Wikipedia:Reference desk/Archives/Science/2011 July 15

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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)

Yes. Please see Observer-expectancy effect. 99.24.223.58 (talk) 02:43, 18 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:

[[1]]? Also see Google translate version: [[2]] — 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)

Not an expert but I kayak and mountain walk with young people and have been on a few specialised first aid courses over the years. Immersion Hypothermia is the usual term for hypothermia caused by being in water. Alansplodge (talk) 23:53, 17 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. [3] 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)

Correct, even the highest frequency RADARs are still non-ionizing. I've heard many experts debate the exact mechanism of biological harm due to a high-intensity radio signal. The most relevant effect is dielectric heating, via coupling into the molecular rotational modes, or resonating with other complicated molecular processes; there are a lot of othe mechanisms that may play a secondary role. Radio signals (VHF and below) have such long wavelengths that they should pass through a human without any effect at all, irrespective of the intensity; but, that theoretical explanation doesn't mean we operate without caution around them. Nimur (talk) 23:39, 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)