Wikipedia:Reference desk/Archives/Science/2010 November 28

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November 28

Sleep and lifespan

A friend of mine said he wants to "experience a longer life", so he's going to cut out an hour of sleep from now on. I thought this was pretty bizarre logic. It got me thinking though, if you were to cut out an hour of sleep from now on, would that shorten your lifespan? Would the extra hours you stayed awake equal the additional hours you would have been alive for? ScienceApe (talk) 02:34, 28 November 2010 (UTC)

Sleep deprivation can lead to immune system and other health problems. However, if your friend is cutting from say 8 to 7 hours of sleep a day as an adult, this could potentially increase lifespan. Simply not sleeping, and yet still expecting one to live much longer is not possible. ~AH1^(TCU) 03:18, 28 November 2010 (UTC)

You may be interested in scheduled napping to achieve more time awake. — DanielLC 05:41, 28 November 2010 (UTC)

I believe there have been studies in mice which show that limiting sleep has a positive effect on lifespan. Here is one article I found, i'm not sure how reputable the source is, Link. Calorie restriction has also been found to increase lifespan in mice but it's thought to not have a huge effect in humans, but there is an effect Link. But you have to ask yourself, if you're going to go through life tired and hungry, is it worth the few additional years at the end of your life? Vespine (talk) 23:13, 28 November 2010 (UTC)

And, of course, it bears stating that what applies to mice doesn't necessarily apply to humans: we are fairly different, particularly in this case. After all, sleeping and dreaming clearly has some important effects on our brains, and our brains are very different to mouse brains. And a lot of popularly-reported studies on how much sleep people need seem to give an average, which is reported as a universal optimum, when of course there is a lot of individual variation. I suspect this is more a problem of the reporting than the studies. Caveas. 86.161.109.130 (talk) 00:50, 29 November 2010 (UTC)

Looking for name of strange wart-like cutaneous growth on human foot with tentacles

Resolved

 – Reflectionsinglass (talk) 13:08, 1 December 2010 (UTC)

Hi. First off, a few notes, I am NOT looking for medical diagnosis or opinion ... except that "diagnosis" might be a sliding rule here. I do not have this problem, no one I know has this problem, and I am not going to lie and say this is for a "book I'm writing". I have been looking every few months for this gross thing, and I can't find it, so I'm turning to this as my last resort. I'm merely curious what it is.

20+ years ago, I caught something on my foot, possibly from a public swimming area (I swam a lot). I went to the doctor and had it treated and it's never returned. But in my adult years, I have been curious as to what exactly it was, since I no longer have medical records of this thing. So please: I hope someone can tell me what it was.

It is not a plantar wart. But it was like a very large wart on the heel of the foot, and it had thick, white tentacular cilia growing from the center. It was really gross, I admit. To cure the thing, I had to pluck the tentacles every night and then apply a strong liquid.

One could ask why on earth I would want to remember such a thing, but I'm simply curious. Again, if I had this problem in real life, at the moment, I would immediately go to the doctor's. I just want to know what it was that I had. Anyway, if this question still breaks some rules, feel free to remove it. Thank you, Reflectionsinglass (talk) 09:25, 28 November 2010 (UTC)

Have you been through our slightly gruesome article List of cutaneous conditions? 87.81.230.195 (talk) 10:16, 28 November 2010 (UTC)

I have! But not thoroughly; it's such a long list, and it's one of the pages I'd been perusing. If it's listed there, it would take me quite a while to find it. I just took another gander, but no luck. Lots of other interesting things that prove to me I was not born to be a doctor :) Reflectionsinglass (talk) 10:53, 28 November 2010 (UTC)

To discount a parasitic infestation: What geographical location were you in when you first noticed it and for the few weeks before? Was blood or other liquid observable when tentacles were removed. Was it painful or just uncomfortable during the day and during tentacle removal. Did you think of the medical tincture applied as being 'strong' because it had a pungent acidic smell, or of alcohol or did it smart, etc.? Were the tentacles smooth all round or did they have texture? Did they end as a point or flattish or bluntly. Where they elastic or not when pulled ( i.e. did they become longer and thinner before coming out). --Aspro (talk) 11:37, 28 November 2010 (UTC)

Hi Aspro. At the time, I was in Connecticut, though I don't recall what season (in case that would be helpful). No blood, no other liquid that I recall. It was not painful, though I do remember some of the tentacles would hurt (if I tugged on them) and I'd leave them alone, but evidently I used tweezers to pull out the ones that didn't hurt. They were smooth; they were the color of cooked white rice and about the same size, with pointy ends, and yes, slightly elastic. I don't know what my mom did with them afterwards, probably just threw them away. I recall the smell of the medicine well: it was not acidic, it was more "mechanical" smelling, like a thick alcohol, definitely pungent. Reflectionsinglass (talk) 04:16, 29 November 2010 (UTC)

The "tentacles" could be hyphae, suggesting something like Phaeohyphomycosis. DuncanHill (talk) 14:39, 28 November 2010 (UTC)

Whoa! No, definitely not that, this wasn't any serious skin lesion like that. Just a bump on the foot with white things coming out of it that had to be plucked and medicated. Went away and I haven't had a problem since. I won't discount "hyphae" in general, but definitely not the ...mycosis. Reflectionsinglass (talk) 04:16, 29 November 2010 (UTC)

If there is a scientific answer to this, it would be a diagnosis that might still be relevant to the OP's health. To arrive at that diagnosis, we would need a back-and-forth exchange of information about symptoms, signs, other conditions. It seems clear to me that this is a request for medical advice, and I suggest that this should end here. -- Scray (talk) 17:03, 28 November 2010 (UTC)

Hi Scray. The people here, including you, know best when to stop. There were no symptoms, signs, or other conditions except what I mentioned above... this would be in the vein of asking, "What was it that I had that was black, hairy, and all over my tongue?" and the answer would be black hairy tongue syndrome (or whatever lol). Not looking for any medical advice, I'm not asking, how it should be treated. In fact, whatever it is that I had was obviously treatable, it was treated quickly, and I've never had a problem since! I honestly think I've given all the info I can, this was a very long time ago. I just thought maybe someone here would have a quick and definite answer, and it didn't hurt to ask. Anyway, one last go, if anyone has any ideas? Reflectionsinglass (talk) 04:16, 29 November 2010 (UTC)

The original poster wrote: "I went to the doctor and had it treated". If that doctor's still around, I'd suggest writing to them to ask what the thing was. You never know, they might still have records. --Anonymous, 03:22 UTC, November 29, 2010.

I doubt it; it's been over 20 years. And tbh, this is just a matter of curiosity. I really won't be hunting this information down. It was just such a curious thing that I caught. Anyways, thanks for everyone's help so far! Again if the matter is over-the-line, feel free to close discussion. I'll check back again soon. Reflectionsinglass (talk) 04:16, 29 November 2010 (UTC)

Thanks for the extra information Reflectionsinglass. Without venturing as far as giving a diagnoses, I think I can explain what happens in these cases. This sort of infestation is most frequently found in the tropics and sub-tropics and rather more rarely in temperate zones but they do happen. A fly will choose a human as its host on which to lay its eggs -especially if one has fallen asleep whilst fishing. A very effective and simple way of dealing with this event is to force the lava out by restricting their air supply with an oily or greasy substance. If this also contains a little turpentine or something similar, that will help keep the wound sterile as well as persuade them to loosen their grip. The little blighters can then be removed with tweezers as they appear. Second-line treatment - Occlusion/suffocation approaches. The fact that it was painless and there were lots of them and shaped like grains of rice are helpful pointers, but there are apparently more flies that can infest humans than I at first thought when you posted you query so I am not going to even hazard a guess. Also, I doubt after all these years if your memory will remember enough details to reliably identify the exact species but there is an identification aid linked to on this sight. Identification key to species of myiasis-causing fly larvae. After many years have past, the brain can size on details which were never really present at the time, so personal I would not bother to search further and from a clinical point of view it is unimportant, so even the treating physician may not know (or need to know) the specie in order to deal with it effectively.--Aspro (talk) 12:37, 30 November 2010 (UTC)

Oh man, that is so gross! I looked at pictures of myiasis and that's just nasty. But that is definitely a tad closer to what I was looking for. I honestly believe that the tendrils were pieces of flesh, rice-sized in girth, but rather longer in length, not larvae, but it was so long ago, who knows. Your suggestion, however, is extremely helpful because of the various types of response to the species. Thanks so much for your help! I'm actually kind of grossed out now, to be honest (lol) and I think I'll wait a few more years to continue my hunt, or maybe I'll just be happy with forgetting the whole thing! Thanks again,Reflectionsinglass (talk) 13:08, 1 December 2010 (UTC)

I'm reminded of the very strange condition suffered by Dede, the Indonesian "tree man". [1] [2] —Steve Summit (talk) 12:44, 30 November 2010 (UTC)

It's been a while since I read about him. I had to specifically Google for his post-treatment appearance and it's definitely better... but not. The poor guy. Reflectionsinglass (talk) 13:08, 1 December 2010 (UTC)

Why shopuldn't you fill a hot water bottle from the domestic hot water supply?

I brought a hot water bottle that says in the instructions"Do not fill using water from a domestic hot water system as this can considerably shorten the life of the hot water bottle". Since it also warns against using boiling water the alternative is to part-heat a kettle. How is partly heating water in a kettle different from heating it in a domestic hot water system? The only difference I can think of is that the water from the hot water tap may have been kept warm for some time, but I can't see how this would make a difference. -- Q Chris (talk) 12:17, 28 November 2010 (UTC)

My loose guess is that it might have to do with impurities in the water — see, e.g. water softening. --Mr.98 (talk) 14:47, 28 November 2010 (UTC)

It's a wonder chemicalinterest has not answered this yet, is he asleep still :) It's the copper that's the problem with rubber. Case studies hot water bottle premature failure Obviously our article on hot water bottles requires this addition by a thermophilic editor who does not like to wake up in a wet bed.--Aspro (talk) 15:07, 28 November 2010 (UTC)

The original poster cited a British URL for the bottle. Many houses in Britain have water systems where only one (I hear) cold-water tap is fed directly from the mains, the hot-water system and other taps being fed from the tank. I can't find a Wikipedia article directly about this, but Water heating#Gravity system addresses it. Anyway, with such a system the hot water is in it longer and has more time to collect impurities. But I can't say if that actually is what they have in mind. --Anonymous, 03:33 UTC, November 29, 2010.

Yes, this is often the case in UK homes. The cold water comes straight from the mains, but if you turn on the hot tap, the water will come from a storage tank, commonly found in the roofspace/attic (although the water which comes out of the tap may be cold for some time depending on the vagaries of the heating system). This is why we were always told not to drink water from the hot tap, as it will be standing water, and tanks often have no lids. You can frequently tell the difference because the water pressure will be higher on the cold tap than the hot one. This page (a forum) contains some anecdotal information. See this from a national DIY chain which explains several kinds of residental water supply systems in UK homes. --Kateshortforbob _talk 14:44, 29 November 2010 (UTC)

Bose-Einstein condensate of light

Many years ago I imagined an idea in a fantasy game, in which people would lay out spheres of "one-way mirror" in the sun until the light would "crystallize" into "flasheesh", a basic magical reagent better known for its recreational abuse by magic users who would shimmer and eventually spontaneously combust from their addiction. It seemed to me just about the most absurd thing I could come up with. Until that is today, when I read someone had done something about like this, and that the Bose-Einstein condensate of photons was being considered as a viable commercial process for solar cells and lasers!^[3]

The above story in Nature News is written to be very accessible, but even so it leaves me with a host of unanswered questions. Why can only a certain number of photons enter the cavity before thermal equilibrium is no longer possible? Where do the photons go, and are they "bound" to the dye molecules? Can you physically shove such a condensate of photons to change their wavelength? When they talk about a "super-photon", are they merely waxing poetic?

As you can tell, I haven't accessed the paper, but this looks like a big story, and I hope that the people who understand it will make a new article to explain it on Wikipedia. Is it time to call the DEA? ;) Wnt (talk) 13:56, 28 November 2010 (UTC)

The photons are trapped in a resonant optical cavity (basically imagine a box with mirrors on all sides, though this box is microscopic and two dimensional). Quantum mechanics selects for wavelengths that are integer fractions of the dimensions of the box. For example, if you had a 1 m box, then you could have 1 m waves, and 1/2 m waves, and 1/3 m waves, etc. The actual box selects for light in the visible spectrum. So that's one selection constraint. The other constraint is that the temperature of the gas should be in thermal equilibrium with the box. (The dye they used is basically there to promote the creation of thermal equilibrium quickly enough that photons can't escape from the box or be absorbed on the walls before equilibrium is achieved.) The energy per photon increases as the wavelength decreases. The result is that certain photon states are forbidden. For example, even a single photon in a high enough state would require more energy than the entire collection of photons at thermal equilibrium is supposed to have. Similarly, the resonant nature of the box forbids very low energy photons from being formed because they would require wavelengths much longer than the box. As you push more and more photons into the box they will try to reach equilibrium, but because certain energy states are forbidden you end up with an excess being forced into the lowest available state. It is this non-thermal excess in the ground state that characterizes the Bose-Einstein condensate.

As for what the result is like, the resulting ground state population is basically a laser. You get a coherent population of photons at a particular wavelength. The trick here is that the wavelength is determined by the physical properties of the box and not the atomic properties of the substances involved. This means you could tune the wavelength by adjusting the size of the box, which could have a variety of practical applications and allow for lasers at wavelengths which we don't have an effective means of generating now. It is also interesting that this system essentially transforms arbitrary light of sufficient intensity into a laser beam (with some unknown efficiency). That could have a variety of applications with respect to solar cells and other processes that require light concentration. Dragons flight (talk) 21:29, 28 November 2010 (UTC)

By "super-photon" they presumably mean many photons in the same quantum state. Lasers do that too, so "super-photons" have been around for a while. This looks like an interesting experiment, but popular science magazines have a habit of reporting everything as though it's going to change the world. Chances are this won't. -- BenRG (talk) 02:41, 29 November 2010 (UTC)

I think I follow what you mean by "lowest available state", but just to check: Photons are bosons not subject to the Pauli exclusion principle, and a Bose-Einstein condensate involves particles all in exactly the same state. So I assume that the lowest available state is simply the longest wavelength that can bounce back and forth between the walls of the cavity. This also means that despite my initial perplexed reception, the photons aren't really "stopped" somehow, but simply bouncing back and forth between two closely spaced mirrors.

But what I don't understand is how the behavior of one photon differs from many. I'd think that even a single photon with a wavelength not matching the walls of the box would somehow be forced to end up having some wavelength that fits, which might be the lowest available state. Again, as bosons, I don't see how the photons can affect one another. Unless the box somehow cools the photons - and if so where does the energy go?

This keeps raising all kinds of questions in my mind:

• It makes me wonder what happens in an ordinary dye laser if the wavelength of the dye slightly disagrees with the spacing of the mirrors. Can you see the emission peak broken up into a set of integral wavelength multiples of the mirror spacing?

• Can photons trapped in a box be switched between spin states? I think it could have spin 1, 0, or -1 hbar per photon, though I'm not sure if that adds up to much. Can you use a box like that as some kind of "photon gyroscope"?

• Can you close off such a box and keep photons trapped inside for any length of time? How good can a mirror be when it is very small?

• Can you use a device like this to capture ambient light and convert it into a single frequency best suited for driving a chemical reaction or other electrochemical process? (I suppose that's also what the solar cells are about) Do the antenna complexes of plants know this physics?

Wnt (talk) 17:00, 29 November 2010 (UTC)

A very clear explanation by dragons flight there. As for interacting photons, recall how a laser work. In some you have maybe one photon knocking an atom to a higher energy state, then a second photon comes along pushing it to an even higher state, then it decays sending out a third photon. So even though photons do not interact, they are causally connected. The two first photons "caused" the third one. I imagine that the photons "interact" through such middle-men in this setup.

To answear your bullet points: Photon gyroscopes already exist. Photons have spin +1 and this won't change that far as I can see. Nor can this collection of photons apparently be trapped any longer than other photons, but the light may "last longer" if there's a delay in re-emitting photons from the dye. As for converting ambient light into a singel frequency, that also exists today in many ways, such as fluorescence chemicals used as whiteners in detergents. So this might be one of many ways to achieve that.EverGreg (talk) 13:31, 30 November 2010 (UTC)

Water not freezing below the bridge

I was walking around in park (the temperature was 0 C or below) and noticed that the water below the bridge and in nearby area for some reason did not freeze (and the birds were swimming there). Why is that? —Preceding unsigned comment added by 89.77.158.172 (talk) 14:31, 28 November 2010 (UTC)

Currents. Kittybrewster ☎ 15:01, 28 November 2010 (UTC)

The bridge may provide shelter from the cold (e.g wind chill factor) and it may also be emitting heat absorbed over the summer / from usage which does just enough to prevent the water there freezing. ny156uk (talk) 15:11, 28 November 2010 (UTC)

The simpler explanation is that the open water has been able to radiate its heat into space but under and around the bridge it has been reflected back. This is why ice can form over-night under a clear desert sky, even though the upper air temperature is above freezing.--Aspro (talk) 15:43, 28 November 2010 (UTC)

Has it been snowing or frosting where you are in Poland recently? If so, it seems likely that they would have been out there laying down salt on the bridge, which is then running off or blowing off the bridge onto the ice below, melting it. Especially if the bridge is a road bridge and not a footbridge, and has a lot of traffic over it. WikiDao ☯ (talk) 19:32, 28 November 2010 (UTC)

As this is a common phenomena under structures which have not seen gritted, I take that explanation with a pinch of salt ;-) No one has mentioned yet, that the air temperature reported is only around the freezing point. Therefore, I was expecting someone to also say, that perhaps the water has not had time to stratify (remember science lessons at school about the density of water and what parts of a lake are the first to freeze and which parts are the last). The water may be a lot deeper around the bridge which would be the reason why that spot will be the last to ice. Here is a link Understanding Pond Stratification. We need the OP to come back with some more observations.--Aspro (talk) 21:04, 28 November 2010 (UTC)

Beneath what other structures does this commonly occur? WikiDao ☯ (talk) 21:22, 28 November 2010 (UTC)

Roofed over boat moorings on pleasure lakes is one example. Common in the Victorian period before people could stay in all night and watch I love Lucy. --Aspro (talk) 21:40, 28 November 2010 (UTC)

An alternate explanation is that they have installed some sort of heaters around the bridge to stop the water from freezing. Having ice directly freezing against the bridge supports could have a detrimental effect on the life of the bridge. They may be deliberately stopping the water from freezing... --Jayron32 21:02, 28 November 2010 (UTC)

That's certainly an alternative explanation, but not a likely one unless "they" have a very cheap source of energy. Slightly more likely is that there is some form of warm water discharge near to the bridge. Dbfirs 21:55, 2 December 2010 (UTC)

Is a common feature of these cases that water is moving near some fixed object (pier, etc.) and/or something is moving in the water (birds paddling around, etc.)? I've often heard folklore (yeah yeah /) that turbulence makes water freeze more slowly, so water lapping at a piling would freeze after a still pond or a smooth gently-flowing stream. Sea ice#Formation of sea ice suggests this isn't a complete crock either. DMacks (talk) 22:07, 28 November 2010 (UTC)

Folk can be right too. Turbulence warms water and Mechanical equivalent of heat is your citation. Cuddlyable3 (talk) 22:47, 28 November 2010 (UTC)

Growing bacteria, beef bullion

I'm trying to grow bacteria with unflavored gelatin in petri dishes. I've heard to add beef bullion to the boiling water, then let it dissolve. Beef bullion is high in sodium, and sodium was used as a preservative in meats. Would sodium inhibit the growth of bacteria? Also, how would you identify the bacteria that grows, and what surfaces would bear the most bacteria? Albacore (talk) 17:00, 28 November 2010 (UTC)

Different bacteria require different Growth mediums. Once you know what you what to grow, you can choose a suitable source to provide the nutrients. Some of these bacteria can be very dangerous in such large quantities that end up in culture dishes -so beware. --Aspro (talk) 17:09, 28 November 2010 (UTC)

I'm really concerned, now that I've thought about it, that you are going to try doing this in the house – don't! Here are two links you might find useful: Safety Guidelines & MICRO-ORGANISMS FOR EDUCATION. The salts (sodium) in the beef bullion doesn't matter. After all, its best diluted down to half the strength normally used for making stock. At that level the salts will have little inhibitive effect. --Aspro (talk) 18:37, 28 November 2010 (UTC)

Geologic Time Scale

Found in the discussion of geologic time is a Geologic Time Scale. Where can a full size copy of this document be acquired?

Rolf Olson Salem, OR —Preceding unsigned comment added by 24.22.3.126 (talk) 18:44, 28 November 2010 (UTC)

Other than Geologic time scale, what exactly are you looking for? BTW: End the Holocene now, ask me how. Hcobb (talk) 18:54, 28 November 2010 (UTC)

How? WikiDao ☯ (talk) 19:38, 28 November 2010 (UTC)

Oh! Don't you read all of Wikipedia from A to Z? You don't need to do nothing, as it finishes in two years time.--Aspro (talk) 21:15, 28 November 2010 (UTC)

There are several diagrams on the discussion page. Do you mean this one:[4]. If so you can use the right-hand download tool. --Aspro (talk) 19:02, 28 November 2010 (UTC)

Your options for obtaining a large size print of a digital image are a) Tiled printing or "rasterbating" using an ordinary A4 PC printer, or b) use a printing company that is equipped to produce large placards. If you just need to present a large image, e.g. for a classroom lecture, consider using a Video projector instead of a paper document. Cuddlyable3 (talk) 09:03, 29 November 2010 (UTC)

For most of the pics, you first click on it, then click on "Full resolution" underneath to get the full image. If you mean the small Graphical timelines wiki table, a screen shot should work there. If you mean the much larger Table of geologic time, then the best I can do is to break it into 3 screen shots and prints those, since it's not a pic but rather a large wiki table. I have a max screen resolution of 1920×1200, but someone with a higher res might be able to print it all on one sheet, although the writing would then be tiny. Would you like us to provide you with it as 3 pics, so that you can print it, or do you know how to do that ? StuRat (talk) 15:02, 29 November 2010 (UTC)

Skinny vs baggy jeans in freezing weather

Being a student up here in Oswego, I know a lot about walking around all day in freezing wind/death snow. But this question has been seemingly unanswerable by my friends and I. What would be, according to science (if it is science that applies here), warmer, skinny jeans or loose, normal fitting jeans? Skinny jeans are closer to the skin, and seem to not let any of the cold air in, but because they are so close to the skin, the cold air gets closer to the skin, too. Looser jeans seem to have more room for the cold air to circulate around your skin. I've clearly tried to think about this for a long time! The jeans are both made of the same fabric, so that shouldn't be an issue. ?EVAUNIT^{神になった人間} 19:00, 28 November 2010 (UTC)

Yes, you need some trapped air. A pair of these underneath would also make all the difference. After all, if they're good enough for Clint Eastwood, they should be good enough for you. --Aspro (talk) 19:09, 28 November 2010 (UTC)

Looser will be better on the basis of allowing sweat to escape, and on the same note will allow hairs to stand out more. Also, what heat is emitted by your legs will travel more freely up the wider pants, creating a chimney-effect (if rather negligible). The baggier jeans will also be made of more fabric. In addition to this, any consideration of moisture favours baggier jeans: Skintights that grow wet will immediately cool down parts of your legs, while baggier jeans can keep this moisture at a range. 88.90.16.188 (talk) 19:11, 28 November 2010 (UTC)

Not answering the question, but there exist flannel lined jeans, such as these jeans from L.L.Bean (not spamming for them, but that's where I got my pair). They are quite comfortable in colder weather, though if they do get wet, they take forever to dry. Back on topic, tighter jeans may restrict circulation in extreme cases, which would be undesirable in colder whether. Buddy431 (talk) 19:34, 28 November 2010 (UTC)

Definitely looser. The amount or air that comes in because the opening is larger is nothing compared to the insulation the air gap gives you. Ariel. (talk) 20:55, 28 November 2010 (UTC)

Best to wear baggy jeans with layers underneath, such as jogging trousers, long underwear, leggings, or all three. Insulation is provided by trapped air, so loose layers are best. 92.15.14.132 (talk) 22:49, 28 November 2010 (UTC)

Old-style jodhpur pants may be best. They were baggy at the top (to allow air circulation inside) but narrow at the ankle (to prevent cold air from getting in). They were actually designed for horse riding, not for keeping you warm, but this would be a nice side effect, if made of the proper fabric (which would wick moisture away, such as cotton). We don't have a good pic of the old-style version in our article, so here's one from somewhere else: [5]. StuRat (talk) 14:45, 29 November 2010 (UTC)

Jeans are utterly unsuitable for cold weather. Get something in a nice woollen-worsted instead. DuncanHill (talk) 14:53, 29 November 2010 (UTC)

Looser jeans with a relatively tight bottom will do the best, I think the style is called "boot cut". Tight jeans just get the cold air closer to your leg. From my OR though, don't worry about your jeans, concentrate on covering your head (toque), neck (scarf), hands (gloves) and feet (socks'n'boots) as that is where the most heat loss (head & neck) and discomfort (hands & feet) occurs. Spend the big bucks on those accessories and they will last for decades. Franamax (talk) 21:56, 29 November 2010 (UTC)

One thing to bear in mind is that denim is a poor insulator, fabric-wise, as it is quite loosely woven and has a high wind chill factor. ([6], [7]). --Kateshortforbob _talk 09:55, 30 November 2010 (UTC)

It depends on what you compare it with. Thin synthetic materials, as in dress pants, can be even worse, and let's not forget bare legs. I was always shocked to see cheerleaders wearing skirts to the bus shop in mid-winter in Michigan. I suppose popularity has it's cost. StuRat (talk) 23:36, 1 December 2010 (UTC)

Sleep, tiredness, exercise

1) Why does taking a lot of exercise in the day make you sleep well that night? 2) Why does not getting enough sleep make you feel tired? You havnt been exercising all night, so why should you feel tired? 3) Why is the tiredness you get from not sleeping enough the same as the tiredness you get from exercising a lot? Do they have any differences? Thanks 92.15.14.132 (talk) 23:10, 28 November 2010 (UTC)

Have you looked at the articles about Fatigue (medical), Physical exercise and Sleep? Cuddlyable3 (talk) 08:52, 29 November 2010 (UTC)

I have now thanks, but they don't answer the questions. 92.24.176.72 (talk) 13:39, 29 November 2010 (UTC)

1) Exercise causes "damage" to the body, which must be repaired by additional sleep. I put damage in quotes, because it's not the usual permanent damage you might think of, but rather easily repaired damage. For example, micro-cracks occur in the bones, which are then filled in with more bone, strengthening them even more than before. Muscle cells are also repaired and expanded.

2) Even without exercise, some damage occurs (especially in the brain and eyes) and sleep is needed to repair that. So, if you don't get enough, your body tells you more is needed, by having you feel tired.

3) I'd expect the tiredness from exercise to be more in the muscles, tendons, and bones, such as aches, and regular tiredness to be more in the brain and eyes, in the forms of mental slowness and eye strain. StuRat (talk) 14:31, 29 November 2010 (UTC)

Circular logic

I had to do an experiment designed to show the "equivalence of mechanical work/energy and heat". This was done by heating a piece of copper with friction. The amount of work was calculated, and change in temperature of the copper was predicted using the heat capacity of copper. This was compared to the actual change in temperature of the copper.

But if the heat capacity of copper is determined experimentally by how much energy it takes to raise a mixed mass of copper one degree, then isn't the whole experiment circular? 70.52.44.192 (talk) 23:16, 28 November 2010 (UTC)

But the heat capacity of copper could be determined using chemical energy, like gas. Vespine (talk) 00:23, 29 November 2010 (UTC)

Or by Resistive heating, where the amount of energy put in can be measured quite accurately by maintaining a certain (known) current over a certain (known) voltage drop for a certain (known) amount of time. Buddy431 (talk) 01:50, 29 November 2010 (UTC)

...and thus you don't need to know the heat capacity of the piece of copper, merely the electric energy V*I*T that causes the same temperature rise as the frictional work. Cuddlyable3 (talk) 08:46, 29 November 2010 (UTC)