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August 30

about electrons...

why are electrons easier to add or remove from an atom than a proton or neutron ? —Preceding unsigned comment added by 122.163.232.226 (talk) 04:20, 30 August 2008 (UTC)

Because they're held by the electromagnetic force, whereas protons and neutrons are subject to the much stronger nuclear force. Clarityfiend (talk) 04:53, 30 August 2008 (UTC)

Or, equivalently, because they are farther distant from the nucleus. --Ayacop (talk) 07:20, 30 August 2008 (UTC)

Protons will be taken up by bases. In fact a loose proton will react with almost any other substance, (even including helium to make helium hydride or hydrogen to make H3+) so a proton is not hard to add to something, it is extremely reactive! Neutrons are easily absorbed in many nuclei. Electrons are very light, but yet not many negative ions are stable. Graeme Bartlett (talk) 09:00, 30 August 2008 (UTC)

Ayacop, that isn't equivalent. They're held by different forces. The protons are actually repulsed by the force that holds the electrons in.

Graeme, You're talking about adding and removing protons from a molecule. 122 is talking about adding it to an atom. If you added a proton atomically to a hydrogen atom, you'd get Helium-2, which would immediately decay into Deuterium, and emit a beta particle. This is nuclear fusion, and is very different, and far more difficult, than if you just added a proton molecularly and made H2+. — DanielLC 15:58, 30 August 2008 (UTC)

What's stopping electrons from actually hitting and joining the nucleus along with the protons and neutrons? ScienceApe (talk) 03:24, 31 August 2008 (UTC)

Among other reasons, the Pauli_Exclusion_Principle. However note that electrons on s orbitals have the peak of their wavefunction right in the center of the core. —Preceding unsigned comment added by 84.187.60.4 (talk) 12:08, 31 August 2008 (UTC)

In the case of the s orbitals, it's because the nucleus is so tiny. The waveform of the electron can collapse anywhere in the s orbital, and is more likely to do so closer to the nucleus, but it's still not likely enough to make the electrons hit such a small target. The Pauli Exclusion Principle just explains why not all of the electrons are in the smallest orbital, and doesn't have much to do with the question. — DanielLC 16:12, 31 August 2008 (UTC)

Purple skin

Why do some people's skin turn purple when they are cold? Does it have something to do with the blood? Minor Contributer (talk) 05:25, 30 August 2008 (UTC)

yes, the blood has its circulation rate reduced in the cold skin so that it does not lose heat. When the blood has oxygen consumed it changes colour from bright red to a dull red or purple. Combined with the bluish colour of empty skin it can look purple. Graeme Bartlett (talk) 09:04, 30 August 2008 (UTC)

Why do some people turn purple more quickly or more oftenly than others? Minor Contributer (talk) 15:24, 30 August 2008 (UTC)

Having poor circulation can do it. You may find Raynaud's syndrome interesting. --Tango (talk) 18:50, 30 August 2008 (UTC)

Another obvious thing, the lighter your skin the easier it would be to see any change in blood colour Nil Einne (talk) 01:16, 31 August 2008 (UTC)

Optical Activity

Hi all,

I was just wondering how do you determine if a moleucle is optically active and why (or explaining why it is/isn't optically active). I know if a molecule has symmetry (i.e. it is achiral) it is not optically active, also, if a molecule does not have a chiral carbon it too is not optically active. But how do i determine if something like 2-bromopentane or 2-bromo-3-methylpentane (both formed from an addition reaction) is optically active?

Thanks heaps —Preceding unsigned comment added by 122.108.169.75 (talk) 05:26, 30 August 2008 (UTC)

If a molecule is not symmetric, it is optically active. So 2-bromopropane is optically active (and you can look up its specific rotation in the usual literature sources, maybe even on wikipedia). Now whether a particular sample of the compound has optical activity, that takes a physical measurement in a polarimeter. If you have a 50/50 mixture of both enantiomers of a compound, the effect of each will cancel the other and the net rotation will be zero. DMacks (talk) 06:35, 30 August 2008 (UTC)

So does optical activity only depend on the symmetry of a molecule? what if I know that there was a satureated molecule (alkene) and it under went an addition reaction to give me 2-bromopentane ? does the addition reaction tell me anything? Also, does a chiral carbon tell me anything about the optical activity of a molecule? —Preceding unsigned comment added by 122.108.169.75 (talk) 07:04, 30 August 2008 (UTC)

Optical activity does not depend on symmetry, nor on chirality, i.e. asymmetric molecules need not have a specific activity. That's why you see compounds with (+) and (-) labeled in addition to D- and L- specification. See also cryptochirality. Optical activity has to be measured. --Ayacop (talk) 07:17, 30 August 2008 (UTC)

Knowing the optical activity of a sample of a compound that is not symmetric can tell you whether the sample is just a single isomer or is a mixture of stereochemistries. But you would need some (potentially difficult) experiment or (very easy) literature search to figure out which isomer you have based on its optical activity. If you know whether your sample is "optically pure" (i.e., a single enantiomer) vs a racemic mixture, you can know something about the reaction mechanism. DMacks (talk) 07:36, 30 August 2008 (UTC)

My homework question asks to explain why 2-chloropentane is not optically active after it is formed via the addition reaction of pent-1-ene and HCl. the molecule is not chiral, so i thought would be optically active, however, how do i explain it is not? —Preceding unsigned comment added by 122.108.169.75 (talk) 08:22, 30 August 2008 (UTC)

one molecule of 2-chloropentane is chiral, with the number 2 carbon being substituted with hydrogen chlorine methyl and propyl. However which side would the chlorine add on? There is nothing to determine a left or right hand chirality, so both are made. Graeme Bartlett (talk) 09:11, 30 August 2008 (UTC)

Sorry i had meant to say that i know the molecule (2-chloropentane) is not achiral, so being that it is not symmetrical, shouldn't it be optically active? so why isn't it? —Preceding unsigned comment added by 122.108.169.75 (talk) 10:19, 30 August 2008 (UTC)

I think DMacks hinted at the answer above and Graeme Bartlett gave you an even stronger hint. Take a look at racemic mixture. Gandalf61 (talk) 15:46, 30 August 2008 (UTC)

Distortion in half-wave rectifier.

Why distortion happened in half-wave rectifier with high frequencysRonilove (talk) 09:29, 30 August 2008 (UTC)

Because it chops off half the wave, so the output does not resemble the input. This is if you are not using it as an amplitude modulation demodulator. Distortion could arise in demodulcation, because after rectification you filter with a capacitor to remove RF, and this could reduce high frequencies. Graeme Bartlett (talk) 10:13, 30 August 2008 (UTC)

I wonder if there might be more distortion at high frequency because of the time of the rectifier to turn on, and the bias level for turn on, and if this might cause part of the waveform to be clipped off. What is "high frequency" depends on the response of the rectifier, its capacitance and other factors. Edison2 (talk) 19:30, 30 August 2008 (UTC)

Some context from the OP would help here. Fourier analysis of an unfiltered half-wave rectified sine wave shows that it has a very high harmonic distortion content anyway. SpinningSpark 21:35, 30 August 2008 (UTC)

Cause of Quantum Decoherence?

According to the section Problems of the article Quantum computer, there are number of practical difficulties in building a quantum computer. One of the major difficulties is keeping the components of the computer in a coherent state. But I still get no sense of what interaction will cause the system to decohere... Is it environmental temperature? some form of noise? CMB? movement of planets, stars? cosmic inflation? Any ideas? Thanks - Justin545 (talk) 11:45, 30 August 2008 (UTC)

What I've usually heard is thermal noise. With say a silicon chip with a quantum dot on it, the chip emits a photon which hits the dot and ruins its superposition. Or the dot could emit a photon that hits the chip. Because of this, proper cooling is a preequisite of many quantum computer blueprints. EverGreg (talk) 15:43, 30 August 2008 (UTC)

Inventing VS Engineering

What exactly is the difference between an inventor and an engineer?

I was under the impression that an inventor is just an amateur engineer, is this true? —Preceding unsigned comment added by Kenjibeast (talk • contribs) 15:41, 30 August 2008 (UTC)

Inventor and engineer should help you differenciate the two. "Engineers are concerned with developing economical and safe solutions to practical problems, by applying mathematics and scientific knowledge while considering technical constraints." and "An inventor is a person who creates or discovers a new method, form, device or other useful means." are the key sentences. —Cyclonenim (talk · contribs · email) 15:46, 30 August 2008 (UTC)

An inventor is someone who had the idea for a device and usually also built it. This someone dosn't have to be an engineer by education. An engineer plan, develop, improve and build devices among other things, but can do their job fine without coming up with a new, original device. There's of course a grey area between an improved and a new device, but you can generally say that the person is an inventor of a new device if he/she can get a patent on it. Also see the term inventor in patent law EverGreg (talk) 15:53, 30 August 2008 (UTC)

There's no reason an inventor has to be an amateur. And there are plenty of inventors that are not engineers. Consider how many patents are filed each year by physicists, biologists, etc. --98.217.8.46 (talk) 17:22, 30 August 2008 (UTC)

"engineer" is more of a job title. "Inventor" is just a description of something you've already done. APL (talk) 19:09, 30 August 2008 (UTC)

In modern times to call yourself an "engineeer" you need to be a graduate of an accredited college in an engineering curriculum. Experience and the passing of tests are required to be a "Professional engineer" entitled to do consulting for others. Some famous inventors of 19th century electrical gadgets, like Samuel Morse and Alexander Graham Bell knew virtually nothing about electricity and had assistants who understood electricity actually develop and build the invention, based on their idea. Others like Thomas Edison , Nikola Tesla and the Wright Brothers were knowledgable of the intricacies of most of their "inventions" and many qualified as engineers by the standards of the time. An invention is often an improvement on someone's earlier idea that did not quite work in a usable sense, perhaps incorporating other improved technologies. (edited)Edison2 (talk) 19:27, 30 August 2008 (UTC)

Spider in My Front Yard

Can somebody identify this spider I found in my front yard? Thanks.--Xp54321 ^{(Hello! • Contribs)} 19:21, 30 August 2008 (UTC)

When asking this kind of question it's important to tell us what part of the world you live in. Australia, Scotland and Mexico have very different bugs. --Sean 19:35, 30 August 2008 (UTC)

Oxnard.:)--Xp54321 ^{(Hello! • Contribs)} 19:36, 30 August 2008 (UTC)

Actually it looks a lot like a Orb-weaver spider which is found in almost every corner of the globe. (If someone finds one on Mars I would be surprised but not shocked.) —Preceding unsigned comment added by 71.100.4.91 (talk) 21:00, 30 August 2008 (UTC)

I have re-arranged your photo so that it doesn't go into the next section. Right-floating is better for left-to-right languages like English.--antilived^{T | C | G} 00:18, 31 August 2008 (UTC)

Thanks!--Xp54321 ^{(Hello! • Contribs)} 00:22, 31 August 2008 (UTC)

Helicopters unable to fly above a pit

Here is an interesting question found on this talk page of this article Udachnaya pipe

"should there be something noted about helicopters unable to fly above the pit? from what has been said or what ive heard, flight above the area causes damage to the helicopter, for example being completely destroyed. i am unsure of the research required, and would appreciate help in this area as with being unable to relocate the source of information, however use of the search query in google may provide sufficient sources of information. thanks."

16@r (talk) 19:48, 30 August 2008 (UTC)

It seems really impossible that flight over such a thing would result in some mysterious damage to the helicopter. THe person who posted that doesn't seem to have any references or proof of any kind. I'd ignore it until/unless proof is produced. If that person attempts to add that information into the article without some pretty decent references - just revert it. Extraordinary claims require extraordinary evidence. SteveBaker (talk) 21:19, 30 August 2008 (UTC)

I'm thinking something along the lines of very strong, unpredictable updraughts coming up from the pit walls - or perhaps some odd wind vortex effect due to the particular shape of the excavation... --Kurt Shaped Box (talk) 22:05, 30 August 2008 (UTC)

Given the north latitude and the depth, it seems plausible that heat release from the relatively deeper earth might cause turbulent updrafting over the pit. Wind effects are also an interesting possibility. Franamax (talk) 22:25, 30 August 2008 (UTC)

I've heard many, many times before that you can't fly over it with a helicopter, precisely because air currents -- but downdrafts rather than updrafts. I don't know whether that's true or just a story, but in any case, the idea of something that big affecting air currents certainly doesn't sound implausible to me. That said, though, they certainly wouldn't damage the helicopter by themselves, but they would make flying over the pit dangerous and could cause a chopper to crash. An example of these stories can be found at here. -- Captain Disdain (talk) 01:24, 31 August 2008 (UTC)

A halfway decent pilot can cope with updrafts and downdrafts if he/she knows they are likely. Unexpected vertical air motion is kinda dangerous - but if you were flying over a big hole in the ground, you'd be expecting it. Look at the number of helicopter flights they take into an out of the Grand Canyon for example. Any steep slope or cliff-face can be the source of an updraft (if the wind is blowing up the slope) or a downdraft (if it's blowing the other way). Helicopters can operate reasonably close to cliff faces and large buildings without problems. So this can't be true. I wouldn't find it hard to believe that helicopters have crashed there - perhaps even due to some careless piloting and that might be the source of some kind of an urban legend - but I used to make flight simulators for helicopters and we'd simulate all kinds of vertical air motion (both expected and unexpected) that pilots would train for. This pit might make it harder to fly a helicopter over/into - but there is no way it's some kind of magical helicopter crusher that mangles anything that comes nearby - that's just ridiculous. SteveBaker (talk) 15:26, 31 August 2008 (UTC)

I think (well, I've always assumed, anyway) that this has involved situations where the chopper is coming in low and actually going into the pit rather than flying a safe distance above it. That's got no basis on anything other than my imagination, though. -- Captain Disdain (talk) 17:59, 31 August 2008 (UTC)

But even that should be no worse than landing on a helipad on top of a tall building. The up/down-drafts around those things are phenomenal but pilots seem to have no problem sticking landings on them all the time. SteveBaker (talk) 20:15, 31 August 2008 (UTC)

Sure. I mean, maybe it was some cowboy pilot with a couple of shots of vodka under his belt. Or just someone who wasn't really qualified to pilot a helicopter; after all this is Russia; I wouldn't be surprised to hear of someone who would never pass the FAA's standards screwing up. And I'm not putting the country down, mind you, but, uh, a lot of the time, they do things a little differently over there. Or maybe it never happened at all. Who knows?

(Speaking of the way things are done in Russia, an unrelated, but amusing anecdote: friend of mine was shooting a science fiction action movie over there, and the production included cooperation from the local army guys, who were hired as extras. Someone in the prop department screwed up and they didn't have the scifi guns for them, so they simply arranged to dress up the troops' rifles on the spot. That was a couple of hundred AK-74s that were actually army property, altered so they could no longer be fired or even properly aimed, because of the scifi crap they welded on them. I mean, I'm sure they compensated them, but from what I understand, the decision was pretty much made on the spot, because they were in a hurry, but I kind of doubt the guy making the sale actually had authorization to sell working weapons to a movie crew. Nobody thought it was a big deal, but my friend, not being Russian, was kinda nervous about the whole thing. Later on they also blew up a whole bunch of aircraft... allegedly because it was cheaper, faster, and easier than using special effects. So, you know, the idea of some unqualified guy just jumping in a helicopter and crashing it when the air currents prove surprisingly treacherous strikes me as entirely credible. But really, who knows?) -- Captain Disdain (talk) 00:48, 1 September 2008 (UTC)

I personally blame the Russian army's experimental EMP howitzer firing range just down the road. The one they haven't told us about yet. --Kurt Shaped Box (talk) 19:27, 31 August 2008 (UTC)

bipolar transistor

Is there a replacement or substitute for the old (1980) bipolar 100mhz, 115 volt, 10 amp, 100 watt complementary PNP/NPN transistors? —Preceding unsigned comment added by 71.100.4.91 (talk) 20:57, 30 August 2008 (UTC)

Do you have a part designation for that? SpinningSpark 21:24, 30 August 2008 (UTC)

You might find something here that will do the job. SpinningSpark 22:01, 30 August 2008 (UTC)

Are you sure about the 100MHz? Finding a 100W Pdiss, 115v Vcb, 10A Ic transistor with that fT is going to be difficult if not impossible.--79.76.176.172 (talk) 02:15, 31 August 2008 (UTC)

Butterfly Bee Insect (Unknown)

Hello,
I have a question about an insect that keeps returning to my Butterfly Bush here in lower Delaware. The insect aforementioned is about the size of a large Bumble-Bee, it consists of a black and yellow striped pattern, wings like a bee, mouth and feelers of a butterfly, and an odd fan shaped tail. It does not seem aggresive as I have been studying it for the last two months, and mingles with the other insects feeding on the bush without incident. I could not find it or any reference in any insect books I have, or google. Any help you could give me would be outstanding.

Thank You,

Brent —Preceding unsigned comment added by 209.244.188.217 (talk) 23:13, 30 August 2008 (UTC)

A bee hawk moth perhaps? Nanonic (talk) 23:23, 30 August 2008 (UTC)

Or a related bug in the family Sphingidae. Deor (talk) 00:12, 31 August 2008 (UTC)

Hemaris thysbe [1] is found in Delaware and would fit the bill.--Eriastrum (talk) 00:28, 31 August 2008 (UTC)

Side note: I planted a few Butterfly Bush plants near the end of my sojourn in my ex-Ontario home with the hard-fought backyard naturalized (wilderness) area. This was for the express purpose of atrracting more butterflies, which they did. Much to my chagrin, given my "naturist" mindset, when I looked up the plant species, they both turned out to be of Asian origin and listed as potential invasive species in temperate North America. Luckily, I didn't water them enough at the start, so I didn't have to actually kill a living thing, my problem was solved after two months. But beware! - Butterfly Bush is not a native-adapted plant. Franamax (talk) 00:37, 31 August 2008 (UTC)

August 31

Magnetic "field lines"

Reflecting my utter confusion on some parts of physics, what are magnetic field lines? The classic grade-school experiment with iron filings on a piece of paper with a magnet below shows field lines; the aurorae are produced by "recombination of field lines in the magnetopause"; and every diagram concerning the magnetic force has those dashed lines from N to S. So is the magnetic force expressed along physically real lines through space? Why isn't the magnetic force expressed on a uniform gradient, why does it have to go through certain "lines"? Which of Maxwell's equations result in a field line where the magnetic field is especially concentrated? And how do we predict that "here be a magnetic field line"? Is this a conceptual tool or a real phenomenon? Confusedly yours, Franamax (talk) 01:04, 31 August 2008 (UTC)

Magnetic field#Visualizing the magnetic field seems to deal with the 'field line' usage. We also have an article field line. I haven't read either, so I don't know if there're any good. Algebraist 01:08, 31 August 2008 (UTC)

Conceptual tool. Magnetic field lines are contour lines that give the direction of the magnetic field at any point in space. There are an infinite number of (hypothetical) field lines.--79.76.176.172 (talk) 02:11, 31 August 2008 (UTC)

The field lines indicate the direction a tiny compass needle would point if placed at that spot. It not the case that magnetic fields are present along certain lines, with points between the lines where the magnet would have no effect on a compass needle. As for iron filings, they tend to clump together and establish a pattern of lines or curves. If the magnet were left and the filings were removed and new filings shaken over the piece of cardboard, the clumpy curves woould be similar but in slightly different places. The closeness of the spacing of the "lines" is a helpful approximation the the flux density variation. Edison2 (talk) 06:23, 31 August 2008 (UTC)

Hmmm. Why do the filings conveniently clump together into lines? Clarityfiend (talk) 06:26, 31 August 2008 (UTC)

I guess that each small splinter attains a N / S-pole. As they are linear in shape, the N-pole of one then "sticks" to the S-pole of the next one, thus forming curves / field lines. --Cookatoo.ergo.ZooM (talk) 10:03, 31 August 2008 (UTC)

The ontological status of field lines can get a little complicated. I have read discussions on this very point by physicist/historian/philosophers. Sometimes they are treated as a mathematical construction, sometimes as a real physical entity. As far as I can tell, at least by conversations with plasma physicists, it's not totally straightforward. --98.217.8.46 (talk) 17:15, 31 August 2008 (UTC)

This is the SCIENCE desk - and science is all about experiments. Here is an easy experiment: Take your fridge magnet, a sheet of paper and some iron filings. Mark the location of the magnet under the sheet of paper, sprinkle your iron filings and trace along the lines that appear with a pencil. Now remove the magnet, shake all the iron filings off of the paper and do the exact same experiment again (making sure you replace the magnet in the exact same spot. If the field lines from the second experiment consistently line up with those from the first experiment no matter how many times you try - then you have good evidence that field "lines" exist because they are a reproducible phenomenon. If they don't line up - if the lines appear in different places each time you do it - then they are a side-effect of the way iron filing rotate to align with the direction of the field and clump together to make "lines". It's my belief that the lines are not real - magnetic fields are continuous functions just like any other field. But hey...go ahead and prove me wrong! SteveBaker (talk) 19:47, 31 August 2008 (UTC)

I get confused when I read in Nature a summary of a paper in Science about "a realignment of Earth's magnetic field lines...lead to luminous polar auroras". It does go on to say the "field snaps back into place". On reflection, I can however buy into the idea that the iron filings clump due to N-S attraction between the individually ferromagnetized particles, presumably the clumping mechanism is stochastic. I'm interested though in 98.217's comment - the geo(/space?)-physicists do tend to talk explicitly about "a" field line reconnecting. Franamax (talk) 22:58, 31 August 2008 (UTC)

Right, that's the issue, I believe. Usually they are regarded as SteveBaker describes but often they are described as being able to break, reconnect, etc., which implies something a little more concrete. I seem to recall the person in question mentioning magnetic reconnection as one of the issues, but honestly, it has been awhile and this sort of intimacy with physics has never been to my taste. --98.217.8.46 (talk) 05:17, 1 September 2008 (UTC)

Where could I buy lead ball bearings?

Preferably 20mm in diameter or so. ScienceApe (talk) 02:49, 31 August 2008 (UTC)

Musket balls?--79.76.176.172 (talk) 02:57, 31 August 2008 (UTC)

Nobody is going to make 'bearings' out of lead - the point of a bearing is to remain perfectly spherical under load - and lead would deform and be an utterly useless material - it's far too soft. However, you can buy spherical BB-gun pellets in lead. As '79 says, you could look for musket balls. Quite a few antique gun enthusiasts must need large diameter lead projectiles. However, I think a lot of them make their own by pouring liquid lead into suitable molds. You could do that too. SteveBaker (talk) 03:02, 31 August 2008 (UTC)

Are you looking for ball mill grinding media? United Nuclear sells grinding media made of lead and antimony which are 12.7 mm in diameter. I'm sure other retailers sell grinding media closer to 20 mm if you search on the internet. Coolotter88 (talk) 20:01, 31 August 2008 (UTC)

Asteroids and comets

What plans are in place to deal with the asteroids and comets currently on a direct collision course with Earth?--79.76.176.172 (talk) 02:55, 31 August 2008 (UTC)

Many asteroid deflection strategies have been proposed, but there are no concrete plans in place. In most cases, the choice of approach would have a lot to with the amount of preperation time available and the size of the threatening rock. Dragons flight (talk) 03:03, 31 August 2008 (UTC)

And composition. A solid lump of rock requires a different approach to a loose pile of rubble. --Tango (talk) 03:06, 31 August 2008 (UTC)

NASA have looked at a range of possibilities - but so far, none of them have been brought to the point where we could actually deploy them. Further testing is needed because there is a severe risk of simply breaking up an asteroid into smaller chunks - which would be just as dangerous and have a larger probability of splattering something important on impact. There are also concerns that errors in calculating the precise orbit of the body might result in us inadvertently turning a one in one ten chance of a problem into a certainty. The best chance we have to do this cleanly is to detect the problematic body many years before impact. The smallest nudge at that time will avoid a problem - but if you leave it until the body is merely months away, it's vastly harder. Right now, we can't detect mountain-sized bodies until they are weeks away. Before we do anything about deflection or destruction - we first need to put serious funding into detection - and that's really not happening. The short answer is that we currently have absolutely zero protection - and at present rate of progress, we probably won't have such protection for decades into the future. SteveBaker (talk) 03:09, 31 August 2008 (UTC)

Oh shit! Well wouldn't it be a good idea if both Russia and America and anyone else were to get together to form a plan to detect and divert these objects which would probably terminate most of the life on earth rather than have petty squabbles about whose got more missiles in the others back yard?--79.76.176.172 (talk) 03:18, 31 August 2008 (UTC)

Why? That is nothing more than opinion. This is a reference desk, not a place to try and get a debate going about how important it is to drop everything and try to fix a problem that will likely never happen while humans are still alive on our tiny little speck of a planet. -- kainaw™ 03:21, 31 August 2008 (UTC)

Likely never? 99942 Apophis —Preceding unsigned comment added by 79.76.176.172 (talk) 04:38, 31 August 2008 (UTC)

Actually it was a question (as indicated by the ? at the end) not opinion, but thats a remarkably cool attitude you have there! Just how sure are you that its probably not going to happen sometime soon?--79.76.176.172 (talk) 03:36, 31 August 2008 (UTC)

See opinion and fact. Any question beginning with "Well wouldn't it be a good idea if..." is asking for opinion, not fact. This is not a discussion forum. There are thousands of discussion forums on the Internet. Use one of them if you feel such a desire to discuss opinions. -- kainaw™ 03:40, 31 August 2008 (UTC)

He did follow up with a legitimate question regarding the probability of an impact event during which humans inhabit the Earth. ScienceApe (talk) 04:38, 31 August 2008 (UTC)

What is your source for that statement that we can't detect mountain-sized objects until they are weeks away? My understanding was that our detection programs were pretty good. --Tango (talk) 03:46, 31 August 2008 (UTC)

We detect and follow a great many objects that are only tens or hundreds of meters in size [2]. Most known objects are followed many years in advance. Yes there are unknown asteroids, and yes some could be very large, but the idea that we only see mountains right before they show up is simply not true. Dragons flight (talk) 05:16, 31 August 2008 (UTC)

I think there is a big difference between detecting a NEO for the first time and tracking it once it has been detected - tracking is much easier than detection. If you look at this NASA list of recent and upcoming close approaches, you can see that some of the objects have been tracked over several years. But if you drill down to the (rather cool) Java interactive orbital simulation for each object, you can see that most of them (especially in the sub-1km diameter range) were very close to the Earth when then were first detected. 1998 UP1, for example, has been tracked for 10 years, but it makes a close approach once a year (because its orbital period is almost exactly 1 year) and when it was discovered in October 1998 it was a few days past that year's close approach. NEO tracking programs seem to concentrate on detecting objects that repeatedly cross the Earth's orbit and make close approaches every few years, so that we can track them and get an accurate enough fix on their orbits to determine whether they will be a danger in, say, 50 or 100 year's time. Gandalf61 (talk) 13:32, 31 August 2008 (UTC)

That was, as you say, detected 10 years ago. Our detection programs have come on a long way since then - I would hope we would have spotted it sooner had it made the same close approach now. Also, I wouldn't consider sub-1km to be mountain sized. --Tango (talk) 14:22, 31 August 2008 (UTC)

I don't know - a cubic kilometer of rock would look a lot like a mountain if you put it in your back yard! But let's consult (say) an encyclopedia: Mountain#Definitions says that in the US, a mountain has to be more than 610m tall and in the UK, over 914m. Something that's 1000m tall qualifies as a mountain. SteveBaker (talk) 16:09, 31 August 2008 (UTC)

Yeah, I looked at those definitions and decided 1km was a good cutoff, so sub-1km wouldn't be mountain sized. Remember, these aren't going to be nice regular shapes, so the 1km presumably refers to the longest axis, the other will probably be significantly smaller. --Tango (talk) 19:30, 31 August 2008 (UTC)

The object that caused the Tunguska event and the object that created Meteor Crater in Arizona were both about 50 m in diameter - tiddlers, but large enough to cause explosions in the 1-10 megatons range. NASA's minimum size threshold for counting an object as a potentially hazardous asteroid is 150 m diameter - see "What Is A Potentially Hazardous Asteroid (PHA)?" at this FAQ. An impact event from a sub-1 km object can still cause massive damage. Gandalf61 (talk) 17:49, 31 August 2008 (UTC)

Sure, they'll hurt, but they're not end-of-world type events. Deaths would probably be comparable to other fairly frequent natural disasters. --Tango (talk) 19:30, 31 August 2008 (UTC)

Well, the 50 meter object that caused the Tanguska event flattened 800 square miles of forest - certainly not an end-of-the-world event...for that you need something like a 1km rock. But translate Tanguska into 800 square miles of a major city - and you have perhaps a million people dead. That would make it the second or maybe third biggest natural disaster ever (after floods in China in 1931 and again in 1887). Of course the probability of such a thing is low simply because cities don't cover much area compared to the surface of the entire planet - so the probability of a direct city impact is small. But as I said before, the size of the disaster is potentially so huge that even with the relative rareity of the event - we really should be more concerned than we are. SteveBaker (talk) 15:57, 1 September 2008 (UTC)

Here is some data for the not-so-worried:

• Tunguska_event#Similar_events shows that megaton-range events happened in 1908 and 1930 and many multi-kiloton (bigger-than-Hiroshima) sized events have happened in the last 50 years or so.
• 50m rocks hit us about every thousand years and can level 800 square miles of land (such as in the Tunguska event in 1908) - an explosion with minimum 5 megatons.
• 1km rocks hit us about every half million years.
• 5km rocks hit us about every ten million years and produce a 100km crater and perhaps 50 megatons of explosive power - the debris would blot out the sun and to terrible things to our crops...billions of people could die of starvation within a year.
• The dinosaurs were likely wiped out by a 10km rock - some of humanity might survive it - but probably 99% of humans would die.

So - there is a 1 in 1000 chance per year of a random 800 square mile chunk of the planet getting wiped out with the force of a very large nuclear weapon - from a rock that's WAY smaller than we're able to detect even at the very last minute. Every decade or so we get hit with rocks that could kill a million people in the very unlikely event they might hit a city. Previous replies suggest that a 1km rock may or may not be detectable soon enough to do something - but it could take out an enormous amount of people and/or cause massive tsunamis.

Once every half million years for a really big rock may sound like a pretty remote chance - but the consequences would be extreme.

The problem with this kind of thing is to balance the probability of it happening versus the scale of the consequences. We spend an immense amount of money to protect ourselves from very probably events (car crashes, house fires, medical mishaps) that are very likely - but which don't affect many people at a time. We have a blind-spot to very infrequent/unlikely events that would take out half the planet. That's an odd thing. It really doesn't matter (on the grand scheme of things) how many people get killed in car crashes - but if a mountain of rock were to wipe out almost all of humanity - then that's something we need to pay attention to.

If there is a one in 500,000 chance of a meteor killing (say) 5 billion people each year (that's only considering the really big rocks) - that's an average of 10 out of every 100,000 people per year. OK - now let's examine: List of causes of death by rate. 20 people per 100,000 get killed in car crashes worldwide (it's more likely in places like the USA - but less likely in (say) India) - so you are twice as likely to die in a car crash than by the consequences of a 10km meteor. The probability of dying in a killer meteor collision is comparable to the chances of dying from one of the more common cancers or a random act of violence (eg a crime, a mass murderer or a domestic dispute). So, from an individual person's perspective - we should be spending at least as much on looking for and deflecting 1km meteors as we do on trying to eliminate street violence. Death by meteor is quite a bit more probable than death by Altzheimer's disease. You are maybe twice as likely to die from a meteor than from your house burning down.

From a purely statistical perspective, we should spend more on meteor protection than on (say) airbags in cars, Altzheimer's research or smoke detectors because no matter how much you spend, you'll never eliminate those things - where there is every chance that would could provide 100% protection against 1km+ meteor strikes. As a species, we should place more 'weight' on a potential species-obliterating-event than on more probable events that (while killing the same number of people on average) are no risk whatever to the survival of our species. You can go one further by saying that we'd also be protecting most other species on earth from obliteration too.

That's only considering the very infrequent planet killers - I guarantee that the first time a once-a-decade sub-50m rock hits a major city, delivering a few hundred Hiroshima-sized bombs worth of damage and perhaps killing a million people, we'll suddenly become VERY focussed on those smaller rocks.

SteveBaker (talk) 19:13, 31 August 2008 (UTC)

You need to take into account cost:benefit ratios. You can almost completely protect a family with one smoke detector for a couple of quid. The cost per family of protecting against small asteroids is probably far far greater (I don't have any figures). Remember, even if we detect them, the cost of actually doing anything about it is probably going to be prohibitive if it's "only" going to save a million people. Using Deep_Impact_(space_mission) as a benchmark (a deflection mission seems roughly similar in parameters), we're talking about $330 million, probably more due to the need to do it quickly. $330 per person sounds pretty reasonable at first glance, but when you consider what else that $330 could be spent on (smoke detectors for 100 families, say), it may not be the best use of limited funds (and funds are always limited). --Tango (talk) 19:30, 31 August 2008 (UTC)

You have the math totally wrong. You can only spread the cost of $330 million over a million people once you know which million people will be affected. Before you know which million you're going to have to save, you get to spread the cost over the entire planet. If $330 million were all it would take to protect six billion people from a one in a thousand chance of death-by-meteor per year, it would be a total bargin! You'd have to put $3 smoke detectors into a lot more than 110 million homes to save a million lives. Remember - death from house fires is 5 per 100,000 people per year. To save a million people over maybe the ten year life of your smoke detectors in a year you'd have to put them 1,000,000x100,000/(5x10) homes...that's two BILLION homes...which would cost six billion dollars - not $330 million...and (furthermore) they'd have to be 100% effective in preventing death from fires - which they obviously are not.

If you are thinking about an after-detection calculation - then look at it like this: We spent considerably more than $330 per person on fixing up New Orleans AFTER Katrina - forget the deaths - the cost of reconstruction alone would more than pay for the mission to deflect a small rock. If a big rock was to hit New York and you asked the million people within the strike zone to pay $330 each to save their homes - I'm pretty sure they (or their insurance companies) would be more than happy to pay up! $330 million is NOTHING compared to the cost of a million lives. The government could justify it in terms of lost taxation revenue alone!

Linked earlier in this discussion, The Sentry Risk Table is an interesting read. It's fascinating how many serious impact events have better odds than a lottery ticket.

For instance, you'd need to buy 3,398 powerball tickets before your odds of hitting the jackpot were higher than the odds of an impact by 99942 Apophis.APL (talk) 19:27, 31 August 2008 (UTC)

So asking people to pay $3,398 each for meteor insurance should be a no-brainer since dying is a much worse event than winning a lottery is a good event. SteveBaker (talk) 20:09, 31 August 2008 (UTC)

Yes, but not playing the lottery ought to be a no-brainer, yet people still do it. --Tango (talk) 22:36, 31 August 2008 (UTC)

Steve, I've got you covered, where should I send my PayPal account information? Special this month only, $3,000 even if you act now! I'll insure you against winning Powerball too. However I won't cover you for the much more liekly chance of getting hit by lightning or contracting the flesh-eating virus (which amazingly I'm not able to find a wikilink for). Franamax (talk) 22:44, 31 August 2008 (UTC)

The lottery is a tax on the statistically-challenged. Sadly, I can't afford meteor insurance because I'm spending all my money on other forms of insurance! SteveBaker (talk) 03:34, 1 September 2008 (UTC)

Oh - and the chance of being struck by lighting in any given year is about one in 300,000 - so that's 0.3 deaths per 100,000 - about 30 times less likely than dying from a planet-killing meteor strike.Necrotizing fasciitis is about half as likely to hit you as lightning...so about 60 times less likely than dying from a meteor strike. Hence it would cost you barely 5% more to throw in insurance for those other two conditions along with your meteor insurance. You see what I mean about people's failure to understand statistics? SteveBaker (talk) 04:27, 1 September 2008 (UTC)

Necrotizing fasciitis. --Tango (talk) 00:33, 1 September 2008 (UTC)

Yeah, that's the one. Why did I use "virus" in my search? I tells ya, we should ask Google to take over our search box! Franamax (talk) 01:52, 1 September 2008 (UTC)

Hey, at least it's not lupus. --mboverload@ 01:54, 1 September 2008 (UTC)

Poisonous things that taste good

I want to compile a list of notoriously carcinogenic/poisonous chemicals that also have a palatable flavor/scent. For example Lead(II) acetate, cyanide (I've heard it smells like bitter almonds), etc.. I would be eternally thankful if you could help me on my way, thank you. Kenjibeast (talk) 06:20, 31 August 2008 (UTC)

How about fat, alcohol (I personally don't like the taste but a lot of people seem to like it), sodium chloride, sucrose ... Nil Einne (talk) 06:57, 31 August 2008 (UTC)

What about water? 93.132.155.98 (talk) 10:14, 31 August 2008 (UTC)

Some like the smokey note which is definitely carcinogenic. --Ayacop (talk) 07:47, 31 August 2008 (UTC)

Fugu, anyone? --antilived^{T | C | G} 07:51, 31 August 2008 (UTC)

I thought about that but in that case I think it's questionable whether they really like the taste or simple the effect of the nicotine they're inhaling. I don't think the same thing can be said for alcoholic beverages because altho some people just want to get drunk, many people claim to like the taste too Nil Einne (talk) 10:59, 1 September 2008 (UTC)

Most kinds of ant poison taste good because it contains sugar to attract the ants. But most kinds also contain strychnine. (Refer to "strychnine" in Wikipedia.) Because of the sugar content, ant poison should be strictly kept away from children. Dogs like sugar too. The safest kind of ant poison comes in a little sealed can that has small holes for the ants to enter. Andme2 (talk) 15:32, 31 August 2008 (UTC)

The ability to smell hydrogen cyanide is genetic, though I assume non-detection is a side-effect of some more useful trait:) Phosgene smells nice. Lots of molecules are made of various sugars (as a class of compounds, not the specific "table sugar" and other sweeteners usually seen in foods. Some saccharaides are wickedly toxic, but don't know how they smell. Even some simple acetals smell nice but have toxic effects (first-hand experience here). DMacks (talk) 19:58, 31 August 2008 (UTC)

I'll nominate ethylene oxide which apparently has a "faintly sweet" odour which I've thankfully never detected - they have honkin' big signs around the EO facilities in refineries and gas plants. And of course, there's benzene, which gave the name to the whole class of aromatic compounds, because it smells sweet while it kills you. Franamax (talk) 22:29, 31 August 2008 (UTC)

Anecdote: I remember driving in for my safety training to a really quite large Texas refinery (Texaco Port Neches) and smelling the kinda pleasant smells wafting in from the hot Texas breeze (I'm Canadian, we don't roll our windows up on hot days). I also remember, after my safety training, sitting in the smoking area smelling those pleasant odours wafting about, and sucking on my cigarette so that its nice familiar toxic compounds could keep me safe. :( Franamax (talk) 00:01, 1 September 2008 (UTC)

Ethylene glycol - found in antifreeze - slightly sweet smell - especially if heated. Very sweet and pleasant-tasting too. Many children and pets have died from drinking small amounts of the stuff, being fooled by the pretty colors it comes in and the super-sweet taste. The merest taste of the stuff is enough to require hospitalisation for a child. Ethylene glycol poisoning has a good deal to say about this nasty stuff. SteveBaker (talk) 03:29, 1 September 2008 (UTC)

Death caps ScienceApe (talk) 21:33, 1 September 2008 (UTC)

A Latin proverb: Dosis facit venemon. "It is the dose that makes the poison." - Lambajan 16:02, 7 September 2008 (UTC)

Breakdown via anti-hydrogen

Could several anti-hydrogen atoms be used to take one proton, one by one, from a neculeus of a normal atom, stepping it through alot of different elements? Or would the normal atom usually decay into two seperate atoms if hit by a antiproton etc? —Preceding unsigned comment added by 58.108.249.161 (talk) 10:09, 31 August 2008 (UTC)

The energy released by a proton-antiproton annihilation event is on the order of 2 billion electronvolts (2 GeV). The binding energy of an atomic nucleus is – for most nuclei – somewhere around 8 million electronvolts (8 MeV) per nucleon (proton and neutron in the nucleus). See our article on Binding energy#Nuclear binding energy curve for specific numbers there. The energy available from the annihilation is more than a hundred times the energy required to blow an extra proton or neutron out of the nucleus.

To be fair, the actual efficiency of transfer of annihilation energy to the nucleus is actually nowhere near 100% efficient. The first publicly available study I found was this one (warning, 7.0 MB PDF). They found that 120 MeV (on average) is transferred to a carbon nucleus, and about 450 MeV is transferred to a uranium nucleus. (That pretty much covers the gamut of atomic weights.) In any event, those energies are quite sufficient to drive fission events, so 'stepping' through elements one by one isn't likely to occur. TenOfAllTrades(talk) 14:59, 31 August 2008 (UTC)

Also, the probability of exactly one anti-hydrogen actually hitting your one atom is essentially zero. Even if this worked - you'd have to fire a lot of anti-hydrogen at a lot of your chosen material. Then you'll have no control of how many anti-hydrogens hit each atom in your material. So even if you could somehow evade the problems that TenOfAllTrades brings up - you'd still be doomed. SteveBaker (talk) 15:14, 31 August 2008 (UTC)

Electron capture could be interesting, though I don't see how to force it on atoms not prone to it (using myons?). But this way you would have excess neutrons very soon. 93.132.155.98 (talk) 17:06, 31 August 2008 (UTC)

(You meant muons, right?) --Anon, 17:36 UTC, August 31.

Right! 93.132.155.98 (talk) 17:41, 31 August 2008 (UTC)

DNA inbreedinng

Do we have an article that explains why inbreeding/incest etc. causes DNA defects and why its eveolutionarily beneficial for genes too not 'mate' with genes that are similair to themselves?--58.108.249.161 (talk) 10:41, 31 August 2008 (UTC)

Have you looked at inbreeding? SpinningSpark 11:05, 31 August 2008 (UTC)

when to plant nectarines from saved pits

I've been eating a bunch of nectarines and peaches lately and I've saved all the pits so I can plant them (mostly nectarines, but a few peaches too). I'd just like to know when would be a good time to plant them and any tips on growing the trees. In case you're wondering, I live in Northeast Kansas.

Also, I just noticed that some of the pits are getting tiny little spots of mold and I'd like to know how to safely store the pits until they can be planted. should I discard the pits that have mold?

One more thing. We have lots of little wild plums around here (I cannot identify the specific species since I'm not a botanist :P), but I know that plums are in the same genus as peaches and nectarines (prunus) and I'd like to know if they would accidentally cross-polinate. If so, would this negatively affect the quality of the fruit?

Thanks ahead of time for your help! 63.245.152.68 (talk) 11:48, 31 August 2008 (UTC)

For growing you will have to crack the pit open as the actual seed is inside, but after that there are not really any special preparations needed, just put the seed straight into some ordinary soil and keep it damp. It will take a long time to germinate though. Also try planting several seeds to increase the chances as in nature it is very rare for all offspring to survive. Remember that if you are growing them to eat, fruit grown from a seed almost never tastes the same as the fruit the seed came from. This is because the fruit you buy in the shops is bred asexually (basically clones the plant) and may have been crossed thousands of times to get it just right, but when you grow a seed it has had its genes all mixed up in independent assortment so you could get just about anything, though most of the time they just taste really bitter. Then again you could get a better fruit than the original, it's a lottery. JessicaThunderbolt 14:47, 31 August 2008 (UTC)

I've found that too. If you have a friend with a good tree - get the pit from that, then you'll have a vastly better chance - also, you'll know that that variety of tree will grow in your local climate. SteveBaker (talk) 15:11, 31 August 2008 (UTC)

'twould seem to me that when the fruit is ripe and falls to the ground would be about right? Saintrain (talk) 23:33, 31 August 2008 (UTC)

I did notice that if you crack the pit open there's a little seed in there that actually resembles an almond (which makes sense as almonds are also in the genus prunus), but it never occurred to me to plant that. I guess it makes a lot more sense that way, though. I'm aware that the fruit probably won't meet my expectations, but I have about 15 pits so I'm bound to get some good fruit someday. About how long does it take for the seeds to germinate? and after they do, how long does it take for them to grow big enough to make fruit?

I wonder if you can eat the almond-like seeds or if they have some sort of poison in them. I'm sure not gonna try, but I am curious.63.245.152.68 (talk) 11:50, 1 September 2008 (UTC)

The peach trees I have seen grown from seed have fine tasting fruit, but the fruit is a little smaller.Polypipe Wrangler (talk) 03:36, 2 September 2008 (UTC)

got about twenty fruit after 7 years, (tree about 2 m tall) but that was with a drought and slow growing conditions.Polypipe Wrangler (talk) 03:39, 2 September 2008 (UTC)

lipid movement in a liposome..

I would like to know a few methods using which one could track the movement of a lipid in a liposome. In the sense, suppose I want to keep observing a lipid molecule for say, 5 minutes, then how do I do that? —Preceding unsigned comment added by Psruthi16 (talk • contribs) 14:29, 31 August 2008 (UTC)

An admitted wild guess here (which I'm not supposed to do), but our article on fluorescent proteins indicates that they can be palmitoylated to mGFP. Palmitoyl is a fatty acid so possibly the GFP-palmitoyl complex could be incorporated into a lipid molecule? However, getting that complex through the liposome membrane would be a different story. Other than that, I got nothin'. Franamax (talk) 22:21, 31 August 2008 (UTC)

Mozzy bites

What the best thing to rub on Mosquito bites? Does spit really help? --217.227.97.121 (talk) 14:56, 31 August 2008 (UTC)

See Treatment of mosquito bites. JessicaThunderbolt 15:02, 31 August 2008 (UTC)

I'm surprised it doesn't mention witch hazel, which works for me every time. Use two applications five minutes apart.--Shantavira|^{feed me} 15:25, 31 August 2008 (UTC)

Wikipedia - the encyclopedia you can edit! SteveBaker (talk) 16:04, 31 August 2008 (UTC)

But not WP:Original research Nil Einne (talk) 10:56, 1 September 2008 (UTC)

Unknown insect

Found a insect that was thought to be an armored snail, it has slimy feet of a snail, but the head of a catapiller, and the shell of a pill bug(rolly polly bug). Cannot find any information on this insect?216.236.163.183 (talk) 15:23, 31 August 2008 (UTC)

It seems unlikely to be an insect. Adult insects all have six legs and a three-part segmented body (head, thorax, abdomen). SteveBaker (talk) 16:00, 31 August 2008 (UTC)

This sounds like a joke question, but I'll assume good faith. You should provide the location and a photograph of the creature to help people here make an indentification. Jdrewitt (talk) 16:05, 31 August 2008 (UTC)

It could be a cherry slug or pear slug. (Why is there no article on this topic?)Graeme Bartlett (talk) 21:35, 31 August 2008 (UTC)

Cherry slug larva

Cherry/Pear slugs (they are both Caliroa cerasi) aren't slugs at all - they are Sawfly larvae from the Tenthredinidae family - we don't have articles about any of that family. The photo at right comes from Wikicommons - but it doesn't seem to be used anywhere in Wikipedia. It looks like the sawflies are a taxonomic mess - a bunch of more or less unrelated species jammed together because they share the same lifestyle - not because they are genetically related. In these cases, the names of the animals may change - but the references I can find in agricultural web sites may well be using some older name. It kinda fits the OP's description - except for the feet. SteveBaker (talk) 03:18, 1 September 2008 (UTC)

Maybe he thought that it has a snail's foot due to its slime secretion?--Lenticel ^(talk) 00:46, 2 September 2008 (UTC)

Magnetic cows

There is a story that's been all over the news media over the last few days about researchers looking at Google Maps and finding that cows (and other herd animals like deer) have a preference for aligning themselves North/South. I'm trying to find out whether they mean that the cows all face with their noses to the north - or whether 50% of them are facing north and 50% south. I've been thinking that a possible reason for doing this (None of these reports seem to be suggesting reasons) is that it might be a way for the cows to arrange for the herd to get good all-round vision for predators. They have eyes out on the sides of their heads to improve their field of view - but they must have a blind-spot behind their thick, juicy, tender rear ends. If the cows pointed in utterly random directions, they'd have pretty good 360 coverage - but if they all pointed North - that would mean that they deliberately evolved a blind spot! However, if 50% faced north and 50% south that would guarantee no blind-spots and they could be using the earth's magnetic field to dramatically reduce the probability of a blind-spot. Has anyone heard a theory for this? SteveBaker (talk) 15:55, 31 August 2008 (UTC)

Am I the only one who has an image of a cow suspended on a piece of string slowly rotating to point north? Seriously, the first thing that crosses my mind is that they are putting the sun to their backs to avoid the glare. Is there any information on cows in Australia or South America? If they face South rather than North that would indicate that it is not magnetic field related. SpinningSpark 16:22, 31 August 2008 (UTC)

Here is the study. It's not clear in the abstract, but I believe they were unable to determine from satellite images which way round cows were standing. The deer tend to be head-north though. To Spinningspark: they tested the magnetic hypothesis by looking at areas where magnetic north is significantly different from true north. It turned out magnetic north wins. Algebraist 16:34, 31 August 2008 (UTC)

...and, according to this summary in The Economist, the researchers averaged out the effects of sun and wind direction. Gandalf61 (talk) 17:13, 31 August 2008 (UTC)

(ec) This report from the BBC says that the deer (all observed in Czech Rebublic) were 2:1 in favour of North over South and as Algebraist said, the satellite images of cattle could not resolve head from rear. It does say though, that cattle in Africa and S America are more NE/SW than N/S and speculate that this is because the field is weaker in these locations. SpinningSpark 17:16, 31 August 2008 (UTC)

This sounds to me like what comes out of the back end of the cow. Cows point the way the boss cow is looking, because there might be something interesting there, and point the other way because they are a hierarchy and standing tranversely is inviting a fight. They orient to maximize warmth on cool days and into the breeze on hot days to keep the zillions of flies away from their eyes. However, if anyone has a copy of the full study, please email me, I'd love to read the whole thing. Franamax (talk) 22:05, 31 August 2008 (UTC)

I drove past a herd of Texas longhorn on the way home an hour or so ago. They were definitely all facing the same way. Now I've checked on Google Maps - I'm 100% sure they were facing nore or less exactly South. So on one entirely not-statistically-valid sample, South wins. Of course that might be because all but one of them are facing the same way as the 'boss cow' - but that doesn't help answer the question: Why does the boss cow face predominantly along the North/South axis?

Anyway - I'm bored with that one...I have a new theory. How do we feel about this one?

At the map resolution at which these photos must have been taken in order to see cows at all, we must be talking about aerial photography done from a plane. Commercially-available satellite imagery is too fuzzy to pick out anything as small as a car - let alone a cow. To get pixels that resolve as a cow - but without telling you which is head and which is tail (as the researchers claim), you must be looking at image pixels that are perhaps a quarter of a meter across. Any higher resolution and the head end would be obvious. That would give you a "cow" that's perhaps 8 fuzzy off-white pixels. If the resolution were a half meter then a cow would be only be about two or three pixels. So what these guys are undoubtedly analysing is the direction based on perhaps just a handful of pixels.

But suppose the aircraft doing the photography were flying east-west and taking a photograph on an oblique angle in order to cover a wide swath of land without having to fly backwards and forwards too many times. When Google stretch that photo to make it look like it was taken looking straight down, then a fuzzy ROUND splotch would turn into a fuzzy elliptical splotch that would be stretched along the north-south axis. So if the original resolution was not quite high enough to resolve the direction the cows were pointing then Google's image processing could easily make it look like they all face the same way...at right angles to the flight path of the aircraft. So...can anyone think why an aerial photography plane would always tend to fly East/West when doing it's photography run rather than North/South? Maybe some kind of air traffic control rules for the altitude they fly at? I know that aircraft flying in certain conditions are separated out at different altitudes depending on the direction they are flying...perhaps at the best altitude for photography, you have to be flying East or West?

SteveBaker (talk) 02:40, 1 September 2008 (UTC)

I only have one air chart (Helsinki), the Malmi and Vantaa approaches and holding zones are variously oriented. But wouldn't aerial surveys be flying in the uncontrolled zone anyway? On this chart, below 1000 feet near the airports and below 1500 feet everywhere else is fly-as-you-like. How high would a survey plane be flying? Franamax (talk) 09:43, 1 September 2008 (UTC)

Thats the same thing i thought. I haven't seen the details of the study, at first you get the impression that its very professionally done, then later you get the impression that it is rather unprofessionally done. Also it should be pretty simple to test this in practice. Get some strong electromagents and put theem around a small field and see if you can get the cow to allign itself.

155.144.40.31 (talk) 05:36, 1 September 2008 (UTC)

Or pick a cow up, move it a few thousand km east/west, put it down again and see if it turns slightly. What would happen if you put the magnet on the cow? Would it spin in circles? :) Franamax (talk) 09:32, 1 September 2008 (UTC)

We just did it to freak you humans out. Joke's over, so moooove along. Sincerely, Elsie. [unsigned]

Well, that way they're not blinded by the sun neither in the morning or the evening. – b_jonas 23:05, 6 September 2008 (UTC)

Path integral formulation

Anyone here who thinks to understand that article? It all looks like technobabble to me. The formula below the heading Time-slicing definition looks as if it's integrating over just one path, not over all possible paths. 93.132.155.98 (talk) 16:13, 31 August 2008 (UTC)

Well, it's about quantum mechanics, what kind of babble did you expect? :) And it's about an idea developed by Richard Feynman, who had an extra several brains packed in his skull. Quantum theory is one of those areas where it becomes very difficult to meet the Wikipedia standard of "anyone should be able to read and understand the article". That can be done, but you'd need a box at the top saying "read these six hundred other articles first". Franamax (talk) 21:51, 31 August 2008 (UTC)

You are right in general, this makes it so difficult to recognize technobabble. In this special case, line integral and path integral seem to be mixed up without warning. 93.132.132.172 (talk) 00:12, 1 September 2008 (UTC)

The path integral is vastly easier to understand than that article makes it look; it's a very simple idea. There's a nice explanation on pages 7–9 of Chapter I of QFT in a Nutshell. We need an introduction like that in the article. If someone will draw the pictures, I'll write the text.

The formula

$\int \limits _{x_{1}=x_{a}}^{x_{1}=x_{b}}\ldots \int \limits _{x_{n}=x_{a}}^{x_{n}=x_{b}}\ \exp \left({\frac {\rm {i}}{\hbar }}\int \limits _{t_{a}}^{t_{b}}{\mathcal {L}}(x(t),v(t),t)\,\mathrm {d} t\right)\,\mathrm {d} x_{1}\cdots \mathrm {d} x_{n}$

in the "time-slicing definition" section is integrating over all paths. A particular tuple of values $(x_{1},\ldots ,x_{n})$ represents a path in which the particle is at position $x_{i}$ at time $t_{i}$, where $t_{1},\ldots ,t_{n}$ are times between $t_{a}$ and $t_{b}$. I don't know how they're choosing the n times or interpolating the position at intermediate times, but it doesn't matter because they're taking the $n\rightarrow \infty$ limit (compare the definition of the Riemann integral).

There isn't anything specifically quantum mechanical about the path integral. It works with any linear wave equation. Schrödinger's equation is linear, as are Maxwell's equations in vacuum. Maybe the article should introduce the path integral using water waves instead of quantum mechanics. -- BenRG (talk) 01:43, 1 September 2008 (UTC)

Leaving the physics aside, I note that the integration variables $(x_{1},\ldots ,x_{n})$ are not part of the integrand. It is all but clear what the $\,x(t)$ has to do with the $\,x_{i}$. If the $\,x(t)$ denoted one ot the $\,x_{i}$ it would be gone after integrating with it and of no use for the others. 93.132.132.172 (talk) 19:02, 1 September 2008 (UTC)

blood

what is the non-living part of blood? —Preceding unsigned comment added by 124.195.198.213 (talk) 16:39, 31 August 2008 (UTC)

Blood plasma. And I'm not sure if red blood cells are considered 'living' as they don't contain DNA. 93.132.155.98 (talk) 16:47, 31 August 2008 (UTC)

RBCs are certainly usually considered living. They have an active metabolism, and die in about 90 days. The definition of living doesn't usually include any criterion that DNA is present. Such a definition would classify some viruses as living and some as non-living on the basis of chemical constitutents rather than activity. - Nunh-huh 16:36, 1 September 2008 (UTC)

I was to say that it didn't contain DNA (as usual in other human cells, and no RNA either, nor any other substance or information) to guide reproduction. (As a thought experiment, I consider candle flames alive and worker bees as dead. I don't really believe in that, but I can't pinpoint what would be wrong with that.) 93.132.132.172 (talk) 20:52, 1 September 2008 (UTC)

Perhaps it would be best to keep such definitions of "living" very quiet...they're probably not helpful here, or if, say, you were to get a job as a coroner. Other than that, no harm no foul. - Nunh-huh 03:02, 2 September 2008 (UTC)

The main objective of wikipedia is to give information to people, but what would that be to a people that doesn't also think? Making people think (for themselves, if ever possible) is a goal that I pursue and hope not to be in conflict with wikepedia goals. 93.132.180.102 (talk) 21:47, 2 September 2008 (UTC)

There are productive ways to think, and non-productive. VItalistic speculation is one of the latter. As are categorizations that are made up rather than essential.- Nunh-huh 00:00, 6 September 2008 (UTC)

Life in the most polluted environments?

Which land weeds or sea creatures are able to survive in the most polluted of environments?--Sonjaaa (talk) 19:13, 31 August 2008 (UTC)

Pollution kills off lichens and bryophytes leaving algae. I can't help you with the toughest flowering plant. However there are different plants that can tolerate differing kinds of pollution. Some can tolerate high copper, others high phosphate, and yet others high acid. Is your pollution smoke, fluoride, acid rain, contaminated water or what? Graeme Bartlett (talk) 21:42, 31 August 2008 (UTC)

Does radiation count as pollution by what you're asking about? Becuase, if so, I would say Chernobyl would be a good place to start, because some stuff does grow there, I think, and the article should have information on the aftereffects. I can't imagine that any other kind of pollution would be as toxic as what happened there, though I could just be basing on what I've heard about it.209.244.30.221 (talk) 14:24, 1 September 2008 (UTC)

Forget the plants at Chernobyl. If you want real radiation resistance, you need Conan the Bacterium: Deinococcus radiodurans. In addition to tolerating huge amounts of ionizing radiation (surviving hundreds of times a dose lethal to humans), this bacterium tolerates dehydration, cold, acids, and vacuum. Genetically engineered versions of D. radiodurans have been developed for bioremediation of toluene and mercury contamination in radioactive waste.

As Graeme notes, however, the answer comes down to what you define as 'pollution'. In the deep ocean, hydrothermal vents spew superheated water laden with hydrogen sulfide—a deadly toxin to most creatures. Whole ecosystems are based on bateria with a taste for this usually-toxic gas. TenOfAllTrades(talk) 17:45, 1 September 2008 (UTC)

Physics Degree

I just met this grad student studying Physics and was wondering what exactly people with advanced degrees in Physics do, job-wise, after they graduate. Do they mostly become scientists? Professors? Or what? 128.239.177.28 (talk) 20:23, 31 August 2008 (UTC)Curious

Apart from your suggestions, I know planetarium operator, semiconductor factory developer, microwave nonlinear materials developer, geophysicist working for mining or oil companies, science teacher. Graeme Bartlett (talk) 21:47, 31 August 2008 (UTC)

From what I've heard, lots of graduates go into computing. —Cyclonenim (talk · contribs · email) 22:29, 31 August 2008 (UTC)

There's actually quite a lot of them on Wall Street as well. Mathematical abilities + major smarts = ideal candidate for a lot of big business. --98.217.8.46 (talk) 22:40, 31 August 2008 (UTC)

The American Institute of Physics keeps track of this sort of thing. Just skimming over a report from a year ago (report here), 43% of people with MSc in Physics end up in the Private Sector, 21% end up at a university, 13% end up working for the government, 12% teach in high school, 8% go into the military, 3% do something else. The report omits this sort of discussion for PhDs but indicates that most of them aim for employment at universities, but only about 25% end up with jobs relating to directly to physics. Most end up doing engineering jobs of some sort. (p. 16 of the report)--98.217.8.46 (talk) 22:52, 31 August 2008 (UTC)

Red jelly growing in fridge

I have something unpleasant growing in my fridge. It is the colour and consistency of raspberry jam. It does not grow in the fridge compartment itself, but inside the small bore synthetic rubber tube that drains the condenstion from the fridge. Every few months the drain becomes blocked and the bottom shelf of the fridge gets wet which is how I know it is time to clean it out again. I have flushed the drain tube countless times, often with neat disinfectant but this alien substance always grows back after a few months. But strangely, it never seems to go anywhere outside the dark inside of the pipe. What is it? Is it dangerous? As it is only ever in the pipe and I don't seem able to kill it, I am wondering if it is a chemical reaction of the synthetic rubber rather than something biological. SpinningSpark 20:37, 31 August 2008 (UTC)

Have you tried freezing it with a fire extinguisher and dropping it into the Arctic? --98.217.8.46 (talk) 23:00, 31 August 2008 (UTC)

I am told Steve McQueen is no longer available for that kind of work. SpinningSpark 23:20, 31 August 2008 (UTC)

Maybe, but I know for a fact that Kurt Russell died on just such a selfless mission. Franamax (talk) 01:41, 1 September 2008 (UTC)

This sounds to me like a slime mould (breaking the rules by guessing, again!). The rubber tube would provide a semi-porous substrate where the organisms could hide from your cleaning attempts. Also I think slime molds can form a biofilm which is resistant to disinfectants, although our articles seem to contradict me on this. The solution seems to be to buy yourself a new tube, or perhaps soak it in an acid or alkali solution for several days? I doubt it is a chemical reaction with the tube since presumably the tube would be gradually consumed in the reaction - unless the sulphur is acting as a catalyst, which I don't think would be the case. (On the subject of slime moulds, check out Dictyo for a really fascinating example of unicellular organisms turning into an animal when necessary - very Wikipedish!) Franamax (talk) 23:26, 31 August 2008 (UTC)

My red jelly has never done anything like that. But by the way, I once saw a documentary about Dictyo or a similar creature which was attacked by an amoeba-like predator which could infiltrate and take over the Dictyo body while it was on the move. You don't know the name of that creature do you? SpinningSpark 00:13, 1 September 2008 (UTC)

Well, Dictyo is an amoeba, so I'd like to see which bigger, tougher amoeba comes along to rough it up. You'd need to create a nutrient-deprived environment to see your mould rise up and fly away in any case, quit paying so much attention to keeping the stuff in your fridge cold. As far as takeovers go, I'm minded of the Wollbachia bacteria, which most unbelievably is a redlink. This is a virtuoso - it invades neurons and gonads, alters reproductive sex-ratios, forces bugs to climb up plants where they can be eaten, the whole nine yards. Please tell me we're not missing an article on Wollbachia!! Franamax (talk) 01:41, 1 September 2008 (UTC)

Yeah - we're missing that one - but you could try Wolbachia instead! :-P SteveBaker (talk) 02:03, 1 September 2008 (UTC)

As I understood it, the predator was another species of Dictyo which did not form moving "slugs" of its own. It hitched a ride on another moving Dictyo until it got somewhere good, then killed it from the inside and used the victims body to produce its own spores. There was a fascinating sequence of a Dictyo colony happily crawling along then suddenly stopping dead in its tracks and starting to grow spores from the invader. SpinningSpark 08:29, 1 September 2008 (UTC)

What type of disinfectant are you using? Perhaps a bleach solution would work well. Flush the tube with a solution made from 1 part household bleach and 9 parts water. (Using neat bleach is much more likely to damage surfaces, and probably wouldn't be any more effective.) For full effectiveness, plug the bottom of the tube and let the solution stand for at least ten minutes. Afterwards, rinse the tube out with clean water (residual bleach may harm the material). For bonus points, flush the line with 70% ethanol (or 70% isopropyl alcohol/rubbing alcohol, if it's easier to obtain) and let air dry. Since it's possible – indeed, likely – that spores or bacterial colonies remain elsewhere on the lower shelves and trays of your refrigerator, you might also want to start the process by wiping down all the exposed surfaces with a 1 in 100 bleach dilution. Don't forget to wear gloves and work in a well-ventilated area, and remember that the bleach solutions may damage or discolour both your clothing and other stuff in the kitchen. TenOfAllTrades(talk) 17:58, 1 September 2008 (UTC)

Why do we find some animals attractive?

Why do humans(at least some humans) think that animals like big cats, wolves, birds, and even certain reptiles, as well as some invertebrates such as insects, are beautiful? Because some of these creatures might be dangerous, standing around gazing at, say, a tiger could be quite an evolutionary disadvantage. 68.123.238.140 (talk) 21:51, 31 August 2008 (UTC)

Just to be sure, are you really asking: "Why do humans(at least some humans) think that animals like big cats, wolves, birds, and even certain reptiles, as well as some invertebrates such as insects, are beautiful?" --hydnjo talk 22:37, 31 August 2008 (UTC)

Are you refering to sexual attraction or "awwww they're soooo cute" beautiful? --mboverload@ 22:39, 31 August 2008 (UTC)

Not quite either of those, actually, but closer to the "cute" interpretation-- why people like to look at these animals, that's what I was getting at. 68.123.238.140 (talk) 23:02, 1 September 2008 (UTC)

The last time a similar question came up here, someone suggested that our concept of 'cuteness' is an inbuilt safety mechanism to prevent us from eating our own offspring. --Kurt Shaped Box (talk) 00:11, 2 September 2008 (UTC)

Bilateral symmetry, anthropomorphic features (like the big eyes of a seal pup or panda bear), flowing "elegant" features would be some of the factors. Also, many sexual adaptations such as the "eyes" on a peacock's tail feathers and the brilliant colouration of male birds would weigh in. Of course, the concept of beauty is like your gas mileage - it varies. I personally find a preying mantis quite beautiful, but others might freak out. Then there's spiders - both beautiful and repellent. Franamax (talk) 23:34, 31 August 2008 (UTC)

The article on furries may be of interest to you. JessicaThunderbolt 12:28, 1 September 2008 (UTC)

At the risk of sounding unscientific, anything that looks beautiful to you follows the Golden ratio at some level or the other. Look at its relation to beauty on goldennumber.net. Sandman30s (talk) 14:58, 1 September 2008 (UTC)

Yeah also could it be said to be a sort of sexual feeling towards said animals esp when you pet them?? —Preceding unsigned comment added by LCMk2 (talk • contribs) 21:16, 1 September 2008 (UTC)

Are you confusing petting and heavy petting? --Kurt Shaped Box (talk) 00:14, 2 September 2008 (UTC)

LOL the only other place I've seen "heavy petting" used was in Ann Landers columns! :) (Well, that and other times - but I generally had my eyes closed or was way too close to actually see it.) Franamax (talk) 00:18, 2 September 2008 (UTC)

There used to be a sign at my local swimming pool that had 'no heavy petting' listed amongst the obvious 'no smoking/no running/no food in the pool/no diving in the shallow end/no bombing/no balls or novelty inflatables' instructions. --Kurt Shaped Box (talk) 00:31, 2 September 2008 (UTC)

Basically, dogs that are kept as pets evolve and are bred to look cute for humans, because that's how the dogs can make people give them free food and that's how pet shops can get the most money from selling you dogs even though it's likely that the buyer would have the same gain by just taking any stray dog from the street (if you pay for vaccination). – b_jonas 23:00, 6 September 2008 (UTC)

Human lungs

Can human lungs grow in response to intense use, like human muscles can? I mean, can they function better because one does a lot of physical exercise? Divers can learn to hold their breath for minutes, what happens to their lungs? Can the VO2 max of adult lungs increase? I realize that the question isn't worded accurately, but I hope I'm clear enough to get an answer. —Preceding unsigned comment added by 24.7.54.224 (talk) 22:20, 31 August 2008 (UTC)

Yes, humans can train themselves to more efficiently take oxygen out of the air. I think Lance Armstrong has some kind of deformity that causes him to get more oxygen, but I could be wrong. --mboverload@ 22:41, 31 August 2008 (UTC)

People who live very high in the mountains develop lungs that are a bit larger than normal. Andme2 (talk) 23:07, 31 August 2008 (UTC)

Also, people that dwell in high elevations produce more red blood cells in order to transport more oxygen. I realize this borders on irrelevant.CalamusFortis 23:45, 31 August 2008 (UTC)

Actually, I think the cell-count adaptation is the primary response. It's awfully hard to increase lung volume, what with the ribs and all. Franamax (talk) 01:28, 1 September 2008 (UTC)

In addition, bigger lungs won't help, if the alveolar surface area is not increased. Oxygenation is primarily a problem of gas-exchange across membranes (and the carrying capacity of blood that has already been mentioned), not ventilation (movement of gas in and out of the alveoli). Scray (talk) 03:20, 1 September 2008 (UTC)

Maybe we can't "improve" the lungs but we can do improve the diaphragm to improve the lung's performance.--Lenticel ^(talk) 00:54, 2 September 2008 (UTC)

Sweet smell from blown up capacitors?

I've blown up various capacitors through various mishaps and I've noticed one thing: the electrolytic ones pop like pop corn and gives out a fairly sweet smell. Does anyone know what compound causes that smell? --antilived^{T | C | G} 23:12, 31 August 2008 (UTC)

Are they on a circuit board? If so, it could be vapourized phenolic resin, which smells sweet but is not a good thing to smell a lot of. Franamax (talk) 23:37, 31 August 2008 (UTC)

Yuck, that just led me through a series of stubby, badly written and unreferenced articles. C'mon science people, lets whip these things into shape! It's too much fun hanging out at the RefDesks... Franamax (talk) 23:42, 31 August 2008 (UTC)

No the smell is still there if you pop a capacitor by itself, and is characteristic of electrolytic ones, so I'm guessing something in the electrolyte? --antilived^{T | C | G} 00:23, 1 September 2008 (UTC)

Ethelyne Glycol is often used in the electrolyte, if I remember correctly. That would definitely give off a certain sweetish smell. Arakunem^Talk 00:27, 1 September 2008 (UTC)

I'm betting on Glycol too - that's the same stuff that's in antifreeze - it smells very sweet if your radiator hose splits and splashes coolant all over your engine. It's also pretty toxic...so you might want to try to avoid it where possible. SteveBaker (talk) 01:59, 1 September 2008 (UTC)

What is the designation/manufacturer/part number on the specific capacitor you blew up? Many things have a safety data sheet - maybe we can trace it that way. Franamax (talk) 01:25, 1 September 2008 (UTC)

Do you know the smell of Askarel (PCB)? I wouldn't call it sweet, but more like a dry-cleaning solvent. Old power correction capacitors and motor starting capacitors contained it. Considered hazardous.Edison2 (talk) 15:04, 1 September 2008 (UTC)

I doubt it's PCB, since the capacitors are quite new. I don't remember the manufacturer of the capacitor but it's just one of the generic 47µF ones lying around, and a few more of various capacities. I guess it's glycol, unless there's a better guess somewhere. --antilived^{T | C | G} 05:11, 2 September 2008 (UTC)

Hydrogen Peroxide and Bacteria

What is the precise chemical reaction that occurs between hydrogen peroxide and bacteria that makes it so effective for killing them?CalamusFortis 23:45, 31 August 2008 (UTC)

Hydrogen peroxide is a reactive oxygen species, which means it is willing to hand off an oxygen atom anywhere it has an excuse. Basically then, any oxidizing reaction will do. Franamax (talk) 23:46, 31 August 2008 (UTC)

That I understand, but what exactly is it oxidizing? The cell walls of the bacteria? Proteins?CalamusFortis 23:48, 31 August 2008 (UTC)

Initially, the cell walls. Oxidation ot the lipid membrane will affect the hydrophilic/hydrophobic balance that preserves the membrane structure and the cell will undergo lysis and spill out its contents. These will also be inactivated in the presence of such a strong oxidizing substance. Franamax (talk) 01:18, 1 September 2008 (UTC)

Not only the cell walls. The article on ROS states, 1. damage of DNA; 2. oxidations of polydesaturated fatty acids in lipids; 3. oxidations of amino acids in proteins; 4. Oxidatively inactivate specific enzymes by oxidation of co-factors. --Ayacop (talk) 10:15, 1 September 2008 (UTC)

Oh, OK. That was the specific answer I wanted.CalamusFortis 22:23, 1 September 2008 (UTC)

You may also want to know that hydrogen peroxide is used by white blood cells to kill bacteria in several ways. H₂O₂ is deposited near bacteria within the leukocyte's phagocytic vacuoles where it reacts with the myeloperoxidase-H₂O₂-halide system to form hyperchlorous acid and/or singlet oxygen; H₂O₂ also reacts with oxygen or with lactoferrin or bacterial iron to form a hydroxyl radical (¹OH), the end products having a direct toxic effect on the bacteria. - Nunh-huh 03:31, 2 September 2008 (UTC)

The Big Bang and Gravity

I know that this sounds like a dumb question, but could anyone tell me how planets, stars, etc. coalesced after the Big Bang? The universe is still expanding, and, in an explosion, matter does not coalesce; it keeps going outward. Hopefully there is a simple answer, and I thank you in advance for your patience. --Freiberg, Let's talk!, contribs 23:38, 31 August 2008 (UTC)

I think it helps if you don't think of the Big Bang as an explosion per se, just the start of our universe. After matter formed, areas where there was more of it simply pulled themselves together. Paragon¹²³²¹ 23:42, 31 August 2008 (UTC)

Hmm. OK, but wouldn´t that expansion of the universe itself cancel that out? Gravity, after all, is by far the weakest force. I could see individual atom forming through the strong and weak forces, but past that, it does not seem to make sense. --Freiberg, Let's talk!, contribs 23:53, 31 August 2008 (UTC)

Gravity is weak, but over short enough distances, it's stronger than expansion. The rate of expansion is, roughly speaking, given by Hubble's Constant, which is about 70km/s/Megaparsec, that is two objects a megaparsec apart will move apart at 70km/s. Our galaxy is only 30 kiloparsecs in diameter, so the recession is far less, it's not that difficult for gravity to accelerate objects towards each other fast enough to overcome that recession. --Tango (talk) 00:20, 1 September 2008 (UTC)

I think I get it now. So the inevitable variations in the initial Big Bang would be enough for various clumps of atoms to form. These clumps are now galaxies, with clumps within that becoming stars, etc. Alright! Thank you for your time.--Freiberg, Let's talk!, contribs 01:32, 1 September 2008 (UTC)

What's really interesting (and bothers me a lot) is that if the universe started out as a zero sized singularity - then it was in all possible ways perfectly symmetrical...as only an infinitely small dot can be. So how did these initial clumps come about? Any distribution of forces, energy, velocity, matter or anything else you could imagine being able to measure should also have been perfectly symmetrical and perfectly smooth. Why did any clumpiness of any kind ever come about if every particle is being pulled in all directions identically? I'm guessing that the answer is of a quantum-mechanical/statistical nature...but it still bothers me that we just naturally assume that there would be even the slightest variation in density that would ultimately lead to bigger and bigger clumps - then stars and galaxies - when the source of all of this stuff was a 100% PERFECTLY symmetrical event - by definition. SteveBaker (talk) 03:53, 1 September 2008 (UTC)

It's not an assumption; it's an observation. WMAP shows that the early universe had variations in density that exactly match the expectations based on quantum mechanical fluctuations in the first microsecond of the big bang. Dragons flight (talk) 04:47, 1 September 2008 (UTC)

Ah - that's good. That was the only thing I could think of that it might be. I was aware that WMAP had shown variation that was sufficient to explain subsequent star/galaxy formation - I wasn't aware that it matched a quantum-statistical model. Well, that's very comforting. Living in a universe where everything was exactly the same shade of beige in every direction would have been less interesting! SteveBaker (talk) 05:56, 1 September 2008 (UTC)

Our article on structure formation has a nice explanation of the end-of-end process. There are several stages. In outline:

1. Cosmic inflation provides an almost-homogenous distribution of matter/energy in the early universe, with small inhomogeneities due to inflated quantum fluctuations.
2. As the universe expands and cools it becomes dominated by matter - mostly dark matter - and gravitational attraction magnifies the inhomogeneities forming dark matter haloes.
3. Radiative cooling and magnetohydrodynamic effects then accelerated the concentration process for ordinary baryonic matter, which forms gas clouds and eventually stars and planets. Gandalf61 (talk) 09:04, 1 September 2008 (UTC)

September 1

Luciferin

How did this compound get its name? I assume it was someone versed in Christian mythology, but who was it?CalamusFortis 00:02, 1 September 2008 (UTC)

I can't give a who, but maybe a why. "Lucifer" simply means "light-bringer", which is what Luciferins do. The relation to the devil may be coincidental. Paragon¹²³²¹ 00:59, 1 September 2008 (UTC)

Yes - I agree. Our article on Lucifer says that the name means "Light bringer" or "Morning Light" - originally meaning the planet Venus. It suggests that the use of the name to apply to Satan is a relatively modern confusion. Lucifer was originally some much hated tyrant King of Babylon...or perhaps Tyre, Lebanon...who subsequently was confused with the Devil. The article is hard-going...I don't recommend attempting to glean anything more meaningful from it unless you are already enough of a linguist to not need to read it! SteveBaker (talk) 03:47, 1 September 2008 (UTC)

As for the who, according to the OED the word was first used (in the French form luciférine) in 1887 by one R. Dubois, in volume 105 of a journal identified by the abbreviation Compt. Rend., which I assume was Comptes Rendus de l'Académie des Sciences. And yes, as explained above, the word has nothing to do with the Devil. Deor (talk) 12:58, 1 September 2008 (UTC)

Here is the link to the article of Dubois Recherches sur la fonction photogénique .--Stone (talk) 21:24, 1 September 2008 (UTC)

Actually, I believe this is the article that the OED refers to. Dubois coins the name luciférine near the bottom of page 691. Deor (talk) 10:45, 2 September 2008 (UTC)

Amount of Potassium iodide in Iodized salt

From Potassium iodide they say that an adult should take 130 mg of it after being exposed to radiation. Hypothetically, how much iodized salt would be equivalent of 130 mg of Potassium Iodide? Would it matter whether it was Potassium iodide or Potassium iodate? From what I understand of Radiation poisoning this only protects the thyroid from Radioactive iodine, which makes me wonder: Would this kind of action really have much of an impact on survival percentages? Thanks. Anythingapplied (talk) 00:17, 1 September 2008 (UTC)

My container of Morton's says that 1 serving (0.25 teaspoons) contains 130 micrograms of Potassium Iodide. So thats 1000 servings to get the thyroid blocking that I assume you're asking about. 1000 servings = 250 Teaspoons, or about 5 cups! I think the sodium would be more toxic than the radiation at that concentration. But yes, KI only protects the thyroid from uptake of radioactive iodine, which is a by-product of a nuclear chain reaction. Arakunem^Talk 01:18, 1 September 2008 (UTC)

Indeed the LD₅₀ of salt is 3 g/kg in rats. Presuming it's fairly similar for humans, that's 300g for a 100kg human. Presuming you can actually consume that much salt I wouldn't think your chances of survival as very high Nil Einne (talk) 09:26, 1 September 2008 (UTC)

Looks like 1 cups of salt is about 300g, so 5 would no doubt result in a very low survival probability. Anythingapplied (talk) —Preceding undated comment was added at 14:55, 2 September 2008 (UTC)

According to one reference from the KI article [3] thyroid cancer rates increased 30- to 60-fold in very young children after the Chernobyl accident. Looking at statistics for thyroid cancer incidence in the UK [4] and using the general rate of 2.5 per 100,000 people, that would mean maybe 1 in 1,000 people would be protected from cancer. That gets a little confusing though when you look at the age-distribution graph, the normal thyroid cancer rate in children under 10 is close to zero. However, since radioactive iodine is known as a risk factor and has a short half-life, and it is very easy and cheap to give people near nuclear plants emergency kits with KI tablets, it makes sense to do so. Note though, the article doesn't say "after being exposed to radiation", KI is used before or during exposure to radioactive isotopes from an accidental release from a nuclear plant (or heaven forfend, bomb fallout) - the theory being to flood the body with stable iodine to prevent the radioactive iodine from being taken up by the thyroid. Franamax (talk) 11:32, 1 September 2008 (UTC)

To answer you other question: yes it only protects against ragiation-induced thyroid cancer and not against cancers cause by any of the other isotopes that are released by a nuclear weapon or accident. However, since this one cnacer represents the biggest single health risk from such an incident, so yes it's worth tryin to defend against. Duringhte cold war, the US government seriously considered a law to require that all households keep a package of potassium iodide tablets (to be distributed by teh electric power company and taped to the fuse box, oddly enough.) The plan was abandoned due to concerns that more deaths would occur due to failure to follow the directions on the package than could be averted by proper use. -Arch dude (talk) 16:17, 1 September 2008 (UTC)

Hmm...that distribution scheme actually makes a remarkable amount of sense. Every home should have a fuse box, and every homeowner ought to know where it is. having the electric company deliver the tablets ensures that every household will get some, and having the electric company staff tape the packet to the fuse box guarantees that the homeowner won't forget and misplace the tablets. Since KI tablets have an essentially unlimited shelf life, the job only has to be done once. Keeping them out of the medicine cabinet prevents them being thrown out accidentally when cleaning out the cabinet, and means that they won't get misplaced or damaged (transferred to a different drawer in the bathroom, moved to a first aid kit that gets left in the car or at the cottage, dropped in the sink and soaked, etc.). In homes with a basement, the fuse box is almost always located there rather than on the main floor of the house—if you've taken cover in your basement during a nuclear attack, you won't have to go upstairs to the bathroom – risking exposure to radiation and additional blasts – to find your KI tablets. TenOfAllTrades(talk) 16:44, 1 September 2008 (UTC)

Potassium iodide tablets are available from internet sources by mail order [5] , with no prescription needed. Just keep'em near your radiation monitor [6] and hope you never need them. Edison2 (talk) 18:03, 1 September 2008 (UTC)

Digital data over radio transmitter

Hello, can i KNow more about transmitting difital data using a Radio Transmitter? Thanks. Praveen Pkmchoudhari (talk) 02:02, 1 September 2008 (UTC)

Well, that's a big subject. Television is about to be transmitted digitally in the USA, we have digital cell phones, we have WiFi connections between computers in our homes, some radio controlled toys use digital commands, radio is used to send commands to the two NASA rovers driving around on Mars...where would you like us to start? Essentially, we have a radio wave that's oscillating at some frequency ("pitch") and at some amplitude ("volume") - you can send digital data (which is basically just a string of 1's and 0's) by changing the frequency a little bit for a '1' and not changing it when there is a '0' (which would be like an FM radio station sends analog audio) - or you can sent the radio wave at full strength for a '1' and turn it way down (or even, off altogether) for a '0' (like an AM radio station sends analog audio by varying the "amplitude" of the radio wave). Do this very rapidly and you can send quite a bit of data in a short time. But there are lots of much more complicated and subtle ways that this can be done.

Perhaps if you could be a bit more specific, we could help you out with a much more detailed explanation. SteveBaker (talk) 02:48, 1 September 2008 (UTC)

The article Packet Radio may help. It's all about trasnmitting digital data using a Ham Radio. APL (talk) 03:07, 1 September 2008 (UTC)

(I don't know about this but I gave your question a title so it's easier to find and neater looking. Sorry for this is minor inconvenience! 88.211.96.3 (talk) 08:42, 1 September 2008 (UTC) )

The magical blue smoke

You know when you get a bit of electronic equipment such as a CRT monitor or a TV, and it dies and sometimes you get pale blue smoke (which my Dad jokingly tells me is the magic blue smoke that makes the TV work). What is this smoke made of and what causes it? Also is there a way to tell what things would produce said mystic smoke when they die, and under what circumstances? 88.211.96.3 (talk) 08:45, 1 September 2008 (UTC)

Magic blue smoke. Yes, wiki has an article on everything. Dragons flight (talk) 09:06, 1 September 2008 (UTC)

applications of lagrangian dynamics

could you plz suggest a website where I can find problems and applications relating to the use of Euler-Lagrangian equations? I am still learning the elementary concepts in Lagrangian dynamics..so, plz see that the problems are not too complicated..thanx.. —Preceding unsigned comment added by 59.93.90.44 (talk) 08:59, 1 September 2008 (UTC)

thin layer chromatography

In TLC, I've always known of the Rf value as the retardation factor, but recently I've seen it referred to as "relative frontal mobility". Anyone else heard of this terminology? Is it correct/acceptable? --TomDæmon (talk) 09:31, 1 September 2008 (UTC)

A google search would suggest it used at least by some. Retention factor is also possible, of course. --Cameron* 11:09, 1 September 2008 (UTC)

MRI machine

Hi

I wanted to know about the cryogen used in MRI machine and can liquid helium be replaced by liquid nitrogen? —Preceding unsigned comment added by Hetal R Shah (talk • contribs) 09:35, 1 September 2008 (UTC)

This depends on the machine using high temperature superconductors. See MRI#Magnet: However, despite its cost, helium cooled superconducting magnets are the most common type found in MRI scanners today. --Ayacop (talk) 10:01, 1 September 2008 (UTC)

The liquid Helium flask will be surrounded by liquid Nitrogen to maintain the Helium at its very low temperature. Liquid Nitrogen is much much cheaper than liquid Helium and is thus periodically topped up preventing the need to replace the expensive liquid Helium. Jdrewitt (talk) 10:26, 1 September 2008 (UTC)

Additionally, no you cannot replace the Helium with Nitrogen because the superconducting coil must remain at a temperature below T_C, the critical temperature where the superconductivity characteristics occur. If the magnet was cooled by liquid Helium originally (i.e. down to less than 4.2 K) then T_C will be far too low for Nitrogen to achieve since Nitrogen freezes at 63 K. See Superconducting magnet. Jdrewitt (talk) 11:38, 1 September 2008 (UTC)

Comercial MRI use Niobium-tin with critical temperature 18.3 kelvins. So Liquid nitrogen with 77K is not sufficient. With other superconducting material maybe but with the stuff maketed now. NO!--Stone (talk) 21:10, 1 September 2008 (UTC)

How can we calculate the chemical energy of a body?

How can we calculate the chemical energy of a body? Can we do that by using the calorific value of it and simply multiplying it by the mass?Anirban Chatterje (talk) 09:38, 1 September 2008 (UTC)

Did you read the article on internal energy? --Ayacop (talk) 10:07, 1 September 2008 (UTC)

Yes, I did.But the thing is that,only the Equation U=3RT/2 can be received.But how can I apply this in case of chemical compounds?Anirban Chatterje (talk) 18:40, 1 September 2008 (UTC)

Mortality of acute pancreatitis

Why is the mortality of acute pacreatitis so high? What are the mortality rates? I am not asking medical advice. —Preceding unsigned comment added by 217.227.75.39 (talk) 10:56, 1 September 2008 (UTC)

The pancreas is a rather important organ, and you only have one of them. Is it really surprising that a major condition affecting it has a high mortality rate? Cardiac arrhythmias tend to be rather bad too Nil Einne (talk) 12:39, 1 September 2008 (UTC)

The pancreas is fragile, and pretty damn important. Pancreatic cancer is a particlarly devastating condition, where Wikipedia states that there is roughly a 5% 5-year survival. Although, my Oxford Handbook of Medicine states that carcinoma of the pancreas carries a less than 2% 5-year survival with a mean survival of 6 months. That said, a procedure called pancreaticoduodenectomy can increase the prognosis to 5-14% —Cyclonenim (talk · contribs · email) 15:08, 1 September 2008 (UTC)

The low survival rate for pancreatic cancer is because it doesn't have well-defined symptoms until the cancer has reached a very advanced stage. The survival rate for early-stage pancreatic cancer is similar to that of any other cancer. --Carnildo (talk) 22:41, 2 September 2008 (UTC)

One way to think about it is as a positive-feedback loop. The pancreas produces zymogens that are usually involved in digesting our food after being pumped through the pancreatic duct into the duodenum (and then activated there, where the lining of the intestine keeps them from harming the host). In pancreatitis, these enzymes become active in the pancreas proper, and begin digesting - a bit like a fire at a fuel refinery. With the proximity of major arteries and bacteria-filled intestines, this makes for a lethal combination. Scray (talk) 15:06, 1 September 2008 (UTC)

This article discusses the high incidence of multiorgan failure in acute pancreatitis. Axl (talk) 18:35, 4 September 2008 (UTC)

regarding physics olympiad

what is the syllabus for physics olynpiad —Preceding unsigned comment added by 122.167.99.51 (talk) 13:29, 1 September 2008 (UTC)

Assuming you're talking about the International Physics Olympiad, the syllabus is here. Algebraist 13:31, 1 September 2008 (UTC)

There are more "Physics Olympiads". I know of two universities that host events with that specific name. -- kainaw™ 13:35, 1 September 2008 (UTC)

evolution

What is the benefit to male big cat reproductive success of leaving the area and pack. —Preceding unsigned comment added by 194.70.73.98 (talk) 15:44, 1 September 2008 (UTC)

It varies from species to species - but what often happens is that young males are forced to leave the group - one older male remains. The benefit to the older male is obvious - he doesn't need help to impregnate multiple females - so less competition is good. The younger male is forced to leave or get into a fight with the leader which he'd surely lose due to smaller body size and inexperience. The young males go off by themselves for a while - those that survive may eventually return and kick out the old male after some kind of dominance battle. Evolutionary benefits are that weaker males don't get to spread their weak genetics to the next generation. Every animal born is a result of the best male genes available from the previous generation. SteveBaker (talk) 16:08, 1 September 2008 (UTC)

I've been told that lions are the only social cats, having organized groups. What other species have pack dynamics? --Allen (talk) 16:56, 1 September 2008 (UTC)

Define pack dynamics. I'd guess most Bovidae have a top dog and yes, many other mammals, too. --Ayacop (talk) 17:33, 1 September 2008 (UTC)

Sorry; I meant what other cat species. --Allen (talk) 19:38, 1 September 2008 (UTC)

As far as I know, you're right. Lions are the only cat that exhibit pack dynamics. ScienceApe (talk) 21:48, 1 September 2008 (UTC)

Hmm. See feral cat colony, for a counterexample. --Sean 22:26, 1 September 2008 (UTC)

One benefit is to avoid inbreeding. I guess it's especially effective when only one sex is moving. 93.132.132.172 (talk) 18:54, 1 September 2008 (UTC)

Carotid artery

What is the best technique for determining the amount of plaque inside the carotid artery? —Preceding unsigned comment added by 79.76.154.239 (talk) 22:21, 1 September 2008 (UTC)

The usual diagnostic test is carotid ultrasound, with the results reported as carotid plaque area. [7]. "Best" is a matter of opinion, of course. - Nunh-huh 22:27, 1 September 2008 (UTC)

A carotid angiogram might give you more information. CT and MRI's are starting to show promising diagnostic results with the advantage of not being very invasive. Ultrasounds tend to be less exact. OrangeMarlin ^{Talk• Contributions} 02:23, 2 September 2008 (UTC)

It rather depends on one's definition of 'best'. Using appropriate techniques, one can definitely get a very precise measurement (arguably better than ultrasound) using CT or (especially) MR methods. But a precise measurement isn't the only criterion. CT exposes the patient to (a fair bit of) ionizing radiation. Usually carotid occlusion is a problem in an older population, so cancer risk is low, but still worth considering. CT instrumentation is also relatively costly, and (with a few rare exceptions) non-portable. MR imaging equipment is extremely costly, entirely non-portable, and not suitable for patients with certain medical implants or prostheses. Ultrasound, on the other hand, is dirt cheap (compared to the other two, at least), portable, widely available, fast, and 'good enough' for most cases.

Of course, for the absolute most accurate measurement, you have to wait for the patient to die, then cut out the carotid artery and have a look. While this is by far the least expensive and most direct method, it has certain drawbacks. TenOfAllTrades(talk) 02:48, 2 September 2008 (UTC)

Back to the angiogram then, which balances risk to benefit. Of course, there would be other signs of vascular disease that would indicate the need for a carotid angiogram. OrangeMarlin ^{Talk• Contributions} 06:08, 2 September 2008 (UTC)

This question is in regard to galvanizing.

Presently I want to start a galvanizing company and during the research I was asking question about what materials is needed to galvanize a metal. Due to fact that businesses are scared of the competition they would not help me with all the information I was looking for.

I would like to know what is requite to melt a cutlery as in temp which should be applied and how would I be able to keep it into silver. More importantly which metal I should use while I’m still studying galvanizing?

My regards Christian —Preceding unsigned comment added by 41.208.48.160 (talk) 22:33, 1 September 2008 (UTC)

Have you looked at galvanization and its links? Ζρς ι'β' ^¡hábleme! 00:04, 2 September 2008 (UTC)

September 2

Solubility of Hydrocodone/Acetaminophen?

This question deals with possibly inappropriate use of controlled substances. Publishing an answer here would not be in the interests of Wikipedia or its readers. I have blanked this question, discussion here. Franamax (talk) 14:18, 2 September 2008 (UTC)

A similar question has been re-posted below, at Wikipedia:Reference desk/Science#Solvents_of_common_pharmaceuticals. -- Coneslayer (talk) 13:01, 3 September 2008 (UTC)

Word for a substance that makes you piss more?

Im pretty sure ive heard a word for substances that make you piss more, but i dont remember what it is. I believe caffeine is an example of such a substance. Anyone know what the word is? --212.120.246.239 (talk) 03:14, 2 September 2008 (UTC)

Diuretic. Dragons flight (talk) 03:17, 2 September 2008 (UTC)

Beer. (You don't buy it, you just rent it). Edison2 (talk) 02:52, 3 September 2008 (UTC)

Would they take it back after it has been uhh... utilised? --antilived^{T | C | G} 05:56, 3 September 2008 (UTC)

Yes. They then resell it as American "beer". DMacks (talk) 05:58, 3 September 2008 (UTC)

natural antibiotics?

I know there are several plants that are presumed to be "natural antibiotics", such as garlic. Is there any indication (journal articles) linking specific herbs with killing specific types of bacteria/viruses? Or it's all just "unproved naturopathy" Mathityahu (talk) 07:22, 2 September 2008 (UTC)

It's very much proven. Instead of pointing you to a specific reference regarding a specific compound (like diallyl disulfide, or better de:Diallyldisulfid Refs 29-35 in the case of garlic) where you should find in the Reference Section links to clinical studies and other papers, I will just mention that plants produce such chemicals because, not having an immune system, they need such stuff to fight the steady attack of microorganisms, see secondary metabolite (which is sadly inadequate). In fact, even your normal antiobiotic comes from other organisms that had to fight bacteria: penicillin is a product of a fungus, and why should there be a difference in the general evolution of plants/fungi, just as there is a plant defense against herbivory?

This does not mean you should abandon your doctor and treat yourself when you're ill. It also doesn't mean every plant antibiotic is suitable for human use, at all. Many fungal and bacterial antibiotics (yes bacteria against themselves) that were discovered have serious side effects, too. --Ayacop (talk) 10:12, 2 September 2008 (UTC)

Thanks for the links, very interesting. Are there any other "proven" herbs? Mathityahu (talk) 19:10, 2 September 2008 (UTC)

Not even one based on randomized-controlled trials. Scray (talk) 01:19, 3 September 2008 (UTC)

Depends on the compound. Myrtol (de:Myrtol) is a standardized terpene extract from Myrtis communis (a myrtle species), and well researched with sinusitis and bronchitis:

• H. Matthys et al.: Efficacy and tolerance of myrtol standardized in acute bronchitis - a multicentre, randomized, double-blind, placebo-controlled parallel group clinical trial vs. cefuroxime and ambroxol. Arneim.-Forsch./Drug Res. 50/-/2000 100-711.[Abstract auf Deutsch]
• R. Meister et al: Wirksamkeit und Verträglichkeit von Myrtol standardisiert bei der Langzeitbehandlung der chronischen Bronchitis - Eine placebokontrollierte Doppelblindstudie. Arzneim.-Forsch./Drug Res. 49/-/1999 S. 351-8 [Abstract]
• P. Federspil et al.: Wirkung von Myrtol standardisiert bei der Therapie der akuten Sinusitis - Ergebnisse einer doppelblinden randomisierten Multicenterstudie gegen Placebo. Laryngo-Rhino-Otol. 76/-/1997 S. 23-7. doi:10.1055/s-2007-997381

metabolic functions of proteins from human/mouse

I'm puzzled. Every major protein in the Wikipedia lists lots of functions in its infobox, and also most of the time, an analogous protein from animals, mostly from the mouse. Now, did they find out all those functions from looking at humans or at mice? Do we generally transfer results directly from mouse to human? Shouldn't mouse results labeled as such? Because if the mouse were such a good model, we wouldn't need clinical studies, would we? --Ayacop (talk) 10:27, 2 September 2008 (UTC)

Usually when you do genetic studies, you do them in a model organism, because it is exceedingly hard to get approval from an Institutional Review Board to do controlled crosses or make transgenics/knockouts with humans. Add to that the 10-20 year turn around for humans to reach sexual maturity, and such experiments on humans themselves become prohibitive. (Not to mention unethical.) To overcome these problems, researchers use model organisms. Mice and rats are usually used because they are mammals, easy to breed, have a (relatively) short life, and present less of an ethical/moral issue than, say, chimpanzees or dogs. For general information "protein X does Y", especially in a metabolic sense, the differences between mice and humans are vanishingly small. While we look vastly different, inside we're pretty darn close. In fact, a large amount of biochemical data has been first collected in yeast, flies or worms, and later been found to be applicable to humans. Now clinical studies are a different issue. When testing drugs small, seemingly innocuous changes, which may have no effect on the normal operation of the organism (such as single amino acid changes), can have a large effect on the efficacy of the drug. But note that there is usually a large body of model organism testing (usually on mice/rats) prior to the start of clinical trials - the in-human tests is to be doubly sure of the results. -- 128.104.112.147 (talk) 17:01, 2 September 2008 (UTC)

Much about real similarities/differences between mice and men is unknown, perhaps because such comparisons depend on difficult studies of rare humans that are homozygous for loss-of-function mutations. One recent example reveals a major difference between mice and humans: the TLR adapter protein MyD88 appears to be dispensible in humans for defense against viral infections and all but a few pyogenic bacterial infections. Scray (talk) 00:44, 3 September 2008 (UTC)

The history of the lab rat is actually pretty interesting. They were chosen originally because nobody cared about rats (in a fit of irony, someone had their house firebombed by zealous animal rights protesters not too long ago for doing research on lab rats), they have relatively short lifetimes (you can go through them pretty quick to see changes), they reproduce quickly, and because they were relatively easy to standardize (the Wistar rat was one of the first successful "branded" model organisms). These are qualities are are in general good for model organisms. Rats are particular useful for human-related research, as noted, because they are mammals along with all of the above reasons. There are, as noted, limitations, but it's a much better place to do a "first draft" of something than on other animals. --98.217.8.46 (talk) 02:21, 3 September 2008 (UTC)

Political parties and teenage pregnancies

How would I get information on whether, for the same socio-economic class, Democrats or Republicans had a larger proportion of teenage pregnancies? I'm wondering about the influence of differing views on topics such as sex education and abstinence-only beliefs.

Thanks! — Sam 12:03, 2 September 2008 (UTC)

The big problem here is that neither political alignment or teenage pregnancy status are statistics that are dependably tracked. The best you can hope for is a very small survey in a very small locality with a high rate of error. If you attempt to make a point using random statistics you find online, you will likely end up with a ridiculous point such as one I saw this past week... Rolla, MO has had a huge influx of frogs. In the last two years, more frog species are being discovered in Rolla than anywhere else in the world. Why are all the frogs suddenly being attracted to Rolla? ... That was taken from statistics showing a lot of frogs being identified in Rolla. Why? The local university started a class in biodiversity and one of the assignments is to locate and categorize frogs. So, in the last two years (since the class started), more frogs are being identified there than anywhere else. I hope that helps explain why you can't grab a statistic here and a statistic there and try to make some point about views on sex education. -- kainaw™ 12:16, 2 September 2008 (UTC)

Generic warnings aside, statisticians have developed many ways over the past, oh, 150 years or so to determine whether or not an effect is just due to bad data or whether it is real or not. The idea that the political ideology of the parents can have an effect on the rate of teenage pregnancy is not out of left field, given that political ideology and feelings about the running of a family have long been known to have been linked, and the issue of contraception is obviously key in that. A friend of mine who lived in a very rural, "red state" area reports that it was often the kids of hard-core fundamentalists who got knocked up in high school because they never learned about sex ed and were afraid to talk to their parents about it. That's an anecdote—and not statistically meaningful—but it does imply a mechanism; a hypothesis which could be tested. --98.217.8.46 (talk) 02:31, 3 September 2008 (UTC)

I don't know about Dems vs. Repubs, but there have been studies trying to determine whether sex-ed or abstinence-only is more effective at preventing teenage pregnancy. For example, this and this say that sex-ed is clearly superior at preventing teen pregnancy. (Incidentally, one of those reports notes that sex-ed also increases sexual activity, which of course some people view as unacceptable, even if that sex is safer.) Dragons flight (talk) 12:33, 2 September 2008 (UTC)

Here's a graph (of dubious origins, though the numerical data is legit) which seems to imply that states in which Republicans are in charge have higher teen pregnancy rates than states with Democrats in charge. That doesn't imply causation though—the same underlying reasons that put one party in charge could be behind the trend (e.g. poverty). So it doesn't mean much (other than indicating that the "Red states" hardly have any monopoly over "family values").

If it were me, I'd want to do a study looking at the politics of the parents (however measured—self-identified would be fine) of kids who get knocked up. I haven't been able to find anything like that, though. --98.217.8.46 (talk) 02:40, 3 September 2008 (UTC)

stripy babies

are lots of baby animals stripy? I know that tapirs have stripy babies to hide them in the dappled forest shade, but why would baby emus be stripy as they live on the plains? Bradley10 (talk) 12:42, 2 September 2008 (UTC)

Plains or not, stripes still help to camouflage an animal. The point isn't so much to "look like your surroundings," but instead to break up the shape of the animal. Likewise a tiger can be very well camouflaged in the jungle, even though that might be surprising to anyone who had seen his bright orange (not very jungle-y) skin. — Sam 13:41, 2 September 2008 (UTC) —Preceding unsigned comment added by 63.138.152.238 (talk)

Also, while it doesn't really apply in this case, zebras are also a plains animal that are very stripey.

Some zoologists believe that the stripes act as a camouflage mechanism. This is accomplished in several ways. First, the vertical striping helps the zebra hide in grass. While seeming absurd at first glance considering that grass is neither white nor black, it is supposed to be effective against the zebra's main predator, the lion, which is color blind. Theoretically a zebra standing still in tall grass may not be noticed at all by a lion. Additionally, since zebras are herd animals, the stripes may help to confuse predators - a number of zebras standing or moving close together may appear as one large animal, making it more difficult for the lion to pick out any single zebra to attack. A herd of zebras scattering to avoid a predator will also represent to that predator a confused mass of vertical stripes travelling in multiple directions making it difficult for the predator to track an individual visually as it separates from its herdmates, although biologists have never observed lions appearing confused by zebra stripes.

-- MacAddct  1984 ^{(talk • contribs)} 13:54, 2 September 2008 (UTC)

It's a popular misconception that camouflage is most effective by making an animal look like the surroundings. Instead most "blending in" is caused by disruption of the shape of the animal. The brain does most of the work of camouflage—if we don't see something that looks like an animal, we don't see it at all. --98.217.8.46 (talk) 23:26, 2 September 2008 (UTC)

• It's also a popular misconception that mammals other than humans do not perceive color. Lions do have color vision, but not as good as ours. However, the term "color-blind" is fair since it is also used for humans whose color vision is not as good as most. --Anon, 06:10 UTC, September 3, 2008.

Wartime camouflage of ships is an example of disrupting the outline. Through a submarine periscope it may be possible to know something is there, but whether it is two or more ships seen in an overlapping view, or ships following each other, or just one ship, may not be clear. This type of camouflage has been called "dazzle painting". Camouflage uniforms, I think, have an outline-disruption effect combined with a blend-in effect. This combined effect has also been used on military vehicles, artillery barrels, tank-gun barrels, and on small arms. Andme2 (talk) 01:39, 3 September 2008 (UTC)

Do the hurricanes have anything to do with global warming?

I've been wondering lately about these hurricanes and cyclones that we hear about all the time in recent years (Katrina, Cyclone Nargis in Burma, and now Gustav). Is there any science that points to these being somehow the result of global warming? It seems to me that they are worse than they used to be, but that might just be confirmation bias screwing with my head. Are they worse than they used to be? More frequent? (I guess the sample size is pretty small, even if they are more frequent it could just be a conincidence).

By the way, I don't have a political agenda here, I'm really just curious, and I haven't heard anyone explain it properly to me. 83.250.202.36 (talk) 14:54, 2 September 2008 (UTC)

I have no idea of the science but the articles Effects of global warming and this part in particular (Effects_of_global_warming#Effects_on_weather) consider the effect that global-warming has on 'extreme weather'. I suspect you will suffer a bit of bias - I think the term is something like time-memory bias or something silly ilke that (look for article list of biases) - essentially the recent past may seem larger/more important in your mind than the distant past, even if both events were of equal size. 194.221.133.226 (talk) 15:15, 2 September 2008 (UTC)

I'm no expert, but I think it's extremely tricky to try to point to a single cause of a hurricane. One thing we know- many of these storms feed on warmth- see Warm core. So, if there are higher air or water temperatures in the areas that have them, I think this will tend to lead to increased storm activity. It's all very complex and unpredictable though - a general trend of bigger storms doesn't mean any particular hurricane season will be bigger. Friday (talk) 15:20, 2 September 2008 (UTC)

Note in the warm core link above that warm water is only half of the story. You need high-level condensation - so you need cooler air on top. If the water is warmer and the air is warmer, it won't help much. If the water is warmer and the air is cooler, you get more power out of the warm core. As for hurricanes, the frequency and strength have not had any significant increase. Much more powerful storms existed in the past and they came in both greater and fewer numbers, varying from year to year. In the recent past (15-20 years), two big changes happened. First, we have a huge number of people moving to the southeast coast so the population of people expecting to be hit is increased. Second, we have multiple 24-hour weather news services letting us know every minor detail of every storm. Combined, we know a hell of a lot more about more storms that are doing more financial damage. -- kainaw™ 15:56, 2 September 2008 (UTC)

The articles mentioned above are all good sources of science, and are most neutral. Check out the top editors of the articles, and you might also post your question to their user talk pages, and they'll point you in the right direction. Always read the citations and/or sources for anything in any Wikipedia article, so that you can dig deeper in the topic. OrangeMarlin ^{Talk• Contributions} 16:18, 2 September 2008 (UTC)

I finally found a rather unbiased graph of the number of hurricanes per year. This one actually counts tropical storms, not just hurricanes. It shows the slight upwards trend in frequency that has been attributed by many sources as a normal cycle between high frequency and low frequency. It does not show the hockey-stick curve projected by alarmists. Also, you can see the most expensive hurricanes in List of costliest Atlantic hurricanes. Ensure you look at the lower table where costs are adjusted for inflation. -- kainaw™ 16:50, 2 September 2008 (UTC)

Um. I don't want to nitpick. But Institute for Creation Research is probably not who I would put my faith in (yuk yuk) for unbiased research. --98.217.8.46 (talk) 01:48, 3 September 2008 (UTC)

I believe that most researchers are claiming that the increase in the NUMBER of hurricanes is too small to be statistically relevent - but the increase in the ferocity of them is a clear trend. Sadly, I don't have a reference for that. (Er...it might be in "An Inconvenient Truth"...I'm not sure.) SteveBaker (talk) 04:03, 3 September 2008 (UTC)

I'm yet another person with unconfirmed uncited information. After Katrina I heard another chemist (not trained in atmospheric science) conjecture "More violent storms seem to be an expected result of global warming. Putting more energy into the system means there is more energy to knock around." She might be wrong maybe maybe global warming means more moisture in the air which will slow storms down but her reasoning rings true to my training and experiencec. But Kainaw also has a point with his "a tree makes no sound if no one is there to hear it" comment.--OMCV (talk) 04:13, 3 September 2008 (UTC)

While I don't agree with the ICR as being unbiased... I used that specific graph because it was unbiased. In fact, I found that it was particularly unbiased by including tropical storms - many of which went to hurricane strength in the past but by rule weren't counted as hurricanes if they died down before making it to shore. In modern times, if a storm becomes a hurricane in the middle of the Atlantic and then dies out, we count it as a hurricane. So, you will usually find graphs showing a particularly high increase in hurricanes due primarily to the method used to identify them as such - not because there are more of them. As for the ferocity of the hurricanes, I added the list of the worst hurricanes to show that the recent ones are not necessarily more violent than past ones. We just put more importance on recent ones. -- kainaw™ 23:50, 3 September 2008 (UTC)

(making this small because it is terribly off topic) And a point on a completely different topic... I am sure there are many who will read my comments and walk away thinking that I don't believe that global warming exists and, therefore, I am a strong supporter of GW and I love my guns and I go to church every day to gripe about how we should bomb all the brown people in the world. Just because I see evidence that the hurricanes are not necessarily occurring in greater numbers or evidence that they are not stronger does not have anything to do with my opinion on global warming - which I wish was not called global warming. It is a terrible problem that most people do not comprehend and, as a result, make rash ignorant decisions about. Just this morning, I was in the elevator and overheard a doctor (obviously educated) tell another doctor that he is looking for jobs in Michigan because global warming is going to flood out the entire coast soon and he doesn't want to live underwater. -- kainaw™ 23:55, 3 September 2008 (UTC)

This new study (doesn't seem to be on Nature's website yet) suggests that the frequency of strong hurricanes has increased in the last 25 years, while the frequency of weak hurricanes has remained fairly constant. Algebraist 00:02, 4 September 2008 (UTC)

That is not new news. There was a well documented lull in hurricanes during the 70's and 80's. So, if you look in the last 25 years, you'll see increase in hurricane activity. If you look at the last 100 years, the increase is there, but it isn't very significant. It is possible that we should still be in a lull but global warming took us out of it early. It is also possible that a 15-year lull was normal and we are returning to a normal level. It is possible that both are true. It is possible that neither are true. I am not claiming that global warming is not affecting hurricanes. I am only claiming that it is very easy to look at the number of storms over the last 100 years and the years in which the most powerful hurricanes occurred and you can see that it is hard to claim global warming took a few baby storms and turned them into dozens of killers. -- kainaw™ 00:29, 4 September 2008 (UTC)

Hurricane question

Is it possible for two hurricanes to collide or would they repel each other? Thanks, Alex--AlexSuricata (talk) 17:24, 2 September 2008 (UTC)

See Fujiwhara effect. They can get close and circle one another, but not truly collide or merge. -- kainaw™ 17:31, 2 September 2008 (UTC)

Of note -- our article claims that they will eventually merge if they don't separate. I've always heard it explained that one storm will weaken the other to the point that it goes away, leaving only the stronger of the two. So, it is up to you to decide if that means they collided and merged. -- kainaw™ 17:32, 2 September 2008 (UTC)

Great, thanks! --AlexSuricata (talk) 23:56, 2 September 2008 (UTC)

Blindness

Can people who have been blind from birth dream or picture things in their minds eye ? —Preceding unsigned comment added by 80.5.198.130 (talk) 18:38, 2 September 2008 (UTC)

I seem to recall that it depends on the cause of blindness. Many blind people can see things in their mind's eye because they have complete visual faculties in their brain but there's something wrong in how their eyes work. I'm not sure they experience it the same way that sighted people (or people who have seen at least once) do, but they are capable of thinking visually and having intuitive understanding of visual metaphors. I suspect they dream as well.

If they are blind because the visual faculty of their brain is seriously impaired, then I suspect not so much. But I don't remember.

This is from a Cognitive Science class I took maybe 6 or 7 years ago so it's not exactly the most reliable information, but I remember it being something that I found interesting at the time. --98.217.8.46 (talk) 01:46, 3 September 2008 (UTC)

Blindsight makes interesting reading in that regard. SteveBaker (talk) 03:51, 3 September 2008 (UTC)

Yeah blindsight is neato, but the opposite, Anton-Babinski syndrome is even weirder, especially in the context of the question.

To the OP: there's really no way to say. The fact is, if someone has been blind from birth, they would simply lack the vocabulary to articulate visual experiences if they had them. Moreover, any attempt to determine empirically (i.e. externally) if they're having visual experience would be meaningless. For instance, imagine an fMRI study was performed to see if V1 (a region of the brain that is believed to be necessary for conscience visual perception, largely due to research on blindsight) is active in congenitally blind individuals. Even if it was shown that this area is active, that doesn't mean they are experiencing visual percepts. The brain is a very plastic organ, and regions that go unused for their normal function are often appropriated by nearby regions. In other words, every brain is different, and people who are born with anatomical or perceptual abnormalities can be expected to have different cerebral organizations than the norm, making the kind of experiment I suggested difficult if not impossible to implement.

So the short version is even if congenitally blind folks have visual experiences, they don't know it because they don't know what visual experiences look like/are (literally), and we don't know it because we have no useful way of accessing their potential visual experience. You'd find the article Mary's room an interesting read. --Shaggorama (talk) 04:42, 3 September 2008 (UTC)

Air-water experiment

This is about a simple experiment which can be considered as a thought experiment or could actually be performed. (This is not a homework assignment, just a question I dreamt up.)

The experiment requires a closed container full of air at atmospheric pressure, and another container of hot water. The closed container has a gauge that measures the difference in pressure between the inside and the outside of the container.

The container is quickly opened and some water is "instantaneously" injected. The water displaces a volume of air equal to the volume of water. Then the container is quickly closed and shaken vigourously, bringing air and water to the same temperature. As the air is heated in the process, it expands increasing the pressure in the container.

Suppose the container volume is V, the initial air temperature is TA, the initial water temperature is TW, and the volume of water injected is VW.

TW is greater than TA, and VW is less than or equal to V.

If VW is zero, the pressure will NOT increase because no hot water is injected. If VW equals V, the pressure will NOT increase because all the air is displaced and none is left to expand.

The tentative conclusion is that somewhere between VW = 0 and VW = V there is a volume of water that will cause the maximum pressure rise.

What ratio of VW/V will give the largest pressure rise? Does this answer depend on the temperatures of the air and the water? Are there other factors that need to be known to work this out?

Wanderer57 (talk) 20:33, 2 September 2008 (UTC)

Water has pressure too, unfortunately for this experiment. Someguy1221 (talk) 20:53, 2 September 2008 (UTC)

Thanks. Unfortunately I'm not clear from this whether Someguy1221 is saying that the experiment makes no sense at all or that the answer is complicated by the hydraulic head of water inside the container (or none of the above). Please will someone give me a less cryptic answer? Wanderer57 (talk) 00:20, 3 September 2008 (UTC)

The water may contain dissolved oxygen and other gases. The shaking may release these gases, which will complicate the experiment. Everyone knows what happens when you open a can of Coke after it has been shaken. But unexpected factors are why an experiment has to be repeated many times, by many people, in many places, and with the same results, before confidence can be placed on the conclusions provided. Even then, "scientific facts" may eventually be shown wrong because the results were misinterpreted by many scientists, or hidden factors were not seen. Yesterday's truth may become today's falsehood. Andme2 (talk)01:10, 3 September 2008 (UTC)

You might want to look up stuff on thermodynamic cycles. To figure out your ideal ratio you are going to have to define most of the other unknowns, for example what is the temperature ratio you describe. In addition the ideal gas laws will not account for the fluids vapor pressure or the fluids ability to dissolve gases (henry's law) both of which are temperature dependent. Basically you need to define things until the only unknown is VW/V. Even then using all these formula just gives a ballpark answer. The best way to determine the ideal ratio would be empirically.--OMCV (talk) 01:30, 3 September 2008 (UTC)

I think Wanderer's question is interesting, so let's start with a theoretical question and then account for the two minor effects later. The theoretical question uses an ideal gas to replace the air, and it uses an "ideal liquid" to replace the water. The liquid is incompressible adn contains no disolves gasses, and the ideal gase does not disolve in the liquid. furthermore, the liquid's volume does not change with temperature. The liquid has a heat capacity of one BTU per pint per degree Farenheit across the entire relevant temperature range. -Arch dude (talk) 01:35, 3 September 2008 (UTC)

Arch dude I think all you need is the gases heat capacity and the temperature ratio (in Kelvin) and the question can be reduced to a complex algebra or simple calculus problem. It would probably be best to use SI units rather than BTU and pints since its easier to convert units. Along these same lines heat capacity and the slightly different specific heat are usually given in (energy)*(mass)^-1*(temp unit)^-1, mass rather than volume since volume is expected to change with temperature while mass does not. It also important to remember that the ideal gas law requires temps in Kelvin making the difference between room temp ~295 K and boiling water at 1 atm 373.15 K smaller then reporting it in other temp units.--OMCV (talk) 03:47, 3 September 2008 (UTC)

What was the point of rubbishing Arch dude's choice of units if you are not then going to actually give an answer in your chosen units? You only need to make conversion easier if you intend to actually convert something. SpinningSpark 22:16, 3 September 2008 (UTC)

I was expecting my units to be laughed at-- that was just a bit of humor, and I happen to knoe the BTU/pint relationshiop for water without looking it up. On sober(?) reflection, our "ideal fluid" must have zero vapor presure, and this one wuill propably not be a minor effect. However, I also do not think we need any math to answer the question. My reasoning is as follows: except for the special case of 0 gas, the pressure is independent of the amount of gas and depends only on the temperature. Since more gas causes more cooling of the overall system, the highest pressure will occur with the smallest amount of gas.I this small-but-nonzero amount of gas has a negligible cooling effect, so the pressure is affected solely by the difference between the original gas temperature andthe water temperature. -Arch dude (talk) 23:57, 4 September 2008 (UTC)

But won't the liquid still have a vapour pressure regardless of whether there is any air in the container? You could take a container already full of water VW=V and add heat by means of a blowtorch - it will eventually explode, won't it? If you slap a pressure gauge on it, the gauge will go up. Franamax (talk) 03:23, 3 September 2008 (UTC)

cellulose

How does cellulose contribute to the cell wall? —Preceding unsigned comment added by 76.18.248.143 (talk) 21:02, 2 September 2008 (UTC)

Have you read cell wall? Specifically, The composition section answers your question. Someguy1221 (talk) 21:13, 2 September 2008 (UTC)

Genes for Skin

Approximately how many genes make up the appearance/type of our human skin including the color? —Preceding unsigned comment added by 70.136.156.69 (talk) 21:39, 2 September 2008 (UTC)

More than a few. Check out Human skin color#Genetics of Skin Color Variation for info on a few of em. --Shaggorama (talk) 04:17, 3 September 2008 (UTC)

What kind of moth?!?!

I have searched but i cannot find what kind of moth, (if it even is a moth,) this is. I found in a public laundry room in Northwest Louisiana. If anyone knows it would awesome to know! Thanks ahead of time for any time taken to find out what kind it is. Nick910 (talk) 21:45, 2 September 2008 (UTC)

Looks like male Eacles imperialis to me. --Dr Dima (talk) 01:53, 3 September 2008 (UTC)

Thanks much Dr. Dima!.Nick910 (talk) 17:48, 4 September 2008 (UTC)

Poppy Seeds

I understand that opium can be extracted from poppy seeds. I was in the store today, saw a 60g container of poppy seeds, and couldn't help but wonder how much opium that could produce (though I'd imagine it's not very much at all). In light of a recent question, I'll be perfectly clear that I have no intention to refine opium, and my questions stems purely from curiosity. Thanks!--El aprendelenguas (talk) 22:37, 2 September 2008 (UTC)

According to this page [8], the alkaloid content of poppy seeds is about 50 parts per million, which cannot have any pharmaceutical effect. DuncanHill (talk) 22:41, 2 September 2008 (UTC)

So does that mean that out of 60g of poppy seeds you could hypothetically extract 3mg of alkaloids, of which about 360 micrograms of which would be morphine? Which would be an incredibly uneconomical way to go about producing opium. (I'm dubious it would work, anyway, since my understanding of opium production is that you need the entire unripe seed pod, and many of them, to produce even just a little bit of the stuff. I'm suspicious that the dried seeds alone could produce anything.) --98.217.8.46 (talk) 23:23, 2 September 2008 (UTC)

Man, where did I read about the guy who ended up in intensive care after he bought several pounds of poppy seeds, boiled them, mashed them up, then shot the mush into his arm with a large bore needle several times, under the mistaken assumption that poppy seeds = opium? It was reasonably recent too. --Kurt Shaped Box (talk) 23:29, 2 September 2008 (UTC)

That was one of our most senior adminstrators. He had a bad day. He's fine now, except for the swollen arm. ...... (that's a joke, eh. ;o) Wanderer57 (talk) 00:27, 3 September 2008 (UTC)

There are many species and subspecies of poppy. As DuncanHill has indicated, the species that provides opium is Papaver somniferum — opium is derived from the latex of this species. The latex is obtained by making slits in the seed pod; this allows the latex to ooze out for collection. Refer to Papaveraceae and Opium poppy in Wikipedia. Andme2 (talk) 00:46, 3 September 2008 (UTC)

I read an article once about a guy who was a baker at a prison, who bought pounds of poppy seeds per day and made a tea or some such extract from it and managed to scratch the opium itch. There was another story about a bus load of Army recruits most of whom failed the drug test when they arrived for basic training, and it turned out it was because they had the poppy seed sandwich, but I do not recall the outcome. Edison2 (talk) 01:31, 3 September 2008 (UTC)

Now that has reminded me of a similar story about athletics officials. They were being shewn some new dope-testing kit which they had bought for a major competition. As part of the demonstration, some of the officials were invited to provide a sample - which they then failed. They had had a continental breakfast, with poppy-seed rolls that day. DuncanHill (talk) 09:50, 3 September 2008 (UTC)

The problem with poppy seeds nowadays is that globalisation leads to other varieties than the low-content ones being used, and other harvesting methods used in a small number of imports. This has led german authorities in a study to propose limits for import of poppy seed, which is heavily used in eastern Germany/Europe for desserts (the poppy plant is the national flower of Republic of Poland BTW, presumably for culinary reasons). Ref: [9] --Ayacop (talk) 07:19, 4 September 2008 (UTC)

Just in case someone thinks this is an urban legend, see this: "snopes.com: Poppy Seed Drug Test Results". Retrieved 2008-09-04.. When I was in grad school, I had a friend who had access to the greenhouse for the university. He did an experiment to see what percentage of poppy seeds would germinate (they're supposed to be sterilized, I believe, to prevent this), and, as I recall, some small percentage (1 or 2%) would germinate. And of course, there's the pharmaceutical company in the midwest that owned farmland to grow poppies for extracting the alkaloids to be purified into morphines (this was before they learned to chemically synthesize it). The field is adjacent to the research headquarters of the company, and occasionally poppies will start to bloom, and they quickly eradicate it. OrangeMarlin ^{Talk• Contributions} 14:49, 4 September 2008 (UTC)

September 3

brown sugar

What is the chemical name of the drug commonly known as "brown sugar" —Preceding unsigned comment added by Dbeein (talk • contribs) 01:05, 3 September 2008 (UTC)

Brown sugar (disambiguation) says: A "street name" for heroin. See also a Google search on "brown sugar" heroin. PrimeHunter (talk) 01:24, 3 September 2008 (UTC)

Clarity of Glycerin soap

Since glycerin soap is simply homemade soap (without glycerin removed), why is it clear and not opaque? Do this have something to do with the alignment or molecular arrangement of the soap molecule with glycerin? Sjschen (talk) 01:13, 3 September 2008 (UTC)

just gossip here, but I thought the clear soaps were first cleaned using ethanol to make them look nice. Polypipe Wrangler (talk) 00:36, 4 September 2008 (UTC)

As I understood it was so that if you dropped it in water, it wouldn't end up being a hazard for you tripping on it because you could clearly see it. 66.216.163.92 (talk) 01:48, 5 September 2008 (UTC)

Separating a test tube mixture

I was given this problem a few days ago, and I was wondering if someone had any ideas on how to do this easily. This is the original question:

"You are given a test tube that contains the following mixture of substances

• sand
• salt
• sawdust
• iron filings
• benzoic acid

Salt and benzoic acid dissolve in water, while the sand, iron, and sawdust (which is

less dense than water) do not. However, benzoic acid does not dissolve until the

temperature of the water is above 50 degrees Celsius. Use this information to devise

a method to separate the mixture so you could return to me 5 vials each containing

one of the five pure substances in the mixture."

My first idea was to use a magnet to separate the iron filings from the mixture. Then you could add room temperature water to the mixture, and strain the contents so that you would be left with salt water that could be boiled and thus separating the salt from the water. But then I can't figure out a way to separate the sand, sawdust, and iron filings from the mixture. Any help would be greatly appreciated! Thanks in advance! - jesusfreak210 (talk) 03:32, 3 September 2008 (UTC)

You're right up until the final statement; you've already separated out iron filings. To separate sand and sawdust, take advantage of their differences in density. anonymous6494 04:05, 3 September 2008 (UTC)

Ok thanks, thats what I was thinking. And the iron filings thing was just a typo... sorry. Thanks again! - jesusfreak210 (talk) 04:14, 3 September 2008 (UTC)

There was an old puzzle of separating salt and pepper; you combed your hair with a plastic comb and the pepper is attracted by static electricity. I wonder if sawdust might be attracted in the same way.--TrogWoolley (talk) 22:10, 3 September 2008 (UTC)

So you add hot water. Then:

• Sawdust floats - none of the others do - so you can skim them off.
• Iron filings are magnetic - so you can stick a magnet into the test tube and pull them out.
• Sand sinks to the bottom - and isn't magnetic - so you can pour off the rest of the liquid and recover the sand.
• Benzoic acid and salt both dissolve.
  • Benzoic acid is only soluable in hot water - so cool the mixture and the benzoic acid comes out of solution and can be filtered out with filterpaper.
  • The Salt can then be recovered by boiling the water until there is none left.

Of course, in reality, you'll have somewhat salty sawdust, iron filings and sand - but you can repeat the process as many times as necessary to progressively dilute the salt to whatever degree of purity you need. SteveBaker (talk) 22:21, 3 September 2008 (UTC)

Steve, I understand your answer was well intentioned, but please try to avoid the urge to outright do students' homework for them. --68.166.144.211 (talk) 15:39, 4 September 2008 (UTC)

Blindness disease

Blindness (novel) and the related Blindness (film) present a plot premised on an epidemic of blindness triggered by some unspecified infectious agent.

I realize that in the real world there are no diseases that causes blindness to spread like the flu. However, I am wondering if there are any communicable diseases at all where blindness is a major symptom. Some form of bacterial agent that affects the eyes perhaps? Thanks indulging my idle curiousity. Dragons flight (talk) 05:02, 3 September 2008 (UTC)

Syphilis and onchocerciasis come immediately to mind. In susceptible hosts (e.g. AIDS but also in others), there are many, including cytomegalovirus, varicella zoster virus, herpes simplex virus, and Pneumocystis jirovecii. It's actually a pretty long list. Scray (talk) 05:06, 3 September 2008 (UTC)

Probably should clarify that only tertiary syphillis and neurosyphillis present with visual problems. You would not experience this symptom with primary syphillis, by far the most common in industrialised nations, since we almost always catch syphillis in it's primary stages before it progresses to secondary, tertiary or neurosyphillis. Tertiary syphillis and neurosyphillis are more common in immunocompromised persons, such as those suffering from AIDS. —Cyclonenim (talk · contribs · email) 10:34, 3 September 2008 (UTC)

Fair enough, but I'm in a U.S. city and I've seen 2 people with sight-impairing ocular syphilis just in the past 6 months. One of them did have HIV (not AIDS), but the other did not and the point is that it's still happening. Scray (talk) 11:21, 3 September 2008 (UTC)

What about viral conjunctivitis? It spreads fast and when people who haven't been exposed to it to get it they often cannot open their eyes with swelling. In West Africa where I used to live it was called "Apollo's sickness" because there was a huge rapid epidemic of it after the return of the moon shuttle. Not permanent but very fast like flu and up to a week of practically no sight.--BozMo talk 15:21, 3 September 2008 (UTC)

At the bottom of the onchocerciasis article, there's a template which can be expanded to reveal all kinds of eye diseases. Notably Trachoma, a bacterial infection which spreads between people and has claimed the sight of 8 million people worldwide. EverGreg (talk) 18:56, 3 September 2008 (UTC)

Solvents of common pharmaceuticals

Removed by original questioner who was fed up with the obstructionist antics, assumptions of bad faith, trolling and general lack of good will of certain editors who really should know better. DuncanHill (talk) 22:58, 3 September 2008 (UTC)

(edit conflict) Yeah, we are now officially less helpful than Yahoo! Answers. (HTH, the technique given involves solvents the OOP said he tried, but maybe the technique is at issue.) -- Coneslayer (talk) 22:58, 3 September 2008 (UTC)

Long-term monogamy in mammals

Which mammals (one example I know is Peromyscus polionotus) show long-term monogamy? Otolemur crassicaudatus (talk) 11:27, 3 September 2008 (UTC)

Swans, parrots, red wolves and humans are a few well known ones. I can't find a full list, but true monogamy is very rare, at least according to this. JessicaThunderbolt 12:00, 3 September 2008 (UTC)

Swans and parrots are mammals now? DuncanHill (talk) 12:19, 3 September 2008 (UTC)

I need my head examined! Thanks for correcting me. JessicaThunderbolt 12:28, 3 September 2008 (UTC)

Physics

Hi, why is physics different than other natural science (studies)? Thank you. —Preceding unsigned comment added by Atacamadesert12 (talk • contribs) 15:33, 3 September 2008 (UTC)

Read physics and natural science and you'll find many answers to your question. -- kainaw™ 16:27, 3 September 2008 (UTC)

I'm not sure exactly what your question is about, but physics, as a natural science, has the distinction of dealing with the most fundamental of abstractions. Other scientific disciplines deal with more complex systems at various higher levels of abstraction. --72.94.50.58 (talk) 00:45, 4 September 2008 (UTC)

Wikipedia:Unidentified flowers

Please identify the flowers at Wikipedia:Unidentified flowers and delete the page once completed. Thanks. Suntag (talk) 16:53, 3 September 2008 (UTC)

No, thanks. — OtherDave (talk) 17:39, 3 September 2008 (UTC)

Maybe you've mistaken us for the Bounty board? JessicaThunderbolt 17:45, 3 September 2008 (UTC)

How much do you want? 93.132.165.7 (talk) 18:31, 4 September 2008 (UTC)

Don't mind the other replies—I personally think this is a perfectly legitimate request for the Ref Desk. We wouldn't be jabbing at Suntag if he had posted the pics on this page and asked us to ID them, would we? If anyone knows of good resources for the identification of flowers (or other plants, for that matter) post 'em here; I'd find it useful information.

For reference, there are half a dozen images of flowers, snapped in Belize. Good hunting! TenOfAllTrades(talk) 19:41, 3 September 2008 (UTC)

I don't. Would you give such a command to a real-life reference desk librarian? --Sean 14:50, 4 September 2008 (UTC)

"A command"? Which command is that? Axl (talk) 19:01, 4 September 2008 (UTC)

Would you ask a "real-life reference desk librarian" about Higgs bosons, evolution or other such things? —Cyclonenim (talk · contribs · email) 20:43, 4 September 2008 (UTC)

That's not a command: that's a question. Axl (talk) 21:13, 4 September 2008 (UTC)

Okay. Would you askdemand that a librarian should define the word entropy? The point stands, we are not librarians. We are a group of people interested in different subjects. —Cyclonenim (talk · contribs · email) 23:26, 4 September 2008 (UTC)

What is the problem? An editor asked politely for people to identify some flowers. He said please and thank you. He didn't clutter up this page with a large gallery, but thoughtfully made a separate page for them. DuncanHill (talk) 23:31, 4 September 2008 (UTC)

"Would you askdemand that a librarian should define the word entropy?"

— Cyclonenim

Would I? I would neither ask nor demand that (as you well know). I already have an idea what entropy is (but would need to look up a formal definition). I know how to find out answers to these "definition" questions without asking for help. However not everyone has these skills, notably newbies (to Wikipedia) and younger people. It is ironic that this area is called "Reference desk". The introduction states "The Wikipedia reference desk works like a library reference desk." The librarians' work at reference desks is mainly to find books and articles, to induct new members, and answer questions about borrowing items from the library. Wikipedia's reference desk isn't a desk. It is viewed by dozens of users who answer questions, often highly specialist (e.g. Higgs bosons). Axl (talk) 07:39, 5 September 2008 (UTC)

I SEVERELY ORDER YOU ALL TO REMOVE INSTANTLY AND WITHOUT THINKING ANY QUESTIONS THAT COULD BY, IN EVEN THE MOST HYPOTHETICAL ASPECT, BE CONSIDERED AS SEEKING FOR MEDICAL, LEGAL OR PROFESSIONAL ADVICE. I FURTHER COMMAND THAT YOU CHECK ANY ANSWERS OF YOURS AS WELL AS OF ANY OTHER PEOPLE AGAINST ALL LAWS OF EVERY EXISTING GOVERNMENT. Hope that helps. And, yea, remove that, too. 93.132.165.7 (talk) 18:31, 4 September 2008 (UTC)

Monogamy and Evolution

From what I understand (which is admittedly very little) about the evolution of our species, monogamy/pair bonding seems to be viewed as a helpful mechanism for protecting the weaker infant and mother and ensuring the replication of our genes. If this is true, I would think that the seperation of parents would be highly unusual, but this is not the case, especially in Western cultures. So why are parents so ready and able to deviate from the course seemingly plotted by our genes? Thanks in advance! 90.192.223.228 (talk) 19:29, 3 September 2008 (UTC)

The basic answer is that monogamy is evolutionarily advantageous to a parent only if it increases their inclusive fitness, which generally equates to the expected number of offspring successfully raised. (The "generally" is there because this simple definition does not take into account the fact that healthier/richer/etc. offspring may themselves have a higher chance of successfully passing on their genes.) Also, monogamy is typically only practical if it is in the interests of both parents — for most species, there's little one parent can do if the other parent decides to just up and leave. Typically, the parent more inclined to leave is the male, since their initial investment in the offspring in lower and the potential gain from seeking more mates higher; thus, monogamy is usually only stable if the improvement in the survival odds of offspring with both parents around to raise them is significant enough to compensate for the reduction in further reproductive opportunities the male must give up to take care of his earlier offspring. This is not quite true, since, if there is some way (e.g. elaborate and costly courtship rituals) for the female to try to predict the "fidelity" of males, they may prefer those males that are more likely to stay around and thereby stabilize monogamy even in the presence of incentives for males to cheat, but it's still a pretty good first approximation.

Even then, the choice between staying monogamous or looking for other mates is in reality not always an either-or decision, and there are strong evolutionary incentives for both parents to try to get "something for nothing" if they can get away with it. For males, this may mean trying to mate with other females even while only looking after one's "primary" family: though the gain may be uncertain, this costs little for the male. For females, it may involve trying to mate with a seemingly fitter, but already paired, male (and thereby hopefully gain better genes for one's offspring) while trying to convince another male to raise said offspring as his own. The end result of all this is a complicated game of cheating and counter-cheating strategies, for which strict monogamy and polygamy are simply two extremes along a wide and complex spectrum.

Incidentally, if anyone thinks I've been basing the above paragraphs on observations of human behavior, that isn't really the case: all this evolutionary complexity is much more clearly observable for example among various nominally monogamous bird species. Indeed, the fact that such simplistic reasoning, based on studies of species with a simple social structure, coincides so well with observed behavior even among such a complex social species as humans is quite surprising. Indeed, it's true that human behavior is in many ways yet more diverse, in large part thanks to our capacity for cultural evolution and for forming complex societies with ties extending beyond the pair level. Nonetheless, that fact that, even among species with simpler, more deterministic social behavior, evolution generally does not favor strict monogamy should at least suggest the unlikelihood of such inescapable genetic imperatives in a species as complex as ours. —Ilmari Karonen (talk) 21:04, 3 September 2008 (UTC)

Insect Identification

I recently found this insect and haven't the slightest idea what it is. It's about two inches long, holds its wings like a damselfly when at rest, and was found in Colorado. Photos one and two of it. Thanks in advance. PetrusCuniculus (talk) 20:07, 3 September 2008 (UTC)

It looks like some species of Dragonfly...but I'm no expert. SteveBaker (talk) 03:39, 4 September 2008 (UTC)

Looks like an antlion. Matt Deres (talk) 17:41, 4 September 2008 (UTC)

It's definitely an antlion. Thank you! —Preceding unsigned comment added by PetrusCuniculus (talk • contribs) 19:17, 4 September 2008 (UTC)

Wifi - any dangers?

Hello wikipedia,

I have no idea if i'm opening up a can of worms here but, here goes. Is there a health risk associated with having your wireless router in your bedroom? I can't find a discussion of the health risks on wikipedia but surely people like the Daily Mail must have ran stories?

Thanks, 82.22.4.63 (talk) 19:47, 3 September 2008 (UTC)

From the discussions I was able to find from a google search, not likely. Maybe if you tape the router to your head and walk around with it 24/7, but besides that? No. Paragon¹²³²¹ 19:54, 3 September 2008 (UTC)

(ec) Depending on the exact position of the router in your bedroom, your significant other may complain about it and demand that you put it somewhere else. Whether this constitutes a health risk is debatable (and may depend on the circumstances), but I do seem to recall some studies suggesting that people with healthy sex lives tend to live longer on average.

Also, if you're thinking of installing the router in your bedroom in order to use a laptop in bed, it's likely that disturbances to your circadian rhythm due to excessive late-night computer use, not to mention the possible ergonomic problems from bad posture etc., may indeed have both acute and chronic health effects.

Finally, please remember that the Reference Desk may not offer any actual medical advice. The standard Wikipedia medical disclaimer also applies. —Ilmari Karonen (talk) 20:01, 3 September 2008 (UTC)

See Wireless electronic devices and health. JessicaThunderbolt 20:05, 3 September 2008 (UTC)

Your significant other may hit you for spending too much time on Wikipedia in the bedroom. Clarityfiend (talk) 02:04, 4 September 2008 (UTC)

It seems very unlikely that WiFi would be a problem. Compare to a cellphone: A cellphone has to push it's signal a mile or more - often through walls - and you hold the antenna less than an inch from your body. WiFi only goes a few hundred feet, it doesn't work well through walls - and you rarely get within a few feet of it. Because the amount of radio energy you might absorb decreases as the square of the range - merely being 100 times further from your WiFi antenna than you are from your cellphone antenna means that the power you'll absorb is 10,000 times less. Since MANY studies of cellphones have failed to produce a conclusive link between cellphone use and general health - we can assume that the risk from WiFi is vastly less than the amount needed to produce any kind of health issue. SteveBaker (talk) 03:24, 4 September 2008 (UTC)

Looking for references about cats

Hello, I just read a couple of facts about cats and I would like to check if they are really true. I would be very pleased if you could confirm or refute these facts, and provide weblinks where I can read more about it.

These facts are:

• a) old age in cats is not gradual like in humans; it appears suddenly, and lasts approx. 1 year before the animal dies.
• b) domestic cats are not very wary when crossing roads. they seldom look around when they are about to cross, and therefore get run over relatively often.

Thanks to anyone who can help. Leptictidium (mt) 20:39, 3 September 2008 (UTC)

I can testify from experience that my cat is very cautious when crossing roads — they are, after all, open areas often populated by big noisy things. If there's any sign of traffic — whether vehicular or pedestrian — on the road, he'll prefer to wait in a suitable hiding place until the way is clear, and when he does decides it's safe to cross, he'll do it quickly. However, I doubt he has a particularly good understanding of how cars actually behave, and thus sometimes his decisions on when it would be best to stay and when to cross may seems, if not unwise, then at least quite surprising from a human viewpoint.

Indeed, I suspect a particular risk is that, for cats, avoiding danger normally means avoiding being seen. Thus, a cat crossing a road will stay hidden in the bushes until he thinks the way is clear, and then dash across. Should the cat misjudge, this gives a human driver very little chance to react and avoid a collision. —Ilmari Karonen (talk) 21:13, 3 September 2008 (UTC)

It varies with the cat, in the second instance. Some cats are very good about roads. Some are not. I've no idea what accounts for the difference. --98.217.8.46 (talk) 21:44, 3 September 2008 (UTC)

BTW I've read Elizabeth Marshall Thomas say that her dog used to listen for cars instead of looking for them; it had no problem crossing the street whenever it was safe. --Kjoonlee 05:23, 5 September 2008 (UTC)

Statistically, the lifespan of a cat kept indoors is 12 to 14 years, while that of a cat allowed outdoors is about four years. [10], [11]. A goodly amount of that difference is due to automobiles. You can read more by Googling for "cat lifespan indoors outdoors". - Nunh-huh 05:33, 5 September 2008 (UTC)

Cystic fibrosis

The article on Cystic fibrosis says: "The CFTR gene is found at the q31.2 locus of chromosome 7, is 230,000 base pairs long, and creates a protein that is 1,480 amino acids long. The most common mutation, ΔF508 is a deletion (Δ) of three nucleotides that results in a loss of the amino acid phenylalanine (F) at the 508th (508) position on the protein. This mutation accounts for two-thirds of CF cases worldwide and 90 percent of cases in the United States; however, there are over 1,400 other mutations that can produce CF.[32]"

My question: do these 1,400 mutations also occur on alleles in the CFTR gene, or do these mutations occur on other genes? If the latter is true, is each mutation also a three-nucleotide deletion? Thanks, Nishkid64 _{(Make articles, not wikidrama)} 21:33, 3 September 2008 (UTC)

All known CF-causing mutations, if I'm not mistaken, are mutations of CFTR. The mutations vary widely in their change and effect, many are insertions of a stop codon, but there's plenty of missense mutations and frame-shift mutations, too. [12] — Scientizzle 22:26, 3 September 2008 (UTC)

This database shows the variety, also including promoter and splicing mutations. — Scientizzle 22:29, 3 September 2008 (UTC)

Another source for references to papers on CF inheritance is the Online Mendelian Inheritance in Man page on cystic fibrosis or on CFTR proper. - Nunh-huh 06:35, 5 September 2008 (UTC)

Invisibility Cloak

This article says that a major flaw in invisibility cloaks is that if you were inside one, the world would be invisible to you. Since objects behind an invisibility cloak are perceived as transparent (hence, invisible), what would it look like if the entire world and universe were transparent? This does not make sense to me. I'm sure you would see something, even if it is just your own reflection. Any ideas?--ChokinBako (talk) 23:05, 3 September 2008 (UTC)

If I understand the article you've linked correctly, from inside you will see the cloak as a black barrier. Algebraist 23:16, 3 September 2008 (UTC)

More accurately, you wouldn't see anything, since it would be dark inside the cloak. This is true by definition, since an invisibility cloak cannot let any light in from the outside without being at least partially visible. I'm not sure offhand what would happen if you had your own light source (e.g. a lamp) inside the cloak: presumably either the light would leak out (thus betraying your location, but still not helping you to see), or, more likely, it would be reflected back from the cloak (possibly in funny ways, since we're talking about some seriously weird optics here). —Ilmari Karonen (talk) 23:31, 3 September 2008 (UTC)

Actually, you could of course make the cloak look like any ordinary (opaque) material from the inside, by the simple expediency of lining the inside of the cloak with said material. —Ilmari Karonen (talk) 23:34, 3 September 2008 (UTC)

You could have a couple of tiny pin pricks for eye holes. Since they could be really close to your eyes, you could see quite well and they would be very difficult for anyone outside to notice. --Tango (talk) 23:39, 3 September 2008 (UTC)

An interesting question would be what happens to light that would've passed through the eyeholes. Obviously, light that hits the eyeholes directly simply goes through the hole and gets absorbed by your eyes, so the holes should appear (mostly) black from the front. But what about the light that would've come out of the cloak through the eyeholes? In general (handwaving away all those pesky details about actual construction of physical invisibility cloaks) I see two possibilities here: it gets either absorbed or retroreflected. The former simply makes the eyeholes appear black from the other side as well. The latter, however, might be more interesting if you were, say, thinking of writing a science fiction story with such devices in it, since it would imply, among other things, that if you were wearing an invisibility cloak in the dark and someone shone a light at the back of your head, your eyeholes would act as retroreflectors. Oopsie... —Ilmari Karonen (talk) 00:56, 4 September 2008 (UTC)

Presumably it would be absorbed, I can't see any reason for it to be reflected, nothing has happened to the other side of the cloak. --Tango (talk) 02:42, 4 September 2008 (UTC)

What silliness. Obviously any reasonable invisibility cloak will magically duplicate each photon that reaches it. That way one photon can be passed to the inside to allow the wearer to see and another can be sent out the back so as to make the wearer appear invisible. Dragons flight (talk) 00:37, 4 September 2008 (UTC)

Yes - and it is very hard to duplicate photons without magic. There is no way that they could have light sensing material in the cloak that could feed video to an interior screen. Cameras and monitors? Truly magic. -- kainaw™ 00:51, 4 September 2008 (UTC)

Without magic it is very hard to remain invisible if your cloak is made of "light sensing material". APL (talk) 01:13, 4 September 2008 (UTC)

Current invisibility cloak research uses fiberoptics to bend light around an object and send the light on its way on the opposite side of the object. If only one out of every million or so photons was detected, it would not destroy the "invisibility" of the cloak. -- kainaw™ 01:16, 4 September 2008 (UTC)

I think we're all missing something. In "real" invisibility research, you aren't expected to be invisible when viewed from every possible direction. The main requirement is for camoflage - and in that case, you probably know roughly where the enemy is coming from - so light coming from behind you has to be absorbed and regenerated at your front - or routed around you or something - but light coming from in front of you could pass through the "cloak" and allow you to see normally.

It would be really tough to make a "cloak" that would make you invisible from every direction because whatever devices are routing light from behind to your front would be blocking some of the light coming from the front toward your rear. When you also consider that light coming from (say) 20 degrees to the right - also has to be detected by sensors that overlay the emitters for front/back transmission - and you rapidly realise that true 360 degree invisibility is very hard to imagine indeed. SteveBaker (talk) 03:33, 4 September 2008 (UTC)

Actually, real invisibility research (no quotes required) does involve being invisible from all directions, as I understand it. See [13]. --Tango (talk) 06:07, 4 September 2008 (UTC)

In a futuristic sci-fi cop story some years ago, cops on a stake-out routinely sat in a car in which each window was a video display of what a camera diametrically opposite saw, so that the cops sitting in the car were practically invisible. But the same camera pointing East could display on the inside of the East window an image for the cops inside to watch. This would clearly yield some parallax artifacts if someone was walking by the car, but might be less obvious than being able to see 2 guys sitting in a car eating donuts and drinking coffee all day. An "invisibility cloak" does not have to be perfect to be better than just standing there in broad daylight. Edison (talk) 04:39, 4 September 2008 (UTC)

The bigger problem is that that only works if you look at the window from directly in front of it. If you look from the side, you'll see something completely wrong. Far better just to have tinted windows. --Tango (talk) 04:52, 4 September 2008 (UTC)

Not so new apparently [14] —Preceding unsigned comment added by TrapdoorTrevor (talk • contribs) 13:47, 4 September 2008 (UTC)

September 4

Zoom H2 Handy Recorder

Sometime ago I saw a link (may have been on a blog) to a page on the audio chips used in the Zoom H2 Handy Recorder. I cant find it now, can anyone help.

Going through walls

Someone told me this once: "Say you had your on a wall. Eventually your atoms will line-up perfectly that your hand will actually go through the wall. But the changes of that happening is so small, it would take millions of years. But even after that it probably wouldn't happen."

Is this true? Is there anything on Wikipedia on this? I think it was from a book or something -- Coasttocoast (talk) 01:36, 4 September 2008 (UTC)

This is the sort of thing someone who is into quantum mysticism would say. Scientifically its crude. Your description is close but even if you described it perfectly its a misapplication of quantum mechanics. The capacity of electrons and protons to quantum tunnel is important to biology and life. It really happens. Atoms (other then hydrogen) are generally too heavy to tunnel in a meaningful way. The larger molecules formed by atoms certainly don't tunnel past each other. Chemical reactions would occur well before any tunneling happened. The person that is made of molecules won't tunnel ever. At least not without the assistance of technology that has yet to be invented or meaningfully imagined. Hope that helps.--OMCV (talk) 02:08, 4 September 2008 (UTC)

That depends on your definition of "in a meaningful way". The diffusion of molecules through solids is in many ways a tunneling process (though there are more factors involved than the tunneling of a single electron). We know from ice cores that something as large as methane will move 10s of centimeters per 100,000 years in ice. Dragons flight (talk) 19:40, 5 September 2008 (UTC)

Roughly speaking, I believe that is true, but it's not millions of years, it's far far more than that. I don't know how to calculate it, but I imagine it's far far longer than the universe will exist (in a state comparable to how it is now, anyway). --Tango (talk) 02:17, 4 September 2008 (UTC)

From what I recall, Brian Greene discusses this in his documentary The Elegant Universe. - 202.168.20.29 (talk) 03:11, 4 September 2008 (UTC)

Gee, Mr. Wizard, I've noted cases where helium or hydrogen passed right through a rubber balloon. Ya fill the balloon, tie it off, and it goes limp in a day. What is the process in those cases? Edison (talk) 04:31, 4 September 2008 (UTC)

That's caused by the rubber being slightly porous, ie. there are lots of tiny holes in it. Helium atoms are very small, so can fit through those holes far easier than the nitrogen and oxygen molecules in air could get out of a regular balloon, which is why helium (not hydrogen unless you were in doing a lab experiment or something - people are not in the habit of button explosive gasses in children's toys!) balloons deflate faster than air ones (you often get them made of foil to stop that). --Tango (talk)

I have had hydrogen in balloons, (yes, lab experiment) and it seems to pass through the rubber faster than helium does. Edison (talk) 18:38, 4 September 2008 (UTC)

H₂ has a molecular mass of 2 grams/mol while He has an atomic mass of 4 grams/mol. Check Kinetic theory#RMS speeds of molecules. Since hydrogen moves faster it collides with the walls more often Kinetic theory#Number of collisions with wall also finding the gaps more often. This principle is the bases of effusion experiments described by Graham's law that are sometimes preformed in pchem classes.--OMCV (talk) 19:16, 4 September 2008 (UTC)

Penis errect in the morning.

Why penis sometime errect in the early morning203.116.34.194 (talk) 05:00, 4 September 2008 (UTC)

See Nocturnal penile tumescence. Kenjibeast (talk) 05:11, 4 September 2008 (UTC)

Drinking water from a bottle of Clorox

Alright, I'm not going to go into why, but I just want to know if there's any way of making an empty bottle of clorox safe to drink water out of. Would a really thorough wash do, or would there still be some sort of nasty residue? Kenjibeast (talk) 05:09, 4 September 2008 (UTC)

Multiple rinses should do the trick. Its the chemical equivalent of washing a nalgene bottle with bleach. In fact bleach bottles used to be choice container for hauling water while climbing El Cap. furthermore adding a small amount of bleach or iodine to stream water is a method killing many of the microbes that might be living in the stream that you don't want living in your GI track. Chances are you will never get the flavor all the way out but you bottles of water will be less likely to grow bacteria. Good luck.--OMCV (talk) 05:45, 4 September 2008 (UTC)

One recommended method of disinfecting water is to add a small amount of household bleach. For details, you might look at the website of the Environmental Protection Agency of the USA.

http://www.epa.gov/ogwdw000/faq/emerg.html

Based on the advice on this website , it seems that an empty bleach bottle, without any further cleaning, is a safe container in which to store drinking water.

(Scented bleach is not recommended.)

Wanderer57 (talk) 05:40, 4 September 2008 (UTC)

I dunno. There are so many other plastic containers out there, I can't imagine why you would be so dead set on a clorox container to bargain with your health. The EPA website is talking about an EMERGENCY, a situation in which the risk of ingesting harmful parasites and bacteria from your water outweighs the dangers of a mild dose of bleach. Also, given that the container is designed to hold bleach and not potable water, the plastic itself might not be optimal (if you're not a fan of BPA anyway). For general drinking purposes, I'd say just find a different container. --Shaggorama (talk) 05:56, 4 September 2008 (UTC)

Allow me to explain myself. It's for a piece of transgressive/postmodern performance art, the legality of which I will have to do some more looking into. However, the main two concerns I know for sure are 1. This act must be safe. as well as 2. A prop is unacceptable, only a legitimate bottle of clorox or similar bleach will suffice. —Preceding unsigned comment added by Kenjibeast (talk • contribs) 06:44, 4 September 2008 (UTC)

How about putting a small amount of water into a clear plastic bag of about the same size as the container, using the weight of that water to slip the bag through the mouth of the container, then filling the bag partway, and anchoring it around the mouth of the container with a rubber band or glue or something? Then, you could drink from it without having the water touch the container? 10:44, 4 September 2008 (UTC) —Preceding unsigned comment added by Scray (talk • contribs)

I think a lot of this is bordering on and surpassing medical advice. We're telling you something is safe based on highly suspicious reasoning about analogs. We're making assumptions about the plastic that bleach bottles are made out of and about the concentrations of bleach. I would seriously take all answers above with some heavy grains of salt. These people are not qualified to make this sort of judgment and their reasoning is extremely dubious. --98.217.8.46 (talk) 12:44, 4 September 2008 (UTC)

Providing the bottle has been thoroughly cleaned and rinsed (just as you would clean and rinse any container used for drinking water) there will be no problem at all. You will need a way of ensuring that only the correct bottle is used in the performance, as a mix-up could have undesirable effects. DuncanHill (talk) 12:49, 4 September 2008 (UTC)

Bleach containers were not designed for holding drinkable beverages. Without checking exactly what the plastic is I'm not sure we can say it's the same as "any contained used for drinking water." I know that in the cases of other chemicals a variety of speciality rinses are used before a given container can be considered to be free of the chemical (in the case of chemical transportation, for example). Again, I would be wary of off-the-cuff advice and analogies with familiar territory unless they are strongly backed up by experience or evidence. --98.217.8.46 (talk) 13:06, 4 September 2008 (UTC)

Household bleach is widely used in the cleaning of food and drink containers and preparation surfaces, and it is inevitable that traces of it remain on those surfaces. The traces which would remain in a thoroughly cleaned and rinsed (I am assuming the questioner has access to ample supplies of potable running water here) would be likely to be insignificant. The container (which is one designed and manufactured for household use by persons having no special training or equipment) is to be used in a performance, not for the long-term storage of water, so the likelihood of harmful quantities of any substances leaching out of the plastic is extremely low. This is not medical advice by any stretch of the imagination, but the OP is welcome to take it as the basis of a risk assessment from someone who has to do loads of the things. The principal risk associated with the activity as far as I can see from the information presented is that the stunt bottle could be confused with other similar bottles in the performance venue, and the props mistress will need to provide adequate controls to prevent this happening. DuncanHill (talk) 13:14, 4 September 2008 (UTC)

Also of interest is the MSDS for Clorox bleach. It provides the concentration of the bleach, the exposure limits, and the appropriate response to ingesting pure bleach. Combined with other reliable information, like the EPA reference above, the OP should be able to reasonably assess the safety of the intended performance. -- Coneslayer (talk) 13:45, 4 September 2008 (UTC)

I just checked the bottom of a Chlorox bottle to see what type of plastic it is. It was labeled with recycling number #2 and HDPE both of which indicate high density polyethylene. In terms of the bottle's plastic it should be no more dangerous than drinking out of a milk bottle and will contain fewer hormones (from the milk). The chemical in bleach are fully water soluble and thus require no special solvent rinses. Besides the chemicals are only toxic at high concentrations (similar to most acids and bases) so the small amount of oxidant left in the plastic to leach into the stored water should do no harm.--OMCV (talk) 13:53, 4 September 2008 (UTC)

epilepsy / impact on brain

hi! i heard that not only alcohol can damage brain cells but also other abnormal conditions (like orgasms(sic!) and epileptic situations). i further read that psychiatric electro shock (it creates a grand mal situation artifically) not only causes no structural changes in the brain[15] but even lets new brain cells grow[16]... can somebody solve that contradiction for me? thx. ps: there they suggested to ask here... bye. --Homer Landskirty (talk) 05:23, 4 September 2008 (UTC)

Let's hope orgasms aren't an abnormal state of the brain :). The only orgasms that cause brain damage are those associated with erotic asphyxiation, otherwise if someone's had a natural orgasm so strong it caused them brain damage....well, I mean... damn. Way to go! Ask them how they did it and spread the knowledge. As for your comment on EST, if a therapy stimulates new brain cells to grow, that IS a structural change to the brain because new connections (i.e. pathways) are being forged. It's not my understanding that seizures cause brain damage outside the risk of the individual hitting their head or obstructing their airway during the seizure. --Shaggorama (talk) 05:50, 4 September 2008 (UTC)

:-) hm... ok... "structural change" was most likely meant as "structural damage" and they were talking of CT and MRI scans which don't give detailed information on neuron-level... i was always bad in biology, but the high electrical energy in the brain during a seizure seems to be a potential cause for electrolysis (when i held a 9V direct current source into a glass of salt water, it changed its color, although salt and water r quite simple compounds...) and thereby necrosis... but i don't insist that it must be like that... --Homer Landskirty (talk) 06:42, 4 September 2008 (UTC)

My understanding is that prolonged seizure, i.e. status epilepticus, causes brain damage metabolically (through accumulation or depletion of noxious or essential substances, respectively). The electrical energy generated is not extreme and I am pretty sure much lower than that needed to damage human tissue. Scray (talk) 10:35, 4 September 2008 (UTC)

As the amount of elecctrical activity in the brain increases, the voltage present in the brain stays the same. Action potentials are all-or-nothing phenomena. --Shaggorama (talk) 15:30, 4 September 2008 (UTC)

twin universe hypothesis

i have a hypothesis which our spacetime is double sided, while a Big Bang and Big Crunch singularities will be avoided, because my hypothesis is that while one side is empty, the other side is full, and therefore, matter will flow to the other side. which is the Big Bang. And like the inflation theory, the stuff flowing through will accelerate, and in later stages, will start to decelerate. at this time, the other side is shrinking, and this is my Big Crunch. Please give comments. —Preceding unsigned comment added by Superwj5 (talk • contribs) 13:05, 4 September 2008 (UTC)

The reference desk is not a discussion forum, and entries to that effect may be removed. Is there a question here? — Lomn 13:17, 4 September 2008 (UTC)

As Lomn say, this isn't really the right place to ask for comments on an original theory. Even despite that, your description is too vague to make any meaningful comments on. --Tango (talk) 13:24, 4 September 2008 (UTC)

It's very, very easy for anyone to come up with random hypotheses like these - but unless they explain absolutely all of known physics AND explain some unexplained phenomena AND predict some testable thing - they are just useless. Unless your hypothesis is grounded in and backed by an IMMENSE amount of physics, it's about as interesting as your next door neighbors holiday photos. SteveBaker (talk) 19:10, 4 September 2008 (UTC)

"explain absolutely all of known physics" is too high a bar - I think that typically, science settles for "does not contradict any existing known physics and either explains a piece of physics that was previously unexplained or is simpler than other available explanations for what it covers" --Random832 (contribs) 19:20, 4 September 2008 (UTC)

Well, it needs to explain at least as much as the theory it is replacing. It can contradict existing theories, but only if it can explain all the same observations. --Tango (talk) 22:01, 4 September 2008 (UTC)

Yes - exactly. Perhaps I should say that it has to provide convincing explanations for all of the currently observed phenomena for which we already have convincing explanations. Doing that alone would be a pretty amazing thing for a radical new theory of the universe - but the bar to replace current theory has to be that it provides something new - preferably an experiment that could be done that would produce a result that the present state of science would not predict. Perhaps explaining something that's not currently understood - or (I guess) being vastly simpler than existing explanations. But making a testable prediction that turns out to be true is the gold standard.

So, for example, nobody took much notice of Einstein's special relativity until he predicted that the sun's gravity would bend the light of a distant star and that this should be visible in a total solar eclipse. When that experiment was eventually carried out (an interesting story in itself) - and it produced the result that Einstein predicted - the world of science was overturned pretty much overnight. So the theory itself (good though it was) didn't attract much interest until it predicted something amazing.

To produce a counter-example, string theory does a good job of providing an explanation for everything we currently know - but all of the predictions it makes have proven impossible to test experimentally. Some claim that the Large Hadron Collider (LHC) will provide some sort of proof - but the jury is still out on that one. Hence we don't usually treat string theory as "The Truth" in the same way we treat relativity.

SteveBaker (talk) 22:43, 4 September 2008 (UTC)

White hole transformation

today, i read that if the Higgs Mechanism or Superstring Theory is correct, then above a magic energy, matter will become massless. Suddenly, I was reminded of that massless black holes become white holes. I then thought when a black hole mass becomes very small, the Hawking Radiation will set it above the magic energy which it will become a white hole. After some time, the energy will decrease below the magic energy. and in supermassive black holes, the accretion disk will also pull the black hole over the magic energy, and the same thing will happen, except that the accretion disk flies away.Please give comments. —Preceding unsigned comment added by Superwj5 (talk • contribs) 13:13, 4 September 2008 (UTC)

There's a lot of unsupported guesswork in this. Can you cite "magic energy" or this rather unusual definition of a "white hole"? Otherwise there's nothing to this. — Lomn 13:16, 4 September 2008 (UTC)

Massless black holes don't become white holes. White holes have mass just like black holes. Also, white holes don't repel matter, they attract it just like black holes. The classical distinction was that white holes emitted matter and shrank, while black holes absorbed matter and grew; but since Hawking noticed that quantum black holes seem to do both, it's no longer clear what the difference between a black hole and a white hole is.

I don't know much about the Higgs mechanism, but I think it's not governed by a magic energy so much as a magic temperature. It's a phase transition; we're in a "frozen" state of the Higgs field right now, and above a certain temperature it "melts" again. Tiny black holes have very high Hawking temperatures, but I don't think you'd notice weird Higgs effects just because of that. Small sizes and large temperatures are related, and there's probably something weird happening with the Higgs field (and all other fields) at close enough distances to any pointlike particle, like an electron, but we don't see those effects at ordinary distance scales. -- BenRG (talk) 15:08, 4 September 2008 (UTC)

Name of interesting microorganism

I took a really great parasitology course in undergrad but i can't remember for the life of me the name of one of the organisms we went over. I remember the professor was talking about opportunistic infections and fungal pneumonia, and he then proceeded to mention another creature that he said was very distinct in that it was comparable in its morphology to (i think?) a stinging cell on a jellyfish or something along those lines. Does this sound familiar to anyone? Thank you so much!

129.252.70.53 (talk) 13:14, 4 September 2008 (UTC) Timmy

The commonest fungal pneumonias are aspergillosis, coccidioidomycosis, histoplasmosis and blastomycosis. From your description, it sounds like aspergillosis is the most likely. Axl (talk) 19:16, 4 September 2008 (UTC)

I think it possible you're thinking of Pneumocystis jiroveci, previously called Pneumocystis carinii, first thought to be a protozoan but now known to be a yeast-like fungus. On the other hands, stinging cells in jellyfish are "nematocysts", and if you were discussing animal diseases rather than human ones, the most likely candidate is Myxobolus cerebralis, which infects fish by piercing them with polar filaments ejected from nematocyst-like capsules. - Nunh-huh 06:25, 5 September 2008 (UTC)

Human breasts-a store for fat?

How large do breasts have to be to produce the required amount of milk? And if they larger than that minimum, then why? Are they also used as a store for fat? —Preceding unsigned comment added by TrapdoorTrevor (talk • contribs) 13:34, 4 September 2008 (UTC)

Breasts must produce approximately 8 ounces of milk every 3-4 hours during breastfeeding. That is pretty much a single glass of milk. Spread among the two breasts, the required size is noticeable, but not great. It is common for breasts to enlarge beyond the required amount. As for fat, breasts are mostly a store of fat. Men have mammory glands as well, but do not store fat in the breasts as usual as women do. Men usually only store fat in the breasts when fat stores throughout the body are already very full. -- kainaw™ 14:35, 4 September 2008 (UTC)

Sociopaths

Are most sociopaths males? If so, what is the reason for this? --Anilmanohar (talk) 19:02, 4 September 2008 (UTC)

Probably yes. This research thesis gives answers to your second question. Axl (talk) 19:50, 4 September 2008 (UTC)

growing biodiesel in your back garden

I drive a diesel car which does about 40 miles to the gallon, about 100 miles a week - so I need 2.5 gallons of diesel every week. Can you grow that in your back garden? Judging by Jatropha oil, that means you would need one quarter of a hectare in your back garden to run my car completely on jatropha. That is if "A hectare of jatropha produces 1,892 litres of fuel" means per year.

Can anyone tell me if I'm right or not? Is it practical to grow jatropha in your garden?89.240.139.65 (talk) 19:37, 4 September 2008 (UTC)

How long is the growth cycle for jatropha? Assuming you can get only one crop a year, you'd have to produce all the oil you need for the following year at once. So you'd need storage. How is jatropha oil recovered? I know with some other veg oils there significant processing, beyond just the extraction/expellation, to remove impurities, moisture, etc. You might be able to skip these, but excess moisture might lower your yield, and impurities might gum up your engine. I think you could do it for personal satisfaction, but it would be a lot of trouble and not necessarily benefit the environement (if that is your goal). ike9898 (talk) 19:45, 4 September 2008 (UTC)

The storage problem isn't a huge one... he needs only 130 gallons/year. I have 2×275 gallon oil tanks in my basement for heating oil, which is a pretty common setup around here. -- Coneslayer (talk) 20:05, 4 September 2008 (UTC)

You would also need to grow something else like corn to make ethanol or buy methanol. Regardless you need an alcohol to transesterification your bio-oils and produce biodiesel. Next you need means to heat/cool/electrify your home. Then after that we need to do that for our work places. Neat stuff to think about.--OMCV (talk) 20:22, 4 September 2008 (UTC)

I seem to recall hearing that your need a federal permit to grow Jatropha in the United States as it is potentially invasive non-native plant. No idea on whether that is easy to get or hard. You might do better with a locally available alternative of some kind. Dragons flight (talk) 21:31, 4 September 2008 (UTC)

Thanks for the warning about permits - I'm English, so I'll get that checked out with somebody. And I'm sure something like an oil tank could keep the rest of it. Anyone know how long it takes the stuff to grow, if it is one year or not?78.144.169.2 (talk) 22:33, 4 September 2008 (UTC)

Our article Jatropha curcas says "While Jatropha curcas starts yielding from 9–12 months time, the effective yield is obtained only after 2 - 3 years time". yield is also affected by planting pattern, and of course you want a preponderance of female plants. DuncanHill (talk) 22:36, 4 September 2008 (UTC)

Hmmm - interesting! I have 1.2 acres (which is about half a hectare) at the back of my house - and my car also does ~40mpg and I run it 100 miles a week...this sounds rather interesting! I guess the other considerations we need to answer are:

• What amount of water and fertilizer does this stuff need to grow year after year on the same land?
• Would you need to do "crop rotation" and thereby have some years in which you'd get no biodiesel because you'd have to plant nitrogen-fixing plants instead?
• What equipment would you need in order to prepare the soil, plant, weed, fertilize and harvest the stuff? Can you rent it? Borrow it? Share it with neighbors who have the same idea as you?
• How much fuel do those machines require in a typical year?
• What "economies of scale" would you fail to achieve by growing so little of the stuff? Are the numbers you're getting based on planting hundreds of acres?
• Does it grow well in your local climate and soil conditions?
• What pests attack your crop and how can you deal with them?
• What waste products remain after extracting the biofuel (eg bits of the plant that aren't used in the production - left over chemicals - that kind of thing)?
• 130 gallons of Diesel costs maybe $650 in the USA...What is the "opportunity cost"? In other words, what other things could you do with that land and whatever capital you have tied up in equipment that might earn you more than $650?
• How much value to you place on your own labor? Seems like you might spend a LOT of hours ploughing/planting/fertilizing/killing insects/weeding/watering/harvesting/brewing - are you committing yourself to manual labor at less than minimum wage? If so, maybe taking a second job for a couple of weeks a year would be a more profitable use of your time?

Lots to think about...but at first sight, it doesn't sound so attractive. The lack of economy of scale is the problem...if you were planting hundreds of acres then the cost of the equipment and perhaps much of your time/effort would be amortized over a larger amount of product...but at this small scale, you can't afford to buy even a small tractor because it would be idle 50 weeks of the year and wipe out your potential savings for MANY years. Without a tractor, ploughing, planting and harvesting 1.2 acres sounds like back-breaking work for at least several weeks a year.

SteveBaker (talk) 23:18, 4 September 2008 (UTC)

10 inches of rain a year, grows well on poor soils, needs little if any feeding, life expectancy of 40 years so not a lot of ploughing or planting to do, resistant to disease and pests. It sounds, from our article, to be a remarkably easy plant to grow. That said, lots of good points from Steve. As usual! DuncanHill (talk) 23:23, 4 September 2008 (UTC)

Why even grow your oil? Everyone I know who operates converted biodeisel cars get their grease from restaurants. They actually get PAID for their fuel because their fuel source doubles as a waste disposal! And they get to feel good because they're recycling used cooking oil. Just another option to consider. --Shaggorama (talk) 04:36, 5 September 2008 (UTC)

It's OK to a point - but a typical small town can't support more than a few dozen cars that way...there just aren't enough deep fryers being emptied often enough. It's OK as an "I'm alright" solution for an individual - but it's not the way forward for mankind in general. Also, I suspect it's only a matter of time until the McDonald's and the Wendy's of this world start to realize that they could actually charge for this stuff. Right now, they don't because they usually have to pay to have it hauled away - and if someone will take it for nothing - it saves them money. But once there are two or three people hanging around begging them for their left-over oil every day, they may realize that they have a valuable commodity and start selling it. What I suspect MIGHT happen is for them to install the equipment necessary to filter and dry the oil on-site and start filling the tanks of their delivery trucks with the stuff - it would be a GREAT PR thing ("We're going green!") and the whole business of vehicles that burn the stuff smelling like fries could be put to considerable advertising advantage. So while this is a great gimmick - it's hardly going to save the planet and it's only a matter of time until that particular well runs dry for the average motorist. SteveBaker (talk) 05:47, 5 September 2008 (UTC)

OK everybody, thanks for your answers to my questions. You need a big garden to run a car on your own jatropha and at the end of the day, it isn't really practical on a domestic scale for non-green warriors because of processing. If someone was paying you for the right to harvest your garden and process the stuff, it would be great, and then you could buy refined jatropha back from them. Then whoever harvests your garden needs LOTS of gardens to do, and you need to persuade people to give up their lovely gardens as well. Alternative fuels is a fringe business (here at least). In my experience, that means don't jump for it right away, use it in blends. And yes, you can get oil from restaurants, but every little helps (pardon my tesco advert). Imagine the effect if everyone kept just a few jatropha plants, and that would avoid the controversy that the biofuel industry takes precious land from food cultivation.78.149.56.198 (talk) 22:39, 5 September 2008 (UTC)

How do a student weight the moon

I'm thinking about how to weight the moon using nothing that a teenager student cannot get hold of. 202.147.44.87 (talk) 23:15, 4 September 2008 (UTC)

Let's assume that you already know the mass of the Earth. From that, Newton's Law of Universal Gravitation, and the equation for uniform circular motion (I'm making the simplifications that (1) the moon's orbit is circular, and (2) the Moon orbits the Earth, rather than both orbiting a common centre of mass), you should be able to get an equation relating the mass, orbital velocity and orbital radius of a satellite. Finding the orbital radius of the moon is a little tricky, but you could probably work it out via a couple of sextants and a parallax argument, and then the sextants will also help you work out its orbital velocity. Not the easiest of projects, but not impossible, either. Confusing Manifestation(Say hi!) 23:48, 4 September 2008 (UTC)

Well, if you knew how much the gravity of the moon affected things on Earth, you'd be able to calculate the mass (not, technically, the "weight"). At first sight, I think you'd need to look at tides - or perhaps the amount the earth wobbles each lunar month because the earth/moon system orbits around a common center that isn't at the center of the earth.

• If the Earth and the Moon weighed the same amount - we'd both be orbiting around a point that would be halfway between the two. But the earth is heavier - so the point about which we both orbit is closer to the center of the earth than the center of the moon. Hence the earth doesn't just rotate on it's axis once a day - it also orbits around that common center once every lunar month. There are probably things you could measure with a telescope that would tell you that...but that's going to require a really accurate telescope - which doesn't sound like something you'd obviously have. This document [17] describes the math - but doesn't explain how you measure the numbers you'd have to plug into the math.
• Measuring the moon's gravity using the effect it has on the tides. You have to be very careful to control for the effect of the Sun's gravity - but in theory, if you know the height of the tide - and you know how far away the moon is, how heavy the earth is...you can figure out the gravity due to the moon - and hence it's mass. The math is in Theory of tides - and it's kinda horrible.
• You'd think (at first sight) that your weight would be less when the moon is directly overhead than when it's beneath your feet - because when it's overhead, it's pulling you upwards and reducing your weight. But sadly, the centrifugal force due to our orbiting around that common center handily cancels that out - which is why we get two high tides each day - one when the moon is overhead and another when it's underfoot. However, you should find a difference between when the moon is directly overhead and when it's at the horizon. It's that difference that accounts for the tides - but perhaps this is a more direct way to measure it - if you have an accurate enough measuring device. Remember, you can't use a beam-balance to do it because the weight of your standard weights is also changing. You'd need a spring balance - or some kind of electronic pressure gauge.

I sure hope there is an easier answer!

SteveBaker (talk) 23:49, 4 September 2008 (UTC)

For what it's worth, Isaac Asimov's book The Double Planet has a chapter on how the moon was weighed. That might be available in used book stores. — Lomn 13:06, 5 September 2008 (UTC)

How about this method:

• Measure the orbital velocity, ω, of the Moon. Its orbital period is about 28 days, so ... let's see ... that's about 2.6x10^-6 radians per second.
• Measure the acceleration due to gravity at the surface of the Earth, g. That's about 10 ms^-2.
• Estimate the radius of the Earth, r_E, using Eratosthenes' method. Let's say that's 6.3x10⁶ m.
• We know that gravitational attraction decreases with the square of distance, so if the Moon is a distance d_M from the centre of the Earth we must have:

$d_{M}\omega ^{2}={\frac {gr_{E}^{2}}{d_{M}^{2}}}\,\Rightarrow \,d_{M}^{3}={\frac {gr_{E}^{2}}{\omega ^{2}}}$

• Plug and chug and we get d_M = 3.9x10⁸ m.
• Measure the angular diameter of the full Moon - that's about half a degree.
• If the Moon subtends half a degree at a distance of 3.9x10⁸ m (neglecting a small correction for the radius of the Earth) then its diameter is 3.9x10⁸ x π / 360 = 3.4x10⁶ m, and so its volume is about 2.1x10¹⁹ m³.
• Assume that the Moon has a similar make-up to the Earth. Measure the density of an average lump of rock, and round this up a bit to allow for higher density towards the centre of the Moon. Let's take an average density of 3,000 kg m^-3. That gives us a mass for the Moon of about 6x10²² kg.

Estimating the radius of the Earth from first principles might stretch a typical teenager, but the rest of the measurements are quite straightforward. Gandalf61 (talk) 13:14, 5 September 2008 (UTC)

You were doing great right up to the point where you assumed the density of the moon. There is no reason to assume that moon rocks have the same kind of density as earth rocks or that the density profile is anywhere near similar to what we know for the earth. The earth has a liquid nickel/iron core - the moon almost certainly doesn't. (And if we cheat and look it up - we find that the earth is nearly twice as dense as the moon...but that's cheating because we're not doing an experiment). The guesstimate you came up with happens to be within 10% of the true number - but that's just luck. If you'd used the same guess to estimate the density of the earth - you'd have been off by a factor of around 2. The problem with weighing the moon is precisely that we DON'T a-priori know it's density. We have to figure it's mass some other way (tides - for example) and use that with our size measurement to deduce a density. SteveBaker (talk) 15:59, 5 September 2008 (UTC)

Yes, the tidal method avoids making assumptions about the make-up of the Moon. However, it only gives you the ratio of the Moon's mass to the Earth's mass. To derive the Moon's mass you need to know the Earth's mass, or equivalently its average density. Asking a student to measure the Earth's mass or density to an accuracy of better than a factor of 2 is quite a tough challenge - they would need to perform a backyard version of the Cavendish experiment. Gandalf61 (talk) 09:34, 6 September 2008 (UTC)

Why is measuring the mass of the earth so tough? We can easily measure g to high precision (stopwatch, rock, tall building) - so we can figure the mass from Newton's law of Gravitation - all we need to know for that is the radius of the Earth. That's obtainable by Eratosthenes method. (And your proposed approach requires us to do that too!)...you can get pretty good precision with Eratosthenes using two tall buildings, two students in different cities with cellphones and tape measures. SteveBaker (talk) 13:37, 6 September 2008 (UTC)

Well, yes, it's easy to determine GM for the Earth by various means. The hard part is determining G at all accurately. If you just give that to the students, then you've done most of the work for them. Algebraist 14:04, 6 September 2008 (UTC)

Indeed. Measuring g and r_E only gives you the product GM_E. It wasn't until the 18th century that G or M_E (or, equivalently, the average density of the Earth) could be measured separately with any degree of accuracy. In 1774 Nevil Maskelyne measured the gravitational attraction of Schiehallion and estimated the average density of the Earth to be 4.5 g cm^-3 - and this took seven weeks of detailed surveying [18]. In 1797/8 Cavendish used John Michell's torsion balance method to get a more accurate value of 5.45 g cm^-3, but this required making very precise measurements. Gandalf61 (talk) 14:54, 6 September 2008 (UTC)

Portion of agriculturally usable land on the surface of the globe

It is said that 29% of the earth's surface is covered by the land mass. What portion of the total surface is usable for agriculture for growing food? 86.33.247.155 (talk) 23:30, 4 September 2008 (UTC)

Agriculture says "Livestock production occupies 70% of all land used for agriculture, or 30% of the land surface of the planet." - so, if I read that right, livestock agriculture covers 30% of all land - and that's 70% of agricultural land. Overall then, there must be more like 43% of all land under agriculture...which is maybe 11% or so of the earth's surface. That number seems high to me - but that's what the article says. It references a UN report - but the link has gone bad - so I can't see the original source. SteveBaker (talk) 00:05, 5 September 2008 (UTC)

That quote says "used", the OP says "usable". There is presumably some unused but usable land (although perhaps not much). --Tango (talk) 00:27, 5 September 2008 (UTC)

Yep. I think it's pretty debatable as to what's "usable" - I mean we COULD erect giant pressurized, heated greenhouses over the summit of Mt Everest - bring in a few feet of dirt and plant stuff right on the top - it's technologically quite possible - but you wouldn't normally say that the summit of Everest was "usable agricultural land". So where do you place your limits? Usable "with what degree of difficulty" is the real question. When you see how (for example) the Dutch reclaimed ocean-bottom with relatively crude windmill pumps - and now they intensively farm it. That's arguably a lot harder than farming Mt Everest so it would be rash to disallow any region on the grounds of technological difficulties - and the way people are steadily mowing down the Amazon rainforest for crops - you can't even ask what we sensibly should farm. We even do agriculture out in the oceans with fish farms - so it's impossible to know what limits to place on such a question. But 11% is evidently what we actually "do" farm. If we're asking what could 'easily' be farmed or 'easily and sensibly and legally' - then I suspect we're already beyond that limit. SteveBaker (talk) 05:06, 5 September 2008 (UTC)

September 5

"base SI quantity"

I have the question: When using the words "base SI quantity for 3mg," would I be referring to "mass", or "gram"? No wiki article exists on Base SI quantity, and as and American trying to learn more about SI, this is somewhat confusing. Thanks, Spencer^T♦C 00:28, 5 September 2008 (UTC)

I don't know about "base SI quantity" but SI base units may be what you are looking for. DuncanHill (talk) 00:41, 5 September 2008 (UTC)

Oh wow, I feel stupid. Thank you very much. Spencer^T♦C 00:42, 5 September 2008 (UTC)

No need to feel stupid (everyone finds new systems of measurement difficult at first), and I am glad to be of help. DuncanHill (talk) 00:44, 5 September 2008 (UTC)

:D. Spencer^T♦C 00:45, 5 September 2008 (UTC)

By the way, the SI unit of mass is the kilogram, not the gram (don't ask me why...). --Tango (talk) 00:51, 5 September 2008 (UTC)

We did use the gram for a while - in the CGS (centimeter/gram/second) system. Now we use the MKS (meter/kilogram/second) system instead (well, strictly "SI" - which is MKS + moles, amps, candelas and kelvins). CGS was very gradually phased out from about 1880 until fairly recently (some fields still use CGS - electrodynamics being the most notoriously stubborn). Mostly because for most practical purposes the resulting numbers tended to get too big in most fields of human-scale things. It's unfortunate that we stuck with 'gram' and therefore ended up with a 'kilo' prefix on a 'base' unit - it would have been nicer if we'd just had some new unit that happened to be the same size as a thousand grams. But that's history - and we're kinda stuck with it. SteveBaker (talk) 04:54, 5 September 2008 (UTC)

I added a redirect so that it is easier to find for the next person who ties this name. Graeme Bartlett (talk) 01:44, 5 September 2008 (UTC)

Gravity question

All humans are attracted to the center of the earth by gravity. So if there was a hole drilled from the north pole threw to the south pole and I fell down it, would I end up in the middle of the earth? —Preceding unsigned comment added by 1000kA (talk • contribs) 00:45, 5 September 2008 (UTC)

Ignoring the fact that such a hole is impossible, yes. You would be weightless at the centre, since the gravity from all the matter surrounding you would cancel out. --Tango (talk) 00:52, 5 September 2008 (UTC)

Well, yes, you would get to the centre, but you would be moving very fast by the time you got there. After passing the centre, gravity would start to slow you down again, and (ignoring various things) you would end up oscillating about the centre. If we're not ignoring air resistance, then you'd end up in the centre after bouncing back and forth a bit. Algebraist 01:16, 5 September 2008 (UTC)

You'd keep bouncing as the gravity of Earth would be cancelled out, but the moon (which is powerful enough for tidal effects) would still be tugging at you - as would a weak tug from the sun which changes relative direction with your orientation to Earth as Earth spins. -- kainaw™ 01:20, 5 September 2008 (UTC)

In the pole to pole hole there would be no Coriolis force as you would get from any other places on the earth. Also the air pressure and temperature would be so high down deep, that the air would be liquid and you would be baked on the way down. Graeme Bartlett (talk) 01:48, 5 September 2008 (UTC)

Dont you mean boiled? —Preceding unsigned comment added by 1000kA (talk • contribs) 02:01, 5 September 2008 (UTC)

An interesting side note: ignoring friction etc., the time to "fall" through a straight hole between any two points on the surface of the Earth is the same as for any other two points. Saintrain (talk) 13:03, 5 September 2008 (UTC)

Darn, you beat me to it. Indeed, if you pretend the Earth is a solid non-rotating sphere of uniform density, and dig a straight shaft between any two points on the surface, and lay down frictionless rails on the bottom of the shaft, and evacuate the tube so there's no air friction, and put a train car on the rails, and let gravity do the rest, it will take you from one end of the shaft to the other in a time of $\pi {\sqrt {\frac {r_{\text{earth}}}{g_{\text{surface}}}}}$, which is about 42 minutes, independent of the endpoints. I think the acceleration you feel is also constant throughout the trip, and equal to ${\frac {r_{\text{min}}}{r_{\text{earth}}}}g_{\text{surface}}$, where $r_{\text{min}}$ is the minimum distance from the tube to the center of the Earth. (This is the acceleration that would be measured by an accelerometer that you took on the trip, which is not the same as your acceleration with respect to the rest frame of the Earth.) On a trip from San Francisco to London you'd feel about 0.78 g. I could live with that. Pretty expensive public works project, though. -- BenRG (talk) 14:19, 5 September 2008 (UTC)

I don't see how acceleration could be constant. When you start, you're at the surface, so that's 1g, in the middle you are somewhere beneath the surface, so that's less than 1g (0g if you're going between antipodal points). --Tango (talk) 18:18, 5 September 2008 (UTC)

In the case of the antipodal points, you're in free fall the whole time, and therefore feel zero g, in the sense that if you carried an accelerometer with you, it would register zero g. 1000kA, if there's enough pressure to liquefy air, there's going to be enough to keep water liquid, if not solidify it. — DanielLC 22:28, 5 September 2008 (UTC)

Mars

I have seen many pictures of mars taken over the years where abnormal structures can be clearly seen (pyramid type things among others). I would like to know why these structures have not been scientifically investigated and why NASA has not sent a probe to these interesting areas? Eg: the face on mars. If you are wondering what I’m talking about search youtube for “structures on mars” There are also areas of photos that have been clearly airbrushed, what do NASA have to hide? 203.202.144.223 (talk) 00:48, 5 September 2008 (UTC)

Have you tried reading about the "Face on Mars" here? DuncanHill (talk) 00:50, 5 September 2008 (UTC)

I have read about the face on mars as an optical illusion, however i have also read that the recent pictures were had been harshly (and unnecessarily) filtered. But there are many other pictures showing other odd things other then the 'face on mars'. I guess another question I have is why would NASA airbrush pictures of mars' surface? 203.202.144.223 (talk) 01:00, 5 September 2008 (UTC)

Another question would be why someone would want NASA, heavily funded by tax dollars, to waste money exploring ideas from some crackpots who know nothing about Mars except what they've seen in video games and science fiction shows? If the crackpots want to investigate all those artificial structures, then let them raise the money to do so. NASA is busy trying to find an optimal location for a sustainable living area should we achieve manned missions to the Mars. -- kainaw™ 01:18, 5 September 2008 (UTC)

So you do believe that those structures are artificial? Even at the minute chance they are artificial wouldn’t that be reason enough to at least investigate them? Or hey, maybe that’s just some crazy opinion of a “crackpot” 203.202.144.223 (talk) 01:40, 5 September 2008 (UTC)

This is one of those "please prove that something doesn't exist" arguments. The crackpots want proof that there are no artificial structures on Mars. If we brought Mars to earth, rock by rock, and examined the entire planet, they would still be claiming the overlooked something. It is a project that has no end and, therefore, would take forever and cost an infinite amount of money and man-hours to complete. So, the answer is a simple no. It is not worth wasting all our money and time on something that has already been examined and has already been proven to all sane people to not exist, but still gives crackpots a big fuzzy feeling when the send their little "NASA is covering this up" messages back and forth on the Internet. -- kainaw™ 01:55, 5 September 2008 (UTC)

Looking past the other issues, it is also impractical at current. After travelling 150 million kilometers, the mars landers come down with a targetting precision of +/- 50 km. I suspect that visiting most "structures" you'd like to look at would be challenging if your starting point is only good to within 50 km. Dragons flight (talk) 02:09, 5 September 2008 (UTC)

Sad, but true - these things are worth a quick check - and NASA have done that. In the case of the "face" they took higher resolution photos - which look NOTHING like a face. They apply an appropriate amount of diligence - but once they've proved to a reasonable degree of certainty that nothing interesting or unusual is going on, they drop it.

Sadly, the nut-jobs on the conspiracy sites simply won't ever give up their crackpot ideas. Check out the "The moon landings were faked" loonies...we have a freaking great HUGE pile of moon rocks in a lab in Houston - I've seen them. There is even a moon rock that you can actually touch. We have movies that can't be faked without genuine low gravity conditions. We have retroreflectors on the moon that you can bounce lasers off of that prove we put man made stuff there. We have brave, honest men with no history of lying or conspiracy who tell us what it was like to be there. We have literally tens of thousands of people who would have all have to have agreed to the conspiracy - and NOT ONE of them has ever confessed to lying or concealing the truth - not even on their death-beds. We have really solid counter-arguments to absolutely every single complaint the crackpots put up...but still, I don't believe that we've ever convinced a single one of them. It's fair enough that you might come up with some strange things you see in those photos (non-parallel shadows, no stars in the photos, etc). But when I successfully explain all of them, you need to say "Oh! Well, then you must be right." - you don't go back, find ANOTHER dozen tenuous things - let me explain those, then find ANOTHER dozen (even more tenuous) things.

There is no way to get rid of these people - no amount of proof will ever make them believe. Would you believe there are still flat-earth believers? Yep - there is an entire web site full of them. You say - but there are guys up there in orbit right now looking down at the earth and they say it's round. They say "So have YOU ever seen that?...Then how do you know?"...then an actual astronaut who HAS been there and seen it says "Yes! I've seen it with my own eyes."...and they say "Ah - but it was an optical illusion due to refraction of light though the atmosphere"...and you say "But refraction bends light in the opposite direction"...and they say "Sure it does in the lab - but have you tested that in the upper atmosphere?". You say "But what about ships disappearing over the horizon?"...and they say "Ah - diffraction through the atmosphere" - and you say "But diffraction bends light the other way...and you just AGREED that it works my way"...and they'll say "But the water vapor alters the sign of the pseudo-magnetic wibble matrix because of quantum grungology and that's why it does it."...and off we go again.

It's an eternal regression - they can come up with crazy crackpot special-case exceptions and toss in random pseudo-scientific babble no matter what. When you do knock down their arguments - they ignore that and move on to an even crazier claim. They pretty much universally don't understand enough science to comprehend why your counter-arguments are valid.

At some point, you have to say "You're an idiot." and move on...doubly so if you are a government funded agency who will get in deep trouble if you spend a few megabucks on proving some crackpot wrong.

So - the 'features' on Mars are no different from seeing bunny rabbits in the clouds. The human visual system has a built-in feature that forces you to try to find pattern in anything you see. Most of the time, this is useful - but sometimes it makes you see faces on Mars, bunnies in clouds, and allows small children to scare themselves silly at bedtime by seeing monsters - which turn out to be shadows cast by toys or whatever.

You can keep on demanding more and more proof - but there comes a point when you're going to be labelled a "crackpot" - and with good justification! Science requires us to observe (We see a face on Mars!) then it requires us to consider the likelyhood that this observation is a meaningful thing - (What are the odds that there is really an artificial construct on another planet? What are the odds that this is just a "cloud bunny"?) - if we conclude that the odds are good enough that there is something really going on - we investigate (we move a Mars observation satellite over the feature and we take a much better photo) - when we find we were wrong, we give it up. We don't go on and on banging on about the same thing. There are much more interesting things to do with our big, clever brains.

SteveBaker (talk) 02:31, 5 September 2008 (UTC)

Thankyou Steve, I appreciate your detailed response. And I am also quite interested these “cloud bunnies” you speak of :p . But in all seriousness going back to my earlier question: (Now I am not asking this as some sort of conspiracy nut as there could be a valid answer) why would it appear that NASA has airbrushed photos of mars’ surface? Going through many pictures including the more recent ones I have come across, i have found a lot of them which appear to have been blurred in specific areas. 203.202.144.223 (talk) 02:56, 5 September 2008 (UTC)

Give me an example. It's hard to argue without being able to see the image you're talking about. Note that NASA's imaging folks are REALLY good. If they wanted to hide something - they'd do a bang-up undetectable photoshop job and you'd never know you'd been fooled. Heck - I can do that easily enough. Look at this photo: [19] - it looks OK - right? Well, in reality, the cute puppy on the right had fought like crazy to avoid being photographed looking cute and had scratched my arm so badly I was bleeding from two 3" long cuts. Two minutes with a good image editor - and you'd NEVER know. So why "obviously" airbrush something and arouse suspicion? But show me the photo. SteveBaker (talk) 04:15, 5 September 2008 (UTC)

Example will be on it's way as soon as i get home from work. Damn you restricted internet access!! 203.202.144.223 (talk) 04:53, 5 September 2008 (UTC)

One reason I know of off-hand is that NASA will typically composite together several photos from a spacecraft in orbit. Because the planet is curved and the picture is flat - the photos don't quite line up properly. Also, one photo may be taken several orbits after the other - and the planet rotated in the meantime - so the sun moved a bit in the local sky and shadows moved a bit. The quick/cheesy way to fix that is to blend together the two images along the seam. The slight mismatch shows up as a blur. It's worse where four photos meet at a corner - so that could explain some blurry patches. You can see this happen in places in Google Maps also. However, there may be other reasons...lets' examine an actual 'suspect' photo. SteveBaker (talk) 05:36, 5 September 2008 (UTC)

check these out: LINK ---> [20]

LINK ---> [21] —Preceding unsigned comment added by 61.68.212.191 (talk) 09:15, 5 September 2008 (UTC)

Wow, it's sooo clearly an alien civilization, and not just a bunch of rocks. :-P I mean seriously. This some stretch of the freakin' imagination. --98.217.8.46 (talk) 11:54, 5 September 2008 (UTC)

The pale crater is simple jpg or digital artefacts from the way the pictures are taken the colour depth is not very high and so you end up by pixles which have a different colour than the next one so you se squares, which are no houses, but look like houses for people who have no knowledge on ditigital images. ---Stone (talk) 13:05, 5 September 2008 (UTC)

The hires video from the samples introduced into the TEGA instrument on the other video is great!! I taked to a scientist working on the project and he said that they had great pain because they where not able to get the sticky mars soil through that screen. This is a test of the groundsupport equipment filmed with a camera held next to the robotic arm. The pictures the robotic arm camera is able to take I have seen for myself here in the house and they are black and white and not that reolution at all. There is no camera on mars capable to make avideo like that. Keller the PI of the RAC would have like to have one, but he has not! So the NASA has no such hires videos at all!--Stone (talk) 13:05, 5 September 2008 (UTC)

The thing I find sad about these kinds of conspiracy theorists (and YE creationists, too), is that there is so much *real* wonder and beauty in the natural world, and they ignore it all to focus on these wobbly figments. I mean, there are shrimp that shoot fish with sonic pistols, and these guys are still nattering on about the moon landing 40 years ago! We should pass a law that anyone who has actually walked on the moon can punch these guys in the face whenever they like. --Sean 14:58, 5 September 2008 (UTC)

So - the moron in the video spends FIVE MINUTES to impart ONE URL (click here - then click here - then click here...OH FOR CHRISSAKES! Just tell me the URL already!). That guy is surely fond of his own voice. Then he takes the image and boosts gain until the underlying JPEG artifacts are visible and spends another FIVE MINUTES pontificating about the amazing "roads" and "buildings" he can see. He's looking at regular shaped features in the lowest couple of bits of an approximated image. Here are some ground-rules:

• Rule 1: Don't EVER do image analysis on JPG images - or images that have EVER been stored in JPG format. You need the original TIFF images that were never compressed with a lossy algorithm. In order to save space, the JPEG algorithm discards information that the un-assisted human eye can't resolve. It approximates colors and introduces "blocky" structure in the image. When you view it at normal resolution and normal brightness on a typical display - you don't really notice the errors it introduces - so it's a great way to make porn take up less space. When it matters - YOU DON'T USE JPEG! When you start messing with the brightness, contrast, zoom or anything else, you'll expose data that was deleted by JPEG in order to save space - and untrained idiots like that moron in the video will start to see...whatever they want to see. The joke is that they're looking at deleted data!

• Rule 2: Any image feature that is aligned with the raster pattern of the image is highly suspect - maybe a camera issue - maybe a compression issue. Features that aren't aligned with the raster are much more likely to be "real".

• Rule 3: Serious experts don't post shakey camera-pointed-at-CRT videos to You Tube. They write papers and present them clearly on nicely formatted web pages. People who are fond of their own voices spend five minutes making themselves sound like experts when in reality they are too dumb to read off the image's URL off the goddamn screen!

Please - don't waste our time with this kind of crap.

SteveBaker (talk) 15:38, 5 September 2008 (UTC)

Metric System

why united states has been slow in adopting the metric system? —Preceding unsigned comment added by Christianlazaro (talk • contribs) 03:41, 5 September 2008 (UTC)

Mostly I think it's a lack of incentive. It's an expensive process. The UK more or less did it - but it took 40 years and things were very messy along the way. It's not just a matter of saying "Now switch over!". Consider just one industry - house-building - you have things like the sizes of wood from which houses are made is a "two by four" - two inches by four inches. But you call that a 5cm x 10cm - then you have an error - it's really 5.08cm x 10.16cm. But having 5.08x10.16cm wood in all of your stores isn't REALLY converting to the metric system - it's just calling things by different names. But you can't suddenly start have sawmills start selling "true" 5cmx10cm wood because it won't fit the door frames and metal tie pieces and so forth - the entire building industry would have to redesign absolutely every component - from wood to nails and screws, pipes, tools, everything! Worse still, 2x4's aren't REALLY 2" x 4" - they start out life as that - but are actually smaller when they are planed smooth. So you have an entire industry based around some rather arbitary sized thing. You can't turn that around overnight because people would still need the old-style sizes in order to repair existing structures. Doors have to fit into door frames. You couldn't expect stores to stock twice as much stuff - half metric and half old-style.

Things go deeper than that. In medicine the Americans use "grains" as their unit of weight for pills and such. The abbreviation for "grain" is "g" - which is the same as "gram"...which is the traditional unit for drugs in the metric world. Now you have to administer a change-over period in which tens of thousands of patients are at terrible risk of being over-dosed or under-dosed.

It's VERY tough. The UK only did it because the rest of the Europeans had already done it - and joining the European community was the way ahead. The US have no such problem.

SteveBaker (talk) 05:18, 5 September 2008 (UTC)

See Metrication in the United States. Metrication in the UK is far from complete; see Metrication in the United Kingdom.--Shantavira|^{feed me} 07:45, 5 September 2008 (UTC)

Technically, the entire U.S. systems is based on the metric system, anyway -- it's just that the ordinary person doesn't know and doesn't care.

The U.S. is a large country; its two largest neighbors, Canada and Mexico, have little influence on how things work inside the U.S. And, as far as that goes, in Canada everyday measures like road-sign distance (in kilometers) or gasoline volume (in liters) have only been metric for 30 years.

As with Canada, where there was also great resistance to the switch, the U.S. will gradually shift.

This is an example of how technological innovation works: it's easier to change when you're not dragging a whole lot of infrastructure. In 1955, nearly 83% of Swedes opposed the idea of a switch from driving on the left to driving on the right, though the change did take place on Sept. 3, 1967 (happy belated anniversary, Dagen H). --- OtherDave (talk) 10:50, 5 September 2008 (UTC)

I can't begin to imagine how bad that must have been - if you drive a car on the side of the road for which it was not designed - then overtaking on a two- or three-lane road becomes a lethally dangerous activity. I've driven my (British) right-hand drive car in France - and I have a right-hand drive car here in Texas too (although I don't drive it on the roads much) so I've done this a bunch of times. Overtaking is a really dangerous thing because you have to pull all the way out into the oncoming traffic's lane before you can see what's coming. Even on a multilane road, pulling out from behind a big truck is dangerous if there is a vehicle in the outside lane is going really slowly for some reason. The Swedes must have known this going into it - but I wonder how many people died for that change before the majority of old "wrong side" cars were finally off the roads?

One problem with metrication is that you've got to start educating people into the metric system from way before you start using it. In the UK, I was in the first group of kids to be taught both systems in parallel - that would have been in the early 1960's - so the education process started a good 10 years before the switch began...and the switch is still going on today! More confusing still - we Brit's also changed our currency from it's old mixture of base-12 and base-20 counting to a decimal system around the same time. That wasn't such a horrible mess though - the switch was actually completed a few years ahead of schedule.

As our article says - just the cost of replacing two million road signs (it would be a hell of a lot more than that here in the USA) is frightening. It's not just the cost of making the signs - you have the cost of installing them - and the difficulty of finding them all! Since existing signs typically round distances to the nearest quarter mile for junctions and to the nearest mile for longer distances - you can't simply convert the miles indicated on the old sign into kilometers and round off the result - because the sum of the two round-off errors could add up to a more-than-1km error in the finished sign. You'd have to go out there and re-measure the distances...and in some cases, reposition the signs pole/gantry. You could easily spend several billions of dollars on that alone. SteveBaker (talk) 11:39, 5 September 2008 (UTC)

For what it's worth, according to Dagen H, most Swedes had left-hand drive cars before the switch, which did cause more accidents, and that was one of the arguments for the switch. I suppose there would be at least minor health and safety benefits to having a single system of units in use throughout the world. It would have saved the Mars Climate Orbiter. :-( -- BenRG (talk) 14:59, 5 September 2008 (UTC)

Just to clarify something SteveBaker brought up in his first reply. We have 2x4's in Canada and that's what we call them. We've never "converted" them to anything else. In a way, building materials like that are the easiest to change because the 2" by 4" is unreal (to the end user) to begin with. Canadians call them 2x4s, we just don't call them 2 inches by 4 inches and the problem goes away. I don't think anyone suggests that switching to metric would be a simple thing for the US, but many of the concerns I've read are more hand-wringing than anything else. Afraid grams and grains might be confused? Then do what we did and use milligrams instead of grams. Don't want to remeasure all your roadways? Then don't and just have them precise (1.7km to next exit) and relocate them later if you really want to. Matt Deres (talk) 12:54, 5 September 2008 (UTC)

To clarify further, a 2x4 isn't 2 in. by 4 in. anyway, at least not when you buy it. Dimensional lumber says it is actually approximately 1+1⁄2 in × 3+1⁄2 in (38 mm × 89 mm) "due to planing and shrinkage as the board is dried." -- 128.104.112.147 (talk) 19:21, 5 September 2008 (UTC) Whoops - just noticed Steve already said that.

Just so we're clear, the UK metrification-process is a lesson in how not to metrify. We measure distance in miles (there was no big switch over of signs), sell petrol in litres, but measure fuel economy in miles per gallon. (As with everything, we have to give the metric equivalent as well, but no one could tell you whether, for example, 10km/litre was good or bad. I certainly couldn't. We also have our own 'british' gallon which 90% of people couldn't convert to a US-one. Or litres for that matter). We measure ourselves in pounds (and stone) but the doctor (and our gym) will ask for our weight in Kg.Similarly, i conducted my whole education in metric (up to and including a maths degree), but couldn't tell you intuitively how tall someone was without using imperial. I would love nothing better than to go fully metric but it just won't happen until a couple more generations. Maybe as americans are generally less parochial and twee they might find it easier adapting. 82.22.4.63 (talk) 17:08, 5 September 2008 (UTC)

Thanks for the clarification; I'm laughing at the notion of gas sold by the liter but used as mpg. I know that Canada used the imperial gallon, a source of endless confusion to Americans even in pre-metric days (along with the strange-colored money and that peculiar letter at the end of the alphabet). For most people, the late Thomas Gilbert thought that learning conversion math was pointless. He developed mnemonics -- e.g., for the temperature outside -- "20 is plenty; 25, swim and dive" -- because in that setting, you just want do know if you need a coat (or gloves, or a swimsuit). --- 22:26, 5 September 2008 (UTC) —Preceding unsigned comment added by OtherDave (talk • contribs)

Why do celestial bodies spin and/or move in a circular motion?

Planets, suns, even entire galaxies all spin and/or move in a circle, and never stop. Why is this? What is causing this momentum? Stranger still,- all tiny bodies (atoms, electrons, etc.) seem to have this quality. Why only the very small and the very big? Now technically an electron doesn't revolve around the nucleus, but it is a useful way of thinking about it, and it's close eneough to make my point here. Anyways, it seems odd that here at our medium mass perspective nothing seems to spin on its own.Hey, I'm Just Curious (talk) 04:09, 5 September 2008 (UTC)

Well, technically, they move in ellipses - not necessarily circles. But the reason is this: If there is no friction and no air resistance then there is nothing to stop the object from moving (any object - not just suns and moons and such). Newtons' laws of motion say that if there are no forces acting on an object, it'll travel in a straight line at constant speed forever. Here on earth, it's just about impossible to get rid of the friction and air resistance - so we tend to have the "gut feel" that objects ought to slow down and stop eventually - but that's not how the universe works. So that's why they keep moving forever.

Why they travel in elliptical/circular orbits is because of gravity. Throw a rock in a dead straight line towards the horizon and it'll start maybe four feet off the ground and arc downwards in a parabola and hit the ground a few feet in front of you. Throw it a bit harder - and it'll go further forwards before it hits the ground. Now - the earth is curved - so if you throw the object REALLY hard (actually a lot harder than you could ever really throw it) - it would go so far forwards that by the time it had fallen four feet, the earth would have curved away beneath it by MORE than four feet. Instead of getting closer to the ground, it would shoot off - getting higher and higher above the ground until eventually, it ends up in space. If you throw it at EXACTLY the right speed, the rate at which it falls would EXACTLY match the rate at which the curvature of the earth causes the ground to fall away beneath it. So in the time it falls 4 feet - it would have travelled so far towards the horizon that the ground was exactly four feet lower - when it falls four more feet - the ground fell away four feet more than that. It would NEVER hit the ground! If there were no air resistance - it would "fall" around the earth forever travelling in a perfect circle. That's an "orbit". So the moon (for example) is just like your rock - it's travelling so fast around the earth that it falls exactly fast enough to avoid hurtling off into space and to avoid hitting the earth. The exact same thing happens as the earth goes around the sun - or the sun goes around the galactic core. So this is how you get perfectly circular orbits.

What happens in space if the object is going just a little bit too slow to stay up in a circular orbit? Well, that's the kind of thing that happens with comets. They aren't going quite fast enough to stay in a perfect circle - so they start to fall closer to the sun. But as they fall for so long (years!) they gradually speed up - and when they get going fast enough, they are going too fast to stay in a circular orbit - so they swing around the sun and shoot off outwards again. Now the sun's gravity is slowing them down - so they go slower and slower until they start falling back towards the sun. They keep this up pretty much forever - orbiting in huge ellipses.

The idea that electrons are little "planets" orbiting the atoms nucleus "sun" is flat out WRONG - it was thought to be true a hundred years ago - and it was (lamentably) still taught in schools in Texas as recently as a couple of years ago - but it's WRONG! So forget that. An electron is a tough thing to pin down - you never really know exactly where it is because in some sense, it isn't in just one place. There is a "probability cloud" - imagine a fuzzy ball of "maybe there is an electron here"-ness surrounding the nucleus. Hence there is no similarity and the question can be "un-asked" rather than answered.

The reason things at "human scale" don't ever seem to keep moving forever is simply that we live in an environment that's full of gas and rough surfaces. Friction and air resistance are absolutely everywhere humans live - so nothing seems to be obeying Newton's laws (they are - but the friction and air resistance apply forces to them). But the guys in the International Space Station are only too familiar with things that move essentially forever. Their home up there is doing exactly that. (Although there is still a teeny-tiny amount of air up there at 300 miles above the earth - so there is still a teeny-tiny bit of air resistance and eventually it would fall back to earth if we left it alone. Hence, each passing Space Shuttle or Russian resupply ship gives it a bit of a nudge to keep it going - and it has some small engines of it's own that could be used for the same thing.

If we were peculiar aliens who lived in deep space without need for air - we'd be surprised that on Earth everything slows down and stops.

SteveBaker (talk) 04:32, 5 September 2008 (UTC)

Pump Stalling Phenomenon

What is the pump stalling phenomenon in case of centrifugal pumps as well as positive displacement pumps?--Ashish V. Kulkarni 05:40, 5 September 2008 (UTC) 05:11, 5 September 2008 (UTC) —Preceding unsigned comment added by Ashishkulk (talk • contribs) 04:55, 5 September 2008 (UTC)

There are two ways that a pump can stall. Assuming a pumping a liquid:

1. if the input is restricted enough the reduced pressure inside the pump will cause cavitation;
2. if the output is blocked, a positive displacement pump will stop. Saintrain (talk) 13:34, 5 September 2008 (UTC)

A positive displacement pump should always have a relief valve in the output ahead of wherever a valve could restrict flow, to prevent breaking the pump or bursting a pipe. Positive displacement usually means the liquid flows or something breaks, beyond merely stalling.Edison (talk) 15:00, 5 September 2008 (UTC)

Cavitation can also occur when you are using the pump at the top of a pipe to pull liquid up too great a vertical height - the maximum height you can pump water that way is about 32 feet for example. Similarly - the output doesn't have to be blocked (even partially) to stall the pump - there could simply be too much output pressure due to the height the liquid has to be pumped. SteveBaker (talk) 12:32, 6 September 2008 (UTC)

sound waves

1. Strike one of the tuning forks with a rubber mallet or the bottom of a rubber soled shoe. Do not hit the tuning fork on a hard surface, doing so, may damage the tuning fork. Listen to the sound. Now press a button on the telephone and listen to the sound generated through the earpiece. Which sound do you think is more complex? Explain your answer. 2. Compared to the tuning fork and the telephone dialer, is the sound of a person humming, a simple or a complex sound. 3. Try pressing the buttons on the telephone dialer. Can you observe any order to the tones? Does the pitch get higher or lower for larger numbers, or does it seem to be random. 4. How do you think the phone company recognizes the numbers that you dial? —Preceding unsigned comment added by 124.43.195.66 (talk) 05:03, 5 September 2008 (UTC)

Please do your own homework. However, you might want to review harmonics. --Kjoonlee 05:09, 5 September 2008 (UTC)

You can answer this question yourself by following the instructions given to you by your lab (i.e. the instructions you give us). The question is asking for your opinions and observations, so there are actually no wrong answers to these questions if you actually follow through with the directions. For future reference, we will not do your HW for you here per policy, but you can at least try to disguise your assignments with a little more guile in the future. --Shaggorama (talk) 05:12, 5 September 2008 (UTC)

Actually, Touchtone or Telephone keypad should be consulted as well as harmonics. But in essence: tuning fork: one pitch, sine-wave with few overtones (i.e. simple waveform); human voice: one pitch, complex overtones; Touch-tone phone keypad: two pitches, each with a simple waveform. - Nunh-huh 06:06, 5 September 2008 (UTC)

My god. You took the time to type out verbatim your assignment. And now you are waiting with baited breath for answers from the internet. If you had just done the assignment as it tells you to you'd be done by now. You get an epic fail. --98.217.8.46 (talk) 13:02, 5 September 2008 (UTC)

"Baited breath" - what are you trying to catch? ;) Franamax (talk) 07:09, 6 September 2008 (UTC)

fatigue

comparison of stress at fillet radius and bending stress at uniform sections —Preceding unsigned comment added by 196.21.39.11 (talk) 08:09, 5 September 2008 (UTC)

There are people here. People need to be talked to in complete sentences. Can you please make some effort in that direction? You don't want to waste this resource by sending them on the wrong path, do you?. --Ayacop (talk) 08:51, 5 September 2008 (UTC)

Our articles on fatigue (engineering), fillet (mechanics) and stress concentration might help you, but, as Ayacop says, you need to ask a clearer and more specific question if you want more pertinent help. Gandalf61 (talk) 09:36, 5 September 2008 (UTC)

Not to pile on you here, but seriously, asking "questions" like this is pretty much ridiculous. No one can even properly figure out what you're talking about, much less what you want to know. And, unfortunately, a lot of people do this. Just asking an actual question would be a big help, and providing just a tiny bit of context would go a long way -- and by that I mean that you're going to get a lot more and better answers when people don't feel like pounding a nail into their forehead when they see yet another more or less incomprehensible post. -- Captain Disdain (talk) 11:01, 5 September 2008 (UTC)

If you mean making stress calculations for weldments using a technique similar to the standard method for uniform sections, take a look at this page. Note thought that these are calculations for stress, not fatigue. Fatigue is the result of repeated applications of stress, so you don't get an answer measured in "lbs per sq.in." or anything like that. Franamax (talk) 07:05, 6 September 2008 (UTC)

matchwood

What timber are matches most commonly made from? —Preceding unsigned comment added by 143.238.144.179 (talk) 10:51, 5 September 2008 (UTC)

Mainly aspen and white pine. Axl (talk) 12:02, 5 September 2008 (UTC)

Remember it only takes 1 tree to make a thousand matches, but it only takes one match to burn a thousand trees... 194.221.133.226 (talk) 12:43, 5 September 2008 (UTC)

For those who are confused by the response... 81.174.226.229 (talk) 13:01, 5 September 2008 (UTC)

If someone is getting only one thousand matches out of a tree, either they are cutting baby trees or they have an incredibly wasteful cutting process. Wanderer57 (talk) 17:34, 5 September 2008 (UTC)

I'd say around 5000. JessicaThunderbolt 19:05, 5 September 2008 (UTC)

There is a long tradition in both western and other cultures of using the names of specific large numbers (like "a thousand") to metaphorically refer to an indeterminately large amount. (e.g. when the Nazis referred to "the Thousand Year Reich", they weren't intending to give back Poland come September 1, 2939.) I'd link to an article, but we don't seem to have "Metaphorical use of large numbers", and the articles "large numbers" and "thousand" don't show anything promising. -- 128.104.112.147 (talk) 19:15, 5 September 2008 (UTC)

If I've heard that once, I've heard it a thousand times. --- OtherDave (talk) 02:23, 6 September 2008 (UTC)

Origin of life

What are the probabilites that universal common descent isn't actually true, and that life on Earth is in fact polyphyletic? Couldn't it be that life arose a few times on this planet, and that the basic similarities between living beings are just convergent adaptations to the same selective pressures? Leptictidium (mt) 12:06, 5 September 2008 (UTC)

Pretty unlikely, if you look at DNA and RNA codes there is ample opportunity for variations, but only small variations occur. And the basic biochemistry seems to be the same for all organisms, there is no detected radically different pathways around suggesting a different source of genomes. If you take a look at the book of Genesis in the bible you can see there were three special acts of creation, with the universe, sea creatures, and humans being the three things created and not made. But in any case you can be pretty sure that human DNA has come from animals. Graeme Bartlett (talk) 12:32, 5 September 2008 (UTC)

You might want to look at abiogenesis you question is discussed ever so briefly here. There are arguments that life is may still originating around volcanic vents at least from the theory I prefer Iron-sulfur world theory(metabolism first). How far this new life gets before more advanced life gets a hold of this proto-life-matter isn't very far. So it is very likely that life started in multiple places, and still is, it just can't out do the life that is already established. This is supported, since, we generally don't see life with proteins and DNA of different Chirality (chemistry) we see homochirality. It is likely that origin sources with different chirality were quickly out competed by sources with a common chirality that could combine traits into a single more advanced system (likely a pre-genetics world). The choice of chirality seems random and there is the possibility that there is a planet of life in the universe that is our molecular mirror, take a look here. A very neat subject that is only studied in a limited way. I hope that helps.--OMCV (talk) 12:33, 5 September 2008 (UTC)

Chances are genetic material was not the first biological matter. See abiogenesis for metabolism first vs genetics first (RNA_world_hypothesis). Amino acids and the resulting proteins are far simpler than nucleic acids acids and their polymers. This makes it more likely that amino acids would form and self replicate before the formation of the more complex coding system for self replicating. An analogy would be: there is machinery that works without software but there it no software that works without machinery. Back to biology, glycine is only C₂H₅NO₂ while adenosine is composed of adenine and a sugar molecule for a grand total of C₁₀H₁₃N₅O₄ before adding phosphates. Sure all the other amino acids are more complex than glycine but its variation at one position. In contrast all nucleosides are made of nucleobase, sugar, and up to three phosphates. This means you need to locate these three pieces before you can make DNA. An inorganic metal center with amino acids as ligands which used available substrate to make more amino acids, a proto-self-propagating-enzyme, was probably the first form of life. As far as the bible is concerned, it is generally not a good source of scientific knowledge even if it has significant spiritual and allegorical knowledge as Augustine of Hippo pointed out very early on.--OMCV (talk) 13:43, 5 September 2008 (UTC)

Yeah, but who would trust a hippo? I wouldn't. --98.217.8.46 (talk) 14:43, 5 September 2008 (UTC)

Your comment is blatantly hippocritical. -- BenRG (talk) 15:04, 5 September 2008 (UTC)

One thing the above comments don't address is that "life" in a basic form might have emerged multiple times on the early Earth only to have the gene pools merge together. Lateral gene transfer, i.e. the transmission of genes between non-descendent organisms, is well-documented at various times in history and among various kinds of bacteria. Many of the hypotheses about what the first life may have consisted of point to organisms with far less stable genetic material and less structured cell membranes, which increases the probablity that if cell-like life arose more than once then the different strains could have exchanged genes. Do enough of that and even independently originating life forms could come to share a common genetic heritage. Dragons flight (talk) 19:31, 5 September 2008 (UTC)

The issue with lateral gene transfer is that in order for organisms to share genetic material they have to have the same type of genetic material. To be the same it means the genetic material has to have the same chirality (chemistry) (in multiple locations) and the same coding system for proteins. Its becomes statistically questionable whether life got all the way to genetics material twice because once would be enough. Once life gets to genetics it becomes a collaborative effort with gene trading galore probably even some amount of advancing or cleaning up of the genetic code. Surely whatever came up with genetics blew everything else out of the water. What I mean by blew them out of the water is that they ate the matter that might have been proto-life (and still do). This all ads up to an explosion of life. All "important" life is likely descended from the system that figured out genetics everything without genetics would be left in their biological dust. If earth was void of life (in theory) it might take a very short amount of time for life to develop here. But the reality is that there is so much life here any new comer "proto-life" gets chewed up by those of us with a foothold. Thanks for the comment, Dragon, I just wanted to expand on it.--OMCV (talk) 20:02, 5 September 2008 (UTC)

You assume they have to be the same, when in fact they merely have to coexist well together. Maybe organisms from your iron-sulfur world met other organisms from an RNA world.  ;-) If one had superior genetic structures and the other had superior metabolic pathways they could complement each other even if initially they had entirely seperate approaches to life. Perhaps it was only later that the connection between genetic material and proteins was made. Its more radical than traditional lateral gene transfer (since in particular we are talking about an era before traditional genes), but it is possible, at least in principle, to imagine that some of the features we see as belonging to all cells today orginiated in independent strains of life. Dragons flight (talk) 20:19, 5 September 2008 (UTC)

I get what your saying; critter (a) developes genetics even though it might not have the best proteins at the time. Critter (b) has better proteins or at least a few the first critter doesn't. As long as they don't kill each other it likely that critter (a) and (b) will exchange chemical systems. I'm no biochemist I don't know if the enzyme or system exists now, but surely there has been a mechanism to produce genetic material from proteins. Its just the microscopic reverse of todays standard direction of making proteins from DNA. If critter (a) had this mechanism it could run around finding all the valuable proteins and record their sequence for posterity. Very good point and neat stuff.--OMCV (talk) 21:18, 5 September 2008 (UTC)

Inducing hyperthyroidism to lose weight?

Are there examples of people trying to ramp up thyroid hormone production (or taking thyroid hormone pills) in order to increase the basal metabolic rate to lose weight? How successful is this approach, or does it likewise increase hunger and cause you to eat more? (not for school) — BRIAN0918 • 2008-09-05 15:25Z

Yes, there are examples. Indeed it's a classic MRCP question. It does cause weight loss. However there are several harmful effects of excessive thyroid hormone levels. After ceasing levothyroxine, the person regains weight. Many of these people have co-existent psychiatric illness that may complicate the clinical picture. Axl (talk) 16:54, 5 September 2008 (UTC)

Interesting. So in order to maintain the weight loss, you would have to continue taking the pills, or exercise more (since apparently eating less simply reduces BMR). When you mention psychiatric illness, are you implying that the excess levels caused mental problems, or simply that the example you cited involved people with mental problems, reducing the certainty of the amount of weight loss caused by thyroxine? — BRIAN0918 • 2008-09-05 16:58Z

According to de:Thyroxin (but without refs), other problems are that increase of metabolic rate can be completely revoked by simply eating more, so you'll be probably hungry (and if that is okay with you then why not simply eat less beforehand?). Also, insulin resistance is increased, the heart and circulatory system is stressed, and for women during menopause osteoporosis risk increases. Finally, hormone and TSH values should be checked constantly if you want to do it right. --Ayacop (talk) 17:11, 5 September 2008 (UTC)

Regarding psychiatric illness, the people who abuse levothyroxine in this way usually have an eating disorder (anorexia nervosa or bulimia nervosa) before commencing levothyroxine. Axl (talk) 17:19, 5 September 2008 (UTC)

And hair loss. Let's not forget about hair loss.  :) OK maybe just with a thyroid storm. OrangeMarlin ^{Talk• Contributions} 23:34, 5 September 2008 (UTC)

It's been used...and it's not a good option. TH regulates many different processes in the body and there can be severe cardiac and bone issues, for example, in those out-of-balance. Here's a case of periodic paralysis from abusing thyroxine. — Scientizzle 23:51, 5 September 2008 (UTC)

americium in smoke detectors

so, how much americium is exactly in an average smoke detector? I know the article says 'less than a milligram' but that's trivially true with a cost of ~$160/mg. --Ayacop (talk) 15:27, 5 September 2008 (UTC)

This says 0.2mg of Americium Dioxide. Fribbler (talk) 15:34, 5 September 2008 (UTC)

Ah, thanks. That's still ~$30/detector but you can get them for much less. So either the file or the price is wrong. --Ayacop (talk) 15:36, 5 September 2008 (UTC)

Google thinks that about $1500 will buy you a gram of americium-241 dioxide. Algebraist 15:51, 5 September 2008 (UTC)

So we're down to 30 cents per detector. — BRIAN0918 • 2008-09-05 16:00Z

If you took the price from [22], note that the $160/mg price is for the isotope Americium-243, whereas ionisation smoke detectors contain Americium-241. Gandalf61 (talk) 15:52, 5 September 2008 (UTC)

Lower cost if you buy in bulk? — BRIAN0918 • 2008-09-05 15:58Z

Certainly too. All my questions have been answered. Thanks again. --Ayacop (talk) 16:50, 5 September 2008 (UTC)

The article says that Americium-241 is fissile with a critical mass of 60 kg (bare, unreflected sphere). Does that mean that with a mere 300,000,000 smoke detectors you'd have enough of the stuff for a nuke? Someone alert the media—this could be the next big thing to get worried about! ;-) --98.217.8.46 (talk) 19:34, 5 September 2008 (UTC)

Radioactive boy scout. Dragons flight (talk) 19:42, 5 September 2008 (UTC)

Right, but even he never tried to make a pure-Americium weapon... --98.217.8.46 (talk) 20:43, 5 September 2008 (UTC)

Monkey wedding

What is the reason of this wedding? Does this serve any purpose? Otolemur crassicaudatus (talk) 15:46, 5 September 2008 (UTC)

It serves about the same amount of purpose as spamming a bunch of nude images on FPC, or linking to this story on RD/S, I reckon. — BRIAN0918 • 2008-09-05 16:17Z

The caption answers your question: "The widlife park organized the wedding in the hope of attracting more visitors, local media reported." Thats about it. Fribbler (talk) 15:51, 5 September 2008 (UTC)

Withdraw post. I should have asked this in Wikipedia:Reference desk/Miscellaneous or Wikipedia:Reference desk/Entertainment, My mistake I asked it in science ref desk. Otolemur crassicaudatus (talk) 16:43, 5 September 2008 (UTC)

Hmm, so you think you'll get a 'better' answer there? 86.4.187.55 (talk) 19:21, 5 September 2008 (UTC)

Yoghurt phobia

I have a phobia if yoghurt, I cant touch it, have it 2 close to me or anything or I will just freak out or breakdown crying. REcently to try an overcome my fear I tryed touching an unopened 'Activia' yoghurt and I almost had a panic attack, also I got a pot of 'Ben and Jerrys chocolate brownie' frozen yoghurt and put my spoon in, poured all the frozen yoghurt off and put my tongue on the spoon, the day I did that I felt completely sick and couldnt eat anything, and was depressed, for the rest of the day. I am slowly dealing with it, those two occasions were big steps, but I was just wondering if there was a name for this phobia or it was common or regognised? 82.16.111.72 (talk) 20:34, 5 September 2008 (UTC)

You really ought to seek professional advice. Other than that, no, it's not got a fancy Latin name and it is not common or recognized as a specific phobia. If it did have a specific name it would probably be Iogurtophobia or something like that (judging from the Latin Wikipedia page for Yoghurt).--98.217.8.46 (talk) 20:41, 5 September 2008 (UTC)

Call it a hunch: but I suspect your condition might have a lot to do with being a bored thirteen year old without much time on his hands who is looking for lulz. Magog the Ogre (talk) 21:27, 5 September 2008 (UTC)

We have a list of phobias, but "fear of yoghurt" is not on that list. On the other hand, it is very common for people to have an aversion to a particular food or ingredient to the extent that they cannot even bear the smell or the sight of it. Gandalf61 (talk) 08:55, 6 September 2008 (UTC)

Cyst or what?

I had what my dermatologist called a cyst under my skin, and I just popped it out. It's a small black capsule and I was just wondering what it is exactly. Coolotter88 (talk) 21:12, 5 September 2008 (UTC)

Have you read Cyst? --Tango (talk) 22:03, 5 September 2008 (UTC)

Yes, I didn't find any help there :( Coolotter88 (talk) 22:18, 5 September 2008 (UTC)

I'm not going to do it myself, but it's very, very likely that this question is going to be removed. The only person who can tell you what it is is someone who can look at it with their own two eyes and give you a professional answer.--El aprendelenguas (talk) 22:58, 5 September 2008 (UTC)

It sounds like the OP has already treated the condition themselves, so this isn't really a request for medical advice. Idle curiosity about medical matters is an appropriate topic for this desk. --Tango (talk) 23:26, 5 September 2008 (UTC)

That is correct, I'm not asking for medical advice, I'm just curious what this thing is that came out of my body. It is a capsule about 1-2 millimeters long. It is fairly hard as I can't crack it with my nail (okay, we're not comparing gemstones here, so yeah). Coolotter88 (talk) 23:31, 5 September 2008 (UTC)

What Tango is saying is that we don't do medical diagnostics here. We leave that to House (TV series) and ER (TV series), both fine TV shows. Really, bring it to your physician. OrangeMarlin ^{Talk• Contributions} 23:33, 5 September 2008 (UTC)

Another way to put it so the OP may possibly understand... Claiming "It's a small black capsule" does not narrow it down to one or two things. It narrows it down to a few thousand (if not more) things. Do you honestly believe that getting a list of a few thousand things that appear to be hard black capsules will provide you any help in any way? Of course not. Take it to a doctor and get a real answer. -- kainaw™ 23:54, 5 September 2008 (UTC)

Have you been hanging out in the jungles of South America recently? -- 71.125.61.216 (talk) 02:38, 6 September 2008 (UTC)

Did it look like these little capsules[23] sometimes found under the skin? Edison (talk) 03:55, 6 September 2008 (UTC)

Some more information like what age are you and where was the cyst would be helpful. However I am going to suggest the most likely possibility. It is a dried up sebaceous cyst (aka comedo) that has encapsulated and separated itself from the surrounding tissue. It is hard because all the oily cheesy secretion and skin flakes have concreted together. I'd be interested to hear what the 'few thousand' other possibilities might be. Richard Avery (talk) 10:28, 6 September 2008 (UTC)

Thank you, that's probably what it is, I was just looking at sebaceous cyst and I had asked my mom what it was (she used to be a doctor). She said the most likely thing was that it was a dried up cyst. That's a good enough answer for me. Coolotter88 (talk) 11:20, 6 September 2008 (UTC)

Need a 3D anatomy applet

Dear Wikipedians:

I'm taking a gross anatomy course right now and am in desperate need of a 3D human anatomy applet that could be run from the browser. Any pointers?

Barring that, are there any good 3D human anatomy software out there?

Thanks,

76.65.15.205 (talk) 22:34, 5 September 2008 (UTC)

Would something like the Visible Human Project do? At the bottom of the article are several links to online viewers. SteveBaker (talk) 02:10, 6 September 2008 (UTC)

September 6

Potassium Carbonate as a Fire Supression Agent

The Scientific American website currently has a news story [24] about a fire suppression "grenade" which uses potassium carbonate as its active ingredient to suppress fire "at the molecular level". It appears that potassium carbonate/potassium bicarbonate is a common ingredient in fire extinguishers (e.g Purple-K). However, none of those pages mention how it works, except for Purple-K saying it "directly inhibit[s] the chemical chain reaction", with the CO₂ smothering being relegated to a minor role (as expected, since potassium chloride also works in fire suppression). - So what is the mechanism for potassium (bi)carbonate fire suppression? -- 128.104.112.147 (talk) 00:19, 6 September 2008 (UTC)

This old patent seems to indicate that part of it is that heating potassium bicarbonate will release both CO₂ and H₂O. Perhaps that has something to do with it? (I'm no chemist) --98.217.8.46 (talk) 00:45, 6 September 2008 (UTC)

See HowStuffWorks --Russoc4 (talk) 02:36, 6 September 2008 (UTC)

I'm pretty sure I sure something on one of Adam Hart-Davies's shows, where he demonstrated glass fire extinguishers (probably Victorian era). They were roughly grenade shaped and sized, and contained bicarbonate of something. DuncanHill (talk) 09:48, 6 September 2008 (UTC)

Consider two Cockatiels, A and B...

Both birds are the same sex and age. Both are descended from many tens of generations of captive-bred stock. Both have been parent raised and kept in an aviary with others of their own kind for their whole lives. A lives in England. B lives in China.

Now suppose that A and B were to be introduced to each other in aviary conditions. Would they be able to communicate and interact with each other in the same way as two wild Cockatiels of the same age and sex from roughly the same area in their natural habitat would - or would there be a significant 'language gap'? --Kurt Shaped Box (talk) 01:23, 6 September 2008 (UTC)

Good question, and I can only imagine they could at least communicate basically. After years of separation in the New World, Americans simply developed a different language from their English ancestors, they don't speak a strange unrelated language called American. Further, any normal bird doesn't answer direct commands like a dog - "sit, fly" etc. Unless, like a parrot, it learns to talk, it's Chinese speaking owners are hardly going to morph it into a different "bird language." Unfortunately it would take a long time to find out, though.78.144.137.205 (talk) 08:51, 6 September 2008 (UTC)

If they wanted to sit around and discuss the current political situation then clearly they would need a common language. But what sort of communication are we talking about. I have never kept these birds but most of their communication is about posture, eye contact, squawking, pecking and scratching. Wouldn't all of that stuff be genetically hard-wired? If you went to a country where you spoke not a syllable of the language I'll bet you could communicate quite a lot without speaking - facial expressions for starters. A smile is a smile and a frown is a frown wherever you go in the world. When you start using language that moves the personal interface (can I say that?) to a higher plane, one not necessarily available to even sibling cockatiels. Richard Avery (talk) 10:17, 6 September 2008 (UTC)

There are really four possibilities here:

1. That parrots learn "language" (or body language or whatever) from their parents. In which case, in your thought experiment, it's likely that the chinese birds would have gradually drifted from the original language - but would that be enough so they couldn't communicate? Who knows? However, you could test this hypothesis with a bird raised entirely by humans who could not have learned from a parent bird and in just one generation would have entirely lost the ability to communicate with others of its species.
2. That parrots have language built in at the genetic level as an "instinct" - and therefore all parrots, no matter how they are raised can communicate.
3. That language is genetic - but that the evolutionary/genetic "drift" would be so rapid that our chinese birds would be unable to understand their English counterparts. This seems unlikely.
4. That parrots don't really communicate with each other much at all making the question entirely moot.

It seems to me that (1) and (4) should be easy to test. If you can eliminate those two then we're down to a genetic/inherited effect - and then if the chinese birds can communicate then it's (2) and if they can't, it's (3).

I presume that such studies have been done for bird-song in general - but perhaps parrots (with their talent of mimicry) are special. That inherent ability to mimic suggests to me that they pick up language from other parrots nearby - so (1) is most likely to be the case and therefore the 'linguistic drift' with the chinese birds may make communication difficult - but perhaps not impossible. But that's entirely supposition based on the idea that mimicry in parrots is there solely to enable them to learn "parrot talk" from their parents and not for some other reason. SteveBaker (talk) 12:25, 6 September 2008 (UTC)

Winter Solstice

Does this help? SteveBaker (talk) 02:05, 6 September 2008 (UTC)

Did the Winter Solstice fall on the 22nd in 1990?

Or how can I track down that info? It's hard to find old calendars... 128.239.177.28 (talk) 01:29, 6 September 2008 (UTC)Capricorn

How about this? -hydnjo talk 02:22, 6 September 2008 (UTC)

Yes, the solstice was at 03:07 UT on 22 December 1990.--Shantavira|^{feed me} 08:20, 6 September 2008 (UTC)

The answer depends on where in the world you live. The solstice occurred at the same absolute instant everywhere inthe world. This was 1990-12-22-0307h UTC, but this was 1990-12-21-2207 EST.-Arch dude (talk) 11:31, 6 September 2008 (UTC)

And if you happened to be in the southern hemisphere, then the winter solstice was at about 15:38 TDT on the 21st of June. Algebraist 13:27, 6 September 2008 (UTC)

Drugs that daze or slow down?

1. What category of drug generally slows down your movement or walking speed?
2. What category of drug drug puts you in a daze, e.g. making you only able to do one thing in the time it would take you to do 2 or 3?

(Or names of specific drugs with these effects)--Sonjaaa (talk) 02:18, 6 September 2008 (UTC)

Depressants. --Tango (talk) 02:22, 6 September 2008 (UTC)

Alcohol (EtOH) being the most prevalent. -- MacAddct  1984 ^{(talk • contribs)} 02:33, 6 September 2008 (UTC)

Thorazine is somewhat legendary in it's ability to put people into a slow-moving, slow-witted daze. --Kurt Shaped Box (talk) 02:47, 6 September 2008 (UTC)

1. Drug-induced parkinsonism, notably antipsychotics (of which Thorazine (chlorpromazine) is one). Axl ¤ [Talk] 10:00, 6 September 2008 (UTC)

Maximum Water Vapor In Air

Why is there a specific maximum amount of water vapor that can exist in air at specific temperatures? A similar question would be 'Why is there a dew point temperature for each air temperature?'. I have searched the internet (and Wikipedia of course) and have not been able to pick up this answer. 172.168.186.87 (talk) 03:04, 6 September 2008 (UTC)

Have you read dew point? It doesn't have a very detailed explanation, but it has a brief one. If you want more than that, you'll have to wait for someone more knowledgeable to come along, I'm afraid. --Tango (talk) 03:12, 6 September 2008 (UTC)

As this is a phase transition you have a critical point in the system. --Ayacop (talk) 07:06, 6 September 2008 (UTC)

While that is correct, of course, it's hardly helpful to the OP, I would think. Basically, two forces are at work here: entropy favours all the water molecules to be homogeneously distributed in the form of vapour, while the attractive Van der Waals forces between water molecules favour the water molecules to be close (i.e., favours the liquid form of water). Now, if the certain amount of water in the air exceeds a certain limit (or the temperature drops below the dewpoint), the attractive forces become strong enough to overcome the entropic forces and it becomes energetically favourable for the system to separate into two phases (drops of liquid and the existing vapour). In the liquid fase, the energy of the attractions is low, while in the gaseous state, the entropic contribution to the energy is low, and the fraction of water that condensates will be such that the total energy of the liquids droplets and the vapour together will be lower than the energy of a system where only vapour would be present. --baszoetekouw (talk) 09:40, 6 September 2008 (UTC)

Mystery critter

Mystery buglie

Two questions: 1) What is it, and 2) Why do I keep finding them in supposedly-sealed packages of food? --Carnildo (talk) 07:02, 6 September 2008 (UTC)

I don't have an answer for what it is, but I think you should be writing to your local trading standards officer as well as the Wikipedia Refdesk. SpinningSpark 08:07, 6 September 2008 (UTC)

Where do you live and what is the country of origin of the food?--Shantavira|^{feed me} 08:22, 6 September 2008 (UTC)

Is it hairy? Anthrenus verbasci - larva side (aka).jpg on the German wikipedia [[25]] looks similar! In english it might be a Dermestidae larve.--Stone (talk) 09:13, 6 September 2008 (UTC)

No, not hairy. --Carnildo (talk) 09:16, 6 September 2008 (UTC)

Western US, the food is mostly dry goods (flour, noodles, rice, etc.) from the local supermarkets. I'm not sure if they're inside the packages to start from, or if they've taken up residence in my pantry and are eating their way into the packages. I only rarely spot them outside the packaging, and they're invariably dead when I do find them. --Carnildo (talk) 09:16, 6 September 2008 (UTC)

It looks a bit like a Mealworm beetle larva. --baszoetekouw (talk) 09:43, 6 September 2008 (UTC)

It could be a waxworm the larva of one of the family of Pyralidae moths. Try image googling 'waxworm'. Richard Avery (talk) 10:04, 6 September 2008 (UTC)

UK Coal Reserves

The table, entitled 'Proved recoverable coal reserves at end-2006 (million tonnes (teragrams))' in the Coal article, under section 'Production Trends', subsection 'World coal reserves', does not include an entry for the United Kingdom. This source states that there are enough 'untapped coal reserves in the UK to last 400 years.' and this source states that there 'are around 250 million tonnes of coal not yet mined in South Wales' (obviously this excludes the rest of the UK). My question is: Is the table incomplete, are the two BBC reports incorrect, or is there another explanation? I've asked this question on the Coal article talk page, but haven't received a response. Thanks, Daicaregos (talk) 08:24, 6 September 2008 (UTC)

The source for that table has the UK with only 220 million tonnes, which is less than 0.05% of the world total, so wasn't included in our table. The source says that it only includes reserves that are known to be extractable under "existing economic and operating conditions", so perhaps they didn't include all the coal mines in the UK that have been closed with coal still in them. Seems an odd decision - they can be re-opened pretty easily if the need arises. --Tango (talk) 08:06, 6 September 2008 (UTC)

Thanks for your reply, Tango. That makes sense (why it's not on the table). Perhaps the discrepancy between your source and the BBC/Media Wales sources will disappear when they next update their table. We'll see. In the meantime I'll update the United Kingdom, economy section to read reserves of at least 220 million tonnes (It currently says 'The UK has a small coal reserve'. 220 million tonnes doen't seem that small to me though). Would you mind posting the link to the reference please, so I can quote it? Cheers :) Daicaregos (talk) 08:24, 6 September 2008 (UTC)

As usual - let's crunch the numbers guys: Fossil fuel power plant says that a typical coal-fired power station uses 10,000 tons of coal per day. (1 tonne == 1.1 ton) So 220 million tonnes (240 million tons) is only enough to run one "typical" power plant for 24,000 days - about 70 years...or 70 power plants for one year. I'm fairly sure there are more than 70 coal-fired power stations of "typical" size in the UK. So 220 million tonnes is NOTHING...not even a year's supply for the UK. That's hardly a significant reserve - in fact it's such an utterly trivial amount as to be essentially negligable - and it certainly doesn't come close to explaining the "400 years" figure. (And this assumes that no coal is used in other industrial uses - such as coke production - which is needed for steel making and other industrial activities) SteveBaker (talk) 12:09, 6 September 2008 (UTC)

According to one of the tables at [26], Britain uses about 50 Megatonnes of coal a year in electricity generation. I am still digginf for information on the UK's coal reserves, but it should be noted that they declined sharply after the Conservative government's pit closures of the 80s of last century. This is because reserves are usually quoted of coal which is both technically and economically recoverable. The costs of reopening a deep mine are massive (dewatering, propping, ventilation etc), so while the coal may be there, at current prices it isn't worth getting it out. DuncanHill (talk) 12:24, 6 September 2008 (UTC)

And this paper [27] suggests that there is a minimum of 7 billion tonnes of coal in the UK suitable for underground coal gasification. DuncanHill (talk) 12:28, 6 September 2008 (UTC)

Body Temperature

I heard of an unusual feature where some people's body temperatures are higher than average, at about 100-102 degrees Fahrenheit. Is this condition real and is there a name for it if so?CalamusFortis 15:14, 6 September 2008 (UTC)

Hyperthermia is one of the dangers of congenital insensitivity to pain with anhidrosis because subjects won't feel that they heat up due to the anhidrosis, similar to people suffering from quadriplegia who have the advantage of normal perception above the shoulder, so they can change to lighter clothing before becoming too hot due to the anhidrosis. --Ayacop (talk) 16:41, 6 September 2008 (UTC)