Wikipedia:Reference desk/Science

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January 4

rodent shrew

Please can you describe to me the droppings of a shrew ? I have been finding around the edge of my lounge carpet droppings that look very simialar to thin grains of rice and knowing these do not fit the description of mice droppings I wondered of you could inform me of what these might be ? I urgently would be grateful of any suggestions.......... thankyou Verona Moore.

"Shrew droppings are similar to a rice grain in size, except for the short-tailed shrew, which may have droppings 1 inch long". From [1] . I don't find anything else...--cloviz 05:04, 4 January 2007 (UTC)

A shrew is pretty specific... Why do you believe it to be one rather than any other rodent? Russia Moore 01:51, 5 January 2007 (UTC)

Shrew droppings have, if sufficiently fresh, a characteristic musky odor. Nothing gross, more like funny (it's not a strong smell). BTW shrews are not rodents at all, more like mini spineless hedgehogs or moles. Dysmorodrepanis 02:45, 6 January 2007 (UTC)

 Please can you identify what this intruder might be and can you suggest how I rid my lounge of this problem also I have 2 small patches on the edge of my carpet that have been nibbled about 1/2 inch square. thankyou for any help

Lens Assembly - Collimating Beam

I want to convert the light from a single LED to a parallel beam so that it can travel further at a given intensity. There is talk of using more than one lens in series but I don't understand. If the light from the first lens is parallel and focused at infinity, the next lens wont make it any more parralel? What could be the point in a multiple lens assembly? --Username132 (talk) 01:11, 4 January 2007 (UTC)

Mmmm - perhaps extra lenses could be added to narrow the collimated beam. That could increase the intensity at a given distance. --Bmk 03:36, 4 January 2007 (UTC)

That's what I was going to say. One lens making the beam parallel will make a beam as wide as the lens which is only the amount of light which is hitting the lens from the LED in the first place, so it won't be any more intense. What I imagine is you use one convex lens to gather the light, then a concave lens somewhere close to the focus to make it parallel. Vespine 03:47, 4 January 2007 (UTC)

You mean take the diverging beam, make it converge to a point and then as its diverging, again use a lens of shorter focal length to make a narrower beam than the first lens produced? Wouldn't this be exactly the same as using the LED in conjunction with the last lens, leaving out the first one (or two)? --Username132 (talk) 01:18, 5 January 2007 (UTC)

On paper, the light 'lines' that you drew could indeed look identical, but, if you just used one lens, the light in the beam would be as wide as the lens and only as bright as the light going into the lens from the side of the LED in the first place. With two lenses, the same amount of light is converged to a much smaller area, then a second lens makes it focused at infinity, this time, the same amount of light that was in the first example's wide beam is in a much narrower beam giving it a much higher intensity.. Does that make sense? If I knew how to upload pictures i'd give you a drawn example;) Vespine 02:42, 5 January 2007 (UTC)

To upload an image go to www.imageshack.com, click on 'choose' and select image from local drive. Click 'host it' and wait for next screen. The last link it provides is the link you need. Then c&p the link into your post or use the image insertion button on forums (not Wikipedia).

Anyway I created a picture which attempts to display the original system, the system as I expect you are proposing and finally my idea. Two types of lens (blue), labelled A and B, B having shorter focal length than A. The LED is red and has a divergence of 10 degrees either side (half angle 7 degrees). Picture is here; http://img295.imageshack.us/img295/826/lensesir1.jpg --Username132 (talk) 20:32, 5 January 2007 (UTC)

Not quite, see the 1st and last image in your pic are exactly the same, you are just drawing lines at different points. Light doesn't travel from the LED as lines, we just use lines to represent what the line is doing at that point. In your first picture you are drawing the outer most lines of light, but you could draw an almost infinite amount of lines between them and all of them would be correct. Amongst that multidute of lines, some would look like the picture at the bottom. To compare lenses, you shouldn't change the lines that are coming out of the LED. What I was trying to explain is this http://img152.imageshack.us/my.php?image=lensdw6.jpg hope you can see it. The first lens focuses the LED light at infinity. You can see three lines into the lens and three lines out, see how widely spaced they are? That is a rough guide to intensity. In the second diagram, the 1st lens has a short focal length, can you see how the three beams converge and then are made parallel, in the second diagram, the light going in is the same, but the light coming out is much more closely spaced, this means the intensity of the beam is much higher.. Does that make more sense? Vespine 02:24, 6 January 2007 (UTC)

Note that when creating collimated beams, it's critical that you either use a small-diameter source, or include a pinhole aperture in the beam-forming optics. An ideal parallel beam (if we ignore diffraction effects) will focus to an infinitesimal point, and the reverse is true: to produce an ideal parallel beam, the source of light should be a pointsource and not an extended source such as an LED or incandescent filament. Try using a cheap diode laser rather than an LED. Diode lasers act like point source of light. The do still require lenses. --Wjbeaty 21:14, 8 January 2007 (UTC)

what is the relationship between a football's pressure and throwing accuracy

what is the relationship between a football's pressure and throwing accuracy —The preceding unsigned comment was added by 75.118.12.166 (talk) 04:47, 4 January 2007 (UTC).

A partly flat ball might be easier to grab and throw, but it might wobble around in the air a bit more. A harder (more fully inflated) ball might be able to "torpedo" a little easier. BenC7 08:24, 4 January 2007 (UTC)

huh? How do you torpedo a sphere? Grutness...wha? 12:44, 4 January 2007 (UTC)

An American football, presumably.

Atlant 13:22, 4 January 2007 (UTC)

(slaps forehead). of course. When he said football, I thought football, not gridiron. My mistook. Grutness...wha? 13:25, 4 January 2007 (UTC)

MythBusters did a segment on that last season, but I can't remember their conclusions. User:Zoe|(talk) 18:53, 4 January 2007 (UTC)

Mythbusters determined that at a lighter weight the ball travels less far (because it carries less momentum I'd guess) but I'm not sure they looked at inflation pressures. Lower inflation pressure might cause the same issue because there's less air crammed in there. They did start filling them with helium as well. Id be curious as to what a football (american) filled with Xenon would do though... Wintermut3 06:31, 6 January 2007 (UTC)

Fast light?

How come light is so fast?

From a physicist's perspective, light goes at the speed it goes, and a better question would be "why is everything else so slow?" There was a time when the universe was hot and most particles moved at speeds close to the speed of light, but the universe has gotten much colder since then and everything has slowed down accordingly. (See Timeline of the Big Bang for more information.) One might argue that, were things not moving slowly, no organized structures could form, and so there wouldn't be anybody to see things moving quickly; this is an argument related to the anthropic principle, and it is my own (educated) idea rather than a statement I've seen in a source. A professional cosmologist might be able to give a better answer, but I'm not sure there is an answer to your question that would be entirely satisfactory. -- SCZenz 06:46, 4 January 2007 (UTC)

I found another (related) answer to this question here. -- SCZenz 06:54, 4 January 2007 (UTC)

A related point is that light must move at the speed it does because it has no rest mass. Special relativity tells us that all massless particles must perpetually move at the speed of light, while any particle with mass will always be slower. Dragons flight 07:14, 4 January 2007 (UTC)

surely light must have mass to be affected by gravity: Gm1m2/d²

That's Newtonian gravitation. While it's accurate enough for most uses, general relativity makes things a little more complicated -- Consumed Crustacean (talk) 19:49, 4 January 2007 (UTC)

Light is so fast because it has no rest mass. That's also why it is the fastest thing. Imagine it like this: an infentismal amount of energy will propel a photon to the fastest speed possible, since there is nothing to push. That's why light is also the fastest speed possible (short of tachyons but ignore those). X [Mac Davis] (DESK|How's my driving?) 20:12, 4 January 2007 (UTC)

Why ignore them. And the theory of relativity proves things can go faster than light. Light also slows down in denser material, hence refraction.Hidden secret 7 21:22, 4 January 2007 (UTC)

Things can go faster than light, but they cannot go faster than c, the speed of light in a vacuum. Tachyons do not exist--they were a nonexistant particle predicted by an early version of String theory. — Dark Shikari ^talk/_contribs 16:24, 5 January 2007 (UTC)

Why is light so slow? If it has no mass, surely it would be able to move very fast with any amount of energy. Also wouldn't it move at the same speed however much energy there was, therefore suggesting it travels at an infinite speed, and we only see it traveling at c because we can't measure infinity.172.200.70.64 20:50, 6 January 2007 (UTC)

Bigger world?

In the future will the world be bigger cause if we keep on burying dead bodies, the decomposed bodies will turn to dirt. —The preceding unsigned comment was added by 74.102.217.142 (talk) 06:01, 4 January 2007 (UTC).

I don't think so, because human bodies are made from eating food, the food comes (directly or indirectly) from plant material, and the plant material is made out of nutrients from the dirt. There really isn't much material being added to, or leaving, the earth as a whole—it just changes forms sometimes. -- SCZenz 06:41, 4 January 2007 (UTC)

Well actually, something like 20,000 tons of material falls to Earth from space each year (most in the form of very fine dust). This isn't actually much from the point of view of making the Earth larger (about one centimeter thickness per million years), but it is still alot more than most people realize. Dragons flight 07:04, 4 January 2007 (UTC)

Still, the world isn't going to get bigger the way the questioner posed. - Mgm|^(talk) 10:12, 4 January 2007 (UTC)

A nice way to think about it is that the stuff you eat today is likely to contain atoms from many different dead animals and indeed dead, decomposed people, in their various stages of evolution. Bon apetit! --Username132 (talk) 13:47, 4 January 2007 (UTC)

Where did you expect the bodies come from? They COME FROM THE GROUND. Conservation of mass anyone?? X [Mac Davis] (DESK|How's my driving?) 20:09, 4 January 2007 (UTC)

Exactly. This is what David Bowie means when he says "Ashes to ashes, funk to funky..." --Username132 (talk) 23:22, 4 January 2007 (UTC)

Gas stove burners

When gas stove burners are ignited, why do they start on the highest setting, and not a lower setting? Thanks. - MSTCrow 09:16, 4 January 2007 (UTC)

I could come up with my own explanation, but I didn't find any solid references. I did find something neat, about all the troubles with a hydrogen barbeque [2] As for the question, just try to light a bbq with the gas on low! --Zeizmic 13:00, 4 January 2007 (UTC)

You need to ensure there's a sufficient volume of the proper fuel/air mixture passing by the ignition system (whether it's a spark or a pilot light). Running on "maximum" helps assure this. Also, I think you'll find there's a bit of human factors/safety going on there: a human can easily hear the high volume gas flow and might notice that ignition hasn't occurred, but if the burner started on "simmer" but failed to ignite, the human user might not notice that much-more-quiet flow of gas.

Atlant 13:31, 4 January 2007 (UTC)

I've seen many stoves that don't, they start on low. When I first came across what you are describing, it was on a bbq, and my guess was that when you are turning the bbq OFF, you turn the lever to the off position but it may not go all the way (especially if the knob has shhifted in its socket a little) and a tiny flame might remain burning that you might not notice, by having the high setting next to the off setting, you are much more likely to notice if the flame is still burning. Vespine 21:56, 4 January 2007 (UTC)

Mass spectrometry vs radio carbon dating

Is mass spectrometry better than radio carbon dating? I understand radio carbon dating destroys much of the material tested while mass spectrometry uses little material. So would this then be New School verses Old School? I am especially interested in this idea as related to artifacts of 2000 years old or younger. Is there scientific testing on such materials that basically do not harm or destroy the artifact at all? Perhaps some sort of electronic scanning? MRI or the like? I am thinking along the lines of old ancient manuscripts. --Doug 14:25, 4 January 2007 (UTC)

modern radio carbon dating uses mass spectrometry see Radiocarbon dating#Measurements and scales.87.102.8.102 19:39, 4 January 2007 (UTC)

Great. Apparently they work far back into thousands of years back. Can this testing only go back say just 500 years. Would the accuracy then still be around 1% (i.e. ink on an old mamuscript tests at 400 BP with accuracy of 4 +/- years; making it then the possible years of 1546 - 1554). Would that be correct thinking? --Doug 20:29, 4 January 2007 (UTC)
P.S. Is there scientific testing on such materials that basically do not harm or destroy the artifact at all? MRI or the like? --Doug 20:31, 4 January 2007 (UTC)

I can't answer your accuracy question properly - though obviously relatively recent sample will have smaller differences in C14 so the error in measuring the C14 will be greater. Also the atmospheric C14 levels may have changed over time - introducing more errors.See radiocarbon dating#calibration

I can however answer your 'PS' - yes there are lots of other methods for testing things that dont harm the sample - however I can think of one off hand that gives a date directly.. For example various types of spectrometry can give the chemical constitution of a sample (uv, ir) - this in turn can give an estimate of the date since different compounds have been used at different times through history eg ink in the 14th century is different from ink in the 20th century. There are methods for chemical analysis that are non destructive.

Some compounds will slowly isomerise or decay over time - this could be used to give an estimate of the age but these reactions are affected by temperature etc - so two manuscripts of the same age can be in different conditions according to how they were stored.87.102.8.102 21:07, 4 January 2007 (UTC)

For something like a 500 year old document being tested for authenticity, there are many methods that could be used:

• Ink: Is it a type of ink in use at that time and location ? Does the ink appear to be 500 years old (some inks fade with time) ?

• Paper: Is it a type of paper/material in use at that time and location ? Does it have a watermark or other identifying characteristic ? If so, is it from the proper time period ? Does the paper/material appear to be 500 years old (some papers yellow with time) ?

• Handwriting: Is that a style in use at the time ?

• Language: Are the words and spelling correct for the time ?

• Provenance: Is there a clear record of the document being created ? Is there a clear chain of custody between then and now ?

• The document may be photographed under different types of light (like UV), in order to verify that it appears the same as comparable docs of that period. This can also help to make faded ink more visible.

StuRat 21:08, 4 January 2007 (UTC)

could a book on a library shelf start turning to dust in a few decades?Hidden secret 7 21:20, 4 January 2007 (UTC)

A few decades, probably not, a few centuries, maybe, depending on how it was constructed, handled, and stored. StuRat 03:36, 6 January 2007 (UTC)

Very good answers. This is especially true pertaining to that of ink of the 14th Century and of a clear chain of custody between then and now. I believe StuRat has been following my other contributions related to Petrarch and Middle Ages questions on the Humanities Reference Desk and has seen my pet project on my User page of The Petrarch Code. A recent item that has steered up much controversy has been my contribution on Codex Vaticanus. I tend to believe this is a manuscript from the Fourteenth Century, not of the first few centuries. This statement alone has received much controversy. This is under the January 3 title: "Scientific testing of Codex Vaticanus". Now it turns out the chain of custody is only from 1475. I have several other reasons (explained later) to believe it is from the Fourteenth Century of 1372 +/- 8 years. Now this of the scientific testing (non destructive) above would prove my point. The other parameters of StuRat would then prove my point further. These other points follow palaeography, but the scientific testing I believe would be the most important to start with.
That of the question by Hidden Secret 7 is a very good question. Another reason I do not think Codex Vaticanus to be some 2000 years old. --Doug 22:35, 4 January 2007 (UTC)

Bioelectricity

Since it is possible to clone body parts is it possible to clone the cells from an electric eel to produce electricity from a nutrient solution? Barringa 16:50, 4 January 2007 (UTC)

Cells alone won't do the job, you'd need to duplicate the fishes' electric organ. - Nunh-huh 18:09, 4 January 2007 (UTC)

Is an electric organ similar to an electric guitar ? :-) StuRat 03:16, 6 January 2007 (UTC)

I beleive that hammond makes some excellent electric organs, though I prefer the Moog :p sorry. But theoretically, yes. On the other hand, the energy efficiency might be quite low given you'd have to include an electrical generation organ and a way to utilize food. Wintermut3 06:34, 6 January 2007 (UTC)

Equivalents to recreational mathematics

Are there some equivalent sciences to Recreational mathematics?Such as recreational biology, recreational physics...Mr.K. 18:37, 4 January 2007 (UTC)

Thinking laterally:

Chemistry - growing crystals

Biology - keeping pets, growing plants

Physics - meccano, messing around with sparks etc87.102.8.102 19:42, 4 January 2007 (UTC)

I think Meccano is closer to recreational engineering. :) — Kieff 20:04, 4 January 2007 (UTC)

When I was an undergrad we used the term "recreational biology" to mean sex. --Trovatore 19:51, 4 January 2007 (UTC)

Oh, and "recreational chemistry" meant drugs. Don't think we had one for rock 'n' roll. --Trovatore 04:39, 5 January 2007 (UTC)

I do a different sort of recreational biology. It is much more difficult.

Spore could be considered a recreational biology game, since it's a biological strategy\puzzle. The Incredible Machine, Armadillo Run or even Scorched Earth or Worms could be considered recreational physics (see Category:Physics-based games). So there are recreational instances of those sciences, but I don't think there's a general area of study based on them, like it happens with mathematics. — Kieff 19:59, 4 January 2007 (UTC)

Astronomy also attracts many amateurs. StuRat 20:59, 4 January 2007 (UTC)

Biology used to be a fairly recreational discipline in the 19th century, where you'd also get a lot of amateurs. Geology as well. But not so much in the 20th century. Astronomy is probably the only discipline of hard science that has a significant amateur community any more, excluding computer science (if you consider it a hard science; I don't). --140.247.251.72 21:04, 4 January 2007 (UTC)

Cooking is chemistry - but I don't know that I'd always describe it as recreational. Natgoo 18:01, 5 January 2007 (UTC)

ornithopters

Apparently They say it isn't possible for one to lift a human, but what is the maximum weight one could feasably lift, and how big would it have to be to do this? Is there any way to work out the required surface area easily if you know the weight? 172.189.77.244 19:03, 4 January 2007 (UTC)

Our article Ornithopter, under the heading "Manned flight", mentions several successful undertakings. What is problematic is human-powered flight: it is not totally impossible, but apparently we are just on the border between possible and impossible. If it is at all technologically possible to move away from that border well into the "possible" area, this cannot be a simple issue of size. Larger wings weigh more and require more force to flap them, and the human power output is a main limiting factor. Next to, perhaps, operators capable of more power output, the key is more likely to be increased efficiency through better designs and materials.  --Lambiam^Talk 19:25, 4 January 2007 (UTC)

Just because something isn't technologically possible, it doesn't mean it can't actually be done. I have never trusted technology, it always seems to go wrong somehow.172.189.77.244 20:21, 4 January 2007 (UTC)

If you can do it, then, by definition, it's technologically possible. StuRat 20:58, 4 January 2007 (UTC)

I never trusted technology either, as it's grounded in reality, and we all know reality has a well known liberal bias... --66.195.232.121 14:47, 5 January 2007 (UTC)

Technology isn't possible. (OP, but I have a name now)Hidden secret 7 21:18, 4 January 2007 (UTC)

Reading this comment on a website on the internet, by the use of a computer powered by electricity, I find that very hard to believe. — Kieff 22:42, 4 January 2007 (UTC)

How do you know you aren't dreaming, or that the internet isn't controlled by magic? But this isn't the point. What about the original question.Hidden secret 7 21:41, 5 January 2007 (UTC)

And how would you know this isn't real and true? Wouldn't everything be simpler if it was true and real? Assuming everything works by magic or is a dream doesn't solve anything, it just makes reality more complex than it seems to be, by all our accounts.

About your original question, it's actually quite difficult to answer. You should find someone who is an experienced ornithopter builder and ask them instead. The physics involved is too complex for back-of-the-envelope calculation, I'm a afraid. — Kieff 11:10, 6 January 2007 (UTC)

The upward force on the ornithopter would be the same as the force of air pushing against the wings, wouldn't it? Could this be considered an inelastic collision? Also would I have to take into account air resistance? If I knew the mass I wanted to lift, and the mass and area of the wingss, could I use this to calculate the speed required, and therefore the force needed at the pivot?Hidden secret 7 21:12, 6 January 2007 (UTC)

You would need to take air resistance into account. The answer to your other questions is "no". Read Bird flight to get some idea of the complexity involved.  --Lambiam^Talk 01:54, 7 January 2007 (UTC)

potatoe clock?

How does a potatoe clock work?

See the eHow Wiki[3]. X [Mac Davis] (DESK|How's my driving?) 19:30, 4 January 2007 (UTC)

That explains how to make one, not how it works. The article here on Lemon battery explains the basic principle. In a potato clock the potato is just acting as a battery. --140.247.251.72 21:00, 4 January 2007 (UTC)

tummy tucks and EKGs

Hi there- Can you please tell me if Tummy Tucks were available in the 1970's and also if EKGs were available in 1965? Thanks.

EKGs were certainly available in 1965. The Nobel Prize for its discovery was awarded in 1924. A more formal name for "tummy tuck" is abdominoplasty. Max Thorek wrote a treatise about abdominoplasty in 1924, so it was certainly available in the 1970s. - Nunh-huh 20:59, 4 January 2007 (UTC)

Faster than light?

Please sign your comments by appending ~~~~ to the end.

Is there anything faster than light?

nothing can go faster than the 'speed of light',c, as anything travelling at this speed would have an infinite mass. As light is affected by gravity it has a mass, but this is finite. Therefore light travels slower than the 'speed of light'. This means things can travel faster than light, but not faster than c.

Of course this is all probably nonsense. Light travels slower through denser materials, especially glass and plastic.Hidden secret 7 21:17, 4 January 2007 (UTC)

Hence how there is a reference to c. Nothing can travel faster than c. "Speed of light" usually refers to its speed in vacuum. - Mgm|^(talk) 12:46, 5 January 2007 (UTC)

And particles can exceed that speed of light through mediums. This causes Cherenkov radiation. X [Mac Davis] (DESK|How's my driving?) 21:34, 4 January 2007 (UTC)

Tachyons are hypothetical particles that travel faster than light. — Kieff 21:28, 4 January 2007 (UTC)

Hypothetical is probably too much. There is no tachyon hypothesis. X [Mac Davis] (DESK|How's my driving?) 21:34, 4 January 2007 (UTC)

Isn't there a theoretical partical particle that comes in pairs, and if one moves, the other does exactly the same thing immediatlley however far away it is?Hidden secret 7 21:44, 4 January 2007 (UTC)

You mean quantum entanglement? That's been experimentally verified. — Kieff 21:51, 4 January 2007 (UTC)

Heisenberg uncertainty suggests that a particles position is imprecise. This could be interpreted as a particle being everywhere in a quantum area at the same time.

Doesn't gravity travel faster than light?

No, general relativity predicts that gravity travels at exactly the speed of light. Experimental evidence bears that out, though within fairly large margins of error. -- Consumed Crustacean (talk) 22:20, 4 January 2007 (UTC)

If so, it doesn't matter anyway. You can't just 'delete' and 're-add' say, a 10-pound iron sphere in order to send information, which is what all of physics is really about. Vranak

Um light does travel at c and photons are massless particles.Light is affected by gravity not because it has mass but rather because gravity bends spacetime. If gravitons exist they would also travel at c, in entanglement you don't really get a real signal travelling faster than the speed of light. I mean you cant use it to send information faster than light. Theresa Knott | Taste the Korn 22:54, 4 January 2007 (UTC)

Tunneling of atomic particles was once said to be faster than light.--Stone 15:44, 5 January 2007 (UTC)

"If gravitons exist they would also travel at c" and lack mass. Dysmorodrepanis 02:56, 6 January 2007 (UTC)

Then how can a black hole's gravity have influence on it's surroundings if it's escape velocity is greater than c? If nothing can come out through the event horizon (excepting some Hawking radiation, but that's very small to have an effect on gravity) then how can gravity waves (or particles) come out? --V. Szabolcs 19:09, 7 January 2007 (UTC)

Quantum entanglement does have weired instantaneous signals however you cannot use them to transfer energy or information faster than light. It's freaky. Theresa Knott | Taste the Korn 01:09, 6 January 2007 (UTC)

The tunneling stuff was not really about entanglement. Basically it utilizes the fact that information is somewhat dislocated on the quantum level and the fact that by tunneling, you decrease the accuracy of measurement and increase the uncertainty of position. More like sleigh-of-hand, - tunneling is "faster" than light (not c however IIRC as it was not in a vacuum) because nothing actually moves; the information is more or less (re)created from scratch (which leads back to entanglement, which works with pairs of particles - determine the state of one and you automatically determine the state of the other no matter where it is in the universe) Dysmorodrepanis 02:56, 6 January 2007 (UTC)

Please, we do not know yet of gravity's speed. X [Mac Davis] (DESK|How's my driving?) 17:30, 5 January 2007 (UTC)

It's not been measured as far as I know. However it is expected to be c. It would be pretty big news if it were not.Theresa Knott | Taste the Korn 01:09, 6 January 2007 (UTC)

Yes we do —The preceding unsigned comment was added by 81.153.52.250 (talk) 23:07, 5 January 2007 (UTC).

Faster than 'light' is reletive to the medium travelled in. Certain things may move faster than the speed of light in a medium through that medium (the source of cherenkov radiation), but nothing has yet been found that exceeds C: the speed of light in a vaccum. That doesn't rule out the possibility of a tachyonic particle with imaginary mass moving faster than C, but in all honesty a tachyon is probably a function of mathematics and not physics, as in it satisfies the equations in a way that it can be superluminal (faster than light), but only because it's mass squared is negative (it's imaginary). Whether anything could exist that way is widely doubted, because it would also have a lot of other wierd properties, EG because mass is imaginary it would speed up as it lost energy (again because mass^2 is negative). It's an interesting thought experiment, but most reputable physicists I've ever read or heard of think that C is the absolute speed limit of 'real' particles. —The preceding unsigned comment was added by Wintermut3 (talk • contribs) 06:39, 6 January 2007 (UTC).

People say that if you shine a light coming from a craft going at lightspeed then the light will still go faster than the craft so maybe there is no speed limit to the universe and we are blinded from our perspective?68.120.229.114 07:03, 6 January 2007 (UTC)

Well a craft cannot go at lightspeed so the question is moot but if you shine a light from a craft going at near lightspeed then no, the light will go at c relative to all observers as per special relativity. Theresa Knott | Taste the Korn 09:49, 6 January 2007 (UTC)

However fast light travels, darkness always gets there first.Hidden secret 7 21:08, 6 January 2007 (UTC)

Travel of light

Is the travel of light simply the "leap frog" effect resulting from the alternation between the magnetic and an electric field of a photon? Barringa 22:28, 4 January 2007 (UTC)

An electromagnetic wave (e. g. light) can be described by the Maxwell equations. While the electric and magnetic field vectors are usually perpendicular, their maxima coincide (your description seems to imply that a maximum of the electric field creates a maximum of the magnetic field after a certain amount of time and vice versa). That may be counterintuitive because the minima also coincide and one might think that the wave would stop at the minimum, but the Maxwell equations contain not only the fields but also their time and space derivatives which are not necessarily zero when the fields are zero. Icek 14:00, 5 January 2007 (UTC)

Delta brainwave?

What is the delta brainwave mentioned in the futurama cartoon? —Preceding unsigned comment added by 74.102.217.142 (talk • contribs) 22:31, 4 January 2007

Assuming that Futurama is referring to the real phenomenon (which, knowing what the show is like, is a questionable assumption :-) ) see delta wave. -- AJR | Talk 00:30, 5 January 2007 (UTC)

Welcome to Wikipedia. You can easily look up this topic yourself. Please see Delta wave. For future questions, try using the search box at the top left of the screen. It's much quicker, and you will probably find a clearer answer. If you still don't understand, add a further question below by clicking the "edit" button to the right of your question title. X [Mac Davis] (DESK|How's my driving?) 17:31, 5 January 2007 (UTC)

Hard body bits

Just curious - apart from the teeth, nails and bones are there any parts of the body which are hard, or is the rest of it squishy stuff? Matt Eason ^{(Talk • Contribs)} 22:32, 4 January 2007 (UTC)

Kidney stones? — Kieff 22:38, 4 January 2007 (UTC)

I guess it depends on whether you call the other cartilage in the body "squishy". —AySz88\^-^ 23:21, 4 January 2007 (UTC)

Hmm. That's a hard on(e)

Hair is sometimes considered 'hard', it's one of the last substances to decompose and apparently along with teeth, it is all that remains if a corpse is devoured by pigs, they'll even munch down the bones. Vespine 00:56, 5 January 2007 (UTC)

Calluses, and the related foreign body response (like an internal callus coupled to a really bad allergic response) can become quite hard. One woman whose breast implants slid around a lot went on a daytime talk show to say that they ended up feeling like baseballs from all the collagen that built up around them. And, as a previous person mentioned, sometimes erectile tissue.--Joel 01:29, 5 January 2007 (UTC)

Isn't there an animal that keeps rocks in its stomach to aid digestion? Or am I imagining things? Melchoir 05:46, 5 January 2007 (UTC)

Several: see gastrolith. On the other hand, also see cow magnet. --Anonymous, January 5, 2007, 06:18 (UTC).

Awesome. Melchoir 07:10, 5 January 2007 (UTC)

Cheers guys, interesting stuff. I can't believe I've gone my whole life without knowing about cow magnets. Matt Eason ^{(Talk • Contribs)} 21:54, 5 January 2007 (UTC)

If you meant people only, then our fingernails and toenails aren't very hard, but they become hooves in some animals, which can be fairly hard. StuRat 02:59, 6 January 2007 (UTC)

Also see otoliths, the tiny stones in the vestibular apparatus of the ears. Also, if you're going to count kidney stones, you may as well count gallstones. --David Iberri (talk) 03:33, 6 January 2007 (UTC)

Resistor value

I want to obtain a controlled variable voltage from a 12 volt car battery to power a full current load which can be done with a variable resistor having a center tap. How many ohms and watts would the variable resistor need to be to span the battery terminals without allowing any (or absolute minimal) current to flow from one end of the resistor to the other but which would allow any amount of current from zero to full current to flow through the tap to power the load? 71.100.10.48 22:44, 4 January 2007 (UTC)

Please see our article on voltage dividers; a potentiometer is just a variable voltage divider. But I'm afraid what you want to do isn't practical with a potentiometer, at least if your load is going to draw any appreciable amount of power because a potentiometer of sufficiently low electrical resistance will waste a lot of power just "idling". A rheostat (a variable resistor without that pesky power-wasting connection to ground) won't waste any idling power, but the voltage drop across it will be sharply affected by the load current and a rheostat will also have trouble getting your load down to "zero volts", although you can get arbitrarily close, especially if the rheostat is "taper wound" (so it has proportionally much more resistance per degree of rotation near the "off" end than at, say, midpoint.

A variable voltage regulator sounds like a much more practical alternative. Think of it as an amplifier for the voltage produced by your potentiometer.

Atlant 23:29, 4 January 2007 (UTC)

For example, a buck converter built in order to allow for a variable tension at output would be a better choice, since you would waste no power in the potentiometer. However, it is a more expensive solution. —The preceding unsigned comment was added by 84.90.42.248 (talk) 17:05, 5 January 2007 (UTC).

January 5

Buzz

Why do transformers buzz?69.29.38.13 00:05, 5 January 2007 (UTC)

Per our article about them, the changing magnetic field causes vibration and magnetostriction (shape changes due to the magnetic field in the transformer core,) both of which can give rise to the hum or buzz that you can often hear coming from transformers. -- AJR | Talk 00:37, 5 January 2007 (UTC)

this website has an excellent and detailed description. Vespine 00:53, 5 January 2007 (UTC)

HMMMMMMMM! Magnetostriction could bee the answer! (couldnt resist this one sorrry)--Light current 01:07, 5 January 2007 (UTC)

Further to your earlier answers, there are several sources of noise in a transformer that cause it to hum:

• Magnetostriction: when magnetic flux flows through a material (such as the steel that makes up a transformer core), there can be a physical change in the size of the material, usually a shrinkage. With each cycle of the alternating supply, the material will change in size twice, so at 100Hz in some part of the world, and 120Hz in others, such as North America.
• Eddy currents are caused by changing magnetic fields intersecting conductors. Most transformer cores are made from sheets of steel, and the eddy currents cause these sheets (called laminations) and any other metal parts of the transformer, such as its windings, to flex to and from each other.
• Very large transformers, such as are found at power stations or high-voltage electrical substations can have electrically-powered pumps and fans to cool them. These can make a noise as they operate, and is usually the greatest source of noise when you stand close to a substation.

In other words, the source of the hum is for the most part vibration. I hope this answers your question; but if not, perhaps you can ask for a clarification. Regards, — BillC ^talk 20:31, 5 January 2007 (UTC)

Talk:Lemming "so do they jump off cliffs?"

This was posted by an anon:

Yes or no (and by the way this is the number 1 reason anyone would visit this page.) there are 3-4 references to this "reputation" they have, from popular literature -- so is it a well-founded reputation???

A good question, and I hope it can be answered clearly and with lots of nifty twists and turns, which can then be supplemented into the article. - RoyBoy ⁸⁰⁰ 00:41, 5 January 2007 (UTC)

They do, if Walt Disney orders them to be herded off for the sake of a nature documentary [4]. The video game variety, by contrast, must be herded to keep them from falling off.--Joel 01:35, 5 January 2007 (UTC)

The lemming article says quite clearly (in the Population fluctuations section) that lemming suicide behaviour is a myth, propogated by the Disney film White Wilderness. It also gives a link to this page which debunks the myth. I've put this same answer on Talk:Lemming. Gandalf61 11:24, 5 January 2007 (UTC)

The myth was populated by the film, but I believe the film got it from an earlier book. 80.169.64.22 16:36, 5 January 2007 (UTC)

Lemmings just GO GO GO driven by hunger and other consequences of population stress (basically, they go bonkers). Being social animals, they have a sort of pack mentality during migration. Formerly, they occasionally drowned en masse in rivers, lakes, etc. SOften enough, some could use the corpses to float to the other side, that's why the behavior has been maintained. Due to habitat restrictions (lemmings do't usually occur in terrain adjacent to rocky shores, they need juicy medaows etc to thrive) only in the rarest instances they'd fall over cliffs, and they wouldn't jump but be pushed rather, by the scores of lemmings coming after them.

Nowadays, they get more often squished en masse by road or rail traffic. Dysmorodrepanis 03:00, 6 January 2007 (UTC)

I don't think any of you have even seen the documentary, because the narrator quite clearly used the words "suicide" being a "myth" when talking about their tendency to jump off cliffs. It goes on to explain the reason lemmings are famous for jumping off cliffs: not suicide, but both migration and perhaps a clever trick to keep the area inhabitable by allowing the food to regrow, thus allowing the lemmings to avoid extinction. Far from propogating the myth, the documentary debunks it. --RockMaster 00:26, 9 January 2007 (UTC)

Twice the focal length? You must be crazy...!

If you place a point of light at twice the focal length of a lens will it converge, and if so, at what point on the other side of the lens? It's not a homework question and I can't find answers at the lens or focal length articles. --Username132 (talk) 01:11, 5 January 2007 (UTC)

Use this formu1a 1/u + 1/v = 1/f —The preceding unsigned comment was added by 88.109.93.42 (talk) 01:24, 5 January 2007 (UTC).

You can use the formula or you can use a graphical method. In the diagram on the right any ray of light that passes through f emerges horizontally from the lense. Conversly any horizontal ray must pass through f. Drawing in the rays means the image must abe at 2f, the other side of the lense and upside down. Theresa Knott | Taste the Korn 01:45, 5 January 2007 (UTC)

Ion Implantation

I've been looking for an ion implantation vendor that can do precious metals at ~7 MeV, or at least within an order of magnitude. Of the three vendors I found on Google, two only do ~400 keV, while one does 1 Mev. The article says 5 MeV is common...am I looking in the wrong place? Can anyone recommend a good vendor? Thanks in advance. --Joel 01:50, 5 January 2007 (UTC)

Using these search terms <"Ion implantation" services MeV> there seem to be many google hits. --JWSchmidt 03:14, 6 January 2007 (UTC)

Crop circles

What exactly are "crop circles" 59.95.4.83 10:22, 5 January 2007 (UTC)

Unsurprisingly, they are circles on crop fields. See the article: crop circle — Kieff 10:30, 5 January 2007 (UTC)

If you mean how they're made, they're made by pranksters with ingenious ideas but simple tools. --Bowlhover 17:52, 5 January 2007 (UTC)

At least the elaborate ones you see nowadays. The circle-shaped ones (as opposed to the disk-shaped ones) that sometimes occur (and perhaps inspired the phenomenon) might also be the product of roe deer in heat, whereas rough disk shapes of flattened crops may be produced by dust devils on occasion. Dysmorodrepanis 03:04, 6 January 2007 (UTC)

soil microbiology

what are the required conditions for growing (pH,TEMPERATURE,CULTUREMEDIA)sulphur bacteria and denitrifying bacteria —The preceding unsigned comment was added by 59.163.146.11 (talk) 12:33, 5 January 2007 (UTC).

Search here for <culture conditions soil bacteria> --JWSchmidt 03:01, 6 January 2007 (UTC)

resistance of wires

i'm doing a report on the resistivity of wires at different temperatures, and from one of my graphs i have the resistivity due to impurities and lattice defects as a negative number, i have a feeling this is just my experiment going wrong as the coefficient of resistivity is also outside the error margins, i'm using a "pure" wire of copper, so is there anyway that impurities or defects would increase the conductivity of the wire, even in small enough quantity's to not normally be recorded? as i was thinking anything added to the lattice will simply distort the repeating pattern making the electrons "hit" the ions more often, thereby creating a positive resistivity due to impurities.--86.29.62.113 13:32, 5 January 2007 (UTC)

You're right. Theoretically, the most conductive Cu is a single, pure crystal with no dislocations or vacancies in it. It's possible that your wire is slightly thicker or shorter than you thought, giving it a lower resistance than a theoretical pure wire of the nominal size. Otherwise, you might want to check your calculations. --128.115.27.10 01:23, 6 January 2007 (UTC)

Ortho-effect & ortho-para positioning(Organic Chemistry)

Sir,

I'd like to know about ortho-effect (definition & short detail) and when the ortho/para product will be the main product(i.e. temperature or steric effect).

I'll be highly obliged if you kindly answer my question.To clear any ambiguity in my question please contact- (email removed)

Thanking you, ours faithfully, Tirtha —The preceding unsigned comment was added by Tirtharahaman (talk • contribs) 16:20, 5 January 2007 (UTC).

ortho/para directors are primarily encountered in electrophilic aromatic substitution reactions, and there's some information about it on our electrophilic aromatic substitution page. DMacks 17:09, 5 January 2007 (UTC)

Sir,

   I wanted know about the ortho effect.Is the article deals with it?!!!Also I want to know the effect of temperature & others in specific ortho-para positioning?

Hippocratic constraints

What are the hippocratic constraints(if any) regarding doctors emailing their patients?

Thanks, HighAnxiety32 16:34, 5 January 2007 (UTC) Jesse

Hippocratic does constraint nobody anymore, because doctors dont do this old ritual anymore (I think for centuries). It's normal laws know!--Stone 17:01, 5 January 2007 (UTC)

And for the rest Hippocratic Oath. --Stone 17:05, 5 January 2007 (UTC)

The question is whether any pledges in the Hippocratic oath constrain email. The answer is yes, the promise of confidentiality, since email is often not secure. While this is only a potential violation of the Hippocratic oath, the use of unencrypted email is a violation of HIPPA-cratic law in the US. alteripse 15:08, 6 January 2007 (UTC)

Biasing a BJT Common Emitter amplifier

In a Common Emitter amplifier (based on a Bipolar Junction Transistor), if I choose to use the constant VBE biasing (using a voltage divider at the base), how should I establish a constant collector current? Should I use a bypass capacitor between emitter and ground or can I use an appropriate voltage divider between +V and ground with the central node connected to the collector in order to establish a constant voltage and, therefore, a constant IC? —The preceding unsigned comment was added by 84.90.42.248 (talk) 16:58, 5 January 2007 (UTC).

I'm not certain I understand the constraints implied in your question. If you hold the base at a constant voltage (relative to the circuit's overall V_CC), then the emitter must be about one diode drop (so, usually, about 0.6v) below the base voltage. I_E is then determined by the sum of the external and internal emitter resistances and I_C will be I_E-I_B (which, for most "large-ish" values of β (Beta) can be assumed to be the same as I_E).

If the external emitter resistance is small or zero, then you really can't use a constant base voltage as a bias as it makes things way too sensitive to variations in R_E and β. In this case, the base voltage divider is usually connected to the transistor's collector rather than V_CC, providing negative feedback that stabilizes I_E and I_C.

Meanwhile, the purpose of the bypass capacitor around any external emitter resistance is to make that impedance low for AC signals while keeping the effects of the resistance for DC signals. This has the effect of maintaining a stable (and low-gain) DC operating point while allowing more gain for AC signals. Remember, the gain of a common emitter amplifier is (roughly) the ratio of the collector resistance over the total emitter resistance (counting the internal R_E of the transistor plus any external resistance/impedance that you add); the bypass capacitor brings the total emitter resistance down to the typical few ohms or tens of ohms R_E inherent in the transistor itself.

Atlant 18:25, 5 January 2007 (UTC)

Bio Reserve

need to know everything about bio reserve---- —The preceding unsigned comment was added by 203.101.13.198 (talk) 17:08, 5 January 2007 (UTC).

Do you mean a nature reserve? --Bowlhover 17:49, 5 January 2007 (UTC)

Biosphere reserve? Rmhermen 22:02, 5 January 2007 (UTC)

48 to 46

i find it strange that no wiki article covers this aspect. My question is that although genes evolve slowly with time, but the change in number of chromosomes in hominids could only have occured at a certain point. Does anybody has an idea when this change occured.nids(♂) 18:37, 5 January 2007 (UTC)

You may want to take a look at this review of theories. - Nunh-huh 18:41, 5 January 2007 (UTC)

Or, right here, Theophilus Painter. Deltabeignet 18:51, 5 January 2007 (UTC)

There's nothing in the Theophilus Painter article that addresses the question of an actual change in the number of chromosomes. It refers to a correction of a counting error. - Nunh-huh 19:09, 5 January 2007 (UTC)

{edit conflict}::Nunh-huh, the link was really helpful, but it doesnt give any specific dates. I understand that we actually dont know the date for this change.

BTW, Deltabeignet, how does the link that you gave answers my question.nids(♂) 19:17, 5 January 2007 (UTC)

Was there a bottle neck 350 000 years ago? Are we definitely certain that the number did not go up from 46 to 48? --Seejyb 23:31, 5 January 2007 (UTC)

Have you seen this page? I cannot find anything better than Genomic Structure and Evolution of the Ancestral Chromosome Fusion Site in 2q13-2q14.1 and Paralogous Regions on Other Human Chromosomes. --JWSchmidt 02:43, 6 January 2007 (UTC)

One thing to note is that people can, and do, survive with either extra chromosomes or missing parts of chromosomes. I suspect that there is a great deal of duplication of genes between the chromosomes to allow this. Otherwise, missing a chromosome, or even part of one, would certainly be fatal. It's not too much of a jump, then, to imagine one population developing with a different number of chromosomes than the majority, and eventually replacing the majority, if the new number of chromosomes had some advantage. StuRat 02:45, 6 January 2007 (UTC)

Well Stu, people do not survive when missing a chromosome. An exception is Turner syndrome. However one may survive if two chromosomes have fused and there is actually no loss of genetic material from the genome but only a reduction in their number. nids(♂) 06:19, 6 January 2007 (UTC)

Even those with Turner syndrome aren't really missing a chromosome, because in ordinary females, only one X chromosome is expressed. --Bowlhover 07:01, 6 January 2007 (UTC)

This article compares chromosome structures in humans and modern apes. It concludes that our common ancestor probably had 48 chromsomes, and that a chromosome fusion somewhere in the human ancestors line led to modern humans having 46 chromosomes. It also presents evidence from wild and domestic animal populations that chromosome fusion can produce fertile individuals who can still interbreed with the "normal" population. Gandalf61 11:00, 6 January 2007 (UTC)

... and our article on Chromosome 2 (human) and this page comparing human and chimpanzee chromosomes support the theory that Human Chromosome 2 is a fusion of ancestral chromosomes. But I can't see any suggestion of a timeline for this event. Gandalf61 11:16, 6 January 2007 (UTC)

Nuclear Fusion

Can you tell me about nuclear fusion and how it works, or link to an article? —The preceding unsigned comment was added by 81.132.66.73 (talk) 19:20, 5 January 2007 (UTC).

see Nuclear fusion for start.nids(♂) 19:28, 5 January 2007 (UTC)

See also Binding energy and note in particular the graph towards the bottom of the article. (Almost) everything tends toward those isotopes in the center; lighter isotopes fuse (join together) towards those middleweight isotopes, releasing energy. The heavier isotopes fission (split apart) towards those middleweight isotopes, releasing energy.

Atlant 22:20, 6 January 2007 (UTC)

metal reaction

what other chemical is made if a metal reacts with gas? i already have hydrogen gas as one of my answers but i need another81.132.103.167 19:43, 5 January 2007 (UTC)----

It depends. What metal, and what gas? The product of reacting iron with oxygen are very different from the product of reacting sodium with chlorine. --Carnildo 20:31, 5 January 2007 (UTC)

Metals tend to reduce - so the product with water gas, HCl gas, HBr gas will be hydrogen plus a salt - an oxide, chlordie and bromide respectively. With other gases the reaction does not produce hydrogen eg chlorine gas reacts with a metal to produce a chloride and probably heat(energy).87.102.33.170 16:02, 6 January 2007 (UTC)

In general I think it can be said they'll form either a salt or an oxide, reacting with a gas alone will often leave little other product, because most elemental gasses will simple react to form the salt (IE Cl gas and sodium, or any halogen and alkali metal really) Wintermut3 03:14, 7 January 2007 (UTC)

January 6

Life or death determination

Death following loss of blood.

When is a potato dead? Edison 02:13, 6 January 2007 (UTC)

It is definitely dead when it is cooked, completely rotten or dried up. Death as a concept is not easily applied to plants as most plants can regenerate from a few cells. Animals can be cloned but it is not the same as regeneration and so cloned animals are not considered a continuation of the life but a new life. --- Skapur 02:21, 6 January 2007 (UTC)

Remarkable. The Wikipedia Google Queen 02:29, 6 January 2007 (UTC)

I would say a plant is only dead when all of it's cells are dead. Also note that each potato is only a small part of the root system of the plant, which may very well still be alive (depending on the farming method). StuRat 02:33, 6 January 2007 (UTC)

I agree that a plant is only dead when the cells die. Even when plucked the cells in a plant are alive, although, in the case of leaves they will begin to enter the senescence program that leads to death. For a potato it is alive until it rots since it is sustaining meristems in the eyes that can form new shoots and roots. It rots, due to bacterial infection i.e. Erwinia carotovora. In fact, the potatoes are not attached to the root system but a stolon. David D. (Talk) 19:16, 6 January 2007 (UTC)

So then that's like asking when an apple is dead. Once you "pick" it, so to speak. Ƶ§œš¹ _{[aɪm ˈfɻɛ̃ⁿdˡi]} 05:27, 6 January 2007 (UTC)

Hmmm, I'm not so sure. You say if you pluck a potato from its plant, the rest of the plant may still be alive, but the potato is dead. But if that potato happens to have an "eye" on it, and you slice off that "eye" and put it in water, it will begin to grow. So it must still be alive. Or not? — Michael J 17:32, 6 January 2007 (UTC)

If a cut rose is placed in water and a root system develops and the plant is perpetuated as a new rose bush, then was the cut flower dead? If cells from a dead animal are cloned and the clone lives, then was the animal still alive? Edison 19:44, 6 January 2007 (UTC)

This is an interesting point. You are now bringing in the distinction between brain dead and physiologically dead. This does not apply to plants but is clearly relevant to animals. Check out the following links Clinical_death and Brain_death. David D. (Talk) 19:47, 6 January 2007 (UTC)

By a dead animal I mean one which has experienced Clinical_death and Brain_death and has perhaps been run over, sliced and diced. Edison 21:22, 6 January 2007 (UTC)

I think you now entering the realm of science fiction. But you may be interested to read about Craig Venter's new company. http://www.syntheticgenomics.com/about.htm David D. (Talk) 21:45, 6 January 2007 (UTC)

I would define death as "the point at which the original can no longer be reproduced, naturally, by what remains". A potato, and many plants species, therefore remain alive as long as it can grow a reasonable facsimile of the original. This isn't true for most small parts of animals, however, which can't regrow a copy of the original. There are exceptions, however, such as the planarian. Cloning doesn't count, since it isn't natural. Also, in the case of animals, it doesn't restore the memories in the brain. StuRat 15:59, 8 January 2007 (UTC)

Struggling Butterflies

A friend on MySpace posted this story on my bulletin:

"A man found a cocoon for a butterfly. One day a small opening appeared, he sat and watched the butterfly for several hours as it struggled to force its body through the little hole. Then it seemed to stop making any progress. It appeared as if it had gotten as far as it could and could go no farther. Then the man decided to help the butterfly.

He took a pair of scissors and snipped the remaining bit of the cocoon. The butterfly then emerged easily. Something was strange. The butterfly had a swollen body and shriveled wings. The man continued to watch the butterfly because he expected at any moment, the wings would enlarge and expand to be able to support the body, which would contract in time. Neither happened. In fact, the butterfly spent the rest of its life crawling around with a swollen body and deformed wings. It was never able to fly.

What the man in his kindness and haste did not understand, was that the restricting cocoon and the struggle required for the butterfly to get through the small opening of the cocoon are God`s way of forcing fluid from the body of the butterfly into its wings so that it would be ready for flight once it achieved its freedom from the cocoon. Sometimes struggles are exactly what we need in our life.

If God allowed us to go through all our life without any obstacles, that would cripple us. We would not be as strong as what we could have been. Not only that, we could never fly."

Is this true? I ask for the sake of spiritual enrichment, because as a student of "A Course in Miracles" I tend to believe that suffering is unnecessary for spiritual development, but because this idea is so implanted in the collective conciousness, we "make" it. It probably doesn't matter, because the natural world does not reflect the spiritual in many cases, but I am curious. Thank you for your time.

24.88.54.247 03:40, 6 January 2007 (UTC) Sarah Ray

Hi, Sarah. First, you should know that the WP Reference Desks are not the ideal location for a spiritual/philosophical discussion, but welcome. Second, you said the word 'suffering', but the story you told used the word 'struggle'. Who says that something that is hard is also a source of suffering? I am familiar with The A Course in Miracles, and (sorry to be giving unsolicited advice) I think that as long as you are conflating challenge with suffering you will be stalled in your spiritual development. Anchoress 03:48, 6 January 2007 (UTC)

If we had no obstacles in life, we would lack the skills necessary to solve problems and get ourselves out of emergency situations. However, if there were no problems or emergency situations to begin with, we won't need those skills. So if there is no suffering in the world, the world would be better, not worse.

In your case of the butterfly, is it not possible for God to distribute the fluid while the puppa is still in the cocoon, so that it doesn't need to struggle to come out? --Bowlhover 04:28, 6 January 2007 (UTC)

Possible. But God made them animals, not puppets. BenC7 07:57, 6 January 2007 (UTC)

But God can change the life cycle of the butterfly to eliminate the need for struggle. He doesn't have to personally help every single butterfly. --Bowlhover 10:34, 7 January 2007 (UTC)

Consider reading Letter to a Christian Nation by Sam Harris. It's short and highly illuminating. This whole issue is actually moot. Religion cannot be constructively applied to science, hence the confusion. Richard Dawkins has much to say on this subject as well, though most religious people consider him infamous. Good luck! Jeeves 08:40, 6 January 2007 (UTC)

Personally I agree with the OP. If there were no struggles everything would be easy and noone would acchieve anything. And if everything was done for us, we would never learn from our mistakes. Also if I was like the butterfly, I wouldn't want any gods to help me and make everything better, as then I wouldn't be me any more. Unless it was a very serious problem, of course.Hidden secret 7 21:03, 6 January 2007 (UTC)

But that's not what the original poster is saying. She is saying that in her belief system suffering is not a factor. Anchoress 05:28, 7 January 2007 (UTC)

Butterfly technical question

Reading this has sparked my interest. Don't suppose there's anyone around here knowledgable about butterflies and would like to tell me whether the bit about the butterfly in the story is true? As in the bit about the fluid going from the body of the butterful to the wings? because it all sounds....a bit suspicious to me. --`/aksha 10:08, 6 January 2007 (UTC)

I've split this off into a separate section. I too am curious about the science – if any – behind this, and I'm hoping that the entomologists in our readership will come out of the woodwork to comment. TenOfAllTrades(talk) 22:33, 6 January 2007 (UTC)

Well the article on butterflies says this: "A newly-emerged butterfly needs to spend some time inflating its wings with blood and letting them dry." From the sound of it, most of the inflation occurs after it leaves the cocoon. In fact, if the cocoon is really that hard to get out of, it would make sense that the wings should be kept as small and uninflated as possible. Strad 00:18, 7 January 2007 (UTC)

Note this is unreferenced WP:OR, but the story interested me:-): I have just been over to our local butterfly breeder (not an trained entomologist, but 20 years breeding experience) to ask. Her comments: She thought the story was a joke, a fanciful fable thought up by some one who has never seen a butterfly emerge from a pupa. A normal butterfly does not struggle to get out of the chrysalis (only moths have silk cocoons). The splitting and emerging from the pupa takes "shorter than it takes you to skin a banana" - quick, simple, easy, no struggle. The pupa bursts it is not "gradually worked open". An animal that cannot expand enough to split the pupa skin is sick. An animal that cannot move sufficiently to exit from a split pupa is sick. Infection apparently does this, the animal gets stuck and dies halfway in the pupa, simply because it is too weak to move normally. She doubts if a healthy normal butterfly can get stuck in a pupa, the covering bursts for a good distance from the bottom almost to the top, and there is no "struggle to get out", rather a clumsiness in executing the first "baby steps" out of a patently open shell, to get going. She has "helped" only one specimen when she happened to be there to see it struggling (tweezers), but would not do it again, since she believes a struggle is a sign that there is something wrong with the butterfly. The "swollen body and shriveled wings" is normal; they always look like that on just emerging; that fluid (probably hemolymph, not blood) helped split the pupa, and will be pumped into the wings to expand them, and then returned to the butterfly's body when the wings have dried. As far as cocoons go (moths), she does not breed moths, but she makes the pertinent point that silkworm moths emerge normally from cocoonless pupae, so cutting the cocoon should make no difference. I would love to see a trained entomologist's angle on this. --Seejyb 05:21, 7 January 2007 (UTC)

Love and P A I N

I'm in love with someone I probably can't get. I'm very curious as to why this psychological state causes actual, physical pain. Specifically, a burning feeling in my chest when I think about that special someone. I guess it's pretty mild compared to, say, cutting a finger open, but still. Has anyone figured out why this happens? Pain means nerves must be being stimulated, yet my body is wholly intact. I imagine this is why love historically came to be associated with the "heart", though the blood-pumping musculature is obviously not directly involved. What gives? Thanks. 24.95.48.112 07:12, 6 January 2007 (UTC)

Thats gives me an IDEA (not IKEA). Love Sickness can be Cured, lol. Sorry for my jokes but this is the best question I have ever seen on the Reference Board. Oh yeah and I have the same symptoms too, the anti-depressants: Celexa, Wellbutrin don't seem to be working for me. --Judged 08:35, 6 January 2007 (UTC)

It resembles the same pain as for anxiety. --Zeizmic 14:42, 6 January 2007 (UTC)

In addition to non-cardiac chest pain associated with emotional stress there is also research on Pathophysiological processes underlying emotional triggering of acute cardiac events. --JWSchmidt 23:12, 6 January 2007 (UTC)

The question, I believe, is why is depression associated with the heart? --Judged 04:18, 7 January 2007 (UTC)

I would guess, neurotransmitters trigger hormonal stress that triggers raised blood pressure and adrenaline rushes and general tension, and increased heartrate. That could all trigger acute cardiac events. Though the above links will be much more informative and authoritative than this guess of mine, which should be seen as a way to explain things in simpler terms. Oh, broken heart might help as well. Also acute coronary syndrome and panic attacks. Carcharoth 06:10, 7 January 2007 (UTC)

:From the above analysis you all relate it to stress, which acts directly on the Heart? How can you compare that with sadness in which there is no stress? --Jones2 11:20, 7 January 2007 (UTC)

• Let me break it down for you, the neurotransmitters affect the whole body not just the brain. For example lack of neurotransmitter Dopamine, causes movement disorders eg. Parkinsons disease. So these neurotransmitters affect the chest region some how, I am guessing this part though, someone want to back me up? --Foundby 17:14, 7 January 2007 (UTC)

• Furthermore we know that neurotransmitters affect the mood in the brain esp. depression, anxiety, alertness, happiness, rage etc. --Foundby 17:17, 7 January 2007 (UTC)

Scientifically speaking Alcohol

Scientifically speaking Alcohol makes a person sick? --Delma1 08:30, 6 January 2007 (UTC)

In excess, yes it can. Ethanol#Metabolism_and_toxicology --Joel 11:02, 6 January 2007 (UTC)

Anything in excess can, but that's where the definition of "in excess" is. Vitamin C won't though! X [Mac Davis] (DESK|How's my driving?) 03:42, 7 January 2007 (UTC)

In response to Vitamin C, that is not completely true. For example, there is a case report about a guy with acute renal failure taking 5,000 mg of Vitamin C per day to fight off an upper respiratory tract infection. It resulted in the guy going to the hospital and was found to have tubular necrosis with massive oxalate deposition. The report goes on to say, "Our patient’s course and our review of the literature again support the contention that vitamin C ingestion may cause significant morbidity and mortality. Vitamin C should therefore not be viewed as a benign, water-soluble drug but rather as a drug that is potentially toxic, not only for diseased kidneys, but also for normal ones given the proper circumstances." - Dozenist talk 15:42, 7 January 2007 (UTC)

Then why does alcohol make you vomit? --Delma1 04:03, 7 January 2007 (UTC)

Vomiting is a "reflex" that eliminates ethanol from your stomach so your liver does not have to metabolize it. -Michael 04:55, 7 January 2007 (UTC)

Well how is this reflex activated due to alcohol consumption? --Delma1 14:03, 7 January 2007 (UTC)

I can't say with any certainty, but I'd assume that the body reacts to the presence of the toxin in sufficient levels by activating the vomiting center of the medulla, either by the vagal system and enteric nervous system being stimulated by the presence of ethanol or via the action of ethanol on the brain's chemoreceptors (by the action of the ethanol metabolite acetaldehyde perhaps?) This is an educated conjecture, but I'm not an expert, so I can't say with 100% certainty. Wintermut3 22:46, 7 January 2007 (UTC)

Type of Science

What the name of the type of science or job that looks for ways to help people from natural resources? Such as the African clawed toad, it has healing abilities. Or using snakes venom to create anti-venom.

Natural medicine? But it is not typically classified as a science, since it includes a number of areas that are pseudo-scientific. Science is also based on repeatable experiments (well, mostly) - and I doubt any experiements on a toad would show that people are healed by it. Possibly some chemical that it produces may be synthesized and be used for beneficial purposes. But then that's a chemical, not the toad itself. BenC7 12:23, 6 January 2007 (UTC)

Maybe... Bioprospecting --Zeizmic 13:24, 6 January 2007 (UTC)

Medicinal chemistry and pharmacology. The majority of new drugs are still being derived from natural substances, even if the molecules are altered to improve the kinetics. alteripse 15:06, 6 January 2007 (UTC)

Anaerobic respiration

I understand that the anaerobic pathway of respiration produces harmful waste products such as lactic acid. This causes fatigue in humans. How, then, can an anaerobic organism survive having lots of these waste products inside them? 86.147.210.9 12:31, 6 January 2007 (UTC)

Anaerobic waste products are excreted by anaerobic organisms, just like any other waste product. As you can read in the article on anaerobic organisms, there are many anaerobic chemical pathways, but they all result in at least one waste product. For instance, yeast, which undergoes fermentation to produce the waste product of ethanol, excretes the alcohol to get it out of its system. In fact, if you put yeast in a bottle with some water and carbohydrates, it keeps producing alcohol until it dies because there's too much alcohol around. Then you have some nice grain whiskey, or whatever. --Bmk 17:48, 6 January 2007 (UTC)

Actually, on second thought, I dont' think the yeast population dies because of the concentration of alcohol - I think the yeast population dies because it runs out of sugars to ferment. Sorry! --Bmk 17:48, 6 January 2007 (UTC)

It depends on the initial concentration of sugar, and on the type of yeast. With a lower concentration of sugar, fermentation proceeds until the sugar runs out; with high sugar concentrations, the alcohol concentration will get high enough to kill the yeast. (In its most extreme form, this comes into play in the making of certain late harvest and icewines, where extremely concentrated grape juices are used to generate a very sweet final product.) To produce alcoholic beverages more potent than about 15% to 20% alcohol by volume, one needs to concentrate the beverage after fermentation using a physical process like distillation. TenOfAllTrades(talk) 15:18, 6 January 2007 (UTC)

What is sleep apnea ?

What is sleep apnea ?

Hi - we have a large article on that subject called sleep apnea (link provided). Please try using the search box before asking here - it will be much quicker. Also, the instructions at the top of this page should be useful - they will tell you how to add new questions. --Bmk 17:48, 6 January 2007 (UTC)

Herpes?

I am a 22 year old male, and the other day I noticed this purple thing on my thigh. It is was like a blister bigger than my thumb-nail, and I put a needle through it and a lot of blood came out, and then i squeezed and all this white stuff (the same stuff that comes out of pimples) came out, a lot of it too. Now Ive read about herpes before, and I saw pictures, but it looks different, it doesnt look the same at all. But i'm worried, is it just a pimple? Thanks

Please direct medical questions to your doctor. In the mean time, you may want to read boil. -- mglg_(talk) 21:19, 6 January 2007 (UTC)

Pimples aren't purple! "The same stuff that comes out of pimples" would be sebum. X [Mac Davis] (DESK|How's my driving?) 03:41, 7 January 2007 (UTC)

sugar

What would happen if someone was on a diet consisting almost entirely of sugar, and very sugary food.Hidden secret 7 21:06, 6 January 2007 (UTC)

Start first with Sugar. Then, here's an article. [5] Seems that you'll rot your teeth and get diabetes. I've known of many young girls that go 'vegetarian', but end up as sugar-aholics. --Zeizmic 22:45, 6 January 2007 (UTC)

• You'd also get serious deficiencies in the foodstuffs you weren't eating like fats, vitamins, aminoacids, fluids, etc, etc. - Mgm|^(talk) 23:38, 6 January 2007 (UTC)
• My Answer was kind of long so I put it on the user's talk page. See the answer here. Sifaka ^talk 00:31, 7 January 2007 (UTC)

Now that's a good thorough answer. X [Mac Davis] (DESK|How's my driving?) 03:43, 7 January 2007 (UTC)

• If they didn't eat any protein with their carbohydrates/sugar, they might get kwashiorkor. --Uthbrian (talk) 09:16, 7 January 2007 (UTC)

Immunizations

Does Mexico require that school children be immunized before entry to school? What immunizations are required? What percentage of school age children are immunized? Thank you, pb

Here's an article from 2002 that says "Mexico more effective than U.S. at immunizing children: Mexico's paternalistic approach has led to a 96% vaccination rate for children ages 1 to 4, compared with 79% of American 2-year-olds." You can see Mexico's immunization schedule here (it's a .pdf file). - Nunh-huh 22:10, 6 January 2007 (UTC)

Do cats and dogs understand tv?

Can they understand that the 2D image represents a 3D scene? I've heard that they often watch a front-loading washing machine, what about tv?

Dogs really can't see very well, but they can detect motion. [6] It looks like 3d is just a dream to them. --Zeizmic 23:55, 6 January 2007 (UTC)

FWIW, my cat seems very interested in ball sports on TV, such as soccer, but ignores all other programmes. Grutness...wha? 00:03, 7 January 2007 (UTC)

Another anecdotal data point, my dog will bark when it sees other dogs on TV (but never normally on the tv just because of motion). Other people describe this too, however I've not studied it closely enough to decide perhaps if perhaps the dogs bark as well and this is what are setting them off. But I'm pretty sure if you just showed a dog running on TV with no sound he does bark. (One Man and His Dog being an example) 217.43.184.59 00:30, 7 January 2007 (UTC)

Does the different persistence of vision (I assume it is different for dogs than that of humans) make it difficult for the dog to see the image on TV? -- WikiCheng | Talk 14:08, 8 January 2007 (UTC)

As others have said, dogs do not actually have very good eye sight (although they have big eyes and can even see behind them a bit), so I wouldn't have thought their persistence of vision is better than ours. TV is 25 frames per second, though interlaced at 50 half frames a second. Humans are perfectly comfortable with much lower refresh rates, so I can't imagine dogs have a problem. 217.43.184.59 20:59, 8 January 2007 (UTC)

Every breath very probably has an air atom also breathed by Julius Caesar

I recall reading that this is true. If that's the case, does the breath I'm breathing now contain an air atom breathed by every human who's ever lived (allowing for the time it takes for air to travel across the world and so on), plus the dinosaurs? Just how many atoms are there in a lungfull of air? Most atoms must have been breathed over and over again by many different people. Does anyone have the calculations that give rise to this belief?

I don't have the calculations, however here is guidance for them: the number of molecules in a certain volume can be calculated by the ideal gas law. You can also, by the information (volume per breath, breath frequency) in the article breathing calculate the total number of molecules breathed during the duration of a human life. Then you need the number of molecules in the atmosphere. There is several ways to get this number - the obvious idea is to try to find the volume of the atmosphere, and use that together with the ideal gas law. However, this solution is non-trivial (the atmosphere has different pressure on different heights). I would use the information on pressure at sea level in the article earth's atmosphere and the information on surface area in the article earth to calculate an approximate mass of the atmosphere instead. Combined with a weighted average molecule mass (calculable from the data in earth's atmosphere), you'd get the total number of molecules in the atmosphere.

Possibly you'll get really obvious numbers from this, but preferably you'd use some statistical hypothesis testing to hopefully confirm the hypothesis. TERdON 00:02, 7 January 2007 (UTC)

Didn't somebody ask a question similar to this a while back? Splintercellguy 00:21, 7 January 2007 (UTC)

Yeah, they did. This very issue is discussed on the book Innumeracy by John Allen Paulos, along with the calculations demonstrating the high probability of it. It is, however, highly unlikely that atoms of the air would travel half the world in, say, a year. — Kieff 00:37, 7 January 2007 (UTC)

It's more impressive than that. From what I've heard (and yes, shame on me for not working it out), each breath we take contains, on average, two atoms of each breath that everyone has taken. (If this turns out to be very wrong, I reserve the right to remove my sig). Bunthorne 00:41, 7 January 2007 (UTC)

I don't see how that would be possible. Atoms don't move around the earth that quickly. Chickenflicker---♣ 07:18, 7 January 2007 (UTC)

Okay, let's have a go. For purposes of this rough estimate we can ignore other substances and pretend the atmosphere is all nitrogen with a molecular weight of 28 -- oxygen is only a bit heavier and other gases are in small quantities). According to air, the total mass of the atmosphere ignoring water vapor is 5.14e18 kg. One mole of air (really nitrogen) is 28 g = 0.028 kg, so there are 5.14e18/0.028 = 1.84e20 moles of air. Each mole contains Avogadro's number of molecules, or 6.02e23, so there are 1.11e44 molecules of air altogether -- rounding to 1e44 will be close enough.

Now, breath says adults breathe 500 to 700 ml at a time. Say 600 ml or 0.6 L. One mole of any gas occupies the molar volume of 22.4 liters at standard pressure, so one breath is 0.6/22.4 = .027 mole, which is 1.6e22 molecules -- again, rounding to 1e22 will be close enough. (That's molecules; the original poster asked how many atoms in a breath, which will be twice that.)

So we have the coincidence that the total number of molecules in one breath is juts about the same as the number of breaths in the atmosphere. So yes, on average each breath you take will contain one molecule -- two atoms -- from Julius Caesar's last breath or any particular previous breath. (Assuming that there has been time for it to mix, of course; obviously it doesn't apply to a breath just taken by someone in a different city.) One complication I have ignored is that atoms get removed from the atmosphere and others added into it over time; I don't think this affects a substantial fraction of the atmosphere over a mere 2,000 years, but I could be wrong.

--Anonymous, January 7, 100% 2007, 06:52 (UTC).

600ml sounds like a lot for just one breath. Or I could just be breathing less than everyone else. Is there any way to find out?Hidden secret 7 11:34, 7 January 2007 (UTC)

Or you could just have no concept of how large your tidal volume is. You could get an actual value by taking a pulmonary function test, though it's probably going to be a bit expensive if taken just to satisfy your curiousity. - Nunh-huh 17:25, 7 January 2007 (UTC)

A plastic bag and a juice pitcher with a volume scale on the side would be cheaper. --mglg_(talk) 22:10, 7 January 2007 (UTC)

January 7

haploid/diploid

If chromosomal duplication happens twice before tetrad formation in spermatogenesis, while the other steps proceed normally, would the resulting 4 sperm cells be considered diploid because they each have 2 copies of a gene or haploid because the 2 copies are of the same homologue? In other words, does the term "diploid" in humans refer only to the total number of chromosomes (twice the number of the haploid state) or the state of having a pair of homologous chromosomes each with differing alleles for the same genes? thanks, N.S.

• Diploid sperm are not very unusual. --JWSchmidt 03:28, 7 January 2007 (UTC)

Binding energy

I'd like to make my own version of this graph. Where can I get a raw set of values for it? I tried googling a bit but all I found were fairly tedious formulae for computing the average binding energy per nucleon and all of that -- surely it is available somewhere more easily? I'm no physicist and would prefer not to have to try and fumble through the calcuations. Anybody have them at hand (or willing to do the calculations for me?)? I'll donate an SVG version of the resulting graph to Wikipedia if that's worth anything to you. --24.147.86.187 04:24, 7 January 2007 (UTC)

I'm afraid I don't have a terribly easy way to get these, but I can tell you the equations in a simple and friendly manner (I hope). Look at List of isotopes (actually a link to a page per element). For any isotope you consider interesting (probably the ones with natural abundance scores in the next-to-last column), take its isotopic mass (fourth column) and subtract 1.00779487489Z (second column) and 1.00866491979N (third column) to account for protons and electrons (first number) and neutrons (second number). You should get a small negative number (the mass defect); drop its sign. Multiply by 931.493581874 (this converts amus to MeV, which are the units in that plot) and divide by the mass number (the first column, or $A=Z+N$; this is also the abscissa in that plot). As an example, for oxygen-16 I get a mass defect of -0.136763737825 u, which corresponds to an ABEPN of 7.96215900105 MeV (remember to divide by 16) — good agreement with the existing plot.

Well. After writing all that, I've just noticed how to get the raw data from that list's reference; what you want is the left-hand column under Binding Energy/A. Note that it's in keV, unlike the plot we have. Hope this helps, even if the majority of it is just background. --Tardis 06:21, 7 January 2007 (UTC)

That's all very helpful, thank you. --24.147.86.187 15:55, 7 January 2007 (UTC)

OK. I tried to use a combination of that data set and your instructions. Here was my Excel equation:

=(([isotopic mass]-((1.00779487489*Z)+(1.00866491979*N)))*931.493581874)/(Z+N)

I have substituted column references with their meaningful variables, there, and I apologize for all of the nesting (I wanted to make sure it would do the order of operations correctly). Now this all looks pretty good except that I end up with what looks like exactly negative values of what I should be getting (oxygen-16 gives me -7.962159004). Now I know I can just multiple by -1 to reverse the sign, but why is it doing this? Have I made an error? --24.147.86.187 16:32, 7 January 2007 (UTC)

I mentioned that you would get negative numbers and should drop the sign on the mass defect. The reason is just semantics: is the energy (or mass) difference between free nucleons (heavy) and ones in a nucleus (slightly less heavy) positive because energy is released when you combine them or negative because the result (not counting emitted energy) has less mass than the raw materials?

As far as the order of operations goes, you can write that most succinctly as $(m-1.0078*Z-1.0087*N)*931.5/(Z+N)$ (decimals abbrevd.) in any program.

However, it occurs to me that I omitted one effect -- the ionization energy of the atom shows up as a further mass defect. Ionization energies are much smaller than the nuclear binding energy, but it will cause an error which in extreme cases (heavy elements have much greater total ionization energy) may be as big as 2% or so. Ideally you need to add up all the ionization energies for an element (regardless of your isotope; this is still an approximation, but a very good one) in eV and so divide by a million to combine with your MeV number: ${\frac {931.5(1.0078Z+1.0087N-m)+{\frac {\sum _{n=1}^{Z}I_{n}}{10^{6}}}}{Z+N}}$ where I have done the sign flip on the mass defect explicitly. I realize, though, that this is rapidly getting complicated; it's probably best just to use the published data. --Tardis 21:02, 7 January 2007 (UTC)

Waterjets for teeth dangerous?

My dad said that Waterpik waterjets (used instead of flossing) are actually dangerous, because the force of the water pushes bateria and such deeper into the gums and even the bloodstream. Is this true, or even possible if used properly? --RockMaster 05:33, 7 January 2007 (UTC)

Follow the directions that come with the device. I looked around and found mostly good results. Excessive use can cause some gum damage, but nothing with the enamel. --Zeizmic 13:22, 7 January 2007 (UTC)

I do not think I have ever heard of a waterpick being dangerous. This is slightly off topic, but I thought I should mention that water picks are not be considered to have replace dental floss. Maybe someone that knows physics better than I would could explain the problem based on forces placed on fluids, but flossing and brushing are considered the most effective preventative measures. Around your teeth, the gums dip down slightly, forming a little trench that circle the teeth. This trench (called a sulcus) is filled with gingival fluid. Throwing water onto the sulcus is not going to be sufficient to wipe away food or bacteria/plaque present. Only physically disturbing the area, such as when using dental floss, can reduce or remove the stuck material. Waterpicks have their uses, which may be why your dentist suggested you to use it because of your particular situation. Your dentist would be able to recommend which locations a waterpick would benefit you, but dental floss will not be replaced by waterpicks anytime soon. - Dozenist talk 15:07, 7 January 2007 (UTC)

Err...it's Waterpik, as in the company. He mentioned a specific case about their pumps being too powerful. And, according to their site at least, their jets are intended to replace flossing. And shouldn't a concentrated jet of water be just as effective, if no more because it's a liquid? Industrial waterjets are very efficient and often just as effective as their solid conterparts. But, this is really neither here nor there. I was just wondering if there has been any actions against the company's jets. --RockMaster 22:44, 7 January 2007 (UTC)

I don't see how water could forcibly push bacteria that are supposadly inside the muscosa of the gums further in—there's a medium between the outside surface and the inside. Waterpiks are supposed to be the best possible form of dental care when used properly aren't they? Of course "talk to a dentist for dental advice." ;) X [Mac Davis] (DESK|How's my driving?) 05:02, 8 January 2007 (UTC)

Tilt-shift Photography

So I've been wondering this since every time I've seen a photo taken with tilt-shift lenses, but I haven't ever found an explanation. What exactly makes a photo taken with a tilt-shift lens look like it was taken in miniature? What is responsible for the "miniaturization?" Maybe another way of putting it is what is the visual difference between a normal scene and a miniature version of that scene?

I think any discussion would be a great way to expand the stub on tilt-shift photography. For an example picture, see this picture. -Michael 05:42, 7 January 2007 (UTC)

A miniature version will all be effectively at one focus (that is, even a small depth of field can focus all of it) and will show very little perspective. Both of these effects arise because it is typically viewed from a distance much larger than the distance from "front" to "back" within the scene. The article on tilt-shift mentions a removal of perspective, so that makes sense; the linked article on faking mentions focus, so that makes sense too. Does that help? --Tardis 06:31, 7 January 2007 (UTC)

From what I can tell, the opposite appears to be the case; the focus is exaggerated, so that only a very small area of the image is in focus. This is a particularly good example that I found on Flickr. Because the trees in the foreground and background are both unfocused, the town in the middle looks very small. I think this effect occurs because focus is proportional to ¹/_{distance to lens}. Because the graph for ¹/_x is steepest for very small values of x, the difference between focus on very small objects is far more exaggerated than very large objects, where since x is often taken to be infinity in photography for objects the size of buildings, the focus is the same for the whole object. The brain notices this gradient of focus, and works out a scale for the object based on this. Laïka 13:39, 7 January 2007 (UTC)

The math in the second post makes sense for sure, but I think that parts of the first ring true as well. I'll digest this a little and see if i can't add anything to the tilf-shift page. Thanks for the answers. -Michael 06:14, 8 January 2007 (UTC)

What is type of this huge spider? Please let me know if you can figure out.

Here is my space, You can see the picture I took http://lionongshop.spaces.live.com — Preceding unsigned comment added by 211.30.34.134 (talk • contribs) 10:03 7 January 2007 (UTC)

I would guess that it is a member of the Argiope genus. BenC7 01:51, 8 January 2007 (UTC)

confidentiallity

'All that may come to my knowledge in the exercise of my profession or in daily commerce with men, which ought not to be spread abroad, I will keep secret and will never reveal.' This is a part of the Hippocratic oath, but can I still trust a doctor not to tell anyone anything, since apparently the hippocratic oath isn't used much any more?Hidden secret 7 11:56, 7 January 2007 (UTC)

Depends partly on where you live, but see physician-patient privilege.--Shantavira 14:02, 7 January 2007 (UTC)

This is taken as absolute in the US, especially if you make a point of reminding the doctor confidentiality is important to you. Breach is grounds for a malpractice suit. There are lots of flaws in the US system but we sacrifice much (including convenience and even quality of care sometimes) to maintain confidentiality. See HIPAA. alteripse 14:31, 7 January 2007 (UTC)

Although it is not legally binding, many MD graduates do take the hippocratic oath upon graduation. Indeed, to many (the current interpretations of) this oath are more important than the law. If you have embarrassment about something you are considering talking to a doctor about, consider that physicians see a lot people with a lot of different problems, and are likely to have seen whatever your problem is many times before. If you are considering disclosing illegal or illicit behavior, consider that a physician is bound by the privilege discussed above. Though a hospital may be able to hold an individual for a short amount of time (usually no more than 3 days) if that person is a threat to himself or others, the treatment and reason for treatment cannot, under most circumstances, be disclosed to police or prosecutors. Tuckerekcut 20:28, 7 January 2007 (UTC)

The end of time ?

I have been re-reading The End of Time by Julian Barbour. As far as I understand it, his thesis in summary is:

• the most objective descriptions of the physical world are timeless descriptions in terms of geodesics in phase space;
• the curve in phase space that represents our own universe happens to have one end in a rare, extremely low entropy state (the Big Bang);
• this asymmetry in our cosmological curve gives rise to the second law of thermodynamics;
• this asymmetry also gives rise to the psychological arrow of time, because a given state can only contain a record or memory of states which have a lower entropy (Barbour's "time capsules");
• and so time is an illusion (although a pervasive and useful one).

Have I correctly understood Barbour's position ? Is it a respectable (although possibly minority) position in mainstream physics, or is it closer to pseudoscience ? Have any other physicists written about similar ideas in accessible publications ? Gandalf61 11:57, 7 January 2007 (UTC)

Hello, 61. What is not an illusion ? Our concepts are based upon representations derived from sensations, feelings ... and time, space, univs are useful concepts. Does it make more sense to tell that a given representation eliminates time ? Let's respect the idea and, if it becomes mainstream, why not ? But it may take time. -- DLL ^{.. T} 18:33, 7 January 2007 (UTC)

Lactose and yeast fermentation

Hi i recently did a biological experiment investigation, involving different respiratory substrates for yeast cells Saccharomyces cerevisiae. I found that lactose hardly respired at all. Why would this be? I thought it could be due to the disaccharide formation of lactose, with galactose, having a sterio isomer which is not fermentable by yeast, but then surely i should get at least some respiration. Or perhaps another angle would be the fact thatthe yeast did not have the appropritate enzyme to break the bond between the saccharides? Any comments or opinions on this matter would be greatley appreciated. — Preceding unsigned comment added by 81.156.37.191 (talk) 08:47, January 7, 2007 (UTC)

Saccharomyces cerevisiae

Can Saccharomyces cerevisiae break down lactose? or does it not have the enzyme lactase?thanks — Preceding unsigned comment added by 81.156.37.191 (talk) 09:03, January 7, 2007 (UTC)

Saccharomyces cerevisiae has nearly no natural lactase activitiy. Genes which provide this activity, such as Aspergillus niger secretory beta-galactosidase, have been inserted into Saccharomyces cerevisiae via recombinent techniques, so there are experimental strains of Saccharomyces cerevisiae which can break down lactose, but no natural strains. ("Saccharomyces cerevisiae Fungemia: An Adverse Effect of Saccharomyces boulardii Probiotic Administration", Raoul Herbrecht and Yasmine Nivoix, Clinical Infectious Diseases, volume 40 (2005), pages 1635–1637: "Saccharomyces cerevisiae expresses significant sucrase and some isomaltase activity but no lactase activity") - Nunh-huh 17:19, 7 January 2007 (UTC)

liquid nitrogen in the tube

The tube deep lines have a problem with overheating. If they converted an old carriage to become a big tank of liquid nitrogen that went round squirting liquid nitrogen everywhere would it have any effect? Typo squotter 16:16, 7 January 2007 (UTC)

Okay, first let me explain the question. This person is talking about the London Underground (familiarly "the Tube") and specifically its deep-level tube lines (the only ones that are "tube lines" in strict usage). London Underground trains are not air-conditioned, and one reason often cited for this is that the deep tube tunnels are so small that there is no room to add air conditioners to the trains. (The fact that the subsurface lines are also not air-conditioned strongly suggests that this is not the only reason, but we're getting outside of science matters if we discuss that.) So this person is proposing a scheme to cool the tunnels instead.

My response to "would it have any effect" is: Yes, it would create a risk of suffocating the passengers by displacing too much air from the tunnels. This might prevent them from complaining about the heat, but is probably not the most desirable way to do so. :–) (Even if the amounts were properly controlled to avoid this, what if the tank developed a leak?) Using liquid air instead of nitrogen would avoid the suffocation hazard, but I believe it would substitute a fire hazard. In addition, squirting cryogenic liquid about the system could be damaging to any equipment (track, signals, wiring, etc.) that it landed on, due to thermal stress.

It's an interesting idea, though. It might be interesting to try to calculate the cooling available that way, ignoring the safety issues, but I'm not prepared to do it now. I do note that cooling the tunnels rather than the trains would only be helpful on the part of the journey when the trains actually are in tunnel; 5 of the 7 deep-level tube lines have long stretches of surface track as well, where the trains will heat up on a hot day.

You may be interested to know that the Channel Tunnel has a pipe carrying cold water through each tunnel, just for cooling. If a decision was made to cool the tunnels, this would probably be a safer approach, although there might not be enough cooling capacity in view of the fact that so much more of the cross-sectional area of the Tube tunnels is filled by the trains than is the case in the Channel Tunnel.

--Anonymous, January 07, '07, 20:52 (UTC).

Such an approach (water in pipes, not liquid nitrogen) is in fact being considered by the Tube ^sauce; since the River Thames soaks into the tunnels, pumps are constantly at work removing thus water from the tunnels. This water could then be used in a heat exchange system to cool the tunnels, but only at the riverside stations. Unfortunately, this means that your idea (basically the same concept) has come too late to win Ken Livingstone's £100,000 prize, though. Laïka 21:34, 7 January 2007 (UTC)

Scientific Question: Regarding Great Intelligence

Scientific Question Regarding Great Intelligence is asked at here, thought you might be interested, it's a little philosophical in nature though : Wikipedia:Reference_desk/Humanities#A_Person_with_Great_Intelligence. --Foundby 16:45, 7 January 2007 (UTC)

Price of Copper and Brass

Hi,

Does anyone know whether copper is more expensive than brass (because it's purer?) There's nothing about it on any of the wikipedia articles on either copper or brass or their talk pages. I couldn't find anything about it on the web.

Thanks, Bioarchie1234 17:40, 7 January 2007 (UTC)

ys, copper is more expensive than brass. You can get some values byt googling "copper cost per ton" and "brass cost per ton", but you'll find that the prices fluctuate widely. - Nunh-huh 18:00, 7 January 2007 (UTC)

Thanks very much! I really appreciate the help. Bioarchie1234 18:04, 7 January 2007 (UTC)

Sculpting a sphere

What are some good techniques for sculpting and measuring a smooth sphere? I'm pretty sure there must be an ingenious way to do it, I just can't think of anything that won't be eye-measured and prone to distortions.

The case in question is that I have a round shape already, and I want to use sandpaper to finish the sphere (by hand, unfortunately that's all I have). I need it as close to a sphere as possible. — Kieff 17:58, 7 January 2007 (UTC)

What is your sphere made of? Bioarchie1234 18:03, 7 January 2007 (UTC)

Wood. — Kieff 18:10, 7 January 2007 (UTC)

This is kind of eye-measured, but it might help:

Get two rectangular pieces of wood that are the same thickness as each other. Clamp them together to make a square(ish) shape. Make sure the sides are longer than the diameter of your sphere. Mark the centre of this square with a pencil, then, with pair of compasses, draw a circle the size of your sphere round this point. Take the two pieces of wood apart and cut out all the wood inside the circle, then file it or use sandpaper on it to get it perfectly circular. Glue the two pieces together and put your sphere in the circular hole. If you hold the square so it is parallel to a flat surface like a table, and so it passes through the diameter of the sphere, and then roll it around the table, you should be able to tell where it is bumpy because it will get slightly stuck. This might only work in principle, but it might work in practice too. I know you were looking for a more scientific method, but this is the best I could do! Hope it helps, if not, leave another message here or on my talk page. Bioarchie1234 19:04, 7 January 2007 (UTC)

I remember a television program (Like Mythbusters -- best guess is the Discovery Channel show "Debunked: Secrets of the Stone Spheres") which discussed the Stone spheres of Costa Rica. They came up with a relatively low tech way of getting the stones to be spherical, although I can't remember what it was. -- 22:32, 7 January 2007 (UTC)

This reminds me of when I learned how to grind a spherical mirror to use in a telescope. The strange thing being that it is a lot easier to grind a perfect sphere then you'd think, all that it involves, surprisingly, is randomness! Take for example a handful of clay, or mince, and roll them randomly between your hands, like you are making a meatball, the same principle applies, if you have a high enough degree of randomness you will end up with a perfect sphere. For a spherical mirror, all you have to do is rotate the mirror and randomly grind the surface, and as if by itself, the mirror will grind to a perfect sphere. Don't really know how to apply that to a wooden sphere but it may get you thinking, I'm thinking of two planks covered in sandpaper and the sphere rolled between them, but not sure how that would work practically, if the sandpaper removes enough material, if you could get it random enough, if it would create flat spots which then might cause bigger deviations… How big is the wooden sphere? Vespine 23:38, 7 January 2007 (UTC)

I saw this done for a wood sphere once - they lined a side-loading drier with sandpaper and put the block in it. After running for a day or so, they had a sphere. The same concept as a rock tumbler I believe. --Kainaw ^(talk) 04:40, 8 January 2007 (UTC)

[7] is the ball race method

channel form efficiency and hydraulic radius

Sorry if this doesn't come under science but I think it does. Anyway: Channel form efficiency and Hydraulic Radius, are they the same thing? I'm pretty sure they are but just need to double check. Thanks. 62.136.81.50 20:49, 7 January 2007 (UTC)

Light pollution

How do I measure how light pollution relates to the population of a certain area? And I'm doing this for a science project (hopefully you haven't seen me on another RD yet). —The preceding unsigned comment was added by Member (talk • contribs) 21:46, 7 January 2007 (UTC).

The population of humans, or some sort of fauna? The latter would be far more interesting, but you have to remember that correlation does not equal causation. Anyway, if it is humans, as I am suspecting, then the best way to do it would be get a light metre, and test several, random, spots within a certain area, then calculate the population/km² (or similar measurement) of that area. Do this in many places, and see what you come up with. --liquidGhoul 00:00, 8 January 2007 (UTC)

Also be wary of the moon's phase. --liquidGhoul 00:01, 8 January 2007 (UTC)

Light is not the same as light pollution. I you use a light metre directly on the sky in the middle of night when it is new moon, once with a clear sky and once when it is fully overcast, the difference should be an indication of the local light pollution. Make sure no light from street lights and such can directly reach the light metre; put it in an upward pointing cardboard tube. If done correctly, the reading for the clear sky should be the same as in a totally dark room, since the light from the stars is negligeable. Of course, the exercise is somewhat meaningless if this is done for one place only. That would be as if I invented a new temperature scale and told you that where I am it is currently 714 degrees on the scale of Lambiam: that conveys no information.  --Lambiam^Talk 06:33, 8 January 2007 (UTC)

Biological night vision

Do animals with very good night vision detect colors in "more" brightness? From searching around, what I understand is that animals like owls have more sensitive rods that allow them to see more colors in the dark. But what does that really mean? Do owls see more colors but that the colors are still in low brightness/intensity, or do they somehow see the colors in more brightness (thus they can sense better contrast, etc.)? Thanks in advance 128.163.241.210 21:49, 7 January 2007 (UTC)

There was recently an article in New Scientist where they touched on this. Apparently, people used to think animals that saw in the dark saw only in black and white. However, they now find that nocturnal geckos definitely have colour vision at night, as do certain moths. Work is still needed as to which other animals have colour night vision. The cones in these animals are much longer than in diurnal animals, closer to rods, which is why people initially mistook them for rods. In case this was unclear, Rods are the sensitive, black-and-white cells, cones are usually less sensitive, but used for colour vision. Skittle 22:46, 7 January 2007 (UTC)

Many animals also have a tapetum lucidum at the very back of their eyes, which reflects light back to the retina to give it a second chance of being detected. If the tapetum lucidum can brighten the image enough for cone cells to function, the animal will have colour vision. --Bowlhover 22:54, 7 January 2007 (UTC)

Percentages regarding gas and water components in inspired and expired air

I have searched etc, and to no avail. I have to do a pie chart with % regarding the gas and water components in inspired air, and then in expired air. Do you have any ideas as to the answer, or where I could source it?

Munchkin MunchkinNZ 22:13, 7 January 2007 (UTC)

% gas and water in inspired air is just a factor of humidity isn't it? If you need percentages of the components of air then that article discusses them. As for Expired or exhalation, that's got to do with cellular respiration, but I'm not sure that article talks about % humidity of exhaled air.. Vespine 23:14, 7 January 2007 (UTC)

For inspiratory air Earth's atmosphere has data which I think comes from NASA. I can't find a Wikipedia reference right now, but you can use the following to get your own figures.You have to assume that the expiratory gas you are describing is end-expiratory gas, i.e. gas from the alveoli. Otherwise the effect of dead space ventilation becomes a problem (fortunately one which one cannot illustrate in a pie chart anyway). One also assumes that you ignore trace gases (e.g. Xenon). I'll give you the normal human end-expiratory PO₂ and PCO₂. End expiratory gas has the following characteristics: The PO₂ is 100 mmHg, the PCO₂ is 40 mmHg, the water vapour pressure would be the saturated water vapour pressure at 37°C, the rest of the expired gas would for practical purposes be N₂. The total pressure of the gas would be 1 atmosphere. The partial pressure of a specifc gas divided by the total pressure of the gas mixture gives you the percentage of gas in the mixture (why is that?) So the figures you require for your graph would be: Atmospheric pressure (mmHg), Water vapour pressure at 37°C (mmHg), PCO₂ 40 mmHg, PO₂ 100 mmHg, PN₂ is (Atmospheric - PO₂ - CO₂ - Water vapour at 37°C). Your whole pie would be 1 atmosphere, and the slices the proportion of each of the four gases. Make sure you understand why percentage of composition can be equated to partial pressure (it has to do with one Avogadro). --Seejyb 04:17, 8 January 2007 (UTC)

VSEPR Bonding

Doing some work with the VSEPR theory which is really not my field. Under VSEPR, what's the shape and bond angle of SCl₂, and is it polar? I imagine that's a terribly simple question to you chemists out there, but I'd like to know. Thanks. Cool3 22:20, 7 January 2007 (UTC)

Sulfur dichloride should be very similar to water given the valences of the atoms involved. Two free pairs should give a roughly tetrahedral shape (thus bent for just the atoms) with a bond angle somewhat less than 109°. However, its polarity would be reversed and much reduced because the electronegativity difference between sulfur and chlorine is less than half that between oxygen and hydrogen and has the opposite sign. See also the reference on water's molecular structure linked from the article. (I also linked your theory and gave you the subscript you wanted.) Does that help? --Tardis 01:12, 8 January 2007 (UTC)

Thanks for the answer. That's what I wanted. Would the angle be about 105 degrees like water, or closer to 109 because of the different polarity? Thanks for the subscript too, I've been on wikibreak for a while and forgot the tag. Cool3 01:55, 8 January 2007 (UTC)

The article here on it gives it as 103°, even less than water's. Sorry, but I don't have any explanation for that real value, nor do I know whether VSEPR would predict it. --Tardis 04:25, 8 January 2007 (UTC)

What is oxidation?

I tried looking it up, but I couldn't understand it. Especially, I can't understand how aldehyde: R-CHO is derived from the oxidation of a primary alcohol. In that context, what does oxidation mean? Thank. —The preceding unsigned comment was added by Legolas52 (talk • contribs) 00:44, 8 January 2007 (UTC).

[An] oxidant removes electrons from another substance, and is thus reduced itself. And because it "accepts" electrons it is also called an electron acceptor. Do you understand this? X [Mac Davis] (DESK|How's my driving?) 05:41, 8 January 2007 (UTC)

Oxidation is the loss of electrons. I'm not an organic chemist, but I would say that the primary alcohol loses electrons, thereby allowing it to bind to the R-group. BenC7 11:06, 8 January 2007 (UTC)

This is a fairly high-school level chemistry problem. At that level, there are three mnemonics to keep in mind

1. OIL RIG 1 (Oxidation Is Loss of electrons, Reduction Is Gain)
2. OIL RIG 2 (Oxidation Is Loss of hydrogen, Reduction Is Gain)
3. Oxidation is gain of Oxygen. To reduce, reduce the number of oxygen atoms

The one that applies here is OIL RIG 2, since the alcohol is losing hydrogen. I'm a third-year chemistry undergraduate, so yeah, I'm aware that the above is in absolutely no way rigorous. But it works for the purposes of revising for a high-school-level exam. GeeJo ^(t)⁄_(c) • 12:45, 8 January 2007 (UTC)

effects of solvents on styrofoam

On Wikipedia's "Polystyrene" article, I noticed that it mentions that there are U.S. regulations prohibiting the use of solvents on styrofoam because it "de-foams" it. What is doesn't mention is what specific kinds of non-aqueas solvents de-foam styrofoam and why. Can anyone tell me (very specifically) why solvents have such an effect on polystyrene? EDIT: Sorry, I found it.—The preceding unsigned comment was added by 68.190.7.99 (talk) 23:29, 7 January 2007 (UTC).

Probably the same reasons acetone defoams it! X [Mac Davis] (DESK|How's my driving?) 04:13, 8 January 2007 (UTC)

Architectural / structural terminology

I once lived in San Francisco's Tenderloin in a 1920s Edwardian apartment building. Looking down on it from above, it was shaped like a capital I (although on preview I see that the font here is giving me a straight, stick-shaped I, as opposed to one with a discernable top and bottom). Two store-fronts and a basement constitued the ground floor. Facing the building from the street, on the left there was a maintenance door. If you went through it, you first went through a short passageway before emerging into an open area (by open I mean exposed to the sky). All the buildings' windows that looked down onto this middle area saw an entrance into the basement, access to the boiler, and the tail end of the trash chute, among other things. I've been to the City's official home page, I've gone through the Architectural glossary and more here on Wikipedia, poured over myriad other sites, and I can not, to save my life, put a construction, building, or architectural term to this open area. Mere curiosity isn't fueling my interest; rather, it's work-related. I realize my description is poor, but I hope it will be enough. Guesses, suggestions, site referrals and more - all welcome. Thanks. Wolfgangus 00:02, 8 January 2007 (UTC)

Are you referring to a "well"? I have looked for something in the line of a "service well", but the overwhelming number of hits are for the adverb and adjective "well", and a very few as part of "stairwell". --Seejyb 16:55, 8 January 2007 (UTC)

Coming from a position of total ignorance, and in light of your efforts, I'm uncomfortable saying this, but according to what I'm reading as definitions for a "well", it doesn't seem to qualify. Service well actually has an attractive ring to me, but in usage it may prove misleading. A while back I'd consulted a construction-management friend who suggested the term draftway but this didn't fit either.

Of course, it's entirely possible that it has no name at all, it's just a structural feature, incidental or otherwise ... but even something so insignificant as a nook is honored with a title, and the space I'm trying to name was probably 10 x 30 ft.

Perhaps I can convince someone in the City offices to glance at the blueprints. Surely they're on file and in some fashion a matter of public record. At any rate, thank you so much for your efforts; I'm grateful. Wolfgangus 19:25, 8 January 2007 (UTC)

January 8

electron hotel

i need to know the answer to n=4

For the hotel californium n=42 is the answer.--JWSchmidt 02:38, 8 January 2007 (UTC)

Wouldn't that be n = 98 ? See the periodic table. You can check it out any time you like. StuRat 15:43, 8 January 2007 (UTC)

Your question isn't clear. First off, what is an "electron hotel" ? StuRat 15:49, 8 January 2007 (UTC)

Hi Stu! googled to find this "Complete electron hotel assignment: Create quality representation of electron orbitals from n=1 to n=4, include filling rules (DUE: Mon, 01/08)." I expect we won't be too late! As for the hotel, it may be taken as an analogy, electrons filling orbitals as customers fill rooms (?) -- DLL ^{.. T} 18:13, 8 January 2007 (UTC)

Diffuse/Lambertian reflection

The Lambertian reflectance article says that it is used as a model for diffuse reflection, and for most of its mathematics links to the Lambert's cosine law article which says that blackbodies obey it (the Stefan-Boltzmann law article corroborates this). However, while diffuse reflection provides equal intensity in every direction, and I was under the impression that black-body radiation carried that property (see for instance the end of the linked section: "the radiation is the same in all directions"), the cosine law does not appear to do so. What gives between these three concepts, each of which is attached to the other two in inconsistent ways? --Tardis 02:21, 8 January 2007 (UTC)

Provisions for recharging electric vehicles from the grid by cities

What cities offer on street parking meters and off street parking spaces which are fitted with electric vehicle recharge stations (including area or spaces reserved for electric bikes under 750 watts) and ask a lower price for recharging than the equivalent energy cost of gasoline? -- Barringa 21:13, 7 January 2007 (UTC)

Note that you can't just do a straight comparison of the amount of electricity to drive X distance versus the amount of gasoline to travel the same distance. This is due to the relative efficiency of electrical power versus gasoline is higher for stop and go traffic than constant speed travel. This is because a gasoline engine still must burn fuel to idle, while an electric engine doesn't need to do so. Thus, the cost advantage of electricity will be higher (or the disadvantage lower) for city driving and rush hour driving. StuRat 15:33, 8 January 2007 (UTC)

Is meme a scientific concept?

Is meme a scientific concept? How does one find out? Is there a procedure to determine if a concept is scientific or not? 202.168.50.40 04:21, 8 January 2007 (UTC)

There is no procedure to determine if something is "scientific" or not, and this bothers some people, and it may or may not be good. There are however, a lot of qualifications that we like to say. I recommend reading: falsification, verifiability, Occam's razor, scientific method, logical fallacy, double-blind, skepticism, peer review, and scientific misconduct. Others are welcome to provide more attributes and related information. However, this is something a bit different. I would say this is a scientific concept, if I had the option of saying it was or it wasn't. This is based on its relation to science, although you could say anything really is related to science, since it can be described most likely somehow scientifically. X [Mac Davis] (DESK|How's my driving?) 05:18, 8 January 2007 (UTC)

I would say that gene is much more 'scientific' than meme; the former has a huge number of ancillary terms surrounding it, while meme does not. Vranak

Gods, there's the problem of measuring how scientific words are? Scientifically related sounds better. "Tau meson" is more scientific than "polyethalane" though? There have got to be ranks in science, with something like, brane cosmology, superstring theory, spintronics, and particle physics being way up top. X [Mac Davis] (DESK|How's my driving?) 13:18, 8 January 2007 (UTC)

I'm just using my intuition, as usual. Vranak

In science we study many concepts that are not scientific of and by themselves: hunger, jealousy, pollution, taste, and so on. The scientific method involves hypothesis testing. The aim is that the process is reproducible, so that other scientist who independently test the same hypothesis will reach the same conclusions. This requires that concepts used in the hypothesis be defined in a very precise way (for instance by operationalization), so that the interpretation is not up to the subjective whim of the individual scientist. It is only in the context of this process that the concept becomes a scientific concept. For some concepts (temperature, energy) there is broad consensus among scientists what definitions to use, so you do not have to supply them each time; they are understood. For a concept like jealousy, no such consensus exists and you'd have to supply an operationalization if you want to make it a subject of scientific research. The same applies at present to the meme concept. One can study certain aspects of the reproduction of human cultural behaviour, where said aspects conform to the notion of memetic transmission. To do so in a scientific way, you probably need to be more precise about how you define the notions involved in your study than by saying "self-propagating cultural unit".  --Lambiam^Talk 13:50, 8 January 2007 (UTC)

People such as Ed Wilson have explained the biological basis for memes. The main problem is that while the physical basis of genes has been very well defined by molecular biologists the neural networks that allow memes to exist are still being investigated....it is a much more technically difficult problem. Secondarily, the idea that our genes have influences on our mental lives it not currently a popular idea within the soft sciences. Anyone who studies the links between genes, memes and culture is attacked by thought police who are not interested in the science. --JWSchmidt 18:24, 8 January 2007 (UTC)

Atmospheric pressure

What would the atomospheric pressure be at an elavation euqual to the bottom of the Atlantic seafloor, but uncovered by water? In other words, if there was an open place on earth where the elevation was that low, would the pressure still be significantly different than sea level?

Klatue 06:23, 8 January 2007 (UTC)Klatue

(I fixed the spelling of the question title.)

This table is extracted from the 1986 edition of the "Rubber bible". The left-hand column is depth below sea level in meters, the right hand air pressure in millibars.

                   0   1013.25
                 500   1074.7
                1000   1139.3
                1500   1206.9
                2000   1277.8
                2500   1352.0
                3000   1429.7
                3500   1510.9
                4000   1595.9
                4500   1684.8
                5000   1777.6

The book does not say how the pressures were determined, and does not go to greater depths, but it's easy to extrapolate approximate values to moderately greater depths. Several of the Atlantic's deep basins have points between 5000 and 7500 meters deep, according to the atlas I checked, so the pressures you're askingabout could go to somewhat over 2000 mb, maybe up to around 2300 mb. --Anonymous, elevation 130 m (or so), January 8, 2007, 08:44 (UTC).

Aren't there mine shafts that deep ? In this case, wouldn't it simply be a matter of measuring the air pressure at the bottom of the shaft ? StuRat 15:21, 8 January 2007 (UTC)

I don't know the answer to the original question, but the deepest mine is about 3585 meters [8] or about 11,700 ft. Cheers Geologyguy 19:04, 8 January 2007 (UTC)

Hall effect sensor/switch identification

I'm trying to identify a Hall effect sensor or switch which I am pretty sure is a switch instead of a linear sensor because three of them are recessed into the stator to commutate a 3 phase DC brushless motor through a controller with what I judge to be a square wave from the amount of torque ripple the motor produces under load at startup. Once up to running speed, however, the motor purrs. The only reference I have is a barely visible designation on two of the sensor/switches which is: "F41.5Gc". The "G" in the "5Gc" could be an "0" or a "6" but I'm with 99% confidence sure it is a "G". It is most likely manufactured in Asia, probably China but possibly elsewhere. Allegro sales office says they are not able to identify it and Google produces no reference or clues. Thanks in advance. Barringa 08:27, 8 January 2007 (UTC)

radio broadcasting

What is the name of the phenomenon in which a radio frequency transmitter transmitting with enough power, causes undesired sound to come from the speakers of and audio system. In every instance that I've heard of it occuring, it was caused when someone has audio system too close to a comercial radio station tower or an amateur transmitter that is using too much power.

Thank you for your help.146.53.3.4 08:38, 8 January 2007 (UTC)

See Audio feedback. Natgoo 10:46, 8 January 2007 (UTC)

I don't think the audio feedback article is relevant. There is no signal feedback from receiver to transmitter, either audio or otherwise, is there? The problem is to do with the signal being to strong, but I don't know of any name for the "undesired sound".--Shantavira 11:12, 8 January 2007 (UTC)

Whoops you are correct. I misread the question in my not-yet-caffeinated state. Sorry. Natgoo 11:59, 8 January 2007 (UTC)

Interference caused by Electro-Magnetic waves of Radio Frequency. In Wikipedia, Radio frequency interference (RFI) redirects to Electromagnetic Interference. Apart from its "usefulness" application in electronic warfare, are there beneficial applications of the phenomenon? It would be unusual if no one has found such a useful application, but I can not think of one. --Seejyb

You might be hearing the RF transmission because it is saturating an amplifier circuit, or because of inadequate shielding or a poor connection on a low level input circuit. I have heard a voice radio signal come out of the speaker of a stereo console, even with the unit turned off. In that case it was either Citizens Band or "Ham" radio, but no aspersions, it just happened he was nearby and a commercial transmitter wasn't. The speaker wiring was acting like a Crystal radio, picking up signal voltage from the radio transmitter, and rectifying it by an imperfect metal to metal contact of a loose speaker connection. There was apparently enough capacitance in the speaker or the splitter capacitor between the bass and treble speakers to serve the function of integrating the RF voltage to make the modulating voice signal audible. In times past, radio experimenters would make a detector out of a broken razor blade, and listen to AM signals through headphones, also with no amplification. They would have an inductance and capacitance combination to tune the reception, but if there is a powerful enough local transmitter, it may drown out the others avoiding the need for tuning. People have reportedly heard radio transmissions through fillings in their teeth. Sometimes a Public address amplifier system picks up radio stations or aircraft transmissions for similar reasons, and bypass capacitors are used to shunt out the RF signals from the microphone inputs. Edison 13:23, 8 January 2007 (UTC)

This reminds me of the time I was in the kitchen making breakfast when my boom box, turned off at the time, said to me (quite loudly) "How's it going, good buddy ?". I, of course, said, "It's going just fine, Mr. Radio, and how are you today ?". StuRat 15:17, 8 January 2007 (UTC)

Gravity

From The Core article:

• Moving closer to the center of the Earth should result in a decrease in the force of gravity, but no such effect is shown in the movie.

Really? Why? And how would one observe such an effect—that is to say, what would happen? --210.246.30.238 10:21, 8 January 2007 (UTC)

Lets say you are in the middle of the earth. Half of the earth is above you and half below. They each attract you with equal and opposite force and cancel out. You feel no force. Something like that.WP 10:39, 8 January 2007 (UTC)

Gravity is caused by attraction of objects. When you bore towards the center of a solid sphere, there is less matter below you to pull you down. So you get lighter. At the center you get zero gravity (which way would it point anyway?) The force of gravity is as if all the mass above you didn't even exist; only the mass below you matters. For a mathematical formulation, see the "solid spheres" section of shell theorem. Weregerbil 10:42, 8 January 2007 (UTC)

(after ec) Great film, but dreadful science ! Our article on Earth's gravity says:

If the earth was of perfectly uniform composition then, during a descent to the centre of the earth, gravity would decrease linearly with distance, reaching zero at the centre. In reality, the gravitational field peaks within the Earth at the core-mantle boundary where it has a value of 10.7 m/s².

As Weregerbil says, the decrease in gravity inside a sphere is due to the "shell effect" - inside a spherically symmetric hollow shell, the gravitational attraction due to the shell is equal in all directions, so the net gravitational force on an object inside the shell is zero. The shell theorem article contains a detailed mathematical derivation of this effect. You could observe the effect because objects in the hypothetical capsule would weigh less as it approached the centre of the Earth. Gandalf61 11:03, 8 January 2007 (UTC)

For convenience the earth is considered to be a point mass, therefore in calculations like this all its mass is located just at the centre of the earth. Gravitiy is proportional to distance from the centre, and I have forgotted exactly what my point is, but I think I have just disproved it. Or I might not have.Hidden secret 7 20:57, 8 January 2007 (UTC)

Gravity of the moon? ...the sun?

The discussion above leads me to wonder: What is the value (in Gs, in the vicinity of the Earth) of the moon's gravitational attraction? ...of the sun's gravitational attraction? It's obviously non-trivial since it leads to tides on the Earth's surface, but I've never noticed the value being stated.

Atlant 15:24, 8 January 2007 (UTC)

Well, let's see ... the distance to the Moon is about 64 times the Earth's radius, and its mass is about 1/80 of the Earth's mass, so the force of the moon's gravitational attraction at the Earth's surface is about 1/(80x64x64) of the Earth's surface gravity, so about 3x10^-6g. The distance to the Sun is about 25,000 times the Earth's radius, but its mass is about 33,000 times the Earth's mass, so the force of the Sun's gravitational attraction at the Earth's surface is about 33,000/(25,000x25,000) of the Earth's surface gravity, so about 5.3x10^-4g. So the Sun's gravitational attraction on the Earth is much greater than the Moon's (which makes sense, otherwise the Earth would be in orbit around the Moon instead of around the Sun), but both are miniscule compared to the Earth's surface gravity.

However, the Moon has a much greater effect on the tides than the Sun does because the tides are caused by the gradient of the gravitational field, not its strength. As our article on tides says: Though the gravitational force exerted by the Sun on the Earth is almost 200 times stronger than that exerted by the Moon, the tidal force produced by the Moon is about twice as strong as that produced by the Sun. The reason for this is that the tidal force is related not to the strength of a gravitational field, but to its gradient. The field gradient decreases with distance from the source more rapidly than does the field strength; as the Sun is about 400 times further from the Earth than is the Moon, the gradient of the Sun's field, and thus the tidal force produced by the Sun, is weaker. Gandalf61 15:54, 8 January 2007 (UTC)

As an aside of sorts, the gravitational effects of the moon are actually great enough to produce earth tides, up and down motions in the rocks themselves. These are on the order of an inch or so, but are measurable with Gravimeters and must be corrected for in gravity surveys for oil exploration, for example. Cheers Geologyguy 16:03, 8 January 2007 (UTC)

Thanks! Yes, I read the Tide article, but I was interested in the absolute magnitude of the force rather than the tidal effects, so thanks for the calculations. And with regard to earth effects, I understand (per a recent article in New Scientist magazine that scientists are starting to believe that these tidal forces may serve as part of the ultimate trigger for earthquakes.

Atlant 17:05, 8 January 2007 (UTC)

I was told that the moon has 3 times the gravitational tidal influence of the sun in my Nautical Science classes. —The preceding unsigned comment was added by 138.29.51.251 (talk) 17:37, 8 January 2007 (UTC).

Work-Energy theorem

Is Work-Energy theorem valid in a non-inertial frame of reference?

Assuming you mean dE_kin = F·ds , where F = dp/dt, I think the answer is no. See Special relativity, which gives formulas for kinetic energy and force.  --Lambiam^Talk 14:28, 8 January 2007 (UTC)

work done by a force

I came across something which seemed peculiar to me - "No work is done by a force on an object if the object moves in such a way that the point of application of the force remains fixed."-Is this true?How? —The preceding unsigned comment was added by 59.93.76.73 (talk) 14:28, 8 January 2007 (UTC).

I'd say no, that's false. Consider two rollers with a tube between them being pulled through the rollers and raised in height. The location of the contact between the rollers and the tube remains constant, yet the tube ends up higher, and thus with more gravitational potential energy, showing that work was done. If they meant that "the point of application of the force remains fixed relative to the moving object", we could disprove that with the example of a rocket. The force remains at the end of the rocket during the entire burn, but still results in work being done on the rocket, again as shown by it ending up higher, with more gravitational potential energy. StuRat 15:06, 8 January 2007 (UTC)

Yes, the statement is true—provided that you're careful about your definitions. The 'point of application' of the force must remain fixed relative to two points: the object itself, and a fixed external frame of reference. In the 'roller' example above, this condition doesn't hold, as the point of contact on the tube is being moved. In the 'rocket' example, choosing the rocket itself as a frame of reference doesn't make sense.

From a technical (some might say semantic) standpoint It falls out of the definition of work (see mechanical work for details and formulae), that requires force to be applied over a distance for work to be done.

From a common sense perspective, the quoted rule applies to 'static' situations, like a brick sitting on a table. There's obviously a force being applied to the brick by the table, and vice versa :gravity pulls down on the brick, the table resists the brick falling through it. There isn't energy being created out of nothing by this interaction; the brick and table don't get warmer, the brick doesn't levitate, etc. There is a force being applied to the brick, but the point of contact is fixed, hence no work is done. TenOfAllTrades(talk) 18:22, 8 January 2007 (UTC)

What is the antonym of feral?

What is the word that describes a wild animal that appears domesticated. This usually happens on an individual basis, like a deer you can feed out of hand. There are stories about wild animals that seemed tame, but then just take off for the wild again.

The word isn't taming, nor is it domestication. It is a rare, technical term. I saw it once in 'New Scientist', but I can't remember what it is for the life of me. Can you help?

Meredith15:52, 8 January 2007 (UTC)15:52, 8 January 2007 (UTC)~

Habituated? —The preceding unsigned comment was added by 138.29.51.251 (talk) 17:38, 8 January 2007 (UTC).

Gas Leak

What are some possible consequences of a city wide natural gas leak? Assuming also trace amounts of Mercaptan, other than the obvious smell of sulfur, which is unpleasent to say the least--66.65.156.162 16:03, 8 January 2007 (UTC)

A good place to start would be an MSDS for natural gas. (Here's one, in PDF.) This outlines some of the health and other hazards associated with natural gas. At moderate concentrations, natural gas is highly flammable; at very high concentrations it is an asphyxiant. TenOfAllTrades(talk) 18:26, 8 January 2007 (UTC)

Bananas

I know that bananas have alot of pottasium. But, what are the benefits or dangers of pottasium? —The preceding unsigned comment was added by 216.253.128.27 (talk) 16:48, 8 January 2007 (UTC).

The article entitled potassium will tell you a lot about potassium; the section of that article entited "Potassium in nutrition and medicine" will probably be most helpful to you. DMacks 17:35, 8 January 2007 (UTC)

Clinical Physiologist.

I am awaiting notification as to whether I am successful in my job application for a position as a Trainee Clinical Respiratory Physiologist. I would like to know what kind of uniform i'd wear in the hospital. Would it be scrubs, normal clothes, white coat etc.

Thanks. Christopher. —The preceding unsigned comment was added by 85.210.129.119 (talk) 18:37, 8 January 2007 (UTC).

Darwinism; the human race compared to other animals

As I understand it, Darwin explains the existance of so many species by a very slow process of evolution whereby the fittest survive. Did he, or any of his successors postulate any explanation for the fact that, although all species appear to have changed over time, the changes in homo sapiens and the capacities that have been developed as a result of them seem so much more spectacular? Put another way, why has no other species developed the use of language, artistic abilities etc etc beyond a rudimentary level?

This is science, so most of it is random chance. And no other animals have much chance to develop art &c, as they are too busy trying to survive.Hidden secret 7 19:39, 8 January 2007 (UTC)

Some other animals have some kind of language like: Birds, Dolphins and Whales. --helohe (talk) 19:55, 8 January 2007 (UTC)

Also, the development of culture is fairly recent in evolutionary time, and once it happened our species quickly achieved a huge advantage. In short, it seems spectacular because we were the first ones, and because it happened just a while back. — Kieff 21:12, 8 January 2007 (UTC)

Just droppin' objects

I'm pretty ignorant. So I need help understanding what the deal is with falling objects all falling at the same rate. While I know and can see this to be true (doing some 'experiments' of my own), I wonder why. If all objects fall at the same rate without the influence of air resistance, when why are some of them heavier than others? If I put an object on the scales it might be 'pulled down' by Earth's gravity more or less than another object. So it would seem that the 'hardness' of the force on the object does not affect the speed that it falls at. That's pretty counterintuitive, as if I shove an object in a gravityless (?) environment hard it'll go faster than if I tap it gently (that'd probably a better analogy if I were tugging on an attached string hard or softly, but whatever). So what's the hole in my understanding? Vitriol 19:35, 8 January 2007 (UTC)

Well air resistance of course is a force that retards falling in an atmosphere, much as friction retards sliding of something sliding on the ground. Air resitance can be so great that a falling object reaches a terminal velocity, and its rate of fall does not increase any more. We do not really understand gravity. All we can do is measure it and form theories or laws about it, like Newton's law of gravity of Einstein's theory of gravity. The weight does not affect the speed in a vacuum, you are correct. Aristotle felt that the weight would affect the speed, and heavier objects would fall faster. Galileo tested this (by rolling objects on an inclined plane, not by dropping things from the Tower of Piza as the popular myth goes). Galileo found all objects fall at the same rate. So...there you have it. We do not know why really just that it happens. --Filll 19:41, 8 January 2007 (UTC)

The trick is that you have to account for mass. Recall one of the formulations of Newton's Second Law of Motion: F = ma (F = force, m = mass, a = acceleration). Rearrange and you get a = F/m; that is, to get the same acceleration of a large mass (compared to a smaller mass) requires a correspondingly larger force. Conveniently, the gravitational force scales precisely with the mass (inertia) of the object, so all objects accelerate at the same rate under the influence of gravity.

Now, there's a much more subtle underlying question that physicists haven't been able to answer satisfactorily here. You can measure mass in a couple of different ways. Gravitational mass is a measure of how strongly an object attracts other matter through the force of gravity. Inertial mass is essentially a measure of how strongly an object resists acceleration. Why is it that these two ways of measuring mass always work out to be equivalent? TenOfAllTrades(talk) 19:52, 8 January 2007 (UTC)

See, I don't think I'm understanding still as what I can glean from what you say a object with a larger mass is pulled on harder by gravity to get it moving in the first place... and gravity doesn't pull on some things harder than others. Doesn't it? Vitriol 20:02, 8 January 2007 (UTC)

Yes, gravity DOES "pull harder" on heavy objects than on lighter ones, according to Newton's Law of universal gravitation. The gravitational force exerted on one object by another is linearly proportional to the mass of the object. -sthomson06 (Talk) 20:53, 8 January 2007 (UTC)

Think about it like this: gravity pulls harder on objects with more mass. But objects with more mass are also harder to accelerate. From the equation F=ma, imagine if you multiplied m by 3 and also F by 3. 3F=3ma, so there's no need to change a. --Bowlhover 21:12, 8 January 2007 (UTC)

N.H. Horowitz

I have found paper after paper by this guy in biology and exobiology etc. He is a professor at Caltech. Is he famous ? Does he need his own biography?--Filll 19:37, 8 January 2007 (UTC)

I-V characteristics of Josephson junctions

Why do people investigate the I-V characteristics of Josephson Junctions, other than for the fact that the I-V curves are not what you would expect from a normal semiconductor junction? i.e. what kind of physical impact / application do the I-V characteristics have say, for example, in SQUIDs (Superconducting Quantum Interference Devices)? --RaGe 20:43, 8 January 2007 (UTC)

Looking for scientific journals

Today on new pages I ran accross someone who has come up with a slightly different theory of the origin of the solar system. He was trying to use Wikipedia to publish his original thought. I prodded his article and explained to him why it doesn't belong on Wikipedia. Now he'd like me to suggest other places that might be more receptive. I'd like to suggest he try some scientific journals but don't know any specific journals to point him towards.

What are some names of journals where he might be able to try to get his theories published? ~ ONUnicorn^{(Talk|Contribs)}problem solving 21:13, 8 January 2007 (UTC)