Wikipedia:Reference desk/Archives/Science/2012 October 24

= October 24 =

Advertisement technique of image, word, and logo
I've noticed a lot of ads are rather plain lately. Specifically, they have a picture which takes up most of the frame, a large word/phrase, and a logo. For example, see Bloomberg Businessweek’s Ad Campaign. What is this form of advertisements called or classified as?Smallman12q (talk) 00:34, 24 October 2012 (UTC)


 * Not science, certainly. -- Scray (talk) 01:42, 24 October 2012 (UTC)


 * Don't know if it has a name, but it's meant as a teaser, so you will read the rest. I certainly don't read ads which present a full page of text. StuRat (talk) 03:12, 24 October 2012 (UTC)


 * Is there a scientific (or at least a literary) classification of ads? Just on my own I would postulate a number of classes of TV ads, for example (print ads, in concept, can be more varied, including even Wikipedia postings) --
 * Allopathic - highlight/exaggerate a product's good features to make you want it
 * Homeopathic - highlights a product's bad features to desensitize you to them (more common than I'd expect)
 * Allegiance - directed to a third-party "customer", emphasizing that they are the top priority (3-4 years ago any program on TV would be supported by several ads that not subtly pointed out their products were usable to spy on the customer, e.g. "You talk, Sync listens" - now they are rare, not sure who/why)
 * Rote - the viewer is meant to learn specific phrases which should then be easier to repeat (there is a current campaign for "Yellow tail" which is the most extreme example of this type I've ever seen)
 * Cargo cult - the customer is presented with a pleasant scenario including a product, e.g. playing with a child or being with a pretty woman, which is supposed to be brought on by having it
 * Identity - the viewer is supposed to believe that his kind of people just have to buy this product to show they are in the group
 * Now this is an ad hoc, ignorant classification, not an answer, which I use only to encourage people to consider that a serious study of the topic is possible, but I have no idea who does such a thing. Given the money involved in the industry, someone must. Wnt (talk) 14:55, 24 October 2012 (UTC)


 * Neuromarketing? ~ AH1 (discuss!) 22:07, 24 October 2012 (UTC)
 * There must be a classification of ad styles ...what do people get MAs in marketing for?Smallman12q (talk) 22:22, 24 October 2012 (UTC)
 * What indeed... you asked the question... -- Jayron  32  03:21, 25 October 2012 (UTC)

Shape of universe
The three graphs in the lead are all smooth. Why? Don't some theories have irregular shapes?GeeBIGS (talk) 02:48, 24 October 2012 (UTC)


 * Well, all modern theories give irregular shapes at the galactic level, due to gravitational distortions of space. I think those graphs are intended to get the concept of the large-scale shape across. Looie496 (talk) 04:28, 24 October 2012 (UTC)


 * See Cosmological principle and Isotropy for the general idea. The Cosmological principle holds that no location in the universe is a privileged vantage point; that is for the purpose of observing the whole universe, any point should give the same perspective as any other, though local geometry may allow for variation (i.e. stars and galaxies are not locally evenly distributed) on a universe-wide level the entire universe should be isotropic and homogeneous (on average, all matter and energy should be evenly distributed).  -- Jayron  32  05:10, 24 October 2012 (UTC)

But don't we know that the superclusters are very inhomogeneous and distort spacetime on a large scale?165.212.189.187 (talk) 16:18, 24 October 2012 (UTC)


 * There was once an active hypothesis that the distribution of galaxies is fractal, but I believe the current mainstream view, based on studies of the cosmic background radiation, is that it is smooth on the largest scales. Looie496 (talk) 17:06, 24 October 2012 (UTC)


 * The answer, 165.212, is if your scale contains inhomogeneity and anisotropy, then your scale is too small. The largest "structure" in the (observable) universe is probably the Sloan Great Wall, which is about 1/60th the diameter of the "observable universe", which itself is an unknown fraction of the actual entire universe.  The Cosmological principle would hold that you need to back out your scale far enough that even structures as large as galactic filaments would "average out".  I know that it is somewhat tautological, but the definition of "inhomogeneity" in the universe is almost identical to the definition of "local", that is if your perspective on the universe can identify inhomogeneous structures, your perspective isn't "backed out" enough.  -- Jayron  32  17:23, 24 October 2012 (UTC)


 * My recollection from cosmology lectures during grad school is that homogeneity is a good assumption for scales that are 1/10 of the radius of the observable universe and bigger. Dragons flight (talk) 18:18, 24 October 2012 (UTC)


 * See (from the same source as the other) or the video ( - a truly great video, but so crippled by jpeg artifacts in this presentation, even at HD that they're all my eyes lock onto when I try to make out the lines of the walls) Probably better sources... Wnt (talk) 19:06, 24 October 2012 (UTC)


 * Also see wormhole, Einstein lens and multiverse theory. Now, if it's possible that one universe could expand into another... ~ AH1 (discuss!) 22:06, 24 October 2012 (UTC)

Blur screen for sight correction?
Is it possible to blur my monitor in such a way that it would correct my vision and I wouldn't need to wear glasses/contacts to see it properly? --89.241.237.237 (talk) 03:39, 24 October 2012 (UTC)


 * No. Bluring reduces the information in the image (the detail), and once removed, nothing odd about your eyes can put it back.  Ratbone 58.170.172.1 (talk) 03:48, 24 October 2012 (UTC)


 * I don't think that's quite the whole story. It's true that turning a blurred image into a crisp image is generally impossible, but that isn't what is being asked for.  If the OP is nearsighted or farsighted, in principle it ought to be possible to put a huge lens in front of the monitor that would have a similar effect to a lens in front of your eyes.  I'm not sure that counts as "blurring the monitor", but it ought to work. Looie496 (talk) 04:25, 24 October 2012 (UTC)


 * Well, yes. But in that case it will be cheaper and a lot more satisfactory to wear suitable spectacles.  Then the OP can also see his paperwork clearly, and read books as well.  Ratbone 58.170.161.168 (talk) 11:14, 24 October 2012 (UTC)


 * If you were to trace rays from a point on your retina to your display, you could map the points on the screen that coorespond to a point in your vision. When you start mapping nearby points on your retina, you would see that the regions on the screen overlap. Unfortunately, in order to resolve this in a way that would be clear, you would have to be able to project different colors in different directions from the overlapped parts of the monitor. You would essentially need a monitor that reproduces a specific light field, so it could simulate having a lens in front of it. 209.131.76.183 (talk) 12:07, 24 October 2012 (UTC)


 * However, with a single object, you should be able to do it. You could have several objects on the screen at once, so long as they aren't close enough to overlap.  You might also be able to quickly alternate between showing objects which do overlap, to give the impression of both being on the screen at once.  This approach might have application where glasses don't work, like when wearing VR goggles. StuRat (talk) 16:28, 24 October 2012 (UTC)


 * No, you shouldn't be able to do it that way. As 209.131 says, it doesn't work unless you can reproduce (or heavily tamper with) the light field&mdash;something that has to be done in hardware, and can't be accomplished with a conventional display, even if only parts of the picture are displayed at a time.  A straightforward thought experiment shows why.  First, consider producing a sharp image of a small point of light: effectively, a single 'pixel' in our display.  In a person with normal (or properly-corrected) vision, our point source of light in reality is focused to a single sharp point on the retina.  In a near- or far-sighted individual, that image of the point doesn't form where it should, but falls in front of or behind the retina; instead of a sharp point, the image on the retina is a broader blur.
 * The neat thing about lenses is that they don't care about which way light travels through them; it gets bent in the same manner in both directions. If we instead imagine a bright, sharp point emitting light from the retina out through the lens of the eye, we'll get a blurry smudge on the computer screen in front of us.  Aha! you say&mdash;if we set the computer to display that blurry smudge on the screen, we know that the lens of the eye can focus the rays from that smudge right back to a sharp point on the retina, and we've solved our problem.
 * ...except that we haven't. While we've solved the problem of how to get a bright spot at one particular point on the retina, we've ignored the rest of the retina entirely.  Unfortunately, that smear on the screen – the one that makes a sharp point in one spot on the retina – gets smeared out even further across the rest of the retina.  (The rest of the retina can see the screen, too.)  It can't be fixed just by picking and choosing which pixels to light up on the computer screen.  (It could be fixed if there were a way to produce negative intensities&mdash;but that's beyond the scope of computer monitor technology.)  TenOfAllTrades(talk) 17:15, 24 October 2012 (UTC)
 * Thanks, that is a good elaboration on what I was trying to say earlier. Basically, if you want that blurry smudge to resolve back into a point on your retina, each bit of that smudge has to only be transmitting light in the same direction that the imaginary light from the retina hit it. If it transmits at other angles, then it ends up hitting other parts of your eye, causing the blurry blob to get blurrier and blobbier. The sum of the thousands of blurry blobs, each pointing light in the right directions, is the light field required to render clearly on the retina. Any point on the monitor is shared by hundreds of blobs, each in a slightly different direction, so each point of the monitor would need to be able to transmit hundreds of different colors along hundreds of different vectors. I've always imagined that this technology would first show up in 3D displays - it would be like looking through a window. Leaning side to side would let you peek around and behind things, and you could focus your eyes on any object. It is pretty neat to realize it could also be used to adapt to a user's vision problems. 209.131.76.183 (talk) 19:39, 24 October 2012 (UTC)


 * You would need control of the phase as well as the amplitude of the generated electric field to be able to have a correction. IRWolfie- (talk) 21:09, 24 October 2012 (UTC)


 * There's a name for it, and it's not Retina Display... - ¡Ouch! (hurt me / more pain) 07:58, 29 October 2012 (UTC)

Matte instead of glossy cars
Why are cars always glossy? The matte exceptions seem to be from niche design companies, but never mainstream manufacturers. OsmanRF34 (talk) 12:16, 24 October 2012 (UTC)
 * Because people associate "shiny" with "new". Shiny cars look newer, a desirable trait when purchasing a new car.  Observe the common English idiom "shiny and new".  -- Jayron  32  13:56, 24 October 2012 (UTC)


 * But a good marketing would be able to sell the idea of "matte is your mate" or something silly like that. OsmanRF34 (talk) 14:49, 24 October 2012 (UTC)


 * There seems to have been a recent trend toward matte paints, specifically black, in mainstream motorcycles. Just do an image search you'll see plenty. SemanticMantis (talk) 14:53, 24 October 2012 (UTC)


 * This is a Reference Desk, so let's try some references, shall we? At least do a bit of Googling before throwing down an opinion.
 * I'll start the ball rolling with these recent columns:, . Hyundai's new Veloster Turbo apparently does come with a matte finish option, as does BMW's 6 Series Gran Coupé.  So why doesn't matte appear on more vehicles?
 * Part of it may be price&mdash;the matte finish carries a significant cost premium (though some of that may be automakers charging what the market will bear, rather than what the finish actually costs them to apply). Part of it is certainly personal preference; go watch an episode or two of Top Gear to see very clearly how different people can have very distinct and emphatic opinions about all aspects of automobile aesthetics.
 * One of the key points, though, appears to be that matte finishes are a lot more delicate, and the care they require is much more finicky. No more automatic car washes.  Don't even think about using standard car polishes.  Don't use terry cloths, cloth, or paper towels when cleaning.   If you rub too vigorously when cleaning you'll leave a shiny spot that can only be fixed with a costly respray.  (For similar reasons, you can't just polish out minor scrapes and scratches.)  Most people don't want to spend that much time, money, and effort on fiddling with their car's finish. TenOfAllTrades(talk) 15:06, 24 October 2012 (UTC)


 * Note the emphasise the point, as mentioned in TOAT's first reference in the Hyundai case at least in the US the customer actually has to sign something saying they understand the risks and special care required for a matte car. (The warranty also doesn't cover poor maintence but this can't be unique to a matte car, it's just more of an issue.) I expect this is a combination of CYA and marketing although it sounds like BMW did something similar . The later ref even goes as far as to suggest a matte finish may be a bad idea if you want to drive the car daily unless you can afford to take care of it (whether yourself or paying a professional) Nil Einne (talk) 15:23, 24 October 2012 (UTC)


 * I suspect we're getting into a semantics question here. I believe the OP is using matte to mean "any non-shiny surface", in which case, it should certainly be possible to provide one at a low cost and with minimal maintenance requirements.  The particular surface which automakers sell as a "matte finish" may be expensive and high maintenance, but let's not tar all dull surfaces with the same brush. :-) StuRat (talk) 22:29, 24 October 2012 (UTC)


 * StuRat got his matte finish from a roller brush and a can of house paint from the Home Depot. Someguy1221 (talk) 22:33, 24 October 2012 (UTC)


 * Nah... rust-colored primer, to mask the actual rust. StuRat (talk) 23:51, 24 October 2012 (UTC)


 * I don't think we're getting in to semantics. For starters, the OP was clearly talking about mainstream manufacturers, not what you can get from some auto store in a dodgy part of town. In any case we're discussing what's actually available. Perhaps it's possible to make this magic matte paint which is cheap, looks nice (well you didn't specify that but I assume it's a given?) but has minimal maintenence requirements. Definitely it's possible that manufacturers and from what I can tell most decent independent vendors who do custom paint jobs for some reason (for exclusivity purposes?) are only making matte finishes which have high maintenence requirements.
 * On the other hand, if you read the earlier sources, it seems unclear how some of the problems can be addressed. E.g. the problem with scratches. Or the fact you can't use automatic car washes (or likely any cheap manu car wash service) because they use stuff designed for gloss finishes. Even this seller of matte paint maintence products, while claiming that the maintenence requirements are overblown doesn't seem to deny these claims although they of course have an incentive to discourage the use of automatic car washes which they do in all cases. The source does claim scratches can be less of an issue because they don't show up so easily which I'm not sure is true depending on the case, but it doesn't seem to deny that when you do get scratches and if they are visible you ultimately can't deal with them like you would with a gloss coat. Note that the source, unsurprisingly, also suggests if you get a bodge matte paint job from someone who either doesn't know or doesn't care what they're doing, you're likely worse of maintence wise which hardly seem surprising.
 * One thing which most of the sources as well as mentions is that matte finishes are a relatively recent trend and therefore products to handle them are also only just really becoming available, which is likely one reason for the maintanence hassles. A key point which the Dr Beasleys source doesn't seem to answer is while it may be true the ideal maintence requirements for a gloss paint are also quite high, perhaps even higher then a matte job, what happens if you're like most car owners and can't be bothered? The other sources imply that for a variety of reasons including the obvious and already mentioned fact gloss finishes are much more common and therefore most products, experience and automatic cleaners are tailored to them, that it's likely your matte job will end up worse then your gloss job in that case. (It seems to me there's a fair chance a somewhat poorly maintained matte finish would end up looking more or less the same as an extremely poorly maintained gloss finish which likely isn't desirable.)
 * Nil Einne (talk) 23:54, 24 October 2012 (UTC)

Chemical Shift Perturbation
In relation to NMR, what is 'chemical shift perturbation' and is it synonymous with the phrase 'chemical shift', if not what is the difference? Please explain assuming little knowledge of advanced NMR. Thanks  Kinkreet ~&#9829;moshi moshi&#9829;~ 13:35, 24 October 2012 (UTC)
 * Perturbation means "disturbance" or "change to", so I would take "chemical shift perturbation" to mean a "change in the chemical shift (from expected shifts). In NMR, the "chemical shift" of a peak is just its location in the spectrum (usually measured as relative to the location of tetramethylsilane, for H-1 and C-13 NMR).  I would understand a "shift perturbation" to be an unexpected (or non-standard) change from the expected shift.  That is, you run an NMR, observe the "standard" shifts, and then usually some change is made to the substance, and you can observe a "perturbation" or "change to" the standard shifts.  This page has some explanation of a kind of perturbation that occurs at the interface between two immiscible phases, that is the molecules along the interface experience a change in their chemical shift in (in this case) N-15 NMR, different from if the substance without the second, added, substance.  Does that make sense?  -- Jayron  32  13:55, 24 October 2012 (UTC)
 * Belated thanks to Jayron. I can understand it a little better now. Thanks.  Kinkreet ~&#9829;moshi moshi&#9829;~ 19:20, 3 November 2012 (UTC)

Is the refractive index of a solution against the concentration linear?
I am doing a physics project which will involve passing a laser through an aqeous solution of Ethylene glycol(antifreeze). Does anyone know if the relationship between the refractive index of the solution and the concentration is linear or at least approximately linear? If not is there any mathematical relationship between the two?

Thanks. — Preceding unsigned comment added by 109.158.65.134 (talk) 15:48, 24 October 2012 (UTC)
 * The results have been tabulated . It is pretty linear, though not exactly.  If you can't access the article, leave a note on my talk page and I can e-mail some of the data to you. Buddy431 (talk) 16:09, 24 October 2012 (UTC)
 * And just to be clear, it's weight percent that's nearly linear with refractive index. Buddy431 (talk) 17:33, 24 October 2012 (UTC)

Precipitation vs Settling vs Sedimentation vs Deposition vs Decantation
Words like these don't always seem totally distinct, could someone please explain the precise definition of each, and make it clear on each article why they are separate concepts? --130.88.99.220 (talk) 16:50, 24 October 2012 (UTC)
 * The first three actually overlap pretty strongly. Deposition is different in that it can apply to a dissolved material -- the first three all apply to suspensions, I believe.  Decantation is entirely different:  it is the process of removing a layer of liquid to leave something behind.  I have edited the decantation article to try to make that clearer.  I'm not a chemist, and anybody who thinks my edit can be improved is encouraged to do so. Looie496 (talk) 17:01, 24 October 2012 (UTC)
 * I disagree about "precipitation". Precipitation (chemistry) usually applies to dissolved materials that come out of solution.  Deposition (chemistry) usually refers to a layer being built up on some existing surface, either through the settling of a suspension or precipitation from a solution (where just "precipitation" might be crystals forming suspended in the solution).  I would say sedimentation is a more precise term than settling: "sedimentation" is usually used for things like red blood cells that settle relatively slowly (or even smaller particles, that need a centrifuge to settle in a reasonable time scale), while the term "settling" could be used to refer to processes that occur on much shorter time scale (i.e. swirl the mixture, and then let it settle for a few minutes before decanting off the liquid).  Just my 2 cents though. Buddy431 (talk) 17:26, 24 October 2012 (UTC)
 * Deposition can refer to a solid coming out of solution, especially in contexts where the solid adheres to another surface, especially in plating, but commonly it also refers to a solid forming out of a gas: see Deposition (aerosol physics) and Deposition (phase transition); deposition is considered the proper name for the opposite phase transition as Sublimation (phase transition). The other uses are not unknown, and in some fields may be more common, but in others the phrase is reserved for a specific type of "settling", usually a solid settling out of a gas.  Sedimentation is reserved for geological settings, usually: one wouldn't usually use sedimentation to refer to precipitation in a beaker in an instructional chemistry lab, though conceptually they're almost identical.  -- Jayron  32  17:30, 24 October 2012 (UTC)
 * "Sedimentation" is used pretty frequently in the biology and biochemistry, with respect to how quickly macromolecules or cells will sediment, usually under centrifugation. See Svedberg and Erythrocyte sedimentation rate for examples. Buddy431 (talk) 17:37, 24 October 2012 (UTC)
 * Also, with regards to precipitation: my understanding (as someone with a chemistry degree who has taught the subject for more than a decade) precipitation and settling or sedimentation are distinct processes: precipitation is the formation of the solid itself, without regards for where it forms. Precipitation means specifically the agglomeration of molecules into particles in the solid phase, and happens before settling, which is the falling of those particles to the bottom of the container.  Indeed, precipitation doesn't have to lead to settling: some precipitates may remain in indefinite suspension.  -- Jayron  32  17:51, 24 October 2012 (UTC)
 * Maybe the people responding here could look at the articles and see if it is possible to give clearer definitions? Even a change to the first sentences alone would be valuable, if they can be made better. Looie496 (talk) 18:03, 24 October 2012 (UTC)


 * Precipitation (chemistry) was just plain broken - an unsourced description given by someone who didn't seem to understand that precipitates can remain in suspension. I took a really quick slash at it but it needs proper sourcing to good texts and a lot more careful evaluation. Wnt (talk) 19:27, 24 October 2012 (UTC)

Thanks for replying so quickly guys & girls. I just wanted to add Solvation to my list of problem words, and was surprised to get some good opinions on this already. I shall check back, please keep discussing! Also my userpage is broken on this English edition but you can chat to me directly on the Arabic version. (perhaps solvation vs solution should be discussed separately?) 130.88.99.220 (talk) 20:06, 24 October 2012 (UTC)


 * Solvation is the process whereby the molecules/ions of the solute (the stuff going into the solution) are broken from each other and bonded to the individual molecules of the solvent. I've seen the term used inconsistently in some cases: Sometimes it refers to the entire process of dissolving: the disassociation of the solute particles and the association of said particles with the solvent molecule: it can also be used to refer to just the second part of the process, the bonding of solvent molecules to individual solute molecules/ions.  In simplest terms, solvation is where individual molecules or ions of a substance get "coated" with molecules of the solvent.  So when sodium chloride dissolves, the individual sodium and chloride ions get surrounded by a "shell" of water molecules that bond to the ions and thus keep them apart from each other.  That's solvation.  -- Jayron  32  02:36, 25 October 2012 (UTC)

At what temperature is surface tension on pure freshwater the strongest?
Hi. See the topic. Thanks! ~ AH1 (discuss!) 22:00, 24 October 2012 (UTC)


 * At 0 deg C (below that it is solid -unless in super-cooled droplet form) as it gets lower as the temp increases until boiling point at STP. --Aspro (talk) 22:48, 24 October 2012 (UTC)


 * In the case of super-cooled water, this link suggest the max is at -22.2 º C : Experimental Values of the Surface Tension of Supercooled Water. Such a cloud of super-cool droplets is something any PPL holder would wish to stay away from. Does this answer your question?--Aspro (talk) 23:07, 24 October 2012 (UTC)


 * However, WP (as always) has an article on Supercooling and that suggests −48.3 °C. It has refs also.--Aspro (talk) 23:22, 24 October 2012 (UTC)


 * If I understand that article right, -22°C is only the lowest temperature that their experimental arrangement could get any results. Quoting the abstract, “A total of 702 individual measurements of surface tension of triple-distilled water were made in the temperature range, 27 to -22.2 C,”; and table I confirms the same.  Presumably water supercooled below that would have even lower surface tension, only they couldn't measure that.  &#x2013; b_jonas 23:09, 29 October 2012 (UTC)

WHY ARE "BELT CONVEYORS" REPEATEDLY REFERED TO AS "CONVEYOR BELTS" ?
A CONVEYOR BELT IS ONLY 1 SINGLE COMPONENT OF A VERY COMPLEX SYSTEM. THE COMPLETE SYSTEM IS CORRECTLY REFERRED TO BELT CONVEYOR. — Preceding unsigned comment added by 208.86.181.160 (talk) 22:06, 24 October 2012 (UTC)


 * English is a remarkably flexible language, allowing a given word or phrase to have more than one meaning, and adapting the "correct" meaning to the general usage over time (as contrasted with languages that formally prescribe correctness). All that said, it appears our conveyor belt article includes both usages, and rather clearly notes that "conveyor belt" can refer to both the specific belt and the collective system. &mdash; Lomn 22:11, 24 October 2012 (UTC)


 * I suggest "conveyor belt" for the belt itself, and "conveyor belt system" for the entire device. A "belt conveyor" sounds like something (such as a chute) at a leather tannery which delivers leather belts from one area to another. StuRat (talk) 22:23, 24 October 2012 (UTC)


 * You are clearly no expert on the English language, or you would use your caps lock key more sparingly. If the OED agrees with you, maybe we can do something about it. Otherwise, no. AlexTiefling (talk) 23:06, 24 October 2012 (UTC)


 * The OP would do well to read the article Etymological fallacy: the original meaning of a word does not get preserved forever, word meanings change and if a word has taken on a different meaning from an older one, it isn't "wrong". -- Jayron  32  02:28, 25 October 2012 (UTC)
 * In a related vein, see also metonymy. TenOfAllTrades(talk) 12:23, 25 October 2012 (UTC)


 * Since you ask, AlexTiefling, the OED says: conveyor belt = an endless belt of rubber, canvas, etc., running over rollers or the like, on which objects or material can be conveyed, and belt conveyor = conveyor belt. Of course the OED derives its authority from usage and not vice versa, but I think this is a powerful argument. Marnanel (talk) 12:32, 25 October 2012 (UTC)