Wikipedia:Reference desk/Archives/Science/2011 December 6

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December 6

Ford Model T

December 5th, 2011 Wikipedia To whom it may concern,

I am participating in a program known as History Day. The theme this year is revolution, reaction and reform. The topic I chose was: Henry Ford Companies and Competition. I have focused on when the Model T first came out to when the newer Model A came out.

Explanation of topic; Revolution; the Model T Reaction; cars released from other companies Reform; the Model A's release

Would you be so kind to take the time to direct me to other sources regarding this topic? It would help if you could include other competition/cars that Ford Motors company had or were released in that time period. Thank you for your time and consideration. Sincerely, Ninja98.203.149.12 (talk) 01:14, 6 December 2011 (UTC)

Look at Ford Model T and Ford Model A (1903-1904). There are plenty of references at the bottom of each article. I also suggest reading the articles.

E=MC² and wind up alarm clocks

Something I've wanted to ask a physicist for some time: given that when you wind up a spring-driven alarm clock, you are storing energy in it, and given that E=MC², does its mass increase as you wind it up? I'm well aware that any increase is going to be small, but will it occur, and if so, by how much? (Ballpark figures accepted - obviously it will vary depending on the spring.) AndyTheGrump (talk) 01:35, 6 December 2011 (UTC)

I shouldn't think so. e=mc² is a description of the conversion of mass to energy, which is not what you are doing when you wind up an alarm clock. You're just storing energy when you wind something, energy that comes from your physical efforts (and, I suppose, more remotely, from the use of ATP by your muscles, which ATP is a result of your biochemistry) and not from conversion of mass into anything.- Nunh-huh 01:44, 6 December 2011 (UTC)

(ec) The short answer is yes, the apparent mass of the clock will increase. The mass increase is indeed proportional to the energy. If someone wants to measure the torque required to wind an alarm clock we could estimate the amount of energy/mass increase involved, but I don't have a wind-up alarm clock handy. For comparison, in a longcase clock, weights most often run from 3 to 5 kilograms [1] and descend through about a meter to drive the clock. Five kilograms raised one meter comes to about 50 joules of stored energy, which corresponds to a mass increase of about 5*10^-16 kilograms, or about 500 femtograms. TenOfAllTrades(talk) 01:54, 6 December 2011 (UTC)

My guess is that the energy/mass increase would be somewhat less for a wind-up alarm clock than a longcase clock, like maybe around 100 femtograms. But yes, the mass definitely increases. Red Act (talk) 02:53, 6 December 2011 (UTC)

Thanks - so it seems I was right. Actually, our mass–energy equivalence article seems to state this explicitly: "A spring's mass increases whenever it is put into compression or tension. Its added mass arises from the added potential energy stored within it, which is bound in the stretched chemical (electron) bonds linking the atoms within the spring". Trying to visualise 100 or so femtograms is difficult, but our orders of magnitude (mass) article suggests we are somewhere in the range of the mass of a small single-celled organism, if I understand correctly. Not a lot, but not entirely negligible - though I doubt you could measure it. AndyTheGrump (talk) 03:44, 6 December 2011 (UTC)

You probably couldn't measure the difference because the dust or grease you add or remove whenever you touch the watch has a much higher mass. – b_jonas 19:57, 6 December 2011 (UTC)

Unofficial record temperature

How can unofficial record temperature happen and what is the basic definition of it. Said Kangerlussuaq, Greenland have unofficial record high of 82F on June 27, 2002. The weatherbase said the maximum record is 75F. Is unofficial temperatures mistakes or error on system.--69.228.24.198 (talk) 01:43, 6 December 2011 (UTC)

"Official" weather measurements are kind of a tricky subject. In the United States, official measuring stations are those where official climate records are taken. This is almost always at an airport, with an automated station which measures temperature, humidity, wind and a few other variables at standardized heights and under carefully controlled and standardized conditions (see Automated airport weather station for more info). There are many airports and other municipal buildings such as schools which have similar weather stations which measure the same data, but which are not considered "official" reporting stations. I'm not exactly clear on the reason for this, but I presume that it is due to the fact that there is only so much money available to properly maintain instruments and perform quality control to ensure there are no biases or errors in the data. I'm not sure about the case for Greenland, but I suspect it is a similar situation: the weather station which measured the higher value was not an "official" climate reporting station, so the quality/accuracy of the data can not be guaranteed.

A related issue is that it is well-known that many "official" records from the first half of the 20th century are questionable in their accuracy; unfortunately there is a lot of political junk that goes along with revisiting old climate data, even when there are clearly problems with it. It is likely that most records from before World War II are inaccurate due to sub-standard instruments, record-keeping, and quality control.-RunningOnBrains^(talk) 02:03, 6 December 2011 (UTC)

After analyzing the data provided in your link, if you notice, the moment that the 82F value is recorded, there is a sharp spike in many of the variables; the temperature, dew point, and barometric pressure all go up substantially one hour, only to return to near the previous values in the next hour (seen more easily here). This is a very good sign that the weather station experienced some sort of error, which is why this would not be considered a record. -RunningOnBrains^(talk) 02:08, 6 December 2011 (UTC)

Wait..., can I ask again? Is there virtual difference regarding guarantee accuracy between unofficial vs. official temperatures. Does official record temperatures make higher guarantee of accuracy and less risk of error than unofficial record temperatures. I think Greenland suppose to have automated technology systems around, so I don't think the temperature records is large errors. All measurement across must be close to identical variables. Is there possibly official record temperature even after 1980 can cause similar amount of error bars?--69.228.24.198 (talk) 05:32, 6 December 2011 (UTC)

It's not just technology failures that can taint weather measurements. Exactly where the sensor is placed makes a difference. Both for temperature and wind-speed. Turbulance from nearby structures may give wind readings that are above or below the true reading, being placed near an object that warms in the sun could cause a problem with a temperature measurement. And of course the equipment itself may not be calibrated right. Even digital equipment may be precise, but wrong. Many public facilities and businesses may record the weather for their own purposes, but they may or may not pay strict, scientific attention to the equipment, how it's installed, etc. In fact, if the measurement is being done by a television station it may even be to their advantage to install the equipment in such a way that it gives more dramatic results.

All that said, I have no idea how the specific government agency that handles such things in greenland does things. APL (talk) 11:03, 6 December 2011 (UTC)

I once had the assignment of recording official US temperatures at a location. There was a little white painted standard wooden structure with louvers for ventilation. I was told that this was required, so that for instance a dark colored, poorly ventilated enclosure did not build up high temperature inside. It may have been a requirement that it be a certain height above ground, and that there be a patch of grass rather than blacktop under it. Today I suppose the instruments are electronic, and clearly there is potential for large variations due to instrument or communications errors. See [2]. Edison (talk) 15:46, 6 December 2011 (UTC)

That wooden structure would be a Stevenson screen. {The poster formerly known as 87.81.230.195} 90.197.66.22 (talk) 11:08, 7 December 2011 (UTC)

I wonder if older tradition method like ordinary mercury therometer non-technological instrument would do a more accurate job on tracking temperatures. I used to have a non-technology mercury theometer it is placed on white woods, near the patue, relative distance from whitetop concrete. I am wondering if older day theometer is still used anywhere any countries in the world like in northern Russia.--69.228.24.198 (talk) 01:13, 7 December 2011 (UTC)

Historically there was a shift from a mercury thermometer in a little white-painted louvered box 5 feet above the ground, and 40 feet from a building, over a patch of grass, to the modern digital thermometer in a white plastic cylinder high on a pole. I suggest that there may be a systematic difference in the temperatures measured by the two systems, as much so as when Chicago Illinois moved its "official weather station" from the roof of the Auditorium Building, 200 feet high, downtown near Lake Michigan [3] to Midway Airport miles inland. Chicago has temperatures "cooler near the lake" in the summer if not in the winter. Later the official weather station moved to O'Hare Airport, which records temperatures 1.9 degrees F lower than Midway. I pity anyone who has to rigorously prove global temperature change based on such "official temperature" measurement, or on any measurement with confounding variables such as the siting and enclosure of the thermometer. Edison (talk) 03:08, 8 December 2011 (UTC)

In New York City, the Weather Bureau recorded a record 99 degrees F in 1881, but when the record was broken by a 102 reading in 1918, the NY Times said the 1881 weather station was on a roof surrounded by other buildings with metal roofs, producing a reading higher than at street level, while the 1918 official thermometer was on a building which yielded lower temps than street level. The "temperature reading" must be "operationally defined." It does not exist in the abstract.

How to fit Dfd, Dwd in Trewartha climate classifications

just said Northern Russia like Verkhoyansk, Yakutsk is E climate. They are qualify is Dfd, or Dwd. If we convert it to Trewartha climate scale, what category will they fit into. Iceland should be EO, it is subarctic maritime, now we got EO which is Cfc, EC is subarctic continental that is Koppen's Dfc, Dwc. Then how about Dfd, Dwd class go into Trewartha. Can Dfd, Dwd like Verkhoyansk or Yakutsk get any of desert climates in Trewartha? Its summer frequently get humid and muggy, often get days in 80s or 90s.--69.228.24.198 (talk) 01:55, 6 December 2011 (UTC)

Both these places are classified as EC because of their dry climate (based on precipitation, not atmospheric humidity which is irrelevant for this purpose). 67.169.177.176 (talk) 02:46, 6 December 2011 (UTC)

Mung bean

I want to know some facts about nutritious value of Mung bean. 1. Is the first table in Moong_bean#Uses is for whole beans without skin , or for whole beans with skin? 2. Will I get the same amount of protein (23.86 g per 100 g) if I eat freshly prepared mung bean paste instead of whole beans? --Foyrutu (talk) 05:37, 6 December 2011 (UTC)

2) Making it into a paste shouldn't affect the protein content. However, your figure of nearly 24 grams of protein per 100 grams is far more than the 7 grams I get when I look it up: [4]. StuRat (talk) 16:56, 6 December 2011 (UTC)

This put the number from "19.5 to 28.5 percent". --Foyrutu (talk) 17:20, 6 December 2011 (UTC)

I see the problem. That was for "dry seed weight", that is, without water. My figures are for the prepared product with water, which, I believe is how you would normally eat them. If you weigh them dry, before preparing them, then you figure would be right. However, that 100 grams of dried mung beans might make some 350 grams, prepared, which is a lot to eat in one sitting (I hope you have Beano !). StuRat (talk) 17:42, 6 December 2011 (UTC)

Both red and green mung beans are usually eaten with skin, IIRC. Azuki bean paste is made from red mung bean and often contains a thin edible outer layer. ~AH1 ^(discuss!) 01:57, 8 December 2011 (UTC)

Noise pollution

What is Ld_n index for noise level measurement, what does it signify? — Preceding unsigned comment added by Intr199 (talk • contribs) 16:18, 6 December 2011 (UTC)

That is the Day-Night Average Sound Level. -- kainaw™ 17:38, 6 December 2011 (UTC)

Microwave oven frequency

I've heard that a different frequency of microwaves would preferentially warm ice over liquid water, while the current frequency does the reverse:

1) Is this true ?

2) Why don't we use that frequency ? StuRat (talk) 17:20, 6 December 2011 (UTC)

I do not believe that a different frequency of microwaves would melt ice faster. To explain why in brief, I'll be very simplistic. Water and Ice are both made of H2O molecules. They are dipole or polar - which means they are like little magnets. In the presence of an electromagnetic wave, the little magnets will try to align with the wave. But, being a wave, it keeps shifting back and forth. So, the little magnets end up shifting too. That movement is where the heat energy for everything else in the microwave comes from. The microwaves are selected to be a certain frequency that gets the most efficient wiggle out of the little magnets.

Why this doesn't work on ice? The little magnets in the ice are frozen in place. They can't wiggle as easy. It doesn't matter what frequency of microwaves are used. They still can't wiggle very well. The only argument that I'd take as a possibility is that a lower frequency might try to make the magnets wiggle slower and, in ice, wiggling slower turns out to be more efficient. But, I'd need to see a real experiment, not just some back-of-the-envelope scribbles. -- kainaw™ 17:35, 6 December 2011 (UTC)

I suspect StuRat is getting confused by the common but inaccurate claim the frequency of microwave ovens is chosen because of resonance of water molecules at that temparature. As we've discussed before on the RD and as microwave oven mentioned, this isn't true and some microwaves don't even operate at 2.4ghz. Nil Einne (talk) 18:16, 6 December 2011 (UTC)

According to our article: "Microwave heating is more efficient on liquid water than on frozen water, where the movement of molecules is more restricted." and "Penetration depth of microwaves is dependent on food composition and the frequency, with lower microwave frequencies (longer wavelengths) penetrating further." So, would lower frequencies lessen the common problem of the food being burnt on the edges with a solid block of ice in the center ? StuRat (talk) 18:45, 6 December 2011 (UTC)

There is a section about the frequency choice in the design section of the microwave oven article. In short The microwave frequencies used in microwave ovens are chosen based on regulatory and cost constraints. Vespine (talk) 01:10, 7 December 2011 (UTC)

OK. What range of frequencies are legal ? Is there any reason why the laws can't be changed to allow lower frequencies ? And what are the cost constraints ? StuRat (talk) 01:13, 7 December 2011 (UTC)

Did you read the section Microwave_oven#Design? It elaborates a bit, like saying that "legal" depends where, but I can't answer your specific questions in any more detail. Seems like microwave ovens operate just fine. If you have a problem with over cooking the outside of your frozen food, the obvious solution seems to be to lower your cooking power and increase your cooking time, rather then ask for microwave ovens to be redesigned. Vespine (talk) 00:47, 8 December 2011 (UTC)

That's exactly what I do, along with thawing foods before I nuke them or using a different cooking device entirely. But having a workaround for a problem doesn't mean I should abandon the quest to actually solve the problem. StuRat (talk) 18:50, 8 December 2011 (UTC)

My microwave is a combo microwave/toaster oven. So, I can run the toaster oven for a minute or so to melt the ice and then the microwave to cook it - all without moving the food. That is one solution. I also like it for pizza. Microwaves make limp reheated pizza. So, I microwave 1 minute and toast 1 minute and it comes out warm and crispy. -- kainaw™ 18:55, 8 December 2011 (UTC)

Interesting. I didn't know it was possible to combine those, as microwaves wouldn't work along with metal coils in a conventional toaster. How does yours manage to avoid arcing ? StuRat (talk) 19:16, 8 December 2011 (UTC)

It doesn't microwave and toast at the same time. So, the insulated coils don't arc. I'm sure there are more safeguards - but I don't really care, as long as it keeps working. I do know that it toasts only from above. If I want to ONLY toast, I put foot on a little stand to get it higher and it toasts faster. -- kainaw™ 19:18, 8 December 2011 (UTC)

Yes, a nice toasty foot can warm you up nicely on a cold day. :-) StuRat (talk) 19:34, 8 December 2011 (UTC)

Poor inventors who don't get the money/recognition they deserve

I heard that the guy who invented the computer mouse has not made much money off of his invention that is used so ubiquitously today. Are there any other examples of inventors who designed something that is used by everyone, but never got the money or recognition that they deserve? ScienceApe (talk) 19:24, 6 December 2011 (UTC)

There are probably many inventions whose inventor isn't known, because they didn't, or couldn't, patent their item. I don't think the general concept of a computer mouse can be patented, for example, but only a particular design for one. StuRat (talk) 19:32, 6 December 2011 (UTC)

Well, the mouse was patented, and no, the inventor never made any money off of his patent, see Douglas Engelbart. --Jayron32 19:44, 6 December 2011 (UTC)

One could say much the same for the inventor(s) of the computer.--Shantavira|^{feed me} 20:04, 6 December 2011 (UTC)

See Practical genius has often gone unrewarded - a knol by Zahid Ameer.

—Wavelength (talk) 20:20, 6 December 2011 (UTC)

There is one name that automatically springs to mind regarding this: Nikola Tesla. -- Obsidi♠n Soul 03:43, 7 December 2011 (UTC)

Well, some of his inventions were rather crazy, like broadcasting electricity to deliver it. StuRat (talk) 04:16, 7 December 2011 (UTC)

True. But then again during his time, it was all about crazy ideas, not to mention industrial espionage :P -- Obsidi♠n Soul 12:17, 7 December 2011 (UTC)

• Thomas Davenport (inventor) was the first inventor to power useful devices with electric motors. He gave public demonstrations of various devices powered by electric motors, but die broke and discouraged. (Wikipedia gives inappropriate credit to Ányos Jedlik), who likely did no more than replicate classroom demo models of motors he had read about, and who did not leave any writing about his motor models until 1861. Edison (talk) 16:31, 7 December 2011 (UTC)

Seems ironic that a user named "Edison" would post in this topic. Goodbye Galaxy (talk) 18:56, 7 December 2011 (UTC)

I'm looking for other good names I might use, which are not associated with the subjects of article I might contribute to. Edison (talk) 02:52, 8 December 2011 (UTC)

The blimp, and its associated wonderful derivatives, have been in rancorous relative disuse since the Hindenberg disaster. ~AH1 ^(discuss!) 01:36, 8 December 2011 (UTC)

When Dennis Ritchie died there were no headlines about him (the headlines were on Steve Jobs who I don't think was nearly as important). 99.43.78.36 (talk) 15:46, 8 December 2011 (UTC)

For sure, the death of the guy who foisted Unix upon us should have had more coverage. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:02, 8 December 2011 (UTC)

The question begged here is about what inventors "deserve". In my experience there's a very wide gap between inventing stuff, and commercialising the invention so as to make money from it. Both parts of the process are vital, and more often than not, commercialising "inventions" tkes much more time, effort, risk and capital than the inventing part. That being the case, its not very surprising that many and perhaps most inventors do not get what they "deserve". --Tagishsimon (talk) 15:52, 8 December 2011 (UTC)

Richard Trevithick invented the railway locomotive and the high-pressure steam engine but died penniless and could only be buried after a whip-round by his colleagues. As Tagishsimon says, lack of commercial accumen played a part, but he was unfortunate that the cast iron rails used for his engines couldn't cope with the weight of them - wrought iron rails were a later development. Alansplodge (talk) 16:41, 8 December 2011 (UTC)

Weak interaction

Could someone check this set of edits? I knew a little when I wrote the article (enough to follow what I was being told) but less now. Grandiose (me, talk, contribs) 19:35, 6 December 2011 (UTC)

Looks correct to me. Dauto (talk) 19:51, 6 December 2011 (UTC)

How do we know the speed of light is constant? Part 2: Gravity Wells

So I came across this conversation in the archives which I can't actually remember if I started (though it sounds like the kind of thing I'd ask): [5]. Okay, so we know that the speed of light is the same because other stars would look hella different if the rules of physics there were completely different (as they would be with any vast changes to the speed of light). So here's a question for you: how would we go about finding out if the speed of light remains constant *outside of a gravity well*? There's not a whole lot to observe in the big spaces between stars. So what sort of experiment would be required to answer my question? (I might be thinking about the Pioneer anomaly a little here...) --Brasswatchman (talk) 21:04, 6 December 2011 (UTC)

Much of modern cosmology is predicated on the assumption that the rules of physics that apply here on Earth are the same rules of physics that apply across the entire universe. For example, significant effort has been spent studying the cosmic background radiation, looking for two things: inhomogeneity and anisotropy. So far, there doesn't seem to be a whole lot of either. In simple terms, this means "as far as we can see, the physics that governs our universe is uniform everywhere."

If you could first contrive a theory that would differentiate between a constant- and non-constant speed of light, and then, secondly, deduce some observation that could validate that theory, and thirdly, if you spent many years of your life scanning astronomical observations seeking observational evidence of the first two parts... well, you'd be a cosmologist, and you could probably be published in a prestigious journal. Nimur (talk) 22:54, 6 December 2011 (UTC)

I'm aware the idea is far-fetched. Just humor me. Consider it as a thought experiment. Let's go with your point about cosmic background radiation -- if the speed of light did change outside of gravity wells, what would the effect on background radiation look like? --192.234.2.90 (talk) 23:18, 6 December 2011 (UTC)

We do have the article Variable speed of light, though it doesn't appear to address your exact scenario. Tangentially related are our articles Scharnhorst effect and Pioneer anomaly. -- 203.82.66.200 (talk) 23:52, 6 December 2011 (UTC)

The "big space" between galaxies is filled with ionized gas which has been observed. A change in the speed of light would affect their observed spectral lines. Also, the pioneer anomaly has been explained as caused by thermal radiation pressure. Dauto (talk) 04:24, 7 December 2011 (UTC)

Good point, Dauto. I hadn't thought of that. --Brasswatchman (talk) 22:28, 8 December 2011 (UTC)

An aside: how do we know that the speed of light is the universal constant, and not the speed of some other particle such as a tachyonic neutrino? The properties of a neutrino are very different from also-massless photons, as neutrinos can travel through most solid matter and don't (AFAIK) have frequencies. ~AH1 ^(discuss!) 01:33, 8 December 2011 (UTC)

Neutrinos are massive particles... and all matter has a frequency (see matter wave). The frequency of a neutrino is E/h. --130.216.55.200 (talk) 22:52, 8 December 2011 (UTC)

Killing me softly ?

I just saw a movie where a murder was committed by slowly pulling a car forward towards the victim who was caught against a fence in a dead end. I was wondering if a car without any speed to it would have the force/pressure required to crush someone to death (I expect that less force would be required to prevent breathing and cause asphyxiation eventually, but that's not what I'm asking about here). The car appeared to be on level ground, with good traction, and caught the victim under the ribs. It was a large car, but I also wonder if a small car could have done the job. StuRat (talk) 21:41, 6 December 2011 (UTC)

In the "yuppie" area of where I live, about 5 years ago according to my terrible memory, there was a road rage incident in which a man in an SUV followed a lady in an SUV into a parking lot. From a very close distance (no running start), he pinned her between the SUVs and killed her. I'm Googling for the old news article to get details, but I haven't found it yet. -- kainaw™ 21:49, 6 December 2011 (UTC)

Seems a question of "starting Tractive force," though the article talks mostly about locomotives. An auto can exert enough starting tractive force to climb up a pretty steep ramp, so on level ground, it could likely exert many hundreds of pounds force. I would expect that a typical car moving forward quite slowly from a standstill could crush the life out of a person, if it was on dry pavement and had normal traction. If it were on ice, the chances of survival would be greater as soon as the tires started to spin. We're talking hundreds of horsepower in some cases. Edison (talk) 21:54, 6 December 2011 (UTC)

Would hundreds of pounds of force be enough to crush you to death ? How much was needed to press a "witch" to death in the good old days ? StuRat (talk) 21:57, 6 December 2011 (UTC)

Crushing (execution) has numbers. WHAAOE. --Jayron32 23:39, 6 December 2011 (UTC)

That lists weights of 400 to 700 pounds, but from the length of time required to kill, it sounds like that was not enough to actually crush them, but only kept them from breathing. StuRat (talk) 00:40, 7 December 2011 (UTC)

I'm fairly certain an automobile can exert well over 700 pounds of force, else how would it move itself... --Jayron32 00:45, 7 December 2011 (UTC)

Rolling resistance? I definitely don't disagree with the other statements, but you definitely do not need nearly 700 lbs of force to start a car moving. I weigh 180lbs and I can get a car moving, on flat ground in neutral of course. Vespine (talk) 00:50, 7 December 2011 (UTC)

A car never has to lift itself vertically, so there is no need for it to be able to produce a force greater than its weight. --Tango (talk) 00:52, 7 December 2011 (UTC)

A car often has to climb a ramp, thus "lifting itself" to an extent based on the angle. 15 degree ramps are common, and a compact car weights 3000 to 4500 pounds For a 15degree ramp and a 3000 pound car, the vehicle has to exert a force of 3000 sin 15 degrees = 776 pounds parallel to the ramp to move. This is not to say the car couldn't climb a steeper ramp, since 20 degree ramps are sometimes used by builders who ignore cars bottoming out and scraping at the top or bottom, of sliding in winter. For a 20 degree ramp and the same car, the force would be 1026 pounds. Edison (talk) 16:26, 7 December 2011 (UTC)

Some hills where I live have a slope greater than 20 degrees, and most cars have little difficulty in climbing them in low gear. Vehicles with a low-range gearbox (such as Jeeps) can climb much steeper slopes if there is sufficient traction. Dbfirs 22:41, 7 December 2011 (UTC)

I don't think being pinned by an auto is analogous to the way they crushed witches. In the former case, the force is concentrated by the bumper; in the latter, the force is distributed by the plate. Think in pounds per square inch. SemanticMantis (talk) 02:28, 7 December 2011 (UTC)

The OP specifically mentions the victim being pinned under the ribs, where a number of your vital organs reside. It's easy to imagine the force needed there to fatally damage something to be far lower then the force that might be required to crush a whole person. Vespine (talk) 03:20, 7 December 2011 (UTC)

Cat's Eyes

Why do the pupils of large cats not contract to the same vertical slits as smaller (housecats) cats? I guess I'm asking if anyone knows the different evolutionary pressure that these small cats underwent to get such a distinctive pupil shape.71.232.14.6 (talk) 23:50, 6 December 2011 (UTC)

Oddly enough, it seems the one body part that the Wikipedia article Cat anatomy does not cover is the eyes. Hm. --Jayron32 00:01, 7 December 2011 (UTC)

I found a pretty decent sounding explanation on this website. Vespine (talk) 00:23, 7 December 2011 (UTC)

Well, I didn’t find that link very informative. Vertical slits, in my view (no pun intended) would allow better 'horizontal' resolution and depth of view. This fits in better, with the type of visual attributes that such a cat would need in order to hunt smaller pray. Think of it, as evolutionary built in astigmatism.--Aspro (talk) 01:09, 7 December 2011 (UTC)

Goat eyes

It's the opposite. Horizontal pupils (such as in bovids, anurans, kangaroos, bottlenose dolphins, and cephalopods) give them very good peripheral vision and motion detecting capabilities especially in flat environments (like the African savannahs or the sea floor). They function as a sort of wide-angle lens and don't exactly give them better depth perception (especially since animals which possess such eyes do not have binocular vision)

Vertical pupils, on the other hand, are simply the contracted pupils of hunters which operate at night or at low-light environments (like domestic cats, some lizards, some snakes, harp seals, lorises). It's the most efficient way of collapsing very large pupils and enable them to still see in full sunlight. Fully expanded, the pupils of these animals are actually round (think Puss-in-boots in Shrek). Compare with human eye dilation, which is achieved by the radial iris sphincter muscle. The latter is much more limited in the sizes it can contract to or attain when dilating.

Both eye types have repeatedly evolved in animals with the same ecological requirements, an example of convergent evolution.-- Obsidi♠n Soul 01:35, 8 December 2011 (UTC)

I heard somewhere that amongst vertebrates with slit pupils, the slits are more often vertical amongst predator species and horizontal amongst prey species, but our pupil article has nothing to say about slit pupils beyond acknowledging their existence amongst "some cats". The reference given there [6] does mention in its abstract that "Slit pupils were only present in animals having multifocal optical systems. Among the felids, small species have multifocal lenses and slit pupils, while large species have monofocal lenses and round pupils. The Eurasian lynx, a cat of intermediate size, has an intermediate eye design. The functional significance of the absence of multifocal optical systems in large felids remains mysterious, because such systems are present in other large-eyed terrestrial vertebrates. " -- ToE 02:05, 7 December 2011 (UTC)

Yes, the propensity is there but it is not absolute. Some vertebrate predators have horizontal pupils as discussed above. Frogs, for example, rely on detecting movement and reacting quickly to catch prey. They don't need the absolute focus and clarity of binocular vision and vertical pupils.-- Obsidi♠n Soul 01:43, 8 December 2011 (UTC)