Wikipedia:Reference desk/Science

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September 18

soil conservation

how does science and technology benefit soil conservation

Science and technology are very important to soil conservation. Without science and technology, soil conservation would be much more difficult. Many scientists and technologists around the world are working very hard to contribute to soil conservation, including Illinois. In conclusion, I think science and technology benefit soil conservation in many important ways. The end. —Tamfang 00:52, 18 September 2007 (UTC)

Well it all starts with doing your own homework... Plasticup ^T/C 00:53, 18 September 2007 (UTC)

Welcome to Wikipedia. You can easily look up this topic yourself. Please see soil conservation. 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} 07:31, 18 September 2007 (UTC)

Fuzzy Logic

Is Fuzzy Logic science or mathematics? 202.168.50.40 03:11, 18 September 2007 (UTC)

Math(s). —Tamfang 03:29, 18 September 2007 (UTC)

I'm not sure I'd call it either science or math. It seems to be used solely by industry; I can't recall a pure mathematician ever expressing interest in it. The mathematician's version of fuzzy logic is Bayesian inference, which has different rules. -- BenRG 10:01, 18 September 2007 (UTC)

Isn't Defuzzification the same as Collapsing the Probability Wave in Quantum Mechanics? What about the similarity between Fuzzy Logic and Quantum Wave Theory. Both seems to deal with "All possible worlds" before collapsing into one observed result. 202.168.50.40 05:24, 18 September 2007 (UTC)

Not really - fuzzy logic is just probability based decision making under another name, wave function collapse is something else that can be related to probability.87.102.7.192 09:41, 18 September 2007 (UTC)

The collapse of the wave function does look like a Bayesian update. This was noticed by the founders of quantum mechanics, and led to a lot of rather embarrassing speculation about consciousness and mind-over-matter (because the Bayesian update is about subjective knowledge, but the wave function collapse is a physical effect). Eighty years later, the connection between quantum statistics and Bayesian inference seems to still be unclear, like everything else about the foundations of QM. But I can say with some confidence that fuzzy logic has nothing to do with QM. -- BenRG 10:01, 18 September 2007 (UTC)

It's applied mathematics. It's a branch most often used in practical technology (mostly computer software) rather than in pure mathematics. SteveBaker 13:16, 18 September 2007 (UTC)

Adjusting to high altitude

I understand that if you go up to 6,000 or 7,000 ft above sea level you can dehydrate and get headaches, and that it can require as much as 6 weeks for your body to adjust. My question: what exactly is the body's adjustment? Do we create more hæmoglobin? Thanks. PaulTanenbaum 04:12, 18 September 2007 (UTC)

Yes (more red blood cells). --> Altitude training. Someguy1221 04:41, 18 September 2007 (UTC)

After many years at altitude, you create too many. --> Polycythemia. --Mdwyer 14:40, 18 September 2007 (UTC)

I don't quite understand. Why is it "too many"? The article doesnt seem to discuss any disadvantages. Yet is calls people with the condition "sufferers". Is the article of poor quality? Capuchin 14:47, 18 September 2007 (UTC)

Polycythemia vera lists many nasty reasons you wouldn't want that particular brand of it. Someguy1221 16:08, 18 September 2007 (UTC)

Suspension of Disbelief

This is a question of psychology. As I am not a psychiatrist or a psychologist, please keep your answers on the simple, non-technical side. Thanks. I don't quite understand this. Can someone please explain? When I watch a film or a TV show, my brain knows and understands that the whole thing is "fake" and not truly happening in real life. A physical example: when I see a character get stabbed ... my intellectual side knows that it is just an actor, reading from a script, with a fake knife and fake blood as props. That is, a real person did not just suffer a real stab wound from a real murderer with a real knife and is now bleeding real blood. An emotional example: when I see a husband/wife argue and fight and get a divorce on a soap opera ... my intellectual side knows that it is just a group of actors, reading from a script, with no real fight or real divorce involved. So, this is my question. If the intellectual / intelligent part of my brain knows and realizes and accepts this, how exactly is it that a film or TV show can get me scared or nervous or happy or sad or whatever? In other words, why do people get scared / nervous / frightened / upset when they see the shark attacking in Jaws and they "know" that the whole scene is a fake / a sham? What is happening with the brain that allows us to experience "fear" in such an irrational manner? (Irrational = "I know that this is all fake and not really scary, yet I am still scared.") Why do people get happy / sad etc. when fake characters on a soap opera engage in a fake wedding or a fake divorce or a fake fight or a fake death or whatever? (fake=fictitious) How is it that the rational / thinking side of our brain / intellect gets "fooled", if you will, by the film or TV show or acting or writing, etc.? Thanks. (Joseph A. Spadaro 05:00, 18 September 2007 (UTC))

Well, I found a paper on it. Here. Someguy1221 05:12, 18 September 2007 (UTC)

I think empathy has a lot to do with it. We are able, and all too willing, to put ourselves in the shoes of the protagonists and "experience" what he or she is going through emotionally. Rockpocket 06:16, 18 September 2007 (UTC)

Our brain hasn't evolved to deal with actors. Capuchin 11:42, 18 September 2007 (UTC)

As with most systems of any complexity, the brain has layers of interpretation from the lowest level perception of colours, shapes, motion, sounds, etc - though the level that recognises people, sharks, water - then into the level that produces 'gut reactions' of surprise, fear, etc - then the higher levels of 'what to do about this'. It's likely that only the highest levels of processing are able to assemble enough context together to realise that this is all fake - the lower levels of processing having already acted on the basis of the information being real. SteveBaker 13:13, 18 September 2007 (UTC)

I am not sure how much empathy comes into play, I have a marked lack of empathy and I don't think I enjoy movies any less than the next person. Although I admit I do prefer action to romance, but that may be more to do with my gender. If you can identify with the situation the actors are in it may illicit more of an emotional response perhaps. Lanfear's Bane 15:42, 18 September 2007 (UTC)

Our article on empathy is a little, ahem, uneven to put it politely, but there are several definitions of empathy. The common one I knew about growing up was, as you suggest, being sympathetic (compassionate) about someone's situation. A wider definition is more about identifying with the other person, putting yourself "in their place", which might be more like what Rockpocket was talking about. You become scared or sad not because you feel sorry for the characters, but because you see yourself in their predicament. Also see Emotional contagion, though the article needs a lot of fact-checking and referencing, etc. Matt Deres 16:28, 18 September 2007 (UTC)

Methanol poisoning

If ethanol treats methanol poisoning, why is alcoholic beverages that contain a small amount of methanol dangerous? Jack Daw 14:20, 18 September 2007 (UTC)

Ethanol DOES NOT treat methanol poisoning.87.102.7.192 14:25, 18 September 2007 (UTC) The article on methanol states that ethanol may be used in cases of methanol poisoning to compete with the methanol for the 'enzyme' that breaks down methanol into harmful components.. This assumes that the breakdown products of ethanol are less harmful than those from methanol. This doesn't stop methanol and ethanol from being poisonous it's just than ethanol is less worse.87.102.7.192 14:29, 18 September 2007 (UTC)

Considering that ethanol is a widely socially accepted form of intoxication and not comparably a poison at all, which methanol is, we can quite safely assume "that the breakdown products of ethanol are less harmful than those from methanol". Jack Daw 15:32, 18 September 2007 (UTC)

A lot depends on the concentrations required to achieve the effect. Ethanol is most definitely toxic in sufficient quantities - we normally drink the stuff heavily diluted with water. SteveBaker 16:46, 18 September 2007 (UTC)

acetaldehyde and acetic acid are far less toxic than formaldehyde and formic acid, because they are more reactive.--134.76.234.75 17:28, 18 September 2007 (UTC)

So what's the answer to this question, are alcoholic beverages containing small amounts of methanol dangerous or not? —Preceding unsigned comment added by 12.217.199.246 (talk) 23:06, 18 September 2007 (UTC)

Yes. In fact all alcoholic beverages are dangerous. In fact everything is dangerous.

Just how dangerous depends, among other things, on how small is small. Poorly made moonshine can definitely contain enough methanol to be a problem. The mere fact that it also contains ethanol is not something you can rely on to protect you, because the ethanol may not monopolize the alcohol dehydrogenase for long enough for your kidneys to remove the methanol from your blood. --Trovatore 02:51, 19 September 2007 (UTC)

Breast size

How many years after first period do the breasts stop growing? --124.254.77.148 14:41, 18 September 2007 (UTC)

They never stop.87.102.7.192 15:06, 18 September 2007 (UTC)

It's going to depend on the individual, of course. We have an encyclopedia article on puberty that may prove useful. Friday (talk) 17:04, 18 September 2007 (UTC)

Both of the above answers are considering different issues. The female breast will mostly stop increasing in size some time after puberty. However as with all living body parts, it does not stop growing until you die. There is constant cellular regeneration as well as some specific changes during pregnancy. Even the size fluctuates somewhat outside of pregnancy. Breast covers this in some detail Nil Einne 21:16, 18 September 2007 (UTC)

erm breasts do get bigger with age (after puberty whatever that is) - that is I haven't yet seen teenage girls with 54DD breasts yet is not uncommon in women of a mature age..87.102.116.240 17:12, 19 September 2007 (UTC)

Read my response carefully. I said sometime after puberty. The precise time varies but it would AFAIK usually be in the late teens of perhaps early adulthood. (This ref [1] suggests you will usually know the final size by 17-18 although obviously there will be some who continue past then) An actually I'm pretty sure natural 54DD breasts are quite uncommon in women of a mature age (although more common then in teenage girls obviously) Nil Einne 20:20, 19 September 2007 (UTC)

Also, remember that breast size fluctuates with weight - if you lose a lot of weight your breasts often shrink in proportion, and similarly, if you gain weight, you gain breast size, as more fat is stored in them. My grandmother has giant ones - but she's a very large woman (and apparently had thyroid cancer, so that could be a cause). Mine fluctuate from a 36D to a 34C when I go from around 170lbs to 150 or so. It's all in how much fat is behind them, sort of pushing them out. Kuronue | Talk 23:38, 21 September 2007 (UTC)

Daisies and temperature

Can real daisies alter a planet's surface temperature the way they can in DaisyWorld? If so, could we theoretically reduce global warming by seeding large areas with white daisies, or delay the early stages of the next ice age using black daisies? NeonMerlin 15:57, 18 September 2007 (UTC)

I suppose so - the effect of the polar ice (white, shiney!) melting and being replaced by seawater (dark) is measurable in terms of increasing the effect of planetary warming...so I guess if you could plant enough daisies, it would have an impact too. It's obviously not a particularly practical scheme though - the areas covered would have to be enormous - and the consequential impact on biodiversity would undoubtedly be serious. SteveBaker 16:44, 18 September 2007 (UTC)

I dunno, but it's similar to a Snowball Earth. I wonder, though, how reflective white daisies are to IR. --Reuben 19:46, 18 September 2007 (UTC)

Yeah - it's hard to say. I'd hazard a guess that they were more reflective than green plants though - leaves are designed to absorb sunlight - petals aren't. SteveBaker 20:54, 18 September 2007 (UTC)

If they are like in Daisyworld, planting daisies won't change the temperature. The numbers of each shade of daisy will move towards equilibrium. — Daniel 22:43, 18 September 2007 (UTC)

That's just because it's a contrived example though. They set it up so that black daisies grow better in cool temperatures and white ones prefer the warm. As the temperature rises, the number of white daisies goes up and the number of black reduce - this causes the white ones to reflect more heat away resulting in the temperature dropping. No matter which way the temperature swings, the daisy growth rates will adjust and pull the temperature back to something they can both tolerate. This doesn't really mimic anything in the real world because the black daisies might very well evolve to be more heat-tolerant in order to out-perform the white daisies on warm days, which would allow the temperature of the planet could spiral upwards in an uncontrolled manner. Still, as a teaching tool, it's not bad. SteveBaker 14:33, 19 September 2007 (UTC)

It's not entirely contrived. After all, the black daisies themselves absorb more heat from sunlight than the white ones. So if both types had the same limits on their absolute heat tolerance (perhaps due to hard physical limits), the white daisies would be expected to do somewhat better at high temperatures and vice versa. Of course, it's still an extremely simplistic model. —Ilmari Karonen (talk) 20:25, 19 September 2007 (UTC)

Liver

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This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

Treating methanol poisoning with IV vodka/whiskey?

Does this actually work in the real world? I've seen this used as a plot device in shows like Casualty and Holby City on several occasions. --Kurt Shaped Box 17:46, 18 September 2007 (UTC)

I cannot imagine any reputable medical facility would use something intravenously that wasn't meant for this route of administration. Surely medical grade ethanol would be preferable? Friday (talk) 17:51, 18 September 2007 (UTC)

In the storyline, it's usually the case that they've run out of ethanol - so they have to raid the drinks cabinet/go down the off-licence. Makes more interesting TV, I guess. There was a scene in House M.D. where Dr. House downs a bottle of whiskey with a methanol victim in order to flush the toxins from his system - instead of say, just hooking a bag to the guy's drip... --Kurt Shaped Box 17:54, 18 September 2007 (UTC)

Well, it'd be sterile... -- Flyguy649 ^talk _contribs 17:58, 18 September 2007 (UTC)

Not saying that this is a healthy thing to be doing (or even a good idea - so don't try it, kids) but I used to know of someone whose party trick was to shoot whiskey into his veins. It didn't kill him - well he was still alive a couple of years ago, at least. He was a roadie for my friend's band - it was all very rock 'n' roll... --Kurt Shaped Box 18:30, 18 September 2007 (UTC)

To answer the question: it's possible, but I'm not sure. I know ethanol is used to treat isopropyl alcohol poisoning, so it's quite possible that it would be used for methanol poisoning. The reasoning behind ethanol's use in isopropyl is that ethanol is competitive to alcohol dehydrogenase. Alcohols, by themselves, aren't nearly as toxic as what they're broken down into (i.e. aldehydes), so the reasoning behind using ethanol in cases of isopropyl poisoning is to simply keep alcohol dehydrogenase busy while isopropyl is being naturally excreted by the kidneys (since it's a small enough chemical and since ethanol is also a diuretic). So, while the person will get ridiculously drunk, he'll live. Also, as far as I know, that's the only prescribed treatment if I remember correctly. So, it would make sense that the same approach would be used in cases of methanol poisoning, but again, I'm not certain. As to the IV route, I haven't heard of it being used. From what I've seen in the ethanol-countering-isopropyl route, it's just given PO (by mouth), since alcohol is irritating to connective tissue and it's readily absorbed from the gastrointestinal tract. --slakr^\ talk / 18:44, 18 September 2007 (UTC)

... which also reminds me. Everything from the GI tract gets first-pass at the liver, so it's a more direct route than IV/IM anyway. --slakr^\ talk / 18:49, 18 September 2007 (UTC)

I think you're thinking of ethylene glycol, not isopropanol. Isopropanol is not really all that poisonous I think; mostly it makes you sick (alcohol dehydrogenase turns it into acetone, which is not all that bad). That makes it a somewhat less vicious way of protecting the government's revenues than denaturing with methanol.

By contrast ethylene glycol turns into oxalic acid, which destroys your kidneys, and methanol turns into formic acid, which makes you go blind. As you say, a little bit of alcohol (a "beer" as an earlier poster put it) will not protect you from this. You need to tie up all the alcohol dehydrogenase until all the ethylene glycol or methanol is removed by the kidneys, which could take some time. I think there's now a less damaging pharmaceutical for doing this, without the brain damage involved in staying hammered for a day or so. --Trovatore 19:10, 18 September 2007 (UTC)

Fomepizole is what you are referring to, but in veterinary medicine it's still fairly common to use ethanol (usually vodka) IV for ethylene glycol poisoning. This is due to the cost of fomepizole and the fact that not everyone keeps it on hand. Interestingly, ethanol, not fomepizole, is the treatment of choice in cats. --Joelmills 19:40, 18 September 2007 (UTC)

Acetone is toxic through ketoacidosis, a condition one wants to avoid. Beer is of far too little of a concentration of ethanol, so whisky (or another high-proof spirit) is used instead. Saturation of alcohol dehydrogenase occurs rather easily with oral absorption of ethanol, as referenced by the linear breakdown curve that countless law enforcement agencies and learn-to-drive schools love to parade around. --slakr^\ talk / 19:22, 18 September 2007 (UTC)

I'm not claiming that isopropanol, or acetone, is exactly good for you. The isopropanol article says While large quantities of isopropanol can be fatal if left untreated, it is not nearly as toxic as methanol or ethylene glycol. The acetone article says Relatively speaking, acetone is not a very toxic compound; it can, however, damage the mucosa of the mouth and can irritate and damage skin. Accidental intake of large amounts of acetone may lead to unconsciousness and death. So I still sort of doubt that you're thinking of ethanol being used to treat isopropanol poisoning. It's much more likely that you're thinking of ethylene glycol, or methanol. --Trovatore 02:19, 19 September 2007 (UTC)

Batteries

Hi all,

If I hook a battery up to an LED, with the appropriate resistor in series, and leave it on, the battery will eventually run out. If I hook up a bigger battery (more volts, say, a 12 Volt battery), and change the resistor so that the correct amount of current is flowing, will the battery last longer? Or will the increase in resistance mean that the battery will be doing more work so there would be no difference?

Thanks! --Mary 18:05, 18 September 2007 (UTC)

See Ohm's law and Power (physics). --slakr^\ talk / 19:02, 18 September 2007 (UTC)

Perhaps more accurately, you'll want to check the amp-hour rating (generally expressed in milliamp hours, or mAh) to estimate battery duration. Voltage really has nothing to do with this, as not all 1.5V batteries are created equal -- do a quick comparison of an AAAA battery with a D-cell. Anyway, to estimate your battery use, divide the battery's mAh rating by the current pulled by your circuit. Note that stacking batteries in series does not mean that you add their mAh ratings together. — Lomn 20:07, 18 September 2007 (UTC) —Preceding unsigned comment added by Lomn (talk • contribs)

Take a look at Battery (electricity) for some averages. Note that although it'll be useful to predict how long your battery will last with a given load (the LED case), it doesn't directly tell you how much energy the battery stores (as explained in the linked page). For example a latern battery which usually AFAIK has 4 F type cells has a mAh of an F type cell. However it's delivering 4x the voltage so has a store of 4x the energy. Assuming you have a perfect voltage regulator (obviously such a thing can't exist) you could power a device for 4 times the length you could with a single F type cell. When you're simply using a current limiting resistor obviously the mAh is all that really matters Nil Einne 21:00, 18 September 2007 (UTC)

Iris Color Change

Are there any reported cases in which a person's iris color had changed from say, dark brown to blue or green, without any diseases involved? --WonderFran 19:30, 18 September 2007 (UTC)

Yep—this came up at the Ref Desk a few months ago (link to archive). There's some good information in Eye color#Eye color change and Iris (anatomy)#Color. TenOfAllTrades(talk) 20:26, 18 September 2007 (UTC)

Want to buy a new parrot/parakeet - suggestions?

I already have a Sun Conure, which is a lovely bird. But she can be a handful at times and very strong willed and independent. I want to get another parrot (to keep alongside her) but I want one that's a lot quieter, tolerates being held and stroked more and doesn't bite without warning as much. Anyone know of any species like this? Thanks. --90.240.248.51 20:57, 18 September 2007 (UTC)

Don't forget to investigate whether your two pets will get along well. It sounds like there is a risk the Sun Conure might attack any new pet. Also, while I've never kept birds as pets, I would presume that as with most pets their temperaments can be quite variable. Although certain breeds may be much more docile, there is no guarantee the temperament will be what you want. You might want to consider adopting an adult from someone who has kept the bird for a while and say knows the temperament Nil Einne 21:11, 18 September 2007 (UTC)

Yep, temperament varies from parrot to parrot - though in my experience, most of them are prone to fits of pique (i.e. sudden biting) if you unwittingly annoy/scare them. The fight/flight response is never too far below the surface in these birds. I've heard that Bourke's Parrots and Lineolated Parakeets are generally pretty calm and quiet as far as psittacines go - but it's all relative. Don't get a Lovebird - it's a complete misnomer. As scrappers and biters go, they're right up there (don't let the cuteness fool you). Separate cages for the Conure and your new bird are a must - at least at the beginning. --Kurt Shaped Box 21:29, 18 September 2007 (UTC)

Color of beta-Carotene

I noticed that beta-carotene is used to color margarine and vanilla ice cream - which are yellow, not orange like carrots which are said to get their color from beta-carotene. Does anyone the real color of beta-carotene? Icek 22:31, 18 September 2007 (UTC)

you can use this to find the exact color of beta-carotene

http://www.ch.ic.ac.uk/wiki/images/0/0d/SpectraCarotene.jpg —Preceding unsigned comment added by 12.217.199.246 (talk) 23:10, 18 September 2007 (UTC)

Carotene, like many other complex pigments, has different colors at different concentrations. "Carotene is a common ingredient used in commercial colored oleomargarine to impart a yellow color. A typical useage level is five (5) milligrams beta-carotene per pound of oleomargarine, or 0.0011%. At this level, the color is light yellow. At 0.011% the color is still yellow. At 0.11%, the color is orange-brown and at 1.1%, the color is reddish-brown." [2] —Keenan Pepper 02:58, 19 September 2007 (UTC)

An interesting side note is that for many years it was illegal in most places to color margarine yellow (thanks to dairy industry lobbying), and in some places they even forced producers to dye it some unappetizing color. --Sean 16:27, 19 September 2007 (UTC)

The things one can learn around here! "Bootleg colored margarine became common, and manufacturers began to supply food-coloring capsules so that the consumer could knead the yellow color into margarine before serving it." margarine#History. DMacks 00:33, 20 September 2007 (UTC)

Hang on, vanila ice cream is white...not yellow

Depends what type you buy, here in the UK it's invariably yellow. Capuchin 10:59, 21 September 2007 (UTC)

September 19

Is this what it appears to be?

Just seen this video. Is this actually a gull seeing a female mallard being attacked (raped?) and deciding to intervene and save her? Hmmm. Opinions? --Kurt Shaped Box 00:17, 19 September 2007 (UTC)

Rape is a form of assault where one individual forces another to have sexual intercourse against that person’s will. I don't think rape really applies outside of humans. Lanfear's Bane 09:31, 19 September 2007 (UTC)

An interesting little scenario. The little I know about gulls leads me to believe that their goals in life are driven by food, territory, food, sex and food. (depending on the time of year) The setting here is some sort of pond or lake where the birds are obviously habituated to human presence and thus probably are used to human food handouts. I think the gull is more interested in the possibility of free food which she/he thinks might be available within the scrabble of bodies. Even the Canada goose has a gander. (ooh, pardon my pun!) I have noticed in places like this where there are largish numbers of birds all looking for a bit of free fodder, whenever there is a bit of a kerfuffle or argy-bargy between a couple of birds all the others tend to gravitate to that point as they maybe associate it with the frantic activity involved in filling your gizzard before anyone else and thus the presence of food.

It also crossed my mind that the gull may have been looking to take the opportunity to finish the stricken duck off itself and dine on some fresh meat. I've seen gulls mercilessly (mercifully? I don't think that the gull really cares either way) dispatching injured pigeons on several occasions. --Kurt Shaped Box 12:48, 19 September 2007 (UTC)

With regard to the the above comment about rape only being a human concept, mallard rape has been referred to for many years and is characterised by the absence of precopulatory behaviour normally seen in these birds and by the additional perceived reluctance of the female to engage in copulation evidenced by her attempts to escape. What is more interesting is that this behaviour often stimulates other nearby males who attempt to join in. Look at this http://elibrary.unm.edu/sora/Wilson/v092n03/p0409-p0409.pdf for further information.Richard Avery 10:17, 19 September 2007 (UTC)

Still, as this does not involve humans it cannot be categorised as rape. Neglect to perform a mating ritual before copulation does not constitute rape. As for other male mallards joining in to classify this as mallard gang rape is bordering on ridiculous. Sounds like we are straying into the realms of anthropomorphism on this topic. Lanfear's Bane 10:32, 19 September 2007 (UTC)

Assumming an animal has the cognitive skills to form an intent to have sex (or not), then in my opinion, rape can exist in that species. Obviously most animals can't tell us their intent, but we can make an educated guess based on behavior, and some animals (e.g. primates, some birds, and dolphins) have mastered enough basic language skills to directly communicate simple desires. 76.231.189.193 17:33, 19 September 2007 (UTC)

Language isn't really required. If the female sticks her rear end up and waits, she's giving consent. If she runs away, she's not. Pretty simple. StuRat 05:49, 20 September 2007 (UTC)

I remember reading about the mallard rape. It did raise a lot of questions as to whether "rape" can occur outside of Homo sapiens. I guess it comes down to whether murder, theft, incest or other human crimes also count. You can find equivalents in nature of many human crimes. This really isn't a Science question but rather Ethics. -- JSBillings 11:49, 19 September 2007 (UTC)

I wish that I hadn't mentioned the 'r-word' now. I didn't mean to start another one of these circular debates... :( --Kurt Shaped Box 12:39, 19 September 2007 (UTC)

My take on the use of 'rape' is that in this context it is an ornithological term to describe a specific pattern of behaviour which appears analogous to the human activity of this name. My sympathies KSB, like Forrest Gump said "Life is ..... Richard Avery 18:15, 19 September 2007 (UTC)

If you, as a human had seen that happening in front of you, you'd have tried to stop it, wouldn't you? Because preventing cruelty and suffering would be the right thing to do if it was within your power to prevent it. Are we that arrogant as a species that we really do believe that we are the only ones with views on what is acceptable and unacceptable? —Preceding unsigned comment added by 84.71.180.141 (talk) 19:39, 19 September 2007 (UTC)

Well I will be very interested when this case hits the duck courts to hear the outcome. How do you punish a duck anyway? Are duck judges severe? As for animals 'desiring' and 'consenting' these are again human emotions and actions. They do not exist outside in the animal kingdom. It's not a case of being so arrogant that humans believe their views are the only acceptable ones - it is however a form of arrogance to project human qualities onto animals and label their actions or instincts with human terms and equivilents. It also doesn't come down to ethics, again, these are human traits. Rape does not exist outside of humans. Or, if I am wrong, feel free to bring one of these thinking, talking, feeling, desiring ducks to me to explain duck law in regard to rape and then I will retract all of my recent comments. Lanfear's Bane 09:33, 20 September 2007 (UTC)

So the only way you'd accept that any animal has thoughts, feelings, desires or agency independent of some kind of mechanistic "instinct" is if it could articulate these qualities to you in English? Hmmmm, talk about arrogant. Maybe you could learn sign-language and find a signing chimp to communicate with, meet 'em halfway... 38.112.225.84 15:02, 20 September 2007 (UTC)

Oh that's right, I forgot that chimps could speak sign-language. I am always wondering what they are talking about on those nature documentaries or in the zoo. Lanfear's Bane 08:48, 25 September 2007 (UTC)

You know, my gerbil ate its babies because a child touched them. Should I take her to court? Seriously, humans and animals are different, especially when it comes to ethics. The way this argument is heading, one could conclude that animals shouldn't be predators anymore. :D --JDitto 01:43, 26 September 2007 (UTC)

Chemical Nomenclature

When considering the hydrogen in a bond, is it treated like a non-metal or a metal? For example, with the compound HF, would it be called "Hydrogen fluoride" (ionic conjugation) or "Hydrogen monofluoride" (covalent conjugation)? Thanks. Acceptable 01:57, 19 September 2007 (UTC)

Hydrogen is named as a metal in compounds with a more electronegative element (for example hydrogen fluoride) and as a non-metal in compounds with a less electronegative element (for example sodium hydride). —Keenan Pepper 02:24, 19 September 2007 (UTC)

Quantum physicist's name?

Someone suggested that I should look into the work of a certain quantum physicist, but now I can't recall the scientist's name. All I can remember is that it sounded something like Muset or Mussay, but I'm not sure. I looked on the list of physicists and no one there sounds like the right one. I know it isn't Harrie Massey or Amédée Mouchez — I was told this man was a contemporary of Star Trek creator Gene Roddenberry. (I hope I'm not waaaaay off on the name, but it's possible!) Thank you kindly. — Michael J 02:25, 19 September 2007 (UTC)

Could maybe be Albert Messiah (last name pronounced roughly mess-ee-yah, not messEYEah)? He wrote a standard graduate or advanced-undergrad text on QM, I think. --Trovatore 02:31, 19 September 2007 (UTC)

Maybe it could be a first-name, Murray Gell-Mann? --Taktser 04:25, 19 September 2007 (UTC)

Archaea or Bacteria, which came first?

Greetings! I finished reading the articles archaea and bacteria, but I still have a doubt as to which domain appeared first on our planet? From what I can gather, the species of the domain archaea tend to be hyperthermophiles living near geysers, that Earth during the Archean eon was much warmer than today, that species adapted to survive at lower temperatures evolved later than the hyperthermophiles, and that the species of the domain bacteria can adapt to a much wider range of temperature environments. Would this mean that archaeon appeared before bacterium? In the article archaea it also states that the archaea are more closely related to the more advanced eukaryotes, would that mean it was bacteria first followed by archaea? Thanks in advance! --Taktser 04:07, 19 September 2007 (UTC)

I think there is no conclusive evidence for one or the other. Studying different genes suggest a lot of gene swapping occured and there is no simple tree structure of organisms. There are more than just extreme thermophiles! Graeme Bartlett 12:30, 19 September 2007 (UTC)

As far as I'm aware, archaea are usually believed to be more closely related to eukaryotes then bacteria. I.E. bacteria diverged first. However I don't know whether there is really an answer to which appeared first. It's a bit like asking which appeared first humans or chimpanzees (or orangutans or something)? The answer is neither since both are modern species. It will depend on your definition of what's a human and what's a chimpanzee. Nil Einne 20:11, 19 September 2007 (UTC)

You know, they could have at the same time too. --JDitto 01:46, 26 September 2007 (UTC)

What is the long term result of electrolysis of water?

During electolysis of water stand alone hydrogen and oxygen gas are split from the water compound. My question is what happens to these gases after this? Can they ever get together again? Or is the process which occurs everywhere lead acid batteries are used, especially in motor vehicles, reducing the global supply of water and accelerating droughts and climate change generally?Vorc 04:57, 19 September 2007 (UTC)

From Hydrogen: "In 1766, Henry Cavendish was the first to recognize hydrogen gas as a discrete substance, by identifying the gas from a metal-acid reaction as "inflammable air" and further finding that the gas produces water when burned."

Another word for burning is combustion:

"A simpler example can be seen in the combustion of hydrogen and oxygen, which is a commonly used reaction in rocket engines:

2H
₂ + O
₂ → 2H
₂O + heat

The result is simply water vapor."

See also Fuel cell, in which hydrogen can be oxidized to produce electricity and water.

(ec)They can get together again. Actually, if you put hydrogen gas and oxygen gas together at room temperature, they will spontaneously reform water. This is a slow process however, unless you provide some spark for the reaction to speed up, in which case you might get something like The Hindenburg. Someguy1221 05:07, 19 September 2007 (UTC)

This was one of my science teachers favourite tricks. As far as I recall, we mixed oxygen and hydrogen in a tin can, pressed the lid on, and somehow ignited it. There was a bang, the lid flew off, and inside the can were a few drops of water.--Shantavira|^{feed me} 07:23, 19 September 2007 (UTC)

Please be careful or people might copy your bad memory... The Hindenburg was lots of nitrogen from the atmosphere to slow things down. If you mix pure hydrogen and oxygen together in a tin you have got a potential gas detonation on your hands which is potentially seriously dangerous (to your hearing in particular)>> some people do it in a balloon but I still wouldn't recommend it. The tin can trick is normally to fill the can with hydrogen (or methane) and light the gas diffusing out of a small hole: you get a brief flame because the mixture in the can is too rich to burn but then enough air gets into the can to mean the flame goes back into the can. Heat generated increases pressure and unless the tin lid can keep about 8 bar in (no, it cannot) you get a loud pop. Any, not the pure gases (the oxygen comes with the rest of air). --BozMo talk 11:42, 19 September 2007 (UTC)

The Hindenburg wasn't helped by the flammable chemicals that they used to paint the thing - if the problem had only been the hydrogen, it would have been a much smaller problem. Hydrogen (being very light) would have carried the fire upwards and away from the passengers and crew - and that would have prevented all of the gas-filled cells from burning, allowing the craft to drift more slowly towards the ground. The flames you see in that infamous newsreel are far too luminous to be hydrogen flames - what you are seeing is the envelope burning. Indeed only about a third of the people on board died - most of those because they jumped from the gondola - the remainder being crew members up at the nose of the craft. Every person who stayed on board inside the gondola, survived. It's unfortunate that this was such a notorious event because a properly designed hydrogen-based Zepplin is a perfectly reasonable aircraft that would be vastly cheaper to run than modern helium-based craft. With modern materials for the gas bags - proper monitoring of oxygen levels inside those bag - construction techniques to isolate a disaster in one gas bag from destroying the others in a chain-reaction - and control of arcing due to static buildup, there is no reason why we couldn't still fly craft like the Hindenburg with at least the degree of safety that we fly jumbo jets. SteveBaker 14:15, 19 September 2007 (UTC)

I disagree. The main safety risk of blimps, dirigibles, zeppelins, and hot air balloons (or any other lighter-than-air craft) is that they can't be controlled in strong winds, which are common and not always predictable. The risk from containing an explosive gas is secondary to this risk. (I do agree that hydrogen-filled craft are not as dangerous as they appear, however.) StuRat 03:23, 20 September 2007 (UTC)

I agree that wind is a major issue when these gizmos are close to the ground - but they have so many advantages in some applications that this problem can be worth circumventing. Forget about carrying passengers - think about freight. Ships are an efficient way to carry goods around the world - but you run into trouble when there are no convenient oceans nearby. Replace a ship with a truly gargantuan airship and suddenly that restriction has gone away. The dramatically smaller drag factor in moving through air rather than water should make airships cheaper to operate and a lot quicker too. But yes - landing and taking off again is a tricky thing (but then so is docking a ship in a heavy current). Lowering cables to the ground and winching the thing down seems like the smart solution. There are also applications for airships in replacing communications satellites and terrestrial radio antennae. The relative cheapness of Hydrogen compared to Helium - and the vastly improved lift capability per unit volume is what is needed to make these things economically feasible - but the "Hindenburg factor" means that nobody wants to invest money in them...which is a shame because the problems that caused the demise of the Hindenburg are easily overcome. Also, only about 36 people and two dogs died in the accident - two thirds of the passengers and crew survived - compared to the 89 that died (just 30 survived) in an MD-80 airliner as it attempted to land in Bangkok a couple of days ago. I guarantee that the Hindenburg disaster will be remembered around the world 100 years from now - but One-Two-GO Airlines Flight 269 will largely be forgotten in...well, come to think about it, I think it's pretty much already been forgotten everywhere outside Thailand. SteveBaker 14:03, 20 September 2007 (UTC)

When you electrolyse water with direct current electricity, you get oxygen coming off of one of the electrodes and hydrogen coming off of the other. This enables one to capture the hydrogen safely without oxygen mixed into it - and if you do that, there is no immediate danger of the gas exploding. SteveBaker 14:15, 19 September 2007 (UTC)

Most of the hydrogen and oxygen will eventually become water again. However, some of the hydrogen may rise to the upper atmosphere and be blown away from the Earth by the solar wind. Of course, nobody would be able to convert enough water to hydrogen and oxygen for this to have any noticeable effect. However, if they could, we would eventually have more oxygen in the air and less water in the oceans, yes. StuRat 03:33, 20 September 2007 (UTC)

It is important to note that there is a very large activation energy for the combination of H2 and O2. Without an ignition source the reaction is very slow —Preceding unsigned comment added by Shniken1 (talk • contribs)

Wouldn't lightning provide the needed activation energy ? StuRat 04:33, 21 September 2007 (UTC)

With deep-cycle lead-acid batteries you can use caps with a catalyst (platinum?) that reforms the gases into water, so that the batteries need less water added later.Polypipe Wrangler 15:08, 20 September 2007 (UTC)

Methanol and Ethanol

If ethanol is used to treat methanol poisoning, is it possible to mix the two at a ratio so that it's no longer toxic (as in methanol toxic)? --antilived^{T | C | G} 05:15, 19 September 2007 (UTC)

Get it into your thick head. Ethanol is poison. Methanol is poison. A mixture of ethanol and methanol is poison. Ever wonder what happens to young people when they drink a lot of alcohol? That's right, they get alcohol poisoning. So whether you drink ethanol or you drink methanol, you are putting poison into your body. The idea that you can mix ethanol with methanol and come up with a solution which is "no longer toxic" is utter rubbish. 210.49.155.132 13:20, 19 September 2007 (UTC)

Yes - agreed. Methanol is horribly toxic - it causes blindness in even quite small doses. Ethanol is less toxic - but it's still nasty stuff in high concentration. If you have life-threatening methanol poisoning then ethanol (being the lesser of two evils) might save your life (but probably not your eyesight)...but the idea that these two poisons somehow cancel out is ludicrous. SteveBaker 13:55, 19 September 2007 (UTC)

I think the question antilived was trying to ask was whether you could create a mixture of the two so that the methanol poisoning would be "treated" by the ethanol consumed with it. From what I can understand from this website [3] Methanol is toxic because it is broken down by the enzyme alcohol dehydrogenase in the liver to form formic acid and formaldehyde. Ethanol in large quantities is administered to a methanol poisoned patient because it will compete for the enzyme with the methanol. This slows down the metabolism of methanol allowing doctors to haemodialysis it away or clear the body through the kidneys (which occurs much slower than being broken down in the liver). Just drinking a mixture of ethanol and methanol is not enough because some of the methanol will still be metabolized in the liver, just over a longer period of time, meaning you are still going to be poisoned. You could try to design the solution so that the amount of methanol metabolized would be minimal and would avoid side affects, but since everyone's body chemistry and alcohol metabolizing ability are different it would be difficult to predict the severity of the poisoning. **DISCLAIMER:** I am not an expert, and trying this would be REALLY REALLY REALLY dumb. Sifaka ^talk 15:27, 19 September 2007 (UTC)

Actually the idea that these two cancel each other out is about the easiest explanation you could give to someone who doesn't understand how methanol poisoning works. Methanol in and of itself doesn't cause the toxic effects. The effects come from byproducts of the breakdown of ethanol in the liver (by the enzyme alcohol dehydrogenase). These cause initially blindness, but it is not necessarily permanent. If treated with ethanol, the ethanol competes with the active site of the enzyme and is broken down into harmless by products. You could probably handle an intake of ~100 times more ethanol than methanol depending on how much methanol you have in you system (which would at least reduce the break down of methanol by a factor of 10^2). This does not take into account the fact that alcohol dehydrogenase has much more affinity for ethanol than methanol. So you can essentially stop the breakdown of methanol into toxic molecules by drinking/injecting enough ethanol. Then methanol is removed only by the kidneys (like 10000:1 Kidneys:Liver) and viola no lasting effects if caught early. If someone had a serious case of methanol poisoning, you really wouldn't be worried about their sight anyway. You would be more worried about keeping formic acid and formaldehyde out of their blood and lungs.
Now I'm certainly not suggesting that it is as simple as getting drunk. You need to go to the hospital so your vital signs can be monitored. CNS depression from both alcohols can cause bradycardia and hypoxia, but this would be easily compensated for in a hospital setting.
And if at this point your still thinking, "But ethanol is toxic too!?" Well, in terms of toxicity, methanol is an F5 tornado and ethanol is a dust devil. The risks of this treatment are essentially negligible in comparison to the almost certain death of someone with a serious case of acute methanol poisoning.
There was apparently an editing conflict.
Mrdeath5493 15:29, 19 September 2007 (UTC)

Ethanol is not some sort of cure that neutralizes all effects of methanol rendering it harmless - you're thinking like it's some sort of acid base reaction, it's not.87.102.116.240 16:36, 19 September 2007 (UTC)

Why are there suddenly so many questions about ethanol being used to treat methanol? — Daniel 22:24, 19 September 2007 (UTC)

You read stuff here and it makes you think of other, related stuff to ask that you never, ever thought that you wanted to know before? --Kurt Shaped Box 22:58, 19 September 2007 (UTC)

Perhaps they are writing a fiction book and need a "home cure" for methanol poisoning ? StuRat 04:56, 20 September 2007 (UTC)

I thought my explanation was pretty clear, but obviously I'm talking over your heads. It is true that ethanol doesn't immediately neutralize methanol's toxic properties, but you really wouldn't know the difference by observing someone being treated with ethanol for methanol poisoning. It will make them better, almost immediately. Even if there was permanent damage, proper treatment will pretty much completely reverse the course of the pathology within 36 hours. There is only one other option for treating methanol poisoning and it is Fomepizole. I live in Arkansas and know for a fact that there are regional ER's that protocol ethanol as a remedy. Sorry to everyone out there that thinks they know what they are talking about, but this treatment works, very well.
Mrdeath5493 05:51, 20 September 2007 (UTC)

But that wasn't the question. What was asked was whether you could mix them from the start in such a way that the methanol wouldn't poison you. The treatment you're talking about requires administration of ethanol on an ongoing basis, until the methanol is out of the system; it's not good enough, I think, to give one dose up front.

All the more so if, as you said, "alcohol dehydrogenase has much more affinity for ethanol than methanol". Because that means the ethanol will get used up, and the body will make more alcohol dehydrogenase, and now the methanol is still around to be turned into formaldehyde (kidneys haven't had time to get rid of it), and the ethanol isn't there to prevent it anymore. --Trovatore 21:07, 20 September 2007 (UTC)

Trovatore, other than being completely wrong in your assumptions you are right. Notice the words "proper treatment" above. One dose probably wouldn't do it. The obvious solution is to add more ethanol (if what was there is gone). Normal saline + diuretic rings a bell too (increased action of kidneys). Also, dialysis can be used. I'm pretty sure that any competent Physician understands the basic concepts of biochemistry anyway.
Mrdeath5493 21:41, 20 September 2007 (UTC)

I don't believe you carefully read the original question. --Trovatore 21:46, 20 September 2007 (UTC)

Well, I don't think you read the Science help desk every day. There have been 2 other similar threads to this one and if read chronologically, you obviously see that most of the users that usually answer questions on the desk don't think ethanol is a good treatment. So, I decided to do some extra homework. Here is a Quote from Current Medical Diagnosis & Treatment. 2007. Stephen J. McPhee et al.

Treatment [for methanol poisoning]

Emergency and Supportive Measures

For patients presenting within 30–60 minutes after ingestion, empty the stomach by gastric lavage (see Antidotes & Other Treatment-Gastric Lavage). Charcoal is not very effective but should be administered if other poisons or drugs have also been ingested.

Specific Treatment

Patients with significant toxicity (manifested by severe metabolic acidosis, altered mental status, and markedly elevated osmolar gap) should undergo hemodialysis as soon as possible to remove the parent compound and the toxic metabolites. Treatment with folic acid, thiamine, and pyridoxine may enhance the breakdown of toxic metabolites.

Ethanol blocks metabolism of the parent compounds by competing for the enzyme alcohol dehydrogenase. The desired serum ethanol concentration is 100 mg/dL. To achieve this, administer a loading dose of approximately 750 mg/kg orally or in a dilute intravenous solution (available from the pharmacy in 5% and 10% solution), and then provide a maintenance infusion of 100–150 mg/kg/h. The infusion will have to be increased to about 175–250 mg/kg/h during hemodialysis to replace dialysis elimination of ethanol.

Fomepizole (4-methylpyrazole; Antizol), blocks alcohol dehydrogenase and can be used instead of ethanol. A regional poison control center (800-222-1222) should be contacted for indications and dosing.

My regional poison control office just happens to be on the same floor as the college of pharmacy I attend. They said they recommend ethanol...Imagine that.
Mrdeath5493 22:03, 20 September 2007 (UTC)

If you read the threads carefully you'll see that few posters have said otherwise. There was one anon who said "ethanol DOES NOT treat methanol poisoning" but then immediately contradicted himself. Everyone else has argued against other aspects, such as injecting a non-medical-grade spirit or trying to make methanol "safe" by including enough ethanol with it. --Trovatore 22:46, 20 September 2007 (UTC)

So I should probably just pretend that you didn't offer an opinion directly contradictory to mine 5 posts up? All that stuff about ethanol leaving the system and methanol breaking down faster... If you hadn't, of course, I would not have pushed my point. On top of the doubts you raised earlier concerning my position, I was referring to this specific comment
"Ethanol is not some sort of cure..."
You are correct in your analysis of the previous posts; almost no one contradicts me there. It does seem, however, that the people who initially said something to the effect of "Treating methanol poisoning with ethanol is stupid..." have retroactively erased their initial statements or just edited them. So, I guess I am preaching to the choir even now.
Mrdeath5493 01:05, 21 September 2007 (UTC)

You shouldn't pretend anything. I never said ethanol was not a treatment for methanol poisoning. I said you couldn't drink a mixture of ethanol and methanol and expect the ethanol to protect you. If you read my comments otherwise, you read them wrong. --Trovatore 01:15, 21 September 2007 (UTC)

So this:
"the ethanol will get used up, and the body will make more alcohol dehydrogenase, and now the methanol is still around to be turned into formaldehyde (kidneys haven't had time to get rid of it), and the ethanol isn't there to prevent it anymore."
was in reference to a mixture of eth/meth in a glass and not about treating methanol poisoning?
My bad.
Mrdeath5493 01:34, 21 September 2007 (UTC)

Purpose of review articles from writer's perspective

Apparently scientists not working for a corporation have to publish in order to recieve grants. Does the publishing of review articles count towards this? If not, why do people write them? --Seans Potato Business 15:25, 19 September 2007 (UTC)

Publishing a review (depending on what it is) can count towards 'recognition' but won't really help to get grants (which need evidence pf original research usually).

However like all published written work payment is usually included.

Plus maybe they just like writing reviews - I'd do that for nothing on a topic that interested me.87.102.116.240 17:07, 19 September 2007 (UTC)

Surprising though it may seem, scientists actually do science - they don't just seek grant money. Publications are there to move science along - not just to get grant money. If publishing a review will help people to get closer to whatever it is they are working on - then writing one is a valuable use of a scientists time. Grants are a means to an end - they aren't the goal of science! (Although sometimes it seems like that). SteveBaker 17:53, 19 September 2007 (UTC)

"However like all published written work payment is usually included." Really? I've never paid nor gotten paid for journal articles. Maybe in some fields or some journals, but certainly the minority in the sciences I know. DMacks 18:20, 19 September 2007 (UTC)

I meant book reviews rather than literature reviews in journals.87.102.116.240 18:29, 19 September 2007 (UTC)

Further to DMacks, the authors often pay a "per page charge" to have articles published or to have colour figures. -- Flyguy649 ^talk _contribs 18:27, 19 September 2007 (UTC)

Note that when they do pay, it will usually be mentioned at the end of the article Nil Einne 20:03, 19 September 2007 (UTC)

When it comes to writing review articles, remember that this requires them to familiarise themselves with the literature and the work they're reviewing. While most scientists writing reviews AFAIK usually work in that specific area already so would already be fairly familiar with the literature, I suspect they would still learn something out of the process. Remember one of the best ways to test how well you understand something is to try and teach it. It may also be an opportunity for them to consider things to teach at university. Writing reviews aren't the only things they do for 'free'. Peer reviewing journal articles is also something most experienced scientists will do but they aren't paid for it. It's considered part of being a scientist. This is actually covered fairly well in Peer review Nil Einne 20:03, 19 September 2007 (UTC)

From a more political (and perhaps cynical) perspective, scientists will often have different hypotheses about scientific fields. Similar data can be interepreted in different ways and an experienced scientist may have a number of papers published in a field that supports one hypothesis, while another scientist may have a body of work that supports a conflicting interpretation. Review articles can help "sway" the scientific consensus towards one of these interpretations. Its no co-incidence that review articles will often contain many, many citations of the author's own original research papers. In a recent review (PMID 15985310) I read, 42 of the 113 citations were by the authors of the review. This has the added bonus of boosting the the impact factor of the journals the authors have published in, and the authors' own H-indices. Rockpocket 21:31, 19 September 2007 (UTC)

Regarding specifically whether you get "credit" for review articles: In my institution, which is a government lab, we have specific minimum requirements for number of original research papers per year. For us, review articles don't count towards this. ike9898 17:25, 20 September 2007 (UTC)

Developmental term I have forgotten

In some organisms, the presence and subsequent contact with of a large number of peers triggers a developmental change causing the individual to become larger than its peers and engage in cannibalistic behavior. I forget what it is called. Any ideas? Sifaka ^talk 15:32, 19 September 2007 (UTC)

Can you suggest one or two species that do this? It might make the search a little easier. SteveBaker 17:48, 19 September 2007 (UTC)

Sorry, I can't remember any in particular, although I think some examples were fish or lizard-shaped amphibians. I read about it so long ago... Sifaka ^talk 18:32, 19 September 2007 (UTC)

GOT IT!!! Cannibalistic Polyphenism It's now a redirect to polyphenism for now... Sifaka ^talk 19:14, 19 September 2007 (UTC)

I changed it to a redirect to the Cannibalistic Polyphenism section of polyphenism. — Daniel 22:17, 19 September 2007 (UTC)

Basic Axioms of Physics

I read somewhere that you could write the basic axioms of physics, which would describe much of the universe around us, on a single index card. I assume that by axioms, the meant the fundamental underlying assumptions. So, 1. Is this true? and 2. What would these axioms be? Czmtzc 20:29, 19 September 2007 (UTC)

I wouldn't really use the term 'axiom' with 'physics'. The axioms of arithmetic or euclidian geometry could certainly be expressed in so little space - but physics is about measurement and experiment. The idea of something being so self-evident that you don't need to prove it is kinda alien to that concept. Perhaps you don't mean 'axiom'...the basic equations of physics are certainly fairly compact - and indeed some physicists suggest that we can finally boil a 'theory of everything' down to an equation that you might fit in so little space - but that's the opposite of an axiom.

As an example, here are the axioms around which all of Euclidean geometry is based:

1. Any two points can be joined by a straight line.
2. Any straight line segment can be extended indefinitely in a straight line.
3. Given any straight line segment, a circle can be drawn having the segment as radius and one endpoint as center.
4. All right angles are congruent.
5. Parallel postulate. If two lines intersect a third in such a way that the sum of the inner angles on one side is less than two right angles, then the two lines inevitably must intersect each other on that side if extended far enough.

SteveBaker 20:52, 19 September 2007 (UTC)

• This might be relevant: Hilbert's sixth problem. --JWSchmidt 21:02, 19 September 2007 (UTC)

We do sometimes use "axiom" in physics to mean the fundamental equations that define a particular theory. For instance, you could say that the Schrodinger equation is an axiom of non-relativistic quantum mechanics. You don't prove it in a mathematical sense, you prove it by empirically confirming the predictions of quantum mechanics. I would choose the Einstein equation and the standard model lagrangian. You could write them both on an index card, if you have small handwriting for the standard model lagrangian! --Reuben 21:26, 19 September 2007 (UTC)

In so far that mathematical axioms are considered to be "true" they are empirically derived, just like physical axioms. They are also based on measurement; counting for example is clearly a measurement procedure. The predicitons of the "addition" axiom can be empirically tested by counting. Just count two heaps of apples, put them together, count again, and compare with the prediction by addition. You see - mathematics *is* physics. —Preceding unsigned comment added by 84.187.37.196 (talk) 22:21, 19 September 2007 (UTC)

I'm not sure a pure mathematician would agree with you. I think they would argue that arithmetic is a set of theorems that depend on the axioms and the axioms are just assumptions built into the thing at the beginning. If, as a result, addition appears to be applicable to the problem of counting things in the real world then all well and good - but the math doesn't depend on it. Notably, the axioms of Euclidean geometry that I posted earlier are not things that are necessarily true in the real world. Mathematicians have a lot of fun by denying one or other of the axioms - or negating one altogether and seeing what pops out. Denying Euclids parallel postulate results in all sorts of interesting non-Euclidean geometries that are interesting but do not necessarily represent 'real world' stuff. In fact, in normal 3-space in our universe, several of those postulates aren't true because of the bending of space-time due to gravity. That in no way invalidates any of Euclids theorems because they only apply in the event that you assume the axioms are true. SteveBaker 22:31, 19 September 2007 (UTC)

As a pure mathematician myself, I suggest the axioms of ZFC (especially replacement and choice) as an antidote to the idea that all mathematical axioms are closely derived from physics. While some would still argue that all mathematics is empirical in nature, most of it has to be extremely indirect. Algebraist 22:57, 19 September 2007 (UTC)

There is a fundamental difference of opinion among pure mathematicians on this point. Oversimplifying wildly, there are two basic schools, the "realists" (or "Platonists"), and the "formalists" (in which camp, just for now, I'm including fictionalists and people like George Lakoff). For a realist, mathematical objects are real (though non-physical) objects, and axioms are not arbitrary but are supposed to describe those things. For example ZFC should describe the von Neumann hierarchy (note that the von Neumann hierarchy is much more intuitively "natural" than ZFC itself). I lean to the realist school myself, and would argue that there is an empirical component to the discovery of axioms, particularly where it comes to things like large cardinals. --Trovatore 23:09, 19 September 2007 (UTC)

Hmmm - interesting! So do you assert that it is somehow wrong to pick a set of axioms that don't match reality and then attempt to prove theorems based on them? Is it perhaps merely so pointless that you don't think it's worth doing? Or are you just saying that the standard set of axioms around which most of mathematics is based is based upon 'reality'? SteveBaker 13:39, 20 September 2007 (UTC)

A little bit of 2, but mostly 3. Certainly there's nothing "wrong" with investigating the consequences of arbitrary axioms, and once in a while it even turns out to lead somewhere. But the importance of the axiomatic method as a whole is somewhat overestimated by most interested outsiders and even a lot of mathematicians. Most proofs are not really axiomatic per se. We tell ourselves that we could, if we had to, convert them into axiomatic proofs by routine methods, and this is probably true, but is almost never actually checked. --Trovatore 17:18, 20 September 2007 (UTC)

OK - I'll buy that. It's a pretty reasonable stance. But we know that not all theorems are provable - but we try to build new theorems on top of older ones that we 'know' were correctly derived from yet older ones - and somewhere at the bottom of the whole pile are a handful of axioms that we can't prove. The iffy part happens if you are pretty certain that some unproven theorem is true - and therefore rely upon it. This effectively introduces another axiom - but one that you hope can be removed at a later date. The only question is whether you argue that those axioms are some kind of self-evident 'truth' or whether you say "this huge pile of theorems is only true if you assume these axioms are true". My view is that the former is a bit limiting because it prevents you from doing things like denying Eulers parallel postulate (even though you generally believe it to be a self-evident truth) - and thereby figuring out non-Euclidean geometry - which would be a shame because it subsequently became very useful in other areas. On the other hand, denying that 1+1=2 might well generate a huge pile of interesting theorems - but if none of them apply to reality, what's the point? Both ways are relevent. SteveBaker 20:03, 20 September 2007 (UTC)

If you want to model a solar system (which can't be modeled accurately with quantum physics) down to the atom (which can't be modeled accurately with general relativity) you'd have to use a theory of everything. As far as I know, any of them can model the universe relatively accurately. No computer is powerful enough to run such a model, and I don't think it's even theoretically possible to make one that can, as it would be modeling itself, but that wasn't your question. — Daniel 02:57, 20 September 2007 (UTC)

It's not always necessary to model the entire universe - there is merit to using a theory-of-everything in order to model something simple. But it bothers most people to have to pick the set of fundamental laws (relativity or quantum theory) depending on the nature of the thing they are trying to figure out. There are cases (such as the Hawkings radiation from a black hole) that are simple enough to simulate in a computer and which require both sets of laws - and they don't agree. The consequences of picking the wrong set of theories in order to solve a particular problem is to get the wrong answer. So there is certainly merit in seeking the theory-of-everything - if only as a way to fix these corner-cases. SteveBaker 13:40, 20 September 2007 (UTC)

You can certainly write some axioms of some of the forms of physics on a card. But that wouldn't get you much. All of Special Relativity, for example, falls out of the following two axioms: 1. Galilean relativity holds for all frames of reference and all forces; 2. the speed of light is seen as constant from all frames of reference. Now that looks pretty simple but it took a lot of big brains (starting with Einstein, but others too) to figure out all of the implications of those two things and it takes a lot of explanation and extrapolation to show how inside those two, simple axioms are things like time dilation and length contraction. General Relativity can almost completely be summed up in the single axiom that gravitational acceleration can be described by the curvature of space and time, but knowing just that gets you almost nowhere in terms of actual physics or calculations.

It should be noted for historical purposes that both of the above are care of Einstein, and that Einstein was himself an explicitly axiomatic thinker, believing that if you started out with the correct axioms (and often a reexamination of simple concepts like "space" and "time" and "acceleration") then everything else would fall out. As an approach it worked very well for things like SR and GR but not well at all for things like quantum mechanics. --24.147.86.187 15:04, 20 September 2007 (UTC)

It sounds to me you may actually be asking for Hamilton's principle which arguably has the whole of physics in a single equation? --BozMo talk 16:30, 20 September 2007 (UTC)

September 20

Plant has its own division?

Apparently, there is one plant that has it's own division, does anyone know what this plant is? TheCoolestDude 13:35, 20 September 2007 (UTC)

Ginkgo biloba. Polypipe Wrangler 15:14, 20 September 2007 (UTC)

Our Ginkgo article agrees...although we should be careful to say that it's the only modern plant in that division, there must have been a number of others that are now extinct. It's likely that the modern Ginkgo is also extinct in the wilds - now only existing as a cultivated plant. SteveBaker 17:18, 20 September 2007 (UTC)

How can I jam a radio controlled car? (In the USA)

can I purchase a device that would jam my neighbors remote controlled car so he would use it elsewhere? his toy is causing problems for my dog as the sound aggravates her.

thank you

rob neal

irvine,ca —Preceding unsigned comment added by 216.154.252.184 (talk) 23:34, 19 September 2007 (UTC)

Someone into electronics correct me if I am wrong, but buying the same type of remote control car and using its remote should work because the two are on the same frequency. Personally I would talk to the neighbor about it first if possible, and if that fails try to move the dog elsewhere where the sound wouldn't bother her before going so far as to attempt to jam the remote controlled car. Another solution you could try if you can't get the neighbor to change his behavior would be to get a source of white noise for your dog. 71.226.56.79 00:36, 20 September 2007 (UTC)

Of course, it depends on the type of radio system. Some modern wireless systems are difficult to jam - especially with such a simple attack as a frequency tone jam. (For example, you can think of wireless mouse and keyboard - both are wireless systems but the communications protocol enables multiple access of some type or other. You should probably seek a non-technical solution to this, lest you escalate the conflict (or turn it into a systematic game of cat and mouse to see whose counter-counter-counter-measures are most effective). Nimur 02:42, 20 September 2007 (UTC)

On the other hand, if he can jam the radio secretly, then his neighbor may just think there's some type of interference and go elsewhere. For certain neighbors, even suggesting that they change their behavior may result in hostility, so that might not be the way to go.

I would think the first step is to find the proper frequency. Using some type of scanner when he uses his remote control might be the way to find the frequency (listen for some frequency where the sound changes when the car turns, for example). Then you would need something that jams that frequency. The car might use an adjustable frequency, though, in which case he might just go on to another. StuRat 03:11, 20 September 2007 (UTC)

The cheapest solution is to buy another radio controlled toy that operates on the same frequency. You'll of course need to find out the frequency it operates on...that would require some detective work. Most toys operate in the 27Mhz or 35MHz range. In the UK, I believe that only model airplanes are allowed to use the 35MHz band - in the US, it seems that both are used. However, within those two bands there are a dozen or more 'channels' - each at a slightly different frequency, you'd need to find the right channel. Some recent remote-controlled toys use infrared (like a TV remote) instead of radio - which will be almost impossible to 'jam' unless you are close to the toy at the time. SteveBaker 13:22, 20 September 2007 (UTC)

In the US, 27 MHz and 49 MHz are both common.

Atlant 16:18, 21 September 2007 (UTC)

You have overlooked the simplest route, beat him up and take it! That, or buy a faster one and run him off the road. Don't work harder, work smarter--Jmeden2000 15:29, 20 September 2007 (UTC)

Doggy issues aside, do bear in mind that generating "Malicious Interference" in the radio spectrum is a crime that the FCC doesn't appreciate much. Saturn 5 20:28, 20 September 2007 (UTC)

How about using that coil thing that uses sparks to generate a lot of radio noise? (Then you'd have the whole street mad at you). 80.2.197.120 20:43, 24 September 2007 (UTC)

Holographic Lightsabre

Can a holographic projector be used to create a safe lightsabre blade? --Ecyrblim 01:09, 20 September 2007 (UTC)ecyrblim

Sure. But can that kind of holographic projector be made in the first place? — Kieff | Talk 01:13, 20 September 2007 (UTC)

Holograms only work when you're looking at them. You can't "project" an image of a blade from the hilt unless the hilt, the blade, and your eye are all collinear, which only happens when you're looking at the blade end-on. -- BenRG 02:46, 20 September 2007 (UTC)

But what they could do is have you hold the hilt of the "light sabre", and see your reflection in a "mirror" which has the light blade added. This would make for a nice illusion at an amusement park. They could even give you a movie of you with the light sabre (for a suitable fee, of course). StuRat 03:03, 20 September 2007 (UTC)

How about just a regular "bright and focused" light and a room with a lot of dust in the air? Light projects out of hilt, reflects off dust in its path. DMacks 05:40, 20 September 2007 (UTC)

The problem with that is making the light stop abruptly three feet from your hand...there is no way to do that without some physical object being in the way. FYI: in the early StarWars movies they filmed the lightsabres by using a solid tube covered with a 'retro-reflective' material that was lit by a light next to the camera. Since retro-reflectors reflect light back towards the source, you ended up with a bright reflection from the lightsabres with very little light reflected off of anything else. In the later movies they used computer graphics (of course). Trust me, if there were any way at all to make a 'real' lightsabre, the toy makers (or at least the StarWars fanatics) would have done so LONG ago. SteveBaker 13:16, 20 September 2007 (UTC)

Most sources I've read state that the light sabers were done by rotoscoping.[4]. DMacks 13:37, 20 September 2007 (UTC)

• Our lightsaber article says: The lightsaber first appeared in the film Star Wars Episode IV: A New Hope (1977). At first, the effect was created by a handle with a motorized spinning reflector and pointing high-intensity light in their direction. The outcome was not satisfying, so in post-production the effect was augmented through rotoscoping. For episodes V and VI the use of reflective tape was abandoned and the effect was achieved by rotoscoping rods made of aluminum and later carbon fiber rods. For the prequel trilogy, the effect was created using computer animation. I have read that in the original Star Wars, right after Darth Vader kills Obi Wan Kenobi, his lightsaber is the original retro-reflective white, rather than red. The rotoscopers missed that scene. No doubt the bastardized re-releases have it colored in. --Sean 15:43, 20 September 2007 (UTC)

• Oh, look! This video shows the shiny spinning saber: [5]. --Sean 15:52, 20 September 2007 (UTC)

Regarding making the light "stop", sounds like a mean-free-path problem…will have to remember this one for a future pchem exam:) DMacks 03:35, 24 September 2007 (UTC)

Socks

Do they mainly were out from the inside or the outside? —Preceding unsigned comment added by 88.109.106.146 (talk) 03:47, 20 September 2007 (UTC)

They usually fail when my townails chop a hole through! So that would be inside. Graeme Bartlett 12:07, 20 September 2007 (UTC)

There's lots of variables to consider, including: How you wear them, e.g., only with shoes, or often just as socks with no shoes; the manufacture of the socks, e.g., whether they are lined, the quality of construction; personal hygiene, e.g., the length of toenails, how often and how the socks are washed. You'd need to define some of these before you could make any type of definite answer. --jjron 12:19, 20 September 2007 (UTC)

One hint, tube socks last longer because the heavy wear doesn't occur in just one spot, but rather in a ring, since you put them on in a different rotation each time. (They also avoid having the heel on the top of your foot when you get dressed in the dark.) StuRat 16:19, 20 September 2007 (UTC)

As Jjron says variables... My socks always wear out, sometimes very very fast on the heel. I believe this is because of the way I walk I somehow cause the heel section to wear out. Indeed it probably doesn't help that because I also wear out the heel section of my shoes this heel section then further damages the socks. I'm pretty sure that my socks therefore wear out from the outside in although possibly it's both but the outside wars out more (i.e. it actually meets in the middle). I've recently purchases some more expensive socks with more reenforced heels, waiting to see how these last Nil Einne 18:42, 22 September 2007 (UTC)

"...you'd get more mileage from a cheap pair of sneakers..." or, in this case, tube socks. Buy them by the pack. They are cheap, and last longer, and are more convenient. You can get them in black. StuRat 02:53, 23 September 2007 (UTC)

You could find out by wearing two identical socks one over the other and seeing which got the most wear. In winter I wear a cotton sock under a wool sock, and the wool sock seems to wear out more quickly. Perhaps this is due to the boot rubbing against the outer sock more, while the sock next to the foot does not move. The cotton is also much tougher though. 80.2.197.120 20:49, 24 September 2007 (UTC)

Engineering Projects

I have just begun with my first year of the four year engineering course in mechanical engineering... i was interested in making a research project... how do i start of?? I haven't a special interest in a particular field, i just follow a particular boom in the field.. as in nanotech,cad,automobile... how do i help myself out of this sitution developing an interest and the research part??? —Preceding unsigned comment added by 210.212.44.7 (talk) 06:32, 20 September 2007 (UTC)

You know, I was in a very similar situation once, and I eventually solved it by switching majors. Uh, but on a more helpful path, I went and found out what professors at my school were researching, and eventually found a project that just seemed really cool to me. I asked the guy, and he invited me on to the project. Someguy1221 06:43, 20 September 2007 (UTC)

So you have to decide on a research project in your first year? I don't think so. Wait until you need to decide. You'll have some ideas by then! —Preceding unsigned comment added by 88.109.4.191 (talk) 00:10, 21 September 2007 (UTC)

Aeroplane Speed -advantage when flying east?

Please consider: a) the earth ratates on its axis at around 2000 kmph b) two airplanes takes off at same time and from same point in opposite direction (east & west) and fly at same speed. c) whether the one flying east will have any advantage over the one flying west because of earth's rotation ? Or whether both the planes will return the same start point at the same time ? If so, why? —Preceding unsigned comment added by 59.182.61.89 (talk) 08:45, 20 September 2007 (UTC)

The planes are flying at the same speed relative to the atmosphere, so what is important here is to understand how the atmosphere moves relative to the surface of the Earth. At low levels (and ignoring local weather conditions) the atmosphere is carried around at the same rate as the surface (we don't experience continuous 2000 kph winds at ground level, do we ?). At higher levels in the atmosphere things become more complicated - see our articles on atmospheric circulation and the jet streams. Gandalf61 09:11, 20 September 2007 (UTC)

My physics teacher explained it that they sort of kept the motion of the earth with them, so their absolute speed included the rotation of the earth - therefore, relative to the earth below, they went the same speed, and if you take the rotation of the earth into account, they also have that same motion in that same direction at that same speed as part of their overall speed, so it cancels out. Which is why when you go up in a hot air balloon, you don't end up traveling laterally - you stay "stationary" because you're really still moving at the same speed as on the ground - the speed of the Earth. Kuronue | Talk 00:00, 22 September 2007 (UTC)

• When I visited the US last year, the plane took significantly less time to return home (east) than it took to get there. If you consider transatlantic travel at about 11 km, there's definitely an advantage. If only JFK wasn't congested at the time, I might actually have reaped the benefits of the whole thing... - Mgm|^(talk) 09:41, 20 September 2007 (UTC)

This is most likely the effect of the Jet stream rather than the rotation of the earth. -- JSBillings 11:50, 20 September 2007 (UTC)

In Australia it's generally considered a cross-country west->east flight (say Perth-Melbourne or Perth-Sydney) will commonly take around half-an-hour less than the same east->west flight (average flight time is about 4hrs). However the reason for this is the prevailing winds rather than the Earth's rotation. The flight speed is commonly varied to allow for the winds, rather than having the planes arriving at unexpected times due to varying winds. --jjron 11:57, 20 September 2007 (UTC)

Any east/west bias in travel time is entirely due to the prevailing wind. It's reasonable to say that the velocity of the aircraft over the ground is it's velocity through the air plus the wind velocity. The rotation of the earth only has an effect to the degree that the coriolis effect affects the winds. Mostly we have to be concerned with large scale weather patterns at a particular altitude (eg the Jet Stream). SteveBaker 13:07, 20 September 2007 (UTC)

Be sure you are measuring true elapsed time for the flights, not comparing starting and ending times in local time zones. It's even possible the arrive before you leave, if following time zones (have we discovered time travel here ? :-) ). StuRat 16:28, 20 September 2007 (UTC)

Any advantage from being carried east by planetary rotation is exactly nullified because the target point is carried east at the same rate. —Tamfang 21:25, 20 September 2007 (UTC)

Indirectly (at least in North America and over the North Atlantic; I haven't flown elsewhere). The prevailing winds blow from west to east, due to the rotation of the earth; that gives flights from west to east a boost in speed over flights from east to west. Look at flight times listed on airline schedules.Gzuckier 13:50, 21 September 2007 (UTC)

differentiator

what type of the wave form pattern we get in case of of differentiator? —Preceding unsigned comment added by Patelshiv (talk • contribs) 12:54, 20 September 2007 (UTC)

The differential of the input signal? —Preceding unsigned comment added by 88.109.4.191 (talk) 15:34, 20 September 2007 (UTC)

The wave form out depends on the input naturally, if the input is rising the output is poisitive, if it is falling the output is negative. If you look at it in the Fourier domain, the output is multiplied by the frequency, so the higher the frequency the more it is amplified, and the lower frequencies are reduced in level. The opposite is the integrator. Graeme Bartlett 11:22, 21 September 2007 (UTC)

A sine wave will turn into a phase shifted sine wave, a triangular wave turns into a square wave. A square wave turns into non physical alternating infinite pulses. Graeme Bartlett 11:31, 21 September 2007 (UTC)

Chest clicking. Not medical advice?

I'm just wondering what interaction is going on here. When I stretch my arms and chest (like the stereotypical tired stretch), I sometimes click something in the front centre of my chest. I'm assuming it's similar to cracking joints. But I don't know of any joint in the front center of my chest that it could be! Any ideas? Please feel free to delete if you still feel this constitutes medical advice. Capuchin 13:03, 20 September 2007 (UTC)

I click sometimes when lying on one side, I understand one of my false ribs is detached at the end. DuncanHill 13:06, 20 September 2007 (UTC)

I'm not going to give you medical advice. This is information relevant to the phenomenon to which you refer;-) Have a look at this http://upload.wikimedia.org/wikipedia/commons/8/85/Human_skeleton_front.svg

and you will see that between the sternum and the ribs are connections of cartilage. These are not bendy articulations but they facilitate a little expansive movement to the ribcage and probably enough movement to produce a little bubble to cause the 'crack'. Thank God, really, because if these cartilage connections weren't there I've got a feeling everyone who underwent commpressive cardiac massage would need to get along to the orthopoedic department afterwards to get their ribs fixed. Richard Avery 14:21, 20 September 2007 (UTC)

I can feel the rib move. DuncanHill 14:58, 20 September 2007 (UTC)

You can dislocate ribs from those joints as well. I've done it twice. First time, I was hit by a bus. Second time, same rib, I woke up and somehow it just dislocated and hurt like hell. -- kainaw™ 15:04, 20 September 2007 (UTC)

Maybe you were the victim of a drug rape? Nil Einne 18:32, 22 September 2007 (UTC)

There's a joint between the xyphoid process and the rest of the sternum that can apparently "pop" in some individuals, for example when taking a deep breath (so says my doc). To my delight (and others' disgust) I can pop mine on command. --David Iberri (talk) 23:44, 20 September 2007 (UTC)

aquatic plants

what is the most favourable form of nitrogen for aquatic plants? —Preceding unsigned comment added by 202.141.78.125 (talk) 13:42, 20 September 2007 (UTC)

It is possible that Nitrification will provide some insights, although it doesn't mention aquatic plants in particular. It seems that the nitrogen-fixing bacteria are soil-dwellers, so there is probably an equivalent version for water-borne ecosystems (either in the form of aquatic bacteria or other nitrogen fixers). Nimur 15:22, 20 September 2007 (UTC)

I think the asker means either nitrate, ammonia as well as possibly nitrite and urea - I think it may depend on the plant which is most readily absorbed - but it is almost certainly one of the first two..87.102.87.157 15:15, 21 September 2007 (UTC)

Props go to any fan fan who answers this Q

Why aren't cooling fan blades shaped like an airfoil ? That is, why are they constant thickness instead of thicker near the leading edge ? I was asked this question and didn't know for sure, but this was my speculation:

• Airfoils are more expensive and more efficient. While this additional cost is justified for aircraft props it is not for electrical cooling fans, where it would be difficult to ever recoup the additional cost.

Was my speculation correct ? StuRat 16:14, 20 September 2007 (UTC)

The Sukhoi 29 is the probably most aerobatic aircraft in the world - as you can (just about) see, it has a symmetrical wing cross-section, showing clearly the myth of 'airfoil' shapes being responsible for generating lift SteveBaker 17:10, 20 September 2007 (UTC)

I don't think so. It's an alarmingly common myth that the cross-section of an airfoil is what causes an aircraft to gain lift...it has a very small effect but the major part of it is the angle of the wing to the airflow. The airfoil cross-section has more to do with controlling turbulance at low speeds - and getting the wing strong enough and yet still have a low drag coefficient. Consider a typical Ceiling fan. Those have flat, rectangular, plank-like blades - and they work very well. A desk fan, on the other hand has fat, more steeply angled blades. The choice of shape probably depends on the ratio of motor torque to blade diameter. A desk fan has to be compact - a ceiling fan doesn't. A desk fan is (typically) enclosed in a safety cage so the blades can spin much more quickly than a ceiling fan can. There are lots of little decisions that go into the design of such things. I would say that the blades of a desk fan more closely resemble a ship or submarine propeller - and the demand for small diameter with a high-torque motor probably drives both designs. SteveBaker 17:03, 20 September 2007 (UTC)

Thanks, but that doesn't seem to address why an airfoil shape is never used for fan blades. Are you saying that avoiding turbulence isn't important in fans ? I do think that turbulence occurs, since I note a small distance from the leading edge is clean, but after a half-inch or so, the fan blades become filthy. I take it that little dirt is deposited by laminar flow but turbulent flow "dashes dirt particles against the blades", causing them to stick. I would also reason that this turbulence would necessarily lower efficiency, since energy is being used to move air chaotically, not in the desired direction. StuRat 17:12, 20 September 2007 (UTC)

In aircraft, you need that thick part of the wing to contain the main structural spar (basically just a girder) - which supports the entire weight of the aircraft in the air and has to flex the other way and support its own weight against massive leverage when the plane is on the ground. This spar is at the center of gravity of the plane (in most designs anyway) - and it's wrapped in that teardrop shape merely to get the air to slip past it efficiently and to promote stability by placing the center-of-pressure as close as possible to the center-of-gravity. By virtue of smaller scale, fan blades can be simple thin plates that are mostly being flung outwards by centrifugal force and are not likely to break from the aerodynamic stresses alone. Hence no big fat girder running down the middle of the blade. So they can have a lower coefficient of drag than an aircraft wing that needs a fat bit in the middle to contain that chunky structural member. Turbulance isn't necessarily such a terrible thing in a fan blade whose main function is to stir up the air - so whilst it's probably undesirable, it's not a serious design issue. With ceiling fans, the cost of the things must be a lot less with flat wooden blades than with curved ones. I guess that with desk fans, which mostly have cast metal or plastic blades, you can have them be any shape you want - so they are more efficiently curved. Another issue with the design of fan blades is the range of speeds they have to operate at. It's possible that you are getting non-laminar air flow at the speed you happen to run your fan - but you'd get smoother airflow if it were running faster. The most likely thing is that aircraft are designed VERY carefully with wind tunnels and such - where ceiling and desk fans are designed as much for looks and cost as for efficiency. SteveBaker 17:33, 20 September 2007 (UTC)

(Come to think of it - if you look at one of those large modern windmills (which are just fans running backwards), the do have aerofoil shaped blades - presumably for the same kinds of structural considerations as aircraft wings). SteveBaker 17:35, 20 September 2007 (UTC)

Another consideration is that, given the RPMs of a desk fan on high, you probably don't want the blades generating lift, or your desk fan soon becomes a floor fan. Saturn 5 20:24, 20 September 2007 (UTC)

I believe "for every action there is an equal and opposite reaction" dictates that if you push air forward with a given force you also push the fan backwards with the same force, regardless of the means used to propel the air. I've definitely had fans fall over as soon as they are turned on. They need sturdy, weighted bases, or to be secured in some way, to prevent this. StuRat 02:01, 21 September 2007 (UTC)

Was my speculation correct ... partially, but I think it misses half the story:

• Airfoils act on the Bernoulli principal, which is a form of reaction - see Newton's third law.
• Curved blades, with no airfoil crossection, are usually designed to work with impulse - they change the direction of fluid flow without airfoil action - see Newton's second law.

Fans can benefit from both these concepts, depending on the design. Also, just guessing, a curved or angled blade made of stamped sheetmetal can probably be designed to act as an airfoil.

Cheap fans use simple shapes because they are cheap, even if an airfoil crossection could improve performance. In other cases, the fan might be an impulse design that doesn't benefit from an airfoil shape. I once saw a high performance fan - it had a stator and a rotor - that put 10 horse power in to the flow. It was less than twelve inches in diameter and only a couple of inches thick, and it could knock you over. It didn't have air foil shaped blades, just cheap stamped curved sheetmetal blades. --Duk 21:58, 20 September 2007 (UTC)

It really annoys me that just about every 'how things work' book says that Bernoulli's principle explains how airplanes fly - it really has almost nothing to do with it. This is one of the biggest pieces of misinformation in even quite serious publications. I offer as evidence the photo of the Su29 I posted above. It has a symmetrical wing cross-section and therefore has ZERO Bernoulli lift...yet it's one of the most nimble aerobatic aircraft in the world! Notice that something like a simple Cessna light aircraft that has a classic 'airfoil' cross section wing can fly inverted - with the Bernoulli effect pushing downwards on the wing. I've flown model planes with planks for wings (a rectangular cross-section). They fly just fine - again no Bernoulli lift whatever. Truly - this is a misconception that is perpetuated everywhere and it needs to be screamed and shouted from the rafters: THE BERNOULLI EFFECT IS NOT WHAT MAKES AIRPLANES FLY!!! SteveBaker 00:19, 21 September 2007 (UTC)

THIS SECTION IS NOT ABOUT WHAT MAKES PLANES FLY, IT'S ABOUT FAN BLADES!!!--Duk 00:51, 21 September 2007 (UTC)

With due deference to SteveBaker's volume, the Bernouilli Effect may not be the primary lift-generation mechanism, but it cannot be completely ruled out in terms of stability analysis and complex fluid flow modeling. The shape of the wing or control surface dramatically affects the airflow, whether in a lift-generating way or not. Nimur 17:57, 22 September 2007 (UTC)

Well, it has everything to do with the angle of attack of the wing. It's funny, just last week I performed an experiment in a wind tunnel using a NACA 0012 airfoil; its primary characteristic is that it is symmetric, yet it still produced lift. It still presents a typical $C_{L}$ v. $\alpha$ graph like the one shown on Lift coefficient, but the only difference is that it has a y-intercept of zero. It still presents stall, whether you are flying upright or upside down. What Bernoulli's effect does is that it generates a non-zero intercept for the graph. Titoxd^{(?!? - cool stuff)} 02:14, 21 September 2007 (UTC)

It seems to me that these discussions about "symmetrical cross sections" are all using the wrong frame of reference. The axis about which one should calculate whether aerodynamic symmetry exists is the air direction line that intercepts the center of gravity for the wing, is it not ? If the wing is symmetrical using this frame of reference, I would indeed expect there to be zero lift. StuRat 02:24, 21 September 2007 (UTC)

Not really. The calculations needed in fluid dynamics turn really ugly if you try to calculate them using a wind-based coordinate system. You always calculate them using a wing-based coordinate system, then do a simple transformation employing the angle of attack to bring them to the other coordinates. If the wing is completely parallel to the wind, there will indeed be zero lift; however, any deviation from that will cause air (or whatever the working fluid is) to have a longer displacement path on one surface, which causes higher speeds and lower pressures on that surface, generating lift. Titoxd^{(?!? - cool stuff)} 02:37, 21 September 2007 (UTC)

It sounds to me like you're saying the same thing as I did, just in a different way. Instead of starting with a wind-based coordinate system, they merely start with a wing-based coordinate system, then do a simple transformation, to get to a wind-based coordinate system. StuRat 04:14, 21 September 2007 (UTC)

Answering the original question: A flat blade at a good angle to the air provides more than enough wind without using much power. There is no need to increase the cost by planing down the blades into airfoils. The higher-quality blades are not airfoils. They are simply curved to better direct the wind in the preferred direction - a process that requires flexible blades, but is still cheap. As for the question about how much lift a simple air foil gives, consider common helicopters. The blades are airfoils for stability. They tilt to create lift. To touch briefly on two other subject mentioned: Stunt planes have wings curved on both sides to provide better stability for flying upside down. The wings (and the plane) feel the same to the pilot either way. For larger planes, such as passenger jets, the body of the plane provides a lot of lift. This goes back to TWA's first airplane purchase. They required the passenger jet to fly from Denver to Kansas City with one wing (I've also heard that it didn't have a tail, but I'm not sure about that). The wings are rather important though because most of the fuel is inside them. When it comes to jets though, keep in mind that they cannot fly at low speeds. As I was told when I started flying TWA's 727 and 747 simulators, jets don't glide when the engines stop. They drop like a rock. -- kainaw™ 02:52, 21 September 2007 (UTC)

Are you kidding us Kainaw? Just a few years back, some large commercial jet 'glided' for over 100 miles, if I remember correct. The plane ran out of fuel because of a metric/standard error. The tanks were filled with litres instead of gallons! I can`t remember the exact flight, but, the 'emergency' glide was to a small set of islands in the Indian or Pacific ocean. Sorry if I can`t remember more particulars, but this was BIG news, at the time. To conclude though, jets CERTAINLY can glide... with a glide-rate of around 16:1 to boot! 64.230.233.222 19:44, 21 September 2007 (UTC)Dave

No I am not kidding. The event you are referring to is Air Transat Flight 236. It "glided" at a fall rate of about 2,000 feet/minute. Note that the pilot knew about the fuel leak (not a metric conversion error) before he ran out of fuel. So, he descended and punched the remaining engine to get forward momentum. Then, he basically fell onto the runway. There is a huge difference between gliding along and falling at 2,000 feet/minute. But, you can define "gliding" however you like. -- kainaw™ 19:54, 21 September 2007 (UTC)

Kainaw, I certainly don`t want to be argumentative since 'falling' at 2000ft/min is surely quite a 'fall', but one must remember that while 'falling' at such a rate, that craft in question was also travelling forward at around 32,000ft/min. What I`m trying to get at is that given both numbers, the craft was far from "drop(ing)like a rock", as you put it. I`m quite certain with that forward speed, that aircraft surely was able to flare some, further decreasing its 'fall' rate. Looking up 'glide ratio' right here on Wiki gave some interesting values: Cessna 150 7:1, modern sailplane up to 60:1, hang "glider" around 12:1, paraglider around 7:1, airliners around 17:1, Space Shuttle 1;1! So, with those numbers in mind, wouldn`t you say THAT craft 'glided' pretty well? Thanks for finding those particulars that I missed,,,,I read the link. I found it very interesting. Thanks again. Dave64.230.233.222 21:00, 21 September 2007 (UTC)

The glide ratio is only half the need for gliding. The other half is the sink rate. Unfortunately, Wikipedia doesn't have an article on sink rates (yet). A good glide ratio and good sink rate make a glider. While a large passenger jet may be able to get a somewhat reasonable glide ratio, the sink rate stinks. So, the longer the jet is "gliding", the less forward momentum it has. The less forward momentum it has, the worse the glide ratio gets. The worse the glide ratio, the faster it falls. That is why the few cases where engines have completely gone out but the jet survived were cases where the pilots had warning and lowered the altitude while increasing speed. Lower altitude means less glide time to the ground. Higher speed means longer glide ratio. I'm sure someone will say that they can nose-dive and pull out to get forward momentum. Large jets are not constructed to handle that maneuver safely. (Although, I've seen a 747 do it in a simulator.) Then, there's the whole issue of the jet going into a crippled mode due to power failure. The little turbine that pops out gives only the basic necessities - not enough for a comfortable flight. All in all, if you set a rock in flight at the same height and speed as a jet, the rock will take a ballistic course. The jet will do a little better, but be much closer to the rock than a glider. -- kainaw™ 04:49, 22 September 2007 (UTC)

Thanks for the extra 'work' Kainaw...good job. A quick 'calculation' shows that the plane 'fell', just taking the vertical aspect of the fall into consideration, at an average speed of about 22-23 mph. I think an ordinairy, i.e. no 'special' aerodynamic qualities, rock would fall with a terminal velocity of, just a guess, 120-150 mph. The high-performance modern glider would 'fall' at about 5-6 mph, I think. Refering to your last sentence above, I believe that 22-23 mph, if correct, and if all other guesstimates are close to accurate, then the jet glided much closer to the rate of the glider than an ordinairy rock. Please correct me if I`m wrong. This will be my last post to this FAN question. Apologies to those 'forced' to listen to these side-tracks. Thanks all. Dave 64.230.233.222 09:07, 22 September 2007 (UTC)

Also check out Gimli Glider for another example of a Large Jet (in this case, a Boeing 767) gliding to a safe landing after running totally out of fuel Bunthorne 03:23, 24 September 2007 (UTC)

What gives airplanes lift

HEY, STEVE BAKER, WHAT GIVES AIRPLANES LIFT ?????????--Duk 00:58, 21 September 2007 (UTC)

Steve, aren't you kind of splitting hairs? The pressure difference between the upper surface of the wing and lower surface create lift. If the aggregate of vectors of lift and thrust are sufficient to overcome gravity then the plane will rise. The Bernoulli equation can be used to estimate lift from airflow over the wings if the geometry of the wings and the angle of attack are known. The longer streamlines generate lower pressure since the air must flow faster from the leading edge normal to airflow, specific location controlled by the angle of attack, to meet back up at the trailing edge. If this condition fails then you have flow separation and a resulting stall. Most standard airfoils have greater curvature on the "top" to increase the lift when flying right side up. If you fly with your symmetrical airfoils at an angle of attack of zero then you have identical streamlines both above and below, zero pressure differential and thus zero lift as predicted and calculated by the Bernoulli equation. Your inverted Cessna better have a proper angle of attack to make the streamlines on the undersurface of the wing longer while upside down or your "Bernoulli lift" will indeed be down rather than up. The reason the airfoil on your aerobatic plane, photo above, is symmetric is because it is designed to give equal "lift" either up or down as per the angle of attack selected by the pilot while flying aerobatically. Large subsonic widebody jets on the other hand will have asymmetric cross sections to maximize lift (greater curvature on top and flatter on bottom) when flying right side up. Indeed, they also have flaps to further extend the asymmetric curvature and maximize lift while landing ... as predicted and calculated using the "Bernoulli Effect". Lazyquasar 01:00, 21 September 2007 (UTC)

And to the Su29 wing design, they are shaped that way so as to provide equal lift regardless of which side is up, as LQ said above. Aerobatic planes tend to spend alot of their time upside down. The wing shape lets them get the same lift from the same alpha (angle-of-attack) in either orientation. Couple that with the massively overpowered engine which essentially "drags" the aircraft through the air regardless of lift, and you get the nimbleness that Mr. Baker described. Yes, Cessnas CAN fly upside down, but to maintain level flight as such requires a very aggressive alpha angle, and a steadier nerve from the pilot (if you've ever done this, you know how easy it is for the aircraft to "fall off" its lift...). I guess my point is that, while the wing angle is a significant element in maintaining lift, it is incorrect to say that Bernoulli Lift from the wing shape plays no part, or even an insignificant part. Saturn 5 14:36, 21 September 2007 (UTC)

Well as "steve baker" says - it's not the bernoulli effect - because the force downwards on the wind due to the curve on the leading top edge of an airfoil does not offset any force gained by having faster air above.

It's the angle of attack that gives lift. Consider "For every action there is an equal and opposite reaction" (newton).87.102.87.157 15:12, 21 September 2007 (UTC)

To be perfectly fair, it is a combination of Bernoulli and Newton that give lift. It is ignoring much physics to say that either Bernoulli or Newtonian lift play no part. Consider this: a "normal shaped" airfoil wing (what we refer to as a NACA 4415 shape, if you want to look it up), will still generate lift even when it is angled 3 degrees down relative to the airflow (3 degrees negative α ). At 4 degrees negative α, the Bernoulli lift is cancelled out by the downward Newtonian (so called Reactive) lift. Saturn 5 15:21, 21 September 2007 (UTC)

Does "bernoulli lift" violate the conservation of momentum principle? or not.87.102.87.157 15:41, 21 September 2007 (UTC)

For example this shape

   >>>>>          XXXXX
   >>>>>        XXXXXXXXXXXXXXXXX
air>>>>>      XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
   >>>>>    XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
   >>>>>  XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

In an horizontal airflow would it get lift, and what would be the forces on it?87.102.87.157 15:52, 21 September 2007 (UTC)

Actually, Bernoulli is a special case restatement of Newton, for a fluid. In your drawing, the air flowing over the top of the wing has further to travel due to the curvature, than the air flowing across the bottom. Therefore it must move faster than the air flowing over the bottom. Since Newton requires conservation of Energy, the faster moving air must be at a lower pressure than the bottom air. The pressure difference between top and bottom results in a net upward force on the bottom surface of the wing. All as a result of Conservation of Energy. Saturn 5 16:04, 21 September 2007 (UTC)

Rubbish - you seem to be assuming that two molecules starting at the front have to meet at the back at the same time. More worryingly what about the forces required to make the air move along the upper surface - total rubbish now fuck off87.102.87.157 17:05, 21 September 2007 (UTC)

Wow.... Sorry you feel that way, but I'm not making this stuff up. Read any physics book, its all in there. Oh and by the way, please also read WP:CIV. Saturn 5 17:11, 21 September 2007 (UTC)

I would like to make it clear that I'm not disputing that a wing with the cross-section shown in 87.102.87.157's post will generate lift. Yes, it will - as more or less every book on "How Airplanes Fly" will be sure to tell you. However, that's grossly misleading when you consider what keeps most airplanes in the air most of the time. This 'Bournoulli lift' effect is simply NOT a large part of the total lift in a normal aircraft and the wing cross-section has more to do with support structure and drag minimisation and stall-safety than it has to do with lift generation. The picture above misleadingly suggests that in normal flight, the flat bottom of the wing is parallel to the airflow. That's simply not true for almost every aircraft at almost every speed. For most planes, there is a well-defined "angle of attack" which is the angle that the flat bottom of the wing makes to the incoming airflow. You'd think that the air pressing against the bottom of the wing would immediately tip the plane's nose down until the wing sliced though the air nice and flat - like in the diagram...but airplanes are more cunningly designed than you perhaps think. Find a nice side-on photo of your favorite 'typical' airplane (try not to pick something weird) and look at the angle of the wing to the fuselage - and also at the angle of the tailplane to the fuselage. Notice how the wing is tilted upwards at the front compared to the tailplane. That's because in normal, level flight, the tailplane (being stuck WAY out the back of the plane, far from the center of gravity) exerts a downward force on the tail that pushes the front of the plane up. This results in the flat underside of the wing deflecting the air downwards just like it does on a typical slab-bladed ceiling fan. That's what's making the lift. There are exceptions...but as a general rule the whole business of the air taking a longer path over the top isn't what's generating the vast majority of the lift - the Su29 shows that elegantly by having a wing that's rounded on the bottom as well as on the top. If it's pointed directly into the airflow as per the diagram above, the air travels the exact same distance above and below - so no pressure differential - and no Bournoulli-effect lift...yet the plane flies perfectly well (in fact AMAZINGLY well in that case - it's one of the most manouverable aircraft in the world). If you are still not convinced, ask yourself why an aircraft points it's nose up at the sky on takeoff? If Bournoulli effect was getting it off the ground, it would keep the flat bottom of the wing parallel to the airflow and take off with the wings parallel to the runway. If we are dualing with references, read Angle of attack which says: The amount of lift generated by a wing is directly related to the angle of attack, with greater angles generating more lift. THAT is what makes (almost all) airplanes fly. There are some exceptions. SteveBaker 18:24, 21 September 2007 (UTC)

Please allow me to clarify a few things. First, before the other gentleman decided to cease having a civil discussion, my explanation of the wing diagram was deliberately simplified because dropping too much physics at one time, before some basic concepts are agreed to, tends to cause heads to explode. In fact, had we proceeded civilly, I would have gone into how, yes, the air molecules do NOT in fact arrive at the trailing edge at the same time. But anyway, you see how that went.

Second, if you notice, I have not said that the lift generated by deflection of airflow off an angled wing does not play a significant part in airfoil lift. In fact, at cruise (30,000 feet, 500kts or so), I'd guesstimate that a good 70-75% of total lift is produced that way. At takeoff, that goes even higher. I'm not arguing that point!!! My comments have been to simply point out that completely discounting the Bernoulli effect is not correct. Bernoulli lift is important because the Reaction lift (equal-opposite reaction from the deflected air molecules), while more powerful than the Bernoulli, is rather unstable by itself, and very sensitive to the slightest change in airflow such as one would find in the turbulent atmosphere. The way one's hand reacts when held out the car window on the highway gives a good example of this.

I'm not duelling with references... the only reference I've cited was CIV, for obvious reasons. :-) Saturn 5 18:41, 21 September 2007 (UTC)

Yes - so we don't actually disagee. In cruise you say that at least 70% of lift comes from the angle of attack - and the rest from the airfoil effect - and I'd probably agree with that (for at least most 'normal' aircraft - we'd have to argue about the Sukhoi and the Stealth fighter for example). Up until a few months ago I used to design flight simulators - mostly for military aircaft - and I could probably quote you some exact numbers - but one never knows what's classified - so I won't. Of course in the case of the Su29, the figure is 100% and I'm pretty sure we could find some kind of a weird-assed plane for which the number was much smaller (although I'm finding it hard to think of one right now). My problem is not denying the existance of this airfoil effect - it's that without fail almost every single book on the subject (especially for kids) says that the airfoil effect is "What Makes Airplanes Fly" - which is to completely miss the point! The measure of misinformation is a crisis level! Go to your local library and take a look at books on the subject and I guarantee that 95% or more get it wrong. In discussion of this subject one should FIRST talk about the angle of attack effect - discussing how that angle is maintained by the tailplane and how the elevators work by pushing up and down on that long lever arm (which is why aircraft have such long tails) to adjust the angle of attack. Someplace way back in Appendix Q of the most erudite books on aeronautics, it should mention the airfoil effect. Issues of stability and flight through turbulant are are VASTLY more complicated - effects such as lift from the fuselage, dihedral/anhedral, tailplane lift...it's all insanely complicated - and it would be oversimplifying to say that this is why we need Bournoulli lift. However, it is true to say that in aircraft where stability is NOT desirable (fighters, Su29's, etc), a symmetrical wing is desirable...so there is clearly some contribution to stability from having a flat-bottomed airfoil. But no matter what - can we PLEASE fix the textbooks?! SteveBaker 19:02, 21 September 2007 (UTC)

(Ok, 8 indents is plenty I think):-) Yes, my 70-75% was based on the 4415 sort of shape, and more specifically the 747-400. Something like 1000 lbf/sq-ft from Reactive lift, 240-ish for Bernoulli. At least my textbook got it right. :) Saturn 5 19:16, 21 September 2007 (UTC)

Then of course we have the F16 which exhibits 'black magic' vortex lift...no Bernoulli and kinda perpetually in stall...weird. Works great just so long as your computer keeps running! SteveBaker 19:59, 21 September 2007 (UTC)

I believe many of the pre-Wright-brothers aircraft were designed around the assumption of pure Bernoulli lift -- which is why they tended not to fly very well. --Carnildo 22:33, 21 September 2007 (UTC)

Yep. One thing that can be said without excessively simplifying the subject is that an unsymmetrical airfoil will have an initial lift at $\alpha =0$. However, that lift is much smaller than lift caused by angle of attack. Then, of course, you have to worry about flow separation and all those nice things... Titoxd^{(?!? - cool stuff)} 22:50, 21 September 2007 (UTC)

Ooooohhhh! I forgot to tell the skeptics to try my poor-mans wind tunnel demonstration! The next time you are riding shotgun in someone's car - take along a paperback book - preferably an nice slim 200 pager - not a 1000 page Stephen King monster! Open the window when the car is going nice and fast and hold the book out into the airflow with the spine pointing into the wind - hold it up high enough to get out of the turbulance caused by the door mirror. You now have a 'wing' with a rectangular cross-section. If you tilt the spine of the book up - you'll easily be able to feel the lift caused by the "angle of attack" effect. OK - so now, push on the pages on the top of the book to make an 'airfoil shape with a flat bottom and a slight bulge on the top. Hold the book so that the flat, bottom surface is parallel to the airflow and see how much 'Bournoulli effect' lift you get. When I tried this, it was hard to tell that there was any lift at all - but if you curve the top edge just right, you can kinda-sorta feel it. If this demonstration doesn't convince you, you're a lost cause! SteveBaker 19:02, 21 September 2007 (UTC)

Well, yes, ramming air against a geometric plane can provide lift, but the high drag that creates makes for rather inefficient use of fuel, does it not ? I believe that's why the airfoil is used, to provide lift without excessive drag. StuRat 18:07, 22 September 2007 (UTC)

• For those who are wondering what on Earth is the NACA xxxx, there's the NACA airfoil article. Titoxd^{(?!? - cool stuff)} 22:50, 21 September 2007 (UTC)

After getting back into flying, my current instructor first recommended, then insisted, that I get the book Stick and Rudder by Wolfgang Langewiesche. My first thought was "why bother with such an old book" (vintage 1944). Hoo boy, was I wrong! It goes deeply into the science of flight. To make a long story short, he agrees that the Bernoulli explanation leaves a lot to be desired. In effect, the airplane goes up because the wing causes a whole bunch of air to go down (remember Newton?). If you're the least interested in the science of aviation, I recommend, nay, insist, that you get hold of his book Bunthorne 03:46, 24 September 2007 (UTC)

Moran's Introduction to Aerodynamics is also quite good for understanding the actual fluid mechanics involved in aerodynamics. It's relatively cheap for a textbook too. Titoxd^{(?!? - cool stuff)} 19:41, 24 September 2007 (UTC)

Dominant and recessive

Why human genes are dominant and recessive? Is it because of their chemical structure or something else? And is it possible to interchange their properties? --85.132.14.38 17:02, 20 September 2007 (UTC)

This question is answered in the Dominance relationship article. To put it simply, it has to do with the fact that we carry two copies of each gene (for the most part), one chromosome from your father and one from your mother. -- JSBillings 17:47, 20 September 2007 (UTC)

Come now, anyone who asks about gene dominance already knows about diploidy. To put it still rather simply: if one allele produces a functioning enzyme and the other doesn't, usually the presence of the former is enough to have full effect; presence dominates absence like light dominates darkness. —Tamfang 21:21, 20 September 2007 (UTC)

Just to clarify, many genes don't have simple dominant and recessive relationships. Even for example the defect in haemoglobin which causes sickle cell anaemia. While the actual disease is only a problem in recessives, carriers of the gene (people with one copy of the 'normal' gene) have a high resistance to malaria (which is believe to be one of the key reasons why the disease occurs in relatively high frequency in some African populations) Nil Einne 18:45, 22 September 2007 (UTC)

It is important to remember the genes themselves do not create the phenotype, it is the proteins (and RNA) they produce which ultimately causes the differences in organisms we call phenotpyes. Dominance and recessiveness are often (but not always) correlated with how the respective alleles' protein products function (or not). There are many ways that dominance or recessiveness can be "created" through mutation so I will give some protein related examples. 128.196.149.20 00:56, 21 September 2007 (UTC) (This is User:Sifaka who can't sign on right now)

• Reccesiveness can be caused by a loss of function mutation. Suppose you have two alleles A (normal) and B (mutated) that make some protein. Allele B is mutated so that its protein can not function properly. If allele A produces enough normal protein to make up for allele B's defective protein resulting in a normal phenotype, Allele A would be considered dominant to B. If allele A alone can't produce enough protein to make up for the deficiency so an intermediate phenotype results, then A and B might be incompletely dominant.

• Imagine if the gene encodes for a red pigment in petals and the mutation in B causes a noncolored protein causing white petals in double recessive individuals. A normal phenotype is red. If allele A can make up for B completely, the flowers are still red. If A doesn't make enough protein though, the flower might be pink.

• Dominance of a mutant allele can be caused if the mutant protein fails to be regulated properly. Imagine a gene with two alleles C (normal) and D (mutated). Allele D has a mutation so that the protein produced has a defect in a regulatory region which controls its activity so that it can't be "turned off". The Allele D is dominant over Allele C because only one copy of allele D is needed to make mutant protein which causes the mutant phenotype.

• Imagine the gene encodes for a red pigment in a flower whose normal phenotype is red on the edges and white in the center. There is a regulatory protein produced in the cells in the center of the flower where it is normally white which tells the red protein not to work here. The mutant protein created by allele D doesn't respond to that signal creating the mutant phenotype of an entirely red flower.

• A gene has a part that encodes for the protein, and also regions to regulate its transcription. A mutation need not be in the parts encoding for a protein (thereby creating a mutant protein), a mutation to a key part of the regulatory region may drastically change the the gene's expression, causing a mutant phenotype.

FTL and the size of the universe

Begging your pardons if this is the wrong place but I couldn't find the information or answers anywhere else on Wikipedia.

I need a logic and reason check on this statement, please:

"If faster-than-light travel is possible, then the universe is not infinite."

Or, if you prefer:

"If the universe is infinite, then faster-than-light travel is impossible."

The logic is as follows:

If the universe is infinite, then there has been infinite opportunity for an advanced intelligence to develop FTL travel and visit us. As we see no evidence for extra-terrestrial intelligence, then at least one of the following must be true:

1. The universe is finite.

2. FTL travel is impossible.

"An infinite universe and faster-than-light travel are mutually exclusive." (corrected stupid typo in this statement AJKGordon 18:28, 20 September 2007 (UTC))

Therefore if experiments conclude that FTL travel is possible, then the conclusion that the universe is finite is automatically deduced. And vice-versa, of course. —Preceding unsigned comment added by Ajkgordon (talk • contribs) 17:54, 20 September 2007 (UTC)

Anyone care to correct or confirm? AJKGordon 17:46, 20 September 2007 (UTC)

There's a clear and fundamental flaw in your logic. An infinite universe (presumably you mean in size) does not necessitate that everything which might happen has happened. — Lomn 18:04, 20 September 2007 (UTC)

Yes, there are indeed quite a few problems with that assumption. First of all, it assumes that advanced intelligences CAN exist and are not somehow eliminated by the laws of physics. Secondly, it assumes that an advanced intelligence would WANT to search the universe for other life - maybe not. Thirdly, it assumes that this has not already happened (maybe they visit suitable planets, seed them with unicellular life and stand back and wait until WE find THEM!). It assumes that FTL travel means infinitely fast travel...maybe you can go faster than light but only twice as fast. Also how long does it take an infinite number of intelligent species, flying at infinite speeds to search an infinite number of stars in order to find an infinite number of less intelligent species like ours? The answer is something like infinity divided by infinity - which can be any number you choose...including zero or infinity. So it's perfectly possible for there to be infinite everything but for there still to be only a one in a trillion chance of us ever being reached and communicated with. There are plenty of holes in your argument that make it perfectly possible to have an infinite universe with infinitely fast travel and no alien visitations whatever. A similar argument to yours (without the need for FTL travel) would say that there are an infinite number of black holes in the universe so how come we haven't been swallowed by one of them? Well, there might be an infinite number of them - but they are spread over infinite distances - so the actual density of them can be whatever you could imagine. So, sadly, your argument is without merit. For the record, we believe that the universe is finite and FTL travel is impossible. However, because space can expand (as a result of the big bang) faster than light (this is NOT the same thing as travelling faster than light) - there are parts of the universe that are receding faster than we could fly towards them - so we can never reach them...which means nothing from those regions can reach us. In that sense, it doesn't matter whether the universe is infinite or not - in either case, we cannot possibly ever reach all of it. SteveBaker 18:05, 20 September 2007 (UTC)

Thanks both. Just want to make it clear it's not my logic! Kids sometimes ask difficult questions! I will reflect on your responses. Thanks again. AJKGordon 18:17, 20 September 2007 (UTC)

Ah - In that case, the short-form, kid-safe answer is: The trouble is that infinity is a slippery concept. If the universe is infinite then it also contains an infinite number of cats - so by your logic, there must be one sitting on my lap right now - and there isn't (you'll have to take my word for that!). That's because those infinite cats are spread over an infinite volume - so the distance between them is infinity divided by infinity which could be any number at all. We know the universe isn't infinite - in fact, about 13.7 billion years ago it was a mere 'dot', then we had the big bang and it's been expanding ever since - but it's not expanding infinitely quickly or we wouldn't be able to see any distant galaxies - so it must still be finite in size. Hubble's law says how fast it's expanding and that gives us an idea of the size - which is most likely about 78 billion light-years. SteveBaker 19:24, 20 September 2007 (UTC)

Hmmm... predicting his response...

A finite but infinitely old universe and FTL travel are mutually exclusive." AJKGordon 18:26, 20 September 2007 (UTC)

Hmmm - I misunderstood that comment initially. No - even if the universe was finite but infinitely old, the aliens might not be here. A finite (spatially) universe only contains a finite number of civilisations at any given point in time - although over the entire past history there must have been an infinite number of them. Because a civilisation doesn't necessarily last forever (wars, etc) - each civilisation might last long enough to look everywhere in the finite universe using their super-fast spaceships - but we weren't there at the time, we were still in our 'primordial ooze' stage and now (millions of years later) maybe the aliens are all dead. Now we are here and they aren't - so they might never find us because we never overlapped in time. But still, it's an academic point because..... SteveBaker 19:51, 20 September 2007 (UTC)

A finite (in size) but infinite (in age) universe is already a mutually exclusive proposition...forget FTL. We KNOW the universe is expanding (even a very basic telescope+spectrometer can show the red-shift in more distant galaxies) - and we know that if it ever stops expanding, gravitation will force it to shrink again and then nothing can stop it from ending in a 'big crunch'. If the universe was INFINITELY old then either it crunched already (it didn't or we wouldn't be here) - or it has already expanded to infinite size. So infinite in size and infinite in age are possible - and finite in both size and age are possible. But besides, we can already look back at the universe as it was soon after the big bang (Cosmic microwave background, etc) - we know for sure it's not infinitely old - hence we know it's finite in size - and we're pretty much 100% certain that FTL travel is impossible. So, sadly, we have finite everything and boring old spaceships that are forever going to be too crappy to let us see much of it. Gene Roddenberry would roll in his grave. SteveBaker 18:48, 20 September 2007 (UTC)

Infinite in size but finite in age is also possible. In fact it's what follows from the simplest models having negative or zero asymptotic curvature.

Of course the observable universe is finite. --Trovatore 18:55, 20 September 2007 (UTC)

Human history is only 10000 years old or so (much less if you limit it to people capable of productively processing the concepts of space and aliens). Even if space was chock full of species with warp drives, maybe they just haven't been interested in making their presence known to a boring backwater civilization like ours. 76.231.189.193 19:52, 20 September 2007 (UTC)

OK thanks, Steve and others. Not sure I get your logic about finite age = finite size and I think that "[virtually] 100% certain that FTL travel is impossible" is over-cooking it a little but that's enough to keep the offspring entertained. Thanks again. But I may be back! AJKGordon 20:18, 20 September 2007 (UTC)

Oh - that's an easy one. The universe is 13.7 billion years old. Back then, the universe was a dot - zero sized. Then we have the big bang and it starts growing. It doesn't grow infinitely fast - the growth rate is finite and approximated by the Hubble's law. So if it started off at zero size and grew at a finite rate for a finite amount of time - then the universe has to be finite in size...and we estimate it's 79 billion light years across right now. Hence finite age means finite size (assuming finite growth rates - which is what we see when we look out there and watch distant galaxies rushing away from us). If there was at some time a brief moment of infinite expansion before things settled down to where they are now then we'd be in deep trouble because the finite amount of matter that was in the universe shortly after the big bang would be spread out over infinite space - and things would look kinda empty around here! So we can be reasonable sure the universe is finite size and finite age. But that's not 100% for sure. Anything further away than 13.7 light years is too far away to see because it would take longer than the life of the universe for the light to get to us...so there is a good fraction of the universe that we'll never be able to examine...maybe it's a lot different from our bit and maybe those parts ARE moving infinitely fast...it doesn't seem likely though. FTL travel is fairly certain to be impossible...sadly...the experimental results testing Einsteins theory of relativity have absolutely all shown it to be 100% correct - and it most certainly says that faster-than-light travel is out of the question. It's not looking likely. SteveBaker 00:01, 21 September 2007 (UTC)

The part of the finite-universe reasoning that you can't check is the "the universe was a dot" part. What we actually get by running the equations backwards to the big bang is that the universe had infinite density, not that it had zero volume. Certainly, if its mass is finite, then it would follow that it had zero volume, but that's begging the question.

I also think you're assuming too much about Einstein's work applying in regimes in which it's never been tested (why don't you like possessive apostrophes, BTW?) but we already know we disagree on that one. --Trovatore 00:29, 21 September 2007 (UTC)

• Fermi paradox. --JWSchmidt 22:36, 20 September 2007 (UTC)

Couple of things I understood differently, Steve. 13.7 billion light years is simply how far light has travelled since the Big Bang, not how far away the furthest objects in the observable universe are away from Earth - that works out as 47 billion years. The 79 (or 78) billion light year size is simply the lower limit of the size of the universe, i.e. the furthest that can be seen with no repeating patterns - repeating patterns suggesting that the universe might be curved and finite within observable limits. (I think I got that right). I was also under the impression the question of whether the universe was infinite or not was still pretty open. (No pun intended). AJKGordon 00:54, 21 September 2007 (UTC)

What about the Fermi paradox, JW? AJKGordon 00:57, 21 September 2007 (UTC)

I pointed to Fermi paradox because this section started with, "....opportunity for an advanced intelligence to .... visit us. As we see no evidence for extra-terrestrial intelligence, then.....", which is the starting point for the "Fermi paradox". People have been thinking about this for a long time and some of the resulting chains of thought are outlined at Fermi paradox. --JWSchmidt 03:06, 21 September 2007 (UTC)

The trouble with the Fermi paradox is that it's not really paradoxical. There are some rough calculations as to the number of possible alien civilisations out there. The numbers have vast error bars on them - so it's possible that the answer is 1 (vis, Us) - and suddenly there is no paradox. Also, (as previously discussed) we shouldn't be surprised that we aren't visited by aliens because of the limitations of the speed of light - and the lack of radio transmissions is unsurprising if their radio technology is on a par with ours because our strongest transmitters would be undetectable by our most sensitive receivers at 4 light years distance (the distance to the nearest star system). The universe could easily have a human-level civilisation on every single planet of every single star and there would still be no possible way for us to figure this out. SteveBaker 04:07, 21 September 2007 (UTC)

Technological civilizations might have developed on other planets of our galaxy hundreds of millions of years ago, providing what strikes some people as plenty of time for evidence of their existence to have reached Earth. Some people have speculated about panspermia and other possible forms of "contact" that might not be easy for us to detect. --JWSchmidt 06:25, 21 September 2007 (UTC)

They may have developed, and they may have died out, like many civilizations have done on this planet. Our own Western civilization has seemed precariously teetering on its own destruction for the last century, and we've only made it to our moon a handful of times. (I also want to just add, that even if we had FTL travel, it would have to be pretty significantly FTL to make interstellar travel something people really wanted to spend the time doing. Even if you were traveling at c it would still take you a long-ass time to get anywhere beyond our solar system. A four-year trip to the next nearest star is still a bit too long for casual travel, even if those on the ship didn't experience any time as passing—you wouldn't want to go on a long trip and come home to find your kids grown up, family dead, etc.) --24.147.86.187 13:09, 21 September 2007 (UTC)

It's impossible to say what FTL travel might do to human perception since all of the math and physics say it can't happen. But the effects of time and distance dilation have a massive effect on this stuff. If we could travel very close to the speed of light, distances between stars would contract and we could move between them in less elapsed time. You don't need FTL travel to zip around the universe like on StarTrek - 99.9999999% of 'c' is plenty. However, this has the side-effect of speeding up time around us so whilst the occupants of a fast ship would live long enough to travel between stars - the remainder of their civilisation would die of old age waiting to hear the results of their travels. At exactly the speed of light, the universe shrinks to an infinitesimally thin two-dimensional object - which is too small to contain your spacecraft - while time speeds up to an infinite degree so the universe ends (big crunch or heat-death...either way) before you can press the "OFF" button on your hyperdrive...never a good thing for crew morale! Beyond the speed of light - we are "in mathematical la-la-land" (a new phrase that I'm becoming fond of) in that lengths, time and masses all become complex numbers (like the square root of -1) - which is simply not possible in our universe...so speculation as to what FTL travel might or might not do is pointless - it can't happen so we can't say what would happen if it did. Things would get plenty freaky at 99.99999% of 'c'. SteveBaker 15:14, 21 September 2007 (UTC)

Science fiction writers have come up with various imaginative ways of side-stepping the Fermi paradox and explaining why our galaxy is not overflowing with alien civilsations. In the Culture novels of Iain Banks, sufficiently advanced civilisations become bored with the material universe and join the Sublimed. In Vernor Vinge's novels FTL travel (and other advances such as sentient computers) is only possible if you are more than a certain distance from the galactic centre - which the Solar System, unfortunately, is not. Gandalf61 13:33, 21 September 2007 (UTC)

I don't think they NEED to do that. The Fermi paradox relies on the Drake equation for it's prediction of the number of civilisations within reasonable distance of us. According to our article, the Drake equation states that:

$N=R^{*}\times f_{p}\times n_{e}\times f_{l}\times f_{i}\times f_{c}\times L$

where:

N is the number of civilizations in our galaxy with which we might hope to be able to communicate;

and

R* is the average rate of star formation in our galaxy

f_p is the fraction of those stars that have planets

n_e is the average number of planets that can potentially support life per star that has planets

f_l is the fraction of the above that actually go on to develop life at some point

f_i is the fraction of the above that actually go on to develop intelligent life

f_c is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L is the length of time such civilizations release detectable signals into space.

Some of these numbers we have good estimates for. We know R*, we have enough evidence about f_p to guess, but so far, the value if n_e is unknown. We've found maybe a hundred stars with planets (and it starts to look like f_p is maybe 0.1 or so) - but so far, none of them have planets remotely like earth. So n_e could be very close to zero. It could be 1.0 divided by the number of stars in the universe - which would mean we are utterly alone here. As for L and all of the f_whatever terms - we have literally no clue about those. We can guess - but the answer could be wildly wrong. So where is this paradox? It's not paradoxical for n_e to be a very tiny number - we don't know enough about planetary formation to say whether Earth is an amazing flook of nature - a unique result of a spectacularly unlikely series of coincidences. So it's not a paradox - it's a result of some of those numbers being rather smaller than we estimated. Science fiction writers don't need to come up with elaborate reasons why the universe is or is not full of aliens - it's simply the result of some assumptions about some unknown numbers in an equation. If you want a Star Wars universe where every tiny little rock (including asteroids) is teeming with life then crank n_e to around 5.0 and f_l to 1.0 and put f_i to maybe 0.5 or so. If you want StarTrek - where most of the universe has been colonised by just a few intelligent species but where most planets are colonisable - then set n_e to a bit less than 1.0 but f_l to a very small number. If you want Asimov's Foundation series where humans are everywhere but no alien life of any kind exists - then push f_l to a smaller number still so that everywhere is livable but all life comes from earth colonisation and set f_i to 1.0 so the one place that has life has intelligent life. By playing around with the unknown numbers in the equations you can get any science fiction setting you like. The Fermi paradox is nonsense until/unless we somehow prove that the f_whatever terms should somehow be big numbers - and yet we still find no life. But how would scientists show that the probability of a civilisation developing technology is a big number when we only have one example (ourselves) to use as evidence? Nah - forget the Fermi paradox. SteveBaker 15:35, 21 September 2007 (UTC)

Steve, I think you might be making the same mistake that many many people have made in the past - claiming that something is impossible when we don't really understand it. Sure, travelling conventionally in accordance with Einstein's famous equations, it seems fairly bullet-proof that FTL is impossible. But we also know, through those very same equations, lots of stuff about folding space and so on that could, theoretically, allow some of these hard and fast rules to be bypassed. Even though we have no idea how to generate exotic matter and other fanciful notions for, say, worm-holes, or indeed if it's even possible, that's "just engineering". Science and technology are two very different things. And the latter doesn't necessarily need to understand the former! AJKGordon 18:35, 21 September 2007 (UTC)

The trouble comes when you add infinite variables to a question... infinite sets can act and interact in funny ways. Probably a bit too complicated for young children, but these discussions of infinite sets and events can be good brain candy (depending on your sweet tooth). --SB_Johnny | ^PA! 19:57, 21 September 2007 (UTC)

Thanks Johnny. 84.98.245.216 20:51, 21 September 2007 (UTC)

Finding Average Acceleration from a Position-Time Graph

So there's this physics question which I can't seem to get. There's a bus, it's got a varying speed along its 3.5 hour trip. From t = 0 to t= 1 hour it position changes from 0 to approx. 25 (the graph is small). Then on leg B of it's journey, it goes from t=1 hour t~2.2 hours. Its position changes fromm x = 25 to x = 33. Then, on leg C of the journey, from t = 2.2 to t =3.5, the bus's position changes from x = 33 to x = 28. Now, I have to find the average acceleration. The answer I know, -8.3km/h². However, the process I don't. I first began by calculating the velocity's (using the slope) of A, B, and C.

So then I got answers such as V(a)= (25km-0km)/1hr = 25km/hr, V(b) = (33km-25km)/(2.2hr-1hr) = 6.6km/hr, and V(c) = (28km-33k)/(3.5h-2.2h) = -3.84km/hr.

Now I proceed to find the average acceleration of each segment, by diving the change in velocity of each segment by the change of time. a) (25km/hr-0km/hr)/(1hr) = 25km/hr². b) (6.6km/h²-25km/²)/(2.2hr - 1hr) = -15.33km/h². c) (-3.84km/h-6.6km/h)(3.5hr-2.2hr) = -8.03km/h².

That adds up to a grand total of of + 1.64km/h²....which is well far from the answer. If any could help me, I'd really appreciate it. Thanks.

207.161.45.29 22:48, 20 September 2007 (UTC)

It seems odd to ask for average acceleration, rather than average velocity, in a problem like this. That said, look at the first equation in velocity, which says how to calculate average velocity; acceleration is to velocity as velocity is to position, so you should be able to use a very similar equation for your problem. (Hint: you'll need some but not all of the numbers you've given here, and some but not all of the ones you don't need to use are wrong.) --Tardis 23:32, 20 September 2007 (UTC)

I do use that same equation, in the second part where I wrote avg. a = (v2-v1)/(t2-t1). I'm not really sure what you mean by the last sentence.. I need to use some of the numbers I came up with, but some of those are wrong? —Preceding unsigned comment added by 207.161.45.29 (talk) 23:42, 20 September 2007 (UTC)

No...this is wrong, wrong, wrong. You've approximated the position curve by three straight lines. A straight line in position means a constant velocity which means zero acceleration. But at the precise point where the two straight lines meet, the velocity changes instantaneously. That's an infinite accelleration for zero amount of time - which throws the math off into la-la-land. SteveBaker 23:48, 20 September 2007 (UTC)

I know the acceleration is zero from Point A to point B, from Point B to C and zero from C to D, but as a whole the acceleration changes because the velocity changes. How would I work this out? —Preceding unsigned comment added by 207.161.45.29 (talk) 23:58, 20 September 2007 (UTC)

No - you don't understand. You have approximated the position-versus-time curve as a straight line from A to B - right? So you can calculate the average velocity over that time from the slope of that line. But if you assume the velocity is constant - then what is the acceleration? Acceleration is the rate of change of velocity over time. Well, if the velocity is constant then there is no change - so the acceleration is zero. OK - so from A to B there is ZERO acceleration. If B-C is also approximated by a straight line (albeit one with different slope from A-B) then the same argument applies - a straight line for position-versus-time means constant velocity and zero accelleration. The velocity changed at point B. So let's plot a graph of velocity versus time. It's a horizontal line from A to B - then the graph goes up vertically and you get another straight line from B to C. Acceleration is the slope of the velocity/time graph. So you had zero acceleration most of the time - but at precisely time B you had...infinite accelleration. So for most of the journey, there was zero accelleration - but at time B there was infinite acceleration. SteveBaker 00:09, 21 September 2007 (UTC)

Okay that does makes sense...but then why in the world does my textbook (wiley 7th edition) give an answer of -8.3km/h²? I've tried nearly every way to get that number pop up in my calculator but it won't. Is the textbook wrong then?

Well, let's assume that your approximation of the three sections of the graph as straight lines is wrong. I think the average accelleration should be the velocity at the very end of the graph minus the velocity at the start of the graph - divided by the time. The rate of change of velocity over time. I don't care what happens to the position and velocity between those two points...right? So measure the slope of the curve at time A (that's the initial velocity), measure the slope at time C (that's the final velocity), subtract one from the other and divide by the total time. SteveBaker 00:25, 21 September 2007 (UTC)

Ahh, and there it is. Thanks for devoting so much time and effort. Thanks again! 207.161.45.29 00:34, 21 September 2007 (UTC)

Please do point out to your instructor that the illustration is crap, in that infinite acceleration is needed between the flat lines, which, of course, is impossible. StuRat 02:17, 21 September 2007 (UTC)

Indeed - yes. I'm a little dissatisfied with the definition of an 'average' - in a situation where you have zero acceleration throughout the period being sampled - with the exception of an infinite acceleration for a zero amount of time...I'm not sure that the mathematical concept of an 'average' can actually be calculated. However...it looks like we answered this one to at least some degree of satisfaction. SteveBaker 14:44, 21 September 2007 (UTC)

The notion of average is actually one of the motivations for introducing such things as the Dirac delta function. If you work at a goldsmithy and get paid in the form of a continuous trickle of gold from the casting pot, we can talk about your wage as a literal instantaneous derivative of value in the gold that's yours, and that derivative is constant (at least over the work day). If your company decides to instead give you weekly paychecks via direct deposit, and the average rate of payment is the same, then the paychecks (which are instantaneous adjustments to your wealth) must each have the value of the week's worth of trickle. The checks can be seen as the limiting process of giving you a larger portion of the "flow" for a shorter period of time: you could have all the output for, say, 3 minutes a week instead of having the trickle. Then the plot of your wealth-rate over time looks like a series of top hats corresponding to those 3 minutes each week. The paychecks are just the limit as the paying-time tends to 0 while the paying-rate grows without bound in such a fashion that their product (integrated over the longest time interval involved, like a week) is constant. On longer time scales (like calculating your yearly salary) the average is all that matters, and the divergent instantaneous values are unimportant.

In the OP's problem, the discontinuous changes in velocity merely correspond to changes that are fast enough that we don't worry about them. A bus could easily change speeds from 25 to 6.6 or from 6.6 to -3.84 kph in a very short time compared to an hour or more of travel at each speed, so (in terms of its overall position) the details of how it changed speeds are unimportant (except to the passengers, who do not want to experience the conceptual infinite acceleration). The average acceleration is quite well-defined, so long as we are sure that we don't cut the graph off in the middle of a change: if the bus came to a stop at the 3.5 hour mark, our value for the average acceleration changes drastically if we include that change or not (or include half of it!) in the analysis. The reason for the trouble is that we are told to evaluate the average acceleration on a precise time interval, so if there's a change at one end or the other there's no way for it to be so fast that we don't have to worry about its precise duration and shape. --Tardis 19:33, 21 September 2007 (UTC)

There is something else confusing about "average acceleration", how to deal with negative acceleration (deceleration). For example, if you accelerate at 1 g to the half-way point of your journey to the Moon, then turn around and decelerate at 1 g for the second half of the journey, does that mean your average acceleration is 1 g or 0 g ? There are different ways of looking at it. I suppose we can call the 1 g answer "the average of the absolute values of accelerations" and the 0 g answer "the average acceleration", to avoid this confusion. In this case, the 1 g answer is definitely more useful, when considering the effects on humans. (Note, this isn't how actual Moon trips have worked, but would provide the most comfortable, quick journey, if energy was not a constraint.) StuRat 16:08, 22 September 2007 (UTC)

Heat Absorbtion

Please go in depth on the following question. Do different colors absorb heat diffently? If so, why? —Preceding unsigned comment added by 208.61.108.71 (talk) 23:06, 20 September 2007 (UTC)

Yes. A coloured object looks coloured because it's absorbing some frequencies of light and reflecting others. The light energy it absorbs turns into heat (in almost all materials). So a black object (which absorbs all frequencies) gets hotter than a white object (which reflects most of it). However, it's not quite a simple as that because lots of the sun's energy comes in the form of Ultraviolet and InfraRed light - and two objects might appear to be the same colour but in fact absorb different amounts of UV and IR making one get hotter than the other. Beyond that, it's a complicated matter to actually predict the total energy gain because when an object gets hotter, it sheds energy by emitting IR radiation too. So some objects emit energy better than others - which greatly confuses matters. SteveBaker 23:45, 20 September 2007 (UTC)

To clarify on Steve Baker's answer, a black object absorbs all visible light frequencies, but not necessarily those outside our vision range. User:Sifaka who is currently IP 128.196.149.20 01:27, 21 September 2007 (UTC)

People never seem to mention that darker objects emit energy easier, too. Because of this, when objects are cooling down, darker object will cool faster and end up being colder than light objects. — Daniel 01:46, 21 September 2007 (UTC)

Are you sure about that ? Why would it's color in the visible frequency be related to it's ability to radiate heat (in the infrared frequency) ? StuRat 02:05, 21 September 2007 (UTC)

I think he assumes that darker objects in the visible spectrum are also typically darker in other wavelengths. --Spoon! 02:38, 21 September 2007 (UTC)

Well, if they were then they'd cool off slower. No - what's going on here is that EMISSIVITY is not necessarily correlated with REFLECTIVITY. The former is associate with shedding heat - the latter in absorbing it. Whilst it is commonly the case that visible colour and IR reflectivity and emissivity are correlated - it's not necessarily true. SteveBaker 03:54, 21 September 2007 (UTC)

Kirchhoff's law of thermal radiation --Spoon! 04:21, 21 September 2007 (UTC)

And Black-body radiation. --jjron 09:01, 21 September 2007 (UTC)

September 21

GEarth blue streaks

I was playing around with the sky part of Google Earth when I came across these really odd parallel blue streaks. Here's a .kmz link to the location: BlueStreaks.kmz. I was wondering if those are actual astronomical thingamabobs or if they're just a glitch that somehow got into the photo-ing stuff.

For those of you who don't feel like opening the .kmz file, here's a picture of the view: Blue Streaks Foxjwill 02:35, 21 September 2007 (UTC)

Satellites can leave streaks like that on astronomy pictures- the camera takes three different color snapshots of each section, so things that move really fast (like satellites) only show up in one color and as streaks because of the long exposure time. Galaxyzoo has a good explanation in section 3. Except that there are two parallel lines here, so it might be something else. 68.231.151.161 03:42, 21 September 2007 (UTC)

Satellites with a complicated cross-section (say, a pair of solar panels) can leave parallel streaks like that. There's a certain lack of scale there, so it could also be something more prosaic, like UFO running lights. --Carnildo 22:36, 21 September 2007 (UTC)

Hypotheticals in chemistry

I posted this question in talk:sulfonic acid 3 weeks back but got no nibbles, so I thought I'd ask it here...

I can guess—but I cannot find a definitive explanation of—what is meant by calling these babies [the sulfonic acids] hypothetical. I suppose it's OK to use a bit of jargon that's well known in chemistry, but I'd suggest creating an entry for it on the "hypothetical" page because at least one reasonably well educated person (me!) cannot fully understand the first sentence of the article, and that's poor design form in Wikipedia.

PaulTanenbaum 02:42, 21 September 2007 (UTC)

Ball-and-stick model of methanesulfonic acid

Chemical structure of sulfonic acid.

I think what it means is that the sulfonic acid shown on the top does not exist in this form (see tautomer). It would convert to sulfurous acid (bottom) in solution because that would a better bonding configuration for the sulfur. However, if rather than a not very electron donating hydrogen were swapped out for a methyl, butyl, etc. group, the six bonded sulfur configuration found in sulfonic acid would be stable enough to exist. Even if it weren't especially stable, it wouldn't have much choice anyway. Unlike the hydrogen attached to the sulfur, an organic group could not be transposed to an oxygen form a err... sulfonylester? (not sure what to call it) because the intermediate would involve an extremely thermodynamically unfavorable carbocation. Methanesulfonic acid certainly exists. Here is the MSDS. http://physchem.ox.ac.uk/MSDS/ME/methanesulfonic_acid.html Sifaka ^talk 05:04, 21 September 2007 (UTC)

Chemical structure of sulfurous acid.

I'll take a stab: if we consider a zwitterionic resonance form of O=S ↔ O^–1–S⁺¹, then we have an H on a partially-positive S (see sulfoxide for a dramatic example). Tautaumerizing puts it on the O instead (quenches partial negative) and leaves a lone-pair on the S (quenches the partial positive). The protons on the carbon attached to S in an alkylsulfonate are particularly acidic, further support for S being non-stabilized by having a non-electron-donating H attached to it. Interestingly though, if you deprotonate sulfurous acid to get bisulfite, then you do get a structure with H on S. Note that carbocationic rearrangements are quite common but they are more often occurring by concerted migrations instead of a carbocation popping off and then later reattaching somewhere else. And they usually need a pretty strong driving force (a preexisting carbocation, a strained ring, etc). DMacks 06:28, 21 September 2007 (UTC)

Much clearer explanation than mine DMacks. Thanks, Sifaka ^talk 07:12, 21 September 2007 (UTC)

building downtown nyc

I heard that south of greenwich st. in nyc there used to be ocean, but it got filled up over the years and reclaimed as land. how can you build skyscrapers on a man-made landfill? Don't you need some strong bedrock to support them? —Preceding unsigned comment added by 12.217.199.246 (talk) 06:12, 21 September 2007 (UTC)

You drive piles down through the fill into the bedrock, below the water line if that's where the bedrock is. —Tamfang 08:08, 21 September 2007 (UTC)

What will happen to this molecule?

While answering the question two above I wondered about the stability of this molecule. After querying NIST Chemistry WebBook and google, I couldn't find any examples of anything like this as a functional group. I figure it must spontaneously react with itself. Assuming 2 molecules reacting with one another, I pushed arrows as shown to produce two Organosulfonic acids. Is this a reasonable assumption for what would actually happen? Organic chem buffs, what do you think? Sifaka ^talk 07:07, 21 September 2007 (UTC)

It is a reasonable explaination of what might happen if you had that radical in a jar...but of course that doesnt mean anything like that will occur :DShniken1 11:59, 21 September 2007 (UTC)

It's a sulphite ester. In genereal no this reaction won't occur because the R-O bond is much stronger than the R-S bond - so the equilibrium constant would prevent the reaction occuring to any noticeable degree.87.102.87.157 15:01, 21 September 2007 (UTC)

I don't have experience with the electronics/stability/reactivity of sulfite esters themselves, but in related structures such as DMSO, the sulfur-bound oxygen, not the sulfur itself, often acts as the nucleophile. HSAB is an interesting way of comparing relative stabilities of these structures. Perhaps by choosing an electrophile (Lewis acid, in HSAB terms) that is particularly soft, one could get reaction at the S or migration of something from O to S? Acid hardness is yet another way of explaining the relative stability of sulfonic acid vs sulfurous acid: H⁺ is a hard acid, O^– is a hard base, S^– is a soft base. A bit of caution here: relative stability is about which structure would be preferable, not whether or how one structure could convert to a more stable one…lots of things are "stuck" in less stable forms because there's no viable mechanism for the change. DMacks 16:14, 21 September 2007 (UTC)

Good point, if R was Br (bromine) I would expect that change, but R often means an alkyl or other hydrocarbon group - I made that assumption.87.102.87.157 17:00, 21 September 2007 (UTC)

After sitting on it for a night I found what appears to be a more plausible multistep reaction which is sort of analogous to a decarboxylation reaction but forms sulfur dioxide gas and some sort of alcohol depending on what the R group is. The most unstable intermediates are protonated oxygens and oxyanions in neutral reaction conditions although this reaction would be catalyzed by acids or bases. Seems more likely to me. Sifaka ^talk 17:25, 21 September 2007 (UTC)

Yup, now we're talkin'! Hydrolysis (cf. R migration O→S) is a well-known process among many types of esters. For alkyl sulfates, both the C–O and O–S bonds are labile under various conditions (loss of an intact sulfate or hydrolysis of the ester bond, respectively), though some of the mechanisms are still being investigated (doi:10.1021/ja0279747 S0002-7863(02)07974-X for example). Sulfite haloesters are also highly reactive at the C–O bond (see thionyl chloride#Use in organic chemistry). Then there are also the various sulfite ester hydrolysis mechanisms (see [http://pubs.nrc-cnrc.gc.ca/cgi-bin/rp/rp2_abst_e?cjc_v77-413_55_ns_nf_cjc Can J Chem. 55 1977 2971-2976). DMacks 17:49, 21 September 2007 (UTC)

mitosis,meiosis in humans

what takes place in mitosis in the human body? what takes place in gamete formation in humans? —Preceding unsigned comment added by 82.206.143.13 (talk) 07:15, 21 September 2007 (UTC)

I would suggest reading the articles mitosis and meiosis to answer your question. Sifaka ^talk 07:21, 21 September 2007 (UTC)

Colourblindness

Are all animals colourblind?124.7.82.159 09:05, 21 September 2007 (UTC)

I would think it unlikely. It might be a good start to think about why animals, in it's broad sense, are coloured. Off the top of my head I'd say there are three drivers for colour in animals.

Camouflage, defensive and offensive.

Attraction for mating or territorial defence.

Chance, as when the animal has other features that don't require specific colouration, e.g. elephants or rhinos.

Clearly perception of colour is important and thus presumably visible in a wide range of animals, birds (of paradise, for example) lizards and cephalopods are three groups that come immediately to mind where colour is used to transmit information. If it transmitted we must assume it is received. Richard Avery 09:21, 21 September 2007 (UTC)

See our articles on color vision and monochromacy where this topic is discussed in (a little) more detail.--Shantavira|^{feed me} 11:26, 21 September 2007 (UTC)

No - most animals aren't colour blind - although that term is a horribly inaccurate one and requires clarification before we can proceed to answer the question.

First let's establish a baseline for comparison. Humans can see only three colours - red, green and blue - and we have other cells in our eyes that detect brightness (without responding to colour) and which are really sensitive to motion. Everything else we see is a mixture of those colours - yellow is a mixture of red and green for example - even 'normal' humans are colour blind in that we are completely unable to distinguish between a mixture of red light and green light (such as is produced by your computer screen when it displays "yellow") and a pure yellow light such as would be found in a rainbow or being emitted by sodium street-lamps. This makes us 'trichromats' - we see everything in terms of three colours plus an overall average 'brightness' value that's mostly useful at night.

People who are "colour blind" are sometimes dichromats with one set of colour detection cells completely missing...or (like my son) they may be trichromats who have weak colour perception in one or more sets of colour detectors making some colours hard to distinguish. Those people don't see things in black and white - they see them in a different range of colours depending on which set of detectors are missing or weak. It's wrong to call such people "colour blind" because they do see colours - but that's the term we use. My son can correctly identify all of the colours in a rainbow - but cannot pass a colour blindness test.

A really unfortunate person might have one or zero colour detectors - and they will truly only see in shades of grey and might truly be called 'blind' to colour.

There are also a very, very few women who are tetrachromats (in fact only one such person has been clearly identified and tested) - they can see colour even better than a typical human...compared to them, we are ALL "colour blind"!

OK - so with those things in mind - how does animal colour perception stack up against us humans:

• Some animals (such as owls) need really good vision at night - they don't bother cluttering up their eyes with useless (to them) colour sensors - but instead pack them with brightness/motion detectors. They see in amazingly low light levels - but they are utterly colour-blind. Their eyes are also somewhat sensitive to Infra-red so they can see 'heat' from warm, furry mice...but I believe that's still a monochrome sense. The world for them must be a lot like using military night-vision devices is for us.
• Some animals (like dogs and cats) are dichromats by nature. The can see in colour - much like a dichromat human - but not with as much colour sensitivity as a trichromat human. I wouldn't call them 'colour blind' so much as 'colour deficient'. We think that humans probably evolved to see in three colours in order to be able to distinguish red and green so that we could tell the difference between ripe and unripe fruit. Dogs and cats are carnivores - they don't care about that - so dichromaticity is fine for them - and the extra space in their eyeballs allows for better night vision - which is good for a carnivore.
• Some animals (such as the goldfish) have as many as seven different colour detectors in their eyes (heptochromats)!! Their world must be just alive with subtle colour because they see colour incredible better than humans. I have no clue why they evolved this ability.
• I read a while back about a species of freshwater shrimp which may have even more than seven colour detector types...perhaps as many as twelve!
• Bees can see in ultra-violet light - beyond the range of our eyes. Otherwise plain-coloured flowers often have elaborate patterning in the UV part of the spectrum specifically to attract bees. I don't know whether they can see different 'shades' of UV light or not...I suspect not.

So, no - animals aren't all colour blind. Some are, some aren't, some see colour better than us, some worse - some can see light outside of the "visible spectrum" that we can see in. But there isn't a simple distinction between being able to see in colour or not - there are huge ranges of colours that humans cannot distinguish - and some things we think of as 'colours' (like magenta) that aren't true colours at all - but merely an artifact of our (relatively poor compared to goldfish) colour vision.

SteveBaker 14:35, 21 September 2007 (UTC)

For a really interesting and thorough discussion of colour-blindness with respect to (scientific) presentations, see this link. The website shows what people with different colour deficiencies see. -- Flyguy649 ^talk _contribs 20:02, 21 September 2007 (UTC)

Have a read of this thread from a couple of months back, WRT to the colour perception in birds too... --Kurt Shaped Box 02:44, 22 September 2007 (UTC)

photons and gravity

Are photons affected by gravity? According to the article on Newton's (outdated?) law on gravity, the force must be equal to zero since photons have no mass. If so, how do black holes "trap" photons? (I have almost no knowledge of quantum mechanics and similar things). Thanks. --wj32 ^{talk | contribs} 09:57, 21 September 2007 (UTC)

In general relativity, mass curves spacetime. In this model, straight lines across spacetime are curved near masses. Since photons travel in straight lines, they will also curve. Black holes curve space time so much that a straight line going out from a black hole (or any straight line that enters the event horizon) enters back into the black hole. A photon following this straight line cannot escape. (I am, of course, vastly simplifying here). Capuchin 10:14, 21 September 2007 (UTC)

You can't use Newton's laws to talk about black holes—the latter are a prediction of General Relativity and have nothing to do with Newton. General Relativity supercedes Newton. --24.147.86.187 13:01, 21 September 2007 (UTC)

That's not entirely true. Somewhere between the periods of "Newton develops theory of gravitation" and "Scientists decide the particle theory of light doesn't work too well", someone pointed out that if light were subject to gravity - and there was no actual reason at the time to suggest that it wouldn't be, even if it were some strange kind of effectively massless particle - then it would be possible to have an object of such a size and mass that its escape velocity would exceed the speed of light, hence creating a black hole. Confusing Manifestation 13:38, 21 September 2007 (UTC)

Indeed. John Michell predicted the existence of black holes in a letter to Henry Cavendish in 1783. The text of the letter is here - the part dealing with black holes is paragraph 16. Gandalf61 13:48, 21 September 2007 (UTC)

So an idea based on a misunderstanding of gravity and a misunderstanding of light counts as a prediction of something rooted in different conceptions of both? Not in my book. --24.147.86.187 00:35, 22 September 2007 (UTC)

Depends on what it means to know/predict something. Someguy1221 00:47, 22 September 2007 (UTC)

Certainly photons are bent by gravity - check out Gravitational lens - in which the bending of light by the gravitational field of some large body out in space is used to magnify the image of more distant objects in exactly the same way that light is bent by a glass lens. There is a photo there showing it actually happening - so it's hard to deny! SteveBaker 16:52, 21 September 2007 (UTC)

• And you don't even need something as massive as a black hole to visibly bend the path of a photon. Light curving around extrasolar planets has been used to discover them. See gravitational lensing. --Sean 17:05, 21 September 2007 (UTC)

The odds of having a planet lens some distant object is really small - as our article points out, it's only been recorded once - and the alignment was too brief for anyone to double-check it. Large objects like galaxies and black holes bend light by so much that a chance alignment is not really needed - so while it's true that you can do this with planets, it's much easier to demonstrate with bigger objects. SteveBaker 17:24, 21 September 2007 (UTC)

Gravitational microlensing had found three planets as of this two-year-old paper. --Sean 20:00, 21 September 2007 (UTC)

I don't really buy that photons have no mass. Experimentally, all they could determine is that they have no mass above a certain threshold which they can measure. But, let's say they are right and photons have no "mass". That really means photons have no rest mass, which is a useless bit of data since photons are never at rest. They do have relativistic mass, however, when moving (which is always), that explains why they are pulled by gravity and why they can exert a pressure on a solar sail. (This may not be the current way of stating things, but I find it useful in explaining photon behavior under Newtonian mechanics.) StuRat 15:43, 22 September 2007 (UTC)

Forgive my Newtonian blundering, but they seem to have a distinct lack of kinetic energy. Plasticup ^T/C 20:42, 23 September 2007 (UTC)

On the contrary -- all of their energy is kinetic.

I think the general rule is, if you naively calculate what will happen to photons in a gravitational field by computing their "mass" as their energy divided by c² and working from there, you will get within a factor of two. For some calculations it's almost exactly a a factor of two; there's probably some deep reason for this but I don't know what it is. --Trovatore 20:48, 23 September 2007 (UTC)

Physics

So this is sort of a bullshit question. As it seems mathematically simple. The question goes something like this: An automobile starts from rest and accelerates to a final velocity in two stages along a straight road. Each stage occupies the same amount of time. In stage 1, the magnitude of the car's acceleration is 3 m/s². The magnitude of the car's velocity at the end of stage 2 is 2.5 times greater than it is at the end of stage 1. Find the magnitude of the acceleration in stage 2.

a1 = v1/t1 (that's obvioius)

a2 = v2/t2 (obvious as well)

v2 = 2.5v1 (seems obvious)

t1=t2 (probably the most obvious)

So given that a1 = v1/t1....v2 = 2.5v1, one can say that a2 = 2.5v1/t1

Since v1/t1 = 3m/s². Now one could play with equations and get a2 = 2.5 (3m/s²) = 7.5 m/s²

However, this is stated as being wrong. Either I made a complete mistake or something else is up. Anyone know what? Thanks HERODOTUS 14:22, 21 September 2007 (UTC)

Your second equation should be a2 = (v2-v1)/t2, and thus a2 = (1.5)v1/t1. Gandalf61 14:39, 21 September 2007 (UTC)

Oh there we go... forgot about getting the change in v. thanks. HERODOTUS 14:45, 21 September 2007 (UTC)

Sky and Planet Earth

What makes the sky and our planet appear blue from outer space?24.91.219.166 14:59, 21 September 2007 (UTC)

Water molecules in the atmosphere refract ("scatter") blue light more than other colors, due to the wavelengths involved. Similar to how a prism refracts a beam of light into a rainbow - some colors are "bent" more than others. Saturn 5 15:35, 21 September 2007 (UTC)

See Diffuse sky radiation. DMacks 16:19, 21 September 2007 (UTC)

See Mie scattering and Raleigh Rayleigh scattering. SteveBaker 16:40, 21 September 2007 (UTC)

Yeah. "Raleigh scattering" is what Hurricaines fans do after the game. DMacks 17:23, 21 September 2007 (UTC)

And the oceans appear blue from above because they reflect blue sky; without atmosphere I guess they'd look muddy green. —Tamfang 19:24, 21 September 2007 (UTC)

No, water is actually blue. It's very faint though, which is why you have to look through a lot of it to really notice. Someguy1221 22:22, 21 September 2007 (UTC)

If you want proof, go to Crater Lake sometime. It's incredibly pure water a few thousand feet deep -- and incredibly blue. The pictures in the article don't do it justice. --Carnildo 22:41, 21 September 2007 (UTC)

Air appears to be slightly blue also - when I looked at the dome of a nuclear reactor from a long distance away it was pale blue, as I walked towards it the colour changes to bright white. 80.0.114.206 13:52, 22 September 2007 (UTC)

INCORPORATION OF INTERMEDIATE FREQUENCY

DEAR SIR. I AM LIAQUAT JAWED FROM KARACHI PAKISTAN. SINCE LAST FIFTEEN DAYS I AM IN A SEVIER CONFUSION THAT AS GIVEN BELOW;

1) WHAT ARE THE BASIC RANGES OF INTERMEDIATE FREQUENCIES FURTHER THAT VHF/UHF DOES COME UNDER THE RANGES OF INTERMEDIATE FREQUENCIES .

2) WHETHER CATV DISTRIBUTION AMPLIFIER OR CATV LINE AMPLIFIERS DO INCORPOATE THE INTERMEIDATE FREQUENCY.

3) WHETHER CAN WE CLASSIFY THE CATV DISTRIBUTION AMPLIFIERS OR CATV LINE AMPLIFIERS UNDER THE CATEGORY OF INTERMEIDATE FREQUENCY INCORPORATING AMPLIFIERS.

WAITING FOR YOUR AN EARLY REPLY.

THANKS AND BEST REGARDS.

LIAQUAT JAWED —Preceding unsigned comment added by Lachi9 (talk • contribs) 16:12, 21 September 2007 (UTC)

Ow! Please type in mixed upper and lower case in future - typing in ALL CAPITALS seems rude to most people. SteveBaker 16:37, 21 September 2007 (UTC)

I suggest you start by studying our articles on radio frequency and CATV. (I'm not sure what you mean by "intermediate frequency").--Shantavira|^{feed me} 18:30, 21 September 2007 (UTC)

We have an article on intermediate frequency - but it doesn't list the UHF and VHF IF's. SteveBaker 20:03, 21 September 2007 (UTC)

For CATV applications in North America, I think the intermediate frequency band is 41 – 47 MHz. --71.175.68.224 15:17, 23 September 2007 (UTC)

fish in water

take a bucket of water full to the brim(water about to overflow) add a fish any type dead or alive,no water will become displaced why is this? —Preceding unsigned comment added by 83.71.37.244 (talk) 18:07, 21 September 2007 (UTC)

Because what you just stated doesn't happen. Water is displaced. If you put something very small in a very large container of water, it is possible for surface tension of the water to bulge upward without overflow - but the bulge is still displaced water. -- kainaw™ 18:09, 21 September 2007 (UTC)

See meniscus for a little more info. That article could do with some more info, but that is the phenomenon you would observe. Saturn 5 18:12, 21 September 2007 (UTC)

If you toss a fish into a bucket of water then the water level goes up. If it's "full" beforehand then it overflows (if there was room for a little more water because of meniscus effects then the bucket wasn't full yet). The questioner is incorrect. Is this some kind of urban legend you read someplace? SteveBaker 20:02, 21 September 2007 (UTC)

If you toss a struggling live fish (or a dead fish from a sufficient height) into a bucket, it may splash it's own volume of water out of the bucket, in which case the waterline on the bucket would remain the same. StuRat 15:27, 22 September 2007 (UTC)

Unless the fish dissolves in the water, it will cause the bucket to overflow (or form a meniscus). If you put salt in a full bucket of water, this will not happen, because the density changes (instead of the volume). Nimur 18:02, 22 September 2007 (UTC)

Sleepless early-hours mulling over past bad events

It seems common for many people to involuntarily mull over past bad events if they are sleepness and half-awake in the early hours of the morning. Does anyone know why there is a psychological tendency for humans to do this? Or how to stop it? Thanks. 80.2.199.116 20:05, 21 September 2007 (UTC)

See cognitive behavioral therapy for the field of techniques on controlling negative thoughts. --Sean 22:05, 21 September 2007 (UTC)

To stop it, you refute those thoughts and think of something pleasant/interesting to you. Alternatively, you can refuse to accept any words in your thoughts, only pictures. Eventually the pictures will fade and you will lose consciousness. —Preceding unsigned comment added by 88.110.12.8 (talk) 02:21, 22 September 2007 (UTC)

Useful advice, but why do humans suffer this in the first place? 80.0.131.244 08:53, 22 September 2007 (UTC)

Very shortly and simply put: our defense mechanisms are not as strong during the night as they are during the day, so unpleasant thoughts have a stronger impact on us. Lova Falk 09:14, 22 September 2007 (UTC)

One theory of sleep is that the brain uses this opportunity to review past events, consider where mistakes were made, and formulate a plan on how to do things better in the future. A semi-sleep state may take on some of these characteristics, too. StuRat 15:24, 22 September 2007 (UTC)

how old is stone bone

Many years ago i found a petrified bone in the bad lands of South Dakota, it appears to be a femar of a four legged animal. The bone has become brittle stone. The bone marrow has become crystalized. Any idea how long it would take for that to happen? Hundreds, thousands, or millions of years? —Preceding unsigned comment added by 69.254.44.75 (talk) 20:20, 21 September 2007 (UTC)

If it's still bone, it's probably not too old, as actual preserved tissue from the distant past is extremely rare. If it's stone, it could be anywhere from thousands to hundreds of millions of years old. See fossils. --Sean 22:09, 21 September 2007 (UTC)

I'd take it to a natural history museum and ask them to tell you what it is. It's probably just a 1000 year old wolf or something similarly worthless, but you never know, it may be some type of dinosaur bone. (Make sure you obtained it legally, though, as some areas, like National Parks, don't let you take fossils home.) Also, how big is it ? (A 10 foot long femur would definitely make it a dino bone.) StuRat 15:15, 22 September 2007 (UTC)

Hmm the article on Mineralisation is incredibly weak, so no help there! —Preceding unsigned comment added by 88.109.137.161 (talk) 01:16, 23 September 2007 (UTC)

As already said, it's most likely modern. If not, and if it is from some legal area in the White River Badlands, it is likely Oligocene in age, more or less, 25 or so million years. Cheers Geologyguy 01:35, 24 September 2007 (UTC)

Any Aussies here?...

I was just at a local bar. We were 'discussing' fall/autumn. Some were saying that TODAY, September 21st was the first day of fall. I said, "No. The official date of fall this year is Sunday, September 23rd." Ok, that`s not a question. One of the patrons said that he lived for several years in Australia, here`s the "Aussie" connection, and that THEY 'celebrate' the changing of the seasons ALWAYS on the 1st of the month of the 'official' change. Of course, they would have 'celebrated' spring, and not fall, but the question is this: Is it true, that they, the Australians, celebrate these 'changes' at the first of their respective months? Seems quite strange to me. Sorry for posting here on the science desk but, I was already 'here', and it DOES have an Astronomy bent! Thanks Dave. 64.230.233.222 21:32, 21 September 2007 (UTC)

The four seasons are more relevant in the southern part of Australia than the northern part. Here in Melbourne:

Summer is Dec, Jan, Feb

Autumn is Mar,Apr,May

Winter is Jun,Jul,Aug

Spring is Sep,Oct,Nov

I'm not sure what you mean by "They celebrate the changing of the seasons" as I certainly do not celebrate the changing of the seasons nor do I know of anyone who does. However the snow bunnies do celebrate the starting of the ski season but not everyone is a snow bunny. 210.49.155.132 22:59, 21 September 2007 (UTC)

Thanks for the reply, umm, 210. To simplify, the aforementioned patron, who spent some time in Australia, said that Australians consider the 1st of the month, 'their' official start of a particular season, be it fall or spring or whatever, rather than the equinoxes and solstices as the official beginnings of said seasons. No REAL celebrating implied. Perhaps I should have utilized the term 'observe', rather than 'celebrate'. Is that TRUE? Sorry for any misunderstanding, and ty again. Dave 64.230.233.222 23:19, 21 September 2007 (UTC)

So you might have heard that the summer solstice (roughly speaking the "longest day of the year", even if it isn't always exactly) used to be called "midsummer", whereas in North America we think of it as the first day of summer. The reason is that average daily temperature somewhat lags the length of the day (it takes a while for the ground and the oceans to heat up), so the hottest three months of the year are roughly the ones between the summer solstice and the autumnal equinox. That makes the summer solstice a convenient marker for the start of summer.

As I understand it, in Australia, for whatever reason, the lag time is a bit less, and they find it convenient to use the first day of the month in which the solstices and equinoxes appear. --Trovatore 00:46, 22 September 2007 (UTC)

I'm in Sydney, and we change seasons on the first day of the respective month, in fact until a few minutes ago I used to think the entire world changed seasons on the first day of the month... As for the lag time of temperature changes and what not, I think the reason we change on the first day is simply because it is easier to remember, given that often the weather does not match the season I'd say the lag times etc are not taken into account. Still that's just my opinion 124.183.147.134 01:24, 22 September 2007 (UTC)

Thanks for the replies folks. And 'Sydney', 124; You`re probably just as surprized to hear that the whole world doesn`t change on the 1st of the respective months as I am to hear that you, in fact, DO change at those times. As I said earlier, seems strange to me. Just as an aside, for the Aussies: What do your calendars say? Is your first day of spring actually written on your calendars as occuring on September 1st? Thanks again all. Dave 64.230.233.222 04:27, 22 September 2007 (UTC)

When it's written on the calendars, yes. However, given that often we get calendars that are actually sourced from overseas, most often produced for the mass market in the US, we will actually find out that September 23 for example is the first day of Autumn (or even worse, Fall), when we're actually three weeks into Spring; d'oh! BTW, I don't mean to enter into a 'your culture is stranger than ours debate', but it always strikes me that starting the season on the first of the month is far simpler - you started this post saying you had a debate about which day was the start of Fall; you never get that debate in Australia as everyone knows it's the first of the month, the only trick can be knowing which month. Cheers, --jjron 12:50, 22 September 2007 (UTC)

Well, except months are arbitrary, fixed by human convention; solstices and equinoxes are not. Aligning our seasons to the solstices and equinoxes makes it look like the seasons aren't arbitrary either. Of course it's really just a trick. If we wanted summer to be the fourth of the year with maximum insolation, it would run from early May to early August (or, I suppose, early November to early February for y'all). --Trovatore 17:15, 22 September 2007 (UTC)

Hahaha. Good replies folks. Thanks to all for your insigthful inputs. Trying to enjoy MY 'last' full-day-of summer here. CHEERS! Dave 64.230.233.222 21:26, 22 September 2007 (UTC)

I think it is important to note one unimportant seasons are in Australia compared to other countries (at least in the north).. School/University terms/semisters in the northern hemisphere is centred around the seasons. You start mid yearat, after "summer", as I understand it. Here in Aus we start at the start of the year, and we dont really consider it starting after the summer break, it is more of the christmas break, this goes for work places as well. It appears to me that the seasons play a much more central role in the daily lives of you northerners so you pay more attention to when each season starts. Also remember there are no (native) desicuous trees in Australia so leaves do not fall off trees in autumn..Shniken1 01:34, 23 September 2007 (UTC)

The culprit for fiddling with the date for the change of seasons in Australia was the original governor of the penal colony in 1788 who, after listening to complaints from his garrison troops of the New South Wales Corps that their winter uniforms were too hot for September decreed that henceforth winter would end at the 31st. August. The other seasons then had also to fall into line. Greetings from Oz. —Preceding unsigned comment added by Vorc (talk • contribs) 07:04, 24 September 2007 (UTC)

Number of neurons in the human brain

What is an estimate of the number of neurons in the human brain? Please cite a research source.72.75.96.28 21:30, 21 September 2007 (UTC)superiorolive

Neurons#Neurons_in_the_brain: "One estimate puts the human brain at about 100 billion (10¹¹) neurons and 100 trillion (10¹⁴) synapses." This review says "Estimates for the human brain range between 10 billion and 1 trillion. The imprecision in these estimates is due almost entirely to uncertainty about the number of granule cells in the cerebellum, a problem that can be traced back to a study by Braitenberg & Atwood (1958). More recent work by Lange (1975) makes a reasonably accurate estimate possible: The average human brain (1350 gm) contains about 85 billion neurons. Of these, 12 to 15 billion are telencephalic neurons (Shariff 1953), 70 billion are cerebellar granule cells (Lange 1975), and fewer than 1 billion are brainstem and spinal neurons." Rockpocket 21:52, 21 September 2007 (UTC)

Thank you for this72.75.96.28 02:21, 22 September 2007 (UTC)superiorolive

Is there any way to stop melanin production in humans?

Is there any way to stop melanin production in humans? And please dont say death or aging or idk. —Preceding unsigned comment added by 81.99.218.58 (talk) 22:28, 21 September 2007 (UTC)

There are chemicals that will permanently depigment human skin. Or so Vitiligo#Treatment would have you believe. Vitiligo, by the way, is a natural condition in which the body has no ability to produce melanin over patches of skin. Someguy1221 22:32, 21 September 2007 (UTC)

Albinism Cyta 10:22, 24 September 2007 (UTC)

September 22

Are there chemicals that will permanently depigment human hair?

Are there chemicals that will permanently depigment human hair? —Preceding unsigned comment added by 81.99.218.58 (talk) 00:06, 22 September 2007 (UTC)

Yes, but such a chemical would have to be cytotoxic, as to do so one needs to destroy the stem cell niche of the hair follicle. There is not a known chemical that can do that specifically without harming other cells. Similarly exposing your head to high doses of ionizing radiation would permanently depigment your hair. It would probably also give you cancer though. The alternative would be to permanently inhibit the melanogenic enzymes, such as tyrosinase. There are chemicals that can do that in a temporary manner, but doing so permanently, and without serious adverse effects, is not currently possible. So if what you really wish to know is if there is a chemical that can safely and permanently depigment human hair, the answer is no. Rockpocket 01:32, 22 September 2007 (UTC)

You dont need chemicals: you just wait till you are old. It happens naturally! —Preceding unsigned comment added by 212.139.98.210 (talk) 20:21, 22 September 2007 (UTC)

This is being obtuse, but technically, bleaching the hair (normally done with hydrogen peroxide) permanently depigments hair. The hair treated with it will never get pigments back. That is, if you chop off your hair and bleach it, it is going to stay bleached! :) --Mdwyer 05:39, 23 September 2007 (UTC)

Colors

So, I was reading the question above on colorblindness, and I had a startling thought. You said we don't perceive real yellow, just red + green, right? So if we were to meet an alien with yellow receptors, they could see REAL yellow, and what we call yellow they'd call redgreen (or whatever)? so we never really see Yellow at all (or any color other than red, green, and blue) in the pure forms? After all, people with no green receptors see red+blue for green, right, which looks TOTALLY different... am I on to something here? Kuronue | Talk 00:47, 22 September 2007 (UTC)

In terms of colour perception, it doesn't really matter whether we see "real" yellow when we can perceive it so well using our three types of cones. A yellow cone could certainly provide an alien with a richer yellow hue perception, but they would all still be variations of the same "yellow" that we see (assuming, of course, the same processing system of perception is in place). The reason we don't need a yellow cone is because its redundant to the three that we have. Rockpocket 02:06, 22 September 2007 (UTC)

Yes, but like, someone who is partially colorblind can distinguish between colors, but they look totally different to them. Just because we can distinguish yellow from blue doesn't mean what we're seeing is anything like actual yellow, right? I mean, green looks like brown to people with a defective cone, so maybe some brownish colors to us are actually shades we can't see properly, things like that... Kuronue | Talk 03:01, 22 September 2007 (UTC)

Well, what is "actual yellow"? Its a wavelength of light. Notwithstanding the the "red" receptor actually has its peak sensitivity in the yellow part of the spectrum anyway, the actual detection mechanism is simply a action potential along an axon in response to the detection of a certain wavelength. The information is processed in the parvocellular layer where certain neurons process red-green differences, and others process blue-yellow differences. Its here that we "see" yellow. If an alien had a different cone, then it would fire in response to the appropriate wavelength, but still need to be processed in some manner. Depending on how these inputs are wired, the alien brain could "see" exactly same yellow as we do or it could interpret the wavelength as any pseudo-colour its brain evolved to conjour up. What is likely is that it could use such a receptor to distinguish multiple shades around that wavelength that would be beyond what we can distinguish. I guess what I'm trying to explain is that a fourth receptor type in the visible spectrum doesn't really offer "new" colours - our system evolved to have that well covered - it simply expands the subtles hues within those we already see. Rockpocket 04:27, 22 September 2007 (UTC)

You could try getting your hands on a yellow light - or a white light with a pure yellow filter, as well as two lights with red and green filters - then try illuminating things - you should be able to tell the difference between the things that are yellow for different reasons.. As an aside I remember that some insects can see ultraviolet light - this lets them see patterns on plants that we humans can't see - for instance flower petals look striped to insects87.102.89.127 12:37, 22 September 2007 (UTC)

Right - there are (at least) two "yellow" colours - one is a mixture of red+green and the other is 'true' yellow - light which has a frequency halfway between red and green. Our eyes can't tell the difference - but you can do experiments to see the difference. Put the 'yellow' light through a prism to spread out it's spectrum. Yellow light from your TV or computer monitor will split into two lines (red and green) but true yellow (from a sodium lamp for example) would form a single line (well, more or less). So these two colours look identical to us - but they are NOT the same colour. In order to get an idea how an alien (or your goldfish) would see these colours, we can try some analogies:

• The analogy of sound: On a piano, you can play two notes 'C' and 'E' together - or you can pick a note midway between C and E ('D'). Does C+E sound the same as D? Nope - not by a mile! But that's the exact same thing as the difference between the two yellows.
• We see three colours - red, green and blue. Green is a frequency between red and blue. So we can ask: How different is red+blue from a frequency halfway between red and blue? Well, halfway between red and blue we have green. What does red+blue look like? Magenta! So for our alien/goldfish, the difference between those two versions of "yellow" might look as different as magenta and green!!! That's a very powerful indication about how poorly we percieve colour. What I find most mind blowing is the little old lady in England who is a tetrachromat - she sees colours that almost nobody else in the world can see. She works in a store selling knitting yarns and she remarked to researchers how she was much better at matching colours than other people...no surprise if others were 'matching' magenta and green and calling them "the same exact colour". WOW!

I talk about the problems with "yellow" - but the same problems are there with "cyan" (midway between blue and green or a mixture of blue and green?). The third colour pair that might be problematic would be "magenta" - but we have a green sensor so we can tell the difference between red+blue and green. But in general, for colours that are more complex mixtures of frequencies - there are colours like a mixture of red, green and true-yellow that are yet different from the other two versions. Even our goldfish friend can't get the full subtlety - for that you'd need a spectrum analyser.

SteveBaker 15:22, 22 September 2007 (UTC)

Finally, one should mention that there might be people who can distinguish the two yellows by means of having two different kinds of cones for the red colour, one shifted towards yellow or orange. More at tetrachromacy. Simon A. 16:00, 22 September 2007 (UTC)

Special Relativity and Mass Defect

This was a question that came to me during a physics class. Einstein's special theory of relativity states that as an objects velocity approaches the speed of light its mass approaches infinity, and that increasing amounts of the input energy used to accelerate (eg from combustion of liquid fuel) is converted into matter. The processes of nuclear fusion and nuclear fission produce energy due to the mass defect where the products have less mass than the reactants. However, as the total mass of the system approaches infinity it follows that the mass defect will also approach infinity, which could possibly overcome one of the problems with fast travel and allow us to come closer to the speed of light than if we used conventional fuels. However, wouldn't this also violate the law of conservation of energy (the total energy of the system must remain constant, with mass being recognised as energy according to E = mc²) as both the mass and thrust of the system would increase without any additional input energy?

I only study basic physics, but it would be great if someone could cast some light on whether or not this would be possible 124.183.147.134 01:19, 22 September 2007 (UTC)

• Short answer: no. There are no such defects in special relativity theory, which has been experimentally confirmed many times. --Sean 02:07, 22 September 2007 (UTC)

Um, I think you might be misinterpreting the word "defect" here. "Mass defect" is not a defect in the theory. --Trovatore 02:19, 22 September 2007 (UTC)

Perhaps I should clarify. The theory of special relativity states that as velocity approaches the speed of light mass will approach infinity (although I'm not sure if this has been proved experimentally). The mass defect is not related to the theory of special relativity, but is observed in nuclear reactions (eg in nuclear fusion two hydrogrens fuse to form a helium, the mass of the helium is less than the combined mass of the hydrogen, and this mass defect explains the energy released). I was wondering what would happen if the two separate situations were combined, as the velocity approaches the speed of light the mass of the system should approach infinity, but if a nuclear reaction is occurring then the mass of the hydrogen and helium will approach infinity, meaning the mass defect of the reaction will approach infinity resulting in the energy produced approaching infinity. If this nuclear reaction was used to accelerate the vessel then it would overcome some of the problems with high speed travel (increasing amounts of energy released from conventional fuels would be converted into mass reducing the effective acceleration and restricting the practical obtainable speeds below that of the speed of light, however if the nuclear reaction produced increasing amounts of energy this would allow the system to continue accelerating at a higher rate) however intuitively it seems to violate the law of conservation of mass-energy... 124.183.147.134 02:47, 22 September 2007 (UTC)

Well, think of it this way. Your spacecraft takes off. Its own mass is an upper limit on how much energy it could possibly generate, ever. That is a very finite value. Therefore, it can never supply an infinite amount of energy. The energy lost in accelerating two hydrogen molecules before fusing them will nullify any increase in energy they will produce thanks to being in a very fast reference frame, relative to whoever is measuring it. Someguy1221 04:56, 22 September 2007 (UTC)

From the point of view of people on the space craft (e.g. in their inertial frame), the fuel isn't moving and hence the mass defect remains constant. Thus from their point of view, the energy they have available to generate thrust doesn't change. However, from an external point of view, it is actually more complicated. Because of time dilation, the apparent rate of the reaction (as measured by an outside observer) would slow down. Hence they would actually be generating less thrust per unit external time as their speed increased. 136.152.153.120 03:42, 22 September 2007 (UTC)

Dear physics student, you may have learned that the mass increases as an object accelerates towards the speed of light. This is true if you're talking about a definition of mass called relativistic mass, which is often discussed in popular works on relativity and sometimes in physics textbooks. Early in the history of relativity, that's what was usually meant by "mass." But it's quite misleading if you start to think about things like nuclear reactions in those terms. Instead, you can use invariant mass, which is more useful for a lot of purposes (it's exactly what you want for thinking about a nuclear reactor on a relativistic spaceship!). Since the 1950's or so, physicists have come to use this definition of mass instead. As you accelerate your nuclear fuel, its invariant mass doesn't increase, and that's what you need to convert to energy. --Reuben 04:03, 22 September 2007 (UTC)

• Saying that nuclear fusion and fission "produce energy due to the mass defect" is putting the cart before the horse; it reminds me of Feynman's complaint about wakalixes. There is necessarily a mass decrease of E/c² in any system that releases energy E in some reaction, but that's not why it releases the energy. Chemical power sources work by forming and breaking chemical bonds, and nuclear power sources work by breaking (fission) and forming (fusion) nuclear bonds. There's no difference between them as far as E=mc² is concerned. —Preceding unsigned comment added by BenRG (talk • contribs) 12:26, 22 September 2007 (UTC)

Right. The mass defect bit of fission, for example, is often used just to calculate the energy released, but it is not a good way of explaining the energy released. And the "energy" released isn't some sort of magical burst of lightning as it is usually shown in little diagrams—it relates to the velocities of the various components expelled from the fission reactions themselves (the fission products and the neutrons). I find a better way of explaining the fission reaction (and calculating much of it) to be in the form of thinking of the two split nuclei as being two extremely positively-charged objects placed right next to each other (just out of range of the nuclear force), and then calculating what the electrostatic repulsion is going to be from each of them. --24.147.86.187 14:16, 22 September 2007 (UTC)

I'm drunk - how to sober up quick

it's nearly 4am in the UK now and I'm drunk after a night out. I'm meant to be in work at 8am. Is there any way of sobering myself up quickly? —Preceding unsigned comment added by 81.79.171.12 (talk) 02:50, 22 September 2007 (UTC)

Not really, there isn't a whole lot you can do as "there are currently no known drugs or other ingestible agents which will accelerate alcohol metabolism" See Blood_alcohol#Metabolism and excretion. The best you can do is try to limit the damage, see Hangover#Possible remedies. Rockpocket 03:21, 22 September 2007 (UTC)

I suggest drinking lots of water or rehyrating sprorts beverage about once every two hours, which will minimize the hangover's effects. 128.196.149.25 03:25, 22 September 2007 (UTC)

Exercise helped me when I was in the Marines. After drinking all weekend, I'd show up on Monday morning drunk, but be nice and sober after a 6-mile run. I attributed it to sweating out alcohol while pumping more blood through the liver and kidneys where it gets cleaned. Then, it could just be that the time it took to run was enough for me to sober up. -- kainaw™ 04:54, 22 September 2007 (UTC)

Was the 6-mile run by any chance your punishment for showing up drunk ? StuRat 15:05, 22 September 2007 (UTC)

I also used to run even after wet nights but I was warned that exercising with alcohol in your blood means a serious health risk. I can't remember the details though. Lova Falk 15:44, 22 September 2007 (UTC)

Alcohol induced memory loss ? :-) StuRat 20:17, 22 September 2007 (UTC)

I never had a hangover, because drinking heavily just made me vomit (my body's defense mechanism in action, I suppose). I do NOT suggest that you induce vomiting, however, since that can damage the esophagus and teeth. In severe cases of alcohol poisoning, hospital stomach pumping can help, if they catch it early enough. You might want to call in sick to work, as that likely won't get you fired, but showing up drunk might. You also need to learn not to drink so heavily that you can't function normally (like going to work). Your pores will likely give off alcohol for several hours yet, so even if you clean up you won't fool anyone with a working nose (that's just about all nonsmokers). StuRat 15:05, 22 September 2007 (UTC)

Are you East Asian? Nil Einne 18:24, 22 September 2007 (UTC)

Only in that if you go to Asia and head East you will hit my house in about 12,000 miles. :-) StuRat 20:13, 22 September 2007 (UTC)

When I have a hangover, I usually take a headache pill, drink a cup of hot black coffee, and go out into the fresh air as soon as possible. Staying indoors will make the hangover remain. It is most important to go out into the fresh air and stay there for many hours. JIP | Talk 16:13, 22 September 2007 (UTC)

Bear in mind according to the above link paractemol is suspected of reducing the activity of alcohol dehydrogenase thereby effectively reducing the clearance rate of alcohol from the blood stream. This may mean that you will not suffer such a severe hangover but the alcohol will remain in your bloodstream for longer and so you will remain drunk for longer. Not a good idea if you have to work IMHO. In any case I would strongly recommend the OP do not go to work if they have to drive, operate heavy machinery or carry out any sort of mission or life critical work (e.g. a doctor, police officer) Nil Einne 18:24, 22 September 2007 (UTC)

Good advice. I have never noticed that because none of my (computer programmer), my sister's (teacher), my father's (architect, CEO), or my mother's (architect, city official) jobs fall under the requirements you mention. JIP | Talk 19:26, 22 September 2007 (UTC)

I find that rubbing tiger balm (or other liniment) into my temples/forehead helps with the headache part of the hangover. A friend of mine swears by taking an early morning sauna at the gym or going for a run with his midriff and thighs wrapped in clingfilm to sweat the booze out - though I think someone mentioned on here a while back that this sort of thing doesn't *really* do anything useful in terms of removing alcohol from the blood... --Kurt Shaped Box 19:46, 22 September 2007 (UTC)

You might metabolize about 4 ounces of alcohol in the remaining 4 hours. Sleep, hydration, coffee. You could consider calling in sick (with the "bottle flu" but don't tell the boss that). Edison 03:19, 23 September 2007 (UTC)

If I'm right it's presently 9 AM in the UK now and yesterday's working day is over. Would be nice to hear what happened. Lova Falk 08:04, 23 September 2007 (UTC)

The easiest way to sober up in such a situation is to call in sick the next morning. It's partially true. Don't make a habit out of it, though. --24.147.86.187 15:21, 23 September 2007 (UTC)

matter and anti-matter .

is the total amount of matter and anti-matter in our universe same ? —Preceding unsigned comment added by Shamiul (talk • contribs) 04:21, 22 September 2007 (UTC)

No, there is far more matter than antimatter thanks to baryon asymmetry. Someguy1221 04:23, 22 September 2007 (UTC)

Well, far more matter has been observed than anti-matter, but the article you linked to mentions that distant regions of the universe may well have large amounts of anti-matter so that there could be equal amounts of both in the universe as a whole. Bistromathic 15:41, 22 September 2007 (UTC)

I read the link in full only after I pasted it here, but now I have another one that might satisfy. Experiments win. Someguy1221 15:58, 22 September 2007 (UTC)

It is now considered very unlikely that a balancing amount of antimatter is somewhere far because at the boundary between the matter and the antimatter region, there should be a violent bright emission of gamma rays, and it is now considered excluded that we would have missed such a thing with our gamma-ray observatories. Hence, the origin baryon asymmetry is considered one of the very big open question in physics. Simon A. 16:06, 22 September 2007 (UTC)

That's very interesting, but I'm afraid most of it went straight over my head! Does this mean that baryon asymmetry should be changed slightly? Does it overplay the possibility of the existence of distant anti-matter? Bistromathic 11:05, 23 September 2007 (UTC)

are there any chemicals that can permanently inhibit the melanogenic enzymes, such as tyrosinase

are there any chemicals that can permanently inhibit the melanogenic enzymes, such as tyrosinase, stoping the production of melanin, in animals? —Preceding unsigned comment added by 81.99.218.58 (talk) 08:27, 22 September 2007 (UTC)

Link. Someguy1221 15:18, 22 September 2007 (UTC)

Note that none of these permanently inhibit tyrosinase, they simply do so, to a greater or lesser extent, for as long as they are applied. Note they also only work on skin, not hair, as delivery to the hair follicle is an issue. Rockpocket 17:31, 22 September 2007 (UTC)

Generally the only way you can permanently inhibit an enzyme is by irreversibly binding or otherwise destroying the enzyme. This works fine in a static system. However in a dynamic system such as a animal it would I assume effectively be impossible to permanently inhibit the enzyme in the animal because even though you can permanently inhibit what is there at one time, more will be produced. Nil Einne 18:12, 22 September 2007 (UTC)

What's the deal with all these "Is there any way to stop <pigment>?" questions, anyway? Just curious, s'all. --Kurt Shaped Box 19:39, 22 September 2007 (UTC)

Retail trend in America

20 year ago Home Depot was able to displace local hardware stores by offering lower prices and better customer service. Years went by. Then Home Depot raised its prices, got rid of even minimal customer services like cutting and threading a piece of galvanized pipe. Anything and everything that did not fall within one standard deviation of average got canned. If you needed 4mm x 12mm screws forget it. Only high profit items like stainless remote control barbecue grills and fancy riding mowers now occupy the entrance to the store. My question is are retail stores now looking to stay in business by selling only the icing off the top of the cake and if so where does that leave the consumer who might need a 4mm x 12mm machine screw or a piece of galvanized pipe cut to 2-1/2 ft and threaded on both ends? Clem 12:01, 22 September 2007 (UTC)

Where does it leave the consumer? Up the creek without a paddle I suppose. But seriously, if major stores are starting to offer such a paltry level of service, presumably that opens up the opportunity for smaller businesses to exploit the market niche that does provide what the consumer wants - and then it's up to the consumer to support those stores by shopping there. Or you might be able to find these types of things in stores that specialise as trades outlets. Unfortunately in our first world consumption obsessed societies it seems that fixing or making things yourself has become very unpopular, as its far easier and quicker (and sadly often cheaper) to go down the Home Depot or equivalent and just buy a new one. BTW, is this a 'Science' question? --jjron 13:06, 22 September 2007 (UTC)

Business and consumer science. Clem 18:36, 22 September 2007 (UTC)

It's the law of supply and demand. If there is high demand for one kind of screw - the prices will be good and everyone will stock them. When the demand is low, the volume is low but the cost of the shelf space to stock them is the same - so either the price goes up steeply or they stop stocking them. You'll still find specialty stores that'll sell you those items - but you'll pay through the nose. Here in Texas, there is a vicious turf war between Home Depot and Lowes - and there are WAY too many of these stores for the amount of business they do - sooner or later one of them is going to disappear. The cut-throat nature of their business means that they have to look at everything they stock and to devote shelf space and staff to those areas that are the most profitable. As for cut and threaded galvanised pipe - geez - get a hacksaw and a set of taps and dies and do it yourself - it's not difficult. SteveBaker 14:53, 22 September 2007 (UTC)

In my case I only needed the pipe cutter which cost $120 at Home Depot and $15 at the local flea market, brand new and $50 on eBay, plus shipping, used. For threaded ends I have simply reverted to shopping at my local plumbing supply store which home depot was never able to run out of town since Home Depot had never committed to the full line of plumbing supplies and because they never installed a computer system. All of the accounting is still done by hand and they still use a 1934 cash register without any problem, perfect inventory control, no overstock or understock, and yet a full line of plumbing supplies. How do the do it? They are the real Artificial Artificial Intelligence, Amazon.com Mechanical Turks. Clem 18:51, 22 September 2007 (UTC)

And if what you say is true then those small mom & pop hardware stores with there oh-so-amazing business model will annihilate the Home Depot's and Lowe's of this world. I'm not holding my breath. The problem is that you seem to assume that retail outlets exist for the convenience of their customers - that's not true. They are their to please their stockholders - and that entails pleasing customers only to the degree that you can extract the maximum money from them...if 0.5% don't come to your store because you don't cut pipe threads - and if the 0.5% of the store/staff that used to do that can be switched over to selling garden furniture to bring in 5% more customers - then that's a huge win and not doing it will cause their competitors to get a better stock price and drive you out of business. The Mom & Pop stores (and I use the one near me too) are only able to do what they do if nobody is selling the bulk easy-to-shift stuff more conveniently and at lower prices just down the road. I guarantee that the one near you is holding on by it's fingernails in the face of 'big box' store competition. You may well go to them for the ikky jobs of putting threads on a piece of pipe (taking 10 minutes of employee time to do it and selling at a net loss for $2.50) - but when you need 500' of copper pipe, you'll go to Home Depot because it's 1/3rd the price. This leaves the Mom & Pop store doing only the inefficient, expensive, less-profitable jobs - which will put them out of business sooner or later. That's just economics though...sooner or later, someone will come up with the business model of selling the rare and difficult parts and offering the complicated services at extortionate rates and you'll wind up with two completely separate businesses. This is not unexpected. Gone are the days when every garage sold gasoline AND had a mechanic on duty to fix and repair stuff. Now, a gas station sells gas and jumk food and very little other automotive services. Now we have specialised muffler, lube, tyre and transmission shops that do one job and one job only. Those places don't sell gasoline. SteveBaker 15:39, 23 September 2007 (UTC)

The business I referenced is a speciallty store and sells only plumbing supplies. You acknowledge that the original Home Depot model of a carry everything general hardware store at prices 10% below anyone else with better customer service is evolving into a model of selling only big ticket or high volume items, along with installation and delivery services, as the means of maximizing dividends for stockholders, rather than to serve every Dick and Harry. Clem 00:30, 24 September 2007 (UTC)

What you describe is the classic result of one business (or a small number of businesses in collusion) taking control of an industry. At first, while they are "on their best behavior", to steal customers from the competition and avoid any consumer wrath, everything is great. But then, once they force their competitors out of business, they turn the screws on the consumer to extract the maximum profit. If any other business tries to compete they are likely to temporarily go back to "good behavior" mode just long enough to regain market dominance. Eventually, other businesses know what's in store for them if they try to compete, so nobody ever tries. It would take a new store with even deeper pockets to knock them out of their dominant position.

One hope for the future is Internet sales. That allows low-volume items to be sold without the need for the huge infrastructure of a brick-and-mortar store which would make such sales unprofitable. I'd see if you can find what you need online. StuRat 14:37, 22 September 2007 (UTC)

In many cases online prices are actually higher and believe it or not many companies, especially the ones who sell on eBay, use high shipping charges in place of or together with a restocking fee to guarantee a non refundable profit - in some cases to the point of hilarity where they simply exchange the item price and the shipping charge. Clem 18:51, 22 September 2007 (UTC)

The future is now. Buy commodity items at fairly low proces at Home Depot or Lowe's. Buy weird stuff on the web. The web prices are reasonably low because of web competition, but you pay for shipping. You can find really unusual stuff on the web that is not otherwise available. -Arch dude 16:09, 22 September 2007 (UTC)

BTW this isn't really a science question from where I stand Nil Einne 18:09, 22 September 2007 (UTC)

What do you do for a living? Its a business and consumer science question. Clem 18:35, 22 September 2007 (UTC)

Business science? You mean economics? That's more of a humanities issue IMHO but I don't want to argue this further Nil Einne 18:55, 22 September 2007 (UTC)

Why would you argue it in the first place? Don't tell me you are one of those persons who thinks questions about literature are literary science questions and belong on the science desk instead of on the humanities desk. Ever hear of the Dewey Decimal system? Maybe you should have a look at it first. Besides, if Wikipedia desk question classification were really an objective issue then a Wikipedia neural network bot would make the decision instead of the OP and a whole new basis for classification would therein be created. Clem 19:06, 22 September 2007 (UTC)

Er I don't quite understand what you mean are you talking to yourself? I don't think literature or economics are really science so I don't think they belong on the science desk no. Maybe you do, that's up to you. But apparently I am not the only one. Also, I don't get the relevance of the Dewey Decimal system to the discussion of whether this is a science question or a humanities one. I didn't say it was completely objective issue obviously there are cases when it is unclear but I don't feel this is one of them. (Also just because something is objective doesn't mean it makes sense to develop a neural network for the purpose.) You are free to disagree in any case although I don't get why you're so defensive about this. If you feel it is, fine, it's not a big issue... The biggest advantage is for you not me. When you put your questions in the most applicable desk, you're likely to get the largest number of helpful responses. Nil Einne 19:55, 23 September 2007 (UTC)

Maximizing profit is based on business science whereas serving customers is based on social science. I'm not interested in esoteric or irrelevant opinion but rather a scientific resolution. Aside from that, if you are not knowledgeable as to the Dewey Decimal system or to classification of knowledge in general then you are not entitled to an opinion. Clem 00:57, 24 September 2007 (UTC)

The OP makes the assumption that all mom-and-pop hardware stores were driven out of business by the big-box stores like Home Depot. Not true. While many small shops did succumb, some — usually in rural areas — survived. They did because many of their customers are farmers. Many farmers don't like going to Home Depots, Lowe's, etc. because for the most part the travel uses up a good part of the work day. Also, when they need something, they need it right away, or the farm shuts down — there's no time to order it. At the local shop, if they don't have it, they make it, just like the old days. There exists just such a store in my hometown. It is well into its second century of operation, being owned and operated by the third generation of the same family that founded it (with a fourth generation ready to take over). The store it defies all modern rules of efficient retail design: It's in an old barn-like building that's dusty, has uneven wooden floors, aisles that are way too close together, a seemingly random arrangement of products. But it's always full of customers! Even if farmers can't take the time to travel to the city, city-folk will come to the country to find what they want. — Michael J 19:15, 22 September 2007 (UTC)

In my reply to Steve Baker's 14:53 reply above, I pretty much said the same thing. However, even though there are still nuts and bolts suppliers who have been here for umpteen years they have decided to install their first computer. It will most likely be a replicant of the retail department store systems that existed back in the mid sixties only using modern equipment and software; the death of "inefficiencies" that mean it still has boxes of 4mm x 12mm stainless hex head screws which are not on display, else they would have long since been sold. Clem 19:50, 22 September 2007 (UTC)

The key to a successful hardware business is if you can walk in with a problem and not be quite sure how to fix it, and someone there within five minutes will not only fetch every tool and part you need, but will sketch out a diagram on the bag on how to do the job. ("The PTO coupling on my 1963 Massey Ferguson keeps slipping when I downshift on a grade.") — Michael J 00:53, 23 September 2007 (UTC)

LOL At Home Depot the guy in plumbing is too busy early in the morning replacing and straightening stock and at other times is to busy with other customers while at the self-serve cashier machine "Miss Annoy" keeps telling you to remove the item from the bagging area (your hat, your kid or the store's pet house fly), to put your item in the bagging area or to wait for the attendant while the attendant is busy talking to a co-worker about the dry spot she keeps scratching that has now started bleeding and will require that she take a break to go to the first aide station to get a band aide while you just want to get the heck out of there an figure out how to keep the POT from slipping on your own without risk of defective information coming from the store. Viva La rural America where Home Depots don't grow! Clem 02:10, 23 September 2007 (UTC)

Yeah - OK - so you're arguing that these are terrible places that nobody would ever go to in order to buy stuff if there was a Mom & Pop store nearby...so how come there are new Lowes and Home Depots appearing at every freeway intersection in America and the Mom's and Pop's are going out of business in droves? It's nonsense to keep harping on about these 'deficiencies' (which I entirely agree with you on) - when clearly their business models are vastly more efficient - and they bring in customers. SteveBaker 15:44, 23 September 2007 (UTC)

Lowe's still provides cut and thread service and to stay in business has expanded the line it carries although this might well change. As for Home Depot and Lowe's being on every corner that is but one of many factors like price that such chains try to conquer - proximity to the customer. In areas where the cost of real estate or current ownership prohibits building a new store older less efficient general hardware stores survive on proximity to the customer alone. Who wants to get on the freeway to go to a hardware store two miles away when they can go around the corner and buy the same item at a higher price but save double the difference in price by paying less for gasoline? The question I am asking is whether abandonment of customer need is giving customer loyalty the chance to change. Clem 06:21, 24 September 2007 (UTC)

"Efficient business model" is just another way of saying that they've managed to give the customer the least for his money. Easy to do, if you're willing to spend a couple of years operating at a loss to run the competition out of business. 69.95.50.15 19:53, 24 September 2007 (UTC)

Thrust sea level/vaccum

Hello

The thrust of the same rocket engine is not the same at sea level and in vaccum, why? The divergent nozzle is adaptable at different pressure?

Tank you —Preceding unsigned comment added by 74.13.154.170 (talk) 13:35, 22 September 2007 (UTC)

I would think the thrust is the about the same.. Maybe because of the added pressure at sea level it is harder for the gas to be pushed out of the engine. Also obviously friction would be greatly increased in an atmosphere, although this wouldn't reduce the thrust it would reduce accelerationShniken1 14:14, 22 September 2007 (UTC)

100% thrust (sea level / vacuum): 1670 kN / 2090 kN (375,000 lbf / 470,000 lbf) 104.5% thrust (sea level / vacuum): 1750 kN / 2170 kN (393,800 lbf / 488,800 lbf) 109% thrust (sea level / vacuum): 1860 kN / 2280 kN (417,300 lbf / 513,250 lbf)

The difference is notable, 25%..... —Preceding unsigned comment added by 74.13.154.170 (talk) 16:04, 22 September 2007 (UTC)

Parts of the USA that have a similar climate to Scotland

Living in England I envy the amount of space people have in the USA - in England land is very expensive and even wealthy people live in small houses on small plots compared with the US.

But in Scotland there is more space, land is cheaper. So if I wanted more space I could in theory emmigrate to the US. But could I achieve the same goal by just moving to Scotland? In many parts of the US the climate is much colder than in Scotland.

So what parts of the USA have similar winter temperatures to winter in Scotland please? And what parts have similar summer temperatures to summer in Scotland please? (These two things are unlikely to be the same places as there is far greater seasonal temperature variation due to the continental climate in the US, and the maritine climate in Scotland). Thanks 80.0.114.206 13:47, 22 September 2007 (UTC)

You might consider the Pacific Northwest, near the coast, particularly Oregon and Washington state. They also are warmed by the Pacific currents, and therefore have a climate similar to England and Scotland (small variation, lots of rain and fog, etc.). See Seattle#Climate for a description of the climate there. And, if you want to include Canada in your list of possibilities, Vancouver Island is a large island warmed by the Pacific version of the Gulf Stream, almost identical to Great Britain in that respect. StuRat 14:01, 22 September 2007 (UTC)

Our article on Köppen climate classification classifies Seattle as type Cfb which is what our article on Climate of Scotland says that region is. This climate is considered unusual in the U.S. though. Rmhermen 14:09, 22 September 2007 (UTC)

Land prices are pretty high around Seattle though. The places in the US with the most temperate climate tend also to be the ones with the steepest property prices. I'm a Brit who lives in Texas - land is pretty cheap (as low as $1000 per acre far from civilisation - more like $15,000 per acre within commutable distances of cities - much, much more in city centers of course). The Texas winter climate is gorgeous - but in the summer, the heat gets rather crazy. My present house (which I designed myself) is on a gorgeous tree-covered 1.2 acre lot - with a view over a nearby lake. But I'm moving down to Austin and I'm probably going to build my new house on a 10 acre 'virgin' lot. There is absolutely no way to do that in England on a programmers' salary. There are a lot of jobs in my particular line of work in California (I'm a Game programmer) - but I can't afford to live there precisely because of insane land prices anywhere within commutable distance of a decent sized city. SteveBaker 14:26, 22 September 2007 (UTC)

Land prices might be high right around Seattle, but I'm sure land can be had cheaply somewhere in the coastal region of Oregon, Washington state, and British Columbia. The search could even be extended to the coastal regions of Northern California and Southern Alaska, which have similar climates. One caution, though, the entire region has some major fault lines, so earthquakes are a possibility. StuRat 14:54, 22 September 2007 (UTC)

Thank you for interesting answers so far, and apologies for not stating the question very well, but what I would like to know are which areas of the USA have a) winter temperatures, and b) summer temperatures, that are similar to those in Scotland. I imagine these would be in a band stetching across the US, somewhere between the cold north and the hot south. I recall seeing in the past climate charts that gardeners use, where the climate is given numbers, and these did have belts stretching from coast to coast. 80.3.44.82 16:24, 22 September 2007 (UTC)

If you want to match both the winter and summer temps, you don't get a band crossing the US, since, as you had noted, there is far more temperature variation within the interior of a continent than on an island. Your only choices are then ocean islands and coastal areas where the temperature is moderated by the oceans. Aside from the area given in the Pacific Northwest your only other choice would be on the Atlantic side. However, since the currents flow south there, not north, you would need to go considerably farther south to match temps with Scotland. Also, since the prevailing winds in the continental US go east, you would need an actual island there, as coastal areas would still be subject to quite high temps in summer, except for those on peninsulas extending well into the ocean. Islands or peninsulas off the coast of the North Carolina and Virginia might work, for example. I suppose you could go as far north as Long Island, New York, and still be close to the climate in Scotland. Earthquakes are less of a concern on the Atlantic side than on the Pacific side, but now you also have to deal with the occasional hurricane. StuRat 17:26, 22 September 2007 (UTC)

Thanks, I did appreciate that the areas for summer and winter temperatures would be different. I aplogise again for not having made this sufficient clear in my oiginal question. Never mind the summer temperatures, what areas or belt across the USA would have similar winter temperatures to those in Scotland? Obviously to the north it will be colder, to the south it woyuld be walmer. Somewhere in between the temperature will be similar to Scotland. Where this belt is, and how wide it is, is what interests me. Thanks 62.253.48.7 13:10, 23 September 2007 (UTC)

It would be more of a U-shape than a band. If you just want to match winter temps, I'd say you'd start at, say Long Island, New York, then go quite a bit south as you go inland, perhaps down through New Jersey, Maryland, Delaware, and Virginia, to North Carolina. Then you would head west, through Tennessee, Missouri, Oklahoma, northern Texas, New Mexico, and Arizona. At this point you would start to get coastal warming and would need to head almost north, through Nevada, Oregon, Washington, British Columbia (Canada), and on to Southern Alaska. Note, however, that those states in the interior will get much hotter than Scotland in the summer (especially in the desert states, like Arizona). To match summer temps, you might start and end at the same places, but arc upwards well into Canada in the interior. StuRat 17:53, 23 September 2007 (UTC)

The influence of being close to the ocean is huge. In Texas, in the winter, the temperature is utterly dependent on the direction of the wind. If it blows from the North - we can sometimes get snow and ice storms. If it blows from over the deserts of Arizona and NewMexico then it can be quite hot - even in the depths of winter. Without the moderating effects of the ocean (which hardly changes temperature at all - and when it does, it does so exceedingly slowly) - you tend to get more wild, unstable weather than you do in a small island such as the UK. So (as others have pointed out) - it's going to be next to impossible to replicate island weather patterns on a huge continent. Even on the coast of the US (where things are a little more stable), weather coming from inland is going to produce different effects from that coming in over the oceans. I'm doubtful that you could find an exact match for Scottish weather at any time of year - yet alone all year round. My advice is to focus on things other than weather - that is a small percentage of life's experience compared to (for example) the total inability to buy decent bacon/beer/strawberries/cheese/...etc in the USA - or the impossibility of buying a dozen acres of virgin woodland with a lake view in the UK. In the end, it doesn't matter much to me whether there is three feet of snow outside - or the temperature outside is above body heat - either way, it's going to be too miserable to go outdoors so I'm going to be stuck indoors or in a car with the heating/cooling cranked up to a bearable level. The relevent number is over what percentage of the year is the weather gorgeous - and for that, your best option is undoubtedly the coast of California - where you can't afford to buy land. So you have to settle (as I did) for someplace like Texas where 50% of the year we have great weather - but property is affordable. SteveBaker 15:12, 23 September 2007 (UTC)

Hello... I'm Frank Necrosis

What is frank necrosis? How does it differ from plain necrosis? JIP | Talk 16:11, 22 September 2007 (UTC)

The term "frank" usually refers to something that is plainly visible, as opposed to covert (I think that's the medical opposite term...) where they have to go looking for it. Saturn 5 17:29, 22 September 2007 (UTC)

I first heard of necrosis from the Pogo Joe level Hello... I'm Frank Necrosis. The Wikipedia article necrosis gave me a general idea of what necrosis is, but a Google search for "frank necrosis" gave me thousands of results for the exact phrase, all of which are related to actual medicinal research, not to Pogo Joe. So this specific term must have some important meaning in medicinal science, which I am utterly unaware of. JIP | Talk 19:04, 22 September 2007 (UTC)

"frank" = "clinically evident". "Frank necrosis" therefore = "necrosis you can see with your eyes" (i.e. diagnosable clinically, without resort to lab tests) vs. "necrosis" = "necrosis visible in pathology slides". - Nunh-huh 19:08, 22 September 2007 (UTC)

I think I understand. It is obvious there is need to differentiate between necrosis you can see with your own eyes and necrosis you need to do pathological research for. So medicine invented "frank necrosis" as a handy shorthand for the former. And of course, the Pogo Joe level name arose of the similarity between the term "frank" and the first name "Frank". JIP | Talk 19:11, 22 September 2007 (UTC)

"invented .. shorthand" is not quite right; the term frank is similarly applicable to other phenomena, and it's not much of a stretch from the ordinary use of the word. —Tamfang 23:55, 23 September 2007 (UTC)

human eye

Re: Wikipedia:Reference_desk/Computing#Wide_screen_Vs_Full_screen

Anyone know what the 'human vision aspect ratio' is?87.102.89.127 16:21, 22 September 2007 (UTC)

This link might help you. I just glanced at it and it looked like what you needed.–Sidious1701_{(talk • email • todo)} 17:37, 22 September 2007 (UTC)

It's not obvious how to define the aspect ratio, because the field of view of the human eye is not a rectangle (nor even a rectangle projected onto a sphere). However, the horizontal angle of view is almost 180 degrees and the verticle angle is almost 120, so the aspect ratio in that sense is about 3:2. —Keenan Pepper 17:57, 22 September 2007 (UTC)

We also have peripheral vision, which is complicated to describe and is linked to visual perception, a psychological concept. It may not be possible to measure the aspect ratio without inventing some application-specific operational definitions. Nimur 18:10, 22 September 2007 (UTC)

Thanks87.102.38.119 22:14, 22 September 2007 (UTC)

Our eyes are circular - and I believe the distribution of cells inside is pretty much symmetrical - so in that sense our instantaneous field of view is circular...an aspect ration of 1:1 - but we can (and do) swivel our eyes from side-to-side much more readily than up and down - so our 'stationary head - moving eyes' total field of view is shorter and wider (I don't know the exact number offhand) - similarly, if head motion is allowed as well as eye motion then there is an even stronger 'horizontal' bias - so we can see almost 360 degrees horizontally but considerably less vertically. Add in shoulder/chest motion and that bias gets larger still. But the reason for wanting wide-screen is simply because in most cases, most of the interesting action is not in the sky or the ground close to your feet - the action of visual perspective means that a short/wide screen is a better fit for "where the action is" than a taller, narrower screen which - for the same area - provides less left-right coverage whilst giving more coverage to the relatively useless areas of sky and near-ground floor. Clearly that's not true in all cases - if you are watching a scifi movie about combat in deep-space then a square screen would make more sense - but movie makers know about the shape of the screen and design their action sequences to fit - so it doesn't really hamper them too much in those cases. SteveBaker 14:59, 23 September 2007 (UTC)

You left out the effect of having two eyes whose fields don't entirely coincide. —Tamfang 23:52, 23 September 2007 (UTC)

Or more simply, you might want wide screen because that's what most of the films you'll watch are. It's not exactly your decision. – b_jonas 18:54, 24 September 2007 (UTC)

Black/Dark Outfit and White/Bright Outfit Regarding To The Sun's Heat Absorption

I heard many times that when we wear black color during daylight will make us hot and sweat more rather that if we wear bright or bright color. This is regarding to common sense that those color (the dark or black ones) absorb heat more than the bright/white ones. Is that true?How is it scientifically explained? Thanks for the explanation

Reno Risanti —Preceding unsigned comment added by 125.161.130.47 (talk) 18:09, 22 September 2007 (UTC)

Email address removed by Nimur 18:11, 22 September 2007 (UTC)

Well the "common sense" explanation does have a scientific answer: dark colors are "dark" because they don't reflect much light — they absorb it. Now it's a bit more complicated than exactly that (since much of the heat energy from the sun comes in non-visible wavelengths, so visible light reflected has a bit more to do with that), but that's basically the essence of it. Now obviously clothing has other factors involved than just color — the type of fabric and cut of it both play large roles in whether or not it allows air to circulate well in it — but if all other things were equal then the color could easily play a large role. --24.147.86.187 18:55, 22 September 2007 (UTC)

You need to look up infrared emissivity--212.139.98.210 21:17, 22 September 2007 (UTC)

mica-porphyrite at Biddlestone NE65 7DT

WHAT MAKES THIS FAMOUS STONE(USED TO PAVE THE ROAD TO BUCKINGHAM PALACE0 SO RED —Preceding unsigned comment added by 84.92.51.198 (talk) 19:28, 22 September 2007 (UTC)

I assume you mean "is a mica-porphyrite which has a characteristic red colour. This stone, commonly known as red whinstone or Harden Red, is exploited at Harden Quarry near Biddlestone." http://www.northumberlandnationalpark.org.uk/nationalparkmineralsplan.pdf colour coud be due to manganese or iron possibly..87.102.38.119 22:30, 22 September 2007 (UTC)

How much of everything is nothing?

This question may or may not even have an answer, but I'm curious. What percentage of the universe actually is matter? Not counting energy, just matter. I know that on the smallest micro-scale, the composition of atoms is a very small amount of matter in the form of sub-atomic particles with mostly empty space. And on the grandest macro-scale, stars and planets and other astronomical objects make up planetary systems that are mostly empty, and even more emptiness between stars with a galaxy, and even more emptiness between galaxies, etc. (There is of course interstellar dust, so do count that, but I would think its total volume is negligible.) So in essence, everything is mostly nothing, am I correct? So that is the question in the header, and the reciprocal would be how much actual matter there is. Any guesses? — Michael J 19:29, 22 September 2007 (UTC)

I'm not sure if anything really qualifies as "solid matter" when you think about it:

1) The universe is mostly empty, but the galaxies are full, right ?

2) No, but the solar systems are mostly full, right ?

3) No, but the planets and stars are mostly full, right ? Not when you consider the gaps between atoms.

4) But the atoms are mostly full, right ? Not when you consider the gaps between the electron shell and the nucleus.

5) But the subatomic particles in atoms are mostly full, right ? (I'm not sure on this one, but guess that they are mostly empty too, with just some tiny quarks inside them).

6) But the quarks are mostly full, right ? (I'm not sure on this one, but guess they are mostly empty, too.)

There may be nothing more than singularities of matter (infinitely small points), much like tiny black holes, when we figure it all out as far as we can go. StuRat 20:05, 22 September 2007 (UTC)

I assure you, it's Turtles all the way down. -Arch dude 22:07, 22 September 2007 (UTC)

See Mass of the observable universe. Then again, the population of the Universe is zero. -- Kesh 22:24, 22 September 2007 (UTC)

Because the fundamental particles of matter (quarks and leptons) have no internal structure (as far as we know), they are usually considered to be point-like objects (although "points" that posses certain properties, such as mass, charge, spin etc.). So, in one sense, everything is made of nothing - the "volume" that we perceive objects as occupying at a macroscopic level is entirely empty space, and the fundamental particles themselves take up zero volume. However, at a quantum level, it is not possible to say for certain where particles are, how many particles there are (see virtual particle) and even what space itself is (see quantum foam) - so the question "how much space does matter really take up" becomes more or less meaningless. Gandalf61 10:25, 23 September 2007 (UTC)

The fundamental particles are merely statistical measurements of position - you can't put a 'size' on them. If you can't meaningfully talk about the 'volume' of an electron. What you can say is that there is a 99% chance that the electron will be within some volume of space - and that's a kinda-sorta representation of how 'big' the electron is - but if you pick an 80% confidence instead - you get bigger electrons. In some sense, every electron is everywhere in the universe at the same time - at some non-zero probability. So either the universe is 100% full or it's 100% empty or anywhere inbetween. It's your call. SteveBaker 14:49, 23 September 2007 (UTC)

This isn't really important, but 99% confidence is a bigger electron then 80% confidence. — Daniel 00:18, 24 September 2007 (UTC)

No, it's the other way around. StuRat 16:22, 24 September 2007 (UTC)

People are fond of saying that the inside of an atom is mostly empty space, but that's not true. In order to make it mostly empty, as opposed to entirely or not at all, you have to apply a double standard, saying that the quarks in the nucleus occupy space while the electrons don't.

Now, maybe there's still a sense in which matter is mostly empty space. The mass density of a white dwarf—which consists of atoms packed as closely as they can be packed—is around 10⁶ times that of a star, so perhaps one can say that the sun is around 99.9999% empty space by that token. Also, the mass density of the sun divided by the ordinary-matter density of the observable universe is about 10⁻³¹, so maybe you can say that the universe as a whole is 99.999...999% empty space, in a certain sense. -- BenRG 12:17, 24 September 2007 (UTC)

Using that argument, can't we extend it to a black hole, which has infinite density at the singularity ? Therefore, anything at less than an infinite density is completely empty, by comparison. StuRat 16:22, 24 September 2007 (UTC)

You could just compare the density of the galaxy or whatever :large construct you want to examine to the density of household materials, like water or air. – b_jonas 18:52, 24 September 2007 (UTC)

Phase shifting

May be a stupid question, but I cant get my head round it. If you frequency modulate a sine wave onto a carrier, then change the phase of the resultant by 90 deg, then discriminate the phase shifted signal, would you get he original signal back but phase shifted by 90 deg? Pleas help its driving me nuts--212.139.98.210 20:10, 22 September 2007 (UTC)

no, because the frequency is determining the demodulated output, phase shifting has no effect on this. It will only effect it if your modulating frequencies are close to the carrier frequency, or the frequency shift you use is tiny. Just imagine you have a FM radio. You step back about a quarter wavelength away from the station (75cm) you get a 90° phase shift. The sound is only phase shifted by a few nano seconds, no where near 90 degrees for an audio frequency. Graeme Bartlett 01:31, 23 September 2007 (UTC)

Ah but imagine the fm spectrum: each sideband a has amplitude and phase. If you were to change the phase of all the sidebands by 90deg, what effect would that have on the discriminated signal? —Preceding unsigned comment added by 88.110.17.120 (talk) 12:54, 24 September 2007 (UTC)

finger-licking

Hi. Why do some people lick their fingers when they read a book, newspaper, pick things up, etc? It's unnesecary and dangerous. For example, they could swallow foreign germs or poisons, spread their own germs to other people, etc. Besides, why don't they just secrete saliva just in front of their lips, and touch that? At least it's safer. I've been pondering this question for years, and so far I've gotten no answer. Why don't they wash their hands instead if they want them wet? Is it to ensure the person doesn't get a papercut, to be able to hold onto the paper easier, to avoid an unpleasent sensation caused by the excessive friction, because other people are doing it, or because it's simply a bad habit? Why do some people do it and others don't? Which places have a higher percentage of people who do this? Does looking up articles on the Internet prevent them from needing to lick their fingers because of the relative lack of paper, or do they just lick their fingers before touching the keyboard or mouse? Do they do it unconciously or voluntarily before flipping a page? Are there higher benifits or risks when performing this procedure? Are there any animals (other than homo sapiens) who have individuals who do this? Do people who do this overall lick more often than people who don't? A few years ago I observed someone doing this, and I tried to ask them why some people lick their fingers, and the subject said they don't have time to answer. Is it because asking such a question is rude in some way? Is there an article on this? Thanks. ~AH1^(TCU) 22:43, 22 September 2007 (UTC)

Well normally licking your finger is to get your finger to 'stick' to the page so you can flip it easily. Hygine wise i'm sure it isn't particularly bad for you, providing your have generally good personal hygiene. I would expect it is a 'learned' thing...so if your parents/close friends/family do it then you might subconciously pick up the habit and do it yourself. Kangaroos regularly cover their body in their own saliva by licking/spitting on themselves and working it in - though they do this to cool themselves down in the heat. Your propose 'secrete saliva' idea is pretty odd - it's i'm sure marginally better but why would you go to that much effort just for something that is so simple and (in reality) pretty darn safe. People seem to be developing an almost obsessive fear of germs (there'll be a word for it somewhere). ny156uk 22:58, 22 September 2007 (UTC)

Mysophobia. 152.16.59.190 00:39, 24 September 2007 (UTC)

I'm pretty sure it isn't dangerous, or at least not any more dangerous than the many things humans do. We're able to put up with most germs and the like because we have immune systems and all that. As for doing it, sometimes it makes it easier to pick up a page, especially if you have been flicking through a lot of pages. Washing your hands is overkill—you want a small amount of moisture on the finger pads to get a little more friction when dealing with paper, not a wet hand. --24.147.86.187 23:24, 22 September 2007 (UTC)

I use a slightly more hygienic method of spitting very lightly on my fingers to moisten them. This avoids putting your fingers in your mouth. —Preceding unsigned comment added by 88.109.137.161 (talk) 01:07, 23 September 2007 (UTC)

There are fingertip moisteners on the market, like Lee's Sortkwik. They are usually greaseless, non-staining, and modern ones have antibacterial properties, as well. People who handle a lot of paper often use either that, or rubber finger covers (similar to Finger cots). --Mdwyer 05:32, 23 September 2007 (UTC)

If the corner of each page is discolored, though, don't do it lest you end up like the dead monks in The Name of the Rose/The Name of the Rose (film).

Atlant 14:25, 24 September 2007 (UTC)

Calculations with uncertainty values

I learned that when I am multiplying two measurements with uncertainty values (±), the uncertainty in the final answer would be the sum of the measurements' relative uncertainties.

eg. (a±x)(b±y)=ab±(x+y)

I need to calculate the area of a circle, and my radius has an uncertainty value. I need to square this radius, which would actually be (r)x(r) Does my uncertainty double, or do I just keep the uncertainty value of one radius? ---Zealz 23:44, 22 September 2007 (UTC)

Your formula for multiplication is not right! You can find a table at propagation of uncertainty that may help. Are you dealing with fractional uncertainties, like 5m ± 20%, or absolute values like 5±1 m? --Reuben 23:51, 22 September 2007 (UTC)

the fractional uncertainty of the radius ---Zealz

${\frac {\Delta X}{X}}={\frac {\Delta A}{A}}+{\frac {\Delta B}{B}}$ is the same thing as what I typed ---Zealz 01:09, 23 September 2007 (UTC)

Yes, I see... the formulas from the article are quite wrong for Gaussian random variables at least. I don't know where those come from. For Gaussian-distributed random variables, you want (σ_X/X)²=(σ_A/A)²+(σ_B/B)². --Reuben 02:47, 24 September 2007 (UTC)

I suggest you just multiply the minimum and maximum values to find the range. For example, if your circle has radius 10 ± 1, your radius ranges from 9 to 11. Thus, the area ranges from 81p to 121p. This can be written as 101p ± 20p. If you find it troubling that the base area of 101p is not what you get when using the base radius of 10, you can alternatively write the answer as $100\pi {\frac {+21\pi }{-19\pi }}$. StuRat 01:50, 23 September 2007 (UTC)

I'm not a mathematician, but calculating the error seems pretty straightforward from the formulas at Propagation of uncertainty. Assuming that the radius is $r_{0}\pm \Delta r_{0}$. Since you said that the error is a fractional value of the radius itself, $\Delta r_{0}=er_{0}$ (so if there is a five percent error, e=0.05). Going by the formula from Propagation of uncertainty, this is true:

${\frac {\Delta X}{X}}={\frac {\Delta A}{A}}+{\frac {\Delta B}{B}}+{\frac {\Delta A\cdot \Delta B}{A\cdot B}}$

(the one you quoted was just an approximation, according to the note). Substituting X for $r_{n}$, $\Delta X$ for $\Delta r_{n}$, A and B for $r_{0}$ and $\Delta A$ and $\Delta B$ for $\Delta r_{0}$, we get:

${\frac {\Delta r_{n}}{r_{n}}}={\frac {2\Delta r_{0}}{r_{0}}}+{\frac {\Delta r_{0}^{2}}{r_{0}^{2}}}$

Substituting $\Delta r_{0}$ for $r_{0}e$, and doing some rearranging we get:

$\Delta r_{n}=r_{n}(2e+e^{2})$

There's your new error. If your fractional error before the squaring was e, then the new error is 2e + e^2. Assuming I haven't done anything extremely stupid, which is always probable. I'm not a mathematician, as I said (which I'm comfortable with, since this isn't the mathematics part of the desk :P) --Oskar 02:25, 23 September 2007 (UTC)

By the way, e^2 will be very small, so simply doubling the error will be a good approximation. For instance, if the e=0.05, then 2e + e^2 = 2*0.05 + 0.05^2 = 0.1025 or 10.25%. That's very close to simply doubling the error for an answer of 10% --Oskar 02:29, 23 September 2007 (UTC)

September 23

Follow-ups to the Kinsey Reports...

I've always been a huge fan of the Kinsey Reports (once upon a time they helped me realise that I was bisexual) and always had the greatest respect for them as science. My question is this: there must have been subsequent studies on the same scale regarding human sexual behaviour, right? I mean, they came out more than 50 years ago now, someone must have done similar studies since. It's not like it's an insignificant area of study. But I've never really heard of any, people always just quote Kinsey's stats (like the one about 10% of males being exclusively homosexual). It's not that I don't think his findings are incorrect (quite the opposite), it would just be nice to have some confirmation. Have subsequent science generally confirmed his results? 83.249.113.29 01:18, 23 September 2007 (UTC)

Well, there's always Masters and Johnson. Most scientists are afraid to study this area, however, as they may be thought of as perverts and belittled by their associates. StuRat 02:42, 23 September 2007 (UTC)

It's still that taboo? Seriously? I thought this was a whole field now :S 83.249.113.29 02:47, 23 September 2007 (UTC)

I think it's taboo in a different way. Other scientists will think "Oh, they just want to get some cheap headlines and be asked onto Oprah, they aren't REAL scientists". And would you rather tell your parents you study to find cures for cancer or study why people perform analingus ? StuRat 02:58, 23 September 2007 (UTC)

Pah! Studying analingus is for pussies. If you want to reap the whirlwind, these are the guys you should work with. [6] Rockpocket 07:46, 24 September 2007 (UTC)

I'm just sayin', it's a pretty fundamental part of human behaviour, it's something that should be studied intensely. 83.249.113.29 03:09, 23 September 2007 (UTC)

There is a serious problem when the thing that is doing the studying (ie one or more human beings) is also the subject that is being studied (humanity). There is a certain 'uncertainty principle' to this. The observer watching a human mating ritual will both embarass the participants - and get somewhat aroused himself/herself. This is simply guaranteed to skew the results. Secretly monitoring such behaviours with hidden TV cameras (which might be one way to avoid perturbing normal behavior if one were studying - say Chimpanzees) is a crime when you try to do it with humans! Maintaining a unbiassed view is impossible - especially when taboos are being violated and things that one has a strong inclination to do in private have to be done in public in order for measurements to be made. People routinely lie about sex - so merely surveying them without actual observation is meaningless too. It is highly doubtful that any of these studies are ever really good science - or that the results will be widely accepted - for precisely that reason. This isn't just to do with sex. We cannot study (for example) genetic differences between people with skins containing different proportions of melanin because we have a taboo on saying things like "Black people can run faster than white people". A scientist wishing to study the genetic basis of some significant parameter such as intelligence is going to find it very hard to publish results honestly if they come out with controversial results. The reason scientists are reluctant to work in these fields is simply a realisation that one cannot do good science or publish honest results in these fields. The reason other scientist disparage the results is the honest realisation that these 'findings' are pretty much guaranteed to be wrong. SteveBaker 14:37, 23 September 2007 (UTC)

Well said. StuRat 17:30, 23 September 2007 (UTC)

StuRat, there are plenty of scientists who study human sexuality. There are academic programs in it at many universities and they are not bereft of members. I'm not sure why you seem to think it is taboo or that any of them are afraid of being seen as headline seekers, but I don't really think you know what you're talking about. Google "human sexuality site:.edu" and you'll find many such programs, professional organizations, and other resources. --24.147.86.187 15:20, 23 September 2007 (UTC)

There are definitely studies into human sexuality. However as others pointed out, this doesn't mean their research doesn't sometimes attract controversy and ridicule. For example, when one group received a grant for research involving 'the hustler, the modern orgasm' and 'the sexual culture of Auckland' it was used by the opposition party here to attack the funding process [7]. While the attack itself had little to do with the research, the fact it was used as an example of potentially poor quality research shows IMHO on reason why perhaps people may be reluctant to study this area. (To be fair, in some cases their choice of titles may not help.) Admitedly in this case IIRC the attack back fired and I'm pretty sure that the politician who made the attack backtracked and said something like as a doctor he knew of the importance of the orgasm and wasn't saying it was unimportant. (Indeed if you look at a more recent response he's a lot more careful not to attack any specific project [8]) Nil Einne 21:13, 23 September 2007 (UTC)

Bluetooth FHSS sync

Any idea how do frequency hop devices get synchronised? —Preceding unsigned comment added by 59.92.240.252 (talk) 01:29, 23 September 2007 (UTC)

The Frequency-hopping spread spectrum article suggests that the receiver and transmitter have a shared order of hopping. The receiver simply listens to a single channel until it hears the transmitter come by. Then, they can stay synchronized from then on. --Mdwyer 05:27, 23 September 2007 (UTC)

Color wheel

Why does the color wheel explain color perception and mixing, when obviously different colors are at different points on a linear spectrum? For example, why does the mixture of red and blue appear purple, when purple is a shorter wavelength than either red or blue? Calliopejen1 01:36, 23 September 2007 (UTC)

Actually, I think I just figured this out for myself at Color circle and Spectral color. How did I never learn that purple and violet aren't the same, or that purple is not a spectral color? Any other explanatory comments are welcome, if you have good thoughts that aren't at those two pages... Calliopejen1 01:43, 23 September 2007 (UTC)

This has more to do with the way our eyes perceive colors than with the colors themselves. Take a look at our article on color perception. — Kieff | Talk 01:49, 23 September 2007 (UTC)

Anytime you are talking about 'purple' and 'violet' or about 'colour wheels' you are talking about human perception of colour. In the underlying physics of the thing there is simply frequency of light - and it's a straight line, not a circle. You have red at the low frequency end of the spectrum and blue at the high frequency end. The idea that you see 'violet' in a rainbow or a spectrum is a myth. The idea of a colour 'wheel' is a convenient way to represent how humans see colours. We can only truly see three colours - red, green and blue. Everything else that we percieve (including white, yellow, cyan and magenta - which is the fancy scientific name for purples, violets and such) is a mixture of red, green and blue perception. When we see yellow light, our eyes produce a weak response from the red detector and a weak response from green - and our brains have learned (rightly or wrongly) to interpret this as yellow. Cyan (sky blue, baby blue) is a mixture of green and blue and magenta is a mixture of red and blue. There is a certain circularity of the perception of colour red-yellow-green-cyan-blue-magenta-red forms a nice 'spectrum' that you can lay out in a circle - and red through blue correspond reasonably well to the linear frequency of the light. But the 'colour' magenta/violet/purple is not a 'real' single frequency colour in nature - it doesn't appear anywhere on a spectrum of white light split up using a prism for example. It's purely an artifact of how our eyes/brain see a mixture of red and blue light. The colour 'wheel' is still useful as a way of talking about complementary colours (technically: 'hues') and other 'artistic' concepts - and it's even sometimes used in fields such as computer graphics (although not as often as a red/green/blue description which matches both how our eyes percieve colour and how a computer monitor displays it). One should not use a colour wheel concept to describe colour for scientific purposes unless one is strictly talking about human colour perception (and even then, it should only be applied to "normal" human vision because it is totally inapplicable to people who are colour blind or tetrachromats). SteveBaker 14:23, 23 September 2007 (UTC)

No offence, Steve, but you need to work on being more concise. Maybe breaking it up into paragraphs would help. Anyway, see also CIE 1931 color space#The CIE xy chromaticity diagram and Metamerism. —Keenan Pepper 15:14, 23 September 2007 (UTC)

I don't think his answer lacked concision. It was fact-dense and answered the question fully. --Sean 14:34, 24 September 2007 (UTC)

How were Telegraph Relays (c1890s) used?

I have an antique telegraph relay, known as a ‘Pony Relay’ that has an electromagnet coil that acts on a hinged moving contact with a silver contact on each side, much like any relay. It has two external binding post terminals for the coil and two binding post terminals for the contacts. Also similar to SPDT relays, it has two thumbwheel adjustable stationary (also silver) contacts. The adjustments vary the space between the contacts, and can also adjust the space between the electromagnet and the iron part of the moving contact. When the coil is not energized, the moving contact is pulled against stationary contact A by a thumbwheel adjustable spring. When the coil is energized, the moving contact lands on stationary contact B. These can often be seen for sale on eBay.

It seems strange to me that both the stationary contacts are mounted on (screwed into) a single metal inverted U-shaped support so that both A and B are electrically connected together. In fact, there are only two external connections to the relay contacts, the moving contact and the support for both stationary contacts, A and B. The coil contacts are isolated.

At the instant when the coil current is turned on, or off, there is a brief (maybe 50 mS?) interruption in continuity (depending on adjustments) while the moving contact is making the transition from terminal A to terminal B. Otherwise, (obviously) there is always continuity between the contact binding post terminals whether the coil is energized or not.

So how is this used in telegraph circuits?

John 03:59, 23 September 2007 (UTC)

A pony relay appears to have been used as an amplifier or to connect together two lines with different battery voltages. If the two contacts on the U are indeed connected, then the relay would appear to perform pulse regeneration. Over the miles of cable the pulse would be weakened and spread out. A relay like this could sharpen up the pulses for retransmission. Does that make any sense?--88.109.137.161 04:41, 23 September 2007 (UTC)

Thanks. Well, I expect pulse regeneration must have been the objective, but the output isn't a copy of the input. Remember that when the coil pulse is on, the relay is closed; when the coil pulse is off, the relay is closed too. Only during the instant when the coil pulse was changing state (either on to off, or off to on) does the relay create a brief interruption in continuity. The contact pulses of continuity would not appear to copy the coil pulses, but it would sort of give the absolute value of the differential of the coil pulses, if you are a math person. I must be wrong somehow.

The pulses that telegraph lines transported in 1899 were dots and dashes of current in the wire from a telegraph key to a sounder. Current flowed during the dot or dash, and none flowed between a dot or a dash. I would have expected it to require a conventional SPST relay to ‘amplify’ that. At 20 WPM, a dot should be around 100 ms and a dash lasts several times as long as a dot, easily followed by this relay. But it isn’t a SPST, it is not SPDT either. Its weird. For a normal SPST relay, the coil would simply energize during dots and dashes, and open between. The B contact only closest to the coil would duplicate that for a different circuit. But there is no electrical way to isolate it from the A contact. (Unless the A contact was not supposed to be silver, but an insulator?) I wish I could see evidence of that on this or other pony relays I’ve seen for sale, but not. John 06:22, 23 September 2007 (UTC)

When the current to the coil is interrupted, there is a brief interruption (you say 50ms) in the output circuit. Therefore the interruption pulse is sharpened up, no? How you can transmit dots and dashes is not clear. Im just wondering why, if the U connects the two contacts, why do you need two contacts (unless you connected two separate pieces of wire) --88.109.137.161 09:37, 23 September 2007 (UTC)

This: http://www.qsl.net/n6tt/bunn12.html is a link to a picture of a Brunell Pony Relay where mine is a Western Electric, but shows the inverted U contact support.

Actually, when the current in the coil is interrupted, (turned off then back on) the output circuit current is interrupted twice, once for each of the coil transitions. When the coil goes off then back on, the points are interrupted: blip...blip. I am don't claim two contacts are needed, they are just there; my wondering why was the motivation for this post. John 14:43, 23 September 2007 (UTC)

Its difficult to see what is happening from that and other photos. Do you have a high res photo you could upload to this page? —Preceding unsigned comment added by 88.111.177.44 (talk) 17:22, 23 September 2007 (UTC)

Is Fig 22 in this link any better?: http://www.telegraph-history.org/bunnell-tel-elec-catalog/page13.htm

John 19:11, 23 September 2007 (UTC)

Whell! not really to be honest! when I use my magnifier on it, the detail just isn't any better. Im trying to help but I just cant figure out how this damn relay works (or is intended to work) without seeing a detail high res image.--88.111.177.44 01:06, 24 September 2007 (UTC)

OK, I took photos:

Photo of my 'Pony Relay' with upper left binding post connected to moving contact and binding post next to it connected to the inverted U-shaped support. Coil binding posts at right behind coil, only one visible, both isolated from contacts.

Photo of its contacts, showing how they are both connected by the inverted U-shaped support.

John 02:58, 24 September 2007 (UTC)

Ah excellent photos. Now looking at your close up of the contact arrangement, my opinion is that the knurled screws and their locking nuts to the left and right are merely intended to adjust the spacing from the armature (perhaps you knew that) They are NOT for connecting anything to. So, where is the U shaped piece connected electrically?--88.110.253.34 03:33, 24 September 2007 (UTC)

It seems obvious to me that when the relay is not energized (no current in the coils) the armature (moving contact) is touching the left hand fixed contact (because of the spring). If a pulse of current is received, the secondary circuit will momentarily be broken, then made. When the input pulse has finished, the secondary circuit will again be broken and then made again so you get two breaks in the secondary current for every pulse passed in the coils. This seems strange for a relay operation.--88.110.253.34 03:47, 24 September 2007 (UTC)

Strange indeed. So, how does this work in a telegraph circuit? John 05:06, 24 September 2007 (UTC)

In looking over many web pages on these and similar things, It seems as though it might have an additional purpose as a telegraph sounder. A quick succession of 2 clicks is a dot, and a longer time between would be a dash. The operator could adjust the timing with the adjustment screws is my guess. This still does not answer the Q of how it acts as a relay though. --88.110.17.120 12:45, 24 September 2007 (UTC)

Gq protein

What does the q in Gq protein mean? Is it an abbreviation for something? --89.27.225.143 07:38, 23 September 2007 (UTC)

"Gq protein" is short for "guanine nucleotide binding protein, q polypeptide pseudogene" = Nunh-huh 10:37, 23 September 2007 (UTC)

That seems unlikely, since a pseudogene doesn't encode a protein. The pseudogene is more likely to have been named after the q polypeptide. So what was the q polypeptide named for? Well, the first paper to describe G_αq is PMID 2123549. Reading that paper the authors explain the named the class, but don't explicitly say why. However, as is often the case, if your read the material and methods, you find hints. They say that the sequence of G_αq was obtained from two clones, Gq3 and Gq7. It appears these clones are named for the PCR primers used to make the clones from the cDNA library. So unless these were all re-named retroactively, its may simply be that the protein was named as such because the primer sets that cloned them had reached q in the alphabet. Rockpocket 21:54, 23 September 2007 (UTC)

Reproducing experiments: practical considerations

Apparently it's important for people to be able to replicate the experimental outcomes of published journal articles. I have some questions about this. Where does the (time and) money come from to support these investigations (can you write a research proposal that just suggests repeating experiments - does it help (or is it necessary) to suggest a different methodolgy to test the same hypothesis)? Is the information publishable if you determine the same thing as the original authors? Do you pick and choose which experiments to replicate based on plausability of original paper/discovery? --Seans Potato Business 13:58, 23 September 2007 (UTC)

A reaearch program aimed at simply and straightforwardly replicating a science experiment or series of experiments would be unlikely to get research funding from the boards who award research grants. It would be unlikely to be approved as the basis for a doctoral dissertation, or to be published in a quality journal. A way around this is to note a possible defect in the methodology of the original experiment and do a replication with improved methods to confirm the result is valid. For instance, Hertz did important experiments in the nature of electromagnetc waves, but he had metal columns in the lab, which might have effected the results. A replication might have been done to see the results still reached the same conclusions when a space free of obstructions was used. There are also important experiments which go a step further. When someone publishes his amazing experiment showing hitherto unknown effects, he may have had an experimental confound, i.e. he may have had an uncontrolled variable which actually caused the amazing effect (like someone serving as a confederate, or simply peeking to produce ESP results). There has also been poor experimental practice and actual fraud. A replication which shows that with the poor experimental practice the effect is replicated, but with improved methodology it goes away, is a very valuable sort of follow-up experiment. Then there is the experiment which first replicates the original result, perhaps with improved methodology, then carries it further to explore additional ramifications. One good experiment usually calls for another to confirm and extend it. In a good research lab, the senior investigator may start off a new grad student doing a replication. This is a cross-check to make sure the original result from that or a different lab is robust and valid, and it also shows that the new researcher is not too careless or sloppy to carry out the experiment correctly. There is a long sad history in science of jealous competitors announcing that new effects are irreproducible, often due to the poor technique of the followup researcher. Edison 19:32, 23 September 2007 (UTC)

Rarely would one set out to simply replicate the experiments of others for that purpose in itself. For groundbreaking technical work, like for example nuclear transfer followed by cloning of mammals, one might set out exactly replicate simply because reporting that different people the ability to do the technique is itself important. Also, using different methods to achieve the same, previously published, finding can itself sometimes be published if the finding is unusual, controversial or fundamental.

However, most of the time replication of initial experiments would be the starting point for further experiments to progress the field. So, Figure 1 of a paper may partly be a replication of previously published data, because you need to establish that - in your hands - you see the same results. Your further figures will be new data based on what you have demonstrated in Figure 1. Other times data is replicated is to compare and contrast with new data. Recently my lab was asked to replicate the data of others during the peer review process, to compare our new findings with theirs. In this case, we were using a a different methodology, so the goal was to show to show that the different methods gave the same results. Finally, replication of data is often an important scientific control. Rockpocket 19:24, 23 September 2007 (UTC)

rabies and E coli

what is the first line of defence in the body against rabies and e coli? —Preceding unsigned comment added by 89.243.19.182 (talk) 15:55, 23 September 2007 (UTC)

Sounds a bit like a homework question, and we don't answer homework questions here. However, we can offer hints. So, the first line of biological defence is usually some sort of physical barrier. To determine what type of barrier, have a read of Rabies#Transmission and symptoms and E. coli#Role in disease. Rockpocket 19:32, 23 September 2007 (UTC)

Difference between "planets" and "stars"

[This might be obvious to the better-informed out there, but I haven't been able to find the answer worded clearly enough for me. My apologies in advance.]

Is the difference between a "star" and a "planet" purely a matter of mass, or is there something else involved? For example, if you had a cube that was 70 Earths long in each dimension, you could fit 343,000 Earths in that cube. That's about as much mass as the Sun. (Slightly more, to be more precise.) Would this cube of Earths collapse together and start stellar fusion automatically? Or would something besides "this much mass in this much volume" be required for a star to be created? Does the mass of this "potential star" need to be made up of specific elements (only hydrogen and helium, for example), or would a solar-mass body with the same proportions of elements as the Earth become a star just by virtue of its mass?

Thank you very much. CSWarren 15:58, 23 September 2007 (UTC)

Usually fusion is required before some object is called a star. The earth is primarily made of iron. I doubt that an object the size of the sun made primarily of iron would undergo sustained fusion. There are border cases when hydrogen gas planets become stars. See Brown dwarf. —Preceding unsigned comment added by 84.187.32.213 (talk) 16:16, 23 September 2007 (UTC)

I don't think you get objects the mass of the Sun made up of iron (except possibly a supernova remnant). There is very little iron in the universe compared with hydrogen and helium, so, if you had that much iron, you would likely have 1000 times as much hydrogen and helium in the same place, and wouldn't even notice the iron in the star (or perhaps black hole, at that mass). Only low mass collections of iron (planets) are able to form without having enough gravitational attraction to pull in and hold all the hydrogen and helium around them. StuRat 17:15, 23 September 2007 (UTC)

The difference between a planet and a star is that a star produces energy by sustained fusion - planets do not. As to whether a star can burn iron - our article on Stellar evolution explains this very clearly - a REALLY big star will fuse hydrogen into helium, then helium, carbon, neon, oxygen, silicon and eventually, iron. But as the article points out: Once the nucleosynthesis process arrives at iron-56, the continuation of this process consumes energy (the addition of fragments to nuclei releases less energy than required to break them off the parent nuclei). - so the star can't live by iron alone - it has to be generating energy from some other source. A star that's big enough to fuse iron would soon afterwards collapse under it's own weight into a neutron star or a black hole or something equally exotic. SteveBaker 21:27, 23 September 2007 (UTC)

Burning a Volleyball

Purely theoretical, but assuming an Olympic-regulation volleyball in a gym with a constant air temeprature of 20 degress Celsius and a barometric pressure equal of that at sea level, how much of an impact force or energy would a player need to hit the ball with in order to set the ball on fire from air friction? Thanks. Acceptable 16:09, 23 September 2007 (UTC)

Certainly enough that the ball would explode way before it ever got near those kinds of speeds. --Oskar 19:38, 23 September 2007 (UTC)

Isn't it more likely that the heat generated by the impact of the paddle would light it on fire? I'm pretty certain the ball would explode even before that speed. — Daniel 23:59, 23 September 2007 (UTC)

"Paddle"?? How do you play volleyball? --jjron 09:09, 24 September 2007 (UTC)

To answer the question, I suspect it would be close to impossible to propel a volleyball to such a speed that it would ignite due to air friction no matter how you did it, much less simply being hit by a player. I'm trying to think if you tried dropping it in from space or something, but I can't really see how it would happen. Mythbusters anyone? --jjron 09:14, 24 September 2007 (UTC)

• Impale it on an aerospike? --Sean 14:51, 24 September 2007 (UTC)

I think the question presupposes some unlikely things. If there's a speed at which a volleyball in air would burn from air friction, I doubt you could get there by hitting it. By the time you whacked it that hard, I bet you'd break it. (I suspect this is what Oskar was saying.) Friday (talk) 14:58, 24 September 2007 (UTC)

Trachea

I'm looking for a few good pictures of the Trachea and the parts that are on the trachea that is related to phonation, like where the vocal folds are, arytenoid cartilages are show, the hyoid bone and it's features, things of that sort. I don't mind if it's computer generated or an actual dissection picture. The better labeled it is the more help it'll be for me. Thanks! --Agester 16:44, 23 September 2007 (UTC)

Have you tried a Google image search ? I found over 53,000 images, one of those should be good: [9]. StuRat 17:04, 23 September 2007 (UTC)

Of course. But i can't exactly find what i'm looking for. I spent the last half hour searching and it's a little fustrating. I came here after i tried looking maybe someone more talented or already have an image might be able to point me in the right direction. The "trachea" search with google images shows the trachea specifically. I'm looking for the parts of the trachea and the phonatory system. --Agester 17:06, 23 September 2007 (UTC)

Try using multiple keywords. I just tried "trachea arytenoid hyoid vocal" (without the quotes) and got this: [10]. StuRat 17:24, 23 September 2007 (UTC)

please answer my questions (iron and sulphur)

What is change simply of iron and sulphur? please answer my question. —Preceding unsigned comment added by 90.195.83.104 (talk) 16:52, 23 September 2007 (UTC)

To answer we need:

1) To understand it, what are you trying to ask ?

2) To find it, so I altered the title to actually mention the topic. StuRat 16:59, 23 September 2007 (UTC)

Iron and sulphur are both chemical elements, so in a sense they don't change. Perhaps reading the articles on those subjects will answer your question.--Shantavira|^{feed me} 17:51, 23 September 2007 (UTC)

They could change to other elements during supernova explosions, but not on Earth, unless you're talking about a few atoms in a particle accelerator. StuRat 18:01, 23 September 2007 (UTC)

Possibly you meant chemical reaction between iron and sulpur which gives Iron (II) sulphide as well as possibly Iron (II) disulphide or polysulphides depending on the ratio of iron and sulphur.87.102.17.252 18:50, 23 September 2007 (UTC)

Your question is not clear enough to answer it. It is unclear because the words "change" and "simply" are too vague and may not be used properly in English. John 19:06, 23 September 2007 (UTC)

Perhaps you mis-spelled and meant to ask about charge states when electrons are added or removed from an atom? Astronaut 19:59, 23 September 2007 (UTC)

Antisocial personality disorder

I read this article long time ago and it said one of its symptoms was frequent wet-dream and now its not there anymore. Why did you change it? Was it the wrong information? —Preceding unsigned comment added by 76.64.128.122 (talk) 19:39, 23 September 2007 (UTC)

It's still there, under the section potential markers. A.Z. 20:05, 23 September 2007 (UTC)

No it isn't. A wet dream is not the same as bed wetting. Rockpocket 20:11, 23 September 2007 (UTC)

I'm betting the original comment that you read was vandalism and someone discovered that and reverted it. It's also possible that this was some wild and unsubstantiated claim that could not be verified with solid references...and for something as unlikely-sounding as this, that would be ample grounds for deleting it. But you can check the edit history, find out who deleted it and ask them why. SteveBaker 21:14, 23 September 2007 (UTC)

reverse culture shock ?

i looked up culture shock and then reverse culture shock and i believe that i fully understood both of them . my question is what do you call it when you have not gone to a foreign country , but have an influx of foreigners (all from the same country) come to your country and try to implement their way of life and language upon you . at first i thought that it would be classified as reverse culture shock but after reading your definition i know that's not it . would it still be called culture shock or is there another term that is used ? thank you 68.161.197.95 20:22, 23 September 2007 (UTC)dg

Sounds a lot like colonization. StuRat 21:10, 23 September 2007 (UTC)

It could be xenophobia, but that term is usually used with a negative or pejorative connotation. Nimur 22:36, 23 September 2007 (UTC)

Cultural imperialism. Clarityfiend 03:22, 24 September 2007 (UTC)

None of our answers so far seem to include the case where poor immigrants (or even refuges) enter a country, then "take over" by numbers alone. StuRat 16:05, 24 September 2007 (UTC)

Numerology

Is numerology considered a science? Or can it be considered as a science? —Preceding unsigned comment added by 66.18.81.196 (talk) 21:25, 23 September 2007 (UTC)

Most would say "no". It is considered a form of pseudomathematics. Rockpocket 21:57, 23 September 2007 (UTC)

Though, the similarly named (but entirely different) discipline of number theory is a realcomplex and reputable form of mathematics. Nimur 22:34, 23 September 2007 (UTC)

Does it stop at complex numbers? What about matricies and quaternions? — Daniel 23:56, 23 September 2007 (UTC)

Sorry, my weak joke started off when I was using "real" as opposed to "pseudo" mathematics. But I thought it would be funny to change real to complex. Sorry if anyone else did not understand. Of course number theory delves far beyond even the real and complex numbers, including other more abstract definitions for number systems. Nimur 04:22, 24 September 2007 (UTC)

Which is the most common chemical in households?

Between Carbon dioxide, carbon monoxide, hydrogen chloride, hydrogen cyanide, nitrogen dioxide, and phosgene, which is the most common in a normal household. —Preceding unsigned comment added by Davidm617617 (talk • contribs) 22:46, 23 September 2007 (UTC)

Are you referring to the air in the house or the items (such as household cleaners) in the house? -- kainaw™ 23:06, 23 September 2007 (UTC)

And forgive my saying, but this sounds like a chem homework question. Saturn 5 00:34, 24 September 2007 (UTC)

Is this by volume or by weight? If by volume I would say nitrogen as it is the major part of air. (76% if i remember correctly) —Preceding unsigned comment added by 88.111.177.44 (talk) 01:11, 24 September 2007 (UTC)

OK just looking at your Q again, I would say CO2--88.111.177.44 01:16, 24 September 2007 (UTC)

September 24

solubility of sugar in water

I need to know what effects temperature has on the amount of sugar that dissolves in water.EG: Will more sugar dissolve if the water is hotter? —Preceding unsigned comment added by Latelearner (talk • contribs) 01:29, 24 September 2007 (UTC)

Yes, more will dissolve in hotter water. Now someone please provide an equation. Edison 02:54, 24 September 2007 (UTC)

It sounds like you're doing homework. Perhaps the article solution will be useful? --Mdwyer 03:35, 24 September 2007 (UTC)

I found a table. [11]. Someguy1221 03:38, 24 September 2007 (UTC)

What's interesting about a sugar-in-water supersaturated solution is that when it cools, the sugar doesn't precipitate out. Rather, it forms a syrup.

Mrdeath5493 04:35, 24 September 2007 (UTC)

Melting point depression perhaps?83.100.254.150 06:48, 24 September 2007 (UTC)

Though if you're trying to do it, you can make sugar crystals at home by providing a crystal seed or a suitable surface. Also, as a side note - the table Someguy posted gives values for glucose, not sucrose... Nimur 04:47, 24 September 2007 (UTC)

It's all sugar ;-) Someguy1221 04:51, 24 September 2007 (UTC)

Yes, and this is why coffee and tea are often served too hot to drink, so that sugar can be easily dissolved in it. If you've tried adding sugar to iced tea, you know it doesn't dissolve all that easily. StuRat 15:59, 24 September 2007 (UTC)

Body Mass Index Calculation

"BMI ... calculated by multiplying one's weight in kg twice, then dividing it by one's height in cm" Is this a valid way to calculate BMI? —Preceding unsigned comment added by 66.238.233.150 (talk) 03:22, 24 September 2007 (UTC)

You could just read our article on Body mass index. --Mdwyer 03:36, 24 September 2007 (UTC)

SI units

$\mathrm {BMI} ={\frac {{\mathit {weight}}\ \mathrm {(kg)} }{{\mathit {height}}^{2}(\mathrm {m^{2}} )}}$

BMI = W/(H^2)

.

Let H = 100 h (conversion from metre to centimetres)

.

BMI = W/(H^2) = W/((100 h)^2) = (1/10000) * W/(h^2)

So we have Weight (W) in kilograms

So we have Height (h) in centimetres —Preceding unsigned comment added by 202.168.50.40 (talk) 04:47, 24 September 2007 (UTC)

202.168.50.40 04:45, 24 September 2007 (UTC)

Thanks for the reply. But my question is if there is alternative ways for reckoning it, say in Japan. The part I quoted is from a book on Japan. Is that incorrect? 71.195.106.60 04:52, 24 September 2007 (UTC)

Our own article suggests the calculation (also its definition) is universal. Someguy1221 05:17, 24 September 2007 (UTC)

From the quotation it seems as if the book has gotten which term should be squared the wrong way around. And yes, it should be the same everywhere, although the significance of a certain BMI does differ between ethnic groups. Recurring dreams 08:39, 24 September 2007 (UTC)

I do seem to recall an alternative that more accurately tried to measure body fat percentage, I think by measuring a person's weight in air and then in water and applying a formula to the two weights. Does this sound familiar to anyone ? Then there was also the less accurate "pinch an inch" method, where calipers were used to measure to amount of fat at the waist. StuRat 15:54, 24 September 2007 (UTC)

Pair of electrons .

Why do electrons in an atom makes pair ; while they repeal each other . Do free electrons also make pair ? Is there any wikipedia article about that ? —Preceding unsigned comment added by Shamiul (talk • contribs) 05:27, 24 September 2007 (UTC)

Pauli's exclusion principle, atomic orbital...Free electrons (truly free, not bound to anything positive) will just repel eachother. Someguy1221 05:47, 24 September 2007 (UTC)

Yes Pauli's exculsion principle is the relevant one here. Basically every electron wants to be at the lowest energy level, but identical electrons (with the same quantum numbers are excluded. Electrons have two spin quantum numbers which allow them to form into pairs. On free electrons, the only example I can think of is Cooper pairs in superconductivity. Cyta 10:31, 24 September 2007 (UTC)

...and here I thought the Pauley Exclusion Principle applied to keeping Jane Pauley off The Today Show. :-) StuRat 15:46, 24 September 2007 (UTC)

particle spin .

As far as i know particle spin refers to the revolving characteristics of an particle about an axis(same as the world spin about it's own axis). My question is : how the spin of particle is defined by number ? as we see the spin of electron and proton is half . why this is half ? please clear my confusion by assuming the world as a fundamental particle . what will be the spin of the world if we assume the world as a fundamental particle ? photon spin is 1 . what does that mean ? does photon also revolve about an axis ?

We have a detailed explanation of particle spin from various different points of view in our article on spin (physics). In general, attempts to interpret quantum spin by assigning classical physical attributes to elementary particles seem to lead to confusion and contradictions. Simplest approach seems to be treat elementary particles as point objects that have an attribute that happens to behave like classical angular momentum, except that it is quantised. Gandalf61 10:20, 24 September 2007 (UTC)

Color and octaves

The human visible spectrum entails about one octave - 380 to 770 nm. Furthermore, the color wheel depends on the upper and lower wavelengths looking the same and seamlessly blending into each other. It's interesting that visual frequencies one octave apart are perceived as similar. What's the physics behind this visual perception? Do other animals also perceive an octave of visual spectrum? —Preceding unsigned comment added by 76.27.209.182 (talk) 06:57, 24 September 2007 (UTC)

Unfortunately the lower frequencies DON't look the same as the upper frequencies - lower = red, upper = blue/violet - the way the colour wheel works is by belending red into blue via purple - it's only real on paper - the upper and lower frequencies DON't look similar - though it would (as you say) be interesting if they did83.100.254.150 07:14, 24 September 2007 (UTC)

I think the upper and lower frequencies look the same, at least to me, and first noticed when looking at a prism in sunlight. Afterwards, it occurred to me that the color wheel was continuous. —Preceding unsigned comment added by 76.27.209.182 (talk) 07:27, 24 September 2007 (UTC)

Your impression is mistaken. Your color wheel contains non-spectral colors, i.e. colors whose perception cannot be induced by any single-frequency light. The colors between red and violet on the color wheel are produced by mixing different proportions of red and violet lights. These colors are non-spectral and don't have a frequency to speak of. (See also chromaticity diagram, and the comment about the horseshoe-shaped spectral locus in particular). --71.175.68.224 10:14, 24 September 2007 (UTC)

I expect it to look like this (from Prism (optics)) File:PrismAndLight.jpg What I can see is red at the top and blue at the bottom - which look different to me - however your perception may be different - if it is - please say more...87.102.21.91 11:53, 24 September 2007 (UTC)

Yes, my perception might differ - or it might just be limitations of the computer screen. The next time you see a real rainbow or prism, not printed or on a monitor, look closely and see if the far end of violet starts to look like the other end of red. It does for me. Not so on the computer monitor, though.

(from farther above) Your impression is mistaken. Great, you seem awfully sure of yourself ;) 76.27.209.182 14:46, 24 September 2007 (UTC)

Yes, if someone says "I think A looks like B", you can certainly say "I don't think A looks like B", but you can't say "No, you don't think A looks like B", that's just silly. Many people think deep red and violet look similar, and I am one. This question is about perception, or what people think they see, not about the physics of the color wavelengths. Some people's brains seem to be wired to see those two colors as similar, so now the question is why this occurs. StuRat 15:30, 24 September 2007 (UTC)

Two (make that Three) Quantum Physics Questions

1. Why are there no spin-1/2 baryons composed of three identical quarks (no nucleon corresponding to Δ++)?
2. Why are chargeless photons sufficient to explain the electromagnetic force between charged particles, while the strong force requires particles, themselves color-charged, to transfer force between colored particles?
3. Why must the quarks bound in a hadron constantly change colors?

Thanks. Ratzd'mishukribo 07:20, 24 September 2007 (UTC)

I could be totally wrong here, but isn't the first one the Roper resonance? —Keenan Pepper 19:27, 24 September 2007 (UTC)

Jelly Shots

If I used vodka instead of water when making jelly would the jelly still set? --124.254.77.148 07:52, 24 September 2007 (UTC)

Vodka has a lower freezing point than water due to the alchohol content. This means it can be hard to get the jelly to set properly, especially if you use pure vodka - you'll often get a pretty 'runny' jelly. It would be easier to get to set if you diluted the vodka considerably with water. (And bonus health warning: be very careful when taking 'jelly shots', as it is easy to rapidly consume large quantities of alchohol, which can have serious health consequences, including potential brain damage or death). --jjron 09:05, 24 September 2007 (UTC)

I'm pretty sure freezing point has nothing to do with with the setting of gelatin. ike9898 17:45, 24 September 2007 (UTC)

Black women's buttocks

Hello, wanted to ask if there's an evolutionary explanation for black women's uniquely fat buttocks. Thanks, 87.68.194.108 09:26, 24 September 2007 (UTC)

May be a common genetic trait for some black women concentrated in certain geographic areas but women and men from White, Hispanic and other races likewise have equally large buttocks though perhaps not as concentrated in one particular geographic location. On the other hand all races seem to have members with buttocks which meet or surpass the designation of a "perfect 10." Clem 10:04, 24 September 2007 (UTC)

You may want to read our article on Steatopygia. Dismas|^(talk) 10:27, 24 September 2007 (UTC)

Interesting, thanx. 87.68.194.108

I can offer some speculation. The main purpose of fat on the buttocks (as opposed to elsewhere on the body) is to provide padding when seated. It would stand to reason, then, that those populations which had to sit on harder surfaces, like stone, would need more padding than those which had softer surfaces on which to sit, like sand or dirt. Since cavemen used to live in caves, this feature would have been positively selected, especially for women, who would tend to stay in the cave watching children, etc., while the men went hunting. Those with little buttocks fat would have risked sores, infection, and possible death. After humans moved out of caves, softer seating surfaces became available, so this feature was no longer positively selected. I imagine a more even distribution of fat has other advantages, such as providing better thermal insulation. Thus, I'd expect this trait to have largely disappeared, especially in colder climates. StuRat 15:20, 24 September 2007 (UTC)

Erm, let me get this straight, are you arguing that men selectively chose to breed with women who would have a more comfortable seat back at the ol' homestead? Does that mean that at some point in geological time men actually considered women's needs when it came to sex? --Dweller 15:27, 24 September 2007 (UTC)

No, I never mentioned sexual selection at all. StuRat 16:12, 24 September 2007 (UTC)

I'm tempted to plaster StuRat's post with the {{fact}} template (), demanding citations for his claims... Nimur 15:34, 24 September 2007 (UTC)

That would mean my statement was speculation, would it not ? I sure wish I'd said that myself :-) StuRat 16:12, 24 September 2007 (UTC)

Goodness me, StuRat, you have excelled this time. Not every phenomona can be explained the simpistic natural section as extolled in popular science. Dawkins et al have a lot to answer for. Rockpocket 20:33, 24 September 2007 (UTC)

Is Dweller suggesting that humans are rocks? -- JackofOz 15:37, 24 September 2007 (UTC)

The "caveman" is an inaccurate stereotype. Early humans, such as the Cro-Magnon, mostly lived in huts and used caves for rituals. We know this because caves in which cave paintings have been found do not show signs of ongoing habitation. Gandalf61 15:39, 24 September 2007 (UTC)

There certainly was a time before which humans (or pre-humans) lived in huts. Where did they live then ? StuRat 16:12, 24 September 2007 (UTC)

The same places non-human primates do now: on the bare ground, in "nests", up on branches, etc. We're not well adapted to life in a cave. Matt Deres 16:31, 24 September 2007 (UTC)

I'm not entirely certain StuRat was being serious. Mind you, I'll let him speak for himself. StuRat? --Dweller 15:43, 24 September 2007 (UTC)

I am serious. StuRat 16:12, 24 September 2007 (UTC)

Lol. That's definitely my cue to log off for a while. Meanwhile, public thanks to Jack for making me smile at the end of a trying day. --Dweller 16:14, 24 September 2007 (UTC)

The idea to sit on something soft instead of something hard seems pretty obvious- even animals do this. I don't see why this would relate to what kind of house you live in. Friday (talk) 16:25, 24 September 2007 (UTC)

I have a vague recollection of a study a few years back that found that on the average black women had a greater degree of lordosis than white women. Gzuckier 17:32, 24 September 2007 (UTC)

• It's the Khoikhoi, and not Africans as a whole, that as a group have the most pronounced posteriors. --M@rēino 19:49, 24 September 2007 (UTC)

ancient cultures and dinosaur bones

What did ancient cultures have to say about dinosaur bones? Clem 09:58, 24 September 2007 (UTC)

The first recorded dinosaur fossil that I know of is in 1819 (by William Buckland). Previous to that, any large bone would most likely be attributed to some sort of mystical creature: A giant, a dragon, a griffon, a god, or a demon - just to name a few. -- kainaw™ 12:30, 24 September 2007 (UTC)

Do you have references for these "dragon" bones, etc.? Clem 14:21, 24 September 2007 (UTC)

Well, if there were systematic record of them, they probably would have been identified as actual animals instead of mythical creatures. The widely accepted first documented study happened in 1819, as mentioned by Kainaw. Nimur 15:10, 24 September 2007 (UTC)

So then all of history, whether correct in its conclusion or assumption of whatever the subject might be prior to 1819 is bunk? Don't think so. In fact by providing such an answer I am beginning to think that whatever might be comming from this desk is more likely bunk instead. Clem 19:45, 24 September 2007 (UTC)

That all of history is incorrect is a ridiculous extension of the above statement. There's no need to be hostile to those that volunteer time to answer your wildly broad and vague question. Here's a link to a site that touches on the origins of dragon myths. There are countless young earth creationist sites that claim that leviathans and behemoths are dinosaurs, and others that rebut those claims. Here's a story about modern, though uneducated, Chinese villagers eating "dragon" bones. — Scientizzle 20:06, 24 September 2007 (UTC)

CATEGORY OF DISTRIBUTION / LINE AMPLIFIERS

kindly let me know that Catv distribution amplifiers/Catv Line Ampliiers can be categorised as a Intermeidate Frequency Amplifiers in terms of CATV(community antenna Television Network) used by Local Cable operator. (SEE WEB PAGE OF M/s.HANGZHOU PREVAIL OPTOELECTRONIC EQUIPMENT CO LTD, (prevail-catv.en.alibaba.com) ITEM NAME; (1) BI DIRECTIONAL TRANSMISSION TRUNK AMPLIFIER (2)BI DIRECTIONAL DISTRIBUTION AMPLIFIERS, (3) 1310N.M CATV AMPLIFERS.

waiting for your most positvie responce. —Preceding unsigned comment added by 116.71.55.121 (talk) 10:08, 24 September 2007 (UTC)

I would not call any of these intermediate frequency amplifiers. The trunk and distribution amplifiers would be categorised as wideband RF amplifiers as they handle a broad range of frequencies. The 1310nm is an infrared wavelength used on optical fibres. The RF is modulated onto the infrared frequency, and the signal can be carried over many kilometers without the loss and frequency distortion that a coax would cause. The intermediate frequency occurs in the televison when the signal is down converted.

Another place that you may see an IF in CATV, is when a satellite DTV broadcast is received the LNB converts the Ku band or C band signal to an L band ranging from 950MHz up to around 1950MHz. Graeme Bartlett 12:37, 24 September 2007 (UTC)

Sunset/sunrise on the equator

Does the sun set and rise at the same time every day day, year round, on the equator? If so, what time? I would have assumed the answer is yes, but the equator article doesn't say anything about it. 220.235.135.146 10:45, 24 September 2007 (UTC)

The sunrise article does, in the fourth paragraph. The times vary throughout the year because of the tilt of the earth. I'm glad you asked this question, because you got me poking around, and I found this [12]. I had just seen one of these again recently and vaguely wondered what it was called. The Wikipedia article on analemma explains all. --Milkbreath 11:13, 24 September 2007 (UTC)

And here I just thought that meant that Emma was anal-retentive. :-) StuRat 15:07, 24 September 2007 (UTC)

Yellow LEDs -- trivia

Red,green, orange and more recently blue led's are common - but where are all the yellow leds - for instance on consumer electronics - is there a reason why they are not used - or maybe I've just missed them.?87.102.21.91 12:19, 24 September 2007 (UTC)

Amber-colored LEDs are common. They are yellow enough. You may be mistaking them for being orange. -- kainaw™ 12:25, 24 September 2007 (UTC)

I've seen amber ones - but they were 'amber' which to my eyes is orangey - how about a truly yellow LED?87.102.21.91 12:37, 24 September 2007 (UTC)

It must be a "style" thing; true yellow LEDs have existed for years and are as inexpensive and electrically efficient as any other color. Lately, "Chernobyl blue" has been the rage, even though blue LEDs are still substantially more expensive than the other visible colors.

Atlant 14:33, 24 September 2007 (UTC)

LEDs do not produce white light (even "white" ones are really just light blue), and as a result, you can't just stick a piece of coloured plastic over the top and make a coloured light - you need instead to dope the LED with trace amounts of various elements. Some of these are more expensive than others (red is much cheaper than blue, for example), so there tends to be bias towards these, but, as Atlant mentions, fashion plays a role too (red LEDs seem kind of 80s today, and red is quite a negative colour and is therefore generally reserved for standby or error states of electronics). In addition, gallium(III) phosphide, one of the commonest LED materials, isn't quite yellow, but more of a yellow-green; as a result, you may perceive this colour as being very green. A cursory glance around my room reveals yellow LEDs in my HDD light, printer standby light, speaker power light and router/firewall Blinkenlights. Laïka 18:20, 24 September 2007 (UTC)

I'll expand a bit on my "fashion" answer. In the beginning, when visible-light LEDs came in any color you wanted as long as it was red, red LEDs were used for everything. But as additional colors began to be available (especially that sickly yellowish-green), LED colors, at least in technical gear, began to be a bit more standardized with sickly-yellowish-green being used for indications that things were "OK" ("power on", etc.) and red LEDs meaning error or fault conditions. Yellow and amber LEDs often are used for "activity" or slightly "off-normal" normal conditions ("high speed", whatever).

Nowadays, true green is replacing sickly-yellowish-green. As this occurs, maybe you'll see more use of real yellow (since it will be more-easily distinguishable from sickly-yellowish-green). And blue, although it's usually a bad choice for both economic and ergonomic reasons (it interacts pretty poorly with human vision, especially as a display backlight), will probably remain popular until supplanted by some new and exciting color like violet or magenta (perhaps via a UV LED plus a phosphor), but those colors may not be perceived as studly enough to become universally-popular. RGB LEDs are also getting popular and inexpensive enough to see common usage. This may also lead to more color choices, perhaps even common user choice of color.

Atlant 18:49, 24 September 2007 (UTC)

LEDs again

The V-I curve for a diode. Nimur 15:13, 24 September 2007 (UTC)

The voltage drop across a led is pretty much it's bandgap.. and V/R = I and light intensity is propotional to current. and the device will have a constant R?

1.So does this mean that the light intensity from an LED is instrinsically fixed. (and if so some previous posts I made were very wrong - but no one seemed to notice..)

2.Or is there a way to change the light intensity from a LED

3.If (2 = No) then does this make OLED TV's a total non-starter?87.102.21.91 12:37, 24 September 2007 (UTC)

The current through the LED is usually determined by the external circuitry (such as a ballast resistor or LED-driver integrated circuit). A few LEDs contain within the plastic package a chip resistor so they draw their rated current when operated on a fixed voltage. A very few LEDs contain a constant-current device so they draw their rated current over a wide range of operating voltages.

Atlant 14:36, 24 September 2007 (UTC)

The LED is a diode, so it is not correct to say it has a "constant R" - that would imply a linear Ohm's law applies. In fact, the current-voltage relationship is very well studied, and is often approximated as a simple exponential (I = Io * exp(V / Vth)). See the graph posted. R is not constant for nonlinear devices. Nimur 15:13, 24 September 2007 (UTC)

bonobos and humans

Among the 3 species: human, bonobo, and common chimp. Can any combination of two of them mate and produce a hybrid offspring?--Sonjaaa 13:27, 24 September 2007 (UTC)

Our article on hybrids does not mention any primate hybrids and there are not many Google hits. On the other hand, some very strange hybrids do occur - see the Toast of Botswana. The proposed human/chimpanzee cross in this news story would be a chimera rather than a hybrid. DNA evidence suggests that bonobos and common chimpanzees became separate species less than 1 million years ago. As species, they are quite close - certainly closer to one another than either species is to humans - so they are probably the most likely candidate species for producing a hybrid. Gandalf61 14:32, 24 September 2007 (UTC)

Human/chimp or human/bonobo hybrids are most likely impossible (different number of chromosomes). Bonobo-chimp hybrids probably can occur (but not in nature as their ranges never overlap). As late as the forties, bonobos and chimps were often housed together in zoos, whether or not any hybrids were born, I'm not sure. --Cody Pope 18:25, 24 September 2007 (UTC)

Actually, chromosome number is not necessarily a barrier to viable hybrids. Donkeys and horses have different numbers of chromosomes (62 an 64 respectively), but produce mules. -- Flyguy649 ^talk _contribs 18:29, 24 September 2007 (UTC)

You may be interested in the Humanzee article. -- 20:48, 24 September 2007 (UTC)

What is the name of this plant?

Mystery shrub

This unusual leaf grows on a shrub that is very common in the Philadelphia area. What is the name of the shrub?

-- Dominus 13:52, 24 September 2007 (UTC)

I suspect it's a Red Mulberry, which sometimes has deeply lobed leaves. -- JSBillings 15:29, 24 September 2007 (UTC)

Peripheral nervous system: autonomic and somatic nervous system

I found this picture on the internet: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/NervousSystem.gif

Is this picture really correct? Does the somatic nervous system really only control muscles that influence the "external environment"? I mean, if I pick up a mug, it both influences my internal environment (in my arm) and the external environment.
And what about when I hold my breath without pulling in my stomach (so it is not visible for the external environment that I'm holding my breath)? I would suppose that motor neurons from the somatic nervous system are activated for this control of my internal environment. Am I right? Lova Falk 14:27, 24 September 2007 (UTC)

I think you're taking "internal" and "external" too literally. By "internal environment", they mean things not directly under your mental control, like digestion, heart rate, blushing, etc., and the fact that you can hear your stomach growling and feel your pulse and see your face turn red doesn't change that. --Sean 15:13, 24 September 2007 (UTC)

I like to be very precise. :) What about consciously holding my breath? Am I right in supposing that this is under control of the somatic system, or is it part of the autonomic system?? Lova Falk 15:34, 24 September 2007 (UTC)

Breathing is an odd bird. See control of respiration. --Sean 15:52, 24 September 2007 (UTC)

I read that page and it said: "Ventilation is normally autonomic, with only limited voluntary override, but an exception to this is Ondine's curse, where autonomic control is lost."

This is still not a clear, no-misunderstanding-possible answer to my question: Is holding my breath controlled by the somatic nervous system or by the autonomic nervous system? Lova Falk 16:08, 24 September 2007 (UTC)

It's both. The intention and voluntary choice to hold your breath leads to your somatic nervous system overriding your autonomic nervous system, however, when you faint and fall over for lack of oxygen, your autonomic nervous system takes back over (unless you've successfully suffocated yourself, and then you're dead). There is a similar situation with winking. (except for the dying part) -- JSBillings 17:34, 24 September 2007 (UTC)

Thank you! That explains it all. Lova Falk 19:08, 24 September 2007 (UTC)

Dorsal root

As I wrote in my previous contribution, I like to be exact. :)

I found this picture on the internet. http://universe-review.ca/I10-13-spinalcord.jpg

I wonder if the arrow to the dorsal root is quite right. It seems to me it should be pointing to the orange-coloured "bulb" to the right of the spine. Is that correct? Lova Falk 15:55, 24 September 2007 (UTC)

No, the arrow is correct, if a little unclear. The bulb is the dorsal root ganglion. Here it is in a picture, a model, and in the flesh. --Sean 18:45, 24 September 2007 (UTC)

Thank you so much! Lova Falk 19:09, 24 September 2007 (UTC)

Seduction techniques

What's the best way for a guy in his early 20s to seduce a really sexy 45 year old blonde woman? Any tips? —Preceding unsigned comment added by 81.76.16.155 (talk) 15:59, 24 September 2007 (UTC)

Do it in a novel, perhaps a bodice ripper.

Atlant 17:16, 24 September 2007 (UTC)

Um, this is the science desk. Still, Welcome to Wikipedia. You can easily look up this topic yourself. Please see seduction. 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. .--Mrs Wibble-Wobble 17:27, 24 September 2007 (UTC)

Vogels minimum medium

What is vogels minimum medium? Is their a recipie I can follow to make it? Or can I buy it somewhere?

Thank you 128.113.36.239 18:28, 24 September 2007 (UTC)

Google tells me you want 'Vogel, H. J., 1956 A convenient growth medium. Microbiol. Genet. Bull. 13: 42–46'. Haven't found it free online yet. Algebraist 18:37, 24 September 2007 (UTC)

[13], page 2 at the top, I believe. -- Flyguy649 ^talk _contribs 18:50, 24 September 2007 (UTC)

Great! I got the PDF, now as I am not ascoiated with a lab, can someone reccomend a site online where I can buy the ingredients called for? I googled lab supply stores but they dont seem to carry these 'basic' chemicals.

Na3 citrate.2H2O 125 g KH2 PO4 250 g NH4NO3 100 g MgSO4.7 H2O 10 g CaCl2. 2H2O (dissolved) 5 g trace element solution 5 ml biotin stock solution 2.5 ml

Thanks again, —Preceding unsigned comment added by 128.113.36.239 (talk) 19:37, 24 September 2007 (UTC)

Sigma could provide you with these. Rockpocket 20:20, 24 September 2007 (UTC)

RTG shields

Can anyone explain what the heavy shield-looking things on the left side of this picture are for? Thanks. --Sean 18:55, 24 September 2007 (UTC)

Shields?

Same reason the secretary has a sound-absorbing cubicle partition:) Looks like this generator/shielding experiment is being run in part of a much larger room. Those things are at-least-potentially spewing radiation, so good to separate them from unrelated projects by distance or shielding (to keep from irradiating other things, and to keep other sources of radiation from interfering with measurements). DMacks 19:54, 24 September 2007 (UTC)

Isaac Newton and Galileo

You have Sir Isaac Newtons birthday listed as 1643, yet other sources have it listed as 1642 same year Galileo died. Which is correct?

Walter Sept 24, 2007 —Preceding unsigned comment added by Wjchristense (talk • contribs) 19:04, 24 September 2007 (UTC)

Isaac Newton was born in England, still on the Julian calendar, on Christmas Day, 1642. If this is converted to a Gregorian calendar date, it would be 4 January 1642/3. Galileo died in Italy, which had already adopted the Gregorian calendar, on 8 January 1642. The events were 361 days apart.

When someone says that Galileo died, and Newton was born, in the same year, they are misleading you. The events only occur in the "same" year if you use one dating system for one, and the other dating system for the other. The dates have been "massaged" in order to create a "good story" where none exists. see [14] - Nunh-huh 19:16, 24 September 2007 (UTC)

Tail vein versus orbital plexus

Why take blood from the orbital plexus of a mouse and not the tail vein? My lecturer (uncertain) suggested it may be easier but I don't see how that could be the case. --Seans Potato Business 19:35, 24 September 2007 (UTC)

This paper compares the techniques. Apparently it can be up to 15 times faster to do it at the eye than at the tail, and that the blood chemistry can be affected by withdrawal site. --Sean 19:49, 24 September 2007 (UTC)

What's going to happen where

Is there a map that shows geographical positions close enough to sea level to be effected by the rise of Earth's water? There's a lot of talk about America's historical landmarks along the coasts being swamped or flooded away, but what about Europe? What about Asia? What about inland places already close to sea level? Is there a place ot find a more impactful example of historical loss other than Jamestown? Beekone 20:16, 24 September 2007 (UTC)

A good starting point would be a Topographic map of the area of intestest. DMacks 20:36, 24 September 2007 (UTC)

Are there any foods that make you happier?

Although some foods such as walnuts contain high amounts of for example serotonin, it is as far as I know unikely that it would be able to pass through the gut wall and then also the body/brain barrier.

Are there any foods that could actually make you feel happier? Thanks 62.253.45.36 20:17, 24 September 2007 (UTC)

Chocolate, perhaps? Also, St. John's Wort is a natural antidepressant, but I don't think it's actually used as food. —Ilmari Karonen (talk) 20:31, 24 September 2007 (UTC)

Evolution of singing

How or why did singing evolve? Thanks 80.2.197.120 20:37, 24 September 2007 (UTC)