Wikipedia:Reference desk/Archives/Science/2007 October 19

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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? Wikipedia'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^-1" 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

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

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^Talk 13:05, 19 October 2007 (UTC)

hint - think about what happens to the DNA. --VectorPotential^Talk 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^Talk 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^(TCU) 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^-2? 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^(TCU) 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|^{feed me} 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 '[singularities are] 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 Wikipedia. — 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 Wikipedia (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^(TCU) 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 Wikipedia, 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 Wikipedia? − 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 Wikipedia 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)^x+y+z 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 [1]. 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 [this] (edit) And [here]'s another person's opinion --Psud 02:55, 20 October 2007 (UTC)

Nobel laureate biologist James Watson

Quote from CNN:

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 Wikipedia 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 [2], 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. [3] 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 Wikipedia 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."[4] --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.[5] 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^Talk 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|^{feed me} 07:40, 20 October 2007 (UTC)