Wikipedia:Reference desk/Archives/Science/2007 November 7

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November 7

my girlfriends disorder?

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Lanfear's Bane | t 09:16, 7 November 2007 (UTC)

Diversity Antenna?

I remember way back in college that there was some discussion about diversity antennas (Using two antennae to increase signal strength or reduce noise, I think). It's was used in disccussion about wireless mics in TV (why many ENG news cameras have two floppy antennae sticking out of their back) I can't seem to find any entry on diversity in regards to radio waves on Wikipedia. What's the science behind it and what's it called? --24.249.108.133 00:08, 7 November 2007 (UTC)

See Antenna diversity. --Milkbreath 00:14, 7 November 2007 (UTC)

The quality or strength of the field can fluctuate wildly from point to point, so if you get the signal from a bad position you can compensate by using the good signal. Also two different polarizations can be used. The signal varies due to diffraction and destructive interference Graeme Bartlett 00:44, 7 November 2007 (UTC)

Sun and moon at midday

I live in the state of Virginia (US). A few days ago I went out to lunch from work on a pristine, blue-skied, bright autumn day...and there it was. The moon, 3/4's full and as clear as if I were looking at its craters on the clearest of nights; only the background wasn't black, it was a blinding bright blue. I looked back and forth at the sun and the moon and my watch (which read 12:45 pm) for quite a while and couldn't believe it. It was beautiful. Sadly, in just an hour the phenomena ceased.

I have lived here all my life (a respectable 27 years) and have never seen the sun and the moon together so prominently sharing the sky of midday. Is there any way to predict when this rare optic event will happen? —Preceding unsigned comment added by Sappysap (talk • contribs) 01:14, 7 November 2007 (UTC)

It sounds as though you saw a sun dog. Possibly due to ice crystals Graeme Bartlett 01:56, 7 November 2007 (UTC)

Actually, the sun and moon share the sky approximately half the time. When the moon is full, it's on the opposite side of the Earth from the sun. When it's at either quarter, it's at a 90° angle relative to the sun and thus above the horizon for about 6 hours of night and 6 hours of daylight. As the moon approaches its new phase, it's in the sky almost entirely during the day.

So as you can see, this isn't rare at all -- it's just a matter of stopping to look up. Additionally, the moon isn't the only celestial object visible in full daylight. Early this year, Comet McNaught was visible in full daylight, and Venus is often visible with binoculars, and with the naked eye at sufficient altitude. — Lomn 02:13, 7 November 2007 (UTC)

(after edit conflict) It's not a rare optical event at all, even though it may seem to be because the Moon is much less noticeable against a bright blue sky than against a black background. The Moon is up exactly as often during the day as it is at night.

Anyways, during your lunch break, the Moon will be up every day from full moon to new moon. The atmospheric seeing wil change from day to day and when you'll see the Moon cripsly will depend on chance. --Bowlhover 02:25, 7 November 2007 (UTC)

The only thing you won't see is a full moon in the daytime sky along with the sun. Just about anything else is possible. (But I agree, a daytime moon can be a lovely sight.) —Steve Summit (talk) 03:16, 7 November 2007 (UTC)

That's not true - at dawn or at sunset, the moon can be on the opposite horizon from the sun and in that case it will be a full moon. Someone reading this is just thinking to argue that it can't be quite 100% full if the sun and moon are both actually visible - and when they do that I'm going to find a large baseball bat and beat them into a quivering heap whilst yelling "AT-MOS-PHER-IC DIFF-RAC-TION YOU ID-I-OT!!". I'm hard - but fair. SteveBaker 03:37, 7 November 2007 (UTC)

Yep. What struck me about the original poster's report is that when the moon is close to full, it spends most of its time in the night sky and not so much in the day sky. (For a crescent moon, of course, it's the opposite.) So to see the moon 3/4-full close to noon actually is fairly unusual. Arbitrarily guessing Richmond for the poster's location, I plugged some different dates into this page and figured out that the date in question must have been Tuesday, October 30. The moon was 73% full and in Richmond it set at 12:50 pm. And of course the moon being close to the horizon triggers the moon illusion and makes the sighting even more impressive. --Anonymous, 07:33 UTC, November 7, 2007.

I saw he same thing on the same day at same time from near Dulles airport. I have lived here since 19770. What was unusual about that day was that the air was extraordinarily free of any pollution. What I noticed first was that the sky far from the sun as the darkest I have ever seen at midday, and there was a very obvious gradient (darker to lighter blue) toward the sun. I attribute the lack of pollution to the fact that we had just had a rain after the longest drought in about 20 years. We usually have a lot of urban pollution and a lot of terpene "pollution" from the mountains to the west. The moon was about half-way from the sun to the darkest part of the sky. -Arch dude 17:42, 7 November 2007 (UTC)

Bindeez to GHB??

Apparently these toys can be converted to 4-Hydroxybutanoic acid when swallowed... The toys apparently can be arranged into some pattern and will set when you put water on them..

http://www.theage.com.au/news/national/victoria-bans-toxic-toy/2007/11/07/1194329268448.html

Anyone know what the beads are made of? 1,4-Butanediol according to http://www.news.com.au/perthnow/story/0,21598,22712449-2761,00.html

So how about a conversion mechanism? Assumingly it has acid is involved in the conversion. Been a while since I've done organic chem but this looks like a very simple conversion... How did this ever get on the market??— Shniken1 03:07, 7 November 2007 (UTC)

Obviously first one of the hydroxy groups gets protonated... draws electon density from the carbon... promotes nucleophillic attack..?Shniken1 03:10, 7 November 2007 (UTC)

Oh well, not to worry - you can still buy them online here: http://www.redsave.com/products/Bindeez-Super-Studio-Design-Centre,,22 (eeeekkkkk!!!!). —Preceding unsigned comment added by SteveBaker (talk • contribs) 03:47, 7 November 2007 (UTC)

[1]. It's a fairly common chemical reaction, although I'm not sure how this would happen in the body, or if it would necessarily happen in this manner. (and damn you, Steve Baker, your edit conflict somehow crashed my web browser.) Someguy1221 03:52, 7 November 2007 (UTC)

In the body it looks like it's converted using alcohol dehydrogenase and aldehyde dehydrogenase (from the 1,4-butanediol article. GHB = 4-hydroxybutanoic acid). Maybe someone with more biochem experience can give more info --Bennybp 03:59, 7 November 2007 (UTC)

The account I read suggested that the toxic versions were made of different stuff to the normal versions, which were a non-toxic glue. So the ones you buy online might be safe. Or not. Skittle 04:01, 7 November 2007 (UTC)

The Counterpartness (Not a Real Word, But You Know What I Mean) of Human Races and Animal Breeds

I know that the topic of whether or not the idea of "human races" is biological or scientific is controversial in general, but what about when comparing them to breeds of animals? The idea of being a "breed of animal" is considered biological and scientific, is it not? And aren't human races and breeds of animals counterparts? And, if so, then why do the words "breed" and "race" exist separately and are not one word, as humans are scientifically animals (I know this has to do with history, but, if my assumptions are right, then why hasn't a word been been developed)? Also, if human races and animal breeds are counterparts, then why is there controversy over whether or not human races are biological and scientific? I know that included a lot of questions, but any help on any part would be great! Thanks! —Preceding unsigned comment added by Pitman6787 (talk • contribs) 05:43, 7 November 2007 (UTC)

A brief answer, but this undoubtedly go further. As you suggest the origin of the words is undoubtedly historical rather biological as the concepts are similar - it's just another case of a different word being used largely through the antiquated ideas of humans not being animals, and the consequences of that mode of thought. Now if you read the breed article you'll see the second sentence says "For a type to be recognised as a breed, there should be a viable true-breeding population." This has always been a big issues with human races - there is not a viable true-breeding population in any so-called race - basically given any contact there is immediate crossbreeding, and there is huge variation within populations. One of the other significant problems is that definitions of human races are distortions - claimed characteristics of given races rarely, if ever, hold true across that 'race'. Another problem is simply the misuse of race given almost any chance - why look for tenuous and largely non-existent differences and claim them as scientific when they will be mainly used for political and discriminatory purposes, and when the truth is that our similarities are far greater than our differences? --jjron 08:14, 7 November 2007 (UTC)

"Now if you read the breed article you'll see the second sentence says....", why bother go that far. The first damn line says a breed is a DOMESTICATED subspecies. So by definition, a human population can't be a breed simply because humans are never domesticated. So we are talking about subspecies. And it is thought, biologically, that the differences between the so called, races, are not significant enough to be classified as different subspecies. Different races have different colored skin, some differences in noses, hair texture, and eyes, but that's it. That's not significant enough to classify as a different subspecies. Perhaps if these groups were isolated and remained isolated for hundreds of thousands of years, then we would observe more pronounced differences between the different human populations. 64.236.121.129 21:10, 7 November 2007 (UTC)

There are several differences between breeds and races, some of which are more a matter of degree rather than clear-cut distinctions:

For one thing, with dog breeds for instance, in general the genetic variation between individuals within a breed is much smaller than the genetic variation between breeds. This is reversed with race: the genetic variation between races is much smaller than the genetic variation of individuals within one race.

Looked at another way, dog breeds in general consist of very clear-cut, genetically isolated populations. In contrast, with humans the prevalence of various genotypes and phenotypes often changes gradually over a geographic area, with less in the way of clear-cut boundaries. Because of the above and other complications, it’s very difficult to try to define and test for race genetically. See Race and genetics.

Within one geographical area, it may feel like there are reasonably clear-cut distinctions between races, if that geographical area contains large groups of people that had been relatively genetically isolated within recent history. For example, it works at least to some degree to group at least a lot of people in the U.S. based on whether most of their ancestors came from Europe, from western Africa, or from southeast Asia. But that moderately workable grouping to a large extent disappears if you consider all the people in the world as a whole, in which there are more gradual genetic variations over geographical areas.

Another difference between breeds and races is that there is a cultural aspect to race. Whether two populations of humans are grouped as one race or two depends a lot on how culturally similar or dissimilar the two populations are perceived as being. This is yet another reason why it is very difficult to try to define race in any rigorous way. See Race (classification of human beings). MrRedact 08:39, 7 November 2007 (UTC)

Material Properties in outer space

Hi, In hearting about the ISS unfurling their solar array and having it tear and all that - it got me wondering... Aren't these materials near Absolute_zero? Doesn't metal and plastic freeze solid at absolute zero? I guess not. —Preceding unsigned comment added by InverseSubstance (talk • contribs) 06:46, 7 November 2007 (UTC)

Why do you think that the temperature at the ISS is near absolute zero? The atmosphere at this height is quite hot. Not that this would matter - the temperature of the ISS is far more dependent on radiative heat transfer. Icek 07:06, 7 November 2007 (UTC)

The problem with this stuff is that somewhere, somehow, some scientist let slip the idea that space is cold. The truth is that space isn't any temperature. Temperature is (essentially) a measure of the average speed that atoms are moving around within some substance. No atoms - no temperature. So let's get rid of that idea. The temperature of spacecraft comes about in the same way things do down here at sea level - you add up the energy coming in (mostly sunlight - but also reflected earth-light and heat generated on-board the craft) - and you subtract the energy going out (by reflection of sunlight, and emission of infra-red light). If there is more energy coming in than going out, the temperature goes up and if more is going out than coming in, the temperature goes down. If the temperature increases, then more and more infra-red light is emitted and eventually you reach a temperature at which sufficient IR light is leaving that the temperature strikes a perfect balance. Similarly if the temperature falls, so does the IR emission and again, the temperature eventually stabilises. This is the same mechanism we have down here on earth - except that we also gain and lose energy by conduction into and out of the surrounding atmosphere and the ground. Also we get more incoming heat from scattered light from the sky.

OK - so those are the mechanisms. What happens with the solar panels? Well, as sunlight comes in, they heat up, the temperature slowly rises and they heat up - and when the spacecraft orbits around to the dark side of the planet, there is no more sun - so the temperature slowly decreases. The space station orbits (from memory) about once every 75 minutes. So the temperature of the craft goes up for about 37 minutes then cools off for 37 minutes over and over again. The large metal components take a long time to change temperature by much so they are going to tend to settle down to some more reasonable average temperature. So imagine a large chunk of metal down here on earth - if you take a large chunk of steel (a car perhaps) at some nice toasty temperature (because you've been driving it) and park it out in the snow in mid winter, would it cool down to freezing in 30 minutes? I don't think so. It certainly won't cool down to absolute zero over just 30 minutes! In earth, the car is cooled both because it's radiating IR light - but ALSO because it's heating up the air around it - that hot air rises and is replaced by cold air - so that's quite an efficient way for the car to lose heat. But up in space, there is no air - so it can only lose heat by radiation. That means that our solar panel will take MUCH longer than the car to drop to freezing point - and VASTLY longer to cool of to anywhere close to absolute zero - and it's only in the dark for 37 minutes in each orbit.

Another way to think about this is to watch the movie Apollo 13. Those guys had to live for nearly a week in an unheated spacecraft. The lunar lander got cold - but no so cold that they couldn't survive in their flight suits. Those spacecraft had to be spun so that one side of the craft wasn't perpetually in sunlight and the other perpetually dark. The ISS orbits - so that's not necessary for them.

SteveBaker 18:58, 7 November 2007 (UTC)

Regarding the original question, the relevant metals and plastics are of course already frozen (solid) at room temperature.

Regarding 70.116.10.189's answer, a little nitpicking: There are atoms - and even molecules - up there, but the density is too low to have a significant impact on the ISS's temperature. Even at more than 780 km height, where ERS-2 orbits, the atmospheric density is at least several hundred particles per cubic millimeter.[2]

And the space station's orbital period is 91 minutes.

Icek 14:25, 7 November 2007 (UTC)

Two Questions about Gravity.

Okay. Why isn't there a "nuetral" gravitational force? Okay. Let me explain. I think I was told by a teacher that, if there were no gravity on a planet, then it would be virtually impossible to reach it, as no force would be pulling you in. But, at the same time, that would seem as if there were a "negative" force keeping you away from the planet. But, why would there HAVE to be a force pulling you INTO a planet to be able to reach it, when there is NO "negative" gravitational force keeping you AWAY from it? That doesn't make any sense to me. Why isn't there "neutrality" in gravity?

Also, wouldn't we not have been able prove that gravity existed until we proved there were "gravities" that have different levels of force than Earth's? My thinking is that, until we proved there were "gravities" with different levels of force than Earth's, the only "gravity" that we knew existed was on Earth, with equal gravitational force on everything. So, basically, as far as we knew, gravity had only only level of force, but, knowing that, how could we prove it existed? I wish you could see into my mind, as my thinking is much better than that --- I just can't put it into words. It's like, since we knew there were different levels of force, we knew there had to be a force at all. Okay. Lets say humans were the only were the species that existed (work with me here), and we still classified the human being as a "species" --- like saying gravity existed when there was only, as far as we knew, one level of gravitational force. So, if there were only one type of species, then how could we prove that the concept of a "species" existed? Or, let's say EVERYTHING in the universe moved at the exact same speed (work with me here). We couldn't prove that a concept of "speed" existed, as, only one speed existed, right? We use the word "speed" because there are different speeds. If everything moved at the same speed, then we couldn't say "He's running fast" or "He's running slowly" or "He's moving at [number]/[unit] [length of time]." We could only say "He's moving", right? Or, if there were only color in the universe, we couldn't call it a color, right? We couldn't prove that the concept of color existed, unless we found a different color, right? It's like, if EVERYTHING in the universe had a quality about it that was the EXACT SAME, then how could you call it or prove that it was a characteristic at all? --- there would only be one type. I hope you know you what I mean. And I'm not saying that, even if there were only one level of gravitional force in the universe, that gravity wouldn't exist. I'm just saying that, before we found out that there are different levels of gravity, we really didn't have any proof that gravity existed --- knowing that there are different levels of gravity REALLY proves that there some kind of force exists, right?

Any help would be great! Thanks! —Preceding unsigned comment added by Pitman6787 (talk • contribs) 06:58, 7 November 2007 (UTC)

Re the first question, that's nonsense. Firstly you wouldn't have a planet without gravity, but let's just say you did. Saying that you couldn't get there because the gravity wouldn't pull you in is like saying you can't navigate to an arbitrary place in empty space because there's nothing pulling you in - but you can navigate through empty space to any given point. Your instincts are right, that there's nothing preventing you getting there. I'll leave the second question to others. --jjron 07:54, 7 November 2007 (UTC)

I would say for the second one, the problem is the inability to test variables that are beyond our capability to create or measure. The ancients knew well that gravity pulled anything that wasn't too light towards the center of the earth, but until Newton, no one figured a way to test gravity outside of the earth. And then finally, Henry Cavendish found a way to both eliminate the earth's gravity from affecting measurement, and measure the gravity between metal spheres. Similarly, until the 20th century, testing the extremes of small distances and great velocities was beyond anyone's capabilities. As such, while we were certainly capable of imagining classical mechanics as applying just the same to such conditions, this was entirely not the case. When people found ways to test them, they confirmed laws that changed the way physicists thought about the world. Someguy1221 08:39, 7 November 2007 (UTC)

Excellent questions ! Why does the gravitational attraction between two bodies depend on their masses but not what they are made from ? Why isn't there such a thing as anti-gravity paint ? Why doesn't anything have negative mass (as far as we know) ? Why is gravitational mass equivalent to inertial mass ? It was thinking deeply about these sorts of questions that led Einstein to the general theory of relativity in which gravitational forces are due to the curvature of spacetime. Gandalf61 10:57, 7 November 2007 (UTC)

Yes, you do some real thinking. What you say about our not seeing a thing that has no variation is quite true. That's part of the reason it took so bloody long to figure it out. Hats off to old Isaac, eh? You might be the one to see the remaining things of that kind. Keep us posted. --Milkbreath 12:17, 7 November 2007 (UTC)

We (well, people like Kepler and Newton) observed the orbits of other moons and planets and deduced from that that there must be a force attracting planets and comets towards the sun and a force attracting moons towards the planets. It's not much of a stretch to deduce that the smaller, lighter things are producing less force than the bigger, heavier things. You can go on to calculate how much force the earth is exerting on the moon - and with a sufficient leap of imagination - that the apple that just fell onto your head was being pulled by the same exact force (well, the apple story is probably apocryphal - but you get the idea). From the outset, we knew of many different sources of this mysterious attractive force. It was hard to quantify it because you can't easily figure out the mass of something that you can only see through a telescope as a blurry dot - but it must have been very clear that the gravity due to (say) Jupiter was vastly greater than that of Mars because you can SEE that Jupiter is huge, even in a primitive telescope. So they knew there was some kind of size/strength relationship. They could also figure out the decreasing pull of gravity as a function of distance. It took more careful experiments with big iron balls and very accurate measurements to get the details and the math exactly right - but the fact that there were differences and that the earth wasn't the only thing that had gravity must have been known for a very long time. SteveBaker 18:56, 7 November 2007 (UTC)

I wouldn't say so. While the idea may have occurred to people, the Aristotelian/Platonic system of celestial spheres was widely accepted (in the West) until Galileo began his astronomical observations in the early 17th century. Someguy1221 19:02, 7 November 2007 (UTC)

Omega-3 fatty acids in water-inhabiting animals

Why are omega-3 fatty acids so prevalent in water-inhabiting animals? They are prevalent in unrelated species, like whales, fishes and crustaceans. I guess they are produced somewhere near the bottom of the food chain. Is there some evolutionary advantage for omega-3 producing water-inhabiting animals? Icek 07:13, 7 November 2007 (UTC)

Quite a few prevelant microalgae produce omega-3 fatty acids. And yes these are on the bottom of the oceanic foodchain, so anything consuming them will also be rich in omega-3 fatty acids. As a matter of fact many fish can barely synthesise their own omega-3 fatty acids, and thus are almost fully dependent on microalgae. As to the evelutionary advantage of producing these specific fatty acids as opposed to producing others I do not know. PvT 12:54, 7 November 2007 (UTC)

Correct design?

Little Boy design is shown as having a round bullet with a cylindrical hole being fired at a cylinder shaped plug that fits in the hole. This arrangement seems counter intuitive to firing the cylinder plug into the cylindrical hole so as to avoid the problem of a rounded projectile twisting out of alignment versus the plug only being able to rotate in the gun barrel. Why was the arrangement shown used instead of the other way around? Clem 07:51, 7 November 2007 (UTC)

Little Boy#Counter-intuitive design. I think your link answered your own question. Someguy1221 08:43, 7 November 2007 (UTC)

The first picture does not seem to show the projectile as a hollow cylinder but rather as a hollow ball. Even with the alignment question answered it is still not totally clear to me why the hollow cylinder has to move instead of the plug. ...until you include the Tungsten-Carbide tamper as part of the movable projectile or stationary target. Clem 09:12, 7 November 2007 (UTC)

I think the first picture is just meant to be schematic in a cartoony way. --24.147.86.187 15:30, 7 November 2007 (UTC)

The page basically says that the larger area is actually more than one critical mass (which is certainly true) but kept from being critical by being in a tube shape (it has a hole in the middle so the uranium isn't too close to itself). If you put that into the large neutron-reflecting tamper you'd run the risk of too many neutrons spontaneously floating around and creating a criticality accident. So you keep that part far away from the neutron reflectors, and only when you bring it together is it subjected to their reflection. I don't know if that is true or not but it sounds plausible to me. You'd have additional problems created by such an arrangement but it might let you use more uranium to compensate. --24.147.86.187 15:33, 7 November 2007 (UTC)

One of the scarier experiments they did when designing that bomb was described in one of Richard Feynman's books - they actually dropped the cylindrical tube part over the core part experimentally to try to measure the amount of neutrons that would be produced - but they arranged that the tube would not stop when it was in the right position for an explosion - but merely keep on going. The theory being that if you could do this fast enough, you could avoid the chain reaction getting big enough to make a nuclear explosion. However, since they weren't 100% sure what the outcome of the experiment would be until they did it, it was always possible for something to go horribly, horribly wrong! Needless to say, this was a pretty dangerous experiment because if anything got stuck or moved just a bit too slowly...KABLOOIE! The building where they did those tests was way, WAY out in the desert! SteveBaker 18:28, 7 November 2007 (UTC)

Actually, they managed to kill at least a couple of people working on the Manhattan Project through careless manipulation of near-critical masses of radioactive material. See Criticality accident#Incidents, Harry K. Daghlian, Jr., Louis Slotin. TenOfAllTrades(talk) 19:01, 7 November 2007 (UTC)

derivation of phrase sex maniac

would like to know what the specific derivation is as not common in english language to use maniac with other terms eg dont describe someone as a chocolate maniac or a drug maniac.86.4.107.45 10:05, 7 November 2007 (UTC)

See Hypersexuality. The concept of hypersexuality replaces the older concepts of nymphomania (or furor uterinus) and satyriasis. Lanfear's Bane | t 10:37, 7 November 2007 (UTC)

Chicken-eating spiders

To my astonishment, I found this statement in the Raising Chickens Wikibooks:

"In south America there is a type of spider that will prey on chickens"

What kind of spider is that? It must be huge... --Taraborn 11:10, 7 November 2007 (UTC)

The Goliath birdeater is native to South America and seems to be a contender for the largest spider in the world [3]. However, despite its name it seems it does not normally eat birds - our article says it got its name because one specimen was once seen to eat a hummingbird. So very doubtful that it, or any spider, could prey on chickens. Gandalf61 12:16, 7 November 2007 (UTC)

...said he a moment before the Gargantua wizardeater, a species as yet unacknowledged by Western science, sank its glistening poisoned fangs into the nape of his neck. --Milkbreath 12:47, 7 November 2007 (UTC)

Don't forget good old Shelob. Lanfear's Bane | t 13:15, 7 November 2007 (UTC)

It can prey on a chicken and still be a pretty modest spider. If it has a venomous bite - then it could certainly kill a chicken and yet be pretty small - that a small spider might eat a small amount of a dead animal might not be surprising. I don't think we can dismiss this just because we can't imagine a two foot spider pouncing on the chicken and ripping it limb from limb with inch long fangs! SteveBaker 18:20, 7 November 2007 (UTC)

Civil engineering: Factor of safety?

in Civil engineering- what is a Factor of Safety ? and why do we use it ? —Preceding unsigned comment added by 82.69.206.166 (talk) 12:26, 7 November 2007 (UTC)

Welcome to Wikipedia. You can easily look up this topic yourself. Please see factor of safety. For future questions, try using the search box at the top left of the screen. It's much quicker, and you will probably find a clearer answer. If you still don't understand, add a further question below by clicking the "edit" button to the right of your question title. .--Shantavira|^{feed me} 13:44, 7 November 2007 (UTC)

Put simply: If you are building (say) a bridge and the heaviest truck you expect to cross it weighs 20 tons, you shouldn't build a bridge that can only support 20 tons because you know damned well that some idiot is going to drive a 21 ton truck across it - and you probably suspect that the steel you built it with is only 95% of the strength they said it would have at the steel mill, so it'll only really support 19 tons anyway. Then you know that the bridge will corrode some over it's lifetime and maybe the crew who build it make a little mistake and don't put the rivets quite close enough together - and maybe you didn't realise that in 100 years time, the bridge will have been painted 10 times and so it's now got half a ton of paint to support as well as that truck. So right at the outset, you look at the 20 ton limit and you say to yourself "I'd better build a bridge that can support 30 tons - and that way I'll be OK no matter what". The extra 10 tons you added is the "Safety factor" for the bridge. Of course you shouldn't over-do this because it's likely that a bridge that can cope with (say) 40 tons will cost twice as much as one that'll only support 20 (or was that 19?). That's all there is to it - nothing complicated. SteveBaker 18:01, 7 November 2007 (UTC)

Too obvious to be realizable?

What is the process by which plant cells transform carbon to oxygen, and can it be synthesized? If so, is that technique applicable to reducing carbon in our atmosphere? If not, how unrealistic an idea is this? Beekone 14:04, 7 November 2007 (UTC)

Photosynthesis is the process by which plants use light energy to convert carbon dioxide and into oxygen and glucose. Your idea of carbon sequestering is a good one...see also our Carbon dioxide sink article. DMacks 14:23, 7 November 2007 (UTC)

See photosynthesis for details on the process. Note that this reaction requires energy (sunlight) to occur, so we would need enormous amounts of energy for significant results (think of how many trees there are in the world, and multiply that by at least 100 to get the total weight of algae, which produce about 80% of our oxygen). From the article, "Through photosynthesis, sunlight energy is transferred to molecular reaction centers for conversion into chemical energy with nearly 100-percent efficiency. The transfer of the solar energy takes place almost instantaneously, so little energy is wasted as heat." This means that not only would we need huge solar panels or lots of nuclear plants to do this cleanly, but we still would be nowhere near as efficient as plants. That's not to say it isn't possible: certainly the reaction produces food on the order of Soylent Green in artificial sugar-rich goodness, which might be very economical in the future. But as far as significantly impacting the CO2, I sincerely doubt it would have much effect. We're better off by first and foremost switching all our power plants to renewable and nuclear sources, which would be necessary for the reaction to have net effect anyway. SamuelRiv 14:30, 7 November 2007 (UTC)

Since when was photosynthesis efficient? Biological processes are notorious for being inefficient. I heard a retired biology professor say that photosythesis was inefficient. 64.236.121.129 16:22, 7 November 2007 (UTC)

Depends what you mean by "efficiency". To quote the article: "This chemical energy production is more than 90% efficient with only 5-8% of the energy transferred thermally." but "Not all wavelengths of light can support photosynthesis.". DMacks 19:21, 7 November 2007 (UTC)

It just struck me as such an obvious solution that surely someone had thought of the implications. I thought I'd leave it up to you guys to drop some knowledge on me. Thanks for pointing me in the right direction, very interesting stuff! Beekone 14:52, 7 November 2007 (UTC)

I do vaguely recall some experimental setup with large polythene bags full of some liquid that you'd lay out in the sun and bubble air through to capture the CO2 and produce some kind of useful product - it's not in widespread use though which suggests that there was some problem with it. But the answer is simple enough - cover a greater percentage of the earth's surface with plants (restoring the sahara to greenery would help for example) and stop cutting down the rainforests and starting forest fires! You can even harvest the plants (so long as you plant new ones immediately afterwards) and either use them to make ethanol/biodiesel to run your car sustainably or (if you actually want to sequester CO2), toss the dead plants into an anaerobic landfill someplace (so they don't produce methane as they rot).

Sadly, the very effect we're trying to prevent (global warming) is the exact same effect that's causing deserts to increase in size and making it harder to grow crops in those kinds of places. SteveBaker 17:52, 7 November 2007 (UTC)

Psychology: person A evaluates B by the evaluation of C, D, E.... for person B.

This happens quite often. Is there a name for this please? And are there any known personality traits of person A that make them more likely to indulge in this? Thanks 80.2.214.75 15:19, 7 November 2007 (UTC)

Could you give an example, or a more detailed question? I'm having a lot of difficulty understanding what concept you might be looking for. On the off chance that I've got it right, is projection the term you seek? TenOfAllTrades(talk) 16:37, 7 November 2007 (UTC)

This sounds like gossip to me! That is, making judgements about people solely based on what you've heard others say about them. 83.249.121.85 16:41, 7 November 2007 (UTC)

"Checking a job applicant's references"? -- Coneslayer 16:42, 7 November 2007 (UTC)

An example: when I was at college girl X was attracted to me in proportion to the amount of esteem that she observed other people had for me; while girl Y was attracted to me irrespective of what other people thought. I am curious about how girl X and Y may differ in personality. I have seen this in men also: I was interviewed for a job once by the boss of my future boss, and when my future boss saw that his boss was taking an interest in me, his behaviour towards me improved greatly. I imagine that this behaviour is associated with authoritarianism, in-groups and out-groups, perhaps Machiavelimism and so on.

Another example could be germans who evaluated people of the jewish faith according to nazi propoganmder, and others who were more resistant to the propoganda. Another example is here http://news.bbc.co.uk/1/hi/scotland/north_east/6273231.stm where it says women are attracted to men according to the attention they receive from other women.80.2.211.126 23:12, 7 November 2007 (UTC)

Energy

We are told that energy can neither be created or destroyed but say a person throws a ball which eventually comes a complete stop, where has that energy gone? —Preceding unsigned comment added by 195.188.208.251 (talk) 17:53, 7 November 2007 (UTC)

It all winds up as heat, thermal energy. Whenever energy vanishes from a mechanical system (throwing a ball is a simple such system), it mostly becomes heat. Someguy1221 18:00, 7 November 2007 (UTC)

Look at potential energy, and also energy in particular 'forms of energy'. it has a bit on a bouncing basketball. and further down the conservation of energyny156uk 18:02, 7 November 2007 (UTC)

Yes - and in the case of the ball, what happened was that the successive final bounces of the ball deformed the rubber that it's made of and that caused the rubber to heat up and the ball to bounce a little less high the next time - the ground too would flex a tiny bit and gain some heat at the expense of the ball. Also every time it bounced, the ball made a noise - which required some of the kinetic energy to be consumed in making the air vibrate - but the moving air has some internal friction which heats the air up a tiny bit as the sound dies away. In the end, it's turning all of that interesting kinetic energy into generalised, diffused heat. But it might take a while - we can come up with some scenarios in which it takes an INSANELY long time to finally turn all of the energy of the ball into heat. Suppose the ball landed on (of all things) a WintOGreen flavored Life Saver and crushed it. A weird property of that particular candy (called triboluminescence) would actually result in a small pulse of blue and UV light to be radiated outwards as the candy was crushed. Of course as that light is absorbed, it too will turn into heat - but a small fraction of the light would head upwards, escape from the earth's atmosphere and head out into space. It could be trillions of years before the light hits a stray bit of cosmic dust - but when it does, you just get some heat. This tendancy for everything interesting to eventually turn into heat is called Entropy and it's really rather depressing. Can we talk about something else now? :-( SteveBaker 18:15, 7 November 2007 (UTC)

Related question

If one were to invent a 100% perfectly efficient machine, would it not produce any sound, as sound would be a result of friction and wasted energy? -- MacAddct  1984 ^{(talk • contribs)} 19:36, 7 November 2007 (UTC)

Yes, exactly. (Except of course if the machine were designed to produce sound, like a loudspeaker or musical instrument.) —Keenan Pepper 19:49, 7 November 2007 (UTC)

The way intelligence grows on the "nurture" side

Hi! After studying the "nature vs. nurture" aspect of intelligence in a high school psychology class, I came up with my own "theory [in respect that I have never read or heard anything related to the ideas in this "theory" before]" on how intelligence grows on the "nurture" side of things. I know this isn't the place to post personal theories and want them to be proven or disproven, but, after thinking about this one, I thought it was a basic enough concept that it would have to have had already been proven or disproven by now --- so I am now simply looking for someone to confirm or deny this.

Okay. My "theory" is that, indirectly, the more you know, the more intelligent you are --- not simply because you know more, but because, knowing that you DO know more, we know that you have used your brain more, which is the reason you're more intelligent. I am relating this to physical fitness. Physical muscles [as opposed to the mental muscle (i.e., the brain)] grow --- along with phsyical fitness level --- as you exercise more. Why wouldn't the same be true with the brain, except with gaining more knowledge other than exercising? The brain is a muscle, too, right? And, so, using that muscle more (i.e., gaining more knowledge) would increase THAT muscle's competency too, right?

Going along with this, I know a lot of people criticize I.Q. tests, saying "Well, the I.Q. test included questions with information I just never learned before! It wasn't fair! Just because I never learned information doesn't mean I'm less intelligent!" But I criticize that criticism, with the information I posted above. Also, or people will say "Just because I didn't receive that high a level of education doesn't mean I'm not intelligent". But, again, I am trying to refute that.

And I think that the statements in the paragraph above are made and thought of because of people's emotions. I know that it isn't always people's faults that they didn't receive that high of a level of education --- and because it wasn't their fault, it would be "mean" to think a person is less intelligent because of a reason they couldn't help. But, whether or not you can help your level of education, (according to what I am thinking) the higher the level of education you have, or the more knowledge you know, the more intelligent you --- indirectly. Again, not because you learned and know more but because you used your brain --- a muscle --- more, which increased its competency.

And I do realize that, with the "nature" side of intelligence, people can still be intelligent, despite low level of education, or lack of knowledge, as their base --- or genitic factor of --- intelligence might have been high at birth. I am just saying that knowing more information is a GENERAL indication of a higher intelligence.

Again, I thought this was a basic enough concept that it had to have been proven or disproven by now. So, which is it? —Preceding unsigned comment added by Pitman6787 (talk • contribs) 19:37, 7 November 2007 (UTC)

Just giving you a few of my thoughts here. Anybody who exercises more, will grow more muscles, but only a few can become top athletes - the ones that have excellent genes. Yes, if you know more, you will get a higher result on some intelligence tests, but people differ in how much information they can gain and reproduce (and by testing this you would rather test memory instead of intelligence), and, more importantly, having a huge fund of information doesn't mean for instance improved reasoning skills or perceptual abilities, which also are considered to be important parts of intelligence. —Preceding unsigned comment added by Lova Falk (talk • contribs) 19:48, 7 November 2007 (UTC)

I'm not sure if you saw this page section: Intelligence quotient#Environment. --JWSchmidt 20:59, 7 November 2007 (UTC)

Re: education. I don't think anyone would argue that a mind well-tested as a mind sharpened. If you are in the habit of dissecting logical arguments, for example, you are going to be better at it than if you were not in that habit. The question is whether that measures what we think of as "intelligence" or not. Expanding that definition to include education makes sense in some cases, but not in others. Look at the test questions from the Army Alpha Intelligence Test (1914-1918). Try and tell me with a straight face that knowing who Rosa Bonheur is, what product Velvet Joe was the mascot for, or what a Wyandotte is measures anything other than exposure and retention of simple factual information? Those are the extreme examples, but everything else in the "informational" section falls under that category; it's entirely possible to be quite bright and just never learn where exactly the pancreas is in one's body; and on the converse it's possible to be quite dumb and know simple things like that. It's well known that total dolts can excel at bar-room trivia; that's not a measure of intelligence of any sort. So clearly some line must be drawn between being asked questions that are purely "educational" and those that are not; knowledge of miscelleanous facts is not what anyone generally considers "intelligence" to be. --24.147.86.187 01:08, 8 November 2007 (UTC)

Re:Sorting it out. We have somewhat sorted out, the answer is "it's complicated, and it's something of an artificial question." Genes provide the template for an organism which then must develop in an environment; they are not mutually exclusive categories in many respects. They are in a complicated relationship, some times more complicated than others. With very simple traits (single-point mutations) it is not too hard to untangle in most cases; when talking about more complicated genetic traits then development starts to play a big role. When talking about something like "intelligence", the exact definition of which is quite murky, then it becomes exceptionally hard to untangle, and many environmental and genetic factors start being at play. But it isn't a simple "x% this, x% that" sort of equation; it's the complexity that comes from having an organism develop, where genetic code tells individual cells what to do, but somehow we are supposed to understand complicated aggregate behavior of an entire organism. It's not that we don't know how to sort some of these things out, but sorting them out in a straightforward way has proven pretty difficult, especially if we are talking about groups that exist in complicated social dynamics that cannot be really reasonably escaped for the purposes of testing. --24.147.86.187 01:08, 8 November 2007 (UTC)

Human Evolution

Well, Heroes is on again tonight. I was just wondering if there are any clues as to how H. sapiens will evolve in the medium term. Obviously i am not expecting spontaneous levitation, telekenesis or other such nonsense - more physiologically. Are humans now capable of purposefully selecting a route of evolution to their own ends? --russ 20:13, 7 November 2007 (UTC)

The things we are evolving are likely to be small tweaks that make us better suited to our environments...not major stuff like being able to fly. One example of a "recent" evolved change has been adult lactose tolerance. Most other mammals (and humans as recently as the ancient Egyptians) are lactose intolerant as adults. When we started farming and milking goats and cows, there was a clear advantage for humans who were able to digest milk. So we started to evolve lactose tolerance and the lactose intolerant people started to decline in numbers. However, in our modern world, it seems very unlikely that you could die without leaving offspring just because you are still lactose intolerant - so it seems like that genetic change hasn't spread throughout the population yet. It wouldn't surprise me if we started to adapt in ways that helped us in the modern world...but genetic changes take thousands of years and our environment has changed so dramatically in just the last 100 years that we havn't had time to evolve to support that change. If I had to go out on a limb and predict something, I'd suggest that we might evolve a way to avoid obesity. That kills off a lot of younger people and certainly reduces their attraction to the opposite sex - so it ought to have a serious impact on reproductive capability. If a gene came along at random that helped avoid that problem then I imagine it would sweep the western world in a matter of just a few thousand years. But you can't KNOW that this will happen.

As for whether we are purposefully driving evolution - in a sense, we always have. By being selective with whom we mate with - we make that choice quite a lot. In terms of using gene replacement therapy we MIGHT make a change. As a matter of fact though, it's possible that we're inadvertently screwing things up rather badly. Think about this. What happens if a married couple want a baby and can't have one? They go to the scientists and magic wands are waved, incantations spoken and (in quite a few cases), a baby is the result. In fact, multiple babies may result in an unnaturally large percentage of the cases. So if there were a genetic cause for infertility that would normally be strongly selected against, we could quite easily accidentally make it not only NOT be selected against - but because of the possibility of multiple births due to fertility drugs, we might even make genetic infertility become a trait that tends to increase over time. That's pretty worrying - but it's exactly the kind of thing that we'd be just stupid enough to do.

SteveBaker 20:27, 7 November 2007 (UTC)

The ancient Egyptians were lactose intolerant? Them and 70% of adults alive today. Algebraist 20:41, 7 November 2007 (UTC)

That 70% seems very high. Even more so are some of the population-specific numbers -- none of the many various Asian Americans I know have ever identified themselves as lactose intolerant, and I've certainly seen them consuming cow by-products before. jeffjon 21:21, 7 November 2007 (UTC)

If milk causes such problems in so many people, why is it so popular? Do only 30% of the population drink milk? Surely people wouldn't drink it if they were afflicted? --212.204.150.105 21:18, 7 November 2007 (UTC)

The degree of lactose intolerance is highly variable in both its severity and its age of onset. Some people don't begin suffering until their 30s or 40s, and even then, many lactose intolerant individuals can drink a cup or two a day without suffering any symptoms. Someguy1221 21:31, 7 November 2007 (UTC)

70% has got to be *WAY* too high. The article says that there are multiple causes - we're talking here about people who are congenitally lactose-intolerant as adults - not people who are that way because of diseases. But even so, there simply is no way that number can be right in any of the parts of the world I've lived in. Out of all of the people I know well enough to have been able to tell - at least 20 or 30 people - I can only think of one who suffers from that condition. If it's 70% then the number should be 15 to 20 of them...there is no way I can not know those people that badly. We've had every one of them over to our home for dinner on multiple occasions - my wife's French - everything has cream sauces and such. No - it's not 70% in Europe or North America. It's gotta be way less than 10%. 70.116.10.189 23:38, 7 November 2007 (UTC)

If 70% seems way too high to you, it’s because of which people you’re typically exposed to. The mutation that allowed lactose to be digested by adults happened quite recently (on an evolutionary scale) somewhere in northern Europe. So if you hang out around people of primarily northern European descent, then the 70% is going to seem high to you. But if you lived in China or Thailand, that figure would seem very low to you. MrRedact 00:32, 8 November 2007 (UTC)

70% was for the whole world. See Image:LacIntol-World2.png. Someguy1221 00:34, 8 November 2007 (UTC)

70% for the world seems right when you factor that there are two large groups that traditionally had lactose-intolerance issues - Africans and Asians. There are a hell of a lot of Africans and Asians in the world, compared to Europeans which have less of an issue traditionally. Americans have a far, far lower rate of lactose intolerance - probably due to various worldwide cultures intermixing genes to allow them to spread faster. Kuronue | Talk 04:54, 8 November 2007 (UTC)

Historically, the idea of humans "purposefully selecting a route of evolution to their own ends" has often been a bad idea, especially with Nazi eugenics. MrRedact 00:49, 8 November 2007 (UTC)

Of course, if we have eliminated natural selection by using fertility clinics, that makes genetic research that much more important. It seems to me that if we want to survive as a species, eventually we are going to have to manipulate our genes, either before or after we are born. 68.231.151.161 01:49, 8 November 2007 (UTC)

I'm not sure that we need any help on that. See also Population, Carrying capacity, Sustainability, and Earth. I think the better question is why are we doing so well as a species, and at what point should we stop trying to let people live longer. All things considered, we're simply going to run out of physical space in which to fit everyone. --slakr^\ talk / 04:40, 8 November 2007 (UTC)

Some argue that humanity’s ecological footprint already exceeds one Earth.[4] But there’s no problem with still trying to let people live longer, as long as we simultaneously reverse the population explosion through voluntary population control measures such as improving access to family planning and reproductive health care and information, eliminating incentives to have larger families, and public education about the consequences of continued population growth. MrRedact 05:21, 8 November 2007 (UTC)

Special Wheel Supported on the Lower Rim

I remember seeing somewhere a wheel that was supported on the rim below the wheel's center point. The vehicle using the wheel had no axles. I assume the rim at the point of support had some kind of bearings. The wheel had nothing inside the rims. This had the benefit of lowering the vehicle's center of gravity. Can anyone point me to a reference for this arrangement? ThreeE 20:54, 7 November 2007 (UTC)

Have you tried Hubless wheel? --TrogWoolley 22:31, 7 November 2007 (UTC)

Perfect. Sbarro (http://www.burningart.com/meico/moto/sbarro/) was the designer I was looking for. Many thanks. ThreeE 23:38, 7 November 2007 (UTC)

Why is the waste disposal system the same as the reproductive system?

Not the same, biologically speaking, but using the same body parts. Why is it like that? Do you peeps think it has some kind of evolutionary function or it's merely a bad design that just evolved that way because it works without any major malfunctions (although there are sometimes malfunctions). 64.236.121.129 21:33, 7 November 2007 (UTC)

Er, not sure what you mean. In mammals the reproductive system is separate in all respects except for the dual-purpose male phallus. In other vertebrates the two systems do vent at the same place, the cloaca.--Eriastrum 23:12, 7 November 2007 (UTC)

And the reason for that arrangement is basically that the original chordate body plan consists of a muscular tube with a hole at each end. Any elaborations on that, such as limbs or extra orifices, are later additions, and are unlikely to occur unless there has been some selection pressure for them at some point. We can thus deduce that, for example, at some point in the evolution of placental mammals there was an evolutionary advantage to females having a separate vaginal opening. Figuring out what the cause of the pressure might've been is left as an exercise for the reader. —Ilmari Karonen (talk) 01:12, 8 November 2007 (UTC)

You don't know what I mean? Drop your pants and see where your sexual organs are, and where your waste disposal organs are. DUH. Come on, this ain't rocket science peeps :). 64.236.121.129 15:31, 8 November 2007 (UTC)

I think this argument is questionable. Sexual reproduction exists outside of phylum Chordata and presumably predates it, so one might as easily discover that the development of a spine was an elaboration on some proto-tubeworm's reproductive system. I don't know what the relationships actually were, but they are presumably very, very old. Dragons flight 03:10, 8 November 2007 (UTC)

That could well be; the point I was making is that the default condition inherited from our proto-chordate ancestors is "one hole in front, one in the rear". That our present body plan, in many ways, still resembles this ancestral model should not be surprising; rather, it's the deviations from this basic body plan that require an evolutionary explanation. Presumably, then, the reason the human reproductive organs are close to the anus is that they used to share the same opening (the cloaca), and that there hasn't been sufficient evolutionary pressure to move them any further from each other than they are. —Ilmari Karonen (talk) 22:09, 8 November 2007 (UTC)

I Cannot think of a good reason why poop is RIGHT by the fun stuff! PS dude above, MAMMALS: NOT SEPERATE at all...Hands and feet,..now that's seperate —Preceding unsigned comment added by 76.168.69.208 (talk) 02:09, 8 November 2007 (UTC)

I'm actually curious as to this as well. Not just humans - most female mammals that I'm familiar with have both vaginal and anal openings within a few inches of each other. Considering how irritated the vaginal opening can get when feces is accidentally introduced (personal experience here - always wipe front to back!), this seems counter-intuitive. Kuronue | Talk 04:58, 8 November 2007 (UTC)

Perhaps, there were some advantages in the prenatal development of these organs that let it evolved in this way. See Development of the urinary and reproductive organs. What about digestive and respiratory systems? They seem to have some overlaps as well. --Vsion 05:43, 8 November 2007 (UTC)

Because this enables humans to cover for most eventualities with just one item of underwear.--Shantavira|^{feed me} 09:07, 8 November 2007 (UTC)

I think it is merely just a bad evolutionary design that stuck merely because it worked satisfactorily, although it is anything but ideal. 64.236.121.129 15:36, 8 November 2007 (UTC)

You shouldn't think of evolution as a design. No men in white suits mulling over the latest design models for the new species. Evolution happens by accident, and for things to change a mutant child must be born whose genetalia are farther removed from their bowels. Maybe move them up to the stomach? It'd be more convenient for child birth. (Every time I think of it, an image pops into my head from the original Alien movie) Man It's So Loud In Here 21:48, 8 November 2007 (UTC)

Looks like a devine example for unintelligent design
--Cookatoo.ergo.ZooM 19:21, 13 November 2007 (UTC)

series of vaccine for rabies

Following an encounter with a rabid fox, I received a series of vaccine for rabies as treatment. A month later I was planning to donate blood at the local Red Cross. Prior to my scheduled time at the Red Cross, I had contacted a physician who had said that it was okay for me to donate my blood. However, the people at Red Cross thought differently and told me that I have to wait up to one year to donate again. Do you know how long a person who has received the series of vaccine for rabies needs to wait and why?Pumpkin68 21:37, 7 November 2007 (UTC)

Time limits are pretty much arbitrary. The (U.S.) Department of Defense concurs with your Red Cross information: they require a wait of 1 year before blood donation if the rabies vaccination was given for rabies exposure (an animal bite, for example); there is no wait if the rabies vaccine was given for other reasons, and the donor is symptom-free. Thus the wait seems to be dictated by the animal bite and not the vaccine. - Nunh-huh 22:27, 7 November 2007 (UTC)

Are other mammals attracted to female mammary glands?

Human males are attracted to girls with big boobs. Is there any scientific evidence that shows other mammals attracted to mammary glands? Like maybe a male Bull poking its nose against a cow's big puffy thing at the bottom (utter? whatever you call it). 64.236.121.129 21:45, 7 November 2007 (UTC)

Not really what you're looking for at all, but slightly related: Koko, the female Gorilla that liked to see and touch human nipples (both male and female). jeffjon 21:57, 7 November 2007 (UTC)

It is my understanding that the male attraction to breasts is part genetic, part culturally trained. The genetic part I always assumed worked on the basis that larger breasts made a female look like they would produce enough breast-milk to rear a large family - thus making them more attractive to the males who wish to spread their seed. Now i cannot say this is scientific, i probably heard it some place and took it as true, and i'm sure there'll be science that shows breast-size has little impact on the amount of breast-milk a woman can produce, but that has been my idea. If this angle is correct then other animals will have an interest in any female/male attributes that show-off to the group/pack that they are fertile/strong, whatever the other sex wishes them to be. So things like Peacocks showing off their fantastic tails to attract peahens (lots of birds have coloured plumage to attract other birds) or the male lions fighting for pack-dominance because that will often lead to them having the best female-mates. Look at sexual attraction ny156uk 00:41, 8 November 2007 (UTC)

I think I can say with a great deal of certainty that other mammals are not attracted to female mammary glands. Check out our cleavage article. And be sure to read the linked citations too (actual pages from the book, I think). --Cody Pope 02:32, 8 November 2007 (UTC)

I think I've heard it speculated that the phenomenon of enlarged female breasts in homo sapiens is an example of an evolutionary arms race, or more specifically, runaway evolution. (This is basically what ny156uk was saying.) —Steve Summit (talk) 03:16, 8 November 2007 (UTC)

All other mammals are attracted to mammary glands. That is the single defining behaviour of mammals (the clue is in the name!) However, in most mammals the attraction wanes considerably on weaning. As far as we can tell, only adult humans consider breasts sexually attractive. Incidentally, investigating how and why mammals find breasts attractive (for suckling, not for staring at in Playboy) and the sensory mechanism through which that attraction is mediated, is what I do for a living. We have some interesting and surprising findings, but I'm afraid I can't tell you what, is it is not yet published. At work today I spent the afternoon timing babies crawl around on naked female breasts. Its a tough job! Rockpocket 09:07, 8 November 2007 (UTC)

Cats which like milk would be attracted to the smell of milk from a lactating female human. Edison 13:11, 8 November 2007 (UTC)

Unweaned mammals (meaning young which still want to nurse) don't seem to care where the meal comes from, as long as they get fed. Simple experiment: Have a post-puberty female human pick up a nursing puppy or kitten. Expected result (because I've seen it many times): If allowed, the puppy or kitten will attempt to nurse. A hungry baby mammal just doesn't care who or what owns the teat; he/she/it just wants a meal. The news is full of cross-species nursing. Even our own legends (founding of Rome) are full of it. -SandyJax 16:13, 8 November 2007 (UTC)

That isn't entirely true, the literature shows that the smell of milk from different species does not always promote suckling in others, irrespective of Romulus' experience. For example, its the smell of 2-methylbut-2-enal in rabbit milk the promotes suckling in rabbits. Human, cat or mouse milk does not promote suckling in rabbits because, presumably, they do not express 2MB2 in their milk. The suckling promoting odors of other mammals have not yet been identified. Rockpocket 19:20, 8 November 2007 (UTC)

I once read a story in the newspaper about a woman who breast-fed a litter of orphaned kittens. That is about all I have to contribute to this thread. --Kurt Shaped Box 20:04, 8 November 2007 (UTC)

It seems that enlarged mammae - at least in other mammals - are the result of ovulation having taken place. As such they are a prime sign of fertility, which, in mammals including homo sapiens, is periodic and not constant. So, the attraction of bigg(er) boobs makes evolutionary sense as it maximises the offspring per copulation.
--Cookatoo.ergo.ZooM 19:43, 13 November 2007 (UTC)

a reaction is either oxidative or non-oxidative, never inbetween

AGEs can be formed via oxidative pathways (e.g. carboxymethyllysine [CML] and pentosidine), via non-oxidative pathways (such as pyrraline), or from highly reactive dicarbonyl precursors, such as glyoxal, methylglyoxal and 3-deoxyglucosone (3-DG). - a reaction is either oxidative or non-oxidative; how can they give three categories then? The dicarbonyl precursors either react oxidatively or they don't... --137.120.53.67 21:47, 7 November 2007 (UTC)

What's an AGE? Delmlsfan 23:42, 7 November 2007 (UTC)

Could be Advanced glycation endproduct, what you get when you cook carbohydrate with protein. Graeme Bartlett 01:05, 8 November 2007 (UTC)

Amnesia

What is the name of the illness where the sufferer experiences amnesia every few minutes? Keria 22:23, 7 November 2007 (UTC)

I forget. -- Coneslayer 22:38, 7 November 2007 (UTC)

Anterograde amnesia. Someguy1221 22:39, 7 November 2007 (UTC)

effect heat has on rubber

$<math>Insertformulahere$</math>

In oxygen atmospheres, combustion is the usual result. Delmlsfan 23:44, 7 November 2007 (UTC)

If you can exclude oxygen, it will give off hydrocarbon gasses and liquids, and leave behind some kind of charcoal. Graeme Bartlett 01:02, 8 November 2007 (UTC)

Vulcanization? Heat equation and heat transfer will get you started on how the energy transfers along the bulk, but your relevant parameters ("k") are going to be temperature dependent and sample deformation will be an issue. At low temperatures, rubber becomes frangible (yet another way to have fun with liquid N₂). At some temperature depending an what you mean by "rubber" (i.e. the stuff that comes out of the tree or any of several commercial products and colloquial usages meaning materials having the characteristic bouncyness of rubber), your sample will melt. Very shortly thereafter, it ceases being rubber, as above. Eldereft 05:44, 8 November 2007 (UTC)