Wikipedia:Reference desk/Archives/Science/2012 October 26

= October 26 =

Evolution of horse - back strength/suitability for riding
Why has the horse evolved to be able to carry the weight of a human on its back? Why do they even tolerate riding?--2.97.23.83 (talk) 08:02, 26 October 2012 (UTC)
 * It would be more accurate to say that horses have been bred for the purpose of humans riding them, and so have been artificially, not naturally selected. Furthermore, this development did not take place in a geological timescale, but over the span of only a few thousand years. Before maybe 1500 BC, horses were used mainly to draw chariots, because they weren't big enough to ride. The situation is similar to modern cattle providing huge quantities of milk, far more than wild cattle. This is not due to evolution, but due to human/artificial selection. - Lindert (talk) 10:09, 26 October 2012 (UTC)


 * Are you sure about the size part? The Hagerman horse is about the size of an Arabian horse, and it dates from 3.5 million years ago.  --140.180.252.244 (talk) 10:50, 26 October 2012 (UTC)


 * Do you have a source on horses not being large enough to ride before their domestication? Our article on evolution of the horse seems to indicate otherwise. Undomesticated horses like the Przewalski's horse appear large enough to support a human rider. A8875 (talk) 10:51, 26 October 2012 (UTC)


 * I'm not saying that no horses existed that were big enough, just the horses that were used by humans early on were small, and then bred larger. Maybe large horses did not live in the area (ancient near east) where they were first domesticated. - Lindert (talk) 11:13, 26 October 2012 (UTC)


 * I recons it was purely coincidental at first, and then there developed an evolutionary correlation. Plasmic Physics (talk) 11:03, 26 October 2012 (UTC)


 * We have an article, Domestication of the horse. With reference to the points raised above, it seems that (according to our article) "recent genetic studies indicate that Przewalski's horse is not an ancestor to modern domesticated horses". Also, one of the first domestications seems to have been by "theBotai culture... who seem to have adopted horseback riding in order to hunt the abundant wild horses of northern Kazakhstan between 3500-3000 BCE" although it's not certain that they didn't just hunt them. Finally, "Horse bones from these contexts (recovered from the middens of various European bronze age sites) exhibited an increase in variability, thought to reflect the survival under human care of both larger and smaller individuals than appeared in the wild; and a decrease in average size, thought to reflect penning and restriction in diet." Alansplodge (talk) 15:17, 26 October 2012 (UTC)


 * It's worth noting in terms of the behavior that in some respects humans just lucked out. Zebras, for example, have never been domesticated to the same degree as the horse, despite a lot of trying. There seems to be something fundamentally incompatible with their natural makeup to easy domestication, as there is for a lot of animals. --Mr.98 (talk) 22:14, 26 October 2012 (UTC)
 * For some pictures of domesticated zebras, see Zebra taxi cab in Brixton Road!;-) Alansplodge (talk) 16:57, 27 October 2012 (UTC)

Chemical castration for woman
Are there any chemical castration procedures for female sex offenders? A8875 (talk) 09:36, 26 October 2012 (UTC)
 * Androgens may contribute to aggression in women (data are conflicting), and one could speculate about whether they would be effective, but I'm not aware of any such procedures. Estrogens do not clearly contribute to aggressive behavior, so I would not expect an analogous procedure for female hormones.  Of interest (not all directly related):, ,  -- Scray (talk) 10:41, 26 October 2012 (UTC)


 * This page has some interesting information: "Even though sexual victimization by either males or females is a traumatizing experience, female offenders are overall not as dangerous as males, and combine the act with fewer aggravating circumstances such as weapon possession, kidnapping, or violence. Perhaps because of this, more cases of female sex offending go unreported." It also states that less than 4% of sex crimes in the U.S. are committed by females, and notes that sex crimes by females tend to be less likely to be repetitive or compulsive than males.  It does not directly answer the question on whether chemical castration is possible, nor does it answer whether it is desirable, but it does make the case that sexual crimes committed by females are distinct from those committed by males, and thus may indicate that a different response to them is necessary.  Just some related ideas.  Doing some searching, I can't find any reliable sources on "chemical castration of women", but several rather unreliable discussions found through searching google with that phrase seem to indicate there is a sense that either it is never done, or even that it isn't possible to do so.  -- Jayron  32  13:26, 26 October 2012 (UTC)


 * Female sexual criminals are not your typical sexual predator or compulsive rapist. There are much more a women having consensual sex with men below the age of consent (so, it's not legally consensual) or women being dragged into some sexual slavery scheme by partners. OsmanRF34 (talk) 16:58, 26 October 2012 (UTC)
 * Is this your impression, or do you have references to support your "answer"? -- Scray (talk) 17:13, 26 October 2012 (UTC)
 * It's a small sample, but the criminal statistics for Sweden in 2011 kind of supports that. Of 18 women sentenced for sex crimes 1 committed rape, and out of 1380 men sentenced for sex crimes 151 committed rape and 16 aggravated rape (statutory rape not included in rape or aggravated rape) (sourceBRÅ, Brottsförebyggande rådet). That's 6 % of female sex offenders and 12 % of male sentenced for rape. I'm sure there are similar statistics for other countries.Sjö (talk) 15:41, 27 October 2012 (UTC)
 * I think it's too small a sample. A quick mental calculation gives huge error bars on the rate of female rapists -- that "6%" is actually something like "0%-14%". --Carnildo (talk) 02:16, 30 October 2012 (UTC)

There are drugs that suppress sex hormones in women as well as men. Examples are gonadotropin releasing hormone analogs such as leuprolide and histrelin. They are used to suppress sex hormones for many purposes, but not to treat female sex offenders for many reasons. As mentioned above: there are very few of them, and nearly all have engaged in consensual sex with adolescents or have been willing participants in abuse of younger children under the direction of a male; an even smaller percentage repeatedly offend. Most importantly there is no evidence that hormones play a role in compulsive sexualized behavior that testosterone seems to in men. alteripse (talk) 19:56, 31 October 2012 (UTC)

Privacy
Can you read my I.P. address?Cinquefoil (talk) 11:35, 26 October 2012 (UTC)
 * No, I can't. Because you have a registered account, your ip address is private from most other users.  A few selected people with checkuser privileges can choose to see your ip address, but they wouldn't be likely to bother unless you were disrupting the project in some way.-FisherQueen (talk · contribs) 11:37, 26 October 2012 (UTC)
 * It's actually more than "they won't bother": Checkusers use of the Checkuser tool is carefully monitored and logged, and checkusers that misuse it can be stripped of it. So, unless you have actually done something to attract the attention of the Checkusers, no one will see your IP address.  Checkusers have to have a justifiable reason to use the tool, and if they don't, there's some 'splainin' to do.  -- Jayron  32  13:15, 26 October 2012 (UTC)
 * There are a lot of ways to "social engineer" it. Like, if I have a site that will tell me the IP addresses of people who look at a picture (or an invisible "web bug") and I send it to Special:Emailuser/Cinquefoil, then if you open it, I know what your IP is (and stuff about your browser too, probably)  Or I could post similar links to some kind of text answers to two questions you ask, see if there's an IP address in common.  The whole web is run by amateur spies on the brink of turning pro, I think. Wnt (talk) 21:06, 26 October 2012 (UTC)

The surface of Saturn
This question was prompted by - stories which get it wrong; the vortex is 150 F hotter, not 150 F!  Still, according to the article, Saturn gets extremely hot, 11,700 C shining-like-the-sunhot, if you go down far enough.


 * How much is known about the temperature profile and cloud composition of Saturn's atmosphere? In particular, is it like Jupiter's atmosphere, where there is a "sweet spot" with Earthlike temperatures and pressures if you go to the right depth?  (Note Saturn also has Earth gravity, making it a rather good opportunity for a sci-fi vacation, I think.  If only you can figure out how to breathe and how not to fall, that is.)


 * What does our article mean when it says that Saturn has a "liquid layer of helium-saturated molecular hydrogen that gradually transitions into gas with increasing altitude" (around 1000 km). I'm aware of the critical point where gas and liquid are the same, but I thought either you were above the critical point and there was no difference, or you were below it and there were two very distinct phases.


 * Saturn is made up mostly of liquid hydrogen that is less dense than water. So why don't all the other heavier elements sink and leave no trace in the atmosphere?  Or is the liquid hydrogen mixed in with a fairly large amount of such impurities?


 * Is there anything that might be found floating on the "surface", if it exists, or which could distinguish a "cartography" of different physical areas?


 * 1000 km might show up on Earth, but relative to Saturn, it's a very thin skin, practically two-dimensional. Do these things like the Great Springtime Storm exist as very wide but not deep features, like hurricanes on Earth, or do they whip up vortices (or something) in the liquid? hydrogen layer?

Some previous discussion, not very satisfying, at. Wnt (talk) 21:31, 26 October 2012 (UTC)


 * It's unlikely that there is such a "sweet spot", the temperature would probably be below freezing even at greater than 100 kPa atmospheric pressure.


 * I hope that you're aware that gravity is a function of height, and not a constant. So, it does not make sense to describe Saturn's gravity without making a reference to a height.


 * I don't understand what you don't understand, concerning the critical point. A trasition through the critical point occurs with increasing depth just as you say.


 * Because of this transition, there is no surface, so nothing can be floating on a surface. Plasmic Physics (talk) 13:09, 27 October 2012 (UTC)
 * It doesn't matter much if it's a few times atmospheric pressure - can you be more specific?


 * The article says that for temperatures between 270 K and 330 K, the pressure is 1-2 MPa. That's more than ten times atmospheric pressure, and it happens to be the exact zone where hydrogen transitions from a gas to a supercritical gas-liquid state. Helium transitions ways before that even. Plasmic Physics (talk) 02:30, 28 October 2012 (UTC)


 * Gravity in the article is in reference to the 1 bar level; anywhere in the atmosphere should be very similar.
 * Critical point (thermodynamics) does indeed show dotted lines at the critical temperature and pressure. I suppose it is the critical pressure that is exceeded in this case at 1000 km?  But that transition isn't "gradual" - it's just an imaginary line between "gas" and "supercritical fluid", I suppose?  But that should not be visible, and it makes no special sense to call it liquid hydrogen beneath it, right? Wnt (talk) 01:44, 28 October 2012 (UTC)


 * A supercritical state can only be achieved when both the critical pressure and temperature have been exceeded. It should really be called supercritical helium/hydrogen. The transition from gas to a supercritical state is not gradual but sharp and well-defined, because of the pressure and temperature boundries. It is the transition of observational properties that is gradual. Plasmic Physics (talk) 02:17, 28 October 2012 (UTC)


 * Indeed, I see now that hydrogen has a critical point of 1.29 MPa, about 12 atm. Where this gets curious is that hydrogen has density 70 kg/m3 as a liquid, 30 kg/m3 at the critical point, whereas air near STP has density a little above 1 kg/m3 -if ordinary air respects the ideal gas law, then it should only be around 12 kg/m3 at this point.  Now heating hydrogen should reduce its density, but will a supercritical fluid respect the ideal gas law?  From the article I'm getting the impression that small differences in conditions alter its density considerably, so I'm thinking no.  I almost wonder if there's a point where ordinary air (let alone heated hydrogen) might be buoyant within the supercritical hydrogen fluid?  But I haven't really thought this through.  Also, what's the solubility of water in supercritical hydrogen?  I have this weird notion of jellyfish, with an inner food reservoir of stored oxygen gas, floating in the sea of supercritical hydrogen? Wnt (talk) 06:59, 28 October 2012 (UTC)


 * Of course "ordinary air" is buoyant. Even so, it doesn't separate out from the supercritical fluid-gas, it mixes yielding ratios proportional to the depth. On earth, the different atmospheric gases (nitrogen, carbon dioxide, oxtgen, argon, etc.) have differing bouyancies. Brownian motion ensures that they don't separate out into layers, I think it is called a Maxwell-Boltzman distribution, we have a page on it. Plasmic Physics (talk) 07:58, 28 October 2012 (UTC)
 * Well, if it's true - and I don't know it is - it would be very surprising to me to find some special set of temperature/pressure conditions where oxygen is lighter than hydrogen, and more so to find them in reality. The point is that a jellyfish, even a single celled ancestor that can remain suspended due to its small size, would be readily able to separate oxygen from the supercritical sea in which it lives, and store it in little vacuoles where it would no longer mix.  I'd read about the notion of "gasbag" organisms on Jupiter before, but had the impression that authors were only thinking of hot hydrogen balloons, designs that life has never created and would seem hard pressed to evolve. Wnt (talk) 13:55, 28 October 2012 (UTC)


 * If Saturn is anything like Jupiter, then complex life is going to have a tough time in the atmosphere of Saturn. Jupiter generates biotoxic levels of high-frequency EM radiation like UV and X-ray, caused by perpetual lighting, so bright you can read a book by them. Plasmic Physics(talk) 01:12, 29 October 2012 (UTC)
 * Sounds like photosynthesis is easier there than I was picturing. :) Really, I think life can resist such mutagenesis if it needs to. Deinococcus radiodurans and all that. Wnt (talk) 01:31, 29 October 2012 (UTC)


 * Just remember that any trip to a gas giant will be an one way trip unless you have engines made of Unobtainium. The gravity well is huge and the exponential mass ratio due to the Tsiolkovsky rocket equation does not make it easier to reach escape velocity.Gr8xoz (talk) 13:32, 27 October 2012 (UTC)
 * I'm a great fan of using nuclear isomers as a power storage, with induced gamma emission. ;) Wnt (talk) 01:44, 28 October 2012 (UTC)


 * What are you implying, if it's not gioing to be easy for a rocket to do the job, then you're supposing an inferior jet-engine can? Plasmic Physics (talk) 02:35, 28 October 2012 (UTC)
 * I was only suggesting a compact energy storage - how you turn that into thrust is another matter. Ion drive perhaps (after you've flown as high as possible) - I don't have any inspired suggestion there. Wnt (talk) 04:06, 28 October 2012 (UTC)


 * In that case, I suggest inventing a slipspace-drive, and tunneling through spacetime. Plasmic Physics (talk) 06:33, 28 October 2012 (UTC)


 * Talking about superciticality, did you know that Venus has an invisible, global ocean of supercritical carbon dioxide? You should be able to notice it as a perpetual fog in the distance. In closer, you should be able to notice a shimmering motion like a mirage, but more ordered, indicating a hydrodynamic flow.Plasmic Physics (talk) 08:22, 28 October 2012 (UTC)


 * This ocean is at least an average of 2.5 km deep, that is the supercritical/gas limit. That makes me wonder how fast the terminal velocity changes in that 2.5 km, does the density change noticably? Plasmic Physics (talk) 01:50, 29 October 2012 (UTC)


 * I added a question about the crux of this (and the part about buoyancy of oxygen above) at Reference desk/Science Wnt (talk) 04:32, 29 October 2012 (UTC)

Why don't my coffee grounds grow mold?
Does it depend on the roast? I use a very dark roast. I can forget about coffee grounds for a week or more and yet no mold grows on them! The other time I was taking over an apartment from someone else and I accidentally drank very old coffee. (I wondered why it was cold-- it was a machine that "stored" the brew in a holding tank, which I didn't know of-- I thought I was drinking fresh brew). It tasted fine. 71.207.151.227 (talk) 22:39, 26 October 2012 (UTC)


 * Well, the (almost) boiling temperature at which the coffee is made would sterilise it. If it's kept well sealed from the air after that, it should restrict growths of many kinds. HiLo48 (talk) 23:01, 26 October 2012 (UTC)


 * Coffee grounds are largely fiber and alkaloid toxins. Any sugar, fat and protein has been denatured or roasted out of them,  Funguses aren't miracle workers--they require actual food. μηδείς (talk) 23:16, 26 October 2012 (UTC)


 * I don't really see why denatured protein wouldn't be a perfectly adequate food source for a fungus. Presumably they need to hydrolyze the protein components to get any nutritional value out of them anyway; If anything wouldn't you expect unfolded protein to be more accessible to proteases and various digestive enzymes? (+)H3N-Protein\Chemist-CO2(-) 00:12, 27 October 2012 (UTC)


 * A lack of moisture is a limiting factor. Mold can grow on coffee. Here are Guidelines for the Prevention of Mould Formation in Coffee.Smallman12q (talk) 01:17, 27 October 2012 (UTC)


 * Yes, wet, used coffee grounds left in the coffee filter in a coffee maker grew an impressive colony of mold, while I was on vacation. StuRat(talk) 02:28, 28 October 2012 (UTC)

how bright is the white dwarf
I don't know the luminosity of the white dwarf will be but I know white dwarf is a comparable size of earth. Is white dwarf going to be 100 times dimmer than solar luminosity, I can't find it anywhere on the internet. But formation and evolution of the solar system said white dwarf will start at 100 times brighter than get dimmer. I also confuse on do white dwarf shrink right away to earth sized diameter, or it will start to be a comparable size with low-mass stars than when white dwarf stars gets older it gets smaller, in other words fresh new white dwarf will be bigger, and full-wedge white dwarf will be smaller. How long will white dwarf last before becoming a black dwarf? 7 billion years? 10 billion years? or White dwarf will start at UV end of stellar spectrum and gradually skew to IR end of stellar spectrum and gradually works toward black dwarf.--69.226.43.174 (talk) 23:42, 26 October 2012 (UTC)
 * White dwarf would be about 100*100=10,000 dimmer than the Sun if it had the same temperature and were the size of the Earth. However the majority of known white dwarfs are hotter than the Sun and therefore more luminous than 1/10,000. You can read more in the white dwarf article. Ruslik_ Zero 12:11, 27 October 2012 (UTC)

Our article said this surface temperature range corresponds to a luminosity from over 100 times the Sun's to under 1/10,000 that of the Sun's I don't get how white dwarf can be at first 100 times brighter than sun, I know white dwarf will have to star from UV end of the spectrum and gradually work way to IR end of spectrum. Does white dwarf have to be immediately the size of Earth, or it will be bigger at the start and then gradually become smaller.--69.226.43.174 (talk) 20:41, 27 October 2012 (UTC)
 * Well the brightness is the fourth power of the temperature. So if a whitedwarf is 5 times hotter than the sun, it would be 5x5x5x5 times as bright or 625 times. Graeme Bartlett (talk) 21:56, 27 October 2012 (UTC)