Wikipedia:Reference desk/Archives/Science/2013 January 24

= January 24 =

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


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


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

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


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


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


 * Is neurotheology a branch of neurology or branch of theology? --PlanetEditor (talk) 08:19, 24 January 2013 (UTC)
 * Since the term originated with Aldous Huxley, I'd be tempted to put it under Philosophy. ~E:74.60.29.141 (talk) 10:14, 24 January 2013 (UTC)


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


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


 * Yes, I strongly agree! SteveBaker (talk) 17:45, 24 January 2013 (UTC)
 * "..seek to reduce religious thinking to mundane (godless) science..." Just like how some researchers seek to reduce vision to mundane neurobiology? Does that mean everything you see is a lie?  Researchers also try to understand the neural basis of logical thinking.  Does that mean logical thinking is useless?  --140.180.242.224 (talk) 19:20, 24 January 2013 (UTC)


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

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


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


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


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


 * If a body was at a position A(x1,y1) at time t1 and at a position B(x2,y2) at time t2, there IS a displacement (irrespective of the path taken to travel from A to B and irrespective of what the velocity or direction of motion of the body was, at A or B). Your statement "there is no displacement between the two points since the direction of motion is different on both points" is wrong. Velocity changes as the direction of motion changes is correct. The point to be noted here is that velocity is a vector (has a magnitude and a direction) and hence the velocity is said to change is there is a change in either the magnitude (increase or decrease in speed) or direction or both. In case of uniform circular motion, the magnitude of the velocity (called the 'speed') remains constant but the velocity is said to change because the direction of motion changes.
 * To find the displacement, you simply draw a line from A(x1,y1) to B(x2,y2). The length of the line corresponds to the magnitude of displacement and the direction of the arrow from A to B corresponds to the direction of displacement. There is no displacement if the length of the line is zero - that is, if A(x1,y1) and B(x2,y2) are the same. — Preceding unsigned comment added by 59.145.142.36 (talk) 04:53, 25 January 2013 (UTC)


 * The direction of motion of either position is irrelevant with respect to the definition of displacement. Distance, in this case, is measured as the total arc length travelled in the total time. Displacement would then be equal to the chord length at an instant in time.
 * Velocity is a vector quantity, whereas speed is a scalar quantity. This means that meaning that velocity is speed given with a direction relative to some reference. Plasmic Physics (talk) 05:42, 25 January 2013 (UTC)
 * Therefore, displacement of a body on a curved path is not zero, but its velocity is zero. Show your knowledge (talk) 05:09, 27 January 2013 (UTC)

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


 * The short (oversimplified) answer is that it is energy that is emitted, not matter. I don't know if this will help with your specific question, but there is a nice page for visualizing this at http://spiff.rit.edu/classes/phys301/lectures/spec_lines/Atoms_Nav.swf (Turn on JavaScript first).
 * Also see:
 * http://curious.astro.cornell.edu/question.php?number=85
 * http://www.ccmr.cornell.edu/education/ask/index.html?quid=257
 * --Guy Macon (talk) 11:58, 24 January 2013 (UTC)


 * The photon is a wave of electromagnetic energy. If you could wiggle around a fist-sized electron in your hand (don't forget to wear your rubber soled shoes) you'd create a huge magnetic field every time you moved it perpendicular to something, and of course greatly increase the electric field if you moved it toward something.  So if you just moved it around in a closed loop, things would be exposed to these changes for a second and then go back to normal - you'd, say, blow out the television in the next room from the eddy currents and so forth.  Photons (for this speed, really long wavelength radio photons) would be the description for what reaches out from your handheld electron at light speed to the equipment in surrounding buildings.
 * You can also look at it that a photon carries energy (any value) and angular momentum (a reduced Planck constant's worth of it, no more, no less) so it is the right particle for the job. You can't use a particle with charge, color charge, strangeness, etc.  Why a particle is used that can move at the speed of light has something to do with avoiding the Higgs mechanism, but you'll need someone who actually understands that if you want to go further that way. Wnt (talk) 16:19, 24 January 2013 (UTC)


 * Guy Macon's answer above is not correct. "Matter" is not a meaningful scientific term. Wnt's explanation is much better except for the part about Higgs mechanism which is not relevant except indirectly. The point is that the electron wouldn't ordinarily be able to produce a massive particle because not enough energy is available for that. But if enough energy is available - for instance in a high energy collision, electron can and do indeed produce other particles such as W bosons and Z bosons. Dauto (talk) 16:47, 24 January 2013 (UTC)
 * Hmmm... A W boson sort of contains the electron, so is it relevant?  But a Z boson mediates neutral current and can mediate electron-neutrino scattering, so I suppose I have to give you that.  But you're right that at high energies electrons interact by electroweak forces, not pure electromagnetism, and thus not purely by photons.  I think this is philosophically different from just plain pair production where indeed any particle can show up when high energy things interact. Wnt (talk) 16:33, 25 January 2013 (UTC)


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


 * Transitions of an electron from a higher atomic orbital to a lower atomic orbital should (with a low probability) be accompanied by the emission of a neutrino and an antineutrino instead of a photon. The main processes of this de-excitation would be (a) the conversion of the electron into a virtual W- boson and a neutrino and the subsequent conversion of the W- boson to an electron and an antineutrino, and (b) the electron emitting a Z boson and the Z boson being converted to a neutrino and an antineutrino. For (a) the neutrino/antineutrino pair would be created in the electron flavor eigenstate, while for (b) the pair could be created in any flavor state.
 * By the way, the original question incorrectly implies that photons are not bosons. Icek (talk) 20:20, 25 January 2013 (UTC)
 * I'm not sure how meaningful it is to ask "why" in this case - this is what we have observed (or rather, what Balmer and Paschen and Lyman and Planck observed) and we have fitted the standard model to these observations. If we had observed electrons emitting unconfined quarks (impossible under the SM) you would be asking why they emit quarks and not photons! 72.128.82.131 (talk) 16:56, 27 January 2013 (UTC)

"Best" university of natural sciences / math in New York City
Engaging in literary pursuits, I ask for a hint concerning the protagonist of my story: What would presumably be the best / most prestigious college/university in New York City for a very gifted student of mathematics, physics and/or astronomy? --KnightMove (talk) 10:40, 24 January 2013 (UTC)
 * I can't myself answer, but those who can will likely need clarification whether you mean right now or at some date in the past. When is your story (or the part of it relevant to the question) set? {The poster formerly known as 87.81.230.195} 84.21.143.150 (talk) 14:08, 24 January 2013 (UTC)
 * The most prestigious university in New York City overall is likely either Columbia University or Fordham University. The two biggest science/technology schools are Polytechnic Institute of New York University (NYU-POLY) and New York City College of Technology, (City Tech).  Columbia School of Engineering and Applied Science as part of Columbia University probably meets all of your requirements: A very highly regarded science and technology school, and a very prestigious university overall.  -- Jayron  32  14:12, 24 January 2013 (UTC)
 * Where are you from? Don't put Fordham in the sentence most prestigious university in New York City. Even Nortre Dame is at least 100 SAT points below Columbia and that's the Catholic Harvard (Fordham is Catholic). Overall. Alot of Columbians like humanities. So Math SAT only Cooper Union might be better, not sure. Also Fordham Bronx campus (at least) is kinda Gothic, if that means anything. Fordham's Manhattan Campus, I've been in that area and didn't notice any Gothicness, or maybe that was Juilliard, or public housing, or Lincoln Center. Columbia is 1897 neoclassical and has existed 260 years. Sagittarian Milky Way (talk) 16:28, 24 January 2013 (UTC)
 * What does SAT scores have to do with prestige? -- Jayron  32  04:18, 25 January 2013 (UTC)
 * Whether SAT scores have an iota to do with prestige or not Columbia's still more prestigious. Though I think they do this kind of thing more in Europe and India where getting in is just score high enough. Or New York City specialized high schools where scores and prestige sort themselves out nicely cause the highest score got first dibs and the 6,106th highest score got the only school left. Sagittarian Milky Way (talk) 18:08, 26 January 2013 (UTC)
 * My story is set in the future - circa 2100. --KnightMove (talk) 23:32, 24 January 2013 (UTC)
 * Cornell will have an applied STEM fields campus on Roosevelt Island then. Sagittarian Milky Way (talk) 01:00, 25 January 2013 (UTC)
 * Perhaps by 2100, Stanford's New York campus will finally be built. (It will help if your story is set in hypothetical fictional universe).  FYI, Sagitarrian Milky Way, Cornell does not have a campus on Roosevelt Island.  They are currently involved in a proposal to build one.  Nimur (talk) 01:03, 25 January 2013 (UTC) I said 2100! Sagittarian Milky Way (talk) 01:14, 25 January 2013 (UTC)

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


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


 * Question 5: A water wave does not necessarily transport water in the direction of the wave (a current does, of course). You can see this sometimes when you see foam or small objects floating on the water, and when a wave passes, the objects move upwards and then downwards again, but they do not move with the wave. Compare this with a rope that is held by both ends: when one end is quickly moved up and down, a wave is seen passing through the rope from that end to the other, but the rope itself does not move horizontally.
 * Question 6: Yes, the electric force acting on a particle is equal to the electric field multiplied by the electric charge of the particle. See e.g. Electric_field. - Lindert (talk) 16:00, 24 January 2013 (UTC)

So far: SteveBaker (talk) 17:40, 24 January 2013 (UTC)
 * 1) Why sunlight appears yellow in color? For the same reason that the sky is blue.  Light from the sun is almost perfectly white (it is naturally, a little bit yellowish - but it looks white out in space) - but as the light passes through our atmosphere, Raleigh scattering scatters blue light throughout the sky - removing blue from white light leaves yellow light behind.
 * 2) Is it possible to polarize electromagnetic radiations other than light using Polaroid filter? Yes.  The reason people wear vertically polarized sunglasses is to eliminate horizontally polarized light, such as you get as light bounces from calm water - which reduces reflections.  So, you could (for example) produce horizontally polarized light by reflecting unpolarized light from a smooth puddle of water.
 * 3) What is the size of the smallest object we can see through naked eyes? I agree with User:PlanetEditor that 1/10th of a millimeter is about the limit...but it's a bit tricky.  You can see (for example) a single dust mote sparkling in sunlight - and while a single particle of flour is too small to see, a bucket of flour is easily visible!  Droplets of water in fog are visible as a cloud - even though none of the individual droplets is visible.  Interestingly, the largest bacteria are just about visible to the human eye.
 * 4) Is it true that transverse waves can only be produced in solids and liquids, but not in gases? Yes.  I don't know why that is though.
 * 5) What is difference between water wave and water current? As User:Lindert said - waves do not transport liquid from one place to another (technically, they don't transport a substantial amount of it by more than a few wavelengths) - but a water current does.
 * 6) Is it true that: "charge * electric field = electric force"? Yes, User:Lindert nailed that one!


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


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


 * I think the real answer to 1 is that sunlight doesn't appear yellow &mdash; when it's overhead. On an overcast day you can sometimes see the disk of the Sun through clouds, and it is not too bright to look at briefly (disclaimer: I'm not claiming it's safe to do so).  To me, in that circumstance, it looks almost perfectly white.  However, if you glance at the midday Sun without a cloud cover, it's too bright and you don't really get a sensation of color, just an urgent desire to stop looking at it as quickly as possible.
 * The times when your eyes will actually focus briefly on the Sun (again, I'm not saying this is safe) are early in the morning or late in the evening. That's when it looks yellow (or orange or red).  I'm not saying the Rayleigh-scattering answer is wrong &mdash; I think that is why it looks yellow or orange or red at those times.  But I don't think it's actually yellow in the middle of the day. --Trovatore (talk) 01:55, 25 January 2013 (UTC)


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


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


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


 * Yes, folk who have answered "x-many mm" and the like have given the wrong answer to the wrong question, as the acuity of the eye is obviously an angular function as Carnildo indicated, being essentially determined by difraction and the ratio of cone light sensor pitch in the fovea to the distance between fovea and lens. According to http://en.wikipedia.org/wiki/Visual_acuity, the angular acuity of a healthy human eye (6/6 vision - the minimum standard for normality) is one arc-minute.  This means that at 6 metres two brightly lit lines can be resolved if at least 1.75 mm apart.  Young healthy adults can focus down to 150 mm (small children, with their small eyeballs can do much better).  At 150 mm, the resolution is thus 1.75 x 0.15/6 i.e., 0.04 mm.
 * But there's more: we have two eyes.  The brain is able to combine the image from both eyes to effectively get double resolution, so we can resolve two lines only 0.02 mm apart.
 * But even this isn't the full story - if it was, we would not be able to see the stars in the night sky - visible stars are as low as 0.0025 arc-seconds! The cone sensors of the eye (and the rods) are area-integrating.  That is, an incoming beam of light can be sensed by a single cone so long as it falls on the cone - the width of the beam does not matter - what matters is the intensity.  In fact, due to scattering in the retina, it doesn't matter if the beam slightly misses a cone.  So, there is NO LIMIT to how small an object we can sense, so long as it is sufficiently bright compared to its surroundings.
 * Ratbone 124.182.17.177 (talk) 11:26, 26 January 2013 (UTC)

Why do we feel more pain in winter than in summer ?
I have observed this many times that we feel more pain in winter than in summer. Why is it so ? A bit more. We write the name of orbits of an atom as K, L, M, N, etc. Why we not write it as A, B, C, D, etc ? Concepts of Physics (talk) 11:07, 24 January 2013 (UTC)
 * I'm sure there's some good logical reason for the second item. For the first, keep in mind that our bodies are accustomed to operating in warmer weather, and our joints get kind of stiff in colder weather. In baseball, the old expression is "bees in the bat handle". In cold weather, if you don't hit the ball squarely, the bat's vibrations can really hurt - way much more so than in warm weather. ←Baseball Bugs What's up, Doc? carrots→ 11:24, 24 January 2013 (UTC)
 * Here is a blog post which discusses exactly the same issue. --PlanetEditor (talk) 11:30, 24 January 2013 (UTC)
 * This is OR on my part, but I doubt that's the full story. I think the most important factor by far is temperature.  When it is cold, the body tries to maintain core temperature by reducing blood flow to the limbs, allowing them to cool, which makes them stiffer and more susceptible to damage. Looie496 (talk) 18:25, 24 January 2013 (UTC)
 * Also with the blood flow reduced - wouldn't the endorphins and other pain relieving chemicals naturally occuring in our body delivered through the blood also be reduced similarly, while the electric signal fires just as quick as warm weather?165.212.189.187 (talk) 19:46, 24 January 2013 (UTC)
 * With regard to the electron shells, see Electron shell and, for Barkla's original use of K and L to name two of them, the third response here. The other shell names are obviously a continuation of Barkla's initial two. Deor (talk) 13:58, 24 January 2013 (UTC)

Klebsiella pneumoniae
"is a Gram-negative, non-motile, encapsulated, lactose fermenting, facultative anaerobic, rod shaped bacterium found in the normal flora of the mouth, skin, and intestines It is clinically the most important member of the Klebsiella genus of Enterobacteriaceae." This sounds like it important to have in our mouth skin and intestines. can someone clarify this, please?165.212.189.187 (talk) 13:36, 24 January 2013 (UTC)


 * It is unclear what is meant by "important". The most appropriate place to discuss this would be on the article's talk page.--Shantavira|feed me 14:10, 24 January 2013 (UTC)
 * The clinical importance refers to its role in diseases. K. oxytoca and K. rhinoscleromatis have also been found in patients but most (significant) Klebsiella infections are due to K. pneumoniae, I think... Ssscienccce (talk) 02:46, 25 January 2013 (UTC)


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

But the article does not use "significant" it uses "important" and in close proximity to the phrase "normal flora". It also doesn't say in the lead that it is harmful in the lungs??GeeBIGS (talk) 07:08, 25 January 2013 (UTC)
 * I'm not sure, but it might mean Klebsiella pneumoniae is the type species for the Klebsiella genus. Oda Mari (talk) 07:59, 25 January 2013 (UTC)

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

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

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


 * Your question is somewhat surprising, for several reasons. Not the least of which is that all word processors give a word count, university teaching staff usually set assignment papers in terms of word count, and in any case by the time you get to post grad, you should have done at least a few joint projects with other students and thus can see how much everyone else writes. And you should know darn well how efficiently or otherwise you use prose by now.
 * I'm not familiar with the templates you mention, but I can think of a few things that can sometimes have a surpising effect on the length. Are any paragraph settings Window/Orphan, Keep with next, Keep lines together, and Page break before turned on in the new template but turned off on the old?  Thse settings when on can make the page count very sensitive to font types, font spacing, margins, and the like.  Averaged over a great number of papers there should not be too much difference, but individual papers can somtimes throw up a huge change, if a certain set of paragraphs just fit on one page, but turning on one of the pargraph settings cause one to jump to the next page - the effect can ripple thru the entire paper.
 * Further, a good typist/author, like a good typesetter, intelligently uses character spacing settings, kerning, and fractional line spacing settings so as to make best use of a page by making small changes in chosen paragraphs - these changes can be well nigh invisible to the reader except for closing up paragraphs. Such changes are entirely acceptable.
 * Regarding whether studies have been done - the answer is yes. The choosing of fonts and styling rules is a complex art that book and magazine publishers have long sweated over as it does indeed cause non-rational impressions in the reader about length, verboseness, and readability.  Not only it is a complex art, it is subject to fashion, like clothes.  What was an "easy read" font or para style years ago is not always regarded as such now.  Ever looked at a textbook or periodical published 60 years ago and thought it was verbose?  Readers 60 years ago didn't think so.  One of the best books I bought, 20 years ago, on this subject, was called The Grey Book.  I don't have it now - partly because I learnt what it had to say, and partly because many of its recommendations are now "old fashion".  Google art of typesetting and enjoy!
 * Readability has always been considered worse on screen than on the printed page, when everything style-wise (fonts, spacing, etc) is the same. However, with today's high resolution displays, with black characters on a white background, there is little difference.  With today's children growing up with Kindles and computers, I expect before long folk will come to regard printed work not as good.
 * When papers and book manuscripts are submitted for publication, traditionally editors asked for .TXT files, not word processor files. However, now days, they all accept the major word processor file formast e.eg., Microsoft Word .DOC and .docx files.  But the first thing they do is run your submission thru a macro that strips off all your beautiful formating and font choice.  They do that for 2 reasons: 1) it gives them a standard "look and feel" so they can objectively assess wordiness, length etc, and 2) when they play with settings to clean it up and make it fit the space they have available for it in their journal or whatever, they don't have to fight with your settings.
 * Ratbone 124.182.2.156 (talk) 15:36, 24 January 2013 (UTC)


 * Sorry, I can't help you on the research you are looking for, but there must be some out there. Some other thoughts: Are these LaTeX formats? Generally, two-column formats are designed to get as many words as possible on the page (to save on printing costs). AMS article format in LaTeX is optimized for readability (have you read the not-so-short guide to LaTeX? It addresses many of these issues). I am not surprised by the conversion you gave. Also, many AMS-style are printed (if they are actually printed) on much smaller pages, which makes the margins more reasonable for a ~80 character line. Generally, you can tell that single-column, double spaced is what is preferred for readability, because that's what all the journals send to their reviewers. SemanticMantis (talk) 17:46, 24 January 2013 (UTC)
 * I question the claim:
 * you can tell that single-column, double spaced is what is preferred for readability, because that's what all the journals send to their reviewers
 * Another advantage of double spacing is it makes it easier to write comments. So whether the reason for double spacing is due to readability or simply to make it easier for reviewers to make comments would seem unclear.
 * Nil Einne (talk) 12:12, 25 January 2013 (UTC)


 * Double spacing was for many years usually specified for university assignment papers & theses because that provided room for lecturers to make comments and corrections when marking. Similarly, journal and book editors for many years requested double spacing, so they had room for hand marking up with edits and typesetting code marks for the typesetter - eg such and such font here, bold there, etc etc.  This only has meaning when the author submits on paper.  It has no meaning today when papers and manuscripts are submitted in electronic form, and are editted, marked up, and typeset on computer.  It never had, and does not today, have anything to do with readability.  Ratbone 120.145.185.57 (talk) 13:23, 25 January 2013 (UTC)
 * All of that is going the way of the Dodo though - with electronic media, the reader can have any font, any size, layout and line spacing they want. Studies on readability might have mattered in an era of print media - but we're rapidly moving away from that so any modern study on the subject would be largely irrelevant.  These days, the issue with such publications is mostly "How can I know whether I can rely upon this?" - so matters of respectability of the web site you got it from and how they do peer-review...that kind of thing. SteveBaker (talk) 17:09, 25 January 2013 (UTC)

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


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


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

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


 * For the maximum luminosity of an accreting black hole, see Eddington luminosity.
 * All three of the "Orders of magnitude..." entries added by the user that added that entry were either dubious or flat-out incorrect, so I have deleted them. Red Act (talk) 18:02, 24 January 2013 (UTC)

Wow, so I made my contribution to Wikipedia, but was the idea somewhat feasible? would it be possible to be THAT luminous? maybe the number is way of, but any idea of the actual order of magnitude of this effect? DST — Preceding unsigned comment added by 86.126.81.148 (talk) 19:18, 24 January 2013 (UTC)
 * As User:BenRG pointed out - you get into such a relativistic mess as soon as you cross the event horizon that it's simply not meaningful to put numbers against it. eg "the entire future of our universe compressed (blueshifted) into a finite time" could potentially imply infinite amounts of future incoming starlight compressed into just a few seconds (if our universe is infinite in span and duration)...which would mean infinite amounts of luminosity from the perspective of someone crossing the event horizon.  That's obviously not the case for an outside observer though.  There are so many caveats about where the observer is when the luminiosity is measured - and the literal impossibility of being there to measure it - or even of being affected by it from outside the event horizon...I wouldn't want to put a number on it.  SteveBaker (talk) 17:04, 25 January 2013 (UTC)

body turning to stone
What is the name of the medicial condition for the person's body turning to stone? It's like Scraladermia.205.173.217.10 (talk) 17:41, 24 January 2013 (UTC)
 * The hardening of the skin is called Scleroderma. However, the body does not literally turn to stone.  That's just some stuff from mythology, creatures like the Cockatrice or the Gorgon.  -- Jayron  32  17:44, 24 January 2013 (UTC)


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


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


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


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


 * Also osteopetrosis (literally "stone bone"). Dragons flight (talk) 12:17, 25 January 2013 (UTC)
 * And here I though Osteo Petrosis was a shipping magnate. μηδείς (talk) 19:22, 25 January 2013 (UTC)


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

Exercise and Sleep
Hi all,

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

Thanks, Sazea (talk) 20:32, 24 January 2013 (UTC)
 * Check this out and see what you think. -- Jayron  32  20:33, 24 January 2013 (UTC)


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