Wikipedia:Reference desk/Archives/Science/2007 March 22

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March 22

Cyclops evolution

Did one-eyed creatures evolve first and then mutated to create two-eyed species, or did the very first proto-eyes always come in pairs? -- LukeSurl 00:18, 22 March 2007 (UTC)

It probably depends on how you define eyes, but the short answer is one-eyed creatures came first. Check out the evolution of the eye article. --Cody.Pope 00:35, 22 March 2007 (UTC)

Two eyes is pretty common in our large predator/prey domain, but that's because we benefit greatly from good depth perception. There are many other animals with more eyes, spiders have eight and bees for example have FIVE eyes! Which I think is amazing, it's one of the few cases where such an organ does not come in one or pairs!! This doesn't seem to be mentioned in our bee article:( Vespine 01:07, 22 March 2007 (UTC)

Hmm, if one eye allows you to see a 2D view of the world, and two eyes allows a 3D view of the world, do 8 eyes allow you to see into the ninth dimension ? :-) StuRat 19:20, 22 March 2007 (UTC)

If it were big enough to be seen, yes. 222.158.162.242 09:05, 23 March 2007 (UTC)

Euglena have a single eyespot, and protista are pretty far down on the evolutionary ladder, so I'm going to second the statement that one-eyed species came first--VectorPotential^Talk 01:14, 22 March 2007 (UTC)

But no one suggests that the human eye has its origins in Euglenia. Eyes (and eye-like spots) have evolved more than once. - Nunh-huh 03:46, 22 March 2007 (UTC)

Well, the wiki article I pointed to actually disagrees: "The development of the eye is considered by most experts to be monophyletic; that is, all modern eyes, varied as they are, have their origins in a proto-eye believed to have evolved some 540 million years ago." --Cody.Pope 05:25, 22 March 2007 (UTC)

That's not a disagreement. The article overstates the degree of agreement on the monophyletic theory, but even if all modern eyes did have a common origin, that doesn't mean that no other eyes have evolved (and become extinct). - Nunh-huh 05:52, 22 March 2007 (UTC)

Well, what about the article about the pineal gland? Some biologists think that it evolved as a proto-eye in land animals before binocular eyes evolved. The article on the pineal gland says: Some evolutionary biologists believe that the vertebrate pineal gland can be evolutionarily traced to a proto-eye structure in early vertebrate organisms. Interestingly, the tuatara's pineal gland functions as a third eye. Jolb 05:33, 22 March 2007 (UTC)

I didn't say that the eyespot evolved into the human eye, just that it came first (: VectorPotential^Talk 17:58, 22 March 2007 (UTC)

As a brief aside, I've been vandalism-patrolling at pineal gland for more than a year now (in fact, the miserable state of that article was a primary motivator in my early Wikipedia contributions - I couldn't bear to see scientific facts so grossly misrepresented). A lot of nuts and new-agers have distorted, mythology-based views about the human pineal gland as a "third eye." At best, it might maybe have had some photo-sensitive properties in some link way back in the evolutionary chain, possibly. (See the article and talk page for more details of the citations, studies, etc). There is no scientific evidence that the current human pineal gland has photosensitive behavior - for one thing, it is deep inside the interior of the head and does not have exposure to light. Any metaphysical/spiritual vision attributed to this endocrine gland is incorrect; it does not participate in the physiological process of sight. This doesn't stop people from CONSTANTLY ADDING THIS INFORMATION TO THE ARTICLE. Even worse, they can even come up with piles of disreputable web-links to support their claim. Sigh. I think I should mark my WikiStress level to Red, and call it a night / week / month. Nimur 07:52, 22 March 2007 (UTC)

The confusion around the pineal gland is due to not understanding that all one needs for a so-called "third-eye" is the presence of an opsin paralogue, such as melanopsin or pinopsin, to detect light. Plenty of fish and frogs express such a gene not only in pineal-like structures but also in their skin, permitting them to detect light without using their eyes. Yet, oddly enough, no-one suggests that skin is a proto-eye. Rockpocket 02:02, 23 March 2007 (UTC)

This isn't exactly what you asked, but I think it may be relevant: bilateral symmetry means that we don't have two copies of "how to make an eye" in our genes. We have elements for "how to make an eye", and for "put an eye here"--more accurately, we have elements for "how to make an eye", "put an eye here" and "duplicate everything across this axis". I'm simplifying greatly, and any evo-devo biologist reading this will be rolling their eyes, but the point is that we only needed to evolve a single copy of the eye gene; the mechanisms that make us symmetrical duplicate it. There's also a good explanation of this over at the Index to Creationist Claims: CB751: Bilateral symmetry is improbable under evolution. Read the link from there as well; it's useful. grendel|khan 19:48, 22 March 2007 (UTC)

Eyes

Do glasses improve vision or ruin it and give you headaches only? Also does eating carrots actually improve vision or is it a myth. 70.48.254.161 02:21, 22 March 2007 (UTC)

Glasses have been around for hundreds of years and they have improved the vision of countless millions of people. There would certainly be people who get head aches from wearing glasses and people who's vision degrades even though they wear glasses, but that may not be the fault of the glasses, and even if it is, there is complete universal and unilateral consensus that the benefit outweighs the risks. As for the second question, the carrot article states it is actually somewhat of an urban myth that carrots are good for your vision. Lack of vitamin A can lead to problems with vision and carrots have vitamin A, so it would be safer to say carrots may help prevent vision problems if you have a vitamin a deficiency, but to say they are good for your vision is misleading. Vespine 03:13, 22 March 2007 (UTC)

Only glasses with bad prescription should give you headaches. It doesn't really improve vision; it just changes the angle of light to compensate for less than 20/20 vision. --Wirbelwindヴィルヴェルヴィント (talk) 03:29, 22 March 2007 (UTC)

Actually, if I'm remembering correctly, it is not that the angle of light is changing, it is that the focal point of your vision is being moved forward or backward, depending on whether you or far or nearsighted. It is basically the same thing that one does when one is focusing the lens on a camera or a pair of binoculars--you move the lens backward or forward until things come into focus. This is discussed in Glasses. There is also a good image of what is happening with corrective lenses in the Hyperopia (farsightedness) topic. Lkusz 09:16, 23 March 2007 (UTC)

• When your vision is imperfect, it is because images aren't precisely projected on your . Glasses can correct this. It doesn't improve your vision - in fact, it's probably still going to degrade - but it makes looking a whole lot easier. How they affect your eyes, is disputed. Headaches can have a variety of reasons:

1. Wrong prescription.
2. Eyes need to get used to glasses because they're new.
3. Wearer doesn't consistently wear the glasses so their eyes have to get used to them again each time they use them.
4. The glasses are too old and you're in need of a new prescription. (Typically replacement should occur every 3 years if there's a significant change)

Talk to an eye specialist to see if the prescription is correct. - Mgm|^(talk) 11:36, 22 March 2007 (UTC)

Carotene, which is found in high abundance in carrots, most certainly does help with vision. In the eye, beta-carotene is converted into a form of vitamin A called retinal. That binds to a protein called opsin in the eye. When light strikes a photoreceptor, the retinal is converted from the cis form to the trans form, which in turn causes an action potential to travel along the optic nerve. The electrical signal is processed into what we perceive as vision. People with vitamin A deficiency experience night blindness. As the depletion of beta-carotene increases, the quality of vision decreases, in extreme cases resulting in blindness. That is why carrots help you see in the dark. Rockpocket 17:40, 22 March 2007 (UTC)

It's true, but most people misunderstand the phrase "good for your vision" to mean that it can actually revert defects in the eye like myopia (i.e. "fix" your eyes or "improve" your vision). —LestatdeLioncourt 06:19, 23 March 2007 (UTC)

One fact I can attest to is that your vision can improve of it's own accord, but not if you wear glasses. Vranak

In what sense and by what mechanism can your vision improve of its own accord, and how do you attest to this? Also, how does wearing glasses prevent this mechanism from working? grendel|khan 19:28, 22 March 2007 (UTC)

The muscles that point your eyes in different directions can also change the shape of your eyeballs to correct for minor defects in vision. If you're wearing glasses, this doesn't happen. --Carnildo 20:08, 22 March 2007 (UTC)

This is a common but unproven theory. A recent literature review found "...no clear scientific evidence published in the mainstream literature supporting the use of eye exercises..." (Rawstron J, Burley C, Elder M (2005). "A systematic review of the applicability and efficacy of eye exercises". J Pediatr Ophthalmol Strabismus. 42 (2): 82–8. PMID 15825744.) -- MarcoTolo 00:03, 23 March 2007 (UTC)

I think the theory is true myself, haven known two people who were like this. But neither of them had remotely bad vision in the first place, so I think it's like teeth; it can repair itself, but if you have a cavity, there's no way it'll repair that. --Wirbelwindヴィルヴェルヴィント (talk) 01:12, 23 March 2007 (UTC)

Perhaps some people's vision may correct itself, but not others. One thing that I have heard from my own optometrist is that as one ages, one starts to become more farsighted. So if one starts out nearsighted, it is true that one's vision could actually improve as one gets older. That is, of course, until one starts to need bifocals.

As far as the comment on the improvement of vision being caused by the muscles of the eye changing the shape of the eyes, what is being referred to here is astigmatism. This is an entirely separate issue from near or far-sightedness. While I am unaware of whether it is possible to improve astigmatism by not wearing one's glasses, even if one was able to remove astigmatism entirely, one would not change near or farsightedness. I know this, as I once had a pair of glasses made to correct just for astigmatism to wear over contacts, so that I could wear them while driving or reading in the days before they made contacts that would correct for astigmatism. Lkusz 09:16, 23 March 2007 (UTC)

Carrots aren't going to help your eyesight unless you have a vitamin A deficiency, which is unlikely. The myth about carrots giving you good eyesight began as World War II propoganda, as a lie used to explain why Royal Air Force pilots were doing such a great job of seeing Nazi bombers attacking at night. The lie was designed to cover up the secret real reason for the RAF's success: radar.[1] MrRedact 01:49, 25 March 2007 (UTC)

Women inventors, inventors of colour

I'm working with Grade 4 American students. They are of both genders and appear to be white, black, hispanic, and asian. We will be building circuits to make a game matching inventors to their inventions.

I'd like to make sure the game has some broad representation in terms of gender and race. I was hoping there would be a Category:Women inventors as a starting point, but that doesn't seem to exist. The first person I thought of was Grace Hopper but I'm not sure kids of that age even know what a compiler is.

So I'd like some inventors, especially women and people of colour, who have invented things the typical grade 4 student would be aware of. Thanks. moink 02:29, 22 March 2007 (UTC)

A few women inventors of things someone that age might know:

• Mary Anderson — windshield wiper
• Josephine Cochrane — dishwasher
• Bette Nesmith Graham — Liquid Paper

Unfortunately those are all a little anti-climactic. The difficulty of course is that non-Europeans and women did not invent at a proportional rate to European men for fairly obvious and well-documented historical reasons until relatively recently when things like educational options and economic situations become more balanced, but things invented relatively recently are going to be so complicated that most grade 4 students aren't going to know what they are (i.e. the Grace Hopper example). --24.147.86.187 03:09, 22 March 2007 (UTC)

Honestly, I feel that if you're teaching children about inventors, teach them about the most important inventors, regardless of their sex or race. If they all happen to be white european males, why try and misrepresent that fact? If you feel they're being brainwashed, you could teach them separately about gender roles and racism. Jolb 03:36, 22 March 2007 (UTC)

"Important" is a tad subjective. Don't worry; I won't be leaving out Thomas Edison. But really, can we order inventions in order of importance? What's more important? Paper or the lightbulb or the car or the dishwasher or the compiler? Who knows? I used all but the dishwasher today. moink 03:52, 22 March 2007 (UTC)

The answer in order of importance of the five you listed is 1) paper (not liquid paper) 2) lightbulb 3) car 4) compiler 5) dishwasher. --Tbeatty 07:42, 22 March 2007 (UTC)

Some inventions change the world. Other don't. The lightbulb is clearly a more important invention than the Johnny Mop or Liquid Paper. Of course we can order inventions by their importance, and though there may be quibbles and debates about that order, it's a far better representation of reality than pretending all inventions are of equal significance. - Nunh-huh 04:58, 22 March 2007 (UTC)

We have Category:Inventors_by_nationality and of course you can peruse Category:Inventors. However, I agree strongly with Jolb - why should race even be an issue? If it were a history class, you might talk about racial segregation, or educational opportunities (lack thereof, for minorities); and how this impacted the trend of inventor social and racial categorization. You could go into great depth about social injustices; and/or about how some great people managed to overcome societal barriers to achieve great accomplishments. But your project is about inventors, not the history of gender and race. As Jolb said, why misrepresent history to pretend that it has always been very inclusive? You might be doing a disservice by pretending that the history of science and technology was conducted according to modern standards and social norms. Nimur 03:49, 22 March 2007 (UTC)

Race and gender are issues when you are trying to motivate young students to feel that people like them have accomplished things. The actual facts hardly matter at that age — no matter what you teach them will be half false anyway, because the fact is that ALL of history is too complicated to be turned into something that a 9 year old can easily grasp and still be factually accurate. (speaking of which, Edison didn't actually invent the lightbulb.) Going out of your way to mix in a few people of color and a few women into a unit about important inventors is neither intellectual travesty nor incoherent — it is a pedagogical exercise, like most things at that educational level. --24.147.86.187 04:19, 22 March 2007 (UTC)

People like them? That hardly sounds enlightened! Surely you are well-meaning. But in honesty, can you tell me that a black child can not identify with Isaac Newton just because he was a white man? That is the core of the problem! A Hispanic, black, white, orange, purple... child should see the science for what it is - an equal platform on which the only important merit is the mind. I am not an Englishman or a German, but I never have any problem respecting the work of great English or German inventors and scientists. We are all "people like us." I think you will be doing great harm to your students if you teach them that they should be like their own kind. Nimur 04:38, 22 March 2007 (UTC)

"People like them." It's a perfectly innoculous phrase. People like me. People like you. It isn't meant in any pejorative sense, and isn't used in a generalizing or stereotyping sense, so don't get huffy and insert it where it isn't implied. And science has not been an equal platform for the mind, and science has not been fully international, and science has not been ignorant of the class, skin color, or gender of the participant. Giving people of all shapes, sizes, colors, etc., good role models is always positive, and counteracts the effects of a harmful media which only tells the stories of white males, IMO. --140.247.249.241 15:54, 22 March 2007 (UTC)

My point is that we should identify people based on their accomplishments, not on their race. There are ten million ways to "categorize" people - racial traits are one of the most useless categories. They don't necessarily reflect anything about the person, their personality, or even their culture. What does it mean to be "like" somebody else? Maybe a black child's mind is more like Isaac Newton than George Washington Carver. Maybe a white child has more in common with a black inventor. Why should there be any lumping of role-models? Each student should not have a personal role-model of matching color, they should match personalities and goals and mental traits. That should be the important characteristic, not the skin color. Nimur 18:41, 22 March 2007 (UTC)

no matter what you teach them will be half false anyway, because the fact is that ALL of history is too complicated to be turned into something that a 9 year old can easily grasp and still be factually accurate.

I disagree. It's wrong to treat children like idiots, and it's wrong to give them misinformation. The fact that kids are taught a lot of misinformation is not because they're incapable of understanding real information, it's because teachers are too politically motivated to give straightforward, accurate information.

Also, I agree with Nimur. By subtly sliding in things specifically on the basis of race and sex, you're subliminally inserting racial and sexual biases. It's also subliminally demeaning to women and (to use your politically incorrect terminology) "coloured people" to be like Man:Lightbulb, Man:Automobile, Man:Modern Physics, Man:Electric Circuits, Black Man:Peanut Butter, Woman:Liquid Paper. Children aren't stupid enough to be fooled into believing that they're all equally important inventors, and without adressing race and sex issues, they might draw the conclusion that women and "coloured" people might not be capable of making important inventions. Jolb 05:23, 22 March 2007 (UTC)

I don't treat children like idiots, but the fact is that history is complicated and messy. I have enough trouble trying to teach undergraduates at an Ivy League institution that history is complicated; 9 year olds can barely remember the simple stuff. Most adults can barely grasp the complexity of history in the end and have silly myths about what type of person Albert Einstein or Thomas Edison was; half of the articles on Wikipedia on these figures reflect these myths entirely. That doesn't bother me — people get things out of history other than strict historical truth, and in fact strictly accurate history is often totally useless for the sorts of things people want to use history for (to teach lessons on how to be a good citizen, on how we all got to where we are today, on how to appreciate change over time, etc.). I say this as an academic historian and as an educator, one who cares very much about teaching as well. --140.247.249.241 15:54, 22 March 2007 (UTC)

the sorts of things people want to use history for (to teach lessons on how to be a good citizen, on how we all got to where we are today, on how to appreciate change over time, etc.) You're plainly revealing that you're inserting a political motivation into teaching history. You're doing something unethical, and it's in the best intrest of future generations for you to not slant your information for political reasons. Jolb 17:29, 22 March 2007 (UTC)

Could you describe some of these silly myths that are in the articles Albert Einstein and Thomas Edison? It would be helpful if you could point them out, as they sound like the sort of thing that could be considered NPOV. grendel|khan 19:27, 22 March 2007 (UTC)

Marie Curie, List of black inventors and scientists Category:African American inventors, Category:African American engineers, Category:Women scientists. That said, I hope your lesson is to show that science is blind to both color and gender. --Tbeatty 07:56, 22 March 2007 (UTC)

Is it? It hasn't been. In fact contributions of women and people of color were systematically de-valued up until very recently, and even today the number of women and people of color in engineering and science is vastly disproportional to their abilities. That's part of the conundrum of teaching this sort of thing; you want to showcase that there was struggle, but that even in struggle there were individuals who were successful, but not make them out to be so exceptional as to be exceptions to a hypothetical rule. Professional and intellectual opinions vary quite considerably on how to best to talk about this, and I certainly don't presume to have an answer. --140.247.249.241 15:54, 22 March 2007 (UTC)

Stephanie Kwolek - Kevlar − Twas Now ( talk • contribs • e-mail ) 08:27, 22 March 2007 (UTC)

If you are including scientists as well as inventors then Rosalind Franklin deserves a mention. Gandalf61 12:00, 22 March 2007 (UTC)

Per most reference books, Thomas Edison actually did invent the light bulb. Ira Flatow, a science writer, listed 23 prior failed attempts, which may be what you refer to. See Jill Jonnes, "Empires of Light, Random House, 2003 for a recent history of the 19th century electrical developments. One could always find a prioir attempt which was unsuccessful and claim that was the "true invention" of something. See also "Edison's Electric Light: Biography of an Invention" (1986) by Paul Israel, Robert Friedel and Bernard S. Finn. Edison 14:26, 22 March 2007 (UTC)

Edison didn't invent the lightbulb, he just came up with one particular model which worked well-enough for mass-market use (specifically because of an innovation in the filament, not the bulb idea as a whole) and managed to sell along an infrastructure to go along with it. See i.e. Thomas P. Hughes, American Genesis: A Century of Invention and Technological Enthusiasm, 1870-1970 (1989). I find it ironic you cite a Paul Israel book as he is one of the bigger debunkers of the Edison myth these days (and an excellent scholar), but in any case it doesn't matter. My essential point is that the history of invention can be terribly, terribly complicated (ergo our Wikipedia encyclopedia page on the light bulb, itself meant to be a condensed summary, still has to devote a lengthy discussion to the question of whether there is a single inventor of the incandescent bulb), and to be strictly accurate one ends up a mire of questions about what it means to "invent" something in the first place. Too complicated for most adults to have any grasp on, clearly too complicated for most kids. --140.247.249.241 15:54, 22 March 2007 (UTC)

Gotta put a word in for Ada Lovelace - generally accepted to be the world's first computer programmer! SteveBaker 23:34, 22 March 2007 (UTC)

Oooh! And Hypatia - who invented a bunch of useful gadgets in about 450AD. SteveBaker 23:39, 22 March 2007 (UTC)

This [2] is a useful list. SteveBaker 23:41, 22 March 2007 (UTC)

Accretion disks

Why does matter orbiting a center of mass always accrete into a disk? Why does matter in oribt all tend to form into a plane instead of into a 3-dimensional sphere? And why is this disk-shaped accretion universal for everything from the rings of planets to galaxies? Jolb 03:28, 22 March 2007 (UTC)

First, angular momentum must be conserved; this explains why the objects are orbiting at a particular radius (elliptical or otherwise), instead of collapsing in to the massive body in the center. Next, I think that the disc forms because the average total angular momentum lies along a single axis (it must, because the total average is a single vector); this axis in turn defines the normal plane of the accreted system. Over time, each individual particle moves towards the system's net (average) angular momentum via collision, gravitation, etc. This is all due to conservation of (angular) momentum. Nimur 03:55, 22 March 2007 (UTC)

PS - See Formation and evolution of the Solar System and planetary formation for further details. Nimur 03:56, 22 March 2007 (UTC)

PPS, this ensemble article goes into brief detail about my statement about individual particles approaching the system's average. If the system is 'well behaved' (i.e. following classical gravitation, to reasonable approximation), then each individual particle approaches the system average with some spread. It's not entirely unlike temperature - each particle's energy is closely spread around the system average. Nimur 04:02, 22 March 2007 (UTC)

Visualization from University of Arizona. Nimur 04:09, 22 March 2007 (UTC)

As an extension of this, let me point out that the rotational inertia of a disk of a given radius and mass (rotating in its own plane) is 25% larger than that of a sphere with the same shape, and the inertia increases as $mr^{2}$ in either (in any!) case. That means that a disk can have a smaller radius and still preserve the total angular momentum, which means that the mass can be closer together; the disk thus has lower energy than the sphere and is more stable. (The fact that such disks tend to be denser/thicker in the middle represents a compromise between reducing the moment (by turning it into a sphere/disk hybrid) and reducing the energy further.) --Tardis 04:59, 22 March 2007 (UTC)

So, to summarize, this is all due to the object's spinning. If the object didn't have any spin at all, it would indeed collapse in a spherical fashion. StuRat 19:14, 22 March 2007 (UTC)

slotted arrays

list the properties of slotted arrays? —The preceding unsigned comment was added by Ambuj0542 (talk • contribs) 05:29, 22 March 2007 (UTC).

1. Slotted
2. Array

You probably mean antennas, though: see slotted waveguide article.

Nimur 05:34, 22 March 2007 (UTC)

google "slotted array" yields this. Its a phased array of slot antennas. -Arch dude 21:16, 25 March 2007 (UTC)

what is to thrive?

what is to thrive? (not the album) —The preceding unsigned comment was added by 60.242.218.72 (talk) 06:50, 22 March 2007 (UTC).

[3] : To grow or increase in bulk or stature; to grow vigorously or luxuriantly, to flourish. Nimur 07:11, 22 March 2007 (UTC)

Try typing it in Wiktionary next time. [Mαc Δαvιs] (How's my driving?) ❖ 18:58, 22 March 2007 (UTC)

This answers the question 'What does it mean to thrive?', but the question asked what is to thrive technically means 'what is meant to thrive?' :] To find the answer to this you want to look up 'Survival of the fittest' in Wikipeda :] You may also want to look under 'Selective breeding' and 'religeon' :] HS7 20:00, 22 March 2007 (UTC)

Also see failure to thrive. --David Iberri (talk) 21:57, 22 March 2007 (UTC)

Too much sodium in the diet

I've tried washing and soaking canned goods and other foods high in sodium but to little avail. Is it possible to compensate and overcome and balance the effect on the heart of the extra high amount of sodium intake from these foods despite the precaution of washing them by adding potassium in the form of salt substitute to your foods? Nebraska bob 07:27, 22 March 2007 (UTC)

I think potassium will be just as bad for your blood pressure as sodium. You should drink more water, reduce your total salt intake, and consult a medical doctor if you have severe nutritional problems. Nimur 07:31, 22 March 2007 (UTC)

This isn't really an answer, more just advice, but the less-processed a food is the less sodium it is likely to contain. So rather than washing processed foods to remove sodium, is it possible to prepare more food from scratch yourself? Then you'll have complete control over the sodium content. Anchoress 07:35, 22 March 2007 (UTC)

Unfortunately fresh meat, vegetables and fruits instead of canned are not always available either because food is purchased in bulk and stored long term where refrigerated storage is not available or the convenience of fast foods is a necessity rather than an option. Drinking more water means urinating more but if that is the only solution for dealing with the extra sodium in highly processed foods then as long as the kidneys can handle it, it is the solution that will have to be used. Nebraska bob 09:36, 22 March 2007 (UTC)

Yeah, soaking those Whoppers must really eat up a lot of time. ;-) I kid. On another note, I wonder if MSG has the same effect on the cardio-pulmonary system that table salt does? Anchoress 20:09, 22 March 2007 (UTC)

Read this article (prepared by a rather brilliant author): [4]. :-) StuRat 18:44, 22 March 2007 (UTC)

Nice work, Stu. But I have a beef; you threw a bitch fit a few months ago when I included potatoes on a list of healthy foods, but I've seen you recommend them several times since. So are you anti-potato or just anti-me? :-( Anchoress 20:13, 22 March 2007 (UTC)

I don't recall "throwing a bitch fit". Whether they are good or bad depends largely on what form they take and what they are compared with. If you compare chili-cheese fries, potato chips, hash browns, or tater tots to steamed broccoli with lemon juice, the spud choices are abysmal. On the other hand, adding some boiled taters to canned soup almost always improves it's nutritional content. A baked potato can be good, but not if you smother it with bacon and cheese, and then toss out the skin (the most nutritious part). Taters always have a high glycemic index, so that is a negative. As for me being "anti-Anchoress", you'll note I came to your defense above on the "METAR report" question. I've generally been on your side most times since we had our tampon fight when we first met. StuRat 21:50, 22 March 2007 (UTC)

Yuck! Too much information! Get a room! --Zeizmic 22:03, 22 March 2007 (UTC)

Sorry Zeizmic, I replied on StuRat's talk page. Anchoress 01:04, 23 March 2007 (UTC)

Thanks to one and all. (BTW - as for the Whoppers, Anchoress, it's getting the salt out of the La Juice before they are soaked that's the problem... Nebraska bob 07:42, 25 March 2007 (UTC)

molectronics

I am currently in my second year of a 5 year Ph.D. program at the U. of Washington (Seattle) (the primary focus being superpartners). Recently, I submitted an article dealing with the field of molectronics. An editor of this website decided that such an entry was doubious, at best. Essentially, I am writing in an attempt to verify the possibility that I know "what the fuck I am talking about."

That possibility has been verified. Of course, the article currently sitting at molectronics is extremely inadequate. Perhaps you could flesh it out on your userpage first, and then move it over into an article. − Twas Now ( talk • contribs • e-mail ) 08:30, 22 March 2007 (UTC)

Maybe it is a better idea to redirect Molectronics to Quantum ComputingMolecular computer, and add a sub-section there with the new content. Nimur 08:34, 22 March 2007 (UTC)

Yeah, if you could put some information or write a bit of an article, or some references or links on your userpage I and we would much like it. [Mαc Δαvιs] (How's my driving?) ❖ 19:00, 22 March 2007 (UTC)

Viagra

This is a question that has been in my mind for weeks... what happens when women take Viagra as an aphrodisiac?--Orthologist 15:34, 22 March 2007 (UTC)

Similar effects: increased turgidity of those structures that respond to sexual excitement with hydraulic events.

Atlant 16:07, 22 March 2007 (UTC)

Increased vasocongestion in the corpus cavernosum clitoridis and vestibular bulbs, just to, you know, use more sciencey words. [Mαc Δαvιs] (How's my driving?) ❖ 18:57, 22 March 2007 (UTC)

This isn't about the aphrodisiacal properties of Viagra, but is certainly a related topic! I wrote a paper last term on the effects of nitric oxide, a secondary messenger that is key for Viagra to function. Viagra causes vasodilation, which improves blood flow, and increases the thickness of the endometrium (uterine lining). There was a study on a small group of women (only four), all of whom had recurring spontaneous abortions (three or more per woman), and all of whom had uterine lining that was thinner than the uterine lining of the average woman (at least 8 mm is typical, yet these women had lining less than 4 mm). It was posited that the reason these women were having spontaneous abortions is that the embryo could not properly implant in the uterine lining. The use of Viagra resulted in successful pregnancies in three of the four women. − Twas Now ( talk • contribs • e-mail ) 21:20, 22 March 2007 (UTC)

Saying about acceptance of an idea

Not sure if this is really the right desk for this, but thought the Science Desk would be more likely to be patrolled by people who'd recognise this.

Ages ago, I remember reading some writer (possibly a sci-fi writer, but I wouldn't bet on it) talk about the stages of acceptance of a problem. It was something like initially claiming there was no problem, then claiming there might be a problem, but there was nothing that could be done about it, then claiming there was a problem, and something could have been done about it, but now it was too late. Obviously, some people's comments on global warming have made me think of this, but I can't remember what it actually said, or who wrote it, or where I read it. Anyone remember this one? Skittle 16:35, 22 March 2007 (UTC)

I might be way off, but I think this is in one of Douglas Adams's later books. Nimur 17:38, 22 March 2007 (UTC)

Could be. But it's also just the sort of thing that Sir Humphrey Appleby would have said on Yes, Minister. --Anonymous, March 22, 2007, 23:20 (UTC).

I think it's either from Hitchhiker's or Discworld. Probably the former. 80.169.64.22 17:16, 23 March 2007 (UTC)

Video Out on graphics card > Broken TV?

My friend hooked up his television to the video out on his graphics card via a scart adapter. The picture was fine at first but after a couple of minutes went black and white and then eventually started jumping around and bluring etc. Now when trying to watch television normally, there is disruption of the picture with it jumping, going black and white, giving a 'no signal' message etc. What could be causing this? --Seans Potato Business 17:06, 22 March 2007 (UTC)

Sounds like a TV is in NTSC mode when it should be in PAL, or vice-versa. Is there a way to restore factory-defaults via a menu or button? If not, try "rebooting" (unplug/replug the television). It is possible, but not likely that the television is permanently damaged; it is probably just in the incorrect mode. Nimur 17:40, 22 March 2007 (UTC)

Picture of the Day

Richard's Pipit

What are the dots on their tongue?

Ancillary question - has User:Kurt Shaped Box or any member of his family eaten this? Nimur 18:11, 22 March 2007 (UTC)

I may have eaten the soup. --Kurt Shaped Box 22:04, 22 March 2007 (UTC)

Most of the time these dots indicate feed this mouth -- sort of like an offspring identification system. Sometimes where there's brood parasitism these marks help the parents figure out which babies are theirs. In Vidua for example, the species that does the parasitism actual has evolved markings to look more like the host species. --Cody.Pope 22:03, 22 March 2007 (UTC)

There's a similar thing in a species of gull (which unfortunately escapes me at the moment), where the adults have a red spot on their beaks, when prodded instinctively by the chicks, a regurgitating reflex will be induced, and Voila! Dinner for small birdies :) -Obli (Talk)^? 01:59, 23 March 2007 (UTC)

Quite a few gull species exhibit that. In the UK, Herring gulls and both Lesser and Greater black-backed gulls have the red spot on their beaks for this purpose. I can't even begin to suggest how/why that evolved... :) --Kurt Shaped Box 07:56, 23 March 2007 (UTC)

There's a number of theories: it may be because the high constrast black-on-yellow makes the bird easier to see in a dark nest, it may trigger an automatic feeding reflex in young birds, or it may be to make it easier for birds to identify parasites as Cody.pope suggested. Albino birds without the markings are often fed less than their young, implying that the markings do have a purpose. They also help bird-keepers: young chicks of different species often look similar, and the markings allow ornithologists to tell chicks apart.[5] Laïka 10:10, 23 March 2007 (UTC)

I was referring to the red spot on the beaks of the adults of certain gull species. Somehow the baby gull knows to peck at this when hungry, whilst at the same time the adult knows to regurgitate food when the spot is pecked. It seems like a very complex system to me - needlessly so, in fact. I just can't think of a single reason why gulls would evolve this. In the species that don't exhibit the red spot, the parent birds just feed each chick in turn (they don't produce large broods and AFAIK, the parent gulls work hard to ensure that each chick gets an equal share) when they return to the nest. --Kurt Shaped Box 17:33, 23 March 2007 (UTC)

What kind of squirrel is this?

I took a picture of this squirrel in New York City (Queens, near the river); it looks like an Eastern Gray Squirrel, but I wanted to confirm before I uploaded it to Commons. Is that what it is? Is this one also an Eastern Gray Squirrel? (The second was taken in eastern Connecticut.) grendel|khan 19:04, 22 March 2007 (UTC)

Great pictures!! I wish I knew which species it is.--Sonjaaa 00:19, 23 March 2007 (UTC)

weight and gravity

If three men, weighing 180, 180, and 170 pounds respectively jump six inches in the air, how much pressure (in pounds) would they put on the surface they were standing on? —The preceding unsigned comment was added by 167.206.19.12 (talk) 15:09, 22 March 2007 (UTC).

Pressure = Force / SurfaceArea

Force = G M1 M2 / r^2

Get the values for G , M1 (earth) , M2 (human) ,r (distance to centre of earth)

Get a pencil and draw out the surface area of the shoes on a big piece of paper

Measure the drawn surface area on the big piece of paper.

210.49.121.183 15:12, 22 March 2007 (UTC)

Easiest way to get the area of an irregular shape like that is to cut out and WEIGH the paper, and divide that weight by the weight of a unit square of the same paper. --BenBurch 15:20, 22 March 2007 (UTC)

I think you guys are missing the question. As the jumpers lift off towards their ultimate altitude of six inches, they impose an impulse on the surface of the Earth. I think the question is asking about this impulse. (The question doesn't ask about pounds per square inch.)

Atlant 16:05, 22 March 2007 (UTC)

Atlant, the question didn't ask about psi per se, but did ask about pressure. Pressure is not measured in pounds; this is likely the source of confusion. Force is measured in pounds (or newtons). Pressure is measured in pounds per square inch, or newtons per meter squared. — Knowledge Seeker দ 18:19, 22 March 2007 (UTC)

The force needed to lift them 6 inches is equal to their mass (in kg)*the distance (im m)*9.81, which is 240.91*0.15*9.81 :) You might be able to work out the pressure from that, but I don't know how :( HS7 16:36, 22 March 2007 (UTC)

That is the kinetic energy that they must acquire to lift themselves 6 inches above the ground, not the force. Energy = force x distance, so they could acquire this energy by exerting a large force over a small distance or by exerting a smaller force over a larger distance. Gandalf61 17:24, 22 March 2007 (UTC)

Impulse is Force x time = $\Delta$ Momentum . Pressure is Force / Area. So, Pressure = ${\frac {1}{A}}{\frac {dp}{dt}}$ and depends on the mechanics of their shoe, the contact time, the time-varying area of contact, etc. It is not an easy question to answer without sophistated, time-varying models of the points of contact. Nimur 18:20, 22 March 2007 (UTC)

Okay, sorry to move this down--I posted the question and I'll be more specific: Three men, 180, 170, 150, pounds (I know I changed the weights, this is more accurate) jump 6 inches off the floor of an elevator. The elevator has a 13 person / 2000 pound weight limit. Would the three men overload the elevator on their landing?

It depends on how they land. If you dropped a large block of metal, it would stop more quickly (its center of mass would move less from the time it hit to the time it stopped moving) than a ninja landing with bent knees, cat-like tread and all that. Consider that for the same amount of work, you'd be, in the first case, dealing with a small d and large F, and in the latter, a large d and a small F. Remember, $W=F\times d$; work equals force applied over a distance. The people are descending with a given kinetic energy, which is the amount of work done in stopping them. This can be done with a large force over a short distance (metal block), or a small force over a large distance (ninja). There's no simple yes-or-no answer to your question. grendel|khan 19:20, 22 March 2007 (UTC)

Really? So it is possible for those three men to overload the elevator? I don't have to know definatively, but it seems like it's a question that some one who knows a bit of physics would be able to fairly surely say "probably yes" or "probably not." Not to nag for an answer, but would you say it's likely the elevator would overload or unlikely that 500 pounds could come down with four times the force off a six inch hop.

Since you insist, I'll do some back-of-the-envelope calculations. Take a 500 pound (227kg) lead brick, and drop it on the elevator's floor. From a six-inch (0.15m) drop, it's got to release (227kg*9.8m/s^2*0.15m) = 334 J of energy. So, given that W=Fd, so d=W/F, then it will break if it deforms less than d = 334 J/(2000lb * 9.8m/s^2) = 334 J/8888 N = about 3.75cm, or an inch and a half. So, if a five hundred-pound lead weight is dropped from six inches' height, and if its center of mass travels less than an inch and a half between the time it hits the elevator floor and the time it stops moving, and it exerts a uniform force on the floor, then that force will be of magnitude two thousand pounds, which will break the elevator. Bear in mind that if you hit that hard, even from only six inches' drop, you'd run a risk of hurting yourself. If you try jumping on a hard surface, locking your knees and hitting on your heels, it'll feel bone-jarring. grendel|khan 21:50, 22 March 2007 (UTC)

I think the answer is almost certainly no, as long as it's just one jump, because the objects involved are men, not rigid objects like metal blocks. The natural way to land is on the balls of one's feet, with slightly bent knees, not on one's heels with straight knees (ouch!). To go over the 2000 pound limit, there would have to be an instant when the men are applying an average of 667 pounds of force each to the floor of the elevator. Given that the men are landing on the balls of their feet, how much force they are capable of applying is limited by the strength of their calf muscles. Going over the average of 667 pounds each would require a strength roughly similar to the strength required by each man getting an extra 500 pounds of weights strapped to their waist, and then rising up onto the balls of their feet. I know I don't have the strength to do that, and I think it's unlikely that any of the three men in question do, either.

If, however, instead of just one jump, the men instead are jumping up and down repeatedly, then the analysis would get more complicated. If the men jump up and down at the same frequency as the resonant frequency of the elevator, then it would be possible to break the elevator without ever appying more than 2000 pounds of force instantaneously, if the elevator damped such oscillations insufficiently. MrRedact 21:47, 22 March 2007 (UTC)

It is possible for a flea to overload the elevator, it just needs really really sturdy legs. —The preceding unsigned comment was added by 84.187.7.58 (talk) 06:15, 23 March 2007 (UTC).

Not really, of course, and the reason why is related to a significant effect that hasn't been taken into consideration above, but perhaps should be: The 2000 pound limit is about the amount of force it would take to damage the elevator cable (assuming there isn't any leeway in the rated limit, which isn't really the case), if the force is applied continuously. But there won't necessarily be any damage just because the instantaneous force applied exceeds 2000 pounds briefly, because the steel cable supporting the elevator is somewhat elastic. For a while after a force over 2000 pounds is applied, the cable will deform elastically, with a relationship between stress and strain governed by Hooke's law. The cable will only be damaged by undergoing a plastic deformation after the excessive force has been applied long enough that the resulting strain on the cable exceeds the cable's yield strength. During the time that the cable is deforming elastically, the cable is absorbing kinetic energy from the object that fell in the elevator car, converting it into potential energy in the cable. Once all of the kinetic energy is absorbed, the only remaining force on the cable is just the gravity on the stationary object, which is way under the rated limit in any case considered above. In the worst case of 100% of the kinetic energy of the object upon landing being transferred to the elevator car (in reality it will be less), the energy the cable needs to absorb is equal to the potential energy of the object before it falls, which is mgd, where g is the accelleration of gravity, m is the mass of the object, and d is the object's initial height above the elevator floor. In the case of a flea, since the mass of a flea is negligible, the maximum kinetic energy a flea can impart on the floor of the elevator car is also negligible, no matter how sturdy the flea's legs are. MrRedact 18:29, 23 March 2007 (UTC)

Indeed; you usually have to take into account a coefficient of safety (as you would are dealing with $\sigma _{allowed}$, not $\sigma _{maximum}$, and $CoS={\frac {\sigma _{maximum}}{\sigma _{allowed}}}$) and even then, $\sigma _{maximum}$ is usually the yield strength of the cable, not the fracture stress. If the high stress is short-lived, then I doubt you would have much of a permanent deformation. Titoxd^{(?!? - cool stuff)} 18:39, 23 March 2007 (UTC)

Yeah, the CoS is important, too, and I think it's pretty large for an elevator. The yield strength of steel is in the ballpark of about 300 MPa, depending on the alloy, which means that theoretically a cable only needs to have a cross-sectional area of about 0.45 cm² to lift 3000 lbs, without even any plastic deformation, much less breaking. The elevator cables I've seen are a heck of a lot fatter than that. I think it's practically impossible for the three guys in this case to physically damage the elevator by jumping six inches. MrRedact 20:36, 23 March 2007 (UTC)

Hibbeler (ISBN 0-13-191345-X) says that Young's modulus for A36 (structural) steel is 200 GPa; the same is true for L2 (tool) steel. 304 (stainless) steel is 193 GPa, slightly lower, but still about three orders of magnitude higher. The ultimate strength of the three alloys is 400, 800, and 517 MPa, respectively. Either way, the three dudes won't do a thing to a well-built elevator. Titoxd^{(?!? - cool stuff)} 05:10, 24 March 2007 (UTC)

Helping a friend study physics

Unfortunately, I haven't studied it myself in a few years, so a few equations are a bit fuzzy, especially since my friend's teacher uses notation that at the very least I am not used to (e.g. capital 'W' for both weight and work). I've managed to figure out most of the equations on the list of equations to study, but a few still elude me:

1. GPE=mgh (it's potential energy, since it's mgh, right? Then what's with the G? Potential energy due to gravity?)
2. P=P_atm+Dgh (it's supposed to be pressure due to fluid, I think, but from which direction is 'height' measured?)
3. Q=mL_f and Q=mL_v (enthalpies of fusion/vaporization with some strange notation)
4. Q=ne
5. E=F/q
6. E=kq/r²
7. W=ΔEPE and V=EPE/q (Alas, I'm not so hot on electrical physics)

So if anyone could help explain these or send me in the right direction, I would most appreciate it. And no, it actually is my friend, not me ;-)

137.99.165.83 21:03, 22 March 2007 (UTC)

First things first: Potential energy is dirctly proportional to acceleration of gravity. After all, the bodies fall faster when g is larger, and initial potential energy is equal to the kinetic energy when the body is touching the ground. Secondly, total pressure is the sum of pressure due to atmosphere plus atmosphere due to fluid. The height is measured from the surface of the fluid. As for the rest, wait for someone else, because I'm not familiar with English physics terms.--Orthologist 21:31, 22 March 2007 (UTC)

I've numbered your equations for ease of reference:

1. GPE is indeed gravitational potential energy.
2. D is density (more commonly denoted by ρ), and "height" there really means "depth" -- distance from the air/fluid interface (at the top) to the point in question.
3. Q here is an amount of heat released or absorbed; m in these equations is just mass. The L_? are the specific enthalpies; "specific" means "per mass" (as opposed to "per mole" or "per volume").
4. Q here is instead an amount of electric charge; n is a number of charged particles, and e is the charge on each one ($\pm$elementary charge for protons or electrons (or electron holes)).
5. E here is the electric field, and F is force; q is the charge on which the force is applied.
6. E here is the same; k is Coulomb's constant, and r is the distance from a charge.
7. W here is work done on a charge; EPE is the electric potential energy. V is voltage, and q here is the charge on a proton.

(Whew, that was a workout trying to guess what all the equations were!) Does that help? --Tardis 21:32, 22 March 2007 (UTC)

The L's in part 3, stand for latent heat of fusion/vapourisation. Latent means hidden as energy goes into changing state, not temperature, so is hidden. And they are specific latent heats as said above (are they also enthalpies? I can't remember my chemistry now!)137.138.46.155 14:47, 23 March 2007 (UTC)

Look at enthalpy of vaporization: it explains the subtle, and often neglected, differences between "latent heat" and "enthalpy of phase change". The "specific" is separate, and just indicates what units you're using. --Tardis 20:42, 23 March 2007 (UTC)

Vasopressin and caffeine (again)

i ave just read articles on Vasopressin and i was wondering if there might be a relation between long term caffeine intake and the brain chemical fonction of Vasopressin like agressivity to other males and bonding to sexual partners clockwork fromage —The preceding unsigned comment was added by 216.113.99.149 (talk) 17:48, 21 March 2007 (UTC).

I think you're a little ahead of the game. I don't believe such a link has been established, which doesn't mean it doesn't exist. However, the caffeine article states the over use and intoxication effects of caffeine, which has been around for a long time, and none of it seems to mention aggression or relationship issues. Vespine 21:58, 21 March 2007 (UTC)

There is known to be cross-talk between caffiene induced and vasopressin induced release of intracellular Ca2+ stores, somewhere at, or upstream of, an endoplasmic reticular Ca2+-ATPase. However, knowing there is a molecular interaction between the two signalling pathways is very different from knowing their behavioural consequences. Rockpocket 22:05, 21 March 2007 (UTC)

i would like to know if (assuming cafeine affects vasopressin in the brain) since caffeine would decrese vasopressin related beaviours it woudnt be as noticable as , for exemple a increase in agression and might not ave been noticed yet in studies on caffeines clockwork fromage

sorry the first paragraph was suposed to be a quote from a previous article

Its entirely possible. A large scale, controlled study on the long-term effects of caffeine on human behaviour would be an expensive and time-consuming experiment. There would be so many confounding factors that an extremely large sample size would be required to identify any significant associations. Nevertheless, caffeine is a psychoactive substance, therefore it would be naive to assume it couldn't effect long term human behaviour, though proving it does would be difficult. Rockpocket 01:47, 23 March 2007 (UTC)

atomic physics

In the atom what keeps an electron from just emiting all its energy until it finally goes and collapses into the nucleus?---- —The preceding unsigned comment was added by 71.116.166.117 (talk) 22:59, 22 March 2007 (UTC).

In atomic physics, electrons don't behave like simple point particles, like they are modelled in classical electrodynamics. Rather, it becomes neccessary to model the electron according to quantum mechanics. In quantum mechanics, an electron being attracted to an atomic nucleus can't just release an arbitrary amount of energy. Instead, the electron can only give off energy in discrete quanta. An electron near a nucleus can only exist in a finite number of possible states, each of which has a particular amount of energy associated with it. An electron can only get "closer" to the nucleus by moving to a state with lower energy, in the process releasing an amount of energy equal to the difference of the energies associated with the two states. Since there are only a finite number of possible states, there exists a state with the lowest energy level (the ground state), from which the electron can no longer lose any more energy, because there do not exist any possible states with a lower energy level that the electron can move to.

I quoted "closer" above because in quantum mechanics, electrons are no longer modelled as being at a precise location, but instead are modelled with a wave function. So at a given point in time, the "distance" between the electron and the nucleus is only meaningful in a statistical sense.

To really understand this answer, you'll have to study quantum mechanics. A good textbook I'd recommend is Principles of Quantum Mechanics, by R. Shankar. Introductory Quantum Mechanics by Richard Liboff is at a little more introductory level, but Shankar explains things better and more thoroughly. MrRedact 02:05, 23 March 2007 (UTC)

Quantum Mechanics. I'm not making fun of you - it's a good question; classically, accelerating charged particles emit radiation. The fact that this is not the case for a trapped electron in an atom was one of the important clues that led physicists to the idea of a wavefunction. Basically, the electron is a wavefunction, not a particle whizzing around the nucleus. --Bmk 02:01, 23 March 2007 (UTC)

This, by the way, was exactly the question that made the Rutherford model impractical, and is what led Niels Bohr to the Bohr model of the atom. Bohr could postulate an atom which would not lose all its energy this way, but he couldn't explain why there were stable states. The first bit of an answer came from Louis de Broglie's understanding of the wave nature of the electron; the more comprehensive answer then came from quantum mechanics. --24.147.86.187 02:51, 23 March 2007 (UTC)