Wikipedia:Reference desk/Archives/Science/2006 August 17

Humanities Science Mathematics Computing/IT Language Miscellaneous Archives

The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions at one of the pages linked to above.

< August 16 Science desk archive August 18 >

Where is the center of earth's land?

Hello,

I was wondering, what is the "average place of land"?

This is how I would define it :

Consider earth as a ball with radius R. Let the origin be its center.

Let A be that part of the surface where there is land.

Define ${\vec {v}}=\int _{A}{\vec {r}}d\sigma$

where ${\vec {r}}$ is a threedimensional vector from the origin to that point on the surface.

The average place would then be $R{\frac {\vec {v}}{||{\vec {v}}||}}$

My guess would be somewhere in Africa?? Evilbu 00:12, 17 August 2006 (UTC)

Don't think just because it is in the center of the map, it is the center of land. I believe it would be in the Middle East, or the Indian subcontinent, but that's just my mind-model with weighting and the shape of the Earth in mind. Probably more accuratley somewhere in the Indian Ocean. — [Mac Davis] (talk)

Well, it will be somewhere inside the earth, deep within the surface, by the given definition. Of course I don't know exactly where, but given that the pacific ocean is the biggest region with no land, it will probably be somewhere on the other side from the center of the earth from the Pacific ocean. --Bmk 02:41, 17 August 2006 (UTC)

Nevermind, I retract that comment. I reread the definition, and it would indeed be on the surface :) --Bmk 03:11, 17 August 2006 (UTC)

I take that the centre of the ball is the origin. Assuming ${\vec {r}}$ is distinct from zero, the definition given results in a vector of length R, so that is not inside. --Lambiam^Talk 03:19, 17 August 2006 (UTC)

Yes, sorry for the confusion. I changed the question, so that it is clear the origin is the center (as I said, assume that earth is a ball)

Does anyone "have" the world in coordinates? Evilbu 16:50, 17 August 2006 (UTC)

There are other ways to go about this... you could find the centre of the largest connected piece of land, for instance. If you wanted to work with lattitude and longitude coordinates, you might have trouble as both coordinate systems wrap around... should the average be adjusted up or down when you add a point? (I can't think of a way to resolve this at the moment.) The one you've suggested sounds good. - Rainwarrior 19:17, 17 August 2006 (UTC)

I wrote a small program in C to calculate this. I used the black pixels in http://visibleearth.nasa.gov/view_rec.php?id=8392, translating the pixels to X,Y,Z coordinates, and taking a weighted average of them (proportional to $cos(\phi )$, with $\phi$ 0 on the equator, and + or - $\pi$ on the poles). The result is 4228.65km beneath the surface, 43°29'41.29" N, 28°7'51.02" E. Here is a link on google maps - sipa1024 23:12, 17 August 2006 (UTC)

Good work! - Rainwarrior 23:46, 17 August 2006 (UTC)

Could you explain this process more? most importantly how you got a result at a distance below the earth's surface, given the information available. --Jmeden2000 15:55, 21 August 2006 (UTC)

The program iterates over all pixels in the image, transforming them to spherical coordinates (r=1,phi & theta in function of row/column in the image), and those spherical coordinates to cartesian coordinates x,y,z. These x,y,z are averaged over all black pixels (by summing them together multiplied with cos(phi), which is proportional to the surface size corresponding with the pixel, en dividing this sum by the sum of all cos(phi)'s). The result is an average x,y,z, which is transformed back to spherical coordinates, and the N & E degrees are calculated from phi and theta, and the depth is earth_radius*(1-R). In the mean time have runned the program again on data from here (43200x21600 image), and the result is 42°22'27.87" N, 29°10'35.38" E, 4244.33 km depth. By the way, evilbu's original question normalised the vector from the center to the average so it was on the earth's surface. I didn't do this, but it's trivial that answer is the same but just at 0km depth :) -- sipa1024 2:01, 22 August 2006 (UTC)

Thank you sipa1024, well done and welcome to Wikipedia! That place is in Bulgaria, about 10 kilometers from Balchik, a Black Sea coastal town. Evilbu 23:30, 17 August 2006 (UTC)

Wikipedia, the encyclopedia anyone can edit....

as long as they have a 4 year degree in math and physics. Isn't it a bit elitest of wikipedia to write all the science and math articles filled with equations and other things that no one can be expected to understand? isn't it contrary to the personal liberty of all peoples that wikipedia should be written in such a way as to restrict knowledge from the common man?--Milboage 00:28, 17 August 2006 (UTC)

If you don't have an advanced understanding of high maths and physics, why on earth would you attempt to write an edit that required such knowledge? Monolingual Basque people are free to edit this too, but they refrain from doing so because they don't understand it, just as you don't understand integrals and trigonometry or whatever. It's inappropriate to require all physics articles to either stick with basic arithmetic or explain the basics of calculus anytime they need to demonstrate a proof just so Joe Everyman can understand it. Why not take a class or (heh) read up the Wikipedia article if you're so interested in a subject? Hyenaste ^(tell) 00:44, 17 August 2006 (UTC)

You can always contribute to the Simple English Wikipedia! --Ed (Edgar181) 01:00, 17 August 2006 (UTC)

I have often complained about this. I know that no math geeks will ever be able to wrap their brain around this complaint, but I'll try again. Being able to recite an equation is not intelligence. Being able to mix and match equations is not intelligence. It is no more complicated than playing with Legos. Being able to take an equation and explain it without math is intelligence. Einstein wasn't a genius because he looked at a graph of energy to mass ratios and realized that it was a constant relationship with a constant equal to the square of the speed of light. He was a genius because he was able to explain relativity without using equations. Steven Hawking is similar. Read A Brief History of Time and notice how few equations there are. Even when he uses one, he quickly dismisses it and goes on to explain the concept in plain English. Unfortunatly, Wikipedia has a bunch of math geeks who are quick to delete any attempt to explain the equations. Why? They claim, "It is right there in the equation! You don't need to explain it!" They will never understand that it isn't a matter of "need". It is a matter of intelligence - even genius - to explain the math concepts without formulas. So, in my opinion, the math geeks just feel inferior and delete anything that they can't do themselves. --Kainaw ^(talk) 01:10, 17 August 2006 (UTC)

Isn't math a simplification of English? One equation of medium complexity = a paragraph of english, to use an equation. Math and english can mesh perfectly if you use the right words, but physics professors sometimes lack in that area.

Well it might help you if you got your words right too. The plural of LEGO is LEGO. No such things as LEGOS. pschemp | talk 03:58, 17 August 2006 (UTC)

If you think you understand relativity "in plain English", you're wrong. Can't be done. Some of the motivations? Sure. Some of the consequences? Those, too. The theory itself? You're only fooling yourself. Until you get into the equations, you simply don't really understand it, period. And that goes for lots of other things.

But achieving an understanding of "some of the motivations and some of the consequences", by a large portion of the population, is infinitely better than the majority of the population having absolutely no clue what relativity means, whatsoever, isn't it ? StuRat 07:43, 17 August 2006 (UTC)

I agree. In addition, it would be impossible to understand quantum electrodynamics using only words. — [Mac Davis] (talk)

Now, it's a valid criticism that in many cases there is accessible material to present, and it's not presented, or not as clearly as it could be. That's absolutely an area for improvement. But it doesn't mean the specialized material shouldn't be there. --Trovatore 01:24, 17 August 2006 (UTC)

Math is of extreme importance to some people. Equations are little meaningless symbols that describe the world around us. Einstein was not a genius because he was able to explain relative without using equations, because he was. You can't just say something you know, you have to write it down, and the language of the universe is mathematics. Stephen Hawking mentioned that in his book a few times I believe. His book was popularized physics, meaning it is meant for the sole purpose of mass nonfiction entertainment. Who the hell would want to read a mathbook for fun? Well real mathematicians and physicists do. I do. If you've ever cracked open a college quantum physics text book... there's quite a bit of math. In fact it is almost all integrals, differentials, partial derivatives, and summations and deltas and dot products. The last time I checked M-theory they had a layman, and smartman section :) That's good. — [Mac Davis] (talk)

I don't think implying that laymen aren't smart is justified. They may very well have higher IQ's than the experts, but just lack experience on this particular topic. StuRat 21:40, 17 August 2006 (UTC)

I sympathize with both "camps" here - and I think there is plenty of room for compromise. For every complex physics or mathematics article, there can be a full mathematical treatement as well as an English interpretation of the idea intended for those unwilling or unable to go through the mathematics. No need for an "either or", I think. BTW, one of my favorite quotes by Feynman here is that "if you can't explain it to a college freshman, you don't understand it yourself" (inexact quote, too lazy to look up). On the other hand, as someone mentioned, "mathematics is the language of the universe". --Bmk 02:32, 17 August 2006 (UTC)

The issue I see is that some level of simplification is required to make complex topics more understandable to the general public. For example, when explaining atoms, the model of electrons in circular orbits about the nucleus is easiest to understand. The probability wave function, orbital shells and energy quanta concepts should only be introduced after the basics are understood. However, when academics get hold of an article, they frequently delete any simplified explanation because it's "wrong". This leaves the general public incapable of understanding the article. StuRat 02:56, 17 August 2006 (UTC)

• It is wrong, it's much simpler to say that the universe is a large poorly lit christmas bulb that's over 200 billion AUs wide, but we can't put that in an article--71.247.125.144 03:24, 17 August 2006 (UTC)

• So then you're in the camp that says "no simplifications can ever be permitted, and if that means the general public can't understand our articles, well, screw 'em". StuRat 03:44, 17 August 2006 (UTC)

• But it's not a simplification at all, it's simply an older theory that really doesn't mesh well with much of anything any more. Electrons don't orbit around at atom at all, why teach something that's false just because it's easier? If anything, this just makes it harder for people to understand concepts like this once they get to a more advanced level. Hence all the questions from people who think that "spin" is describing the act of an electron physically spinning around an atom..--71.247.125.144 12:51, 17 August 2006 (UTC)

• It's a version which can actually be shown visually, and is all that's needed for basic chemistry, using the outer circular orbit as the valence shell, for example. For most people, this is all they need. For those who go on to theoretical physics, they can learn the more difficult to understand models. For an analogy, globes of the Earth are also "wrong", in that the Earth isn't a hollow cardboard sphere with countries in different colors, but they are still quite useful. StuRat 15:27, 17 August 2006 (UTC)

Well, no. To have an article on, say, the exterior derivative without equations would be doubly useless: Serious students couldn't get any useful information from it, and casual readers, if they ever cared about such a thing, would have to spend hours reading other dense articles just to understand the "plain English" explanation. Further, as someone pointed out above, though every article can be edited by everyone, not every article should be edited by everyone. You should only edit articles you actually know something about, and if your knowledge of math doesn't go beyond college algebra then you shouldn't be editing math articles. But let me hasten to add that this isn't because math is special, or because I'm a snotty nerd with a math degree. I don't know jack about Hindi phonology, so I don't edit it. The same should go for everyone and every subject.

I don't know much about Hindi phonology either, funnily enough. But thanks for the mention.  :--) JackofOz 09:46, 17 August 2006 (UTC)

Then how would you like to try to read an article on Hindi phonology which is only understandable by those with a phD in the subject ? StuRat 07:15, 17 August 2006 (UTC)

That said, there's a good argument for, where possible, giving both a technical and non-technical explanation. The articles on relativity do a fine job of that, as do articles on several other well-known physics topics. Unfortunately that's just not always practical. It really does take a rare talent to convey these advanced ideas in simple ways, and for many of them it's just not worth the effort (see above r.e. "exterior derivative"). --George 05:06, 17 August 2006 (UTC)

The need for simple explanations also varies by topic. Those which are terms known to the layman, like "atomic theory" or "relativity", are likely to be viewed by laymen, and should thus have at least a portion which is simplified enough to be understandable by the layman. The simple part should come first, with all the equations coming later. On the other hand, topics which are of no interest to anyone but academics can be as needlessly complicated as they choose to make them, it's of no concern to me. StuRat 07:11, 17 August 2006 (UTC)

"The untrained man reads a paper on natural science and thinks: ‘Now why couldn't he explain this in simple language.’ He can't seem to realize that what he tried to read was the simplest possible language – for that subject matter. In fact, a great deal of natural philosophy is simply a process of linguistic simplification – an effort to invent languages in which half a page of equations can express an idea which could not be stated in less than a thousand pages of so-called ‘simple’ language." —Thon Taddeo in A Canticle for Leibowitz

• There are much more fields than science and maths. So you don't need to edit those if you don't get them. While some may need some edits to make them more accessible, I think it's pretty much impossible to write maths articles and articles on some science issues without equations. And some articles will be hard to access to lay men no matter what you do. You can't expect someone without a degree to go indepth into quantum physics, for example. For articles like that you should stick to the intros. - Mgm|^(talk) 07:30, 17 August 2006 (UTC)

• Yes, there are "much more fields", like grammar, for example. StuRat 15:42, 17 August 2006 (UTC)

I doesn't edit those :-) --Serie 21:48, 17 August 2006 (UTC)

I totally agree with StuRat again for a change (?). Articles should (initially) be written by people who know much about the subject, but they tend to have too little understanding of how little understanding the non-initiated have. So after they are 'done' (which they never are af course - problem) others should copy-edit at least the intro to make that understandable to laymen.

But this is not restricted to scientific subjects. I've got an ongoing issue over this at British Isles (terminology). I started that article to give people who are confused by the whole terminology (like I was) a simple overview, thus:

• Britain = Great Britain = England + Wales + Scotland (politically) = the largest island (geographically)

• The United Kingdom (political) = England + Wales + Scotland + Northern Ireland

• The British Isles (geographical) = Great Britain (the island) + Ireland (the island) + many smaller surrounding islands

This may not be entirely correct, but it will instantly clear up a lot of issues for those who haven't a clue. Exceptions to this can then follow. At the moment it's relatively ok because I recently changed it, but over time people will start adding stuff, clogging up the intro, which goes against the purpose of the article.

More in general, I think an article should start with a simple explanation for the non-initiated and then go ever deeper, so that people can read from the top down until they have reached the point where it goes to deep for them. Of course this is an ideal that is difficult to realise, partly because there also has to be a division in differnt sub-subjects (although that can be largely somved by referring to more specialised articles), but one should try to come as close as possible to that ideal as possible. By the way, the simple English Wikipedia is meant for people who are less proficient at the language, not the subject.

That said, something that slightly irritates me is writing entities out, like 'kilometres per hour'. Why not 'km/h'? Or can we not assume people to know what that means? But then that's what we have links for. DirkvdM 07:44, 17 August 2006 (UTC)

Music cannot be translated into words without loss of content. Reading the lyrics is not the same as hearing the song. Why should we expect mathematics to be any less rich and deep ? Gandalf61 11:17, 17 August 2006 (UTC)

Using the music analogy, imagine we are in a world where most people are deaf. Should we say "you can't really understand music, so go away, this article is only for those who can hear". Most people can't understand math formulae either, so an article which only contains those, and no simple explanation, says the same thing to them: "get lost !". StuRat 15:42, 17 August 2006 (UTC)

Yes, that would have completely killed the soundless music industry, and prevented deaf music from growing into the multimillion dollar business that it is today o: --152.163.100.74 17:15, 17 August 2006 (UTC)

The deaf can appreciate many aspects of music, like the poetry in good lyrics. They can also "hear" virbations, and have even been known to dance to them. StuRat 18:28, 17 August 2006 (UTC)

For an example of why 'simple' explanations aren't always right: simple.wikipedia on Heisenberg: that isn't simple, it's wrong, without operators, commutators, and wave functions, certian aspects of QM just can't be translated into plain English--71.247.125.144 13:00, 17 August 2006 (UTC)

It is completely true that articles should be made at least someone comprehensible to people without advanced degrees. Encyclopedias are meant to be general reference works, not specialized subjects. That being said, one does not have to re-explain the wheel each time if you edit carefully. If I wanted to explain how a nuclear bomb worked, I wouldn't go over all of the details of nuclear fission, what an atomic nucleus was, and so forth, each and every time I brought it up. The linking system makes it easy to reference other topics and allow the reader to go investigate if they are stumped.

Unfortunately many of our technical/math/science articles are not written with the slightest idea that a non-expert would be wanting to read the subject. Articles are supposed to have introductions which provide context and explain in layman's terms what the rest of the article is to be about. Even something like, "This is useful for solving these sorts of problems," (the latter being linked) is valueable, since it allows one to get someone of an idea of what the point is.

Obviously you can't re-write all articles to make perfect sense to someone who understands nothing about the subject. But you should be able to make it so that by clicking around, they can get at least a passing understanding of where a given topic fits within a larger field. Many of our articles do this, because people have taken the effort to make them do that. Many unfortunately do not. I am surprised at the stubbornness of some of those who have commented here. The entire point is to share knowledge, and sometimes that means finding ways to explain it that are clear and can be readable by all. Put the general description first ("This principle relates to X and Y, and is useful for Z problems.") and the technical description only after that ("Expressed as the following dozen equations..."). And people who argue that math is clearer than English are obviously and clearly missing the point. Generally speaking our articles should be comprehensible by someone with a little college education. That doesn't mean they should understand the entire article or the details, but they should understand what the article is basically about. --Fastfission 15:48, 17 August 2006 (UTC)

I agree. Expanding on your note about articles that are missing a simplified explanation - even a simplified introduction. It isn't that nobody is trying to write a simplified section. The math elite are deleting the simplified sections with comments like, "That is already expressed in the formula." The rule should be that even if it is already expressed as a formula, if someone wants to simplify or generalize the topic for the non-formula-reading public, they should be allowed to do so. As it is right now, the math elite are hijacking all math-related articles and fighting hard to keep non-math people out of their private playground with comments like, "If you can't read the formula, you won't understand it anyway." Well, I feel they should all stop using Wikipedia. If you don't know PHP (the scripting language behind Wikipedia) and you don't know the algorithm used to handle diff/patch functions and you don't know server load balancing techniques and you don't know how to create your own TCP/IP packets... you won't understand anything on Wikipedia. So, just go away. --Kainaw ^(talk) 15:59, 17 August 2006 (UTC)

Kainaw, as it happens, recently, before your intervention on this page, I happened to be looking at your user page and saw your strongly expressed opinion, and I took a look back through your contrib history to see if I could figure out what prompted it. Couldn't find it. Could you please point me to the example(s) you have in mind, so I can see what you're talking about? It's certainly possible that your characterizations are accurate, for that example (or three); I'm not saying this sort of thing doesn't go on. On the other hand, if you're rephrasing equations literally in English (say, annotating "E=mc²" with "that is, energy equals mass times the square of the speed of light"), well, that's just silly. So I'd really like to see the example. --Trovatore 16:46, 17 August 2006 (UTC)

Geez, Trovatore, doesn't that sound a bit "nosy" to you ? StuRat 18:12, 17 August 2006 (UTC)

Honestly, I just don't see it, most wikipedia articles are written well below university level, in terms of the math that they use, if you take an article on something like QED and drop it from a freshman university level, down to a high school level, it loses all meaning--152.163.100.74 17:19, 17 August 2006 (UTC)

(inserted above next post after edit conflict)

Look at Zipf's Law - specifically the last paragraph in the introduction. I had to fight for that. Everyone involved kept saying "It's in the equations - just look further down the article, stupid." I said that it is easy to explain in English - without a formula (I don't consider 1/f a "formula"). This went back and forth - even including people telling me that what I wrote is entirely incorrect (though it is a paraphrasing of Zipf's own work). Finally, the paragraph remains and anyone who doesn't understand the "simple" formula has a shot at understanding the 1/f relationship. I ran into the same issue on a statistics page (standard deviation, I believe). Do you need a degree to understand standard deviation? No. Just go through it step by step: Calculate the mean. Subtract each value from the mean and square the result. Average the results. Take the square root of that. I haven't checked the article lately, but I am certain that the clear English description of how to calculate StdDev has been replaced by formulas. I avoid the math articles now because I find the elitist attitude of the math geeks annoying. --Kainaw ^(talk) 17:49, 17 August 2006 (UTC)

I just looked at the tuple article and it is written in a way that I like. The intro is clear and easy to understand. Then, there is a Formal Definition section that is heavily laden with math-speak. After that is a Computer Science section heavily laden with pseudo-code. If you don't know squat about math or computers, you can still read the intro and have a firm grasp on the concept of a tuple. --Kainaw ^(talk) 19:18, 17 August 2006 (UTC)

Any scientific concept can be explained both at a complex mathematical level, such as in a refereed journal or an advanced college textbook, at the lesser level of Scientific American, and at an introductory level such as in TV science programs or illustrated books for scientifically-inclined children. If a practicioner of a field cannot explain the principles of something in words, at various levels of specialized terminology, I question that he really understands it. Electromagnetic wave theory was first laid out by Michael Faraday, who had zero algebra and no ability to write or solve equations. The equations were set down by Maxwell, who discussed the underlying experiments, findings, and predictions with Faraday and wrote that their conceptions agreed in every detail. In a college class in engineering, one student told the professor she could solve the equations and get the right answer, but she did not have an understanding of the phenomena. He said that getting the right answer was all there was to understanding. I beg to differ. A verbal or a physical understanding of the phenomena described by equations contributes meaning beyond symbol manipulation. The calculus equation is often developed long after the laboratory phenomena have been studied. Perhaps the break here is between theoretical physics, say, and experimental physics. I am amused when I read a physics textbook which asserts that Joseph Henry or other 19th century physicists stated thus and such, then the text shows a differential equation Henry never wrote, never saw, and might not have been able to comprehend. Edison 17:46, 17 August 2006 (UTC)

Since the goal of Wikipedia is to spread knowledge, it's ironic that many of the academics here seem to have the opposite effect (restricting access to knowledge by removing all simplified explanations). StuRat 18:20, 17 August 2006 (UTC)

I have thought of making the same complain myself. Many articles seem written by mathematicians for mathematicians. While its good to have the maths stuff for those who can understand it, please could people try to include a simpler layman's description at the beginning of the article. After all, an encycopaedia should be about explaining things to people, not just providing a [[precis] of knowledge.

• I still don't understand the complaint, wikipedia articles are already written below the level that they would be taught in a university. Would you suggest an article on spin states that was written for a grade 7 or 8 audience? Most articles are already written at a high school level, and suffer for it. I'll never understand people who are so put off by even having one or two equantions at the bottom of a page that they'll just give up--205.188.116.74 21:41, 17 August 2006 (UTC)

I am in complete agreement with Edison's comments above. The article should not be limited to either the layman or expert level. All descriptions should be heirarchical, proceeding from the general and "plain english" description, all the way up to the necessary technical details. One does not negate the other. - Rainwarrior 00:42, 18 August 2006 (UTC)

I would add the following to refocus on the issue: A plain english - even an extremely generalized almost correct description - should be allowed even though it is also repeated in the equations. The complaint continually comes back to the refusal of math-focused editors deleting English descriptions of topics because "it is in the equation". This is not an attempt to remove the equations. It is an attempt to allow non-equation-reading people to get an ounce of insight into math topics and, possibly, take enough interest in them to learn to read the equations. --Kainaw ^(talk) 13:06, 18 August 2006 (UTC)

Except that I've never seen anyone do that, ever. The only time people remove 'simplified' text, is when the 'simplification' comes as the result of a severe misunderstanding of the material, where people tend add things like 'common knowledge' to an article. For instance, suppose that a cat, the biological organism, exists only as a mathematical abstraction, now suppose that someone with no knowledge of cats comes along and then tries to add some 'common knowledge' in a factual way, such as, "..It is commonly understood that cats, if they were real, have 9 lives, and can come back to life whenever they feel like it, much like timelords" That's not being removed because it's not an equation, it's being removed because, while simple, is written from the perspective of someone who obviously doesn't understand the topic of the article. And while in the case of cats it would be pretty easy to explain the error to the person in question, but supposing that 'cats' were purely theoretical, and no one had ever seen one in person, then such an explanation would probably degenerate into a philosophical debate on whether you could really prove that cats don't literally have 9 lives. "No, cats may be theoretical, but my model shows that they can't come back from the dead", "no, but you model is all in math, i'm just trying to simplify it, most people don't know math and shouldn't have to", "yes, but cats don't actually have the ability to defy death", "it's close enough, it's just so people can understand cats without having math", "yes, but that's just plain wrong, cats don't literally have 9 lives", etc.....--71.247.125.144 13:30, 18 August 2006 (UTC)

Science fiction: stellar explosions and disc formation.

In many science fiction television programs, particularly - in my memory - star trek, when a stellar object such as a planet or star, etc. explodeds the ejecta forms a two-dimensional disc which rapidly expands from the centre of the explosion. Is there a scientific basis underlying this effect, or is it purely artistic license? I looked at accretion disc, but it only appears to deal with collapsing matter, not mentioning ejected matter; ejecta is also no help. Thanks in dadpants,
-somesortamoniker. 88.144.1.63 02:09, 17 August 2006 (UTC)

Nah, I think it's just for visual coolness. I have nothing to back this up, except the intuition that nothing would cause such a violent asymmetry in the explosion. --Bmk 02:38, 17 August 2006 (UTC)

I first noticed this in Star Wars, when the Death Star exploded. It had a deep equatorial trench, however, which might be presumed to cause that effect. A rapid rotation might also cause such an effect. In general, however, if a spherical object exploded, I would expect a spherical debris field. StuRat 02:41, 17 August 2006 (UTC)

I should mention that planets don't usually spontaneously explode, so if they do, there's a mighty funky mechanism at work, probably available only from Starfleet command, which means it could look like anything. --Bmk

I second visual coolness. — [Mac Davis] (talk)

When there's gravity and an atmosphere about, there's lots of interesting shapes that explosions can take, mushroom clouds, dust rings. In space, they should probably just explode apart in all directions, and the fires would probably disappear quickly as the oxygen escapes. I think it was just modeled after explosions on earth that produce an outwardly expanding shock wave, and figured it looked more interesting given a planar shape than a spherical one. The earliest one of these I can think of in movies would probably have been from the end of Alien. - Rainwarrior 04:06, 17 August 2006 (UTC)

It is widely beleived that supernova explosions are one way to produce the transient relativistic jets we see as gamma ray bursts in addition to a general blowing apart in all directions. So instead of a blast along the equator, these would be localized pulses, possibly aligned with the axis of rotation. Dragons flight 07:43, 17 August 2006 (UTC)

File:Nova-NASA.gif

Two novas, one of each type. Here, the spherical one looks a lot cooler, I think. DirkvdM 07:55, 17 August 2006 (UTC)

I think they're both spherical, it's just harder to see a thin spherical shell when viewed straight on (in the middle) than when viewed edge-on. StuRat 15:11, 17 August 2006 (UTC)

I was thinking the same thing. The fiery ring might just be the edge of a sphere which shows up only because it's thicker from that angle. - Rainwarrior 19:11, 17 August 2006 (UTC)

Doner kebabs

Why do they taste so nice when I eat them, yet make my stomach feel soo bad up to 12 hours later? --Kurt Shaped Box 05:53, 17 August 2006 (UTC)

Has every single donair you've ever eaten made you feel this way? If yes, then you might be allergic to something in them. If it's just one vendor, and you don't actually get sick from them, I'd guess either it's that they're using homous and you aren't used to eating beans, or the yogourt sauce (tzatziki, although it has a different name) is a bit off. Anchoress 06:02, 17 August 2006 (UTC)

The ones round here (UK) are mutton, salad and garlic mayo in a pita bread. I always feel bloated and usually wake up early the next morning with heartburn. I know, I should probably just stop eating the damn things. --Kurt Shaped Box 06:07, 17 August 2006 (UTC)

Could also be the raw onions (some places use them) or maybe cuz they're so greasy? Some people get upset stomachs from that. Anchoress 06:04, 17 August 2006 (UTC)

Yup, raw red onions usually - and they are greasy. --Kurt Shaped Box 06:07, 17 August 2006 (UTC)

If mutton disagrees with you, might I suggest making them out of seagull bagel meat ? :-) StuRat 06:12, 17 August 2006 (UTC)

How many gulls would be required to make up one elephant leg? By all accounts, they're pretty lean birds --Kurt Shaped Box 06:21, 17 August 2006 (UTC)

The more the better, clean out the whole neighborhood ! :-)StuRat 07:00, 17 August 2006 (UTC)

Eating seagull bagels is a health risk because of high mercury levels. It is safer to use rats. --Lambiam^Talk 09:24, 17 August 2006 (UTC)

... just not "stu" rats, ok. Those things'll kill ya.  :--)

Nasty critters. — [Mac Davis] (talk)

Yea, once they bite onto something, they just won't let it go. :-) StuRat 01:04, 18 August 2006 (UTC)

You say that almost as if it's something you're proud of.  :--) JackofOz 02:11, 18 August 2006 (UTC)

See also Donner Party. Edison 17:49, 17 August 2006 (UTC)

I always reserve tables under that name at restaurants, I find they don't want to keep you waiting long enough to get hungry, with a name like that. :-) StuRat 17:59, 17 August 2006 (UTC)

The longer they make you wait, the fewer seats your party will need. --LarryMac 18:01, 17 August 2006 (UTC)

Yes, but they need an extra plate, for the bones. StuRat 19:08, 17 August 2006 (UTC)

I know why. Recently I walked past a Donner Kebab establishment, and I saw the cook with part of the grill literally in the gutter of the road next to a rainwater drain where he was 'cleaning' it. I thought at the time that what he was doing must have been illegal as well as being very unhygenic. Even in the UK I suspect such places are not inspected very often and they could have very bad hygiene.

I feel the same after a doner kebab. However, i have come to realise that it is the copious alcohol imbibed earlier in the evening - a pre-requisit to finding kebaba an attractive proposition - that leads to me feeling sick the following day. Rockpocket 01:46, 18 August 2006 (UTC)

why does water boil at low pressure?

Why does water boil at low pressure? —The preceding unsigned comment was added by Mearom (talk • contribs) 06:17, August 17, 2006 (UTC).

I assume you are asking why water boils at lower temps, when under lower pressure. This is also true of other liquids. Basically, pressure "pushes" the water molecules together to form a liquid. With less pressure, you reduce this effect. High temps cause rapid movement of water molecules, which makes them "break free" from the bonds that hold the water together as a liquid. So, temp and pressure both interact with each other to determine the boiling point of any substance. StuRat 06:27, 17 August 2006 (UTC)

Figured that, never could find any reference on it, though

Read our article on Boiling. Already the first sentence kind of explains it. --Lambiam^Talk 09:34, 17 August 2006 (UTC)

So pressure and temperature determine the state. Rock melts (becomes a liquid) at high temperatures. The lowest pressure you can get is vacuum. However, rocks in space aren't liquid. Neither an answer nor a question, just playing with some thoughts. DirkvdM 08:03, 17 August 2006 (UTC)

as far as i know melting point isn't too effected by pressure, since neither phase is in equilibrium with a gas. but i could be missing something obvious... Xcomradex 09:10, 17 August 2006 (UTC)

The density of a gas is quite different from a liquid, under normal conditions, while the density of solids and liquids are usually similar. In the case of water, the density of the liquid is actually higher, meaning pressurized water freezes at a lower temp. StuRat 15:06, 17 August 2006 (UTC)

A Phase diagram is a good way to see how the phase varies with temperature and pressure, and how changing those conditions affects the melting/boiling/sublimation point. DMacks 16:21, 21 August 2006 (UTC)

poltergiests are in my water!

Sometimes when water is cold and in a bottle, un opened, it rapidly turns to slush upon opening —The preceding unsigned comment was added by Mearom (talk • contribs) 06:52, August 17, 2006 (UTC).

If it's below the freezing temp (at normal air pressure), the higher pressure in a sealed container may keep it from freezing, until the bottle is opened, then the lower pressure allows it to freeze. StuRat 06:58, 17 August 2006 (UTC)

thank you

i think the phenomenon has more to do with supercooling. Xcomradex 09:11, 17 August 2006 (UTC)

The water is supercooled, and agitation initiated nucleation. I've seen this question asked three times before, although it has never happened to me. I am still waiting! — [Mac Davis] (talk)

Try looking in your beer bottle, rather than your water bottle. ;) pschemp | talk 05:50, 18 August 2006 (UTC)

I seem to remember at one time not long ago that there wasa type of beer available that was cooled to such anextent that it came out as slush. Very nice on a hot day. I havent seen it around lately.--Light current 16:22, 19 August 2006 (UTC)

biochemistry

can anyone say why ATP is called high energy component compared to ttp ,gtp,ctp??? —The preceding unsigned comment was added by 59.163.146.11 (talk • contribs) 08:11, August 17, 2006 (UTC).

atp is used quite a bit, but some enzymes specifically use gtp instead. i'm not sure (other than rna/dna synthesis) what the pyrimidine triphosphates are used for. Xcomradex 08:55, 17 August 2006 (UTC)

As to why this is, it appears to simply be an arbitrary "decision" that was made early in the history of like. I once asked my biochemistry professor the same question, and have since posted his reply to Talk:ATP. It's somewhat lengthy, and has a user reply attached to it that I think you might find illuminating. – ClockworkSoul 19:55, 17 August 2006 (UTC)

FOOD SCIENCE

CAN ANYONE SAY ?WE CONSUME PROTEINS , VITAMINS, CARBOHYDRATES,FATS....DO ALL OF THEM NECESSARY...WE CAN GET ALL OF THEM FROM PROTEINS THEN WHATS THE NEED OF TAKING THEM INDIVIDUALLY??? —The preceding unsigned comment was added by 59.163.146.11 (talk • contribs) 08:15, August 17, 2006 (UTC).

loud. i suggest you read http://en.wiki.x.io/wiki/Nutrition#Nutrition_and_Health Xcomradex 08:50, 17 August 2006 (UTC)

First of all, there are essential fatty acids and essential amino acids which your body cannot make from proteins. Secondly, the nitrogen load from eating enough protein to make enough glucose to make enough fat would be prohibitive. There are individuals with inborn errors of metabolism who have to go on diets which restrict certain large groups of nutrients, such as phenylalanine. InvictaHOG 11:53, 17 August 2006 (UTC)

You cannot live on protein. If you are asking about the Atkin's Diet, than I would like to mention the idea behind that is not that you can live on only protein. — [Mac Davis] (talk)

Underwater Communication

In underwater, for example like in oceans...can the electro magnetic waves be used for communication?...For example.,submarines...If so, then Is UltraSonic wave used only for navigation and detecting of depth?..Can ultrasonic wave be used to send data too?...Also is there any UltraSonic Image procesing system available to detect the object under sea?...

Yes, electromagnetic waves travel slightly slower in a water medium, but they are used. Ultrasonic waves I do not think can be used for telecommunication although, they do contain information. That is how SONAR works after all... — [Mac Davis] (talk)

You certainly could send info using ultrasonic waves, using a simple Morse Code, if nothing else. However, I believe subs typically use Ultra Low Frequency radio waves to communicate. StuRat 17:45, 17 August 2006 (UTC)

How much more complex could you get? — [Mac Davis] (talk)

See Extremely low frequency. Electromagnetic waves of high frequency are absorbed by water. The deeper the receiver, the more absorption. The higher the frequency, the more absorption, IIRC. Dep in the ocean, no light penetrates, and light is just high frequency electromagnetic waves. The U.S. at one time had an extremely low frequency transmitter, 50 hertz or so, to send messages to submerged ballistic missile submarines worldwide.Edison 17:56, 17 August 2006 (UTC)

Do electromagnetic waves really slow down in water? I had always thought that they travel at the speed of light? (What about light? Does light slow down in water as well? Wouldn't it change colour?) - Rainwarrior 19:06, 17 August 2006 (UTC)

As for changing color, sort of. Light is composed of all colors, and by blocking all colors but blue (in freshwater) and blue-green (in seawater), the color does "change" to become blue or blue-green. Technically, it isn't really a change, though, but rather removing everything else. Compare this to if you had a bowl of M&M's then removed all except the blue ones. It isn't really right to say you changed the color of the M&M's to blue, but, nonetheless, when you look into the bowl, you do see just blue. StuRat 19:14, 17 August 2006 (UTC)

Err, I didn't mean "sunlight", and that's not what I meant be colour change. Absorbtion I understand. What I was asking is whether EM waves slow down in water, and if they do, shouldn't their wavelength change (thus changing their colour)? - Rainwarrior 19:57, 17 August 2006 (UTC)

It does travel at the speed of light; the speed of light, that is, in water. Light also slows down in air but not by much. See refraction. I think it only changes color at changes of velocity. AEuSoes1 20:11, 17 August 2006 (UTC)

All EM waves (including light, of course) slow down in water (or most any other substance, including air), and their wavelengths do change. But, of course, the wavelength will change again when they exit that medium (possibly into your eye), and so it doesn't affect their perceived color. Put another way, the frequency doesn't change as a ray passes through different media, so we can associate the color with the frequency instead for conceptual clarity. It's also worth noting that not all frequencies are slowed by the same amount, and so the wavelengths get bunched up and the light of different frequencies is split into different directions. This is known as dispersion, and is the operating principle of a common prism. Finally, the speed of light is properly the speed of light in a vacuum only; its modern significance comes from its invariance as viewed by various observers rather than its constancy in all environments. However, it is possible to view transparency as an interference effect between waves (or photons) that are in fact propagating at c, so in that sense the waves are travelling at the "true" speed of light, just with some congestion along the way that slows down the actual transfer of energy. Hope this helps. --Tardis 20:34, 17 August 2006 (UTC)

Ah, so even if you are underwater, because the light has to leave the water and enter your eye, the colour does not change to your perception! Interesting. This is a good answer, thankyou. (I think my confusion was not understanding that they speed up again when leaving the medium.) - Rainwarrior 23:09, 17 August 2006 (UTC)

Thanks Friends..That was indeed helpful.I'm doing an Underwater Autonomous Robot project..It's gonna aid me lot..One more from this discussion is that if Deep water absorbs light and from your saying if it absorbs much of high frequency light waves,then wouldn't the color be appearing as Redish?..<VIBGYOR>.If it absorbs high frequency of light wave, then I presume that the red light having the lower frequency shouldn't get absorbed and hence it should be visible,while Blue color gets absorbed..But why this doesn't happen?..I maybe wrong but I have this doubt for a long while..Plz Help me clear my doubts

According to Water, water absorbs infra-red, and a tiny amount of visible red. So, no, it absorbs the lower frequency visible light. Rainwarrior 22:39, 19 August 2006 (UTC)

bikini atoll

is it still radio active? —Preceding unsigned comment added by AOL (talk • contribs)

• Please stop asking random questions from AOL proxies--152.163.100.74 17:33, 17 August 2006 (UTC)

• Why? User:Zoe|(talk) 21:50, 17 August 2006 (UTC)

• Becuase 152.163.100.72 (talk · contribs), one of the 3 proxies AOL gives to the RD/h, keeps spamming that page full of trollish questions, and even inspired a 15 minute block, which of course impacts any other AOL people trying to edit the same page--205.188.116.74 22:05, 17 August 2006 (UTC)

Every place on Earth is radioactive to some extent. Please read the article on nuclear radiation. — [Mac Davis] (talk)

Well I think we can be a bit more helpful than that.. I think we can assume he/she means "are the levels of radioactivity there still highly elevated from the nuclear testing which took place there in the 1940s and 1950s?" I assume they mean the entire Pacific Proving Grounds site, not just the Bikini atoll (the Rongerick and Tongelap Atolls were also exposed as a result of testing at Bikini, and testing took place at Enewetak too).

The water around the atoll is not radioactive anymore. On some islands, though, there are radioactive isotopes (specifically cesium-127) in the soil and plants because of the fallout from the tests. Whether these elevated levels of radiation are dangerous is a matter of dispute, since even elevated they are low levels (and the effects of low level radiation have been disputed for a lonnng time). See this page for a discussion of the different findings. Even if the levels are dangerous, they pose a risk only to people who would inhabit the islands over the long term and who would be eating things grown there. To remove the cesium you'd have to take off the top foot of topsoil or so, or to spread a chemical which will prevent the re-uptake of the cesium. This page goes into some of the options currently discussed. This site has a lot of information on the US radiation assessment program for the Marshall Islands. --Fastfission 17:38, 17 August 2006 (UTC)

What do you think about the dangerousness of different strengths of radiation? — [Mac Davis] (talk)

I don't know enough about the medical effects to have an informed answer in general. I do know though that depending on how you tweak the models you end up with very different responses. For example, if I only consider the radioactive effects of being near cesium-137, then there is really almost no danger at all. If cesium-137 is still around then it must be very weakly radioactive (i.e. have a very long half-life). However if we start thinking about injesting cesium-137, then we have to wonder if it is attracted to bones or other organs in particular. I believe, though I wouldn't put money on it, that cesium-137 will bind with bone marrow easily. That's bad, because then you have a weak emmitter sitting inside you in one place for a long time, and over the long run that can lead to cancer. This is why plutonium is dangerous too. It's not that being around plutonium will necessarily make you sick, but if you get it into your lungs it will just sit there and radiate for a decade or so and eventually you will have a much higher chance of developing cancer. So you'd have to know a lot about the specific path of exposure to know for sure what the long term effects are likely to be, because something which is completely innocuous in one situation (i.e. you can eat plutonium without much ill effect, as it will just pass through you, and holding it will do no damage, since your skin can stop the alpha rays) can be very bad in another (i.e. if you breath plutonium, then you could have a real long-term health problem). I think visiting the Marshall Islands is perfectly safe, radiation wise. If I lived there, though, I wouldn't eat the plants on a regular basis, even though the UN/DOE/etc. have assured that they think it is safe. They might be right, but it seems like an unnecessary risk, especially since the effects of low level radiation are, despite decades of research, still very controversial among experts. --Fastfission 19:14, 17 August 2006 (UTC)

Caesium-137 has some useful information about the biological effects. Here is a CDC report on the effects, too. -- Scientizzle 19:44, 17 August 2006 (UTC)

Awesome. Yeah, I got the number wrong which made finding info on it pretty hard. ;-) It deposits in muscle, not bone. --Fastfission 20:19, 17 August 2006 (UTC)

I prefer women who wear no bikini atoll. :-) StuRat 19:05, 17 August 2006 (UTC)

Oddly enough, I haven't heard that one yet, despite working on this stuff for a number of years... good job. --Fastfission 19:14, 17 August 2006 (UTC)

Brilliant. - Rainwarrior 19:59, 17 August 2006 (UTC)

Indeed, quite witty. Good show, old sport. Black Carrot 19:59, 17 August 2006 (UTC)

Limiting magnitude

Is it possible to see a galaxy (or any other object with a large apparent diameter) if the sky is brighter than its maximum surface brightness?

Also, how much does one's visual acuity affect their limiting magnitude? For example, if I have 20/13 vision and the faintest star I can see is magnitude 4.2, what's the faintest star a person with 20/20 vision can see under the same conditions? How about someone with 20/30 vision? 20/10? --Bowlhover 19:15, 17 August 2006 (UTC)

I can't understand how anyone could see something less bright than the sky, at the time, no. On a bright day, it's even hard to see a full moon. And visually acuity makes a huge diff, too. An extremely near-sighted person would also find it impossible to see anything less bright than the moon. StuRat 21:31, 17 August 2006 (UTC)

But if the object's surface brightness is very close to, but just lower than the brightness of the sky - then surely you'll receive (roughly) twice the number of photons from the region of sky with the galaxy, than in the surrounding sky-glow - if you have a sensitive enough telescope/eyes/photon detector, then it's surely going to be possible to measure the extra photons (and hence "see" the galaxy), even though the surface brightness of the galaxy is lower than the background skyglow. Of course the brighter the sky and fainter the surface brightness of the galaxy, then the difference in the overall brightness of the region with the galaxy than the region without is going to become very small and your instruments (or eyes) are not going to be able to pick it out of the background glare. Richard B 20:14, 18 August 2006 (UTC)

Something that emits twice as many photons doesn't appear twice as bright, however, but only slightly brighter. That's just how our eyes work. StuRat 00:40, 20 August 2006 (UTC)

True, but it should appear brighter and therefore (theoretically) visible. If you have some sort of photon counter (say, a decent ccd camera), then, provided you get a long enough exposure, then it should be possible to see galaxies with surface brightnesses much lower than the general skyglow.Richard B 12:05, 20 August 2006 (UTC)

That might work, yes, but I believe the questioner was asking about use of the naked eye to see these things. StuRat 15:55, 20 August 2006 (UTC)

Electrical generator

155.239.56.64 19:43, 17 August 2006 (UTC)Please would you be kind enough to explain to me how an electrical generator produces electricity. Thank you. James. 155.239.56.64 19:43, 17 August 2006 (UTC)

There are a lot of different kinds of generators, but probably the most common works like an electric motor. If you move a magnet next to a wire, its magnetic field will generate a little bit of electricity in that wire (see Electromagnetic induction). In the generator, usually you have large coils of wire, thus allowing the magnet to stimulate many wires at once. So, some magnets are rotated around next to some coils, and electricity comes out of the coils. Electrical generator will probably explain this better. - Rainwarrior 20:07, 17 August 2006 (UTC)

Just to clarify, in order for a moving magnet to cause a current in a wire, there must be a circuit - i.e. the wire must be in a loop of some kind - the requirement according to Maxwell is that the magnetic flux be changing over time. There is only magnetic flux if there is a bounded surface (I'm sure Rainwarrior knew this - just clarifying). Basically the magnet creates a non-uniform magnetic field in space, so as the magnet is rotated or moved near a circuit, the magnetic flux changes through the circuit, and an electric current is induced. --Bmk 01:41, 18 August 2006 (UTC)

Yes, it is extremely important that the wire is part of a closed circuit. Forgot to mention that, thanks. - Rainwarrior 05:00, 26 August 2006 (UTC)

Color of Blood Question

I know that unoxygenated veinous blood isn't blue/purple, but a dark maroon. When a person gets a mid-sized cut on a vein, how long will the blood take to absorb the oxygen in the air and turn a bright red oxygenated color? Please only answer if you have a source or are completely sure. Thanks! Reywas92 20:53, 17 August 2006 (UTC)

It is immediate. Otherwise, you would at some time have had the fortune of observing blood turn red. You might have cut yourself on a vein that you can see is greenish. — [Mac Davis] (talk)

Though it should be noted that blood oozing from a wound is still a considerably darker red than arterial blood. In fact, I'm not sure blood from a wound is a noticably different color than blood drawn from a vein (even though the former is exposed to oxygen in the air, and the latter is not). - Nunh-huh 21:13, 17 August 2006 (UTC)

It takes a little time, maybe a few seconds, it kind of depends on what vein. If the vein is bringing back blood from a well-used muscle that needs oxygen it will look different than if only some of the oxygen is used. This is partially due to the fact that, and read carefully: Hb binds oxygen less actively if it has less oxygen in it. This sounds counterintuitive, but when O2 is put into a red blood cell, it makes that cell want to absorb more O2. So if the blood is deoxygenated, it resists being oxygenated again, so it actually turns from maroon to dark red rather slowly. Once it has a little oxygen, it absorbs more readily, and so it very quickly goes from dark red to bright red. To summarize, as with most things, "it depends..."Tuckerekcut 22:47, 17 August 2006 (UTC)

If you think about the diffusion of oxygen into a volume of blood, there's no physical way it can be immediate. Also, venous blood never looks the same bright red as well-oxygenated arterial blood - I suppose that the blood begins to separate and clot before it is fully oxygenated. And deoxygenated blood can look purplish/bluish - you see this quite often in codes. InvictaHOG 05:33, 18 August 2006 (UTC)

Second Color of Blood Question

My teacher said that when an early doctor sailed to the very hot tropics and took a venous blood sample, he found that it was already red, not dark maroon. My teacher said that it is because the heat of the tropics caused the cells to not accept the oxygen from the red blood cells, causing the red blood cells to go back through the veins still carrying the oxygen, so they are still red. I disagree and say the blood reacted with the air and absorbed the oxygen, turning them red. Who is right? Please only answer if you have a source or are completely sure. Thanks! Reywas92 21:02, 17 August 2006 (UTC)

What an early doctor said is not necessarily the case. Perhaps there is no need to explain an observation that cannot be replicated! Maybe you should ask your teacher which doctor that was. In any case, here in the 21st century, if we are going to be talking about the oxygen content of blood, it should be measured directly instead of inferred from blood color. Can your teacher provide information about studies on O₂ content of blood in the tropics vs temperate climes? - Nunh-huh 21:20, 17 August 2006 (UTC)

Your teacher sounds wrong to me. If the cells "didn't accept the oxygen", they would die, and so would the person. StuRat 21:22, 17 August 2006 (UTC)

In fairness to the teacher, his argument would seem to be that the cells' need for oxygen is more than adequately met by the O₂ in the blood (which is generally true: blood is not completely desaturated when it returns to the lungs), and that tissue needs less oxygen in the tropics, so the blood is less desaturated there (it is this latter part that seems most dubious). - Nunh-huh 22:06, 17 August 2006 (UTC)

At higher temps, chemical reaction rates increase, including organic reactions, meaning even more oxygen would likely be needed, not less. This is the opposite of hypothermia, where reduced oxygen usage has been recorded. StuRat 23:20, 17 August 2006 (UTC)

The early doctors were usually good observers, and this one was probably right with his observation. The explanation given by the teacher is not that clear, but in a way the heat, the tissue cells and the return of O2 rich blood could be related. I can conceive of severe heat causing an unusual begree of vasodilatation in an effort to increase heat loss. If the gentleman's peripheral circulation was so rapid that the O2 supply to the limb was greatly in excess of the cellular O2 use, this would lead to a raised venous O2 saturation. This effect would be called arterio-venous shunting (of oxygenated blood), meaning that the arterial blood never gets close to the capillaries and surroundings anyway. If the subject were able to maintain an adequate blood volume (i.e. the circulation could be increased without blood volume being a limiting factor), the rise in venous O2 content would be expected, because much more O2 was going to the limb than the cells in the limb needed, and was coming back to the heart unabsorbed by the cells. Note though, that this has nothing to do with the cells not getting enough O2, or somehow being prevented from absorbing the O2. --Seejyb 23:08, 17 August 2006 (UTC).

Article Request: Hemocromotosis

Hello:

I'm wondering if it would be possible to request an article on the topic of Hemocromotosis (a genetic condition which results in excess iron in the blood.)

Information does exist on the web, however, contradictory information exists even between credible sites such as www.mayoclinic.com AND http://www.cdnhemochromatosis.ca/.

A Wikipedia article would be greatly appreciated.

Thank you, Ashley604

It's the spelling that's the problem. Hemochromatosis. - Nunh-huh 22:02, 17 August 2006 (UTC)

My apologies for the spelling error. That's just how confusing it gets. (The British spell it HaEmochromatosis, further "muddying the waters.") I just can't understand the contradictory information out there between respected peer-reviewed medical journals, and institutions like the Mayo Clinic. ((I have found condtradictions concerning symptoms, genetic prevelance in the population, treatment--other than phlebotomy, and what were the acceptable levels of iron in the blood.))

No, the root was always haemo. What "mudded the waters" was the Americans dropping the "a" from "ae" dipthongs and the "o" from "oe" dipthongs (eg. encyclopaedia, foetus, faeces, ...) JackofOz 22:43, 17 August 2006 (UTC)

while there should be rough agreement between lists of symptoms, you shouldn't expect to find identical lists (as we point out, there are a maddening variety of symptoms), or uniformity of opinion on indications for phlebotomy. And prevalence will differ with different populations (and no two studies manage to study identical populations). Some sites may combine more than one mutation in one figure, adding to confusion. For information, you should probably prefer peer reviewed journals over nearly any web site. - Nunh-huh 00:31, 18 August 2006 (UTC)

Engine braking

When driving on a steep downhill road in my home town, I see the following road sign saying:

ENGINE BRAKES PROHIBITED USE LOWER GEAR

According to the Engine braking article, engine braking means turning to a lower gear so that kinetic energy of the car is transferred to faster turning of the engine, and thus slowing car down instead of having to use regular brakes.

I understand that both methods have their advantages and disadvantages - engine braking may mean more noise, but regular braking wears down the brakes.

But as for the sign, in my perception, it contracits itself. The first line says they don't want drivers to use lower gear, and second line says they DO want drivers to use a lower gear. So how should I understand it? - GeNe, 17 August 2006 (UTC)

What the sign is calling "engine braking" sounds like the use of the jake brake to me. Our article on engine braking is rather vague, and seems to include both the jake brake and using a lower gear, which might be more properly called "transmission braking", and is also a technique advised to use on cars where the regular brakes have failed. StuRat 22:38, 17 August 2006 (UTC)

That article was quite clear. In my car I can slow down on a hill by throwing the automatic into second or low. It works because of the design. Apparently a diesel doesn't have the same physics, so it doesn't slow down quickly just by down-shifting. If you throw the switch to modify the valves, then it can slow down with an enormous noise. So I suppose the 'quiet' way is to approach the slope slowly, rather than rapid downshifting, and then use a low gear. I suppose that keeps the truck slower using rpm-friction. --Zeizmic 23:57, 17 August 2006 (UTC)

As StuRat has said, the sign is most likely referring to jake brakes, and therefore addressed to drivers of large trucks who would have such equipment on their vehicle. Notice that it does not say "Engine braking prohibited", but "Engine brakes prohibited." The main reason for this is that engine brakes make a lot of noise. This is addressed in the jake brake article. The average automobile driver should feel free to downshift at will. --LarryMac 13:22, 18 August 2006 (UTC)

A diesel does experience engine braking from just moving to a lower gear just like a regular car. The braking provided by the engine by doing this is not sufficient for steep slopes while carrying heavy loads, though. So an engine brake or Jake brake (a specific brand of engine brake) is used, where the momentum of the truck drives the engine which then compresses air (without fuel) in the cylinder and instead of the compressed air "bouncing" the cylinder back on the down-stroke (using little energy), the air is released through the exhaust valve. This release of the compressed air into the exhaust system is far noisier than the normal operation of the engine. The Jake brake is preferred because over-use of the brakes can cause them to overheat and lose effectiveness or fail entirely. —Bradley 14:55, 18 August 2006 (UTC)

shortwave transmitter

What's the cheapest method you can think of to build a shortwave transmitter?--205.188.116.74 22:44, 17 August 2006 (UTC)

Depends on what kind of transmission you have in mind. Attach two wires to a battery, scratch the wires against a nail file, will generate a mess of radio frequencies (perform the experiment near a radio to confirm). To send an actual signal see transmitter for a circuit diagram. For a licensable (legal) transmitter see amateur radio operator and the links in there; also visit your local library and book shop for radio amateur books. To set up a SW radio station... uh, I'm out of ideas. What kind of transmitter do you want to build? Weregerbil 06:44, 18 August 2006 (UTC)

Upon reflection I don't actually recommend you do the battery + nail file experiment. Too many ways things can go wrong: too powerful a battery (the nail file could explode), the experiment shorts the battery which can destroy it (not smart using an expensive cell phone battery), the battery could heat up and do damage, or you could get sparks that hurt you, ... Weregerbil 06:54, 18 August 2006 (UTC)

What kind of nail file did you have in mind that could explode?! Anyway, connecting one of the wires to the battery via a resistor could save the battery (or would the power loss ruin the transmission?), and I wouldn't worry to much about sparks. —Bromskloss 01:10, 21 August 2006 (UTC)

When is a bird 'born'?

Quick question - help to settle a debate for me (about the date of birth of one of my pet birds, as it goes). When would you guys consider a baby bird to have been 'born' - when the mother bird first laid the egg, or when the baby bird eventually emerged from the egg? I believe the latter - my associate believes the former. --Kurt Shaped Box 22:47, 17 August 2006 (UTC)

• Birds can lay unfertilized eggs, that should answer your question--205.188.116.74 22:49, 17 August 2006 (UTC)

I would go with the hatch date, too, as a bird is about as developed when it hatches as a person is when born. Need I ask what species of bird we're talking about ? (I'm picturing you wanting to know when to serve the birthday cake, LOL). StuRat 23:02, 17 August 2006 (UTC)

Just one of my budgies. No, he's not getting a cake. ;) --Kurt Shaped Box 00:44, 18 August 2006 (UTC)

The wiki article says: "Birth is the process in animals by which an offspring is expelled from the body of its mother." Under this definition, your friend is right. However, this is not always the way things work. If I was counting the birthday of a bird, I would count from it hatching. With my frogs, I count from metamorphosis (when they first leave the water), as the tadpole duration can vary a huge amount. Just use what is most convenient. --liquidGhoul 06:55, 18 August 2006 (UTC)

I agree with hatching. Some fertilized eggs don't hatch, so in that case you can hardly say the bird was ever born?--Shantavira 07:12, 18 August 2006 (UTC)

Hence the adage, "don't count your chickens before they've hatched." --Fastfission 16:29, 18 August 2006 (UTC)

How about biscuits, bacon, and scrambled unborn chickens for breakfast?Edison 15:30, 18 August 2006 (UTC)

No, if you called the laying of the egg "birth", I would think you would call an fertilized but dead egg "stillborn". Regardless, "birth" isn't the correct term in the first place. The correct terms for laying and hatching are, respectively, laying and hatching, which could well answer your question right there. But, if you're using analogy anyway, just pick whichever you think fits best. There are aspects of both that would make "birth" an acceptable metaphor, most of which have already been described. I would, personally, lean towards the date of hatching as a bird's birthday, since the main feature of a birthday to me is that, for the first time ever, a particular being has entered the world of air and openness. I've heard, incidentally, that there are eastern cultures that celebrate the anniversary of a person's conception instead (something to do with astrological significance), so I wonder which one they'd go for. I could certainly see taking the moment a bird's full genetic code assembled as the moment they came into the world, and hence possibly their "birthday". It's not really a biology or vocabulary question, and the right answer is whichever one you think captures the spirit of the thing more. Black Carrot 21:52, 18 August 2006 (UTC)

Phelp's Box

I'm editing an article that talks about a Phelp's Box. It says, "At her birth a host of physical abnormalities were present, including a severe curvature of the spine. As a result, she was forced to spend hours each day and night in what was then called a Phelp's Box, a device that resembled a shallow coffin. Earlier in the century children with severe curvature of the spine were placed in a Phelp's Box and strapped as flatly as possible. The only part of the body that could be moved was the head. It was not only physically confining, but extremely painful as well."

"Phelp's Box" is not in Webster's Third New International Dictionary. It is not in Merriam-Webster's collegiate Dictionary, 11th edition. Google was not helpful either. It had one link that talked about an article similar to the one I'm editing, but the link was no longer active (freegroups.net/groups/pastormail/read/?0::3578 - 13k - Supplemental Result ).

So ... is or was there ever such a device? Does it have a different name now? I'm assuming "earlier in the century" refers to 20th century, not 21st. I do appreciate your help in verifying the facts.

Here are some more 'torture' devices, but no box. [1] --Zeizmic 00:05, 18 August 2006 (UTC)

I found one (unhelpful) hit which manages to use two different spellings: I read the story of an invalid girl. One of her several sicknesses was a tendency to for her spine to curve. She laid strapped in a Phelps box. (Philip's box looks something like a coffin.) Possible the story this pastor read draws upon the same source as your article. --Lambiam^Talk 05:07, 18 August 2006 (UTC)

It's probably a Phelps brace (not box), named after Winthrop Morgan Phelps, an orthopedic surgeon who focused on bracing as a treatment for things such as scoliosis - he had an interest in cerebral palsy. InvictaHOG 05:26, 18 August 2006 (UTC)

EMP

Supposing for a second that you wanted to generate an EM pulse, and were on a tight budget, how would you do it?--205.188.116.74 00:08, 18 August 2006 (UTC)

Here's one idea which I thought up, and have never tested, which I'll give you as long as you understand that reading the following represents an agreement that you will never actually do this and if you do it is completely at your own risk and that you understand that you will probably die or blow up your cat or your friends, and you will be arrested and sent to Guantanamo bay and kept there forever: pipe + lots of big gauge wire + bomb + big magnet. Cap the pipe on one end, wrap the heavy wire around the pipe as many times as possible, then connect the two ends, put a fuse in it, pour in a lot of gunpowder, drop in the magnet, light the fuse, and run like heck. The heavier the wire gauge, the better, because it will survive for more of the explosion, and will make a better pulse. Also, note that the idea is not to actually blow up the pipe, just to blow the magnet through the pipe at high speeds. I think that's kind of how the air force does it. I seem to remember they disabled one of Saddam's propaganda TV stations with a similar EMP. And by the way, see the article electromagnetic pulse for more info, and electromagnetic bomb. --Bmk 02:27, 18 August 2006 (UTC)

I think you just conjured up a graphite bomb. — [Mac Davis] (talk)

Just make sure that whatever you are planning to do with the device, make sure you don't bring a liquid on the plane with you because, as we all know, tomato sauce or cologne never gets out of carpet, being a terrorist weapon, while computers and communications are totally replaceable~

don't ask why you would bring tomato sauce on a plane, unless you want to be a terrorist~

Bmk you just described a crude form of an explosively pumped flux compression generator, a device used to generate emp pulses in a military setting, among other uses. you might like to read the article for a better way to use bomb + magnet + wire to generate a current pulse. Xcomradex 06:54, 18 August 2006 (UTC)