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December 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)[reply]

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)[reply]

Thanks! It's a 940 nm emitting LED (by tagging gun I meant a gun that can be used in 'laser tag'). --Username132 (talk) 02:41, 28 December 2006 (UTC)[reply]

The problem with plastic in IR is that it has a lot of absorption peaks. Glass has absorption peaks too, IIRC, but they are really close to the end of the IR scale and are not as jumbled as plastic's peaks are. What you should do is test whatever plastic is most convienent. If you are only using one wavelength of light, the absorption of plastic at that wavelength will be constant and you should be able to calibrate inorder to compensate (but, you may lose too much signal, in which you may want to try a different plastic).--Acewolf359 16:34, 29 December 2006 (UTC)[reply]

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)[reply]

One of my anatomy books calls them "blunt papillae". I don't know their function, if any. --Joelmills 04:33, 25 December 2006 (UTC)[reply]

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)[reply]

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 --

. 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)[reply]

The minerals in the water, as well as the taste leached from the water bottle. --Bowlhover 02:58, 25 December 2006 (UTC)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

I found this report (doi:10.1016/S0048-9697(01)00915-9) quite interesting. —Keenan Pepper 00:38, 26 December 2006 (UTC)[reply]

The poster of the memory effect comment changed the subject on us. Most of this conversation was concenrning reverse osmosis, a method of water PURIFICATION. This process actually removes the impurities from water and leaves pure water (more precise, it actually removes that water from the impurities, but that is unimportant). What the memory effect person is talking about is DILUTION, and his support statement is MOSTLY accurate. When the theretical concentration in a solution is smaller than Avagadro's number, it is possible to enconter samples which contain none of the substance in question.

Aquafina bottles, as are sold in the US, contain only O.R. water and no minerals. Coke does add minerals to their water brand, Dasani, and thus I am in agreement with 72.202.150.92.--Acewolf359 16:46, 29 December 2006 (UTC)[reply]

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)[reply]

"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)[reply]

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)[reply]

As a side note, the Norwegian plant used electrolysis as detailed at Norwegian heavy water sabotage. Hipocrite - «Talk» 15:27, 25 December 2006 (UTC)[reply]

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)[reply]

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)[reply]

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)[reply]

howstuffworks.com also has some good information. - Akamad 22:10, 25 December 2006 (UTC)[reply]

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. [1] X [Mac Davis] (DESK|How's my driving?) 23:07, 25 December 2006 (UTC)[reply]

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)[reply]

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).[reply]

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)[reply]

This would also apply in India, as it is a party to the Single Convention on Narcotic Drugs.[2] This means that the sales of methadone without a doctor's prescription is a crime. --Lambiam ^Talk 18:55, 25 December 2006 (UTC)[reply]

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)[reply]

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)[reply]

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)[reply]

There is no easy correlation between max acceleration and max velocity. --Lambiam ^Talk 18:58, 25 December 2006 (UTC)[reply]

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)[reply]

Dinosaur movement and lizard movement are not very similar in any case. Theropods were more similar to an ostrich in that respect, while sauropods came closer to an elephant (in both cases, "more similar" is relative), and so on. Mammal ancestors on the other hand moved similar to lizards, with legs splayed out to the sides. But in these, still, acceleration would be a problem of mass. Some small, early therapsids probably came very close to lizards. Dysmorodrepanis 04:40, 28 December 2006 (UTC)[reply]

And aren't lizards not descened from dinos anyway?--Acewolf359 16:49, 29 December 2006 (UTC)[reply]

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)[reply]

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)[reply]

Is that all? I'd think it would be way, way more than that. Anchoress 14:45, 25 December 2006 (UTC)[reply]

That's probably only the readily available portion of memory, like the proper way to spell kat. :-) StuRat 16:11, 25 December 2006 (UTC)[reply]

Yes, the rest is taken up by the operating system. :) V. Szabolcs 11:14, 26 December 2006 (UTC)[reply]

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)[reply]

Yeah, I guess it depends on whether it's a Microsoft Neural Network, lol. Anchoress 15:43, 25 December 2006 (UTC)[reply]

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)[reply]

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. --W o o ty Woot? contribs 02:26, 26 December 2006 (UTC)[reply]

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)[reply]

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)[reply]

not more than two orders of magnitude off. Uh. Right. :) X [Mac Davis] (DESK|How's my driving?) 23:00, 25 December 2006 (UTC)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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. —D a niel (‽) 19:14, 26 December 2006 (UTC)[reply]

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)[reply]

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)[reply]

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)[reply]

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).[reply]

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)[reply]

By what means have you determined the probability to be zero? Adaptron 10:33, 28 December 2006 (UTC)[reply]

Are you talking to me? I don't know what probability means in this context. Create 1000 universes and see how many of them have a God? So what makes you think I have "determined" any such thing? You, however, made a claim as if it is an established fact, so it is fair to ask for your arguments supporting that claim. --Lambiam ^Talk 11:31, 28 December 2006 (UTC)[reply]

My claim, if any, is only that you have not provided the equation you are asking me to provide with a zero probable or possible result for the existence of God in either one or in an infinite number of universes. By not so providing then your own logic leaves an infinitesimal chance that God exists in at least one universe. The problem is that many youths and some adults think that the space between their ears constitutes the universe and doubt the existence of God because they have not [yet] found Him there. Adaptron 16:10, 28 December 2006 (UTC)[reply]

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)[reply]

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)[reply]

Darwin was a Creationist by the way. The very last sentence of his book "Origin of Species" claims that the "Creator" is responsible for it all. This last sentence is used to recap the entire book. Darwin capitalizes the word "Creator" in his book. Zeno333 08:50, 20 January 2007 (UTC)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

You could look at potentiometer#Theory of operation .8-| --Light current 21:38, 25 December 2006 (UTC)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

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)[reply]

Power, Electrical?--71.247.120.5 23:05, 25 December 2006 (UTC)[reply]

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)[reply]

BTW, it doesn't "describe" anything, it's merely a definition. —Keenan Pepper 00:24, 26 December 2006 (UTC)[reply]

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)[reply]

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)[reply]

The first is gravitational potential energy, the second kinetic energy. Clarityfiend 02:55, 26 December 2006 (UTC)[reply]