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December 18

trismus &faciculations of upperlimb during menstrual cycle

married women aged 29yrs with h/o subserosal fibroid (4.5*2.3cms ) (primary infertility )h/o trismus& fasiculation during menstrual cycleon &off episodes -2yrs .Are these symptoms related to menstrual cycle 0r there might be systemic cuase —The preceding unsigned comment was added by 202.54.91.201 (talk) 03:56, 18 December 2006 (UTC).

Not enough info, and probably too individual a case to give a general answer. Obviously, see a doctor for a better answer. alteripse 04:02, 18 December 2006 (UTC)

Sexual abstinence

What are the biological effects of prolonged male sexual abstinence?141.161.34.125 05:43, 18 December 2006 (UTC)

You'll probably find the information you're looking for at Go Ask Alice!, which can be found here. --HappyCamper 13:14, 18 December 2006 (UTC)

I believe that a British study last year concluded that there are no negative effects in your average male -- for about five days. After that... you do the math. :) Vranak 16:42, 18 December 2006 (UTC)

See also Blue balls.  --Lambiam^Talk 16:57, 18 December 2006 (UTC)

If I not mistaken, 'blue balls' traditionally refers to the condition where a male has been excited by his partner, but not to the point of *******. Not simple abstinence. Vranak 17:41, 18 December 2006 (UTC)

Maybe the user is looking for specific information, along the lines of this: Effect of abstinence on sperm acrosin, hypoosmotic swelling, and other semen variables. Perhaps there are effects on blood serum of various hormones as well? Effects of that? Any specific, scientific information? This is a science reference desk, correct?141.161.98.108 21:43, 18 December 2006 (UTC)

See also this: Prostate Specific Antigen Levels: Effect of Sexual Activity. "Determine whether six lifestyle factors (dietary fat, smoking, sleep, alcohol consumption, physical, and sexual activities) associated with non-prostate cancer-related, elevated prostate specific antigen (PSA) levels" "Men who were more sexually active at time T1 were at higher risk of a falsely elevated PSA level >4.0 ng/ml at time T2."141.161.98.108 21:50, 18 December 2006 (UTC)

Does abstinence in this case include masturbation, or sexual intercourse only? I can't imagine how they would be different in health benefits. (Excluding those old ideas like blindness) Crisco 1492 07:53, 21 December 2006 (UTC)

Human Adaptations

I had a weird train of thought, and then thought of this -- I tired looking for answers but I couldn't find anything:

When the species Homo Sapien evolves, what new key characteristics will it possess (micro or macro evolutionary changes)? —The preceding unsigned comment was added by 68.15.52.92 (talk) 06:51, 18 December 2006 (UTC).

I saw an article on this in the newspaper a few weeks ago, I think it was adapted from a reputable source like Nature. But the reality is any prediction for how something may evolve in the future is simply guesswork, whether it be humans or anything else. Organisms will adapt to their environment but we can't predict what the environment will be like, or what adaptations may be favoured, especially as other organisms are also evolving. The best guesses tend to continue on the main trends in human evolution over the last few million years - e.g., further increased brain size, continued hair loss, etc. But as I said above, no one can really say. That's one of the interesting things about historical processes like evolution - they're perfectly explicable after they happen assuming you have enough details, but can't be predicted beforehand. Of course, there's also the possibility that we will be able to use our technology to control our own evolution, such as through genetic engineering, nanotechnology implants, etc. Try a Google search on something like predictions human evolution, you'll find stuff like this--jjron 07:21, 18 December 2006 (UTC)

Arent we,like all other animals, evolving slowly all the time?--Light current 13:36, 18 December 2006 (UTC)

Resistance to disease would be one major adaptation. For example, those who live in Africa and are resistant to AIDS, either based on their behavioral drives or immune system, have a substantial evolutionary advantage over those who aren't. In the developed world the evolutionary pressure is less, because fewer people die, and are thus unable to pass on their genes, due to AIDS. StuRat 13:59, 18 December 2006 (UTC)

The evolutionary pressure is certainly not "less" in the developed world, just different. There would be no pressure only if every person had exactly the same chance of reproduction. Please can we stamp this notion out? alteripse 20:17, 18 December 2006 (UTC)

My post was on resistance to disease. Since disease has less of an effect on reproductive success in the developed world, there is less evolutionary pressure to increase resistance to disease there. However, there is likely more evolutionary pressure in other areas of human biology, yes. StuRat 02:29, 19 December 2006 (UTC)

Which means simply that the factors favoring or impeding reproduction in the developed world are different than those in the underdeveloped world, not that they are less-- that is the misconception suggested by your assertion and re-asserted explicitly by the uneducated author of the next comment. alteripse 15:27, 19 December 2006 (UTC)

Saying the factors are different is essentially the same thing as saying that some factors (like disease resistance) are more important in certain regions (like Africa) than they are in other regions (and, symmetrically, other factors are more important in the reverse regions). We aren't disagreeing here, just using different terminology for the same thing. StuRat 15:46, 19 December 2006 (UTC)

(Edit conflict) Nonsense. In the first world, modern medicine and civilisation has dramatically increased the chance of a human being surviving from conception to reproductive age. It hasn't removed selection pressure entirely (that's basically impossible) but it has decreased the evolutionary drive by a huge amount. Maelin (Talk | Contribs) 02:34, 19 December 2006 (UTC)

You are simply and utterly wrong on this. Modern humans have not transcended reproductive selection, just altered the major factors. Your message suggests you lack a basic understanding of natural selection. Educate yourself. alteripse 15:27, 19 December 2006 (UTC)

I would suggest precisely such a lack of understanding on your part, except that I try not to be so rude in debates. Selection pressure is strongest when it is hard for an organism to survive from conception to reproduction. In such a situation, every biological advantage is precious and every disadvantage is severe. For humans in the first world, it's now quite easy to survive to adulthood - which is obvious from the recent (last few hundred years) increase in human populations. Where once a child born blind would almost certainly not survive to adulthood, now they are marrying happily and having children of their own. Where once susceptability to disease would have likely killed a person during childhood, now modern medicine saves their life - and on they go. We aren't altering the major factors, we're eliminating them. Some new ones may arise as a result of our new lifestyles, but there is no reason to believe they will be as strong as the ones we are steadily working to remove. Maelin (Talk | Contribs) 02:12, 20 December 2006 (UTC)

You really don't understand reproductive selection, do you? Any heritable characteristic that is not universally present in all human beings and is associated (just asssociated, not even causally) with more less reproductive success than average for the population is subject to natural selection. This can be skin color, by a dozen putative direct and indirect mechanisms, it can be susceptibility to environmental chemicals that affect the estrogen receptors, it can be metabolic efficiency and tendency to gain fat or defend fat in food-abundant or food-sparse environments, it can be a differential social habit like breastfeeding or age of first childbearing that is associated with a host of heritable ethnic factors, it can be ability to detoxify environmental chemicals, or the fashion of underwear (affecting sperm count) if the underwear choice has a statistical association with any genetic/ethnic factors, or it can be personality tendencies like libido, shyness, or risk-taking, or cultural practices that delay childbearing like valuing education and women's rights, or genetic susceptibility to addictive substances in the environment that might impair bearing and protecting an infant. You have absolutely no evidence whether or which of these factors might be as important as the genes associated with susceptibility to cholera, or rotavirus, or measles, or malaria, or tuberculosis, or AIDS. You have far too narrow an understanding of possible selection pressures. And yes, ignorance that stubbornly defends itself against evidence and education does strain my civility. alteripse 02:37, 20 December 2006 (UTC)

Please do not post in this thread again until you can do so in an adult fashion. I have not attempted to belittle your intelligence and I'd appreciate the same courtesy. Debate can not continue in the face of outright aggression. Now, I find your assertion that things like choice of underwear and support for the women's rights movement pose as much of a selection pressure as things like susceptability to tuberculosis to be difficult to swallow at best. Sure, there are still selection pressures operating on humanity. I never disputed that. My claim is that existing pressures are insignificant in comparison with those of the past. Obviously there are still external factors that affect whether a child will grow up and procreate. However, I dispute that those selection pressures that exist today have as strong an effect as those that existed before we began to alter our environment to suit ourselves. Maelin (Talk | Contribs) 02:53, 20 December 2006 (UTC)

There are several factors that determine if a person or other animal passes on it's genes. Surviving to reproductive age is one, yes, but there is also the number of offspring produced and the portion of them which survive to reproductive age. While the first and third factors are now less significant in the developed world, due to the high percentage of survivors, this makes the second factor, number of children produced, an even more important measure of reproductive success. StuRat 15:53, 19 December 2006 (UTC)

Remember that survival means nothing to evolution if one does not reproduce. So while medicine has reduced mortality and increased potential fecundity remember natural selection is only relevent if an indvidual reproduces. Beckboyanch 06:52, 21 December 2006 (UTC)

Humans in the future will smell better. —Pengo ^{talk · contribs} 08:02, 28 December 2006 (UTC)

A drop of water in space

I wonder what would happen to a drop of room temperature water when suddenly released into space (or into a vacuum chamber with a temperature of nearly absolute zero). Would it just freeze to a small block of ice, or it wouldn't have time to freeze and it would boil (or possibly explode) first because of the extremely low pressure? Is it the same thing that happens to water when released from the captivity of pressure and the plasma in a particle accelerator when it is no longer contained by the electromagnetic field? --V. Szabolcs 09:03, 18 December 2006 (UTC)

It would slowly evaporate. A vacuum has no temperature; only matter can have a temperature. In space there is nothing to conduct heat away from the water.--Shantavira 09:26, 18 December 2006 (UTC)

It might freeze (cold) and then sublime (low pressure) - I doubt it would explode - a large piece wood be so cooled by any evaporation that the process would stop until it is warmed by some external source, this is the case with comets which are mostly ice..83.100.250.252 09:38, 18 December 2006 (UTC)

As for the plasma/ice comparison - it's similar - but I don't know enough to say more.83.100.250.252 09:38, 18 December 2006 (UTC)

Let me first talk about something I know. If you put water in a vacuum system, at room temperature, and pump the air away, parts of it will boil while other parts freeze. (If the water contains much dissolved air, the boiling will be violent.) Presumably it is evaporative cooling that causes some parts of the water to get cold enough to freeze. After a short time while, you have only ice left, and then, if you wait for many hours, the ice will sublimate away. Now for your actual question. If the water drop was in zero gravity and not in a container, the boiling would probably break it into pieces. (If the water had a lot of dissolved air, this would be many tiny pieces.) After a short time you would have a few ice shards. Eventually these would sublimate away. Cardamon 09:51, 18 December 2006 (UTC)

Shanti is correct in that there is nothing to conduct heat one way or another. However the mechanism at work must be that of radiation. Every body above absolute zero will radiate electromagnetic energy (heat) into space. The maount radiated will depend onthe emissivity and temperatureof the body according to [1] I think. Also every body that is not completely refelective or transmissive at all wavelengths must, by definition, absorb energy. Now we have the dileema: does it freeze or does it boil?

The temperaure of such an object can be calculated by using an energy balance equation such that the radiated enegry is equal to the absorbed energy. In this case the temperature must be stable. In the case of a blob of water, it is highly unlikely to recieve more radiation than it emits (unless near a star) and therfore would probably end uo as ice (like some comets).However, to be sure one would have to do the energy balance calculations 8-)--Light current 12:58, 18 December 2006 (UTC)

OTOH See [[2]] and an interesting question is: what would happen if you threw a small lump of ice into space? Would it sublimate?--Light current 13:23, 18 December 2006 (UTC)

During the Mercury program, and the Gemini program when the astronaut dumped urine from a container out into space, or when water vapor was vented, it froze into little crystals of ice, which reflected sunlight in a sparkling pattern. They referred to it as the "Constellation Urion." [3] Granted, ammonia isn't water, but an ammonia leak on the International space station left an astronaut covered with an inch thick layer or ammonia crystals. He was instructed to brush off what he could, then just stay outside an extra orbit, sightseeing, while more of the crystals sublimated. So I would go with the answer that is would quickly freeze into crystals, then sublimate in a matter of hours. Edison 15:56, 18 December 2006 (UTC)

OK well we cant deny the facts, but what would you say actually cuases the sublimation. Is it just the low (zero) pressure?--Light current 16:01, 18 December 2006 (UTC)

Yes the low pressure (and the vast emptiness of space) - if a water molecule evaporates it's very unlikely to find it's way back - space after all is pretty much the opposite of a closed system.83.100.250.252 17:40, 18 December 2006 (UTC)

Hmm the phase diagram [[4]] for water shows that at low pressure and temp, water could be either solid or gaesous. —The preceding unsigned comment was added by Light current (talk • contribs) 16:17, 18 December 2006 (UTC).

Thanks for the explanations. As I understand now, maybe it boils for a very very short period of time, after which its fill freeze quickly and after that, sublimate. --V. Szabolcs 20:38, 19 December 2006 (UTC)

Or maybe not 8-)--Light current 04:50, 27 December 2006 (UTC)

Formation of a comet

The above question reminded me of another question: How do comets form (or reform) ? That is, they have been described as "dirty snowballs", so the ice should sublimate at a low rate all the time, and at a high rate as they near the Sun (shown by the trail). So, how do they replace this lost mass ? Is it just by ramming water molecules found in space ? They don't appear to be large enough to have a very substantial gravitational field which would be sufficient to pull in water molecules at the speeds they move through space. And, if they don't replace this mass, I would expect comets to have lost all their mass by now, if they are as old as the solar system. StuRat 13:54, 18 December 2006 (UTC)

Why should the ice sumblimate without heat? I dont believe its does. I believe that comets do get some of their ice sublimated as they approach the sun. THis results in the famous comet tails which always point away from the sun due to the solar radiation/particles etc. Since most of the time the comets are a long way from the sun, their icy shells do not sublimate most of the time. Also the amount of ice necessary to give those tails is probably minimal. So Halleys comet should have its tail for a few more million years hopefully. 8-)--Light current 14:00, 18 December 2006 (UTC)

Comets are short-lived (cosmologically speaking). They lose 0.1-1 percent (some sources say even more) of their mass each time they enter the central solar system. They may gain some insignificant amounts of mass back when they are far away from the Sun (at perihelion any collisions with external particles are more likely to reduce mass than increase it.) Eventually what's left is an asteroid, or simply nothing if the comet had no rocky nucleus to begin with. Better hurry if you want to see Halley's Comet; some estimate it is going to lose its volatiles in just another 5600 years. The good news is that the Oort cloud has a good supply of fresh comets; as old comets evaporate, new ones are hurtled towards the inner solar system when they randomly destabilize each others' orbits. Weregerbil 14:19, 18 December 2006 (UTC)

They do not replace their mass if they are in a orbit close to the sun. They slowly desintegrate and after some cycles (depending on course mass and composition) they break apart and are absorbed by the planets of the solar system as meteors, you see in the night, or like the ones which hit Jupiter. I never heard of a comet with a rock as nucleus so thea desintegrate to near nothing. The question how comets form is unsolved. The ice and carbondioxide and the organic materials need low temperatures to form solide bodies, this indicates low temperatures. The minerals detected by stardust and deep impact indicate temperatures above 1000°C at their formation. This gives a slight difference and a monstrous headache for some comet scientists. Rosetta (spacecraft) will give all answers you want in 2014!--Stone 14:49, 18 December 2006 (UTC)

There is speculation that at least some comets have enough mass to end up as asteroids: [5]]. But much of this is indeed conjecture. Btw, the 5600 year remaining lifetime for Halley's comet I quoted above is something I found on one web site; can't say how they came up with that figure. Another site says it loses 0.1% each pass, giving it of the order of ten times that long. Who knows. Weregerbil 15:12, 18 December 2006 (UTC)

Yeah thanks Weregerbil. Thats why i 'vaugified' my previous answer.--Light current 15:15, 18 December 2006 (UTC)

Decaffinated coffee beans

Can someone explain how coffee beans are made 'decaffinated'?

At what point, and how is the caffine removed from the beans?

thanks

81.129.212.135 12:07, 18 December 2006 (UTC)

Welcome to Wikipedia. You can easily look up this topic yourself. Please see Decaffeination. For future questions, try using the search box at the top left of the screen. It's much quicker, and you will probably find a clearer answer. If you still don't understand, add a further question below by clicking the "edit" button to the right of your question title. --Shantavira 12:58, 18 December 2006 (UTC)

Then what do we do with the unwanted caffeine? To make billion tons of Red Bull? -- Toytoy 13:50, 18 December 2006 (UTC)

Put still this is not enough. They make artefical one, because the demand is high for coke and pepsi!--Stone 14:52, 18 December 2006 (UTC)

---

Very good question!

The word 'decaffinated' is a massive fraud.

Beans are not decaffinated: they are caffeine-free by default. Only by roasting beans do you develop caffeine. Vranak 16:39, 18 December 2006 (UTC)

That's contradicted by Caffeine, Decaffeination, Coffee processing, and Coffee. DMacks 17:21, 18 December 2006 (UTC)

Yes, I can't find anything that supports it either. Vranak, what chemical do you think is present in raw coffee beans that is turned into caffeine by roasting? —Keenan Pepper 17:24, 18 December 2006 (UTC)

It is easy to extract caffeine from green coffee beans! Water is good enough! So there is caffeine already in green beans!--Stone 17:34, 18 December 2006 (UTC)

I believe I read this off a placard in Starbucks. However, if this is contradicted across numerous articles in Wikipedia, what I said earlier should be regarded as suspect and wrong until I can check back. Cheers Vranak 17:37, 18 December 2006 (UTC)

Caffeine, like many other plant alkaloids, is the weapon created by plants against insects and other plant eaters. Humans have big livers, therefore, we can break down many plant alkaloids. We even enjoying taking some of them. Anyway, caffeine exists in live plants. Roasting only makes coffee beans taste better. End of story. -- Toytoy 22:30, 18 December 2006 (UTC)

Drying out silica gel

Can I revive a sachet of silica gel beads (dehydrate them again) in the microwave? --Username132 (talk) 16:03, 18 December 2006 (UTC)

• According to this, yes (but be careful.) --jpgordon^∇∆∇∆ 16:09, 18 December 2006 (UTC)

Of course once the gel is dry, the water will be gone and it wont heat so efficiently, will it? What happens if it overheats? --Username132 (talk) 16:24, 18 December 2006 (UTC)

If it gets very hot - it could sinter (possibly) or fuse (ie melt together - unlikely) - this would reduce the ability of the gel to absorb the water next time.83.100.250.252 17:42, 18 December 2006 (UTC)

Walking

what is the right amount of walking i should do weekly? —The preceding unsigned comment was added by 82.167.47.141 (talk) 16:14, 18 December 2006 (UTC).

It will depend upon:

• Your current physical condition

• Your end goal (for example, weight control, desire to become a long-distance race walker, etc.)

Perhaps you want to tell us more? And, of course, only your doctor can tell you whether a given amount of walking will be good for you, personally.

Atlant 16:30, 18 December 2006 (UTC)

Couldn't agree more -- it's totally dependant on how you feel. Weather plays a huge factor here. I find that even if I'm full of energy and the temperature outside is nice, if there's a lot of glare through the clouds, I don't like being outside much.

That said, I walk many kilometers each day (usually), and I consider it to be the second most vital factor in my continuing well being. The first of course is a healthy diet.Vranak 16:37, 18 December 2006 (UTC)

Well assuming you are in good health (the recommendation is to always check with your doctor before embarking upon a fitness routine), IIRC the documentary Supersize Me said 4-5 kilometres a day of walking (including just getting from A to B) was the threshold between healthy and not so much. I don't know if that info is any use to you. Anchoress 16:41, 18 December 2006 (UTC)

Walking alone isn't enough to keep you fit and healthy. You need to do some sort of exercise that will get your heart rate up 3 times a week to lower your risk of heart disease and otherwise stay healthy. Walking is probably better than nothing though, especially if you live in a hilly area. You need to check with your doctor if you plan NOT to do exercise ever in your life. —Pengo ^{talk · contribs} 20:54, 18 December 2006 (UTC)

Pengo, that information isn't consistent with my recent reading; do you have refs for your assertion? I know that used to be the belief, but I've seen a lot of recent data that suggests close to VO2 max exercise isn't necessary for heart health. Anchoress 21:01, 18 December 2006 (UTC)

Walking 'not enough to get fit' (bbc news). My claims likely misrepresenting this study, but it doesn't look like it's out of date as yet. It compares a 10,000-step exercise programme (as mentioned by Chairboy+Rmhermen below) with a more traditional fitness regime of moderate intensity. —Pengo ^{talk · contribs} 01:40, 19 December 2006 (UTC)

Yeah, but the walking participants in that study were working 'at their own pace', and (contrary to the description), the article doesn't say that walking cannot provide the health benefits of a moderate exercise program, but specifically the 10,000 steps program of light exercise apparently does not. It's possible for a lot of people to walk quickly enough to, as the article describes, be winded but able to speak a couple of sentences at the end of the workout. Anchoress 07:20, 19 December 2006 (UTC)

Mmm, I would say that broadly speaking, walking 10-30 kilometers per week will be quite enough to keep you in shape. That said, I do favor more vigorous exercise, say, once a week. I find jogging to be terrible for your joints over the long term. Sports like hockey and soccer that demand lots of moving, turning, flexibility, and overall robustness will really get you in good shape, as long as you don't over-do it. Vranak 21:59, 18 December 2006 (UTC)

A common figure used to describe a healthy amount of walking is 10,000 steps a day. The distance this would cover would be dependent on your stride, of course. - CHAIRBOY (☎) 21:33, 18 December 2006 (UTC)

Link to 10,000 Steps Program Rmhermen 22:39, 18 December 2006 (UTC)

books

How do I go about obtaining printed books from Wikipedia

I don't think that Wikipedia sells books.--Azer Red Si? 16:36, 18 December 2006 (UTC)

If you read German, there's de:Wikipedia:Publikationen, but I don't know of similar projects for any other languages yet. —Keenan Pepper 17:14, 18 December 2006 (UTC)

Video games a cure for ADD?

I heard somewhere a while ago that video games actually help to relieve the symptoms of ADD/ADHD by stimulating the areas of the brain that are underdeveloped because of ADD, and that people with ADD have a higher tendency to become addicted to them because their brains unknowingly crave that stimulation that they provide. Is this credible or no?--Azer Red Si? 16:36, 18 December 2006 (UTC)

Without having any field-specific knowlege, I'd say it is quite doubtfull. General sonsensus is that videogames may increase the occurance of ADD/ADHD becuase they reward a short attention span. If you can find the source that you heard this from, it may be easier to evaluate credibility. 216.254.24.10 19:10, 18 December 2006 (UTC)

But maybe the argument will work on your parents... alteripse 01:40, 19 December 2006 (UTC)

Quantum Mechanics

Hello,

I recently started studying Quantum Mechanics and find the mathematical beauty of this theory quite exceptional. But I haven't really had the opportunity of working with real example, and am still baffled by many animations I find on the net (e.g. http://www.kfunigraz.ac.at/imawww/vqm/pages/samples/104_18a.html or http://www.kfunigraz.ac.at/imawww/vqm/pages/samples/107_12c.html). I would have liked a little link or explanation on how it would be possible to obtain these results (for example, being able to find the curve in the second example as a function of time and position to be able to reproduce a similar graph). And generally, what is the method to obtain such visualizations (e.g. http://winter.group.shef.ac.uk/orbitron/, which obviously depends on isosurfaces, but how would one obtain the equations corresponding to the wave functions ?) ?

In general, I would like to know how one obtains such visualisations (are numerical methods important ? etc...).

Thanks --Xedi 17:22, 18 December 2006 (UTC)

Yes, the topic is very beautiful...it's sort of tricky to answer your question, so let's see if this is good enough to keep you interested. There are a small number of quantum mechanical systems which can be solved exactly, so for those, generally, the plots are based on analytic solutions. The hydrogen-like atom is an example. For more complicated systems, you'll need to resort to more advanced methods such as density functional theory. Numerical methods are at the heart of advanced approaches (and also where all the neat research is taking place today), so in a sense, it's good to know. However, to understand the general concepts, typically, small systems which can be solved with pencil and paper give plenty insight into quantum mechanics. --HappyCamper 20:05, 18 December 2006 (UTC)

Thanks for the hydrogen-like atom link, it's very helpful ! But then, what about the rest ? I mean, for the tunnel effect, for example, where does that visualisation comes from (I mean, mathematically) ? --Xedi 20:18, 18 December 2006 (UTC)

There's some stuff at Quantum tunnelling...but isn't so clearly written. Finite potential barrier (QM) has better information. Essentially, what you do is solve the Schrodinger equation for a system with a step potential, and the one of the solutions that comes out of the calculations is this "tunneling". It depends on the energy of the step and the incident particle. There's a nice drawing at the bottom of the article too. --HappyCamper 21:45, 18 December 2006 (UTC)

Personally I think the best bet is to go through it historically - start with the failings of classical mechanics at the turn of the 20th century (the UV catastrophe and such) and work forward from there. If you can get a cheap second-hand copy, there's a chapter of Atkins' Physical Chemistry which has an excellent introduction. As it's an undergrad chemistry text there's a decent balance between the maths and the actual qualitative effects. Sockatume 05:12, 20 December 2006 (UTC)

Weight Fluctuations

I watch my weight on a daily basis, and note that it fluctuates by as much 2Kg on successive days, eg. 94Kg, 92Kg, 93Kg, 94Kg. Measurements taken at the same time each day on a fully functional scale, with a pretty much regular exercise, eating , drinking, toilet habit. The question then is how can one account for these wide weight fluctuations over such a short period ? Does atmospheric pressure perhaps vary sufficiently from one day to the next to create the effect of "more atmosphere pressing down on my shoulders ?" --Dr snoobab 17:52, 18 December 2006 (UTC)

Water retention. Anchoress 18:00, 18 December 2006 (UTC)

I have had similarly-anomalous weight fluctuations, that I cannot account for merely by thinking about water retention or defecatory diminishment. I am inclined to say that atmospheric conditions can indeed affect weight measurements, in the order of a kilogram or two.

However, I will not say this. I will instead ask: on what surface are your placing your weigh scale? Carpet will not do! Vranak 19:18, 18 December 2006 (UTC)

How on earth can atmospheric conditions affect body mass? Actually, fluid retention is a much more likely explanation. If Mick Jagger, who's 145lbs of solid bone and muscle, can lose 5 pounds during a concert, you or I can gain or lose a pound or two of water weight in a day, due to excess carbohydrate consumption, excess salt consumption, or the reverse. Anchoress 20:49, 18 December 2006 (UTC)

How about temperature effects? I'm sure the reading on the scale depends on ambient temperature, although it might take very large temperature swings to make that much of a difference. -anonymous6494 20:57, 18 December 2006 (UTC)

Well, atmospheric conditions will affect your skin, flesh, and pores, of course. Mick may lose a few pounds of fluid during a concert via evaporation and perspiration. So I guess we're saying the same thing: fluid retention or fluid loss will account for the difference. I'm merely adding that atmospheric conditions will affect how much fluid you retain, or lose. Vranak 21:55, 18 December 2006 (UTC)

Type and quantity of food you eat, water retention (or excretion), bowel movements, swaeting, loss of moisture overnight all have a part to play.--Light current 23:59, 18 December 2006 (UTC)

What type of scale is it ? A balance scale ? StuRat 02:15, 19 December 2006 (UTC)

Normal Bathroom Scale in good condition on a solid flat tiled floor. Thanks for the answers so far !--Dr snoobab 03:54, 19 December 2006 (UTC)

When you say 'normal' scale, I assume you mean the ones with a dial and needle setup rather than say the digital ones. These are a bit notorious for minor fluctuations in measurements, especially the cheaper ones. When using these you must also be wary of parallax errors. These are very easy to make and are independent of the device (i.e., they're an error of the user). Can I suggest you do a little experiment. Weigh yourself say ten times over a ten minute period where the other factors suggested above will have no effect, and see if you get identical results. Try a similar experiment over a longer period, say five times over an hour (without eating, drinking, going to the toilet, or moving the scales) but go away and do something else between measurements and again compare results. See if you get any variations, and if so, whether the variations show a trend. --jjron 14:38, 19 December 2006 (UTC)

I had a "normal" bathroom scale which would tend to stick when the air was moist, like right after a shower. Thus, it would either read high or low, depending on where it decided to stick. StuRat 16:44, 20 December 2006 (UTC)

How does panting reduce heat?

I've been wondering this from some time. According to your article, "Animals with a body covered by fur have limited ability to sweat, and rely heavily on panting to increase evaporation of water across the moist surface of the tongue and mouth". Apparently it has something to do with evaporation of water, which I'm guessing is a release of heat. But this makes no sense; how does increased evaporation in the mouth help cool off the entire body? Much help appreciated ! Xhin 20:41, 18 December 2006 (UTC)

Just like any other cooling mechanism (sweating, elephant ears, etc). The cooled blood flows through the body, distributing the cooling properties. Anchoress 20:51, 18 December 2006 (UTC)

Also, evaporation and radiation have an effect. Evaporation has a cooling effect from any membrane that's wet, and radiation comes into play: By breathing, you're effectively increasing the available surface area for heat to be transfered to. Before breathing/panting, you only have your skin. When you breathe, you pull cool air into your lungs, it is heated by the radiated heat of your internal surfaces, and when you breathe out, the air carries heat with it. Panting would increase the airflow that this cooling method uses, much like blowing a fan over something carries heat away faster, assuming it is suspended in a medium that is cooler than the object. It's all about entropy in the end. - CHAIRBOY (☎) 21:31, 18 December 2006 (UTC)

Panting gets outside air into the body, and inside air out of the body, so to speak. As internal body temperatures are hotter than outside temperatures (unless you live on Venus), panting is an expediant way of swapping hotness for coolness. Vranak 21:52, 18 December 2006 (UTC)

Thanks for your help! As a follow-up question, how does it help when the external temperature is hotter than the internal temperature? (say, a hundred and five or so degrees.) Again, much help appreciated ! Xhin 22:13, 18 December 2006 (UTC)

It is not just a matter of heat being "carried away". Evaporation does actually absorb heat from the environment, thereby cooling it. That is also how the refrigeration of most fridges works, by the evaporation of the refrigerant, thereby achieving temperatures way below the external temperature.  --Lambiam^Talk 22:26, 18 December 2006 (UTC)

Evaporative cooling has the potential to lower the temp of a damp object relative to the surrounding temps. StuRat 23:55, 18 December 2006 (UTC)

I reckon than an overheated dog will cool down faster if he's panting in a freezer than panting in a sauna. In fact, I'm quite certain of that.

That said, your body has to put some effort into 'warming up' frigid air, so keeping comfortable when overheated is not a trivial linear equation by any stretch of the imagination. Vranak 00:01, 19 December 2006 (UTC)

Think of evaporative cooling this way: the temperature of water is the average amount of energy its molecules have. If you evaporate some of the water, the hottest molecules escape, because only the hottest molecules can escape. What are left are cooler molecules, so the temperature goes down.

If you pant in 40-degree weather, evaporative cooling will cool down the blood in your tongue, which will cool down the rest of your body. However, the hot air itself will warm up the blood in your lungs, which will warm up the rest of your body. So I think panting in 40-degree weather will actually make you hotter. --Bowlhover 01:42, 19 December 2006 (UTC)

I disagree. It would be a zero-sum gain, meaning the air is warmed up no more than the tongue is cooled down. However, the heat in the air will mostly not go back into the dog's body. Instead, mostly 40 degree air would be drawn into the dog's lungs, cooling it further. (Note that I was assuming 40 F, which is just over freezing temp, you probably meant 40 C, which is just over body temp. Still, evaporative cooling might work up until something like 50 C.) StuRat 02:01, 19 December 2006 (UTC)

Yes, I was talking about 40 degrees Celsius (that's the world standard, isn't it?). Of course evaporative cooling still works at that temperature, but even if it cools the tongue as much as the air itself heats the lungs, the lungs have more blood and will therefore have a greater effect on body temperature. --Bowlhover 03:12, 19 December 2006 (UTC)

Did anyone find a reference in Wikipedia for panting? I do not find a description of the physiology of panting. --Seejyb 12:06, 19 December 2006 (UTC)

The energy lost from panting when external tempature is hotter than internal tempature do to the energy lost due to phase changes. Q=ml where q is in joules m is mass and l is the latent heat of vaporization. for water that number is 2.26x10^6 j/kg so for every kilogram of water vaporized one loses 2.26x10^6 joules even if the external temp is hotter than the internal. compare this to the energy lost by the change in temp. the equation is heat supplied or removed in changing the heat of a substance is Q=mcΔT where q is the the heat supplied or lost (in joules) m is mass c is the specific heat of the substance and ΔT is the change in temp (in C) waters specfic heat is 4186 j/kgC. so for a ten degree C change in temp for 1 kg of water is 41860 J about 2% of the erngy lost due to phase change. (feel free to check my math i did it all in my head) Beckboyanch 07:17, 21 December 2006 (UTC)

Gargle salty liquid

Why does gargling with really salty water help sooth a sore throat? I've been doing this whenever I have a sore throat for years and it works like a charm! Dismas|^(talk) 21:31, 18 December 2006 (UTC)

According to Gargling, " Gargling with a solution of table salt is known to provide relief for a sore throat because as a natural dehydrator, salt draws water from the inflammations in the throat by osmosis, killing the bacteria which cause the sore throat." Friday (talk) 21:33, 18 December 2006 (UTC)

Generally speaking, swimming, washing, frollicking in, bathing wounds in, and even gargling with unpolluted sea water is wonderful for just about any ailment -- except thirst. Vranak 21:44, 18 December 2006 (UTC)

I don't think the question has been answered. Killing bacteria should not cause INSTANT pain relief, but this salt water method does, at least for 30 minutes or so. --Username132 (talk) 09:33, 23 December 2006 (UTC)

Through the process of osmosis, the swelling is nearly instantaneously eradicated. The swelling causes pain; thus, instant pain relief. —The preceding unsigned comment was added by 70.114.249.248 (talk) 22:48, 23 December 2006 (UTC).

How dangerous, if ingested, is shampoo?

I have swallowed a small amount of shampoo about an hour ago (around 0430 at +8 GMT, malaysia) containing the following: Water, Sodium Laureth Sulfate, Lauramidopropyl Betaine, Sodium Cocoamphoacetate, cocamide MEA, laureth-4, Fragnance (That's all it says), Glycerin, Sodium Benzoate, Polyquanternium-10, alchohol, sodium citrate, PEG/PPG-20/22, Butyl ether Dimethicone, Bis(C13-15 Alkoxy), PG Amodimethicone, Quaternium-33, Citrus Aurantium Bergamia (Bergamo) Fruit extract, Butylene Glycol, propylene glycol, Cl 42053, Methylcloroisothiazolinone, Mentha piperita (peppermint) leaf extract, methylisthiazoline, and eucalyptus globulus leaf extract. The product was Feather® Nature Plus Fresh & Lively Shampoo.

Since I'm feeling fine now my question is: "Is the shampoo really dangerous and, if it is, how much of it would it take to cause permanent and/or fatal consequences?"

—The preceding unsigned comment was added by 219.95.43.30 (talk) 21:41, 18 December 2006 (UTC).

Seek immediate medical attention. Hipocrite - «Talk» 21:43, 18 December 2006 (UTC)

Simply call your GP, or the GP on duty. They know the proper way to get toxicity information. Wikipedia is hardly the place for this. Arakrys 02:40, 28 December 2006 (UTC)

Where I live, in North America, it's common for phone books to list emergency numbers at the front, and they often have free, 24 hour poison control phone numbers that people can call for advice. Does something like that exist in your region? If so, call them. If not, I agree with the previous posters about medical attention. Anchoress 21:51, 18 December 2006 (UTC)

I have removed two comments which attempted to diagnose the severity of the poster's medical condition, prescribed a course of action, or offered a prognosis. I ask that people remember that we can't diagnose or prescribe here on the Reference Desk, that we definitely don't do so in emergent cases, and that we absolutely don't do so for minors. TenOfAllTrades(talk) 23:05, 18 December 2006 (UTC)

I feel almost completely fine now though except for the headache-nausea thing which could be easily explained by 10 hours at the computer. What I've been reading so far about Sodium Laureth Sulfate so far has me still a little worried, stuff like this that I know are biased but still put me into minor panic mode when I read stuff like "can't be metabolized by the liver" and "male fertility loss". Since there's no more need to diagnose and offer prognosises my latest query would then be on the severity of the shampoo in question or any shampoo. I've edited the top with links and the relevant query.--219.95.43.30 23:43, 18 December 2006 (UTC)

Check out some of these links. Anchoress 23:19, 18 December 2006 (UTC)

Did you swallow the actual liquid shampoo or the lather? I can understand accidentally getting lather in your mouth. --24.249.108.133 23:19, 18 December 2006 (UTC)

Actual lather but a while ago I used some liquid soap as mouth wash with no ill effects. I'll check the contents in a moment. It had Sodium Laureth Sulfate, too. And formaldehyde! Hmm. I never swallowed, though. Anyway could you guys tell my how much of the Feather® Nature Plus Fresh & Lively Shampoo would it take to kill a person please? It'd make an awesome opening for conversation (Did you know if you somehow ended up drink x amount of shampoo you'd suffer x horrible symptoms and die?!)--219.95.43.30 23:43, 18 December 2006 (UTC)

Now that you're all well and nothing I say could be construed as medical advice, here goes. I would venture to say that a healthy adult would not be able to kill her or himself by ingesting regular shampoo. Is it a good idea? -absolutely not, it will make you terribly sick, detergents tend to cause violent diarrhea, but this actually helps the stuff pass through you more rapidly. There were a lot of chemicals in that bottle you had, but probably in pretty small amounts; ingredients are listed by weight, and you need very little perfume to smell up a bottle, so probably anything listed after "fragrance" is not too copious. Anyway, even if it smells good, shampoo probably tastes awful, and the near instant vomiting reflex will prevent too much from getting into you anyhow. Also, I would recommend very strongly against getting medical information from the internet unless you are very confident in the source. The web site you linked has no credibility in my book. And neither does much of anything here. If you want medical advice, ask a physician. If you want information on chemicals, look up the MSDS. If you want to settle a bet or are just mildly curious, that's when to consult wikipedia. Tuckerekcut 00:40, 19 December 2006 (UTC)

The MSDSs often go way over the top though, just look up sodium chloride for a good example of this. Plugwash 00:59, 19 December 2006 (UTC)

Haha, the first hit for "MSDS sodium chloride" gives the M. musculus intracervical LD50. (It's 131μ, in case you care). Remember girls, cervical dilators and the dead sea don't mix.Tuckerekcut 01:54, 19 December 2006 (UTC)

Keep in mind that SLS is also an ingredient in most toothpastes and shaving gels. Formaldehyde is usually found in ultra-cheap generic brand shampoos, at least in the USA. It's a cheaper preservative than parabens (but even $2 Suave shampoos are formaldehyde free). --24.249.108.133 23:34, 21 December 2006 (UTC)

For future reference the National Poison Centre [6] would probably be your best bet if your unsure. If you don't know the number, call up Telekom directory services. In some cases, the product may have a number on the back which you can dial. With fairly toxic substances, there will usually be emergency medical instructions as well. Of course, you could either head to hospital or dial 999 if you're genuinely concerned or unsure. If you do head to hospital, make sure you bring the product with you. I would say in many countries, arguably Malaysia as well, if the product doesn't have specific warnings you're probably okay if it's a small amount. You might get sick, but it's unlikely to be anything serious enough to require hospitalisation or emergency medical treatment IMHO. But I can't guarantee this and would urge anyone who ingests something to seek help just in case Nil Einne 14:35, 21 December 2006 (UTC)

Creation of the VCR internal clock

I read the article regarding video machines and it gave very good information regarding the history of vcr's.

I am trying to determine who the inventor of this aspect of the vcr machine is.

Can you help? —The preceding unsigned comment was added by Dedele34 (talk • contribs) 22:56, 18 December 2006 (UTC).

Good question. The VCR article discusses the evolution of the timer mechanism throughout the article, but the word "clock" is never even used. —Pengo ^{talk · contribs} 01:50, 19 December 2006 (UTC)

I remember the older style VCR machines that had an inbuilt clock (I think usually LEDs) which you could also program your shows by, but a separate mechanical counter for the tape. The mechanical counter didn't give you an indication of the actual time taken, just like the tape counters in the old audio tape decks. So which aspect of the clock do you mean, the clock, the program timer, or the counter? Really, all of these were adapted from earlier devices as mentioned, they weren't actually invented for the VCR. Setting the timer to record a show is really just a modification of what alarm clocks do. --jjron 07:46, 19 December 2006 (UTC)

IIRC, some very early Sony U-matic video cassette recorders actually used an analogue clock mechanism; I think I owned one once. I'm not sure the idea of putting a clock in a VCR was ever really "invented"; I think it would have to count as being "obvious". Even a pretty old audio cassette recorder of mine has a switch you can flip that will cause it to automatically enter either record or play mode when power is first applied. Combined with an external timer switch, even it can record programs in your absence.

Atlant 12:30, 19 December 2006 (UTC)

Sense of touch

I often have a very unpleasant feeling while touching some kinds of textiles (something like a combination of formication and kicking by current), and the feeling remains some time after. What's going on (and eventually how to avoid this, except wearing gloves). :) Bisley

The obvious first question: what type of textiles? Man-made fibers (polyester, acrylic, nylon, spandex etc), I am guessing? Vranak 23:55, 18 December 2006 (UTC)

Wool and acrylic, may be some other types used for pullovers in particular. --Bisley —The preceding unsigned comment was added by 83.142.184.86 (talk) 00:32, 19 December 2006 (UTC).

Hyper sensitivity to electrostatic discharge? That's my guess. I don't even know if that's a condition. —Pengo ^{talk · contribs} 01:41, 19 December 2006 (UTC)

I have no idea how to explain this or what to recommend. I think reading about reiki might help though. Vranak 02:36, 19 December 2006 (UTC)

Maybe you have hyperesthesia. - Cybergoth 05:14, 19 December 2006 (UTC)

Quite a few people cannot touch a peach, and even the idea of touching one makes them shiver. If you have the same, it has something to do with the fuzziness. Spandex should be fine, but velvet is sheer torture. It is a tactile equivalent of what other people have with the sound (and the idea) of a nail scratching the blackboard. There is almost certainly a word for this condition, but I don't know it. For eating a peach, it may help to wet it, but wetting is usually not practical and also possibly not helpful for textiles. Other than avoiding it, there seems to be little choice but enduring it.  --Lambiam^Talk 09:12, 19 December 2006 (UTC)

Interesting that our article formication redirects to anogther page ... --HappyCamper 16:35, 19 December 2006 (UTC)

Another name may be paresthesia. That does not explain your sensation, simply labels it:-) --Seejyb 23:23, 19 December 2006 (UTC)

Perhaps a bit OT, but I know someone who can't stand wool. Personally, I don't really have a problem with any fabric but I absolutely can't stand the sound of polystyrene. Nil Einne 14:38, 21 December 2006 (UTC)

December 19

Forensic bloods tests...

I just had this, I think, ridiculous argument with my neighbour about certain substances in the blood, that are tested for forensically. I haven`t checked any of your resources here, sorry. I thought I needed a specific response. 'She' said that cocaine is AUTOMATICALLY tested for, in blood tests, but that anti-freeze, ethyline glycol isn`t. " I " said that ANYTHING 'has to be' tested for...nothing is AUTOMATIC. Who is correct. Thank you for ANY replies. Andrrea216.218.116.1 01:05, 19 December 2006 (UTC)

There are many types of "forensic blood test"s-- the term refers to any test done for legal purposes (as opposed to medical treatment or research, say). An alcohol level drawn after suspected drunk driving is a forensic blood test, as is a sample run on a corpse to determine whether certain kinds of drugs were involved in a death, or drawn from a criminal suspect to see if he can be connected to crime evidence. What context were you arguing about? alteripse 01:37, 19 December 2006 (UTC)

Ty Alterprise...the 'keyword' here is AUTOMATIC. Is cocaine automatically tested for in a port-mordem blood test, regardless of asuumptions of cause of death. I hope that clears my querry somewhat. Andrea216.218.116.1 01:55, 19 December 2006 (UTC)

It also depends on the location, some places will test for more things than others. StuRat 01:56, 19 December 2006 (UTC)

"everything" could be tested for, but that would consume two things the police don't have spare: time and money. so i'd say they test for things they suspect in the real world (as opposed to shows like CSI, where a battery of random testing can be done in a single montage). Xcomradex 02:38, 19 December 2006 (UTC)

The police, like hospital emergency rooms, use standard "tox screens" offered by commercial laboratories. These generally include drugs of abuse (cocaine, amphetamines, opiates, alcohol, benzodiazepines, barbiturates), but generally don't include substances which are ingested only accidentally (or administered for nefarious purposes), such as ethylene glycol. Obviously if foul play or poisoning or a specific poison were suspected, a different toxicology test would be ordered. Ethylene glycol poisoning is most often suspected on the basis of a suggestive history, the presence of an increased anion gap, acidosis, and confirmed by testing only after treatment has begun. A routine post-mortem toxicology screen would almost always include cocaine, and almost always not include ethylene glycol. - Nunh-huh 03:28, 19 December 2006 (UTC)

Nothing is tested for "automatically", whatever you mean by that. Someone makes a policy at a local level, or makes an individual decision for an individual case. The specific tests obtained according to policy or for the individual case would depend on what was available readily and what specific problems were suspected. As mentioned by Nunh-hunh, in many areas there are standard "batteries" of tests referred to as a "toxicology screen" that are obtained if a drug or poison effect is suspected. The contents of these screens have varied in different years, different locations, and different laboratories. alteripse 04:55, 19 December 2006 (UTC)

The difference with your neighbour may simply be in the point of view associated with the use of the term "automatic". When she says it is "automatically tested for", she may mean that the people ordering the test don't have to do "something specific" to get the cocaine screening, since it is routinely tested for, so from their point of view it will happen as it were "by itself", "automatically". The lab people probably have to do something specific to obtain the lab results; from their point of view it is not quite automatic.  --Lambiam^Talk 09:27, 19 December 2006 (UTC)

Thank you all for your fine responses. Andrea216.218.116.1 16:05, 20 December 2006 (UTC)

Pseudoephedrine shelf life

What is the shelf life of pseudoephedrine pills? Can they last for decades? Do they have to be stored in an especially cool or dry place?

The reason I ask is that I just found out about the stupid sales restrictions in the US and I'm worried it might become even harder to obtain. In that case a supply will have been a good investment, and if not, it doesn't matter because I use it often and would have bought that much eventually anyway. And if some people from the FDA come to see me, I don't care because I'm not running a meth lab. Is there anything wrong with this plan? —Keenan Pepper 03:06, 19 December 2006 (UTC)

Based on Sudafed, the tablets should have shelf-life of a couple years if kept in a light/water proof pill bottle at room temperature. As with any question of this kind, you should refer primarily to the documentation accompanying the pills. Dragons flight 16:02, 19 December 2006 (UTC)

Pseudoephedrine of itself if kept in a closed dark bottle (no light, limited oxygen) would last for many many years. Exposure to light - especially outdoors with uv is a sure way to cause it to 'go off'. This shouldn't be a problem for you.

Cool dark dry places are always the best - but the difference between store at 20C and 10C would be negligable.

Keep them in the packaging - or if they are in a bottle - you could put cling film or similar between bottle and lid to ensure an airtight seal - probably not necessary though.

Other substances in the pills eg the filler might alter the shelf life.83.100.158.248 18:18, 19 December 2006 (UTC)

I remember reading in an article in some magazine that the efficacy of medicines in pill form lasted far longer (years) than the "use by" date, although it might drop a little (say 95% effective instead of 100%). In fact, a quick Google search revealed [7]. howcheng {chat} 18:40, 19 December 2006 (UTC)

I was wondering what you want the pseudoephedrine for - and what are these sales restrictions. 83.100.158.248 18:56, 19 December 2006 (UTC)

Pseudoephedrine is a very effect nasal decongestant. Unfortunately it can also be used to create methamphetamine. Thus, in the US there are federal regulations as to how it can be sold. Not having bought any recently (the phenylephrine that replaced it works decently for me), I can't testify as to the restrictions, but I remember reading in the papers that it's basically a cap on the amount you can purchase, and I believe you may have to sign a log book when you buy it (like when you pick up a prescription). However, it's still widely available at all major pharmacies -- just at the pharmacy desk instead of on the shelf. howcheng {chat} 19:00, 19 December 2006 (UTC)

I can't help noticing that phenylephrine would be a good precursor for methoxyamphetamine - maybe that will be controlled as to the amount that can be bought too.

(above wasn't added by me) Here in NZ, it's quite restriced as well. Not sure of the specifics. But many pharmicies, especially the smaller ones don't stock it (to avoid being robbed) and I think some of the ones that do will only sell it to customers they have an existing relationship with (I don't think this is a legal requirement) Nil Einne 14:42, 21 December 2006 (UTC)

I should take the opportunity to point out that if you knowingly take medicines that are past their sell by date you may be at a disadvantage legally if something goes wrong. I just have to mention that obviously - the sell by date is there for your safety (and safety of the company that produces them from expensive legal cases etc etc). I wouldn't recommend stockpiling.83.100.158.248 19:09, 19 December 2006 (UTC)

The chemistry with link to MSDS page says that it is "stable", mentioning also: "Combustible. Incompatible with strong oxidizing agents. May discolour upon exposure to light." The requirement for the MSDS "stability" entry is that it must state: "1. Conditions to avoid. 2. Incompatibility with other materials. 3. Hazardous decomposition products. 4. Hazardous polymerization." So if there are no warnings about such events, and the stuff is kept dry, dark, and cool, (in N2?) it seems pretty safe. The original articles (Pubmed) describing the "stability of pseudoephedrine" are dated 1955 and thereabouts, so one would have to search a live library for those. --Seejyb 23:48, 19 December 2006 (UTC)

Not a lawyer by any means but are you sure of your claims from a legal standpoint? Here in NZ, I would say if something did happen to you because of the drug, you would probably still be entitled to compensation or whatever if something happened to you because of the drug provided you could prove it wasn't because of the drug being past it's sell by date. This could be difficult in some case, but I would say if the effect was a documented problem with the drug that later became known. If there was believe the drug being past it's sell by date could have made the problem worse, then there would probably be a consideration of relative liability I guess. Of course it can be rather difficult to prove a drug was the cause of your problem, and liability issues are different in NZ anyway so you don't tend to get the big lawsuits that seem to be the norm in the US. Nil Einne 14:53, 21 December 2006 (UTC)

Contradicting Articles

Unless I'm mistaken, the marijuana article implies in the lethal dose section that more marijuana is required orally for a lethal dose than smoked, while the THC article implies that more is required smoked than eaten for a lethal dose. If I am mistaken, could somone please say so and possibly explain why, or if I'm not could somone tell me which article is correct. BeefJeaunt 06:18, 19 December 2006 (UTC)

Both of the articles that you linked specify 1270 mg/kg as the LD50 for THC administered orally. I see no contradiction.141.161.222.56 09:07, 19 December 2006 (UTC)

For the LD50 (in rats) I see this:

Cannabis (drug): orally: 1270 mg/kg; inhalation: 42 mg/kg.

Tetrahydrocannabinol: orally: 1270 mg/kg; smoking: "much more".

To reconcile these claims, we need to assume that "much more" than 96.7% of the THC is lost through burning or exhalation, which seems really high to me (no pun intended). Rather, I suspect the editor of the "much more" statement in the THC article mistakenly assumed that the inhalation LD50 is essentially the same as for oral administration, so that the wording "much more" reflects the editor's (reasonable) assumption that in smoking much more than 0% of the THC does not make it to the body.  --Lambiam^Talk 09:55, 19 December 2006 (UTC)

You're probably right. That was apparently added here [8] in an attempt to improve the previous anon's addition. More importantly perhaps, there's IMHO no such thing as a LD50 that's much more. LD50 is a specific measure and it's determined in a specific way. If you haven't determined it, then you don't know what the LD50 is. There's also AFAIK no such thing as a smoking as a method of ingestion. Only inhalation. LD50 also only works on pure compounds. There'no such thing as an LD50 of marijuana or of table salt. Only THC and sodium chloride Nil Einne 15:12, 21 December 2006 (UTC)

Parasitic wasps and humans

What would happen if a parasitic wasp were to try to lay its eggs into a human? JIP | Talk 10:34, 19 December 2006 (UTC)

What species? 68.39.174.238 13:47, 19 December 2006 (UTC)

It'd get swatted :-). No, seriously, parasitic wasps tend to lay their eggs in invertebrates, predominately other arthropods such as caterpillars, moths, flies, spiders, etc, and generally in the immature stages of these arthropods. The wasp larvae are internal parasites of the host, and ultimately kill it. Thus the hosts are fairly specific, and are probably genetically programmed into the wasp. If, despite this, it did try to lay in a large mammal like a human, even if it did get the eggs laid it would only be in or just below the epidermis and the eggs would either be destroyed by the body's defences or would not be able to get to a suitable location in the body in order to survive. And if it did overcome all these obstacles, when the larva matured, it would not kill the host, so would probably die itself anyway. --jjron 14:15, 19 December 2006 (UTC)

parasitic wasps (braconidae, ichneumonidae, sphecidae, etc.) paralyse their prey temporarily or permanently; the prey is then consumed slowly by the vasp larva(e). Some wasps also remove antennae of the prey insect. The larvae are "genetically programmed" not to gnaw at the vital organs of the prey until the very last moment, to keep the prey alive as long as possible (sad but true). I do not think that would work with large mammals as prey, so human kind is probably safe. Why there are no wasps preying, say, on mice is beyond me. Oestridae flies, on the other hand, are known to parasitize large mammals. Larvae develop under the skin (see botfly), in nasal passages, or in the intestines. The results are rather nasty, though very seldom fatal. Dr_Dima.

Not really adding anything to the discussion in terms of wasps, but did you guys read about those couple of botflies that were burrowed into a guy's balls for three weeks and then surgically removed while still alive? (Warning: Crude language in the poem.) DAY-um! That's got to be way worse than that one time I swallowed some shampoo. Waaay worse.--Itrade

aromatic carbon

Heya,

I usually read the articles in spacedaily every day and today there is an article entitled:

The Basic Rules of the Universe.

In it, Pascale Ehrenfreund states a great deal concerning carbon found in the universe and puts special importance on aromatic carbon.

Unfortunately I loose her around here - what is aromatic carbon? Why is it so important? Is it what makes carbon able to create the complex structures which allow life?

So I've had a little look at google but all the answers are hard core chemistry - which isn't much use when I'm not getting the fundimental idea of what it is or what it relates to.

Any/all help would be greatly appreciated.

Kind regards. —The preceding unsigned comment was added by 194.63.116.72 (talk) 13:33, 19 December 2006 (UTC).

This may be of use to you: Aromatic_hydrocarbon. —The preceding unsigned comment was added by Moffo (talk • contribs) 13:37, 19 December 2006 (UTC).

Hi, (it always helps if you can link to stuff you're asking about - I found it anyway here http://www.spacedaily.com/reports/The_Basic_Rules_Of_The_Universe_999.html I put it in so other people can read it.)87.102.5.69 13:47, 19 December 2006 (UTC)

"Aromatic" in organic chemistry means there's a benzene ring in it somewhere: Basically six carbon atoms in a hexagonal circle. 68.39.174.238 13:48, 19 December 2006 (UTC)

Polycyclic aromatic hydrocarbon is definately the article you should look at.87.102.5.69 13:56, 19 December 2006 (UTC)

A little more here http://www.astrochem.org/PAHs.html87.102.5.69 13:57, 19 December 2006 (UTC)

To add one more to the list of recommended reading; see aromaticity. --Ed (Edgar181) 13:58, 19 December 2006 (UTC)

Personal allergy

Is it possible for one person to be allergic to another? Marco polo 20:16, 19 December 2006 (UTC)

Ye-es...though it's pretty rare. The most-reported manifestation (though still quite unusual) is for a woman to be allergic to her sexual partner's sperm: [9].

If you have allergic reactions when a person is present, it's much more likely a reaction to that person's cosmetics, perfume, deodorant, skin cream, laundry detergent, fabric softener, pet dander or fur, etc. than to the person himself. TenOfAllTrades(talk) 20:36, 19 December 2006 (UTC)

I don't see how someone could be allergic to an actual person, instead of the things the person wears/eats/uses. We're all made up of almost the same substances. --Bowlhover 20:42, 19 December 2006 (UTC)

As noted in the article I linked, women can be allergic to male sperm. Sperm contains (among other things) proteins secreted by the prostate gland. These proteins are not going to be present in a normal human female body—and may, therefore, be recognized as foreign by her immune system. That's why sperm is just about the only bit of a human being likely to provoke an allergic reaction. TenOfAllTrades(talk) 20:48, 19 December 2006 (UTC)

Right. I meant other than sperm. --Bowlhover 21:53, 19 December 2006 (UTC)

The need for matching blood types is essentially another example. Getting donor blood with the wrong antigens will provoke an immune response. Dragons flight 21:56, 19 December 2006 (UTC)

If we're talking internally, people generally don't match in their Human leukocyte antigens. Donor organs ideally need to match. BTW, while people can be allergic to sperm I believe, if they're allergic to one of the proteins in semen but not sperm, I would suggest it's more accurate to say they're allergic to semen. Nil Einne 05:39, 22 December 2006 (UTC)

Super Natural Events

Hi. I read somewhere there was a phenomenon where a Different You from a Different Dimension crosses over to visit the You Now in This Dimension. Does anyone know what this is called or where I can read information on this?

It's a popular science fiction device. Murray Leinster is often credited with writing the first story to use it ("Sidewise in Time", 1934). (My mistake; the characters do switch universes, but don't meet their counterparts.) See Parallel universe (fiction). Clarityfiend 21:52, 19 December 2006 (UTC)

So there isn't actual documentation of people experiencing this?

There isn't really any scientifically verified documentation of ANYTHING supernatural happening, full stop. Otherwise organisations like Skeptics Society would probably have to give up... As far as documentation of people claiming things like this happening, there are plenty. JZ Knight is one contemporary example of such a person. Not quite exactly the situation you are talking about though. Vespine 00:18, 20 December 2006 (UTC)

It would be something like seeing your Doppelgänger, thought to be a bad omen. Edison 04:04, 20 December 2006 (UTC)

I imagine you would teach your Doppelganger some of the differences between your dimensions, and you'd both learn a valuable moral lesson before he/she left. He'd go on to jump the shark in the fourth season and dwindle into obscurity. Sockatume 06:29, 20 December 2006 (UTC)

Ouch! I'm *sure* you aren't talking about a certain vampire slayer! ;) --24.249.108.133 21:36, 22 December 2006 (UTC)

Blind People

I've been wondering can a person who is born blind, form mental images and visualize things? --soccerman —The preceding unsigned comment was added by 204.16.236.254 (talk) 23:08, 19 December 2006 (UTC).

Your 'mind's eye' is informed by far more than just visual information. Even memory plays a big role. Vranak 15:42, 20 December 2006 (UTC)

(after edit confict) The term "mental image" usually denotes a more abstract concept than image in the sense of a picture offering a two-dimensional visual representation. While people born blind do not visualize things in the latter, stricter sense, they have mental imagery like everyone else in the more general sense. They can certainly form an internal "image" of shapes and spatial relationships, and for instance mentally rotate objects to see how they would fit together, often better than most seeing people. And yes, they use the verb "to see" metaphorically themselves just like I did in the last sentence.  --Lambiam^Talk 15:50, 20 December 2006 (UTC)

I work with the blind, and they do fine with things that are both visual, and non-visual, like object shapes. Those who have been blind since birth do have trouble with things that are only visual, though, like colors and shades. Light, on the other hand, can be "visualized" by feeling sunlight on their faces. StuRat 16:24, 20 December 2006 (UTC)

You might be interested to read "The Country of the Blind" a short story by H.G.Wells about a man with normal sight visiting a country whose inhabitants have been blind for 15 generations. Not particularly scientific but very enlighting. Keria 17:04, 20 December 2006 (UTC)

Thanks to everyone who has helped answer my question. You've all been very helpful. --soccerman

Musical Appeal

I was wondering, why does some music appeal to some people while not to others? (Is there a Wikipedia article about this?)--Codell ^{[ Talk]} 23:20, 19 December 2006 (UTC)

Same reason art or food or anything appeals to some people while not to others. —Keenan Pepper 17:07, 20 December 2006 (UTC)

December 20

New cochleas

Due to the ossification of a person's cochleas, a cochlear implant is only partially provided. Typically, a string of electrodes are fed into a cochlea that has dead or damaged "hairs". However, with cochlear ossification, such threading is not possible. A drill, being straight, cannot make room along the spiral shape of the cochlea, but instead penetrate the cochlea at two angles for insertion of only a partial array of electrodes. This damages the cochlea permanently, which is why cochlear implant users generally leave one ear available for future advancements. My question is this: What would be the science behind providing someone with new cochleas, if the damaged cochlea was the reason for a person's deafness? I imagine two methods -- growing cochleas in a petri-dish in the lab (someone grew an organ successfully this past month, so this seems possible), or the implantation of cochleas from an organ donor. What would be the difficulties with these methods as well? —Erik (talk • contrib) - 00:32, 20 December 2006 (UTC)

In mammals, it can be tricky to get axons to grow to their "normal" targets in an adult brain. Regeneration and replacement in the vertebrate inner ear. --JWSchmidt 01:02, 20 December 2006 (UTC)

What about cochlear implantation, not the artificial method? —Erik (talk • contrib) - 01:55, 20 December 2006 (UTC)

Same problem as JWSchmidt pointed out: it's not just the ear it's the brain that has lost the ability to hear. --Cody.Pope 03:24, 20 December 2006 (UTC)

Not sure if I understand. Where would the axon growth take place? When people go deaf, their hearing can be restored with cochlear implants because the technology serves as a substitute function to the cochleas. I don't think it means that the brain loses the ability to hear, as I know someone who has been deaf for 7 years and will get a cochlear implant in the coming year based on doctor's recommendation. What is the difficulty in placing organ donors' cochleas in deaf people to replace the damaged cochleas -- is it the connection between the new cochlea and the old brain that must be made? —Erik (talk • contrib) - 03:47, 20 December 2006 (UTC)

When signals from a sensory organ cease traveling to the brain, the areas of the brain receiving those signals go into atrophy. Meaning that over time, those brain areas decay. Depending on the age of the individual, reconnecting or replacing the organ can have some effect. However, as we age the brain become less plastic, meaning that it becomes harder and harder to re-grow/re-connect those areas lost to atrophy. So, concerning a cochlear implant, whether it be artificially or an actual donor implant, the amount of information that brain can interpret as sounds will always be far less than before. --Cody.Pope 04:01, 20 December 2006 (UTC) Also, sorry about the minor confusion as I didn't read JWSchmidt comment quite close enough. --Cody.Pope 04:07, 20 December 2006 (UTC)

What if the implantation of organ donors' cochleas happened shortly after a person went deaf? For example, the person is stricken with bacterial meningitis and loses his hearing. Can the person recover his hearing by receiving new cochleas shortly after his hearing loss? I'm just curious about the issue of implanting foreign cochleas (like how it compares to receiving a new hand) or what medical constraints prevent us from doing that now. —Erik (talk • contrib) - 05:36, 20 December 2006 (UTC)

I'm not sure, but if you check out the image, I'd say the area is just to delicate to remove. The cochlea is directly connected to the vestibular canals, and if you did anything to them you'd loss your sense of balance. The implant, while somewhat invasive, is just placed in the cochlea. --Cody.Pope 22:12, 20 December 2006 (UTC)

There is some research investigating the ability of new axons to grow into the Organ of Corti; Engraftment and differentiation of embryonic stem cell-derived neural progenitor cells in the cochlear nerve trunk: growth of processes into the organ of Corti, Auditory hair cell explant co-cultures promote the differentiation of stem cells into bipolar neurons. --JWSchmidt 14:30, 20 December 2006 (UTC)

Sauna questions

1) Should I have any doubt bringing a Ipod or a water bottle in the sauna? I keep thinking that it's possible that the humidity or sweat will mess up the inside of the Ipod.

Hrm. I'd advise against it. The humidity might well be an issue. --Brad Beattie (talk) 01:28, 20 December 2006 (UTC)

2) How many calories burn while in the sauna?

3) Also, do calories always burn at a steady pace no matter how long you go (doing the same thing for a long time) or do they burn more and more as you keep burning?

4) AND, how do you change the color of your signature? PitchBlack 01:04, 20 December 2006 (UTC)

Check out the my preferences link at the top right of the page when you're logged in. The signature field is where you want to change things. Try to make sure you respect the signature guidelines when you change things though. --Brad Beattie (talk) 01:28, 20 December 2006 (UTC)

(Edit Conflict)

1) The inside of a sauna is extremely dry, so humidity is very low. The high temperature might not be great for your iPod if you put it down on a hot surface, and your sweat will be bad for it if it gets inside, but if those two things don't happen, the iPod will be able to outlive you in a sauna.

2) Fewer than you would burn at the bus stop. Since a sauna is hotter than your body temp, your body will try to scrub off heat by sweating, opening peripheral blood vessels, and slowing metabolism. You will dehydrate faster, but you will burn calories slower.

3) A given movement/exercise/lifestyle will always burn the same amount of calories (more or less, I know I'm gonna get heckled for that one), however, the energy source your body uses for that exercise will change over time from sugars to fats and protein (I won't get into it...). You can add two 30 min aerobic sessions together and get the equivalent of a one-hour session, if that is what your asking.

4) see Customisation#User_name_and_signatures Tuckerekcut 01:41, 20 December 2006 (UTC)

So, will you have any benefit of burning calories for a long time (about an hour), or will it be the same as if you do 6 10-minute aerobic sessions? PitchBlack 02:39, 20 December 2006 (UTC)

Should be about the same. Tuckerekcut 02:47, 20 December 2006 (UTC)

Don't bring water or iped into sauna. The water can ruin the heating mechanism, and the heat can ruin the music mechanism. Second, don't worry about how many calories you burn. The idea of a sauna is something like 'sweating out toxins', though even this is probably not quite accurate. Vranak 03:27, 20 December 2006 (UTC)

Googling for sauna calories (try it!) suggests a sauna does burn calories at a pretty high rate. Are those search results based on medical studies or are they marketing? You tell me! As to an iPod in a sauna: don't. If you look at the manual of most any electronic device it will specify an operational temperature range, and a sauna is almost certainly way out of that range. Some types of saunas have high moisture ("steam room"), some are dry, so that may or may not kill your iPod too. Weregerbil 13:31, 20 December 2006 (UTC)

empirical formula

how do i get the empirical formula, when given percent composition of a substance :49.3% C, 6.9% H, 43.8% O. i got 4.10 for the ratio of C and cant figure out from there will someone please walk me through,thanks --69.140.210.163 03:35, 20 December 2006 (UTC)

Assuming the percentages refer to weight/mass, you need to convert all three to moles (you've already calculated it for C). You'll end up with decimal places, so multiply them till you get the smallest integers. Clarityfiend 04:54, 20 December 2006 (UTC)

A good way to get to integers here is to divide through by the smallest value. For example if you wind up with 0.12 H, 2.38 C, 5.43 O (just pulling numbers out of thin air) you'd divide each by 0.12. Sockatume 05:18, 20 December 2006 (UTC)

Following on from what the others have said you should get the ratio:

49.3/12 carbon : 6.9/1 hydrogen : 43.8/16 oxygen (the atomic masses of carbon, hydrogen and oxygen are 12,1 and 16 respectively)

4.108c:6.9h:2.7375o = 1.5c :2.52h : 1o (divide by 2.7375)= 3c : 5.04h : 2o

So it's probably C3H5O2 - did that make sense?87.102.4.227 11:43, 20 December 2006 (UTC)

Text Color

In Wikipedia, how do I change the color of the text that I encode? For example, some usernames have different text colors and even different color combinations. How do I do that? I'm creating a userbox and I want to make color combinations on the text. Moonwalkerwiz 04:05, 20 December 2006 (UTC)

Like this? Clarityfiend 04:39, 20 December 2006 (UTC)

Better, like this (or better yet, never mix color information in with the content, and let the CSS stylesheet handle it). —Keenan Pepper 17:03, 20 December 2006 (UTC)

Please don't do that in your signature, though, I hate having to edit a page where most of the text is for the fancy signatures, so I can barely even find the actual content. I don't think anyone over the age of 5 really needs to have a Punky Brewster [10] signature, anyway. StuRat 15:58, 20 December 2006 (UTC)

honey

Can eating a lot of honey be bad for you (other than making you fat)? --Shanedidona 04:46, 20 December 2006 (UTC)

Have you looked under honey --Light current 04:53, 20 December 2006 (UTC)?

I think eating too much of anything can be bad for you, especially something as sugary as honey. --jjron 09:06, 20 December 2006 (UTC)

Typical honey analysis

   * Fructose: 38%
   * Glucose: 31%
   * Sucrose: 1%
   * Water: 17%
   * Other sugars: 9% (maltose, melezitose)
   * Ash: 0.17%

Which sugars? --Light current 09:17, 20 December 2006 (UTC)

I don't see too many complex carbohydrates in there! Or anything else particularly nutritious. --jjron 09:43, 20 December 2006 (UTC)

I have to disagree with some of the misconceptions above. I happen to think that natural-esque sugars (honey, maple syrup, unadulterated fruit juice etc) are fine. You'll stop eating them when your body has had enough. It's stuff like high-fructose corn syrup and refined white sugar that you have to be leary of, as they seem to be added to just about everything made north of Mexico.

Also, the quality of honey makes a big difference. Try to get honey made on a small scale by a small company, not in a generic 10-pound tub at the nearest MegaMart. Vranak 15:36, 20 December 2006 (UTC)

Honey is one of the best forms of sugar, but it's still sugar, so you should limit consumption as much as possible. StuRat 15:53, 20 December 2006 (UTC)

Hmmmm! I thought bees made honey (not companies)--Light current 17:25, 20 December 2006 (UTC)

Think of bees as little cows -- you gotta treat them right for them to produce good honey. Or at least have nice flowers nearby for them to drink nectar from.

Also, limit[ing] consumption as much as possible is not quite what I recommend. If you have a sweet tooth, it's because your body craves sugar. Why would you fight a natural urge? Vranak 23:12, 20 December 2006 (UTC)

Well, just limiting your "natural urges" to food and drink, you would likely eat an extremely unhealthy diet rich in bad fats, bad cholesterol, sugar, salt, excess calories, and other nasties, and totally devoid of vitamins, minerals, fiber, etc., leading to an unhealthy life and an early death. StuRat 21:19, 21 December 2006 (UTC)

Large amounts of sugar consumption can be bad for your teeth. BenC7 01:17, 21 December 2006 (UTC)

This is true. But the healthier you are (and thus the healthier your mouth is), the less sugar troubles your teeth. Vranak

I am skeptical about a different appetite for "natural" sugars versus any other sugars. Do not ASSume that fructose is somehow superior to glucose. Edison 05:52, 21 December 2006 (UTC)

Another potential downside of honey is that it has a relatively high glycemic index:

Sugar      GI
========   ==
honey    - 73
sucrose  - 65
lactose  - 46
fructose - 23 [11]

This means that, relative to other forms of sugar, it rapidly increases your blood sugar level, causing your body to rapidly produce insulin to compensate, resulting in a "sugar crash" later on. So, don't avoid honey completely, but do try to limit your consumption. StuRat 16:26, 23 December 2006 (UTC)

A tangent- in the movie Super Troopers the cops chug maple syrup. Would this cause any damage? -- Sturgeonman 22:37, 27 December 2006 (UTC)

Chemical Reaction

I have a problem with a certain AP Chemistry word problem. I am supposed to turn this into a chemical equation. "A clean iron rod is inserted into a solution of iron (III) sulfate" Would adding more iron simply push the equilibrium further to the products side. Would I wind up with Fe + Fe³⁺ + 3SO₄^2- → Fe₂(SO₄)₃? This problem seems so simple, but it's making me feel so stupid, like I'm missing something extremely obvious. Thanks. Ivan 05:22, 20 December 2006 (UTC)

I suddenly had a thought that it might be redox. Is it? If it is, I'm still stuck. Ivan 05:29, 20 December 2006 (UTC)

The reaction between the iron rod and the iron sulfate solution is indeed redox (note that the net charge is not balanced on the two sides of your equation), but the answer does not require actually using the balanced redox equation for it. Rather, note that the question tells you it's an equilibrium reaction, and consider what kinds of chemical things one includes when talking about an equilibrium. Insoluble solids? Soluble molecules and ions? Gases? Solvents? Catalysts? Etc. DMacks 06:39, 20 December 2006 (UTC)

A study of the relevant redox potentials will tell you that the following redox equilibrium will be established. It is technically reverse disproportionation. The sulphate ions play absolutely no part at all. Fe + 2Fe³⁺ <----> 3Fe²⁺. --G N Frykman 07:24, 20 December 2006 (UTC)

Adding more iron does not change the equilibrium constant, since it is calculated based on the concentration of the chemicals involved in the reaction. Solids have a concentration of 1, so adding more would not change it. BenC7 01:20, 21 December 2006 (UTC)

Evolution question

If evolution is correct, are European people more physically related to monkeys than, say, African people? European people resemble monkeys' pink skin and straight hair... is it fair to assume then that black people are in more advanced stages of human evolution, because they don't physically resemble monkeys? They don't have the skin and hair of monkeys. So what now? I'm not an expert on this field... so tell me. PS: I don't think I've ever seen a monkey with black skin. ► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 06:32, 20 December 2006 (UTC)

If evolution is correct? No, human beings are all the same species, certain races are not more or less related to other primates. Variations in skin tone and hair colour and texture are adaptations only tens of thousands of years old which occurred in response to environmental differences. Anchoress 06:37, 20 December 2006 (UTC)

Human skin color might be of interest. —Erik (talk • contrib) - 06:38, 20 December 2006 (UTC)

Look in the face of a Gorilla! Its black! He is related to me to the same degree than to African people, because we all come from a small group of people who lived in east Africa millions of years ago. To use the skin colour as marker for evolution has a long tradition, and caused some of the awful theories of Herrenrasse and other ideas which made alot of people suffer.--Stone 08:31, 20 December 2006 (UTC)

According to the most widely held views of scientists, all modern humans are descended from a small group of people living in Eastern Africa some time in the last 200,000 years. The article on Mitochondrial Eve may be of interest to you. As the others have said, no human group is more or less related to apes or monkeys than any other group - we are all equally related to the same common ancestors as apes such as chimps and gorillas some time in the last 5 - 8 million years. (Incidentally, this group split from monkeys much earlier. Contrary to repeated use in popular culture, chimpanzees are apes, not monkeys.) Skin colour is a lousy determinant of anything; in some human groups it is thought skin colour is controlled by as little as a single gene. Hair also tells you little - my mum has curly hair, my sister and brother have wavy hair, I have straight hair, we all have dark hair but my other sister has straight blonde hair; ultimately, so what? Which of us is more like a monkey? --jjron 09:01, 20 December 2006 (UTC)

I believe that primates, and mammals in general, typically have either black skin or pink skin. Pink is more typical under fur, with black being more common in areas exposed to light, such as lips, noses, finger/toe pads, etc. Straight hair/fur is also far more common in mammals than curly hair. StuRat 15:49, 20 December 2006 (UTC)

Based on skin colour, I'd think that maybe European people are more related to domestic pigs, and African people to Wild Boars.  --Lambiam^Talk 16:07, 20 December 2006 (UTC)

People don't evolve from monkeys. Rather people and monkeys evolve from a common ancestor. From an evolutionary viewpoint I think it is fair to say that Europeans, Africans and monkeys are equivalently advanced as a species with their own adaptations and traits.

Cool, thanks. ► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 06:03, 21 December 2006 (UTC)

A bit late but bear in mind Race is a contentious issue in science anyway. Not all scientists feel it's a meaningful concept Nil Einne 10:57, 21 December 2006 (UTC)

lysergic acid diethylamide

given determination and a basic understanding of organic chemistry (college course), would it be in the realm of possibility to synthesize this with obtainable chemicals using obtainable glassware and lab equipment? i ask this as a fan of the substance, and as someone with an interest in chemistry. i figure i would be enjoying myself with the process, but also gaining something useful.

Why not take a trip to LSD?--Light current 09:28, 20 December 2006 (UTC)

The sythesis of LSD from readily obtainable chemicals and glassware would be a difficult undertaking. I doubt that it could be accomplished by anyone without graduate-level experience in organic synthesis and lots of money. In the lab LSD is instead made easily from lysergic acid which is isolated from ergot fungus and not something that just anyone can go out and buy. --Ed (Edgar181) 15:14, 20 December 2006 (UTC)

No-op microprocessors

As all microprocessor instructions finally boils down to 0/1 through output pins. This means that we can build a microprocessor that does nothing but just generates 0/1 through output pins, in a desired way. Functionalities can be built on the top of such microprocessors. Such processors would be very much simple (?) to build. Do we already have any thing like this? V4vijayakumar 09:59, 20 December 2006 (UTC)

See Programmable logic array. Also ROMS serve in such a capacity as well as its many, many variations. Essentially you put an address in and get the desired data out.Adaptron 10:39, 20 December 2006 (UTC)

DSP digital signal processor might be of interest as well. Very specialised digital circuits may fit the bill - eg a chip that decodes Mpeg audio to pcm - need no instructions (though note in this case 'instructions of a sort' are built into the compressed data)- sorry I don't know enough to give you a specific example.

I very very simple example of what you describe would be a logic gate on a chip an example of this is 7400 series. (Good question in my opinion by the way)87.102.4.227 12:31, 20 December 2006 (UTC)

Look up Microsequencer and Microcode and Bit slicing. Back in the mainframe days, microprocessors were built up from very simple parts; far simpler than a microprocessor chip. Inside of each complicated machine language instruction, the microsequencer would be executing several simple instructions in microcode. Even today, some hobbyists use these concepts when building their own computers from logic chips, or from AND gates, or even from individual transistors. --Wjbeaty 03:37, 21 December 2006 (UTC)

ASICs I think is what you are looking for. Microprocessors derived from ASICs. Microprocessors derived from ASIC requirements for multiple digital watches. Rather than create different chips for each watch product, they designed a single chip that did the basics (fetch, decode, shift/add, store) and could be put in mulitple products with a ROM of instructions to implement the specific function. --Tbeatty 03:20, 21 December 2006 (UTC)

owner/investor model

In terms of economics or business science I know there is an ownership/investor model in which only management and labor, i.e., the employees are the owner/investors and that this model of ownership/investment is highly successful but is there also a model to replace conventional non-profit foundations in which contributors for instance to the Wikipedia can benefit financially as well? Adaptron 10:37, 20 December 2006 (UTC)

A project with a model similar to what you're proposing is used in microloans. StuRat 15:41, 20 December 2006 (UTC)

Not really. microloans suggest financial assistance. The model I am looking for is directed not at assistance but at just compensations for services contributed voluntarily but with a sence of obligation for intellectual, social or other esoteric reasons more so than personal financial gains. Kind of like when mom bakes you some cookies not for any financial reward or compemsation but becasue she loves you and so you take out the trash not because you get an allowance but becasue you love her. Adaptron 18:02, 20 December 2006 (UTC)

I think you might misunderstand the purpose of microloans, which is twofold:

1) Lending money to help people, and the community, by giving them "seed money" to start or expand a small business.

2) To make a profit from interest paid on the loans.

Thus, it's not entirely a charity or entirely a business, but a bit of both. StuRat 03:08, 21 December 2006 (UTC)

You might also be interested in communes, where each person is expected to contribute in a different, non-financial, way. StuRat 03:11, 21 December 2006 (UTC)

Ions affecting Rheumatoid Arthritis

Good day,

I am looking for any documented research regarding the subject of ions affecting Rheumatoid Arthritis. My dad is 56 and has suffered from this disabling disease for over 30 years. Rheumatoid Arthritis is the inflammation of tissue. He experiences severe joint and muscle pain, fatigue, and other common related symptoms. He suffers excruciating pain with little-no relief. His condition has worsened substantially and his joints have gradually become grotesquely deformed. Although there is currently no conclusive 'cause or cure', he is adamant that ions affect his disease. He experiences severe attacks before thunderstorms or whether changes. We live in South Africa and are exposed to climate changes such as thunderstorms and cold fronts. Is there any documented literature relating to how and why ions affect Rheumatoid Arthritis, and how this can be prevented?

I sincerely appreciate your help.

Regards, Claudie FreemanClaudie33 11:54, 20 December 2006 (UTC)

I believe that storms do affect rheumatoid arthritis, but not because of "ions", the air pressure changes common in storms (typically a rapid air pressure drop) cause the inflamed membranes to swell to equalize the pressure, which can be quite painful. This suggest that one treatment would be a hyperbaric chamber, where the pressure could be slowly increased and kept at a high level. Unfortunately, once removed from the chamber, his symptoms would return, and quite possibly be worse than before. Thus, this isn't a good treatment, after all. StuRat 15:07, 20 December 2006 (UTC)

There is a fairly small body of rigorous scientific study of potential links between arthritis pain and changes in the weather. Nevertheless, if you search PubMed using a search term like arthritis AND barometric pressure then you will hit some studies. Some papers suggest no statistically significant correlation [12], while others find a weak correlation [13], [14].

For studies that found a statistically significant correlation, increased pain tended to associated with lower temperatures, high humidity, and/or falling barometric pressure. Note that these conditions tend to be common right before thunderstorms. The mechanism which ties these factors to an increase in arthritis pain are not well understood; the explanation provided by StuRat above has been proposed as one possibility. TenOfAllTrades(talk) 15:13, 20 December 2006 (UTC)

Additionally, cold can worsen the condition and should be avoided. The living human body is full of ions, and the influence of the weather on that is completely negligeable. Some discussion of the effect of the weather: [15], [16], [17].  --Lambiam^Talk 15:20, 20 December 2006 (UTC)

In humans there seems to be not one, but various meteorological factors that alter pain perception (as opposed to arthritis as such), but these have not been defined. Whatever the cause, one would expect your dad's doctor to institute effective pain management. --Seejyb 23:59, 20 December 2006 (UTC)

Is my daughter being poisoned?

My children have never been sickly. But in the last nine months both have had severe illnesses!!! My daughter who is 12 years old is scheduled for a colonoscopy and an endoscope this friday. Is this normal for someone so young? In march of this year my 15 year old son had headaches so severe he was getting paralized on his right side with each worsoning headache. He had all the major tests done, ie, MRI, CAT Scans, Spinal Tap, Blood work...etc. but in the end NOTHING!!!! His symtoms stopped withing two weeks of me arriving where they live. About six weeks later, my daughters symtioms started. Her symtoms don't include headaches though. She is having trouble eating and drinking anything!!! She has been very ill!!! Then someone pointed out that maybe it's not my children, but their stepmom. I don't want to jump to any conclusions, but this is my children I'm talking about and I'm at a loss here!!!!! I always thought she was great with my children, but she has done everything she could to keep me from even knowing about my children's illnesses, and I'm still in the dark about almost everything!! The childrens father seems to be no help whatsoever, so that isn't an option. Any suggestions or symtoms of poisonings that match would be greatly appreciated!!!

Thank You from the bottom of my heart!!!!

Kristie L. Hawkes concerned Mom

We are not able to help with medical diagnosis. Please seek medical attention. If you are unsatisifed with your current doctors, seek second opinions. Hipocrite - «Talk» 13:03, 20 December 2006 (UTC)

You should in any case discuss your fears with the doctors treating your children.  --Lambiam^Talk 14:49, 20 December 2006 (UTC)

Might be psycological. From what you have said this is far to serious to expect reliable help here in Wiki. Find a competant mental health counsellor. I would suggest getting HFS involved, but sometimes getting them into your life can be a Trojan Horse.

When the above poster said psychological, h/she meant for your children, not you. --68.149.31.252 09:34, 21 December 2006 (UTC)

Agreed, have them specifically test for common poisons. I don't know how you can bring this up with your children in a subtle way, but perhaps you could say "Don't ever eat or drink anything that tastes even the least bit 'funny', as it may have gone bad or be contaminated". The idea here is to get them to be cautious without making unproven accusations of poisoning that could destroy your family. StuRat 15:03, 20 December 2006 (UTC)

Regrettably, this is not the forum for making diagnoses, even if we could help. Vranak 15:33, 20 December 2006 (UTC)

As long as you understand that medical advice here may be worth what you pay for it, I will give you some. Intentional poisoning seems far less likely than many other explanations. There have been very few cases of parents or stepparents giving a chronic poison (chronic means over a long period of time) to two children except in the context of Munchausen by proxy syndrome, and this sort of thing has a very distinct flavor: the parent is driving the medical evaluations and simply moves on to another doctor when the doctor is unwilling to "play" any more. It would take two different poisons to produce such disparate responses; how likely is an adult to choose two different ones? To produce what result and for what motive? It would also mean that your previous assessment of her as a caring parent was in error, and I would tend to trust that assessment. I would drop that line. I would not recommend questioning your children about funny tasting things: it would not confirm or refute your suspicion and it will be disturbing to them (either about you or her) if they understsnd what you are getting at.

Finally, there are far more common explanations for the symptoms you mentioned. Headaches with transient one-sided weakness and a negative workup is a recognized migraine variant, and there are no tests that will be positive. You havent told us why your daughter "is having trouble eating and drinking anything" --- whether that is because of pain, or vomiting, or fear of something like choking or fatness, or because someone is trying to make her do so. For unexplained gastrointestinal symptoms that persist, sooner or later a doctor will offer endoscopy. It is what gastroenterologists do. Good luck. alteripse 22:16, 20 December 2006 (UTC)

If not intentional, are you sure it's not something environmental? Sometimes mold allergy for example can get very severe if the mold is toxic. It is an invisible deadly killer and difficult to diagnose. Mold can be very difficult to find, such as a leaking bathtub affecting a bedroom wall behind cupboards. Your house may have to be tested for toxins especially mold. Sandman30s 14:06, 21 December 2006 (UTC)

To Refreeze.. Or not to Refreeze

Why is it considered so bad to refreeze meat products?

Micro-organisms survive the freezing process, and multiply upon thawing. Their colonisation and digestion activities are made easier by the microscopic tears that occur in frozen meat due to the formation of ice crystals. Re-freezing just puts these new micro-organism colonies in cold storage, waiting to again multiply upon defrosting, and the degradation of the meat fibres due to ice crystals repeats upon the second freeze. And finally, the meat decomposes faster after freezing due to the previously-mentioned factors, decreasing the quality of the meat. Anchoress 16:30, 20 December 2006 (UTC)

But to "save" the meat, one can cook it thoroughly and freeze the prepared dish. --Seejyb 11:23, 21 December 2006 (UTC)

Although if you're not going to cook it within a day or so and you're not going to throw it away, I would suggest refreezing is better then leaving it in the fridge. Nil Einne 11:39, 22 December 2006 (UTC)

Random Question

Ok sorry for the mad random question but I thinik its necessary to get an answer. Anywayz, my gf and I are planning on having a serious romp tommorrow and I want to be more than prepared. Is there a way to increase the amount of semen I produce, or is there not a way to do anything. Thanks, yo, I'll be coming back later. Peace.— Preceding unsigned comment added by LukeHughes (talk • contribs) 16:33, 20 December 2006

Semen production is relatively constant, I think. One obvious way is to conserve it ahead of time by not ejaculating for a while. Friday (talk) 16:42, 20 December 2006 (UTC)

According to the manual, masturbating until you are close to ejaculation a few hours before intercourse does the trick. I'm not sure how increased output will make you "more than prepared", though. yandman 16:51, 20 December 2006 (UTC)

It would if pregnancy is the goal. Anchoress 16:57, 20 December 2006 (UTC)

Producing more semen does not automatically mean producing more sperm. Friday (talk) 17:01, 20 December 2006 (UTC)

Eat lots of protein and don't ejaculate until then. StuRat 17:24, 20 December 2006 (UTC)

As most people think 'beef or chicken' when the word protein is used, I would remind you that dishes containing lentils, rice, beans, nuts, seafood and so on are excellent sources of protein that no one suspects as having any negative long-term effects.

Also, auto-stimulation sans release may help, as Yandman suggested. Regardless, the main thing is to enjoy yourself, and not get all caught up in volumetric analysis. If your girlfriend is doing her part, such considerations are needless. Vranak 17:39, 20 December 2006 (UTC)

And drink plenty of fluids too. And if you want to go that way, stimulate your prostate, not producing more sperm but more seminal fluid.

Well what you want to do is up to you, but unless you've both recently been checked for STDs and are in a commited relationship and pregnancy is the goal I would suggest the amount of semen you produce is unimportant since it should all end up in the condom/s you use. At the very least, I hope you've considered birth control... Nil Einne 10:52, 21 December 2006 (UTC)

Where is the origin/homeland of the Mongol (Chinese) race?

H.G. Wells in his outline of history suggests that Chinese civilization has a different origin from the rest of the world. What was the route of the Chinese race from their origins most likely in Africa to their current position today? For example the homeland of the Caucasian race has been suggested in Tibet, India, Iran and of course the Caucaus, I'm not aware of any theories for the Mongoloids. I would really appreciate a geographical trace from their origins to the present. How and where did the Mongoloids begin diferentiating from the human common ancestor? I've heard theories of them evolving from both caucausiod and negroid sources as well as theories of independent evolution. --Maddoz 17:37, 20 December 2006 (UTC)

The recent single-origin hypothesis suggests we all evolved in Africa and then spread across the globe. --Cody.Pope 20:56, 20 December 2006 (UTC)

Alternatively Multiregional hypothesis gives a slightly different view suggesting that homo erectus and homo sapiens are the same species and local populations or 'races' have come about by "selection, mutation, genetic drift, and gene flow." (from the article)

and Hybrid-origin hypothesis emphasises two (or more) distinct 'species' of human that had evolved separately: "..all of the genetic variation between the contemporary human races is attributable to genetic inheritance from at least two widely divergent hominid species, or subspecies, that were geographically dispersed throughout ... prior to the evolution of modern Homo sapiens sapiens"87.102.4.227 21:15, 20 December 2006 (UTC)

So that's the background - I too would be interested in an answer..87.102.4.227

LD50

Does anyone know of a good database for various LD50s? My usual database is ok, but it's a bit dated--74.66.242.190 18:06, 20 December 2006 (UTC)

B12

Around what peak wavelength is the Soret band for vitamin B12? Does it have one?? Just curious since it looks so much like a heme--74.66.242.190 18:39, 20 December 2006 (UTC)

Even if it doesn't have a Soret band, doesn't it at least have a strong absorption band in the visible/near visible range? Any response would be appreciated--74.66.242.190 13:47, 21 December 2006 (UTC)

weight

if a bag of cotton and iron bar reads 100gmsin a weighing machine . in reality which is heavier?why? (i think its got something to do with uptrust) answer before 21st december2006,10pm

This almost sounds like a homework question. Our articles on weight and mass be helpful. Friday (talk) 19:57, 20 December 2006 (UTC)

This is a variation on a classic brain teaser. The U.S. version goes something like this: "Which is heavier, a pound of feathers or a pound of lead?" Googling will most assuredly give you more info than you'll ever need. The key question is - what do you mean by "heavier"? -- 21:28, 20 December 2006 (UTC)

See also Buoyancy and Weighing scale.  --Lambiam^Talk 09:04, 21 December 2006 (UTC)

I prefer "which is heavier, a 16 ounces of feathers or 16 ounces of gold ?", as that brings into play the fact that most things are measured in avoirdupois weight, but precious metals are measured in troy weight. StuRat 01:15, 21 December 2006 (UTC)

That doesn't work, because only an idiot uses ounces for feathers :-P Nil Einne 10:47, 21 December 2006 (UTC)

Are you using the snow leopard def of "ounce" ? StuRat 22:08, 21 December 2006 (UTC)

Matter

Given the exchange and dispersion of matter, how likely is it/how often do we inhale/consume and/or incorporate into our own protein structure molecules that were once in some historical figure, say Abraham Lincoln? 216.130.233.77 22:46, 20 December 2006 (UTC)

The probability that molecules have been incorporated is pretty low; after we die, our complex macromolecules tend to get digested. The food that we eat comes from plants (which survive pretty much on water and carbon dioxide) or from animals that ate plants. So there's little likelihood that whole biomolecules made it through. (It is possible that you're breathing some of Lincoln's oxygen or drinking some of his water, though.)

If we just look at atoms, we can take a rough guess. Figure you weigh about sixty kilograms and that about a third of that is carbon. That works out to about 1500 moles of carbon atoms. (Obviously, you're made of other atoms, but this is just back-of-the-envelope.) Roughly speaking, that's about 10²⁷ atoms.

Let's see here—there's about 1900 gigatons of carbon in the biosphere (see carbon cycle for more info). Figure that about 1% of the total available carbon (we include water-dissolved carbon dioxide, surface carbonate deposits, and atmospheric carbon dioxide and carbon compounds) is in the biosphere at any given time; that gives us a total of about 10⁴³ carbon atoms from which living things might be made.

So, about one carbon atom out of every available 10¹⁶ is incorporated into your body. To make a Lincoln takes about 10²⁷ carbon atoms; yeah—the odds are pretty good that some of those are common. (Your odds get even better if we choose to look at all the atoms of the body, and if we count all the atoms that you've consumed, excreted, inhaled, or exhaled over your lifetime.) TenOfAllTrades(talk) 23:16, 20 December 2006 (UTC)

John Allen Paulos briefly mentions this sort of thing in his book Innumeracy. According to him, the probability that you just breathed a molecule exhaled by Julius Caeser's last breath is over 90%! The argument is similar to the one given by TenOfAllTrades. — Kieff 00:29, 21 December 2006 (UTC)

Here's a passage from A short history of nearly everything:

We are each so atomically numerous and so vigorously recycled at death that a significant number of our atoms—up to a billion for each of us, it has been suggested—probably once belonged to Shakespeare. A billion more each came from Buddha and Genghis Khan and Beethoven, and any other historical figure you care to name. (The personages have to be historical, apparently, as it takes the atoms some decades to become thoroughly redistributed; however much you may wish it, you are not yet one with Elvis Presley.)

Lincoln was born much later than these people, so I would guess we all have ten million of his atoms. Of course, people who live close to where Lincoln lived have many more of his atoms than someone from China. --Bowlhover 00:34, 21 December 2006 (UTC)

"We are all made of star dust...or dinosaur crap...it all depends on how you choose to look at things." StuRat 01:07, 21 December 2006 (UTC)

Good point, Stu. I'd say dinosaur crap is mostly made of star dust :) Dr_Dima.

I'd like to take this opportunity to point out the difference between atoms and molecules. Although you're most assuredly going to have some of the atoms of any given historic person, it's doubtful you'll have any of the molecules. Even simple molecules like water and oxygen get rearranged. In biological systems water is broken apart routinely in the synthesis and destruction of biological molecules. Even in a "inert" glass of water, water molecules are feverishly exchanging hydrogens. Oxygen molecules are split up upon respiration and combustion, and then reformed with different partners in photosynthesis. Even nitrogen molecules get broken and reformed during nitrogen fixation and denitrification. So atoms are reused, but molecules, even simple ones, are not. -- 17:35, 21 December 2006 (UTC)

December 21

Name this bug

Okay, like a silverfish, but 90% grey and not opaque in any way. No longer than a quarter of an inch, likely about 4 mm. It lives in the Greater Toronto Area, and invades bathrooms of commercial buildings. Any ideas? -- Zanimum 00:09, 21 December 2006 (UTC)

Would it be possible to get us a picture of it? Also, you might be interested in this website called What's That Bug? — Kieff 00:15, 21 December 2006 (UTC)

Sorry, I kill them as soon as I see them. Seeing that website, they actually look not at all like a silver fish. They're essentially a tear drop shape, and there's no visible antenna or legs. The colour I'd say is more of a Prussian blue meets Old Lavender. -- Zanimum 00:21, 21 December 2006 (UTC)

That bug site is great! The profiled sow bug was also from Toronto and had also invaded. [18] --Zeizmic 01:52, 21 December 2006 (UTC)

Pantheon building maintenance ?

Question reposted from Humanities:

How can a building with a large hole in the top be practical ? I'm assuming it's completely open to the outside air, although, with modern technology, it could be closed off with a window. There are several issues I would think having a large hole in the dome would cause, how are each of these addressed ?

• Water damage from rain. StuRat 00:59, 21 December 2006 (UTC)

• Sun damage from UV light. StuRat 00:59, 21 December 2006 (UTC)

• Birds and flying insects living in the building. StuRat 00:59, 21 December 2006 (UTC)

• Temperature control. StuRat 00:59, 21 December 2006 (UTC)

The interior is concrete (the upper part) and marble, and will suffer very little from rain and sunlight. Rome is not a very rainy city anyway, but rain will only reach the floor, and there are little holes all around the middle to drain any rain water. Rome has a mild climate and is also rarely very cold (the average low in the coldest month is 5 Celsius), and when it is hot the oculus actually helps.

I see. How do they handle birds and flying insects ? StuRat 19:50, 21 December 2006 (UTC)

5 C average isn't cold? Are you insane? When it reaches 10 degrees C here I think it's cold... :-P Nil Einne 11:37, 22 December 2006 (UTC)

But you're not a building, I presume. For building maintenance, rain followed by freezing or snow + thawing + freezing is bad, as the water gets into tiny cracks and expands when it freezes, making the cracks deeper every cycle. During the day it is (on the average) much warmer in the coldest months.  --Lambiam^Talk 17:31, 23 December 2006 (UTC)

Insects would get in anyway through the "front door". I see birds (pigeons, starlings) all the time in large public buildings, like train stations and shopping malls; here, if they get in, at least they'd know how to get out again.  --Lambiam^Talk 21:19, 21 December 2006 (UTC)

While some can get in anyway, it seems like the problem would be much worse with a giant hole in the roof. StuRat 16:08, 23 December 2006 (UTC)

From above the opening must look dark, and most bird species appear to have an inhibition against diving into a dark hole.  --Lambiam^Talk 17:31, 23 December 2006 (UTC)

Melons

How are seedless watermelons grown? Crisco 1492 01:38, 21 December 2006 (UTC)

Have you read the article seedless fruit? Anchoress 01:45, 21 December 2006 (UTC)

That would do it. I just searched specifically for melons. Crisco 1492 07:48, 21 December 2006 (UTC)

tension in a rope

If the two ends of a rope in equilibrium are pulled with forces of equal magnitude and opposite direction, why is the total tension in the rope not zero? -Sruthi

A homework question? Remember that Tension involves internal forces. --Wjbeaty 03:28, 21 December 2006 (UTC)

My high school physics teacher said that in a movie where barbarians rip a man in half by tieing him between 4 horses, they could do just as well with 2 horses and a fixed object. Maybe that will be helpful. Edison 05:59, 21 December 2006 (UTC)

Sruthi, imagine yourself in the position of Edison's man where you are being pulled in two directions with forces of equal magnitude. Though you are in equilibrium, would you not feel the tension and pain? :-). The tension in the rope would be zero if it is being pulled in just one direction by just one force, but then it wouldn't be in equilibrium. It would move in the direction of the force. -- WikiCheng | Talk 06:35, 21 December 2006 (UTC)

I think, though, that the objective of quartering someone is to rip them into four parts, not three. So two horses and two fixed objects is insufficient, although three horses and one fixed object would be (sufficient). But Edison, did you have had the same sadistic physics teacher that I had? Mine used the example of dangling one of the long-haired young women in the class from our second-story classroom window to illustrate tension -- sheesh! Atlant 12:35, 21 December 2006 (UTC)

The net force on the rope (or on any part of the rope) is zero, because the rope is in equilibrium. But the tension is not the same as the net force. The tension is the internal force in the rope (in either direction) that must exist in order to conform to Newton's third law - in other words, if you pull on a rope with force T, it pulls back on you with force T. Gandalf61 08:52, 21 December 2006 (UTC)

How can you tell if a gemstone is real?

Much help appreciated. 68.67.112.91 03:16, 21 December 2006 (UTC)

Well, Id think about the only way to be sure is to have it appraised by a jewller, or similar. Vespine 03:24, 21 December 2006 (UTC)

Well, what are things that the jeweler does that a layman can do? 68.67.112.91 03:47, 21 December 2006 (UTC)

According to Gullible.info: "Pearls will dissolve in vinegar, opals in chlorine bleach, and cubic zirconia in hydrogen peroxide." I guess you could try that, for starters. bibliomaniac15 03:58, 21 December 2006 (UTC)

Apart from pearls I don't think the above is right? Could the web sites name 'gullible' have anything to do with it?87.102.7.27 11:00, 21 December 2006 (UTC)

It all depends on what type of gem it is (or might be). Each gem is different (obviously) so different tests are usually needed to distinguish each type from likely imitations of that it. DMacks 04:01, 21 December 2006 (UTC)

If you have a good eye, you can generally just tell if something is valuable. It's no coincidence that precious gemstones refract light in pleasing ways. ←Vranak→

One test, for diamonds, is that they will scratch glass. There are some other things hard enough to scratch glass, too, but if your "diamond" won't, then it's not real. StuRat 07:59, 21 December 2006 (UTC)

Of course it also depends on what you mean by real. A number of gemstones can now be produced artificially with such a quality that they are difficult if not impossible to distinguish from 'natural' gemstones. Indeed, I recall a programm quite a while back where the people claimed they could produce rubies just like 'natural' rubies. The only reason you could tell them apart was because these people chose to put some sort of UV reactive dye I believe. Similarly there was an article in New Scientist I think sometime the last year or two where it was mentioned that the only reason someone was able to tell the gemstone was artificial was because it was too perfect. I think it was diamond which agrees with this link I found [19]. Point being, if by real you mean natural, it's getting increasingly difficult to tell the difference Nil Einne 13:51, 21 December 2006 (UTC)

Yes, diamonds, for example, can be made out of coal. (In fact, they are nothing else than a form of carbon) With high enough pressure and temperature, they can be created artificially. Maybe that's the way how the natural ones were formed a few million years ago. --V. Szabolcs 16:34, 21 December 2006 (UTC)

Did somebody say Occam? ←Vranak→

Different diffraction implies different material. Mr.K. 21:44, 21 December 2006 (UTC)

Somepeople can tell what a gemstone is just by looking at it, maybe with the aid of a loupe (magnifying glass), clearly a jeweller will not use a destructive test to check a gemstone. The tests I am aware of rely on refraction - measure the refractive index, and spectrum - measure the color spectrum of the gem. Other forms of spectroscopy can also be used - such as infra-red spectroscopy. The results no doubt are compared with known values for specific types of gem.. A gem dealer or jeweler will probably have the equipment to do this in the 'back room'.87.102.11.80 13:41, 22 December 2006 (UTC)

As User:Vranak says "If you have a good eye, you can generally just tell if something is valuable." - there's no real need for the above tests I mentioned.. though they can be useful in grading a gem for quality or certificating them.87.102.11.80 13:44, 22 December 2006 (UTC)

Craft

If I built a craft that had a balloon that gave the craft lift(but not all of it to reduce ballon size) and I had engines capable of producing 300 pounds of thrust and the craft wieghed around 300 pounds what is the smallest the balloon can be?72.147.86.89 05:04, 21 December 2006 (UTC)

If the weight, including engine and payload, is W, you need a total upwards thrust of more than W for lift-off. If the upwards thrust of the engines equals T, and T is less than W, you need an additional amount exceeding W−T to be supplied by the balloon. The data you give (W is around 300 lbf, T = 300 lbf) is not sufficient to determine if you need any additional lift at all, and if so how much. Using the metric unit of kgf (where 300 lbf = 136 kgf), it is the case that for a helium balloon you get about 1 kgf of lift for every cubic metre. So if, for example, W = 150 kgf, you need a balloon of 14 m³ (or actually a bit larger because that is just on the border, and there is also the (small) weight of the balloon itself). That is about the volume of a sphere whose diameter is 3 metre.  --Lambiam^Talk 09:40, 21 December 2006 (UTC)

I Like that answer thank you.

Query if the lift needed is 150kg and I get 1kg lift per cubic meter - don't I need 150m³ balloon?87.102.11.80 13:36, 22 December 2006 (UTC)

No, because that 14 meter cubed is only giving me part of the lift while my 300 pound thrust engines are giving me the rest. I have mislabled lift it is actually buyancy that the ballon is giving be.208.61.154.198 21:21, 22 December 2006 (UTC)

The darkest hour is just before dawn.

Is there any truth in this statement. It would seem more likely that the darkest hour would be at the midpoint between sunset and sunrise. Is there a scientific explanation that would make this clear.

davidwinkelaar

I believe that night, between maybe an hour after sunset and maybe an hour before dawn, is of equal darkness, except that the position of the Moon may also have an effect. The saying means "things seem the worst right before they get better". StuRat 07:51, 21 December 2006 (UTC)

Yeah. It's a statement of psychology, I'd say. It isn't really any darker just before dawn, but it's been dark for a long time, and you're getting tired of it. --Anonymous, December 21, 08:26 (UTC)

I largely agree with StuRat except to point out it's more complicated then just the moon. Obviously stars can have an effect. Most stars are obviously in a fairly constant position in one day but planet's especially, like Venus do vary. Obviously this pales in comparison to the moon but if the moon isn't visible it could arguable have enough effect. More importantly though, cloud cover can obviously very significantly affect how dark it is. Obviously this depending on the weather, not the time of day but it's an important factor to consider. And the level of ambient light will probably vary depending on the time of night if you're in a urbanised area. Even if you can't necessarily see many lights, anyone interested in star gazing will probably know how much light 'pollution' there is in cities (obviously atmospheric pollution is another factor) . Of course, a lot of this is fairly constant but in residential areas especially, there will be a difference depending on the time of night. So in conclusion, when it's the darkest depends on a lot of factors so it's difficult to actual say. The statement is simple a metaphor Nil Einne 10:08, 21 December 2006 (UTC)

You are right, the statement is wrong - the darkest hour is indeed halfway between sunset and sunrise (excluding the moon). The coldest hours are just before dawn however. I agree with the above posters that the statement only makes sense as a metaphor. If it was used as a scientific statement it is just wrong.87.102.22.58 11:18, 21 December 2006 (UTC)

I've spent many days outside at dawn this year, and while it is most certainly coldest right before dawn, I haven't noticed any trend in the photon department. Vranak 16:44, 21 December 2006 (UTC)

I think the darkest hour is the hour before dawn (or rather, the hour before astronomical twilight). By that time, most people would have gone to sleep and turned off their lights, reducing light pollution. You might think light pollution doesn't have a large effect on sky brightness, but in large cities it has a much larger effect than even the Moon.

By the way, the Sun doesn't affect the sky anymore after astronomical twilight. It doesn't matter if it's 19 degrees below the horizon or 53 degrees below; it's set too far to matter. --Bowlhover 17:06, 21 December 2006 (UTC)

Are you sure about this? Here in the northern hemisphere, I notice that the sky still retains a slight azure tint throughout cloudless summer nights -- but during the winter, not so much. →Vranak←

In my area (Toronto), the sky is always bright blue, even in the dead of night. I think this is due to light pollution, since the sky was completely dark when I visited the Dominican Republic (which doesn't have as many city lights).

Although the Moon does affect sky brightness, the stars and planets have a negligible effect. Even the Milky Way, the zodiacal light, and the [[gegenschein] contribute more to sky glow. --Bowlhover 04:44, 22 December 2006 (UTC)

I guess the key question is in the absence of the moon (as I mentioned), light polution (i.e. in a very rural area), the zodiacal light (which AFAIK doesn't occur in equtorial regions so this isn't that uncommon) whether the stars and planets will still have a neglible effect Nil Einne 05:16, 22 December 2006 (UTC)

I am aware of the metaphorical meaning of the statement. Also, the moon, stars, city lights, cloud cover, etc. are all variable and would all have an impact on a given day. Living in the northern hemisphere, latitude 54, I am also aware that the sky in the summer can glow long after sunset, and begin to glow long before sunrise, even on a cloudless day, but if we could eleminate the effects of all these and other variables, I was wondering if there could be some scientific reason I am not aware of for the literal meaning of the statement. [davidwinkelaar]

The saying is perfectly true for humans, and refers to what we see, not to the optical instrument measurement of light levels. It describes our experience, not the reality of that which is outside of ourselves. Given constant low light levels through the night, humans see less just before dawn. Reason: Due to a diurnal cyclic changes, the threshold for discrimination is at its highest just before dawn, meaning it takes more light to trigger the optic system. Therefore it seems darkest. See this article:Visual resolution in humans fluctuates over the 24 h period. Remember high threshold = low sensitivity. Possible problem: Given the very high levels of light contamination in Northern hemisphere countries (see The World Atlas of the Artificial Night Sky Brightness, especially the detailed maps), it may be that a present day citizen of those countries would never in his life discover this basic fact which has been known to humans for millenia. --Seejyb 09:45, 22 December 2006 (UTC)

Yes - that would be great - if it were true - but it starts to get brighter hours before dawn. Which people can see, with their eyes..87.102.11.80 12:33, 22 December 2006 (UTC)

You seem to be aware of the phenomena associated with twilight, but you have not experienced the phenomenon to which davidwinkelaar is referring. The fact that he asked means that it was strange to him as well, and that what the saying was claiming is inconsistent with his observations, which you are simply now repeating. In this case, the saying is valid, the observations invalid, for reasons unknown to the observer such as yourself. Your observations are limited to your experience, as determined by your environment and the number of times that you have been outside in the cloudless, moonless, dark at the appropriate hours, removed from all light pollution. I suspect you may hail from a country where light pollution over virtually the whole land area is in the gray areas of the map referred to above. In unpolluted (by light) night such as humans all knew until 150 years ago, the observation is valid in the right circumstances. Before dawn refers to before astronomical twilight, as mentioned by Bowlhover. The brightening before sunrise that you refer to is that twilight, as described in the twilight article. A point which I did not make, is that the days is coldest just after dawn, and not, as claimed in one of the replies above, just before dawn; but that is another issue. --Seejyb 02:31, 24 December 2006 (UTC)

Plus 'visual resolution' means the accuracy with with you can see - it doesn't mean 'light sensistivity'.87.102.11.80 12:36, 22 December 2006 (UTC)

Yes, the title of the paper does seem not to answer the question, but reading it would correct your view. If after reading it, you do not understand that in the human mind a drop in resolution (in darkness) means an increase in the sensation of darkness, feel free to ask again. It translates to "I don't see so well a while before dawn, it seem to be darker."--Seejyb 02:31, 24 December 2006 (UTC)

Water and Sodium Electric Power

I'll appreciate to receive information about water and sodium can make electric power. It's related to fuel cells. Thank you

Don't know much about this but fuel cell has a list of which Direct borohydride fuel cell and Molten-carbonate fuel cell may be of interest. I don't think anyone has ever suggested elemental sodium be used for a fuel cell. I don't think this would be a good idea somehow. If you're interested in what happens when you mix sodium and water, take a look at this link [20] which has a bunch of videos such as [21] (although as far as I know the skipping behaviour has been observed and was known about long before this experiment) Nil Einne 10:45, 21 December 2006 (UTC)

It's simple - simply connect a sodium rod to a wire, connect another wire to another elctrode (copper or iron would do), connect the two wires to a load eg lightbulb/ dc motor etc and then put both the wires in water - it's an electrochemical cell - however from the above posts you can see that this is not a safe thing to do.

The electrode reactions would be...

Na >> Na+ + e-     2e- + 2H20 >> H2 (gas) +2OH-

Sodium is a very reactive metal - the "sodium rod" would not make a particularly good electrode. The half cell reactions would proceed quite fast. In a fuel cell, you typically want slow, sustained reactions. --HappyCamper 12:20, 21 December 2006 (UTC)

Yeah like the videos I linked to above so. Not something you would want for a fuel cell IMHO :-P Nil Einne 11:47, 22 December 2006 (UTC)

I found Molten salt battery and a molten pure sodium battery. [22] No such fuel cells though. --Zeizmic 14:13, 21 December 2006 (UTC)

My guess is that Nil Einne's answer is what the questioner was asking about, and possibly for a public relations reason. In the DaimlerChrysler article about their minibus, they use the phrase "...the minivan, which runs on salt and water,..." This may well become the popular concept of what a sodium borohydride fuel cell is. Calling the thing "Natrium" makes this even more likely. Is this then a PR job: homely, simple, "obviously safe", making it more man in the street friendly? --Seejyb 20:59, 21 December 2006 (UTC)

Actually I don't really know whether calling the thing natrium or sodium would be better. What happens when videos of sodium explosions start propping up and people don't understand the difference? I do think saying the thing runs on salt is a bit misleading, since sodium borohydride isn't what people think of when you talk about salt and I wouldn't want someone using it instead of normal table salt... But I guess that doesn't stop companies using it :-P Nil Einne 11:43, 22 December 2006 (UTC)

Papular Mucinosis

Papular Mucinosis

Any extra information on this condition would be greatly appreciated.

Wikipedia does not yet have usable information. You can look for "Lichen Myxedematosus" on the web. The sites rarediseases.about.com and www.emedicine.com are places to start. The former is much easier to understand than the latter (for which you may have to look up every third word:-)). --Seejyb 22:34, 21 December 2006 (UTC)

Vacuum balloon

Is there a material which is strong enough that a hollow sphere (or other form) of it can be evacuated without collapsing, yet light enough that with a vacuum inside it, the average density of the structure becomes less than that of air, and therefore it floats? Laïka 14:58, 21 December 2006 (UTC)

Great question. I saw a poster in FSU's physics building that discussed assembling a lot of long, thin balloons into a cylinder, covering the ends, then evacuating the center of the cylinder. They had all these fancy equilibrium equations that proved it could work, and I think someone had already built one. Unfortunately I can't find any mention of it with Google, because I can't think of any good keywords. —Keenan Pepper 15:36, 21 December 2006 (UTC)

http://www.freepatentsonline.com/4534525.html seems to involve something like it. —Keenan Pepper 15:39, 21 December 2006 (UTC)

Well if the thickness is t (the density of the substance d) and radius is r the mass of the sphere is 4πr²td, and the volume 4/3 πr³. The density is of air 1.2 kg/m3, so the thickness must be given by

4πr²dt = 4/3 πr³ x 1.2

dt = 1.2r/3

t = 1.2r/(3d) (or less) (in SI units d is in units of kg/m3)

Now all you need is the thickness of a given solid capable of not breaking under a pressure of ~10⁵ Pa (Nm^-2)... Maybe someone else can help here.87.102.22.58 16:16, 21 December 2006 (UTC)

Also if S is the force a planar sheet of a material can support without breaking there is the relationsip (note S is the maximum tensile or compressive load)

S = Pr where P is the pressure, and r is the radius of curvature of the sphere.

So if S is proportional to t the thickness we get: (S=kt)

S/k =t and t <= 1.2r/(3d)

Pr/k <= 1.2r/(3d)

3Pd/k <= 1.2

3Pd/1.2 <= k

So we need a material that has k (the ratio of breaking force to a given thickness "Newtons per meter") that is greater than 3Pd/1.2 = 250,000d where d is the density (in kgcm^-3).

Can anyone supply this figure for different substances?87.102.22.58 16:54, 21 December 2006 (UTC)

I think we can safely assume that a sphere is the optimal shape since it would enclose the most vacuum (can you enclose nothingness?) for the least surface area (so weight of surface material). Plus, its uniform shape would best withstand the compressive forces of the outside atmosphere.

Still, my engineering gut feel suggests there's no material yet that's strong enough, although I'd bet that a carbon composite material comes close, and I'd love to be proven wrong just for the fun of seeing a practical device.

Atlant 16:57, 21 December 2006 (UTC)

I think I made a mistake in the above relating force required to support a spherical arch - I've corrected that now.

Given that k is the ration of the maximum tensile strength to thickness k will be the yield strength eg for glass ~4000MPa, steel ~400MPa,

So 3.10⁵6000(density steel)1.2=1,500,000,000Pa (1,500MPa>400MPa not strong enough)

and 3.10⁵4000(density steel)1.2=1000,000,000Pa (1000MPa<4000MPa strong enough)

So it looks like (in my simplification) that a glass sphere would be strong enough - but not a steel one. (I can't guarantee I haven't made a mistake here - the equations I have used don't take into account the change from tensile load to compressive load as one goes from outside the sphere to inside..double correction - the load is all compressive unless the sphere deforms..)

But it looks to me a the strength to weight ratio of a glass (and by extension a ceramic such as alumina) is great enough to hold back the pressures inside a sphere containing a vacuum of sufficient size to make the overall thing big enough to float.87.102.22.58 17:33, 21 December 2006 (UTC)

However actually making such a thing is another thing...87.102.22.58 17:34, 21 December 2006 (UTC)

There seems to be a lot of discussion on this, found with Google. From my engineering perspective, the structural forces are huge, and you have very little lift force. You can see from the typical construction of a bell jar (sad article), that glass has to be very thick, and a steel vacuum chamber is also very heavy. --Zeizmic 17:53, 21 December 2006 (UTC)

yes bell jars are thick (1cm to 1inch) but much thinner glass vessels will support vacuums - provided there are no hairline cracks! - a big factor in the thickness of bell jars is pure safety.87.102.22.58 18:03, 21 December 2006 (UTC)

I agree that bell jars are 'overbuilt'. I pull hard vacuum on regular lab vials all the time and I've never had one break. ike9898 18:22, 21 December 2006 (UTC)

Agree about the forces - using the method above the thickness seems to be 0.1/(yield strength in MPa) times radius - so for a 1m glass balloon the thickness will be 0.1/4000 m = 0.025mm - quite thin! (but not impossible!!)87.102.22.58 18:00, 21 December 2006 (UTC)

The implosion of an evacuated glass balloon would be a wonderful thing to see, but I would not want to be riding in its basket! Still, this is a wonderful example of Ref Desk at work: to run the calcs and compare the required material properties with the existing. Thre would have to be a safety factor, so that the strength would need to be some multiple of the calculated minimum. Edison 19:19, 21 December 2006 (UTC)

As an aside I can't help thinking of blowing a bubble of 'bubble gum' - made of a polymer that cross links when exposed to uv light - when the bubble is big enough - turn on the uv - to cross link and harden - then evacuate...83.100.255.234 19:23, 21 December 2006 (UTC)

But that ex-post-facto evacuation will be problematic; one of the many reason's you'll need Edison's safety margin is that the omphalos from which you evacuate the sphere will be a point where implosion stress accumulates.

Atlant 14:02, 22 December 2006 (UTC)

The join between the sphere and the inlet could easily be specifically strengthened - it would only contribute a miniscule amount to the total mass if the balloon is 1cubic meter, and the 'evacuation pipe' is say 0.5cm.. (Thanks for saying omphalos by the way)87.102.11.80 15:10, 22 December 2006 (UTC)

(You're welcome. How often does one get a chance to use that word, ehh ;-) ? Atlant 19:28, 22 December 2006 (UTC))

Rather than discuss if it's possible, let me assume that it is, and instead discuss if it's desirable. That is, would such a device have a superior lift per volume than a similar-volume balloon, filled with hydrogen or helium, floating in air.

Air = 1.293  g/L
He  = 0.1785 g/L
H   = 0.089  g/L

Helium has a density of 14% of air and hydrogen has a density of 7% of air. So, the best improvement you could hope to make on lift is 14% (16%, technically) relative to a helium balloon and 7% (8%, technically) relative to a hydrogen balloon. I don't see any possibility of creating a pressure structure adequate to withstand normal air pressure for less than a 16% weight gain. So, it's a completely impractical way to proceed. StuRat 19:34, 21 December 2006 (UTC)

Is everybody just ignoring what I said? You stick a bunch of inflated balloons together, then evacuate the hollow space between the balloons. It's the only good way to do it. StuRat, you're ignoring that helium costs money. —Keenan Pepper 02:32, 22 December 2006 (UTC)

But how would you evacuate the air without making the balloons' skins stick to each other? About the cost of helium: it's pretty cheap, but is it cheaper than making a container that can withstand vacuum? Considering what the other users said about using a thin layer of glass, I really don't know. --Bowlhover 05:04, 22 December 2006 (UTC)

The poster just asked if it were possible - not for a cost analysis.. (By the way no way will "You stick a bunch of inflated balloons together, then evacuate the hollow space between the balloons" ever work - unless I have greatly misunderstood.87.102.11.80 12:42, 22 December 2006 (UTC)

Bowlhover, the balloons are wedged tightly together, and the vacuum is helping to keep them together. 87.102.11.80, what do you think will happen? —Keenan Pepper 22:41, 22 December 2006 (UTC)

I don't understand. If the balloons are together, that means there's no vacuum. --Bowlhover 02:06, 23 December 2006 (UTC)

Come on, think a little harder. Say there are ten long, thin balloons arranged in a cylinder. Balloon number one is touching balloon number two, but balloon number one is not touching balloon number three. There's a big hollow space in the middle, which can be sealed off with two end caps, and it's not going to implode if you suck the air out of it. The system is in mechanical equilibrium, and the overall density is less than that of air. —Keenan Pepper 04:44, 23 December 2006 (UTC)

If you try to evacuate such a space the balloons would just expand inwards to fill it. Think about a balloon in a bell jar - when the pressure is decreased the balloon expands.87.102.4.34 10:35, 23 December 2006 (UTC)

They expand inwards a little, but not to the center (making them wedge-shaped, with sharp corners?) because they're not infinitely flexible. This has actually been built, so stop trying to find reasons why it's impossible. —Keenan Pepper 23:06, 23 December 2006 (UTC)

This document http://www.ualberta.ca/~edtechpd/tutorials/probes/activities/LessonIdeas-ExtraProbes.doc from the answer to another question shows that ballons burst at 1.1 to 1.2 atm (see page 4 Graph of pressure as balloon is inflated)- thats when the pressure differential is 0.1 to 0.2atm - in your example the pressure differential would be at least 1atm (since the balloons must inflated to at least 1atm to inflate at all) - in this case the ballons will have surely burst already - unless they were very special balloons. Explain that then (or give a link to this balloon assemblage).87.102.4.126 11:16, 24 December 2006 (UTC)

Sorry, I can't read that because it's in Microsoft Word format. Does it say all balloons are equally strong and break at the same pressure, or does it say balloons of some particular kind break at that pressure? I said I got the idea from a poster; I've been trying to find something about it on the Web, but no luck so far. Feel free to continue this discussion on my talk page. —Keenan Pepper 01:34, 25 December 2006 (UTC)

(New ident) It does make a kind of sense to me; the balloon would collapse, but as it did so, the pressure inside the balloons would increase and begin to force the balloons back out. Incidently, some balloons must be able to withstand near-vacuums; a weather balloon can reach 40 km, where the pressure is 0.00286 atm. Laïka 22:39, 25 December 2006 (UTC)

Right, it's in mechanical equilibrium, because the pressure inside the compartments gives the structure rigidity and prevents the hollow core from collapsing. Weather balloons, though, expand as they rise, so the pressure difference between the inside and outside (the important factor) is much less than one atmosphere, so that's a bad example. —Keenan Pepper 00:08, 26 December 2006 (UTC)

Evolutionary Biology perspectives on Fear of Speaking in Public

In the past years I've been amazed at how so many of the strange social behaviors and feelings of humans and other animals have been explained so well by evolutionary biology.

My question is -- has anyone heard of an evolutionary explanation for the very prevalent phobia of public speaking (glossophobia)? Wikipedia says that 75% of people have some sort of fear of public speaking -- yet, my intuition tells me that being able to comfortably speak in front of a group would greatly improve one's chance of gaining a mate. Why the disconnect? Why are so many brains afraid of something so socially beneficial?

Thanks in advance for any answers, theories, ideas! -Quasipalm 19:38, 21 December 2006 (UTC)

I have studied evolutionary strategies extensively, as well as the human condition. Although it may be human vanity that leads us to draw a line between ourselves and 'the animals', this distinction is not altogether a bad one to hold.

Human society is much more complex and convoluted than animal colonies, so it's not always a good idea to apply methodologies used to study the latter to the former.

In layman's terms: us humans are a relatively messed-up bunch. Fear of speaking in front of others is more a reflection of that, than features inherited through evolution, I think.

Caveat: When I say 'us humans', I can and only should speak for the society I'm most familiar with: Anglo-North American. ←Vranak→

Speaking in front of a group puts one in the focal point of atention. This is not a spot a lot of people want to be in. You are screaming hey, look at me I'm important listen! In a sense you are placing yourself above the others since they are supposed to listen to you. now this isn't a big problem with small groups of people or people you know. It gets iffy when you need to speak to a group of strangers. Imagine being a prehistoric human meeting a strange tribe. Would you wnat to draw atention to yourself? Heck no, you want to get the heck outa there.

Not to mention the fear that you might fail. You might get ridiculed or worse. Otherwise I can't really think of anything else right now. 62.194.89.68 20:38, 21 December 2006 (UTC)

"Blending in" is an excellent survival strategy. Until recently, an invading army would often execute all opposing "public figures", but leave the bulk of the population alive. So, speaking in public and thus becoming a public figure, was not the best survival strategy. Also, speaking in public when you said something that people disagreed with would often get you killed, as well. Keeping your opinions to yourself can help to keep your head on your shoulders: "Swear allegiance to the flag, whatever flag they offer, never hint at what you really feel." - Silent Running - Mike and the Mechanics. StuRat 20:56, 21 December 2006 (UTC)

Whatever the theory, it would have to be based on genetics, with a reasonable correlation between a fear of public speaking and an increased rate of reproduction. That seems rather unlikely to me. Less tenuous may be that an appropriate fear of failure may lead to an increase in survival and reproductive efficiency. Could it be that 75% of persons get appropriate and inappropriate fear "mixed up", as Vranak suggested, and that this inappropriate fear is determined to a large extent by upbringing, education and environment, not by your evolutionary biology? Then again it may be that inappropriate fear is indeed a characteristic that improves survival and reproductive rate, so that fear of public speaking is but a manifestation of this irrationality that may have evolutionary advantages. --Seejyb 22:23, 21 December 2006 (UTC)

Just a thought, fear of public speaking = fear of rejection, by peers and possible mates, this whould certianly have serious consequences on one's reporductive fitness. --Cody.Pope 22:35, 21 December 2006 (UTC)

This seems like a rather complex phenomena, some mixture of generic fear and things of that nature. I too am skeptical that there could be a good evolutionary explanation that wasn't just a just-so story. --24.147.86.187 23:35, 21 December 2006 (UTC)

I guess I would rephrase my question as performance anxiety rather than just fear of public speaking. I've read up on it and the fear many (most) people experience when speaking in public is often cited as a fight-or-flight response. Including the release of adrenalin, increased heart and lung action, etc. That's what got me thinking of the causes of a response and evolution. It seemed strange to me that standing in front of a crowd and speaking would illicit such a response. Overall these are very thought provoking responses everyone! -Quasipalm 00:26, 22 December 2006 (UTC)

Well the "fight or flight" response is a general response to stressful situations and for the reasons described above, it is a stressful situation. Perhaps the name is confusing you, althought it's called that, don't assume your response must be to literally fight or flee, especially given the complexities of human social interactions. Of course you are fighting in a way. Speaking in public can be taught of as a form of "fighting". The alternative is "flight" i.e. don't take part. At a guess, I would say quite a number of people, especially teens exhibit the same response in response to infatuations but again, it's not fighting literally but pursuing the infactuation is a form of fighting (e.g. calling the person, asking the person out on a date etc) Nil Einne 05:11, 22 December 2006 (UTC)

You talk of fear and anxiety but let’s not forget quite a few people actually get a big kick out of it (is it adrenalin?) some I’m sure to the point of a form of addiction. Keria 11:17, 22 December 2006 (UTC)

"Stable" Hydrogen?

This is purely a construct; I need a bit of "pseudo science" for a book plot:

Is there a plausible chemical method to render hydrogen less reactive? I'm looking for a cheaper alternative to helium to use as a lifting gas for giant blimps, "cities in the sky" etc., but without the dangerous flammability of hydrogen. Yes, I know it isn't actually possible, what I want is a plausible lie. The plot may connect the substance to a search for a safer way to store and transport hydrogen for the coming "hydrogen economy," so spending a few megabucks in research would be plausible.

It seems to me that, as carbon can form stable forms via co-bonding with other carbon atoms, so, perhaps, "stable hydrogen" might be formed by similar hydrogen-hydrogen bonds? The result would be a diatomic molecule, functionally similar to monatomic helium, but without the messy nuclear fusion reaction needed to create real helium.

Any ideas?

Well, it's completely nonflammable in the absence of oxygen, so why not use that ? You could also have it mixed with some gas, like Halon, which bonds with any free oxygen it finds. StuRat 19:53, 21 December 2006 (UTC)

A couple of minor nitpicks. The Halons don't bond with free oxygen; rather, they quench radicals that are generated as part of the burning process (species like H· and ·OH) which normally perpetuate the combustion reaction. Bear in mind that adding Halon in sufficient quantities to prevent combustion (typically about 5% by volume) will totally blow the buoyancy benefit you got from using hydrogen.

That said, might you be able to get away with a double-envelope design? Make the bulk of the envelope hydrogen, surround it with a layer of helium (or even fire suppressant of some sort) and add sensors to the outer envelope to detect hydrogen. Again, it's a question of whether or not the extra envelope weight blows the buoyancy benefit of hydrogen. (Of course, if I'm holding up a city then I'd want the balloon to have double walls and lots of compartments anyway....)

Or, for floating cities, get rid of the lifting gas entirely. Suspend the whole thing on carbon nanotube cables (see skyhook (structure) for various related principles).

It all depends on how far in the future you want to set this, and which sorts of techniques might make useful plot devices. :D TenOfAllTrades(talk) 20:14, 21 December 2006 (UTC)

Thanks for ideas so far, but we're moving too far afield. I'm not looking for plot devices, just a stable form of hydrogen. Any chemists out there?

I do not see stable hydrogen being easy to make in plausible way, but you do have the claims of cold fusion to work with, i.e. it produces helium (and energy) from hydrogen at low temperatures in the appropriate circumstances. You have a reasonable literature on the possibility of such processes already, and you are not bound by the need for real life observations to develop it further. Such a process may be modified specifically for helium production, with energy as merely a beneficial byproduct. --Seejyb 21:56, 21 December 2006 (UTC)

"The University of Queensland, Australia, has just spun off a company to manufacture a new storage medium for hydrogen, using magnesium allows (sic) with a sponge-like nanostructure"[23] So perhaps some nano-engineered metal-hydride sponge structure that allows an unprecedented packing efficiency. Use for example palladium[24], which might be doped with rare earth metals.  --Lambiam^Talk 23:09, 21 December 2006 (UTC)

Lets call it Aerogel but from metal. Acting like the copper net used for miners lamps to make it impossible that the fire goes through the net, because the heat is absorbed so fast that the flame deminishes. This small metal bubles are filled with hydrogen and its like building a wooden raft you simply take a few m3 of this airfloating material and you stand on it. Take several km3 and build your city in the sky!--Stone 23:17, 21 December 2006 (UTC)

Regarding the diatomic hydrogen being stable, hydrogen already exists as H₂, which is presumably what hydrogen balloons used, so that wouldn't be the answer. 80.169.64.22 11:45, 22 December 2006 (UTC)

H₂ is stable - but burns/explodes with air - eg Hindenberg disaster.87.102.11.80 13:29, 22 December 2006 (UTC)

I would suggest if you going to use psuedo science why not go the whole hog and totally make up a new element.87.102.11.80 13:29, 22 December 2006 (UTC)

Two suggestions 1) A Device that disables the ability of the hydrogen to form chemical bonds. 2) A Device that fills the blimp with free electrons. The electrons natural repulsion would fill the blimp, and the electrons have even less mass than Hydrogen. The blimp material would have to be a non conductor, and/or the device would have to be able to repentish the electrons as fast as they bleed away. Of course, the fire hazard would be replaced by danger of electrocution. Jokem 14:53, 22 December 2006 (UTC)

I don't know about anyone else, but I personally hate science fiction writers who give "scientific" explanations which are demonstably wrong (with current scientific knowledge). It's sort of an uncanny valley type of effect. I have no issue with science fiction devices and explanations which are theoretically possible but not yet feasible (e.g. space elevator) and even those which the theoretical possiblity is still debatable (wormholes, time travel). On the other side, I can completely except and enjoy science fantasy and even fantasy writing where the author deliberately ignores physical reality and just waves his hands about explanations. What really annoys me is those authors who want to have it both ways -- make up devices that we know *can't* exist, and then make up some pseudoscientific explanation, flaunting the fact that they've read A brief history of time (but probably not understood much of it). Unfortunately, as I understand it, simultaneously non-flammable and buoyant hydrogen is something current science "knows" can't exist. Sure there are some theories like Blacklight Power's hydrinos, but those are pretty universally held to be quackery. My suggestion to you is to go the Science Fantasy route -- wave your hands. E.g.:

Naive Farm-Planet Raised Protagonist: "They're filled with hydrogen? Isn't that dangerous?"

Knowledgeable City Dweller, Who Takes the Protagonist Under His Wing: "Not at all. They call it 'The Soltero Process.' You have to be a Fifth-Level Quantum Physicist to understand the math, but it renders hydrogen completely safe."

You can thus "explain" why hydrogen doesn't react, but not have the explanation be grating to someone who is more knowledgeable on the topic than you are. -- 16:23, 22 December 2006 (UTC)

Of course, in a science fiction setting, Helium should be cheap. It is the second most common element in the universe ... WilyD 17:44, 22 December 2006 (UTC)

You could say that because it's the future, there are materials strong enough to make a vacuum balloon (see two posts above). This would be both incredibly safe (you can't set fire to a vacuum!) and fairly cheap (assuming it's the future, some sort of carbon fibre, which could be made from just about anything, would be a lot cheaper than hard to get helium). Laïka 18:47, 22 December 2006 (UTC)

EE - Why do fast battery chargers have larger power bricks?

I was looking into rechargable NiMH AA and AAA batteries. I noticed that the faster the charger, the larger the "power brick" needed for the unit. "Slow" chargers (4-8 hours) don't even use power bricks. But 60 min charger use a medium sized brick and 15 min chargers use huge bricks that are larger than the actual charger. Why is this? --24.249.108.133 22:56, 21 December 2006 (UTC)

An interesting observation. Most likely because it takes more watts and more amps to charge the batteries to the same volt-amp rating in a shorter time. This requires bigger wire in the transformer windings to limit voltage drop and heating of the conductor, as well as a larger cross section in the iron laminations of the transformer core to prevent saturation of the metal. Edison 00:29, 22 December 2006 (UTC)

I also noticed this when I worked in a power tool shop. Cordless tools follow a similar pattern, the crappy chargers are small no frills type things while the super duper fast chargers are quite large and fancy. I don't know the details but the fancy super fast chargers actually have quite a lot of circuitry in them, I always guessed to monitor temperature and voltage and vary the input for the optimum effect. Vespine 03:08, 22 December 2006 (UTC)

The problem is likely to be that as charging time decreases, current increases in inverse proportion, e.g. from a 60min to a 20min charger, the current has to triple. But, according to Joule's law, heat production increases exponentially with current, i.e. by the square of the current. So in our example we would have nine times the heat production, and have to build the transformer correspondingly more robust. For the slowest and quickest of the chargers you described, the difference in heat production is (24x24) 576 fold .--Seejyb 11:17, 22 December 2006 (UTC)

Listing of AC power cord plugs?

While I found Electrical_plug very useful, I'm also looking for a list of the female ends of AC power cords. There seem to be two popular styles in the USA. There is the triangular three hole used to power computers, monitors, Xbox360 and other high-draw equipment. And there is the two hole type used to power VCRs, DVD players, and other consumer electronics (some are rounded on the left and the right while others are squared off on one side). What are their official names? --24.249.108.133 23:11, 21 December 2006 (UTC)

Aren't these just the "Type A" and "Type B" North American ones described on that Electrical plug page? Those descriptions refer to the NEMA connector page, where you can learn about the different specific designations of them. DMacks 23:44, 21 December 2006 (UTC)

I know what you mean - see IEC connector - was I right?87.102.22.65 02:26, 22 December 2006 (UTC)

You are surely correct; there are several styles of "IEC Inlet Connectors" depending on the amount of current and the need (or not) for a safety ground/earth connection. These are worldwide standards and make it easier for the manufacturer to sell their equipment anywhere in the world, simply by exchanging the power cords (and assuming, of course, the ability to work with both "120" and "240" volt power).

Atlant 14:10, 22 December 2006 (UTC)

Spot on! Thank yo very much! --24.249.108.133 22:15, 22 December 2006 (UTC)

black holes

black holes are theorized to form from neeutron stars right. so when a neutron star collapses onitself it slows light down more and more until bam it can escape, so would a black hole apear to be a neutron star, based on the same theory that makes it apear as tho an object goin into a black hole issuspended in space. iwould appreciate someone giving their thoughts on this because i dont know enough fysics yet but am doin a paper on them. --69.140.210.163 02:30, 22 December 2006 (UTC)

Once I figured out what you were saying it seems exactly right. Quote from the article Black hole:

Such objects for a while were called frozen stars since the collapse would be observed to rapidly slow down and become heavily redshifted near the Schwarzschild radius. The mathematics showed that an outside observer would see the surface of the star frozen in time at the instant where it crosses that radius. —Keenan Pepper 02:36, 22 December 2006 (UTC)

One correction. It doesn't slow light down, it just bends its path so it can't get out. Clarityfiend 04:28, 22 December 2006 (UTC)

In order for you to continue seeing something, photons have to keep hitting your eye. Those photons would normally be continuously emitted by the star, but that's not the case for black holes. It may be that the last light to escape the star would show you how it looked just before collapse, but that light would not remain visible for long. — BRIAN0918 • 2006-12-22 17:04Z

I recall my undergrad astronomy teacher saying that the "final image" you would see would eventually fade into blackness. That never made sense to me — I would expect it to be a sudden disapperance, as the light either could or could not cross the radius. But I am neither a physicist or an astronomer. --Fastfission 17:39, 22 December 2006 (UTC)

No, fade into blackness is correct. Basically, the "time dialation" you see for the object increases to infinity as it approaches the event horizon, and so you never see it cross the event horizon. But because time passes for the object very slowly (from your perspective) it releases less and less photons per second, and so gets dimmer and dimmer (plus increased gravitational redshifting makes it redder and redder. WilyD 17:42, 22 December 2006 (UTC)

Poseidon

Is the wave phenomenon used in the movie Poseidon real, and if so, what is its cause? I was watching the movie yesterday and the wave broke my suspension of disbelief because it seemed utterly impossible. I considered a tsunami, but the ship was too far out to see for that to have had an effect. Crisco 1492 03:00, 22 December 2006 (UTC)

It's real (although, not having seen the movie, I don't know how close the depicted wave was to real ones). See rogue waves, and its section on causes. --Anonymous, December 22, 2006, 03:22 (UTC).

If i remember well in the first movie the wave occured by a clear calm night and as such doesn't seem possible. Keria 11:08, 22 December 2006 (UTC)

Rogue waves can travel great distances, far from the storms that provoke them. Essentially, they are just the extremes of the stochastic processes that produce any ocean waves. IIRC, there was once a famous one that swept hikers off an oceanside cliff in Maine.

Atlant 14:21, 22 December 2006 (UTC)

The main believability problem I had with the wave scenario is that at sea, waves tend to have a very minor amplitude since they have a LOT of water to work with, and then when they come ashore the full strength of the surge is realized as water gets shallow and the energy becomes concentrated. I am no environmental scientist, but I really doubt a several hundred foot high wave can exist for more than a mile or two out at sea before it flattens dramatically. --66.195.232.121 16:07, 22 December 2006 (UTC)

66.195.232.121 is correct. Tsunamis and other waves in the deep ocean do not have large amplitudes at the surface; this occurs near land when the water bottom shallows. Geologyguy 16:22, 22 December 2006 (UTC)

Read the article. --Anon, Dec. 22, 18:30 (UTC).

RTFA? (Read the fucking article?) X [Mac Davis] (DESK|How's my driving?) 01:42, 23 December 2006 (UTC)

The wave occurs on a clear night, like the original. And, having read the article, I'm still confused. It seems beyond the realm of possibility for said wave to occur, although if they've been tracked scientifically, it may be true. I personally don't think too many people are aware of the Rogue wave phenomenon, and as such, most critical viewers would lost said suspension of disbelief. Crisco 1492 23:30, 22 December 2006 (UTC)

Until they see the evidence! We have a few satellites that have tracked them, I bet you can find sites in the ex links. X [Mac Davis] (DESK|How's my driving?) 01:42, 23 December 2006 (UTC)

This site has a nice pic of an approximately 25 meter (81 foot) high rogue waves breaking over the deck of an oil freighter: [25]. StuRat 15:57, 23 December 2006 (UTC)

Awesome pic. Shame it isn't in the public domain. Crisco 1492 00:51, 24 December 2006 (UTC)

Solar system and stardust

Where did it come from. If we are all made of stardust, which star?--Light current 04:57, 22 December 2006 (UTC)

I think Timeline of the Big Bang and Big Bang should provide your answers Nil Einne 05:03, 22 December 2006 (UTC)

If any star contributed to the nebula that formed the solar system, it probably contributed by adding supernova debris. Any star that went through a supernova is dead, and therefore not a star anymore. --Bowlhover 05:15, 22 December 2006 (UTC)

The sun is at least a third generation star (based on the relative abundance of heavy elements), meaning that it is star that coalesced from material that had been mixed with supernova ejecta from previous stars that had in turn already been mixed from supernova ejecta of previous stars. Dragons flight 09:57, 22 December 2006 (UTC)

Yes so if were all made fronm the original nebula, both the sun and the planets were made from the same stuff?--Light current 15:38, 22 December 2006 (UTC)

The sun and planets originally formed from the same stuff, but over time, objects have bombarded the planets, adding new stuff. — BRIAN0918 • 2006-12-22 16:50Z

I would say both were, and are, made of the same stuff. However, the original mix was very heavily weighted towards hydrogen and helium, but most of this was lost from the planets, especially the terrestrial planets, as they have insufficient gravity to hold light elements in the atmosphere. Such elements tend to be blown away by the solar wind. Thus, free hydrogen and helium are now somewhat rare on the terrestrial planets. StuRat 15:51, 23 December 2006 (UTC)

The stellar population article tells that "As of 2006, no Population III stars have been found", meaning that original nucleosynthesis of elements heavier than helium, such as carbon and oxygen that form organic molecules is still a theory : We are stardust, but of virtual stars.

The fact that we cannot observe those stars or reproduce the exact condition prevailing when they were born does not mean that science requires acts of faith. It just means that some science facts are not in the reproductible paradigm, thanks G.D. -- DLL ^{.. T} 19:18, 22 December 2006 (UTC)

December 22

Electric Kettles

Just to clarify, by an electric kettle, I mean a device into which you pour water, turn it on, and then it boils the water and turns off automatically, not a device which maintains water near boiling point.

One day I wondered how a home-variety electric kettle knows when the water is boiling, so as to stop operating.

A few tests showed that (at least the four or five different kettles I tested, all of different brand and make) there is a small hole inside the kettle, near the top (above the maximum amount of water line), which is evidently intended for the steam produced by boiling the water.

I verified that assumption with the following three experiments.

Firstly, I removed the lid of the kettle, and started the boiling process, and waited. The kettle didn't stop heating the water even as it was boiling, and then almost immediately after closing the lid, the kettle shut down. I repeated this process several times to make sure it wasn't just chance that immediately after I replace the lid the kettle shut down.

The next experiment was to remove the lid of the kettle, and cover it, so that the small hole is outside the closed area. Again, several times, the kettle never stopped, until I removed the covering, and then closed the lid.

The final experiment was to cover the kettle in the same way as the previous experiment, except to include the hole in the closed space. This time, the kettle stopped by itself.

My conclusion is that the kettle's stopping mechanism relies on the small hole near the top of the device.

I raised three hypotheses as to what mechanism is actually used:

1. Testing conductivity - Air is very resistive, perhaps air with steam is a better conductor
2. Pressure - As the water is heated, steam is generated, increasing air-pressure inside the kettle
3. Temperature

The question is, what IS the mechanism? I haven't gone as far as taking apart a kettle, but I did try to find the answer on the web, and neither wikipedia nor HowStuffWorks had an answer, and web-searches gave only one answer, but the site in which it was seemed dubious.

--89.0.134.155 12:26, 22 December 2006 (UTC)

Just too say I too can confirm this experiment and believe the small hole to contain the 'mechanism'.87.102.11.80 12:46, 22 December 2006 (UTC)

I'm pretty sure mine works with a simple bleed-off pressure switch, the pressure build-up is similar to a whistling kettle. But I've looked everywhere and can't find anything definitive. If you go to Google Patents, you find every sort of mechanism that is possible. --Zeizmic 14:24, 22 December 2006 (UTC)

A suggestion for another experiment: put the nozzle of your hoover near the spout, and turn it on at the same time as the kettle. It should lower the pressure enough for a pressure switch not to work. What happened? yandman 15:29, 22 December 2006 (UTC)

THe most common method IMO, is a pressure trip mechanism attached to the on/off switch. You could test that simply by actrivating the on switch and blowing down the hole( keetle empty and disconnected). Souldnt take miuch presssure to trip it off.--Light current 15:44, 22 December 2006 (UTC)

OTOH, thinking about it more, after the steam has dipersed anand the kettle emptied, I cant get my kettle to switch on again. So in mine, it cant be pressure. It could be a bimetallic strip attached to the on/off switch--Light current 15:49, 22 December 2006 (UTC)

Coffee makers commonly and teakettles sometimes use a "Klixon" thermostat [26]. This is a small metal button with two Faston tabs that connect to the electrical circuits. In "drip style" coffee pots, the thermoswitch is set just above boiling point so when the main heating element runs dry, the switch heats above boiling and opens the electrical circuit to the main heater. A small heater in parallel with the thermostat now can operate, keeping the coffee in the caraffe warm. Hysteresis keeps the theromstat from re-closing until it has become quite cool (but it does cycle occasionally while the coffee is being kept warm). Percolators (and presumably, Light current's teakettle) use a slightly different scheme so the termostat can open before the water has boiled away but only after boiling has occurred for a given period of time, short for the tea kettle and longer for the percolator.

Atlant 16:05, 22 December 2006 (UTC)

Actually, I forgot to mention that I already did test blowing into the hole to see if it would trigger the switch, and it wasn't triggered, which points against the whole pressure idea.

But, thermostats seem unreliable for too - water's boiling point varies with air-pressure, and I haven't heard of special makes for people living in high altitudes (in which water boils at a measurably lower temperature, which may cause such thermostats never to trigger).

89.0.134.155 23:01, 22 December 2006 (UTC)

my friend took his broken kettle apart one day and said (hes an enigneer) theres a bimetallic strip in the switch that clicks it off —The preceding unsigned comment was added by 86.29.50.118 (talk) 01:00, 23 December 2006 (UTC).

All the recent (past 15 years) automatic kettles I've seen had this steam hole. The switch in a kettle which I converted from automatic to non-automatic was a bimetallic strip - which I assume they still are. The strip was specifically shaped to be bistable, i.e. tended to stay shut until it has absorbed enough heat to very rapidly flip over to the open state. This is where your hysteresis comes in, it is built in to stop a buzzing switch, and sparks flying, and the smell of burning plastic... The metal strip flips when it has absorbed a certain amount of heat, and this rate of heat absorption has to be greater than that which it is losing by conduction and radiation. Hot air (low thermal capacity) in relatively small volumes would not heat the strip up quickly enough to overcome heat loss , but steam would, since it gives off heat of condensation to the metal strip (but see "Even later, more breaking news" below). The pressure in the kettle at boil is not much above atmospheric, so that a kettle set for a certain pressure alone would not work at higher altitudes (Which is patently not the case, these switches do work at higher altitude. For living altitudes of 0-2000m, we cannot buy high altitude and low altitude kettles, the way we can low and high pressure tennis balls). Nevertheless, while the switch itself is not pressure activated, there does need to be enough pressure inside the kettle to cause an adequate flow of steam through the orifice to the switch, else it would simply not cycle - as when the lid is not closed properly. Late breaking news: My 20 year younger kettle flips the switch when mains power is cut, which implies that the strip is held by an electromagnet - its shape is probably not that important. This is likely to be a more recent safety feature, in that a stable closed contact (ON) can be maintained only while current flows. The over heat cut out switch (dry run protection) is mounted in the base, next to where the mains power enters. Even later, more breaking news: A point which my wife now made to me (While pointing out that my imminent application of a screw driver to the new kettle would be seen as a death wish, and that "as she loves" me she would fulfill my wish:-) is that one cannot get a steady flow of hot air from a dry kettle, so that my theory about thermal capacity is probably over complicating the issue. I will test that with a hair dryer rigged up to ventilate the switch, but Occam is often right. --Seejyb 05:50, 23 December 2006 (UTC)

Is it possible that a bimetallic strip could be used to control a much greater current by means of an electrical relay - thus avoiding 'sparks flying' when the bimetallic strip switches..87.102.4.34 10:38, 23 December 2006 (UTC)

Yes, quite likely, what with steam being involved. The bistable nature would explain the hysteresis, the sparking being less relevant. --Seejyb 14:52, 23 December 2006 (UTC)

Why are skis no longer made from wood?

I was wondering what are all the adventages that modern carbon fibre skis hold over their wooden counterparts? (Also it would be greatly appreciated if you could explain the physics behind an answer) Thanks —The preceding unsigned comment was added by 81.145.240.41 (talk) 13:00, 22 December 2006 (UTC).

A higher modulus, more strength, better formability, ease of integrating steel "edges", better durability with little care, and no rot.

Atlant 14:28, 22 December 2006 (UTC)

Consistency. Using synthesised materials means that every ski will perform exactly the same, and cannot fail due to some chance element in the grain of the wood.--Fangz 15:18, 22 December 2006 (UTC)

Hmm I believe making skis from wood can be a knotty problem but the Heroes of Telemark did it!--Light current 01:08, 23 December 2006 (UTC)

Be quiet, LC, ... or should I say schuss ? :-) StuRat 15:34, 23 December 2006 (UTC)

Textual vs Pictorial Memory

How do textual and pictorial memory compare? In the short term, and in the long term?--Fangz 15:16, 22 December 2006 (UTC)

In the brain or in computers?

Atlant 15:55, 22 December 2006 (UTC)

I suspect he means the brain; it would likely have been phrased quite differently if it was in respects to computers. --24.147.86.187 16:54, 22 December 2006 (UTC)

It varies from person to person. What would one expect of an analphabet or a blind person - I don't know. You could get some ideas at How do Presentation Modality and Strategy Use Influence Memory for Paired Concepts?, and take it from there. --Seejyb 18:22, 22 December 2006 (UTC)

I am told that people remember things better in pictures and sounds, rather than in words (spoken or written). I think intuitively most people would agree - but I have only anecdotal evidence. 220.253.91.28 01:07, 23 December 2006 (UTC)

Water displacement

Does an object in water displace the same weight of water as the object?129.112.109.250 16:35, 22 December 2006 (UTC)

• If you put a bowling ball in a tub full of water, and then put a balloon (the same size as the bowling ball) in the water, they both displace the same amount of water, but they weigh a lot different. So, the two objects don't weigh the same, but what do they have in common? — BRIAN0918 • 2006-12-22 16:46Z

• Archimedes Principle may be what you're looking for. WilyD 17:39, 22 December 2006 (UTC)

Short answer: yes. In Brian0918's example, the situation is different because you would have to force the balloon down. If no force is applied, it would displace its itsy bitsy teeny weeny weight. Clarityfiend 17:56, 22 December 2006 (UTC)

But only if the object does not sink. If it is made of iridium, it weighs more than 20 times the water it displaces.  --Lambiam^Talk 18:11, 22 December 2006 (UTC)

Ok, if I am understanding this, it sounds like if 2 objects have the same volume the amount of water they displace is equal regardless of their weight.129.112.109.252 18:29, 22 December 2006 (UTC)

If they float, they displace a volume of water equal to their weight. Clarityfiend 18:38, 22 December 2006 (UTC)

If they sink they displace a weight of water equal to their volume. Jokem 19:03, 22 December 2006 (UTC)

As phrased these two together have a curious chiastic structure. I'd formulate it as follows:

• If they float, they displace an amount of water of the same weight.
• If they sink, they displace an amount of water of the same volume.

 --Lambiam^Talk 21:16, 22 December 2006 (UTC)

If you want to know the weight and the volume of an object fill a container that will hold it to the very top with some arrangement to direct the overflow into a container with volume marked off in increments. Place the object in the water and catch the overflow. If the object floats the weight of the overflow is the weight of the object. This can be found approximately from volume: 1 kg of water is approximately one liter of water (approximately). Next then submerge the object without allowing your hand to go below the surface of the water. The total volume of overflow will then equal the volume of the object. If the object sinks then its weight can be measured by hooking the end of a rope thru a ceiling mounted pulley and the other to a big bucket. Fill the container with water until the object lifts off the ground. The weight of the water will equal the weight of the object. (Correct me if i'm wrong.) 71.100.6.152 19:45, 22 December 2006 (UTC)

I see Harvard has a cannon ball boat puzzle illustrating the above on one of their sites. Which reminded me of a story about the person who had to check whether the king's (or emperor's) gold cannons were really gold, and use immersed displacement of water for volume, and Archimedes' principle - using barges - for weight, thus calculated density. Was it in a novel? Eastern, possibly Siam?? I forget... It would make a nice reference for this question, which surely comes up every now and then. --02:14, 23 December 2006 (UTC)

Are you thinking of Hiero's crown (Vitruvius, On Architecture 9.9[27])? EricR 02:32, 23 December 2006 (UTC)

No, this was definitely cannon, but I shall research Hiero's crown and keep it as a reference for the purpose of questions. It is seems to be a similar story, and the smaller object may make a demonstration possible. The name "Shogun" popped up in my head, but I have no copy of the book. That would make the reference recent fiction, rather than old legend, and I would go for the legend angle. --Seejyb

Slight nitpick: the weight of an object which is floating actually is equal to the sum of the weight of the water displaced and the air displaced. While the weight of the air displaced is normally trivial, this isn't true for light objects, where there may be little, or no, water displaced. It's wrong to conclude from this that a balloon or other lighter-than-air object is weightless, however. StuRat 15:23, 23 December 2006 (UTC)

Something else interesting, is that the water is sometimes displaced without having anything but air in that location. Insects, lily pads, etc., which use surface tension to float "above the water", actually deform the surface of the water somewhat:

      bug
--+   ***   +---- waterline
   \  /|\  /
    +-----+

StuRat 15:29, 23 December 2006 (UTC)

Gauss (unit)

The article relates Tesla (unit) to Gauss (unit) but no where can I find pounds of force per square inch pull or repulsion related to Guass or Tesla. Can you provide a definition? 71.100.6.152 18:57, 22 December 2006 (UTC)

More info on the force exerted will be found at Electromagnet. Please ask for more info if needed beyond what is in the article. Edison 19:03, 22 December 2006 (UTC)

Perhaps it will help if I explain what I am doing... I'm drawing a diagram of a horseshoe permenant magnet on top and a horseshoe electromagnet on the bottom so that you have the shape of a racetrack. In the Java or Excel code I am letting the viewer/user enter by mean of control knobs the surface area of the permanent and electro core faces, the Gauss for the permanent magnet, the weight of the permanent magnet, the weight of anything sitting on top of it, the number of turns of wire around the electromagnet core, and the amperes and voltage being supplied to the electromagnet. The code then displays the lifting force and other parameters of the unit for the purpose of measuring the weight of the load per the amount of ampers required to keep the cores from touching. It seems like all of the necessary information is there but I keep getting hung up on what seem to be extraneous variables like air gap which might possibly be ignored. 71.100.6.152 21:17, 22 December 2006 (UTC)

Experience such as that of Michael Faraday showed that the smoothness of the contact between the surfaces had a huge effect on the lifting power due to small air gaps. The electromagnet article shows the relation of the different variables: the ampere turns, the ares, the length, etc. Not sure why you want to use a permanenet magnet and an electromagnet; it might be simpler to posit an electromagnet and a soft iron pole piece/ keeper. Faraday in the 1830s went from electromagnets lifting ounces to electromagnets lifting thousands of pounds, and did some nice parametric experiments, with parallel versus series windings, number of turns, etc. Edison 08:18, 23 December 2006 (UTC)

The reason is as a classroom, science fair or museum interactive educational software. The reason for the permanent magnet is that I'm in this demonstration levitating (repulsing) rather than attracting. 71.100.6.152 10:37, 23 December 2006 (UTC)

Use 2 horseshoe electromagnets, and allow the circuit for one 2 by switched via a 2 pole double throw switch to either attract or repel. Plus it can all be done with, say 1 D cell alkaline battery. You could also connect a separate D cell (or perhaps even AA cell) to each horseshoe magnet. This would tie in easier to electrical technology such as motors. If one horseshoe is fixed in place and the other can move toward and away (supported by a spring or a counterweight (it would move nicely as it would if it were at a fixed distance but free to rotate. If the electric supply is a D cell alkaline, it could supply 1/3 amp for hours, or 1/2 amp for a demo. This means keeping the coil resistance above 3 ohms, so a great many turns of say #28 magnet wire could go on the horseshoe. A 1 cell battery holder could be mounted on each horseshoe.Edison 19:17, 25 December 2006 (UTC)

Bromelain, the protease enzyme in pineapple

Why does pineapple, which is not made of protein, contain a protein digesting enzyme?

For my A-level biology coursework I am finding the optimum pH of Bromelain. This is an enzyme (possibly a group of enzymes?) present in pineapple fruits, (Papaya has a similar enzyme, papain). I assume that enzymes are energetically expensive for the plant to make, but I can't work out how this one benefits the plant. Some possible theories I have come up with:

-The earlier bromeliads which later evolved into the pineapple plant were insectiverous and used the protease to digest their food (if so, why is the enzyme present in the actual fruit of the plant?)

-Pineapples disperse by explosion. The protease digests part of the fruit which is made of protein to make the dispersion more successful.

I would also be grateful if anyone knows the optimum pH of bromelain. 81.154.254.217 19:07, 22 December 2006 (UTC)Siobhan

This scholarly review may give you some clues towards another theory of why plants evolved protein digesting enzymes. Rockpocket 20:05, 22 December 2006 (UTC)

Oh, and bromelain extracts typically have an effective pH from 4.0 - 8.0 and an optimal pH from 4.5 - 5.5. (see this pdf file). Rockpocket 20:16, 22 December 2006 (UTC)

This article: Multifunctional role of plant cysteine proteinases(pdf) gives an overview of the functions of all of these proteases. I gave it a quick look through, and it does suggest answers in a general way - they have many functions, but there seems to be much work still to be done. Following up on the references section of the article may help to provide specific detail. This article I cannot access the full text: Kotaro Konnoi, Chikara Hirayamai, Masatoshi Nakamurai et al. Papain protects papaya trees from herbivorous insects: role of cysteine proteases in latex. The Plant Journal. Volume 37 Issue 3 Page 370 - February 2004. doi:10.1046/j.1365-313X.2003.01968.x. The url is to an abstract. This is more pay to get science: Andreas Schaller, A cut above the rest: the regulatory function of plant proteases. Planta, Volume 220, Number 2 / December, 2004. DOI 10.1007/s00425-004-1407-2. I hope it helps, one grows weary of sifting through enzyme ads targeting the public gullibility about life saving foods:-) --Seejyb 04:07, 23 December 2006 (UTC)

I would guess that it's a protection from insects. StuRat 15:12, 23 December 2006 (UTC)

Dec 23

Motorway building

How long does it take to build a motorway from scratch? Forget about greenbelt land and planning rejections and pretend that it's 100 miles long. Living in the 21st Century, I seem to take motorways for granted, there seems to be a lot of roads built in very little time and I can't comprehend how it's happened so quickly. How many people would you need to employ? How much tarmac would you need. It just doesn't make sense! ImbalancedZero 23:17, 22 December 2006 (UTC)

Without trying to come up with exact numbers, I'll just observe that the time required depends critically on how many people (and machines) are used. At one extreme you could have one crew starting at one end of the road, building one carriageway, working toward the other end, stopping work on the main road whenever they had to build a bridge or a slip road, and finally working back building the other carriageway. At the other extreme, if there are 25 intersecting roads, you could send out 25 bridge-building teams and 100 road-building teams, building both carriageways in both directions from each cross road until they met. In practice something in between would apply, of course. But there would be a real difference between a road needed as a top-priority military project and one being built because there was a bit of money left in this year's budget.

As to "how much tarmac", I think modern freeways are normally paved mainly with concrete, and an optional layer of asphalt (tarmac) on top. The total thickness of the two materials, supposing that to be what you really wanted, is probably something like 18 inches or say 50 cm. Four lanes (say 18 feet wide) and four paved shoulders (say 10 feet) makes a total width of 112 feet (say 35 m). 100 miles is 160 km. So that's 0.5 x 35 x 160,000 = 2,800,000 cubic meters of asphalt and concrete. If it's say 2.5 times as dense as water, that'd be 7 million tons. Plus a bit more for slip roads (ramps) and a fair bit more bridges. Understand that this is just a rough estimate -- I don't know the actual width or thicknes. It shouldn't be too far off, though. --Anonymous, December 23, 00:04 (UTC)

In the United States, we never build roadways out of concrete anymore. Instead, we put about two plies of tarmac down over 12" or so of crushed stone. It's terrible construction practice, and in the North, with winter freeze-thaw cycles, the roadway is guaranteed to start falling apart within five years or so, but it sure does keep highway construction gangs employed.

Atlant 20:23, 23 December 2006 (UTC)

Anonymous is very close, probably close enough for an acceptable answer. If I was at work I'd have access to precise figures, but, sadly, I am not at work right now. In any case, a rule of thumb from the local department of highways here states that a mile of highway (2 lanes wide) can be paved per day. Actually estimating daily production rates and total construction time is an art form, and thousands of variables are involved. You can see some of what goes into it in this document. The local terrain, of course, has a big effect if there is a lot of grading required. Generally, though, the construction company has a strong incentive to complete the job on time, and usually will get a bonus for completing the job early. 192.168.1.1 10:52am, Dec 23 '06

I see lots of roads made out of thick concrete slabs with rebar in them. It is on a gravel base with asphalt on top in some cases. Edison 19:19, 25 December 2006 (UTC)

Battery Producing Two Voltages Simultaneously?

Say I was constructing an electrical device to be battery powered and I needed both 12v and 9v supplies. Would it be acceptable to create a 12v battery from eight 1.5v cells and by inserting an additional connection in between the sixth and seventh cells, get a 9v and 12v connection from the same battery? --Username132 (talk) 23:45, 22 December 2006 (UTC)

This will work, but the cells supplying 9 V will be discharged sooner. Consider: if the 12 volt load is 0.3 amps, and the 9 V load is .1 amps, then the 6 cells making up the 9 V section will have a load of.4 amps, which would discharge them long before the additional 2 cells supplying only the .3 amp load go flat. Because of this, the 9 volt load would see its supply voltage drop a little faster than the 12 Volt load. If you had a charger charging the entire battery at 12 volts, the cells would be unevenly charged and the whole arrangement would give unsatisfactory service. If the cells were promary cells or if they were removed from the device and all charged individually, you would have better operation. If the tapped 9 V circuit drew only a much smaller current tham the 12 volt load, or if it were intermittent, you would also get better service. You could always change the cells around periodically to even out the load. Edison 00:29, 23 December 2006 (UTC)

But using a suitable resistor would allow me to get about 9v from 12c supply, supposing that the reistance of the 9v device was constant? --Username132 (talk) 01:33, 23 December 2006 (UTC)

If the 9 volt load is reasonably constant, a voltage divider circuit can produce the 9 volts, at the expense of a constant flow of wasted current through the two resistors comprising the voltage divider. If the 9 volt load is a constant resistance a single dropping resistor might work, at the cost of the energy dissipated in the dropping resistor. A three terminal regulator circuit could be used to produce a constant 9 volts over wide variations of load, once again at some small constant flow of wasted current, but could certainly be a sound choice. Integrated circuits are also available which could step up a lower battery voltage to a higher voltage for some part of the circuit. Edison 08:10, 23 December 2006 (UTC)

Kettle Boil Off

My math's teacher had a "boil-off" with some friends in which they used their kettles to boil a certain amount of water, hoping that their kettle would be the fastest. He was asking us (his A level students) for advice. It's all over now, but I have wondered many times since, how could one optimise one's chances of winning a boil off? How difficult would it be to modify a kettle to include two heating elements, powered by seperate plug sockets? --Username132 (talk) 23:55, 22 December 2006 (UTC)

Electricity, water, and red hot heating elements are a recipe for accident or injury, so modification of the electric kettle is not recommended. Edison 00:31, 23 December 2006 (UTC)

Given the constraint that you have no post consumer modification of the electric kettle, the question is which kettle should you bring to the competition. (i.e. which kettle on the store shelves should you buy. Since you are looking into converting electrical energy into thermal energy, you aren't really concerned with "efficiency", as due to the law of conservation of energy and the laws of thermodynamics, any energy which you "lose" in inefficiency will be converted to heat (which is what you want anyway). Thus, what you want is the kettle capable of drawing the most electrical energy, or the one with the highest wattage. -- 01:27, 23 December 2006 (UTC)

And one with good insulation, to make sure that the heat generated by the element is retained in the water. Maelin (Talk | Contribs) 09:25, 23 December 2006 (UTC)

Lowering the pressure can cause water to boil sooner, even at room temperature. Now, how you can lower the pressure of the water without making it obvious, that's the trick. StuRat 15:06, 23 December 2006 (UTC)

Brightest Bulb On 12v At Low Cost

I want to make a device the flashes as brightly as possible, so it might be seen from 50+ meters away in daylight. Device must operate from 12v and be (as always) as cheap as possible. What kind of bulb might do such a thing? --Username132 (talk) 23:59, 22 December 2006 (UTC)

Does the flash unit on cameras count? --Bowlhover 01:30, 23 December 2006 (UTC)

It does! There are xenon flash blubs available on ebay - suppose I want to power such a thing from a 12v car battery - what circuitry am I going to need? It needs a "trigger" apparently, but these have three prongs - how does it wire up? --Username132 (talk) 04:47, 23 December 2006 (UTC)

Could you adapt a disposable camera? It has all the circuitry in place. - CHAIRBOY (☎) 05:55, 23 December 2006 (UTC)

I'm no expert in electronics, but I think all you need are a xenon flash bulb, a capacitor, and a battery. When charging the capacitor, connect the battery's terminals to the capacitor's terminals and disconnect the bulb from the capacitor. When making the flash, disconnect the battery from the capacitor and reconnect the bulb. --Bowlhover 17:46, 25 December 2006 (UTC)

I'm hoping for something higher powered. I failed to mention that I want the flash to be seen at 50+ meters in _all_ directions. --Username132 (talk) 05:59, 23 December 2006 (UTC)

Another possibility: visit the local car spares and accessories shop, and examine one of the rotating roof lights that plug into the accessory power plug (c******** lighter) of your car, being attached to the roof by a permanent magnet. Those that emergency workers use are 12V, easily visible in daylight, and should not be too difficult to emulate using scraps. They are, however not as bright as camera flash lights. --Seejyb 06:04, 23 December 2006 (UTC)

Please do not tinker with electronic flash circuitry, since it steps up the battery to hundreds of volts and stores the energy in capacitors. This can cause electricution, similar to the units hospitals use to defibrillate. People have died tinkering with electronic flashes. Perhaps find a pre-assembled strobe unit which just plugs into the 12 volts. Edison 08:05, 23 December 2006 (UTC)

But those beacons aren't bright enough for my application. One watt simply wont do. I probably wont electrocute myself because the circuit will be enclosed when I switch it on. --Username132 (talk) 09:01, 23 December 2006 (UTC)

I'm no expert but it seems to me that you can in theory make a one-off flash as bright as you like, no matter how limited your power source is, as long as you have a large enough capacitor and a quick and efficient means of discharging it. However, storing a large amount of energy in a capacitor and discharging it rapidly sounds like a risky thing to do, especially if you are inexperienced - read this hazards and safety section. So I would second the views of other responders - find a ready-made solution or find an expert to help, but do not attempt a DIY solution. This sounds like it could turn into a Darwin Awards situation ! Gandalf61 09:34, 23 December 2006 (UTC)

Perhaps some old-fashioned magnesium flash bulbs would be in order. They generate their light from combustion, so need very little energy to trigger the rapid oxidation of magnesium. Of course, they are one-time use, as well, so you could only use them for a limited number of flashes, depending on how many you buy. Eventually your car battery would go dead, but that would be after hundreds or thousands of flashes. StuRat 14:55, 23 December 2006 (UTC)

Can you not pick up a slave flash unit from your local photography shop. Theyre not too expensive.--Light current 18:11, 25 December 2006 (UTC)

Correlation

1) Is there ANY correlation between dirty/sweaty hair and acne?

2) Is technology something that can be progressed gradually, or can we make a huge leap with what we have now?

3) I've read somewhere around here, I think in "Senescence" that one day we'll have the technology to stop aging. According to that, can there be any guesstimate as of how long it will take for us to achieve that? PitchBlack 00:23, 23 December 2006 (UTC)

1. In my experience, yes. They are both symptoms of an underlying conditon, though, so washing your hair will generally do little to improve complexion.
2. In my observance, technology does indeed improve in fits and starts. Right now, there seems to be a lot of rapid improvement across all areas of science.
3. I question the assumption that technology is the key to immortality. Why not just a good diet and outdoor exercise? ←Vranak→

1. No. See Acne#Causes of acne.

2. It's not necessarily a case of either-or. Both can occur. See innovation and invention.

3. See wishful thinking. BenC7 01:17, 23 December 2006 (UTC)

1) I would say both are symptoms of excessive fat consumption, and, in the case of acne, trans-fats in particular.

2) Both. World wars seem to particularly spur on technology leaps.

3) I think we can lengthen the lives of biological bodies, but not extend them forever. The weak link is the brain. We might eventually get to the point where we can replace every other organ when the old one fails, but replacing your brain means replacing "you". However, if the brain can be copied into a computer, then, with backups and redundancy, it would be possible for that "brain" to live forever. Of course, many would argue that the brain in the computer isn't really "you", but rather a soulless copy of you. I would expect these type of advancements over the course of centuries, not decades. StuRat 14:49, 23 December 2006 (UTC)

HOW TO find a PDF copy of the book?

the title of the book is: Futures, Options, and Swaps, by R. Kolb, Blackwell publishing, 4th ed. 2003 —The preceding unsigned comment was added by 150.210.171.79 (talk) 00:10, 23 December 2006 (UTC).

Wouldn't that be an illegal copy? Then, we cannot help you. — Kieff 02:14, 23 December 2006 (UTC)

Not necessarily; some websites that sell books also sell them in electronic format. After a Google search, however, I couldn't find any PDF copy of "Futures, Options, and Swaps". --Bowlhover 04:02, 23 December 2006 (UTC)

In that case if you must have one the only option seems to be to contact the publishers adn ask if they can do that for you.87.102.4.34 11:47, 23 December 2006 (UTC)

Casino Royale Poison

Template:Spoiler In the latest James Bond movie, he suffers a cardiac arrest after drinking a spiked martini. Is there really such a poison that can create that effect in that little time? --The Dark Side 02:10, 23 December 2006 (UTC)

A google search for "fastest-acting poison" turns up this forum page which suggests that nicotine taken orally in sufficient quantities could cause unconciousness within a few seconds and death within a minute. --Robert Merkel 03:41, 23 December 2006 (UTC)

If I remember correctly, the poison in the move was identified as either digitonin or digitoxin. They're related compounds, both of which are used in small amounts as heart medications; overdoses can cause arrhythmia, tachycardia, fibrillation, and cardiac arrest. As far as that goes, the movie gets it mostly 'right'. On the other hand, as far as I know neither one acts as quickly as the movie suggests. In real life, oral doses take tens of minutes to hours to get into the bloodstream and take effect. They are occasionally administered intravenously if more rapid action is required, but obviously the movie martini was taken orally and not IV. (This is the same school of movie science that lets investigators on CSI run a sample through a gas chromatograph in thirty seconds.)

Something that might fit the bill is batrachotoxin: one of the very potent toxins secreted by certain species of poison dart frog. It is efficiently absorbed through the mucous membranes and generates cardiac symptoms similar to those seen with digitonin overdose. On the other hand, it may also cause paralysis (batrachotoxin is a neurotoxin); perhaps we could write that off as the explanation for James' loss of coordination.

Our article doesn't identify an antidote, though it does offer suggestions on what treatments might work if you're desperate enough. Perhaps MI6 has some very good medical researchers on staff. TenOfAllTrades(talk) 06:40, 23 December 2006 (UTC)

I believe high doses of caffeine can also cause a heart attack (much higher levels than you can get from drinking coffee). StuRat 14:41, 23 December 2006 (UTC)

When he drank the salt water, was that to slow the poison or to force himself to vomit up the poison? --The Dark Side 01:23, 25 December 2006 (UTC)

I'd say to vomit, as that is a commonly used emetic. Drinking lots of water is sometimes also used to dilute certain poisons, but there's no reason for it to be salt water, in that case. StuRat 12:29, 25 December 2006 (UTC)

Estimating backup time of a electric backup power device

Is it possible to estimate the length of time an electric device can be powered by a battery-based uninterruptible power supply (UPS)? I was thinking one could use a device such as the Kill-A-Watt[28] to measure how much electric power was needed for a device. But how would one use that information along with the specifications of a UPS to know how long the UPS could power the device? Thanks for any ideas! --71.171.1.236 02:27, 23 December 2006 (UTC)

Typical UPS specifications include: Watts, VA and time. The VA is volts times amps, which is greater than the watts because anything other than a resistive load draws more volt-amps than it does watts. With a resistive load they would be the same. I tested early personal computer UPS units over 20 years ago with a resistive load box. When new, it would supply the rated volt amps for the specified time. Examining the current from the batteries, it was clear that it was stressing the batteries toward the end of the time. As their voltage dropped, the invertor circuit drew more and more current from the batteries to maintain the rated output to the bitter end. This was a somewhat destructive test, since the batteries were being drained at about a 1 hour rate (the rated time) instead of a more normal 10 hour rate. If the load were, say, half of the rated load, the carry time would more than double. Thus there is no simple mathematical answer to the question posed, except to say that a well designed UPS, when new, should supply the stated watts (or volt*amps) for the stated time, and should supply a lower load for a correspondingly longer time, but to a longer time than simple reciprocity would suggest. On the other hand, if the battery is beyond its service life, or has been repeatedly discharged to shutoff, the carry time at full load will be less than when it was new. I do not recommend loading it beyond its rated load. Edison 07:55, 23 December 2006 (UTC)

Faraday Cage Use In Security

The pharmaceutical production plant where I work is enclosed in a Faraday cage but I want to know why? There are no radio communications in there that I'm aware off - does it protect again interference that may damage equipment? --Username132 (talk) 05:57, 23 December 2006 (UTC)

Do you mean there is a metal or wire mesh structure surrounding the building, or than each room is separately in such a cage. or that all internal walls are covered in sheet metal or wire mesh? It would be more common to enclose certain labs in a Faraday Cage. If the entire building were externally shielded, cell phones radios and pagers would not work, but when someone tried to make a cel call or used a Walkie Talkie it could affect the delicate equipment being shielded. There are various industry standards for the level of electromagnetic interference a piece of equipment should withstand. Edison 08:01, 23 December 2006 (UTC)

WOW! Edison is answering a question on Faraday! ;-) -- WikiCheng | Talk 18:30, 23 December 2006 (UTC)

Is is possible that the whole metal cage is grounded to earth - a way of preventing sparks?87.102.4.34 10:44, 23 December 2006 (UTC)

Thermocouples are sensitive to EM radiation (among other devices). I suspect it's a way to guarantee that temperature sensitive operations aren't altered by spurious radiation. --Tbeatty 18:54, 23 December 2006 (UTC)

Why quarantine astronauts?

Respected Reader, I would like to ask you this question, "Why are astronauts quarantined after they come from space. --""""

There are various reason. Radiation, disease, etc. Read the article quarantine. Sign your posts with four tildes, rather than quotations by the way. :) --Proficient 08:46, 23 December 2006 (UTC)

Until we are not sure that no extraterrestrial viruses or bacteria exists against which we have no immunity, it seems logical to impose a quarantine.--V. Szabolcs 10:19, 23 December 2006 (UTC)

I'm not sure that "quarantine" is quite the right word, as that implies the public is being protected from infectious diseases they may have. I think it's more that they need time to recuperate, especially from the negative effects changes in gravity have on the body. StuRat 14:22, 23 December 2006 (UTC)

Historically, the early Apollo astronauts who went to the Moon were quarantined on their return because, at the time, scientists weren't absolutely certain that the Moon was free of disease-causing organisms. This precaution was dropped after it was determined that the lunar surface is sterile.

As far as I know, astronauts since are not quarantined after their return from space. However, NASA does keep a watchful eye on their returning astronauts. Though not quarantined, a returning astronaut might as well be—there will be a post-flight debriefing and any number of medical tests. As StuRat says, an astronaut who has spent an extended length of time in freefall will take some time to re-adapt to live in one gee.

Before launch, astronauts are quarantined to prevent them from being exposed to any nasty communicable diseases, and to allow any infections they do have to surface. In addition to being kept isolated, their diet is also carefully monitored. (You don't want to send someone to space with salmonella poisoning or the flu, right?) Access to medical care is very limited in space, and a sick crewmember can't work very hard (if at all). TenOfAllTrades(talk) 14:48, 23 December 2006 (UTC)

Please be aware that Wikipedia cannot give medical advice to astronauts so if you are seeking medical advice you must see a physician. -THB 18:15, 23 December 2006 (UTC)

Critical criteria for human life...?

Where can I find the exhaustive and extensive list of ranges of values of the criteria necessary for human life to evolve from the Big Bang to the present, i.e., size of the sun, the distance from the sun of the life supporting planet, formation of an atmosphere, evolution of amino acids and certain proteins and cycles such as the Krebs cycle, etc.? I am looking for things that are absolutely critical to the evolution (existence and then maintenance) of human life anywhere in the cosmos. Adaptron 10:01, 23 December 2006 (UTC)

For a general overview see rare Earth hypothesis, anthropic principle and fine-tuned universe - although I doubt that you will find the precise quantitative data you ask for, as many parts of the argument involve the extrapolation of probabilties from very few examples. For the other side of the argument see mediocrity principle, Texas sharpshooter fallacy and survivor bias. Gandalf61 11:30, 23 December 2006 (UTC)

I also think it's a mistake to assume that all other life must be identical to humans and thus require identical environments. Just on Earth, we see an amazing variety of life, including life that isn't dependent on the Sun for energy, but feeds off deep ocean sulfur vents. There's no reason to think that such organisms couldn't eventually, or on some other planet, evolve intelligence comparable or beyond our own. StuRat 14:13, 23 December 2006 (UTC)

Its quite possible that even more "exotic" life forms exist but my inspiration for asking is not so much to consider the other life forms that could have evolved but rather but rather because of the realization that of how many, many thing had to fall and stay within certain range values, time frames and sequences of events in order for human life to exist at all. I mean think about it. The universe is basically the inside of a vacuum chamber and yet here I am able to make these comments today. Adaptron 16:31, 23 December 2006 (UTC)

That's where "life as we know it" comes into play... --Proficient 19:34, 23 December 2006 (UTC)

anyone got a manometer?

What is the pressure inside an inflated party balloon? 1.1atm,2atm,1000atm????87.102.4.34 11:45, 23 December 2006 (UTC)

If the graph on page 4 of this Word document is accurate and for a typical balloon, it is about 110 to 112 kPa, or 1.09 to 1.11 atm. I hope you don't think human lungs could supply a pressure of 1000 atm: that is about the pressure when you dive to a depth of 10 km, well beyond the crush depth of even an Alfa class submarine. That is about the depth of the Challenger Deep, the deepest known point in the oceans.  --Lambiam^Talk 14:41, 23 December 2006 (UTC)

Excellent thanks.

My back of envolope tells me that the energy stored (and released when it pops), for a smallish party balloon is (1 litre volume) of the order of 10 Joules..87.102.4.34 15:51, 23 December 2006 (UTC)

That's the equivalent of 0.000000000002 kilotons of TNT (or 0.002grams of TNT [bang!]).87.102.4.34 15:56, 23 December 2006 (UTC)

Just to avoid any confusion I used the approximation change in Energy =(pressure x volume)_initial - (pressure x volume)_final to find the actual work done is more complex and approx. 1/10th of this.87.102.4.34 17:33, 23 December 2006 (UTC)

A water manometer could be a long piece of clear aquarium tubing filled with water. See how tall a column of water the balloon can support when blown up and connected to the tube of water. (Not: do it outside, since water may spray around.) Then note the pressure equivalent of that column of water. I do not remember the exact equivalent, but isn't it something like 32 feet of water per 1 atmospherre? So a tenth of an atmosphere would be around 3.2 feet? There should be a water reservoir between the balloon and the water column. Consider a clamp to hold the water tube while the blown up balloon is connected. Open the clamp with the water level close to the final one so the balloon pressure does not drop while it is pushing up water, but not so high that the descending water column pops the balloon. (again, this sounds like an outdoor experiment, use adult supervision, wear eye protection, etc etc.. Edison 20:12, 24 December 2006 (UTC)

resultant forces

Is it true that the resultant of a gravitational force is also gravitational,that of an electromagnetic force is electromagnetic and so on?

-Sruthi

There may be a problem with terminology here. The term "resultant" in mathematics and physics is usually applied to the net result of adding two or more forces (or other vector quantities). You could have the resultant of a single force, but it would just be a very indirect way of referring to the force itself, so it would be unusual to use the word "resultant" in this sense. But in this rather odd sense, then yes, the "resultant" of a gravitational force is a gravitational force. On the other hand, if you mean "result" rather than "resultant", then the "result" of applying one or more forces to a body is an acceleration - see Newton's second law. Accelerations don't come in different types - they are just accelerations. So it would be incorrect to say that the "result" of a gravitational force is a "gravitional acceleration" - it is just an acceleration (or, alternatively, a change in momentum). Gandalf61 13:27, 23 December 2006 (UTC)

You might have meant "for an object in equilibrium, (zero resultant forces), is it necessary that all forces be of the same type ?". In that case, the answer is no, with a boat being a simple example. Gravity pulls it down and water pressure/buoyant force pushes it up. StuRat 14:08, 23 December 2006 (UTC)

A force is a force. It doesn't matter if it is gravitational or magnetic. Adding to StuRat's answer above, another example is that you can keep a magnet 'floating' on top of another one if you make the like poles face each other. Here, the weight of the magnet (gravitational force) acting downwards and the repulsion between the like poles (magnetic force) acting upwards nullify each other to keep the upper magnet in equilibrium. Usually, it is sufficient to say that a force of x Newton acts on a body in a perticular direction. It does not matter whether the force is caused by gravity or magnetism or a spring or just plain pulling by hand. In effect, the answer to your question (is it true that ...) is No. It is not true -- WikiCheng | Talk 17:36, 23 December 2006 (UTC)

Ear remedy for loud bang

Having been subjected to a firecracker explosion within close proximity of my private hearing space, I was wondering what I could do to somehow attentuate any bad effects that may arise form this occurance. There is a bluntness in my right ear, closest to describing it would be a clogged ear sensation.

-:( -— Preceding unsigned comment added by 83.5.227.70 (talk • contribs)

Medical advice and diagnosis comment deleted. -- TenOfAllTrades(talk) 16:42, 23 December 2006 (UTC)

Suggested diagnosis comment deleted. -- TenOfAllTrades(talk) 17:13, 23 December 2006 (UTC)

You might have a perforated eardrum. If so, that requires medical attention. In any case, avoid any further loud noises. (Loomis 12:34, 27 December 2006 (UTC))

Ten Of All Trades, are you objecting to the first or second part of the sentence? Tragic romance 06:04, 24 December 2006 (UTC)

If you have a perforated eardrum, that requires medical attention. In any case, avoid any further loud noises. (Tragic romance 00:30, 24 December 2006 (UTC))

A firecracker exploding near the ear results in "acoustic trauma" much as being hit by a car results in a "motor vehicle accident". Try googling that term to find information on what has happened to you. There is also an article in Wikipedia on "noise induced hearing loss" although it focuses on chronic trauma.

The answer to your actual question is that, no, you can't attenuate the damage as it has already been caused, only time can heal it, just like in any other injury to your body.

Of course, there is no way to get diagnosis or treatment recommendations without being examined by a health care provider. Unfortunately, because of the holiday, if you want to see a physician you will have to go to an emergency room or, more appropriately, an urgent care center. That might not be a bad idea as it is possible that the force was sufficient to rupture the eardrum and if that has happened there are precautions you need to take to prevent infection. -THB 18:07, 23 December 2006 (UTC)

Says who? I just called my doctor and her office is seeing patients through the whole 'holiday'. Both celebratory practices and health care practices vary through the English-speaking world; it is important for us (question answerers) to try to remember this when answering questions. Anchoress 18:14, 23 December 2006 (UTC)

In that case, please call Anchoress's physician to schedule an appointment. -THB 18:16, 23 December 2006 (UTC)

Questioner is in Poland. -THB 18:22, 23 December 2006 (UTC)

Unfortunately, we can't diagnose your condition over the internet. You should seek the advice of a qualified medical professional, who can discuss the incident with you in detail, analyze your symptoms, and – if necessary – call you in for a physical exam or to prescribe tests. More briefly—call your doctor with any questions. TenOfAllTrades(talk) 16:42, 23 December 2006 (UTC)

Only a doctor can really evaluate damage that has been done to your ear. S/he will tell you what treatment (if any) is going to improve the condition. It is important to get this looked at as it may be a perforation.--Light current 18:10, 23 December 2006 (UTC)

Uh, it's kinda stupid to delete a comment, but link to the now-deleted comment, innit? In any case, the comment was not an attempt at a definite diagnosis with a recommended course of action; it was more of a suggestion that may better arm the person asking the original question when they do contact a medical provider. I don't see how deleting it served any good except to pretent to police the reference desk rules. 192.168.1.1 whatever.

Frankly, if someone has some information to give that may be of use, they should be able to give it. This nonsense is causing a disruption of Wikipedia. People's posts should not be getting deleted. This disclaimer at the top of the page is plenty enough without a big to-do every time someone asks a medically oriented question. I should have nipped this in the bud when I saw people's email addresses being removed when they almost certainly wouldn't come back to view the answers but rather expect them in their inbox. Gosh darn it, if I want my email address displayed, I'd gosh diddly darn display it; somewh(email edited to protecdt the user from spam) ail.com. I'm 21 years old, an adult and should be allowed to make my own decisions without molly coddling to protect me from spam. --Username132 (talk) 20:04, 23 December 2006 (UTC)

Doesn't seem like medical advice; it seems like common sense. If you have a perforated eardrum, it requires medical attention. Avoid any further loud noises -- common sense. In order to be "medical advice," the comment would have to say "If you avoid further loud noises, then you will be cured of/ will be treating/ will be at risk of, etc. But it doesn't. All it does is tell you to avoid further loud noises, and does not make any suggestion of what benefits or risks that entails. 71.97.74.56 00:23, 24 December 2006 (UTC)

Capacitor Calculations

What specification of capacitor is required to deliver 300 J at 150 V over 5 seconds and what to deliver 1 J at 12 V over 0.01 seconds? This is not for homework (I'm not a students and when I was (and hopefully will again be in a few months), it's biologically orentated!). I would like to know how you arrive at these specifications, so I can work things out again when I get more precise info. --Username132 (talk) 15:29, 23 December 2006 (UTC)

See our article on capacitance for the relationship between energy, capacitance and voltage. Note that the discharge time does not affect the capacitance, although it may affect the type of capacitor that is best for the job. Note also that the voltage across the capacitor does not stay constant as it is discharged, but decreases linearly with the charge left on the capacitor. Gandalf61 16:47, 23 December 2006 (UTC)

You're going to have to be a bit more specific about your needs. Bear in mind that the voltage and current from a capacitor (discharged across a constant resistance load) fall off with a first-order exponential decay. To get something close to a constant voltage, you either need to have a capacitor that has much higher capacitance and won't discharge fully, or employ some electronics.

The time that a capacitor takes to discharge (for moderate rates of discharge) is largely dependent on the load to which you attach it. (Lower resistance = higher current = faster discharge, and vice versa.) If you're planning on rapidly and repeatedly charging and discharging, be aware that you may need to provide cooling for the capacitor.

The total amount of energy stored in a capacitor is given by

$E_{\mathrm {stored} }={1 \over 2}CV^{2}.$

For example, if you want to have a starting voltage of 150 V and total stored energy 300 J, then you need at least a 0.027 Farad (27 mF) capacitor. Note that such a capacitor will only start out delivering 150 V. The voltage will decay to zero as the capacitor discharges. (For reference, the leftmost capacitor in the back row of Image:Capacitors Various.jpg is rated at 5 mF and 100 V.)

If instead you had a 100 mF capacitor at 150 V (this would be a very substantial capacitor), you would only be down to about 130 V by the time you had drawn off 300 J. TenOfAllTrades(talk) 17:09, 23 December 2006 (UTC)

Right! The questioner doesnt say what waveform he requires at the load. In problems of this sort, it is essential to know this. Or is he just interested in energy transfer? for instance, there are ways to deliver square pulses from an energy staorage circuit, but Im not sure if that is what the OP wants 8-)--Light current 17:39, 23 December 2006 (UTC)

Thanks for all your interest. Maybe a capacitor is the wrong way to go about this. Here's the dealio - I'm considering a game called 'laser skirmish', like laser tag but outdoors, like airsoft but not illegal (yet!) in the Netherlands. What I want to do is construct a simulation of a small [nuclear?] bomb in which after switching the circuit on, a random time is set between say 20 and 60 minutes. After completion of the time, another circuit is acivated which counts down 30 seconds and plays a 30 second clip of an air-raid siren (cheaper to do with electronics than an actual electromedchanical siren) before "detonating". The detonation should consist of an intense flash of light, shortly after which, 100 (470 mW) IR LEDs arranged in a 2x50 circle around the device are simultaneously lit with the desired signal (58 kHz carrier signal with another 1.8 kHz signal embedded into it (I'm unacquainted with this topic)) that activates the sensors and "kills" anyone caught in the blast which may last a few seconds. The device then plays an all-clear siren and game-play continues. It should run from a 12v car/motorbike battery.

The strobe will need some kind of capacitor and trigger unit. The LEDs are quoted with a surge current of 3A - specs are here http://pdf1.alldatasheet.com/datasheet-pdf/view/45652/SIEMENS/SFH400-3.html

You can probably see a connection now, between some of the questions I've been asking recently. --Username132 (talk) 19:34, 23 December 2006 (UTC)

Regarding using 12V power, I would suggest instead buying a 12V -> 110V power inverter like this one for $65USD, then using off-the-shelf 110V products to piece it together with minimal need to build your own circuits. A couple time delay relays for another $50USD or so, and a few of these inexpensive mini strobe lights for $12USD and you have all of the parts needed for the timing and strobe light circuit. No need to solder anything! You may want to disassemble part of the housing around the strobe light head, so that the bulb has a wider field of view, and with minimal handyman skills that shouldn't be difficult to do without compromising the integrity and safety of the high-voltage circuits inside. Hmm... I used to build stuff like this all the time. Can I build it and sell it to you? 192.168.1.1 2:25pm, 12/23/06

Given your intended use had you considered connecting a capacitor and electrical relay in parallel to a smaller battery - and using the relay to switch the 'psuedo bomb' - as the capacitor charges the effective resistance of the capacitor is low - so most of the current goes into the capacitor - as it becomes fully charged the resitance rises and so more current will flow into the relay - eventually there should be sufficient current to trip your relay. It's a simple and relatively inaccurate timing method..87.102.4.126 11:22, 24 December 2006 (UTC)

Blood color ?

If grasshoppers have white blood and lobsters have blue blood, does this mean they lack red blood cells (made red by the presence of iron in hemoglobin) ? If so, how do they transport oxygen ? StuRat 16:47, 23 December 2006 (UTC)

There is a pretty good list of alternatives to iron-based hemoglobin for the transport of oxygen at Hemoglobin#Other_biological_oxygen-binding_proteins. I believe lobsters have Hemocyanin which is copper based; not sure about grasshoppers. --TeaDrinker 16:56, 23 December 2006 (UTC)

Insects do not transport oxygen in their blood, but rather rely on a network of tracheal tubes to deliver air directly to their tissues. For more details, see Insect#Morphology and development. —Ilmari Karonen (talk) 18:28, 23 December 2006 (UTC)

Medicine books

Can somebody, please, tell me a list of books typically needed for a medicine degree? Thank you very much.

This would depend greatly on which university you went to. It would also depend on what you wanted to specialize in. BenC7 01:55, 24 December 2006 (UTC)

It would depend especially on which country you are speaking of. In America, it's possible to give a general outline for all (specialties really only come into play in postgraduate training). In the first year, there are basic sciences: Medical Biochemistry; Human Anatomy; Clinical Ethics in Medicine; Medical Embryology; Medical Genetics. In the second year, the study of disease and treatment: Microbiology; Clinical Medicine; Pharmacology; Pathology. In the third year, clinical rotations in Psychiatry; Obstetrics and Gynecology; Internal Medicine; Family Medicine; Surgery; Pediatrics. In the fourth year, clinical rotations (including about four elective clerkships, and Acute Care Clerkship; Ambulatory Care Clerkship; a Subinternship in Internal Medicine, Surgery, or Pediatrics; Neurology Clerkship; Advanced Cardiac Life Support. And of course each course requires its own textbook. I can list some standards, and anyone should feel free to add to the list. But these really are useful only in the context of concurrent coursework; I don't know that you'd get much benefit from them otherwise. Many courses are taught from handouts, with the texts as supplementary reading and references. - Nunh-huh 03:08, 24 December 2006 (UTC)

• Anatomy:
• Biochemistry: Stryer, Biochemistry
• Embryology:
• Genetics:
• Pathology: Robbins and Cotran's Pathologic Basis of Disease
• Microbiology:
• Pharmacology: Goodman & Gilman's The Pharmacological Basis of Therapeutics
• Psychiatry:
• Obstetrics & Gynecology:
• Internal Medicine: Cecil Textbook of Medicine; Harrison's Principles of Internal Medicine
• Surgery:
• Family Medicine:
• Pediatrics: Nelson Textbook of Pediatrics
• Clinical handbooks: Washington Manual of Therapeutics; the Harriet Lane Handbook: A Manual for Pediatric House Officers; Bates' Guide to Physical Examination and History Taking

The basic books in the first two years of American medical school typically include one standard text on each of the following: biochemistry, embryology, anatomy, genetics/cell biology, physiology, histology, microbiology, neuroscience, pathology, pharmacology, behavioral science, physical diagnosis. The specific books are usually specified by the professors, and typical US prices are $50-150 each. Books for the clinical rotations are more variable, as students have more choices: many buy an abbreviated or synopsis text for areas of lesser interest but a full standard textbook for their areas of greatest interest out of the following: internal medicine, general surgery, psychiatry, pediatrics, obstetrics ($50-200 each). Most students buy brief clinical handbooks for use on the wards ($20-50 each). Most students buy additional texts on areas of specific interest such as cardiology, or infectious diseases, or fluid & electrolytes, and there are many different topics like this ($50-300 each). Finally, many students buy study guides of various types ($30-50 each). Lotsa books lotsa money. alteripse 02:51, 24 December 2006 (UTC)

Searching for a way of contacting Neurosurgeon Yasargil and his Swiss Surgeon Team

I am searching for the address to contact Yasargil and his team ( supposedly the best in the world) because my friend, a 41 years old mother of three, desperatley needs a second opinion concerning breastancer with metastasis to the brain. Norwegian Healthcare does not have any more treatment to offer her. Is there anyone who knows the address of this fabulous team? If so I will be for ever grateful! Merry Chistmas.

Best regards

Vigdis Bjørnøy Totengata 10 0658 Oslo Norway

I shall say no more than quote the entry from the second google entry for Yasargil:"Ask your physician to discuss your case with Dr. Yasargil. For a consult, please call Dianne Yasargil, RN at (501) 686-5270, or send an e-mail to Niketa Webb at the address WebbNiketa at uams.edu." --87.74.20.6 18:01, 23 December 2006 (UTC)

Flower blossom

What makes flowers blossom vigorously?Or otherwise, how can flowers be made to blossom vigorously?

What does "vigorously" mean here ? Quickly ? StuRat 21:57, 23 December 2006 (UTC)

I mean to say in great amount or in great number with large bunches.

Generally it depends on the specific type of flower, can you be more specific? Seraphimblade 10:16, 25 December 2006 (UTC)

Normal hearing and perforated eardrum

My father was subjected, many years ago, to an explosion at close range that perforated his eardrum. His hearing as far as I can tell is ok for his age. So, is it possible to have a return to 'normal hearing', having had a drum perforated by a loud explosion.--Light current 18:32, 23 December 2006 (UTC)

Yes, a ruptured tympanum can heal without permanent hearing loss. Here's more info: [29] from the U.S. gubmint because Wikipedia has nothing about it as it's incomplete. -THB 18:38, 23 December 2006 (UTC)

Of course, you should check with your father's doctor, to be sure! We can't answer medical questions. :P 192.168.1.1 11:05am, 23 December, 2006, Merry X-mas, etc.

There is a huge difference betweeen health education and diagnosis & treatment. Health care professionals have a duty to educate. -THB 22:26, 23 December 2006 (UTC)

So are you saying we should be offering medical advice to the readers?--Light current 22:38, 23 December 2006 (UTC)

I think there's some misunderstanding here. We're not supposed to diagnose people's medical problems ("this is what's wrong with you") or prescribe treatment ("this is what you should do") but giving general medical knowledge is perfectly fine. THB's answer was excellent. —Keenan Pepper 23:25, 23 December 2006 (UTC)

Give The Focal Length Game!

The seller of these lenses does not know the focal length. I sent instruction of how to estimate it using paper and a window but am still awaiting a reply. I'm impatient. Can someone give the focal length from this picture [30] and the 64 mm diameter and 9 mm depth? --Username132 (talk) 18:46, 23 December 2006 (UTC)

Your question asks for an opinion or a guess. Sorry, we are only allowed by the administrators to refer you to Wikipedia articles. This is a Reference Desk, not a chat room. Please ask your question in a chat room. Sorry. -THB 18:55, 23 December 2006 (UTC)

I've reworded my question to demand a more assertive answer. --Username132 (talk) 19:12, 23 December 2006 (UTC)

Thanks! -THB 19:32, 23 December 2006 (UTC)

I may be wrong, but I dont think you can tell just from the dimensions. I think you need to know the refractive index of the material as well. THe method you outlined above would seem to be the simplest method:

Use parallel light beams from a distant object and focus the image on a piece of card. Since

1/u + 1/v =1/f where 'u' is the object distance, 'v' is the image distance (both from the lens) anf f is the focal length. Since the object can be considered to be at infinity , u= inf, the distance from the lens to the card is its focal length. If the seller cannot do this 10 second experiment, is he worth dealing with?--Light current 20:42, 23 December 2006 (UTC)

I figured someone would bad-mouth the seller ;) Indeed they are worth dealing with since, just like I don't have much choice about using Easyjet, there aren't many people selling lenses on ebay. I need it to turn an infrared beam with a 6 degree half-angle from an LED into a parallel beam that will range about 200+ meters (for a laser tag gun). Apparently I want a short focal length but a small magnification - I'm not sure why a large maginification should disperse the light more, and figure the larger the magnification, the smaller the focal length. Optics was one of my least liked aspects of A level physics... blurgh --Username132 (talk) 22:09, 23 December 2006 (UTC)

OK I didnt bad mouth him- I asked if you wanted to deal with him. Ok you do. Now the bad news. THis is not as simple as it may first appear. Are these lenses made of glass? If so you may have a problem getting sufficient transmission of IR through it. You may in fact need a plastic lens. Also have you considered using a conical plastic reflector from a torch instead? You may want to see our article on Infra red for more details on the transmissivity of different materials 8-)--Light current 22:30, 23 December 2006 (UTC)

Sorry; I wasn't attacking you. I just figured someone would question whether I ought to deal with the seller on the basis stated. I had no idea that glass absorbed IR but I can't find it in the infrared article either (although I do note that it specifically mentions the use of plastic lenses). Thanks for the tip. I've reported back to the laser tag forum that I've also been using, so they don't make the same mistake. --Username132 (talk) 23:29, 23 December 2006 (UTC)

Do you know more about the lens - is it convex? is one side flat? Also if you can describe it's type that would be helpful - is it described as spherical, aspherical etc.? Perhaps most importantly what is is made from glass, plastic etc.? The focal length could be estimated given the inner and outer thickness, the width and the refractive index of the lens, as well as the shape of the lens.87.102.4.34 21:26, 23 December 2006 (UTC)

I posted all the scanty details they gave, however, the provide a picture [31] from which it appears to be a fat little glass biconvex thing. Could you give a ball-park figure or could it really be anything? Ideally, it should be no longer than 30 cm but less is more for accurate 'lasering'. --Username132 (talk) 22:09, 23 December 2006 (UTC)

Well it should easily work for your 6 degree half angle - a big guess at the focal length would be 10-20cm - most likely closer to the 10 but I really can't say - if you want ir you should use a parabolic reflector - just buy a torch with the reflector at the front - cut off the front plastic part of the torch (use a hot knife or a saw) - the reflectors are usually metallised on the inside and should reflect ir into a beam really well - if you are interested - ask another question.87.102.4.126 11:28, 24 December 2006 (UTC)

by the way torch is called flashlight in some backward parts of the world - look a the link - the green one - second picture would do - put the led where the bulb is - cut off the front 'glass' (it'll be plastic)(cut the back of the torch off as well i guess) and hopefully that's what you wanted???87.102.4.126 11:32, 24 December 2006 (UTC)

What is that green stuff inside grasshoppers when you squish them?

Sometimes it is yellowish green. What is the name of it and what is the chemical composition? What is its funcshun?-THB 19:36, 23 December 2006 (UTC)

Error, grasshopper disassemble. (bonus points for catching the reference)

Short Circuit, of course! Seraphimblade 10:19, 25 December 2006 (UTC)

"Hemolymph". Leave those grasshoppers alone and read their article instead. Femto 20:14, 23 December 2006 (UTC)

"What is that red stuff inside humans when you squish them?" — The answer to both questions is the same. — Kieff 20:27, 23 December 2006 (UTC)

All that shit is blood? It's like 80%???? It doesn't taste salty. -THB 20:32, 23 December 2006 (UTC)

No, some of that "blood" is shit, which is no doubt why it doesnt taste salty. alteripse 20:49, 23 December 2006 (UTC)

Err... I was thinking of "their guts mixed with blood"... — Kieff 20:57, 23 December 2006 (UTC)

Thank you to all of the people who gave valid, well, reasoned answers. Meta-comments belong on the talk page and have been moved there. -THB 21:14, 23 December 2006 (UTC)

How to write elements

(moved from Miscellaneous Reference Desk)

On my homework, I have to write out "LiCl". I know this is Lithium and Chlorine, so do I just write "Lithium Chlorine", or does it have to be "Lithium Chloride" or "Lithium Chlorate". I just need someone to explain to me how that all works. Thanks, Musli Miester 18:47, 23 December 2006 (UTC).

The term, LiCl, does not simply represent the two chemical elements independently, but actually represents a compound of the two. See Lithium chloride for more info. Lithium perchlorate, LiClO₄, also contains oxygen and Lithium Chlorine doesn't exists as a single entity. Rockpocket 18:54, 23 December 2006 (UTC)

I know they are bonded ions. I just want to know how to properly write them. Musli Miester 18:56, 23 December 2006 (UTC)

You write out the name of the molecule. In this case, lithium chloride. See chloride to see why that is so as opposed to, say, chlorate. --Justanother 19:03, 23 December 2006 (UTC)

chloride refers to a chemical compound in which one or more chlorine atoms are covalently bonded in the molecule. Chlorates are compounds that contains the chlorate ion (ClO₃⁻) with chlorine in oxidation state +5. Rockpocket 19:12, 23 December 2006 (UTC)

Chloride is a monatomic ion, it's not covalently bonded to anything. —Keenan Pepper 23:12, 23 December 2006 (UTC)

You need to know that the Lithium is thought to be Li⁺ and the chlorine is thought to be Cl^-, the charge on the ion changes the name. If you knew that and just need the names then Ions#Common_ions would be a good place to start looking - note negatively charged ions usually end in "ide" (eg S^2- is called "sulphide"), positively charged ions often don't change the name (eg Ca²⁺ is still called "calcium").

If you didn't know the charge on the atoms then say so and someone will try to explain that. Hope this helped you.87.102.4.34 19:19, 23 December 2006 (UTC)

Okay... Does it work the same when with polyatomic ions? EG: Mg(HCO₃)₂ - Magnesium and hydrogen sulfite? Musli Miester 19:21, 23 December 2006 (UTC)

See Dictionary of chemical formulas --Justanother 19:33, 23 December 2006 (UTC)

ps Bicarbonate not hydrogen sulfite --Justanother 19:43, 23 December 2006 (UTC)

Taking into acount the above corrections - yes (HSO₃^- would be hydrogen sulphite).

The name is "Magnesium hydrogencarbonate" (oxygen containing ions often have the ending -ate.) The charged HCO₃^- ion is called hydrogencarbonate.

Just to confuse things hydrogencarbonate is also called bicarbonate. You don't need to say di-hydrogencarbonate because the formula is already known - the magnesium always has a plus 2 charge so there must be two of the hydrogencarbonate ions.

Most people learn by using the names - and the endings (ide, ate etc) are consistent eg all monoatomic ions are ended in "ide" Iodine becomes iodide I^-, Oxygen becomes oxide O^2-, Phosphorus becomes phosphide P^3-.87.102.4.34 20:02, 23 December 2006 (UTC)

Sexual Safety

if two virgins have sex, i.e. no previous intercourse, within reason (i.e. no 1 in a million chance ofone of them having caught aids of a rusty nail or something) what protection does using a condom offer that the female going on the pill wouldnt? -172.159.187.49

A condom offers the same protection to everyone who uses it correctly. If you're asking for us to give spitball estimates of the chances of disease transmission in the circumstances above, I'm not sure that's a good thing to ask. Many STDs are transmitted in other ways, so the "1 in a million" shot you're describing above isn't very accurate. But, this question is really asking for medical advice, which should come from a doctor. Ned Wilbury 21:04, 23 December 2006 (UTC)

No you completely misunderstood the question. Im asking if there are any diseases which can be transmitted via intercourse that virgins could possibly have within reason, as no doubt they could have aids, but living in a western country, the chances are less than one in a million (that one of them has aids) so they neednt worry. So do you understand what im asking now?

The chance that a virgin will have AIDS is a lot better than 1 in a million; you can also get it from sharing needles, from birth (if your mother had it), from blood transfusions, etc. StuRat 21:55, 23 December 2006 (UTC)

The pill is better at preventing pregancy than condoms. However, you should never assume your partner is disease free. Anyway, you could get sick from analingus, for instance, even if your partner is disease-free. Frankly, it's not worth the risk outside of an established relationship to have sexual intercourse without barrier protection. If you are Catholic, you should talk to your priest about birth control. -THB 21:13, 23 December 2006 (UTC)

Sure, you could get herpes just from kissing or through oral sex. Hepatitis, too. There are diseases that you can get without having sex that can then be transmitted via sex, in addition to natural stuff like e. coli infection. -THB 21:21, 23 December 2006 (UTC)

Ok cheers, that answers my question pretty conclusively. Thanks!

I'd like to add, and I'll probably get told off for it, but I'm still a believer in nature! If two people are virgins, and in love and been in a relationship for six months and have seen a doctor to get tested, I can't say I think condoms are mandatory, if you want to have kids you'll eventually have to stop using them anyway;) Yes there was probably better then one in a million chance that I got a STD when I lost my virginity without a condom, but I'm glad I took that chance. Maybe I was lucky, maybe if 10 people do it one of them does catch something, it is safer to use a condom, don't listen to me, make up your own mind, weigh up the risks and live with the consequences. Vespine 22:06, 26 December 2006 (UTC)

Rider question

If one person has normal herpes, is it possible to induce genital hepers in your partner by means of oral sex?--Light current 00:39, 24 December 2006 (UTC)

Yes. I believe they're caused by one and the same virus. Don't play with herpes! --Username132 (talk) 00:51, 24 December 2006 (UTC)

So when you ve got cold sores, you shouldnt have oral sex with you bf/gf. is that right?--Light current 00:59, 24 December 2006 (UTC)

The herpes virus is present even in the absence of visible sores. If you have oral or genital herpes, a Dental dam and/or condom should be used at all times. Hipocrite - «Talk» 01:07, 24 December 2006 (UTC) Hipocrite

So any one I had unprotected oral sex with could now have genital herpes?--Light current 01:11, 24 December 2006 (UTC)

That is a correct interpretation of the information provided above. - CHAIRBOY (☎) 01:13, 24 December 2006 (UTC)

Oh Shit!--Light current 01:19, 24 December 2006 (UTC)

The herpes simplex article indicates that generally the oral and genital manifestations are the result of difficult viruses (HSV-1 and HSV-2). --24.147.86.187 03:25, 24 December 2006 (UTC)

Meaning?--Light current 04:05, 24 December 2006 (UTC)

He meant to say 'different' viruses, meaning the tranmissibility of oral to gential and versa must be lower than oral-oral or genital-gential. He meant the chance of infection of your partners is lower than you may have originally concieved, although we don't know how low. At university, we we're told, "don't do it, man!"!

Without having had the other person under observation for their lifetime, it would be impossible to know that a claimed virgin is an actual virgin. People have been known to lie about their sexual activity. Therefore the same safe sex practices should apply to relations between purported virgin as for relations between non-virgins. Edison 20:25, 24 December 2006 (UTC)

Things that go bang

What various ways of there of creating a loud 'bang' sound, similar to 'party poppers'? Basically for scaring my friends! --Chachu207 ::: Talk to me 21:42, 23 December 2006 (UTC)

See the article on Explosive material. You must promise not to be a terrorist. -THB 22:13, 23 December 2006 (UTC)

He said terrorizing his "friends" was the whole point. alteripse 02:55, 24 December 2006 (UTC)

Depends how you want to use it. A paper bag or balloon might do the job, but you could just as easily say BANG, which would actually be the more environmentally-friendly option. Do you have any scenario in particular in mind? --Username132 (talk) 22:13, 23 December 2006 (UTC)

Newspaper Poppers are surprisingly loud, if you make them right. It's a little like cracking a whip. —Keenan Pepper 23:09, 23 December 2006 (UTC)

Haha, I remember those from middle school. X [Mac Davis] (DESK|How's my driving?) 00:17, 26 December 2006 (UTC)

Helium crisis

Some people seem to think that now that the national helium reserve will be liquidated, we will run out of helium, or at least experience a severe spike in its price due to the scarcity after squandering such a resource. So, how much He is left to be extracted from the Earth before it starts to run out? Are there any estimates?--Deglr6328 01:05, 24 December 2006 (UTC)

The US Geological Survey, in this PDF indicates the US produces about 84 million cubic meters of helium per year, and also has been withdrawing about 50 million cubic meters per year from the reserve. Domestic consumption is about equal to production, at 84 million cu m per year, and the US is a net exporter of helium (one of few mineral commodities for which this is the case) to the tune of about 50 million cu m per year. So it looks like we'd just stop exporting it. The report says the US reserves of helium amount to 3,600 million cu m, or 43 years at current consumption rates. Cheers Geologyguy 03:24, 24 December 2006 (UTC)

hm! interesting. that's quite a lot! *scratches off of list of trivial things to worry about*...--Deglr6328 03:54, 24 December 2006 (UTC)

So why did the US ever decide to store so much ? Do Congressmen just really like to give helium balloons to their mistresses/pages ? StuRat 04:48, 24 December 2006 (UTC)

For various space age stuff and airships when they were previously all the rage, aparently. Oh and by the way, if I ever inexplicably develop a musical talent I am TOTALLY naming my band The Helium Crisis so don't you dare even think about it. :) --Deglr6328 06:24, 24 December 2006 (UTC)

Will they all sing will high falsetto voices, Chipmunk style ? StuRat 12:21, 25 December 2006 (UTC)

So the US doesn't need to worry; they just stop exporting it. The rest of us however are in deep trouble! The end is nigh! *Starts stock-piling helium canisters in the attic* --Username132 (talk) 10:52, 24 December 2006 (UTC)

Don't worry, I'd be willing to bet that if and when international demand justifies it, US private sector producers will increase production of helium to meet that demand. Cheers Geologyguy 15:26, 24 December 2006 (UTC)

See our articles National Helium Reserve and Helium#Applications for reasons why the U.S. government might want to have helium handy. TenOfAllTrades(talk) 16:10, 24 December 2006 (UTC)

Once used, most helium escapes into the atmosphere and ultimately bleeds into space because it is too light to be trapped by the Earth's gravity. Hence all the helium we have is left over from the formation of the Earth. Absent someone inventing cheap fusion, helium is basically irreplacable. So what is the value of dwindling and irreplacable natural resource? Apparently not as high as one might think. Dragons flight 18:26, 24 December 2006 (UTC)

But, depending on the quantity on Earth, it may take millions of years for us to use it all up. If so, this really isn't much of a concern. StuRat 12:15, 25 December 2006 (UTC)

I would say that liquid helium is actually tremendously important, which means squandering so much of it is really kind of silly--71.247.120.5 23:14, 25 December 2006 (UTC)

The atmosphere still contains only about 24 trillion cubic metres of the stuff. This is indeed worrisome; what are we going to do when it runs out? Since the rate of depletion does not depend on consumption but only on the bleeding off into space, I propose that NASA envelop the Earth with a big balloon.  --Lambiam^Talk 00:48, 26 December 2006 (UTC)

Don't be silly, there isn't enough rubber to make a balloon that size--71.247.120.5 00:52, 26 December 2006 (UTC)

Dec 24

Observation whilst feeding the gulls...

I was giving the gulls their lunch today and I noticed another odd behaviour pattern (actually, it's something they usually do but I've never really thought much about it). The (small) black-headed gulls often see the pile of food first, yet flutter around in the air above, or perch nearby for several minutes. No bird seems to want to be the first one down to eat. The (large) herring gulls and great black-backed gulls have no qualms about hanging back and dive down to stuff their faces as soon as they become aware of the food.

At this point, the BH gulls see their larger relatives eating and descend en masse to join in. They usually don't end up with much of a feed and get pecked at and chased quite a bit. I've tried to figure this in my head - do you think the black-heads, being much smaller and more vulnerable on the ground are waiting for the big gulls to land before they decide to eat, figuring that the bigger, stronger, more aggressive birds will protect them from any passing predator? In a way, it seems counterproductive - less food and more aggro, especially considering that there are very few predators of gulls in an urban environment. Opinions? Anyone else noticed them doing this? --Kurt Shaped Box 01:37, 24 December 2006 (UTC)

Sounds to me like the smaller gulls are simply being considerate of their larger brethren. A couple points:

1. A bigger gull needs to eat more per day to stay alive; I wouldn't assume that it's beyond a small gull to know this and act accordingly, waiting to snack on little crumbs.
2. No doubt a tacit pecking order has been established, and if a small gull were to violate it, it would be on the receiving end of some 'social pressure'.

——Vranak→

Thanks for your answers, folks. Does anyone know how much your average 'large white headed gull' eats per day in the wild? I know from personal observation that they can eat about the same amount as a human in one sitting (then they go off to rest, digest and take a nap). I'm not sure if they eat as often as we do if given the opportunity. --Kurt Shaped Box 10:06, 24 December 2006 (UTC)

I'm interested in what gulls eat, period. I mean, I'm sure it has it all listed in the gulls article, but I can never discern what it is they peck off the ground. --Vranak 19:10, 24 December 2006 (UTC)

I usually feed my local gulls cooked meat, bread, cheese or whatever kitchen scraps I have lying around most lunchtimes. I cut/break it all into smallish pieces, bag it, then tip it into a pile in my garden. Gulls have their preferences but will eat just about anything organic if they're hungry enough. They'll kill for food if they have to but they usually just scavenge. --Kurt Shaped Box 22:31, 24 December 2006 (UTC)

Maybe the small gulls don't have as keen of a sense of smell so rely on the big gulls to tell them if the food is safe to eat. If the big gulls eat it, then they know it's fine for them to eat, too. StuRat 04:46, 24 December 2006 (UTC)

I think it's more likely dominance/submission behaviour. Anchoress 05:22, 24 December 2006 (UTC)

It may be an order of feeding based on strength or fear of harm, but that does not explain the smaller birds actually waiting until the larger, stronger birds appear. Nor does it explain why the smaller birds then come down to feed while the large ones are still there. A clue might be found in the fact that these birds are all in the role of scavenger, as opposed to hunter. When hunting they can select the type of food which they are suited to catch, kill and ingest, i.e. appropriate to their strength and abilities. When scavenging they have to take whatever there is. In this situation, if they perceive the food as too large to break up into small edible pieces, they may simply be waiting for larger birds with the ability to tear off the skin of a dead fish, or slit open its body, before taking what they are capable of from the left overs, i.e. this may be the only way for them to get at the meat inside. This determinant of feeding order (or lack of it) has been described for a mixture of sea and land based birds feeding on carrion and seems to be valid in the case of vultures specialised for eating specific parts of a dead animal (I enjoyed the bit in the first article on how a bird was more interested in defending his territory than in actually eating the fish). The crucial point of such an explanation is how the birds perceive the food, i.e. do they think they are capable of successfully breaking up the food into eatable pieces. This theory may possibly be assessed by lumping similar food all together in a large piece, or spreading it out as small bits, and comparing behaviour. --Seejyb 11:30, 24 December 2006 (UTC)

Gulls do have this huge personality flaw (I'm not sure what the more scientific amongst us would call it) when it comes to considering it more important to strut around with chest puffed out, defending a pile of food from the other gulls than actually eating it themselves. Invariably, the lone 'dick waving' bird gets overwhelmed by sheer weight of numbers and ends up being pecked and jostled out of the way, often ending up with no food at all. There's also the 'must steal food from another gull' mindset. One bird picks up a piece of meat and flies away with it, at which point the majority of the other gulls give chase, leaving behind the rest of the food for the two or three birds that hung back to eat at their leisure - whilst the others flap, squawk and squabble in the air above. --Kurt Shaped Box 22:43, 24 December 2006 (UTC)

Gulls aren't the only ones with this defect. Watch kids get jealous of each other's Xmas presents; they show no interest in the toy until the other kid does, then they all of a sudden have to have it, LOL. StuRat 12:11, 25 December 2006 (UTC)

I suppose it makes sense to fight for every scrap in their natural environment when food/desired objects are scarce - I guess that it's a survival instinct built into most living things. If another of your kind possesses something (be it food, nesting material, or a toy), then it must be of value for survival and therefore it would be advantageous to possess that thing yourself. However, some gulls have definitely figured out that in an urban environment, where the food supply is plentiful and almost 100% assured, that they don't need to do this - and that it's actually beneficial to let the 'sheep' do their thing and nip in when they're distracted. I guess it just comes down to individual intelligence and life experience. --Kurt Shaped Box 23:58, 25 December 2006 (UTC)

cognitive intelligence - name for the occurrence of role reversal between subject and object in test situation.

Definition of incident for which a name or term is being requested:

(first part)

When your research leads you to the point of discovering that you have previously been unwittingly playing the role of the subject in someone else's experiment.

(second part)

Being thus aware as to the presence of observation, the subject then embarks on behaviour directed to illicit a response from its observers, for the benefit of acquiring knowledge on them.

For example;

(first part)

A psychologist was taking turns locking different animals inside a small room. After the door was shut, he would observe the animals behaviour through the keyhole. He continued doing this and taking notes until he came to a chimpanzee. He shut the chimp in the wooden room, put his eye to the keyhole only to observe that the room now appeared dark. The chimp had put it's eye to the keyhole on the other side of the door.

• There is no name except role reversal for this contrived situation. alteripse 15:56, 24 December 2006 (UTC)

Are you asking whether there exists a name for this situation, or are you asking for suggestions for a newly-made-up term? I agree with alteripse that you're not going to find an existing name for this. The first part made me think of the famous Milgram experiment. While contrived, I vaguely remember a science fiction story that had the same premise, where the original observers were aliens.  --Lambiam^Talk 16:09, 24 December 2006 (UTC)

Niklas Luhmann's term observation of the second order (Beobachtung zweiter Ordnung) comes to mind, a relevant key to his theory on social systems. Though his definition of observation is different than common usage and mostly refers not to psychical but to social systems (such as economy or religion) which observe their environment and themselves, while also observing the observations and so forth. Observed and observer switching roles back and forth, flickering hierarchies - Douglas Hofstadter might have called it a strange loop.---Sluzzelin 00:25, 25 December 2006 (UTC)

Aged whiskey

is 50 year old whiskey ok to drink?

As long as it has been properly stored, emphatically YES. Enjoy; you are undoubtedly the subject of envy for most of the people who read this. Anchoress 05:20, 24 December 2006 (UTC)

"50 year old whiskey" might not mean what you think. Whiskey "ages" in the cask, but (unlike wine) once it's decanted into a bottle it largely doesn't. When you buy whiskey the age on the label is the time it spent in the cast - if it spent another ten years in the bottle on a shelf somewhere, it's still the same "age" it was when it was bottled. Now, if the whiskey really is labelled "50 year old" on the bottle, it's been in the cask for 50 years. I'm not aware of any major manufacturer who keeps their product in the cask remotely as long; 21 years is just about the limit. The longer the whiskey is in the barrel the stronger it gets (slightly), and the more flavour will percolate from the wood into the spirit. After 50 years the whiskey will be very heavily flavoured, and very dark in colour. I rather suspect too much so. Now if you mean some old whiskey you found, say that was 20 year old when it was bottled in 1976. That's still just 20 year old whiskey, and always will be. -- Finlay McWalter | Talk 13:35, 24 December 2006 (UTC)

Rumour has it that Johnnie Walker Blue has 50-60 year old elements to it. --jpgordon^∇∆∇∆ 18:27, 25 December 2006 (UTC)

It is not a universal constant that wood-flavoured beverages taste better than not. I recently tried a bottle of 'Naked Grape' white wine that boasted of it not being aged in oak. It was quite good. Vranak

If it's been sealed in the bottle all this time it should be fine, by which I mean not poisonous. It might not taste so good, however, but that's for you to judge. StuRat 12:06, 25 December 2006 (UTC)

Dominant genes?

I was wondering whether something such as dominant genes existed. I am doing a holiday job in Canal Walk shopping mall in Cape Town, where I see thousands of people everyday. What I have noticed, is that almost 9/10 couples which have a parent with dark hair and a parent with blonde hair and blue eyes, the children end up with the blonde hair and blue eyes. I have also seen hundreds of Europeans who have married with Asian people (mainly Japanese, Chinese and Malaysian people), who also have one parent with blonde hair and blue eyes, then the children also end up with blonde hair and blue eyes. I thought that if this was meant to go on, one day we'll all have blonde hair and blue eyes. PS: All of the Asians who I asked if they were related to these blonde children said they were. This is really something that fascinates me. Anyone with information about this? ► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 07:29, 24 December 2006 (UTC)

There certainly are dominant genes and recessive genes. The genetics of human skin and eye colour are beginning to be understood by scientists (indeed, just this week a huge breakthrough was made in understanding the genetic basis of blue eyes [32]). Regarding the idea that "one day we'll all have blonde hair and blue eyes", actually quite the opposite has been proposed. Since blonde hair (and to some extent, blue eyes) are recessive to darker pigmentation, it has been suggested they will die out at some point in the future [33]. If I may offer a personal observation (and I have a PhD in pigmentation genetics, so it is informed to some extent): this is quite a strange thing for a human geneticist to propose, really, as by their very nature truly recessive genes tend not to "die out" completely unless there is a very strong selective pressure on them. I don't see men running from blondes in disgust (or indeed vice versa if the female response to the new Blonde Bond is anything to go by) Therefore, I suspect this story has been spun by the media somewhat. Rockpocket 09:43, 24 December 2006 (UTC)

This article mentions the fact that many human have hair that grows darker as they mature. Some adults that would not be called "blond" were "blond" as children. --JWSchmidt 01:08, 25 December 2006 (UTC)

monoline roots

sir/madam, I am interested to know more about monopoline roots.I been told that these are used to cure aids/hiv.I request resourceful persons to provide some more light on the topic . thanx, ajay jain <email address removed for security>

Many things are "said" or sold to cure or prevent AIDS. Mistrust anyone who wants to sell you something for which there is no evidence of efficacy. There are degrees of evidence, and no evidence of a reliable degree supports use of these roots for these purposes. alteripse 15:53, 24 December 2006 (UTC)

I can't find any information on the Web on "monopoline", except that another name is kanamrutakadugandha. I can't find any information on kanamrutakadugandha, except that another name is "monopoline roots". Most pages are about people asking what it is, or where they can buy it, or others trying to sell it. If there had been any research into whatever this is, there would have been at least some information somewhere. The use of untested drugs of unknown composition and strength can be dangerous to your health.  --Lambiam^Talk 23:45, 24 December 2006 (UTC)

Perfect Hurricane

Reading the article on the Great Storm of 1703, I noticed the term "Perfect Hurricane." What is it's meaning? Crisco 1492 10:05, 24 December 2006 (UTC)

It means a textbook example of a hurricane, including features like a well defined eye and eye-wall, symmetrical arms/feeder bands, etc. See perfect storm for the source of the term. StuRat 11:41, 25 December 2006 (UTC)

Squeeze Those LEDSs!

I have some LEDs to use that have a rated current of 300mA but a surge current of 3mA - can this surge current be exploited to acheive greater light intensity without damaging the LED? --Username132 (talk) 10:58, 24 December 2006 (UTC)

Surge current is 3A right (you wrote 3mA)?

Probably not continously - clearly something that works well at 300mA will still last for a long time at 310mA - the higher you go the more likely the thing will 'blow' - the life is shortened. However you could try pulsing to a higher current - if you have a suitable circuit - for instance at 1km 3A on 1/10sec of a second is more noticable than 3mA continuous - I can't say that doing this won't shorten the life of the bulb though. If the average current exceeds the rated continuous current the thing will start to overheat..87.102.4.126 11:39, 24 December 2006 (UTC)

FYI, when you overheat an LED they tend to explode, POP, little shards of plastic flying everywhere--71.247.120.5 12:36, 24 December 2006 (UTC)

Huh? No way. I overheated lots of LEDs and the worst that happened was that the inside turned brown and the thing heated up and melted. No explosion. Nothing. You generally don't have to worry about overloading an LED unless you're in a room full of nitrogen triiodide. Ilikefood 23:48, 25 December 2006 (UTC)

If you apply a surge at just the right voltage they'll pop instead of browning out--71.247.120.5 00:17, 26 December 2006 (UTC)

In the 1970s, Hewlett-Packard reported (in an article in HP Journal about the design of the HP-35 calculator) that an LED repeatedly pulsed very briefly appeared brighter to the human eye than an LED carrying a continuous current with the same average value. For this reason, they chose to multiplex the 15 digit display of the HP35 one LED segment at a time rather than the more-usual one digit at a time. (The energy was stored in inductors and then dumped into the LEDs.) I don't remember whether they cited a reason for this effect and I certainly don't know if it's still true with modern LEDs, but it might be one reason to consider exploiting the surge-current rating of an LED.

Atlant 14:58, 26 December 2006 (UTC)

One Device. One Non-rotating Speaker. 360 Degrees

I want sound from a single speaker to be effectively spread over 360 degrees without rotating it. I figure if the speaker is directed towards an appropriately designed surface, sound will be directed in all directions. It doesn't need to carry far - 60+ m radius is fine. Eighty or so desicbels at source. --Username132 (talk) 11:10, 24 December 2006 (UTC)

The hi-fi world is full of these - 'fire' your sound device up or down onto a conical or similar surface - http://www.fcsurplus.ca/shopping/shopexd.asp?id=1525 is this picture you can see the cone, the speaker is above the cone. The sound reflection cone is supposed to be hard and rigid - to get good sound reflection. As for the volume - I think horn speakers get quite loud - (the sort that garble the announcements at train stations (in the UK at least)87.102.4.126 11:45, 24 December 2006 (UTC)

I would second the upward or downward speaker pointing at the outside surface of a cone on the speaker axis. Some commercial systems use this method.--Light current 19:42, 24 December 2006 (UTC)

Also see the description of the "Walsh" transducer at Loudspeaker#Conical bending wave transducers.

Atlant 15:03, 26 December 2006 (UTC)

Reading in the Dark

Is it really bad for you? If so, why? Sashafklein 11:33, 24 December 2006 (UTC)

If you feel like your eyes are straining, or you're getting a headache, it's definitely a bad idea. It's a matter of personal sensitivites though. I sometimes read by a single candle without much trouble, though not for more than ten minutes at a time. --Vranak 19:05, 24 December 2006 (UTC)

This is a folk medicine concept, and likely bogus. There is no evidence and it makes no sense that using your eyes in dim light harms them. alteripse 19:16, 24 December 2006 (UTC)

It does open up your irises though and maybe your depth of field and focussing ability is reduced. I know mine is.--Light current 19:45, 24 December 2006 (UTC)

I remember reading a couple of years ago a science news article reporting on research in which the hypothesis had been investigated. The outcome was that no significant ill effects had been found. Sorry, I have no reference for this except my memory, and I have no information about the actual content of the research – such reports by science journalists are often seriously misleading.  --Lambiam^Talk 23:55, 24 December 2006 (UTC)

Yes. i remember reading a report which finally stated that reading in dim light does not damage the eyes any more than using a camera in dim light damages the camera. But I know that to read in dim light, you need to strain your eyes a bit but may be the effect is just temporary. In any case, I believe that it is not good. whenever you need to strain your organs to do something, I believe that it may not be very good. -- WikiCheng | Talk 17:48, 25 December 2006 (UTC)

Regardless of whether you believe it, I must politely call it nonsense. You strain muscles to build muscles. You strain your brain to build your brain. In the case of reading in dim light, it is your brain that does the straining, not your eyes. alteripse 19:45, 25 December 2006 (UTC)

Yeah a bit like straining your 'ears' to hear quiet sounds does not harm them. Its not the transducer that is being strained, its the processor that is having to work harder.--Light current 20:04, 25 December 2006 (UTC)

I concurr. X [Mac Davis] (DESK|How's my driving?) 00:10, 26 December 2006 (UTC)

I don't think it is just the brain. The eyes do strain to open the pupil as wide as possible. In dim light, I suppose the eyes will have some difficulty in focusing. I don't agree with the analogy of straining the muscles to build them. You can not make your eyes better by reading in dim light, unlike the muscles. It is the unnecessary strain I was referring to. Even in case of muscles, you can't build them just by straining them. It will do more harm than good -- WikiCheng | Talk 04:02, 26 December 2006 (UTC)

I thought the pupils opened up automatically and you have no direct control over pupil size. as per our article:

In humans and many animals (but few fish), the size of the pupil is controlled by involuntary constriction and dilation of the iris in order to regulate the intensity of light entering the eye. This is known as the pupillary reflex. In bright light, the human pupil has a diameter of about 1.5 millimeters, in dim light the diameter is enlarged to about 8 millimeters.

--Light current 04:07, 26 December 2006 (UTC)

Custard Bread?

Will adding custard mix to my mixture for banana bread make banana and custard bread or something barely edible? --Username132 (talk) 11:34, 24 December 2006 (UTC)

It's impossible to guess the result, just try it. Your financial loss, if a failure, will be trivial! But reduce the amount of water you add, to compenate for the custard. Let us know, here, how it turns out - Adrian Pingstone 11:42, 24 December 2006 (UTC)

Baking in progress. Stand by... --Username132 (talk) 12:16, 24 December 2006 (UTC)

If that fails, simply mix the custard up normally, and serve it on the banana bread... Laïka 13:32, 24 December 2006 (UTC)

How is it coming? Must be done now. Don't leave us in suspense over the holidays...  --Lambiam^Talk 16:21, 24 December 2006 (UTC)

Sorry about that. It came out okay. It should be noted that I used powdered custard and less than half the water one would usually require to make it up. I felt it was a little dry but everyone else seemed to like it. --62.100.22.29 00:51, 25 December 2006 (UTC)

FYI, if the goal is to make the banana bread smoother, finer, richer, etc, a couple of tablespoons of mayonnaise would work better. The problem with powdered custard mix is that it's usually just flavourings, colourings and either cornstarch or tapioca, no real 'custard' (i.e; eggs and cream), just absorbent starches (sometimes some powdered milk). This would have the effect of bulking up your baking, without actually adding anything useful to it. And FWIW, tinkering like that with a finer cake, like a plain cake or an angelfood etc, could actually ruin it. But cooking experiments are fun, I'm glad it turned out OK at least. Anchoress 05:02, 25 December 2006 (UTC)

Using custard to moisten the finished bread is a good idea, but you didn't implement it in quite the right way. Instead of mixing the custard in with the banana bread mix and baking them together, I'd encourage you to prepare the banana bread and custard separately, then combine them when served. A nice layered presentation would be good, with banana bread on the bottom, custard next, then more banana bread on top. I would keep them separate until ready to serve, however, as the custard may make the banana bread soggy after a while. StuRat 11:32, 25 December 2006 (UTC)

The ultimate expression of this might be the trifle or the Italian rum cake.

Atlant 15:06, 26 December 2006 (UTC)

Infrared Filters

I want to optimise the sensitivity of some infrared sensors, for using in laser tagging games. I've noticed that there are being produced some IR filters that block a lot of visible light from the sun, allowing most IR to pass through. My question pertains to the usefulness of these filters, since the IR sensors should only be activated by IR light anyway (sure, the suns light included IR, but the filter doesn't protect against sun IR, just sun visible light). Is it worth bothering with? --Username132 (talk) 12:34, 24 December 2006 (UTC)

Depends on the intensity of the IR from the sun cf the intensity you are trying to recieve from the source Transmitter. Iwould think a filter centered on your IR wavelength couldnt do any harm and in fact may stop false triggering. Is the IR source modulated?--Light current 17:36, 24 December 2006 (UTC)

It is modulated and you must be right - the sensors must react to non-IR light. However the signals are indeed modulated. --62.100.22.29 00:54, 25 December 2006 (UTC)

OK If its modulated , you can make a circuit to respond only to the modulation ( a detector circuit). Then you only have the problem of sensor overload from the sun. Filters may achieve this 8-)--Light current 01:10, 25 December 2006 (UTC)

I'm wondering how the IR sensor can detect IR. Doesn't it have to use a filter to do so? --Bowlhover 17:50, 25 December 2006 (UTC)

Well the semiconductor types are desinged to be sensistive to just a small range of wavelengths . See Infrared_detector--Light current 18:01, 25 December 2006 (UTC)

Even they all seem to have a filter in front of them, though. It commonly appears weirdly-purple when viewed in visible light.

Atlant 15:09, 26 December 2006 (UTC)

Immitation compulsion

In a similar if not identical occurance of a child imitating an adult is one of the recognized reasons for society having laws against everything from Jay walking to playing basketball in the street to spiting on the sidewalk because other people have a tendency to compulsively imitate others in doing whatever they may see others do? Adaptron 13:30, 24 December 2006 (UTC)

No. Laws are to prevent the first person from doing it, not the second. alteripse 15:50, 24 December 2006 (UTC)

But laws are not written on the basis of speculating what someone might do but rather on the knowledge of what someone has done. Adaptron 21:41, 24 December 2006 (UTC)

While I don't think those laws are a good example, there are laws against "corrupting a minor", which is more like what you're talking about. They usually focus on minors being encouraged to have sex, use drugs and alcohol, etc. StuRat 11:23, 25 December 2006 (UTC)

Yes, now take that idea and apply it to peers or the more or less feeble minded. "Monkey see monkey do" kind of thing. Although a thing might make perfect common sense not to be done the law against it is necessary because some people do not have any common sense and when others see them doing the thing the seeing of it may outweigh their common sense as well. The law is there merely to outweigh the lack of common sense rather than to be oppressive or the work of a bunch of control freaks. Example: a law against playing basketball in a busy side street that happens to be a very common route that the majority of people take to get home. Some kids who lack common sense actually seek out friends who live on such streets so that can have more fun by making traffic one of the opposing players. Adaptron 03:03, 27 December 2006 (UTC)

Perhaps think more along the lines of game theory: what harm is it if I send you just one unsolicited advertisement via email, or perhaps throw a hamburger wrapper from my car window? But if the same behavior is global, so everyone throws a hamburger wrapper from their car window perhaps several times a day, then the city streets turn into snow-drifts of trash overnight. That's why littering is defined as a "bad thing." But *I* didn't cause the problem with my one wrapper, it was EVERYONE ELSE who did it. Yet everyone else is the same as me, and has identical reasoning, so they become angry at the thousands of litterbugs around them, yet don't stop littering. (And your little spammer-business should be perfectly legit, since its the millions of OTHER spammers who are wrecking the internet.) Then an extra party is added in the form of a policeman who writes you a $200 ticket even if you discard a tiny wadded-up gum wrapper on the street. And the terrible punishment applies even to *ME*, when obviously it should only apply to everyone else, since the huge litter problem is caused by all those thousands of strangers, not by me.

See what's going on? I want to be a "cheater," but at the same time want nobody else to cheat, because if they do, it makes the world a rotten place to live. I want to remove the inconvenience of having to save up my car trash and take it to the trash can, rather than just pitching it out the car window. One person's litter harms nobody. But as a human being, I'm just one identical bacterium in the huge culture dish, so whatever "bad" things I do will very probably be done by billions of other people as well, and that's what makes them "bad." One person spitting on the sidewalk is not problem, but what if 100K people in a city start doing it? We each cut down three trees, and Earth's forests vanish. We each catch five fishes, and no more fish exist. It has nothing to do with copied behavior, and everything to do with huge numbers of identical "actors" who all naturally end up performing the same actions for the same reasons.--Wjbeaty 07:15, 27 December 2006 (UTC)

One interesting effect related to this conversation is two methods of litter control. The "normal method" is just to let litter accumulate until it gets to a point that justifies hiring a crew to clean it up, then wait until it gets to such a level again. A newer approach, however, is to hire people to immediately clean up any litter. At first, this would seem to be less efficient, as most of the time this person won't be picking up litter, but only waiting around. However, when human psychology is taken into account, this strategy is effective, as few people want to be the first to litter, but many people are willing to add more litter to an area that is already littered. Thus, the majority of littering can be eliminated via this method. StuRat 14:15, 27 December 2006 (UTC)

Fluorescent light is dead...

In my bathroom, I have a standard 50W fluorescent lamp, which is fairly new (purchased in the last year or so). It is one of those ones which allows for "instant" powering up (not the like the older ones where you had to hold down the button to "charge" it up). In any case, the lughead repairman fixing some piping in the wall managed to drop it, breaking the bulb. I bought a new bulb, but now the lamp doesn't really work: it starts to "power up", gets very bright, and then shuts off completely. If you turn it off and on again it usually requires a few seconds in the "off" position before it will even do the "powering up" again.

Any idea about what's happened here? Is it fixable? Is it a problem with the bulb, or the lamp? Any thoughts? --24.147.86.187 17:26, 24 December 2006 (UTC)

Do you know if its got an electronic ballast or an inductance one (heavy coil in the base unit)? If its been dropped, who knows what circuit rearrangement there may have been inside the fitting. Its probably not worth trying to fix it.--Light current 17:40, 24 December 2006 (UTC)

I'm pretty sure it is a ballast. I opened it up awhile back and found there wasn't much to these lights -- a few wires here and there, the ballast being the only thing of any substance (a little plastic box). --24.147.86.187 22:36, 24 December 2006 (UTC)

Are you sure you bought the correct replacement bulb? I wouldn't expect a ballast (whether electronic or magnetic) to break upon being dropped. ("50W", by the way, isn't a standard size for any fluorescent lamp in common usage.)

Atlant 15:11, 26 December 2006 (UTC)

Lips

Why is homo sapiens appaerntly the only mammal to wear his lips on the outside?--Light current 17:51, 24 December 2006 (UTC)

As long as you realize that the answer to this type of question is basically a just-so story, I will tell you one. Humans have preferred to have sex with people with fuller, more visible lips, so there has been selection pressure over the eons for fuller, more visible lips. I realize this is perilously close to a tautology, but that is the problem with this type of explanation. Why do we prefer to have sex with people with fuller, more visible lips? I dunno, we just do. alteripse 19:12, 24 December 2006 (UTC)

Yeah its not quite the same kissing a chimp!--Light current 19:31, 24 December 2006 (UTC)

Alteripse's just-so-story is also called sexual selection, but the article doesn't mention lips. Are we really the only creatures wearing our lips on the outside, or are ours just red and more noticeable to us? What about other primates or the white rhino, for instance? ---Sluzzelin 19:57, 24 December 2006 (UTC)

OK a white rhino has nice juicy lips. Cant think of any other primates.--Light current 21:06, 24 December 2006 (UTC)

Why is the neutron more massive than the proton?

The neutron consists of two "down" and an "up" quark, the proton of two "up" and a "down" quark. An "up" quark has a charge of +2/3, a "down" quark has a charge of -1/3. So the quarks inside a proton repel each other much more than the quarks inside a neutron, meaning that you need more energy to hold them together. Since energy is mass, the proton should be heavier. Furthermore, the "up" quark creates a stronger electric field than the "down" quark, hence stores more energy, hence should be heavier. Both effects should add up and you (or rather, I) would expect the proton to be more massive than the neutron. Why does nature refuse to follow this logic? Thanks, AxelBoldt 20:59, 24 December 2006 (UTC)

You assume that the interaction between quarks can be described in terms of the electromagnetic force (mediated by photons), but the theory of quantum chromodynamics describes it as strong interaction, mediated by gluons. The properties of this strong force are completely different from the other fundamental forces.

True, both proton and neutron hang together because of the strong force, but I don't see how that would cause a larger mass for the neutron; the situation seems to be symmetric and based on the strong force alone I would expect equal masses. Quarks do feel the (comparatively weak) electromagnetic force in addition to the strong force, and this effect is not symmetric. AxelBoldt 01:34, 25 December 2006 (UTC)

Simple: down quarks have a greater intrinsic energy than up quarks. What I want to know is why the greater intrinsic energy of the down quarks in the neutron so nearly cancels the greater interaction energy of the proton (why their energies are so close). —Keenan Pepper 01:53, 25 December 2006 (UTC)

And of course like every child that has not yet tired of the game, I'll continue asking: why is the down quark more energetic, hence more massive? Is there any deeper way to understand it beyond "that's the way it is"? Thanks, AxelBoldt 20:24, 26 December 2006 (UTC)

nniepe

Dec 25

IR Transmissibility Of Materials

Is a more significant amount of IR light absorbed by glass than by normal transparent plastic? I need a lens for an infrared tagging gun but everyone seems to use glass lenses (probably because they're easier to find). Sure, perhaps there is a special plastic that transmits IR effectively, but is it the same for all plastic? Is it worth using a plastic lens (the ones on torches and bikes aren't designed for condensing into an intense beam (which is what I need to fire 200+ meters). --62.100.22.29 01:00, 25 December 2006 (UTC)

Depends on what's meant by "infrared." What's a tagging gun? For example, 750 nanometer light is IR, yet it's exactly the same as deep red light, and will pass through any normal transparent material. On the other hand, 10,000 nanometer light is also IR, yet it passes through white polyethelene and opaque silver germanium, but it's blocked by glass and water. The cheap way to handle 10,000nM light is to bounce it off a curved reflector, preferably polished copper. So, are you talking about "Near IR" coming from an LED, or "Longwave thermal IR" coming from a warm human body? If it's LED light, glass or plastic lenses should work fine. --Wjbeaty 06:51, 27 December 2006 (UTC)

The jagged things in a dog's mouth

No, not the teeth. What are the jagged bits on the bottom lip of the dog in this pic? I've had several dogs throughout my life and never known what those things did or why they're there. Dismas|^(talk) 01:57, 25 December 2006 (UTC)

One of my anatomy books calls them "blunt papillae". I don't know their function, if any. --Joelmills 04:33, 25 December 2006 (UTC)

I suspect they are used to spread drool about when they shake their heads, perhaps as a method of scent marking ? StuRat 11:03, 25 December 2006 (UTC)

I don't think they have any function, except to remind us that such dogs are perhaps bred a little too far from their original form --

This wolf has sensible-looking gums

. Vranak

Different tastes of bottled water

What makes different brands of bottle water taste different? To me, Aquafina tastes "sweet" while Evian tastes "metallic". --72.202.150.92 02:07, 25 December 2006 (UTC)

The minerals in the water, as well as the taste leached from the water bottle. --Bowlhover 02:58, 25 December 2006 (UTC)

Aquafina is really just RO water (just very pure water with nothing dissolved in it), which tastes "sweet" to me too sometimes, especially if I'm really thirsty. The others like Evian are "mineral water" which are "hard water", that is to say, they taste like crap because they contain dissolved calcium, magnesium and carbonate ions. Why people pay money to drink such things is beyond me, as the actual amount of Ca and Mg contained per liter is trivial compared to other dietary sources. --Deglr6328 09:14, 25 December 2006 (UTC)

It just depends on what you're used to. I grew up and live in a place (Vancouver, British Columbia), that has amongst the purest tapwater in the world. Pure in the sense of soft, lacking in minerals. I practically gag when I drink mineralised water, while people who are more accustomed to harder water think Vancouver water is 'tasteless' and 'bland'. Anchoress 09:19, 25 December 2006 (UTC)

Probably. I grew up drinking some of the most horribly hard water you can imagine, hot water heaters would die wretched unspeakable deaths within a mere 1-2 years. I hated the taste but got used to it after a while of living there. Then, I started work at a place where I could get as much free RO water as I wanted and I was hooked immediately. Its all I ever drink (well, when I drink water at home anyway) now. Also, curious as to the validity of the pernicious urban ledgend that drinking deionized water will kill you because its supposedly "hungry for ions" and will leach them out of your body, I did a little experiment where I drank it for a week or so. I'm still here..... :o) As I suspected, no noticeable effect at all. --Deglr6328 09:30, 25 December 2006 (UTC)

There's a few brands of bottled water coming out of New Zealand now, that are all high in silica. Very different taste, and I've had quite enough of it after a few bottles. Then there's Fiji water, which is exceptionally pure -- very little in the way of minerals. Aquafina I wouldn't touch with a ten foot pole, it's just refined tap water with all sorts of unnatural salts added to it, which are not readily absorbed by the human body. Vranak 18:23, 25 December 2006 (UTC)

People seem to entertain such strange ideas about tap water/bottled water/purified water. Regular Aquafina is simply tap water treated by reverse osmosis. It is highly pure water with no dissolved salts. That's it. The source of water is totally irrelevant, it could just as well come directly from a sewage treatment plant and you would never know the difference once it had been filtered and treated by RO filtration. Water molecules are water molecules and they don't have a "memory" about where they've been before. See newater (whose advisory board ironically seems to suffer from the same "too pure to drink" nonsense ideas that I explain as bunk above).--Deglr6328 22:30, 25 December 2006 (UTC)

On the contrary, isn't there an arbitrarily-persistent 'memory effect' of water? I seem to remember reading something about researchers diluting water more and more, and detecting a trace element every time.

And the last time I looked on the side of an Aquafina bottle, it listed all sorts of chemical salts that had been added in order to make it look like you have purchased a healthy beverage. Has this practice discontinued? Vranak

Well, are you looking at a bottle of FLAVORED water?? The water memory effect you are thinking of is pseudoscientific.--Deglr6328 19:43, 26 December 2006 (UTC)

It could be Aquafina in the United States is very different from the rest of the world. In the USA, Coke's Dasani adds minerals, but Pepsi's Aquafina does not. --72.202.150.92 02:13, 27 December 2006 (UTC)

I found this report (doi:10.1016/S0048-9697(01)00915-9) quite interesting. —Keenan Pepper 00:38, 26 December 2006 (UTC)

Heavy water production

I read the article on heavy water, but I'm still not sure how it's produced by humans, such as in the Norwegian Heavy Water Plant the Germans wanted control over during the Second World War. Could someone please clearify or send me in the direction to learn more about how it's produced by machines? --Anthonysenn 07:20, 25 December 2006 (UTC)

"Produced" implies that it's created. Although it could possibly be created using a nuclear reactor or particle accelerator, it's easier to just isolate naturally occurring heavy water. Since it is, as the name implies, heavier than normal water, the method used in Norway was to separate it using a centrifuge, which makes the weight difference more apparent (similar to being in a high gravity environment). The heavy water sinks to the "bottom" (outside of the centrifuge). By tapping off the water from this location, and repeating the centrifuge process, it's possible to purify it further and further, with each step, until eventually a very high purity of heavy water can be obtained. You do need to start with a huge quantity of water to get a tiny amount of heavy water, however, especially since the centrifuge process only collects a small portion of the heavy water from all the water put through the centrifuges. This requirement for huge quantities of input water means that the production facility must be located on a body of water. Note that the "waste water" is perfectly fine to return to the body of water, being identical to normal water except for a somewhat reduced level of heavy water. There are also several other methods for isolating heavy water. StuRat 10:35, 25 December 2006 (UTC)

Right, except no. Our article on Girdler sulfide process details the production process, which does not involve centrifuges. Hipocrite - «Talk» 15:25, 25 December 2006 (UTC)

As a side note, the Norwegian plant used electrolysis as detailed at Norwegian heavy water sabotage. Hipocrite - «Talk» 15:27, 25 December 2006 (UTC)

So, to clarify, heavy water is "produced" (although "purified" or "concentrated" might be a better term) by isotope separation. Some isotope separation techniques involve gas centrifuges (enriched uranium can be produced this way), but for heavy water production, the most common method is a chemical method, the Girdler sulfide process. The method actually used at the Norsk Hydro plant in Norway was a third method, involving electrolysis. Gandalf61 22:17, 25 December 2006 (UTC)

lasers

how do lasers work

They emit pulses of light at one frequency (color). Being the same color allows the light to spread out less than normal light. See our laser article for details. There are also similar devices, such as masers (which emit microwaves of a single frequency), etc. StuRat 10:24, 25 December 2006 (UTC)

Also, technically, no laser is truly monochromatic, so if I had to pick one thing that summed up laserness, I'd pick a population inversion--71.247.120.5 23:02, 25 December 2006 (UTC)

howstuffworks.com also has some good information. - Akamad 22:10, 25 December 2006 (UTC)

The site I would most recommend for you is this one, by the University of Colorado I believe. Easy to understand, and explains it very well. [34] X [Mac Davis] (DESK|How's my driving?) 23:07, 25 December 2006 (UTC)

Here's an ultra-simple explanation. Explaining lasers to my grandmother. Lasers contain a light-amplifying material. It's a lot like grey sunglasses, it doesn't distort what you see, but instead of making light dimmer, the special material makes it brighter. (Imagine a pair of sunglasses which brightened everything you saw.) That's the first idea. The second idea is the infinite mirror tunnel. Have you ever seen what happens when two mirrors face each other? If you stick your head between them, and if the mirrors are aligned parallel, then an "infinite tunnel" appears inside the mirrors, and in the distance the tunnel fades to greenish darkness. The tunnel looks dark because the light that forms the "virutual tunnel" is passing through some layers of greenish glass each time it bounces between the mirrors. If you're looking a thousand layers deep into the tunnel, you're seeing through two thousand layers of glass. OK, now what happens if we combine our magical light-amplifying sunglasses with the infinite mirror tunnel? Stick the amplifying material between the mirrors. As the light bounces back and forth, it becomes brighter and brighter. Down inside the virtual tunnel, the tunnel will not fade into dimness, instead the deeper parts will look brighter, and the very deepest parts will appear to glow intensely bright. Also, any light that travels a bit sideways will end up hitting the sides of the "infinite tunnel" and be lost. Only the light that goes straight down the middle of the virtual mirror-tunnel gets amplified continuously. We end up with very bright light trapped between the two mirrors; light made of parallel light rays, as if the light was coming from a tiny bright star buried miles deep inside the infinite tunnel. If we now replace one of the mirrors with partially-reflecting mirror, then part of the trapped light will be able to zoom past the mirror and come out as an intense parallel beam. This light is very weird because it seems to come from a tiny pointlike source. If we passed it through a convex lens, the beam will focus to an incredibly intense point which can be used to burn through materials. In this way laser light is far "sharper" than light from any other source. (If we tried to concentrate the light from a light bulb, we'd just end up with a small upside-down image of a light bulb. But if we do the same with light from a laser, we end up with an intensely bright microscopic dot which can be used as a cutting tool.) Laser light has other weird characteristics because, as the light travels down that infinite tunnel, some colors of light get amplified a bit more than others. After the light has traveled long enough between the mirrors, most colors aren't amplified as much as one color, and in the end only one incredibly pure color survives. Laser light is like a pure sound from a flute, while normal light is more like the roaring crowd at a football game. Or even better: laser light is like the high pitched pure-tone feedback squeal that happens whenever a microphone gets too close to a loudspeaker. Laser light *is* feedback, since the mirrors send the light rays back through the amplifying material over and over forever until a "loud squeal" builds up. Scientists have found all kinds of strange and interesting things which can be done with "pure single-tone" light. Holography is just one. --Wjbeaty 06:40, 27 December 2006 (UTC)

Hmm I like that story. I like the description of monochromaticity, and how the beam is automatically narrowed. Its a resonant circuit. Maybe a Fabry-Perot resonator with amplification! So: its an oscillator. In fact they were going to call it an oscillator but no one wanted to back a LOSER 8-) --Light current 07:07, 27 December 2006 (UTC).

Methadone

Dear Wikipedia users,

I am trying find out the drug "Methadone" in India. I have tried at several medical stores in small town in North India, nobody seem to have any idea about what this drug is. Is there any other name used for this particular drug in India? Could you please help. Becaue, a friend of mine is in urgent need of the drug.

Thanks,

Thupten G.

In the Western world, methadone is classed with the most restrictive protocols, there would be nowhere that you could get it legally without a prescription, which would be very difficult to procure. Have you talked to a doctor? Good luck. Anchoress 13:10, 25 December 2006 (UTC)

This would also apply in India, as it is a party to the Single Convention on Narcotic Drugs.[35] This means that the sales of methadone without a doctor's prescription is a crime.  --Lambiam^Talk 18:55, 25 December 2006 (UTC)

Methadone is definitely not available in India. It can be prescribed in some other countries to treat cough, pain, and opioid withdrawal. Substitutes include dextromethorphan, codeine, dihydrocodeine, morphine, buprenorphine. Using any of these drugs without knowledge is considered extremely dangerous. Please do not harm your friend by home treatment without consulting a professional. If it is a matter of withdrawal, do not be taken for a ride by an addict looking for temporary relief, even if it were a loved one. At least read this summary, so that you are not manipulated to feel guilty about the situation. The article confirms that uncomplicated opioid withdrawal is not an immediate life threatening emergency, except in a person with severe heart or blood pressure problems. If I misinterpret your situation, please forgive me. The pharmacist should be able to help you from the above list - they all have articles in Wikipedia. --Seejyb 02:09, 26 December 2006 (UTC)

Lizard speed indicative of dinosaur speed...?

Recently on a trip to Florida a friend and I were standing in a parking space on a very cloudy day when we spotted a four inch (approximately) lizard dashing for a distance we measured to be over a meter to grab an insect about the size of its head and then dash back to the sidewalk in about a second (We estimated this by retrieving a golf club from the car to duplicate the speed and distance we observed by swinging the club back and forth and counting off the seconds... one thousand one, one thousand two, etc.) Would this speed scale up to a larger lizard (dinosaur) like a Velociraptor or Tyrannosaurus rex? Merry Chrismas everyone 71.100.6.152 13:31, 25 December 2006 (UTC)

No. There are limiting factors with muscles as to the speed they can go. So if you scaled up the size of the lizard, the speed does not scale up proprtionately. Secondly, the lizard needs to feed on insects, which are fast animals. Therefore, they have to be exceedingly fast. A dinosaur predates on much larger, slower animals, and therefore has no need to go as fast. Force = mass x acceleration , so if the acceleration is high (as in the case of the lizard), the mass must be low. If the mass is high, such as in the dinosaur, and the acceleration is high, then the force to move the dinosaur would be astronomical, and no muscles can do this. --liquidGhoul 13:40, 25 December 2006 (UTC)

There is no easy correlation between max acceleration and max velocity.  --Lambiam^Talk 18:58, 25 December 2006 (UTC)

The example given was obviously a case of fast acceleration. The max velocity of the dinosaur and the lizard may be similar, but it is not something which is scaled up because of size. --liquidGhoul 22:33, 25 December 2006 (UTC)

THE BRAIN

hello & merry x-mas,

does anyone know what the brain would be in bytes, eg if my mp3 player is 512mb and my laptop is 80gb wha would my brain be. Im pretty sure that you could measure the brain in bytes because i think it works in the sameway as a computer, kinda, with simple on and off values; 0 & 1.

thanks, --90.240.210.165 13:49, 25 December 2006 (UTC)

The brain doesn't work in the same way as a computer, and doesn't work with simple on and off values. It's not clear to me that comparisons with computer hardware are particularly informative or interesting; nonetheless they are made. One estimate is that human memory is roughly comparable to a few hundred megabytes. - Nunh-huh 13:58, 25 December 2006 (UTC)

Is that all? I'd think it would be way, way more than that. Anchoress 14:45, 25 December 2006 (UTC)

That's probably only the readily available portion of memory, like the proper way to spell kat. :-) StuRat 16:11, 25 December 2006 (UTC)

Yes, the rest is taken up by the operating system. :) V. Szabolcs 11:14, 26 December 2006 (UTC)

The article on neural networks may be interesting in this context, if you see what it can do with only a few nodes all of a sudden it doesn't sound so weird that the brain would only be a few hundred megabytes. Besides, a few hundred megbytes is still very much, it just doesn't sound like much because we're so careless with diskspace. - Dammit 15:24, 25 December 2006 (UTC)

Yeah, I guess it depends on whether it's a Microsoft Neural Network, lol. Anchoress 15:43, 25 December 2006 (UTC)

A few hundred MB seems to be too less to store all the data like what all we have seen and heard, with all the properties like the sizes, places, events, the smell, the colour, the touch, the sounds etc etc. StuRat may be right -- WikiCheng | Talk 17:38, 25 December 2006 (UTC)

I think "memory" is referring to volatile, short term memory as comparative to RAM in this case, not storage/non-volatile long term hard-drive/flash type memory. --Wooty Woot? contribs 02:26, 26 December 2006 (UTC)

Having studied both Computer Science and Psychology, I can say that a computer and a human brain are readily-comparable on many different levels: just not storage capacity. The 'apples and oranges' cliche doesn't even come close to expressing the fundamental, poorly-understood differences between the two. --Vranak 18:19, 25 December 2006 (UTC)

An often quoted number for the number of neurons in the human brain is 100000000000 (100 billion, or 10¹¹). I don't know if this is a matter of everybody parrotting everybody else or the result of serious research, but it is probably not more than two orders of magnitude off. The number of synapses must be 100 to 1000 times larger, so we may be getting into the tera range. The numbers you gave in your question are all about memory size. Since we do not know how human memory works, we have no basis for giving any numbers there.  --Lambiam^Talk 19:12, 25 December 2006 (UTC)

not more than two orders of magnitude off. Uh. Right. :) X [Mac Davis] (DESK|How's my driving?) 23:00, 25 December 2006 (UTC)

You might enjoy The Age of Spiritual Machines by Ray Kurzweil. There is also the much older The Cognitive Computer: On Language, Learning, & Artificial Intelligence by Roger C. Schank and Peter Childers. As several have mentioned above, the architecture of the human brain isn't a single-processor Von Neumann architecture computer, so it's a bit hard to quantify all those axion/dendrite connections as bits and bytes; they're more like minterms in a PAL.

Atlant 15:26, 26 December 2006 (UTC)

Evolution versus Creation...?

Both POVs (points of view) seem to rely upon the fact that we exist today and in the past as the basis for their respective positions. Although the Creationist's POV is not scientifically provable it would seem that the Evolutionist's POV is provable. Yet where is the step by step list of each and every critical event which did and did not happen that permits our existence today as well as in the past such as the formation of the Sun and Solar System, the range of distance from the Sun which the Earth fell within, the absence of a collision with any other body that would have turned the Earth into shrapnel, development of the amino acids, RNA and DNA and their environments, critical proteins, Krebs Cycle, etc. ? Merry Christmas and Happy New Year from Adaptron 14:14, 25 December 2006 (UTC)

You may wish to review our articles on Formation and evolution of the Solar System, Big Bang, Evolution and Abiogenesis. Hipocrite - «Talk» 14:41, 25 December 2006 (UTC)

Additionally, just because one does not know every step does not mean that one solution is not more plausible than the other. Science does not claim certainty. --24.147.86.187 17:03, 25 December 2006 (UTC)

You see a camcorder, and wonder where it came from. You research how camcorders work, how the lens are made, what the circuit boards do, what records information on the tape, how the tape is played back, etc. But you still don't know how the metal that's in the camcorder was made. Would you conclude that the camcorder was made by a tornado (which makes no sense whatsoever) just because you don't know how metal is mined, or would you conclude that since you've seen most of the manufacturing process, the camcorder was made by humans? --Bowlhover 18:21, 25 December 2006 (UTC)

We have an article on evolution to go troll. I will block either of you if you try to start an evolution debate here. And a blessed Lord's nativity to both of you. alteripse 19:39, 25 December 2006 (UTC)

If you are going to issue threats for asking a legitimate question without intent of debate but only to find a list even if it is full of holes then perhaps I should send an email to PayPal and let them know that my donation was a big, big mistake as well as to pass the word around... Otherwise stay in your box Jack. 71.100.6.152 03:28, 26 December 2006 (UTC)

This was not a legitimate question, but the usual opening move in the familiar tedious debate. We have pages and pages of it at the evolution article for those who want to indulge, and there is a many gigabyte website entirely devoted by the debate. It does not need to occur here also. And Merry Christmas to you as well. alteripse 03:40, 26 December 2006 (UTC)

Sounds like you are not only accustom to making threats but to starting an arguement. Therefore I will not repeat myself. Such a list is valid from any point of view although it starts with references including the evolution article and another that was given along with particular comments and the need for your attitude to evolve as well. 71.100.6.152 04:08, 26 December 2006 (UTC)

I suppose that in the vastness of the one universe in which we happen to exist, it was bound to happen somewhere. Of course in those places where it didn't happen there'd be no one around to ask this very question nor an admin to... oh, nevermind.  ;-) --hydnjo talk 19:55, 25 December 2006 (UTC)

Even if we blame our existence on chance it is still a phenomenal occurrence that deserves consideration of all the things that could have gone wrong and yet went right. 71.100.6.152 04:25, 26 December 2006 (UTC)

I won't pretend to have thought enough about your ponderings to give you a deep answer, but if you are genuinely pondering, you might be interested in pondering the anthropic principle. —Pengo ^{talk · contribs} 04:51, 26 December 2006 (UTC)

If the size of the universe is infinite, and the large-scale distribution of matter, at some time in the past, followed the same random distribution everywhere, and the laws of physics allow intelligent life to arise spontaneously anywhere with a probability greater than 0, then the probability for such life to arise in infinitely many places equals 1 (100%). This holds however small the initial probability is, for example one in 10¹⁰⁰ per billion years in a portion the size of the observable universe.  --Lambiam^Talk 10:14, 26 December 2006 (UTC)

Then if we have infinite camcorders parts(in number) and infinite tornados come will they make infinite (in number) whole camcorders? Wow, that is not intuitive to believe. Hevesli 10:26, 26 December 2006 (UTC)

If it is possible at all that a tornade by accident assembles a whole camcorder out of parts lying around, then indeed, the answer is yes. This is an application of the "infinite monkey theorem". It is also counterintuitive that a dumb monkey will type out the complete works of Shakespeare without even a single error purely by accident, but that is what the theorem says.  --Lambiam^Talk 11:28, 26 December 2006 (UTC)

Another version (I like infinite monkeys) is that all your (yes, you personally) details, and life story, are encoded in binary format somewhere along the decimal expansion of π (pi). Also encoded are the final chapter of Harry Potter (in Morse Code, 3 being dot, 4 being dash and 5 being a gap), a list of Amazon IDs for all the presents you should buy this Christmas and a sequence of numbers that, when arranged in a grid and squinted at, form a map detailing where exactly you left your house keys (I'm assuming you have house keys).

To discuss the actual question made by the questioner (we wouldn't want to digress, would we?), there is, to my knowledge, no definitive list of an explanation for every stage that took us from the Big Bang to where we are today. This is primarily because there is not as yet (although I'm sure some will turn up soon) one field dedicated to what you ask. The list would have to go into so many fields that it would most likely be impossible to make. The explanations are spread about in papers around the world, but they nevertheless exist. Notwithstanding this, I'm sure that some elements of the anthropic principle would still have to come into it: if we were destroyed, we wouldn't be asking about why we weren't. To conclude, there is, alas, no such list, but we have faith (ah, irony) that each stage of it exists somewhere, and is understood by at least someone. —Daniel (‽) 19:14, 26 December 2006 (UTC)

The anthropic principle will take more time to read than I've spent and which I will spend to fully comprehend it, however: The backbone of the list I am seeking is of course time although the list itself is interdisciplinary. Both the evolutionist and the creationist within me are both marveled although polar. The evolutionist is in shock that we exist at all until random chance is considered but then, like the huddled monkeys in 2001 a space odyssey, is cautioned by the thought of what might now still go wrong as the result of chance while the creationist is determined to take action to see that chance is overted. That said I think a list would be really neat and is necessary so that both evolutionist and creationist might have a comprehensive, if not mutual, understanding. Adaptron 03:53, 27 December 2006 (UTC)

Here is an example of such a list. Although originating from the Anthropic Principle POV they are still meaningful in terms of chance given infinite size, if not time, of the universe: Let me knwo if you do not find these interesting even from the evolutionists POV:

• Gravity is roughly 1039 times weaker than electromagnetism. If gravity had been 1033 times weaker than electromagnetism, "stars would be a billion times less massive and would burn a million times faster."

• The nuclear weak force is 1028 times the strength of gravity. Had the weak force been slightly weaker, all the hydrogen in the universe would have been turned to helium (making water impossible, for example).

• A stronger nuclear strong force (by as little as 2 percent) would have prevented the formation of protons--yielding a universe without atoms. Decreasing it by 5 percent would have given us a universe without stars.

• If the difference in mass between a proton and a neutron were not exactly as it is--roughly twice the mass of an electron--then all neutrons would have become protons or vice versa. Say good-bye to chemistry as we know it--and to life.

• The very nature of water--so vital to life--is something of a mystery (a point noticed by one of the forerunners of anthropic reasoning in the nineteenth century, Harvard biologist Lawrence Henderson). Unique amongst the molecules, water is lighter in its solid than liquid form: Ice floats. If it did not, the oceans would freeze from the bottom up and earth would now be covered with solid ice. This property in turn is traceable to the unique properties of the hydrogen atom.

• The synthesis of carbon--the vital core of all organic molecules--on a significant scale involves what scientists view as an astonishing coincidence in the ratio of the strong force to electromagnetism. This ratio makes it possible for carbon-12 to reach an excited state of exactly 7.65 MeV at the temperature typical of the centre of stars, which creates a resonance involving helium-4, beryllium-8, and carbon-12--allowing the necessary binding to take place during a tiny window of opportunity 10-17 seconds long.

Taken from God the Evidence by Patrick Glynn

-- Adaptron 14:43, 27 December 2006 (UTC)

That's like winning a lottery ticket and saying "oh, God must have created that and placed it into my hand". You know that you won the lottery, but do you also know about the many who didn't?

Additionally, we do not need water for life, because there are many other liquids that life on other planets could evolve to use. Nor do we ice to be less dense than water; if Earth's climate never dips below the freezing point, why do we care whether ice sinks or not?

Finally, carbon is vital to life ON EARTH. It may not be so vital elsewhere. --Bowlhover 15:22, 27 December 2006 (UTC)

This is the problem with either POV. The chance that God could exist is not zero yet the chance that "life as we know it" could exist without water or the transition back and forth from ice to water (since this is one means which has been demonstrated as to how nucleic acids were created although possibly in comets as well) you need to care whether ice sinks or not and admittedly so do I. My POV therefore is to remain open minded since A.) I do not necessarily take the Bible literally and even if I did does not mean it is not encoded which even if it were not the absolute details are not therein revealed and since a list of absolute requirements for life put life by chance at such absolute risk that I might as well commit suicide now as to wait for this planet to be destroyed by an asteroid that doesn't like us very much. Adaptron 17:36, 27 December 2006 (UTC).

Can you give a reasoned lower bound on that chance that God could exist, like: "The change that God could exist is at least p", in which p is replaced by a positive numeric value, like 0.00001 or something. I'm curious what reasoning you think could support such a statement. I know how to compute the chance of winning the lottery, but not how to estimate the chance of the possibility of God. But I'm willing to learn.  --Lambiam^Talk 22:48, 27 December 2006 (UTC)

The chance of an asteroid hitting Earth within the next 10 years is very low. However, if one did hit, would you flatly refuse to believe it just because the probability was very low? --Bowlhover 22:12, 27 December 2006 (UTC)

If I beleived in God and therefore creation of the universe by Him even though my mind might reason that there was a very low probability for the exitance of God then it is very likely I would apply the same reasoning to the possbility of evolution. Becasue the Biblical story of creation is so general it is quite possible that if and when all the details of evolution were revealed that they would simply be the details of how the universe was created by God. That said its a mute point whichever side you take until all the facts are known. The purpose of my question, however, is to have a better understnding and appreciation for events that have occured in the past which have resulted in the way things are today. Another example: "If the pilgrims were off by a single degree, Thanksgiving dinner would consist of aligator from Florida." ...from a robotics discussion regarding encoder error due to slip. Have a nice day. Adaptron 23:03, 27 December 2006 (UTC)

Usefulness of solubility

What is the usefulness of the concept 'solubility'? Won't all mixtures appear "unsolved" if you "zoom in" enough? Jack Daw 20:31, 25 December 2006 (UTC)

If some substance is dissolved, all molecules can participate in reactions. If present only in solid form, only molecules at the surface can participate. This makes quite a difference.  --Lambiam^Talk 21:21, 25 December 2006 (UTC)

If one substance is soluble in another, that means they mix spontaneously and will never separate unless the conditions change. If it's insoluble, that means they separate spontaneously and won't remain mixed. The concept has nothing to do with scale. —Keenan Pepper 00:31, 26 December 2006 (UTC)

What if a solution of NaCl and water was poured out of a bowl molecule by molecule; wouldn't they separate? Jack Daw 01:27, 26 December 2006 (UTC)

Not spontaneously. If you tried to catch all the water molecules in one bowl and all the salt molecules sodium and chloride ions in another bowl, you'd be trying to create a Maxwell's demon. —Keenan Pepper 01:40, 26 December 2006 (UTC)

IM not a chemist, but my understanding of a solution is that it is a mixture at the molecular level. S So if you 'zoom in enough' on a solution, you could see all molecules of the solute mingling quite closely with those of the solvent. Correct me if Im wrong. 8-)--Light current 04:42, 26 December 2006 (UTC)

I think you'll find that many ionic compounds dissociate in solution, so there aren't any molecules of salt while the salt is dissolved in the water.

Atlant 15:32, 26 December 2006 (UTC)

Agreed NaCl is an ironic compound in that it sorta half comes apart in solution and is therefore not a very good example. So if you zoomed in to a salt solution, you would see water molecules, Sodium ions and chlorine ions all floating about and bumping into each other. Is that right?--Light current 20:45, 26 December 2006 (UTC)

That's my understanding as well. A simple solution of sucrose in water would be more like what the original question was wondering about.

Atlant 12:26, 27 December 2006 (UTC)

I think that when you are talking about individual molecules the concept of solution loses meaning. Isn't a chemical solution a property of groups of molecules? ike9898 17:07, 26 December 2006 (UTC)

Calculating voltage

What is the formula for calculating the voltage after its gone through a resistor? If I start with 9 volts what is the formula where I reduce the voltage according to the ohms of the resistor? Thanks. Ilikefood 21:04, 25 December 2006 (UTC)

The voltage "drop" or the difference in voltage between the two ends of the resistor (as measured from the same reference sometimes called "ground") can not be calculated unless you know the current going through the resistor. See Ohm's law for a more detailed explanation. --hydnjo talk 21:20, 25 December 2006 (UTC)

If you have a circuit with two resistors with resistances R₁ and R₂ and a power source with voltage V, then the voltage difference will be split proportionally over the two resistors: (R₁/(R₁+R₂)×V and (R₂/(R₁+R₂))×V. So to calculate the voltage drop over a resistor with resistance R₁ you need to know the combined resistance R₂ of the rest of the circuit.  --Lambiam^Talk 21:29, 25 December 2006 (UTC)

You could look at potentiometer#Theory of operation .8-| --Light current 21:38, 25 December 2006 (UTC)

A helpful way to understand the concept in Lambian's response is to imagine that R₂ has a value of zero. In that case the voltage after going through R₁ would be zero. --hydnjo talk 21:43, 25 December 2006 (UTC)

ummmm... lets see... I've got a (slightly used) 9v battery, but the article here doens't say the typical current for a 9v battery and neither does the battery package. If I had a 390 ohm resistor and a 470 ohm resistor (separate, in different projects), what would the voltage be after each one? Thank you very much. Ilikefood 23:58, 25 December 2006 (UTC)

From these comments it's clear you don't understand the concept of electric current. A battery doesn't have a "typical current" at all. If the battery is disconnected, no current flows (except a tiny leakage current). If you create a short circuit by directly connecting the two terminals, a high current flows that drains the battery quickly and may heat it up and damage it. Practical circuits can be anywhere between these two extremes. If you create a simple circuit with a 390 ohm resistor connected to a 9 volt battery, the amount of current that flows should be 9 V / 390 Ω = 23 milliamps (ignoring the internal resistance of the battery itself). I'll let you figure out the 470 ohm case yourself. —Keenan Pepper 00:22, 26 December 2006 (UTC)

ummmm... I also like food! Getting back to your question, there may be a problem in that the formulae that we are citing represent "ideal" conditions. So, when you ask practical (real world) questions and use terms such as "(slightly used)... battery" things get a bit sticky because the "ideal" conditions don't exist in the "real" world. The question you are asking certainly would have an answer but the additional information required would probably be unknown to all of us (you included). Also, I think that you have a curiosity about this which is admirable but as Keenan Pepper (above) suggests, there is a disconnect between the information you are seeking and what we here can provide. --hydnjo talk 00:42, 26 December 2006 (UTC)

It may be a good idea to see the Voltage source and current source articles. A battery acts (almost) the same as a pure voltage source.--Light current 00:53, 26 December 2006 (UTC)

On the other hand a "(slightly used) 9v battery" (the dimensions of which we are only guessing about) hardly qualifies as an almost pure voltage source so be careful about extrapolating from the articles cited to your "real world" situation. --hydnjo talk 01:14, 26 December 2006 (UTC)

It always depends on the load. A 9V battery in a flashlight acts more or less like an ideal voltage source, but if you shorted out an ideal voltage source, enough current would flow to melt and vaporize the wire you used to short it out! 9V batteries don't vaporize wires, so they differ significantly from ideal voltage sources in those conditions. —Keenan Pepper 01:38, 26 December 2006 (UTC)

Also 9v batteries have internal resistance and as they are used it increases. This along with the maximum rate the chemical reaction occuring in a battery can take place limits the current. --- Skapur 02:09, 26 December 2006 (UTC)

Yes but its far more like a voltage source than a current source, which is how the OP was originally mistakenly envisioning it. And of course the only thing that differentiates any source of emf from an ideal voltage source is not its current capability, but its internal resistance.

In answer to Keenan, it is possible for a 9v battery to vaporise a piece of wire if the wire is thin enough. You cannot rely on the internal resistance of the battery to limit the current to below the critical current density in the wire. It may or may not vapaorise depending on the size and resistance of the wire. Thats how fuses work. 8-)--Light current 02:20, 26 December 2006 (UTC)

This equation describes... what?

Been trying to find the article related to what a particular function describes, the function is P = E/t or maybe E = P/t, not sure, but it has to do with work being performed within a certain time frame. Ring a bell to anyone? Thanks in advance, Jack Daw 22:53, 25 December 2006 (UTC)

• Power, Electrical?--71.247.120.5 23:05, 25 December 2006 (UTC)

See Power (physics) where it says Power equals energy divided by time, or energy equals power times time ( if power is constant). Edison 00:18, 26 December 2006 (UTC)

BTW, it doesn't "describe" anything, it's merely a definition. —Keenan Pepper 00:24, 26 December 2006 (UTC)

Well power P is the rate of doing work or expending energy E (same thing). So: Power = energy/time or P= E/t--Light current 00:57, 26 December 2006 (UTC)

Power, that's the one, thanks. And what's E = mgh and E = .5mv^2? I'm afraid my English language skills don't include the realm of physics! Jack Daw 01:17, 26 December 2006 (UTC)

The first is gravitational potential energy, the second kinetic energy. Clarityfiend 02:55, 26 December 2006 (UTC)

Dec 26

Orbit of a particle

Does the orbit of a particle (whose radius is of course greater than zero) turn into a spin when the radius of the particle's orbit is reduced to zero? 71.100.6.152 01:10, 26 December 2006 (UTC)

What are we talking about here, classical mechanics or quantum mechanics? —Keenan Pepper 01:49, 26 December 2006 (UTC)

How about an answer for both. 71.100.6.152 03:20, 26 December 2006 (UTC)

Quantum mechanical spin is an internal degree of freedom of a particle which is unrelated to motion in space. It is not related to orbital motion, and moreover the total spin of a particle cannot change (total angular momentum can be affected by external forces). Part of the strangeness of QM spin is that one cannot think of a QM particle as a body with finite radius. Classical spin is also somewhat different from spatial angular momentum. A particle which is in an orbit with some angular momentum does not necessarily spin. If every point in a solid body is at rest with respect to all other points in the body, it is not spinning. --Bmk 16:11, 26 December 2006 (UTC)

Assuming for the moment that the core or the Earth and Moon are fix relative to their surfaces they still spin. The spin of the Earth is not a core to surface relation but rather an Earth to Sun, Moon and Stars relation while its orbit is a relationship to the Sun. The Moon orbits the Earth yet does not appear to spin by observers on the Earth but in relation to the Sun and stars it does spin in sync with its orbit around the Earth so your classical physics answer puzzles me. It seems like what you are saying is that if the surface of a body moves in relation to its core then it spins and that this is not the same as its surface orbiting its core. Maybe the problem is just semantics. 71.100.6.152 21:16, 27 December 2006 (UTC)

How to seep and steep herbal teas and remedies

I have encountered the terms “SEEP” and “STEEP” (I may have misspelled the second term) in relation to the creation of herbal teas and remedies. I am a bit confident that “seep” is the process used in my coffee maker. These terms are often used in hiking and camping books in the editable plants section. These books never seem to explain the method. I have been unable to find a source explaining the processes (both in modern terms and ancient methods). Also the terms always seem to be two very different processes.

To "steep" is to leave an object (such as a tea bag) in (usually hot) water to disperse flavor, etc. Your coffeemaker is doing an action similar to steeping. To seep is for water to permeate an object (usually used in a way that the "seep" is unfavorable, like "wow, the rain seeped through my tent"). Seep is usually a general term, and steep is a term used in making drinks. I'm guessing your recipes are telling you to steep tea bags or loose tea - this is just a term for sticking it in hot water for a few minutes. --Wooty Woot? contribs 02:23, 26 December 2006 (UTC)

Agreed. Also, since many people are unfamiliar with the above usage of "steep", they may mistakenly substitute the word "seep", since that word, they know, does have something to do with liquids. StuRat 13:55, 27 December 2006 (UTC)

Budgie video on YouTube

Just found this: http://www.youtube.com/watch?v=Xe2Jb3U21vA

There's some logic at play here but I'll be damned if I know what it is. Any suggestions? --Kurt Shaped Box 02:06, 26 December 2006 (UTC)

Bored housepets enjoy play too? Vranak

Yeah, I know it looks like he's just messing around but the bird's glances back and forth between the string of beads and the lone bead make me think that he's actually trying to do something with them position-wise. Sometimes he'll walk halfway to one or the other, stop to think for a moment, then turn back. --Kurt Shaped Box 23:46, 26 December 2006 (UTC)

Capacitance of batteries.- its a hard one this!

Any one got any idea of the inherent ac capacitance between the terminals in batteries and whether this capacitance bridges the internal resistance?? In other words, what determines the battery's impedance? 8-)--Light current 02:27, 26 December 2006 (UTC)

Well, looking at the battery purely as a black box, there must be capacitance both between the two terminals of the battery and also between the battery and the surrounding environment. I'd guess that the capacitance to the environment is pretty small. I'd further guess, given the construction of most batteries, that the terminal-to-terminal capacitance is pretty small also, although some NiCd and lead-acid gelled-electrolyte batteries use a rolled-up construction that probably has quite a bit of inherent capacitance.

If you're really interested and you have a capacitance meter, it'd be pretty easy to measure: just put a known-value blocking capacitor in series with the battery, short the combined battery-capacitor series circuit (so the blocking cap charges up and no inrush current damages your meter), attach the series circuit to your meter, and unshort the series circuit. Take the reading you get from the meter and, using the known value of the blocking capacitor, solve the series circuit for the unknown capacitance of the battery. If the blocking cap is of large value compared to the reading of the meter, then just take the reading of the meter directly as the capacitance value of the battery.

Atlant 15:42, 26 December 2006 (UTC)

Needless to say, I have never measured this nor heard of anyone doing so and of course normally we decouple the batteries from the circuit with a large capacitor. So one question is, assuming a baatery with low internal reistance, like a lead acid job, is it really neccessary to put large electrolytics across it for low freq decoupling. I am ignoring the inductance of the battery leads as this will only be important at the higher frequencies.

And yes of course Atlant, the method you suggest should work well at the spot frequency of the meter. I suspect, though, that the 'capacitance' actually rises with decreasing frequency (due to the chemical reaction effects) such that, at DC, you actually end up with the 'capacity' of the battery Q =it =CV. So C = it/V which is going to be quite large even for a 1 A hr cell. --Light current 18:23, 26 December 2006 (UTC)

You are correct, of course, that at low frequencies classical capacitance becomes meaningless for a battery; thanks for pointing that out. Also, apropos a topic you and I were discussing quite some time ago, folks who build real neighborhood-thumping car stereos often put large "ultracapacitors" in parallel with their car batteries (or at least, near the welding cables with which they feed their power amplifiers). They do this to provide the maximum transient power to their window-breaking amplifiers. And the manufacturers of hybrid cars are also looking at this, seeing as how ultracapacitors can be very rapidly (and efficiently) charged and discharged without the cycle-life issues that affect classical batteries. So they're investigating a two-level energy storage hierarchy with ultracaps first and batteries second.

Atlant 18:43, 26 December 2006 (UTC)

Actually, I think the capacitance of batteries is fairly huge, up in the Farads realm, since it arises from the atomically-thin insulating "Double layer" on the surface of the battery plates. The electrolyte is a conductor, and so are the battery plates, so the only insulator of significance is the surface double-layer where the charge-pumping effect originates. If we construct a battery where the two plates are made of the same metal, then we end up cancelling out any charge-pumping process, and this produces zero output voltage. Yet in that case the capacitance of the double-layer still exists, and as long as we avoid driving chemical reactions by applying voltages above ~1v to the plates, we can measure the battery's capacitance directly. It's the capacitance of two double-layers in series, and can be as high as tens of Farads. Don't forget that supercapacitors and ultracapacitors are based on just this same effect. They use carbon-powder electrodes immersed in sulfuric acid solution, and both of these materials are conductors. The dielectric in the ultracapacitor is the double layer, but in order to be useful at voltages > 1V, these capacitors use many double-layer capacitors wired in series. --Wjbeaty 05:55, 27 December 2006 (UTC)

If I get some time, I'll wander off to our precision LCR bridge. Alternatively, a capacitance of Farads ought to show up as a huge pulse of current if the battery is short circuited; that ought to be pretty easy to detect with a 'scope, current probe, and low-value series resistor (so I don't magnetize the current probe too badly; ours is rated 30A peak).

Atlant 12:28, 27 December 2006 (UTC)

Okay, I did some research. I used the test rig I recommended above (with a capacitor in series with the battery) and our HP 4284A Precision LCR bridge. My series capacitor was a "1000" μF alumin[i]um electrolytic which was actually running on the wimpy side at about 900 μF. I took readings at 20 Hz, 100Hz, 10KHz, and 10 KHz, stopping there because my rig was apparently starting to resonate and had gone noticeably inductive at 100 KHz. For batteries, I used a brand new alkaline "AA" (LR6) cell and a stone cold dead alkaline AAA cell. The resulting battery capacitances:

• 20Hz: AA=2991 μF AAA=946 μF
• 100Hz: AA=2907 μF AAA=287 μF
• 1KHz: AA=2332 μF AAA=161 μF
• 10Hz: AA=1086 μF AAA=99 μF

I think it's safe to say that ordinary alkaline cells have "hundreds to thousands of microFarads" of capacitance, but there's no evidence that this design of batteries has "Farads". And I also think it's safe to say that Light current's hypothesis is also born out: the dead AAA showed a very noticeable rise in "capacitance" as the frequency dropped, quite possibly due to electrochemical storage rather than real capacitance. It's interesting that the fresh ("fully-charged") battery didn't seem show much of this effect. Now, who wants to do the same experiment with a "rolled-construction" battery, where it wouldn't surprise me to see much higher capacitance values, including the "ultracapacitor" effects hypothesized by Wjbeaty?

Atlant 15:45, 27 December 2006 (UTC)

Atlant these results are extremely interesting! And thanks so much for taking time to do these tests (especially at work!). I just wondered if your last frequency reading should be 10 kHz.

Its intersting to note the reduced capacitance of the 'dead' cells cf the new ones. This may be due to the incresed esr of the 'dead' ones. Actually if your bridge does Q factor (or Dissipation) that would indicate the series resistance!

The results do indeed seem to confirm my gut feeling that healthy batteries do indeed have sufficient capacitance for general low frequency decoupling purposes. (which maybe is how designers of cheapo transistor radios got away with out big storage caps. More thoughts later.8-)--Light current 19:35, 27 December 2006 (UTC)

Riskiness Rankings

Just about every country has some sort of environment conservation legislation. This legislation often ranks species by how close they are to becoming the next Dodo or Pyrenean Ibex. So there are many systems for ranking plants and animals. Often independent bodies also do ranking (such as the World Conservation Union).

I'm trying to flesh out a list of as many of these ranking systems as possible with:

1. What are the categories for the ranking system?
2. Who's the group or organisation who assigns the rankings?
3. What country or countries are involved?
4. What's the Act that makes it official? (if any)
5. Does the rank apply to the global population or only the one in that country?

Just about every country has a system, so please check if your country, or your favourite country, to the list on the Conservation status page. If you don't know the answer, try googling. There are a lot of Acts and systems and it's a monumental task putting them all together. Any help appreciated. —Pengo ^{talk · contribs} 05:08, 26 December 2006 (UTC)

Some more specific questions:

• Do threatened species of Australia protected under the [[Environment Protection and Biodiversity Conservation Act 1999

EPBC Act]] have to be threatened globally, or just in Australia? (the legislation looks vague: see part 7, but perhaps there are specific cases or something?

• Same question for the US's EPA. Do species need to be threatened globally or locally to qualify? (Canada only considers how threatened a species is within its borders)
• What categories or protection is there in New Zealand, Argentina, Belgium, South Korea, Cyprus, Seychelles, Mauritius, Libya, Barbados, Tonga, Chile, Uruguay, Puerto Rico, (your country here)...? —Pengo ^{talk · contribs} 05:42, 26 December 2006 (UTC)

• • I am pretty sure that the EPA is governed in this respect primarily by the Endangered Species Act. In this act, species are considered threatened if they are close to global extinction. Species can be either "threatened" or "endangered", the latter defined as closer to extinction. Though the law's mandate is primarily for the USA there are also some stipulations in it about international cooperation which I have not parsed through. --24.147.86.187 14:39, 26 December 2006 (UTC)

electroscope

A zinc plate is connected to a electroscope. if the electroscope is negatively charged, when ultraviolet radiations falls on the zinc plate, the leaves of electroscope fall down. if the electroscope is positively charged, nothing happens to the leaves. why? —The preceding unsigned comment was added by Skanthckd (talk • contribs) 06:52, December 26, 2006 (UTC).

What does it mean for something to be negatively charged? Read up on electric charge. And what does ultraviolet radiation (no plural please; "radiation" is a mass noun) do? Read up on the photoelectric effect. Combine the information you find in these two articles. By the way, it was Einstein's explanation of the photoelectric effect won him the Nobel Prize in physics.  --Lambiam^Talk 09:59, 26 December 2006 (UTC)

Well, the electroscope is obviously losing negative charge somehow. How do you think this could happen ? How does illumination with ultraviolet light cause this ? How quickly is charge lost ? What happens if you change the brightness of the UV light ? Would light of other wavelengths have the same effect ? The best way to find an answer to your question is to do some experiments with a real electroscope. If this is not possible, you can always read our article on photoelectric effect instead. Gandalf61 10:02, 26 December 2006 (UTC)

Hey, what about electroscope for additional info ?--Light current 21:32, 26 December 2006 (UTC)

Eyes

Are the eyes of a near-sighted person smaller than the eyes of a regular person? And does it look weirder because when i take my glasses off and i took a picture off me i look sooooooooo weird.

Farsightedness (hypermetropia) can be caused (one of the reasons) by the eyeball being too small but regarding near sightedness (myopia), nothing has been mentioned. But I suppose that myopia can be caused (one of the reasons) by the eyeball being too long -- WikiCheng | Talk 08:56, 26 December 2006 (UTC)

Near-sighted people may have a tendency to squint when trying to focus on something in the distance without corrective glasses. This may look strange if you're not used to seeing it, but you would almost certainly be aware of doing this. The glasses make your eyes appear slightly smaller, so taking them off should actually have the converse effect to people (possibly including you) used to seeing your face with glasses on. But aren't you used to seeing yourself without glasses in the mirror?  --Lambiam^Talk 09:46, 26 December 2006 (UTC)

I think I saw some stuff on Howstuffworks. Here's some. [[36]] - Nearsightedness. And [[37]] about corrective lenses. And a comparison of refractive vision problems in general - [[38]]. Hope that helps!! FruitMart07 03:04, 27 December 2006 (UTC)

Friction

Please help me solve this problem-

A small block of mass 'm' is kept at the left end of a larger block of mass 'M' and length L .The system can slide on a horizontal road.The system is started towards right with an initial velocity 'v'.The friction coefficient between the road and the bigger block is 'u' and that between the blocks is u/2.Find the time elapsed before the smaller block separates from the bigger block.

Thank you. —The preceding unsigned comment was added by 59.93.67.55 (talk • contribs) 10:03, December 26, 2006 (UTC).

Is this literally how the question is phrased? Letting o indicate the smaller block and X the larger block, I can imagine (at least) two possible initial situations:

  XXXXXXXXXX
  XXXXXXXXXX   ------>
_oXXXXXXXXXX__________

Situation 1: smaller block strictly to the left of the larger block

  o
  XXXXXXXXXX
  XXXXXXXXXX   ------>
__XXXXXXXXXX__________

Situation 2: smaller block at the left on top of the larger block

In situation 1, it is not clear how the friction between the blocks plays any role. The coefficient of friction for the smaller block is not given, so it would be impossible to tell what will happen. If this is a homework assignment, then I assume the intention is that there is a definite solution, ruling out this interpretation of the question. (Also, homework problem statements tend not to provide irrelevant data, like L and the u/2 would be).

In situation 2, the smaller block will start decelerating due to the force of friction with the (also decelerating) larger block. The relevant mass for determining this force is m. The large block will start decelerating due to the force of friction with the road. Note that the relevant mass for determining this force is M+m as long as the smaller block is on top. However, that decelerating force will partly be countered by the smaller block: in conformance with Newton's laws (action = reaction), the same force of friction that pulls on the smaller block towards the left, pulls on the larger block towards the right. So the net force acting on the larger block is the difference between these two forces. Now you can give the equation for the right end of the larger block as a function of time, and likewise for the position of the smaller block, which I guess should be idealized as a point particle with zero width; when the latter exceeds the former, the smaller block will fly off (or fall off) at the right end.

However, there is a complication. If the velocity of the larger block reaches zero before the smaller block flies off, the larger block will come to a halt, and not start moving in the opposite direction (to the left). Then the smaller block will continue, but the equation for determining the fly-off moment has changed. And, finally, if L is large enough the smaller block may then too come to a halt before it reaches the right end and flies off, and in that case the two will remain together forever.

I hope I got this right, what with all the interpreting and the complications, and I hope this helps. If you get stuck in solving this, tell us where you got to and how you are stuck, and we'll see if we can help you go on.  --Lambiam^Talk 11:21, 26 December 2006 (UTC)

Physics

hey are there any shortcuts to be knowing all the stuff your physics teacher knows? any good sites or books? Thanks (sorry but im an ambitious man!) —The preceding unsigned comment was added by 219.78.44.181 (talk • contribs).

Brain transplantation/Mind transference? (But watch out for Abbie Normal's brain.) Visit Rekall or the teacher on Star Trek?

Seriously, I don't know how much your physics teacher knows, but if you want to understand physics, then you will have to be willing to invest work in your studies, either now or as a result of accumulated life experience. It will also help you greatly if you already understand basic trigonometry and have studied or are simultaneously studying calculus. It also helps if your mind is oriented towards logic, so after being told about principles "A" and "B", you can generalize and extend that knowledge to principles "C", "D", and "E".

I really don't think there are any "shortcuts".

Atlant 17:43, 26 December 2006 (UTC)

Hi, User 219... I don't have a concrete answer for you, but perhaps checking THIS google result might get you started. Are you looking for info on High School or University level physics? That would help with the answers, to be sure. Good luck! Anchoress 17:27, 26 December 2006 (UTC)

I dont think there are any shortcuts. Your physics teacher has worked hard to go thro school, taken one or two degrees and put in many hours hard thinking over the years working out the best way to teach physics. The latter part we call experience. There is no real substitue for it. Although you may be able to memorise a load of facts, that does not mean you understand things and without understanding, I think prospects are limited. However, if you purely want to bluff your way through, there are many jokey books, like bluff your wa thro computers etc. Another alternative is to buy a dictionary of physics and learn the words and their meanings. 8-)--Light current 17:57, 26 December 2006 (UTC)

You mave have heard the phrase: You cant put an old head on young shoulders

Thats what it means.--Light current 18:00, 26 December 2006 (UTC)

Try The Physics Classroom, Free High School Science Texts, Textbook Revolution, and Free-Ed.net. The last one has a couple of semesters' worth of university physics lectures on video. BenC7 00:47, 27 December 2006 (UTC)

There certainly are big shortcuts! I've relied on three of them throughout my entire career. The first one is: search for errors in your textbooks, sensitize yourself to contradictions between separate textbooks, then learn to "un-teach yourself" the information you've found to be wrong. This is incredibly effective because introductory textbooks are full of misconceptions that their authors believe and never question. These misconceptions become barriers which prevent your further learning: like trying to build a brick building on a pile of rocks. So, if you manage to remove the mistakes from your head, you'll quickly gain unusual expertise. You'll learn faster than everyone else because you've defeated barriers which prevent speedly learning in all others who still harbor those misconceptions and can only learn very slowly. Defeating one major misconception is worth weeks of normal study (weeks, if not years!) Yet it doesn't exactly speed up your learning. Instead it lets you learn at the pace which SHOULD be normal, but is actually far faster than the slow crawl of everyone else who has been taught those misconceptions. (Here are a few I've found: http://amasci.com/miscon/)

Here's another: don't ever try to thoughtlessly "record" or memorize information from books or relayed by teachers. Instead, always assume that books are badly written and full of errors. Try instead to "own" the incoming information by taking it apart and finding alternate ways to describe it to yourself. Be a skeptical textbook editor, not a gullible textbook reader. This does make for very slow going in school, and makes you a "backwards student," but later it allows you to go far beyond all other students. You'll REALLY UNDERSTAND physics, as opposed to just having a head full of disconnected and possibly erroneous facts. And if you're studying on your own, the process becomes easy because there's no classroom pressure to race through the material in lock step with others. I finally heard about another person who learned physics in just this way: Richard Feynman, who said "what I cannot create, I do not understand." That's it! That's exactly it: you cannot memorize someone else's physics explanation, instead you have to disassemble it and then use the parts to construct your own version. This is an ENORMOUS shortcut, since it puts you far ahead of all students who are just trying to memorize facts without understanding, and who will forget all of it after the next exam. Here's another way to say it: it turns you into a physics teacher. You'll never forget any of it no matter how many decades go by. And as you study more physics, it all starts connecting together into a vast mental machine which starts functioning on its own. Those who don't do this, they end up with a big pile of parts inside their heads, but no "machine."

Here's the third: stop being an egotist. Get into a "zen" state where you don't take your mistakes personally, and where you aren't threatened by information which demonstrates that your current understanding is embarassingly faulty. I stumbled into this particular shortcut by my early religious upbringing which had some eastern concepts. Over decades I saw that many other students were greatly slowed down in learning physics because they had something I didn't: a huge need to protect their egos, protecting their self image of having perfect error-free knowledge. For them, admitting their mistakes and going back to revise their understanding was a huge deal. They'd go into denial and fight fiercely against admitting their errors, fight even more fiercely against ever letting them be discovered by others, and perhaps remain trapped in obvious misconceptions which they couldn't stand to find or fix. Now this would be fine if teachers and textbooks were totally accurate, because in that case our tendency towards errors would be much reduced. If someone needs to be right all the time, there'd be no problem if they actually WERE right all the time. But since teachers and textbooks are extremely imperfect, and misconceptions are the norm, emotional intolerance of personal errors becomes a huge learning barrier. Learning physics involves lots of trial and error, so in a very real sense you have to cultivate a taste for error: to seek out your embarassing personal errors. Do just that, and as with the other shortcuts, you race far ahead of everyone who isn't doing this stuff. --Wjbeaty 05:19, 27 December 2006 (UTC)

I have a friend who manages to get by without knowing or using a single physics formula, by instead substituting purer maths, using imaginary numbers and integration, for example, when working with projectile motion. Seems to work for him --124.243.155.3 09:02, 27 December 2006 (UTC)

North Atlantic oscillation

Can anyone point me to theories explaining the causes of the North Atlantic oscillation? Thank you! Marco polo 16:20, 26 December 2006 (UTC)

Brian Fagan, in his book "The Little Ice Age", has a lot of information about it but no clearly defined theories as to ultimate cause, as far as I can see. Geologyguy 16:30, 26 December 2006 (UTC)

You can find some information on http://www.met.rdg.ac.uk/cag/NAO/Models.html.  --Lambiam^Talk 00:06, 27 December 2006 (UTC)

Is it possible to turn woman into a sex addict?

If I inject some of form parasite into an unwilling women say Toxoplasma_gondii, would she turn into a sex addict. If I'm caught would I go to prison? 202.168.50.40 01:29, 27 December 2006 (UTC)

   With regard to your second question, I would hope so. --hydnjo talk 01:35, 27 December 2006 (UTC)

       * Extending my response out of order (if I'm allowed): I had no idea that there would be such controversy about this trollish subject matter and had hoped (naively) that saying such behavior would result in prison time (if caught) would end the thread. It seems that that is not the case at all and that the un-crisp boundaries of proper vs criminal behavior are now being debated under this heading and that is wrong in this venue. If I had any hand in this by remarking that it was "my hope" that such behavior (implicitly) would be criminal then I'm sorry for inflaming this sorry subject and it's resultant debate. If on the other hand something useful happens well, that's WP.--hydnjo talk 03:43, 27 December 2006 (UTC)

   Well you have linked the appropriate page. Have you read it? Esp this bit:

   For women: * A tendency to be more outgoing, friendly and more promiscuous * They are considered more attractive to men compared with non-infected controls "In short, it can make men behave like alley cats and women behave like sex kittens" — Nicky Boulter

--Light current 01:37, 27 December 2006 (UTC)

   BTW, your're not planning on wearing a mask whilst you do this dirty deed are you? 8-)--Light current 01:39, 27 December 2006 (UTC)

   Administering any substance with the capability of changing someone's physiology or mental state without their knowledge or consent is illegal in most jurisdictions. It doesn't have to be deadly in order to be considered poison. It's 'administering a noxious substance', and it's a crime. Using the altered state to commit another crime severely compounds the penalty. Anchoress 02:50, 27 December 2006 (UTC) 

Squirrels

We were wondering why a squirrel's tail is so bushy. No doubt there is more than one advantage (and disadvantages), but has science reached a concensus on the primary reason? --Bob K 18:08, 26 December 2006 (UTC)

Added insulation in cold weather (when squirrels will fold their tails up along their backs, essentially adding another layer of fur). Distortion of their body image as seen by predators (so the predator gets confused and grabs at the tail and not the squirrel's body; you often see "short-tailed" squirrels where this strategy obviously paid off at least once). Perhaps a little bit of aerodynamic resistance (counterbalancing) as the squirrels bound along.

Atlant 18:32, 26 December 2006 (UTC)

I thought that the tail also brought some reproductive advantage. For example, I thought that I had read that squirrels prefer to mate with other squirrels with bushy and attractive tails, which are a sign of health and good genes. Marco polo 18:41, 26 December 2006 (UTC)

Absolutely for balance. Ever seen a squirrel hop from one tree to another? It's quite a feat, and no doubt a tail-less squirrel would be much more prone to plunging to the forest floor — which I have also seen. Vranak

That explains all of the mass and the flexibility, but none of the bushiness. (Squirrel: It's none of your bushiness.)  --Lambiam^Talk 21:19, 26 December 2006 (UTC)

But squirrel tails are not massive! You can see this if you've ever seen a backlighted squirrel: their tails are just like rat tails except for more fur. If they're used as counterbalancing, at least some of the effect must be the aerodynamic resistance of all of that fur in the tail.

Atlant 12:42, 27 December 2006 (UTC)

I've noticed that squirrels like to shake their bushy tails at you when they're feeling defensive. The bushier the tail, the more of an impression it makes on interlopers. Vranak

If they didn't have big bushy tails, they 'd be called rats! 8-)

Speculating: they might be like the detachable tails of lizards: when a big preditor makes a grab for the squirrel, all it gets is a mouthful of bushy fur. --Wjbeaty 04:38, 27 December 2006 (UTC)

Cation and anions

How do you determine the Cation an Anions of a compund? Dragonfire 734 18:02, 26 December 2006 (UTC)

If it's a positive ion (missing electrons), it's a cation. If it has extra electrons, it's an anion. --Wooty Woot? contribs 18:19, 26 December 2006 (UTC)

(Perhaps beating the point to death...) The cations (those missing the electrons) will go towards the cathode, the negatively-charged electrode where they can re-acquire that missing electron. The anions (those with an extra electron), conversely, go towards the anode, the positively-charged electrode where they can give up that extra electron.

Atlant 18:35, 26 December 2006 (UTC)

Hmm maybe worth an extra few strokes!

• The term CATion derives from the fact that these ions are attracted to the CAThode (negative electrode) in an electrolytic cell. Cations are therefore positvely charged.

• The term ANion derives from the fact that these ions are attracted to the ANode (positve electrode in the cell). Anions are therefore negatively charged.

--Light current 21:20, 26 December 2006 (UTC).

BUt how do you determine it for example the compound CO2? Dragonfire 734 22:18, 26 December 2006 (UTC)

What happens when CO2 dissolves in water? You get an acid, right? Which acid? What are the properties of acids in general, and this acid in particular, when it comes to forming ions?  --Lambiam^Talk 00:02, 27 December 2006 (UTC)

Well I suggest you look up carbonic acid. THen if you have any further Qs come back here.

heres the dope from that page anyway:

Carbonic acid has two acidic hydrogens and so two dissociation constants:

H2CO3 ⇌ HCO3− + H+

Ka1 = 2.5×10−4 mol/L; pKa1 = 3.60 at 25 °C.

HCO3− ⇌ CO32− + H+

Ka2 = 5.61×10−11 mol/L; pKa2 = 10.25 at 25 °C.

--Light current 01:25, 27 December 2006 (UTC)

Classification of an amoeba

I need to know the classification of an ameba thanks Chris H.

Hi, Chris. Try reading the amoeba article. If you have any further questions, check back here. Anchoress 18:52, 26 December 2006 (UTC)

Bacteria in the Intestines

The large intestine hosts several kinds of bacteria that deal with molecules the human body is not able to breakdown itself. This is an example of symbiosis.

We can be fairly certain that if we were able to hypothetically remove, all at once, every bit of the bacteria from the intestines of the average human being, the bacteria itself would almost certainly perish without its host. But what about the human? Would they be likely to perish as well, in the complete absence of this intestinal bacteria?

Have the two systems developed complete codependency? Are many of the normal flora present in our bodies likely to belong to similar codependent relationships? And I believe that pregnant mothers pass down their bacteria to the fetus. Is this correct?

Thanks ahead of time...71.246.38.187 21:34, 26 December 2006 (UT

I imagine the substances (such as cellulose) would simply be excreted with feces. This might prove a problem with excessively large or pointy undigestible material, but by the time it gets to the large intestine it's probably done its damage anyway. --Wooty Woot? contribs 03:16, 27 December 2006 (UTC)

Gut bacteria are, in fact, quite important for our health. Even besides the assistance in various digestive tasks, including absorbtion of broken down materials, they also produce much of our vitamin K₂, without which we are unable to perform such vital tasks as clotting. We would live without them, very likely, but it wouldn't be an especially pleasant life. Leave your bacteria alone, they are your little, little friends. – ClockworkSoul 03:53, 27 December 2006 (UTC)

I beleive dysentery has the undesirable effect of killing most of the bacteria in the gut.(although our page doesnt say so)--Light current 06:10, 27 December 2006 (UTC)

Oral antibiotics commonly do have that bad effect as well.

Atlant 12:44, 27 December 2006 (UTC)

The immediate problem with the use of broad spectrum antibiotics is that they don't kill all the bacteria, leading to overgrowth by species usually kept "in line" by the others, with the possible result of C. difficile enterocolitis, toxic megacolon, and death. - Nunh-huh 13:11, 27 December 2006 (UTC)

Paternal Age

Paternal Age ==

Might Wikipedia be interested in my research on the connection between advancing paternal age and sporadic cases of these conditions: Ihave found research papers on the following conditions all finding increased incidence with advancing paternal age

Multiple Sclerosis, Diabetes Type 1, Athoid/dystonic cerebral palsy, hemiplegia, Acute Lymphositic Leukemia, pre-menopausal breast cancer, some Alzheimer's, shorter life for women (fathers 45+), prostate cancer, epilepsy, some early childhood cancers, schizophrenia, autism, Multiple edocrine neoplasia type 2B, Hemophila A X linked maternal grandfather, progeria, marfans, achrondroplasia, aperts, some heart defects, other very rare disorders, Down Syndrome if the mother was 35 or older and the father was 40 or older [39] if this information can be used by someone for an entry or for inclusion with entries already in wikipedia I would be happy to give the citationsAnniepema 21:53, 26 December 2006 (UTC)

Wikipedia has Maternal age effect.....I suspect we are rather weak on this topic. --JWSchmidt 00:59, 25 December 2006 (UTC)

There has been a recent spate of inclusions/reversions on this topic on the menstrual cycle page, perhaps you should check there to see if your contributions would help. Anchoress 04:41, 25 December 2006 (UTC)

Anchoress maybe you didn't read that I was asking about interest in paternal age. The paternal age effect has to do with ,for instance, the ground-breaking work of NP Singh et.al. from the Unversity of Washington in Seattle in the research paper "Effect of age on DNA double-strand breaks and apoptosis in human sperm" In this research it was found that the percentage of sperm with highly damaged DNA and DNA break numbers was statistically significantly higher in men aged 36-57 than in those aged 20-35 years, but percentage apoptosis was statistically significantly lower in the older group. This finding was the first to suggest that there was an age related decrease in human sperm apoptosis. This new finding may indicate deterioration of the healthy sperm cell selection process with age. Also the work of James F. Crow on the high rate of spontaneous mutation in the sperm which increases with age is relevant and Andrew Wyrobeck's research on sperm DNA damage with age.. Anchoress I think you read the last part about the maternal age effect and not my question about if there was any interest research on paternal age Anniepema 21:51, 26 December 2006 (UTC)

No, I read exactly what you were asking about, and as I said, there was just an inclusion on the menstrual cycle page about that exact topic; interestingly enough - since you have expressed an interest in providing references - asking for a reference. I'm curious to know why you thought I had mis-read your question? Anchoress 08:24, 25 December 2006 (UTC)

I wouldn't have expected menstruation to be dependent on paternal age, myself, but perhaps I'm wrong. StuRat 11:13, 25 December 2006 (UTC)

As for an article on paternal age, sure, that would be great. However, since Wikipedia has a "no original research" rule, you need to only use sources in published works. If your own research is published, that's fine to use, but you can't include info from any unpublished studies you've done. StuRat 11:13, 25 December 2006 (UTC)

Sorry Anchoress

I didn't understand that the statement about male sperm be freshly made was what you meant by the new inclusion. The opposite argument is made about the many genetic diseases associated with older paternal age at the time of birth because of all the cell divisions to make new sperm.

Excerpts from geneticist James F. Crow's "The High Rate of Spontaneous Mutation:Is it a health risk" PNAS August 1997

"Paternal Age Effect"

"How can we account for a higher mutation rate in males than in females? The most obvious explanation lies in the much greater number of cell divisions in the male germ line than in the female germ line. In the female the germ cell divisions stop by the time of birth and meiosis is completed only when an egg matures. In the male, cell divisions are continuous and many divisions have occurred before a sperm is produced. If mutation is associated with cell division, as if mutations were replication errors, we should expect a much higher mutation rate in males than in females. "At age 20 the number of(sperm) cell divisions is about 200, at age 30 it is 430, and at age 45, 770."

This makes the strong prediction that the mutation rate should increase with the age of the father, since the older the man, the more cell divisions have occurred. On the other hand, there should be no age effect in females."

Let me interject at this point that there is a well-known maternal age effect for traits that are caused by errors in chromosome transmission. The kind of accident that leads to a child with an extra chromosome is strongly associated with the mother's age (15). There may be a slight paternal age effect, but the far more striking effect is maternal. My concern, however, is with gene mutations which, when those with small effects are considered, are much more frequent." .... Anniepema

Can anyone write any kind of acceptable entry in wikipedia on the paternal age effect that is well written and neutral?Anniepema 06:34, 27 December 2006 (UTC)!Anniepema

Dec 27

Lack of Visual 'Imagination'

I am unable to "visualise" anything. If I close my eyes, I see only the back of my eyelids and have never been able to summon an image.

And whilst I very rarely dream (or remember them as I'm sure people will claim), the very few I recall having have not had any pictures, but more like reading a story -- I know what is happening but not in pictures.

This has always been the case, though I only realised when I was a teenager that when people said "visualise" they were being literal and could actually see pictures in their head!

My question, is there a name that describes this psychopathology, and is it a common thing? Any studies regarding this and how it relates to creativity and inteligence? Is it perhaps an autistic spectrum disorder?

This facet of myself does not worry me and any information will not be taken in any way as medical advice. So any pedants can please leave other more useful responders free to speculate.

86.132.225.66 00:35, 27 December 2006 (UTC)

Who knows — maybe dreaming is more 'pathological' than not dreaming! At any rate, I do not recall learning about this or any similar condition while studying psychology.

Dreams serve to enlighten and evaluate, so perhaps a lack of dreaming, or lack of visual imagination, is a good sign that you are already quite enlightened, open-minded, free of social bias, and so on. Vranak

I've had colleagues who were not "visual thinkers," and their understanding of science was entirely verbal. Perhaps they lacked the ability to see pictures in their heads? By analogy, I've heard about people who can play actual music in their heads, whereas I'm more limited and can only remember how a tune goes but not hear instruments playing it. I'm definitely a visual thinker, but when I see a picture in my head, it's nothing like an image on my retina. It's more like a memory. If I visualize a dark background with a square made of glowing green lines, I can't exactly see it, instead it's more as if I'm remembering what such a vision looks like. I can make this green memory-square shrink and grow, rotate, change colors, etc. But it's only as detailed as a fuzzy memory, and if I try to add too many details to this vision, I'll lose track of some of them. On the other hand, I've heard of visual thinkers whose internal vision is just as accurate as reality, and who can build incredibly detailed objects and then continue to "see" them. If visual thinking can range up to that high ability, then it probably ranges down to where it's so fuzzy that it becomes useless. --Wjbeaty 04:36, 27 December 2006 (UTC)

Although "imageless dreams" are regularly reported, this is the first time I hear of someone who otherwise has normal vision only having such dreams. Most people report having at least occasionally dreams that are visually as vivid as they experience the world when awake. In contrast, visual imagination is normally not reported as having a quality of vividness, in accordance with Wjbeaty's comment, and neither is visual recall of a familiar image. From the scant reports on people with vivid visualization, it is not clear whether this is coupled for imagination and recall. The usual lack of vividness of recall is in marked contrast with the ability of many people to have a vivid recall – often involuntarily – of sounds and in particular melodies. But most people are unable to "imagine" a new melody. Apparently these various abilities are not tightly coupled.  --Lambiam^Talk 10:15, 27 December 2006 (UTC)

If you are really unable to visualize at all, that would be very interesting from a cognitive perspective. You might offer yourself up to a university for some MRI scans — I have a feeling cog sci graduate students would be very interested in seeing how your brain looks, whether or not the visual centers look the same as other people's. Because even blind people can usually visualize, because they still have the same brain hardware as the sighted. It's very, very interesting that you cannot, though you can still see fine? It is very curious. --24.147.86.187 14:24, 27 December 2006 (UTC)

Did you try painting the back of your eyelids - if not, just imagine! -- DLL ^{.. T} 18:31, 27 December 2006 (UTC)

Is red and pink coral illegal in Canada?

Hello,

I recently was caught by surprise at seeing some beautiful red coral and silver jewellry pieces in a local ethnic gift shop. I have never seen red coral jewellry before in Canada (but I haven't searched extensively!), and for some reason I have always thought it was illegal. Upon questioning the salesclerk, she answered that it was not illegal as the coral was already dead before it was obtained for use in making the jewellry.

1. Are products made from red coral illegal in Canada? 2. Is one being ecologically ignorant in wearing jewellry with red coral?

Thank you! 74.115.30.54 01:11, 27 December 2006 (UTC)

First, the argument that "it was already dead before it was obtained" is bogus. If the store sold you something that was illegal, the next thing they'd do is order another one, which someone would kill, and then it too would be "already dead". The idea of such prohibitions is to stop the dealing in such products in order to remove the motivation for the killing.

It appears that there is no specifically Canadian law about coral products. Canadian federal laws can be read and searched at the Department of Justice web site, and their search finds nothing containing the word "coral". However, that doesn't make it legal. Canada is a signatory to the Convention on International Trade in Endangered Species, and several species of corals are regulated under this treaty. I have no idea whether there are any red corals that do not fall under CITES and whose sale is therefore legal.

--Anonymous, December 27, 02:18 (UTC).

I assume the clerk meant that the coral had died, not from the actions of those collecting it, but from something else previous to that time, like pollution, for example. I believe tusks collected from elephants which died of natural causes can also be sold legally in some places, but there is a certification process used to prove that this is, in fact, the case. I'd expect something similar for coral. On the plus side, such a program may serve to satiate the demand, thus reducing poaching. StuRat 13:26, 27 December 2006 (UTC)

I don't know anything about why red/pink coral may be illegal in Canada, but why must you be ecologically ignorant from wearing coral? Endangered species in the United States can often be found to be plentiful in one area, and almost gone in the other (thus they are endangered, there). What if red coral is plentiful some other place in the world? Just being skeptical! It is my understanding that coral is fairly plentiful, and not that tough an organism (small salinity changes or temperature changes, or water current changes can severly stress it), even though the volume makes up for it. Correct me if I'm wrong about that. X [Mac Davis] (DESK|How's my driving?) 22:39, 27 December 2006 (UTC)

skins compression clothing

I was wondering what effects the use of skins compression clothing have on athletes in terms of both performance and recovery. I was also wondering what is the difference between skins and other brands on the market

muscles

Is it harder for asian males to get lean muscles through weight-lifting compared to other races?

I don't know an answer, but this is related to somatotypes. I do not believe one can look at it by race very well, however it is possible that different somatotypes are found in different magnitudes in different races? Many scientists argue the existance of "races." Don't worry, we still believe in marathons. X [Mac Davis] (DESK|How's my driving?) 22:34, 27 December 2006 (UTC)

Science name

What is the name of the science that deals with the size and shape of the Earth? My sister got asked this, and didn't know. I'm just interested! --Thelb⁴ 09:04, 27 December 2006 (UTC)

Planetary science (aka planetology)? Clarityfiend 09:13, 27 December 2006 (UTC)

Geology ? (or surely one of the many links at the end of the article) -- WikiCheng | Talk 10:01, 27 December 2006 (UTC)

Geodesy? Weregerbil 10:48, 27 December 2006 (UTC)

Ding! Ding! Ding! We have a winner. Clarityfiend 11:29, 27 December 2006 (UTC)

What was a man able to withstand of wounds and injuries during the past (medieval times)

hey there 'Wikipedia-people', your doing impressively well with this site. I love it =D

I have questions about how much would a man be able to withstand in the past when it came to wounds and injuries from melee-weapons and effects from extreme cold in the medieval age.

i realize that what i am about to ask might seem very strange questions, so to take away any curiousity around it if any, I just say i'm writing a book/novel and so i need facts about this and that, and i use Wikipedia a lot as a source of information, and i realize my questions may not have direct answers, but rather 'guiding' answers that points me in the right direction. If you have any idea at all, that is.

1) A man who takes a axe-cut across forexample his hip-bone so strong that his hip-bone are broken/crushed and that his skin and flesh are sliced open to a big open wound, blood flowing out of it quite good, would he stand any chance of survival ? in the past, i take take it they had no methods of 'fixing' broken body parts, like we have today when we go through surgery and such. but would he die in just minutes, or would he die a slow lingering death that stretched for over days ? Would he fade slowly and eventually 'fall to sleep' relatively peaceful due to blood-loss or would there be chances that he died by the injuries itself first ? or would it be chances to save him ?

2) Say that this axe-wound was made out in the wild, in arctic, cold and harsh lands far away from civilization. If there were forexample -15 degrees or even colder, would the cold have ANY impact on 'freezing' the wound and stopping the bleeding on such a big wound ? any impact at all? if any, then HOW strong impact? would it help keep pressing cold snow over the wound ?

3) how big and bad could a wound be before the cold no longer could HELP stop the bleeding from it?

4) what methods did they normally use to treat battle-wounds and stop bleeding ? forexample a an arrow-wound or a lesser sword-sting or lesser sword-slash?

5) If one falls through the ice and into the water, and then gets up on land relatively quickly how long would you be likely to survive in the wild with temperatures as low as -15 or lower? a few minutes, right ? ofcourse, one would have to tear of all clothes in a hurry, as the cold and wet clothes will only add to make you frozen. But then what ?

6) was it possible that a bludgeon-weapon (war-hammer, mace, morning-star, flail, club etc.) could kill a man THROUGH leather, mail or steel-armor in ONE blow ?

if these questions fits better under "culture", since its from the past, just say and i'll put it there instead, but here stood "physique" so...

thank you, Krikkert7 10:58, 27 December 2006 (UTC) Krikkert7

I can't answer all your questions, but I can answer some. First, people in olden times have survived remarkable injuries; Samuel Pepys had a gallstone taken out without any long-term ill-effects; the son of a mediaeval king (sorry don't remember his name) had an arrow painstakingly removed from - I think his head - and lived, but of course, on the flip side, many many people died of injuries that would be easily treatable today. I think it was King Richard the Lionhearted who died of a fairly minor (well, serious but not mortal) shoulder injury.

As to your first question, even nowadays with fast and efficient medical care, people die of injuries to the femur, even with the skin unbroken; it would be unlikely that your medieaval hero would survive. The speed of his death would depend on whether or not the femoral artery was nicked or collapsed as a result of the injury; if yes, death could be in 10s of minutes or sooner; if no, then he would die of gangrene or shock.

As to cold and injury, cold is seldom good for any serious injury, particularly those that involve blood loss, because it hastens shock, the depression of the cardio-pulmonary system, blood flow and blood pressure that results in unconsciousness, heart failure, organ failure, and ultimately death. The only good field treatment for serious, bloodletting injury is compression, and I am sure many mediaeval warriors knew this.

I hope others can expand upon my answers and answer your other questions. Anchoress 11:19, 27 December 2006 (UTC)

Interesting questions. I'll try to give some answers. Know this is just speculation, (although intelligent speculation i'd hope).

1. The person would probably faint from the pain. The most immediate way this man would die is from blood loss. An axe-cut that deep would cause a LOT of blood loss, with the person dying in minutes-hours depending on the exact location of the cut. The Axe Cut could easily have damaged his internal organs, or the broken bone could have stabbed up and damaged his internal organs. The next biggest concern is infection. If he doesn't die immediately, the wound will most likely be infected. There're ways to prevent infection (salt, alcohol, burning), but none of these are all that reliable. With no antibiotices, he'll die in days-weeks depending on how big the wound is. So for chances of survival - i'd say very low. Although it does depends on where exactly the wound is and how serious it is. Even if the man miraculously survived on his own, you can be sure he'll never be able to walk or even stand again with a hip bone that badly damaged. Even so, he probably won't survive more than a few years.

2. I'd say the person would most defintely die in those conditions. The cold would 'freeze' the wound, stopping bleeding and halting infection. But...-15 degrees is VERY cold. THe axe cut would also rip of clothing, exposing not only the wound but the entire body to the cold. Being exposed to -15 degree whether causes a whole lot of problems, as Anchoress has already described above.

3. depends on how cold. If we're talking -15 degrees...i'd say the blood would freeze pretty quick - no matter how big/bad the wound is. But in that kind of temperature, the person would die anyway from the cold.

4. you mean with modern medicine? Well...i don't think many people get such battle wounds these days. I'd guess they'd deal with arrow-wounds the way they deal with bullet wounds (so surgically remove the arrow, stop bleeding, antibiotics to prevent infection, stitching...etc.). Back in the medieval times...dunno. HIstory was never my thing. But i'd guess it'd be just a matter of pulling out the arrow, and bandaging it and hope it stops bleeding. If the wound was very bad, they'd probably use this technique that involves basically burning the wound. There's a special word for it but i forgot. I'm not sure how it works, but it's supposed to stop bleeding. Salt/alcohol/heat would be used to kill bacteria, and hence prevent infection. Then the person would just have to rest, and hope his body can make it.

5. if the water was -15, then someone falling into it won't be able to climb out. It'd send you into shock - both phyiscally and mentally. You try jumping into a pool of cold water on a cold day without preperation, and see how quickly you can get yourself out. plus, climbing out of the ice is not easy. That's why so many people die from skating on frozen lakes/rivers - because they fall in and can't get out. I mean, if you fall through the ice, you'd be falling through a small hole. Climbing out is not so easy. Just think about how you climb out of a swimming poll without using the ladders. Then imagine doing that in -15 degree water, with slippery ice. And...can this guy even swim?

6. yeah. If you hit hard enough and at a vital spot. You get hit on the neck/head with a bludgeon-weapon that's swung right...and you'll die. Leather doesn't offer much protection. Not sure about mail or steel armor. But from my understanding, armor protects more against slashing weapons. it's like...when a bludgeon weapon hits, the force of the blow will push you back regardless of armor. So if it's swung with enough force, i don't see why it wouldn't still be able to damage/kill. I doubt the armor can absorb that much shock - a clear hit would kill the person, especially if it's in a vital spot.

--`/aksha 11:53, 27 December 2006 (UTC)

The biggest difference between then and now is the risk of dying from infection. They would have been perfectly capable of preventing most infections, by cleaning the wound (say by pouring whiskey on it) and by only wrapping in sterile cloth (say by boiling the cloth), but didn't know that wrapping the wound in old dirty rags would cause an infection, so were likely to do more harm than good. StuRat 13:20, 27 December 2006 (UTC)

If the water was -15 degrees (F or C) it would be frozen solid, so he would not fall into it. (perhaps onto it). People up until the 1930's when sulfa drugs were introduced and the 1940's when Penicillin was introduced often died of very minor infections, despite the best medical care. The son of President Calvin Coolidge got a small blister from a tennis shoe which got infected and he died despite all available medical science. Yet a few hardy souls survived amputations, penetrating wounds of the head in which a steel bar passed all the way through the brain, Phineas Gage (1848) and wounds which left an open fistula into the stomach Alexis St. Martin (1822). Edison 17:19, 27 December 2006 (UTC)

What was a man able to withstand of wounds and injuries during the past (medieval times) - PART 2

Hey, THANKS LOTS FOR UR ANSWERS on my previous questions!!! ...but now you got me going for more with all those good answers :D :P

---

Ur very helpful to me!

7) As for the the guy falling in the water, i was thinking more like he got help from some mate/friend who drags him up quickly. i understand he would still go in shock, and die HOW FAST??? how would the process go about ? would he sit quite unmovable, shaking ? not able to speak, and in shock as said? and eventually his body would not be able to take it anymore, and he would FADE SLOWLY ? or would it all happen more quick and brutal ? i guess his friend would do him a favour by ending his misery quick... :S

8) And quite interesting i think, how would this guy who pulled him up fare ? how would his arm and hand fare ? (Ofc, his hand has to be put into the icy water and get wet to pull his friend up - say he's quite strong and able to do so with only one arm) I take it chances would be BIG for him to be hit by frostbite, or maybe he would be WITHOUT ANY DOUBT in such a harsh climate? At least his fingers and hand would be greatly in risk, no ? However, if he quickly dry the arm and hand as best he can with something dry and then wraps arm/hand in as much cloth he can to generate warmth, he may be able to "recover", no ? - even though they are out in the wild with extreme cold...

9) And.. as I know, if frostbite gets to bad, and gets infected or is hit by gangrene, one has to amputate the limb/bodypart that is infected. i tried read about amputation ( in the past) but found nothing about how they stop the bleeding... i mean, if u forexample saw of someone's leg or arm, HOW ON GODS GREEN EARTH are you going to be able to stop the bleeding from such a big open wound? the blood must flow out in less than a minute ?!?! :O i read scarcely that they lingate the main arteries and veins BEFORE the 'operation', but they didnt do that in the past did they ? and how would they be able to do that before they had sawn the leg/arm of ?

10)you say extreme cold is bad for any big wound, and i guess i see the logic in it. the cold goes straight INTO your body through that huge open wound i guess and chills down/cools down and kind of freezes your INSIDE, affecting inner organs and all that much much faster. but you did not give me an opinion on how fast he would die when counting'in the extreme cold. so... ?

thank you Krikkert7 14:48, 27 December 2006 (UTC) Krikkert7

Lipitor and grapefruit

How dangerous is eating a daily grapefruit while on the lowest dose of Lipitor?

We really can't tell you how dangerous it is, but you should avoid it, as grapefruit causes many meds to stay in the system longer than usual and thus have more of an effect than usual. Of course, if this effect was predictable, just reducing the dosage of Lipitor would solve the problem. Unfortunately, I don't think anyone has studied it to know exactly what the magnification factor on Lipitor is, so any reduction in dosage would be little more than a guess, therefore I would just avoid grapefruit, instead (which is a shame, because grapefruit is really good for you). Perhaps we can get the gov to fund a university study ? StuRat 13:07, 27 December 2006 (UTC)

There have been many such studies. Lilja JJ, and co-investigators ( Clin Pharmacol Ther 1999; 66: 118-27) found that grapefruit juice increased Lipitor's availabilty by about 2.5 fold. Another, Effects of grapefruit juice on the pharmacokinetics of pitavastatin and atorvastatin.Br J Clin Pharmacol. 2005 Nov;60(5):494-7 Ando H, et.al, found that grapefruit juice increased the mean AUC(0-24) of atorvastatin acid by 83% (95% CI 23-144%). The problem is that such studies do not predict the magnitude of the effect in any given person. So that even were someone able to keep their daily grapefruit juice intake constant, they would need individual testing for blood levels of atorvastatin and its metabolites to determine its effect. That's just not practical, and it's much easier just to avoid the grapefruit. - Nunh-huh 13:22, 27 December 2006 (UTC)

See also Cytochrome P450 oxidase, the specific enzyme pathway affected.

Atlant 14:17, 27 December 2006 (UTC)

The effect is variable, as grapefruits have widely differing concentrations of the relevant bioactive compounds, and therefore not usable in a reliably predictable way.  --Lambiam^Talk 15:45, 27 December 2006 (UTC)

Nuclear war

What effects would a full-scale nuclear war have on humanity?

Obviously they'd be negative, but as for the scale of the destruction, I can't get a clear answer. I mean, take a look at pop culture:

• On The Beach - All human life is completely wiped out, even though no nuclear weapons were deployed in the southern hemisphere
• The Outward Urge - The northern hemisphere is reduced to a poison wasteland, the southern hemisphere survives and thrives.
• Threads - Life survives even in the worst hit areas. Of course, it's not a good life.
• Jericho - You can live right in the heartland of America and everything will be fine! :)

Which is the closest to the truth? Battle Ape 13:57, 27 December 2006 (UTC)

Hypothetical fallout pattern from a nuclear attack against the USA (actual direction of plumes would be at the whim of weather patterns). Even those areas not directly hit would be massively affected. Notice that the heavy attacks against the US midwest are due to the fact that such areas are sites of missile basing and would be prominent targets.

Most scientists don't think nuclear winter would occur, but that isn't much of a consolation. Aside from having most large population centers destroyed, the nuclear fallout would deposit lots of very nasty radioactive poisons over most of the rest of the world as well, as well as raise the level of background radiation considerably. Could humanity survive? Maybe, but it would be a very different sort of survival than we have now. Would civilization survive? Probably not as we know it. Oy. In any case we have an article on nuclear warfare which might be helpful. Of the above choices, I'd go with Threads. --24.147.86.187 14:14, 27 December 2006 (UTC)

One effect that is often under-considered (at least in popular media) is the effect on the world's economic systems. The 9/11 attacks, an attack which was relatively small-scale as war-making goes, had a vastly-disproportionate effect on morale in America (and to a lesser extent), worldwide and this propagated into substantial downturns in the US and global economies. You can bet that after a full-scale nuclear exchange, there just aren't going to be that many people buying (or manufacturing) large-screen plasma TVs; we'll be lucky if the world doesn't starve to death from lack of global trade in food. Also not inconsiderable will be the fact that a full-scale exchange will remove many of the cities that are home to the world's financial systems. It's a sure bet that the aftermath won't be pretty, and Dr. Steven Falken's strategy (of living quite near a primary target site) may well look to have been quite appealling in retrospect.

Atlant 14:27, 27 December 2006 (UTC)

Not just starve to death, but all of those bodies left to rot because there are not enough people around to bury them, or even care to do so, will be cess pools of disease just waiting for the next unwary traveller who passes by (or, who, starving, decides to eat the dead, or dying, corpse). User:Zoe|(talk) 17:54, 27 December 2006 (UTC)

Most of the population is in the cities, and those would be the prime targets. Thus most of the people would be eliminated, which is lot's fewer mouths to feed. So starvation? Who knows, certianly an overload of canned food would be available, and the can would protect the food inside from fallout. Would there be too many people left to live off the land after the radiation subsided? Who knows, and it depends a lot on the type of nuclear war, how many 'salted' nuclear weapons would be used? etc. 12.10.127.58 22:36, 27 December 2006 (UTC)

Most of the population is in the cities...

Citation for that? Although I suppose it depends on what you define as a city elligible of being on the receiving end of a nuke or ten.

Atlant 22:48, 27 December 2006 (UTC)

According to the World Almanac, using US 2000 census data, 226 million (80.3%) lived in metropolitan areas. About 135 million lived in the 25 largest metro areas. Cheers Geologyguy 22:57, 27 December 2006 (UTC)

Tracking of dynamically-changing objects on TV

I am searching for an algorithm (or an approach) which could help track identified (outlined) objects seen on TV set. Say, if I capture a TV broadcast to a medium (tape, hard disk of a computer, etc.), is there a solution to help identify (maybe outline) an object on the screen, and then have it "automatically" tracked?

An object on TV (raster or bit-mapped) typically has the following characteristics: Its shape changes. IT appears multiple times (imagine a ball passing behind a player momentarily in a sports broadcast). Its trajectory changes. Depending on lighting and reflections, its color is not consistent, etc. Any suggestion is welcomed: An approach, a particular field of study, one or more algorithms dealing with raster-based or bit-mapped graphics.

Where should I start? Where should I research for an answer?

If you cannot think of a specific answer, is there a particular area of research or commerce I should focus on?

Thank you. I look forward to your creative suggestions and guidance!

Kelar12 14:42, 27 December 2006 (UTC) KT

The article on video tracking may be of help. - Dammit 14:55, 27 December 2006 (UTC)

Try edge detection. That's on what most of the visual tracking algorithms are based. --V. Szabolcs 22:59, 27 December 2006 (UTC)

Fatty Acid Enzymes

How do the desaturase and elongase enzymes that operate on fatty acids know which types of fats to act upon? For example, why do enzymes like delta-6-desaturase "know" to operate primarily on EFAs, and not saturated or monounsaturated fats? Frankg 15:02, 27 December 2006 (UTC)

Enzymes have active sites that are very specific for their substrates and can distinguish between the different structures of the fats. David D. (Talk) 17:36, 27 December 2006 (UTC)

What was a man able to withstand of wounds and injuries during the past (medieval times) - PART 2

Moved to combine with original section above. Anchoress 21:05, 27 December 2006 (UTC)

Trans fat question

Many food labels claim a food product has 0% trans fat, but if the first ingredient in the product is partially hydrogenated oil, how can this be so? Can the trans fat be separated out and removed? Arilcv 20:35, 27 December 2006 (UTC)

The regulations in the United States, for example, allow less than 0.5g of trans fat per serving to be labelled as 0g. There are oil factionation methods that would probably allow the trans fat to be removed, but they may be more expensive than just using a different kind of oil (i.e. one that isn't hydrogenated). If partially hydrogenated oil is in the ingredients list, the product contains trans fat. Frankg 20:52, 27 December 2006 (UTC)

instrument for measuring an orifice diameter

What instrument can you use to measure a very small orifice diameter?

How small are we talking?

If very small maybe a travelling microscope might do the job.--Light current 21:19, 27 December 2006 (UTC)

I was hoping to get a more quantitative measurement, to the tenth decimal. How would I use a microscope to do this?

A very fine vernier caliper might be better. -GTBacchus^(talk) 21:25, 27 December 2006 (UTC)

[40]--Light current 21:29, 27 December 2006 (UTC)

Umm - "tenth decimal" - you want to measure the diameter with a precision of 10^-10 metres i.e. 100 picometres or better ? That's the same order of magnitude as atomic bond lengths. I'm not sure that degree of precision is either realistic or meaningful. Gandalf61 22:33, 27 December 2006 (UTC)

Choose one of:

• Calibrated wires of various sizes; see which just clears the orifice
• An optical comparator (a specialised microscope that projects onto a large screen and is used to make precision measurements of tiny things; 'shame there's no article about these, but see [41])
• A scanning electron microscope.

Atlant 22:57, 27 December 2006 (UTC)