Wikipedia:Reference desk/Archives/Science/2007 August 6

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August 6

Saw

Hello. I'd like to know the name of this kind of saw. Are they simply called "hand crank saw"? Since Google only gives 7 results for that, I suspect there's some special name for the tool. Thanks a lot.--K.C. Tang 02:00, 6 August 2007 (UTC)

It is quite a peculiar tool, I don't believe it is very common, I worked in a tool shop for about 6 years and never saw one, or sawed with one... ahem.. Anyway, I would call it hand powered scroll saw, which gives another 7 Google hits:), technically, it is a scroll saw, just that it is crank powered, I don't believe that makes is a "different tool" with a special name: Just like a hand drill, a pneumatic drill and an electric drill are all still drills. Vespine 02:04, 6 August 2007 (UTC)

I see, thanks a lot!--K.C. Tang 04:53, 6 August 2007 (UTC)

Fret saw oddly doesn't show an image of the saw itself (I've got one, but it's rusty and all the blades are broken), but if you image google it there are some examples, without the crank, though. Given that a fretsaw is meant for very delicate work, going around all sorts of (sharp) corners rather than following straight lines, I wonder if the crank would be very helpful. DirkvdM 08:27, 6 August 2007 (UTC)

I'd guess at fretsaw or jigsaw (hand cranked) - I'm more familiar with treddle operated versions (using the feet).87.102.34.140 08:32, 6 August 2007 (UTC)

It's hard to understand why anyone wold power a fretsaw with a handcrank located so unhandily low. This would mean you need one person to power it (unskilled labor) and the other to operate it. Much more common to have a foot-powered treadle and make it a one man operation. Edison 14:38, 6 August 2007 (UTC)

I'm guessing that the saw is operated with the 'saw beam' facing away from the body - a bit like riding a racing bike? - that does still leave the problem of only having one hand to turn the thing thats being cut. (Bet they were very easy and cheap to make though..)87.102.34.140 17:53, 6 August 2007 (UTC)

Ants

I saw an ant colony doing this today. The ants were just huddled near the entrance to their nest and sort of shuffling around a little. This is in southern Arizona around 3 PM. It had rained a few hours earlier and it was in the mid 70s. What were they doing? 68.231.151.161 03:05, 6 August 2007 (UTC)

They look like red harvester ants to me. I saw them when I was in the Mojave. I noticed a peculiar social order. Some ants would go out searching for food - which is hard in the desert. Others would hang out at the opening to the hole. The ones who ventured out would drop off what they found at the opening and all the ones there would examine it and take it in if they liked it. The foragers would go back out again to find something else. If we stopped the foragers from getting back, the hole would get full of ants waiting for food to arrive - and I suspected they assumed something huge was coming because they would work themselves into a frenzy waiting for something to arrive. -- Kainaw^(what?) 03:15, 6 August 2007 (UTC)

With all that stress, I wonder if there would be a need for an ant psychiatrist. Or would there be too great a danger of ants becoming invisible if you shrink them? DirkvdM 08:30, 6 August 2007 (UTC)

RE: Kainaw's story: Hehe, it's like psycoanalyst playdirt :D SGGH ^speak! 22:39, 6 August 2007 (UTC)

Gene Transfering

Jellyfish and coral genes transferred into bacteria, which are then spread on an agar plate to create a fluorescent beach scene.

Is it possible to transfer a gene for any good characteristic from an animal and add it to human DNA so that a human can have the advantage of this animal  ????? Spiderman is an example ( I know it is just a comic book but scientifically it seems possible ? )

Well, the technology is available to make it possible to transfer genes from animals or plants to humans, but it would be legally and ethically dubious to do so. Scientists regularly transfer genes between (non human) animals though (and put human genes into animals). One of the most common transgenes is one that encodes Green fluorescent protein from a jelly fish. When you put it in other animals they glow green. See Alba (rabbit) or Fluorescent green pig for examples (image here). The image to the right is an example of different coloured fluorescent proteins in bacteria.

Note however, that adding a single gene is very different creating a web-firing, acrobatic Spiderman from spider genes. That kind technology is not currently possible. To take another comicbook character as an example. It would be relatively easy for scientists to create a green-skinned human, but not to give him the rest of The Hulk's extra-human characteristics. Rockpocket 04:59, 6 August 2007 (UTC)

Expanding on the above, adding a gene to an organism merely adds the ability of said organism to produce a specific strand of RNA. Generally, this has the effect of adding the ability of producing some specific protein to an organism. Genes are often added to bacteria or yeast (or even human cells) so they can produce a specific protein, for either experimental or other purposes. If you've taken enough biology, you can imagine that simply giving a human the ability to produce one, or any number of extra proteins will not transform him into a superhero (or supervillain). For all organisms (us included), the control of production of proteins (making them only under specific conditions, in specific cells of the body, delivered to the right parts of the cells) is generally as important as the proteins themselves, and evolution has produced very finely tuned methods of DNA control. RNA isn't only used to create protein, however, as they can also be used to shut off or simply slow down production of a protein the target organism can already produce. Transfecting a target organism with a gene for miRNA, shRNA or siRNA can be used to this effect. As for possible medical applications of this in humans, causing cells to over or underproduce some particular protein can be used to mitigate the effects of various diseases, through gene therapy. A branch of current AIDS research is exploring the use of various gene therapies, including the introduction of a shRNA that targets viral RNA, for example. Anyway, back to the original question, "good characteristics" are almost never the result of a single gene, but rather the coordination of several genes with the rest of the organism. Someguy1221 06:16, 6 August 2007 (UTC)

Right now it's impossible to do. Like what the other users have said, complex characteristics require many genes. DNA is merely a template to produce proteins. Proteins interact w/ each other and other chemicals to make organs and carry out chemical reactions. Genes interact with each other in complex networks, so adding something new to that network may mess up the whole system. Even if we know all the genes that make web-shooting possible, we have to know exactly how it would interact with other genes in our DNA. I don't know if we'll ever reach that stage in science; it may belong only in science fiction 128.163.224.199 17:40, 7 August 2007 (UTC)

I think the main problem with this is that even if you get the materials that are needed, you still have a long way to go. To use Spiderman as an example, even if you added a gene to produce the proteins that make spider silk and they somehow managed to combine correctly to produce the substance, spiders cannot "shoot" their silk out of themseves. To do this, you would have to put a musculature similar to human lips to "spit" the silk out. Or, you would have to make the silk drain into a "bag" (similar to the gall bladder or the urinary bladder) that can squeeze hard enough to squirt out the silk. The second idea sounds like it would work better, but it would be much much harder to engineer, not that it matters because even the first idea is FAR beyond our current capabilities as we still don't know exactly why certain genes are activated in certain organs. (Every cell (except gametes) in a human's body has practically the same DNA. Why is it that only cells in the retina produce melanopsin, a protein necessary for sight?)69.205.180.123 16:08, 8 August 2007 (UTC)

Does electrons attract or repeal photons ?

Does electrons attract or repeal photons ? Will a negetively charged body attract photons or it will repeal photons ?

Photons don't have a charge, so are unaffected by it. The photon will be very very very slightly attracted to the electron through gravity. Capuchin 07:46, 6 August 2007 (UTC)

And vice versa, of course. With gravity, the attraction is mutual. DirkvdM

There's some quantum physics thing about how when two electrons pass it triggers one to send a photon to the other, which manifests itself in the electromagnetic forces making them repel each other. That would happen with any charged particles. I don't know much about it, though. — Daniel 21:49, 6 August 2007 (UTC)

Electrons have no political or legislative power, hence they cannot repeal photons 68.39.174.238 02:03, 10 August 2007 (UTC) PS. I know that's a little smart, but the question has been ably answered above, and so don't think that this is preventing a correct answer

The Epidermis

What happens when UV rays shine on uncovered bare skin (Human Skin)? Also, is the reaction different from a light,darker and black skin?

I would guess you're looking for sunburn or suntan, if that's any help Rawling4851 09:45, 6 August 2007 (UTC)

Melanin, Human skin color would be of use too. Capuchin 10:52, 6 August 2007 (UTC)

Concerning the risk of skin cancer you might want to read more about thymine dimers. Mrdeath5493 16:21, 6 August 2007 (UTC)

If you are interested in what happens at the molecular level, melanogenesis is what you want. Rockpocket 21:07, 6 August 2007 (UTC)

spin of neutron etc

Does anyone know what (if any) forces or other interactions result from the spins on neutrons?87.102.34.140 09:37, 6 August 2007 (UTC)

Spin gives a magnetic moment to the neutron, so that it is affected by an inhomogenous magnetic field. See Stern-Gerlach experiment. Bo Jacoby 13:13, 6 August 2007 (UTC).

A linear vector is not a good model for the magnetic moment here? If a the magnetic moment could be expressed as a linear vector in 3dimensions it would be impossible to quantise since it could assume any orientation. Is this correct? (There is no electric charge on a neutron)

If so what is the type of symmetry of the magnetic moment?87.102.34.140 13:40, 6 August 2007 (UTC)

The magnetic moment has the same symmetry as the spin. When you know the answer, why do you ask? Bo Jacoby 13:52, 6 August 2007 (UTC).

But the classical decription is not right? I'm looking for the article that describes the nature of the quantised spin, please.87.102.34.140 14:04, 6 August 2007 (UTC)

Not only is the classical description not right, there is no classical description of spin. No point like particle, such as an electron or quark can have classical angular momentum. I assume the article you want is Spin (physics). Section 4 of that article talks about spin and magnetic moment. Cyta 07:13, 7 August 2007 (UTC)

genetic intelligence

There's a lot of info on 'racial intelligence' but have there been any studies on IQ or similar relating to hair colour? I'm thinking specifically of people with ginger (orange not red) hair colour, in my limited experience ginger hair seems to be associated with (for want of a better phrase) being "as thick as pig shit"? (without exception) I'm willing to accept that I may have developed some sort of bias.

Have there been any proper studies of this?87.102.34.140 09:37, 6 August 2007 (UTC)

This seems unlikely, although not impossible. You might however want to have a look at negative attitudes towards redheads and the genetics of human hair colour. You might also want to have a peek at the article on prejudice. Lanfear's Bane

Yes, doesn't mention stupidity as being a trait. I'm not sure how comfortable I would be with confirmation (furiously backpedalling) - erm I could have worded the question better.87.102.34.140 13:09, 6 August 2007 (UTC)

Hmm, seems like your own bias. In my experience, people with 'ginger' hair made up a higher proportion of the higher sets at school than would be expected from the proportion of the general population that has ginger hair. I'm not saying that this means people with ginger hair are brighter than average, just that my experiences run directly contrary to yours. I'm also intrigued by your seperation of orange from red hair, which is highly subjective and probably feeds into this; if you meet a bright person with ginger hair, you call it red. Skittle 13:06, 6 August 2007 (UTC)

Perhaps when you come up against a general prejudice you might lack a sizeable social circle and have more time to yourself to study? Lanfear's Bane

I imagine it's unlikely that anyone would ever get funding to do a "Statistical Analysis of Intelligence Measures as a Function of Hair Colour" is it. Though no doubt clowns would drag them down a few points, no?87.102.34.140 18:32, 6 August 2007 (UTC)

The quick answer is "No", there has been no serious studies linking hair colour to intelligence, but the question is perhaps not as ridiculous as one might think. While IQ is not a genetic trait in itself, there are factors that might contribute to one's IQ that could be effected by red hair. Red hair is largely a result of a variant allele of the MC1R gene. It used to be thought that MC1R was only expressed in melanocytes and thus the effects would only been seen on hair colour, but in the last few years some studies have shown that MC1R has an effect on pentazocine analgesia (pain relief) in humans. [1] Specifically, people with (certain types of) red hair have a decreased sensitivity to some types of pain. (This fits in nicely with anecdotal evidence from anaesthetists who have noted that people with red hair often require less anaesthetics than those of other hair colours.) So, while it is still a huge jump from modulating opioid receptor signalling to assumptions about intelligence, it nevertheless shows a role for MC1R in neurons, and opens the door for futher research into links between red hair and neural signalling. If this subject is of interest to you, I would recommed reading Marion Roach's Roots of Desire: The Myth, Meaning and Sexual Power of Red Hair, Bloomsbury USA, 2005. ISBN 1-58234-344-6. (A book that I have the dubious honour of featuring in!) Rockpocket 19:57, 6 August 2007 (UTC)

Sidenote: I used to think Willeke Alberti (no photo alas) was your archetypal dumb blonde, but I completely changed my opinion about her when I heard her say "I may be dumb, but I'm not blonde." DirkvdM 19:35, 7 August 2007 (UTC)

Peacock snake diet

According to myth, peacocks eat poisonous snakes without coming to any harm, but is it true?--Shantavira|^{feed me} 10:23, 6 August 2007 (UTC)

This search [2] seems to confirm that peacocks do indeed eat snakes. Venom that is lethal to us may not harm them in the slightest. Don't forget the good old mongoose which is well known for eating snakes. The rhabdophis tigrinus of the rhabdophis genus of snakes even eat poisonous toads [3] and use the poison for their own protection which is a bit of a kick in the teeth for the old toad. Lanfear's Bane

It is also possible that the poison is neutralized by the digestive process before it can enter the blood stream (I think I saw something in a David Attenborough series to that end). A small cut in the mouth, however, could prove fatal if this is the case. Also, I think mongooses can be killed by cobra venom, they are just super good at avoiding the bit (our mongoose article also suggests they don't eat the cobras anyway). --Cody.Pope 13:24, 6 August 2007 (UTC)

Maybe the birds are smart enough to avoid eating the head and the poison glands. Humans eat snakes too - we aren't immune to the poison and we don't die! SteveBaker 18:57, 6 August 2007 (UTC)

And don't forget that there's a difference between poisonous and venomous. Many snakes are venomous (produce venom), but not poisonous (harmful to eat). Even humans can eat certain types of snake meat (rattlesnake tastes gamey). GeeJo ^(t)⁄_(c) • 19:08, 6 August 2007 (UTC)

Borahborah 08:57, 16 August 2007 (UTC)== volume of photon . ==

could anyone inform me how much space is occupied by a photon ? does the volume of photon increases with increasing energy of photon ?

Photons can only be accurately described in the quantum sense, which assumes them to be dimensionless points. They do have a wave function that can be described mathematically. 151.152.101.44 16:57, 6 August 2007 (UTC)

You can use the Heisenberg uncertainty principle to find the likely place to find a photon. As the energy of the photon increases, the size decreases. In fact the size will be proportional to the wavelength, so photons could be considered to be hundreds of meters in size if they were AM radio wave energies. GB 22:10, 6 August 2007 (UTC)

Let's apply the usual concept of volume to a photon. The volume of matter we usually deal with is closely related to the repulsion between particles. We measure the "volume" of a proton by seeing how closely we can pack them before the repulsion becomes too strong. In that sense, photons do not repel each other, and therefore do not have volume. The result? you can "pack" an infinite amount of photons into the same small space. --Waldsen 01:00, 7 August 2007 (UTC)

Photon's are commonly thought of as their own anti-particle in the sense that electromagnetic waves experience destructive interference. Once the constituents of a particle/ anti-particle pair, say a positron and an electron, collide they will anhihilate each others' energy. This limits the number of same frequency photons one can contain in a closed vacuum. Borahborah 08:57, 16 August 2007 (UTC)

Oil refining energy consumption

Reading articles about oil refinery, Cracking (chemistry) etc. I find it obvious that the oil refining process takes up a lot of energy. How is this energy obtained? For example, is some of the refinerys own output used as fuel, or is it common to have a coal plant or some other source of heat (nuclear power, bioenergy) close to/at a refinery? The latter option makes sense to me, since that would increase the gain of precious hydrocarbon products from crude oil. Or is the energy consumption actually so little that building a separate plant would not pay back investment?

Additionally I would like to know what is the amount of energy needed to produce a gallon of gasoline or diesel and other petroleum products. SGJ 15:02, 6 August 2007 (UTC)

You may find the article EROEI, and its linked references, of interest for the second question. Cheers Geologyguy 23:08, 6 August 2007 (UTC)

Cooling down the body

First I play squash. Often I lose, but I always get very, very hot, and am pouring with sweat. Usually we hit the showers fairly soon after, withing 5-10 minutes off the court. There is a cold water shower, along with the hot ones. It feels pretty good to run my head, and often my entire body under the cold water, and I think this should be cooling my entire body down. But...after the shower and dressing, I find I'm still sweating profusely. I started to wonder if the cold water is actually closing my skin pores, trapping the heat inside, and preventing me from cooling down more or more quickly. I know that in China they drink hot tea to lower body temperature. Bluh. Anyway, can anyone tell me the biology involved, and the best, quickest, most thorough way to bring down my body temp after strenous exercise?

Most likely while your skin temperature is quickly decreased by a cold shower, it would take much longer to lower your core temperature. So while you may feel cooled off after a few minutes under the cold shower, you are still overheated. Personally, If I need to stop sweating after a GYM workout, I will go an gently swim in the pool to completely cool off--Czmtzc 16:19, 6 August 2007 (UTC)

Closing the pores on your skin doesn't "trap the heat inside." Sweat cools your body down through evaporative cooling, and is not going to be more efficient than running cold water over your body. Rapidly lowing your skin temperature, however, could cause the blood vessels to contract near your skin, limiting blood flow to it, thus temporarily reducing the rate at which your body can expell heat after you leave the shower. I just lay down in a cool room after I've worked up a sweat, but that's just me. Complete physical inactivity is a good way to produce as little new heat as possible. 151.152.101.44 16:52, 6 August 2007 (UTC)

Best way to lower your core temperature? Iced cream or cold cold beer.(etc) (Taken internally!)--SpectrumAnalyser 17:28, 6 August 2007 (UTC)

Sorry - that's really not true. Unless you ate/drank an insane amount of the stuff. If you weigh (let's say) 150lbs - and you drank a pint of beer at close to freezing, a pint is about a pound of liquid - so you've added 1lb at zero centigrade to 150lbs at 37C. So if the liquid were evenly distributed (which it certainly won't be) - it would cool you down by AT MOST about a quarter of a degree C. The best way to cool off is what they do in hospitals when they need to drop someone's core temp - which is an ice-bath. But swimming in a nice cool pool is probably the less insane way to do it. SteveBaker 18:55, 6 August 2007 (UTC)

Sorry to disagree but my doctor has told me on a number of occasions that the best way to reduce an elevated temperature is to drink lots of cold drinks (or ice cream etc). Anyway 0.25 deg is quite significant in terms of body temperature and I wouldnt be satisfied with just ONE pint, would you? Also you draw a false conclusion that the liquid has to cool the whole body: it just has to cool the core (I don't know the mass of the human core - but I'm sure someone will enlighten us)

--SpectrumAnalyser 22:18, 6 August 2007 (UTC)

I mean, a SIMPLE Google search shows this [4] on the first page for instance. And humans are very similar to pigs (Some say humans are pigs but thats another story)--SpectrumAnalyser 22:31, 6 August 2007 (UTC)

When I'm really hot and sweaty, I find that I get the most thorough cooling effect by getting in a warm shower, then gradually lowering the temperature. I think the anonymous user who brought up vasoconstriction hit the nail on the head regarding your problem: regardless of your core temperature (which really doesn't fluctuate all that much anyway), if you suddenly immerse yourself in the cold, your body will assume that it needs to conserve its heat and restrict bloodflow to the skin, reducing the efficacy of the shower. Consuming an ice cold pint of beer is almost always a great idea, but doing it while you're really hot isn't going to be that pleasant ('ice cream' headache, possible cramps, etc); give yourself a few minutes to cool off and then down one (but watch out for dehydration). Matt Deres 22:44, 6 August 2007 (UTC)

Me, I find that in warm and humid (e.g. summer in Boston) weather, I sweat pretty profusely for a while after a workout no matter what I do. I've assumed that my problem is that even though *I* know I've stopped working and am planning on resting for a while, my stupid body doesn't, and it's staying at the ready, with the turbochargers on and the metabolic rate elevated and the cooling system (i.e. the sweat glands) pumping at maximum rate, just in case I ask it to run another mile for me or something. —Steve Summit (talk) 23:49, 6 August 2007 (UTC)

Of course they do say that when someone has hypothermia, you must not give them a double-brandy because that dilates the blood vessels, bringing them closer to the surface, making them cool off even more (Take *THAT* stupid St.Bernards with the mountain rescue brandy barrel around your neck!)...which ought to mean that if you need to cool off, a swift shot of strong alcohol might just do the trick. (Well, I'm not actually recommending this - but if you needed an excuse - it's a thought!) SteveBaker 00:50, 7 August 2007 (UTC)

Note that the peripheral vasodilation caused by alcohol may reduce the risk/severity of frostbite, by keeping the blood flowing to the extremeties. (See, for example, Sullivan and Covino, 1953, "Peripheral Vascular Responses to Frostbite as Influenced by Alcohol" Am J Physiol 175:61-64.) So the St. Bernard isn't really out to get you. It's a tradeoff; you'll feel warmer – and your skin will stay warmer – initially, but your core temperature will drop faster if you stay out in the cold. TenOfAllTrades(talk) 02:18, 7 August 2007 (UTC)

Apparently St Bernards never carry brandy, this myth originated with a famous painting. Now when they are seen with barrels it is purely for the benefit of tourists who don't know better. (Thankyou QI!) the wub "?!" 12:50, 7 August 2007 (UTC)

I'm no doctor, but I would assume that cooling down as quickly as possible after exercise is not to be recommended. It may be unpleasant to be hot, but a gradual cooling may be healthier. Certainly physiotherapists recommmend a 'warm down' of the muscles rather than just stopping exercise to avoid any damage. Cyta 07:18, 7 August 2007 (UTC)

Sorry to object, but I don't see how cooling down quickly would negatively affect the body; surely returning to normal body temperature is alright, even if it's quick, as long as you don't get the body colder than it should be? Workouts do not cause the body temperature to increase significantly anyways, and there would be a major problem if it did.

Has anyone tried keeping the clothes consistently wet with cold water to cool down? Evaporative cooling and wind chill will be very effective if you have just a little moving air. --Bowlhover 19:04, 7 August 2007 (UTC)

I try to cool large veins and arteries where they approach the surface: that is my neck, around the groin and, to a lesser extent, under my arms. I imagine that by cooling my blood, which is then transported to my body core, I lower my core temperature faster than I would by general surface cooling. Although maybe the effect is purely psychological. 199.172.246.196 14:58, 9 August 2007 (UTC)

Since most heat is dissipated thro the head, it makes sense to try to cool that part. I found keeping my hair wet helps quite a bit in hot weather. Also eating lots of ice cream!--SpectrumAnalyser 15:04, 9 August 2007 (UTC)

Seeing the sky from Jupiter's atmosphere

If you were inside Jupiter's atmosphere, at a point where the air pressure was about the same as Earth's, would the sky turn dark at night and reveal the stars? What about the planet's moons? If not, why? 58.7.115.223 16:22, 6 August 2007 (UTC)

Well let's think about why the sky is bright during the day and dark at night, on Earth. The answer is the Sun (which is a star). The sun produces a lot of light. So do other stars. At night we see other stars (besides the sun), but they don't light up the sky like the Sun because they are very very very far away compared to the Sun. Air pressure has very little to do with seeing the sun or the stars. If you look at a picture of Jupiter and read about its atmosphere, you might be able to determine that at ~100kPa you would be well below several cloud layers. This would impede your ability to see the Sun or other stars. So in summary, air pressure doesn't affect your ability to see the sun or stars. However, in order to answer the question, it useful to know where in Jupiter's atmosphere the air pressure is comparable to the Earth's so you could know how deep you would be embedded in the clouds of Jupiter.Mrdeath5493 17:02, 6 August 2007 (UTC)

That's not entirely true. On the moon (where atmospheric pressure is essentially zero) - the sky looks black all the time - even when the sun is sitting right in the middle of it. So pressure must have some effect. The colour of the sky is determined by a bunch of effects (Raleigh scattering, Mie scattering, etc) - all of which depend on small particles suspended in the air. If the air pressure is low, those particles will rapidly settle out and the atmosphere will be pretty clear - and the sky will be dark. If the pressure is higher, it's viscosity will be higher and teeny-tiny particles will stay aloft longer - resulting in more scattering and a brighter sky. The difference between Jupiter (at an altitude where atmospheric pressure is earth-like) and Earth is that the atmospheric density gradient will be much lower for Jupiter. On Earth, the air pressure changes pretty quickly with altitude - on Jupiter, much less so. That means that above Jupiter, there would be much more atmosphere above you than there is on Earth at the same pressure (I think I have that the right way around!) - which will certainly change the ability of dust to settle out - resulting in a change in the colour of the sky. Jupiter is indeed further from the sun - so the sun is dimmer and (one presumes) the sky would also be dimmer - since our perception of colour is different for different brightnesses (in dim light, colours tend to take on a blueish hue for example), that throws another complication into working it out. Also, Jupiter has a whole bunch of different gasses in it's atmosphere - those absorb and refract light differently than our Oxygen/Nitrogen mix. So I'm pretty sure the answer is that the colour of Jupter's sky would certainly be different from ours - but sadly, I don't know enough science (or have enough data) to predict what it might be. I don't think anyone successfully predicted Mars' sky colour for example. (Mars has an orangey sky - but has blue sunsets). SteveBaker 18:46, 6 August 2007 (UTC)

Just picking a minor nit, but Rayleigh scattering (which is the primary cause of the blue color of Earth skies) isn't due to suspended particles but the air molecules themselves. However, as you note, its effects may be masked by the presence of sufficient amounts of dust or other suspended particles in the air, as is the case for Mars. —Ilmari Karonen (talk) 19:00, 6 August 2007 (UTC)

Pretty much - yes. Technically, Raleigh scattering is when the particles are smaller than the wavelength of light - Mie scattering is when they are larger - both contribute to the colours in our sky. The blue and the red/orange sunsets come from Raleigh scattering from molecules - the more misty whites and greys from Raleigh/Mie scattering from small particulates and water droplets. On Mars, Raliegh and Mie scattering from the dusty atmosphere makes the orange during the day and Raleigh makes the blue sunsets. (At least, I think that's how it goes). SteveBaker 20:08, 6 August 2007 (UTC)

Seems to me that the gas composition would have the biggest effect of all, much more than the thickness of atmosphere above you. Jupiter's atmosphere is mostly hydrogen, which is why the atmosphere above you would be thicker. The wavelengths of light scattered by hydrogen would be substantially different than that scattered by air, leading to a completely different color. As for what that would look like, I haven't a clue. anonymous6494 01:25, 7 August 2007 (UTC)

Why wouldn't it look exactly like the photos of Jupiter, with the sky being dark brown in some places on Jupiter and light brown in others? The brown colour is not because of light scattering by hydrogen or helium, but rather absorption by ammonia and hydrogen sulfide [5]. Celestial objects will look perfectly crisp and clear from Jupiter's atmosphere, not blurry like the view through dusty air because there's no Mie scattering.

The Rayleigh scattering article seems to imply that the colour of the scattered light doesn't depend on the substance, so a pure hydrogen-and-helium atmosphere will be blue like Earth's. The colour, though, may be less intense because those two elements are lighter than oxygen and nitrogen. --Bowlhover 20:48, 7 August 2007 (UTC)

The issue is not necessarily how much pressure there is. The issue is, how many molocules are able to come somewhere in between the light source (the sun) and the observer (you) Obviously, the more pressure, the more molocules, but I don't know how many molocules have to be present before the "blue sky" (or whatever color) becomes visible. Probably, if you went on the Space Shuttle or another spacecraft, the "blu sky" would gradually fade into black, but how quickly it did this would depend on how good your eyesight is, and whether that particular part of the atmosphere was in motion relative to a vertical line drawn to the earths center, thereby slightly influencing the depth of the atmosphere. Again, I don't know positively if what I am saying is correct, but I think it makes sense. 69.205.180.123 16:24, 8 August 2007 (UTC)

pinprick sensation

i am getting burnig pinprick sensation in my rt big toe since 2 month.previously, i had similar senstion in my lt arm.the sensation is at one point only.i consulted for same,but no relief!

It looks like you are requesting medical advice. If you are, you should see a medical professional (ideally a physician). It is against wikipedia policy to give medical advice. SorryMrdeath5493 16:43, 6 August 2007 (UTC)

It seems the symptoms may be severe enough to interfere with your ability to type. If this is indeed the case, then, whatever the cause may be, I would definitely second the suggestion to consult a physician. —Ilmari Karonen (talk) 19:05, 6 August 2007 (UTC)

Or else try using the fingers. --TotoBaggins 20:40, 6 August 2007 (UTC)

You mean instead of his "rt big toe". Maybe gout?Myles325a 02:52, 9 August 2007 (UTC)

The guy says he already consulted a physician - I suppose someone could guess maybe? Or alternatively I suggest you seek a second opinion.87.102.75.182 17:53, 7 August 2007 (UTC)

It could be Gout. --Mdwyer 19:29, 7 August 2007 (UTC)

Them having seen a physician (or indeed having 'consulted for same' with some un-named source) is no reason for us to guess. They should see a qualified professional, not be given any medical advice (guessed or otherwise) on the internet. There are lots and lots of things it could be, of varying severities. See a Doctor. Skittle 14:28, 8 August 2007 (UTC)

Where do we get so much energy???

I MUST KNOW

I am just a kid of 15 from Bangladesh. My knowledge is not that great but i must know the answer to my problem.

I live in 14 th floor. Assuming the height from ground to be 100 metres and my weight to be 500N, it would take me (500x100=50000joules) of energy to go up to my apartment if I were to walk all the way up the stairs. I did it twice. Now, did i actually spend FIFTY THOUSAND JOULES of energy????? Where did I get that sort of energy???? Is there any thing wrong with my math????

ADIDS

People get their energy from the food they eat. By my calculations, your 50,000 newton-meters works out to about 12,000 calories. The calories that are used to measure food energy are really kilo-calories, so this means you burned 12 calories as this term is commonly used. You're taking in probably 2000+ (kilo) calories per day in food, so you only spent a small portion of your daily energy intake while climing those stairs. Friday (talk) 20:11, 6 August 2007 (UTC)

Thanks man. I didn't know how much energy i got fom my diet. 2000kilocal per day! Thanx for the info! ADIDS

Food stories a tremendous amount of energy. My chemistry teacher had an experiment, as probably most chemistry teachers do, where they show how much flame and spark you can get out of common cereals if you heat them in the right way and release all of the energy at once. It's a lot more than one might think. --24.147.86.187 20:36, 6 August 2007 (UTC)

Look at it like this: One 8oz can of Coke (non-diet) contains 105kCal!! You have to run up and down stairs half a dozen times to work off the calories from one of those (and then you'll be so thirsty, you'll need another one!) SteveBaker 21:40, 6 August 2007 (UTC)

Well, that calculation assumes that all the energy in the Coke's sugar goes into moving Adids up the stairs, whih of course is not true. I don't know what the actual efficiency is but I'm sure it's not more than 50% or so. Failing to factor in inefficiency can discourage people from using exercise for weight loss, which would be unfortunate, because it's one of the best ways. Of course dropping Coke from your diet isn't a bad plan either. --Trovatore 22:30, 6 August 2007 (UTC)

It's worth noting that we use a great deal of energy just sitting around. The benefits of exercise are not so much the energy which is burned (which is relatively insignificant as noted above), but in what it does to our metabolic rate. Donald Hosek 22:51, 6 August 2007 (UTC)

For a fixed weight, there is more energy in chocolate chip cookies than in dynamite. The only advantage of explosives is that they can release lots of energy really quickly. For food it is okay if it is released more gradually. Dragons flight 21:56, 6 August 2007 (UTC)

Don't give homeland security any ideas, or we'll be barred from taking Oreos on plane flights... --24.147.86.187 22:14, 6 August 2007 (UTC)

Dragons flight, that's an interesting point about cookies, do you have a cite handy for it? I don't particularly doubt it, but I'd like to see the numbers (and get involved with the research!) Matt Deres 22:50, 6 August 2007 (UTC)

It's a factoid that Richard A. Muller uses in his Physics for Future Presidents. You can probably find it in his chapter on Energy, but I don't have a more specific reference or specific stats. Dragons flight 22:55, 6 August 2007 (UTC)

Informally it's pretty clear why it's true, though. Dynamite and other non-exotic explosives have their oxidizers as part of the mix (sometimes within the molecule, sometimes not -- nitroglycerin is an example of the former, gunpowder of the latter). Whereas the cookies are mostly just the burnable stuff (well, depending on how moist they are, I suppose). If you were to add the weight of the oxygen from the atmosphere to the weight of the cookies, dynamite might not suffer so badly in comparison. --Trovatore 23:03, 6 August 2007 (UTC)

After making a number of simplifying assumptions, the average human, at rest, uses about 125W just to stay alive. At first this seems unreasonable, but consider: if you put a 125W lightbulb inside a human-sized, human-shaped balloon in a comfortable room, you probably think it's reasonable for the balloon's surface to be at about body temperature. -Arch dude 22:46, 6 August 2007 (UTC)

If you accept the figure that the human body uses 100 to 150 moles of ATP a day, that roughly translates to running on about 40 to 60 watts, averaged over a day. It depends, of course, on exactly what you count as the body's use of energy. Do you count energy lost converting food energy to ATP? That would certainly produce a figure of about 125, and I guess you can assume that, since even though the wasted energy is not used to drive any specific process, it does help keep us warm by quite a bit. Someguy1221 04:10, 7 August 2007 (UTC)

May be you should also have a look at this article to find out more about calories and also the efficiency of the body. -- WikiCheng | Talk 05:22, 7 August 2007 (UTC)