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January 6

Looking back in time through space

In terms of looking into space, does anyone know, in light years, what is the furthest back in time man has peered? Are we talking thousands or millions of years here? 79.75.238.142 (talk) 02:37, 6 January 2009 (UTC)

More like billions: . StuRat (talk) 02:43, 6 January 2009 (UTC)

It's a substantial fraction of the time since the big bang. We've observed and mapped the "cosmic background radiation" - which according to our article was just 400,000 years old at the time. We believe the universe is 13.7 billion years old - so the answer is something like 13,699,600,000 years. (OK - we should be rounding that to 13.7 billion). (That's "years" not "lightyears" - a light year is a measure of distance - not time). In some sense, it's not possible to look further back in time than that because there was nothing like atoms for photons to bounce off of - so we've pretty much seen as far back as it's possible to see. SteveBaker (talk) 05:15, 6 January 2009 (UTC)

If you consider detecting microwaves to be a method of "peering", the cosmic microwave background radiation has been travelling in space since the universe first became transparent to light 13.7 billion years ago, 400 000 years after the Big Bang. It isn't possible to detect light from any earlier time because earlier photons were continuously being emitted and scattered before travelling any appreciable distance.--Bowlhover (talk) 05:11, 6 January 2009 (UTC)

There are two potential ways to "look" even further back in time. One is the detection of the cosmic neutrino background: neutrinos decoupled from the rest earlier than the electromagnetic radiation of the cosmic microwave background. The other method would be to look for gravitational waves from the earliest epochs of the universe. Alas, we do not have the technology for detecting either of these backgrounds yet. --Wrongfilter (talk) 13:42, 6 January 2009 (UTC)

Yes, agreed. Although detecting neutronsneutrinos and gravitational waves stretches the definition of the word "see" further than I'm comfortable with! I'd prefer "infer from". I believe the CMB is the first detectable electromagnetic radiation (although you could probably argue with using the word "see" for microwaves too!). SteveBaker (talk) 15:07, 6 January 2009 (UTC)

Careful - neutrinos, not neutrons. --Tango (talk) 01:28, 8 January 2009 (UTC)

oops! all better now! good catch. Thanks. SteveBaker (talk) 16:41, 8 January 2009 (UTC)

Considering the observations of specific objects see the Hubble Ultra Deep Field. --mikeu 17:15, 7 January 2009 (UTC)

Potassium supplement dosage

I was at the health food store this weekend and looked at Potassium supplements. I was surprised that they were all 99mg and only supplied 3% of your RDA. Any one know why they are all capped at 99mg? A person would have to take 33 tablets to get the full recommended daily allowance! --71.158.216.23 (talk) 03:00, 6 January 2009 (UTC)

The reason is that an overdose of potassium can kill you, so they don't want to take any chances that the supplement, along with your normal diet, will do that. The 3% is just so they can claim their supplement has a valuable nutrient in it. Potassium is actually what they use in lethal injections (in much higher dosages, of course). See hyperkalemia. StuRat (talk) 04:53, 6 January 2009 (UTC)

That explains the reason why there would be a limit. If all the tablets are exactly 99 mg, then a likely reason for that particular size is that someone wrote the law or regulation so as to say "any tablet containing 100 mg or more of potassium requires a prescription" rather than "any tablet containing more than 100 mg of potassium requires a prescription". Perhaps at the time the next-largest size below 100 mg was 50 or 75 mg, and they assumed it would continue to be, but manufacturers saw a loophole and created 99 mg tablets in order to gain a competitive advantage and stay within the law.

In that paragraph I'm just guessing, but I do know about a similar occurrence in the field of railroads. In 1922 the Interstate Commerce Commission in the US was trying to reduce the number of train crashes due to signals being passed at danger, so they mandated the installation of measures such as automatic train stops on all railways that allowed trains to run at 80 mph or more. And the result is that to this day a large number of main US rail lines have a speed limit of 79 mph. --Anonymous, 07:56 UTC, January 6, 2009.

The Universe

Could it be possible that the universe is spherical and when one looks through a telescope in any direction they could see all the way around the universe back to ones position at earth in the future,assuming light would bend around the universe and also assuming one had a telescope that powerfull.Grimmbender (talk) 03:58, 6 January 2009 (UTC)

Sounds like you mean the universe being on a spherical surface not being a sphere itself. Consider standing on Earth: if you go forward a long distance along the surface you come back to where you are. But if you are underground and you move in a straight line (cartesian, not spherical) you wind up bursting through the surface and heading out into space. The only way "universe is a sphere" would lead to "seeing forward back to behind you" is if light somehow bounced (or tunneled, or whatever) around when it got to the edge. DMacks (talk) 04:21, 6 January 2009 (UTC)

A sphere is a surface. The solid that you're thinking of is a ball. Technically, he should have said 3-sphere. I think it should actually be 3-spherical cone, to account for space expanding through time. Anyway, I think we all know what each other mean. — DanielLC 21:06, 6 January 2009 (UTC)

It is possible that the universe wraps around itself like that (I think we'd be talking about a hypersphere or something) - we don't know for sure - but if it does, we'll never be able to do the experiment you're thinking about because the 'observable' universe appears to be smaller than the entire universe. Because the speed of light is the universal speed limit - we can only ever see or know about parts of the universe that are close enough for light to have travelled from there to here in less than the time since the big bang. Anything further away than that (including, perhaps, the back of your own head) is forever too far away to ever be visible. SteveBaker (talk) 05:05, 6 January 2009 (UTC)

"The back of one's head is inches from the eyes but too far away to be seen." DMacks sends contents of coffee mug out for tox-screen. DMacks (talk) 05:17, 6 January 2009 (UTC)

I haven't seen anything later than this and this. It looks like the Universe is a closed Poincaré dodecahedral space, it is a "small universe" with positive curvature, and yes, we can see all the way around it (same glowing spots from the CMB in different parts of the sky). This is difficult stuff, I can put the cites here or send copies of various papers and reviews to anyone interested. Franamax (talk) 07:41, 6 January 2009 (UTC)

"same glowing spots from the CMB in different parts of the sky" -- sweet Christ that's weird! --Sean 13:04, 6 January 2009 (UTC)

Wow! That is REALLY cool! But doesn't that just prove that back at 400,000 years after the big bang (which is when the CMB was 'formed') - it was all close enough to be within the observable universe - but the expansion of space (which happens faster than the speed of light at large distances) has since made everything so much larger that now we can't see it all anymore? This is tricky stuff - and the theories are changing rapidly - so it's hard to know what is considered to be "true" on any given day! SteveBaker (talk) 15:02, 6 January 2009 (UTC)

Almost no cosmologist accepts the conclusion of those papers currently. I think they blame the apparent effect on cosmic variance. Here's a slightly more recent analysis that reaches an opposite conclusion. The best bet right now is that the universe doesn't wrap around at the scale we can see, as SteveBaker said.

Practically everyone believes that the part of the CMB that we can see was all in causal contact at one time, since it's pretty hard to understand the uniform temperature otherwise. But according to current dogma that time was before the inflationary epoch, while the fluctuations in the uniform temperature arose during the inflationary epoch, at which point the different parts of the CMB sphere had lost contact with each other. Even if that's wrong, it's hard to imagine what mechanism (other than a wraparound universe) could produce correlated fluctuations of the specific kind you expect to see in a wraparound universe. (As the paper I linked explains, you can expect to see correlated circles, regardless of the details of the wraparound.) -- BenRG (talk) 17:48, 6 January 2009 (UTC)

Hmm, interesting stuff. The paper you link doesn't completely falsify Luminet, but it looks like Cornish et al bought a bigger computer and kept at it. Here they devote a paper to trashing all notion of a dodecahedron. So we still don't know the shape of the Universe and the LHC is still busted. C'mon scientists, get it together! :) Franamax (talk) 19:21, 6 January 2009 (UTC)

Four fundamental interactions as four formulas

It's my understanding that the inverse square law applies to gravitation for most intents and purposes, but with famous exceptions such as the Mercury anomaly. I'm trying to understand (1) why exactly the relativistic understanding of gravity changed the actual calculations of orbit, and (2) whether all the fundamental interactions can be expressed as simply as gravitation (either Newtonian or Einsteinian) can. I know this is a "big" question, so feel free to contribute whatever you can — don't feel pressured to answer the "whole thing"! Also, let me know exactly how I am thinking about this incorrectly, as is usually the case with me and quantum physics.${\displaystyle \sim }$ Lenoxus " * " 05:01, 6 January 2009 (UTC)

It's not quantum physics here, but general relativity. Mercury does obey the inverse square law for gravity, but space is behaving weirdly. I think Kepler problem in general relativity will answer most of your question (if you get the maths, which I don't just now ;-). --Stephan Schulz (talk) 09:11, 6 January 2009 (UTC)

There are four known fundamental interactions: gravity, electromagnetism, strong nuclear and weak nuclear. Gravity, at least the Newtonian model of it, is pretty simple to understand. Electromagnetism isn't too bad, that's just Maxwell's Equations. It doesn't get it down to one equation but close. I haven't seen a simple expression for either of the nuclear forces. DrAstro (talk) 21:25, 6 January 2009 (UTC)

There are only three! Electroweak theory (unifying what was known as electromagnetic interaction and weak interaction) is well-established, and I think it's the one that's best understood. Gravity is hard to test experimentally because it's so weak, and the strong interaction is hard to compute because it's so strong. Icek (talk) 23:50, 6 January 2009 (UTC)

Thanks for all your responses! They've all helped a lot with my understanding of the subject. I think I'll rephrase my question as follows: Has all of physics been "in principle" narrowed down to the consequences of the fundamental forces, and if so, does that mean that everything in the universe can be understood as a consequence of three or four equations and the wave/particles they affect? (Obviously, the whole deal is a heck of a lot more complicated than that, but it's just that I figured that physicists wouldn't keep saying "just four/three forces!" if something like, say, momentum or thermodynamics was really just as fundamentally "mysterious" as gravitation.) ${\displaystyle \sim }$ Lenoxus " * " 20:56, 8 January 2009 (UTC)

All three theories are still subject to experimental tests (this is science!). And furthermore, not everything in the universe can be understood exactly because there are 3 theories and not just 1 (there are situations where all interactions are important, and the predictions are different depending on how you combine results from different theories). Attempts to get 1 theory for electroweak and strong interactions are called Grand Unification Theories (GUTs). Most attempts to get 1 theory for all three interactions are called quantum gravity as they are quantum mechanical in nature (Roger Penrose thinks that it should be non-quantum mechanical).

The equations are:

• for gravitation, the Einstein equations
• for electroweak interaction, the equations resulting from applying the Lagrangian formalism to the electroweak Lagrangian
• for strong interaction, the equations resulting from applying the Lagrangian formalism to the quantum-chromodynamical Lagrangian

The latter 2 are quantum field theories, while general relativity (the theory of gravitation) is not quantum mechanical.

Icek (talk) 00:19, 9 January 2009 (UTC)

So to re-re clarify, there are formulas for each force, but not just one per interaction. Even though I understood that the different models/formulas/understandings conflict with one another in various ways, I guess I'd always assumed that each basic interaction got its own formula that could be described in concise language, the way each of Newton's laws can — and that everything beyond that involved the "mixture" of the formulas, something complex enough it couldn't all be done a priori. To put it all another way, why does an interaction that requires multiple formulas get to be considered "one" interaction, instead of the Standard Model saying, "Here are the ten fundamental forces that together produce gravitation, and here are the four that produce electroweak", ect? Thanks again for keeping up!${\displaystyle \sim }$ Lenoxus " * " 01:12, 9 January 2009 (UTC)

(Clarification: I know the Standard Model doesn't actually include gravity, but you know what I mean ${\displaystyle \sim }$ Lenoxus " * " 03:45, 9 January 2009 (UTC))

Maybe I can illustrate the reason using a simple example in electromagnetism - why e. g. Coulomb interaction and magnetic interaction are not considered separate interactions (I will neglect the weak interaction as well as quantum mechanics).

Consider 2 balls, each having a charge of +q. Now these balls are initially at distance x from each other and are traveling at the same velocity v (parallel to each other). The Coulomb interaction now says that they will repel each other. The magnetic interaction says they will attract each other because each moving charge is also an electric current. You can add the forces (you will always get a net repulsion, but of course smaller than the Coulomb repulsion).

Now consider the same problem in the inertial frame moving also at velocity v - the balls are initially stationary in this frame. They only repel each other by Coulomb's law. You might think this is a contradiction, as the repulsion is larger in one frame than another one, but it isn't, when viewed in the context of special relativity. Time dilation makes everything consistent (if the acceleration caused by the forces calculated for one frame is Lorentz-transformed to the other frame, the acceleration is the same as the one calculated from electromagnetism in the other frame).

My point is that a purely electrostatic phenomenon in one inertial frame has magnetic components in other inertial frames.

Icek (talk) 11:14, 9 January 2009 (UTC)

All right, I think that covers everything I was wondering to the best of my understanding. Thanks again to everyone, especially Icek! ${\displaystyle \sim }$ Lenoxus " * " 20:50, 11 January 2009 (UTC)

mech engineering related(new idea)

i want to do project on solar pumps,in a new way.i want that hand-pump must be operated automatically. for that my idea is that like in IC as connecting rod connects piston and crank, in this my idea is to connect piston(some long rod may be connected along its axis)and handle of hand pump by a connecting rod, so that linear motion of piston causes handle to move so taht we can get water w/o human. my question is whether we can achieve this.pls answer its urgent —Preceding unsigned comment added by 210.212.223.138 (talk) 05:55, 6 January 2009 (UTC)

See Newcomen steam engine from 1712. Substitute solar energy for coal fired boiler. Edison (talk) 15:32, 6 January 2009 (UTC)

It doesn't sound very efficient to me, as there is an unnecessary conversion from rotational motion to linear mechanical motion. Instead, I suggest a small submersible pump, which pumps water into an above-ground tank when the Sun shines, to be poured out of the tap as needed. It would need a shut-off valve that triggers when the tank is full. This allows water to be had at night as well as the day, and doesn't waste solar energy when nobody wants water but the Sun is out. If in a cold climate at winter, you would need to protect against freezing by insulating the tank and/or placing it partially underground or inside a heated building (or, a more fun option is to add grain alcohol to the tank). StuRat (talk) 21:44, 6 January 2009 (UTC)

Ice in craters of Mercury

There may be ice in craters at the North Polar region of Mercury. How many creaters with possible ice in them? What is the diameter and how deep? —Preceding unsigned comment added by Johnz Johnz (talk • contribs) 09:29, 6 January 2009 (UTC)

At first I thought this might be similar to the problem of measuring a coastline, that it's always longer if you look for smaller details. However, craters below a certain size probably can't support any ice, because the sunlight hitting the lip would warm the inside of the crater enough to melt any ice. This, of course, wouldn't apply to craters inside a larger crater, and thus in permanent shade. BTW, why not any at the South Polar region ? StuRat (talk) 21:30, 6 January 2009 (UTC)

Ice In An Unlikely Place: Mercury states that there are "about 20 circular areas" and there is a radar image/map at The Discovery of Water Ice on Mercury --mikeu 14:14, 8 January 2009 (UTC)

Atomic masses

which element is chosen as a standard for measuring the atomic masses?why? —Preceding unsigned comment added by 59.103.70.116 (talk) 09:32, 6 January 2009 (UTC)

According to atomic weight the standard is 1/12 of the mass of an atom of carbon-12. I think the isotope is chosen because it has the same number of protons and neutrons. A historical account can be found in . EverGreg (talk) 10:16, 6 January 2009 (UTC)

If you look at that "historical account", it specifically says that the carbon-12 scale was suggested because "because of carbon's use as a secondary standard in mass spectrometry" and because it gave numerical values close to the old scale used by chemists (which was based on a natural mixture of oxygen isotopes). Also, I remember reading in one of Isaac Asimov's monthly science essays that carbon-12 was adopted because it was particularly easy to measure and for the same reason regarding the numerical values. This is likely an interpretation of the same facts: if it was used as a "secondary standard" that was probably because it was easy to measure. --Anonymous, 19:34 UTC, January 6, 2009.

And don't copy the above word-for-word, everyone will know :) hydnjo talk 04:44, 7 January 2009 (UTC)

chemicals for surgical gloves

i am small scale manufacterer of surgical gloves. i want to improve my product. so, i want a chemical composition for (natural latex)surgical gloves. Thanking you.Arijitkm (talk) 10:08, 6 January 2009 (UTC)

Natural latex is a polymer of isoprene. Graeme Bartlett (talk) 10:58, 6 January 2009 (UTC)

Makes me wonder where my hospital gets its surgical gloves :( hydnjo talk 04:41, 7 January 2009 (UTC)

Definition of "Life"

How do we define "Life"? I have already looked up in a number of books. One said "Life is a set of characteristics which distinguish living organisms from non-living objects" but I want a definition without relativity with non-living things. Please note this is not a homework. Many thanks. —Preceding unsigned comment added by 59.103.70.227 (talk) 12:31, 6 January 2009 (UTC)

There is no hard, fast, agreed-upon definition for life. As our article notes, "to define life in unequivocal terms is still a challenge for scientists, and when derived from an analysis of known organisms, life is usually defined at the cellular level." Further, we note that life exhibits all or most of a given (and itself flexible) set of criteria. Our article contains many further attempts to phrase a concise definition. — Lomn 14:04, 6 January 2009 (UTC)

Well, "life is the process that organisms go through during their lifetime", perhaps? I'm not sure it's reasonable to demand a definition that doesn't relate to non-living things, though, simply because I'd say a big part of the definition is precisely that it's not a part of the non-living things. Not that you can't define it otherwise, but it might not be a very good or informative definition. -- Captain Disdain (talk) 14:06, 6 January 2009 (UTC)

See Life. It has a section on "definitions." -Arch dude (talk) 14:37, 6 January 2009 (UTC)

One annoying problem for definers is that with the advent of computers, it's pretty easy to take any reasonable definition that they come up with and write a computer program that fulfills that set of criteria. Since biologists are pretty snobbish about such things and don't want computer software classified as "alive", we can pretty much mess with their heads by doing this. Sadly, "life" like so many other words is just a label we humans use to attach to things and nature does what nature wants regardless of our petty classifications. Consider, for example, efforts to define the word "Planet" - astronomers wanted desperately to keep Pluto as a planet but to exclude all of those interesting new bodies we kept finding further and further out (eg Sedna) - it proved impossible to come up with a reasonable definition for the word that would exclude things they didn't like and include things they did. So we end up with a tortured definition that excludes Pluto and upsets a huge number of people. It's kinda silly because it's just a word - it doesn't prove anything. It's the same with the word "Life" - whether it includes viruses - whether it excludes computer software that reproduces, evolves, etc - whether synthetic life forms made of lipid bubbles with weird chemicals instide count or not...these are just issues with the human obsession with naming things and trying to categorize them with black and white terms. In the end, some things reproduce some don't - some eat and defecate - some don't, some respond to external stimuli - some don't. Our biology teacher in high school was an old lady who never married and had no children - when she taught us the (then) standard definition with the mnemonic "RINGPERM" (REPRODUCTION, INGESTION...argh...yadda, yadda...I forget...MOTION!) - some idiot from the back of the class yelled "You've never reproduced - so you must be dead" - which actually reduced the poor lady to tears. So let's not obsess about the word - but instead use it loosely as the need fits and resort to formal definitions of capabilities when it actually matters. SteveBaker (talk) 14:53, 6 January 2009 (UTC)

I've heard there are two kinds of people: These who divide things into distinct categories, and those who don't. What would be the criteria for determining whether a potato is "dead" or "alive" when it is on a shelf in my kitchen? It arrives full of vitality, and eventually sprouts. If planted, it would produce roots and leaves and more potatoes. Seems to be alive. But if I remove the "eyes" when it arrives, surely that does not mean it is suddenly dead, any more than a steer is dead. If I boil it long enough, that would seem to make it dead. If it rots, that would also seem to make it dead, although full of bacteria. Edison (talk) 15:22, 6 January 2009 (UTC)

Indeed - "There are 10 kinds of people in the world - those who understand binary numbers and those that don't.".

The example you give exhibits the same problem as the guy at the back of my high school biology class - we aren't defining whether some particular instance of a thing is "alive" at this precise instant - we're asking whether an entire class of things can be considered to be "life". Reproduction does indeed seem to be an important feature of life (rocks don't make copies of themselves - bacteria do - but viruses can only do so with help from something that is in itself able to reproduce) - but an individual creature may be considered to be alive even if it has not nor ever will reproduce. Indeed, creatures who are born with some congenital defect that prevents them from reproducing are not pronounced "dead". That's because we're talking about a general property of all such creatures - not of one individual. So the definition of "life" doesn't really encompass the issues of whether your potato is alive or not right now. That is the subject of an entirely different fuzzy term: "death" - which doctors and medical ethicists struggle with all the time...which is a similar debate - but over an entirely different word. Coming back to the "10 kinds of people" joke - the problem is that when you try to treat words like "planet", "life" and "death" as binary states, you get into a lot of trouble - and the two kinds of people you were talking about overlap fairly strongly with the 10 types I'm talking about! SteveBaker (talk) 16:03, 6 January 2009 (UTC)

The Stewart Test is probably the best you can do outside of a given context. --Sean 16:13, 6 January 2009 (UTC)

I remember reading a Lyall Watson book on the subject of "what happens after death", which was similarly ambiguous about the definition of "death". --TammyMoet (talk) 19:15, 6 January 2009 (UTC)

Entropy and life#What is life?. Schrödinger and Lehninger both state that life can be said to be anything which feeds off of negentropy. I think Gibbs free energy also has something to do with it. --Mark PEA (talk) 20:44, 6 January 2009 (UTC)

The trouble with negative entropy is that all sorts of things that are very clearly not 'alive' (refrigerators, for example) exhibit that. It's very easy to show it by (for example) programming a robot to sort a pile of randomly colored lego bricks into piles of red, blue, green and yellow. The entropy of the blocks after sorting is less than when they were randomized beforehand - so the robot is producing negative entropy...do we want to call a really simple 'bot qualify as 'alive'? I don't think so. SteveBaker (talk) 05:11, 7 January 2009 (UTC)

I've seen arguments, based on some definitions of life, that black holes are actually alive. They slowly move towards food sources. They maintain a high gravity within themselves which is the only thing keeping them from exploding. And there were a bunch of other arguments to attempt to satisfy the various established conditions of life. Anythingapplied (talk) 21:52, 6 January 2009 (UTC)

Again - if you make a bad enough definition - you'll either let in a lot of silly things like refrigerators and black holes - and you'll exclude a bunch of things like celibate biology teachers. I do think that (the capability of) reproduction is one of the touch-stones of life - so refrigerators and blackholes should certainly be excluded for that reason alone. I can't think of anything that I'd call "alive" that doesn't have the capability to reproduce (even if only at the cellular level). You need other caveats to avoid things like fires from being declared 'alive' (a fire creates more fire - it consumes food and produces waste - it moves away from places where there is no food and into places where there IS food - it is born and eventually dies - it breathes oxygen and expels CO2 - it consumes animals and plant material for nutrition). To exclude fire - you have to require inheritance - that some attribute of the parent is handed on to the offspring. But a definition that excludes 'artificial life' computer software (like Conway's Game of Life for example) is exceptionally tricky.

A LOT of the definitions to "Life" come down like Oliver Wendell Holmes, Jr.'s definition of obscenity, to paraphrase, "I may not be able to define it, but I know it when I see it". The problem is that any basic definition of life either excludes things which should probably be considered alive (like viruses and prions.) or includes things which should probably not be considered alive (like computers and fire and black holes and all sorts of weird things). --Jayron32.talk.contribs 13:23, 7 January 2009 (UTC)

Whistle in water

When dip into water I hear (as everybody, hopefully) a sort continuous whistle, or hiss. I wonder what it is, and where it's coming from. Is it just my eardrums under the effect of the pressure, or is it a kind of ground noise that propagates particularly well into the water? --PMajer (talk) 13:27, 6 January 2009 (UTC)

You are hearing the underworld. Try to talk into the water... Do you hear replies? —Preceding unsigned comment added by 94.27.209.85 (talk) 13:52, 6 January 2009 (UTC)

no but I can read it --PMajer (talk) 14:44, 6 January 2009 (UTC)

I think it's like when you hold a seashell to your ear (actually, pretty much any concave object - a teacup for example - will do) and "hear the sounds of the ocean". What you're hearing is the blood flowing through your head that's being reflected back into your ear because of the unusual acoustics. SteveBaker (talk) 14:38, 6 January 2009 (UTC)

If blood makes a faint noise as it circulates, a microphone should pick it up and it could be amplified and heard. Furthermore, the microphone could be placed on any part of the body. I have never read that to be the case except for an audio stethoscope placed over the heart. Just what does a stethoscope pick up anyway? Blood rushing through heart valves? And what is a heart murmur? And just what is heard when a sea shell is held near the ear - is it resonance to ambient noise? No, a sea shell is too small to resonate to audible sound. Also, if two persons place their ears together, they will not hear anything, so why does a sea shell pick up sound emanating from the ear, and reflect it back? –- GlowWorm —Preceding unsigned comment added by 174.130.253.174 (talk) 23:43, 6 January 2009 (UTC)

There are lots of conflicting explanations around - and many pooh-pooh the old blood-flow explanation. However, putting a seashell over a microphone doesn't produce any sound at all - so THAT explanation is bogus. I wouldn't expect a microphone held over your body to produce a sound - the concavity of the seashell is acting like a 'retroreflector' - sending all of the blood supply sounds precisely back into your ear...that has the effect of amplifying that very subtle sound to the point where you can hear it. You can actually use your hand in place of the seashell - and that lets you adjust the shape. A flat palm doesn't produce anywhere near as much white noise as a cupped palm. The 'resonance' theory fails miserably here because that soft bag of water that is your hand can't possibly resonate in the same way as a seashell or a teacup - so how come it sounds the same? My 'focussing' explanation also explains why two people's ears put close together don't do it - the ear is carefully evolved to absorb the energy from feint sounds and translate them into nerve impulses - so it's not gonna reflect ANYTHING. Sure - this isn't a 100% accepted explanation - but it does fit the facts better than the others. SteveBaker (talk) 04:52, 7 January 2009 (UTC)

@GlowWorm: Your questions about what the stethoscope picks up, are answered in the articles Heart sounds and Heart murmur. --NorwegianBlue 15:29, 7 January 2009 (UTC)

Charges on a sphere

Imagine positive charges confined to the surface of a sphere. If there are two positive charges then they will move apart until they are "poles apart".

But I have difficulties imagining three positive charges. If the location of one of the charges, is defined as position A, where will the other two charges be located relative to position A? 122.107.203.230 (talk) 13:40, 6 January 2009 (UTC)

While I'm not certain that charges would behave in this fashion, three equidistant and maximally distant points on a sphere are on a plane that bisects the sphere, 120° apart from each other. — Lomn 14:01, 6 January 2009 (UTC)

...and 4 would be located on the points of a regular tetraeder that is circumscribed by the sphere. Both solutions are non-unique unless you fix at least two of the points. --Stephan Schulz (talk) 14:10, 6 January 2009 (UTC)

• For greater clarity, in English that's a tetrahedron. --Anon, 19:36 UTC, January 6, 2009.

Thanks! --Stephan Schulz (talk) 22:32, 6 January 2009 (UTC)

I would expect a charged conductive sphere to have evenly distributed charges, in the absence of an external field. The "charges" would not generally isolate themselves to a small number of distinct locations. Do you consider each of your "positive charges" to be one atom which has given up an electron? What is the experiment, or thought experiment, exactly?Edison (talk) 15:15, 6 January 2009 (UTC)

The total energy of 3 unit point charges constrained on the unit sphere, ${\displaystyle \scriptstyle {\frac {1}{2}}\sum _{i\neq j}|x_{i}-x_{j}|^{-1}}$, is certainly minimized exactly when the charges are in the positions described by Lomn (equilateral triangle on a maximal circle). This is easy to see by direct comparison (one first proves that they have to stay on a maximal circle, then that they have to be equidistant). The general geometrical problem of the minimal energy position of n unit charges on the unit sphere is called Thomson problem (yes, we have it!!); here there are some nice pictures . Note that the problem is not even obvious in the unit disk version; in particular for ${\displaystyle \scriptstyle n\geq 12}$ the configuration of minimal energy is not on the boundary of the disk, a 1985 result by A.A.Berezin . --PMajer (talk) 16:17, 6 January 2009 (UTC)

Well, for 2, 3, and 4, it is easy, because they correspond to the 1-, 2-, and 3-simplices, respectively, because they all fit in 3 or less dimensions. However, I wonder if there is an easy systematic way to compute the optimal solution for higher numbers; say, if you had 17 charges. I wonder if the solution is even unique (up to rotations and reflections of course) in that case. --Spoon! (talk) 05:35, 7 January 2009 (UTC)

well, no... 4 is not that immediate, still it's true that it is the regular tetrahedron. In the reference above you can find a list of the numerical solutions up to n=400 and also interesting links --84.221.209.108 (talk) 09:44, 7 January 2009 (UTC)

By the way, I see in the wikipedia article that the solution for n=24 is still unique up to rotation and reflections, but not up to just rotations (it is not congruent by rotations to its mirror reflection, like a hand). It is given by the vertices of the snub cube, a chiral polyedron--PMajer (talk) 16:16, 7 January 2009 (UTC).

Breathing in cold weather

When I want to go to sleep, I unconsciously breathing using my mouth. Is it normal? When I remember I try to breath using my nose, but in a while it's just getting back using mouth. Is it a phenomenon in cold temperature or is it just me? Second question, when breathing in cold weather, the air we breath in should be converted to our body temperature, right? How cold it is that human will feel uncomfortable breathing in cold temperature? What about people who is standing in an -20 degree Celcius environment, is the air temperature would change from -20 to 37 degree just within a few seconds? Thanks for the response. roscoe_x (talk) 15:55, 6 January 2009 (UTC)

See, believe it or not, "Mouth breathing". The nose warms air before it gets to the lungs more efficiently than the mouth does, so I would expect nose-breathing to be a better cold-weather strategy. As for the temperature that would cause discomfort in breathing, I suppose that that depends on the person. The coldest I've been out in is minus 5 Farenheit, about...let's see, 32 is zero, 1.8 per degree, 5 below is 32 + 5, 37 divided by 1.8 is times 5/9, roughly 20 below, Centigrade, I mean Celsius. I don't remember having trouble breathing, but that's me. --Milkbreath (talk) 20:54, 6 January 2009 (UTC)

I sometimes feel a burning in my lungs when breathing extremely dry, cold air. It starts somewhere around 14°F, or -10°C, but, as I said, the humidity may also play a part. When it gets colder than that, I try to breathe through a scarf, as that gives the air more time to warm up. For someone at the South Pole at it's coldest, I'd expect they'd want to use a tube to breathe through, wrapped several times around their torso, so it warms up a lot before hitting their lungs. StuRat (talk) 21:22, 6 January 2009 (UTC)

I've never heard of someone using a tube for breathing like that in Antarctica, but then again, I'm sure that people improvise a lot down there. It kinda makes sense to me, but also potentially very, very inconvenient, not least so because when the cold gets really extreme, most flexible things -- like long plastic tubes -- tend to become rigid and brittle. Do they really do that? Man, it's a fascinating place.

Anyway, as for breathing in cold temperatures, I've been at and around -30 degrees Celsius, which isn't a lot of fun, but I don't recall having much trouble breathing, at least when compared to how my nose and cheeks felt at the time. That said, if you run around or do something else that makes you breathe heavily, you'll definitely feel it in your lungs. It's certainly not very gentle weather, especially if it's windy (though make no mistake, it's almost balmy compared to the South Pole during the cold season). -- Captain Disdain (talk) 23:21, 6 January 2009 (UTC)

I've been out in -40C (also -40F) a few times and didn't have much trouble breathing. However, I noticed a strange sensation in my nose that I think was the water vapor in my breath freezing on the hairs in my nose. After about 5-10 minutes my sinuses started to hurt and they cooled down. After that if I took a deep breath my throat hurt, but I never noticed any problem with my lungs. Of course they are in your chest and should be at core body temp, which should stay high unless you're getting ready to freeze to death.Tobyc75 (talk) 03:39, 8 January 2009 (UTC)

How much the air warms up before it hits the inside of the lungs depends on how much, and how fast, you are breathing. If you are running or shoveling snow vigorously, it won't have much time to warm up. StuRat (talk) 20:25, 9 January 2009 (UTC)

NEUROLOGY/RADIOLOGY

Gaining immunity to the common cold?

Hopefully, this question isn't considered medical advice. Per the Misplaced Pages article, "Common colds are most often caused by infection by one of the more than 100 serotypes of rhinovirus, a type of picornavirus. Other viruses causing colds are coronavirus, human parainfluenza viruses, human respiratory syncytial virus, adenoviruses, enteroviruses, or metapneumovirus. Due to the many different types of viruses, it is not possible to gain complete immunity to the common cold."

I have 3 questions:

1) Does that mean that each time someone catches the common cold, he or she builds an immunity to that particular virus? (I'm pretty sure the answer is yes, but I want to confirm.)

2) As a person gets older (ignoring the effects of aging) is he/she less likely to get a cold since he/she may have immunities to dozens of cold viruses?

3) Does the immune system 'forget' how to fight a virus if it's been a long time since it encountered a virus? For example, I were 100 years old, would my immune system remember how to kill that cold virus I had when I was 20?

216.239.234.196 (talk) 16:32, 6 January 2009 (UTC)

The problem with immunity to viral diseases is that viruses mutate so quickly. You catch this year's strain of cold - now you're immune so you probably don't get another cold this year - but as the virus makes its way around the world and comes back the following season - it's mutated to the point where your immunity stops working and you catch it all over again. That's why (for example) influenza shots have to be given each year - and the manufacturers have to guess which mutant of the 'flu virus will strike this time around.

SteveBaker (talk) 17:58, 6 January 2009 (UTC)

1) Yes.

2) Not really, as the strains to which they have developed an immunity no longer exist, having died out after a significant portion of the population became immune to them. Entirely new strains replace them.

3) Yes, loss of immunity does occur over time. First there is a period of partial immunity, then eventually none at all. StuRat (talk) 21:11, 6 January 2009 (UTC)

2) Yes to some extent. The Spanish flu is supposed to have affected younger people disproportionately because of this. Dmcq (talk) 08:35, 7 January 2009 (UTC) Sorry I see the latest theory is that people who had a good immune system died because of a cytokine storm and the old with weaker immune systems livd through that. Dmcq (talk) 08:52, 7 January 2009 (UTC)

Fighter plane firing a bullet

What is the effect on the speed of a fighter plane chasing another when it opens fire? What happens to the speed of pursued plane when it returns the fire? Please explain. Also note, it's not a homework. Many thanks. —Preceding unsigned comment added by 59.103.69.24 (talk) 20:33, 6 January 2009 (UTC)

I think recoil is a good place to start. Also see Newton's laws of motion- in particular, the third law. Friday (talk) 20:36, 6 January 2009 (UTC)

And yes, there are extreme instances of this. The A-10 Warthog's main gun has a recoil on par with the thrust of one of its two engines (see the GAU-8 article). — Lomn 21:36, 6 January 2009 (UTC)

Shape of Planets

What is the reason for all the planet has spherical shaped? 91.140.217.144 (talk) 21:42, 6 January 2009 (UTC)

Because they're massive enough that their gravity is strong enough to pull them into a hydrostatic equilibrium. In fact this property is now part of the definition of a planet. Algebraist 21:45, 6 January 2009 (UTC)

Note that they aren't perfect spheres, however. They are all somewhat elliptical due to centripetal force, and can have some "lumps" as well. StuRat (talk) 01:04, 7 January 2009 (UTC)

Oblate spheroid is the actual term for their shape, in case you were wondering.-RunningOnBrains 01:15, 7 January 2009 (UTC)

A simple way to think about this is that gravity is pulling everything as close together as they can get. Any bits of the planet that were a lot further away from the center than the rest would tend to move to be closer to the center...this results in everything ending up at the same distance - and the geometric shape that has everything at the same distance is a sphere.

Think of it another way - if the planet was (say) a cube - then there would be eight amazingly tall mountains (one at each corner) - these would be so massive that they would tend to slump and collapse under their own weight - so gradually, the planet would turn back into a sphere again.

The reason planets are slightly 'oblate' (squashed at the poles and fatter around the equator) is because they are spinning and at the equator (where they are spinning faster) the centrifugal force slightly opposes gravity - that "weaker" gravity results in that bulge.

Only 'lumps' that are small enough and strong enough to stay put under their own weight can withstand that tendancy to becoming spherical - hence mountains here on earth don't get bigger than Mt.Everest. On lower gravity worlds (Mars, for example) there are bigger mountains - "Olympus Mons" is truly, stunningly gigantic!

SteveBaker (talk) 04:33, 7 January 2009 (UTC)

See geoid and equipotential surface. If a planet's surface were covered by liquid then (in the absence of tides) the liquid would assume a shape such that the local apparent gravity vector (true gravity vector - centripetal force vector) was everywhere perpendicular to its surface - this shape is a geoid. Rock, unlike liquid, is able to resist tangential forces, so it can form mountains and valleys that deviate above and below the geoid surface. Gandalf61 (talk) 11:32, 7 January 2009 (UTC)

Deliriants vs. Hallucinogens

Hi, just a quick question. What is the difference between a hallucinogen and a deliriant? I have heard the 2 terms and don't know the difference.Cssiitcic (talk) 23:08, 6 January 2009 (UTC)

Delirium says: "While the common non-medical view of a delirious patient is one who is hallucinating, most people who are medically delirious do not have either hallucinations or delusions". --Sean 00:10, 7 January 2009 (UTC)

Hallucination is the sensing of objects which are not in the real world. There are halucinations of every sense (visual, auditory, tactile, etc.) but the common thread is that our brains tell us something is there which is not. Thus, a hallucinogen causes that reaction in the brain. One can be perfectly lucid and still be having a hallucination. Delirium is a loss of lucidity, that is one becomes less than perfectly responsive to the outside world. Its not that you see stuff thats not there, its that your brain does not react "appropriately" to stuff that IS there, so you don't recognize the real world for what it is. It is also entirely possible to be delirious without hallucinating; and there are of course situations where both are occuring... --Jayron32.talk.contribs 13:11, 7 January 2009 (UTC)

To confuse matters Delirium tremens does cause hallucination as one of its symptoms. 76.97.245.5 (talk) 16:21, 7 January 2009 (UTC)

I think the general view is that hallucinogens produce hallucinations which the person is aware are hallucinations. Where as deliriants produce more vivid hallucinations (like those in dreams) which the person is not aware are hallucinations. --82.21.25.219 (talk) 17:51, 7 January 2009 (UTC)

The above was me by the way. I don't like to recommend anecdotal evidence, but trip reports are one of the only sources of evidence for this kind of thing (due to obvious legal and ethical reasons). If you are further interested in this kind of thing, on Erowid compare the trips of say magic mushrooms () with belladonna (). My judgement is that being on a typical anticholinergic delirant is like dreaming whilst being awake, which could cause some large issues such as walking into roads or cutting your self completely unknowingly. --Mark PEA (talk) 18:10, 7 January 2009 (UTC)

January 7

This

How is Avobenzone formed? What is the science behind Methylchloroisothiazolinone? What is it's occurrence in nature?96.53.149.117 (talk) 00:53, 7 January 2009 (UTC)

Methylchloroisothiazolinone (also commercially known as Kathon CG when mixed with methylisothiazolinone) is a synthetic preservative. Thus it is made by humans via a series of chemical reactions and is not known to be generated in a naturally occurring process (at least not at significant levels). I'm not sure what you mean by the science behind it, but it is a known human allergen that can cause contact dermatitis, and has been shown to be mutagenic and cytotoxic in some studies. Rockpocket 08:43, 7 January 2009 (UTC)

Transistor configuration in a radio Tx/Rx

Picture: I've been looking up simple radio transmitters/receivers on the net.

1. In many sites, as in the above picture there is capacitor connecting the collector and emitter of the transistor which is connected to the antenna. What is that for?
2. Also in the above picture of a receiver and many others, the input from the antenna seems to be given to the collector. As far a I know, in all three configurations of the transistor, base and emitter are used for input. what is this connection?

59.93.4.189 (talk) 09:36, 7 January 2009 (UTC)

For #1, maybe impedence-matching (see Antenna tuner)? Or wait, do you mean the "10" or the "50"? DMacks (talk) 18:31, 7 January 2009 (UTC)

Interesting circuit. It maybe looks like a self oscillating mixer at first sight. Perhaps the input signal is large. Since the detected output seems to operate a relay, perhaps this is a remote control Rx?--GreenSpigot (talk) 04:33, 8 January 2009 (UTC)

The first transistor is in sort of common base config. There may be coupling between the emitter coil and the collector coil which would make an oscillator. The input signal is fed to the collector and to a parallel tuned circuit in the collector and so would not see much loading at the res frequency of the collector tank.--GreenSpigot (talk) 04:39, 8 January 2009 (UTC)

Unless of course, the input signal is intended to make the input circuit oscillate (at its res freq) and thereby generate a signal that can be rectified later in the circuit to operate the relay!--GreenSpigot (talk) 04:42, 8 January 2009 (UTC)

The frequency f0 on the diagram is 27.145 MHz, which is RC Yellow Band. That first stage is an oscillator, no doubt, and it looks like it must drive that antenna; you can't take input on the collector like that. What it's using for input, I can't tell, and the mess leading to the relay is a mystery, too. That second transistor might be biased to chop the waveform into class-c, and the final has a little power supply in the bias, fed by the output signal, that looks like AGC. What the relay controls is anybody's guess. The 50p across the transistor is there because the circuit didn't work right unless it was there, basically; it shunts higher frequencies around the transistor so they're not amplified. --Milkbreath (talk) 15:39, 8 January 2009 (UTC)

It seems pretty obvious that the signal flow in the diagram is from left to right. In that case the oscillator is acting as a receiver (albeit a strange one). Otherwise there is no control of the oscillator and the rest of the circuit is junk. But I believe the rest of the circuit amplifies and detects the oscillator output to drive the relay.--GreenSpigot (talk) 16:52, 8 January 2009 (UTC)

1. It has to work because, not just in this site, but in many other sites there is similar diagram with the input from the antenna given to the collector with a capacitor connecting collector and emitter. I'm using Qucs and/or gnu spice right now to see what happens when the 50p is changed...
2. It is OK to rpleace the antenna with a signal source with 50 Ohm resistance in series, right?
3. Another funny thing is that if the o/p of the first stage is taken from above the 10uH i.e @ at the other end of 50p, the waveform there is stronger(!) than if o/p is taken from above the tank circuit. Since you said the first stage looks like an oscillator I'm going to take a look at regenerative receivers.
4. Another thing is that the 40n is a large value as far as 27MHz is concerned (.147 Ohm reactance). So even on the presence of the 5.6k Ohm resistor, the place that they take o/p of first stage is practically @ Vcc or ac-ground. Any way I'm probably going to try anther circuit. 59.93.21.70 (talk) 10:59, 9 January 2009 (UTC)

If you are going to simulate this circuit on spice, I would use a representative source impedance to simulate the aerial. However, I cant tell you what that would be as it depends on the design odf the aerial. its unlikely to be 50 ohms, more like 300 ohm i think.GreenSpigot (talk) 21:50, 9 January 2009 (UTC)

Quantum Physics - The double Split Experiment

The concusion for the double split experiment was that particles behave differently when 'being observed' - ie it was mysteriously just the ACT of us OBSERVING that changes particle behaviour. Is it not possible that it was the observing APPARATUS ITSELF that was interfering with the particle behaviour & therefore the experiment ? How exactly did they detect the respective particles (photons/electrons)- what type of apparatus did they use? No one ever questions this? —Preceding unsigned comment added by 165.145.151.160 (talk) 10:09, 7 January 2009 (UTC)

"The" double slit experiment isn't one experiment like the michelson-morley experiment, it's an experiment that can be performed in the classroom and has been repeated with several different variations. The idea that it's the observation that causes the wavefunction to collapse is the Copenhagen interpretation of quantum mechanics, which is still being debated. So yes people question this, but it's more a debate about interpretations of quantum mechanics than a debate on what apparatus to use. EverGreg (talk) 10:29, 7 January 2009 (UTC)

What that is referring to is simply that in order to measure anything of any order of magnitude or size, you must modify it. For example, if you wish to measure the piece of wood you are using to build a tree house, you must manipulate that piece of wood with your hands, use a tape measure of sorts, and determine a length. Not that the action really changes the size or shape of a piece of wood. But when you are dealing with attempting to observe something as small as a electron or photon etc, there's nothing small enough to really measure directly. So, when studying electrons, scientist bounce other electrons off of the object or subject and observe the trajectories after impact and deduce from the deflections the properties of the object/subject. If you wanted to observe a red wavelength photon, and bombard it with electrons or white wavelength photons (light), you are going to add energy to your subject and thus, change its color or in some cases, composition and structure completely. There are new encryptions for computer lines using this quantum mechanic. They are already calling it Quantum cryptography. Hope that helps a bit.... Operator873 (talk) 10:25, 7 January 2009 (UTC)

Thanks Operator873 - but surely knowing that alone - that there is no way to observe the electrons without disturbing them and their path, it brings renders the results of the experiment inconclusive? All I'm hearing is this massive hype about how this experiment has opened a whole new door into science in that things arent really there until we observe them - and all of this is based on an experiment which has 'fake' results? —Preceding unsigned comment added by Nickylaatz (talk • contribs) 11:12, 7 January 2009 (UTC)

One question is if the Heisenberg principle is caused by a real uncertainty of the underlying system, or is caused only by the fact that to measure a system, we necessarily need to disturb it. The surprising thing with the double slit experiment is that over time a double slit inference pattern forms even if we can guarantee that only a single photon (or electron for that variant of the experiment) is in the experimental apparatus at any one time. If we consider a photon as a discrete particle, each of these photons flies through exactly one of the slits and has no way to interact with the other slit, or other photons. Still, in sum the photons behave just as interfering waves would. This strongly suggests that photons (and electrons, and other particles) "really" have wave-like properties, and hence do not have one discrete position, but are spread out in space. --Stephan Schulz (talk) 11:59, 7 January 2009 (UTC)

Except that if we place a detector of some sort to determine WHICH slit the electron passes through... If we make any attempt to identify the specific slit, then we end up with two discreet bands immediately behind the slits, whether we fire one electron at a time or many. Again, the addition of the measuring device appears to change the nature of the light from wave-like behavior to particle-like behavior. Or, light is doing the same thing in both cases, and its our measuring device which changes the experiment... --Jayron32.talk.contribs 13:05, 7 January 2009 (UTC)

First off, we're talking about the observer effect. The Heisenberg uncertainty principle has nothing to do with it. Second, it's not so much that light has wave-like properties as theoretical waves have light-like properties. Also, theoretical particles have light-like properties. Third, Jayron, the measuring device doesn't change the nature of the light (or electrons or whatever you use). It just causes the waveform to collapse and expand from there, and behaves like it would if there was a single slit, which makes sense, as it's only going through a single slit. — DanielLC 16:26, 7 January 2009 (UTC)

There are at least three things being discussed in a big tangled mess here. Firstly - indeed it is impossible to measure the position and speed of an electron without disturbing it in some way. Secondly - even without that - the precise position and speed is unknowable because an electron is a fuzzy probability cloud not a solid 'dot'. Thirdly, the duality of particles and waves do indeed seem to act such as to make things like the double-slit experiment do different things depending on how you measure them. The first of these is (I think) easy to understand. You can't measure something without affecting it in some way - duh. If it's small enough then the way you affect it makes a HUGE difference - but for large objects, it doesn't. The second of these is definitely a bit strange - but it's clear that "this is how the universe works" - and just because it seems weird to beings like us that learned and evolved in a 'macro-scale' world doesn't make it any the less valid. The really REALLY disturbing one is the double-slit experiment where the outcome depends qualitatively on how you look at it. Fire one photon at a pair of slits - it interferes with itself just like a wave that's travelled through both slits and you get a diffraction pattern. Put a photon counter in the way to figure out which slit the photon went through and you get an answer as to which one it passed through - but as if by magic, the diffraction pattern goes away and the particle seems to say to itself "OK - if you want me to behave like a particle - so be it - so you don't get a diffraction pattern anymore."...but how did the part of the light that went through the other slit in the first experiment "know" that you had a detector on the other slit - which could be some distance away? That's weird...it IS a whole new thing for us to understand.

I've personally done the double-slit experiment (we did it in 1st year college physics) - and I have to tell you that it's completely compelling. It's not just some flakey result - or something that's open to interpretation - it works and it's a really simple experiment. At small scales, the universe is a very weird place - but that's because we're not equipped to think in terms of the way it works at those scales - not because it's wrong. The problem is with our brains - our "common sense" - which turns out to be a mere approximation of the way things are that's only valid at large scales. It's like an astronomer saying that bacteria don't exist because he can't see them with his telescope. Our minds are simply unable to do this...but the universe doesn't care about that - it works however it works. SteveBaker (talk) 18:02, 7 January 2009 (UTC)

SteveBaker (talk) 18:02, 7 January 2009 (UTC)

Steve, I've observed two copies of your signature, so you must have sent it through two slits. There's no interference pattern, however, so there must have been a detector used. :-) StuRat (talk) 19:04, 7 January 2009 (UTC)

No, not quite. For such a small number of Steves, you get a probabilistic result. He may constructively interfere with himself here. --Stephan Schulz (talk) 21:15, 7 January 2009 (UTC)

Probably Steve has built his own home setup to search for gravitational waves. Franamax (talk) 23:08, 7 January 2009 (UTC)

Steve, you did the quantum mechanical double slit experiment in a first-year physics lab? With individual particles, and a detector at one of the slits? And it was "a really simple experiment"? In 1970 or 1980 or whenever you went to college? I find that hard to believe. Plenty of physics labs include a "double-slit experiment" that consists of observing a diffraction pattern from a laser, but that's explainable with Maxwell's equations. -- BenRG (talk) 04:56, 8 January 2009 (UTC)

Just playing devil's advocate here, my professor demonstrated the double-slit experiment to us my freshman year in lab, and I performed it in my sophomore year. It really is simple, though the equipment involved (ultra-dim lightbulb, with a photodiode capable of detecting single photons) was a bit complex by itself. I was able to perform it, with multiple distances, comparing one- and two-slit results, in just 3 hours.-RunningOnBrains 05:33, 8 January 2009 (UTC)

Yep - it's been a long time - but I believe we used a sodium lamp as the light source (it produces nearly monochromatic light - not quite as good as a laser - but enough to show the effect) - the photon counter was some kind of electronic gizmo - a photo diode is a possibility. But the photoelectric effect (which is what you use to count photons with) was demonstrated in the 1850's - so it was certainly around in 1975. I kinda recall a techtronic's storage scope might have been the way we recorded photons arriving at the detector...but honestly, it's been too long for me to recall the details. We had pretty good science labs in British universities back then - they took this kind of undergrad stuff rather seriously compared to modern colleges who find it cheaper to teach it out of a text book. SteveBaker (talk) 16:39, 8 January 2009 (UTC)

It seems pretty obvious to me that the problem is your 'photon counter'. How does this photon counter work, exactly? This rather crucial aspect of the double slit experiment always seems to be glossed over. People say, "but if you watch to see which one the photon goes through, the interference pattern vanishes! Amazing!" and glide right over the part where you have to explain just exactly how you "watch" a photon. Like many ideas in quantum mechanics, this seems to be an impressive conclusion drawn from some very dodgy reasoning. Maelin (Talk | Contribs) 05:20, 8 January 2009 (UTC)

The photon counter works because of the photoelectric effect - which is important because that's the effect that led Einstein to show that light acts like particles. Einstein won a Nobel prize for that work. It's effectively a solar-cell - a photo-diode - which produces electrons when struck by a photon. If you can find a decent translation of Einstein's paper on the photoelectric effect - you'll find it pretty compelling as an explanation of why light "is composed of particles"...that guy was actually rather smart! SteveBaker (talk) 16:39, 8 January 2009 (UTC)

Aaaaaaaah - Maelin - this is PRECISLY what I'm on about!!!!! Maybe if we watched it in a different way, with different non-intrusive apparatus/method, it would NOT collapse after all. It might be OUR EQUIPMENT causing this MYSTIFYING, effect that so maany other science ideologies are BASED on!!!! One day we might think....OH...&#$*!.....it was our stupid equipment. —Preceding unsigned comment added by 165.145.103.161 (talk) 06:35, 8 January 2009 (UTC)

It's known that the effect isn't caused by interaction with the apparatus. See interaction-free measurement and the linked articles. In the case of the double-slit experiment, consider the fact that the "photon detector" at one of the slits, however it works, only detects half of the photons. If the measurement effect were due to physical interaction then you ought to see a 50% interference pattern on the screen from the photons that evaded the measuring device (combined with some other pattern from the photons that were detected). But that's not what quantum mechanics predicts and it's not what's observed. The photon's behavior is also modified by the fact that it could have interacted with the measurement apparatus but didn't. -- BenRG (talk) 10:38, 8 January 2009 (UTC)

Indeed. Quantum theory is SO bizarre and SO contrary to people's expectations that great minds have tried to wiggle their way out from under the experimental evidence pretty much since Einstein got everyone excited about the problem again. This is a very well proven thing. Much of our modern electronics wouldn't work if it wasn't true. Have you ever seen a blue LED? Ever used a flash memory? Well there you are then. No quantum theory - no MP3 players...you choose! SteveBaker (talk) 16:39, 8 January 2009 (UTC)

I'm perfectly happy to accept that light behaves neither like billiard balls nor like water waves, but I refuse to accept that the universe alters its behaviour on the basis of whether humans are looking at it. How does this photon detector work? Why does it only pick up half the photons? Why don't I just stick an opaque photosensitive screen over one of the slits? Now I've transformed it into two single slit experiments! There's a "photon detector" that won't miss ANY of the photons. Can anybody here who accepts the result of this experiment actually, genuinely explain the precise mechanism by which these photon detectors work? The linked articles on interaction free measurement are unintelligible. Maelin (Talk | Contribs) 00:26, 9 January 2009 (UTC)

Well, you may refuse all you like - but that's what happens. The photon detector works via the photoelectric effect - for which we have an article. I think BenG says it only picks up half the photons because he's imagining an experiment where only one of the slits has a photodetector behind it. Just imagine two photodetectors - one behind each slit - then you know exactly where the photons went...it doesn't help you. The diffraction pattern DOES disappear when you try to find out where the photons went. Yes, it's deeply weird. I know you're going to start looking for trivial errors in the experimental approach - but don't you imagine that far greater minds than either yours or mine have not been examining that question for the close to hundred years that we've known of this 'wave/particle duality' thing? The effect IS real - and we use it (and it's consequences) all the time in day to day electronics. Like I said - the universe is WEIRD at the quantum level. SteveBaker (talk) 06:03, 9 January 2009 (UTC)

To make it even more weird (correct me if I'm wrong though), if you use entangled pairs of photons and send each one of the pair to a different double-slit experiment, counting the photons at one of the experiments also destroys the interference pattern at the other one. At least I think I've read that paper... Franamax (talk) 06:42, 9 January 2009 (UTC)

Steve, I don't like this "my head hurts and so should yours" approach to explaining quantum mechanics (to quote you from a thread below this one). The basic quantum rules have been known since the 1920s. You can learn them and use them to figure out the outcomes of experiments of this kind. It's not magic. People are fond of saying that no one understands quantum mechanics—a virtually meaningless statement. Do you understand gravity? Sure you understand some things about it, but do you really truly understand it, at the deepest imaginable level? Of course not. The quantum rules are unsatisfying as a just-so story about the universe, but so is every aspect of current physics. Why are there three particle generations? Why is the strong force so elegant and the electroweak force so ugly? The explanations for these things, if we ever find them, will probably be unsatisfying themselves. That's the nature of the frontiers of physics.

Also, the quantum rules may be strange, but so are "the classical rules". People are just more used to them. They happily talk about "unbiased coins" that have a "50% probability" of coming up heads, blissfully unaware of what crazy nonsense they're spouting. It's impossible to make sense of classical probabilities, and all of science is based on them (all experiments have error bars), so all of science is meaningless. Yet somehow it works anyway. Quantum mechanics is no more absurd than that.

I think I'd better revise my previous response in this thread. The measurement effect is due to interaction with the device, in that it is the construction of the device—the nucleons and electrons that make it up—that dictates its effect on the experiment, not mysterious measurement dust that adheres only to measurement devices. But quantum mechanics happens to have a concept of null measurement, or null interaction, which doesn't exist in classical physics, and which says that an interaction that could (probabilistically) have taken place, but didn't, has an effect that's very similar to the effect when it does take place. The presence of the apparatus introduces a possibility of interaction, and that has an effect on the behavior of the system even in trials where no interaction actually takes place (in the ordinary classical sense—things bouncing off of each other, if you like). To put it another way, interference effects show up when information about which way the particle went is lost, and conversely, interference effects don't show up when information about the path is retained, in any form whatever. A detector at one of the slits yields which-path information whether or not it detects a particle (if it doesn't detect one, that's evidence that the particle didn't go that way). As a result it affects the interference pattern whether or not it detects a particle. This can all be formalized. -- BenRG (talk) 08:42, 9 January 2009 (UTC)

Actually - I agree with pretty much everything you just said. Of course there is no special status for the 'observer' - but that IS how the system appears to act in practice - you try any way you can to find out which slit the photon went through - and the diffraction pattern goes away. No matter how clever you try to be - no matter how you sneak up on the photons - they never seem to get caught in the act of being both wave and particle at the same time. The circumlocution required to say that without invoking "magic observer dust" is even harder for the general public to understand. SteveBaker (talk) 20:43, 9 January 2009 (UTC)

Sorry? The photoelectric effect? You mean the one where a photon hits a bit of metal and is absorbed and an electron pops out? So let's see. You have two slits, and photons go through them and, wow, even though we know that light has particle behaviour (due, in fact, to the photoelectric effect), it turns out to still have a wavelike behaviour because we get interference patterns even if we only send one photon through at a time. And then, what, you shove a bit of metal in front of one of the slits, and sit there catching the electrons that pop out as the photons are absorbed, and you say, "Look! The interference pattern has collapsed now that we are observing the system! Amazing!" Obviously you've ruined the experiment because you've stuck a bit of damn metal in front of one of the slits to catch the photons. If you still got interference patterns EVEN WITH one of the slits blocked up by your detector, now THAT would be really amazing. But this is like being amazed that a Magic Eye vanishes if you hold your hand over one of your eyes. Maelin (Talk | Contribs) 09:04, 9 January 2009 (UTC)

Maelin....spot on...you and I are of like minds. Theres all this scientific talk meandering off in a thousand directions, without actually adressing the plain and simple issue....The device/detection method..is there irrefutable proof, that its not the PHYSICAL equipment CAUSING this effect? If someone says No, fine. If someone says yes....without redirecting to any 'thought experiments' as backup, please explain in laymans terms (well as close as possible - this IS quantum physics) WHY this is the case... —Preceding unsigned comment added by 165.145.117.62 (talk) 10:24, 9 January 2009 (UTC)

I want to know exactly HOW it is that photons are detected, do they fire electrons at it? does someone have the details (in simple terms) of how they detect the photon? Where do they detect it? at the slit or anywhere between the slit and the screen? thise sort of details? Can someone tell me exactly how the experiemtn is set up? in a vacuum? whats the detector etc etc? —Preceding unsigned comment added by 165.145.117.62 (talk) 11:15, 9 January 2009 (UTC)

Here's a weird proposition for possible explanation of the double-slit experiment outcome ... Perhaps photons and electrons (and maybe even all things 'teeny tiny quantumy') naturally exist & travel around as WAVES (naturally being on their own without any interferrence of other particles) ...or frequencies if you will. BUT - As soon as you introduce another different tiny PARTICLE (in this case electron to a photon-wave or photon to an electron-wave) , the wave collapses, and photon-wave becomes photon-particle and suddlenly EXISTS and ofcourse visce verce.......

If all this were true, how scary would it be that in total darkness, nothing really exists ?? eeeeek!!!!! —Preceding unsigned comment added by 165.145.117.62 (talk) 12:45, 9 January 2009 (UTC)

Agh! Do you REALLY thing all of these scientists are so stupid that they didn't notice that they blocked up one of the slits?!? What kind of bozo's do you think these people are?! No - of course they didn't do that. If you're going to start congratulating yourselves for showing up an "obvious" flaw - and thereby dismissing all of fundamental physics as we know it - theories that actually work in practice to make things you probably use every day - then you REALLY need to crack open a book and read about it first. Einstein spent the largest part of his life (after General Relativity was complete) trying frantically to get rid of this result in some clever theoretical manner. If you think you can do what he failed to do over 30 years - and do it in the space of a few minutes - you are bigger fools than you can possibly know!

SteveBaker (talk) 20:43, 9 January 2009 (UTC)

Steve, try looking at this from our side. As I said, I will accept the particle-wave duality thing. But then this part of the double slit experiment gets turned into some incredible, ineffable nonobservability principle in which the quantum universe behaves differently when certain bipedal carbon based life forms are looking at it. That's terrible science. Positing that humans are somehow magical observers with the capability of altering quantum behaviour is on par with suggesting leprechauns to explain rainbows. I frequently see people explaining quantum mechanics to laypeople and they seem to be perfectly happy to draw totally ridiculous conclusions like "the universe knows when we're watching!" for the sake of eliciting a "wow" response. Surely the reason the quantum behaviour changes is more mundane. Surely the behaviour changes not because "humans are watching" but rather because "when humans want to watch they stick apparatus in that muck up the experiment". The problem is that nobody is ever willing to explain precisely how humans "watch" the experiment so we can never explore this more sensible explanation. Maelin (Talk | Contribs) 02:13, 10 January 2009 (UTC)

Many people are willing to explain, in fact we have an article about it. Note how that article has a "confusing" tag on it? That reflects why "because humans are watching" ends up being the explanation - the concepts are much more deep than why my car wouldn't start this morning in the rain. The incredible ineffable bit is in my comment above, when you use entangled photons and send them to two different experiments, and by "ruining" one experiment, you ruin the other one a mile away, at exactly the same time. That's like explaining why none of the cars started today. Steve already said, it's WEIRD!!! Franamax (talk) 12:15, 10 January 2009 (UTC)

dextrose & ct scans

why must dextrose be held for a period of time prior to performing a ct scan? —Preceding unsigned comment added by Cecollins64 (talk • contribs) 10:11, 7 January 2009 (UTC)

Have you read our article on Computed tomography? --Jayron32.talk.contribs 13:25, 7 January 2009 (UTC)

I can't see anything in that article that's relevant; perhaps I've overlooked it. In any case, I suspect that our questioner may be thinking of a PET scan (or a combined CT/PET scan) rather than a CT scan per se. The PET scan article indicates that dextrose should be held if the PET scan uses fluorodeoxyglucose (FDG) as its tracer molecule, as glucose/dextrose etc. would compete with the tracer for uptake. - Nunh-huh 13:58, 8 January 2009 (UTC)

Darting PVDF membrane magic trick

I recently prepared a peice of PVDF membrane by soaking breifly in methanol, and then transfering to a container of water. I noticed that the strip of membrane darted around the container, hitting the sides and bouncing back. Eventually it slowed down and stopped but what caused this? --129.125.160.178 (talk) 13:40, 7 January 2009 (UTC)

Sounds like Brownian motion. Apparently some reaction took place which gave off energy that became motion. Hopefully others will have the specifics. StuRat (talk) 18:54, 7 January 2009 (UTC)

Brownian motion only is visible at the microscopic level, it is probably osmotic pressure. Graeme Bartlett (talk) 21:01, 7 January 2009 (UTC)

The behavior sounds more like you get when you drop a small piece of dry ice onto water - the rapid liberation of gas from the dry ice makes it behave like a hovercraft and it rapidly zips around the surface. If this membrane absorbed a ton of methanol and then for some reason caused it to evaporate out when it came in contact with the water - then the methanol vapor would make it zip around like that. Sadly, I don't know enough about this weird membranous stuff to comment further. SteveBaker (talk) 15:47, 8 January 2009 (UTC)

Scabies

What causes intense itching in scabies? —Preceding unsigned comment added by 59.103.69.8 (talk) 14:34, 7 January 2009 (UTC)

Our article gives two causes: "action of the mites moving within the skin and on the skin itself", and "presence of the eggs produces a massive allergic response" - Nunh-huh 15:07, 7 January 2009 (UTC)

you better have an explanation for this

This question has been removed. Please do not start debates or soapbox on the Reference Desk. Matt Deres (talk) 17:10, 7 January 2009 (UTC)

I (Matt Deres (talk)) have reinstated the question:

In my heart I know that God simply cannot exist. Yet I keep finding things that seem to debunk current "scientific" understandings of how the universe, the earth and humanity came to be. How can there be identical lines of DNA coding in identical order for the structure of an eye in an octopus as in a human when they aparently evolved seperately and the order of the sequence wouldn't effect the program the lines were switched? Why do people cling to the idea that fossils don't form for millions of years when a quick trip to the local quarry will present fossilised mining equipment and boot prints? Why do we still place our faith in carbon 14 dating when it has proven inaccurate every single time sombody has tried to trick the system? Is there really a single scrap of evidence that supports evolution over intelligent design? Can anybody show me an intermediate fossil of any missing link which hasn't been found to have been tampered with? When Dawkins himself is saying that the only plausible explanation for this particular universe happening is that there are infinite parralel universes with every posibility, siting the existence of this universe as proof of this theory, what seperates the Athiests from every other faith based religion? —Preceding unsigned comment added by 194.80.240.66 (talk) 16:53, 7 January 2009 (UTC)

OK - I'll bite:

• In my heart I know that God simply cannot exist. - If you want to treat things as a scientist then the "in my heart" stuff has got to go. You need a reason.
• Yet I keep finding things that seem to debunk current "scientific" understandings of how the universe, the earth and humanity came to be. - When that happens, scientists get very, very excited - because it means we can learn something new.
• How can there be identical lines of DNA coding in identical order for the structure of an eye in an octopus as in a human when they aparently evolved seperately and the order of the sequence wouldn't effect the program the lines were switched? - What makes you think that's true? I doubt very much that enough research has been done into the DNA responsible for the development of eyes in Octopii and Humans to know this. Where did you find this information? Sure, there will be proteins and other structures that are common between the two systems - but that's because those chemicals were probably used for something else before they came to be used inside eyes - and hence they would have evolved prior to the last common ancestor of man and cephalapod. My inclination is to yell "BOGUS!!!" at this claim - until/unless there is some solid proof that it's true.
• Why do people cling to the idea that fossils don't form for millions of years when a quick trip to the local quarry will present fossilised mining equipment and boot prints? - Eh? There is no fossilised mining equipment. Boot prints are a different matter - a print can fill with something like concrete that sets hard in a short period - but technically that's not a fossil. Again - I don't believe this claim. Fossils do indeed take a very long time to form...and we can easily prove that.
• Why do we still place our faith in carbon 14 dating when it has proven inaccurate every single time sombody has tried to trick the system? - Sure you CAN trick the system (eg by injecting some extra carbon-14 into your sample or irradiating it with a strong neutron source). But if you DON'T trick the system - if you use it honestly - it works rather well. But this is true of ANY scientific process. If I write a scientific paper that says that the rate that a pendulum swings is proportionate to the weight of the pendulum times it's length (which is NOT true BTW) - then should everyone rush off and build clocks on that basis? Hell no! You repeat my experiment first (and you find it's wrong - so you publish a report saying why - and then nobody trusts me anymore). Trusting the scientists that did the C14 dating in any particular case is certainly important - and that's why we have things like peer review and the general principle that we don't trust the results of some experiment until it's been independantly verified. The fact that it's POSSIBLE to cheat - doesn't make the testing any less valid providing we stick to the rules for scientific acceptance.
• Is there really a single scrap of evidence that supports evolution over intelligent design? - YES! Absolutely! Ask anyone who runs a hospital about how bacteria evolve immunity to our drugs. Examine the way that humans have become lactose-tolerant in response to the domestication of cattle. Actually READ Darwin's book - it's really quite compelling. (Heck - I read the bible from cover to cover - it's the least you can do to return the favor!) I'd turn the question around - where is there any piece of evidence that intelligent design is true? I've never seen anything.
• Can anybody show me an intermediate fossil of any missing link which hasn't been found to have been tampered with? - Sure - go to any decent natural history museum that has rows of fossil human skulls - what's on display is likely to be replicas - however, if you politely ask the curator whether you could please examine the original bones - they'll generally find a time when you can come and do that. You'll see a set of gradual changes from something that's clearly not "human" into something that is - with very small changes at each stage along the way. It's completely compelling. This claim from the intelligent design nut-jobs that there are these enormous gaps in the fossil record is completely bogus. Bear in mind that these people are more than happy to lie to you about stuff like this - they don't have independent testing and peer review - any idiot publishes something - and the rest parrot it as if it were truth. Take nothing on trust - go to a good museum and see for yourself.
• When Dawkins himself is saying that the only plausible explanation for this particular universe happening is that there are infinite parralel universes with every posibility, siting the existence of this universe as proof of this theory, what seperates the Athiests from every other faith based religion? - I don't recall hearing or reading that Richard Dawkins said that. However, he's just one more person who has an opinion - your use of "himself" as though he were some great high-priest of science and/or atheism shows your need to have a heirarchy of priests telling you how to think. The world of both science and atheism don't work like that. He's just another guy with an opinion...and sometimes (albeit rarely) he's wrong.

We don't know (and almost certainly CAN'T know) about the existence of parallel universes. I personally find them to be a rather elegant (if deeply weird) explanation for things like the 'Schrodinger's cat' thought experiment - but there are no solid reasons why the alternative explanations involving the effect of observers on wave-function collapse is an equally valid explanation that is only slightly weird. Certainly, the explanation of why the universe happens to have the properties it has comes down to something like "well in order for there to be thinking beings to ask the question - it has to be how it is". So either the universe just happens to have properties that are suitable for us...and that's all just a coincidence...or perhaps no matter what properties the universe might have, some form of intelligent beings would have arisen - and it just happens that it come out this way...or PERHAPS it was all magicked into existance by The Great Pink Aardvark In The Sky...or perhaps there are an infinite number of parallel universes and the ones that have properties close to the one we happen to live in all have intelligent beings asking this question on THEIR Misplaced Pages reference desks. I don't think we have an answer for that one. Occam's razor (which is a great principle to live by) says that we should pick the simplest explanation until we have evidence to the contrary - so "it's all just a coincidence" is probably the best guess that most scientists would give...although if they are honest, they'll add "but we don't know for sure". Science is not 'finished' - there are things we don't know yet. It's still possible that something like string theory will come up with a reason why the fundamental constants of the universe come out the way they are - it's possible that there is some simple reason why the speed of light is what it is - why the charge on the electron is just right for making atoms and molecules work. Certainly you can be an atheist without subscribing to the "many worlds hypothesis".

SteveBaker (talk) 17:33, 7 January 2009 (UTC)

I'd also like to add, that while science will never be able to provide all the answers, as there's always more to learn, the same is true of religion. Just as we don't really know the reason for the existence of the universe, saying God created it doesn't help, as we then need an explanation for where God came from. If you accept that God was always there, or just mysteriously popped into existence, how is that any different from accepting that the universe was always there or just mysteriously popped into existence ? StuRat (talk) 18:50, 7 January 2009 (UTC)

Anyone who has spent any time in the usenet talk.origins debates would immediately recognize the questions above as creationist trolling, notwithstanding the "I believe God doesn't exist" disclaimer preceding them. I see this so often from creationists, it's hard for me to assume good faith here. ~Amatulić (talk) 19:08, 7 January 2009 (UTC)

I agree - but if you simply delete or refuse to answer, that will be a victory for the nut-jobs. "You suppressed me" is a rallying cry. So - I prefer to take the OP at face value, answer the questions as posed as honestly and accurately as possible...pretty much what we always do around here. Nothing the OP said is hard to explain or refute - except for the things that don't seem to be true. I'd be VERY surprised if there was any evidence that Octopus DNA has similar coding to Human DNA for the process of eye development. If there is no evidence for it - then it's almost certainly untrue. I have no clue why ANYONE would imagine that construction equipment becomes 'fossilised'?!? That can only be a misunderstanding of what the term means. All we can do for the people afflicted with this terrible meme-infection is to try to educate. It's what we do here. SteveBaker (talk) 19:35, 7 January 2009 (UTC)

It's at least controversial that the octopus and the human eye represent convergent evolution, as previously thought. There is about a 70% genetic similarity, probably traceable to a conserved ancestral gene set. For a discussion of the genetics of the convergent evolution of the camera eye, see Ogura, Atsushi (2004). "Comparative Analysis of Gene Expression for Convergent Evolution of Camera Eye Between Octopus and Human" (PDF). Genome Research. 14: 1555–1561. Retrieved 2009-01-08. {{cite journal}}: Cite has empty unknown parameter: |month= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help). It's not the data that's suspicious, but rather the idea that the data somehow does anything but support evolution. It's a good example of science being self-correcting (as new data is obtained, understanding changes), and nothing for creationists to be shouting "Aha!" about. - Nunh-huh 01:05, 8 January 2009 (UTC)

The problem with the creationist/ID people's take on data like this is that the work isn't done yet. I'd have no problem with their extreme brand of scepticism if only they applied the same standards to their own theories. Where are the peer-reviewed journals? Where are the chains of logic and evidence for this nutty idea they have? I can't be merely sceptical about their stuff because they don't HAVE any stuff. There is some dogma - but zero evidence. SteveBaker (talk) 03:27, 8 January 2009 (UTC)

I cannot help quoting myself from these desks. I apologize for this. So, I have a theory about the existence of God, that may possibly be of some help. I am convinced, with some good arguments indeed, that God exists, and does not exist, at the same time. This may sound contradictory at a first glance; but after a short reflection, you'll agree there is no real contradiction; clearly it looks paradoxical to us just because our mind is limited. But if you think, anybody is able to just exist, or, just not to exist: evidently God, in his/her omnipotence, is able to do both simultaneously. Of course I can't prove this as a theorem, but I wish to remark that this principle allows to explain quite easily any Religious Dogma, Sacred Mystery etc. (for instance: the Trinity Mystery, 3=1, follows as an exercise from 1=0). Moreover, this principle embraces and welcomes all different points of view in matter of faith and religion, including the heretical and the schismatic ones, and even atheism, and in fact smooths their differences, which are a source of animosity and misunderstanding between men. I am, correspondingly, believer and not believer at the same time. A position very suitable for tolerance indeed, and I am delighted to confront it with any other one (who created the stars? God. When? Never. etc)--PMajer (talk) 01:17, 8 January 2009 (UTC)

Great - so you have a theory. It's not falsifiable so I can't prove it's not true - and you have no evidence so you can't prove that it IS true. The trouble is that I could sit here all day and all night for weeks and weeks and type in other theories...my current 'Pink Aardvark' theory for example - the Russel's teapot-in-orbit-around-Mars theory. The problem for every thinking being on the planet is to know which theory to pick. Why a here-but-not-here-God and not a bunch of pink aardvarks? You have no evidence - neither do I - I can't disprove yours and you can't disprove mine...but the problem is that there are a million - or a billion - or a trillion of my crazy ideas and only one of yours. Mine are all just as plausible as yours. With no way to choose between them - they are all just as probable. So what are the odds that your's is true? Zero...near as dammit. So as rational beings, our only LOGICAL conclusion is that there are no gods - and that things that are unfalsifiable might as well be ignored - at least until we have some pretty solid evidence. It's POSSIBLE that you're right - but it's utterly, astronomically improbable. So I call "BOGUS" on your theory...like every other religion on the planet it's a complete pile of crap. SteveBaker (talk) 03:11, 8 January 2009 (UTC)

hey, hey, that's just irony... which doesn't mean I'm not serious. I personally do not feel the religious problem, nor I feel the need of having any belief about it more than about the teapot. But I equally respect who has a religious faith and who has not --with a small personal sympathy for the latter, statistically. But: as long as they remember that their belief is just a personal belief (in particular, that has nothing to do with science). So, I strongly agree and sympatize with what you wrote, except your last sentence, to whom I give, I'm sorry, a kind of self-referencing collocation.--PMajer (talk) 10:46, 8 January 2009 (UTC)

Your theory has certain resemblances to negative theology, PMajer. Deor (talk) 13:51, 8 January 2009 (UTC)

I hope you liked it. I invented it expressly for discussing with creationists, as a young student, one day that they knocked at my door, having great fun. And to their credit, they gave to my theory much more credit that I have gathered here --that's no problem of course, it's kind of friendly fire that I'm used too (after all Matt Deres knew very well what he did when removed the OP). So, I give you my theory for free, should they knok at your door too. As to the originality issue, I'm sorry to firmly decline any resemblance with negative theology ;) --PMajer (talk) 15:47, 8 January 2009 (UTC)

I cannot help quoting myself from these desks. I'm sorry - where was the quote? Anyway, if you want a good argument for the existence of god(s), how's this one? I'll even use science against itself. According to the many worlds interpretation of quantum mechanics, there may be an infinite number of alternate universes. If there are an infinite number of alternate universes, it is inevitable that god(s) will exist in at least one of these universes. After all, if an infinite number of monkeys can type out the script for Hamlet, an infinite number of universes will have god(s) in at least one of them. Now, where do I collect my Nobel prize? :) 216.239.234.196 (talk) 13:52, 8 January 2009 (UTC)

In one or more of these universes, for sure; most likely even in the present one according to it's level ;) --131.114.72.215 (talk) 14:02, 8 January 2009 (UTC)

There are several problems with '216s suggestion:

1. We don't know that many-worlds is true. We may never know that it's true - it's a neat explanation - but it's absolutely unfalsifiable right now - so it's up there with the teapot, the aardvarks, and god(s). Invoking an unfalsifiable claim in order to "prove" another unfalsifiable claim is exactly like me saying: "The universe is ruled by Pink Aardvarks and I believe that Pink Aardvarks create gods as a kind of hobby. Hence god exists."...that's an unbelievably stupid argument - but it's logically no different than claiming that god must exist because there are infinitely many universes when we can't prove that there are infinitely many universes.
2. Most versions of many-worlds say that the laws of nature would be the same in all of the universes because they are all created as a result of quantum events such as Schrodinger's cat. You stuff the cat into the box - the poison gas is either released by a quantum event or not - our universe splits into two copies that are utterly identical EXCEPT that the poison gas is release in one and not in the other. In this (more likely IMHO) version of many worlds, the only differences between them are the consequences of all of the quantum events since the big bang. However, it doesn't seem likely that the speed of light or the charge on the electron would be any different in any of those other universes. If the laws of nature are identical in all parallel worlds then gods (which require 'magic' in order to make them omnipotent) can't exist in the other universes any more than they can in this one. That busts your argument wide open. However, you may choose to define "gods" as "super-advanced life forms" and note that "any sufficiently advanced technology is indistinguishable from magic". But these so-called gods still can't fly faster than the speed of light or precisely measure both the position and momentum of an electron. Hence they are neither omnipotent nor omniscient - which I think disqualifies them from the "God" title for most religious nuts.
3. So maybe you're right - but who cares? These gods could not possibly affect us in any way shape or form - so we needn't bother worshipping them or fretting about whether they are planning to send us to hell for our little indescretions where we'll be tortured for an infinite amount of time by those guys with the pointy tails, tridents and bright red skin.
4. If you accept the common definition of a god as "a creature with omnipotent powers" - something with literally no limits on capability - then your claim that there are an infinite number of universes containing gods which (because they have literally no limits on their powers) would allow them to be able to cross the boundaries between universes. This would inevitably lead to an INFINITE number of them deciding to come to our universe and an INFINITE number of them would be messing around in our lives. An infinite number of them would choose to manifest themselves. If you believe THAT then you have a huge problem with the whole worship thing! No matter which one you pick - you're in deep trouble with the other infinity-minus-one of them!

So - no - you don't get to sneak God past the laws of physics like that. This is another very stupid theory. Sorry. SteveBaker (talk) 15:27, 8 January 2009 (UTC)

I think 216 was ironic too --PMajer (talk) 19:44, 8 January 2009 (UTC)

If so then both you and 216 need to stop making "ironic" posts because as far as most of us are concerned, the appropriate adjective is not "ironic" - it's "wrong". Stick to writing the truth please. (Personally - I think you're just falling back on that when I shred your crazy theories into teeny-tiny shreds with rather elementary logic.) SteveBaker (talk) 00:17, 9 January 2009 (UTC)

Steve, maybe you need to start asking if people are being ironic if their comments seem absurd. You seem to find it difficult to tell, even when it is the sort of thing that the person writing would have likely believed impossible to misunderstand. These were people who were actually supporting what you were saying, attempting to demonstrate the absurdity of some opposing views. There's nothing wrong with asking (particularly in a text-environment), and this could have been much jollier. :) 130.88.52.75 (talk) 17:40, 9 January 2009 (UTC)

Maybe you are right that irony is not appropriate here, and could be misleading for a simple-minded reader. Ok, bye. PS: As to my poor theory, it's even too kind of you to give it a microsopic, still non zero probability... thanks (you know, there is inside a minor problem with the Principle of contradiction... have a look to it btw, just to improve your elementary logic)--PMajer (talk) 14:07, 9 January 2009 (UTC)

Along with quite a few other people on the science and computing desks - I have Asperger's syndrome - and telling whether people are joking or being ironic is EXCEEDINGLY difficult for me because I can't put myself in your head as most people can. Hence, I have to take your words at face value and reply accordingly. Your reply didn't seem at all absurd - just WRONG...no more and no less wrong than many of the other posts to this thread. So it's not just 'simple minded' folk who'll have problems! In online conversation, you have to 'write defensively' - assuming that things that you don't say clearly (such as things that are intended as irony) will likely be misinterpreted. <joke>Feel free to use fake <irony> tags where necessary!</joke>SteveBaker (talk) 20:12, 9 January 2009 (UTC)

Steve, you know you have difficulty spotting irony. I assume you allow for this in everyday life, and people who know you also allow for this. Those of us here who know you well enough to realise the problem also allow for it. But since you are aware of the problem, when someone who cannot reasonably be expected to know you well enough to allow for this says something ridiculously wrong it would help if you considered the possibility that this could be irony. You could then ask them (indicating that this is a real question, because you have difficulty telling). All would be well. 79.66.109.89 (talk) 17:41, 10 January 2009 (UTC)

You don't need to has Asperger's to have difficulty spotting irony in written communication between people from different cultures with different native languages. It's important to take that into account when writing stuff. I think 216 did take it into account, though - the comment in question does have a ":)" at the end, which would normally suggest it isn't meant to be taken seriously (";)" would be clearer, though) - Steve probably missed it. --Tango (talk) 19:19, 10 January 2009 (UTC)

Simply sticking a smiley on the end of an entire paragraph quite utterly fails to convey the intended meaning. I saw the smiley - and paid good attention to it - but it seemed to me to apply only to the "Now, where do I collect my Nobel prize?" sentence at the end (which clearly WAS intended as a joke). Then when people say things like: "hey, hey, that's just irony... which doesn't mean I'm not serious."...I doubt that even the most capable non-Aspie could make sense of that! SteveBaker (talk) 15:29, 11 January 2009 (UTC)

It's not fair play to stir up debate and then object to the form your counterpart's discourse takes. I'm just sayin'. --Milkbreath (talk) 14:13, 9 January 2009 (UTC)

I appologize. I didn't mean for that post to be taken seriously. Anyway, it is not merely a very stupid theory, it is absurd. 216.239.234.196 (talk) 16:56, 9 January 2009 (UTC)

I don't think you need to apologize. Your joke was funny and with its sort of social utility. You even put a ":)" should one risk to take it seriously...--PMajer (talk) 19:03, 9 January 2009 (UTC)

Steve, as I said, it's no problem for me being misinterpreted when I am ironizing. The problem with irony is that one can not ironize saying "I'm ironizing", because that would kill the ironic effect --I suppose you know it very well as you are suggesting ironically the use of "irony tags". I was really convinced that was impossible to misunderstand "his/her omnipotence" or "1=0 implies 3=1" however. Anyway, I took my risk and then I found quite funny, and not at all offensive, finding myself victim of friendly fire, as I wrote. Your further reaction however sounded somehow authoritarian and priest-like (stop ironizing... write the truth...). Notice, by the way, that the hate of laughing, seen as diabolic manifestation, is an old Christian Church theme, an evergreen in fact. As to the truth, of course I do not have it, nor it is aim of science to get it, so I just can't write it. But I also understand that after you gave a very clear and valuable point-wise response to the OP, it might appear somehow a lack of respect towards science, or towards you, that somebody added an unnecessary remark, so that's no problem also. Anyway, the content of my ironical post was no joke, it's a remark that I believe important to repeat, although obvious. I agree that religion, when used to explain phisical phenomena, as pseudo-scientific theories like creationism claim to do, is bogus. The main and first reason (IMHO) being, that assuming that God sends comets does not even explain if there will be another one, not to say when. Nevertheless, as a personal, inner belief, religious faith has to be respected; which should be an obvious thing, and it is not in practise, as far as I can see reading news. Faith has to be respected even because we have no logic nor probabilistic argument against it. You can well argue that white-beard God is as likely to exist as one of the N = one Googol other weird mutually-exclusive deitys, including all Pink Aardvarks, just by an indifference principle, and that therefore each of them has probability not more than 1/N to be true. But this is quite a weak argument, for I can say that indifference is a good principle for you in absence of other reasons for you, but as I like spaghetti, Spaghetti Monster for me is kind of special, and not at all like the others, so I am free to grant him a larger probability. Or I can also say: ok I'm democratic, let's give equal probability to each weird deity, but then the same probability also to "no gods at all". As a result I get quite certainly one weird deity that I'm happy with --no matter which one it is, since I'm democratic (this was the content of 216's intelligent joke, as I intended it). Then you have to admit that "no gods at all" is a special hypotesis for you that you grant with a larger probability than existence of werid deitys. It's ok for me, but then our probabilistic proof of unconsistency of gods falls in a petitio principii: God has probability zero beacuse has probability zero. I personally do not feel the need of giving any measure of certainity to neither hypotheses, I am not even curious to know if there is a God or not. As soon as it remains a personal choice, let everybody be free of believing or not. The point of course is that we have to fight improper use of faith like: "since my God is omnipotent and he gave me this land, this land is mine", or "since my God is omniscient and gave me this booklet, what is written here is true", or "since my God knows all about sex, you shall do it this way and not that", or "my God gave you your life so you are not free to die". --PMajer (talk) 19:30, 10 January 2009 (UTC)

Does this represent inertia?

If I drop an egg on to a hard surface and the egg Breaks (obviously). Is this a representation of inertia at work?? —Preceding unsigned comment added by 65.184.51.249 (talk) 17:47, 7 January 2009 (UTC)

Eh... inertia is involved, to be sure, but I wouldn't consider that a good representation of "inertia at work" -- I'd think it's a better representation of acceleration/g-forces and structural load limits. Specifically, I don't think the tendency of the egg, or of the egg's contents, to remain in motion is what causes the egg to break.

I suggest that examples a fixed force on differently massed objects would be a more clear representation -- for example, it's easier to impart motion to a baseball than a shotput (a mass difference factor of about 50). — Lomn 18:08, 7 January 2009 (UTC)

Urgh...kinda related. Newton's 1st law (which is really talking about inertia) says that an object will keep moving in a straight line at constant speed until acted on by an external force. So your egg is trying to move at constant speed until it hits the hard surface. The inertia of the part of the egg furthest from the surface is still trying to do that when the front end hits...so it's resistance to that change in speed is what imparts a force against the surface. So the egg has to decelerate to a stop - and because F=ma (yep - that Newton fellow again...the second law this time) that accelleration imposes a force against the surface. Then (because every action has an equal and opposite reaction - per Newton's third law) the surface has to push back with an equal but opposite force...which cracks open the egg. So I suppose you could maybe argue that inertia started the whole chain of events (which in reality is just one event). If the egg had no mass or no velocity - then it would have had no inertia and it would have simply stopped without breaking. But the first law is really just a special case of the second. When F=0 (there is no force acting on an object), and m > 0 (it has mass) F=ma says that 'a' has to be zero...so no accelleration is possible. If you look at it like that, then the whole 'inertia' thing is a bit of a non-event because it's just a special case when there are no forces lying around. So I dunno. There are better examples. Swing an object around on the end of a piece of string - then let go of the string. As soon as the force due to the tension in the string drops to zero - the object goes off in a straight line...which is a perfect example of inertia in action. SteveBaker (talk) 18:30, 7 January 2009 (UTC)

This reminds me of bad test questions I always had, where the answer was "kind of, but not really". Unfortunately, they were always true or false questions and I never could quite guess which way the teacher was going to rule. StuRat (talk) 18:37, 7 January 2009 (UTC)

I'm going to go ahead and say "No". The law applies to objects not being acted on by outside forces. The law says nothing about when happens when you DO apply an outside force. So the only cases you can say Inertia applies is when there are no outside forces, or more realistically, no significant outside forces. In this case we have two forces: The force of gravity and the force of the ground acting on the egg. Both of these forces are significant since without either one the egg would not break. Anythingapplied (talk) 23:36, 7 January 2009 (UTC)

If an egg was on the seat of a moving car,going, say 60 miles per hour, not constrained from moving forward, and you suddenly applied the brakes, the egg would continue moving forward until it hit something. It might break on the dashboard. This is why wearing seatbelts/shoulder straps is a good idea. Edison (talk) 23:47, 7 January 2009 (UTC)

.249, are you sure you didn't mean to say entropy rather than inertia? Because, yes, the fact that intact eggs break all the time but broken eggs never become intact is a classic example of increasing entropy. --Sean 13:03, 8 January 2009 (UTC)

Buying Optical fiber

How much does it cost? (an estimation is enough) Where can I buy it? (and similar things) --Mr.K. (talk) 18:27, 7 January 2009 (UTC)

A Google search on "Buy optical fibre" turned up many possible places. However, you need to be MUCH more specific about what you need. There are many different things called "optical fibre". There is cheap, short glass fibre that is used in things like toys and those lamps that are made from a bundle of fibres. There is hugely pure glass for which a 20 mile length of the stuff is more transparent than a single pane of window glass. There is single-mode and multi-mode fibre which had graded refractive index that varies from the core to the outside to better 'steer' the light...there are bundles of fibres where the arrangement of the fibres is identical on both ends of the 'cable' so you can send pictures through it. There are bundles of fibres that are just to get light from A to B where the fibres can be all muddled up inside the cable. There are fibres encased in various sheaths to protect them and there are bare fibres with no sheaths. The length you need makes a MASSIVE difference to the price. If there are connectors on the ends of the fibres - or if the ends are cut at precisely 90 degrees and carefully polished so they make a good optical connection - then that's yet another parameter. In short - I can't give you even an estimate on price. But do the Google search and you'll find out for yourself. SteveBaker (talk) 18:37, 7 January 2009 (UTC)

If you don't want to buy them for industrial purposes, but for a DIY project you could try a company that buys electronic scrap. Old copiers and fax machines have a strip of (rather short) good quality optical fibers. Apart from that, as Steve said we can only guess. Lisa4edit76.97.245.5 (talk) 23:40, 7 January 2009 (UTC)

January 8

problem in thermodynamics

friends, if hydrogen and oxygen are present in a sphere of radius of 6cm, in a ratio of 2:1, and they are burned, what will be the pressure exerted on the walls of the sphere? will it be able to move a vehicle with a mass of 25kg if appropriately transmitted? —Preceding unsigned comment added by 117.193.227.111 (talk) 02:10, 8 January 2009 (UTC)

The former would appear to be highly dependent on the quantity of hydrogen and oxygen. The latter seems unlikely; "if appropriately transmitted" seems to be the core problem rather than a minor issue to gloss over. — Lomn 02:40, 8 January 2009 (UTC)

To clarify my dismissal of the second part of the question: what motive force does a closed pressurized scuba tank provide? None. The vessel is rigid and has no opening, just as you appear to have theorized with a "sphere of radius 6cm". There's nothing to "appropriately transmit." If you're willing to allow for a nozzle of some sort, then yes, said pressure can move a vehicle of any weight. It just may not move it much. — Lomn 02:51, 8 January 2009 (UTC)

Yeah - I think we can assume that the OP has a valve on the outside of the sphere that lets air in or steam out depending on...whatever...and some kind of a piston or turbine or something to efficiently extract energy from the reaction. In an IDEAL world - any amount of pressure can move any mass of object - but in the presence of friction, the force of 'static' friction ('stiction') will actually prevent things from moving at all - unless there is a reasonable amount of energy liberated from the sphere. I rather suspect nothing would happen - but that's "gut feel" kind of a thing. SteveBaker (talk) 02:59, 8 January 2009 (UTC)

Well, you'd have the same mass of steam/water/water-vapor left inside. It's kinda tricky to figure out the pressure of the water vapor versus the pressure of the hydrogen/oxygen mixture because there is temperature change as a result of the exothermic reaction and a lot would depend on how well that temperature is maintained subsequently. So I rather think there would be not a whole lot of change. If the water would condense back to a liquid - then the pressure inside would drop to essentially zero - but water boils at room temperature in a vacuum - so we know that's not gonna happen. Well - assuming there is SOME change - then with appropriate transmission, we need to know about the frictional forces for your vehicle - the mass of the vehicle doesn't help us to calculate that. In a perfect frictionless world, any force, however small can move a vehicle of any mass - albeit pretty slowly! So you really havn't given us anything like enough information. Sorry! SteveBaker (talk) 02:46, 8 January 2009 (UTC)

An aside - hydrogen was used as the fuel in the very first vehicle powered by an internal combustion engine, which was built by Swiss inventor François Isaac de Rivaz in 1807. Gandalf61 (talk) 10:45, 8 January 2009 (UTC)

That's true - but it was working like a gasoline engine. Inside the cylinder would be AIR and hydrogen. When the hydrogen burned with the oxygen, water was formed but the remaining nitrogen from the air (4/5ths of the air is nitrogen, remember) would be heated by the combustion - expand greatly and force the piston down the cylinder. Our OP is talking about pure oxygen & hydrogen - so there is no nitrogen there to act as the "working fluid" (in heat engine terms). I don't know whether water vapor (which would be all that was left inside the OP's sphere) would have more or less pressure than the original gasses because that depends on heat and initial pressure - and we don't know what those are without knowing a lot more about the 'engine'. These days, we know that reacting hydrogen with oxygen from the air in a 'fuel cell' to produce electricity without generating heat is the way to go with hydrogen fuelled vehicles. Hydrogen simply doesn't have enough energy density to efficiently replace gasoline in conventional cars. SteveBaker (talk) 15:05, 8 January 2009 (UTC)

The volume of a ball of 6 cm radius is V = 904.8 cm. I assume the H2/O2 mixture is initially under standard pressure (p = 101,325 Pa) and at standard temperature (T = 25 °C = 298.15 K) - the amount of substance is p*V/(R*T) according to the ideal gas law (do I need to mention that the units have to be correct when you do the calculations?). Multiply that by 2/3 in order to get the amount of water resulting from the combustion (1 mol O2 + 2 mol H2 -> 2 mol H2O).

Now look up the standard enthalpy change of formation for water - in the gaseous state it's ΔH = -241.8 kJ/mol. Approximating water vapor as being an ideal gas, you can first calculate the pressure of the water vapor at standard temperature by p₀ = (amount of water)*R*T/pp₀ = (amount of water)*R*T/V (edit: you don't need that), then compute the temperature rise as ΔT = ΔH/c_V, where c_V is the (molar) heat capacity at constant volume (c_V = 6*R for an ideal gas with 3 internal degrees of freedom, like water is approximately). Now you can again use the ideal gas law to compute the resulting pressure at the temperature you just calculated, with the volume of the ball and the amount of substance of water.

This will be an upper limit for the pressure. Once the combustion process is over, the pressure will fall again as heat is conducted through the spherical shell. Also note that water vapor is not really an ideal gas and also that at high temperatures, the heat capacity increases, so the total temperature will be a bit lower than what you get from the simple calculation.

Icek (talk) 15:18, 8 January 2009 (UTC)

So what's the answer? Did you crunch the numbers? Well, anyway - if the thing were to work, the ball would have to be a pretty chunky piece of metal (probably) - so the conduction of heat away from the resulting water vapor would probably be significant. SteveBaker (talk) 19:31, 8 January 2009 (UTC)

It's only 1.166 MPa, but the temperature is quite high, 5145 K (which means that it will be considerably lower at least due to vibrational degrees of freedom; they raise c_V to 9*R for higher temperatures). Icek (talk) 11:33, 9 January 2009 (UTC)

i am the one who asked the question. the sphere is connected to a piston. the object is situated in a frictionless region. what will be the acceleration produced? pV=nRT p * 0.001 = 0.0442*8.3136 * 5145 0.001p = 1890

        p= 1,890,000

that is nearly 19 atmospheres. what force will be exerted on a piston connected to an outlet in the sphere? —Preceding unsigned comment added by 117.193.224.137 (talk) 13:41, 10 January 2009 (UTC)

I think you forgot to multiply by 2/3, as 3 mol H2/O2 mixture become only 2 mol water. Then you get the value I stated in my last answer - between 11 and 12 atmospheres (and in reality it will be even less, for the reasons mentioned above). For the force on the piston, you only need to multiply the pressure by the area upon which the pressure acts in the right direction on the piston (most likely the piston is a cylinder (of radius r) and the area is rπ). You may ask how the force decreases when the piston moves out. Of course that also depends on heat transfer, but assuming no heat transfer, for an ideal gas p*V is constant (see adiabatic process for the details). Icek (talk) 14:41, 10 January 2009 (UTC)

In Electric current(AC-230V) transmission-household wiring, why cannot we sense Nutral current using normal Current tester?

why cannot we sense Nutral current using tester? —Preceding unsigned comment added by Ranga333eie (talk • contribs) 05:19, 8 January 2009 (UTC)

There is no such thing as neutral current. A neutral wire simply completes the circuit by carrying the alternating current from the live wire, and is usually the same potential as (and connected to) earth/ground. So there's nothing to measure. (Note that this DOES NOT mean it's safe to touch the neutral wire, it's not or at least not always.) Nil Einne (talk) 13:35, 8 January 2009 (UTC)

Purely for the sake of pedantic completeness, there is neutral current - but it's definitely not something you would measure with a current tester. Gandalf61 (talk) 13:55, 8 January 2009 (UTC)

Aarrh, I hate quantum physics and its wacky names ;-P Nil Einne (talk) 18:11, 8 January 2009 (UTC)

If you were to insert an ac ammeter into the neutral lead of a household appliance then of course you would measure the electric current drawn by that appliance so I dont understand the Q (or the above answers for that matter). The neutral is only connected to earth in any installation at the consumer unit.--GreenSpigot (talk) 18:22, 8 January 2009 (UTC)

In some countries, a 230 volt appliance has a hot lead (at 230 volts relative to earth ground) and a neutral lead, which is connected to earth ground back at the power panel, so has very small voltage difference from ground, as well as a safety ground wire, which carries no current if the equipment is working properly, but could carry fault current if the insulation failed somewhere in the circuit. In these locations, the neutral current should be equal to the hot lead current on the equipment power cord. In other countries like the U.S., a 230 volt to 240 volt appliance has 2 hot leads, each at 120 volts relative to ground, as well as a ground conductor. Each of the hot leads should carry the full load current, and there is no neutral conductor. The safety ground should carry no current under normal conditions. Edison (talk) 19:44, 8 January 2009 (UTC)

Perhaps the OP doesn't understand the difference between voltage and current, or is using the word 'current' in the colloquial sense of 'something to do with electrical power'. I say this because most householders lack the equipment to measure the current in their mains (house current) wiring. All most people have is a voltmeter or a neon tester, so perhaps when the OP writes "current tester" he really means "voltage tester". In that case, as Edison says, the neutral wire may be at or near ground potential and so a voltage tester will read practically zero. To check the actual current in the neutral wire without breaking it, you need a current clamp. --Heron (talk) 20:41, 8 January 2009 (UTC)

To do much electrical testing. it's good to own an RMS multimeter and a current clamp. A wattmeter/kwh meter is also useful. Edison (talk) 05:23, 10 January 2009 (UTC)

Light as waves AND particles

Our first observation of waves and wave like action in nature was with ripples of water in a pond. The little particles of water are moving in a wave like fashion up and down. This is what we picture in our heads when we think of light waves also....Why is it that it is incorrect to assume that light can't be light particles moving up and down in a wave like fashion....why can it only be one or the other PARTICLE or WAVE? How is it that they proved that photons dont move up and down in a wave like fashion as they travel? —Preceding unsigned comment added by 165.145.103.161 (talk) 10:12, 8 January 2009 (UTC)

Light exhibits properties of both wave and particle. It is not "one or the other". But it also is not a particle moving in a sine pattern up or down. Such a model would not explain interference, for example, or standing waves as in a microwave. --Stephan Schulz (talk) 10:38, 8 January 2009 (UTC)

I like it! Proof of the wave nature of light using chocolate: . SteveBaker (talk) 19:28, 8 January 2009 (UTC)

Light is very different from water or sound or other kinds of waves. It's not correct to say that light "is a wave" - we should say rather that "under some circumstances it behaves like a wave". Ditto for particles. Photons are definitely not "normal" particles. But it's certainly not as simple as photons (particles) wobbling up and down...that's a bad image to have in your head. Why is this bad? Well, it's just not how things are.

The 'wave/particle' duality thing is best demonstrated in the double-slit experiment (which we described and discussed a few questions ago). If you take a water 'wave-tank' and make a ripple pass through two slits in a wall of some kind - then the ripples that spread out on the other side of the wall will 'interfere' with each other. As the peak of one ripple crosses the peak of another - they add together to make a double-sized ripple - and where the peak of one ripple crosses the trough of another, they cancel out and leave calm water. This produces an "interference" pattern of radial lines that is quite distinctive. Soundwaves can be made to do the same thing.

So if light "is a wave" we should be able to do the same thing. So we take a sheet of glass - paint it black and score two very thin lines into it that are very close together. Then we can shine a source of light at the glass and look for interference patterns. If you do that experiment - you get interference patterns that look EXACTLY like the ones you got from your water tank experiments. Hence (you conclude) "light is a wave"! Hooray! Problem solved - right? Nah...not that easy.

Along comes that nice Mr Einstein. He observes experiments on what is called "the photoelectric effect". This is a situation where you have something like a solar-cell and you shine light on it and look at the electricity that comes out. Let me quote from our article photoelectric effect:

"Eduard Anton von Lenard observed that the energy of individual emitted electrons increased with the frequency, or color, of the light. This was at odds with James Clerk Maxwell's wave theory of light, which predicted that the electron energy would be proportional to the intensity of the radiation. In 1905, Einstein solved this paradox by describing light as composed of discrete quanta, now called photons, rather than continuous waves."

So this experiment can ONLY be explained if light is a bunch of little particles. So "light is particles"! Hooray! Problem solved right? Nah...not that easy.

We've still got to explain the double-slit experiment. We have double-slit which says "wave" and photoelectric-effect which says "particle". They can't both be right can they? ...Well, sadly, yes they can. But it gets weirder. You want to take the red pill and see where this rabbit-hole leads? OK.

So - someone has the bright idea to put the two experiments together. We take our double slit and we shoot single photons at it...if the particle theory is correct then the photon goes EITHER through the left slit OR the right slit - and so it can't interfere with itself...right? Nah...'fraid not. Even if you shoot a SINGLE photon at the double-slit, you STILL get interference. So the photon must be acting like a wave and going through BOTH slits. OK - but we can use the photoelectric effect to build a detector for single photons. When the photon hits the solar panel, we can look at the electricity it produces. So let's build a 'photon counter' and stick one behind each of the two slits. If the photon is a wave that's going through both slits then we'll count "half a photon" in each detector - right? Nah...sorry. Wrong again.

This is where things get SERIOUSLY weird.

When you try to count the number of photons going through each slit - you find that it behaves just like a particle and either one or the other photon counters kicks in. You know which slit the photon went through - for sure. So how come it's interfering with itself if it didn't go through the other slit? Well - guess what: When you set up the experiment to count the photons - the interference pattern disappears - as if by magic. This is deeply - DEEPLY strange. When you decide to try to treat the light as particles - it somehow magically KNOWS that you're trying to do that - and obligingly behaves like particles. It's wave-like properties disappear BECAUSE OF THE WAY YOU ARE MEASURING THE RESULTS. If you switch off your photon counters - the interference pattern obligingly comes back.

My head hurts - and so should yours.

At the quantum level where photons and such like play - the universe simply doesn't behave the way 'common sense' says it should. Our brains are simply not equipped to understand this. So - light is a..."something"...that behaves like a wave when we try to treat it as a wave and like a particle if we do that instead. Try not to rationalise this as a particle that's moving in a wavelike manner because that doesn't explain the double-slit experiment at all. A particle that wobbled like a duck on a pond as a ripple goes by wouldn't be able to go through both of the slits in the double-slit experiment...so it doesn't help.

Sadly, there is no simple thing you can hold in your head that explains what a photon is.

When you get into relativity, light is even weirder. It's the only thing in the universe that can travel at the speed of light. Anything else that tried to do that would have infinite mass and time for it would literally stop...photons don't seem to be bothered by that at all. They have perfectly sensible masses and they behave quite sensibly at that speed.

SteveBaker (talk) 14:56, 8 January 2009 (UTC)

Maybe time for photons does literally stop, sort of like the opposite of someone falling past an event horizon. For an outside observer the guy slows down until he's going imperceptibly slow and finally freezes and fades. But the guy just experiences himself falling a bit and getting stretched to death. Maybe photons don't have any perception of time, but when you watch them you don't see that weird effect at all. Maybe that explains some of the weird quantum EM effects. Just a thought.. Pez00 (talk) 18:28, 8 January 2009 (UTC)

Gravity also travels as fast as light. Light technically only refers to a certain spectrum of electromagnetic waves, all of which move at the speed of light. The stuff you mentioned before relativity applies to everything. I've heard the double-slit experiment has been done with buckyballs. Pez, you can't plug the speed of light into the relativistic equations. You could get it to work with limits, though. — DanielLC 19:53, 8 January 2009 (UTC)

It's -> Its

Wrong, SteveBaker, the fotoelèctric effect finds the fotòn is a—a—wave. Rather, it's the elèctròn and its associated transition thas is the mote. The same goes for the two-slit experiment: The elèctròn, whose inner size is the classic radius and outter size is its causal radius (by propagation—that is, its field) inducts the charges in the whole target and both slits, in the same way your finger can strike two keys on a keyboard, and reaches a path between the slits. It's not a wave by itself; its wave is the fotòn. -lysdexia 21:27, 8 January 2009 (UTC) —Preceding unsigned comment added by 69.108.164.45 (talk)

I'm sorry - but the photoelectric effect article (which I quoted directly) says otherwise. Here is the quote again:

"Eduard Anton von Lenard observed that the energy of individual emitted electrons increased with the frequency, or color, of the light. This was at odds with James Clerk Maxwell's wave theory of light, which predicted that the electron energy would be proportional to the intensity of the radiation. In 1905, Einstein solved this paradox by describing light as composed of discrete quanta, now called photons, rather than continuous waves."

If you think that's incorrect and can provide references to prove it - then you should go to the photoelectric effect article's Talk: page and argue it there. However, I'm very sure that you're wrong. SteveBaker (talk) 00:14, 9 January 2009 (UTC)

I do not contradict your quote. -lysdexia 02:44, 17 January 2009 (UTC)

if an acid is added to a salt...?

what would happen to a salt if an acid is added to it? —Preceding unsigned comment added by 121.96.121.79 (talk) 10:41, 8 January 2009 (UTC)

I'm pretty sure it would depend on what acid and what salt. Nil Einne (talk) 11:59, 8 January 2009 (UTC)

The rule from high-school chemistry is "Acid + Alkali = Salt + Water"...salt is the end result of a reaction with acid - so it's hardly going to react with the acid further. So GENERALLY - nothing. However, there are a lot of exotic chemicals that we call "salts" and a lot more that we call "acids" - and that leaves open the possibility for all sorts of exciting reactions in the right combinations. Basically, we're going to need a lot more information. SteveBaker (talk) 14:28, 8 January 2009 (UTC)

You're missing a key ingredient:

Dilute acetic acid plus sodium chloride plus tuberous starch sections (hot) equals Delicious!

On a more serious note, SteveBaker and Nil Einne are quite right — we need more information. In the example above (without the fries), mixing acetic acid and sodium chloride (an acid and a salt, respectively) has no particular effect. On the other hand, mix acetic acid (vinegar) with sodium bicarbonate (baking soda), and you get the carbon dioxide bubbles which feature in every kid's science fair volcano.

And it gets worse — depending on how you choose to define 'acid', you can fit a vast number of reactions under the 'salt plus acid' umbrella. Using the Brønsted or Lewis definitions of an acid, many 'salts' are 'acids'. TenOfAllTrades(talk) 15:00, 8 January 2009 (UTC)

Mensa and god

I recently encountered someone who was a member of Mensa who also believed in god. Why would an otherwise intelligent person believe in supernatural beings? Surely, this person is smart enough to know better. But obviously isn't. This seems to be a paradox. Is it a question of emotion versus logic? Or intelligence versus knowledge? How is this possible? 216.239.234.196 (talk) 15:09, 8 January 2009 (UTC)

The only criterion for membership in Mensa is a high IQ, so the question is how well IQ correlates with a realistic world view. I think that even if IQ was a measure of a person's ability to cope with reality, 132 would not be good enough to get you clean over the god hump. But it isn't. IQ, that is. A measure of that. Sophistication, I've heard it called—nothing much to do with a problem-solving, mathematical intelligence. And your nerdy genius types are often colossal crackpots. Take Feynman with his goddam bongoes. --Milkbreath (talk) 15:52, 8 January 2009 (UTC)

IQ is a measure of ability to do IQ tests, nothing more. There is a correlation between that and intelligence, but it isn't particularly strong. However, you do get otherwise intelligent people believing in god(s), I think it's a matter of them being capable of reasoned decision making but choosing not to do so in the case of their religious beliefs - religion is all about not questioning what you've been told. --Tango (talk) 15:56, 8 January 2009 (UTC)

You said "There is a correlation between that and intelligence but it isn't particularly strong." You really need to define "intelligence" better before you make claims like that. All tests test only what the test tests. That's nearly a tautology and hardly even worth mentioning. If you say there's a correlation to "intelligence", but it isn't very strong, then you must be comparing IQ results to some other measure of intelligence. Unless you explain what that is, your statement has no meaning.

I know you're only saying what many, many others have said before (Some with modesty, others with sour grapes), but that's no excuse on the reference desk. APL (talk) 16:20, 8 January 2009 (UTC)

It's a fair point. Can I get away with saying "any reasonable definition of intelligence"? (Reasonable is, as always, defined as something I agree with. ;)) The problem is that intelligence (in the sense that the word is commonly used to mean, which is the only real definition of any word) isn't really quantifiable. It's a measure of collection of abilities and any weighting of them to get a single number is going to be completely arbitrary. Exactly what it means for a numerical measure to be correlated (however weakly) with something unquantifiable, I'm not sure, but I think everyone knows what I mean (the various abilities we include in intelligence are correlated themselves, so you can often at least put people into bands, even if you can't give them a precise number, there will be people that don't fit in any band, though - such discrepancies are often associated with learning difficulties). Incidentally, tests do generally measure more than just what they test - we interpret the results of the test in order to draw more useful conclusions. For example, a reading test tests whether or not someone can read a given bit of text, but what it measures is how good they are at reading in general (it doesn't measure this perfectly, of course). In order for a test to be used to measure something more than just what is actually being tested there needs to be a strong correlation between the two things - the ability to read a given sentence and the ability to read other similar sentences are very strongly correlated, so reading tests are useful. Similarly, the existence of a particular bacteria in a blood sample is strongly correlated with the existence of that bacteria in the rest of the person's blood, so we use tests on blood samples to measure things about the blood in general. The ability to solve the extremely obscure questions in an IQ test isn't strongly correlated to anything particularly useful. --Tango (talk) 16:43, 8 January 2009 (UTC)

a bacterium. "whether or not" means "whether or not whether". Someone is not a they. -lysdexia

"a bacteria" is commonly used to mean "a species of bacteria", "bacterium" refers to a single cell. I don't understand your second point. The use of "they" as a gender-neutral 3rd person singular pronoun is very widespread. The English language is defined simply by how people use it, so it being widespread means it is, by definition, correct. In future, if you don't have a refutation for someone's arguments, keep quiet, don't pick holes in their English - and if you are going to, at least do it right. --Tango (talk) 21:04, 8 January 2009 (UTC)

This question is based on the assumption that there is proof that God does not exist. In order to ask this question (without being a simple troll), the questioner must provide the proof that God does not exist, which all intelligent people must know, and this otherwise intelligent person is ignoring. -- kainaw™ 16:27, 8 January 2009 (UTC)

There is no proof of the non-existence of some kind of god and never will be since it isn't a mathematical statement, so a mathematical concept like "proof" is irrelevant. However, intelligent people generally draw conclusions about reality based on evidence, and there is no evidence of the existence of any kind of deity. obligatory link to Occam's razor --Tango (talk) 16:52, 8 January 2009 (UTC)

The proof

There is nothing which cannot be described by maths and loghics—so there can be such a proof; otherwise, one could not bring up the whim of "God" in the first stead, or contrast one God with another God, say what God is and is not or has and has not. God must be supernatural and infinite. However, the world and everything is natural and finite—otherwise, it would be God—so World and God cannot meet; that is, be in the same univers. By definition, if the world is natural it must make itself; otherwise, there would be nothing different between creation and creator as the former would also be supernatural and indistinguabil from God. As we cannot know God, there is no God and the world has nothing to do with God. The three kinds of god—theotèt (of theism, lord god), deotèt (of "deism", "god"), and pantheotèt (of pantheism, heaven-and-earth god)—with a mind informed of their proper meanings, can be stripped of their god-name for the first and last kinds and relegated intom natural and modern terms. The other kind left has nothing to do with mest of the world's sense or belief about God, so if god=God, god is everyways proven not.

I'll go with the others and say belief in God is dependent on ineducation—or more exactly, a miseducation of everything they believe in, which is mostly a monotheistic coverup of pollatheistic pagan roots. Their scriptures are ripoffs of Sumerian-Babilum creation and disaster stories, along with their misunderstandings of the size, scale, and shape of the world; whenever the Tanac or Vivli says something is true of the whole world or earth, it is wrong. Both texts (the Vedas too) like to blow up the lifetimes of their first men by some factor—12 or 60 or 360—by a spuriose reckoning of the year-day relationship as godly bodies rather than "heavenly" bodies. Every monotheism in order to please the old world makes up many Gods of their own, between five and eiht by my count, which are in sooth accessories of God but which they call servants of God, but which are nonetheless heavenly beings with God-like powers who pull off the same functions as the older pagan Gods. Kristianity, by exemplar, has pneýma, Immanuel, Ghabriel, logho, Mikael, basileia, and decsio—and the other Abrahamic religions hav variations of such, all in exact correlation with their pagan Gods, which I count fivefold (without the sun and moon) to sevenfold (with the sky and heaven). I'm about to finish a treatise against Creation and Creationists, with such a master list of Gods and other details against Ghenesis. My earlier writings can be found at Google Groups and Beliefnet, and some of the links are also where I proved, manifold, how there are no black holes. (Hint: The black hole is not a relativistic hýpothesis, but a classic and Newtonian one.) -lysdexia 20:09, 8 January 2009 (UTC)

All mathematical theorems are of the form "A implies B". "There is a god." is not of that form, so cannot be a mathematical theorem (I guess you could try "We observe the universe as we do, therefore there is a god.", but I don't see how you could translate that usefully into something you can do mathematics with). The existence of a god is a matter for theology, mathematics doesn't come into it (science can impose restrictions on what kinds of gods are likely to exist by finding evidence which contradicts the relevant religion, but you can't contradict the whole concept of religion). --Tango (talk) 21:15, 8 January 2009 (UTC)

There had already been a mathematic proof for God with transfinite sets in extrapolation—which faild, as it would expect any nominally trivial being. Likewise, one can use the same sets as a mathematic proof against God. -lysdexia 23:45, 8 January 2009 (UTC) —Preceding unsigned comment added by 69.108.164.45 (talk)

Intelligent people can also draw conclusions such as: We do not know what happens after death. If there is no God and you do do not believe in God, that is fine. If there is no God and you do believe in God, no real problem. If there is a God and you do not believe in God, you may be punished in whatever happens after death. If there is a God and you believe in God, you may be rewarded in whatever happens after death. How is that less intelligent than "I ain't seen nun'it so's I ain't believin' nun'it!" -- kainaw™ 17:15, 8 January 2009 (UTC)

Pascal's Wager is not exactly new. It's also not valid for any number of reasons. But to add another angle: What you propose really is the 1984 approach. "Say that 2+2=5 or I'll hurt you". I refuse to worship a god who needs such crude methods (and believing without worshiping is typically worse than not believing at all, of course). --Stephan Schulz (talk) 17:24, 8 January 2009 (UTC)

I'd say the main reason it isn't valid is that it seriously stretches the definition of "belief". In what way is such a conclusion a belief? It's just going along with it because it has the greatest expected outcome. I, too, would refuse to worship a God as megalomaniac and sadistic as the Christian God, even if I did believe in Him. --Tango (talk) 17:42, 8 January 2009 (UTC)

Pascal's wager is perfectly valid for the claim that I made. I stated that it is possible for an intelligent person to believe in God. Your response is that you refuse to believe in God. The point of this thread is not if you believe in God or not. The point of this thread is: Is it possible for an intelligent person to believe in God? Is your claim that you are the only intelligent person and, since you refuse to believe in God, no intelligent people believe in God? -- kainaw™ 17:41, 8 January 2009 (UTC)

• I would say that a person practising religion because of a decision based on Pascal's wager does not "believe in God". (And, do you really think someone that is meant to be omniscient would fool for such nonsense?) --Tango (talk) 17:58, 8 January 2009 (UTC)

• Why not? Those Sabbath mode ovens have been fooling Him for years.  :) --Sean 20:32, 8 January 2009 (UTC)

(And one of my favorite factoids: The bible is the most shop-lifted book in America...maybe people don't learn the "Thou shalt not steal" thing until AFTER they read it!) SteveBaker (talk) 22:05, 8 January 2009 (UTC)

• I have not claimed that it is impossible for an intelligent person to believe in god at all. On the contrary, I'm very much aware that many intelligent people do. Pope Benedict XVI would be a current example, as would be Kenneth R. Miller. For historical examples, Alhazen comes to mind, or Isaac Newton. But Pascal's Wager is not a good reason to do so. It assumes, without any reason, a particular configuration of god or gods and the afterlive. Under that assumption (there is one god, and it will treat me better if I pretend to believe in it for the expected gain in the afterlive, and I pick the right god from the many possible ones to believe in), it is valid. But what if Thor is pissed off because I believe in that Christian upstart? Or what if god despises people who only believe in him for the pay-off? --Stephan Schulz (talk) 18:16, 8 January 2009 (UTC)

You can strategically pick your god :) Thor hitting you with his hammer or being reincarnated as a hamster can't possibly be as bad as hell. Pez00 (talk) 18:33, 8 January 2009 (UTC)

Have you ever hit your thumb while nailing down a board? But by your argument, I would have to pick the god or godess that will treat non-believers the worst. Kali, here I come! ;-) --Stephan Schulz (talk) 18:42, 8 January 2009 (UTC)

Don't fall into the trap of thinking that religion is only worthwhile as an answer to the 'unknown', and that as science progresses and uncovers these secrets that religion becomes less and less worthwhile. Religion isn't like that in practice - it may be a cultural tradition, it might be a philosophy or guide for a person, it might be of comfort to them, or make them feel self-worth/purpose in life. Intelligent people are not devoid of wanting things that religion provides, and the fact that they are 'intelligent' enough to realise their belief isn't founded in perfect logic/scientific truth doesn't prevent them getting value from practicing their religion. The pursuit of knowledge and the pursuit of happiness are different things. Additionally we are not 'logical' beings, we can happily exist with giant contradictions and we fool ourselves into believing something that to every outside is blatently lies. Finally just to note - i'm not religious in any way, but try to appreciate that the 'truth' isn't necessarily what's right/important. 194.221.133.226 (talk) 16:43, 8 January 2009 (UTC)

I think you're confusing the issue here. The OP specifically asked why an intelligent person may believe in God. Not why an intelligent person may be religious. You can and many people do participate in religious ceremonies or religion for cultural reason, as a guide etc. However while it may be more likely that such people will believe in God, it's not a precondition and many people don't Nil Einne (talk) 18:52, 8 January 2009 (UTC)

To be honest, I think I may have confused the issue, too. I did not consider that there can be a distinction between being religious and believing in god. I don't suppose you know of any articles about people who are religious but don't believe in god? 216.239.234.196 (talk) 19:08, 8 January 2009 (UTC)

Take a look at cultural Judaism for starters. These include people who may be involved in religious ceremonies and practices for cultural reasons, without actually believing in God. Indeed there are even ancient religions e.g. Buddhism which don't even have the concept of God. And new ones are cropping up e.g. Unitarian Universalism and other Liberal religions have no defined God (although some people involved in them obviously do believe in God) and many of the new age religions lack God. For those who do like the sense of community etc given by religion but who don't believe in God, as churches and the like are appearing . Douglas Adams a self described radical atheist, funeral was held in a Christian church with Dawkins in attendance. Parents sometimes attend church to give their children a change to explore religion or because they believe it's beneficial in other ways but don't believe in God themselves . I've tried to avoid referring to these people as religions since whether you consider these people religious or not is an unnecessary distraction. I would say many are religious e.g. Buddhists, those involved in new age religions etc i.e. all of those with a sense of spirituality are religious, even though they may not believe in God. Indeed you could go further since it appears to me the OP was specifically asking about the Abrahamic monotheism concept which most Eastern religions lack. Of course you could argue that many of the spritual religious beliefs have the same problem as the concept of God and therefore it makes as much or little sense for an intelligent person to believe in them but I don't think it's a simple matter. To me, the idea of an omnipotent being (particularly one who punishes the 'wicked' for enternity although that's obviously not a precondition for believing in God) makes less sense then the idea we are all connected on a spiritual level. Then there are also those without any spirituality, i.e. do it solely for the sense of community, moral guidance etc who you could probably say are not religios but they still "participate in religious ceremonies or religion for cultural reason, as a guide etc" as I stated even though they obviously don't believe in God. P.S. You may want to ake a look at religion. Nil Einne (talk) 10:26, 9 January 2009 (UTC)

At my church we have professionals is many, many areas including biologists, chemists, physicists, doctors and surgeons, lawyers, architects, engineers etc. All these areas require intelligence, logical thinking and the like. Whatever their/my personal reasons may be, religious beliefs have very little correlation with intelligence in my honest opinion. As the IP above me has noted, it's not always in a search of God and the paranormal, its often a cultural reference in how to live in a generally accepted better way (with a few nutjobs taking it too far). —Cyclonenim (talk · contribs · email) 17:23, 8 January 2009 (UTC)

You can have a sense of morality without being religious. What does visiting a given building every 7th day and worshipping a mythical figure have to do with living in a "generally accepted better way"? There have been studies which have shown a significant correlation between level of education and religious belief (the higher the level of education you've achieved, the less likely you are to be religious) - you can argue than education and intelligence are not the same thing (and you would be right, of course), but your examples are all of highly educated people, so such studies are relevant. --Tango (talk) 17:42, 8 January 2009 (UTC)

There are also studies that show that older people tend to be more religious. So, can we safely assume that religion is a product of age and life experience? Is there a correlation between age and education? Do these correlations have no cause-effect relationship? -- kainaw™ 17:46, 8 January 2009 (UTC)

Unless such studies have been repeated at different times, you need to be very careful what conclusions you draw from them. It could well be when you are born that is significant, not how old you are. --Tango (talk) 18:00, 8 January 2009 (UTC)

@Tango, sorry I didn't mean imply that only religious people can me moral. I'm saying that almost all religious people are, it's an almost ensured way of living morally. It's not going to church and worshipping a God as such which has anything to do with living your life a better way, it's adapting to the guidelines given in religious texts (of which many are now bound socially as well as religiously). How do such studies as you mentioned above help discourage my point? The vast majority of adults at my church are well educated and successful, and still religious. Studies based on religous belief and education is essentially like going and doing a survey of "Are you religious?" at an educational establishment. —Cyclonenim (talk · contribs · email) 18:13, 8 January 2009 (UTC)

Sorry, but being religious does not seem to increase your chance of living a moral life. For one, many religious demands are outright immoral ("stone the witch!"), but also, believing in a religion does not at all imply that you follow the moral rules of that religion at all. "We are all sinners..." --Stephan Schulz (talk) 18:38, 8 January 2009 (UTC)

Two things. First as I noted above, being religious and following religious guidelines doesn't require you to believe in God which is the real question at hand. As also noted above, many people can and do do so without believing in God. Technically the guidelines may require you to believe in God but people can and do choose to ignore that part as nonsense in their opinion. Second I think many would argue the guidelines have been bound socially long before they appeared in religios. They would say the reason they appeared in religious texts is because of the social tradition Nil Einne (talk) 18:58, 8 January 2009 (UTC) Edit: Struck out being religios to avoid confusion Nil Einne (talk) 10:26, 9 January 2009 (UTC)

Intelligent people can usually understand that there are things that logic and science can't deal with. Do you believe in beauty? Science cannot really measure that sort of thing and logic can't prove it exists. With no available evidence for or against, belief in god(s) is more or less a matter of personal taste. I don't think you can particularly draw conclusions about intelligence based on the god question. Friday (talk) 17:50, 8 January 2009 (UTC)

There's a lot of defense you can throw behind the idea that a god exists, but a better question would be which religion do you believe in? Christianity? Try to reconcile all we know about the age of the universe and the earth with a recent creation and a god who "is not the author of confusion". Scientology? Perhaps the most relevant example; reason screams against their doctrine Pez00 (talk) 18:18, 8 January 2009 (UTC)

To be fair, it's only a small radical fringe of Christians who believe in a young Earth. Friday (talk) 18:22, 8 January 2009 (UTC)

Personally I'm not altogether happy that I think all that God stuff is rubbish. I know the statistics show that religion is correlated with wealth happiness, and more children. I feel like the person who was offered great health, wealth or wisdom by a genii and asked for the wisdom, and a moment later says 'Oh I see now I should have asked for the wealth' :) Dmcq (talk) 18:34, 8 January 2009 (UTC)

Correlation != causation. You are assuming that wealth comes about BECAUSE of religion - but how do you know it's not the other way around? People with a lot of money on their hands have nothing better to do maybe? Correlation with more children has GOT to be because so many religions encourage more children (eg by making women subsurvient to men - or by banning condoms). Without studies into causation - these statistics don't tell you a whole lot...it's possible for example...that like US politicians, you're doomed to becoming a social outcast in wealthy society unless you tell people that you are religious. So everyone lies. It's possible that in the past there was causation - and because children of religious parents tend to be religious - and children of wealthy parents tend to be wealthy - the statistical 'ghost' of that causation lives on. We simply don't know. Suffice to say that I consider myself reasonably well off - and I'm a total atheist. I only have one child - but family size correlates inversely with wealth - so we can't make any conclusions about that. SteveBaker (talk) 19:41, 8 January 2009 (UTC)

Believe it or not - we have an article on the subject: Religiosity and intelligence - broadly speaking the percentage of religious people does go down with increasing intelligence - more or less independently of how "intelligence" is defined. (eg IQ or educational achievement or job title) - however, almost every statistical test you apply comes out like a bell-curve - so it's no surprise that even in people with the highest IQ - there are a few who buck the trend. Mensa's requirements for entry really aren't that great - and it's rather well established that you can pass their test even if your initial IQ is too low simply by practicing a lot. Since practicing IQ tests doesn't really shake your religious beliefs to their very core - we may conclude that this is all very unsurprising. IQ tests really only measure how good you are at IQ tests. Some very smart people (Einstein comes to mind) are very incapable at getting through their daily lives - a narrow intelligence is a very different thing from a broad one. However, it is still mostly true to say that in general...statistically speaking...smart people are less likely to believe in God. There is a reason for that. SteveBaker (talk) 18:57, 8 January 2009 (UTC)

There is a lot of discussion about Pascal's wager here. This needs to be shot down in flames. It suffers from what I'm now going to be calling "The Pink Aardvark Gambit". I have decided to believe that giant Pink Aardvarks with terrifying levels of technology are ruling the universe and if you don't pray to them every day (using telepathic thought projection) - they do horrible things to you after you're dead. It's a new religion - I just made it up. I have no evidence for it - but a part of it is that all believers have to send $10 to the Wikimedia foundation in order to supplicate the holy Aardvarks. You seem skeptical...

But if I merely apply Pascal's wager - magically, it's all true. If there are no Pink Aardvarks, it costs you almost nothing to pray to them redundantly - if there are then it's going to save you an infinite amount of torment in the after-life. Multiply the probability of their existance by the cost of praying to them and the result is non-zero - multiply the cost of torment for a day by an infinite number of days and the result is infinite.

...and with a brief *POP* of logic - everyone must now believe in my Aardvarks. So are all you religious nuts now believing in Aardvarks? No? What happened to this claim that Pascals Wager is worth a damn? You guys seem to have changed your mind.

The problem is that the wager assumes you are betting only on one very special thing (the existance of a very specific Christian deity). But a mathematician isn't going to let you get away with that. You have to apply a rule like that to everything to which it's relevant. So my Pink Aardvarks, the Invisible Pink Unicorn the Flying Spaghetti Monster, ever OTHER religion on the planet - and every conceivable concept like that - including a bunch we haven't thought of yet. When you do that, you multiply the 'cost of believing' number by the number of things you might have to believe in. Now, the wager doesn't look so good. You have an infinite personal belief "cost" balanced against an infinite "penalty" if any one of those things might happen to be true. So Pascal's wager says that you either need to spend 100% of your existance in a dedicated effort to believe and supplicate every concievable crazy religion - or you've got to say "screw it" and get on with your life without god or gods or unfalsifiable beliefs of ANY kind. Rational people take the latter - stupid people go and ask a priest who doesn't know much math and is perfectly prepared to lie to you in order to keep his job.

SteveBaker (talk) 19:22, 8 January 2009 (UTC)

Hey, that's pretty good. Can you get that published by a reliable source so we can include it in the Pascal's Wager article. 216.239.234.196 (talk) 20:21, 8 January 2009 (UTC)

I don't have a cite off hand, but I believe that Pascal had previous, less famous, proofs that the christian god was the only possible god that offers infinite bliss. (And in a wager of this sort, infinite bliss trumps all other forms of reward.) If you accepted that, Pascal's wager would suddenly seem a lot more attractive.

In any case it's a good answer to the original question. He was clearly an intelligent person who believed in god. APL (talk) 21:07, 8 January 2009 (UTC)

Tribes and nations everywhere on earth have always had some sort of god or gods. There has been only a very few exceptions. These exceptions were in tribes that had a very low level of general civilization – they lived little better than animals and ignored inner religious promptings. However, as the human race evolved from an earlier type of anthropoid, it developed a dim understanding or feeling that there is a higher being or beings. It could be called a hunch. But it was a powerful hunch that appeared in all parts of the world before there was contact between the people in different places. From that hunch, specific gods were created. There was also a desire to relate to these gods by worship. Most early religions were terror religions which inspired fear. In ancient Egypt, for instance, the gods took the form of grotesque animals which could not be regarded with any feeling of worshipful friendship or personal closeness. But as time went by, there seems to have been a sort of evolutionary development in religious understanding. Religious views that seemed more suitable, more true, were adopted. The multiple gods were replaced with a single god. The concept developed that this one god was a beneficent god. Furthermore, this god was not just beneficent toward human beings, he also wanted humans to be good to each other. ("Love ye one another.") In some cases, rather than a religion developing gradually, it was abandoned when a more suitable religion was introduced by missionaries or conquerors. This happened with Christianity and Islam. In a further evolutionary development, Christianity abandoned the concept of Hell and damnation by ignoring those concepts. The evolution of religious understanding may be likened to a lesser concept – the development of typography. Many forms of typeface have been designed, and there was the question of which was easiest to read. Tests were made in which people were given texts in various typefaces and asked which was easier to read. The readers' opinions varied somewhat, but the general consensus was that Times New Roman, and some fonts very similar to it, were the best typeface for ease of reading. So it has been with religion. Down through the ages, countless millions of people have considered religion. Most of these persons simply accepted what they had been taught. But there were a few persons who developed new major or minor viewpoints on religion. Their views were considered by others, and were either adopted as being better, or discarded as being useless, harmful, or wrong. (Fundamentalists rejected all change. Thus, they do not allow religious evolution.) Abandoning the concept of Hell is an example of a major evolutionary development that has, in effect been adopted. Thus, while there is no proof that God exists, the concept of the evolutionary development of religion offers intelligent persons a way to accept a current interpretation and manifestation of the near-universal hunch that God does exist. – GlowWorm —Preceding unsigned comment added by 174.130.253.174 (talk) 20:47, 8 January 2009 (UTC)

A shorthand for what you are saying is that religion is a 'meme' - an idea that spreads itself much like a gene does. Memes reproduce (for example when I tell you a joke and you tell the joke to someone else) - and they evolve (someone tweaks the wording of the joke to make it a bit funnier - or changes "polish guy" to "irish guy" to better fit the times). In short, they work just like genes do. Things like "money" and "rock music" are memes - and so is religion. Thinking of it like that is instructive because it lets us consider analogies. Successful memes outlast unsuccessful ones. But note that a meme doesn't have to be a truth in order to be popular - it just has to be something that someone will tell someone else. Hence we get all sorts of Internet memes that turn out to be hoaxes - but if they are funny or amazing they become more popular than truth and they are VERY tough to kill.

The reason (I believe) that religion has shown up in so many cultures - possibly by "parallel evolution" - is that they have acquire power. If someone in a primitive atheistic village gets the idea that because an Aardvark stole his shoe - and that year his crops did better than his neighbour that maybe if he leaves a shoe next to the anthill then maybe his crops will do better the following year. He does this and there is maybe a 50/50 chance that it works. If it DOES work - then he'll tell everyone else and they'll all do it. If the crops are good the following year (again, by chance) then everyone believes that this guy has found the answer to why crops mysteriously fail sometimes. But he's a clever guy and he realises that he can make a killing here. He says "Well, actually - the Aardvark spoke to me and said that I'm the chosen one and I have to deliver the shoes to the anthill every month."...now you have a high-priest - his power will grow he can give up farming - when people's crops fail despite the offering of shoes to the Aardvark he makes up excuses ("Oh - did you forget to turn around three times before you came to me with the shoe?") large books will be written about the precise protocol - acolytes will flock to him because they have the possibility to sit around in the big comfy temple without working. Before you know it - it's everywhere and they own their own cable TV channel and have people with Aardvark badges on their lapels demanding donations outside shopping malls throughout the holy month of March. The fact that the meme builds itself from a series of coincidences is enough to ensure that sooner or later every civilisation is going to get infected by one. The very process of evolution is (ironically) what polishes and perfects the meme over the generations. Meme's that attract followers and money and respect grow in popularity - religions that are a pain to deal with fizzle out. Natural selection at work.

SteveBaker (talk) 21:56, 8 January 2009 (UTC)

lysdexia's first assertion that everything can be described by maths and logic is false. Gödel's incompleteness theorems. At the first hurdle! —Preceding unsigned comment added by 92.16.196.156 (talk) 00:22, 9 January 2009 (UTC)

Be REALLY careful around Godel's theorem. It's a bomb that'll take off your head if you aren't careful with it! It DOES NOT SAY that math and logic don't work or that they don't have descriptive power. It says that there exist some theorems that can neither be proved nor disproved. No all theorems - not even most theorems..."some". It also doesn't say that mathematics somehow "goes wrong" and produces the "wrong answers". What happens is that there are circumstances where math doesn't have an answer - not that an incorrect answer is produced. But Godel's work has to be taken alongside such things as the Church-Turing hypothesis which asserts the equivalence of essentially all logical systems. Godels theorem actually says that ANY system of thought that has enough power to describe things in a reasonably powerful manner will suffer the exact same problems. That means that your brain can't solve these problems in ANY manner - the things that Godel says can't be proven by math can't be solved by other means either. SteveBaker (talk) 05:38, 9 January 2009 (UTC)

I am aware of the meaning of Gödels theorems. I didn't say it produce false results, just that not everything can be described by maths, or that with a mathematical system that does describe everything, you cannot prove that it is consistent. Either way you can never have a complete proven description of the universe; and something that is assumed is only as good as the basis on which it was assumed. —Preceding unsigned comment added by 92.16.196.156 (talk) 19:41, 9 January 2009 (UTC)

This is a rather extreme version of the "God of the Gaps" problem. Gods are supposed to be omnipotent - it's really the defining feature of the mythologies - the Christian religion will not allow ANY limitations to be imposed on their God's powers. This blows the 'incompleteness' thing out of the water because what you propose is a god that can only remain hidden by being restricted to things that the Godel theorem says that we can't prove. Since there are an AWFUL lot of things that math can prove, that results in a God who is only free to act in the most narrowly defined ways imaginable! So, while you're right in saying that there are possible versions of supernatural thought that math cannot dismiss - that doesn't include any of the world's major religions. Hence your point is only of very restricted value in this debate. SteveBaker (talk) 20:03, 9 January 2009 (UTC)

The Abrahamic god is omnipotent, and that's a defining feature, but I don't think the Norse, Greek or Roman gods are - they have conflicts with each other and there are even stories of humans tricking the gods. --Tango (talk) 00:47, 10 January 2009 (UTC)

To respond to stevebaker; A god is not restricted by mathematics, as many deists believe that mathematics and the like have descriptive but not governing power. Usual arguments assert that mathematics is a construct of human ingenuity and was created to describe; but has no meaning in the actual universe. And also that logic and maths are only true within the universe, not outside of it, where god exists. And so any arguments against god from mathematics are almost irrelevant. From the point of view of a scientist, this often appears to be a cop out, and evasive to the issue; but importantly, it does not make any assertions that that can be disproved, or even logically argued against. 92.16.196.156 (talk) 19:19, 10 January 2009 (UTC)

Maths doesn't describe the universe, that's science's job. You need to combine mathematical theorems with a mathematical model in order to find out anything about the universe, and models are the realm of science. --Tango (talk) 00:47, 10 January 2009 (UTC)

Pedantry. —Preceding unsigned comment added by 92.16.196.156 (talk) 19:22, 10 January 2009 (UTC)

False dichotomy

See the work of the late Harvard University evolutionary biologist Stephen Jay Gould, especially Rocks of Ages. Saying that having a strong background and understanding of science and mathematics, or even of being "intelligent", is somehow mutually exclusive is a false dichotomy. Its like saying "You cannot like apple pie and drive a motorcycle". Science and religion do not have to serve the same purpose in a person's life. It is entirely reasonable, for example, to fully understand and accept the tenets of evolution, cosmogonic physics, and every single commonly accpeted scientific fact, and yet science for many people does not answer the questions of purpose and being and the entire field of Ontology. Science explains the mechanistic aspects of the world quite well, but it does not answer the questions such as "Why are we here?" Even if the answer to that question for you is "There is absolutely no reason at all.", science cannot even begin to answer that question. There are many people for whom the answers to those questions are different than that.

Look at it another way. I can take apart a beautiful and intricately made watch. I can understand fully how the watch is made, I can study and understand every part and every working and movement of the watch, take it apart, put it together again, etc. etc. Such understanding of the workings of the watch, however, in no way proves that the watchmaker does not exist, or that the watch arose spontaneously. Understanding the details of creation to the most exacting detail does not disprove the creator. Neither does it prove the creator. You must arrive at your belief in a creator, or in a belief in a spontaneous universe, entirely by faith. Having a different focus of that faith (either in God or in his non-existance) is in no way connected to intelligence or scientific understanding, or anything else except your own personal faith. --Jayron32.talk.contribs 00:52, 9 January 2009 (UTC)

I don't see a dichotomy here at all. What you are talking about is the concept of non-overlapping magisteria. One problem with this is that many religions do make claims about the physical universe, and thus the different realms of science and religion do overlap in practice. --Stephan Schulz (talk) 01:01, 9 January 2009 (UTC)

Science can answer the question "why are we here?" - because of the chain of events which happened before we were here, so many that I don't know them all and can only pick a few, very obvious ones out out: the big bang, the creation of our solar system, abiogenesis, very probably the Cretaceous–Tertiary extinction event and a whole lot of mutations along the way. As for the claim of false dichotomy... Say we have two neuroscientists, who happened to be part of the 15-man sample of this study. These two neuroscientists often argue about the existence of God and religion, spirituality, etc. After taking part of the study, it is found that the one who is for God/religion/etc has low 5-HT_1A binding potential (implying a low number of 5-HT_1A receptors) and the one who is against God/religion/etc has high 5-HT_1A binding potential (implying a high number of 5-HT_1A receptors). This relationship between spirituality and 5-HT_1A binding potential (especially in the raphe nuclei) is also found in the other participants. Although no cause-and-effect is shown here, shouldn't the spiritual neuroscientist ask the question: "Why will my colleague (the non-spiritual neuroscientst) go to hell for having a higher expression of 5-HT_1A receptors?". This is where the intelligent spiritual person has to start asking some questions about his faith. --Mark PEA (talk) 21:36, 9 January 2009 (UTC)

Or one could say that the increase in 5-HT_1A receptors is a biochemical response in the brain to having a higher faith; that is that having an internal spiritual life has measureable phisiological effect on the body. Thus, your friend will go to heaven because he has a belief in God; and the 5-HT_1A receptor activity is merely a side-effect of that faith. --Jayron32.talk.contribs 03:26, 10 January 2009 (UTC)

Okay, I made a bad point because correlation doesn't show causation. Coincidently or not somebody earlier said that people tend to get more religious as they get older (causing scrutinizing replies about validity of such studies), and this study shows that 5-HT_1A binding potential declines with age. Throwing a spanner into the works would be to start discussing 5-HT_1A agonists such as LSD, psilocin, etc. These compounds are termed entheogens as they can induce spiritual experiences in users. Of course they bind to a host of other receptors (5-HT_2A being the most well known) and this is why I say a spanner in the works as someone would have to do some research where a person is given LSD along with a 5-HT_1A antagonist to see if spiritual experiences are suppressed. Another problem is the functional selectivity of LSD/psilocin relative to 5-HT. I'm just covering all the bases here seeing as I doubt we can prove a causality between 5-HT_1A receptor expression and spirituality due to ethical and legal reasons (at least not for another 20 years or however long it takes for attitudes to change). --Mark PEA (talk) 14:34, 10 January 2009 (UTC)

However, the initial question did not ask about the tenets of a specific religion, or even about how a personal belief in religion which can work with an understanding of science. Rather, the question asked about a rather general belief in the existance of an intelligent creator, i.e. God. There is organized religion, and then there is personal religion. There is what has been written down and codified by people in the past, and then there is how people work the entire system into their own world view. My point is that it is not inconsistant to have a world view which both holds the existance of an intelligent creator (God) and which also fully understands the mechanisms of His creation. Any claims that these fields are somehow in conflict or mutually exclusive is themselves creating false conflict where there is none. A scientist who tells you that evolution and the big bang somehow proves there isn't a God (as opposed to disproving the literal explanation of creation in Genesis 1, which is entitely different) is committing the SAME falshood as a priest who tells you that if you believe in God, you must disbelieve evolution... --Jayron32.talk.contribs 13:15, 9 January 2009 (UTC)

Ignoring all this worthless bickering, here are some stats on Canadian MENSA religious beliefs compared to the general population. They seem to be less religious, but not to the degree that the AAAS is less religious (I can't find exact numbers but I remember them being very disproportionately non-religious.--droptone (talk) 13:30, 9 January 2009 (UTC)

The original question is flawed - "otherwise intelligent" and "know better." Whether you believe in/are discussing the divinity of a carpenter from Judea, or a Flying Spaghetti Monster, it's that Dawkins' own invisible, garage dwelling dragon is fundamentally unknowable. This is fundamentally a redress of the Prime Mover argument - which is "right?": the atheist construction of "before" is a non-sequitor as regards the Big Bang, or the theistic notion that His Noodly Appendage/the Word fait lux'd? It is, by definition, unknowable, so a person of any conceivable intelligence could hold any conceivable opinion on the subject. This is exactly the same as holding an opinion on the fate of Schrodenger's cat before the box is opened.

On to my OR synthesis of the trollbait, I think Greg Manique (sp)'s perspective on teaching economics is on point. I'm paraphrasing to paint in broad strokes, but generally college students tend towards "very liberal", and as they finish his course, they tend towards conservative (of course, given the starting point, it's difficult to go anywhere and not qualify it as such). At the risk of being misunderstood as insulting, I suggest a view which reflects opportunity cost and personal belief systems may be on point. It is "easy" to believe in a simple belief system which answers a lot of questions (let us say, the belief and questions of a child). It also becomes "easy" as one is educated to dispel both, and "difficult" to build a new, complicated belief system that holds together in the light of such education. That's not to assign right or wrong anywhere along the line - but where does God fit if the appearance of humaniform intelligence is stripped of its "miraculousness" and reduced to a set of equations which any schoolboy could solve? Well, it's a bit harder to fit God into the role of He who Determined The Constants Which Would Tidily Result In An Anthropomorphic Principle (heck, it's hard to even just formulate the question with that as an answer). As a consequent, you can move along the scale of education and find that the trend is reducing religiosity - it's a fundamental economic principle that the higher the cost, the less of a good is demanded. That said, Jesuits have always been my favorite example any time this subject comes up - I believe per capita they hold the most Ph.Ds (unsourced - if anyone has a source, I'd appreciate it, even a dispelling), and a fair share of those aren't just "theological studies" (which would be cheating from the perspective of this conversation) but rather, things like, oh, molecular biology. A degree which, for some definitions of intelligent, does sort of go hand in hand. (although correlation is not causation)

For what it's worth, I believe in God, and I would emphasize the word believe. I don't know there is a God. That would be what my intelligence directs me to state - what with that bizarre top 0.001% percentile IQ of mine. But I'd agree that dogmatism for its own sake is irreconcilable with intelligence, and there's a pretty good trend of historic elder statesmen of science lapsing into dogmatism (versus religion) being a sure sign of their having "lost touch." 98.169.163.20 (talk) 00:41, 10 January 2009 (UTC)

What IQ test was it that said you were in the top 0.001th percentile? Few if any IQ tests are accurate at such high levels due to the lack of a sufficient sample size to test them on, such high IQ's need to be measured specially by an expert. --Tango (talk) 03:42, 10 January 2009 (UTC)

Ayup, belief in god and intelligence aren't mutually exclusive. I'd qualify for mensa (or at least I would have when I took the IQ test... my gray matter may have declined a bit in the intervening decades), and if you ask me, I'll say yes, I believe in god. It depends on the meaning of "god" and "belief" though: most conservative christians wouldn't deem my particular belief to be a belief in god (in fact, many of them don't consider my sect (Quaker) to be christian at all. It's not an intelligence issue though: It wouldn't surprise me in the least if Osama bin Laden had a very high IQ. --SB_Johnny | 15:34, 11 January 2009 (UTC)

Umm...

Guys, I'm pretty sure here is not the appropriate place to have this discussion. Can you take this somewhere else? I think we all know nobody is going to 'win'. Cheers, --Joe_Work 04:41, 13 January 2009 (UTC)

Solar power for a house

My south facing house has an area of about 500 square feet of available space for solar panels. If I were to maximize the available area with soalr panels, what could I expect to "power" in my house? Undoubtedly, there are many variables, but I am wondering in general. Just my lights? Maybe lights and electronics? My hopes are too high? —Preceding unsigned comment added by 209.161.223.61 (talk) 15:43, 8 January 2009 (UTC)

What latitude do you live at and what is the weather like? And what time of year are you considering? Those are the key variables, I think, and they will make a massive difference. Under poor conditions, you'll get next to nothing, under good conditions you may be able to get several kilowatts, maybe even more, that will certainly power your lights. However, you would need batteries to store the energy until you need it (powering lights directly by solar power is rather pointless!), so power isn't the best measure, we need to look at total energy. If you're getting around 20 kilowatt-hours a day (which seems reasonable if you are somewhere pretty sunny and at a fairly low latitude), and you're pretty energy efficient, you might just about be able to power everything. You would need a connection to the national grid to make up the shortfall during winter or a few days of overcast (you can only have so many batteries), and also to sell any excess. (Note, these are all back of the envelope calculations with extremely approximate assumptions, but my conclusion is that, depending on where you live, you may well be able to make a significant contribution to your energy needs with 500 sq ft of solar panels. If you want something more precise than that, it will take more research and would require knowledge of your location.) --Tango (talk) 16:15, 8 January 2009 (UTC)

Also, consider to set aside something for a solar hot water and possibly heating system. These are typically better value for money and a more efficient use of solar power than solar electric systems. --Stephan Schulz (talk) 16:20, 8 January 2009 (UTC)

Thanks for the feedback. I live near Toronto, Ontario, Canada. I know that there are a lot of variables so would need to consult with a professional company to get an accurate measure. I wanted to get a general sense of things (which I now have!) —Preceding unsigned comment added by 69.77.185.91 (talk) 17:40, 8 January 2009 (UTC)

One major thing when you don't have that much strong sunlight is to try to get the solar panels to be as close to being at right angles to the sun's rays as possible for as much of the day as possible. As far North as Ontario, the sun is low enough in the sky that putting the panels on a vertical wall might make more sense than on a flat or sloping roof - a simple rule of thumb is that the amount of light you get varies as the cosine of the angle between the sun's rays and the direction the panel is pointing. If you are investing in a lot of panels, its worth considering some motor-driven means to track the sun across the sky. Everything moves very slowly so the motor can be geared down fairly dramatically and your motor can be small and energy efficient. SteveBaker (talk) 18:47, 8 January 2009 (UTC)

The earth's surface receives ~1 kW / m^2 in direct sunlight. If your system is say 15% efficient you could get as much 7500 W from 500 sq. ft. if the sun was directly above your installation (with no clouds or other impediments). The average 3 person American household uses a time averaged 400-700 W of electricity, so your peak production should be way more than you need for the entire house. Once you add in other factors (e.g. nightfall, cloudiness, latitude, etc.) your average power generation from solar would be much less than your peak possible, but with 500 sq ft of panels there is still a good chance you would make more electricity on average than your home can consume. If you are serious about pursuing this, you can get solar power companies to evaluate your location and give you a more rigorous estimate of what to expect. Dragons flight (talk) 21:42, 8 January 2009 (UTC)

You know, many people around the world are either using clean technology to power their homes and live off the grid, or for internal heating. Solar, wind, and corn are just some examples. There's also a store in Toronto called EfstonScience which is a passive solar building that uses solar for internal heating. The GTA doesn't get much sun in the winter, though, especially considering it's often cloudy (although sometimes it does snow under a clear sky). You need a way to store your power so it can be used later and at night. If you can make enough power, I believe there's also a way you can "sell" your power to the grid and earn money doing it. ~AH1 23:44, 8 January 2009 (UTC)

Look up insolation. Dragons flight numbers above look OK. If its persistantly cloudy for more than a few days then your lifestyle will have to adapt. The panels still give at the worst about 1/20 power. A 5kW system with appropriate battery bank will definately give you lights, TV, computers 4 hours, stereo, fridge but no electrical heating (except electric blanket). Of course on sunny days (after batteries are filled up) you will have a massive surplus, to run airconditioners etc. I've never heard of a domestic house with such a large system. Also, the shading on the house will result in a much cooler house (good in summer). I actually live in a off-grid solar powered house (gas for cooking, wood for winter heating, very little airconditioning). About 2kW nominal. Batteries set up to go for about 4 cloudy days. Polypipe Wrangler (talk) 13:27, 11 January 2009 (UTC)

Temperature at which Magnesium ignites

At what temperature would a piece of magnesium ignite in air? (Magnesium says molten magnesium is highly flammable and gives the melting point of magnesium, but doesn't say it has to molten to ignite and doesn't say melting is sufficient.) RJFJR (talk) 16:17, 8 January 2009 (UTC)

No idea if this is what you're looking for, but Magnesium is listed at Autoignition_temperature#Autoignition_point_of_selected_substances. It's way below the melting point so I guess you have to melt it in partial vacuum to keep it from burning. Pez00 (talk) 18:20, 8 January 2009 (UTC)

Or, more easily, under an inert gas atmosphere, either a noble gas, or possibly something as cheap and abundant as Nitrogen. --Stephan Schulz (talk) 18:46, 8 January 2009 (UTC)

Not nitrogen--most active metals react with it and some even have specific warning labels about not using nitrogen atmosphere. See Magnesium nitride. DMacks (talk) 19:38, 8 January 2009 (UTC)

Thank you. That's what I was looking for but didn't know what to call that temperature. RJFJR (talk) 20:39, 8 January 2009 (UTC)

Colorlessness of a solution

I want to quantified how 'colored' a solution is, without regard to wavelength (within the visible range). The idea is that I am formulating a product for which the ideal is colorlessness; I'd like to be able to quantify how far from this ideal various versions of the product are, but ignoring that one might be a little green, and another might be a little red, etc.

The only idea I've had so far was to use a spectrophotometer to scan the entire visible range and integrate the area beneath the transmittance curve, and subtract this from the value that you'd get from 100% transmittance at all wavelengths. I'm afraid this is probably a little naive. Can you suggest a better way? I think I also have access to meters for getting Lab color space values, if that would be better. ike9898 (talk) 19:06, 8 January 2009 (UTC)

That will work, but you may have to correct for the visible range (if ambient light isn't equally intense across the spectrum, your result may get skewed by a strong absorbance at a wavelength that doesn't matter much practically. How about a white light (or a lightbulb, or something else corresponding to "what looks like broad-spectrum visible") and a similarly broad-spectrum (non-monochromator or filtered) PMT/photocell/photoresistor/etc? Still need to correct for visible-range, but at least you're starting with ambient-light spectral characteristics. You don't need the accuracy (I don't think?) of X decimal places at each wavelength, just the overall transmittance. DMacks (talk) 19:36, 8 January 2009 (UTC)

Any one have any more input? I'd like my method to be reasonably defensible when put into a paper. ike9898 (talk) 22:05, 8 January 2009 (UTC)

Do you want it to be colourless or transparent? They are different things. You seem to be describing transparency. --Tango (talk) 23:58, 8 January 2009 (UTC)

An important article dealing with this is the Beer–Lambert law, which describes the relationship between the intensity of a color in a solution to the properties of that solution. --Jayron32.talk.contribs 00:34, 9 January 2009 (UTC)

If you do choose to integrate over wavelengths, you should probably weigh the integration using the photopic Luminosity function. If the "application" of the transparency is not related to human vision (eg. it is for a light sensor), then the sensor's spectral response curve would be an appropriate weighing function. Weighing ensures that you don't have to pick arbitrary limits for what constitutes visible light - the weighing function will smoothly roll off into the limits of human/sensor vision. From an experimental standpoint, try to obtain the highest possible concentrations of your solutions, because measuring very small Absorbance is generally hard (unless you have good equipment). Someone42 (talk) 10:43, 9 January 2009 (UTC)

Yeah, for this application I'm really concerned with color as perceived by humans. With regard to measuring absorbance, I've always been warned that I is hard to get an accurate reading for solutions that are too concentrated (A>1.2). ike9898 (talk) 20:46, 9 January 2009 (UTC)

knotty problem

regarding entanglement on the quantum level, is there a limit to how many things can be entangled with each other? 86.155.28.235 (talk) 19:34, 8 January 2009 (UTC)

Not as far as the theory is concerned and not as far as anyone knows, but there is a limit on the extent to which entanglement has been tested. Quantum algorithms depend on entangled states more complicated than any that have been created experimentally so far, and one of the reasons for trying to build big quantum computers is as an experiment in basic physics, to see if the world can actually sustain that level of entanglement. -- BenRG (talk) 20:26, 8 January 2009 (UTC)

It is very likely that most of reality is entangled with itself, as all the particles now in existence have interacted with each other in the past. Graeme Bartlett (talk) 20:31, 8 January 2009 (UTC)

what would be the consequences of this? 86.155.28.235 (talk) 23:11, 8 January 2009 (UTC)

You could expect that any measurement made will affect the potential results from any other measurement, but in unknown ways. For example if you measure the speed of a particle it will affect the results of a speed measurement of another particle that collided with it in the past, or collided with a particle that it collided with earlier etc. I am sure there will be many more consequences, physical and philosophical that I am not aware of yet. Graeme Bartlett (talk) 01:20, 9 January 2009 (UTC)

This doesn't sound right to me. Entanglement is not one measurement affecting another (ignore the popular books claiming it is), it's just a statistical correlation that's stronger than is classically possible. We don't see such super-classical correlations in the world at large, only in carefully isolated systems (because of quantum decoherence). Different parts of the universe are similar in a way that suggests former interaction (e.g. the CMB is uniform), but that's classical correlation at most, and it's problematic to even call it that since you need multiple trials to establish a correlation and we've only got one universe. -- BenRG (talk) 06:55, 9 January 2009 (UTC)

A more used term is universal entanglement. This results in decoherence and is on way to explain how macroscopic reality is so different to the quantum experience. Graeme Bartlett (talk) 05:38, 9 January 2009 (UTC)

If the sun went out...

Assume the sun either disappears somehow or stops giving off all forms of radiation right now. If this happened(I realize there's hardly any way it could, but this is a hypothetical question) how long would it take for Earth to become uninhabitably cold? How long would it take for Earth to cool down to absolute zero? 69.224.37.48 (talk) 19:46, 8 January 2009 (UTC)

It is doubtful that earth will cool to absolute zero as a result of the sun disappearing, even space isn’t that cold.--Apollonius 1236 (talk) 00:52, 10 January 2009 (UTC)

Uninhabitably? Difficult to say. Depending on the lengths to which humans are willing to go, it could take quite a while. Geothermal energy will continue to be useful for billions of years, most likely. That said, I'd guess that surface temperatures would plummet below freezing within a week (consider that temperature drops of 10-15°C overnight are common). For absolute zero, not until the heat death of the universe. Thanks to the cosmic background radiation, temperatures bottom out at about 3 Kelvin or so. — Lomn 19:52, 8 January 2009 (UTC)

We could probably support a small number of humans using geothermal energy (the remaining fossil fuels and tidal energy will also help), but given that all life outside of specially constructed biospheres would be dead it would be difficult to support a large number of humans - we would need to support an entire ecosystem as well to oxygenate the air and to provide food. I'm not sure how long we could support them for, though - as the Earth cools down the energy required to heat the biosphere increases and I'm not sure how cold the Earth would get and how quickly (uninhabitable without technological assistance within a year, certainly, since crops would all fail, but more than that, I don't know). --Tango (talk) 21:33, 8 January 2009 (UTC)

Land and air gets cold a lot faster than oceans because the mixing in the surface layers mean you have to remove heat from a substantial volume of water. In a previous reference desk thread it was estimated that it could take months for the tropical ocean to start freezing if you assume a typical 50 m mixed layer. Dragons flight (talk) 21:58, 8 January 2009 (UTC)

I don't feel like searching for that discussion (which I don't recall, so it may have been before my time), but I can try and repeat it (standard disclaimers about back of the envelope calculations apply). According to insolation (assuming I'm reading it correctly), a square metre of tropical ocean would receive an average of 250W from the Sun. Since the ocean doesn't change temperature much, we can assume it is losing that much too and would continue to do so if the sun went out (at first, anyway). For a 50m mixed layer, we need to cool 50m of water. The specific heat capacity of water is about 4 J cm K. Let's say the water starts off at 25C. That means we need to remove 4*25*50*1,000,000=5,000,000,000J. At 250W, that would take 20,000,000 seconds, or nearly 8 months. And that's just for it to start freezing, it would take longer for it to completely freeze. That's all very approximate, though. --Tango (talk) 23:41, 8 January 2009 (UTC)

I don't think the water would have time to mix in this 50 m layer, as the top would freeze too quickly, at such low atmospheric temps. And the important factor is when the surface of the oceans freeze over, as that's when they cease to provide significant heat and moisture to the atmosphere. This would happen far sooner than when the ocean freezes solid. Since temps drop at night by about 2°F per hour, that would mean a 48°F per day drop in the absence of sunlight, at least at first, as it would drop off more slowly when it became really cold. So, after a couple days, the air temps will have dropped by about 100°F, which should cause the ocean's surface to freeze over in a few more days. This means that it would become too cold to survive in an unheated house, even in an island at the equator, in a few days. Even a heated house would likely lose so much heat through the walls that it would become unlivable shortly thereafter. Also, at those temps contraction and brittleness may cause houses to split in half. StuRat (talk) 18:15, 9 January 2009 (UTC)

I don't think it would drop to absolute zero, since the Earth has internal heat. Maybe geothermal heating could work for a while. ~AH1 23:32, 8 January 2009 (UTC)

As Lomn said, it wouldn't drop to absolute zero due to the CMB, geothermal would keep it well above even that 3K for billions of years, though. It would still be far too cold on the surface to support life as we know it pretty quickly (although the lack of light may be more deadly than the lack of heat). --Tango (talk) 23:56, 8 January 2009 (UTC)

The current geothermal heat flux of ~50 mW/m^2 would keep the surface at 30K if treated as a black body. Dragons flight (talk) 00:23, 9 January 2009 (UTC)

The other thing, and it has nothing to do with the Earth's internal heat, is that it will never drop to absolute zero (which is an asymptotic condition anyways) because the entire universe has an ambient temperature of roughly 2.725 K; so that is the theoretical lowest temperature that the earth could reach. In practical terms, the final temperature of the universe (and thus the lowest temperature the earth will reach) at the end of time will likely be higher than this, as the warmer parts of the universe will be slightly heating up the colder parts over time as well, so when the entire system equilibrates, it will fractionally higher... --Jayron32.talk.contribs 00:31, 9 January 2009 (UTC)

But the universe expands, which causes the CMB to red-shift over time, i.e. the energy density goes towards zero. Surprisingly, the time the Earth would need to cool down is quite long, even on a cosmological scale. I think we discussed this before. --Stephan Schulz (talk) 00:41, 9 January 2009 (UTC)

2.7 K is the current CMB temperature; it declines as the universe expands. In the limit of a flat universe, the CMB temperature (along with everything else) asymptotes to zero K. See also: Heat death of the universe. Dragons flight (talk) 00:40, 9 January 2009 (UTC)

Great minds... ;-). Does anybody else have the feeling that edit conflicts are now very often resolved automatically? DF's answer was not there when I started editing, and I got no conflict, either. --Stephan Schulz (talk) 00:44, 9 January 2009 (UTC)

Yes, I've noticed a lot of messages getting posted at almost the same time in the wrong order, which seems to be due to automatic resolution of edit conflicts. --Tango (talk) 00:47, 9 January 2009 (UTC)

As an engineer and a musician of sorts, I find the projected heat death of the universe depressing. If there is to be no practically exploitable difference of potential, and the universe is just a uniform, flat, cold, mucky bog at 3 K (or 2.7 K, or whatever K), no useful work could be done and there would be no need of engines or power transmission or power conversion. Thus there would be no need for engineers, even if life of some form existed. There might be a need for poets, or composers, to write dirges for what had once been, but there would be no means of performance. Edison (talk) 05:34, 9 January 2009 (UTC)

Thinking requires energy, so there can't even be poets. --Tango (talk) 12:41, 9 January 2009 (UTC)

I'm fairly sure I've explained this before - but WTH. Advanced future civilisations will be able to transfer their minds into computers. Surviving the heat death of the universe is then a matter of gradually reducing the clock rate on those computers such that enough energy can be accumulated for a single thought from the increasingly microscopic temperature variations as we head towards 3 kelvins. Since the universe merely asymptotes towards a situation of zero available energy, those beings will start to require exponentially more time between thoughts - but with everything slowing down like that, this would be a positive advantage because they would be in perpetual 'fast forward' - with time rushing on at an ever increasing pace. I believe this allows a sufficiently advanced civilisation to continue to live their lives for as long as they can stand the boredom. SteveBaker (talk) 19:54, 9 January 2009 (UTC)

I think it depends on how quickly the temperature approaches zero - if the time between clock cycles is forced to increase quickly enough then there would only be enough time for a finite number in an infinite amount of time. At a guess, I'd say it depends on whether the integral of temperature over time from now to infinity converges or not. --Tango (talk) 00:55, 10 January 2009 (UTC)

Alcohol

Disclaimer: this is NOT asking for medical advice - merely trying to find the answer to an argument!

During a conversation the other day, the subject came up about a man who has given up beer and started drinking vodka instead - as vodka is apparantly less fattening. I thought the man was being quite ingenious in trying to lose weight as the fattening effects of beer are well known (hence the term "beer belly!") but my friend said it wasn't as apparantly spirits are much worse for the liver than beer. I argued that this was not the case as provided he drink the same number of units of alcohol, the effect on the liver would be no different...so here's the question.

1. Is say 8 units of alcohol drunk as vodka (about 200ml I think) any worse for the liver than 8 units of alcohol drunk as beer (about 4 pints of standard 4% ABV beer)? Obviously there are other factors at play that would affect how the alcohol is absorbed, such as the individual's body and how much they've eaten etc but assuming all other factors are the same?

2. Would the guy in question actually lose any weight by substituting beer for vodka? OK, silly question as obviously the answer would be no if (as I suspect in this case) said guy did little excercise and ate loads of junk food but if it was just the beer that was making him fat, would this actually work? I've never heard of that method of losing weight before. Beer presumably has loads of carbohydrates in it therefore loads of calories but I presume vodka would too? Alcohol is made from sugar isn't it and sugar is a form of carb?

Answers on a postcard (oh OK then, on here) please to settle this question! —Preceding unsigned comment added by 78.33.180.73 (talk) 19:59, 8 January 2009 (UTC)

I think one factor to consider is the effect of drinking large quantities of liquid on the muscles keeping the stomach in place: usually they become stretched to cope with this volume and that's what gives men the "beer belly", not the deposition of extra fat round the middle. So if you switch to vodka, as long as you're not diluting it with a pint of lemonade or coke, the volume will be less and the stomach muscles will not need to stretch in order to cope. Of course, your mate will then need to do exercises to tighten his stomach muscles and get rid of the beer belly. No gain without pain as they say. --TammyMoet (talk) 20:07, 8 January 2009 (UTC)

Are you drinking the vodka straight or mixing it with orange juice or something? If the latter, keep in mind that those add calories to the drinks. 216.239.234.196 (talk) 20:16, 8 January 2009 (UTC)

Vodka does have fewer calories per serving than beer. And, you will lose weight any time you're using more calories than you're taking in. So, a reduction in your caloric intake is good for losing weight, as is increasing the calories you burn. The calories in vodka (and pretty much any liquor) is from alcohol, not carbs. Fermentation changes the sugars into alcohol- after that, it's not sugar anymore. There would be sugar left over that did not ferment, but in a distilled beverage this sugar is not in the end result like it is with beer or wine. Friday (talk) 20:18, 8 January 2009 (UTC)

Be careful. According to this, there are 30 calories in 100 ml of beer and 222 calories in 100 ml of vodka (at 40%, which is slightly lower than what I'm used to). So even if a serving of beer comparable to 100 ml vodka is 700 ml, there would still be more calories in the vodka excluding the mix. And according to this, one gram of alcohol has more calories than one gram of carbohydrates. Here's another comparison. Zain Ebrahim (talk) 20:47, 8 January 2009 (UTC)

It says 55 calories in a shot of vodka. Compare with 100 or so calories for even a very light beer. There are no carbs in (normal) liquor, so liquor is the winner if you're looking to maximize alcohol content and minimize calories. Friday (talk) 20:51, 8 January 2009 (UTC)

Even for a pretty light beer, a pint is worth about 2 shots of a spirit alcohol wise. Assuming Zain's figures are correct, 570ml (about one UK pint) of beer would be 171 kcal. 1ml of alcohol in vodka would require 2.5ml of vodka, which would be 5.55 kcal. For the beer to have a calorie to alcohol ratio of 5.55kcal/ml it would need an alcohol content of 5.4%, which is a pretty strong beer. So, assuming the 30kcal figure holds for all beers (the source actually says 30kcal is for stout, bitter is 32 and lager 40), most beers are slightly worse than vodka in terms of calories per unit of alcohol, but strong ones are pretty similar. If you do switch from beer to vodka, though, you need to make sure you drink more water, since you aren't getting the water from the beer. --Tango (talk) 21:59, 8 January 2009 (UTC)

Water from the beer?? lol.. Beer is a diuretic, it makes you pee more then you drink, the resulting dehydration is one of the main causes of hangover.Vespine (talk) 05:24, 9 January 2009 (UTC)

No, that's wrong. In medieval times, small beer often was the staple drink for people, as water was likely contaminated. It's quite hard to get a hangover from normal beer alone, simply because it's 95% water - and this is also the main reason why it makes you pee. --Stephan Schulz (talk) 08:24, 9 January 2009 (UTC)

The ~5% of alcohol in the beer will still increase your frequency of urination, so the water in the beer isn't the only reason for peeing. If you go to the pub and drink 4 pints of water in the space of 3 hours, you will urinate fairly often. If you drink 4 pints of beer, you will urinate more often. The best time to rehydrate yourself from alcohol induced dehydration is after alcohol's effects on vasopressin have worn off, so that your body isn't just getting rid of any water you intake whilst intoxicated. --Mark PEA (talk) 20:36, 9 January 2009 (UTC)

Yes, but we're not comparing beer to water, we're comparing beer to vodka. --Tango (talk) 00:56, 10 January 2009 (UTC)

What is it in beer that is a diuretic? Isn't it the alcohol? Drinking vodka will also make you pee more, but it doesn't have the advantage of including lots of water, so it dehydrates you more. --Tango (talk) 12:44, 9 January 2009 (UTC)

Alcohol blocks vasopressin release from the pituitary gland. Vasopressin is required to re-absorb water from urine. Axl ¤ 18:38, 12 January 2009 (UTC)

Child and Adolescent psychotherapist

Hello, I'm de:Benutzer:Widescreen from German WP. I'd like to know what kind of education and trainig Child and Adolescent psychotherapist got to have, to work in a Hospital or by there own. (excuse my bad english). In USA & GB please. Widescreen 20:08, 8 January 2009 (UTC)

In the UK, I don't think there are any restrictions on who can call themselves a "psychotherapist". I think anyone explicitly practising psychotherapy in a hospital would be a psychiatrist, which is a type of doctor and they have the same medical degree(s) as any other doctor (they just specialise in psychiatry after they qualify). --Tango (talk) 23:24, 8 January 2009 (UTC)

"Psychotherapist" is definitely a licensed profession in the US. Not to the same degree as "psychiatrist", which requires a medical degree, but the US has a variety of licensing standards for anyone who professes to "treat" or "diagnose" patients for specific psychological conditions. Dragons flight (talk) 00:29, 9 January 2009 (UTC)

Or, of course, you could be a psychologist, which requires a degree in psychology. There are psychologists working in hospitals. See here for a job description of a psychologist's role in the NHS in the UK. However, treatment, as implied by 'therapy', is limited to psychiatrists. Psychologists do the talking and counselling instead. At least this is how I think things work here. —Cyclonenim (talk · contribs · email) 23:40, 8 January 2009 (UTC)

Counselling sounds like a kind of treatment to me. Prescribing drugs is definitely restricted to psychiatrists, but beyond that, I'm not sure how it works. --Tango (talk) 23:44, 8 January 2009 (UTC)

In US, psychotherapy can be provided by psychiatrists, psychologists, counselors or social workers and their education, and the type of service they provide, will vary accordingly. See the Occupational Outlook Handbook pages I have linked to, for more details. Abecedare (talk) 00:11, 9 January 2009 (UTC)

If you are an psychiatrist, you can work with both, adults and childs in USA & GB? Theres no specialization needed in Child and Adolescence? If you are an psychologist or social worker you can work as an psychotherapist (adult and child) in Hospital and as an own offer in USA. In GB only psychiatrists. I've read for example Peter Fonagy (GB) is trained in child and adult psychoanalysis. Is this an privat amusement? Got this education effects on the status in the health system? What about other Schools of Therapy for example Cognitive behavioral therapy? Got they any training in child psychology or is this part of the clinical psychology education? Widescreen 09:02, 9 January 2009 (UTC)

In the UK there are basically two kinds of recognised professional working in this field. Psychiatrists are qualified as medical doctors and then also in psychiatry as their specialism, then in child psychiatry as a sub-specialism. The other kind of professional is a clinical psychologist who has a doctorate in clinical psychology (D.Clin.Psych.), a qualification that is equivalent in level to the PhD. These people would usually first have a first degree and perhaps also a master's degree in psychology and then would take their doctorate part-time while also training in the NHS. There are also postgraduate courses in clinical counselling. Itsmejudith (talk) 13:38, 9 January 2009 (UTC)

Ok, Thanks a lot. What about USA? Widescreen 18:35, 9 January 2009 (UTC)

What's the lowest point in Badlands national park?

Pleas place {{tb}} on my talk page when you have an awnser.--Ipatrol (talk) 22:03, 8 January 2009 (UTC)

As the lowest point in the park isn't particularly noteworthy (unlike in, say, Death Valley), it isn't listed there. I doubt if any source will list such info, for the same reason. A topographic map of the park could be used to determine the lowest point, but I can't find any which are available for free. So, I don't know the answer. (If you're British and leave a beer at that point, though, it will then be the lowest pint in the park. :-) )StuRat (talk) 19:32, 9 January 2009 (UTC)

If you can find a brit who'd leave a pint of beer behind after hiking through the badlands - that would certainly be a new low point. SteveBaker (talk) 19:45, 9 January 2009 (UTC)

Do you mean a topographic map? Algebraist 19:48, 9 January 2009 (UTC)

A quick scan over the park in Google Earth gives the impression that the lowest point would likely be between 2,300 and 2,400 feet. Elevations in this range can be found at the eastern end of the northern "finger" of the park projecting eastward. The lower elevations appear to lie along the park's boundaries. Here is a Google Maps style USGS map interface. Click the "Topo" button to get topographic maps. Zoom and pan, etc, to figure it out the hard way. Elevations appear to be shown in metres. Zooming in past a certain point brings up the higher resolution topos. There's probably a way to calculate it automatically with some kind of GIS like tool, but I can't think of how offhand. Pfly (talk) 07:57, 10 January 2009 (UTC)

Never mind, 2460 at sage creek. I had to look at something from the USGS on geopubs.com P.S. sorry for the typo :-)--Ipatrol (talk) 20:42, 12 January 2009 (UTC)

January 9

Do we know if egg-laying is painful for birds?

Is laying an egg be as painful for the hen bird as childbirth is for human women? I'm just guessing that no-one has researched this in any great depth - but the thought crossed my mind when seeing these videos on YouTube. It certainly doesn't look as though it's fun for her - put it that way. Anyone have any info? --Kurt Shaped Box (talk) 00:11, 9 January 2009 (UTC)

I believe the main reason for the amount of pain human women have during childbirth is that the process works the same way as in other mammals, but with the pelvis rotated 90 degrees (to enable us to walk upright), so it doesn't quite work as "planned". Also, the large size of a human's brain (and therefore head) at birth relative to their pelvis in adulthood (compared to other mammals) is going to cause problems. So, I would expect (without evidence to the contrary) that egg-laying is as painful as childbirth in a typical mammal, which is significantly less than in humans. Someone else may well have evidence to the contrary, of course. (Also, quantifying pain is extremely difficult just within humans, trying to do so meaningfully between different classes is going to be next to impossible.) --Tango (talk) 00:25, 9 January 2009 (UTC)

Yeah, I suppose. Birds (or at least the species I'm familiar with) seem to have an incredible tolerance to pain - or at least they're better at keeping a stiff upper lip than we are. I've seen gulls trying to walk on two badly broken legs without crying out, or even losing their composure. A budgie of mine that caught a toenail in the wire of its aviary and ripped it off trying to escape squeaked in pain exactly once when it happened, then afterwards *seemed* completely unconcerned. Though I'd guess that their biochemistries would be screaming out if we were to examine samples of their blood... --Kurt Shaped Box (talk) 01:29, 9 January 2009 (UTC)

Well, eggs are a lot more, er, "vagodynamic" than babies, for one, and presumably if a woman were to give birth every second day or so like chickens lay eggs, it would get significantly less painful. My impression from watching my hens is that the process is more along the lines of taking a satisfying shit. --Sean 01:33, 9 January 2009 (UTC)

Speaking as a guy with no kids (so I might be completely and utterly wrong) - but it's the contractions (not the 'passage' of the infant itself) that are the main cause of pain in childbirth, aren't they? --Kurt Shaped Box (talk) 01:38, 9 January 2009 (UTC)

The crowning is apparently one of the most painful parts. --Tango (talk) 02:20, 9 January 2009 (UTC)

Also, while the same situation applies to me as KSB I suspect one of the reasons the contractions are painful is because of what happens during them Nil Einne (talk) 09:36, 9 January 2009 (UTC)

What happens during a contraction? Isn't the contraction what is happening? The muscles around the cervix contract, dilating it. --Tango (talk) 12:47, 9 January 2009 (UTC)

I'm pretty sure that what women refer to as a 'contraction' refers solely to a contraction of the womb. The cervix thing is called something else (is effacement the correct word, or does that just refer to the end result of the process?). --Kurt Shaped Box (talk) 03:24, 10 January 2009 (UTC)

According to Cervical dilation, contractions of the womb cause the cervix to dilate. It seems I was slightly incorrect to say "the muscles around the cervix", it's the muscles around the uterus (which is connected to the cervix). --Tango (talk) 19:25, 10 January 2009 (UTC)

A chicken egg seems larger than the mother's skull, whatever that's worth in comparing human childbirth pain with egg-laying pain. The chicken should be laying a quail egg for it to be comparable. But, then, maybe a hen has a larger pelvis relative to the egg than a human mother does relative to the baby's skull. Edison (talk) 05:22, 9 January 2009 (UTC)

Shouldn't you be comparing it to the body size rather then skull size? Part of the reason is because the chicken has a rather small head compared to its body compared to humans. Nil Einne (talk) 09:38, 9 January 2009 (UTC)

Indeed, the reason I mentioned heads above is because with human babies the head is the largest part. That's not the case with chickens. --Tango (talk) 12:47, 9 January 2009 (UTC)

O.K., I agree it is a meaningless comparison. Edison (talk) 17:12, 9 January 2009 (UTC)

Another data point for my "it's not particularly painful" opinion is that childbirth is usually injurious -- and commonly fatal (absent medical care) -- to the mother, while egg laying almost never is. --Sean 11:56, 9 January 2009 (UTC)

Our maternal death article states that 'The historical level of maternal deaths is probably around 1 in 100 births'. Now I've started this, I'd be quite interested in seeing the figures relating to how many 'attempted layings' result in egg binding (which nearly always results in a nasty, slow, lingering death without human intervention) in hen birds of various species. I do however suspect that this data does not exist (or only exists for domestic chickens - which lay far more eggs than they would naturally anyway). --Kurt Shaped Box (talk) 03:38, 10 January 2009 (UTC)

A good layer can put out 200 eggs per year, so at the human death rate that would mean the average hen only lasts for six months of laying, which is certainly not the case. --Sean 18:35, 11 January 2009 (UTC)

Using the definitions of pain from the article, "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage" or "Pain is whatever the experiencing person says it is, existing whenever he says it does" then we cannot know if the bird doesn't talk. We should define our terms before answering. Icek (talk) 11:59, 9 January 2009 (UTC)

It's also notable (according to many mothers that I've spoken to) that the memory of the pain goes away amazingly quickly - after a matter of days, I believe - leaving a strange memory of it being a rather easy, even enjoyable, process...overlaid with a rational knowledge that it simply cannot have been so. This mental 'censorship' of the event is clearly of evolutionary benefit - if women remembered in full lurid detail what they had to go through the last time they gave birth - they'd be much less likely to go and do it again! SteveBaker (talk) 19:43, 9 January 2009 (UTC)

(Oh - and I'd like to personally thank Sean for coining the word "vagodynamic"...I can see it having widespread use in the manufacture of certain sex aids and porn movies. The science of vagodynamics holds all manner of interesting prospects for the future! :-) SteveBaker (talk) 19:43, 9 January 2009 (UTC)

If our universe is an open one, is not that a a paradox?

Assuming that the bing bang theory is true, it would have sense to think that the matter is eternal going on from big bang to big crunch (not a big crunch exactly)over and over again, but if the universe is an open one.. wich is the origin of the "extremely dense and hot state point" that gave origin to the big bang expansion? --Starlingmaximilian (talk) 01:10, 9 January 2009 (UTC) Thanks and sorry for the poor english. —Preceding unsigned comment added by Starlingmaximilian (talk • contribs) 01:10, 9 January 2009 (UTC)

That's an excellent question, and not one we have a clear answer too. There are some theories involving multiverses, or you can go with "God did it", or probably one of numerous other ideas I can't think of. There is no widely accepted answer among the scientific community though (it's difficult to even work out what the question means, "what happened before the big bang" makes no sense since time started at the big bang, so it can't have a cause in the usual sense). --Tango (talk) 02:25, 9 January 2009 (UTC)

It's certainly a question that doesn't have an answer just now. It's possible that we'll never be able to answer it because when all of existance is contained in a literal singularity - then all information from "before" the singularity has been erased. If no information whatever passed between what came before - through the Big Bang - and on to us, how could we ever work out what came before? The "Big Crunch" hypothesis was a rather elegant and satisfying one - but sadly, it doesn't appear to be true. One kinda comforting thing is that the answer doesn't matter. For the same reason that we can't find out what happened before, there can be no influence from that time on present or future times - so the knowledge is purely a matter of satisfying curiosity - it wouldn't lead to further insights - useful inventions - or anything of that sort. SteveBaker (talk) 05:11, 9 January 2009 (UTC)

Perhaps all previous universes were closed, and this was the first big bang with enough oomph to be open. Last call, drink up, heat death awaits! --Sean 12:01, 9 January 2009 (UTC)

It seems to me that the oscillating universe model is just as bad in this respect, as we have no explanation of what created the universe, either way. (Or, if an OU is assumed to always have existed, why exactly that would be and how is that any better than saying that God always existed and then created everything ?) StuRat (talk) 17:10, 9 January 2009 (UTC)

The thinking about the oscillating universe (at least prior to the information BenRG explains below) was that if the big crunch singularity DID look exactly like the big bang singularity - then because they are both zero sized dots containing all of everything - then when the big bang goes off - the results are 100% identical each time. So the last time around, there was a SteveBaker sitting at a computer typing this exact answer into a web site called Misplaced Pages - and making the same spilling mistooks too. If every universe is IDENTICAL to every other universe - then that is 100% equivalent to saying that time is looped - and then we have no beginning and no end - a circle of time that simply exists. Sadly, things like the randomness inherent in quantum theory - and the stuff that BenRG explains below - means that this cannot and would not work out like that. Big Crunch was simplistically very elegant - but it's not true - so we're having to look for another answer. SteveBaker (talk) 19:34, 9 January 2009 (UTC)

The oscillating universe model is unworkable because a big crunch is not a time reversal of a big bang. Entropy continues to increase when the universe contracts, and matter becomes increasingly clumped, in contrast to the big bang where matter is extremely uniform. The big crunch singularity doesn't look like a big bang singularity and you can't really graft them together.

Also, there was no big bang. The so-called "big bang" model that's used to describe the present-day structure of the universe has a singularity about 13.7 billion years ago. But the model is not valid in the vicinity of the singularity, so that part of the model isn't used; instead it's cut off at a finite distance from the singularity and grafted on to some other model (like inflation). The big bang model still works well to describe the present-day universe and cosmologists still quote "time since the big bang" since it's a convenient way to identify events in that model. But those times aren't measured from any physically meaningful origin point, since the big bang singularity that would be the origin of the measurement was removed from the model. If you go back 10 seconds from "10 seconds after the big bang" you might end up in the middle of the inflationary epoch, or in some totally unknown pre-inflationary state, or past the beginning of the universe, depending on the details of the pre-big-bang physics. The age of the universe also depends on the pre-big-bang physics, and could be anywhere from 13.7 billion years to infinite. -- BenRG (talk) 18:55, 9 January 2009 (UTC)

Roger Penrose currently has a non-complete but interesting proposition called conformal cyclic cosmology which does not require the previous universe to collapse for a new one to 'big bang'.

Strength of intermolecular forces

I know that dipole-dipole attractions hold solids and liquids together for polar molecules, and that london dispersion forces hold the solids and liquids for nonpolar molecules.

However, given several molecules (their formulas), I was asked to determine which had the "strongest intermolecular attraction"

For example, between (A) H2NCH2CH3CH3NH2 and (B) CH3CH3CH3NH2, I thought that (B) would have the strongest intermolecular attraction since the molecule is polar, whereas (A) is symmetrical and thus doesn't have a dipole moment. However, my teacher said that (A) has two sites, one on each end, where opposite partial charges between the molecules can attract each other, so (A) has stronger intermolecular forces. I am very confused: how can (A) have stronger intermolecular forces when the molecule does not display a dipole moment and thus has no dipole-dipole attraction. I thought we had to look at the polarity of molecules as a whole, not the polarity of individual bonding regions. Can someone please explain? —Preceding unsigned comment added by 68.111.75.89 (talk) 04:11, 9 January 2009 (UTC)

Intermolecular attraction is often local, especially for polar/ionic effects: "an amine group" is able to hydrogen bond, regardless of whatever else may be happening anywhere else in the molecule. Also, (A) doesn't actually look like you think it does...writing the way you did reinforces a very incorrect fiction for the overall molecular geometry. DMacks (talk) 05:17, 9 January 2009 (UTC)

Also, molecule A, being a rather long chain alkane, will have free range of motion around each C-C bond, and will assume whatever conformation will be the most stable. Get a simple molecular model kit and build it; you can easily make a "V" shaped conformation with the amine groups at the tips and a CH2 at the point. With that conformation, one can easily see (even ignoring H-bonding effects) that one can make a conformation which is quite polar; the question then becomes whether the energy of the intermolecular forces in THAT particular conformation can overcome the energy difference between that conformation and, say, the somewhat more stable "straight chain" conformation. Of course, none of that matters much because the H-bonding effects from the 2 amine groups overwhelms any other forces. However, my explanation could possibly work for a molecules where, say, the H's are replaced by say CH3 groups or something like that.

The questions about intermolecular forces are not as simple as often made out in a high school chemistry class, as there are often factors that, for simple reasons of time constraint, cannot be taught. There's lots of factors happening here, and one needs to consider all of them... --Jayron32.talk.contribs 13:06, 9 January 2009 (UTC)

Lightning

Hi, here are some questions my son has been asking me and I would be interested in hearing some thoughts. I'm not sure if I've answered him correctly...
1. If lightning follows the path of least resistence, why does it strike the highest point? Surely it should bypass a pole for example and go through the air and hit the ground?
2. When lightning strikes the ocean, how far does it spread? Does it kill fish on the surface only?
3. Somewhere I've read that a single lightning strike can power New York for a year. Why can't scientists capture lightning and harness its power? What are the challenges faced in doing this? (this one got me thinking too)
thanks, Sandman30s (talk) 11:39, 9 January 2009 (UTC)

1) Because the electrical resistance of the pole is enormously less than that of the air. Algebraist 12:26, 9 January 2009 (UTC)

3) Your source was wrong. The amount of electricity New York uses in a year is rather more than the amount of energy released by a hydrogen bomb, let alone a lightning bolt. Algebraist 12:31, 9 January 2009 (UTC)

(ec)Lightning follows the path of least resistance, yes. But air has a much higher electrical resistance than the pole in question. I don't know anything about the ocean question, but the energy will dissipate very quickly in the water. And the meme about the single lightning strike powering New York for a year is simply wrong. A lightning's power is in the terawatts, but it's lifetime is very short. The energy is impressive, but not that big. I may have dropped a zero here or there, but I come to about 500kWh for one lightning strike - theoretically enough to cover the electricity used by maybe 1000 average flats for one hour, not 10 million for a year. The problem is reliably capturing that energy and releasing it in a controlled manner. --Stephan Schulz (talk) 12:47, 9 January 2009 (UTC)

Our article on Resistivity has info to help quantify the first question. Resistivity is the measure of how much a substance resists the flow of electricity; i.e. low resistivity = high conductance. Air, being made of gasses, has large gaps between individual molecules, meaning that in order to conduct electricity, one has to force electrons to jump across a HUGE gap. At standard earth conditions, a good approximation is that most gases are 1/1000 as dense as solids or liquids; so all other things being equal, gases should be 1000x more resistive to electricity than solids. Of course, there is a huge variability in the resistivity of solids, largely due to how strongly those solid materials "hold on" to their electrons; however for nearly all but the most exotic materials, air is almost ALWAYS more resistive. So electricity will only stay in the air for the shortest distance possible... As far as number 3 goes; the difference between harnessing the electricity in a lightning bolt and generating it in a power plant is something akin to harnessing the power of a nuclear bomb and using nuclear fuel in a nuclear power plant... It may be possible to a point to do so, but there are so many more practical means of generating electricity. --Jayron32.talk.contribs 12:59, 9 January 2009 (UTC)

I wouldn't say that the density of the material is the most important factor in electrical conductivity, but rather whether the material has free electrons. Metals tend to have this, so conduct electricity well. You can get electricity to flow long distances through a vacuum or some very thin gases, such as those in fluorescent and neon signs. StuRat (talk) 17:02, 9 January 2009 (UTC)

Number 2 was asked here a while back, only about a lake instead of the ocean. Same difference. Here is the answer from that question. --Milkbreath (talk) 13:07, 9 January 2009 (UTC)

Algebraist and Stephan are correct about question (3). Here is an estimate from "All About Lightning" (ISBN 048625237X) by Martin A Uman: it would take 100,000 lighting-conducting towers in a moderately lightning-hit area to produce as much power (100 MW) as one small power station. --Heron (talk) 20:18, 9 January 2009 (UTC)

Thank you all for the answers. A link within that lake strike link above says "A single lightning stroke can deliver a billion electron volts and 100,000 amps" - can someone compare this to a power plant (to end up with a megawatt figure) and let me know how you did the calculation? (sorry I should've paid attention in grade 11) and BTW that New York figure was from a children's encyclopedia but he can't remember which one, although he could have been wrong - perhaps it's for a day rather than a year. Sandman30s (talk) 20:35, 9 January 2009 (UTC)

An electron volt is a unit of energy - namely the amount of energy that one electron gains if it is accelerated through a potential difference of one Volt. This is a very small unit, roughly 1.6E−19 Joule. A billion (US style) is 1E9, which makes one billion electron volts 1.6E-10 Joule, or approximately nothing. A billion (European style) is 1E12, which makes a billion electron volts 1.6E-7 Joule - again, roughly nothing. I suspect the linked article is not a reliable source. 100,000 amps is not a unit of energy, but a current, and the energy depends on the potential difference again. I estimated around 500 kWh above, based on numbers from Lightning. That is 1800MJ, or the output of a 100MW power station over 18 seconds. --Stephan Schulz (talk) 21:13, 9 January 2009 (UTC)

My answer to #1: The high electric field initiates a leader from pointy objects. This leader ionizes the air up to the charged cloud. Only then does the return stroke occur. Surely this must be covered in our article on Lightning? Hmm article seems to say that leaders are initiated from the cloud. But Ive seen a pic of a leader emanating upward from a tree before the main strike.--GreenSpigot (talk) 21:40, 9 January 2009 (UTC)

My answer to #2: This is the 3D version of the 2D problem of cows getting killed due to the surface electric field in the region of a strike. Cow have rather a large 'wheelbase' so can pick up more volts than say humans for a given field strength in the ground surface. What is the maximum electric field strength that fish can stand? Maybe some one has modelled this scenario?--GreenSpigot (talk) 21:57, 9 January 2009 (UTC)

My answer to #3: What is the duration of the average strike? Work out volts x amps x time (gives you energy) and you'll see why. --GreenSpigot (talk) 22:00, 9 January 2009 (UTC)

3) I hope little Johnny is in graduate school, because the matter of electrical power is frightfully complicated. First, Stephan Schulz is right, of course; that website is bogus. But we can take average figures from our article "Lightning" and get a ballpark figure, bearing in mind that no two lightning bolts are the same, and they vary greatly.

First we need to get the terminology straight, because it is not straight right out of the box. When we talk about lighting up New York, we're talking about power. Sort of. What the electric company calls "power" is really what everybody else calls "energy". A watt is a unit of power, but power companies actually sell kilowatt-hours, each one a thousand watts used for an hour. It's like having ten 100-watt lamps on for one hour. A kilowatt-hour can be expressed any way you like, but one good way is in joules of energy, a joule being one watt-second (you're starting to get comfortable with the concept, aren't you?). One kilowatt-hour is 3.6 megajoules, or 3.6 million joules.

You want to calculate the power (energy) in a lightning bolt given only volts and current. Our article says, "...approximately one gigavolt (one thousand million volts) for a 300 m (1000 ft) lightning bolt" and "With an electric current of 100 kA..."(100,000 amps). (They call it a "thousand million" because the Brits and the Americans call that different things sometimes, but let's call it a "billion" here.) The formula for electrical power is P=EI, that is, power equals electromotive force (i.e., volts) times current (I forget why it's "I". Mostly because "C" means about 15 other things already, I think.). This is really power, and the answer is in watts. If we apply this to our lightning, we get one billion times one hundred thousand, so by adding exponents of ten we get 10 to the 9+5, or 10 to the 15th power, which we can call 100 terawatts or 100 times ten to the 12th. So far so good, but we need to calculate the energy, what the "power" companies admittedly aptly call "power", you remember. Our theoretical lightning bolt lasts for something like 300 milliseconds, or 0.30 seconds. We're shooting for joules (watt-seconds), so we simply multiply, getting 30 terajoules, or 30 million megajoules. As I'm sure you recall, a kilowatt-hour is 3.6 million joules, so 30 million million must be divided by 3.6 million, giving us 8,333,333 kilowatt-hours. That's a whole lot of energy.

I found a website that claims that New York City uses some 12 million megawatt-hours a year, which, to match our units, is 12,000 million kilowatt-hours. Divide that by the energy in a lightning bolt, and we get 1440. That means that our lightning bolt can power NYC for 1/1440 of a year, which is 1/1440 times 365 days, or about a quarter of a day: 6 hours. That's a lot of energy.

Too much, I think. I don't like that billion-volt figure. Sure, it takes a billion volts to ionize 1,000 feet of air, but once the current starts, the voltage is going to go way down. I've heard figures of some tens of millions of volts, call it 50 million, which sounds more reasonable. So, we can divide our answer by one billion divided by 50 million, which is 20, so 8,333,333 divided by 20 is about 417,000 kilowatt-hours. And six hours divided by 20 is 18 minutes. --Milkbreath (talk) 00:28, 10 January 2009 (UTC)

Unfortunately, the high voltage and the high current do not exist at the same time ( the voltage at ground level is (by definition) approx zero). Ever heard of Source impedance? and the impedance of an arc--GreenSpigot (talk) 01:09, 10 January 2009 (UTC)

(edit conflict)As for #3, not only is it difficult to store the energy from a lightning strike, but one time I asked that same question, and it turns out that lightning is Direct current, and the type we use is alternating current. So unless you can somehow store all that energy in a giant capacitator to ensure a constant supply, add a gigantic reverse-AC/DC adapter, transport the electricity in wires, and step down the voltage for safe use in homes, I would think that energy from lightning would be too difficult to manage. ~AH1 01:12, 10 January 2009 (UTC)

Milkbreath, the 300 miliseconds you assume is much to long. It's ok for a full lightning strike, but an individual discharge only takes about 0.4 milliseconds. A strike consists of several bolts, and the breaks in between are about 99% of the total time. So by that you are off by a factor of 100. --Stephan Schulz (talk) 01:17, 10 January 2009 (UTC)

Yeah, it did seem long, but I couldn't find a figure in the article, so I went with the caption on the picture at "Lightning#Discharge". So if we divide by 100, it's still a lot of energy, but it will only run the Big Apple for 10 seconds, which is the sort of range I expected when I started this. --Milkbreath (talk) 01:29, 10 January 2009 (UTC)

CO2 in a fish tank for plants

I keep fish in a tropical aquarium and I'm trying to encourage better plant growth. It has been suggested that I introduce a CO2 injection system to up the amount of CO2 in the water. Could I just add some fizzy bottled water every now and then? Wouldn't this add more CO2? Would there be any risks to the fish? Thanks.91.111.119.120 (talk) 12:51, 9 January 2009 (UTC)

Adding carbonated water might boost the CO2 -- I'm not sure what the injection system would actually inject (basically, whether it'd be acidic or not). As for risks to the fish, it seems likely. I strongly suspect that ingredients apart from water and CO2 are in whatever bottled water you have -- even chlorinated or fluoridated water would present hazards, and treatments like those might not be required listing on the side of the bottle. — Lomn 13:50, 9 January 2009 (UTC)

Fizzy bottled water is probably a bad idea as this will be (I believe) more acidic than your usual tapwater, upsetting the pH of your aquarium. Not to mention the hardness of some fizzy drinks. When it comes to plant growth, have you tried other remedies first? This includes fertilizer for the plants (which go well with most fish but some snails and shrimps are sensitive to it) and changing the fluorescent light to one optimized for plant-growth. The choice of plants also matter of course. EverGreg (talk) 14:06, 9 January 2009 (UTC)

Soda water is acidic, but there's no way around that — adding CO₂ to water makes it acidic regardless of the source. If that's the only problem (I don't know this), you can easily offset the acid by adding something alkaline to the tank also. Drops meant to alter the pH of an aquarium are available at any supply store. --Tardis (talk) 16:23, 9 January 2009 (UTC)

If you're already aerating the water for the fishes' sake then CO2 won't be a limiting factor. Have you considered the benefits your aquatic plants would receive from improved illumination? Upping the light supply with grow lamps will dramatically boost plant vitality.--Digrpat (talk) 18:45, 9 January 2009 (UTC)

Consider LED grow lamps if temperature is an issue. APL (talk) 20:31, 9 January 2009 (UTC)

This site might help. - - see particularly the DIY yeast reactor. (This is what they have to say on other plant related issues - ). The more costly issue than introducing CO₂ into the water is going to be the fact that you'll have to monitor the chemical composition of the water more closely and frequently. Don't know about DIY test kits. _Lisa4edit76.97.245.5 (talk) 08:20, 10 January 2009 (UTC)

Many types of soda water have quinine in them, and although I don't know what effect it will have on fish I can't see it being good. -Pete5x5 (talk) 08:14, 11 January 2009 (UTC)

How is it that all life on Earth descended from a common ancestor and not multiple ancestors?

One thing that has always wondered about as far as evolution goes is the concept that all life on Earth descends from a common ancestor. It seems to me that if life was created in primordial soup, it would have done so multiple times. That is to say, if one pool of primordial soup produced life, so would a second pool of primordial soup, a third pool, a fourth, etc.. Also, it seem to me that life could have formed more than once within the same pool of primordial soup. Therefore, there should be multiple ancestors and multiple lines of descent, not a single common one. How is this possible? Does this mean that one line of life wiped out all the other ones? Or is the spontaneous generation of life so unlikely that it only occurred once on Earth? (If that latter, is this a possible explanation for the Fermi Paradox?) I'm aware that we have articles on evolution, abiogenesis and common descent but other than a single sentence in the common descent article, "The theory of a common ancestor between all organisms is one of the principles of evolution, although for single cell organisms and viruses, single phylogeny is disputed" I don't see anything that specifically addresses my question (but maybe I missed it). 216.239.234.196 (talk) 14:25, 9 January 2009 (UTC)

There are two point here. The first is that, given enough resources, life grows exponentially. Hence, without competition, once the first life has been established, it will spread very quickly (on an evolutionary time scale). The second point is that once one kind of life has been established, the very existence of this may inhibit the formation of an independent strain, as the existing life forms are much better at consuming precursor molecules and structures than potential proto-life strains. Thus, even if it takes an average of only a million years or so for primordeal life to develop, the chances of two independent strains are very low. Thirdly, as we now know, there has been and still is a horizontal exchange of DNA, e.g. via viruses. Thus, the tree of life really is a complex graph, and only the major gene flow follows the tree structure. --Stephan Schulz (talk) 14:39, 9 January 2009 (UTC)

I don't think anyone is saying life couldn't have evolved more than once here on earth. However there is no evidence of more than one line, the form that gave rise to our current DNA and RNA. For all I know there could be some other form of life on earth not reproducing that way but I very much doubt it. It may be there was more than one form of life and the current form was just far better and the other form just died out, just look how many good viable species go extinct nowadays - there's a lot of competition. It is all speculation though without any evidence and I wouldn't hold my breath waiting for some evidence to come along. Dmcq (talk) 14:54, 9 January 2009 (UTC)

In addition to the points above, I also would say that the spontaneous generation of life may be so unlikely, that not only did it only occur once on Earth, it may not have occurred on many other Earth-like planets where it could have. We may be the only planet in the universe, or even among many parallel universes, where it did occur. One piece of evidence that it may be more common than this is that life seemed to evolve shortly (on geological time-scales) after the Earth cooled, which would seem to indicate that life occurs as soon as conditions exist which allow it. StuRat (talk) 16:49, 9 January 2009 (UTC)

According to this scientific American article some microscopic life forms that may have evolved from a different common ancestor than the ancestor of Archaea, Eubacteria and Eukaryotes may still exist today.--Apollonius 1236 (talk) 00:24, 10 January 2009 (UTC)

To be very careful about that article - it doesn't anywhere say that there is any evidence for this. It says that there are a lot of people LOOKING for that evidence - and that it could hypothetically be true - but it goes on to say that every single time someone THINKS they've found such a thing, it's only ever turned out to be a weird-but-still-related-to-us kind of a creature. SteveBaker (talk) 14:12, 10 January 2009 (UTC)

It's not conclusive that there was only ever one start for life on Earth - it's possible that our ancestor was simply able to out-evolve the competition and eliminate them in the (L-O-N-G) period before we have good fossil records. However, from all we know - this does nicely support the possible extreme coincidence required to get that first life-form started. The "abiogenesis event" (the moment when something that wasn't alive became alive) is a hard thing for science to explain - and if we had conclusive evidence that it happened many times then there would be a severe problem - because explaining how it came about from 'chemistry' alone is tough. But the fact that it probably happened only once gives us an elegant 'get-out-clause'. If the event happened only once in billions of years and over billions and billions of gallons of ocean water (or tens of thousands of volcanic vents or whatever) - then the probability of that event MUST be vanishingly small. That not only allows us to hypothesise quite amazingly unlikely events - but it actually means that a more causal explanation would have to be wrong! We are therefore required to imaging such incredibly unlikely things as the completely accidental arrival of just the right amino-acids in one place and in just the right order to make a self-replicating molecule form from a bunch of random interactions. That's a spectacularly unlikely thing. But if it only had to happen once in all of time and within all of the oceans on all of the planets in all of the galaxies in an enormous universe (or possibly, even a multiverse) - then any event that's possible will have happened somewhere at some time. That makes life appearing somewhere in the universe an almost certainty! By the 'anthropic principle' - we are (by definition) the product of that one event. This changes the science dramatically. If there had been multiple abiogenesis events - we'd be in deep trouble with the religious nuts. SteveBaker (talk) 19:22, 9 January 2009 (UTC)

I'm not sure I understand your last point. Are you saying: We'd be in trouble with religious people because if abiogenesis is common and therefore science should be able to explain it but can't? If so, it just means that science can't explain it yet. We're all just passing through history. 216.239.234.196 (talk) 20:22, 9 January 2009 (UTC)

Yes - pretty much. They'd be able to say "See how Godsome intelligent designer is creating all of these new creatures - and your evolutionary theory can't explain them because they are all clearly totally unrelated"...or something like that. However, if there has only been one such abiogenesis event EVER - in the entire history of the universe perhaps (think 'Panspermia' or the Anthropic principle) - then it only has to be possible for a molecule to come about that way and a really LOW probability of such an event is merely confirmation of it's viability as an explanation. Anyway - it's no big deal - just an observation - we may yet find the true cause of that event. SteveBaker (talk) 05:16, 10 January 2009 (UTC)

I think its important to note that there is a difference between "all extant life on earth" having evolved from a common ancestor, and "all life on earth" having evolved from a common ancestor. When the beginnings of life were brewing in the primordial soup, there may well have been lots of different pre-RNA forms that stored, transmitted, and duplicated "genetic" information. These could have evolved independently. If you wish to define these as "alive" then all living things may not have evolved from a common ancestor. There could even have been other forms of "life" that evolved from the iron-sulfur world or any other mechanism that we are unaware of. Some of these would be doomed to failure, restricted by the limits of their own basic chemistry. These could have bounced around for many millions of years "surviving" in the unique environment at that time. But we do know that only one chemistry had the right combination to develop to the point in prehistory where that we could detect it. And all the others must perished, as the environment changed and no longer became optimal for the genesis of life. This isn't such a huge stretch of the imagination, because we know that also happened to whole lineages of DNA based life.

We don't know whether this happened, or if it did, how long or how advanced different types of life could have co-existed. There is no evidence for it, but not evidence against it either. We just don't know (yet). Rockpocket 05:31, 11 January 2009 (UTC)

Orders of magnitude for force...?

Hi. Why isn't there an orders of magnitude table for force? (Like there are for pressure, mass, etc. etc.) It'd be nice to have one, no? Kreachure (talk) 16:30, 9 January 2009 (UTC)

Sure, but this isn't the place to request a new article. This is: Requested_Article#Topic_areas_in_applied_arts_and_sciences. You might also leave your request on the talk page for orders of magnitude . StuRat (talk) 16:37, 9 January 2009 (UTC)

Well okay then, I just thought there was a particular reason for there not being one. Sorry... Kreachure (talk) 16:52, 9 January 2009 (UTC)

I LOVE those order-of-magnitude pages - please, get proactive and make one. It's so useful when answering a question here to be able to say "...and that's as heavy as an aardvark!" or "...and that's as fast as a rifle bullet!". Good catch! SteveBaker (talk) 19:08, 9 January 2009 (UTC)

If you're mentioning aardvarks because you're trying to memorize the dictionary, I see you've made very little progress. --Bowlhover (talk) 21:15, 9 January 2009 (UTC)

Ah - but how do you know which end I started reading from? Ha! The force exerted by a falling Zygolophodon would be harder to figure out because they are extinct...although I think I could definitely guarantee at least a couple more orders of magnitude than the animal at the other end of the dictionary! SteveBaker (talk) 02:33, 10 January 2009 (UTC)

So do I, so I made one: Orders of magnitude (force). --Heron (talk) 20:08, 9 January 2009 (UTC)

How else would we know how many football fields long anything was? hydnjo talk 20:25, 9 January 2009 (UTC)

Thank you, Heron. That's more like the kind of reply I was hoping to get. Can I say I just love Wikipedians sometimes? :) Kreachure (talk) 20:56, 9 January 2009 (UTC)

This thread inspired me to take a look at Orders of magnitude (pressure). I'm not the most mathematical guy, but I notice that the entry for the atmospheric pressure on Pluto has "10 Pa" in the "Magnitude" column and "0.5 Pa" in the "Pressure" column. That doesn't seem right; is "10" perhaps an error for "10" (or, less likely, "0.5" an error for "0.005")? Deor (talk) 23:18, 9 January 2009 (UTC)

@Deor: "I'm not the most mathematical guy," ...But when she smoothed her curves she nearly broke my spline... --Scray (talk) 23:40, 9 January 2009 (UTC)

Yes, Scray, I too was thinking of the Kinks when I typed that. Deor (talk) 01:48, 10 January 2009 (UTC)

Yes, it's one of my fav songs. We need more songs with punchlines like that. StuRat (talk) 06:29, 12 January 2009 (UTC)

I think the table is correct, Deor. The "10" section is supposed to include all values from 1 mPa up to 0.999 Pa. I agree that it looks odd, but it will look less odd if someone can find examples for the 1 mPa and 10 mPa orders of magnitude. --Heron (talk) 13:46, 11 January 2009 (UTC)

Cnidocysts stronger than a bullet??

Hi (again). After I found sources for the cnidocyte article claim that a cnidocyst accelerates to over 5,000,000g, I noticed that the cited source also says that despite its small mass, it's able to produce over 7GPa of pressure, "which is in the range of that generated by some bullets". According to orders of magnitude (pressure), the weapon discharge of a bullet is of 400MPa. I would like to know if all this makes sense. Even if it doesn't, I would like to know how a cnidocyst actually matches up to a bullet. Would it be able to puncture (on the microscopic level) a flak jacket significantly, for example? Thanks in advance, Kreachure (talk) 16:50, 9 January 2009 (UTC)

The deal is that the forces involved are proportional to the mass as well as the accelleration (F=Ma - Newton's law). While the accelleration is high - the mass is TINY (much lower than a bullet) - so the force exerted on the cnidocyte is very small indeed - much MUCH less than a bullet. That's why we make bullets out of lead (or depleted uranium) - because they are HEAVY. If you make a bullet out of foam polystyrene...you know what would happen. Similarly, although the cnidocyte might well survive the impact with the flak jacket - it couldn't deliver anywhere close to enough energy to make a hole in it. SteveBaker (talk) 19:06, 9 January 2009 (UTC)

But then how is it able to exert so much pressure? Is it wrong? Because the most conservative estimates I can find are along the lines of 10^7 Pascals, and the pressure a bullet exerts would be around 10^6 Pascals. My guess is that the microscopic area of effect is what makes the number jump so high, but the pressure is indeed there at the tip of that microscopic harpoon, no two ways about it. So, could you say that at the microscopic level, a cnidocyte is indeed as powerful as, or even more powerful, than a bullet? Kreachure (talk) 21:31, 9 January 2009 (UTC)

I suppose you could, but it raises what is in my opinion a more relevant question: have you stated anything of meaning? I'd stick to "x exerts more pressure than y" and not attempt to make any claims such as "more powerful" in such ludicrous cases of apples-to-oranges. — Lomn 22:22, 9 January 2009 (UTC)

Okay, forget the word powerful if you want. My question would be if the cnidocyst does indeed exert more pressure at the microscopic level than a bullet, enough to puncture an armor-like material. I've heard that it's able to puncture through the shells of some sea creatures, so that's pretty impressive considering it's just a microscopic needle... Kreachure (talk) 22:33, 9 January 2009 (UTC)

The pressure is high because pressure is force divided by area. The area is TINY - so even though the force is also pretty small - the area is much smaller. So, yeah - the pressure is high...but the force didn't change. Breaking things is about ENERGY - not pressure. Because the mass is so small, there is a microscopic amount of momentum - hence no damage when the cnidocyst (I love typing that word!) hits the body-armor. SteveBaker (talk) 02:21, 10 January 2009 (UTC)

Hmm... well, I guess that makes sense. Thank you. Kreachure (talk) 13:53, 10 January 2009 (UTC)

Protein Engineering

Does anyone have a good classification system for the following methods used to engineer proteins, enzymes in particular: direct evolution (1), rational design (2), site-directed mutagenesis (3), computational protein design algorithms (4), random mutagenesis (5), DNA shuffling (6), RACHITT (7), StEP (8), SCOPE (9), SISDC (10).

I think it's best divided into (1) and (2) and that (1) is sub-divided into (5)-(10) and that (2) is sub-divided into (3) and (4). Is this a good classification or does someone have a better one? 90.221.241.97 (talk) 19:57, 9 January 2009 (UTC)

Don't ignore the part about folding. It will make your classifications more extensive, but more useful. Two proteins that come up identical after processes (1) or (2) can be entirely different animals if they are folded differently. There are a couple of searchable databases around for proteins. Check the archives. We've had a couple of questions from user Seans potato business. 76.97.245.5 (talk) 21:14, 9 January 2009 (UTC)

January 10

Force of rain dropping

Looking at our new page Orders of magnitude (force) I thought it might be nice to add something "down to earth". I was thinking of the force of rain hitting the ground. Unfortunately I sort of got stuck half way though. At a diameter of 1 mm we could assume a drop to be spherical and I think a drag coefficient of 0.1 for a smooth sphere could be applied (or do we need a rough sphere at .4?). That should give us the terminal velocity in free fall. I got 0.523598775 mm for a volume and seem to remember 1 liter of water weighs one kg. 1 L our page says is 1 cubic decimeter. Anyone willing to lend a hand?_Lisa4edit76.97.245.5 (talk) 00:05, 10 January 2009 (UTC)

you underestimate the diameter alot http://hypertextbook.com/facts/2001/IgorVolynets.shtml --Digrpat (talk) 00:44, 10 January 2009 (UTC)

To work out the force you would need to know how long it takes for the drop to slow down and stop, I'm not sure where you would get such data. --Tango (talk) 01:02, 10 January 2009 (UTC)

Isn't there a math desk? I did some math, and I got about 23 millinewtons with a 5 mm raindrop going 9 m/s and stopping in its diameter. Smaller than I expected, but ballpark, I think. I got the 5 and the 9 from our "Rain" article, and I let it stop within its diameter, although there would certainly be some splashing to mess up all our perfect mathematics. Wait and see what others get before you do anything. --Milkbreath (talk) 01:09, 10 January 2009 (UTC)

But we're talking about article-space here. You can't treat it like the WP:RD and calculate your own numbers. You have to cite reliable sources. Any calculations we'd do here would be irrelevent because they'd fall under OR or Synthesis. SteveBaker (talk) 02:16, 10 January 2009 (UTC)

Oh, right. Pesky rules. --Milkbreath (talk) 02:28, 10 January 2009 (UTC)

What do we have to do to get the ref desk designated a reliable source? It's far more reliable than most newspapers I've read... --Tango (talk) 03:15, 10 January 2009 (UTC)

I'm torn berween being happy that so many of our schools apparently do "Original Research" with our definition being that close to the bottom of the pit and being sad just how often we let principles get in the way of achieving something useful. There certainly are good reasons for our OR rules, but when rules start to be applied for the sake of following "the rules" they unfortunately tend to incur a high cost in diminished results. I'm with Tango. I've seen many examples of some "nutcase" with an impressive degree putting something in a book and all of a sudden it's "true and valid". One of my favorite quotes is "Nothing exists till a white man has written about it in a book." Sad, but only too true.

@dgrpat I had chosen 1mm for a diameter since bigger raindrops are not spherical as the link from rain - says. Thks for your help everyone, anyway. —Preceding unsigned comment added by 76.97.245.5 (talk) 07:28, 10 January 2009 (UTC)

Yes - I think the OR rules are a bit over-enthusiastic in cases where math and well-understood, established physics is concerned. In a case like this, it's reasonable that we should cite references for the diameter of the rain drop and perhaps provide links to the physical principles we used to calculate the force - but the actual calculation itself ought not to fall foul of the rules. However, it does (notably the 'synthesis' part). But the "No Original Research" part is what saves us from the worst of the nut-jobs with crazy theories who'd like to promote them as fact on Misplaced Pages. NOR means that they've got to find some reliable source to publish their crazy theory as fact before they can come and annoy us with it...that's a good thing overall. SteveBaker (talk) 14:05, 10 January 2009 (UTC)

I agree with Tango. don't want to discourage Lisa4edit from adding useful examples, but I'm not convinced that the 'force' of a raindrop hitting the ground is a meaningful quantity. A falling raindrop imparts momentum to the ground and dissipates energy, both of which can be calculated fairly reliably, but there is no single number than you can call the 'force'. The force will increase from zero as the bottom of the drop hits the ground, up to some maximum or series of maxima that depend in an impossibly complicated way on the shape of the splat that the drop makes as it disintegrates, and then decay to zero again. Even if we allow OR, the result is not going to be useful. --Heron (talk) 13:11, 11 January 2009 (UTC)

Suggestion for (original) research: (Might make a science project for someone). I wonder if, experimentally, one could note the effect of one raindrop hitting a leaf (or some elaborate experimental raindrop target) and noting the deflection, by videography, then measuring the force needed to produce the same deflection. In physics lab we fired a 22 caliber bullet into a block of wood free to swing, and noted how far it swung with the embedded bullet, measuring the energy and from the mass, the velocity of the bullet, and compared it to a standard velocity meter which had 2 rotating paper discs a certain distance apart. Or would this deflection measurement due to a raindrop only give us energy? A leaf would be springlike, whereas the wood block was gravity restored to its original position. If there were a substance delicate enough that a falling raindrop could break it, that could be a force measurement. A delicate enough strain gauge should be able to directly measure the force. Perhaps a target attached to a phono stylus could measure the force. Edison (talk) 20:29, 11 January 2009 (UTC)

Crude death rate map

In my wanderings around wikipedia, I came upon this map of the crude death rate for different countries of the world. When you see a map like that, you have an expectation of how it will look, you expect at least some correlation with affluence. You know, Europe, the US, Canada, Australia and a few others will be really pale, while Africa would stand out sharply, and South America and Asia somewhere in between (like this map, for instance). And while it does follow some of those conventions (Africa having a high rate, for instance), there are a number of things in there that are really strange. All of Europe, besides Ireland, are fairly high on the scale. Mexico is lower than the US and Canada. In fact, the countries with the lowest rate are Mexico, Saudi Arabia, Jordan, Syria, Algeria, Libya, Venezuela, Paraguay and Ecuador. It's not exactly the list of countries you would expect to stand out in a map like that. I mean, seriously, Syria is kicking Scandinavia's ass! So what's up with that? I mean, if your country really is really dirt poor, then it seems to have a high death rate (as evidenced by Africa), but once it passes a certain threshold, it looks essentially random. But it can't be completely random, because all of Europe is one color (which would be an extraordinary coincidence). There has to be some factors lowering the score for some countries, but I can't for the life of me think of what they might be. Any one got any ideas? Belisarius (talk) 02:04, 10 January 2009 (UTC)

I presume that's because there are two drivers of longevity - health-care is one driver - but the other is healty eating and good exercise. In the US, terrible diet and a tendency for people not to exercise appropriately somewhat cancel out. Other countries have better healthcare - others, whilst being more 'primitive' in the realms of healthcare have people who don't weigh too much and who get plenty of exercise. SteveBaker (talk) 02:12, 10 January 2009 (UTC)

The map you cite is from the CIA World Factbook. They have a "notes and definitions" page where it says under "death rate":

"This entry gives the average annual number of deaths during a year per 1,000 population at midyear; also known as crude death rate. The death rate, while only a rough indicator of the mortality situation in a country, accurately indicates the current mortality impact on population growth. This indicator is significantly affected by age distribution, and most countries will eventually show a rise in the overall death rate, in spite of continued decline in mortality at all ages, as declining fertility results in an aging population."

--Milkbreath (talk) 02:26, 10 January 2009 (UTC)

Since the death rate is deaths per 1000 population, it makes sense that countries in Europe would have higher death rates, since their population growth has plateaued. In most of Europe, the general population growth rate is flat or actually negative; thus deaths in Europe represent a greater proportion of the population in any given year than in countries with rising populations. The U.S. probably has similar longevity expectations as Europe, however since the population growth is higher, the number of deaths as a proportion of the population is driven downwards. In countries with appalling health conditions and lower longevity expectations, even high population growths are offset by MUCH higher death rates. Because death rate is intertwined with such data as birth rate, immigration, and emigration the number is probably less of an important indicator of overall living conditions than is perhaps life expectency, which is not dependant upon changing populations... --Jayron32.talk.contribs 03:16, 10 January 2009 (UTC)

I like the aging population thing, that sounds like it's the reason. Even though affluent countries have low mortality rates for individual age groups, because the population is, comparatively speaking, so old, the overall death rate is higher. That indeed makes sense. Belisarius (talk) 04:18, 10 January 2009 (UTC)

The infant mortality rate map also shows a skewed picture. Compare e.g. to this site Among the industrialized nations the U.S. and Canada keep performing below par. Some of the reasons cited for the U.S. are a high rate of teenage pregnancies, unavailability of quality health care for low income and illegal immigrant families with higher than average birth rates in those same population segments, and at least one study cited that due to improved prenatal care and fertility treatments babies were being delivered that were pre-term and/or of poor health to begin with. _Lisa4edit 76.97.245.5 (talk) 07:05, 10 January 2009 (UTC)

Yes. Even though developed countries have lower death rates at each age compared to developing countries, they have higher overall death rates due to their relatively older population. You need to compare actuarial tables across countries to get a more accurate picture. Zain Ebrahim (talk) 07:30, 10 January 2009 (UTC)

op amp

why the op amp is given the dual power supply? what the meaning of dual power supply? how to know weather the capacitor is charging or discharging? —Preceding unsigned comment added by KARTHICK18ECE (talk • contribs) 11:49, 10 January 2009 (UTC)

First of all, have you read our Operational amplifier article? It's VERY good.

• Op-amps typically have power supply pins labelled something like V_s+ and V_s- but those are really just 'power' and 'ground'. They aren't labelled like that because sometimes you'd like to amplify signals that go from negative voltages to positive - in which case V_s- is just the negative power rail rather than ground. The OpAmp doesn't care about where true ground is so the pins are labelled as two power rails rather than as power and ground...but that's what they are (essentially).
• When you talk about "the capacitor" - do you mean the internal 30pF compensation capacitor? I'm not quite sure what you mean by that question - or why you'd care what was going on with it. It's slap in the middle of a ton of other circuitry inside the chip - so you certainly can't measure its charge directly.

SteveBaker (talk) 13:59, 10 January 2009 (UTC)

Since Karthick is talking about the power supply, perhaps he means the power rail decoupling capacitors. In the case of a dual-rail op-amp then there are two of them. A 'discharged' capacitor is one with zero volts across its terminals, and a 'charged' capacitor is one that has a non-zero (either positive or negative) voltage. When the circuit is switched on, both capacitors 'charge' until they reach the supply voltages. When the op-amp draws a surge of supply current, both capacitors briefly 'discharge' to supply the extra current. Then, after the surge ends, both capacitors 'charge' up again from the supply rails. --Heron (talk) 13:03, 11 January 2009 (UTC)

Ah - yes. That's a good thought. In which case, the capacitor is essentially just filtering out noise from the supply rails. Presuming that the capacitor is large enough and the noise level low enough, the capacitors should be essentially fully charged all the time...but if you went with capacitors with insufficient rating or a capacitance too low for very low frequency noise - then all bets are off. It's rather hard to think of that in terms of capacitor charge states rather than thinking in terms of low-pass filtering math. SteveBaker (talk) 16:59, 11 January 2009 (UTC)

Recuperation after a stroke

Why do some people recuperate their abilities after a stroke? After damage of neuronal tissue, it is gone forever, isn´t it?--Mr.K. (talk) 16:27, 10 January 2009 (UTC)

There are a large number of variables separating the prognosis of two patients. The location of the stroke, the kind of stroke, how quickly medical assistance was secured, the general health of the individual, genetic predisposition, etc. are all factors that come into play and there are probably several more. Any one of those could influence how much damage is done. While neurons generally can't re-grow, it could be the case that the stroke took place in an area where the deficiency was less obvious or where there was enough good tissue to compensate for the damage. In some cases, the recuperation is more like re-learning, as the patient slowly regains ability by having different areas of the brain take the load for the damaged bit. See stroke recovery for great deal of information. Matt Deres (talk) 16:42, 10 January 2009 (UTC)

Pretty much agreeing with Matt. It's not quite as black and white as you might believe. Stroke recovery is highly dependent upon many factors, such as those Matt listed above. Neurons often cannot repair themselves, but working neurones around them can take up the workload in some cases. Recovery generally depends upon how damaged the tissue is (+how widespread), and the time before medical teams stepped in. —Cyclonenim (talk · contribs · email) 17:22, 10 January 2009 (UTC)

For a little bit more of what Matt and Cyclo are talking about when they say other parts of the brain take the load, Neuroplasticity#Treatment_of_brain_damage. --Bennybp (talk) 20:14, 10 January 2009 (UTC)

January 11

Polarisation and magnetisation

In electromagnetism, there is an ${\displaystyle \mathbf {E} }$ field and a ${\displaystyle \mathbf {B} }$ field. When there are objects present (as opposed to only vacuum), we often introduce the ${\displaystyle \mathbf {D} }$ and ${\displaystyle \mathbf {H} }$ fields, as tools to aid in our calculations. Still I would say ${\displaystyle \mathbf {E} }$ and ${\displaystyle \mathbf {B} }$ are the physical fields – the ones charged particles actually respond to.

When an object is penetrated by an electric field, its material can get polarised, which means that inside it, an electric dipole moment density ${\displaystyle \mathbf {P} }$ arises. This is due to the so called "bound" charge density ${\displaystyle \rho _{\mathrm {b} }=-\nabla \cdot \mathbf {P} }$ into which the positive and negative charges of the material arrange themselves in response to the felt electric field. The amount of polarisation is typically proportional to this field: ${\displaystyle \mathbf {P} =\chi \varepsilon _{0}\mathbf {E} }$. The bound charge contributes just like other, "free" charge to the electric field: ${\displaystyle \nabla \cdot \mathbf {E} =(\rho _{\mathrm {f} }+\rho _{\mathrm {b} })/\varepsilon _{0}}$. Note that this means that the polarisation in a point inside the object depends not only on the external, free charge, but also on the polarisation everywhere else throughout the object. Now, the ${\displaystyle \mathbf {D} }$ field is defined as ${\displaystyle \mathbf {D} =\varepsilon _{0}\mathbf {E} +\mathbf {P} }$ so that ${\displaystyle \nabla \cdot \mathbf {D} =\rho _{\mathrm {f} }}$. Thus, ${\displaystyle \mathbf {D} }$ is what ${\displaystyle \mathbf {E} }$ would have been (save for a constant factor) if there were no ${\displaystyle \rho _{\mathrm {b} }}$, i.e., if there were no object present.

Analogously to polarisation, we get magnetisation ${\displaystyle \mathbf {M} }$, corresponding to a "bound" current density, when a material is penetrated by a magnetic field. We define ${\displaystyle \mathbf {H} =\mathbf {B} /\mu _{0}-\mathbf {M} }$, which is what ${\displaystyle \mathbf {B} }$ would have been (save for a constant factor) in the absence of the object. Finally, and here comes my question, I would expect ${\displaystyle \mathbf {M} }$ to depend on the actual ${\displaystyle \mathbf {B} }$, but rather, one writes ${\displaystyle \mathbf {M} =\chi _{\mathrm {m} }\mathbf {H} }$, as if the magnetisation isn't affected by what happens in other parts of the object. How can this be?

I just now realise that by rearranging, I can get ${\displaystyle \mathbf {M} =\mathbf {B} \chi _{\mathrm {m} }/(\mu _{0}(1+\chi _{\mathrm {m} }))}$, so now it looks like ${\displaystyle \mathbf {M} }$ does feel ${\displaystyle \mathbf {B} }$ (and in my mind therefore can be affected by conditions in other parts of the object). On the other hand, I can also get ${\displaystyle \mathbf {P} =\mathbf {D} \chi /(1+\chi )}$, losing the nice behaviour of the polarisation. How should all this be interpreted really? —Bromskloss (talk) 01:59, 11 January 2009 (UTC)

I got a question if water can explode?

Sometimes Im haulin a freight of it and its got hydrogen in it. Just like the Hindenberg,- and that exploded. What if the hydrogen escapes? I got lots of guys sodering around here and dont want no ambulance or clean up bill.--Troy da truck driver (talk) 02:59, 11 January 2009 (UTC)

It takes a lot of energy to separate the hydrogen in water from the oxygen, it's not going to happen accidentally. See Electrolysis of water if you want some details of the work required. --Tango (talk) 03:12, 11 January 2009 (UTC)

Hell, you got to have one of those expensive degrees/toilet paper that I aint got to cut thru that thick fog of nebuloformulas. Please explain the article to me in beer drinking, wife beater English, if you'd be so kind.--Troy da truck driver (talk) 03:30, 11 January 2009 (UTC)

I know you're trying to be funny, but "wife beater" kills the mood. --Scray (talk) 03:48, 11 January 2009 (UTC)

"Wife-beater" is a kind of t-shirt. - Nunh-huh 05:18, 11 January 2009 (UTC)

Simply, the most dangerous thing that is going to happen to water is that it gets very hot and starts to boil. Have many people soldering nearby do you think it requires to heat a freight tank of water enough to get it boiling? Or lets put it another way, if large tanks of water were likely to explode when situated near to heat, do you think fire departments would use water to douse fires? Rockpocket 04:49, 11 January 2009 (UTC)

Water is like the ash you get after you burn a lump of wood. Water is the 'ash' left over after you burn hydrogen. You can't burn ash and you can't burn water - same deal. Ash has no energy left in it - neither does water. You have nothing to worry about. SteveBaker (talk) 05:27, 11 January 2009 (UTC)

OP says he's not hauling water but hydrogen. So I guess the question would be "Can a hydrogen - air mixture explode." I'm also not quite sure we can blow off water exploding quite so fast. See BLEVE. It's not a question whether water can burn but more of whether you get a chain reaction of rapid (heat) expansion AFAIK. I once went to a lecture by a guy who mentioned "anything can explode if you get the distribution of particles fine enough." I've been wondering about that ever since. --76.97.245.5 (talk) 06:06, 11 January 2009 (UTC)

• No, he said he's hauling "it and it's got hydrogen in it"; in other words, "it" is water, as per the question title. --Anonymous, 07:09 UTC, January 11, 2009.

A BLEVE only happens with pressurised, flammable liquids - water isn't flammable and whoever trucks water under pressure? The question is quite clear: "...if water can explode". Our OP realises that water CONTAINS hydrogen - and that's the cause of the concern. Whoever told you that "anything can explode if you get the distribution of particles fine enough." was an idiot. Only combustible things can explode - no matter how fine you get the distribution of particles. A fine mist of particles will increase the RATE of reaction - but it can't conceivably alter the DIRECTION of the reaction. If it did, then you could make a perpetual motion machine by alternately burning water then burning hydrogen. This is a stupid discussion. There is only one possible, conceivable answer and that is a simple, unequivocal "NO!". Let's not muddy the waters for an already confused OP. SteveBaker (talk) 06:53, 11 January 2009 (UTC)

The previous example relating water to ash says it all. Genius! -Pete5x5 (talk) 08:17, 11 January 2009 (UTC)

Just to play devils advocate: Could I use water as the fuel for a nuclear fusion explosion? Of course pressure and temperature would need to be extremely high, and the water would be dissociated already. But would a neutral plasma of two parts hydrogen and one part oxygen start a fusion reaction under the right conditions? For extra points: If yes, how exotic does it have to be, and how efficient would it be compared to pure hydrogen? --Stephan Schulz (talk) 08:33, 11 January 2009 (UTC)

Apparently I misread OP's post. Not wishing to confuse him I'd have to ask him to consider the following as unrelated to his post. I can't agree with Steve's assertions that BLEVE requires flammable liquids. Our article expressly states that that isn't so. As for the "idiot" there seem to be quite a few of them with impressive bits of "toilet paper" on their walls. 76.97.245.5 (talk) 09:38, 11 January 2009 (UTC)

Regarding vapour explosions, water can cause a vapour explosion by boiling in a pressurised environment, but it still needs an energy source to heat the water (seeing as water is not combustible and so cannot release any energy through chemical reactions with natural present chemicals), and seeing as the OP mentioned soldering as the only concerning energy source, I think we are safe, as a soldering is not capable of boiling any significant amount of water at any rate even if it is foolishly left submerged. —Preceding unsigned comment added by 92.16.196.156 (talk) 15:25, 11 January 2009 (UTC)

If the water is super-hot, you can of course have a steam explosion. --Sean 18:40, 11 January 2009 (UTC)

There is another way that water can explode, when it freezes in a rigid container, such as glass. Since it increases in volume when it freezes, this can cause the container to rupture. StuRat (talk) 06:09, 12 January 2009 (UTC)

Audio quality - sampling rate versus bits per sample.

I'm trying to make a Arduino computer board play music and simple sound effects - such as you might find in a computer game. Various trade-offs in the $4 computer hardware(!) mean that I have a choice between higher frequency sampling rates and higher number of bits per sample. The system can't do both high sample rates AND high sample precision. If I want to double the sampling rate - I have to knock off one bit from the sample precision. If I want to add a bit of sample precision, I have to halve the sampling rate.

I can have 8kHz sampling rate with 10 bits of precision - or 16kHz with 9 bits or 32kHz with 8...and so on.

How do I make the trade-off to get the best quality of sound to the human ear? Does it make a difference whether I want to play sound, voice or sound effects? I also have an RC audio filter on the output - and I can choose the resistance and capacitance to do whatever filtering is needed.

SteveBaker (talk) 07:05, 11 January 2009 (UTC)

One thing to consider is Nyquist frequency: for example, if you care about sound components with frequencies >8kHz, you really need >16kHz sampling but if you can convince yourself that you only care about somewhat below 8kHz, you can probably get away with 16kHz sampling. O'Reilly's Web Design in a Nutshell has this to say about sample-rate: "As a general guideline, audio files that are voice-only can be reduced down to 8 KHz. Sound effects work at 8 Khz or 11.025 KHz. Music sounds acceptable at 22 Khz." Here is a breakdown of ranges of some sound types. Or get a CD of some representative types of sounds and fiddle with the equalizer to see what range cutoff doesn't sound crappy. DMacks (talk) 07:41, 11 January 2009 (UTC)

Yeah, yeah - I understand all of that. I want 22kHz (roughly the upper limit of human hearing) and that needs >44kHz (because of Nyquist). I'd also like to have at least 12 bits of precision per sample. But I simply can't have that much because this project is engineered down to a price - not up to a quality-bar. I know I can't get what I want - and the music is going to sound pretty bad. But what I need is to do the very best I can with what I have in a $4 Atmel AVR computer! What I'm really looking for is the relationship between "perceived sound quality" and the sampling rate AND (importantly) the number of bits per sample....perhaps "dynamic range" is the thing I need to think in terms of...but I'd like some science. SteveBaker (talk) 16:47, 11 January 2009 (UTC)

Perhaps the best way to find out the answer is through experimentation. Start with a high-quality audio file of the type of music you want to play, reduce the sampling rate and/or precision, and see what combination gives you the best compromise. Not actually having tried it myself, my inclination is to go with 32 kHz at 8 bits. Having way too little bandwidth leads to very noticeable reduction in quality. Compare, for example, FM radio's 15 kHz audio bandwidth against AM radio's less than 5 (IIRC); the difference is dramatic. --98.114.98.136 (talk) 17:24, 11 January 2009 (UTC)

Again, the link I posted breaks down different types of sounds (including "voice" and "piano", which seem representative of two of your three areas of interest) and what quality various eq bands contribute. Seems to support 98's 32kHz sample-rate thought, given that up to 8kHz sound components look pretty important, therefore 16kHz sample would probably distort badly there. DMacks (talk) 19:31, 11 January 2009 (UTC)

Is the limit in RAM or CPU speed? If it's RAM (or for that matter, flash memory, EEPROM or IO pins), try the Sanguino instead ? If 4K isn't enough, wait 3 months and you may have 16k . BTW, while I'm not an audio engineer I strongly suspect for speech only 8k with 10 bits might be better. Most speech codecs are 8kHz, even say G.711's μ-law algorithm and A-law algorithm which in terms of perceived quality are still some of the best telephony codecs around (admitedly that's because all of the other ones have concentrated on bandwidth). I'm sure there most be some listening tests out there that will offer some help. You may want to try the Hydrogen Audio forums (people who really understand audio and science hang out there and do double blind tests etc, not the junk OMG my $200 cable has so much better air or OMG fibre optic gives so much better quality for my digital audio then coax or other mumbo jumbo kind) Nil Einne (talk) 21:35, 11 January 2009 (UTC)

No - it's not exactly RAM or CPU that's the problem here. The ATmega chips don't have a 'real' digital-to-analog converter. They use a technique called PWM (Pulse-Width Modulation) whereby there is an internal hardware counter that counts up to some specified value then turns on a digital output pin - then it counts up to a different specified value and flips it back to a zero again - the resulting digital signal is then integrated with a simple RC low-pass filter to make a true analog waveform. The ratio between the "on" and "off" time is therefore the "analog" value. So we have a '1' bit emitted for 'A' clock cycles and a '0' but emitted for 'B' clock cycles - and my software can set A and B as frequently as is reasonably necessary to maintain the sample rate (I could certainly update those numbers at 20kHz - maybe at 40kHz if I don't need much CPU time to do everything else). So here are the 'givens':

• A+B must equal the clock-rate divided by the desired audio sampling rate.
• A/B gives the voltage.
• A and B are both integers
• The underlying clock ticks at 8MHz (I can't change that - it's the clock frequency of the chip).

So if I make the sample rate be (say) 8kHz - then A+B=1000 clock ticks and I can vary A from 0 to 1000 and B from 1000 to 0 and end up with A/B having values from 0 to 1 in steps of 1/1000 - ie a 10 bit sample precision. If I make the system run at 16kHz then A+B=500 clock ticks - so A can be anywhere between 0 and 500 and B anywhere from 500 to 0 - and now A/B is accurate to only 9 bits. So there is a straight trade between sample frequency and sample precision.

I could do this experimentally - but there are several reasons why not:

1. I'm getting a little deaf and at 54 years old my high frequency hearing is crap. 16kHz might sound OK to me...but not to anyone else!
2. The software for replaying audio on such a horribly limited machine is a bitch to write - there is all sorts of ugly trickery involved and changing the sample frequency and precision is FAR from a matter of changing a command line parameter and running it again! It takes me HOURS to write the code because each precision trick requires different data compression and byte alignment.
3. I'd like to understand the relationship that's underlying this. These two numbers are GENERALLY completely unrelated in terms of performance - but here they are tightly (and annoyingly) coupled!

SteveBaker (talk) 23:15, 11 January 2009 (UTC)

Steve, Would your system allow for "subband processing" with variable bit-allocation ? Say, using 12 bits/sample for 0-500Hz range (sampled at 1000 samples/s), 11 bits for 500-2000Hz and so on. The system design problem will be significantly more complicated but it will permit a better quality/processing-power tradeoff - at least if you were designing a system from scratch. Abecedare (talk) 21:47, 11 January 2009 (UTC)

I'm not outputting simple sine waves - these are things like short audio samples or waveforms made by 'FM-synthesis' and driven with MIDI-like note-on/note-off data for music with four note polyphony. So I don't really know what frequencies are present in the music signal - but for sample data, I could probably do some offline processing to extract two bands of frequencies. I could certainly do something different for speech than for music if that helps. I suppose I could use multiple PWM outputs (I might have one or two to spare) added together off-chip...but splitting my audio into bands in realtime is a bit 'ikky'. It's worth thinking about though - that's definitely food for thought - thanks! (However, I'd STILL like to understand the relationship between sample frequency and sample precision in terms of how they affect perceived quality. SteveBaker (talk) 23:15, 11 January 2009 (UTC)

To address your last point (understand the relationship between sample frequency and sample precision in terms of how they affect perceived quality) on a completely theoretical level:

1. Essentially, you are looking for the bandwidth B vs (quantization) noise Q tradeoff. As a starting point, you can compute the information theoretic channel capacity, making the usual AWGN modelling assumption, to see whether (8kHz, 10 bits) is "better" than (16kHz, 9 bits).

2. However the channel capacity results are likely to be quite irrelevant to your problem, since they ignore all a priori information about the source (voice, music) and receiver (human ear). So here is another strategy:

• For large enough number of bits M, one can confirm that the quantization noise is white and compute its noise level (power spectral density) Q,
• Now analyze the spectrum of your "typical" audio signal. We would expect this spectrum to level off or start decreasing for higher frequencies.
• Roughly speaking, there is no point in preserving the spectral components of the audio signal that are not "significantly" larger than the noise at that frequency. So this provides an upper bound on the largest "useful" sampling frequency corresponding to number of bits B. Now we play around with different choices of B's to try to get the useful sampling frequency and achievable sampling frequencies to "match" as closely as possible.
• This scheme is likely to be better than (1), since it at least takes some account of the properties of the signal source. But it is still has several problems, such as (a) it ignores any properties of the human ear, (b) the optimal scheme will depend upon the audio source (voice vs music vs type of music, say samba vs classical :) ) and (c) even for a fixed audio source (i.e., fixed spectral shape) the optimal scheme will depend upon the volume ( at which the audio is played dynamic range), since playing the music at half the volume is equivalent to reducing the number of "true" encoding bits used by 1, or doubling the quantization noise level.

3. One can further extend the above scheme to account for at least some information about the hearing system. For example, we know that the ear is less sensitive to higher frequencies (see adjoining image). So before comparing the audio spectrum with the noise source in (2) above, we can "weigh" it by the hearing sensitivity (see noise shaping, for a related though non-equivalent idea). Of course, this scheme too is completely heuristic and far from perfect, since, in addition to the problems noted in (2), the sensitivity curves are derived by playing a single tone at a time, and ignore effects like frequency masking.

In summary, the question you pose has a far from straightforward answer! Note: I know you have a information theory background, so I have not bothered to explain or even wikilink all the techical terms or write down the formulas for computing channel capacity, converting between number of bits B and noise level Q etc. And the problem of defining the terms written in quotes ("weigh", "useful" ," better", "match" etc.) is left as an exercise for the student. :) Abecedare (talk) 01:15, 12 January 2009 (UTC)

Another point to note: Typically for music we care about (perceived) fidelity, while for noise the goal is often intelligibility. That means, that in order to do a real good job we need to consider not only the different spectral properties of these two sources, but also worry about how these sources are processed cognitively. Incidentally, all these issues arise not only in the field of audio compression but also in the design of hearing aids/cochlear implants, where the design engineers have to work under severe physical size and power consumption constraints. Abecedare (talk) 01:23, 12 January 2009 (UTC)

Getting Younger Every Day

A 50-year-old Arctic explorer is 10 feet from the North Pole. He walks around the Pole, moving from West to East. As he does that, he crosses the International Date Line and the date moves back one day. He walks around the Pole again, and the date moves back again. How many times does he have to walk around the Pole to beome 25 years old? – GlowWorm —Preceding unsigned comment added by 174.130.253.174 (talk) 09:59, 11 January 2009 (UTC)

Assuming what you're saying works, 25*365 times. (But it doesn't work)124.169.223.172 (talk) 10:10, 11 January 2009 (UTC)

Not enough - you forgot the leap years. Since the number of leap years in 25 years varies depending on when you start walking - we can't give a single answer. (And it's a silly question - so I'm not going to bother working it out.) SteveBaker (talk) 16:07, 11 January 2009 (UTC)

This is one of those questions like how many eggs does a Leghorn rooster lay in a week? The effect of crossing the International Date Line is not cumulative. If it's Friday 10:00 on one side and Thursday 10:00 on the other that difference still persists after you've spent 14 min walking around the pole and crossing from Friday 10:14 into Thursday 10:14. The time line separates "locally observed" times. If you wanted to follow the time zones you'd have to adjust your watch every minute, half-minute or three quarter-minute till you get back to the dateline (not quite accurate because there is some odd stuff in the Pacific for 2 hrs every day.) Your explorer could always invent a new calendar that counts years differently. As a positive side effect he can do that in his tent while sipping hot cocoa instead of having to walk around in the cold. 76.97.245.5 (talk) 10:52, 11 January 2009 (UTC)

It doesn't work (aside from the obvious reasons) because as the explorer walks around the pole, he crosses 23 other time zones. If he's following the rules, he puts his watch ahead one hour every time he crosses a time zone - then puts it back 23 (not 24!) hours when he crosses the International date line. Hence he "ages" 23 hours and then "gets younger" by 23 hours on every loop. Overall - no gain! SteveBaker (talk) 16:07, 11 January 2009 (UTC)

Why 23? UTC-12 does exist.See also File:Timezones2008 UTC-12.png Nil Einne (talk) 20:58, 11 January 2009 (UTC)

The time zones don't have such a simple structure. There aren't 24 wedge-shaped zones converging at the poles. I know they use New Zealand time "throughout Antarctica" (i.e. at the few research stations in Antarctica), so you won't cross any time zone boundaries walking around the pole down there. I doubt the north pole is in any defined time zone; polar explorers can set their watches however they want. Also, there are a lot more than 24 times zones. Many nations and parts of nations are a half-integral number of hours from UTC, like India at UTC+9½. The Chatham Islands are at UTC+12¾! Even the integral offsets from UTC range from UTC−12 to UTC+13 (26 choices, not 24). Here's the map I extracted most of these factoids from: . Then there's daylight saving time. Different regions might use the same time for some parts of the year and a different time for other parts because their DST start and end dates are different or one of them doesn't have DST. And DST goes in opposite directions in the northern and southern hemispheres.

But none of this matters because it's trivially true that the total time change around any closed loop will be zero, regardless of the nature of the zones. -- BenRG (talk) 21:20, 11 January 2009 (UTC)

Actually a few research stations (in Antartica but not the South Pole) do use different timezones, see , and . Sometimes a research station belonging to a specific country will use that countries timezone but others use the timezone of their supply base which is commonly NZ Nil Einne (talk) 08:55, 12 January 2009 (UTC)

On the plus side, if he does try it he'll never have to fret at turning 51 years old. (He probably won't even survive a day) Nil Einne (talk) 20:54, 11 January 2009 (UTC)

Yes, it has to do with time zones. There are 24 time zones around the earth. As the explorer exits each time zone, he sets his watch forward 1 hour. When he crosses the International Date Line he sets his calendar back 1 day. When he exits a time zone at 11:xx a.m. he sets his watch to 12:xx p.m. The date does not change. But when he exits a time zone at 11:xx before midnight, he sets the watch to 00:xx a.m., and he must also set his calendar forward 1 day. He then completes his walk to his starting point, setting his watch forward as he exits each remaining time zone. When he gets back to his starting point, he will be older by the time it took to walk around the Pole. Briefly put, he sets his watch forward by 1 hour 24 times in his walk around the Pole. That counteracts setting the date back 1 day when he crossed the International Date Line. – GlowWorm. —Preceding unsigned comment added by 174.130.253.174 (talk) 20:53, 11 January 2009 (UTC)

Apparent Size of the Moon

One night driving somewhere I noted that the moon appeared very large. This brings a few questions to mind. Does the apparent size of the moon change with season? Does the apparent size of the moon change with variations in the atmosphere? Finally, does the atmosphere cause any permanent shift in apparent angular size of objects outside the atmosphere? Noodle snacks (talk) 12:24, 11 January 2009 (UTC)

The apparent size of the moon is a psychological phenomenon. Ses . - Nunh-huh 12:36, 11 January 2009 (UTC)

• Nevertheless, the OP's observation is correct. The full moon yesterday night was the largest we'll see in 2009, according to this source and others. --NorwegianBlue 13:04, 11 January 2009 (UTC)
• Yes, a part of of the effect is psychological. But the moon also is an an elliptical orbit. Since it moves around the sun with the earth, the full moon sometimes will be further from the earth (when the long axis coincides with the line earth-sun at the time of the full moon, and the longer part of hat axis is away from the sun, or in show-off lingo, when apogee and full moon coincide), and sometimes will be closer to the sun (again, the extreme case is the alignment of the axes and the longer part of the long axis pointing towards the sun). At the moment, we are in the "close moon" scenario, and a number of newspaper have reported on this. See and . --Stephan Schulz (talk) 13:17, 11 January 2009 (UTC)

The Moon appearing larger when it is close to the horizon compared to when it is high in the sky (the Moon illusion) is almost completely psychological.

As for optical phenomena due to Earth's atmosphere, there is atmospheric refraction which causes objects close to the horizon to appear higher up than they really are (and also causes obects slightly below the horizon to appear above the horizon). This has a very small effect upon the apparent size of the Moon near the horizon: It is smaller than higher in the sky, but only in the vertical direction; this is because the atmospheric refraction is smaller at the upper limb than at the lower limb, and this difference is larger closer to the horizon.

And regarding the distance of the Moon from Earth, it does vary, as NorwegianBlue and Stephan Schulz already mentioned. But because the Moon's orbit ellipse itself rotates (the period is somewhere between 8 and 9 years), the largest full Moon doesn't always occur in the same season.

Icek (talk) 16:09, 11 January 2009 (UTC)

There certainly ARE some very small, very subtle effects due to distortion by the atmosphere and the nature of the moon's orbit - but those effects are negligable compared to what we're discussing here. The practical problem with the moon is purely an optical illusion. When the moon is high in the sky - away from terrestrial objects - you have nothing to use to estimate it's "size" - so your perception of the size "goes into free-fall". Interestingly - I recently managed to prove this theory quite conclusively using computer graphics. In my flight simulator graphics system (where the image is projected onto the inside of a 30 foot dome using lasers!), there is no atmospheric distortion (or any other kind of distortion for that matter). The number of pixels covered by the moon on the screen didn't change AT ALL - yet people STILL claimed that the moon changes size! I noticed this because one of my managers spotted the "change in the size of the moon" as I moved it around in the sky - and complemented me on having gone to the trouble of writing software to simulate the "atmospheric effect"!! Hey - I'll take all the credit I can get OK? SteveBaker (talk) 16:18, 11 January 2009 (UTC)

Also, the biggest full moon anytime in either 2008 or 2009 was on December 12, 2008. So if you saw the moon then, there's a good chance you might have noticed a larger-than-usual moon. It was also brighter than normal, some people in Florida reported the moon to be "pulsating". ~AH1 18:39, 11 January 2009 (UTC)

How satisfying. Last night (Sat 10th) my wife commented that the moon looked bigger and brighter than normal, and she was right (for once). Rockpocket 19:47, 11 January 2009 (UTC)

What are recent developments in Internal Combustion Engines?

(SB: Added this title) SteveBaker (talk) 15:55, 11 January 2009 (UTC)

what is the recent development in IC engines? —Preceding unsigned comment added by Just.chintu (talk • contribs) 13:21, 11 January 2009 (UTC)

6 stroke ICs. For one. —Preceding unsigned comment added by 92.16.196.156 (talk) 16:11, 11 January 2009 (UTC)

There are so many to choose from! Gasoline direct injection is pretty cool - it's what lets my MINI Cooper'S get 35 to 40 mpg and still push the car from 0-60 in under 7 seconds with a top speed around 140mph! SteveBaker (talk) 16:23, 11 January 2009 (UTC)

It's not very new, but I believe the Wankel engine has recently become more widespread. --Sean 18:46, 11 January 2009 (UTC)

What IS relatively new about the Wankel that's made is more useful is the bearings used at the tips of the rotors. As the rotor (the only moving part!) spins, the tips rub against the cylinder walls and that wear made for short engine life. Evidently the folks at Mazda have found a way around that - which makes their Wankel look pretty attractive. SteveBaker (talk) 22:39, 11 January 2009 (UTC)

One neat trick I liked in the '08 MINI Cooper is the idea of using the starter motor to accelerate the car from stationary to a few miles per hour before the spark is turned on an the engine fires. Sadly, for some bizarre legal reason, this isn't allowed in the USA - so the US variant (that I have) doesn't do it. But the idea is clever: An IC engine doesn't run at all well at very low RPM - and even in first gear, you're "lugging" the engine as you pull away from a standing start which is very bad for it - so this trick increases engine life. Secondly, IC engines have very poor torque at low RPM - and electric motors have the same torque at all RPM - so they do well at getting the car rolling and that saves you fuel. Finally, in stop-start traffic, you are effectively driving an electric car. It's a cheap way to get hybrid-like performance without all that fancy extra 'stuff'. Aside from a slightly more robust starter motor, all it takes is a little extra software in the computer. It's really annoying that this isn't legal in the USA - some stupid law that could be 'fixed' at the stroke of a pen would save a lot of gasoline and engine wear. I believe BMW will be putting this feature in all of their new cars this year. SteveBaker (talk) 22:39, 11 January 2009 (UTC)

tingling in the chin

(Question removed)

Sorry - we are not allowed to diagnose medical conditions on the WP:RD. If you (or anyone else you know) is concerned about their health - they should seek immediate medical advice. Sorry. SteveBaker (talk) 17:21, 11 January 2009 (UTC)

Levitation - frogs or otherwise.

The article Orders of magnitude (magnetic field) says:

1.25 T - strength of a modern neodymium-iron-boron (Nd2Fe14B) rare earth magnet. A coin-sized neodymium magnet can lift more than 9kg.

...and...

16 T - required strength to levitate a frog

I've seen the Discovery-channel show that demonstrates the levitating frog - and there is a reference in our article that backs up the 16T number...does this mean I can levitate a frog with just a dozen or so coin-sized Neodymium magnets? Seems like I'd be able to feel that kind of a pull on my finger...which seems kinda unlikely. There has to be something wrong here...but what?

SteveBaker (talk) 17:19, 11 January 2009 (UTC)

Magnetic fields can't possibly be cumulative like that. Otherwise why would 100T be so hard to obtain, if you could just stack up 100 coin-sized magnets? (I'm not saying this as someone who knows much about magnetic fields, but it's clear from the article that even "just" 45T is pretty freakin' difficult to obtain, and so it can't be just a matter of stacking up magnets.) --98.217.8.46 (talk) 18:00, 11 January 2009 (UTC)

Yes - that's kinda what I was thinking - I just wanted to understand the physics of it. SteveBaker (talk) 22:24, 11 January 2009 (UTC)

Don't the magnetic field lines have to be coherent? Using 16 different magnets would result in crossing lines of magnetic force (which go from pole to pole). The diamagnetic repulsion then wouldn't have a single vector. (See also Magnetic levitation) Franamax (talk) 22:48, 11 January 2009 (UTC)

Here's some physics for you: . All you have to do now is figure out how the B fields of 16 magnets combine. ;) Franamax (talk) 22:56, 11 January 2009 (UTC)

Phosphate pit

What exactly is a phosphate pit? Thank you. (Joseph A. Spadaro (talk) 17:57, 11 January 2009 (UTC))

Do you have context? I could refer to the hole left after open-pit mining for phosphate ore. Rockpocket 19:39, 11 January 2009 (UTC)

Thanks. The context is the following news story, in which a murder victim's body was found floating in a phosphate pit: . At first when I read the story, I imagined that the murderers stored / hid their victim's body in a type of drum (or some such). After reading the story, it sounds like the victim was swimming in some type of open water (river, lake, pond, or whatever). That is the context. The story left me confused. Thanks. (Joseph A. Spadaro (talk) 19:45, 11 January 2009 (UTC))

I expect thats what it is, then. Mulberry, Florida, where the event took place, is the "Phosphate Center of the World."

I still don't "get it". Per the above reply, there's an open hole left after mining for phosphate ore ... OK. But, then what? What was the murder victim swimming in? This open hole just gets filled with water from the rain, etc.? And forms a lake or pond? I am still not "getting it". What exactly did the murder victim jump into and swim away in? Any clarification? Thanks. (Joseph A. Spadaro (talk) 20:00, 11 January 2009 (UTC))

Any open hole without sufficient drainage from the bottom is obviously going to get filled with water over time (well unless it's in a desert). This happens with tin mines in Malaysia File:Taiping lake gardens with hills behind.jpg and is bound to happen with open-pit phosporus mine too. These things are usually very deep so would probably be a convient place to hide a body. Nil Einne (talk) 20:33, 11 January 2009 (UTC)

See our article on Quarry. You will see several pictures of quarries (i.e. open pit mines) which have been filled in by rain water. When I was a kid, there was an old abandoned granite quarry where we used to go diving. It looked a lot like this pic: File:SandersQuarryIndiana.JPG. --Jayron32.talk.contribs 20:35, 11 January 2009 (UTC)

OK ... thanks ... I basically "get it" now. So, the headline of the news article could just as easily (and accurately) have stated that the murder victim's body was found floating in a lake (instead of using the term "phosphate pit") ... is that correct? Or did I miss something there? Thanks. (Joseph A. Spadaro (talk) 20:41, 11 January 2009 (UTC))

This was a local newspaper, so I presume they expected most people to understand the term. It's obviously more descriptive and accurate then simply 'lake' which could be any number of things and doesn't really convey the same meaning to me Nil Einne (talk) 20:46, 11 January 2009 (UTC)

Yeah, a phosphate pit or a quarry is definately different than a lake. If the local paper reported a body found in a phosphate pit, I would understand exactly what it meant, and a lake is something different. The problem is exactly as Nil Einne describes; the local paper is written for the local audience, which understands that phosphate pits will fill in with water, and so have no problem understanding the intent of the writer. For people who do not live in areas with these structures, it makes less sense. --Jayron32.talk.contribs 22:09, 11 January 2009 (UTC)

For purposes of hiding a body, the typical abandoned open pit is a much better choice than the typical natural lake. In general, a natural lake is a lot shallower than an man-made pit, although there are many exceptions. If you are careful to carefully attach weights, the body is much less likely to be found in the pit than in a lake. -Arch dude (talk) 02:26, 12 January 2009 (UTC)

light

is it true or false that mirages are due to the effects of refractions —Preceding unsigned comment added by 82.38.52.19 (talk) 19:14, 11 January 2009 (UTC)

See mirage. 62.128.252.85 (talk) 19:42, 11 January 2009 (UTC)

Briefly: true. SteveBaker (talk) 22:21, 11 January 2009 (UTC)

"Super greens" pills

Hi all,

Is there any value to those "super greens" or "super foods" pills they sell in health food stores or Whole Foods, those packed with spirulina, greens (wheat grass, broccoli, spinach, etc.), probiotics and so on? Are there any studies even suggesting that they might improve one's health? Can they really provide the "equivalent of a full day's serving of fruits and vegetables?"

I eat pretty healthy -- all home-cooked, lots of veg -- but I'm wondering whether adding these on top of my regular meals is silly or might be healthy.

Thank for any thought (I know -- not medical advice), — Sam 146.115.120.108 (talk) 21:47, 11 January 2009 (UTC)

Just to note... Drop the "I eat pretty healthy..." part of your question and it is a request for reference material, not a request for medical advice. As for studies, I assume you want unbiased scientific studies. The companies manufacturing these products do studies. Basically, they pop a pill or whatever they are marketing. Then, they wonder if they feel better. Of course. So, the pill must make everyone feel better. The lack of scientific studies by these companies leads to injunctions like this. -- kainaw™ 22:15, 11 January 2009 (UTC)

How can you pack a pill with all that stuff? Either it contains such small amounts that it's pointless or it actually contains certain things extracted from them (and is probably just like standard dietary supplements like multivitamins and iron supplements). There have been lots of studies on whether dietary supplements actually help (eg. see Multivitamin#Scientific assessment) and they have differing results. If you have a poor diet or are otherwise at risk (pregnant women, for example), then supplements can certainly help (although they obviously aren't a complete replacement to good food). If you are eating well and aren't at risk, then it is less clear, but if there is a difference it is probably small. With regards to the particular pills you mention, you need to read the packet and find out what is actually in them and in what quantities - if it doesn't break it down into different vitamins and minerals and whatever then you can guarantee that it is completely worthless. --Tango (talk) 22:19, 11 January 2009 (UTC)

Doing X will "flush the toxins out of your body"?

Hi all,

There are plenty of things that health websites and experts talk about that are supposed to remove toxins from the body -- drinking lots of water, fasting, sweating, exercise, detox diets, etc. etc.

Have there been any studies at all that show that doing any of the above things actually leads to a measurable decrease in the quantity of toxins in the body?

Thanks, Sam 146.115.120.108 (talk) 21:58, 11 January 2009 (UTC)

You must define what you mean by "toxins". Whenever I hear that term used in any advertisement for any service or product, its with 100% certainty that the product or service being sold to you is pure bullshit. There are many processes which the human body uses to filter waste materials from itself, generally the liver converts the offending material into something somewhat less offending, and the kidneys remove the material from the bloodstream and send it to the bladder, from whence it is eliminated by urination. If the material is genuine waste (i.e. material that is part of normal metabolic processess, but which must be removed from the body) this is the most common way for removal of it from the body. If you believe that this process doesn't work right for you, and have a genuine medical problem, please seek the advice of qualified medical professionals and not random strangers on teh interwebz. --Jayron32.talk.contribs 22:06, 11 January 2009 (UTC)

To the best of my knowledge, no. At least, not in relation to detox diets and the like - keeping hydrated, getting plenty of exercise and eating a healthy diet are all good things and may well help reduce toxin levels. For example, not drinking large amounts of alcohol is going to reduce the amount of alcohol in your system, but there's no need to stop eating completely in order for your liver to process alcohol (in fact, there's a good chance it would harm the liver's ability to function). If you want advice on how to stay healthy, go see a doctor, the internet is full of misinformation on such matters. --Tango (talk) 22:10, 11 January 2009 (UTC)

There was an interesting BBC New article on this just the other day. Rockpocket 22:47, 11 January 2009 (UTC)

Please correct me if I am wrong, but there is some evidence that milk thistle and NAC might be helpful to your liver. A Quest For Knowledge (talk) 01:00, 12 January 2009 (UTC)

Plenty of plants have medicinal uses, a very large number of our medicines have their origins in plants. If milk thistle does work then scientists will find out by doing trials and studies and will isolate the substance in it that does the job and then work out how to turn it into a drug. That's how pharmacology works. --Tango (talk) 01:53, 12 January 2009 (UTC)

Tango, you are quite correct. Unfortantly, an entire industry has sprung up selling alterative suppliments, some of which might work and some of which might not. But which ones are which? How does the average consumer know how to make such a decision? Until science conducts exhaustive studies of alternative suppliments, we don't really know which ones are which are legit and which ones are complete nonesense. These companies are making billions of dollars while science catches up to their claims.

In fact, I've thought about this problem a few times. I wish I was a billionaire philanthropist so I could create a legitimate scientific institute for the sole goal of examining (either confirming or debunking) the claims of the alternate medicine and alternate sumplement industries to find out which ones (if any) actually work. For years, we've had thousands and thousands of kids lifting weights and eating creatine because they think they it help them become stronger. But does creatine actually work? If so, how much? There does appear to be some evidence for creatine's effectiveness, but off the top of my head, I don't think that there has ever been any exhaustive, third-party, double-blind, peer-reviewed studies of creatine. Some of us have seen the so-call 'male enhancment' (a euphemism for penis enlargement) products on late night TV which are obviously bullshit, but are there any double-blind, peer-reviewed studies that actually make this conclusion? (There's only one product that I am aware of that can actually increase the size of the human penis but you rarely hear about it.) The two I referenced earlier, milk thistle and NAC have some scientic evidence to believe that they might actually be beneficial. Pardon my soapbox, but I guess what I am saying is that science moves too slowly and it would be nice if some effort was made to confirm/debunk the supplement industry. A Quest For Knowledge (talk) 05:26, 12 January 2009 (UTC)

I've had similar thoughts myself, although my solution is government funding of university studies to separate the wheat grass from the chaff. I would tend to trust the results of such studies, as long as those who benefit from sales of the supplements were not allowed to fund or otherwise influence them. Yes, this would be an additional tax burden on the public, but I feel there are a large number of potentially useful and inexpensive products out there, and once we knew what they were, we could benefit enormously. I'd also like to see cooperation between different nations and universities to divvy up the work load, much like the Human Genome Project. StuRat (talk) 05:44, 12 January 2009 (UTC)

Radar turns on a radio?

I was reading in Misplaced Pages:Reference_desk/Archives/Science/2009_January_5#Ray_that_stops_internal-combustion_engines and one person claimed tha radar directed at a radio will turn it on and make it play music. Google can't find anything relevant ot his topic, but is it true if you direct a powerful radar wave at a radio, suddenly the radio turns on and plays music with the radio unplugged? Thing is in ghost haunting stories, usually the ghost will turn on the radio with the radio unplugged. Are you ready for IPv6? (talk) 23:14, 11 January 2009 (UTC)

I can't see why it would play music, but it might play a single tone or something. It would be playing the radar wave itself. The radio only needs to be plugged in so that it can amplify the signal, if the radar is powerful enough then it wouldn't need amplification to be audible. --Tango (talk) 00:07, 12 January 2009 (UTC)

I guess the theory is that the radar would somehow induce enough voltage into the radio to power it even though the On/Off switch is in the Off position. Then it would simply power up as usual - and if it happened to be turned to a music station - it would play music. However - it's hard to imagine so much voltage induced in JUST the right place - without it also being induced somewhere undesirable and blowing up some critical component. So it all sounds a bit 'iffy'. Certainly not ALL radios would magically do this - most would do nothing, some would fail disasterously...MAYBE one in a thousand would play music. SteveBaker (talk) 00:28, 12 January 2009 (UTC)

Don't radios, like any other piece of electronics, require a positive power rail and a negative/ground power rail to function properly? How would a radar induce such a thing? Just having current randomly flowing in the wires isn't going to do anything useful. --Tango (talk) 00:41, 12 January 2009 (UTC)

Or if it was plugged in the radar might be picked up by the leads going to the "on" button, and switch the radio on. Depending on the type of switch. I'm not sure how likely that is, though. APL (talk) 00:14, 12 January 2009 (UTC)

If it was an electronic switch, then maybe, but I think most radios have mechanical switches (you press a button and it makes or breaks a physical connection). It could happen if the radio wasn't off but was actually just on standby, I guess. --Tango (talk) 00:26, 12 January 2009 (UTC)

I guess this is theoretically possible, but I think there would need to be an antenna/coil connected in a different way (to the power supply of the radio?) to actually generate any power. Very unlikely if at all possible. -Pete5x5 (talk) 05:14, 12 January 2009 (UTC)

January 12

A pile-up limit?

Regarding this from a local newspaper reader's response to a major traffic pile-up report:

I've never been able to understand 50 car pile ups. I'm not trying to be funny but you would think that after 40 or 45 cars are in a huge pile, it would give that 49th and 50th car a chance to slow down and avoid the mess. - Christian, Plaistow

...and it made me wonder if there is a "limit" beyond which the "huge pile" would prevent any further collisions. Honestly, I could never have come up with this one on my own :( -hydnjo talk 00:36, 12 January 2009 (UTC)

Do 50 car pile ups actually happen? I've never seen more than 5 or 6 cars involved in one accident. --Tango (talk) 00:38, 12 January 2009 (UTC)

What was I thinking? We, of course, have an article: Multiple-vehicle collision. Apparently they happen when there is poor visibility, so I guess the 49th and 50th cars don't know about the accident until they're part of it (you would think they would at least hear something, though...). --Tango (talk) 00:47, 12 January 2009 (UTC)

.Real time. Happened today (11 Jan '09 in Derry NH US) which is why the newspaper questioner posed the question. -hydnjo talk 01:02, 12 January 2009 (UTC)

Looking at our article, a vastly disproportionate number of pile ups seem to happen in North America (although that could be at least partially accounted for by our well known bias towards featuring topics from North America). I visited the US for Christmas and we drove from North Carolina to Florida and back and the standard of driving I saw did seem significantly worse than I see in the UK. Are Americans just really bad drivers? --Tango (talk) 01:50, 12 January 2009 (UTC)

Nothing is more American than tailgating, not using your turn signal, and talking on your cell phone while driving. Besides, speed limits are a guide for the absolute slowest you should be driving.</sarcasm>

Not having ever driven outside of North America, I couldn't give you an estimate as to how well drivers are compared to elsewhere in the world, but Americans do own more cars per capita than anyone else, so a high accident rate would not suprise me. I understand this is getting away from the OP's question, but just throwing my two cents in.-RunningOnBrains 02:26, 12 January 2009 (UTC)

I drive a Honda Civic but aren't Americans morely to drive bigger cars? I would imagine that heavier cars are harder to stop. A Quest For Knowledge (talk) 04:43, 12 January 2009 (UTC)

This is the incident in question, and it appears the snowy conditions contributed to the big pile-up. I don't know what kind of regulations they have in Massachusetts, but I gather that there is no mandatory use of winter tires -- at least this article on the topic seems to imply that while getting winter tires is a good idea, it's up to you. If that's indeed the case, I'm not at all surprised that cars can't stop in time; you can break all you want, but if you don't have traction, the car isn't going to just stop. Furthermore, if the drivers aren't experienced in driving under those conditions, that's going to compound the problem. Here in Finland the use of winter tires is mandatory throughout the winter months, and I believe one of the requirements for even getting a driver's license is a practice session or two on a slippery track, with snow and ice during the winter, and simulated conditions during the summer. It's not terribly difficult, but if a driver suddenly caught in snow and ice doesn't have any prior experience with trying to drive under those conditions with crappy summer tires that just aren't up to the task, things are bound to turn bad. I don't think a 50-car pile-up under conditions like that is the least bit surprising.

A pretty impressive example of snowy conditions with drivers who not only clearly don't have winter tires, but are also absolutely clueless as to how to drive on ice can be found here. I'm pretty sure the conditions on the Massachusetts freeway in question were nowhere that bad. Still, that video is enlightening; I'm kind of amazed by how these people lose control over and over again, smash into cars, and yet they step on the gas repeatedly. You'd think that after a couple of collisions they'd realize that what they're doing just isn't working... Luckily, no one seems to get seriously hurt in the video, as the cars are moving pretty slowly, but that's more luck than anything else. -- Captain Disdain (talk) 03:15, 12 January 2009 (UTC)

Oh, something I forgot: a lot of this comes down to braking distance. I don't know how fast the cars were moving, but since it was an interstate, it strikes me as feasible to assume that the cars might have been traveling at nearly 50 miles an hour. Typically, the braking distance from 50 mph is about 30 meters. In crappy conditions like this, it may easily be twice that -- say, 60 meters, or about 200 feet. And that's assuming that the driver reacts instantly when something happens up ahead. At 50 miles an hour, if it takes you a second to actually start braking, in that time alone your car has traveled 20 meters, or over 60 feet, which is obviously going to be added to your overall braking distance. And if you're already slipping and sliding all over the place and trying to avoid crashing (or other cars that are on equally shaky wheels close by), or trying to see the road through snow that's still coming down -- for example -- things like that are probably not doing your reaction time any favors, either. What this means is that even if you're a careful, skilled and properly prepared driver yourself, that may not be enough, since even though you may be able to stop, the car behind you may not. You can get first hit from behind and then be pushed into the car in front of you. -- Captain Disdain (talk) 03:36, 12 January 2009 (UTC)

Note, the accident was in New Hampshire, not Massachusetts. Yes, the article you linked to does start off talking about students from UMass but they were traveling through NH on their way to Vermont. And to answer your inquiry, Captain, I've never heard of any state that requires snow tires in the winter months. Even here in Vermont we only have yearly inspections for the general safety of the vehicle. It does not include any provision as to the type of tire on the vehicle. And back on topic... Vermont, New Hampshire, and Massachusetts are rather hilly to say the least, so it's possible that the vehicles were on a downward slope to begin with. Also, some of those involved may have crested a hill only to find that there was nowhere to go but up their fellow driver's tail pipe! Dismas| 05:15, 12 January 2009 (UTC)

Oh, New Hampshire. My bad! Teaches me to read properly, I suppose. -- Captain Disdain (talk) 05:23, 12 January 2009 (UTC)

Yesterday I watched a someone a few cars ahead of me drive into a traffic light poll because the conditions were so bad. There was no white-out, they could obviously see the light, they were just driving too fast for the conditions and couldn't stop. If the roads are bad I could see a 50 car pileup happening, especially on highways when people have to stop from 90km/h or more. -Pete5x5 (talk) 05:21, 12 January 2009 (UTC)

One thing which people seem to be forgetting that it's likely the case that some of the vehicles involved in the pile-up did stop in time. For example, it's easily possible the 49th vehicle stopped but war rammed by the 50th vehicle into the pileup. I.E. Remember that in any accident the only one you can resonably sure is at some fault is the one at the far back. Everyone else could be more or less innocent victims of the one at the far back (unlikely in a 50 vehicle pileup but definitely possibly in a 4 car one.) Also I'm not sure but when you have a 50 vehicle pileup does it automatically mean that all vehicles are touching? I suspect not. Therefore it's rather easy to imagine the 49th vehicle stopped well short of the vehicles in front but because the 50th idiot was tailgating and/or not paying enough attention they rammed the 49th who still didn't hit the car in front but would not be considered part of the pileup. If the 49th vehicle was a defensive driver and they knew they had more then enough time to stop they may have braked less hard if they'd felt the idiot at the back wouldn't stop in time but hardly a major fault Nil Einne (talk) 08:07, 12 January 2009 (UTC)

Winter tires?

In the above discussion, what exactly is meant by "winter tires" ? Does this mean studded tires or tires with chains ? I believe chains are actually illegal in many places in the US because they damage the roads. StuRat (talk) 05:29, 12 January 2009 (UTC)

Winter tires are tires that have a softer compound and more siping to grip the road better in icy conditions. They can be studded but many passenger cars tires are not studded. You'll often see this on plow trucks and various other work trucks. My friend has studded tires since he does construction and is often not on pavement because the driveway hasn't been put in yet. Check Nokian tires' web site for some pics. They sell a popular brand Hakkapeleeta or something like that. I can never spell it right... Here is a direct link. Dismas| 05:35, 12 January 2009 (UTC)

You almost got it, it's Hakkapeliitta -- and "peleeta" is actually close enough to how it's properly pronounced, so all in all, you're not handling our monstrous heathen language badly.

A big reason some people prefer unstudded winter tires is that they make less noise, and some of them can be legally used round the year. Studs will definitely give you better traction, though. As for snow chains, they aren't generally in use in Finland, although they sometimes use them for snow plows and the like if the conditions are bad enough that the plow couldn't move without really heavy duty traction. It's pretty rare to see them on normal cars outside rural areas, but they aren't illegal (though I guess some models of them may be, as the law requires that the snow chains must be of a model that doesn't do "significant" damage to the roads). -- Captain Disdain (talk) 05:53, 12 January 2009 (UTC)

Snow tires degrade much faster than all-season tires during warmer temperatures, so it's generally not a good idea to leave them on all year round, unless you live in a very cold place. I know that in many places in Canada (southern Ontario at least) tires with any type of studs or chains are illegal, and yet in some other parts where there are many less traveled roads (northern Ontario and the more northern provinces) I think it's the law to have chains with you. -Pete5x5 (talk) 06:26, 12 January 2009 (UTC)

Similarly, starting this winter drivers anywhere in the province of Quebec are required by law to use winter tires during the winter. (I suppose visitors from outside Quebec are exempted, but I don't know.) There were news reports about how many peopel had left it until the last minute to get them, with predictable results at the tire stores. It's too soon to know, but they were hoping for a significant reduction in accidents. --Anonymous, 06:35 UTC, January 12, 2009.

Blood Diseases.

What is Haemeachromatosis?202.161.70.74 (talk) 02:15, 12 January 2009 (UTC)

I suspect it is a misspelling of Haemochromatosis.-RunningOnBrains 02:16, 12 January 2009 (UTC)

Or a misspelling of hemochromatosis. :) - Nunh-huh 02:43, 12 January 2009 (UTC)

White metal?

I was cleaning my stovetop today, and I was struck by the fact that the surface appears to be a shiny white metal. Maybe the color is just a coating, but if so it is a very durable one that can resist things like heat and scouring pads. My impression though is that the color is the actual color of the material that the stovetop was constructed from. Shiny white seems to be a fairly unusual color for a metal (as opposed to silver or gray), so I'm curious, what material is this likely to be and how common is it? Dragons flight (talk) 02:34, 12 January 2009 (UTC)

We have an article, white metal, that discusses the kinds of metals that go into very light coloured alloys. It talks about jewellery, rather than stoves, though. --Tango (talk) 02:57, 12 January 2009 (UTC)

Are you sure the stovetop is metal rather than a white glass-ceramic stovetop? I would suggest googling the brand of stovetop you have to be safe. 152.16.15.23 (talk) 02:59, 12 January 2009 (UTC)

I suspect it will just be a layer of enamel paint. If you scratch it deeply enough, you'll find the shiny steel underneath. The paint is thick and tough enough to withstand a lifetime of ordinary scouring.-gadfium 03:05, 12 January 2009 (UTC)

On a stove it would rather be enamel rather than enamel paint. The latter may be used on fridges and other appliances that are not exposed to high temperatures. True enamel is powdered glass (sort of) that is baked onto the (metal) surface at 1,500-1,600 F The powdered material melts and produces a hard surface coating. Scratching it off your stovetop would only cause irreparable damage (Enamel touch-up paints are not for use on stove tops for the same reason they don't use enamel paint on them.} If you look at an edge though like e.g. at a burner hole you might see some metal underneath. If you really are after causing damage, chipping or cracking the material works better than scratching. (OR the edge of a heavy pot will do.) white used to be the standard for appliances. (They even used to be called "white goods" in some places.)--76.97.245.5 (talk) 04:58, 12 January 2009 (UTC)

As an aside, major appliaces are still known as whiteware in NZ and I believe Australia. See for example Nil Einne (talk) 07:56, 12 January 2009 (UTC)

If a magnet sticks to it, it is sheet steel with some kind of coating. – GlowWorm. —Preceding unsigned comment added by 174.130.253.174 (talk) 05:53, 12 January 2009 (UTC)

This

How is Avobenzone formed? What is the science behind Avobenzone? What is it's occurrence in nature?96.53.149.117 (talk) 03:07, 12 January 2009 (UTC)

Why the continual reposting of this query? Please see the response to your Jan. 7 post, above or in the archives. -- Flyguy649 03:22, 12 January 2009 (UTC)

Benzophenone

How is Benzophenone-9, Benzophenone-3, Benzophenone, etc. formed? What is the science behind Benzophenone-9, Benzophenone-3, Benzophenone, etc.? What is it's occurrence in nature?96.53.149.117 (talk) 03:25, 12 January 2009 (UTC)

Have you read Benzophenone? Algebraist 03:28, 12 January 2009 (UTC)

No, sunscreen is the relevant article. Cacycle (talk) 04:57, 12 January 2009 (UTC)

ICOS or Icos?

I'm editing an article on ICOS, the U.S. biotech company acquired by Lilly, but I'm unsure about the capitalization. Many documents say ICOS, but many other documents, like newspapers, say Icos. The article previously had ICOS, but today I changed everything to Icos, seeing the newspaper articles, and the fact that it's a shortening of icosahedron. But now I'm having doubts. A friend who was an employee says that higher-ups told him/her it was ICOS. Which is it? Thanks for your help! Shubinator (talk) 04:05, 12 January 2009 (UTC)

If you search the Lilly site it seems to be "ICOS". I guess they would be a reliable source. --Scray (talk) 05:03, 12 January 2009 (UTC)

Per WP:MOS-TM, names should generally be written in the fashion preferred by other English authors, and not necessarily in the fashion preferred by the company itself. This avoids drawing special attention to specific companies just because they indulge in excess capitalization of gimmicky formatting. Based on what I see, "Icos" is probably the correct approach. Dragons flight (talk) 05:32, 12 January 2009 (UTC)

cannibis

In what ways is everyday use of cannibis benefitial/harmful to overall mental and physical health? —Preceding unsigned comment added by Shschrgrs (talk • contribs) 05:20, 12 January 2009 (UTC)

Have you read the cannabis article and followed the various reference links? Dismas| 05:29, 12 January 2009 (UTC)

Torque

I can't grasp why increasing the distance from the axis of rotation that a force is applied will increase the angular acceleration. I understand the usual explanation given by work, but this involves the assumption that work applied by the force and the work experienced my the rotating object must be the same. Is there to derive this property of torque someother way, like through newton's second law?

Copolovian Mischief

I a recent brodcast on medical malpractice on teh NBC I heard Dr.Smith talk of COPOLOVIAN MISCHIEF!!I remeber reading about this in NYT also a few months agao.Googling did not give me any joy.Does anybody know what it is?

A question on gravity

I was studying string theory, and a chain of effects were set into motion leading all the way back to gravity, when a concept dawned on me - Gravity is traditionally thought of as a force that pulls objects together, thus people and objects are pulled towards Earth as Earth is pulled towards the sun. However, if such a pulling force were to exist then wouldn't it cause these objects to pull in towards eachother, causing planets to collide with the sun? I realize this question may sound simplistic to physicists but I am lost. Thanks! 71.54.120.113 (talk) 03:16, 12 January 2009 (UTC)

It is indeed true that if an object A pulls on object B with a particular force, then object B will also pull on object A with exactly the same force. This is just what Newton's third law of motion says. However, unless the objects are moving pretty much directly towards each other to start with (or sufficiently slowly directly away from each other), they will not necessarily collide. In the case of the gravitational force, whose size varies as the inverse square of the distance separating the bodies, the two bodies will either perform elliptical orbits about their center of gravity, or recede from each other indefinitely along parabolic or hyperbolic paths.

In the case of the solar system, the Sun is so much more massive than any of the planets that the attractive forces between the planets themselves is negligible in comparison, and the force exerted by each planet on the Sun doesn't move it very much (even though the size of that force is the same as the size of the force exerted on the planet by the Sun). The ratio of the tangential velocities to the radial velocities of most of the planets is of such a size that they orbit the sun in elliptical paths with very small eccentricities (i.e. paths which are very nearly circles).

—David Wilson (talk · cont) 11:57, 12 January 2009 (UTC)

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