit (talk) 22:50, 20 May 2007 (UTC)

• concentrated radio waves

Sure -- but what energy do you use to generate and concentrate those radio waves?

I was thinking about using background radio waves (eg, from radios or satellites or astronomical objects) concentrated in the same manner as a radio telescope, using radiowavemirrors to concentrate the energy. Thanks. -- AstroHurricane001^(T+C+U) 22:01, 20 May 2007 (UTC)

Sure you can do this, but the amount of energy you get is tiny. There's a reason radios have a few stages of amplifiers to boost and filter the signal coming off the antenna. You might consider this sort of thing for micro-scale energy harvesting, but there are usually better alternatives for this (chemical, mechanical, etc). -- mattb 02:21, 22 May 2007 (UTC)

• energy from pressurised air leaking into a vacuum

Sure -- but how long will your vacuum last?

• electrons from matter
• short wavelength radiation to strip off electrons

What do these mean?

Sounds a little like betavoltaics... —Keenan Pepper 20:45, 20 May 2007 (UTC)

I was thinking about, since electricity is partially made of electrons, to use those electrons from normal matter, and send them into the powerlines, for electricity, and unlike betavoltaics, should probably not require dangerous radioactive material.

The problem, as I mentioned above, is getting those electrons to move.

Hold an unconnected piece of wire in your hand. Make it a bare piece of wire, no problem. It contains billions of electrons, but they're not going anywhere. They're not under any "electrical pressure" (voltage), so you don't get shocked. But you can't get any useful work out of the electrons in that wire, either, because they're just sitting there.

Now, there are lots of ways of imparting energy to those electrons, to give them some voltage so that a current can flow and do some useful work. The easiest way to get the electrons moving is to wave the wire around in a magnetic field. Presto! A current is generated; the electrons move. If you now connect the wire to a light or motor, you can make the light light up or the motor move. You've generated electricity! But: you had to do work, with your arm, waving the wire in the magnetic field. You had to do exactly as much work as the light bulb dissipated, or the motor did. In fact, you had to do a little more work than that, because no generator, no wire, no light bulb, and no motor is 100% efficient. And although you generated this energy, you did not create it; you just transferred some energy from the breakfast you ate this morning. --Steve Summit (talk) 23:03, 20 May 2007 (UTC)

• bacteria

Probably possible, if there's an untapped food source.

This is actually possible directly, not just using bacteria to create ethanol as was mentioned above ([7], [8]). The idea here is that, at a molecular level, extracting energy via digestion for the bacterias' use is just a charge transfer process, and under the right conditions we can siphon off a little. Eldereft 07:39, 22 May 2007 (UTC)

• controlled antimatter annihilation

Sure -- but only if we find some hitherto-unsuspected but readily-available cache of antimatter. Otherwise, you've got to create the antimatter, and that'll take at least as much energy as you'd get back out.

• moonlight

is just sunlight reflecting off a rock, and it's all we can do to extract electrical energy economically from bright, daytime sunlight.

• gravity
• the strong and weak forces

These are just forces, they're not energy sources.

Yes, but I was thinking, for example (and only as an example, there are many other possible alternatives), that maybe you could use gravity to pull down a supply of fluid, etc, quite similar to hydroelectricity, to rotate and generate the generators' power. Thanks. -- AstroHurricane001^(T+C+U) 22:01, 20 May 2007 (UTC)

No, not "Yes, but I was thinking". The point here is "No, force is not energy".

It's very easy to generate electricity from gravity -- sort of. Be at the top of a tall tower (or a steep mountaintop cliff) with a rope, a rock, a capstan, and a generator. Wrap the rope around the capstan, so that if the rope is pulled, the capstan will turn. Connect the capstan to the generator. Tie the rope to the rock. Drop the rock into space. Gravity pulls the rock, the rock pulls the rope, the rope turns the capstan, the capstan turns the generator, presto, you've got electricity.

Until the rock hits bottom. Then, no more electricity.

If there happen to be a lot of rocks on the top of the mountain, you can keep this up for a little while. But eventually, when you run out of rocks to drop, you're stuck. You can haul some of the rocks you dropped back up, but of course to do that you're going to have to expend just as much of your own energy as you got out of the rock as it fell. You might as well have turned the capstan by hand yourself, and eliminated the middleman.

For purposes of producing energy (or, rather, attempting to produce energy, that is), gravity is just like a spring. You can get energy out of a compressed spring, but you had to expend energy to compress it in the first place. You can get energy by dropping something from a height, but somebody had to expend energy to raise the object to that height.

Hydroelectric dams don't extract energy from gravity. They extract energy from the weather systems that lifted the water vapor that fell as rain to feed the streams and rivers that filled the reservoir behind the hydroelectric dam. Since those weather systems are all powered by the sun, in a sense, hydroelectric energy is "just" another form of solar energy. --Steve Summit (talk) 00:59, 21 May 2007 (UTC)

• colliding atomic particles

Not sure what you mean here. Those collisions (by some definition) happen in all chemical and nuclear reactions, including the ones we already use for generating electricity. But they aren't energy sources in and of themselves.

Pardon me if I'm wrong, but I suspect you may not have a solid grasp of the concepts of force and energy, and the law of conservation of energy. Electricity is a very, very convenient medium for transmitting energy around, but it doesn't just spring into existence magically. Every kilowatthour of electricity we generate -- by any means possible, including those we haven't invented yet -- requires an input of at least 3.6 million joules of energy. That energy has to come from somewhere -- either from the sun, or from fuels (biological, chemical, or nuclear) which tend to be expensive and in limited supply. TANSTAAFL. —Steve Summit (talk) 20:27, 20 May 2007 (UTC)

In fact, scratch the "tend to be". All fuels are expensive, and this is due to a perfect collision of the laws of economics and physics. It's like this: 1. Energy can neither be created nor destroyed. 2. Energy is valuable. 3. Ergo, any fuel that can be converted to energy is, economically, just about as valuable as the energy you can get from it.

[Now, it's true, before someone corrects me; ever since Einstein my lemma #1 has not quite been true; energy can be created, and in fact you can get c² of it for each unit of mass you manage to convert directly to energy. If we ever succeed in creating controlled, self-sustaining nuclear fission nuclear fusion, the energy landscape will be very, very different. (However, IMO we'll then have a new kind of global warming problem, but that's OR on my part so I'll stop now.] --Steve Summit (talk) 21:36, 20 May 2007 (UTC)

Surely you mean nuclear fusion. We have have hundreds of power plants that turn controlled, self-sustaining (as long as you keep feeding in fuel) nuclear fission into energy. --24.147.86.187 22:19, 21 May 2007 (UTC)

I certainly did, thanks. ("And stop calling me Shirley." :-) ) --Steve Summit (talk) 23:12, 22 May 2007 (UTC)

Hi. Thanks for solving my question, although I've but a few replies to your questions. Also, your mention of global warming has spawned three new ideas: How about using greenhouse gases to produce heat and electricity, or using a greenhouse-like structure to trap heat, and use it to make electricity, or using photosynthesis for electricity? Thanks. -- AstroHurricane001^(T+C+U) 22:01, 20 May 2007 (UTC)

In order:

How are you going to make electricity from (say) carbon dioxide? I can't see an obvious way.

Trapping heat is all very well, but you need an energy source: where's the heat going to come from? If from the sun, then there are (probably much better) ways of converting sunlight into electricity already.

Using photosynthesis for electricity is what you're doing already when you burn fossil fuels and so on. Or are you thinking of a more direct method? Algebraist 22:24, 20 May 2007 (UTC)

The confusion of forces with energy sources by the questioner smacks of the 1830's era when Thomas Davenport, a blacksmith, saw a strong electromagnet invented by Joseph Henry, which could lift a ton. He thought that a strong magnet equalled a powerful energy source, ignoring the counsel of Henry and others that electricity at that time was generated by batteries, that force was not energy, and that the cost of zinc meant that the motors Davenport invented and patented were then uneconomical no matter how cleverly he applied them to railroads or printing presses. Davenport eventually died insane and impoverished, and the electric motor was re-descovered by others. He didn't even get credit for his priority of invention, when years later dynamos could generate electricity economicalyy from coal or oil fireed steam engines. Edison 15:09, 21 May 2007 (UTC)

Hi. Thanks for all your answers, and even though I don't have time to respond to all of them, I appreciate your help. Thanks. -- AstroHurricane001^(T+C+U) 15:50, 21 May 2007 (UTC)

On the controlled nuclear explosion aspect, you might check out PACER. These things have been proposed before; they may be feasible but they are difficult from an engineering point of view and carry with them additional difficulties (like making any water that you turn into steam very radioactive and needing careful containment). It is easier to get energy from nuclear reactions out of plain old nuclear reactors, and far safer. Aside from the radiological issue, there is also the problem that in order to power your explosion reactor you need to be sending nuclear bombs out to the power plants — not the safest thing to do in a world already worried about proliferation. --24.147.86.187 22:06, 21 May 2007 (UTC)

Varenicline and dreaming

One of the listed side effects for varenicline (Chantix) is changes in dreaming. In my experience over the last two weeks that has included increased vividness and improved recall afterwards. What would be the mechanism for this? --Joelmills 19:30, 20 May 2007 (UTC)

I know that the brain has two main phases of neurotransmitter activity. During waking hours, dopamine and acetylcholine are most active within the CNS. When the mind is unconscious, serotonin and melatonin predominate. Dreaming is most vivid during Rapid Eye Movement sleep, often psychoactive drugs will effect these sleeping patterns indicated by delta waves.

Arctic Waters - Why so prolific?

I've been watching the (amazing!) "Life on Earth" series - and was struck by what seems an anomalous thing. Why is it that the arctic oceans are teeming with life and nutrients - the place to be if you are a whale or a seal or something - when the tropical waters have minimal amounts of nutrients - little plankton, krill, etc?

This seems like the complete opposite of what you'd expect - life is ultimately powered by the sun - and there is a heck of a lot more sunlight in tropical waters than in the arctic.

What's going on here? SteveBaker 20:08, 20 May 2007 (UTC)

I think your point is valid, but ocean currents, especially the thermohaline circulation, tend to flow from warmer to colder waters due largely to convection, thus carrying the nutrients to the poles. Sorry, don't have time to elaborate further. An interesting article I read last week was talking about new findings showing the amazing richness of the deep Antarctic waters, and made a similar point about how you would expect them to be low in life being so far away from the sun, with so little light penetrating to the depths. --jjron 01:04, 21 May 2007 (UTC)

The book which accompanies the Planet Earth TV series says:

"In the oceans, the variety and quantity of life is also determined mainly by the availability of energy from the Sun. The top 100m or so of sunlit, shallow waters contains 90 per cent of life in the oceans. Here it is the availability not of water but of vital nutrients, especially phosphorus and nitrogen, that has shaped marine communities. Though tropical seas receive the largest amounts of sunlight, they are, with the exception of the coral reefs and seagrass beds, largely deserts. This is because these waters are calm, allowing most of the the nutrients to sink to the depths. The ocean's greatest riches tend to be found in rough temperate seas or where upwelling currents provide a good supply of nutrients."

and

"The vast blue desert of the tropical oceans receives ample supplies of sunshine, but once again, lack of nutrients limits phytoplankton growth - the algae at the base of most marine food chains. Tropical oceans are the famously calm seas of the doldrums, and there is little surface mixing to bring nutrients up from deeper water. Neither do these waters benefit from the regular supply of nutrients that rivers bring to shallower waters on the continental shelf."

So that explains why the tropical seas are pretty short of life. The northern and southern oceans, which are subjected to a mighty battering from storms for more than half of the year, undergo much greater mixing so that nutrients are brought up from as far down as 200 m. This fuels the phytoplankton bloom in spring, which feeds the copepods (Arctic) and krill (Antarctic) which drive the marine food chains. --YFB ¿ 03:25, 21 May 2007 (UTC)

Cold water can contain more dissolved gasses (including, y'know, oxygen) than warm water. How significant is that difference here? —Tamfang 19:58, 21 May 2007 (UTC)

Lightning safety

Hi. I wanted to know what activities are safe and which aren't to do during an electrical storm inside a building if lightning stikes nearby. Here is the list:

• turning on a light
• urinating
• inserting a lightbulb into an electric light
• using magnets
• walking
• going to the basement
• opening a window or keeping one open
• touching a doorknob
• swimming
• editting wikipedia
• using an elevator
• putting on or taking off staticy clothes
• touching a washing machine
• lighting a fireplace
• turning on a gas powered furnace
• touching an appliance
• opening a door
• touching a metalic or wet object
• combing hair
• throwing something outside
• lighting a candle
• skating on an ice rink
• going to the top of a building

So, which are safe and which are not? Thanks. -- AstroHurricane001^(T+C+U) 20:14, 20 May 2007 (UTC)

Here's an idea: Read http://www.lightningsafety.noaa.gov/indoors.htm to get a general idea, remove any of these that are obvious, and leave the ones you're still curious about. You'll get better answers with a shorter list. —Keenan Pepper 20:49, 20 May 2007 (UTC)

editing wikipedia - never safe, electrical storm or not. --88.110.39.243 22:24, 20 May 2007 (UTC)

LOL! Well, it's not like some random wikipedian will emerge through the computer and eat your brains, right? Thanks. PS. if it's not safe, then why are you editting it ;-) ? Hehe. -- AstroHurricane001^(T+C+U) 22:32, 20 May 2007 (UTC)

Actually, editing Wikipedia is the most risky one, though if Astro had included using a telephone (landline) or watching television that would also be risky. This is because those devices probably have electrical connections outside the house, to the telephone line or an aerial. If a lightning strike is possible, switch off your computer and don't use the phone. I once had a answering-machine melt because of a lightning strike. I was using my PC at the time, but although it went dead at the time, it fortunately survived. (I now have a surge protector of course.)--Shantavira|^{feed me} 08:23, 21 May 2007 (UTC)

Mythbusters tested quite a few of these: they found that having a shower was very dangerous (current passed from the shower, through the person, to the plug hole). Swimming could be dangerous; it depends where the lightning is relative to the drains of the pool (lightning always wants to flow to ground, and the metal drain pipes are the best route, so it will try to find a route to these drains, through people if necessary). Opening a wooden door is unlikely to be dangerous, as electricity will not want to flow through the door, but touching a metal door while standing on a metal surface (such as a metal fire-escape) could be very dangerous. Taking off clothes which produce static shouldn't attract lightning towards you at all; nor should lighting a candle or using magnets. Standing on top of a tall building would be incredibly dangerous though; you'd become a human lightning rod! Urinating would probably be safe, as although electricity can travel through urine, the stream tends to break up into individual droplets which cannot transmit 'leccy (as shown again by Mythbusters). Laïka 08:35, 21 May 2007 (UTC)

Hi. Can you show me the link to the mythbusters episode where they tested this? Thanks. -- AstroHurricane001^(T+C+U) 15:59, 21 May 2007 (UTC)

Principly in MythBusters (season 2)#Phone in a Thunderstorm, although MythBusters (season 2)#Appliances in the Bath and MythBusters (season 2)#Peeing on the Third Rail also covered it. Laïka 20:46, 21 May 2007 (UTC)

merging of storms

Hi. Is it possible for a very low-pressure storm, say, a tornado or hurricane, to merge with another one, if the two or more came really close? Would their low pressure centres cause them to come closer and merge, or would the speed at which they spin past each other cause them to fling each other away? Has this ever happened before? I know about an effect where hurricanes come close to each other and swirl around each other, and when a storm absorbs another, but I'm talking about when two storms like hurricanes or tornadoes or galaxies come very close together and of similar intensity collide nearly head-on at a steady, but not too rapid pace. Is it possible for them to merge and for their centres to collide? Also, if the Andromeda Galaxy collided with ours, wouldn't all the mass from the supermassive black holes, dark matter, orbiting satellite galaxies, and even M33 cause their centres to come together and merge, possibly exploding, and while it heads toward the Virgo cluster and the great attractor, could it cause other galaxies to fluctuate and merge, causing the supercluster to merge into itself? Thanks. -- AstroHurricane001^(T+C+U) 20:24, 20 May 2007 (UTC)

Yes - see 1991 Halloween Nor'easter (aka "The Perfect Storm") for example. SteveBaker 20:35, 20 May 2007 (UTC)

Ok, thanks, but what about the Andromeda and ours? Are they going to collide, if the gravitational effect takes place? Thanks. -- AstroHurricane001^(T+C+U) 15:55, 21 May 2007 (UTC)

Galaxies do sometimes collide and merge; see [9] [10] [11] [12]. But in the process some of the mass gets thrown out of both and scattered. —Tamfang 20:05, 21 May 2007 (UTC)

Yes they are going to collide ... in the sense that whereas there are currently two spiral galaxies, in five billion or so years things will settle down with one larger elliptical galaxy (a recent paper modeling the merger, with link to movie). Run that another few gigayears and you should have a well-defined galactic plane and maybe spiral arms. The interactions shaping this merger, however, will be almost purely gravitational (see Bullet Cluster for how this is not quite true - the noninteracting dark matter has been slightly separated from the normal matter as the latter is slowed by collisions). The combined galaxy will certainly have a different effect on local cluster dynamics than the individual galaxies do, but the merger is more like two rain clouds than two baseballs. Basically, space is big, and two objects are far more likely to go into orbit around each other than actually collide - see also conservation of angular momentum and gravitational slingshot for how stuff gets kicked out into high orbits instead of all just falling into the center at once. Eldereft 09:02, 22 May 2007 (UTC)

Why do magpies like metallic objects?

My grandma was telling me today about how a magpie stole her wedding ring, many years ago. She'd taken the it off to do the washing up and the bird flew down, put its head through an open window and boldly grabbed the ring from the windowsill.

What exactly is the deal with magpies and their obsession with shiny metal (the European Magpie article only touches on the subject briefly)? Why do they need it? What do they do with the stuff after they've collected it? --Kurt Shaped Box 21:21, 20 May 2007 (UTC)

I've heard they use shiny things to attract or look good in front of potential mates. "Hey look at all the shiny things I got, will you marry me?" Not so different from humans really. —Pengo 00:38, 21 May 2007 (UTC)

I don't think they need it as such, but (like a lot people) are just attracted by shiny things. Some birds, the bowerbird is a notable example, use brightly coloured objects to decorate their bowers and attempt to attract mates. I don't really know, but perhaps magpies put this shiny stuff in their nests and hope to attract mates - if it attracts one bird to take it, perhaps it could attract another bird, a potential mate, to the nest. --jjron 00:42, 21 May 2007 (UTC)

The concept of Bling may be effective across species. Why do humans need necklaces and earrings and various other bejewelled piercings? Edison 14:58, 21 May 2007 (UTC)

Actually, that makes perfect sense. Heh. --Kurt Shaped Box 23:09, 21 May 2007 (UTC)

derivation for the moment of inertia of a sphere

Hi. I need a derivation using calculus of the moment of inertia for a solid sphere of uniform density (which is 2/5 MR^2). Only I need it so that the derivation doesn't require the knowledge of any other moments of inertia(such as a disk's or hollow sphere's). I'm in high school and understand math through BC calculus, so if you need to use more advanced stuff (which I think you do), try to quickly explain it please. Thanks. --71.185.134.107 21:30, 20 May 2007 (UTC)

I (a pure mathematician by inclination) have sufficiently forgotten physics that I can't readily do this. However, I can point you to this website, which looks ok, where the MoI of a sphere is derived from that of a disk (also explained on the site). If there's anything there you don't understand (BC calculus means nothing to me I'm afraid) then come back here and I'll try to help. Algebraist 22:07, 20 May 2007 (UTC)

Thanks, but what I meant by without knowldge of any other moments of inertia is that you don't even calculate other moments of inertia within the proof and this proof uses the MoI of a disk.

By the way, BC Calculus is basically the first year of calculus in college, except it's in high school.--71.185.134.107 22:28, 20 May 2007 (UTC)

Still lost, I'm afraid, you're talking to a parochial Englishman. So you aren't allowed to use other MoIs, even if proved. Why is that, anyway? I'll think about it (and try to find a pen :P); I suppose your best bet is just to bash out the integral. Algebraist 22:37, 20 May 2007 (UTC)

If I change co-ordinates to cylindrical polar co-ordinates and use the word Jacobian, will you understand that? Algebraist 22:54, 20 May 2007 (UTC)

I have solved the problem using cartesian co-ords alone. Due to the ghastliness of the expressions, I'm putting them on your talk page, not here. Algebraist 23:13, 20 May 2007 (UTC)

Hi. There's nothing on my talk page. As to what I understand, I understand the coordinates but I dont know the word Jacobian, but I supppose I'll click on that link.--71.185.134.107 23:17, 20 May 2007 (UTC)

After much texing, there is now. That (unless I've made a mistake) is a direct calculation of I in cartesian co-ords. It would be more sensible to transform into cylindrical co-ords (the integrals are somewhat nicer), which is more-or-less equivalent to using the moment of inertia of a thin disk. Algebraist 23:44, 20 May 2007 (UTC)

Thank you very much.--71.185.134.107 00:08, 21 May 2007 (UTC)

Alex Chiu - "Better living through the power of magnets"...

I'm fully aware that Alex Chiu and his magnetic healing theory is a laughing stock amongst the scientific community - but reading some of his stuff has left me a teeny bit curious. Has anyone ever actually tested his devices with an open mind and documented their findings in an unbiased, scientific manner? I can easily find lots of writings online, basically taking the piss out of the guy and calling him names - but little in the way of hard science. --Kurt Shaped Box 22:36, 20 May 2007 (UTC)

Nobody wants to waste their precious time or money in constructing a proper scientific test of the "magnetic healing theory". You, Kurt, can take the honor of being the first to do so. When you have done the experiment, do come back and report to us. Thank you. 202.168.50.40 22:59, 20 May 2007 (UTC)

I said I was curious - not that I was born yesterday... ;) --Kurt Shaped Box 23:10, 20 May 2007 (UTC)

I'd be interested to see a photo of him, since he claims his "gorgeouspil" (which he takes) makes people more beautiful than supermodels. He also claims to be able to reverse aging, cure herpes and cancer, and predict the future. Next thing you know, he'll claim he can win the war in Iraq. Clarityfiend 23:04, 20 May 2007 (UTC)

There's an interview with him here. I'm straight but I don't think he's necessarily a bad-looking looking bloke... :) According to this, he also apparently sleeps with his head beside an electromagnetic coil and has experimented with passing electrical currents through his bathwater. --Kurt Shaped Box 23:10, 20 May 2007 (UTC)

Apparently sleeping with your head next to an electromagnetic coil causes a particular type of brain damage which makes you think you can cure anything. :-) StuRat 23:45, 20 May 2007 (UTC)

Yeah, but is he more fab than Fabio? (too lazy to download) Clarityfiend 23:23, 20 May 2007 (UTC)

Since it's rather expensive to do legitimate scientific tests, I'd prefer that we spend that money on things with a higher probability of being legit, like herbs that have been used for generations for healing. I don't think all such herbs work, but I bet that some do. StuRat 23:49, 20 May 2007 (UTC)

We all know that's total malarky. Next think you know Stu will be telling us that mold extract can cure infections. Someguy1221 00:06, 21 May 2007 (UTC)

...or that willow tree bark can cure a headache. StuRat 00:23, 21 May 2007 (UTC)

Science isn't about taking a vast number of random, untested theories from people with no training and no scientific approach - and one-by-one disproving them (or perhaps once in a million times - finding they are true). Just read this help desk - we regularly get two or three perpetual motion machine ideas every week - despite the impossibility of perpetual motion being one of the most well proven things we have in science. That's a total waste of time and money for trained scientists. A far more productive use of time is to find things that are well known to actually work - which we don't understand - and to ask "Why?" - or to extrapolate from known knowledge into the unknown by probing the outer edges of our understanding. It's really, really well documented that magnets have almost zero effect on the human body. Millions of people have had CAT scans - the magnets on those things are insanely powerful - and they have absolutely zero documented effect on humans. We live in the earth's magnetic field 24:7 - no effect. We've had people live on the Moon for several days - far away from the Earth's magnetic field...no effect. It's simply a waste of everyone's time to investigate every crackpot idiot - especially since neither they nor their 'believers' are going be swayed by what your careful investigations prove. SteveBaker 00:12, 21 May 2007 (UTC)

If Chiu had an electromagnetic coil similar the ring around Uranus it might be easier for him to sleep with his head up it. Asking for research grant to replicate or refute his claims would do little to advance the career of a medical scientist. It might be worked into studies of the claimed detrimental effects of electromagnetic fields on human health. Maglev railways and even subways/elevated trains with a 600 volt DC third rail have large magnetic fields, so effects should be obvious on the conductors/motormen. I have seen offices where there was a large enough DC magnetic field to cause the image on a computer monitor to move halfway off the screen, due to a battery backup system on the other side of a concrete wall. Health effects on the workers? They did not know there even was a magnetic field at theor work location until they got a computer in the 1980's. Edison 14:52, 21 May 2007 (UTC)

In Chiu's defence (I can't believe I just typed that!), as I understand it, his theory involves the application of magnetic fields to very specific parts of the human body for extended periods of time, with the polarities carefully aligned - rather than the general random exposure one might receive on a maglev train or from a battery backup system... --Kurt Shaped Box 20:57, 21 May 2007 (UTC)

Ample research has been done on the topic of magnet therapy. Practically every study finds it no more effective than a placebo. I don't know anything about Chiu's claims that would distinguish them from magnet therapy in general. Even if it were marginally effective it is certainly nothing close to the panacea that he claims it to be. --24.147.86.187 22:01, 21 May 2007 (UTC)

Chiu's claims go beyond mere healing into the realm of metaphysics. I read an essay on his site years ago (dunno if it's still there) about how he believed that magnets were the root cause of all human misery but could also be used to redeem us. It was pure BS - but it was still an entertaining read. As far as I remember, it went something like this: He postulated that every living thing on earth is comprised of cellular magnets and that the clashing of our own individual magnetic fields creates net repulsive force and an unbridgeable distance between one human mind and another - a gap which we all fill with negative emotions as a defence mechanism against the fear of 'not knowing what the other person is thinking'. Supposedly, if we were able to harmonise our magnetic fields, all human consciousness would be as one - which is a Good Thing, according to Chiu. He also equated this 'body magnetism' to the Eastern concepts of chi/qi/ki.

He had long essays about how gravity = magnetism and how magnets are responsible for the predator/prey relationship in animals too (the zebra runs from the lion because their magnetic fields are of the same polarity). I think he said that the sun was heated from within by trillions of rotating super-magnets too. --Kurt Shaped Box 22:39, 21 May 2007 (UTC)

Rotating super-magnets? Did he mean protons?  :) – b_jonas 12:27, 22 May 2007 (UTC)

This kind of thing exemplifies the problem of not following the scientific method. If there are "cellular magnets" then let's do an experiment. Compasses are affected by magnetism...so let's see if a human can walk in front of magnet and make it deflect...hmmm...nope. So if there are cellular magnets they must be much less powerful than (say) the Earth's magnetic field because the earth can easily deflect a compass needle. So we may deduce that these cellular magnets are thousands of times less powerful than the earth. Mmmm'K - but if cellular magnets are causing things like the emotional interplay between humans, how come our emotions aren't dramatically affected depending on whether we're facing North or South? This is a simple experiment - a child could do it. But Chiu evidently hasn't - or he wouldn't be saying this stuff. Similarly - if the sun was powered by magnets, we'd see a change in the way compasses point between day and night - but we don't. Lions would hunt differently when facing North than South...the whole pile of crap just collapses in the face of the simplest experiment with apparatus you can pick up for a buck or so. Now he'll just say that these are cellular magnets that can't be detected with compasses - but that's just saying that this isn't magnetism - at all and that he needs to find another term for this effect he thinks he can measure. However, if his "cellular magnetism" is some completely separate phenomenon from the regular kind of magnetism then he wouldn't be able to make piles of cash by selling magnetic bracelets and shoe inserts to gullible old ladies - so he can't come right out and say that. However you cut it - this guy is another charletan. SteveBaker 17:15, 22 May 2007 (UTC)

I've always wondered this. Do these alternative therapy guys/mystic healers/charlatans/quacks/whatever the hell you want to call them generally genuinely believe that their own methods are effective and that they're really saving lives - or do they go into it with the express intention of making money from the gullible and desperate? I don't suppose that it matters in the grand scheme of things - but still... --Kurt Shaped Box 21:01, 22 May 2007 (UTC)

Probably depends on the guy in question. Some of them are genuine, but deluded. Some of them are basically con men. As for using a compass, Chiu, like all of these guys, would probably have some answer which is predicated on believing in his theory in the first place. It's not necessarily an inappropriate response — look at the string theorist wiggle whenever something they predict comes out slightly wrong — but it certainly doesn't inspire belief. --24.147.86.187 13:48, 23 May 2007 (UTC)

My head's spinning...

What is a propeller spinner? Spinner says it's a propeller, but in Albatros D.III, it says "Austrian pilots often removed the propeller spinner from their planes, since it was prone to falling off." Clarityfiend 22:45, 20 May 2007 (UTC)

According to [13] it is A cone-shaped piece of an airplane, mounted on a propeller, which reduces air resistance, or drag. Here is an image of a propeller spinner for model airplanes: [14]. --mglg_(talk) 23:18, 20 May 2007 (UTC)

Looks like our Spinner page was wrong. Fixed. --Steve Summit (talk) 00:42, 21 May 2007 (UTC)

Perhaps the person who originally wrote that spent too much time under a Beanie, where one might actually refer to the entire propeller as a "spinner".

Atlant 13:06, 21 May 2007 (UTC)

Not to be confused with Spinner (porn industry), a term once applied to the tv character Ally McBeal on the eponymous show. Edison 14:43, 21 May 2007 (UTC)

When someone is cold = liquid snot. When someone is warm = solid boogers

Why??????? That makes no sense???--0rrAvenger 23:55, 20 May 2007 (UTC)

Just an educated guess really - if it's warm the warmer air being constantly inhaled and exhaled will evaporate more moisture out of the snot thus leaving it dryer and more solid. If it's cold, less evaporation, watery snot. --jjron 00:46, 21 May 2007 (UTC)

I don't agree, I've definitely had a runny nose in hot weather, and especially when eating hot soup I almost always get a runny nose, even if I don't have a cold. Vespine 01:21, 21 May 2007 (UTC)

If you're cold (and especially if you have a cold), your nose runs. No mystery there. The mucus is excreted in a runny state, and since it's being excreted voluminously, it runs right out of your nose. I think this is one component of the defense mechanism: as it runs out of your nose, it takes viruses and other pathogens with it.

But if (for whatever reason, like because it's a warm sunny day, and you're healthy) your nose isn't running very much, what little residual mucus it does contain has plenty of time to lose moisture and congeal. This is especially true when it isn't raining such that there's more dust in the air to get mixed in with the snot to form a nice conglomerate. (But I'm speculating, too; I don't know if this is the right answer.) --Steve Summit (talk) 01:21, 21 May 2007 (UTC)

I think we'd need to take some control over this 'experiment'. We need to take a person with the same runny nose, say with a cold, and put them somewhere warm and somewhere cold, then compare the composition of their snot. What Steve and Vespine are saying is fine, but lacks this control. Now, I seem to remember that my nose runs less when I have a cold if I go into a warm environment. I think that's what OrrAvenger was originally asking, why this was so. --jjron 02:54, 21 May 2007 (UTC)

Don't just mean to be contrary but actually, what I was trying to do is point out the fact that what OrrAvanger was saying lacks this control. Vespine 05:18, 21 May 2007 (UTC)

It doesn't necessarily lack the control, but exactly what he was asking is open to interpretation. As you interpret it, you are right that you can't just make a blanket statement about it. It seems a bit pointless to me to answer it like that though, which is why I say you need the controlled experiment. OrrAvenger could clarify the question a bit. --jjron 06:48, 21 May 2007 (UTC)

When I'm cold, my nose is runny. When I'm warm, my nose is stuffy. I don't know what else to say.--0rrAvenger 14:50, 21 May 2007 (UTC)

Well, I think it is to do with vasoconstriction and vasodilation. When you get cold, your veins and stuff constrict under the skin, thus widening the passage in the nose, allowing the mucus to run easier. When it is hot the veins swell etc, thus restricting passage of mucus etc through the nose. Just an educated guess.

Rage Virus

Seeing as some chemicals (like in chocolate, which makes you feel good) can affect your emotions, is something like a Rage Virus as seen in 28 Days Later and 28 Weeks Later possible? --81.179.110.37 22:34, 20 May 2007 (UTC)

Rabies can make animals crazy, so I suppose it doesn't sound impossible. Vespine 00:06, 21 May 2007 (UTC)

Toxoplasmosis is a nasty disease, carried by a quarter of the population, which causes the infected to take risky behaviour; infected mice will become attracted to cat urine, while humans drive less responsibly[15], develop a lower IQ and become more promiscuous. Infected men become anti-social and angry, while women become outgoing and friendly. That's a huge change in a person's personality just from a common disease. Laïka 08:43, 21 May 2007 (UTC)

Infection by the Dicrocoelium dendriticum flatworm gives ants a raging desire to climb somewhere that a sheep might eat them. --TotoBaggins 20:24, 21 May 2007 (UTC)

A virus could, theoretically, be genetically modified such that it were to infect and alter the function of the adrenal glands or, perhaps, the serotonin circuits of the brain. Altering the functions of neurotransmitter or hormone signaling systems with a viral vector is technically feasible; very difficult, naturally, but not impossible. — Scientizzle 22:16, 21 May 2007 (UTC)

Ice cream in hospitals

Why do hospitals give out ice cream? Yes, it's particularly ice cream that patients get "as much as they want". Where does this come from? --88.193.241.224 19:08, 20 May 2007 (UTC)

[disclaimer: this is speculation on my part]

Why wouldn't they? Because it's "unhealthy"? But if hospitals served only (one definition of) the "healthiest" food, it might be boring and/or unpalatable to lots of patients. But patients need to be happy to get better, and they can't be happy if they're eating gruel. (I'm oversimplifying here, but I hope you get my point.) There's a tradeoff to be made between "healthy food" and comfort food, and it could be that someone decided that ice cream was comfortable enough, and not so unhealthy, that it could be provided. (Also, besides being a comfort food, ice cream is of course soothing to sore throats, which lots of hospital patients have for various reasons.) —Steve Summit (talk) 19:55, 20 May 2007 (UTC)

[P.S. With that said, a lot of hospitals serve pretty crappy food, not because it's healthy or unhealthy or comforting or grueling, but rather because they contract with the same sorts of food-service companies as other large institutions do, and with an institutional food-service company... well, you get what you get.]

One advantage of ice cream and a few other foods, like Jello, is that it quickly melts and becomes a liquid, making it far easier on a digestive system that may be impaired. Healthy food, with lots of roughage, is not so easy to digest. So, while healing, it makes sense to eat ice cream. Just make sure there isn't any Olestra in that ice cream. StuRat 23:17, 20 May 2007 (UTC)

I got as much ice cream as I wanted when my tonsils were removed. It was supposed to help the healing process. I have no idea, if this is a myth, but I was 6 and couldn't care less. ^^

Ice cream can also possibly numb pain, and is no way unhealthy. Just like Jello, patients need quickly metabolizable sugar, and ice cream has plenty. Also, everybody likes it! [Mac Δαvιs] ❖ 04:16, 21 May 2007 (UTC)