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January 23

Do grass grow?

nip this in the bud

The following discussion has been closed. Please do not modify it.

I mean, no matter how long I spend looking at grass in a lawn I have NEVER seen it grow with my own eyes. Yes there are time lapse photography but if you do not see it grow with your eyes, how do you know if the grass were teleported out and slight longer but identical grass were teleported in to replace it? 202.177.218.59 (talk) 02:33, 23 January 2013 (UTC)[reply]

Because teleportation is impossible, since it violates the Heisenberg uncertainty principle. 24.23.196.85 (talk) 02:36, 23 January 2013 (UTC)[reply]

Clearly, the replacement blades of grass are stored in Russell's teapot. TenOfAllTrades(talk) 02:44, 23 January 2013 (UTC)[reply]

Assuming good faith, you might be interested in epistomology. SemanticMantis (talk) 03:18, 23 January 2013 (UTC)[reply]

I understand that some types of bamboo, which is a grass, grow so quickly you can actually see and hear it (groaning sounds). See bamboo#Ecology. StuRat (talk) 08:46, 23 January 2013 (UTC)[reply]

Why doesn't the sun float away like a balloon?

If the sun is made of helium why doesn't it float away like a balloon? — Preceding unsigned comment added by 82.132.216.9 (talk) 09:05, 23 January 2013 (UTC)[reply]

Helium rises in the Earth's atmosphere because it is pushed up by the air around it. Basically, the Earth pulls harder on the air than it does on the helium, thus the air goes down, and the helium up. There is no such force in space, because there is no air, and because it is outside the Earth's gravitational reach. Also, the helium in the sun is much denser than the helium in a balloon, and there are other, heavier elements in the sun too.

For more information about how and why the sun and the planets move, see e.g. Planetary_orbit#Newton.27s_laws_of_motion and Solar_System#Structure_and_composition. - Lindert (talk) 09:25, 23 January 2013 (UTC)[reply]

It's not true that the sun is "outside the Earth's gravitational reach": the earth gravitationally attracts the sun with the same force as the sun attracts the earth, and the effect is the earth's orbit around the sun. AndrewWTaylor (talk) 12:02, 23 January 2013 (UTC)[reply]

You're right, I stand corrected. What I meant to say was that gasses near the sun are not very much affected by the Earth's field in comparison to other forces which are far stronger. - Lindert (talk) 17:14, 23 January 2013 (UTC)[reply]

I remember several children's science books that used to say that Saturn would "float on water." Here's one, Saturn at the BBC Solar System website. This fact is supposed to be surprising! Saturn is a gas giant; most of the planet's volume is comprised of low-pressure hydrogen, helium, methane, and ammonia - almost entirely in the gaseous state. For perspective, that portion of Earth that is in the gaseous state - what we call our atmosphere - also floats on water! Otherwise we'd have oceans in the sky!

When we talk about astronomical-scale objects, it's important to keep in mind that simple approximations about buoyancy break down, because the simplest approximations of gravity break down. If you ever took an elementary physics course, you may have studied fluid pressure and approximated it using the potential energy relationship, explained in our article as the "local approximation" equation. That equation totally doesn't work over large distances - like when we're measuring things the size and density of planets. For studying these objects on these length scales, the most important effect is gravity, not fluid pressure - so buoyancy is usually not even considered. If you get into technicalities, some scientists actually model the solar wind as a fluid (albeit, as an electromagnetically interacting charged plasma - "magnetohydrodynamics") - so some of the equations familiar to fluid dynamicists do show up, with a lot of adjustments.

And of course, if you study the sun's interior, it will be no surprise that the less dense parts of the sun "float to the surface" of the sun - in a constant cycle of swirling and electromagnetically-interacting convection. You can read about helioseismology to see how we study these enormous masses of constituent gas as they "float around" inside the Sun. If you want to start straying farther from common terminology, you could technically even call the solar wind a special case of "stellar" gas escape - with is a thermally-driven buoyant process: hot gas is floating away into space. Nimur (talk) 16:51, 23 January 2013 (UTC)[reply]

Almost the entirety of Saturn is liquid. The gas of Saturn is probably more like a layer of plastic wrap around a basketball or baseball. Sagittarian Milky Way (talk) 16:40, 24 January 2013 (UTC)[reply]

Well, it's a self-gravitating, cold, gas-like, liquid-like, fluid-y ball that orbits the sun. What's the difference between gas and liquid? Most people use the terminology to vaguely refer to something about the compressibility of the substance... I'm not sure that's really a legitimate or useful distinction in a giant self-gravitating ball of stuff. Nimur (talk) 22:39, 24 January 2013 (UTC)[reply]

The point is the density of the stuff it's made of is liquid-like, liquid hydrogen, while a number of times less dense thatn oil or gasoline, is 2 orders of magnitude denser than air, and in the planet the density is increased further by compressioon. It may be a supercritical fluid and liquidey, gassy, hydrogen metal or whatever but imagining it filled with gas like in a balloon is wrong. I remember hearing that plastic wrap around a basketball thing about Jupiter. Okay so even if that is a bit of an exaggeration and I forgot about the reduced gravity of Saturn making the atmosphere even thicker it's still a big mantle of 99.9% not gas by mass surrounded by a crust of gas. Sagittarian Milky Way (talk) 15:01, 26 January 2013 (UTC)[reply]

Passing out when hurt and evolution

I've just been wondering about how sometimes, when you get hurt badly (especially when you receive a blow to the head), the brain will essentially just shut off for a while and you will pass out. Now, I know from painful experience with the occasional stupid accident that there is a point where the level of pain becomes unbearable and where passing out and waking up a couple hours later in the hospital is a real blessing, but I'm wondering how this mechanism could have evolved - because it seems rather inefficient and dangerous to me. Let's say you're an early humanoid or an animal, you're happily walking around the steppes, then suddenly you're hit by a falling rock or tree branch or something - you pass out and you're just lying around motionless for a couple hours, being easy prey for any predator who happens to come along. I understand that depending on the type of injury you received you might hurt yourself even more while trying to get away, and in any case you could probably only stumble around slowly after an accident, but at least you could try to get to safety if you didn't pass out, instead of just presenting your edible and tasty body to predators on a silver plate - all of which could be avoided if our brains had some sort of limit for the level of pain we feel. So...has there ever been any research done into that? How could this mechanism have evolved, and what evolutionary advantage (or lack of disadvantage) can there be to passing out?

And just in case it's necessary, let me add that this is not one of those "if evolution is true, then how come we have eyes/giraffes/whatever" questions - I have no doubts whatsoever about evolution in general, I'm just idly curious in this instance. -- Ferkelparade π 11:06, 23 January 2013 (UTC)[reply]

Not every characteristic we have was evolved for some advantageous reason. Evolution often results in things that were NEVER an advantage. A well known example is the routing of the urethra through the prostate gland in male humans. It is an obvious consequence of having evolved from earlier life forms but has resulted in nothing but trouble for men. If humans were designed from the outset to walk upright while carrying things in our hands, instead of being a modification of a pattern for walking on all fours without a load, you can be sure our backs would look a lot different, and not have the current spine design that results in picking up a mere 30 kg weight, well within muscle strength, causing a load of a few tons on a bit of gristle below L4 about 7 or 8 cm across. I suspect that getting knocked out is one of those things - a disadvantage inherited from early life forms that needed a modicum of decision making capability at the mouth end. An obvious solution would be a standby brain somewhere else, or a brain inside the chest, but that is just not possible with the DNA we inherited. Floda 120.145.189.213 (talk) 12:09, 23 January 2013 (UTC)[reply]

A possible explanation:

http://cogprints.org/5046/1/2006_C.A.R_LETTER_Fear_response_of_Opossums.pdf

More info on it:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC506859/

--Guy Macon (talk) 12:23, 23 January 2013 (UTC)[reply]

It probably would have been possible for evolution to develop the enteric nervous system into the main nervous system if that was worthwhile - but having the brain just beside the eyes, ears, nose an mouth certainly looks more efficient to me. Dmcq (talk) 16:52, 23 January 2013 (UTC)[reply]

Most large predators (lions, bears, wolves, etc.) are more likely to notice a slowly-moving prey item than a completely motionless one. In other words, stumbling around slowly is more likely to draw a predator's attention. 24.23.196.85 (talk) 05:12, 24 January 2013 (UTC)[reply]

Another possible explanation is that it evolved in response to fights for dominance. That is, when one person was damaged enough to pass out, this made it clear that the other won the fight, and thus stopped the fight before either was killed. Being able to decide who is in control without actually killing anyone would be an advantage to a small group, which otherwise might have had trouble maintaining it's population. StuRat (talk) 07:01, 24 January 2013 (UTC)[reply]

I'm fairly certain sturat is completely wrong. To my knowledge, it is not the norm for animals in fights for dominance to knock each other into unconsciousness - rather, one side usually backs down or is killed. Anyway, I'd question the very premise of the question, that not passing out is beneficial. I would postulate that during that passed-out period, your body is carrying out some vital life-saying processes without which you would certainly die or suffer permanent brain damage. Someguy1221 (talk) 07:10, 24 January 2013 (UTC)[reply]

He's wrong alright. Note that the OP asked about passing out in response to a blow to the head. In such cases, for humans as with almost any animal, a blow hard enough to knock you out has a high risk of brain damage including permanent damage, and also a risk of death sometime later, eg from blood clots. If you are knocked out, there is an immediate risk of death from loss of control over the epiglotis. We often see in the news media that someone has died from the so-called one punch kill - where someone has punched someone else hard enough to render them unconscious while they are still falling - the loss of the reflex to tilt the haed up and use one's hand as shields means that the victim will strike his head on the ground from the fall. If the ground struck is in fact a small rock or concrete the result is often death. This is not an evolutionary result. Loss of consciousness occurs because the brain simply cannot remain functional under impact. Note that the links provided by Guy Macon, are, if you read them, about syncope, not a response from blows, and are to that extent irrelavent. Floda 121.215.130.102 (talk) 08:41, 24 January 2013 (UTC)[reply]

Evolution is about improving statistical outcomes. Suppose there was a genetic "choice" - have version 'A' of some gene that gives you a bigger brain with less "cushioning" or have a mutated version 'B' that gives less susceptibility to blackouts but the extra cushioning left less room in the skull for the bigger-brain benefit? Certainly, choosing 'A' will result in some people dying because they get knocked out and eaten by the predator rather than staying conscious and running away...but choosing 'B' might result in yet more people dying because they are too stupid to avoid being attacked by predators and so get attacked more often. The big question is: Does that mutation from the 'A' to the 'B' version of the gene result in statistically more children being born to people who have that mutation?

If that's the kind of trade-off we might have, then you could easily imagine that a genetic change that made us less susceptible to being knocked unconscious being selected against because it brings worse outcomes overall - and therefore disappearing from the gene pool...and that's all that evolution cares about. Is this better than that at making babies? This results in a bunch of ridiculous designs - but that's life...literally!

SteveBaker (talk) 15:58, 24 January 2013 (UTC)[reply]

I wonder why mice shake when afraid and scream when hurt (I panicked after being surprised at how much shaking force didn't unglue him (like the Achilles heel myth but with olive oil and fingers) and feared he might do anything to get off now that I've shaken him vigorously. The glue didn't fail till he broke bones on the floor. Poor mouse.) It wastes energy and screaming like a squeak but loud tells carnivores where a small injured food is. Though in it's credit it turned quiet on second ~4, while it was so hurt it didn't move. Mice are not social (I think), it's not for calling for help. He was still gimpy weeks later (though not as much) so that injury is survivable. Sagittarian Milky Way (talk) 15:54, 26 January 2013 (UTC)[reply]

Fascinating, multi-faceted question. Personally I think the OP is referring to issues of Evolutionary biology much of which seems to be highly theoretical, and cognitive neuroscience another field with many uncertainties, still. Ask five brain doctors and I bet you get five different answers. I don't pretend to know who's right or wrong, but I think it has something to do with how & why the brain shuts the body down in other circumstances. E.g. when drinking too much, you pass out to prevent drinking more. That may not always be the best solution to the problem, notwithstanding specific circumstances and further risks, but it's a biological judgement call based on how those panic-mode neurons evolved. I also think it's related to the pain threshold sub-question, again shutting everything else down to assess the internal situation. And by the way, the brain is still active while you're unconscious, so it's starting a diagnostic and recovery process (if possible), before you regain consciousness. I'd hope that my brain would be able to wake me up if i was being gnawed on by a hyena, even if it meant interrupting some hard-wired pit stop. My 2c. El duderino ^(abides) 21:01, 27 January 2013 (UTC)[reply]

Curricula/syllabuses for math & science education in secondary education

I'm looking for curricula/syllabuses for math & science subjects in secondary education that are generally regarded as well designed and modern. I'm hoping that the info would be available for free or at low cost. I'm trying to see how the curriculum of our local school district compare to elsewhere in the country (US) and in the world. If particular curricula/syllabuses have a reputation of being biased, unevenly covered, or faddish, I'd be interested to know when doing a comparison.

Any pointers to where I can find the info? Thanks. — Preceding unsigned comment added by 173.49.10.182 (talk) 14:15, 23 January 2013 (UTC)[reply]

Does this meet your needs? If so, you will find other syllabuses on the websites of the English exam boards. There's a list of them here, and the articles have links to the websites.

To explain some of the terminology, you will probably want to search for GCSE and A Level qualifications - GCSE being an exam taken at age 16, A Level at age 18. Students are free to sit an exam from any of the exam boards, though usually the school will choose which exam board to use for all their students in any particular subject. The standard of examinations is very similar between boards, although the exact subjects covered does vary. This is more obvious in the Humanities (one board might cover the Cold War whilst another focuses on the rise of Communism in Russia, for instance) than in Maths and Science, but some differences can be noted. - Cucumber Mike (talk) 15:27, 23 January 2013 (UTC)[reply]

Any teacher worth their salt knows which exam boards set less rigorous exams in a given subject, giving their students a better shot at a higher mark. And they know which ones will set more interesting exams, if achieving a good mark isn't an issue for their students. It's why some independent schools use the more rigorous International GCSEs. 86.163.209.18 (talk) 13:04, 25 January 2013 (UTC)[reply]

Oh, I meant to say that the National Curriculum for England for each subject is freely available: http://www.education.gov.uk/schools/teachingandlearning/curriculum/secondary You might find this pdf of the national curriculum for mathematics (from 1999) clearer: https://www.education.gov.uk/publications/standard/publicationDetail/Page1/QCA-99-460 Here's the same for science: http://dera.ioe.ac.uk/4402/ Key Stages 3 and 4 (and 5 if A-levels) are secondary school level. Maths especially is structured around the "National Curriculum levels" (although slightly less than it was few years ago), which means someone might be working on level 4 work when they're 10, or when they're 13, depending on their progress. 86.163.209.18 (talk) 13:24, 25 January 2013 (UTC)[reply]

The Australian standard curriculum is located at http://www.australiancurriculum.edu.au/. However, this curriculum and education standards are under considerable controversy, getting a lot of flak in the media. It has been established that Australian school students are not achieving educational standards that are achieved in other countries. This is OD, but having interviewed young people for jobs from time to time over several decades, and being a graduate of the Australian education system myself (to post grad level), I can tell you that kids today get nothing like as good an education that previous generations got. Young immigrants from Asian and European countries show up good in interviews. The main issue that I see is that Australian children do not get a good grounding in spelling, grammar, and writing good prose from personal research; their natural curiosity about "why is it so" is killed by teacher attitudes, and instead of getting a science education focused on starting with fundamentals and building up from there, they get an odd mix of unrelated topics mixed up with ethics. Our Prime Minister has expressed concern about the situation throughout her time in office - however her and her education minister hasn't figured out yet what to do about it. From what I see it seems that the USA and Britain are not much better off, for similar reasons. If you would like to know why and to what extent curricula and education standards have dropped over the years in the USA, Britain, and Australia, I suggest asking in separate questions. Ratbone 124.182.17.177 (talk) 11:50, 26 January 2013 (UTC)[reply]

The Chinese "Popcorn" Cannon

http://www.youtube.com/watch?v=lhTdAMWiYeo (demo of a U.S. franchisee of a Chinese popcorn chain)
http://www.youtube.com/watch?v=Ta5jh9VglDw (... their Chinese franchisor)
http://www.youtube.com/watch?v=SRHlEMlfArA (pop rice Gangnam Style)
http://www.youtube.com/watch?v=P0zgZ-m1J3o (an industrial pop rice cannon)
http://www.youtube.com/watch?v=NoMQm2WGM9Q (firing Battleship Yamato's 18" guns!!!)
http://www.youtube.com/watch?v=GBeTvvdBnOk (pop rice Vietnam Style, a very different way)
http://www.youtube.com/watch?v=_MrXFXFGTKo (handmade Indian popcorn, how lovely ...)
http://www.youtube.com/watch?v=B7UmUX68KtE (the correct way of making good ole popcorn)
http://www.youtube.com/watch?v=q1v52f1TrWg (John Madden and his Chinese franchisee)

Is it a good idea to use the Chinese popcorn cannon to pop corn?

Generally, I have only seen people make pop rice using this thing because thanks to today's international trade and advanced agriculture, Chinese people can obtain very cheap popcorn and pop them in the correct "Swedish way". People only use these cannons to pop rice and ordinary corn. Yes, Chinese people certainly know how to use a kettle. It's just milk in China is expensive. Many have to use soybean oil instead of butter.

However, I guess this cannon can be less efficient when it comes to make popcorn because corn is much larger than rice. Therefore, the former cooks much slower than the latter. It takes longer to cook corn using the cannon and it's more likely to burn the corn. I guess this Chinese cannon is good for making popped rice. It may not be a good way to make popcorn.

Is the Indian way of making popcorn a little better? I mean if you use hot salt to cook popcorn (Chinese people use hot sand and syrup to cook chestnuts), the contact surface is increased, cooking temperature is also higher, and popped seeds do not contact the salt (they float to the top) so they are less likely to become charcoal. And the very little salt on the popped corn's surface makes it taste good.

The Japanese video clip clearly shows the before and after samples. I measured the sizes and the popped rice seems to be about 20 times larger than rice. The pressure within the cannon shall be 20 times atmosphere. There must be a practical limit where rice can be popped without breaking apart.

If you put one grain of rice into the cannon. The very limited moisture inside the rice cannot generate so much steam to increase the cannon's pressure so it's not going to pop.

If you fill up the whole cannon with rice. The rice probably contain so much water and finally it may generate too much steam.

There must be a "sweet spot" where so much rice generates so much steam and make the pressure high enough to pop the rice correctly.

I also wonder how could the Vietnamese use hot sand to pop rice. I thought popping rice requires a pressure cooker. Anyway, they are not John Madden. -- Toytoy (talk) 16:14, 23 January 2013 (UTC)[reply]

The "cannon" or pressure vessel contains limited amount of air. Heating it only increase the air pressure a little bit.

To make it easier to analyze. Let's assume the cannon contains ideal gas (PV = nRT) and dried rice. Without water in the rice, if the temperature goes from 300K to 600K, the pressure shall be doubled. The rice is burnt and it's still not going to pop.

Now we add a drop of water in the vessel and restart the experiment. Water shall vaporize and greatly increase the vessel's pressure (forget about calculations). A drop of water generates much steam. Now "n" increases and "P" also increases as a result. I know water vapor is far from ideal gas.

If we add more water, certainly there will be more vapor. "n" and "P" shall be increased greatly. The rice may not pop because in this thought experiment, the rice contains no water. Vapor outside the rice cannot be used to pop the rice.

But you know what I mean anyway. It's just a simplified way to analyze the system.

If rice contains a little moisture. More rice inside the cannon means more water and more pressure when the cannon is heated. So this cannon is quite interesting. If you put to little rice, it's not going to pop. If you put too much rice (or the rice is too wet), it may generate too much pressure.

The only way to guarantee success seems to be watching the pressure gauge. When it reaches a predetermined pressure (probably depending on the type of grain, e.g., short grain rice, basmati rice, jasmine rice, winter red hard wheat, ... something like that), you must open it to pop the grains. I think this is very different from making popcorn the "traditional way".

If you put only a grain of popcorn inside the pan, it's going to pop anyway.

However, I think you must have a minimum amount of rice in the cannon to guarantee a successful pop. -- Toytoy (talk) 17:00, 23 January 2013 (UTC)[reply]

Voltage required to accelerate a proton?

Resolved

How much voltage would be required to constantly accelerate an initially stationary, free proton by say 17 meters/sec/sec for, say 23 seconds? Would a "voltage density" variable be required for the calculation? 75.220.14.192 (talk) 17:12, 23 January 2013 (UTC)[reply]

Well after 23 seconds it would be travelling at 391 m/s, which with KE = 1/2 m v^2 and a mass of 1.67262158 × 10-27 kilograms means it has 1.2785602988599 x 10^-22 Joules which is 0.0007991001867874375 electronvolts over 3325 m is 2.4*10^-7. Hope that helps--Gilderien Chat|List of good deeds 17:42, 23 January 2013 (UTC)[reply]

Yes, that helps immensely. Thanks!

75.220.14.192 (talk) 23:23, 23 January 2013 (UTC)[reply]

Hmmm... somehow I came up with a slightly different figure when I ran through. I think a voltage density is at least implied, though the above way avoids actually calculating it. 1 volt = 1 kg m²/C s². So (electron mass kg/electron charge C) * 17 m/s² = (9.1E-31 kg/1.6E-19 C)*17 m/s² = 9.7E-11 volt/m. To keep that up for 23 seconds, during which the particle moves 1/2(23*17 m/s)(23s) = 4496 m, requires a total voltage difference of 4496*9.7E-11 = 4.4E-7. Wnt (talk) 01:54, 24 January 2013 (UTC)[reply]

Plug in C=1.6E-19eV/V and the proton's mass to get 1.77E-7eV/m. -Modocc (talk) 07:06, 24 January 2013 (UTC)[reply]

The answer should be 0.000798eV/4496.5m = 1.77E-7 eV/m. -Modocc (talk) 07:06, 24 January 2013 (UTC) -Modocc (talk) 07:06, 24 January 2013 (UTC)[reply]

Dang it, we have three people and three answers? This is why people shouldn't use Wikipedia to do their homework! Wnt (talk) 16:39, 24 January 2013 (UTC)[reply]

I just ran through my figures again and yes, my distance was slightly out and it is actually 4496.5 metres and therefore 1.78 x 10 ^ -7 eV/m to 3 significant figures.--Gilderien Chat|List of good deeds 17:57, 24 January 2013 (UTC)[reply]

When converting from Joules to electronvolts using the online conversion site here: http://www.onlineconversion.com/energy.htm I got a slightly different result 1.2785602988599e-22 joule = 0.00079801423904 electronvolts to yours. Thus, 1.774745333125764e-7 eV/m which I truncated, but it could be rounded upward... with double rounding, but looking at the article on rounding, I see it should be probably be rounded only once and downward to 1.77 as I did, so I'll stand by my answer. --Modocc (talk) 18:33, 24 January 2013 (UTC)[reply]

Hmm I agree from your answer it should be rounded down, but with mine, which was slightly higher, it should have been rounded up. Probably the different accuracy of our conversions at each stage.--Gilderien Chat|List of good deeds 15:22, 26 January 2013 (UTC)[reply]

Lifespan of a blackhole

How long does a black hole lasts ? What happens to those clouds and ashes which revolves around the black hole ? Want to be Einstein (talk) 17:27, 23 January 2013 (UTC)[reply]

Hypothetically, all black holes will evaporate via Hawking radiation, so long as their rate of accretion is less than their rate of evaporation. However, there's a nice calculation in that article which shows that even for a black hole which is not adding mass to itself, it's lifespan is something like 40-50 orders of magnitude longer than the age of the entire universe. So, it is unlikely that any black hole will entirely evaporate before the heat death of the universe, which is as close to "forever" as there is. --Jayron32 17:31, 23 January 2013 (UTC)[reply]

So, then we would have a period with a universe containing just black holes, and nothing else of interest ? StuRat (talk) 18:31, 23 January 2013 (UTC)[reply]

Note that the article equivocates, with many "citations needed", about heat death of an open or flat universe, which we think we have. "Near" absolute zero is not "at" absolute zero, if one is willing to consider processes occurring over much longer time scales. I've been rather inspired by the concept of "neutrino nuggets", for example... [1] Wnt (talk) 18:56, 23 January 2013 (UTC)[reply]

Our article Hawking radiation says that "For a black hole of one solar mass (1.98892 × 10^30 kg), we get an evaporation time of 2.098 × 10^67 years — much longer than the current age of the universe at 13.73 ± 0.12 x 10^9 years." And that's based on the assumption that the temperature of the surrounding universe is absolute zero. In fact, for that evaporation process to begin, you'd have to wait for the cosmic microwave background temperature - currently 2.7K - to fall below the innate temperature of the black hole, which is about 100nK (about one thirty-millionth of the current temperature), which is also a process which takes an unspeakably long time.

Pretty much any conceivable matter in the vicinity of a black hole will have fallen into it in a period of time that, relative to these timescales, is effectively zero. AlexTiefling (talk) 17:42, 23 January 2013 (UTC)[reply]

Note that tiny black holes evaporate much quicker and the super-massive black holes in the center of galaxies much slower. StuRat (talk) 18:33, 23 January 2013 (UTC)[reply]

Yes, but with the exception of primordial black holes, which may not exist, no black holes are smaller than 1 solar mass. Black holes form after the supernovae of massive stars, and the star needs to be at least 8 solar masses to undergo this process, creating a black hole of 3 solar masses. --140.180.244.202 (talk) 00:26, 24 January 2013 (UTC)[reply]

There are other theoretical ways to form micro black holes. StuRat (talk) 06:54, 24 January 2013 (UTC)[reply]

...which would indeed evaporate via Hawking radiation in a short amount of time. SteveBaker (talk) 14:13, 24 January 2013 (UTC)[reply]

Sound

What is the speed of sound on the moon?--YanikB (talk) 19:37, 23 January 2013 (UTC)[reply]

The Apollo 17 Lunar Seismic Profiling Experiment Final Summary report yielded V_p = 8.3 ±0.4 km/s below the superficial layers of lunar rock. The atmosphere of the moon is too sparse to meaningfully discuss sound-speed. Nimur (talk) 19:43, 23 January 2013 (UTC)[reply]

There is no atmosphere on the moon - so sound doesn't travel at all. (Well, I suppose you could argue that it travels *though* the moon - as a siesmic wave - in which case the speed would be pretty similar to the speed of seismic waves on earth - which is around 8000ms^-1.) But assuming you mean the speed that sound travels - like here on earth - through the air - then it doesn't travel at all...there simply is no sound. If you are thinking about the speed that sound would travel inside a spacecraft (like the Apollo lunar module) - then it would be the same as the speed in a similarly pressurized vessel on earth. SteveBaker (talk) 19:45, 23 January 2013 (UTC)[reply]

Irrelevant to the question. Free feel to continue discussion inside hat.

The following discussion has been closed. Please do not modify it.

Considering just the earth, we know the speed of sound is faster in water and in solids than in air. Given that, is there a significant difference in the speed of sound, in air at sea level vs. in air high in the Himalayas, for example? ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:49, 23 January 2013 (UTC)[reply]

Absolutely yes. That's why pilots of very fast, very-high-altitude airplanes must understand their Mach number very carefully. You may find this section of our sound-speed article helpful. Nimur (talk) 19:55, 23 January 2013 (UTC)[reply]

From Speed of sound:

In fact, assuming an ideal gas, the speed of sound c depends on temperature only, not on the pressure or density (since these change in lockstep for a given temperature and cancel out). Air is almost an ideal gas. The temperature of the air varies with altitude, giving the following variations in the speed of sound using the standard atmosphere - actual conditions may vary.

^{[citation needed]}

Effect of temperature on properties of air
Celsius temperature θ [°C]	Speed of sound c [m/s]	Density of air ρ [kg/m³]	Characteristic specific acoustic impedance z₀ [Pa⋅s/m]
35	351.88	1.1455	403.2
30	349.02	1.1644	406.5
25	346.13	1.1839	409.4
20	343.21	1.2041	413.3
15	340.27	1.2250	416.9
10	337.31	1.2466	420.5
5	334.32	1.2690	424.3
0	331.30	1.2922	428.0
−5	328.25	1.3163	432.1
−10	325.18	1.3413	436.1
−15	322.07	1.3673	440.3
−20	318.94	1.3943	444.6
−25	315.77	1.4224	449.1

Given normal atmospheric conditions, the temperature, and thus speed of sound, varies with altitude:

Altitude	Temperature	m·s⁻¹	km·h⁻¹	mph	knots
Sea level	15 °C (59 °F)	340	1225	761	661
11,000 m−20,000 m (Cruising altitude of commercial jets, and first supersonic flight)	−57 °C (−70 °F)	295	1062	660	573
29,000 m (Flight of X-43A)	−48 °C (−53 °F)	301	1083	673	585

--Guy Macon (talk) 20:01, 23 January 2013 (UTC)[reply]

Very interesting. There is a significant difference in the speed at different altitudes. That's one factor. But thinness affects sound also. Let's suppose I could magically ascend with a boom-box set at some particular volume. As I rise in the atmosphere, would the volume slowly become fainter until there was too little air to sustain sound waves? To put it another way, if the moon somehow magically had an atmosphere whose various altitudes matched those of the earth? Would sound operate the same way as on earth? (I'm thinking the answer is "Yes", but I'm just wanting to be certain.) And what I was really thinking about was not the moon, but Mars, which does have a thin atmosphere, which tends to be very cold. So, given the above info, would sound at the surface of Mars be both slower speed and lower volume? Again, I'm thinking "Yes", but I defer to the experts. 20:14, 23 January 2013 (UTC) — Preceding unsigned comment added by Baseball Bugs (talk • contribs)

Yes, there is a difference in the ability of the medium to efficiently transmit the sound, but this is irrespective of the speed the sound travels. Thinner air doesn't transmit the sound any slower, however thinner air has less molecules available to transmit information, so there is some greater loss of information, hence greater loss of volume at greater distances. --Jayron32 20:41, 23 January 2013 (UTC)[reply]

Sound waves need a medium to propagate - unlike (for example) radio waves. You may recall from High School science class the "Bell jar experiment" - (an electric bell in a glass jar) - As you pump-out the air in the jar, the bell gets quieter and quieter - until you reach a near-vacuum and you can't hear it at all, but you can still see the clapper banging. At altitude, the speed doesn't change, (disregarding temperature), just the volume (intensity) of the wave. ~:74.60.29.141 (talk) 20:43, 23 January 2013 (UTC)[reply]

Yes, I do recall that now. It's been a while. :) OK, so if I'm understanding correctly, for the OP's question about the speed of sound on the moon, assuming he's talking about atmospheric sound waves, would be that if the moon had a measurable atmosphere, then the speed of sound would be a function of the air temperature. As it stands, there is no defineable air temperature on the moon (to speak of) because there is no air (to speak of). ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:54, 23 January 2013 (UTC)[reply]

And I failed to notice the earlier reference to Atmosphere of the Moon, which indicates that technically the moon has an atmosphere, but it's extremely thin. So, supposing that it could transmit sound waves, the speed would be a function of whatever micro-measurable temperature it has, hence it would be very slow; and the volume of any such sound waves would be extremely low. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:00, 23 January 2013 (UTC)[reply]

At the moment I can't find sources for this, but... essentially, you need enough air molecules so that they can "bang into each other" in order to propagate the sound energy. Warmer molecules, being in a more energetic state, (and occupy a larger volume of space) can more easily (and quickly) transfer the sound (motion) to other molecules. [There are equations somewhere, for those who like to do the math] ~:74.60.29.141 (talk) 21:32, 23 January 2013 (UTC)[reply]

As I understand it the speed of sound depends on the density of matter. 5000 m/s in solid, 1500 m/s in liquid and 340 m/s in the air. What is the density of matter at moon ground level?--YanikB (talk) 00:02, 24 January 2013 (UTC)[reply]

Did you read above? The speed of sound in a gas depends on the temperature of the gas primarily. Density has little to do with it. --Jayron32 02:00, 24 January 2013 (UTC)[reply]

I've hatted the majority of this discussion, because it's completely irrelevant to the OP's question. The OP didn't ask about the speed of sound at various altitudes on Earth; he asked about the speed of sound on the Moon. Nimur and SteveBaker already gave the answer, and there is no need to confuse the OP with irrelevant details that are clearly well above his level of understanding. --140.180.244.202 (talk) 05:23, 24 January 2013 (UTC)[reply]

Does this show us something new about African Grey Parrot behaviour?

Apparently, this guy has taught his parrot to drive. Seriously. As I'm sure that most of us know already, African Grey Parrots are one of the most intelligent of birds - but is the one here doing something, in terms of actually controlling and directing the buggy, that we didn't think that they could do already? --Kurt Shaped Box (talk) 23:47, 23 January 2013 (UTC)[reply]

Well, it would be nice to see a peer reviewed source ... this isn't an answer, but just looking at it, my feeling is that if the parrot can be persuaded to stay on that perch, it's bound to mess with the lever. I don't see any sure sign that it is directing the vehicle to a destination - it comes toward the camera in many of the clips, but there is likely a strong selection bias in what we're seeing. It seems like every time the vehicle jiggles, it stops, and the bird is liable to move the lever any which way when it starts again. But... I can't rule out that they really have something there, either. Wnt (talk) 01:35, 24 January 2013 (UTC)[reply]

Please check 2:09 of the video

Does the bird intentionally avoid driving over the pebbles? -- Toytoy (talk) 04:32, 24 January 2013 (UTC)[reply]

It looks that way, but then again as Wnt mentions, it could be selection bias on the part of the inventor. I'd love to know if the parrot definitely gets on the buggy and uses it with the intention of *going somewhere* - which I think would be evidence of something quite significant, as opposed to just (say) going backwards and forwards and spinning in circles at random. As for the bird stopping every few seconds - it's been suggested in the YouTube comments that he's stopping to check where he's going and look on the ground in front, which necessitates (due to limited binocular vision) turning his head sideways and craning his neck. This would be amazing if true. --Kurt Shaped Box (talk) 06:39, 24 January 2013 (UTC)[reply]

See 1:43, where the parrot fails to avoid driving over pebbles. --140.180.244.202 (talk) 08:19, 24 January 2013 (UTC)[reply]

That task doesn't seem beyond the capabilities of an African grey parrot to me. It's not particularly good at it, but may get better with practice. StuRat (talk) 04:46, 24 January 2013 (UTC)[reply]

Note that the inventor is Andrew Gray. Did he change his name to match the parrots ? :-) StuRat (talk) 04:44, 24 January 2013 (UTC) [reply]

This may not be as difficult or incredible as you might at first imagine. Here is a robot vehicle that is controlled (semi-successfully) by a cockroach. He mentions other robots controlled by guinea pigs and siamese fighting fish! SteveBaker (talk) 17:54, 24 January 2013 (UTC)[reply]

Math for astronomy degrees?

Do you have to be good at math to get undergrad and grad degrees in astronomy or astrophysics? Reflectionsinglass (talk) 23:53, 23 January 2013 (UTC)[reply]

Yes, or at least be able to pass advanced math courses. The BA of Astronomy degree from Boston University lists both Differential Equations and Linear Algebra, plus the necessary prerequisites, in their "Recommended" area (I have not attempted to determine their specific nomenclature for graduation requirements). — Lomn 00:10, 24 January 2013 (UTC)[reply]

It depends on what you mean by "good at math". To get an undergrad astrophysics degree, you will definitely need to be familiar with 3rd year physics, including Lagrangian mechanics, quantum mechanics, electromagnetism, and thermal physics. All of these courses require, at the very least, familiarity with calculus and some knowledge of linear algebra, along with the mathematical concepts from the courses themselves. That said, upper-level university math courses are usually proof based, and focus on rigorously proving some theorems at an abstract level. Science courses don't usually require as much rigor or as many proofs, because physical phenomena are more well-behaved than the crazy functions that mathematicians can think of. In this sense, it's not necessary to be good at math in order to do astro. Don't be fooled, however: if you were to take a random astro student and compare his math abilities to that of the average university student, he would be much better. He would certainly have counted as "good at math" in high school, unless said high school was exceptionally prestigious and focused on the sciences. --140.180.244.202 (talk) 00:21, 24 January 2013 (UTC)[reply]

I am not aware of any major accredited university that grants undergraduate degrees in astrophysics. If anyone knows of one, please feel free to post a link to that program; I would be interested to read about it. It is far more common to pursue an undergraduate degree in physics, or math (or even chemistry or biology), and then pursue graduate study in a physics department. Few graduate programs even have an "astrophysics" department; most graduate astrophysics Ph.D. students are rolled into the physics graduate program under the guidance of one or more specialized faculty. Nimur (talk) 00:31, 24 January 2013 (UTC)[reply]

It depends on what you mean by "major", but see [2]. I agree that what you said is a much more common route. --140.180.244.202 (talk) 00:37, 24 January 2013 (UTC)[reply]

Also, Earth and Space Exploration, from Arizona State University. It is worth emphasizing that there is a distinction between astronomy and astrophysics. Nimur (talk) 00:39, 24 January 2013 (UTC)[reply]

(ec) While I'm inclined to agree with your impression, there are at least a few schools that seem to have – or have recently had – an undergraduate program in astrophysics. There are a number of schools and individuals that refer to offering or acquiring an "undergraduate degree in astrophysics". The College of Charleston is one; McMaster University in Canada offers a physics degree with Astrophysics Specialization; UC Berkeley's Department of Astronomy has an astrophysics major; Princeton University's Department of Astrophysical Sciences offers an astrophysics major. (I'll be honest, I was a bit surprised at how many schools actually do have a distinct, degree-granting 'Department of Astronomy/Astrophysics' or similar.) TenOfAllTrades(talk) 00:53, 24 January 2013 (UTC)[reply]

Leicester University has this course, and you will see there is no mention of maths related subjects on that page. It may be lurking in the detail. --TammyMoet (talk) 10:39, 24 January 2013 (UTC)[reply]

Umm, actually, it's in virtually every sentence on that page.

"Astrophysics is the application of physics and mathematics..."

"You will study core topics in physics and mathematics"

"The core programme builds upon the First Year foundations and includes relativity and particles, waves and fields, condensed matter physics and electromagnetism." (as I mentioned in my previous post, all of these are typical courses for a physics student, and require mathematics)

"Core topics include quantum physics, atoms and nuclei, radiation and matter and plasma physics." (again, all typical physics courses)

"The core programme includes fluid dynamics, quantum solids, and statistical physics." (requires statistics) --140.180.242.224 (talk) 20:51, 24 January 2013 (UTC)[reply]

Astrophysics "is taught at Oxford as part of the undergraduate Physics degree", with an option for much of the third year (of the three-year course) being an astrophysics project. (Astrophysics is a sub-department of the Physics department.) "Everyone who applies to study Physics or Physics and Philosophy at Oxford must sit the Physics Aptitude Test. There are no exceptions". Try out a sample of that test, including its mathematics components, here. The main target audience for that test would be British 17 and 18 year olds, pretty much all of whom would be studying both Physics and Mathematics, and possibly Further Mathematics, at A-level in the UK equivalent of high school. Less aggressively selective universities may not be as concerned about mathematical aptitude. --Demiurge1000 (talk) 12:15, 24 January 2013 (UTC)[reply]

January 24

USAGE OF DNA PRIMER

CAN DNA PRIMER BE USED INSTEAD OF RNA PRIMER DURING REPLICATION — Preceding unsigned comment added by 14.139.187.146 (talk) 05:43, 24 January 2013 (UTC)[reply]

Didn't you just ask this ? StuRat (talk) 06:45, 24 January 2013 (UTC)[reply]

Slightly different question. But yes, it can be, at least for purposes of laboratory experiments (see oligonucleotide). I don't recall offhand if oligonucleotides transfected into cells end up being used as primers in lagging strand replication, but I assume they would be (you could tell if they were radiolabelled or otherwise substituted ... must be something that uses this, hmmm... ah, sounds like [3] and [4] go this way. But this is recent work and there's still some detectable caution in their wording.) Wnt (talk) 16:28, 24 January 2013 (UTC)[reply]

Neurotheology

Is it secular neurobiological explanation of religious belief or religious attempt to take over science? --PlanetEditor (talk) 07:16, 24 January 2013 (UTC)[reply]

From a quick look at our article, it seems that it purports to be the former, though to me at least it looks like applied hogwashology. Have they thought of looking for a neurobiological explanation for believing in neurobiological explanations for religious belief, I wonder? AndyTheGrump (talk) 07:34, 24 January 2013 (UTC)[reply]

How is it hogwashology? How is your last sentence related to whether or not it's hogwashology? I've read articles by reputable neuroscientists on neurotheology, even though it's a new area of research whose conclusions are often controversial. I don't see how it's a religious attempt to take over science, since it is clearly based on scientific principles rather than religion. --140.180.244.202 (talk) 08:16, 24 January 2013 (UTC)[reply]

Is neurotheology a branch of neurology or branch of theology? --PlanetEditor (talk) 08:19, 24 January 2013 (UTC)[reply]

Since the term originated with Aldous Huxley, I'd be tempted to put it under Philosophy. ~E:74.60.29.141 (talk) 10:14, 24 January 2013 (UTC)[reply]

I'm pretty sure it's not an attempt by the religious to take over science. Most of the books and papers on the subject seek to reduce religious thinking to mundane (godless) science - and I'm sure that religious people will not take kindly to that. However, the studies that have been done, and the theories floated are not methodologically sound - and that's unfortunate. So we have some kind of general indication that religious thinking is a mundane result of brain chemistry or cultural evolution or some such thing. That's not surprising because we find religions and religious thinking in all societies and in distant branches of humanity who have been separated from mainstream thinking for a very long time. That suggests that there is some underlying cause for this peculiar set of ideas - and it would be surprising if science couldn't turn up some reasons for this. But right now, I'd have to say that as far as mainstream science is concerned, we don't have any solid answers yet - just some tantalizing hints at ways to look for an answer to this phenomenon. Religious people really don't want science to come up with answers like "such-and-such chemical in the brain makes people have faith in god" - or "such-and-such gene causes belief in god"...that would be very bad for them...and worst still: "Take this little pink pill and you'll become an atheist within 24 hours". These results are unlikely to come about - but not impossible. SteveBaker (talk) 15:40, 24 January 2013 (UTC)[reply]

The range of topics described in the article runs the gamut from serious research to pure quackery. Approach this area like a World War soldier crossing a minefield, carefully probing each intended step with a bayonet. Wnt (talk) 16:24, 24 January 2013 (UTC)[reply]

Yes, I strongly agree! SteveBaker (talk) 17:45, 24 January 2013 (UTC)[reply]

"..seek to reduce religious thinking to mundane (godless) science..." Just like how some researchers seek to reduce vision to mundane neurobiology? Does that mean everything you see is a lie? Researchers also try to understand the neural basis of logical thinking. Does that mean logical thinking is useless? --140.180.242.224 (talk) 19:20, 24 January 2013 (UTC)[reply]

Indeed. My experience is that atheists assume religious people would be upset by evidence that specific brain structures increase or decrease religiousity, or are involved in spiritual experiences, whereas religious people are generally not bothered, or even look for this stuff because they expect to find it (that is, it fits with their belief that such structures should exist in the human brain). Because "take this pink pill and you'll become an atheist" is as valid as "take this blue pill and you'll be able to sense God's presence" or "take this green pill and you'll be able to see have everything points to a spiritual meaning". 86.163.209.18 (talk) 10:31, 25 January 2013 (UTC)[reply]

Displacement of a body on a circular path

This is not my homework question. A body is moving around a circular path, this means it is changing position as well as direction at every instant of time. Is the displacement of the body being changed at every point during its motion on a circular path ? Show your knowledge (talk) 10:20, 24 January 2013 (UTC)[reply]

The displacement is a sine-squared function of time. Plasmic Physics (talk) 10:42, 24 January 2013 (UTC)[reply]

Yes. The displacement increases till the body reaches the other (diametrically opposite) side of the circle and then decreases till it becomes zero when the body reaches its original position. See Displacement_(vector) — Preceding unsigned comment added by 59.145.142.36 (talk) 11:36, 24 January 2013 (UTC)[reply]

Suppose a body moves from one point to another on a circular path. On both the points, the direction of the body is along the tangent to the point i.e., at both the points its direction of motion is different. This means that there is no displacement between the two points since the direction of motion is different on both points (i.e., velocity changes as the direction of motion changes). Therefore, in this case displacement is not the shortest possible distance between the two points. I don't know whatever I mentioned is right or wrong. Please, make it clear whether I am right or wrong. Also state something about the sentence which is in bold font. Thanks! Show your knowledge (talk) 03:22, 25 January 2013 (UTC)[reply]

If a body was at a position A(x1,y1) at time t1 and at a position B(x2,y2) at time t2, there IS a displacement (irrespective of the path taken to travel from A to B and irrespective of what the velocity or direction of motion of the body was, at A or B). Your statement "there is no displacement between the two points since the direction of motion is different on both points" is wrong. Velocity changes as the direction of motion changes is correct. The point to be noted here is that velocity is a vector (has a magnitude and a direction) and hence the velocity is said to change is there is a change in either the magnitude (increase or decrease in speed) or direction or both. In case of uniform circular motion, the magnitude of the velocity (called the 'speed') remains constant but the velocity is said to change because the direction of motion changes.

To find the displacement, you simply draw a line from A(x1,y1) to B(x2,y2). The length of the line corresponds to the magnitude of displacement and the direction of the arrow from A to B corresponds to the direction of displacement. There is no displacement if the length of the line is zero - that is, if A(x1,y1) and B(x2,y2) are the same. — Preceding unsigned comment added by 59.145.142.36 (talk) 04:53, 25 January 2013 (UTC)[reply]

The direction of motion of either position is irrelevant with respect to the definition of displacement. Distance, in this case, is measured as the total arc length travelled in the total time. Displacement would then be equal to the chord length at an instant in time.

Velocity is a vector quantity, whereas speed is a scalar quantity. This means that meaning that velocity is speed given with a direction relative to some reference. Plasmic Physics (talk) 05:42, 25 January 2013 (UTC)[reply]

Therefore, displacement of a body on a curved path is not zero, but its velocity is zero. Show your knowledge (talk) 05:09, 27 January 2013 (UTC)[reply]

Why do electrons emit photon, not other particles ?

When a higher orbit electron comes to a lower orbit, it emits photon. Why don't it emit other elementary particles (like boson or any other) ? What are the possible reasons behind this ? Sunny Singh (DAV) (talk) 10:30, 24 January 2013 (UTC)[reply]

The short (oversimplified) answer is that it is energy that is emitted, not matter. I don't know if this will help with your specific question, but there is a nice page for visualizing this at http://spiff.rit.edu/classes/phys301/lectures/spec_lines/Atoms_Nav.swf (Turn on JavaScript first).

Also see:

http://curious.astro.cornell.edu/question.php?number=85

http://www.ccmr.cornell.edu/education/ask/index.html?quid=257

--Guy Macon (talk) 11:58, 24 January 2013 (UTC)[reply]

The photon is a wave of electromagnetic energy. If you could wiggle around a fist-sized electron in your hand (don't forget to wear your rubber soled shoes) you'd create a huge magnetic field every time you moved it perpendicular to something, and of course greatly increase the electric field if you moved it toward something. So if you just moved it around in a closed loop, things would be exposed to these changes for a second and then go back to normal - you'd, say, blow out the television in the next room from the eddy currents and so forth. Photons (for this speed, really long wavelength radio photons) would be the description for what reaches out from your handheld electron at light speed to the equipment in surrounding buildings.

You can also look at it that a photon carries energy (any value) and angular momentum (a reduced Planck constant's worth of it, no more, no less) so it is the right particle for the job. You can't use a particle with charge, color charge, strangeness, etc. Why a particle is used that can move at the speed of light has something to do with avoiding the Higgs mechanism, but you'll need someone who actually understands that if you want to go further that way. Wnt (talk) 16:19, 24 January 2013 (UTC)[reply]

Guy Macon's answer above is not correct. "Matter" is not a meaningful scientific term. Wnt's explanation is much better except for the part about Higgs mechanism which is not relevant except indirectly. The point is that the electron wouldn't ordinarily be able to produce a massive particle because not enough energy is available for that. But if enough energy is available - for instance in a high energy collision, electron can and do indeed produce other particles such as W bosons and Z bosons. Dauto (talk) 16:47, 24 January 2013 (UTC)[reply]

Hmmm... A W boson sort of contains the electron, so is it relevant? But a Z boson mediates neutral current and can mediate electron-neutrino scattering, so I suppose I have to give you that. But you're right that at high energies electrons interact by electroweak forces, not pure electromagnetism, and thus not purely by photons. I think this is philosophically different from just plain pair production where indeed any particle can show up when high energy things interact. Wnt (talk) 16:33, 25 January 2013 (UTC)[reply]

W-bosons do not in any meaningful way contain electrons. Dauto (talk) 18:33, 26 January 2013 (UTC)[reply]

Transitions of an electron from a higher atomic orbital to a lower atomic orbital should (with a low probability) be accompanied by the emission of a neutrino and an antineutrino instead of a photon. The main processes of this de-excitation would be (a) the conversion of the electron into a virtual W^- boson and a neutrino and the subsequent conversion of the W^- boson to an electron and an antineutrino, and (b) the electron emitting a Z boson and the Z boson being converted to a neutrino and an antineutrino. For (a) the neutrino/antineutrino pair would be created in the electron flavor eigenstate, while for (b) the pair could be created in any flavor state.

By the way, the original question incorrectly implies that photons are not bosons. Icek (talk) 20:20, 25 January 2013 (UTC)[reply]

I'm not sure how meaningful it is to ask "why" in this case - this is what we have observed (or rather, what Balmer and Paschen and Lyman and Planck observed) and we have fitted the standard model to these observations. If we had observed electrons emitting unconfined quarks (impossible under the SM) you would be asking why they emit quarks and not photons! 72.128.82.131 (talk) 16:56, 27 January 2013 (UTC)[reply]

"Best" university of natural sciences / math in New York City

Engaging in literary pursuits, I ask for a hint concerning the protagonist of my story: What would presumably be the best / most prestigious college/university in New York City for a very gifted student of mathematics, physics and/or astronomy? --KnightMove (talk) 10:40, 24 January 2013 (UTC)[reply]

I can't myself answer, but those who can will likely need clarification whether you mean right now or at some date in the past. When is your story (or the part of it relevant to the question) set? {The poster formerly known as 87.81.230.195} 84.21.143.150 (talk) 14:08, 24 January 2013 (UTC)[reply]

(edit conflict) The most prestigious university in New York City overall is likely either Columbia University or Fordham University. The two biggest science/technology schools are Polytechnic Institute of New York University (NYU-POLY) and New York City College of Technology, (City Tech). Columbia School of Engineering and Applied Science as part of Columbia University probably meets all of your requirements: A very highly regarded science and technology school, and a very prestigious university overall. --Jayron32 14:12, 24 January 2013 (UTC)[reply]

Where are you from? Don't put Fordham in the sentence most prestigious university in New York City. Even Nortre Dame is at least 100 SAT points below Columbia and that's the Catholic Harvard (Fordham is Catholic). Overall. Alot of Columbians like humanities. So Math SAT only Cooper Union might be better, not sure. Also Fordham Bronx campus (at least) is kinda Gothic, if that means anything. Fordham's Manhattan Campus, I've been in that area and didn't notice any Gothicness, or maybe that was Juilliard, or public housing, or Lincoln Center. Columbia is 1897 neoclassical and has existed 260 years. Sagittarian Milky Way (talk) 16:28, 24 January 2013 (UTC)[reply]

What does SAT scores have to do with prestige? --Jayron32 04:18, 25 January 2013 (UTC)[reply]

Whether SAT scores have an iota to do with prestige or not Columbia's still more prestigious. Though I think they do this kind of thing more in Europe and India where getting in is just score high enough. Or New York City specialized high schools where scores and prestige sort themselves out nicely cause the highest score got first dibs and the 6,106th highest score got the only school left. Sagittarian Milky Way (talk) 18:08, 26 January 2013 (UTC)[reply]

My story is set in the future - circa 2100. --KnightMove (talk) 23:32, 24 January 2013 (UTC)[reply]

Cornell will have an applied STEM fields campus on Roosevelt Island then. Sagittarian Milky Way (talk) 01:00, 25 January 2013 (UTC)[reply]

Perhaps by 2100, Stanford's New York campus will finally be built. (It will help if your story is set in hypothetical fictional universe). FYI, Sagitarrian Milky Way, Cornell does not have a campus on Roosevelt Island. They are currently involved in a proposal to build one. Nimur (talk) 01:03, 25 January 2013 (UTC) I said 2100! Sagittarian Milky Way (talk) 01:14, 25 January 2013 (UTC)[reply]

Some simple questions

1. Why sunlight appears yellow in color?
2. Is it possible to polarize electromagnetic radiations other than light using Polaroid filter?
3. What is the size of the smallest object we can see through naked eyes?
4. Is it true that transverse waves can only be produced in solids and liquids, but not in gases?
5. What is difference between water wave and water current?
6. Is it true that: "charge * electric field = electric force"? --Britannica User (talk) 10:47, 24 January 2013 (UTC)[reply]

For question 1, see this. For question 3, 0.1 mm long object can be seen by the naked eye (20/20 vision). --PlanetEditor (talk) 11:19, 24 January 2013 (UTC)[reply]

Question 5: A water wave does not necessarily transport water in the direction of the wave (a current does, of course). You can see this sometimes when you see foam or small objects floating on the water, and when a wave passes, the objects move upwards and then downwards again, but they do not move with the wave. Compare this with a rope that is held by both ends: when one end is quickly moved up and down, a wave is seen passing through the rope from that end to the other, but the rope itself does not move horizontally.

Question 6: Yes, the electric force acting on a particle is equal to the electric field multiplied by the electric charge of the particle. See e.g. Electric_field#Parallels_between_electrostatic_and_gravitational_fields. - Lindert (talk) 16:00, 24 January 2013 (UTC)[reply]

So far:

Why sunlight appears yellow in color? For the same reason that the sky is blue. Light from the sun is almost perfectly white (it is naturally, a little bit yellowish - but it looks white out in space) - but as the light passes through our atmosphere, Raleigh scattering scatters blue light throughout the sky - removing blue from white light leaves yellow light behind.
Is it possible to polarize electromagnetic radiations other than light using Polaroid filter? Yes. The reason people wear vertically polarized sunglasses is to eliminate horizontally polarized light, such as you get as light bounces from calm water - which reduces reflections. So, you could (for example) produce horizontally polarized light by reflecting unpolarized light from a smooth puddle of water.
What is the size of the smallest object we can see through naked eyes? I agree with User:PlanetEditor that 1/10th of a millimeter is about the limit...but it's a bit tricky. You can see (for example) a single dust mote sparkling in sunlight - and while a single particle of flour is too small to see, a bucket of flour is easily visible! Droplets of water in fog are visible as a cloud - even though none of the individual droplets is visible. Interestingly, the largest bacteria are just about visible to the human eye.
Is it true that transverse waves can only be produced in solids and liquids, but not in gases? Yes. I don't know why that is though.
What is difference between water wave and water current? As User:Lindert said - waves do not transport liquid from one place to another (technically, they don't transport a substantial amount of it by more than a few wavelengths) - but a water current does.
Is it true that: "charge * electric field = electric force"? Yes, User:Lindert nailed that one!

SteveBaker (talk) 17:40, 24 January 2013 (UTC)[reply]

2: Steve, you've answered the wrong question. It's not 'can we polarise visible light other than with a polaroid', but 'can we polarise EM radiation other than light'. And I feel sure that the answer is 'yes', but I don't know how. AlexTiefling (talk) 09:48, 25 January 2013 (UTC)[reply]

4 isn't quite correct. Liquids (By that I mean Newtonian liquids) like gasses cannot carry transverse waves (s-waves). Only solids can do that. The reason for that their Shear modulus is zero which gives s-waves zero speed. In other words, they cannot propagate. Dauto (talk) 18:43, 24 January 2013 (UTC)[reply]

I think the real answer to 1 is that sunlight doesn't appear yellow — when it's overhead. On an overcast day you can sometimes see the disk of the Sun through clouds, and it is not too bright to look at briefly (disclaimer: I'm not claiming it's safe to do so). To me, in that circumstance, it looks almost perfectly white. However, if you glance at the midday Sun without a cloud cover, it's too bright and you don't really get a sensation of color, just an urgent desire to stop looking at it as quickly as possible.

The times when your eyes will actually focus briefly on the Sun (again, I'm not saying this is safe) are early in the morning or late in the evening. That's when it looks yellow (or orange or red). I'm not saying the Rayleigh-scattering answer is wrong — I think that is why it looks yellow or orange or red at those times. But I don't think it's actually yellow in the middle of the day. --Trovatore (talk) 01:55, 25 January 2013 (UTC)[reply]

Astronomer Phil Plait does not agree with Steve on his answer to #1. In his book, Bad Astronomy (pages 45-47, available on Google Books), he lists several purported reasons why the sun appears yellowish and basically shoots them all down. In terms of the Raleigh scattering, there's not nearly enough going on to turn the sun yellowish. In short, he says the reasons are not clearly understood to anyone and it's not known how or why it looks the way it does. Matt Deres (talk) 03:17, 25 January 2013 (UTC)[reply]

3) I wonder if you can see smaller objects in special circumstances, like floaters in the eye. StuRat (talk) 03:40, 25 January 2013 (UTC)[reply]

The smallest object you can see unaided is a function of the angular visual acuity and minimal focal distance of your eye. Angular acuity is fairly constant from person to person, but nearsighted people have a closer minimal focal distance than average, letting them see smaller objects. --Carnildo (talk) 01:58, 26 January 2013 (UTC)[reply]

Yes, folk who have answered "x-many mm" and the like have given the wrong answer to the wrong question, as the acuity of the eye is obviously an angular function as Carnildo indicated, being essentially determined by difraction and the ratio of cone light sensor pitch in the fovea to the distance between fovea and lens. According to http://en.wikipedia.org/wiki/Visual_acuity, the angular acuity of a healthy human eye (6/6 vision - the minimum standard for normality) is one arc-minute. This means that at 6 metres two brightly lit lines can be resolved if at least 1.75 mm apart. Young healthy adults can focus down to 150 mm (small children, with their small eyeballs can do much better). At 150 mm, the resolution is thus 1.75 x 0.15/6 i.e., 0.04 mm.

But there's more: we have two eyes. The brain is able to combine the image from both eyes to effectively get double resolution, so we can resolve two lines only 0.02 mm apart.

But even this isn't the full story - if it was, we would not be able to see the stars in the night sky - visible stars are as low as 0.0025 arc-seconds! The cone sensors of the eye (and the rods) are area-integrating. That is, an incoming beam of light can be sensed by a single cone so long as it falls on the cone - the width of the beam does not matter - what matters is the intensity. In fact, due to scattering in the retina, it doesn't matter if the beam slightly misses a cone. So, there is NO LIMIT to how small an object we can sense, so long as it is sufficiently bright compared to its surroundings.

Ratbone 124.182.17.177 (talk) 11:26, 26 January 2013 (UTC)[reply]

Why do we feel more pain in winter than in summer ?

I have observed this many times that we feel more pain in winter than in summer. Why is it so ? A bit more. We write the name of orbits of an atom as K, L, M, N, etc. Why we not write it as A, B, C, D, etc ? Concepts of Physics (talk) 11:07, 24 January 2013 (UTC)[reply]

I'm sure there's some good logical reason for the second item. For the first, keep in mind that our bodies are accustomed to operating in warmer weather, and our joints get kind of stiff in colder weather. In baseball, the old expression is "bees in the bat handle". In cold weather, if you don't hit the ball squarely, the bat's vibrations can really hurt - way much more so than in warm weather. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:24, 24 January 2013 (UTC)[reply]

Here is a blog post which discusses exactly the same issue. --PlanetEditor (talk) 11:30, 24 January 2013 (UTC)[reply]

This is OR on my part, but I doubt that's the full story. I think the most important factor by far is temperature. When it is cold, the body tries to maintain core temperature by reducing blood flow to the limbs, allowing them to cool, which makes them stiffer and more susceptible to damage. Looie496 (talk) 18:25, 24 January 2013 (UTC)[reply]

Also with the blood flow reduced - wouldn't the endorphins and other pain relieving chemicals naturally occuring in our body delivered through the blood also be reduced similarly, while the electric signal fires just as quick as warm weather?165.212.189.187 (talk) 19:46, 24 January 2013 (UTC)[reply]

With regard to the electron shells, see Electron shell#History and, for Barkla's original use of K and L to name two of them, the third response here. The other shell names are obviously a continuation of Barkla's initial two. Deor (talk) 13:58, 24 January 2013 (UTC)[reply]

Klebsiella pneumoniae

"is a Gram-negative, non-motile, encapsulated, lactose fermenting, facultative anaerobic, rod shaped bacterium found in the normal flora of the mouth, skin, and intestines It is clinically the most important member of the Klebsiella genus of Enterobacteriaceae."

This sounds like it important to have in our mouth skin and intestines. can someone clarify this, please?165.212.189.187 (talk) 13:36, 24 January 2013 (UTC)[reply]

It is unclear what is meant by "important". The most appropriate place to discuss this would be on the article's talk page.--Shantavira|^{feed me} 14:10, 24 January 2013 (UTC)[reply]

The clinical importance refers to its role in diseases. K. oxytoca and K. rhinoscleromatis have also been found in patients but most (significant) Klebsiella infections are due to K. pneumoniae, I think... Ssscienccce (talk) 02:46, 25 January 2013 (UTC)[reply]

The meaning is that it is normally found in the mouth, skin, and intestines, where it is generally benign, but if it gets into the lungs it can cause pneumonia, which is clinically significant. In other words, the clinical significance comes from the fact that it can cause harm when it gets into the lungs, not from the fact that it commonly appears elsewhere. Looie496 (talk) 00:38, 25 January 2013 (UTC)[reply]

But the article does not use "significant" it uses "important" and in close proximity to the phrase "normal flora". It also doesn't say in the lead that it is harmful in the lungs??GeeBIGS (talk) 07:08, 25 January 2013 (UTC)[reply]

I'm not sure, but it might mean Klebsiella pneumoniae is the type species for the Klebsiella genus. Oda Mari (talk) 07:59, 25 January 2013 (UTC)[reply]

Those not sure about questions need not respond. I thought this was an understood concept.165.212.189.187 (talk) 15:12, 25 January 2013 (UTC)[reply]

Typesetting and the perception of wordy/terse prose

I recently had to switch an unfinished paper from two-column IEEEtran format to AMS. The length went from about 2.2 to about 6.2 pages. (It has 5 equations, 3 lists of variables, and no tables or figures.) Since the AMS template is much closer to what I used as an undergrad, and I was expecting a smaller difference, this means my previous grad-level papers have been a lot longer than I thought compared to my undergrad work.

Have any studies been done on how formatting affects a reader's perception that prose is wordy, concise or terse, or on how much editing and expansion is done to a draft even in the absence of a page-count guideline? Are the effects the same on paper as on the screen? Neon Merlin 14:14, 24 January 2013 (UTC)[reply]

Your question is somewhat surprising, for several reasons. Not the least of which is that all word processors give a word count, university teaching staff usually set assignment papers in terms of word count, and in any case by the time you get to post grad, you should have done at least a few joint projects with other students and thus can see how much everyone else writes. And you should know darn well how efficiently or otherwise you use prose by now.

I'm not familiar with the templates you mention, but I can think of a few things that can sometimes have a surpising effect on the length. Are any paragraph settings Window/Orphan, Keep with next, Keep lines together, and Page break before turned on in the new template but turned off on the old? Thse settings when on can make the page count very sensitive to font types, font spacing, margins, and the like. Averaged over a great number of papers there should not be too much difference, but individual papers can somtimes throw up a huge change, if a certain set of paragraphs just fit on one page, but turning on one of the pargraph settings cause one to jump to the next page - the effect can ripple thru the entire paper.

Further, a good typist/author, like a good typesetter, intelligently uses character spacing settings, kerning, and fractional line spacing settings so as to make best use of a page by making small changes in chosen paragraphs - these changes can be well nigh invisible to the reader except for closing up paragraphs. Such changes are entirely acceptable.

Regarding whether studies have been done - the answer is yes. The choosing of fonts and styling rules is a complex art that book and magazine publishers have long sweated over as it does indeed cause non-rational impressions in the reader about length, verboseness, and readability. Not only it is a complex art, it is subject to fashion, like clothes. What was an "easy read" font or para style years ago is not always regarded as such now. Ever looked at a textbook or periodical published 60 years ago and thought it was verbose? Readers 60 years ago didn't think so. One of the best books I bought, 20 years ago, on this subject, was called The Grey Book. I don't have it now - partly because I learnt what it had to say, and partly because many of its recommendations are now "old fashion". Google art of typesetting and enjoy!

Readability has always been considered worse on screen than on the printed page, when everything style-wise (fonts, spacing, etc) is the same. However, with today's high resolution displays, with black characters on a white background, there is little difference. With today's children growing up with Kindles and computers, I expect before long folk will come to regard printed work not as good.

When papers and book manuscripts are submitted for publication, traditionally editors asked for .TXT files, not word processor files. However, now days, they all accept the major word processor file formast e.eg., Microsoft Word .DOC and .docx files. But the first thing they do is run your submission thru a macro that strips off all your beautiful formating and font choice. They do that for 2 reasons: 1) it gives them a standard "look and feel" so they can objectively assess wordiness, length etc, and 2) when they play with settings to clean it up and make it fit the space they have available for it in their journal or whatever, they don't have to fight with your settings.

Ratbone 124.182.2.156 (talk) 15:36, 24 January 2013 (UTC)[reply]

Sorry, I can't help you on the research you are looking for, but there must be some out there. Some other thoughts: Are these LaTeX formats? Generally, two-column formats are designed to get as many words as possible on the page (to save on printing costs). AMS article format in LaTeX is optimized for readability (have you read the not-so-short guide to LaTeX? It addresses many of these issues). I am not surprised by the conversion you gave. Also, many AMS-style are printed (if they are actually printed) on much smaller pages, which makes the margins more reasonable for a ~80 character line. Generally, you can tell that single-column, double spaced is what is preferred for readability, because that's what all the journals send to their reviewers. SemanticMantis (talk) 17:46, 24 January 2013 (UTC)[reply]

I question the claim:

you can tell that single-column, double spaced is what is preferred for readability, because that's what all the journals send to their reviewers

Another advantage of double spacing is it makes it easier to write comments. So whether the reason for double spacing is due to readability or simply to make it easier for reviewers to make comments would seem unclear.

Nil Einne (talk) 12:12, 25 January 2013 (UTC)[reply]

Double spacing was for many years usually specified for university assignment papers & theses because that provided room for lecturers to make comments and corrections when marking. Similarly, journal and book editors for many years requested double spacing, so they had room for hand marking up with edits and typesetting code marks for the typesetter - eg such and such font here, bold there, etc etc. This only has meaning when the author submits on paper. It has no meaning today when papers and manuscripts are submitted in electronic form, and are editted, marked up, and typeset on computer. It never had, and does not today, have anything to do with readability. Ratbone 120.145.185.57 (talk) 13:23, 25 January 2013 (UTC)[reply]

All of that is going the way of the Dodo though - with electronic media, the reader can have any font, any size, layout and line spacing they want. Studies on readability might have mattered in an era of print media - but we're rapidly moving away from that so any modern study on the subject would be largely irrelevant. These days, the issue with such publications is mostly "How can I know whether I can rely upon this?" - so matters of respectability of the web site you got it from and how they do peer-review...that kind of thing. SteveBaker (talk) 17:09, 25 January 2013 (UTC)[reply]

Inner horizon of a supermassive black hole

Hello, The orders of magnitude article: http://en.wikipedia.org/wiki/Orders_of_magnitude_%28power%29, gives as the greatest power the luminosity of the inner horizon of a black hole. Could I maybe get some more info, as I cant find anything in this direction on Wikipedia. TY.DST — Preceding unsigned comment added by DSTiamat (talk • contribs) 14:27, 24 January 2013 (UTC)[reply]

That seems like kinda sketchy information - it was added (without references) by an IP editor without a long history of editing here. The "inner horizon" (aka the "Cauchy horizon) is some kind of singularity inside the event horizon - where it can't be observed and interpretation of the physics is exceedingly tricky anyway. I'd be deeply skeptical of the reliability of this number without a lot of additional information from reliable sources. SteveBaker (talk) 15:18, 24 January 2013 (UTC)[reply]

I think Red Act was right to delete it. However this is a known issue with the standard interior solutions for rotating and/or charged black holes, as seen in the Penrose diagram on the right of this image for example. Light travels along 45° diagonal lines everywhere on these diagrams. The uppermost point of the diamond labeled "our universe" is the infinite future, whereas the line extending "northeast" from that and labeled as an inner event horizon is not at infinity—you can actually theoretically cross it. This creates the problem that as you cross it you should see the entire future of our universe compressed (blueshifted) into a finite time. Aside from the fact that this would fry you with gamma rays, this is supposed to be a vacuum solution of GR, and there's no way you can claim that an infinite amount of electromagnetic energy can be approximated by a vacuum, or described in GR at all for that matter. For this and many other reasons people don't take these interior solutions very seriously. -- BenRG (talk) 19:02, 24 January 2013 (UTC)[reply]

Thank you for the answer, Mister Baker, I also doubted the number, but is there any kind of information available on this subject? TY DST — Preceding unsigned comment added by DSTiamat (talk • contribs) 16:38, 24 January 2013 (UTC)[reply]

For the maximum luminosity of an accreting black hole, see Eddington luminosity.

All three of the "Orders of magnitude..." entries added by the user that added that entry were either dubious or flat-out incorrect, so I have deleted them. Red Act (talk) 18:02, 24 January 2013 (UTC)[reply]

Wow, so I made my contribution to Wikipedia, but was the idea somewhat feasible? would it be possible to be THAT luminous? maybe the number is way of, but any idea of the actual order of magnitude of this effect? DST — Preceding unsigned comment added by 86.126.81.148 (talk) 19:18, 24 January 2013 (UTC)[reply]

As User:BenRG pointed out - you get into such a relativistic mess as soon as you cross the event horizon that it's simply not meaningful to put numbers against it. eg "the entire future of our universe compressed (blueshifted) into a finite time" could potentially imply infinite amounts of future incoming starlight compressed into just a few seconds (if our universe is infinite in span and duration)...which would mean infinite amounts of luminosity from the perspective of someone crossing the event horizon. That's obviously not the case for an outside observer though. There are so many caveats about where the observer is when the luminiosity is measured - and the literal impossibility of being there to measure it - or even of being affected by it from outside the event horizon...I wouldn't want to put a number on it. SteveBaker (talk) 17:04, 25 January 2013 (UTC)[reply]

body turning to stone

What is the name of the medicial condition for the person's body turning to stone? It's like Scraladermia.205.173.217.10 (talk) 17:41, 24 January 2013 (UTC)[reply]

The hardening of the skin is called Scleroderma. However, the body does not literally turn to stone. That's just some stuff from mythology, creatures like the Cockatrice or the Gorgon. --Jayron32 17:44, 24 January 2013 (UTC)[reply]

Perhaps you are thinking of locked-in syndrome? Bielle (talk) 17:53, 24 January 2013 (UTC)[reply]

See gout and tophus. μηδείς (talk) 18:17, 24 January 2013 (UTC)[reply]

A gorgon is not actually required, but Fibrodysplasia ossificans progressiva is no less fearsome for it. Wnt (talk) 18:29, 24 January 2013 (UTC)[reply]

Let's not neglect Nephrogenic systemic fibrosis. Agree that none of these are "turning to stone". -- Scray (talk) 05:13, 25 January 2013 (UTC)[reply]

Also osteopetrosis (literally "stone bone"). Dragons flight (talk) 12:17, 25 January 2013 (UTC)[reply]

And here I though Osteo Petrosis was a shipping magnate. μηδείς (talk) 19:22, 25 January 2013 (UTC)[reply]

In fantasy fiction, the widely used term is "petrification". —SeekingAnswers (reply) 01:31, 27 January 2013 (UTC)[reply]

Exercise and Sleep

Hi all,

When it comes to sleep and exercise, does the intensity of the exercise generally affect the quality of the sleep? Do higher levels of exercise lead to a higher internal body temperature when sleeping, or dehydrate the exerciser more? Does the time when the exercise is performed mitigate these in any way?

Thanks, Sazea (talk) 20:32, 24 January 2013 (UTC)[reply]

Check this out and see what you think. --Jayron32 20:33, 24 January 2013 (UTC)[reply]

Given that you can cool down to a potentially harmful extent within minutes of finishing exercising (so I heard :) ), and rehydrate fairly adequately within maybe half an hour, I find it extremely unlikely that the body temperature and dehydration issues are relevant. (Unless we're thinking of very young children who can run around like crazy for an hour then suddenly "get tired" and fall fast asleep on chair/sofa/anywhere). Maybe relevant in the sense of it not being a good idea to finish an exercise session and then fall asleep 2 minutes later, but who does that? --Demiurge1000 (talk) 20:51, 24 January 2013 (UTC)[reply]

January 25

Cellular co-transport

I understand the basic idea of co-transport (the passive diffusion of a species, usually an H⁺, Na⁺, or K⁺ ion is coupled with the transport of another species, usu. which the membrane is impermeable to such as glucose, against its concentration gradient). What's confusing me is: a lot of resources I've consulted indicate the use of the energy "stored" in the ion's gradient. I'm not quite getting how this leads to any sort of energy being "stored", because as I understand it, were the membrane permeable, the concentration gradient would be balanced out through random motion of the particles, not some sort of attraction. So where does this idea of energy being built up by an electrochemical gradient come from? Second, if the membrane is impermeable, and transport proteins can change shape upon binding with an appropriate substrate, why is active transport even necessary, since in theory, even if the external concentration were lower than the internal concentration, the membrane and lack of active site on the interior would prevent outward diffusion, while random motion of the molecule outside would lead to it eventually entering the active site anyway (I guess this one is partially related to why is energy required to overcome this gradient, which I guess might be answered if the first question is answered) Bramble claw x 03:49, 25 January 2013 (UTC)[reply]

You're right, the ion concentration would even out due to Brownian motion if it were not actively maintained. I can see why you would question a vague concept of "energy storage", but instead think in terms of membrane potential (that's not a bad article by the way, the first figure caption has a nice simple explanation). It's also not quite right to treat a plasma membrane as either permeable or impermeable, they're selectively permeable. The combination of those two articles gives a more comprehensive answer than I could hope to give here, hope they help! Jebus989 ^✰ 13:31, 25 January 2013 (UTC)[reply]

I think it's the idea of "potential energy" messing me up here. I just had a look at chemical potential, where it's said that "Movement of molecules from higher chemical potential to lower chemical potential is accompanied by a release of free energy". Why? I can understand gravitational potential energy, in that elevating an object means it will have more kinetic energy going down, but I don't understand chemical potential energy, seeing as particles move randomly (as opposed to in a certain direction as would occur in gravity). And yes, I know the plasma membrane semi-permeable, but it is impermeable to ions unless they travel through a transport protein (either passively or actively). What I'm suggesting is that since ions cannot diffuse out, even if the interior had a higher concentration, wouldn't a randomly moving particle outside eventually enter the binding site of the transport protein, which could then change shape (as s result of the bonding of substrate, assuming that's how passive transport proteins (and I don't mean ion channels) work) to add the particle to the already high concentration? Since the particle is moving "randomly", there really isn't anything making it move away from the high concentration. Bramble claw x 03:33, 26 January 2013 (UTC)[reply]

Mathematically, the energy is accounted for by the entropy term in the equation. Since entropy is lower with a concentration gradient than when it's equalized, entropy increases; thus the -TS term becomes more negative, i.e. energy is released. It's statistical in nature. In the absence of an energy gradient for the operation of the transport protein, as with any other reaction it is reversible. Consider a badly designed revolving door, where people coming in go through the door clockwise, but people going out have to go through counterclockwise. Clearly, if the number of people on either side of the door is around equal, the door isn't going to do much turning. On the other hand, if there is a gradient, the door starts rotating, and energy can even be tapped off it to run the escalators (a brilliant old idea of mine) or something. The energy is obviously subtracted from the kinetic energy of the people (who then replenish it muscularly). In the concentration gradient model, the energy comes from the kinetic energy of the molecules, a function of temperature, thus the T which is multiplied by the S. S is analogous to the net number of people going through the revolving door (in minus out), T is analogous to the average velocity of the people passing through. Gzuckier (talk) 06:28, 26 January 2013 (UTC)[reply]

Oh... I was under the impression transport proteins only allow for movement in one direction? Bramble claw x 19:10, 26 January 2013 (UTC)[reply]

To begin with, consider the business of adding water to acid. You have a nice big container half full of concentrated sulfuric acid, you want to dilute it 50-50, so you just fill her up, right? Except, well... the acid gets angry. It turns out that a container half full of water and half full of acid has free energy to give away when they get mixed. I don't think I ever learned the physics of this one, but I assume that the Gibbs free energy remains constant, and G(p,T) = U + pV − TS ; if the entropy S goes up (due to mixing) then the Gibbs free energy goes down, so the solution has to give energy away somehow to meet conservation. So yes, an electrochemical potential contains energy - you can have a little hole in a membrane between acid and not-acid and get energy out of it in various ways, ranging from simple heat evolution in our example to the more sophisticated methods of extracting energy from the mitochondrial proton gradient in cellular respiration. Wnt (talk) 00:30, 27 January 2013 (UTC)[reply]

Different types of pepper

Excluding specific chemical testing, and assuming I'm not interested in the color of the resultant dish, is there any practical reason to add ground black pepper to a stew in which I put ground cayenne pepper? I mean to say, is the taste of the spiciness different enough that there's any real reason to add black pepper assuming I'm already going to be putting in cayenne because I find that black pepper alone doesn't provide a spicy enough taste. DRosenbach ^{(Talk | Contribs)} 03:53, 25 January 2013 (UTC)[reply]

To me the taste is rather different. A quick glance at the articles suggests that the heat is perceived by the same pathway, but there are other aspects of the flavor of these spices besides the heat alone. --Trovatore (talk) 03:56, 25 January 2013 (UTC)[reply]

Black pepper comes from the berries of the Piper nigrum plant, and the heat comes from piperine. Cayenne pepper is from the Capsicum annuum plant, and the heat comes from capsaicin. They have completely different tastes. That being said, in cooking anything that works is OK, so try it both ways and see which you prefer --Guy Macon (talk) 04:04, 25 January 2013 (UTC)[reply]

Absolutely the tastes are different, and they work differently and have different flavor profiles; black pepper has Piperine as its major flavor component, and the heat of black pepper is actually its secondary use; black pepper is (like salt) a flavor enhancer; when used properly it doesn't just add its own flavor to foods, it makes foods taste more, well, more. That is, when you add the right amount of salt and pepper to a steak, you don't taste it as salty and spicy, you taste it as more beefy. When you add it to chicken, it makes it more chickeny and so on. Of course, if you use too much of it, like with salt, it will start to provide too much of its own flavor. Sometimes, in some dishes (like Steak au poivre) the actual flavor of the pepper is what you are going for. But in general, black pepper is an indispensable ingredient in cooking. Watch a cooking show or two. You'll notice they add salt and pepper to like, every single thing. That isn't to make everything taste peppery and salty. It's to make it taste good. Now, Cayenne gets its heat from Capsaicin, which is a different substance, which tastes different and works in dishes differently. Capsaicin doesn't really enhance flavors like piperine does, it is mainly a source of piquancy (spiciness) and nothing else. So, if I'm cooking any dish at all, I add pepper before it is cooked. Not tons, but the right amount to everything doesn't make things taste spicy or peppery. Cayenne, on the other hand, is just about adding spiciness to food. So yes, you would add both as needed, because each serves a different purpose. But as guy says, cooking is about trial and error. Cook the dish multiple times, and tweak it each time. If you like the taste of one over the other (or those you are serving do), then go with that. --Jayron32 04:12, 25 January 2013 (UTC)[reply]

I love Jayrons' answer. But incidentally: Steak au poivre is supposed to be made with crushed raw, green peppercorns and not with the ground up remains of dried black peppercorns. That makes a big difference to the flavor - and also to the texture. SteveBaker (talk) 14:12, 25 January 2013 (UTC)[reply]

I think that's likely to be one of those "my grandma makes it different than your grandma" issues (of course, not many grandmas make steak au poivre, but I digress). There's likely no "official" stance on the type of peppercorns used, but I've not heard that the "true" steak-au-poivre requires green and not black peppercorns. Some variations maybe do, but others do not. I've googled a half dozen different recipes for it, and I can't find any that require that particular stricture. Most just call for fresh cracked black peppercorns. A few of the more snooty ones recommend mortar-and-pestle treatment, but that's about it. --Jayron32 14:19, 25 January 2013 (UTC)[reply]

You fancy-schmancy Wikipedia types with your "reliable sources" and your "looking it up". In my day we just pulled an answer out of a hat, and if anybody said we were wrong we called him a Nazi Pedophile Bed-wetter and made fun of his spelling. Young whippersnappers have no appreciation for the old ways -- now get off my lawn! --Guy Macon (talk) 18:35, 25 January 2013 (UTC)[reply]

Like. Best. Answer. Ever. --Jayron32 22:41, 25 January 2013 (UTC)[reply]

You had hats? You softies. Wait'll I tell you where we had to pull our answers out of. Gzuckier (talk)

Why do we cry?

Why do human shed tears when in distress? Do any other animals also do so? --Yashowardhani (talk) 06:26, 25 January 2013 (UTC)[reply]

Have you read the Wikipedia article titled Crying? --Jayron32 06:50, 25 January 2013 (UTC)[reply]

(Wow! That's a great read!) SteveBaker (talk) 14:05, 25 January 2013 (UTC)[reply]

See also, Crying, which can induce crying. μηδείς (talk) 19:46, 25 January 2013 (UTC)[reply]

My unWikipediable opinion is that the biochemical arguments (release of toxins or hormones or whatever) mentioned in the article aren't sustainable in the face of questions re evolution (why don't other animals need to get rid of their toxins and hormones) and physiology (there are plenty of more efficient ways in which the body gets rid of stuff without needing a few ml of not very concentrated tears). My guess would be a byproduct of our neoteny/paedomorphism; our retention of infantile characteristics into adulthood, a typical way in which mammals (at least, maybe other animals too) evolve reduced aggression and increased social cohesiveness past puberty, and a characteristic well documented in our particular species of ape. In that view, the crying and the attendant concern, assistance, and/or reduction in aggression from other humans is a retention of the similar reaction humans have to a crying baby, which is of obvious evolutionary value. Now that you've made me think about it, I'm going to have to see if there are any citable third party refs that have similar ideas that I can cite in the crying article..... Gzuckier (talk) 07:06, 26 January 2013 (UTC)[reply]

Prenates and Being Alive

scientific answers have been addressed, and this has degenerated into debate

The following discussion has been closed. Please do not modify it.

Do prenates (zygotes, embryos, and fetuses) meet all of the seven characteristics of life? In regards to homeostasis, aren't embryos before implantation able to survive in a petri dish (without using anyone else's body to sustain themselves)? In regards to reproduction, can't zygotes reproduce asexually by division for 14 days or something like that? Thank you very much, and please provide sources if you are able to. Futurist110 (talk) 08:44, 25 January 2013 (UTC)[reply]

Just a note that "able to reproduce" is a tricky one to apply. Neonates cannot reproduce, nor can infertile adults or woman past menopausal age, but we classify all of these as alive. 86.163.209.18 (talk) 10:24, 25 January 2013 (UTC)[reply]

Life is not an absolute well defined thing any more than a table or the colour blue is. However by most definitions such cells are alive. I don't know what your particular list of seven features to look out for is but for any such lists you'll have people pointing out fairly obvious things that should be included and others which shouldn't - but they are normally for things like viruses or memes or cells that have been frozen. Try giving a good complete definition of a table first and see if you can do it in 100 words or less without finding exceptions. Dmcq (talk) 10:38, 25 January 2013 (UTC)[reply]

Just because a zygote is able to survive in a petri dish dose not mean it's capable of homoeostatic regulation, as temperature, humidity and atmosphere are all controlled, or it would last very short indeed. As for asexual reproduction, the only thing that sort of comes close is the formation of monozygotic twins, which occurs at the fertilised oocyte stage, not later. And I second Dmcq, what is your particular list, and why is it better than anybody else's? Fgf10 (talk) 10:42, 25 January 2013 (UTC)[reply]

By the same token, a neonate left in a bed by itself will not survive for very long, nor would any of your body cells even though they are alive. I imagine Futurist is working from the standard "seven signs of life" taught in schools, often summarised by "Mrs Gren", which I would expect anyone who has studied biology to have learnt and examined before learning its weaknesses and issues, just as Futurist is doing. 86.163.209.18 (talk) 12:59, 25 January 2013 (UTC)[reply]

Do you mean the The Seven Pillars of Life? If so, it's a fairly recent conception. There are other seven signs of life I find out there, but from what I can tell, they aren't covered anywhere on wikipedia which IMO tells you how much significance they have to real world biology. I did biology in university, but never learnt any 'seven signs of life' that I recall (most of these 'seven signs of life' I find seem to be targeted as secondary school level biology which I also did but don't recall learning it there either). Nil Einne (talk) 13:11, 25 January 2013 (UTC)[reply]

No, that appears to be about some recent author's invented terms and categorisation. "MRS GREN" has been taught in both primary and secondary schools for at least several decades, and unpicking it and uncovering its weaknesses is a common way of getting secondary school pupils to think analytically about categories and empirical evidence. 86.163.209.18 (talk) 14:54, 25 January 2013 (UTC)[reply]

Some primary and secondary schools sure. It's definitely not a universal thing as your reply suggested. Nil Einne (talk) 17:45, 25 January 2013 (UTC)[reply]

Likewise, I've never heard of this, and I'm a biomedical researcher. Probably an American thing that never made it across the pond. Don't assume everybody is taught the same thing as you are, especially not when it's something as meaningless as that. And use of a slightly less condescending tone would be appreciated.

Now on the science front, I was not debating the definition of life, but of homoeostasis. A cell of my body is not able to maintain homoeostasis, not is a neonate capable of full homoeostasis, as it is limited in thermoregulation. Fgf10 (talk) 14:59, 25 January 2013 (UTC)[reply]

Nope, not a speck of American. If you read condecension into my tone, it was probably my annoyance at your comment sounding quite hostile ("why is it better than anyone else's") to someone who was asking a typical question that fits with an extremely common list taught to children, indicating that you were probably being snippy to a teenager asking a scientifically curious question that was completely appropriate to their stage in education. If you had googled their terms, you would probably have found some likely looking lists, and the clues that this is something taught to children at a certain stage in their education. 86.163.209.18 (talk) 15:05, 25 January 2013 (UTC)[reply]

I was meant calling it by some corny name like "The pillars of life", not of the phenomena themselves, which (although as flawed a definition as there are), are know quite widely indeed. Fgf10 (talk) 15:19, 25 January 2013 (UTC)[reply]

There are some things in science that do not have precise definitions because they are inherently "fuzzy" - and "life" is one of them. "Planet" is another word like that - hence the arguments over whether Pluto is a planet - which has nothing whatever to do with Pluto - and everything to do with the effort to apply a sharp division to a continuous range of phenomena.

At some age, if you remove a foetus from the womb, it'll die instantly without a lot of intervention. A little later and it'll survive for a few minutes, later still, a few hours. When a baby is born at term, it'll survive for maybe a day without food and attention. When you're 40 years old, you'll still die after a few days to a week without water and after a month or so without food. There is no hard line that defines when an organism is independently alive because we all need support systems of one kind or another.

We know that a rock is definitely not alive - and that an adult human definitely is - but there are just so many grey areas in between that no one set of rules can possibly draw that sharp line that you're looking for here. These "seven signs" lists (and many, many other efforts to define "life") work reasonably well when applied to an entire class of objects. Take, for example "Reproduction": We know that humans (as a group) can reproduce - so humans are generally considered to be "alive". However, I know quite a few people who can't reproduce - they are too old, or have had irreversible surgery to prevent them from reproducing. These people don't pass the "Reproduction" test - but we consider them to be "alive" because they belong to a general class of "alive" objects..."Humans". Doing the same thing for viruses is really tough - and so it's becoming for so-called "a-life" (artificial life made inside a computer) - or various efforts to make artificial cells in the laboratory.

At these fuzzy grey boundaries, this word is utterly arbitrary and using it to drive some kind of hard binary decision is fraught with difficulties. Hence the abortion debate here in the US - which (from a scientific perspective) is a completely fatuous argument because it is entirely about the meaning of a word that has no meaning in this realm of existence.

So there is no answer to the OP's question - nor should there be. The best response is to un-ask the question: "The word 'life' has no meaning at these levels of existence"...and I think that's the best answer you'll get here today.

SteveBaker (talk) 13:58, 25 January 2013 (UTC)[reply]

To take SteveBaker's excellent analysis of the situation and add to it a bit; at best we have a definition for LIFE, in the sense of the entire system; we have a good concept of what the entire living system is and how it works, even the "edge cases" that SteveBaker notes above clearly fit into the "Life" classification; viruses, for example, did not arise on earth via geologic processes; they are part of the "living system" and are integrated into it. Absent the same system that created you and me, viruses would not exist. The problems come with coming up with any sub-classification of life that doesn't apply to the whole system. Once you try to define what it means for some part of the system to be a "living thing" you run into all sorts of problems. Even groupings of life run into the Species problem, concepts like ring species throw what should be the simplest classification concept (what is a species?) into a tizzy. The virus problem is itself another definition issue (are viruses alive and are viruses life are different questions, and possibly get different answers), as is the "when is a fetus alive" question. The answer is there is no absolute meaningful line that can be drawn which is beyond dispute. Any definition will defy consistency. Which isn't to say that any moral, ethical, or legal questions which arise are somehow invalid, but it does mean that people need to look for somewhere other than the scientific answers for resolving the moral, ethical, or legal conundrums surrounding the issues of what life is. --Jayron32 14:15, 25 January 2013 (UTC)[reply]

Woah woah woah, surely nobody argues that a foetus isn't alive. All the cells in your body are alive. A foetus is definitely alive, just as it is definitely human. The debate on a reasonable level is whether it is an independently living being, and whether it is a person. Nobody would dispute that the cells in your heart are both alive and human (barring an interspecies transplant), but obviously your heart is not an independent living thing, nor is it a person. A neonate is generally considered not only alive and human, but an independent living thing and a person. The debate is at what point between "egg and sperm" and "human being doing algebra" you consider the living cells to become a separate human person. The "is a foetus alive?" thing is very much just a "discover the limits of definitions of life" task. 86.163.209.18 (talk) 14:50, 25 January 2013 (UTC)[reply]

That's pretty much what Steve and I both said in different words. When someone asks "is a fetus alive", or "is a virus alive" or something similar the double question implied, but unasked, is "what is alive". Even the notion of "independent life" depends on a given definition of "independent". Another unasked question inherent in these sorts of discussions is "when is it morally OK to end life", and people often try to skirt the tough answer by establishing thick black lines where they can carefully say "well, that's not really alive, so it's not even a moral question, it's a scientific one". On the contrary, there isn't a good black line we can draw for a fetus where we can say "at this point in time, it is worthy of the same treatment as an adult human, but before this moment, it isn't any different than a fingernail clipping or any other discardable living tissue" That line does not exist, and the moral dilemmas about what sorts of "life" is accorded what sorts of "rights" is simply not a question one can answer by looking for hard-and-fast "scientific" definitions. It's the sort of thing that individuals and societies need to constantly wrestle with, and you can't shortcut the hard moral problem by looking to "Science" to provide convenient easily definable boundaries. --Jayron32 14:58, 25 January 2013 (UTC)[reply]

Right - and for the abortion debate, the rational science-based solution is to recognize that this is not a black and white situation with 'bright line' definitions - and instead say that the circumstances for allowing an abortion should narrow progressively starting from conception (when it should be ridiculously easy) to the last trimester or so (when it should obviously be illegal). A gradual scale where it would require more and more extenuating circumstances and increasing levels of oversight to allow it would permit a rational balance between the rights of the unborn and the needs of the mother - and a kind of infinitely adjustable scale that could be adapted as new science and the needs of society are updated over time. But here in the USA that kind of debate is impossible because both sides are in entrenched positions and dare not give up an inch of ground. If we had such a sliding scale, the stakes for each small update to it would be much smaller - so debate would be less partisan - and without the demand for an impossible "bright line" answer, science could provide rational input to the decision process. SteveBaker (talk) 16:35, 25 January 2013 (UTC)[reply]

I don't think there should be any doubt that zygotes are alive, and if they don't meet every aspect of a definition, that casts doubt on the definition. Certainly anyone at an in vitro fertilization clinic would make a huge distinction between a live zygote and a dead zygote; put it that way. However, even a live human may not be alive in terms of consciousness, and thus in the legal sense, as evidenced by brain death. But people still are very careful to preserve the life of organs taken from a brain dead donor. I dislike these definitions of life for many reasons, not the least of which is that they seem to make it harder rather than easier to reason through simple exercises like this. Wnt (talk) 16:24, 25 January 2013 (UTC)[reply]

The problem with these "fuzzy-reality/bright-line-words" problems ("Is a foetus alive?", "Is Pluto a planet?", "Is my cat intelligent?") is that they aren't matters of science. The science of these things can often be perfectly well understood - but we're stuck with problems that are purely linguistic in nature. That's often OK - there are branches of science where we only care about the 'aliveness' of rocks and of people - and the word "life" is perfectly well-defined and understood. But when it comes to asking "Is Pluto a planet?" - then we can't answer and we should not attempt to do so.

The correct response to that question (and to to this one) is "Why do you care?" - and generally, the reply to that is what enables us to come up with a rational response. In the Pluto question - perhaps some university "Department of planetary studies" needs to know whether they are allowed to spend money studying that particular rock? Maybe a museum is putting together a model of the solar system to hang from the ceiling and needs to know whether to include Pluto or not? The answer to those questions shouldn't hinge on some bizarre and artificial description relating to circularity of orbits or Pluto's ability to clear other bodies from it's region of space! Those are ridiculous criteria for deciding those questions - yet, the "bright line" definition of "planet" that we now have has indeed been used to decide those two matters...and it's ridiculous!

So the actual underlying reason for asking the question is what is important. So in this question - is the OP really asking about the appropriateness of abortion laws or something else? The answer to whether some arbitary definition of a word in the English language applies or not tells you nothing whatever about the answer to the actual scientific or moral problem that the OP is trying to resolve. So we should find out what is really being asked and - if it is a scientific matter - endeavor answer that question instead.

SteveBaker (talk) 16:52, 25 January 2013 (UTC)[reply]

This got me thinking: how many mothers who are contemplating abortion would go through with it after they watched a 20 min video of those new hd ultrasounds of their fetus? I'll bet the mom would say "that's alive" after watching it.165.212.189.187 (talk) 17:44, 25 January 2013 (UTC)[reply]

Whether we consider this complex decision-making issue from the legal standpoint, or from the scientific standpoint, or from the moral standpoint; establishing "alive-ness" is neither necessary nor sufficient for basing a decision. Furthermore, watching a video of something doesn't even establish "alive-ness." (Did you read any of the discussion above about how subtle the definition is, and how difficult to pin down it can be in certain circumstances?) Nimur (talk) 18:50, 25 January 2013 (UTC)[reply]

Tell that to every person who ever saw one of these videos.165.212.189.187 (talk) 19:22, 25 January 2013 (UTC)[reply]

The emotion reactions of a person who is pumped full of mood-altering hormones when faced with an image with many parameters that were chosen by an engineer is a poor basis for making public policy decisions. And your use of the term "alive" just highlights the fuzziness everyone is talking about. I had a kidney removed a few years ago. I saw an ultrasound of it first. I would say that it was alive. I would also say that it was human (not a human, but definitely a human kidney). And, assuming a some reasonable advances in cloning technology, it had the definite potential to become an adult human being. And, of course, the elephant in the room is that some people, for religious reasons, believe that there is a bright line and no fuzziness at all. --Guy Macon (talk) 19:03, 25 January 2013 (UTC)[reply]

You might want to investigate the more relevant concepts of person and organism next time you are bothered by the notion of murdering your kidney. Rather a bright line there. μηδείς (talk) 19:19, 25 January 2013 (UTC)[reply]

I am not trying to load my question. I am simply adding to the thought process. If you can get the mother to watch that and still choose to do it she would not be fit to be a mother anyway, if she was swayed by it to have it, surely no one would make her get an abortion. Guy, you obviously never saw a video of what i described, or you surely would not compare it to a fetus, wow. should we feel sorry for your kidney that it didn't get a chance to be colonized into a baby?165.212.189.187 (talk) 19:16, 25 January 2013 (UTC)[reply]

At this time, it is clear that 165.212.189.187 is not requesting a science reference, and is seeking to start a debate. Please feel free to find an alternative internet forum to discuss this issue, which is very nuanced. The Wikipedia Science Reference Desk is not the correct place to have that discussion. Nimur (talk) 19:37, 25 January 2013 (UTC)[reply]

No, nimur, if you read my question I am asking it is purely scientific: how many mothers after watching the video would still get an abortion? Hypotheticals are asked all the time here. Anyone?165.212.189.187 (talk) 19:49, 25 January 2013 (UTC)[reply]

Closed per Baker, Nimur, myself. μηδείς (talk) 20:15, 25 January 2013 (UTC)[reply]

I disagree with closing this. Perhaps a few people veered slightly off topic, but the scientific question about the definition of life is perfectly valid. More sources (or at least wikilinks) per paragraph might help defuse things. Wnt (talk) 23:15, 25 January 2013 (UTC)[reply]

Closure doesn't imply a problem with the responses, just with continuation of debate. Your position on medical issues is well known. If you want this re-opened, open a discussion at the talk page. μηδείς (talk) 23:23, 25 January 2013 (UTC)[reply]

Agree fully with the closure. As soon as I saw the "not be fit to be a mother" comment I realized that this was not a science question. --Guy Macon (talk) 23:28, 25 January 2013 (UTC)[reply]

The person who said that was 165.212.189.187. The OP was Futurist. Just saying. --140.180.242.224 (talk) 23:54, 25 January 2013 (UTC)[reply]

like I said scientific — Preceding unsigned comment added by GeeBIGS (talk • contribs) 00:13, 26 January 2013 (UTC)[reply]

and here GeeBIGS (talk) 00:15, 26 January 2013 (UTC)[reply]

the ultimate point of my argument is that the mother can be the compass for finding that thin line that everyone is talking about. It is such a delicate subject that who better than "where the rubber meets the road" to guide the less informed and ignorant nonpregnant talkers.GeeBIGS (talk) 00:23, 26 January 2013 (UTC)[reply]

Poor eyesight and the black death

I remember reading somewhere on the internet that the reason there are so many short sighted people around, despite the obvious evolutionary disadvantage, is that whatever genes contribute to shortsightedness, also make one less likely to die from certain diseases (I thinkt he black death was referenced, not sure though). I can't remember where I came across this I can't find anything to support this idea in a google search now. Is there anything to this idea? — Preceding unsigned comment added by 89.101.203.150 (talk) 20:24, 25 January 2013 (UTC)[reply]

Shortsightedness has been attributed to the rise of farming (as opposed to hunting) and its prevalence in the Chinese with an old farming civilization been given as evidence. I've never heard anything about black death genes, but the plague did hit denser farming societies worse, so perhaps there's a correlation, if not a cause. μηδείς (talk) 20:33, 25 January 2013 (UTC)[reply]

Our article is surprisingly disappointing on the origin question, both about individual and population genetics. If anyone has some sourced info on this I'd be very interested as well. Shadowjams (talk) 05:24, 26 January 2013 (UTC)[reply]

Maybe if you're nearsighted you're more efficient at picking the infected fleas off your body.Gzuckier (talk) 07:11, 26 January 2013 (UTC)[reply]

I don't see how farming could give rise to shortsightedness; what I heard (though I don't have any references I'm afraid) was that it is a consequence of reading and writing and perhaps a generally indoor lifestyle.--Shantavira|^{feed me} 09:58, 26 January 2013 (UTC)[reply]

The argument was not that farming causes poor eyesight, but that it allows people who, if they would otherwise be poor hunter-gatherers, to survive by farming. μηδείς (talk) 18:55, 26 January 2013 (UTC)[reply]

Recent research would suggest that a lack of sunlight is a cause of myopia. However, reading the CNN article, I don't see much evidence that the correlation with sunlight exposure is stronger than with the amount of near work (reading). Specifically, they find more myopia in highly urbanized, academically focused regions, but they didn't find differences between Scandinavian and Southern Europe regions. If they find correlation with being "academically focused" and based on that assume a (reverse) correlation with the amount of time spent outside, yet they don't find a correlation with the amount of sunlight available, then why propose a relation with exposure to sunlight anyway?? Remarkable that we haven't got a more definite theory yet for such a widespread condition. Is it perhaps because any "cure" would likely have detrimental effects? Can't imagine a policy recommending allowable daily intake levels for books... Ssscienccce (talk) 11:15, 26 January 2013 (UTC)[reply]

Tidal locking planets

Why are there many tidally locked moons in our solar system, but no planets tidally locked to the sun? Tarcil (talk) 20:26, 25 January 2013 (UTC)[reply]

Have you read about Mercury's spin-orbit resonance? Nimur (talk) 20:28, 25 January 2013 (UTC)[reply]

Thanks ... But it looks like it is only Mercury, and only partially. Why so rare compared with moon tidal locking? Tarcil (talk) 21:54, 25 January 2013 (UTC)[reply]

I was going to speculate that the gravitational gradient is smaller in the case of the planets, because the planets are so much smaller than the sun, but then I thought about Deimos... --Guy Macon (talk) 22:03, 25 January 2013 (UTC)[reply]

how dare you speculateGeeBIGS (talk) 00:29, 26 January 2013 (UTC)[reply]

I would guess that it's because the planets are much farther away from the sun than moons are from their planets, so that the sun exerts a lower gravitational acceleration on the planets than the planets do on their moons. Taking orbital period as a measure of the gravitational acceleration seems to bear this out. In the List_of_gravitationally_rounded_objects_of_the_Solar_System, the planet with the shortest orbital period is Mercury, with ~88 days. The moon with the longest orbital period is ~~Callisto, with ~17 days~~ Iapetus, with ~79 days, and all the moons listed are tidally locked.--Wikimedes (talk) 03:54, 26 January 2013 (UTC)[reply]

Tidal_locking#Moons says about the same thing.--Wikimedes (talk) 05:18, 26 January 2013 (UTC)[reply]

Cool, thanks - Tarcil (talk) 03:35, 28 January 2013 (UTC)[reply]

Can insects get angry?

Topic says it all. ScienceApe (talk) 20:48, 25 January 2013 (UTC)[reply]

"Anger" describes an emotion, but it seems all that we can observe from insects is behavior, especially since their manner of communication and expression is so different from our own that it's hard to draw parallels. However, here is an article describing attempts to detect emotions in bees. Insects can certainly become aggressive, but that doesn't necessarily imply anger, like we can't deduce from a bee's 'dance' that she is happy. - Lindert (talk) 21:04, 25 January 2013 (UTC)[reply]

What's the practical difference between emotion and behavior? Doesn't emotion just promote a certain kind of behavior? ScienceApe (talk) 00:41, 26 January 2013 (UTC)[reply]

There's a huge difference. You can have an internal emotional sensation, but that internal process is not required to cause a specific course of action. A person may get angry and yell, or punch someone, or may in fact do nothing; but their actions are not directly tied to that emotion. A person may show no outward signs of an emotional response, but it doesn't mean they didn't have it. --Jayron32 01:20, 26 January 2013 (UTC)[reply]

That's the basic difference between a feeling and an emotion. Feelings that are expressed are emotions. Feelings that are unexpressed are just feelings. (I always laugh when I'm told someone was "visibly emotional"). There's one school of thought that it's impossible not to express a feeling, even if it's virtually entirely internalised. Highly skilled observers say they can always detect a feeling, because the energy required to suppress its expression is apparent in other ways, however minuscule. Then it's down to the visual acuity of the observer, and their knowing what to look for. -- Jack of Oz ^[Talk] 22:15, 26 January 2013 (UTC)[reply]

I am not aware of this distinction. Could it be an Australian thing? I'm fairly certain there is no such distinction in American English, and the Wiktionary entry doesn't mention it. --Trovatore (talk) 22:22, 26 January 2013 (UTC)[reply]

Think of it this way: If you're talking on the phone to someone who's describing their emotional state, all you know is what they say and the tone of voice they use. They might say "I feel angry that abc happened"; they'll never talk in terms of "emotions". Now, observe someone who's clearly angry; you know this by the lack of calmness in their actions. This exhibition is the emotion, and that's why people say someone was "visibly emotional" (all they really need say is they're "emotional"); observers never report on the "feelings" of emotionally distressed people, only on what they can see, i.e. their emotions. What they're feeling internally is the feeling that caused them to act this way. If you want a reference, this is as good as any.-- Jack of Oz ^[Talk] 06:49, 27 January 2013 (UTC)[reply]

Well, honestly I don't find any coherent assertion in that reference, but whatever distinction they're making, it does not appear to be the same as yours. Yours at least makes sense, though I don't agree with it. Theirs, as far as I can tell, doesn't.

In any case, our article does not use the word in your sense. It says explicitly that emotion is a subjective experience. --Trovatore (talk) 10:34, 27 January 2013 (UTC)[reply]

can chimps get angry? Can humans get angry?GeeBIGS (talk) 01:00, 26 January 2013 (UTC)[reply]

I think the key word you should check out is "Anthropomorphism". ~:74.60.29.141 (talk) 03:00, 26 January 2013 (UTC)[reply]

If you check out emotion which mentions non human animals a few times, you'll find we also have an article on Emotion in animals which doesn't mention insects but primates. Nil Einne (talk) 03:32, 26 January 2013 (UTC)[reply]

I think we can answer this with a definite "No!", I don't think it's possible that they could have an exactly comparable emotion. Our article on anger says that the defining characteristics of anger in humans is raised blood pressure and the release of adrenaline and noradrenaline. Insects don't have blood (they have hemolymph) and their circulatory system is wildly different from ours - so it's extremely unlikely that they'd get higher pressure in those systems for similar reasons - or that it would feel the same to them as high blood pressure does to us if they did. Worse still, as far as I can tell from cursory research, insects produce neither adrenaline or noradrenaline - and they don't seem to have any analogous hormones. So really, they can't possibly feel what we do. Obviously there may be some analogous "fight or flight" reflex - but it would be a massive stretch to assume that they'd feel it the same way we do when it happens because all of the responses in humans cannot possibly happen in insects. SteveBaker (talk) 05:35, 26 January 2013 (UTC)[reply]

Whilst agreeing with the accuracy of answers by Steve and others above, anyone who has disturbed a nest of bees, wasps, hornets (etc) cannot help but observe that the aggressive defensive behaviour of these insects certainly makes humans feel that the insects are angry! Dbfirs 08:32, 26 January 2013 (UTC)[reply]

It has been established for considerable time that the emotions, especially anger, arise from and are behavior modes set by a part of the brain that arose early in evolutionary terms. According to my dictionary, anger means hot dipleasure; often invoving a desire for relaliation; inflamed; irritated; excited with anger; of threatening aspect. That certainly describes those bees etc Dfiers mentioned. There's nothing in this definition that requires self awareness or behaviour that is not instinctive. It also describes exactly a species of ants that live in my back yard, when I poke at stick into their nest entrance. Being ants, I'm certain that they don't have self-awareness like higher mammals and humans, but they certainly do get angry. They normally don't bite if you stand gently within 100 mm of the nest entrance, but if you poke a stick in their nest entrance, they'll search outwards 500 mm or more and they will bite. Further, W Grey Walter (British neuroscientist - see http://en.wikipedia.org/wiki/Grey_Walter) showed 60 years ago that a robot brain showing stimulus-triggered emotions can be constructed with nothing more than two radio valves and a handfull of basic electronic parts. So, insects have well and truely sufficient neurons to do the job. Of course they get angry. Ratbone 124.182.17.177 (talk) 10:54, 26 January 2013 (UTC)[reply]

You maybe don't need self-awareness to have emotions, but you do at least need phenomenal consciousness, aka qualia. Attributing "emotions" to a couple of vacuum tubes strikes me as a deliberately reductive redefinition of the word. --Trovatore (talk) 22:04, 26 January 2013 (UTC)[reply]

Bees (like most creatures) are programmed to defend themselves and their groups. We can't ever know what's in the mind of a creature so far removed from the human creature. We associate their buzzing with "anger" - but their buzz is simply caused by their wings. Likewise, we talk about storms as if they were living things: "angry" clouds, etc. This is how folk religions arose - anthropomorphism, as noted earlier. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:45, 26 January 2013 (UTC)[reply]

I don't agree that "We can't ever know what's in the mind of a creature so far removed". If we do brain scans on angry people, and see what parts of the brain are active, then do a scan of "angry" bees, and see the same spots are active, this is a good indication of a similar process. StuRat (talk) 17:58, 26 January 2013 (UTC)[reply]

Um, "brain scans" of bees and "same spots active" as in people makes no sense. Bees don't have a central nervous system that has any major analogous parts to humans in any way. You might as well try to figure out if humans can fly by examining the structure of human wings, or try to figure our how humans use their antennae. --Jayron32 18:08, 26 January 2013 (UTC)[reply]

Don't they have brain stem, at least ? They must have visual, audio, and smell/taste/touch processing areas, too. StuRat (talk) 23:09, 26 January 2013 (UTC)[reply]

See http://insects.about.com/od/morphology/f/Do-Insects-Have-Brains.htm Richerman (talk) 23:35, 26 January 2013 (UTC)[reply]

For study of insect brains, it can be more convenient to observe activity in visible wavelengths using a dye for calcium imaging. See [5]. For a comparison of insect and vertebrate CNS development, see [6]. (For that matter, anything in [7] is bound to make good reading!) Wnt (talk) 00:14, 27 January 2013 (UTC)[reply]

This is a pretty interesting topic. The spinal cord and a bit of the brainstem can be matched between insects and vertebrates on the basis of gene expression patterns. For higher brain areas the picture is more complicated. Recently, though, there has been a plausible claim that a structure in the insect brain called the mushroom bodies is homologous to the cerebral cortex of mammals. But none of this would be helpful in assigning emotional states to insects. Looie496 (talk) 01:20, 27 January 2013 (UTC)[reply]

Tracking the limbic system among vertebrates was apparently no simple task.[8] I'm having quite some difficulty finding a paper willing to mark the spot on the bee brain that corresponds. My gut feeling is that there is such a spot... Wnt (talk) 19:12, 27 January 2013 (UTC)[reply]

Danceable pulsars

Where can I find information on individual pulsars with a period between 0.45 and 0.55 seconds? Better would be audio recording of clicks from such a pulsar. Really awesome would be a live feed of those clicks. Thank you! Rotcaeroib (talk) 22:35, 25 January 2013 (UTC)[reply]

The nearest I can find for you is PSR J0357+3205 which pulses with a period of 444.10 ms (ref). You won't get a live feed, because someone would have to be pointing a radio telescope right at one just when you need it, and they'd surely want to be pointing their radio telescope at other things instead. To get an idea of the actual signal that comes from such a pulsar, see the plot on p24 of this paper. That's not a playable audio waveform in itself - you'd need either to use it to modulate a tone or, with a level trigger, as a MIDI event gate. To get the actual raw signal received from a given pulsar, you may have to contact the research groups using an instrument like Fermi Gamma-ray Space Telescope and see what they have. -- Finlay McWalterჷTalk 01:00, 26 January 2013 (UTC)[reply]

Some pulsars outside of your chosen rangfe seem danceable...

http://www.youtube.com/watch?v=uHEVo-LkDrQ

http://www.youtube.com/watch?v=gb0P6x_xDEU

http://www.youtube.com/watch?v=ZHv_eE2bvSs

http://www.youtube.com/watch?v=HSyRMotOhoM

http://www.astrosurf.com/luxorion/audiofiles-pulsar.htm

http://www.astro.cornell.edu/~deneva/psr_sounds/pulsars_sounds.htm

http://www.radiosky.com/rspplsr.html

--Guy Macon (talk) 08:49, 26 January 2013 (UTC)[reply]

If you're interested in danceable astronomy, you may want to check out this. A fascinating lecture which I was lucky enough to attend "live" (one of the few benefits of living in Waterloo is the close proximity of the Perimeter Institute). Matt Deres (talk) 15:54, 26 January 2013 (UTC)[reply]

This is a pulsar catalog, and is as complete as you're likely to get. You can filter by period (p0 > 0.45 && p0 < 0.55), and see exactly what data is available for each pulsar. There seems to be around 200 pulsars that fit your criteria. --140.180.242.224 (talk) 19:10, 26 January 2013 (UTC)[reply]

January 26

Opel truck

What's the maximum number of people that can squeeze into an Opel Blitz truck? Thanks in advance! 24.23.196.85 (talk) 01:38, 26 January 2013 (UTC)[reply]

The German article (de:Opel_Blitz) has technical specifications, including maximum weight, and sizes, for various truck models. Those should help you set some reasonable bounds. Nimur (talk) 01:45, 26 January 2013 (UTC)[reply]

It has no specs for any of the WW2 models -- and those are the ones I want to know about. 24.23.196.85 (talk) 02:03, 26 January 2013 (UTC)[reply]

If you're wondering about the ability to move soldiers in WWII, the answer is "how desperate are you?". If you're not worried about things like "safety" or "keeping the truck working next week", you can fit a rather incredible number of people on one truck. On the other hand, for routine operations, a good rule of thumb is that one truck can carry one squad of soldiers with full equipment. --Carnildo (talk) 02:17, 26 January 2013 (UTC)[reply]

Thanks! ~~And would 12 soldiers be a squad?~~ The article says it would be. 24.23.196.85 (talk) 03:42, 26 January 2013 (UTC)[reply]

Its supply carrying capacity is more important than its infantry carrying capacity. 3 tons. There are space for 10 seated facing each other in the back, from seeing one.--89.101.197.30 (talk) 14:25, 26 January 2013 (UTC)[reply]

Echoing 89's comment, supply capacity really is a far more interesting number than troop capacity. The WW2 German Army was, on the whole, very poorly mechanized. Our Horses in WW2 article notes that a standard German infantry division had about 250 trucks (and 2,500 horses) for about 20,000 troops. While you can put troops in those trucks, you obviously can't put anywhere near all of them in, and that leaves your division moving at foot speed -- de-emphasizing the troop-carrying capabilities of the truck. The Panzergrenadier divisions were well-mechanized (and far more closely resembled the majority of British and American infantry units in that regard), but there weren't many of them. — Lomn 15:54, 26 January 2013 (UTC)[reply]

For me personally, troop-carrying capacity is more interesting -- my actual question was whether a total of 12 French Resistance fighters could fit into an Opel Blitz, and whether there would be any room left for a few concentration camp escapees to share space with the dozen Maquis on board. 24.23.196.85 (talk) 04:55, 27 January 2013 (UTC)[reply]

I'm sure that in an extreme need, you could fit that many people into the truck. It wouldn't be comfortable - but it's clearly possible. The thing about vehicles of that era is that they typically had very low horsepower compared to modern vehicles. That German article says that the 1945 version produced 73.5 hp and weighed 5,500lb. Compare that to a comparably heavy, modern Ford Explorer (280hp, 5,000lb!) - and you can see that despite weighing a little more, the 1945 Opel has less than a quarter of the power-to-weight ratio of a modern 'people carrier'. Put 15 guys in there (let's say 150lb each - maybe 200lb with weapons & packs...3,000lb total) and the truck now has maybe a sixth of the power-to-weight of a modern truck. The German wikipedia article says it has a maximum payload of 7,200lb - so the frame and suspension could easily manage even 30 people. Of course your Opel must be a yet older model - so I'd expect similar weight but even less horsepower...but it would be nice to know those two figures to be sure.

But with such an awful power-to-weight ratio, instead of 0-60mph in 12 seconds(ish) in an Explorer - your acceleration in a heavily loaded 1945 Opel is going to be 6 times worse! In reality, it wouldn't ever reach 60mph - but if it could, it would take a minute and a quarter with foot mashed to floor to get there! So what would happen would be that the thing would have very poor performance - you'd probably have to drive it in a lower gear, keep your speed around 30mph and go up hills at walking pace in 1st gear - and you might have to have the guys get out and push on a really steep road...but that's how trucks were driven back then. But in low gear, I'm sure it could manage. If the people would physically fit in there - I'm sure it would carry them OK. In times of great pressure, I'm sure our brave Maquis would be happy to hang on the outside - lay on the roof, etc. SteveBaker (talk) 16:21, 27 January 2013 (UTC)[reply]

You can seat two guys in the cab, ten in rear seats, and anyone else has to squaton the floor between the seats in the back. Of course, at slow speed, you could cram 20+ guys in the back, three or four in the cab and 10+ hanging on to the outside. There are some funny world war ii pictures of this type of thing around.--89.101.197.30 (talk) 20:54, 27 January 2013 (UTC)[reply]

So, 20-25 people would fit in just fine, at the expense of greatly reduced speed and acceleration (which is fine by me, and can actually help to build dramatic tension) -- is that right? 24.23.196.85 (talk) 00:41, 28 January 2013 (UTC)[reply]

It the 1945 truck specifications aren't too different from the pre-1945 version, then yes. To be clear about the performance thing: On a smooth, level road, top speed is determined overwhelmingly by atmospheric drag...but acceleration is all about mass - so in the best conditions, the overloaded truck might be able to get up to a reasonable speed eventually. However, on a rough road or when going uphill, the mass is again important. Another thought is that those old vehicles had really bad brakes - and deceleration (just like acceleration) is determined mostly by the amount of weight it's hauling around. So if you ever did get it going fast, it would be really poor at braking. If you make the thing too top-heavy, there might also be a roll-over risk when cornering hard...the ability to corner fast also depends greatly on the weight of the thing. SteveBaker (talk) 13:08, 28 January 2013 (UTC)[reply]

Nutrition facts of cooked chicken

Wikipedia article on Chicken (food) and Nutritiondata have different data. Our article says 100 g of cooked chicken contain 26 g protein, Nutritiondata says the figure is 31 g. From where will I get a reliable and accurate nutrition information? --PlanetEditor (talk) 04:48, 26 January 2013 (UTC)[reply]

Those are close enough that both could be in the normal range. The breed of chicken, how the chicken is raised and cooked, whether it's white meat or dark, whether the skin is removed, etc., could all account for the difference. StuRat (talk) 05:03, 26 January 2013 (UTC)[reply]

What StuRat said. Checking the website that is the source for the data in the Wikipedia article has hundreds of different variations on cooked chicken, and it isn't readily apparent which specific entry the Wikipedia data is drawn from, but given the variation likely, it doesn't seem impossible that both sets of data are correct, for any given value of "chicken". --Jayron32 05:07, 26 January 2013 (UTC)[reply]

(edit conflict)Not to mention that two chickens will not necessarily be identical, so the amount of protein in them would be different (for example, if you were more muscular than I, you'd likely have more protein). Those numbers are from different sources, which likely took the mean of the protein content of many chickens, so if different chickens were used to calculate the numbers, you'd get different values. Bramble claw x 05:09, 26 January 2013 (UTC)[reply]

the nutritiondata page specifies Chicken, broilers or fryers, breast, meat only, cooked, roasted, the usda page which is the source for the wikipedia table says 28.93 gm for Chicken, broilers or fryers, meat only, roasted; that reduces the difference to 7% (don't know which particular chicken entry of the multiple varieties given in the usda page was the source for the 26). Considering that the nutritiondata number is only precise to 0 decimal points, i.e. 3%.... as we used to say in biology lab, "within 10% means it's the same". Gzuckier (talk) 07:32, 26 January 2013 (UTC)[reply]

Here's an entry from NutritionData.com which seems to match our Wikipedia article: [9]. However, our article giving the protein value down to .01 gram seems a bit silly. Perhaps technical limitations prevent rounding different nutrients differently in the same table, or they just thought everything should be rounded the same as a style issue. StuRat (talk) 05:17, 26 January 2013 (UTC)[reply]

Thanks everyone. Another question, which part of chicken contains maximum amount of protein? --PlanetEditor (talk) 05:31, 26 January 2013 (UTC)[reply]

I'm going to guess that also varies by chicken. The obvious answer is "the muscles" (which have lots of the proteins actin and myosin) as opposed to "the bones" which are made largely of calcium phosphate and collagen (which I suppose is also a protein). Bramble claw x 05:35, 26 January 2013 (UTC)[reply]

Looking through the NutritionData.com charts, it looks like the breast. I'd guess that's because other parts, like the back, wings and thighs, contain a larger percentage, by weight, of bone. They probably should compare the various pieces without the bones, to remove this bias. StuRat (talk) 05:54, 26 January 2013 (UTC)[reply]

Not just formed by bone, but indeed chicken wings, thighs, and legs, all contain a significantly higher proportion of fat (in the edible parts) than chicken breast. Source - those nutrition labels they force them to stick on the packages in the UK. Whether the difference is made up mostly by protein or not, I wouldn't say for certain, but I would guess it's likely. --Demiurge1000 (talk) 06:22, 26 January 2013 (UTC)[reply]

It says 64 grams of cooked chicken is water. Slight differences in meat dryness probably change protein per 100 g alot. Also, don't go overboard with the protein eating, it is possible to eat too much. Sagittarian Milky Way (talk) 03:53, 28 January 2013 (UTC)[reply]

Rain = snow depth

What would be the equivalent snow depth of 2 inches of rain? In other words, if 2 inches of rain fell as snow, how deep would the snow be? --TammyMoet (talk) 17:31, 26 January 2013 (UTC)[reply]

It depends on how wet/dry the snow is. 10 inches of snow to 1 inch of water is the common rough estimate. — Lomn 17:41, 26 January 2013 (UTC)[reply]

(ec) As noted in snow gauge, the 'rule of thumb' ratio often used in comparing rainfall to snowfall is 1:10—that is, one inch of rain is roughly the same amount of precipitation as ten inches of snow. (In reality, however, a whole bunch of ambient factors affect the density of snow. 3 to 5 inches of really dense, 'wet' snow may melt down to an inch of water, whereas it might take 30 or more inches of really light, fluffy snow.) TenOfAllTrades(talk) 17:43, 26 January 2013 (UTC)[reply]

Also note that snow compresses after it falls. So, it will become steadily more dense, the longer it sits on the ground, eventually becoming ice, with almost the same density as water. This is especially true of snow which is compressed by the weight of snow above it, or where people or cars pass above it. StuRat (talk) 17:53, 26 January 2013 (UTC)[reply]

Cold snow is drier, due to absolute humidity. Sagittarian Milky Way (talk) 18:14, 26 January 2013 (UTC)[reply]

Thank you all! (Currently breathing a sigh of relief that the rain we had last night wasn't snow.) --TammyMoet (talk) 20:08, 26 January 2013 (UTC)[reply]

Note that you generally get far less moisture falling as snow than as rain, since you only get snow when it's cold, and cold air holds much less moisture to begin with. However, the snow might seem like more, both because it takes up more room, and because it sticks around, versus rain which usually goes down the nearest drain, soaks into the ground, or evaporates, in short order. StuRat (talk) 20:31, 26 January 2013 (UTC)[reply]

See Snow#Density which has some references. And no, snow, of a single season, does not become ice. Snow that does not melt in the summer may eventually turn into glaciers. If the snow has become ice in a single season then it is due to partial melting and later refreezing. CambridgeBayWeather (talk) 19:14, 27 January 2013 (UTC)[reply]

You apparently haven't seen a road after cars have driven over snow a few days. Solid ice results, unless salt is used. StuRat (talk) 04:50, 28 January 2013 (UTC)[reply]

In fact, during the Battle of the Bulge, it only took one day of tanks driving over snow-covered roads to turn the snow into ice -- despite constant plowing, salting, etc. 24.23.196.85 (talk) 07:12, 28 January 2013 (UTC)[reply]

In my immediate experience ten days ago (on the South coast of England), a day of lighter-than-usual pedestrian traffic on town pavements ('sidewalks') can be sufficient to turn 3 or so inches of snow into uneven ice. I walked most of 5 miles into work (buses and other vehicles proving unable to cope on inclines) in the near-virgin snow quite easily, but walking a mile to the railway station that evening was far more difficult. {The poster formerly known as 87.81.230.195} 84.21.143.150 (talk) 14:45, 28 January 2013 (UTC)[reply]

I'm talking about paved roads in Yellowkinfe after months of vehicles passing over them. CambridgeBayWeather (talk) 14:47, 28 January 2013 (UTC)[reply]

Formal term for re-mapping of a set of values to other values.

Hi,

Please help me find the above technical term.

Quantisation is the proces of remapping values to a smaller set of values (many-to-few), but what is the term where the number of values in the set remain the same, but the data points change value? (edited , sorry the following is an example of the sought after term, not quantisation, so the example is:)

There data points at the start are: 1, 3, 5, 7, 9. Some of the data points values are changed by some algorthym or process, or so that they align with some other value set, and the resultant values are 1.5, 3, 5, 6, 8 respectively.

This is not quantisation, as the number of data points has not been reduced. Only the values of each data point have been realigned to a new set of values.

What term could describe this?

Thanks, Dale. — Preceding unsigned comment added by Califauna (talk • contribs) 20:16, 26 January 2013 (UTC)[reply]

Not an an answer, but the first case, where you remap data to a smaller set, is known as "hashing", at least in computer science. In the second case, I'd simply call it "remapping". StuRat (talk) 20:27, 26 January 2013 (UTC)[reply]

In mathematics this sounds like a function. Ulflund (talk) 22:01, 26 January 2013 (UTC)[reply]

Yes, although when applied to data points I think the term transformation is more widely used. Looie496 (talk) 01:03, 27 January 2013 (UTC)[reply]

Thanks for the above. All excellent. — Preceding unsigned comment added by Califauna (talk • contribs) 03:58, 27 January 2013 (UTC)[reply]

January 27

Does the dog recognize me?

I have a business associate whom, for the past 2 years, I meet with exactly once a month, and not more. About half the times I meet him, he has his dog with him. I always greet the dog, and the dog nuzzles me and licks my hand (the dog does this with everyone it meets). So this is a dog whom I see on a roughly regular basis once every 2 months (on average) for just a brief moment over the past 2 years. I'm just curious: does the dog recognize me from these short 1 to 2 minute encounters, or am I just some random stranger to the dog every time? Put another way, if I happened to run into this dog at random in a park without its owner, would the dog recognize me? I know that the reverse is not true (if I ran into this dog at random in the park, I could not be certain that it was this dog and not another dog of the same breed and coloring). —SeekingAnswers (reply) 01:00, 27 January 2013 (UTC)[reply]

If you asked this about a person who has encountered you twice a month for the past two years (say, a waiter), it would be impossible to say, right? Well, it's no more possible to say for the dog. They are very good at distinguishing people by smell, but unless the dog shows some overt sign of recognition, some behavior that distinguishes you from other people, there can't be a solid answer. Looie496 (talk) 01:09, 27 January 2013 (UTC)[reply]

It would be a pretty poor waiter who would not recognise a regular customer. In a quality restaurant, waiters will check the bookings to refresh their memory, so that when you arrive roughly on time, they can say something "So nice to see you again, Mr StuRat", while faking their sincerity with a big smile. However, as far as the dog is concerned, he might or he might not - it depends on how different you are, in the dog's perception, to other humans he meets. Some humans will greet a dog, some won't, so just greeting it probably won't be enough. If your business associate treats you differently to other people, the dog might cue on that, but it seems unlikely. It's easier to tell with certain breeds of dog that have clearly different sorts of barks for different purposes. I visit my cousin about every 2 to 3 months or so. She has a labrador. It barks (once) whenever it detects someone comming to the door. If it is someone in my cousin's immediate family, in other words poeople who are there nearly every week, the dog announces them with a certain soft bark. If it is a stranger it gives a louder more harsh bark. If the dog knows the person, it gives another sort of bark - when I arrive it gives that sort of bark. My cousin calls it the "family bark". Incidentally I pretty much ignore the dog. Another way you can tell if a dog recognises you as friend, is if he approaches you with ears lowered (sometimes ears and head lowered), and walks 360 degrees around you. The more intelligent breeds do this. Poodles are useless - they just bark and don't use dog greeting etiquete - which is why other breeds of dog despise them. Wickwack 121.215.68.88 (talk) 03:13, 27 January 2013 (UTC)[reply]

It would be strange to the point of pathology if the dog didn't recognize your smell the second time he met you. That's the whole reason for the smell the hand greeting---to get to know your smell--not to check if you have bacon between your fingers. There are too many books on dogs, like Cziksentmihly's and The Dog Whisperer's. You might try Temple Grandin's works. And animal intelligence and dog behavior. But the answer is yes. μηδείς (talk) 03:36, 27 January 2013 (UTC)[reply]

I would bet that the dog recognizes you. I have five dogs, so this throws off my example a bit but hear me out. One of the dogs is more... hostile, I'll use that word for now, to strangers than the rest. So we have a method of introducing him to new people who we want him to trust in his house. We don't get a lot of guests and so when we do, they've normally been away for some time. Long enough to be similar in scope to your example. When those people come over, we don't have to go through the introduction every time. Between the members of my pack, they somehow know who is okay to let in and who isn't, which is handy when we need someone to feed the pack on some day that we might be gone. Dismas|^(talk) 04:05, 27 January 2013 (UTC)[reply]

It took me two or three readings of your last sentence to realize that the preposition on went with some day and not with feed. --Trovatore (talk) 06:10, 27 January 2013 (UTC) [reply]

Yes, and by recognize all that may be meant is an association of your smell with the tag friend or foe. It's not like they have to remember names, phone numbers, etc. Olfaction is powerful and primitive. μηδείς (talk) 04:18, 27 January 2013 (UTC)[reply]

Yeah, the recognition of individuals is really a different thing from memorizing the 12 times table. I'd say the best estimate for the average ability and amount of variation of dogs in recognizing people is that it's equal to the ability of humans recognizing individual dogs. I.e., it's probably easier for either to recognize members of their own species, but there are still plenty of cues provided by individuals of a different mammalian species. Gzuckier (talk) 06:11, 27 January 2013 (UTC)[reply]

Dogs are wolf-descendent pack animals - and their eyesight isn't that great. They mostly rely on their incredible sense of smell to recognise pack members and bond with them. That's why they sniff friends and strangers alike. So I think it's reasonable to assume that the dog recognises you - but there is no easy way to know whether it cares or not. So it could be: "<sniff>...not a pack member...<Meh>"...or "<sniff>...oh yeah...that guy who was nice to me a couple of weeks ago <happy>". In my experience, a dog never forgets a free snack...so if you're prepared (and the owner doesn't mind) with a small doggy treat every time you meet the dog - I'm 100% sure you'll get a wild greeting each time! SteveBaker (talk) 15:52, 27 January 2013 (UTC)[reply]

Our article Gray_wolf#Intelligence says that a trained wolf recognized its master after a three-year absence. (I haven't looked into this further) Wnt (talk) 19:08, 27 January 2013 (UTC)[reply]

Interchangeable parts?

Resolved

I recently got a new HP laptop and was wondering if I ought not use the AC charger from my previous Dell for my new HP. I read the details of the AC chargers from their backs and they both say ~~90V~~ 90W and everything else seems to be pretty much the same, and the male inserts for both the HP and the old Dell charging appear identical and both fit into the female port on my new HP. As an aside, when I say "old Dell" I don't mean that it's 15 years old, but rather perhaps 5 years old. DRosenbach ^{(Talk | Contribs)} 01:08, 27 January 2013 (UTC)[reply]

maybe ;/ - assuming the voltage output (not input!)/wattage/polarity of connector/size of connector/AC or DC/ is identical, then possibly. however some newer models have special circuitry that can identify the charger that has been plugged in to ~~keep a nice tight grip on the market for replacements~~ prevent damage to the laptop. Output voltage is very unlikely to be 90v - usually somewhere between 9 and 19 volts - and this will be critical to make sure you have correctly identified before you plug it in. 90w of power seems plausible. There are so many variables, having had a number of laptops over the years, I've never seen one that was interchangeable with the charger of another manuf yet. If you plug it in and it wrecks your laptop, it won't be covered by the warranty. ---- _nonsense ferret 01:18, 27 January 2013 (UTC)[reply]

Yes -- you got me. It was 90W, not 90V. But it does say V85 on one of them. DRosenbach ^{(Talk | Contribs)} 04:02, 27 January 2013 (UTC)[reply]

There's probably other ways to invalidate the warranty if you really wanted to, but your method should do exactly that just fine. --Jayron32 01:19, 27 January 2013 (UTC)[reply]

If both input and output voltage are the same and the connectors are the same, they should be interchangeable, and it should be okay swapping them. —SeekingAnswers (reply) 01:24, 27 January 2013 (UTC)[reply]

If the power and voltage output match and the connectors fit, than you should be OK. That will not invalidate the warranty (even if it did, how would they know?). Dauto (talk) 02:12, 27 January 2013 (UTC)[reply]

Electronics Engineer here: Please post exactly what each power supply says on it, including a description of any graphics that have a "+" "-", "~" or "- - - - -" as part of the diagram. "Pretty much the same" is not good enough to risk your laptop over. --Guy Macon (talk) 03:30, 27 January 2013 (UTC)[reply]

OP here -- OK, I didn't realize what was necessary to make them compatible. The new HP AC charger reads "Output: 19.5V --- 4.62A" and the old Dell AC charger reads the same. The only difference is that the old Dell reads "Input: 100-240 V ~ 1.5A 50-60Hz" and the new HP reads "Input: 100-240V ~ 1.6A 50-60Hz." Other than the difference between 1.5A and 1.6A, the only other difference is that the new HP includes the term "wide range input" whereas the old Dell charger does not. DRosenbach ^{(Talk | Contribs)} 03:38, 27 January 2013 (UTC)[reply]

Your original post said "both say 90V". Do they still both say this, or neither of them still say it, or one doesn't? --Demiurge1000 (talk) 03:43, 27 January 2013 (UTC)[reply]

Ha! Yes, they still both state everything I've already included above -- this last post was merely adding because someone made a comment about specifics regarding input and output. They are both 90V chargers. One of them says V85. I'm lost because I don't know the difference between watts, volts or amps. Here's a photo of the two. DRosenbach ^{(Talk | Contribs)} 03:48, 27 January 2013 (UTC)[reply]

This is a good thing to give knowledge about, but please note that the Wikipedia Refdesk does not give advice, and will not be offering compensation should your toasted laptop be found in the ruins of your burned-out house. Telling people sources about how laptop connectors are identified and categorized, of course, is within the purview. Also note that the Computing Refdesk might have additional experts. Wnt (talk) 03:40, 27 January 2013 (UTC)[reply]

Now that I see the stats, I should follow up what I was saying more specifically: is it possible that the greater power consumption (1.6 A) will mean there's an increased risk that the old laptop adaptor will overheat and catch itself or the surface it's lying on on fire? Wnt (talk) 03:50, 27 January 2013 (UTC)[reply]

I agree with the previous respondents - there is a lamentable lack of standardization between laptops - so you have to use an abundance of caution. Even if the voltage, current, frequency and everything else are the same - and the connector physically fits, there is also the issue of whether the inner pin is positive or negative...generally there is a little diagram that shows you that. If you're 100% sure they are identical - then it should work - but it's a definite risk, so if you aren't 100% sure, then don't do it. I'd want to check at least voltage and polarity with a meter before plugging it in. SteveBaker (talk) 03:44, 27 January 2013 (UTC)[reply]

The above advice is spot on. It was pretty much what I would have started my answer with before posting the following:

The "Output: 19.5V --- 4.62A" is your DC output voltage and current. Same is good, but having the plus and minus reversed would be very bad. Most power supplies tell you which goes where. For example you will see a little circle inside a circle with one or the other labeled "+" or perhaps a dashed line above a solid line. You didn't tell me about any of those, so I am not 100% sure that they are not reversed. One solution would be to find a friend who owns a voltmeter and knows how to use it and have him check the supply.

"Input: 100-240 V ~ " is the input voltage. Like most modern laptop power supplies it runs from pretty much any voltage (Japan is 100V, parts of Europe are 240V). The "~" means "AC".

1.5A or 1.6A is the input current, but that's the highest it can get (laptop using the full 4.62A and input at 100VAC). It will usually be a lot lower. The 1.5 and 1.6 are almost certainly just slight variations on those assumptions and can be ignored. "50-60Hz" is input frequency (US is 60, Europe is 50)

If it were my laptop and I was sure about plus and minus not being switched, I would try powering up my old laptop with the new power supply first (less valuable) and keep my hand on the supply to see if it is getting hot. If I didn't have the old one any longer, I personally would try it on the new, but as was detailed above, that's your decision, and you know what they say about following advice you got from strangers on the Internet...

EDIT: after writing the above but before posting, I saw the pictures. There is that circle in a circle I was talking about, and they match. In my opinion, this is less risky than using a no-name replacement power supply that claims to be compatible, but again, it is your decision to make. --Guy Macon (talk) 04:20, 27 January 2013 (UTC)[reply]

Thanks! DRosenbach ^{(Talk | Contribs)} 04:26, 27 January 2013 (UTC)[reply]

Getting here late, but as somebody who started out by destroying tube type radios and just recently melted a 9 volt wall wart by pulling too much current, I'd say that based on the two pictures above the two power supplies are absolutely interchangable. I wouldn't be surprise if a lot of the ICs inside were the same. The V85 means nothing, that's just some manufacturer's particular ID; the .1 Amp difference on the input ratings is unimportant, given that the minimum wall outlet has 15 amps to offer, and is just as likely to be a difference from one sample of the same item to another as between the two manufacturers. What's important regarding meltdown of the power supply is the output Amp rating, and that's the same; as the above poster implied, given that both manufacturers can be considered reliable, it's likely that both supplies meet their specs. Gzuckier (talk) 06:02, 27 January 2013 (UTC)[reply]

Agreed, I'd be willing to take the risk with my own laptop (after having made all the checks above). Most of the control circuitry is within the laptop, so it just needs an appropriate voltage and current. I have seen two pieces of expensive equipment ruined by plugging in the wrong power supply (even thought the plugs were a perfect fit), so it is wise to check very carefully before "trying out". (And, as mentioned above, none of us can be sued if we are all wrong!) Dbfirs 09:18, 27 January 2013 (UTC)[reply]

Thanks to all who contributed. I'm posting this with my Dell working off of the new HP charger and so far, there's been no fire. DRosenbach ^{(Talk | Contribs)} 18:22, 27 January 2013 (UTC)[reply]

Wooden coffer

I have a small antique wooden coffer that I need to reinforce. The problem is that the bottom panel is simply nailed in, and I fear that it is not designed to support 70 kg of weight. It measures ~36 x ~27 x ~17 cm, and is constructed from ~13 mm thick wood. How should I reinforce the chest in a way that preserves its 1910 style. Pehaps iron straps? Plasmic Physics (talk) 06:58, 27 January 2013 (UTC)[reply]

Iron straps (with big, protruding rivets) would indeed be best -- two L-section straps, one at each end, should be able to hold the weight. 24.23.196.85 (talk) 07:29, 27 January 2013 (UTC)[reply]

As a note, the iron fixtures, such as the hinges are attached via flat head, slot screws. Plasmic Physics (talk) 07:44, 27 January 2013 (UTC)[reply]

In that case, matching screws would be better stylistically (not to mention more practical to install). 24.23.196.85 (talk) 07:57, 27 January 2013 (UTC)[reply]

Wouldn't 4 smaller straps, two a side, distribute the load more evenly? Or is there a reason for only using two? Plasmic Physics (talk) 08:16, 27 January 2013 (UTC)[reply]

Yes, four straps is also an option -- two is just the minimum. 24.23.196.85 (talk) 00:25, 28 January 2013 (UTC)[reply]

If it's antique - I'd want to do a non-destructive "fix" - or at least one that didn't affect the outside appearance of the thing. So how about a box-within-a-box? Construct a strong container (from metal, plastic, heavier-grade wood, whatever) that fits tightly inside the original box but which can better take the weight and connect to whatever is going to be used to lift it. The antique becomes more of a decorative 'skin' around the "real" box which does all of the work of containing and distributing the load. SteveBaker (talk) 15:42, 27 January 2013 (UTC)[reply]

Along that train of thought (that any alteration would reduce it's value as an antique), another option would be to support the bottom externally. I'm assuming here that it has legs which slightly lift the bottom. In this case, you could place, underneath it, plywood of the proper thickness and cut to the same width and length as the bottom, so it would be supported. However, you'd need to be careful never to lift the coffer while loaded. If you can do that, you can both use it, and preserve it's value, in this manner. StuRat (talk) 17:50, 27 January 2013 (UTC)[reply]

It's not particularly valueable as an antique, is has more of a sentimental value. It doesn't have legs, the whole idea is to make it liftable when loaded. I need to stop the bottom panel from either cracking, or the nails pulling out. Plasmic Physics (talk) 00:09, 28 January 2013 (UTC)[reply]

There is a problem with using a box within a box: the internal box is still resting on the bottom, so you haven't really changed anything. Plasmic Physics (talk) 00:09, 28 January 2013 (UTC)[reply]

You mention 70 kg of weight. Is this 70 kg of weight that you are planning on putting into the box? Does it look like any of the "wooden coffers" when doing a Google image search for "wooden coffer"? Bus stop (talk) 00:23, 28 January 2013 (UTC)[reply]

Yes, I'm planning to put it in the box. Putting it on the box seems a bit absurd as to defeat its purpose. No, those coffers are too ornate. My dad told me that as far as he knows, it was made by his grandfather, although it looks suspiciously like a Boer ammunition box that's received a coat of wood stain. Plasmic Physics (talk) 01:08, 28 January 2013 (UTC)[reply]

Is it similar to one of these? Bus stop (talk) 01:48, 28 January 2013 (UTC)[reply]

Yes, it is. Plasmic Physics (talk) 02:19, 28 January 2013 (UTC)[reply]

I guess one consideration is replacing the bottom panel, perhaps with strong plywood, such as aircraft plywood. Perhaps screws will hold sufficiently well, depending on the side panels to which they would have to be attached. Retaining the original appearance would depend on choice of materials obviously. The metal straps idea sounds sound. Bus stop (talk) 03:55, 28 January 2013 (UTC)[reply]

Another thought. Metal sheathing could be secured all around the bottom. If the thin metal sheathing were cut to length and bent lengthwise at a right angle, it could probably then be tacked in place with a sequence of relatively small nails or tacks, relatively closely spaced. Four such sheaths might reinforce the four angles at which the sides of the box adjoin the bottom of the box. Locating the materials as well as the tools for working the materials may present an initial challenge but it may be doable and worth it. I would think the sheet metal used need not be particularly strong as its functionality would be continuous along all edges. Whether to replace the bottom or not would of course depend on the strength of the original bottom. Bus stop (talk) 04:21, 28 January 2013 (UTC)[reply]

Stone Age Malthusianism and Cornucopianism

I've read some articles suggesting that resource peaks, climate change and unsolved substitution problems would often have been the issue of the day for preagricultural tribes. Has any work been done on the fitness and popularity of Malthusian and Cornucopian memes (population control, food rationing, exploratory migration etc.) in such an environment, and the difference instinct and cognitive biases would have made? Neon Merlin 14:19, 27 January 2013 (UTC)[reply]

About migration: It's apparent that migrations took place, particularly between remote Pacific Islands (like to Easter Island), which would have had a high risk associated with them (if a major storm hit them in transit, they would all be dead). The only reason I can see to take such a risk is if there was no other option. That is, those people would have died had they stayed put, quite possibly because the resources there were stretched to the limit. However, I don't know if those migrations took place before or after agriculture developed. StuRat (talk) 17:43, 27 January 2013 (UTC)[reply]

Well the Polynesian / Malay migrations happened after agriculture was developed, and they brought pigs, chickens, and other crops where they travelled. Graeme Bartlett (talk) 04:50, 28 January 2013 (UTC)[reply]

Proton Density of Various Materials

Resolved

I'm wondering what the lower and upper bounds of average proton density for various materials and substances might be? I realize this is going to depend a lot on the type of molecules present (eg: density of fruit is much less than that of lead) - I'm just interested in ballpark figures anyway. 75.228.159.2 (talk) 15:13, 27 January 2013 (UTC)[reply]

Very roughly speaking, most atomic nuclei contain approximately equal numbers of protons and neutrons. Since protons and neutrons have (again, approximately) the same mass, about half the mass of most solids is down to the protons, so about half of the total mass density is the proton (mass) density. (The contribution by electrons is negligible.)

Two important caveats. First, heavier nuclei have proportionately more neutrons (to take an extreme example, uranium-238 nuclei contain 92 protons and 146 neutrons), so if you're looking at elements further down the periodic table you'll want to account for that. Second, the most abundant isotope of hydrogen (hydrogen-1) is a single proton and no neutrons, so pure hydrogen is essentially all protons by mass; extremely hydrogen-rich compounds like methane (1 atom carbon-12 and 4 hydrogen atoms gives 10 protons and just 6 neutrons) will also have a proton-enriched composition.

As an aside, the term 'proton density' is also used in magnetic resonance imaging to refer to the abundance of hydrogen-1 only, and not to protons that may be part of other heavier nuclei. TenOfAllTrades(talk) 16:25, 27 January 2013 (UTC)[reply]

Ballpark figures: The Atomic mass unit is 1.66×10−27 kg, which is the weight of one proton. Whit a crude assumption that protons represent half of the total mass, you get: lead, about 11000kg/m³ would have 11000/(2*1.6×10−27) or 3*10³⁰ protons per m³, water has 3*10²⁹ protons per cubic metre... Should be correct within 30% I think. Unless I made a mistake somewhere... When you're talking about MRI's, this answer is likely not helpful...Ssscienccce (talk) 16:52, 27 January 2013 (UTC)[reply]

Contributing to medical knowledge

Last year I had a run in with a prescription medicine which resulted in my emergency admimssion to hospital. I am wondering if there is a medical database in existence that I can contribute my experience of this drug to? (not medical advice of course) --TammyMoet (talk) 16:54, 27 January 2013 (UTC)[reply]

I'd actually like to see a "Rate My Drug" site where people rate drugs based on side effects, effectiveness, etc. This would have the potential to let people know of problems with drugs far earlier than the normal regulatory process, which unfortunately is filled with conflicts of interest, at least in the US. I wonder, could drug makers sue such a site, even if they post disclaimers that "These are only the opinions of our members". StuRat (talk) 17:36, 27 January 2013 (UTC)[reply]

Here's a real answer: FDA's MedWatch is a great tool, just click the "Report a serious medical product problem" link under "Resources for you" on the left. -- Scray (talk) 17:42, 27 January 2013 (UTC)[reply]

Thanks Scray for that link, however it won't work with my version of Firefox (!) and I guess I should have mentioned, I'm in the UK. Is there a similar site for the UK? --TammyMoet (talk) 18:17, 27 January 2013 (UTC)[reply]

TammyMoet: sorry that wasn't quite what you needed. I don't see a similar tool for UK/EMEA consumers. -- Scray (talk) 22:59, 27 January 2013 (UTC)[reply]

There's the yellow card scheme Jebus989 ^✰ 11:48, 28 January 2013 (UTC)[reply]

I wouldn't be surprised if on the whole this is discouraged by the powers that be, as it might be be as useful as your would think at first. Patients on the whole lack the knowledge and jargon to accurately describe what is happening to them, leading to possible confusion and contradictory evidence. If this goes via health professionals at least (one would hope) it gets reported in an accurate manner. Fgf10 (talk) 18:39, 27 January 2013 (UTC)[reply]

I'm sure the medical professionals involved reported the adverse event at the time. However, there were symptoms which have disappeared since I stopped taking the tablets which I didn't report at the time because I didn't associate them with the drug in question. It would complete the information around the incident if I could report this cessation of symptoms somewhere. --TammyMoet (talk) 19:33, 27 January 2013 (UTC)[reply]

Well, the "few experts" versus "many novices" paradigms come up often, including here at Wikipedia. The idea here is that many novices can provide more, and hopefully better, info, than a few experts. There are other examples, like stock markets being used to "rate" companies, compared with expert opinions. One problem with "experts" is, that since only a few control the data, they can be bribed or otherwise have a conflict of interest, while it's impossible to do so with millions of people. For example, avoiding damage to the company's profits may also be a concern for the experts, while the novices are only concerned with the health of the patients. StuRat (talk) 04:29, 28 January 2013 (UTC)[reply]

The whole issue of the international development and marketing of therapeutic drugs has some serious concerns. The commercial drugs world is driven much more (perhaps exclusively) by commercial gain than any other reason. Information about the effects of medicines is frequently withheld by manufacturers. It is a murky world. Bad Pharma by Dr. Ben Goldacre lays out clearly and authoritatively the shortcomings of the medicines market, a frightening but essential read if you are concerned about this topic. Richard Avery (talk) 07:44, 28 January 2013 (UTC)[reply]

Good grief. Some of you have some very unrealistic ideas of why drug reactions are not often "reported" to the FDA, or to the medical literature. By far the LEAST likely explanation is that a doctor whose patient has a reaction to a drug wants to conceal it to protect company profits (Stu: "well if there really was a conspiracy you would say that, wouldn't you?"). The real explanations (1) Reporting is just more unreimbursable paperwork. Doctors in the US spend hours of each day on data collection and entry that patients and payors demand but do not expect to pay for. If it takes 15 minutes to do a drug reaction report on Medwatch, would you pay your doctor to do it? (2) Uncertainty. The patient may be certain that the daily fukitol pill she has been taking for 2 years caused her hair to turn green last week, but the doctor will not be sure that it is not simply coincidence unless the same effect has happened to multiple people taking it. (3) Diffused responsibility. These days, at least in the US, the doctor who prescribed the drug and the one who handled the side effect problem are often different. (4) Ignorance of process. Not sure how many doctors even know about Medwatch. Certainly not all. The percentage of US doctors who have had a patient suffer a side effect from a medication: 99%. Percentage of US doctors who have reported even one reaction to Medwatch: I doubt it's 5%. (5) Pointlessness. Most doctors are aware that nothing happens after a Medwatch report except paperwork. If the drug has been widely used for years, the side effect has already been known. If the side effect is an unknown one, especially if trivial or self-limited, like a headache, it's unlikely due to the drug. Your doctor may not spend as many hours as you imagine pondering your problems when your are not in front of him, but I promise you he does not get paychecks from pharmaceutical companies to keep you ignorant or deny problems. alteripse (talk) 12:38, 28 January 2013 (UTC)[reply]

If they give an IQ test to someone who's had a coma, do they subtract the coma length from the chronological age?

What if it's only 0.1 years? (I would still do it) They never asked me if I'd had a coma when they did it in school, though. Come to think of it, are things like brain damage from hits and hypothermia accounted for in the bell curves? Sagittarian Milky Way (talk) 18:31, 27 January 2013 (UTC)[reply]

I don't think anyone can tell exactly how much of an IQ score is a result of "mental age", experience and knowledge, and how much of it is a result of the physical age of the brain. Subtracting the duration of the coma would raise the score for a child but lower the score for an adult, so an adult would have to perform better on the test if he had been in a coma, which seems unlikely. Ssscienccce (talk) 23:47, 27 January 2013 (UTC)[reply]

Adult IQ test results are compared to adults of all ages, so chronological age doesn't really come into play. With children, adjusting the chronological age (say, pretending that a ten-year-old was only five after waking up from a five-year coma) would render IQ testing completely ineffective at measuring the effects of this long hypothetical coma. I'm not sure I completely understand the rest of your question though. EricEnfermero ^Howdy! 00:09, 28 January 2013 (UTC)[reply]

Our article Intelligence quotient discusses IQ and age. The gist of it is that once upon a time there was one test for children that computed IQ = (mental age / chronological age)*100. That computation is no longer in use. Also, all adults are usually lumped together; a 25 year old who answered all the questions the same way as a 50 year old would be assigned the same IQ score.. Jc3s5h (talk) 00:04, 28 January 2013 (UTC)[reply]

Are you sure? He showed me dividing the mental age by the actual, and it wasn't *that* many years ago. And yes, age isn't involved for adults. Sagittarian Milky Way (talk) 03:34, 28 January 2013 (UTC)[reply]

Those bell curves of IQs. Are they raw data, or do they adjust them for anything? Like is 100 the average of everyone, or the average of everyone if no one had their intelligence artificially altered by things such as brain damage from accidents, thalidomide, lead paint, crack babies and other drug abuse (maternal and personal), their time in a coma, and possibly other things? Shouldn't 50 be commoner than 150 in real world data? For some things you'd want the raw data (like calculating how many mentally retarded need care), for others you'd want the cleaned up data. Sagittarian Milky Way (talk) 03:34, 28 January 2013 (UTC)[reply]

The bell curves are the raw data -- if the researchers want to compare IQs of selected subgroups of people, they essentially have to select scores from just those subgroups and compile the data for those groups from scratch. 24.23.196.85 (talk) 07:28, 28 January 2013 (UTC)[reply]

Seasonal changes in temperature

I cannot reconcile the reasons why we have such differing seasonal temperature differences with the answers I have accessed.

If the seasons are mainly dictated by the tilt of the earth, then why should such a small difference in distance (to or away from the sun) of at the most, a few thousand miles cause this when the earth is 93 million miles from the sun? I understand that the earths orbit is elliptical, but given that when the earth is furthest away from the sun (July) the northern hemisphere has its summer. Surely this would be like having a roaring fire in a big room 20 meters away and expecting to feel a difference if you move 1mm nearer? 86.138.72.18 (talk) 18:49, 27 January 2013 (UTC)[reply]

From what I understand, it's not the distance between the earth and the sun but the distance through the atmosphere that the heat radiating from the sun must past through to reach the surface of the earth. Thus, the portion of the hemisphere that is tilting towards the sun is receiving its solar radiation through the thickness of the atmosphere, while that portion of the hemisphere tilting away from the sun receives its heat filtered through a non-straight line through the atmosphere, thus being 1.2, 1.5, etc. of the thickness of the atmosphere, and that's what's causing the dissipation of enough solar radiation to create what we perceive as the drastic temperature changes associated with the seasons. That's whats meant by more direct sunlight as explained in the seasons article. DRosenbach ^{(Talk | Contribs)} 19:01, 27 January 2013 (UTC)[reply]

Also this. Shine a flashlight at the center of a ball. Shine it at the edge (same distance) and move your head over that area. It's dimmer. Sagittarian Milky Way (talk) 19:05, 27 January 2013 (UTC)[reply]

To rephrase that: if you hold up a quarter to the Sun, it will get nearly the same amount of light anywhere - North Pole, equator, noon, sunset - subject only to the atmospheric absorption mentioned and some minor differences in distance. But if, in order to be face on to the Sun, that quarter is lying on its edge on an ice floe at the North Pole on the equinox, it casts a shadow all the way toward a distant horizon. All that ice shares the light now blocked by that one lousy little quarter. If it's lying flat on the ground at the Equator, it gets the same light on that one little spot. Wnt (talk) 19:18, 27 January 2013 (UTC)[reply]

Never thought of it that way -- nice! DRosenbach ^{(Talk | Contribs)} 21:24, 27 January 2013 (UTC)[reply]

A quarter? HiLo48 (talk) 20:37, 27 January 2013 (UTC)[reply]

A small cupronickel object about an inch :) Or are you seriously asking what it is? Sagittarian Milky Way (talk) 20:54, 27 January 2013 (UTC)[reply]

HiLo48 comes from an enlightened land where Vegimite is considered to be a delicacy and the coins are 5c, 10c, 20c, 50c, $1 and $2. The closest in size to the 24.26 mm (Inches? We don't need no stinking inches!!) US 25c coin ("quarter") is the 25.00 mm $1 coin. And we really shouldn't use US coins as examples, many Wikipedia editors live elsewhere. --Guy Macon (talk) 21:21, 27 January 2013 (UTC)[reply]

A quarter-dollar is a 25 cent piece. Do you call a 20 cent piece a "fifth" ? This could lead to disappointment when your kid tells you he just found a fifth in the driveway. :-) StuRat (talk) 04:46, 28 January 2013 (UTC) [reply]

Some of the above is right, some is wrong. The core reason why the Northern hemisphere gets less heat from the sun in winter is because it intersects less sunlight. The sun always illuminates about half the Earth (there is some minimal wiggle room because the sun is larger than the Earth, and also if you take into account atmospheric refraction). In northern summer, the pole is pointing (a bit) towards the sun, and more than half of the northern hemisphere is in the sun. So it gets warmer than average. To make up the difference, less than half of the southern hemisphere is in the sun, so that part gets colder. --Stephan Schulz (talk) 19:38, 27 January 2013 (UTC)[reply]

Or, to put it another way, unless you are near the equator, during the summer the sun gets higher in the sky (warmer for the same reason that the noonday sun heats the ground more than the sun right before it sets does) and the days are longer and the nights shorter. --Guy Macon (talk) 20:38, 27 January 2013 (UTC)[reply]

A simple experiment I recall from High School science class: in a darkened room shine a flashlight at a given distance directly overhead (90°) on a piece of graph paper. Count or calculate the number of squares that the light covers. Do the same (same distance) but this time have the flashlight at a specific angle (eg: 45°) - The number of squares covered by the light is larger. Think of the flashlight as a "beam" of sunlight. The same amount of light (energy) is spread over a larger area, and thus the energy per "square unit" is less. For me, this helps explain why a change of angle on the Earth's surface (due to axis tilt) creates a seasonal difference in temperature. ~:74.60.29.141 (talk) 23:02, 27 January 2013 (UTC)[reply]

P.s.: this experiment explains how latitude affects climate; but also helps explain seasonal variation - which also includes shorter daylight hours, etc. 74.60.29.141 (talk) 23:14, 27 January 2013 (UTC)[reply]

You may be interested in the information given here. If you can download series it will tell you all you wanted to know but were afraid to ask about the Earth's orbit and its effect on the seasons. Richerman (talk) 23:55, 27 January 2013 (UTC)[reply]

... and, just to show that distance from the sun makes only a very small difference, the northern hemisphere is currently nearer to the sun in winter and further away in summer. Dbfirs 12:26, 28 January 2013 (UTC)[reply]

January 28

Why don't the the sunrise and sunset times go the other way at the solstice?

While we're on the subject of the Earth's orbit... I always assumed that after the 21st of December, or thereabouts, the sunset got later each day. However, when I look up the sunrise and sunset times for about this time for, say, London, although the days begin to get longer overall after the solstice, the sunsets don't necessarily get later or the sunrises earlier - one or the other will happen but not both together. There seems to be a couple of weeks discrepancy either side of the solstice before everything coincides and we get both a later sunset and an earlier sunrise on the same day. What causes the discrepancy? Does it depend on where you are on the surface of the Earth and if so, is there somewhere where everything changes on the day of the solstice and the following day the sunrises start to get earlier and the sunsets later? Richerman (talk) 00:22, 28 January 2013 (UTC)[reply]

It would work that way if the earth's orbit was both flat and circular. However, it isn't. The earth's orbit is oblique (offset by an angle to the plane of the solar system) and the orbit is an ellipse. As a result, there is are the deviations you note from the expected "symmetry" at the equinoxes. See Equation of time for these corrections. --Jayron32 00:39, 28 January 2013 (UTC)[reply]

Ah, right - so am I right in thinking that the solstices and equinoxes only seem less variable because they are measured in days rather than minutes? Richerman (talk) 00:53, 28 January 2013 (UTC)[reply]

I'm not quite sure what your getting at, but one cause of variation of the time and date of the solstices and equinoxes is that our calendar is not exactly one tropical year long, so the times of these phenomena vary quite a bit depending on how long it has been since a leap day. Jc3s5h (talk) 01:15, 28 January 2013 (UTC)[reply]

Analemma. Wnt (talk) 01:30, 28 January 2013 (UTC)[reply]

Interesting answer Jayron. I see the point of the elliptical motion, but I don't get the relevance of the inclination of the Earth's orbit relative to the solar system. If the other planets weren't there, there would be no plane of the solar system other than the Earth. Or am I missing something? IBE (talk) 07:33, 28 January 2013 (UTC)[reply]

What you've got is a complex interaction of several planes, none of which line up. There's the ecliptic, which is the plane that the sun occupies in its apparent motion in the sky if you hold the earth still. Then there's the Celestial equator, which is a projection of the earth's equator out to infinity. These planes are offset from each other by an angle; that angle is called the "obliquity" of the Earth's orbit. The fact that these planes don't match has to be taken into account when calculating the difference between the "mean solar day" (i.e. an exact 24 hour period measured on the clock) and the "apparent solar day", which is the time between the reappearance of the sun in the same position on successive turns of the earth around its axis. Over the course of an entire year, this averages out to the exact 24 hour day, but on any given day of the year, the length of the actual day (from the sun appearing in the same location on successive turns of the earth) varies depending on exactly where the earth is in its orbit. Both the ellipsoidal nature of the orbit, and the angle of the rotation relative to the ecliptic (the obliquity defined above) will shorten or lengthen the actual length of the day. These differences account for the fact that, for example, the day doesn't lengthen uniformly as one moves away from the solstice: the shortest day is not the same as both the latest sunrise and the earliest sunset, which is what the OP was asking about. In New York City this past December (see [10]), for example, the Winter Solstice occurred on December 21, however the earliest sunset occurred on about December 8 (4:28 PM) and the latest sunrise didn't occur until sometime during the first week of January (7:20 AM). There's thus a discrepancy caused by the Equation of time: The shortest daylight (solstice) of the year is neither the day with the earliest sunset, nor the day with the latest sunrise. It would be if the earth had a perfectly circular orbit AND had a perfectly perpendicular one WRT its axis. The fact that the earth's orbit is neither circular nor perpendicular is why there is a discrepancy. --Jayron32 07:51, 28 January 2013 (UTC)[reply]

I was with you until nearly the end. If the Earth's orbit were perfectly circular, and its axis perpendicular to the plane of that orbit, there wouldn't be a 'shortest day' - all days would be alike. AlexTiefling (talk) 10:19, 28 January 2013 (UTC)[reply]

Oh. Yeah. Duh. Well, skip that part. --Jayron32 14:04, 28 January 2013 (UTC)[reply]

Also, it's important to note that the length of a day is sinusoidal, with very little change near the peak (summer solstice) and trough (winter solstice), and rapid change at the vernal and autumnal equinoxes. This allows minor effects from the non-circular orbit, etc., to have a noticeable impact around the solstices, while those effects are swamped out at the equinoxes. StuRat (talk) 04:40, 28 January 2013 (UTC)[reply]

We are accustomed to thinking that the length of a day is 24 hours. Our clocks accurately measure 24 hours each day but the length of a day, measured by observing the position of the sun above the horizon, is only 24 hours when averaged over a whole year. It actually varies on a daily basis – sometimes a little longer than 24 hours and sometimes a little shorter. Relative to a clock, there is a discrepancy on all but a couple of days a year. This discrepancy aggregates and causes a difference between clock time and solar time. It is this difference that causes the day of earliest sunrise to occur a couple of weeks before the summer solstice, and the day of latest sunset to occur a couple of weeks after the summer solstice. Similarly, the day of latest sunrise occurs a couple of weeks after the winter solstice; and the day of earliest sunset occurs a couple of weeks before the winter solstice.

The reason for the slight variation in the length of a day, measured by observing the position of the sun above the horizon, is because the Earth’s orbit is elliptical rather than circular. When the Earth is closest to the sun it is moving at its fastest; and it is moving at its slowest when it is farthest from the sun – Keppler's Laws. Also the distance to the sun influences the angle through which the Earth must rotate before the sun appears above the horizon in the same position as the previous day. Dolphin (t) 11:41, 28 January 2013 (UTC)[reply]

The asymmetry of dawn and dusk puzzled me for about 40 years (at least on the occasions I thought about it) because it is world-wide and no geographical features can explain it. It was only when I properly understood the equation of time (explained above) that I realised I was looking for an explanation of something not real, but created artificially by clocks. Sunrise and sunset are always symmetrical about local noon (except for local geographic effects), but local noon drifts each side of clock noon, causing an apparent asymmetry with earliest sunset seeming to occur in early December, and latest sunrise being not until early January by the clock. The reason (put simply) is that local noon is changing rapidly with respect to clock time around the winter solstice. This will not always be so -- see Milankovitch cycles. Dbfirs 12:17, 28 January 2013 (UTC)[reply]

Oooh. I like that answer even better than mine. --Jayron32 14:05, 28 January 2013 (UTC)[reply]

ninhydrin

ninhydrin is said to test for the prescence of amino group so it can be used in factories manufacturing textiles from milk does it have any effect on food substrate that it can not be used in the later future — Preceding unsigned comment added by 212.49.86.44 (talk) 05:47, 28 January 2013 (UTC)[reply]

I've never heard of that particular usage of ninhydrin. It's main use is to turn purple in the presence of free amines; there are several specific uses in the Wikipedia article titled ninhydrin. If you have a link to the usage you are talking about, could you provide it here so we can look at it and help you out? --Jayron32 06:05, 28 January 2013 (UTC)[reply]

T90 and leclerc tanks autoloader

How the ammunition is transferred to the autolloader after it becomes empty ( from outside or inside the tank ?) do you think it is practical to have the ammo seperated ? does not that expose the crew to the threat of being attacked during reloading the autoloader? how much time does it take to reload the autoloader ? — Preceding unsigned comment added by Tank Designer (talk • contribs) 12:57, 28 January 2013 (UTC)[reply]

From the look of things here, the remaining 21 rounds stored outside the autoloader would have to be reloaded from the outside ("special packing cases in the hull" doesn't sound much like a glovebox to me). As for whether this is practical, etc, all design considerations are tradeoffs. Certainly every tanker would love to carry a few hundred rounds of ammo, all immediately and internally accessible, without otherwise impairing the performance of the tank, but that can't be done. Russia has a long history of reasonable tank design, and I strongly suspect that their tactical doctrine maps to having at most 20 rounds available per engagement, at which point the tank retires from direct combat to re-arm. Web fora discussing the T-72 put in-field reloading by the commander and gunner from carried ammo at 10-15 minutes under such conditions. — Lomn 14:52, 28 January 2013 (UTC)[reply]