Wikipedia:Reference desk/Archives/Science/2012 May 27

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May 27

Driving speeds and fuel efficiency

This one has been bugging me -- as I recall, one of the rationales behind the late, unlamented 55 MPH national speed limit in the United States was that it was purported to increase fuel efficiency. So far I've not been able to deduce exactly why driving at slower speeds would have an impact on fuel efficiency: Certainly the chemical structure of gasoline has exactly the same potential energy regardless of how fast it's being pumped into the engine, no? So I'm wondering by exactly what physical mechanism higher driving speeds reduce fuel efficiency. Evanh2008 (talk) (contribs) 01:55, 27 May 2012 (UTC)

Really fast cars seen to be built with primarily speed in mind, not fuel efficiency, so they might be thinking that a relatively low speed limit would eliminate those cars, leaving the slower, fuel-efficient cars. (Which doesn't mean they're thinking right—there's no limit on how slowly one can drive a car with a really high top speed.) Whoop whoop pull up ^{Bitching Betty | Averted crashes} 02:02, 27 May 2012 (UTC)

Actually, that isn't it at all. Even economy cars can go considerably faster than any speed limit I've ever seen (I got my 1982 Toyota Tercel, a utilitarian ride if there ever was one, well in excess of the top "85" listed on the speedometer. I was probably going about 100). Every car has an optimal speed for which it has a maximum fuel efficiency. Of course, a stopped car, or one barely crawling, has a terrible fuel efficiency, because the engine is doing a lot of running for very little forward motion. However, at the upper end, things like rolling friction and wind resistance become a serious drag (pun intended) on fuel economy. On my current car, a 1999 Ford Escort (again, the textbook definition of a "basic ride") this seems to be at around 70 MPH, but each car is likely different, and perhaps the cars of the 70s and 80s did have peak fuel efficiencies around 55 MPH. Cars have changed considerably since that time. --Jayron32 02:29, 27 May 2012 (UTC)

I actually think cars of that era were designed with higher cruising speeds in mind. However, they weren't very aerodynamic, so the drag at higher speeds would be more of a problem. I doubt if the lower speed limit actually saved any gas, though. In some cases, it wasted gas, as in driving through hilly areas, where you had to ride the brakes down each hill to keep from going over 55, wasting gas and burning brake pads all the way. Then there's the effect that slower cars stay on the road longer, and this causes more traffic jams, which waste gas. StuRat (talk) 02:44, 27 May 2012 (UTC)

Then there's also the (well documented) effect that faster cars have more accidents, and this causes more traffic jams, which waste gas. 203.27.72.5 (talk) 04:05, 27 May 2012 (UTC)

And if a 55 mile per hour speed limit actually made all cars go 55, that would be a valid point. However, you get some doing 55 and others still going 85, which is a recipe for a disaster. StuRat (talk) 04:09, 27 May 2012 (UTC)

In general, your car is using least fuel when the engine revolutions are lowest. Since fuel efficiency is how much fuel you burned for distance covered, the most efficient point is usually where the speed:engine revs ratio is highest. This is normally when you're in top gear with the revs just high enough to prevent the engine from labouring. In my old '88 Nissan Navara this was about 60km/h. In my shiny new Toyota Yaris, I have no idea, because it's an auto so I don't look at the tachometer. 203.27.72.5 (talk) 03:35, 27 May 2012 (UTC)

Kinetic energy goes up quadratically in velocity; if you double your speed, you quadruple your KE. So since the amount of energy needed to increase your speed by 1 unit increases with velocity, the amount of gas needed to get the same effect on velocity increases with velocity. Simplest terms: how much gas you need increase your speed increases with your speed; so, yes, the slower you are going, the better your fuel efficiency, all else being equal. (Going 80 raises your KE by a factor of 16/9 over what is at 50, that's an extra 44% of your KE at 50 than what would be expected.)Phoenixia1177 (talk) 04:18, 27 May 2012 (UTC)

You are assuming the only energy used by a car is to get it up to speed. In reality, that is a very minor portion. Most of the energy is lost to inefficiency, drag, and rolling resistance. If your model was correct, then driving at a constant speed on a level highway with no turns would only require gasoline during the acceleration phase, and you could turn the engine off and cruise for the rest of the trip. Or, to put it another way, you said "all else being equal", but "all else" is nowhere near equal. StuRat (talk) 05:00, 27 May 2012 (UTC)

I don't disagree with that, nobody mentioned KE yet and it does depend upon velocity, so figured I'd add it. Although, when you lose speed, it will, again, take more energy to resume the speed you were at; or, in other words, you're going to end up expending more energy to compensate for those effects at a higher speed due to what I said above. On the other hand, this isn't really my area of understanding and it's late, maybe I'm being stupid and not seeing something. :-) Phoenixia1177 (talk) 05:07, 27 May 2012 (UTC)

I did a test in my car a few months ago. At 72 MPH I got about 25 MPG; at 55 MPH I got about 33 MPG. Bubba73 ^{You talkin' to me?} 06:05, 27 May 2012 (UTC)

May we ask what year and model car ? Larger and older cars tended to be geared for higher cruising speeds, while smaller, newer cars are geared for lower cruising speeds. It would also be interesting to see more data points, to know just what you optimal cruising speed is. And how long was each test ? For short tests, like 100 miles or less, there would be considerable error in the calculations. StuRat (talk) 17:58, 27 May 2012 (UTC)

It is a 2011 Chevrolet Impala. It has a digital indicator showing the mileage you are getting. It was on cruise control on a flat interstate highway for long enough to get a good reading. Bubba73 ^{You talkin' to me?} 05:03, 28 May 2012 (UTC)

Don't know if any of you have heard of the online encyclopaedia called Wikipedia but it has a explanation of aerodynamic drag. Just thought I'd mention it. --Aspro (talk) 16:00, 27 May 2012 (UTC)

But surely, drag is perfectly proportional to the speed at which the car is traveling, no? Drag at 60 MPH would be exactly three times as much as that at 20 MPH, and would have three times the negative effect on the velocity of the car, but the car had three times as much velocity and was traveling with three times more force to begin with. The force imposed on the car by drag is both equal and opposite according to Newton's third law, so wouldn't it balance out? Evanh2008 (talk) (contribs) 22:34, 27 May 2012 (UTC)

Drag effects are different for laminar and turbulent flow. Increasing the speed increases the turbulent flow. 203.27.72.5 (talk) 22:44, 27 May 2012 (UTC)

Ah, so something like a drag crisis brought about by the (possibly exponential?) increase in the Reynolds number involved in the relevant equation? Evanh2008 ^{(talk|contribs)} 23:24, 27 May 2012 (UTC)

Aerodynamic drag is proportional to the square of the speed of the airflow relative to the car, so at 60 MPH drag is about 9 times its value at 20 MPH. That's one of the main reasons that fuel economy drops at high speeds. Wikipedia's article on aerodynamic drag is atrocious; a somewhat more useful explanation is here. Short Brigade Harvester Boris (talk) 01:38, 28 May 2012 (UTC)

The energy required to overcome the drag is proportional to the cube of the speed.--Srleffler (talk) 18:30, 29 May 2012 (UTC)

I really cannot figure out why in the entire above speculative conversation about why cars might be most fuel efficient at speeds below their maximum possible speed (and the side speculative conversation about whether the claim is, in fact, true) no one linked to our own actual article about Fuel economy in automobiles. Section 3 on "Fuel economy statistics" isn't the be-all and end-all on the subject, I'll grant you, but it does at least have the merit of citing clear studies showing that the efficiency does peak somewhere in the neighborhood of 40-60 mph for most models, and offers some relatively clear plausible explanations for why this is so (though I think that section could be articulated in more depth, if anybody has the skills to do so). Jwrosenzweig (talk) 01:51, 28 May 2012 (UTC)

Internal combustion engines have an "efficiency band" they are designed for, Engine_efficiency. One advantage of hybrid vehicles is that their IC engine only need to run at one specific RP,M so they can be designed to have a very narrow and in turn very efficient operating band. Vespine (talk) 23:56, 28 May 2012 (UTC)

However, that only applies the the type of hybrid which solely uses the combustion engine to charge the battery, and then runs an electric motor off the battery. This has the disadvantage of limited range and power. The type of hybrid which can also use the combustion engine to supplement the electric motor, either for greater acceleration or range, should be designed to be efficient over a wider range of speeds. StuRat (talk) 19:16, 29 May 2012 (UTC)

Yes sorry, of course, I'm not sure I was aware of the "other" kind of hybrid you mention.. Vespine (talk) 03:20, 30 May 2012 (UTC)

I plan my next car purchase to be that type, with a model which also allows direct charging by plugging into any outlet, since it will be flexible enough to allow me to use gasoline or electricity, or both, depending on their relative prices and availability. StuRat (talk) 04:33, 30 May 2012 (UTC)

Why are there no albino horses?

Title says it all… Whoop whoop pull up ^{Bitching Betty | Averted crashes} 01:56, 27 May 2012 (UTC)

There also a breed of horse known as the "Albino Horse" or more specifically the "American Albino Horse", which doesn't have albinism, but is still white. Searches on the internet for Albino Horse usually results in the breed, which gets a bit confusing, because people need to be reminded that Albino Horses aren't actual albinos. See here for the breed. The reason that there aren't any actual albino horses is that the gene that causes albism isn't present in horses, per this article. Searching through google, it appears that some horses have what is called "partial albinism", which is also known as hypomelanism, though none have total albinism, aka amelanism. There appears to be several different genes at work here in several different species, that is there is not a single gene or a single mutation responsible for all forms of albinism in all species, and it appears that horses simply don't have the genetic trait that leads to total albinism in their makeup. --Jayron32 02:23, 27 May 2012 (UTC)

There are no horses with albinism as it is understood in people, rats or rabbits. With the caveat that most horses people think are "white" are actually grays with a fully silvered-out hair coat, genetically "white" horses are not actually hypomelanic; though they have unpigmented skin and sometimes have blue eyes. Genetically, production of pigment has been suppressed by the action of the genes that cause various types of white coats. "White" horses have pigment in their eyes, most are brown-eyed, a few are blue-eyed, but there is never the red-eyed version you see with, for example, rabbits. There also is not such a color breed currently named the American Albino any more, either; the people who started that registry had an interest in what we now know to be dominant white, cremello, cream champagne, and sabino-white horses, though the genetics were not understood at the time (hence that 1947 article cited above is quite outdated. There was also an issue at the time of several American mainstream breed registries refusing to register white or light-colored, blue-eyed horses due to various concerns about breed purity and the potential lethality of a couple of genes. Once they understood the genetics better, the "Albino" registry changed the name (many years ago) to the American creme and white horse registry. Now that mainstream registries understand color genetics better and have mostly repealed their "white rules" against white horses, cropouts and cremellos, the "albino" organization appears to have become defunct. The simplest coat color in horses is actually chestnut (aka "red"), which is, basically, created via pheomelanin, the same mechanism that makes people blonde or redheads. All the forms of white in horses are created by some kind of mechanism that suppresses other color pigmentation genes. I'm not a geneticist, but I helped the person who was when we did all the horse coat color articles, so I hope this helps. Montanabw^(talk) 19:42, 27 May 2012 (UTC)

But why aren't there any? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 21:52, 27 May 2012 (UTC)

Well, "Why" is more of a philosophical/teleological question than a scientific one, isn't it? Evanh2008 ^{(talk|contribs)} 23:05, 27 May 2012 (UTC)

How so? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 01:27, 28 May 2012 (UTC)

You asked "Why aren't there true albino horses", and I gave links and explained "It isn't in the genetic makeup of horses to have true albinism," There is no more why, from a scientific perspective. The question cannot possibly be answered to any more completeness, so if you persist in asking "why", then you are now asking for deeper "why" questions, which science is entirely unequipped to answer. If the answer given is unsatisfactory, then perhaps "God made them that way" will work, because other than citing sources (admitedly old, but a source nonetheless) which states that horses don't have the genetics that allows for albinism, I'm not terribly sure how to answer... --Jayron32 02:19, 28 May 2012 (UTC)

Are we saying that albino horses would only happen if there were genes in horses that led to that? (and that there aren't such genes in horses?) Are we, further, saying that we don't really know why there are combinations of genes in other mammals that lead to albinism, we just know that there are? Maybe Whoop has just missed the second part, which is quite easy to do? --Demiurge1000 (talk) 02:28, 28 May 2012 (UTC)

Albinism is defined as the lack of melanin with the presence of nonfunctioning melanocytes. Why are there no horses with nonfunctioning melanocytes and a lack of melanin? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 16:18, 28 May 2012 (UTC)

Because evolution has not led to such a combination. --Demiurge1000 (talk) 16:35, 28 May 2012 (UTC)

Is the genetic cause of albinism known with some reasonable certainty? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:37, 29 May 2012 (UTC)

I'll admit it's the damnedest thing. There are a couple theories. The most prevalent one (though based on a small study with many flaws) is that an "albino" horse gene as we are discussing it here is an embryonic lethal when it occurs, with either the embryo failing to form/being reabsorbed or being spontaneously aborted, possibly the result of homozygous dominant white. The other is that, basically, the genetic mechanism just doesn't happen. Either way, there are white horses but no albino horses anywhere in the world, ever. White patterning in horses is problematic in general, we have neither proven nor disproven the homozygous lethal in dominant white, and while tobiano and sabino appear to have no health problems, frame overo causes lethal white syndrome (still not an "albino" foal) when homozygous, splash white is linked to deafness, the leopard complex that creates the spots on an Appaloosa is linked to blindness, and even gray horses have a higher-than-normal rate of developing melanomas. Don't know if this is an issue for white-ish animals in other species or not, but definitely a "thing" for horses. Montanabw^(talk) 18:35, 29 May 2012 (UTC)

Do we know that albino horses never occur ? Or is it possible it's just so rare that we've never recorded one ? Do we have examples of extremely rare albinism in other species ? StuRat (talk) 02:46, 30 May 2012 (UTC)

To say that albinism does not occur in horses coz their genes don't cater for it, is like saying that some substance brings on sleep coz it has a "soporific property". Other animals have albino specimens, and if horses do not, the correct answer might be: "We have no idea at present". Now isn't that a lot more concise and accurate than making out you have an answer when you don't? Myles325a (talk) 06:29, 30 May 2012 (UTC)

We have no hypothesis at presence that has really solid support. The embryonic lethal is the best we have. And StuRat, given how obsessed people are about white horses, if one lived, it would be trumpeted to the skies; a red-eyed horse! OMG! Instant fame and fortune. Yeah, we'd know. ;-) Montanabw^(talk) 23:06, 30 May 2012 (UTC)

Or they might just think it looks sickly and kill it. StuRat (talk) 23:12, 30 May 2012 (UTC)

(ec)I think I'd rather look at this interesting question from the other end. What makes an albino person? Let's stick to "oculocutaneous" albinism affecting both eyes and skin at once. In theory I suppose you could have an ocular albinism gene crossed into a white horse background and end up with something that looks pretty albino, but I'm not going to look into it now. Well, there's OCA2 [1] OCA1A [2] and OCA1B (tyrosinase) [3], OCA3 (TYRP1) [4], OCA4 (MATP) [5], and an albinism-deafness syndrome of unknown etiology on Xq24-26 AFDN [6]. Plus six types of Hermansky-Pudlak syndrome and one Chediak-Higashi syndrome, for a total of eleven known as of 2003. [7] The question then becomes - are these genes mutated also in horses, and if so, what is the effect? Note that not all human "albinos" under these syndromes have truly red eyes; some have gray or blue eyes.

Now of course, not every mutation at a gene associated with albinism in humans will actually be an albino, so for example you can have blue eyed humans, and the leopard complex and congenital stationary night blindness in horses apparently is associated with OCA2 [8] TRPM1 [9], though those are not albino horses.

But the real issue, as explained in the White (horse) article, is that albinism is defined more narrowly in animals than in humans, which in my mind makes this in part a semantic issue. Tyrosinase, coded by the Color gene (c locus), is one of the genes involved in creating melanin pigment. [10] But fetishizing that only this gene is an "albino", though useful in the sense of identifying specific genes, is somewhat counterproductive when there are white horses out there, because you could have a horse that fits the bill perfectly and it still would not be a "true albino" by that definition, unless you found an actual tyrosinase mutant as the cause. Note that the horse C (cream dilution) locus is not tyrosinase [11], but it is controlled by MATP [12] Thus the very light "cream" horse color is generated by the same means as humans with "type 4 oculocutaneous albinism", but it is not called an albino horse. This still doesn't answer why horse tyrosinase mutants are not forthcoming, however. Wnt (talk) 23:56, 30 May 2012 (UTC)

How often should sausages be turned on the BBQ?

My view is that the goal has to be to get enough heat to the middle to cook that the sausage right through. Every time the sausage is turned it has to start the process of getting heat to the middle again, while the bit on top that has just been heated will cool down a bit.

So I feel that sausages should only be turned once.

Is there a good reason for the common practice of turning them many times? HiLo48 (talk) 03:11, 27 May 2012 (UTC)

I think once is sufficient, but don't really see a disadvantage to more than once. One advantage might be grill marks on all sides, if you do maybe 1/4 turn each time, instead of just the top and bottom. StuRat (talk) 04:06, 27 May 2012 (UTC)

It isn't true that "every time the sausage is turned it has to start the process of getting heat to the middle again". If it were true, sausages would be impossible to cook no matter how you did it. Looie496 (talk) 04:28, 27 May 2012 (UTC)

Sorry, I don't see the logic in that post. HiLo48 (talk) 04:32, 27 May 2012 (UTC)

I do:

1) The heat continues to sink in from the side which was previously grilled.

2) The side that was away from the grill is cooler, but not as cold as it was when you started grilling. It will have warmed up considerably from ambient heat in the grill (especially if the lid was closed). Thus, the second side often takes less time. StuRat (talk) 04:52, 27 May 2012 (UTC)

Just cooked some brats on the grill tonight, and as usual, I cook them on 4 sides, giving about even time to all four sides. That way I end up with an evenly browned skin, and even cooking all the way through. I also parboil the brats in beer and onions before grilling, which cooks them most of the way through anyways, but when I grill them I always try to grill 4 sides for evenness. For pre-cooked sausages (like Kielbasa or something like that), I still try to cook evenly on 4 sides. --Jayron32 05:03, 27 May 2012 (UTC)

Perhaps the grill-each-side-only-once approach is just fine if each side is given the "right" amount of time at the "right" temperature.

Not knowing the right parameters very precisely, I (and probably many others) would tend to turn the sausages multiple times in the hope that things would somehow balance out. (I can't put it much more unscientifically than that. :o) Wanderer57 (talk) 14:01, 27 May 2012 (UTC)

True, and there may be other reasons to turn it more often:

A) You want to check the bottom anyway, to make sure it isn't burning, so might as well turn it to see the bottom.

B) Turning it often keeps it from curling up on one side.

C) You want to have it ready whenever somebody asks for one, so getting the grill marks on all sides quickly, then putting it off to the side to keep warm, is the way to have it be ready, and yet not burnt, for the maximum amount of time. StuRat (talk) 23:48, 27 May 2012 (UTC)

See also here. Count Iblis (talk) 16:24, 28 May 2012 (UTC)

Remember that the heat is not constant between treatments. If you have a very hot grill, and you turn the sausage "continually", the time spent away from the heat averages out with the time spent facing toward it for any infinitesimal bit of meat. So by turning "continually" you can keep the outside at the perfect cooking temperature (on average) and have the heat penetrate from all angles toward the center, with maximum effect. Wnt (talk) 00:11, 1 June 2012 (UTC)

Never before seen color

Is it possible that there exists a color that has never been seen by any human eye? -- 96.55.20.179 (talk) 05:02, 27 May 2012 (UTC)

Depends on what you mean by color. There are many wavelengths of light which humans can't perceive, indeed visible light represents a tiny fraction of the breadth of electromagnetic waves. There are some color combinations which we also cannot put together; for example even though there can be reddish-orange, there is no reddish-green. You may find Impossible colors and Imaginary color to be an interesting read, and more generally Color vision, which is way more complex than you may realize. --Jayron32 05:07, 27 May 2012 (UTC)

(edit conflict)Plenty, microwave, gamma, radiowave, x-ray, infrared. Plasmic Physics (talk) 05:09, 27 May 2012 (UTC)

(edit conflict)Your perception of color is entirely limited by the variety of cone cells in your eyes. You probably have three types, and the relative activity of a group of cone cells in a small area of your retina determines what color your brain interprets. It's important to know that what you see as colors is merely your brain's interpretation of the input coming from your eye. There are plenty of "colors", combinations of wavelengths, that are different in their physical reality but identical as interpreted by your brain, as well as "colors" your eyes can't see at all. The only way to see truly "new" colors would be to add a new variety of cone cells to your eyes. Unless you were born with tetrachromacy, you're stuck with the known colors. Someguy1221 (talk) 05:10, 27 May 2012 (UTC)

Barring an unforeseen evolutionary development or artificial modification to the human eye structure, you won't be seeing any new colors anytime soon. We know which wavelengths constitute the visual spectrum, and pretty much all of them occur naturally. The only way to "see" new colors would be to somehow extend the visual range of humans further into the ultraviolet and/or the infrared through modifying the ocular structure. Evanh2008 (talk) (contribs) 05:14, 27 May 2012 (UTC)

Fascinating answers. Thank you all. -- 96.55.20.179 (talk) 05:33, 27 May 2012 (UTC)

I have to disagree. Certain animals can see colors that humans can't, as described in color vision, so IMO, the answer is yes. Clarityfiend (talk) 05:43, 27 May 2012 (UTC)

You disagree with whom? Your answer is in concurrance with every answer given so far... --Jayron32 06:05, 27 May 2012 (UTC)

The previous answers have all assumed an implicit "but might be seen by a human eye". The previous answers have mostly addressed that unstated condition, while ClarityFiend has provided an answer to the question as stated. --ColinFine (talk) 12:53, 27 May 2012 (UTC)

• Clarityfiend hints at the issue that in evolution of color vision birds, reptiles and teleost fish have 4 types of cone cells to sense colors, but most mammals only see 2. Evolution of color vision in primates has bodged together 3 to give us Trichromacy. Thus fish see colors we can't. . . dave souza, talk 07:45, 27 May 2012 (UTC)

Mantis Shrimp are the animal with the best known colour vision. They have 16 different photoreceptor pigments. SkyMachine ⁽⁺⁺⁾ 08:23, 27 May 2012 (UTC)

Would it be possible to construct a device to 'see' these extra colors artificially? -- 96.55.20.179 (talk) 00:51, 28 May 2012 (UTC)

See Infrared astronomy, Radio telescope, Ultraviolet astronomy. You can see images from these spectra if the detail is displayed in our visible spectrum. If by "see" you mean "see directly with your mind" as different colours to the ones you already can see, then that would require a computer/brain interface or genetic engineering. Also some humans may currently be able to see some extra colours SkyMachine ⁽⁺⁺⁾ 02:08, 28 May 2012 (UTC)

Interestingly, the answer is almost certainly "YES". As reported in a recent Scientific American, researchers used gene insertion techniques to give experimental animals (lab rats if I remember rightly) tetrachromic retinas. Their brains adapted to the extra colour info and standard training experiments verified that the rats were conscious of the extra colours. This isn't terribly suprising, as a range of experiments with people needing artificial limbs showed that the brain is very "plastic", as psychologists term it. Therefore, if gene insertion techniques were used on a human to give him a fourth cone type, he would be able to consciously see the extra range of colours. Another famous experiment, that proved how flexible the brain is, was conducted in the early 1960's: A volunteer was given special prism spectacles that inverted his vision of the world around him. It took about 2 weeks, but his brain adapted and he saw his surroundings the right way up with the spectacles on. Those of us who are acutelyt shortsighted know that spectacles result in an image on the retina smaller than normal. But the world does not look samll to us - it looks normal. So it is entirely reasonable to say you could build a set of "spectacles" equiped with video cameras that are sensitive to an extended colour range, say 300 to 900 nm (near infrared to ultrviolet) and connect them to electronic circuits to compress/remap this range down to 420 to 660 nm (the normal range for human eyes) and present the range-compressed image on screens in front of the eyes. After some "training", ie wearing the "spectacles" for a priod of weeks or months, whatever it takes, the brain would almost certainly be conscious not of getting an artificial image, but be conscious of a natural seeming extended colour range. At first, normal colours would appear washed out, but after a while, the brain would adapt, and normal colours would look normal again. Whe presented with (say) a pure red (630nm), he would see it it as pure red, even though the "spectacles" are presenting his eyes with (say) 570 nm (orange/brown) in order to "make room" for infrared. And if presnted with someting emitting say 880 nm (infrared) he would see it as a coulur unlike any other, even though the spectacles are presenting him with (say) 660 nm (deep red). The only problems I expect is that the "spectacles" would be bulky and heavy, and the ability to distinguish between two colours nearly the same would be diminished. Technical issues are that available video cameras do not have anything like the contrast range of human eyes, and cameras with extended colour range and spacial resolution to match the eye are not commercially available. I might try building said spectacles myself - it sounds interesting and might have novel uses. Don't be tempted to patent it - by posting this, I've put it in the public domain, and you cannot succesfully patent "prior art" - what is in the publuc domain. Ratbone58.167.234.178 (talk) 02:18, 28 May 2012 (UTC)

I wonder if that could work to give 360° vision, if such viddy-glasses gave a wide angle front view to one eye and a wide angle rear view to the other eye. Perhaps even multiple cameras placed around the head with their images continuosly cycled through each eye. How far can the brain adapt to such different visual modes without being stuck in permanent vertigo. SkyMachine ⁽⁺⁺⁾ 03:22, 28 May 2012 (UTC)

Damn, I was totally planning on going out and stealing your idea to make "bulky and heavy" spectacles that diminish the "ability to distinguish between two colours". I guess it's just not my lucky day.Then again, I could always make them in China; they don't seem to care too much about patents and copyrights and such... 203.27.72.5 (talk) 03:24, 28 May 2012 (UTC)

Yet more prior art. SkyMachine ⁽⁺⁺⁾ 03:36, 28 May 2012 (UTC)

Presenting the front 180 deg to one eye, and the rear 180 to the other should work, but with some limitations. Primarily, it would kill your ability to accurately range find, because this is optically dependent on both eyes seeing substantially the same image. It could be more hazardous to drive a car, as images of other cars falling on the blind spot in one eye would not be covered by active retina in the other eye. I knew a girl once, who lost an eye due to some weird infection. She became somewhat accident prone. What you could do, is use anarmorphic lenses to present a full 360 degree view, laterally compressed down to 170 degrees (the approximate normal range of each eye), to each eye. That should work fine. Your sequential presentation idea will not work, as if the rate of presentation is faster than the flicker perception rate, you'll just see superimposed images (if two separate objects of the same colour overlap, the brain has nothing to go on to separate them), and if the rate is lower, you'll be driven mad by the flickering. Ratbone58.170.179.82 (talk) 15:47, 28 May 2012 (UTC)

This is an interesting conversation. I have no idea whether, given some weeks, the brain could eventually adapt to distinguish two different scenes if frames were alternated at close to the flicker-fusion rate. It's obviously not the original design, but.....

Even so, there are limits to what can be done in "software". You can't recover full RGB vision and have UV/IR/Xray etc. at the same time. If you compress the frequency range, sampling far-red and far-blue won't give the same colors as sampling the existing curves. I'm not sure if you'd get the same or better performance by simply adding the out-of-range frequencies in an overlay to normal vision (IR in red frequencies, UV in blue etc.) Wnt (talk) 21:23, 28 May 2012 (UTC)

It has been well demonstrated in a number of ways that the brain is extremely "plastic", to use the term that pschologists use. Here's a similar example that you may have experienced yourself: I own a pair of tinted sunglasses. Immediately I put them on, everything I look at seems to be a little dark, and have a greenish tinge. But, if I wear them for a while, I become unaware of it, and everything looks the correct colour and brightness. But the brain cannot do what is not possible. Toward evening, it seems to get darker earlier. If you use devices to map a wide colour range down to the range that your retinas can sense, then you must loose some ability to distinguish between two closely similar colours. So you will have full RGB+FarRed+Ultra of whatever, but not precise RGB+FarRed+Ultra. But overlaying will not work - the brain has no way to distinguish between (say) 630 nm red, that is natural 630 nm red, from some other colour that has been overlayed to 630 nm. In effect, you would sense the overlayed emission, but you would be colour blind in the overlayed range. In short, the brain can, if required, translate a shifted colour back to the correct perception, but it cannot recover information that has been thrown away. Ratbone124.178.38.230 (talk) 02:44, 29 May 2012 (UTC)

In regard to sequential presentaion, there is another potential problem. It was shown by W Grey Walter (http://en.wikipedia.org/wiki/Grey_Walter) in about 1950 that if the whole retina in both eyes is presented with a flickering light at close to the flicker just-perception rate, the brain gets confused and funny things happen, such as headaches and partial functional blindness. At a flicker rate a little lower, you can induce epileptic-like fits in normal people. Ratbone124.178.38.230 (talk) 03:05, 29 May 2012 (UTC)

SleePology

anytime i am being waked up not FROM REM-SLEEP, i feel tiredness all day. i am curious for the scientific name of this phenomenon, and thirsty for some documentation. the most important for me is to know how could i manage to obliterate this feeling when available, without sleeping or taking Caffeine---who didn't help. thousand thanks guys. 79.183.175.233 (talk) 14:12, 27 May 2012 (UTC)

There are things like caffeine that increase alertness, but there really isn't any substitute for sleep. Looie496 (talk) 23:36, 27 May 2012 (UTC)

I've seen devices that claim to wake you in between REM cycles so that you don't get that 'still tired' feeling when you wake up. Dismas|^(talk) 01:13, 28 May 2012 (UTC)

I'd track down whatever wakes you from REM sleep on a non-emergency, and eliminate it. If it's an alarm clock, then you need to get to sleep earlier so you will have completed your REM sleep by then. StuRat (talk) 01:53, 28 May 2012 (UTC)

But what is the name of this phenomenon?, and if i didn't wake at REM, how could the problem be solved? thanks. 79.177.164.158 (talk) 07:16, 28 May 2012 (UTC)

The phenomenon of needing REM sleep ? I doubt if there's a name for that. If you finished your REM sleep and then were awakened, you should have gotten all the REM you needed. StuRat (talk) 04:22, 29 May 2012 (UTC)

StuRat, seems you didn't understand me. the phenomenon i direct to is : "feeling tired in the rest of the day because of BEING WAKED NOT-IN-REM-SLEEP". thanks. 79.177.180.234 (talk) 10:06, 30 May 2012 (UTC)

Well, all phases of sleep are useful, or we wouldn't have them. Perhaps you just aren't getting enough sleep total ? How much do you average per night ? StuRat (talk) 19:00, 30 May 2012 (UTC)

offcourse, but i want to WAKE only in REM sleep. i get enough sleep. between 5-7 normally ant naturally.

While there are some people who only need that much, most people need more. StuRat (talk) 20:49, 30 May 2012 (UTC)

I don't know what the name of that supposed phenomenon is, but your sleep issues are something that the field of chronobiology might be able to address. Alfonse Stompanato (talk) 20:15, 30 May 2012 (UTC)

Light deflection by gravity

If one studies light deflection by gravity from the classical mechanics point of view (i.e.: neglecting any relativistic calculations), assuming light as particles, one can find from the hyperbolic trajectory that light deflection in radians would be about

$\theta \approx {\frac {2GM}{rc^{2}}}$

which is half of that predicted by general relativity. The question is what was the value of deflection achieved experimentally and is there an article or reference that had studied this deflection from pure mechanics?--Almuhammedi (talk) 14:19, 27 May 2012 (UTC)

The first article you linked you is about experimental tests of relativity, and those tests do observe the relativistic figure (ie. twice the classical one), as that article says. --Tango (talk) 19:05, 27 May 2012 (UTC)

Thanks Tango. First I didn't find an article for that and then I modified my question by adding that link without reading.--Almuhammedi (talk) 10:35, 28 May 2012 (UTC)

Intestinal aganglionosis

Why is intestinal aganglionosis survivable in humans but fatal in horses? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 15:40, 27 May 2012 (UTC)

Probably because we are willing to do more to try to save people than horses. Would you be willing to spend $100K to save a person ? How about a horse ? StuRat (talk) 17:13, 27 May 2012 (UTC)

Indeed. It takes pretty major surgery to correct in humans, and we don't tend to do major surgery on horses. Even a broken leg is fatal for a horse, because we shoot them. We could treat a horse with a broken leg if we really wanted to, but it tends not to be considered worth the cost and the prolonged suffering for the horse (and the horse may not ever recover well enough to work again anyway). For humans, on the other hand, anything that prolongs life is generally considered to be worthwhile. --Tango (talk) 19:11, 27 May 2012 (UTC)

String theory

Searching "string theory is " in Google, the first three suggestions are bullshit, wrong and stupid. Why is it that there is so much opposition against string theory? I mean I know that it currently does not make predictions and all that stuff, but this? Also, is there a standard for when exactly theories can be popularized, because in the case of string theory, it seems to be a little too soon since we are not very sure about it's validity, or am I wrong?--Irrational number (talk) 16:09, 27 May 2012 (UTC)

In addition to being untestable, this also leads to the problem of there being many variations on the theory. So, which version is right ? Or are they all right (perhaps in a multiverse sense, where each string theory variant applies to a different universe) ? I'd argue that the standard for accepting a theory is when more evidence supports it than refutes it. StuRat (talk) 17:08, 27 May 2012 (UTC)

If there is any evidence that refutes a theory, then you reject it, so that definition doesn't work. You can't just talk about accepting a theory, you need to talk about choosing between theories. You choose a theory based on which one makes the most confirmed predictions while not making any incorrect predictions. The reason string theory is so popular is because it is better than anything else we have. While we don't have any direct tests of it, it still explains more observations than any other theory. --Tango (talk) 19:18, 27 May 2012 (UTC)

I don't agree. There is evidence to refute the wave theory of light, and also evidence to refute the particle theory. Rather than abandon both theories, we instead say it sometimes behaves like a wave, and sometimes like a particle, essentially accepting both theories. StuRat (talk) 23:41, 27 May 2012 (UTC)

Actually we developed a new theory. Wave–particle duality is a central postulate of quantum theory, which is distinct from classical theories that used waves and particles as two different ways to model matter and energy. 203.27.72.5 (talk) 03:16, 28 May 2012 (UTC)

It still doesn't seem quite settled, what with the double slit experiment weirdness. You end up with "it behaves like a particle when anybody looks at it, and a wave if they don't". StuRat (talk) 04:19, 29 May 2012 (UTC)

It's perfectly settled. Light is neither a wave nor a particle. When we say that it behaves sometimes like a wave and sometimes like a particle, we are simplifying for those who are not able to understand the physics in more detail.--Srleffler (talk) 18:47, 29 May 2012 (UTC)

There's still plenty that's unsettled, like in the delayed choice quantum eraser experiment. StuRat (talk) 19:10, 29 May 2012 (UTC)

I stand by what I wrote. The nature of light seems confusing if you insist on thinking of it as a wave or a particle. It is not either of those things. Waves and particles are sometimes useful models, but like any model used in physics will lead you astray when applied outside of its realm of usefulness.--Srleffler (talk) 06:05, 30 May 2012 (UTC)

When I search Google for "string theory", with or without the quotes, the only anti-string-theory result on the first page is this comic, which is pretty mild. But when I enable autocompletion and type [string theory is] I do get "bullshit", "wrong", "stupid", and "not science" as the four suggested completions. I don't think this is a good indicator of general sentiment about string theory. It probably just means that people are less likely to type other opinions about string theory as search terms. -- BenRG (talk) 17:33, 27 May 2012 (UTC)

I would note this sort of autocompletion thing is hardly unusual. For me (since as we've discussed before it depends on your location and country specific site you're using), the autocompletion results for 'Obama is ' are, in order 'the antichrist', 'a lizard', 'osama', 'a cactus', 'hitler', 'evil', 'a muslim', 'a democrat', 'an idiot', 'gay'. Similarly, 'america is 'doomed', 'retarted', 'my hometown', 'corrupt', 'the best country ever', 'dying slowly', 'rising', 'in the heart' (the next 2 are 'sparknotes' and 'summary' for that book or whatever it is) Nil Einne (talk) 11:16, 28 May 2012 (UTC)

Poynting vector about a charge moving at constant velocity.

Consider a point charge $Q$ at the origin moving at constant velocity $v$ along the $z$-axis of a cylindrical coordinate system. Using the notion of displacement current and Ampère's law, one can calculate the magnetic field about the charge to be ${\vec {B}}={\frac {\mu _{0}QvR}{4\pi (z^{2}+R^{2})^{\frac {3}{2}}}}{\hat {\phi }}$ (analogous to the Biot-Savart law). In spherical coordinates, the electric field is easily given by Gauss' law ${\vec {E}}={\frac {Q}{4\pi \epsilon _{0}r^{2}}}{\hat {\rho }}$ for radial unit vector ${\hat {\rho }}$. Now, when we try to find the Poynting vector, we get ${\vec {S}}={\frac {{\vec {E}}\times {\vec {B}}}{\mu _{0}}}={\frac {Q^{2}v}{16\pi ^{2}\epsilon _{0}r(z^{2}+r^{2})^{\frac {3}{2}}}}{\hat {\theta }}$, which seems to form a "bubble" of energy flow in the direction of the motion of the particle. Does this shape have to do with how the particle brings its own electric field with it, which in itself contains energy? — Trevor K. — 16:26, 27 May 2012 (UTC) — Preceding unsigned comment added by Yakeyglee (talk • contribs)

Yes, the Poynting vector gives you the energy flux associated with the change in energy density. So, if you have a closed volume, then this will contain an amount of electromagnetic energy, which will change due to the moving charge. The rate of change is equal to the Poynting vector integrated over the surface area. Count Iblis (talk) 17:30, 27 May 2012 (UTC)

Why would being low on freon cause ice to build up around the AC unit's pipes inside?

If someone is skilled at explaining things in simple terms to non-professionals, that'd be great. 69.243.220.115 (talk) 16:41, 27 May 2012 (UTC)

It might stay on continuously, since it's operating at low efficiency and failing to go down to the temperature set on the inside thermostat. However, the on/off cycle may be essential to allow the condensation/frost on the pipes time to evaporate/sublimate back off, before it gets a chance to build up. Besides the obviously solution of adding more Freon, you might also want to insulate those pipes to keep the warm, moist air away. You could also add some electronics to manually cycle on and off periodically, but that would reduce the home cooling even further. And also try to keep the humidity down inside: Open the bathroom window and close the door when you shower, don't boil things on the stove with the lid off, etc. StuRat (talk) 16:58, 27 May 2012 (UTC)

In the past, I fixed my car air conditioner by adding freon, after determining that it was low on freon. While low on freon, the refrigerant tubing was at a temperature below the freezing point of water. When it had the proper amount of freon, it was a few degrees above the freezing point of water. It can cool the air just fine without being cold enough for ice to form. A refrigerator/freezer, on the other hand must be at a much lower temp (around zero F) to keep the freezer at the desired temperature, so a defrosting cycle is necessary. A buildup of ice insulates the refrigerant coil and results in the compressor operating more of the time. Edison (talk) 18:08, 29 May 2012 (UTC)

Sulfur nitrides and nitrogen oxides

Since sulfur nitrides and nitrogen oxides are valence isoelectronic with each other, why do dinitrogen dioxide (N₂O₂, valence isoelectronic with disulfur dinitride), tetranitrogen tetroxide (N₄O₄, valence isoelectronic with tetrasulfur tetranitride), polynitroxyl ((NO)_x, valence isoelectronic with polythiazyl), monosulfur dinitride (SN₂, valence isoelectronic with nitrous oxide), trisulfur dinitride (S₃N₂, valence isoelectronic with dinitrogen trioxide), tetrasulfur dinitride (S₄N₂, valence isoelectronic with dinitrogen tetroxide), and pentasulfur dinitride (S₅N₂, valence isoelectronic with dinitrogen pentoxide) not exist? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 21:34, 27 May 2012 (UTC)

Nitrogen only can exceed a valency of 3 with elements more electronegative than it, so anything whose Lewis structure includes more than 3 bonds on nitrogen to sulfur atoms does not exist. Sulfur also doesn't like to form double bonds, as do most period 3 and higher elements.--Jasper Deng (talk) 21:42, 27 May 2012 (UTC)

But what about the nitrogen oxides valence isoelectronic with known sulfur nitrides? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 21:44, 27 May 2012 (UTC)

Actually, they probably do exist, but are unstable because it's too easy to disassociate those oxides - the nitrogen cannot manage to hold on to another nitrogen for long.--Jasper Deng (talk) 21:48, 27 May 2012 (UTC)

Catenane structural formula

How would the structural formula of a catenane be written? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 21:49, 27 May 2012 (UTC)

You would criss-cross covalent bonds as necessary; it's probably best to include the C's for carbon atoms.--Jasper Deng (talk) 21:52, 27 May 2012 (UTC)

There are examples in the article you linked to. 203.27.72.5 (talk) 22:09, 27 May 2012 (UTC)

No, I meant how would you write it, not how would you draw it. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 22:16, 27 May 2012 (UTC)

How would you write the structure of buckminsterfullerene with something chaged inside? Or a carbon nanotube storing hydrogen? These supramolecular structures are not usually written, probably because it would be complicated both to formulate and to interpret, whereas drawing them is relatively simple. 203.27.72.5 (talk) 22:39, 27 May 2012 (UTC)

"Sharp diagnosis"

"The suction rectal biopsy was considered the gold standard for sharp diagnosis.[19]" This is a quote from the article Hirschsprung's disease.

Is "sharp diagnosis" a medical term and if so what does it mean? Thanks, Wanderer57 (talk) 23:32, 27 May 2012 (UTC)

"Accurate" would be a better term. I don't have access to the source to check its wording, but since the authors are Italian it is possible that their English skills were less than perfect. Looie496 (talk) 01:26, 28 May 2012 (UTC)

Or maybe "intelligent". "Sharp" is sometimes used to mean that, but it isn't the appropriate choice of words in this context, and poor translations are full of those. StuRat (talk) 02:16, 28 May 2012 (UTC)

A "gold standard" test is one that always, or almost always, gives the correct result, or at the very least is correct more often than any other test. This is about accuracy. Looie496 (talk) 05:47, 28 May 2012 (UTC)

In the context of diagnostic criteria and a Gold standard test, it sounds awkward. A diagnosis in that context is a binary thing, and doesn't need qualification with "sharp" or "exact" or whatever. I checked the original source, and rephrased the sentence using wording closer to that of the cited paper. --NorwegianBlue ^talk 10:25, 28 May 2012 (UTC)