Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

July 13

Cultural or instinctive - revulsion at homosexuality

I recently read comments on a forum where a large number of people used the argument "I find the idea of homosexual acts disgusting, therefore homosexuality must be absolutely wrong (or evil)" in one form or other. This is obviously a flawed argument; I could use it to say that celery soup is absolutely wrong or evil! I found it interesting that so many people find the idea of homosexual acts disgusting though. Especially since though I support gay rights and equal treatment for homosexuals at a deep level I feel revulsion at the thought of homosexual acts.

Is this revulsion some deep instinct, maybe something to do with a persons sexuality? I have heard some homosexuals say that they find the idea of sex with someone of the opposite sex disgusting, which would support this. On the other hand it is clearly not universal as there are bisexuals. It seems there is some evidence that it is instinctive and some that it is learned or cultural. Has any research been done on this. -- Q Chris (talk) 12:35, 13 July 2011 (UTC)

Dont Know of any studies, but my my analysis(guess): Feeling disturbed with homosexual interactions may help choose the a partner of the right sex, (i.e. on the straight and narrow path) especially as a strong attraction for both sexes must be coded in the same genome. As most people judge "what's disgusting for me to do is disgusting even if you do it" instinctively this may explain homophobia.

fMRI data indicates that homosexual's brains respond in almost exactly the same way as members of the opposite sex will to smelling estrogen/testosterone. May be in homosexuals the instinctive dislike also is reversed.Staticd (talk) 13:12, 13 July 2011 (UTC)

My instinct is that disgust towards homosexuality is almost certainly a learned trait. Within human culture, it is not universal at all; many cultures have no problems with it at all (see Ancient Greece) and some practices, which in some cultures are viewed as homosexual, are commonplace in others (Cheek kissing among males in say France, or hand holding among Arabic males). Among non-humans, behavior that would be described as "homosexual" is commonplace; male dogs will copulate with each other (heck, a male dog will copulate with a lampost) and such behavior is common among the Bonobos, which are genetically among the closest relatives of humans. Negative reactions towards homosexuality are likely strongly corrolated towards cultural reactions towards non-procreative or extramarital sex in general. --Jayron32 14:50, 13 July 2011 (UTC)

That's a very good point about other cultures. At first I was surprised at how such a culturally learned feeling could seem so instinctive and natural - but then it feels just as natural and instinctive to feel revulsion at people eating Witchetty grubs, or locusts -- Q Chris (talk) 21:15, 13 July 2011 (UTC)

Well bearing in mind that the acitivity is ABNORMAL, its not surprising that many people are nauseated by it. — Preceding unsigned comment added by 78.148.128.45 (talk) 15:09, 13 July 2011 (UTC)

You may wish to read the messages to which you are responding...you may learn something. DMacks (talk) 15:23, 13 July 2011 (UTC)

Define abnormal. Dauto (talk) 15:37, 13 July 2011 (UTC)

Abnormal means most people dont do it. — Preceding unsigned comment added by 78.148.128.45 (talk) 16:29, 13 July 2011 (UTC)

Most people don't ride unicycles. Do you find unicycle-riders disgusting? AndyTheGrump (talk) 16:32, 13 July 2011 (UTC)

Of course they are disgusting: sticking a wheel with a pole attached up thier backsides: what could be more abnormal?

Most people don't get college education, most people don't run marathons, most people don't play the piano, most people don't work for the navy, most people don't sing at church choirs, most people don't travel abroad, most people don't ... you get the point. Do you find any of those activities nauseating? Obviously you haven't given that topic too much thought. Why should anybody care about what you think then? Dauto (talk) 19:08, 13 July 2011 (UTC)

I believe the bad attitude tends to be stronger in men than in women, and a major part of it is a dislike of the idea of being "hit on" by another man, because it places one in a feminine role and can easily be seen as a challenge to one's own masculinity. Looie496 (talk) 16:37, 13 July 2011 (UTC)

Many men get rather turned on by the sight of two women making out, and will pay good money for pornos portraying such activity, so for them, homosexuality per se is no bad thing. But when it's two guys - "oh, that's different, it's unnatural, it's filthy". Yeah, right. -- Jack of Oz ^{[your turn]} 19:46, 13 July 2011 (UTC)

Maybe studies have been done on the more general question of whether any particular attitude is "instinctive" or "cultural".

Googling "identical twin social attitudes -wikipedia" gets some possible results which will take some reading through. Pages 64 to 67 of http://www.vipbg.vcu.edu/vipbg/HGEN619/eaves99tr.pdf covers the attempted measurement of the "conservatism scale" and social attitudes of identical and non-identical twins. Table 9 "Summary correlations between relatives (pooled across sexes) for social attitude measures" summarises the results. To this non-expert it appears that identical twins correlate more strongly than non-identical twins in their attitudes to sexual permissiveness, politics, religion and so forth (implying attitudes are partly inherited?) but it would be interesting to see other studies, and conclusions by Reference Desk experts. 84user (talk) 23:38, 15 July 2011 (UTC)

Metamorphosis in humans

The metamorphosis of amphibians is well known, triggered by thyroid hormone, and involves such characteristics as the development of a new stratified layer in the skin, the differentiation of the cerebellum, and various skeletal alterations (see anuran for a more complete list). In humans, these alterations are less apparent, as they occur during fetal development - the same changes in the skin, for example, occur between weeks 9 and 24 of gestation (see [1] - the tadpole-like epithelium is periderm, beneath which a thick stratified epithelium forms, followed by apoptosis of the periderm). At least in mice, responsiveness to thyroid hormone is important for cerebellar maturation.^[2] Also, a transient opercular flap (expanded second pharyngeal arch) seems to be characteristic of higher vertebrate embryology.^{PMID 21632625}

Some questions...

• The situation with thyroid hormone in human embryos is complex: the placenta develops to be fully supplied with maternal blood by 12 weeks or so, bringing in a supply of thyroid hormone; but the embryo also supplies its own hormone by 20-22 weeks. There are multiple receptors. What is the closest we can come to seeing a "paedomorphic human"? (i.e. one not undergoing "metamorphosis", though human paedomorphism is more typically used to refer to heterochrony later in development)

• Regeneration of limbs is famously lost in frogs after metamorphosis. Looking at the development of human embryos,^[3] it is apparent that they have well developed limbs long before the apparent metamorphosis as defined by the skin transformation. Do these limbs regenerate if severed? (Admittedly, I doubt experimental evidence is available, but you never know what kinds of accidents will happen...)

• Am I reinventing the wheel here - has someone published a comprehensive list of similarities between human fetal developmental events and metamorphosis? Wnt (talk) 14:23, 13 July 2011 (UTC)

Not a biologist, but I remember the notion from high school bio "Ontogeny recapitulates phylogeny". Edison (talk) 14:44, 13 July 2011 (UTC)

Annihilating a human

The size of the blast fireball.

Sort of a silly question. If you were to turn the mass of an average human (say, 170 pounds) into energy, how big would the resulting explosion be? --Goodbye Galaxy (talk) 15:21, 13 July 2011 (UTC)

The Tsar Bomba, the largest nuclear bomb ever detonated (1,400 the size of Little Boy and Fat Man combined), had a yield of 50 megatons of TNT. By E = mc², this equates to ca. 2.3 kg of mass converted to energy. A 170 kg mass completely converted to energy would result in about 1.5 × 10¹⁹ joules of energy (about 7600 megatons of TNT). According to Orders of magnitude (energy), this is about the same as the yearly electricity production in the U.S. as of 2005. -- 174.31.204.164 (talk) 15:42, 13 July 2011 (UTC)

Niiiice (you switched pounds for kilos, but I get the picture). Thanks. --Goodbye Galaxy (talk) 15:51, 13 July 2011 (UTC)

Also, if you are annihilating the human with an equal sized mass of antimatter, it would be 2x as big because the antimatter mass would count as well. Googlemeister (talk) 15:51, 13 July 2011 (UTC)

(EC x 2) The question was about 170 pounds, i.e. about 77 kilograms, which is equivalent to about 7 exajoules. However, I don't see how you could easily convert nearly all of the human into, say, photons without annihilating it with 77 kg of antimatter, in which case the total mass involved would be about 154 kg, which is equivalent to about 14 exajoules, which is close to your answer by coincidence. Red Act (talk) 15:59, 13 July 2011 (UTC)

Yeah, I should have clarified in my question that the annihilation was due to magic. --Goodbye Galaxy (talk) 16:03, 13 July 2011 (UTC)

DNA question

What % of the weight of a human would their DNA be? Is it a significant amount or something like 1/1,000,000th of a percent? Googlemeister (talk) 15:37, 13 July 2011 (UTC)

According to this page there are about 6 x 10^-12 grams of DNA per human cell. There are probably a few trillion cells in the human body (not counting red blood cells, which lack nuclear DNA); estimates are imprecise. If those numbers are correct, you get several grams of DNA, a significant amount, although well under 1% of the total. Looie496 (talk) 16:28, 13 July 2011 (UTC)

(ec)It's easier to figure this out than look it up (I said before starting ;)) ... though someone ought to chase down a number so we can cite it in the article. To begin with,

TMP = 320.1926 g/mol; dAMP = 331.222 g/mol; dCMP = 307.197 g/mol; dGMP = 347.2243. A molecule of water (18.01528 g/mol) is lost from each of these on polymerization, and we always find A with T, G with C. That gives us 615.384 g/mol for a T-A base pair and 618.391 for a G-C base pair. The precise mass of one genome will thus depend on the GC-content very slightly, and of course will be proportional to the genome size. The first of many confounding biological factors creeps in when we realize that "the" genome size doesn't exist; NCBI listed 3,101,788,170 bases in a very nearly complete reference sequence, but individuals vary, and apparently there are still a few hard-to-sequence repetitive regions missing small bits of information.^[4] Still, to boldly take that number and plunge ahead, and using 41% for the G+C content (I can't find a more precise number - due to the repeat problem, and the fact that repeats have very unusual G+C contents, there may not be a better number even from all that sequence data) we get:

3101788170 * (0.41 * 618.391 g/mol + 0.59 * 615.384 g/mol) / 6.0221415 × 10²³ /mol = 3.17 × 10^-12 grams

This is the mass of a haploid genome per cell (such as sperm); most cells carry 2n (in G1 arrest) or 4n (G2 arrest, while preparing for mitosis, etc.); some carry vastly more (trophoblasts, etc.). But on average the cells get bigger in proportion to the number of genomes they have, so it's more the type of cell that matters.

For example, a sperm head is roughly 4-5 micrometers long; from a drawing of the typical sperm it appears 25/40 as wide and 13/40 as thick (but with a hollow spot in front, so let's call it, oh, 10/40);^[5] this gets us 4.5*(5/8*4.5)*(1/4*4.5)*(4/3)*(3.14) = 59.6 cubic micrometers = 59.6 x 10^-12 cubic centimeters (=ml). (error corrected, sorry!) So one genome per sperm head works out to about 3.17 x 10^-12 / 59.6 x 10^-12 = 0.0532 g / ml = 53.2 g/l = 5.32% w/v. But as you see from this work, I could be off by quite a bit!

Now the "typical mammalian cell", according to cell nucleus, has a 6 micron round nucleus which is 10% of the volume. 6 * 6 * 6 * (4/3) * (3.14) = 904 cubic micrometers. Twice the DNA in such a space is still only 6.28/904 = 6.94 grams per liter, or 0.694 % (w/v). And in the cell as a whole it is one-tenth of that - 0.694 grams per liter or 0.0694%. Of course, that's not counting the extracellular space, which in some tissues is quite substantial... Wnt (talk) 16:52, 13 July 2011 (UTC)

Using fractionally distilled oil products to fractionally distill crude oil

It takes heat energy to bring a barrel of crude oil to the temperature required to fractionally distill it obviously, and the products of the fractional distillation have the ability to be used as energy. But how much crude oil can you fractionally distill from the energy you get out of whichever hydrocarbon is used as fuel after fractionally distilling one barrel of crude? In other words, you start with one barrel of crude, you use unknown energy given to you to fractionally distill it, you get products, including whatever X amount of product that can be used for fractionally distilling crude oil. How much crude can you distill with X? 20.137.18.50 (talk) 20:29, 13 July 2011 (UTC)

A lot more complex <g> especially since some of the products from the crude are, indeed, used as fuel in the process. And they do not use one single hydrocarbon for the purpose. Cheers. Collect (talk) 20:33, 13 July 2011 (UTC)

(edit conflict)That is a complex question, and you aren't likely to get a solid answer in just a single number or quick sentenece of explanation. It depends a LOT on which distillation product you are using (propane, butane, kerosene, gasoline, etc.) as your heating source, and what the particular make-up of the crude is (different crude from different parts of the world have WILDLY different compositions). I'm sure that, if given a specific formulation of crude, and a specific product of that crude, you could work it out trivially, but there's no guarantee that your answer will be widely applicable. For example, if you know that your crude is 10% propane, and you know that propane generates 50 megajoules per kilogram, and you know how many joules of energy you need to fully distill the crude to its final products, you can work out if the system is self-sustaining or not. However, such calculations would be purely pedagogical in the sense that the exact same set of calculations would need to be done for each application. There's no universal number that you could apply to all crude. --Jayron32 20:39, 13 July 2011 (UTC)

Yes, I didn't say it in so many words, but the question in my head as I was forming the question was about how self-sustaining or efficient the average refinery's average blend is, in terms of how much energy product is left after they use energy to make their products. It seems like when you add up all the energy that really goes in, not only considering the refining (which is the only thing I considered in my question), but also all the energy that goes into getting it out of the earth and transporting the crude from the drilling site to the refinery and from the refinery to the points of consumption for each type of product, the whole process must be very negative.20.137.18.50 (talk) 20:44, 13 July 2011 (UTC)

Non-negative net value of energy from petroleum prodution by a long shot. Elsewise, the industry would cease to exist. Collect (talk) 20:53, 13 July 2011 (UTC)

Energy returned on energy invested is an article on the topic. DMacks (talk) 21:41, 13 July 2011 (UTC)

If it was negative, it would not be a source of energy. Dauto (talk) 21:48, 13 July 2011 (UTC)

Waste heat recycling is an essential component of any production chemical engineering process, but the most efficient refinery processes are usually closely held trade secrets which depend on the detailed geometric configuration of the particular refinery. 99.24.223.58 (talk) 00:43, 14 July 2011 (UTC)

Practical Applications of Room-Temperature Superconductors

I'm writing a science fiction story in which a society with similar technological development to ours has developed a superconducting material that retains this property up to temperatures of 300-400 celsius. I'd like to add some color around the effects of such an invention, but not being an engineer, I'm at a loss. The article on technological applications of superconductors has some ideas (like more efficient tokamaks, the main point of the story) but it seems like superconductors operating at true room temperature (and, as a premise, reasonably cheap to make) would have more applications than the power grid and maglev. For instance, couldn't you use them as part of a telecom network by adding phase variances to the power without disrupting the transformers on either side? It's my understanding that in a superconductor although the electrons themselves wouldn't necessarily move particularly fast the electric current would move at almost the speed of light so the power grid would double as a fiber-optic network. Just an idea, might be wrong; any other thoughts? 24.215.229.69 (talk) 22:59, 13 July 2011 (UTC)

Superfast computing? --Jayron32 23:06, 13 July 2011 (UTC)

Just don't repeat the sort-of error of Larry Niven's Known Space series: a superconductor is not necessarily a perfect heat conductor. Or so I've heard... Wnt (talk) 23:16, 13 July 2011 (UTC)

Of course, the idea behind fiction is "to make stuff up for entertainment purposes". Thus, the idea behind science-fiction is "to make stuff up about science for entertainment purposes". Also see Clarke's third law, which is intended to apply to science fiction. Science fiction generally fails when it gets too technical, since it invariably gets more wrong the more it tries to make itself sound like "real science". That's why Arthur Clarke wrote his third law; the idea is that you should just leave your advanced technologies somewhat "magical". Let the reader know enough about it to know that it does work, without trying to make the reader know how it works, since the how is almost always wrong. --Jayron32 23:24, 13 July 2011 (UTC)

Resistance is heat production, so presumably a room temperature superconductor could be cooled to slightly under room temperature and still be used to draw heat away from other components? I'm not sure what the point is either, to be honest. I'd rather have more efficient electrolysis anodes, if we're going to be searching the space of alloys. 99.24.223.58 (talk) 05:08, 14 July 2011 (UTC)

Electric signals move at a good fraction of the speed of light in ordinary wires. If I recall correctly, the speed is 2/3 c in coaxial cable (like for cable TV). We don't use optical fibers due to the speed of propagation, but rather due to the fact that light can travel a long distance in a fiber without the signal degrading.--Srleffler (talk) 01:30, 16 July 2011 (UTC)

Cloud rays

Is there any name for the phenomenon when the corpuscular-like sun rays get the cloud's color (like the pink ones on the photo)?--Brandmeister t 23:17, 13 July 2011 (UTC)

Virga. --Jayron32 23:19, 13 July 2011 (UTC)

Thanx, updated the file info. Brandmeister t 23:29, 13 July 2011 (UTC)

Wait. That might not be right. Virga is rain that does't reach the surface. If it reaches the surface than it is called rain. Dauto (talk) 23:53, 13 July 2011 (UTC)

Dauto is correct. The image in question appears to feature two areas where precipitation is reaching all the way to the ground; these are called rain shafts (no article??). -RunningOnBrains^(talk) 00:12, 14 July 2011 (UTC)

Right, that's rain backlit by the sun. Note also that the premise of the question isn't right: sun rays don't get their color from clouds, rather the reverse. Looie496 (talk) 00:16, 14 July 2011 (UTC)

Strange, I thought they were rays, reverted. Apparently a file mover is needed then. Brandmeister t 00:37, 14 July 2011 (UTC)

I'm a filemover on Commons. What do you need it named to, "Backlit rain shafts"? --T H F S W (T · C · E) 17:32, 14 July 2011 (UTC)

Yep. Or something like that. Brandmeister t 11:07, 15 July 2011 (UTC)

I just made an article for rain shafts titled Precipitation shaft. Please feel free to contribute! BearGlyph (talk) 17:41, 22 April 2016 (UTC)

Antimatter bomb

How big would the explosion be from annihilating 1 kg of antimatter with 1 kg of normal matter? --134.10.116.13 (talk) 23:45, 13 July 2011 (UTC)

See Mass–energy equivalence. Remember that mass is mass, regardless of whether it is matter or antimatter. Plug 2 kilograms into the equation for the mass, the speed of light for c, and you will get out the amount of energy. For explosive energy, the standard is to convert the joules of energy into a TNT equivalent. You can do that math pretty easily as well. --Jayron32 23:54, 13 July 2011 (UTC)

As for how big the explosion would be, that's a bit more complicated than finding the yeild. In space the size of the fireball would roughly vary with the cube root of the yeild. In a plane it would vary with the square root. So, you get something between those two with a surface explosion. StuRat (talk) 02:33, 14 July 2011 (UTC)

The size, in terms of volume, of the exlposion itself will also be highly dependent on the local atmospheric conditions; for example the density of the air, which is itself dependent on things like temperature, humidity, and barometric pressure, and may not be uniform over the course of the explosion, complicating matters. That's why it is much easier to speak of the "size" of an explosion in terms of energy content (which is how the strength of explosive materials is usually quoted, in TNT equivalents which I cited above) rather than in terms of volume. --Jayron32 04:28, 14 July 2011 (UTC)

July 14

Toilets

I was recently in Hanover, beautiful place btw, if you ever have the chance, but nevermind that, anyway, the private toilets are different. They have a kind of "platform" in the bowl that the, erm, solid releases, fall o, which does not have water, then there is a lower area in the back that the flush pushes it into that has water. Here in the states by contast the releases drop directly into the water, like a true bowl. The US toilets have the problem of excessive and uncomfortable splashing, but the German toilets have the problem of the odor of faeces not submerged. Is there a middle ground that solves the splashing problem without creating the odor problem? Thanks. 12.177.253.250 (talk) 00:19, 14 July 2011 (UTC)

There seem to be a wide variety of alternatives listed at Flush toilet#Bowl design, but it's hard to tell which have the best splashing versus odor trade off by looking at them. You might want to ask on a plumbing forum such as this one. 99.24.223.58 (talk) 00:48, 14 July 2011 (UTC)

Modern dual flush toilets from Australia would seem a sensible middle ground. Your personal output is quickly drowned, but much less water is consumed than in a typical American toilet. And less splashing. As an Australian visiting America it made me feel comfortably at home to find them at Grand Canyon Village, a town with water supply challenges. HiLo48 (talk) 06:56, 14 July 2011 (UTC)

Original research, but the low seat versions seem to be the best, as the drop is only a couple of inches. It just slides into the water rather than dropping. Also see Wikipedia:Reference_desk/Archives/Science/2009_March_16#German_toilet for more information on the German attitude.--Shantavira|^{feed me} 07:55, 14 July 2011 (UTC)

I came across this toilet design in Poland at my aunties house. After the 1st time I used it and made a mess I learned to lay a piece of toilet paper down 1st which greatly reduces the chance you'll need to clean up after. Vespine (talk) 23:16, 14 July 2011 (UTC)

German toilet currently redirects to the stub washout toilet (which is considerably smaller than the flush toilet#Washout toilet section). From reading elsewhere, I've understood that the primary motivation behind this design is to allow easier examination of the stool for hygienic and health purposes, a cultural practice. -- 203.82.93.119 (talk) 02:21, 15 July 2011 (UTC)

Neutrino

What's the mass of a neutrino? --134.10.113.106 (talk) 01:28, 14 July 2011 (UTC)

Read the article with the surprising title of neutrino which will answer your question, especially the section with the hard to understand title of "Mass". If you have any questions about what you read in that section, feel free to come back and ask them. --Jayron32 01:39, 14 July 2011 (UTC)

Or to put it in a less blunt way, we're volunteer human beings here, some of us quite busy with real lives. While I love answering questions for the curious, I don't like answering questions which would be easily answered by typing the word you're curious about into the Wikipedia search bar. I suggest you read neutrino; the answer may surprise you.-RunningOnBrains^(talk) 03:32, 14 July 2011 (UTC)

Please see Neutrino#Mass. 99.24.223.58 (talk) 04:59, 14 July 2011 (UTC)

It gives "masses" as eV, which aren't mass. --134.10.113.106 (talk) 06:54, 14 July 2011 (UTC)

Electronvolt#Mass suggests otherwise. Can someone confirm that 1 eV is 1.78*10^-33 grams? 99.24.223.58 (talk) 07:14, 14 July 2011 (UTC)

Strictly speaking an eV is a unit of energy, not mass. However, (as the eV article states) the mass-energy equivalence principle makes it equivalent to 1.78266173 * 10^-33 grams [6]. -- CS Miller (talk) 08:38, 14 July 2011 (UTC)

Just in case this needs clarification, as the Electronvolt article states, in natural units where c=1, eV is a unit of mass (as well as momentum, energy, etc.). Alternatively, sometimes people write eV/c^2. 80.187.151.104 (talk) 05:56, 17 July 2011 (UTC)

Breaking molecules

When you cut a piece of plastic, are you actually cutting through molecules, or just separating molecules from one another? What about other material such as wood? When water is smashed about like in a blender or a huge wave crashing, is there enough energy to break any water molecules apart? — Preceding unsigned comment added by 86.186.8.147 (talk) 02:29, 14 July 2011 (UTC)

You are seperating molecules from each other, not breaking intramolecular bonds. In general, intermolecular bonding is relatively weak, which is why you can seperate molecules from each other fairly easily. In substances which are not composed of discrete molecules, but rather consist of a massive network of nearly identical bonds, like titanium or sodium chloride or diamond, the material is actually quite hard to break. But for substances composed of molecules, it is usually fairly easy to seperate the molecules from each other, comparitively speaking. --Jayron32 02:32, 14 July 2011 (UTC)

Plastics vary by polymer length. If you cut some plastics with a power saw, they will ionize (you can often smell ionized plastics which smell like burnt plastic.) The same is true of wood, except that ionized wood smells more like burnt wood than burnt plastic. Water can not be ionized in a blender. Nor will ocean waves spontaneously ionize. 99.24.223.58 (talk) 04:51, 14 July 2011 (UTC)

Whether you are breaking molecules or not depends on molecule size. Water has very small molecules, so there is almost no way to break them apart by physical means (chemical or electrical means are all that can do it). With plastics, if the polymer is long enough, you will actually be breaking molecules apart (wood is made of cellulose, but I don't think the individual molecules are quite as long). --T H F S W (T · C · E) 17:28, 14 July 2011 (UTC)

The comments about the smell when cutting plastic and wood are probably wrong. Cutting plastic or wood with a power tool produces a lot of heat via friction. It's more likely that you smell burning plastic because you are actually burning the plastic.--Srleffler (talk) 16:31, 16 July 2011 (UTC)

Oppositional defiant disorder - Political abuse of psychiatry?

So a child's parents tell them to follow religious teachings, and the freethinking child disobeys parents, smoke pots and have sex, will they be diagnosed with Oppositional defiant disorder? Or all anarchists (including Noam Chomsky LOL), according to APA, are suffering from ODD? [7][8] Why APA is abusing psychiatry in Soviet-style? --111Engo (talk) 03:30, 14 July 2011 (UTC)

On a further research, I found this discussion. See the last post by Bruce A. Now I'm confused. Is it associated with children only, and the media misrepresenting the manual? --111Engo (talk) 03:39, 14 July 2011 (UTC)

Is this a question? Are we allowed to give more than one answer? AndyTheGrump (talk) 03:41, 14 July 2011 (UTC)

Well, you really shouldn't put much weight in Yahoo answers, and the manual in question certainly does not seem to support the claims made by the article to which you linked. In all instances they are (implicitly) describing children or adolescents being oppositional or defiant toward adults, and a person must meet at least four of the criteria, only two of which have to do with disobeying authority. They also state that the behavior must persist for "at least 6 months", and must present an "unwillingness to compromise", none of which seem to apply to civil disobedience. That is certainly not the meaning intended by the writers of this book (doctors are people too). They really should have included the phrase "routine requests", since the real manifestation of this disorder is supposed to be when a person will not comply with a simple request like "Sir, please put your pants back on. This is a family establishment." Of course, I think it's another buzzword term to excuse people for acting like assholes (read: overdiagnosis and self-diagnosis of ADHD and Aspberger's), but that's my personal (and, admittedly, only slightly educated) opinion. -RunningOnBrains^(talk) 04:00, 14 July 2011 (UTC)

I would indeed take such psychiatric practices with a huge grain of salt. It is not like the industry has a spotless track record! The criteria require that children who vehemently disagree with rules might be angry in two identifiable ways - which should scarcely seem a surprise under the circumstances. Psychiatry is a matter of people having problems and someone trying to fix them - where "having problems" means that someone doesn't act the way the person in a position to pay the bills wants. Wnt (talk) 04:37, 14 July 2011 (UTC)

To confront the "hidden question" in the OP's post, with many behavioral disorders, there is a modern trend towards overdiagnosis and medicalization. This does not mean that the disorder itself is not real, just that everyone who claims to have the disorder, or who are assigned the disorder by a medical professional, may not in fact have it. In other words, there are real people with real problems that may need real help. However, this is complicated by the fact that personality traits which are considered outside of the normally acceptable pallate of personality traits have themselves been confused with genuine behavioral disorders, and thus people, even well trained medical professionals, confuse when someone has a genuine need for medical intervention, versus where someone is just differently wired, but not in a manner which interfers with normal life. At one time, mental disorders which were treated medically were limited to serious psychoses like schizophrenia, but over recent history there has been a trend to treat what used to be considered as normal (if somewhat annoying in certain social situations) personality traits as disorders. --Jayron32 04:40, 14 July 2011 (UTC)

Hmmmm... how about female hysteria? According to the article it affected 25% of women, including symptoms like "irritability, loss of appetite for food or sex, and 'a tendency to cause trouble'". Sounds like a rather closely related condition, no? Wnt (talk) 04:52, 14 July 2011 (UTC)

That's sort of the point. There may have been real women with real psychological problems that needed real theraputic or medical intervention. But by overdiagnosing such a rediculous number of women, with perfectly normal personalities, as "hysterical", it both wasted the resources of the medical system and masked the real problems of the few real women who may have needed real help. A third problem is a sort of "backlash" against people who really have mental disorders, since the public has become quite aware of overmedicalization. For example, some kids really do have ADHD. But so many kids that don't have it are mistakenly diagnosed with it that people believe that the disorder doesn't really exist, and that the label is just an excuse for parents to drug their children and keep them compliant. The kids that really do need drugs to manage their disorder thus get stygmatized as "not having a real disorder" when they actually do, because all of the kids that actually don't have it give everyone else a bad name. Again, I am not in full agreement with the OP here, in the sense that I recognize that behavioral disorders of all types do exist, but the tendency to make every socially inconvenient personality trait one of these disorders does a disservice to literally everyone involved. To the OP's point, there really are people who have a mental disorder that makes them violent and unmanagable in the face of authority, to the point where they need genuine theraputic and/or medical help. That we confuse these people with genuine mental problems, with other people who have healthy brains but choose to be nonconformists, is the real problem. Its not the non-existance of the disorders, its the overassigning of the disorder to people that don't have it, that is the problem. --Jayron32 05:05, 14 July 2011 (UTC)

Do you mean: 1. behavioral disorders of all types that actually exist do exist, 2. behavioral disorders of all types ever thought to exist do exist, or 3. behavioral disorders of all types currently thought to exist do exist? (Excuse me if this question seems confrontational, I'm probably exhibiting challenging behaviour.)  Card Zero  (talk) 09:28, 15 July 2011 (UTC)

Are you asking whether it will be easy for religious parents to find psychologists predisposed to their opinions in order to lock up or drug children who don't believe their superstitions? Or suggesting that we must all ask our local psychological licensing authorities how they would protect against such a situation? Or are you a victim of vindictive religious parents who have tried to have you locked up or drugged? Or are you a religious parent seeking to lock up or drug a freethinking child? Context is important here. 99.24.223.58 (talk) 04:58, 14 July 2011 (UTC)

Yeah, context is important ... it's important so some holier-than-thou people of a non-religious sort can lecture the questioners and answerers about the "unethical" and contrapolicy nature of "giving medical advice". Wnt (talk) 05:15, 14 July 2011 (UTC)

The direct answer to the OP's question is that this diagnosis is only applied to children, so describing it as a Soviet-style abuse of psychiatry is off the mark. Looie496 (talk) 05:14, 14 July 2011 (UTC)

Similarly, the governmental system in Cuba in the 1960s wasn't Soviet-style, because it only applied to Cubans.  Card Zero  (talk) 09:19, 15 July 2011 (UTC)

If you have ever met an ODD child or known people that work with them regularly, you immediately know the difference between a child that has a behavior problem and one with a conduct disorder. ODD is a true mental disorder, meaning it is not rational or in many cases controllable. An ODD child could be told not to do something they don't even WANT to do, but they would do it just because they are told not to. They are some of the more sadistic people you'll ever meet, they will do things just to be contrary or as annoying as possible. ODD is a conduct disorder with all that implies, including being a potential pre-requisite to a diagnosis as an adult of antisocial personality disorder, also called Sociopathy. There's a big difference between a poorly behaved child and a potential sociopath-in-the-making. HominidMachinae (talk) 08:32, 14 July 2011 (UTC)

Severe weather warning beeps on radio

The local radio stations in Salina, Kansas owned by Morris Communications ([9]) will sometimes, when there is a severe thunderstorm warning or tornado watch/warning affecting their listening area but when they are not in continuous severe weather coverage, turn on some system that inserts a particular beeping sound once every couple minutes (more than just a simple beep...I believe the best way to describe it is a set three higher beeps followed immediately by three slightly lower beeps lasting about one second total, repeated after a little less than one second for a total duration of about three seconds). While touring the radio stations' facilities a few years ago I caught a glimpse of the hardware used to insert these beeps into the broadcast audio (fittingly labeled "SEVERE WX BEEP GENERATOR"). I went looking for information on such equipment today, but I can't seem to find anything about them using Google, despite the fact that I'm fairly certain other radio stations use variations of them (with different sounding/patterns of beeps) as well. What exactly are these severe weather beep generators and where can I find information on them? Ks0stm ^(T•C•G) 05:15, 14 July 2011 (UTC)

I believe that the article Emergency Alert System will answer many of your questions. It even has pictures of some of the equipment used, which may be exactly what you are looking for. I also see bluelinks to more specific articles on the equipment. --Jayron32 05:28, 14 July 2011 (UTC)

Actually, it wasn't EAS related...this is some system that they manually turn on when there are the severe weather alerts I mentioned in effect for their listening area and that remains on, producing the beeps, until the severe weather alert has expired or been cancelled, at which time they switch it off. The only EAS broadcasting that these stations do are EAS weekly/monthly tests. Ks0stm ^(T•C•G) 05:34, 14 July 2011 (UTC)

Ah. In that case, you seem to be looking for some sort of tone generator or Signal generator. There are hundreds of these things out there. The section titled "Pitch generators and audio generators" has a little bit on them, but not on any specific models. --Jayron32 05:40, 14 July 2011 (UTC)

Planck unit for luminosity

Does a Planck unit exist for luminosity and if so, what is it in terms of candelas? Widener (talk) 07:24, 14 July 2011 (UTC) Oh and if it happens to be a derived Planck unit, I would also like to know what it is expressed in terms of the fundamental Planck units. Widener (talk) 07:42, 14 July 2011 (UTC)

Planck power, but I can't convert because candelas are apparent luminosity instead of bolometric. 99.24.223.58 (talk) 07:47, 14 July 2011 (UTC)

Exactly right. luminosity really isn't a physical quantity and candelas really aren't a physical unit so a Planck unit for them is meaningless. Dauto (talk) 13:46, 14 July 2011 (UTC)

Correcting what I said above. I meant to say Luminous intensity isn't a physical quantity (That's the one measured in candelas). There is nothing wrong or un-physical about luminosity which is measured in Watts. Dauto (talk) 15:27, 14 July 2011 (UTC)

I suppose luminous intensity (apparent luminosity) is a real physical quantity based on radiation in the visible spectrum. But x Watts of white light is still x Watts. As a practical matter, for quantities that large, there is really no way to assume that much power would be measurable because it would ionize any observer or measurement apparatus. [10] has some details that might help. 99.24.223.58 (talk) 22:07, 14 July 2011 (UTC)

Luminous intensity depends on the physiological response of the human eye. That means it is not a "pure" physical quantity. Dauto (talk) 00:27, 15 July 2011 (UTC)

We would have to know the shape of that response curve (for three kinds of cone spectra, maybe we can use a normal distribution to approximate) to get the ratio between uniform spectrum wattage and white light wattage. Then we would be able to answer this. Sorry, that wouldn't help either, because the integral of +1 over (0, +infinity) for a uniform spectrum is probably undefined, or if it's not it should be in this case. Thank you. 99.24.223.58 (talk) 22:29, 15 July 2011 (UTC)

See Luminosity function for the shape of the response curve.--Srleffler (talk) 16:42, 16 July 2011 (UTC)

Question about animal blood analysis .

Italic text I want to know what are the normal medical values for a hematology tests

in dogs. Thank you in advance . 95.107.197.63 (talk) 09:09, 14 July 2011 (UTC)

Does this website help? canine bloodwork Zzubnik (talk) 10:42, 14 July 2011 (UTC)

Exotic matter

Is it possible to create a liquid phase consisting entirely of protons confined in a Penning trap? If it is, and assuming that does not exist at STP, what is the pressure equivalent of the boiling point at 1 nK? Plasmic Physics (talk) 10:35, 14 July 2011 (UTC)

No, liquid implies contact, and the coulomb barrier for that compression seems to be greater than could realistically be expected to be applied from external sources. Consider the power required to simply keep two protons in contact. 99.24.223.58 (talk) 10:51, 14 July 2011 (UTC)

OK, but what about extraordinary conditions like in special types of stars, where protons are crushed together? Then again that's not really a liquid, it's more like a supersolid. Plasmic Physics (talk) 11:41, 14 July 2011 (UTC)

Neutron stars exist because they are composed of neutrons, which are neutral and thus not all that repuslive. The repulsive forces involved in condensed protonic matter may be hypothetically calculatable, but likely the result would be so huge to be meaningless. --Jayron32 11:56, 14 July 2011 (UTC)

Agreed - I think we are talking about degenerate matter here, but I don't see how that can be constructed just from protons alone. Nearest equivalent is metallic hydrogen, which, in its solid form, is a lattice of protons surrounded by a sea of unbound electrons. Gandalf61 (talk) 12:06, 14 July 2011 (UTC)

It strikes me that if you beam pure protons straight into a black hole, it nonetheless will not achieve infinite charge, because the Hawking radiation will become biased. Is it possible to calculate a maximum possible charge density for a black hole? Is that the upper limit for concentration of charge in that volume of space, regardless of the nature of the containing force? Wnt (talk) 17:28, 14 July 2011 (UTC)

Does the article Charged black hole lead you to some solutions to your problem? --Jayron32 18:02, 14 July 2011 (UTC)

(EC) You are probably right about charged black holes having a limit as to how much charge they can have. According to the cosmic censorship hypothesis, non-rotating charged black holes with r_Q > r_s/2 in the Reissner–Nordström metric, where r_Q is a radial measure proportional to the black hole's charge and r_s is the black hole's Schwarzschild radius, do not exist in nature, because that would result in a naked singularity. Red Act (talk) 18:07, 14 July 2011 (UTC)

I would have preferred a derivation based on the impossibility of shooting the particle into the field because (for example) virtual pairs would be sure to interact with it and spirit the charge away - rather than an unproved ban on singularities in free space - but it does give a ready number. The article says that

$r_{Q}^{2}={\frac {Q^{2}G}{4\pi \epsilon _{0}c^{4}}}$

and the total radius r_S in which the charge is confined is simply 2r_Q. Thus Q <= (r_S/2)(c²)sqrt(4πε₀/G) = sqrt(3.1415927 * 8.85418782×10⁻¹² F·m⁻¹ / 6.6738480×10⁻¹¹ m³ kg^-1s^-2) (299792458 m/s)² r_S /2

= sqrt (0.416794806 s⁴·A²·m^-2·kg^-1·m⁻⁴ kg¹s²) (8.98755179 × 10¹⁶ m² s^-2 r_S/2

= 2.90116587 × 10¹⁶ C/m r_S. Unless I fouled up... And I did, thanks Dauto for spotting the factor of 2 I forgot about Wnt (talk) 18:56, 14 July 2011 (UTC)

N.B. one actual unit of charge, (1 / 6.24150965(16)×10¹⁸) C, should then be confined to occupy at least r^S = (1 / 2.90116587 × 10¹⁶) m/C (1 / 6.24150965(16)×10¹⁸) C = 1.38063158 × 10^-36 m or 1/11.7 of the Planck length. Odd... Wnt (talk) 19:10, 14 July 2011 (UTC)

What's odd about that? Dauto (talk) 19:44, 14 July 2011 (UTC)

Well, the Planck length is special in terms of when the Compton wavelength of a black hole just barely fits inside the Schwartzschild radius, but I haven't heard of a similar fundamental role in defining charge. If 11.7 were some simple/predictable number, it would mean the various fundamental constants described above could be defined in terms of one another - one less fundamental constant. Wnt (talk) 22:56, 14 July 2011 (UTC)

What you did was calculate $2\alpha ^{\frac {1}{2}},$ where $\alpha \,$ is the fine structure constant.

$r_{e}^{2}={\frac {e^{2}G}{4\pi \epsilon _{0}c^{4}}}=\alpha l_{P}^{2}$

Dauto (talk) 23:31, 14 July 2011 (UTC)

Ah! Thanks for setting me straight. I've fixed the factor of 2 error in the calculations above. The conclusion we reach, then, is that the smallest possible black hole contains a Planck mass and no more than the Planck charge within a Planck length. Assuming (!) that no force of nature is stronger than a black hole event horizon, then within any sphere of space of radius N Planck lengths, there can be no more than N Planck charges. Where the Planck charge happens for some bizarre reason to be about 11.706 ordinary charges. Wnt (talk) 23:46, 15 July 2011 (UTC)

How are charged black holes related to my scenario? Plasmic Physics (talk) 02:55, 15 July 2011 (UTC)

They are not, except for the fact that they are ways to pack positive charged particles. Dauto (talk) 15:04, 15 July 2011 (UTC)

I was hoping to work out the upper limit for charge concentrated in a region of space (and did) but it is absurdly high for normal purposes, except maybe over some vast distance. Wnt (talk) 23:46, 15 July 2011 (UTC)

Well, I'm not looking for the greatest number of protons that can be squeezed in a known volume, only the possibility of a liquid phase with a distinct boiling point. If there isn't such a case anywhere in the universe then that's a good answer. Plasmic Physics (talk) 00:57, 16 July 2011 (UTC)

That seems to be the answer. Dauto (talk) 13:55, 16 July 2011 (UTC)

July 15

mental retardation questions

Are autstic people retarded? Are people with cerebral palsy retarded? Are people with brain damage retarded? I know that retardation is a real term, not just offensive slang, so this is why I ask this type of question.--68.197.153.156 (talk) 01:04, 15 July 2011 (UTC)

Mental retardation is typically a measure of IQ. Any number of conditions can lead someone to have such a low IQ that they are considered clinically mentally retarded. Very severe autism, brain damage, and cerebral palsy can cause mental retardation, but one could not say as a rule that all autistic, etc. people are mentally retarded — many are not. Many autistic people, for example, have extremely high IQs; many people with brain damage do not have their IQ affected. --Mr.98 (talk) 01:14, 15 July 2011 (UTC)

Also, the term "mental retardation" is falling out of favor in the medical community, in favor of the terms "intellectual disability" or "physical disability". I don't get the change personally, probably political correctness, but the definitions should be the same. -RunningOnBrains^(talk) 01:53, 15 July 2011 (UTC)

Perhaps an example of the euphemism treadmill. AndrewWTaylor (talk) 07:52, 15 July 2011 (UTC)

The problem with the question when applied to autism is "what do you mean by retarded?" It's not just political correctness, its a lack of specific meaning. By the dictionary defintion of retarded it implies that mental development is a linear process and that for some it stops early. Like "his mental age was that of a four year old". But normal kids are not simultaneously capable of extreme concentration on a topic and unable to interprete body language. Normal kids are potty trained before they learn to read. The concept of "mental age" doesn't work. When you consider people with different disabilities, you find that a label like "retarded" is useless. Whether your goal is to treat the condition, accomodate the person better or just know what to expect in terms of behaviour, you can't avoid drilling down to the specifics. Autism in particular, is over such a wide spectrum that you can't avoid dealing with individuals. EverGreg (talk) 08:50, 15 July 2011 (UTC)

The OP says retardation is a real term. I'd be interested to know what the OP thinks it means. Literally it seems to imply something parallel to what is sometimes called slow development. That's not the same thing as low IQ. Another problem with these terms is that usage varies dramatically around the world. I don't know where the OP is from. I know a lot of people with cerebral palsy. Very few have low IQ. Many are insultingly called retarded at times. It's a minefield. Unhelpful word. HiLo48 (talk) 08:57, 15 July 2011 (UTC)

It's not just a euphemism (as EverGreg pointed out). Many people lack or are deficient in the ability to accquire specific skills - theory of mind, reading body languague, understanding grammar etc. "retardation" is not accurate and does not help in understanding the condition. With regard to brain damage, people can lose many different faculties- they my develop emotional disorders: inability to concentrate or mood swings(for eg frontl damage), Difficulty in forming or recalling memories, languague deficits (either speaking or comprehending), Arithmetic(yes lose the ability to do arithmetic without losing the idea of numbers, its true), etc while retaining all of their other faculties. Depending on the severity and the type of disabilities present, patients are classified as intelectually disabled. — Preceding unsigned comment added by Staticd (talk • contribs) 09:14, 15 July 2011 (UTC) Staticd (talk) 09:15, 15 July 2011 (UTC)

Cerebral palsy does not generally cause mental disability. It's a brain disorder that affects motor control, producing physical disabilities. So, even if one does find the term "retarded" useful, it isn't really accurate to apply it to someone with CP. I agree though with the posters above, that "retarded" is not generally a useful term; it is better to be specific.--Srleffler (talk) 02:07, 17 July 2011 (UTC)

Yes, thanks for triggering me to check the Cerebral palsy article. It explicitly describes it as "motor conditions that cause physical disability". Intellectual disability is not part of cerebral palsy. Since nobody, including the OP, has been able to define "retarded", I cannot say whether that word applies, but it's clearly best avoided. HiLo48 (talk) 02:33, 17 July 2011 (UTC)

On heat flow.

I recently read a post on a forum which stated the following:

"Heat is the flow of thermal energy from one body to another. Objects feel hot or cold depending on how fast heat is transferring between the objects. The rate of heat flow is determined by both the temperature difference and the thermal conductivity between the two objects. For example, touching a steel pole at 32 F will feel colder than a wooden pole at 32F."

I'm inclined to believe that this is a false statement but, who knows? So... errr... Is it true? — Preceding unsigned comment added by 186.29.119.171 (talk) 01:20, 15 July 2011 (UTC)

Yes, it is true. Dauto (talk) 01:40, 15 July 2011 (UTC)

This is the reference desk, not the yes man desk. Not only are the statements true, there are relevant articles: Heat, Specific heat. μηδείς (talk) 01:43, 15 July 2011 (UTC)

It was just answering the question, Jeesh...Heat conduction is another useful link. Dauto (talk) 01:54, 15 July 2011 (UTC)

Umm, can I ask anyone to expand on the reason of why the steel pole would feel colder than the wood pole at the same temperature? — Preceding unsigned comment added by 186.29.119.171 (talk) 02:02, 15 July 2011 (UTC)

I think it is related same reason a thermos or styrofoam cup keeps your coffee hot longer than a metal cup would on a cold day. It is the same reason why we make cookware out of cast iron and cooper but never wood (also because the wood would probably catch on fire, ha ha). It is the same reason we make mittens out of wool, not out of aluminum. Because some things are better conductors of heat and electricity, while other things are better insulators.--Fran Cranley (talk) 02:07, 15 July 2011 (UTC)

To put it another way, the steel pole has more specific heat capacity to cool your skin's nerve ending's much faster than the wood. 99.24.223.58 (talk) 04:54, 15 July 2011 (UTC)

Not exactly. This has nothing to do with specific heat, and everything to do with thermal conductivity. Specific heat capacity of steel is actually much lower than that of wood. Specific heat capacity refers to a substance's "temperature/energy" relationship; that is the amount of energy contained in a given mass of the substance at a certain temperature. Steel's lower specific heat means that it will gain more degrees of temperature with an equivalent amount of energy than wood will; however the key factor missing in determining why the steel feels colder is the time factor. Steel feels colder, despite having a lower specific heat, because it the heat it does conduct away from your skin is conducted away on a faster time scale than the wood does. In other words, I can get 1 joule of energy out of my skin in less time when it touches steel than when it touches wood. Ultimately, the wood's temperature will go up less than the steel's temperature will once they both have absorbed that 1 joule of energy from my skin, but the difference in sensation has less to do with the final temperature than with the speed at which that joule of energy is extracted from my skin. --Jayron32 05:18, 15 July 2011 (UTC)

Both. Thank you. 99.24.223.58 (talk) 22:20, 15 July 2011 (UTC)

Let me give it a shot too. Your perception of hot or cold comes from the temperature of the thermosensitive nerves just under your skin. They are being heated to by blood behind them and they are being cooled from the front by the thing you are touching. Depending on the rate at which the cooling occurs( i.e the conductivity of the object) the "heat" gets "dammed up" to different levels and the skin reaches different equillibrium temperatures.

This is somewhat analogous to the rise in water near your foot when you step into a stream: the height reached depends on the rate flow of water and the resistance. (both follow approximately dQ/dt=KdT/dx and dV/dt=Kdh/dt)Staticd (talk) 07:11, 15 July 2011 (UTC)

In simpler terms: because the wood pole doesn't conduct heat as well, when you touch it your hand quickly warms up the pole at the point where you are touching it, so the pole doesn't feel all that cold. The steel pole conducts heat well, so the metal carries the heat from your hand away, allowing you to feel something much closer to the "true" temperature of the pole.--Srleffler (talk) 19:05, 17 July 2011 (UTC)

MOST LIKELY AVENUE

PRECEDING REMOVED. WIKIPEDIA I REALIZE VERILY WELL THAT THERE MIGHT NOT BE "1" ANSWER. I WOULD LIKE TO KNOW, IF HUMANITY WERE, THIS IS TO SPEAK HYPOTHETICALLY, MODIFY ITS OWN GENOME: 1. WHAT IS THE MOST LIKELY TIMING AND LOCATION THIS WILL HAPPEN? (RESEARCH UNIVERSITY, GOVERNMENT PROGRAM, INDUSTRY, STARTUP, ETC). 2. WHAT IS THE "MOST LIKELY" AVENUE TO PREVENT THIS. THANK YOU. I AM HAPPY TO READ REFERENCES. 188.222.102.201 (talk) 02:00, 15 July 2011 (UTC)

NOTE, I MEAN FULL BRED MODIFIED GENOME. REAL HUMANS FROM GENETICALLY MODIFIED HUMAN DNA. ALSO, THERE IS A THIRD PART OF MY QUESTION: IS THERE ANY INDICATION WHATSOEVER (AGAIN, REFERENCES PLEASE) THAT THIS HAS ALREADY BEEN DONE, GIVEN THAT CROPS ARE MODIFIED WITH IMPUGNITY ALL THE TIME THANK YOU--188.222.102.201 (talk) 02:01, 15 July 2011 (UTC)

I think there is probably not a better answer than to point you to our article on human genetic engineering. (Please don't write in all-capital-letters -- it comes across as shouting.) Looie496 (talk) 02:06, 15 July 2011 (UTC)

The laws forbidding interracial marriage were a recent attempt to modify the human genome. 99.24.223.58 (talk) 04:57, 15 July 2011 (UTC)

I'd say it's already happening, but in tiny steps. First we've seen gene therapy to remove, repair, or deactivate defective genes which cause diseases. Next perhaps will be some simple cosmetic changes, like eye color. Then we might get into more substantial changes, like height. From their we might start tinkering with emotions and intelligence. StuRat (talk) 06:53, 15 July 2011 (UTC)

Matter acceleration to speed of light...?

Yes, I understand that special relativity states that no particle with non-zero rest mass may ever reach the exact speed of light because its mass would approach infinity as it would get closer, which would imply infinite energy and bla, bla, bla. But, this same theory also predicts that matter and energy (which can accelerate to that speed) are the same entity, bringing me to my question.

Why is it, exactly, that matter cannot travel at the speed of light, whereas energy, which is theoretically the same entity as matter, can?186.29.119.171 (talk) 02:42, 15 July 2011 (UTC)

Photons are massless particles, and as such, must move at the speed of light (being, in fact, the embodiment of light). Anything with mass would require an infinite input of energy, as you note. Neutrinos are nearly massless, and move at nearly the speed of light. Acroterion (talk) 03:05, 15 July 2011 (UTC)

That is exactly kind of answer I was trying to avoid... Let me re-phrase, then. Fundamentally, what makes matter different from energy so that it may not travel at the speed of light? I mean, I perfectly understand the basic principles of both special and general relativity, but I just have to wonder why this happens, if they're supposedly the same entity.186.29.119.171 (talk) 03:18, 15 July 2011 (UTC)

Don't think of "matter" as being different than "energy", because you are really comparing apples and oranges. It's like saying "Why is apple different than color". Color is a property that an apple has, while apples have other properties as well, like texture, taste, size, etc. etc. Matter has many properties, like charge, spin, momentum, volume, and "mass" is but one of the properties of matter. Mass and energy are the same thing, the distinction in names is partly historical, and partly to distinguish between "potential energy that is tied up within a substance" (which is all mass is) and "kinetic energy that is moving an object around", which is what we usually think of when we call something "energy". One of the "defining" characteristics of "matter" is that it has a mass, which is another way of saying that it has the ability to trap and hold onto energy indefinitely; particles like "photons" that have "no rest mass" basically just means that photons have no internal potential energy of their own, and exist solely as vehicles to carry kinetic energy. So remember, matter and energy isn't the same thing, it's "mass" and energy that is the same thing. As far as why matter has the mass form of energy, that is the $64,000 question in physics today. The most accepted hypothesis of the source of mass is the Higgs mechanism, but as yet experimental proof, in the form of positive confirmation of the Higgs boson, eludes physics. If you want to think in very lay man's terms (and that's all I am capable of thinking in anyways) the Higgs mechanism is a way of explaining how energy became trapped in matter in the first place, providing matter with "mass". --Jayron32 04:30, 15 July 2011 (UTC)

Another source of confusion is the incorrect belief that light is the same thing as energy, or that is "pure" energy. Dauto (talk) 12:33, 15 July 2011 (UTC)

Exactly, energy is a property of light, just as mass is a property of matter. But it is not identical to it. Light has other properties; unrelated to its energy content. Light, for example, also displayed properties like polarizability and photons themselves have spin which is unconnected to their energy content. --Jayron32 14:56, 15 July 2011 (UTC)

I think I understand the question being asked, and am not sure that it has been directly answered. Let's say we have a photon of a certain energy. By E=mc^2, can we not say that that photon is equivalent to a small but finite mass? And if so, how could it have infinite speed? I think the proper answer should be that the photon is equivalent to a certain rest mass, and that the problem arises when you unconsciously smuggle back in the velocity. You have forgotten that if E=mc^2 then m equals not E alone but m=E/c^2 and the velocity has been divided out. The photon is only equivalent to a small but finite rest mass which is at rest To speak of a rest mass not at rest is to introduce a contradiction. μηδείς (talk) 20:14, 15 July 2011 (UTC)

I think the question is a good one and it has an interesting answer in the Standard Model of particle physics. In the Standard Model, everything in the world (except gravity) is described by what amounts to a more complicated version of the electromagnetic field. It's a quantum field, but you don't need to understand the quantum aspect to understand the origin of mass.

Start with the electromagnetic field. You probably know that electromagnetic waves (light) can be polarized. You can describe any polarization state as a combination of two "basis states". For example, if you take horizontal and vertical polarization as your basis states, diagonal polarization is a combination of the two—simultaneous oscillation up-down and left-right—and circular polarization is also a combination, but with the horizontal oscillation offset in time from the vertical by a quarter period (as shown here).

There are exactly two circular polarization states: one rotating clockwise when viewed from behind and one rotating counterclockwise. These two states also work as a basis for all polarizations, and there's something special about them: they are "the same for all observers". Horizontal polarization turns into vertical polarization if you rotate your frame of reference, but clockwise circular stays clockwise circular when rotated, and also when you change the speed of the reference frame. This means that the electromagnetic field can be decomposed into two independent fields, one purely counterclockwise ("left handed") and one purely clockwise ("right handed"), in an observer-independent way. In theory, one could exist without the other.

The electromagnetic field is called a massless field because it has a certain natural correspondence with a theory of massless particles moving at the speed of light. If you write down the equations for a field with a nonzero rest mass m, it turns out to correspond to left-handed and right-handed fields that are coupled together with a coupling strength proportional to m². (If m=0 then the coupling is zero and the polarized fields are independent, as above.) Coupling means that a vibration in one field induces a vibration in the other. You can (if you like) think of independent fields as independent pendulums, and coupled fields as pendulums connected by a spring whose spring constant is the coupling strength (m²).

So a massive particle/field is two massless particles/fields of opposite circular polarization coupled together. You can think of this in the following way: all particles move at the speed of light. But massive particles sometimes change into particles of the opposite handedness. They retain their angular momentum; because of the opposite handedness, that means they reverse direction. So slower-than-light motion is back-and-forth motion at the speed of light. Your average speed can be zero even if your instantaneous speed at every instant is c.

In the Standard Model, all of the fundamental fermion fields exist in only one handedness. There's no direct coupling to mirror-image fields because there aren't any. Instead, there are more complicated couplings involving pairs of fermion fields (that have opposite handedness, but aren't mirror images) and the Higgs field. So it's not quite right to say that the Higgs field gives mass to particles—without the Higgs interaction, you don't have massless electrons and quarks so much as you have a bunch of one-handed massless fields that don't pair up in any natural way. Before the discovery of neutrino mass, it was thought that there simply is no "right-handed neutrino field", that is, no field that could be Higgs-coupled to the left-handed neutrino field without violating conservation laws. So neutrinos were purely left-handed and also massless—those two things go together. -- BenRG (talk) 22:38, 15 July 2011 (UTC)

Here's how I'd put it. Rest mass increases according to velocity, with infinite mass at the speed of light. Light has finite mass at the speed of light - i.e., if you could slow down light, it should have zero mass. Problem: you can have slow light. But I think however it's slowed - which I've heard doesn't really involve absorption and reemission - it somehow avoids this fate. Wnt (talk) 01:15, 16 July 2011 (UTC)

Thank you very much for the explanation, BenRG; It really helped me understand a bit more about the "God particle," hehe. Let me see if I get it right:

The Higgs Field somehow couples to the one-handed massless field and kinda "wraps" the field into a massive one, a perception that would go in hand with the semi-accepted view that mass is just wrapped up energy. By a field's handedness I am inclined to believe that you speak of the spin of the particles, which would mean that massive fields will always end up with half-integer spin. There is, however, what I perceive as an apparent contradiction in your explanation, that is, you mention that "In the Standard Model, all of the fundamental fermion fields exist in only one handedness. There's no direct coupling to mirror-image fields because there aren't any. Instead, there are more complicated couplings involving pairs of fermion fields (that have opposite handedness, but aren't mirror images) and the Higgs field"

Could I ask you, or anyone, to explain that to me, please?190.25.11.138 (talk) 02:14, 16 July 2011 (UTC)

Even though BenRG's post is, as always, very interesting and informative, it is not the answer to question, as I understand it. The answer is much simpler than that. The difference between photons and massive particles (lets take an electron as an example) is the fact that photons have zero rest mass while electrons have non-zero rest mass. BenRG's answer explains the origin of that rest mass but that's really not essential to the answer. The point is that the equation E=mc^2 is not telling you that mass can be converted into energy and vice-versa. That equation is telling you that mass IS energy and vice-versa. So a photon, having energy, will also have mass even though it has zero rest mass which is the mass it would have if it could be at rest, which it cannot do. An electron, on the other hand, has a rest mass which means it has a non-zero rest energy. When an electron moves it has more energy added to this rest energy which also means added mass. An electron cannot move at the speed of light because that would require infinite energy and infinite mass, which is not possible. Based on what I said above it becomes clear that the concepts of mass and energy are redundant. Because of that, physicists by convention use the word mass to refer to the rest mass (and rest energy) and use the word energy to refer to the total energy (and total mass). This is a midway change of notation which implies a change in the mathematical relationship between mass and energy. The equation E=mc^2 isn't valid any more! The correct equation now is $E={\sqrt {m^{2}c^{4}+p^{2}c^{2}}}$ where p is the momentum of the particle. For a particle at rest (p=0) that equation reverts back to the familiar E=mc^2 and for a massless particla such as a photon the eqution simplifies to E=cp. I hope that helps clarify the relationship between mass and energy. Dauto (talk) 14:31, 16 July 2011 (UTC)

Evolution reloaded

I saw the question titled Evolution a few days ago. While evolution has by no means stopped in general, I think it is relatively accurate to say that humans are no longer affected by Darwinian natural selection nearly to the degree that the natural world is. With modern medicine, no matter how maladaptive mutations are, the sufferers can oftne be kept alive long enough to propagate it to offspring (if it is propagable) and non-genetic diseases that would not have nearly the widespreadness that they do owe their success to modern medicine again keeping people alive and able to infect others (ie, AIDS). Moreover, the development of civilization and trade has made gradual adaptations for changing food availability almost obsolete. (Nowadays it seems that the natural next step of human evolution will be to propagate genes for promiscuity and hyperfecundity) QUestion: About when (I'm looking for a range, not a specific event) did humans stop being as affected by evolution? grazie. — Preceding unsigned comment added by 24.92.88.206 (talk) 03:17, 15 July 2011 (UTC)

That is completely not true either. There is no evidence that humans have stopped being "affected by Darwinian natural selection". That stance implies two spheres of existance, the natural, and the human, and somehow would imply that different sets of rules existed for human life than exist for "natural" life. Its a popular sentiment, which has a long history, and which I should note has no basis in science. Humans are under the same sorts of evolutionary pressures that all life forms are, and our genetic make up is open to the same sorts of changes as any life. Why must modern medicine be viewed as counter to evolution or something likely to "stop" it, rather than broadly as just another adaptation that the human animal has developed to adapt to its environment. It really isn't any different than any other trait in that regard. Humans are continuing to change, genetically, and will continue to do so for the forseeable future, on an evolutionary time scale. Our adaptations may change how our genes are passed on, and the rates at which changes happen, but really that isn't a uniquely human situation, every life form has adaptations which allow it to stabilize its gene pool for a time being; it's why we have distinct species with any history of stable phenotypes at all. Seriously, humans are not distinct from nature, and evolution has not stopped for us. As long as we keep having sex, and having children, we will keep evolving. --Jayron32 03:41, 15 July 2011 (UTC)

I completely agree with the above. I would just like to add that I think this misconception might stem, in some cases, with our human inability to conceptualize the sheer time scales that are involved in evolution. Estimates for the emergence of our species are at around one or two HUNDRED THOUSAND years, and we aren't a particularly old species at all. That means if you travelled back in time 100 or 200 thousand years, humans would have been pretty much exactly the same, enough that you could have viable offspring with them. It might be more valid to ask a crocodile the question of their species since fossil ancestors up to 84 million years old don't seem to be any different then crocodiles alive today. Vespine (talk) 04:22, 15 July 2011 (UTC)

Modern medicine is also extremely young - Semmelweiss introduced hand-washing around1850, and Pasteur worked in the 1860s. The pill was introduced 100 years later. And of course, only a very small part of the human population has access to most of modern medical technology. But that is not the core of the issue - the core is that we do not eliminate selection pressure, we just change it. --Stephan Schulz (talk) 06:10, 15 July 2011 (UTC)

Even assuming perfect healthcare, there are so many factors affecting the chances of survival and reproduction in modern society that natural selection is still central to human evolution. That is, human evolution is not dominated by genetic drift. Genes affect obesity, genes affect your behaviour, genes affect the chances of addiction, how you respond to medication, the chances of conceiving a baby and your ability to care for it. And if any of the preceding is not true, evolution could produce a new gene that does affect that trait, improving the person's fitness. In fact, human evolution has been shown to have sped up since the stone age, due to new ways of living, more diseases and new food. Some evolutionary theorists also predict that modern society, where people can take on more specialized tasks and be better cared for by healtcare, will speed up human evolution even more. The parallel pointed to is the wolf, which has been unchanged for many thousands of years and well adapted. But when the wolf was domesticated, it was freed of the evolutionary pressure in the forest, exposed to new evolutionary pressures and hence diversified into numerous types of dogs in the blink of an eye, evolutionary speaking. Far from being unaffected by evolution, humanity is being carried on a roaring wave of evolutionary change. EverGreg (talk) 08:31, 15 July 2011 (UTC)

The main thing that very recently changed is survival rate to adulthood. If this is maintained for a couple of hundred thousand years (and I am not saying I think it will be maintained, it very well may be a 200 year temporary anomaly), we may see a significant shift in human evolution towards sexual selection being the only trigger for evolutionary change, rather than a combination of natural selection, sexual selection and other things that are happening in the wild. --Lgriot (talk) 08:50, 15 July 2011 (UTC)

With our technology humans do not necessarily need to undergo physical change to adapt to different environmental pressures such as becoming more hairy in colder climates. We have developed the ability to modify our environment to suit our physical characteristics - clothing, shelter, furnaces, air conditioning, etc. This has to a significant extent eliminated much of the pressure driving physical evolution. Much of human evolution in the last hundred-thousand years or so has been behavioral rather than anatomical or physiological. Notable exceptions are traits such as the survival of lactase in adults in populations that use animal milk in their diet beyond infancy. Roger (talk) 09:14, 15 July 2011 (UTC)

Diseases such as alcoholism, other addictions, flu, other pathogens, etc. are still selecting us. In some areas, yes, we're under less selection pressure. Imagine Reason (talk) 13:11, 15 July 2011 (UTC)

Doing fine with 10,000 IU/day of vitamin D

Half a year ago, some people here suggested that taking 10,000 IU/day of vitamin D is dangerous, See here

I think most experts would say something like: "10,000(0) IU/day is probably safe for most people", but perhaps Count Iblis will let us know in a few years whether he has suffered benefit or harm from this dosage. Personally, I would prefer to err on the lower side in the absence of regular medical monitoring. If I had some 50,000(0) IU tablets, and wanted to use myself as a guinea pig, I would cut them in half and take half every three days, but please don't take this as medical advice because I have no medical expertise. Dbfirs 21:26, 21 December 2010 (UTC)

He won't be able to let us know as he will be dead or disabled. 92.15.26.185 (talk) 16:26, 22 December 2010 (UTC)

While this discussion happened half a year ago, I've been taking roughly 10,000 IU/day for almost two years now (I estimate how much I get from the Sun and then I supplement that to 10,000 IU/day). The year before that I took 5,000 IU/day. Now, I'm doing fine but obviously that's not proof that this is due to Vitamin D. It does show that vitamin D at a dose of 10,000 IU/day is not going to cause people to suddenly drop dead after a year or so as was sugested in that thread.

Some rough figures about my fitness levels: I used to work out 3 times per week before 2008. I would run at moderate to high speed for 20 minutes. My resting heart rate was in the mid 40s, often it would be close to 50. I had tried but failed to increase my fitness by attempting to gradually train a lot harder. It just didn't work out well. So, I wasn't very fit and I had difficulties improving my fitness.

Around 2008, when I started to take high dose vitamin D, gradually increasing exercise intensity and frequency did work. Today, I exercise 5 times per week, I do 35 to 40 minutes of fast running. My resting heart rate is usually between 37 and 40 bpm. Heart rate recovery rate after 35 minutes of running is typically 40 bpm/minute (heart rate drops from 160 bpm to 120 bpm in one minute). When I measure this at the start of the exercise, I find larger values, typically 60 bpm/minute.

Clearly, this is a huge increase in fitness. While it isn't proof that vitamin D has anything to do with this, it does make it unlikely that Vitamin D is interfering with vital body functions in a negative way. That it may help boost athletic performance is consistent with these findings.

Now, from the literature, we can get some clues that 10,000 IU/day is what one needs for optimal health. In this article, you can deduce from the relation between vitamin D dose and increase in calcidiol concentration, that the half life of calcidiol is not constant, it depends on the calcidiol level until you reach values of about 200 nmol/l. This means that vitamin D use by many cells is turned off below this level, the lower it is the less your body uses vitamin D. At low levels your body only uses vitamin D for calcium metabolism. This then suggest that even people with values as high as 150 nmol/l should be considered to be vitamin D deficient.

Then, in this article, we can read that breast milk does contain enough vitamin D for babies, but only if the mother takes about 6,000 IU/day of vitamin D. At lower doses e.g. 2,000 IU/day for the mother, the breast milk does not contain the known minimum amount babies need (400 IU/litre). So, the fact that we routinely give babies vitamin D supplements because "breast milk does not contain nearly enough vitamin D", should be a red flag that something is deeply wrong with current medical practices/thinking.

We don't need to dig deep to find the source of the problems. The reason why almost all pregnant women are severely vitamin D deficient can be found here:

"Vitamin D supplementation during pregnancy remains controversial largely due to severe misconceptions about the potential harm it may cause to the fetus,” said Dr Hollis. “Surprisingly the scientific debate has made little progress since Dr. Gilbert Forbes made a recommendation of 200 IU (international units) per day in 1963, which was based on a hunch.”

This flawed recommendation made it difficult to conduct studies to determine the correct level, because the correct level is so much higher than what was thought to be toxic. It has now been found that:

"In our study subjects, a daily dosage of up to 4,000 IU of vitamin D was required to sustain normal metabolism in pregnant women,” concluded Dr Hollis. “Furthermore, following decades of speculation into its safety our research has demonstrated vitamin D supplementation to be both safe and effective.”

Then another piece of flawed research led to the 2,000 IU/day UL. We can read here that:

95 µg (3800 IU) vitamin D3/d This clinical trial, conducted by Narang et al (14), involved 30 healthy adults divided among treatment doses of 10, 20, 30, 60, and 95 µg vitamin D3/d. No adverse clinical effects were reported, but the highest intake produced a significant increase in serum calcium to 2.83 mmol/L, a concentration slightly above the reported upper normal level of 2.75 mmol/L. Serum 25(OH)D was not measured. These results are very different from those in later studies that used higher doses given to larger cohorts and for longer durations. Thus, these results are inconsistent and conflict with the preponderance of the clinical trial database for high-dose vitamin D and therefore are not considered to credibly contradict the 250 µg NOAEL.

So, dead wrong, but still used as the standard to this day by many national medical institutions to set the UL at 2,000 IU/day!

In reality, the dose you need to take to get ill is huge:

A comprehensive review of the literature revealed that the serum 25(OH)D concentrations associated with hypercalcemia were almost exclusively the result of very large doses of vitamin D, and in all instances serum 25(OH)D concentrations reached concentrations well into the hundreds and even thousands of nmol/L (44). This is consistent with the data derived by Mason et al (45) and reported recently by Morris (46), which concluded that, on the basis of the relation between the 2 parameters, a serum 25(OH)D concentration of ≥700 nmol/L may be needed to evoke hypercalcemia in normal adults.

With 40,000 IU/day you will only barely approach such dangerous levels. Count Iblis (talk) 03:36, 15 July 2011 (UTC)

Is there some bit of knowledge we can help you learn about, Count, or are you just interested in ranting here? This sort of long, wall-of-text rant isn't really appropriate for the refdesks, and as you aren't a noob, I wouldn't have expected you to be reminded of that. --Jayron32 03:43, 15 July 2011 (UTC)

Questions: What proportion of the human population has a diet that includes vitamin D in such quantities? And did our hunter-gatherer ancestors routinely get vitamin D in such quantities? And if so, how was this obtained? (I don't actually know the answer to any of these questions - they aren't rhetorical, for me at least). It seems to me that natural selection can hardly have made us dependant on vitamins we don't get from our diet, so I have to ask what has changed that makes it so essential to do anything other than eat the same stuff we have been, and carry on procreating at an alarming and unsustainable rate... AndyTheGrump (talk) 03:47, 15 July 2011 (UTC)

For reference the practice is called Megadosing or Megavitamin therapy. There is really very little if any evidence that megadosing on ANY vitamins is a good idea. Even our Vitamin D article has some information which makes it sound like a bad idea: Using information from the National Health and Nutrition Examination Survey a large scale study concluded that having low levels of vitamin D (<17.8 ng/ml) was independently associated with an increase in all-cause mortality in the general population.[153] However it has been pointed out that increased mortality was also found in those with higher concentrations, (above 50 ng/ml).A sophisticated August 2010 study of plasma vitamin D and mortality in older men concluded that both high (>39 ng/ml) and low (<18 ng/ml)) concentrations of plasma 25(OH)D are associated with elevated risks of overall and cancer mortality compared with intermediate concentrations. Vespine (talk) 04:08, 15 July 2011 (UTC)

Our hunter-gatherer ancestors obtained most of their vitamin D through photosynthesis. I've heard anecdotal evidence (a nutritionist told me) that less than an hour of average African savanna sunshine per day onto a quarter of the total skin area is sufficient to supply all the Vit D a human needs. Roger (talk) 09:35, 15 July 2011 (UTC)

On one point above, breast-fed infants in the UK are not routinely given Vitamin D supplements, or any other supplements. The World Health Organisation recommends that infants should receive nothing but breast milk for the first six months. That currently forms the basis of NHS advice. Itsmejudith (talk) 14:35, 15 July 2011 (UTC)

Of course, nothing prevents the mother from taking appropriate supplements, which would (at least to some crude approximation) be mixed into the milk just as if they'd been shaken into a bottle of formula. Wnt (talk) 17:45, 16 July 2011 (UTC)

Yes, as explained here (free version here), the mother needs to get about 6000 IU/day. Count Iblis (talk) 18:07, 16 July 2011 (UTC)

Jayron, this is an answer to a question asked half a year ago, I was asked then to report back how I was doing.

AndyTheGrump, as Roger points out, we get vitamin D from exposure to UV radiation. Half an hour in the Sun is enough to produce 10,000 IU. Now, what has happened over the last few centuries is that we're spending so much times indoors that we don't get the 10,000 IU/day and diet will only get you a fraction of this. That may be just enough to prevent problems with your bones.

Vespine, the Wikipedia Vitamin D article has been severy compromized by POV warriors. It's a classic example of how Wikipedia's mantra of "Not Truth" indeed does compromize accuracy, despite what the regulars at WP:V say. There are a huge number of scientific articles that point to doses of the order of a few thousand IU/day being able to prevent illnesses. Almost always when someone (not me) tries to edit in such a result, it's been reverted, on the grounds that one needs to wait until some review article writes about it. However, that standard is not used to include the results suggest that vitamin D may cause health problems.

Itsmejudith, where I live, all breastfed babies are recommended to be given 400 IU/day. Count Iblis (talk) 15:05, 15 July 2011 (UTC)

I had a test for Vitamin D, 25-Hydroxy (Calciferol) and it said the normal range was 30-100 ng/mL. It said any result <10 was "suggestive of deficiency," 10-30- was "suggestive of insufficiency," 30-100 was "suggestive of sufficiency," and >100 was "suggestive of toxicity." 400 units from a daily multivitamin had left me in the "insufficiency" range, on an earlier test, and a daily 1000 unit supplement in addition to that got me up in the high 30's, in the standard range. Two doctors have told me that the middle of the "standard range" would not be better than the lower end of the standard range, though some studies showing benefits increasing through the 30's. Why would someone take mega-supplements and not get a test, citing other random things like pulse rate, when the level might be in the "toxic" range? As for sun exposure, a friend in his 70's has had about 15 pieces of skin cut off his body in operations over the last 2 years due to melanoma attributed by his doctor to large amounts of sun exposure over the years. Seems a high price to pay to save money on vitamins. Edison (talk) 16:38, 15 July 2011 (UTC)

There is still a lack of agreement over the recommended dosage and toxicity levels. Those of us who see no sun for weeks in winter might benefit from high doses, but I'm not sure I want to try the 10,000 IU/day recommended by some researchers (and reported on by the BBC about a year ago) until further research shows that it is perfectly safe. At this time of year, no supplement is necessary, of course, for those of us who are able to go outside in sunlight. Dbfirs 17:16, 15 July 2011 (UTC)

Indeed, and that's why I'm sticking to my own advice :) . Count Iblis (talk) 17:44, 15 July 2011 (UTC)

Let me just mention that Nature had a nice news article about this controversy only last week. Looie496 (talk) 22:59, 15 July 2011 (UTC)

young earth creationism

when i was a child in Sunday school my teacher used to tell me that fossil records were put on the earth by Satan in order to deceive humanity. God knows this sunday school teacher was kooky, but is there any notable strain of young earth creationist thought that endorses this view, and where might I read more about it (not about YEC in general, but specifically about the claim that Satan concocted all the evidence of evolution, etc.)--Fran Cranley (talk) 03:47, 15 July 2011 (UTC)

Religious questions typically don't go down too well on the science ref desk. What I've learned after taking a bit of an interest in the creationism debate is that it's essentially pointless trying to reason with creationists. I've debated with creationists who basically change their stance on a point from one argument to the next to suit their view, then fail to understand why that might be a problem in their position. I don't think they really have strict "sects" or "doctrines" delineated by details such as the argument you describe, I think for the most part it's just a case of "reject the scientific evidence for evolution" and everyone just fills in the gaps as best as they can.Vespine (talk) 05:35, 15 July 2011 (UTC)

There are some articles about research institutes like Geoscience Research Institute and Institute for Creation Research plus the Creation Research Society that may be a good place to start looking for relevant information/links. To be fair, having to stare at fossils when it's freezing cold and wet for a prolonged period of time is enough to make even an atheist geoscientist believe they were put there by Satan. Sean.hoyland - talk 06:49, 15 July 2011 (UTC)

Where in scripture does it say that God granted Satan the right to create? Plasmic Physics (talk) 07:25, 15 July 2011 (UTC)

Nowhere, but then again, it also says nothing about birth control being evil, but that hasn't stopped the entire Roman Catholic Church from crusading against it. -RunningOnBrains^(talk) 07:52, 15 July 2011 (UTC)

I don't accept the RCC's authority over religious matters, especially since they have injected so much of their own doctrine into scripture throughout the times. The assumed authority which they entertain, leads their followers to blindly place their trust in their word, without confirming in the scriptures for themselves, as is instructed within it in any case. This is kind of ironic, since the only way you would know that, is if you actually bothered to read the scriptures. Plasmic Physics (talk) 08:08, 15 July 2011 (UTC)

The scriptures were written by humans too. Why trust them over the humans in the RCC? Or vice versa? thx1138 (talk) 14:33, 15 July 2011 (UTC)

As a more accessible example: charging of interest on a loan is expressly forbidden by the Jewish, Christian, and Muslim holy books, and yet it seems that does not stop the entire world from running on it. -RunningOnBrains^(talk) 13:45, 15 July 2011 (UTC)

I think a more common YEC explanation of fossils is that they are the remains of antediluvian life. As has been noted, the idea that they were created to deliberately deceive humanity - either allowed by God or directly created by God - leads to a tricky moral dilemma. Gandalf61 (talk) 08:44, 15 July 2011 (UTC)

Professor Ian Plimer, professor of mining geology at the University of Adelaide (in Australia), wrote a great book titled Telling Lies for God. That title says it all. Dolphin (t) 08:49, 15 July 2011 (UTC)

There is no "God" to science. Zzubnik (talk) 11:08, 15 July 2011 (UTC)

Isn't it great that everyone has the right to have an opinion? Plasmic Physics (talk) 11:10, 15 July 2011 (UTC)

Einstein wrote about his belief in a "cosmic religion" in 1930. Years later in a letter he wrote "I cannot conceive of a personal God who would directly influence the actions of individuals or would sit in judgement of creatures of his own creation. My religiosity consists of a humble admiration of the infinitely superior spirit that reveals itself in the little we can comprehend about the knowable world. That deeply emotional conviction of the presence of a superior reasoning power, which is revealed in the incomprehensible universe, forms my idea of God." He also said "God is cunning but not malicious," "God does not play dice," and "I want to know how God created the world." He said "I am not an athiest." A Deist is not an athiest(though I'm not sure if Einstein was a Deist like some of the US Founding Fathers, who believed in a God who was like a great cosmic watchmaker who built the universe and set it in motion, then stepped back. Edison (talk) 16:21, 15 July 2011 (UTC)

I agree. If everybody had the same opinion, life would be boring, there would be no discussion, no passion. Zzubnik (talk) 11:34, 15 July 2011 (UTC)

I disagree with Zzubnik on this. I personally find opinions very boring. Facts and hypothesis are much more interesting. And you can discuss facts and hypothesis, so there would still be discussions. --Lgriot (talk) 12:07, 15 July 2011 (UTC)

I am inclined to disagree with myself and agree with Lgriot. — Preceding unsigned comment added by Zzubnik (talk • contribs) 13:00, 15 July 2011 (UTC)

People talk about opinions far too much. There is no opinion is this discussion. Whether or not there is a god is a matter of fact. It's a fact that people disagree about, but it's still a fact. Either the people that say there is a god (or gods) are wrong, or the people that say there isn't a god are wrong. They can't both be right. The key feature of an opinion is that people can hold contradictory opinions without that meaning one of them is wrong. --Tango (talk) 19:50, 17 July 2011 (UTC)

The book Omphalos by naturalist Philip Gosse, 1857, points out that living things go in cycles, and always bear evidence of some earlier existence, which he called "prochronism." See Omphalos hypothesis. Gosse was not arguing against God having created the world, he was just arguing that whatever instant it was created, it would have pointed to a spurious earlier existence. Unless Adam and Eve were bald, they were created with hair that implied growth before existence. The same view would not rule out seemingly ancient fossils, light coming from stars billions of lightyears away, mountains seemingly eroded over millions of years, or layer after layer of sediment with evidence of evolving forms of plants and animals. He did point out that the world could have been created in 1857 with a complete historical record. . Creationists I have questioned often agree that when God created trees in the Garden of Eden, that is Adam had cut one down on his first day there, he would have found tree rings in it which suggested it had been there for years. It would not have been some odd homogenious plastic wood material inside, although some creationists picture Garden of Eden trees with no growth rings inside, and Adam and Eve without navels. Animals and plants would generally have misleading evidence of prior existence. Religionists of the 1850 complained that it would "make God out to be a liar." Edison (talk) 17:01, 15 July 2011 (UTC)

That's, of course, why it is impossible to use reason to argue with YEC proponents, or any other form of intelligent design/creationism belief. One can literally argue that God created the entire universe one second ago and did so with everything in it in the state it is right now, including our memories, and such an arguement requires no actual evidence to back it up, because any evidence wouldn't be able to prove or disprove the assertion. It is an unfalsifiable proposition and so holds absolutely no scientific merit at all. It's completely pointless to try to argue the point. In other words, one can hold that such a statement could be true for any given range of "could", but one cannot operate scientifically around that statement, so there is no point in trying to prove it scientifically. From a scientific point of view, such propositions can be ignored as though they don't exist. --Jayron32 17:11, 15 July 2011 (UTC)

I don't see why it would have to be Satan. It seems to me that a Creationist could argue that God placed fossils and other spurious things on Earth in order to test our faith. This argument would be virtually impossible for scientists to refute; it is remarkable to me that it is so rarely used. Looie496 (talk) 17:08, 15 July 2011 (UTC)

Much of recorded history includes religious authorities trying to revise or explain superstitions, including by apologism which often results in the creation of other superstitions. The idea that satan placed fossils underground is probably in the folklore stage, without much written documentation beyond hushed whispers. One might wonder whether all of the evidence in biology and radiochemistry suggesting a billions of years-old Earth will go through the same stages. 99.24.223.58 (talk) 18:51, 15 July 2011 (UTC)

God would not have created false evidense of an ancient earth to test our faith, it is said in scripture that He is not a god of chaos, but of order; and it is said that He does not deceive.

If there is apparent contradiction between what we observe and what is written, then is due to a lack of our understanding and interpretation of scripture. Most scientists agree that scientific conclusions aren't perfect, but merely describes the best approximation of what we have the plessure of observing, and so is always in a state of refinement. Plasmic Physics (talk) 00:49, 16 July 2011 (UTC)

This rather entertaining page asks: "Why didn’t the Dinosaurs try to eat Adam and Eve?" Final answer: "two interpretations: (1) God planted the fossils as a test of Faith. (2) Satan planted the fossils to mislead us to fill up Hell with ever burning souls. Whichever it is - doesn't really matter. You can only believe what is in the Bible." It finishes with a short discussion on whether Satan has visited the moon. Americans are so funny. Alansplodge (talk) 19:22, 17 July 2011 (UTC)

cancer stage

How long will it usually take for a carcinoma to transfer from one stage to another? — Preceding unsigned comment added by 199.224.149.10 (talk) 09:39, 15 July 2011 (UTC)

This is really an "it depends" kind of question. "Cancer" is not one disease, but many. The time it takes to progress from one "stage" to another depends on the definition of "stage" for a given cancer, and it depends on the multitude of individual factors within an individual. One of main factors is probably random chance -- whether a mutation arises that gives that cancer cell an advantage and allows it to spread faster than other cancer cells. This is also a very difficult question to answer scientifically, since most cancers are detected when they are large enough to be seen on some type of screening study or because they are causing symptoms (like a lump, or bleeding). We have no idea how long the "cancer" has been present in that person prior to detection. We can assume a constant growth rate and project how long it might have taken for one cell to grow to a tumor of a certain size, but that is complete guesswork and makes a very naive assumption (consistent rate of cell growth and death). Once a cancer has been detected, the inclination of the physician is to treat it (remove it or give chemotherapy), which pretty much excludes the possibility of measuring the time it takes for that cancer to progress (and you could imagine that a scientific study designed to measure time to progression would involve serious ethical questions, especially for early stage, more treatable cancers). I don't think you're going to find a simple answer here. --- Medical geneticist (talk) 10:28, 15 July 2011 (UTC)

Zoophilia

I know that not many people have done these types of experiments, but how do higher animals react to rape by a human? Would a female chimp, for example, react in a similar way to unwanted vaginal penetration by a human as a female human? My guess would be yes, since chimps are a monogamous species and presumably don't appreciate sexual contact by a stranger, but I also have no experience with this.

I'm asking because Wikipedia's article on zoophilia implies that much of the debate around it concerns whether or not it's cruel to animals.--140.180.16.144 (talk) 09:40, 15 July 2011 (UTC)

"chimps are a monogamous species"...I think not. Sean.hoyland - talk 09:43, 15 July 2011 (UTC)

I want to know why do some animals like Orangutan are attracted to humans? They are different species. then how do the attraction occur. How do they feel about it? Is it reverse zoophilia, homophilia? --111Engo (talk) 10:12, 15 July 2011 (UTC)

Not sure what you mean by "why", or "how do they feel about it", unless you're looking for an evolutionary reason. Why are you attracted to human males/females? How do you feel about it? I don't think orangutans have any more of a reason or justification than you do. --140.180.16.144 (talk) 11:33, 15 July 2011 (UTC)

Why do I attracted to humans? Because it is coded in my DNA, my gene, it is my biological instinct. But Orangutans have different gene. This is why I am asking why do they attracted to humans? --111Engo (talk) 11:40, 15 July 2011 (UTC)

Also is there other instances where other animal are attracted to humans? --111Engo (talk) 10:14, 15 July 2011 (UTC)

What about dogs? Then again, they would go for inanimate objects, so that doesn't say much. Plasmic Physics (talk) 11:49, 15 July 2011 (UTC)

I remember reading a news report on the multiple cases of sexual abuse of horses ocurring during nights in Texas somewhere. In the news report, it was described how the horses became apprehensive toward humans, and developed a general mistrust. If anyone can track down that article, it might be of some use. Plasmic Physics (talk) 11:55, 15 July 2011 (UTC)

These are just good friends. (video) Cuddlyable3 (talk) 14:49, 15 July 2011 (UTC)

Does knowledge of psychological experiments influence participants' behaviour?

I'm curious about whether psychological experiments are influenced by participants' foreknowledge, particularly for experiments where people end up behaving in ways they wouldn't expect to. For example, if a researcher decided to recreate the Stanford Prison Experiment (or the Milgram experiment or the Asch conformity experiments or something similar), would the results be different if the participants were aware of these experiments, even though they were not told they were taking part in one?

PS. Since I'm here - I vaguely recall reading about an experiment which studied peer pressure or conformity (I think), where a group of people were instructed to remain in a room. After some time, they started hearing noises - screams or cries for help outside the door. All but one of the group were secretly actors, who were to discourage the non-actor from investigating the noise. I haven't been able to find information on this and can't remember the name - did I imagine it? --Kateshortforbob _talk 13:06, 15 July 2011 (UTC)

Knowledge that one's behaviour is under observation always puts doubt about how the results of the types of experiment you mention was influenced. More credible results may come from analysis of behaviours in non-experimental conditions with the analysis unknown to the subjects. The main difficulty then is to show whether an observed correlation implies causality. Cuddlyable3 (talk) 14:42, 15 July 2011 (UTC)

Some folks have read about famous psychology experiments such as the Milgram experiment, or seen them portrayed on TV, but a great many are quite ignorant, as shown by the lackluster results of many tests of general knowledge. A clever experimentr can make subjects think the experiment is about one thing, when it is really about something else. It was very easy for Milgram to do his experiments back in the day (Especially because there were then few rules against causing psychological harm to participants in such experiments). Many experimenters are not very scientific or careful in their work, and just want to get their master's thesis accepted or to get published and gain tenure, so they may ignore participants "figuring out what is going on." A good experiment would have some kind of awareness assessment questionnaire, to determine if the subject was aware of the published related research. Charlatans just go ahead and publish studies, ignoring whether subjects figured out any ruse the experiment was engaged in, or whether the demand conditions of the experiment affected the results, or whether the subject had "figured out what the (unstated) point of the experiment was," or whether the subject had invented a strategy such as noticing in a reaction time experiment with 2 response choices, that one response never repeated more than 3 times in a row, allowing an "instant" response after the same response was called for 3 times in succession. (The last issue can be dealt with by having practice runs or noncounting runs which have the same response repeated more than 3 times in a row). Edison (talk) 15:59, 15 July 2011 (UTC)

You have a good point -- it has often seemed to me that psychologists too frequently presume that experimental subjects fully believe the stories they are told. Regarding the second part of the question, interest in that topic was first provoked by shock at the circumstances of the murder of Kitty Genovese in 1964, and led to research that is described in our articles on the bystander effect and diffusion of responsibility. Looie496 (talk) 16:56, 15 July 2011 (UTC)

capacitance

In alternating current ,the potential drop across a small capacitor is very large compared to a larger capacitor since smaller capacitor has more reactance(charging and discharging current is less). but my doubt is we know that voltage means the charge difference,but accumulated electrons on smaller capacitance plate is very less compared to a larger capacitance plate. according to voltage meaning,the larger capacitance has more voltage compared to smaller capacitance but smaller one has more voltage drop why? please clarify my doubt in deep and also in 3d picturesvsnkumar (talk) 13:57, 15 July 2011 (UTC)

An ideal capacitor is wholly characterized by a constant capacitance C, defined as the ratio of charge ±Q on each conductor to the voltage V between them:

$C={\frac {Q}{V}}$

That means that changing the voltage on a large capacitor involves moving a larger charge Q than the same voltage change on a small capacitor. See the article Capacitor. It doesn't have much of 3-D pictures except photographs of real capacitors. Cuddlyable3 (talk) 14:29, 15 July 2011 (UTC)

"Voltage means the charge difference" is wrong. Voltage is partly determined by the charge difference, but also by how much the positive and negative charges are separated. Looie496 (talk) 16:43, 15 July 2011 (UTC)

You are right to express doubt that voltage is determined by capacitance because the voltage drop will depend on the circuit. I assume that you were thinking of the two capacitors connected in series. You might find our article Hydraulic analogy helpful in visualising why the "higher pressure" is across the smaller "tank with rubber sheet". Dbfirs 16:58, 15 July 2011 (UTC)

Do you have an article about hydrocution:

[[11]]? Also see Google translate version: [[12]] — Preceding unsigned comment added by 88.8.79.148 (talk) 14:56, 15 July 2011 (UTC)

Is it cold shock or thereabouts ? Sean.hoyland - talk 15:03, 15 July 2011 (UTC)

(edit conflict) The french article says (by my own translation) that "Hydrocution is a cardiopulmonary arrest caused by a difference in temperature between a liquid (usually water, hence the prefix "hydro") and the skin. The shock can cause a loss of consciousness and drowning. According to "Éditions Larousse", the term is recent, 1953 from "electrocution", the self-same term created in English by combining "electro" and the "cution" from "execution". I'm not sure what the term in English may be, but the nearest concepts I can think of is that this is Shock (circulatory) brought on by hypothermia. I'm not sure there is a medical term for hypothermia specifically caused by being immersed in water. The subsection Hypothermia#Water seems to be the nearest en.wikipedia content on this, but perhaps someone who spends more time in the medical field could find you a better link. --Jayron32 15:12, 15 July 2011 (UTC)

"Hydrocution" seems like a silly neologism, because it appears to imitate "electrocution," as a form of "execution," but does any country really try to kill the condemned by dunking them in cold water, at least since the end of witch hunts in the 17th century. Edison (talk) 15:43, 15 July 2011 (UTC)

Hey, give the French a little bit of credit. They invented a new word. For the French, that is an amazingly rare event, as far as they are concerned the French language is an immutable gift from God himself, and to alter it is tantamount to blasphemy. People have gone to the guillotine for less. --Jayron32 16:45, 15 July 2011 (UTC)

Wiktionary has an entry but with a very general definition. I don't think the word deserves a Wikipedia entry in English unless it becomes an accepted medical term. Dbfirs 16:43, 15 July 2011 (UTC)

Is this related to the Mammalian diving reflex? Roger (talk) 16:56, 15 July 2011 (UTC)

snow cover

About what % of the world's landmass is continuously covered by snow for at least 2 consecutive weeks in an average year? Googlemeister (talk) 15:32, 15 July 2011 (UTC)

That may be a difficult number to come by, because it's so specific. (For example, that criteria is not one of the standard data product results generated by NOAA's snow climatology group). But, you can find archived raw data for U.S. and international snow cover at the NOAA National Operational Hydrologic Remote Sensing Center archive page. They also produce interactive reports and maps for recent data. The US Snow Climatology center website may also be useful.

NASA's Global Snow Coverage interactive map is made using MODIS data; you can download MODIS data directly from NASA MODIS data archive and analyze that data yourself. MOD 10 intermediate data product is listed as "snow cover"; and the algorithm used to derive that parameter is provided for your use on the Algorithms page. There is a nontechnical overview explaining how to derive snow-cover from infrared observation.

Presumably, to proceed, you will need to download a year (or multiple years') of archived data; and you can easily construct a program to determine the number of points that satisfy the "snow cover" criteria for 2 consecutive weeks during the year. Nimur (talk) 15:50, 15 July 2011 (UTC)

tetanus

Is it possible to get tetaus from penguin bites? I work with penguins and often get biten, I have not had a booster and wat to know what the chances are of getting infected with tetanu. — Preceding unsigned comment added by 41.2.63.234 (talk) 18:57, 15 July 2011 (UTC)

Which species of penguins do you work with, and what is the location? Googlemeister (talk) 19:03, 15 July 2011 (UTC)

We are not permitted to give medical advice on Wikipedia, and an answer to this question would definitely be medical advice. You should discuss the question with an appropriate health care provider. Looie496 (talk) 19:18, 15 July 2011 (UTC)

You might also consider talking with the occupational safety and health officer at your institution, who would have more information about your situation and indeed whether tetanus is even something to be concerned about with penguin bites. It may be that there are other vaccinations that would be more appropriate for person who handles penuguins in the course of their work. --- Medical geneticist (talk) 12:10, 16 July 2011 (UTC)

summers in Tundra climate and Northern Siberia

Do tundra climates often get 62 F or higher in summer temperatures. That is because western coast of Greenland gets over 60F in summer quite often. Dfd cities in Russia like Yatsuk and Verkhoyanysk gets 15 straight days in 90sF. That is why I am wondering about the tundra northern coasts parallel to Siberia/Russia around 70 degrees latitudes, are they likely to get above 60s or 70/80 in the summertimes. Is this common enough for the near 70 degree latitude lands to get 62 F or higher in the summer seasons. Is this possible they can have few days in the 70s or 80s in tundra lands.--69.226.40.132 (talk) 20:15, 15 July 2011 (UTC)

Tundra suggests they might be defined by their low temperatures and inhospitality to trees than by their high temperatures, and coastal climates are usually more moderate, especially in areas where tropical storms are uncommon. So I can't answer a question phrased as "often" very confidently or definitively, but I suspect the answer is yes. 99.24.223.58 (talk) 20:27, 15 July 2011 (UTC)

When I said common I meant at more than once a year in the summer period. Yakutsk is 62 N latitude it is still getting days above 90s, been a week, same as Verkhoyansk, this week it will have one day in the 90s. I was shocked by that, subarctic term seems overated sometimes they suppose to have average temperatures in summer month below 70s, it is actually scorching in the Siberia arctics than moderating what the temperature suppose to be. I was surprised. Upervavik, Greenland is 73 N latitude, it does get 60s at least once a year. All the west coast Greenland gets 60s at least once a year. I was asking if northern tip of Siberia gets 70s/80s nearly every year or only some years. I was asking if they get 60s more than once year or not every years. Go to wunthergrounds. Barrow, Alaska gets 60s almost every year. Common, semi-common is arbituary vocabulary.--69.226.40.132 (talk) 22:47, 15 July 2011 (UTC)

Androgens

The Prenatal development article says that until week 5 a fetus is not male or female, only once androgen production starts does it turn into a male. If the androgen production was supressed somehow, would a baby with a Y chromosome develope a female body type and have a vagina? 109.209.3.93 (talk) 20:25, 15 July 2011 (UTC)

Maybe. There are several degenerate chromosome conditions which result in a variety of sexual organ development. The development of any of the several dozens of tissue types in a typical mammal are probably controlled by multiple chemical signaling paths. So while many of these systems prevent problems, there are a lot of moving parts and things will go wrong on rare occasions. While any major birth defects are likely to result in a nonviable fetus, the sexual organs are not vital for the individual's survival, so sexual organ differences are some of the more common congenital malformations to be observed in healthy births. Many of them can be so completely corrected by surgery that the patient will be able to live a healthy sex life with no idea that there was ever any problem. More often, births with no apparent malformations will be infertile, but this is rare in general. For more information, see PMID 20079588 and PMID 20541154, the former of which lists an email address for a corresponding author if you have more detailed personal questions or seek a referral to a specialist in your locale. 99.24.223.58 (talk) 20:53, 15 July 2011 (UTC)

The hormonal control of internal genital development is somewhat distinct from the development of the external genitals. If a functional Y chromosome is present, the SRY gene will kick off a cascade that leads to the formation of testes, production of antimullerian hormone, and regression of the female internal organs (Mullerian ducts). Assuming that only androgen production is suppressed, the baby would most likely have male internal genital structures but the testes would fail to descend (cryptorchidism) and the external genitalia would appear to be female. This is similar to what happens in androgen insensitivity syndrome, where instead of lacking the androgen hormone, the body is unable to respond to the androgen. The converse situation is the situation of hormone excess (see congenital adrenal hyperplasia for example), where a female fetus can develop normal female internal structures but undergo masculinization of the external genitalia due to the excess androgen hormone. Of course, things can get a lot more complicated depending on the situation. See intersex for more information. --- Medical geneticist (talk) 21:38, 15 July 2011 (UTC)

Estrogen

I read somewhere that there is Estrogen in rain water.

1. How did it get there?
2. How comparable is the amount of Estrogen in rain water to the amount of Estrogen a m2f transexual person takes to develope breasts?

109.209.3.93 (talk) 20:25, 15 July 2011 (UTC)

For clarity, I guess you are talking about environmental exogenous hormones. Sean.hoyland - talk 20:35, 15 July 2011 (UTC)

The article about Hormone replacement therapy (male-to-female) gives information on estrogen use but does not specify dose levels quantitively. Cuddlyable3 (talk) 23:16, 15 July 2011 (UTC)

Estrogen in rain water is highly unlikely, it is a relatively heavy molecule, a steroid derived from cholesterol, which is waxy, and certainly doesn't evaporate. You must mean ground water. μηδείς (talk) 00:18, 16 July 2011 (UTC)

No, there are xeno-estrogenic compounds in rainwater. Sean.hoyland - talk 05:12, 16 July 2011 (UTC)

please. I am with Medeis on this; chemically having estrogen and related compounds in rain water makes absolutely no sense. It would need to be significantly present in gaseous form, and gaseous estrogen makes absolutely no sense at all. Unless there are compounds which are in rain water that can induce the body to make more estrogen (perhaps some effect of nitrogen and sulfur oxides or other small molecules), I'm not sure I can see a mechanism which could produce estrogen from rain water at all. If you are saying that there is estrogen and related compounds actually in the drops of water falling out of the sky, that's an extraordinary claim that need extraordinary proof... --Jayron32 05:19, 16 July 2011 (UTC)

estrogenic rainwater Google scholar. Take your pick. Sean.hoyland - talk 05:27, 16 July 2011 (UTC)

Thanks. Perusing several of those, it isn't actually steroids like estrogen that are in the rain water, it is smaller molecules that interfer with the body's estrogen processing systems in various ways. I think we're crossing wires here; Medeis and I seem to be reading "estrogenic" to mean "the actual estrogen molecule and other similar steroids" while the term really means "any compound which may interfer with the body's estrogen systems", molecules that are sometimes termed Endocrine disruptor. Am I getting this right? --Jayron32 05:33, 16 July 2011 (UTC)

Yes, see my first comment above at 20:35, 15 July 2011. Perhaps the phrase "It's raining cats and dogs" originated in a similar Chinese whispers way. No one seems to say that anymore. Sean.hoyland - talk 05:45, 16 July 2011 (UTC)

"It's raining steroids and endocrine disruptors" just doesn't have the same ring to it, now does it? --Jayron32 05:48, 16 July 2011 (UTC)

There IS however some concern that the vast use of oral hormone therapy for birth control has lead to increased levels of estrogen in groundwater, and some studies have shown that this is leading to problems in some amphibians. There are lots of other unmetabolized drugs they've looked for and found as well. Drinking the water in some areas can give you a measurable but subclinical dose of prozac for instance. HominidMachinae (talk) 19:04, 16 July 2011 (UTC)

I wonder how that compares to vegetable estrogens such as from soy. 99.24.223.58 (talk) 18:17, 17 July 2011 (UTC)

Radio flux

The present age has many radio stations and other radio transmitters such as mobile/cell phone masts, not to mention electric wiring. How much radio energy would pass through a one metre cube of air per second, situated near the ground in central London or New York? How would that compare with the amount of light or infra-red energy passing through? 2.97.208.91 (talk) 21:36, 15 July 2011 (UTC)

Unless someone spends a lot of time next to a radio transmitter, the amount of energy they absorb in the infrared would be much greater. Isn't the thermal blackbody peak of room temperature somewhere in the infrared? It is important to point out that natural ionizing electromagnetic radiation is usually only on the ultraviolet side of the visible spectrum, except in fires maybe. 99.24.223.58 (talk) 22:26, 15 July 2011 (UTC)

I was hoping for some numbers, in watts. 92.29.125.215 (talk) 23:12, 15 July 2011 (UTC)

Sorry, watts is not the proper unit, because ionizing watts are much more deleterious than non-ionizing watts. Also, the increased incidence of brain cancer in cell phone users mentioned in PMID 21084892 is much more easily explained by exposure to trace industrial solvents on handheld (and ear-held under high humidity perspiration conditions) electronics than by the energy of a cell phone's radio transmitter. Even if the same amount of radiation was transmitted as ionizing radiation, the carcinogen exposure would pose the greater risk. Please see PMID 16580876 for more information. 99.24.223.58 (talk) 23:19, 15 July 2011 (UTC)

I'm not interested in the health aspects, nor am I interested in ionising radiation either, I'm just curious about how much radio energy there is out there. 92.29.125.215 (talk) 23:39, 15 July 2011 (UTC)

You can measure it with a voltmeter and ammeter connected to a collection of relatively prime length antennas in parallel behind a rectifier bridge at the frequency response curve you want in radio and/or microwave frequencies, and compare that energy measured against ground to that shown by a thermometer inside a black airtight can. You might want a transparent window to read the thermometer. You might also be able to estimate by making assumptions about the power output, quantity, and median distance of the various kinds of radio and microwave transmitters in the vicinity. That would be essential information for the calculation. Where are the main broadcast radio and television transmission antennas located in London? Downtown skyscrapers? Special purpose towers? 99.24.223.58 (talk) 00:26, 16 July 2011 (UTC)

From the wikipedia article: ground level insolation(avg over earth) 250W/m². 1366 at the atmosphere, 1000 for sunny noondays at the equator. Assume that most other light n infrared wont change the ball park. [13] gives the power output of trnsmitters to be ~100W for mobile towers. at 10m thats ~1W/m². Push it an order of magnitude either way. Hope its useful. Staticd (talk) 09:01, 16 July 2011 (UTC)

For perspective: a HAM radio user's equipment (the S meter) is often marked in "dB μV/m" (decibels microvolt per meter). That should give you a hint that: (1) the typical radio signal's elecric field strength is small (microvolts per meter); and (2) the variation in field strength occurs over several orders of magnitude, even during a single session tuning to a specific, stationary transmitter: so it needs to be measured in a decibel (logarithmic) scale.

We usually measure electric field; we can convert this into incident electromagnetic power (the conversion depends on many many non-ideal factors, including wave frequency, bandwidth, antenna efficiency, and so forth). In some radio bands, we measure incident magnetic flux, or induced current, or other metrics; and again, can convert this to incident electromagnetic power.

Typically, if you are receiving a signal from a modern FM radio station, or modern ATSC / digital HD American television broadcast, you will find yourself in the microvolt/meter range, which is somewhere in the neighborhood of 10^-12 watts per square meter radiant flux. (That's an inconvenient unit, which is why we don't use it!) And, of course, it depends on your distance to the transmitter, and the transmitter's power, and the weather, and many other factors.

I have personally worked with large research radio transmitter facilities; we sometimes use power levels far above this range. In such cases, the facility is usually controlled access and humans are not permitted to approach the transmitter when it is on (a safety precaution leading to the ominous trope of "secret government laboratories"). In fact, such safety precautions are just safety warnings: the area may contain harmful levels of radio energy. Higher-power (and thus more dangerous) facilities than this one employ security systems and controlled entry procedures that are more difficult-to-ignore.

If you're interested in the theory, here is an excerpt from (if I recall correctly) the Navy basic RADAR electronics textbook, RADAR Systems Engineering Handbook hosted at the University of Hawaii: FIELD INTENSITY and POWER DENSITY. You can download a full copy of this textbook at this website. Nimur (talk) 16:21, 17 July 2011 (UTC)

Yes, RADAR transmitters can cook tissue like a microwave oven. But in both cases that is still non-ionizing radiation, right? So the burn danger is more like internal tissue overheating danger, unless I'm mistaken. 99.24.223.58 (talk) 19:03, 17 July 2011 (UTC)

Double nuts on bolt

Is it true that putting two nuts on a bolt rather than one means that the nuts are less likely to come loose from vibration etc? If true, what is the engineering reason for this? 2.97.208.91 (talk) 21:40, 15 July 2011 (UTC)

See this page. --Jayron32 21:42, 15 July 2011 (UTC)

Seems like something that should be a see-also at Locknut or listed at Positive locking device, but not sure what the target page would be. DMacks (talk) 22:05, 15 July 2011 (UTC)

I'd think a soft washer, such as rubber, would absorb vibration energy and transform it into (a tiny amount of) heat, instead of rotating the bolt loose. Another option is thread lock (no article ?). That's an adhesive/glue appplied to the threads before the nut is screwed on. StuRat (talk) 00:41, 16 July 2011 (UTC)

Thread-locking fluid, maybe needs a redirect or two. DMacks (talk) 14:14, 16 July 2011 (UTC)

I've always followed the practice of putting an extra nut on, I think the operative theory might be increasing the friction by increasing the number of threads gripped. Perhaps it doesn't fulfill any purpose except making me feel more secure. HominidMachinae (talk) 06:00, 16 July 2011 (UTC)

Did you read the article I linked above? It may help you feel more secure in knowing the science behind the practice... --Jayron32 06:02, 16 July 2011 (UTC)

I did indeed, I should be more specific. I was TOLD that the operative theory was more friction means less loosening, and I followed it because it's what my dad always did. Now that I know there's a basis behind it I do actually feel better about it. Though obviously for anything serious a lock-nut or locktite is the way to go. HominidMachinae (talk) 08:43, 16 July 2011 (UTC)

July 16

Papaya leaves

I have some papaya plants. Their leaves are pretty typical for a young papaya and similar to File:Carica papaya Leaf 2000px.jpg. However, one fairly young plant about 2m tall, has developed small vertically oriented irregular but mostly ovate leaves in the centre of the large flat leaves where the palmate veins meet, one small ovate leaf per large palmate leaf (see File:Leaf morphology.svg. I've not seen these before. Does anyone know what they are and what they are for ? Sean.hoyland - talk 07:03, 16 July 2011 (UTC)

Can you post a picture? Dauto (talk) 15:34, 16 July 2011 (UTC)

Yes, probably. I'll try tomorrow...assuming the sun rises. Sean.hoyland - talk 16:02, 16 July 2011 (UTC)

Here's a picture. Sean.hoyland - talk 01:39, 17 July 2011 (UTC)

Weight of water in the clouds

What volume of the earth's water is held in the clouds at any one time? (either in percentage terms or in a nice equivalent to X olympic swimming pools!)ny156uk (talk) 10:24, 16 July 2011 (UTC)

Around 39%, including soil moisture. See here. Rcsprinter (talk) 10:37, 16 July 2011 (UTC)

Actually, that page says it is about 39% of 1% of 3% including soil moisture which is about 0.01%. Dauto (talk) 15:30, 16 July 2011 (UTC)

And actually, it's even less than that. That 39% figure is the measure of soil and atmospheric moisture, and there is likely much more water in gaseous form in the atmosphere than in liquid form in clouds. This source gives a figure of 12900 km³ as the total water in the atmosphere, which is 0.001% of the total water on Earth.

As a very rough estimate of how much is contained in clouds, I make the following calculation: approximately 60% of the earth is covered by clouds at any given time, and the average liquid water path for clouds is approximately 0.1 kg/m² (source). Knowing the surface area of Earth is 510,072,000 km², with a little math we can find a rough estimate of 51,000,000,000,000 kilograms (1.12×10¹⁴ lb) as the weight of water in all the world's clouds (a very rough estimate), which leads us to a volume estimate of 51 cubic kilometres (1.8×10¹² cu ft). So it is obvious just from these rough calculations that very little of the water in the atmosphere is actually contained as water in clouds. You can do a little math yourself if you'd like the volume in some other form, since I'm philosophically opposed to the "swimming pool" as a unit of volume. -RunningOnBrains^(talk) 22:13, 16 July 2011 (UTC)

Also please note that weight and volume are completely different things. -RunningOnBrains^(talk) 22:20, 16 July 2011 (UTC)

I wanted to suggest considering that the area of the sphere at the height where clouds reside is higher since the radius of this sphere will be larger than that of Earth, but I've done the math and the difference is about two tenths of a percent, so negligible. --Ouro (blah blah) 07:16, 17 July 2011 (UTC)

Thanks for the responses everyone! ny156uk (talk) 08:40, 17 July 2011 (UTC)

Neanderthal and Denisova genome findings; bearing on the age of Genetic Adam and Genetic Eve?

Two studies in the news recently concluded that Neanderthals and Denisovans are likely to have descendants among humans living today, i.e. they interbred with our ancestors.

The studies did not find that the mtDNA or Y-chromosome of either Neanderthals or Denisovans correspond to any known haplotype of modern humans. My question is, what can we say about the likelihood there is Neanderthal or Denisovan ancestry along the direct matrilineal or direct patrilineal line of modern humans, corresponding to a mtDNA or Y-chromosome haplotype in modern humans that scientists simply haven't come across (yet)? If that were the case, it would push back the dates of Y-chromosomal Adam and mitochondrial Eve to either half a million years ago (in the case of Neanderthals) or a million years ago (in the case of Denisovans), correct?

What I am curious about is, if we assume for the moment that the conclusions of these two recent articles are correct, i.e. that between 1% and 4% of the genomes of people in Eurasia is derived from Neanderthals and something like 6% of the genome of Melanesians is derived from Denisovans, then is it reasonably possible that either (or both) originated extant mtDNA or Y-chromosome haplotypes? Or would that be highly unlikely on the basis that such haplotypes in living humans would already have been documented? Mathew5000 (talk) 10:54, 16 July 2011 (UTC)

An extremely small Neanderthal/Denisovan haplotype population cannot be ruled out. Dauto (talk) 15:25, 16 July 2011 (UTC)

Healing of throat after radiotheraphy

how long does it normally take for a throat to heal after radiotheraphy for throat cancer? — Preceding unsigned comment added by 121.210.236.13 (talk) 12:21, 16 July 2011 (UTC)

Consult a qualified doctor. As stated at the top of this page we cannot give you medical advice. Cuddlyable3 (talk) 13:14, 16 July 2011 (UTC)

And it really isn't even about "advice" in this situation. It's just an "it depends" type of question that requires one to know about a whole host of specific variables, and even then may not be amenable to answering. We have articles on head and neck cancer and radiation therapy for general information, but I don't think you are going to find a simple answer to your question. --- Medical geneticist (talk) 15:13, 16 July 2011 (UTC)

Yeah, this has got to be dependent on the dose and resultant tissue damage. 157.22.42.3 (talk) 01:49, 17 July 2011 (UTC)

haloperidol--long term effects on children?

Does anyone know of studies or have information on the long term effects of Halperidol on children? What about if the child stops taking it--do the effects wear off quickly? Thanks, Rich Peterson24.7.28.186 (talk) 16:59, 16 July 2011 (UTC)

The article you linked says this: Children and adolescents are particularly sensitive to the early and late extrapyramidal side effects of haloperidol. It is not recommended to treat pediatric patients. Use is indicated only if the psychiatric or neurologic disorder is so substantial as to be completely intractable by all other means.

I suggest that it is not appropriate for the Ref Desk to say more and that you should indeed consult a medical professional. Bielle (talk) 17:12, 16 July 2011 (UTC)

Asking for primary sources is definitely within our purview, he's not asking for medical advice he's asking if anyone has studied the problem. If there was ever a clinical trial done on juvenile applications of the drug the study should have been published. From the above quote it appears as if they have investigated its use, so I'm guessing that is available. HominidMachinae (talk) 18:58, 16 July 2011 (UTC)

Turning up the music volume

This one may be in the archives, but if so I couldn't find it...why do people often feel the urge to turn up the volume when a song they like is playing even if they're able to hear it fine before they turn up the volume? Is there some psychological or biological effect that causes this behavior? Thanks, --Ks1stm (talk) ^{[alternative account of Ks0stm]} 23:23, 16 July 2011 (UTC)

you mean other than the obvious reason? (like moving closer to a tv when something you like comes on, even though you've seen the tv "fine" from across the room? or bringing a newspaper closer if you're actually interested in a particular article, as opposed to glancing through headlines? ) 188.222.102.201 (talk) 23:39, 16 July 2011 (UTC)

That's just another description of the behaviour, rather than a reason for it. I've wondered the same thing. HiLo48 (talk) 00:45, 17 July 2011 (UTC)

To help concentrate on the song and block out other sounds? Dismas|^(talk) 10:58, 17 July 2011 (UTC)

Since powerful audio amps and big speakers became common in the 1960's part of the rock music experience has been for the listener to feel his/her clothes and body vibrating from the blast of the music, and if it is loud enough it also blocks any possibility of conversation as opposed to appreciation of the music. Thus a generation or two with significant hearing loss. Edison (talk) 12:47, 17 July 2011 (UTC)

What kind of bug is this?

Sorry for the less-than-perfect picture. I used my cell phone camera. It's about 2-3cm long and was seen in northern Virginia. Peter Michner (talk) 23:46, 16 July 2011 (UTC)

Looks like a cicada skin to me. --- Medical geneticist (talk) 00:05, 17 July 2011 (UTC)

compare these images: μηδείς (talk) 00:10, 17 July 2011 (UTC)

Time sequence photos of a Tibicen dog day cicada molting in Ohio, US

Discarded cicada skin

Good call and absolutely correct. Once I looked up at its dorsal side, I saw the big crack down the middle. Peter Michner (talk) 16:22, 17 July 2011 (UTC)

July 17

Peripheral Lung

I'm from a non-scientific background, but as part of my research I'm reading an article that discusses the effect of various asbestos fibres on the lungs. A sentence reads 'The rod-like amphiboles appear to penetrate the peripheral lung more readily than chrysotile fibers'. What is the 'peripheral lung'? Does it simply refer to the edges of the lung? Or is it a term of art? Cheers Joaq99 (talk) 10:56, 17 July 2011 (UTC)

Yes, it's just the outside of the lung as opposed to the central part. It's the part that is adjacent to the pleural cavity, and it's probably, in context, a somewhat unnecessary adjective. - Nunh-huh 12:44, 17 July 2011 (UTC)

Diamond test

How can I tell if my diamond is real, at home ? It does appear to scratch glass, but just barely. Would any fake diamonds scratch glass ? Is there any other home test ? (I do realize that a professional appraisal will be needed, but want some indication, before that.) 68.79.93.3 (talk) 00:17, 17 July 2011 (UTC)

Wikihow has a whole list of tests: #3 (reflection), #10 (fog test) and maybe #9 (heat probe) seem to be the simplest to try. Clarityfiend (talk) 01:15, 17 July 2011 (UTC)

Thanks, that looks useful. Unfortunately, many of those tests are subjective, and only mean the stone "probably is" or "probably isn't" a diamond. I was hoping for an absolute, objective test. 68.79.93.3 (talk) 03:01, 17 July 2011 (UTC)

You will have to ask an expert. It is pretty tough to differentiate a synthetic diamond from a real one. — Preceding unsigned comment added by 88.8.79.148 (talk) 13:51, 17 July 2011 (UTC)

That's because synthetic diamonds are real diamonds. Dauto (talk) 15:12, 17 July 2011 (UTC)

Yes, the question does not make clear what the OP means by "real." Do you mean "a stone cut from a natural monolithic carbon crystal that was mined in the ground"? Or, do you mean "a very high-quality carbon crystal with few chemical impurities, negligible optical aberrations, and no visible inclusions or discoloration"? Nimur (talk) 16:34, 17 July 2011 (UTC)

I have the impression that real means "not costume jewelry". It is starting to look like the OP found a box of shiny stuff under the bed and really has no idea what it is. Looie496 (talk) 17:41, 17 July 2011 (UTC)

In that case, I'd think one of the easiest ways would be to find the density by carefully weighing the unknown things and then finding the volume by measuring the displacement in a graduated cylinder or something like it and comparing that to the density of diamond, which is about 3.5–3.53 g/cm³. This would be better at ruling things out, since other things could also have a density within this range, but a density far outside this range would do well to rule out diamond. Peter Michner (talk) 20:24, 17 July 2011 (UTC)

SEEKING JOB INDIA

HOW CAN I GET JOB IN MECH ENGG FEILD IF I HAVE SUBJECT BACK.BUT COMPLETED MY DIPLOMA IN MECH ENGG — Preceding unsigned comment added by 223.176.146.116 (talk) 07:52, 17 July 2011 (UTC)

Firstly, turn off caps lock. Typing in capitals makes it sound like you're shouting. Secondly, can you rephrase your question so it's more clear? It doesn't make much sense at the moment. Bear in mind that, on the whole, we know very little about the Indian education system and job market. Your best choice would be to contact your educational establishment's career service or write to an engineering company and ask. Brammers (talk/c) 08:45, 17 July 2011 (UTC)

Seriously, the ability to write a sentence in grammatical English people can understand, and to explain clearly what you want - these should help you no matter what the situation may be in your field. Wnt (talk) 15:26, 17 July 2011 (UTC)

If you are looking for a list of open mechanical engineering positions in India, try something like http://www.engineerjobs.com/jobs/mechanical-engineering/india/ If you think language issues might be preventing your employment, you might try http://englishcentral.com or the like. 99.24.223.58 (talk) 18:24, 17 July 2011 (UTC)

Yellowing of beige office equipment over time

It seems that the beige hard plastic often used in office equipment in the recent past turns yellow over time. What is the cause of the yellowing? Is it exposure to light? UV? Heat? Something in the air? — Preceding unsigned comment added by 98.114.146.248 (talk) 09:51, 17 July 2011 (UTC)

In years gone by this phenomenon was due to cigarette smoke! After the smoking ban in offices in the UK, I haven't noticed it as much. --TammyMoet (talk) 10:20, 17 July 2011 (UTC)

According to this patent, brominated flame retardants are to blame. Brammers (talk/c) 10:40, 17 July 2011 (UTC)

How is a rocket supported at the launch pad before ignition?

Before ignition, how is a rocket supported (mechanically) on the launch pad? Is it supported at its bottom? Or is that on its side? — Preceding unsigned comment added by 98.114.146.248 (talk) 09:57, 17 July 2011 (UTC)

A launch pad usually includes a vertical service structure or launch tower, which is connected to the rocket at various points and provides access for pre-lauch checks, fuelling and crew transfer - see File:Saturn V and service structures.jpg for an example. I am not sure how much mechanical support it actually provides. Gandalf61 (talk) 10:17, 17 July 2011 (UTC)

The tower prevents the rocket being tipped sideways by the wind, but it doesn't support the weight of the rocket (which gets very heavy once it's been fuelled). Instead there are pylons built around the flame pit which mate with hardpoints on the undersurface of the rocket, between the rocket motors. These support the weight of the fully fuelled launcher. In the case of the Saturn V (and I think in many others) the pylons were integrated with the hold-down arms (in the photo on that page the vehicle rests on the light-coloured block at the top of the arm pylon). A photo of the Saturn V pit with the hold-down arms in place, but without the vehicle, is here, and one with the vehicle resting on the pylons (and with a temporary maintenance deck covering the pit) is here. The other function of the hold-downs, incidentally, is as their name implies - they hold the vehicle down for the second or two between when its engines start and when they're confirmed to be at full power. If the vehicle was unrestrained then it might flip over during that phase, when the motors have spooled up at different rates and so provide asymmetric thrust. The launch control systems keep the hold-down arms in place, holding the rocket back against its own massive thrust, until they've confirmed that all the motors are fully at power and the flight dynamics system is able to stabilise the rocket by gimballing the motors. A longer discussion of the Saturn V ground systems is here. -- Finlay McWalter ☻ Talk 11:06, 17 July 2011 (UTC)

On the pad, the weight of the Space Shuttle's SRBs (indeed the whole vehicle) is carried by the SRB hold-down posts, although in this case the holding-down is ceased when an explosive severs the bolt, rather than a complicated arm swinging out of the way. A video showing the SRB post is here; the technician explains that for the Shuttle system the SRB posts hold the weight not just of the SRBs but of the external tank and the orbiter (so they don't have hold-downs or pylons of their own). Note that, because the SRBs are solid, the sequence is different from the Saturn V sequence I discussed above. In this case the orbiter's main engines fire and the vehicle is held down until they're confirmed to be at full power; then (nearly simultaneously) the SRB hold-down posts are exploded and the SRBs are lit (with the vehicle unrestrained). This is because a liquid-fuelled engine can be shut off if something goes wrong, but once an SRB is ignited it burns to term (and there's no dynamic control over its level of thrust), so there's no ground abort mode left once they're lit. -- Finlay McWalter ☻ Talk 11:20, 17 July 2011 (UTC)

Things are very different for a Soyuz launcher, however. There's no pylons, no separate hold-down arms or bolts, and really no tower. Instead a Soyuz pad has four huge arms which fold out from the corners of the pad (lots of photos here). Images of a Soyuz held by its arms are here and here. These arms hold the weight of the laden Soyuz rocket as it's fuelled and prepared. Before launch a further service arm is withdrawn, leaving the rocket hanging over the pit ready to go. When the motors are fired these arms act as the hold-downs; once everything is stable and at power, the arms retract (rather vigorously) and the launcher is unrestrained and takes off. -- Finlay McWalter ☻ Talk 11:32, 17 July 2011 (UTC)

A video of Soyuz TMA-9 launching is here. There are actually two service arms (the first is retracted about 1 minute into the video, the second only a few seconds before the engines are lit). Note that the vehicle spends nearly 10 seconds held down while the first stage engines spin up. -- Finlay McWalter ☻ Talk 11:40, 17 July 2011 (UTC)

Without a hold-down system, a sudden gust of wind could topple a rocket, since it is extremely tall, typically, compared to the width of the base. There is little inherent stability, with the center of mass so high up. I suppose the launch is delayed and the crew does not enter the capsule if weather trends make such gusts likely, and they could certainly monitor the surrounding air mass with weather balloons and aircraft. Edison (talk) 12:44, 17 July 2011 (UTC)

Is there an obvious reason why all rockets may not be launched from a below-ground Missile launch facility ? The underground silo protects against wind and can provide side support over the whole length of the rocket, and possibly increase thrust at launch by constricting the exhaust outlet. Cuddlyable3 (talk) 14:45, 17 July 2011 (UTC)

Wind isn't a big issue, as it's easily solved by systems you need anyway (the hold-down system and the service tower). Even silo launches don't try to constrict the launch exhaust (ref, see also Flight magazine 25th May 1961). A silo configuration forces you to vertically integrate the vehicle (with cranes): the Russians seem to generally prefer horizontal integration of Soyuz - they assemble it horizontally on a big arm, and then swing the whole thing to vertical at the pad (although the Ariannespace Soyuz facility will use vertical integration for the Fregat and payload (ref, with extra-naff music). And a silo forces you to integrate at the launch site, so you tie up the launch site preventing it being used for another launch in the mean time - both the NASA vertical-integration on a movable platform and the Russian horizontal integration on a TEL-like boom allow the vehicle to be constructed elsewhere, while the pad is being used by someone else. A silo, especially for a large rocket, is tremendously expensive to build and a pain to run. The only plus I can see for a civilian launch from a silo is that you get to control the weather, but every time a Shuttle can't launch because it's a bit cold (for, you know, Florida), you can almost hear sniggering from Plesetsk (which, for example, is scheduled to launch three rockets, including a Soyuz/Fregat, in December, when winter temperatures get down to -30°C). -- Finlay McWalter ☻ Talk 15:53, 17 July 2011 (UTC)

Furthermore, silos are expensive; all joking aside, the space industry does not spend money unnecessarily. A silo launching facility is a lot of very complicated construction and design effort, and really only amounts to a "peripheral" engineering objective to the space-craft. Four seconds into the mission, the entire launchpad facility serves no purpose.

I also have a vague recollection that some element of SALT II or a more recent proliferation treaty that regulated underground launch facilities; so, civilian rocket launch facilities may have to make special accommodations to comply with necessary international treaties. Underground silos, civilian or otherwise, might constitute a "hardened facility." Here's some specific language from START I: "...Such a space launch facility is still subject to the provisions of subparagraph 4(b) of Article IV of the Treaty, which limit the aggregate number of silo launchers"; and a silo is defined as a "structure located in the ground." So, treaty compliance may be a (non-obvious) reason to put the civilian rocket launchers above ground. Nimur (talk) 16:48, 17 July 2011 (UTC)

That said, there are civilian launches from silos. The Dnepr-1 is launched from silos at Baikonur (a map on this page suggests there are at least four) and from Dombarovsky. That's because Dnepr is based on the military silo-based R-36 missile, and it was easy for them to keep launching from a silo. (Although Tsyklon, another R-36 based launcher, is launched from a pad, e.g. at Plesetsk 32). -- Finlay McWalter ☻ Talk 17:16, 17 July 2011 (UTC)

I'm not a lawyer, but I read the above as "subject to the treaty provisions...," not as "forbidden." Undoubtedly, the conversion of an ICBM into a civilian space vehicle drew the attention of the treaty verification folks. In fact, this BBC News article from 1999 suggests that the conversion may have been part of the treaty compliance to eliminate SS-18 missiles. Nimur (talk) 17:59, 17 July 2011 (UTC)

Yes, I imagine that's correct (I didn't mean to imply the contrary). In fact I'm slightly confused about the Kazakh deployments of the SS-18: R-36 (missile)#Deployment lists its only operational deployments in the KSSR as at somewhere in the Semipalatinsk oblast (the NE) and the Turgay oblast (which Britannica suggests is in the NW). Neither is at all near Baikonur/Tyuratam. So either the silos at Baikonur were purely for the test program (and very possibly didn't count towards the treaty either) or they've actually been built or adapted from other uses to support Dnepr launches. Anyway, we're diverging a bit from the OP's original question about weight-bearing on the pad. I confess I can't find concrete (sic) evidence about how R-36/Dnepr launched, but videos of Tsyklon launching from Plesetsk suggest it has a pylon style support, and ditto for Zenit. -- Finlay McWalter ☻ Talk 18:19, 17 July 2011 (UTC)

water temperature -> air temperature equivalent conversion rate

I've been doing some SCUBA diving lately, just went out today and the water temperature was about 10 degrees. I know that water conducts heat away from the body a lot more efficiently than air so I was wondering if there is some equation or conversion chart to work out what air temperature this would feel like. (e.g when you read a weather report and it says "Temperature: 10 Feels like: 8" because of wind chill or other factors, what does water "feel like"?). Benjamint 11:38, 17 July 2011 (UTC)

I went through a few months of NAUI training courses and never recalled any such "conversion" or even a rule of thumb. What I do recall is the "what thickness wet-suit to use" chart. You can find such charts everywhere, here's a wetsuit vendor chart with temperature-guide.

Another detail I recall that was strongly emphasized is the "expected time until hypothermia" chart: the number of minutes a clothed swimmer or diver can expect to remain conscious at various water temperatures. I think this was reproduced in the NAUI textbook; you can also find it online by searching for "cold water survival." Navy Preventative Medicine manual has such a chart, and FM-55-501 also publishes a survival-time chart. As a diver, because you are fully submerged, your survival time is much lower than a surface swimmer; but you compensate some by wearing a wetsuit (or a dry suit). The most unintuitive thing is that hypothermia will set in even if the water is as warm as, say, 75° F (23° C) - it just takes about 3 to 6 hours; and the diver will lose consciousness and suffer health effects just as if the water were slightly above freezing. Nimur (talk) 17:11, 17 July 2011 (UTC)

why does suntan lotion (all brands) have a characteristic smell?

is it because there is a single anti-UV chemical, and it has that smell, or what? The same is not true for any other "category" of lotion... 188.222.102.201 (talk) 12:01, 17 July 2011 (UTC)

Cocoa butter? --Jayron32 12:43, 17 July 2011 (UTC)

I don't think they all smell the same. Most of them smell of coconut oil to me, but some (Ambre Solaire) smell of bergamot oil. --TammyMoet (talk) 17:51, 17 July 2011 (UTC)

Female Common Snapping Turtle

How old must a female common snapping turtle be before she can lay eggs74.14.157.157 (talk) 13:52, 17 July 2011 (UTC)

I don't know but I know a man who might. It's a website dedicated to turtles, I'm sure they can help you. Richard Avery (talk) 14:11, 17 July 2011 (UTC)

4 to 6 years.[14] 99.24.223.58 (talk) 18:47, 17 July 2011 (UTC)

Citation of self-published blogs?

If I were to blog on new scientific proofs or concepts I've been working on, I have self-published these and, to the best of my understanding, I have automatic copyright protection to them. I also know that most journals do not accept material that's been already published or under copyright, so blogging would normally cut-off that avenue. I am not sure if journals make exceptions to this, so how often do scientists find themselves blogging ideas without the benefit of peer-review and their blogs being cited accordingly? I will add that I have a rather large financial incentive to retain copyrights and a public interest in making my ideas public ASAP. --Modocc (talk) 15:53, 17 July 2011 (UTC)

There is negligible monetary value in the copyright of an academic paper; if there is value it is in patentable ideas, and it's a central part of patenting that the ideas are kept secret until the patent is submitted. So I don't understand what you mean when you say you have a financial incentive in the copyright. In general, many universities and research labs attempt to "measure" the success of a scientist with schemes that weigh the publication of papers in respectable journals, and the citation of papers in other papers published in such journals. From a scientific and public-interest perspective scientists might very well want to rush their findings out as quickly as possible (via things like blogs and arXiv); if doing so was to the detriment of the chances of being published in a journal, researchers who did so would be cutting their own throats. -- Finlay McWalter ☻ Talk 16:44, 17 July 2011 (UTC)

Much of what you said is true to an extent, however the success of any writing is based on merit and any interest in it. In addition, it would be incumbent on researchers to cite previously published material no matter where it is published. Also, a popular or well-cited blog might bring the researcher a financial reward (and the exact amount is not always that important anyway, which is why I suppose arXiv exists). In my case, I making claims that could upturn some very entrenched and widely accepted dogma. I'm interested in knowing whether or not there are many examples of blogs being cited. --Modocc (talk) 17:08, 17 July 2011 (UTC)

Of course there are examples. There are hundreds of thousands of volumes of research journals. Academic journals range from reprints of informal mailing-lists and conferences, to prestigious magazines read by millions of academics worldwide. What matters is, do such examples of citations of self-published works exist in your preferred journal? If you are aiming for a highly prestigious journal, the answer is "almost certainly not." Nimur (talk) 17:15, 17 July 2011 (UTC)

Thanks. I am not aiming to be cited by any particular journal. I just want to get some of my ideas out there into the public arena as soon as I can manage it. --Modocc (talk) 17:31, 17 July 2011 (UTC)

Blogging is relatively new, but for decades scientists have been writing books chapters that often are not peer-reviewed and raise all the same issues. The basic principle is not to say something in an unreviewed forum if you intend to say exactly the same thing later in a reviewed forum. It is certainly possible to cite book chapters in a scientific paper, and it ought also to be possible to cite blogs, as long as they have some assurance of permanence.

Let me also point out one other important fact: the vast majority of peer-reviewed scientific publications are about presenting evidence, not just presenting ideas. To jaundiced scientists like me, ideas are a dime a dozen -- it is evidence to support them that really matters, and the forum in which an idea was presented is of little importance. So what it comes down to is this: it is fine to discuss your ideas in a blog, but don't use a blog to present your experimental data. Looie496 (talk) 17:36, 17 July 2011 (UTC)

I once wrote to a physicist if he would be interested in reviewing one of my ideas, and he wrote back only if it made a prediction. Perhaps he has missed out on making an important observation or prediction; the waste basket perhaps. In any case, I know that with our large populace engaged, ideas abound, which is why both merit and interest (which correlates strongly with shared knowledge and intelligence) matters. and empirical evidence can often increase both. Providing a new model to fit existing evidence is also important and I will be doing that. --Modocc (talk) 18:14, 17 July 2011 (UTC)

Any scientific theory that isn't predictive is completely worthless as a scientific theory. In fact, if it's not predictive it's probably more of a "Theory" than a "Scientific theory".

But, don't be confused about the kind of prediction the scientist wants. It's not some prognostication about the future. In science a prediction is "If we ran the experiment X, we would get result Y if my theory is correct, and result Z if my theory is wrong."

The first step to having people not roll their eyes at your scientific theory is to provide a way to test if it's right or wrong. Ideally a test that could be done now with current technology, but that's not strictly required. APL (talk) 22:00, 17 July 2011 (UTC)

I'm guessing you would get more constructive feedback (even if some of the feedback isn't constructive) from submitting to ArXiv than trying to go directly from blogging to submission to peer reviewed journals. Also, I suspect journal editors will appreciate, provide better feedback for, and respond more favorably to unsolicited amateur submissions with preprints on ArXiv. As others have pointed out, the financial interest in copyrights is often dwarfed by the financial interest in patent rights. 99.24.223.58 (talk) 18:53, 17 July 2011 (UTC)

I see your point clearly, but if my work sits on arXiv, that may reduce their incentive to reprint it and at this point, I'm not planning on a reprint (and if my current work has merit I will likely get to reprint or publish a derivative work anyway). The ArXiv option is tempting, because I certainly hope to get some constructive feedback, but I'd like to do that by soliciting it from different people, especially from those that are likely to be more receptive to the somewhat difficult mental gymnastics of shifting from the current paradigm. I also want to update my material on a real-time basis as I am getting that feedback, so perhaps I'll worry about a more permanent and formal publication later... I think. --Modocc (talk) 19:24, 17 July 2011 (UTC)

chemistry

is a saturated solution a true solution? — Preceding unsigned comment added by 14.98.121.141 (talk) 16:08, 17 July 2011 (UTC)

Yes, until it precipitates, which can happen, for example, sometimes because of mechanical shock, impurities, or radiation, as well as because of the usual factors of time, temperature, pressure and evaporation. 99.24.223.58 (talk) 18:56, 17 July 2011 (UTC)

pancreatic vs bile duct cancer

Do we call it 'pancreatic cancer' if cancer cells originate in bile duct and grow to pancreas as the stage naming, treatment and severity differs? Also, how do we find the source of origin of cancer cells? — Preceding unsigned comment added by 122.174.40.59 (talk) 20:36, 17 July 2011 (UTC)

Maybe. Cell tissue type can be determined by staining, microscopic analysis, observation in in vitro cultures, some antibody tests, genetic sequencing and maybe karotyping, among other methods if I remember correctly. 99.24.223.58 (talk) 21:59, 17 July 2011 (UTC)