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Contents 1 March 27 1.1 What kind of squirrel is this? 1.2 Electrical Resistance Of Rubber 1.3 Cost of argon 1.4 piston analysis 1.5 Rolling bush 1.6 concurrent multiplier in nephron 1.7 atom 1.8 Markers 1.9 Common chimp vs. bonobo 1.10 Crossed covalent bonds 1.11 Gas Laws 1.12 Search for life 1.13 Pluto, still technically a planet? 1.14 Dehydrated fruit 1.15 Saponification 1.16 Burning Question 1.17 So, if we were to detect a fleet of alien ships entering orbit above the earth tomorrow... 1.18 silencer 1.19 In the event of alien spaceships arriving at earth 1.20 Cinema sound v. ordinary sound 1.21 How to increase IQ 2 March 28 2.1 Spitting and wiggling 2.1.1 WP styling mystery 2.2 hormone therapy capillary breakdown 2.3 Multimillion dollar idea? 2.4 Limit? 2.5 Photosynthesis. 2.6 Energy = Photon? 2.7 Energy 2.8 Chaos Theory 2.9 Linear beam theory 2.10 ethylamine 2.11 Fire preservation 2.12 airborne radio direction finder 2.13 Blood pressure during sickness 2.14 what the **** 2.15 Are teeth techically considered bones? 2.16 Photons 2.17 Bug 2.18 Below Freezing Temperatures & Pipe lines 2.19 Possible explanations for the hexagonal storm on Saturn? 2.20 Observing drug resistance developing by mutation 2.21 Iapetus (moon of Saturn) as a Death Star-style artificial alien world/spacecraft thing... 2.22 physics 2.23 The farting vegitarian 2.24 Color of light 2.25 Seeing under water 2.26 Barometric reading and water-vapor pressure 2.27 How to reduce the temperature of something 3 March 29 3.1 Female Vs. Male Orgasm 3.2 self propulsing water vortex 3.3 microprocessor heat 3.4 Domestic Mains LED 3.5 Linear and squared heat dissipation 3.6 piston analysis details.. 3.7 Breathylizers & Smoking 3.8 water in a container for a long time 3.9 How can I stop my macaw going broody this year? 3.10 Descendants of a common ancestor 3.11 Viruses 3.12 How does microwave crisper paper work? 3.13 Glycolipid & Electric Microscopes 3.14 assignment help--speed of light/color question 3.15 LM3914/5/6 IC 3.16 Does Einstein have a bacon number? 3.17 Radiation sickness 3.18 Allergies and Plasmapheresis 3.19 Half-life 4 March 30 4.1 glasses 4.2 How do compass work? 4.3 some organic stuff 4.4 Blood Pressure 4.5 Rhinitis vs. Cold 4.6 how does a bidirectional turbine function? 4.7 The upside of smoking - less minor, annoying colds? 4.8 exemestane 4.9 Suckling young 4.10 What's the average price to build a wind turbine? 4.11 The Hum 4.12 Finding Alien Intelligent Signals - So What? 4.13 Nuclear Steam Generator 4.14 Comparing European Magpies with Black-backed Gulls again... 4.15 science project build a volcano 4.16 Bullet in the air? 4.17 Pre-implantation Genetic Diagnosis 4.18 Magnetic energy 4.19 Animal fat and Boric acid 4.20 A Health Diet 4.21 Bladder size 4.22 flame temperatures 4.23 Psychology !! 4.24 Sexing at Great Panda 4.25 HELP PHYLLIS CREATE A SAMPLE TREE DESTINED FOR CUTTING? 4.26 Coke vs Speed 4.27 Excercise and body heat 4.28 I'm the most intelligent person in the world 4.29 What makes things soft? 4.30 What will happen if you break a magnet 4.31 coral and sea level changes 4.32 Earth resources - oxygen production 4.33 Great Apes 4.34 Is this stuff for real? 4.35 Sunblock and tanning 4.36 cable modem

[edit] March 27

[edit] What kind of squirrel is this?

(I asked this a week ago, but didn't get a response, so I'm trying again now.)

I took a picture of this squirrel in New York City (Queens, near the river); it looks like an Eastern Gray Squirrel, but I wanted to confirm before I uploaded it to Commons. Is that what it is? Is this one also an Eastern Gray Squirrel? (The second was taken in eastern Connecticut.) grendel|khan 04:25, 27 March 2007 (UTC)

Yep, they are both Grays (the latin escapes me at this hour of the morn). Grays also come in black morphs and occaisionally partial albino.Rana sylvatica 09:02, 27 March 2007 (UTC)Rana sylvatica

It says Sciurus carolinensis on the Eastern Gray Squirrel page linked to in the question :) HS7 14:38, 27 March 2007 (UTC)

Thanks! Uploaded as Camouflaged squirrel.gk.jpg and Squirrel closeup profile.gk.jpg. grendel|khan 04:52, 28 March 2007 (UTC)

[edit] Electrical Resistance Of Rubber

When we use a mains tester to check the mains voltage, it glows even if we are wearing rubber slippers. Maybe rubber would conduct lightning( Very very very high voltage & current), but how does it conduct domestic household (220v RMS)Mains??210.212.194.209

Is it possible that a charge is flowing into your body through your hand, and the charge is accumulating, even though it has no route to flow back out ? If so, I would expect the flow to end quickly. StuRat 04:49, 27 March 2007 (UTC)

Your rubber slippers aren't conducting; your body's self-capacitance is sufficient to enable a tiny amount of current to flow through your body, which is enough to light the tester. MrRedact 04:55, 27 March 2007 (UTC)

Also,if its one of those neon lamp testers, you only need a very small (safe) current of a few hunderd microamperes to light them up —The preceding unsigned comment was added by 88.110.24.123 (talk) 18:29, 29 March 2007 (UTC).

[edit] Cost of argon

In Canada and the U.S., what's the average price of a small argon tank, used for welding, that holds approx. 30 cubic feet of argon? --Bowlhover 04:45, 27 March 2007 (UTC)

eBay says $65.00 USD for a 20 CFM tank. this site says a refill will cost you $0.50/CF for a refill. You will need a regulator, also. -Arch dude 13:47, 27 March 2007 (UTC)

[edit] piston analysis

i wanted to know about the experimental stress and thermal analysis done on the piston with details on calculation, material propertis and related performance values conducted on two wheelers.

waiting for the answer

likhith shetty

—The preceding unsigned comment was added by 59.92.135.80 (talk) 06:27, 27 March 2007 (UTC).

"The piston"? Which piston? "Calculation"? Which calculation? "Material properties"? Which materials? I don't even have the slightest clue what you're asking for, could you elaborate? -- mattb @ 2007-03-27T19:14Z

Motorcycle engines perhaps? —The preceding unsigned comment was added by 88.110.24.123 (talk) 18:32, 29 March 2007 (UTC).

[edit] Rolling bush

Hi! I'd like to know, what is the name of the ball-like, rolling bush wich usually runs in the american desert? (I.e., it's usually shown in comics or tv-shows to represent the effect of a bad Joke...) --IlSoge aka Sogeking 08:27, 27 March 2007 (UTC)

Tumbleweed. Natgoo 09:02, 27 March 2007 (UTC)

Thanks a lot!! I'm going to translate the article on it.wikipedia. Bye!! --IlSoge aka Sogeking 09:23, 27 March 2007 (UTC)

"A rolling stone gathers no moss ... but a stationary Bush gathers all sorts of crap." StuRat 15:23, 27 March 2007 (UTC)

[edit] concurrent multiplier in nephron

i understand that the concurrent flow multiplies the gradient of ~200mOsm b/w the ascending loop of Henle and adjacent medullary interstitium, in to a gradient of approximately ~900mOsm b/w the inner meduallary ('elbow' of loop of Henle) and cortex, but what is the purpose of this system? (if anyone could make it my knowledge of the system clearer- how the functional anatomy and physiology are related e.g. what is the purpose of urea cycling?- would be very much appreciated)

[edit] atom

Hey I would like to know ALL the energy and particles that are released from the nuclei of an atom. I just want to confirm that I have them all...

I'm not sure I fully understand what you're looking for. Could you list for us what you have so far? TenOfAllTrades(talk) 13:06, 27 March 2007 (UTC)

Yes, that may be best because there are quite a bit and it depends on the application and level for which ones you "want." If it is radioactive decay, in high school, it's normally just alpha particle, beta particle, gamma ray. [Mαc Δαvιs] (How's my driving?) ❖ 15:02, 27 March 2007 (UTC)

[edit] Markers

Which biochemical molecule/enzyme/protein can be used as a marker for Pancraetic juice and duodenal juice in regards to calculating the oxidative stress? 218.248.47.12 11:40, 27 March 2007 (UTC)

[edit] Common chimp vs. bonobo

I never understood why scientists focus so much on the patriarchal Common Chimpanzee. It's clear that the egalitarian and sex-positive Bonobos are way cooler. Any thoughts on this?--Sonjaaa 13:41, 27 March 2007 (UTC)

Maybe it is because we found the chimps earlier, and most of the original scientists were men :) HS7 14:03, 27 March 2007 (UTC)

Nice question phrasing :). Perhaps we study chimps more because they are more widely available for study? [Mαc Δαvιs] (How's my driving?) ❖ 15:06, 27 March 2007 (UTC)

• Regular Chimpanzees are more convienently located. WilyD 15:09, 27 March 2007 (UTC)

Human society is historically patriarchal. I also think Chimpanzee's are a closer relative genetically. --Tbeatty 15:11, 27 March 2007 (UTC)

True, but who cares? Bonobos are located in the interior of Zaire - not the easiest place to go study them. It's simply an issue of pragmatism. It's the same as why we know more about the Earth than about Neptune - it's just easier to study the earth, because it's easier to get to. The idea what we'd choose which to study based on the outcome of the study is fairly easy to identify as flawed. WilyD 15:24, 27 March 2007 (UTC)

You could study them though. Find out why Bonobo's can't drive cars.  :) --Tbeatty 15:16, 27 March 2007 (UTC)

I'm not sure it matters if men or women found the apes, and not sure if a patriarchy or matriarchy matters to most scientific study either. [Mαc Δαvιs] (How's my driving?) ❖ 15:48, 27 March 2007 (UTC)

Soon, the question may be meaningless as it appears that Bonobos, at least in the wild, are on the verge of going extinct. :-(

Atlant 16:18, 27 March 2007 (UTC)

[edit] Crossed covalent bonds

What's the meaning of a "crossed" bond in a molecular diagram like between carbon and nitrogen in sinigrin? 193.171.121.30 13:52, 27 March 2007 (UTC)

I'm gonna go with "mouse slipped while drawing the structure." DMacks 15:42, 27 March 2007 (UTC)

Yes, in this case it is a mistake: there should be a N=C double bond there, like in this image. I'll fix the image. Laïka 19:18, 27 March 2007 (UTC)

[edit] Gas Laws

How can the gas laws work for all gases, even though molecules are different sizes in each gas? —The preceding unsigned comment was added by 199.197.123.76 (talk) 15:19, 27 March 2007 (UTC).

That's why they're sometimes called the "Ideal gas laws". You've got some good intuition about how reality is different...see ideal gas for more discussion. DMacks 15:45, 27 March 2007 (UTC)

In particular, look at the assumption about the actual volume occupied by the gas molecules that is built into the ideal gas model. The Van der Waals equation gives a better approximation when the size of the gas molecules cannot be neglected, and, as you would expect, it contains a term that does depend on the molecular size. Gandalf61 16:47, 27 March 2007 (UTC)

[edit] Search for life

should we expend considerable energy and resources looking for intelligent or natural life in the universe or is it a waste of those resources? —The preceding unsigned comment was added by 198.190.213.4 (talk)

Personally I think it is rather a waste. The likelihood of finding any intelligent life at this particular moment seems to me to be quite small (I take a pessimistic reading of the Drake equation) and the vast interstellar distances make communication quite difficult and actual travel nigh impossible (unless our understanding of physics is vastly, incredibly wrong). On top of that I have a rather pessimistic view of how contact between intelligent species would occur — humans can't seem to be civil with their own species, lord knows how they would interact with aliens. That being said, the current "search for life" (i.e. SETI, etc.) does not strike me as "considerable enrgy and resources", so I am not necessarily advocating slashing their funding. But I wouldn't try to make an all-out effort, no. But nobody really asked me, did they? ;-) --140.247.249.200 15:55, 27 March 2007 (UTC)

Intelligent life is a separate prospect altogether, but a more feasible target is primitive life forms. If either Darwin or the Terrestrial Planet Finder ever get off the ground, we'll (hopefully) be able to analyse terrestrial exoplanet atmospheres, which could indicate life. (Who knows, they might even turn out to be intelligent!) Note that those missions are primarily designed to look for planets, not life. And in our own solar system, there's the possibility of life on Mars, Enceladus, Europa and Ganymede, in rough order of likelihood. Mars is well covered, and it seems very likely that NASA's next flagship mission will explore one of those last three. So while there's no chance of definitively finding life for a very long time yet (ie without sending something specifically to look for it) we might have a slightly better grasp of the probabilities in the next few decades - all without spending vast sums designed only to look for life. Spiral Wave 16:18, 27 March 2007 (UTC)

What about the ide that, if intelligent life existed and it were more intelligent than us, there would be no need to search, because they would more likely find us. And speking about a less developed alien civilization, we have no tools to detect them. --193.16.218.66 16:59, 27 March 2007 (UTC)

Not really - finding us is very different from contacting us. The first is probably straightforward for anyone within like 30 parsecs, much worse farther out. Contacting us takes the same time back as our signal took to get there. Even though a more advanced civilization would be better equiped to detect us, they'd have a much larger and deeper footprint (radio emission and who knows what else) that they'd be much easier to us to detect than the reverse. So we'd see any older civilization before they'd see us.

That said, if they're very far away (say kiloparsec scales) it'd be almost impossible to do anything about knowing where they were - the position the signal came from wouldn't be enough to let us know where the civilization is now, or where it'd be when we could get a signal to it. WilyD 17:16, 27 March 2007 (UTC)

Or if it even still existed... Hey, I doubt that extraterrestrials are above doing bad things to each other and their planet(s). --Kurt Shaped Box 17:32, 27 March 2007 (UTC)

Agreed, but if they are as self-destructive as humans, you could expect them to self-destruct shortly after getting nuclear weapons, just like we probably will. So, the violent, intelligent species are likely to be rare, as they don't last long. Personally, I think plant eaters would likely evolve into a more gentle intelligent race, given enough time, than predators. Of course, there are some violent herbivores, like hippos, so there's no guarantee. StuRat 17:47, 27 March 2007 (UTC)

I don't agree that any intelligent life could easily find us, as the emissions we've sent out thus far (radio, TV, etc.) are so weak you'd be lucky to pick them up much past the Moon. For someone on another planet to pick the signals up they might need an antenna the size of a planet, and then the signals might still be impossible to distinguish from background noise. I suppose we could send a strong signal, but it would be difficult without a specific target for a narrow beam transmission. A very powerful signal would be needed for a general direction signal to be picked up by even the nearest solar systems (say a series of nuclear bombs detonated at the edge of the solar system in a prime number sequence). But, since we aren't doing anything like this, this leaves us the option of detecting signals sent from other planets. The likelihood of there being other intelligences trying to contact us seems low, I agree, but considering how drastically it would effect humanity (hopefully positively) if contact were made, it seems reasonable to spend some resources on it. StuRat 17:37, 27 March 2007 (UTC)

Lists are frequently made of "best guess" stars that are fairly near and hold reasonable prospects for supporting a civilisation, and - although I can't source this, so I think I might be imagining it - a few years back SETI or some other organisation might have transmitted a narrow-angle radio beam (the Arecibo message, again?) towards half a dozen of them. It'll be a few decades before we get a reply, of course!

Another frequently raised issue is the everyone's listening problem, but there are reasonable arguments against it. Spiral Wave 18:31, 27 March 2007 (UTC)

I think the existence of life seems most interesting from a philosophical point of view. Most scientists seems to agree by sheer numbers its likely something is out there, but what conversation could we have if it takes decades or even longer to send a message. Certainly unlikely to be any face to face contact. At best it'd make religious people think again, and maybe tell us something about abiogenesis. I don't believe we can tell anything at all about the probability of life starting from a sample of one.137.138.46.155 07:18, 28 March 2007 (UTC)

It's hard to say what life elsewhere tells us about the probability of abiogenesis events. If the nature of their biology is broadly similar to life on earth then panspermia would perhaps be a more reasonable hypothesis with abiogenesis remaining a statistically very improbably event. SteveBaker 17:05, 28 March 2007 (UTC)

[edit] Pluto, still technically a planet?

(Moved from Village pump (news) )

Well, to start out i do not really know much about this subject. I actually wanted to know if pluto is still a planet and will be that way, or is there still heated discussions about if it is.This topic is so old, but i would like some confirmation on the subject.

keeping its title as planet or not? Inkwhitw 02:43, 26 March 2007 (UTC)

This is the wrong forum. The short answer is "it's a dwarf planet, technically different from a (unqualified) planet". See Pluto and 2006 definition of planet. --Stephan Schulz 02:55, 26 March 2007 (UTC)

As brought up in a previous discussion, there is no such thing as a all-powerful governing body that can demand what is and is not a planet. The same group that decided to call Pluto a planet when it was discovered has now decided that they will no longer refer to it as a planet. They strongly suggest others decide to use their definition. However, it is up to you. If you like, you can call your dog a planet. Nobody will arrest you - though you may risk spending time in a padded room. --Kainaw ^(talk) 17:10, 27 March 2007 (UTC)

And the debate just centers around a classification. There are several kuiper belt objects that are the same size as or larger than Pluto, and there are some fairly large objects in the asteroid belt. Rather than calling all of these planets, they decided to separate the definition into "Planet" and "Dwarf planet". There are probably several possible justifications for doing so, but it's largely just a matter of separating the objects by their "importance". -- Consumed Crustacean (talk) 17:18, 27 March 2007 (UTC)

As a matter of interest, are the "Give us back our 9th planet!" people still campaigning and gathering signatures? --Kurt Shaped Box 17:47, 27 March 2007 (UTC)

I say it's a planette. Clarityfiend 21:56, 27 March 2007 (UTC)

Just be aware that 2006 definition of planet contains at least one error. "Debate within the IAU led Julio Fernández and Gonzalo Tancredi of Uruguay[5] to suggest proposals to redefine the term "planet" so as to ....." The error is the word "redefine". As Definition of planet tells us, there never was a scientific definition of planet until 2006. That may sound surprising, but it's the case. In view of certain developments in astronomy, the IAU decided it was time for a formal definition, and took a stab at it. The definition they came up with excluded Pluto. JackofOz 22:24, 27 March 2007 (UTC)

[edit] Dehydrated fruit

What chemical changes happen when you dehydrate fruit (besides the obvious loss of water) ? The color often changes, like blue grapes changing to brown raisins, or plum plums turning into black prunes. The taste changes as well. These changes are apparently not reversible, as soaking raisins or prunes in water doesn't get you back to grapes and plums. Also, would the dried fruit plus the amount of water removed be nutritionally identical to the original fruit ? StuRat 17:19, 27 March 2007 (UTC)

According to dried fruit, it loses Vitamin C. --Kainaw ^(talk) 17:24, 27 March 2007 (UTC)

I believe browning in food from cooking or drying is due to the Mallard reaction or Maillard reaction - I forget the spelling. This reaction is connected with the production of acrylamide, a possible carcinogen. I've never been able to find any information about the amount of acrylamide in raisins or sultanas, but prune juice and hence presumably also prunes have a very amount of acrylamide in them, as do olives. Perhaps not many people know that olives are processed before we eat them; off the tree they are very bitter I think. 62.253.48.20 21:52, 27 March 2007 (UTC)

Thanks, but a word was missing in your reply. Did you mean "very high" or "very low" ? StuRat 03:20, 28 March 2007 (UTC)

Sorry I meant to type "very high". The article on browning in food says there is also enymic browning, which occurs in black tea they say. 80.1.88.53 08:33, 28 March 2007 (UTC)

An FDA test in March 2004 found no acrylamide (this probably means less than 1 ppb) in raisins (but up to 267 ppb in prune juice). [1] Icek 01:04, 29 March 2007 (UTC)

[edit] Saponification

Why is NaOH added slowly during saponification? (This isn't how we did it in the lab, but I have a question which mentions the process used for mass production of soap and it says that the NaOH should be added slowly) —LestatdeLioncourt 17:19, 27 March 2007 (UTC)

Bit of a guess (maybe a soap expert will arrive soon): Saponification is an endothermic reaction. If you add the NaOH all at once, the temperature of the mixture will drop, slowing the reaction. Sorry for lack of definates. Skittle 19:14, 27 March 2007 (UTC)

[edit] Burning Question

ok within the past 2 months i saw two shows that contradicted itselves. it was about bullets hitting a car. Mythbusters said that a car cannot protect you if your inside it when its being shot at. that the bullets go straight through killing or damaging what ever is inside. however on a recent show on Discovery (sorry cant remember the name think its new) they said that its not easy for bullets to enter your car that they might go in but they wont be leathal if they do. I want to know which one is telling the truth? am i safe inside my car or would i stand a better chance making a run for it? thanks for your time! Maverick423 17:28, 27 March 2007 (UTC)

There are many kinds of bullets and many different cartridges firing them. The answer won't be as simple as a plain yes or no. I would not depend on a normal car offering much protection- they're not designed for this. However, when a bullet hits something, even it it goes through, it may fragment, get deflected, or slow down. A heavier bullet will usually penetrate more than a lighter one. It's going to depend a lot on what it hits. Simple sheetmetal or glass won't give you much protection, but other parts of the car may stop some bullets effectively. See also terminal ballistics. Friday (talk) 17:39, 27 March 2007 (UTC)

For example, if someone is shooting from far in front of your car, and you duck down behind the dashboard, they would have to shoot through the engine compartment to hit you, and the bullets are likely to be stopped or at least deflected by the engine block and other components. On the other hand, if they fire through a window, there is very little protection for you. StuRat 18:03, 27 March 2007 (UTC)

Sweet thanks much! Maverick423 17:47, 27 March 2007 (UTC)

Mythbusters actually did the experiment - right there - where you could see it. They took a pretty typical car and shot at it with a wide range of guns - and the bullets went right through - and in most cases back out the other side. You could see it happen. You can't deny that evidence. However: Yes the bullet must lose some energy in punching through the car's body - and if much of your body is hidden behind parts of the car it may be a little harder for the shooter to aim at you - so hiding in a car might not be such a terrible idea. The engine block of the car and the heavy suspension parts ought to stop pretty much anything though - hiding on the opposite side of the engine bay to the shooter would be effective. SteveBaker 17:00, 28 March 2007 (UTC)

[edit] So, if we were to detect a fleet of alien ships entering orbit above the earth tomorrow...

...and they started honking/grunting/screeching/whatever over the airwaves at us, how on earth would we even begin to try communicating with them? I mean, it's not as if there'd be anything with which to compare their language with and as far as I know, the concept of a 'universal translator' is still in the realms of science fiction. So, what would humanity's collective linguistics boys and girls do? --Kurt Shaped Box 17:45, 27 March 2007 (UTC)

put their heads between their legs and kiss their um. well that does sound intresting however i belive that if a alien race did enter our solar system, they would be able to study our language via radio waves which means they can make a translator for us and stuff =P.Maverick423 17:49, 27 March 2007 (UTC)

If they have been studying us they may have already decoded our languages before they make contact. If not, assuming they have visual sensors of some type, you could show pictures and give a word for each item (you would need to pick one language to teach them, of course). This would work well enough for physical objects. Next, verbs could be conveyed by showing "jumping", etc. We might never get to the point of communicating about intangible concepts like "God", however. StuRat 17:56, 27 March 2007 (UTC)

And if they leave a book behind and you decode the cover to say "To Serve Man", beware ! StuRat 17:58, 27 March 2007 (UTC)

There's a good chance we'd start with something like the Arecibo message or the Pioneer plaque, attempting to establish binary representation of numbers and agreement on basic physical constants. — Lomn 18:41, 27 March 2007 (UTC)

Even if language doesn't follow a universal rule it does, by its very definition, have conventions and ways of establishing meaning. Which is not to say it would be easy, but once you got beyond the question of "how, in a technical sense, do they communicate" (i.e. hearing the right frequencies, looking for the right signs, etc.) I am not sure as a decoding problem it would be at all insurmountable, or much different from how people were able to show up on odd islands half-way around the world and find ways of communicating with natives. --24.147.86.187 18:42, 27 March 2007 (UTC)

Ah, but you're assuming they do hear, or see, or whatever; just maybe at different frequencies than we do. If there's one thing we should learn from nature, it's that it frequently throws up anything we can think of, and several things we can't. In that regard, some of you might be interested in this forum thread where the same subject was discussed; including what any aliens might make of our multitude of languages, assuming they get to decoding first. Spiral Wave 18:56, 27 March 2007 (UTC)

It stands to reason that they would have to have some way to sense the world around them, using the electromagnetic spectrum, sound or vibrations, touch, chemical sensors, etc. I can't imagine aliens who are totally oblivious to their environment ever being able to travel to other plants. StuRat 20:56, 27 March 2007 (UTC)

Of course; but I think the main point, as someone mentioned in that thread, is that unless you know what that sense is, you've no way of knowing where to even start. Spiral Wave 21:26, 27 March 2007 (UTC)

Take a look at the Arecibo message and the Pioneer plaque - don't read the descriptions - just try to figure out what they mean. They are practically useless - you can figure out the numbers OK - but even humans with a knowledge of earthly biochemistry would have no chance at guessing those few pixels in a wiggly line with an ungodly large number next to them represents the spiral structure of DNA along with the number of base-pairs that compose it...that's useless! The standard (and plausible) method used in most sci-fi scenarios such as 'Contact' is to send beeps representing the prime numbers - then send them again with a base-10 representation of the number to establish how we represent numbers - then send stuff like 2 squiggle 2 splotch 4, 6 squiggle 3 splotch 9 ....from which the aliens can deduce the symbols we use for + and = and that we use infix notation for arithmetic...we can build on that to show most of our mathematics. We can use numbers to convey numbers of protons and neutrons in the elements and scale from that to show chemistry. We can send pictures of objects using prime-number-sized raster images and attach names to objects to start to list nouns. We can send videos to show how these things look in life. Once they know the words for apples and elephants we can show an apple above an elephant and use 'apple wibble elephant' and then an elephant above an apple and use 'elephant wibble apple' to show the meaning of the word "above"...with time and some inginuity we can teach them our language. Then we can match sounds to words and teach our audio communication strategy. All the while, we can imagine they'd be trying similar strategies with us - and with luck this will make sense. SteveBaker 03:29, 28 March 2007 (UTC)

Why wouldn't they stealthily acquire access to the World Wide Web and be Wikipedia editors (and likely admins) before they ever uncloaked the ships and hailed our leaders? Edison 05:10, 28 March 2007 (UTC)

I thought we were postulating intelligent aliens! ;-)

Meanwhile, folks might want to consider the question of bandwidth and the fundamental forces. Any communications medium worth its salt would need to have a bandwidth that is proportionate to the rate at which data is processed and it would have to employ one of the fundamental forces. Primarily because the strong and weak nuclear forces are kinda short range, and because gravity is so difficult (for us, at least) to manipulate, we've settled on electromagnetic interactions. (And yes, the pressure waves of sound in air are, at their root, an electromagnetic interaction of molecule acting on molecule.) Within the scope of the electromagnetic force, we've also settled on bandwidth-appropriate communications. Sounds extend from infrasonic to ultrasonic, but are still limited by how well sound waves propagate in physical materials. We've pretty much got the EM band covered as well. And even if the encoding is odd (say they communicate by changing an area of chromatophores on their, umm, err, "bellies"), we'd probably figure it out given enough time. Of course, if the first message is "Surrender or we'll anihilate your planet with antimatter!", we may not have much time to figure it out.

Atlant 11:17, 28 March 2007 (UTC)

Na, that'd be a bluff - they wouldn't destroy the planet. It'd be a complete waste of all that time, effort and energy spent travelling many light years to get here. Sure, if the aliens were hostile, they may want to colonize the earth or strip it of resources and consider humans a pest to be eradicated but I doubt they'd just think 'aw, fuck it!' blow the whole place up, then head for home. --Kurt Shaped Box 15:17, 28 March 2007 (UTC)

Yeah, but wot about ta bypass? Got to have bypasses, y'know! Progress, don'tcha know?

Atlant 16:08, 28 March 2007 (UTC)

What do you mean, WHY does it have to be built? It's a bypass... You've got to build bypasses. -- mattb @ 2007-03-30T23:31Z

(Undent) Aliens might have a much longer term view of the universe than we do. Suppose they've placed their intelligence into computers (a likely advance that we might well make sometime soon) - they could copy their minds from one machine to another and attain immortality of a sort. They might have very long memories - and they might plan over very long timescales because they anticipate living that long. From a perspective of millions or hundreds of millions of years - they might well have found from long and painful experience that new upstart civilisations will eventually compete with them for resources. They may have had long and difficult wars with other advanced civilisations. With that long term view - it would make a lot of sense to wipe out new civilisations long before they become problematic. As discussed below, they could wipe us out with very little effort if they did it right now - if they wait a million years, it could be much more difficult for them. So it's perfectly possible - logical even - for them to seek out civilisations that (whilst not a threat right now) are growing in technology - and to wipe us out with no more qualms than we have in killing off troublesome vermin like rats or whatever. SteveBaker 16:39, 28 March 2007 (UTC)

Or perhaps they could wipe out alien civilizations by seeding them with genes to make them violent enough that they always self-destruct, once their weapons become powerful enough (due to technology) ? This might help them get past any moral objections they have with destroying civilizations which aren't a threat, since, if those civilizations never develop powerful weapons, they never self-destruct. StuRat 17:06, 28 March 2007 (UTC)

We have an entire article on the question, Communication with Extraterrestrial Intelligence, which might benefit from the above answers. -- Beland 21:24, 31 March 2007 (UTC)

[edit] silencer

If you shoot a gun directly on a persons chest would the person have acted as a silencer on the air propelled by the explosion? —The preceding unsigned comment was added by Bastard Soap (talk • contribs) 19:40, 27 March 2007 (UTC).

This was proven in a episode on Discovery channel think it was one of those forensic evidence thing and then again i think it was on TLC either way they proved that shoting a bullet into a body at point blank range *meaning acctual contact with the skin* can creat a silencing effect. they tried this out on a dead pig and got the same results. now that i think of it it might of been a mythbusters thing since they like to use pigs alot. anyways i hope it helps. Maverick423 20:25, 27 March 2007 (UTC)

Interesting. I would have expected the pressure to force the gun away from the body, creating an escape route for the sound. StuRat 20:52, 27 March 2007 (UTC)

yea well they said that the pressure goes into the body following the bullet and the hollow hole left behind from the bullet passing through acts as a silencer. Of course as like all silencers it doesnt completely silence the bullet but it muffels it. it sounded like a thud instead of a shot. its really quite intresting =)Maverick423 20:58, 27 March 2007 (UTC)

Do not request gun silencing advice. Ask a professional hit man instead. Edison 05:07, 28 March 2007 (UTC)

It's the sudden release of built-up-pressure as the bullet exits the muzzle that produces the "bang!". Contain (and slowly dissipate) the gases and there's no bang. Powder-actuated tools are a pretty good example of this. Most of the gas expansion goes into doing work on the load (via a piston) and no sharp release of gas occurs. As a result, the tools are surprisingly quiet.

Atlant 11:24, 28 March 2007 (UTC)

[edit] In the event of alien spaceships arriving at earth

Does anyone here doubt that at least one country on earth will have already developed some kind of top-secret 'UFO killer' weapon, to prepare for this eventuality (just in case the worst happens and the bugs are not friendly)? --84.68.222.205 22:14, 27 March 2007 (UTC)

The USA, China, and Russia have all developed anti-satellite weapons. Further, for targets in low orbit, intercontinental ballistic missiles can be re-targeted to hit them. --Carnildo 22:40, 27 March 2007 (UTC)

It's hard fighting from the bottom of a gravity well. And anti-satellite weapons are only good against satellites, which aren't noted for dodging very much. Just pray that they don't see us as prey. Clarityfiend 01:32, 28 March 2007 (UTC)

I most definitely doubt we have secret UFO-killing weapons. In fact I very much doubt we'd stand any chance at all against a determined interstellar attacker. As Clarityfiend points out - if they have the capability to travel between stars - they can drop mountain sized rocks on us by nudging them out of the asteroid belt with the right orbital characteristics to hit earth. It might take years for them to hit us - but these hypothetical aliens would have to be a patient species to have undergone decades of travel to get here. There is absolutely nothing we could do about a swarm of incoming asteroids - we'd be unlikely to even detect they were coming until they were just a few weeks away. We have no weapons that could reach as far as the asteroid belt - and we have no way to stop incoming house-sized asteroids. They could probably aim them with enough precision to wipe out entire cities. But if they had the technology to get here in the first place - their technology would more advanced that we could possibly imagine - who knows what they could do to us if they felt like it? The 'asteroid bomb' idea is just one of a bazillion ways they could get us - and we'd probably never see it coming. They wouldn't even need to be that far ahead of us. We won't have interstellar travel for a hundred years - but we'll probably have nanotechnological replicators in 20 years. If the aliens are 100 years ahead of us in interstellar travel - then they could easily be 20 years ahead of us in nanotech. If so, they could seed our atmosphere with self-replicating nanotechnology 'bots - a container the size of a coffee can would probably do the job - and the nanobots could selectively take out higher life forms leaving the majority of our ecosystems intact. We'd die in a few weeks or months without ever knowing the reason why - let alone having a way to unleash our hypothetical secret weapon on them. SteveBaker 02:51, 28 March 2007 (UTC)

I think you made a huge leap there, self replicators in 20years, man how can you produce a nanosynthetic lab which can synthesis other nanolabs and is also a killing machine? I think we will need a lot more than 20 years, if ever.Bastard Soap 09:04, 28 March 2007 (UTC)

(Nanotech robots that can replicate themselves using local resources are not at all infeasible - just look at terrestrial bacteris!) OK - so if you don't believe 20 years - pick 100 years, 200 years. Whatever number you decide. These aliens could quite easily be a BILLION years more advanced than us. What we do know for sure is that we have absolutely no clue as to how to solve all of the problems of interstellar travel - they (by definition) do - so we know for sure that they are a lot more advanced than we are. Let's go with 100 years as an utter minimum - they must be a minimum of 100 years more advanced than us. How much can technology advance in 100 years? Let's not speculate - let's use our own history.... If you look back to humans from 100 years ago - 1907 - seven years before the first world war - and think about how easy it would be for us to take them out (humans from today playing the role of 100 years more advanced aliens). In 1907 we had no radar - we had machine guns and battleships - no submarines - no military aircraft (civilian aircraft had only been around for three or four years) - no tanks - no missiles - defensive technology was all about digging a trench and hiding in it - or having 10" of steel plate wrapped around your ship which has wooden decks - horse-born cavalry with sabres were still considered a pretty nifty weapon. A one hundred year more advanced civilisation could have nuked them into oblivion - or carpet-bombed them from 40,000' - heck just one modern battle tank could take out most of an entire division of the period - they'd have no defense against even our conventional forces. Put yourself in the position of a 1907 military officer - our forces can see in the dark! They can communicate over distances of thousands of miles! They can see where all of your troops are (from orbit!). They have missiles that can chase you as you run away. They can drop soldiers out of the air! Bombs just fall from the sky from craft that are just a tiny dot in the sky! They have one tiny bomb that can annihilate an entire city! Their troop transports are immune to our weapons! Their soldiers are unkillable...I shot a one of them square in the chest at point blank range and he just kept on coming! (Bullet-proof vests were unknown in 1907!) Let's face it - even just 100 years of technological advance is indistinguishable from magic. These hypothetical aliens could be a thousand, a million or a billon years ahead of us. We'd die without even knowing we were under attack - it's ridiculous to think otherwise. SteveBaker 16:06, 28 March 2007 (UTC)

I perfectly agree with you that we would be completely toast, basically just the gravity well could be our demise but self-replicating bots seem an impossibility. You would need countless reagents and machines to make the necessary alloys or polymers or whatever and mould them into shape, not to metion building incerdibly complex electric circuits, maybe they would even need a nuclear reactor to be able to synthesis the necessary elements they would need to build themselves (you know I wouldn't imagine bots could be created from dirt). Biological warefare is an other thing but still for some reason that never really kills off any population it halfs it out doesn't it? But probably they would have come up to some solution to that, maybe a virus that mutates continously releasing new children every day.Bastard Soap 20:09, 28 March 2007 (UTC)

I wonder: how do you develop a defense system without knowing anything about the enemy's weapons? --Bowlhover 04:07, 28 March 2007 (UTC)

I expect it would work as well as Montezuma having prepared a "Spanish galleon killing weapon." Edison 05:05, 28 March 2007 (UTC)

We have nuclear weapons. We can make bigger nuclear weapons. I suppose it would be possible to design a fast, powerful surface-to-orbit missile capable of carrying a huge nuclear payload (if the need arose). We may not know anything about alien weapons and technology but it would be reasonable to assume that most things that exist can be harmed by a large enough thermonuclear explosion (or several in quick succession). --Kurt Shaped Box 15:25, 28 March 2007 (UTC)

Did you read ANYTHING I wrote? If these aliens are sitting out in the asteroid belt pushing big rocks out of orbit to drop onto us - our fastet rocket would still take three months to reach them. They have all that time to move out of the way of it...or shoot it down with a counter-missile a couple of months before it reaches them. But if they hit us with a customised virus or nanobots - we'd die before we ever knew that aliens existed - let alone finding them - let alone taking action against them. SteveBaker 16:06, 28 March 2007 (UTC)

Yes, I wasn't ignoring what you wrote. I was merely hypothesizing on the options that would be open to us in the event of a fleet of ships entering orbit above the earth with hostile intent (supposing that they didn't do any of the nasty things you suggested to us). --Kurt Shaped Box 16:20, 28 March 2007 (UTC)

But why would they get that close? We tend to think in terms of weapons having to be launched from short ranges in order that the victim has no time to dodge or defend themselves - but when the target is a planet and your weapon of choice is a mountain of rock or a teeny-tiny vile of lethal viruses or nanobots or something - there is no need to get close. They'd be several AU's away. Any of our weapons would take months to reach them - so they'd have plenty of time to react and avoid them. Why would they get within range of our weapons? SteveBaker 17:32, 28 March 2007 (UTC)

They may be technologically advanced but it doesn't mean that they are intelligent, they may be intellectual snobs who don't percieve us as able to do them any damage. Comming near us would be a way to show how superior they feel.Bastard Soap 12:33, 29 March 2007 (UTC)

Wouldn't we just send Will Smith and Jeff Goldblum (with his PowerBook)?

Atlant 11:40, 28 March 2007 (UTC)

Or we could use their own Martian heat ray against them. Spiral Wave 18:18, 28 March 2007 (UTC)

I remember hearing that President Raygun said something along the lines of how great it would be if aliens came and threatened earth as it would give the various nations a reason to unite and kill the invaders. At the time I was just dumbfounded that the best scenario he could come up with for us/them contact or a united planet was war. --killing sparrows 04:44, 29 March 2007 (UTC)

[edit] Cinema sound v. ordinary sound

When I've been to the cinema (or movie theater as our transatlantic friends would say) I've noticed how the sound has a particular quality to it. I assumed this was due to the acoustics of the cinema.

Yet recently I saw and heard a movie DVD being played in a shop, and it had the same quality of sound.

How does this sound differ from ordinary sound, how is it obtained please? 62.253.48.20 22:18, 27 March 2007 (UTC)

It mostly has to do with the quality of speakers. Put on some headphones that say "Professional" or "Bose" on, and you'll notice that sound is much better. Clean sound, with nice bass and lack of sound coloration are a few things. I'm sure somebody can give you better answer than I can. [Mαc Δαvιs] (How's my driving?) ❖ 22:29, 27 March 2007 (UTC)

Thanks, but I do not mean sound-quality in terms of fidelity, but the characteristic cinema sound, which might be due to - I'm just wildly guessing here - the attenuation or amplification of lower sounds, reverbaration, close miking etc. 62.253.48.20 22:34, 27 March 2007 (UTC)

Cinema sound systems use at least four channels: left, right, center, and surround. This difference might account for the effect you're hearing, and high-quality home theater systems do have these extra channels as well.

It would help to answer the question if you could somehow describe this "characteristic" particular quality you're hearing, if you could. —Steve Summit (talk) 22:57, 27 March 2007 (UTC)

Well, I think it is mostly the fidelity, the loudness, and the channels. Perhaps even an equalizer kind of presetting? On a lot of televisions you can set it to "movie" in the sound options and it will sound more "movie-ish." I've found a lot of high-definition shows sound better, like House and 24. [Mαc Δαvιs] (How's my driving?) ❖ 00:19, 28 March 2007 (UTC)

Were those speakers at the store Bose? Bose is known for their wooden sound chambers where sound travels through before actually exiting, as well as the vibration from the wood itself. Those would create a sound not unlike cinema sound, I think. --Wirbelwindヴィルヴェルヴィント (talk) 04:18, 28 March 2007 (UTC)

The sound I heard in the shop came from an ordinary LCD television with built-in speakers. I do not know how to describe 'cinema' sound. Perhaps the bass is more amplified than normal, or maybe higher pitches are surpressed. Think about the difference in sound between a tv documentary and a high-quality movie in a cinema. 80.1.88.53 08:42, 28 March 2007 (UTC)

I think part of what you're hearing is a lack of compression. That is, the cinema sound occupies a very wide dynamic range whereas television sound is pretty much two volumes: Medium for the shows and LOUD for the commercials.

Atlant 11:45, 28 March 2007 (UTC)

That could be it! Why some songs sound much more... "epic" than other ones. I bet 300 (movie) sounded great at the theater :) [Mαc Δαvιs] (How's my driving?) ❖ 22:42, 28 March 2007 (UTC)

[edit] How to increase IQ

Someone recently asked if there was a pill to increase IQ. My prescription for increasing IQ would be to get into the habit of regularly reading any non-fiction books that interest you, and doing puzzles and so on. I would suggest regularly eating small quantities of raw unsalted nuts, since the brain is mostly fat and its now thought that there are many different types of fat, and that these less common fats found in nuts etc are beneficial. Plus, of course, eating oily fish such as sardines, which have the least amount of mercury in them due to being young fish.

But is there any evidence that doing a lot of reading really increases your IQ? 62.253.48.20 22:29, 27 March 2007 (UTC)

The verdict is normally the best way to increase IQ is to practice taking IQ tests. "IQ is just a number and doesn't mean that much." Eating small quantities of raw unsalted nuts, or fish does not make you smarter or increase your IQ. Go with reading books and the Wikipedia and going to a university. I'm sure somebody else can give better replies on this one too. [Mαc Δαvιs] (How's my driving?) ❖ 22:40, 27 March 2007 (UTC)

Mac Davis, you are absolutely incorrect in this statement. A properly calibrated IQ test cannot be studied for. Psychologists debate whether any "properly calibrated" tests do exist, but they work pretty darn hard to make some, and corporations and research institutions exist to constantly evaluate present testing methods. The real question is whether you believe in the idea of general intelligence, which IQ measures. You should read the IQ article to get a better idea of what it means. Nimur 16:34, 29 March 2007 (UTC)

If one is suffering from a particular deficiency or reversible pathological process which limits higher brain functions, then a pill replacing or repairing these things could increase IQ. However, short of that, I don't believe it is possible. IQ theoretically is a measure of reasoning ability (the article adds a few more things, but none contradict the rest of this entry). It does not depend on factual knowledge (thus reading, while possibly serving as practice in decoding reasoning scenarios, will not increase IQ). It does not depend on brain size (as long as the brain has all the right parts, there does not appear to be a correlation between size and intelligence). Also, the neurons of the central nervous system are pretty much in place by adulthood. If the supporting cells (the parts that use fat to insulate long axons, schwann cells and oligodendrocytes) do not have enough fat to make myelin, then one will have worse problems than low IQ. ^tucker/_rekcut 22:47, 27 March 2007 (UTC)

Rebuttal: Although User:tuckerekcut raises noteworthy points, I will assume that it is indeed possible to raise "IQ" just for the sake of argument, and provide unsubstantiated speculation as to how it could be accomplished. In case you didn't get that, this does not reflect serious research, and is merely offered as food for thought. YMMV.

Step by step:

1. To the extent you can, become increasingly aware of the purely symbolic nature of human knowledge representation and understanding
2. To the extent you can, become increasingly aware of your own dominant modalities for processing those symbols, and appropriately adjust your learning strategies to best reflect your personal strengths. Treat this as a form of regular exercise.
3. To the extent you can, practice the previous steps until your chunking capacity for symbolic manipulation increases. This will include your ability to discover novel relationships, the speed and consistency with which you make these discoveries, and your ability to translate that understanding to new categories of knowledge.
4. If and when you have succeeded with the previous steps, you should discover a new set of symbols to work with, repeat the process.

To put in more concrete terms, although you may never become a Chess grandmaster, you can certainly improve your ability by practicing the game on a regular basis, against increasingly skilled players. A beginning player will think in "chunks" of how the individual pieces move on the board. A grandmaster will think in "chunks" that consist of strategies, entire games, entire classes of players and even factors beyond the gameboard itself. dr.ef.tymac 23:18, 27 March 2007 (UTC)

Those are actually some of my favorite replies back ever on the reference desk. Great job guys! :) [Mαc Δαvιs] (How's my driving?) ❖ 00:16, 28 March 2007 (UTC)

As with anything, practice makes you better. So if you want to do better at IQ tests, do more of them. Whether this actually makes you more intelligent is another question.--SlipperyHippo 00:19, 28 March 2007 (UTC)

My personal feeling about the important kind of intelligence, which in my view means being able to make unexpected creative leaps in whatever your field of endeavor might be, is that you need a lot of raw material stuffed in your brain in order to give those leaps some footholds. You could do worse than spending a few hours per day reading Wikipedia. --TotoBaggins 01:46, 28 March 2007 (UTC)

There is strong evidence that some (if not all) IQ tests get easier with practice. However, there are several distinct types of IQ test - if you practice one kind - get a higher score - then re-test with the other kind - your score on the second kind of test isn't any better. That shows that you aren't getting smarter by practicing IQ tests - it just means that IQ testing methodologies need more work. The trouble with intelligence is that there is no solid definition of what it is. Most people distinguish intelligence from knowledge - so reading lots of non-fiction books (which increase your knowledge) probably don't increase the thing we understand to be intelligence. But without a solid definition of what the word means, it's hard to be definite about that. Read widely across all subjects - and read deeply into a few that interest you - that's the best you can do. Make a practice of hitting "Random article" on Wikipedia every night before bedtime - read all of all three articles you get. I've been doing this almost since the start of Wikipedia. You'll be amazed at how fast your general knowledge grows by doing just that. But don't cheat - if you get a random article that doesn't interest you - read it anyway! But you need to read deeply in some widely disparate subjects. For me - I'm currently learning how the 'Unreal game engine' works (because I'm trying to get a job that needs that knowledge) and I'm learning to read Egyptian Hieroglyphics because a beginners book on the subject was reduced to $3 in my local bookstore! SteveBaker 02:33, 28 March 2007 (UTC)

To add to my original question (different address numbers - same person) I would also suggest reading a quality newspaper everyday. This gives you confidence as you know as much as or more about things than other people, and you can understand and assess what people in intellectual tv programs are going on about. Plus of non-fiction books, I'd suggest reading more science and psychology books, less or no literary- or art-criticism, since the former helps you think about the actualities of the real world and do or think constructively.

As someone who has taught many different ability ranges, my impression is that achieving success in life is as least as much related to an individuals conscientiousness and diligence as their IQ. Perhaps we should have CQ tests to focus people on the desirability of being conscientious. Personally I have little faith in IQ tests - I failed the old-fashioned British IQ test eleven year olds called the eleven plus but still went on to obtain post-graduate degrees. I remember the old IQ tests were very culturally-dependant, and I expect they still are. Being unfamiliar with puzzles and maths etc will give you a lower IQ score than you deserve. People can have a high paper-test IQ, but they are held back by so many things such as low self-confidence, timidity, fear of failure, self-image, and many other things that superficially they seem to be someone of lower IQ. 80.1.88.53 09:08, 28 March 2007 (UTC)

That's a bogus answer. What makes you think that the testing that goes on in the process of awarding a post-grad degree is a better test of intelligence than passing an intelligence test?!? That's a ridiculous proposition! Degrees in most (if not all) subjects require vast amounts of rote learning as well as some intelligence. So a good memory (which most people agree does not correlate with whatever it is we think of as "intelligence") might have gotten your through your degrees despite your poor "intelligence-as-measured-by-IQ-test-results". SteveBaker 18:14, 29 March 2007 (UTC)

Getting a post-graduate degree could easily be a better test of intelligence than doing an IQ test. Because the degree measures many things not just the narrow things measured in an IQ test; its a bit much to expect on short IQ test to measure your IQ for all time. On the other hand IQ tests could reveal high intelligence in someone who does not think of themselves as academicly orientated. I failed my eleven-plus, but I got high scores in IQ tests I did years later as part of assessment for promotion, plus I got a high score in the GMAT test. I'd also add to my prescription that you should also buy a good dictionary and look up words you don't know. 62.253.44.173 18:50, 30 March 2007 (UTC)

Yes, there is a pill! (Or rather, to qualify it, there there may soon be). Read this article from Scientific American: The Quest for a Smart Pill --JianLi 04:34, 1 April 2007 (UTC)

Ooops, sorry that link requires a subscription. You can get it free at [2]. --JianLi 04:35, 1 April 2007 (UTC)

[edit] March 28

[edit] Spitting and wiggling

So I was making that noise you can make my putting your tongue between your lips and forcing air out, often called spitting, while I was looking at a clock with a digital readout, and I found the numbers were wiggling, jiggling just above the chamber door. So I asked why I perceive the numbers as wiggling, jiggling just above the chamber door, if they have to do with my eyeballs actually moving, but Leonore only quoth "nevermore." Thanks for the big help Lenore. What do you say? [Mαc Δαvιs] (How's my driving?) ❖ 00:10, 28 March 2007 (UTC)

(Lenore is your raven?)

(And don't you mean a raspberry?)

The digits on many clocks and other digital displays are multiplexed -- they're actually lit in sequence, one at a time. (This ends up reducing the wiring.) But the sequencing happens fast enough that, normally, you don't notice it; the persistence of vision means they seem to all be on all the time. You can see the actual sequencing effect with a display on a device small enough to hold in your hand and wave around: if you can move it fast enough in a direction perpendicular to the row of digits, you can often get them to spread out, like this:

12:34:56   (stationary)

1          (moving

 2          quickly

   3        downward

    4       .

      5     .

       6    . )

Now, if you jiggle your head in certain ways, it somehow causes a stop-action effect with your eyes. (It's as if they can't or don't blend smooth motion as they normally do.) For example, many people have noticed that if they watch a television or an (older) CRT monitor at a distance while eating something crunchy, strange horizontal black lines or bands appear on the screen. These are in fact the unlit portions of the raster, that you normally don't see, because even though only one raster is being scanned at a time, your eye usually fuses them all together.

So what I believe you're seeing -- and I believe I've noticed the same sort of thing myself -- is those individual digits in your clock lighting up at slightly different times and while the vibration of your head is making them appear to be in slightly different positions.

—Steve Summit (talk) 00:38, 28 March 2007 (UTC)

[P.S. I was going to link to our article on multiplexed display for the explanation of why digital display digits are typically lit one at a time, but the article doesn't didn't seem to exist yet. Here's the answer: suppose the digits are standard seven segment ones, and suppose there are six of them. Suppose further that the clock contains a single IC containing most of the circuitry. Now, how many wires will we need between the chip and the display (or, more importantly, how many pins will the chip have to have for display output)? If we used the obvious, naïve approach, we'd need 7 × 6 = 42 wires. But if instead we have 7 outputs for the 7 segments on any digit, and 6 outputs to say which digit to light up just now, we can do it with only 7 + 6 = 13 wires. The circuitry on the chip has to be a bit more complicated to do the multiplexing, and the display potentially has these subtle flicker effects, but it's usually considered to be well worth it for the pin savings. —Steve Summit (talk) 00:51, 28 March 2007 (UTC)]

Holy crap! Awesome answer! I've wondered about that for many years when putting -- ahem -- vibrating objects on my chin and looking at ssd clocks. Nice work. --TotoBaggins 01:50, 28 March 2007 (UTC)

(Multiplexed displays now exists, but feel free to help improve it!)

Atlant 12:29, 28 March 2007 (UTC)

You can also make an oscilloscope trace seem to jump around by chewing carrots or celery. Edison 05:02, 28 March 2007 (UTC)

Also, you can play Tetris on the oscillosope by pressing the two buttons next to the knob. Titoxd^{(?!? - cool stuff)} 05:41, 28 March 2007 (UTC)

WP:AGF. WP:AGF. WP:AGF. MAC DAVIS, WHY DID YOU POST THIS NONSENSE? Nimur 16:38, 29 March 2007 (UTC)

[edit] WP styling mystery

[prolly belongs in Computing, but bear with me...]

So this is strange. The little wave-the-clock illustration above is supposed to look like:

12:34:56   (stationary)

1          (moving
 2          quickly
   3        downward
    4       .
      5     .
       6    . )

But the  's I carefully formatted it with, that show explicitly in the wikisource and that display fine when I preview, are turned into ordinary spaces when the page is rendered for real. Yet this happens only here on the RD, not (say) on my sandbox page when I experimented with it just now to see if there might be a workaround. What gives? —Steve Summit (talk) 03:52, 28 March 2007 (UTC)

It is the <code> tag. Titoxd^{(?!? - cool stuff)} 05:41, 28 March 2007 (UTC)

What, the <code> tag turns &nbsp; into plain space? What kind of sense is that? Let's try it without the <code>:

12:34:56 (stationary)

1 (moving

2 quickly

3 downward

4 .

5 .

6 . )

Nope. Same problem. —Steve Summit (talk) 12:41, 28 March 2007 (UTC)

Huh. Now the original one has fixed itself (though the one without the <code>'s is still broken). I wonder if the archiving made a difference? —Steve Summit (talk) 00:12, 31 March 2007 (UTC)

[edit] hormone therapy capillary breakdown

does there exist a link between hormone therapy in later life for menopause symptoms and capillary bleed out shown on the face?

[edit] Multimillion dollar idea?

Shortly after purchasing a new Atari 512 personal microcomputer which sported a new built-in 3½ inch floppy disk drive to replace the TRS-80 Model II business computer I was using the thought occurred to me: wouldn’t it be nice if you could take this little diskette that fits so nicely in a shirt breast pocket with you to any retail store and have the receipt (in addition to the printed paper receipt) recorded on it for use as data input for your own personal computer at home. Since then most businesses have upgraded from virtually indestructible receipts printed on real paper using real ink to thermal receipts which degrade faster than the store return policy deadline. Updating this idea by replacing the 3½ inch floppy diskette (although they are still in use for various reasons) with a magnetic strip card, smart card or even a ram disk my question is: wouldn't this be a really great idea for some little startup venture company in Silly-Conehead Valley to make the founder rich, rich, rich? 71.100.175.98 05:18, 28 March 2007 (UTC)

Thanks for the idea. I'll remember you while drinking my pina colada. Well, they'd need to have some way to make sure people don't forge data or change data too. --Wirbelwindヴィルヴェルヴィント (talk) 05:39, 28 March 2007 (UTC)

Well, I would hope that you would remember me like mom and dad with a big fat check every year! Actually such a receipt could have an encrypted duplicate for official purposes but the true purpose of my intent was simply assist me in keeping home inventory by handling order management so that all I had to worry about was digging out the printer from beneith all the other computer stuff whenever the old hardware said it was time to go to the store. 71.100.175.98 05:51, 28 March 2007 (UTC)

Mmm, then a completely electronic version would be nice. Such as, you would be able to get the data off the store's site or something. Because a hardcopy and an electronic copy is probably going to slow down the line in most cases. And with my luck, I'll be stuck behind the ones who write checks that take 5 minutes to process and then digs all over their purse trying to find their little memory stick for their receipt. --Wirbelwindヴィルヴェルヴィント (talk) 05:55, 28 March 2007 (UTC)

Well actually the thin "temporary" magnetic cards such as Wal-Mart and Home Depot and other stores use for refunds without a receipt would most certainly be sufficient for the purposes mentioned above. 71.100.175.98 06:21, 28 March 2007 (UTC)

It would be cool to use it for retaining warranty information and such too. The issue of forgery could be dealt with using encryption. The store could encode the data both in clear-text for you to read and in encrypted form. When time came to prove that the data was real, a public-key decrypt of that data would prove that the item number, price, store number, date and storage-media serial number all match up. A standard magnetic stripe card won't work though - a credit-card type of card can only store about 1000 bits of information. That's only about 150 characters - just barely enough to store one purchase. If you went to a supermarket and bought 50 items, the card wouldn't have enough capacity for just that one visit - for an entire year's worth of purchase you'd need much more than that. Even a floppy disk at 1.44Mbytes would be marginal. A 'smart-card' could contain comparable amounts to a floppy disk - half megabyte smart cards are common - multi-megabyte cards are in use in cellphones and such. SteveBaker 15:43, 28 March 2007 (UTC)

I certainly find such an idea to be technically feasible, now the issue is the business case for it. I would expect it would be most valuable for businesses which sell to other businesses, such as office supply stores. If a secretary is sent out to buy office supplies, it would be far more efficient to have an electronic receipt for accounting than many paper receipts which would have to be manually entered into the system, possibly introducing errors in the process. This convenience, in turn, might make business customers more willing to shop at stores which offer this service. This increase in customers might make up for the added expense of the office supply store maintaining a dual receipt system for those customers who still want paper receipts. I would expect there to be less of a business case for those companies which sell directly to the public, and not to other businesses. For example, how many people would want an electronic receipt for a movie ticket ? There are also some disadvantages, like the inability of the customer to verify that the receipt is correct when they receive it (unless they have reading equipment right there). For example, I often find mistakes on my grocery receipt, and have them make the corrections immediately. If I didn't find the mistakes until I got home, it wouldn't be worth the effort of returning to the store to make the correction. StuRat 17:00, 28 March 2007 (UTC)

The way to market such a thing would be to make a gadget that is plug-compatible with the little thermal printers in cash registers that has a USB port or something on the side. You could fit it inside a cash register and make it copy everything that goes to the thermal printer off the USB port. Rather than have some special card reader - just use a standard memory stick. Give those gadgets away for free to the right kinds of business supply stores and sell them at cost to manufacturers of cash registers. Then make your money selling software for the customer's PC's to read the (encrypted) files from a USB drive and put it into the right format for all of the common business/accounting software. I think that's a viable buainess model. SteveBaker 17:41, 28 March 2007 (UTC)

[edit] Limit?

Is there a limit to how many photons can fit in a prticular space? (I guess that would be proportation.) And is there a limit to how many photons can be emited from a (any?) particular source? What I'm trying to ask is the concept of intensity, but I don't really know how to describe it. Hope my last sentence helps. Thanks.100110100 06:29, 28 March 2007 (UTC)

At the same time? 71.100.2.150 06:38, 28 March 2007 (UTC)

Yes, how many photons can fit in a specfic space at the same time. We are presuming the photons are not moving.100110100 06:42, 28 March 2007 (UTC)

I think you'll have a problem there, photons always move at the speed of light, because they have no mass. If they have no mass and they aren't moving, they have no energy, and thus they don't exist, so your question is "how many nothings can you fit in a particular space?" which is division by 0 and undefined!? Capuchin 06:50, 28 March 2007 (UTC)

Heh, there's a number of things wrong with your logic Capuchin. :) For the original question, perhaps it would be something involving... an infinite amount. Perhaps? At first I thought the answer would have to do with the wavelength of the photon, but that's irrelevant since it is 3D space we're looking at. [Mαc Δαvιs] (How's my driving?) ❖ 06:57, 28 March 2007 (UTC)

Yeah I realise that, I just like making people think a bit :p Capuchin 06:58, 28 March 2007 (UTC)

Yes, I knew that photons are always moving. Ok, let my pose my question in a different way. How many photons can hit a specific point in space at one time? Thanks.100110100 07:00, 28 March 2007 (UTC)

Photons are [bosons] so infinitely many can fit into one quantum state, so choosing a quantum state that fills your space (the photons could be moving by bouncing in a box say, not stationary) you could have infinitely many. Although of course this would give you infinite energy, pretty hard to contain!137.138.46.155 07:47, 28 March 2007 (UTC)

Then again, we've not only had bosonic condensate, but fermionic condensate. [Mαc Δαvιs] (How's my driving?) ❖ 18:34, 28 March 2007 (UTC)

If you call it a Singularity then you might not also be able to call it space but probably where an infinite number of photons are located. 71.100.2.150 08:46, 28 March 2007 (UTC)

Thank you. Is photon energy?100110100 07:48, 28 March 2007 (UTC)

Energy can be infinite in any point in space?100110100 08:19, 28 March L2007 (UTC)

I'd just like to comment that Capuchin's first comment was correct. There is no such thing as stationary light. Light "stops existing" when it stops moving. —LestatdeLioncourt 13:24, 28 March 2007 (UTC)

Yes, but his application of that fact to the question was in error. The fact that photons can't be stationary does not prevent an infinite number of photons from existing in one space at one time. Whether anything else prevents this, such as some type of quantum interference, I don't know. StuRat 16:46, 28 March 2007 (UTC)

So, where we stand now, it seems to be you can fit as many photons as you have into even one particular point in space, simply because they are bosons? [Mαc Δαvιs] (How's my driving?) ❖ 18:34, 28 March 2007 (UTC)

Wait a second... there's this thing called the Bekenstein bound. Bekenstein got a bound on the entropy of a black hole, and according to his work he got it to work also, possibly for any space. A question is “Is there a finite amount of information in a spacetime unit?” Some people say yes, some people say no, and this is what we are discussing aren't we? If we call a photon a small collection of information as we would any particle, say, particle x, we would write down the quantum spin, location, energy, ect. According to the HUP, the precision of information you want to detect is proportional in some way to the amount of energy it takes to record it (think atom smashers, HRTEM). So, I bet there is a bound between how much information you can get, because the more precise you get, the more information you get, the more energy you spend, and there is a bound on energy density, something like the Schwarzschild radius, because if you pass the bound on energy density, spacetime collapses, and you get a black hole.

r_S is the Schwarzschild radius, G is the universal gravitational constant, m is the mass of the gravitating object, and c is the speed of light in a vacuum.

Gerard 't Hooft, from the Netherlands made a very general principle called the holographic principle. It is very controversial and vague, and postulates that any physical system, has a finite amount of discrete information, of 0s and 1s, bits, and the amount grows, proportional to the surface area of the spacetime unit grows (not as the volume, interestingly, just like "black hole physics"). So it looks like a holographic projection onto a plane, of a three-dimensional system, and it is usually explained in popular science by saying that looks like it is saying something like that things are two dimensional instead of three dimensional, which is a relation in saying that things might be instead of four dimensional, more, and we are actually only living in a hologram of a larger reality. Kind of like in the Matrix, how there is a larger reality that is much out of our sight, that the reality normally seen is only a projection.

A non-rotating black hole's photon sphere is a spherical boundary of zero thickness such that photons moving along tangents to the sphere will be trapped in a circular orbit. If it is zero-thickness, then that means photons would pile on top of each other, kind of, overlapping each other. So? I guess the answer is still "I don't know" Sorry for probably a confusing and maybe speculative reply. [Mαc Δαvιs] (How's my driving?) ❖ 18:50, 28 March 2007 (UTC)

But I'm trying to use relativity to explain the quantum. Maybe it's more simple. Photons are bosons, so the answer is yes. "As many as you want." [Mαc Δαvιs] (How's my driving?) ❖ 17:36, 29 March 2007 (UTC)

See Energy density. Nimur 16:40, 29 March 2007 (UTC)

[edit] Photosynthesis.

I realise that the equation for photosynthesis is given both in our article and in most textbooks as Obviously 6 H2O on each side can could be cancelled. Why isn't it? What role do the extra water have? Capuchin 06:53, 28 March 2007 (UTC)

No, the 6 H2O cannot be cancelled. That's as far as I can help you with it. The rest has to do with chemical balancing, & I'm sure other people could help you with the, more complicated, pedology.100110100 07:05, 28 March 2007 (UTC)

Think of the equation as already in lowest terms.100110100 07:06, 28 March 2007 (UTC)

I'm aware of this, hence this question, but I don't know why those extra water are there :), maybe a small edit to the original question. Thanks anyway :) Capuchin 07:13, 28 March 2007 (UTC)

Your welcome. Maybe I am also at fault. On the left side you have 6*2+12 oxygens. That means you must have the same on the other side. If you cancel out the 6 H20s on both sides, the equation will not balance.100110100 07:25, 28 March 2007 (UTC)

I could restate the question as "Why is wrong?" Capuchin 07:35, 28 March 2007 (UTC)

Hhhhmmm, ok you might be right, maybe I was thinking of somthing else, sorry to cause you trouble.100110100 07:44, 28 March 2007 (UTC)

It's okay, I still love you, now, anyone know why those extra water are there? Capuchin 07:46, 28 March 2007 (UTC)

uhm total amount of H's is the same there buddy (12H2 = 24 H) —The preceding unsigned comment was added by 145.24.133.60 (talk) 09:11, 28 March 2007 (UTC).

It's the same in both, isnt it? 24 in the first one and 12 in the second. Capuchin 09:14, 28 March 2007 (UTC)

OK, you can cancel the waters out if you are only interested in the net results of the reaction. However, in reality, the waters on the left are split to make the oxygens on the right. The waters on the right come from the carbon dioxide on the left. This was unexpected as it was easier to imagine the oxygen coming from the carbon dioxide. The general reaction is CO₂ + H₂A -> CH₂O + 2A + H₂O. A can be oxygen OR it can be S in some green photosynthetic bacteria. An experiment was done with ferricyanide too, and eventually radiolabelled water proved the source of the oxygen was water not carbon dioxide. Have a look at a biochemistry text book if you happen to have one lying around - most of these details were from Voet and Voet. Good question, btw! Aaadddaaammm 09:42, 28 March 2007 (UTC)

Deindented. Thanks, this is exactly what I suspected but didnt know the specifics of it. Thank you! Capuchin 09:49, 28 March 2007 (UTC)

[edit] Energy = Photon?

Is energy photon? Is photon energy? Thanks.100110100 07:49, 28 March 2007 (UTC)

Energy is a bit more of an abstract concept than that — photons have energy (radiant energy) and are an extremely basic form of energy transfer but they are not, in and of themselves, the definition of energy. See the "forms of energy" section of the energy article for some more detail. --24.147.86.187 09:46, 28 March 2007 (UTC)

A photon is a quantum of energy, so I guess that you can say that it is energy. This issue once came up in class, when a friend of mine asked what happens to a photon after its energy is absorbed by an electron (we were studying the photoelectric effect and Bohr's model of the atom). I guess this must be due to a common mistake in phrasing: when we say "a photon's energy", it's as if we're implying that photon has energy apart from other things. A photon is really nothing but energy. —LestatdeLioncourt 13:20, 28 March 2007 (UTC)

A photon is really nothing but energy. As is all other matter. -- mattb @ 2007-03-28T16:09Z

While all matter can be converted to energy, I wouldn't go so far as to say that it currently is energy. That would be like saying that a pile of construction material is currently a house. StuRat 16:40, 28 March 2007 (UTC)

You can easily be confused by it, but matter is not energy. As StuRat said, matter can be entirely converted to energy, but it is not energy, and vice versa. The amount of energy you can theoretically get is where E=mc² comes from. [Mαc Δαvιs] (How's my driving?) ❖ 18:29, 28 March 2007 (UTC)

Okay, granted, I should've said "there is a matter and energy equivalence". I only meant to hint that there's a reason photons (and all quanta) have a special name rather than simply being called "energy". -- mattb @ 2007-03-28T18:55Z

Whether matter is a form of energy, or is only something that can be converted to and from energy, isn't a well-defined question, because the term matter isn't well-defined. It isn't possible in practice to say precisely how much of a closed system is matter, vs. how much is energy. "Mass" is well-defined, "energy" is well-defined, but "matter" is an old-fashioned, vague word that only really works well as a concept distinct from energy when dealing with non-relativistic phenomena. MrRedact 21:56, 28 March 2007 (UTC)

I didn't read matt's answer, and it was probably the best. Down at the quantum level, no body really cares what is energy or what is mass—it's the same, measured in various denominations of eV. I suggest reading our article, mass in special relativity. It is difficult to explain, but the invariant mass (more often known as "rest mass" is different from "relativistic mass." Perhaps Baez would be better[3]. Still kind of complicated. This answer is more comprehensive[4] [Mαc Δαvιs] (How's my driving?) ❖ 22:20, 28 March 2007 (UTC)

[edit] Energy

Energy can be infinite in any point in space?100110100 08:19, 28 March 2007 (UTC)

There is a finite amount of energy in the universe and it is conserved. Except for potential quantum weirdness that I don't know about, the answer should be no. --24.147.86.187 09:49, 28 March 2007 (UTC)

There would be infinite energy density at a gravitational singularity (a finite amount of energy, but in an infinitesimally small volume). However, this may be only a theoretical concept - I don't think a naked singularity has ever been observed. Gandalf61 12:57, 28 March 2007 (UTC)

According to the laws of physics at current there is a finite amount of energy. At gravitational singularities, the mathematics and laws of physics break down, so we aren't too sure about a lot of things involving that. [Mαc Δαvιs] (How's my driving?) ❖ 18:28, 28 March 2007 (UTC)

It is better to say, "current theory and observation supports a finite energy universe." We may be very, very wrong. Nimur 16:41, 29 March 2007 (UTC)

[edit] Chaos Theory

What is the Chaos Theory and who propounded it? —The preceding unsigned comment was added by Bhavikmehta2685 (talk • contribs) 08:19, 28 March 2007 (UTC).

You know, this place works somewhat like an encyclopedia. Capuchin 08:22, 28 March 2007 (UTC)

We appreciate it if you try to look it up yourself, and if you can't understand it ask for help in understanding it. Next time you can just type in "Chaos theory" in the search box to the left at the top of the page and click "Go." [Mαc Δαvιs] (How's my driving?) ❖ 19:10, 28 March 2007 (UTC)

[edit] Linear beam theory

(Also cross posted to the Mathematics desk - sorry I don't know which one is appropriate since this is mostly an Engineering question.)

I've been trying to find references on the dynamics of a cantilever beam (assume Euler-Bernoulli beam equation) coupled to a forced mass-spring-damper system, but unfortunately I haven't found any that use a partial differential equation formulation rather than a Lagrangian approach. I'm trying to model this as with the BCs u(0,t) = 0, u'(0,t) = 0 (fixed beam BCs) and u''(1,t) = 0 (zero bending moment) and .

Does this look reasonable to anyone? Or should there be a term in the BCs as well as the one?

Also, if anyone has any suggestions on analytical solutions to this that would be great!

Thanks Davidbarton 09:13, 28 March 2007 (UTC)

That looks vaguely like a cantilever with a harmonic damper hanging off the tip. Off hand I don't think it has an analytical solution, in general mixing discrete and continuous systems results in an unsolvable equation. I'd use Rayleigh-Ritz method or FE, or look up the answer in Blevins. Another approach is the theory of receptances, which describes how to mate two simple systems, but I have forgotten how to do that. Neither Rao or Thomson discuss this case, that I can see. Greglocock 05:59, 29 March 2007 (UTC)

[edit] ethylamine

which reactant when added to bromine and sodium hydroxide give ethylamine?

X+Br2+NaOH = CH3CH2NH2

Technically this is not homework, it was an exam question and I can't seem to find it.Bastard Soap 11:14, 28 March 2007 (UTC)

Nothing obvious, especially since amines react with halogens to form N-X compounds, see chloramine. Cacycle 12:56, 28 March 2007 (UTC)

Hofmann rearrangement? DMacks 16:12, 28 March 2007 (UTC)

Yep, that's the one, Hofmann is my man. Any of you guys know the mechanism involved?Bastard Soap 23:37, 28 March 2007 (UTC)

Should be in any undergrad orgo text. The reagent soup forms electrophilic bromine, which halogenates the amide nitrogen (so Cacycle was actually exactly right:). You're under basic conditions, so deprotonate the N to get an anion, which rearranges to form an isocyanate: carbon attached to carbonyl of amide migrates to the N, halide is lost. From there, it's the same as in the Curtius rearrangement and Schmidt reaction (pages which have more mechanistic details about that rearrangement step, albeit in slightly different structures): hydrolysis and loss of carbon dioxide. DMacks 01:05, 29 March 2007 (UTC)

I deleted his reply by mistakeBastard Soap 10:58, 29 March 2007 (UTC)

[edit] Fire preservation

My school aged son is researching the properties of fire, and one area of interest is the techniques used in the past to "preserve" fire - such as the use of slow burning torches, carrying embers from home to home in the event a family's fire went out, etc. Any idea where we can find a discussion regarding of how fire was "preserved" in the past? Thanks —The preceding unsigned comment was added by Hedaku (talk • contribs) 12:31, 28 March 2007 (UTC).

There is some mention of this in our article Making fire. I've looked around for more details, but to no avail. --Zeizmic 14:33, 28 March 2007 (UTC)

I remember a fictional account of this in one of Jean Auel's books; I think it was The Valley of Horses. ike9898 19:18, 28 March 2007 (UTC)

Check a Boy Scout Handbook, and check the Foxfire series of books, and check Mother Earth News. I found re :banking th coals: [5]. Also [6] from "Plimouth Plantation . As a safety note, don't do this, since the fire can also blaze up unexpectedly and start a conflagration, expecially with campfires or a fireplace or firering which would allow flames or sparks to reach combustible substances. There were ways of carrying an ember from house to house, but I could not find a reference. Edison 23:02, 28 March 2007 (UTC)

See specifically "The Foxfire Book" edited by Eliot Wigginton, Anchor Books, NY, 1972, ISBN 0-385-07353-4.The chapter "Cooking on a fireplace, Dutch oven and wood stove, says that (p 160) before modern furnaces were in homes, fires were kept burning all day in the winter to heat the house. After an hour or so there would be a bed of hot coals from the partially burned wood, which could be used to roast potatyoes and othr foods such as nuts and onions, or even to bake bread. At night the coals were covered with a thich layer of ashes. In the morning the coals were exposed and fresh wood was added and the fire would spring up. In the summer, ashes were raked over the coals between meals when cooking was done. P162 says coals from the fireplace could be used to start a fire on the wood burning iron stove. My own grandmother grew up living this way. Edison 16:51, 29 March 2007 (UTC)

[edit] airborne radio direction finder

explain the principle of operation of airborne radio direction finding system with block diagram? —The preceding unsigned comment was added by Ambuj0542 (talk • contribs) 12:36, 28 March 2007 (UTC).

We have several articles about this topic; they may help you with your homework.

Atlant 12:37, 28 March 2007 (UTC)

Well fancy this... Direction finding -- mattb @ 2007-03-28T14:23Z

[edit] Blood pressure during sickness

I woke up today rather ill indeed, and while this is of course something I should ask a doctor about rather than you lot, I was wondering if it is common to experience higher blood pressure and a higher pulse during illness similar to flu. 81.93.102.185 16:00, 28 March 2007 (UTC)

Do not request medical or legal advice. Ask a doctor or lawyer instead. --TotoBaggins 17:09, 28 March 2007 (UTC)

I know I definitely do. It's terrible, I can feel it in my eyes too. [Mαc Δαvιs] (How's my driving?) ❖ 18:25, 28 March 2007 (UTC)

Thank you, Mac Davis. I was only worried if this was an additional thing gone wrong. I will in any case make contact with a doctor within a day, I need notification for school anyway... ;) 81.93.102.185 18:55, 28 March 2007 (UTC)

[edit] what the ****

I have been blocked, what happened? No, seriously I have been. My computer signs out whenever I go into a reference desk, so I have to sign back in again each time, and occasionally I forget and go to answer a question. But today it has suddenly started coming up saying I have been blocked whenever I do this. But it goes away when I sign in again.

Also what is up with all the alien related questions the reference desks have sprouted recently, did I miss something important?

HS7 19:12, 28 March 2007 (UTC)

I see no reason to believe you've been blocked. -- mattb @ 2007-03-28T19:45Z

Unless of course someone applied an anon only block to your IP for some reason, sharedip? public computer? anything like that?--VectorPotential^Talk 19:48, 28 March 2007 (UTC)

What alien questions? I can only think of one or two farther up the page. Now the seagull questions... now that's another story! xD [Mαc Δαvιs] (How's my driving?) ❖ 19:51, 28 March 2007 (UTC)

One question frequently spawns many similar questions. I've even been caught spawning, from time to time. StuRat 20:37, 28 March 2007 (UTC)

[edit] Are teeth techically considered bones?

I don't think that they are, but I didn't see the question clearly answered in either article (although I may have missed it, I was skimming). What is the technical name for the type of tissue that makes up teeth? Thanks ike9898 19:15, 28 March 2007 (UTC)

I think the outside bit is called enamal, which is almost bone :) No idea what the rest is called, but I suspect all of my whatever it is have rotted away, so they can't be that important :( HS7 19:18, 28 March 2007 (UTC)

Actually, enamel isn't "almost bone". It's really not even a tissue, since tissue contains cells and enamel is acellular. Moreover, enamel is much harder than bone; in terms of hardness, dentin (which comprises a good hunk of a tooth's volume) is between bone and enamel. --David Iberri (talk) 21:37, 28 March 2007 (UTC)

Look at the article teeth about a third of the way down a diagram shows what a tooth is 'made of'. Look up each respective 'item' and you can probably make a judgement. bone will help as it defines a little more 'openly' what consistutes being called a bone. ny156uk 19:37, 28 March 2007 (UTC)

Thanks for the help but I am really looking for an answer from the perspective of histology. Histologists seem to have a heirarchical classification for tissue types and I would like to know how bone and tooth relate to each other in this sense, i.e. are they both members of some larger class? What is that class called? ike9898 20:40, 28 March 2007 (UTC)

Well, you probably won't like the answer :). But the study of the microscopic structure of teeth and bones is called "hard tissue histology". Sorry it couldn't have been something fascinatingly Latin.... - Nunh-huh 20:58, 28 March 2007 (UTC)

I guess I'm not being clear. I'm not interested in the name of the study of teeth and bones. My real question is at the title of this section. Are teeth technically considered bones or not? Assuming they are not, can someone point me in the direction of something that explains the relationship between teeth and bones? ike9898 21:06, 28 March 2007 (UTC)

No, teeth are not bones. They are histologically distinct. Teeth and bones are both classified as "hard tissue". - Nunh-huh 21:11, 28 March 2007 (UTC)

The differences between the two are pretty great. The most salient similarity to me is that both are made largely of hydroxyapatite (calcium and phosphate crystals). In teeth, these crystals comprise much of the dentin; in bone, they form the inorganic component of bone matrix. Cheers, David Iberri (talk) 21:34, 28 March 2007 (UTC)

Just to reiterate the above: no, teeth are not bones. (They're often included in skeletons probably because they, like bone, contain large amounts of mineralized matrix that survives decomposition.) — Knowledge Seeker দ 06:24, 29 March 2007 (UTC)

[edit] Photons

Will enough photons in a singularity collapse into a black hole?100110100 19:42, 28 March 2007 (UTC)

Great questions :) I suggest you should ask them on physicsforum's general physics discussion[7]—you can get better answers there from actual physicists and professors, then here. See Geon (physics). [Mαc Δαvιs] (How's my driving?) ❖ 19:43, 28 March 2007 (UTC)

I'm going to venture a guess: no, since photons have no rest mass, so I don't believe they themselves distort spacetime. This is nothing but a wild guess by someone who is totally unqualified to answer, though. -- mattb @ 2007-03-28T19:47Z

The Einstein field equations say oppositely I believe, and the article I suggested does too. [Mαc Δαvιs] (How's my driving?) ❖ 20:00, 28 March 2007 (UTC)

Yes, I believe that once the energy density of a small region becomes high enough, a singularity should form. There's nothing that says it needs to be in the form of (rest) mass; but it'd take a hell of a lot of photons directed simultaneously at a single point. Penrose-Hawking singularity theorems briefly touches on the notion, too. Spiral Wave 00:46, 29 March 2007 (UTC)

[edit] Bug

Can anyone help the Test Match Special commentary team and identify this insect? It's in Guyana, if that's any help. Thanks! →Ollie (talk • contribs) 20:18, 28 March 2007 (UTC)

I'm not sure, but I sure wouldn't want to be on the soccer team which has to play against it ! StuRat 20:34, 28 March 2007 (UTC)

But that wouldn't be cricket. Skittle 22:18, 28 March 2007 (UTC)

[edit] Below Freezing Temperatures & Pipe lines

How does a city keep the water and seawge pipes running when the temperature is below 0 C? --Shines8 21:04, 28 March 2007 (UTC)

The pipes are buried beneath the frost line. --Steve Summit (talk) 21:27, 28 March 2007 (UTC)

And note that even under the frost line water can turn to ice in city pipes in cold enough weather, such as described in this article from New Jersey. Pipes in homes can also freeze, and one way to help prevent pipes from freezing is to keep your water running a bit. I wouldn't be surprised if the fact that water is probably running almost constantly in large city pipes further reduces the risk of those pipes freezing when underused or unused pipes at similar depths might (just a guess). --Dugwiki 21:48, 28 March 2007 (UTC)

And occasionally a pipeline runs above the frost line (crossing a bridge, for example), but in that case, the diversity factor helps ensure that water is always flowing in the pipeline, even if it's hard to believe that people are flushing their toilets that late in the cold night. --Atlant 22:39, 28 March 2007 (UTC)

Thanks for the answer. I understand that having the pipes below frost line, has an effect of insulating it from cold. I was just wondering, in my city, it sometimes goes to to -25 C, and that times when I trun on the hot water tap there is so much pressure (its like it wants to come out), whereas the cold water tap seems to have no pressure (it doesnot want to come out). Do you know why this happens? The hot water boiler is at the basement of my apartment building. --Shines8 00:33, 29 March 2007 (UTC)

In the kind of system in my house, the pressure of the incoming water supplies pressure to all the pipes, both hot and cold. So if I found the cold water pressure lower at the tap, it would indicate a partially blocked pipe. However, I know nothing about apartment systems. Possibly the hot water system does not pass the pressure through from the input pipe and has a separate pump, but that's just a guess. Why not ask the building manager? --Anonymous, March 29, 2007, 01:26, edited 06:00 (UTC).

[edit] Possible explanations for the hexagonal storm on Saturn?

I read an article in the paper today about the hexagonal storm at Saturn's north pole, but I haven't found any freely accessible articles, either here or elsewhere, that offer possible explanations for the weird shape (why isn't it elliptical or circular?) Can anyone post some reasonable natural scenarios which would produce a hexagonal stormfront? Just curious, thanks. Dugwiki 21:15, 28 March 2007 (UTC)

It most likely has to do with this[8]. I do not believe this is natural on Earth, but that does not make it void for Saturn, the wind velocities are much higher there. The pentagon shown looks a lot like the hexagon on Saturn. I'm sure we'll have a picture uploaded soon. [Mαc Δαvιs] (How's my driving?) ❖ 21:51, 28 March 2007 (UTC)

Thanks, very interesting article and experiment. That definitely sounds to me like a likely explanation. Dugwiki 22:28, 28 March 2007 (UTC)

It's not really an explanation, just an observation that we are able to create the same effect in a bucket. While fascinating, we don't have any model that would predict exactly which polygons should occur under which conditions. It's still a mystery. StuRat 00:19, 29 March 2007 (UTC)

How bizarre, I've never seen anything like that before. Could it be the result of some resonant (m=6) mode, perhaps? That Nature article doesn't really suggest anything, but perhaps someone else has attempted the problem since then. Spiral Wave 00:35, 29 March 2007 (UTC)

Do we know why certain crystals, such as snowflakes, are hexagonal (or form other polygon shapes) ? If so, perhaps a similar cause underlies this phenomenon. StuRat 00:38, 29 March 2007 (UTC)

Snow#Geometry offers a couple of explanations, neither definitive, but I don't think the process can be the same - that's a bottom-up process, this looks more like the collapse of a larger (non-)structure. The Saturn article suggests it may or may not(!) be a standing wave, which would also have been my first guess. But that still doesn't explain how it formed, of course. Spiral Wave 00:53, 29 March 2007 (UTC)

The thing that freaks me out most is that whilst the experiment in the spinning bucket elegantly demonstrates how this hexagon came to be as a perfectly natural phenomenon - it goes nowhere in explaining why Saturn has this at only one of it's two poles. If it were a natural result of fluid dynamics at a particular speed and with a particular type of fluid - why isn't it there at both poles? SteveBaker 18:05, 29 March 2007 (UTC)

A complete wild guess, but it could be seasonal, and shift from pole to pole between winter and summer. Saturn is in roughly the same place in its orbit now as it was when the Voyager images were taken of it 30(-ish) years ago, and we haven't been observing it very closely in the intervening time. Saturn's wind systems aren't perfectly symmetrical from hemisphere to hemisphere either, so vanishing from one hemisphere needn't imply it should appear at the other. Perhaps we'll be able to rule that one out in about 15 years! Spiral Wave 23:31, 29 March 2007 (UTC)

[edit] Observing drug resistance developing by mutation

Hello. I am a layman interested in various evolution issues. Is there a clear example of a bacteria population adapting to antibiotics or other drugs, where the trait that gives drug resistance clearly came from a mutation and NOT from recombination, transposons, or some form of DNA transmission? Actually, any example of a population that has clearly adapted to its environment due to mutation, rather than recombination, will do. Also, how do we prove that it really is mutation and one of those other factors? I asked a similar question before, I hope no one minds. 69.223.174.232 22:05, 28 March 2007 (UTC)

Mutation is relatively rare, so one would have to observe thousands, millions, billions, or even trillions of cells to actually observe a mutation taking place, at least under normal circumstances. However, if the cells are exposed to mutagens, the odds of detecting a mutation can be significantly improved. StuRat 22:16, 28 March 2007 (UTC)

One common cause of resistance to the antibiotic vancomycin is a single changed amino acid. DMacks 22:44, 28 March 2007 (UTC)

Yes, there are many examples. It's pretty easy to comprehend, too. Since many antibiotics work by interfering with an enzyme, a mutation causing a change in the structure of that protein could cause resistance. With enough infections and enough antibiotic use, the chance become quite high. That being said, if you mean a case where we actually observed a bacterium developing the original mutation, I'd say that's quite unlikely. — Knowledge Seeker দ 06:29, 29 March 2007 (UTC)

Mutation can be induced fairly easily in bacteria. If you cultivate bacteria on a petri dish with a low concentration of antibiotic, they will develop resistance to the drug as shown by the colonies that survive. Bacteria do not go through meiotic recombination, and a colony of "clones" can be easily isolated removing the chance of DNA transmission from outside. This leaves transposons, and outright mutation of genes as the source of resistance. Since transposons are genes that move from one place to another within the bacterial genome, resitance can not come directly from a transposition, unless an error (or mutation) occurs in the transcription process. -Czmtzc 16:10, 29 March 2007 (UTC).

These guys are irradiating rice to induce mutation, and then selecting the ones with desirable qualities for further breeding. They've released three strains so far. --TotoBaggins 05:01, 29 March 2007 (UTC)

There are lots of examples of this out there - it's a truly proven thing. But my favorite example is Lactose tolerance in humans. Evidently in the times of the early Egyptians (a few thousand BC) all adults were lactose-intolerant because in times prior to widespread farming practices, there was evolutionary benefits to babies being tolerant of lactose in their mother's milk only for as long as it took them to wean onto solid foods. Beyond that point lactose intolerance would kick in and the growing child would be unable to drink the milk that younger siblings might need. Lactose intolerance is "normal" in most mammalian adults for this reason. When we started keeping (and being able to milk) cows, goats and sheep - the inability of adults to tolerate lactose became a negative thing because in times of famine we'd have to slaughter cattle for food rather than living on milk and cheese. Over the past 4,000 or so years, we have evolved lactose tolerance in adults. The process clearly isn't quite complete because lactose intolerant adults are still to be found. Interestingly this 'problem' of lactose intolerance is most common in more civilised societies where famines are essentially unknown and there is no longer evolutionary pressure to complete the process. The genetic difference is clearly that the ancient mechanism that used to turn off our ability to digest lactose at around two years of age must have malfunctioned (perhaps in just one individual) as a result of some kind of mutation - descendents of that person could survive and reproduce when others died (or at least were too sick to breed) because the only option left was to drink milk and eat cheese or slaughter your livestock for food causing worse problems on the following year. We tend to think of evolution as something that happened millions of years ago and to other species than us - but it's very clear from this example that it's still an ongoing process in humans. SteveBaker 18:00, 29 March 2007 (UTC)

Interesting stuff, but our map of lactose intolerance seems to tell the opposite story to what you're saying in the second half of your post. The US and Europe may or may not be more "civilized" than sub-Saharan Africa and East Asia, but they can hardly be said to to have suffered more famines. --TotoBaggins 21:43, 29 March 2007 (UTC)

As I recall, it's somewhat complicated by the fact that the domestication of milk-producing animals started later in places where 'hunter/gatherer' lifestyles prevailed - so the native populations in those places have had less time to evolve. I need to go back and find where I read about this...I recall an article pointed at by something that was in turn pointed at by Slashdot a couple of months ago. I know that this hardly counts as an adequate reference! Also, some less advanced societies (such as the Kenyan Maasai) have come up with ways to 'fix' the problem of lactose intolerance by mixing cows blood and urine with the milk before adults drink it. One presumes that this does something to the chemistry to make the milk more digestible - I have no clue what. SteveBaker 05:05, 30 March 2007 (UTC)

I seem to recall that they mixed cow's blood and milk and drank it, but not urine. The urine they used as a "disinfectant" on wounds and such. They didn't kill the cows to get blood, either, but cut them and took an amount that wasn't too much for the cows to handle. StuRat 00:30, 31 March 2007 (UTC)

[edit] Iapetus (moon of Saturn) as a Death Star-style artificial alien world/spacecraft thing...

This crackpot-sounding theory used to be mentioned in the Iapetus (moon) article but all reference to it seems to have been deleted now. Anyone able to remember the main gist of it? It was an entertaining, thought provoking theory - even if it was 99.99999% net.crank BS. --Kurt Shaped Box 22:10, 28 March 2007 (UTC)

See Mimas (moon)#Mimas_in_fiction_and_film. StuRat 22:19, 28 March 2007 (UTC)

Is this what you are talking about? →Ollie (talk • contribs) 22:26, 28 March 2007 (UTC)

Na, it was definitely Iapetus - the 'great wall' around the equator was mentioned as being something to do with the 'framework' of the thing. As far as I can remember, it was postulated that what we see now is the result of millions of years of erosion stripping away the surface layers of the 'hull'. --Kurt Shaped Box 22:26, 28 March 2007 (UTC)

Yes Ollie! That's exactly what I was thinking of! Thanks very much! --Kurt Shaped Box 22:27, 28 March 2007 (UTC)

I always liked the way Iapetus has the same circular indentation in its northern hemisphere. I thought the resemblance was striking long before anyone pointed it out to me! Spiral Wave 00:27, 29 March 2007 (UTC)

Maybe that was the exhaust? ;) --Kurt Shaped Box 00:42, 29 March 2007 (UTC)

As a matter of interest, how much energy would be required for a spacecraft this size (1.805635±0.000375×10²¹ kg according to the article - presumably heavier when spaceworthy) to reach the speeds necessary (say, a significant %age of the speed of light) for interstellar travel? --Kurt Shaped Box 00:54, 29 March 2007 (UTC)

Ignoring relativity (because it's too much effort) a quick calculation shows that getting that mass to about 10% light speed would require about 8×10³⁵J, or approximately 200 yottatons of TNT. Equivalently, (and again ignoring relativity) to get any object to 10% light speed you'd need to annihilate 0.5% of the object's mass and somehow harness all that as kinetic energy.

Short answer: a lot. Algebraist 01:34, 29 March 2007 (UTC)

Could humans build something that big? I don't mean make it fly, just create a structure of that size in space? --84.69.54.85 01:50, 29 March 2007 (UTC)

Not at present, no, but way in the future, why couldn't we even build a Dyson sphere ? StuRat 03:39, 29 March 2007 (UTC)

Whoa. I'd never even heard of the yotta- prefix! Big bird. That's ignoring the energy required to slow it down and stop at the other end too. --Kurt Shaped Box 10:47, 29 March 2007 (UTC)

Yeah - I wouldn't want to try aero-braking on that sucker! SteveBaker 17:12, 29 March 2007 (UTC)

But as to the effort to "build something that big" - I think it depends on what you mean by "build". Think "hollowed out moon" and not "death-star construction". If you started with a suitable "icy moon" of that size - then hollowed out your living quarters, space for the engines - and gradually consumed the rest as fuel in getting it from wherever it was to wherever you want it to be...then it might not be outrageous. Assuming you have the patience to do it over many, many generations, you could use fairly small engines over a L-O-N-G period of time to push it around. Once you get it closer to the sun (which is relatively easy because it's "downhill"), the ice on the surface would start melting, you could sculpt even fairly large features just by laying reflective foil over the areas you want to keep as mile-thick 'solid structure' (made of ice of course) and dumping some carbon-black over the areas you'd like melted into ocean-sized fuel tanks. Pumping the warmer liquid down into the core of the planet would allow you to hollow out big spaces for vast living quarters, etc. The internal volume of even a small moon could be turned into continent-sized living areas. If you were prepared to spend lots of effort and many thousands of years - I think you could maybe do it with present day technologies. We tend not to think much beyond our own lifetimes - so such a project is unlikely - but maybe you'd need to do it because you saw some looming catastrophy that required you to relocate the entire ecosphere someplace. The sun going nova or something nasty like that...It's certainly not impossible. SteveBaker 17:12, 29 March 2007 (UTC)

I disagree that it's easier to go towards the Sun than away. Once in a stable orbit, I believe it takes approximately as much energy to move closer to the object you are orbiting as away from it. An exception is if you are close enough to the object to encounter resistance from gases and dust. StuRat 18:15, 29 March 2007 (UTC)

Um...maybe. Yes - perhaps you're right. But it doesn't really change the argument much. SteveBaker 04:51, 30 March 2007 (UTC)

Heh. I guess that there'd be room for more than two of every animal that way... ;) --Kurt Shaped Box 21:49, 29 March 2007 (UTC)

[edit] physics

what the difference between ampere and ampere-hour

—The preceding unsigned comment was added by 202.53.9.25 (talk) 22:15, 28 March 2007 (UTC).

An ampere is a measure of electrical current, and an ampere-hour is a measure of electrical charge. Dimensional analysis is something helpful here, if you want to multiply the current and time. Try reading the articles and wait for a better response, heh. [Mαc Δαvιs] (How's my driving?) ❖ 22:23, 28 March 2007 (UTC)

An ampere is a unit to measure the current, or rate of flow of charge. Amp-hour is a unit to measure the amount of charge the flows over a certain period of time. Ampere-hour is comperable to coulomb. 1 amp-hr = 3600 coulombs. Electricity terminology is sometimes easier to understant if u use water analogies. Think of ampere-hours as liters or gallons of water, while amperes are the rate at which water flows through a pipe (like 2 liters per minute or 5 gallons per hour).

Funny how nicely water and electricity mix. [Mαc Δαvιs] (How's my driving?) ❖ 22:28, 28 March 2007 (UTC)

[edit] The farting vegitarian

Why do some foods (beans, peanut butter, eggs..) make you fart? I noticed they're all alternative sources of protein... does that have anything to do with it?

I would suggest reading Flatulence. Has all the answers and more. [Mαc Δαvιs] (How's my driving?) ❖ 22:21, 28 March 2007 (UTC)

In a perfect world, there would beano gas. StuRat 00:22, 29 March 2007 (UTC)

But then we would all asphyxiate. − Twas Now ( talk • contribs • e-mail ) 15:24, 29 March 2007 (UTC)

Yes, that would certainly be flatal. StuRat 18:10, 29 March 2007 (UTC)

I heard that flatulence will get you anywhere. And if it doesnt, you can always make a big stink about it ;-) —The preceding unsigned comment was added by 88.110.24.123 (talk) 18:26, 29 March 2007 (UTC).

[edit] Color of light

Why is the color of light usually described as a wavlength (for example 700 nm red) instead of a frequency? Wouldnt it be more apropriate, because frequency does not depend on the medium (air, glass, water) whereas wavelength does? for example that same light, will still be the same red when it passes into a lens or glass of water, but the wavelength will not be anything close to 700 nm.

The equation is this:

Where lambda is the wavelength, c is the speed of light, and f is frequency. As you can see they are inversely proportional, and as far as I know, it is just convention. We could just as easily say the frequency. The higher the wavelength the lower the frequency, the lower the wavelength, the higher the frequency. [Mαc Δαvιs] (How's my driving?) ❖ 23:26, 28 March 2007 (UTC)

I'm not sure of the actual answer but if you look at all electromagnetic waves you generally find that at low frequencies (DC-RF), frequency is used as the main means of description. At higher frequencies wavelength is used. The dividing line seems to be in the THz band, which historically people have had great difficulty generating or measuring so hasn't been used much. I would guess that at the lower frequencies the radiation is often associated with electronics which operates at an easily measurable rate and that the wavelength is long enough to be practically difficult to measure, meaning that frequency is the obvious choice. This convention has now extended up to RF & microwave frequencies. On the optical side it was historically difficult to count fast enough and you could easily measure wavelength via macroscopic apparatus like Young's slits for example. At smaller wavelengths, like X-rays, you can again relate the wavelength to physical length measurements like atomic spacing, making wavelength the natural choice here. JMiall 23:38, 28 March 2007 (UTC)

Ah yes, that is right. In radio we designate radio frequency regions for different level licenses, high frequency, very high frequency, extremely high frequency. [Mαc Δαvιs] (How's my driving?) ❖ 01:28, 29 March 2007 (UTC)

The "level of the license" and the frequency of operation have nothing to do with each other. Amateur radio bands exist at many frequencies, including a few openings in sub-millimeter waves (normally those frequency ranges are for "space-craft communications" and "military radar").

Also, whether you measure in wavelength or frequency often depends on the machine/instrument you are using to measure the wave. The two are tightly related, and depending on your needs, you can work in either domain. It's a simple unit conversion detail - almost like "inch/centimeter" conversion: pretty irrelevant as far as the science goes; highly important to make sure you use the right units.Nimur 16:50, 29 March 2007 (UTC)

It's not color until it is received by our cone cells and perceived by our color vision system. So we don't really need to make allowances for traveling through different mediums since all of our eyes are the same. Also while a certain wavelength will be percieved as a certain color (say green), there can be mixtures of wavelenghts (say blue and yellow) that might produce the same color perception. Color is more of a subjective construct than a physical reality. If we want to do physics experiments we can just think of it as radiation and not worry about the color -- Diletante 01:53, 29 March 2007 (UTC)

Even that is an over-simplification. The word "Color" (or "Colour") refers only to our perception of frequency/wavelength. We have a very poor sense of colour vision indeed - although it's good compared to many animals - it's a lot worse than (for example) Goldfish. Our eyes have three kinds of colour sensors which are responsive roughly at the frequency of red, green and blue light. We do NOT sense the frequency of the light directly. Each of the sensor types is most sensitive to light at it's ideal frequency and progressively less sensitive at frequencies above and below that level. Hence, (for example) pure yellow light (such as might be produced by a sodium street lamp) at a frequency roughly midway between 'pure' red and 'pure' green will weakly stimulate the red sensors and weakly stimulate the green ones - and will not stimulate the blue ones hardly at all. As far as the red sensors are concerned, there is no difference between dim pure red light and bright pure yellow light. Our brains have learned to "see" yellow when both red and green sensors report roughly equal amounts of stimulus. In fact, the colour display on your computer can't even generate yellow light (that is to say light at the frequency of a sodium lamp)...when you put a patch of "yellow" up onto your screen, the computer is actually displaying a mixture of pure red and pure green that fools our brains into reporting that there is yellow because the two kinds of sensors are equally stimulated. This is a weird thought...but it's true. It's as if you could play two notes on a piano at the same time and instead of hearing a chord composed of two pure frequencies, you could only hear a kind of 'average' frequency that would be indistinguishable from playing a single key on the piano somewhere between the two you chose! Fortunately for musicians (but perhaps unfortunately for painters!) our ears don't work like our eyes in that respect.

Anyway - to return to the question. It doesn't matter that the speed of light is different in air and water because our retinas are sitting in a big puddle of liquid inside the eyeball - so only the speed of the light through that liquid matters - and that's a constant. So it doesn't matter whether you talk about the wavelength or the frequency - the result is the same because the speed of light through the optical humor is always the same no matter whether your eyes are underwater or not. SteveBaker 16:51, 29 March 2007 (UTC)

[edit] Seeing under water

How is it possible? doesnt the cornea lens depend on its refractive index being significantly higher than that of air/vacuum? doesnt it have a refractive index too close to that of water (after all, like other tissue, its mostly water) to be able to focus the light? even if it is slightly higher index, doesnt changing medium surrounding a lens drastically alter its focal length? Also, a related problem, how do cameras work under water.. same problem.. right? (asuming the camera's front lens is in direct contact with the water).

You're absolutely right: if the lens (human or camera) were in direct contact with the water, it wouldn't work. (And if you've ever opened your eyes under water, you've seen this.) Divers can see clearly underwater only by wearing a mask, so that their eyes are in air as expected, and the air/glass and glass/water interfaces are all flat and so merely linearly refractive. Underwater cameras are either encased in a housing which functions similarly, or have an outer lens whose outer surface is flat. —Steve Summit (talk) 03:07, 29 March 2007 (UTC)

Underwater cameras can work without a housing because the refractive index of glass is still sufficiently different from water to produce a lensing effect if the glass is shaped appropriately for underwater use. Many so-called underwater cameras are in fact just normal non-underwater cameras encased in a waterproof housing as Steve Summit says - but that's because it's more convenient to use a conventional camera's lenses than to grind special ones. The problem with our eyes is (as you suggest) that the refractive index is almost identical to water and thus they have little or no focussing power when directly in contact with water. Water has a refractive index of 1.33 and glass 1.5. SteveBaker 16:36, 29 March 2007 (UTC)

I confess I was speculating somewhat when I suggested that an unhoused underwater camera might have to have "an outer lens whose outer surface is flat", but what I was worried about (before suggesting the contrary, i.e. that the glass could instead be "shaped appropriately for underwater use") was that the refractive index of salt water might be significantly different from fresh, and everything else being equal you wouldn't want a camera that could work well in one but not the other. (Was I wrong about the differing refractive indices?) --Steve Summit (talk) 21:57, 29 March 2007 (UTC)

Whoa wait a sec howcome is it that i can see clearly more or less under water? i mean i wear glasses and all and without them im blind however under water i can see clearer, and if i have my glasses on as well i can see even better at times. are my eyes diffrent or does it have to do with the water acting as a sort of corrective lens? Maverick423 20:30, 29 March 2007 (UTC)

Well - from the preceeding argument, you can see that it's definitely possible. The lens in your eye is either bending the light too much to focus it on your retina - or not enough (depending on whether you are short or long sighted - I'm too tired to figure out which it is right now). The amount that the light is bent by the lens depends on the difference between the refractive index of the air or the water and that of the lens in your eye. If your eye bends the light too much when in air, it would bend it quite a lot less in water and - yes - it's possible that by a lucky coincidence this could give you better eyesight underwater than in the air...in fact, your ability to see clearly underwater would be better than someone with 20:20 vision underwater! We've been assuming that the refractive index of the lens in your eye is similar to that of water - but it might be just different enough to let you get a good focus. Yeah - I could easily believe that. SteveBaker 04:47, 30 March 2007 (UTC)

[edit] Barometric reading and water-vapor pressure

Hi, I ran an experiment where I mixed HCL with water, and put a strip of Mg metal into the solution. I measured the temperature, pressure, and volume. I used an eudiometer tube and let the chemical reaction take place, then I flipped the tube upside down and put it into a solution to even out the pressures outside and inside the tube. The barometric reading was 769.82 torr, and the water vapor pressure was 23.8 torr.My question is: Why is it necessary for me to make a water-vapor correction of the baraometer reading? Thanks for the help! —The preceding unsigned comment was added by 76.188.176.32 (talk) 23:35, 28 March 2007 (UTC).

Nevermind, I have figured it out on my own. Another question comes to mind.. I have determined the molar volume of the hydrogen, but it was .89% off. (22.2 instead of 22.4). Where did this error come from?

That low level of error could come from anything; inaccuracy in the readings, round-off error, or some combo of both. StuRat 00:12, 29 March 2007 (UTC)

[edit] How to reduce the temperature of something

In the article Helium-4 I read: "When helium-4 is cooled to below 2.17 kelvins (–271 °C), it becomes a superfluid, with properties that are very unlike those of an ordinary liquid."

How do they refrigerate something to -271Cº? —The preceding unsigned comment was added by 190.30.12.141 (talk) 23:56, 28 March 2007 (UTC).

Ah, take a gander at Cryogenics. -- mattb @ 2007-03-29T00:00Z

This is just a thought... temperature and volume are directly related (Charles's Law). If the volume of the substance is decreased, then the temperature is also decreased. To reduce the temperature to -271K..try reducing the pressure also. —The preceding unsigned comment was added by 76.188.176.32 (talk • contribs).

That effect is used in refrigeration, yes. However, they decrease the pressure of the refrigerant, then cool the target with the refrigerant, as opposed to decreasing the pressure of the target directly. This allows them to repressurize the (now warm) refrigerant, which then becomes hot, then cool the refrigerant using air, depressurize it again to make it cold, and repeat the cooling process indefinitely. StuRat 00:46, 29 March 2007 (UTC)

Speaking of refrigeration, its article is quite useful. --Bowlhover 04:02, 1 April 2007 (UTC)

[edit] March 29

[edit] Female Vs. Male Orgasm

What is it about the female body that allows it to experience longer orgasms ( average: 20 seconds) While males only experience an average of a 5 second orgasm? —The preceding unsigned comment was added by 68.7.0.44 (talk) 00:41, 29 March 2007 (UTC).

This was already answered when you asked on WP:RD/M. -- mattb @ 2007-03-29T00:47Z

But there was no answer! It was probably better asked on the science desk anyway. Our article on ejaculation suggests a few seconds higher, 10 to 15 contractions, with an average of 0.6 s per, and increasing about 0.1 s per. I don't know why either. It's not their bodies, it's their brain. [Mαc Δαvιs] (How's my driving?) ❖ 01:33, 29 March 2007 (UTC)

It certainly is our bodies! The brain just takes us to the cusp. − Twas Now ( {{talk • contribs • e-mail ) 15:23, 29 March 2007 (UTC)

The brain is the most powerful sex organ.--Ķĩřβȳ♥♥♥ŤįɱéØ 16:58, 29 March 2007 (UTC)

Good. But the orgasm is a physiological phenomenon, not merely something that occurs in your mind. That is why you feel it mostly in your groin, and diffusely throughout your entire body (assuming it is a good orgasm). − Twas Now ( talk • contribs • e-mail ) 22:09, 29 March 2007 (UTC)

[edit] self propulsing water vortex

would it be possible to create a water vortex that sustains itself by aving a very large cylindrycal container with a conical botom with a hole at its tip and ave a tube going from that hole to the top of the container and ave the presure from the weight of the water pump enough water to the top of the container and direct it in the right manner to ave a self sustaining vortex?

also would aving a swirling patern in the conical part of the container help in guiding the water to promote a swirling motion?

i am looking in to the fact that to create a vortex , the larger the amount of water you ave proportionaly the smaler the percentage of that amount as to come in motion to create a vortex

clockwork fromage —The preceding unsigned comment was added by 216.113.96.184 (talk) 00:41, 29 March 2007 (UTC).

What you propose sounds like a perpetual motion device, which is not possible. So, you will need a pump in the process to start and keep the water moving. A swirling pattern would help, but would need to be a very specific pattern, not just any swirl would work. If the pattern goes in the wrong direction for your hemisphere or at a pitch which doesn't match the speed of the water, it would be counter productive. Adding the water at the top of the water edge entering approximately tangent to the waterline is perhaps an easier way to encourage a whirlpool to form. However, if the depth is correct for the amount of water flowing out the hole in the bottom, a vortex should form without any additional effort on your part. Incidentally, do you by any chance 'ave a Cockney accent ? StuRat 00:59, 29 March 2007 (UTC)

i dont think this could be called a perpetual motion since all the motion is produced by gravity and nor perpetuating itself , tthe question is could enough water be pushed by gravity all the way to the top to generate a vortex , and no i dont ave a Cockney accent, i live in quebec clockwork fromage

Well, all that would happen is that the water would rise in the tube to the same level as in the cylinder, after some dynamic oscillation where it would go a lot higher, then a lot lower, than a little higher, then a little lower, and eventually end up at the exact same height as in the cylinder. An exception is if you had an extremely narrow tube, then it would permanent go higher, due to capillary action. If you don't have a Cockney accent, what's with all the missing leading "h"'s ? StuRat 02:06, 29 March 2007 (UTC)

are you sure this would happen in a very large tank with ,lets say more than 100 ton of water ? and woudnt it be possible to concentrate the presure of the weight of the water by having a conical botom in the tank?

No, it doesn't work that way, the pressure is exactly the same at the bottom of the huge tank, regardless of the shape of the bottom, and that will exactly equal the pressure of the tube, once the tube contains the same depth of water. Thus, an equilibrium is maintained at that point. The pressure is solely dependent on the depth of the water, not the quantity. StuRat 03:32, 29 March 2007 (UTC)

i supose it woudnt work eighter if you ad the tube go above the water line then come back in the water than filled it up completely and then creating a vortex, the action of the vortex woudnt be enough to ave water go trough the system

It sounds like you are talking about using suction. While that can be used to raise water above the initial level, this is only true if it leaves the tube into a tank with a lower level than the tank where it enters, like this:

  Flow direction ->
      _____  
     /     \
 |~~/~~|  | \   |
 |     |  |~~\~~|
 +-----+  +-----+

StuRat 04:43, 29 March 2007 (UTC)

See siphon. Gandalf61 12:24, 29 March 2007 (UTC)

It doesn't matter that gravity is involved - such a device would still violate at least one of the laws of thermodynamics - so it's not going to happen. Whatever your device does, there is internal friction within it that requires energy to overcome - and which dissipates as low grade heat. So energy continually 'leaks' out of the system and that has to be replenished to keep it running - hence if you don't feed some kind of energy into it to keep it swirling it'll slowly run down and eventually stop. With a nicely shaped chamber and a lot of water, it might take a long time because there isn't a lot of internal friction - but it'll stop swirling after some number of hours. A common mistake of amateur perpetual motion 'inventors' is to assume that gravity (or more often magnetism) is a source of infinite energy - gravity is a force - but forces and energy are not the same thing. SteveBaker 16:25, 29 March 2007 (UTC)

Wouldn't air pressure have an effect, as the surface of the container is likely to be a lot more than that of the tube :) HS7 18:57, 29 March 2007 (UTC)

[edit] microprocessor heat

Hello, I am wondering how the heat in microprocessors is generated, I can't seem to find it in any article. I entered a local science fair with a microprocessor related project recently and I described transistor leakage to one of my judges. However, one of the criticisms I had was that I did not point out the other reasons for microprocessor heat or give a chart/figures as to how much heat each reason generates. Do you know a source that could point me to something like this? I am looking for how heat production is rising due to clock cycle and things other than transistor leakage/power density I may have missed. Thank you. —The preceding unsigned comment was added by 24.231.205.94 (talk) 01:45, 29 March 2007 (UTC).

How about plain old electrical resistance ? Unless you use a superconductor, that's always a factor, I believe. StuRat 02:12, 29 March 2007 (UTC)

(edit conflict):I don't know about any raw data to give you, but I'm pretty sure it's just heat from electrical resistance isn't it? Why does it get so much hotter the more you overclock? [Mαc Δαvιs] (How's my driving?) ❖ 02:14, 29 March 2007 (UTC)

Because the thing is consuming more electricity. --Anon, March 29, 2007, 02:37 (UTC).

More electric current, to be precise. As a result, you substantially increase the amount of Joule heating, which is the primary thermal loss mechanism in electrical circuits, AFAIK. Titoxd^{(?!? - cool stuff)} 02:39, 29 March 2007 (UTC)

Informally, here's the issue: any electronic gate, no matter how small -- and a microprocessor contains millions of them, albeit all very small -- requires that some number of electrons be added or removed to turn the gate on or off. If you want the gate to turn on or off faster, you've got to transfer those electrons faster. The electrical unit of current -- the ampere -- just counts a flow of electrons per second. (Strictly speaking it's coulombs per second, of course, but a coulomb is just a certain number of electrons.) So to switch a gate twice as fast means transferring the same number of electrons in half the time, which means twice the current. But any time you run a current through a wire, and unless the wire is a superconductor, there's at least some resistance. When you pass a current through a resistance, a certain amount of energy is dissipated, usually as heat. (This is the Joule heating that User:Titoxd was referring to.) The amount of energy (heat) dissipated is in fact I²R, where I is the current and R is the resistance. So if you double the speed of a processor, to a first approximation you quadruple the amount of heat it's going to have to dissipate. If the heat sink isn't big enough to dissipate that heat fast enough, the chip gets hotter. (There are other factors involved, too, but I think this one is the most basic.) —Steve Summit (talk) 03:48, 29 March 2007 (UTC)

On a quantum level the heat is due to electrons losing kinetic energy in collisions with lattice atoms and other electrons, releasing quasiparticles called phonons which are basically heat. There really isn't much more to be said about the source of heat in simple non-optoelectronic semiconductor devices than has already been said... Current zipping through transistors (and to a lesser extent, interconnects) dissipates power in the form of heat. Incidentally, this is one of many reasons large-scale VLSI transistors keep getting smaller; smaller transistors have smaller gates which require less charge to form a channel which in turn requires less driving current thereby allowing quicker mode switching with less current (and less heat). Of course this is a very simple view, but it's one aspect of thermal scaling. -- mattb @ 2007-03-29T03:59Z

Overclocking usually increases the voltage and decreases the current. However, the Power (P = V * I) is overall increased, due to more wasted power at higher voltage ("the voltage goes up more than the current goes down"). There are many reasons for this; you might read up on CMOS or MOSFETs to learn about their operating principles. —The preceding unsigned comment was added by Nimur (talk • contribs) 16:54, 29 March 2007 (UTC).

Er... If you increase CMOS rail voltage, it will increase gate drain current as well, this is exactly why voltage scaling in CMOS has a square law relationship with power dissipation. Look at the derivation for the saturation current density formula for the MOSFET. -- mattb @ 2007-03-29T17:16Z

Edit: Okay, in fairness it's not EXACTLY why, but you could make that argument. Anyway, I'm not sure it's totally accurate to say that the power is wasted. Higher FET saturation current reduces the gate delay product (I think that's what they call CV/I.. been awhile since I've done VLSI). Of course you also see increased heat generation from the higher drift velocity, more hot carrier effects in gates, etc which may have been what you meant anyway (forgive me if I misinterpreted you). -- mattb @ 2007-03-29T22:26Z

Take a look at a datasheet for any standard processor or microprocessor. Increasing frequency requires higher voltage. Increasing voltage decreases current consumption, as a general rule of thumb. Here, for example, is a M16C Microcontroller or this Pentium datasheet. For a given frequency, higher V means lower I. Power always gets wasted. How much? Depends on the processor. It's too complicated of a device to use the transistor-level current relationships to determine it. Nimur 22:42, 29 March 2007 (UTC)

Higher voltage is required for higher clock frequency because you potentially need to reduce gate delay product to satisfy the tighter timing requirements. Boosting rail voltage accomplishes this by increasing gate saturation current per the various MOSFET models (square law, bulk charge, etc). I don't contest this fact, and it is supported by your data sheets. Let's move on.

Your latter claims I still disagree with and I see no support for them in either of the linked data sheets (can you cite a page rather than making me go through the trouble of looking up every usage of "current" and "power"?). What is this "general rule of thumb"? I explained why increasing supply voltage to a CMOS structure will increase the drain current, what is your explanation for your claim?

I didn't mean to imply that power is not wasted in ICs. If I gave that impression I'm sorry for being misleading. I was only pointing out that you seemed to be looking to the wrong sources for wasted power. It's an unavoidable truth that transistors require energy to operate, and there are better parasitics to blame for "wasted power" than the primary transistor operation. You can chastise me for over-simplification, but I am loath to point out that you originally used the formula for DC power dissipated by a purely resistive load as part of your explanation of (admittedly complex) IC thermal issues. Sure, I'm only considering dynamic power dissipation using the simple CV²f type model, which doesn't include non-ideal current components like hot electron effects and Fowler-Nordheim tunneling, nor does it include power losses in interconnects and contacts. However, I didn't think I'd be criticized for using a common first-order approximation that is a rule of thumb used by most of the VLSI people I know.

I don't accept an explanation to the tune "it's too complicated to explain, here are some data sheets". If you feel I'm wrong, please don't hold back the details. I'm happy to admit my shortcoming if I've made a mistake, but I'd like a better explanation than P=VI and a couple of random data sheets. -- mattb @ 2007-03-30T02:38Z

Maybe you can think about this another way, using simple formulas if you'll allow me that liberty. The charge stored on a capacitor is by definition Q=CV. Consider the capacitor that forms up the gate of a MOSFET. If one increases the rail voltage, the amount of charge stored on each gate connected to V_DD must increase as well. Getting more charge onto the gate requires either more current or more time to supply. We've already agreed upon the fact that increasing the rail voltage for a CMOS device allows for higher clock speeds, so I hope you'll allow me to be so bold as to rule out the "more time" possibility without much further explanation. This leaves us with the first option, more current. Increasing voltage requires increased current to charge the FET gates, but you still end up with lowered propagation delay (τ=CV/I, recall) since the drive current of the previous transistor increases proportional to the square of gate voltage per transistor I-V models (assuming that the current logic stage is being driven by another gate, as is typical). This is my very simple first-order explanation of the matter, do you see a hole in this logic? I'm not a CMOS person by any means, so if I missed something obvious in thinking up this explanation please point it out. -- mattb @ 2007-03-30T03:00Z

[edit] Domestic Mains LED

My socket has an LED which connects drectly to the mains and it glows to indicate potential.But I thought that LED are to be run in reversed bias mode and need a DC supply to glow.Is this a new type of LED???210.212.194.209

LEDs emit light most efficiently when forward biased. The LED on your socket is connected to some additional circuitry to reduce the voltage and limit current flow. There's no reason you couldn't run an LED off the AC mains waveform, but if it weren't rectified the LED would blink at the rate of the line frequency. -- mattb @ 2007-03-29T05:59Z

Most efficiently? LED are forward biased. You can damage the LED if you reverse bias it, depending on the voltage. --Wirbelwindヴィルヴェルヴィント (talk) 06:41, 29 March 2007 (UTC)

Yes, most efficiently. There will still be spontaneous emission from a reverse biased LED, though the injection efficiency is practically zero and therefore the internal quantum efficiency is terrible. Heck, there is spontaneous emission of photons in Si CMOS devices, but the efficiency is poor (though this is compounded by the E-k band structure in addition to carrier populations that are non-ideal for spontaneous emission). Reverse biasing an LED will not damage it so long as you don't allow the reverse bias current to exceed a safe threshold corresponding with the device power rating. You're probably thinking of the avalanche and Zener breakdown regimes in reverse bias, but despite the name these are not inherently destructive so long as (again) current is externally limited. -- mattb @ 2007-03-29T12:19Z

The single LED device may in fact have a pair of LEDs inside oriented oppositely. Check using an ohmmeter after disconnecting from the mains. -Arch dude 16:39, 29 March 2007 (UTC)

Over here the frequency of AC currents is around 50Hz, which I suspect would be difficult to see, if the light was flashing that fast, but then I would expect rapid flashing like that to damage the light, and most people wouldn't design a circuit that damages equipment in it :) HS7 17:14, 29 March 2007 (UTC)

You can buy "bicolour" LED's like that. They shine red when biassed one way and green the other. If your light is orange or yellow you can bet that's what they did because there are no natural yellow or orange LED's. You can't see them flickering red/green/red/green at even 10Hz - let alone 50 to 60Hz. LED's can flash on and off millions of times per second without any damage whatever - they don't heat up and cool down like lightbulbs! Many old-fashioned LED pocket calculators (for example) would turn the LED display on and off again briefly about 20 to 30 times per second to save battery life - so this is a well-known, well-understood technique. SteveBaker 17:33, 29 March 2007 (UTC)

Not trying to be overly nitpicky, but there are yellow and orange LEDs; you can accomplish both colors with InP and GaP heterosystems. -- mattb @ 2007-03-29T18:32Z

There's no reason that sort of operation would damage an LED. The light emission mechanism is very different from the incandescent process used by lamps. -- mattb @ 2007-03-29T17:28Z

Just to drive mattb's point home: LEDs are perfectly happy running on pulsing current, even current of quite high frequencies. Most automobile LED tail-lights operate in exactly this fashion: they pulse-width modulate the current through the LEDs to produce the two intensities ("tail light" and "brake light" intensities) required. And if you sweep your eyes across the average LED tail light, you'll see the "break-up" that is caused by the operation of the PWM.

50 Hz flashing is definitely visible, especially if your eyes are in motion or you're observing the light with your peripheral vision. 60 Hz flashing is usually visible. LED Christmas lights are very noticeable because of their flickering. On the other hand, if the LED lamp has the two diodes in anti-parallel (so the overall light flashes at 100 or 120 Hz), nobody is likely to notice the flickering of the light except through stroboscopic effects.

Atlant 16:29, 30 March 2007 (UTC)

Yes indeed, though LEDs have a cutoff frequency just as all other junction devices. Especially when you consider the case of cycling between reverse bias (carrier depletion near the junction) and forward bias (heavy carrier injection at the junction), it takes some time for the charges to accumulate/deplete. This time is given by the carrier lifetime, and is the primary limit on high frequency operation. You can reduce this time constant, of course, but it has its trade-offs (and the easiest ways to reduce the lifetime are also very detrimental to the LED quantum efficiency, so I imagine very high speed LEDs are rare). -- mattb @ 2007-03-30T18:34Z

Sure, but the cutoff frequency for small LEDs is somewhere up in the megahertz range. I once did a design that pulsed a "bus activity" LED at about a megahertz (though integrated somewhat by the FCC-mandated RFI filtering) and it worked fine.

Atlant 18:55, 30 March 2007 (UTC)

Mid megahertz range sounds about right... In my mind I was thinking of certain types of diodes that are intentionally doped with deep level trap state creators to make them perform up to extremely high frequencies. I'd imagine a detailed data sheet for most LEDs would tell you what the cutoff frequency under various conditions is (obviously it's higher for small signal forward-bias-only operation).-- mattb @ 2007-03-30T23:36Z

[edit] Linear and squared heat dissipation

How come an overclocked processor's heat output increases linearly with the clock frequency and exponentially with the voltage increase? The voltage makes sense to me because of how power is defined in regards to current squared times resistance, but I do not understand the linear increase. —The preceding unsigned comment was added by 24.231.205.94 (talk) 05:36, 29 March 2007 (UTC).

Assuming that transistors only consume power while changing modes (not really true, but let's assume), the more times you cause synchronous circuits to switch per second, the more power they dissipate. It's a linear correlation. -- mattb @ 2007-03-29T06:01Z

Current in the microprocessor is dissipated in discrete impulses (for simplicity's sake, let's say one impulse per clock cycle). As the clock rate goes up, the voltage and the amount of charge per impulse (I_i) remain the same so the current consumption is roughly I_i*F, linearly proportional to the the frequency F.

By comparison, raising the voltage also raises the current per impulse so that has the classical V² relationship.

Atlant 16:35, 30 March 2007 (UTC)

[edit] piston analysis details..

the piston i have chosen s of a 4-stroke two wheeler of about 100cc engine using petrol as the fuel. now can i know the magnitude and types of forces actin on the piston and also the temparature in the piston surroundings under working conditions. can you plese help us.

                                                                    waiting for the reply
                                                                      likhith and sagar

See internal combustion engine, two-stroke engine. The primary force acting on it is pressure due to combustion of the gasoline (petrol). This must work against the drive-chain load attached to the engine (e.g. the weight and dynamics of the vehicle are connected through gearings, etc). A 100 cc engine has a power of ~ 10 - 15 horsepower; you can calculate force from power and velocity of the piston ( P = F V). Nimur 17:04, 29 March 2007 (UTC)

Didn't they say it was a four-stroke engine ? For the temp, I would suggest using a thermometer with a probe at the end of a wire. You can even mount the display on the handlebars, if you wish. StuRat 18:03, 29 March 2007 (UTC)

[edit] Breathylizers & Smoking

A cop friend of mine once commented that he could smell the liquor on my breathe, then he went on to explain that smokers like me are easy to pick out when we've imbibed. My Q then is this... Would the fact that I do smoke cigarrettes have any effect on the reading from a breathylizer? It makes sense that we as smokers are easy to detect since we inhale more deeply then non smokers, but is it neccessarily indicative of our blood alcohol level? —The preceding unsigned comment was added by Rana sylvatica (talk • contribs) 10:26, 29 March 2007 (UTC).

When using a breathalyzer, you are required to blow out for so long that it doesn't matter how deep you normally inhale. As for the effect of smoking on a breathalyzer, there is none to speak of. Again, the person taking the test has to inhale deeply and blow out for a long time. Your friend was likely pointing out that the smell of a smoker's breath causes non-smokers to quickly focus on the source of the odor - which would also quickly focus in on the smell of alcohol. In my opinion, it is not possible in any way for a smoker to comprehend this concept. I've tried to explain to smokers that the smell of smoke follows them everywhere they go, but they simply claim that they don't smell it. --Kainaw ^(talk) 13:41, 29 March 2007 (UTC)

They're probably not lying. Smoking impairs the ability to identify odors, and can even cause anosmia. So smokers are relatively insensitive to smells, and are notoriously bad judges of how they themselves smell. - Nunh-huh 14:34, 29 March 2007 (UTC)

And of course if you are around a smell for a long time, you tend to stop noticing it :) HS7 17:09, 29 March 2007 (UTC)

[edit] water in a container for a long time

Why water put in a container for a long time (a few weks maybe) could cause the container surface slippery? What really caused it? roscoe_x 11:41, 29 March 2007 (UTC)

Probably a microbial agent growing in the container. -- mattb @ 2007-03-29T12:22Z

Per Matt, see biofilm. TenOfAllTrades(talk) 17:41, 29 March 2007 (UTC)

This wouldn't happen with pure water in a sealed container. However, there will always be some impurities, like minerals and a few bacteria. That alone may be enough for them to grow. In home canning, the contents are always submerged in boiling water to sterilize them, before storage, to stop anything from growing in them. The good news is that the things which grow in a water container usually aren't dangerous, so very few, if any, people die each year from that cause. StuRat 17:59, 29 March 2007 (UTC)

Hi StuRat. Could you share your source for that advice with us? I am concerned that (unsterilized) containers – especially those which are exposed to warmth and light – may well harbor harmful organisms. These may not kill individuals who have a healthy immune system, but may still cause disease and discomfort. TenOfAllTrades(talk) 18:10, 29 March 2007 (UTC)

It's more in the form of never hearing of a case of drinkable water, after being placed in a sealed container, becoming toxic from bacterial action. If you've heard of any instances of this, I'd be glad to retract my statement. I have heard of numerous other forms of water contamination, such as E. coli contamination, in well water, from dairy farm run-off. StuRat 18:21, 29 March 2007 (UTC)

I heard somone call into a radio show saying that they had gotten sick from bottled water they had been storing in the hot trunk of their car for some time. I can't remember the particular microorganism that was responsible. I also don't know if it was bottled tap water or commercially bottled. Chlorination probably goes a long way in preventing such a situation. -- Diletante

The heat element makes me think it's more likely they suffered a reaction to chemicals in the plastic container which leached into the water. This happens slowly normally, but is greatly accelerated at high temps. StuRat 00:21, 31 March 2007 (UTC)

If it's exposed to direct sunlight (as opposed to car-trunk heating) the UV from the sun will actually kill off the microbes. I believe there was a development program that taught people to bottle their water and put it in the sun before drinking it in areas where water quality was poor, and less people got sick as a result. I wish there was a wikipedia article I could refer to on this, but there is an article on reuse of water bottles. —Pengo 01:12, 31 March 2007 (UTC)

[edit] How can I stop my macaw going broody this year?

It's getting to that time of year again where my hyacinth macaw starts going into nest buiding, mating and egg-laying mode. She gets a lot noisier, more aggressive and starts chewing holes in anything she can chew holes in, pulling wallpaper off, trying to squeeze into any gap she can squeeze into and refusing to come out, regurgitating food, etc. She also seems to take every time I stroke her as some sort of 'come on' (anyone that's owned a parrot knows what I mean with the tail lifting and 'that funny look' in the eyes). It's like her personality changes for two months of the year, like owning a completely different bird. She's laid infertile eggs in the past and I want to avoid it happening this time, as it's not good for her body. Is there any way to prevent her from going broody this year? Something I can add to her water, an injection, or anything really. Thanks, Chris. --84.64.224.134 14:09, 29 March 2007 (UTC)

I wouldn't recommend messing with your bird's hormones. Why isn't it healthy for a bird to lay an egg? It's completely natural. − Twas Now ( talk • contribs • e-mail ) 15:19, 29 March 2007 (UTC)

And miss out on a Macaw-egg omelette? Nimur 17:07, 29 March 2007 (UTC)

Just don't let the bird see this, or you may pull back a bloody stub the next time you pet the bird with your finger. StuRat 17:52, 29 March 2007 (UTC)

Sounds like a phone call to your local vetenarian would be a good plan at this point. Maybe they can 'fix' parrots like they do dogs and cats? I'm guessing from your description that it's not the egg-laying per-se that's the problem so much as the weird behavioral traits. SteveBaker 17:40, 29 March 2007 (UTC)

If birds work like many other animals, it's too late once they have gone into "heat". The hormonal changes have already caused permanent changes in their brain. "Fixing" the bird at this point should stop the actual egg-laying, but probably not all of the mating behavior. StuRat 17:52, 29 March 2007 (UTC)

I don't think that you can have birds 'fixed'. I've kept birds on and off for years and I've never heard of anyone doing that. Anyway, when a female parrot goes into breeding mode, it's best to avoid petting her anywhere except the top of the head. Top of the head = social grooming of the kind that any parrot would do to any other friendly parrot, anywhere else (particularly the back, the undercarriage or under the wings) could and probably will be seen as a sexual advance by her and may precipitate mating behaviour and egg laying. --Kurt Shaped Box 21:40, 29 March 2007 (UTC)

It's mainly the behaviour that's the problem but laying infertile eggs is not good. Considering that she tends to just lay another one if you take the egg away, I'm worried about her becoming egg bound or suffering from bone problems due to low calcium. Childbirth is also natural but it has risks to the mother. --84.64.224.134 19:03, 29 March 2007 (UTC)

[edit] Descendants of a common ancestor

Is there any sort of formula for determining what percentage/number of the descendants of a Common Ancestor have X% or 1/X genetic similarity to the progenitor? I'd like to get the numbers (roughly) for 1/16 or 1/32 after several hundred years, assuming inbreeding is allowed eventually, of course. -- nae'blis 14:50, 29 March 2007 (UTC)

Depends what you mean by "genetic similarity". If you look at the whole of an organism's DNA then all defendants will be very similar genetically to their ancestors. However, attention is usually focussed on those parts of the genotype where there can be viable variations between individuals - these variations are called alleles. The Hardy-Weinberg principle gives the stable long-term distribution of the varieties of a single allele across a population - it is usually stated in terms of a gene locus that can be occupied by either of two alleles, but it can be generalised to more than two alleles. There are certain assumptions built into this model which may or may not be reasonable in a given real-life scenario. Gandalf61 15:27, 29 March 2007 (UTC)

In terms of pure gene count, the differences between individuals within one species are a microscopic fraction of the whole. So your X% is never going to get anywhere close to 1/32. The difference in genes between a typical human and a typical chimpanzee (of the same sex) is far less than 1%. Between humans of the same sex it's got to be WAY less than that. I'd be surprised if it was as much as 1/1000 for any two humans picked at random - and for people as closely related as you suggest it's gotta be way less than that. SteveBaker 16:12, 29 March 2007 (UTC)

Hmmm, good point. I was thinking along the lines of royal blood or blood quantum laws, and shouldn't have used the actual word 'genetics'. I'm looking at lineage. -- nae'blis 16:14, 29 March 2007 (UTC)

I think we need a better definition of what you are asking. If you mean what I think you mean - then (since I'm British and my wife is French) - my son is 1/2 French. If he marries a British girl, his kids could be said to be 1/4th French, and if they marry Brit's their kids will be 1/8th French and the following generation 1/16th French. Hence the degree of "Frenchness" gets to your 1/16th level in 4 generations. If the average person has kids at age 25 (I have no clue whether that's a good average - but it's probably not far off and it makes the numbers come out nicely!) then it takes something like 100 years for that to happen. But this is an odd idea - "Frenchness" isn't a simple gene...even 'pure' Frenchness is probably not even measurable at a genetic level - it's just another one of those odd human customs to track such fractions of heritage. The same applies to "Royal blood" I guess. SteveBaker 17:20, 29 March 2007 (UTC)

Sure, that makes sense. Okay, I'll be more concrete: A (fictional) family founds a kingdom without primogeniture, but with a tanistry-based system of rulership. All rulers and high-ranking officials in the kingdom must demonstrate that they are a scion of the original founder (once your lineage is good, it's merit-based). After a dozen generations or so, the family tree of course branches uncontrollably with more people than positions; they begin to institute rules for 'how close' you have to be to the founder's main bloodline. Inbreeding is the best way to do this, so I'm trying to determine if there's any way to discern that ratio, short of wide-scale genealogy. It doesn't have to be particularly feasible with current science; magic or advanced tech would work just as well, so long as the concept holds any validity at all. If I'm completely off-base or the only answer is genealogical analysis, so be it; this is for a story, after all, so it doesn't have to be exact. Thanks for your interest/replies so far. -- nae'blis 18:43, 29 March 2007 (UTC)

I think only genealogical analysis will suffice, as multiple lines of descent will occur in the scenario you describe. You might be interested in the coefficient of inbreeding, though (or not: ) - Nunh-huh 21:43, 29 March 2007 (UTC)

The simplest way is to look back up the generations of your family tree until you reach the generation at which the original 'king' was alive. Suppose you are third generation. You have two parents, four grandparents and eight greatgrandparents. If there has been in-breeding of some kind then some of those eight will turn out to be the same person...right? It might be that one of your mother's grandfather's was the original king - and also that he was also the grandfather of your father. Hence you have 'two copies' of that original king in your lineage - so you are more eligable than someone who only has the king in his lineage once. To be 100% fair and to cope with the problem of generational shift where the king might be both your grandfather on your mother's side and your great-grandfather on your father's side, you'd have to calculate the percentage of your parentage at each generation that is 'the king'. So having the king be your great-great-grandparent is worth 1 point for each time he appears in that generation, having him as your great-grandparent would be 2 points (per time), as grandparent, 4 points, as parent, 8 points. With such a scheme, the son or daughter of the king would always have the most possible points - unless someone was the son of the original king and their mother was the daughter of that same original king (Eeeewww!)....is that clear? SteveBaker 04:34, 30 March 2007 (UTC)

If it's for a story, you can get ideas from other stories, for example lots of relatives of kings &c can do a something that non relatives can't :) HS7 19:00, 29 March 2007 (UTC)

Or if magic is allowed, you could just try Magic :] HS7 20:53, 29 March 2007 (UTC)

I understand that by relatedness, you mean the relatedness above the baseline (say 99.5 percent or whatever it may be). I would like to point out that you cannot actually determine that number of, or percentage of descendants unless you make an assumption like "each person will have X children which will survive to adulthood and have X children of their own". Regardless, a fine explanation for relatedness is provided in Richard Dawkins' The Selfish Gene (1989 Edition). This approach works forward, finding a percent relatedness from two given relatives; I think you are looking to work backward, finding a certain number of relatives from a given percent relatedness. This means you will have to manipulate the equations to solve for the unknown. Anyway, I will provide some necessary explanation as it is described in Dawkins' fantastic book, The Selfish Gene (I've added the numbers before each paragraph for convenience):

1. First identify all the common ancestors of A and B. For instance, the common ancestors of a pair of first cousins are their shared grandfather and grandmother […] we ignore all but the most recent common ancestors. In this sense, first cousins have only two common ancestors. If B is the lineal descendant of A, for instance his great grandson, then A himself is the 'common ancestor' we are looking for.
2. [Now] count the generation distance as follows. Starting at A, climb up the family tree until you hit a common ancestor, and then climb down again to B. The total number of steps […] is the generation distance. For instance, if A is B's uncle, the generation distance is 3.
3. [Then] multiply ½ by itself for each step of the generation distance. […] If the generation distance via a particular ancestor is equal to g steps, the portion of relatedness due to that ancestor is (½)^g.
4. [However, if A and B] have more than one common ancestor we have to […] multiply by the number of [common] ancestors. First cousins, for instance, have two common ancestors [their shared grandparents], and the generation distance via each one is 4. Therefore their relatedness is 2 × (½)⁴ = ⅛. If A is B's great grandchild, the generation distance is 3 and the number of common 'ancestors' is 1 (B himself).

— Richard Dawkins. The Selfish Gene 1989 Ed. (pp. 91-2).

I said you will have to manipulate the equations. Whereas these equations tell you Rel = k × (½)^g, given k and g, you want to find g = log₂ (k/Rel) given Rel and k. (Let Rel represent 'percent relatedness', k represent 'number of common ancestors', and g represent 'generation distance' as it is defined by Dawkins). The article on genetic distance may help, and it offers a different approach (maybe more comprehensive, but I only skimmed). Hope this helps! − Twas Now ( talk • contribs • e-mail ) 02:44, 30 March 2007 (UTC)

Thank you all; you've given me a lot to work on. -- nae'blis 21:50, 30 March 2007 (UTC)

[edit] Viruses

Currently, Model_organism#Viruses list viruses under the subsection "Important model organisms". But are viruses organisms? I didn't know whether to ask this question on the Wiki help desk or here, since I want to tag the section with a template explaining that the classification of viruses is controversial, but don't know what to use. But if I ask it there, I won't get the right people I want, as I want those with knowledge in science to answer. Or maybe I'm just confused? Thanks.--Ķĩřβȳ♥♥♥ŤįɱéØ 17:34, 29 March 2007 (UTC)

There is debate on whether viruses, especially retroviruses, are alive. I would interpret the word "organism" to mean "a living or nonliving entity which is organized", in which case it qualifies. In any case, it's probably "close enough" to being alive, having evolved from things which were alive, to be included in that category. StuRat 17:44, 29 March 2007 (UTC)

But going by that definition, aren't Viroids, Prions, etc. also "organized"?--Ķĩřβȳ♥♥♥ŤįɱéØ 17:51, 29 March 2007 (UTC)

Yes, they are. StuRat 18:16, 29 March 2007 (UTC)

Mostly viruses are considered not to be alive, although there is a minority that say they are, and both sides understand pretty well that it is not clear, is what I've gotten. [Mαc Δαvιs] (How's my driving?) ❖ 18:45, 29 March 2007 (UTC)

If you have a totally naturalistic world-view, then viruses would certainly be classed under "things that can reproduce themselves and pass on information to descendants", and whether they're any more alive than you are is strictly a linguistic issue similar to drawing the line between a rock and a boulder. --TotoBaggins 20:10, 29 March 2007 (UTC)

Separately, I don't believe tagging the page as controversial would be appropriate here, since that's more for when editors can't agree, and most editors can agree that the borderline of "life" is fuzzy and controversial. Just because the subject is controversial, doesn't mean the article is. --TotoBaggins 20:13, 29 March 2007 (UTC)

In any case the viruses listed there are often used as classic examples of a "model organism", whether or not they are considered "life" or not. An article on model organisms which did not mention TMV would be ridiculous — TMV is one of the most model organisms and to call it anything else because of pedantic insistance would be counter-productive to say the least. --24.147.86.187 21:37, 29 March 2007 (UTC)

Basically "alive" is a concept that doesn't particularly help anyone understand viruses. People who worry about whether viruses are alive or not are concerned about their understanding of what "alive" means, not what viruses are. - Nunh-huh 21:40, 29 March 2007 (UTC)

[edit] How does microwave crisper paper work?

How does that silvery paper work in microwaves to toast bread and allow food to get crispy? --24.249.108.133 18:02, 29 March 2007 (UTC)

I can't believe we don't have an article for Crisping sleeve! In lieu of that, I offer the following, from our article Microwave oven - "Some microwavable packages (notably pies) may contain ceramic or aluminum-flake containing materials which are designed to absorb microwaves and re-radiate them as infrared heat which aids in baking or crust preparation. Such ceramic patches affixed to cardboard are positioned next to the food, and are typically smokey blue or gray in color, usually making them easily identifiable. Microwavable cardboard packaging may also contain overhead ceramic patches which function in the same way. The technical term for such a microwave-absorbing patch is a susceptor." --LarryMac 19:03, 29 March 2007 (UTC)

Hm, I wonder about the accuracy of the statement in that article as regards infrared. Is the material really facilitating a quantum photon absorption/emission process (plausible; it happens in some solids), or is it simply absorbing the microwave energy and heating up, transferring that heat mostly by conduction/convection? If the latter is the case, this wouldn't be the first time someone has confused infrared light with heat. -- mattb @ 2007-03-29T19:11Z

Good catch; the article should probably be fixed. --LarryMac 19:14, 29 March 2007 (UTC)

I'm not sure if it's an error or not, just something to be suspicious of. -- mattb @ 2007-03-29T22:16Z

[edit] Glycolipid & Electric Microscopes

I am very uncertain about the structure of glycolipids. Please provide an example (preferably a diagram) of a glycolipid, and explain the parts of the structure of the glycolipid. I also need to know what makes glycolipid a "lipid". If you can, please tell me if there is anything such as an "electric microscope" (apparently I am not referring to electron microscopes). Thank you very much. --Freiddie 18:25, 29 March 2007 (UTC)

A glycolipid is a lipid with a sugar attached :) But this is an encyclopedia, you can search for answers yourself on it, and in my experience very few people are likely to tell you any more than that :( HS7 18:55, 29 March 2007 (UTC)

Follow the links from Glycolipid for structural examples. What makes a glycolipid a lipid is the fact that it is derived from one, see the article. The term 'lipid' comprises several structurally different molecules that are relatively insoluble in water, and rich in carbon and hydrogen. Sugars, on the other hand, are rich also in oxygen, and soluble in water. When you join the two together, you get a molecule with a hydrophobic end and a hydrophilic end. Glycolipids are an important part of the cell membrane, see the image in that article, which shows their location in the membrane. The hydrophilic end points towards the aqueous exterior, while the hydrophobic part points towards the central, 'fatty' part of the membrane. Googling for "electric microscope" yields images mostly of ordinary light microscopes. I suppose they are are 'electric' only in the sense that they have a light bulb, which requires electricity. --NorwegianBlue ^talk 20:48, 29 March 2007 (UTC)

Thank you all.--Freiddie 10:00, 31 March 2007 (UTC)

[edit] assignment help--speed of light/color question

Trying to find the answer before my student son does...any suggestions or the right answer to this question? Someone out there must want a dad to look good!!!

Speed of light is 70mph. You are approaching a light at 20mph. The police at the light sees the light as red. What color do you see? Wave length of re is 700nm (nanometer)...yellow is 600nm... green is 500nm...blue is 400nm —The preceding unsigned comment was added by Harryprguy (talk • contribs) 20:00, 29 March 2007 (UTC).

??? The Speed of light is approximately 186,000 miles per second. Is this supposed to be a Redshift problem? In that case, approaching a light at 2/7ths the speed of light will cause the light to be blueshifted. I'm not sure to what extent, however.--Ķĩřβȳ♥♥♥ŤįɱéØ 20:18, 29 March 2007 (UTC)

The Speed of light is around a few hundred miles per hour in some places, so it could be 70mph in others :] HS7 20:37, 29 March 2007 (UTC)

Kirbytime, that's the speed of light in a vacuum. The slowest speed of light I can recall is 17 m/s, which is around 38 mph. — Knowledge Seeker দ 23:36, 29 March 2007 (UTC)

the equation is v=Δλc/λ, which can be rearranged to give Δλ as vλ/c (I think) with v as 20mph and c as 70mph and λ as 7*10^-7m :) HS7 20:41, 29 March 2007 (UTC)

But this give me a Δλ of 31, and therfore blueshifted light with λ of 669, which looks a lot too high, so I think someone with some idea of the subject should check my replies :( HS7 20:48, 29 March 2007 (UTC)

That looks prettier >_>--Ķĩřβȳ♥♥♥ŤįɱéØ 20:52, 29 March 2007 (UTC)

Use the relativistic redshift formula from the article: . --Tardis 21:15, 29 March 2007 (UTC)

Also, wouldn't there be an error in measurement since the length of the wavelength (in nanometers) isn't reduced as well? Is your son taking a physics course in college?--Ķĩřβȳ♥♥♥ŤįɱéØ 21:23, 29 March 2007 (UTC)

[edit] LM3914/5/6 IC

Hey, I'm not sure whether to ask this here or in the Computing section, but I thought I'd give it a shot. I'm looking to make a circuit using a LM3914, LM3915 or LM3916 IC, a dot/bar display driver. The circuit needs to deal with inputs of 0-3V. However, I'm struggling to find a good guide on the web for how to calibrate the intervals etc. as my electronics knowledge is fairly limited. I'd greatly appreciate a good guide or help on what to do!

Many thanks! --Fadders 20:31, 29 March 2007 (UTC)

Can you give me more detail on what you're trying to do? Or at least, the intervals you're speaking about? Glancing at the LM3914 datasheet, it says it's linear steps, meaning if you use 3 volts as the Vref, then each step will be 0.3V, assuming 10 steps. In order to achieve this, since the chip has a regulated 1.5 V Vref, you have to create a circuit where if you input 3V, a voltage divider will step it down to 1.5V. This can be done simply with two resistors in series with the same values, and taking the voltage across one of them, so when 3V is put across the resistors, each of them will be 1.5V. Tell me if you need anything else clarified. --Wirbelwindヴィルヴェルヴィント (talk) 05:03, 30 March 2007 (UTC)

That's making more sense to me than the data sheet did! I'm basically wanting a range of 0-3V, with each bar representing 0.3V. Could you give me advice as to what goes on what pin?

Thanks! --Fadders 16:42, 30 March 2007 (UTC)

The easiest way is to connect a constant 3V to R_HI. Failing that, you can use the RefOut pin to generate the more or less constant 3V. This isn't exactly 3V, but connect a 1K resistor to RefOut (R1 on the datasheet), and then a 2K resistor (R2 on the datasheet) in series with it. Then connect that to ground. Connect RefAdj to where R1 and R2 meet. Now, connect R_HI to RefOut. This should give you approximately 3V on R_HI. Now you just need to connec V_CC, the diodes, and the source. --Wirbelwindヴィルヴェルヴィント (talk) 05:40, 31 March 2007 (UTC)

[edit] Does Einstein have a bacon number?

Einstein must have been featured in a lot of old newsreels with various other famous people. Does he have a Bacon number? I couldn't find anything besides his Erdos number of 2. —dgies^t_c

• maybe... --24.147.86.187 21:33, 29 March 2007 (UTC)

Gott spielt nicht dieses Kevin Bacon Spiel. --TotoBaggins 21:48, 29 March 2007 (UTC)

Roughly translatable as "God doesn't shoot craps with Kevin Bacon", I presume? alteripse 23:56, 29 March 2007 (UTC)

The Oracle of Bacon gives Einstein a number of infinity[9], meaning that it can't find any link. Laïka 07:22, 30 March 2007 (UTC)

[edit] Radiation sickness

How can it kill immediately? Do so many ions form thatcompletely remodel the cells?Bastard Soap 22:01, 29 March 2007 (UTC)

The ionizing radiation article has a pretty good discussion of the effects on animals. -- mattb @ 2007-03-29T22:14Z

Short answer is that radiation sickness does not kill "immediately", although our article on radiation poisoning says that the highest levels of acute radiation exposure can cause coma in seconds or minutes and death within a few hours due to total collapse of the nervous system. Gandalf61 11:14, 30 March 2007 (UTC)

[edit] Allergies and Plasmapheresis

Theoretically, could allergies be treated temporarily by plasmapheresis since it removes antibodies from blood and replaces them with sterile fluid?

This is a medical question, but I think it is fair game.

~~thanks ip address whatever~~ —The preceding unsigned comment was added by 139.225.242.164 (talk) 22:50, 29 March 2007 (UTC).

No, because it doesn't completely eliminate them and they can be produced again. However, having said that, there are many case reports of other types of antibody-mediated diseases in a "crisis stage" (e.g., thyroid storm in Graves' disease) being substantially and quickly improved with plasmapheresis. alteripse 23:54, 29 March 2007 (UTC)

[edit] Half-life

Stupid question, but does half-life mean that if something has a half-life of say 5 days, is the product entirely gone after 10 days, or is is half of the remaining half gone - 75% after 10 days? Jack Daw 23:24, 29 March 2007 (UTC)

It's not stupid at all. [Assuming it has a constant half-life,] it means that 1/4 will remain after 10 days, 1/8 after 15 days, 1/16 after 20 days, and so on. Half-life has more. — Knowledge Seeker দ 23:31, 29 March 2007 (UTC)

Knowledge seeker is right about the strict meaning of the term, especially when used with respect to an idealistic, mathematical model. In such a model, the remaining amount can never reach zero but approaches it asymptotically. Radioactive decay is one of the original uses of this concept and it approximates the ideal. However in many biological contexts (e.g., drug half-life or effect half life) the term is used whenever the initial degradation kinetics resemble an ideal half-life curve, but complete elimination (at least to practical unmeasurability) does occur in a finite time. Not so much nitpicking as elaborating. alteripse 23:50, 29 March 2007 (UTC)

Great question i always wondered this too. so technicly if radio active decay with a half life of 1 year was left alone for 1000 years there would still be a trace of the decay right? this was so confusing in science classes. oo and also to add to this lets say a barrel was filled to the top with the same substance and left for one year when you opened it again would it be half full or does that work diffently?Maverick423 01:06, 30 March 2007 (UTC)

Yeah, there would be traces of decay, that's why there are still traces of radioactive material on earth even though no new radioactive material has formed for millions of years. In the barrel, well, that might happen if the whole substance was subject to decay but nothing is ever that pure, if it was you would instantly have a nuclear explosion on your hands, this is how an atom bomb works, in reality, most radioactive materials only have a very small component that is radio active, so in reality, even if you left it for a half life or two or three, you wouldn't actually notice any physical difference to the material. For example depleted uranium looks pretty similar to enriched uranium. Vespine

What a misleading answer. Atomic bombs do not work by radioactive decay at all, they work by nuclear fission. There is a big difference there. The difference between enriched uranium and depleted uranium has nothing to do with decay (enriched does not decay into depleted, or vice versa). A barrel full of any old radioactive material—no matter how radioactive—would never behave like an atomic bomb unless it were one of the specific materials that could undergo fission (and even then it would not likely perform quite like an atomic bomb; it would probably fizzle). --24.147.86.187 13:45, 30 March 2007 (UTC)

Just to clarify: enriched uranium is uranium with 235 protons and neutrons, and only this isotope is usable for nuclear weapons. Depleted uranium has 238 protons and neutrons; it's still uranium and still radioactive, only with 3 more neutrons than U-235. --Bowlhover 03:53, 1 April 2007 (UTC)

Hey thats intresting to know so the old stuff glows the same as the new stuff =D thanks much vespineMaverick423 01:52, 30 March 2007 (UTC)

haha:) Sorry I don't know if you are kidding or not, but enriched uranium and most radioactive materials don't actually glow. There certinally are radioactive things that glow, but that's usually becuase something else has been done to it. Vespine 04:22, 30 March 2007 (UTC)

Think of it like this - imagine every atom in the radioactive material was a penny. If the half life is (say) 1 day - then every day you toss all of the coins and remove all of the ones that come up heads. At the first toss you have billions and billions of coins - and you'll be removing almost exactly half of them each day - as the number of coins gets smaller, the fact that things are in fact happening at random starts to become more and more obvious. Once you are down to (say) 8 coins (atoms) that are still showing tails (still radioactive), you'll toss them and the odds are you won't get exactly four heads - you might get more or you might get less - so the amount of coins won't exactly halve each day (it never did EXACTLY halve - but there were so many that the difference was negligable). Once you get down to the last coin, it might show up heads on the next toss - or you might (by chance) have to toss it half a dozen more times until the atom eventually decays (and the coin comes up heads). So for large quantities of atoms (and any amount of substance that's enough to measure contains an ungodly number of atoms), it'll decay by almost exactly half every half-life - but when there is almost no radioactivity left, it might completely decay quickly - or it might take a very long time to completely decay...it's just random at that point. SteveBaker 04:20, 30 March 2007 (UTC)

Furthermore, you seem to be thinking of a barrel full of 'stuff' decaying down so that after one half-life has gone by the barrel is half empty. That's not how it works.

(Indeed not. So instead of thinking about flipping bunches of coins and incrementally removing the ones that come up heads, imaging painting them black, and leaving them in the pile, and thereafter, only re-flipping the coins that haven't yet been painted black. —Steve Summit (talk) 00:47, 31 March 2007 (UTC))

The radioactive atoms don't disappear - they decay into something else. That might be something completely non-radioactive or it might be something that's actually MORE radioactive with a shorter half-life or into something that's less radioactive with a still longer half-life. So you might start with a barrel full of one thing - and after a half-life has elapsed have a bucket that's still full - but it's a 50/50 mixture of the original substance and (say) inert lead or some non-radioactive isotope. The bucket won't ever be gradually getting empty. SteveBaker 04:20, 30 March 2007 (UTC)

Unless, of course, the decay product is a gas. --Bowlhover 03:53, 1 April 2007 (UTC)

Although there might actually be a tiny reduction of mass, due to some conversion of mass into energy which leaves the barrel as heat or some form of radiation. StuRat 00:14, 31 March 2007 (UTC)

Oh, it'd be more significant than that, wouldn't it? All those alpha and beta particles and whatnot being emitted are carrying away actual rest mass, too, not just energy. —Steve Summit (talk) 00:47, 31 March 2007 (UTC)

Wow, didn't expect so many answers, thanks all. Related question, equally stupid: If there's a set half-life for the amount of something, is the half-life half of the original half-life if the amount is cut in half? (that's a lot of halves) Jack Daw 19:10, 31 March 2007 (UTC)

The half-life isn't for any particular amount of something, it's for the something. We don't say, "One kilogram of Uranium-235 has a half-life of 700 million years." We just say, "Uranium-235 has a half-life of 700 million years". If you start with one kilogram of U-235, after 700 million years you'll have half a kilogram of U-235 and half a kilogram of Thorium-231 and other stuff. If you start with half a kilogram of U-235, after 700 million years you'll have a quarter kilogram of U-235 and a quarter kilogram of other stuff. —Steve Summit (talk) 20:10, 31 March 2007 (UTC)

Indeed, the half life is for the particular isotope species, and does not depend on mass, for the most part. That principle is what allows radiometric dating to work. If you have something with a half-life sufficiently large (⁴⁰K comes to mind), you can measures the amount of the radioactive isotope and its byproduct, and date rocks. If you want to date old bones, you probably want to use ¹⁴C, which has a half life of 5700 years. Titoxd^{(?!? - cool stuff)} 23:21, 31 March 2007 (UTC)

[edit] March 30

[edit] glasses

Why do some glasses lenses have white circles near the outside or white edges? —The preceding unsigned comment was added by 219.88.165.55 (talk) 04:32, 30 March 2007 (UTC).

White circles? I've never seen one of those. Are you referring to Glasses or Camera Lenses? The white edges you see are mostly Total internal reflection of the glass acting like a mirror and reflecting the incoming light, and thus make it look brighter and looks like white edges. --antilived^{T | C | G} 04:59, 30 March 2007 (UTC)

Why doe some of the lenses edges seem more noticeable and bigger than others

Maybe you're noticing the thickness of the lens. The edge that fits into the frame can appear white or grey. Dismas|^(talk) 06:09, 30 March 2007 (UTC)

Not talking about the bifocals lenses, right? --Wirbelwindヴィルヴェルヴィント (talk) 06:37, 30 March 2007 (UTC)

Nearsighted people wear concave lenses to correct their vision to normal. These are thinner in the center than at the edge, resulting in thick edges. If the person has astigmatism, there is an additional cylindrical component to the lens shape, which can make the edges even thicker in one axis of the lens. An extra cost option for lenses is to polish the edge, which otherwise has a "frosted" appearance and is more noticeable. Glass lenses are typically thinner than plastic lenses, but "high index" plastic lenses are thinner and lighter than cheaper plastic lenses. A stronger prescription for nearsightedness makes the edges of the lenses thicker, as does having larger "avaitor style" lenses. Edison 18:06, 30 March 2007 (UTC)

Well, no, because all eyeglass lens are "meniscus-shaped", whether the prescription is + or - D (RTFA :)

[edit] How do compass work?

How do compass work? —The preceding unsigned comment was added by 134.139.194.18 (talk) 06:29, 30 March 2007 (UTC).

Wikipedia has an article about it, check it out at compass. Return if some questions remain unanswered. --V. Szabolcs 06:35, 30 March 2007 (UTC)

[edit] some organic stuff

Can somebody tell me how to do these reaction? —The preceding unsigned comment was added by Bastard Soap (talk • contribs) 10:48, 30 March 2007 (UTC).

What do you mean by "do" ? Do you want a balanced equation, instructions on how to combine the reagents (temp, etc.) to get the desired reaction, or what ? StuRat 00:06, 31 March 2007 (UTC)

I would like to know the conditions and the reactants necessary for these reactionsBastard Soap 09:14, 31 March 2007 (UTC)

[edit] Blood Pressure

Suppose if a person does weight lifting excercise only with right hand and not with left hand, then blood pressure of only right hand will increase or there is increase in blood pressure in both the hands. Why? —The preceding unsigned comment was added by 203.94.214.34 (talk) 12:00, 30 March 2007 (UTC).

The blood system basically a long tube full of blood. It is very similar a hose with water flowing though it. So, you are asking a question similar to: If you put water in one end of the hose, will the water pressure only increase on the end you put water in? No. There is no restriction on the flow of the water. In the blood system, there is almost no restriction. Blood pressure increases throughout the body. If you've seen a power lifter before, you can see the pressure increasing all the way to the top of his head when he does a dead lift. --Kainaw ^(talk) 12:25, 30 March 2007 (UTC)

So, is the blood pressure in an erect penis the same as flaccid? [Mαc Δαvιs] (How's my driving?) ❖ 16:29, 30 March 2007 (UTC)

Hmm interesting that should come up! I think it must be higher, but look up penis and tumescence, and maybe hard on —The preceding unsigned comment was added by 88.110.49.118 (talk) 00:56, 31 March 2007 (UTC).

Blood flow is restricted during an erection. I specifically stated that the blood pressure is pretty much the same in an unrestricted system. Inability to restrict blood flow in the penis is a common cause of erectile dysfunction. --Kainaw ^(talk) 14:35, 31 March 2007 (UTC)

[edit] Rhinitis vs. Cold

This is not a request for medical advise. I suffer from year-round rhinitis and it seems that, despite my suffering and dependence on Claritin, I do not contract the cold virus as much as the people who work or live around me. I wonder if that might have anything to do with my sinuses constantly draining making it difficult for the virus to flourish. Any thoughts? --Juliet 14:05, 30 March 2007 (UTC)Auto-Unsigned -->

[edit] how does a bidirectional turbine function?

I recently read that tidal barrages or other tidal energy converters, make use of bidirectional turbines that will spin and generate energy regardless of whether the water is flowing in or out past the blades. I believe that the turbines do not spin around in order to keep the blades in the same position relative to the movement of water, and they rotate in the same direction (ie. clockwise) regardless of the water flow. I understand why the rotors would move if the water is flowing in a single uniform direction, but my question is how does this work in this situation where the direction of water flow can reverse completely but still spin the rotor blades the same way? Is it completely due to the shape of the blades, and how is this accomplished? Is this a relatively new concept? 220.34.254.226 14:18, 30 March 2007 (UTC)

Well, a simple propellor-type turbine is equally (in-)efficient running in either direction. I would guess that the turbine itself does reverse direction. For AC power generation, rotation direction doesn't necessarily matter. -- mattb @ 2007-03-30T14:58Z

Are you sure the turbines rotate in the same direction regardless of the water flow direction ? That doesn't seem likely, since it isn't necessary to generate AC, as noted by the previous responder. If they did want to accomplish that without turning the entire turbine around, they could reverse the pitch on each blade. This would be rather complicated and you would need to go with flat blades instead of curved, however, so would reduce efficiency. I believe some helicopters have the ability to change their blade pitch, so it is possible. StuRat 00:01, 31 March 2007 (UTC)

"Some" helicopters?!? Read the helicopter article, there, Stu: they all do; it's central to the way they work.

The vehicles that merely sometimes have variable pitch propellers are prop airplanes and boats. "Rather complicated" it may be, but it's quite routine; it's done all the time.

(Aside: just a few days ago I heard about an accident in which some researchers working with an autonomous underwater vehicle in the water behind a support vessel asked the captain of the vessel to make sure his engines were at "all stop" so that the rotating propeller couldn't accidentally damage the vehicle in the water. Unfortunately the intent of this request wasn't communicated accurately, and as it happened, this boat had a fully variable-pitch prop that could drive the boat forward, or in reverse, or be in neutral, all by varying the pitch of the prop blades, and all while the propeller continued to rotate in the same direction. So when the captain put the controls at "all stop", the prop was still turning, and the AUV did accidentally come into contact with it, and was basically cut in half.)

—Steve Summit (talk) 00:36, 31 March 2007 (UTC)

I think you and Stu are talking about different pitches. Helicopters all have the ability to change the pitch, as in the way the entire blade tilts. Stu is probably talking about changing the angle of individual blades relative to the plane normally parallel to the blades. --Wirbelwindヴィルヴェルヴィント (talk) 17:26, 31 March 2007 (UTC)

I'm not seeing the distinction -- can you elaborate? —Steve Summit (talk) 18:02, 31 March 2007 (UTC)

In one, you're changing the angle of the entire rotor, and in the other, you're changing how sharp of an angle the blades of the rotor has in respect to the entire rotor. --Wirbelwindヴィルヴェルヴィント (talk) 18:27, 31 March 2007 (UTC)

I think you're misunderstanding how a helicopter works. When you say, "changing the angle of the entire rotor", are you imagining that the angle of the propellor shaft changes with respect to the body of the vehicle? Are you imagining that if the helicopter wants to go forward, the whole rotor tilts forward? That's not the way a helicopter works.

The blades of a helicopter's main rotor are all variable-pitch, and they actually vary their pitch individually and continuously as the rotor rotates. If the helicopter wants to go forward, each blade moves so that it has a higher angle of attack when it's swinging over the rear of the helicopter (generating slightly more lift), and a lower angle of attack when it's swinging over the front (generating slightly less lift), and thus causing the entire helicopter to both pitch and move forward. If the helicopter wants to roll to the right, the blades move so that they have a higher angle of attack when they're swinging over the left side, and a lower angle of attack when they're swinging over the right, and this causes the whole helicopter to roll to the right. —Steve Summit (talk) 19:55, 31 March 2007 (UTC)

[edit] The upside of smoking - less minor, annoying colds?

As an on-off heavy smoker, I have noticed that during my smoking periods, I tend to suffer from less minor colds, runny noses and sore throats (ashtray throat and smoker's cough in the morning excepted). It has been suggested to me that this is because the cigarette smoke kills off some of the cilia in my respiratory system and prevents the mucous from being brought up from the lungs. Does anyone know if there's any scientific basis for my observations - any studies, anything?

The downside, of course is that when I do get a cold, I get it bad. Which usually persuades me to stop smoking for a couple of months. --Kurt Shaped Box 15:52, 30 March 2007 (UTC)

I would guess that minor colds you've had you just dismissed as "smoker's cough", so you only noticed the serious ones. BTW, did any of the gulls you raised pick up your bad habit ? :-) StuRat 23:55, 30 March 2007 (UTC)

The gulls don't have the manual dexterity to hold the cigarette. Webbed feet, yaknow - it's like trying to smoke whilst wearing mittens. :)

I know the difference between smokers cough and a cold - I only get smoker's cough first thing in the morning. Just a few hacks to get everything moving and I'm good to go... --Kurt Shaped Box 00:25, 31 March 2007 (UTC)

I was just thinking about this over the winter, with everybody getting sick. I figure there must be some benefit to smoking, and it might be protection from colds. The usual thinking that smoking is for weak-willed, dirty, hedonistic people just doesn't convince me. There's a good reason for even the most questionable of habits. Vranak

This is interesting, because after I quit, I got sick 3 times in the period of 4 months, including a sinus infection. While I was smoking, in those 6 years (not even heavily), I got through some years without really getting sick. And I didn't smoke enough to have the smoker's cough either. --Wirbelwindヴィルヴェルヴィント (talk) 09:50, 31 March 2007 (UTC)

Maybe you gave your cold viruses cancer? Also, I've heard many ex-smokers aver that when they quit smoking they got the worst cold of their lives. One of them's doctor said it was because they had lesions in their lungs from smoking for so long, but a thick layer of mucus (a reaction to the smoke) was protecting them from the air, but when that went away, they were open sores. :( --TotoBaggins 14:40, 31 March 2007 (UTC)

I, too, have heard that when people quit smoking they tend to get bad coughs/colds for a while, then when those go away they tend to get healthier than they were. If the 'fewer annoying colds' were because of the mechanism Kurt suggested, this wouldn't actually be fewer minor colds, but fewer symptoms caused by your natural response to get rid of infection. So, some cilia die and the mucous hangs around in your lungs. Minor infections without so much coughing and hacking up mucous. Yay? No, because the infection hangs around for longer, since it is harder for you to get rid of it. Presumably, hence the worse colds when you actually get them. Note, all this is assuming the mechanism that Kurt described. Skittle 10:39, 1 April 2007 (UTC)

[edit] exemestane

i was reading (in wikkapiediea)about the effects of over use of testostrone and came across arotomase inhibitors, such as exemestane i read;

Irreversible steroidal inhibitors such as exemestane form a permanent bond with the aromatase enzyme complex

dose that mean if a person took exemestane then there production of estrogen would for the rest of there life be damaged/blocked? if so, how dose it work? —The preceding unsigned comment was added by 77.98.97.52 (talk) 16:04, 30 March 2007 (UTC).

The inhibitor works by forming a (strong, irreversible) chemical bond with the enzyme complex. Consequently, each drug molecule can permanently disable one complex. However, the body is capable of synthesizing new enzymes; in fact, this happens continuously. The old, disabled complexes will be disassembled and disposed of, and mostly be recycled into new proteins. New enzymes will be created, which are not blocked.

In other words, the drug can knock down the enzyme's activity, but eventually (barring other problems) the disabled enzyme machinery will be replaced. TenOfAllTrades(talk) 16:09, 30 March 2007 (UTC)

[edit] Suckling young

Humans generally have one baby at a time but the females have two teats. Doesn't make too much sense when viewed according to the numbers but it adds to symmetry of the body and allows for the baby to still get nourishment if there was something wrong with the one and only teat. Dogs and cats have many puppies or kittens in a single litter and the females have six (if I'm not mistaken) teats. More young, more teats, makes sense. So why do cows, who generally only have one calf at a time, have four teats? Is there an evolutionary reason? Dismas|^(talk) 16:37, 30 March 2007 (UTC)

Humans have a lot of left-right symmetry. This may have provided some useful redundancy (lose the use of an an eye, still not blind). Injury or infection to one breast still allows the mother to feed an infant. The breasts each produce a certain amount of milk (not tapping a common reservior) so there is more nutrition for the baby or babies. Twinning occurs in 1/89 of human pregnancies. Edison 17:57, 30 March 2007 (UTC)

But enough about humans, let's talk about the cows. Even though typing direct questions into Google usually isn't the best search method, I gave it a shot and found an explanation. There are several more relevant links using that search. --LarryMac 19:48, 30 March 2007 (UTC)

Interesting, thanks! I figured it had something to do with ancestors having more young. Dismas|^(talk) 20:01, 30 March 2007 (UTC)

One thing which that source implied, but didn't actually say, is that having extra nipples doesn't do much harm, but having too few does, as some offspring don't get to feed and die (usually the "runt" of the litter). So, if they had a good reason to have more nipples in the past, due to more offspring, there isn't much evolutionary pressure to reduce the number of nipples now that the average litter size has decreased to one. StuRat 23:52, 30 March 2007 (UTC)

Just a further comment with regards to humans. A hungry infant can easily drain both breasts completely of milk. Now, in theory, a single breast could be made to hold as much milk as a normal woman's two do, but the irritation caused by drawing from a single nipple would probably increase the risk of infection and would certainly increase the discomfort. Having two sources of milk also allows the mom to switch back and forth or to favour a sore side. Matt Deres 22:02, 31 March 2007 (UTC)

[edit] What's the average price to build a wind turbine?

Let say a 2-3 MWatt wind turbine. roscoe_x 18:35, 30 March 2007 (UTC)

I put "wind power 2 mw" into google and this was the first hit GE 2.5 MW WindTurbine There is an ordering information link that requires you address and contact information. I would suppose that a significant part of the price is delivery and installation, seeing as the technical specs say that the rotor blade diameter is 100 meters. That would explain those trucks you sometimes see on the road with what look like giant wings carried on their flatbeds. According to this article Wind Power FAQ there is a capitol cost of about $1.5 million per Mega watt for wind power. But that probably includes the economy of scale for a wind farm with many turbines. This company Home Turbine sells a 10 Kw home version with a 7 m diameter rotor for around $27,900. (tower extra)Czmtzc 19:53, 30 March 2007 (UTC)

[edit] The Hum

Does sensitivity to The Hum start at birth, or can it suddenly develop in adolescence or later? NeonMerlin 19:10, 30 March 2007 (UTC)

HMMMM! Good question ;-) —The preceding unsigned comment was added by 88.110.49.118 (talk) 21:02, 30 March 2007 (UTC).

Also, does it always affect both ears? NeonMerlin 00:47, 31 March 2007 (UTC)

Human sensititvity to real sounds at high and low frequencies generally decreases with age; see Hearing (sense). It's unclear whether any given report of The Hum is due to a real sound, or some internal biological phenomenon which may or may not depend on age. -- Beland 21:51, 31 March 2007 (UTC)

[edit] Finding Alien Intelligent Signals - So What?

It is often said that the day intelligent signals from outerspace are found, humanity will be somehow changed forever. But why? Quantitative evidence of alien intelligence would be, of course, a fantastic scientific discovery. But why would there be any changes on the way we live on Earth? (A face-to-face encounter with aliens would be entirely another ball game, but this is not the question here.)--JLdesAlpins 19:32, 30 March 2007 (UTC)

For one, it would discredit all the religious leaders who have claimed that we are their god's only children. Dismas|^(talk) 19:38, 30 March 2007 (UTC)

(Just a thought: It takes far less than alien intelligent signals to discredit some religious leaders--JLdesAlpins 19:46, 30 March 2007 (UTC))

Religious leaders would claim that the alien signals were fake. —The preceding unsigned comment was added by Czmtzc (talk • contribs).

Or they could interpret the signals as being messages from heaven, that prove that their faith is correct. Religious leaders have a lot of creativity when it comes to explaining why contradictions with physical observations or even contradictions within the faith are no indication of the invalidity of the faith. I'm sure they would come up with explanations very quickly as to why signs of intelligent life elsewhere don't contradict any part of their faith. MrRedact 20:28, 30 March 2007 (UTC)

The idea is that suddenly we wouldn't be (oh so) alone as the only life forms in the universe able to send signals into space. Oh to receive space signals from another form of life! It's like when you first a video phone but no one else had one, and then finding out someone in Japan has one too, so there's suddenly this potential to communicate with someone with your cool new device so your friends wont all think you're a dick for wasting money on a video conferencing phone when no one else has one, except that the distance is too far, the language barriers are too great and you don't really have anything to say anyway. Except this is a new life form that will be completely impractical to hold a conversation with inside the timeframe of a lifetime. That must be oh so much more thrilling than having a face-pulling competition with a chimpanzee, or having a sei whale look you in the eye, or have a dolphin know you're pregnant before you do, or having a parrot insult your rude guest with a phrase it's never used before, for now we have another form of space-signal-enabled lifeform to communicate with. And most excitingly, we wont have the practical means to destroy its habitat. Maybe I'm too cynical, and I'm maybe I haven't answered your question at all. —Pengo 00:31, 31 March 2007 (UTC)

I am of a similar opinion to the original poster: I don't know where the idea that the discovery of extraterrestial intelligence would result in a united humanity came from, but it seems pretty half-baked, and likely little more than plot device. It assumes that people are the way they are simply because of the contents of the heads, their beliefs and so on. The material conditions of life, geography, what we eat, the state of our bodies, are what really makes our lives what they are. By comparision, thoughts and beliefs are trivial, arbitrary, and capricious. If an alien signal were discovered, so what? Add one more species to the millions we already know about. Oh, I guess some people still think that animals are a seperate category of beings. How quaint. Vranak

Yes, and from the more expansive documentaries I've seen about the universe, even if there were Aliens transmitting a signal from some distant planet - not ony would it take us freakin' ages to get there making it completely unworth it - but most of the communication would be outdated - the signal would be several years old - and if the signal was by way of LIGHT - then we're really screwed, because then the communication is reallllllly old. So our best shot is actually if aliens come visit us personally - 'cos right now it's impossible to even think of visiting their planets. Sad, very sad Rfwoolf 11:36, 31 March 2007 (UTC)

I agree that it wouldn't change much. It's like in Hitchhiker's Guide to the Galaxy where all the dolphins in the world disappear, and it's all over the news and is a big deal for a while, but a year later, you can't still have headlines blaring "DOLPHINS: STILL MISSING!". Nuclear weapons are a similar example: they could kill us all due to adventurism or simple accident, but no one seems to mind too much. --TotoBaggins 14:30, 31 March 2007 (UTC)

There are many possibilities with regard to the acquisition of advanced technologies, which may or may not be described by the message. I can certainly imagine number of scenarios where major changes in military and scientific strategy and spending would be radically changed, as the possibility of extraterrestrial attack or visitation suddenly became more likely, or as the world suddenly had a pressing desire to communicate with or visit the new civilization in a reasonable amount of time. There are also possibilities for serious conflict as various parties disagreed over who had the right to send messages back to the aliens, and what the content of those messages should be, especially given the possibility of human extinction due to a hostile alien civilization or an accidental biological contamination. There are also potential implications for radio, television, cellular phone, and other forms of communication which leak signals into outer space. -- Beland 21:58, 31 March 2007 (UTC)

[edit] Nuclear Steam Generator

I was wondering how much water could a bomb like Tsar Bomba convert into steam?67.127.97.111 23:05, 30 March 2007 (UTC)

Do you mean, if all of the energy released by said bomb was converted into heat, how much water could it boil? -- mattb @ 2007-03-30T23:27Z

The first part of the calculation is to put that energy into a useful unit. At 50 Megatons, and 4.184×10⁹ joule/megaton, I get around 200×10⁹ J or 2×10¹¹ J. Now we need to figure out how much water that will boil. The heat of vaporization of water is 40650 J/mol, so I get that we could boil about 5 million moles of water. The mole density of water is 55.49 mol/L, so I get about 90,000 L of water. Not really all that much, is it ? (Note that this assumes the water was already almost boiling temp, if it started at room temp even less would be boiled because more energy is needed to heat it up.) StuRat 23:33, 30 March 2007 (UTC)

The specific heat capacity of liquid water is about 75.327 J/(mol K), so it takes about another 5650 J/mol to get the water from room temperature up to boiling temp, or a total of 46300 J/mol to get the water up to boiling temp and then vaporize it. Otherwise doing the calculation the same way as above gives a more accurate answer of about 81.4 kL. —The preceding unsigned comment was added by MrRedact (talk • contribs) 01:16, 31 March 2007 (UTC).

So is this correct that 81.4 kL is 81.4 cubic meters of water, so it's like a cube of water == ~4.3 meters on the side? That seems amazingly small when you look at shots like Bikini Baker! --TotoBaggins 14:14, 31 March 2007 (UTC)

Umm ... 1 megaton is 4.184×10¹⁵ J, so I think you need to multiply the above volumes by a factor of 10⁶. Gandalf61 14:49, 31 March 2007 (UTC)

Yes, you beat me to the edit. StuRat above accidently used the conversion factor for Joules per megagram instead of Joules per megaton, and I just used his number without checking it. With that correction, the answer should actually be 81.4 GL, which is the volume of a cube 433 m on a side.MrRedact 15:13, 31 March 2007 (UTC)

One has to be bold indeed to calculate out an answer like this and publish it, since it is so easy to use megagram instead of megaton, calorie instead of kilocalorie, or lightning bug instead of lightning bolt. Credits to StuRat for being the first to respond, and why is it so easier to find mistakes than to avoid them? Edison 16:29, 31 March 2007 (UTC)

Awesome thank you StuRat for that immediate responce everytime I post a thought experiment question you are one of the few who always answers it, and thank you everyone for your answers.68.120.81.220 04:38, 1 April 2007 (UTC)

[edit] Comparing European Magpies with Black-backed Gulls again...

The pairing up and nest-building has started again for both species. Question: Why is it that the magpies raise more chicks per year than the gulls? The magpies here typically raise six or more chicks to fledging, whilst it's rare for the gulls to rear more than two. Gulls live longer than magpies (15+ years vs. 5-ish) - does this have anything to do with it, or is it the case that young magpies are more vulnerable than young gulls? From what I've seen around here, the majority of the magpie chicks survive to join the (ever growing) flock. Both species aggressively defend their young and the flock in general from predators. --Kurt Shaped Box 00:08, 31 March 2007 (UTC)

(Answer without knowing any more facts than what you've said) The obvious answer (guess) is that the birds raise as many chicks as they're likely to be able to find food for. However, it could be a case of r vs K selection, e.g. if magpies could expect a larger number of their chicks to die young they may have more to compensate, even though they couldn't expect to feed them all, while seagulls have a more concentrated effort in raising their chicks.. But food-limitation is the simplest explanation. —Pengo 00:59, 31 March 2007 (UTC)

I would say the life-span is the critical factor. That is, gulls, living longer, can afford to take their time and put their energy into raising a small number of offspring properly each year. Magpies, on the other hand, are in a race to pass on their genes before they die, so much have more offspring each year. This, in my opinion, causes the higher chick mortality rate in magpies, as they must each start out smaller, and each get less attention (and, more importantly, food), from the parents. StuRat 05:50, 31 March 2007 (UTC)

[edit] science project build a volcano

My 11 year old grand son needs instructions on how to build a volcano for his science project.Do you have any instructions? Chicago Grandma —The preceding unsigned comment was added by 69.3.101.156 (talk) 04:08, 31 March 2007 (UTC).

google science fair volcano. Approximately 964,000 hits, mostly useful. If you need further help after looking at a few of these, please ask a more specific question. Good luck in the science fair. As a recent judge in a high school science fair, I reccommend that your participant's project should focus on a particular aspect of whatever phenemenon your "volcano" exhibits. -Arch dude 04:39, 31 March 2007 (UTC)

It would also be cool to have a couple of model villages, and experiment with known or imaginary methods of diverting the "lava", then demonstrate them. --18.214.0.137 15:22, 31 March 2007 (UTC)

An actual volcano? Might be a little too much to ask of an 11 year old? 80.229.228.229 20:30, 31 March 2007 (UTC)

[edit] Bullet in the air?

If someone shot a bullet into the sky , would it come back down or would it go into space?? —The preceding unsigned comment was added by 74.102.217.142 (talk) 04:58, 31 March 2007 (UTC).

It would fail to reach escape velocity, and come back down. —Pengo 05:20, 31 March 2007 (UTC)

A rifle bullet can travel at 1200 meters/second[10] whereas the escape velocity of the Earth is 11,200 m/s. (And "larger guns" can fire at 1500 m/s) —Pengo 05:28, 31 March 2007 (UTC)

Also, I don't even think it's possible to fire an object from the surface fast enough to leave orbit, as the object would slow down due to air resistance. Thus, the initial speed would need to be far higher than 11,200 m/s for the object to still be going at escape velocity after it clears the atmosphere. An object moving at such a high initial velocity in the air would likely burn up in the atmosphere. Thus, all rockets launched from Earth provide thrust until they clear the atmosphere, instead of relying on a high initial velocity to carry them clear. StuRat 05:37, 31 March 2007 (UTC)

There seems to be some confusion about escape velocity - that's the velocity you need to escape from an earth orbit and go off into the sunset, or wherever. To get 'into space' you need a bit less than that (nearer 7800 m/s, to get into an Earth orbit and stay there) but that's still much, much faster than can be achieved by the sort of gun that shoots bullets, and doesn't take account of drag or the potential energy you have to gain to climb to orbital altitude (~100km) against gravity. Project Babylon is an example of the sort of gun you need to shoot things into orbit. --YFB ¿ 11:14, 31 March 2007 (UTC)

This reminds me on the Columbiad. Verne calculated the parameters quite accurately, we only should find a suitable material that wouldn't melt. Would the Space Shuttle's armor survive it? --V. Szabolcs 14:27, 31 March 2007 (UTC)

See Project Babylon and Project HARP. People have tried, and it's certainly possible, just not all that practical for most payloads. --bmk

Maybe an enormous ring of superconducting magnets similar to a particle accelerator that could fling satellites into space would change that (see NewScientist story).--JLdesAlpins 16:14, 31 March 2007 (UTC)

[edit] Pre-implantation Genetic Diagnosis

Can PGD be used to avoid children from inheriting Marfans Syndrome? If so, what are the risks involv

59.94.30.2 05:34, 31 March 2007 (UTC)

Have you read our preimplantation genetic diagnosis and Marfan Syndrome articles ? I don't know if they contain the answer, but they might. StuRat 05:42, 31 March 2007 (UTC)

They don't contain the answer. The answer is "yes". One article to consult for further details is Spits C, De Rycke M, Verpoest W, Lissens W, Van Steirteghem A, Liebaers I, Sermon K. Fertil Steril. 2006 Aug;86(2):310-20. Epub 2006 Jun 6. PubMed - Nunh-huh 15:25, 31 March 2007 (UTC)

[edit] Magnetic energy

Does it exist?If so, where can it be found?How does man make use of it? —The preceding unsigned comment was added by Invisiblebug590 (talk • contribs) 09:45, 31 March 2007 (UTC).

Have you read the Wikipedia articles on Magnetism, Electromagnetism or Electric motors? Nebraska bob 10:37, 31 March 2007 (UTC)

Also, check out Inductor, a neat device that man uses to store said energy! --bmk

But beware of popular pseudoscience pertaining to magnetic energy. Magnets are sometimes incorrectly viewed as a source of energy in perpetual motion devices, and magnets are ascribed healing properties in magnet therapy for which there is little if any scientific evidence. MrRedact 17:28, 31 March 2007 (UTC)

Thank you for catching this. There is certainly a lot of unfounded pseudoscience around involving magnetism.

That's for sure. There is one where a home made device spins a magnet around past your forehead and it was suppose to make me smarter or sleeper or my memory better but now that its running I forget which one. 71.100.167.232 02:39, 1 April 2007 (UTC)

[edit] Animal fat and Boric acid

Will animal fat disolve Boric acid (or will Boric acid desolve in animal fat)? Nebraska bob 10:33, 31 March 2007 (UTC)

[edit] A Health Diet

Can anyone recommend any decent health diets (Not to be confused with weight-loss diets)? Nothing too controversial, but something 'tangible'. I mean it's all very well giving me a food pyramid - but what about TANGIBLE lists of things I can eat?
Particularly, I'm not a fan of bread (or wheat), or milk/cheese, and I'm worried that I eat too much meat - so basically if you coud recommend any 'tangible' health diet for someone like that, I'd appreciated it Rfwoolf 11:40, 31 March 2007 (UTC)

• Reduce or eliminate refined sugar and flour, junk food and fast food.
• Eat a variety of fruits and vegetables, try to hit 10 servings a day.
• Eat a variety of nuts and seeds.
• Eat beans and legumes.
• Eat cold-pressed oils, aim for monosaturates and unrefined nut oils.
• Eat unprocessed foods wherever possible.
• StuRat will recommend seafood, that's not on my list but I have no objection to it.

--Anchoress 11:44, 31 March 2007 (UTC)

And BTW I'm not advocating a vegan diet, but just listing the things you should try to eat for a healthful diet. Meat, dairy, whatever else you usually eat I'm not saying don't eat it. The two most important things for improving diet are a) reducing processed, fast, refined, and sugar-laden foods, and increasing fruits and veggies. Anchoress 11:47, 31 March 2007 (UTC)

Well thanks for that, I suppose I should have added that I'm not highy physically active and so eating for example an avacado - I don't know if this would be a bad idea if I have more than one a day? And what about fruit, should I fill myself up with loads of fruit? Anyways, thanks for your help. Rfwoolf

Also be aware that although fruits are far better than refined sugar that frutis do contain sugar and for a person who is not physically active they can cause weight gain. In this regard the keyword is calories - as in watch those calories! You can do lots and lots of veggies, however, but remember calorie counting is the thing! Nebraska bob 12:34, 31 March 2007 (UTC)

v/v avocadoes etc, yes don't over-do it, but personally I am more concerned about nutrient density than calorie density. Avocadoes are high in calories, but they are also very nutrient dense, with lots of good fats and anti-oxidants. I wouldn't eat four a day, but I know a lot of people who make a point of eating one a day, and they're not fat. It's a question of - in part - what you're replacing it with. If you say to yourself, 'Oh, that avocado's too high in fat/calories, I'd better not eat it,' what are you eating instead? If it's broccoli florets and carrot sticks, maybe yeah, it's a worthwhile trade-off. But if it's a bagel with non-fat cream cheese or a bag of air-popped popcorn, or a taco or a hotdog, you were probably better with the avocado. Anchoress 12:55, 31 March 2007 (UTC)

And whaddaya know, check out our article on healthy diet. Anchoress 13:14, 31 March 2007 (UTC)

Also if you are not that concerned about calories the pecans in pecan pie are extremely nutritious! Nebraska bob 13:56, 31 March 2007 (UTC)

Thanks all! I should mention I found a useful website - www.sparkpeople.com (free) where you sign up and it has a calorie couter or over 10 000 foods and it assesses you BMI as well -so that's how I'm going to track my caloric intake. And thanksto Nebraska Bob and Anchoress for your input. Rfwoolf

Remove all meat (if you feel like protein go for seafood), remove all trans fats (aka hydrogenated oil), oats and granolas are good, lentils, unadulterated rices, olives, beans, refried beans, Kettle Chips or other similar products are healthy, potatoes in general are good, I find cheeses more palatable if they've been melted & browned, go for a variety of ethnic foods, particular Japanese (sushi), Greek, Italian, and Indian. Avoid fast food like the plague -- even Subway. Obviously fruits and veggies are good (and fruit juices), but realistically just eat them when you feel like eating them; an all-carrot diet just isn't sustainable. Above all trust your senses: eat what smells and tastes good. The one exception is trans fat: you don't taste it, and it doesn't cause problems until later, when your poor body tries in vain to digest it. Good luck and congratulations on wanting to go healthy, that's the most important step! Vranak

[edit] Bladder size

I weigh about 95.25 kilograms and my bladder holds between 336 and 710 grams when I'm active and wakes me up at 726 grams. Is this average or is my bladder size bigger or smaller than normal? 71.100.167.232 13:50, 31 March 2007 (UTC)

Our article suggests that the normal maximum volume of the urinary bladder is about 500 mL, and that most people feel a desire to urinate when it reaches somewhere around half that capacity. The various sources on this page suggest maxima ranging from 500 mL to as high as 1000 mL. TenOfAllTrades(talk) 15:14, 31 March 2007 (UTC)

[edit] flame temperatures

I'm having a little trouble following the entry on Flames, and my question is this: If the temperature of a flame goes up as the color of the flame moves along the spectrum towards white, where would that place something like Methane, which I think burns blue? Seems obvious that a blue flame would be on the other end of the temp spectrum, but I can't seem to verify this in the entry. Any help? Wolfgangus 14:32, 31 March 2007 (UTC)

I think that flame color has more to do with the fuels that are burning than the temperature of the plasma. It isn't a black body radiator. -- mattb @ 2007-03-31T16:52Z

The "flame color" section of flame says that the color depends on both the emission spectrum and the temperature of the flame. Different materials burning at the same temperature can emit different colors. -- Beland 22:13, 31 March 2007 (UTC)

Ok - thanks for the help. Wolfgangus 10:04, 1 April 2007 (UTC)

[edit] Psychology !!

Sir .. I wanted the notes for Rehabiliation of Psychology? please provide me .. as UPSC syllabus i needed ?

Thanzxs.....

• Um, Wikipedia is an encyclopedia, not your psychology professor... -- Beland 22:06, 31 March 2007 (UTC)

[edit] Sexing at Great Panda

One question: is this is a male or a female Great Panda? Well, I would say male, but I've lost my naturalist exam in the Berlin Underground. Thanks a lot in advance for your help. --87.160.242.75 16:39, 31 March 2007 (UTC)

[edit] HELP PHYLLIS CREATE A SAMPLE TREE DESTINED FOR CUTTING?

I want to track exactly what would happen to birds and animals living in that tree. My focus is on animals living in forest destined for mass destruction. Post your aswers on my blog: <address removed>

Compiling for publication a Profile, I would appreciate information from math whizzes who would calculate numbers. How many birds might nest there? Squirrels? Bugs?

Some questions: The animals: Do the animals receive a warning of any kind that their tree is no longer safe? Do they flee in time? Do they find another home easily? What do they do when the first cut shakes the tree? The cutters: What do the cutters see when they first cast their eye on the tree? Do they look for nests? Do they discuss the destinies of its inhabitants? Look for them? Help them? Laugh? Cry? Ignore?

Every tree is a community. When it is cut, What happens to its residents? Where do they go? Are they forewarned? Do they run away and find a home elsewhere? Do they survive the cut and stay with the tree through thick and thin? Does someone care whether this particular critter lives or dies?

Q: What is happening on our tree as the signatures are being written? Q: What critters live in it and on it at that moment in time? Q: How many of each kind of resident lives on a tree? (example: RED ANTS - about 8,000 red ants live on a tree 71' tall and 2' in girth.)

How many cocktail napkins would our tree make? 20,000? How many toothpicks? How many stickies? How many stir sticks? Paper cups? Party hats? Newspaper pages? Party invitations. Coasters. Business cards. Flyers. Shelves. Hangers. Shingles. Tiles. Pencils. ETC. ETC.

THANK YOU FOR LISTENING. It's a one-time effort on my part to begin compiling a powerful picture that won't go away until the suffering it represents goes away. Phyllis contact: <address removed> —The preceding unsigned comment was added by Niaih (talk • contribs) 19:46, 31 March 2007 (UTC)

Phyllis, I have removed your blog address, as it is probably not wise to show it on a forum as widely read as this one. I have also somewhat re-formatted and trimmed you contribution to highlight the questions within it. You may get some answers to your quantitative questions here. Gandalf61 20:40, 31 March 2007 (UTC)

[edit] Coke vs Speed

I took a drug and alcohol class in school and I was told cocaine has a higher high than speed, but does not last that long. Speed last longer but the high is not as intense. I was talking to someone and they told me speed has more intense highs, which is correct?

From purely anecdotal experience: they have different types of highs, I am not sure how you would qualify them are more or less intense or not—this strikes me in the end as a qualitative question that is not going to be easily answered even if there is quantitative data available on the line of neuroreceptors and the like. Cocaine is a jittery, adrenaline-like, aggressive high. Speed is a euphoric, "my mind is blasted into heaven", "I can really concentrate" sort of high. After doing cocaine you want to do more immediately (it has a harsh, immediate come-down) but if you don't get any more you feel okay after a little bit. After speed you want to do more in the long term (the come-down is more gradual, but you feel the need to feed it more, and as it is a lot cheaper in price you often have more of it to do) and it is incredibly easy to develop a more serious physical dependency.

Both are incredibly bad for your body and can lead to all sort of short and long-term damage to your nerves, your cardiovascular system, your teeth, and your nose; they are not worth it, in my opinion, as someone who has tried both during an ill-focused youth. I made it out of that scene more or less scratchless, by some miracle (and after one very close brush with the law), but I was more or less the exception: almost everyone else I knew there did not go on to accomplish very much and many ended up in jail in the long term. Both of the drugs pretty much have the immediate effect of turning you into an asshole at the very least; not exactly an attractive quality.

This is just my take on it—potentially too much of a soapbox for the reference desk—based on my experience. I'd stick to pot if it were me making the same choices all over again — neither of those two uppers really beat getting toked up and being completely contented eating an entire box of macaroni and cheese with some good friends. (Disclaimer: I no longer do anything but occasionally drink, and even then not very much. I guess I grew up.) --24.147.86.187 22:50, 31 March 2007 (UTC)

Coke's brutality is in the cycle: you ride a line for ten or fifteen minutes- then you spend the next 10 or so minutes trying to convince yourself you're still on that last line, then finally you go back to the plate. as the night goes on these minutes shrink while your lines get longer and longer. Meanwhile speed is a less-desperate affair. Guy above has it down well: coke=adrenaline-ish, speed intensely, hard-driving euphoria. additionally, a gram of good speed can last 1-2 days. a gram of coke: if you're lucky, an afternoon. Wolfgangus 05:55, 1 April 2007 (UTC)

[edit] Excercise and body heat

If its dangerous to have a high fever, why is it not dangerous to exercise? When I run for a long time (few miles), I feel as if I am way hotter than any fever I have ever had.

• The article Hyperthermia explains in some detail about the dangers of heat. In general, when you exercise, your body sweats and takes other automatic measures to keep your body temperature in a safe range. But if you say, exercise on a very hot day, it is certainly possible to get dangerously warm. Your subjective perception of your body's real temperature is not always accurate, but we don't have very much information about that which I can find at the moment. It would be nice if we had an article on the perception of temperature. -- Beland 22:20, 31 March 2007 (UTC)

See also Thermoregulation. -- Beland 22:22, 31 March 2007 (UTC)

[edit] I'm the most intelligent person in the world

I'm pretty sure I am. What can I do to prove it? --Taraborn 22:44, 31 March 2007 (UTC)

I could tell you, but that would sort of defeat the purpose. —Steve Summit (talk) 22:49, 31 March 2007 (UTC)

Deathmatch against Marilyn vos Savant. — Kieff | Talk 23:22, 31 March 2007 (UTC)

I'm too sexy for my shirt. --Right Said Fred 23:37, 31 March 2007 (UTC)

If you're such a genius, why do you have to ask? --24.147.86.187 00:01, 1 April 2007 (UTC)

That's easy to prove. Just win a couple of Nobel Prizes and a Fields Medal. There shouldn't be any doubt after that. -GTBacchus^(talk) 00:23, 1 April 2007 (UTC)

I wouldn't say prizes are any better measure of intelligence than are IQ tests. There's a lot to be said for environmental factors. Plus, I think it's rigorously impossible to "prove" that you're the most intelligent person in the world without meeting every person in the world and matching wits with them in some universally unbiased intelligence test. Failing that, I think you might have to settle with the lesser (but still illustrious) title of "most egotistical person in the world". -- mattb @ 2007-04-01T00:44Z

LOL well said Matt. --Bmk 01:16, 1 April 2007 (UTC)

Matt, I wouldn't say prizes are the "best" "measure" of "intelligence" at all. However, my remark above is what I would say to somebody asking how they can prove that they're the "most intelligent person in the world". That person doesn't need an answer, they need perspective. -GTBacchus^(talk) 02:04, 1 April 2007 (UTC)

The question is based on a very weak proposition, namely, that a relative ranking of the human population of Earth by IQ (or whatever quantifiable measure you personally choose to determine "intelligence") would necessarily represent a total ordering.

This ranking would have to be antisymmetric, transitive, and total for a "most intelligent" to even be definable, let alone provable. For example, if Alice > Bob > Charlie then it must follow that Alice > Charlie (transitivity). That means that Alice beats Bob on every dimension of "intelligence" implies Alice beats everyone on every dimension of "intelligence". All that would be necessary to demonstrate your question is meaningless would be to construct a head-to-head "intelligence" measure in which Charlie beats Alice. Even if Alice won the Nobel and the Fields, Charlie could beat Alice at a single game of Go and the whole scheme goes down the crapper. dr.ef.tymac 01:29, 1 April 2007 (UTC)

If youre so smart, ask yourself the question I do every day: "Why aint I rich?"

Reduce an infinite number of equations having an infinite number of variables with an infinite number of states to minimum form instantaneously. Nebraska bob 01:46, 1 April 2007 (UTC)

Ahh, it's so easy to disprove. Since I know how to prove whether you are the smartest person in the world, that makes me smarter than you. Ergo, you are not the smartest person in the world. Pretty logical. --Tbeatty 02:07, 1 April 2007 (UTC)

[edit] What makes things soft?

The other day I was sitting around wondering what makes certain fabrics subjectively softer than others, and this led me to the article soft matter, which doesn't really explain what makes things soft. There are actually many different types of softness, most of which can be considered the opposite of some type of hardness. I've accumulated a list of such properties and their scientific names in the article hard matter. I think the sort of softness I'm thinking about is the opposite of roughness, though the article roughness only talks about a technical definition of surface roughness which is not what I mean. Texture seems like it's a disambiguation page that wants to be turned into a real article, and touch and tactile are not much help, either.

In particular, I'm wondering what kinds of structures differentiate soft vs. rough or prickly fabrics, skin, etc. Are the effects produced at the molecular level, or due to larger-scale structures (and if so, at what scale)? What role is there to play for interlopers like moisture and oils? -- Beland 23:00, 31 March 2007 (UTC)

Cloth "smoothness" is measured by the thread density. It is measured in Deniers (See Denier (measure)) Raul654 23:04, 31 March 2007 (UTC)

[edit] What will happen if you break a magnet

What will happen if you break a magnet into two pieces? I did a lot of research on this, but it seems every source state that "there will be a new north and south pole created at the point it break. No monopole magnet has been discovered." But, how do you explain the fact that the two pieces repel at the point it breaks? I break quite a few bar magnets and circular magnets, they all repel at the point they break. How do you explain that? If one of the two pieces switch pole (which it seems to be), how do you determine which piece switched pole? Rockvee 00:46, 1 April 2007 (UTC)

It depends on which way you break it, I think -- parallel or perpendicular to the N-S axis.

If you have a bar magnet, like this:

+-----------------+

|NNNNnnnn ssssSSSS|

|NNNNnnnn ssssSSSS|

+-----------------+

and if you break it in half, I believe it develops new south and north poles, like this:

+-------+ +--------+

|NNNnsSSS> >NNnsSSS|

|NNNnsSS< <NNNnsSSS|

+--------+ +-------+

and I believe that the two pieces will attract each other and stick together.

However, if you have a flat magnet, like this:

+-----------------+

|NNNNNNNNNNNNNNNNN|

|SSSSSSSSSSSSSSSSS|

+-----------------+

and you break it in half parallel to its N-S axis, like this:

+-------+ +--------+

|NNNNNNNN> >NNNNNNN|

|SSSSSSS< <SSSSSSSS|

+--------+ +-------+

then if you try to put it back together, its N face will be next to its N face, and its S to its S, and they'll repel each other, and it'll be as hard to put the pieces back together as it would be to put two of those flat magnets next to each other. —Steve Summit (talk) 01:04, 1 April 2007 (UTC)

wow, thanks for your clear answer! However if I remembered correctly, I break a bar magnet perpendicular to it's pole (1st case in ASCII diagram), it still repel. I used quite long and thin bar magnet with poles at the thin ends so I don't think I break it parallel to its pole.Rockvee 01:18, 1 April 2007 (UTC)

Yeah, that's what it sounded like you meant. All I can say is, next time you have the chance, try the experiment again. —Steve Summit (talk) 01:40, 1 April 2007 (UTC)

hmm, did you check the specifications of your magnet? sometimes the really long, thin ones are magetised on the long thin sides, not the long wide sides or the short thin sides. Coolotter88 01:53, 1 April 2007 (UTC)

The magnets are labeled S and N so I am sure poles are on the thin sides Rockvee 02:50, 1 April 2007 (UTC)

It's worth remembering that the magnetic field of a bar magnet is simply due to the overlapping magnetic fields of all of its atoms, which are mostly aligned. Whether a magnet is in one piece or in two pieces being held together, the alignment of the atoms' fields is the same, and the resulting external magnetic field is the same. -- Beland 03:15, 1 April 2007 (UTC)

[edit] coral and sea level changes

--Nodman69 au 01:22, 1 April 2007 (UTC) my question is if sea levels a couple of thousand years ago were much lower than today how can coral reefs be millions of years old seems they grow a lot faster than people are saying if sea levels have been have been increasing at such a dramatic rate sorry it just dosent make sense to me if someone could explain in simple terms for a simpilton like me i would appreciate it--Nodman69 au 01:22, 1 April 2007 (UTC)

I don't understand what you're asking - note that, although sea levels have been rising due to the melting of ice caps, even 1 million years ago, there were oceans - the only reason oceans are rising is ice cap melting and icebergs falling into the ocean, and that's blamed on global warming, and that's not been going on for the whole million years. ST47Talk 01:38, 1 April 2007 (UTC)

The earth has been warming since the last ice age. Glaciers have been retreating since the last ice age. That's pretty much the definition of ice age. I don't think the current global warming has seen actual measurable rises in see levels in the last 100 years. It's just too small a time scale. Ice ages are defined by whether glaciers are expanding or retreating. And lets look at the scale as well, the rise in sea levels is relatively smal compared to the overall depth of the ocean. I think the ocean average 2 miles deep. Sea level rises are measured in feet over millenium and millimeters over the last 100 years. The daily tide change is significantly more than any of globale warming changes. --Tbeatty 02:20, 1 April 2007 (UTC)

While coral species have been around for millions of years, living coral reefs exists no deeper than 50-100m. The above-posted chart (from sea level rise) shows that sea level has risen this much in the past 20 thousand years or so. Our article on the Great Barrier Reef points out the difference between fossilized coral in the area, which is indeed millions of years old, and the current living reef, which it says is about 20,000 years old. Perhaps there is some confusing about dead vs. living coral in the information you were looking at. Global warming is not the only threat; see Coral reef#Threats_to_reefs. -- Beland 03:06, 1 April 2007 (UTC)

[edit] Earth resources - oxygen production

I know that the ocean is suppose to produce most of Earth's oxygen but how much oxygen is produced by a square mile of sugar cane plants versus a square mile of rain forest? (same location) Nebraska bob 02:31, 1 April 2007 (UTC)

[edit] Great Apes

I have looked up almost everything on great apes and I've read that The United States Academy of Science has made a purposal to change chimpanzees scientific genus from Pan to Homo; which was made just last December. So I went to change the two chimpazee species on wikipedia to Pan or Homo, and it was re-edited and called me a vandlest. bibliography: www.greatapeproject.org —The preceding unsigned comment was added by 76.101.9.145 (talk) 04:06, 1 April 2007 (UTC).

I don't believe such a change would be accepted by the majority of the scientific community. Splintercellguy 04:35, 1 April 2007 (UTC)

The article bonobo already mentions such a proposal: "But there is still controversy. Scientists such as Morris Goodman[4] of Wayne State University in Detroit argue that the Bonobo and Common Chimpanzee are so closely related to humans, their genus name should also be classified with the Human genus Homo: Homo paniscus, Homo sylvestris, or Homo arboreus. An alternative philosophy suggests that the term Homo sapiens is actually the misnomer, and that humanity should be reclassified as Pan sapiens. In either case, a name change of the genus is problematic because it complicates the taxonomy of other species closely related to humans, including Australopithecus." The first part seems plausible, but the part about "alternative philosophy sounds like bullshit. --JianLi 04:37, 1 April 2007 (UTC)

[edit] Is this stuff for real?

It seems so much like a hoax, but it's on BBC. [11] [12] --Gujarat10 04:11, 1 April 2007 (UTC)

Depends of what do you mean by "real". Is there any magic force\energy that permeates the universe and all living things, that we can use to achieve super-human strength? Not really. This is just good ol' exercise and training. Martial artists develop strengthened muscles, tendons and skin, denser bones, control over pain, discipline, self-confidence and will power. That's all it takes to bend metal bars or pull a truck full of people with your penis. It just takes good training and patience. The qi stuff about it is just junk mysticism that really just distracts people from how amazing our bodies truly are. — Kieff | Talk 04:54, 1 April 2007 (UTC)

[edit] Sunblock and tanning

Does using a sunblock with SPF of lets say 70 get you less tanned than using spf30 or no sunblock? Or does it just block out the bad sun rays?

[edit] cable modem

i am thinking of getting comcast high speed internet with a cable modem. in order to use the service can i use a telephone jack to connect the modem or do i have to have a cable connector outlet nearby. the cable silver or gold thingy that sticks out.--logger 07:39, 1 April 2007 (UTC)

Typically one hooks up the cable modem to the coaxial cable jack that can also carry cable TV. Splintercellguy 08:11, 1 April 2007 (UTC)