Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

April 11

could a black hole exist at the center of a neutron star?

thanks, Rich76.218.104.120 (talk) 03:12, 11 April 2013 (UTC)

Not indefinitely. Plasmic Physics (talk) 03:30, 11 April 2013 (UTC)

What he said. Neutron star matter is expected to be fluid, so it would presumably just flow into the black hole and be consumed over time, and you would not have a neutron star for very long. Someguy1221 (talk) 06:16, 11 April 2013 (UTC)

And by "not very long" we're probably talking milliseconds! SteveBaker (talk) 11:22, 11 April 2013 (UTC)

perhaps you're right, whether it would be milliseconds or microseconds or days or what. I wondered if rapid rotation would play a role. But subatomic particles that decay in microseconds or less are still of interest in physics. i've also heard that very small black holes don't eat much, so i'm not convinced by the mere fact of of a LOT of [fluid or otherwise] mass pressing in on a black hole inside a neutron star would for sure cause it to take in all the neutron star's mass. If the black hole were small enough, i thought the "black hole evaporation" tendency could be roughly cancelled by the ready availability of mass inside the star.{to keep the black hole going, yet have the neutron star containing it exist for a "long" period of time}76.218.104.120 (talk) 12:28, 11 April 2013 (UTC)

Black hole evaporation ius one of those unproven ideas like gravitons, string theory, branes, etc. Much may be written but far less proof exists. Rmhermen (talk) 12:57, 11 April 2013 (UTC)

Thought I would check those intuitive answers with a back of an envelope, non-relativistic, much hand waving calculation. Assume that the rate of growth of the black hole is limited by area of its event horizon, the speed of light and the density of the surrounding material. Then in a "best case" scenario (or worst case from the POV of the neutron star) we have

${\frac {dm}{dt}}=4\pi r^{2}c\rho$

and for a non-rotating black hole r is the Schwarzschild radius

$r={\frac {2Gm}{c^{2}}}$

so

${\frac {dr}{dt}}={\frac {8\pi G\rho }{c}}r^{2}$

Integrating this gives

${\frac {1}{r_{0}}}-{\frac {1}{r_{t}}}={\frac {8\pi G\rho }{c}}t$

where r₀ is the initial radius of the black hole. If r_t is much greater than r₀ then we have

$t\approx {\frac {c}{8\pi G\rho r_{0}}}$

Taking a typical density at the centre of a neutron star to be 10¹⁸ kg/m³, then I make the time taken for the black hole to absorb the whole star to be of the order of 0.2 metre seconds divided by the initial radius of the black hole. For a millimetre sized black hole, this gives a timescale of minutes rather than milliseconds. Gandalf61 (talk) 13:16, 11 April 2013 (UTC)

Your calculation neglects the (very important) fact that the density around the black hole would not remain constant during the collapse. Dauto (talk) 15:59, 11 April 2013 (UTC)

Look for instance [1] where a detailed computer simulation shows that the collapse happens in less than 10 ms. Dauto (talk) 16:16, 11 April 2013 (UTC)

Haven't looked up the paper yet, but I'd just point out a possibly very important consideration: All that mass going into the black hole is going to be accompanied by a truly spectacular release of energy. Maybe enough to blast away part of the neutron star? Don't know; it's not like I can solve the equations (or even formulate them) in my head. Does the paper take that into account? --Trovatore (talk) 16:19, 11 April 2013 (UTC)

shall i take away a "yes" to the original question--that a black hole can exist inside a neutron star, regardless of how long it lasts?76.218.104.120 (talk) 04:24, 12 April 2013 (UTC)

Yes. Plasmic Physics (talk) 04:34, 12 April 2013 (UTC)

I hate when a potentially simple answer is complicated with obtuse mathematics and peripheral theory. It is akin to verbosity. Plasmic Physics (talk) 04:46, 12 April 2013 (UTC)

Well, I hate trivial soundbite answers because they are so facile and uninformative. I didn't know that a black hole could absorb something as massive as a neutron star in milliseconds. Now I know that (a) yes it can and (b) the scenario has been studied in detail. So I have learned something. Gandalf61 (talk) 09:04, 12 April 2013 (UTC)

With respect to the OP, it doesn't matter whether you learned something does it now? Giving a concise answer takes priority over divergent exploration of related notions. Its only fair to first answer the OP's question, before endulging in such a manner of discussion. Plasmic Physics (talk) 09:40, 12 April 2013 (UTC)

Well, I certainly don't think the OP learned anything from your trite "Not indefinitely" response, beyond the fact that you couldn't be bothered to take their question seriously. Thanks to the further discussion, we know how long it takes for the neutron star to collapse, and we have an source for that information. Gandalf61 (talk) 10:34, 12 April 2013 (UTC)

You're missing my point - the OP never inquired for an expanded answer, which is clear from his most recent post. Plasmic Physics (talk) 11:06, 12 April 2013 (UTC)

Actually I learned a lot from all of you and I appreciate both Gandalf's and Plasma's help! I'll admit I did press for a yes or no which in past inquiries I have not always gotten, due to a delightful tendency(No sarcasm here, it's not just delightful, it's also educational)of refdeskers to go off on tangents. -Rich199.33.32.40 (talk) 21:42, 12 April 2013 (UTC)

8th dimensional space

so i was looking at 8th dimensional space page the quantum entanglement and alternate realities i need help to see if i am right

so pretty much 8th dimension is saying there our many universe like ours but different at the same time and if one were to get to one of these many dimensions it would cause a tear in space causing a new reality and if one travels though many tears it cause confusion in the universe meaning the quantum entanglement if my idea of what these are are wrong let me know plases — Preceding unsigned comment added by 99.12.149.156 (talk) 03:36, 11 April 2013 (UTC)

I can't see how you got all that from our article on Eight-dimensional space, so you must have been reading this somewhere else. Sorry to tell you, but it sounds like a bunch of science fiction nonsense. Someguy1221 (talk) 06:18, 11 April 2013 (UTC)

You should be asking the real expert: particle physicist Buckaroo Banzai. Clarityfiend (talk) 07:15, 11 April 2013 (UTC)

There is some confusion here. The word "dimension" has two meanings:

• In the sense of "eight dimensional universe", the meaning is like "three dimensional universe" - we'd be talking about a universe where there are more directions you could move in than just the north-south, east-west and up-down that we are normally aware of.
• In the sense of "travelling between dimensions" - we're talking about "parallel universes".

Generally, scientists only use the first of those two meanings. The two meanings of the word are not connected or related in any way.

When we are considering quantum entanglement and things like certain interpretations of the Schrondinger's Cat thought experiment - then we are talking about parallel universes...not extra spatial dimensions. "Tears" that allow you to move between parallel universes are in the realms of speculation and science fiction. As far as I know, there is no evidence that they might exist from mainstream physics...quite the contrary in fact...there is reason to assume that they'd be fundamentally walled off from each other.

When we're talking about "extra dimensions" in ideas such as string theory - then we're talking about "directions you can move in".

You're basically stuck in this universe - and whether there are others (due to quantum effects, for example) is an undecided question.

SteveBaker (talk) 11:22, 11 April 2013 (UTC)

There is one more scientific usage of the term "dimensionality" - the usage in the sense of degrees of freedom in a generalized coordinate system. For example, if we are describing an n-body simulation, it is common to call this a n dimensional problem, (or even more accurately, a 6-n dimensional problem, for example, accounting for velocity and position of each object in conventional dimensions x, y, and z; by extension, you can add one dimension to each degree of freedom in the problem). When we generalize a coordinate system, we can apply constraints based on physical law, and reduce the complexity of the problem to a lower dimension.

In this usage of the term, it is frequently helpful to understand the distinction between the rank and the size of a problem-space. A problem can be n-dimensional, but modeled with extra dimensions; this is called "degeneracy", and it can be helpful for practical purposes, even if it adds no new information. Nimur (talk) 21:07, 11 April 2013 (UTC)

This is almost surely a reference to http://www.tenthdimension.com/ — whether that pseudo-spatial interpretation is worth anything is beyond the scope of this comment. --Tardis (talk) 03:12, 12 April 2013 (UTC)

cyanoacrylate bond inhibitors

I recently bonded some rubber like swim fin material to itself and a glass fiber and resin material using a high quality cyanoacrylate with the manufacturer's 'filler' powder for plastics and rubber. Initially the bond seemed to hold but failed after several 20-30 minute uses on a swim fin in a chlorinated swimming pool. I am thinking that the bond may have been effected by residual chlorine compounds left on the surface prior to bonding. Other uses of the bonding product yielded exceptional results on similar rubber like materials where chlorine was not involved. Are there known adverse effects to bonding where chlorine compounds are present? What other chemical conditions might adversely affect bonding? Suggestions?

A prompt reply would be appreciated.

Walt Silfies - 50.53.114.100 (talk) 07:11, 11 April 2013 (UTC)

I don't see anything out there about reactions with chlorine - just about the only thing that I see might be that cyanoacrylate doesn't stick well to glass - so perhaps the glass fiber material is the cause here. That sounds like a bit of a stretch to me - but it's all I could find. SteveBaker (talk) 15:43, 11 April 2013 (UTC)

can you examine to see what failed? i.e. did the glue come loose from the rubber, or from the fiber/resin, or did the glue stick to both but deteriorate itself? my experience with cyanoacrylates and rubber is that it works very well (I use it to patch pinprick holes in bike tire tubes) but that hasn't involved immersion. re chlorinated compounds, stuff like chloroform is a good solvent for many plastics but whether that exists in enough concentration in a pool and/or whether it would attack acryclics, I don't know. Gzuckier (talk) 16:49, 12 April 2013 (UTC)

Perception of pain, which part of the brain is the gatekeeper?

I've always wondered how people can exert so much control over their perception of pain. If the stimulus is the same, the same sensory neurons fire and in the end the same regions in the brain get stimulated to an equal degree, then how is it possible to change your perception of pain, between the same stimuli? When I am on an operating table, unconscious, does my " body " still feel pain, even though I don't " know " that it is there? Can the part of my brain that is conscious effectively act as a signal limiter? Who is the gatekeeper? Has any research been done on this? 137.224.239.102 (talk) 08:45, 11 April 2013 (UTC)

Basically, the thalamus, though it isn't a conscious process. See nociception for details. - Nunh-huh 09:40, 11 April 2013 (UTC)

Many aspects of pain are still very mysterious to us, and the answers to the questions really aren't known with any clarity. Part of the difficulty is that what we call pain is actually a mixture of several aspects -- Ronald Melzack identifies three that he calls "sensory-discriminative" (sense of the intensity, location, quality and duration of the pain), "affective-motivational" (unpleasantness and urge to escape the unpleasantness), and "cognitive-evaluative" (cognitions such as appraisal, cultural values, distraction and hypnotic suggestion). (Note: I've copied that from our pain article, which is worth reading.) Each aspect is implemented by a different brain system, and differently affected by brain manipulations. We are only beginning to understand the systems and their interactions. One thing that is clear is that there is a lot of "top-down" circuitry that allows higher brain levels to modulate signals at lower levels, even down to the spinal cord. Looie496 (talk) 15:42, 11 April 2013 (UTC)

Thanks for the answers! :) 137.224.239.102 (talk) 17:42, 12 April 2013 (UTC)

Are there drugs that boosts willpower?

Are there drugs/medicines that boosts willpower? — Preceding unsigned comment added by 50.100.191.39 (talk) 18:41, 11 April 2013 (UTC)

Certain stimulants like Ritalin have this effect. Many students who study boring subjects like law take such drugs. Count Iblis (talk) 18:54, 11 April 2013 (UTC)

Law's only boring for most people. Some of us actually enjoy it. Shadowjams (talk) 15:01, 12 April 2013 (UTC)

Read:Dutch courage. Alcohol can depress some parts of the brain (as can some other drugs) that usually inhibit some forms of action. People that show the quality of having great will-power often have a low level of fear. Amphetamines were taken by the hand-full by American pilots during the second world war, because they did not only keep them alert but made them feel immortal and fearless, yet people may not survive very long with just that attribute. I think therefore, you may be asking about the type of will-power that brings successes. That requires a blend of other attributes. In that respect, I haven't come across any drugs that can have any long term benefit. Before anybody else steps in and pontificates, I'm not including Entheogens because these require the individual to also intellectualize (e. i., WORK) on seeking out whatever understanding they can glean from their experimental voyages. Will-power proper, I think, is a product of clear thought. Trying to think and carry out a plan of action whilst one's brain is under the influence of supposed artificial enhancements -will not achieve this. --Aspro (talk) 20:33, 11 April 2013 (UTC)

The question is ill-formed. There are various reasons besides akrasia that people lack the will power to do things--fear; lethargy; craving; compulsion. There are all sorts of drugs to treat anxiety, hunger, tiredness, OCD. So the broad answer is yes, drugs from caffeine and alcohol, to cigarettes and amphetamines, to xanax and zoloft all effect the mind. μηδείς (talk) 21:51, 11 April 2013 (UTC)

Given that a question is a request to be informed, I think that goes without saying. 202.155.85.18 (talk) 02:02, 12 April 2013 (UTC)

It's a good question, Medeis is being too glib about it. Although we usually think of willpower as a good thing... however it's probably better characterized as drive. In most mammal's evolution pleasure (or avoiding pain) and drive were yolked together, but in some instances, and especially when you start having fun with various plants, those two are distinct. There is a lot of really nuanced research on the subject... and then there's breathless articles comparing a book/movie to real life that center around modafinil. But also testosterone, amphetamines, and all sorts of other psycho active drugs affect motivation. It's quite complicated. Shadowjams (talk) 14:59, 12 April 2013 (UTC)

The basic problem here is that the concept of willpower is essentially dualistic. In terms of the "ghost in the machine" metaphor, willpower is the degree to which the ghost exercises control over the machine. But whenever one tries to understand dualistic concepts in biological terms, one runs into unsolvable boggles. Looie496 (talk) 15:37, 12 April 2013 (UTC)

Exactly, the question is based on the false assumption that there's some one thing called willpower and that a certain drug can turn its knob up higher. There are all sorts of reasons why one might fail to achieve a goal one has in mind. μηδείς (talk) 17:21, 12 April 2013 (UTC)

Launching yourself from lying on the ground to upright position using only your arms muscles

Are there people who can do this? I've seen people do so-called Muay Thai push-ups, so it seems to me that it is possible. It would require more strength than you need to do the Muay Thai push-ups, but then there are people who can do hundreds of these in a row. However, I've never seen or heard about people who can launch themselves up from lying to standing position using a push-up move. Count Iblis (talk) 19:17, 11 April 2013 (UTC)

Lying on your back or chest? I can do "kip-ups" which is lying on back to standing upright. But this involves alot of leg motion.165.212.189.187 (talk) 20:17, 11 April 2013 (UTC)

I found this, but I suspect some trickery. Alansplodge (talk) 21:59, 11 April 2013 (UTC)

I agree it looks suspicious. For example, just before the young man gives a big push to get up to the vertical, the bottom of his T-shirt rides upwards a couple of inches for no apparent reason. Now if the whole thing were actually performed in reverse and then played backwards, I can imagine the bottom of the T-shirt riding upwards as he fell forwards and downwards, and then extending to its proper position after he came to rest. Dolphin (t) 08:16, 12 April 2013 (UTC)

It's beyond "suspicious"...it's an obvious fake, and a very poor one at that. YouTube demonstrations of any kind have to be viewed with deep suspicion - there are *FAR* more fakes than there are real demonstrations. SteveBaker (talk) 16:36, 12 April 2013 (UTC)

Agreed - I was just being charitable. Alansplodge (talk) 18:09, 12 April 2013 (UTC)

I bet you could do it on the moon, although you may have to take off the space suit. Gzuckier (talk) 16:51, 12 April 2013 (UTC)

Oh no you don't - Charlie Duke shows how it's done. Alansplodge (talk) 18:16, 12 April 2013 (UTC)

Ha, so except that fake video, no real evidence! Perhaps the Refdesk volunteers should try this and upload videos of their attempts! Count Iblis (talk) 12:31, 13 April 2013 (UTC)

I don't suppose using a trampoline is allowed? :) Wnt (talk) 22:15, 13 April 2013 (UTC)

It would be an interesting experiment to get some really fit volunteers and a variable slope that can pivot from 0 degrees (flat on the ground) up to 90 degrees (like a wall). By finding the minimum angle from the ground we could make a good guess whether it is impossible; If nobody volunteer could push themselves upright at a slope of less than 45 degrees I would think that doing it from zero degrees would not be humanly possible.

You would need fit volunteers of various builds (heavy muscled to light athletic) and heights. My guess would be that the shortest people with a light athletic build would do best. -- Q Chris (talk) 13:57, 15 April 2013 (UTC)

April 12

Low mass white dwarf actually currently exist

Since the article said white dwarf can be 0.17, do the white dwarf dwarf being 0.17 actually exist currently, or is it just the estimation of the stars did not yet come off the main sequence. Is this true alot of white dwarf are binary stars, can 0.5 solar mass white dwarfs? is it more common for white dwarf to be single star system, or binary star system? Is white dwarf all the exact same size on single star system/non-binary star ssytem? or the Solar mass determined by white dwarf has to determine exactly how big the white dwarf has to be?--69.226.42.134 (talk) 00:36, 12 April 2013 (UTC)

I struggle to see how a very small white dwarf (such of 0.17 solar masses) could form other than from a small red dwarf collapsing. Red dwarf stars live for a very long time, so none of them are dead yet. That would suggest there are no very small white dwarf stars. A lot of stars are in binary systems and they will generally remain in those systems when they die, so yes it is true that a lot of white dwarfs are in binary systems - I don't know if it is more than half, though. The size of a white dwarf is determined by the size of the star that formed it. In a binary system, there might be some transfer of matter between the stars that can change things. In a non-binary system, there obviously won't be. Does that answer most of your questions? I found them a little hard to understand... --Tango (talk) 11:43, 12 April 2013 (UTC)

Stars loose a substantial fraction of their original mass when they go through the late stage of red giant/Asymptotic giant branch and planetary nebula stage, so the white dwarf may end up much lighter than the original star. With that said, I have to say I don't really know what the lightest white dwarfs masses are. Dauto (talk) 19:09, 12 April 2013 (UTC)

See SDSS_J0106-1000. Ruslik_Zero 19:19, 12 April 2013 (UTC)

Fascinating case! I'm trying to picture what it will look like as they get very close together. I suppose Roche lobes can't actually have condensed matter going all the way to the center because it should be under zero pressure there. I suppose if humanity somehow doesn't self-annihilate, the more lunatic descendants of our race will dive through that strait for excitement. When the stars do start to fuse ... I suppose they'll still be rotating too fast to have enough pressure in the center for helium fusion, but it would start somewhere under the combined pole?Wnt (talk) 22:13, 13 April 2013 (UTC)

Bird evolution

Are the falcons, parrots, and sparrows really the closest relatives of one another, as people say? If so, who evolved from whom in this taxonomy? And also, if the falcons and the passerines are so closely related, which of the passerines are the most closely related to the falcons? (I'm guessing it would be the swallows, based on purely morphological info, but I can't be sure). Oh, and are the whippoorwills more closely related to the swifts, or to the owls? 24.23.196.85 (talk) 05:50, 12 April 2013 (UTC)

None of those groups evolved from another of them. Their most recent common ancestor was a member of neoaves but not of any of those groups (according to our articles). All falconiformes are equally closely related to all passerines. Regardless of which falcon and which passerine you pick, you get the same ancestral species as their most recent common ancestor. And according to our articles, whippoorwills are more closely related to swifts than to owls. Looie496 (talk) 06:43, 12 April 2013 (UTC)

(EC) You may be thinking of discussion surrounding some recent studies like [2] [3] [4] [5]. You should be able to read both studies (the former may require free registration) and although they may be a little difficult for someone without a biological background to properly understand, you should get some idea and should also be able to view the various trees shown and seek help here to understand the parts which are confusing. The 2008 study (first 2 links) in particular was and is I believe regarded as fairly significant, you should be able to find a fair amount of discussion of it in blogs and other such sources, although looking for the better ones may be difficult, I think [6] is okay. As mentioned in our article Evolution of birds#Classification of modern species, this is still an area of some flux (as with quite a lot of taxonomy, particularly given the increasing ease of genomic analysis) and the 2008 study is obviously only about 5 years old although I don't know specifically how well the relationship between the species you mention is supported. I would note statements like 'who evolved from whom in this taxonomy' should generally be avoided when talking about extant species as neither extant species is going to be the same as the ancestral species. Similarly for statements like 'which of the passerines are the most closely related to the falcons' as most likely they all have the same most recent ancestral species. Nil Einne (talk) 06:51, 12 April 2013 (UTC)

Thanks! Maybe I should have put the question about "who evolved from whom" another way: which of the three orders (falcons, parrots and passerines) is the closest to their common ancestor, and which is the most distant? 24.23.196.85 (talk) 01:06, 13 April 2013 (UTC)

Most evolutionary biologists would consider them all to be equally distant from the common ancestor. That's because the usual way of measuring distance is time since the split. There are other possible measures, for example disparity between genomes (which can vary because there is some variability in rates of mutation). Even for that you would probably find that they are all at nearly the same distance, and it would be quite difficult to find out which is closest. Looie496 (talk) 02:19, 13 April 2013 (UTC)

Right, I was asking about genetic distance from the common ancestor. But I wouldn't be surprised if the answer comes out to be "Insufficient Data". Thanks for the info! 24.23.196.85 (talk) 03:29, 14 April 2013 (UTC)

Sediba's hands.

Can anyone figure out what's going on with Sediba's hands in the skeleton on the right, here? μηδείς (talk) 10:00, 12 April 2013 (UTC)

Have you mis-read the caption? H sediba is in the middle. The one on the right is a chimp. Rojomoke (talk) 12:13, 12 April 2013 (UTC)

I assumed the caption above was for the picture above--but please look at the hands (and the snout) and tell me if that looks like any great ape you've ever seen. The thing has effing flippers. Or am I missing something? μηδείς (talk) 12:59, 12 April 2013 (UTC)

There seem to be a few fingers missing. Dauto (talk) 14:32, 12 April 2013 (UTC)

It might help to look at http://www.boneclones.com/KO-303.htm. Looie496 (talk) 17:10, 12 April 2013 (UTC)

According to Looie's link the shape looks right, It still seems quite odd that the hand is the length of the femur. μηδείς (talk) 17:15, 12 April 2013 (UTC)

A Google search provides images of chimp skeletons (also orangutans and gibbons). The hands in OP's picture are in the foreground and the phalanges of the left hand are splayed, which makes the hands appear larger, but the relative size does seem to be typical of a chimppanzee. The snout length and nasal opening do appear different than in other images of chimpanzee skeletons, but these are the only images I've seen recently, so I'm far from expert.--Wikimedes (talk) 19:39, 12 April 2013 (UTC)

So in other words the chimp is standing with his hands toward the camera, like this? I suppose that would explain the otherwise apparently freakish proportions. μηδείς (talk) 19:57, 12 April 2013 (UTC)

Motion of electrons

What type of motion of electrons around the nucleus? It is circular, periodic, uniform, non-uniform or other motion? Scientist456 (talk) 12:27, 12 April 2013 (UTC)

No one knows, I asked a similiar question here some time ago. Plasmic Physics (talk) 12:36, 12 April 2013 (UTC)

I suggested two types of motion, which are both wrong (now I know): random teleportation; and they exist everywhere at one in the form of an electronic fog, the mass and charge density profile of which is described by the schrodinger equation. Plasmic Physics (talk) 12:40, 12 April 2013 (UTC)

Electrons don't move in a classical motion. Indeed, they are not classical particles. Their distribution probability is governed by quantum physics. Some simplified models assume discrete circular orbits with additional constraints. See Bohr model, Matter wave and Pauli exclusion principle. --Stephan Schulz (talk) 12:46, 12 April 2013 (UTC)

So, basically they slosh? μηδείς (talk) 13:00, 12 April 2013 (UTC)

... and sometimes they tunnel. See atomic orbital for more information. Gandalf61 (talk) 13:10, 12 April 2013 (UTC)

Periodicity figures strongly in quantum mechanical treatments of particle motion (basically to prevent particles from interfering with themselves), see for example particle in a box. Atomic_orbital#Orbitals_table has drawings of the shapes of probability distributions of single electrons of different energy levels orbiting a nucleus.--Wikimedes (talk) 19:13, 12 April 2013 (UTC)

From my limited knowledge- the electrons are in various shaped shells which are a probability density function. There is something called the measurement problem [[7]] which prevents the particle from behaving in the classical sense. — Preceding unsigned comment added by Ap-uk (talk • contribs) 23:32, 13 April 2013 (UTC)

That considers where they move, not how. Plasmic Physics (talk) 13:12, 15 April 2013 (UTC)

Invasive species

Humans have invaded the entire planet, each and every continent, oceans, destroying all ecosystems and making other species extinct. They why humans are not considered invasive species? --Yoglti (talk) 16:53, 12 April 2013 (UTC)

Who says that humans are not considered invasive species? Looie496 (talk) 17:12, 12 April 2013 (UTC)

See Gaia hypothesis. --TammyMoet (talk) 18:27, 12 April 2013 (UTC)

the idea of invasive species is a matter of point of view, really. it's not like the biosphere of the earth is defined or has a defined goal. one species piggy backs on another and ends up in a new area and does well. doesn't matter if it's in the bilge of a ship or the large intestine of a dinosaur. but as far as being responsible for extinctions, we are definitely number one, i would guess Gzuckier (talk) 20:01, 12 April 2013 (UTC)

Why Wikipedia article Invasive species does not list humans? --Yoglti (talk) 09:43, 13 April 2013 (UTC)

Because we're too arrogant? It's not really the point of the article, we don't really compete in any ecological niche any more, we're "out of the race" so to speak. Vespine (talk) 23:04, 14 April 2013 (UTC)

Probably because almost every definition of the term "invasive species" is contingent upon some activity, presence, and demarkation by and of humans. For the most part, invasive species wouldn't be invading without humans. ~ Amory (u • t • c) 17:29, 15 April 2013 (UTC)

Limits of knowledge

If knowledge, memories, thoughts, are just connections made in our brains, does that mean that knowlede has limits? I mean its possible that we might not even comprehend all there is to know about the universe?203.112.82.128 (talk) 17:52, 12 April 2013 (UTC)

Yes, you can only store a finite amount of information in your brain. You can't even know the exact state of your own brain, because that would require at least the full brain capacity while a lot of that is already in use to perform essential functions. Count Iblis (talk) 17:56, 12 April 2013 (UTC)

Haldane's Law (excuse the archaic language): "The universe is not only queerer than we imagine, it is queerer than we can imagine" --TammyMoet (talk) 18:26, 12 April 2013 (UTC)

yeah, after studying a lot of philosophical basics lately (The Great Courses, better than my college humanities requirement) i've come to doubt not only that humanity is capable of understanding the underlying reality of the universe, but that there even is an underlying reality; as well as that humanity is capable of understanding the functions of "mind" as distinct from brain. Gzuckier (talk) 20:07, 12 April 2013 (UTC)

However, with the invention of writing, it became possible to store knowledge outside the brain. And, with the internet, we can now potentially quickly access all knowledge we have accumulated. Wikipedia, of course, plays an important role in all of this.

I like to think of knowledge like a program and data. The data can be stored outside the brain, with the brain just holding the program to use that knowledge. For example, say I want to determine the volume of a sphere. I access the data externally, to get the formula to calculate it. The formula is V = 4πr³/3. Now I use the program in my brain to determine that r means the radius and π means ≈3.14159 (or I look that up, if I don't know it already). I then use the program in my brain to tell me how to multiply, divide, and cube numbers, probably using a calculator. This is a very simple example, but we can potential solve much more complex problems in this manner. StuRat (talk) 20:21, 12 April 2013 (UTC)

I apologize but i think im looking for a different answer and its my fault because i didnt formulate my question well. What im trying to get into is, say a coin, there is only heads and tails, so there is just two outcome if you flip a coin, now go to our brains, there is just limited number of combination of connections in our brain right? Now my question is, given that the method on how we understand things are just one combinations of our connections in our brains, is it possible that there are certain data in our universe that we will never understand simply because its something that needs to be a set of connection that our brain is not capable of doing? for example, back to the coin, is there a data that niether heads nor tails can understand? Im not a native english speaker so please try to understand and thanks in advance. 203.112.82.1 (talk) 22:01, 12 April 2013 (UTC)

but that's the question; how is information stored in the brain? it's definitely not the way it is in computers. to me it seems to be more diffuse; i.e., you can forget what your grandmother looked like, but you won't forget that you had a grandmother, or that your grandfather was married, or that your mother had a mother, or what a grandmother is in general. it's like every concept/meme has a bunch of loose ends that tangle up with the loose ends of other concepts, somehow, in such a way that much of the structure assembles itself from what it connects to. as if you have a grandmother-shaped region in your model of the world, and even if you've forgotten or never had the memory of your senses in reference to your grandmother to fill in the hole, that grandmother-region still must exist and be referred to as grandmother by the rest of your mental world. so, what are the limitation of something like that in terms of finite number of neurons and synapses? well, you certainly can't know everything about the universe in perfect detail, i.e. the state of every subatomic particle, but that might be as much an effect of the finite amount of time you have to investigate than of your storage. Gzuckier (talk) 01:14, 13 April 2013 (UTC)

• Tangentially related to this discussion are concepts like the Bekenstein bound and Bremermann's limit. The math and physics there is pretty dense, but the concept is sound: there has to be an upper limit to the amount of information we can store about anything, and how well we can retrieve it. We can't know the entire universe, because to store information about the entire universe would require an entity at least as large as the universe and separate from it. The entire field which deals with quantifying information, including its storage and retrieval, is known as Information theory, which in part deals with the very question of how much information can be stored in a given medium. For example, the theoretical maximum amount of information stored in your brain is constrained by the number of cells and synapses in your brain. Now, this theoretical limit is probably orders of magnitude more than the functional limit, but it's a starting point, and indeed, is a subject which is well studied and explored, if you have the time to research it and the ability to weed through some fairly arcane mathematics. --Jayron32 05:30, 13 April 2013 (UTC)

• But that's why we have models. A simplified model allows you to store most of the important information about an object in much less space. Take the blueprints for a building. They may not note where every nail is, but you don't normally need to know that, and, if you need that level of info, you can go and look for the nails at that time. StuRat (talk) 17:59, 14 April 2013 (UTC)

It is already clear to me that there is a limit in how much info our brain can store, im more interested in what is the limit of what our brains can understand. In theory, if i study hard enough, i would be able to understand special relativity , but is there any concepts out there that our brains are not wired to understand? I mean of course if the answer is yes, we wont know the things we were not able to know, im just curios if there is any research or concepts that tackles this subject. I dont know if gzuckier already answered this, if so, can you please explain more 203.112.82.128 (talk) 17:53, 13 April 2013 (UTC)

I'm not sure I grok what you mean by "understand". You say "are there any concepts out there that our brains are not wired to understand". Concepts are all human-created things, so theoretically no, there is no concept which cannot be understood by any human. In order to be a concept, it has to have been conceived by somebody, which means that at least one person understands it. Now, colloquially, there are certain famous "concepts" which have been (jokingly or a bit tongue-in-cheek) said to have been incomprehensible. Lord Palmerston famously said of the Schleswig-Holstein Question that "Only three people...have ever really understood the Schleswig-Holstein business—the Prince Consort, who is dead—a German professor, who has gone mad—and I, who have forgotten all about it." and Richard Feynman once famously said of Energy, "It is important to realize that in physics today, we have no knowledge what energy is." Now, that doesn't mean that these problems are entirely incomprehensible (many historians have extensively studied the Schleswig-Holstein question, for example, and some I am sure have a good handle on it, and energy is something which many physicists study extensively, Feynman's quote is merely a negative assertion of the Dunning–Kruger effect, which notes that the deeper physicists get into energy, the harder it is to define it in as simple terms as, say, a high school physics text does). But fundamentally, no, there is no concept which is entirely incomprehensible to any humans insofar as any coherent concept is a human-created thing in the first place. If you really want to get deep into this, do some reading in the branch of philosophy called Epistemology. --Jayron32 03:30, 14 April 2013 (UTC)

When I say "understand" I mean when you are introduced to a data, your brain rearrange its connections so that you would comprehend the data in front of you. and since brain is just a finite thing, I assume there is only finite ways of rearranging those connections, meaning there's a limit of what we can "understand", I dont think im asking about the philosophy of it but simply the physical limits of our brains. 203.112.82.1 (talk) 16:03, 14 April 2013 (UTC)

In this sense, you can understand everything. The brain is capabable of universal computation (the limits only being the amount of data it can process). At various levels, if there is anything to understand about some natural phenomena, you can formulate it in terms of simple equations, which the brain can easily handle. If it's not a matter of something you can formulate using a few bits of information, then you cannot say that there is a clear cut explanation for the observed phenomena, as it would depend on a large number of variables. So, there would then be nothing to explain. Count Iblis (talk) 16:18, 14 April 2013 (UTC)

You seem to have ignored my comment on our ability to store information externally to our brain. To use a computer analogy, the RAM is the where the "programs/intelligence" is normally stored, but the data is largely on the hard drive or other external media. Similarly, humans only need to store the intelligence in their brains, and can access the data from other sources, like Wikipedia. StuRat (talk) 17:54, 14 April 2013 (UTC)

Oh no, I understand your answer that knowledge can be stored outside of our brains, but I just thought that it is not what I'm asking about. To use your computer analogy, what i was asking is if there is a file type that my computer cannot read, for example the brain is capable of reading .jpg or .gif files, but is there a .wiki of .xyz that we will never comprehend? 203.112.82.1 (talk) 20:37, 14 April 2013 (UTC)

Well, you can have a file too large to store the entire thing in RAM at once. The computer then uses paging space or other methods to store parts of it externally. It works out that to solve most problems, you only need to keep a small portion of the data in active memory at any time (although it certainly is faster if you can keep it all there). StuRat (talk) 13:36, 15 April 2013 (UTC)

Ok, when you say "file too large to store", I assumed your answer is still regarding the limit of data our brain can store, which is not why im asking, or maybe i just didnt understand the answer.203.112.82.128 (talk) 16:02, 15 April 2013 (UTC)

Stud finders

Looking at the reviews of stud finders on Amazon, all of them have mixed reactions. Some people say they work as they should and others say they don't. I'd like a stud finder but would like one on which I can rely. Are some people just using them wrongly? Some people say they're inconsistent. --2.97.27.107 (talk) 17:54, 12 April 2013 (UTC)

They are many types of walls and a few types of stud finders. Most work fairly well on modern drywall (plasterboard)-type walls. But on my old over-an-inch thick plaster/gravel/horsehair on metal lath walls, none ever work. Rmhermen (talk) 19:05, 12 April 2013 (UTC)

I've tried out maybe 4 or 5 different types over the years, both the magnetic (looks for nails) kind or the electronic (capacitance I assume) kind, not any of them worked any better than just pounding on the wall and listening for the change in sound. Gzuckier (talk) 20:09, 12 April 2013 (UTC)

Yeah, I think I'm just gonna knock on the wall. Thanks 2.97.27.107 (talk) 21:08, 12 April 2013 (UTC)

Drilling exploratory holes with a really thin drill bit is another strategy, the idea being that the holes are so tiny you can patch or cover them easily and they will never be noticed by most observers. HiLo48 (talk) 23:05, 12 April 2013 (UTC)

Studs are also spaced a standard distance apart, usually, so once you've found one, a ruler is usually helpful. In most houses, electrical outlets and switches are required to be in junction boxes which are bolted to a stud. In the United States, the standard is 16 inches center-to-center between studs. So, if you start at the wall switch, find the stud it is attached to, then measure off 16 inches, you should find another stud. And so on. --Jayron32 03:55, 13 April 2013 (UTC)

Maybe. 16" is a modern standard for exterior walls in many locations. But other walls (especially interior) may be 12", 16", 18", 19.2" or 24". Not to mention doubled studs, ones moved over for pipe runs, bizarre window framing. And it depends on local codes for climate, hurricanes, type of stud, etc. Construction practices have changed greatly even in recent years. Rmhermen (talk) 16:16, 13 April 2013 (UTC)

Most stud finders I think, work well for most people. The problem may be in part that complaints are, as the OP opinions, by some people who don't know how to use them properly and impart because some walls (as found by editor Rmhermen above) defeat the capabilities of cheap stud finders. Borrow a cheap stud finder to see if it suits your walls – if so good – answer obvious. If not borrow a professional stud finder. If you find that better -then buy one. Don't know what part of the world your in but a professional quality SUB-SCANNER M12 is not expensive when you consider how much it would cost you to get a professional trades person in to do the job. These detectors have the necessary discrimination to cope with most walls.Aspro (talk) 19:31, 13 April 2013 (UTC)

biology

Is there possibility of multiple nipples in one brest of a human female ?If so then what is the reason? — Preceding unsigned comment added by Titunsam (talk • contribs) 18:25, 12 April 2013 (UTC)

The article you want is probably supernumerary nipples. Rmhermen (talk) 18:53, 12 April 2013 (UTC)

Um, witchcraft. μηδείς (talk) 19:58, 12 April 2013 (UTC)

Francisco Scaramanga. Though i don't think Christoper Lee is female. --Jayron32 02:32, 13 April 2013 (UTC)

It is not limited to females (or humans for that matter) Roger (Dodger67) (talk) 12:03, 13 April 2013 (UTC)

the real star wars universe in 2014?

I want the real Star Wars universe by next year please. Contact NASA. SmallSoldiers123 (talk) —Preceding undated comment added 21:39, 12 April 2013 (UTC)

Is there a question? But here is NASA's contact page. Cheers. --Wirbelwind(ヴィルヴェルヴィント) 22:06, 12 April 2013 (UTC)

Resolved

April 13

Minimum population required for the survival of a race.

The article on Angam Day currently states:

Upon eclipsing a population of 1,500, a number considered to be the minimum required for the survival of a race, Angam Day was declared.

Does a race really need a minimum population of 1,500 to survive? If true, why? If false, how many people does a race need to avoid extinction? Thank you in advance. --190.19.69.254 (talk) 04:33, 13 April 2013 (UTC)

Hmmmm. That's a pretty ugly part of that article. I would much prefer that the term ethnic group had been used throughout. Race is an unclear word with unfortunate connotations. The article Nauruan people, linked from Angam Day, avoids the term race completely. I note that the claim of 1,500 being the minimum number for a race to survive is unsourced. That's not good, and only makes things worse. I went hunting and couldn't find a source myself. You've got me thinking about what we should do with the article. HiLo48 (talk) 04:54, 13 April 2013 (UTC)

Reads like unmitigated bullshit to me. What makes an ethnic group (or race) a distinct unit is a shared culture. I'm not sure there's any arbitrary lower or upper limit on that, merely that the group has a certain level of cultural cohesion and distinctiveness, and I certainly can't find any literature that indicates that there's some official or "scientific" or whatever reason that would indicate that 1500 is some magic number. --Jayron32 05:00, 13 April 2013 (UTC)

The article clearly states that the number 1500 came from Brigadier General Griffith, the Australian administrator. It does not claim that the number has any deeper validity. It doesn't cite a source for that, but I don't see anything implausible about it. Looie496 (talk) 05:17, 13 April 2013 (UTC)

The article makes that assertion, but that assertion (nor the quote from Griffith) has any sources to support it. The big issue is if Griffith said directly, "if the Nauruans were to survive as a race, the population should be no less than 1,500.", then we would need to put quotes around that, as I have done, and provide a footnote to make it clear where the quote comes from. Without sources, the statement really shouldn't stand, however. --Jayron32 05:22, 13 April 2013 (UTC)

For what it's worth, I've managed to work out that the person referred to here is Thomas Griffiths (general). I'll add a wikilink to our article (and fix the spelling). Looie496 (talk) 16:46, 13 April 2013 (UTC)

The problem is extremely difficult for human populations because "survive" can mean "not all die" or "survive as a distinct culture". But if a group of people were cut off from the rest of humanity for some considerable time (either physically cut off - or culturally unwilling to take mates from outside of their cultural group) - then genetics and inbreeding would be the problem. The considerations in our Minimum viable population article would take effect. For large vertebrates, the accepted number is between 500 and 1000 individuals if the population is carefully managed (ie scientists decide who breeds with who!) - and more like 4,000 if not carefully managed. On that basis, you might think that 1500 people isn't enough - but it's in the right ballpark, and this isn't an exact science. But that kind of complete elimination of mating outside of that cultural group seems unlikely.

A classic example of how this can happen is the Pitcairn Islands - which was uninhabited until six men, eleven women and a baby arrived there after the infamous "Mutiny on the Bounty" incident in 1790. Since the island was hundreds of miles from any other land - and not of much interest to anyone, the hapless mutineers were left alone - and (inevitably) the population steadily grew to around 600 people. This is widely accepted as being the most inbred group of humans in the world. But even with such extreme in-breeding, the occasional outsider has managed to add enough genetic variation to keep the population viable - and according to most studies, they aren't suffering too badly.

Who says they aren't suffering too badly? Law enforcement in the Pitcairn Islands. Seems like they were raping children with impunity there till 1999. Sagittarian Milky Way (talk) 02:57, 15 April 2013 (UTC)

So we can conclude that there isn't some magical cutoff at 1500 people...at least not genetically. SteveBaker (talk) 13:16, 13 April 2013 (UTC)

Since the entire human race has an effective population size of probably around 5,000 (if not less) then no. Culture does weird things though. ~ Amory (u • t • c) 17:26, 15 April 2013 (UTC)

someone wrote a program to find that out. i just can't remember who, or the program name, or when. 70.114.248.114 (talk) 03:48, 14 April 2013 (UTC)

Is 2 centuries a long enough test to falsify the 1,500/4,000 individuals inbreeding rule? Sagittarian Milky Way (talk) 02:57, 15 April 2013 (UTC)

Seasonality of human hair growth

My friend, in her early seventies, is convinced that her hair grows more quickly in the Spring and more slowly in the Winter. Her evidence for this is the much shorter length of time it takes for white roots to appear after she has dyed her hair. (I have no reason to doubt her eyesight.) This sounds like folklore to me but I can find nothing to indicate that anyone has ever studied the matter. Thank you for your help. — Preceding unsigned comment added by 109.12.63.61 (talk) 07:24, 13 April 2013 (UTC)

This is an interesting question, as it is one of the few topics on which I think the written word does not match reality. If you google (google "rate of hair growth") or search in textbooks, you find almost all estimates lie in two categories: Those which say hair grows at a constant rate of 0.5 inch (13 mm) per month no matter what (the Wiki article human hair growth is one example), and those that say it varies depending on age, health, intake of certain vitamins, race, and a few other minor factors and is between 7 mm and 20 mm per month, which seems much more likely. What seems difficult to find is any refrence that says it varies depending on where on the head it grows from, and there's no reference that says it is seasonal, depite the fact that it most definitely IS seasonal for other mammals. Hairdressors are taught that it grows at a constant rate.

However, in my experience, it grows considerably faster on the back of my head and neck, and a lot slower on the top of my head. It also grows quite a bit faster in autum and slowly during winter. This is reflected in when I need to go to the hairdressor. I'm also in my seventies. I'm sure that it grew faster when I was younger, but suspect that the variation in growth rate was hidden when I had a younger thicker hair.

In my experience, cutting hair very short and cutting frequently casues it to react by growing faster. However hairdressors are taught that that is a fallacy. I had a friendly argument about it once with a hairdressor friend, so I experimented over a two year period, keeping records. I was right. However, I live in a hot climate, and cutting hair short probably raises skin temperature. If I lived in a cold climate, it may well be that cutting hair short would lower the skin temperature and therefore the growth rate. This suggests a conflict between two factors: skin able to grow hair faster when it is warm during warm weather, and the evolved capability of mammals to grow a thick winter coat in time for winter.

Wickwack 121.215.67.60 (talk) 08:41, 13 April 2013 (UTC)

You're in your seventies and it still grows on the top of your head? I'm jealous. HiLo48 (talk) 08:45, 13 April 2013 (UTC)

Don't fret too much. It grows so slowly on top, and so thinly, it might as well not bother. But I still need to have it cut from time to time. Wickwack 121.215.67.60 (talk) 08:54, 13 April 2013 (UTC)

Sorry Wickwack, although I defer to your superiority in age, I'm afraid hairdressers are taught that hair grows at different rates according to both position on scalp and time of year. Now if only I could find a reference for it. (I know they're taught it as I sat in on some of the sessions for the hair students when I was a therapy mature student about 5 years ago.) --TammyMoet (talk) 13:45, 13 April 2013 (UTC) I found this study which looks like a pretty neat exemplar of how to do citizen science! --TammyMoet (talk) 13:51, 13 April 2013 (UTC)

Very good Tammy! I only wish that age did bring superiority! Perhaps hairdressers are better taught in your country (the UK if I remember right), or perhaps knowlege has been updated since the hairdressors I've known did their training. I've found them adamant that it grows at a constant rate. The study you found has some limitations though - for instance they assert that temperature has little to do with it, but haven't proved it. One reasonably expects that hair growth rate is dependent on skin temperature, but the skin temperature relationship to climate would be confounded by the human practice of adjusting clothing to suit the season. They tested only one person. Did they check that she had the same diet/nutrition/calorific intake throughout? Wickwack 121.221.31.213 (talk) 14:34, 13 April 2013 (UTC)

You're indeed right to highlight the role played by diet and nutrition in hair growth: the study also failed to take blood samples to check on the endocrine status of the subject as I've found elsewhere that thyroid status affects hair growth as does oestrogen/progesterone status in women. It's not a complete study by any means, but an example of what can be achieved by someone wishing to follow the scientific method and make a difference. --TammyMoet (talk) 15:37, 13 April 2013 (UTC)

ques on tetrahedral and octahedral voids

A compound formed by two element a&b the anion b are located at the corner of the cube and face centres whereas cation a occupy all the tetrahedral void what is the simplest formula of the compound? — Preceding unsigned comment added by 70.39.184.248 (talk) 09:59, 13 April 2013 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Roger (Dodger67) (talk) 11:59, 13 April 2013 (UTC)

What is a microstate?

Entropy is by definition $-k\sum _{i=1}^{\Omega }P_{i}\ln P_{i}$ where k is Boltzmann's Constant and $P_{i}$ is the probability of a particular state given our limited knowledge of the system. But, how is state defined? What fully characterizes a physical state?

150.203.115.98 (talk) 10:26, 13 April 2013 (UTC)

It is the complete information about the system. Suppose you have two systems in different physical states, then that means that there exists an experiment that you can do on the systems which will have a different outcomes, at least statistically. If on the other hand the two systems are in the same physical state, then no experiement can have (statistically) different outcomes.

You can then try to define the state of a system by specifying a list of experiments and what the outcomes of each of these experiments should be. In quantum mechanics, the outcome of a measurement is, in general, not pre-determined. Now, you do one experiment and then immediately repeat that same experiment you will get the same outcome (in the limit that the time between them is zero). If you do experiment A and then experiment B, you can compare that with doing this the other way around. If there is no difference, then measuring B will give you independent information than you get from measuring A. You can then add another such experiment C that doesn't interfere with A and B. If you try to make this list of experiments larger and larger, you will find that some point, you can no longer make this list larger. You will then have what is called a "complete set of observables" for the system. Then the state of a system is completely defined by specifying a list of the outcomes for each of the obsevables contained in such a list. The outcome of any other experiment can be predicted (in the form of a probability ditribution over the possible outcomes) when the state is specified. Count Iblis (talk) 12:27, 13 April 2013 (UTC)

That's really interesting, and I can see the article Complete set of commuting observables now. A state is basically characterized by its measurable properties, which makes sense, especially from a pragmatic point of view. It doesn't really make sense to call two states "different" if there doesn't exist any experiment, even in principle, to distinguish between them.

Now, suppose you have a physical system, and you want to change its state. How would you do this, in general?

150.203.115.98 (talk) 15:09, 13 April 2013 (UTC)

Changing state is already described in "general" terms. In various branches of physics, state change is described mathematically; for example, in quantum mechanics, physicists talk about "applying an operator" to the system. This is about the most precise and generalized way we can describe changing state for one variable, subject to physical constraint. Unfortunately, such generalization tends to be a bit obtuse, and some people find these decriptions difficult to intuitively connect to experimental physical systems. This is because the specific way you change a particular state for a particular system depends on what physical process corresponds to the change of that state variable. In other words, we write a very clean mathematical formalism to describe an operator; but it is not always immediately evident how that operator corresponds to an experimental procedure.

For example, in atomic physics, one state variable models the energy-level of the electron; you can change that energy level by (in general) applying an energy transform operator to the electron. In specific cases, that operation manifests as compton-scattering; or shooting laser photons at the atom; or colliding the atom with other warm atoms (thermal excitation); and so on; in each case, practical details arise; it may be impractical to change one state-variable without affecting thousands of other parameters. Nimur (talk) 16:57, 13 April 2013 (UTC)

An example of a particular state is an associated energy level, such as the ground state of a partice. Plasmic Physics (talk) 12:28, 13 April 2013 (UTC)

In thermodynamics, a microstate describes the position and momentum of every particle. It's the full description of the system. For example, with N particles, "particle 1 is at (3,2,5) and moving at 3/ms north, particle 2 is at (4,5,1) and moving at 9 m/s east, etc" counts as a microstate. A macrostate is something you care to measure on a macroscopic scale. For example, what's the density of the gas? How uniform is the gas? What's the velocity distribution of its particles?

There is an inherent arbitrariness in the definition of a microstate. If particle 1 is moved by 1 nm, does that count as the same microstate, or a different one? How about 0.0001 nm? First, this doesn't actually matter--entropy is defined as the logarithm of the number of microstates, so changing the precision with which you distinguish microstates only changes entropy by a constant. Differences in entropy would stay the same. Second, quantum mechanics sets a fundamental limit on how accurately you can measure phase space. dx*dp cannot be smaller than Planck's constant, because the uncertainty principle says you can't simultaneously measure position and momentum more accurately than that.

Over time, systems tend towards the macrostate with the most microstates. For example, their velocity distributions tend to become the Maxwell distribution. "A uniform gas" accurately describes many more microstates than "a gas in a container where half the container is empty". This isn't surprising--of course if every microstate is equally likely, and the particles randomly choose one, that microstate would most likely correspond to the most likely macrostate. This tendency towards the most likely macrostate is the second law of thermodynamics. --140.180.240.67 (talk) 18:34, 13 April 2013 (UTC)

Does that agree with the definition Count Iblis gave? And, don't you need to know other properties of the particles such as their mass, charge etc.? And

150.203.115.98 (talk) 20:10, 13 April 2013 (UTC)

You do. I was giving a simplified classical view of an ideal monoatomic gas, which I think is helpful for intuition. For such a gas, all the molecules can be considered point sources with no charge and the same mass. Sorry for not stating this explicitly. --140.180.240.67 (talk) 20:20, 13 April 2013 (UTC)

Eyesight

Can a teenagers social development be affected by poor eyesight? — Preceding unsigned comment added by 176.250.139.80 (talk) 11:15, 13 April 2013 (UTC)

Yes. (Strange question.) HiLo48 (talk) 11:21, 13 April 2013 (UTC)

Obviously anything that affects communication affects social development. However, what do you mean by "poor eysight"? Deficiencies that can be corrected with spectacles should not affect it, except to the extent that wearing spectacles may temporarily affect self esteem or may limit playing in team sports. Wickwack 121.221.31.213 (talk) 11:30, 13 April 2013 (UTC)

If you hadn't just admitted to being in your 70's, calling glasses "spectacles" would have told me. :-) StuRat (talk) 04:04, 14 April 2013 (UTC)

One tries to write for an international reader here. "Glasses" has multiple meanings, (e.g., magnifying glass) while "spectacles" has only two, and it's obvious which of the two meanings applies here. Wickwack 121.221.215.92 (talk) 09:49, 14 April 2013 (UTC)

...And of course it's a matter of degree. If the person's eyesight was sufficiently good that glasses were only needed for some specific task like driving or reading - then the effect should be very small indeed. On the other hand, I know an adult who's corrected eyesight is so bad that he can only read things a few inches from his nose - even with thick, heavy glasses. He can't drive, play video games or watch TV at all. Since those are all major teen social activities I'm sure that must cause significant social impairment in teenagers. On the other extreme, my son is mildly red/green color blind and sailed through most of his teenage years without even knowing it - which implies that there was no social impairment whatever. So the answer to our OP is obviously: Yes, it's possible for extremely poor eyesight to cause serious social impairment - but mildly poor eyesight does not cause impairment. It's not a very useful answer without knowing details about a specific case - but in that case we'd be unable to offer advice because it would constitute "giving a medical prognosis" - which we're strictly prohibited from doing. SteveBaker (talk) 12:48, 13 April 2013 (UTC)

While I don't disagree it's a matter of degree and quite variable depending on the imparity, I don't think it's as simple as you suggest particularly since the question was about 'social development be affected' which can be very broad. For example, depending on the person's interaction with peers, teachers and parents, I imagine it's entirely possible they will go through their teenage years with a mild myopia without really realising it, yet it will still affect them (e.g. they will avoid certain activities and be less good at them then they would be if it were corrected). Of course the same could happen for a whole host of other reasons. As Wickwack mentioned, even with perfect correction with glasses it can still have effects since it can affect self esteem, interaction with peers and in some cases the presence of glasses makes it more difficult to participate even without considering those effects. (Again these can also arise for a whole host of other reasons.) Contact lenses can help, but have their own issues. And depending on factors like whether the person is going to need glasses in addition (for times when they don't want to or can't where contacts), the level of the correction required (particularly astigmatism), how frequency the prescription changes and the price in the locale, contact lenses may not be financially possible. Of course for some people and in some places, corrective lenses of any kind may not be possible for financial reasons. Nil Einne (talk) 14:21, 13 April 2013 (UTC)

http://www.youtube.com/watch?v=ls2lC7DQFMI --Digrpat (talk) 23:06, 13 April 2013 (UTC)

In the case of uncorrected poor vision, there can be an interesting split in school. Some will move to the front of the classrooms, in order to see what the teacher is writing on the board, and tend to become "teacher's pets", while others will give up and fall behind in school. Either path could potentially negatively affect their social development. StuRat (talk) 04:12, 14 April 2013 (UTC)

Last spacecraft launch to orbit with *one* astronaut?

When is the last time that a spacecraft launch occurred which made at least one orbit that only had *one* astronaut in the capsule. If this was a private company, when is the last time that a National space agency did so. In either event, was the last launch in the Mercury program the last time the United States did so?Naraht (talk) 11:35, 13 April 2013 (UTC)

The most recent manned space flight with a single crew member seems to have been Shenzhou 5, the first manned space flight of the People's Republic of China, in 2003. Gandalf61 (talk) 12:23, 13 April 2013 (UTC)

The last U.S. single astronaut mission was Mercury-Atlas 9 in 1963. The last Soviet one may have been Soyuz 3 in 1968. No private company has yet done orbital flight. The company SpaceX is trying to do the first private manned orbital spaceflight in mid-2015 but it will carry a crew of three. Rmhermen (talk) 15:30, 13 April 2013 (UTC)

Cost of RNA vs protein

Hi Ref Desk,

I'm wondering what the energy cost to cell is for making an RNA molecule vs the protein for which it codes. Intuitively, I would say that the protein is much more expensive, but a study ([8]) suggests that RNA costs 5x more energy than a protein (49.3 phosphate bonds per nucleotide (x3!) vs 30.3 per amino acid)! I can't find any other estimates to compare this to - any tips?

Cheers,

Aaadddaaammm (talk) 12:16, 13 April 2013 (UTC)

It's not common for someone to come to us with a good reference in hand - thanks! You probably are aware already, but I should say a key thing to bear in mind here is the difference between total synthesis vs. polymerization of precursors. RNA and protein are both going to get degraded sooner or later back to amino acids and XMPs, so the total synthesis doesn't really apply except in growing populations of cells.

So far as I recall, the basic ratio for polymerization should be just one pyrophosphate released per charged amino acid in aminoacyl tRNA synthetase, with that energy being sufficient to power the ribosome, but EF-Tu/eEF-1 contributes another phosphate bond to improve accuracy. (Note that pyrophosphatase makes the PPi effectively count as two bonds split) Other elongation factors exist, for example EF-G at the end of the protein. I can't rightly recall at the moment where the other ~P the author of your reference comes from during elongation. So we're talking about 3 ~P I can count (ignoring the one extra at the end), 4 according to the author, plus parts. By comparison, I would count the "cost of polymerization" in the RNA as being a PPi per bond created (i.e. XTP to XMP). So to me the ratio that would seem to matter in steady-state metabolism would seem more like 2:3 with the amino acid being only a bit cheaper than a codon.

Anyway, what's interesting to me about this is that the selective pressure against having a high level of mRNA and protein per cell seems like it is going to be much less for an organism that remains in a stable state for a long period of time than one which is is exponentially growing. If an organism's whole ecology is geared toward putting on weight and splitting, that seems like it ought to lead to different overall gene expression level than if it is trying to hide for a long time and avoid getting eaten. Hmmm... Wnt (talk) 19:48, 13 April 2013 (UTC)

It's worth bearing in mind that a single mRNA molecule, once transcribed, can be translated multiple times. (Heck, multiple ribosomal complexes can attach to the same mRNA simultaneously, allowing translation of multiple copies of a protein at the same time from a single mRNA: [9].) What this means is that the energy 'overhead' cost of one mRNA molecule can – potentially – be 'amortized' over many, many translated protein molecules. In other words, even if transcription is 'expensive' on a per-base basis, it still accounts for a relatively small part of the entire protein biosynthesis energy budget because mRNA is reusable. TenOfAllTrades(talk) 03:23, 14 April 2013 (UTC)

Spatial Encoding

Since my question has been removed I post it here.

What are the typical computer video compressions algorithms names which use the human retina approach?2A02:8422:1191:6E00:56E6:FCFF:FEDB:2BBA (talk) 21:09, 13 April 2013 (UTC)

(I see where this was removed from Talk:Retina) - unfortunately, it is possible that this still isn't the best place, that Wikipedia:Reference desk/Computing would get you better answers. I'm certainly not aware of any video compression that attempts to follow the retina's approach literally. Figuratively... I can't tell. For example, if I do a Google search for "video compression" "edge finding" I get [10], but I can't really say whether that method of finding dominant edges to align stereo pairs has any relation to the biological scheme at all; certainly it is not a direct copy.

My gut feeling is that the two circumstances aren't comparable because we accept a huge loss of resolution from our retina. We aren't aware of individual rod and cone inputs on their own. So any computer algorithm that worked just like the retina would be seen as a really crummy way to store an image, until such time as the images are sooo high res that we really don't care. I think... Wnt (talk) 22:01, 13 April 2013 (UTC)

Why do you say there's a huge loss of resolution? As far as I know the eye's resolving power is pretty close to the cone spacing. -- BenRG 00:15, 14 April 2013 (UTC)

Our vision isn't nearly as good as it seems. We have lots of blind spots where we looked at something bright and burnt out a few cons and rods, or a blood vessel covers them, etc. Why don't we see black spots all over our field of view ? Out brain does an amazing job at filling in the missing spots. Unfortunately, this also means we aren't always seeing reality, but sometimes just what our brain makes up to fill in the gaps. StuRat (talk) 07:09, 14 April 2013 (UTC)

Perception is reality. 202.158.66.204 (talk) 09:56, 14 April 2013 (UTC)

Thanks for the quick answer I had thought to this. There are projects for getting 60TB per hard drive for the end of the decade. As it did for The GB step,there are reason to full the space. there will exist camera that would produce 25GB images with actuals compression techniques.

I can't imagine diffuser aren't planning the result for video download.I'm sure the algorithms are already written.

By the way I was thinking about the retina side only (no real care about the second eye) and not the decompression methods.

The method of "decompression" is always varying from person to person and time (optical nerves and human brain ). 2A02:8422:1191:6E00:56E6:FCFF:FEDB:2BBA (talk) 22:28, 13 April 2013 (UTC)

My knowledge of the spatial encoding in the optic nerve is based entirely on having read the article section just now, but it looks very similar to the wavelet transform, which is used in JPEG 2000, for example. The most popular video compression formats right now (e.g. h.264 and all versions of MPEG) don't use wavelets, but do use the discrete cosine transform, which is closely related. All image and video compression is based in one way or another on human vision. Even "uncompressed" images represent colors as RGB triples, a representation that's closely tied to human standard color perception. -- BenRG 00:15, 14 April 2013 (UTC)

• I don't really see how the retina can be compared to any image compression algorithm. The huge difference is that the retina has quite a small high-resolution zone, called the fovea -- it is roughly the size of your fist held at arm's length. The most important type of compression the retina uses is to represent only this very small region at high resolution. Nothing like that could work for a computer representation, because there is no way of knowing what part of an image will be the focus of attention. (I'm oversimplifying a bit, but I don't want to flood the board with verbiage.) Looie496 (talk) 03:15, 14 April 2013 (UTC)

Plaster of Paris as a structural material yet it is relatively water soluble, what gives?

Calcium sulfate dihydrate, the main component of plaster of Paris, has a solubility of 2 g/L. Yet this material is used to make all sorts of structural materials. So what I am trying to figure out is why doesnt this stuff dissolve? Perhaps the plaster components are relatively crystalline and have a low surface area, but still I would think that after a few years or decades (see Borujerdis House as one of many antiquities made of P of P) of rainy weather that it would be corroded away. Or, maybe this material is not used for exteriors very much except in dry climates.--Smokefoot (talk) 23:53, 13 April 2013 (UTC)

Paster of Paris is never used as a structural material, not in my country anyway. The term "structural" denotes a material that is load bearing. Plaster of paris is only used in non-load-bearing and decorative applications - someting else underneath (brick, concrete, framework, etc) takes the load - load being either static & dynamic downward forces due to gravity and/or wind loading. Actually, the ability of moisture to wreck plasterwork can be considered a virtue. It lets you know you have rising damp, or a leak in the roof, well before real structural damage is done, and it is easily repaired at mimimal cost. Where used as suspended ceilings where it must sustain its own weight, it is re-inforced with cellulose fibres or other semi-woven material.

I know nothing about the Persian building you cited, but none of the inticate work shown is structural. There's nothing wrong with using plaster work to decorate ceilings and other inside surfaces - this is extremely common in modern western buildings. Despite the labelling on the images, I expect the exterior decoration (which is applied, not structural) is all water-resistant stucco, not plaster. Wickwack 121.215.41.163 (talk) 02:56, 14 April 2013 (UTC)

Oh, good points. I used the wrong wording (structural). My question is simpler - why would anyone decorate the exterior of any building with a material that is fairly water soluble. --Smokefoot (talk) 03:04, 14 April 2013 (UTC)

Read Whitewash. Also note that Persia had (and still has) a rather dry climate, so water solubility wouldn't have been a big problem there. 24.23.196.85 (talk) 03:38, 14 April 2013 (UTC)

I thought so too, but fortunately I checked before writing my first post. It turns out that their annual precipitation (680 to 1700 mm) is somewhat greater than the precipitation where I live (Western Australia), hardly dry, and you certainly would not use plaster on an external surface here. That's why I think that the external decoration is not plaster but stucco. One of the characteristics of whitewash is that is a non-durable paint (once popular in the US) requiring regular re-application. If you used it for the sort of decoration depicted in the OP's link, you'd soon end up with a smooth surface and no decoration. Wickwack 60.230.245.70 (talk) 06:29, 14 April 2013 (UTC)

I think that stucco and plaster of Paris are the same thing (despite what is stated in stucco), calcium sulfate, which is fairly water soluble, so now what? --Smokefoot (talk) 12:32, 14 April 2013 (UTC)

There are various recipes for stucco. Stucco can indeed be made with plaster of paris. It can also be made with portland cement, which makes it completely waterproof, but with a lower quality finish. It also gives an ugly grey colour, but that can be fixed with pigments. There are a number of other water resistant mixes, eg lime-based (as in mortar used to stick bricks together), and you can also use a combination of plaster of paris with cement to give a degree of water resistance. Wickwack 124.182.15.108 (talk) 12:50, 14 April 2013 (UTC)

The answer might just be Relative humidity. Homes which use plaster are usually heated (which lowers the average RH). In older homes that have old fashioned larder rooms, the plaster in them (if they are plastered at all) often become crumbly. Plaster needs to be fairly damp in order to disassociate like this. In the tropics, were relative humidity is high and a artificial heat is not required, then plaster is seldom seen. If it is used, then a lime based wall coating is probably leaning towards hydraulic lime and that is not plaster of paris.Aspro (talk) 20:02, 14 April 2013 (UTC)

• Could plaster of Paris be used in Lath and plaster construction? --Jayron32 04:26, 15 April 2013 (UTC)
  • Certainly. By the 20th century, that's what it mostly was -- it dries much faster than the older lime-based plaster, and has fire protection qualities. --jpgordon^{::==( o )} 14:53, 15 April 2013 (UTC)

In common usage it seems that term Plaster of Paris (CaSO4·2H2O) is used mostly for its pure form but it is also known as gypsum. Its pure form could be used for plastering Lath but its setting time might be a bit too quick for a plasterer to get a good finish over a large surface. Builders gypsum is almost the same thing but it is modified to give a longer working time (i.e., Plaster of Paris multi-phased by the addition of lime etc). Pure lime plaster on the other-hand takes very much longer to cure. The latter, is only needed today for re-plastering some old buildings (especially stone and mortar dwellings) that where built without a damp-proof course. So yes. the white stuff one can buy from art & craft shops called Plaster of Paris will do the same same job. --Aspro (talk) 15:32, 15 April 2013 (UTC)

Lath and plaster was, of course, only used for indoor work, mostly in the USA. Wickwack 120.145.63.92 (talk) 00:50, 16 April 2013 (UTC)

April 14

What is this engine part?

What's the part in the red oval?

Shown is a picture of the engine of a 2004 Ford Escape. The silver cylindrical part in the red oval has a cable socket coming in on the left. I just repaired the cable and got the vehicle to work again, the problem being that it would start up fine but die within a second, unless I gave it gas, in which case it would keep running, until I took my foot off the gas, at which point it died. So whatever this part is seems to be related to the idling circuit. Like I said, the car works now. I'm just curious what the part is. Peter Michner (talk) 04:29, 14 April 2013 (UTC)

I'm pretty sure that's the oxygen sensor. But I'm not a mechanic. --Jayron32 04:46, 14 April 2013 (UTC)

Scanning some other stuff, it could also be part of the Exhaust gas recirculation (EGR) system. There's a bit called the "DPFE sensor" or "Differential Pressure Feedback (EGR) sensor" which looks like it is in about this location. I think this diagram is from a 2001 Ford Escape, and the DPFE sensor looks to be in about the location it is in your picture. But I'm just guessing here. --Jayron32 04:56, 14 April 2013 (UTC)

Thanks, looks like it's definitely called the idle air control valve Peter Michner (talk) 06:35, 14 April 2013 (UTC)

4D strorage device

How would one encode information onto a 4D crystal such as the example recently created? Plasmic Physics (talk) 07:20, 14 April 2013 (UTC)

Would there be any advantage over a conventional 2D storage device such as a USB stick? Plasmic Physics (talk) 10:04, 14 April 2013 (UTC)

I think you probably mean 3D, not 4D? If that's the case, see 3D optical data storage and Holographic data storage. Red Act (talk) 12:56, 14 April 2013 (UTC)

I think the question refers to this weird press release. As near as I can make it out they made a simple quantum system that has angular momentum in its ground state and for some reason called it a "4D crystal". Since it's in the ground state, you can't encode any information into it. -- BenRG 15:52, 14 April 2013 (UTC)

If anyone cares, here's the paper and here's the theoretical treatment it cites. The theoretical preprint, which is by Frank Wilczek, starts with a point particle confined to a circle through which there's a magnetic flux. He shows that the ground state has nonzero (orbital) angular momentum and seems to think that's surprising, having apparently forgotten that the ground states of a lot of atoms have that property. He discusses how this counterintuitive result can possibly be true. The answer, of course, is that the particle is uniformly smeared around the circle; it's a "clock" whose hand is in a uniform superposition of all directions at all times. It's rotating, but it doesn't tell time. He then introduces more particles to the loop and a mutually attractive force and shows that they clump together, and seems to argue that this clumping will counteract the smearing out. I don't know how a guy who won a Nobel prize for explaining the structure of hadrons could make that mistake, but as far as I can tell he did. In reality switching from a point particle to a clump changes nothing because the clump is a composite particle (like a hadron) whose position can be characterized by a single angular parameter, and the wave function in terms of that parameter is the same as before. It has to be because a ground state is a state of definite energy, and in a state of definite energy the probability density is time-invariant. He even mentions that fact at the start of the paper, but seems to believe he can circumvent it. Really bizarre. The experimenters have the same misconception about the state they created, but they're experimentalists so it's easier to understand. Wilczek's preprint is apparently unpublished, and maybe PRL accepted the experimental paper because of something interesting on the experimental side. They should have made them drop the crystal-power nonsense, though. -- BenRG 20:03, 14 April 2013 (UTC)

The thought occurs to me that Frank Wilczek may have been making an elaborate joke. He also speculates about iGlasses and iQuasicrystals (the "i" meaning "imaginary", possibly also a play on words). — Quondum 20:56, 14 April 2013 (UTC)

I think if it was a joke he would have said so by now. Imaginary time is an actual thing. Respectable physicists have written weirder preprints, like the ones coauthored by Holger Bech Nielsen claiming that the LHC exploded because of a Higgs-discovery-prevention mechanism in the laws of physics. -- BenRG 18:18, 15 April 2013 (UTC)

That is exactly what I'm talking about. So what did the experiment actually achieve? Plasmic Physics (talk) 13:10, 15 April 2013 (UTC)

I didn't read most of the paper, but they confined a number of charged ions to a circular path at very low temperature, so that they ended up in a ground state (effectively absolute zero). They threaded a magnetic field through the circle, which shifts the ground state into one where the ions have a fixed nonzero angular momentum. It's not a clock, though, because if you measure the position of the "hand" you'll get a random value that's uncorrelated with the time of the measurement. (One way of seeing that is the uncertainty principle: the angular momentum is exact so the angular position is totally indeterminate.) And it seems quite ridiculous to call it a crystal, much less a 4D crystal. I doubt this configuration of ions is useful for anything. Maybe it was an impressive experimental achievement to create it—I don't know.

By the way, I just now noticed that there's a Space-time crystal article. I can't critique Wilczek's paper in it, of course, because that would be original research. -- BenRG 18:18, 15 April 2013 (UTC)

If there truely existed such a thing as a codeable 4D crystal then it would circumvent the problem noted below by StuRat. All data is at the surface, just not all the time, so it should be possible to write as well as read. Plasmic Physics (talk) 22:42, 15 April 2013 (UTC)

However, 3D storage may make sense to replace 2D. Or, a convoluted surface like in the brain, designed to increase surface area. This would get by the problem of how to access and change data deep inside a 3D object (something like a CAT scan could conceivable read data inside a 3D object, but changing it is a bit more of a challenge). So, maybe 3D storage for read-only memory, with convoluted 2D storage for read/write memory. StuRat (talk) 18:08, 14 April 2013 (UTC)

Compromised title

When searching for "Thin Layer Extraction" one is only redirected to the article "Liquid-Liquid Extraction" that refers to "Thin Layer Extraction" through a dead link. There exists apparently no article by the name "Thin Layer Extraction" to be edited. I have prepared an extended article on "Thin Layer Extraction" and I am unable to create it under this name. How else can one assign a title to a new article? RogerLie (talk) 14:23, 14 April 2013 (UTC)

Questions like this are better asked at the Help desk, but I'll answer anyway. The trick for bypassing a redirect is, after clicking on Thin Layer Extraction and being taken to the Liquid–liquid extraction page, note at the top a line saying Redirected from Thin Layer Extraction. If you click on the link in that sentence, you are taken to the redirect page. You can then edit it to turn the redirect into an article, or you can look at the Page History, which, to save effort, is here.

I note when I look at the page history that you already created a version of that article, back in 2009. It was turned into a redirect a few months ago because an editor felt that the article did not establish that the topic is sufficiently notable. In other words, it is not clear that the term is used in the literature to a significant degree. If you think you can resolve that issue, then you can either edit the redirect page to turn it back into an article, or else revert back to your earlier version and make improvements to it.

If you have further questions about how to edit articles, please ask them at WP:HELPDESK. Regards, Looie496 (talk) 15:09, 14 April 2013 (UTC)

RAST

Is RAST test an example of RAS syndrome?? My textbooks all say that "RAST" stands for "radioallergosorbent" (presumably the T is the final t in that word, which would make it more correctly RASt) and google doesn't show anyone referring to it as a RAS Test. 2.98.248.78 (talk) 15:35, 14 April 2013 (UTC)

The Department of Redundancy Department is definitely interested in this question. Looie496 (talk) 15:56, 14 April 2013 (UTC)

Yes. Affirmative. StuRat (talk) 18:12, 14 April 2013 (UTC)

Power-to-weight ratio: electric and combustion motors

What of both have a better power-to-weight ratio? Even not considering the storage (battery/tank), can an electric motor ever have a better power-to-weight ratio? OsmanRF34 (talk) 19:28, 14 April 2013 (UTC)

See Power-to-weight ratio. The Hi-Pa Drive electric motor has a (theoretical) power/weight ratio of 2.92 hp/lb, better than the Wankel engine at about 1.0 hp/lb, and much better than a conventional Otto engine. The advantage of IC is not so much the weight of the engine, but the weight of the fuel compared to the equivalent battery. Tevildo (talk) 22:10, 14 April 2013 (UTC)

Much lower percentages of waste heat can't hurt. Sagittarian Milky Way (talk) 03:33, 15 April 2013 (UTC)

Shouldn't this graph be periodic?

Why is the current/voltage diagram in Franck-Hertz experiment not actually periodic? Why is there an overall upward trend? Wouldn't you expect the function to be truly periodic according to the theory presented in the article?

150.203.115.98 (talk) 22:43, 14 April 2013 (UTC)

No. As voltage increases, electrons are drawn more quickly from the cathode and through the mesh, so current increases. This isn't surprising--if you increase the voltage across a resistor, current increases, and for similar reasons. --140.180.243.134 (talk) 23:27, 14 April 2013 (UTC)

A resistor isn't really the best comparison in this case, although the basic principle is correct. The null hypothesis for the experiment is that it should behave like a vacuum diode, so the curve would follow Child's law, I ∝ V^(3/2), if there were no interaction between the electrons and the gas. Tevildo (talk) 23:29, 14 April 2013 (UTC)

That certainly explains why the current increases between the peaks, but shouldn't the current drop down to zero at each multiple of 4.9 Volts, and start again? 130.56.234.8 (talk) 01:49, 15 April 2013 (UTC)

But it does drop down almost to 0 at each multiple of 4.9 volts. It doesn't get to 0 completely because some of the electrons don't encounter an atom before hitting the anode, and some of the electrons that encounter 1 atom don't encounter another, etc. --140.180.243.134 (talk) 05:34, 15 April 2013 (UTC)

Right, but that's not what the diagram shows; the diagram shows a long-run increase, an overall increase, as well.

150.203.115.98 (talk) 05:40, 15 April 2013 (UTC)

Are you perhaps confused by the fact the diagram is not current v time, but current v voltage? With higher voltages, electrons are more likely to be excited (or whatever the correct term is) even when the voltage is a multiple of 4.9v. The potential difference would be an average, but there would be fluctuations at the "particle" level so that some small portion of the electrons experience a potential difference not precisely a multiple of 4.9v. The higer the voltage, the larger the portion of electrons not precisely in that 4.9v region ergo the higher the current. Vespine (talk) 07:00, 15 April 2013 (UTC)

I don't think that per-particle KE variation is the principal reason for these effects. We never expect for the current to be 0: the only place we could have that is at na V (for a first excitation of a eV), but in that case the region (near the accelerating grid) in which the electrons can experience inelastic collisions is vanishingly small. The increase in the minimum for each "period" is then easily explained by the increased total flow of electrons. --Tardis (talk) 13:12, 15 April 2013 (UTC)

Yes I think I had it kind of backwards sorry, it's the absorbtion of electrons that reduces the current, so the fact there is a small current is explained by the fact that not all electrons are absorbed, even if they have the required energy to do so.. Vespine (talk)

April 15

The science (if any) of sunglass tints

I understand that glasses can usefully cut UV light (and that visually transparent lenses can do this perfectly well). And I understand that people may wish to reduce glare, to hide their eyes, or even to, uh, look at the world through rose-tinted glasses in order to tint the world rose.

I'm puzzled by the other claims for the benefit of various colors. This PDF from the American Academy of Ophthalmology tells readers that yellow is "optimum for object definition" and that amber "allegedly makes distant objects appear more distinct, especially in snow or haze" (my emphasis).

My understanding of color is very shaky but I do understand (or misunderstand) that filtering of visible light of some waveband may improve perception of light in other wavebands. Thus I suppose one could design a sort of experimental environment in which the definition of objects would be helped by yellow-tinted sunglasses. But in the larger, multicolored world, how could yellow, or any other color, be optimum for the definition of objects in general?

I've tried Googling for this but mostly just get retailers. Of course retailers want to shift product and have an interest in persuading novice anglers, skiers, etc. that experienced/expert anglers, skiers, etc. benefit from a certain tint of sunglasses. What I don't see is evidence or reasoning. Is there anything too this, or is it just old husbands' tales? (I'm guessing that it's more masculine than feminine.) Morenoodles (talk) 09:02, 15 April 2013 (UTC)

The problem with blue is that it seems to be defracted/reflected by everything, such as fog. So, if you block the blue, you can see more clearly in fog. On the other hand, on a perfectly clear day, I don't think it makes much difference. Then there's the negative effect of messing up color perceptions, making traffic lights look wrong, etc. StuRat (talk) 13:30, 15 April 2013 (UTC)

So, do you have any references to support your conclusions, or are you just giving the OP guesses, StuRat? TenOfAllTrades(talk) 14:17, 15 April 2013 (UTC)

What StuRat says are true statements...but you'd have to read a dozen different articles to pull together all of the disparate facts that make it so...hence, I'm not going to dig up all of the article names either! The atmosphere (by virtue of the Raleigh and Mie scattering mechanisms) takes the blue light out of sunlight and scatters it in all directions equally. That means that there is less sharpness to the blue light that we see because it's coming from absolutely everywhere. The problem is much worse at longer distances because the light from distant objects is also being scattered - making the blue part of the light "fuzzy". The complementary color of blue is yellow - and yellow-tinted glasses filter out much of that blue light. The result is a slightly dimmer image with less blue in it. Our eyes are able to adjust to the lesser amount of light coming in - so that effectively boosts our sensitivity to the colors that are not being scattered so badly - which makes everything look sharper - especially in the distance. SteveBaker (talk) 15:09, 15 April 2013 (UTC)

Thanks, Steve. I'm amazed that Ten doesn't know that blue light scatters more. That's the reason the sky is blue, after all, as the blue light coming from the Sun scatters the most, while the reds and yellows scatter far less. StuRat (talk) 17:34, 15 April 2013 (UTC)

No, StuRat's statements are inaccurate and misleading. It is true that atmospheric molecules scatter blue light more than red, due to the strong wavelength dependence of Rayleigh scattering. However, nowhere does StuRat use the word "scattering", and it's not true that objects generally "defract" (diffract?) or reflect blue light. For a fixed aperture size, diffraction has a larger effect for long wavelengths, as you can see from the first equation in the section on single-slit diffraction.

It is also not true that fog preferentially scatters blue light. If that was true, fog would appear bluish, but it's actually white. The theoretical reason for this is that Rayleigh scattering is an approximation of Mie scattering that only works when the scattering particles are much smaller than the wavelengths they scatter. For large particles, like the water droplets that make up fog, Mie scattering is not strongly wavelength dependent. See this link, for example: "Mie scattering is not strongly wavelength dependent and produces the almost white glare around the sun when a lot of particulate material is present in the air. It also gives us the the white light from mist and fog." --128.112.25.104 (talk) 01:09, 16 April 2013 (UTC)

Blood Circulation

HI! I'm just studying about Blood Circulation and I need some clarification. 1. Why do RBC's pile up in blood vessels during blood circulation and what this process is called? 2. What is Haemocytometer? 3. What is Microcystic Anaemia? Please help me in clarifying my doubts. 114.79.141.44 (talk) 10:43, 15 April 2013 (UTC)

"Pile up" is a rather vague term, but you might find our articles on coagulation, hemocytometer and microcytic anemia helpful. Gandalf61 (talk) 11:01, 15 April 2013 (UTC)

Most populous species

Which is the most populous species in terms of total world population? Bacteria are not a single species. Human population is 7 billion. Which species has a world population that exceeds 7 billion? --Yoglti (talk) 12:12, 15 April 2013 (UTC)

Have a look here [11] for a good discussion on exactly your question. The answer seems to be krill, btw. Aaadddaaammm (talk) 12:40, 15 April 2013 (UTC)

Sorry, krill are probably the most abundant animal. I'd guess that pretty much any bacteria beats them. Some back of the envelope calculations: total bacterial cells on earth = 5x10^30 [12]. Number of bacteria species: more than 10 million (largest estimate) [13]. Let's say 10 billion to give the microbiologists some breathing room. Then the most abundant bacteria has at least 5x10^30/10 billion = 500 quintillion cells! This beats krill by 500 quitillion / 500 trillion = 1 million times. Wooo! Aaadddaaammm (talk) 12:50, 15 April 2013 (UTC)

(ec) It's estimated that there are 350 trillion krill out there. You might think that they win because of that - but not even close!

Consider that some species of cyanobacteria can double their population size in 6 hours...given enough space and nutrient, a single bacterium can produce:

• 2 bacteria in 6 hours.
• 65,000 in 3 days.
• 4 million in 5 days.
• 270 million in a week.
• ...and exceed the number of humans in just 9 days.

We don't stand a chance.

In a cup of yogurt, in your refrigerator, there are at least three billion bacteria per milliliter...although not from a single species. But if you killed all of the bacteria in a 10 gallon barrel of yogurt - then added one cyanobacterium and waited, then in a bit less than two weeks, they'd outnumber all of the krill on the entire planet by a comfortable margin.

Consider this - there are 10 trillion "good" bacteria in the gut of every single human being. Of those, about 50% come from just five species. So there are roughly 5% of each of those major species...which means that there are at least 500 billion bacteria of just one species in your gut right now. Our gut bacteria have the krill outnumbered by just the amount in the guts of a moderate sized football arena full of people.

So I don't know what the answer is - but it's not krill or humans...it's got to be some kind of bacterium or other uni-cellular organism.

...unless we decide to say that viruses are "alive" because if we count them, then the bacteria will be outnumbered to a crazily high degree.

SteveBaker (talk) 15:00, 15 April 2013 (UTC)

This is no kind of direct answer, but the query reminded me of a possibly apocryphal story: when asked what the study of nature could tell us about the Creator, J.B.S. Haldane supposedly replied only that one could conclude that He had, "an inordinate fondness for beetles." --Mr.98 (talk) 17:44, 15 April 2013 (UTC)

See "Lists of organisms by population".—Wavelength (talk) 17:52, 15 April 2013 (UTC)

What is the most populous macroscopic species other than humans? --Yoglti (talk) 00:34, 16 April 2013 (UTC)

What do you consider macroscopic? wiktionary:macroscopic says "Visible to the unassisted eye." Krill and insects are visible. And do you include plant species? Some of those are quite large and frequent in forests. PrimeHunter (talk) 01:35, 16 April 2013 (UTC)

D-mannose

This substance works by letting E-Coli bacteria to attach to D-mannose and be "escorted" out of the body. The reliable sources about how it functions can be found on the WP:MEDRS discussion.

My question is, is that mechanism of action is absolutely unique? Is there any medicine on the market or in the development that works not by killing bacteria, but rather by allowing bacteria to attach to it? Thank you.

P.S. I'm asking this question, because it's a very interesting mechanism of action that may not result in bacteria resistance. Ryanspir (talk) 14:54, 15 April 2013 (UTC)

(1) Not unique - for example, proanthocyanidins in cranberry juice are thought to have a similar effect. In addition, the Tamm-Horsfall protein may inhibit uropathogens in the same way.

(2) Resistance to this mechanism was described at least 30 years ago (PMID 6105132). This is not surprising - adhesion mechanisms are quite mutable. -- Scray (talk) 20:26, 15 April 2013 (UTC)

quassia amara L. against glucose

In Brazil they use the tea of quassia amara-L to control the glucose. Do you know it? — Preceding unsigned comment added by 151.62.28.190 (talk) 15:07, 15 April 2013 (UTC)

Our article on quassia amara doesn't discuss that use, but there is a small amount of scientific literature on the topic, for example PMID 21480415. Looie496 (talk) 15:40, 15 April 2013 (UTC)

EKG words

Hey there, I have a question about the ElektroKardioGrama, the question is: Why Dr Willem Einthoven has used in the words p-q-r-s-t for the graph, precisely? what was his meaning in these words just (and not another like ABCDE)? מוטיבציה (talk) 15:24, 15 April 2013 (UTC)

From our article here, "Originally, four deflections were noted, but after the mathematical correction for artifacts introduced by early amplifiers, a fifth deflection was discovered. Einthoven chose the letters P, Q, R, S, and T to identify the tracing which was superimposed over the uncorrected labeled A, B, C, and D. [14]". That reference discusses your question quite thoroughly, let us know if you don't have access. Aaadddaaammm (talk) 15:31, 15 April 2013 (UTC)

Thank you, I have not paid attention to that. מוטיבציה (talk) 20:06, 15 April 2013 (UTC)

What is muscle stiffness and how does massage work?

What exactly is actually happening when we have stiff muscles? Wikipedia redirects to DOMS, which I don't mean (or maybe I do but I don't realize). I am talking about the stiffness which occurs after long periods of holding the same position, after sleep, or due to disuse of a muscle. How does massage help in anyway? Many of my friends have their joints cracked and muscles massaged, yet when I read wikipedia many of these treatments are treated as pseudoscience. What does massage actually do? 137.224.239.102 (talk) 17:09, 15 April 2013 (UTC)

I'm not sure the literature provides solid answers, but I'll give you my own thoughts. I believe there are at least three things going on: (1) overuse of muscles causes swelling, which means entry of fluid into the tissues, and massage moves some of the fluid around; (2) muscle tissue is full of sticky proteins and has a strong tendency to form glue-like adhesions -- massage breaks up the adhesions; (3) massage activates stretch receptors in the muscles and thereby causes effects on the nervous system. There is certainly a lot of pseudoscience in the field of massage therapy, and people sometimes overreact against it, but it doesn't seem to me that there is much doubt that basic massage is genuinely helpful for sore muscles. Looie496 (talk) 17:27, 15 April 2013 (UTC)

It might be as simple as temperature. That is, if you are in a cold environment, and haven't used your muscles recently, they may be below the ideal operating temperature (more so on muscles in the arms and legs than on the torso). All chemical reactions are highly dependent on temperature, and that includes those which cause our nerves to fire and muscles to contract. A massage might raise the temperature just enough, by friction and increased blood flow, to make them work properly. StuRat (talk) 17:26, 15 April 2013 (UTC)

I'm a fully trained Swedish masseuse. Muscle stiffness and soreness after exercise is due to a build up of lactic acid in the tissues, which a good sports massage will help to break down so that it can be eliminated: soreness can also be due to small tears in muscles. Massage aims to increase blood flow to tissues so that healing can occur quicker than if left. The sort of stiffness that occurs after a period of inactivity is different as there is no lactic acid to break down. I believe the problem lies in the shortening of certain muscle fibres and tendons which occurs in these circumstances. There is another problem which is that lymph is secreted constantly and circulates around the body - but has no pumping system of its own: it relies on muscle movement and the pumping of the blood around the body to promote the movement of lymph. If the body stays in one place for a long time, lymph gathers in much the same way as water does and tissues swell. Manual lymphatic drainage is one massage technique which gives some relief to people who suffer lymphoedema: other techniques involve strapping and compression. --TammyMoet (talk) 17:51, 15 April 2013 (UTC)

"seabrid" ?

What does the word "seabrid" mean? It is an adjective to refer to the morphology of leaves. --İnfoCan (talk) 17:17, 15 April 2013 (UTC)

I'm pretty sure that's a misspelling of "scabrid", which means slightly rough to the touch. Looie496 (talk) 17:35, 15 April 2013 (UTC)

advanced directives

when do you start implementing advanced directive? — Preceding unsigned comment added by Ucclemm (talk • contribs) 19:06, 15 April 2013 (UTC)

See Advance health care directive. The precise circumstances when it becomes active will depend on jurisdiction and the wording of the document, but it's basically when the patient lacks capacity to make (or communicate) decisions regarding his or her treatment. Tevildo (talk) 19:51, 15 April 2013 (UTC)

a book of blood tests (or with another medical laboratory tests)

Hello, I'm looking for two things, and I would like to get a help for that. The things are: 1. a book which includes the best matter about the blood tests (or tests of laboratory at all, but only medical tests -of course). This book should be with clear information about' like how is each tests made in laboratory, and what is the normal levels of the results etc. (Of course, It's very important to me that this book will be the most recent) 2. website that includes much as possible of the above. — Preceding unsigned comment added by מוטיבציה (talk • contribs) 21:18, 15 April 2013 (UTC)

Buffer Zone

What is a buffer zone? I've heard of a buffer capacity, but not of a buffer zone. On a graph, where is the buffer zone located?

Thank you.

--Jethro B 22:46, 15 April 2013 (UTC)

I normally hear the term buffer zone in a geographic or general sense, like "administrative assistants create a buffer zone between the executives and the public". Did you want it's meaning in a chemistry context ? I know you can add acids or bases to a buffered solution, up to the buffer capacity, before the pH changes substantially. Perhaps they are also calling this the buffer zone. StuRat (talk) 23:28, 15 April 2013 (UTC)

StuRat is correct in regard to buffered solutions. See http://uccpbank.k12hsn.org/courses/APBioI/course%20files/assignments/chapter2homework05.html. However, the term buffer zone has a more general use in graphs: It can be used to describe any straight line or approximate straight line portion of a graph between 2 points of inflexion, outside of which the graph slopes or curves quite differently, there being different processes happening on either side of the buffer zone. Ratbone 124.178.59.243 (talk) 00:03, 16 April 2013 (UTC)

The buffer zone is the region of the titration curve where the Henderson-Hasselbach equation applies. It is any point in the titration where both parts of a conjugate acid/base pair are present; for example where you have HC₂H₃O₂ molecules and C₂H₃O₂^1- ions in the same solution. --Jayron32 00:10, 16 April 2013 (UTC)

Thank you. Not a fan of the Henderson-Hasselbach equation. I prefer using the buffer equation, then using the [H+] value or [OH-] value to calculate the pH. But whatever you prefer! So you're saying it'd be the part of the titration curve from the beginning when the conjugate acid or base is added (mL>0), until the equivalence point (since past the equivalence point, you're just adding excess acid or excess base)? --Jethro B 01:25, 16 April 2013 (UTC)

The Great Apes

Hello, here's my question. If raised as an exotic pet, which would prove to be the least agressive and risky of the two: a bonobo, or an orangutan? — Preceding unsigned comment added by JadeGuardian (talk • contribs) 23:00, 15 April 2013 (UTC)

You might have a different problem with bonobos, when they try to mate with everything in sight. StuRat (talk) 23:32, 15 April 2013 (UTC)

Lol, that's what I thought. Maybe a tufted capuchin will do... --JadeGuardian (talk) 23:44, 15 April 2013 (UTC)

First, let's be very clear. Great apes make horrible pets, and there are serious ethical objections. Apes are today illegally poached from their native habitat, and they continue to rapidly approach extinction. Wildlife_trade just makes them go extinct faster. Read the articles. Here's some specific reasons, for orangs: ([15]) and for bonobos: ([16]). In fact, many people think that apes are persons, see Great_ape_personhood. Even if one could navigate (or criminally ignore) the financial and legal (CITES) hurdles of owning an ape, they would still make terrible pets. Now that that's out of the way, I'll note that some single wild animals can successfully be kept by amateurs, but they tend to be species that are not naturally gregarious or social. This is simply because it would be necessary to provide for dozens of animals to maintain any semblance of natural conditions. Make of that what you will. SemanticMantis (talk) 23:45, 15 April 2013 (UTC)

Oh, no, I'm just as much for animal rights as anyone, that was just more of a hypothetical question. I'm not looking for a pet or anything... --JadeGuardian (talk) 23:48, 15 April 2013 (UTC)

Hypothetically, either could become sexually aggressive towards humans, and be sold off as a research subject for experiments that would be unethical if performed on humans. Not so hypothetically, see the sad history of Oliver_(chimpanzee). The article recounts "Janet Berger herself claimed that Oliver was becoming attracted to her when he reached the age of 16.[4] He mounted her and tried to mate with her. After he tried it several times it became apparent that Oliver was a threat to Janet, and had to be sold." SemanticMantis (talk) 00:01, 16 April 2013 (UTC)

I don't think SemanticMantis has it correct. His cited references are about it being ethically wrong to acquire and keep primates as pets, not about whether they would make good pets once you've got one. Dogs are both gregarious and social - and millions of single dogs are kept as pets and companions by millions of individuals and families. However dogs have three important charecteristics built in: they assign their human master the role of Leader (the alpha male or alpha female), they instinctively want to help and protect both alphas and puppies (they seems to identify children as human puppies), and they are quite intelligent but not TOO intelligent. In addition, humans look and smell so different to dogs that I suspect that dogs just don't see humans in the least bit sexually attractive. These characteristics are not present in anywhare near the same degree in orangatangs and bonobos. One should also note the "randy teenager" phenomenon. We once got a male kitten and a female puppy at the same time. They played together and slept together and got on really well. The dog's growth rate way outstripped the kitten's, but that didn't seem to matter. One day though, when the cat got to it's equivalent to the human teenager years, it tried to have sex with the dog. (I assume that a dog makes, for a cat, a right uggly cat, but that cat was horny. It took a while to figure out what to do, but managed it) The dog made it VERY clear that penetration was not acceptable, and from then on their relationship was much cooler. It ended completely when the dog, now 10x the size of the cat, accidentally knocked the cat flying. One supects that if the cat was 10x the size of the dog, the dog would have had a very sorry life indeed, raped and beaten repeatedly. Wickwack 120.145.63.92 (talk) 00:43, 16 April 2013 (UTC)

Thanks Wickwack, I realize what I wrote was unclear. I thought about dogs and cats while I wrote, quite a bit. But I stand by what I said: dogs and cats are domesticated animals, not wild animals; thousands of years of artificial selection result in a number of behavioral changes. Even "as fast as possible" is ~12 generations, in the case of the dedicated Russian fox domestication experiment). So we can't really expect a wild animal to behave towards humans like a domestic animal might. It is true that sometimes a social instinct can be co-opted in favour of the humans, and it was likely a role in the domestication of dogs (e.g. Domestication_of_the_dog#Promise_of_food.2Fself-domestication). But I would still advise against a single wild wolf kept as a "pet," and I think my link to Oliver the chimp provides an example of "whether they would make good pets once you've got one." SemanticMantis (talk) 01:14, 16 April 2013 (UTC)

Ah! You have a point I overlooked - a very long period of domestication breeding undesirable characteristics out and desirable characteristics in. A wild dog native to Australia is the dingo. Keeping them has been illegal, and whether or not they make good pets is controversial. Many people have done so succesfully though, claiming they have a personality quite similar to dogs. Small numbers of Australians have kept kangaroos - a somewhat gregarious social animal with no history of domestication. Also quite physically capable of killing a human. My cousin had a pet kangaroo and always claimed it was good loving pet, but more difficult to house train than a dog. They have plenty of photos of roo and children cuddled up together. It's really only satisfactory if you have plenty of land area, which my cousin had (10 acres). We once had a neighbour who had a red kangaroo (they grow as high as a man and are downright dangerous in the wild) without any problems, except that it liked to go on long runs and could jump any fence - you need tolerant neighbours. Roos are cheap to keep as they get their own food (Grass and leaves. If you have any nice flowers in the garden, they eat them. If you catch them in the act and say sternly "Bad Roo!", they hop 3 or 4 m away and look at you as though you are weird). Wickwack 124.182.145.187 (talk) 01:48, 16 April 2013 (UTC)

Read The Murders in the Rue Morgue. Looie496 (talk) 23:54, 15 April 2013 (UTC)

Not a bonobo or an orangutan, but Project_Nim_(film) is an excellent doco. The impression that I got was that after a certain size / age, any of the apes become too unpredictable to be safe. I listened to a podcast recently with a primatologist, who did say that unlike all the other apes, a bonobo has never been observed to kill another bonobo, and they exhibit behavior that appears like remorse. In one particular case a bonobo would cower in the presence of a researcher whose finger it had "accidentally" bit off.. Not really comforting IMHO  :) Vespine (talk) 00:36, 16 April 2013 (UTC)

Bonobos will also happily tear monkeys apart and eat them! (see a recent question with a link). I realize now I've gone on way to much on this question, so I'm out now :) SemanticMantis (talk) 01:19, 16 April 2013 (UTC)

World population of brown rat

What is the global population of brown rat? --Yoglti (talk) 01:49, 16 April 2013 (UTC)

Brown rat doesn't seem to have totals, but you can infer some things from the article, i.e. the estimated ratio of rats to humans. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:14, 16 April 2013 (UTC)

How are subatomic particle conceptualized?

If they cannot be seen through the most advanced electron microscope, how are they discovered? How are their properties known? How atomic structure known when it cannot be seen? --Yoglti (talk) 02:37, 16 April 2013 (UTC)