Wikipedia:Reference desk/Science

Reference Desk

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Greatest Common Factor / Least Common Multiple Problem

I recently went to a math competition and this problem is bugging the heck out of me. Can anyone show how to solve it as well as provide the useful laws?

Q) A positive integer 'n' has the property that the least common multiple of n and 36 is 500 greater than the greatest common factor of n and 36. What is 'n'? Written mathematically: LCM(36,n) - 500 = GCF(36,n)... n=?

Thanks C. Nelson 22:26, 2 October 2005 (UTC)

Earliest Fossil Egg

Where was the earliest fossil egg found?

-anon

As yet, we do not have an article on Fossil eggs nor does our fossil article provide much detail. However, these articles by The San Francisco Chronicle on dinosaur fossil eggs [1] and the National Geographic on bird fossil eggs [2] should be of some assistance to you. I have added Fossil eggs to Wikipedia:Requested Articles so that someone can write an article on this topic. Capitalistroadster 00:08, 23 September 2005 (UTC)

which part of the tree contains live wood?

• Depends on the tree, but potentially all of it. -- Jmabel | Talk 05:34, 23 September 2005 (UTC)
  • Well, it does depend on the tree, but most "normal" trees (not, for example, palm trees) have living cells in the outer sections of their trunks (except the bark) and dead cells in the interior and the bark.

    Details: There is a thin, roughly cylindrical shell called the vascular cambium, which is where a tree does its growing. The outside of the cambium produces new phloem cells, which do "food" transport. The inside of the cambium produces new xylem cells, which do water & nutrient transport from the roots. Old phloem gets shed with the bark, but old xylem just sticks around, forming a core made of dead cells that provides structural support to the tree. Most trees add a new layer of xylem each year. The old dead xylem layers are the rings one can see on a stump.

    It appears to little-old-nonexpert-me that this ability to make a single, strong core out of dead xylem is probably one of the main factors that allows trees to grow so tall. Lots of plants have this phloem/cambium/xylem structure, but in many of the smaller ones, the cambium does not form a single large cylinder, but rather many small ones (vascular bundles). Thus, the xylem is scattered and strength is lost. I imagine this is one reason you will never see (say) a celery tree. On the other hand, the multiple bundles probably allow for faster growth ("growing like a weed"). Interestingly, palm trees have the multiple vascular bundles, but can still form large, strong trunks.

    Much of this is hinted at in our tree and xylem articles, but never quite stated. Maybe it should be.

    — Nowhither 00:14, 24 September 2005 (UTC)

Any Airsofters in the LA county area?

Any Airsofters in the LA county area?

Oh Jesus Christ. Is the concept of the Reference Desk that dense and foreign to some people? Garrett Albright 12:21, 23 September 2005 (UTC)

That's a valid question, just not the kind you want to answer. Superm401 | Talk 13:44, 23 September 2005 (UTC)

• It's an easy question to answer, and perfectly valid. Given the huge population of LA, and the burgeoning popularity of Airsoft, the answer is indubitably, "Yes". --jpgordon∇∆∇∆ 14:38, 23 September 2005 (UTC)

• Okay, please do not bite the newcomers. To the original poster: The answer is "yes", there are airsoft players in that area. Perhaps you are one of them. However, that is obvious. I would guess that your real reason for posting here is to meet airsoft players (?). If so, then you are in the wrong place. The Wikipedia Reference desk is for answering factual questions, not for meeting people. A quick Google search turns up many airsoft-oriented websites. I suggest you try one of them. — Nowhither 00:20, 24 September 2005 (UTC)

Electron - Proton

What we have been taught is that electron revolves around a proton because of electromagnetic force of attraction. But this force is same for both the electron and proton. This is when we neglect other forces like Gravitation since it is only 1/100 th times of electromagnetic force acting. Then why do electrons revolve around the protons instead protons can move around an electron??

Yes, the force on the two is the same (in accord with Newton's third). However, the proton is 2000 times more massive that the electron, so it remains relatively stationary. Just like the Earth orbiting the Sun, both objects actually orbit the center of mass, but the center of mass is closer to the more massive body. In both cases, the more massive body is so much more massive, that you can often neglect the massive body's revolution. -Lethe | Talk 02:24, 23 September 2005 (UTC)

Isn't it a bit 'oldfashioned' to think of an electron evolving around the nucleus? This is 'particle-thinking', but elementary particles can also be seen as waves. I envision electrons and other 'particles' as sort of pulsating three-dimensional waves. Lomn mentions in 'Volume of the proton' above, that the position of electrons can only be expressed in probablistic terms. If the electron can als be seen as revolving around the nucleus then I can only rhyme all this together by seeing the electron as occupying the same space (on average) as the nucleus, just covering a wider area. So the amplitude of the wave would have to be (much) bigger. If I'm talking gibberish feel free point that out to me :) . DirkvdM 14:00, 23 September 2005 (UTC)

When one starts discussing particles as small as this, the distinction between particle and wave mechanics gets blurred, since both properties can be present when quantum effects present themselves. Discussing it in probablistic terms is one way of expressing it, but there is a mode of thought that a paricle really occupies a 'quantum area' of space and exists everywhere in that space simultaneously, whereas probablistic theory suggests it has a chance of being at an point based upon a formula.

It is a bit "old-fashioned", yes, but it is not too far from the truth. "Electrons evolve around a positively-charged nucleus, to which the are attracted by Coulombic (electrostatic) forces" is a correct statement: they just don't obey Kepler's laws... Physchim62 14:32, 23 September 2005 (UTC)

It is old-fashioned (which doesn't stop almost every physics student from doing the calculation at some point), but the principle still applies. When treating the proton and electron as a two-body problem, you can reduce it to a one-body problem with a reduced mass orbiting about the center of mass. Since the electron is so much smaller than the proton, the reduced mass is basically the electron mass, and the center of mass is basically the proton position, so you're basically solving a problem with a stationary proton.

When you actually treat the situation quantum mechanically, it turns out that you can make the same transforms (it's the same potential afterall), and you end up solving a quantum mechanical problem of a reduced mass in a symmetric potential about the center of mass. So although the result is different, you can make some of the same conclusions: that the proton is relatively unaffected and that the solutions for the wavefunction of the reduced mass will basically be the wavefunction (orbitals) of the electron. There's more information at hydrogen atom and hydrogen-like atom. — Laura Scudder | Talk 14:32, 23 September 2005 (UTC)

Wintergreen LifeSavers

Why do wintergreen lifesavers "spark" when chewed? ---12.37.12.134 --12.37.12.134 02:29, 23 September 2005 (UTC)

It appears to be a form of triboluminescence. This seems a useful explanation.-gadfium 03:40, 23 September 2005 (UTC)

The American roulette?

If two persons both eat the same amount of beef each and every day from the same large pool of cattles, which person is more likely to get mad cow disease in the long run?

1. Mr. A: Eat hamburgers made from grinding and mixing many many many cattles' meat.
2. Mr. B: Buy a frozen cattle carcass each time and eat the dead body from head to tail.

I guess Mr. A's risk is much higher than Mr. B's. But could it be possible that by mixing a few thousand dead cattle's meat at a time, the concentration of bad prion would become too low to be threatening? -- Toytoy 03:38, 23 September 2005 (UTC)

In the UK, it's thought those who got vCJD generally got it through hamburgers and the like. Bad slaughtering practices are much more problematic when you don't do it yourself and then mince the remains to cover any mistakes... Shimgray 11:56, 23 September 2005 (UTC)

I would agree that it's Mr. A because the smallest piece of meat you can realistically grind is still probably large enough to contain millions of prions. Superm401 | Talk 13:41, 23 September 2005 (UTC)

OK, I know you can't use meat puree to make a good hamburger. A piece of hamburger, in theory, may only have hundreds of cattles' meat in it. Then how about sausages such as hot dogs? These products are manufactured in very big factorie (lots of cattles), the meat is pulverized and then thoroughly mixed. Does it make franks more dangerous than hamburgers? -- Toytoy 14:05, 23 September 2005 (UTC)

More cows means more dilution, so the amount of germs you ingest may be below some threshold. I've heard that in order to get malaria you have to get bitten by an infected mosquito several times (don't know how many and over what period of time). Mad cow disease might be completely different though. Just a consideration. DirkvdM 14:20, 23 September 2005 (UTC)

Look again at what I said above. A grinder(not blender) probably outputs shreds of meat that are maybe about, say, half a gram. I don't know how many prions could fit in that, but I'm pretty sure it's 100s of 1000s. I think that's enough to infect you. Then again, I could be wrong. But there's my argument. Superm401 | Talk 20:48, 23 September 2005 (UTC)

Difficult to say, because we don't know the level of infectiousness of the prion involved, but my feeling would be that route A is more hazardous (for the reasons discussed above). Physchim62 14:37, 23 September 2005 (UTC)

1. 1 is eating many many cattle over a long period of time. #2 is eating one cattle over a long period of time. Assuming every cow you eat has an equal chance of having bad prions in it (big, artificial assumption), it would seem that #1 would be more statistically more hazardous. --Fastfission 22:51, 23 September 2005 (UTC)

I guess it is still unknow how much prion would cause one to be infected. If we hire many vegetarians and feed them infected meat and wait a decade, we may learn what are the minimum prion concentrations to infect 10%, 20%, ... 50%, ... 90% and 100% of people after consumption of a portion of beef. But we simply cannot try this on people ... at least to vegitarians.

Had anyone tried this on animals? -- Toytoy 00:40, 24 September 2005 (UTC)

To bring a bit of perspective to the whole "mad cow" panic, it's worth remembering that in the 20-or-so years since BSE became apparent, fewer than 160 humans have died in the entire world from nvCJD. Eating lots of hamburgers is vastly more likely to kill you from heart disease than CJD. -- Arwel 13:24, 24 September 2005 (UTC)

Very possibly, many cases were not diagnosed, some of them are still hidden, but the actual numbers may still be a very low number in comparison of other kinds of deadly food poisoning or long term health hazards (tran fat, salt, cholesterol ... problems).

I guess it is because this disease has a very low rate of transmission among animals and humans. A cow eating dead cows has a very low chance to get the disease. A man eating infected cows also does not ge it most of the times. However the rate is not that low to make this disease a non-issue.

I also wonder if dilution plays a part in lowering the rate of infection. Are hamburgers more dangerous than steaks? Are hot dogs even more dangerous? Shall we restrict or increase the size of the batc during meat processing if mad cow is the only concern?

If a tiny itsy bitsy piece of meat is infectious, then an infected cow broken apart into a million pieces may infect hundres if not thousands people. If that itsy bitsy piece of meat is not infectious, then possibly no one gets mad cow because of it. -- Toytoy 14:54, 24 September 2005 (UTC)

Read the article on prions. Even one madcow prion can infect a human. Since this prion predominantly affects the central nervous system, the risk of the two persons would depend on how the animal(s) is/are slaughtered. If care is taken to avoid knifing the CNS's (most infectious part) of the mass-load of cows, but not the one .... Besides, cooking the meat to the point of denaturing the prion would nullify the risk. Mad cow has been around forever under the name "Creutzfeldt-Jakob disease" and you probably have as good a chance of catching it from one of those few people as you do from the cow meat.

Oil

For some reason, my face is always oily, why does this happen and is there a way of preventing it from happening?

Thanks, Tasha

The simple answer is that skin oils help protect your body against attack by microorganisms. Excess production can be due to many factors that vary greatly from person to person, including, but not limited to, diet, exercise, climate, medical conditions, and ethnicity. I think it would be a good idea to talk about this with your family doctor, who is more knowledgeable about your circumstances than we are.--inks 06:56, 23 September 2005 (UTC)

What is evolution?

See evolution. - Fredrik | talk 04:59, 23 September 2005 (UTC)

Bermuda Triangle

What is Bermuda Triangle?

• See Bermuda Triangle. -- Jmabel | Talk 05:36, 23 September 2005 (UTC)

branded product marketing

(no question asked)

Did you have a question? — Nowhither 00:24, 24 September 2005 (UTC)

Start with category:brands. -- Ancheta Wis 23:07, 1 October 2005 (UTC)

Quarks

Are there important differences between atomic nuclei and quark matter such as quark-gluon plasma? How can it be experimentally determined that a nucleus is composed of distinct nucleons? ‣ᓛᖁ♀ᑐ 05:33, 23 September 2005 (UTC)

• For the second question, the idea has been round since Prout's hypothesis in the early nineteenth century. The integral nature of atomic number was demonstrated by Henry Moseley, who discovered what is now known as Moseley's law. The last major paradox was resolved by the work of Francis William Aston, who demonstrated the existence and integral mass of isotopes. Physchim62 19:46, 24 September 2005 (UTC)

australian native animals

where is the emu found in australia?

Throughout most of it. See [3]--inks 06:46, 23 September 2005 (UTC)

Or you could try our article on emus, which has a picture representing their range. --Robert Merkel

Although generally not in metropolitan areas, I've never seen an emu near the city, so generally rural areas on the map at emu. --Commander Keane 10:50, 23 September 2005 (UTC)

Why does wind gust?

I know that wind is caused by air movements from areas of different pressure - and the closer these areas of different pressure are to each other the stronger the wind it. I also think I know that its the rotation of the earth that stops it all evening out into one average pressure area. I don't understand though why the windspeeds are not constant but they gust - sometimes much more than others? Thryduulf 08:10, 23 September 2005 (UTC)

Because pressures are not a constant, even in a given location at a particular time of year. Chaotic variations in temperature and water vapor concentrations mean pressures are always changing as well. This in turn results in varying windspeeds. Superm401 | Talk 13:35, 23 September 2005 (UTC)

Does it cause cancer?

My friend asked me an uncertain question concerning blood clotting (coagulation), so I got Wiki to help him solve his question, here it is: Does it cause cancer (anything cancer, like blood cancer etc) if sb had serious blood clotting?

• Excessive blood clotting is certainly a problem, but as far as I know it doesn't cause cancer. Cancers are malignant cells with excessive growth and even they need an uninterrupted blood flow to deliver nutrients to their cells. So I would say serious coagulation is just as bad for cancers as it is for normal tissue. See Cancer and Leukemia and for more info. - 131.211.210.12 11:13, 23 September 2005 (UTC)
  • Even if excessive blood clotting -did- lead to cancer, you would not live long enough for it to grow to any significant size. You would almost certainly die of a heart attack or stroke not long after blood clots started forming in your circulatory system.--inks 12:05, 23 September 2005 (UTC)

Usually the causal relationship runs the other way—a cancer that affects the blood-forming tissue of the body (the bone marrow) leads to over- or under-proliferation of megakaryocytes–cells that turn into platelets and cause clotting–leading to clotting disorders.

Large tumours secrete chemical signals that drive angiogenesis:the formation of new blood vessels. (Without a blood supply, cells at the center of a large tumour don't receive sufficient nutrients and oxygen, and the tumour stops growing.) These new blood vessels tend to be irregularly formed and tortuous in shape; the blood flow in them is turbulent and disordered. This turbulent flow tends to encourage clot formation; those clots can be dislodged and cause trouble elsewhere in the body.

Also, there is a correlation between deep vein thrombosis or pulmonary embolism (blood clots in the deep veins of the leg and clots in the lung, respectively) and diagnosis (recent past or future) with cancer. The mechanism for this is not well understood (as far as I know) but probably has to do with clotting stimulated by inflammation of tissue around the tumour site.

So to answer your question—no, clots probably don't cause cancer. Cancer, however, can cause clots. TenOfAllTrades(talk) 13:27, 23 September 2005 (UTC)

Example tutorial of TI-92PLUS

Do anybody know about the usage of TI-92PLus?I recently given a assignment which want me to write a programme by using this calculator.If possible,please give me some examples or tutorial of the programme?Is there any websites related to the programming of this calculator too?Thanks.

I suggest you start by reading the manual, if it's anything like the one for the TI-83 Plus, you'll find plenty of examples in there. --Pidgeot (t) (c) (e) 13:42, 23 September 2005 (UTC)

I agree. The TI-83 Plus manual is excellent, I made a game on it with no other reference. Bart133 (t) 23:27, 28 September 2005 (UTC)

\offtopic Well, it's got to be better than the HP-39G+ manual. I'm trying to learn how to program this and the manual actually tells you how to use about four commands, then says "The functionality of the rest of the commands is left as an exercise to the reader". splintax ^(talk) 09:40, 30 September 2005 (UTC)

Help using Internet explorer

I am using Internet explorer. All these days, I used to download pages, disconnect, and view pages later. But suddenly, for the last ten days, when I close the browser windows and open it later, I cant view pages offline. It says 'page not available offline'. What should I do? I tried by going to Internet options, but after that dont know what to do. Please help.

Your cache may be filled. Try clearing it through Internet Options, as well as verifying that its settings are correct.

Alternatively, you can use Save As to save a (temporary) copy of the page to yuor harddrive so you can view it from there after you disconnect. --Pidgeot (t) (c) (e) 17:20, 23 September 2005 (UTC)

If you install another browser (and while you're at it, why not make it a better one like Mozilla, Firefox or Opera ... ) and try it with that, then at least you'll know if the fault lies with the browser or that you should look elsewhere. This is also a much more general tip. Keep an alternative handy, such as a second ('free') internet connection. DirkvdM 06:28, 24 September 2005 (UTC)

You might also wanna check you are visiting the same pages. Some script-generated pages cannot be cached by the browser.--Fangz 12:58, 26 September 2005 (UTC)

I think the questioner is using the "offline pages" functionality in IE to save a cache of pages so that they can go back and look at them later on, without connecting (presumably they're using a dial-up connection). Try clicking "Favourites", and "Add to favourites" on the website you want to cache, and then select "make available offline" and click Customize. Follow the instructions and you should get the problem sorted out. :-) splintax ^(talk) 04:13, 3 October 2005 (UTC)

what exactly is a buckeye

Have you checked buckeye? In the context of Ohio State, it refers to the first entry in the disambiguation. — Lomn | Talk / RfC 17:54, 23 September 2005 (UTC)

Thunder/lightening

I have read both the articles related to this subject but I'm still not sure about one thing. Can thunder occur without the presence of lightning, and visa versa. Thanks, DEE

Lightning causes thunder, so as a general rule, no and no. However, many things other than lightning can cause sounds similar to thunder (explosions, sonic booms, and so forth) and it's not always possible to observe both lightning and thunder at once. — Lomn | Talk / RfC 18:24, 23 September 2005 (UTC)

Ehm, when you observe thunder and lightning at once you might not be able to tell the tale :) . But more seriously, there are different sorts of lightning, such as Ball Lightning, which makes a crackling sound if any at all. Strangely, the lightning article doesn't mention St. Elmo's Fire (which I'll amend next), which, I imagine, won't make any sound either. By the way, my grandmother once saw a lightning ball come in through a window, hover for a bit, and go out again. Only after her death did people learn that such things really exist. The poor woman was branded a liar. No-one ever believed her. DirkvdM 06:53, 24 September 2005 (UTC)

Someone did a lecture about ball lightning in a class I had the other day, but they were fairly vague and seemed to write it off as almost pseudoscience. I'm off to check out that article - thanks for the reminder. :) splintax ^(talk) 09:48, 30 September 2005 (UTC)

Austim and Music Therapy

I am looking for any information on the treatment of autistic children through music therapy. Anything about it's effectiveness, methods, etc, would be incredibly helpful. I would also like to find any information disagreeing with this method. Thank you so much.

anon

• I don't know the answer to your question, but hopefully you can find something by reading our article on autism and the list of autism-related topics. I believe there are several Wikipedians with a special personal interest in autism, so that area has received some attention. Bovlb 19:39, 23 September 2005 (UTC)

Genetic Engineered Food

Seems to me the risks far outweigh the benefits, yet USA Agribusiness is gung ho headed that way. Am I missing something, or is there a failure of government oversight of a business area that does not give good enough lip service to quality of safety?

Risks:

• Many nations want grain, and animal products from grairi, where there was no genetic engineering. The USA is no longer able to serve those markets, because of massive contamination, and inability to police the contamination. For example, a farmer who tries to make the pure product, cannot, because contamination is freely in the winds that other farms "breathe." Thus, as genetically engineered byproducts filter down the food chain, the USA locks itself out of more global markets.
• Today in much of South and Central America, and southern states of USA, there is a real serious problem with Killer Bees. This is a man made problem, that came about thanks to experiments in breeding a better honey producer, but the experiment had very negative consequences.
• Once upon a time, there was Mad Sheep disease (Scrapie) caused by short cuts in managing food supply in agriculture, which spread to cattle, so then there was Mad Cow disease, then there were experiments to try to understand this using Deer in captivity, deliberately given the disease so that we had Mad Deer, but due to the experimenters not understanding how the disease could spread, the Mad Deer in captivity licked fences, which were also licked by Wild Deer at edges of the enclosures, so now Mad Deer was in the wild, and eventually spread to all of North America, which gave the disease back to animals in agriculture, such as pigs, and to the animals that eat Deer, such as mountain lions. So we are on a collision course with a worse disaster, fueled by efforts to do cost savings in agriculture, with government oversight that is driven by rear view mirror to past disasters, rather than oversight of theories about future risks.

Benefits:

• When there is a wide range of quality of animals producing eggs milk meat, whatever, this is a breeding technique to make copies of those that are the best.
• Genetic engineering, cloning, and Transgenetics is a real cool thing to do. Any company that announces successes will get oodles of money from venture capitalists who think there's lots more profits down the road from this.
• Ok, we know there are major disasters down the road, but we can still make oodles of profits capitalizing on the industry that is exploring this high risk area, then hopefully get out of the business, before the disasters put them out of business.

AlMac|^(talk) 22:40, 23 September 2005 (UTC)

AlMac: The question of whether using genetically modified organisms to produce food is a Good Thing is one I will leave to you and others to decide. However, you missed some of the most important entries in the "benefits" list. Most of these, in the end, deal with cost. Using GMOs we can produce food more cheaply. We do this by creating GMOs that, compared to their natural counterparts:

• Produce more food.
• Have greater disease resistance.
• Mature faster.
• Can grow in more adverse climates.

By making food more cheaply, food producers get to spend less money. Someone might say, "Yes, because they are greedy." Well, I'm greedy too. I want a lower food bill. Don't you?

It should be noted that cost reductions also have applications in combating hunger in developing nations. As does creating a GMO that produces more nutritious food than its natural counterpart.

Lastly, I'd note that at least one of your "Risks" arguments isn't quite right. "Killer bees" were not created through modern genetic engineering, but through old-fashioned interbreeding. This phenomenon has been going on for thousands of years and, in general, has been quite safe and successful. A single isolated example is not a good argument against it. And it is certainly not an argument against modern genetic engineering, since it was not used in this case.

Again, I am not arguing a position here. I just saw that your list of "risks" and "benefits" seemed awfully lop-sided. You asked whether there has been a failure of government oversight. I'd say that is quite possible.

— Nowhither 00:44, 24 September 2005 (UTC)

And mad sheep, cow and deer diseases have nothing to do with genetic engineering (or am I now missing something?). Which leaves only the first risk from AlMac's list. Which is scary enough by itself. But I've heard of another one. Genetic engineering can also be used to make crops more resistant to pesticides, which means farmers may (and will) start using them more liberally, which has to have negative side-effects.

But more in general, genetic engineering is rather like a boosted form of old-fashioned interbreeding, which in turn is a boosted form of natural selection. In both cases things are left less to chance, which means developments go faster. And with interbreeding we've created a situation in which diseases can spread much faster. Whole fields of plants that are all the same means that if a disease is introduced it will spread very fast. Add to that that the plants are selected on specific traits and not others, thus possibly leaving out natural defence mechanisms we don't understand yet (and there's a whole lot we don't understand when it comes to the mechanisms in nature). The lack of biodiversity also means that if a disease spreads it will wipe out all plants. That's the result of the first boost. This second boost has a potential to go farther still, which is scary.

To come back to the original question. If all this is left entirely to private companies the risk is way too high that they won't care about the long-term effects. I'm ultimately in favour of using genetic engineering (if only for scientific research), but it has to be done with extreme care, not rushing things. And private companies are by their very nature not made of the right stuff to do this. This has to be done by governments. So yes, there's a failure of government oversight. Moreover, the governments of not just the US but in the whole world should not just restrict themselves to oversight, but completely take over the industry. We're meddling with something we don't sufficiently understand. DirkvdM 07:27, 24 September 2005 (UTC)

I see something missing from your list of benefits. It's not just more food, but we can get better food. A great example is golden rice, which is as easy to grow as normal varieties, but has more vitamin A. It was designed specifically to help areas with vitamin A shortages (like most of Africa Image:Vitamin A deficiency.PNG). I think someone who wasn't used to a full belly might disagree on whether the risks really outweighed the benefits. — Laura Scudder | Talk 08:05, 24 September 2005 (UTC)

why is the sky blue

See Diffuse sky radiation. — Nowhither 00:47, 24 September 2005 (UTC)

The short answer is one quoted from a radio commercial I've been hearing lately: "All colors have wavelenghts that are diffused by oxygen and nitrogen. Since blue has the shortest wavelength, it's diffused up to ten times more, so the human eye sees more of it than any other color." I hope I haven't broken any rules by quoting that! Btw, what the heck did that article say? I couldn't make heads or tails of it. Hermione1980 01:01, 24 September 2005 (UTC)

No you didn't break any rules. See Fair use. What that means is this: oxygen and nitrogen are the two most common substances in air. "Diffused" in this case means "scattered". Light is a form of (very rapid) vibration, waves in other words; the wavelength of light is the distance it travels in a single vibration/wave. Different wavelengths of light are seen as different colors. Red is longest (in the visible range), then orange, yellow, green, with blue/violet being the shortest. Shorter wavelengths are scattered more. That means that red and yellow light tend to pass straight through the air, while blue light tends to bounce around a little. Almost all the light in the daytime sky comes from the sun. But blue, since it bounces around, may look like it is not coming straight from the sun, but rather from many directions. Thus, the sky, away from the sun, appears blue. — Nowhither 01:17, 24 September 2005 (UTC)

See also Rayleigh scattering. TenOfAllTrades(talk) 01:26, 24 September 2005 (UTC)

-1=1

A "proof" for the idea that -1=1 was posted on your page about the imaginary number i. I have replicated it in this question for quicker reference:

-1=i*i=sqrt(-1)*sqrt(-1)=sqrt(-1*-1)=sqrt(1)=1

However, your page says that this is incorrect because square roots only work for real, positive numbers. Your page on the number -1 says that -1^2/2=-1 and sqrt(-1^2)=1 therefore 1 cannot equal -1. However, a friend of mine says that this is incorrect because sqrt(-1^2)=sqrt(-1) though -1^2=1; I have written to you in order to resolve this dispute.

Thank you for your time and patience.

I'm not sure exactly what you're intending to say here because of the way you've written the math symbols. Can you go back and put gratuitous parentheses to make clear exactly what you mean(particularly at "-1^2/2=-1"). However, I can tell you you're friends wrong in saying sqrt((-1)^2)[by the way "-1^2" means "-(1^2)" so you should have said "(-1)^2" but I knew what you meant]. sqrt((-1)^2)=sqrt(1)=1, because the inside is simplified first by order of operations. Superm401 | Talk 01:16, 24 September 2005 (UTC)

This problem can be explained in several ways. My favorite explanation is that there is no "nice" function called "sqrt" on the complex numbers. Numbers have two square roots. But a function has to have a single value. When we deal with square roots of positive real numbers, we fix this by letting "sqrt" of a positive real number be the positive square root, not the negative one. But there is no nice way to fix this problem for complex numbers in general. This is probably what was meant by the statement that "square roots only work for real, positive numbers". In particular, the problem with the "proof" above is in the third equality:

sqrt(-1)*sqrt(-1)=sqrt(-1*-1).

There is simply no way to define "sqrt" as any sort of square root function that makes this true.

As for your dispute, your friend is wrong. The statement

sqrt((-1)²) = sqrt(-1)

is false for all ways of defining "sqrt" as a square root function, since this says that sqrt(1) = sqrt(-1), while those two numbers (1 and -1) have no common square root.

The lesson to be learned from all this is that we don't get to apply supposed mathematical "rules" anywhere we want, but only where they do, in fact, apply. And rules that apply in certain special cases may not apply in general. In particular,

sqrt(a) × sqrt(b) = sqrt(a × b)

works fine when a and b are nonnegative real numbers. That's what we were all taught in school, and it is correct. However, this does not mean that this applies more generally to all pairs of complex numbers. In fact, it does not.

— Nowhither 01:10, 24 September 2005 (UTC)

None of the explainations here make sense to me. The part about the square root of a real number being defined as the positive root is true. The part about no nice way to fix this for complex numbers is not true. Square roots of negative numbers are defined as mapping to the set of imaginary numbers, thus 'i' is an imaginary number equal to square root of -1. Also, i*i is defined as equal to -1 because of this.

i is indeed a square root of -1, but so is -i, and (-i)*(-i) is also -1. You can't say that i is "equal to the square root of -1", because "the square root of -1" describes two numbers that are unequal. So how do you tell them apart? You can't say "take the positive one as the square root" like you do for real numbers, because neither i nor -i is positive. (Don't let the notation deceive you; remember that i and -i are perpendicular to being positive or negative.) RSpeer 05:17, 25 September 2005 (UTC)

• Look at it this way. In school we were taught that the rule "sqrt(a) × sqrt(b) = sqrt(a × b)" is correct for all positive real numbers. Maybe you missed the "positive real numbers" part, but, I can assure you, it was (or should have been) mentioned. Now, does this rule apply to complex numbers in general? No, as the original problem in this thread shows. It may seem intuitively true to you that this rule applies to anything with a square root. However, in mathematics, we do not base our notions of truth on intuition; we prove them to be true. Many properties of the complex numbers seem non-intuitive to people familiar only with the real numbers. This is perhaps one of them.

  And, regardless of whether it seems right, it is true that there is no nice way to define a square root function on all complex numbers. If you want to be formal, then substitute "continuous" for "nice".

  — Nowhither 17:47, 26 September 2005 (UTC)

5ht receptors

(no question asked)

Did you have a question? — Nowhither 01:11, 24 September 2005 (UTC)

Please review our article on Serotonin, and ask again if you need more detail.-gadfium 03:04, 24 September 2005 (UTC)

Codec hell

Well, I just got my computer and was trying to open a few video files, so I downloaded some codec packs. The first was ACE mega codec pack. It was great, opened tons of stuff, except this one divx video with some interleaving problem... Well, I removed ACE, and got a few other codec packs from free-codecs.com (k-like, xp and all in 1).

Installed all in 1 first. Didn't work. Uinstalled it. Installed XP. Didn't work. Uninstalled. Insalled k-like. It worked. But now WMP won't open the most basic video files (wmvs), and the automatic download of codecs feature returns an error (no appropriate codec could be found).

So, this sucks. Not even half of my videos are opening right now and I was wondering what I should do. Is there any tool that lets me remove ALL codecs from my computer, so I can get them all again? Is there any immediate problem on not having any codecs installed? Help! Kieff | Talk 01:30, 24 September 2005 (UTC)

Can't help with codec removal, but if you just want to play the videos, VLC player opens just about anything, and you don't have to mess with codecs.[4]--inks 20:24, 24 September 2005 (UTC)

You may be able to uninstall and reinstall Windows Media Player, or upgrade to a newer version, which will fix the codec problems. Rob Church ^{Talk | Desk} 21:14, 25 September 2005 (UTC)

Whilst I'm happy to recommend VLC player myself having used it these past couple of days, it doesn't seem to open the .wmv files I have.

Well, I managed to uninstall WMP and reinstall it. Things seem to be working now, thanks everyone. I'll avoid codec packs after this incident. Kieff | Talk 19:33, 26 September 2005 (UTC)

APPLICATIONS OF GRAPH THEORY TO COMPUTER SCIENCE

Sir,

Can you get me any three applications of graph theory to computer science" and what way it is used and details about that. Thank you. --anon. Question reformatted by Robert Merkel 08:53, 24 September 2005 (UTC)

Well, actually, I can, but I've done enough homework for one lifetime. Have you considered reading our article on graph theory, or perhaps your textbook? By the way, DON'T USE ALL CAPITALS BECAUSE IT'S INTERPRETED AS YELLING!--Robert Merkel 08:53, 24 September 2005 (UTC)

How temperature affect the atmosphere pressure?

Can you tell me how temperature affect the atmosphere pressure at an area?Is there any equation uses to calculate the atmosphere pressure of a place which related to the change in temperature?

• Yes there is. Try Combined gas law (and the related laws mentioned in the article. Atmospheric pressure may also be of interest to you. - Mgm|^(talk) 11:59, 24 September 2005 (UTC)

Alternative to the Big Bang theory

I've long had an alternative to the Big Bang theory, which surfaced when I gave an answer to Wikipedia:Reference_desk/Science#A_Variable_Speed_of_Light hereabove. I'm very much a layman when it comes to this field, but I made a prediction that went against the accepted theories but turned out to be correct, which is a bit of a theoretician's wet dream :) . So I now venture to put this theory before you. Here goes.

As a kid I heard the expanding universe explained as a balloon with dots on it. On that everything moves away from everything else, which is exactly what we observe in the universe. But then I wondered, how do you know a balloon expands? My thought was that you know that because the only alternative is that the room you're in (and everything else) is getting smaller. Which would be silly. The simplest solution is held to be true, which is that the balloon expands. But for the universe there are (by definition) no surroundings to compare with. There is no reference frame, so one has to assume the size of of the universe is given. I couldn't think of a solution then.

But later I realised that you can also compare the sizes of the universe and everything in it. If the size of the universe is given then the stars and such must be getting smaller. Hmmm, stuck again.

Later still I imagined falling into a black hole. I was supposed to get stretched out. But that's seen from the framework of an outside observer. For me, I'm part of the spatial framework that gets expanded. Also, time gets ever slower form the perspective of the outside obeserver, but, again, I live in that timeframe, so from my perspective it will take me forever to fall into the black hole. So for me nothing changes (right?). Except that I see everything around me moving away from me. Hold on, I thought, couldn't that explain the aforementioned phenomenon? What if we are caught in a collapsing (part of the) universe? But then I realised that as things are further away they will accelerate away ever faster. And acceleration is not what happened, right? Stuck again.

Until a few years ago someone (Riess or Perlmutter?) discovered that exactly that is the case. When I heard of this I jumped out of my chair. After the initial enthusiasm I didn't know how to present this idea. No-one would take me seriously. Now, finally, I've found a place where knowledgeable people might be bothered to hear me out. So. Any thoughts on this?

By the way, I don't necessarily suggest we're falling into a black hole. I suppose being attracted to anything sizeable enough will have a similar effect. And since everything is attracted to everything else there might not have to be anything special going on. Though if it's that simple I find it unlikely no-one will have thought of this before. Or have they?

Also, as for the other two bases for the Big Bang theory, I don't have an explanation for the background radiation. The abundance of light elements suggests a fairly 'young' universe, which would still be possible if we're in the middle of the Big Crunch. DirkvdM 09:26, 24 September 2005 (UTC)

Hi DirkvdM. I know a reasonable amount of physics and will try to give a few comments. If we were in a collapsing part of the universe, then nearby galaxies would be moving toward us. This is only true of the Andromeda galaxy, and that is accounted for by the attraction of ordinary gravity. Everything else is moving away.

If we were falling into a region of extremely strong gravity, black hole or otherwise, that would be more clear from nearby conditions than from faraway objects.

It is also important to understand what is involved in the expansion of the universe. It is the actual expansion of the "fabric of space", rather than simply objects moving away through ordinary static flat space.

Let me know if that helps at all; I'm happy to discuss further here or on User_talk:SCZenz. -- SCZenz 22:07, 29 September 2005 (UTC)

Yes, everything moves together when moving towards a common attractor (such as a black hole or 'everything itself' so to say - the Big Crunch idea). But that is from the perspective of an outside observer who doesn't take the distortion of the space/time fabric into account. But for those inside, space is stretched out more than that (the 'more' here is an assumption that is essential to my theory). Put differently, if I'm falling into the black hole (or whatever) I accelerate towards it. Anything that's ahead of me will have gained a higher acceleration and thus move away from me from my point of view (but is that accelerated? My gut says it is :) ). Likewise, anything that's behind me will do so too, but at a lower acceleration. Sideways this is a bit more complicated, but I believe a similar reasoning applies.

You say that the effects of falling into a black hole are more noticeable nearby than for things far away. But I assumed that the distortion of space/time counterbalances the acceleration. Or rather, there is no acceleration, just the distortion. An outside observer who superimposes his local frame on my situation observes an acceleration I don't perceive.

More in general, distortion is a misconception, because that assumes an absolute reference frame, which there isn't. What I perceive as distortion is really just the difference between my local distortion and the distortion of another place I observe. So to call the time/space there distorted is really a 'lococentric' (?) pov. DirkvdM 11:55, 30 September 2005 (UTC)

I am not an expert on this stuff either. My understanding is that there are several theories on the nature of the universe. One is that it starts with the Big Bang then after expanding to some size, it slows down the expansion, because of the gravity of the parts of the universe pulling at each other, and eventually begins to collapse again. So there's a bunch of theories whether it will expand forever, if it will collapse, or if only our part of the universe is expanding. Some of this has to do with hidden mass and studies of some patterns of energy.

Have you heard of quasars (spelling?)? These are humongous point sources of energy. One theory is that we are seeing the light from the original Big Bang which bounces off the edges of the universe, less and less frequently as the edges get further away, and by studying the pattern of quazars we can map the shape of the universe.

I would prefer to think that what quazars are, are the light from intelligent travelers traveling close to the speed of light, away from us (they are red shift quazars, which is all that can be seen by observers through our atmosphere. If there was blue shift astronomical bodies, we would not see them by astronomy on the planet. If we study the heavens from telescopes in orbit, then we might see a bunch of blue shift stuff, such as an intelligent visitor headed our way. However, I not think we looking for this. Telescopes in space are looking for stuff to expand the knowledge of terresterial astronomers who are already distorted view of looking through the rose colored glasses of our atmosphere, as opposed to starting over in study of our univers. AlMac|^(talk) 18:12, 29 September 2005 (UTC)

Why would the drive system of an alienship put out so much energy as to equal the light of a star? And why aren't any of them heading sideways, rather than directly away? -- SCZenz 22:07, 29 September 2005 (UTC)

When the alien ship is traveling close to the speed of light, its mass is close to infinite. This applies to the mass of all of it, including the ejecta of its propulsion system. They could be traveling in all directions. One flaw in my theorizing is the question of how long they would be blasting in some direction, relative to how long we see the red shift quazars through telescopes under our atmostphere. AlMac|^(talk) 01:08, 30 September 2005 (UTC)

armed forces transport

can you please tell me where i could find information on the modes of transport the armed forces use?

Are you interested in a specific country's armed forces, or armed forces in general?

If you're interested in a specific country, you might consider going to that country's page and using the military links from there; for instance, for the United States you'll probably browse from there to the Department of Defense page and then the pages for the individual services. From each of those, you might get a list of vehicles, for instance the United States Air Force link has a link to a page called List of military aircraft of the United States.

If you're interested in this topic in general, the United States is still probably a good area to explore, as the US military has logistics capabilities unrivalled by any other military force. --Robert Merkel 10:29, 24 September 2005 (UTC)

gravitation ????

Hello:

Why is it that only one side of the moon always faces earth? If you take an apple and rotate it around a lamp you'll find of you keep the axis facing the same direction all parts of the orange will be reflected as it revolves around the lamp. But the moon has to slowly rotate in such a way that it keeps its one side visible to the earth and as far I can tell it has been showing the same side of the moon for thousands of years? This can't possibly be a coincedence, but I don't see how Newtonian laws of gravity apply to this question.

Will Sperry Kunming China

Will: It's because of tidal forces and friction.

To begin with, do you understand why the ocean has tides? The Moon pulls a bit more on the water close to it, than it does on the Earth as a whole. So there is a bulge of water on the side of the Earth nearest the Moon. Similarly, the Moon pulls harder on the Earth as a whole than on the water far from it. So the Earth gets pulled away from the farthest ocean, resulting in another bulge of water on the side of the Earth opposite the Moon. And that is why we get high tides during the full & new Moon (or nearly so; the land gets in the way of water flow, which makes it all a good deal more complex).

Now, the Earth pulls the same way on the Moon, "trying" to create a bulge on the near & far sides if the Moon. This has two effects. First, if the Moon didn't always show the same face to the Earth, then as it rotated, it would get squashed in various directions. The resulting friction would turn part of its rotational energy into heat, thus slowing its rotation (relative to the Earth). Second, if the Moon is not a perfect sphere, it would have a tendency to settle in a position in which the bulge(s) faced either toward or away from the Earth.

And that is what happened. The Moon is not a perfect sphere, tidal friction slowed it's rotation, and it settled in a position in which the bulges are aligned toward/away from the Earth.

Of course, similar logic would suggest that the Earth should always present the same face toward the Moon. Why doesn't it? First, the Earth is bigger, so it has more angular momentum to keep it going. Second, the Moon is smaller, so there is less tidal force to slow the Earth down. But if we wait long enough, and no other factors intervene, and the Moon stays in its current orbit, etc. (which won't happen), then the Earth should eventually present the same face to the Moon all the time.

— Nowhither 11:21, 24 September 2005 (UTC)

Why would there be a specific bulge? (Maybe)Once upon time, millions of years ago, was the moon rotating around an axis and the earth's gravity finally slowed it down, to its current rotation? And why would friction effect the moon when it is in space where there is no friction? The tide analogy seems obvious because of the fluidity of water, but the solidity of the moon would seem to make a bulge less of a factor as the tides are effected by the moon. Over millions of years do these factors create slight changes that finally effect a final result?

Will Sperry Kunming China

Will, there is indeed friction in space; the laws of physics aren't somehow different in orbit around the earth. You're correct in that there's no air resistance (space being close enough to a vacuum for all practical purposes) but there is still internal friction within the moon. You can demonstrate friction inside solid objects be bending a paper clip back and forth until it breaks, and noting that the metal near the breaking point becomes warm. Similarly, friction within the moon's core can lower its kinetic energy. But yes, it seems plausible that the moon was at one point rotating at a different speed. --David Wahler (talk) 16:09, 24 September 2005 (UTC)

I thought this was a freak thing, caused by an uneven distribution of the matter inside the moon or a violent thing happening to the moon in its past, such as it tearing away from the Earth. The moon article states that the most accepted theory is that just that happened, caused by an impact by some third big object. However, the same section supports the above theory. But then this should also have happened to other moons. Is that the case? DirkvdM 19:04, 24 September 2005 (UTC)

DirkvdM: Yes, most of the known moons in the solar system are tidally locked. See Tidal locking. — Nowhither 19:57, 25 September 2005 (UTC)

It's called Tidal lock. The theory is, eventually every orbiting body becomes tidal locked to its parent body over time. Even the Earth to the Sun. - Cobra Ky (talk, contribs) 19:08, 24 September 2005 (UTC)

Drawing electrical circuits

Are there any freeware or shareware programs available for preparing diagrams of electrical circuits? I can't find any reference to them in the relevant articles. Physchim62 11:02, 24 September 2005 (UTC)

A search for "circuit" at Freshmeat.net turns up a number of packages. I haven't tried any of them myself (though I'm probably about to as an amateur PIC programmer). --Robert Merkel 12:19, 24 September 2005 (UTC)

Check this out at Wikisophia. Lots of other goodies there too which you might find useful. --HappyCamper 13:09, 24 September 2005 (UTC)

EAGLE is one I've used, which has the notable feature of being able to automatically lay out circuit boards for fabrication. (Not sure if that's something you need, but you might want to give it a look.) --David Wahler (talk) 15:57, 24 September 2005 (UTC)

There is a very good freeware called TKGate for Digital Cicuits Simulation and a very good GUI. In order to run tkgate on Windows, you will need to install Cygwin along with X11 and the X11 version of tcl/tk (as opposed to the native Windows version). For details see the Cygwin Cygwin Installation Page. As of TkGate 1.8.3, the configuration script now contains Cygwin specific code and should not require any modification.

However, for Analog Circuits, you can use Spice

Pause Break

On my QWERTY keyboard, what does the button "Pause/Break" do? --Dangherous 11:10, 24 September 2005 (UTC)

There is a brief explanation on IBM PC keyboard. These days, it's not used very much (except by gamers). --Robert Merkel 12:16, 24 September 2005 (UTC)

optical computing

What is optical computing? How does it work? What are its applications(please mention any brands or products already in use)?

Did you try reading our optical computer article? --Robert Merkel 12:09, 24 September 2005 (UTC)

md5 status?

What's the current status of the md5 hashing algorithm? There are numerous attacks noted against it, but would it be possible to easily explain what is possible and what not? And will sha-1 have the same problems soon? Thanks

Assuming you've read Md5#Practical_effect_of_cryptanalysis and find it unclear, what it's saying is that it is possible and fairly easy to construct two different inputs which result in the same MD5 hash value - however the currently known methods for doing this do not generalize to finding a second input that results in the same hash value as an arbitrary given first input. MD5 is often used as a checksum to "guarantee" the validity of downloadable software files. This weakness does not mean it's easy for someone to generate an alternate version of an arbitrary downloadable with the same MD5 hash. What it does mean is that if I have full control over the downloadable file, I might be able to create two versions that have the same hash value. MD5 is also often used as a mechanism to store or transmit passwords. The MD5 article does not mention this, but modern processors are fast enough to compute the MD5 value for all possible, fairly short (8 characters or less), inputs which means if I can access the MD5 hash value for your password and you have a fairly short password, I can find out what your password is. This is one reason users are often told to use long passwords. There are some theoretical weaknesses in SHA-1, but no currently known method for "fairly easily" generating two different inputs with the same SHA-1 hash value. SHA-1 also takes long enough to compute that a brute force attack on passwords is only possible for shorter passwords. -- Rick Block (talk) 14:56, 24 September 2005 (UTC)

I agree, but I would elborate that SHA-1 has also been found to be weaker than desired, although not yet in the same "fairly easily" collidable way that MD5 has. Finding a collision for SHA-1 is believed to be within the capabilities of a massive distributed Internet search (ala Distributed.net). Because of this, cryptographers (who are a conservative bunch) suggest using a different hash function in new designs, although there's not that many obvious alternatives at present. The SHA-2 variants remain unbroken for the time being. (I would also argue that the difference in speed for computing hashes for SHA-1 and MD5 is small enough that it's not worth relying on it to give any significant advantage against dictionary attacks.) — Matt Crypto 18:58, 28 September 2005 (UTC)

How to produce endorphin

(no question)

1. Laugh.

2. Enjoy.

--Sum0 17:51, 24 September 2005 (UTC)

-2 Stick your hand in a bees' nest

-1 Whip yourself with nettles

0 run a marathon

Tonywalton  | Talk 00:48, 25 September 2005 (UTC)

Alternator wire

what is the maximun voltage drop allowed on an alternator wire on a vehicle
(added header to question - Mgm|^(talk) 14:22, 24 September 2005 (UTC))

I assume you mean "allowed by law". I imagine that would vary from country to country. You might want to indicate what country you are referring to? (In any case, I don't know the answer.) — Nowhither 20:01, 25 September 2005 (UTC)

Roentgenium's Color

If we could somehow produce enough Roentgenium to be visible to the naked eye (ignoring decay), what color would it be?

Probably silver-gray in colour. From its electron configuration, it will behave as a metal. With few exceptions, that's the colour that you get. TenOfAllTrades(talk) 17:33, 24 September 2005 (UTC)

Storage size

What is the storage size of a hard disk, Tape, CD-ROM,CD recordable and a DVD please can someone answer this one asap

Sounds like homework, but since it's so simple: with publicly available drives up to at least 2TB (although this is an external drive), up to 800GB, 650-700MB, 650-700MB, and 4.7GB (8.5 for a dual layer disc), respectively. For #3 and #4, larger variants DO exist, but they are fairly rare, and for #5, the capacity is twice as much for dual-sided discs. --Pidgeot (t) (c) (e) 17:28, 24 September 2005 (UTC)

It is related to the hardware ability to store & get at stuff in very small sizes (IBM has a quantum computer which records data at an atomic level, but this is still laboratory technology) and the addressing scheme. I think that 64-bit is pretty much the standard in what is economically available, but IBM reputedly has 128-bit in testing. AlMac|^(talk) 18:46, 24 September 2005 (UTC)

Who discovered the treatment of Malaria?

See malaria. — mendel ☎ 22:36, 24 September 2005 (UTC)

How much does 7 liters of gasoline weigh?

Could someone who remembers more of high school chemistry tell me how much 7 liters of liquid gasoline weighs? Either metric or imperial, doesn't matter. Thanks. --Brasswatchman 20:09, 24 September 2005 (UTC)

• Depends on the type of gasoline. Is it leaded or unleaded? High or low octane? Gasoline is usually a mixture of different components and the composition can differ per produced batch. I'm afraid giving a single answer is going to be quite difficult. - Mgm|^(talk) 20:19, 24 September 2005 (UTC)

• Our density article say gasoline's density is 0.73 g cm^-3. (I assume that's an average value, seems to match the value I got from a quick google). 7 litres is 7000 cm^3, so it would weigh 7000 * 0.73 = 5110 g or 5.11 kg. -- Bob Mellish 20:32, 24 September 2005 (UTC)

• I wasn't looking for anything exact, just average. Great. Thanks, both of you. Brasswatchman 9:53 PM EST, 24 September 2005.
  • Alternatively, just buy a gas can, weigh it, put 7 liters of gas in it, weigh it again, and check the difference... ;) I like to go for the easy way out. --Phroziac^(talk) 01:15, 29 September 2005 (UTC)

Stanis?aw Ulam

How is Ulam pronounced - You-lam or Uh-lam ? Tintin 20:54, 24 September 2005 (UTC)

I've always used the latter, but I can't say if that's correct or not... Shimgray 20:55, 24 September 2005 (UTC)

According to Polish language, it would be more like Oo-lam. Physchim62 21:06, 24 September 2005 (UTC)

Yes, Oo-lam. Stan-iss-wav Oo-lam. I don't know what that is in IPA. Proto t c 13:09, 26 September 2005 (UTC)

Help me begin understanding Prolog...

Since my professor doesn't seem to intend on replying to my e-mail (this is not a homework assignment, but I have to understand the basics of this silly language in less than 10 days before the first test), I'll throw this question to fellow Wikipedians, whom I hope some know Prolog.

Given this file:

line(2, 2, 4, 5).
line(1, 2, 4, 5).
line(1, 1, 4, 4).

linelen(line(X1, Y1, X2, Y2), Z) :- DX is (X2 - X1)**2, DY is (Y2 - Y1)**2, sqrt(DX + DY, Z).

I am able to do this:

?- linelen(line(1, 5, 3, 6), Z).

And get a valid result for Z. However, if I attempt pattern-matching:

?- linelen(line(A, B, C, D), Z). or ?- linelen(L, Z). It gives me ERROR: Arguments are not sufficiently instantiated. (I've also tried all sorts of other things, all of which give me this error -- this is the most basic, though, where I began trying to write this function).

Why is it not pattern-matching? I expected it to give me the lengths of each line that I declared as previous facts, but for some reason, it is not doing this. Is there something I'm not understanding right about how pattern matching works in Prolog? I think I understand it pretty fine, but it's the syntax that seems to be killing me. What would be the "correct" way to implement this function?

Also, could anyone recommend a really good book about Prolog? Our course textbook is the one written by Mr. Ivan Bratko, who I understand had a hand in standardizing Prolog, but unfortunately it's not really that good a textbook when it comes to explaining things clearly. A good example of a programming language manual that "clicks" with me is the one for Lua written by Roberto Ieruschamily(sp?) -- are there any Prolog books like that out there? --I am not good at running 00:22, 25 September 2005 (UTC)

It's been a while since I've worked with prolog, but I think your problem is that line(A, B, C, D) is returning false. Prolog only knows what you tell it, so if I for instance wrote a program:

related(marge, lisa).
related(marge, bart).
related(marge, selma).
related(snowball II, snowball III).

Then I'm simply telling it that all the above three statements are true. So if I input related(selma, bart), it'll return true while related(snowball II, lisa) will return false. Or if I input related(selma, Z), it'll return one of marge, lisa, or bart as Z.

So your first three lines are doing exactly what I did above, only nowhere in there is there A, B, C, D, so line(A, B, C, D) will always be false. What I think you want is to cut your entire program down to:

 linelen(X1, Y1, X2, Y2, Z) :- DX is (X2 - X1)**2, DY is (Y2 - Y1)**2, sqrt(DX + DY, Z).

Like I said, it's been a while, but hopefully that helps. — Laura Scudder | Talk 00:40, 25 September 2005 (UTC)

Awesome, that seems to work. I had to do this on the query line though: ?- line(A, B, C, D), linelen(A, B, C, D, Z).. I didn't know that query lines could contain comma-delimited multiple phrases (I thought only rules could) but it seems to work, in fact be required to get it working right. Thanks! --I am not good at running 01:21, 25 September 2005 (UTC)

I think the other way to do this would be to match one of the facts in your fact base before doing the arithmetic computation as part of the linelen definition, i.e. I think linelen could be:

linelen(line(X1, Y1, X2, Y2), Z) :- line(X1,Y1,X2,Y2), DX is (X2 - X1)**2, DY is (Y2 - Y1)**2, sqrt(DX + DY, Z).

The issue is the computations cannot be done on uninstantiated variables (could be if you defined your own version of the operators using facts from the factbase). The key is you have to make sure any variables you're doing arithmetic on are instantiated to actual values at some point before you try to do the arithmetic. I learned Prolog from the Clocksin and Mellish book (a long time ago). -- Rick Block (talk) 16:41, 25 September 2005 (UTC)

Hmm that approach seems to give neater-looking results when going for an entire series of defined line(etc, etc, etc, etc). facts, but it doesn't seem to be as flexible beyond that. I rewrote my linelen as per your example, but now it only seems to allow pre-defined lines, and answers "No." for arbitrary arguments. example:

?- linelen(A, Z).

A = line(2, 2, 4, 5)

Z = 3.60555 ;

A = line(1, 2, 4, 5)

Z = 4.24264 ;

A = line(1, 0, 4, 4)

Z = 5 ;

A = line(-5, 7, 1, 10)

Z = 6.7082 ;

A = line(10, 0, 39, 60)

Z = 66.6408 ;

No

?- linelen(line(2, 7, 320, -4), Z).

No

I definitely have a better understanding of how Prolog matches patterns now than I did two days ago, especially as to how it behaves when arguments are instantiated in the definition vs. being instantiated in the query lines before the actual function. Can't wait til I get around to tinkering with cuts and fails :) --I am not good at running 19:47, 25 September 2005 (UTC)

gravity

what is gravity, how does it act on mass. D Armstrong

The answer to these questions get quite complex and philosophical; see gravity for some discussion. There are two standard theories of gravity: Newton's law of universal gravitation, which for predictive purposes is almost always "close enough", and general relativity, which can provide predictive answers in those relatively few situations where Newton's laws give slightly incorrect answers. However, general relativity is incompatible with quantum mechanics, which is our model for understanding the other fundamental forces of the universe acting at a very small scale. Therefore, our understanding of the fundamental forces of the universe is incomplete; the models we have are incomplete approximations. So ultimately, we don't really know what gravity "really" is, but we have models that can predict what it will do. But what does it mean to know what gravity "is", anyway?

Aren't you glad you asked? --Robert Merkel 03:47, 25 September 2005 (UTC)

Also see Intelligent Falling :) -- Rick Block (talk) 04:27, 25 September 2005 (UTC)

how to handle demand of medical services

Find out what the United States is doing, and do the opposite...more seriously, if I'm understanding your question correctly you might be well served by starting with our (brief) article on heatlh economics health economics, health maintenance organization, managed care, and linked articles. No country is particularly effective at handling this problem; that is, unless you take the view that the ability to pay is the proper and only criterion for determining how medical treatment should be allocated. --Robert Merkel 12:10, 25 September 2005 (UTC)

military

i have to do a presentation on how to decrease cost of military?

Firstly, I'm assuming you're American. If you're not, recalibrate this advice to specifically search for items related to your country...anyway...

Do your own homework, but have you considered doing a Google search for, say, "defense budget waste" and seen what comes up? Tried a similar search on an electronic newspaper archive, if your educational institution has access to one? Oh, and just because I'm feeling super-generous, here's one big hint: missile defence... --Robert Merkel 04:03, 25 September 2005 (UTC)

Less wars. Ojw 10:41, 25 September 2005 (UTC)

That would be fewer wars or less war. Sorry :) DirkvdM 11:20, 27 September 2005 (UTC)

I suggest you read the 9/11 commission report, and similar reports from similar commissions (about 2 a year going back in history to infinity), especially about Congress doing a competent job on oversight and cut out the pork. AlMac|^(talk) 18:22, 29 September 2005 (UTC)

The percentage of GDP that goes into the military and national defense like internal security varies by nation. In the USA it was about 3% before 9/11, I suspect 4-5% now. One way to cut this down that hopefully will not happen, is to reduce it to zero, then pretty soon you no longer have a nation, because you been conquered, and now you spending 100% to the conquerors. AlMac|^(talk) 21:19, 30 September 2005 (UTC)

media

How to protect people from media?

You could lock them in a room with no televisions, radios, magazines, books, internet access, etc� Not sure why you would want to do this, though. Perhaps your question could use some clarification? Garrett Albright 10:30, 25 September 2005 (UTC)

multinational organization

How to hsndle problems created by big and large multinational organization?

• That depends entirely on the problem and the organization in question. Please be more specific. If you are unhappy with a product or service provided by a large organization, try writing a letter of complaint. - Mgm|^(talk) 07:49, 25 September 2005 (UTC)

Determinants

In my far younger days, when I was but a lad running through the meadows and marvelling at the glory of the morning dew, I briefly studied some matrix-theory. Alas, those days are long gone now, and what very little I learnt has mostly been passed into the forgotten lore-section of the library that is my memory.

Now, however, I'm going to need a little help with determinants, don't ask me why :P Our article Determinants is not totally clear on this issue (ie. it's probably perfectly clear and I'm an idiot, anyway I intend to clear it up a bit if I get a satisfactory answer here)

I remember this much: If you want the determinant of a 2d-matrix you go

${\begin{vmatrix}a&b\\c&d\end{vmatrix}}=ad-bc$

And for three dimensions you go:

${\begin{vmatrix}a&b&c\\d&e&f\\g&h&i\end{vmatrix}}=a{\begin{vmatrix}e&f\\h&i\end{vmatrix}}-b{\begin{vmatrix}d&f\\g&i\end{vmatrix}}+c{\begin{vmatrix}d&e\\g&h\end{vmatrix}}$

So far so good, right? My question is, does this extend to higher dimensions? That is, would the determinant of a 4d-matrix be:

${\begin{vmatrix}a&b&c&d\\e&f&g&h\\i&j&k&l\\m&n&o&p\end{vmatrix}}=a{\begin{vmatrix}f&g&h\\j&k&l\\n&o&p\end{vmatrix}}-b{\begin{vmatrix}e&g&h\\i&k&l\\m&o&p\end{vmatrix}}+c{\begin{vmatrix}e&f&h\\i&j&l\\m&n&p\end{vmatrix}}-d{\begin{vmatrix}e&f&g\\i&j&k\\m&n&o\end{vmatrix}}$

This seems fairly trivial, but i felt it would smart to ask. Ohh, and by the way, marvel at my l33t TeX sk11lz! gkhan 05:20, 25 September 2005 (UTC)

Very good, your evaluation of the determinant is correct. Remember that you can expand along any row or column as well as the first row. Enochlau 11:57, 25 September 2005 (UTC)

But mind the changes in sign! ${\begin{vmatrix}+&-&+&-&...\\-&+&-&+&...\\+&-&+&-&...\\-&+&-&+&...\\...&...&...&...&...\end{vmatrix}}$ --R.Koot 19:11, 25 September 2005 (UTC)

gkhan: You should know that determinants, while being a useful theoretical tool, essentially never need to be computed. If you are simply curious about this, then that's fine. If you are interested in learning about how determinants fit into matrix theory, no problem. But if you have some practical computation for which you think you need to compute the determinant of a large matrix, then I would advise you that there are probably better ways to do your computation. — Nowhither 20:08, 25 September 2005 (UTC)

Yes, I realise that :P I'm simply curious, if I ever need to compute it, I'll use Mathematica :P gkhan 22:13, 25 September 2005 (UTC)

Places where the pressure change most obvious in one day

Is there any place where the atmosphere pressure at that place would change very obvious in a day?Could it be beaches?

The most atmopsheric pressure changes during a short period of time is when a strong tropical cyclone is approaching, preferably at a high rate of speed. For example, atmospheric pressure bottomed out in hurricane Rita at 917 mb I believe while the worldwide average is 1014 mb. -Drdisque 06:12, 25 September 2005 (UTC)

• Do aeroplanes count? BTW, I heard a figure for 897 mbar for the minimum of Rita: the standard atmospheric pressure is 1013.25 mbar. Physchim62 10:05, 25 September 2005 (UTC)

FYI, and just to clarify, a mbar / mb is short for Millibar, where a bar is 100 kilopascals. So a millibar is 0.1 kPa or 1 hectopascal.

Information Technology Spending Patterns by Activity Sector

Hello,

As part of my Executive MBA Programme, I am examiniing Information Technology Spending Patterns by Activity Sector.

Would anybody have any sources, articles that have looked at this question in detail? I am particularly interested in the Finance, Retail and Manaufacturing Industries and in the Europe, Middle East and African region,

Thanks

Seanjoseph

--Seanjoseph 10:28, 25 September 2005 (UTC)

1. Do a Google Search for "Research" and you will find tons of organizations that do different kinds of research, publish research reports, some of them available on-line. Google also has numerous competitor search engines, some of which are better suited to some kinds of searches.
2. Visit each of the groups, such as Gartner Forrester many many others, and at each one use THEIR search engine, or Google limited to their domain, to find research they have already done in the areas that interest you, and which are available to you for free, Review the abstracts of those research reports to see if any of them meet your needs.
3. If not yet successful, change the search to include those that you can purchase, for sums like $50.00, $250.00, thousands of dollars.
   1. For example, here is a link to a 4 page report which you can download for $ 250.00 from Forrester Research How Italian Consumers use Banking Channels which was just published Sep 23 of this year.
   2. At that kind of pricing, and your broad range of permutations that you need data on, you need to get as much as you can from the free sources.

AlMac|^(talk) 18:28, 29 September 2005 (UTC)

Dr. Salam's Nobel Prize

what was the theory of Dr. Salam, for which he was awarded Nobel Prize in 1979 ?

See Nobel Prize in Physics. The prize was given "for their contributions to the theory of the unified weak and electromagnetic interaction between elementary particles, including, inter alia, the prediction of the weak neutral current", so it looks like he was one of the co-creators of the electroweak theory. Our article on that isn't very helpful, though... Shimgray 11:45, 25 September 2005 (UTC)

In a nutshell, he unified the theory for the symmetries which govern charged particles and those particles which suffer radioactive decay. Ancheta Wis 11:20, 1 October 2005 (UTC)

Hurricanes - how are the formed and where?

How are hurricanes formed, and where do they begin? Apart fro the western US do other arts opf the world get hurricanes? e.g. S. America, Europe, Africa, Asia? Signed Sarah B

• Geography_of_Cape_Verde <--try this one and also Cape_Verde-type_hurricane--205.188.117.71 04:05, 29 September 2005 (UTC)

• See Hurricane. --jpgordon∇∆∇∆ 15:02, 25 September 2005 (UTC)
• Our Tropical cyclone article is worth a look too as that is what they are called in northern Australia. Capitalistroadster

question plz

can you tell me how water can be purified by sand gravel and pebbles or can it be only purified by sand and gravel, not pebbles. plz answer me back as soon as possible. i need to give as much information as i can to my teacher tomorrow</math>

• Just pebbles isn't enough. They will only filter out the biggest things out. Our article on Water purification may be of use to you. - Mgm|^(talk) 20:01, 25 September 2005 (UTC)

Breath Waste products

What two waste products are contained in your breath?

• Is this, by any chance, a homework question? Notinasnaid 19:26, 25 September 2005 (UTC)
• I'm by no means an expert on anything biological so don't take my word for this, but sometimes the tonsils (or whatever those two holes in the back of your throat are) will develop thick gobs of pus -- white blood cells, I think -- causing a really horrible odor in your breath. I usually get this when I have a cold and sore throat. I wouldn't be surprised if this were one of them, considering it's gross as hell like you'd expect from a "waste product", so look into that and see if it's true --I am not good at running
• Don't forget good ol' Carbon Dioxide.--inks 20:47, 25 September 2005 (UTC)
• air - oxygen = carbon dioxide + nitrogen. --R.Koot 21:01, 25 September 2005 (UTC)

education

demographic educational levels in spain?

You might be interested in our article Demographics of Spain.  --  W  P Talk 06:01, 28 September 2005 (UTC)

If you go to the CIA World Fact Book, it has by nation, things like literacy rates for men, women, other subdivisions relevant to that nation. AlMac|^(talk) 21:21, 30 September 2005 (UTC)

Iron Supplements & Dental Caries

Does Supplementary Iron drops in childrens cause dental caries? ---~~|

As a molecular-biologist-in-training, I would be surprised if they did. Have you tried searching with those terms on Pubmed? [5] --inks 02:18, 26 September 2005 (UTC)

The Color Spectrum

When was the Optical Color Spectrum founded? Who dicovered the wavelengths and in what year did the factual evidence occur?

Isaac Newton discovered the spectrum (I belive he discovered it in his anno mirabilis, 1666), although he thought light was made of particles (which it turns out it kinda is, and well, kinda isn't). The first to surmise that light was made from wavelengths I'm pretty sure was Thomas Young using his double-slit experiment in 1801. By the way, that experiment, it's ridiculusly cool. What do you mean by factual evidence? Both Newton and Young had factual evidence (Newton saw the spectrum, Young saw the wave-interference). For more info, see Optical spectrum gkhan 03:27, 26 September 2005 (UTC)

Well, Newton recognised the spectrum for what it was. After all, the spectrum is shown in things like the rainbow, so the first person to notice that is lost in the mists of time. --Fangz 12:49, 26 September 2005 (UTC)

Noticing the colours of the rainbow is not the same as realising that they're constituent parts of white light. And the first person (as far as is known, I must admit) was not Newton but Roger Bacon, in the 13th century. That's 4 centuries before Newton! This guy was way ahead of his time in many fields and deserves to be just as well known as Newton, Aristotle, Galilei and the like. He could be seen as the first modern scientist, although he did dabble in stuff like alchemy as well, but then that was the chemistry of the day, so to say. DirkvdM 11:28, 27 September 2005 (UTC)

How many fault lines are there

A whole bunch. Each boundary lines is a geologic fault, but according to the article, there are a whole mess of faults that are nowhere near any tectonic plate-boundaries. gkhan 03:34, 26 September 2005 (UTC)

Gravity and its effect on the human body

Hi Science Wizards; My question is ,does Gravity have any measurable effects on the human body and if so how are these effects measured ? Does gravity effect the body different at night then during the day ? Are its effects different if we are standing or lying down?

                                    Thank you , this site is great ,Sincerely Dennis NIgrelli

Gravity has many effects on the human body. Off the top of my head, I can think of how the fluid pressure in the feet is higher than in the head when you're standing, thus the need to elevate the feet for many medical problems. Another issue is that gravity causes the pressure and stresses in you're skeletal system. I know of at least one bio-engineering researcher studying how to grow artificial menisci who has discovered that to grow them properly, you need to simulate the force on them that would be present in a growing child. You might be interested in the sorts of medical experiments that NASA has performed on its astronauts on how low-gravity environments affect the body, sometimes called space medicine. — Laura Scudder | Talk 04:02, 26 September 2005 (UTC)

(added after Edit conflict, so I might be parroting a little) Does gravity have any effect on the human bodies? Throw yourself off a skyscraper and check ;). That is, earth has a very big effect on the human bodies, it keeps us on the ground. Prolonged abscence of gravity is very harmful for the human body, your bones start to degrade almost instantly. Thats why astronauts has to be carried off their shuttles. Night and day or standing or lying down has no effect, the only thing that affets gravity is mass of the two objects (in this case, your bodymass and the mass of the earth) and distance to center of gravity (=center of earth). There is however a noticable difference in weight (note:weight, not mass) is if you are closer to the equator. At the equator, you are farther from the center of the earth (since earth isn't a perfect sphere) and you are influenced by the centrifugal force of the rotating earth. I've heard that it's a few Newtons difference from Sweden where I live (which would translate to a few hundred grams). gkhan 04:08, 26 September 2005 (UTC)

In case you are not enrolled in a space program, I've heard (although couldn't find it in Wikipedia, so it could be urban myth) that your spinal disks compress during the day due to gravity, so that at the end of the day you are a couple of centimetres shorter than you are after a nights rest (when you are horizontal your disks can expand). --Commander Keane 06:41, 26 September 2005 (UTC)

Another aspect of gravity affecting the human body is its effect on those subject to high-G, for example fighter pilots. A high-G turn can cause the pilot to lose vision and eventually consciousness. They wear special suits, G-suits, to help protect against it. Which brings me to the other point. There is no difference between the effect of G at night or day, but it does make a difference if you are lying down or not. You are less prone to blackout if you are lying down. DJ Clayworth 17:08, 26 September 2005 (UTC)

Heat suits and ambient vs. radiant heat

This crazy moon-man suit protects the wearer from 1500�F ambient heat and 2000�F radiant heat. This less-crazy moon-man suit still maintains 2000�F radiant heat, but only 200�F ambient. What do they mean by "ambient" and "radiant" heat? What sort of things would one need a 2000�F/200�F suit for? I read over Heat and Thermal radiation and understand what thermal radiation is, but I can't figure it out in terms of those suits. (Not that I need to know for any practical reason, but it's bugging me that it's not obvious to me.) — mendel ☎ 04:46, 26 September 2005 (UTC)

As I understand it, ambient heat is the temperature of air in a location, and radiant heat is the temperature to which a solid body in that location would be raised to by the thermal radiation. You can reflect thermal radiation, but you can't "reflect" the ambient temperature, so it's not surprising that it's much easier to protect against radiant than ambient heat. --Robert Merkel 05:47, 26 September 2005 (UTC)

Oh, and this page on that website says pretty much the same thing I just did. --Robert Merkel 05:50, 26 September 2005 (UTC)

I must have read right past that section, thanks. I'm now thinking about "1500� in the shade!" — mendel ☎ 19:16, 26 September 2005 (UTC)

Computer Safety - list of free mp3s

Through a site I trust (a wiki no less!) I discovered something called Webjay which appears, according to its newbie FAQ, to offer playlists of free mp3s compiled by users who simply link directly to external legal mp3 files, (eg this playlist of tracks John Peel is supposed to have played).

I've never previously been scared of mp3 files. As far as my knowledge goes, mp3 files are not a security risk to my machine. But, I suppose this just seems a little too good to be true ;o) My question is, simply, is it safe?

Whilst I'm here, what do Wikipedian Windows users use for anti-virus software? I have always used Norton, but due to some of the ways I've been using my machine lately I've come to share the seemingly prevalent view that Norton slows down your system. --bodnotbod 06:24, 26 September 2005 (UTC)

The corporate versions of Symantec anti-virus are less resource-hungry than the consumer versions. I don't know why. I run Symantec Client Security on my Windows machines. I don't know if a consumer can buy it - I got it for free from work before I left. I've heard AVG is quite reasonable and it's free for non-commercial use.-gadfium 06:47, 26 September 2005 (UTC)

I would be very surprised if a .mp3 or .m3u file posed a security risk in itself (of course, you can rename any file to a .mp3/m3u). ATM, I don't run any anti-virus software, and have not for a few years. Then again, I don't use MS Outlook either :)--inks 10:49, 26 September 2005 (UTC)

I recall hearing about some programs that had a security error with ID3 tags, allowing a buffer overflow. I don't believe it's a threat if you use an updated player, though, like Winamp 5.10.

As for anti-virus, AVG is a very good program. Not to mention free. ^_~ --Pidgeot (t) (c) (e) 11:08, 26 September 2005 (UTC)

• At the moment I run a free version of AVG anti virus. - Mgm|^(talk) 08:06, 26 September 2005 (UTC)
  • At home I run AVG free on my laptop and AVG paid-for on my main PC. The main benefit of the paid-for version is the customisability (if there is such a word) of the tests and test/update scheduling. Unless you want to fiddle with settings and the like then the free version is more than adequate. Thryduulf 14:24, 26 September 2005 (UTC)
    • Well, that's quite a vote of confidence in AVG. I too am pretty good, I believe, in terms of surfing safely and did manage not to get any nasties for years without running any guard at all. The only thing that's stopping me dumping Norton immediately is that - if I recall correctly - I only PAID to renew my subscription about 4 months ago. But I've already lost the money and there's no point being a damn fool about using a slowed computer unnecessarily, I suppose. --bodnotbod 01:32, 27 September 2005 (UTC)

Hurricanes

Dear Sirs,

I am currious to know if the water picked up over the ocean by a hurricane and is later dropped over land, is salt water or fresh water when it hits the ground? How does the hurricane suck the water up and if the rain droped is fresh, where does the salt go? Does the salt stay in the Ocean because it is too heavy or does it evaporate during the picking up of the moisture process? --[User:24.58.206.102|24.58.206.102]] 14:02, 26 September 2005 (UTC)

First, please do not indent text by pleaving blanks at the start of paragraphs on wikipedia. it formats your text as mon-spaced, unwrpped, which is good for a few special purposes, but not for ordinary text.

Secxond, the water evaporates from the ocean surface and joins the hurricane as water vapor. This leaves the salt (and anything else dissolved) behind. Thus any rain is fresh water. DES ^(talk) 14:13, 26 September 2005 (UTC)

I believe it's just tornadoes that suck up thing. Right? DirkvdM 11:51, 27 September 2005 (UTC)

Rubbish, not everyone believes in water vapor, molar heat capacaties are just the work of evolutionsits and other unsavory types (; trying to force their damn theories on everyone, I like my globe flat, and pancake like, not all spherical like *some* people want it

In USA all you have to worry about with what "sucks up" is tornadoes and man made out of control. Elsewhere in world are water spouts that behave something like tornadoes except are over water.

Also a lot of the water that ends up on the ground in the aftermath of the Hurricane, did not come from the sky, but from the surface, either via storm surge, or flood control breakage. [User:AlMac|AlMac]]|^(talk) 18:40, 29 September 2005 (UTC)

Computers Solving Mathamatical Problems

Do mathamagicians accept that computers can solve very complex problems?

for example. The four colour map theory has been solved by computers for a massive ammounts of polygons. However, many people still say that it has never been solved as a computer did it.

I dont get it! Please help

While it has been proven, many mathematicians find an exhaustive search so unelagant they don't want to call the verification of all posibilities a proof. One very good reason is that such a search does not give provide a deeper insight in why this it is true, which is often considered more important than the fact that it is true (see four color theorem). Also, most problems cannot be solved in this way, because an infinite number of cases have to be tested, or an amount simply too large. For example, the weak goldbach conjecture. Also if we would be able to lower this bound so that we could do a computer search, this would be rather pointless as the conjecture is of no practical use and a computer search would provide no intellectual challence. --R.Koot 14:22, 26 September 2005 (UTC)

The various computer-assisted proofs of the four color theorem are examples of a method of mathematical proof called proof by exhaustion. A computer-assisted proof by exhaustion involves the following steps:

1. Show that a problem can be reduced to solving a finite (although possibly very large) number of special cases
2. Devise a method of solving any one of these special cases through a finite (though again possibly very large) number of calculations
3. Write a computer program to apply this method to each of the special cases, with cross-checks to detect mistakes in design or programming or run-time errors
4. Run the program
5. Publish the program, the results and an explanation of the method in an accessible form.

Only step 4 is actually carried out by the computer. The reservations that some mathematicians might have about such proofs are more to do with the difficulty of completely validating any long and complex proof, and the lack of insight inherent in the proof by exhaustion method, rather than the fact that a computer has been used. Gandalf61 14:44, 26 September 2005 (UTC)

Original poster: You have perhaps been reading some out-of-date information.

It is true that we are not very happy with large computer-based proofs, because they are not very elegant and they give us little insight into what is really going on. Further, they force us to base notions of absolute truth on whether some particular electronic circuits were functioning properly.

However, the most important problem with the mid-1970s Appel-Haken-Koch proof of the Four Color Theorem is that no one has ever checked it independently. A group of researchers (Robertson, Sanders, Semour, Thomas) decided to do the checking in the early 1990s. They eventually found it easier to produce their own computer-aided proof, which followed similar lines, although it was a bit simpler. This proof has been checked independently. Further, you can download their program and run it yourself.

So now we can be quite confident that we do have a proof of the Four Color Theorem. And mainstream mathematical culture generally accepts computer-aided proofs these days. Although we still prefer traditional proofs, for the reasons of elegance and insight that I mentioned above.

— Nowhither 18:04, 26 September 2005 (UTC)

Just as a sidelight, computers can still be useful for numeric methods of calculation. For instance, there exists a class of mathematical functions which an integral exists, but cannot be found. A computer can approximate the value of such an integral using numeric methods when traditional mathematical methods cannot.

what is the freezing temperature of alcohol?

Does alcohol freeze as how water would freeze? If so what temperature does it freeze at?

There are many different kinds of alcohol, and they all have lower freezing (and boiling) points compared to water, which freezes at 0�C, or 32 F. The one you're probably thinking of is ethanol, which is the alcohol in alcoholic drinks. In normal atmospheric conditions, ethanol freezes, in much the same manner as water, at -114.3 �C, or -173.74 F. Proto t c 15:08, 26 September 2005 (UTC)

A minor nitpick...the low molecular weight alcohols freeze and boil at much lower temperatures than water; the longer chain ones freeze and boil and higher temperatures. Methanol (one carbon), ethanol (two carbons), isopropanol (rubbing alcohol, three carbons) are short chain alcohols. By the time you get out to dodecanol (also called lauryl alcohol) you're up to twelve carbons, and the stuff freezes and boils at 24�C and 260�C, respectively. TenOfAllTrades(talk) 16:16, 26 September 2005 (UTC)

Alcohol is also hydroscopic (i think that's the term), which means it attracts water. Normal rubbing alcohol has 30% water in it. When they make "moonshine" (ethanol), the still is used to boil the alcohol off the water, which boils at a much lower temperature. Anyway, having an amount of water in will raise the freezing point. --Phroziac^(talk) 01:10, 29 September 2005 (UTC)

Andrew C. von Eschenbach

What is his biography?

See Andrew von Eschenbach. TenOfAllTrades(talk) 16:06, 26 September 2005 (UTC)

Computer storage media

What are 5 different storage medias with their descriptions, capacity levels, advantages, and disadvantages? Where did you get this information? --63.199.33.66 16:40, 26 September 2005 (UTC)

Please refer to the instructions at the top of the page, and note that Wikipedia is not here to do your homework for you. I would recommend starting at our article on data storage devices, and working from there to find the information that you need. TenOfAllTrades(talk) 16:51, 26 September 2005 (UTC)

DYOH, but a similar question was answered above at #Storage size. Garrett Albright 19:21, 26 September 2005 (UTC)

I dont think its homework... Would you classify a extra credit project "Homework"?

Of course. I already did my time in the public school system and four years of university. I've done my share of schoolwork, and I'm really not interested in doing any more anytime soon, and especially not someone else's. Garrett Albright 18:51, 29 September 2005 (UTC)

diseases?

what is the difference between a communicable disease and a pathogenic disease?

• Pathogenic diseases are caused by pathogens (outside sources) while communicable diseases are diseases that can be transmitted between individuals. Most diseases that are communicable are caused by pathogens, but not all pathogenic diseases can be transmitted.- Mgm|^(talk) 22:06, 26 September 2005 (UTC)

Next round of the endless Moth Identification Game

My friend is keen to have this moth (right) identified, which he describes as "huge". Any takers?

File:Reeses huge unidentimoth.jpg

I'm suffering from an identity chrysalis

--bodnotbod 18:57, 26 September 2005 (UTC)

Isn't this an Owl butterfly? Rmhermen 13:46, 27 September 2005 (UTC)

Well, it's a world I know nothing about, much less the subtleties - but on a quick look at the link it would certainly seem to match. I'll pass that on, thank you. --bodnotbod 17:50, 27 September 2005 (UTC)

orcas

Hi. Are the Orcas in the fiords of Norway there yet? Thanks.

permutation cipher

• See Permutation cipher. - Mgm|^(talk) 22:08, 26 September 2005 (UTC)

What is the purpose in standards of wiring?

The subject pretty much sums up the question.

Why do you ask? You see, the way you ask it makes it sound a bit like a homework question. Notinasnaid 19:53, 26 September 2005 (UTC)

Standards (such as AWG-American wire gauge) save money, reduce effort, and create repeatable results. Ancheta Wis 11:28, 1 October 2005 (UTC)

You also might be interested in knowing about standards for the manufacturing of wiring. AlMac|^(talk) 04:01, 3 October 2005 (UTC)

what is dual axle white balance

I'm assuming you meand "dual axis". Color temperature provides a hint: "Color temperature" is sometimes used loosely to mean "white balance" or "white point". Notice that color temperature has only one degree of freedom, whereas white balance has two (R-Y and B-Y).. So I'd guess (never having seen the expression before, and only coming up with a single Google hit) that simpler cameras use a one-dimensional adjustment (color temperature), calling it "white balance"; while fancier ones (like the Canon EOS series, the only context in which Google found something) have a two-dimensional adjustment. --jpgordon∇∆∇∆ 22:22, 26 September 2005 (UTC)

Space

How did the space program come to in the US after world war 2? -jody

• Perhaps our NASA article can help you find some answers. - Mgm|^(talk) 22:11, 26 September 2005 (UTC)
• The program to get German rocket scientists (and, indeed, rockets) out of Germany was known as Operation Paperclip. Shimgray | talk | 23:28, 26 September 2005 (UTC)

Ironically, you could say that the USSR got the space program into the USA. Werner von Braun was brought to the USA to work on nuclear missiles (since he had designed the V2). He really wanted to work on space rockets, but only after the USSR went to space did politicians start listening to him. DirkvdM 12:00, 27 September 2005 (UTC)

Traditionally, until sputnik, the US space program was hopelessly underfunded, then sputnik was a shock to the US psyche, much like Hurricane Katrina is a recent shock leading to a renewed effort to do a competent job managing infrastructure and disaster avoidance. After the US Space Program got to the Moon, US public support for funding evaporated, and NASA got kind of Lost in Space. AlMac|^(talk) 18:50, 29 September 2005 (UTC)

See space race. Ancheta Wis 11:32, 1 October 2005 (UTC)

Chemistry

Dear Chemists:

I need to know exactly how much HCL acid and distilled water to combine to arrive at a liter of 1.5M solution of dilute HCL acid. Note: I am using 31.45% Muriatic acid for this project. If possible, please tell me how you arrive at the answer.

Thank you in advance! Docfrickey

I should point out that you'll never be more than premedfrickey, if you really need wiki to do your general chem homework--205.188.117.71 03:59, 29 September 2005 (UTC)

Let me try. From Hydrochloric Acid (which is Muriatic acid by a different name), we know that HCL is 36.46 g/mol. For 1L containing 1.5M, you need 36.45*1.5=54.675g. A 31.45% solution of HCL has 31.45g (or 0.86 mol) of HCL/100ml, so you need 1.5/0.86*100ml=174ml of 31.45% HCL solution. Make up to 1L with 826ml of distilled water. Can someone else check my numbers? I was never very good at this :) --inks 23:18, 26 September 2005 (UTC)

These values of 174ml of 31.45% HCl and 826ml distilled water are correct. You get a solution of exactly 1.5M.Borbrav 05:48, 27 September 2005 (UTC)

To be precise, you should use 174ml of 31.45% HCl, and then add enough water to make 1000ml of solution. The water you need to add might not be 826ml, because there's no guarantee that volume is conserved when mixing liquids. Chuck 22:44, 27 September 2005 (UTC)

• Docfrickey,

I have removed your e-mail address. The response isn't by e-mail and keeping it in such a high-traffic site means you will receive plenty of Spam and Phishing attempts. Capitalistroadster 05:59, 27 September 2005 (UTC)

Muriatic Acid contains Zinc Chloride, I hope this does not mess up the experiment.

I can find no indication that Muriatic Acid is HCL + Zinc Chloride. Everything I've found so far says it's an old name for Hydrochloric Acid. I would venture that if there is ZnCl in your HCL solution, unless told otherwise you should assume there are trace quantities only, and ignore it with regards to your calculations. Also, tell your chemistry teacher (or lecturer) to stop using outdated terminology! :)--inks 21:44, 27 September 2005 (UTC)

You would never do it this way for at least three reasons:

1. 31.45% Hydrochloric acid is corrosive and so it is difficult to measure an accurate volume.
2. Solutions of hydrochloric acid at that concentration tend to lose hydrogen chloride gas to the atmosphere, so you cannot be sure of the exact concentration.
3. Volume measurements are intrinsically inaccurate (0.1% accuracy at best), so the calculated concentration would not be sufficiently precise for further high precision work

Message to your teacher ('cos this sound like a homework question): think up more realistic situations for your students' exercises! Physchim62 14:59, 28 September 2005 (UTC)

No. Point 1: Corrosivity hardly affects measurement especially in glass instruments; Point 2: Yes it does off-gas, but it is hardly significant. In fact, these concentrations are standard laboratory stock; Point 3: Volume measurements are accurate and precise enough for a wide variety of applications. Rmhermen 03:36, 29 September 2005 (UTC)

Point 1: Of course corrosive liquids can be measured in glass apparatus if you know what you're doing (I can remember pipetting bromine as a postdoc), but it is not recommended if there are alternative solutions (as here); Point 2: Standard lab stock is 35–37%, you would be a fool to trust a concentration given to four significant figures; Point 3: True, but you would never prepare either a standard solution (ie precise concentration) or a reagent solution (imprecise concentration) by the method that the questioner requests.

For reagent 2M hydrochloric acid, add 200 mL conc. hydrochloric acid to 800 mL water. For standard 0.1M hydrochloric acid, start with the reagent diluted acid as prepared above, titrate it against sodium carbonate using methyl orange as the indicator, dilute it appropriately and retitrate the diluted solution to obtain the precise concentration. Physchim62 07:40, 29 September 2005 (UTC)

how much water does asparagus use

How much water does Asparagus use to grow? To cook? To wash his car with? Our article on Asparagus has links at the bottom to websites describing how to grow and cook it, and hopefully one of them contains what you want to know :) --inks 00:35, 27 September 2005 (UTC)

mission critical

Wht does mission critical mean?

It denotes something (or even someone) that is of crucial importance to a particular objective, or mission. Very generally, without a mission critical item, the mission cannot proceed or be completed.--inks 00:44, 27 September 2005 (UTC)

1. Think of the infrastructure that is essential to some mission or objective. If the Infrastructure fails, then the objective fails. Examples:
   1. In the aftermath of Hurricane Katrina many hospitals lost electricity, telephones, ability to be resupplied by ambulances, did not get fast enough helicopter service, so they were not able to keep all the patients alive. In this sense we can say that some of the infrastructure of the hospital was mission critical to the patients who were in dire straits.
   2. Think of the role of computerized recordkeeping to the notion of business continuity. If the computer gets trashed, if the backups are ruined, then perhaps the business cannot continue operating. Thus a system, for keeping backups out of harms way, is said to be critical to the mission of keeping the business continuing.

AlMac|^(talk) 18:55, 29 September 2005 (UTC)

What is this insect?

red & black bugs eating daisies in the desert

Long time answerer, first time asker: What is this insect? The photo is from Anza Borrego Desert State Park near San Diego, CA.

Thanks, --Joel 02:34, 27 September 2005 (UTC)

Do insects eat while copulating? :) DirkvdM 12:04, 27 September 2005 (UTC)

Sure, they use their short lifetime very efficiently, and so would I if I thought I could get away with it. Shantavira 17:06, 28 September 2005 (UTC)

I can add more photos if that would help, but I'm still curious as to what these things are.--Joel 16:07, 29 September 2005 (UTC)

Lightning?

What is lightning?

Have you seen our article about Lightning? It has some wonderful photos, and explains the phenomenon well.--inks 05:47, 27 September 2005 (UTC)

records management.what is a record?it's life cycle& why do organisation maintain records?

Our Records management article should provide some assistance. Capitalistroadster 09:22, 27 September 2005 (UTC)

Do you personally pay any kind of taxes? Do you keep any records so that you can correctly calculate them and prove what you owe in case you get audited? Companies are even more interested in making sure they do not get over-taxed. AlMac|^(talk) 01:11, 30 September 2005 (UTC)

Quantum Decoherence

What does quantum decoherence means? I know its the collapse of the wave function, but what exactly is it. Can anyone exlain it in a simple, conventional way without using much maths?

FireFox Bookmarks Directory

Where is the directory path in which favorite sites are bookmarked in Firefox Mozilla browser?

For 2000/XP, look in C:\Documents and Settings\<Windows username>\Application Data\Mozilla\Firefox\Profiles\default.7pr, assuming you aren't running with multiple profiles. --Pidgeot (t) (c) (e) 11:34, 27 September 2005 (UTC)

A simplified version of the above is

%AppData%\Mozilla\Firefox\Profiles

You can't paste the "default.7pr" because the extension varies by installation. However, you go into the default folder and grab bookmarks.html

algorithms

• see Algorithm. Capitalistroadster 03:57, 28 September 2005 (UTC)

How to clean up acid spill?

Depends upon how much acid, also depends upon what kind of acid. Small spills can be cleaned up via adding a base, or alkaline substance found around the home. Typical substances are Sodium bicarbonate, ammonia and lye. Sodium bicarbonate will froth profusely in contact with acid, ammonia can be toxic in large concentrations so make sure you have plenty of ventelation, lye will burn the skin if left in contact for a prolonged period so make sure you wash it off or even wash with a solution of vinegar. Some acids, like prussic acid are deadly poison so get out of the area fast, others like acetic acid found in vinegar are not very dangerous, so washing with water would be good enough. Large spills often are taken care of by nature herself as carbonates in the soil react and neutralize the acid.

Still a lot depends upon the acid, how much and where the spill was.

If your worksite is in OSHA's jurisdiction and keeps big jars of acid around, it should have a "spill kit" with thick rubber gloves and a box of deluxe cat litter, which both absorbs and neutralizes. The absorbent they use for chemical spills often has a pH indicator in it, so that it turns from pink to blue when you've used "enough" (subject to the manufacturer's judgment, this might be "more than a reasonable person would use in any circumstance"...). Plain cat litter will work just as well, if you use common sense and don't get out the broom until the acid is completely soaked up.

I also aggree with the earlier editor that it matters what type of acid (LSD, for instance, is another matter entirely), but also what concentration: if you have spilled a large ammount of glacial acetic acid, you might have trouble breathing in that room until the cleanup is done, so it might be wise to call someone with a respirator and the training to use it properly.--Joel 22:21, 27 September 2005 (UTC)

production manifolds

platform

er...platform lists quite a few subjects, from shoes to weapons, cars to politics, oil, tectonics, computers, and railways. Read through it until you find what you're looking for, or come back with a more thorough question. Or try wiktionary:Platform if your command of the English language is the problem.--Joel 22:35, 27 September 2005 (UTC)

What is NokiaNet?

Hi,

I have been in the mobile wolrd for in excess of 15 years and I have come across a type of Service similar to Blackberry but referred to as NokiaNet.

I will appreciate if anyone can help me understand what this Service is?

Many Thanks

Rohit

What are all the hidden processes in windows XP?

If I press ctrl+alt+delete, I currently have 31 processes running, most of them unknown by me.

Is there any place (preferably wikipedia) I can find a list of what these are?

You can usually just type the process name into a search engine (like Google) and you'll find information on it as the first result.

Or, you can list them here, and we can try to tell you what they are. --Pidgeot (t) (c) (e) 15:08, 27 September 2005 (UTC)

five sense's

• what are the five sense's ?

• See five senses. --R.Koot 15:49, 27 September 2005 (UTC)

• also, note that there seem to be more than 5 --WhiteDragon 17:38, 28 September 2005 (UTC)

• See also Greengrocers' apostrophe. --bodnotbod 18:01, 27 September 2005 (UTC)

Jumpdrive's, Compadibility, size, and price.

Can anyone please help, and find information about a Lexar Jumpdrive secure, 256MB, and any other type of Jumpdrive, Nerd Key, Flash Drive. I am looking for the size, a advantage, a disadvantage, and a discritption. Any ideas? -Lord Ned

• Dere are plendy of user reviews ad Ciao of various dypes of sdorage. Epinions hosds dem doo. I expecd, if you were do dake a look ad Amazon you'd drack down commends of the producds of a derrific boundy of some magnidude. Also please see Compuder Sdorage, Flash_memory (bah!) and USB_Flash_drive (double bah!) --bodnotbod 18:19, 27 September 2005 (UTC) (or Bodnodbod. Dang I wish I'd acdually called myself dad ad de oudsed.)

KK Thanks Lord Ned

That's a pretty bad cold you have there. DJ Clayworth 21:44, 28 September 2005 (UTC)

carbon dioxide in the body

I understand that carbon dioxide buildup in the body is what triggers "air hunger" in a heavy carbon dioxide environment, but that a helium environment wont cause such a reaction, leaving a mamal unable to sense the loss of air and therefore vulnerable to suffocation. Is this true?

• Yes, I believe it is, at least in humans (not sure about all mammals). The body doesn't detect lack of oxygen, it detects too much CO2. So if you displace the oxygen in a room with an odourless gas like He or N2, there's no feeling of suffocation to warn you that you can't breath. -- Bob Mellish 17:50, 27 September 2005 (UTC)

• Though if you're a member of the popular mammal species homo sapien, and are in company, you might detect an unhealthy amount of helium in the atmosphere when you all start talking like Disney's Chip 'n' Dale --bodnotbod 18:49, 27 September 2005 (UTC)

No, no, no, DrBob. The CO2 in the blood that drives breathing comes from body metabolism, not the surrounding air. Prevention of breathing it out is what makes you feel out of breath. Breathing is also driven by hypoxia or rising acid level, but these drives are weaker than the CO2-linked response. alteripse 21:09, 27 September 2005 (UTC)

• So what mechanism prevents you breathing out CO2 in a non-oxygen atmosphere? Or am I misunderstanding you? -- Bob Mellish 22:05, 27 September 2005 (UTC)

Nothing prevents you from breathing out CO2 in a low oxygen atmosphere. That's why people can sometimes die of hypoxia as long as they can exhale CO2. alteripse 00:21, 28 September 2005 (UTC)

Let me see if I can make it clearer. There are at least 5 types of control for the physical act of respiration: (1) voluntary breathing, e.g., blowing at something or talking; (2) involuntary neural control based on a rhythm of breathing controlled by neuronal pacemaker cells in the medulla; this is what keeps someone breathing in a vegetative state and why a brain injury that affects the medulla can kill someone; (3) chemical control by arterial blood carbon dioxide levels; rising levels stimulate breathing; (4) chemical control by arterial blood oxygen levels; falling levels stimulate breathing; and (5) chemical control by arterial blood acid (pH) levels; falling pH stimulates breathing. The CO2 and acid in the blood are generated by aerobic metabolism of body cells no matter what you are breathing.

Exhaling CO2 does not depend on the content of the ambient atmosphere but whether your lungs are working and your airway is unobstructed. Physical obstruction of breathing by a hand over your nose and mouth will prevent you from exhaling CO2 and inhaling O2, as will prolonged closure of the epiglottis as occurs in drowning; as will failure of respiratory muscles (e.g. Guillain-Barre syndrome) or severe lung disease (e.g., adult respiratory distress syndrome). In all these cases you die with a high CO2 level in your blood, low pH, and low O2 level.

However if nothing impairs your breathing but the oxygen is removed from the air, you will continue to exhale CO2 but your O2 level will fall. Most people and animals sense this before they become unconscious from hypoxia but not always, and increased breathing of a low-oxygen atmosphere does not improve the oxygen levels and the person or animal will become unconscious fairly quickly. This is why people are overcome by collections of heavy gas in sewers or chemical tanks, and a rescuer can die of hypoxia before extricating the initial victim. Just before their respiration becomes impaired, they will have a low blood O2 level and a low CO2 level; as the hypoxia affects the medulla and breathing ceases the CO2 and acid level will abruptly and rapidly rise.

The earth's atmosphere is about 21% O2 but less than 1% CO2. The rest is mainly nitrogen, but you can substitute all kinds of other gases like helium as long as you supply at enough oxygen and the other gas is not intrinsically harmful (like carbon monoxide). CO2 is not a damaging gas, but breathing an atmosphere of 21% O2 and 79% CO2 would result in rising levels of CO2 and acid in the blood because gas exchange in the lungs depends on a gradient between blood and ambient air.

Of the chemical controls, the CO2 drive is stronger than the O2 or pH drive. All of the chemical controls can gradually habituate to altered levels (e.g., as occurs in emphysema) and sudden changes can cause problems. A sudden drop of blood oxygen that causes hypoxia will impair and damage the brain in minutes. A sudden drop of CO2 (e.g., from hyperventilation) will upset the acid/base and cation balance of the blood and can cause a variety of symptoms, including panic. A sudden rise of CO2 in some circumstances can actually impair brain function and the neural drive to breathe: this is referred to as "CO2 narcosis".

Finally, it seems that all air-breathing vertebrates have similar respiratyor control mechanisms. Antoine Lavoisier discovered some of the properties oxygen by observing the effect on mice of altering their ambient air. This is probably way more than anyone wanted to know but does it answer your question? alteripse 08:59, 28 September 2005 (UTC)

So to summarize briefly, in a helium evironment, you would still have hypoxia and pH inbalances. Therefore, you would know to keep breathing, but the drive wouldn't be as strong because there was no CO2 build-up. Because you wouldn't be able to get any oxygen, you would die of hypoxia, possibly recognizing your discomfort but possibly not noticing before you fell unconscious then died. Is that basically right? Superm401 | Talk 21:39, 28 September 2005 (UTC)

You got it! alteripse 18:50, 1 October 2005 (UTC)

Fish

is goldfish coldblooded? - anon

• Fish are coldblooded by definition. - Mgm|^(talk) 20:32, 27 September 2005 (UTC)

Actually, I believe by their physiological processes rather than by human definition. alteripse 21:11, 27 September 2005 (UTC)

Tuna tend to keep an elevated body temperature, and swordfish have special muscles which keep their retina and optic nerves warm [6], but yes, most fish (especially small ones!) are cold-blooded.--Joel 23:13, 27 September 2005 (UTC)

Gasoline Shelf Life

Hi! I was wondering how long automobile gasoline lasts when stored in ideal conditions? Does its quality diminish? Does it last practically indefinitely? What happens? What does it turn into? The first question is the most important to me so feel free just to answer that one. Thank you very, very much! ~~Charles Reid (Houston, TX)

According to Chevron, their gasoline can be stored for about a year under ideal conditions[7]. We do have an article on Gasoline, although it doesn't seem to say much about long term storage.--inks 21:27, 27 September 2005 (UTC)

I recall a question on this a while back. The answer I got from my small-engines teacher when I was in high school is that it gets "gummy", which I assume means polymerization of the unsaturated hydrocarbons that are the most cost-effective way to boost octane number.--Joel 23:27, 27 September 2005 (UTC)

Also worth noting that in some countries gasoline is classed as hazardous, and it is illegal to store it in any quantity. Also note that in time gasoline will cause some types of container, especially plastics, to deteriorate. Shantavira 17:16, 28 September 2005 (UTC)

I also took a small engines course. I don't know the chemical terms for it, but it will partially solidify into a useless goo. This happens mostly in small things like the insides of a carburetor, but not in any significant quantity in a larger container. A while back, I took apart a carburetor that had been sitting with gas in it for a few years, and it had large chunks in the "bowl". --Phroziac^(talk) 00:30, 29 September 2005 (UTC)

Is that why it is stored in those drums?

Through being a moron and leaving gas in things when they haven't been used in years, I can firmly say that pretty much anything made to hold gas will not deteriorate from gas. I know that gasoline will melt pop bottles fast though... --Phroziac^(talk) 00:30, 29 September 2005 (UTC)

Gasoline will only stay fresh for about a month in a vented container, such as a fuel tank. It will change, and can cause a lot of engine troubles, such as the engine not running properly. It can also coat the inside of the engine with excessive amounts of junk. Interestingly, when it goes bad, the smell also changes, it smells more like actual varnish or paint then gasoline. You can, however, use a "fuel stabilizer", such as Sta-bil, which can be found at hardware stores, lawnmower shops, and automotive shops. It will last indefinitely with fuel stabilizer, as long as the container isn't open to the air. This includes vented gas tanks, though it will obviously stay fresher if it's sealed. Never leave unstabilized fuel in the fuel system for an engine for more then a month or so, it will gum up inside the carburetor or fuel injectors fairly quickly, and often requires soaking the carburetor in a cleaner and rebuilding it. I don't know anything about fuel injection systems, other then they are much better then carburetors. Also, this next part is original research, but apparently kerosene can be stored indefinitely in a sealed or vented container, and diesel goes bad faster then gasoline. --Phroziac^(talk) 00:30, 29 September 2005 (UTC)

Dr. Meyer

Kastle invented the presumptive blood test in the 1900's using phenolphthalein, then was further developed by Dr. Meyer later on. What was his first name?

Blood test for what? alteripse 21:24, 27 September 2005 (UTC)

I think he's referring to the inventors of the Kastle-Meyer Color Test, which uses a solution of phenolphthalein and hydrogen peroxide to detect the presence of blood via a color change. There is a passing mention of it in phenolphthalein. I've had no luck with Googling for Dr. Meyers full name though.--inks 21:35, 27 September 2005 (UTC)

Satellite imagery

Are there any satellites up there that will photograph to the clarity and detail of showing a man or woman walking on earth ?

If I told you, I'd have to kill you :) Our article on spy satellites has several listed that have a resolution of less than 1m...so a person lying down might be distingusihed. However, a person standing up would present a much smaller cross-section to the satellite, the size of which would probably fall below the resolution availible.--inks 22:42, 27 September 2005 (UTC)

Diffraction means that a much smaller angular resolution than the 1m reported would require either a) extremely large apertures (which are difficult to fit onto a rocket) or b) extremely small wavelengths (the atmosphere is opaque to ultraviolet light lower than a certain limit). However, if the satellite takes many, many photos of the same thing from different angles, number-crunchers with fancy algorithms can create a synthetic aperture to get around this problem. Unfortunately, this means much greater latency, and the requirement that whatever you're spying on stand still for many hours, something most people can't be relied on to do. If a large flock of satellites ganged up and all snapped a photo at the same time, they could pool their data and give an image fairly quickly, but that would be extremely, extremely expensive.--Joel 23:20, 27 September 2005 (UTC)

Would the satellites/cameras all have to be in different positions? Wouldn't a bunch of cameras on one satellite or even just one camera taking several shots be enough? I've wondered about this with ordinary cameras. If you take one shot the grain is the result of the resolution of the sensory chip or film used. If you take a series of shots, all slightly moved (which will automatically happen if you hold the camera in your hand) and you lay those images over each other (compensating for the movement, which will therefore have to have been measured) then the pixels will mostly only partially overlap. So one spot that's much smaller than a pixel will be measured in different ways, from which one may calculate the value for that spot as if one would have had a smaller pixel capturing that spot. It's sort of like a Very Large Telescope array. There the telescopes are not in the same position, but considering the distance to what's measured compared to the distance between the telescopes that hardly seems relevant. Another reason for getting not so sharp an image would be imperfections in the lens, but then that could be solved by using different lenses (ie different cameras). Part of me says this makes sense and another part of me says it's complete nonsense. Can someone make me whole again please? :) DirkvdM 19:47, 28 September 2005 (UTC)

But imagine you're a spy agency with no oversight, and can afford a CCD with unlimited resolution: eventually, the other components will impose resolution limits. I think the "different place" part is actually necessary once the aperture, rather than the sensor, is what limits your resolution. In this case, the aperture shouldn't overlap too much with where it was before/with the other aperture, but recording the difference in perspective isn't absolutely necessary, as it could also be calculated as part of the process of combining the images. But you can never put a sattelite in exactly the same place twice anyway. Geosynchronous sattelites are an apparent exception, but there's still some wobble involved. Part of the reason large arrays of radio telescopes are necessary is the huge wavelengths found in radio, compared to visible and to practical aperture sizes. I think perhaps several pictures from "the same place" could be combined to boost resolution when the CCD is the limiting factor, but it would take a different sort of math as far as I know.--Joel 16:58, 29 September 2005 (UTC)

And would that math then be complicated? Suppose I'd take several shots in rapid succession (all shifted slightly like I said), then shouldn't it be possible to write a computer program that combines them to a sharper image? (even if that would take my computer all night, it would still be handy for some photos like night shots (preventing blur)). DirkvdM 19:54, 29 September 2005 (UTC)

Yes, it appears to be quite complex. Do a Google search on "optical aperature synthesis" and see what you can find...--Robert Merkel 05:55, 30 September 2005 (UTC)

A few years ago, I saw an image taken from a satellite, of a little boy in his back yard, looking up. The boy was the son of one of the NASA scientists, and the scientist had told his son what time to walk out into the back yard and look up. The image was very clear, and the boy's face was perfectly visible and identifiable. User:Zoe|^(talk) 05:52, 1 October 2005 (UTC)

cascading pareto chart

hematology

so wot's yer bloody question?

• See Hematology. - Mgm|^(talk) 07:49, 28 September 2005 (UTC)

standards in wiring

What is the purpose of standards in wiring?

largely so that other electricians than the one who installed it can go in and quickly be able to figure out how it works. Also, so that devices made by different manufacturers will be compatible with one another. -Drdisque 02:49, 28 September 2005 (UTC)

Safety is also an issue.

.9999� = 1?

How does point nine repeating (.9999�) equal one?

1-0.99� = 0.00000000... There are several other nice proofs, but I'm not sure if we have an article on the matter. I'm sure someone else can help you with that though. --fvw* 03:24, 28 September 2005 (UTC)

One way to see this is to observe 1/3 = .333..., so .999... (which is clearly 3 times .333...) must be the same as 3 times 1/3. Another way is to convert it to a fraction. Let X=.999..., then 10X=9.999..., and 10X-1X = (9.999... - .999...) = 9, so 9X = 9, i.e. X=1. If none of these do it for you, you might try the explanation at http://mathforum.org/library/drmath/view/55746.html. -- Rick Block (talk) 03:34, 28 September 2005 (UTC)

Actually, we do have an article on this: Proof that 0.999... equals 1 --Pidgeot (t) (c) (e) 12:14, 28 September 2005 (UTC)

From a no-equations-involved standpoint, we know that there are infinitely many numbers between any two distinct numbers on a number line. Now, what form would a number take to be greater than 0.9999... and less than 1.0? No such number exists, therefore 0.9999... and 1.0 are not distinct (that is, they are equal). — Lomn | Talk / RfC 13:27, 28 September 2005 (UTC)

Use a calculator to square the square root of 2 and deduct 1. This will confirm that 1 is 0.9999.... ;-) Shantavira 17:22, 28 September 2005 (UTC)

For the hapless reader that doesn't reallize the above is a joke, see round-off error and the field of numerical analysis that studies that kind of thing. - Taxman ^Talk 18:40, 28 September 2005 (UTC)

It basically follows from the completeness property of real numbers. Read the properties section of that article if you really want to dig into the gory stuff. Our article doesn't use the infimum and supremum language I learned in advanced calculus, but that was a while ago and I forgot the completeness formulation in those terms. Those articles cover the basics. - Taxman ^Talk 18:40, 28 September 2005 (UTC)

Aren't natural numbers and rational numbers mixed up here? I suppose one might argue that 0.99999.... equals 1.00000.... . But 1 (without a decimal dot) is a natural number and 0.9999.... might come infinitesimally close to that, but never reaches it. So for all practical purposes they're equal, but mathematically they aren't. Right? DirkvdM 21:04, 28 September 2005 (UTC)

Again, see the article, but to summarize, any two unequal real numbers (reals) have an infinite quanitity of reals between them. What reals are between .99999... and 1? Superm401 | Talk 21:45, 28 September 2005 (UTC)

0.999... can only be defined in terms of the limit of a series. The series is in the rationals, and it converges to a natural number, 1. That's it. One important fact you need to know is that there are no infintesimals in the theory of real numbers. There are some funky theories you get in logic courses that have infintesemals, and you can do stuff with them instead of limits; I don't know how you would define 0.9999.... in that scheme, but it's irrelevant anyway. -- SCZenz 21:57, 28 September 2005 (UTC)

severe hypoglycemia

• Our Hypoglycemia article may be able to help you out. Capitalistroadster 05:57, 28 September 2005 (UTC)

How can I view a unix manpage in Microsoft Windows?

How can I view the unix manpage <http://ccdoc.sourceforge.net/downloads/ccdoc.man> in Microsoft Windows? �Masatran 07:24, 28 September 2005 (UTC)

You can download Cygwin and install it. When done, save the file to the man directory and a man ccdoc should be enough, or download and compile the ccdoc source (again, in Cygwin).

Afterwards, you can add the bin directory of your Cygwin installation to your path to be able to read the man page without having to enter bash every time. --Pidgeot (t) (c) (e) 09:37, 28 September 2005 (UTC)

Also try looking for programs to convert manpages to something you can read [8] Ojw 21:25, 30 September 2005 (UTC)

BEARD GROWTH

our forefathers ,most of them atleast, who originated from primates stopped using their tail which eventually led to most of the tail missing from the present day human.on the same logic with extensive shaving off of the beard since ages, why is it that it has not stopped growing? thanks. vinod.--219.65.45.74 10:27, 28 September 2005 (UTC)28/9/2005 1600h

• because that doesn't have much to do with evolution, you should get better teachers.. also human population growth is exponential, that means at some point, we break the evolutionary mold, in shorter words, we're an evolutionary dead end, much like the neanderthal, and you know what happened to that guy--205.188.117.71 03:54, 29 September 2005 (UTC)

It isn't enough that something not be useful for it to evolve away, it needs to have a detrimental effect. (See vestigial organ) A tail has muscles, bones, etc that need maintainance (and maybe get in the way for certain types of walking). I don't think a beard takes much of the body's resources to make. And I imagine that shaving has been in practice for a very tiny fraction of the time that not-using-one's-tail has. Frencheigh 10:38, 28 September 2005 (UTC)

"stopped using their tail which eventually led to most of the tail missing". No, it didn't. That is similar to the evolutionary theory of Lamarck, which has been disproven. Lamarck believed(among other things) that use of organs would cause them to grow while disuse would make them shrink. Again, this is not correct. Evolution occurs through natural selection(or "survival of the fittest"). In summary, all individuals pass traits(phenomes) to their children through genes. Those individuals that are most successfully adapted will be more likely to reproduce, as well as likely to reproduce more. Therefore, more descendants will have their phenomes and genes than those of the less successful individuals. Eventually, only the descendants with the superior adaptations survive, forming new species. Genes are modified through mutation. Superm401 | Talk 21:59, 28 September 2005 (UTC)

There are many evolutionary explanations for the distribution of human body hair. Some are plausible; some seem like just-so stories. alteripse 11:26, 28 September 2005 (UTC)

What is sirolimus

See sirolimus. The fastest way to find information and articles in Wikipedia is to use the Search box on the left side of your screen. TenOfAllTrades(talk) 16:19, 28 September 2005 (UTC)

multiple sclerosis

I'm not sure what your question is. See our article on multiple sclerosis for lots of information on that topic, however. TenOfAllTrades(talk) 16:19, 28 September 2005 (UTC)

hydrogen bonding

there are two types of hydrogen bonds.(1)intermolecular (2)intramolecular.amongst these,which one is more strong and why?

By any chance, was intermolecular forces supposed to read as Van Der Waals forces ? you may as well post the entire problem, I could use some practice with my differentials--205.188.117.71 03:51, 29 September 2005 (UTC)

According to Hydrogen bond, it's an intermolecular bond. So I assume that the intramolecular case you refer to would just be an "intermolecular" bond between two atoms that happen to be far apart in the basic covalent structure of the same molecule (contributing, e.g. to protein folding). That being the case, I would expect the two cases to be of equal strength if all else is equal. -- SCZenz 15:43, 28 September 2005 (UTC)

Please refer to the top of this page, and note that Wikipedia isn't here to answer your homework questions. TenOfAllTrades(talk) 16:16, 28 September 2005 (UTC)

On the bright side, if that was a homework question, what I said almost certainly wasn't the answer the instructor was looking for. ;) -- SCZenz 17:30, 28 September 2005 (UTC)

Cephlapods and regeneration

Can a squid or an octopus regenerate tentacles if one is severed?

• "the squid's tentacle would not grow back "[9] Samw 21:56, 30 September 2005 (UTC)

Wikipedia Problems??

I have noticed when i try to edit a post, i have to click on the "Edit" button for the post above. Has anyone else noticed this? Or is it just me?

This sometimes happens when a section header is not formatted correctly. Fixed (I think). --hydnjo talk 01:47, 29 September 2005 (UTC)

I think the poster is thinking as I did at first, and assuming a section's edit button is the one that follows the text. In fact a section's edit button is the one on the same line as the section's title, above the horizontal rule that preceeds the text; not the one that sitting there, temptingly, right where your addition will go. I found this counter-intuitive. And for long sections the edit button has scrolled off-screen. Sharkford 14:38, 30 September 2005 (UTC)

Lord Ned

Lordned 17:39, 28 September 2005 (UTC)

The section edit link in the default skin is to the right of and just slightly above the section title. This can make it look as if the link applies to the previous section, when it does not. This is, I'm afraid, just soemthing you need to get used to. DES ^(talk) 17:53, 28 September 2005 (UTC)

On related issues, you delete a duplicate section by editing the whole page and removing it, or by editing one of the duplicates and deleting the entire contents, including the section header. I did this for your duplicate post. Also when you start a line with a space character it produces a fixed-font, un-wrapped, boxed text. This is usually not what is desired. Do indents by starting the line with one or more colons. It is not standard on wikipedia to indent the first line of a paragraph. DES ^(talk) 17:53, 28 September 2005 (UTC)

Ok, Thanks. When i went to try and edit the post, i click on the wrong edit "Opps"

That happens. Alos on discussion pages (like this one) it is a good idea to sign your comments with four tildas (like this ~~~~). DES ^(talk) 18:01, 28 September 2005 (UTC)

One more note; sometimes if there are multiple images stacked up next to an article, it will cause flaky behaviour of the [edit] boxes. None will appear next to one or more sections, and they will all pile up ([edit] [edit] [edit]) next to a later section in the article. TenOfAllTrades(talk) 18:39, 28 September 2005 (UTC)

he he... lol."::One more note; sometimes if there are multiple images stacked up next to an article, it will cause flaky behaviour of the [edit] boxes. None will appear next to one or more sections, and they will all pile up ([edit] [edit] [edit]) next to a later section in the article" thats one big problem...

63.199.33.66 16:38, 29 September 2005 (UTC)

puna multa

Dear all. I am trying to find out any information about "puna multa" which should be the name for a traditional finnish (scandinavian?) type of timber treatment based on natural whiting and rye flour. Please if you find any info let me know at ivan.nemec@chello.cz. Thank you.

Hmmm. A number of links come up in Finnish when I Google that phrase, but my Finnish is, um, limited :) You might try asking one of the people listed at the Finnish Wikipedia Embassy if they can help you. --Robert Merkel 04:26, 29 September 2005 (UTC)

Bad hurricane cycles

I was once told that every 40-43 years, a major hurricane strain happens. Is this true? If so, are the years correct?

Check our article on hurricanes; specifically, the "long-term trends in cyclonic activity" section. There is a very approximate estimate of a 50-70 year cycle for the Atlantic basin, though full-ocean coverage has not existed long enough to make a firm statement in that regard. — Lomn | Talk / RfC 20:15, 28 September 2005 (UTC)

hydrogen peroxide

Has an article here, if you, in fact, wanted to learn something about it. Not to pour salt in your wounds, but if you need something specific (that's not already in the cleverly hidden article), perhaps you should ask a question. ByeByeBaby 19:48, 28 September 2005 (UTC)

quantitative methods and physical planning

how do these quantitative methods help in the physical planning field?

Which quantitative methods? Chuck 20:35, 28 September 2005 (UTC)

I'll guess it's a follow-on to a homework question that the original poster should do himself. — Lomn | Talk / RfC 20:54, 28 September 2005 (UTC)

Lagrange Minimization procedure

Since you know how to frame the Section header as "==Lagrange Minimization procedure==" then please follow up with an actual question. Wikipedia is not a search engine. --hydnjo talk 00:00, 29 September 2005 (UTC)

Actually, someone using the "add a new question" link at the top never uses wikiformatting to create the header. However, the above is correct -- this is not a search engine. However, this link over in Miscellaneous may help out. — Lomn | Talk / RfC 02:16, 29 September 2005 (UTC)

Epidemics indiana 1850 - 1860

Since you know how to frame the Section header as "== Epidemics indiana 1850 - 1860==" then please follow up with an actual question. Wikipedia is not a search engine. --hydnjo talk 00:00, 29 September 2005 (UTC)

indiana

Hey, I live in Indiana! You might want to review the instructions at the top of this page, particularly the part that says "Questions are answered by humans, not computers. This is not a search engine." Chuck 22:21, 28 September 2005 (UTC)

PEANUT SKINS

ARE THEY GOOD FOR YOU TO EAT? JANET F.

Assuming that you don't mean the "shells" (the hard outer part that we usually throw away) but rather the thin, maroon colored "skin", I'd presume that they aren't bad for you to eat or they wouldn't be so readily available that way, but I suppose that same answer would apply to the hard outer shell as well! Also, the "meat" within called the peanut are OK for some folks and deadly for others. So, I have no idea if they "ARE THEY GOOD FOR YOU TO EAT? JANET F.", that's between you and your doctor. I can only tell you that they are not bad for me to eat. --hydnjo talk 00:25, 29 September 2005 (UTC)

If I had to guess, I'd say that they're not harmful. (I'm making the same assumption as Hydnjo does about what constitutes the 'skin'.) I suspect that they're loaded with insoluble fibre, which is good for your digestion. On the other hand, I find them a bit bitter and kind of dry, and they can cause an unpleasant tickle in the back of my throat when I eat them.

Ah; Google is your friend. An interesting link here. Apparently peanut skins are used as animal feed–suggesting that they're not harmful. It seems that they contain a number of useful fatty acids, too. TenOfAllTrades(talk) 01:44, 29 September 2005 (UTC)

what is a cell?

"Cell" can have many different meanings, depending on its context. Have a look at Cell and see which one you are interested in. Chuck 23:29, 28 September 2005 (UTC)

wonderland

who is the blue ferry?

Although this is when rather than who, I hope this is of some help. --hydnjo talk 00:31, 29 September 2005 (UTC)

Perhaps you mean the Blue Fairy, from the novel Pinocchio, who also features in the movie A.I.: Artificial Intelligence.-gadfium 03:45, 29 September 2005 (UTC)

What day is the North Pole tilted furthest from the Sun?

whatever day is the middle of winter in the northern hemisphere Jeremybub 02:46, 29 September 2005 (UTC)

• I don't think so. See solstice. The first day of winter. --jpgordon∇∆∇∆ 02:52, 29 September 2005 (UTC)

On the winter solstice, which is usually December 21, but can vary by up to a day (depending on leap year adjustment). Shantavira 08:58, 29 September 2005 (UTC)

What is the act of using your senses to view the world? 11 letter word

How about "observation"? --jpgordon∇∆∇∆ 02:52, 29 September 2005 (UTC)

Are we solving crossword puzzles here now? DirkvdM 12:49, 29 September 2005 (UTC)

Feces and foot

I just stepped barefoot on what appeared to be human shit in an urban alleyway in the Eastern United States. I was quick and enthusiastic with the soap and the water, but I am still concerned about infection risk. Contributing to my concern are that I have a three-day-old cut on the soul of that foot and that there was next to the shit what in the dim light of the alley could have been a spoonful of jam or an enormous clot of blood. I didn't step in this second substance, but am thinking that neither dropping blood clots nor shitting in alleys are signs of health on the part of this mysterious person with whom I have suddenly become so intimate. Am I in danger? Are there any symptoms I should watch for? Thanks — Pekinensis 03:26, 29 September 2005 (UTC)

• Pekinensense,

I would contact your doctor as soon as you are able. It is probably best to be safe than sorry in these circumstances. Capitalistroadster 04:11, 29 September 2005 (UTC)

Have you been vaccinated against Hepatitis B? If not, this is something to bring up on that doctor visit. - Nunh-huh 06:37, 29 September 2005 (UTC)

And, if you haven't already, clean the wound and disinfect it with something like iodine (the most common brand name solution is called "Betadine" as per normal first aid procedures. --Robert Merkel 04:21, 29 September 2005 (UTC)

Relax. You have already taken care of it with soap and water and your injury was more aesthetic than biological. But what the heck were you doing barefoot in a dim alley? alteripse 09:55, 29 September 2005 (UTC)

Thank you all for your answers. I've decided not to worry about it. I have been immunized for Hepatitis B. What was I doing? I was taking out the trash and thinking about February when I stepped in the same substance in the same place, and that the Universe would not be so perverse as to repeat such an incident when I happened to be barefoot. Thanks again. — Pekinensis 16:45, 2 October 2005 (UTC)

Elemental lithium

I have searched the Internet for a while now, and cannot find the answer to this question:

How much elemental lithium is in 300 mg of lithium carbonate?

I know, for instance, that 120 mg of lithium orotate contains 4.8 mg of elemental lithium. I need this information for comparison sake, as I run a Yahoogroup of people taking -- or switching to -- lithium orotate.

Sincerely, Gerald L. "Moss" Bliss, D.D. ALT-therapies4bipolar Yahoogroup

According to our article on lithium salts, the chemical formula of lithium carbonate is Li₂CO₃. That there's one carbon and three oxygen atoms for every 2 lithium atoms in lithium carbonate.

From our entries on lithium, carbon, and oxygen the atomic mass of each is 6.974, 12.0107, and 15.9994. From this, we can calculate the fraction of the compound that is made up of lithium is:

${\frac {2\times 6.974}{2\times 6.974+12.0107+2\times 15.9994}}\approx 24\%$.

Therefore, 300mg of lithium carbonate would contains about 72 mg of elemental lithium.

Please note that Wikipedia does not give medical advice, and that incorrect dosage calculations are a regular cause of avoidable deaths in hospitals. So, whatever you do, please don't start dosing yourself purely on the basis of some quick calculations of somebody who hasn't done chemistry since high school.--Robert Merkel 04:15, 29 September 2005 (UTC)

To illustrate the problem, that equation should be

${\frac {2\times 6.974}{2\times 6.974+12.0107+3\times 15.9994}}\approx 18.86\%$

or 56.5 mg lithium for 300 mg lithium carbonate. Be aware as well that the bioavailability of metal ions is different for different salts. Physchim62 09:10, 29 September 2005 (UTC)

Whoops! I wasn't trying to illustrate the point, but hopefully people will take notice of the warning now that I've demonstrated how easy it is to screw up! --Robert Merkel 12:27, 29 September 2005 (UTC)

are the stars we see in the nights sky actually suns

They are actually stars, and the Sun is a star. Many of the stars are just like the sun, though some are much bigger, much smaller, or otherwise different. Some people, especially science fiction writers, do use the word "sun" (not "Sun") to refer to other stars, but to avoid confusion it's best to stick to "star". Notinasnaid 07:54, 29 September 2005 (UTC)

Except the Morning Star and Evening Star. -guety is talking english bad 14:53, 29 September 2005 (UTC)

suns and stars

Are the stars we see in the nights sky actually suns? and are there any other suns in our galaxy that is equal or higher in size as our own sun? Africadeedee

Yes, almost all of them are, except a very few might be planets. There are lots of other suns in our galaxy which are as big or bigger than our sun, but there are even more which are smaller. The smaller ones are usually dimmer, so the ones you can see are mostly the larger ones. See our article on stars for more details. If you find that article is too complex for you, then look at the Simple English article on Stars.-gadfium 05:32, 29 September 2005 (UTC)

It's a dirty leftist conspiracy, the stars are merly a painting, that jesus made 6000 years ago when he created the earth, which was flat at the time, he also created dinasours then too, and they lived in harmony with early man in the garden of eden until man was cast out, then jesus took a rib from the first dinasour, named adamsour, and created the iguana.. problem solved, all that 'DNA' nonsense is just a trick to make science look silly--172.208.123.70 14:34, 2 October 2005 (UTC)

Nuclear blast in eye of hurricane..

What would happen if someone detonates a nuclear device inside the hurricane eye. Will it disperse the hurricane system, nothing happen, or just something else will happen? What if they used the Soviet Era 'The Czar' super-sized H-bomb. Does it even matter if the device is detonated inside the eye, outside of it (near the clouds spur) or even an airblast above the hurricane system ? Thank you very much in advance.

bukhrin

I don't think anybody's ever asked before, though you probably could do a simulation if you had access to weather-forecasting computer code. One side effect that's easy to predict is the distribution of dangerous nuclear fallout over a wide area, which could render places in its path uninhabitable for years, perhaps even decades, afterward. --Robert Merkel 07:47, 29 September 2005 (UTC)

though you probably could do a simulation if you had access to weather-forecasting computer code. Don't forget to budget for several days on the nearest supercomputer. :)--inks 12:18, 29 September 2005 (UTC)

It would probably not do much to disrupt the hurricane. The energy in a hurricane (see [10] for example) is several orders of magnitude greater than the yield of existing nuclear bombs. Fredrik | talk 11:01, 29 September 2005 (UTC)

Interesting experiment though. A FAE (Fuel-Air Explosion) approaches the strength of a Nuclear Weapon by purely chemical means, so if this were done there would be no nuclear fallout from it.

They only approach the yield of the tiniest nuclear weapons, though. --Fastfission 16:03, 29 September 2005 (UTC)

I doubt it would do anything at all. Even a Tsar Bomba sized blast pales in the overall, cumulative energy present in a hurricane. If you look at our entry on kiloton you can see how much more raw energy natural phenomena has in general (the reason that the bombs seem so big, of course, is that they release all of their energy into a relatively small space and over a very small amount of time). --Fastfission 15:36, 29 September 2005 (UTC)

The NOAA answers this question in their Hurricane FAQ. — File:Ontario trillium sig.pngmendel ☎ 17:08, 29 September 2005 (UTC)

1. Delivering a nuke to the eye of a storm would require some fancy footwork, missile technology not something that your average troublemaker might have in the near term.
2. Do Google search ... there are places where you key in geographic location and how big some event to see damage from WMD, giant meteor strike, earthquake, other disasters.
3. Watching on TV news huge traffic jam of people evacuating at last minute, it occurs to me we are kind of asking for trouble, since this goes on TV news world wide to all kinds of audiences.
   1. major hurricane is coming, approx where, announced days in advance
   2. local leaders take forever to discuss the implications of what is obvious to everyone, who knows anything, such as
      1. here comes category 4-5 and the flood control is only designed to handle category 3, and the city is under sea level, so after landfall it will be under water
   3. during that predictable time frame when the local leaders cannot decide what to do, terrorists blow up major escape highways with conventional explosives, stockpiled in geographic areas where the Atlantic hurricane season is known to be active.

AlMac|^(talk) 19:12, 29 September 2005 (UTC)

To paraphrase NOAA:

• Before implementing this plan, you have a hurricane to deal with.
• After implementing the plan, you have a hurricane and a nuclear explosion.

Ojw 18:50, 1 October 2005 (UTC)

migraines

• Our Migraine article is quite detailed and would be a good place to start. Capitalistroadster 08:07, 29 September 2005 (UTC)

how to improve migraines

• Our Migraine article contains extensive information on migraine treatment. Your doctor will probably be able to advise of treatments if you suffer from them. Capitalistroadster 08:09, 29 September 2005 (UTC)
• Improve them? Few sufferers want them to get worse. Cure them perhaps was what you wanted to ask about. AlMac|^(talk) 01:15, 30 September 2005 (UTC)

how wind blows?

Is it because of earth's revolution or change in air density due to sun light?

Have you tried reading our article on Wind? There should be some information there. From what I can ascertain, there are a variety of types of wind that have different causes.. but you should definitely read that article. splintax ^(talk) 08:42, 29 September 2005 (UTC)

All wind is fundamentally caused by pressure differentials. Many factors affect that pressure, and the differing linear speeds(though constant angular speed) of rotation at different latitudes affect apparent direction. See also "Why does wind gust?" above. Superm401 | Talk 13:59, 29 September 2005 (UTC)

construction technology of rotating buildings

could you please show me the details and sections of rotating buildings?? and if possible the criteria etc too to implement it. 2nd year student, amrita

Several cities have restaurants on top of high buildings, in which only the top rotates. You sit at window seat, and in an hour it has rotated so you get to see the whole city. I have never heard of an entire building rotating. AlMac|^(talk) 19:15, 29 September 2005 (UTC)

Glasgow Science Centre does. Or was supposed to, anyway. Notinasnaid 22:22, 29 September 2005 (UTC)

The largest and most numerous rotating buildings would probably be radio telescopes. I think they use circular tracks, along which a motor on the outside of the building travels. Ojw 19:47, 1 October 2005 (UTC)

mobile phone

Hi,

my question is "why mobile phones are not allowed in petrol bunks?

Bharathi.

• Some people believe the static electricity create when a mobile phone is used could cause an explosion which would be detrimental near petrol. However, the Mythbusters tried to cause an explosion using mobile phones and couldn't succeed unless they purposely created loads of static electricity (far more than a phone could generate). Still, there have been accounts of faulty and exploding batteries in phones which could still cause problems near petrol. Hope than answers your question. - Mgm|^(talk) 11:01, 29 September 2005 (UTC)

I'm not satisfied with their test, actually: they didn't set the phone to vibrate. In most direct current electric motors, the commutator throws up sparks several times a second as the motor runs. But in fact, I agree that this is more a question for the "culture" section of the reference desk...one reason I'm unhappy with this recent segmentation of the project.--Joel 17:49, 29 September 2005 (UTC)

• They did do a follow-up experiment to address multiple issues viewers brought up, but I can't remember the result. Sorry. - Mgm|^(talk) 19:12, 29 September 2005 (UTC)
• Surprisingly I found an article on MythBusters Episodes the mobile phone myth is listed in season 1 (episode 2) and season 2 (episode 14). - Mgm|^(talk) 19:23, 29 September 2005 (UTC)

It failed both times. --R.Koot 10:10, 30 September 2005 (UTC)

Botany

I want to know what is exactly subdiecious condition. If in a dioecious species, if the males are converting temporarily to hermaphrodites, what we can call this condition?

I believe the article for you is plant sexuality. It seems to give two answers to your first question, one more specific than the other, but both make "subdioecious" seem like a plausible anwser to your second question. — Pekinensis 13:08, 29 September 2005 (UTC)

Energy Drink Question

I was wondering if XS Citrus Blast energy drink was really made up of things that gave you energy or if it is simply caffeine with some flavor added in. Next, I was wondering if it would simply be better to just by a can of coke instead of the energy drink?

--Thanks, J

Found this using google. Active ingredients: Taurine, Caffeine, Ginseng, Vitamin B3, Vitamin B5, Vitamin B6, Vitamin B12. My guess would be that this contains more caffeine than a coke, so you need to drink less of it for the same effect. --R.Koot 16:08, 29 September 2005 (UTC)

If your diet is extremely bad, you might feel a lack of energy due to mild pellagra or some other deficiency disease, in which case XS Citrus Blast would make you feel revived beyond the sugar and caffeine...but eating a balanced diet would make you feel even better.--Joel 17:12, 29 September 2005 (UTC)

Is evolution scientific?

One of the reasons often given for not teaching Intelligent Design is that it is "not scientific", which as far as I understand means it cannot be experimentally disproven. What makes evolution "scientific", or rather what experiment would disprove evolution?

I don't think it's real at all, just another leftist conspiracy, much like... gravity, and that whole "round earth" business, If the earth is really round, and it really spins around the sun, then why don't I fall off when I'm on the bottom? Answer that smart guy--172.208.123.70 14:29, 2 October 2005 (UTC)

Evidence of evolution might be a good place to start. -- SCZenz 15:26, 29 September 2005 (UTC)

What you are referring to is the notion of falsifiability. Whether or not evolution is falsifiable depends on who you ask (creationists would probably interpret it to say no, philosophers might sit on the fence, scientists would say yes) — as a philosophical concept, it is not as cut-and-dry a test as people opposing creationism/ID usually make it out to be (though I personally think that in this instance, their overall conclusion is probably correct).. A lot of depends on whether you are taking evolution "as a whole" the entity which needs to be falsified or whether or not you are taking specific claims, and a lot of it also depends on what version of falsifiability you use. One fairly intelligent page which argues that evolution is falsifiable is Talkorigins.org: Evolution and Philosophy. --Fastfission 15:27, 29 September 2005 (UTC)

That is correct. I do not of any experiment that would disprove evolution, but that does not mean someone won;t come up with one sometime. This is impossible with Intelligent Design as you could always counter with "it was designed that way", while with evolution the theory has to modified or discarded. See Lamarckism, evolution, evidence of evolution, Intelligent Design and scientific theory for some more information. --R.Koot 15:28, 29 September 2005 (UTC)

Another way in which ID is unscientific is that it does not deal with a repeated mechanism of the natural world that operates under self-consistent rules. It just has some being who does what he feels like. -- SCZenz 15:33, 29 September 2005 (UTC)

Science restricts itself to hypotheses, theories, mechanisms, and processes that are consistent with our knowledge of the material world and explicitly excludes claims about supernatural processes or knowledge. Science cannot and does not claim that God does not exist or did not create the world, only that such claims cannot be evaluated from a scientific perspective and are not likely to advance our scientific understanding of the material universe. Since first proposed, an enormous amount of experimentally verifiable and directly observable evidence has supported the validity of the basic process of evolution and no evidence strongly undermines it. It is possible to imagine that several million years ago, several thousand years ago, or several minutes ago God created the world exactly to seem as if evolution is occurring, but none of these hypotheses fit with other scientific knowledge or seem likely to advance other scientific understanding or can be proven or disproven scientifically.

Science does not exclude the supernatural, but says that so far the supernatural does not lend itself to any scientific analysis, which is not quite the same thing. (But its so close it is the same thing for all practical purposes).

The objections that most intelligent people have with the idea of Intelligent Design are that it is (a) presented dishonestly (as not being intended to promote fundamentalist Christianity), (b) confuses people about what science is (by incorporating miracles and supernatural processes in scientific knowledge), and (c) misrepresents our current understanding of evolution (which is both dishonest and confusing). Most intelligent Christians make a distinction between evolution as a scientific way of understanding the changes and interrelationships of living things on earth, and most intelligent scientists do not claim to be able to scientifically prove or disprove the existence of God or whether he had a role in the formation or history of the universe. Does that help? alteripse 15:41, 29 September 2005 (UTC)

(adding during edit conflict with above three responses)

A scientific theory (versus just any ole theory) is one that makes testable predictions. As you intimate, a theory without testable predictions is impossible to disprove and rather useless to a scientist. So for instance, I could come up with a theory of everything that was simply a list of observed occurances: in other words a theory that simply described the way things are and said "this is how it is". That theory would not be a scientific theory, because it would make no new predicitions, not to mention being really unsatisfying as it wouldn't "explain" any observations with underlying principles.

A prof of mine once said, "every great theory swallows it's predecessor whole," meaning that for a new theory to gain ground it needs to explain all the behavior described by the old theory while making an entire set of new, experimentally testable predictions. A great example is quantum mechanics, which swallowed Newtonian mechanics whole and then made an entire set of new predictions which have been tested rather extensively. It's not complete, but it's more complete than Newtonian mechanics, so it was eventually accepted by the scientific community, which is now trying to find the next, more complete sucessor theory.

In contrast, Intelligent Design — like my first example — makes no testable predictions. It is therefore not a scientific theory and is completely ignored as a possible replacement for evolution by the majority of the scientific community.

Right now, evolution is backed by so many observations that all scientific debate in the field centers on the details, not the basic principle of evolution. I cannot therefore anticipate anyone developing a scientific theory that can explain all those observations without also having evolution at it's core. — Laura Scudder | Talk 15:43, 29 September 2005 (UTC)

(adding during edit conflict with above four responses)

Evolutionary biology is a living science which is full of falsifiable hypotheses. Every publication in systematics which overturns existing ideas about systematics disproves some idea about evolution. If existing phylogenies say that species A and species B are more closely related to one another than they are to species C, that is an evolutionary hypothesis. Now, suppose someone comes along and looks at the genetics of the two species and concludes that species A and C are closely related, and species B is more distantly related. Assuming that their data are sound, this person has disproven an evolutionary hypothesis. Another way of disproving evolution would have been the discovery of an invariant fossil record - that, no matter how far back you go, you find the same set of modern living species. If you could find modern species in hundred million year old strata, then you would have evidence to disprove the hypothesis that the species you found evolved.

It's a little like heliocentric theory - when it was proposed that the earth revolved around the sun, there was a competing hypothesis that the sun revolved around the earth. Heliocentricity was confirmed experimentally, so now someone could come along and say "this is an unfalsifiable theory". Difficult to falsify it now (although there are still geocentrists out there), because it has already been falsified. Similarly, the existence of a fossil record makes it look like evolution is unfalsifiable because there is overwhelming evidence that it has taken place. But it still remains falsifiable. Guettarda 15:46, 29 September 2005 (UTC)

Has geocentricity been fansified? As I understand it the theory works, but is just much more complicated than heliocentricity and it's customary to work sith the simplest solution. DirkvdM 19:43, 29 September 2005 (UTC)

Just a few notes: theories often don't swallow entire previous theories whole (they often decide previous aspects of theories are not longer worth paying attention to, a la Thomas Kuhn); and in this case we're not talking about falsifiability in the sense that any given result will necessarily either favor one whole theory or another (the heliocentric question is not a great example in this case, as there are no "phases of Venus" to compare it to in evolution); and lastly, one of the other reasons that scientists say ID is "not science" is because it invokes non-natural causes as explanations (i.e., it invokes the supernatural), and "science" deals only with the natural world (once you start a science of the "supernatural" world, there is no end of explanations which are equally plausible). The requirement of science to use methodological naturalism has been criticized by IDers (notably Johnson) who say that it necessarily promotes an atheistic view of the world (even though it was originally formulated by Christian scholars, mind you). None of these critics, though, have adequately (in my mind) provided an acceptable view of what a non-materialist methodology would be which doesn't immediately snowball into the possibility of introducing supernatural explanations into anything we don't understand (as a related problem, see god of the gaps). What "is" and what "is not" science is a difficult thing to determine, though, and after a few centuries of intense debate nobody has yet come up with a great way of determining such a thing (see demarcation problem). So it's a sticky issue in a philosophical sense. But most of this (on both sides) is more about politics than it is true philosophy. --Fastfission 16:15, 29 September 2005 (UTC)

re: "...what experiment would disprove evolution?" JBS Haldane famously said fossil rabbits from the Precambrian era would disprove Darwinism. David Sneek 18:07, 29 September 2005 (UTC)

There are lots of 'holes' in evolutionary theory, based partly upon inexplicable fossil evidence. But due to the fact that this evidence was created long before people were around to observe it, it is entirely possible the evidence has been corrupted in some way which is not detectable yet, or maybe ever. Take Piltdown Man as an example.

I think we have deviated from the original question significantly. The answer is yes, the theory of evolution is scientific, for that reason it remains a theory and probably will for some time as the complexity of proving it or disproving it will require a lot of modification of the theory.

Falsification is really about designing an experiment, making a prediction and checking if that holds true. So you might claim that you could create a new animal out of an existing animal. Such as a Russian experiment I once head of where over tens of years tame foxes were created by interbreeding the meekest specimens over and over again. But if something like this fails then that doesn't prove that you couldn't have make it work if you would have done it differently. The big problem here is that there are too many factors at play to design a good laboratory style experiment. Which makes it almost impossible to falsify the evolution theory (or rather too easy, which would invalidate any falsification). And it's even worse with fossil evidence. There's always the chance that you'll find an animal you can't explain. But if you only know the overall way evolution works and not all the intricacies then it's quite possible you can't think of a solution yet. But the point is that it is falsifiable (there is the possibility to find something that disproves it) and that makes it scientific.

Also, as said before, there is just too much evidence to suport it. It 'works', as proven by farmers who have bred loads of types of animals to suit their needs. And it just makes too much sense. It is hard to believe that it might not work. Offspring are on average like their parents and less adapted individuals are less likely to get offspring. Both true right? Take it from there and you get evolution. Whether this explains everything (such as the origin of life) is an altogether different matter. But that this basic form of evolution takes place is just too unavoidable not to be true. DirkvdM 19:43, 29 September 2005 (UTC)

The accumulation of previous evidence has nothing to do with whether a theory is falsified or not or replaced with another. The Newtonian theory accounted for every observation thrown its way with the exception of about three. But those three (perihelion of Mercury, Michelson-Morley experiment, and lastly the deflection of starlight around the sun) were enough to topple the whole thing for most physicists in favor of Einsteinian Relativity in the early 1910s. "Falsification" doesn't at all mean "replace with something totally difference which gives totally different answers." Young Earth Creationism will never be the answer to a falsified evolution (too many simple observations contradict its "predictions" over and over again), but that doesn't mean that the current understanding of evolution (as either fact or theory, in the Gouldian sense) is the last word in any event. --Fastfission 02:25, 30 September 2005 (UTC)

Indeed, falsification has nothing to do with whether there exists an alternative. Forgot to react to that. DirkvdM 17:32, 30 September 2005 (UTC)

AirBus 360 Questions

Does anyone rember the AirBus 360 Emergancy landing? What if when they touched down on back wheels, one (Or both) of the back wheels broke? Would it tip over, and rip the wing off, and the jet enginer blow up? Or would it just tipp and scrapte the tip, and spark? Any Ideas appreciated Lordned 16:44, 29 September 2005 (UTC)

Did you mean JetBlue Airways Flight 292, which was an AirBus 320, or this another incident? In any case, commercial airplanes always touch down on their back wheels first--if one broke, the results would be rather catastrophic, I suspect. Even less-than-complete landing gear collapse can result in ground loop, according to the landing gear article. -- SCZenz 18:11, 29 September 2005 (UTC)

Chemical Structure of HCl

Gah! I'm supposed to be finding the structual formula for Hydrochloric acid. Even on google, all I get is various diagrams of drugs. Help!

• Please tell me this is a joke.. no wait, hold on, while I'm here does anyone know the chemical formula of H2O?--172.208.123.70 14:26, 2 October 2005 (UTC)

The structure of HCl is very simple, it is just H-Cl, now hydrochloric acid is a bit different as HCl needs to be dissolved in water to act as an acid, but the term structural formula is not very appropriate to that.

Have you looked at the Wikipedia article: Hydrochloric acid? --hydnjo talk 20:48, 29 September 2005 (UTC)

Hydrochloric acid is an ionic solution, meaning it consists of H⁺ and Cl^- ions moving around freely in solution (presumably in water). As such, it has no molecular structure. If you mean hydrogen chloride gas, it's just the two atoms with a single covalent bond: H—Cl. --David Wahler (talk) 13:59, 30 September 2005 (UTC)

Mallard Duck

I was told mallard ducks lay from 8 to 13 eggs before they start incubation. My duck has laid 19 eggs and shows no signs of incubating them. How long can the eggs survive and will she ever incubate them? Thank You

Mallards are wild birds. But farmyard domestic ducks are bred from Mallards, and can look similar. Farmyard ducks have been selectively bred (1) to lay more eggs (makes more money for the farmer) and (2) to ignore their eggs after laying (so the farmer can collect them up, and so as not to waste time that the duck could spend laying yet more eggs). So I suspect your bird is a farmyard duck. If you want to hatch the eggs, you will need to buy an incubator and become a poultry farmer. MPF 21:26, 29 September 2005 (UTC)

On the other hand, it might just be simpler to make some omelettes. ;-) Shimgray | talk | 21:34, 29 September 2005 (UTC)

Portable Application Environments

What are Portable Application Environments? How about mobile computing systems? What would you need to know to be a software programmer in these fields?

Thanks! James

This ZDNet article (which is the first result that came up in a Google search) explains that portable application environments are, essentially, an API that can be implemented to run on multiple operating systems and architectures. The Java programming language and its associated bits are the best known example, while the Microsoft .NET environment is another (along with a compatible open source project, the Mono development platform).

I assume that mobile computing systems refers to developing software for personal digital assistants and advanced mobile phones.

To become a professional software programmer in this field, like other types of programming, you should ideally go to college and do a degree in software engineering or computer science. To get experience in these specific portable application environments , you can download basic development tools for at least Java and Mono for free, and start learning them yourself. If you own a PDA or some mobiles, you can download development tools for them, too, and start experimenting with programming on them.--Robert Merkel 22:59, 29 September 2005 (UTC)

where is ghana ?

• See Ghana, which has a location in the first line and a nice clear map. Shimgray | talk | 21:22, 29 September 2005 (UTC)

Hybrids and percentile differences in DNA

What is the percentile difference in DNA between Horses and Donkeys?

For two species to hybridize what is the minimum percentage of DNA that they must have in common? Or does it vary based on the complexity of the organisms?

What is the greatest percentile difference bewteen DNA in Humans?

p.s. How do I watch just my question? --RPlunk 22:17, 29 September 2005 (UTC)

I do not believe you can put your question in Wiki watch list. Here is how I watch my question(s) (only one so far):

1. Post the question hopefully correctly.
2. Get to table of contents and use that to link to the question.
3. The url is now just of the question.
4. Use my browser to capture this place to return to at a later date or time.
5. Do so.

AlMac|^(talk) 01:19, 30 September 2005 (UTC)

who was galileo?

• Who was he?? A heathen I say!!! Spouting heracy about the sun not rotating around earth!!! I'll believe that when I see it.....dirty revolutionists, gravitaion is JUST A THEORY!!!!!!!--172.208.123.70 14:24, 2 October 2005 (UTC)

If you try typing "Galileo" into the search box on the left of this page, and had clicked "search", the very first link is to Galileo Galilei, the subject of your question. --Robert Merkel 22:42, 29 September 2005 (UTC)

Should there be a template for this sort of response? ;) -- SCZenz 22:53, 29 September 2005 (UTC)

I was going to create one which had the format of {{seearticle|Galileo Galilei}} but the amount of coding there is really not much less than "See our article on Galileo Galilei". Plus, we'd lose an opportunity for snarky comments! --Fastfission 23:44, 29 September 2005 (UTC)

But we could put a snarky comment in the template, and make the same one every time! Wouldn't that be fun? -- SCZenz 00:28, 30 September 2005 (UTC)

Create a special 'insult of the day' template that changes each time you view it -- that way you can spend your time coding MediaWiki instead of working at the reference desk. Ojw 21:16, 30 September 2005 (UTC)

Seizure Trigger?

In my psychology class today, while the prof was lecturing about seizures and the brain areas that cause them, another student actually experienced a seizure. Those around him began to call for help and the prof had someone call an ambulance. What I would like to know is whether or not such episopdes can be triggered simply by the discussion of the disorder, or if the lecture and the actual seizure could in any way be related. The prof was not showing any multimedia sequences when the event occured. Thanks

Seizures are not triggered by discussing them, but pseudoseizures can be. alteripse 01:16, 30 September 2005 (UTC)

Peer-to-peer wiki?

Would it be technically possible to develop something like a wiki on a peer-to-peer basis? I am thinking of the vulnerability of wikis to censorship, particularly the Chinese Wikipedia, which has been blocked in the past. I am not proposing anything, just wondering whether it would be possible. Thanks.--Pharos 22:58, 29 September 2005 (UTC)

Yes, it is certainly possible, but who's to stop the censors from blocking the place to download the client from? -Drdisque 00:45, 30 September 2005 (UTC)

Technically possible? Sure. Easy? Not so much. The file sharing peer-to-peer programs (like kazaa or Napster) solve a problem closer to traditional web servers which is distributing the same content to lots of users. Rather than music or video files something like these programs could easily distribute static web pages. The question these sorts of clients throw out to the distributed network is basically "does anyone have a copy of <x>"? All the copies are presumably identical, so if any peer has a copy it's good enough. The essence of a wiki is that the web pages are writable as well as readable by anyone. This makes the question that would need to be thrown out to the distributed network "who has the most recent copy of <x>"? The naive peer-to-peer way to do this requires asking everyone in the network, which would not be feasible for anything except a trivally small network. The trick would be to allow the question to be answered without explicitly asking everyone in the network. If there aren't any centralized servers keeping track of all the content and who has what, I think this is at least a reasonably difficult problem. -- Rick Block (talk) 01:25, 30 September 2005 (UTC)

Aside from the problem of efficiency, there's also the question of security and vandalism prevention. There's nothing to stop anybody from setting up a peer which replaces every page in the wiki with spam and always distributes it as the most recent version. Perhaps you could set up some sort of dynamic, voting-based blacklist but it's not likely to be very easy. --David Wahler (talk) 13:51, 30 September 2005 (UTC)

Global warming

What is global warming?

Please see Global warming. -- Rick Block (talk) 00:20, 30 September 2005 (UTC)

Tis just a wacky liberal conspiracy theory, like evolution and gravity....!

what is carbon dating

Not my sister, I can tell you that much! Seriously, though, see Carbon dating. -- SCZenz 00:37, 30 September 2005 (UTC)

Is that the kind of snarky comment you wanted to put in a template? :) DirkvdM 18:05, 30 September 2005 (UTC)

Nah, that's the kind of snarky comment that proves we shouldn't have a template. It only works with carbon dating...! ;) -- SCZenz 20:18, 30 September 2005 (UTC)

In reference to this specific snarky comment, one would hope that whomever your sister is dating, that they contain substantial amounts of carbon :) --Robert Merkel 04:29, 3 October 2005 (UTC)

History of Prednisone

Who discovered Prednisone and which drug company owned the rights before it became a generic drug?

• It was invented by Arthur Nobile. Not sure when the patent expired. --jpgordon∇∆∇∆ 01:38, 30 September 2005 (UTC)

Your link says the company was Schering. alteripse 01:55, 30 September 2005 (UTC)

what is the name for water tension

The surface tension of water, probably. AySz88^-^ 02:42, 30 September 2005 (UTC)

What is circular DNA?

Can anyone tell me what circular DNA actually is? What is its difference with double helix DNA? Does it duplicate in the same way as double helix? Where can it be found? [this is not a homework question! It's just that I can't find anything about this in my books and google didn't help much] Thanks in advance.

Circular DNA is just what it sounds like: a strand of DNA that is formed into a loop. It replicates like all other DNA, it just doesn't have loose ends. It can be double-stranded or single-stranded. Some places you'll find it: plasmids, bacteria, and mitochondria. - Nunh-huh 03:04, 30 September 2005 (UTC)

In most cases, it's double-stranded, and in those cases, it's not different from a double helix; it still has a double-helical structure. The scale at which the double helix appears is much smaller than the scale of the circle formed by the DNA. Imagine if you took a telephone cord (the coiled kind used to connect the handset to the base on corded phones), unplugged both ends, then plugged both ends into one of those connectors usually used to connect two cords. The cord would now be circular on a large scale, but still coiled--helical--on a smaller scale. Similarly, double-stranded circular DNA is still a double helix on a small scale, and circular on a larger scale. Chuck 16:56, 30 September 2005 (UTC)

Also most bacteria have an enzyme complex that methylates their own DNA as a way of distignuishing it from invading viral DNA, it's essentially a way of adding specificity to certian bacterial lysases, so they don't cleave their own genetic material by accident.. I'm not sure but I imagine it would be hard to methylate helical DNA, but I don't know if the methylation would nesseserily change the conformation, of it it just takes advantage of the conformation change--172.208.123.70 14:16, 2 October 2005 (UTC)

Ignition point of wood in the absence of flame?

I am trying to find out at what temperature will wood ignite in the absence of an open flame? 150 degrees? 160 degrees? Peace. Denis.

• I couldn't tell you for sure, but I'm confident it depends on exactly what kind of wood we're talking about. Redwood? Oak? Maple? Mesquite? - Cobra Ky (talk, contribs) 04:00, 30 September 2005 (UTC)

I believe at least book paper spontaneously ignites at Farenheit 451 (233 Celsius), hence, the name of the book. I would expect most woods would require a higher temperature. -- Rick Block (talk) 04:16, 30 September 2005 (UTC)

Respirable Liquid

Hi. I saw in a movie AND in a misc documentary a "respirable liquid" where animals (including us) can breath with some resistence because the liquid is more dense than the air. Can someone please help me to find out what kind of liquid it is and his formulae? Thank you all in advance. Baruch.

Please see liquid breathing. -- Rick Block (talk) 06:22, 30 September 2005 (UTC)

Information system management

What is meant by metadata? What is meant by intranet and extranet? What is meant by an automated system?--Andeep 06:21, 30 September 2005 (UTC)Andeep

• See metadata, intranet, extranet and automation. - Mgm|^(talk) 07:47, 30 September 2005 (UTC)

Why a pair of bones?

Human beings (and possibly all vertebrates) have two bones parallelly placed in their limbs: Radius and Ulna in the arms and Fibula and Tibia in the legs. But why two bones instead of one? I mean why did the humans body evolve in such a way as to have a pair of bones? What advantage does having two bones have over one single bone that is strong enough ?

Impact and forces are spread over a larger area, without the additional weight that one big bone would add. Additionally, if one bone is broken, then the other will provide some kind of support whilst it heals. This is not important now, but a long time ago, in early land based animals, this may have been a difference between that creature surviving or dying (and this makes a big difference over a few million years of evolution) Proto t c 10:07, 30 September 2005 (UTC)

In additions to the excellent reasons given above, two bones work better than since our joints do not freely rotate in all directions. Think about pronating and supinating your hand when your elbow is held still at 90 degrees. Try to imagine a one bone system that would allow that. You will get the idea. Finally, historical contingency: i.e., many biological mechanisms are not the most efficient imaginable but show traces of gradual imporovement over earlier versions that originally served for other functions. alteripse 10:26, 30 September 2005 (UTC)

staggered vs eclipsed conformations

hi, mu question is what kind of steric energies contribute to the energies of staggered conformations, and which ones contribute for the energy of eclipsed conformations in the case of ethane. thank you

cabi.

• hum, let me think, DO YOUR OWN HOMEWORK, and also, try a little harder to rephrase the question so it doesn't sond like it's right out of a text book, they do have a verbal section on the MCAT you know?--172.208.123.70 14:10, 2 October 2005 (UTC)

• Steric effects are mostly caused by the repulsion of the cloud of electrons surrounding atoms in close proximity of eachother. - Mgm|^(talk) 07:51, 30 September 2005 (UTC)

sex toy

I have a problem in my penis physic and I wanted to know if there is a artificial penis which could be able to inject my cum to my wife's reproduction system or not .

Artificial insemination is indeed possible, but it's not performed with toys. In vitro fertilisation may be another option if you wish to have a child but are not physically able. The best way to start would be to simply get in touch with your doctor. Of course, the Wikipedia:Medical disclaimer applies. Garrett Albright 09:46, 30 September 2005 (UTC)

Right, not toys but kitchen utensils, like a basting syringe. NOTE: I am not recommending you try this and can think of a few potential risks. alteripse 10:21, 30 September 2005 (UTC)

Actually, I remember reading about a strap-on dildo that served this purpose. AFAIR, it was used by women when they wanted to simulate a male ejaculation, but you could obviously use it in this case by using real semen instead of fake. ? Kieff | Talk 10:33, 30 September 2005 (UTC)

Need a documentation tool for C

I have many C files with Javadoc-style comments. Each statement contains a comment before it. I need to generate documentation from this. I am looking for a tool which takes the C files and generates a file from which the documentation and the corresponding source code can be easily extracted (ie, more easily than by parsing the source code). I tried Ccdoc but it processes only header files. I tried Doxygen but it loses the correspondence between the comments and source code. —Masatran 12:44, 30 September 2005 (UTC)

You can set Doxygen so that it creates HTML files that are visually identical to your source code, except with code colouring, and hyperlinks everywhere so that you can follow relationships -- this output seems to be much closer to what you describe than the default doxygen output. Haven't got a copy handy to tell you what the option's called, I'm afraid. Ojw 21:13, 30 September 2005 (UTC)

Unique Human bodypart?

Hi, is there a body part unique to humans? e.g. eyebrows. Thanks - Ieuan Willox

I can't think of an obvious one. However, teeth are often unique to a given species - one of the points of contention over homo florensis involves the numbers of roots on a molar, or something - so you could possibly argue that our teeth are, in fine detail, unique to humans. Other than that, I suspect most things are shared with some form of ape. Shimgray | talk | 13:10, 30 September 2005 (UTC)

The obvious one is People have a much larger brain than any other creature.

Not at all, a wale brain weighs nearly 8kg (next to our puny 1.5kgs), see Whale for more information. --fvw* 13:29, 30 September 2005 (UTC)

Didn't know that, that is why I go to Wiki

Actually, contrary to popular belief, whale brains are pretty unimpressive for their body size, and don't really imply great intelligence (some dolphins, though, do have rather large brains for their body size).--Pharos 15:38, 30 September 2005 (UTC)

Of course the human brain doesn't nesseserily imply intelligence either (;--172.208.123.70 14:05, 2 October 2005 (UTC)

Eyebrows look unique, but most other creatures are so furry the eyebrow is just part of the fur

I don't think there's any, because we didn't evolved all that as a species except for parts of the brain. ? Kieff | Talk 14:47, 30 September 2005 (UTC)

I suppose your phrase was supposed to be "we didn't evolve all that recently as a species". Good point, because we are rather lonely as a species; there's just one race (contrary to popular belief) and our closest relatives aren't all that close (apparently somewhere in our evolutionary history we made a very 'close escape' somewhere). So it's only because we're so young that we haven't evolved further away from other animals. But what parts of the brain are you talking about? I thought that it was just the size (relative to our bodies) that makes our brain unique. DirkvdM 18:29, 30 September 2005 (UTC)

Thanks for correcting. And in respect to that part of the brain, see neopallium and hippocampus for instance. ? Kieff | Talk 07:32, 1 October 2005 (UTC)

A philosopher might say that "consciousness" could count as a body part, but the cognitive scientist would ponder what that would mean and whether or not we know enough to exclude chimps and dolphins from this category. The historian would note that this debate goes back hundreds of years, even before the theory of evolution was accepted in any form. --Fastfission 15:31, 30 September 2005 (UTC)

Here's a philosopher who certainly wouldn't utter such nonsense! :) DirkvdM 18:29, 30 September 2005 (UTC)

Oh, so there's no unique body part, I was sure I'd read somewhere that there was but I must be wrong. I need this information for something I'm writing,and it wouldn't really need to be unique, I suppose, just unique of animals native to Britain? I know I'm asking a lot but I hope you can help.

Do our close primate relatives have Appendixes? User:Zoe|^(talk) 06:09, 1 October 2005 (UTC)

Do they have a belly button? (and did Adam?) Ojw 18:16, 1 October 2005 (UTC)

Speed of light - where's the energy?

If the speed of light slows down when a photon (or em wave) meets an air-glass boundary, then what source of energy accelerates the light photon (or em wave) back to air-speed when it traverses the glass-air boundary?

It turns out that the photon loses no energy when it enters glass, even though it slows down, and therefore needs no extra energy to speed back up later. For the energy of photons we generally write $E=h\nu$, and the frequency ν doesn't change when the photon enters a medium.

I can't come up for a great explaination of why the energy doesn't change, but I can think of an experiment that might make you think it's plausible: tie together three sections of string such that the middle section is a thicker, heavier variety than the first and third sections, tie the end of your Franken-string to the wall, and start moving the other end up and down to make waves. You should see that the waves slow down in the middle bit, but no one is there at the string junction slowing down and then speeding up the waves.

There's no one taking energy out at the first knot and putting it back in at the second knot, so the wave must have the same energy when it's faster in the lighter string as when slower in the heavier string. Hope that helps. — Laura Scudder | Talk 14:16, 30 September 2005 (UTC)

There's an important distinction between the 'speed of light' and the speed of the photons that make up that light. Our article on speed of light has a good explanation of this phenomenon. Essentially, photons travel a the full (vacuum) speed of light at all times. When they travel through a medium (like glass) they repeatedly run into and interact with particles (atoms and molecules in the medium)—the photons are absorbed and then reemitted. These interactions take a small but appreciable amount of time, reducing the apparent average velocity of the light through the medium.

Since the probability of these interactions varies with the wavelength (energy) of the photons, the speed of light in a medium is dependent on wavelength. This is how prisms are able to split light into a spectrum. TenOfAllTrades(talk) 14:26, 30 September 2005 (UTC)

Of course, you can have a fairly self-consistent understanding of light as waves, as long as you stick to the medium. The experiment above with strings of different weights also works in water of various depths. EM waves slow down in a medium because some energy goes into polarizing the medium, e.g. a slight shift in the electron cloud of the molecules the wave passes through. All three of these illustrate a very general concept called impedance, which has to do with the difficulty of creating the displacement/polarization that makes up the wave.

It's interesting to note that this slowing effect happens even when absorption and emission of a particular wavelength are forbidden by quantum mechanics, and so cannot be explained fully by Ten's analogy. But, as in his model, almost all of the energy of polarization is passed along to the next section of medium as the wave travels. The real brain teaser is, where is the energy stored as the photon travels through vacuum? If there's no medium to polarize, what holds the electric field? The short answer is, the photon speeds up so much that, according to special relativity, the media on either side of the vacuum appear to be touching one another from its perspective. Due to length contraction, it doesn't notice any gap at all, even a gap lightyears wide; due to time dilation, the energy is stored for exactly 0 time, therefore no medium is needed to store it.--Joel 19:31, 30 September 2005 (UTC)

A note about 'forbidden' transitions in quantum mechanics. You can actually get away with a great deal if you do it very quickly—very short-lived states have a very broad associated energy uncertainty. Joel's description fits best if you want to deal with photons as waves; the absorption/emission model works best if you want to deal with photons as particles. TenOfAllTrades(talk) 21:01, 30 September 2005 (UTC)

Educational technology companies in Boston

Are there any companies or projects working in educational/instrunctional technologies in Boston?

Thanks for any help!

Mary

Yes, almost certainly. Surely a Boston Yellow pages would be more useful than wikipedia in locating them. Ojw 18:11, 1 October 2005 (UTC)

CHANGES IN CHEST&LUNG VOLUME

WHEN PERFORMING THE HEIMLICH MANEUVER, HOW DOES THIS ACTION CHANGE THE VOLUME OF THE CHEST AND LUNGS? WHY DOES IT CAUSE THE FOOD TO BE FORCED FROM THE AIRWAY? WHOSE LAW EXPLAINS THIS?

THANKS

Have you read the Wikipedia article: Heimlich maneuver? --hydnjo talk 17:07, 30 September 2005 (UTC)

AND NEXT TIME COULD YOU REFRAIN FROM SHOUTING PLEASE? 

Thank you. DirkvdM 18:47, 30 September 2005 (UTC)

It sounds like your teacher wants you to say "The Heimlich maneuver decreases the volume of the lungs" and "Boyle's Law explains this". You should read the latter article to find out why... - Nunh-huh 03:06, 1 October 2005 (UTC) (People don't breathe ideal gases, but it's close enough for government work<g>).

Penis Roll

On last week's episode of "Going Tribal" on the Discovery Channel, the host has his penis "rolled" by natives and it "jumped back into his body". Exactly what does this mean, what occurs, and how did this come to be considered a good idea? Also, does it work in reverse?

Oysters and spirits fact or fiction

I've heard that mixing raw oysters and spirits ("hard liquor") can cause "harmful effects". Exactly what are the effects, and WHY? Or is this just a myth?

Well there is a connection in that some folks thought that the alcohol would kill any "bad" contaminants. It didn't and so started the urban legend. But on a more sober note, this FDA publication documents some potentially severe interactions. --hydnjo talk 19:22, 30 September 2005 (UTC)

That's not really an interaction. Alcoholism can cause liver disease, and liver disease increases susceptibility to Vibrio vulnificus, and oysters can be a source of Vibrio, but having a drink with your oyster causes no problems per se. - Nunh-huh 22:17, 30 September 2005 (UTC)

Correct, I did muddle interaction and susceptibility. The "urban legend" that I was referring to was the belief that if the oysters were of dubious origin then dunkin' them in spirits would rid it of Vibrio (which it didn't) and so when the ill effects occured the eater (rather than blame his poor judgement) would blame the oyster/alcohol combination to save face. --hydnjo talk 23:49, 30 September 2005 (UTC)

Supposedly oysters increase libido and liquor reduces inhibitions, it is not hard to imagine this can result in unexpected parents.

If the two of you have decided you'll sup on oysters and spirits in the first place, I suspect you're half-way there anyway.... - Nunh-huh 22:17, 30 September 2005 (UTC)

... how could you tell? Cheers, --hydnjo talk 23:27, 30 September 2005 (UTC)

Myth or not, I have eaten oysters at several restaurants which had specific cautions on the menu to avoid (much) consumption of spirits with oysters. No reasons were given. Notinasnaid 22:51, 1 October 2005 (UTC)

Urban legends do have a way of infiltrating our culture. Hey, if it's on the menu (or on the television set) it must be true. --hydnjo talk 06:09, 3 October 2005 (UTC)

tickling

Why can you not tickle yourself but shy away when someone tickles you.

Read the Wikipedia article Tickling and the Research section there has an explanation. --hydnjo talk 19:06, 30 September 2005 (UTC)

Apparently, you can tickle yourself, if there's a delay (or other signal-processing step) between your actions and your perception of their effects. I think the experiment involved a motor pushing against your hand -- if someone else controlled it, it tickled. If you controlled it, it didn't tickle. If there was a delay (i.e. no obvious correlation between your movements and the sensation) then it tickled more the longer the delay was. Ojw 18:10, 1 October 2005 (UTC)

Ozone Layer

What fraction of incoming solar UV light does the ozone layer absorb?

If you read the Ozone layer article you will get a better appreciation of what is going on. You'll also find the answer to your question there. --hydnjo talk 19:38, 30 September 2005 (UTC)

Software Chronic Crisis

can anyone explain or send me a link of a summary of Software's Chronic Crisis TRENDS IN COMPUTING by W. Wayt Gibbs, ???

• Set book? Notinasnaid 19:57, 30 September 2005 (UTC)

• • Is this what you are looking for? --hydnjo talk 20:40, 30 September 2005 (UTC)

Mysterious Smokey Lines Around Nuclear Explosions

In many photographs of nuclear explosions I often see smokey lines off to the sides (see [11] for an example). What causes these lines and why do they happen? I've heard of the rope trick effect but these aren't cause by guy lines, and they�re visible for some time after the initial fireball.

• I believe that these are deliberately set markers, so that the effects of the shockwave on the surrounding air can be seen. See [12] for more. -- Bob Mellish 22:12, 30 September 2005 (UTC)

Thanks! I never imagined they were from smoke rockets. I always thought they were some product of the explosion themselves. --138.162.140.37 22:35, 30 September 2005 (UTC)

Butyric acid and odour of socks and blue cheese

Recently in my chemistry class we synthesised esthers using alcohols and carboxyilic acids. One such acid was butyric acid, a smell with a characterstically bad smell.

• I'm going to assume you mean esters, since esther isn't a word--172.208.123.70 14:03, 2 October 2005 (UTC)

My science teacher said that it was this acid that caused the smell of blue cheese and of smelly feet, but neither the wikipedia entry nor a web search seemed to agree with him. Is butyric acid responsible for these smells, and if not, what chemicals are?

• Our article on Butyric acid says it can be found in rancid butter, parmesan cheese and vomit. I don't know whether it can be secreted by smelly feet, but I live for the person with those feet if that's the case. - Mgm|^(talk) 22:29, 30 September 2005 (UTC)

Some things are agreed on: butyric acid has a very unpleasant odor, and it is butyric acid that gives rancid butter or spoiled meat their noxious aromas. Butyric acid is also found in sweat. I suspect that the smells of "smelly feet" and of blue cheese are rather complex affairs, and that the scent of butyric acid is a component of both smells, but that opinions may differ as to which scents predominate in these complex aromas (indeed, I rather suspect that the "mix" varies from foot to foot and cheese to cheese.... - Nunh-huh 22:29, 30 September 2005 (UTC)

It is plausible. Butyric acid is usually formed by the bacterial metabolism of fats, and sweat contains some fat. Physchim62 10:18, 2 October 2005 (UTC)

How does the Internet work?

We have a nice article on the Internet and HowStuffWorks also has a nice article on the infrastructure of the internet (click here) which happens to be the second result if I type the question you asked into Google (click and see). Please consider using a search engine to find your answer first. - Mgm|^(talk) 22:33, 30 September 2005 (UTC)

Heart

What causes blood to enter the right atrium of the heart?

You really should read the Heart and Atrium (anatomy) articles. They will will most likely answer your question. If you still have some confusion after reading the articles then come on back and we'll try to clear things up. --hydnjo talk 00:14, 1 October 2005 (UTC)

I don't think those articles actually do help much - nothing there that I can see on venous physiology. Blood is returned to the heart mostly via the deep venous circulation. These deep veins are enclosed inside contracting muscles, and contain valves that prevent backflow). Sixty percent of the blood present in the calf veins is expelled into the popliteal vein (below the knee) with a single, normal calf muscle contraction. [13]. The deep venous circulation goes into the inferior vena cava (from the legs) or superior vena cava (from above) and thence into the right atrium (from whence our articles have it covered). - Nunh-huh 02:52, 1 October 2005 (UTC)

In reading those articles I concluded that the return flow to the right atrium was a result of the pressure caused by ventricular pumping action that is, pumping blood by the action of the right ventricle into the pulmonary artery and then when it returns from the lungs through the pulmonary veins it goes into the left atrium. Then after going through the mitral valve, the blood is again pumped by the left ventricle this time through the aorta. This final pumping action results in pressuring blood flow throughout the body and returning it through the superior and inferior vena cavae into the right right atrium and through the tricuspid valve into the right ventricle and so on. This is what causes blood to flow (enter) the right atrium. That was my understanding after reading our articles. --hydnjo talk 04:56, 1 October 2005 (UTC) Strike my flawed response. --hydnjo talk 18:32, 1 October 2005 (UTC)

Then our articles are defective! The left ventricle doesn't supply the force that returns the blood to the heart. See [14], [15]. Mean circulatory pressure has no physical meaning as a driving pressure behind venous return. Normal Central Venous Pressure (though it can't be said to control venous return) is only about 2-6 mmHg. - Nunh-huh 07:23, 1 October 2005 (UTC)

Electron migration speed

When I close a switch to a circuit, someone down the line will be aware of that action at (nearly) the Speed of light. My question is, what is the speed of the individual electrons or what is the speed of electron migration as opposed to the signal speed? I hope I said it right, --hydnjo talk 01:27, 1 October 2005 (UTC)

You ask good questions<g>. This is a very complicated subject. See if this page is helpful. - Nunh-huh 02:55, 1 October 2005 (UTC)

This page (thanks Nunh-huh) is exactly what I was looking for. And also this (thanks SCZenz). My comments in the following paragraph have to do with something entirely different, I confused myself again. --hydnjo talk 19:52, 1 October 2005 (UTC)

I was inspired to ask this question from the query above: "Speed of light - where's the energy?" I think I found the answer at Current (electricity) which states that (electron migration speed) "in the near-vacuum inside a cathode ray tube, the electrons travel in near-straight lines ("ballistically") at about a tenth of the speed of light." The link above "(this page)" was also helpful but I was wondering about the speed of electron flow as a fraction of the Speed of light. That's what I was curious about. --hydnjo talk 04:05, 1 October 2005 (UTC)

Actually, I believe that in wires individual electrons are moving extremely slowly (a few cm per hour), and that the electrical signal, while much faster, still travels much slower than the speed of light. See here. -- SCZenz 06:01, 1 October 2005 (UTC)

My chemistry teacher used to quote 1mm per second, but I don't know his source for that number. Ojw 18:04, 1 October 2005 (UTC)

Capillary action and glass a couple small questions.

Hello. And thank you for your time first of all. Ill just cut to the bone.

I have found capillary tubes on the internet at .4 -.6 mm ID. What i would like to do is bend it about 120 deg. Actually i would like to bend sevral tubes together. The thing is im not to good at working with glass. If i were to heat the glass to the point i could bend it i fear i would collaps the id or at the least distort it to the point it would no longer work. With a copper pipe you can simply place a spring slightly larger than the OD of the pipe so as to hold its "roundness" as you make your bend. But with glass and being so thin to begin with i think i would have problems getting and keeping the glass hot enough withought being to hot to get a good bend. If possable i would like to bend say 20 tubes together and hopefully end up with extra capallary paths by default in the space between the tubes. But i also think bending more than one at a time would stretch the outer tubes or crimp the inner ones. And heating all evenly could be tricky.

My question is: How could i bend capillary glass and not destroy the id. And if possable how could i bend more than one at a time so as the bend is matched? How shallow of a bend would i need? And how could i bend more than one so that they could be stacked together close enough. Preferably a way i could do this in my garage without spending a ton of money. : )

Also all the searches i find on capillary action use water. I have read that water and glass is one of the best ways to observe capaillary action as they work great together. But i cant seem to find to much information on other liquids capillary properties. For example does mercury work well in a capaillary sence and what material tube would work well for that. It seems to have good surface tenssion. --68.42.226.224 01:41, 1 October 2005 (UTC)

Heated mercury can get into your bloodstream. It is a poison. The capillary action article indicates you are probably better off choosing another liquid besides mercury, as it would work in reverse. Ancheta Wis 11:56, 1 October 2005 (UTC)

what is a medicinal plant starting with ne

Well here is a start: Ne and then on to Nee and then finally to Nel. I hope it's in there somewhere. --hydnjo talk 04:18, 1 October 2005 (UTC)

Neem is a medicinal tree. --nixie 10:40, 1 October 2005 (UTC)

Category:Herbal & fungal drugs/medicines suggests Nettle. Thryduulf 10:51, 1 October 2005 (UTC)

Time problem

I'm taking the PSAT/NMSQT in a few days, so I need some help. How do you solve the problems that go something like "The clock above shows a time of 5:00. If the clock keeps accurate time, what time will it show exactly 125 hours later? --Neutrality^talk 04:30, 1 October 2005 (UTC)

This is a modular arithmetic problem. If it's 5:00 now, how many hours until the clock shows 05:00 the next time? Ans=24, or perhaps 12 depending on whether we're talking about a 12 or 24 hour clock. So the key is to realize every 24 (or 12) hours gets back to 05:00, so it's 05:00 24 hours later, and 48 hours later, and 72 hours later. The "in between" numbers are just like adding 1-23 hours to 05:00 but starting with a base that's the nearest multiple of 24 (or 12). What this is, is the remainder after dividing the total number of hours by 24 (or 12). 125 hours later is just like 5 hours later (remainder when dividing 125 by 12 or 24 is 5), so the clock says 10:00. -- Rick Block (talk) 04:43, 1 October 2005 (UTC)

125 = 12 * 10 + 5 (=24 * 5 + 5), so the clock will be 5 hours' ahead of its starting position, i.e. 10:00. You just have to look for convenient multiples of 24.

More generally, there's a lot like this in student math competitions, which sounds a bit like what you're doing. For example, the famous 17.5% VAT problem (take 10% by moving the decimal place, halve it to get 5%, halve that to get 2.5%, and add those 3 numbers to get 17.5%) -- it definitely pays to be sneaky and look for the shortcuts. Ojw 17:53, 1 October 2005 (UTC)

In addition, how does one solve problems like this quickly:

How many three-digit numbers greater than 240 can be formed by using three different digits from the set of {1, 2, 3, 4}?

--Neutrality^talk 04:39, 1 October 2005 (UTC)

For numbers greater than 300, you have the possibilities of '3' or '4' followed by any of the remaining digits, following by one of the remaining digits again. This is 2 ('3' or '4') x 3 x 2 = 12 possibilities. For the numbers between 240 and 300, you must select '2' as the first digit, then '4' as the next digit, and then there are two possibilites for the third, so you have an additional 1 x 1 x 2 = 2 results. Total result = 12 + 2 = 14. Most such problems are just a matter of multiplying out the possibilities, but in this case the constraints meant we had to break it into two problems.-gadfium 04:55, 1 October 2005 (UTC)

In general, the number of ways to order (permututate) X different objects is is X! (the factorial of X, i.e 1*2*3*4*...*X). For instance you can order A,B,C in 3!=1*2*3=6 ways(ABC, ACB, BAC, BCA, CAB and CBA). This is because you can select the first thing in 3 ways, the second in 2 ways, and the third in only 1 way, ie. 3*2*1=6 ways total. Hope this helps gkhan 11:32, 1 October 2005 (UTC)

You can start with 2 numbers (3,4). Then you have a choice of 3. Then you have a choice of 2. 2*3*2 = 12. Then notice a couple of possibilities you've missed (241,243). Total 14.

More generally, consider how much time pressure there is. If you can count the results quicker than doing a formula, write down the answer and move on -- multiple-choice tests don't give you any marks for an elegant solution applying formulas from permutation theory, but they often do reward people who can solve 200 questions per hour with reasonable accuracy. Ojw 18:02, 1 October 2005 (UTC)

statistics

What are the limitations of Statistics?

As in what? Prediction? ? Kieff | Talk 10:56, 1 October 2005 (UTC)

If you have a mathematical viewpoint, Statistics all looks like guessing and you can never be sure that you can depend on what you are looking at. (Statistics was first developed for Kings so that they could tax their realms more efficiently. Thus they didn't have to worry about exact answers.) But statisticians can give you the amount by which your guesses are likely to be wrong. Ancheta Wis 11:47, 1 October 2005 (UTC)

statistics is only as accurate as the data set that the statistis are based on. Also, they are subject to systematic bias, however there are tests for such bias, but correcting it usually involves adding another counteracting bias. However, if one knew the true values, then there would obviously be no need to do statistics. -Drdisque 20:48, 1 October 2005 (UTC)

Limit Definition of a Derivative

Find the slope of y=x+1/x at (5,26/25) using the limit definition of a derivative. (I can use the differentiation formulas, but the limit is what troubles me here.)

$m=\lim _{x\to 5}{\frac {x+{\frac {1}{x}}-{\frac {26}{25}}}{x-5}}$.

This reduces to $m=\lim _{x\to 5}{\frac {25x^{2}-26x+25}{25x\times (x-5)}}$. As you see, the numerator of the second limit is prime; I can't evaluate the limit because of the (x-5) in the denominator.

Please help me.

--Henry

$m=\lim _{x\to 5}{\frac {x+{\frac {1}{x}}-5-{\frac {1}{5}}}{x-5}}.\ \mathrm {Next} ,m=\lim _{x\to 5}{\frac {(x-5)+({1 \over x}-{1 \over 5})}{x-5}}$.

Now cancel the (x-5)s out of every term in the expression on the right.

Therefore,$\lim _{x\to 5}(1-{1 \over 5x})=1-{1 \over 25}={24 \over 25}.--Henry$

(added after edit conflict)

First off, it's not 26/25, it's 24/25 :P

It was a coupl of years since I done this, but oh well :P. You're limit definitition is all wrong. The definition of a derivative of a function f(x) is

$f'(x)=\lim _{h\to 0}{\frac {f(x+h)-f(x)}{h}}$

which becomes

$f'(5)=\lim _{h\to 0}{\frac {5+h+{\frac {1}{5+h}}-(5+{\frac {1}{5}})}{h}}$

which simplifies to

$f'(5)=\lim _{h\to 0}{\frac {24-5h}{25-5h}}$

Cheers gkhan 07:43, 1 October 2005 (UTC)

There are two definitions of the derivative. You've each written one of them. -- SCZenz 19:25, 2 October 2005 (UTC)

Wha? Look, last time I checked this was still the ENGLISH Wikipedia! Take your strange language to http://math.wikipedia.org/wiki/ --inks 10:36, 1 October 2005 (UTC)

d00d! y00 suxz! m4th is teh l337 :D gkhan 11:20, 1 October 2005 (UTC)

TV on the computer monitor

I am wondering if such equipment exists that'll put (cable) Television onto my desktop computer monitor. I am not talking about streamed TV over the internet, I want to somehow plug my monitor and speekers into the TV cable line. To do this I would need a cablebox (to change channels), are there any that can connect to my Monitor?

I apologize if my question is badly written, I am tired. -anon

You can't do it without a peripheral card in your PC that accepts your television standard. Right now the TVs that can also serve as computer monitors cost more than bottom of the line PCs. You won't save any money at the moment. This is not an accident. Ancheta Wis 11:38, 1 October 2005 (UTC)

If you already have a video card that will accept Video/Sound Out (or even SCART) somehow, it would just be a matter of connecting it to the right outputs on the cablebox. Have I missed something here?--inks 23:48, 1 October 2005 (UTC)

Normalization of scale

How normailzation of scale is done before performing data anlysis.

First find the largest number in the data set. Then divide your results by that number. Be sure to state that number in your displays. Ancheta Wis 11:34, 1 October 2005 (UTC)

Normalization of scale

Is it necessary to perform normalization of data before data analysis.If so how normailzation of scale is done before performing data anlysis.

sandeep

This depends on what sort of data you are working with, and what sort of information you wish to extract from it. What sort of data are you working with? You might, say, use the standard deviation of the data set as a relative measure if it is finite. You might also want to read nondimensionalization too. --HappyCamper 20:04, 1 October 2005 (UTC)

planets

Planets? ? Kieff | Talk 16:40, 1 October 2005 (UTC)

• Planets!!! Rofl, what is the question?--172.208.123.70 13:54, 2 October 2005 (UTC)

what is dsl?

I suppose you mean Digital Subscriber Line? ? Kieff | Talk 16:40, 1 October 2005 (UTC) Also, in urban slang the acronym can be used to describe "dick sucking lips" -Drdisque 20:42, 1 October 2005 (UTC)

Aluminum can alloy

It says in the magnesium article that it is a component in aluminum soda cans. I can't seem to find any other sources that agree with that. Can anyone verify/disprove that?

what is epidemiology

see epidemiology. Thryduulf 17:27, 1 October 2005 (UTC)

Periodic Table

What is an element that I can see as a soild, liquid, and gas?

Since all solids and liquids distort light enough for you to "see" that something is there, any element that is colored as a gas would fit your criteria. Chlorine is an example but I am sure there are others. alteripse 20:58, 1 October 2005 (UTC)

• Bromine or iodine. Physchim62 10:23, 2 October 2005 (UTC)

what is an catalytic antibody

It's an antibody with catalytic properties, duh... pay attention during your lectures... you specifiy an antibody to mirror the properties of a biological molecule with catalytic activity, usually some sort of enzyme... then you have an analog of an enzyme reactive site that you can target to specific tissue types... try here Catalytic Antibody if it exists--172.208.123.70 13:52, 2 October 2005 (UTC)

Off-Label Use; FDA Application for

Am advised that before a clinical study utilizing an 'already approved' medication (to kill a newly discovered microorganism) will be 'monitored' by a medical Institutional Review Board (IRB) - an application for its (the medication's) "Off-Label Use" must have been submitted to the FDA.

A means of potentially eliminating the No. 2 killer, heart disease, (including stroke, TIAs, carotid artery blockage and other cholesterol related vascular disease) has been discovered and utilizes a well known, broadly used antibiotic to kill the microorganism that causes vascular plaque buildup and other 'unwanted calcium' related conditions.

Can you tell me the procedure for filing such an application with the FDA - for "Off-Label Use" of a medication and where I can find a copy of the application form?

Thank you.

Moving this unsigned question here from the Helpdesk--inks 23:38, 1 October 2005 (UTC)

Most likely, your IRB is requiring you to submit an IND (Investigational New Drug) or NDE (New Drug Evaluation) application with the FDA [16] because your study does not qualify for a waiver. If you don't already know how to do this, you need help from someone who has experience with the process. It's not a task for the weak-hearted, and it can't be done on the basis of advice from Wikipedia! You can start by asking your IRB for additional information. You might also have a look at the FDA site. (I'm assuming you know about previously conducted studies which have failed to show benefit from antibiotics with regard to plaque; (2 studies were published in the April 21 2005 issue of the New England Journal of Medicine) - you'll need to include a literature review in your application.) [17] - Nunh-huh 01:30, 2 October 2005 (UTC)

You pick up the telephone and you call your hospital's IRB. You have to take a several hour course on ethics of human research in order to be a principal investigator for a research project involving people. Then you have to write up a description of your trial (the protocol) and a sample informed consent form. Then you make an appointment to present it to your hospital's IRB at one of their regular meetings. Be prepared to discuss relative risks and some skeptical questions if you are planning to offer your experimental treatment instead of a standard treatment. Remember, part of ethical resarch is designing a study that will have the power to provide a useful answer for the time, trouble, and potential risk of the subjects. What trial design did you have in mind? What recruitment method-- your patients, newspaper ad, referrals? I suspect I am not the only one who thinks anyone who is asking wikipedia how to do medical treatment research is pretty unlikely to know what he is doing or have the resources to do it, but we'll be happy to tell you the procedure. alteripse 01:49, 2 October 2005 (UTC)

convert 1 kilometer to miles

convert 1 kilometer to miles

The easiest way to perform these converions is to use Google - just type 1 kilometre in miles into the seach box, click "search", and you will get the result: 1 kilometer = 0.621371192 miles. Thryduulf 11:00, 2 October 2005 (UTC)

Molecular Biology Techniques / PCR

What is the use of Nonidet P40 or Tween 20 etc. detergents in Polymerase Chain Reaction?

AA

Xenon

What are the main properties of Xenon?

Have you looked at our Xenon article?-gadfium 07:46, 2 October 2005 (UTC)

neurons

can neurons regenerate? - anon

• Very slowly and as far as I know only in young people. Perhaps our article on neurons has some more useful info or links. - Mgm|^(talk) 11:06, 2 October 2005 (UTC)

Very hot area of research. There is now evidence that regeneration can occur in many types of human neurons, and even in adults, against general beliefs from observation of neuroscientists and doctors for most of the last century. You can find articles by searching medline or pubmed for "nerve regenertation". Even googling it gets lots of hits. alteripse 01:22, 3 October 2005 (UTC)

bermuda triangle

Perhaps you are looking for our Bermuda Triangle article? Thryduulf 10:57, 2 October 2005 (UTC)

SNP

what is SNP

To me it means the Scottish Nationalist Party, but the the SNP page gives several other uses as well. Thryduulf 13:50, 2 October 2005 (UTC)

How do the tiny flaps of gills enable the fish to absorb as much oxygen as possible?

Please tell me ASAP.Tdxiang 13:22, 2 October 2005 (UTC)

See Gills. Thryduulf 13:48, 2 October 2005 (UTC)

3D Shape Problems

what is the "End Area" of a 3d shape, can someone explain this term and also how do you find the End area of a Cuboid, triangular prism and cylinder? Also can someone please explain to me how do you find the width of any 3D shape? can someone please help me?

regards nmak3000

Activation of Windows XP

Suppose you have an old computer, and you had to reinstall windows, but suppose you don't know where your activation code is??? Is there anyway to extract that information from the computer itself?? Or are you just out of luck, and have to go buy a new installation disk from microsoft?

Hmm, maybe this could help somehow: http://www.annoyances.org/exec/show/article03-200 ? Kieff | Talk 17:15, 2 October 2005 (UTC)

What are the cultural/ethnic considerations of clients with ESRD?

I'm not sure exactly what you mean by your question, but perhaps you can find some info at Chronic renal failure.

Dental polymers

I'm trying to find information on the use of polymers in denistry, but I'm unable to find any such information on either the Polymer or Denistry pages on Wikipedia. Any suggestions/information?

-Josh/Sycron

• See Dental fillings. --jpgordon∇∆∇∆ 20:37, 2 October 2005 (UTC)

Deriving a logarithm series

How would one go about deriving the following logarithm series expansion?

ln((1+x)/(1-x)) = 2(x + (x^3/3) + (x^5/5) ... )

Thanks in advance! This has been bugging me all day!

This one isn't too bad, but it takes a couple of steps. Bear with me. Oh, and we'd better assume $x\in (-1,1)$. Now, then, first it'll help to split up the problem as follows:

$ln({\frac {1+x}{1-x}})=ln(1+x)-ln(1-x)$

Now we'll work on the second term, and later get the first from it. First, note that

${\frac {1}{1-x}}=1+x+x^{2}+x^{3}+...$

(To see this, just multiply both sides by 1-x.) Now integrating both sides from 0 to x gives:

$-ln(1-x)=x+{\frac {x^{2}}{2}}+{\frac {x^{3}}{3}}+{\frac {x^{4}}{4}}+...$

From this, replacing x by -x, we get

$ln(1+x)=x-{\frac {x^{2}}{2}}+{\frac {x^{3}}{3}}-{\frac {x^{4}}{4}}+...$

Which going back to the first equation gives

$ln({\frac {1+x}{1-x}})=(x-{\frac {x^{2}}{2}}+{\frac {x^{3}}{3}}-{\frac {x^{4}}{4}}+...)+(x+{\frac {x^{2}}{2}}+{\frac {x^{3}}{3}}+{\frac {x^{4}}{4}}+...)=2(x+{\frac {x^{3}}{3}}+{\frac {x^{5}}{5}}+...)$

Hope that helps! -- SCZenz 20:40, 2 October 2005 (UTC)

ATP (adenosine triphosphate)

Since ATP is the direct source of energy for body cells, why not bypass the lengthy digestion and cellular metabolism process for carbohydrate breakdown and eat ATP directly?

• because, if you ate it, it would pass through your digestive system and well, be digested, same thing with just about all your cellular components, you have to synthesize your own--172.208.123.70 21:39, 2 October 2005 (UTC)

It also costs thousands of times more than sugar or starch. alteripse 22:39, 2 October 2005 (UTC)

Mammalian metabolism tends to convert most dietary nutrients into the simple sugar glucose before it degrades it and captures the chemical energy as ATP (via NADH + H+). Hence a drink containing glucose is a perfectly acceptable way to provide the body with an energy precursor. I suppose it beats an iv injection of ATP !

Taylor series expansion in x-a

How would one expand g(x) = sin(x) in powers of x-pi? I have the solution to this, but I haven't been able to get there on my own. Any expanation with steps would be appreciated! Thanks!

Try letting y = x - π, then using sin(x) = sin(y+π) = sin(y)cos(π)+cos(y)sin(π) = -sin(y). Then do the usual expansion about y=0, and substitute back in what y is. Does that work? -- SCZenz 23:15, 2 October 2005 (UTC)

When in doubt, you can always go back to the most general definition of a Taylor expansion near x = a:

$f(x)=f(a)+f^{\prime }(a)(x-a)+{\frac {1}{2}}f^{\prime \prime }(a)(x-a)^{2}+\ldots {\frac {1}{n!}}f^{n}(a)(x-a)^{n}+\ldots$

Notice that this expansion is what you want for a = π and f(x) = sinx. Then

$f(\pi )=\sin \pi =0$

$f^{\prime }(\pi )=\cos \pi =-1$

$f^{\prime \prime }(\pi )=-\sin \pi =0$

$f^{3}(\pi )=-\cos \pi =1$

$f^{4}(\pi )=\sin \pi =0$

Now we can see a pattern: these values of the derivative will simply repeat, and the Taylor series will be:

$\sin x=-(x-\pi )+{\frac {1}{3!}}(x-\pi )^{3}-{\frac {1}{5!}}(x-\pi )^{5}+{\frac {1}{7!}}(x-\pi )^{7}\ldots$

Which matches exactly the expansion of -sin(x - π), which is what you get with SCZenz's method. — Laura Scudder | Talk 23:34, 2 October 2005 (UTC)

glass that shifts from translucent to transparent?

I was wonderin what the type of glass that shifts from translucent to transparent is called. I am an currently designing my own house and am looking to include it in my plans. It is a glass that appears to be clear but when a switch is turned or the door it is made of is closed it becomes much like frosted glass, I have to assume that this is electrically induced, but you know what they say you do when you assume. An example os this the bathroom stall doors in the "Real World: Austin" house. I would greatly appriciate a name and if possible the website of the company that produces it. Thank you very much for any help.

70.22.39.248 23:20, 2 October 2005 (UTC)John

One would think they just stick a lightsource of some kind behind the glass, which allows it to change from transparent to opaque at the flip of a switch, probably normal glass would do--172.208.123.70 23:27, 2 October 2005 (UTC)

Actually, they are special materials (and a large window can cost as much as a human kidney on the black market!). Unfortunetly, our article on the subject is just a stub: Electrochromics. ? Kieff | Talk 00:11, 3 October 2005 (UTC)

what are possible health effects of drinking diet soda?

I already know how bad regular soda is (high calories, high sugar), but I don't know about any negative health effects of diet soda yet. Are there any? --[[User:Revoluci�n|Revoluci�n]] ([[User talk:Revoluci�n|talk]]) 23:56, 2 October 2005 (UTC)

I think this might interest you: health effects of aspartame ? Kieff | Talk 00:13, 3 October 2005 (UTC)

Kieff seems to have it right, I was thinking of phenylalanine, but apparently aspartame is the compound based on that which is found in most 'diet sodas'. I remembered that on Coke cans here in Australia, they warn of the presence of phenylalanine.. perhaps Diet Coke may be useful to you? splintax ^(talk) 03:58, 3 October 2005 (UTC)

I believe that most sodas are moderately acidic, even the diet varieties, and the acid will destroy tooth enamel. See [18].-gadfium 01:22, 3 October 2005 (UTC)

what are the four classes of organic compounds?

See Organic chemistry. The four classes would probably be Aliphatic, Aromatic and Heterocyclic compounds, and polymers. Although you might want to edit your question to be a bit more specific. splintax ^(talk) 03:54, 3 October 2005 (UTC)

what is miasma?

A very pejorative term for mist, or something bad suspended in the atmosphere. Among the politically correct, "special air" is now considered preferable. alteripse 01:05, 3 October 2005 (UTC)

Geometry Area or a Square

What is the area of the square ABCD that has a diagonal of length 12cm?

See pythagorean theorem, and note that a square is just two right triangles. -- SCZenz 01:24, 3 October 2005 (UTC)

More specifically, two isoceles triangles. --jpgordon∇∆∇∆ 03:09, 3 October 2005 (UTC)

I know I'm doing this person's homework for them, but just to clarify - I'll solve the problem. Squareness implies that all sides are equal in length. From Pythagoras' theorem we get:

$a^{2}+b^{2}=c^{2}$

Since c is the length of the diagonal (or the hypotenuse of the triangle inside the square), and a = b (because they are sides of a square), we can say:

$a^{2}+a^{2}=12^{2}$

$2(a^{2})=144$

$a^{2}={\frac {144}{2}}=72$

We could find the square root of 72 to find the side length of the square, but keep in mind that the area of the square is simply the side length squared. Therefore, the area of the square is 72. splintax ^(talk) 03:49, 3 October 2005 (UTC)

Hair texture

Humans evolve different traits according to their environment. For example, people who originated in places close to the equator tend to have darker skin, because it has more melanin and protects them from the sun and skin cancer. Why do black Africans (and I have also heard New Guineans and possibly other people that I don't know about) have curly hair that is so different from most other people who have straight hair (what environmental or other factors led them to develop this type of hair and why was it an advantage)? --KForce 05:39, 3 October 2005 (UTC)

Did you read Hair? This quote may be helpful:

The diameter of a human hair ranges from about 18 µm to 180 µm. In people of European descent, blond hair and black hair are at the thinner end of the scale, while red hair is the thickest. The hair of people of Asian descent is typically thicker in diameter than the hair of other groups.

Cross-section shape of human hair is typically round in people of Asian descent, round to oval in European descent, and nearly flat in African peoples; it is that flatness which allows African hair to attain its frizzly form. In contrast, hair that has a round cross-section will be straight. A strand of straight round cross-section hair that has been flattened, for example, with an edge of a coin, will curl up into a micro-afro.

Hope that helps, although it doesn't answer your question completely. splintax ^(talk) 03:51, 3 October 2005 (UTC)

can birds fly in vaccum

No. See aerofoil and bird flight. Guettarda 05:28, 3 October 2005 (UTC)

• Not to mention that birds breathe. -- Jmabel | Talk 05:29, 3 October 2005 (UTC)

blood vessels in eyes

When you look at a human eye, there is the inner part which is colored and the surrounding area which is white. However in the white part of your eye, you can often see red blood vessels. It appears that sometimes you see more of them than other times (when there are a lot of them, I think it's called blooshot eyes?) What causes these blood vessels to appear more at certain times, is it a sign of an unhealthy eye, and what can be done to prevent lots of blood vessels from appearing or to make visible ones go away? --KForce 05:38, 3 October 2005 (UTC)

Many reasons, one of which is Conjunctivitis. --hydnjo talk 06:00, 3 October 2005 (UTC)

What is analog telephony and its chief concepts?