If an electron has no size, how does it have a magnetic north and south? Bubba73 ^{You talkin' to me?} 04:13, 17 September 2012 (UTC)[reply]

Because it has a spin, and thus an axis of spin, and thus directionality. --Jayron32 04:17, 17 September 2012 (UTC)[reply]

OK, and that spin is not the same as classical spin, right? Because you can't tell if a point is spinning (in fact it doesn't make sense for a point to be spinning). Bubba73 ^{You talkin' to me?} 04:23, 17 September 2012 (UTC)[reply]

Yes and no. It is not "Classical" spin, in that there is no internal structure to an elementary particle, so there is nothing to "rotate". Nonetheless, it is a fundemental form of angular momentum, and it does impart the sort of properties onto a particle that one would expect it to have if it did have an internal structure which could spin classically. Think of it as a quack without a duck... --Jayron32 04:32, 17 September 2012 (UTC)[reply]

Eyes without a face. Gzuckier (talk) 04:48, 17 September 2012 (UTC)[reply]

I could ask "then how does it have angular momentum if it has no size" - but I won't. Bubba73 ^{You talkin' to me?} 05:04, 17 September 2012 (UTC)[reply]

Well, the answer is it does. If you really want to understand how physics works on the "fundemental particle" level, you need to divorce yourself from what you experience with your senses. That is, don't try to logic yourself out of the existance of things which do exist, but which don't make sense on the "big world" level. Fundemental particles don't exist as little balls, even little balls with no dimensions; the most accurate models don't even treat them as discrete objects in that way. Its just there is this property of all fundemental particles that behaves as one would expect "rotation" or "spinning" to behave if the particles were, say, a basketball. Except they aren't, but the property still exists. We call it spin, but there isn't anything to spin. That is, it is spinning without anything that spins. It shouldn't be any harder to grasp than waves that vibrate without anything to vibrate in (i.e. the wave model of light), and yet we're happy to accept light as waves that don't vibrate anything. Same deal here. Just as you can have a wave that doesn't vibrate any substance, you can have a spin in an object that has no dimmensions. --Jayron32 05:31, 17 September 2012 (UTC)[reply]

Resolved

Thank you. Bubba73 ^{You talkin' to me?} 05:46, 17 September 2012 (UTC)[reply]

I wonder if it has tiny Eskimos and seals and polar bears and penguins...Gzuckier (talk) 04:50, 17 September 2012 (UTC)[reply]

Heh, this mental image of tiny people and animals sitting on electron poles is quite amusing. Thanks! :D —SeekingAnswers (reply) 14:51, 17 September 2012 (UTC)[reply]

It's just like the real north pole and it therefore does not have penguins. CambridgeBayWeather (talk) 15:34, 17 September 2012 (UTC)[reply]

If it's an anti-electron, it has negative spin. Does that mean the subatomic sun rises in the west instead of the east, or that penguins are at the north pole instead of south? I'm concerned because the lighting-variation and/or penguining could interfere with an important research project. DMacks (talk) 20:49, 18 September 2012 (UTC)[reply]

• I think that saying an electron has no size is absurd. It is fuzzy with about a Compton radius. See Rydberg atom, where electrons dutifully orbit macroscopically just like Bohr described. The electron is a little cloud of probability density, and while you don't have any good way to grab a piece of it and feel it spinning about its center, I don't know of any reason why you can't think of it actually doing that. Wnt (talk) 15:45, 17 September 2012 (UTC)[reply]
  • Well sure, that's based on defining the electron based on the laws of Classical mechanics. It's a fine model, but we've discovered a whole shitload of physics since then. --Jayron32 17:59, 17 September 2012 (UTC)[reply]
    • I'm sure I saw a report in Nature, at some point or another, demonstrating that the electrons in highly excited states (30 or so) could actually be visualized as blobs far away from the nucleus, but I'm having trouble finding it at the moment... Wnt (talk) 21:59, 17 September 2012 (UTC)[reply]
      • There's lots of ways you can visualize an electron. It depends mostly to what end you are using your model. Different models serve different purposes. --Jayron32 03:59, 18 September 2012 (UTC)[reply]

Hmmm, found something: Rydberg ionization spectroscopy: "As the electron is promoted to higher energy levels, the spatial excursion of the electron from the ionic core increases and the system is more like the Bohr model picture." Wnt (talk) 06:03, 18 September 2012 (UTC)[reply]

Someone above said "then how does it have angular momentum if it has no size". Maybe it's the other way around? everything we know has angular momemntum AND size, it's like when people thought that "cold" was a thing, not the lack of it. Like if you touch ice, it feels like the cold is going into your fingers, not that heat is being sapped out. It makes sense to our senses, but it's not really a great interpretation of reality. Vespine (talk) 22:28, 17 September 2012 (UTC)[reply]

Electrons have no size?! O_o my life was a lie! Asmrulz (talk) 20:38, 18 September 2012 (UTC)[reply]

Have there ever been any surrogate mothers over 70 in India? Neptunekh2 (talk) 05:17, 17 September 2012 (UTC)[reply]

According to Pregnancy over age 50 there have been two women in India who have given birth past their 70th birthday, but both before their 71st birthday, so that depends on what you mean by "over 70". --Jayron32 05:26, 17 September 2012 (UTC)[reply]

This is a bizarre question. Neptunekh2, are you sure you understand what a surrogate mother is? Or are you asking whether any woman over 70 has used another woman as a surrogate mother? Looie496 (talk) 06:22, 17 September 2012 (UTC)[reply]

Has any woman over 70 has used another woman as a surrogate mother That's what I mean to ask.

Has any woman over 70 used a surrogate mother? It wouldn't be unreasonable, particularly since surrogacy doesn't require genetic material from the social mother. That sort of info is harder to track down, though, as "someone who didn't deliver a baby" isn't terribly remarkable from a records-keeping standpoint. There's a good chance that some rich person who wants an heir has done it at some point. On the other hand, if we ask whether any woman over 70 has been a surrogate... well, per Jayron's comment above, there are two cases of Indian women who, at 70, gave birth to children conceived with donor eggs. Since they intended to keep the children themselves, though, I'd think the bigger question is whether that constitutes surrogacy. — Lomn 18:07, 17 September 2012 (UTC)[reply]

How would I go about solving the following Q ?

A) You are given three resistors: two 4Ω resistors and one 6Ω resistor. Given that each individual resistor can dissipate up to 1 watt of power before burning up, how much total power in watts (W) can the smallest-valued composite resistor dissipate before burning up?

I know p = iv = i²r = v²/r, but I don't know either i or v. I can't seem to figure this out; I must be missing something obvious. Any hints ?

StuRat (talk) 07:11, 17 September 2012 (UTC)[reply]

First, find the value of the "smallest-valued composite resistor", basically all three resistors in parallel.

${\displaystyle R_{\mathrm {total} }={\frac {1}{{\frac {1}{R_{1}}}+{\frac {1}{R_{2}}}+{\frac {1}{R_{3}}}}}={\frac {1}{{\frac {1}{4}}+{\frac {1}{4}}+{\frac {1}{6}}}}=2.67\Omega }$

Let the total power be x, it follows that

${\displaystyle x={\frac {V^{2}}{R_{\mathrm {total} }}}={\frac {V^{2}}{2.67\Omega }}}$

Rearranging and we have:

${\displaystyle V={\sqrt {2.67x}}}$

For parallel resistors, the smallest resistor would consumer the most power, thus we have:

${\displaystyle 1W={\frac {V^{2}}{R_{\mathrm {smallest} }}}={\frac {V^{2}}{4\Omega }}={\frac {2.67x}{4\Omega }}}$

${\displaystyle x=1.5W}$A8875 (talk) 07:41, 17 September 2012 (UTC)[reply]

Thanks, but I see a math error on the first step:

        1        
 1/4 + 1/4 + 1/6

         1         
 6/24 + 6/24 + 4/24

   1  
 16/24

 24/16 = 1.5Ω

StuRat (talk) 07:55, 17 September 2012 (UTC)[reply]

However, when I completed the problem with that correction, I got 2.67 watts, which is the correct answer. Thanks ! StuRat (talk) 08:04, 17 September 2012 (UTC)[reply]

I intentionally inserted the error to prevent you from copying down the answer without working out the problem yourself. Oh who am I kidding, I can only dream of being that clever. You're most welcome.A8875 (talk) 08:08, 17 September 2012 (UTC)[reply]

LOL. Well, you helped me with circuits and I helped you with fractions, an equitable exchange. Thanks again. StuRat (talk) 08:18, 17 September 2012 (UTC)[reply]

Is there a good scientific reason why these images of our place in the universe are cylindrical? Dismas|^(talk) 10:08, 17 September 2012 (UTC)[reply]

Probably to give a sense of what is the orientation of these bodies in 3D...--Irrational number (talk) 12:04, 17 September 2012 (UTC)[reply]

Usually images of this type have a vertical line from the discs to each object, which unambiguously shows its location in 3D (example). These don't, though, so I can't think of any reason why they should have the discs at all. -- BenRG (talk) 23:04, 17 September 2012 (UTC)[reply]

While it may not add much actual 3D information it does create an impression of 3D. Without it you'd just have points on a plane. For some objects it limits the possible positions: anything shown above the long axis of the upper ellipse has to be in the distant half of the 3D space, anything below the long axis of the bottom ellipse has to be in the half closer to you as observer so to speak (because otherwise they would fall outside the top or bottom plane of the cylinder. Ssscienccce (talk) 17:31, 20 September 2012 (UTC)[reply]

After reading hypothetical types of biochemistry I have some questions, but based on personal experience here, if I list them out in one section most of them are neglected, I ask them in different sections (is that wrong? anyway, sorry if it is). My first question is as follows. Carbon is the best candidate for ET life (any life) because of its ability to form (of course with the use of other elements) giant molecules that are not (necessarily) repetitive and do not (necessarily) behave the same in different parts of them (I think that's the best way to summarize it?). Life as we know, although not entirely "made" of aminoacids, can not function without them. Could there be other types of carbon based biochemistry that use other "minor" elements, possibly making more use of halogens or metals or even semi-metals? The article gives only one example (I mean seriously? oxocarbons?) and I just want to get a bit up to date on this, I mean carbon chemistry is so diverse. Also, can the presence of aminoacids in meteors used as an evidence that if there is ET life it has a very similar chemistry to our life and thus other forms of carbon chemistry are improbable?--Irrational number (talk) 12:30, 17 September 2012 (UTC)[reply]

The root problem is that "life" is not well-defined in a way that is universally acceptable or applicable. This is discussed at length in our main article, definitions of life. It so happens that under most conditions, carbon chemistry produces the most elaborate sustaining chemical reactions; so it's common to find complexity whenever carbon is involved. If complexity is a critical constituent of your definition of life, it's a fair bet to say that carbon is very likely to participate. And, for all we have studied exotic carbon reactions, none seem more complex than those which result in organic molecules: carbon, hydrogen, nitrogen, oxygen, and a few other important elements. This is not to say that all forms of complexity involve carbon. The magnetohydrodynamics of ionized hydrogen and helium are very complicated, yet involve no carbon. Semiconductor devices can exhibit incredible properties, and they need not involve any carbon. But, of all the self-assembling complex systems we are aware of, conventional carbon-chemistry (in salt-water solution) seems the most well-suited to any commonplace definition of life. Nimur (talk) 14:18, 17 September 2012 (UTC)[reply]

To highlight one of Nimurs points: Consider the problem of things like viruses and prions. Clearly, viruses and prions are among the realm of the living; nothing purely geologic creates them; they come from the process of Life as a big concept. They are also independent in the sense that, unlike say the skin cells you slough off or something like that, they are genetically distinct from other life forms. But they are not "alive" under most definitions. So you get the apparent paradox that a virus is not alive, but it is part of life. The nice little boxes we, as humans, try to categorize things only work most of the time. Around the edges, there are plenty of cases where our nice little categories simply don't work. --Jayron32 17:57, 17 September 2012 (UTC)[reply]

.Um... prions aren't genetically distinct. They just happen to fold into different shapes, one of which convinces your own prions to become traitors and switch to the other shape. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 18:39, 17 September 2012 (UTC)[reply]

Fair enough. But prions are still part of life, but not alive, like in the same way we think of viruses. No non-biological process has ever produced a prion. --Jayron32 18:56, 17 September 2012 (UTC)[reply]

In that same article, it argues that silicon is not a good candidate, but one of the reasons it gives is a bit weird, it says that such a life must absorb O2 and release SiO2 which can make the animal choke to death (and goes on to say that temperatures must be higher than usual so that SiO2 can be in liquid from, blah blah...) but it's like we're taking a familiar C-based cell, taking out all the C's and replacing them with Si, while this is a bit flawed because biochemistry as we know it relies on the properties of Carbon, not silicon. Doesn't it require for a hypothetical Si-based life to have a different biochemistry and therefore metabolism? I mean there are many other candidates for a Silicon compound that can be released easily other than molten SiO2, like TMS (which is a good candidate if the life is partially based on Carbon too) which is volatile. Also, the article argues that if life could be silicon based, it would be in here because terrestrial planets are mainly silicon, but do we have enough examples to conclude anything?--Irrational number (talk) 12:41, 17 September 2012 (UTC)[reply]

The article actually comes up with some good reasons - while the solidity of SiO2 is surely an obstacle that can be evaded, the lack of double bond formation sounds much more serious. What isn't said there - a lack of double bonds is particularly serious because conjugated double bonds are the "wires" by which our biochemistry often transfers charge at the molecular level. Look at chlorophyll and accessory pigments like carotenoids and anthocyanins, for example, and you'll see that they have these "wires" arranged not only to serve as antennas to receive the energy in the light, but to transfer the charge around within pretty large complexes. Then the energy is transferred on plastoquinone, which uses the quinone double bond structure to take up electrons and move them around. Of course, computer designers know that silicon is not useless for making circuits and solar panels, but it's a different technology - for now very macroscopic and thus inaccessible to early evolution - and it remains to be seen how elegantly it would be used in an independent origin of life. Wnt (talk) 16:25, 17 September 2012 (UTC)[reply]

What if by some fluke, carbon, nitrogen and oxygen is only present in trace amounts, and instead the atmosphere is composed of phosphorus and sulfur gas? I imagine a superheated planet with high atmospheric pressure, where silicon sulfide is exhaled as a gas by silicon based life, and liquid deterated sulfane has replaces water. Plasmic Physics (talk) 06:48, 18 September 2012 (UTC)[reply]

The real point is not that silicon is a bad candidate for life, but that's it's a bad candidate for life resembling what we are familiar with. Someguy1221 (talk) 06:56, 18 September 2012 (UTC)[reply]

When Arguing whether or not some elements can be the base of life forms or solvents, many are eliminated from the list based on low cosmic abundance. But doesn't it assume that there is a pretty even distribution of elements in the universe? Is that a correct assumption? Also, aren't different kinds of stars likely to produce different proportions of elements? Like stars with different metallicity? Could uneven distribution of elements make other kinds of biochemistry more possible?--Irrational number (talk) 12:50, 17 September 2012 (UTC)[reply]

Actually no, the elements with fewer protons are far more common then the other elements and as expected there is an article specifically on this issue, although it isn't exactly linear and their are some interesting outliers. In general stars all function generally the same. They start out largely hydrogen and overtime convert a chunk of that to helium and lesser and lesser amounts into higher elements before dying or exploding. Chris M. (talk) 13:56, 17 September 2012 (UTC)[reply]

This is a very Drake equation-esque problem. The answer is simple, if you break it apart into constituent pieces. What is the probability that some phenomenon that meets your definition of life will develop, given a certain soup of chemical precursors? How likely is that soup to exist, given abundance curves predicted by stellar nucleosynthesis? Multiply these probabilities, and sum over all possible cases that meet your criteria, and you have your answer. We can quantitatively predict certain parts of the formula, such as the cosmic abundance of various elements, based on astrophysical observations. Other parts of the formulation are as-yet unknown: we don't have great estimates for "how likely" life will evolve in a billion years, given any set of conditions. Again, you can break that problem into sub-problems with better bounds on the probabilities; but the end-all is that we have more unknown variables in the mix, so we can't compute a definitive result. Nimur (talk) 14:33, 17 September 2012 (UTC)[reply]

Considering that there are natural objects which concentrate heavy elements, like planets, moons, comets, and asteroids, the answer is that elements are highly unevenly distributed throughout the cosmos. And, in an area with many previous supernovae, the relative abundance of heavy elements should be increased even before this concentration effect. StuRat (talk) 18:57, 17 September 2012 (UTC)[reply]

Supernovae tend to produce elements in roughly the same proportions (since it is the same process going on), so lots of supernovae in an area will just produce more metals (ie. elements heavier than helium), not different relative abundances of metals. --Tango (talk) 22:30, 17 September 2012 (UTC)[reply]

Are you sure about that ? I was under the impression that you rarely get anything heavier than iron in a normal star (and then only in the final stages). Therefore, an area which had never had anything but normal stars would be deficient in heavy elements, while one that had lots of supernovae in the past would contain quite a lot. StuRat (talk) 02:56, 18 September 2012 (UTC)[reply]

Majority of the elements heavier than iron are produced by s-process, which takes place during the final stages of the evolution of low mass stars. Ruslik_Zero 18:46, 18 September 2012 (UTC)[reply]

Sorry, I thought we were comparing many supernovae against few supernovae rather than none. An area which has had no supernovae nearby will have different relative abundances, that is true. --Tango (talk) 19:32, 19 September 2012 (UTC)[reply]

This: The Elements: Their Origin, Abundance, and Distribution, by P. A. Cox of Oxford, is one of the most fascinating and well written books I have ever read. μηδείς (talk) 02:03, 18 September 2012 (UTC)[reply]

Referring back to this question, I finally tried squeezing the cans because they were, in fact, cardboard. I didn't even have to cut the cans.— Vchimpanzee · talk · contributions · 15:38, 17 September 2012 (UTC)[reply]

Wow, it took you 3 years to try that ? Presumably we can mark this resolved. StuRat (talk) 19:01, 17 September 2012 (UTC)[reply]

Yes. I forgot the cans were even there. But I found them and I was almost out of the newer cans.— Vchimpanzee · talk · contributions · 20:19, 19 September 2012 (UTC)[reply]

Hi,
I look on a climate map:
and I saw that from some reason the Arabian Desert is hotter than other places in the same longitude; I ask whyExx8 (talk) —Preceding undated comment added 15:53, 17 September 2012 (UTC)[reply]

I assume you mean latitude, because areas north or south of Arabia are likely to have colder temperatures. It has to do with the how the wind blows. In that band of latitude, the wind blows west to east (see Trade wind) so before getting to Arabia, the winds basically traverse the entirety of Africa (the Sahara Desert). The land doesn't cool the air as much as the water does (the cooling effect of water is due to its high heat capacity). Other areas on that same band of latitude, like India and Central America, may have lower average temperatures because the prevailing winds have long stretches of water over which they can cool the air. --Jayron32 17:52, 17 September 2012 (UTC)[reply]

The image in the trade winds link actually shows easterly winds over the Arabian peninsula. - Akamad (talk) 22:37, 17 September 2012 (UTC)[reply]

In addition to having a large land mass in the tropics and winds blowing in the proper direction, another issue is elevation. South Asia looks ripe, but the Hindu Kush and Himalaya mountains break up what might otherwise be a massive desert. Those, in turn, are the result of the plate tectonics of the Indian subcontinent ramming into Asia. The Americas, on the other hand, have both a smaller land mass in the tropics, and mountains (the Rockies and Andes), so have only small deserts.

However, note that you can get a different type of dessert desert at altitude, such as the Gobi and Atacama. StuRat (talk) 19:06, 17 September 2012 (UTC)[reply]

Indeed, but neither the Gobi or Atacama are particularly hot. The OP seems to be asking about temperatures. --Jayron32 20:04, 17 September 2012 (UTC)[reply]

Or Bombe Alaska. -- ♬ Jack of Oz ♬ ^{[your turn]} 22:16, 17 September 2012 (UTC)[reply]

thank you all very much! Exx8 (talk) —Preceding undated comment added 23:14, 17 September 2012 (UTC)[reply]

You're quite welcome. I'll mark this resolved. StuRat (talk) 02:37, 18 September 2012 (UTC)[reply]

Duplicate question removed; see Have there ever been any surrogate mothers over 70 in India? above. — Lomn 17:57, 17 September 2012 (UTC)[reply]

Can someone point me in the direction of references which tell me which types of Clostridium would infect cats? --TammyMoet (talk) 19:49, 17 September 2012 (UTC)[reply]

You should state that our clostridium article doesn't discuss this. StuRat (talk) 19:52, 17 September 2012 (UTC)[reply]

Well, I can point you in the direction of references by suggesting that you do a Google Scholar search for feline clostridium infection. That brings up a number of papers describing various sorts of clostridium infections, but not any sort of authoritative review. Looie496 (talk) 19:58, 17 September 2012 (UTC)[reply]

Thanks both for confirming my own searches. --TammyMoet (talk) 01:40, 18 September 2012 (UTC)[reply]

I've heard that scientists have recently discovered a "skinny" gene which makes it harder for some women to put on weight despite how much they eat. Could the same gene be responsible for some men finding it difficult to put on muscle mass despite working out and eating properly? Clover345 (talk) 19:56, 17 September 2012 (UTC)[reply]

There are actually dozens of genes that affect metabolic rate -- no way to tell which one you are talking about. Most of them probably wouldn't affect muscle mass gain to a great degree, if a person eats enough to allow the necessary nutrients to be available in the bloodstream. "Enough", of course, means more for a person with a high metabolic rate than for a person with a low metabolic rate. Looie496 (talk) 20:07, 17 September 2012 (UTC)[reply]

(edit conflict) Just as there's no single factor that determines weight (it's a combination of genetics, diet, physical activity, and other environmental factors), there's no single "skinny" or "fat" gene. There are combinations of genes that predispose a person toward a lighter or heavier weight, but the effect of individual genes or combinations of genes remain poorly understood. Yes, some combination of genes that causes some women to not gain weight could have the same effect in men, but the fact that genetics affect weight has been known for many decades (it's no recent discovery) and is no miracle solution for those wishing to adjust their weight upwards or downwards given the vast number of genes involved and the complexity of their interactions. —SeekingAnswers (reply) 20:16, 17 September 2012 (UTC)[reply]

Possibly possessing ability to eat grass+leaves without cooking or flight removes the need for intelligence? And pure carnivorism would severely limit a planet's intelligent species population. I believe a lack of the hunting tools being integral (claws, long teeth, etc.) foments intelligence (also foments modern warfare because ancestors had less to lose from unarmed aggression). And why aren't there any walking creatures that gets at least some energy from photosynthesis? If these things were possible what would their bodies and evolutionary history look like? 96.246.70.87 (talk) 21:26, 17 September 2012 (UTC)[reply]

There is a "walking creature", the pea aphid, which gets energy from sunlight. Our article doesn't cover it, but see Photosynthesis-like process found in insects-gadfium 22:05, 17 September 2012 (UTC)[reply]

The rest of the question is asking for pure fanciful speculation. We only have the life we see here on earth as a sample. Looking at the life we have discovered so far and extrapolating what we think might be possible has been notoriously unreliable and flawed. We just can not possibly know what is or isn't possible with our sample size of "one". Vespine (talk) 22:20, 17 September 2012 (UTC)[reply]

(ec) The argument against flying creatures becoming sapient is that heavy brains are a problem in flight, and for strict carnivores that their limbs are not going to be adaptable for tool use. Nevertheless, our article on animal intelligence notes the intelligence of cephalopods, bears, corvids, parrots, and cetaceans, particularly dolphins, the latter being obligate carnivores. I don't think we will have anything definitive to say until xenobiologists have examined intelligent life on several planets. μηδείς (talk) 22:21, 17 September 2012 (UTC)[reply]

I know that it has been suggested, following the Alex studies that African Grey Parrots may be (somewhat?) sentient. They fly, and are mostly herbivorous creatures. --Kurt Shaped Box (talk) 22:59, 17 September 2012 (UTC)[reply]

Grass is a very poor source of nutrition, which is why cows, etc., have to spend so much of their time grazing. While you could have an intelligent cow, you probably couldn't have a technologically developed cow because it wouldn't have the spare time to spend inventing things. Meat is a much more concentrated food source (animals like lions often only each once every few days). --Tango (talk) 22:41, 17 September 2012 (UTC)[reply]

Every vegetarian would beg to differ. Chimpanzees would, too; they're mostly herbivorous and don't spend all their time eating. --140.180.242.9 (talk) 02:38, 18 September 2012 (UTC)[reply]

I don't know any vegetarians who eat only grass, but cooking vegetables vastly increases the nutritional potential for humans. Dbfirs 06:24, 18 September 2012 (UTC)[reply]

Two things 1) Chimpanzees eat meat and insects as well. They hunt and eat monkeys, for example. They are omnivores. 2) Chimpanees don't eat grass, which is calorie poor and mostly undigetible cellulose. Chimpanzees eat mostly fruit, which is high in easy to digest sugar and very calorie dense. See Common_chimpanzee#Diet_and_foraging. Not every plant material is equal. What cows eat is very different from what Chimps eat. Now, Gorillas eat a lot more grasses and leaves and pith (the meaty part of woody plants), but they spend a lot more time foraging than Chimpanzees, and generally lead a less active and more sedentary lifestyle. Food source and behavior are closely related. See Gorilla#Food_and_foraging. --Jayron32 05:09, 18 September 2012 (UTC)[reply]

Intelligence seems to arise in a large part due to biological arms races. Unfortunately, much of the discussion of alien intelligence arise in the context of science fiction, so as for references....but see Sagan's Intelligent Life in the Universe (book). μηδείς (talk) 23:32, 17 September 2012 (UTC)[reply]

BTW, I think the relevant word here is sapience, not just sentience. There is little doubt most higher animals are sentient. μηδείς (talk) 23:43, 17 September 2012 (UTC)[reply]

What is the biological arms race that led to human intelligence? (warning: idle speculation) I would be suspicious of another explanation: complex patterns of environmental change. If you look at a place like the Okavango Delta (my personal favorite suspect for the cradle of several human species) you see an environment that ranges from desert to mostly submerged every year; one marked by rivers and islands and grassland and forests and bizarre salt deposits; one where fires ravage the land every year, and those less intelligent die in front of it while others follow behind it and enjoy cooked meals. I suspect many species are what might be thought of as highly intelligent under very specific circumstances, but that a multiplicity of threats and opportunities make for a more generalizable intelligence. And now humans, having thrived on drastic climate changes for so long, can scarcely help but cause them on their own. Wnt (talk) 05:59, 18 September 2012 (UTC)[reply]

It is certainly true that humans have used our intelligence to thrive in a wide variety of environments (I don't know any other complex life that can thrive in arctic tundra, tropical rainforest and deserts), but is that the pressure that caused us to evolve intelligence? Lots of animals cope with varying climates, but mostly by migration. The fact that we didn't need to migrate allowed us to develop agriculture, which freed up time for other technological developments, so it is certainly very important. It is difficult to distinguish between cause and effect, though. We can't even properly identify when behavioural modernity arose with any certainty, so trying to identify the cause is probably futile. --Tango (talk) 11:39, 18 September 2012 (UTC)[reply]

@ Wnt. Other humans. The article itself mentions intraspecific biological arms races. Not that it says much. Read Nicholas Wade's Before the Dawn. μηδείς (talk) 18:25, 18 September 2012 (UTC)[reply]

Seems like bootstrapping to me. If humans developed intelligence in a biological arms race with other humans who became intelligent -- why not squirrels? Heck, we know the squirrels are locked in a cloak-and-dagger contest to secure their caches of nuts against rivals with keen eyes and a good memory... Wnt (talk) 04:01, 19 September 2012 (UTC)[reply]

Because squirrels don't live in small 30-member warring bands, or lie to each other, or woo their mates with complex strategies, whereas the lifetime mortality rate of young males due to intergroup violence is about 30-35% for chimps and tribal humans. Read Nicholas Wade. μηδείς (talk) 17:24, 19 September 2012 (UTC)[reply]

The only thing I can think of that might play a role: while hunting requires some intelligence (see how wolves hunting in pack behave), I assume that such a basic function wouldn't offer much opportunity for developing or discovering new skills. Eating is an essential, daily requirement, changing a winning strategy could get you killed. For animals living in herds, the same applies when it comes to attacks by predators, surviving is the norm. For solitary prey however, most attacks will result in death. Adopting a different strategy doesn't effect outcome when it's worse, but a better strategy increases the survival rate. Maybe natural selection would favour predators and herds that stick to a routine, and solitary prey that are inventive, creative. Just an idea... Ssscienccce (talk) 14:48, 19 September 2012 (UTC)[reply]

An interesting idea, but what observation are you trying to explain with it? Early humans weren't solitary prey... they tended to be predators more than prey and were very social and lived in groups. --Tango (talk) 19:34, 19 September 2012 (UTC)[reply]

Ssscienccce's model would work with bears which hunt alone and Elephants which don't hunt. They both have large ranges, remember many varied resources, and are quite creative. μηδείς (talk) 01:30, 20 September 2012 (UTC)[reply]

That's the opposite of what Ssscienccce was saying - neither bears or Elephants are solitary prey, yet they are creative. --Tango (talk) 18:13, 20 September 2012 (UTC)[reply]

Not trying to explain an observation, the OP asked about other species developing intelligence, I'm just suggesting how the odds could depend on the type of species. Humans aren't exactly build as a predator, they don't have the speed to escape most predators, and a herd of them would just be an all you can eat buffet for wolves, lions, tigers etc... That may be why they needed intelligence. Ssscienccce (talk) 17:54, 20 September 2012 (UTC)[reply]

Science is all about explaining observations. Having interesting ideas isn't much help if what they predict doesn't match what we see. --Tango (talk) 18:13, 20 September 2012 (UTC)[reply]

Hi, I would like to know what is the length of the hair under the average scalp of a human. thank you Exx8 (talk) —Preceding undated comment added 23:13, 17 September 2012 (UTC)[reply]

I haven't had much luck finding hair follicle length in humans, but in mice it seems to vary (sinusoidally, for some reason) over their lifetime from 250 to 1500 μm: [1]. StuRat (talk) 02:21, 18 September 2012 (UTC)[reply]

I googled "hair follicle millimeter" and this source says 3-4 mm. μηδείς (talk) 04:27, 18 September 2012 (UTC)[reply]

...which is 3000-4000 μm, for comparison. StuRat (talk) 06:05, 18 September 2012 (UTC)[reply]

A reliable secondary source PMID 21919898 indicates a range in hair follicle length of 580 μm (for vellus hair) to 3864 μm (for terminal hair) in humans (full statement: "The dimensions of the scalp hair follicle are well documented in morphometric analysis (Fig. 2). The total length (mean ± SD) of the follicle and the length of the infundibulum differ significantly in terminal (3864 ± 605 μm) and vellus hair follicles (580 ± 84 μm)."). -- Scray (talk) 12:05, 18 September 2012 (UTC)[reply]

I've been told nobody knows where the habitable zone will be in 7.6 billion at the tip of future RGB but with the Habitable zone of foreign stars, it is pretty easy how to calculate where the habitable zones is in on remote stars by luminosity and size of star. The red dwarf star's habitable zone is where Mercury is, and the large blue stars' habitable zone is where 2 AU is. Is figuring out the habitable zones in remote solar systems direct, or is it an estimation. When people use an instruments to look at foreign solar system, they can see all the planets they have in the star, like red dwarf star, they have the rough picture about the habitable planets, and one red dwarf star system is pretty similar to our solar system, it has four rocky planets three gas giants, and two ice dwarfs. Is figuring out the luminosity and the size of star the only way to determine the habitable zone. Can detecting stars involves missing information, I thought when an astronomer look through blue stars through high-tech telescope or spacecraft, they can see all the planets they have, includes gas giants and ice dwarfs they have.--69.226.32.74 (talk) 01:52, 18 September 2012 (UTC)[reply]

I don't believe they can see extrasolar planets directly. Instead, they find them by measuring how the star wobbles (red-shift/blue-shift changes) or how it's luminosity changes as the planet passes in front of it. So, yes, it's just an estimation. So far, they can only detect large planets by these methods, but, of course, life could also exist on a small planet. StuRat (talk) 02:04, 18 September 2012 (UTC)[reply]

Believe. :)--Robert Keiden (talk) 04:51, 18 September 2012 (UTC)[reply]

Interesting. Looks like they've improved the methods of blocking the star's light since last I read up on it. StuRat (talk) 06:04, 18 September 2012 (UTC)[reply]

I am wondering is it because the small planets like Mercury, Venus, Earth, and Mars are close-packed together, and Jupiter, Saturn, Uranus, and Neptune are far separated apart which leads difficult to predict habitable zones, could that be the case? Did any astronomer try to figure out the habitable zone on far-distant planets at another star? If we have another giant stars which is 100 times bigger than sun they can find out by far distant planets the same distant as Saturn and Uranus, or sometimes when planets are so far from the star, looking at extrasolar planets they cannot see it.--69.226.32.74 (talk) 02:26, 18 September 2012 (UTC)[reply]

The Sun's luminosity and size are the main factors. If Venus had an Earth-like atmosphere, it would probably be habitable (though it might be a bit warm). Mars, too (but a bit colder).--Robert Keiden (talk) 04:51, 18 September 2012 (UTC)[reply]

I don't see how the placement of planets affects the habitable zone (only whether those planets are in it). And, yes, astronomers are very much interested in finding extrasolar planets in their star's habitable zones. However, a few points to consider:

1) Distance from the star and the size and type of star aren't the only factors. A large planet will tend to be hotter at the same location as a smaller planet. And a planet with a major greenhouse effect (like Venus) can be much warmer than one without it. Even moons of large planets can be warm, due to tidal heating.

2) The whole concept of a habitable zone is based on the idea that liquid water is needed for life, when other solvents, like liquid methane, might also work, at much lower temperatures. StuRat (talk) 02:33, 18 September 2012 (UTC)[reply]

The main reason for uncertainty in the Solar System's habitable zone 7.6 Ga (billion years) from now is that we're not sure how much the Sun will expand when it reaches RGB, and exactly how bright it will be. The HZ is likely to start somewhere beyond the asteroid belt, and end somewhere before Neptune, but it could be pretty narrow. Until we understand the evolution of the Sun better, the best we can do is guess.--Robert Keiden (talk) 04:51, 18 September 2012 (UTC)[reply]

Robert, what you meant by it can be pretty narrow. It is because Jupiter, Saturn, Uranus, and Neptune are currently vastly far apart, and also star's temperature drop, and planet's orbit expands, is that another key for unknowns/unclear. If HZ happens to Saturn's system can we sequentially predict what will happen for Uranus, or it doesn't necessarily follow the pattern.--69.226.32.74 (talk) 05:06, 18 September 2012 (UTC)[reply]

You can think of it as a ring around the Sun. Right now, the ring is wide enough that there are 2 or 3 planets inside (whether Venus is just inside or just outside is debatable). In 7.6 Ga the ring will be farther out. There could be 2 or 3 planets that fit inside it, or there might be 1 or none. Maybe Jupiter, maybe Saturn, maybe Uranus, maybe Neptune, some of the above or none of the above. Mars will be too hot. Mercury and Venus will be toast. Earth will be either covered with lava or be toast. By that point, if there are any people still around, they probably won't be living in the Solar System. And they will probably have more interesting things to worry about...--Robert Keiden (talk) 06:06, 18 September 2012 (UTC)[reply]

Okay, another way to look at it: The sequence is predictable, but we don't know how far it will go. Maybe something like this:

• 2 Ga ago - Venus, Earth, Mars
• Present - Venus(marginal), Earth, Mars
• 1 Ga from now - Earth(marginal), Mars
• 4 Ga from now - Mars(marginal)
• 6 Ga from now - Jupiter(??), Saturn(??)
• 7 Ga from now - Jupiter(???), Saturn(???), Uranus(???)
• 8 Ga from now - Jupiter(????), Saturn(????), Uranus(????), Neptune(????)
• 11.5 Ga from now - Venus (which no longer exists), Earth (if it still exists will be crispy fried)
• 12.0 Ga from now - Mercury, Venus (which no longer exist)
• 13.0 Ga from now - Mercury (which got eaten by the Sun around 7-8Ga)
• 14.0 Ga and after - none

--Robert Keiden (talk) 06:06, 18 September 2012 (UTC)[reply]

You oversimplified a little bit on Venus, Venus may still be around, just less likely than Earth.--69.226.32.74 (talk) 06:26, 18 September 2012 (UTC)[reply]

The changes in the Red Giant phase are quite rapid when compared to main sequence stars, though. If it starts in 6 Ga, it will probably be over in another ~0.2 Ga.

6 Ga from now: Red Giant phase begins. Jupiter, Saturn

RGP+0.1Ga: Jupiter(?), Saturn, Uranus.

RGP+0.2Ga: Saturn(?), Uranus, Neptune, and some trans-neptunic minor bodies. End of Red Giant phase. If Earth survives, it'll have an iron-nickel atmosphere by then.

RGP+0.3Ga: Earth(if still around), Mars?

RGP+0.4Ga: Venus if it's still around (although Red giant says it won't)

The main problem is that scientists cannot "watch" anything that slow. In 0.2 Ga we'll be able to predict with much greater accuracy how big the sun will be in its Red Giant phase, and how long it will stay a giant. - ¡Ouch! (^{hurt me} / _{more pain}) 11:51, 18 September 2012 (UTC)[reply]

In the Newtonian two-body problem, the masses are assumed to be point masses. What if the size of one or both objects is not negligible compared to the distance between them (say a moon of Jupiter). Is the solution still the same as if they are point masses? Bubba73 ^{You talkin' to me?} 02:20, 18 September 2012 (UTC)[reply]

Not exactly the same, as you get tidal effects, which cause the orbit to decay (very slowly). Although, I think if the body was absolutely rigid and uniform at each depth, then, by the shell theorem, it would behave exactly as a point. StuRat (talk) 02:23, 18 September 2012 (UTC)[reply]

Just a little quibble. The orbit might decay but it might also rise. In fact, that's what's happening with our moon which is actually slowly moving away from the Earth. Dauto (talk) 14:48, 19 September 2012 (UTC)[reply]

I was under the impression that the term "orbital decay" included both cases, but our article seems to agree with you. Do you know of a term for an orbit of ever increasing altitude and a term encompassing both ? StuRat (talk) 21:16, 19 September 2012 (UTC)[reply]

Gravitational force is what is known as a central force - that is, it appears to come from a point located at the object's centre of gravity. StuRat's shell theorem is a special case of this, applying to spherical objects. So, yes, neglecting tidal damping, the solution is the same, once you have the location of the centres of gravity in each object. Distance does not matter. See wiki article on central force. Wickwack121.215.23.108 (talk) 02:40, 18 September 2012 (UTC)[reply]

Resolved

Thank you both. Bubba73 ^{You talkin' to me?} 02:51, 18 September 2012 (UTC)[reply]

You're quite welcome. StuRat (talk) 04:31, 18 September 2012 (UTC)[reply]

What do you call the irreversable process which occurs when molucular compounds such as ScH₃ condense from the gas phase into a non-stoichiometric interstitial alloy (ScH_2.9), eliminating trace hydrogen in the process? I don't think that it is polymerisation. Plasmic Physics (talk) 03:07, 18 September 2012 (UTC)[reply]

Adsorption? --Jayron32 03:55, 18 September 2012 (UTC)[reply]

That doesn't seem correct, because the initial molecule does not retain its identity. An actual chemical reaction is taking place, adsorption could be the initial stage, but there's more to it. Plasmic Physics (talk) 04:06, 18 September 2012 (UTC)[reply]

That sounds like chemical precipitation or an analog of it. μηδείς (talk) 04:21, 18 September 2012 (UTC)[reply]

Does trawling papers describing this behaviour of ScH₃ (or analogous compounds) not reveal an appropriate term? Brammers (talk/c) 22:10, 18 September 2012 (UTC)[reply]

No. Plasmic Physics (talk) 02:22, 19 September 2012 (UTC)[reply]

I can't remember which it was, nettles or thistles, but one of them, our biology teacher told us 30ish years ago, is equipped with prickles made of a form of sugar glass - the former seems more likely, considering the nettle's trichomes, which are brittle and snap on contact to release toxins...

Is there any truth to this at all? Do plants produce glass?

Thanks Adambrowne666 (talk) 04:25, 18 September 2012 (UTC)[reply]

Yes, it is true. Nettles have microsized silica based spines. Plasmic Physics (talk) 04:31, 18 September 2012 (UTC)[reply]

Sorry, but silica crystals are not glass, especially not candy glass. μηδείς (talk) 05:27, 18 September 2012 (UTC)[reply]

I didn't say that it was glass, I said "yes" to "is there some truth to this". Plasmic Physics (talk) 05:49, 18 September 2012 (UTC)[reply]

You probably would have been better off with a "not exactly" than a "yes"; but I only indented to show temporal sequence, my post was not a criticism of yours. The OP is the one who asked about glass and candy glass. μηδείς (talk) 06:00, 18 September 2012 (UTC)[reply]

Would temporal sequence be unclear if your entry were below PP's but on the same level? —Tamfang (talk) 22:01, 18 September 2012 (UTC)[reply]

OK, lets not make the whole conversation about indentations. We should settle that while there is a prescribed Wikipedia indentology, Medeis was simply unaware of it: Wikipedia:Indentation. I made the same mistake before I changed to the prescribed one. Now let us leave it at that. Plasmic Physics (talk) 22:10, 18 September 2012 (UTC)[reply]

You will find most people simply indent one from the post above no matter what. I tend not to indent at all specifically when I want to make it clear I am not responding to any response above mine. But I don't like when people use the same indentation as the person above them without an asterisk, as it sometimes makes it look as if the second party's post is a continuation of the one he didn't indent from. I have even had a lunatic tell me I couldn't place my post below his no matter how I did or did not indent it. Oh well. Back to the question, back in the day before Alvarez I remember reading the dinosaurs went extinct due to the rise of the grasses, which had a high silica content, grinding their teeth down and starving the plant eaters. μηδείς (talk) 01:29, 19 September 2012 (UTC)[reply]

Doesn't sound like much of a theory to me. Dinosaurs would have evolved harder teeth, more frequent replacement of teeth, eating things other than grass, etc., in response. StuRat (talk) 02:01, 19 September 2012 (UTC) [reply]

The OP might like to read a in-depth explanation of how biomineralization with silica forms the nettle hairs. See: Advances in inorganic chemistry, Volume 36 As edited by A. G. Sykes On pages 147 & 175.]--Aspro (talk) 09:22, 19 September 2012 (UTC)[reply]

Thanks, all - just what I needed - thanks for the link too, Aspro Adambrowne666 (talk) 09:43, 19 September 2012 (UTC)[reply]

What is the highest gradient stretch of railway in England between two stations ? — Preceding unsigned comment added by Tarka4 (talk • contribs) 07:25, 18 September 2012 (UTC)[reply]

If by "highest gradient" you mean "steepest", then Lickey Incline could be what you're looking for. - Karenjc 08:21, 18 September 2012 (UTC)[reply]

I concur with the Lickey Incline, but only if you mean (a) still in use and (b) standard gauge railway. We have a List of steepest gradients on adhesion railways which gives others. --TammyMoet (talk) 08:24, 18 September 2012 (UTC)[reply]

Surprisingly, the above article doesn't mention the Docklands Light Railway where the entrance to the tunnel from the original London and Blackwall railway viaduct to the tunnel to Bank has the steepest gradient on any British railway at 1 in 17 (5.88%) (according to this article).--Shantavira|^{feed me} 08:48, 18 September 2012 (UTC)[reply]

There is also the short section on the line that links Exeter Central with Exeter St Davids (sometimes called the 'Exeter Incline' I think), which is variously claimed to be 1 in 31, 33, 36, 37 or 39, from what I've been able to find, but it's definitely steep. Mikenorton (talk) 18:09, 18 September 2012 (UTC)[reply]

Are black holes point particles?165.212.189.187 (talk) 15:40, 18 September 2012 (UTC)[reply]

Perhaps the singularity can be considered as such, but not the event horizon. StuRat (talk) 16:00, 18 September 2012 (UTC)[reply]

(ec) No. And maybe yes. The event horizon is a useful, usable physical concept that has dimensionality. On the other hand, the gravitational singularity is at least potentially a point particle (in a non-rotating black hole), though there's a good chance that's an artifact of the math rather than the true physical representation. — Lomn 16:03, 18 September 2012 (UTC)[reply]

Lets say for argument sake it is an artifact. What is being done to address the artifact?165.212.189.187 (talk) 16:33, 18 September 2012 (UTC)[reply]

You may be interested in reading the Cosmic censorship hypothesis and the Black hole information paradox, which is one way of addressing it. In this case, it amounts to throwing up your hands and saying "fucked if I know", but with lots of equations instead of words to say that. --Jayron32 16:36, 18 September 2012 (UTC)[reply]

See Fuzzball (string theory). Wnt (talk) 16:53, 18 September 2012 (UTC)[reply]

OK, let me rephrase my second Q: Lets assume that its an artifact, ie. it is not a point particle but in fact a very volumious "black star." now knowing that the math is returning the artifact of a point cant we learn how the math is wrong? THe math must be "using" space-time as an inherent part of how we measure not only that black star but everything else also, in other words taking the space-time for granted?165.212.189.187 (talk) 14:12, 19 September 2012 (UTC)[reply]

The short answer is that there isn't any verified theory of quantum gravity. With black hole singularities you're trying to calculate the effect of something very small (normally the purview of quantum mechanics) with a theory worked out for the very large and very heavy (general relativity). The two, as currently formulated, are incompatible, which explains why you end up with "nonsensical" results like singularities. I believe the general impression is that once a workable theory of quantum gravity is developed, infinite density singularities will "disappear" in more the complete calculations. (The same sort of thing has happened before in quantum mechanics - see renormalization). -- 205.175.124.30 (talk) 01:12, 20 September 2012 (UTC)[reply]

Another way to look at it: A singularity means (by necessity) an object of zero volume, and thus of infinite density. Infinity is math's way of telling you you screwed up somewhere. Or less colloquially, any model contains some approximation of reality. Sometimes, the nature or source of the approximation is unknown, but the fact that some calculation gives you "infinity" for any measurable quantity is usually a remind that you're still working with a model. --Jayron32 04:55, 20 September 2012 (UTC)[reply]

Well, there do seem to be some physical phenomena which are indeed "infinite". Superconductivity means infinite conductivity, for example. A Bose–Einstein condensate is another example. StuRat (talk) 05:12, 20 September 2012 (UTC)[reply]

Well, kind of. Superconductivity is a physical zero, not a physical infinity. The key property is resistance, and in a superconductor, the resistance drops to zero. Saying that the conductivity is infinite is just a mathamatical restatement, since conductivity is the mathematical inverse of resistance. But the physical property itself is resistance, and physical properties can measure zero. They just can't be infinite. You can't, for example, have a truly infinite resistance: any real material will conduct an electric current given a sufficiently large voltage. There are Superinsulators, but these probably don't have truly infinite resistance (despite what our article says), merely very large resistance jumps (5-6 orders of magnitude) when cooled to very low temperatures.this paper for example, contests that the resistance is trule "infinite". In a singularity, the density (the physical property) would be actually infinite, which is a physical impossibility. See Gravitational singularity, where it explains quite well: "Many theories in physics have mathematical singularities of one kind or another. Equations for these physical theories predict that the ball of mass of some quantity becomes infinite or increases without limit. This is generally a sign for a missing piece in the theory, as in the ultraviolet catastrophe, renormalization, and instability of a hydrogen atom predicted by the Larmor formula." --Jayron32 05:45, 20 September 2012 (UTC)[reply]

I'm not seeing the difference. A black hole singularity has zero volume, and thus infinity density, just like a superconductor has zero resistance, and thus infinite conductivity. And what makes resistance the fundamental property, and not conductance ? StuRat (talk) 16:42, 20 September 2012 (UTC)[reply]

There is a fundemental difference. If I have zero money in my pocket, I can say that I am infinitely broke. That is mathematically true, but the difference is the absence of the money in my pocket. That's a physical zero that I can call an infinity by performing some math on it (taking the inverse). But just as it is actually impossible to have an infinite amount of cash, but not to be infinitely broke, it is impossible to have an infinite resistance, but not an infinite conductance. For any inversely related pair of named properties, you're always going to have one of which relates to a physical quantity or property that ultimately ties to the physical components of the system. The difference is the difference between Intrinsic and extrinsic properties. Anything which requires the intrinsic properties of the material to be infinite is a physical impossibility. In a material, the intrinsic property is resistivity (resistance is dependent on the amount and shape of the material as well as the resistivity. Consider what causes conductivity: a substance conducts electricity if you can get its electrons to move into the "conduction band" as explained by Electronic band structure. Now, here's the thing: the distance between the conduction band and the valence band is never infinite, that would require an electron to take an infinite amount of energy to be able to promote to a higher energy level: that doesn't happen. You can have zero resistance if the conductance and valence bands become degenerate (that's what a superconductor is), but there is no physical way to have an electron which can take an infinite input of energy and stay put. So resistivity is the intrinsic property, because it starts counting at zero and goes up from there. Conductivity can never be zero. --Jayron32 18:12, 20 September 2012 (UTC)[reply]

Aren't the mass and volume of the singularity also the intrinsic properties, with density being merely a derived value ? StuRat (talk) 17:04, 21 September 2012 (UTC)[reply]

Again: OK, let me rephrase my second Q: Lets assume that its an artifact, ie. it is not a point particle but in fact a very volumious "black star." now knowing that the math is returning the artifact of a point cant we learn how the math is wrong?165.212.189.187 (talk) 12:38, 20 September 2012 (UTC)[reply]

Per the first answer to your last rephrase: no, not yet. What theories we currently possess yield a singularity, and no theory that resolves the singularity has yet gained anything approaching widespread acceptance. So no, right now, we can't, though we're trying. Perhaps someday we will be able to resolve the matter (although direct experimental verification of phenomena within an event horizon is unlikely to ever happen). — Lomn 13:18, 20 September 2012 (UTC)[reply]

Addendum: bear in mind that the solution to "learn how the math is wrong" isn't "get rid of the singularity", it's "get rid of the singularity with a theory that is at least as accurate as current theory in all other regards". The former is trivial, but also meaningless. — Lomn 13:21, 20 September 2012 (UTC)[reply]

Hear, hear. ;-) --Modocc (talk) 13:58, 20 September 2012 (UTC)[reply]

Who first came up with the theory that the act of observation materially affects that which is being observed? Our article doesn't say. --TammyMoet (talk) 17:58, 18 September 2012 (UTC)[reply]

Which Observer effect are you asking about? There are several unrelated concepts known by that name, so before we can nail down where the particular usage originated, we need to know which usage you are asking about. --Jayron32 18:27, 18 September 2012 (UTC)[reply]

Did I not make it clear? Someone once said that if you observe a situation (particle, wave...) then the act of observation affects that thing that is being observed. The Observer effect (physics) article is not one of our best, and only says that it is often confused with Heisenberg's uncertainty principle - but doesn't say who first come up with the Observer effect. --TammyMoet (talk) 19:11, 18 September 2012 (UTC)[reply]

Actually, you didn't in your question make any mention of the physics effect, compared to the other observer effects, such as the one from psychology. In that case, the concept of the "obersver effect" is very closely related to the Copenhagen interpretation and other similar interpretations of quantum mechanics. I don't know if we can narrow down exactly which physicist invented the specific word formulation "observer effect" to describe it, but as a concept the idea that the observer fundementally changes a quantum system (as opposed to merely recording what was indetermined before their observation) is, as far as I know, very closely tied to the Copenhagen interpretation. Other interpretations don't necessarily hold it to be true, except in the trivial sense that photons striking things causes them to change. --Jayron32 19:18, 18 September 2012 (UTC)[reply]

A bit more: The observer effect in physics is predicated, by the Copenhagen Interpretation, on Wave function collapse, which as a concept was devised by John von Neumann to deal with what was known as the Measurement problem. So there's a lead for tracking down the concept. --Jayron32 19:21, 18 September 2012 (UTC)[reply]

Hmm, this is an interesting question. I have always thought of this as being derived from Complementarity, but I've never really tried to zero in on the specific origins of the observer effect before. I'll dig through some of my books on this subject tomorrow if I get the chance... I suspect that one of Max Jammer's many books holds the answer, here. --Mr.98 (talk) 02:39, 19 September 2012 (UTC)[reply]

Heisenberg was the first to do analysis of measurements, the accuracy they would provide and the disturbance they would cause, as a function of the wavelength and thereby the energy of the photon. That's what he expressed in his uncertainty relations (or relation, if using the vector form). Bohr and Heisenberg concluded that statistical distributions only existed potentially, and the potentiality is made effective by the measurement itself. Einstein pointed out an observer effect at the Solvay conference (not saying he called it that), that a negative measurement could also collapse the probability wave. The Copenhagen School holds that the description given by the wave function of the interaction is optimal. When the observer reads the result, the knowledge changes the probabilities. But since the Copenhagen school holds that our description was optimal before we read the result, the reading itself has changed the system. Schrodinger objected , with his cat paradox. von Neumann disagreed with Schrodingers conclusion that the observer in effect killed the cat, according to the copenhagen interpretation. Neumann extended the system to include the observer, as made up of atoms etc. The change in the observers consciousness by registering the result changes the total wave function. Einstein, Podolsky and Rosen came up with another paradox, and so on... Ssscienccce (talk) 15:36, 19 September 2012 (UTC)[reply]

I, somewhat before, acquainted with (acqired?) an idea about "space elevator"(cf.Space elevator).

I am now obtaining infornation mainly from newspaper, television, radio in Japan. And from as far as information I have tells me, as material for fiber, two of "strong" ones possible, recently developed, are "carbon nanotube" and "carbon graphite"(which I read in newspaper article, as I remember, maybe not for space elevator).

I am now wondering, is it possible to have something like "gas-filled fiber", a fiber in which gas is, and hopefully supporting it and/or light (lighter than the atmosphere)?

Like sushi (talk) 21:18, 18 September 2012 (UTC)[reply]

A space elevator goes all the way through the atmosphere; at higher altitudes there isn't much outside air, so to be buoyant there would have to be even less gas (by mass) inside such a structure. There isn't such a magical flying-gas. Science fiction authors have toyed with the idea of producing a nano-tech vacuum aerostat, where the carbon nanotubey-thing is evacuated, but is so strong that it keeps a larger size and holds up against external air pressure. But that's even more science fiction than a space elevator. -- Finlay McWalterჷTalk 21:32, 18 September 2012 (UTC)[reply]

Ah. In non-buoyant(?) atmosphere, how about hydrogen, helium... And how about charging them to make it with more pressure?

Like sushi (talk) 01:55, 19 September 2012 (UTC)[reply]

Retyping, with Mr. or Ms. (?) A8875 commenting below,

it should have been something like:

Ah. To be buoyant in the atmosphere, how about hydrogen, helium... And how about charging it for more pressure?

And I noticed, hydrogen can be dangerous, by itself, and helium is difficult to charge, as I learned.

So, how about mixed gas of two instead?

Like sushi (talk) 03:06, 19 September 2012 (UTC)[reply]

At the the diagram on the Space elevator nicely demonstrates, the vast majority of the structure is in space, where there is nothing to be buoyant against. Atmospheric density falls to essentially 0 at 40km above Earth, while the space elevator must go to 35,800km. The part of the elevator within the buoyant atmosphere is less than 0.1% of the overall structure. A8875 (talk) 21:49, 18 September 2012 (UTC)[reply]

So, in buoyant(?) space, it can be, at default, vacuus inside?

Like sushi (talk) 01:55, 19 September 2012 (UTC)[reply]

Please refer to buoyancy. I think you have the (extremely common) misconception that some gasses, like hydrogen and helium, are "light" and thus will float up no matter what. In reality, it's the difference in density that makes things float. Since vacuum has a density of 0, nothing can have buoyancy in a vacuum. A8875 (talk) 02:10, 19 September 2012 (UTC)[reply]

Perhaps something with negative mass, although physicist haven't found such a thing yet. StuRat (talk) 02:19, 19 September 2012 (UTC)[reply]

Part of the point is that a space elevator does not NEED to be buoyant! It connects the surface of the earth to a geostationary satelite, the satelite is what hold the cable up. Sort of how the chain on a hammer throw is kept taught by the rotation of the ball at the end. The only complication is that the cable would drag a regular geo-stationary satellite out of geo-stationary orbit so you just put the satellite further out, so that with the cable the satelite will be geo-stationary. Vespine (talk) 02:32, 19 September 2012 (UTC)[reply]

The forces on the cable from gravity pulling it down at one end and the satellite pulling it up at the other end might be enough to snap the cable, though. This problem could be eliminated if the cable was neutrally buoyant at all points. However, for the large portion beyond the atmosphere, this would require that it have zero net mass. StuRat (talk) 03:12, 19 September 2012 (UTC)[reply]

Sorry. I took, without reference, "buoyant" may mean something similar to "vacuus".

Retyping:

So, in space where there is no need to be "buoyant", it can be, at default, vacuus inside?

Like sushi (talk) 03:06, 19 September 2012 (UTC)[reply]

If structure can include space with less heavy gas than the atmosphere, more structures are possible, with a little bit of additional "float", I think.

Like sushi (talk) 03:06, 19 September 2012 (UTC)[reply]

I doubt this is what the original poster meant, but I notice he used the word "charged". Is it possible, in space, to build a very long, highly charged fiber and keep it charged by connecting it to a power supply (with reasonable losses) - and if so, is there any way that this might improve the fiber's tensile strength? (True, you'd think charges would push away from each other and make things worse, but though I don't know anything about materials science I know it's not all that simple) Wnt (talk) 04:09, 19 September 2012 (UTC)[reply]

It is not a, perhaps, usually conceieved "power supply", but does cosmic ray help?

Like sushi (talk) 06:25, 19 September 2012 (UTC)[reply]

And maybe to be added, being light, by itself, may alliviate burden.

Like sushi (talk) 06:32, 19 September 2012 (UTC)[reply]

Slight escaping of gas, if there is, may "support" some form of material.

Like sushi (talk) 07:01, 19 September 2012 (UTC)[reply]

As I recognize myself, I am not good at probability, but fiber, usually not spherical, and probably positioned longer vertically, would be, lighter gas inside and heavier gas outside, if pressure is probabilistically neutralised, very slightly "expanding" horizontally, for outside gas needs to be pressured more.

Like sushi (talk) 07:21, 19 September 2012 (UTC)[reply]

With gas, probably vertically longer fiber slightly expanding horizontally, would additionally "pull" a little, though atomic bond would be more burdened.

Like sushi (talk) 20:03, 19 September 2012 (UTC)[reply]

Would, charging cable, positive, negative, positive, negative, ...in turn, improve "tensile strength"?

For positive-positive, negative-negative shortest distance being twice positive-negative, negative-positive shortest distance,

coulomb force for nearest positive-positive and negative-negative pair would be, without other effects,

one-forth of coulomb force for nearest positive-negative and negative-positive pair,

next nearest such being addtionally, but not so differently distanced,

and if number of postively charged parts and negatively charged parts are the same,

positive-negative and negative-positive pairs would be more than positive-positive and negative-negative pairs.

Like sushi (talk) 13:57, 19 September 2012 (UTC)[reply]

Salts are like that, but I don't know of any that are strong. Even after some consideration, I don't actually know why ionic bonds are weaker than covalent bonds, though if I had to guess, it would be because you can separate the participants in an ionic bond and both retain octets, whereas one or both members of the covalent bond would lose them.

Another idea would be if you had something with alternately charged side groups, but usually I'd think that just building another covalent chain there would be stronger. Still, I don't actually know it couldn't strengthen a structure in the right situation... and looking up Kevlar, I see that indeed, its separated partial charges (-O^- and N⁺-H in the enol resonance structure) contribute to its structural strength. Wnt (talk) 03:43, 20 September 2012 (UTC)[reply]

I have activity time series data of animal activity for various parameters (speed, curvature, etc.) I would like find stochastic models (maybe a Markov chain?) that would "explain" or "be consistent with" the time series, i.e. finding the coefficients or parameters of such a consistent model. Any elegant model would be a good start. Is there a way to fit a stochastic model to time series data, just like one would fit a regression curve to data? (Maybe by running the stochastic model n times to get statistically-determined parameters?) The parameters would quantify noise compared to determinism, or maybe explain a noisy decay profile.

The original motivation was to find more sophisticated parameters than a time constant to explain the decay profile of animal activity following a stimulus, because I have a feeling that k in y' = -ky would in fact get smaller (approach zero) as y approached a baseline value (since activity doesn't decay to zero as exponential decay would imply, but reach a baseline). 128.143.218.78 (talk) 08:36, 19 September 2012 (UTC)[reply]

You will find some useful information at time series analysis. SemanticMantis (talk) 15:10, 19 September 2012 (UTC)[reply]

For instance, the Box-Jenkins methodology might be useful, though I caution that it would take a fair bit of math/stat/computer prowess to do all that correctly. SemanticMantis (talk) 02:18, 20 September 2012 (UTC)[reply]

Is this image (found in this BBC story) the first instance of one satellite photographing another, or is this sort of thing routine? Your Username 04:14, 20 September 2012 (UTC) — Preceding unsigned comment added by Hayttom (talk[reply]

It has been going on for a while in the military. Article on satellite to satellite imaging Zzubnik (talk) 11:35, 20 September 2012 (UTC)[reply]

Is it possible to copy a qubit in a way that destroys the original (e.g. for transferring data from one quantum computer to another) to avoid violating the no-cloning theorem? --168.7.234.182 (talk) 05:16, 20 September 2012 (UTC)[reply]

Yes. -- BenRG (talk) 14:55, 20 September 2012 (UTC)[reply]

How? --168.7.235.89 (talk) 17:34, 20 September 2012 (UTC)[reply]

You do it in the same way you do anything else in your quantum computer, however that is. For example if you've implemented a controlled NOT gate with laser pulses or something, you can swap two qubits with three consecutive CNOT operations by the trick described in XOR swap algorithm. Quantum teleportation is another way of moving a qubit from one place to another which might actually be useful over large distances, assuming quantum computers ever become useful at all. You can also physically move the object storing your qubit from one place to another. -- BenRG (talk) 20:26, 20 September 2012 (UTC)[reply]

There should exist a unitary map U that acts on two qubits as:

U(a|0> + b|1>)|0> = |0>(a|0> + b|1>)

S, the qubit the unknown state is moved to is initialized to be |0>, and then after U acts, that qubit's state is what the first qubit's state was, while the first qubit is now in the state |0>. All you have to do is check that U is a unitary map. Count Iblis (talk) 18:06, 20 September 2012 (UTC)[reply]

Also, if the state is known to be in either |0> or |1> (or any other set of two prior specified orthogonal states) it's possible to copy the state without destroying the original state. This allows classical information to be copied. Count Iblis (talk) 15:34, 20 September 2012 (UTC)[reply]

I hate to collapse everyone's wave function here, but quantum computing is just a fantasy. Fortunately, reality is just down the hall and to the right... 66.87.126.54 (talk) 22:26, 20 September 2012 (UTC)[reply]

If a (food) plant is subjected to 40*10⁻¹¹ Pa for 30 minutes or so before being returned to normal pressure 101 kPa. Would it die or not grow as usual anymore? how does seeds fare? Electron9 (talk) 05:49, 20 September 2012 (UTC)[reply]

The plant might be dehydrated, although 30 minutes might not be too bad. I suspect a seed would do better. StuRat (talk) 05:54, 20 September 2012 (UTC)[reply]

If it froze, the cell walls would burst, and it would die. Zzubnik (talk) 08:06, 20 September 2012 (UTC)[reply]

Freezing? Plasmic Physics (talk) 09:23, 20 September 2012 (UTC)[reply]

It won't freeze, as a vacuum doesn't conduct heat, and unless the vacuum box is in a freezer or some such, the plant won't lose enough heat via radiation to freeze, because once the plant and the walls of the box are at the same temperature, the box will radiate just as much heat back to the plant as the plant will to the box. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 10:03, 20 September 2012 (UTC)[reply]

That depends on how the vacuum is achieved. If the vacuum is achieved by pumping out the air after the plant has been placed in the container, then the temperature of the progressively thinned air will drop, in accordance with the kinetic theory of gasses. If the vacuum is as good as 40 x 10^-11 Pa, pumping was slow enough to allow some conduction, and the air mass before pumping was greater than the mass of the plant, it will certainly be frozen. Wickwack120.145.206.111 (talk) 13:10, 20 September 2012 (UTC)[reply]

If it freezes, it will die for the reason ZZubnik gave. In any case, during pumping and venting, while not frozen, the moisture content of the plant will rupture the plant and then crush it, as there will be a pressure diferential between internal moisture and the container air. Wickwack120.145.206.111 (talk) 13:16, 20 September 2012 (UTC)[reply]

No it won't. The plant structure will likely be able to withstand the vapor pressure of water, which is for example only 17.3 mmHg at 20°C. See also Vacuum: Effects on humans and animals, if animals recover from vacuum exposure up to 90 seconds, I'm sure some plants will be able to last much longer. Tardigrades can even survive days in vacuum. Ssscienccce (talk) 15:12, 20 September 2012 (UTC)[reply]

I award Ssscienccce a Ref Desk Point for being the first, and so far only, participant in this thread to even try to present a genuine reference of any kind – even to a Wikipedia article – in response to this question, rather than just guessing. TenOfAllTrades(talk) 16:23, 20 September 2012 (UTC)[reply]

In the published literature, there's Wheeler et al., who offer us "Plants survive rapid decompression: Implications for bioregenerative life support", Advances in Space Research 47(9):1600-7. The experimenters grew a variety of different food plants (wheat, lettuce, radish) and then pumped them down to as low a pressure as they could achieve with their rig (about 1.5 kPa, or about 11 mmHg) and kept them there for 30 minutes. A week later, the plants were harvested; the authors found no difference between the plants exposed to decompression and control plants.

However, that study comes with a couple of howevers. First, the decompression was not rapid—their pumping apparatus took five minutes to get down to 5 kPa, so if you're hoping to include the effects of 'explosive' decompression (oops, my space station split in half), you'll have to look elsewhere. Much more significant, the minimum pressure achieved, 1.5 kPa, is comparable to the boiling pressure of room-temperature water. (Water has a vapor pressure of 1.5 kPa at about 13°C). The authors believe that there was enough water in their plants and (particularly) in their hydroponic apparatus to maintain a low-pressure water-vapor atmosphere for the duration of their test, even under constant pumping. This means that their plants avoided the worst effects of a really hard, dry vacuum—a high effective relative humidity cut down on the rate of water loss, and the low-but-perceptive ambient pressure prevented fast evaporative cooling of the plant tissues down to their freezing point (which would have caused the sort of damage Wickwack expected). For the purposes of the study – the aerospace question of 'what happens to our greenhouse on Mars or in orbit if it gets a leak?' – the conditions were reasonable. For answering the question of what happens to naked plants under a half hour of real, hard vacuum, the conditions were too gentle. TenOfAllTrades(talk) 16:23, 20 September 2012 (UTC)[reply]

• Is the level of vacuum quoted by the OP so low as to be practically unobtainable with vegetation in a practical vacuum chambr? In space the experiment would be easy, but in an earthly lab, a hard vacuum is not easy to obtain. In early lightbulb research it was fantastically difficult to get the extreme vacuum needed, perhaps one microPascal, since gases would be released from a filament or from the glass itself. The miniscule pressure would be maintained for a good while with continued pumping. The vegetation would be thoroughly desicated by the time a hard sustained vacuum was arrived at. The moisture and other gases from the seeds or vegetation would present a challenge in many earth-bound labs. Edison (talk) 18:53, 20 September 2012 (UTC)[reply]

The "rapid decompression: Implications for bioregenerative life support" rapport as suggested by User:TenOfAllTrades is on the right track. I saw the Outland (film) (1981) movie where a hitman inside a huge green house tries to kill marshal (Sean Connery) in a space suit outside. However it backfires as the windows crack and explode and suck him into space. The green house is built on the moon surface with a steel skeleton that holds transparent windows in between the grid mesh. The question then is if plants are somewhat recoverable? for continued food (and oxygen?) supply, or if it has to be eaten directly and any leftovers has to be discarded? I think LEO, Moon and Mars (or it's moons) surface are the most likely candidates. The scenario is likely a small piece of debris crack the windows causing explosive decompression, follow up patching and then recompression. Growing again takes time, and one better have stored spare supplies in the meantime. So quick recovery is essential. Electron9 (talk) 23:51, 20 September 2012 (UTC)[reply]

How has the scale and frequency of volcanic activity changed over geological time? Is there any evidence that the radioactive material in the earth's core is less active than in earlier geologial times? — Preceding unsigned comment added by Quantumt (talk • contribs) 08:28, 20 September 2012 (UTC)[reply]

See History of the Earth for a general overview. There's lots of links there to take you to more information. See also Archean and Hadean for more details. --Jayron32 11:22, 20 September 2012 (UTC)[reply]

It is certain that military submarines and other kinds can submerege and rise by filling their ballast tanks with either sea water or air so as to rise, but this mechanism is so complex and exlusive only to large sophistcated submarines, but how do miget submersibles or even the pre-modern ships of this kind like the Nautilus submarine rise or dive. In other words what is the basic, simple principle simple for this "rise-dive" activity for small submarines? Please provide links to illustrations or diagrams concerning the topic. — Preceding unsigned comment added by Rt56h3 (talk • contribs) 13:25, 20 September 2012 (UTC)[reply]

They did more or less what the ones do today: take on water (ballast) to sink, pump it out again to rise. For the Nautilus, the metal keel served as a ballast tank, and the pumps to remove the water for rising are visible on this diagram. Similarly on this diagram of the Turtle you can see the pumps and where the ballast would enter in, at the bottom, and go into a bilge tank. On this diagram of the American Diver, the ballast tank is the long little compartment at the bottom, and there is a little pump in front of the guy steering. It is not really a complex mechanism — let water in when you want to sink, pump it back out when you want to rise. The difficulty and complexity only comes when the volumes of water are huge, as they are with modern military submarines on account of their great sizes, but early submarines were terribly small, so required a lot less water to sink, and a lot less energy (e.g., enough to be delivered by a man operating a hand pump) to rise. For a more modern example, notice the numerous ballast tanks here for DSV Alvin. --Mr.98 (talk) 13:46, 20 September 2012 (UTC)[reply]

It's worth noting that submarines can also control their depth to some extent using their diving planes - as long as they have forward motion. AndyTheGrump (talk) 17:24, 20 September 2012 (UTC)[reply]

I have read on some book that say that human growth according to height will stop at age 18 (female) and 20-21 (male).I'm wondering if this age (the age that human stop to grow) is fixed or it depends on the age where puberty comes?Let say if a male had an early puberty,will he have an earlier age where he will stop to grow (in height)?118.101.54.28 (talk) 14:54, 20 September 2012 (UTC)[reply]

It's a bit dense, but in the section Determinants of growth and height of our Human height article, it states that it is those ages are on average, if all else is normal (no growth-related diseases or conditions). That means it doesn't literally stop on your birthday of those ages. It also appears that puberty causes a growth spurt, but it doesn't say that it affects the timeline overall. Mingmingla (talk) 16:51, 20 September 2012 (UTC)[reply]

In looking stuff up in Neville's textbook Oral & Maxillofacial Pathology, 2nd Edition (2002) for the recent peer review on "meth mouth", I found it very odd to see the editors treat oral trauma from sexual practices in the way that they did. They begin the section with, "Although orogenital sexual practices are illegal in many jurisdictions, they are extremely common." There is even the following sentence: "Recurrences are possible with repetition of the inciting (exciting?) event."

To me, this seems very unprofessional. The section on lead poisoning mentions the legalities of lead solder in passing, but this just seems like the authors/editors are trying to make a statement. I would understand if this was published in the 1940s when society was more prudish, but 2002 seems a bit late for such comments. Does anyone else find this odd? DRosenbach ^{(Talk | Contribs)} 17:35, 20 September 2012 (UTC)[reply]

When the book was published (2002) there were many states in the U.S. that still had sodomy laws on the books, most of which prohibited any form of non-genital intercourse. See Sodomy laws in the United States. It wasn't until 2003 that the last 14 states (including the large states of Florida, Texas, and Michigan) had their laws overturned by the Supreme Court. I'm not sure there was any widespread or serious enforcement of these laws in most cases, but the fact remains that the statement "orogenital sexual practices are illegal in many jurisdictions" is perfectly factual. If one takes "many jursidictions" to mean in the entire world, then there are still many places where it is illegal. The author is not passing a value judgement, merely stating a fact regarding the legality of the practice. --Jayron32 17:50, 20 September 2012 (UTC)[reply]

I find it hard to see what is unprofessional in what you have quoted. The "inciting event" means the event which led to the condition. Inciting does not mean exciting. --TammyMoet (talk) 18:04, 20 September 2012 (UTC)[reply]

But to be fair, "incite" is almost always used in connection with violence, hatred, rioting or other negative events. One doesn't incite joy or happiness. -- ♬ Jack of Oz ♬ ^{[your turn]} 21:15, 20 September 2012 (UTC)[reply]

One could argue that oral trauma is a negative event:) DMacks (talk) 21:24, 20 September 2012 (UTC)[reply]

where my question related to stress is. it is surprising because before i can give you clarification that how your answer is not satisfying me you have deleted. i dont want that you keep it in the list but at least give me chance and time to work upon it. — Preceding unsigned comment added by Drcsjain (talk • contribs) 17:50, 20 September 2012 (UTC)[reply]

It was removed. You can see it and the responses by clicking this link. The reason provided for its removal was "rmv discussion, non-question, not appropriate for the RD". In other words, you didn't ask a question that can be answered here. Sean.hoyland - talk 18:17, 20 September 2012 (UTC)[reply]

Well, why was the OP's question, and my answer, removed? What is an "rmv discusion?". While the OP did not structure his question very well - he first implied he is an expert - it is still a valid question. And somehow he worked the word religion into it, but it is not clear whether he meant religion as in a religious belief system or meant it to mean carefull thought. He in effect stated that he had been working on a topic, formulated a theory, and asked us if he is on the right track. That is considerably better than many questions we get where there is no evidence the OP has made any effort to solve homework at all. How is this question different to that of, for example, one submited by "Floda", Distribution of translational and rotational kinetic energy in a gas? This was allowed, but it is the same style of question - the OP presented an understanding he had, but was unsure of, and asked for confirmation. Wickwack124.182.2.57 (talk) 01:09, 21 September 2012 (UTC)[reply]

I watched a video made by David Attenborough saying sometimes when slugs exchange sperms their penis get stuck together so either both or one of their penis gets chewed off by the other slug and that slug carries on only as female from that point. Since it can not exchange sperm with other slugs anymore, can it still reproduce? How? How do sperms travel from the penis to the ovary anyway? Thanks! --RexRowan^忍(Ninja signal) 19:34, 20 September 2012 (UTC)[reply]

See Apophallation for a short description. If you search for that name outside of Wikipedia, you'll likely get more info. --Jayron32 21:24, 20 September 2012 (UTC)[reply]

Approximately how long would it take a live oak seedling to grow from a seedling to 20 feet (6.096 meters) tall? Bubba73 ^{You talkin' to me?} 20:54, 20 September 2012 (UTC)[reply]

Various sources say they grow at up to 3 feet per year when young, so somewhere around 10 years, given good conditions, seems about right. Looie496 (talk) 21:03, 20 September 2012 (UTC)[reply]

Why do some people pop other people's pimples?

The reference desk does not answer requests for opinions, Do not start a debate, please provide encyclopedic references answering
The following discussion has been closed. Please do not modify it.
Why women like blowing up other people's pimples so much?--85.52.87.164 (talk) 23:05, 20 September 2012 (UTC)[reply] Where's the source that says they do? HiLo48 (talk) 23:10, 20 September 2012 (UTC)[reply] (EC) What are you talking about? Whoop whoop pull up Bitching Betty | Averted crashes 23:12, 20 September 2012 (UTC)[reply] The reference desk does not answer requests for opinions or predictions about future events. Do not start a debate; please seek an internet forum instead. μηδείς (talk) 23:27, 20 September 2012 (UTC)[reply]

Come on, that's not really assuming good faith, I think the above replies are unnecessarily terse. Maybe it is a common misconception, in which case the above are still not appropriate or helpful replies. However I suspect most people who have had a couple of girlfriends will testify to this. I have never felt an urge to squeeze someone's pimple myself and I know no other guy who has admitted it either, but my wife and most girlfriends I've had absolutely love it, it's almost like a Christmas present when I let my wife squeeze a pimple on my face, which isn't very common. As to why? Google women love popping zits and there's lots of discussion, but yeah, not much of it is refferenced. I don't think that makes it a completely invalid question.. I suspect it's just preening instinct.. Vespine (talk) 23:39, 20 September 2012 (UTC)[reply]

I have de-hatted the discussion. Please discuss further at WT:RD. --Jayron32 23:43, 20 September 2012 (UTC)[reply]

The question as posted was quite offensive, assumes as fact a ridiculous claim, and invites debate. If there's an objective way to answer it it can be done as currently edited. μηδείς (talk) 00:46, 21 September 2012 (UTC)[reply]

I disagree that it is a ridicolous claim and I honestly don't see why you find it offensive.. Like I said, IF it is a misconception, it's a VERY common one, so I would put the burden of proof back on you and ask why you think it's a ridicolous claim? Vespine (talk) 00:57, 21 September 2012 (UTC)[reply]

If the question is offensive, ignore it. If it contains a ridiculous claim, correct it. If it invites debate, don't start one, and instead point to reliable sources. I mostly read here on the Ref desk, yet even I'm getting sick and tired of Medeis treating the Ref desks as his personal property and censoring all discussions he doesn't personally like. --140.180.242.9 (talk) 01:06, 21 September 2012 (UTC)[reply]

Which foods or beverages boost the metabolic rate; which are known to decrease it? Ankh.Morpork 00:17, 21 September 2012 (UTC)[reply]

Hello

The article on PCS mentions, but does not explain why, a severe onset of PCS may cause blurred vision in conjunction with the pain. Is this a pain response of some kind? Is there a biological rationale behind it or is it about some manner of overwhelming sensation? I've attempted to google it and to look through references for the PCS article, but little came of that. If someone could elaborate I would sure appreciate it, so thank you in advance for any help!

83.108.141.42 (talk) 00:51, 21 September 2012 (UTC)[reply]