Wikipedia:Reference desk/Archives/Science/2010 December 21

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December 21[edit]

Does an Alpha emitter also emit Beta?[edit]

Does an Alpha emitter also by necessity emit Beta radiation? Because over time the source will become highly charged and it seems to me it has to release some electrons (although possibly at low energy). I'm thinking especially of an RTG in a spacecraft (i.e. vacuum). Ariel. (talk) 00:51, 21 December 2010 (UTC)

Not really. Beta emission is a different process than just losing electrons from the electron cloud. Excess electrons in the electron cloud after alpha emission will just drift off; while beta decay is basically just an electron, IT involves formation of that electron from the conversion of a neutron into a proton. Different processes. --Jayron32 01:25, 21 December 2010 (UTC)
I know the process is different - I was wondering about the end result. (I guess it's not called beta emission if the process is different.). My question is: Would an alpha emitter spark occasionally? I can only imagine the ionization of air would allow it to neutralize, and in a vacuum I assume they ground the RTG? Or, does the alpha particle grab an electron on the way out? Ariel. (talk) 02:00, 21 December 2010 (UTC)
At the bulk level, it is hard to track individual electrons with any meaning. Alpha particles end up, eventually, as neutral helium. Whether they grab an electron "on the way out" from the parent atom, or whether they grab electrons from some other bit of matter, and then that bit grabs from something else, down the line, is probably undeterminable. Uranium-238 decays into Thorium-234 and Helium. The electrons just all kinda work out. --Jayron32 02:51, 21 December 2010 (UTC)
Yep, air ionization is definitely one way of balancing charges. Odds are the smoke detector in your home contains a very tiny piece of americium-241, which is used to continuously ionize a small amount of air inside the detector. A small amount of current flows between electrodes on opposite sides of the ionized region; the presence of smoke particles reduces the ionization of air, triggering an alarm when the corresponding reduction in current is detected.
On the other hand, this effect is only important for very small pieces (or least, very thin pieces) of radioisotope. While alphas emitted from the surface atoms may travel a few inches in air, the mean free path of 1 MeV alpha particles in most solid matter is down between 20 and 50 microns [1]. In other words, the vast bulk of alpha particles generated within a fuel rod (for example) come to rest less than a millimeter from where they were created. If this occurs in a metallic alloy, then there are plenty of electrons sloshing about to sort out any local accumulations of charge.
Note that you can get some pretty interesting effects if you work in nonconducting systems. While I'm not aware of anyone using alpha particles this way, one can spray intense beta rays (high-energy electrons) at a block of plastic; at reasonable energies (a few MeV to a few tens of MeV) electrons will penetrate a few centimeters. Charges build up inside the plastic until an edge of the block is grounded. This triggers breakdown of the plastic's resistance, and all the accumulated charge drains out at once. This abrupt current damages the plastic, leaving a Lichtenberg figure. TenOfAllTrades(talk) 04:00, 21 December 2010 (UTC)
In space, (i.e., an RTG on a spacecraft), there will be an interaction called the Debye sheath or plasma sheath. Because space is not a complete vacuum, but is actually a very sparse plasma, the buildup of charge will cause an electrostatic response in the surrounding plasma. The characteristic scale-length and the magnitude of this response is determined by the amount of charge and the parameters of the (not-totally-empty) region of space. The average distance between particles, the percentage of ionized to neutral particles, and the energy of the ions, all determine the "thickness" of this sheath region, where bulk electrostatic effects are detectable. This will include accumulation of electrons to form a layer around the positively-charged object. Beyond the edge of the sheath, (the far field, so to speak), the alpha-emitter appears totally neutral, because charge has been conserved and has shielded any electrostatic interactions. Nimur (talk) 17:34, 21 December 2010 (UTC)

Poison mushroom[edit]

I've been a long time collector and eater of wild mushrooms. I definitely know how to identify the small variety of edible mushrooms I eat (Chanterelles and Porcini mostly) as well as a large number of poisonous or just undesirable varieties. So here is the question, why would mushrooms evolve toxicity? Some mushrooms have strong bitter taste/peppery or a foul smell despite being nominally edible, this I can understand as it definitely keeps me away The most deadly species like Amanita phalloides take many hours even days before causing symptoms so I don't imagine this would be an effective deterrent against being eaten, at least by large animals. Some mushrooms like the Fly Agaric are brightly colored and attractive like fruit but are also poisonous or at least unpleasantly hallucinogenic, why evolve this combo? The only things I can come up with are that these toxins are not evolved as a deterrent but are the byproduct of some other process or that they evolved as they culled the populations of animals who eat them and thus left only the phenotype who avoids their variety. --Leivick (talk) 09:13, 21 December 2010 (UTC)

The bright red Fly Agaric may be an example of warning coloration. Bright colors can serve to attract, as in flowers, or to repel, as in poison dart frogs. There is something to be said for the `by product' theory. For example, defensive compounds in mushrooms may be selected for because they decrease invertebrate predation (a large source of selective pressure). Mammals may not exert much selective pressure on a given species, but still experience deleterious effects from ingestion. SemanticMantis (talk) 15:08, 21 December 2010 (UTC)
The mushrooms an animal eats are just the "tip of the iceberg" and eating them does not normally kill the whole organism. Killing you in a few days is a completely adequate way of keeping you from being too much of a nuisance to the organism, and is an excellent way of stopping you from passing on any "ooh that looks tasty" genes to descendants. --Sean 15:19, 21 December 2010 (UTC)
It may also be worth bearing in mind that the toxic quality of any given fungus (or plant) may be coincidental. Not everything about fungi, plants and animals has evolved for protection. Richard Avery (talk) 16:02, 21 December 2010 (UTC)
The effective inhibition of RNA polymerase is something that will kill just about any living organism. Is it possible that these mushrooms (like Amanita) secreting amatoxins are actually doing so primarily as a means to compete with other fungi for their cool, damp, dark ecological niche? Remember that another genus of fungus – Penicillium – secretes antibiotics to ward off competition from bacteria. Does anyone know if the amatoxins are broadly toxic to other fungi (Amanita has presumably evolved to be resistant to its own toxins, but what about other mushrooms?) or to prokaryotes? If that's the case, then the effect on vertebrates (or even on invertebrate animals) may be a minor, almost coincidental one. TenOfAllTrades(talk) 16:04, 21 December 2010 (UTC)
This is OR. The distinctive colour and texture of the fly agaric is broadly similar to carnivorous plants that purposefully attract insects for the purpose of devouring them. Given the reason for its name, I wonder if the poison was developed in part to draw flies in, kill them, and so enrich the soil the mushroom was growing in. Just a guess on my part, so take that with a grain of salt. Despite being a featured article, our article doesn't seem to touch upon any theories regarding why these mushrooms are so toxic. Our article on mushroom poisoning also doesn't seem to touch on why mushrooms have evolved this defense, though it does say that relatively few mushrooms are poisonous, let alone deadly (though when they are...) Matt Deres (talk) 00:58, 23 December 2010 (UTC)

wet dreams[edit]

Are nocturnal emissions the male body's way of getting rid of stale sperm? If that isn't the case then how come women get wet during sexy dreams? —Preceding unsigned comment added by (talk) 10:33, 21 December 2010 (UTC)

Wikipedia has an article about Nocturnal emissions. Their reported incidence is not often enough to match the continual production of sperm and so they cannot be called the male body's only way of disposal. Human sperm has a finite lifecycle estimated[2] as 42 days and if not ejaculated they are absorbed into the body at the vas deferens. After a vasectomy, the testes still produce sperm which are blocked and die in the vas deferens but this site warns that sperm beyond the blockage may survive up to seven months. The logic of the 2nd question is unclear because a women's vulva when sexually stimulated is lubricated by secretions from the Bartholin's glands, which has nothing to do with sperm production. Cuddlyable3 (talk) 15:14, 21 December 2010 (UTC)
Bear in mind that sperm constitute only a small proportion of semen, which is what is actually expelled; the bulk of the seminal fluids is produced outside the testes, primarily in the prostate gland (25-30%) and seminal vesicles (60%). Since the production of these fluids is independent of the testicles and does not turn on and off like a tap according to how much is already "loaded in the chamber", so to speak, periodic flushing of any excess unused by procreative or autostimulatory activities occurs in the form of nocturnal emissions, and I am fairly sure (though cannot find an immediate Wikipedia reference) that seminal fluid production and nocturnal emissions continue following the cessation of the sperm supply through vasectomy or even testicular castration.
Although women do not, obviously, produce seminal fluid, they do produce homologous fluids for lubricatory and perhaps other reasons, and the article on nocturnal emissions explicitly states, "women are also capable of having them." Similar considerations of excess production disposal presumably apply.
It is widely assumed (he weaselled) that during nocturnal emissions, it is the sensation of ejaculation/secretion that give rise to the "sexy dreams" rather than the reverse. (talk) 01:15, 22 December 2010 (UTC)
It can also be widely assumed on the basis of diligent and exhaustingive empirical bio-studies employing the relevant gender-specific appendage activated manually in a turgid modality that the referred emission is obtainable with comparatively equal facility throughout the diurnal cycle and is therefore not necessarily correlated exclusively with the crepuscule or nocturnal phase of solar illumination absence so I have heard. Cuddlyable3 (talk) 10:35, 22 December 2010 (UTC)
You don't say. Do go on. -- Jack of Oz [your turn] 08:19, 23 December 2010 (UTC)

Straight back, diaphragm[edit]

If I sit with my back straight, does it make the diaphragm to be less restrained? It is a common explanation in meditation lessons, and it also makes intuitively sense (however, laying on the side also seems to be good for unrestrained breathing). Quest09 (talk) 14:32, 21 December 2010 (UTC)

Yes. When sitting straight up, gravity acts on the contents of the abdomen to pull them downwards. This makes the work of the diaphragm easier. When lying down on the back (supine), the abdominal contents press against the diaphragm, so the diaphragm needs to work harder. The diagnosis of "diaphragmatic paralysis" can be shown by measuring the spirometry ("lung capacity") when sitting up and lying down. In people with diaphragmatic paralysis, there is a big difference. Here is a report that remarks on this: "Paralysis of the diaphragm may be suspected in a patient ... in whom the vital capacity falls appreciably in the supine position." Axl ¤ [Talk] 10:44, 23 December 2010 (UTC)


Is it true that most oncologists (about 80%) when polled said they would not use chemo on their families or themselves? — Preceding unsigned comment added by Kj650 (talkcontribs) 16:23, 21 December 2010 (UTC)

I have not heard of it before but it seams reasonable given that most of them does not need it be curse they do not have cancer. --Gr8xoz (talk) 16:54, 21 December 2010 (UTC)
Presumably the OP means "as a treatment for cancer," durrr. --Mr.98 (talk) 17:11, 21 December 2010 (UTC)
I assume this is the origin of whatever statistic you are thinking of. The sample sizes are not huge, and the specifics of what kind of cancer are rather specific, and even then the number is not nearly as large as 80%. Additionally, the original "very high" (~75%) poll was over 20 years ago; even this one, which is well over 10 years ago, 64% said they would use chemo. I don't know what it would be today — medicine of this sort changes rather rapidly, and 10 years can make a big difference. --Mr.98 (talk) 17:14, 21 December 2010 (UTC)
It sounds like the typical position of some doctors like Matthias_Rath (a real doctor in Germany) who advocate to treat many diseases (including AIDS, diabetes, cancer) with vitamin supplements (that can be bought from them for a reasonable fee) rather than with the 'poisonous' mainstream treatment. Quest09 (talk) 17:31, 21 December 2010 (UTC)
I think that's a little extreme. There are significant numbers of oncologists who think that chemo is not the best treatment. That doesn't make them all quacks who believe in the miraculous powers of vitamin supplements. Chemo is an intense and possible detrimental form of treatment, and not the only one, and not necessarily the best one. Just because you aren't in favor of it doesn't mean you're in favor of quackery. Just because you're skeptical of a supposedly mainstream response doesn't mean you're necessarily in favor of the fringe response. --Mr.98 (talk) 19:43, 21 December 2010 (UTC)
I expressed myself wrongly. I don't mean that oncologist against chemotherapy are quacks. Chemotherapy might not be the best choice for some treatments. I wanted to say that quacks use phony statistics (like 80% of oncologist are against chemo), taken out of context to bash chemotherapy, and to offer you an 'alternative' like a high dosage of a vitamin supplement (which you have to buy from them, overpriced). Quest09 (talk) 20:30, 21 December 2010 (UTC)
It is important to recall that 'cancer' isn't one disease but many, and 'chemotherapy' isn't one particular treatment but a regimen tailored to the given patient and disease. It's extremely misleading to talk about 'chemo' as a single monolithic process or treatment. Different chemotherapeutic agents have very different side effects and different (often disease-specific) efficacies. Different patients will respond in different ways, and may find antinauseants and other supportive treatments more or less effective.
I would be very surprised if you were to find a practicing oncologist anywhere in an industrialized, first-world country who would flatly refuse chemotherapy for themselves or family members. Instead, what I am certain of is that you will find are oncologists who under some circumstances – of disease progression, life expectancy, and predicted marginal benefit – would opt not to undergo chemotherapy themselves, while still offering their patients a choice in similar circumstances. Consider a hypothetical (and grossly oversimplified) case involving a patient with advanced metastatic disease and a median expected survival time of one year. Suppose that an aggressive chemotherapeutic regimen will probably make the patient miserable for a month; the statistics say that on average his expected survival will be extended by two months and his chance at five-year survival will increase by some trifling amount. Good tradeoff, or not? There isn't a 'right' answer in some situations. TenOfAllTrades(talk) 01:38, 22 December 2010 (UTC)
I did a little bit of research into this a while ago and I think the critical statistic which is left out of the opponents of chemo therapy is "quality of life". Yes the pure "survivability" statistics for a lot of cancers treated with chemo seem far from stellar, and the chemo does make you feel miserable for a few months, but after that you might have a few years of relatively decent life. Without the chemo or radio therapy, the cancer will just grow unchecked and the pain and suffering it causes to those who didn't opt for therapy is what's NOT discussed by people who oppose chemo. Vespine (talk) 02:17, 22 December 2010 (UTC)

Chemotherapy has had some really amazing strides in the past few years. I'm going to go out on a limb and say if the hominid toxicity of 3-BrPA is anything like its toxicity in other mammals, the retiring baby boomers might not end up a net health care negative. Ginger Conspiracy (talk) 06:55, 22 December 2010 (UTC)

The colour of this morning's lunar eclipse[edit]

February 2008 total lunar eclipse John Buonomo.jpg
2010-12-21 lunar eclipse Orlando FL.jpg

Hi. Compare the two images, one from the latest eclipse (right) and the other taken during the eclipse of February 2008 (left). Both have a reddish hue, but the most recent one is darker. Is this due to the recent volcanic activity? Thanks. ~AH1(TCU) 17:25, 21 December 2010 (UTC)

Before anyone jumps to conclusions, note that the February 2008 image is a digital composite of 1180 frames captured over a three-hour period. The amount of digital postprocessing required to synthesize and perform superresolution from more than 1,000 images is huge - so use caution before jumping to any conclusions about any characteristic of these images. (I was tipped off that something was a little "weird" when that image appeared to resolve lunar features that even I have a hard time shooting through my 200mm Newtonian reflector). The color and light intensity should be considered false color, and unless you have detailed information about the compositing method, avoid making inferences about true light intensity from it. Nimur (talk) 17:43, 21 December 2010 (UTC)
It's not totally unreasonable to say volcanic ash might affect how the moon looks from earth, but i don't see why you would only notice the effect during a lunar eclipse. Also, i don't think the rate of volcano eruptions is any different then in 2008 except maybe for maybe Eyjafjallajökull, that article shows the spread of the ash cloud so you should be able to tell if it's at least plausible that's what caused it. Hint: if you are in america: no; if you are Europe: maybe. Also relevant from the Volcanic ash article it states Volcanic ash particles have a maximum residence time in the troposphere of a few weeks. The finest tephra particles remain in the stratosphere for only a few months, they have only minor climatic effects, and they can be spread around the world by high-altitude winds. This suspended material contributes to spectacular sunsets. This confirms it's possible for the view of the moon to be affected for months after an eruption, but again I don't see why you'd only notice it during a lunar eclipse. Vespine (talk) 02:08, 22 December 2010 (UTC)
I have to say I don't know the answer, but I want to clarify some things. First, it's true that the recent eclipse is darker. Sky and Telescope gives a Danjon estimate of 2.5-3 for the 2008 eclipse and 2 for the 2010 eclipse (see and, although these numbers are early estimates, and it's frustratingly difficult to find accurate brightness data on past eclipses.
Second, to answer Vespine, notice how the Moon appears red during totality, even though it's completely inside Earth's umbra. The only light that reaches the Moon during totality has to refract around the Earth, which means it has to travel thousands of kilometers through Earth's atmosphere. This light is red for the same reason sunrises/sunsets are red, and it's heavily affected by volcanic dust for the same reason volcanic eruptions cause brilliant sunrises/sunsets. Another way of looking at it is that some light from every sunrise and sunset on Earth is leaving the atmosphere, hitting the Moon, and reflecting back. So if you watched the recent eclipse from North America, part of the light that reached the Moon during totality would have passed through European skies, because the Sun was rising in Europe around that time. -- (talk) 03:40, 22 December 2010 (UTC)
I admit I actually didn't consider the light passing through the atmosphere on the way to the moon, only passing from the moon back to earth. I thought since the atmosphere is only a tiny part of the diameter of the earth it would only have a very small impact on the light behind the earth, but refraction around the earth makes perfect sense when you explain it like that. Thanks. Vespine (talk) 05:38, 22 December 2010 (UTC)
I was not referring to the Icelandic eruption, but rather the more recent volcanic eruptions such as those at Mount Merapi, Mount Bromo and Mount Bulusan. ~AH1(TCU) 17:26, 22 December 2010 (UTC)

Does sleep deprivation do permanent damage to the brain?[edit]

In the Wikipedia article it is mentioned that sleep deprivation has temporary effects. However, it is not mentioned if prolonged lack of sleep has any permanent effects on the brain.
So does it have permanent effects on the brain, or are they limited to them time spent under sleep deprivation? -- (talk) 17:40, 21 December 2010 (UTC)

It might be difficult to study this, since clinical studies would be unethical, leaving us with only apocryphal cases. An even if a case is verified, would it be clear whether sleep deprivation caused the brain damage or the brain damage led to insomnia, and hence sleep deprivation ? StuRat (talk) 21:29, 21 December 2010 (UTC)
When you say prolonged lack of sleep do you mean staying awake for multiple days straight? Or do you mean not enough sleep each night? Ariel. (talk) 21:34, 21 December 2010 (UTC)
Sorry for not making it clear. When I say "lack of sleep" I mean staying awake for multiple days, not having little sleep at night. I would also like to know after what period of time the damage starts.--The Dimak (talk) 16:25, 22 December 2010 (UTC)
What about Stress (biology), which may accompany the sleep deprivation, causing effects on the organism which indirectly affect the brain. If the subject is under extreme internal or external pressure to finish writing some work, to finish a construction project, is in combat, is fleeing a menace, or is deliberately being kept awake by a captor, researcher or interrogator, would the prolonged release of cortisol or adrenalin directly affect the brain? The stress article mentions "ulcers, depression, diabetes, trouble with the digestive system or even cardiovascular problems, along with other mental illnesses." Some heart rhythm disturbances can cause blood clot formation leading to stroke. Digestive disturbances or diabetes can affect the blood chemistry, thus affecting the brain. Edison (talk) 17:20, 22 December 2010 (UTC)
The complete absence of sleep will eventually cause death. Brain damage could occur somewhere in this range. ~AH1(TCU) 17:21, 22 December 2010 (UTC)

See: Fatal familial insomnia. Count Iblis (talk) 22:38, 22 December 2010 (UTC)

That's not exactly what the OP is asking. FFI is very rare prion disease in which the brainstem is damaged first, followed by a host of autonomic problems including insomnia, followed by death. It is a pretty horrific disease, to be sure, but the OP wants to know if physically staying awake for multiple days at a time could cause brain damage. --- Medical geneticist (talk) 12:58, 23 December 2010 (UTC)
As noted, heart disease or stroke resulting from the concomitant stress could permanently damage the brain, as could the severe hypoglycemia resulting from diabetes caused by the stress. People rarely stay up for days on end just because it is fun to do so, without some powerful and likely stressful motivator. Edison (talk) 05:29, 24 December 2010 (UTC)

radio-metry and its uses in optical instrumentation[edit]

what is radiometry and its types uses in optical instrumentation — Preceding unsigned comment added by Mahi09 (talkcontribs) 17:58, 21 December 2010 (UTC)

Have you read our article on radiometry? Photometry_(optics) and Photometry_(astronomy) may be of interest, they refer to similar fields of study, but restricted to visible light. SemanticMantis (talk) 18:45, 21 December 2010 (UTC)

why does skin on your face get wrinkled and how does cream help?[edit]

why does skin on your face get wrinkled and how does cream help? (talk) 20:44, 21 December 2010 (UTC)

The Wrinkle page might help explain why skin wrinkles. Most skin creams are just emulsions of oil and water and just provide a temporary moisturizing effect, making your skin appear less wrinkled. Most of the other compounds advertised in skin creams (Like vitamin A, E or other antioxidants) are not proven to do anything at the level of the amounts in the cream. -- JSBillings 21:12, 21 December 2010 (UTC)
The main effect is from ultraviolet exposure from sunlight. That's why you hardly ever see a wrinkled vampire. :-) StuRat (talk) 21:24, 21 December 2010 (UTC)
(...nor any other kind of vampire.) Botulinum toxin type A is BION an approved cosmetic for temporarily fixing skin wrinkles, see Botox#Cosmetic. Cuddlyable3 (talk) 21:44, 21 December 2010 (UTC)
Wrinkle cream helps those who sell it to make money through the vanity of others. HiLo48 (talk) 22:12, 21 December 2010 (UTC)

Basement temperatures[edit]

If an unheated basement or pit ten feet deep had a well-insulated roof, what sort of temperature would it have during the year in northern europe? I have been unable to find this kind of information. Thanks (talk) 22:53, 21 December 2010 (UTC)

There are too many variables to give a definitive answer. Temperatures vary considerably throughout northern Europe. Deep pits tend to remain at a fairly constant temperature if there is no strong airflow to the atmosphere and there is good insulation, but there would still be some variation according to air temperature. The temperature would tend to follow that of the ground at a similar level if the walls and floor are uninsulated. There may be some areas where the pit would be below the freezing-point of water all winter, and others where it would become uncomfortably hot in summer. Dbfirs 23:29, 21 December 2010 (UTC)
My grandparents had a basement used as a pantry, just dug into the ground under their house, in a small town north of Warsaw in Poland. It's not northern Europe but I believe this was not uncommon practice all around Europe. The fact it had a house on it that was kept warm in winter would have played a big part in it never freezing. I don't think insulation, no matter how "good" without any source of heat would do something similar. Insulation just makes the escape of heat slower, but without a source, the heat would eventually escape. Earth it self is a very good insulator, in seasonally frozen ground I believe you wouldn't expect the ground to freeze more then a few to several feet deep so insulation might work, (it would probably help if was black to capture as much sunlight as possible, however in places of permanent frost like areas of Siberia and Alaska the ground can be frozen to hundreds of feet where I doubt any insulation would do very much. Vespine (talk) 01:51, 22 December 2010 (UTC)
Yes, it does very. For instance, at Cheddar Gorge, the caves stay at a steady 52°F -which is just right for maturing traditional cheddar.[3] The article about the Geothermal gradient explains more.--Aspro (talk) 10:36, 22 December 2010 (UTC)
It depends very strongly on how deep you are. Near the surface (like a basement) it's going to vary winter/summer - but once you go deeper it starts to vary less and less, basically the earth both insulates it and acts as a heat sink/source. Ariel. (talk) 11:22, 22 December 2010 (UTC)

A basic pit with a sealed roof will act like a "fruit cellar" and stay substantially above the outside temp in the northern winter. The dimensions and insulation level of the roof would be important factors in the actual air temperature. In the Northern US winter temps drop to perhaps -30F (-34C) and the frost line drops fairly deep. The basement footings or house foundation must be below this frost line to prevent "heaving" or movement due to soil freezing below the footings. This may be 5 feet (1.52 meters) in Minnesota. In northern Canada or Alaska there is permafrost. The pitwall would approximate the soil temperature, with the deeper portion at a more constant temperature, but in Minnesota, the soil down to 5 feet would be below freezing. Convection currents inside would circulate warmer air from the bottom up along the walls, so the soil or wall temp would be a bit warmer near the surface than in undisturbed soil of the same depth. In an abandoned house, especially if it is not sealed against air circulation and infiltration, and without the benefits of heating or the retention of solar heating, it is common for the frozen ground to break the basement walls and force them inward, near the ground. I have also seen basement wall broken where rainwater of snowmelt from the roof is allowed to dump next to the foundation, so pooled water next to the cellar wall freezes and expands and causes it the wall to break and tilt inward. I have seen the air temp in an unheated shallow basement of a heated house in the northern US stay near freezing for days when the outside temp is many degrees below freezing. A cave completely below ground might have air temperature at about the average yearly temperature for the area, although as the depth went far below ground, like a gold mine, the temperature would rise significantly. Edison (talk) 17:04, 22 December 2010 (UTC)