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October 19

Sand

what does sand consist of —Preceding unsigned comment added by 72.179.169.101 (talk) 00:18, 19 October 2007 (UTC)

You could try our article on sand. Andrewjuren(talk) 01:30, 19 October 2007 (UTC)

Most often grains of quartz, but some beaches have other minerals, such as coral fragments, or feldspar. Graeme Bartlett 03:14, 19 October 2007 (UTC)

Trebarwith Strand is made of tiny sea-shell fragments, and is beautifully soft and golden. The sand used to be used to manure acidic soils. DuncanHill 15:31, 19 October 2007 (UTC)

Reflectivity

How do you calculate how much light is reflected off an object? Thanks, —Preceding unsigned comment added by Jeffrey.Kleykamp (talk • contribs) 01:16, 19 October 2007 (UTC)

My first guess would be to use a light meter. Andrewjuren(talk) 01:33, 19 October 2007 (UTC)

Use a reflectometer of course! —Preceding unsigned comment added by 88.109.65.125 (talk) 01:47, 19 October 2007 (UTC)

I mean using math to calculate the reflectivity of an abstract object. Jeffrey.Kleykamp 02:00, 19 October 2007 (UTC)

Hmmm, reflectivity you say. Did you look it up? —Preceding unsigned comment added by 88.109.65.125 (talk) 02:07, 19 October 2007 (UTC)

Given what? —Keenan Pepper 06:00, 19 October 2007 (UTC)

For a mirror-like surface, use the Fresnel equations. For a diffusely reflecting surface, Lambert's cosine law is applicable in most cases. See also diffuse reflection. Simon A. 85.127.182.162 13:19, 19 October 2007 (UTC)

Have you looked at Albedo? --Mdwyer 06:08, 21 October 2007 (UTC)

Bass speakers

Why cant they make base speakers that are very small but sound ggod and bassy yet? —Preceding unsigned comment added by 88.109.65.125 (talk) 02:14, 19 October 2007 (UTC)

Try the articles on loudspeakers and woofers. Delmlsfan 03:00, 19 October 2007 (UTC)

One simple way to view it is that low notes or sounds put out by the bass speaker have a long wavelength. They need to move a big volume of air to create a loud sound, so you need a bigger speaker, or transducer to move that air. Also when a speaker cone moves the side moving fowareds pushed the air out of the way, but it will tend to rush around to the other side of the cone, rather than propogating as a sound wave. This will cut the volume especially as you go lower in frequency. THis is alleviated with a large speaker encolsure. Graeme Bartlett 03:13, 19 October 2007 (UTC)

Good sounding bass speakers are much smaller now than they were 40 or 50 years ago, so at least progress has been made. Edison 05:30, 19 October 2007 (UTC)

Also try articles relating to hearing (Equal-loudness contour is one)- human ears are much less sensitive to the same amplitude of bass sounds than higher pitched sounds - so the amplitude of bass sounds has to be bigger to sound 'as loud' - this means the speaker has to move more when vibrating - hence the size - unfortunately this means the answer to you question is no..87.102.7.57 12:07, 19 October 2007 (UTC)

Is there a unit of energy called "Dq"?

I read in a book that ligand field stabilization energy of a transition metal such as manganese can be measured in Dq, for example -20Dq. What is the unit Dq? Misplaced Pages's disambig page for Dq doesn't have it. Shalom (Hello • Peace) 04:38, 19 October 2007 (UTC)

I think it is just kj/mol like any other energy... —Preceding unsigned comment added by Shniken1 (talk • contribs) 08:51, 19 October 2007 (UTC)

Yeah confirmed, kJ/mol :D--Shniken1 08:58, 19 October 2007 (UTC)

Where is it confirmed?87.102.7.57 12:05, 19 October 2007 (UTC)

Please confirm that yoy know what you are talking about before answering.87.102.7.57 12:15, 19 October 2007 (UTC)

A long shot - might you mean Bq, which stands for Becquerel? That's a measure for radiation, and radiation is energy (right?), so it could be taken as a measure of energy. Probably all wrong, what I said here. It's really another way of saying Hz. Or is that all wrong too? DirkvdM 09:41, 19 October 2007 (UTC)

Sorry DirkvdM fully wrong :P.. Bq is number of decays per second, not really Hz (cycles per second). Radiation is not energy, although it has energy... Dq a unit of energy in kJ/mol, don't know what it is called though --Shniken1 09:52, 19 October 2007 (UTC)

Are you sure it's not just a variable like "x" of "Fx" - because a search turns up nothing about Dq as a unit..

Note a unit of energy eg Joules, Calories, Ergs etc have values ie 4.2Calories = 1 Joule or something. A variable doesn't eg if A has f energy in kJ then "f" is not a unit of energy.87.102.7.57 12:04, 19 October 2007 (UTC)

DirkvdM isn't really as wrong as you think. Hz and Bq are both "/s" or "s" in SI base units. --196.210.103.191 08:31, 23 October 2007 (UTC)

I had a discussion about this before. My pov is that if two quantities are described by the same unit then either they are the same thing (if it looks like a banana and feels like a banana and tastes like a banana ... ) or you've got them defined wrong. DirkvdM 08:10, 24 October 2007 (UTC)

I imagine you read something like this http://butane.chem.uiuc.edu/pshapley/312/Lectures/L25/index.html

Here Dq units are energy, but the amount is not defined. So 1Dq could be anything in kJ etc.

Dq is not (of it self) a measure of energy

Dq ARE NOT units of energy.87.102.7.57 12:13, 19 October 2007 (UTC)

I know less than Sergeant Schultz about all this, but I'm starting to think it's "dQ", delta Q or change in Q. "Q" stands for "charge" a lot of the time. Urk. --Milkbreath 12:15, 19 October 2007 (UTC)

Even though you deleted.. Q can mean energy as well as charge - specifically heat . see First law of thermodynamics - (but not in this context)87.102.7.57 12:45, 19 October 2007 (UTC)

Flu shot

Washing hair

Is it necessary to wash your hair for health of hair and scalp or not? If so how often is best? —Preceding unsigned comment added by 88.109.65.125 (talk) 12:22, 19 October 2007 (UTC)

It's obviously not necessary as humans went hundreds of thousands of years without shampoo. The hair itself is dead so "health" doesn't apply to it, but of course the health of the scalp and that of the person the scalp belongs to is reflected in the hair. I can't think of any problem a bit of grime around the scalp would cause - presuming the grime in question isn't made of the sort of toxins that float around in the air of modern cities. --Psud 13:14, 19 October 2007 (UTC)

Yea, but you don't want it to smell bad dude. 64.236.121.129 13:41, 19 October 2007 (UTC)

People doing fieldwork in remote areas commonly go weeks between hair washes, in fact between washes at all. Your body quite quickly achieves a steady-state, it's not really objectionable, as you get used to your own smell. Still need hand washes for hygeine reasons of course, but otherwise not a problem, as long as someone else isn't downwind. Mikenorton 14:12, 19 October 2007 (UTC)

If only smell is a problem, can one use some sort of hair scent/ deodorant etc? —Preceding unsigned comment added by 88.109.246.205 (talk) 22:17, 19 October 2007 (UTC)

You might like the Dreadlocks article. There's a product available in the US called "Shower to Shower", I think. It appears to be a cornstarch- or talc-based powder that absorbs oils and greases, and also deoderizes. The scent problem has a sort of diminishing returns problem. After a while instead of smelling like stale human, you start smelling like stale Patchouli. --Mdwyer 06:06, 21 October 2007 (UTC)

Biology

What do conjugation and binary fission have in common? —Preceding unsigned comment added by 68.209.98.104 (talk) 13:02, 19 October 2007 (UTC)

They both have wikipedia articles: conjugation & binary fission.--VectorPotential 13:05, 19 October 2007 (UTC)

hint - think about what happens to the DNA. --VectorPotential 13:40, 19 October 2007 (UTC)

• One commonality is that I know a lame joke about each (sort of):

1. Q: What did the sign on the physicist's door say? A: "Gone fission"
2. Q: Why did the grammar teacher enjoy being in prison? A: All the conjugal visits!

Thank you, I'll be here all week. --Sean 13:47, 19 October 2007 (UTC)

heart attack!

"The appearance of some isozymes in the blood is indicative of tissue damage and can be used for clinical diagnosis. For instance, an increase in serum levels of H₄ relative to H₃M is an indication that a myocardial infarction, or heart attack, has occurred"

I got this from an old textbook, the question is how exactly can serum levels be used to indicate a heart attack?--VectorPotential 13:45, 19 October 2007 (UTC)

The enzyme used in this test is lactate dehydrogenase (LDH). LDH is made up of four subunits, each being either an H subunit or an M subunit. Certain tissues have different combinations of subunits in their LDH.

• LDH-1 (4H) - in the heart
• LDH-2 (3H1M) - in the reticuloendothelial system
• LDH-3 (2H2M) - in the lungs
• LDH-4 (1H3M) - in the kidneys
• LDH-5 (4M) - in the liver and striated muscle

When a cell dies, it releases the enzymes that were contained within it. Normally, trace amounts of each of these can be found in the blood as the result of normal cell turn-over. However, following a heart attack, for example, large amounts of heart LDH (the 4H variety) will be released into the blood and can be measured with a laboratory test. This can be used to confirm that a myocardial infarction has occurred, especially if there were atypical symptoms such as a lack of chest pain. Andrewjuren(talk) 14:22, 19 October 2007 (UTC)

Note that LDH has been largely replaced by troponin and creatine kinase analysis in most cases because of the greater cardiac specificity and the fact that Tp and CK more rapidly increase following a myocardial infarction. See cardiac marker for more. --David Iberri (talk) 04:05, 20 October 2007 (UTC)

Lights at night appearing 'blurred'

I noticed that when i'm out at night, lights tend to appear blurred. When i say 'blurred', i don't mean i can't see the light clearly. I can see the light very clearly, but there're like...'lines' of light coming off it. So a round light (like the light from a street lamp) doesn't look like a round light - it looks like a round light in the middle of a 'star' of light.

It's sort of difficult to describe. But imagine that you get a bit of water in your eyes, and then you look at a bright light and squint. You can still see the light fine, but the 'edges' of the light become blurred and there're these long 'rays' extending from the light.

I'm short sighted, and i noticed that this always happens when i'm out at night.

- It only happens when i look at relatively bright lights at night. Lights look fine during the day, or in artificial light (i.e. the lights in my room don't look blurred) - Lights that are very far away look fine (e.g. from cars far away). It's mostly lights from cars directly in front of beside me, and lights from all the street lamps around me. - it's a *lot* worse when i wear contact lens (as opposed to just glasses)

I've always wondered why this happens. I've heard that seeing bright lights at night as being 'blurred' like this could be a sign of glucoma, or at least high pressure in the eyes. Is this at all true, and if so, should i be worried? I mean...i'm short sighted and have astigmatism, would either of them cause this?

Thanks, --124.191.80.78 13:50, 19 October 2007 (UTC)

Yeah, honestly, this falls under "don't ask medical questions here". Make an appointment with your optomitrist (or, even better, a ophthalmologist, if you have one). If your vision has changed in any way at any point for long periods of time, you really should see a specialist about it. They can tell you if it's something to worry about or if you just need to up your prescription. Nobody on here is going to be able to reliably diagnose you based on just a simple description of symptoms, even if we were qualified to do so. --24.147.86.187 14:00, 19 October 2007 (UTC)

All medical advice aside, this is to some extent completely normal. In fact, this is so common that both the object in the night sky (which should appear as a point source) and the shape that you actually see share the same word: See Star (disambiguation). — Sebastian 18:22, 19 October 2007 (UTC)

It sounds like some form of lens flare or optical aberration. From your description, it's not possible to tell if it's normal or not: your best bet is to seek professional advice. --Carnildo 22:44, 19 October 2007 (UTC)

Alright, here's another version of the question for those paranoid about medical advice. For as long as I can remember, when I look at any bright light outside in the dark (so I'd assume this applies to any roughly point source of light much brighter than its background), I can see a streak of light extending from the light downward at a single angle. This streak appears and/or becomes longer when squinting. I see this with and without glasses, and with glasses, the lights do not appear at all blurry, so I'm not thinking it's my vision here. Further, I see an eye doctor once a year, and have never been diagnosed with anything other than near-sightedness, lest anyone repeat the "you have glaucoma" answer. So the question is, very simply, what optical aberration or illusion have I just described? Someguy1221 23:05, 19 October 2007 (UTC)

In the excellent book Light and Color in the Outdoors, by M.G.J. Minnaert, there is a section called "Bundles of rays that appear to be emitted by bright sources". It says, in part, "...lights seem at times to cast long straight rays toward our eyes...; along the edge of each eyelid lachrymal moisture forms a small meniscus by which the light rays are refracted. ...the rays are refracted at the upper eyelid in such a way that they seem to come from below; the source gets a downward tail, and the lower eyelid gives, in the same way, an upward tail. ... The rays appear at the very moment the eyelid begins to cover the pupil; to a short-sighted observer this is easily visible, for the source of light, which he sees as a broadened disk, is at that moment partly screened off. ... The rays are not quite parallel, not even those to one eye. ... The reason for this is evidently that the edges of the eyelids, where they cross the pupil, are no longer horizontal, and each bundle of rays if at right angles to the edge of the eyelid that causes it..."

He also mentions that the effect is strengthened when seeing with "half-closed eyes", or squinting. Perhaps this is what you are seeing? There are many many other curious and interesting effects described in this book. Pfly 06:41, 20 October 2007 (UTC)

Sounds like it could be it. Does the book, by any chance, contain artists' impressions of this? Someguy1221 07:06, 20 October 2007 (UTC)

Well, whatever complicated explanation you give the questioner I will bet large amounts of money that he has an early cataract, I have experience with this problem, both personally and professionally. No big deal but he should get to see a professional in the near future to get an affirmed diagnosis. Some future feedback would be interesting. Richard Avery 11:10, 20 October 2007 (UTC)

Godels constitution loophole

Did anyone ever find out what Godel's aledged loophole in the US constitution was or will it forever stay in the secret of the judge's office? One link from the article offers a few (pedantic) guesses but not more. Keria 13:56, 19 October 2007 (UTC)

According to the links in the article, he didn't even tell the judge. My only problem with Tribe's answer (that you could, hypothetically, amend the Constitution in order to render it null) is that it's not a "logical contradiction" at all by any standard that someone like Godel should find interesting. A document which says "this document can be modified" is not a contradiction; maybe it's a loophole towards dictatorship (albeit a very obvious one and one which is quite hard to exploit, for that exact reason—they realized in the 18th century that if you made modifying the Constitution too easy it would be meaningless), but that's not the same thing as a contradiction. --24.147.86.187 15:04, 19 October 2007 (UTC)

• As the first article cited points out, "It should be remembered that while Gödel was supremely logical, he was also supremely paranoid and not a little naive." The US Constitution contains lots of concerning passages to those who might read it literally and/or mischeviously. The thing is, the judges never read it this way -- even famed literalists like Antonin Scalia actually apply historical precedent and rules of canon about avoiding absurd or abhorrent results. So long as the executive and legislature obey the Constitution enough to let the judges do the interpreting and then respect the judges' results, the little holes (like the President's ability to start an undeclared war, or Congress's power to determine the qualifications of its own membership) never threaten the Republic itself. So I chalk it up to Gödel's paranoia, brought on by the harrowing experience of seeing several of Europe's supposedly stable democracies come crashing down in rapid fashion. A dictatorship could happen in the USA just as in Europe, but it would happen through force or popular revolution, not through sneaky legal channels. --M@rēino 15:07, 19 October 2007 (UTC)

• A dictatorship of "emergency" seems much more likely to me than an overt coup. —Tamfang 01:49, 21 October 2007 (UTC)

Spelling nit -- if you don't want to look for the ö key to spell "Gödel", then please remember to use the "e". The spellings Gödel and Goedel are both acceptable; Godel is just an error. --Trovatore 18:19, 19 October 2007 (UTC)

rubber band paper airplane

Hi. I've tried launching paper airplanes by rubber band via a rubber band hook for the last few years. I'm wondering, are there any records for height, distance, speed, etc, in this category? Is there a maximum hypothesical limit for each of the category, assuming that they are built with common household materials? Is there anything that can be done to make them fly better? What makes some of them fly well and others crapily? Would they, at least hypopthesically, fly farther and longer when launched from a mountain, possibly onto a town below, or would they lose energy and stall or crash? Does angle affect distance? What is the best angle to launch one of these if you want more distance? Can such a plane be built to have more lift without increasing as much drag? Are there any real planes launched in this manner? Would a plane fly better with one rubber band, or by stretching a chain of bands linked together? Would it fly farther if the ground ahead of it was lower than the ground from it was launched? Is it possible to use wind to make it gain forward distance or height, and if so, how? Is there a way to retrieve one from a roof without having to physicly climb the roof? Does a card plane fly better than a paper one? Is it better to use a plastic straw or reinforced paper for the fuselage? Is it possible to attatch roaters, propellers, etc, without increasing more drag than thrust? What is the best design to minimize drag but still have enough lift? Could one that has enough thrust fly on the moon, where there is no lift or drag? Does attatching sand to the behind of the plane where it will fly out of it increase thrust or hinder it? Would it fly faster and farther (please, please, DO NOT try this at home or anywhere else) if launched while on a forward-moving object or veichle? How does a curtain manage to slow such a plane to a halt while it will damage a solid object? If such a plane is launched from the exosphere, would it burn up before it reached the ground or would drag prevent it from doing so? If such a plane were able to somehow reach the sound barrier, would it break or burn up? Is it possible to determine the maximum speed from a still object, height and distance from a flat gound, without launching it? Does a flick of the wrist prior to launch cause it to fly further or faster? Does rain during flight slow down the plane? Would it fly farther/faster/higher if it were lighter or heavier? Is it possible for such a plane to stall if launched horizontally? What can be done to prevent the plane or its hook from crashing into the launcher's fingers? Is there a certain speed that paper cannot handle? Does low or high pressure affect the plane's performance? Is it possible to remote-control such a plane if the things were attatched? Is it possible for an animal to mistake one for a bird? Would it pick up speed or slow down if it were launched straight down from say, a cliff? Does this type of plane act more than an arrow than a paper airplane? Thanks. ~AH1 14:04, 19 October 2007 (UTC)

What a huge question. I'll break that up a bit for easier digestion! (my answers interspersed with the questions where I can be bothered after typing all that up) --Psud

1. are there any records for height, distance, speed, etc, in this category?

There are records for hand-thrown paper planes (26 seconds - from level ground - thrown by hand) - and there are records for rubber-band powered endurance (but the winners of those have propellors and they aren't made of paper - very thin balsa with exotic thin plastic sheeting (kinda like solid soap-bubbles!). But I've never come across a record for rubber-band launched paper planes. SteveBaker 21:17, 19 October 2007 (UTC)

2. Is there a maximum hypothesical limit for each of the category, assuming that they are built with common household materials?

There would be maximum hypothetical limits. Cardboard, paper, balsa wood, etc can only handle certain accelerations. In fact no matter what limits you put on materials, there would be limits on performance - all materials have limits of exposure to acceleration and heat, for example.SteveBaker 21:17, 19 October 2007 (UTC) I'm pretty sure I wrote that (But I'm sure you'd have said the same, SteveBaker!) --Psud 21:47, 19 October 2007 (UTC) Correct me if I'm wrong :)

3. Is there anything that can be done to make them fly better?

Yes. Careful attention to weight, strength and aerodynamics. --Psud

Also, having a place with no wind and some nice thermals.

4. What makes some of them fly well and others crapily?

Usually drag and balance. An understanding of aerodynamics is useful. --Psud

Placement of the center-of-gravity is key. Wing area is going to be a nasty trade-off for you because larger area will stretch the glide-phase (because of lower wing-loading) but worsen the launch phase (because of higher drag). Having some dihedral on your wings will aid stability. SteveBaker 21:17, 19 October 2007 (UTC)

Rather difficult to put variable geometry wings on a paper/cardboard plane. --Psud 21:54, 19 October 2007 (UTC)

5. Would they, at least hypothetically, fly farther and longer when launched from a mountain, possibly onto a town below, or would they lose energy and stall or crash?

Certainly would fly further. Whether it would stall and crash would depend on the plane's trim --Psud

Given the likelihood of wind on a mountain, a paper plane wouldn't fly but 'flutter' (or what's the right word here?). I doubt it would reach the town without touching the ground. You'd have to make it considerably heavier. DirkvdM 08:20, 20 October 2007 (UTC)

6. Does angle affect distance?

Probably. Try it out, make a plane that flies well and launch it at different angles. There will be a particular angle where it works best. --Psud

In still air, an angle just slightly higher than 45 degrees is best. But that assumes your plane will stabilise and glide well. SteveBaker 21:17, 19 October 2007 (UTC)

7. What is the best angle to launch one of these if you want more distance?

Experiment with different angles until you find one that works best for your plane and your situation. Note that it may be different on a windy day vs a still day. --Psud

8. Can such a plane be built to have more lift without increasing as much drag?

It's always a tradeoff. See Lift-induced drag --Psud

9. Are there any real planes launched in this manner?

Not really, but Navy aircraft launched from an aircraft carrier are launched with the assistance of a catapault. --Psud

Before we had steam catapults, they launched planes with bungee cords...but that was a long time ago. Modern gliders can be launched with a tow cable and a winch - which amounts to something very similar to the tension on a rubber band. SteveBaker 21:17, 19 October 2007 (UTC)

10. Would a plane fly better with one rubber band, or by stretching a chain of bands linked together?

Try it and see. Let us know the result. --Psud

11. Would it fly farther if the ground ahead of it was lower than the ground from it was launched?

Yes. Just like with the mountain.

12. Is it possible to use wind to make it gain forward distance or height, and if so, how?

Yes. Launch a light, high drag plane with the wind and it will fly much further. I once won a school paper-plane competition like that, made a light plane with large wing area, trimmed the plane to glide slowly and threw it straight up. Wind carried it 200m. --Psud

True - but high winds tend to be turbulant - and that will do bad things to your stability - which will mess up your glide-phase. So there are limits! SteveBaker 21:17, 19 October 2007 (UTC)

13. Is there a way to retrieve one from a roof without having to physicly climb the roof?

Try a tool with a long handle, a rope. But no really effective ways that don't risk wrecking the toy. --Psud

14. Does a card plane fly better than a paper one?

In some situations. Paper planes get better endurance, card planes can fly faster. --Psud

15. Is it better to use a plastic straw or reinforced paper for the fuselage?

Try it and see. I'd expect the paper to withstand the forces involved better. --Psud

16. Is it possible to attatch rotors, propellers, etc, without increasing more drag than thrust?

Only if the rotors or propellers are powered. --Psud

17. What is the best design to minimize drag but still have enough lift?

Depends on what you're trying to achieve. Make different models with different wing length, different wing area. See which works best. --Psud

18. Could one that has enough thrust fly on the moon, where there is no lift or drag?

With impossible materials, yes, if you aimed it carefully enough. Practically? No. No rubber bands exist that could deliver that sort of power. --Psud

The escape velocity of the earth is 11km/second. Good luck with that! (A paper plane doesn't have enough stiffness to handle that kind of speed into an oncoming wind of 11km/sec! SteveBaker 21:17, 19 October 2007 (UTC)

The question was on the Moon, not to the Moon. It wouldn't really fly because there is no air to fly on. But it would remain in the air (in the vacuum?) for some time because the Moon won't pull on it as hard. If you'd make it really really heavy (so huge) it might even get enough momentum to go into orbit. Except that it would crumble under its own weight. DirkvdM 08:38, 20 October 2007 (UTC)

On the moon. Okay, it'd fly like a cannonball - that is, ballistically. And I see no way it'd crumble under its weight being launched into lunar orbit from the moon. Oh, really heavy. Right. Or you could just use a very long chain of vacuum safe rubber bands to give it the requisite velocity over a longer time. --Psud 08:58, 20 October 2007 (UTC)

19. Does attatching sand to the behind of the plane where it will fly out of it increase thrust or hinder it?

Hinder. Unless the sand is thrown backwards under power, for example by a rocket engine. Detailed explanations can wait for someone somewhere where it's not 1am. --Psud

20. Would it fly faster and farther (please, please, DO NOT try this at home or anywhere else) if launched while on a forward-moving object or veichle?

Yep. Fly faster or fold up. If it was strong enough to handle the airspeed. --Psud

That has the same effect as the wind - except that as the car passes the plane, there is guaranteed to be a lot of turbulance. SteveBaker 21:17, 19 October 2007 (UTC)

I don't usually drive any vehicles at home. :) Or was that your joke? DirkvdM 08:40, 20 October 2007 (UTC)

21. How does a curtain manage to slow such a plane to a halt while it will damage a solid object?

Curtains flex and spread the impact over time, china vases don't. --Psud

22. If such a plane is launched from the exosphere, would it burn up before it reached the ground or would drag prevent it from doing so?

Probably wouldn't burn up. I would expect it to have enough drag, but that depends on its relative velocity when it's released. Hitting the atmosphere at orbital velocity would not be conducive to the survival of the toy. Hitting the atmosphere at relative velocity of a few metres per second would work. --Psud

I disagree. The problem is that at very high altitudes, there isn't enough air to slow it down - no matter the size or shape. The drag is almost zero. So it would fall faster and faster under gravity. Then when the atmosphere does start to thicken up, the object is going so fast that the friction will make it burn up - so I'd say "Yes - if you started out high enough". SteveBaker 21:17, 19 October 2007 (UTC)

Consider SpaceShipOne. It falls from ~100km and needs practically no heat shielding because it is high drag and has no lateral motion. For both 22 and 23, I say that a paper or similar plane doesn't have the inertia to burn up. --Psud 21:44, 19 October 2007 (UTC)

How heavy can a paper plane be? Unless it's huge, it would not gain enough momentum to burn up. DirkvdM 08:42, 20 October 2007 (UTC)

Oops, Psud said that, I think, but with a different term. What is the formula for inertia? The article doesn't give one. Or is it F=ma, so kg.ms? DirkvdM 08:55, 20 October 2007 (UTC)

23. If such a plane were able to somehow reach the sound barrier, would it break or burn up?

If you dropped it out the window of a supersonic plane, the toy would break rather than burn. --Psud

At merely supersonic speeds - yes. At maybe 8x the speed of sound, maybe not. SteveBaker 21:17, 19 October 2007 (UTC)

24. Is it possible to determine the maximum speed from a still object, height and distance from a flat gound, without launching it?

Yes, but it's hard. Easier to make prototypes and test them. --Psud

Not without some pretty hard science. Predicting the flight path of a fluttery, flexible thing is tough to do - even with the latest 'virtual wind tunnel' software. Also, flight at very small scales is less well researched than for big planes. SteveBaker 21:17, 19 October 2007 (UTC)

25. Does a flick of the wrist prior to launch cause it to fly further or faster?

Yes, if it imparts more velocity. --Psud

26. Does rain during flight slow down the plane?

Yes. The wings will get wet, presuming they are not damaged by the water, the water will make the plane heavier and mess up its balance. --Psud

The impact of a single raindrop would knock a paper plane off-course and off-balance. Not good! SteveBaker 21:17, 19 October 2007 (UTC)

27. Would it fly farther/faster/higher if it were lighter or heavier?

Depends on the state of the relevant part of the world at that moment. Try it and see. --Psud

28. Is it possible for such a plane to stall if launched horizontally?

Yes. If it is trimmed to climb, it will stall --Psud

Definitely. SteveBaker 21:17, 19 October 2007 (UTC)

29. What can be done to prevent the plane or its hook from crashing into the launcher's fingers?

Practise. --Psud

...or gloves! SteveBaker 21:17, 19 October 2007 (UTC)

30. Is there a certain speed that paper cannot handle?

Yes. Depends on the paper and the construction of the paper toy. --Psud

31. Does low or high pressure affect the plane's performance?

Yes. High pressure is better for duration, low pressure is better for darts that fly like an arrow. --Psud (later edit: But on the scale of small toy planes, I doubt you'd notice. See density altitude

32. Is it possible to remote-control such a plane if the things were attatched?

Remote control gear is available that works with very light indoor planes. Probably possible, certainly very hard to make an RC paper plane. --Psud

33. Is it possible for an animal to mistake one for a bird?

Yes. --Psud

34. Would it pick up speed or slow down if it were launched straight down from say, a cliff?

It would slow down, a rubber band catapault plane's launch speed is almost always higher than its terminal velocity --Psud

35. Does this type of plane act more than an arrow than a paper airplane?

Depends on whether it's shaped more like an arrow or a plane. Try throwing it from your hand, if it flies, it works like a plane, if it follows a parabolic arc to the ground, it's more like an arrow. --Psud 14:35, 19 October 2007 (UTC)

You should also read "Making Paper Airplanes That Really Fly" by Nick Robinson. I believe he is a world record holder for (hand-thrown) paper planes. I imagine his designs would be the best for rubber-band launching too. He throws VERY fast! Another world record holder has a web site http://paperplane.org with lots of goodies. Plans for another world record plane are here. I also found A flight simulator for paper planes SteveBaker 21:23, 19 October 2007 (UTC)

First of all, WOW! I never thought the reference desk could give such great answers! Unfortuneately I don't have enough time or paper to do all those tests. Finally, a few more questions. Do these planes rot over time? Are these planes well-known to the paper aircraft community? Would it last longer if it were made semi-waterproof with tape, or would that just make it too heavy to fly? Do bulletproof or baggy clothing help improve safety if there is an area where many people are launching these? If one were to fly on Jupiter, would it burn up? Would a larger one launched with larger paper clips and larger rubber bands fly farther? If a tiny camera were programmed to take pictures and attatched to the plane while it is launched straight-up, how far would one see? Thank you all so much for your answers. I really think some of you refdeskvolunteers deserve a barnstar (although I haven't transisted into barnstar-giving season just yet), I really do. ~AH1 14:55, 20 October 2007 (UTC)

Can you never ask just one question!? --Psud 10:48, 23 October 2007 (UTC)

Do these planes rot?

Yes, but if kept dry they'll last much longer than your interest in them. --Psud 10:48, 23 October 2007 (UTC)

Are these planes well known to the paper plane community?

I didn't even know there was a paper plane community! These sort of planes were well known to me when I was flying paper planes 2 decades ago. --Psud 10:48, 23 October 2007 (UTC)

Would it last longer if it was made semi-waterproof with tape; would it make it to heavy

No it wouldn't last longer, and the tape wouldn't really make it too heavy, it'd just mess up it's structure. Paper is fairly rigid, paper covered in tape is floppy. --Psud 10:48, 23 October 2007 (UTC)

Do bulletproof or baggy clothing help improve safety if there is an area where many people are launching these?

Unless they have hardened noses, they're not all that dangerous. Even with hard plastic nose-cones, you wouldn't notice being hit by one through a woolen jumper (pullover). Baggy clothes would be sufficient. --Psud 10:48, 23 October 2007 (UTC)

If one were to fly on Jupiter, would it burn up?

It certainly wouldn't survive the fall towards the centre of Jupiter. Burn up? I don't know. Be destroyed? Certainly. --Psud 10:48, 23 October 2007 (UTC)

Would a larger one launched with larger paper clips and larger rubber bands fly farther?

Yes, although you would probably need to use different materials. --Psud 10:48, 23 October 2007 (UTC)

If a tiny camera were programmed to take pictures and attatched to the plane while it is launched straight-up, how far would one see?

Say you pointed it straight up, from the equator, at midday, you would clearly see the sun in the picture from the camera. The sun is ~150,000,000km away (~93,000,000mi). Launching at night you could probably see stars, depending on your camera. I'd say you could see pretty far. --Psud 10:48, 23 October 2007 (UTC)

How can I tell the difference between male and female seagulls just by looking?

Is there a way? --90.242.17.158 15:15, 19 October 2007 (UTC)

The short answer is no. It is quite difficult, even for experts. However, as you will see from the article, there are many different types of gull, and it is possible that some of them are more easily sexually distinguishable than others.--Shantavira| 18:16, 19 October 2007 (UTC)

If you see an egg-shaped object emerging from the gull's hind quarters, then it's a female. DuncanHill 18:18, 19 October 2007 (UTC)

Or impressively constipated. --Carnildo 22:52, 19 October 2007 (UTC)

In that case of Herring Gulls, the male is generally (though not always) larger and heavier, with a slightly longer skull and larger beak. It's only really apparent when you see a bonded pair side-by-side, though. --Kurt Shaped Box 11:12, 20 October 2007 (UTC)

earth science

the study of the motion of planet earth and the other planets are called what? —Preceding unsigned comment added by 157.130.162.178 (talk) 15:28, 19 October 2007 (UTC)

Planetary mechanics is a subfield of celestial mechanics. Marco polo 15:49, 19 October 2007 (UTC)

Understanding singularities

I am a person without a strong background in physics. Can someone explain to me in layman's terms how it is possible for the enormous mass of a supermassive black hole to exist within a singularity, or a point without volume? Where do all of the protons, neutrons, and electrons go? Surely they occupy some volume? Or am I wrong that the singularity encompasses the supermassive black hole? Does the black hole actually have some volume? Thank you. Marco polo 15:52, 19 October 2007 (UTC)

I also lack a strong background in physics, but from gravitational singularity, we have ' generally a sign for a missing piece in the theory.' While general relativity admits solutions such as the Schwarzschild metric, which describes a black hole with a singularity at its centre, this may well be a problem with GR and not with the universe: see black hole#Singularity at a single point, for example. It is hoped by many that a proper theory of quantum gravity will resolve these issues, but we haven't got one yet. Algebraist 16:18, 19 October 2007 (UTC)

To put it simply, scientists are not certain whether black holes have volume or not. Under relativity you can have an infinitely dense, zero volume space, but under quantum mechanics and string theory you cannot. Still, science has occasionally come across phenomena that do not make intuitive sense, but are true nonetheless. -- HiEv 16:44, 19 October 2007 (UTC)

• As I read supermassive black hole and this NASA page, not everyone says that a black hole is a point without volume, but I wonder if everyone is using the same definition of "volume". --JWSchmidt 16:56, 19 October 2007 (UTC)

I believe what you are dealing with there is the volume enclosed by the event horizon of a black hole, rather than the volume of the singularity where (according to GR) all the mass has ended up. Algebraist 17:00, 19 October 2007 (UTC)

I am still having trouble understanding this, though perhaps it is beyond my mental ability. After attempting to read Schwarzschild metric but failing to understand it completely, I have the impression that "space-time" is so altered within the "event horizon" of the black hole that the matter within it appears from outside as if it has no volume. Is this to say that the rules of physics that apply outside of the black hole no longer apply inside it, such that it either 1) somehow contains volume where there appears to be none or 2) atomic particles somehow cease to occupy volume? Thanks again. Marco polo 19:29, 19 October 2007 (UTC)

Well, according to general relativity, the laws of physics go completely crazy at the centre of the black hole. This is, in all probability, because general relativity is wrong here. In any case, we have no good theory for telling us what actually happens at this point. Algebraist 21:36, 19 October 2007 (UTC)

How about this: fundamental particles are points with a volume of zero. If you stick a whole bunch together, the volume adds up to zero. That works for relativity.

According to quantum mechanics, they are waves, like light, and like light, they can overlap. They can't have a zero volume, which is why a singularity is often thought to have a very small, but nonzero, volume. This might not be right, as my education in the subject is limited to what I found on Misplaced Pages. — Daniel 22:43, 19 October 2007 (UTC)

Pauli exclusion principle says, "According to general relativity, in the centers of black holes the gravitational forces would become so intense that everything would break down into fundamental particles, which are supposedly point-like with no internal structure. All of these particles could then pile up at one zero-dimensional point because the gravitational forces would be greater than the degeneracy pressure. This would seem to violate the Pauli exclusion principle, but since the interiors of black holes are beyond the event horizon, and thus inaccessible to experimental verification, this hypothesis remains untested." --JWSchmidt 04:27, 20 October 2007 (UTC)

Energy, inertia, or force required to cause injury

A non-profit my father volunteers for maintains a number of recycling bins. The bins had large, heavy, bear-proof steel lids. The lid on one closed unexpectedly and injured a person. They've removed the steel lids and want to replace them with plastic. However, local authorities (in a small town, who have nothing better to do) want some analysis to show that the plastic lids won't hurt anybody. I can do the basic physics of the problem, and get the approximate velocities, or kinetic energy, or whatever, of the lids upon closing. But I can't find a source that will tell me how much energy (I think energy might be the way to go?) or inertia is required to injure a person. The scenario we have in mind is a lid falling on a person's hand. Anyone know where I can find out how much energy or inertia would be required to cause injury? Thanks, moink 15:52, 19 October 2007 (UTC)

I believe tests are used using 'crash dummies' rather than calculations.

However a good search term for you would be "Injury/Impact Biomechanics"87.102.7.57 16:30, 19 October 2007 (UTC)

You might want to watch a few episodes of Mythbusters. They'd make a ballistics gel hand and arm with simulated or real bone inside, and drop a few lids on it to see what happens. On the math, don't forget that plastic is usually more flexible than metal, and thus it temporarily deforming around the limb will help reduce the impact as well. Good luck! -- HiEv 17:16, 19 October 2007 (UTC)

Thanks to both of you, but I have no intentions of performing any experiments. I am a very poor experimentalist, and this is not a high priority in my life. I'm annoyed enough at having to produce a page worth of freshman-level physics. moink 19:26, 19 October 2007 (UTC)

The trouble is that the nature of the impact depends on the shape and speed and weight of the lid at the moment of impact - speed and weight can certainly be quantified - but it's going to make a world of difference whether the edge is thin or fat - and that's not something you'll easily be able to calculate against known human data. If it's not REALLY obvious that it can't hurt someone - then I agree that a simple experiment is required. But personally - I'd stick one of those hydraulic/pneumatic cylinders between the lid and the bin - the kind you use to prevent a door slamming - you can buy them for very little in most DIY stores. That ought to slow things down to the point where nobody would even imagine that it could hurt someone. SteveBaker 20:54, 19 October 2007 (UTC)

If you want it to be bear-proof it helps if the bears can't smell what's inside (assuming nothing spills on the outside through careless use). So a rubber ring (possibly even on both the lid and the bin) would help to seal it off and have the pleasant side-effect that it wouldn't hurt an ill-placed hand as much. Also, the shape will affect the wind resistance, and if it's a lighter material like plastic, that can help. DirkvdM 09:03, 20 October 2007 (UTC)

wind speeds

Is there a map showing the locations of the average and maimum highest and lowest wind speeds on the planet? —Preceding unsigned comment added by Kadiddlehopper (talk • contribs) 16:05, 19 October 2007 (UTC)

Firstlook.com uses google maps to find windspeed. I hope this helps! --JDitto 18:46, 19 October 2007 (UTC)

• Mt. Washington (New Hampshire) has the highest recorded surface wind speed, apparently. --Sean 18:58, 19 October 2007 (UTC)

And lowest is, of course, zero, and has been recorded virtually everywhere. Did you have some other measurement in mind when you asked about that? — Lomn 19:29, 19 October 2007 (UTC)

Well of course in both cases I'm looking for at duration, i.e., places where zero for instance has been recorded for the longest perior of time as the maximum lowest and where lowest average, say .5 MPH, might be the lowest average for the longest period of time. Clem 20:52, 19 October 2007 (UTC)

That's just the US, alas, and he asked about the world. And I'm very interested in knowing that too, also at different heights, for the entire atmosphere, so up to 100 km high. Of course nothing anywhere near that precision, just an overview. And for the different times of year. I looked for that a while ago on Misplaced Pages (starting with wind), but found nothing, just very general indications. Maybe someone else can do better? DirkvdM 09:09, 20 October 2007 (UTC)

Well, then, you might be pleased to know the US is one of the stormiest places in the world. If the record for New Hampshire isn't the highest, then the highest windspeed recorded is inside an F5 tornado, in the US of course. Hope this helps. ~AH1 15:01, 20 October 2007 (UTC)

I have a Steam Engine Powered Automobile circa 1880's

We have a Steam Powered Automobile circa 1888 +-. My interest is in finding authorities of historic Steam Powered Automobiles from the 1800's to determine it's historic significance and also fair market value for sale. It has been kept in immaculate condition. I may be contacted at <contact details removed for protection>. Thank you. Jon Borovay <detail removed for protection> in the United States. —Preceding unsigned comment added by 76.3.30.44 (talk) 16:06, 19 October 2007 (UTC)

Jon, thanks for your question, I've removed your contact details, as any answer will be posted here, and we want to protect you from spam emails or hoax calls. DuncanHill 16:08, 19 October 2007 (UTC)

Now come on... Jon is an adult and knows the risks of publishing his contact information and which the rest of us might like to have in order to contact him. STOP PLAYING GOD! —Preceding unsigned comment added by Kadiddlehopper (talk • contribs) 16:12, 19 October 2007 (UTC)

Jon is new to Misplaced Pages, and may not have read the instructions not to post email addresses or telephone numbers, or be familiar with the standard practice at this desk of editors redacting them. DuncanHill 16:14, 19 October 2007 (UTC)

Without the contact info there is no point is retaining the post. If you are going to delete it then delete the whole thing. Also you have failed to inform Jon that he can include his email address in his preferences if he wants to be contacted which makes deletion here fairly stupid. —Preceding unsigned comment added by Kadiddlehopper (talk • contribs) 16:17, 19 October 2007 (UTC)

He could read the answers here (assuming he ever came back!)87.102.7.57 16:23, 19 October 2007 (UTC)

Do you, User:Kadiddlehopper, find it difficult to recover lost content from Misplaced Pages? − Twas Now ( talk • contribs • e-mail ) 09:35, 20 October 2007 (UTC)

Back to the question... Steam car and the references given there may be of use. Algebraist 16:55, 19 October 2007 (UTC)

Questioners are not allowed to leave contact information. It says so right at the top of every ref desk page. It is highly inappropriate to hold these kinds of internal debate here - please take it to the Talk: page. SteveBaker 20:45, 19 October 2007 (UTC)

Without debate all registered users have an email option in their user preferences. One need only register and provide an email address to be contacted by any other user. This information has not been provided to the OP until now. Clem 21:03, 19 October 2007 (UTC)

Never mind what some people unilaterally consider allowed or not. It's for his own protection. This is not just a Misplaced Pages thing. Everyone hates spam (I think I can safely assume) and posting your email address is a sure invitation for it. Also, that is not the way the ref desk works - others want to read the answers too, to avoid overlap and out of interest. If you want to still send the guy an email, look it up in the history. Or as an alternative, the address could have been commented out between the tags <!-- and -->. DirkvdM 09:18, 20 October 2007 (UTC)

Jon: You should try The Steam Car Club of Great Britain - or The Steam Automobile Club of America. An email to either of those organisations should get you what you need. SteveBaker 20:45, 19 October 2007 (UTC)

Is matter infinitely divisible?

I believe according to the standard model, the smallest unit of matter is the quark. But realistically speaking, wouldn't matter be infinitely small, with each component made up of smaller components, infinitely? 64.236.121.129 17:22, 19 October 2007 (UTC)

Well, you seem to be in line with that great physicist Dave Barry, who reports on an experiment thusly: "I have examined cheese very finely, and as far as I am able to determine, it is made up of cheese". Or words to that effect. But why "realistically" should matter be infinitely divisible? As far as I know no one has proved that quarks have no smaller parts, but none have been found, either. --Trovatore 17:26, 19 October 2007 (UTC)

I say realistically because of mathematics. For example, the amount of points between two points on a line, is infinite. You can take an infinitely small fraction of the number 1. It seems to make sense. 64.236.121.129 17:50, 19 October 2007 (UTC)

Mathematics is not the same as physics. The status of mathematical objects is debated (part of an underlying non-physical Platonic reality? Linguistic metaphors? Merely a way of rephrasing formal sentences provable by mechanical manipulation?) but almost no one identifies them strictly with physical objects. Which admittedly does leave unexplained why they work so well at predicting physical outcomes -- there's a famous essay by Eugene Wigner on the subject. --Trovatore 17:55, 19 October 2007 (UTC)

Sure it's not the same as physics, but shouldn't its basis be in reality? It is supposed to model real world phenomena. Without mathematics, physics would be impossible to understand. Physics depends on mathematics. 64.236.121.129 18:22, 19 October 2007 (UTC)

"Reality" is not necessarily the same as "physical reality". There are more things in (Platonic) heaven and Earth.... But also, there's a difference between a useful model, and a perfectly faithful model. The real numbers might be the first without being the second. --Trovatore 18:25, 19 October 2007 (UTC)

Possibly, although I think it's a valid possibility. Btw, I don't believe in heaven. 64.236.121.129 18:36, 19 October 2007 (UTC)

Quite right - it is a valid possibility - but is is (mostly) easier to work with integers (atoms).. (in the same way that it's often easier to integrate numerically eg simpson's rule than it is to get an antiderivative)

It's worth noting that in the engineering field continuum mechnanics rules.. eg analysis of bending force of a bar - but without the atoms we need a new way to label materials 'steel' or 'copper'87.102.7.57 18:57, 19 October 2007 (UTC)

Actually, in many cases it's precisely the reverse of your first point. We know that the underlying process breaks into discrete bits, but it's easier to model them as a smooth integral (or solution to a differential equation) than it is to sum up the discrete parts. Arguably that's what makes the real numbers useful in physics at all. --Trovatore 20:02, 19 October 2007 (UTC)

I'm not sure - say for a crystal lattice - the lattice energy is obtained as a sum (using point charges) (eg NaCl Q(x,y,z) = (-1) where x,y,z are integers - if the charge was smoothly distribued eg Q(x,y,z) = sin (x+y+z) then obtaining the lattice constant would be doubly difficult. That's the sort of thing I meant anyway.87.102.7.57 20:23, 19 October 2007 (UTC)

See atomism and infinite divisibility for some of what has been thought on these matters. Algebraist 17:38, 19 October 2007 (UTC)

In one sense you're asking about Continuum mechanics and assuming it extends to very small things.. and why not?

One reason a lot of scientists assume quantisation of matter eg atomism is that 'we' need a reason to explain why different things are different - one easy way is to assume that things are made up of building blocks like atoms - not quantising can make it seem more difficult to explain why matter can be different things - it's an easy way out to draw the line at the atom - and say all things are built up from those atoms.

Just because atomic theory exists and works doesn't make it instrinsically right, or infinitely divisible matter wrong, but the atomic model works quite well in many ways so there's no need to look any lower/smaller.

The disambiguation page Quantization has a good sentence

Quantization is the procedure of constraining something from a continuous set of values (such as the real numbers) to a discrete set (such as the integers).

One big question is 'is the constraint of atomism just a model/construct for the understanding of matter or is it physically real' .. you'll have to decide for yourself - but I hope you find the links useful - as well as atomism there's also Infinite divisibility - however since modern science favours atomism you may be pretty much on your own when it comes to finding out more about infinite divisibilty - the problem is that no one is really looking for an 'atomic continuum'...87.102.7.57 18:17, 19 October 2007 (UTC)

If string theory is true - then no. Super-strings would have to be the ultimate things (in fact, the ONLY things). If it's not true, then I suppose we might ultimately decide that there was something inside the Quark. SteveBaker 20:33, 19 October 2007 (UTC)

You might also want to read about Planck length. Even if things were infinitely divisible (which it appears is not the case), you would not be able to precisely measure anything smaller than a Planck length without destroying it. Also, when attempting to simulate reality, mathematics should follow physical observations because there is no guarantee that reality will follow mathematics in all cases. When reality and math disagree, it's the math that needs to be corrected. Finally, imagine the universe is made of something like LEGO blocks, you may be able to keep dividing an object many times, but eventually you're going to be left with indivisible blocks. Being able to divide something many, many times does not mean you can divide it infinitely. -- HiEv 16:44, 22 October 2007 (UTC)

Earth From Space at Night (earth lights?)

hi,

im looking for pictures of the earth at night where you can see all of the lights from the urban areas, in particular the UK and Western Europe. Image:Earthlights dmsp small.jpg / Image:Earthlights dmsp.jpg <<<here are examples of what i mean from WP]]

(the science desk seems the most appropriat (spel?) place for this Qu. if its ment to be somewhere else please tell)

(also you are welcome to put any responses on my talk (my user: Plague of Death))

thanks, --84.71.169.30 18:30, 19 October 2007 (UTC)

This "Astronomy Picture of the Day" might be what you're looking for. Also try google maps. (I don't have it, but I've heard it was good.) --JDitto 18:53, 19 October 2007 (UTC)

Visible Earth - exactly what you need, I think. The 30000x15000 pixel GIF image is spectacular. SteveBaker 20:29, 19 October 2007 (UTC)

Extra credit if you can find the People Utopia of North Korea. --DHeyward 05:46, 20 October 2007 (UTC)

Ice cream

I bought some ice cream the other, took it out of the freezer and left it out sitting for some time (know I shouldn;t have done so, but anyways...). well, the ice cream kinda melted a bit but then I put itback into the freezer. I took it out again today and there is something crunchy (guessing to be ice) why does the ice cream separate? I mean ice cream's an emulsion, got that, but it should contain emulsifiers to keep it from separating right? what's happened? —Preceding unsigned comment added by 82.46.27.191 (talk) 18:41, 19 October 2007 (UTC)

The ice cream does contain ice crystals -but they are very small - to get these crystals very small the 'cream' has to be frozen very quickly.. When you re-freeze melted ice-cream the crystals form slowly - It's a general rule that the slower the crystals take to form the bigger they will be - that's why your re-frozen ice cream has big ice crystals and is crunchy.87.102.7.57 18:49, 19 October 2007 (UTC)

If you stirred the cream while it was freezing that would have helped - however it's difficult to stir things while they are in the freezer!87.102.7.57 18:51, 19 October 2007 (UTC)

The poor man's solution to this is to keep the ice cream in a durable, well sealed container, placed inside another container, and fill the space inbetween the two with ice and salt. Then continuously agitate the container in some manner as the ice cream slowly refreezes. Someguy1221 18:54, 19 October 2007 (UTC)

The rich man's solution being to buy an ice cream maker. Algebraist 21:31, 19 October 2007 (UTC)

The other' rich man's solution is to freeze icecream by pouring liquid nitrogen over it. The mix freezes so quickly that the ice crystals end up incredibly tiny. --Psud 22:15, 19 October 2007 (UTC)

A normal man's solution would be to either enjoy the crunch (or stir it into a milk shake?) or buy some new icecream. DirkvdM 09:22, 20 October 2007 (UTC)

Another explanation is recrystallisation. At high sub zero temperatures (ie. just below 0C), small ice crystals have a tendency to grow into larger ice crystals. It's to do with the curvature of the ice surface favouring a lower number of large ice crystals over a large number of small ice crystals. Anyway, this may be causing the course grain of the ice cream. As an aside, there are proteins that inhibit this process - some ice creams have them added for exactly this reason. See . Aaadddaaammm 23:02, 19 October 2007 (UTC)

See surface energy for why material tends to agglomerate to an existing crystal rather than nucleating a new crystal domain. Eldereft 19:46, 23 October 2007 (UTC)

Toilet light switch

is there any particular reason that toilet light switches are always outside? (giving irritating people the chance to switch off the lights amidst your shower???) —Preceding unsigned comment added by 82.46.27.191 (talk) 18:43, 19 October 2007 (UTC)

I've never seen that, actually. Maybe a UK thing? Someguy1221 18:52, 19 October 2007 (UTC)

I built an extension onto my house in England a while back - which had a shower+toilet room. The building inspector made me move the lightswitch out into the corridor before he would approve the extension. There are building laws in the UK (and probably in the USA too) to prevent any electrical outlet from being within some number of feet of a shower because of the risk of water getting into the switch and zapping you when you try to turn off the light. In a really small room (such as the one we built) it's completely impossible to get the light switch far enough from the shower. Putting the light outside of the room solves that. But if there is just a toilet+sink in there - or if it is a much bigger bathroom - it shouldn't be a problem. Our main bathroom in that same house has the lightswitch inside the bathroom. The rules for this sort of thing are much more stringent in the UK because house circuits are all 240v - which will give you a much more serious shock than 110v. The apartment I'm currently living in (Austin, Texas) has a light switch that is alarmingly close to the shower - so for sure the laws are more relaxed here. SteveBaker 20:05, 19 October 2007 (UTC)

I wonder if any of the many types of switches designed for moist environments would suffice for being placed close to the shower? DMacks 20:13, 19 October 2007 (UTC)

Probably the concern is with water running down behind the switch-plate - when you're talking about 240 volts...everything gets much more serious! SteveBaker 20:22, 19 October 2007 (UTC)

Yup. The ones I've used have the whole junction-box sealed. Or you could go crazy and do full-scale explosion-proof wiring, packed conduits and boxes, etc., especially important if you eat a lot of tacos. Yeah, just easier to move the switch outside though.DMacks 20:32, 19 October 2007 (UTC)

It sounds like you are not aware of the suspended cord toilet light switch (or "bathroom switch") - which totally distances the operator from the switching mechanism eg http://www.diy.com/diy/jsp/bq/nav/nav.jsp?action=detail&fh_secondid=9288943&fh_location=%2f%2fcatalog01%2fen_GB&fh_search=light+switch&fh_eds=%c3%9f&fh_refview=search&ts=1192827548442&isSearch=true (might be a slow loader)

Image here http://www.letsautomate.com/11546.cfm - because it is fixed to the ceiling drips do not affect it.87.102.7.57 21:03, 19 October 2007 (UTC)

You can also build or buy your own remote control on/off switch that only requires 2 to 5 volts for the mosfet gate. I installed passive infrared with long duration timers so I'm never left in the dark unless my shower takes longer than up to a setting of 45 minutes. Also for the UK 240 volts you can by x-10 battery operated remote control switch that would allow you to put the remote in the bathroom and replace the original switch in the hall with the relay and receiving unit. The remote just glues or screws to the wall, mirror, or shower door, since some are sealed and waterproof. May not operate under water, however. Clem 22:12, 19 October 2007 (UTC)

Why all so complicated? Just a normal light switch high on the wall, near the ceiling next to the door, where water is less likely to reach it, possibly with extra rubber sealing (there's also steam), and operated with a cord. That's pretty standard in the Netherlands. Actually, just the rubber sealing would be enough. Such rubbery push buttons are pretty standard. DirkvdM 09:35, 20 October 2007 (UTC)

Notice that the question is about toilet (not bathroom) light switches on the outside. I've noticed too in some places, but I can't remember where. Not very common, though, because it's really silly. DirkvdM 09:35, 20 October 2007 (UTC)

Sailing stones

Has anyone ever setup a camera and an Anemometer and recorded the movement of the stones and the wind speed? Clem 22:02, 19 October 2007 (UTC)

Why does silver tarnishes upon exposure to ozone, hydrogen and sulphide or air containing sulphur?

As quoted at in the subject, why does it tarnish? Chloejr 22:50, 19 October 2007 (UTC)

Because of oxidization, I believe certain elements combine with the silver in a process similar to rust. See also Tarnish(if you haven't already). SmileToday☺(talk to me , My edits) 23:35, 19 October 2007 (UTC)

math

my name is tarun can you halp me

12h = 48 —Preceding unsigned comment added by 4.236.108.103 (talk) 23:29, 19 October 2007 (UTC)

We are not here to do your homework, however, you should consider using the techniques suggested here. If all else fails, see the Elementary algebra article, or go to another website. SmileToday☺(talk to me , My edits) 23:32, 19 October 2007 (UTC)

That's a little complex, SmileToday. The simple version has two rules:

• Do the same thing to both sides of the equals sign
• Try to get h on it's own

12h is 12 times h; so in this case, you need to divide the left side by 12 to get one h. Thus you also need to divide the right side by 12.

• 12h / 12 = 48 / 12

or

• h = 4

--h2g2bob (talk) 23:46, 19 October 2007 (UTC)

veterinary

my name is nazrul i need halpto do my projetthank you my qusin is

1who does this profession halp —Preceding unsigned comment added by 4.236.108.103 (talk) 23:34, 19 October 2007 (UTC)

Our article veterinary medicine may help you. The profession helps animals, but also helps their owners, who may be farmers or pet-owners etc. Some vets will specialise in treating wildlife, or animals in zoos, and so help with conservation. DuncanHill 23:39, 19 October 2007 (UTC)

Once again, we are not your personal assistants, nor here to do your homework/projects. I suggest you look up the article and read it for yourself instead of asking us both at the help desk and here. SmileToday☺(talk to me , My edits) 23:39, 19 October 2007 (UTC)

math

why you gise dont halp as this na paire thisis bad —Preceding unsigned comment added by 4.236.108.103 (talk) 23:38, 19 October 2007 (UTC)

I cannot understand your question. The latter part of the sentence makes no sense. Please consider using correct spelling and/or grammar. SmileToday☺(talk to me , My edits) 23:40, 19 October 2007 (UTC)

If you're asking why people here didn't help, they did. You got a few unhelpful comments, but also your math question was answered and you were given the technique for how to solve questions like that yourself; your question about veterinarians, and someone gave you a link to the veterinary medicine page which I'm sure told you that veterinarians are doctors for non-human animals. I presume English is a second language to you so if you're asking anything else and not getting an answer, it may be because English speakers here don't clearly understand you. --Psud 02:53, 20 October 2007 (UTC)

Fingers on chalkboard...

Can someone point me to a relevant article or explain the scientific reason some people get chills due to certain sounds such as fingers squeaking across a chalkboard? Thanks! 24.229.119.116 23:43, 19 October 2007 (UTC)

Try (edit) And 's another person's opinion --Psud 02:55, 20 October 2007 (UTC)

Nobel laureate biologist James Watson

The controversy began with an October 14 interview Watson gave to the Sunday Times, which quoted him saying he was "inherently gloomy about the prospect of Africa" because "all our social policies are based on the fact that their intelligence is the same as ours, whereas all the testing says not really."

Watson also asserted there was no reason to believe different races separated by geography should have evolved identically, and he said that while he hoped everyone was equal, "people who have to deal with black employees find this is not true."

The biologist apologized "unreservedly" Thursday for his comments and said he was "mortified" by the words attributed to him.

I must agree with and support Watson's observations without reservation and I am not racist or prejudice. In all my years of experience in living around and among educated and uneducated Blacks I have likewise observed that they seem to be disconnected from the mainstream of history going back past about 200 years. While Blacks may demonstrate "equal" intelligence in regard to affairs of recent events such as in technology and barring situations which relay upon historical knowledge (or persons who have it) they are consistently unaware or ignorant of constants embodied within mainstream European and Asian history, even when they are knowledgeable as to the historical facts. They simply seem unaware of and unaffected by certain critical turning points in history (such as the Bubonic Plague) occurring more than 200 years ago, which easily accommodates a label of ignorance. Is there anyone who can attest to the opposite of this fact?

Multimillionaire 23:48, 19 October 2007 (UTC)

No opinion, but Race and intelligence. Someguy1221 23:51, 19 October 2007 (UTC)

That article, however, regards "intelligence" as aptitude versus knowledge. Certainly the British found that the Zulu had great "aptitude" but lacked knowledge of "modern" battlefield tactics. My reference to incurable ignorance regards knowledge versus aptitude which the article fails to address. Multimillionaire 00:00, 20 October 2007 (UTC)

No offense, but this is a big issue, and one which is quite politically charged. If you are going to bother to post your opinions on it, you might poke around in the reading a bit more. The measurement of "intelligence" as a scientific entity has never been able to separate innate and learned knowledge well; it is unclear how one would actually test for "innate" knowledge and Watson's basic logical error is in confusing the somatic (how a group or person may be at the moment) and the genetic (what is innate, in-born), much less their connection, which is quite silly for someone as educated as him (but not surprising—he's never been a terribly subtle thinker in many respects). Your own loose anecdotal evidence about people being "disconnected from the mainstream of history" is not a scientific argument nor a scientific approach to reasoning about the question, and your regard for their "ignorance of constants in history" sounds quite laughable to an academic historian—I do not know of any such constants myself!

Just to throw my POV out there, lest you misinterpret it: I think it's of course possible that the population groups with their heritage in Africa could, on average, have different innate aptitudes in intelligence; the question is whether it has been demonstrated. Certainly the current state of Africa cannot be mistaken as an "even playing field" economically or socially with Western or even Eastern societies. --24.147.86.187 02:21, 20 October 2007 (UTC)

"Innate" knowledge is not what I am referring to but something more akin to the inherited knowledge of the Bubonic Plague. Such knowledge is not innate but rather passed from generation to generation. Those to whom it is passed from original personal experience may benefit from a greater impact than those who simply read or hear about it, at least to the extent of it becoming a constant among the many constants and variables in your decision making which you can not help but to weigh. Clem 06:48, 20 October 2007 (UTC)

My experience in Canadian high schools is that, almost always, the black students excel in physical education but perform poorly in all other subjects. They also misbehave with much greater frequency and severity than the average student does; talking in class, using swear words, using violence, and failing to complete homework are done very regularly. Black students are nonexistent in the gifted education course for my grade, and they are usually the lowest-performing students in most classes. However, interestingly, the number of black students in special education isn't disproportionally high.

I do not know the specific nationalities of the students I consider black, but a large number is from Jamaica instead of Africa. I am excluding Indian and Middle Eastern pupils from the race group because of obvious skin colour differences.

Please feel free to post any reasons why my experiences may not represent the black population as a whole. I am simply stating my personal experiences as truthfully and objectively as I can, and am not trying to be racist in any way. --Bowlhover 04:10, 20 October 2007 (UTC)

This kind of thinking would make me laugh if it weren't so harmful. It's not the intelligence, whatever that is, of a race but the incidence of genius worldwide that matters. We are all pretty dumb on balance the world over. Where's the African Isaac Newton, you ask? Probably starving to death at the age of one as we type. Where is the European Isaac Newton? Long dead. And without milieu, even genius come to nothing. Let's pave the way for the next Newton, whatever color he or she turns out to be, instead of digging pitfalls.

Haven't you ever had your ass kicked at chess by a black man? You should try it. --Milkbreath 04:49, 20 October 2007 (UTC)

That's a good point. I'm glad you mentioned it. I thought I was pretty good at playing chess until my butt was kicked in boot camp, not by a Black but by a White. Now-a-days my butt gets kicked by chess programs written over 20 years ago. But if we are going to talk about logic then I must point out that a better test than winning at chess might be the number of multiple state variables that one can reduce to minimum form. Currently the Dalai Lama seems to be doing pretty good and I know many Blacks who on a regular basis can bring an issue into absolute focus, so what is the problem? The problem is that the number of variables and states that Blacks are dealing with may not go back much past 200 hundred years. While they seem to have resolved all those variables going back farther in time it turns out to be not resolution that is responsible for their coming to absolute focus in a short amount of time but rather their ignorance of and non inclusion of these additional variables and their states. Sort of like playing an end game where the number of pieces and moves are greatly reduced. Sure they may be able to process an equal or greater number of variables and states to whip butt in chess, but the point is that for whatever reason they either do or can not include the variables of which they know nothing about. Whites, on the other hand have inherited these variables and states and when it comes to reducing a political or social or economic problem to minimum form, have a far greater burden on their hands due to the number of variables and states they must include. Clem 06:26, 20 October 2007 (UTC)

Could somone clarify what "..disconnected from the mainstream of history going back past about 200 years" actually means - taking it literally I'd assume that this means that 'blacks get low scores in history tests' - why be suprised - mainstream history is white history.. I don't get big scores on vedic literature or american history - I'm not american or indian. Have I not understood.. It's just that this just doesn't seem even relevent..87.102.17.46 11:07, 20 October 2007 (UTC)

It really sounds like someones saying "there needs to more black geeks"87.102.17.46 11:08, 20 October 2007 (UTC)

I don't understand why this concept is so hard to grasp. It is the same thing as divisions in grades in school. The first grade is a prerequisite for the second grade. The second grade is a prerequisite for the third grade, etc. If you have never attended school prior to age ten lets say and then have the opportunity to attend school, do you start in the fifth grade because of your age or despite your age start in the first? You may long to hang with the fifth graders because they are your own age but you may not be able to do so successfully because you are not in the same grade. If your personal heritage is limited in the same way then guess what? You are in the same boat. If you lack about 4,000 years of directly inherited European history or European heritage and you integrate into a society that is based primarily on 4,000 years of directly inherited European history then guess what? You may feel that you deserve to be or that you belong in the fifth grade but without the prerequisite of the earlier four grades guess what? Clem 14:53, 20 October 2007 (UTC)

These issue are covered at Misplaced Pages pages such as Race and intelligence. One tool for trying to explore the relative contributions of genes and environment is the Twin study. There is discussion of results that have been obtained using such methods at "Race and intelligence", Race and intelligence (explanations), Race and intelligence (interpretations) and Race and intelligence (test data). --JWSchmidt 16:27, 20 October 2007 (UTC)

You are missing the point. The point being that due to Watson's work everyone assumes he is (was) referring to genetic differences (although if he were talking about Neanderthal man I would make that assumption too) whereas he might be referring to the disconnection with inherited majority culture, as explained above, that Blacks will forever have even if they intrabreed with Whites since inherited culture is not a birth right but a birth opportunity which might not be accomodated by parents due to death or desire. Multimillionaire 18:08, 20 October 2007 (UTC)

Winning a Nobel prize does not make someone immune to daft and non-scientific ideas - Linus Pauling, for example, had some fairly loopy ideas about the use of vitamin C as a cancer treatment. The part of the subsequent discussion that I really don't follow is Kadiddlehopper/Clem's "4,000 years of directly inherited European history". My father-in-law believes that Western civilisation entered a downward spiral when Latin stopped being a compulsory subject at school. Is Clem advocating we should resurrect the lost secrets of henge design and long barrow construction ? Seriously - many young people are not very interested in the history of their country or culture. This does not depend on the colour of their skin, neither does it prevent them participating fully in modern society. Gandalf61 16:34, 20 October 2007 (UTC)

Circumcision comes to mind. Multimillionaire 22:48, 21 October 2007 (UTC)

Why don't you ask Clem? Clem 18:11, 20 October 2007 (UTC)

Personally I think this is just a case of "white professor makes classic black gaffe - realises it's insulting and apologises" - nothing to see here - move along please.

However henge design and long barrow construction sounds great - is there a course I can take in this ? - I fully encourage any actions of this sort.87.102.17.46 16:57, 20 October 2007 (UTC)

...and then it could be a matter of calling a Spade, a Spade, a henge, a henge or a barrow, a barrow. Clem 18:38, 20 October 2007 (UTC)

There is a long and distinguished history of Nobel Laureates demonstrating using their celebrity to further their kooky, unorthodox or plain prejudiced ideas. As mentioned above Linus Pauling is an example, Kary Mullis is another. Watson is well known in the scientific community for his propensity for making loose associations between solid genetic data and wider social observations. Inevitably, this tends to rely on stereotypes. For example, I have heard him speak publicly in person twice. The first time, in Berkeley, California, he made some unfounded associations between race and virility based on the observation that melanocortins (which promote melanin production) appear to result in erections when injected. The scientists present just shook their heads. I later saw him speak in Edinburgh, Scotland and there he made some faintly misogynistic comments about woman scientists.

His recent comments are typical of Watson - the suggestion that racial selection may result in differences in "intelligence" (however you choose to define it) is controversial certainly, but not inherently unscientific if you stick to the facts. However, what tipped him over the line was his use of skin colour as a proxy for race, his use of the "them and us" language (suggesting they black people are inferior to us, white people), and the stupid comment about "people who have to deal with black employees find this is not true". The suggestion that one can infer something about a race based on "dealing" with a number of individuals of a certain skin colour is ludicrous and scientifically flawed. Add to the fact that he said this in a national newspaper and you can see what the fuss is about. These comments say more about Watson the man than Watson the scientist. If you read his books, you can begin to understand his insecurities and the frustrations he suffered during his life. However, given his position as the poster-child for the genetics community, these comments have done the field a huge disservice. Having spoken to colleagues about this - including some faculty at Cold Spring Harbor - the consensus appears to be that Watson will be encouraged to enjoy his retirement sooner than he might have anticipated. Rockpocket 18:39, 20 October 2007 (UTC)

Rather than speaking through the medium of 'the group' could you tell us what you think? - you seem to be saying that he should be sacked - but unwilling to actually attribute it to yourself.87.102.17.46 19:27, 20 October 2007 (UTC)

Also are the melanocortin comments unfounded as you say??

And these mysogenistic comments - could you quote or cite them?

And then you say "His recent comments are typical of Watson" - do you know him well? seriously?

Then you suggest that "If you read his books, you can begin to understand his insecurities and the frustrations he suffered during his life" - is this some sort of apology for him, or what.

I mean seriously at first judgemental - followed by brief psychoanalysis - maybe you should consider what it is like to be in the spotlight.87.102.17.46 19:59, 20 October 2007 (UTC)

I'm not in a position to influence the board's decision, which was why I attempted to provide what the wider community appears to think rather than what I do. However, since you ask, I think Watson has made enough questionable comments that this probably shouldn't be explained away as a slip of the tongue. I think that, for the benefit of Cold Spring Harbor and the people of colour that work there, the Board should ask him to resign and, if he doesn't, he should be sacked. This isn't really the place to have a discussion about opinions on this matter - I'm happy to discuss it further on your or my talkpage if you would like. However, on points of fact: Melanotan appears to promote penile erectins , melanocyte-stimulating hormone (MSH) stilulates eumelanin production. People with darker skins have more eumelanin. Melanotan is an analogue of MSH. Based on those basic facts, Watson proposed his theory. I can't quote verbatim his comments in Edinburgh, it was some time ago. To be fair to him they were not outrageous, more the sort of politically incorrect thing your grandfather would say. I don't know Watson well. I interviewed with him for a day a number of years ago and I have briefly spoken with him a few times since. However, everyone in the community has their own anecdote about what Watson said to them one time. Its disappointing if you spend any time with him and don't have a story to tell afterwards. If you wish a response to your other comments, ask me on my talk page. Rockpocket 20:30, 20 October 2007 (UTC)

So maybe next you see him you could tell him that he should leave for the benefit of coloured people? And people 'expect' and anecdote of 'what he said' (Oh My God I cant believe he said that! to exaggerate ) - and for this means he should leave - maybe you should prepare a dossier of what he may have said and present it to him for comment. - it's just ridiculous what you are saying.

And no - I don't want to come to your talk page for a bum party thank you very much.87.102.17.46 20:52, 20 October 2007 (UTC)

But what you and your colleagues are forgetting is that genome classification, like it or not, is around the corner and no one will be able to escape the ramifications of that. One little gene responsible for the amount of melanin instead of the actual amount might be enough to send someone to the back of the bus, due not to Watson's opinion but rather to his work. Clem 18:56, 20 October 2007 (UTC)

I don't think anyone is forgetting that at all. Even if people choose to discriminate based on genotype instead of phenotype, its still discrimination. Arguing that people who have black skin are less intelligent than those whith white skin, is no more scientifically justified than arguing women with blonde hair have larger breasts than women with red hair. Its shoddy science, and mixes social constructs with scientific ones in irresponsible and misleading manner. There are scientists addressing the genetics of race in a serious and scholarly yet accessible way, for example Armand Marie Leroi gives a really interesting lecture on it. Unlike the general public, who generally view medicine and physiology Nobel prize winners in science with something approaching reverence, the scientific community is more pragmatic. Watson is is a smart man, and his contribution to the field was seminal. Was. All he has done in the last 10 or 15 years is wrote memoirs and spout his personal - and largely unsubstantiated - theories. Its a sideshow but one tolerated, and to some extent encouraged, because meeting him is like experiencing history hand. When the sideshow starts attracting bad publicity, it appears the community are thinking that its time for it to stop. Rockpocket 20:33, 20 October 2007 (UTC)

The stabbing continues.. Stick the knife into the old guy - is that the answer. A nigger wouldn't do that (fact) - but you have no problems with it. This is disgusting.87.102.17.46 21:30, 20 October 2007 (UTC)

A "bum party"? Sounds fun. You asked my opinion and, hence, I gave it. I don't believe an individual should be a Chancellor of an academic programme that has an expressed purpose to educate the best students from around the world, of all races, when that individual has made public statements that appear to be racist at worst and demonstrates extremely poor judgment at best. My point is that, from personal experience, the questionable statements of his that were reported in the media are not as isolated as one might think. The opinion is more or less shared by the people I have discussed this with in the community. Feel free to take that information with all the authority due of an anonymous person in the internet, of course. If you have insight in this beyond what you have read in the media, I'd be happy to hear it, but otherwise I'd appreciate it if you could avoid personal insults, thanks. Rockpocket 21:51, 20 October 2007 (UTC)

Yes, and while were there - this is the science desk - not a tea room for gossip, rumours, and your personal opinion. Which for some reason you seem to think is relevent. Try the tea room or similar please.87.102.16.28 08:24, 21 October 2007 (UTC)

Thanks for your responses 87.102.16.28. However, the OP invited Rockpocket's opinion as well as his facts, not the attitude you seem to have developed. Try to be a little nicer. The science desk is not the place for a cat fight. Multimillionaire 11:32, 21 October 2007 (UTC)

• There is a link to the recent The Sunday Times article about Watson from the James D. Watson page. The Sunday Times reported that Watson said, "....that you should not discriminate on the basis of colour...". Reacting to the The Sunday Times report, Watson has said, "To all those who have drawn the inference from my words that Africa, as a continent, is somehow genetically inferior, I can only apologize unreservedly. That is not what I meant. More importantly from my point of view, there is no scientific basis for such a belief." As to the scientific basis of Watson's positions, The Sunday Times reported that Watson referred to "tests" when making his comments about differences in intelligence. Data from such tests are discussed at Race and intelligence (test data) and other related Misplaced Pages pages. Watson recently said, "The overwhelming desire of society today is to assume that equal powers of reason are a universal heritage of humanity....It may well be. But simply wanting this to be the case is not enough. This is not science. To question this is not to give in to racism. This is not a discussion about superiority or inferiority, it is about seeking to understand differences, about why some of us are great musicians and others great engineers." --JWSchmidt 00:13, 21 October 2007 (UTC)

Okay so Watson is not a racist. Great. So where does that leave us? Do we round up all the musicians and test their DNA and then deny entrance to music school of anyone not having genetic aptitude? What everyone seems to be forgetting is that I may have an identical twin I do not like to hang with because he or she has developed a personality I do not like. Same thing for Blacks. Suppose they turn out to be smarter according to DNA/intelligence test results? Maybe I don't want to hang with them, invite them to my club or over to my house, not because I am a racist but because they are too smart. 71.100.9.205 02:24, 21 October 2007 (UTC)

We are not yet in a position where whole genome analysis is generally available for individuals (unless you are James Watson or Craig Venter). Even if it were, we are not able to associate complex, ill-defined phenotypic concepts such as "intelligence" with specific alleles. So its not currently a realistic problem to have to worry about today. Also "being black" isn't a race, so to associate genetic correlations with race (should they be found) with a couple of genes that cause skin colour isn't scientifically robust.

However, Watson is right in one respect, just hoping that race is not a consideration in the genetic future is not enough to make it true. There might be a point in the not so distant future where we are in a position where genetically justified racial discrimination is a practical reality (beyond the current situation, where there can be issues over medical insurance and specific disease-causing alleles). This is something ethicists, policy makers and our society will have to wrestle with. However, this is all the more reason that those people in positions of responsibility and influence should be extremely careful not throw terms and concepts around that are scientifically unsound (such as confusing skin colour with race). Rockpocket 02:51, 21 October 2007 (UTC)

I think Watson has consistently argued for using genetic knowledge to empower people. Many parents prefer genetic research, genetic testing, genetic counseling and reproductive choice over genetic ignorance and leaving the fate of their children at the mercy of random genetic mutations. Is it more ethical to empower people to control their genetic futures or to throw up your hands and say, "this is knowledge that we dare not contemplate, these are topics we dare not even discuss"? --JWSchmidt 03:12, 21 October 2007 (UTC)

If we're straying from science into ethics etc, Gattaca is probably relevant as are probably a lot of other links. (And you seem (to me) to be writing as if in these cases it is a choice between the same child, with or without the genetic 'flaw'. If this were the case, there would be less discussion of the ethics) Skittle 23:01, 22 October 2007 (UTC)

Much of the "debate" over "choice" is driven by belief that it is unethical to abort human embryos that are found to have genetic defects. Is it ethical to deprive parents of the chance to decide for themselves if they want to raise children with genetic defects? In Gattaca, "genetic engineered in-vitro to be the optimal recombination of their parents' genetic material," is science fiction. I suspect that it will be many decades before there will be that kind of genetic engineering. Right now, it is possible to do in vitro fertilisation and genetic screening of the resulting embryos prior to implantation. Some parents who are trying to have healthy children while avoid genetic diseases will gladly make use of such tools for genetic screening of their children. --JWSchmidt 03:13, 23 October 2007 (UTC)

I'm not interested in entering into a debate, and was actually just thinking that people could suggest places where these ethical questions have been considered (as in the film Gattaca). However, over-simplifying the issues involved doesn't help, nor does surrounding words in "scare-quotes". If it were all down to a choice for the health of the child, there would be no ethical debate. As it is, we clearly differ (hugely) in what we consider ethical; I accept this, and really do not want to discuss it as it will just result in us both framing the debate in different ways. None of this is science, although it involves science. So can we recommend some places where people have pondered these things? Skittle 07:29, 23 October 2007 (UTC)

The National Information Resource on Ethics and Human Genetics claims to have, "the world's largest collection of material relevant to medical ethics and biomedical research". see also
--JWSchmidt 05:14, 24 October 2007 (UTC)

I certainly agree that the individual has a right and science the obligation to provide the individual with the means of knowing on the basis of his genome who and exaclty what he is in relation to his follow human beings past and present. My concern is that instead of empowering the individual that science will end up empowering the government or insurance companies or other interests instead. 71.100.9.205 04:14, 21 October 2007 (UTC)

This is where scientific research and science policy, and scientific ethics merge. Scientists rarely avoid addressing scientific questions because the findings could be used for immoral or improper purposes. However they do (or should) avoid research for immoral or improper purposes themselves. There is a subtle and undefined line between these two things. For example, a gene found that is associated with a risk of developing a treatable disease (like BRCA2). Great, we can screen people for that disease and prevent many from dying from breast cancer. However, we can also permit insurers to demand someone whose mother died of breast cancer be screened before they offer them insurance. Does it really matter what the purpose in mind of the scientist was when he worked to develop the test, it doesn't change how it could be used? Scientists unearth new knowledge, how that knowledge is used - for good or for bad - is down to policymakers. So if you have a concern (and its a very valid one, I would say) then its your political representative you should be concerned with, not the research. (A corollary to that, of course, is that scientists should probably keep their mouths shut when it comes to policy and focus on the research, otherwise they are fair game.) 05:50, 24 October 2007 (UTC) —Preceding unsigned comment added by Rockpocket (talk • contribs)

"scientists should probably keep their mouths shut when it comes to policy" <-- What we need is more former actors and a bunch of people who know nothing about science to determine our science policy for the new millennium. We already have the definitive guide to science policy, it covers everything.
--JWSchmidt 16:05, 24 October 2007 (UTC)

Quite, but the people get who the people vote for (usually). Anyway, it appears CSH took the politically expedient approach and welcomed his early retirement. Rockpocket 18:42, 25 October 2007 (UTC)

scince

nazrul is the right veterinarian

2 I think many doctor degrees and receive extensive training in veterinary medical practice, and there are many they career fields open to those with veterinary degrees other than clinical practice. —Preceding unsigned comment added by 4.236.108.103 (talk) 23:48, 19 October 2007 (UTC)

Is there a question here? SmileToday☺(talk to me , My edits) 23:54, 19 October 2007 (UTC)

Yes

Are there any careers for qualified vets other than veterinary practice.. Yes a few - for instance as a goverment official making guidlines for animal care standards, or perhaps in the slaughter of animals, or in animal related disease control for instance pest control..I'm sure there are others.87.102.17.46 09:58, 20 October 2007 (UTC)

math

2+56 45*78954 789/7765

Use a calculator, such as the ones generally found on most operating systems. We will not do your homework for you, but we can help if you do not understand. SmileToday☺(talk to me , My edits) 23:54, 19 October 2007 (UTC)

Those questions are rather disparate, I know six year olds who can easily calculate 56+2 (which is the same as 2+56) using the method of holding up two fingers and counting from 56, folding down one finger at a time. The number they stop on is their answer (56, 57, 58... answer's 58). But the other are far beyond that level and would require a calculator or high school level maths and pen and paper. If this is homework and you're allowed to use a calculator, use a calculator and it'll be simple. Otherwise get a pencil and some paper ready, and consult long division and multiplication algorithm. Is there such a think as a mathtroll? --Psud 03:11, 20 October 2007 (UTC)

Probability

This is a question I found in my previous entrance papers. As u all know I am a Math major and does not understand any significant reasoning for this question. Dont be surprised me in asking a bio q, in contrary to my usual phy doubts (esp. Relativity doubts).

"What is the probability for a couple of having 4 sons ? " Ans:a) 1//4

   b)1/8
   c)1/16
   d)1/32

Answer given is 1/32. I dont understand any way to calculate the probability as you see how many timees the couple mate etc. are not given.

Help me ASAP. Oasa 23:55, 19 October 2007 (UTC)

{edit conflictx2} Because the chances of having a son are about .5, then that to the fourth power is 1/32(?). It works because they are independent events. Although I do understand the issue with the question, as it is not particularly specific. SmileToday☺(talk to me , My edits) 00:03, 20 October 2007 (UTC)

It's binary. Zero for girl, one for boy, 0000 is four girls, 1111 is four boys and the number of possible sets minus one. The answer is 1/16. The question is poorly worded. I guess you are supposed to assume that there are four and only four children, because otherwise you can't calculate an answer. Unless they mean "four in a row". --Milkbreath 01:49, 20 October 2007 (UTC)

Thank you SmileToday, but see I cant get you fully, can you explain more.Oasa 01:44, 20 October 2007 (UTC)

The question could read: Assuming that a couple has four children, what's the probability of them all being boys? Does it make more sense to you written like that? --Cody Pope 01:50, 20 October 2007 (UTC)

SOrry cody pope, the questijon is not like that and is exactly that I hv quoted. I cant make out any explanations as the couple may mate infinitely and result in getting all daughters. Why cant it contribute to sample space. Independent Event , how can it be dont it depend on which chromosome comes from the Male. Any logical explanation my frnz..... Oasa 02:10, 20 October 2007 (UTC)

By the way is the book wrong or you ? .5 ^ 4is 1/16 and not 1/32 which is correct and how ? Oasa 02:39, 20 October 2007 (UTC)

The book is definitely to blame here. Not only doesn’t it list some important assumptions, the most important being that the couple has exactly four children, but it gives the wrong answer for the set of assumptions that I think it’s making!

There are several other important assumptions that I presume the book is making: 1) The probability that a baby will be a boy is always exactly 1/2, independent of any other factors such as the genders of a couple’s previous children. 2) When a couple chooses to stop having children is independent of the genders of the children they’ve already had. 3) Either none of the children the couples in question have had have died, or the mortality rates of boys and girls are equal.

With the above assumptions, the genders of the babies a couple has is a Bernoulli process with p=1/2. The number of boys there are in families of four children will then follow a binomial distribution with n=4 and p=1/2. The answer to the problem could be computed from the probability mass function of the binomial distribution with k=4, but the easier way is to just use the definition of statistical independence. Either way, the answer is supposed to be 1/16, not 1/32.

In reality, the simplifying assumptions the book is making don’t model the real world very accurately. With the assumptions the book is implicitly making, 1/16 = 6.25% of families with exactly four children include four boys. In reality, more like 9.1% of families with exactly four children include four boys. MrRedact 04:16, 20 October 2007 (UTC)

My guess as to why the author gives 1/32 instead of 1/16 is that they committed a thinko in trying to avoid the common error of confusing 'the probability that all four children have the same gender' and 'the probability that all four children are male'. In the former case, the probability that the first child has a gender is (simplified to) 1, leaving only three coin flips for each successive child having the same gender as the first one. Eldereft 05:19, 25 October 2007 (UTC)

nazrul

nazrul thank for halp ing me —Preceding unsigned comment added by 4.236.108.103 (talk) 23:59, 19 October 2007 (UTC)

Kazi Nazrul Islam?--VectorPotential 00:44, 20 October 2007 (UTC)

Nazgul? --24.147.86.187 02:22, 20 October 2007 (UTC)

I suspect someone called Nazrul is thanking someone for their answers to his previous questions.--Shantavira| 07:40, 20 October 2007 (UTC)

October 20

Nerves

Why do some nerves in our body like in our fingers able to reattach or grow back together after they have been severed (not in all cases) while the nerves in our brain or around it are not able to?

The general rule is that axons (which make up the substance of nerves) do not regrow in the central nervous system (brain and spinal cord) while those of the peripheral nervous system (like those innervating the fingers) have at least some modest ability to do so. Specific reasons involve peripheral nerves' ability to maintain basement membrane integrity following nerve injury, the ability of peripheral glial cells to provide a substrate for axonal regrowth, and the secretion of axonal regrowth-inhibiting molecules by some gilal cells in the CNS. See nerve regeneration, which should answer some of your questions. --David Iberri (talk) 04:01, 20 October 2007 (UTC)

The search for molecular mechanisms continues. For example, see Nogo A. --JWSchmidt 04:13, 20 October 2007 (UTC)

How did they figure it out?

Seventy-one percent of Earth's surface is covered by water. How has this been calculated? - Pyro19 04:19, 20 October 2007 (UTC)

I suppose you're wondering how can we tell with all the untold and transient rivers, brooks, lakes, ponds and puddles and swamps in the world? Obviously, no truly precise figure even exists, it changes constantly and the boundary between dry land and water is quite fuzzy. But the Earth's surface area is about 500 million square kilometres (200 million square miles), so one per cent of that is about half the land area of the U.S. or Canada. If you just count the oceans and seas and major lakes plus a rough estimate for all the rest, you can be sure that your result will be accurate to plus/minus one per cent.--Rallette 08:38, 20 October 2007 (UTC)

A Monte Carlo estimate would actually be pretty straightforward. Just pick, say, 1000 random uniformly distributed (over the sphere, which is the only mathematically tricky part) co-ordinate points and check each point (easily done with modern technology such as Google Earth, but also possible simply by visiting the place in question) to see whether it happens to be covered in water. For a more accurate estimate, pick more points. —Ilmari Karonen (talk) 11:03, 20 October 2007 (UTC)

A disadvantage of using a Monte Carlo method is that it converges rather slowly. In order to get an answer that's twice as accurate, you have to use four times as many points. You can instead get linear convergence by using an equally-spaced grid of sample points on an equal-area map projection of the earth. With one of these maps, equal areas on the map correspond to equal surface areas on the earth, which is crucial to this calculation. Of the equal-area projections, the various Gall-Peters projections have an advantage in that you can have a rectangular grid of sample points that completely covers the planet, without any of the sample points being "off the map". As with the Monte Carlo method, you just count what percentage of the sample points are over water. MrRedact 20:22, 20 October 2007 (UTC)

Suger Free products

Are the ingrediants of suger free products safe for health ? —Preceding unsigned comment added by Aalokjani (talk • contribs) 06:42, 20 October 2007 (UTC)

You'll have to be a lot more specific than that, although we do have a section on health controversies involving specific sugar substitutes. Someguy1221 07:03, 20 October 2007 (UTC)

Depends on what they are and, more importantly, in what quantity. Sugar itself is one of the unhealthiest ingredients in a lot of food eaten in the West simply because there is too much in it. Avoid food that has sugar added to it. Or substitutes, for that matter, if that is what you're asking about. DirkvdM 09:46, 20 October 2007 (UTC)

• Some people believe sugar substitutes have their own dangers and you are forgetting that food without added sugar often has high amounts of fat. Anything can be bad for your health if you don't do it in moderation. If you use sugar moderately, there's no danger in using non-sugarfree products unless you are allergic. - Mgm| 10:36, 20 October 2007 (UTC)

Too much Sorbitol can give you diarrhoea. Compulsive sugar-free Polo munchers beware. --Kurt Shaped Box 12:15, 20 October 2007 (UTC)

Don't listen to the widespread myths about added vs. "natural" sugar. Sugar is just sugar. Of course, there are different kinds of sugar, like sucrose (this one is most often meant when one just says "sugar"), glucose, fructose, galactose, mannose etc., but they cannot be separated into added vs. natural.

And you cannot be allergic to sugar.

Considering the original question, you should be more specific, but you may be interested in knowing how ADIs (acceptable daily intake) are established: Mammals (often rats) are fed a certain amount of the substance in question every day, for their whole life. Different doses are tried, and the animals are dissected. The dose (in amount of substance per kg body weight per day) at which no significant pathological differences are evident when compared to animals not fed with the substance is then divided by a safety factor (usually 100). Icek 16:45, 20 October 2007 (UTC)

Also, if you feed the hummingbirds - please don't give them sugar substitutes under the mistaken impression that it's 'healthier' for them. Yes, people really have done this. --Kurt Shaped Box 18:52, 20 October 2007 (UTC)

That's awful. If the hummingbirds can't tell the difference and it is their nearest 'food' source, they'll slowly starve to death. Actually, with the metabolism of hummingbirds, they might even die in a day or so. Reminds me of a vegetarian couple who had a dog (why?) and decided the poor animal should eat vegetarian too. I'm tempted to say people like that should not be allowed to have children. I don't mean that in an eugenetic sense, but rather that with all their good intentions they might end up torturing their own children. DirkvdM 17:25, 21 October 2007 (UTC)

Dogs are not obligate carnivores and can happily and healthily survive on a careful vegetarian diet. If they were feeding their cat a vegetarian diet, that would be a different matter. Honestly, it's like the Canary Islands all over again. What kind of trivia fiends are we, if regulars don't know these commonly-known 'little known facts' :) Next thing you know, they'll be claiming the tomato isn't a fruit... Skittle 22:47, 22 October 2007 (UTC)

There was a vegan kook I once encountered on a message board who was feeding tofu and meat substitute products to his OWL! The belligerent little fool didn't seem to see the correlation between the owl's diet and its constantly getting sick and would berate anyone who suggested that he put his politics aside and give it some real meat. He also tried to keep the bird in the same aviary as his finches at one point - with predictable (though not for him) and distressing-for-him results. --Kurt Shaped Box 23:35, 22 October 2007 (UTC)

At least the owl would have gotten some meat. --Psud 11:05, 23 October 2007 (UTC)

Surface tension of oil drop on water surface

I want to write an algorithm which models the behaviour of oil floating on a water surface. What are the forces etc. I need to take into consideration? Especially, what are the formulae for surface tension in this situation? Thanks. Jakob.scholbach 08:59, 20 October 2007 (UTC)

Fluid dynamics and Brownian motion might help you. − Twas Now ( talk • contribs • e-mail ) 09:22, 20 October 2007 (UTC)

Is it that you want a static model - ie giving the shape of the oil drop - in this case gravity Displacement (fluid) and for the surface tension the oil/water and oil/air surface energy - would be useful? Was it static or dynamic? —Preceding unsigned comment added by 87.102.17.46 (talk) 09:53, 20 October 2007 (UTC)

Well, I have in mind an algorithm/formula which solves the following: I have an oildrop on a (static) water surface, the boundary of the water container is somehow given. What form will the oildrop take eventually? For example, if it looks like two circles, which are "glued" along some intersection (thus somewhat resembling the 8), I want the algorithm to figure out that the form will separate into two smaller oildrops, as long as the container does not allow merging the 8-figure into one single (larger) drop. Thanks for the help. Jakob.scholbach 10:02, 20 October 2007 (UTC)

Right that's a static model.. It can be done... Have you tried working out the simpler case of when a drop of water is on a flat (could be glass) surface? and would you need more help to do this? If you can do that then the oil on water case should be a possibiity.87.102.17.46 10:22, 20 October 2007 (UTC) sorry misread

Actually there's not much reason for it to break into two drops at all - for it to do that would require some one stirring it, or a lot of currents in the water. If the water is perfectly still then the oil drop would spread out to a circular thin sheet. That's what would (almost certainly happen)

But you ask for the opposite it seems - for a drop to separate into two smaller drops... If this occurs then will those drops separate into 4 even more small drops? If so you may end up with a monolayer

Can you re-explain - the description is a bit confusing.87.102.17.46 10:28, 20 October 2007 (UTC)

I didn't know that a glass surface is easier. If you could provide help on this, this would probably be sufficient for my purposes. (Eventually, I want to apply it to an image recognition process, so it does not exactly matter to use the most rigourous approach, as long as it still works). Thanks again Jakob.scholbach 10:29, 20 October 2007 (UTC)

I'm talking about something like . The black gadget is the oil-drop. The red lines are the boundary of the container. Thus (I suppose) the drop could not attain its optimal (spherical) form, but should separate into two smaller drops. These could (and would) take spherical form and would not split into smaller drops. Jakob.scholbach 10:37, 20 October 2007 (UTC)

Right - that's complicated.. First of all I can assume that the oil is repulsed by the sides of the container - (otherwise it will just stick to the sides - with hemispherical ends I imagine).

With reference to the glass I was thinking at first you meant the cross sectional shape eg

The main factor here is that the edge of the drop (the perimeter) is at higher energy than the innards - this is why drops of water are spherical/circular - to minimise the perimeter length/surface area.

So for your drop to split into two you would have to show that the two drops have a lesser perimeter than the whole drop.. Actually I don't think this is the case.. I think it's probably the other way round ie two small drops would fuse together.

Anyway I could help with the cross section problem - but I don't think I can solve this one. Hopefully someone else will.. If you get no luck I would try the maths desk - someone there would (hopefully) have sufficient skill to be able to solve this.

Just to clarify though - do you want a 'formula' that gives the shape of the drop as a function of time? (it might be possible to 'bodge' this..)87.102.17.46 11:00, 20 October 2007 (UTC)

OK. I don't need an exact formula, which tells the evolution of the drop(s) depending on the time etc. I just want to find a model which (in a computer image recognition situation) tells me to separate the above two parts into two separate ones. I thought the drop model is the right one. But I don't have to stick to this. Just something which quantifiably tells me: the point, where the two parts "kiss" is not optimal, in the sense that a drop would "try" to change its shape there in order to minimize its boundary length locally at this point/area. Jakob.scholbach 11:31, 20 October 2007 (UTC)

In terms of the image recognition - would searching for circles work - in the case where the figure 8 situation occurs it should recognise two circles - assuming you look for circles using a boundary condition and set the program to register a circle when ~70% or more of the circle boundary is present?87.102.17.46 11:51, 20 October 2007 (UTC)

Regarding your sample image, instead of splitting in two, wouldn't the smaller portion of oil (on the left) actually get pulled into the larger portion (on the right)? It's rather like having two identical balloons with different amounts of air in them connected. The fuller balloon will take most of the air from the less full balloon because the tension on the outside of the less full balloon is higher than it is on the fuller balloon. (see here) -- HiEv 17:27, 22 October 2007 (UTC)

Hm. That may work. I didn't think in this direction, though, as the forms may also be rather elliptic or oval. Jakob.scholbach 12:08, 20 October 2007 (UTC)

Distance to the moon and sun calculation

Indian proto physicist/mathematicians calculated the distance from earth to the moon and sun early in human history (was it 2 millenia ago?). What method did they use? Keria 09:34, 20 October 2007 (UTC)

I can't find a reference for that - though I looks likely that they knew that the sun diameter/earth-sun distance ration was 1/108 - this can be obtained by angular measurements.

The article Indian astronomy doesn't mention it - is there a reference for this?87.102.17.46 09:50, 20 October 2007 (UTC)

See Parallax#Lunar parallax and Parallax#Solar parallax.--Shantavira| 12:03, 20 October 2007 (UTC)

A Greek astronomer did such a calculation "2 millennia ago": see Aristarchus of Samos and Aristarchus On the Sizes and Distances. I don't say that it wasn't done in India also; ancient Greek learning is more remembered in western countries. --Anon, 13:48 UTC, October 22, 2007.

DVD-R Strange optical effect

When looking at a white light (bulb) reflected through a dvd-r I get a strange optical effect.

1. A primary reflection (slightly coloured due to the funny colour of the disc)

2. Some bands of colour that I'd expect due to diffraction.

3. 3 sub images of the light source (quite in focus like the primary reflection) except that they are coloured blue, green/yellow and red. (these are obtained by titling the disk so that the primary (whiteish) image is not visible)

What can be the cause for (3.) - the images are a. in focus b. clearly three different colours and c. not smeared like I would expect for diffraction.87.102.17.46 11:26, 20 October 2007 (UTC)

What do you mean by "relfected through"? Exactly what kind of DVD-R are you using? How close is the DVD-R to the bulb? --JWSchmidt 15:50, 20 October 2007 (UTC)

"Reflected by" I should have said. (I'm not looking through the disk). (ie my eyes are on the same side of the disk as the light)

Make = MAXELL (if there's more info tell me what to look for..)

The DVD-R is 4-10 ft from the bulb.

Another point the 'reflected' monochrome images are smaller (less than 1/2) the main reflected image.

The red image is quite blurred

The blue and green/yellow are quite clear though - I can see in the 'reflection' features on the light..Because the lampshade is round - I can see 3 different coloured lampshades - clearly as 3 round objects (the images overlap)87.102.17.46 16:27, 20 October 2007 (UTC)

(And I'm looking at the recording layer obviously not the top surface with 'maxell' etc printed on it)87.102.17.46 16:31, 20 October 2007 (UTC)

Note It looks like the bands of colour in 2. were from an external light source.87.102.17.46 19:05, 20 October 2007 (UTC)

• I only see one reflected image using two other brands of DVDR and an incandescent light bulb. --JWSchmidt 02:10, 21 October 2007 (UTC)

Commercial DVDs are often multi-layer. You might be seeing a reflection off the two layers, and the face of the disc. You might not see it on a DVDR, since many of them are single-layer (4GB) --Mdwyer 05:56, 21 October 2007 (UTC)

Would the diffraction from a monochromatic light source form an image (the light is fluorescent)87.102.16.28 08:20, 21 October 2007 (UTC)

Fluorescent lamps don't actually put out "white" light. They have strong peaks at the particular colors emitted by Mercury (element) and a redish component emitted by the phosphor. You're seeing a separate image for each wavelength that's prominent in the light; the ones that are "smeary" are because there, the spectrum of the light is more-continuous, without strong individual "peaks" (colors).

Atlant 17:14, 21 October 2007 (UTC)

Thanks I finally worked that one out.. There's a related question about diffraction below if you can help.87.102.0.6 13:38, 22 October 2007 (UTC)

Physics-solid state

What is "spin injection"?How could it be done?Is a superconductor material used for it? —Preceding unsigned comment added by 80.66.179.40 (talk) 12:58, 20 October 2007 (UTC)

It's the generation of polarized electrons - see spin pumping and spintronics. Icek 17:11, 20 October 2007 (UTC)

...Of course, if someone wants to write an article on spin injection, we'd all be pleased to see the redlink turn blue. TenOfAllTrades(talk) 17:37, 20 October 2007 (UTC)

I think a superconductor is not used - or at least is not neccessary for this process.87.102.17.46 17:45, 20 October 2007 (UTC)

Placed in the cold

say a person is placed in an environment where he constantly feels cold. given that he consumes the same amount of food (or rather the same energy intake) would he get fatter or thinner? would he get fatter because his body would respond to the cold by becoming a better fat storer and build up layers of fat and that his body slows down metabolism to conserve energy; or would he get thinner because his body would try to generate heat to keep warm?--82.46.27.191 14:23, 20 October 2007 (UTC)

Presuming that the person's weight and food intake were perfectly balanced before being put out in the cold, he would get thinner. Shivering uses energy, if food (energy) intake remains the same, he'd get skinnier until he reached the weight that his energy intake/expenditure could support. --Psud 15:11, 20 October 2007 (UTC)

This article is about rats, but it describes results for humans: "data are available to suggest that early exposure to cooler environmental temperatures may increase body weight in humans as well". --JWSchmidt 15:42, 20 October 2007 (UTC)

That article is describing an experiment where the rats were raised in various temperatures, and had access to as much food as they needed. The original question states "same energy intake". The article also describes the effect of rearing temperature, not the effect of putting an adult animal which grew up in "normal" temperatures into a cold environment. --Psud 23:19, 20 October 2007 (UTC)

If energy expenditure would in the long run cause the torso to hypothermiate (that's probably not a verb :) ) then it would make sense to keep that warm at the expense of the (relatively expendable) limbs, possibly even by storing fat (no idea). But the body would not know that, at least at first. And that this makes sense (to me) doesn't mean that's what the body would do. Of course it's also a matter of how active you are, but I suppose you mean sitting still. In such a case the body starts to shiver at first (an observable fact), which keeps the whole body warm. But you're talking about a much longer period of time, so maybe after a while the body will 'get the message' that this is permanent and change its strategy. Then again, if you're talking about such a long time, then the cold can't be too severe, or you'd die before any weight-effects can be observed. This reminds me of the partizans in Belarussia who started as escapees from nazi prisons and had to endure up to months in the cold before they found a partizan camp (those forests are huge and of course the partizans were trying not to be found). So maybe that would be a good source - a real-life experiment. DirkvdM 07:17, 21 October 2007 (UTC)

use of fins(extended surfaces)

why is the use of fins sometimes avoided? —Preceding unsigned comment added by 59.95.220.51 (talk) 18:11, 20 October 2007 (UTC)

It's not entirely clear what subject is being asked about - could you be more specific as to what sort of fins?87.102.17.46 19:06, 20 October 2007 (UTC)

To reduce drag perhaps. Or because they can catch in your throat. Unless you are able to give us some context, perhaps it would help to read the article on fin which tells you under what circumstances fins might be employed.--Shantavira| 09:18, 21 October 2007 (UTC)

Can transfusion cure diseases?

If we do multiple transfusion in the case of AIDS or malaria, why does it not cure a patient? Some part of the virus/parasites are getting out of the blood, aren't they? —Preceding unsigned comment added by 83.59.233.33 (talk) 18:18, 20 October 2007 (UTC)

• I'm not sure about malaria, but I do know that the HIV virus incorporates its viral DNA into a cell's nucleus, so even if the blood is transfused, said DNA could just be activated to make more viral particles. Also, not all infections go through the blood stream. Sometimes a virus can simply invade a neighbouring cell through a near-direct interaction. You really gave the answer yourself. Some of the virus will be in the blood, but not all of it, so targetting the blood alone won't cure the patient. - Mgm| 18:26, 20 October 2007 (UTC)

• In the case of AIDS, it is commonly accepted that the HIV virus is responsible for the disease. In a blood transfusion, you (optionally) remove some of the blood from the patient and replace it with blood from a donor. Soon after this new blood is given to the patient, it, too, would become infected with the HIV virus. You would have to drain all of the blood out of a patient, "rinse" the blood vessels, and then refill the patient with new blood. As far as I know, such a process is not possible in modern medicine. The other problem you would encounter is that transfused blood from a donor has white blood cells removed, so the patient would be very susceptible to disease. Andrewjuren(talk) 18:36, 20 October 2007 (UTC)

OK, some virus will be in the Bone Marrow, but it can also be chemically destroyed. So, how does the virus can still be there? —Preceding unsigned comment added by 83.59.233.33 (talk) 18:43, 20 October 2007 (UTC)

I asked a similar question a while back myself WRT to HIV/AIDS. I got some good, detailed answers. Have a read. --Kurt Shaped Box 18:47, 20 October 2007 (UTC)

I recently read that with current drugs, HIV can be killed in all parts of a person's body, except in the brain (where it is safe behind the blood-brain barrier) and the testicles (where presumably a similar barrier exists). --Psud 23:16, 20 October 2007 (UTC)

But without either one, you probably wouldn´t wanna live anymore would you? :p --antilived 06:10, 21 October 2007 (UTC)

Replacing some of the blood would be like bloodletting, which doesn't help against infections. But suppose we would try to replace all the blood. I doubt if that can be done. Blood transfusion is meant to replenish the blood of someone with severe blood loss. One might also use it to reduce the concentration of some substance in the blood (don't know). But a virus would have to be completely wiped out, so all the blood needs to be replaced. And unless you do the transfusion at a coronary artery, where all the blood passes through, you'll always miss some of the blood. But let's be optimistic and suppose one complete transfusion (about 5 l of blood) would replace 90% of the blood. With the second transfusion you'd have replaced 99% (not mathematically entirely correct, but this is just an indication). To reduce the remaining blood to one drop (say 5 mm) you'd have to replace 1/100 = 99.99999% of the blood. That would require 7 complete transfusions (how many donors would that require? About 100?). But that one drop would still hold enough viruses to get you sick again. I don't know any of the details here, just wanted to point out this issue. DirkvdM 07:59, 21 October 2007 (UTC)

The easy answer: HIV isn't just in the blood, it's other places too, and so a complete blood exchange would not result in a cure for AIDS. Psud alludes to these "reservoir sites" in his answer. Similar answers apply to most forms of malaria as well, where parasites in the liver would not be removed by blood transfusion. Also: the coronary arteries are small, and only a tiny amount of blood passes through them at any one time. They are terminal arteries, not major arteries. - Nunh-huh 09:00, 21 October 2007 (UTC)

On second thought, if there is some stage in the parasite's life cycle where it needs to get into the blood, it might still work. Isn't that the case with malaria, the cause of the fever resurging every two or three days because the parasites break out of the cells and go into the bloodstream to infect new cells? Suppose you could continuously refresh the blood with some affordable substitute, then wouldn't that eventually reduce the number of parasites to something the body can deal with? At least it would reduce the severity, which could be a life saver. Of course the substitute would have to be really cheap if it is to be used in such high quantities for (usually) the poorest people on Earth. DirkvdM 17:34, 21 October 2007 (UTC)

As cheap as quinine, you mean? - Nunh-huh 00:41, 22 October 2007 (UTC)

Probably not, but the problem is that anti-malaria drugs are becoming ever less effective and new ones don't come fast enough. And that includes quinine, I believe, but I can't find the word 'resistance' in the article. DirkvdM 07:15, 22 October 2007 (UTC)

Old school antibody production (for research applications)

Since antibodies used in research can be so expensive, do some scientists still prepare them the old fashioned way, raising an immune response in an animal? If you happened to do a lot of research with a few different proteins, it would surely be economical to end up with a hybridoma, producing your favourite antibodies? Is the amount charged reasonable, or are they rolling in profit? --Seans Potato Business 19:29, 20 October 2007 (UTC)

Making antibodies for research use is not cheap, but if you will be using large amounts of a particular antibody it might be worth making your own. Sometimes there is a well-defined antigen that efficiently stimulates antibody production in rabbits. Immunizing a few rabbits with such an antigen can provide you with antiserum that might cost you many thousands of dollars to buy commercially. Making your own rabbit antisera is easy to do if your institution routinely houses rabbits. Hybridoma production requires some special skills and equipment. If you have access to cell culture facilities and your institution houses mice, then it might be worth trying to produce a monoclonal antibody. Growing and screening hybridoma cell lines can be labor-intensive. However, many hybridomas have been made by research scientists, and if you ask around it is often possible to find someone who will send you the hybridomas you want. Then you just need to culture them and collect the culture medium. Of course, anytime you make your own antibodies, you have to take the time to characterize them. If you just need a small amount of an antibody, it is best to just pay a commercial source. --JWSchmidt 20:37, 20 October 2007 (UTC)

Imperfections in gel electrophoresis

What causes those imperfections, where bands appear to diverge in the same way a person's handwriting might leave the lines on which they're writing, if they look up from the page and continue to write? Sometimes, you see an individual line which is kind of squiggly. My guess would be uneven application of electric current and/or, maybe more likely, uneven density of the gel due incomplete mixing and/or different rates of cooling. Are the likely and/or are there any other contributing factors? --Seans Potato Business 19:50, 20 October 2007 (UTC)

It sounds like you are describing several different problems. Sometimes the gel is not polymerized in a uniform way. One way this can happen is if you forget to mix the gel's solution before trying to form the gel. Another common problem is loading unequal samples on the gel. This can either be different volumes loaded into wells or use of different buffers for some of the loaded samples. For individual lanes, irregularities can be generated by having samples containing high molecular weight substances or undissolved solids that do not migrate normally through the matrix of the gel. Sometimes a dirty or damaged glass plate is to blame. --JWSchmidt 20:17, 20 October 2007 (UTC)

This page (and the links on it) show a whole bunch of real-life gels that have suffered various indignities. Do any of them look familiar? TenOfAllTrades(talk) 04:39, 21 October 2007 (UTC)

opu

thank you

what is theveterinary

hofast make veterinary  —Preceding unsigned comment added by 209.2.60.95 (talk) 19:55, 20 October 2007 (UTC)

We have articles Veterinarian and Veterinary surgeon

To become a "vet" as it is commonly known takes 5 to 6 years at degree level. Prior to that school or college course need to be taken and examinations passed. So quite a long time.87.102.17.46 20:04, 20 October 2007 (UTC)

(edit conflict) When you say "the veterinary", I assume you mean the noun meaning "animal doctor". Normal American English uses "veterinarian" for the noun, but "veterinary" can also be used that way, especially in England, or parts of it, I believe. In fact, the words "veterinarian" and "veterinary" are synonymous both as nouns and adjectives. And, yeah, we help people, but it takes a minute or two. Jeeze. --Milkbreath 20:06, 20 October 2007 (UTC)

Yes that's right - it can take a while to get a good answer - sometimes only minutes, but more often hours or even days. The questions stay on this page for up to a week and then get archived. It's very rare for a question to go unanswered.87.102.17.46 20:33, 20 October 2007 (UTC)

shokna

you dont halp any bardy . —Preceding unsigned comment added by 209.2.60.95 (talk • contribs)

Perhaps you are looking for this...Homework Help. Clem 20:50, 20 October 2007 (UTC)

Crystals Being Grown in Space

I have come up with a perplexing issue. I have heard that there was a project in which they put frozen crystal compounds into tubes and launched them in space to see how they would grow. Was there ever a project like this and if so when? What data did they collect? 71.142.239.228 22:42, 20 October 2007 (UTC)Macky

Are you referring to protein crystallization experiments? Rockpocket 01:31, 21 October 2007 (UTC)

I believe I am. Thank you for responding.(UTC)Macky —Preceding unsigned comment added by 71.142.239.228 (talk)

October 21

bamboo

Does the earth/soil that Bamboo grows in become depleted to the point that would classify it as non-sustainable? —Preceding unsigned comment added by 76.79.66.37 (talk) 00:09, 21 October 2007 (UTC)

It looks like translation from Dutch is taking place at our Crop rotation article. I don't see Bamboo on the list. However, either of those links might help you.--Mdwyer 05:52, 21 October 2007 (UTC)

Bamboo is essentially no different from any other crop. If it is being harvested, then the soil will eventually become depleted. If it is growing wild, or for decoration, it can sustain itself for many generations because the nutrients are being recycled.--Shantavira| 12:02, 21 October 2007 (UTC)

Female cats

Please respond from a past experience if you've had a similar situation to deal with. We have a female cat that is mostly indoors and plays by herself. She avoids wild cats and we keep her away from the occasional male cat. Could there be a cordial relationship between her and a female wild cat? —Preceding unsigned comment added by 61.17.221.186 (talk) 05:31, 21 October 2007 (UTC)

Just to clarify - are you asking us if we think that your cat is a lesbian? --Kurt Shaped Box 05:38, 21 October 2007 (UTC)

Wild cats are solitary creatures. Domestic cats are territorial and they don't welcome other cats unless they are brought up together. You will find more information at Cat#Cohabitation.--Shantavira| 09:34, 21 October 2007 (UTC)--Shantavira| 09:34, 21 October 2007 (UTC)

Do you mean "wild cat" as in feral cat or really a wildcat? I think it will differ quite a bit if you are talking about domesticated-but-feral or totally undomesticated cats. --24.147.86.187 14:48, 21 October 2007 (UTC)

I have to disagree (slightly) with Shantavira. Domestic cats (pet or feral) are social to some degree as studies of colonies of feral cats have shown. It is true that those cats which grow up together are the most likely to become buddies. However, it is possible to introduce adult cats to each other such that they become friendly or at least tolerate each other. Thus it is possible that a wild (feral) female cat could become friends with a female pet domestic cat. It depends on their individual personalities and the circumstances of their introduction.--Eriastrum 19:00, 21 October 2007 (UTC)

• You might also be interested in the Misplaced Pages article Homosexuality in animals. There's no info on cats, but the article does report on positive accounts of homosexuality among lions. --M@rēino —Preceding comment was added at 18:17, 22 October 2007 (UTC)

diffraction image

1. Can a diffraction grating make an image of a monochromatic light source?

2. (see Misplaced Pages:Reference_desk/Science#DVD-R Strange optical effect )When using a DVD-R to look at a poly-monochromatic light source the reflected image is many (~5) times bigger than the images I assume to be due to diffraction. Why is this?87.102.16.28 11:47, 21 October 2007 (UTC)

Plant question

Could somebody please tell me what plant species this is?: http://en.wikipedia.org/Image:Plantbathroom1.JPG http://en.wikipedia.org/Image:Plantbathroom2.JPG and if it would have been around in the Mesozoic era, and if it would have existed even before and survived the Permian–Triassic extinction event? Thank you. (PS: I seemed to have made a mess of uploading photos, sorry! am not sure exactly how to do this, if anyone can correct, please do, thanks.)--AlexSuricata 15:59, 21 October 2007 (UTC)

It looks like an asparagus fern. Ferns have been around a long time. According to Geologic time scale, they arose in the late Carboniferous, before the Permian. Whether that species was around then, I don't know. By the way, wait for the steam from your shower to dissipate before you try to take pictures in your bathroom, OK? --Milkbreath 16:16, 21 October 2007 (UTC)

It's not steam, it's the 1/2-second exposure time. You can't take exposures that long without a tripod, or at least resting the camera on something. The Olympus FE-120 has a built-in flash, right? You should use it. —Keenan Pepper 18:39, 21 October 2007 (UTC)

I agree with Milkbreath that the plant is probably "Asparagus Fern", however, it is not a fern. Despite its common name it is a much more modern flowering plant related to lilies. It used to be Asparagus plumosus, but the genus Asparagus has recently been split. The current botanical name for Asparagus Fern is Protasparagus plumosus.--Eriastrum 18:51, 21 October 2007 (UTC)

The asparagus fern would not have been around in the Mesozoic, so only its ancestors survived. Graeme Bartlett 01:10, 22 October 2007 (UTC)

Personally I'm somewhat doubtful that any species living today was around in the Mesozoic era. While some animals and plants have survived relatively unchanged for a long time, it doesn't mean that they are completely unchanged or are the same species. You might want to read living fossil Nil Einne 07:10, 22 October 2007 (UTC)

Why the electricity transmission voltage is generally multiples of 11?

I have thought of this question for a long time, but haven't got a satisfactory answer anywhere. Why is the AC electricity supply voltage always in multiples of 11. For example, in US/European countries, it is 110V; in some Asian countries, it is 220V. The high voltage supply lines are generally 110kV, 220kV, 66kV etc. In general, if you observe the AC transmission voltage, it will be in multiples of 11. —Preceding unsigned comment added by Kanwar rajan (talk • contribs) 16:05, 21 October 2007 (UTC)

This question has been asked here at least 3 times before - see Misplaced Pages:Reference desk archive/Miscellaneous/November 2005#Electricity voltage, Misplaced Pages:Reference desk/Archives/Science/2006 December 6#value of voltage in power supply and Misplaced Pages:Reference desk archive/Science/May 2006 part 2#High voltage power supplies for the answers. Laïka 16:16, 21 October 2007 (UTC)

Added those to Misplaced Pages:Reference desk/FAQ. Note that it's only 110V in the US. The EU had 220 and 240 V and standardised to 230V. DirkvdM 17:52, 21 October 2007 (UTC)

It's not even 110 volts in the US; it's usually 117 VAC ± some amount and we commonly refer to it as "120". Today, at my house and according to two different DVMs of unknown callibration, the mains power is reading 121.4 and 121.7. 'Guess the power company is in cahoots with the light bulb company, ehh?

Atlant 18:57, 21 October 2007 (UTC)

...especially the "long life" bulbs you can buy at Wal-Mart and manufactured by GE. More like 30 to 300 hours instead of the 1300 sold as. 71.100.9.205 19:19, 21 October 2007 (UTC)

Leaky coax antenna and Cable

I had a question regarding a previous post where it stated that someone had a college radio station that used leaky coax cable and it was limited to just the buildings. Did the buildings have to have leaky coax or any other cable put into the buildings to make this work? —Preceding unsigned comment added by 67.127.97.65 (talk) 16:19, 21 October 2007 (UTC)

As I recall, it was simply laid onto the roofs of the buildings. But it was a long time ago! We were broadcasting on 998kHz/300m AM....oh - but wait - this is Misplaced Pages.! There is an article about it: UKC Radio...Wow!SteveBaker 18:01, 21 October 2007 (UTC)

So, in order to get the coax antenna to work, if first must have coax cable laid out around this center you want to get reception in, is that correct? —Preceding unsigned comment added by 68.120.228.255 (talk) 01:07, 22 October 2007 (UTC)

and also in the interior of the space that you want to cover, if its a large area. From Steve's experience the signal only travels a dozen or so meters from the cable. You should be able to cover a cave, pipe or tunnel with one run of coax. Graeme Bartlett 01:14, 22 October 2007 (UTC)

Would it not work if it were from one antenna to another antenna if both are leaky coax antennas? —Preceding unsigned comment added by 67.122.136.43 (talk) 19:36, 22 October 2007 (UTC)

Green bins and gulls

Hi. I've been wondering, if a town or municipality adopted the green bin policy, where compostable trash goes to farmers' fields instead of landfills and garbage cans, what would happen to all the gulls who partially epend on the trash for food, as well as the other animals who depend on it partially (eg. rats, mice, ants, raccoons, foxes, etc)? Would they die off, or have to find other sources of food? For example, I know the gull population around most school properties are quite dense. My main question is, if the green bins decreased the amount of food garbage in garbage cans, landfills, etc, would the gull population increase or decrease in density around schools and parks? I know racoons can often poke around in garbage cans, but putting all the food scraps in the green bin, which can often be closed with a latch, might solve the problem. Similarily, would the raccoon population increase or decrease in areas such as schools where there is often a lot of litter, or would they have to move out of cities and towns which have adopted this policy where there is not enough food? What about rats and otehr animals? Where would each animal gather the most in population density across the municipality? Also, where do the squirrels get all those peanuts an acorns? Thanks. ~AH1 16:30, 21 October 2007 (UTC)

In our area you can find very well fed raccoons, foxes, rats, mice and ants living on nothing more than left over dog and cat food. Any place people eat outdoors is another great source like bus stops, employee lunch tables (or the employee/customer bicycle rack which some employees and customers prefer). 71.100.9.205 19:22, 21 October 2007 (UTC)

The gulls would probably just move on somewhere else where food was more readily available. There's a landfill a few miles from my house that's in the process of being sealed. Apparently, the number of gulls at the next landfill along (30 miles or so) has almost doubled. I hypothesized that my town was going to be overrun with flocks of aggressive, starving gulls once they started covering up the refuse with plastic and earth but so far, it doesn't seem to have happened like that at all. The usual 'town gulls' are still here, of course - continuing to do what they do (how sad is it that I can now recognize individual gulls by location of favourite perch, plumage variations and scars/old injuries/deformities?). I guess that there must've been two separate flocks with different habits all along. --Kurt Shaped Box 19:49, 21 October 2007 (UTC)

artifiial eye Interface

If I wanted to interface an electronic circuit such as a CCD array to the human ocular nervous system what kind of interface would I need? I know that I would probably have say like a surface with "hair" on the back of the CCD chip that sent out nerve pulses individually for each pixel and where nerves could attach but then would I have to use genetic engineering to get the nerves to attach to each "hair" and even still what material would I use to make the "hairs" so that the genetically engineered nerves would attach and stay attached like the granular surface of metal joint replacement? (...or will Mother Nature throw me to the ground and squat on me for thinking these thoughts?) Clem 19:37, 21 October 2007 (UTC)

It has been somewhat done with varying degrees of success. See Visual prosthetic, although it doesn't give many technical details. --Bennybp 22:26, 21 October 2007 (UTC)

Why would you need genetic engineering? The 'hairs' would have to send out the same signals that whatever you're replacing (the retina, I assume) normally send out, and the nerves should connect. Afaik. I'm no expert in this field. That is, assuming those nerves regenerate. Is that what you were referring to? DirkvdM 07:27, 22 October 2007 (UTC)

I'm assuming that if a nerve ending is disconnected from a receptor that it might regenerate and reconnect... but not to an artificial ocular nerve ending unless the disconnected nerve was somehow genetically reengineered to cause or to allow it to reconnect to the artificial "hair" nerve ending instead, or as well. Clem 10:39, 22 October 2007 (UTC)

I don't know much about genetic engineering, but can you do that in already existing living tissue, and on that location? Anyway, genetic engineering seems a lot more difficult than mechanical engineering of the 'hairs'. Or maybe a layer of living tissue could be attached to the artificial eye interface before implantation. And amybe that might be genetically engineered, so you get your way after all. :) DirkvdM 17:22, 22 October 2007 (UTC)

It's not a matter of genetics. You really can't replicate the precise interface between eye and brain - it's too complicated, too weird (compared to a CCD camera array at least) - and may even be wildly different between any two individuals. You'd have to connect it up any old how to the nerve endings and rely on the brain to re-learn how to see using the new device. Part of the problem though is that the eye doesn't send "pixels" to the brain - it sends higher level concepts like "there is a 32 degree diagonal light/dark transition moving left-to-right at 10 degrees of arc per second". Since our electronics won't be doing that, the brain proper has to do work that would normally be done by the layers of neurons on the back of the retina. So it's unlikely that your eyesight would ever be as good as a real human eyeball. But having said that, people have managed to "see" with something as crude as a grid of a few thousand little pins strapped to the back of their hand - one pin for each pixel. It's amazing how the brain can learn that stuff. SteveBaker 20:27, 22 October 2007 (UTC)

Wow, do you have a link for that? I'd really be interested to learn more about that.

But it depends on what exactly you are replacing. If it's just the retina, then the interpretation done by the eye will remain intact. DirkvdM 06:34, 23 October 2007 (UTC)

geomagnetism

these r some terms "1.magnetic poles,2.geomagnetic poles,3.geographical poles,4.physical poles,"and i m finding my self nowhere among them.do some tell me wat is the basic differences in them in easy words?Roar2lion 20:56, 21 October 2007 (UTC)

Misplaced Pages has Geographical pole, Magnetic pole, North Magnetic Pole, South Magnetic Pole. --JWSchmidt 21:04, 21 October 2007 (UTC)

Geomagnetic Pole redirects to magnetic pole, which suggests they mean the same. But I suppose 'geomagnetic' refers to Earth, not the poles of other astronomical bodies, so the redirect isn't entirely correct. I changed the page to reflect this. Not sure about the layout, but at least it's clearer now. DirkvdM 07:47, 22 October 2007 (UTC)

On second thought, doesn't 'North Magnetic Pole' refer to one pole of other astronomical bodies too? DirkvdM 08:05, 22 October 2007 (UTC)

The 'geo' prefix in geomagnetic pole is just to distinguish it from other magnetic poles which do not happen to be associated with planetary bodies. Eldereft 20:35, 23 October 2007 (UTC)

The Greek word geo means 'Earth'. And afaik, the prefix is always used in that sense. DirkvdM 09:05, 24 October 2007 (UTC)

We have the (geo)magnetic poles (where a compass points), the rotational axis of the earth and the axis about which that first rotational axis precesses over a period of 25,800 years. (The gyroscope animation in the precession article shows the difference between the last two rather nicely.) There are also the two points on the surface of the earth that mankind has arbitarily decided to label 90 degrees of latitude north and 90 degrees of latitude south. Which ones have which names though? SteveBaker 15:02, 22 October 2007 (UTC)

The rotational axis of the Earth gives the physical/geographic poles, which are at ± 90°; Santa Claus lives at +90°. Precession of the equinoxes has no particular cartographical significance, though it does mean that your astrological sign is wrong. Eldereft 20:35, 23 October 2007 (UTC)

Cold beverages?

Why do people prefer to drink most beverages cold, even if not in a very hot environment? Is there any kind of physiological basis to this preference? Thank you very much for your time!

24.88.103.234Timothy —Preceding comment was added at 22:25, 21 October 2007 (UTC)

I would suggest that since most drinking water is not heated, the ability to drink hot liquids would not have much of an evolutionary advantage, except for geologically active regions with hot springs. Confusing Manifestation 22:32, 21 October 2007 (UTC)

You've never been to Europe and been served room-temperature beer, have you? Americans have the biggest craze for cold beverages in my experience. Delmlsfan 22:37, 21 October 2007 (UTC)

Because they're delicious? --ffroth 23:32, 21 October 2007 (UTC)

The coldness induces an almost numbing effect to the mouth. Acceptable 00:12, 22 October 2007 (UTC)

That explains abominations like Bud Light and XXXX, for sure ;-) --Stephan Schulz 00:18, 22 October 2007 (UTC)

Aussies like their beer even colder. And they have special stubby holders (no article? Jack, here lies a task for you) to make sure it stays cold (google images). However, drinking cold drinks doesn't really cool you down. It cools you down inside, but your torso needs to stay a constant temperature. So your body starts generating heat to get the torso back to the right temperature. So you actually heat up. So what I did in the land of Oz was take the beer out of its stubby holder and use it to cool my wrists, which did cool me down. After a while, when the beer had warmed up enough, I drank it. The Aussies declared me nuts. And right they were, just not in this case. :) DirkvdM 08:04, 22 October 2007 (UTC)

Around here(CA/USA) they are called Can/Bottle Cozies... and I thought there was an article for them somewhere near that name, but be damned if I can find it. Dureo 11:50, 22 October 2007 (UTC)

I've seen it spelled 'Koozie' (which gets you a bazillion ghits for companies that sell customised koozies/cozies) - but I can't find an article with that name either. It's getting hard to find common household items that don't have articles about them so I can't help feeling we're just not looking in the right place. If someone does find an article, let's #REDIRECT the heck out of it! SteveBaker 14:50, 22 October 2007 (UTC)

Ah, my link now redirects to drink cozy - both the article and the redirect have been created by TotoBaggins today, it appears. Probably a passer-by here. Btw, we now have a stub on the stubby holder. I suggest we leave it like that (hold that stub). :) DirkvdM 17:33, 22 October 2007 (UTC)

Mountain Laurels

Is Texas mountain laurel the same sort of plant as the "mountain laurel" with white flowers in North Carolina? —Preceding unsigned comment added by Vultur (talk • contribs) 23:48, 21 October 2007 (UTC)

Welcome to Misplaced Pages. Try searching for "Mountain Laurel" in the Search box to the left. You'll find it will immediately bring you to the article for Kalmia latifolia (the latin name for Mountain Laurel). You'll notice that at the top of the page, there's a link to the Texas Mountain Laurel article, Texas Mescalbean. You can see from the articles that the two plants come from different Order and Families, so they are definitely two distinct plants. -- JSBillings 13:21, 22 October 2007 (UTC)

October 22

Immune system chemical synthesis

For great justice and so forth, 217.43.117.117 01:03, 22 October 2007 (UTC)

Yup, that's pretty accurate. T cells can generate a huge variety of T cell receptors and B cells can generate a wide variety of antibodies. The mechanism for this is called V(D)J recombination. --David Iberri (talk) 01:44, 22 October 2007 (UTC)

See Adaptive immune system. The immune system cannot manufacture all kinds of substance. Instead it makes protein variants that can be combined together in many combinations. These proteins can recognise surface shapes on the invader cells, and trigger an immune reaction. Graeme Bartlett 01:46, 22 October 2007 (UTC)

Humans produce many variants of antibodies and T cell receptors so that they can recognize essentially all possible antigenic structures of chemical compounds...even synthetic ones that may never arise outside of the laboratory. People such as Stuart Kauffman have described how there has been evolutionary selection of gene recombination and somatic cell mutation mechanisms active in cells of the immune system providing the ability to produce "universal coverage" and recognition of all possible chemical structures. There is strong evolutionary selection against long-lived animals that do not have a universal defensive toolkit for recognizing potential pathogens. --JWSchmidt 02:05, 22 October 2007 (UTC)

Ah, universal coverage was probably the capability I read about, which my memory somehow transmuted to synthesis. Maximal "Win" respondence, chumnly-good-thanks 217.43.117.117 00:56, 24 October 2007 (UTC)

Compound light microscope

What part of the compound light microscope is responsible for resolution? Thanks, anon. —Preceding unsigned comment added by 70.23.73.94 (talk) 02:25, 22 October 2007 (UTC)

Not much of an answer but my guess would be the objective lenses. After all, they are the things you look through to observe something... Obviously lens of higher quality (such as certainGerman lenses) have better quality and last longer. Hope this helps. Valens Impérial Császár 93 03:09, 22 October 2007 (UTC)

Resolution is a product of the size of the viewing aparture and the magnification - increasing either of them lets you resolve smaller details. The limiting factors tend to be related to the quality of the lenses - but also the amount of light you can get without cooking the sample (as either aparture or magnification goes up - so does the amount of light you need). At some point, the wavelength of light becomes a limitation - and refraction and interference effects start to be very noticable. Hence electron microscopes for the very highest magnifications. SteveBaker 14:03, 22 October 2007 (UTC)

Time Machine

Theoretically, what parts would be required to create a time machine. Far fetched, I know but just wondering

Valens Impérial Császár 93 02:58, 22 October 2007 (UTC)

Depends what method you plan on travelling in time with. The simplest way to travel in time is ... do nothing, whereupon you will travel through time at a rate of 1 second per second. If you want to travel into the future a bit faster, find yourself a really fast rocket and let special relativity do the rest (see twin paradox). Alternatively, dig yourself a gravitational well and watch the rest of the universe fly past (getting out of the well may prove a little trickier). If you actually plan on travelling into the past, then we're getting into the really theoretical stuff, but theoretically if you can develop a form of exotic matter that doesn't behave like all the matter we know now, you can force open a wormhole and, with a little trickery, have a time machine that will take you back - but only as far back as the wormhole itself has existed. If you're desparate on going back even further, or at least to 1984, better start working on a flux capacitor. Confusing Manifestation 03:20, 22 October 2007 (UTC)

Why don't we have an article on second per second? DirkvdM 08:08, 22 October 2007 (UTC)

We have an article on time travel.--Shantavira| 08:10, 22 October 2007 (UTC)

...and then, of course, there is also memory and imagination. Multimillionaire 10:15, 22 October 2007 (UTC)

In the mean time you can have a look at Stephen Baxter's The Time Ships and Michael Moorcock's The Dancers at the End of Time both exquisite time travel SciFi novels. Keria 13:41, 22 October 2007 (UTC)

Or if you just wanted to have a peak you could teleport a super telescope a few thousand lightyears away and have a look at the earth. No sound and the signal back would have to be teleported too. Keria 13:46, 22 October 2007 (UTC)

That just moves the problem one step further down the chain. Instantaneous teleportation is the same thing as time travel to the past - and it's disallowed for the exact same reasons - the information in your teleportation 'beam' can't travel faster than light. If you send the mirror out there by 'normal' means - then when you look back at the earth through it, you'll be looking into the past alright - but you won't ever be able to see back to a time before the mirror was launched. Using a TV camera and a VCR to "record the past" is a much easier way to do that! But forward-direction time travel is not difficult - between having a nice long sleep and waking up 12 hours into the future and zooming around the universe at relativistic speeds - we've got that covered. SteveBaker 13:58, 22 October 2007 (UTC)

Ah, that brings me back a few years. In my early teens I came with this brilliant idea to travel in excess of the speed of light and then look back with a very strong telescope to examine the dinosaurs. Worrying about how to complete this very difficult task gave me sleepless nights. Seriously. :) The problem of how to get the info back didn't even occur to me then. DirkvdM 17:47, 22 October 2007 (UTC)

Yep - but travelling faster than light is as impossible as reverse-direction time travel - and that's because they are (in some respects) the exact same thing. If you can only fly away from the earth at 99.999% of the speed of light - then the light from the moment of your launch will overtake you and can never be caught up with (even without relativity messing you up). So you can never see back in time before the moment of the launch. Staying home and launching a mirror has much the same result. SteveBaker 19:51, 22 October 2007 (UTC)

Or, to spin it another way, reverse-direction time travel is as possible as faster-than-light travel. If you can send something (a physical object, or simply information) faster than light, through Some As Yet Unknown Process, and if the Unknown Process works in a frame-independent way, then you can also send the thing backwards in time. Do we have an article on the tachyonic antitelephone yet? If not, someone should write it, as the question comes up on a somewhat regular basis. --Trovatore 20:37, 22 October 2007 (UTC)

Actually, concerning looking back into the past, we do that already when we look at the stars. The light from the nearest star (excluding the Sun) took several years to reach us. For most stars it's millions or even billions of years. Add to that that space is curved, which means it can (and will?) eventually return to the place it originated from. So if we'd know where to look, we might see an image of our solar system. Of course, if we only find one such place we'd only see one set period in time, going at a normal speed, so we can't fast forward or rewind. And we'd need an exceedingly powerful telescope, and even then the image may be heavily blurred because of what has happened to it in the meantime. It's like looking through a turbulent atmosphere, except much worse. And we wouldn't be traveling in time, just looking back. DirkvdM 06:48, 23 October 2007 (UTC)

Compound light microscope

What part of the compound light microscope is responsible for resolution, the smallest distance at which two points can be distinguished as separate? Thanks, anon. —Preceding unsigned comment added by 70.23.73.94 (talk) 03:47, 22 October 2007 (UTC)

Its down to the objective lens of the Optical_microscope. The wavelength of light and the angle it subtends at the lens combined witht he diameter of the lends determine the resolution. Also the refractive index of the media below the lens affects it, so an oil immesrsion lens can improve resolution. Graeme Bartlett 04:27, 22 October 2007 (UTC)

Nano GOld Reactivity

Any idea why is bulk gold inert but Nano Gold reactive and acts as a catalyst???210.212.194.209 —Preceding comment was added at 05:33, 22 October 2007 (UTC)

Do you mean as in ? Without knowing the details of the reaction, I would suggest that (a) while gold is highly inert, that doesn't mean that it's completely unreactive, and compounds such as Gold (II) chloride and Gold (III) chloride do exist, and (b) a substance doesn't have to take part in a reaction to be a catalyst, it can also provide a surface for the reaction to take place. Confusing Manifestation 06:45, 22 October 2007 (UTC)

In general finely divided metals are more reactive because they

have a greater surface area

have a higher surface energy

It's the higher surface energy part that is important here - in general atoms in the centre of the metal are more stableised (have lower energy) than those at the edges - this is because those at the edges are in contact (bonding with) less atoms - there are less atoms around them

So in a nanopowder - because the particle size is very small (<1000 atoms perhaps) there is a greater percentage or higher energy gold atoms..

In the extreme case each gold atom would be totally separated - if this could be done thr gold would be very reactive...87.102.0.6 14:15, 22 October 2007 (UTC)

YECism and alleles

So I was conversing with a creationist relative of mine and she mentioned Ken Ham. I think people familiar with Young Earth creationism can dispute it in many ways but I thought I might approach it in a fairly simple manner. One of the implications of Ham's claims is that the alleles present today for each gene is the same number or less than at the creation of the Adam and Eve. What I'm thinking is that if there is a gene in humans that has 5 or more alleles (because Adam and Eve would only be have 4 or less between them) then that would provide for an easy and straightforward refutation of this explanation that I can then use the next time I go to a family wedding. I'm hoping for something verifiable. Can anyone help me out? Ƶ§œš¹ 07:16, 22 October 2007 (UTC)

You'll find more than 5 alleles for most sites studied (for example, one study of phenylketonuria showed 27 mutated PAH alleles representing 19 different haplotypes ). Don't expect that to convince young Earth creationists of anything. (Nor should it, really: they by and large don't reject the idea of random mutation, or even natural selection, they just reject the idea that they result in speciation.) - Nunh-huh 07:26, 22 October 2007 (UTC)

Frankly, if you can find a gene out there with less than 4 alleles that's pretty interesting...It must be very new or under high selective pressure. Almost every gene has many variants. CFTR (gene) has more than a 1000. — Scientizzle 15:49, 22 October 2007 (UTC)

On another hand there can't be more than 5 possibilities for a single base locus: A,C,G,T or omission. —Tamfang 19:19, 22 October 2007 (UTC)

Almost true. You can have insertions, too. And they can be of widely variable size, from 1 base to long sequences (see VNTR). But, even if we just go with 5 possibilities, add a second point mutation anywhere in the gene and now there's 25 possible variants. Three? 125. Onward and exponentially upward! — Scientizzle 19:37, 22 October 2007 (UTC)

I'm counting an insertion as something-vs-nothing at a new locus; otherwise the possibilities are infinite. —Tamfang 19:31, 23 October 2007 (UTC)

Yeah - you just can't argue with those guys. The problem is that if nothing changes - and if we're all descended from two people - how come there are so many different skin/eye/hair colours (to take a really obvious example) in modern humans. Modern evolutionary theory says that we are all descended from a single common ancestor - and in that regard, the Bible isn't so far off. So, for the sake of argument, let's call those early humans "Adam" and "Eve" - we don't know their real names - or if they even had names, so these are as good as any.

But the problem comes about if you claim that we haven't evolved since then. If that were so then all genes in all humans would have had to come from those two individuals and been inherited without change. There would be just three different X chromosomes (two from Eve and one from Adam) and just one Y chromosome (from Adam) in the entire population! This would mean that all men would be of three possible genetic types - and there would be just three different kinds of women! Was it Adam or was it Eve who carried the Sickle-cell disease gene? What about the genes for color blindness, dark skin colour, blue eye colour, blonde hair colour? But looking out at the population, we have (i) men who are colour blind, (ii) men who have sickle-cell disease, (iii) men who have both colour-blindness and sickle-cell disease, and (iv) men who have neither. Just on the basis of those two genetic diseases, we know that there must be at least four kinds of male genetic possibilities (way more than that in practice of course!) But right there, you've defeated the idea that all men have the same Y chromosome as Adam and either Adam's or one or the other of Eve's X chromosomes.

So it's very clear that genes MUST have mutated since the first common ancestor of all humans - which means that any complicated argument over alleles is kinda pointless. Once you accept that genes can mutate and are inherited - then evolution and speciation are unavoidable consequences.

However, God (or perhaps the tooth fairy or the FSM) may have just have yelled "Abracadabra" and made it all happen with a wave of a magic wand...so who knows?

SteveBaker 13:49, 22 October 2007 (UTC)

• If you're arguing from reason while she's arguing from faith, you can not possibly win. No matter what ground you gain, she can always retreat to the gaps. My solution to this problem in my own extended family is to limit my biological assertions to things like, "My, what a beautiful turkey!". --Sean 15:43, 22 October 2007 (UTC)

It doesn't matter what you argue with a Creationist, most will just say "goddidit" as an explanation (or rather, a non-explanation, since there is no explanation for how/where/when/why some god supposedly did it nor any objective evidence supporting such an assertion.) If, for example, you point out that there must be more alleles, then they can just say that God added more later. The evidence however, strongly supports the scientific theory that life began with simple single-cell organisms, and the process of evolution is the best explanation for how we ended up with the variety we have today. Evolution is a well tested scientific theory, while creationism is an untestable religious claim. The real question for a YEC is if things were created as they believe, why then is there so much objective evidence to the contrary supporting an older Earth/Universe and the evolution of life? -- HiEv 18:12, 22 October 2007 (UTC)

Thank you for your answers. My aim in regards to my YEC relative is not to shake her faith but to get her to stop asserting that she's spouting science. As a follow up question, Scientizzle said that a gene with less than 4 alleles must be very new. Is my understanding of the genes for blood type missing something? I thought there were just three alleles: A B and O. Ƶ§œš¹ 18:57, 22 October 2007 (UTC)

I should have said "likely" rather than "must" to make the statement more accurate, but a small number of alleles is suggestive of very recent evolutionary history (not much time to develop mutations that could spread into the population) and/or strong selective pressure (mutations in said genes tend to be strongly deleterious). As for ABO blood type, it's really not only 3 alleles but 3 groups of alleles (A, B & O) that are very widely distributed in the general population. There are subtypes within each of the 3 groups (examples: PMID 16215642, PMID 16081582, PMID 11896341, PMID 15787730, PMID 14617382). From this paper, the number and type of variants is suggestive of "positive selection for allelic diversity." Interesting stuff, eh? — Scientizzle 19:24, 22 October 2007 (UTC)

The very reason I answered in terms of genetic traits like eye colour, sickle-cell, colour-blindness and such is that these are things you can actually see for yourself every day. You don't need heavy-duty science and counting hard-to-prove things like alleles - you don't need to worry about any of those things. If the Adam-and-Eve story is true - and if genes never mutate/change - then there can only possibly be three kinds of men and three kinds of women in the world - and we all very well know that's not true. I think I remember a StarTrek episode where everyone on the planet was a clone of a handful of survivors of some terrible accident...that's how the world would be with only three X chromosomes and one Y that went forever unchanged. This is MUCH easier to argue - and if your relative can't find a good argument to cover this much easier-to-observe phenomenon - then she's doomed when it comes to deeper stuff. SteveBaker 19:47, 22 October 2007 (UTC)

The three kinds of men is fine, but the three kinds of women, I think, is slightly off. If (between them) Adam & Eve have 3 X chromosomes (let us call them A, B, and C), then one can have 6 kinds of women (leaving out recombination, because that's the kind of ignorant yahoos we are): AA, AB, AC, BB, BC, CC - Nunh-huh 16:47, 23 October 2007 (UTC)

Electronics

what will happen if you give a dc supply to a a.c machine? —Preceding unsigned comment added by 210.212.241.236 (talk) 08:22, 22 October 2007 (UTC)

Depends on what type of AC equipment it is. If it has a transformer inside or if it's an induction motor, it will simply short out and likely to destroy the coils in it, but if it's something like a newer cell-phone charger which uses PWM to regulate voltage and doesn't contain transformers, I suspect that it would happily run on DC as well. --antilived 09:44, 22 October 2007 (UTC)

Your suspicion is absolutely correct; many modern devices that use switching power supplies with high-frequency transformers will run just as happily on a DC input as an AC input; occasionally, it's even specified as permissible.

Atlant 00:09, 23 October 2007 (UTC)

I'd expect an acrid smell, smoke, and fire in that order with increasing capacity of the DC supply and robustness of the AC device, ordinarily. A loud SNAP often accompanies these symptoms. Either the supply or the device or both would be toast, probably. I always shield my eyes when I try things like that. Safety tip. --Milkbreath 11:30, 22 October 2007 (UTC)

It's always good to shield oneself when doing a smoke test. The SNAP would probably be from the noise-emitting diodes referenced in the linked article. --LarryMac | Talk 18:07, 22 October 2007 (UTC)

morbidity/mortality tables - not

I've searched these but they are not what I want. I'm looking for the number of persons still living at various ages rather than those who have died. Not only still living but their weights, how many cigarettes they smoke, etc. For instance I want to be able to ask: how many people are still alive at age 70 that have a BMI of 35, 30, 25, etc. How may at age 65 smoke a pack a day, two packs a day, etc. I feel this will give me a better idea of how to judge how long I might live by matching my habits with those who are still living rather than those who have died. Multimillionaire 09:48, 22 October 2007 (UTC)

Perhaps try one of the death test's? Lanfear's Bane | t 12:18, 22 October 2007 (UTC)

Touch-sensitive fern

I used to own a fern with leaves that folded up and shrank when something (usually my finger) came into contact with them. What species is it? -- _{Escape Artist Swyer Articles touched by my noodly appendage} 11:06, 22 October 2007 (UTC)

Mimosa pudica. - Akamad 11:34, 22 October 2007 (UTC)

This weed isn't a fern BTW. Also you might be thinking of Mimosa diplotricha. This has a fairly similar behaviour to pudica but is more tree like. BTW, for those who haven't seen it before before the M. pudica article has some videos. Having grown up around these things, they are blase but during a biology class at university, it was interesting to see how amazing it was to people who'd never seen one before. Nil Einne 19:09, 23 October 2007 (UTC)

Using the stomach to clean the blood

Say someone swallows a dangerous substance like a bunch of paracetamol (entirely hypothetically - I've not just poisoned myself and now contemplate the hideous process I'm about to suggest). Gastric lavage (removing the toxic substance from the stomach) is a common first step in treatment, but of course that only gets the poison that's in the stomach - that which has passed into the bloodstream is still there. Now that poison got into the bloodstream by passing through the stomach wall; unless that wall has strong "one-way-street" properties, couldn't one use the stomach to remove the poison? What I'm suggesting is

1. do a full gastric lavage
2. fill the stomach with several litres of water (of a salinity TBD); let's call this "the irrigant" for now
3. the poison will then (hopefully) move across the stomach wall (from the blood into the irrigant) until the blood and the irrigant had the toxin at the same concentration
4. change the irrigant for a fresh supply, and repeat until the concentration of the poison in the recovered irrigant (and hopefully in the blood too) is below the danger level

In practise you'd probably change the irrigant continually, with an inflow and outflow pipe, like the way swimming pool water is processed. And maybe you'd manipulate the salinity of the irrigant to encourange outflow (perhaps making up the shortfall on the blood side with an IV drip).

So, does the stomach lining allow this reverse motion to occur, and has anyone done a procedure like this?

And more extreme yet, couldn't the same thing be done in the lung using liquid breathing (with the breathing fluid as a continually changed irrigant); I guess the advantage being you get a lot more surface area and a different membrane to work with. -- Blobject 13:59, 22 October 2007 (UTC)

I can't quite figure out why people think the reference desk is the place to propose innovative new medical treatments. No, no one uses gastric lavage or liquid breathing to eliminate systemic poisons. One reason would be that hemodialysis or even peritoneal dialysis (a similar process to the one you propose, but effective and less uncomfortable) are available for that purpose. And of course, paracetamol has a specific remedy that is needed to prevent liver damage that would not be addressed by any of these. - Nunh-huh 15:33, 22 October 2007 (UTC)

Who else would you take these ideas to? I certainly wouldn't want to mention this to my doctor in case he agreed that it would be beneficial in my case! (The trouble with this idea is that if the stomach 'worked both ways' as suggested by our OP, then every time you took a drink of plain water on an empty stomach, it would pull all of the nutrients out of your blood! I have no idea why that doesn't happen - but the fact that it obviously doesn't means that this idea won't work.) SteveBaker 19:37, 22 October 2007 (UTC)

The reason it wouldn't work is because the stomach mashes things up: it starts digestion, but doesn't do the absorbtion. Absorption occurs primarily in the small and large intestines. Oh, sure, some stuff gets absorbed in the stomach (some small lipid soluble molecules like aspirin and alcohol - in the process causing a bit of irritation) but it's not a particularly heavily vascularized surface. Since the stomach pH is less than 3, it would hardly do to have a lot of opportunity for exchange between its lumen and the blood, where we do our best to maintain a pH of 7.40. - Nunh-huh 20:31, 22 October 2007 (UTC)

OK - but that only moves the question down an organ or two. Why doesn't this happen in the small intestine for example? SteveBaker 21:04, 22 October 2007 (UTC)

My guess would be that it does happen, but that then the nutrient-filled water gets re-absorbed. There's a natural line of speculation that follows this point, but I'm not going to go there. --Trovatore 21:24, 22 October 2007 (UTC)

You are both assuming that molecules in the intestine are only absorbed passively (down a concentration gradient). This is not at all the case. Active transport by carrier proteins on the apical surface of the intestinal lumen ensures the unidirectional flow of materials into the body. That is not to say that there isn't some degree of bidirectionality possible or present, but that absorption in the intestine is not the same as diffusion in the lungs (where gas exchange is entirely passive). Andrewjuren(talk) 21:44, 22 October 2007 (UTC)

You may be interested in our article on dialysis, especially peritoneal dialysis -- 15:45, 23 October 2007 (UTC) —Preceding unsigned comment added by 128.104.112.63 (talk)

Even under the assumption of passive transport only (yes, some compounds can diffuse through the stomach wall), you would also have to consider the partition coefficient. The chemical environments of the stomach and the bloodstream are quite different. A molecule moving from the stomach into the blood can change (eg. pH change can alter protonation state, which may then lead to further chemical changes) and become "trapped" in the blood because its new state can no longer cross the stomach-blood barrier. A partition coefficient that strongly favours retention in the blood would suggest that your proposal is theoretically possible, but highly unfeasible. Blood is also distributed throughout the body, whereas the stomach contents are localized. 142.103.207.10 00:55, 24 October 2007 (UTC)

Moon observations

On Friday night (20/10/07), I noticed something interesting about the moon and wondered if the science community could explain a thing or two to me.

I was walking in London and it was a cloudless night. At approx 7pm I noticed that the moon was almost exactly half/half shining and occluded (is that the right word?), with the line between the two almost immaculately vertical, creating an illusion of a clockface showing 6 o'clock, if you see what I mean.

A couple of hours later, I happened to be walking once more and noticed that the proportion had (of course) remained almost exactly 50-50 light and dark, but the angle had shifted so that using my clock analogy it was more like 5 past 7.

Questions (some of these are a little embarrasing):

• Was my observation accurate?
• Is this a common (even nightly) phemonenon?
• If I'd seen the moon again later on would the angle have become even greater, and if yes, how far will the face appear to rotate?

Cheers. Arrrrooooooo! --Dweller 15:43, 22 October 2007 (UTC)

Yes, yes, and yes. See lunar phase. The moon looks like that at its last quarter (just gone) and first quarter, each of which occur monthly. Its angle with the sun doesn't change much over the course of a couple of hours, so it's still half illuminated by the sun, but the Earth rotates quite a lot in that time and thus the apparent angle with the Earth. The final "angle" at the time it sets depends on the season and your latitude.--Shantavira| 16:39, 22 October 2007 (UTC)

No, No, and No! Dweller - I dispute your observations - and I'm quite sure Shantavira either misunderstood the question or is WAAAAY off the mark (lunar phase says nothing of relevence to this question).

When the moon is exactly half-illuminated, the angle of that 'terminator' line to your local horizon depends on where you are on the surface of the earth. (Using your clock-face analogy...) You'd have to be standing on the North or South pole to get that perfect 6:00 look. If you are on the equator - the moon will appear to be at 3:15 - and somewhere in-between, 7:05 or 8:10. I suspect that if you live in the UK or Canada (oh - yeah - you said "London") - you were seeing it at 7:05 the whole time (it varies a bit through the year because the earth's axis isn't vertical). London is at 51 degrees North latitude - so you're rotated about 39 degrees from the 'vertical' North pole - but since this is winter, the earth's axis is tilted backwards in the northern hemisphere - so you can knock off about another 7.5 degrees for the axial tilt. So I calculate that your head was tilted by about 31.5 degrees to the "vertical" - which would give you the moon looking to be at almost exactly 7:05 per your second observation. (Wow! That worked *perfectly*!! Isn't science wonderful?) - I can't explain your first observation - except to say that I think you were incorrect. But if the moon is high in the sky, it can be hard to judge...perhaps that's it.

I explained some time ago how (when I lived in UK where I was born and lived 40 years), the new moon mostly looked like a slightly tilted letter 'C' - when I moved south to Texas, I was physically shaken to see that the new moon looks more like a 'U' - and that rotation is the same effect we're talking about here. I mean, intellectually, I know it makes perfect sense - but deep down, the Texas moon just seems "wrong" at a very visceral level! I had always wondered why some ancient religions talked of the moon being a 'boat' in which the god travelled across the skies. That made no sense when it was 'C'-shaped - but from closer to the equator, you could easily see how the 'U' shape would approximate the hull of a boat. Of course nothing changes on the moon - it's just that when you are standing on the equator, your head is turned sideways 90 degrees compared to when you are standing on the north pole. SteveBaker 19:23, 22 October 2007 (UTC)

Sorry, Steve, you're quite mistaken. If you play around with Stellarium you can choose the date and location specified by the original poster and see that his observations are exactly right. As the moon is transported across an arc of the sky, its orientation relative to the nearest point of the horizon does indeed change. Geography does go into it, but by no means is the orientation completely fixed for a given geographic location. You can get a "perfect 6:00 look" very far from the poles, with the cutoff latitude depending on how close you require the moon to be to the horizon. --Reuben 21:09, 23 October 2007 (UTC)

Edible mold and fungus (mushrooms)

How did we first discover what's good and what isn't? Did people just literally eat some moldy food, to discover if it made them sick or not? Some mushrooms are poisonous some are edible, but there's no way to know unless you eat it first. Do people just eat everything in sight, then report on whether it is edible or not? 64.236.121.129 16:00, 22 October 2007 (UTC) Did people literally just eat moldy food at random, then remark, wow this tastes great? 64.236.121.129 16:04, 22 October 2007 (UTC)

While there is a degree of trial and error, observation also plays a key role. People can observe what other animals eat (and don't eat) and thereby gain a degree of confidence as to its safety and nutritional merit. Additionally, there's no need to repeat the question -- you can click the "edit" link to the right of the section header to amend, clarify, or otherwise respond. — Lomn 16:56, 22 October 2007 (UTC)

I wasn't repeating my question. Misplaced Pages was giving me an error message when I was posting it, so I just kept trying to repost the question, but it looks like it did post it after all. 64.236.121.129 18:29, 22 October 2007 (UTC)

An explanation I once heard of how people discovered alcohol it that someone buried some grains somewhere 'for a rainy day'. Then when that day came he discovered the grain had gone off. Being hungry he decided that he would eat it anyway and discovered that it had a rather pleasant side-effect. The moral of the story being that people will eat anything when they're hungry, even if their first impulses tell them not to. Another thing is a survival technique to test food that our ancestors may have figured out too (apart from watching what other animals eat, which is also a standard technique). If you're not sure if something is edible, first rub it between your fingers, then under your armpit, then on your lips, then put some in your mouth, chew and spit. If any of these tests results in a unpleasant feeling, don't eat it. Then swallow a little bit and wait for a few hours (maybe longer). If you don't get sick, you can eat more and wait. If you still don't get sick, it's safe to eat. DirkvdM 18:02, 22 October 2007 (UTC)

There seems to be some kind of assumption that we all woke up one day and had to figure this out. It's not like that at all - we evolved to fit our environment - to be able to eat the things that we need to eat and to seek out the things we've evolved to manage. We evolved from apes (we are apes). Apes that don't have language somehow know not to eat rotten food or unripe fruit...so do we. Human diets didn't suddenly arise - we've been gradually adapting to what's around us for millions of years. The exceptions are fruits and vegetables that came into our environment very suddenly and very artificially from a long way away. When (for example) the Tomato was first introduced into Britain, it was widely believed that they were poisonous unless cooked very completely. There is a story of a guy who grew tomatoes around that time - who knew they were not poisonous even when eaten raw - and in order to publicise this fact, he put up a poster in the town square saying "At such and such time Mr so-and-so will PUBLICALLY EAT A RAW TOMATO on the church steps." - which resulted in a large crowd of people gathering to watch this foolhardy exploit...which (of course) ended without incident. SteveBaker 18:58, 22 October 2007 (UTC)

Yea I heard about that Tomato story. Interesting to say the least, but we did have to figure these things out. Who would honestly eat a moldy piece of cheese? Yes we evolved, yes we are apes, but there's no voice in the back of my head that says eating this moldy thing is not going to make me sick. Some mushrooms are good to eat, others are poisonous, how can we know what's good and what isn't without some expert saying so? There are some mechanisms that help us determine what's good to eat, smell for example, but that doesn't work on everything. Certainly not mold, which is what I'm asking about. 64.236.121.129 19:46, 22 October 2007 (UTC)

Certainly not on death caps either. They apparently taste good. --Kurt Shaped Box 22:13, 22 October 2007 (UTC)

I think a lot of it’s a matter of avoiding starvation. Given a choice between eating a food that one is familiar with and eating something that may or may not work as a food, the obviously preferable choice is to eat the familiar food. But even today, a lot of people are often faced with a choice of eating something that may or may not work as a food, and eating nothing at all. Given that eating nothing at all will lead to certain death, the safer choice is to eat whatever you can, even if you have no clue as to whether it might make you sick or kill you. If you live and it tastes good, then great, you’ve just discovered a new food. If it kills you, then there was no harm in trying it, because you were going to die anyway. MrRedact 06:06, 23 October 2007 (UTC)

Steve, most of the time humans will have had plenty of time (generations) to figure out their surroundings, but especially for humans that would not have been true all the time. Take the original Americans who crossed the Bering Strait and traveled to the southern end, roughly 10,000 km, in roughly 10,000 years. That's on average tens of km per generation. But it will more likely have happened in leaps and bounds. And habitats sometimes change rather abruptly. This is an extreme example, but learning to live in a very different environment is something that humans will have had to do at least every now and then, considering they spread all over the Earth. And it's no coincidence that that is something humans are particularly good at - that's probably the most important reason humans spread all over the world.

Btw, the point is some humans do eat rotten food, such as french cheese and thousand year eggs, which only illustrates our huge adaptability. DirkvdM 07:15, 23 October 2007 (UTC)

That's the thing, of course we eat rotten food. The question is, how can anyone possibly know it's still edible despite being rotten? It's one thing to just eat something because you are starving, it's another thing to specifically prepare rotten food, which without preparation would be inedible. Those eggs are a good example, because someone has to prepare something like that in order for it to be edible. How could they know how to prepare such a thing? If you eat any other rotten egg, you get sick, but when it's prepared in that specific way, it's ok. How do they figure these bizzare things out? It would be equivilant to just sticking an egg in a bunch of random ingredients for a couple of months, then eating it to see if it tastes good or not... 64.236.121.129 13:34, 23 October 2007 (UTC)

Whoa. Those are some funky-looking eggs. What exactly is the chemistry behind that? --Kurt Shaped Box 07:59, 23 October 2007 (UTC)

On rotten cheese, a friend regularly takes a small cheese and places it under a large glass cover. He then waits for months as the cheese grows white filaments until it has filled the space available. That's when it's good to eat. Quite a delicatessen apparently. . What about when we start to eat and drink food that might not be rotten really hasn't much good in it? To think that Coke is one of the best selling drinks amazes me. I might prefer the mutant cheese option. Keria 08:06, 23 October 2007 (UTC)

Well, the mouldy cheese could be just an example of someone eating it, liking the taste and then deciding to experiment with it, tweaking the taste. Same with beer - most beers taste horrible, but get you drunk. So it makes sense to then start experimenting with the taste until it is also pleasing to drink. The eggs could just originally be a poverty thing. people looked for a way to keep them long, ate them despite the foul taste, and then became used to it. It's certainly an acquired taste. I once saw a documentary in which people who ate such eggs were presented with French cheese and wondered how on Earth anyone could eat something so revolting. Stranger is sago (at least some variety of it, I learn now), which is poisonous and has to be ground and washed to leech out the poison. How do people find that out? I can't imagine someone accidentally doing this, because it's a long and labour-intensive process, without which the sago would remain lethal. DirkvdM 18:50, 23 October 2007 (UTC)

Dirk, by "French cheese" do you mean some particular cheese (the way we use "Swiss cheese" to mean Emmenthaler, or "American cheese" to mean "light-orange colored petroleum byproduct"? The French cheese link just redirects to a list of French cheeses, and I don't know of any particular cheese called French cheese. --Trovatore 20:26, 23 October 2007 (UTC)

Oh, sorry, that may be a dutchism. By French cheese I mean mouldy cheese, such as brie. But there are also mouldy English cheeses such as stilton. And of course Danish blue isn't French either. DirkvdM 06:46, 24 October 2007 (UTC)

Out of curiosity, did the title of this thread set up an echo in anyone else's head, Forty-two pounds of edible fungus/in the wilderness a-growin' ? --Trovatore 07:56, 24 October 2007 (UTC)

Thelper1 vs Thelper2

How is Th1 and Th2 competition advantageous? Can't a humoural and cytotoxic response complement each other? Th1 promotes macrophage function, Th2 promotes antibody production, but opsonisation by antibodies is supposed to render microbes susceptible to phagocytosis? Competition between proinflammatory and anti-inflammatory response, I can understand, but this is different - the two should go hand in hand... —Preceding unsigned comment added by Seans Potato Business (talk • contribs) 17:37, 22 October 2007 (UTC)

In general, the responses of these two cell types do compliment each other. Certain cytokines will direct the majority of a response either down the cellular or immune routes, but you are right to suspect that opsonization (specifically b-cell mediated Ig opsonization) does aid the macrophages in phagocytosis. However, compliment is effective in opsonizing many typical bacterial molecules even without immunoglobulin. It is advantageous to have multiple ways of attacking bacterial (and other) invaders; that way, there is always a back-up method should a defensive mechanism fail. (and indeed, individuals who lack any one of the immune defensive molecules or routes typically have pronounced immunodeficiencies). Tuckerekcut 20:34, 22 October 2007 (UTC)

Induced C`urrent

How would I calculated the current and voltage induced in a wire a certain distance from a vibrating charge? Thanks, *Max* 23:06, 22 October 2007 (UTC)

Faraday's law of induction. SteveBaker 02:03, 23 October 2007 (UTC)

(edits to repair bot damage) Arakunem 02:20, 23 October 2007 (UTC)

The article on Faraday's Law discusses a coil or wire loop moving relative to a magnetic field. The questioner asked about a moving charge. Edison 17:09, 23 October 2007 (UTC)

Is there a single equasion that I could use with minimal calculus? *Max* 00:13, 24 October 2007 (UTC).

October 23

Phase of quantum probability amplitude for reflection from a potential change

Part of my quantum mechanics assignment is to calculate the probability amplitude that an unbound particle will reflect back from a potential well. The final answer is given, and I keep getting an answer that differs from the given one by a constant phase factor but is otherwise identical. Am I correct in thinking that this phase difference is caused by considering the reflection as taking place at a different point within the potential well, and that the particle picks up the phase difference between the two nominal reflection points? If so, how is the phase relationship between the incoming and reflected wavefunctions usually specified? Do you always need to specify both a reflection probability amplitude and a nominal reflection point, or is there a simpler way? —Keenan Pepper 03:46, 23 October 2007 (UTC)

Let me guess: Does the phase factor that you've calculated make the answer a little less simple to express? In that case, my guess is that the difference between the answers is just a matter of a constant phase factor being considered unimportant to the problem at hand. After all, the overall phase of a quantum mechanical wavefunction is arbitrary. The only time a phase relationship between two unbound wavefunctions is important is when you're dealing with an interference effect between two parts of what's really one wavefunction, such as with a double slit experiment or something. An unbound particle reflecting back from a potential well is basically a scattering experiment, in which I don't think one usually cares about the phase relationship between the incident and reflected wavefunctions. The phase relationships between different parts of a bound state, however, is a different matter. MrRedact 05:39, 23 October 2007 (UTC)

Right, but our professor is very attentive to detail, even pedantic. I doubt he would just arbitrarily change the phase without telling us. Anyway, thanks for your answer. I feel confident it's not an error on my part now. —Keenan Pepper 12:38, 23 October 2007 (UTC)

Lobe-Finned Fish

My biology teacher owns a very peculiar preserved fish which appears to be a lobe-finned fish, though only the two front fins appear to resemble primitive limbs. It appears very primitive (non-bony, thick body and long thick tail) and is covered in large, thick, plate-like scales (the underside is bare and flat, and has two seemingly vestigial fins tucked flat against the body) and has a worm like lure on it's head. It almost resembles a frog without the tail, but with backwards bending knees (the limb like structer of the front fins is highly pronounced). The lobed-fins look like they were used for crawling, as the fish is most likely a bottom feeder. It is about 6 inches long, and the original color is no longer apparent. It was caught off the coast of florida on the ocean floor (unkown depth) and even after extensive research my teacher and the troller fisherman who caught it have found no-other like it nor anyone who is able to identify it's taxonomy. I'll try to get some pictures of it but for now I was wondering if anyone might be familiar with this description. BeefJeaunt 05:42, 23 October 2007 (UTC)

Part of the description sounds like some sort of angler fish - which have the bait, look a bit froggy, and despite not being lobe-finned fish have quite lobe shaped fins..87.102.17.104 11:16, 23 October 2007 (UTC)

Is it possible that your teacher is spinning you a story about what's going on here - "even after extensive research my teacher and the troller fisherman who caught it have found no-other like it nor anyone who is able to identify it's taxonomy". So your teacher somehow gets his hands on this bizarre unidentifiable fish, researches it with the troller (trawler?) fisherman, and then can't get it identified. Surely he would take it to a reputable university department or something like that to try to get identified professionally, and they would be very interested in it if it was really unable to be classified; I can't imagine them just shrugging their shoulders, saying they don't know, and giving it back to him to sit on a shelf (consider the reaction to the coelacanth when one was first caught in 1938 for example). --jjron 13:40, 23 October 2007 (UTC)

It seems reasonably improbable that the fish is actually lobe-finned (there are very few extant species). There are many species of fish, so finding one which even an experience fisherman is not familiar with is not terribly unusual. Your best bet is to take it to a fisheries collection (Florida Museum of Natural History is a good place to contact), but you'll probably need an expert to make the identification. --TeaDrinker 03:57, 25 October 2007 (UTC)

Speed of light

When we say that speed of light cannot be exceeded, what is the frame of reference? Keria 08:54, 23 October 2007 (UTC)

That's true in every inertial frame of reference! The speed of light is exactly the same in every inertial frame of reference. That's one of Einstein's postulates of special relativity. For more information, see the Introduction to special relativity article. MrRedact 10:16, 23 October 2007 (UTC)

And not to be totally pedantic, but the most simple and accurate way of stating it is the speed of light is independent of the velocity of the light emitter. The reason for the restatement is that 1. it emphasizes what is really going on in terms of its constancy (the speed of a wave is always independent of the velocity of its emitter; if it wasn't, the Doppler effect wouldn't work. Light isn't terribly special in THAT regard, though because it is light, it has very important implications for space and time, ergo Special Relativity) and 2. light can, in fact, vary in speed: the speed of light in a vaccum is different than the speed of light in a medium (that is, it can be slowed down in, say, water). So rather than saying it is "constant" I think it is a little more clear to say that it is "independent"—it also avoids the appearance of tautology that baffles many new physics students (the analogy with sound is an easy one), makes it more clear why Einstein and his buddies knew it was "constant" from a theoretical point of view, and reminds people that thinking of light as little particles only reflects some aspects of its nature. --24.147.86.187 12:01, 23 October 2007 (UTC)

Yes inded and that's exactly my problem (now I see I might have worded the quesion poorly): How do you know when the speed of an object or particule (say some intergalactic one) would be approaching the speed of light if we don't have a frame of reference to calculate from? Would we consider the known universe as stable and not moving so that all absolute speed should be seen as the speed relative to our universe? But then how can we be so sure our universe is not moving and say in one direction an object could go 1.5 times the speed of light relative to the universe and the opposite direction never more than 0.5 times the speed of light while never actually exceeding the absolute speed of light? Keria 12:15, 23 October 2007 (UTC)

Well, you can measure the speed of an object from any reference frame, but no matter what the case it will not bypass the speed of light. Which is to say, they will not be exceeding the speed of light in any reference frame. Sound a little weird? Well, that's sort of the essence of Special Relativity. Instead of another observer seeing them as bypassing the speed of light, they will have disagreements about the amount of space they have covered in that time, or the amount of time it took them to cover that amount of space. In either case they will never see them go faster than 300,000,000 meters per second. (At least, that's my basic understanding of it. Someone correct me if I am mistaken about my reasoning.)

In any case, you have to use a different velocity-addition formula when working within special relativity—it doesn't work quite the same way as it does with simple Galilean velocity additions. Unlike Galilean relativity, where you could have one observer see the other exceeding the speed of light, the relativistic velocity-addition formula has the inability to exceed the speed of light hard-coded into it in a rather elegant way. --24.147.86.187 13:07, 23 October 2007 (UTC)

To take the first part of your question, you can't. There's no absolute measurement of speeds in relativity—only (surprise) relative ones. If you take a sealed box that's travelling at some constant speed, there's no experiment that you can do inside that box that will tell you anything about how fast the box is travelling relative to anything outside the box. The idea of the luminiferous aether has no place in relativity.

If you have an intergalatic particle travelling at some constant speed, the physics works whether you say the particle is moving quickly and the galaxy it's passing is at rest, or if you say the galaxy is moving quickly and the particle is at rest. It's totally equivalent; you may run across the phrase 'There are no privileged frames of reference' in your reading.

In a larger sense, the Universe is just like that sealed box. We don't get any information about what's going on 'outside'; heck, there probably isn't any 'outside' to talk about. You can, if you wish, treat the entire Universe as moving with some constant velocity, and you'll get the same results out of your equations and experiments. (Indeed, all you accomplish is making the math slightly more complicated.) TenOfAllTrades(talk) 13:20, 23 October 2007 (UTC)

Perhaps the simplest way to say this is: For everyone and every thing in the universe, every other thing has to be moving slower than the speed of light relative to them (unless it's a photon when it's moving at exactly the speed of light). SteveBaker 14:05, 23 October 2007 (UTC)

Hm? No, an object farther away from you than the edge of your observable universe is moving faster than the speed of light relative to you. --Trovatore 15:43, 23 October 2007 (UTC)

Good luck ever observing that ;-) Someguy1221 17:22, 23 October 2007 (UTC)

That's not the point. Whether something is true of "every thing in the universe" is an ontological question, not an epistemological one. --Trovatore 17:37, 23 October 2007 (UTC)

If there were an object that was just outside my observable universe moving faster than light relative to me - then what do you imagine it and I would look like to an observer halfway between the two of us? For that observer, the laws of physics are the same as they are for me. SteveBaker 23:05, 23 October 2007 (UTC)

Who said they weren't? But I admit this does get a little tricky and I don't have it all worked out. The thing to keep in mind is that this is inherently a GR problem; you can't simply apply SR formulas like the addition-of-velocity one and expect them to work unmodified. On a related note, the choice of coordinate systems becomes somewhat less canonical -- we can't speak of an inertial coordinate system that extends from you out to near the edge of your observable universe. I think this is called lack of distant parallelism or some such. --Trovatore 23:14, 23 October 2007 (UTC)

I was hoping a real general relativity expert would step in and explain this, but that hasn't happened, so I'll go ahead and give it my best shot. Hopefully, the following doesn't have any errors that are too blatant:

If an object is farther away from you than the edge of your observable universe, then it's ambiguous as to how fast it's moving away from or toward you. However, it's definitely moving slower than the speed of light.

Speed is fundamentally a local phenomena. The only way you can unambiguously talk about the speed relative to you of something at a distance is if both you and the distant object share an inertial frame of reference. That is, you and the object have to be within a region of spacetime which is flat, or at least close enough that a flat spacetime is a good enough approximation for the problem at hand. But when you're talking about something beyond the observable universe, the curvature of the universe becomes a critically important part of the problem. The problem is that a speed is the spatial distance between two events, divided by the time difference between the two events. But when you're talking about large distances in a curved spacetime, it becomes ambiguous as to how to separate a distant spacetime interval into space and time components. In a curved spacetime, it's impossible to set up a distributed system of clocks that are all synchronized with each other, because the curvature of spacetime makes clocks at different points in spacetime run at different speeds. So unlike with special relativity, with a curved spacetime it's impossible to define any single global coordinate system that keeps time separate from space everywhere. Instead, what general relativity does is to "stitch together" a continuous set of inertial frames of reference, each of which is only used locally. The metric tensor defines the global geometry of the spacetime manifold, and is unambiguous everywhere. But the coordinate system in which one chooses to express the components of the metric tensor at a given event, which is what defines the difference between space and time at that event, varies from point to point, and is to a large degree arbitrary.

Given a local inertial frame of reference used in one place, like an inertial frame of reference in which the earth is more or less at rest, there isn't a single "correct" local inertial frame of reference that should be used at a remote location, such as near a star that's beyond our observable universe. You can arbitrarily choose a local inertial frame of reference near that star, in which the star is moving in any direction at any sub-light speed you want. But in whatever local inertial frame of reference you use for measuring the remote star's speed, it's moving at less than the speed of light in its local inertial frame of reference.

Although in an expanding universe, light from a distant star may never be able to reach us, it's not valid to say it's because the star is moving away from us at faster than the speed of light. Instead, a valid description is that the space in between us and the star is expanding faster than light can overcome. More technically, the metric tensor that describes the distance between nearby points in the space in between us and the distant star is changing over time, such that the distance between any two points gets bigger as time progresses. MrRedact 02:40, 24 October 2007 (UTC)

Well, the above seems a bit internally contradictory -- if speed is fundamentally a local phenomenon (please don't use "phenomena" as a singular), then how can it make sense to say that the star is moving away slower than the speed of light? I do think you're right that the situation is a bit ambiguous because there is no inertial frame including both objects, but that doesn't seem to stop people from describing stars at high redshifts as "moving away from us at 99.999% of the speed of light" or whatever. Whatever definition of speed is used in that description, must surely describe the star past the horizon as moving away faster than the speed of light. --Trovatore 02:49, 24 October 2007 (UTC)

Ah, poking around a little I found the basis of a good candidate for a notion of the speed at which the star is regressing. Give us, and an observer at the distant star, a time coordinate t equal to time since the Big Bang according to a comoving observer -- that is, an observer for whom the background radiation is isotropic; roughly speaking such an observer will be at rest relative to nearby stars or galaxies or maybe galactic clusters. At any t, draw a geodesic between the event point represented by us when we have time coordinate t, and the one at the distant star at time coordinate t. Let s be the length of this geodesic. Now consider ds/dt.

I think it will probably be at least approximately correct that this measure of speed will be less than the speed of light for stars within our observable universe, and greater than the speed of light for stars past the horizon. However it's not my field of expertise and I'm not sure of that. But at least there's a well-defined question on the table; maybe someone who actually does know can settle it. --Trovatore 03:16, 24 October 2007 (UTC)

I didn't actually say that the distant star is moving away slower than the speed of light, merely that the star is moving slower than the speed of light, meaning that in no matter what local inertial frame you use to measure the star's speed in, the star's speed is slower than the speed of light in that inertial frame.

It looks like you're right in that if you choose to define the speed of the star relative to us as being ds/dt, where s is the comoving distance between us and the star (just one of a number of distance measures that could be used) and t is the cosmological time (just one of a number of measures of time that could be used), then the speed of the star relative to us is greater than the speed of light. The principal that "nothing can move faster than the speed of light" isn't violated, however, because the "speed" involved is a measure of the metric expansion of space, not the speed of an object moving within space. Indeed, in the comoving coordinates, both us and the star are roughly at rest. MrRedact 11:48, 24 October 2007 (UTC)

After reading more closely, I see that the definition of the comoving distance is not the same as the length of a spacial geodesic measured along a hypersurface of constant cosmic time. The comoving distance is defined as not changing in time, and isn't even well-defined for an object outside of the observable universe, so it doesn't work to have s be the comoving distance in defining ds/dt as the relative speed. It does work to instead use the length of a geodesic, which is what you used in your definition. MrRedact 14:18, 24 October 2007 (UTC)

Thank you very much for all your answers. Keria 18:54, 24 October 2007 (UTC)

Tap water

hi, i'm now living in the UK, is it safe to drink directly from the tap? in countries i've lived in before it is always recommended to filter the water first... —Preceding unsigned comment added by 82.46.27.191 (talk) 13:37, 23 October 2007 (UTC)

Except under very unusual circumstances, yes, you can drink tap water in the UK (and most other European countries). If not (e.g. due to contamination), that information will be well advertised via TV, radio, and newspapers. You might want to check if you are living in a very old building where the piping may still contain lead. But even in that case, it the risk is only significant for long-term exposure. --Stephan Schulz 13:48, 23 October 2007 (UTC)

In buildings with lead pipes you just need to let the water run for a few minutes so that the water that's been sitting in the pipes for a long time is gone before you take some to drink. But aside from that, yes - it's OK to drink UK tap water. SteveBaker 13:59, 23 October 2007 (UTC)

Every country has its germs. Some more (and more dangerous ones!) than others, but you always run the risk of getting diarhoea when abroad, wherever you go. But at least in (western) Europe you're not likely to get anything serious, so don't worry and drink the tap water. Except when you're just there for a few days maybe, in which case only drinking bottled water would not be too much of a hassle. especially when you're on a business trip, and can't afford to get sick. But even then I would consider it rather over the top. Keep in mind that tap water in (western) Europe is meant to be perfectly safe to drink. I just pointed out the few minor reservations you might have. DirkvdM 19:08, 23 October 2007 (UTC)

Is it possible to use nanomachines instead of electricity?

Like, instead of electricity doing "work", the nanomachines do the work instead. Is this possible? 64.236.121.129 14:54, 23 October 2007 (UTC)

See mechanical work and nanotechnology for some articles that might be relevant. Something has to power the nanomachines, right? That might still be electricity. Friday (talk) 14:58, 23 October 2007 (UTC)

Firstly, we don't have nanomachines - and there are grave doubts that they are even possible. But if we do someday figure out how to make them, they'll need power from somewhere. Most likely we'd power them with laser light - but it's possible they could be powered from chemical sources in whatever media they are working. In that respect they are no different from normal-sized machines. Just as an industrial robot could be powered from electricity or gasoline or solar cells - it would be the same thing with nanomachines. So they aren't going to somehow "replace" electricity - although they may well be powered by electricity. Probably the best way to think of them would be as teeny-tiny robots - or perhaps like bacteria or virusses that we designed ourselves. SteveBaker 15:04, 23 October 2007 (UTC)

Yea I know we don't have nanomachines. If we did, I would already know the answer. Anyway, what powers the nanomachines doesn't necessarily have to be electricity. Hmm, I guess what I'm getting at is, is it possible to create something that is powered by something other than electricity (so it's impossible to be electrocuted) or something that can blow up like gasoline. Our bodies for example aren't powered by electricity (although there are electrical signals), nor by anything that is combustible. 64.236.121.129 15:39, 23 October 2007 (UTC)

These machines would probably not carry "batteries" as such - and you wouldn't want to connect them up with wires - so electricity doesn't seem like the natural thing to power them with. They might maybe have an onboard chemical fuel supply - but more likely, I think we'll be powering them by shining laser light onto them from outside - or perhaps using chemicals in whatever fluid they are floating in to generate power. There are other possibilities though - they could be powered by something like a clockwork motor or something like a flywheel that stores energy and can be made to give it back as required. Things work very differently on a nano-scale and things that aren't considered very useful at the macro-scale are often extremely useful at the nano-scale (and vice-versa). For example, it's been widely suggested that nano-bots would use mechanical computing parts - like Babbages Difference engine or the TinkerToy computer that students put together at MIT. Pushrods and gears at that molecular scale would work more quickly than the transistors in an electronic computer! So it's possible that something like a clockwork motor could power such a machine.

But the bottom line is that we don't really know how we'll power these things...if indeed they are possible at all. SteveBaker 16:03, 23 October 2007 (UTC)

It has to be possible to power them. After all, viruses, bacteria, amoebas, cells, etc can utilize energy, so we know that it is possible. If they can do it, then it can be replicated. It's not easy to emulate, but it's possible. 64.236.121.129 16:40, 23 October 2007 (UTC)

Right - those things are (mostly) powered from chemicals in their environments and they have a small on-board chemical fuel supply to tide them over between meals. We could do the same thing. On the other hand single-celled plants are solar powered. We could do that too. If nanomachines are ever built 'for real', and if they are designed to self-reproduce (Drexler's "assemblers" for example) then there is the risk of Grey goo - when the machines go nuts and try to convert the entire planet into more machines! Having them powered by something that's not naturally "out there" is a way to prevent that. If you powered them by shining a laser of a specific frequency onto them - then if they went nuts, you could simply shut off the laser and they'd all switch off. Giving them a fixed internal power source (like a molecule-sized clockwork motor) would have a similar effect. But, as I said before, we are an awful long way from having such things - and it's a bit premature to be discussing details of things like power supplies when there are much more serious problems to be solved. SteveBaker 20:29, 23 October 2007 (UTC)

Grey goo. Pah. Amoebas are self powered and exist solely to make more amoebas. I see no grey ameobic goo. --Psud 10:23, 24 October 2007 (UTC)

See Micropower for a discussion of some nanomachines and nanogenerators (some recent articles on this topic are listed on the talk page but not yet incorporated in the article). Edison 17:01, 23 October 2007 (UTC)

density and volume of electron, proton (atomic structure)

dear sir

i am eswar .nice meeting you.

i would like to ask a question related to basic particles of atom

what is the numerical value of elctron and proton densities in kg/meter cube ?

what is the numerical value of elctron and proton volume in cubic metere ? —Preceding unsigned comment added by Eswar kumar p (talk • contribs) 15:05, 23 October 2007 (UTC)

The very first sentdnce of the Proton article tells you the size and mass. The Electron article also tells you the mass and has some discussion of the size (in terms of the "classical electron radius"). DMacks 15:14, 23 October 2007 (UTC)

Anomalous hair

I have a hair follicle which is unusually long, some 2-3 times a normal hair and also white. It is notably to say that it always grows in the same place. I had asked my biology teacher if it was a case of mosaicism but he negated it without offering me an explanation. So guys, any ideas on what is it?—Preceding unsigned comment added by 193.188.46.61 (talk) 16:43, 23 October 2007 (UTC)

Your biology teacher isn't allowed to give out medical advice - and neither are we. SteveBaker 16:06, 23 October 2007 (UTC)

Lighten up. He isn't asking for medical advice. Theresa Knott | The otter sank 17:16, 23 October 2007 (UTC)

Your biology teacher is allowed to give out biological information, and so are we. Having a long white hair should not ordinarily make one suspect mosaicism. Why does a long white hair need explanation, anyway? - Nunh-huh 16:40, 23 October 2007 (UTC)

The melanocytes in this particular follicle have apparently ceased to function earlier than in your other follicles. If you were a mosaic or chimera, there would, I suspect, be a wide range of other readily observable manifestations. Gray hair says that white hairs can appear as early as childhood without any particular or worrisome cause. Just out of curiosity, is it growing more quickly than your other hairs, or is it more robustly rooted, and so does not fall out as readily? Eldereft 22:06, 23 October 2007 (UTC)

It is medical advice he is asking. He presents us with evidence and asks for a diagnosis. Please don't. Questions and answers removed. Lanfear's Bane | t 23:26, 23 October 2007 (UTC)

I felt the question was for an explanation of a biological phenomenon. The was no indication that the questioner regarded this as a medical problem in any way. Are we to assume that any and all questions of human biology are in future to be deleted? DuncanHill 23:39, 23 October 2007 (UTC)

Astonishing. Someone so unacquainted with what medical advice actually is that he removes a question about the causes of a white hair while leaving advice on how to remove ear-wax on the same page. This despite two people who had already indicated there was no advice. - Nunh-huh 00:17, 24 October 2007 (UTC)

I was going for 'here are some possibly related articles,' but fair enough. Eldereft 00:20, 24 October 2007 (UTC)

safe fungi

how can I tell if fungi is safe to eat? —Preceding unsigned comment added by 213.228.203.153 (talk) 16:57, 23 October 2007 (UTC)

Eat it and see if you die. All joking aside, that's close to the answer. Try to find a local field guide. For instance, I have one for Colorado mushrooms. It lists a number of them, including their safety. It lists some as "Edible, but unsafe" because they are too easily mistaken for poisonous varieties. Failing that, there are methods to test plants for safety, of which you might be able to find in hard-core survivalist stuff. --Mdwyer 17:14, 23 October 2007 (UTC)

Assume it is unsafe unless you already know it is safe or if someone whose expertise you totally trust tells you it is safe. There are a lot of poisinous fungi out there and many of them look very similar to harmless ones. Theresa Knott | The otter sank 17:11, 23 October 2007 (UTC)

Short answer: There is no, clear, simple rule to tell the difference between poisonous and edible fungii.

Longer answer: When I was learning to program simple artificial intelligence systems, one class problem was to write a computer program that could take a lot of facts about classes of object and find rules to distinguish between them. So, for example, you could type in all of the information about 50 different kinds of car (top speed, fuel consumption, 0-60 time, number of doors, weight, etc) - then tell the system which cars were sports cars and which were not. The system would go off and work out which parameters about the car mattered and to what degree they mattered in classifying whether it was a sports car or not (so in this case, it would figure out that top speed and accelleration were important, having two doors was less important but still relevent - but fuel consumption had little or no bearing on how the car was classified). Then you could put in the data for a new car - and the program would unerringly be able to tell you whether it was considered a sports car or not by applying the rules. Anyway most of the class got good working programs to do this and at the end of the class, we were given a database containing all of the characteristics of a bazillion kinds of mushrooms and toadstools (including whether each one was poisonous or not) - and asked to "Find the rule to distinguish poisonous from edible". Nobody's program out of the entire class was able to find a common rule...and the reason for that is: There isn't one...it was a "trick question". SteveBaker 20:21, 23 October 2007 (UTC)

Off-topic: Did you do that in Prolog? I used that language once to write a program with which you could find the ideal place for you to live on Earth. Put in the characteristics and it gave the locations that had all those characteristics (well, actually it was limited to South America and had a very low resolution because I had to manually build the entire database). DirkvdM 09:29, 24 October 2007 (UTC)

From my first answer at 'Edible mold and fungus (mushrooms)' 10 threads up: "If you're not sure if something is edible, first rub it between your fingers, then under your armpit, then on your lips, then put some in your mouth, chew and spit. If any of these tests results in a unpleasant feeling, don't eat it. Then swallow a little bit and wait for a few hours (maybe longer). If you don't get sick, you can eat more and wait. If you still don't get sick, it's safe to eat." This info from a hard-core survivalist (no, not one of those idiots who stock up centuries worth of food in case the world ends). DirkvdM 09:29, 24 October 2007 (UTC)

Bad advise unless the other option is starving to death. The death cap, for example won't irritate your fingers, armpits or lips, but will quite cheerfully kill you a few days later unless you can get a liver transplant in a hurry. Half a cap will likely kill a person. Capsicums (or I think US of Aians call them bell peppers) are tasty and nutritious, and will fail the test. --Psud 10:39, 24 October 2007 (UTC)

It takes days to kill you? That's very unusual. DirkvdM 18:51, 24 October 2007 (UTC)

I agree. The death cap is deadly, but tastes good. Evolution at work right there. Eat food that you know is safe only. Leave the guessing to the starving person who has no choice. 64.236.121.129 13:57, 24 October 2007 (UTC)

So you're saying "look it up". Good advise, but I suppose the questioneer thought of that too. :) I got this from the SAS Handbook by John Wiseman. This time I bothered to look it up and under 'mushrooms' it says that there are no reliable general rules to identify edible mushrooms and boiling doesn't help either. You have to KNOW beyond doubt if it is an edible mushroom. And (translated back into English): "Unlike plants, for which the simple edibility test can be done, they have to be either identified or avoided. The deadly varieties don't taste unpleasant and the intoxication symptoms sometimes set in only after hours." So not days, but still, it turns out you guys are right. However, if identified beyond doubt as edible, they are a good food source which, in the right season, is available in abundance. Fortunately, they can also be easily conserved by drying. The book advises to learn a few real well and stick to those. It also advises to learn to identify amanites, the ones to particularly avoid. The most deadly is amanita phalloides, the death cap, followed by amanita virosa. Symptoms start slowly after 8 - 24 hours. After that a clear improvement, but in 90% of cases one will die after 2 - 10 days due to liver problems. No known antidote. Ah, so it does take days in this case, but it's not the poison itself that kills but the failing liver. Btw, the book also describes some nasty symptoms (including hallucinations) for the famous amanita muscaria, although one will generally recover. Note that I ate a whole muscaria once (for the hallucinations), but noticed nothing. However, that was a few days after I picked it, because I had started with tiny bits, ever bigger, until in the end I ate the remaining half. If only there weren't such idiotic drug laws, then people like me wouldn't do this sort of thing. Anyway, the muscaria article says "The effect is highly variable and individuals can react quite differently to the similar doses. Deaths from A. muscaria are extremely rare. The amount and ratio of chemical compounds per mushroom varies widely from region to region, season to season, further confusing the issue. The vast majority of mushroom poisoning fatalities (90% or more) are from having eaten either the greenish to yellowish to brownish mottled death cap (A. phalloides) or one of the destroying angels (Amanita virosa)." DirkvdM 18:51, 24 October 2007 (UTC)

Bathroom smelling of salt

Whenever I'm away from home for more than a day, when I come back home, my bathroom smells strikingly strongly of salt. The smell goes away by the next morning. What the heck is causing this? JIP | Talk 17:00, 23 October 2007 (UTC)

What does salt smell like? If the plumbing traps are drying out, it might be sewer gasses. It might be things growing in the traps. If you use those giant chlorine pills in your toilet tank, it could be chlorine gasses from it. In other words, I have no idea. --Mdwyer 17:09, 23 October 2007 (UTC)

It's like smelling something pulled up from under the sea. I do not think it's a problem with the house's plumbing, otherwise I would smell it constantly. I first experienced it when undergoing my civilian service training, which took three weeks in a training facility in another town. Weekends were free, so I came back home for every weekend. When I first opened my door on Friday evening, I was met with this salty smell. On Saturday morning, it was completely gone. It must be something related to my senses getting used to something, but how come I only ever notice it in my own apartment, not in my parents' apartments or at my workplace? JIP | Talk 18:47, 23 October 2007 (UTC)

Sounds like the smell of damp/cold places - which you probably get used to when you live there.. I seem to remember a pantry which was unheated having a smell that could be described as salty..87.102.10.72 22:10, 23 October 2007 (UTC)

Muscle cells

• On what factor does the strength of the muscle cells rely on ??
• can it be strengthened without increasing its size but by altering its components to make it strong as metal?

plz answer both Qs —Preceding unsigned comment added by 212.71.37.98 (talk) 17:12, 23 October 2007 (UTC)

A muscle's strength is dependent largely on how many myofibrils it contains. Now, saying "as strong as metal" is a meaningless comparison. The strength of a muscle is its ability to exert a force, whereas the strength of a metal is its ability to resist deformation. Someguy1221 17:28, 23 October 2007 (UTC)

The answer is no. The amount of force a muscle can exert is proportional to it's cross-sectional area. So bigger means it can exert more force - there isn't anything you can do to make it exert more force except by making it thicker.

"As strong as metal" is quite utterly meaningless. How strong is Mercury at room temperature? (Hint - it's a liquid!) Which metal are we talking about? What temperature? Are we talking about strength in tension or in compression or in bending? Take a length of electrical wire (copper) and try to snap it by just pulling on it...you'll never manage it. But bend it back and forth a few times and it snaps easily. Even your smallest muscles can be bent back and forth millions of times during your life and they don't snap.

Part of the trouble here is that you are using the word "strength" to mean two quite different things. When we talk about someone being "strong", we are probably talking about the amount of weight they can lift or something. That's a measure of the force your muscles can exert. When we talk about "strength" in metals, we're talking about the amount of weight they can passively hold without breaking. So whilst you MIGHT be trying to compare the amount of weight a steel cable could hold without snapping to the amount of weight a chunk of muscle could hold without snapping - that wouldn't be the same as the weight that could be lifted by contracting that same muscle. SteveBaker 20:05, 23 October 2007 (UTC)

Sanitation

(Aaw, lost what I wrote in an EC...) Is there anything I can do to sanatize my desk besides using clorox wipes and putting on GermX before eating, because we're having staph outbreakes at my school. I could probably get a hold of most things (disenfectants), but I need to know what they are. Thnx!YДмΔќʃʀï_C← 10-23-2007 • 19:36:16

While it's tempting to recommend that you use the time-honored method of subjecting it to a temperature similar to the inside the sun for a few seconds, I must regretfully assume that you are speaking in practical terms. "Creative" methods such as that excluded, I'd just recommend washing your hands a lot and using the disinfectants, etc you mentioned above. Maybe the article Staphylococcus could give some useful information as well.
Ah, here we go: this section talks about alcohol being a good disinfectant specific to the bacteria:

Alcohol has proven to be an effective topical sanitizer against MRSA. Quaternary ammonium can be used in conjunction with alcohol to increase the duration of the sanitizing action. The prevention of nosocomial infections involve routine and terminal cleaning. Non-flammable Alcohol Vapor in Carbon Dioxide systems (NAV-CO2 systems) have an advantage, as they do not attack metals or plastics used in medical environments and do not contribute to antibacterial resistance.

Hope this is useful. Pyrospirit (talk · contribs) 22:51, 23 October 2007 (UTC)

polymer

which materials are anti_markin about absorbing ink? —Preceding unsigned comment added by 85.133.156.36 (talk) 20:37, 23 October 2007 (UTC)

I'm not entirely sure what you're talking about. Could you provide more context to your question? Pyrospirit (talk · contribs) 23:01, 23 October 2007 (UTC)

You need something with a strong non porous surface, such as glass or metal. The ink will be erasable. FOr polymers you face the additional problem that the solvent in the ink may be able to dissolve the polymer or soften it, allowing the ink to pentrate the surface and be hard to remove. Melamine resin or Formica (plastic) are pretty good at resisting staining. Look at anything that might be used on a kitchen bench or whiteboard. Graeme Bartlett 01:34, 24 October 2007 (UTC)

Toadstools and snakes

I think I know two things: that no shelf mushroom is poisonous, and no snake with longitudinal stripes is venomous. Are these things true? --Milkbreath 21:23, 23 October 2007 (UTC)

There is no simple rule to distinguish poisonous mushrooms from edible ones - although what you say here isn't exactly that. Our article says that most shelf mushrooms are inedible - but doesn't say whether any are poisonous. I'd be VERY skeptical about that rule. About the snakes though. I find your claim here rather surprising too. I guess it depends on what you call a 'stripe' and just how 'longitudinal' it has to be. The Yellow bellied sea-snake is certainly pretty venomous - and I'd call that a black/yellow longitudinal stripe pattern...but maybe you can weasel out of that by saying that it's a 'sea snake' and you meant only land snakes - or that it's not really a "stripe" per-se but merely a top and bottom coloration. SteveBaker 22:37, 23 October 2007 (UTC)

The pit viper Trimeresurus popeorum has ventrolateral stripe. I also came across this bizarre image of what the photographer claims is the deadly Bungarus fasciatus which normally has striking yellow and black lateral stripes, but in this case sports black and yellow longitudinal stripes. The picture has the accompanying text: "Bungarus fasciatus : mutazione genetica. Raro esemplare con una lunga fascia dorsale nera al posto della tipica colorazione ad anelli." I caught the word genetic mutation but that is a pretty drastic change from the normal patterning. Mistaken identity possibly? EDIT: It appears to be the venomous elapid Hemibungarus sauteri an "Asian coral snake" Sifaka 04:20, 24 October 2007 (UTC)

Actually it seems like a few of the "Asian coral snakes" in the venomous genus Calliophis seem to be longitudinally banded and strikingly colored. See this picture of Calliophis bivirgatus. Sifaka 04:51, 24 October 2007 (UTC)

Followup: says that the Sulphur Shelf mushroom (Polyporus sulphureus) poisoned seven members of the The Mycological Society of San Francisco (who REALLY ought to know better!). Our article Laetiporus confusingly describes it as edible (and gives it a totally different Latin name?!?) - but then goes on to say "About half of the population has an allergic reaction to this type of mushroom, with cases being more pronounced in older mushrooms."...yeah - so it's edible, but you have a 50/50 chance of being allergic to it. Hmmm - I call your claim "Busted". SteveBaker 22:45, 23 October 2007 (UTC)

Right you are. But, heyyyy...does ya got sumpin against weasels? --Milkbreath 23:00, 23 October 2007 (UTC)

To my knowledge none of the bracket fungi appear to be truly deadly poisonous, but then again some dangerous fungi can grow in a manner where they superficially resemble bracket fungi. It also doesn't help that most bracket fungi taste like tree bark with similar toughness. Incidentally Chicken of the Woods (Laetiporus sulphureus is the correct name for Polyporus sulphureus) is actually very commonly eaten and supposedly tasty; however it needs to be cooked before eating. The poisoning described above was probably at worst an upset stomach, vomiting, and maybe some diarrhea, nothing requiring any hospital attention. Sifaka 03:16, 24 October 2007 (UTC)

Hmmm - so what you are saying is that it may be true that bracket/shelf mushrooms are not poisonous - but there is no good rule for identifying that something actually is a bracket/shelf mushroom and not a look-alike. OK that makes our OP technically correct - but not usefully/safely correct! If 50% of people have an allergy to the mushroom - I'd be surprised if the symptoms were upset stomach, etc - we'd see allergic reaction symptoms. Of course an allergic reaction doesn't mean that the mushroom is 'poisonous'. But I don't think I'll be eating them anytime soon! Bottom line has got to be that it's just not safe to use this 'rule' to identify edible mushrooms. SteveBaker 04:28, 24 October 2007 (UTC)

Steve you appear to be right. I read it over and found this ], but it seems only mature specimens cause the trouble. Sifaka 04:36, 24 October 2007 (UTC)

• It's too bad 'shroom-hunting is so tricky. I wonder if you couldn't just come up with some type of litmus test for the most popular substances these things use to kill you. --Sean 21:27, 24 October 2007 (UTC)

internal violation

My big brother wants to join the army but his mates keeps teasing him that during his medical he's going to be internally violated. But I'm to sure about this, I want to know (1) does the doctor internally violate recruits and (2) what purpose does this serve? —Preceding unsigned comment added by Everyone knows someone called Dave (talk • contribs) 22:29, 23 October 2007 (UTC)

What country/army are you asking about? - hydnjo talk 22:47, 23 October 2007 (UTC)

Probably doing a Rectal examination - possibly for Prostate issues. SteveBaker 22:54, 23 October 2007 (UTC)

If that is violation, then I have once been violated by a woman (a doctor). (no prostrate problems, I can happily tell you.) DirkvdM 09:45, 24 October 2007 (UTC)

To paraphrase Tony Soprano, "I don't even let people wag their finger in my face!". 38.112.225.84 15:26, 24 October 2007 (UTC)

• I would be very surprised to learn that young men receive prostate exams in a standard recruiting physical. It's much more likely that your brother will just receive a check for any weaknesses around the inguinal canal, which could lead to an inguinal hernia. This exam gets quite personal, but it's no "unsolicited finger in the anus". --Sean 19:19, 24 October 2007 (UTC)

Is that the legendary stand-in-a-line-and-"please cough whilst I hold your testicles" thing? --Kurt Shaped Box 20:41, 24 October 2007 (UTC)

Yes, although they don't actually hold your testicles. Rather, they "slide" a finger or two up alongside the spermatic cord. Only for some reason, "slide" usually turns out to mean "jam". :-) --David Iberri (talk) 21:14, 24 October 2007 (UTC)

• I get my revenge by turning my head towards the doctor. --Sean 21:29, 24 October 2007 (UTC)

October 24

Frosty Freezer Food

I've gone to my freezer to heat up a prepackaged frozen entree. And when I take it out of the box, I notice the food beneath the plastic wrap is buried in a heavy coat of ice crystals. Usually there are none. Does that mean this entree had defrosted at the store? Is it safe to eat? What causes frozen foods to develop ice crystals? (like that nasty layer of snow on old ice cream?) --24.249.108.133 00:29, 24 October 2007 (UTC)

It could be condensation from the air when it was frozen. The vapour pressure of water is temperature-dependent, so when the food/container was warmer before packaging, there was more moisture in the air. Once the package was sealed and frozen, that amount of moisture became higher than the decreased vapour pressure at the lower temperature. This causes the "excess" moisture to crystallize out as ice. Your food should be safe; the ice simply means it wasn't packed in a vacuum. 142.103.207.10 01:00, 24 October 2007 (UTC)

You might want to see our article about Freezer burn.

Atlant 12:46, 25 October 2007 (UTC)

Does the Earth's magnetic field rotate daily w.r.t the solar system?

Obviously, the Earth's rotation must have an effect on the magnetic field, because of the difference between magnetic and axial north, but can we say the field spins with any certainty, assuming that would be well-defined? 217.43.117.117 01:14, 24 October 2007 (UTC)

The earth's magnetic field spins along with the earth. It does slowy drift over the years, so that the magnetic poles shift over the years. The field will affect the space around the earth, out to the distance where the solar wind dominates the magnetic field. Graeme Bartlett 01:40, 24 October 2007 (UTC)

Yeah - 'true North' (as in "the axis of rotation") and 'magnetic North' (the place where the magnetic field lines converge) disagree. As the earth rotates the location of 'magnetic North' stays still relative to the surface of the earth (at least on the scale of days and weeks - it moves slowly on the scale of months and years). Hence, you would be able to measure a daily rotation of the field-lines if you were stationary with respect to the Sun. SteveBaker 04:15, 24 October 2007 (UTC)

Actually, relative to specified location of the Earth's surface, the magnetic pole describes an rough circle with a radius of tens of miles over the course of the day because it is deflected away from the position of the sun due to the magnetic field of the solar wind. Dragons flight 07:06, 24 October 2007 (UTC)

Wow! Interesting. The wobble due to the misalignment of magnetic and rotational poles is around 1000km (and moving by 40km per year right now) - so this adds a few percent to the overall effect. I guess that makes our answer to the OP's question more like: "97% Yes, 3% No". Of course there is this theory that the earth's magnetic field is about to do one of it's major North/South 'flips' any time now. All bets are off if that happens! SteveBaker 14:23, 24 October 2007 (UTC)

: Thanks for the replies guys - very informative. There's still one thing on which I'm not clear, but I didn't express the question very clearly: If magnetic north was identical to axial north then would the magnetic field be spinning with the earth? Do you see what I mean, the effect of the angle between the magnetic and axial poles gives the field a wobble, but apart from that wobble, is it spinning with the earth? The reason I asked if the question was well-defined is that I'm not sure in what way a spinning magnetic field would be differentiable from a non-spinning one. To illustrate, if i had an magnet and put it inside a spherical shell, and simply span the shell without the magnet spinning, would it be possible to determine from outside the shell whether the magnet span with it or not? What if it was an electro-magnet and was attached rigidly to the shell, but now we turn the magnet off, spin the shell a little and then turn it back on. Can we now tell from outside that the magnet has rotated on its axis? In the limit, would continous rotation be any different to this? Perhaps the answer has something to do with the dynamic nature of ferromagnetism... In any case, further ellucidation would be greatly appreciated. 217.43.117.117 01:53, 25 October 2007 (UTC)

Reading magnetic declination, it would seem that the earth's near-surface magnetic field does rotate along with the earth itself, even if such is not explicitly stated (what is stated is that the magnetic declination at any position on the Earth doesn't change much except over a period of years). It's the case that the magnetic field lines in the space around the earth are more oblong on the dark side due to the solar wind. So I would guess that the currents generating the Earth's magnetic field are roughly in sinc with the Earth's rotation, and the major daily influence on it is the solar wind. Someguy1221 02:21, 25 October 2007 (UTC)

Water, Specifically the acquifer under Pahrump Nevada

I have looked everywhere I can think of for the answer. We bought a home in Pahrump Nevada (Zip Code: 89060)and at the time we were told "The second largest acquifer in America is under Pahrump and stretches from the test site in the north and the Amorgosa valley to under Pahrump.

I was also told that the acquifer is 4755 feet deep, which would be a lot of water!

If you can help me with this problem, I would really appreciate it. I don't know if Wickpedia has ever processed an article on this subject, but I can hope.

Ted Farson (contact information removed to reduce spam) —Preceding unsigned comment added by 12.110.33.171 (talk) 01:25, 24 October 2007 (UTC)

What is your problem, were you misled? Graeme Bartlett 01:43, 24 October 2007 (UTC)

I googled on "pahrump aquifer site:gov" and found this and this (be sure to see the clickable Fig.s). --Milkbreath 03:41, 24 October 2007 (UTC)

Water content of canned tomatoes

How much water is in one 796ml can of ground tomatoes? NeonMerlin 06:18, 24 October 2007 (UTC)

A tomato could have 95% water, so 756 ml of water. Graeme Bartlett 07:07, 24 October 2007 (UTC)

Charge conservation in electrochemical cells

Hi I am trying to show mathematically that the voltage across an electrochemical cell will decay with time. Is this a valid approach? ${\displaystyle I={\frac {Q}{t}}}$ and ${\displaystyle V=IR}$
--> ${\displaystyle V={\frac {Q}{tR}}}$

Clearly R is a constant, but is Q for particular electrochemical cell? Or should I use ${\displaystyle \Delta Q}$? Also does this value of Q or ${\displaystyle \Delta Q}$ change depending on the ratio of concentration of ions in the half cells (according to the Nernst equation initial voltage is the same for the same ratio of product ions and reactant ions)?

My problem comes down to applying the conservation of charge to electrochemical cells. Thanks in Advance

Lots of dupes removed. Lanfear's Bane | t 09:08, 24 October 2007 (UTC)

This slow internet connection is getting annoying. I would've beaten you to the punch if loading didn't take so long. - Mgm| 09:14, 24 October 2007 (UTC)

No. It looks like your using a similar method to that used to find find the voltage accross a capacitor. eg see http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capdis.html for a solution

The electrochemical cell doesn't store electricity as 'charge' - but as changes in the chemistry of the contents..

The usual method to calculate the voltage is to start with the energy change for the process happening eg Fe + Cu2+ >> Fe2+ + Cu Energy change = E (kJ/mol) then divide by the number of atoms to get the energy change per atom (call this X).. Since a charged particle of charge q requires energy X to move through a potential V ie X=qV gives V=X/q (q is the charge released by the reaction)

If X is constant then V is constant - however X can change for various reasons - mostly due to concentration.. (the are models of this - mostly the Nernst equation)87.102.94.157 11:45, 24 October 2007 (UTC)

Virtual Reality for video games, and resolutions

Is there a limit to how high of a resolution can be displayed in a VR headset? From my understanding, VR headsets have very low resolutions, especially compared to computer monitors or high definition televisions. Also is it possible for VR headsets to replace televisions or monitors for video games? I know it has been tried with some failed attempts (virtual boy, but will it ever catch on? What kind of technological challenges need to be overcome before it becomes a practical technology? 64.236.121.129 14:40, 24 October 2007 (UTC)

The limit is the resolution of the headset itself. Most of the cheap ones use LCD displays of fairly poor resolution (the kind you have in cellphones typically) - and that's the limiting factor. In my last job (Flight Simulation), we had 1600x1200 stereo head-mounted displays - you could buy a REALLY nice sports car (think 'Lamborgini') for the cost of one of them - and they were extremely fragile! The 1280x1024 device is here: . The problem with it 'catching on' is that to do it right is still too expensive and if you do it wrong, people get headaches, nausea, eyestrain, etc. We just need lower cost, higher resolution panels and cheaper optics. The display resolution problem is obvious. The optics problem is 'eye relief' - you can't put a simple pair of screens into some glasses - your eyes don't like focussing down at one or two inches for long periods of time. You need 'collimating' optics to allow them to focus on a virtual image at least half a meter away (preferably more). But it can certainly be done - it's just a matter of cost. SteveBaker 15:38, 24 October 2007 (UTC)

Body Strength

what is the main compononet that gives the muscle cells its strength and can a compononet be added to make it strong as metal????

Please see the section above where this has already been asked and answered. — Lomn 16:46, 24 October 2007 (UTC)

can you permanentaly stop PKC (Protein Kinase C) activity in vivo ?

if yes, with what? —Preceding unsigned comment added by Poppynash (talk • contribs) 17:00, 24 October 2007 (UTC)

Kind of. Isoenzyme-specific PKC inhibitors such as Go6976, safingol or rottlerin, and broad-spectrum PKC inhibitors such as bisindolylmaleimide may partially or fully inhibit PCK function in vivo, but only for as long as you continue to provide the inhibitors to the cells of interest. You can't just apply a single dose of inhibitor an expect PKC to stop functioning permanently. That is not possible. Rockpocket 18:31, 24 October 2007 (UTC)

Some Protein kinase C isozymes have been been knocked out using mice as the experimental system. --JWSchmidt 01:24, 25 October 2007 (UTC)

Time Dilation

Assuming a traveller sets of from the Earth at a constant velocity of half of the speed of light for a round trip of 8 years (as experienced from the Earth's reference frame), would I be correct in saying that the traveller only experiences approximately 6.928 years? --80.229.152.246 21:02, 24 October 2007 (UTC)

Yeah, you got the right answer. A real traveler doing a round trip like that would want to spend a total of on the order of a year doing all the accelerating and decelerating involved, so he doesn't get squished like a bug. Accelerating to half the speed of light in just a day or two is not something you want to do! But special relativity classes tend to just ignore that little detail, and assume that the acceleration duration is a negligible portion of the trip. MrRedact 22:30, 24 October 2007 (UTC)

Er, why would you take longer than a day or two? At constant 9.8m/s^2, you hit the speed of like in about 8.5 hours. --Wirbelwindヴィルヴェルヴィント (talk) 23:05, 24 October 2007 (UTC)

Might want to check your figures there (assuming "like" is a typo for "light"). I think you dropped about three zeroes. Not counting relativistic effects. --Trovatore 00:04, 25 October 2007 (UTC)

Guys - this is not exactly rocket science! v = a.t - so t = v/a - if you want to go at (say) half the speed of light with an accelleration of 1g then you have t = (2.998x10/2)/9.8 seconds which is over fifteen million seconds which is about 177 days. So - yeah - you need six months to get to half the speed of light and another six months to slow down again at a comfy 1g. So MrRedact is exactly right and Wirbelwind needs some more calculator batteries! We are wise to choose half the speed of light because you can pretty much not worry too much about relativistic effects at that speed (for back-of-envelope calculations at least). You can't reach the speed of light no matter what - and even getting reasonably close to it is going to take you an insane amount of time. SteveBaker 01:22, 25 October 2007 (UTC)

I agree with everything Steve says -- except the part where he says "this is not rocket science"! --Anon, 08:04 UTC, October 25, 2007.

Incidentally, the original poster referred to a round trip "at constant velocity", which is impossible if "velocity" is being used as a physicist would to mean a vector quantity. At constant velocity, you can't turn around and come back! But a round trip at constant speed is possible by traveling in a circle, for example. (The half year-or whatever of acceleration would then have taken place before the trip began.)

Sorry, that should be 'a trip of around 8 years'. That's what asking questions when you are far too tired does... --80.229.152.246 11:54, 25 October 2007 (UTC)

For the circular trip to take 8 years at c/2, the circular path must have a circumference of 4 light-years and therefore a radius of 2/π light-years or 6.02×10 m. To stay on the circular path therefore requires a continuous thrust (centripetal acceleration) of v²/r = (1.50×10)/(6.02×10) = 3.74 m/s or about 3/8 gee. At least, that's as perceived in our external reference frame; I'm not sure how relativistic effects might change it in the spacecraft's frame. --Anon, 08:07 UTC, October 25, 2007.

Strong Force vs. Electromagnetic Force

How close do 2 protons have to be for the Strong Force to overcome the repulsion of the Electromagnetic Force? Sappysap 18:18, 24 October 2007 (UTC)

It never does. Luckily for us. If Helium-2 were a bound state, all the stars would explode. --Trovatore 18:33, 24 October 2007 (UTC)

Wow! Diprotons, thank you for telling me about them. One follow-up fantastical question if no one minds :) Can an analogy be made between nuclei, which attract at short distances and repulse at long distances, and matter in general which attracts at short distances (say within the range of a galaxy) but seems to repulse at long distances (galaxies are all moving away from each other)? Perhaps the large scale acceleration of galaxies isn't due just to the momentum from the Big Bang. I'll gladly share a Nobel Prize in Physics for any helpful consideration! Sappysap 18:51, 24 October 2007 (UTC)

The movement of galaxies away from one another over long distances is not do to any repulsive force between them, but merely to the expansion of the universe, which only overtakes gravity at long distances. Someguy1221 19:36, 24 October 2007 (UTC)

Possible to generate a magnetic field to repel bullets?

Is it possible? —Preceding unsigned comment added by 64.236.121.129 (talk) 19:31, 24 October 2007 (UTC)

Well, if theyre made from iron, maybe. The earth has such a shield - the magnetosphere - which, according to our article Van Allen Belt is equivalent to 1 millimetre of lead. (That number of course applies to charged particles, not uncharged bullets, so we can be off "by a long shot", but it should give you an idea of the magnetudes (sorry about the silly pun) involved.) — Sebastian 19:46, 24 October 2007 (UTC)

However, since bullets aren't made from iron or other ferromagnetic materials (they're primarily lead, often with a copper jacket), the short answer to the question is "no". Bullets are not magnetic, and so cannot be repelled by a magnetic field. — Lomn 19:51, 24 October 2007 (UTC)

That's not quite right - a non-ferromagnetic conductor moving in a magnetic field will have a current induced in it - and hence become an electromagnet - and could be deflected.. I still imagine that in practice the answer is no - the magnetic generation apparatus would be massive - the best way to utilise it therefor would be to hide behind it!87.102.94.157 19:57, 24 October 2007 (UTC)

What if, the generation device was powered by some kind of advanced Micropower, along with other advanced technologies. Hypothetically, with advanced technology, is it scientifically possible? 64.236.121.129 20:10, 24 October 2007 (UTC)

If we're going to jump that far, why even bother with magnetism? We might as well jump to science fantasy and invent some Treknobabble about reversing the polarity to stop the bullet. In that case, sure. But I'll stick with "no" for my answer. A magnetic field will not stop a bullet. — Lomn 20:47, 24 October 2007 (UTC)

Because we know magnetism exists, and micropower, is also an area of scientific research. "Trecknobabble" as you put it, doesn't and isn't. 64.236.121.129 20:56, 24 October 2007 (UTC)

Magnetism exists -- but there's no reason to expect it to have any effect. Micropower is just a power source, providing the same power as any other power source, and a particularly ill-suited one. Thirdly, your (first) post throws out unspecified "advanced technologies". So you're asking hypothetically, with a theorized power source of dubious merit, using other things that aren't even articulated (much less things that exist), can we use a force that doesn't have a relevant effect to do what we want?" I could say that cold fusion could amplify the strong nuclear force of tissue paper to stop bullets and be just as scientifically useful. — Lomn 21:15, 24 October 2007 (UTC)

An electro magnetic field would affect the movement of bullets. I think 87.102 already pointed that out to you. I don't think the OP was asking you, but he's asking if a powerful electro magnetic field would stop bullets. I think he just added "advanced technology" to mean making the power source small, and extremely powerful. The answer is yes, with enough energy, an electro magnetic field can. Also I must remind you to be civil, and helpful. No need to be condescending with words like "trecknobabble". It's not very helpful, and only serves to ridicule the question. Malamockq 02:59, 25 October 2007 (UTC)

Lomn's mad haha. Anyway I think we already established that a magnetic field would affect a bullet. That's relevant. I'm not sure you have the proper education in this field to answer my question. 64.236.121.129 13:44, 25 October 2007 (UTC)

Lead conducts electricity right? Couldn't the kinetic energy in the bullet be converted to electrical energy and get dissipated in internal resistance inside the bullet? 64.236.121.129 20:04, 24 October 2007 (UTC)

Not really. While moving through a magnetic field perpendicular to the bullet's direction of motion, a voltage will be induced across the bullet. However, once the maximum voltage is reached, electron flow stops, and the magnetic force on the electrons in the bullet will still equal that on the protons, and so there will be no net magnetic force on the bullet. Now, since all materials have at least some diamagnetic character, you could try to repell the bullet in this manner. However, it generally takes the most powerful sustainable magnetic fields to simply counteract gravity using diamagnetism, so good luck deflecting a moving bullet with it. Someguy1221 20:18, 24 October 2007 (UTC)

The voltage induced will cause a current eddy current might be useful here - it's possible that using a field strong enough to deflect a bullet would induce such a current that the bullet (lead) is melted due to resistance heating - so now you'd be hit by moltenlead . no good.87.102.94.16 12:47, 25 October 2007 (UTC)

• If you could diamagnetically accelerate a frog with sufficient velocity towards the bullet, it would stop it. --Sean 21:22, 24 October 2007 (UTC)

Perhaps you should use Electromagnetic radiation to zap the bullet with so much energy that it evaperates before it strikes you — a laser ray gun should do the job, but it will have to be very high power to deliver enough punch! Graeme Bartlett 06:09, 25 October 2007 (UTC)

Geeky TV

Do you guys just love Big Bang Theory? Like you've been waiting for this show you're entire lives, right? Beekone 20:45, 24 October 2007 (UTC)

Utter, utter, utter, utter', CRAP. Proper science geeks like: (a) Top Gear, (b) Mythbusters, (c) Junkyard-Wars/Scrapheap-Challenge (before they screwed it up in the last couple of series). SteveBaker 20:51, 24 October 2007 (UTC)

and look around you for a laugh. Theresa Knott | The otter sank 22:43, 24 October 2007 (UTC)

Right - I "lost it" at "H twenty" - hydnjo talk 00:57, 25 October 2007 (UTC)

"Germs originated from Germany, before spreading rapidly to the rest of the world" RHB - Talk 22:51, 24 October 2007 (UTC)

OMG those are funny! I had the best laugh today watching the Maths episode than I've had in many months. I was laughing uncontrollably with tears in my eyes for several minutes, triggered by the absurdity of the first story problem. MrRedact 07:12, 25 October 2007 (UTC)

Top gear? I assume you mean the BBC car show. That's not science, that's everyday technology. No, it isn't even that - the little I have seen of it is not abut the innards of a car, but about how fast it accelerates and how it looks. Yawn. Instead, try World Solar Challenge, a current event, or DARPA Grand Challenge, the next edition of which will be in just over a week, on 3 November. Especially the latter is so much at the forefront of technology that science geeks can't help but be thrilled. And it's bound to be shown at a tv set near you. On top of that, it's about something that could help save the planet ("Oh, Flash, I love you. And we only have a few years left to save the Earth!"). DirkvdM 07:17, 25 October 2007 (UTC)

How do enzymes evolve?

When I asked my Biology teacher, he fobbed me off with "lots of proteins are created, the beneficial enzymes are the only ones that survive further i.e. survival of the fittest except enzymes aren't alive." Our FA on enzymes mentions little on the subject. Is there any proper, researched mechanism for their evolution? Thanks, RHB - Talk 22:47, 24 October 2007 (UTC)

Beneficial is very vague. What's beneficial for one species could be death for another. bibliomaniac15 A straw poll on straw polls 23:10, 24 October 2007 (UTC)

Which of course suggests that organisms which create proteins that kill themselves off are not going to be the fittest. Which illustrates well, of course, the idea that the enzymes are not what is being selected for—its the protein creation by the organism. --24.147.86.187 23:22, 24 October 2007 (UTC)

Your teacher is more or less correct. Enzymes don't evolve. They function like little tools in the cell, so your question is like asking how hammers evolve. But the DNA that gives instructions for how to make an enzyme is subject to random mutations. If that piece of DNA does mutate, then the resulting enzyme may work better, or worse, or show no functional change. If the change makes the enzyme work better, let's say faster or use less energy, then the cell stays alive and that change is passed on to future generations: a different enzyme structure than before. But usually the change makes the enzyme work worse and the cell dies. Delmlsfan 23:27, 24 October 2007 (UTC)

Misplaced Pages has Molecular evolution. --JWSchmidt 00:12, 25 October 2007 (UTC)

Enzymes don't evolve (indeed, they're not alive), organisms that produce the enzymes evolve, and the ones that produce the right enzymes are the ones that survive, to put it simply. Or do you mean to ask how the first enzymes came about? One theory is that they are being made in certain areas of space (forgot the details) and that some of those landed on Earth and kick-started the evolution of life. I am surprised there is nothing on this in the enzyme and protein articles. At least, I can't find it. DirkvdM 08:06, 25 October 2007 (UTC)

Size limit of the human body

I remember reading somewhere that there's a theoretical limit to how large we can become evolutionarily speaking due to the fact that as we get larger our weight increases volumetrically but bone strength only increases in cross-section so eventually our skeletons would be unable to support our bodies. Anyone know what the limit might be? Exxolon 23:08, 24 October 2007 (UTC)

Misplaced Pages has Robert Wadlow, "the tallest person in medical history for whom there is irrefutable evidence". --JWSchmidt 00:03, 25 October 2007 (UTC)

I remember hearing about a much lower limit when falling on you're face becomes potentially lethal. That limit wasn't much larger than our current size. — Daniel 02:57, 25 October 2007 (UTC)

You say "we" and "human body" as if you're talking about humans, but "evolutionarily speaking" as if you're talking about some future species that might be descended from humans but would not be called human. In the latter case, there is much more scope for growth despite the square-cube law by evolving thicker limbs the way hippos and elephants have. The limit in that direction must be at least as large as the largest land animals that have ever lived, i.e. the larger dinosaurs. You could even imagine a being with dinosaur-strength legs but in great numbers like a millipede. I can't imagine any circumstances where that sort of body would be advantageous for an intelligent being (for one thing, the food requirements would be immense!), but it would be physically possible.

On the other hand, if you're talking about beings we would recognize as human, then the limit is set by how far we could evolve in the direction of thicker bones and stronger muscles and still be recognized as human. That is, it's basically arbitrary. --Anonymous, 08:18 UTC, October 25, 2007.

After edit conflict:

Right, that's what I thought too. Our walking on our hind legs makes us rather different from other animals that got to be very big. But of course we could evolve back to four-footers (for whatever 'reason'). In which case I don't see what would stop us from becoming as big as dinosaurs. Btw, do you mean big or tall - weight or length? DirkvdM 08:22, 25 October 2007 (UTC)

A different solution would of course be to go another step 'back' in evolution and enter the water again. Whales are the largest animals that ever lived. And they are supposed to be fairly intelligent, so maybe it wouldn't be such a stupid thing to do. :) DirkvdM 08:25, 25 October 2007 (UTC)

Honey

I bought some honey, the kind that comes in a plastic bear, and now that it's down to the last quarter or so of the bear I've noticed that the remaining honey is extremely grainy and thick, even to the point where it's a struggle to squeeze it out. Also, the honey is now a different, lighter, color than when I first got it. Was wondering if anyone knew why this might be? Thanks. 38.112.225.84 23:12, 24 October 2007 (UTC)

Sounds like it's crystallizing (probably various sugars that were dissolved in the liquid). DMacks 23:45, 24 October 2007 (UTC)

If you set the bear in a pan of hot water the honey will go back to normal. --Milkbreath 23:52, 24 October 2007 (UTC)

Bear? What bear?

I also assume it's crystallisation, but isn't that caused by drying out? So how would heating it help? And would it remain uncrystallised after it has cooled down again? DirkvdM 08:30, 25 October 2007 (UTC)

Here is a picture of the bear. But I don't know why honey gets fluid again when it's warmed. Lova Falk 09:00, 25 October 2007 (UTC)

The sugar that has crystallised redissolves when warmed. There's a more scientific explanation for why this happens if you ask...87.102.94.16 12:42, 25 October 2007 (UTC)

I know enough science to know that if you don't use mathematics you're talking crap, but I don't mind talking it. I wonder if there's a userbox for proficiency in crap. Honey is a supersaturated solution of sugar in water. If there is nowhere for a crystal to get started, that is, the inside of the container is smooth, it will sit like that a pretty long time, but eventually a crystal will get started and the jig is up. That's how you make rock candy. If you heat the solution the water can hold more sugar in solution, and the crystals redissolve. --Milkbreath 13:05, 25 October 2007 (UTC)

String Theory

There have been countless complaints all over the classroom. This weird, nerdy kid in my class is COMPLETELY and UTTERLY obsessed with string theory. He happened to ask every teacher he's met so far about string theory. What is string theory, anyways? Asking just out of curiousity, and a way to shut him up. I looked it up, but I eventually decided that if I devoted my life to deciphering that page, I'd be eternally confused. I'm no math or science geek here. Make your explanation simple enough for my simple mind to understand. Heh. Had to get all complaints out of my system. Sorry 'bout that. —Preceding unsigned comment added by 68.100.133.160 (talk) 02:06, 25 October 2007 (UTC)

No big problem but in the future please edit your posting rather than reposting the entire new version. I've deleted your earlier versions. Also it's a good idea to sign your posts with four tildes like this: ~~~~ . hydnjo talk 02:20, 25 October 2007 (UTC)

As basically as I can put it...In physics, fundamental particles (like quarks and electrons, not protons and neutrons, which are made of quarks) are usually considered to be dimensionless (lacking extent in any direction) points in space (when it's a particle, and not a wave, but you wanted simple, so don't ask). In string theory, they are considered to have extent in one direction, making them little curved lines (or strings) instead of points. This leads to a number of very wierd predictions, like the existence of more dimensions than we can see or experience, and particles that have never been observed. The problem with string theory is that while it agrees with "normal" physics, its new predictions are entirely unprovable with any imaginable technology, let alone any existing technology. Someguy1221 04:06, 25 October 2007 (UTC)

I'll try to go even a little simpler, assuming very little knowledge of science: String theory deals with the very smallest parts that everything in the universe can be divided into. If you divide practically anything that exists, like your body for instance, into its very smallest parts, you'll get four kinds of parts: "electrons", which are the smallest pieces of electricity that there can be, "photons", which are the smallest pieces of light that there can be, and a couple other wierd parts called "quarks" and "guons". Those little parts are the smallest things that exist; you can't split them up into anything smaller. In fact, with the normal way that scientists make the most accurate possible calculations about how those parts behave, they treat those parts as not having any size at all. One of those little parts is treated as just being a point with no size.

String theory is a newer way of making calculations about how those little parts behave. In string theory, those little parts are no longer treated as being just a point with no size. Instead, the little parts are treated as being a little curvy line.

Another way that string theory is different from the normal way of making calculations about how the little parts behave is that according to string theory, there exist extra dimensions that we normally don't notice. A "dimension" can be thought of as a combination of a direction and the opposite direction. Space is normally treated as having three dimensions: up and down is a dimension, left and right is a dimension, and forward and backward is a dimension. Any other other direction in space can be treated as being a combination of directions in those three dimensions. Time also counts as a dimension: if you're sitting perfectly still, you can think of yourself as moving forward in the time dimension. Time works a little differently than space does, so space and time are two different kinds of dimensions. String theory says that there also exists a third kind of dimension, that is, a third kind of direction that something can move in. We don't normally notice those extra dimensions because the extra dimensions loop back around, such that if you go just a very little ways in one of the extra directions, you wind up right back where you started from.

To change the subject, if you have any interest at all in gaining some understanding about your classmate, you might want to check out Misplaced Pages's article on Asperger's syndrome. Weird, nerdy, and completely and utterly obsessed with a topic as geeky as string theory sounds an awful lot like someone who may have Asperger's syndrome. Asperger's syndrome is not too uncommon among people with ultrageeky occupations like mathematicians and physicists. MrRedact 06:17, 25 October 2007 (UTC)

If the questioner has any interest at all in gaining some understanding about their classmate, the best approach is to talk to him, treat him as a person, and drop the "weird", "nerdy", "geeky" labels, which are both insulting and stereotyping. Only a qualified professional can make a diagnosis of Asperger syndrome. Gandalf61 08:45, 25 October 2007 (UTC)

If you indeed have a simple mind, then maybe the simple English Misplaced Pages article on String Theory is what you are looking for. :) DirkvdM 08:39, 25 October 2007 (UTC)

Well, you don't have to have a simple mind to have difficulty incorporating advanced scientific information. If you don't already know what a quantum and a quark are, much less are ready to accept the idea of 11 dimensions, then it's going to be hard to jump into an article on string theory. --24.147.86.187 12:46, 25 October 2007 (UTC)

A nice, easy book you might recommend your inquisitive-yet-annoying friend is Brian Greene's The Elegant Universe, which is all about String Theory. If you are interested in getting the low-down without reading much, there is a PBS series by the same name which is totally online now. Check it out! --24.147.86.187 12:42, 25 October 2007 (UTC)

Also, if you want to shut him up, just say, "Well, that sounds interesting, but until they come up with a way to test it, it might as well as be a religion as far as I'm concerned. An untestable theory is not much different than an article of faith." Which might drive him over the edge. ;-) One of the big issues with string theory is that at the moment there is no real way to determine whether it is correct or not; it doesn't make easily testable hypotheses. Some scientists see this as a temporary thing while others consider it to be signs of great flaws. --24.147.86.187 12:46, 25 October 2007 (UTC)

Acceleration to near-light speeds

What's the speed of an object moving with a constant acceleration (from its point of reference) with respect to time from its point of reference and from the starting point of reference (when its speed was zero)? Does this question fit better on the mathematics page? — Daniel 03:27, 25 October 2007 (UTC)

It's not terribly hard to work it out -- start from the relativistic addition-of-velocities formula, figure out the change in velocity-in-lab-frame with respect to time-in-ship-frame at a particular velocity (remember to take the existing time dilation into account!) and integrate. From memory I think it may be tanh(at), where a is the acceleration, t the time, "tanh" is the hyperbolic tangent, and you're working in a system of units where the speed of light equals one. But I'd have to re-derive it to be sure. --Trovatore 03:34, 25 October 2007 (UTC)

I just did the integration without assuming special units, and got c*tanh(at/c), which works out to tanh(at) once you put it in said special units. Someguy1221 04:13, 25 October 2007 (UTC)

No, no - everybody knows that the speed of light is 137. In units with ħ and e set to one but the Fine-structure constant retaining its required dimensionless value, that is. For anyone wandering through wondering what is the deal with the funny units, they are useful because physicists like to be lazy efficient. Trovatore's answer is patently dimensionally incorrect to anyone dragging the constants along, but the result must have units of velocity (there is Someguy's first c), and the argument of tanh must be dimensionless (at has units of velocity, so the must be another c to cancel). This only works if both the original formula and the subsequent math are correct, but using c = 1*(3*10 cm/s) units actually makes the algebra less cumbersome and clarifies the presentation without sacrificing accuracy or rigor. Eldereft 06:03, 25 October 2007 (UTC)

I really can't tell -- are you trying to make a joke, or are you genuinely crusading for the units that you prefer, or what? For dealing with a relativistic but presumably non-quantum problem, it's much more common, convenient and sensible to choose units such that c=1, rather than to sacrifice the convenience of c=1 in order to make ħ and e be 1. Trovatore's answer is perfectly correct using the very commonly used choice of units for this type of problem. I'm not trying to start an argument or anything; I genuinely just don't understand why you made this comment. MrRedact 06:58, 25 October 2007 (UTC)

See hyperbolic motion (relativity). -- BenRG 13:02, 25 October 2007 (UTC)

TERRESTRIAL PLANT GROWING COMPLETELY IN WATER

I FOUND THAT A TERRESTIAL PLANT IS COMPLETY SUSTAINING IN WATER EVEN IF COMPLETELY DETACHED FROM SOIL.ANOTHER THING IS THAT IT DOESNT HAVE ITS NORMAL ROOT WHILE FALLING INTO WATER.BUT ALSO IT GREW ADVENTITIOUS ROOTS AND SURVIVED.ANOTHER PLANT OF SAME SPICIES GREW ADVENTITIOUS ROOTS EVEN IF IT HAD ROOTS IN SOIL,WHEN ITS SHOOT IMMERSED IN WATER. MY QUESTION IS THAT HOW DO A TERRESTRILE PLAND SHOW SUCH A VARIATION IN CHARACTER? HOW CAN IT GROW IN WATER WHILE IT IS CMPLETELY DATACHED FROM SOIL AND WITHOUT ROOTS? IS IT SHOWING ANCESTRAL CHARACTER? —Preceding unsigned comment added by 59.93.40.184 (talk) 05:21, 25 October 2007 (UTC) --59.93.40.184 05:31, 25 October 2007 (UTC)

Such a plant could grow for a while on the minerals dissolved in the water or stored already in the plant. If the water is ground water, it may in fact have similar minerals available to the plant as it would have in soil. Even rain water will have some nitrates dissolved. However in pure water the plant will eventually suffer mineral deficiency and go yellow, and die. It would not be due to ancestral throw back, but due to the fact that the main ingrediantes plants need are water and air. Graeme Bartlett 05:54, 25 October 2007 (UTC)

Don't shout. Shouting is rude. You are rude. I refuse to read your question. DirkvdM 08:59, 25 October 2007 (UTC)

What Dirk means is that typing in ALL CAPITAL LETTERS is frowned upon in online discussions. It is more difficult to read large blocks of text that are in all caps. On the internet, words in all caps are usually interpreted as 'louder', or 'shouting'; as in the real world people online are more inclined to stand and listen to you if you 'speak' clearly and quietly. I hope you'll keep that in mind in the future, and I'm sorry that Dirk bit your head off. TenOfAllTrades(talk) 13:45, 25 October 2007 (UTC)

This phenonoma is well known - try hydroponics - also try a web search for "hydroponics + adventitious root"87.102.94.16 12:39, 25 October 2007 (UTC)

Power lines noise

Hi,everyone. Whenever I walk under the highly raised power transmission lines,I hear some humming sound(not birds),but it seems to come from the vicinity of the wire circumference.I thought it was because of rainy season.but it appeared in summer too,and in all seasons.later I guessed it couldbe due to capacitance effect, but I'm unsure.Anybody can prove this?.. —Preceding unsigned comment added by Balan rajan (talk • contribs) 05:42, 25 October 2007 (UTC)

Corona discharge. There might be other contributing effects, I'm not sure. Someguy1221 05:58, 25 October 2007 (UTC)

It gets worse where there is salt on the power lines, after rain it can wash off the contamination. This also casues EMI electomagnetic interference. Graeme Bartlett 06:02, 25 October 2007 (UTC)

How did you get salt on the power lines!87.102.94.16 12:37, 25 October 2007 (UTC)

Really long, non-conducting salt shakers, of course! Seriously, in any area near the sea coast, there's actually a surprising amount of salt in the air as a result of droplets of seawater evaporating and leaving microscopic nuclei of salt. These microscopic bits of salt accumulate, partly as a result of electrostatic effects.

Atlant 12:58, 25 October 2007 (UTC)

It's almost certainly 50 or 60 Hz mains hum - just like you can hear from a transformer (power pack) - the interaction of the oscilating current with the earths magnetic field causes a 50 or 60Hz physical vibration. Add the sound of corona discharge (crackly) - and that should be it...87.102.94.16 12:36, 25 October 2007 (UTC)

• I once read that if you ask a person to make a constant hum without specifying the pitch, some high percentage of people will hum at whatever pitch their country's electrical equipment hums at. No sources, of course. :( --Sean 13:14, 25 October 2007 (UTC)

Salt can also of course speed up rusting, so presumably powerlines and the apparatus that holds them near coastal areas not only rust more quickly but hum more frequently and louder on average. Lanfear's Bane | t 13:25, 25 October 2007 (UTC)

color vision

sir, I would like to know more about color vision in different animals.For eg.do bulls and cows recognise differen colours? —Preceding unsigned comment added by 59.93.24.4 (talk) 12:02, 25 October 2007 (UTC)

Have you looked at our color vision article yet? Do you have further questions?

Atlant 13:03, 25 October 2007 (UTC)

Expanding Universe...Are we all getting bigger?

In the ant on a balloon model of the expanding universe is the ant getting bigger too or just the balloon? Sappysap 13:34, 25 October 2007 (UTC)