Wikipedia:Reference desk/Archives/Science/2007 December 8

= December 8 =

Final cause of death in cancer
I never understood why cancer was so deadly. Yes, you do have an abnormal growth/tumor growing somewhere in your body, but I don't see why that would eventually cause death. If there was a tumor within a blood vessel that directly caused a stroke or heart attack, then the cause of death in that case is quite obvious. But in "normal cancer" (if such a thing exists), what is usually the final cause of death?
 * I asked myself that same question a year or two ago, and the answer I came up with after a bit of research is nobody really knows. They don't do autopsies on cancer deaths, and the oncology community seems to be concentrating on getting rid of the cancer to the exclusion of finding out exactly how it kills. Some ideas are that the tumor sometimes, of course, impinges on something vital like the pancreas and you die from the trauma to the vital part. Brain tumors are obviously going to kill you by compressing the brain. But the main deadly effect of a tumor seems to be that it disrupts your chemistry. Tumors produce all sorts of nasty chemicals as though they were a gland, which accounts for the weight loss that accompanies them. But nobody as far as I could find out has determined exactly which chemicals do what when. I remember thinking at the time that there might be a way to live with cancer if we could counteract that process, but what do I know? --Milkbreath (talk) 01:54, 8 December 2007 (UTC)


 * Take a look at metastasis. In many cases, a primary tumor can be surgically removed, but once cancer cells start to spread away from the primary tumor there is a greater chance that the cancer cells will not be stopped by treatment before they disrupt the function of a vital organ. For example, see melanoma and Surgical Excision of Metastatic Malignant Melanoma Involving the Tricuspid Valve.--JWSchmidt (talk) 02:54, 8 December 2007 (UTC)


 * A study of 506 terminal cancer patients (J Med. 1975;6(1):61-4) found the cause of death was:
 * Infection (36%, and was a contributing factor an an additional 68%)
 * hemorrhagic and thromboembolic phenomena (18%, and were contributory factors in an additional 43%)
 * Respiratory failure (19%, and a contributory factor in an additional 3%)
 * Organ failure after invasion by neoplastic cells (10%, and was a contributing factor an an additional 5%)
 * Cardiovascular insufficiency (7%, and a contributory factor in an additional 3%)
 * Cachexia (1% and as contributory factor in another 0.4%)
 * That was done over 35 years ago, so the distribution may have since changed, but it is nevertheless indicative of how tumors disrupt the normal function of our organs by diverting resources away to feed their growth. This results in organ malfunction as the tumor invades, vascular malfunction as blood vessels are grown to feed the tumor and starve the tissues. As the patient loses weight because the tumor takes all their nourishment, they begin to get weaker which leaves the more prone to infection, and the immune system cannot fight infection as well. Rockpock  e  t  03:03, 8 December 2007 (UTC)
 * Indeed, a more recent study suggests infection is better controlled these days and has been overtaken by the other causes, in J Thromb Haemost. 2007 Mar;5(3):632-4 the authors report: "Of 4,466 patients enrolled on study, 141 (3.2%) patients died during the period of observation ... A majority of patients died of progression of underlying cancer (n=100, 70.9%). Among non-cancer causes of death, thrombosis and infection were the leading contributors (n=13, 9.2% for each). Thromboembolic events contributing to death included myocardial infarction (n=3), stroke (n=2), cardiac arrest (n=2), ischemic bowel (n=1) and VTE (n=5). Infectious events contributing to death included sepsis (n=10), pneumonia (n=2), and bacterial meningitis (n=1). Other causes of death included respiratory failure (n=5), aspiration pneumonitis (n=2) and bleeding complications (n=2). Cause of death was reported as unknown in 5 patients." Rockpock  e  t  03:16, 8 December 2007 (UTC)


 * Ummm - A study of 506 terminal cancer patients (J Med. 1975;6(1):61-4) found the cause of death was: Infection (36%, and was a contributing factor an an additional 68%). Now, 36% + 68% = 104%. Shome mishtake shurely? DuncanHill (talk) 07:45, 8 December 2007 (UTC)


 * Maybe they meant 68% of the remaining deaths? I can't find this paper. J Med.  Which journal of medicine? Someguy1221 (talk) 08:06, 8 December 2007 (UTC)
 * Mmmmm. Good point. Perhaps I paraphrased incorrectly and they meant, as Someguy suggests, 68% of the other deaths. The article is PMID 1056415  Rockpock  e  t  21:03, 8 December 2007 (UTC)

How to solve Physics Problem by Using Kinetic Energy Principle?
So, a ball weighing 2.6 kg falls from a state of rest 55 cm. It then lands on a spring that decompresses 15 cm. Assuming the acceleration of gravity is (-)9.8 m/s and that there is no air resistance, what is the k value of the spring?

OK, so according to KE Principle:

Wnet=deltaKE or Wnet=KE'-KE

Since the ball is at rest in the beginning and end, the right side of the equation equals zero:

Wnet=0

We also know that W=Fd

Fnetd=0

So the net forces is that of the spring, which is described as Fs=-kx, and the force of gravity, which is desribed as Fg=mg,

(-kx+mg)d=0

At this point I am kind of unsure what d is supposed to represent, but I guess d=.7 m. m=2.6 kg, x= (-).15 m, g=(-)9.8:

.7(.15k+2.6*-9.8)=0

k=(25.48/.15)~170

By using the Law of Energy Conservation (E=E'), I got a value that was about 10 times this, and I am certain I did that work right.

I also tried:

d1(-kx)+d2(mg)=0, where d1 is the distance over the force of the spring was applied and d2 is the distance over the force of gravity was applied.

(.15*.15k)+(.7*2.6*-9.8)=0

.0225k=17.836

k~790

Closer, but the answer is still twice that.

Any advice would be greatly appreciated. —Preceding unsigned comment added by 24.125.31.205 (talk) 05:31, 8 December 2007 (UTC)


 * Your first method is not what you're trying to solve: You're working out the force, not the energy. I would just work out the V of the ball when it was at rest, using $$V = mgh = 2.6 \cdot 9.8 \cdot 0.7 = 17.836$$. Hooke's law say $$U = \frac{1}{2}kx^2$$, substituting in the variables you get $$17.836 = \frac{1}{2}k \cdot 0.15^2$$, simple algebra re-arranging gives $$k = \frac{17.836 \cdot 2}{0.15^2} = 1585.42$$. You just forgot to multiply the energy stored in the spring by 2 when you're finding k. --antilivedT 09:14, 8 December 2007 (UTC)

Electric Shavers
In TV commercials, those guys just keep shaving every which way but I wanna know if that is really possible. I mean with a regular razor you cant shave against the grain right? So with an electric razor is it possible? If yes, why? And if not, then what are the consequences of shaving against the grain? —Preceding unsigned comment added by 202.83.169.98 (talk) 07:33, 8 December 2007 (UTC)


 * I shave against the grain. My face is fine...Someguy1221 (talk) 08:07, 8 December 2007 (UTC)
 * Shaving. Moving against the grain can help force the hairs into the small holes that give access to the moving blades. --JWSchmidt (talk) 15:01, 8 December 2007 (UTC)
 * Some say that (blade) shaving against the grain forces the hair beneath the skin and leads to ingrown hairs, but it doesn't bother me (and leads to a much closer shave). —Steve Summit (talk) 17:07, 8 December 2007 (UTC)


 * I have very heavy, thick whiskers. Although I have a full beard, I shave my neck and upper cheeks every day, and I use a regular two-bladed disposable razor most of the time. If I did NOT shave against the grain, I'd not be able to have a clean shave, but would have uncomfortable stubble left behind. If I use an electric razor I never get as close a shave as a simple cheap Bic disposable razor. I've never discovered the advantage of using an electric razor. Why would I want to buy an expensive razor that requires electricity to run and doesn't shave as close? Saukkomies 19:18, 8 December 2007 (UTC)


 * Less time/mess? If I had to bother lathering up every morning, I'd probably have a long, droopy moustache in addition to a long, scruffy beard... ;) --Kurt Shaped Box (talk) 19:22, 8 December 2007 (UTC)


 * Who lathers up? Heh. I never have used any kind of shaving cream or anything like that. I just find that shaving as soon as possible after I shower in the morning that my skin is moist and warm enough from the shower that I do not need to put anything on my skin to prepare to shave. I do make sure to wash the skin that is going to be shaved while in the shower - freshly washed skin helps the razor to work better. But lathering is such a drag! I agree with you Kurt, if I had to lather to shave, I'd give it up altogether. As it is, I spend perhaps 30 seconds on the entire shaving process each morning - and there is no mess to clean up since the whiskers get washed immediately down the drain when I rinse the razor off in the flowing water. Keep in mind that my whiskers are exceptionally thick and dense, and I am also quite prone to razor burn. But I have very positive results from simply shaving right after I shower, not using shaving cream, going against the grain, and using a regular double bladed non-electric razor. Saukkomies 19:34, 8 December 2007 (UTC)


 * The rotary electric shavers cut in different directions around the circumpherence of each 'pad' anyway - I don't think it matters that much which direction you move the body of the shaver. (But then, I havn't shaved in 10 years...so what do I know?) SteveBaker (talk) 00:02, 9 December 2007 (UTC)


 * I went electric(al) because I like it. I find it easy, no lathering and no need to buy a cartridge (razor) every fortnight. Non-electric razors are quite expensive here in Argentina. Well, that's my call.
 * As Steve points out, electric shavers cut in different directions. I'd usually make a series of movements: against the grain, then circular (clock/counterclockwise) moves, etc. Pallida  Mors  23:54, 9 December 2007 (UTC)


 * I use an electric razor almost daily and shave against the grain. My skin tends to be drier than it was when I used a cartridge razor, but I have never suffered a single drop of blood, and to me that's worth it.  --M @ r ē ino 20:19, 10 December 2007 (UTC)

Hermaphrodites
What are hermaphrodites? How are they born?--61.2.17.179 (talk) 08:59, 8 December 2007 (UTC)--61.2.17.179 (talk) 08:59, 8 December 2007 (UTC)


 * Hermaphrodite. If you have a more specific question, feel free to ask it.  Someguy1221 (talk) 09:07, 8 December 2007 (UTC)
 * There happens to be a wonderful article here on human hermaphroditism. (But stay away from the bottom quarter if you don't like yucky things!) Someguy1221 (talk) 09:21, 8 December 2007 (UTC)


 * I didn't see anything "yucky" there. It was just a description of a different culture's relationship to gender and sex. Not that I'd want to live there, but Western cultures sure don't have it all figured out either! Sauda d e 7  14:51, 8 December 2007 (UTC)

Unknown type of digital or optical distortion
The camera was handheld but in the past whenever I have seen a blur it has included the whole picture. I though digital cameras exposed the whole scene at once rather than scanning the picture maybe like an old TV camera would do. What method of taking the picture and/or what action could cause this type of digital or optical distortion? Multimillionaire (talk) 11:52, 8 December 2007 (UTC)


 * Light coming from the bicycle into your camera being refracted due to the difference in density of air in that area. Just a wild guess though, might be wrong :P. Oidia (talk) 11:58, 8 December 2007 (UTC)


 * Is this the entire photo, or is it the corner of a larger photo? --Psud (talk) 13:45, 8 December 2007 (UTC)
 * Its the whole photo. Multimillionaire (talk) 22:39, 8 December 2007 (UTC)
 * The date in the corner suggests it is an entire photo. I'd say you weren't holding the camera/cellular phone still when taking it. The distortion is circular in nature with intensity increasing towards the bottom left hand corner. I'd say you pivoted the camera when shooting. --Ouro (blah blah) 14:08, 8 December 2007 (UTC)
 * If it's a digital camera which uses a focus feature, it may have decided to focus on the top right of the frame, which would explain why the focus goes from very sharp (top-right) to completely blurry (bottom-left). Some digital cameras zoom in an out to try and focus on certain things usually when you half-depress the button, so it may have been in the middle of doing this when you took the photo and it even seems likely that you did this and moved the camera. There are of course other possibilities. Rfwoolf (talk) 20:05, 11 December 2007 (UTC)


 * It's a common problem with certain cell-phone cameras. They use a pure electric shutter (no mechanical shutter at all), and it takes a while to read the entire image, during which the camera was moved.


 * They take a picture by exposing and reading each line of the sensor in turn. The exposure of each individual line is fairly quick, so the image doesn't look blurred, but because the lines aren't all exposed at the same time, the image can look warped.  If you want some more examples, there were some spectacular photos of airplane propellors posted here a few months ago. --Carnildo (talk) 23:03, 11 December 2007 (UTC)

Identify squirrel species
Squirrels of this kind are very common where I live. What species is this? - Sikon (talk) 13:19, 8 December 2007 (UTC)


 * Where do you live? (That's important). It is some type of tassel-eared squirrel. Not a Kaibab Squirrel squirrel though. Sauda d e 7  14:54, 8 December 2007 (UTC)


 * Novosibirsk, Russia. - Sikon (talk) 16:32, 8 December 2007 (UTC)
 * Could be a Eurasian red squirrel. --Milkbreath (talk) 17:35, 8 December 2007 (UTC)
 * I agree - in winter they have grey fur over their bodies with the red fur remaining over head and paws - that's something you don't see in other squirrels (as far as I know). (The SteveBaker (talk) 23:57, 8 December 2007 (UTC)

Blacksmithing messes with my hair
Good morning Wikipedians!

I spent the afternoon yesterday (Saturday) working over a coke fuelled forge. The coke proved excessively hard to light, and so we employed barbecue briquettes to get the fire going. I ended up with a fair bit of ash in my hair, and my hair felt tangled and matted. When I got home, I rinsed (but didn't wash) my hair. But my hair remains tangled feeling, and I'm thinking I probably need to wash it to get it back to something like normal. Other probably relevant things I noted were:
 * There was a bit of sulpher in the fire, evidenced by yellow deposits which formed on the coke and sulpherous smell when I rinsed my hair. I'm pretty sure the sulpher came from the briquettes, as there was no evidence of it once the fire was burning only coke.
 * There was a fair bit of sweat in my hair
 * A diffuse white flame burned over the fuel in the forge while it was burning briquettes and coke at the same time
 * My hair is about 15cm long measured from scalp to tip of a handful of hair
 * The forge has no hood over it, so my hair was exposed to radiant heat, but there is no evidence that it was scorched at all.

My first thought was that it was the sweat that turned my hair into a tangled mess, but I expected that to be fixed by a rinse. Any ideas, or suggestions for how to prevent the same in future? --Psud (talk) 15:02, 8 December 2007 (UTC)


 * We may need a bit more information. Since it sounds like washing (as opposed to rinsing) your hair is a big deal for you, I'm guessing you don't do it every day -- and perhaps you go for long periods without washing your hair.  If so, your hair will have a lot more of its natural oils in it than many/most of us are used to.  Also, it's possible that you have some unusual (to me) hairdo, such as dreadlocks or a mohawk, perhaps requiring added substances to keep it in place.  All of these possibilities increase the number of unusual reactions that could have taken place between your hair and the heat/fumes/ash given off by the forge. —Steve Summit (talk) 16:58, 8 December 2007 (UTC)


 * Hair washing isn't a big deal, I just didn't have any shampoo handy. Hairstyle is fairly conventional. No "product" to hold it in place. Hair was washed 3 days ago (usually wash it weekly(, but have gone for up to 3 months without washing hair - but that's another story)). --Psud (talk) 17:42, 8 December 2007 (UTC)
 * Ash is very alkaline and can react with oil in the hair to make soap. Also if you overheated your hair it could be frizzed and weakened, so that it will easily tangle and break.  Give the hair a good brushing to remove the broken bits, and dust, and to help untangle it! Graeme Bartlett (talk) 21:41, 8 December 2007 (UTC)
 * Have you tried a liberal dose of conditioner? Vranak (talk) 22:41, 8 December 2007 (UTC)
 * I fixed my hair with a washing and far more conditioning than I would normally use. I take it from lack of comments suggesting the possibility that the copious quantities of sweat wasn't the cause. Speaking of sweat, for anyone who hasn't tried it, blacksmithing is an odd thermal experience - ambient air temperature away from the forge was 33°C (~92F), the radiant heat of the forge heated all of me above the top of my leather apron causing me to sweat profusely, all of me below the top of the apron was cooled by the sweat but not particularly heated by the forge, so I felt incredibly hot from the shoulders up, and was shivering below that. --Psud (talk) 11:59, 9 December 2007 (UTC)

I think that Graeme Bartlett got it right. Ash+hair oils+water(sweat) = soap. Soap makes hair clump, lack of oils make hair "bad". Also meshes with what happens when I wash it - shampoo lathers as if my hair was already clean, and I needed two doses of conditioner to get it near normal again. By the way, I notice no one complained that I was asking for medical advice. --Psud (talk) 22:11, 11 December 2007 (UTC)


 * Hair is already dead. There is probably no rule against giving post mortal advice :)  --Cookatoo.ergo.ZooM (talk) 23:49, 11 December 2007 (UTC)

Laptops
Which laptop is the best for home usage:

1) Acer  2) HP   3) Compaq   4) Dell 5) Sony Vaio

In terms of specifications{Speed and hard disk capacity} and the regularity of usage..... —Preceding unsigned comment added by Garb wire (talk • contribs) 15:07, 8 December 2007 (UTC)


 * You could get all different specifications of laptop from those companies. Some Acer laptops are better than some HP laptops and some HP laptops are better than Acer laptops. What exactly is "home usage"? You sound like you'd be fine with one of the cheapest (internet browsing, typing letters). I'm guessing that someone who needed a more powerful computer (image/video editing, first-person shooter players) would not have asked the question you just did. If you confirm what it is you want to do with the machine, someone else will confirm that you only need something cheap. --Seans Potato Business 15:16, 8 December 2007 (UTC)


 * Apple. But Really, you should ask this on the Reference desk/Computing page, this one is just for Science. The People on the Computer page are incredibly smart and helpful. Good Luck. Sauda d e 7  15:31, 8 December 2007 (UTC)
 * And so he did :) --Ouro (blah blah) 20:24, 8 December 2007 (UTC)
 * Did Saudade7 just call us all stupid and unhelpful? I feel...somehow abused.  :-)  SteveBaker (talk) 23:51, 8 December 2007 (UTC)
 * Tough one. But seeing as some of us also do participate at the Computing RefDesk, I'd say you shouldn't feel too bad ;) --Ouro (blah blah) 06:43, 9 December 2007 (UTC)

Flame from engine exhaust
In the film Grease, you see flames coming from one of the cars two exhausts. What's that all about? --Seans Potato Business 15:12, 8 December 2007 (UTC)


 * I've heard of hot rodders making modifications specifically for this purpose. I don't remember details, but the gist is that they inject something flammable into the exhaust system near the end, at the flip of a switch.  I don't remember if they also need a spark there or if the exhaust ignites it.  Alright, here is a link to a commercial vendor of modern kits for this.  They explain how their kit works.. Oh, they're fiddling with the engine to pass unburned fuel through rather than injecting new fuel at that point, then they ignite it with a spark.  Hmm, not sure how I feel about that.  But, it's all only for looks anyway.  You will also see naturally produced exhaust flames from cars like dragsters whose only "exhaust system" are a couple feet of headers, which just open right to the air.  In that case, they're not doing anything on purpose to produce the flames, but they get them anyway.  Friday (talk) 16:59, 8 December 2007 (UTC)


 * I don't think such a device would be legal in the UK. There are strict regulations regarding emissions. Does that not apply in the US? —Preceding unsigned comment added by Seans Potato Business (talk • contribs) 17:53, 8 December 2007 (UTC)


 * I imagine it's not legal in many parts. But, not every place in the US does emissions testing.  And, if you don't hit the button during the test I imagine you'd have normal emissions.  Friday (talk) 17:57, 8 December 2007 (UTC)


 * As I understand it, testing is done everywhere but the strictness of the test depends on the level of urbanization. The only exemptions I know of are for the poor.  It is illegal to modify any emissions control devices.  --DHeyward (talk) 19:53, 8 December 2007 (UTC)
 * No, testing is not done everywhere in the U.S. In fact, it is not common at all. Only major urban areas which badly fail on pollution tests are subject to EPA testing. A few states may also have testing but I couldn't even tell you which ones, if any. Rmhermen (talk) 19:04, 10 December 2007 (UTC)
 * These guys: http://www.eatmyflames.com will sell you a kit to do that for around $50. They are of course illegal in most places around the world.  They generally require that you remove the catalytic convertor from your exhaust - so it's 100% certain that you aren't going to pass emissions testing even if you don't turn it on during the test. SteveBaker (talk) 23:48, 8 December 2007 (UTC)

Formula One Car Speed
I'm researching the properties of carbon fiber. Could anybody tell me how much force the carbon fiber shell on a Formula One car must withstand? SevenFiveOne (talk) 15:20, 8 December 2007 (UTC)
 * Here is a document from the FIA that seems to have some info. Sections 3.17 and 16.1 look promising. From what I saw, the shell isn't considered so much part of the impact protection, so the specs for that deal only with deflection caused by the airstream. --Milkbreath (talk) 16:33, 8 December 2007 (UTC)


 * I the car has good aerodynamics (as it really ought to if it's a Formula 1 car) then there should be very little aero forces on the shell. The strength of the car comes from it's internal metal frame.  So I don't think there is much stress on the carbon fibre parts anyway. SteveBaker (talk) 20:22, 8 December 2007 (UTC)

Hydrogen Cars - Potential Future Issue?
understand the only 'output' out of the exhaust for hydrogen cars is water. I was interested whether this might cause a potential problem in the future for high-usage roads like motorways. If there are, say, 10,000 cars an hour going through 1 mile of road all expelling a small amount of water - well would that mean the roads might always be wet/damp thus making braking distances longer? I guess the ouput of one hydrogen car wouldn't be much but with 1000s would it become more of a problem? ny156uk (talk) 16:35, 8 December 2007 (UTC)


 * Such problems might indeed be a problem, for instance with cold weather, but they will also easily be solved. Think for instance about tyres/asphalt with better water disposal qualities, or simply putting the exhaust on the side or in the middle and building draining facilities at those spots in the roads. - Dammit (talk) 16:43, 8 December 2007 (UTC)


 * If there is also waste heat, maybe they could use it to evaporate the waste water? No idea if they really do this, just speculating.. Friday (talk) 17:21, 8 December 2007 (UTC)


 * Of course, the water does come out as vapor. (Indeed, the fact that the water resulting from virtually any combustion reaction comes out as vapor rather than liquid water represents a significant form of waste heat in itself, and accounts for the distinction between HHV and LHV.)
 * So the first result of large-scale use of hydrogen-fueled cars would be an increase in the humidity immediately surrounding busy motorways. In cold weather, or on a morning following a chilly night when the pavement is still cold, I can easily imagine this resulting in significant condensation on the roadway surface.  It would be an interesting back-of-the-envelope calculation (which I am nevertheless not going to undertake just now) to try to quantify this effect. —Steve Summit (talk) 17:48, 8 December 2007 (UTC)


 * As an aside, water vapor is a greenhouse gas as well. How come this isn't a concern?  --DHeyward (talk) 19:55, 8 December 2007 (UTC)


 * Because the amount of water the atmosphere can hold is a factor of temperature. Once the humidity gets high enough for that temperature, the water just rains back down.  It doesn't have the long-term cumulative effects that other greenhouse gasses have. --  Hi  Ev  06:42, 9 December 2007 (UTC)


 * We should point out that regular gasoline cars generate a lot of water in their exhausts too - perhaps not as much as a hydrogen car - but even so - it's quite a bit. Just watch your car exhaust with the engine running on a cool day and you'll see water dripping out of the end.  I really don't think you'd even notice the change over in terms of water production.  Water vapour is only a problem as a greenhouse gas if it makes it up into the upper atmosphere.  The water vapor from car exhausts is mostly going to wind up like the water that evaporates from rivers, lakes and oceans - forming clouds. Louds do trap sunlight - but they also reflect it away out into space. SteveBaker (talk) 20:19, 8 December 2007 (UTC)

Temperature and Breathing rate
If someone fell into a pool of freezing water and remained there for an hour, would they still survive? And if they did, would temperature somehow be connected to it? Thanks, <font color="#00ff00" size="3" face="Monotype Corsiva">Valens <font color="#000000" face="Cambria Math">Impérial <font color="ff0000" face="Century">Császár <font color="#0000ff">93  17:00, 8 December 2007 (UTC)


 * They would almost certainly not survive, and of course temperature would have everything to do with it. See hypothermia. —Steve Summit (talk) 17:14, 8 December 2007 (UTC)


 * There are people who have swum in freezing water - but even with a lot of preparation and vigerously exercising - they can't survive for long. You hear stories of people falling overboard from arctic fishing boats who died from hypothermia in less than two minutes.  So evidently a lot depends of preparation - but I don't think it's possible to survive an hour.  Your body simply can't generate enough heat to maintain a minimal body temperature with that much loss of heat. SteveBaker (talk) 20:08, 8 December 2007 (UTC)


 * According to our hypothermia article, there are reports of children being resuscitated after two hours (!!), but those cases are certainly exceptional. (But they're why I said "almost certainly" instead of "certainly".)


 * Also according to our article, you're "not dead from hypothermia until you're warm and dead". The interesting thing about hypothermia is that it involves (or, depending on how you define things, it is) a natural, biological, hibernative or suspended animation state.  But it's very tricky for humans to revive from.  There's a story of 16 hale Danish sailors who sometime in the 1980s were rescued alive after bobbing in the North Atlantic for ninety minutes or so after their ship sank out from underneath them.  While being fed and warmed in the galley or sick bay of the rescuing vessel, all 16 of them dropped dead. :-( —Steve Summit (talk) 20:57, 8 December 2007 (UTC)


 * Also take a look at Mammalian diving reflex, which suggests that a dip in cold water changes breathing significantly. --Mdwyer (talk) 20:10, 10 December 2007 (UTC)