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January 30

Rice and Play-doh

Having visited my baby brother recently, and having decided to make rice for dinner, I'm struck by the similarity in scents given off by the cooking rice and the new Play-doh my brother got for Christmas. Why do they smell nearly the same? It's kind of putting me off my dinner plans... Kuronue | Talk 01:04, 30 January 2009 (UTC)

Was your brother's Play-Doh home-made? It's possible to make your own with rice flour. Apparently the real stuff uses wheat flour though. — Matt Eason ^{(Talk • Contribs)} 02:07, 30 January 2009 (UTC)

Nope, brand new, little yellow containers. He got a set designed to make hamburgers and hotdogs as well as a set of four neon colors. Someone on IRC suggested maybe the surfactant is a rice protein? Kuronue | Talk 02:11, 30 January 2009 (UTC)

I'm not sure about the smell, but rice and play-doh may have a few similar properties. They are both sticky and easy to mold into shapes. It's easy to smudge cooked rice and use it as a type of glue, which dries after a while. ~AH1^(TCU) 19:32, 30 January 2009 (UTC)

I'm extremely glad you noticed that too. I've used the-point-at-which-rice-doesn't-taste-like-play-doh as my cooking indicator for years, and people never seem to know what I mean. School rice always tasted like play-doh, presumably because it was undercooked. While unable to answer your question, I just wanted to thank you for reassuring me :) 79.66.71.197 (talk) 23:14, 30 January 2009 (UTC)

Digestive grinding stones

Dinosaurs and birds eat stones and this is supposedly good for the digestive system. I do not drink 2 litres of water any more because I know that if I do not pump the whole thing around, it's not very good for your stomach and your kidneys. If I started swallowing big stones, would I eat less and digest more or would it constipate me until I got surgery? What shape and size of a stone and how often to swallow one or what stones are the best mineral? ~ R.T.G 02:24, 30 January 2009 (UTC)

You are not a bird or dinosaur. Eating stones will not help your digestion, and may well do you harm. Don't do it. Algebraist 02:28, 30 January 2009 (UTC)

interesting idea. Here's a question ... what's the easiest but most dangerous weight loss techniques? a) intestinal parasites - tapeworms Giardia, b) amphetamines, c) fasting (I hear you aren't hungry after a week or so)? TungstenCarbide (talk) 02:57, 30 January 2009 (UTC)

Drinking more (water not softdrinks or coffee/tea) is actually good for you. See Dehydration and Fluid balance. While one can get into trouble drinking excessive amounts of water in one sitting (Water intoxication), drinking 2 liters throughout the day may just about cover what you need. Not drinking water when you are thirsty doesn't sound like a great idea. Your body tells you when it needs water. No clue where you found the information this might be bad for you, but I'd check whether you might not have misunderstood something or whether maybe the writer might have not thoroughly researched the topic. For certain medical conditions doctors may advise you on restricting your water consumption, but that should always be done as instructed by a qualified medical professional. Dietary minerals are only the same as minerals on a chemical element level. The body requires certain forms of these minerals and in combination with certain other chemicals. Even dietary supplements which are a far cry from eating rocks [1] aren't metabolized as efficiently/in the same way as minerals from food sources. [2]76.97.245.5 (talk) 04:05, 30 January 2009 (UTC)

DIY surgery is an easy but very dangerous weight loss technique.-gadfium 04:21, 30 January 2009 (UTC)

FYI, under Crocodiles it says this: "Many large crocodilians swallow stones (called gastroliths or stomach stones) and they are believed to be of use in acting as ballast to balance their body. Other suggestions have been made that they may have a function similar to that of grit in birds, which is in crushing food." In other words, to help them dive deeper, and birds chip away at grit, not stones. And opera diva Maria Callas was rumoured to have lost 80 lb thanks to a tape worm. She put it down to chicken salad. Julia Rossi (talk) 07:59, 30 January 2009 (UTC)

I was looking at Speckled Mousebird which appears well written and says they swallow "pebbles" and I just know that some dinosaurs and lizards eat rocks. The truth may be that drinking only water does more good for you. I am 6 feet and between 11.5-12.5 stone, I eat a medium to large cornflakes in the morning and around five medium to large teas every day, fairly average but if I add two full litres of water to that without exercising to exhaustion (at least) I get runs to the toilet or sore kidneys/sore larger stomach/thirst for loads of water (like diabetes). I always intended to drink 2 liters as per doctors recommend but I just can't do it. I do know water is good for me but took me a while to see the over-excessive part. I think what is meant to be said is that "The most healthy people drink 2 liters of water a day" rather than "Drink to liters of water a day to make yourself healthy". I may have small kidneys or something but that is unlikely (lol, say nothing) and I can eat a lot so my stomach couldnt be too small. I would have thought that swallowing stones big enough for grinding stuff would be difficult for people. It's funny, when my family were all on Slim Fast, the rumour went around that there was worms in it and that it was recalled but I don't see that on snopes or the search engines, lol, 90s paranioa! I beleived that whole-heartedly. Crocodiles only eat once or twice a year (true carivores do not eat all the time, I !can't! find a reference to that if anyone knows of one for the crocodile article, I think they eat between 3 and 18 or 3 and 6 months or something the [wikiversity] page is good but can't find that on animal planet or anything). ~ R.T.G 13:01, 30 January 2009 (UTC)

Birds and reptiles swallow stones because they can't chew. Humans have molars for that, swallowing rocks won't help your digestion because your food is already mashed enough by the time it gets to your stomach. Rocks would either get stuck in your digestive system requiring surgery to remove them, or cause a very unpleasant bathroom experience when they passed through. -- Mad031683 (talk) 17:26, 30 January 2009 (UTC)

Some snakes can eat without even biting... they don't swallow rocks do they? (I think it's right you would need a surgeon) ~ R.T.G 20:54, 30 January 2009 (UTC)

Eosinophil

The normal range of eosinophil counts is 0 to 4 %. What does 7% mean? Thank You! AJ —Preceding unsigned comment added by Adrianajensen (talk • contribs) 03:49, 30 January 2009 (UTC)

Eosinophil granulocyte? Whith questions like yours it always helps to let us know what you need the answer for. We can't give medical advice and won't do homework. 76.97.245.5 (talk) 04:12, 30 January 2009 (UTC)

Don't get me wrong, but isn't a 7% eosinophil count simply termed 'increased eosinophil count'? —Cyclonenim (talk · contribs · email) 07:46, 30 January 2009 (UTC)

It's called Eosinophilia. Meaning um.... "increased eosinophil count". Medical jargon eh? Fribbler (talk) 10:42, 30 January 2009 (UTC)

More to the point, eosinophilia can mean either "a larger proportion of eosinophils among the white blood cells" (which is all that 7% tells you), or "a higher than normal absolute number of eosinophils in the body" which is what an absolute eosinophil count would tell you. In either case, there's virtually no significance to a single reading that's marginally high (like 7%), unless there's a clinical setting that would make it so. So as in all these cases, the doctor who ordered the test is the one who has to tell you if this (mildly elevated) value means [1] nothing or [2] something. Persistent elevated values, or isolated significantly elevated values, would make one think of allergies and parasites first, and other things in the differential in the eosinophilia article second. - Nunh-huh 11:35, 30 January 2009 (UTC)

What makes heating a house using geothermal inefficient in the US

When I was in Germany I encountered many people who had installed geothermal heating in their houses. (Geothermal heat pump) When geothermal is mentioned in the media in the US there is usually a comment that it's inefficient here. Comparing the climate information for Germany and Georgia temperature can't be the factor that makes the difference.[3] Climate of Georgia (U.S. state) Since I find it hard to believe that the Germans would install inefficient heating systems, does anyone know what makes things that different here? 76.97.245.5 (talk) 05:46, 30 January 2009 (UTC)

I'm surprised that you'd say "inefficient". The reasons I've heard (and they aren't unique to the USA) are that geothermal is expensive to set up - and that it's not necessarily "renewable". The way it works is that you pump cold water down into some hot rocks and then pump it back out again - and when it comes back, it's hot water that you can use to heat your house and make hot water via heat exchangers. There are two problems with that:

1. It's great when your primary energy cost is heating - but it would be useless in large parts of the USA where you need air conditioning to cool the house over a large fraction of the year. To convert the hot water into electricity and then use the electricity to run your A/C is a much bigger problem.
2. The capital cost of all of that drilling and pumping is not a one-time problem. The rocks at the depth you can afford to drill down to aren't really all that hot - and after years of use, you can actually drop their temperature significantly - causing the geothermal plant to run less and less efficiently. So the geology of the area matters.

What is really needed is a larger scale plant - where you drill much deeper so that instead of getting water back out, you get steam - then you can run a turbine and easily generate electricity from that.

However, I'm a little surprised that there isn't more emphasis on that approach here. But honestly - I think a combination of large wind farms and nuclear power will ultimately be the US solution...possibly augmented by rooftop solar panels.

For homes - our best bang-for-buck would be to sink some serious money into better insulation. My house (which has four times better insulation of a typical American home consumes about a third of the amount of electricity that my neighbours use. This added about 5% to the construction cost of the house - and pays for itself in about 5 years. Why aren't all houses built like that? Well, it's because of 'sticker shock'. People buy what's cheapest without looking at the future running costs. What is needed is government grants that pay that extra 5% directly to the home builder - and recoup the money from the electricity companies who are required to charge (say) twice as much for domestic electricity to houses that were built under this scheme - giving half of that back to the government as a tax. That way, everyone wins. The consumer gets slightly reduced electricity bills - and without having to pay a cent more for their houses. The electricity companies get to build less power plants yet still make more profit in the long run once they don't have to pay the "new house" tax on their electricity. The government gets reduced dependence on non-renewable fuels and could (with care) make a profit on the grant scheme. Everyone wins through greenhouse gas emissions reductions. You could also give people the option to pay the extra 5% on their house cost - and NOT have doubled electricity prices from then on. This is easy to do - all it takes is someone in government to sign the right bit of paper to make it happen.

That's a much better bang-for-buck than any other form of new power generation system - and it works in hot climates as well as cold ones.

SteveBaker (talk) 12:03, 30 January 2009 (UTC)

Also, geothermal energy is far more efficient when there are "hot rocks" near the surface. In the US, such places tend to be public land, like Yellowstone National Park, and thus unavailable for this kind of development. I'm not aware of Germany having much of this geology, but Iceland does, so geothermal is far more practical there than in the US.

Finally, when comparing whether geothermal energy makes sense in a nation, we should consider the cost of alternatives. The US has vast, cheap supplies of natural gas, which is used for heating in much of the US. If Germany lacks this, and must instead import natural gas from unreliable sources like Russia, then investigating home-grown alternatives like geothermal energy makes more sense. StuRat (talk) 13:06, 30 January 2009 (UTC)

Thanks Steve and Stu. The "only works with hot rocks and large plants" arguments was what didn't work for me in comparison since in Northern Germany there aren't hot rocks where I saw it done (it's mostly leftover ice-age rubble and marshland) and they do it in small units, too. So the difference is that they don't do AC and don't have local fuel resources (if you don't count canola oil which is used in some diesel engines there.) That makes more sense. 76.97.245.5 (talk) 15:28, 30 January 2009 (UTC)

I believe Steve and Stu are confusing Geothermal heat pumps with Geothermal power. It is the latter where you pump water over very hot rocks and use the steam for heating and for electrical generation. Most geothermal heat pumps don't need hot rocks, and in fact work best when the ground source is a moderate temperature, usually slightly below room temperature (50-75 F, 10-25 C). Unlike geothermal energy, you're not trying to extract energy from the ground, you're simply using it as a stable, very large capacity heat bath, to which you attach a heat pump (a conventional air conditioner is a heat pump). As the efficiency of heat pumps is related to the temperature differential between the two sides, having the "outside" being very close to the inside temperature greatly increases efficiency. So instead of running an air conditioner where you dump excess heat from your 72 F (22 C) into the 100 F (38 C) outside, you dump it into the 60 F (15 C) ground, which is much more efficient, electrically speaking. Also in winter, you can "reverse" the heat pump, pulling heat from the ground and dumping it into your house, which takes much less electricity than creating the heat directly from the electricity. As to why they aren't common in the US, I'm not sure. One reason may be that most people, even otherwise well read and knowledgeable ones, haven't heard of them. Part of that may be due to installation costs. There's a big up-front cost to put the radiator in the ground and to buy the size/quality heat pump needed. Although it'll probably save you money in the long term, when building the house it's much cheaper to put in a simple furnace/air conditioner combo. Adding the system after the house is build means tearing up the lawn. Another big reason may be that natural gas, propane, fuel oil, and other petroleum based products are massively less expensive than electricity in the US. I think it's cheaper to burn gas/oil for heat in winter versus pay for the electricity to run the heat pump, even though the heat pump is more energy efficient. Without the winter savings, the payback period gets much longer, especially in the north where air conditioning is only lightly used. Increases to petroleum prices in the future, however, may see more systems installed in the US. -- 76.204.94.153 (talk) 18:33, 31 January 2009 (UTC)

Geothermal heat pumps use an electric compressor to increase the temperature of a fluid. This fluid is used to collect heat from outside the buiilding at a low temperature and transfer it to an internal space at a higher temperature. Rather than measuring 'efficiency' of these systems, it is better to use the measure 'coefficient of performance'. This is a measure of how much heat is transfered to the building as a proportion of the electricity used by the system to transfer this heat. For many systems, this coefficient is around 3 - ie 3 times as much energy is transfered into the building as is consumed by the compressor. However - the electricity that is being used has probably come from burning coal or gas (depending on where you live). These power plants generally have an efficiency of around 30% - ie 30% of the energy in thc coal or gas ends up in your home as electricty. From an environmental viewpoint then, you are using the same amount of raw energy if you intall a gas heater in your home as a ground source heat pump (assuming coefficient of performance of 3 and power system efficiency of 30%). Before purchasing systems, it is worth carrying out a study to calculate the net energy gain and how much this will cost you. Im afraid I dont know what other reasons would alter the 'efficiency' of such a system between nations. TomStroud 16:50, 5 February 2009

Just to update my figures - modern gas power stations can be about 50% efficient and good ground source/air source heat pumps can have a cop of 4 - therefore providing an overall system efficincy of 200%!! TomStroud 22:08, 9 April 2009 (UTC)

UFOs

So if I understand correctly, accroding to currently established thinking in the scientific world, it is mathematically highly probable that extraterrestrial life exists, but it is too unlikely that such an alien life has the means or intelligence or technology to conduct intersteller travel - so UFOs being real is ruled out. That is, alien civilisations probably exist, but we can never contact them. Is that correct? ReluctantPhilosopher (talk) 09:35, 30 January 2009 (UTC)

See Fermi paradox and Drake equation. It's all a giant guess where those little green buggers are. Someguy1221 (talk) 09:48, 30 January 2009 (UTC)

Wow, I never knew there was a named paradox for that. Thank you, Someguy1221 :-) ReluctantPhilosopher (talk) 10:21, 30 January 2009 (UTC)

We know that the speed of light is the cosmic speed limit. We know that the closer you get to that speed - you need exponentially more energy to accelerate and decelerate. This makes interstellar travel exceedingly difficult and costly no matter what technology you use. Also, aliens that do have the capability will have to dedicate a large fraction of their resources to each craft they launch - so they are unlikely to simply go out visiting stars randomly looking for life. No - they are going to do what we do. Search the skies for radio signals - and look closely at exo-planets with spectrographic signatures that indicate life. Then they'll probably beam a high power, tightly focussed beam of radio waves containing the usual stuff like sequences of prime numbers and digital pictures with prime-number dimensions.

Consider that we've only been putting out radio broadcasts at any reasonable power for about 50 years. Even with close-to-the-speed-of-light spacecraft, an alien civilisation would have to be within 25 light years to even know we're here and then come visiting. Worse still - it is interesting to note that with the most powerful radio telescopes we have - we would be unable to detect the most powerful radio transmitter we have at the distance of the nearest star (4 light years). So the aliens would not only have to be close enough to have heard us and have had time to get here - they ALSO need to have some pretty amazing radio-telescopes. So the fundamental limits of the laws of physics (the speed of light, relativity, the inverse square law of electromagnetic radiation) make it unlikely in the extreme that an alien civilisation could possibly show up on our doorstep anytime in our lifetimes. Unless these aliens are VERY close to us already they have literally NO WAY to even know we're here. There really aren't many stars that close to us - so unless intelligent alien life is VASTLY more common than even the most optimistic Drake-equation predictions, it isn't coming visiting anytime soon.

IMHO, unless our alien species has extraordinary long lifespans and/or a biochemistry that allows them to shut down cognitive facilities and preserve their bodies without consuming resources over a long trip (eg cryogenics) - we aren't ever going to see them in person. What we MIGHT get would be their computers...some kind of robotic emmisary. We know that if we had to send something to (say) Alpha Centauri (4 light years away), we'd probably send a robot because it could take a few hundred years to get there - and four years to report back - but since it could be shut down for most of the ride, we could probably do it.

But think about that for a moment. If that's all they are going to send, they might as well just transmit the plans to build that computer - plus all of it's software and data over a radio link and have us build it for them - rather than spending all of that effort to physically transport the computer to us. So IMHO, the SETI effort has vastly more chance of success than the UFO spotters do!

The only time I could imagine an alien species coming to visit us in person would be in some vast colony ship. If aliens see the imminent demise of their star - then they might consider packing everyone into some vast 'generational' ship - maybe a hollowed out asteroid or comet - maybe spin-stabilised for gravity with huge nuclear/fusion power plants providing energy with a complete 'biosphere' on board to provide their people some kind of a bearable lifestyle. This craft might take thousands of years and hundreds of generations to slowly plod from one star system to the next. If something like that shows up - we're in real trouble because they'll have started out on their journey thousands of years ago - having looked carefully at our planet by astronomical means. But thousands of years ago was back before we dominated the place. And seen from 50 light years away, there would have been no indication of a pre-industrial society living here. So they'd have seen a highly suitable environment for their people and set off. Then, (presumably to their extreme horror) as they start to approach their new home, they see a budding intelligent civilisation start to appear on it! As time goes by they see us develop nuclear weapons and space craft - and then (worse still) we start screwing with the atmosphere and heating the place up! They have millennia to plan what to do about that - but when they get here, they won't be happy - and that'll be a big surprise to us! Think "Independence Day (movie)" - but without the possibility to use a computer virus to take them down (which was one of the worst "and then the aliens all die" endings since the cop-out at the end of War of the Worlds!).

SteveBaker (talk) 11:37, 30 January 2009 (UTC)

"Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space." Douglas Adams Gandalf61 (talk) 12:40, 30 January 2009 (UTC)

I think someone else pointed this out before. If an alien civilization did send a probe to our solar system (assuming their probes are similar to ours) it would be so small that it could pass through our system without ever being noticed. A Quest For Knowledge (talk) 14:53, 30 January 2009 (UTC)

There's also the problem that if life DOES exist, that it somehow must exist at only a slightly (say a thousand years or two) more advanced state than we are in. It is entirely statisticly more likely that alien life does exist, but is millions of years, evolutionarily speaking, behind us, or millions of years ahead of us. Either way, there is a good chance that the evidence of that life has either not reached us yet, or that civilization is long past, and the evidence of it has already blown past us. The idea that there is an alien civilization at all in history is pretty good; the idea that there is an alien civilization close enough to us to detect and within that relatively narrow window of emiting the sorts of radiation that are detectable is mindbogglingly small. Also, consider that we generally confine out understanding of alien civilization to this Galaxy. Make a few tweaks to the Drake equation, and you may well find that you can come up with an average of one technological civilization per galaxy. In that case, we may not be alone, but there may very well be no conceivable way for us to ever contact or have knowledge of these other civilizations. --Jayron32.talk.contribs 16:38, 30 January 2009 (UTC)

I little aside here: can people PLEASE stop using "UFO" as a synonym for "Spacecraft from a sentient alien race". I can't tell you how much that pisses me off, even these renowned so-called "Ufologists" do it. There is no doubt in the entire world that UFOs exist. What is in doubt is whether some of these UFOs were alien spaceships.</rant>-RunningOnBrains 17:26, 30 January 2009 (UTC)

It has definitely not been ruled out that UFOs that are alien spaceships exist. Tens of thousands of sightings have been reported worldwide, from an unusual light in the sky, to multiple witnesses reporting a spaceship over a mile wide, to reported abductions by aliens. Most of these reports can be explained by more rational possibilities, and most scientists reject the notion that alien spaceships have visited Earth, citing lack of evidence. The always remains, however, a handful of sightings with very good credibility and which still cannot be explained. I personally don't believe the Fermi paradox is so hard to solve, and this is just one reason why. There is also a list of UFO sightings. ~AH1^(TCU) 19:23, 30 January 2009 (UTC)

I'm not sure if that was directed at me, but I certainly wasn't implying that all UFOs have logical explanations. You can't prove a negative, so obviously its possible that some unsolved UFO incidents are in fact extraterrestrial craft of some kind. I'm just saying saying that sometimes people get caught up in the hype of a supposedly-paranormal event and don't look for obvious solutions. I cite Occam's razor: is it more likely that that mysterious craft in the sky is an alien spacecraft, or some secret government project? Since we know that governments perform classified experiments with aircraft, and we don't know if extraterrestrial life exists, it makes sense to believe the latter unless there is serious evidence to the contrary. Similarly, is it more likely that the person telling the story about the spacecraft that landed in his yard had a hallucination, is crazy, or is lying? We know those kind of people exist in the world, but we don't know if aliens exist. It's certainly not a foolproof argument, but it helps me sleep better at night.-RunningOnBrains 19:42, 30 January 2009 (UTC)

"The always remains, however, a handful of sightings with very good credibility and which still cannot be explained. I personally don't believe the Fermi paradox is so hard to solve, and this is just one reason why" - so there are credible non-explained UFO sightings? That's what I wanted to know. Thanks ReluctantPhilosopher (talk) 17:35, 3 February 2009 (UTC)

Mitochondrial DNA from sperm to zygote

I recently saw a cautious quotation in a book saying that in most organisms the mitochondrial DNA is derived only from the egg. So what exceptions are known ? Shyamal (talk) 11:39, 30 January 2009 (UTC)

Never mind, found it here http://mbe.oxfordjournals.org/cgi/content/full/18/7/1168 Shyamal (talk) 11:44, 30 January 2009 (UTC)

Scientific question

number of stars which appear from earth incerase? —Preceding unsigned comment added by Sovit mundhra (talk • contribs) 13:15, 30 January 2009 (UTC)

You need to clarify your question, especially the use of the word "increase". Are you asking if the number of stars visible from Earth is increasing ? If so, I'd say not with the naked eye, no. It's possible that better telescopes could increase the number of stars we can see, but such new telescopes tend to be located in space, like the Hubble Space Telescope, to avoid interference from Earth's light sources and atmosphere. StuRat (talk) 14:06, 30 January 2009 (UTC)

If you're asking whether the number of stars visible from any one location on Earth to the naked eye is usually increasing, then no. Most locations are suffering from more and more light pollution. ~AH1^(TCU) 19:13, 30 January 2009 (UTC)

To add insult to injury the universe is expanding, looks like a solid no on all fronts.Bastard Soap (talk) 08:09, 5 February 2009 (UTC)

Firing a pistol sideways

Is there any real advantage in turning a pistol 90 degrees to the right when shooting? Gangsta style, in other words. If not, why do people do that? --84.66.59.206 (talk) 14:08, 30 January 2009 (UTC)

We seem to have two articles on pistol shooting technique: "Modern Technique of the Pistol" and "Point shooting". I skimmed them both, and neither seems to mention specifically the style you're asking about. "Point shooting" does, however, suggest there is value in this style, especially at close quarters, speaking of methods that "do not rely on the sights, and ... strive to increase the shooter's ability to hit targets at short range under the less than ideal conditions expected in self defense and combat situations." The stereotypical Hollywood "gangsta" style of firing—with one hand, held above the level of the head, and with the gun held sideways—would lend itself to certain combat situations, such as firing blind over a wall or in through a high window. Also, the one-handed style leaves the off hand free for other uses, such as balance, reloading prep, or parry. The high hold makes it more difficult for your opponent to seize the gun or disarm you at close quarters, and the downward angle keeps the muzzle on your foe if he ducks, an instinctive reaction. Offhand pistol shooting can be made fairly accurate through practice, and whatever style one uses, practice will probably bring sufficient accuracy for short-range work. Also, being accustomed to firing from awkward positions and around obstacles, and combining hand-to-hand fighting with pistol must surely increase a combatant's chances of survival. So, "gangsta" style would be a valuable addition to a pistol fighter's repertoire, I think. On the other hand, if you don't practice and are more than ten feet away, it would be pure luck if you hit anything that way. You might as well shut your eyes, too. The prescribed methods were arrived at by discovering what works; the guy who lived through the gunfight wrote the book.

As for "why", I can't even say that the style is ever used in the real world. I don't live in an area where people do any such thing ever, and I don't go where they are likely to. But, if it is a common practice, my guess would be it's done for intimidation—to express the earnestness of one's intention to shoot—and to keep a downward trajectory with an eye to minimizing collateral damage in an urban setting. --Milkbreath (talk) 14:56, 30 January 2009 (UTC)

Anyone who was really serious about hitting someone, gangster or not, would fire in a way to maximize that—which doesn't look as "cool" so nobody does that in music videos. --98.217.14.211 (talk) 15:08, 30 January 2009 (UTC)

Mightn't be relevant, but standing side-on presents less of a shooter's body to his opponent - so perhaps it's defensive. Bazza (talk) 16:03, 30 January 2009 (UTC)

NY Times: It's to look cool, but makes it harder to control the gun. WikiAnswers suggests it may be used in movies to show more of an actor's face, to look unusual, or as the result of a misunderstanding about some legitimate shooting tactics. --Maltelauridsbrigge (talk) 16:11, 30 January 2009 (UTC)

Yeah, pretty much all gun use in Hollywood shows a lack of basic understanding. Also, the downward angle to reduce collateral damage sounds reasonable, except that I doubt people having gunfights in cities (and not aiming) care much about that. Friday (talk) 16:23, 30 January 2009 (UTC)

As I understand it (IANAG), when 'someone other than the intended target' gets shot by mistake, the attitude is very much "well, if (s)he didn't want to risk getting shot, (s)he shouldn't have been hanging around those assholes" or "some folks are born lucky, some ain't". Back on topic though - as the NYT link suggests, I think that it's often a case of the gangstas (many of whom are little more than kids) seeing the sideways-shooting thing in gangsta movies (or the dual wield thing) and simply believing that it's an effective way. Thinking about it though, if you're firing a pistol from a car window, there may be a (perceived?) benefit in being able to rest the flat of the wrist against the window frame in order to steady your shot. --Kurt Shaped Box (talk) 17:30, 30 January 2009 (UTC)

Whatever rational they may use in their heads to try and justify collateral damage, I'm somewhat doubtful that they really don't care at all about collateral damage. For staters, they would know the cops are far more likely to be concerned it they kill an innocent bystander then another 'gangsta'. Also as Sean suggested below it's likely many don't want to kill anyone and I suspect even less an innocent. I think most people, even criminals do still have some moral compass even if it warped and may not stop them doing incredibly bad stuff. As with most matter, oversimpfying the people involved is a mistake. Of course this doesn't mean avoid collateral damage is a consideration in sideways shooting actually I agree there's a good chance it isn't. Nil Einne (talk) 17:19, 1 February 2009 (UTC)

Perhaps its intent is to *reduce* accuracy. Why would a gangsta want to do that, you ask? I can think of two reasons: 1) as a form of stotting, which is something gazelle will sometimes do to slow themselves down when being chased by a predator, as a way of saying "I'm such a badass I'll even give you a better shot at me", and 2) because even gangstas would probably prefer not to kill anyone; On Killing documented that many soldiers would deliberately miss their targets, and they -- in contrast to our gangsta -- were in a situation where they would be rewarded rather than punished for a successful shot. --Sean 18:16, 30 January 2009 (UTC)

According to one cop, it's done because it looks cool. DMacks (talk) 20:10, 30 January 2009 (UTC)

Engineering Book for Children

Please advise if there is a book which explains the basic priniciples of engineering that is geared toward children between the ages of 5 and 8 years old. Any type of engineering is fine. Thanks! --Emyn ned (talk) 14:09, 30 January 2009 (UTC)

The Way Things Work by David Macaulay. Gandalf61 (talk) 14:37, 30 January 2009 (UTC)

Actually, just about anything by Macaulay would work. He's got LOTS of great books for kids on all sorts of architecture and engineering, including Pyramid and Castle and Cathedral and most of these had filmed versions as well, IIRC. --Jayron32.talk.contribs 16:31, 30 January 2009 (UTC)

Quantam Mechanics, de Broglie wavelength, baseball

We know that the debroglie wavelength, which applies to all matter is given by h/p = h=mv. Suppose there was a baseball or pingpong ball traveling at a slow enough speed, or with a small enough mass such that the de broglie wavelength was visible (a) or the debroglie wavelength was large enough to measure, (b) on the magnitude of meters. What physical phenomenon would result? —Preceding unsigned comment added by 128.8.177.117 (talk) 14:10, 30 January 2009 (UTC)

What you're basically asking is "how would a very macroscopic object look if we regarded it as a quantum-sized object" which isn't terribly sensible. But let's just say, well, if a baseball could exhibit quantum wave effects, then you could do things like diffract it. It would, in certain ways, act like a wave. How would that "look"? Heck if I know. That's the problem in trying to apply quantum effects to macroscopic objects—it just doesn't make sense to our clunky macroscopic brains. --98.217.14.211 (talk) 14:26, 30 January 2009 (UTC)

Hm, my physics teacher tried to explain this to us at school. I really should have a deeper understanding of these matters now (and also this was back in 1988), but I don't and as far as I remember it goes like this: If you keep hitting ping pong balls through a slit (or two slits, whatever) at a wall (slit large enough for it to pass through, obviously), most of them would go through unimpeded (and hit the opposite wall directly behind the slit(s)). A few however would change direction (it'll probably look as though they bounced off the edge of the slit), *but* the funny thing is if you mark at the wall where the balls hit, over time you'd get a diffraction pattern. Wave of the ping-pong ball interfering with itself. 195.128.250.163 (talk) 22:34, 2 February 2009 (UTC)

My UFO Story or What did I see?

When I was a little kid, maybe about 5 - 7 years old, I saw what I thought to be a UFO an alien space craft. It looked like a half-moon, with red lights on each tip. That is to say that it was sort of a white-ish half circle with red lights at the tips. It flew across our backyard. I wasn't the type of kid to simply make up stuff or not be able to tell the difference between imagination and reality, so I think I really did see something. This probably would have been the mid to late 1970s. I lived in a major metropolitan area (Chicago) so if it really was an alien space craft, I would think that it would have been reported by lots of people, and I don't recall anyone else reporting this. Of course, I'm not sure I was old enough to be able to read a newspaper, so maybe it was reported, but I don't recall any of the neighbors talking about it. Anyway, I'm not one of those UFO nuts so I assume that there's a rationale explanation that doesn't involve aliens from outer space. But I don't believe it was my imagination either. Is there any type of aircraft that matches this description or comes in any way close to it? I lived a few miles from Midway Airport so there would have been a high volume of air traffic in my neighborhood. A Quest For Knowledge (talk) 14:46, 30 January 2009 (UTC)

You note that the UFO had red lights on each tip. Typically aircraft have a red light on one of the wing tips (presumably this is port side) and a green light on the other side (I presume this is the starboard side) as in ships. They also have a red beacon on the top and bottom of the fuselage. See: http://www.aerospaceweb.org/question/electronics/q0263.shtml You don;t mention whether it was day or night but since you could tell the colour of the fuselage was white then it must have been daytime or close to night. I can't tell you much about aircraft types but I would suggest if a plane was banking heavily, to line up with the runway of Midway for example, and orientated wierdly then just a typical jumbo could look a bit like a UFO to a 5 - 7 year old. Jdrewitt (talk) 15:28, 30 January 2009 (UTC)

I'm pretty sure it was night, or at least evening. A Quest For Knowledge (talk) 15:33, 30 January 2009 (UTC)

One point: You said "I saw what I thought to be a UFO". Since UFO stands for "Unidentified Flying Object", that's precisely what you saw. Unfortunately, many people use UFO to mean "alien spacecraft", which is a horrid misuse of the term. StuRat (talk) 15:56, 30 January 2009 (UTC)

How large did it appear in the sky? Did it appear larger or smaller than a half-moon in the sky? Did you notice any detail other than the red lights? Did it move towards the curved part of the half-circle, or the straight-edge part? Did it appear more yellowish or more bluish? How fast did it move? Did it move in a straight line or a more erratic pattern? Did the brightness of the object change at all during its flight? How long did you see it for? These questions may be useful in assisting the possible identification of the object. ~AH1^(TCU) 19:27, 30 January 2009 (UTC)

It sounds from the description like an airliner with the top and bottom beacons and some section of the fuselage between being lit up for some reason....perhaps some of the light from a landing light glinting off of the fuselage. The circular cross-section of the fuselage would certainly produce a semi-circular or 'moon-shaped' white area - and some part of the wing could cut it off to make a semi-circle...and it's no stretch to imagine the red beacons above and below. So there are without doubt ways to explain this UFO without resorting to little-green men. Even if that's not a perfect explanation - even if it requires a really extended set of coincidences (eg two planes flying parallel to each other to make two red lights with a third aircraft closer to you providing the white shape...or something) then it's still vastly more likely than that it was a flying saucer. This is the thing that UFO nuts don't appreciate. Even if there is only a one in a million probability of some particular chance formation of lights happening on any given observation means that perhaps 300 people will see such a phenomenon every single night...in the USA alone! In fact, when you stop to think about it - it's quite amazing that you don't hear more reports than we actually do! 20:15, 30 January 2009 (UTC)

If there was an airport nearby you might have seen a mirage. Good ones are so rare that one just doesn't expect it could have been that. I once spotted a perfect one of a bicycle on a neighbor's roof. All I could think was "What the...". Thank goodness aliens aren't reported to ride bicycles. (Except maybe in baskets.) 76.97.245.5 (talk) 20:57, 30 January 2009 (UTC)

AstroHurricane001 - I think it looked bigger than the moon. Probably at least twice as big. It was white-ish. I don't think there was a yellow or blue tint. It didn't streak across the sky like a lightning bolt and nor did it hover. I guess I would say it appeared to fly at a speed consistant with an airplane. It flew in a straight line, no crazy 90 degree turns that defy the laws of physics or anything like that. I passed overhead in maybe 2-3 seconds. A Quest For Knowledge (talk) 21:29, 30 January 2009 (UTC)

I and a friend of mine, an ex–Navy Seal, sat in a pickup truck and watched Venus for half an hour around sunset one time because it looked for all the world as if it was something in our atmosphere. Of course, we thought it was Venus, but neither of us had been keeping abreast of our planet positions, so we tested our theory by observation. I'm saying that two unsuperstitious, rather intelligent men were momentarily fooled by appearances. I have no doubt whatsoever that a similar phenomenon is responsible for 100% of the unexplained sightings of UFOs. As a kid I watched The Day the Earth Stood Still a hundred times, so I'd like nothing better than to take our new friends to our leader, but it ain't gonna happen. --Milkbreath (talk) 16:15, 31 January 2009 (UTC)

Skywarn Spotter Training

Does someone need to register with SKYWARN to take part in one of their classes. I can't seem to find the answer.Nick (talk) 19:01, 30 January 2009 (UTC)nicholassayshi

NEVER MIND!!! —Preceding unsigned comment added by Nicholassayshi (talk • contribs) 19:11, 30 January 2009 (UTC)

Atlantic hurricane tracks

Hi. In the image of the Atlantic hurricane tracks from 1851 to 2005 (see right), could anyone identify the following hurricanes shown in the map:

• The storm which tracked over southern Lake Simcoe as an extratropical storm at TS strength (wait, is it the Galveston hurricane of 1900?);
• The storm that made it across Mexico as a TD and tracked into the Gulf of California;
• The hurricane that tracked through the center of the Cape Verdes as a cat. 1, then quickly strengthened into a cat. 2;
• The hurricane that made it through the channel between Ireland and Iceland as a fully tropical cat. 2, then weakened to a cat. 1 as it passed north of Scotland;
• The hurricane that crossed northwestern Ireland as a fully tropical cat. 1;
• The extratropical storm which tracked across Ireland, Wales, and England at cat. 1 strength; and
• The extratropical storm that hit Lisbon, Portugal while weakening to TD strength.

Anyone able to identify these? Thanks. ~AH1^(TCU) 19:02, 30 January 2009 (UTC)

One quick answer:

• The hurricane that made it through the channel between Ireland and Iceland as a fully tropical cat. 2, then weakened to a cat. 1 as it passed north of Scotland;: Hurricane Faith (1966)

You could try contacting one of the regular members of Wikipedia:WikiProject Tropical cyclones. Someone there might be best able to answer your question. --Jayron32.talk.contribs 20:37, 30 January 2009 (UTC)

The storm that crossed Mexico and entered the Gulf of California is Hurricane Debby (1988). –Juliancolton ^{Tropical Cyclone} 20:40, 30 January 2009 (UTC)

Robert Burns and gold conductor

Robert Burns wrote a poem on wedding rings

She asked why wedding rings are made of gold;
I ventured this to instruct her;
Why, madam, love and lightning are the same,
On earth they glance, from Heaven they came.
Love is the soul's electric flame,
And gold its best conductor."

Where would he have got the idea that gold was the best conductor? I know silver and copper are better but Volta only invented the electric cell in 1800 and Burns died in 1796. Dmcq (talk) 19:17, 30 January 2009 (UTC)

I believe he meant that gold was love's best conductor, not gold. flaminglawyer 19:35, 30 January 2009 (UTC)

See history of electromagnetism. People knew about electricity (long) before batteries were invented. --Sean 20:00, 30 January 2009 (UTC)

Ben Franklin had experimented with electricity during Burn's lifetime, for example. bibliomaniac15 21:25, 30 January 2009 (UTC)

Thanks very much. I hadn't realized about them testing conduction using electrostatic machines. Following up that Franklin I came upon something by Joseph Priestly where he thought gold was a better conductor than silver. Burns kept up with things like that so that's probably where he go it from. See The Conducting Power of Gold which describes Priestly's experiments on the conductance of wires. I'm really quite surprised that his method gave the wrong result. He connected wires together of the same diameter and the one that didn't melt was the one he said was the better conductor. I would have thought the gold wire would have melted before the silver one as it has a higher resistance and has only a slightly higher melting point. So seemingly Burns was right according to the best science of the day. Dmcq (talk) 23:42, 30 January 2009 (UTC)

Resolved

Dmcq (talk) 00:45, 31 January 2009 (UTC)

Islam...

we all hear that Islam is the most expanding religion now ... why is that ... and whats the proof that its the right religion ... i heard they have scientific proofs that their book(Quraan) did talked about recentlly dicovered scientific facts before more than 1000 years ... thank you ...? —Preceding unsigned comment added by 212.38.147.41 (talk) 20:59, 30 January 2009 (UTC)

Extraordinary claims require extraordinary evidence. It's no good basing your whole philosophy of life on what's most popular, or what you heard; look it up! I doubt there's anything there, but who knows, maybe while riding on his magical horse Muhammad spied a coelacanth. --Sean 23:29, 30 January 2009 (UTC)

I would be interested in some evidence of these prophecies. I have not heard of them, do you have some reference that can be followed up? Dmcq (talk) 23:53, 30 January 2009 (UTC)

will i heared about how there shuttels couldnt leave the earth atmosphere but through acertain places in the atmosphere and such things ... i will look for it , but this will take time . —Preceding unsigned comment added by 94.249.99.222 (talk) 05:36, 31 January 2009 (UTC)

The number of Muslims is growing because, like poor people worldwide, they have a high birthrate.

Claims for amazing scientific insights in the Qur'an (like the old assertion that baseball is a Russian invention, and the ludicrous claims for the Kim dynasty in North Korea) derive from a deep societal inferiority complex. If the Qur'an, which among other things posits a flat Earth, were really a repository of advanced scientific knowledge, the Muslim world would not have to wait for Western scientific advances, and then claim that they were predicted 1400 years ago. Orthodox Muslims would be at the forefront of science and picking up Nobel Prizes in bunches. That they are not highlights the emptiness of such claims.

B00P (talk) 13:32, 31 January 2009 (UTC)

However, Islamic scholars were at one time far ahead of their counterparts in the West. Arabic Islamic scholars gave us algebra, algorithm, and alkali. Arabic Islamic mathematicians also gave us the cipher for zero. The BBC has a programme which is being shown at the moment called "Science and Islam", and the OP may wish to investigate the re-runs on the iPlayer. This link gives you Jim Al-Khalili's article. [4] —Preceding unsigned comment added by TammyMoet (talk • contribs) 15:12, 31 January 2009 (UTC)

There is no doubt that at one time, arabic mathematicians and other scientists were streets ahead of the the europeans. Quite how they lost that advantage is hard to say - but I've gotta guess that adherence to overly strict religion has a lot to do with it. When clear, open-minded thinking is discouraged in favor of mindless obeyance of some thousand-year-old tradition - science is guaranteed not to flourish. One only has to see the rise of christian fundamentalism in America doing precisely that. The pressure to tell our kids that evolution isn't one of the most solid scientific theories that we have - and the efforts to suppress stem cell research - signs of denial of the Big Bang - denial of global warming - these are classic examples of the same nonsense happening here. Newton was the closest thing modern science had to a priest at the turn of the last century. When Einstein said he was wrong - people were sceptical - when it was PROVEN that Newton was wrong (well - in realms beyond where he could test at least), the scientific world changed. Well, now we know conclusively that the garden of eden didn't happen - it's time to drop that dusty old book and go with something a little more real. 72.183.123.248 (talk) 23:55, 31 January 2009 (UTC)

...But what does the OP mean by "right religion"? The one referring to the real God? I hope he's not such a naive thinking, come on. A religion is an anthropologic and cultural phenomenon, and as such you shall explain its degree of success. And, of course, there is the individual contribution of some genial persons. Take for instance Paul of Tarsus, the inventor of Christianism: a true genial mind thinking big, like was John D. Rockefeller for capitalism. Had it been for the first Christians, they would have disappeared in few decades, like dozens of other messianic religions continuously appearing in that area. Paul was initially planning to make a career, as a Jew, fighting these Christians, but it was really not a worth job; then had the great idea (the anecdote says he drop from the horse at the illumination): "but what the holy fuck am I doing wasting my time in fighting these guys": he entered the bunch and in few weeks became their chief. He called himself "Apostolus", to make it clear. Then, he made special offers to everybody for joining the Christians: you don't need to be free man; you don't need to be circumcise; you don't need to be a man either, and many other facilities. He managed to become Roman citizen and to have the support of Rome. Nothing similar had been seen before. Recall that the oldest and more important religion of the area, Judaism, was extremely strict and very proud about its tradition. This way in few times he took over all small religions around and became the first Religious Group of the area, just like Rockfeller's Standard Oil at Cleveland when he swallowed every single refiner around. He too was thinking big, and started proselitism travelling and sending letters all around the Mediterranean sea, and finally got to Rome. To have an idea of his accuracy in all detalis, think of how he just planned the clothing. "I wanna last at least a couple of millenniums or so: who is here around that was able to do so? Egyptians, of course". Consequently, the clothings for the new religion were inspired to the Faraons fashion (look at the Pope, how dressed he goes around). Just to communicate: "We will stay here around forever". Of course you are free to think that there is the God's hand in the expansion of Christianism, or of Islam, or that Rockfeller was a philanthropist, &c... pma (talk) 00:22, 1 February 2009 (UTC)

A God that monitors which religion s growing fastest or is biggest or some combination of the two. A God that jumps on the latest bandwagon. That's a good one. Sounds like a politician, I am your leader, tell me what you want. Dmcq (talk) 12:07, 1 February 2009 (UTC)

will.. assuming there is agod ... and god want to give you a life way ... a path to walk on , some kind of ascale so you can know right from wrong ... now , how did you think that god should make you belive that he do exist , what kind of proof would you accept , will its easier to think that mother nature did this ... our creation not but acoincidence ... but if your ascientist then god will convince you by science

fact 1 ... in quraan ... sura(The believers) from(12-14) ([23:12] We created the human being from a certain kind of mud. [23:13] Subsequently, we reproduced him from a tiny drop, that is placed into a well protected repository.

[23:14] Then we developed the drop into a hanging (embryo), then developed the hanging (embryo) into a bite-size (fetus), then created the bite-size (fetus) into bones, then covered the bones with flesh. We thus produce a new creature. Most blessed is GOD, the best Creator.) this fact wasnt known before 1400 years ago ... i dont find any source said that this fact was known before the 1900 . so the question is did muhammed knew that ... or this is some kind of evidance from god .

fact 2 ... in quraan ... sura(women) (56) ([4:56] Surely, those who disbelieve in our revelations, we will condemn them to the hellfire. Whenever their skins are burnt, we will give them new skins. Thus, they will suffer continuously. GOD is Almighty, Most Wise)

will ... this one talk about that humans couldnt feel but by there skin ... so if your skin gets burned you will feel nothing and this is aproven fact in the modern science ...

so did you still think that muhammed knew that before 1400 years ago ... if not so who did ...??? —Preceding unsigned comment added by 94.249.85.66 (talk) 17:51, 2 February 2009 (UTC)

It is obvious that you have not checked any of what you say. Where people pick up the slightest thing in favour of their point of view are are blinkered to conflicting evidence is called confirmation bias. The reference desk will I'm sure be happy to help you check up on each particular item in your list. Dmcq (talk) 14:51, 3 February 2009 (UTC)

Hey 94, have you ever read the Iliad? To make only one example, the author perfectly knows about the flies laying eggs in the dead bodies, and the generated larvae eating the corpses (Iliad T ,25-28); read it, I'm not talking of allegories to be interpreted, but of precise statements even more clear that the ones in your quotation: and they are 1000 years older than yours. And the spontaneous generation has been confuted only in 1668 by Francesco Redi. But nobody claims that the Iliad's author was inspired by God (though, concerning how to write epic poems, he is a god). Now, the point is that if you say: "what is written in this book is God's word, therefore is right because God is omnisicent", it is not correct, because the complete statement should be: "In my opinion what is written in this book is God's word, therefore is right because etc.."; and since you are not God, the appeal to God does not give any authority to that book, nor to your opinion. Without offense, I cannot understand why so many religous people are so dumb that they don't see this small yet important logic detail. I do not even understand why so many people are so concerned about claiming that God exists/ God does not exist: but why to care about it? Suppose one proves one statement or the other: will this solve one of the thousands problems of the earth? Will this stop men to kill each other? You are free to believe or not, and I will respect your feelings, but keep it for you, and remember that it's just your opinion (and if you positively happen to find a real and true proof in one sense or the other, not just bullshit, no need to tell me: I don't think I would be so interested). --pma (talk) 02:07, 4 February 2009 (UTC)

Gravity escaping black holes.

How can gravity escape from a black hole? Taemyr (talk) 21:16, 30 January 2009 (UTC)

Complicated question, especially considering no one is entirely sure what gravity is represented as in our universe other than a feature of space-time curvature. Although it's believed to be conducted by a particle called the graviton, there is, as yet, no proof of this particle existing. The following website goes into a lot of detail in one of it's answers. It was a good read. Clicky. —Cyclonenim (talk · contribs · email) 21:25, 30 January 2009 (UTC)

Thinking more, another point of view is that black holes only attract particles into them due to gravity. If gravitons mediate this force, then they are doing the attracting, and are therefore unlikely to be affected by the field itself (since they must be massless). —Cyclonenim (talk · contribs · email) 21:29, 30 January 2009 (UTC)

Your speculation in general would be wrong. Massless particles, such as photons, are affected by gravity. We would however assume that massless gravitons are not themselves a significant source of gravity, which is an important distinction. (By contrast, gluons are themselves a source of the strong force and this ultimately leads to quark confinement.) However, as you say, gravitons are unobserved, so this is theoretical at the moment. Dragons flight (talk) 06:16, 31 January 2009 (UTC)

I was under the impression that gravity can't escape the black hole, and the gravitons pulling everything in are hawking radiation. The idea that gravity isn't effected by gravity wouldn't explain why black holes can have an electric charge. — DanielLC 22:19, 30 January 2009 (UTC)

I've never heard anyone propose gravitons are hawking radiation. I think you have a few things mixed up. And I'm no physicist but I really don't follow your logic about gravity being affected by gravity having anything to do with the electric charge. Gravitons shouldn't be affected by gravity—they are gravity. You can't electrocute electrons, it just doesn't make sense. --98.217.14.211 (talk) 01:11, 31 January 2009 (UTC)

Gravity being effected by gravity has nothing to do with electric charge. Gravity escaping a black hole does. Photons, which are effected by gravity, can mediate the electromagnetic force between the black hole and another object. There's no reason why gravity couldn't do the same. Also, I find it hard to believe that any particle could not be effected by gravity. What's keeping you from sending gravitons up, changing them to photons, sending them back down, changing them back to gravitons, etc. to create a perpetual motion machine? — DanielLC 16:45, 31 January 2009 (UTC)

And how exactly does one turn a graviton into a photon, now? Again, I don't see the logic in "gravity escaping a black hole"—gravity escaping gravity. Doesn't make a wit of sense to me—the gravity is not attracted by gravity, it is gravity. I think you're taking the particle model a little too literally here, or at least negating that the graviton must be massless. My understanding of this is not deep, to say the least, but I really don't follow your logic at all here; it seems totally implausible, sorry. --98.217.14.211 (talk) 17:07, 31 January 2009 (UTC)

Gravitational waves are a form of energy, just like electromagnetic waves. If you just want an example of how to convert between the two, you could use a charged pendulum. The gravitational waves would cause the pendulum to swing, and the moving charge would emit electromagnetic waves. Why would gravitons being the mediator of gravity prevent them from being effected by it? Photons are massless too. — DanielLC 00:57, 1 February 2009 (UTC)

You're confusing your own logic. Gravitons wouldn't be affected by gravity, just as photons aren't affected by light—because they are light! We're not saying gravitons won't be affected by gravity because they're massless, but rather because it is gravity. —Cyclonenim (talk · contribs · email) 20:34, 1 February 2009 (UTC)

We were overdue for a black hole question! Gravity does not escape from the object causing it, instead it is an effect on the space time by the mass. It may help you if you consider the formation of a black hole. To start with the mass is not behind an event horizon, and casues gravity in the normal way. As the mass approaches being a black hole, the mass or total energy does not change and the field remains the same. From your point of view outside the black hole, you never see the mass enter the black hole, so you would never see a vanishing of the gravity causing material. Graeme Bartlett (talk) 23:16, 30 January 2009 (UTC)

Books on string theory

After reading the thread above, and finishing the book, The Elegant Universe], I was wondering if someone could propose a book to follow on with string theory which is perhaps a tad more mathematical but still not a full-on dive into the realms of complicated mathematics. By this, I mean I'm an A2 student so I'm not sure I'd understand much more than A level maths. —Cyclonenim (talk · contribs · email) 21:22, 30 January 2009 (UTC)

I haven't read any so sorry can't recommend anything but String theory#Further reading gives some popular books, maybe google some of the titles and look for reviews. Jdrewitt (talk) 23:03, 31 January 2009 (UTC)

= January 31 = WE USE 10% OF OUR BRAINS, IT IS A PROVEN FACT, ONLY INSANELY SMART PEOPLE LIKE ALBERT EINSTEIN CAN USE MORE HE USED 13%, IT HAS BEEN PROVED, NO ONE HAS EVER BEEN KNOWN TO USE MORE THAN 13%

momentum object

If a point object is rotating at radius r, and the radius of rotation is suddenly halved, by the consevation of angular momentum the velocity will double. But how then is linear momentum conserved? Is there a force acting tagentially to the radius? —Preceding unsigned comment added by 70.52.46.213 (talk) 00:00, 31 January 2009 (UTC)

It's hard to imagine any mechanism that would abruptly reduce the radius without exerting some force - and right there, you've blown all hopes of appealing to conservation laws. SteveBaker (talk) 00:51, 31 January 2009 (UTC)

Right, there would have to be a radial force to reduce the radius, but this force would be perpendicular to the motion and so would not affect the speed of the object. —Preceding unsigned comment added by 70.52.46.213 (talk) 01:25, 31 January 2009 (UTC)

For every action, there is an equal and opposite reaction. Linear momentum will be conserved for the entire system, meaning that the barycenter of the two rotating objects will not exhibit a change in momentum. You can't have it both ways with the "instantaneous" change of velocity... any real force, such as a rocket propulsion system, would operate on a conservation of momentum principle. If the linear momentum of the space craft changes, then so must the linear momentum of the earth, or of the rocket exhaust gases, or some other entity. Nimur (talk) 01:52, 31 January 2009 (UTC)

I agree, but there still isn't a force acting in the plane of the object's motion. How can the tangential speed change is there isn't any force acting in the same direction? —Preceding unsigned comment added by 70.52.46.213 (talk) 02:41, 31 January 2009 (UTC)

In that case, (say an orbiting spacecraft fires a rocket towards the planet, with no component of the impulse along the current tangential motion), then the tangential speed does NOT change. The object moves to a lower orbit, and the orbit becomes elliptical, because it now has a tangential velocity that is too fast for circular orbit at the new radius. See orbital transfer for a good overview, and Hohmann transfer orbit for a specific example with diagrams of this situation. Nimur (talk) 16:48, 31 January 2009 (UTC)

Wouldn't that violate convservation of angular momentum and Kepler's Third Law?

No. If you're worried that something is violating conservation, make sure you consider all the components of the system. Don't forget the rocket exhaust gases! Those have mass and momentum, and they go somewhere! Let me emphasize - the rocket exhaust gases are not a "small effect" - they are the entire means of momentum transfer. Nimur (talk) 19:14, 31 January 2009 (UTC)

For concreteness, let's suppose the point mass is moving in a circle on a table and tethered to a string. Further suppose that string isn't simply anchored but instead feeds through a hole in the table so that someone underneath can shorten the string by pulling on it. As someone pulls on the string, the point mass will have a component of its velocity that it radial (i.e. carrying it towards the hole). Since the tension in the string is no longer perpendicular to the motion, that tension will act to increase the velocity. Incidentally, since the total velocity is increasing the centripetal acceleration must be increasing as well, which implies the puller will have to exert increasing amounts of force to continue. Dragons flight (talk) 05:53, 31 January 2009 (UTC)

Sorry, why would the tension force not be perpendicular to the motion?

Because the "pulling-in" motion needed to reduce the length of the string involves moving the object in the same direction as the tension. Dragons flight (talk) 19:11, 31 January 2009 (UTC)

Wouldn't that mean that there's a torque being applied, and that the angular momentum would increase? —Preceding unsigned comment added by 70.52.46.213 (talk) 23:22, 31 January 2009 (UTC)

No, if you calculate everything from the axis of rotation about the hole in the table, then the radial vector ${\vec {r}}$ (which is always measured from the axis of rotation) stays parallel to the force at all times and consequently the torque is always 0. In the case described above the velocity ${\vec {v}}$ ceases to be perpendicular to ${\vec {r}}$ during the transition but that is simply the same as saying that the object is not moving in a perfect circle. Dragons flight (talk) 00:09, 1 February 2009 (UTC)

Really - the bottom line here is that if you don't account for absolutely ALL of the forces, precisely, mathematically (not "Um - it seems like this...") then anytime you find anything weird going on, you are missing something. Probably something simple. Dragon flight's observation about the changing angle of that shortening string is a classic case in point. You think about the mass moving tangentially to the circle and the string acting at right angles to it - but the moment you pull on the string, the mass is moving in a SPIRAL - not a CIRCLE - and the string is not quite at right angles anymore because a line at right angles to a spiral doesn't go through the center of the spiral. Simply discounting this effect because it seems negligable is OK...right up to the point where you proclaim that you've managed to violate some fundamental law! Then you must carefully backtrack over your assumptions and find out where you screwed up. In this case, a spiral isn't a circle - so different math applies and I'm 100% certain that if you crunch the numbers, it'll come out right. It's not necessary for us here on the RD to actually do that - it's sufficient to point out "you've missed this effect" and move on. 72.183.123.248 (talk) 23:40, 31 January 2009 (UTC)

Ah thank you very much, I think I understand. Now for a loosely related question: Consider the table with hole and rope running through it apparatus mentioned above. If the spinning object had mass m, and was fired at a tangential velocity v at a radius r from the hole, and the other end of the rope was attached to a brick of mass mv^2/(rg), would the brick fall? —Preceding unsigned comment added by 70.52.46.213 (talk) 00:59, 1 February 2009 (UTC)

It seems to me that it wouldn't move. The thing to check for here is stability: if the brick falls a tiny bit, how does the force change? The radius decreases, so the rotator accelerates, and the centripetal force increases, opposing the falling brick. Conversely, if the brick rises, the centripetal force is reduced and lets the brick fall again. --Tardis (talk) 04:40, 4 February 2009 (UTC)

general theory of relativity

please explain this formula for a tenth grade student in detail$R_{\mu \nu }-{1 \over 2}g_{\mu \nu }\,R+g_{\mu \nu }\Lambda ={8\pi G \over c^{4}}T_{\mu \nu }$ thanks —Preceding unsigned comment added by 117.193.228.220 (talk) 01:44, 31 January 2009 (UTC)

I'll direct you to the key terms (i.e. metric tensor, stress-energy tensor, Ricci tensor, Ricci scalar and cosmological constant), but I believe it is impossible to explain this in detail to someone with a tenth-grade level of understanding. I won't rule out that some tenth graders may be able to understand it, but if they did so it would indicate a mastery of significant college level topics. In general, we also have an articles on Einstein's field equations and introduction to mathematics of general relativity as well as general relativity and introduction to general relativity. That last one in particular might be where you want to start. Dragons flight (talk) 06:06, 31 January 2009 (UTC)

I think it can be explained in a fairly simple qualitative way. The first part of the equation, $R_{\mu \nu }-{1 \over 2}g_{\mu \nu }\,R$, is called the Einstein tensor. It describes the extent to which space and time are curved or bent away from flat or Euclidean space-time. The term on the right hand side, $T_{\mu \nu }$, is the stress-energy tensor. It describes the amount of matter, gravitational energy and electromagnetic energy at or near a given point in space-time. Ignoring the cosmological constant, $\Lambda$, for a moment, we have

$R_{\mu \nu }-{1 \over 2}g_{\mu \nu }\,R={8\pi G \over c^{4}}T_{\mu \nu }$

which says that the curvature of space-time at each point in space-time is proportional to the amount of matter and energy near that point. The constant of proportionality, ${8\pi G \over c^{4}}$ is numerically very small when we measure it in everyday units of metres, kilograms and seconds - so this means that it takes a very large concentration of matter or energy to bend space-time by any measurable amount. But if you get enough matter close enough together - say something the size of a planet - then it will bend the surrounding space-time so that nearby objects tend to move towards it. This bending of space-time is what we call "gravity".

The cosmological constant term, $g_{\mu \nu }\Lambda$, means that even where there is no matter or energy density, and the stress-energy tensor is zero, space-time still has a built-in tendency to be curved. From observations of distant stars and galaxies, cosmologists now think that Λ has a small positive value, which means that space-time has a built-in tendency to expand. What we aren't yet certain about is the actual physical source of this built-in expansion - what exactly causes Λ to be greater than zero, and what gives it one value rather than another.

(Yes, yes, I know this is incomplete. If anyone feels I have over-simplified or missed out an important point, feel free to add your own simple explanations). Gandalf61 (talk) 11:09, 31 January 2009 (UTC)

The equation is expressed in terms of tensors and you really need to understand these before you can understand the equation. Our article on tensors is quite confusing for beginners. Instead, I recommend that you read the opening chapter of of this book which you can read online. It explains the concept in a very accessible way. SpinningSpark 11:47, 31 January 2009 (UTC)

electrodepostion of copper, efficiency of cathode?

In an experiment when measuring the percentage copper in copper ore by electrodeposition, i have read that cathode efficiency (which is the ratio of weight of metal deposited and the weight that would be if all the current had been used for deposition) is not always 100%, why is this? —Preceding unsigned comment added by 146.179.199.116 (talk) 15:48, 31 January 2009 (UTC)

Not every electron coming off that cathode reduces a copper ion to make copper metal. Some may reduce hydrogen, some may make a negative ion, some may reduce something that is immediately oxidised. Graeme Bartlett (talk) 21:09, 31 January 2009 (UTC)

Make our brain store memory.

Well we're all obviously familiar with how the brain functions in relation to storing memory and all. But just last week i was just sitting down and doing some random thinking when it struck me.....how is it that when we experience something really good or really nasty or anything for that matter the brain stores it in the memory.....something like your first girlfriend or your first day at your first job or your children's wedding day ,it automatically gets stored in the brain.....but at other times when you experience something and you know it ain't that great a memory but you want it to last forever and no matter how much you tell your brain "STORE IT" -- it never will. So my question is WHY?..WHY can't we tell our brain to store memory for us? Wouldn't that be such an amazing thing?You know like a normal hard drive....where you write something in a notepad file and save it and VOILA! its stored on your hard drive forever unless something tragic happens to it.On the same lines WHY can't ALL HUMANS DO THE SAME?ANd i mean like you just tell your brain - integral of cos(x) is sin(x) and it just saves it the first time you tell your brain to do it such that it never gets deleted from your memory I know the neurons get destroyed and all and the memories might get lost but even then in the short term .....example a year!Imagine a student whose a science student and hates history but has to pass it.If he just read through the textbook in one full day and told his brain to remember it ,he would not have to study it ever again and at the end of the year when the exams get over he could easily ask his brain to remove that memory.Wouldn't it be terribly advantageous?Why haven't we as humans tried this on a large scale?Or as a matter of fact why is it not possible? STEVE,if your reading this do answer! i know you might have something to say on this!Vineeth h (talk) 15:52, 31 January 2009 (UTC)

You can force yourself to memorize things, by repeatedly thinking of them many times, over many days. For example, flash cards can be useful to memorize things for a test. If, however, you don't care about it after the test, and never think about it again, it will slowly fade from memory after that. Only thinking about it from time to time will cause the memory to be retained. StuRat (talk) 16:01, 31 January 2009 (UTC)

Have also a search to the archive of this RD, because I remember this is a recurrent topic, although I do not remember exactly everything that has been said --you know, it's human memory pma (talk) 18:34, 31 January 2009 (UTC)

Unfortunately we don't know how the brain functions in relation to storing memory. We have clues and models based on those clues, but we don't have a a precise mechanism worked out yet. Further, memory is is probably encoded by many different mechanisms, depending on what type. For example, most people can "tell themselves" to remember something trivial and recall it a short time later. Some people are extremely good at this and others poor, probably for genetic reasons, but most people can get reasonable good at it with the right training. But long term memories (such as events in your life that made an emotional impact) are likely to be encoded in a very different way. They way these sort of memories are stored and retrieved do not lend themselves to that sort of training, and thus are outwith conscious control. This is probably a evolutionary relic of the origin of the two types and what parts of the brains they are encoded in. How and why is not known for sure, but I'm sure there are lots of models out there. Rockpocket 18:56, 31 January 2009 (UTC)

I imagine noradrenaline has something to do with long-term storage of memories, and other catecholamines which are released whilst experiencing something highly emotional. Where as revising is not at all emotional. --Mark PEA (talk) 23:25, 31 January 2009 (UTC)

See amygdala, part of the limbic system of the brain. The amygdala is involved in learning under particularly emotional conditions (fear, reward, etc.). It's hooked up to the hippocampus which is known to be involved in memory formation. You might be able to harness the amygdala for learning, say calculus, but you'd have to make the accompanying stimulus either really good or really nasty...--- Medical geneticist (talk) 04:25, 1 February 2009 (UTC)

Well thats all good...but you guys still haven't understood my question.....We've all seen "the matrix" right?Or atleast i'm hoping most of you have.Well you know how NEO finds out that they're all infact controlled by machines and stuff......like someone else is controlling them.....well in the same way.....well StuRat you said if we keep saying it over and over again we'll remember it.....but its going to fade away really really soon....and definitely wouldn't last a little over a month!....Its almost as if we aren't in control of our brain!...we can't make it do anything we wan't it to do.....its the brain making us to what IT wants us to do!.....so the real question was that we aren't in total control because like the others mentioned.....various chemicals are responsible and stuff and these aren't released because we tell them to be.....its our brain making all this happen!.....so it may sound pretty dumb but really if you think about it you really can't make your brain to much.....its like your a slave to your brain most of the time....It's like a symbiotic relationship.....we have the brain to make decisions and the brain has our skull for protection! but its just that its got a more parasitic character cause its in control almost all the time.......So really will be ever be able to be in total control over our brain? Yohttp://en.wikipedia.org/enwiki/w/index.php?title=Wikipedia:Reference_desk/Science&action=edit&section=41u know literaly make it do even the SMALLEST of things that we want it to! You know i was just thinking of some more advantages.....think of a person with a tumour somewhere on their body and suppose that there's a cancerous growth of cells there...well instead of the doctor having to do something to break down the cancerous cells we could just take in the medicine orally and tell our brain to transfer the medicine via the blood stream and control it to move in such a manner that it directly reaches the tumour and starts working on it.....Well i don't know about you guys but it'd be pretty interesting if we could do this......and i do have some more crazy ideas but it'd be quite long.....so in short WHY CAN"T WE DO THIS!Vineeth h (talk) 06:00, 1 February 2009 (UTC)

On a practical level, we can't do it because we don't have the molecular mechanisms in place to do so. How exactly would your brain transfer medicine via the blood stream directly to one cell? Our bodies don't work by magic, they use electrical signals, chemicals and proteins to communicate between cells. Even if you can come up with some feasible mechanism for how this could work, it would require millions of years to evolve. For 99.999999999999% of human evolution there was no anti-cancer medicines, so there was no advantage to evolving a mechanism for delivering it!

On a more fundamental level, you are making the mistake of thinking of your consciousness as a little person sitting in in your skull, pushing buttons and telling your body what to do. It doesn't work like that. What you think of as "you" - really your consciousness - is created by your brain. So ultimately it controls you, because "you" don't exist outside the electrical connections of a few million neurons. If it makes it easier to understand, consider that your genes encode a brain that has made a "Matrix" that your consciousness exists in. Your genes have reserved a part of the brain, the cerebral cortex, for your consciousness to use for its own ends. Its this part that your consciousness has some control over. But your genes keep the rest of the brain for itself, particularly the limbic system, which is involved in emotion, instinct, and long term memory. These things are really important in ensuring your survival (and hence the survival and reproduction of your genes, which is the ultimate goal). Hence your genes are going to make sure it is reserved for these important functions, and not "stolen" by your consciousness to store some history homework for a week! Rockpocket 08:28, 1 February 2009 (UTC)

With all due respect, Rockpocket, aren't you unquestionably implying materialism in that reply? --ReluctantPhilosopher (talk) 16:12, 1 February 2009 (UTC)

Yes, I am. I purposely expressed a rather simplistic eliminativist explanation for maximum contrast with the OP's position. Rockpocket 19:25, 1 February 2009 (UTC)

But should we be peddling our prejudices on the refdesk? ReluctantPhilosopher (talk) 15:13, 2 February 2009 (UTC)

If forgoing a spiritualist explanation in favor of a purely scientific answer is prejudicial in your opinion, then yes. This is a science refdesk and science deals with matter, molecules, cells and their interactions. Neuroscientists, in general reject dualism. Reflecting that in an answer is hardly peddling prejudice in my opinion. That said, the OP may also be interested in reading our rather good philosophy of mind article, and make up his own mind. Rockpocket 20:31, 2 February 2009 (UTC)

The degree of conscious control that out OP considers would be rapidly lethal to us! If we could consciously control all of that super-delicate machinery - without the slightest understanding of how it works - then you could easily make a mistake and kill yourself. Protecting your body from your conscious mind is a vital part of what makes our bodies work. Suppose you got distracted and forgot to make your heart beat - or if you turned off blood supply to your left leg and forgot to turn it back on again! No - this would be nothing short of a death sentence! SteveBaker (talk) 15:00, 1 February 2009 (UTC)

The OP should read up on determinism and Free will#In science. "You" cannot control your brain's actions because "you" are the result of your brain's actions. Of course this sparks many debates with almost all religions and the whole topic of spirituality. Ethical issues are discussed in the determinism article also (i.e. is someone with a psychological illness guilty of their actions, when they commit a crime). You can then ask the question if other mammals have free will, if anything with a CNS has free will, or maybe even a bacterium. Or you can just believe that neurons process it all and there is no "spirit" --Mark PEA (talk) 20:19, 2 February 2009 (UTC)

Grrr... if only I had the references... I will eventually get them and fix the biased articles written by materialists and determinists. I already fixed the free will article some time ago which, in all it's magnificence, had no section on libertarian (non-compatiblist) free will at all before. _lol ReluctantPhilosopher (talk) 16:45, 3 February 2009 (UTC)

If anyone can help me out here... two of the references I am looking for are the ones that say that 1) Physicists today reject out of hand any theory that denies free will (I heard this in a program on Discovery channel about the current theories of the universe and its origin), and 2)Most physicists try to keep free will out of their theories because it confuses matters (I read this on some webpage). Or may be I'll have to ask at the humanities web page. I know some wonderful philosophers who are much clearer on the issue involved in the discussion of free will than most of the physicists. Read this for starters. It's a must read for those who think the issue of free will can be settled through physics --ReluctantPhilosopher (talk) 17:03, 3 February 2009 (UTC)

Best way to pour liquid out of a cup without it dribbling down the side?

Does physics have something to say about this? Thank you Louis Waweru  Talk  16:05, 31 January 2009 (UTC)

Surface tension is a general idea of liquid sticking together as a blob (cohesion among itself) rather than just going with gravity as a perfect liquid would, and adhesion to the vessel could then pull that blob away from "straight down". More technically, consider the contact angle between the liquid and the edge vs the angle at which the edge is while pouring. DMacks (talk) 17:42, 31 January 2009 (UTC)

In fact, for this operation chemists usually have a glass stick into the lower vessel, so that the liquid adhere to it instead of adhering to the cup's side, especially when the liquid has to be poured very slowly. This also works for everyday needs, of course. Another way to prevent adhesion to the cup (only for kitchen use) is, pouring the water or milk with a certain velocity; I follow this method with reasonably good results, say I made only few disasters, very seldom. It's important to remember that the lower cup has to be stable enough, otherwise the flow just take it away on the floor. pma (talk) 18:25, 31 January 2009 (UTC)

So, putting a chopstick or something in the lower glass, and pouring onto the chopstick? Is that the idea? (Just tried it, works much better!) Louis Waweru  Talk  19:21, 31 January 2009 (UTC)

Yeah, just hold the chopstick over the top of the container you need to pour liquid out of and let the liquid run down the chopstick into the other cup. 96.242.34.226 (talk) 19:42, 31 January 2009 (UTC)

And if you need to use it frequently, you may want to get the apposite tool, which is named stirring rod (here [5] is a quick view). There are of various sizes, both for lab and kitchen, usually by glass. If you google it you'll find a lot of info about where to find it, and how to use it properly (like this [6] for lab's use). pma (talk) 20:05, 31 January 2009 (UTC)

I've noticed this problem is worst when pouring a small amount out of a large container, especially when the liquid is quite thick. This comes up often with liquid laundry detergent. One solution I've seen is a double circular rim. The detergent pours out of the inner rim. The outer rim catches any spills, and they slowly dribble back down a drainage hole (DH) back into the container. The top screws on outside the outer rim. Here's a cross-section:

         INNER
          RIM 
         |    |
   <-  | |    | | OUTER           HANDLE
 POUR  | |      | RIM      +-------------------+
  DIR  +-+  DH /           | +---------------+ |
         |    /            | |               | |
     +---+    +------------+ +---------------+ +--+
     |            CONTAINER                       |

StuRat (talk) 01:56, 1 February 2009 (UTC)

Electric shock

Is there a danger of getting an electric shock when a person(standing on the ground) touches one of the wires of two phase generator of electricity that is not grounded? —Preceding unsigned comment added by 202.70.74.181 (talk) 17:46, 31 January 2009 (UTC)

Definitely. It sounds like that arrangement is a guaranteed way to create a life-threatening electrocution hazard. Worse yet: the most dangerous hazard is the possibility that the wiring is not correct, or does not match the schematic, or otherwise has high voltage and high current in places you might not expect. Even a wire which "should be" safe may actually be live. You should always assume a wire is live and dangerous unless you are trained to make a more thorough assessment. Nimur (talk) 19:18, 31 January 2009 (UTC)

Well its definitely not a safe thing to do but I think the question was more theoretical. If the generator is genuinely isolated from earth then you should not get a shock if you were to touch only one conductor. However, it is too difficult in practice to prevent accidental grounding in a real electrical distribution system. The only places this is done to my knowledge is on oil rigs were sparks to ground are a bigger safety hazard than electric shock and even then there are additional safeguards. SpinningSpark 01:25, 1 February 2009 (UTC)

Urban legend regarding pitbulls

Is there any truth to the claim that if a pitbull is allowed to taste human blood, it will become uncontrollable and keep attacking humans to experience that delicious taste again(and likely have to be euthanized)? Is this true of any dogs, or any animals? 69.224.37.48 (talk) 19:51, 31 January 2009 (UTC)

No. — Lomn 22:38, 31 January 2009 (UTC)

No. They don't do that for (for example) cow blood. A dog that once tastes a steak doesn't subsequently lose all control of itself whenever there is another steak around. Why would human blood be any different? Nope - this is nonsense...please tell whoever told it to you. The world needs fewer of these stupid urban legends. 72.183.123.248 (talk) 23:24, 31 January 2009 (UTC)

Okay, no, dogs that taste human blood don't inherently go crazy and become uncontrollable. However, there is still some legitimate cause for concern. An animal that bites people may be sick or dangerously vicious (not because blood makes it crazy, but because it was already violent to begin with). The former may be treatable, while the latter might be controllable with reasonable precautions. There is also a risk that some animals that bite people might come to think it is okay to do so again in the future, i.e. a form of learned behavior, so one needs to be careful about not encouraging such behavior. In general, a dog that has bitten people is probably one that it is best to keep away from unfamiliar people and take greater care around. I will also note that it is common in many jurisdictions to euthanize animals that have attacked people. Dragons flight (talk) 00:28, 1 February 2009 (UTC)

There is cause for concern - sure. If a dog gets the idea that it is the alpha-dog in the 'pack' of humans with which it lives then the humans who live with it had better plan on taking back the alpha slot - or being continually hassled by the dog. If the dog tries this on - you need to wrestle it to the ground - roll it onto it's back - place your hand around it's throat and squeeze gently. This says "I am the dominant animal in this pack and don't you ever forget it!". You also need to ensure that when you and the dog approach a doorway - you go first. Don't feed the dog until AFTER the family has eaten. Make a point of taking away the dog's food while it's eating (you can give it back later). Basically, it's got to know that it's place in the pack is somewhere below the lowest human. This seems a little sad - but a dog is happy to be what it is. What they don't like is uncertainty. 72.183.123.248 (talk) 02:14, 1 February 2009 (UTC)

That's good advice ....248. There are no bad dogs just bad owners. Richard Avery (talk) 08:40, 1 February 2009 (UTC)

Its good advice except for the rolling the dog on its back part. This actually says to the dog "I am going to kill you." Would you feel comfortable living with someone who was threatening your life everytime you walked in to the room? Especially bad if the dog is violent. Don't do this. Livewireo (talk) 20:34, 2 February 2009 (UTC)

i dont want JOWLS

how do i keep from getting JOWLS when im old. i'm 25. this is not a request for medical advice. —Preceding unsigned comment added by 82.120.227.157 (talk) 21:07, 31 January 2009 (UTC)

There are exercises you can do. One is to bring your bottom lip over your top one and hold it there for 5 seconds, then relax. Then do the same thing while smiling. Also keeping all your teeth helps! --TammyMoet (talk) 21:39, 31 January 2009 (UTC)

Unfortunately, a lot of this stuff is genetic; if you dad and/or mom had jowls, you are more likely to have them as well. --Jayron32.talk.contribs 22:25, 31 January 2009 (UTC)

February 1

How delicate is the universe?

If the universe was one millidegree cooler would it be nonexistent? Would it regret not having created me to gaze at it's wonders? One little atom out of place and the whole thing collapses? Is it that sensitive? Has a mini universe ever been created in the labratory under slightly different conditions? If so, I wonder if any scientist ever snapped and became "God" of his newly created universe?--Dr. Carefree (talk) 00:47, 1 February 2009 (UTC)

$(no)^{6}\,$

SpinningSpark 01:28, 1 February 2009 (UTC)

If you don't have an answer - please don't answer. K'thnks. 72.183.123.248 (talk) 01:48, 1 February 2009 (UTC)

Well, on the bulk scale - the universe is the exact temperature it is for some reason or other (I don't know why) - if it were even a millionth of a degree different than it actually is then there would have to be something different about it at the start. The subtle difference in temperature might not be enough to make a very large difference - but the fact that things were different at the outset might be exceedingly significant. The cosmic background temperature is around 3 degrees kelvin - so a 'millidegree' would represent an 0.3% change - that implies a pretty large change in one or more fundamental constants or one or more laws of physics. That would cause who-knows-what consequences...maybe stars don't form or planets don't orbit. It's really tough to speculate on (a) what might cause a one millidegree difference and (b) what the consequences of that difference might be.

We haven't created any other universes - we have no idea (even in principle) how to do that - and the amount of energy that might take sounds like it would be impossible for us to obtain...but who knows? Was our universe created by some little green man with a white lab coat and a petri-dish? We don't know - we can't ever know - so it's pointless to speculate.

The 'anthropic principle' really does apply here. If the universe were different than how it is - then we could be different too - and we'd still be asking the exact same question of the different universe. If the universe were different in some other ways, then perhaps sentient beings would be impossible - or perhaps stars would not form - perhaps even atoms might not exist. In those cases, there would be nobody there to speculate. If we buy into the idea that there are an infinite number of universes out there - then (by definition) we MUST live in one that allows us to have to evolved - so the precise conditions (however far-fetched) that are required to make a creature exactly like us MUST be the conditions in any universe in which we are present to observe it. The anthropic principle is a less comfortable explanation than "The charge on the electron absolutely has to be such-and-such because <some really good reason>" - but in the absence of such a reason, it is a good explanation.

72.183.123.248 (talk) 01:48, 1 February 2009 (UTC)

Temperature isn't constant, either in time or space, so it can change without any significant consequences (depending on what caused the change, there may be other consequences in the details, but the basic structure of the universe and physics would be the same). It's more interesting to consider what would happen if various physical constants were changed. I've heard that changes to some constants of less than 1% would make it impossible for stars to form, or other consequences that preclude life as we know it. So, in that sense the universe it pretty sensitive. We do, of course, have an article: Fine-tuned Universe. --Tango (talk) 14:00, 1 February 2009 (UTC)

The current temperature of the Universe (which I take to be the temperature of the cosmic microwave background) is 2.725 Kelvin. As the Universe expands its temperature drops, and it will be cooler by 1 millikelvin in about 5 million years (computed with Ned Wright's cosmology calculator [7]). If there are astronomers around at that time, they will measure a lower temperature than we do today and there will be nothing weird about that. The actual temperature is largely a contingent feature of the Universe, it is not prescribed by any physical principles; it is more a question of when it is measured. There is presumably a time window of some sort in the history of the Universe in which intelligent life can form and exist, and that time window can be translated into a "temperature window". That window is, however, certainly much larger than the 1 Millidegree (or 5 million years) you quote. Incidentally, 1 millidegree corresponds roughly to the accuracy of our measurements of the mean temperature of the CMB. --Wrongfilter (talk) 14:25, 1 February 2009 (UTC)

How much would an outside observer (an alien scientist, if you like) be able to determine about life on Earth as a whole...

...from the study of one living earth creature? Supposing the one creature was (just an example chosen at random from the bird articles on my watchlist) a Green Cheeked Conure of the female sex. By examining just this one bird as a representative of all life, what (correct) conclusions could be drawn? --Kurt Shaped Box (talk) 02:07, 1 February 2009 (UTC)

Quite a lot, I would imagine. If the scientist could keep the poor creature alive (which would be very hard) he'd know something about atmosphere, temperature range, gravity, etc. But the odds are good that the creature would be dead in short order...but even so, you'd find a lot about biochemistry. With technology like ours, it might take a long time to figure out things like DNA - but that depends on how similar we are to them. If (for example) they are very similar to us - then the relative differences would tell them a great deal in detail. If they are very different from us (I dunno - silicon-based lifeforms from a high gravity, high air pressure planet where temperatures hover around 100degC all the time) - then they'd see that the spindly legs and the light build implies less gravity - and the nature of the lungs and flimsyness of the musculature for operating the lungs would suggest that there is a less dense atmosphere than they are used to. Liquid water everywhere in the body tells them that the temperatures must be lower...there's a lot they could figure out. But I doubt those silicon beings would be able to fathom out the function of DNA (for example) with a dead parrot. 72.183.123.248 (talk) 02:25, 1 February 2009 (UTC)

Nothing about life as a whole. Any generalized conclusion would be invalidated by nonprobability sampling. The only think one could infer would be that there is at least one species that can fly, has feathers, has DNA, etc. They could infer things about the earth's environment, though Rockpocket 02:32, 1 February 2009 (UTC)

Thanks. When I posted my Q, I was actually thinking about how human astronauts would go about studying the life in the hypothetical oceans of Europa from a single specimen, or a small number of specimens that they managed to fish out by pure luck during a manned mission. --Kurt Shaped Box (talk) 02:50, 1 February 2009 (UTC)

First off the scientist would have more than one species in their hands. The bird is essential a viral and bacterial colony. Furthermore by looking at the organelles of the cells they could infer a great deal out evolutionary history. They would be sure that there was "at least one" but it would be foolish not to infer such a complex creature is at least representative of a portion of the unknown planets life. Just from the design of GI track the scientists would know some constraints concerning its diet even if the bird had its stomach pumped before abduction. If they could read the birds genetic structure they could probably start making extrapolations about its genetic heritage and evolution. If I found an alien critter that couldn't live in our environment I would promptly freeze it and start looking for the things I've described above. Of course the first thing to do would be to get a handle on its fundamental chemical make up which I didn't discuss but we haven't provided time constraints. It would take years, huge amount of resources by our standards, and a host of researchers but it would be ultimately informative.

I know modern science insists on postulating that there are endless possible forms life, ie alternative biochemistry. I believe this more was developed to avoid developing a anthrocentric perspective which makes sense. At the same time I've never heard of any molecular system that could accomplish the task that our proteins and DNA accomplish. No one has been able to suggest anything reasonable for silicone biochemistry. This lack of an alternative wouldn't be a big deal if there was more elements to discover but there aren't. So it seems reasonable to expect a fair amount of convergent evolution; which we see all over the place in nature, my favorite example is social insects. The alien very well may have the opposite chirality on a molecular level, run some metabolic process the opposite way, and have a drastically different appearance. But odds seem high to me that they evolved to manipulate metal in a very similar way we did. Hell even their bodies temperatures upper limits are probably governed by the temperature at which most proteins denature around 40C. I say that with full respect for extremophiles while noting that they are all unicellular or close to it. Multicellulars don't do real well above 40C unless its at high pressures. Thus the qualification begins. So I'll end there, comment please.--OMCV (talk) 03:05, 1 February 2009 (UTC)

I wrote my answer before the last entree you might want to check out [8] it talks about life sense devices with the potential to be on future space missions.--OMCV (talk) 03:09, 1 February 2009 (UTC)

Interesting, thanks. I wonder if NASA has yet devised a 'standard procedure' for the handling and storage of extraterrestrial biological specimens, what with the manned Mars and deep-sea Europa missions possibly happening in the not-too-distant future? I can't help but wonder what they'd actually do if they chanced across something macroscopic. --Kurt Shaped Box (talk) 17:27, 1 February 2009 (UTC)

OMCV makes a good point, we shouldn't under-estimate how much scientific value one can obtain from a single sample. I know I said the "only thing" one could infer, but even proving that there is at least one alien species that respires, has carbon based DNA etc would without a doubt a scientific discovery of the century. Moreover, comparative studies of our vast knowledge of life on our own planet would enable many general conclusions to be drawn, many of which would probably prove to be correct. But taking these beyond the level of hypothesis would require greater sampling, though. Rockpocket 03:11, 1 February 2009 (UTC)

If they fail to understand anything, they can safely say that Creationism has control over Earth too :) manya (talk) 04:24, 2 February 2009 (UTC)

explanation on tensors

please help me, a tenth grade student in detail abt tensors. please. i have understood the special theory of relativity but i want to do the same on general theory of relativity. --Harnithish (talk) 02:40, 1 February 2009 (UTC)

There is some information in the tensor article regarding applications to physics, and links from there to more detail. If you have a specific question, people here may be able to help if you state it clearly. For some aspects of tensors, the math RefDesk may be a helpful alternative. Best wishes for your studies - sounds like you are off to a great start! --Scray (talk) 17:17, 1 February 2009 (UTC)

The simple answer is that tensors are complicated beasts, and as a 10th grade student you would almost certainly have trouble understanding them. However, that doesn't mean you shouldn't try, and as such it would probably be good for you to first get a grasp of vectors and matrices, and of calculus - particularly solving differential equations. Tensors are then an extension of vectors and matrices, and then in differential geometry and GR calculus is added into the mix. You might also want to track down the book "Gravity: An Introduction to Einstein's General Relativity", by James Hartle, which takes an approach that avoids a lot of the tensor calculus and looks more at things in terms of undergraduate physics. Confusing Manifestation(Say hi!) 23:30, 1 February 2009 (UTC)

books on physics theories

is there some book which can be e-downloaded freely on quantum theory, string theory, general theory of relativity and something exciting for the students in the age group of 14-16--Harnithish (talk) 02:58, 1 February 2009 (UTC)

I don't know about the age range - but here are the freely downloaded "books" that I could find:

Wikibooks (a Wikipedia sister project) has two books on Special relativity [9] - one at undergraduate level and another at an 'intermediate' reading level that only requires basic algebra as a prerequisite. There is a general relativity book - that appears to be about half-finished - but it looks too complex for 14-16 year olds because it goes into tensor algebra and such. This is alse a book on String Theory that's in the process of being written - but it's very sketchy right now. We also have This Quantum World - which also seems a little high level - although 16 year old's might manage it if they have been doing calculus at a level similar to British 16 year-olds rather than the rather pathetic level that it's taught at in US high schools.

Project Gutenberg has a vast repository of free eBooks - including Einsteins' own book on Special and General relativity:[10] (you can read it in the original German too!) - It's actually surprisingly readable. They have Lorentz's book on the same topic [11]

Wikisource (yet another Wikipedia sister project) has [12] which is Einsteins rebuffing of people who disbelieved in relativity. It's somewhat entertaining. Wikisource also has [13] Einstein's book that I mentioned earlier.

Wikiversity (yeah - guess) has a couple of 'courses' on Quantum theory: [14], [15] on Special relativity and [16] on General relativity.

Sadly, most of those things descend into a sea of equations pretty quickly. Surprisingly, perhaps, Einsteins' works are the pretty approachable if you take it slowly and work to understand each part before skipping on to the next. Well, I'm not sure I helped very much...but that's what I found. SteveBaker (talk) 00:18, 2 February 2009 (UTC)

Hey, how do they know they've discovered methane (tm?) gas on Mars?

That's like,-way over there. And we're we're like,-down here. Were at the center of the universe (comparatively speaking). With no machinery or people on Mars, how can they tell? Sometimes I wonder if scientists are just desperate for headlines and figure we'll believe anything. Sorry.--Hey, I'm Just Curious (talk) 03:28, 1 February 2009 (UTC)

By using NASA's Infrared Telescope Facility and W. M. Keck Observatory both in Hawaii. The scientists attached spectrometers to the telescopes to spread light into its component colors. They looked for dark areas in light spectrum where methane was absorbing sunlight reflected from the Martian surface. They found three - so-called absorption lines - which together form a definitive signature of methane. They were able to distinguish the Martian methane from that in Earth's atmosphere because the lines were disturbed in sync with the planets motion. Rockpocket 03:37, 1 February 2009 (UTC)

There is an example of of methane's IR absorption fingerprint on Methane (data page) near the bottom of the page.--OMCV (talk) 03:42, 1 February 2009 (UTC)

Well, we do have quite a bit of machinery on Mars - Spirit rover and Opportunity rover for example. We also have Mars Reconnaissance Orbiter and something like four other spacecraft in orbit around Mars. But in this case the information was obtained spectrographically from an earth-based telescope. We routinely collect spectrographic data from stars that are millions of lightyears away - so this isn't that tough to do! Each chemical absorbs and reflects light differently - which is why some things look different colors to others. By splitting the light coming from Mars' atmosphere into a spectrum (a 'rainbow' if you like) there are lots of dark lines corresponding to colors that should be there in the sunlight - but aren't there in light reflected back from Mars because something is absorbing it. Some of those missing lines evidently correspond exactly with the precise colors that methane gas absorbs. The exciting thing is that methane cannot exist long in the atmosphere of a planet - so whatever put it up there is still making the stuff!! Since the most common source of methane on Earth is animals - one possible reason for the methane to still be there in the Martian atmosphere is because there are still living creatures there...which would be a very exciting conclusion! Sadly - as with the other signs of life on Mars that we've seen, this is not 100% conclusive because there are complicated non-biological processes that could possibly produce methane too. SteveBaker (talk) 04:50, 1 February 2009 (UTC)

I don't know, but we can smell the methane gas around Uranus from here. —Preceding unsigned comment added by 82.120.227.157 (talk) 14:28, 1 February 2009 (UTC)

Methane is an odorless gas....oh...wait...you were trying to be funny right? Oh, OK - well...um...ha,ha then. SteveBaker (talk) 14:48, 1 February 2009 (UTC)

Now, the next step for the scientists is to determine whether the methane was produced by biogenic or abiogenic sources. This is why the news became so exciting. ~AH1^(TCU) 17:54, 1 February 2009 (UTC)

Are you saying that there's something living on the surface of Uranus?

Sorry. --Kurt Shaped Box (talk) 17:59, 1 February 2009 (UTC)

Clearing Brush

I was wondering about the activity that former President Bush enjoyed at his Crawford Ranch. What does "brush" consist of? What is the purpose of clearing brush? Is it to use the soil for agriculture? Once the brush is cleared, what is usually done with it? What kinds of tools are used to clear brush? Is the process mechanized, or still done by hand? Are there people who do this as a profession? 211.109.12.170 (talk) 04:31, 1 February 2009 (UTC)

The brush normally consists of fallen tree branches (or entire trees), dead bushes, fallen leaves, etc., and sometimes also live trees or bushes. The primary purpose of clearing brush is to prevent fires from spreading. A secondary purpose is to allow easy access to the property, which might otherwise become overgrown. Some of the smaller items could be raked up, larger branches would need to be carried off individually, and the largest branches (or entire trees) would need to be cut up and then carried away. The leaves are likely composted, while branches could possibly be burnt in a fireplace. (Leaf-burning is usually prohibited, since it puts out a lot of smoke.) StuRat (talk) 04:43, 1 February 2009 (UTC)

(Hmmm - we don't really have any kind of an article on brush wood and brush (disambiguation) doesn't mention it.) Wiktionary says that 'brush' is plant growth that's larger than grasses and smaller than trees. Once you've collected it, you can burn it - but you can also toss the stuff into a wood chipper which chops it up into teeny-tiny chunks that can be used as a mulch to help keep weeds from growing around desirable plants. Other machinery could be anything from an axe or a Machete to a chainsaw. There are also Brush hogs and brush mowers that chop the stuff up and leave it on the land. These exist as large lawn-mower-like contraptions that you walk behind - or bigger ones that you tow behind a tractor. The purpose of clearing brush on a working ranch is to allow the cattle to gain access to the grass beneath - and to reduce the risk of wildfire. While you can use machinery out in open areas - in tight corners where there are trees, it's a mostly manual process. There are people you can pay to clear your brush - but it's essentially an unskilled and fairly mindless task...the perfect thing to occupy the time of a US president.

President Bush's ranch out in Crawford (not far from where I lived until recently) probably contains a bunch of bushy texas cedar trees (they aren't true cedars) that have the annoying property of having branches that grow out parallel to the ground as the tree gets bigger - these die off - but don't fall off. So a group of these trees forms an impenetrably woven mass of thin, dead, spikey branches that even a cow won't walk through. Getting in there with a machete (and occasionally, a chainsaw) allows you to remove all of these dead lower branches and produce a nice tree with a clean trunk and a bushy green top. Clearing the lower branches of cedars improves an otherwise useless piece of land by allowing both humans and animals to get into it. Since the branches are dead anyway - this does no harm to the trees and the resulting mulch is useful. With my wife and I, a chainsaw, a couple of machetes and a gasoline powered wood-chipper, we were able to clear the lower branches from an acre and a half of cedars around our house over a couple of weekends. Removing the dead trees also let in more light and gave us a large stock of logs to burn in our open fireplace. 10 years later, the lower branches of the cedars have not grown back and the resulting improvement of the land is well worth the effort. SteveBaker (talk) 05:18, 1 February 2009 (UTC)

I think President Reagan also talked of doing brush clearing. But I think both presidents spoke of it in a double sense. Clearing away brush meant not only eliminating unwanted undergrowth, it also meant clearing away liberal ideas and negating progressive legislation. – GlowWorm. —Preceding unsigned comment added by 98.17.34.148 (talk) 06:07, 1 February 2009 (UTC)

Very interesting, thanks all! I also looked at that disambiguation page without finding anything. I previously had the misconception that clearing brush involved pulling out live undergrowth. I wonder if removing all the dead wood hurts the ecosystem? Does one generally remove all the brush or just paths to give accessibility and act as fire breaks? I wasn't aware of the double meaning and history of the expression - also interesting! 211.109.12.170 (talk) 06:42, 1 February 2009 (UTC)

Whether you'd only remove brush that's obstructing access or remove it all depends on your local fire department. In some counties fire prevention requires that you basically strip everything between the height of grass and grown trees. The county in California we used to live in traded increased fire safety for erosion of hillsides and mudslides this way. Controlled burning of underbrush is not practiced in residential areas, but has proven successful in some managed forests. It's not for the layman, though, and can't be done during a drought. 76.97.245.5 (talk) 10:57, 1 February 2009 (UTC)

I think that brush clearing might well involve removing live vegetation. If the Wiktionary definition is correct then live as well as dead material can be considered "brush". In the context of the Crawford ranch - it's possible that there was some 'undeveloped' acreage that had a lot of live brush in it that would need to be cleared for the purposes of increasing the amount of land available for cattle. Removing dead material certainly does hurt the ecosystem - the nutrients that were absorbed from the soil in growing that material is not being returned through the normal processes of decay - so if you did this repeatedly, the nutrient levels in the soil would indeed decline. Also, the rotting wood acts as food and habitat for insects and such like. In the case of the ranch, this may ultimately be a problem. In the case of my back yard, the chipped brushwood was spread back onto the land - so there was no loss. SteveBaker (talk) 14:42, 1 February 2009 (UTC)

Well to my Rocky Mountain brain, brush is Sagebrush (disambiguation). He's clearing tough woody shrubs to enable edible grasses to grow. He's making food for cattle. --Mdwyer (talk) 18:43, 1 February 2009 (UTC)

Kaiser Bill spent a lot of time chopping wood for the silent movie newsreel cameras. Any coincidence? It is mediagenic busywork. Edison (talk) 03:00, 2 February 2009 (UTC)

ina pasture, "brush" is basically anything except the grass, clover, and alfalfa. If a pasture is left fallow for more than about two years, brush (small woody bushes) starts to grow and crowd out the grass. The farmer must then cut down the brush before using the pasture. You typically use a bush hog for this. -Arch dude (talk) 00:14, 3 February 2009 (UTC)

About the cooling and heating of the air as an affect of clouds

Note:this question was moved from Portal:Weather by User:Runningonbrains.

About the cooling and heating of the air as an affect of clouds. It was hard for me to understand why the air is cooler when there is a clear sky and warmer when clouds are present. It has the same principals as a vacuum or a fridge. A vacuum, for example. The point is to have a space with no air in it, so that it will suck up all of the dirt you have on your floor. But if you are going to take all of the air out of an area, the excess wind has to have somewhere to go. If you feel a slight breeze on your legs while vacuuming, this is where the excess air is exiting. Perhaps a better example is a fridge, as it contains the same components, heat and cold. In order to make a refridgerator, the heat in that space must be removed. As with a vacuum, (and the air) the heat must go somewhere, so it it expelled out the back. Like both of these examples, the heat is dispelled out of the clouds. Clouds are made up of tiny ice/water droplets. These obviously are very cold. When the heat exits, it must go somewhere else, so it goes to the surrounding air. When there are no clouds in the sky, the heat that exits the clouds normally does not exit, and the cold that is captured in the clouds is not inhibited by the boundaries of the cloud, therefore spreading in the surrounding air. This is why it is generally colder when there are clouds in the sky, and generally warmer when there are no clouds in the sky.-—Preceding unsigned comment added by Smartcookie1596 (talk • contribs)

Even though, as you say, the clouds are made of tiny, cold ice and water droplets. Then think of them as a sort of igloo. Despite being cold themselves, they have an insulating effect on the Earth. Its not that clouds cause the Earth to be heated, they more effectly trap the heat that is already here than do cloudless days. The effect is that the clouds act as a blanket of sorts. It should also be noted that its not that simple, since the ambient temperature can affect cloud formation as well; warm air rises and warm air carries more humidity than does cold air, so rising warm air has the effect of creating more clouds. On colder days, there is just less moisture in the air, and less "lift" bringing that moisture to altitude where it can create clouds. --Jayron32.talk.contribs 12:14, 1 February 2009 (UTC)

Yes, clouds work based on the greenhouse effect. That is, like the glass in a greenhouse, they let light from the Sun in but don't let heat back out. (Well, they let most light in and block most heat from escaping.) So, the effect is that it warms up more quickly below the clouds during the day, and cools off more slowly during the night. The "extra heat" is actually in the form of less heat radiated into space. So, in other words, space (and the air above the clouds) is cooler when the Earth is covered with clouds. Of course, there's such a small amount of heat added to the many widely spaced objects in space that it doesn't increase the temp there by a measurable amount. StuRat (talk) 14:23, 1 February 2009 (UTC)

This is a very complicated effect that is giving the climate change modellers headaches. On nights and winter days, low clouds trap in warm air, while when there are no clouds, the heat escapes to space. On a summer's day, clouds cool the air because they block the heat of the sun. When it's clear, however, humidity can still build up, which makes it feel even hotter than it is. High clouds during daytime can also cool temperatures: when the entire American air fleet was grounded for three days following 9/11, the average temperature of the entire continental United States rose by 1 C (1.8 F), because the cooling effects of the high clouds produced by the contrails were removed. In the same manner, some man-made pollutants are not only contributing to global warming, but they're hiding its effects as well. Soot, found in brown clouds of pollution travelling across the Indian and Pacific oceans, cause warming by absorbing heat and decreasing albedo when they land on ice in the Arctic, but they also hide the warming effect by blocking sunlight during the day. This also produces global dimming. Clouds play an important, but confusing, role in determining the effects of climate change. When factoring the possible effects of clouds and water vapour in global warming simulations by computer models, the upper limit for possible temperature rise in the next 100 years rises from 6C (11F) to 11C (20F). PS. What's your question? ~AH1^(TCU) 17:46, 1 February 2009 (UTC)

what is the detail standard of MS20995AB32 or NASM20995AB32

Hi, I need to know the detailed standard of these MS20995AB32 or NASM20995AB32. I cannot get free information online. Is anyone can help? —Preceding unsigned comment added by Decowire (talk • contribs) 07:37, 1 February 2009 (UTC)

If you have a university or engineering college nearby they usually have a reading room with all/most of the standards. Otherwise you might get lucky if you contact local manufacturers or associations. OK it's an military aircraft part, a wire to be exact. That can get tricky, doubt a reading room would have that. 76.97.245.5 (talk) 10:47, 1 February 2009 (UTC)

IMHO this is a very vague question, surely you could have provided some context to this question, you might know exactly why you want/need this information and what the numbers relate to but I suspect that to everyone else it is just some number. What specifications are you actually after? Googling finds: http://www.casa.gov.au/rules/1998casr/021/021c99s2c09.pdf Which states:

Wire type	Material	Colour	Size	ID
Shear or Seal Wire for Magnesium Parts	Aluminium Alloy (Anodized)	Blue	0.032 inch	MS20995AB32 9525-01-031-1086

but I don't know if that has answered your question, probably not. Jdrewitt (talk) 14:25, 1 February 2009 (UTC)

Clones and lung problems

I was reading this article about the newly cloned extinct ibex (first time they've cloned a extinct animal, woot!). There is this line:

Sadly, the newborn ibex kid died shortly after birth due to physical defects in its lungs. Other cloned animals, including sheep, have been born with similar lung defects.

Why is this the case? (Assuming we know). Unless they somehow keep screwing up the DNA is some specific way, I would guess it has to do with the insemination process rather than the cloning process? Looks like that is what took Dolly_(sheep) down for the count too. Anythingapplied (talk) 08:44, 1 February 2009 (UTC)

I remember reading at the time this was first noticed that the best guess of those involved was the ageing process: in other words, the cells that had been cloned were the same age as the parent and therefore had degraded through the ageing process. --TammyMoet (talk) 09:54, 1 February 2009 (UTC)

Yes, in reproductive cloning, the cell nucleus from one individual is placed into an embryo which has had it's nucleus removed. The problem is that the cell nucleus has an "age", as defined by the length of it's telomeres, and thus any organism cloned from the cell will continue to age, starting from the age of the organism which contributed the nucleus. Using a younger donor for the nucleus will help to reduce this problem. StuRat (talk) 14:05, 1 February 2009 (UTC)

In the future, it's quite likely that this can be fixed by increasing the length of the telomeres in the DNA before implantation. An additional problem for cloning extinct animals is finding a suitable animal to provide the womb for the developing animal. In the case of an ibex, there are plenty of similar species around that will work - but if you were thinking in terms of 'bringing back' (say) Giant Sloths - then there would be considerable difficulties even with suitable DNA. The problems with cloning for extinct species can also be fixed without telomere lengthening by cloning both a male and female of the species and breeding them (possibly artificially) before their short lives expire. The lambs born to Dolly seem perfectly normal - so this appears to be a viable approach. SteveBaker (talk) 14:26, 1 February 2009 (UTC)

Despite the speculation, the answer is no-one really knows. Some clones appear perfectly fine, others die early. We don't really have enough of them to do the controlled experiments to determine if there is any pattern. In Dolly's case, she was probably the most abnormal sheep in history in terms of her environment, therefore we have no real way of knowing whether her lung disease was due to being a clone, due to being kept indoors, or just dumb bad luck. If and when cloning becomes commonplace, we will be able to control for these factors and answer your question. Its worth noting, though, that when IVF was first being developed there was all sorts of concerns that it was unnatural and would lead to defects and premature death. There is still debate over that subject, but the worst cases scenario never panned out and IVF is extremely well tolerated. Rockpocket 19:47, 1 February 2009 (UTC)

In addition to the telomere length problem mentioned earlier, there is also the possibility that epigenetic plays an important role in cloning. Every cell has a pattern of silenced and activated genes in its DNA, called "epigenetic programming". In short, this means that the DNA is chemically modified to change its structure. To become a fully potent stem cell (to then develop into an embryo), these "activation marks" have to be erased to enable a "start from scratch" for the new organism (and in most cases, this works perfectly, which is still not really understood). Some studies suggest that a "faulty start up" of the genetic machinery is sometimes involved when stem cells don't really become totipotent after nuclear transfer. And one could speculate that this could also lead to minor defects, let's say in lung development, when only a fraction of genes is not properly "reset". TheMaster17 (talk) 09:16, 2 February 2009 (UTC)

It seems odd though that this kind of genetic problem would affect the lungs in preference to other organs in so many cases. SteveBaker (talk) 16:24, 3 February 2009 (UTC)

Nothin' for nothin', but it could be that they have many other defects that don't have time to kill the clones before the bum lungs do. --Milkbreath (talk) 16:31, 3 February 2009 (UTC)

But perhaps it's all for the best, since, as anyone familiar with bad sci-fi knows, clones are all evil and have laser beams that shoot out of their eyes. :-) StuRat (talk) 14:43, 4 February 2009 (UTC)

Day with the most number of deaths

In recorded history, on which day did the most people die? Thanks LotsOfJam (talk) 10:19, 1 February 2009 (UTC)

List of causes of death by rate quotes the World Health Organization as estimating that 58 million people died in 2005, and slightly less in 2002. That's 158,904 per day. We can assume that there will be some seasonal variation, especially since the world population is concentrated in the Northern Hemisphere, but I don't know how to allow for that.

The largest death toll in recent years caused by a disaster was the result of the 2004 Indian Ocean earthquake, with 229,866 deaths, according to our article. Almost all of these are likely to have died on the day of the earthquake, 26 December 2004. Together with the average death rate per day calculated above, that makes 388,770 deaths on that day.

While I don't have figures for the average daily death rate in much earlier years, the 1556 Shaanxi earthquake killed about 830,000 people. I don't know how many of these were killed in a single day; probably most of them. This places 23 January 1556 as the answer to your question. Some unknown number of people will have also died unrelated to the earthquake around the world on that day. The article World population doesn't give a population for around that date, but we can assume it was between 300 and 800 million. Someone else can provide a refinement of that range, I'm sure. You could look at Life expectancy and try to calculate an average number of deaths per day to add to the earthquake figure if you want a total number of deaths for all reasons on that day.

The article List of natural disasters by death toll gives a number of disasters with much higher death tolls, but these were spread out over a month or two, and probably didn't result in such a high number of deaths in any single day as the 1556 earthquake.-gadfium 11:24, 1 February 2009 (UTC)

For comparison, the firebombing of Tokyo on the night of March 9-10, 1945 is probably the biggest man-made catastrophe in a single 24-hour period, with an estimated 100,000 dead. That total is somewhat more than died from the immediate effects of the nuclear bombing of Hiroshima and Nagasaki (which of course occurred on separate days). Dragons flight (talk) 11:39, 1 February 2009 (UTC)

Concerning daily death rate, Mortality rate gives a crude death rate (annual) of 9.6 per thousand. That would be 2.63 per day per 100,000. The caveat here is that 9.6 per thousand is the *current* crude death rate, which was probably different hundreds of years ago. 152.16.59.190 (talk) 11:45, 1 February 2009 (UTC)

information in Dutch about Cryptosporidium parvum

Hello,

I would like to now more about Cryptosporidium parvum because we have ill animals with this illness.

Can you send us informaion in Dutch??

Thank you very mutch.

J en M Steeghs Holland.

Sorry, no. We're not supposed to give out medical (or even vetinary) advice. Also, we're only able to provide advice in English. You need to see a veterinarian. We have an article on Cryptosporidium parvum - but it's only available in English, German, Spanish, Polish and Indonesian. SteveBaker (talk) 14:12, 1 February 2009 (UTC)

You could try the informatiebalie on the Dutch language wikipedia, although that seems to be a surprisingly quiet place. --Wrongfilter (talk) 14:26, 1 February 2009 (UTC)

Should my adam's apple be perfectly symmetrical?

←Sorry, but this most certain should not be answered by anyone here, Wikipedia does not provide medical advice. You stated that you were concerned about it being cancer in your original question. That's most certainly a request medical advice, and I must insist that you seek help from a medical professional rather than asking a question here. My apologies for removing the answers from other users, but I do feel this is in the OP's best interest. —Cyclonenim (talk · contribs · email) 19:10, 1 February 2009 (UTC)

Correct. You are right, Cyclonenim. --VanBurenen (talk) 19:24, 1 February 2009 (UTC)

Sound in Water

I have just been informed (on Mythbusters) that sound travels 5 times faster underwater than in air, due to the closer proximity of the molecules. Why, then, does it not sound at a higher pitch?--KageTora (talk) 15:44, 1 February 2009 (UTC)

It's easy is see why. That sound travels faster in water only means that the time it takes for sound to travel from a source to an observer is short than in air. However, peaks of successive cycles still experience the same delay traveling from the source to the observer. If they are separately by time $\Delta t$ at the source, after the same delay, their arrivals at the observer will still be separated by $\Delta t$. --98.114.146.178 (talk) 17:14, 1 February 2009 (UTC)

To put it succinctly,

$\lambda *f=v_{sound}$

wavelength times frequency = wave speed

In water, the wave speed has changed, and the wave length has changed, but the frequency is still the same frequency due to the source of the noise. Nimur (talk) 17:35, 1 February 2009 (UTC)

Air waves vibrate the ear drum. That stimulates auditory nerves to convey nerve impulses to the brain. If the air waves are at an audio frequency, the brain then experiences "sound". The actual nature of what the brain experiences is as much a mystery as the brain's experience of "color" in response to impulses on the optic nerves. With audio air waves, does the brain respond to the wavelength or frequency of the received audio signal? Is the wavelength of the nerve impulses the same as the wavelength in air? What if the ear channel was filled with water; as Nimur has pointed out,the frequency would be the same but the wavelength would be different; would the sound experienced by the brain be different? – GlowWorm.

Does the brain respond to the wavelength or the frequency of light? – GlowWorm —Preceding unsigned comment added by 98.17.34.148 (talk) 16:11, 2 February 2009 (UTC)

The brain does not respond to light directly; light is first converted by the rod cells and cone cells in the retina, and the messages are passed over the optic nerve. The cone cells, responsible for color vision, probably respond to frequency, rather than wavelength, because the detection of light is a photochemical reaction. In any case, the eye is a fairly controlled, non-dispersive medium with a fixed index of refraction so the frequency and wavelength should be directly related. See visual perception for a high-level overview. Nimur (talk) 17:10, 3 February 2009 (UTC)

Setting up a temporary "cleanroom" at home

What can you do to set up a low-dust environment at home (a makeshift cleanroom of sorts) for cleaning/servicing dust-sensitive equipment (say a scanner)? --98.114.146.178 (talk) 16:53, 1 February 2009 (UTC)

Avoid rooms with carpet. You may be able to buy a HEPA filter but it has been my experience that these are useless. Nimur (talk) 17:35, 1 February 2009 (UTC)

I would say the emptier a room the better. If you have a completely empty room, vacuum the floors, walls and ceiling and then wash them with a wet cloth. It goes without saying that you should keep the door/s (and any windows) closed at all times and turn off any fans. I would expect you'd get a reasonably dust free room although obviously not even close to enough to make microchips Nil Einne (talk) 17:39, 1 February 2009 (UTC)

I suppose take a look at cleanroom for a start. An air filter is a good idea. This might be excessive for your purposes, but a mycology lab used a HEPA quality airfilter to keep contaminating spores and bacteria from mucking up growth media plates. A wood turner I know uses a standard shop vac to cut down on the dust. Before you start, wash down all the surfaces of wherever you set up, including the walls, floor, and ceiling if you can get to it. Maintaining a positive air pressure in your work environment is a good idea. A lot of cleanrooms I have seen have those cleanroom sticky mats which pull dirt and dust from your shoes when you walk over them. Google cleanroom sticky mat for suppliers. As far as ersatz goes, someone from slashdot had this method for making an improv cleanroom:[17]. Hope this gives you some ideas. 152.16.15.23 (talk) 17:48, 1 February 2009 (UTC)

It might be easier to make a chamber with gloves and a window rather than a room you go into yourself. Make sure theres no gap around the HEPA filter. Dmcq (talk) 18:04, 1 February 2009 (UTC)

If you're just trying to keep particulates off a work surface (and you're not worried about nasty fumes or biohazardous materials), the solution may be a laminar flow cabinet. The simplest models are enclosed at top, bottom, and sides. Room air is HEPA-filtered and blown in along the back wall, over the work surface, and exhausted into the room at the front. (The picture in our article shows a Class 2 device that is designed for biohazardous materials; it is equipped with germicidal UV lamps, and the second set of vents at the front of the cabinet collects the exhaust air to refilter it. What you would need is a much cheaper version which exhausts direct to the room — more like this, this, or this.) TenOfAllTrades (talk) 18:36, 1 February 2009 (UTC)

For one off or infrequent use, things like an Atmos bag can act as a portable glove box provided you have a way to fill them with a filtered supply of air. Dragons flight (talk) 23:18, 1 February 2009 (UTC)

TenOfAllTrades beat me to it. Just make an enclosed workbeanch. Improvise a sealed passthrough with gloves. Air enters the top and is drawn through the bottom. Calculate the required flowrate to maintain laminar conditions.

Not sure if you want a medical cleanroom or a fabrication cleanroom, but the following is what I've seen in fab plants. You want smooth surfaces inside, use stainless and Polypropylene. PP is an inexpensive high purity plastic. Exposed stainless steel should be passivated (there is a certain type used in the semiconductor industry that electrochemically blows off surface impurities). In fab pants, new equipment gets a 'superclean' cycle; swab every inch with isopropyl alcohol and special towelettes (made for clean rooms). No paper or pencils allowed inside! (you can order special cleanroom paper). Also, look into a positive pressure feed and looping the air through the filter (polishing). --TungstenCarbide (talk) 00:32, 2 February 2009 (UTC)

PS, not sure what you want a clean room at home for but if it's to screw with your disk drive be careful, that usually requires a class 100, which takes a lot of effort to achieve. --TungstenCarbide (talk) 00:46, 2 February 2009 (UTC)

Back when window-modding of computer hard drives was in vogue, the recommended method for creating an ad-hoc cleanroom was to steam up the bathroom and let the steam (and hopefully any airborne dust) settle out on the walls, then work quickly while it was still humid. This would result in a working hard drive about one time in three. --Carnildo (talk) 01:05, 3 February 2009 (UTC)

The OP said he wanted one for cleaning a scanner. 99.50.50.41 (talk) 17:11, 3 February 2009 (UTC)

Identify plant?

Does anyone recognize the plant at [18] (other pictures of same plant at [19] and [20])? The photos were taken in July in Connecticut. RJFJR (talk) 17:40, 1 February 2009 (UTC)

Is it Echium vulgare or Viper's bugloss? Julia Rossi (talk) 22:18, 1 February 2009 (UTC)

I read the article and it could be. Thank you. (I'm disappointed it doesn't flower perennially, those flowers were pretty and I was wondering if I could plant some). RJFJR (talk) 01:38, 2 February 2009 (UTC)

I guess it depends how you want to feature it. All by itself is too much for it as a monocarpic type of perennial, but mixed with others varieties, it would just keep coming along, if that helps. It looks quite tough, self-seeding in the roadside turf like that. I'd try taking it home to grow roots and all, or leave it on the surface of prepared soil, to shed some seeds on the spot. Julia Rossi (talk) 03:46, 2 February 2009 (UTC)

what are the best arguments for there being no objective truth?

what are the best arguments for there being no objective truth?

See Relativism, also it is a good idea to study objectivism. It used to be a good way to be a bright young pain in the neck and get some groupies to make out with but I think it's a bit passé now. Dmcq (talk) 21:56, 1 February 2009 (UTC)

What are the arguments for there being an objective truth? As far as I know its a reasonable assumption.--OMCV (talk) 21:58, 1 February 2009 (UTC)

It's an unfalsifiable proposition. I can never prove that there IS objective truth because you can always say that whatever evidence I offer is a figment of my imagination. The best we could hope to offer is some kind of Occam's razor kind of thing - but even that is a bit flakey. I don't think there can be any evidence the other way either. If you have proof that there is no objective truth - then that, in itself would be an objective truth - so we can show by reductio ad absurdum that no such proof can exist. Hence we might as well operate under the assumption that universe exists and we along with it because the world would be a mighty boring place otherwise. SteveBaker (talk) 23:23, 1 February 2009 (UTC)

(At some point in this discussion - I'm going to need to say that "Philosophers are a waste of quarks" - I thought I'd get it over with early.) SteveBaker (talk) 23:33, 1 February 2009 (UTC)

A lot of it comes down to defining what one means by "objective" and "truth", as well. Both of those are often presented as if they are straightforward concepts, when both can be quite difficult to nail down in a precise way. --98.217.14.211 (talk) 00:59, 2 February 2009 (UTC)

Electron configurations

For my homework (let me finish, I'm attempting it) there's the following question:

"If the oxidation state of Vanadium is +3 in VCl₃, what is the electron configuration vanadium in VCl₃ and explain why it is considered a transition metal"

I've worked out that I think the configuration is 1s²2s²2p⁶3s²3p⁶4s², but this would mean that it's not a transition metal since it has an empty 3d orbital. I'm guessing I've made a mistake with filling 4s before 3d in this case, should it be 4s¹3d¹, or 4s⁰3d²? Cheers. —Cyclonenim (talk · contribs · email) 21:57, 1 February 2009 (UTC)

Yes, your last configuration is correct (4s⁰3d²). The common rule is that transition metal cations (but not neutral atoms) will lose their s electrons before their d electrons. (Don't worry, I made this mistake until I was well into college :) ) --Bennybp (talk) 22:25, 1 February 2009 (UTC)

Ah I see, thanks. So they empty first just like they fill first? —Cyclonenim (talk · contribs · email) 22:27, 1 February 2009 (UTC)

The statement The common rule is that transition metal cations (but not neutral atoms) will lose their s electrons before their d electrons. needs more qualification. The idea that s electrons empty first just like they fill first is "fudge" general chemistry teachers teach to avoid going into details. Logically and experimentally it doesn't make sense. The electron configuration model your using is accurate when the neutral transition metal is not bound to anything and in its ground state. Finding a unbound transition in a ground state is more the exception than the rule. Most metal centers have something that is described as a coordination sphere or they have metal metal bonds. In solid VCl₃ for example every Vanadium bound to six chlorides (which is shares with neighbors) forming a common octahedral coordination sphere. Once there is a coordination sphere even if the metals not oxidized such as [M(O)L_n] its best to discuss them in terms of ligand field theory or if you are old fashioned crystal field theory. Either way the electron configuration is then described by the d electron count which fits experimental results for metals in complexes (in most situations). With that all said most general chemistry classes are looking for the answer in the form Bennybp provided. Good luck with your chemistry studies.--OMCV (talk) 23:10, 1 February 2009 (UTC)

(ec) Thanks for your expansion, but I do believe that is probably a stage ahead of what I need to know currently. I'm currently studying A level Chemistry, which is a step below an undergraduate degree in terms of scale. The 'general chemistry teacher explanation' is probably good enough for now, but it was an interesting read nonetheless :) —Cyclonenim (talk · contribs · email) 23:16, 1 February 2009 (UTC)

(post ec)What Bennybp said is often true for the transition metals, although you usually fill the 4s before the 3d orbitals according to the Aufbau principle. Some transition metals even in their "neutral" state will "push" electrons from the Ns to the (N-1)d if it means they will have 5 or 10 electrons in their d orbital. Common oxidation states of first series transition metals have 3, 5, or 6 electrons in their d orbital. (I speculate the reason for the 3 and 6 have to do with 3 of the d orbitals being lower energy than the other 2 in certain situations) I go by the principle the more electrons an atom has the more likely it will violate the filling order you would expect. See Atomic electron configuration table

In the first row transition metals the violaters in neutral are:

Chromium with [Ar] 3d⁵ 4s¹. Chromium (III) ([Ar] 3d³) is the most stable, Chromium (II) and (VI) come up often, while (I) is rare although it would seem to make sense.

Copper with [Ar] 3d¹⁰ 4s¹ but note that its most common oxidation state is (II) (3d⁹) rather than (I) (3d¹⁰) which you think would make sense

First row transition metals lose their 4s² electrons before the 3ds with the following common exception: Cobalt (III) (4s¹ 3d⁵). Manganese III and Manganese VI may also have an unexpected electron configuration but I can't find a source to verify it. See [21] for more. 152.16.15.23 (talk) 00:28, 2 February 2009 (UTC)

That last post just isn't up to speed; the author clearly doesn't understand transition metal electron configurations. The "push" idea is still based on metal center not bound to anything and in its ground state situation. As for "common oxidation states" it goes beyond speculation into imagination on the authors part. a quote from his reference.

Some oxidation states, however, are more common than others. The most common oxidation states of the first series of transition metals are given in the table below. Efforts to explain the apparent pattern in this table ultimately fail for a combination of reasons. Some of these oxidation states are common because they are relatively stable. Others describe compounds that are not necessarily stable but which react slowly. Still others are common only from a historic perspective.

This citation is mostly accurate but I would also say most of the M(0) oxidation state are common as well as and few other neglected configuration suchg as Co(I). Its enough to say first row transition metal centers vary from d⁰ to d¹⁰ and depend on many features directly tied to the specific metal center. I can personally verify that Co(III) is usually low spin diamagnetic d⁶. If you don't know what you are talking about don't write anything.--OMCV (talk) 01:00, 2 February 2009 (UTC)

Please don't criticize other editors for attempting to help, especially when they've cited a reliable source. There's always someone that knows more than you do, and the great thing about open discussion is that we all can learn if we listen (or read...). --Scray (talk) 02:21, 2 February 2009 (UTC)

Ok, your right I should have just said that they were wrong and didn't read the source they cited. The personal aspect was a mistake.--OMCV (talk) 03:12, 2 February 2009 (UTC)

There seems to be a disconnect here. There are two ways of answering the question; the easier method is "here's a heuristic (aka rule to follow) which will produce the right answer" and the other is to explain what is really happening. Its possible to apply the heuristic and get the right answer almost all the time, and never understand the physics behind what is going on; at the A-level a student is probably on the "heuristic" level; it is not until one gets to about 3rd year of an undergraduate chemistry degree that one begins to understand the actual bonding symmetry and nature of the metal-ligand bond to the degree that OMCV is describing. So yes, OMCV is scrupulously correct here in his explanation, however no high school chemistry student is going to have the background to parse his explanation. Hence, the heuristic trick of "add 4s before 3d" and "remove 4th level before 3rd level" to get the answer here. --Jayron32.talk.contribs 04:24, 3 February 2009 (UTC)

Frankly I wonder why anyone teaches that form of electron configuration since its utterly meaningless and just makes things confusing latter on. I guess all the other elemental electron configurations are comparably meaningless formalisms used solely to familiarize student with quantum numbers of atomic orbitals and little more. So what Jayron32 said is true and the configurations mentioned above are gospel truth right through the chemistry GREs (at least in the states).--OMCV (talk) 04:37, 3 February 2009 (UTC)

Actually, what I said was that the use of electron configurations is a "heuristic" (aka a teaching tool) as a means of preparing students who otherwise lack the background to learn such concepts. All students in the United States who go on to major in chemistry and chemical engineering degrees learn The Truth(tm) during their studies, usually in physical chemistry and advanced inorganic chemistry classes; though freshman level college chemistry almost always introduces the basics of Hybridization theory and Molecular orbital theory, which begins to deconstruct the standard "high school model" of the atom. Rather than being confusing, it allows a student to get a cursory understanding of the quantum model of the atom, without necessily having to work with Schrodinger's equations and eigenstate functions and all that fun stuff. For a high school student who has no interest in pursuing a career in chemistry, its probably good enough. There's not enough time in the 4 years of high school to teach every student every fact ever learned in every discipline ever. --Jayron32.talk.contribs 05:36, 3 February 2009 (UTC)

As it turns out the ACS accreditation and most universities in the US don't require a regular inorganic chemistry class let alone and "advanced" one for a chemistry degree; And d electron counts aren't covered in every pchem class either. I think pchem could easily be expanded to a year and half and still be a superficial survey of material. My point was that I question the value of the way the atomic "electron configuration" is presented even as a "heuristic" teaching tool and wonder if it is more "historic" (like our appendix). I think this sort of "historic" concepts is an issue in chemistry for example why is crystal field theory still taught and the language of oxidation and reduction is cumbersome? Although I could never unlearn it, I see the value of developing more logical language? The origin of the term "reduction" is from the mass lost when taking a metal oxide to it metallic form, "oxidation" is adding the oxygen back to the metal form to make the metal oxide. Each term boarders on many related meanings which makes the concepts very hard for student to learn.

I understand people taking a survey of the field won't get all the details but it would be nice if chemists didn't waste their time with busy work. All the quantum number are good information but it seems as if the electron configurations are designed to act only as test questions. You note that Hybridization theory and Molecular orbital theory deconstruct the "high school model", as a side note hybridization is taught in most high schools these days since its hard to talk about sigma or pi bonds with out it; Back to my point which is that I think that your ability to see a deconstruction is mostly insight on your own part and no thanks to standard teaching methods. My experience with undergraduates is that they have a hard time connecting what their learning with the real world. They treat science as ritual or game that needs to be played for a year or two in college. They don't feel the need to make chemistry self consistent. I think it might be easier for them if they weren't taught so many contradictory models or at least identified them as contradictory models. If you look classic general chemistry texts like Chang or Silberberg at no point does it say heads up kids now that you are using the hybridization model or MO model, carbon doesn't have the 2s² 2p² configuration anymore. On most general chemistry final you will find questions on each of the three subjects but never have a question asking the students to compare and contrast the hybrization model with the MO model let alone and how our understanding of atomic orbitals work into each model. Then there is the big secret even most chemistry majors never internalize which is the Schrodinger's equations and eigenstate functions only work for a one electron system, the hydrogen like atom; Every other application is an approximation, the value of which is often questionable. I know it might sound like I'm missing your point but I actually appreciate you writing so that I can vent on the subject. Have a good one.--OMCV (talk) 13:21, 3 February 2009 (UTC)

Gaur image

I've been searching tirelessly to no effect for an image that shows an average human next to a gaur. I'd like to see how big it looks, thanks. --Taraborn (talk) 22:06, 1 February 2009 (UTC)

Here's one next to a 4x4 http://flickr.com/photos/pixbykris/2307472690/in/photostream/ Jdrewitt (talk) 22:29, 1 February 2009 (UTC)

I think the gaur facing off the pickup truck is a young one or a female. Wikipedia says a gaur is larger than a bison - that's pretty big. Wiki gives weight and shoulder-height of the gaur. A full grown male can weigh more than a ton and a half. If it was me driving that pickup, I'd put it in reverse and tromp on the accelerator - fast! :) GlowWorm. —Preceding unsigned comment added by 98.17.34.148 (talk) 23:23, 1 February 2009 (UTC)

Well maybe its not fully grown, but it still looks pretty heavy to me though, can easily see that one being a ton, and is the same height as the truck. Jdrewitt (talk) 10:16, 2 February 2009 (UTC)

Here's a couple, [22][23] both dead. I don't think it's very safe to stand next to a live one. SpinningSpark 01:31, 2 February 2009 (UTC)

Testing for air tightness

Is it true that one can test a container for airtightness just by using a lamp in a darkened room to see if any light leaks out? Is so, then you are not airtight?--GreenSpigot (talk) 23:51, 1 February 2009 (UTC)

That method is useful for showing you gaps at edges and joints especially when the material is dark. There are problems of course if the material you used isn't opaque, or you seal edges with a transparent material like epoxy. Then the light can leak out through the epoxy, but the container may really be sealed. On the flipside, you can imagine a case where a series of switchbacks occurs which blocks the light although the material isn't airtight. I suppose it you really wanted to check for airtightness, you could pump said container to a higher pressure, seal it and see if the pressure decreases over time or stays constant. You could also fill the container with colored smoke, water, or some other gas or liquid and look for leakage that way. 152.16.15.23 (talk) 00:47, 2 February 2009 (UTC)

While that method may give you an indication, it is obviously not going to be definitive. Consider the inside of a camera, it is lightproof, but not usually airtight, or even watertight. If you are just checking the hoses of a compressor, for instance, it might not be important that there is a small amount of leakage. If you are dealing with something dangerous like silane on the other hand, you need to use a more professional method. Leaks will usually occur at joints in pipeworks, inspection covers, access plates etc. One way to test is to slightly pressurise with air and use bubble leak detector solution on all the joints prior to letting in the working gas. SpinningSpark 02:24, 2 February 2009 (UTC)

When building rockets, we are very concerned with quality of seals. Rather than a binary "airtight"/"not airtight", we rate a particular vessel as pressure-tested to a certain pressure. Usually this is accomplished by hydro testing, in which the sealed vessel is filled with pressurized water and held at pressure for a specified quantity of time (e.g., "holds 1500 psi water for 10 minutes with no leak" would indicate a pretty darn good seal). I would never trust this "lightbulb test" - light does not "leak", and is a terrible analogy for finding a gas or fluid path. Nimur (talk) 03:52, 2 February 2009 (UTC)

One disadvantage to this method is that an object with a small leak that could have been fixed, or no leak initially, could be destroyed. StuRat (talk) 10:04, 2 February 2009 (UTC)

Sure, but you can start at lower pressure and work up to the rated pressure test. A catastrophic failure at 1500 psi may be manifested as a slow trickle leak at 800 psi. Also, because water doesn't expand or contract volumetrically by any significant amount when depressurized, there's not a lot of danger from a hydro test (pressurizing with gas could lead to explosive decompression). Nimur (talk) 13:26, 2 February 2009 (UTC)

The light test may also fail to detect materials which are gas-permeable, such as certain plastics. StuRat (talk) 10:07, 2 February 2009 (UTC)

Some critical structures (and one that I happen to know about is rollercoaster tracks) are pressurized with nitrogen and have continual monitoring of the gas leakage rates. Any sudden decrease in the rate of leakage can be attributed to a crack or failed weld somewhere in the system leading to it being shut down and tested. These systems are pretty amazingly sensitive - they have to be calibrated to cope with things like the expansion of the metal as the sun shines on it - which increases the volume and temporarily decreases the pressure. SteveBaker (talk) 14:56, 2 February 2009 (UTC)

the optimal test for you is going to depend on the kind of container you are using and how you will be using it. Anyway, here's a leakage test that's used for gas lines: pressurize the container, then spray it's surface with a soapy solution. Bubbles will form at leak locations. --Shaggorama (talk) 19:47, 2 February 2009 (UTC)

To avoid further unnecessary speculation, I should say at this point that the container is a loudspeaker reflex cabinetGreenSpigot (talk) 19:46, 2 February 2009 (UTC)

Just be thorough. Some good tips on sealing your project can be found here. -Shaggorama (talk) 19:59, 2 February 2009 (UTC)

With a speaker enclosure, being perfectly gastight isn't really necessary because the high pressure impulses are of very short duration. All you need is to ensure that the 'impedance' of the leaks is sufficiently high. Although...are you perhaps the OP who was talking to us a month or so ago about making pressurized speaker enclosures to effectively reduce the size of cabinet needed or something? SteveBaker (talk) 16:21, 3 February 2009 (UTC)

SteveBaker is probably referring to the December 14, 2008 discussion. If the questioner is using a pressurized gas, such as SF₆, safety precautions should dictate the seal. Nimur (talk) 17:14, 3 February 2009 (UTC)

Steve:1. All the speaker books and sites say the cab must be airtight (even tho you have a hole for the port).

2.I agree that the impedance of the leaks should be higher than the impedance of the port; but just how high is ::::that?

3.Yes I am

4.But I have reverted to a conventional design using ordinary atmospheric air because of supply and sealing

difficulties with SF6!--GreenSpigot (talk) 18:55, 3 February 2009 (UTC)

February 2

Blood tests

Over a lifetime annual physical exams and diagnostic lab work will have taken blood from the elbow veins many, many times. Is that ever a concern in non-immunodeficient individuals? Thanks. Imagine Reason (talk) 01:32, 2 February 2009 (UTC)

Do you mean, could someone be harmed by removal of blood from the same location? The venipuncture article has information about this procedure. The risks are quite minimal, and relate to the puncture of skin, the vein, and any inadvertently-punctured structures nearby. Removed blood must be replaced through hematopoeisis and other processes, but this is a systemic, not local effect. In other words, if you have blood removed always from the left antecubital fossa, this has no special effect on the blood present in the left arm 10 minutes later - circulation takes care of that. By the same token, the blood tests taken from one arm are expected (within certain levels of approximation) to represent the rest of venous blood. Perhaps I misunderstand your question, though. --Scray (talk) 02:10, 2 February 2009 (UTC)

I guess there might be a question about scarring or weakening of the vein itself...but I have no idea. SteveBaker (talk) 02:40, 2 February 2009 (UTC)

Even under ideal conditions, there is always a small risk of infection associated with venipuncture. If proper precautions are taken and the individual has a reasonably healthy immune system, this risk is quite small. (I don't have statistics handy, but bear in mind that otherwise healthy individuals are permitted to donate blood, platelets, or plasma hundreds of times, generally without incident.)

Repeated insertion of intravenous lines can lead to local scarring of the vein, making it more difficult to insert a needle in the future. This is sometimes a problem for repeat blood donors, and more often a problem for intravenous drug abusers or for individuals who have chronic illnesses requiring frequent, recurring blood draws.

Problems may also arise in individuals whose blood clotting is severely compromised. TenOfAllTrades(talk) 04:33, 2 February 2009 (UTC)

Repeated access to the blood stream is a big problem for hemodialysis patients. That's why they get AV grafts to help with any scarring of a natural vein. --Ayacop (talk) 11:14, 2 February 2009 (UTC)

Snow fleas

Why do snow fleas cluster on the surface of snow? There can be little of nutrient value there. They particularly seem to cluster on the sides of indentations in the show surface, such as footprints. Is there any explanation for this? Thanks. Marco polo (talk) 02:05, 2 February 2009 (UTC)

There can well be all kinds of algae (see Snow algae and Chlamydomonas nivalis) thriving in the thawing snow. There can also be a lot of microscopic detritus adhering to the surface of the snow, especially in the depressions of the surface. I would guess snow-fleas gather to feed on that. --Dr Dima (talk) 03:05, 2 February 2009 (UTC)

Dwarfism due to gas attack?

Are any of the chemical weapons used in the First World War known to cause reproductive genetic damage? Could such damage cause dwarfism? I recently met a man, approximately five feet tall andwith a prepubescent-sounding voice, who said that because his grandfather sustained a gas attack while serving in the war, his mother and all her siblings have dwarfism. A mutual friend describes him as a "storyteller" but confirms he is 25 years old. NeonMerlin 02:48, 2 February 2009 (UTC)

To establish it as a credible fact, there would need to be more than a single incident. I found this book, Veterans at Risk, by the Institute of Medicine (U.S.). Committee to Survey the Health Effects of Mustard Gas and Lewisite, Constance M. Pechura, David P. Rall. "Sulfur mustard causes chromosome breakage and induces sister chromatid exchanges in a wide variety of cells. Epidemiologic studies have also led the International Agency for Research on Cancer to classify sulfur mustard as a human carcinogen. These observations underscore the potential of this compound to induce genetic damage. They also suggest that sulfur mustards could be a reproductive toxin." Dwarfism does not appear specifically mentioned. Nimur (talk) 03:37, 2 February 2009 (UTC)

Wouldn't it have been quite cruel by the grandfather to father more dwarfs after he saw what his first offspring became? That's why I don't believe this. --Ayacop (talk) 11:08, 2 February 2009 (UTC)

Try not to be too judgmental of other peoples' reproductive decisions. Families affected by genetic conditions are often in an excruciatingly difficult situation trying to decide whether or not to have additional children. To say that it was "cruel" for the grandfather to try to have more children after the birth of an affected child is not warranted. We don't know the circumstances of his situation. --- Medical geneticist (talk) 14:49, 2 February 2009 (UTC)

Plus, that presupposes that life as a dwarf is so absolutely horrible that it would be better if they'd never been born. Do you think that if you asked the siblings whether they considered their father cruel to bring them into the world, they would reply that they'd rather not have been born? If you had an ugly child, would you consider it cruel to have anymore when you saw what the first 'became'? Do you think the man NeonMerlin met should never have been born? I find it very hard to get my head round this point of view. After all, he wasn't taking non-dwarf children and 'making' them dwarfs. 79.66.57.25 (talk) 18:12, 3 February 2009 (UTC)

An alternative explanation could be that the grandfather sought some sort of external rationalisation for the fathering of dwarf offspring as he may have been unable to accept that it was a genetic anomaly within himself. Richard Avery (talk) 11:36, 2 February 2009 (UTC)

Achondroplasia, the most commonly recognized form of dwarfism is caused (in the vast majority of cases) by a de novo mutation of a particular nucleotide of the FGFR3 gene. It is plausible that chemical agents that are known mutagens such as mustard gas could increase the rate of spontaneous mutations at mutable sites such as this. However, I couldn't find any references citing such an event. I doubt that the OP's 5' tall friend could have achondroplasia, which is usually associated with much shorter stature (around 4'4" for males) and a very recognizable appearance (disproportionately short limbs vs. trunk). Probably something else leading to proportionate growth restriction, which may or may not be true dwarfism. --- Medical geneticist (talk) 15:17, 2 February 2009 (UTC)

Wind powered

Can you build a machine that moves downwind faster than the wind, without using anything but the wind as a source of energy? Nadando (talk) 05:10, 2 February 2009 (UTC)

I can imagine a machine that operates in two alternating modes. First, it affixes itself to the ground and deploys a windmill to collect and store energy. It would then retract the windmill and use that stored energy to propel itself. Given a sufficiently efficient design (large, lightweight, and reasonably streamlined), the average velocity could exceed the original wind velocity. It might even be possible to take that design a step further and design a machine for continuous operation by having multiple parts that cycle between wind-collection and streamlined advancement. -- Tcncv (talk) 06:29, 2 February 2009 (UTC)

From the article, sailing - "When moving, the motion of the boat creates its own apparent wind. Apparent wind is what is experienced onboard and is the wind that the boat is actually sailing by. Sailing into the wind causes the apparent wind to be greater than the true wind and the direction of the apparent wind will be forward of the true wind. Some extreme design boats are capable of traveling faster than the true windspeed." Nimur (talk) 06:38, 2 February 2009 (UTC)

Here's a fun video which I found while searching... Under the ruler faster than the ruler. Nimur (talk) 06:49, 2 February 2009 (UTC)\

That's not what he asked. Many sail boats are capable of traveling faster than the true windspeed. The question is whether you can go downwind faster than true windspeed. The traditional answer to this problem is no. When the boat matches the windspeed the relative airspeed drops to zero and the boat can not accelerate. APL (talk) 15:55, 2 February 2009 (UTC)

You could split the energy 'generation' by using windmills that transfer generated energy by microwave laser to the ship. In effect, the amount and with it the speed is thus only limited by that of light. --Ayacop (talk) 11:02, 2 February 2009 (UTC)

Given a straightforward interpretation of the question (can a sailboat or the like move downwind faster than the wind?), the answer is no. Once your machine reached windspeed, it would have no further thrust. However, it may be worth noting that sailboats move fastest when the wind is abeam (that is, at right angles to the direction of motion). It might be possible under those circumstances to exceed wind speed in a non-downwind direction. — Lomn 14:12, 2 February 2009 (UTC)

removing duplicated posts... Nimur (talk) 14:29, 2 February 2009 (UTC)

Yes but it wouldn't go faster all the time. A windmill gathers the electric for a while, then it takes off faster than the wind. Wind is a force of gravity and convection. If you can beat gravity downwind or turn it sideways, you may do it. ~ R.T.G 14:17, 2 February 2009 (UTC)

Actually wind has much more to do with pressure gradient force than any of those things </nitpicking> -RunningOnBrains 00:34, 3 February 2009 (UTC)

Certainly it's possible to sail a yacht faster than the prevailing wind. If you have a decent keel - you can aim the boat at (say) 45 degrees to the wind - so the wind is coming from behind - but at an angle. Suppose the wind is blowing from the South - and you are sailing towards the North-East. If your sail was 100% perfect and your boat was infinitely slippery - then for every kilometer the wind moved northwards, you'd move a kilometer northwards AND (because the keel is preventing you from being blown sideways) a kilometer to the east. Your net speed is therefore about 1.4 times the wind speed. Sailing ever closer to 90 degrees to the wind would theoretically make you go yet faster. The practical limit of how close you can get to that ideal depends on the design of the yacht. Land-yachts (which have wheels instead of a keel and have a MUCH lower coefficient of drag than a water-bound yacht can get up to 100mph in a mere 30mph wind! SteveBaker (talk) 14:47, 2 February 2009 (UTC)

OK, but he asked specifically about sailing downwind. Ever since I first heard this problem years ago, I've wondered if a solution like Tcncv's solution above could work, alternating between energy storage and energy use. I can't see any reason it wouldn't in theory, if you could get good enough parts. (If continuous down-wind motion is required, you could imagine all sorts of crazy schemes, imagine two pontoons alternating between stored energy and energy use and leap-frogging each other. Between them is the passenger compartment being dragged along by ropes at the average speed.) APL (talk) 16:06, 2 February 2009 (UTC)

Perhaps this isn't the paradox that physics professors would have us believe. Discussions here, and here. Personally, I fully don't understand how these devices are claimed to work. I'm not sure that they do, or if they do that they work for the reasons provided. APL (talk) 16:36, 2 February 2009 (UTC)

There seems to be very few videos of these devices actually going against the wind 'in the wild' as opposed to a treadmill. Even then they don't seem to make any attempt to measure the speed of the craft or the wind. I suspect wishful thinking of the same sort that plagues perpetual motion inventors. APL (talk) 16:43, 2 February 2009 (UTC)

Rule #1: Anything at all that you find on peswiki.com is crap...anything...no exceptions!

Rule #2: All videos on Youtube that purport to break the laws of physics are faked.

The video of the craft moving rapidly along the road with the little white flag flapping out of the back was probably running downhill. In the shots of the treadmill tests, how do you know there isn't a big fan just off-camera? Scepticism is required here. We KNOW these machines can't possibly work (see Rule #1 above) - it's just a matter of why. Since we know for 100% sure that people WILL fake videos on YouTube (see Rule #2 above) - it's just down to the tedious business of figuring out why. Because you don't know what's happening off-camera, it's a trivial matter to do this stuff. SteveBaker (talk) 03:03, 3 February 2009 (UTC)

OK - so here's another idea. Let's suppose you have a yacht with a big sail and a very slippery hull. We imagine it being pushed through the water VERY close to the wind speed with the wind right behind it. We imagine that if we were able to go any faster than the wind then the sail would collapse and turn into a parachute - slowing the yacht down again - so there would be no way to collect more energy. But we forget that the boat is now moving very fast compared to the water. So could we not deploy a turbine to collect energy from the water that's rushing past at high speed - and use that to produce a little more power to overcome the drag of the 'parachute' sail? I rather doubt it because in order to move at the same speed as the wind (and parallel to it's motion) you need a zero-drag hull - and as soon as you increase the drag by extracting energy from the water - you're going slower than the wind.

OK - so if we are talking about the speed of the yacht in a direction parallel to the wind velocity - then what I said before doesn't work. So can a yacht (or anything else for that matter) move faster than the wind IN THE DIRECTION THE WIND IS BLOWING. I think the answer is a definite "NO" - but it takes some jiggling around with frames of reference to prove it.

It's easier if you forget the wind and think in terms of the frame of reference of the yacht. From the point of view of a yacht with a really HUGE sail and a super-slippery hull that's moving at almost exactly the speed of the wind - and parallel to it - then from the perspective of a guy sitting on the deck, you have (let's say) negligable forward wind speed - but lots and LOTS of water coming towards you. Your hull is so slippery that despite the huge speed of the water - it produces negligable drag - so you can just sit there - despite the negligable wind-speed relative to you. So to move forwards (ie to move faster than the wind - as a "stationary" observer would say)...you have to turn that backwards water motion into forward motion of the boat...but you have to do it in such a way that the drag-force of the water on the front of the boat doesn't increase by as much as the thrust you're generating from it.

I don't see how that's possible - it seems like it would be a violation of conservation of momentum. You can't have the yacht move forwards without the water moving backwards even faster than it is now.

We can go one step forward from there. Since the wind speed is negligable when viewed from the yacht's perspective - we could pretend the yacht was sitting there in a vacuum - with just the water flowing past it's hypothetical zero-drag, zero-friction hull. If it could somehow move forwards against the flow - then we could transfer our mental coordinate system to the frame of reference of the water itself. It would appear that our boat is moving at uniform speed relative to the water (which it can do - per Newton's laws - providing it has a zero-drag hull) - but then suddenly it accelerates without any source of motive power! Where did the energy come from? SteveBaker (talk) 19:57, 2 February 2009 (UTC)

If you use the difference between wind speed and water speed to produce energy, the boat will have a limitless source of energy, and the boat can have arbitrarily low friction, so there's no limit to how fast it can go. Interestingly, even if you only use the wind and the boat (or airplane, which would work better for this case), you can still go faster than it. Imagine the air is stopped and you are moving, which is equivalent. Turn around. Of course, that limits your top speed. — DanielLC 22:59, 2 February 2009 (UTC)

You didn't read a single word of what I just wrote - did you? It's a matter of conservation laws. The boat has to (at some point) travel at the same speed as the wind. At this point the air is stationary relative to the boat. So you have a boat travelling through water - and according to Newton's laws - it'll continue at a constant speed until acted on by an external force. Where is that force coming from? It can only be from the water (since the air is effectively stationary relative to the boat). In order to extract energy from the water, you need to change it's momentum. But conservation of momentum says that you have to push the water YET FASTER behind the boat in order to allow it to move forwards. So what concievable thing could SPEED UP the water and use that to make the boat go faster? Nothing - because to do so is to violate all three laws of thermodynamics. So this CAN'T work...it just can't. SteveBaker (talk) 03:03, 3 February 2009 (UTC)

The question was about traveling downwind. I don't think there is any known or theoretical craft that can do that. APL (talk) 00:09, 3 February 2009 (UTC)

I'm pretty certain it should be possible to make a land vehicle that goes downwind faster than the wind. I'm not certain if that video where they claimed it was happening really had a machine that would do it as it would be quite difficult to achieve. The under the ruler faster than the ruler video shows the principle. You just have to use the wind instead of the ruler. An interesting aspect is that using a turbine it should go in the opposite direction to which one would expect when the wind blows on it, I couldn't see in the video if that was happening. Dmcq (talk) 00:08, 3 February 2009 (UTC)

These are two VERY different scenarios. By going faster than the wind, you actually introduce forces in opposition to your movement, as opposed to the ruler, which is still providing a forward thrust to the cart.-RunningOnBrains 00:34, 3 February 2009 (UTC)

They are not different scenarios. You might see it easier if you attach little paddles round the big wheel in the video and only blow over the top wher the ruler went. The paddles at the top would still go slower than the wind even though the vehicle goes faster. The same would happen with a turbine suitably geared. This is why the turbine would appear to be going round the wrong way. Dmcq (talk) 01:12, 3 February 2009 (UTC)

Several people have pointed out scenarios where one can reach speeds faster than the wind by traveling at an angle to the wind. If you can do that, then all you need is a way to efficiently turn. Carry that extra momentum with you as you turn to the same direction as the wind, and you will for a while be able to coast at a speed faster than the wind. Once you lose momentum, turn back to an angle to pick up speed again. Lather. Rinse. Repeat. Assuming the vehicle can turn efficiently enough and coast at very low drag, it should be possible for one to travel with an average velocity greater than the wind. Dragons flight (talk) 00:49, 3 February 2009 (UTC)

There is no denying that you can attain a SPEED greater than that of the wind. Yachts do it all the time. The question is whether you can move fast IN THE DIRECTION THE WIND IS BLOWING (ie: If the wind is blowing from the south, can you move northwards faster than the wind. Zigzagging does indeed let your speed be much higher than the wind - but your net progress IN THE DIRECTION OF THE WIND won't be any faster at all. SteveBaker (talk) 03:03, 3 February 2009 (UTC)

Steve, if you are moving faster than the wind speed at a angle and you turn to the direction of the wind, then conservation of momentum will now have you moving temporarily faster that the wind in the direction of the wind, at least until friction and air resistance slow you down to match the wind speed. This may not be practical in a boat, but I am fairly sure one could achieve useful results with a sail car. The turning allows one to achieve temporary bursts of speed in the direction of the wind that exceed the speed that the wind blowing behind you could support. In other words, by zig-zagging under the right conditions, one can achieve an average speed in the direction of the wind that is faster than the wind. Dragons flight (talk) 06:36, 3 February 2009 (UTC)

Momentum is a VECTOR quantity - not a SCALAR. SPEED is not the same thing as VELOCITY - and momentum is MASS x VELOCITY - not MASS x SPEED. Hence when your boat turns a corner - momentum isn't being conserved so some energy input is required. Bottom line is that to turn a yacht you need either a winch or some big muscular sailors hauling on ropes. That's an energy input - and once you have that, it's not a closed system anymore - so all bets are off. SteveBaker (talk) 16:14, 3 February 2009 (UTC)

Actually, I think the key factor is the water. By turning the boat (which requires a small amount of energy input, admittedly) you change the hydrodynamics and the water pressing against you is what changes your velocity. Consider a glider - the energy required to move the flaps (or whatever part of the glider it is that makes it turn) is minuscule compared the the energy required to turn the glider around, that extra energy comes from the air (well, I'm not sure there's an actual transfer of energy, but in any case it's interaction with the air that changes the momentum). --Tango (talk) 16:22, 3 February 2009 (UTC)

Nearly all of the force to turn a car, boat, plane, etc. is provided by the ground, water, air, etc. Just as throwing a ball against a wall, causes it to bounce back with no additional expenditure of energy, pushing against the ground can change one's direction of travel at virtually no cost. Also, when traveling at an angle to the wind in your boat, you are already using the force of the water to provide the cross-wind acceleration for your boat, so it was never a closed system to begin with. Dragons flight (talk) 17:57, 3 February 2009 (UTC)

Are sailboats and yachts limited to wind speed when heading directly downwind? Yes. However, the original question involved a "machine that moves downwind", and is not limited to a sailboat (with relatively few moving parts). We are free to design a much more complicated machine, one such design I put forth below.

• The machine would consist of multiple Wind Energy Collection Assemblies (WECAs) that would take turns collecting, converting, and supplying energy to the base assembly that would use that energy to drive its propulsion system.
• Each WECA would contain a wind collection device, such as a turbine, plus a ground support structure (legs) that would brace the WECA against the ground.
• Two or more WECAs would be mounted on a tank-track-like system that would rotate such that the top of the track remains stationary relative to the ground, while the bottom advances at 2x vehicle ground speed.
• Each WECA would have a deployed and retracted configuration. While a WECA is on the top of the track, it would deploy its support structure and wind energy collection device. As the back end of the machine reaches a WECA. that WECA would disengage its ground supports, retract its wind collection device, and configure itself in a compact arrangement for transport to the front of the machine, where it will redeploy for another cycle.
• Energy collected by the WECAs would be used by the base assembly to power the machine's propulsion system, such as power driven wheels, and to replenish any energy lost by the other moving parts due to mechanical friction.

Would it work? The ground supports will transfer the reactive force from the wind energy collection to the ground, so there is no force acting against the WECA track. With an even number of WECAs on the track, conservation of momentum will allow the WECAs to rotate through the system with no sustained energy requirements. The mechanism for deploying and retracting the WECA could be designed using energy recovery techniques. A streamlined enclosure would be designed around the propulsion system and the lower part of the WECA track (including the advancing WECAs) to minimize air resistance. Note that the energy gathered is dependent on the gradient between the wind and the ground, and does not depend on vehicle speed.

Energy collection would be limited by the size of the deployed wind collection devices, which could be arbitrarily large. Some energy collection opportunity would be lost during the time its takes for each WECA to reconfigure itself between deployed and retracted. Energy losses would include vehicle aerodynamic drag, the aerodynamic drag of the retracted WECAs being transported internally, ground friction, and the mechanical friction from the sum of all moving parts. With good engineering, this loss could be kept to a minimum (theoretically approaching zero). The difference collected and lost energy is available for propulsion, and could accelerate the machine up to a speed at which the energy losses match the energy collected. Theoretically, with a machine of sufficient scale and engineering perfection, there is no upper limit.

Could it be be built? I believe it would be quite an engineering challenge, but I think the concept is sound. Have I missed anything? -- Tcncv (talk) 03:56, 3 February 2009 (UTC)

Yeah - you've missed EVERYTHING! As the vehicle accelerates to a speed equal to that of the wind - there is a point when there is zero relative wind-speed. To someone standing on top of the vehicle, it would be exactly like the wind just stopped blowing. At that moment, where do you collect the energy from to accellerate the vehicle to higher speed? It's exactly like saying that I could make my car go faster by collecting the air that's pushing against the front of the car at 50mph and use that to make the car go faster. You simply can't do that - it's a perpetual motion machine and the laws of physics won't let you do that. This whole thread is just a matter of people wildly speculating without looking at the very basic underlying physics. There is simply no such thing as perpetual motion. I don't care how clever you get with WECA's and other bullshit - I don't even have to read your long explanation. You can't beat the laws of thermodynamics no matter how hard you try - period. Just give it up. 16:06, 3 February 2009 (UTC)

Right. From the reference frame of the vehicle, the wind has stopped moving. But now the ground is moving BACKWARDS. THAT is what you harness. Get out of the mindset of thinking that your energy comes from air moving relative to the vehicle. It doesn't. It comes from the GROUND and the AIR moving RELATIVE TO EACH OTHER. Maelin (Talk | Contribs) 16:44, 3 February 2009 (UTC)

Maybe you missed the part where the wind energy collection is performed when the assemblies are stationary relative to the ground and in fact braced against the ground, so it is indeed able to collect energy from the wind while as other parts of the machine advance ahead of the wind. But it seems that the main attention of this topic is focused on the internet hoax, so I'll just sit back and watch those discussions. They are quite entertaining. -- Tcncv (talk) 01:33, 4 February 2009 (UTC)

It certainly is possible. Here is a video of some fellows testing such a device under fairly careful conditions. They first show the video of someone performing the experiment on a road, and then produce a replica of the device on a treadmill. Maelin (Talk | Contribs) 15:52, 3 February 2009 (UTC)

You can't tell anything from those videos. Remember: a YouTube video does not constitute scientific evidence - people make fake YouTube videos all the time - and we get asked about them here all the time. The device running down the road is probably going downhill - the road looks level - but if the camera is mounted horizontally in the car and the car is going down the same hill - then that's exactly how it WOULD look. In the case of the treadmill, there is probably a fan blowing on it off-camera. Please don't fall for that kind of crap. This is a classic "free energy" nutjob thing - it's been around for years - along with all of the other crazy perpetual motion machines. SteveBaker (talk) 16:06, 3 February 2009 (UTC)

Here they take a good surround shot of the setup while the device is running to show that there are no fans or other such cheats going on. There is a whole sequence of these videos under this user account showing how they made the device and how it works. Maelin (Talk | Contribs) 17:20, 3 February 2009 (UTC)

I've just had a good look at that video and it all seems to be in accord with how I would expect such a machine to work and the fan is turning the way I thought it would rather than how a hoaxer would do it and th proportions seem about correct. I believe it is all kosher. I'm surprised it worked quite so well, perhaps there is hope for one that would actually work in 5 knot winds on water. Dmcq (talk) 16:22, 3 February 2009 (UTC)

How do you account for Steve's point that when travelling at wind speed, there is no wind? Where does the energy come from to get you past that point? Are you trying to collect energy from the wind going backwards once you are faster than wind speed (having used stored energy to get there)? Doesn't the added drag from such a system at least balance the energy gain? --Tango (talk) 16:27, 3 February 2009 (UTC)

When travelling at wind speed the propellor is driven by the wheels to cut into the wind and pull the cart forward into the wind. Drag will eventually limit the speed but is not enough at that point to overcome the energy generated using the difference between the air speed and the ground speed. Dmcq (talk) 16:36, 3 February 2009 (UTC)

The energy comes from the fact that the air and the ground are moving relative to each other and that for all intents and purposes they are immutable things. The fact that it's air just confuses matters - you'd be better to look at those charming "Under the ruler faster than the ruler" videos (first one here) to see how such a system is perfectly plausible. Maelin (Talk | Contribs) 16:42, 3 February 2009 (UTC)

Ok, I'm getting there... this is related to that weird "the bottom of a wheel is stationary" thing, isn't it? While I know and understand that it's true, it's very weird... In the case with the ruler, limiting friction with the paper is pushing the cotton reels forwards, while dynamic friction with the ruler is pushing it backwards, but with less strength, this gives a net forwards force. Very weird... --Tango (talk) 17:12, 3 February 2009 (UTC)

No, I'm not there... Why is the friction with the ruler less than with the paper? I can see from the video that it must be, but I can't see how... --Tango (talk) 17:24, 3 February 2009 (UTC)

You could actually have teeth on the ruler ground and bobbin rather than depending on friction. Dmcq (talk) 18:16, 3 February 2009 (UTC)

Well, that's just friction taken to a macroscopic scale, it's the same principle. --Tango (talk) 18:30, 3 February 2009 (UTC)

I have now done the experiments shown in under the ruler faster than the ruler vdeos (with a Teddy bear and Upsy Daisy as spectators) and I can confirm they with just a little tweaking they work very well. Dmcq (talk) 20:57, 3 February 2009 (UTC)

If these craft perform as advertised, why does no one race them against a similar cart with a square-rigged sail? Why does no one measure their speed and compare it to wind-speed.

Treadmill tests are unconvincing. Out of context experiments testing false analogies are one of the pillars of free energy self-delusion. (Yes, I understand that in this case the energy is not free.)

I understand that energy can be extracted from the fluid moving at a different speed, but in doing so you pick up momentum from the fluid. The energy you extract from the fluid is not free.

At the zero-wind point, any energy extracted from the wheels clearly comes out of the craft's forward velocity. The idea that that same energy could somehow be put back into the craft for a net acceleration does not make sense. APL (talk) 20:54, 3 February 2009 (UTC)

The idea is that the energy comes from the ground, which is moving relative to the craft (it's in contact with the ground, so the whole Earth has to be included if you want a closed system, and there is plenty of energy available there). I haven't quite got my head round it yet, but I'm certainly not as sure as I was that it's impossible. --Tango (talk) 22:16, 3 February 2009 (UTC)

I understand that, but (from the craft's perspective) how do you extract that energy without picking up equivalent momentum from the moving ground? Or, to put it another way (From the grounds perspective) how does the craft extract energy from it's own wheels without slowing the wheels, and it's own forward velocity?

It's obviously possible to extract energy from the ground-air system. But if both portions of the ground-air system are going against you, I don't see how you're going to extract the energy without picking up an equivalent amount of momentum in the 'wrong' direction.

And most importantly, if all these people have built devices that claim to do a certain thing, why is there no evidence, even on YouTube, that they can do that certain thing? Why are there only videos of them doing other things? Nobody else finds that suspect? APL (talk) 13:56, 4 February 2009 (UTC)

This video shows how you can take advantage of two things moving in the same direction (relative to you) to move in the opposite direction (or equivalently, how to move in one direction faster than either of the two things you are using for power). This is a set of videos of people who have built devices that do precisely that using the wind. Air moving over stationary ground (wind) is equivalent to the ground moving under stationary air (a treadmill in a closed room). Maelin (Talk | Contribs) 15:36, 4 February 2009 (UTC)

I think I'm going to satisfy my curiosity by building one of these things and buying myself a hand-held Anemometer.

If it works at all then I'll add an R/C servo to the back wheel. That'll make it worth the effort even if it doesn't break the faster-than-wind barrier.

I'll report back in a week or two. (Longer if I can't find a parking lot without snow on it.) APL (talk) 18:01, 4 February 2009 (UTC)

do insects have kidneys?

… and if it has a different name, which is it? I'm sure they have, as they also have blood which must be cleaned somehow. The insect article anatomy picture doesn't show anything, nor does the kidney article have an evolutionary section. --Ayacop (talk) 10:55, 2 February 2009 (UTC)

Do they have blood? they dont have a circulatroy system. And the insect article says that they have no closed veins or arteries. So I dont see how there could be a fluid analogous to blood from larger organisms. —Preceding unsigned comment added by 129.67.37.225 (talk) 11:43, 2 February 2009 (UTC)

The equivalent of blood in insects is hemolymph. I believe it does carry waste away from cells, so I guess there must be some way of filtering it. I've found a paper ([24]) talking about it. I haven't researched it in detail, but there is clearly something that serves an equivalent purpose to kidneys in insects. --Tango (talk) 11:51, 2 February 2009 (UTC)

See Malpighian tubule system. Gandalf61 (talk) 12:04, 2 February 2009 (UTC)

Do not expose to direct sunlight

Does that mean "while switched on"? ~ R.T.G 13:49, 2 February 2009 (UTC)

No. APL (talk) 13:51, 2 February 2009 (UTC)

Well its short but i sort of believe it :) ~ R.T.G 14:18, 2 February 2009 (UTC)

It depends, though. If it's a camera with a sensitive image sensor, it might not do to point it at the sun: but if the shutter is closed because it's off, nevermind.

It would help to know what the heck you're talking about...but unless it's a bomb with a solar-powered detonator...it's hard to imagine anything that would be damaged by sunlight exposure ONLY when it's switched on. SteveBaker (talk) 14:37, 2 February 2009 (UTC)

Many plastics break down in the presence of UV light from direct sunshine and many types of paper yellow and weaken; such products should always be kept out of direct sunlight. StuRat (talk) 17:47, 2 February 2009 (UTC)

Yes, indeed - but why only "while switched on" - as the OP asks? SteveBaker (talk) 18:57, 2 February 2009 (UTC)

I just made a general comment about why to avoid direct sunlight, which applies when on or off. My comment wasn't an answer to you, it only appeared to be because you hadn't indented your answer to the Original Poster. StuRat (talk) 21:59, 2 February 2009 (UTC)

In my student days, I turned on a sensitive detector while the lights were on in the observatory, thereby annoying my astronomy professor. Clarityfiend (talk) 19:32, 2 February 2009 (UTC)

Turning it on and off shouldn't have made any difference. Un-capping it in sunlight would be the problem. SteveBaker (talk) 20:22, 2 February 2009 (UTC)

Maybe they are trying to avoid the equipment becoming toast or starting a fire.76.97.245.5 (talk) 20:56, 2 February 2009 (UTC)

LCD screens can be damaged by prolonged sun exposure. I can only find forum postings as sources [25], but I'm pretty sure it's true.-RunningOnBrains 00:41, 3 February 2009 (UTC)

Well, my lcd monitor can get some direct sunlight from behind it and I just was switching it off or closing the blinds and it is only temporary but I had to worry if it was still getting damaged (and my computer is in the same situation). Sometimes the sun is hot around here, even when its been snowing, so hopefully I don't wreck my little monitor or my nice computer. Although not using as much energy as CRT, LCDs do cope with more localised heat but that doesnt mean that UV doesn't degrade it. ~ R.T.G 12:10, 3 February 2009 (UTC)

The degradation due to sunlight is the same no matter whether it's turned on or off...it's a pretty tiny effect though. I wouldn't worry about it personally. SteveBaker (talk) 15:14, 3 February 2009 (UTC)

OK thanks Steve ~ R.T.G 16:36, 3 February 2009 (UTC)

"Pretty minimal"? Depends where you live. [26] Gwinva (talk) 22:11, 3 February 2009 (UTC)

wind power

Is there any wind power or wind mills to generate current for a individual home(220v) in a city?Prince sha (talk) 14:32, 2 February 2009 (UTC)

If you google for "domestic wind power" you'll find a ton of small windmills suitable for powering an individual home. Their effectiveness in a city may be a little tricky though - adjacent buildings could do some very strange things to your wind-flow. Also, in a confined space you may find that your local planning laws prevent you from putting one up. SteveBaker (talk) 14:40, 2 February 2009 (UTC)

Plus small single domestic installations rotate fast and make a lot of noise. However tiny top up wind turbines to provide a small amount of electric power are possible although uneconomic. [27] discusses one put up by the leader of the opposition in the UK. --BozMo talk 14:47, 2 February 2009 (UTC)

Wow! In the study, one of the domestic wind turbines didn't generate enough electricity to power it's own electronics! Ouch! The average turbine produced 214 watt/hours per day...so three or four lightbulbs. They say that on average people are saving 33 UKpounds per year from their 1500 UKpound investment. Since I very much doubt they'd survive 45 years of continual service - they'll never pay for themselves. However, the study also showed that one of these turbines that they studied DID produce enough electricity to run the house because it was situated on top of a 10 storey building. So it all CRUCIALLY depends on where the thing is situated...because anything from using more electricity than it makes(!) to running your entire house is a pretty huge range - and if the average is a 45 year payback time - then you'd better be installing it somewhere very much better than the average household is managing to do! SteveBaker (talk) 20:21, 2 February 2009 (UTC)

Hand over your geek card, Steve... It's "watt hours", not "watt/hours" - it's power times time, not power divided by time. And three or four lightbulbs might use around 214 watts, not 214 watt hours (unless they were on for an hour). You're a disgrace... --Tango (talk) 16:09, 3 February 2009 (UTC)

Old-fashioned windmills have wide, slow-turning, blades. Modern wind-powered generators have narrow blades. Would wide, slow-turning blades be best for low wind velocities? It seems that the wide blades would generate more torque, which would partly compensate for their slower speed of rotation. A wide-blade windmill might also make less noise. —Preceding unsigned comment added by 98.17.34.148 (talk) 17:35, 2 February 2009 (UTC)

It's probably safe to assume that the manufacturers already tried that. It's certainly notable that airplane and helicopter propellers (which are really just backwards windmills) are all very skinny - but boat and submarine propellers are always very fat and short...and so are desk fans and airconditoner fans. SteveBaker (talk) 20:21, 2 February 2009 (UTC)

For mounting on the roof of a city building, such as a 3 story apartment building, consider a vertical axis wind turbine. They are more attractive than the horizontal axis ones, and can be mounted much like a TV antenna, resting on a plate on the roof and guyed to the wall of the staircase projection. Installation cost/payback is the question. Edison (talk) 20:25, 2 February 2009 (UTC)

Savonius wind turbines are easiest to DIY. Although they are less efficient the low installation cost makes them one of the more economical choices for a home installation. AFAIK they are also less fragile in case of occasional high winds, which can break DIY horizontal axis designs. Studying wind patterns throughout the year to find the best location for installation is definitely indicated. Just putting it on the roof of a shed because it looks good there isn't the thing to do. 76.97.245.5 (talk) 21:13, 2 February 2009 (UTC)

Many are available for that and as I live in a windy area myself I was enquiring about it and a very good expert swore to me black and blue that they need to be way up in the air, that rooftop ones are more or less crap. Now I looked into it a lot and if you have a lot of wind I reckon you could get you lighting and stuff but to be fair to the guy (the guy involved in Scoraigwind as it happens), to power your cooker and fridge etc. you need wind strong enough to force the blades against strong magnets. You need something like 20 metres clearance for the best wind and in a city, the houses slow the wind down, nevermind tall commercial buildings and apartment blocks. ~ R.T.G 16:42, 3 February 2009 (UTC)

In saying that, if you can put one up in the air (citys wont let you do that) you can make them out of car alternators with a basic mechanical, carpenting skill. Look at http://www.scoraigwind.co.uk it gives stacks of info and links ~ R.T.G 16:45, 3 February 2009 (UTC)

People who "Don't like music"

I have a friend who has claimed over the years that he "doesn't like music" and I believe him. Oddly enough however if you spend time with him you'd think he's hyperactive and he will ALWAYS be humming or singing a song - usually with the lyrics corrupted to something else - or just repeating a tune to a popular song. This might seem contradictory, but I gather he doesn't intentionally listen to music, but if he hears any it will get stuck in his head.
Notably, he has a form of dyslexia, an above-average IQ and above-average level of general knowledge. He strictly only listens to talk radio.
Based upon his remarks I assume he has no "appreciation" of music, and has no favourite songs".
Do you have any references or explanations for this type of thing?
From my unhelpful googling for other cases, someone suggested checking if he's tone deaf or has other audio-perceptual problems - but the other day in the car he managed to hit the requested note when repeating a song -- and all his other songs tend to be in tune.
Rfwoolf (talk) 17:06, 2 February 2009 (UTC)

If it comes to that, a lot of people don't like classical music.

Maybe he doesn't like music precisely because it gets stuck in his head, which can be annoying. StuRat (talk) 17:43, 2 February 2009 (UTC)

I have no explanations, but I can do anecdotes, if that helps: I have nothing against music, but I rarely make an active choice to listen to it. It just doesn't interest me. I have great difficulty making out the lyrics in songs, but I don't know if that is cause or effect. I hum and sing to myself about as much as anyone else, I think. I am a mathematician and am quite interested in music from a technical perspective, and I do appreciate music when I do listen to it. I have, at various times, played the recorder, piano and trumpet, although never had the dedication to get anywhere with them. I'm not dyslexic, but I do have an above-average IQ and level of general knowledge (like most Ref Deskers, I guess!). I don't know if any of that helps. --Tango (talk) 18:40, 2 February 2009 (UTC)

One explanation may be rooted in human communication. Research found that when people are talking they are trying to reach a common "hum". Individuals higher up in the hierarchy literally "set the tune" with lower level people "chiming in", (Our language developed phrases for this before science found what was going on.) So people who are attuned to communications are more prone to being influenced by ambient muzak. (I bet you can find the study wigh some googling. I'm afraid I'm a bit too busy to dig it up.) There's even an association that has been trying to limit the use of muzak. My sympathies to your friend. It must be somewhat like hearing the phone ring running to pick it up and finding it was on TV. 76.97.245.5 (talk) 20:36, 2 February 2009 (UTC)

Thanks for the interesting comments. The idea about communication is interesting and I will continue to monitor his communication skills and communication behaviour. I'm still trying to fathom through what you're trying to say though - are you saying people that tend to "set the tune" would be put off by music, while those of us that "chime in" would like to 'chime in' to a song? Or are you saying conversely that those of us that are better at communication in terms of oration, diction, tone, emphasis, expression etc would appreciate music more than those who lack the aforementioned? (I tend to think that a person's taste in music could be linked to that -- people that favour rap music for example, compared with those that favour classic music, or those that favour jazz, or heavy rock - surely it is about expression, and therefore no matter how tone-deaf, monotone, tone-deaf, or communicationally unadept an individual is they will always find something in the musical spectrum that they like??). I will keep thinking. Thanks again Rfwoolf (talk) 22:08, 2 February 2009 (UTC)

For myself I can't see why people would want to listen to a piece of music more than once or a couple of times. There may be a few films or books one wants to read more than once but going around listening to the same bit of music 50 times just seems weird to me. Dmcq (talk) 09:42, 3 February 2009 (UTC)

"Music is a drug" is a common layman's cliché. Pleasurable drugs are often readministered, so I would guess pleasurable music is "readministered". --Mark PEA (talk) 19:54, 3 February 2009 (UTC)

First time listening to anything worth relistening to is much less good than the follow ups; as you start anticipating the patterns and experiencing more of the details it just gets better and better. It can feel a bit like the music is slotting into your mind: as you relisten, the slot for it becomes a better fit. 79.66.57.25 (talk) 00:14, 4 February 2009 (UTC)

Dmcq, you seem to inhabit a different world than the bulk of humanity. The manufacturers of CDs, MP3s, musical instruments (and previously LPs, EPs and cassette tapes), have a ready-made market, because music is one of the great unifiers. There are some pieces of music I've listened to literally thousands of times, and hope to listen to them thousands of more times. Why? Mainly because I enjoy them, and they give me pleasure. Sometimes it's because they just happen to be playing on the radio while I'm tapping away on my keyboard; but I never think "Oh, I've heard that before, so I'll put a CD on". No, if I like it, I like it. (And even if I did do that, I'd still be choosing a CD I'd heard before; because we don't buy CDs just to listen to them once and never again; that would be extremely poor value for money.) I might think "I don't like that particular piece playing now, and it's going to go on for another hour or more, so I'll turn it off and put something of my own choice in the CD player or the record player" (yes, I still have lots of vinyl LPs). Similarly, I've played many pieces on the piano literally thousands of times, and will continue to play my favourites thousands of more times. Naturally, every performance is at least subtly different from every other, just as every recording of the same piece is at least subtly different from every other. But leaving that aside, if there were only 1 recording of some work I really love, I'd happily listen to it over and over and over. Books are different. I might re-read a favourite book, but usually with a gap of at least a year since the last reading. Having pictures on your walls is analagous. They're there because you like them. You don't walk into your loungeroom and think "I've seen this picture before, so I'll take it down and put a different one up" - do you? And you'd then have to change it again the next day, and the next day ... No, it keeps on giving you pleasure, so you keep it there so it can continue to keep on giving you pleasure. That might stop if you decide to redecorate your room, but that's a different matter. So, if the bulk of humanity likes listening to the same music many, many times, but a small %age of people don't, who are the "weird" ones? -- JackofOz (talk) 00:59, 4 February 2009 (UTC)

Earthing

What is the reason behind earthing a electric neutral wire.If earth is used for conducting electricity then why does a wire needed for it? —Preceding unsigned comment added by 120.89.115.198 (talk) 18:22, 2 February 2009 (UTC)

The earth is only there for safety purposes, it makes sure any electricity that gets to the wrong place (eg. the metal casing of the device) goes safely the earth rather than shocking anyone that touches it. The neutral is there is complete the circuit in ordinary circumstances. --Tango (talk) 18:33, 2 February 2009 (UTC)

In some countries the "neutral" isn't earthed, but is "negaitve live". It is a perfectly valid way of doing things, but isn't the UK way. -- SGBailey (talk) 18:46, 2 February 2009 (UTC)

Which particular countries are you thinking of? I would be interested in how they do it.--GreenSpigot (talk) 19:40, 2 February 2009 (UTC)

Also in those countries, is the negative live always negative or does it have alternating voltage on it?--GreenSpigot (talk) 20:13, 2 February 2009 (UTC)

May be one of those urban legends. Or I may have been thinking of US 240V supply. In any case I haven't found a reference, so forget it. -- SGBailey (talk) 21:49, 2 February 2009 (UTC)

(edit typos)In the early days of telegraphs and telephones, it was discovered that substantial money could be saved by running only 1 wire per circuit from terminus to terminus, and using a buried metal plate or ground rod to connect to the earth at each terminus. When 2 wires were used per circuit, it was called a "metallic" circuit. There was less noise and crosstalk with a 2 conductor metallic circuit. Some high voltage DC transmission lines have a + and - conductor, but in an outage of one conductor, they can operate with the other conductor and a ground conductor. In your home, the grounding of the neutral is a safety measure. Without it, a transformer failure or a broken high voltage line falling on the wires to the house could result in the full high voltage being on all the wires in the house, electrocuting anyone who came near anything electrical. What is a "negative live? Maybe they refer to providing 2 wires with 240 volts between them. In countries I am familiar with, there would still have to be a ground conductor from the utility to the building to ground the switch/breaker/fuse enclosure, so that an insulation failure does not energize it at 240 volts to ground. This would be true even if it is 3 phase service or 240 volt service without a neutral. Edison (talk) 20:21, 2 February 2009 (UTC)

AFAIK, Neutral is earthed by the the electricity company at the substation. Earthing neutral in your home sounds a bad idea that would unbalance the system. Earthing earth should be done locally (and at the sub-station). -- SGBailey (talk) 21:49, 2 February 2009 (UTC)

That's my understanding as well (at least for the UK). --Tango (talk) 22:48, 2 February 2009 (UTC)

In a typical U.S. home, we get a single "240VAC" phase delivered on two wires plus a ground wire to the Electrical distribution panel in the home. At the distribution panel, ground wire is tied to anther ground wire that in turn runs to a long copper rod that is driven into the earth outside the home. In the panel, the house neutral and the safety ground are both connected to the panel ground. approximately half of the home's "120VAC" circuits use one of the two hot wires and neutral. The other half of the "120VAC" circuits use the other hot wire and neutral. the "240VAC" circuits in the house are connected to both hot wires. -Arch dude (talk) 00:08, 3 February 2009 (UTC)

From our article on ground and neutral, it seems that both European and North American installations generally link earth and neutral wires at some point between the final distribution transformer and the end user's fuse or breaker panel. Separate earth and neutral wires are only maintained inside the residence. TenOfAllTrades(talk) 00:02, 3 February 2009 (UTC)

So ArchDude, in the US home you get 2 phases: each of 120V balanced about ground. Is that what you are saying?--GreenSpigot (talk) 01:04, 3 February 2009 (UTC)

Nope, it's single phase, or split-phase. You could say one line is ∠0° and the other ∠180°, but that's just a matter of how you are measuring, there is still only one waveform. It's "balanced" if there are equal loads on each line and there is no current through the neutral. The neutral wire between the breaker box and the pole transformer carries a current equal to the difference in the currents of the other two lines (see Kirchhoff's Current Law). Typical distribution systems in the U.S. are "wye circuits" and are grounded at the breaker box, the pole transformer, each pole, and the step-down transformer at the substation. Most transmission lines, and i think some distribution systems are "delta circuits"—no neutral wire so no connection to ground.—eric 02:57, 3 February 2009 (UTC)

Also, SGB seems to be contradicting him/herself by at once saying that earthing the neutral in the home is a bad idea and then proposing that it should be done locally (in addition to the substation)--GreenSpigot (talk) 01:10, 3 February 2009 (UTC)

see Earthing system.—eric 03:03, 3 February 2009 (UTC)

As noted in previous Q&A, in U.S. residential wiring the power company provides one phase with 120 to ground from each hot wire and 240 between the hot wires. The neutral and ground conductors are bonded together at the transformer and then at the house main breaker panel. In the house, the neutral carries the imbalance between the 2 hot conductors back to the main panel, if 2 hot wires and a neutral are used as a set. More modern wiring provides a neutral for each hot wire, since with electronic loads the neutral currents do not cancel like they tended to with resistive or reactive passive loads. There are some customers in downtown areas who get 120/208 volt service, since they actually are provided with 2 phases 120 electrical degrees apart. Each hot wire is 120 volts from ground/neutral, and the voltage between them is 208 volts. This system is for the benefit of busnisses who need three phase service, and who just have the third phase brought in. Edison (talk) 16:11, 3 February 2009 (UTC)

Would lens flares ever have motion blur?

I was just curious if real world lens flares would ever have motion blur? --70.167.58.6 (talk) 19:32, 2 February 2009 (UTC)

Motion blur is a consequence of the recording technique you are using - film, digital photosensors, etc. If the light source is moving - then the lens flare must also move - and the recording media can't tell whether the light that's hitting it is a lens flare or light from an actual object - so, Yes - lens flares do exhibit motion blur in things like cameras, etc. Human eyes don't exhibit lens flare per-se - although you do get effects like starbursts from bright light due to the behavior of our eyelashes. Our brains visual cortex "hides" motion blur from our consciousness - so we don't really "see" it as such - although if you could monitor the output of a rod or cone cell, it would have to be there because no image sensor can ever be infinitely fast. SteveBaker (talk) 20:06, 2 February 2009 (UTC)

[medical Q] identify a tool

What is this tool called? It's, I think, informally called a "stripper" and is used, if I understand it correctly, to clamp an IV (infusion) tube and roll the tube through the tool in order to push the tube's contents down along the tube and out.—msh210℠ 22:00, 2 February 2009 (UTC)

Yes, "stripper" is correct. The same tool is pictured in online catalogs here and here. --Scray (talk) 04:00, 3 February 2009 (UTC)

So much for "Wikipedia has an article on everything. Nimur (talk) 17:20, 3 February 2009 (UTC)

Thanks much, Scray.—msh210℠ 17:53, 3 February 2009 (UTC)

@Nimur, see Stripper (tool). Created tiny stub now, added to disambiguation page, and added a redirect from Tube stripper. Everyone, please improve it. --NorwegianBlue ^talk 21:41, 3 February 2009 (UTC)

Black dwarf sun and planets drfiting

The time the sun becoems a black dwarf, is it trillion of years. Since sun will have lost about 90% of gravity by the time it becomes a white dwarf, is this possible Uranus and beyond would have flown off it's orbit? Why will planets eventually drift away and left with black sun with no planets around it?--69.226.46.118 (talk) 23:22, 2 February 2009 (UTC)

According to Stellar evolution#White dwarfs, the Sun should only lose about 40% of its mass. The planets will move into higher orbits, but they won't escape completely without some kind of external interaction (another star passing close by, perhaps). Baring such interactions, the radiation of gravity waves will cause a loss or energy and the planets will very slowly spiral in (over the course of trillions of years, if not longer). --Tango (talk) 00:11, 3 February 2009 (UTC)

• They said on Formation and evolution of the Solar System eventually sun will just be left with no planets orbiting around it. And what does and the planets will very slowly spiral in (over the course of trillions of years, if not longer). mean?--69.229.108.39 (talk) 00:53, 3 February 2009 (UTC)

  General relativity predicts that orbiting objects will emit gravity waves. This means there is a loss of energy so the planet will fall towards the sun (just friction causes a ball rolling round inside a funnel to fall towards the middle). On the scales of planets orbit the sun (rather than, for example, neutron stars orbiting each other), this effect is tiny, so it would take trillions of years for the planets orbits to decay noticeably. --Tango (talk) 15:12, 3 February 2009 (UTC)

Talking about 90% of gravity is awkward since the force of gravity changes over distance. It would be better to talk in terms of mass. Assuming a circular orbit for Uranus, the mass of the sun required to keep it in place at a certain distance r and orbital velocity v is

$m_{sun}={\frac {r{v}^{2}}{G}}$

where mass is in kilograms, r is the distance from Uranus to the earth in meters, and v is the velocity of Uranus orbiting the sun in meters per second and G is the gravitational constant. If Uranus hasn't slowed down or changed its radius from the sun appreciably by the time the sun loses a significant portion of its mass, you can see that rv² will stay the same but because the mass of the sun has dropped

$m_{sun}<{\frac {r{v}^{2}}{G}}$

This means that Uranus's orbit must change. Either it will settle out in an orbit more distant from the sun or it will escape entirely. For it to escape the gravitational effect of the sun it must have a high enough velocity. The escape velocity is given by:

$v_{e}={\sqrt {\frac {2Gm_{sun}}{r}}}$

which expressed in terms of v_e is

$m_{sun}={\frac {{v_{e}}^{2}}{2Gr}}$

If $m_{sun}<{\frac {{v_{uranus}}^{2}}{2Gr}}$ then Uranus will escape. I leave it as an exercise to the reader to determine if Uranus will escape given the questioner's parameters. (Translation: I feel too lazy to track down the speed of Uranus, the average orbital radius and plug it in myself) 152.16.15.23 (talk) 00:54, 3 February 2009 (UTC)

February 3

Front and back

There is a form of Antipredator adaptation where the front end of an animal looks the same as it's back. What is this called? (... and do we have a page?) 76.97.245.5 (talk) 00:18, 3 February 2009 (UTC)

The Rubber Boa when threatened hides its real head under the rest of its body and uses its fat stumpy tail as a decoy to lure predators into attacking its back end rather than the front. Its apparently convincing judging by individuals observed with quite a number of scars on the tail. I don't know if this type of mimicry has a particular name. 152.16.15.23 (talk) 01:03, 3 February 2009 (UTC)

Then there's the creepy earwig. StuRat (talk) 15:04, 3 February 2009 (UTC)

Just found the name for it: Automimicry 152.16.15.23 (talk) 01:33, 3 February 2009 (UTC)

Thanks a million.--76.97.245.5 (talk) 01:46, 3 February 2009 (UTC)

Breeding budgies and cockatiels

Is it possible to work out what the baby birds will look like, just by looking at the colour and markings of the parents and not knowing anything about their genetics or pedigree? The Budgerigar colour genetics and Cockatiel colour genetics articles don't really answer my question and use wording that I don't really understand. --84.68.231.212 (talk) 00:44, 3 February 2009 (UTC)

To help with understanding the wording, I would start by looking at Dominance (genetics) and dominance relation. If you can look at your birds and determine their phenotype you can hazard a guess at their genotype and do a Punnett square to determine what patterns of genes the offspring will receive. Once you know the genes the offspring have, you can hazard a guess at what phenotype they will have. You probably will not be able to determine appearence absolutely as there are many genetic factors which interact with one another (see Variable Expressivity and Penetrance) and some aspects of appearence are determined randomly. It may help if you can describe what varieties of birds you have: i.e are they an albino variety? Have a look at the list of common names for Budgerigar varieties and that mess of description in Cockatiel colour genetics. 152.16.15.23 (talk) 01:29, 3 February 2009 (UTC)

btw (sorry, don't have an answer - I never breed my birds for colour), those '...colour genetics' articles (which I've been minimally involved with) could probably do with a good cleanup and some rewriting from a more general perspective. Hint, hint... ;) --Kurt Shaped Box (talk) 02:51, 3 February 2009 (UTC)

Antidepressent

Medical question removed SteveBaker (talk) 02:26, 3 February 2009 (UTC)

I'm not sure that this question:

"This section says that semen has antidepressant properties. What would be the effects of injecting semen intravenously? Would shooting up semen (that's a horrible pun :) ) give you a better mood? flaminglawyer 01:10, 3 February 2009 (UTC) "

-constitutes a request for medical advice. The Flaming Lawyer is simply posing a hypothetical question (as lawyers do).

The answer, by the way, is that you'd most likely die suddenly from the semen embolism lodging in your cerebral arteries (causing a stroke) or coronary arteries (causing a myocardial infarction). So don't do it!

The Semen article does mention the putative antidepressant qualities of semen, based largely on an article published in New Scientist, in which the authors claim that women engaging in unprotected penile-vaginal intercourse scored better on depression scales than women who used condoms. It doesn't seem terribly responsible to promote unprotected sex, when at best their results indicate only an association, and not causation. The article speculates about the antdepressent effect of orally and anally administered semen, but has no supportive data. That's why the WP article uses the phrase "may have antidepressent qualities".

Stay safe! Mattopaedia (talk) 06:33, 3 February 2009 (UTC)

On further thought, it could also be very much like an amniotic fluid embolism. Still another reason to heed my previous advice - don't do it! Mattopaedia (talk) 13:05, 3 February 2009 (UTC)

Perhaps depressed women insist on condom use because they are depressed - they fear an undesired outcome and that is related to being depressed. If this is true, condom use is an effect, not a cause. —Preceding unsigned comment added by 98.17.34.148 (talk) 17:19, 3 February 2009 (UTC)

Or perhaps, despite the best efforts of condom manufacturers, unprotected sex is just more enjoyable. --Tango (talk) 19:50, 3 February 2009 (UTC)

The authors claimed to have eliminated potential sources of bias from their study design, but, as can be seen from these two responses, that would be essentially impossible in this case. There's innumerable potential associations and confounding factors. I suspect the study lacks sufficient scientific merit to be published in a peer-reviewed journal. The other problem is that claims of this nature seem to prompt people to make socially irresponsible comments that might encourage impressionable youths to engage in unsafe sexual practices. I don't think unwanted pregnancies and sexually transmitted diseases are particularly enjoyable, or have any antidepressant qualities. Mattopaedia (talk) 03:08, 4 February 2009 (UTC)

It has been suggested that chronically depressed women insist on the use of a condom during intercourse because of their greater fear of undesired consequences. This leads to the question of whether car drivers (men and women) who have depression syndrome take more care in driving than other persons do. Statistics on injuries to drivers in car accidents would be a source of information on this. Furthermore, do persons with depression syndrome take more care to avoid accidents of all types than other people do? Hospital statistics on patients hospitalized by accidents would be a source of information. If happy people are more accident prone, can it be said that, to some degree, they are happy-go-lucky? —Preceding unsigned comment added by 98.17.34.148 (talk) 10:21, 4 February 2009 (UTC)

If happy people are more accident prone, maybe they should be called happy-go-unlucky. —Preceding unsigned comment added by 98.17.34.148 (talk) 13:56, 4 February 2009 (UTC)

Brain wave crosstalk

Is it theoretically possible for one person's brain waves to spill over into another nearby person's brain and affect its functioning? NeonMerlin 02:15, 3 February 2009 (UTC)

No. The signal strength is VASTLY too small - and there is nothing in our heads that is even remotely like an antenna. SteveBaker (talk) 02:25, 3 February 2009 (UTC)

(after ec): Given the frequency range of the brain waves is roughly 1 - 100 Hz, most people think it is not possible. Many household and industrial appliances of the last 100+ years produce or used to produce much stronger electromagnetic emissions in that range than your neighbor's brain ever will. Still, there are no reports I am aware of that link any of these appliances to any systematic disruption or alteration of the thought process. --Dr Dima (talk) 02:32, 3 February 2009 (UTC)

Theoretically, could brain waves be transferred over a wired connection between two brains, as a matter of interest? --Kurt Shaped Box (talk) 02:36, 3 February 2009 (UTC)

Yes. You can use electrodes of appropriate types to inject any current(s) into any area(s) of the brain, provided your experiment conforms with the ethics requirements. You can therefore record a signal from one brain, amplify it, filter it, and inject it into another brain. That process will, most likely, not transfer any thoughts or qualia, though. For example, simply injecting current into a primary visual cortex location may produce a percept of a phosphene (small flash of light) at the corresponding retinotopic location; but not much more. Injecting a more complicated waveform is likely to have the same result, as the brain activity of the "donor" and "recipient" is neither coherent nor even necessarily similar. So a USB port on someone's forehead is still quite a few years away :) . On a somewhat related subject, you can also look at the deep brain stimulation article. --Dr Dima (talk) 03:08, 3 February 2009 (UTC)

Look there are (literally) a trillion neurons in your head. Maybe 10% of them are firing at the same time. That makes about a hundred billion teeny-tiny electrical signals...the total 'transmission' would be like all of the cellphone calls from the whole of planet earth all mixed up together...times about a thousand! If you don't have a trillion wires - you can't carry all of the information. But worse still (MUCH WORSE STILL) the arrangements of the memories and neural connections in my brain are TOTALLY different from yours. It's not a matter of connecting neuron A in my brain to Neuron A in yours, then B to B, C to C. My thoughts relate to my memories in ways that totally don't translate to those in your brain. So this isn't gonna work...and it's technically ridiculous. SteveBaker (talk) 03:23, 3 February 2009 (UTC)

Heidi (my wife) often knows what I'm thinking :) -hydnjo talk 04:03, 3 February 2009 (UTC)

'::::::Please explain "qualia." Edison (talk) 05:37, 3 February 2009 (UTC)

Women's Intuition, man's terra incognita.--Lenticel ^(talk) 05:39, 3 February 2009 (UTC)

Qualia. Richard Avery (talk) 08:34, 3 February 2009 (UTC)

Islam ... previous article

Removed Welcome to the Wikipedia Reference Desk. This is a place for people to ask questions that they are having trouble finding the answers for themselves. It is not a chat board or discussion site. There are many forums you can visit if you would like to expound your views on religion; this is not one of them. Thank you. 79.66.57.25 (talk) 08:20, 3 February 2009 (UTC)

Well, it's certainly great to see such an unbiased search for knowledge! Can we have the soap box back when you're done?

Anyway, I'll play along: if you think that people 1400 years ago didn't know that an embryo turned into a fetus, and so forth, you're wrong. (Furthermore, a fetus doesn't first grow bones and then cover them with flesh, so if that's what Mohammed thought, he was wrong.)

Likewise, the idea that you can only feel if you have your skin is wrong. (In fact, that's so obviously wrong that it boggles the mind. Haven't you ever heard of a toothache, for example?) If you mean that you can only experience a touch through skin, that's also wrong -- although it's certainly true that there may be no sensation in burned skin, the human somatosensory system also works in muscles and even bones. It's just that we aren't usually aware of such sensations. (What, you think they didn't have third degree burns 1400 years ago?)

As for what it would take to convince me that God exists, hey, I'm easy. A miracle will do just fine. It doesn't have to be a big miracle, either, it just needs to be unambiguous. He could use his awesome power to levitate me for a moment. Or he could appear to me and tell me to get with the program. Or he could turn someone I know and love into a pillar of salt, give me a dose of that Old Testament tough love. Trust me, I'll convert in a flash. I'd probably end up being a real zealous bastard, too. -- Captain Disdain (talk) 08:43, 3 February 2009 (UTC)

If God's going to turn people into pillars of salt, make sure he turns a few into pillars of pepper, for those of us who need to avoid salt in our diets. :-) StuRat (talk) 14:57, 3 February 2009 (UTC)

Trolling... —Preceding unsigned comment added by 129.67.37.225 (talk) 14:00, 3 February 2009 (UTC)

The OP sounded to me like someone who is genuinely ignorant of basic anatomy rather than a troll, though yes this is a reference desk for asking questions rather than just pushing ones opinion. Dmcq (talk) 15:31, 3 February 2009 (UTC)

Anyone who tries to push such opinions on this Reference Desk typically gets their arguments ripped to tiny little shreds under the withering force of actual science...I don't know what they think they might achieve by doing that - but for sure it ain't gonna make any converts. Quite the opposite in fact! SteveBaker (talk) 16:34, 3 February 2009 (UTC)

Even if you were made to levitate or to turn into a pillar of salt, you couldn't even rule out the possibility of it being an advanced alien species fucking with your brainBastard Soap (talk) 17:34, 3 February 2009 (UTC)

Well I'm willing to give the OP the benefit of the doubt and concede that God is a possible cause if I see someone transformed into a pillar of salt. Can't say I'd be particularly worried if it is god or an advanced alien species. Would it make much difference? Dmcq (talk) 18:22, 3 February 2009 (UTC)

I agree, there is little difference between a god and a super powerful alien that can turn people into salt (a feat that would require a Level 3 god, by Steve's classification). Seeing someone turn a person to salt wouldn't make me believe they had created the universe (although I would certainly listen to what they had to say on the subject). --Tango (talk) 19:10, 3 February 2009 (UTC)

Yes I'd certainly be willing to listen to them. As in what do you call a 200Kg gorilla with a machine gun?. (answer) Dmcq (talk) 20:36, 3 February 2009 (UTC)

Yes - transmutation of atoms (which I guess is what's required to turn someone into a pillar of salt) is a pretty impressive trick - but it's not proof of god-hood. We can do limited, small scale transmutation ourselves...so it's only just barely a "level 3" kind of a trick. Given the probabilities of each I'd definitely wield my mighty "+2 Razor of Occam" and go with "high tech alien" or perhaps even "Area 51 human". I'm not believing in any god who is unable to convince me that they can change the value of PI at will...although if they plan to actually DO that - would they please pick another universe to do it in! I don't really want to suffer the consequences of circles not joining up properly anymore! SteveBaker (talk) 20:42, 3 February 2009 (UTC)

The boundary between level 3 and 4 is highly subjective. Level 4 can be thought of as a variable level that increases as you learn about the universe, and approaches level 3. A level 3 god could certainly do it (there's nothing in the laws of physics to forbid rearranging protons, neutrons and electrons into a new pattern), very advanced level 4 gods probably could too. Creating a universe is a rather difficult feat to place - level 3 gods might be able to do it if you don't mind it being identical to the one they started in (barring initial conditions), however they wouldn't be able to observe the new universe in any way (it would probably look like a black hole to them, at least according to one multiverse theory). A level 2 god could observe it (and make it slightly different, too) by fiddling around with the speed of light in order to travel between universes. So, I think a god on a par with the Abrahamic god would need to be at least level 2. Heaven and Hell might require some level 1 stuff, though. I'd be happy if a god could prove themselves at least level 2, I think asking for level 0 is a bit much (primarily because thinking about them gives me a headache). Of course, power itself does not make one worthy of worship (a god that murders people for harmless curiosity doesn't sound worth worshipping to me...). --Tango (talk) 22:28, 3 February 2009 (UTC)

Quite interesting this Steve's classification! So level 0 corresponds to the top: still I don't understand why your classification doesn't leave a chance for further more powerful levels. Since there is no limit to the human imagination, I think that an open scale system should be more suitable (e.g. something likethis! ). Notice that the Cathar heresy exactly stated that the standard God (the old testament one) was not the top level (and was also quite a bad guy too), and that there was another God above! pma (talk) 23:18, 3 February 2009 (UTC)

I actually did agonize over that. Firstly, I'm a computer geek and counting from zero is "What We Do". It's really tough to conceive of something more powerful than changing mathematical truths (I certainly can't think of something more amazing than that). The idea that "there is no limit to human imagination" is something the Disney corporation would like to tell you...but actually, I think there are almost certainly limits - and I hit mine at "Level zero". It's tough to even imagine how much power level 0 would give you...let alone imagine something significantly more powerful than even that. I decided that if you could think of such a thing, you'd still be free to use negative numbers. I specifically didn't want to anthropomorphise the system too much by placing the zero point at where we are and then counting upwards towards the 'changer of mathematical truth'. My dog finds my ability to be able to make food appear as if by magic from a can to be godlike - so it's not unreasonable to need to talk about level 5, 6 and 7 abilities. As to the marginal difference between level 4 and 3 - I wanted a level corresponding to about where our science is - and a higher level representing the "Any sufficiently advanced technology is indistinguishable from magic" idea - hence I decided to separate 3 and 4 (it also fitted what I wanted to explain in that Ref Desk answer). I suppose you could say "Level 4 amazes SOME humans", "Level 3 amazes ALL humans". At level 4, you can influence people's thoughts - have telepathy - it's a REALLY powerful thing...fundamentally more than we can currently do...but certainly not more than we could imagine. Well, whatever, it's just a silly idea that enabled me to more easily explain a point - if you don't like it, feel free to make up your own scale! Let's not get too anal about it! SteveBaker (talk) 02:08, 4 February 2009 (UTC)

Mm. I was, of course, saying that these things would be enough to convince me. (Accompanied by a clear message that this was caused by God, of course; otherwise I could mistake it for any number of other things I haven't previously believed in.) I mean, if my ass were to be lifted off this seat right now by some kind of an invisible and impossible force, and a big, booming, and downright divine voice told me that this is the miracle, now get with the goddamn program, that'd probably convince me of God's existence. (That said, I did use the word "unambiguous" in there, so it'd have to be pretty clear-cut -- a picture of Jesus in my oatmeal wouldn't do it.) I'm sure I could come up with other scenarios, such as aliens, or delusions, or whatever, but once you go far enough with that, I might as well start wondering if I'm just a butterfly who's dreaming that he's a man, you know? No, I'd probably just go with it, at least as a strong working assumption.

It probably wouldn't make me like God, though. I mean, I'm fine with horrible things happening because that's just the way things are in our chaotic universe, but if there's a guy out there who could do something about it, but can't be bothered, and yet demands worship, that doesn't strike me as someone I'd love and respect. But I'd probably believe that he exists. -- Captain Disdain (talk) 01:19, 4 February 2009 (UTC)

That bothers me too. After I sat down and actually read the Bible from cover to cover (mostly to see what the big fuss was all about) - I got the clear impression that this God was an evil bastard. No consistancy - a vicious streak a mile wide - certainly not "fair" or "moral" by our modern standards. If he existed....sheesh...that doesn't bear thinking about. I certainly wouldn't feel like worshiping him - but on the other hand a literal infinity of the worst kind of pain and torment is a lot to bear for a point of view. But I don't think I could ever honestly like him - and for sure he's gonna know that. So what's the point in bothering? I guess that proof of the existence of the christian god would be a really bad-news kind of a day! SteveBaker (talk) 02:13, 4 February 2009 (UTC)

Which reminds me of this review of Alexander Waugh's book "God: A Biography" - "Alexander Waugh relates the following story in his book, God – The Biography. Randolph Churchill, son of Winston, had been annoying his friends by talking too much. They wagered he could not keep quiet for a week. Churchill, a keen gambler, thought he could win the bet by reading the Bible. But he didn't last long. After a few pages, he was heard to exclaim, "God! God's a shit!" If you read Waugh's book, then you will draw the same conclusion. For God is vindictive, blood-thirsty and, quite clearly, as mad as a hatter." DuncanHill (talk) 02:31, 4 February 2009 (UTC)

Personally, I've always thought the wonderful little bet God has with Satan about whether Job really is faithful to God illustrates the point beautifully. Now, Job was a big shot. He had seven sons and three daughters, and he had thousands of lambs, camels, and other animals, as well as a plethora of servants. He was like the Donald Trump of his age, except, you know, he's a nice guy, and full of faith. Probably made do without a comb-over, too.

So, Satan shows up one day after walking the Earth, and God essentially starts to brag about how loyal and righteous Job is. Satan scoffs at this; his argument is that it's no great feat for Job to love God, because God protects him from harm. To Satan, Job is like a guy who makes a big deal out of not being a racist when he lives in a white gated community and doesn't even know a single black person. God isn't having any of this, of course; He insists that Satan is full of crap, Job loves Him because Job is thoroughly righteous, no matter what. To prove His point, God withdraws His protection from Job so Satan can see if he can crack Job.

And Satan doesn't mess around, given this opportunity. He goes to town on poor Job's ass. His kids? Dead. His cattle? Dead. His servants? Dead. Job gets horribly and disgustingly sick, but he doesn't die, because that's where God draws the line -- after all, if Job dies, he can't settle the bet. Job wails and rips his clothes and is generally miserable, as anyone would be. Some of his friends try to talk some sense into him and suggest that he must've done something to piss off God, but while Job is sad that his life is utter shit, and he wishes he could die, he still insists that his friends are nuts; God is an awesome dude and He doesn't need to explain Himself to anyone. In fact, Job gets mad at his friends for messing with his head, and hopes that God does something soon before his buddies manage to convince him -- which, to me, sounds like Job knows reason when he hears it, but denial, well... it's not just a river in Egypt. This all goes on for a good while, even by the Bible's standards. Basically, Job keeps saying "shut up, I'm righteous, God giveth, God taketh away, I really, really hate my life and everything in it, but that's how it has to be if God lets it happen, you guys don't know what you're talking about, I sure hope God lets me make my case to him soon, shut up already."

Finally, God, who has been listening to Job's incessant whining and gotten sick of it, makes an appearance and basically tells Job that he should just shut the hell up and take it like a man, because He made everything and Job wasn't even there then, so who's Job to talk back? He flexes His awesome muscles and Job is humbled (presumably, he wasn't quite humble enough yet, since he dared to point out that all this wasn't a lot of fun). Job quickly says that God is right, yea, verily the Lord is awesome beyond belief and if Job spoke out of turn, he's awfully sorry. So God is happy to hear this, and then turns to Job's friends and gives them stern talking-to for all their sass, but He lets them off easy, because they're Job's buddies and presumably at this point even God's kind of aware that He's gone overboard and He should wrap it up. I know how He feels. Bear with me, I'm almost done.

So, to make up for all this horrible insanity He has inflicted on Job (or, technically, let Satan inflict, but the difference strikes me as insignificant), and also to reward Job for letting God win His little bet with Satan, God gives Job twice the cattle he had before, and even new sons and daughters, and Job lives to be a 140 years old and see a whole bunch of grandchildren.

Which kind of makes for a nice ending, I guess, but somehow I'm not seeing the part where this makes up for, oh, the murder of Job's offspring and the servants. And yet somehow the moral of the story is supposed to be that Job was a pretty smart guy to stick with God, and look how well off he ended up, and that's how we should all go about our business. The part about God being a complete rageaholic bastard about the whole thing isn't something people generally remark on, and yet it strikes me as the key element in the entire story. -- Captain Disdain (talk) 03:53, 4 February 2009 (UTC)

people as comunities need rules,regulations,because different cultures do see things from anthor aspects ... where hitting women considered to be barbarian act some where ... some where else its acceptable ... what do look like wrong for you its the most right for me ... so whats wrong and whats right ... what is the basic scale were i can judge actions . thats the idea of god ... humans is on the earth for ever and they never agree ... war never stops ... people kill each other for money ... for oil ... what seems to you as war for freedom in iraq ... to me its occupation .

so ... to belive in god is to admit his right to guide you throug your live ... to give you away of live ... some rules and regulation for you to follow ...

then ... the big question is ... if there is agod how should he prove his existence to you ... what is the ultimate proof to you ... will ... god wont do a miracle for each one of us ... so that he chose to send prophet , maybe its to hard to belive , but it could be the truth ... iam not trying to convert any body ... iam just looking for the truth just like you ...i hope some day i will see the naked truth just in front of my eyes .. thank you for helping ...?? —Preceding unsigned comment added by 79.173.236.134 (talk) 12:13, 4 February 2009 (UTC)

That's a common argument - but it doesn't hold true when you hold it up to the light of scientific enquiry.

Your hypothesis is that we need a god because we need limits on our behavior. OK - an experiment to determine whether that was true would be to look and see if our jails are full of atheists and if there were very few religious adherents who wind up doing terrible things.

But just look at how many people who claim religious devotion are in jail (or worse) - and look at how many atheists live good, "moral" lives obeying the laws of the land and standards of common moral decency. I don't have the numbers - but it's pretty clear that if this is what religion is "for" - it's largely ineffective in that goal. So I declare your hypothesis to be a false one.

Let's pick an atheist at random...me for example. I have never been to jail in my life - the only laws I've ever knowingly broken have been that I habitually drive faster than the speed limit (hardly a moral issue - and one that none of the great holy texts have much to say about!)...but yet I'm a hard-core atheist. For me, god or gods are PRECISELY as believable as Santa Clause and the Tooth Fairy - yet I believe that I live a good and moral life. I believe that following the laws of the country I'm living in is important...and there are other 'moral' standards that I believe we should all follow in order to make life pleasant and interesting. So I help little old ladies across the street - I give money to charity (not religious ones) - and I do good works (like answering questions for curious people on this reference desk) - I don't pirate video games or music. Next week I'm giving a pro-bono lecture to students at UT Austin on color theory. Not because I'm being paid for it (I'm not) - but because I believe we need to help our kids to know more. I do this without any concern that if I don't, I won't spend eternity with 47 virgins - or on some fluffy cloud with Angels playing annoying harp music at me ("Hey God - could you get these angels to do some Metallica songs for me? Oh - they can't violate the copyright...uh - OK - back to the Brahms then. K'thks."). I don't worry for an instant that I might be tossed into a fiery pit for eternity no matter how I behave. I do what I do because that's a comfortable way to pass my time. So without god or gods - I'm still living a life that I think most religious people would say was pretty much OK...apart from the lack of praying or church attendance and my annual(ish) speeding ticket fine.

In your view - why shouldn't I go off and commit all sorts of horrible crimes because I don't have a god to tell me what to do? But like most atheists - I don't. On the other hand - the most frequently shop-lifted book in the USA is the Bible. Our jails are full of religious people. Their beliefs didn't even slow them down when it came to them performing all sorts of heinous acts.

We have laws - both the ones passed by our governments and the ones we agree are a part of 'common decency'. Humans clearly don't need an entire complicated mythological structure along with the threat of eternal damnation to keep 'reasonable' people obeying those laws. Yet even in the presence of those religious strictures, religious people STILL end up in jail in vast numbers. So what on earth makes you think we need god(s) to do that? Religion is both unnecessary and ineffective when it comes to keeping people on the moral high-ground. That's not just my opinion - it's what we see happening around us every day.

SteveBaker (talk) 13:36, 4 February 2009 (UTC)

Personally, I find the idea that belief in God or fear of Hell somehow keeps us moral kind of frightening. I mean, I avoid doing evil because it's the right thing to do, not just because I'm afraid of the consequences. -- Captain Disdain (talk) 14:16, 4 February 2009 (UTC)

"Let's pick an atheist at random...me for example." Hey! That wasn't very random! APL (talk) 16:35, 4 February 2009 (UTC)

It was perfectly random - but taken from a VERY small sample size! :-P SteveBaker (talk) 19:18, 4 February 2009 (UTC)

the big question will be ... if there is a god , what is the proof you will need to admit his existance ... ??? if you can answer this question , then we could start to look for this possibility ... and the next question will be do god exist? ... thank you —Preceding unsigned comment added by 79.173.236.134 (talk) 20:09, 4 February 2009 (UTC)

What proof would you need that Santa Claus exists? I'm guessing you'd need to see a fat guy in a red suit zipping across the sky in a sleigh pulled by flying reindeer who can actually deliver toys to a large fraction of the population of the earth in one night. OK - well, for me, this is a comparable thing. So I'll settle for a god who can prove his/her existence by clearly demonstrating the power of omnipotence. This requires the god to perform an action that could not conceivably come about in any other way...changing the value of PI for example...let's have the god change the ratio of the ratio of the diameter to the circumference of a planar circle to 3.0 for the whole of Thursday - then put it back how it was again on Friday. I'd be pretty convinced. You see, you misunderstand the problem here. Nothing that's just "out there" in nature will convince an Atheist. We're happy to find scientific explanations for even the weirdest things (Quantum theory for example) because it's vastly easier to believe that than some unfalsifiable assertion like an arbitrary omnipotent being. But if I have to pick one - let's see your god change the value of pi or make 2+2 equal 19.74 for a few hours next week - he can do absolutely anything - right? The typical problem with this approach (at least for most christians) is that they'll tell you that god refuses to prove his existence in such crass and obvious ways because he wants to test your faith. Well, for those of us who have no faith - that's simply a ridiculous cop-out. The guy is omniscient for chrissakes - he can just look into your brain and SEE whether you have faith - why does he need to "test it"? So really - he has to do something active. Failing that, you have a "God of the gaps" problem - where your god can only be obvious in the teeny tiny cracks where science doesn't yet have the answers. Every year those gaps get smaller and smaller as we learn more about the universe and have less and less 'need' to have things explained with a shrug of the shoulders and a "Well God must have done it then". If you expect me to point to one of those tiny gaps and say "Well, I don't understand why the speed of light is exactly what it is - perhaps you could use that to convince me of the existence of god." SteveBaker (talk) 21:10, 4 February 2009 (UTC)

Changing the value of Pi seems rather ... destructive.

I'm not sure that I want the fundamental nature of geometry, and possibly even mathematics itself altered to satisfy SteveBaker's curiosity. (Admittedly, I wouldn't mind learning a few cosmic truths myself.)APL (talk) 02:55, 5 February 2009 (UTC)

P.S. Your last sentence sort of trails off at the end there, it could mean a couple of very different things depending on how you finish it.

In 1997, the Federal Bureau of Prisons released the professed religious adherence rate of those in the U.S. Federal Prison system:

"Christians make up about 80% of the American population AND prison population. However, Atheists make up about 8% of the American population but only 0.2% of the prison population. On the flip side, only about 1-3% of Americans are Muslim, but 7.2% of inmates are Muslim."

Being a christian makes you 40 times more likely to break the law and wind up in jail than if you are an atheist. So these rules laid down by god to stop all of this misbehaving REALLY aren't working so well are they? Muslims are at least 80 times more likely to offend than an atheist. That's not a borderline finding - that's pretty amazingly decisive! The inescapable conclusion is that religion most certainly DOES NOT help people to stay on the straight and narrow. To the contrary! It amazes me that if you believe your god is going to toss you into a pit of fire and brimstone for all of eternity - that you'd even consider taking one tiny step away from being a model citizen...but aparrently, that's not the case. Actually (but hardly less controversially) the reason for this is probably that better educated people have a much higher incidence of atheism than the general population - and better educated people are much less likely to commit crimes. That hardly helps the OP's argument though! SteveBaker (talk) 20:43, 4 February 2009 (UTC)

I believe the comparatively high percentage of Muslim inmates when compared to the percentage of Muslims outside of prison has to do with a lot of people converting into Muslims while in prison, either because of a religious conviction or simply because being a part of the Muslim community in prison makes life easier. In fact, now that I Googled a little, this article seems to support that. Notably, apparently only 20% of inmates remain Muslims after they're released, which would suggest to me that convenience plays a big part in it... -- Captain Disdain (talk) 21:25, 4 February 2009 (UTC)

And you could certainly argue that the numbers are small - so you don't have a decent statistical sample - and that perhaps the US legal system discriminates against Muslims after 9/11...there are lots of possible reasons for there to be proportionately twice the number of Muslims than Christians result. But the 40:1 ratio of christians and/or muslims to atheists is a really dramatic result. You can't explain that away so easily. Certainly no matter what you argue - you can't conclude that people need religion in order to teach them right from wrong - as our OP claims. The evidence is completely the opposite. Religion somehow ENCOURAGES bad behavior. Quite how that would be is a little mystifying - but the evidence is right there in the numbers. SteveBaker (talk) 22:18, 4 February 2009 (UTC)

Oh, I agree. I just wanted to say that people shouldn't read the statistics to mean that Muslims commit a particularly great number of crimes, because a lot of these people became Muslims after they were convicted. It'd be interesting to see some statistics on what they were before that. The guy in the article compares Islam to Christianity, so he was probably a Christian before his conversion, but of course that's just one man. Still, I'll take a semi-educated guess and say that most of these converts probably weren't atheists before. -- Captain Disdain (talk) 22:35, 4 February 2009 (UTC)

To OP (79.173.236.134): I personally do not believe in the God that you believe in (the omnipotent, omni-everything-else type). I don't study physics, so I have no idea whether a God can exist, as in one that set the laws of the universe pre-big bang - assuming there is only one universe (tautology?). I do however, know with a 99.9% probability that there is no heaven or hell. The main reason being because I am an organism and I cannot suffer/feel pleasure eternally. Homeostasis states that the pleasure/suffering will just become normal, so it will no longer be suffering/pleasurable. I also have never seen heaven or hell, nor heard of any evidence proving its existence. I sometimes do wonder though, if heaven or hell did exist, which form of you would go there? A person who dies aged 89, would they be the 89-year-old of them? PS: The 0.1% uncertainty comes from the brain in a vat problem, which I'm just willing to risk doesn't exist, and even if it does, that still doesn't prove that there is a heaven or hell. --Mark PEA (talk) 22:05, 4 February 2009 (UTC)

The homeostasis thing is nicely addressed in Dante's Inferno. It's an odd book - but worth the read. But if your god is omnipotent and the 'thing' you're in while you are in heaven/hell is not a normal earth-issue body - then homeostasis might just not apply anyway. If God wants you to suffer he can just magic away your adaptability to pain. Similarly, heaven sounds a bit...well...boring really...but perhaps he can magic away your boredom too. When faced with literal omnipotence, all bets are off. SteveBaker (talk) 22:18, 4 February 2009 (UTC)

Some good refutes. However in the end, I am still an organism whose behaviour is determined by my genetics (nature) and my upbringing/environment (nurture). God punishing me for illegally downloading copyrighted material because I'm very frugal and prioritise a mortgage over a DVD is like me smashing my computer up because it throws errors at me. The reason I'm frugal may be a form of risk-aversity (debt is risky), possibly due to a higher than average number of D₂ dopamine autoreceptors [28]. The reason my computer throws errors at me may be due to the software or operating system being coded badly. --Mark PEA (talk) 01:42, 5 February 2009 (UTC)

Map projection where area is proportional to a statistic

Resolved

I've read somewhere that it is possible to generate a map where the areas of the countries are proportional to some statistic (such as population), however, the countries are still recognizable. Any info on that? —Preceding unsigned comment added by Lev (talk • contribs) 07:58, 3 February 2009 (UTC)

There's a little bit at cartogram. Both this and the main map article are disappointingly short, though. --Anonymous, 08:54 UTC, February 3, 2009.

While the article isn't great, you can find some maps from a search. E.g. Population 1 Population 2 GDP per capita (2000) Nil Einne (talk) 09:33, 3 February 2009 (UTC)

You may want to read our article on Geographical information system which is much longer, and may be what the OP is talking about. --Jayron32.talk.contribs 12:32, 3 February 2009 (UTC)

What the weather feels like

Resolved

On the news they say the temperature is 3 deg C, but it feels like 0 deg C. The latter is attributed to the wind chill factor. Then how do they measure these two temperatures? Why aren't they the same?--DFS454 (talk) 12:13, 3 February 2009 (UTC)

The two articles you should read are Wind chill and Heat index, the former tends to make us feel colder, and the latter warmer. With both of these, the relevent measurement is how fast your body dissipates heat. How warm or cold you feel is a factor of how fast your body is losing energy. This will be dependent on ambient temperature, but it is ALSO dependent on other factors as well. With wind chill, the wind (moving air) will tend to pull heat from your body faster, making you feel colder. With heat index, high humidity will make you sweat less, thus decrease your rate of cooling, thus make it feel warmer. Your perception of the temperature is largely based on how fast your body cools off, not on any direct measurement of the temperature outside of your body. Thus, "wind chill" and "heat index" corrected temperatures tend to be more useful to people, who, after all, are mostly concerned with how to correctly dress for the outdoors based on what they will feel like... --Jayron32.talk.contribs 12:30, 3 February 2009 (UTC)

As for how to measure wind-chill, use a wet bulb thermometer (a normal thermometer with a wet rag tied around it). A dry bulb thermometer (just a normal thermometer which is kept dry) is used to measure the regular temperature. StuRat (talk) 14:49, 3 February 2009 (UTC)

What's going on is that a layer of air is trapped close to your skin (eg by hair or clothing) which is close to body temperature. This insulates us from feeling the 'true' temperature of the air. When the wind blows harder - that layer of air is moved out of the way and we feel more accurately what the TRUE air temperature is. So when there is no wind, 3degC feels a certain way - but when the wind blows, it feels colder. Someone in the dim and distant past figured that 3degC with a 10mph wind feels like 0degC with no wind (or whatever it is) so we have this concept of 'wind chill'. Similarly at temperatures above body heat - when it's 40degC here in Texas - you feel cooler when there is NO WIND than when there is wind...same deal, the air near our skin has been cooled by sweating - but when the wind blows you feel hotter. Sadly, this is far from being exact science - if you have more or less clothes on then your experience of the wind chill will be different than the forecasters have stated. Humidity can also affect our feelings of high temperatures (hence "Heat Index") because when the air is very humid, sweat cannot evaporate anymore and we can't cool ourselves off naturally. When the air is very dry, sweat evaporates more easily and we feel cooler - even though the temperature is the same. So, again, we have this somewhat ad-hoc concept of 'heat index' that takes that into account and says that even though the air temperature is (say) 35 degrees C, it "feels like" 38 degrees because it's so humid. Of course if you've covered every inch of your body with antiperspirant...your mileage may vary! SteveBaker (talk) 15:01, 3 February 2009 (UTC)

(It has been pointed out to me that I shouldn't be encouraging people to cover every inch of their bodies with antiperspirant...I kinda thought that was inherent in what I just said - but just to be REALLY, REALLY CLEAR: If you cover yourself with to much antiperspirant, your body will be unable to shed heat - if you get into any kind of warm situation - you could easily get a life-threatening dose of hyperthermia. That's hypERthermia - not hypOthermia.) SteveBaker (talk) 16:29, 3 February 2009 (UTC)

Excellent thorough answers, thanks everyone--DFS454 (talk) 17:06, 3 February 2009 (UTC)

Which is more prestigious as an honour;FBA or FRS

Both there are regarded as apex academic honours in Britain.Which is more prestigious? —Preceding unsigned comment added by 212.247.70.129 (talk) 13:53, 3 February 2009 (UTC)

FRS. There is also the business that people outside science need an honour like that so they know whether the person is distinguished or not whereas for the FBA they would be known for what they did anyway without it. Dmcq (talk) 15:20, 3 February 2009 (UTC)

Is that really true? My uncle (an economist) was made an FBA, but I doubt many people outside his field (or his sideline as a chess problemist) would have heard of him. In any case, the two awards apply to different areas, so they aren't directly comparable (is there anyone who has both?). I would guess that more people are familiar with FRS than with FBA. AndrewWTaylor (talk) 15:30, 3 February 2009 (UTC)

Answering my own question, it seems there are plenty of people with both awards]. AndrewWTaylor (talk) 15:31, 3 February 2009 (UTC)

The reason I asked teh question was that I have difficulty accepting Amartya Sen FBA is any less distinguished than many FRS's.Also there have been many FRS's who have nothing to do with science-Margaret Thatcher,Lord Hailsham and in the past people like Erasmus Darwin or Samulel Pepys. —Preceding unsigned comment added by 212.247.70.129 (talk) 09:43, 4 February 2009 (UTC)

Um... Amartya Sen has a Nobel Memorial Prize in Economics. I don't think many people are worried about whether his FBA is distinguised enough. Can't speak of Margaret Thatcher or Lord Hailsam but I wouldn't give much weight to 19th century holders. It's often true that various awards etc had a lot more to do with who the person knew and how much money they had then what they achieved in the past, it isn't necessarily a good indication of what the award means nowadays. Personally being unaware of either abbreviation, when I saw what they were I did recognise the FRS much more then the FBA (actually I still don't think I've heard of the FBA much) but perhaps that simply reflects the fact I have much more of a science background. Edit: Somewhat proving my point perhaps, his article didn't even mention he was a FBA until I added it as a cat. I didn't add it to prose 'coz I wasn't sure where to fit it Nil Einne (talk) 10:38, 4 February 2009 (UTC)

Erasmus Darwin was a scientist. Algebraist 11:47, 4 February 2009 (UTC)

My apolgies.I meant his son Robert Darwin the father of the famous son!!!He was a doctor and had nothing to do with science as such! —Preceding unsigned comment added by 212.247.70.129 (talk)

Margaret Thatcher got an honours degree in chemistry and worked as a food technologist until she entered politics. Some might say she should have stayed as a food technologist... --TammyMoet (talk) 13:36, 4 February 2009 (UTC)

Protein Supplements in diet

If you are doing significant amounts of anaerobic workouts, with an eye to maximum power gain in the relevant muscles and muscle mass gain, every 2 - 3 days; when is the best time in relation to working out to supplement your diet with extra protein? Would it be before working out, so that it is in your system as soon as your body starts repair the damage; or would it be after so that the protein comes in when the body is doing most of the growth over the next few days? Are there any other specifics or dietry supplements other than protein that can aid muscle growth without causing you to build up fat? —Preceding unsigned comment added by 129.67.37.225 (talk) 14:07, 3 February 2009 (UTC)

There was a question on the reference desk quite recently about this, see: Wikipedia:Reference_desk/Archives/Science/2009_January_18#Muscle_Tone_and_Protein_Intake. The general consensus is to eat protein as soon as possible after the workout. Read the studies for further information. --Mark PEA (talk) 16:47, 3 February 2009 (UTC)

Concerning your other question about building muscle while not fat, my answer is that's not a simple thing to do in the same day or even week for that matter. If your goal is to build muscle than you definitely want to have a daily caloric excess with a lot of protein. This means you'll be taking in more food than you are working to burn off. It is possible to have balance that allows muscle growth with fat loss, but you don't have to do that (its a lot easier to build with an excess). Most professionals alternate every 3-4 months between a muscle growth regimen and a fat cutting regimen. So they build muscle for 3 months with a caloric excess (picking up some body fat along the way is guaranteed). Then for 3 months they run (a lot) while maintaining a caloric deficit but still consuming protein post-workout. The result in the long run is (relatively) large, well defined muscles. --Mrdeath5493 (talk) 04:17, 4 February 2009 (UTC)

Boolean logic

A+(B+C)=(A+B)(A+C) and A+(!A)B=(A+!A)(A+B)

It struck me that if you consider A+ as a single varible things seem to make sense

Let A+=Z

Z(B+C)=(ZB)(ZC) and Z(!A)B=(Z!A)(ZB)

I wanted to ask if this method of considering things makes some sense or not? Bastard Soap (talk) 17:29, 3 February 2009 (UTC)

You have turned a boolean variable and an OR operation (+) into a different variable, and an AND (multiply) operation. This is not generally a valid conversion. In the case you provided, it looks like the resulting equations were valid, but this is because of distributivity, not because of your conversion. See boolean algebra to review notation and valid operations. Nimur (talk) 17:50, 3 February 2009 (UTC)

A couple other thoughts:

• What does Z actually mean? What is represented by "A or"? What's its truth table? If your intermediate step doesn't have meaning, then it's a bad route to pursue. Consider the invalid proof of 2=1 where symbols are used to disguise a divide-by-zero operation.
• Consider the trivial case of A+B. How does ZB (by your proposed conversion) evaluate?

So yeah -- as above, no, this is not the way to proceed. — Lomn 18:54, 3 February 2009 (UTC)

Yeah - you're definitely on the wrong track by "considering A+ as a single variable"...there is no way that can be the right thing. Can you give us a bit more context? (You might also want to take this to our Math desk - it's not really a science question). SteveBaker (talk) 20:04, 3 February 2009 (UTC)

I can see a way you might be able to formalise such an approach using group actions. "A+" is an element of a group (actually, it may not be a group, but that's not important) which acts on whatever set it is that these variables take values from (the power set of the universe? I don't do logic...). If it works at all, it would end up being equivalent to the standard approach (where + is a binary operation), I think, just more confusing. (The set A+ is a member of is isomorphic [as whatever type of object it is] to the set A is a member of, so you just have a set acting on itself, which basically gives you a binary operation). --Tango (talk) 20:15, 3 February 2009 (UTC)

Gluing MDF

Which is best? Im using PVA but it doesn't seem to work that well.--GreenSpigot (talk) 18:57, 3 February 2009 (UTC)

We have an article, Wood glue, that may help. PVA ought to work, are you applying enough pressure while it dries? You'll probably need to put it in a clamp, or put some very heavy weights on it, applying pressure by hand isn't likely to be enough. --Tango (talk) 19:04, 3 February 2009 (UTC)

MDF is pretty loose fibrous stuff - glue alone won't hold it unless you are gluing over a very large area. Screws and nails don't work well either. I generally use metal or plastic brackets and screw through those using a PVA glue to stop gaps from opening if the joint flexes. If glue is the only answer, I'd try Gorilla Glue (which is just amazing stuff). But make sure you follow the instructions - Gorilla Glue is catalysed by water so the surfaces have to be slightly dampened - it also foams and expands and if you don't clamp it really firmly - it just pushes the joint apart instead of being forced into the pores of the wood. Also - whether with PVA or Gorilla Glue - make sure you're working somewhere warm - most glues don't set well at very low temperatures. SteveBaker (talk) 20:01, 3 February 2009 (UTC)

Im coating both surfaces with pva before sticking together but the glue really soaks into the mdf. Should I size the mdf first?--GreenSpigot (talk) 20:31, 3 February 2009 (UTC)

Re Linking abbreviations to disambiguation pages or not linking at all: I think I've got it figured out: Maryland Deathfest and Paralyzed Veterans of America. Right? --NorwegianBlue ^talk 20:58, 3 February 2009 (UTC)

And we do in fact have an article on Gorilla Glue. --NorwegianBlue ^talk 21:02, 3 February 2009 (UTC)

sorry for inexact link. PVA should of course link to Polyvinyl_acetate--GreenSpigot (talk) 01:19, 4 February 2009 (UTC)

Also, I dont believe I linked Medium-density_fibreboard--GreenSpigot (talk) 01:22, 4 February 2009 (UTC)

I've also used (a product similar to) Gorilla Glue (in Australia it's also sold as a variety of the Selleys product "Aquadhere") & I'll agree with Steve that it's an amazing product, but it has to be firmly & evenly clamped. If you're trying to end-glue MDF, this may not work so well. In that case, or as an alternative, you could also try using a contact adhesive like "Liquid Nails" Which doesn't tend to penetrate the timber so much. It also has to be firmly clamped though. In either case, its probably best to leave the job clamped for at least 24 hours to allow full curing of the glue to give maximum bond strength before stressing the join. —Preceding unsigned comment added by Mattopaedia (talk • contribs) 03:30, 4 February 2009 (UTC)

I've not had a lot of luck with gluing MDF and have pretty much given up on trying. Use a combination of prefab wood dowels and Minifix knockdown fittings (Don;t know a generic name. I just buy them out of the drawer at my "home improvement" center.) This is what they look like [29]) Or use cross-dowels [30] and wood dowels. If you measure and work with high precision you'll get a tight joint and you can use a dab of glue on the dowels if you like. OR Used to be you had to cut your own dowels from dowel rod stock, but now most "big box" stores carry the prefab ones and they're real easy to use.

76.97.245.5 (talk) 00:00, 5 February 2009 (UTC)

Sorry I didn't explain. I am trying to glue 2 sheets of [Bendy MDF] together to form a curved surface.--GreenSpigot (talk) 01:33, 5 February 2009 (UTC)

Space

I am asking this question by making some amendments. How many countries have succesfully landed on space through their scientists? Which are thsese countries? —Preceding unsigned comment added by 196.200.102.42 (talk) 19:06, 3 February 2009 (UTC)

What does "landed on space" mean? Space isn't a solid object... --Tango (talk) 19:11, 3 February 2009 (UTC)

It's also worth noting that all spaceflight endeavors have required contributions from scientists around the world. No one redevelops Keplerian laws of motion, von Braun's rocketry advances, or innumerable other necessary scientific or engineering advances that make spaceflight possible. As Isaac Newton famously noted, those who see farther do so only by "[standing] on the shoulders of giants." — Lomn 19:19, 3 February 2009 (UTC)

No country has gone into space without a lot of help from scientists from other countries. The Russians and Americans would have taken a lot longer to do what they did without all of the German scientists they took on board at the and of WWII. The Chinese, Indians and Japanese used Soviet era Russian and US technology to a large degree. It's truly an international thing. The physicists who worked out the principles came from all over the world.

Please try to phrase your question more clearly. It's really not very clear what exactly you are asking. SteveBaker (talk) 19:50, 3 February 2009 (UTC)

Your phrase "through their scientists" makes it sound like you mean those involved in actually developing space flight, as not all travelers are scientists . (Not sure of the percentage.) However, if you mean those who have actually gone into space, we do have a list of space travelers by nationality.Somebody or his brother (talk) 22:57, 3 February 2009 (UTC)

It is worth noting that this questioner's IP address maps to Eritrea, and it is probable that she/he is a non-native English speaker. Judging from Languages of Eritrea, it is likely that the questioner will understand at least one of the following articles:

• Veicolo spaziale (italiano)
• مركبة فضائية (Arabic/ عرابي )
• صاروخ

Our English articles, Spacecraft and Spaceflight, are available in many other languages as well. Hopefully this will help... Nimur (talk) 15:50, 4 February 2009 (UTC)

Electric motor speed

In the syncronous motor speed formula RPM = 120 f / P where 120 is constant, f is frequency, and P is number of poles, what does the constant 120 represent and how is it derived? —Preceding unsigned comment added by 167.75.254.253 (talk) 19:43, 3 February 2009 (UTC)

Well, revolutions per minute is 60 times revolutions per second (which is what 2f/P would be, since frequency is presumably measured in Hertz, or s^-1). I'm not sure where the factor of two comes from. --Tango (talk) 19:53, 3 February 2009 (UTC)

There are two axles. —Preceding unsigned comment added by 82.124.81.87 (talk) 19:54, 3 February 2009 (UTC)

(ec) Well, if 'frequency' is in Hertz, (seconds^-1) and the answer is in revolutions per minute - then that 120 is really 60 x 2 because there has to be a factor of 60 to convert seconds to minutes. So we really need to ask where does the constant '2' come from? I don't know the answer to that - but it's a lot easier to explain a factor of two than a factor of 120! SteveBaker (talk) 19:54, 3 February 2009 (UTC)

I'm betting the 2 comes from a standard motor having 2 poles, and thus you're back to frequency. — Lomn 21:17, 3 February 2009 (UTC)

The number of poles was already in the equation as P, so that can't be right. What about the 2 pulses of electricity what make up each cycle of the alternating current? That makes sense to me. --Anonymous, 07:12 UTC, February 4, 2009.

That P is also in the equation does not mean a constant cannot be conceptually related to it. However, phases of electricity seems to also be a reasonable guess. — Lomn 13:53, 4 February 2009 (UTC)

Photons having momentum

How do photons have a momentum, when they are massless? Is it because we can equate energy to be mass (e=mc2), and they have a large velocity, therefore a large momentum? —Cyclonenim (talk · contribs · email) 20:24, 3 February 2009 (UTC)

It's not their velocity that gives them energy, it's their frequency (E=hf). You can assign a photon a relativistic mass, but I don't think it's particularly useful to do so. Instead, you need a more general definition of momentum (which I can't remember without finding my GR notes, which are several hundred miles away). I'm sure this has been discussed quite recently on this desk, though, so perhaps searching in the box at the top for 'photon momentum' would help. --Tango (talk) 20:31, 3 February 2009 (UTC)

I thought the general definiton of momentum was mass x velocity? In which case, frequency doesn't particularly help. Relativistic mass, however, might? —Cyclonenim (talk · contribs · email) 20:37, 3 February 2009 (UTC)

Nevermind, I found the answer here. Seems I walked right into a common misconception. —Cyclonenim (talk · contribs · email) 20:38, 3 February 2009 (UTC)

We now live in a world of Quantum Mechanics. So although it seems photons ought to be massless waves they exhibt particle-like behaviour also. See Wave particle duality. You and I also have a wavelength although it is of the order 10E^-50m. See De Broglie's wavelength on the duality link --DFS454 (talk) 20:45, 3 February 2009 (UTC)

The conventional definition of momentum, mass*velocity, is only one way of defining momentum. It can also be defined as a derivative in position-space coordinates, $\mathbf {p} ={\hbar \over i}\nabla =-i\hbar \nabla \,\!$. See this section for details of the mathematics and physics behind such definitions. Nimur (talk) 16:26, 4 February 2009 (UTC)

How long will it take to go to Mars?

How long is the Orion spacecraft is supposed to take to go to Mars in 2020? And if, hypothetically, we use the same spacecraft, how long would it take to go from earth to Pluto? --Emyn ned (talk) 21:39, 3 February 2009 (UTC)

See Colonization of Mars#Getting there – it's in the order of 6-9 months, but I don't think that Orion are anywhere near advanced enough in their planning to have fixed a passage plan. Bearing in mind that orbital patterns and gravitational effects play a big part in getting from one planet to the other, I couldn't safely say if the same spacecraft could make it to Pluto at all. If you wanted you could do a direct comparison of the orbital radii of Earth, Mars and Pluto and work out how many times further the minimum distance is, then assume the average speed is the same, but be warned that the result would probably be out by huge factors from reality. Bigbluefish (talk) 22:37, 3 February 2009 (UTC)

Earth-to-Mars spacecraft often use a Hohmann transfer orbit, which requires about 260 days of transit. Barring an unexpected revolution in spacecraft propulsion, that's a good estimate for Orion. Per the formula in the article, a Hohmann transfer from Earth to Pluto would require 46 years. Clearly, a different spacecraft, designed for a different sort of orbital transfer, would be required. The New Horizons probe, for instance, is using gravity assist to reach Pluto in less than 10 years -- of course, it's not stopping at Pluto, so that's not an acceptable mission parameter for Orion, either. — Lomn 22:47, 3 February 2009 (UTC)

Unmanned probes often use a Hohmann transfer orbit, or something close to it. Manned craft could well use something quicker (one plan I've seen is to send most of the equipment on a slow Hohmann orbit and then send the people along later on a quicker orbit - this means you only have a fairly light craft [relatively speaking] going along the high-energy orbit). --Tango (talk) 22:54, 3 February 2009 (UTC)

Melting tarseal

These [31] NZ news articles describe problems with the Desert Road tarseal melting. What temperature would it have to reach for this to be a problem? The air temp is only 28°, but the direct sunlight would heat the road beyond that, of course. (NB. tarseal is unknown to WP: it's an NZ word, but I don't know if it's more correctly defined as tarmac, bitumin, asphalt, asphalt concrete....) It is also worth noting that tarseal melts regularly in Auckland, on a smaller scale. Gwinva (talk) 21:55, 3 February 2009 (UTC)

this site suggests that asphalt road base doesn't really melt, per se, but gets more and more liquid as it reaches 250-300degrees F. --Mdwyer (talk) 23:45, 3 February 2009 (UTC)

I've seen asphalt get like that. In particular, when trying to change a tire on such asphalt, the jack just sank into it. StuRat (talk) 00:03, 4 February 2009 (UTC)

It sounds like "tarseal" is probably the same thing as chipseal. --Carnildo (talk) 01:18, 4 February 2009 (UTC)

I agree, and have been bold (just a little) in creating a redirect for tarseal. --Scray (talk) 02:11, 4 February 2009 (UTC)

Bathymetry

Now that Google Earth allows users to view the inside of the world's oceans, I was wondering when was the seabed first mapped in its entirety? And how often does this need to be updated? Ottre 23:48, 3 February 2009 (UTC)

This surely depends on the resolution of the mapping you're talking about. You could sail across an ocean and check the depth a few times on the way and call it mapping. The history since then approximates a progressively more detailed map, and I'm sure that when some oceans first started getting mapped in high detail, other "less interesting" ones were still mapped with crude radar techniques. There probably wasn't really a "eureka" moment. Bigbluefish (talk) 01:41, 4 February 2009 (UTC)

I dont think all the seabed has been mapped as yet. Its not quite as easy as taking a photo from space!--GreenSpigot (talk) 02:54, 5 February 2009 (UTC)

February 4

Speed of light, sound

My first question: At the end of the 19th century, before Einstein, before Michelson-Morley, everybody seems to have known that the velocity of light was independent of the speed of its source. Why and how? (Or did they? Is this Lorentz's doing?) I'm not finding the answer on the speed of light page—it just asserts that experimental evidence has proved it. But how did people know this then? My second question: is the speed of sound (in whatever medium you choose) dependent on its source? Yes? Sorry if I sound confused, but I've somehow gotten confused. --98.217.14.211 (talk) 02:35, 4 February 2009 (UTC)

I don't think that's the case. People knew the speed of light, more or less. However, the margin of error was far larger than the speed of measurable sources. James Bradley's 18th century experiments established the speed of light within 1% of the presently accepted value; however, that's still an error of six million kilometers per hour. You can't stick a light source on a car moving 100 kph and make a meaningful estimate about the new speed of light with an error four orders of magnitude larger. I don't think there was any general awareness of the specific properties of the speed of light prior to special relativity; certainly there was no concept of why it should be so.

As for sound, the speed of sound in a medium is independent of its source. The medium is what matters. — Lomn 03:32, 4 February 2009 (UTC)

It really was the other way around. Pretty much everyone thought that light was vibrations in a universal medium that filled all of space. They seeked to prove that hypothesis by measuring the speed of light in different ways (eg in the direction the earth was travelling versus looking in the opposite direction) expecting to get different answers showing the earth's progress through this universal material. But the precision of their experiments never seemed good enough to find that difference. Now we know that there IS no difference - so they'd never have succeeded. Sound is not like light - only light (well 'electromagnetic waves' - light, radio, ultraviolet, infrared, microwaves, etc) behaves in this peculiar manner. SteveBaker (talk) 03:52, 4 February 2009 (UTC)

Well, I'd have to disagree there. The speed of the earth's movement around the sun was known with a decent degree of accuracy (~15 km/s), as well as the speed of light. So the necessary accuracy was known, and when the Michelson-Morley experiment was performed, it was known that its accuracy (~8 km/s) should've been enough to detect the aether. This is why the Michelson-Morley experiment is the famous one, and what lead Einstein to postulate that the speed is constant. --130.237.179.182 (talk) 06:19, 4 February 2009 (UTC)

It should be noted that Einstein denied being significantly influenced by the Michelson–Morley experiment. Algebraist 11:43, 4 February 2009 (UTC)

The article you looked at about the speed of light has a bit on this. See the bit about Römer and the moons of Jupiter. If the speed of light depended on the source then the light from a moon coming towards us would get to the earth aster than when it was going away on the other side. So one would see the one coming back sooner than expected and the one going away later than expected. Dmcq (talk) 10:32, 4 February 2009 (UTC)

The luminiferous aether theory accounted for the fact that the velocity of light was independent of the motion of its source. The more surprising implication of the Michelson–Morley experiment (1887) was that the velocity of light also appeared to be independent of the motion of the observer. The reality of the aether was still not doubted, so in an attempt to reconcile the Michelson-Morley result with the aether theory, Lorentz developed the Lorentz ether theory (1895). The underlying idea was that the aether was still real (how else could light propogate through a vacuum ?) but the laws of physics were so structured that motion relative to the aether could never be detected - this principle of relativity was first proposed by Henri Poincaré. Einstein's step of genius in the development of special relativity in 1905 was to realise that the Lorentz transformations did not depend on the assumption of a special fixed frame of reference, and hence the whole idea of the aether could be dispensed with. Gandalf61 (talk) 11:59, 4 February 2009 (UTC)

People have known that light travels faster than sound for thousands of years by simple observation. If you see a person make a loud sound by, say, smashing a rock with a hammer, from more than ~200 feet (60 meters) away, you see the action before you hear the sound. That question would be like asking "when did people discover that trees grow over time". It;s just something that people would notice, once we evolved a high-functioning brain.-RunningOnBrains 18:46, 4 February 2009 (UTC)

There's no doubt that the fact that the speed of light is vastly higher than sound has been known for a VERY long time. But that's not the distinction we're making here. It's that the speed of light is independent of both the source and the observer - no matter how fast either of them are moving relative to each other OR to this notional 'aether'. That's not true for sound - and that's the KEY distinction here because from that very odd fact comes all of the relativistic weirnesses. SteveBaker (talk) 19:08, 4 February 2009 (UTC)

Ah. Question-reading FAIL.-RunningOnBrains 19:49, 4 February 2009 (UTC)

Steve, I'm skeptical of your statement about sound here. As best I understand it, the speed of sound in a given medium is a constant (and our speed of sound article appears to support this). The perception of sound varies with the speed of the emitter/observer, certainly (per the Doppler effect) -- but that holds for light, too. So apart from relativity's assertion that the speed of light is intrinsically tied to the nature of the universe, I'm at a loss for how the invariant speed of light is significantly different from the invariant speed of sound. Frankly, I expected it to be a far more profound difference when I first entered this thread, but I'm not seeing it. — Lomn 21:23, 4 February 2009 (UTC)

I think he's saying that its possible to move within the medium in which the sound is traveling, therefore changing the "speed" of sound, but since there is no lumeniferous ether, this is not possible with light. Example: Say you are moving at 50 mph, and something in front of you is making noise. In your reference frame, sound is actually moving 50 mph faster', and appears higher in pitch than in the frame of the noisy object. The light waves appear to be slightly higher-energy in your moving frame, but the speed of light appears to be the same, and, in fact, IS the same.

As a related question: would the Doppler effect be noticed if there was a stationary observer, but with, say, a 50-mph wind? For example, if there was a train whistle in a 50-mph cross-wind, would it sound different upwind vs. downwind? I would have to think so...-RunningOnBrains 21:37, 4 February 2009 (UTC)

I'm going to say "no" on your 50 mph thing, as otherwise, you wouldn't have stuff like sonic booms and other faster-than-sound phenomena. It's just a frequency shift. Saying that "the speed of sound seems faster because the frequency is higher" appears fundamentally identical to "the speed of light seems faster because the object is blue-shifted" -- "seems" and "is" remain separate things. — Lomn 23:47, 4 February 2009 (UTC)

There's never a Doppler shift for an emitter and receiver at relative rest, regardless of the wind speed (as long as it's constant). -- BenRG (talk) 00:15, 5 February 2009 (UTC)

Time Travel and Fate

I'm all too familiar with the different types of problems that arise from time travel (yay for sci-fi), but there's one type that particularly confuses me; the idea of fate. Here's my example:

Say that you're in a building and you fall through a trapdoor into a pit in the ground. You can't get out by yourself no matter how hard you try, but suddenly another you comes along and helps you out of the hole. He then points you down the hall in the direction he came from and walks in the opposite direction. You go in the direction he pointed, and find out it's a dead end. When you come back to the pit you find yourself stuck in it and realize this is how you originally escaped; by helping yourself. You have become 'future you' and MUST help 'past you' out of the hole and point him in the direction in the dead end. Otherwise you would never have been helped by yourself and would still be stuck in the hole. But how can you HAVE to do something? What happens if you choose to just walk around the hole and leave?

In this example, can you be independent of the actions you have already taken / the choices you have already made? -Pete5x5 (talk) 05:04, 4 February 2009 (UTC)

The situation is impossible, so it makes no sense to ask questions about it. This is the science desk, not the science fiction desk. --Anonymous, 07:15 UTC, February 4, 2009.

Oh, let's not be too hasty here. It's a good question -- sure, it's an impossible situation, but that doesn't mean there's no science about it. Let's say it did happen to you. First of all, there's the Novikov self-consistency principle, which essentially states that only timelines that are consistent are possible, meaning that if you wouldn't do it, then it wouldn't have happened. That sounds complicated, but it's actually very simple: you have a choice about it, and you choose to help yourself, because that's how it happens. (Read the article, it's pretty fascinating stuff!)

So what happens if you choose to walk around the hole and leave? It's a meaningless question, because you don't. To properly understand this, you shouldn't think about it in terms of inevitability; when you're in that situation, you just do it, because that's what you choose to do. It's that very choice that enables the situation to exist. If it helps, you might think of it like this: the situation is no different from any other situation you encounter every instant of your existence. What if you didn't post the above question? Then you wouldn't be reading this answer. Is it fate that you read it? Depends on how you look at it -- you chose to come back and read it. Or, alternatively, perhaps you chose differently, or got hit by a car, and never read this. Is that fate? The point is, it works out the way it works out, and you cannot make a choice that doesn't lead you to this moment. It's just that most of the time, you have no reason to be aware of this process in any way.

The Many-worlds interpretation of quantum mechanics, on the other hand, might suggest that when you travel in time, you actually enter another timeline -- which would be completely identical to the one you left. In this instance, you could leave yourself in the pit, because he wouldn't actually be the same you, even though he would be completely indistinguishable from you.

This may not make it any easier to grasp the concepts involved, of course. It tends to be kind of mind-boggling stuff by its very nature. It's great! -- Captain Disdain (talk) 08:16, 4 February 2009 (UTC)

The protangonist in such stories is usually not aware of the paradox at the time. In your example, you may not recognise yourself when you're helping yourself out of the hole, perhaps because it's very dim light and the you in the hole is wearing a hoodie. Perhaps enough subjective time has passed since you were helped out of the hole that you've forgotten about it.-gadfium 08:28, 4 February 2009 (UTC)

It is indeed a fictional matter - constructing a paradox from a fictional situation is kinda meaningless. From a scientific perspective, there really isn't much of a problem. Free will doesn't exist. We do what we do because the laws of physics work out that way. So if the state of the neurons and chemical pathways in your brain when you are in the hole are such that you'd decide not to help yourself out - then no help will come. If help does come it's because the chemical pathways will lead inexorably to you helping yourself out. You might FEEL like you decided to do it for some particular reason - but in truth, free will is an illusion. So you'd come to the edge of the hole - think about how interesting it might be to cause a paradox - then inevitably - for some reason or other, you'd decide to help yourself out of the hole - then walk off, confident in the "knowledge" that you COULD have not done so had you not wanted to. But this is fiction and there is no real answer here. SteveBaker (talk) 13:03, 4 February 2009 (UTC)

Excellent answers. There's more to be said about this (specifically the many-worlds theory), but it will have to wait until after I've done a little more reading. Thanks! -Pete5x5 (talk) 22:24, 4 February 2009 (UTC)

Resolved

Isaac Newton's scientific fraud

In the Oxford Dictionary of scientists I found mention of probably a fraud committed by Newton.There was a dispute as to who had invented the calculus.The Royal Society was asked to adjudicate between Newton and Liebnitz.

It set up a Committee heded by the then President and ruled in Newton's favour.The only problem was that the President of the Royal Society was Newton himself and he headed the enquiry!!!Does this not tantamount to scientific fraud?(Ramanathan) —Preceding unsigned comment added by 212.247.70.129 (talk) 13:34, 4 February 2009 (UTC)

You may find our article on the history of calculus useful. — Lomn 13:49, 4 February 2009 (UTC)

That would be a rather severe conflict of interest, not fraud. There are some who have so much respect for authority that they can't believe that any authority in such a high position could ever be wrong. For example, there was the idea that the Pope was infallible. StuRat (talk) 14:33, 4 February 2009 (UTC)

I'm not sure that the Pope is a great example -- those who accept his infallibility (in the limited scope in which it applies) do so because of God rather than his human authority. — Lomn

It sounds like the OP really means "scientific misconduct", which is a much more vague phrase. Serving on your own ethics committee would definitely be misconduct under modern regulations, but modern regulations can be pretty strict and certainly would have been viewed as wholly unnecessary in the 17th century. --98.217.14.211 (talk) 01:52, 5 February 2009 (UTC)

There is more information in our article on the Leibniz and Newton calculus controversy. Gandalf61 (talk) 14:40, 4 February 2009 (UTC)

Breast enhancement scams

Not more than a few minutes ago, I heard an ad on a popular Chicago radio station (B96) about a "scientific" study requesting volunteers for Latavi [32], a breast enhancement supplement. Without ever hearing about Latavi before, my internal bulls**t meter was flying off the scale. I've seen lots of these sorts of scams before, but what got me was not that they used the word "scientific" at least twice but that instead of asking for customers, they framed it in a way that they were conducting a scientific study, as if they were interested in doing a serious study in determining its effectiveness. Anyway, I'm sorry if this question isn't appropriate for the Reference Desk, but how are these ads allowed to go unchallenged? Certainly, this is a scam and a case of false advertising. If a company sells a product that does not do what it claims to do, isn't this a contractual violation? Or perhaps the question most appropriate for this Reference Desk is "Do any resources exist to fight this sort of BS?". A Quest For Knowledge (talk) 13:52, 4 February 2009 (UTC)

I see three possibilities:

1) As you suspect, it's a total scam and the "volunteers" for the "study" will be hit up for money ("a small processing and registration fee"). This probably is illegal, but regulators of advertisements have been asleep at the wheel for many years in the US. If they ever do anything at all, the company can just close and open under a new name and continue the same scam.

2) It's the first phase of a marketing campaign for some fake substance. In this phase, they will give it to many people, some of which will report that it worked miraculously, due to the placebo effect and/or wanting to get on TV, and the company will then use those interviews to sell the product in an infomercial later. That's probably legal, unfortunately. Only stock investments seem to be required to give actual statistical info, anyone else can show these type of total BS testimonials and get away with it, possibly with a "results not typical" disclaimer written so small at the bottom that nobody can read it.

3) It really is a scientific study. There are substances which could result in breast growth (hormones). However, taking them would cause all sorts of nasty side-effects and this seems most unwise. The FDA, however, has approved many such meds of questionable value with life-threatening side-effects. If the pharma companies give a truckload of money to the right politicians, they can get just about anything approved, it seems. StuRat (talk) 14:28, 4 February 2009 (UTC)

Free will doesn't exist

I don't want to take the time travel thread off in a tangent, so I'm creating a new thread. In that thread, Steve Baker stated:

"Free will doesn't exist. We do what we do because the laws of physics work out that way. So if the state of the neurons and chemical pathways in your brain when you are in the hole are such that you'd decide not to help yourself out - then no help will come. If help does come it's because the chemical pathways will lead inexorably to you helping yourself out. You might FEEL like you decided to do it for some particular reason - but in truth, free will is an illusion."

While I agree with this (I'm a determinist), I've seen where the indeterminism of quantum mechanics is used as an argument against the non-existence of free will. I was wondering if anyone can shed any light on any possible contradiction between quantum mechanics and the non-existence of free will. (I've read the section on Determinism, quantum mechanics, and classical physics but it doesn't help me much.) A Quest For Knowledge (talk) 14:18, 4 February 2009 (UTC)

That is certainly one perspective, unfortunately it is somewhat an axiomatic proposition. Perhaps the focus on the elementary physics aspects of human behavior is something of failing to see the forest for the trees. There are certainly some well established philosophical/psychological thought systems (for example, the behaviorism of B. F. Skinner) which hold the same basic position. However, its far from a settled matter. Existentialism takes the counter position, that free will is absolute, and that the problem of the human condition boils down to our inability to deal with our own free will in a rational matter. The deal with using elementary physics (the trees) to explain human behavior (the forest) is that there is of course the real possibility that there is something in the interactions along the way which allow for free will. Its sort of a modern day Zeno's paradox; the idea that because you can quantify every aspect of free will in infinitessimal detail that it some how does not exist. Just as Zeno's axioms make some incorrect assumptions, so does this one. Also, the faith that only science may explain all aspects of the human experience is something which itself cannot be determined by scientific methods; concepts such as "mind" and "soul" lie outside of the realm of science. You may deny their existance on that basis, but there are others who would contend that while ALL facts and theories arrived at by scientific methods can be taken as reality, the converse (that ALL reality can be arrived at by scientific methods) is not necessarily true. To believe that the soul doesn't exist is as axiomatic belief as the belief that it does. --Jayron32.talk.contribs 14:39, 4 February 2009 (UTC)

Steve Baker is a hard incompatibilist. I, personally, am a compatibilist. — DanielLC 17:13, 4 February 2009 (UTC)

"Pessimistic" - not "Hard". Clearly quantum theory - and chaos theory both ensure that we don't have a 'clockwork universe' - so there is randomness there and determinism fails at the level of small things like brain cells and complex things like brains. What I cannot accept is that there is some metaphysical 'thing' that lets our "free will" affect how the quantum/chaos dice roll to make the brain function the way we want it to. There is absolutely zero evidence for that - it's just wishful thinking. SteveBaker (talk) 17:51, 4 February 2009 (UTC)

There are some pretty solid experiments that show that the conscious part of our brains doesn't even make any decisions - let alone 'free' ones! Instead some lower level computational unit does that and leaves the conscious mind to rationalize it perhaps several seconds after it's happened. It's all rather disturbing - but the evidence is quite convincing. There have been many studies where some stimulus is applied and consciousness has been shown to lag seconds behind the response to that stimulus. I can offer you some references and examples later today - but I'm away from my books right now. SteveBaker (talk) 17:51, 4 February 2009 (UTC)

I've said similar things before about your mind doing it's own thing, everything for better or worse being predestined, etc. There seems to be something strange going on here, however. That being thatwe can actually have a conversation about free will itself! But even the thought to think about thought had to "appear". (!).....Is this why HP Lovecraft said that if we try to figure out the universe we'll go insane?Dr. Carefree (talk) 18:18, 4 February 2009 (UTC)

Steve, I think you're talking about Benjamin Libet and Free_will#Neuroscience. But there seem to be competing interpretations of those experiments. --Allen (talk) 18:32, 4 February 2009 (UTC)

Yes - but since the events of the 1980's - there have been many more experiments from many other researchers. I, myself (in the course of routine graphics work in Flight Simulation) have seen some odd behavior when using an 'eye tracker' that's hard to explain any other way. It's almost as if the unconscious mind is actively 'editing' streams of events to keep the 'world view' of the conscious mind consistent - and if the conscious mind IS making any decisions, they are of a 'global policy' nature rather than the 'micromanagement' that we feel we are doing. But there is no doubt that we have a lot to learn. SteveBaker (talk) 19:01, 4 February 2009 (UTC)

The annoying thing about free will is the evasiveness of the term. There's all this compatibilism stuff which gets very philosophical. Firstly, most people will agree that the term should be more like "constrained will", because it is definitely not "free". You can't choose to fly, turn invisible, etc. Then you have to factor in things that are almost certainly out of our control, like instincts, although some people can train them selves to control them to a certain extent. For example, most people can't touch a hot iron (appliance) for more than 2 seconds, others may be able to train themselves to withstand the pain, but this still isn't proof for free will. Other things include a need for food, drink, shelter, sex, etc. So now we can go on to "conscious" things like speech or behaviour. Someone with selective mutism will be in a situation where they are desperate to say something to someone, but is incapable. I watched a documentary in which an autistic child showed many signs of mutism, and was prescribed fluoxetine. Within 2 weeks they were much better at communicating. Maybe those who argue for free will say that the non-physical spirit can be manipulated by physical substances, or the physical substance contains some non-physical "stuff" that interacts with the spirit, but that argument seems to basically render the spirit obsolete. --Mark PEA (talk) 20:51, 4 February 2009 (UTC)

A hell of a question...

(Moved from Misc. Desk.) StuRat (talk) 15:40, 4 February 2009 (UTC)

1) Which foods, drinks, and food additives contain significant amounts of sulfur ?

2) I believe eggs do (which would include eggnog), but is it the whole egg or just the yolks ?

3) How much sulfur do we need in our diets ? (I'd like both a minimum and maximum, if any). StuRat (talk) 18:24, 3 February 2009 (UTC)

Partial answer (#3) - http://www.worldhealth.net/news/sulfur claims no RDA is set because a diet sufficient in protein will already have enough. Friday (talk) 18:28, 3 February 2009 (UTC)

Onions and friends make you cry by forming a mild sulfuric acid on the surface of your eyes. Searching for "sulfur" in On Food and Cooking might be a good start. --Sean 18:45, 3 February 2009 (UTC)

My friends make me cry by being mean to me but they don't usually throw chemicals in my eyes! ;) --Tango (talk) 19:47, 3 February 2009 (UTC)

I once squirted a friend in the eye with some cheap lemon-flavoured soft drink, turned out to have so much citric acid in it it made him cry for ages. ;) ~ mazca ^t|c 18:35, 4 February 2009 (UTC)

1) King Garlic of course!! Sulfur is there under the form of alliin allicin and other compounds, and gives you the characteristic smell in your breath and in your skin. Notice that the sulfur breath comes from the lungs via blood circulation, so teeth brushing is hopeless if you do not want to smell. pma (talk) 18:52, 4 February 2009 (UTC)

1) Dried apricots (and some other dried fruits) are often preserved with sulphur dioxide. It is also used in winemaking. Gwinva (talk) 20:18, 4 February 2009 (UTC)

Partial answer to #1. I think the bulk of sulfur in biological tissues (including foods) is in the form of cysteine and methionine, two of the amino acids used to make protein. If this is true, foods low in protein are probably low sulfur and vice versa, although different proteins will have different amounts of sulfur containing amino acids. ike9898 (talk) 22:06, 4 February 2009 (UTC)

Showing CO2 => global warming in a lab

Is there an experiment that one can set up in a high-school science lab that will show that C02 is a greenhouse gas, that is, that it warms the earth? Say I took two aquariums and filled one with C02, would I be able to get a measurable change in the temperature of the aquariums? Is there a better setup?

Thanks! — Sam 63.138.152.238 (talk) 15:55, 4 February 2009 (UTC)

The Mythbusters did a fairly convincing experiment. They made a pair of large cuboid frames and covered them with polythene to make enclosed, gas-tight boxes. They filled one with CO2 and left the other one full of air - then shined bright studio lights on them to simulate the sun and monitored the temperature inside each. The CO2-filled container got hotter - QED. SteveBaker (talk) 16:40, 4 February 2009 (UTC)

Thanks. Were the boxes about the size that one could construct in a regular high-school lab? (I'm not wondering about the veracity of the claims -- we actually want to do the experiments ourselves!). — Sam 63.138.152.238 (talk) 16:43, 4 February 2009 (UTC)

You'll probably need them to be at least 1 cubic meter for some efficacy, and don't use exhaled air, which is only 4% CO2 (last I checked). Or, even better, get identical cars from two of your students, fill one with CO2 (instruct the student to open all the doors and turn on the fan to let out the CO2 for a while after the experiment finishes), stick a pan of cookies in each, and see which one gets baked faster. ~user:orngjce223 how am I typing? 16:59, 4 February 2009 (UTC)

That won't work. The glass in the car's windows would cause a greenhouse effect far stronger than the CO2 you'd filled the cabin with. APL (talk) 17:18, 4 February 2009 (UTC)

Yes - I don't like the car idea at all...there are all sorts of reasons why that's a bad idea. The Mythbuster boxes looked to me to be about 2m tall by about 1m by 1m...about two cubic meters. I don't know that they need to be that big though. To produce a good effect, make sure they are at the same temperature at the outset...if you can, get a pair of identical heat-lamps to shine into your two containers. You'll need bottled CO2 in order to get the concentration up high enough. Methane is another greenhouse gas - it's much more effective than CO2 - but it's also kinda inflammable - so maybe a bit dangerous for a school experiment! SteveBaker (talk) 21:38, 4 February 2009 (UTC)

I have never seen a mention anywhere of why CO2 is a greenhouse gas. I am not a physicist or chemist, but I think it must be because CO2 has a high specific heat compared to the nitrogen and oxygen that make up most of the atmosphere. If this is correct, the students could be told that. Wikipedia, under Specific heat capacity, has a college-level discussion that is too advanced for HS students (and for me!), but it includes a moving diagram of atoms vibrating in a molecule that would be suitable for the students if you can project it on a screen. - GlowWorm. —Preceding unsigned comment added by 98.17.34.148 (talk) 20:10, 4 February 2009 (UTC)

Carbon dioxide absorbs infrared light much more strongly than do nitrogen or oxygen gas. Consequently, when infrared light - heat - is radiated from the Earth's surface, more gets absorbed by a CO2-rich atmosphere that would be absorbed by a CO2-poor atmosphere. Instead of that heat escaping into space, it just warms up the air — that's the greenhouse effect. TenOfAllTrades(talk) 21:01, 4 February 2009 (UTC)

The Wikipedia articles for carbon dioxide, oxygen, and nitrogen give figures for the specific heat capacity of these substances. But I don't know enough about it to be able to compare them. - GlowWorm —Preceding unsigned comment added by 98.17.34.148 (talk) 00:20, 5 February 2009 (UTC)

I don't see why the specific heat capacity matters - it's a matter of the absorption/transmission and reflection spectra in the infrared range. CO2 (or more correctly CO₂ - if you can be bothered to type all of those <sub> tags) absorbs and reflects infrared light - light from the sun is all over the spectrum - so some of the IR light gets absorbed and some gets radiated out into space - but all of the other wavelengths go right through. The light hits the earth's surface and turns mostly into heat - which causes infrared light to be shot back out into space...unless there is a greenhouse gas in the way - in which case the heat is either absorbed into the atmosphere - or reflected back down to earth again. This traps the heat under the blanket - and we slowly cook. Pound for pound CO2 isn't the worst greenhouse gas - but there is a heck of a lot of it. Carbon monoxide, Methane and Water vapor are also to blame. Water vapor is something of a mixed blessing because it not only traps the Infrared - but it also reflects visible light out into space and thereby contributes a little to the cooling effect - albeit at the cost of "global dimming" - making the world a darker place. That in turn shuts down the photosynthesis in plants and results in less CO2 being absorbed...so you don't really win much that way! SteveBaker (talk) 00:51, 5 February 2009 (UTC)

It seems that the "absorption" part of "absorption/transmission and reflection spectrum" would be a factor of specific heat. Transmission and reflection will keep infrared radiation moving around. Absorption will trap infrared radiation and convert its energy to vibration in atoms or molecules. It is the atoms or molecules that store the heat - and the amount they can store depends on the specific heat of the atom or molecule. I am suggesting that CO₂ stores more heat than oxygen and nitrogen. The CO₂ heat sink thereby keeps more heat energy near the surface of the earth. Oxygen and nitrogen let more infrared radiation bounce around and eventually let more of it escape into space than CO₂ does.

The CO₂ molecules radiate heat as well as absorb it. So also do oxygen and nitrogen. When the sun is shining, the absorption and radiation by atoms and molecules strike a balance. (Heat radiation from the earth also enters into it as well as the sun.) CO₂ has more heat energy to radiate. So at night, when no heat is received from the sun, CO₂ keeps the air warmer than oxygen and nitrogen. - GlowWorm. —Preceding unsigned comment added by 98.17.34.148 (talk) 03:24, 5 February 2009 (UTC)

P.S. The transmission and reflection of CO₂ also enters into it. They counteract the absorption effect. The absorption/transmission and reflection characteristics of the three gases put CO₂ in the fore in global warming, - GlowWorm. —Preceding unsigned comment added by 98.17.34.148 (talk) 03:40, 5 February 2009 (UTC)

Effect of snow on rails

As many of you may already know, heavy snow in London, England bought public transport to a standstill including rail transport. I would like to what the technical/scientific reasons, which caused trains to be suspended or delayed are if there are any and why it could not have been prevented. Thanks in advance. Clover345 (talk) 18:38, 4 February 2009 (UTC)

The main reason is that snow and ice go in the railroad switches and lock them. Northern countries lines usually have switches with electric resistors and even hot air devices like this [33], but in any case an exceptional low temperature is a problem. And if there is no heater in the switches (like in many southern countries), even a small snow may be a problem; in such cases one old but still good remedy to unlock a switch is to get off the train an piss on it. Old steam trains of course had a perfect source of boiling water for this. --pma (talk) 19:35, 4 February 2009 (UTC)

By the way, another form of switch heater just burns some fuel, making flames right next to the rails to heat them up.

Another problem with snow is that it is somewhat conductive electrically. On electric railways using a third rail power supply, like most subways and the South London commuter lines, if the snow reaches the height of the live rail it can short-circuit it. (Overhead-wire power supplies are immune to this, but more vulnerable to wind. A buildup of ice can render either one ineffective, as the ice is not conductive enough to pass the amount of power a train needs.) I would think snow would also be able to interfere with track circuiting sometimes, although I can't recall reading of any actual incidents of that. Fine powdery snow can also interfere with trains by blowing into the electric motors and short-circuiting them -- this is the origin of the much-misunderstood phrase "the wrong kind of snow" and it was also a problem in the US with the famous GG-1 electric locomotives until the airflow around the motors was changed. --Anonymous, 23:15 UTC, February 4, 2009.

Bird on wire not getting zapped

Why don't birds get zapped when they rest on a power line? The explanation from my textbook is that the two feet of the bird are the same potential/voltage, so the current doesn't flow through the bird. But, isn't the bird as a whole in lower voltage than the wire/power source? That means the current should flow through the bird. 128.163.116.27 (talk) 21:39, 4 February 2009 (UTC)

Through the bird to where? --NorwegianBlue ^talk 22:26, 4 February 2009 (UTC)

Birds sometimes do get zapped that way. It depends on how high the voltage is and the physical setup. If we're talking about the distribution grid, the bird will probably be all right as long as it doesn't land with any part of itself too near ground or another line with a different phase. Your question is not trivial, in fact it goes to the heart of what electricity is. Your question makes some false assumptions, most importantly that the only danger to the bird is the current in the wire, but if we make the same assumptions, the reason the bird does not get zapped is that in order for there to be current from one point to another there has to be a voltage difference. In the case of our bird, current would have to enter one foot and exit the other. The bird's feet are only about an inch (2.54 cm) apart, so the bird makes a parallel circuit with the wire. The resistance of a thick copper wire an inch long is approximately zip point shit, as we say in the trade (zero), and that of the bird, say, 1000 ohms. So by the equation for current in a parallel circuit, only a very tiny amount of current will flow through the bird. --Milkbreath (talk) 22:58, 4 February 2009 (UTC)

Strictly speaking, a very small amount of electricity will flow into a bird landing on a high-potential wire. (Indeed, there will even be an oscillating current in and out of the bird on an alternating current wire.) In effect, the bird acts as one plate of a very low-value capacitor. When it first lands on the wire, current will flow into the bird until the potential of the bird matches the potential of the wire. Under alternating current conditions, small currents will flow in and out as the bird's potential follows the alternating potential on the wire.

In practice, the total capacitance of a bird is trivial. If we model a bird as a conducting sphere with radius 5 cm (have you heard the joke about the cow, the farmer, and the physicist?) – an electrically-reasonable approximation – then the capacitance of the bird is about 5 picofarads. Assuming a very high-voltage transmission line operating at 500 kilovolts (kV) and 60 hertz (Hz), the peak current into or out of the bird is a bit less than 1 milliamp (mA). From our article on electric shock, 1 mA is about the minimum threshold of sensation for a flowing current; we wouldn't feel anything less. I can't comment on whether or not birds are more sensitive.

The bird would get less than 0.5 mA through each leg, and even smaller currents distributed out through the rest of its body. So, no shock, and no visible effect, even though there is a small amount of current flow. For smaller transmission and distribution lines (with potentials down to a few hundred volts), the peak current would be even more trivial. TenOfAllTrades(talk) 23:23, 4 February 2009 (UTC)

"Assume a spherical avian capacitor...", I like it! --Tango (talk) 23:26, 4 February 2009 (UTC)

TOAT, you've also not mentioned the bird as an inductor. Anyone want to try to calculate which current is higher, that due to the bird's self-capacitance, or that due to the induced EMF in the bird from the changing magnetic field? --Trovatore (talk) 03:23, 5 February 2009 (UTC)

February 5

Prism's and white LED's.

I'm doing a presentation at UT Austin in a couple of weeks - and I'm going to be talking to a bunch of budding computer geeks about color. My mission is to entertainingly undo the mess that people are usually taught on the subject of color. All the wierd stuff we talk about here all the time basically. It's called "How to successfully argue that black is white, magenta is a shade of green and yellow probably isn't yellow". Anyway, one thing I want to do is to split some white light into a spectrum using first an incandescent lamp and then a white LED flashlight - and I'm hoping to get a relatively smooth rainbow out of the incandescent lamp flashlight and some nice, narrow red, green and blue lines out of a white multi-LED flashlight. I don't YET have a prism - that's on order (gotta LOVE the Internet!). But I won't have a lot of time between it arriving and needing to do the talk - so experimentation needs to be minimized. Hence I have a few questions of an 'optical' nature...

1. I presume I need to use a fairly narrow 'slit' of light going into the prism. Any advice on how narrow? I'd like the spectrum to be as big and as bright as possible - it doesn't matter if it's a bit blurry so long as it's really obvious that not all "white" light is made up of "all the colors of the rainbow" as we're all (incorrectly) taught in school.
2. According to our various articles, there are two kinds of white light LED's - one is a blue LED with a yellow phosphor, the other is an infrared LED with red, green and blue phosphors. I want the latter type. I have a white LED flashlight - which kind is it likely to be? Is there a way to tell before my prism arrives? I tried looking at it through a red filter...but I rather doubt how good the filter really is at excluding yellow. If I'm actually going to get a yellow and a blue line - I'll have to resort to PLAN B and buy some of the correct kind of LED's and wire them up myself.
3. I'd like to capture the light from a computer monitor and produce a spectrum - I guess I need to converge the light somehow onto my slit and thence into the prism...but how to do that in practice seems a little tricky.
4. I'm also looking for a source of pure yellow light (ie the kind that WON'T split into red and green through the prism). I know a sodium lamp would do it - but I don't have one of those sitting around anywhere. I have one of those yellow emergency lights that you 'snap' to mix two chemicals...is that going to do what I want?

Any ideas?

SteveBaker (talk) 00:23, 5 February 2009 (UTC)

1. Two slits was the way it used to be done - problem - you lose >99% of the light - so make sure the lecture room has curtains (most have?) and suggest getting a low light video camera to capture the small image - then project it using a DLP onto the big screen.

Alternatives - very short focal length lens.

Better alternative - use a 'laser prism' to capture the light - eg a cylindrical prism with one end silvered and the other polished - put the led inside a silver foil bag illuminating the side of the prism, and just let one end of the prism poke out of a hole. (It can help if the sides of the prism are rough like frosted glass)

The above method is approximate and may not work very well..

OOPS sorry misread the question - ignore the above then... —Preceding unsigned comment added by 87.102.126.244 (talk) 01:13, 5 February 2009 (UTC)

2. Use the dvd/cd as diffraction grating (again in a darkened room) - this does work (so persevere) - I can see quite clearly what the energy saving light bulb I'm using is made up of using this method - you need to look off the axis of the main reflection...

3. dunno - maybe the silver foil and cylinder trick above may help. NOTE that the circular disc at the end of the prism will act as a 'point source' of light with diameter (blurry-ness) similar to the diameter of the disc - therfore placing a lens with the disc at the focal length of the lens should produce a roughly parallel beam. (thin cylinders and short focal length lens help here to reduce the width of the beam.)

4. as a rusty chemist the answer is almost certainly (probably) see Chemiluminescence - the article suggests that often the reaction (when you break the stick mixing the chemicals) produces uv light, and a sensitiser (uv fluorescence) makes the coloured light - the fluorescents can be expected to be likely to be monochromatic - but not as narrow a range of frequencies as the sodium d-line - ie a braod peak.87.102.126.244 (talk) 00:58, 5 February 2009 (UTC)

Sorry I don't have much to add here, except that I would definitely plan to have some slides showing your best results from practice sessions. It your plans work in the room, you can skip those slides, but if the demo fails you have something cool to show. I've done enough demos to know that you need something "in the can". --Scray (talk) 02:14, 5 February 2009 (UTC)

Oh...WOW! Thank you *SO* much '87 !! The CD trick works great! I should have thought of that. So I could have saved myself some money and not bothered with the prism. The trick is not to look for the reflected light on the ceiling or the wall opposite but instead to look directly at the CD surface. It's like having your own personal spectrograph! The best part is that I bet 90% of the kids at the lecture will bring laptops - so I just have to hand out a bunch of blank CD's and we can do it "live". And exactly as predicted, the LED flashlight produces red, green and blue lines - and the incandescent lamp makes a full spectrum.

Per User:Scray - I've taken photos, but the trouble is that a digital camera has it's own 'spin' on color. So the photos I took of green light coming off of the screen - that looks green to my eyes - looks green with a blue fringe to the camera. So I suppose the camera's blue sensor is sufficiently sensitive to the higher frequencies of green coming off of my LCD monitor such that it's seeing a blue fringe that's not there "in reality".

The "yellow" glow stick (well, it's yellow on the package) turned out to be red. Argh! The orange-ish colored streetlamps in my neighbourhood are modern high pressure sodium lamps so they don't come out as pure orange. And the orange turn signals on a 2007 MINI Cooper are white bulbs filtered through orange plastic and show mostly red light with a dash of green. The box of yellow LED's I bought at Fry's are evidently a red and a green LED packaged in the same housing...the CD spectrometer proves it.

So - the new (and rather important) question is:

• What source of pure yellow (NOT RED + GREEN) light can I find cheaply and easily? (Of course I could always cheat and use photoshop!)

SteveBaker (talk) 03:26, 5 February 2009 (UTC)

The thing that pops to mind is a low-pressure sodium-vapor lamp. I don't know how cheaply they're available, or how easily. --Trovatore (talk) 03:31, 5 February 2009 (UTC)

Yeah - they used to be in street lamps - but people hated the color - so now we have the high-pressure variety that produce a whiter light. I'm heading out soon to cruise the local malls and see if I can find some old parking lot with an old-fashioned low pressure lamp. SteveBaker (talk) 04:19, 5 February 2009 (UTC)

Oh — but if you have access to a Bunsen burner in the classroom, you could make your own version. Just hold some rock salt in the Bunsen flame to get the sodium line. Obviously I take no responsibility for the safety of this suggestion; that's your lookout. --Trovatore (talk) 03:52, 5 February 2009 (UTC)

Yes - but I bet you get all sorts of other colors from the gas and the chlorine in the salt. SteveBaker (talk) 04:19, 5 February 2009 (UTC)

Incidentally - I found this: [34] - very cool. SteveBaker (talk) 04:19, 5 February 2009 (UTC)

Very nice! Regarding a source for pure yellow, I did find this description of pure-yellow LEDs, but I doubt they're on the market yet. I don't suppose you have an old yellow street lamp handy? BTW Steve, chapeau - your questions on RD/S are as interesting as your answers. --Scray (talk) 04:28, 5 February 2009 (UTC)

Sinkholes - Geology

Looking at locations of sinkholes in the pennines I notice that many occur in lines close together on contour lines (eg~same height) - as I think that sinkholes are made by collapse of underground caverns caused by erosion of the limestone bedrock this seems wrong - I would expect the sinkholes to go downhill, or occur in a fashion unrelated to the overlying height map.

Can someone explain what is going on. Thanks.87.102.126.244 (talk) 00:48, 5 February 2009 (UTC)

In ignorance of the actual geology there, it is possible that the limestone only forms a bed of limited vertical extent, then the sinkholes only appear along the bed of limestone on the contour. Another possible cause is faults or formation when the sea level was at this level (Probably not this as these are mountains). Graeme Bartlett (talk) 03:37, 5 February 2009 (UTC)

Jupiter and Saturn

Steve, since you said humans can still see the planets OK, but the colors I thought will not be right to humans. What you menat SteveBaker (talk · contribs) by and that light would be spread over your entire retina instead of concentrated in one place from what you said about Jupiter. Saturn looks gold-yellow in the images taken by satellites. The problem is if Saturn is ambient to golden color, we won't see the ygolden colour with our crummy color vision if I'm right with your point. I don't know what you menat by Jupiter earlier. I myself, have scratch my mind, and go over it 10 to 15 times before I understnad your post. Sometimes, I'm not yet comppletely sure.--69.229.108.39 (talk) 01:18, 5 February 2009 (UTC)

Just 1101 this time, if I've counted right. Not much of a message. Maybe there's information hidden in some more sophisticated way — in fact the colo(u)r thing could just be a red herring. --Trovatore (talk) 02:22, 5 February 2009 (UTC)

• What are you talking about? What you mean by herring?--69.229.108.39 (talk) 04:39, 5 February 2009 (UTC)

See steganography. --Trovatore (talk) 04:45, 5 February 2009 (UTC)

Science related to Neuorlogy

HOW DOES THE NUMBER OF NEURONS IN THE BRAIN INCREASE? WHAT IF WE USE OUR BRAIN MORE EFFECTIVELY OR MUCH MORE CONCERN THE QUANTITY OF NEURON? —Preceding unsigned comment added by Mustekke6184 (talk • contribs) 02:52, 5 February 2009 (UTC)

(I edited your post to remove the awful formatting). I think long-term potentiation may be what you are after. I'm not aware of any ways of increasing the number of neurons in the brain, why would you want to do that exactly? --Mark PEA (talk) 03:12, 5 February 2009 (UTC)

For increasing number of neurons you may look at Neurogenesis. For learning processes that do not involve neurogenesis (most don't) see synaptic plasticity, Long-term potentiation, long-term depression. You may also want to look at synaptogenesis. As far as efficiency of neural "computation" in biological systems is concerned, I can't think of any publication that is understandable to the general audience. Just ask questions and we'll try our best to answer. --Dr Dima (talk) 04:32, 5 February 2009 (UTC)

Calculating Molality

I'm working on some Chemistry homework and for one problem I have to calculate the molality of concentrated Sulfuric acid. The information I am given is the density: 1.84 g/mL and the mass percent of solute: 95%.

I assume for calculation's sake that I have 1000g of solution. Because of the mass percent, I should have 950g of H2SO4 and 50g of water. Thus from that I calculate the moles of solute to be 9.69 mols. Since the density of water is 1 g/mL, I calculate I have .050L of water. Thus the molality is calculated as 9.69mols solute /.050L of solvent = 194 mols/kg. Is this correct? It seems like a ridiculously high number to me compared to those in the other examples. Have I done something wrong? I guess what I'm also having trouble wrapping my head around is dissolving nearly a kilogram of H2SO4 in only 50 mL of water. According to the density, my total solution volume should be 543.5 mL. I feel like I have misstepped somewhere but I cannot figure it out.

Help is appreciated 198.82.110.57 (talk) 03:13, 5 February 2009 (UTC)

You should be dividing by the volume of the solution not the solute, after all the molarity of a 100% substance is not infinite. Graeme Bartlett (talk) 03:33, 5 February 2009 (UTC)

Dimensionally analyze what you did by writing everything out as multiplication with labels next to the values. If what you get at the end is x moles of solute/1 kg solution, then you have done it correctly. 96.242.34.226 (talk) 03:48, 5 February 2009 (UTC)

I just got more confused by the first reply. I divided my moles of solute (9.69 mols) by the mass of my solvent (.050 kg)to find my molality, which came out to 194 mols/kg. If I divide by the volume of the solution, that just gives me molarity, not molality. Or were you referring to a different step? If so, please elaborate. Thanks. I can't find any error in my calculations.198.82.110.57 (talk) 03:55, 5 February 2009 (UTC)

The major problem I think you're having is dividing by mass of solvent, when you should be dividing by mass of solution. However, (as suggested above by 96.242.34.226) I also think you should go back to the beginning using the density and mass percent provided, and dimensionally analyze from beginning to end (using specific units like "kg H2SO4", "kg solution", etc). --Scray (talk) 04:08, 5 February 2009 (UTC)

But my textbook and everything else I have found online explicitly state that molality = moles of solute/kilograms of solvent, not kilograms of total solution 198.82.110.57 (talk) 05:07, 5 February 2009 (UTC)

Chemical Content

Hey, I'm doing some research and I'd like some help finding the articles I'd need! I'd like to know...What ingredients in the liquids (orange juice, Coke, Red Bull, milk, salt water) are considered "chemicals"? For example...salt water has salt; milk has calcium. —Preceding unsigned comment added by 69.178.20.243 (talk) 04:51, 5 February 2009 (UTC)