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

January 31

Valproic acid as a way to a musical talent.

Well, well, well. I've always thought the musical talent, especially the absolute ear, that is the ability to perceive tones as parts of musical scale is genetically driven. You have to be born with it. Encyclopedia Britannica I recall claims there are 3 genes that govern that. Now in the latest Week magazine, which is a short compendium of assorted facts, they published a result of latest study whereas people were given Valproic acid and lo and behold they develop absolute ear. I wonder what the erudite public think about it.

Along the same lines, there has been apparently not an apocryphal story that a Canadian individual sustained a head trauma and after that he found himself with a musical ability that manifested in him learning to play 3 or 4 musical instrument and at the time of the report he was going through the rest of symphony orchestra. How about that? Thanks, --AboutFace 22 (talk) 01:13, 31 January 2014 (UTC)

The usual term is absolute pitch. The original source for the information you are referring to is http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3848041. If you are interested in this topic, the book Musicophilia by Oliver Sacks tells a number of curious stories about the relationship between music and the brain, including gains in ability as a result of brain damage. Looie496 (talk) 05:23, 31 January 2014 (UTC)

Great question, which raises so many others! The study was small, but the result was impressive - I'll want to see it duplicated. More to the point, I'll want to see if it has benefits in trying to pick up a foreign language as an adult! Also, there are a range of HDAC inhibitors; even ordinary butter (containing esters of butyrate) may be a weak one. I'd like to see if the correlation holds up for all such inhibitors - and if so, why exactly is histone deacetylation tied to memory? That certainly suggests some things having to do with epigenetic markup of specific genes as a means to remember, which can potentially extend even between generations. See [1] And we always thought it was a joke to say that guys think with their balls! All those billions of neurons, yet to imagine that the hidden complexities of one single gamete might conceal a meaningful fraction of the mind. Wnt (talk) 06:09, 31 January 2014 (UTC)

I suppose I'm verging on medical advice here, but one should be careful about experimenting with this sort of stuff. There are probably functional reasons why the brain closes off critical periods at a certain age. It's not inconceivable that re-activating critical periods could lead to erasing of certain types of memory, for example. Looie496 (talk) 18:54, 31 January 2014 (UTC)

Well, the trouble with this information (the original one) is that many people are prescribed Depakote which is divalproex sodium. Is it different from valproic acid so much? Nobody have heard that the Depakote recipients all of a sudden begin playing Mozart. It is hardly congruent in my opinion. --AboutFace 22 (talk) 17:46, 31 January 2014 (UTC)

There's a discussion with some of the authors of the paper here. there was a report on it in New Scientist here but you will need a subscription to read it all. They did say in there "The brain shuts down critical periods for good reason – it would be disastrous to have it rewiring itself extensively for the rest of your life." although Hensch says that as it's an approved treatment for mood disorders and epilepsy he didn't think that was a problem. They also said it may have implications for the treatment of several disorders, including autism, that may result from mistimed critical periods. Richerman (talk) 21:48, 31 January 2014 (UTC)

Valproate is a well known anticonvulsant, not well known for memory problems (though our article does provide an impressive list of pleiotropic side effects that seems in keeping with the fundamental nature of histone modification). My assumption would be that the reopening of critical periods either (a) isn't all that dramatic, or (b) only affects things for which there was no selective pressure in prehistory. It's the latter alternative, of course, that is potentially exciting. Wnt (talk) 23:40, 2 February 2014 (UTC)

Nuclear fuel and skin

How properly to hold nuclear fuel pellets

It would appear from this image that it's best to hold nuclear fuel with tongs or something else to prevent direct skin contact with the fuel. But what if you touch it with your fingers for a few seconds? Surely you wouldn't instantly notice a huge effect; Louis Slotin's encounter with the demon core initially gave him "only" a weird taste in his mouth and a burning sensation in his hand (this is far far smaller, and it's clearly not critical), but I wonder if you might start experiencing some sort of sensation later. I also don't know whether this kind of exposure would be associated with a statistically significant increase in radiation-related illness down the road. Finally, note that I'm definitely not in a position to be touching nuclear fuel, and I wouldn't if I could; it's not a medical advice question :-) Nyttend (talk) 01:51, 31 January 2014 (UTC)

Unused nuclear fuel gives off mostly alpha radiation, which is almost entirely stopped by your skin. Also, as long as it's for a uranium reactor, it has such a long half-life that it's not particularly radioactive anyway. I imagine the "best practices" might be to avoid touching it, out of an abundance of caution, to keep from dissolving any trace of it in your sweat and somehow getting it inside your body, where it would be slightly more risky, if only as a heavy metal. Or, possibly, the caution is in the other direction (avoid contaminating the pellet somehow, not sure with what).

Now, if it's used nuclear fuel, that's another matter entirely. Then you've got lots of much more radioactive isotopes. --Trovatore (talk) 02:06, 31 January 2014 (UTC)

Hadn't even thought that the tongs might be there to prevent me from damaging it. Thanks for the explanation re alpha radiation (been way too long since I had classes at all related to this; I didn't even know where to look), and also the pointers on the spent fuel. I was indeed assuming that we were talking about unused fuel pellets, basically because I got the impression from Spent fuel pool and Spent nuclear fuel that the used pellets are left in the rods rather than being taken out by people with tongs. Nyttend (talk) 02:22, 31 January 2014 (UTC)

Think you will find the the tongs are to reduce the contamination of the gloves which can then be deposed of as low level waste. The gloves (if they don't have any perforations, make the hands easier to clean without setting of the radiation hand-body- monitors before exiting from the facility. In short, it is all part of the confinement of hazardous materials. Anything I handle with tongs (including the mother-in-law's cremated offerings on the barbecue) I consider, as not fit for entering my personal bio-space.--Aspro (talk) 18:04, 1 February 2014 (UTC)

It comes down to money. Wikipedia has an article called Low-level radioactive waste policy of the United States. A cubic meter of spent and compressed (to reduce volume) gloves, contaminated with a few micro-curies of enriched Uranium (– thanks to those tweezers in the photo), should be less radioactive than a cubic meter of natural uranium ore. Thus, cheap to dispose in a suitable landfill site.--Aspro (talk) 00:01, 2 February 2014 (UTC)

RGB colour model

The CIE xyz color space. y is luminance, and x is some combination of not-blue colors chosen to be non-negative, I think. Wnt (talk) 02:53, 31 January 2014 (UTC)
y is not luminance. You are probably confusing it with (capital) Y. This space is CIE xy, not CIE XYZ. -- BenRG (talk) 10:09, 31 January 2014 (UTC)

At RGB color model and various other articles, it is mentioned that the RGB model cannot reproduce all colours, but I can't find a clear explanation of why. Any perceived colour can be described by three numbers, measuring the levels of response of the three types of receptor in the eye. Why is it not always possible to reproduce those three numbers by combining the correct quantities of red, green and blue, for some sensibly chosen red, green and blue wavelengths? Three equations in three variables should be solvable? 86.130.66.42 (talk) 02:24, 31 January 2014 (UTC)

From reading the article, I get the impression that it's saying basically "This color model doesn't explain how we end up with some of the colors, but we've not come up with a better explanation". Beyond that I can't say; I am unable to understand concepts such as chromaticity and color triangles properly. Nyttend (talk) 02:29, 31 January 2014 (UTC)

The article Imaginary color may be getting at something for you. --Jayron32 02:33, 31 January 2014 (UTC)

The CIE 1931 color space article explains some of it. Basically, the idea is that absolute monochromatic light runs around the edge of the true color palette, and choosing just three colors from that don't give all the possibilities because you don't have red, blue, and green receptors - you have cones that are maximally sensitive to those frequencies. So a violet color might excite blue less, but green even less proportionally to it than the blue + some red color you would get on a computer screen. The thing I don't get myself, however, is why the RGB color triangle doesn't touch the curve running around the edge of the color space at the frequencies of the emitters. Wnt (talk) 02:53, 31 January 2014 (UTC)

There are a lot of color spaces called "RGB". CIE RGB does use monochromatic primaries, and there are probably others. sRGB doesn't because it isn't practical to use monochromatic primaries in real displays, and with only 8 bits per color channel it's good to be able to discriminate more colors within the actually reproducible region. Incidentally, the cones aren't actually maximally sensitive to red, green, and blue. -- BenRG (talk) 10:09, 31 January 2014 (UTC)

A large part of the problem is that in the real world, light can be infinitely bright - but in these chromaticity diagrams, there is an absolute white. Another issue is that the frequencies chosen for R, G and B don't perfectly match the peak of the sensitivity curves for the sensors in human eyes - and because people differ in what those frequencies are, the match can never be perfect. Note, for example, that women are much more sensitive to small differences in colors midway between blue and green than men are. The chromaticity diagram (and it's physical incarnation in TV screens and computer monitors) is a compromise. SteveBaker (talk) 03:14, 31 January 2014 (UTC)

"A large part of the problem is that in the real world, light can be infinitely bright - but in these chromaticity diagrams, there is an absolute white" – this makes no sense. In all of these 2D diagrams, the brightness is normalized (it's the third dimension). The white on that diagram is a white of arbitrary intensity. "Another issue is that the frequencies chosen for R, G and B don't perfectly match the peak of the sensitivity curves for the sensors in human eyes" – it's true that they don't match, but that has nothing to do with the problem. Given how close the L and M peaks are, matching the primaries to the peaks would make color reproduction much worse. -- BenRG (talk) 10:09, 31 January 2014 (UTC)

w o w -- I never heard this one before. Looking it up it seems there's something to it. [2] -> [3] [4]. This might have to do with differences in brain development based on androgens, or the fact that women inactivate different copies of color-sensing genes in different cells, at least potentially allowing a weak version of tetrachromatic vision. This seems to have potential consequences for Wikipedia itself. For example, consider a .svg figure in which different levels of infant mortality on a continent are shaded differently. Potentially we could (with some upgrades to the software) allow users to define parameters so that these would be generated on the fly differently, so that women could have a setting to have more levels of mortality labelled than the same figure as viewed by men (and the color blind would have their own options, perhaps grayscale and even fewer levels, etc.) [Of course, I do not mean to imply that these settings should be imposed other than by individual choice of the user!] Wnt (talk) 05:42, 31 January 2014 (UTC)

RGB system of color representation is a vector system. The problem is that the vectors that constitute the basis are not orthogonal. The origin of the system of basic vectors is located outside of the plane of reference that we see as the color triangle. They intersect the plane of reference at the corners of the triangle. There is no way to express a color outside of the triangle through the basic vectors. Apparently the basic vectors (the coordinate system) were chosen for technical reasons. --AboutFace 22 (talk) 03:31, 31 January 2014 (UTC)

I don't understand what you mean by "not orthogonal" here. The problem is that you can't form a triangle covering the whole color space unless the vertices (the primaries) are outside the color space, i.e. not physically realizable colors. -- BenRG (talk) 10:09, 31 January 2014 (UTC)

• (OP) I had a later thought. Three equations in three variables should be solvable, but solutions to some cases may require negative amounts of R, G and/or B. Is this the answer? Is it the solutions that require a negative R, G or B that cannot actually be realised in the RGB model? 86.130.66.42 (talk) 03:38, 31 January 2014 (UTC)

In a word, yes. Treated as an unbounded linear system (a vector space), if any scalar multipliers for a set of basis vectors is permitted, the entire space could be reached. Impose range limitations on those scalars, and effects such as this arise. —Quondum 06:23, 31 January 2014 (UTC)

Yes, I think that's the best answer to your original question.

Some people above seemed to think that this is an accident of physiology and/or poor standardization, but it's actually (almost) unavoidable. If you have trichromatic vision and the cone responses are linear (output proportional to the number of incoming photons at a given frequency) and nonnegative (more photons doesn't decrease the output), then, ignoring intensity, the space of possible cone responses is a triangle. The monochromatic spectrum is a curve inside the triangle. The physically realizable colors are the convex closure of that curve. The primaries you choose for your display have to be physically realizable. The color sensations you can reproduce with them are the convex closure of the primaries, i.e., a triangle inside the curve inside the triangle. There's no way the inner triangle can be the same as the outer one, or even large enough to cover all the physical colors. Your choices are to pick unphysical primaries (like CIE XYZ) and have positive coordinates for every color, or pick physical primaries and have negative coordinates for some colors.

(This would be avoided if the monochromatic curve was actually triangular, but that would imply poor hue discrimination near the vertices, so it's probably evolutionarily disfavored.) -- BenRG (talk) 10:09, 31 January 2014 (UTC)

Thank you both for your affirmative answers. I get it now. Follow-up question: I have never knowingly seen any colour that I felt could not be reproduced on an RGB display (ignoring non-reproducible effects caused by texture, reflectivity, etc.). The colours that I see around me don't look any different to my eye in real life than they would in a good colour photograph. Are other people's experiences the same or different? 86.169.184.247 (talk) 13:48, 31 January 2014 (UTC)

To your follow-up question, there is an example photograph at this similar question in which SteveBaker was asked to stop posting unreliable information about his "pet subject". 84.209.89.214 (talk) 14:52, 31 January 2014 (UTC)

You mean the photograph here? I see a probable difference in intensity between the photograph and the real thing, due to the fact that my monitor cannot pump out a sufficiently bright light, but I do not see any obvious difference in colour (admittedly, I do not have the apparatus to hand at present to compare). What difference am I supposed to be seeing? 86.169.184.247 (talk) 21:36, 31 January 2014 (UTC)

The triangle covers every hue (angle from the white point) but not highly saturated colors (more distant from the white point). Highly saturated colors are pretty rare in the real world. It's also worth mentioning that the area outside the triangle is not nearly as large perceptually as it looks in these coordinates—see MacAdam ellipse. -- BenRG (talk) 07:59, 1 February 2014 (UTC)

To 86.169.184.247, yes the photograph of a sodium flame. Its color reproduction is inadequate when compared with an actual sodium flame. Similarly, I challenge anyone to show a color-faithful photograph or video filmed under ordinary (not high pressure) sodium street lamp illumination. The qualified adequacy of additive and subtractive triple-primary color production processes in photography, printing and television encourages a simplistic assumption about human trichromacy, rather like Brahe's Tychonic system could be promoted as adequate for most astronomic purposes. Unfortunately for those who claim that 3 primary colors on your monitor can reproduce any color (having themselves perhaps never looked properly at the rainbow's spectrum or understood why they need to read an article such as Gamut) or claim that God's scripture forever obviates Heliocentrism (not caring to look at what Galileo could see through his telescope or perhaps just too fond of being adulated as Pope instead of plain Maffeo Barberini), scientific understandings neither of color vision nor of cosmology can be stifled for long by bigotry, itself a product of ignorance that should be out of date. 84.209.89.214 (talk) 15:09, 1 February 2014 (UTC)

Erm, well, it's true that triple-primary systems can't reproduce every color, but I don't think it has cosmic significance. Even cheap digital camera sensors can distinguish all of the colors that the human eye can, including the super-saturated colors, with only three color filters. The problem is that reproduction is harder than detection, not that human technology is inferior to biological technology. The mistake that many people (such as Steve) make is thinking that detection and reproduction are the same. -- BenRG (talk) 22:18, 1 February 2014 (UTC)

I discovered something interesting the other day: that digital cameras can detect the light from a TV remote control (maybe "everyone" knows this, but I didn't). Funny thing though, when I tried it, it looked white on the camera screen. Why doesn't it look a deep red? 86.161.61.104 (talk) 18:27, 2 February 2014 (UTC)

Well, there is a certain kind of flower that grows along the banks of the Lehigh River which I recall is so intensely red as to ... defy description. It seems to shimmer with an inconstant color, as if the eye is unable to sustain an understanding of it; it is as if it were a hole in the cosmos through which one could peer to some other universe where the sole commandment was "let there be red!" Unfortunately, the time I was there I ... lost track of the one I'd taken, meaning to look up what it is, but I was very much impressed, and it doesn't show up in RGB. Wnt (talk) 21:42, 31 January 2014 (UTC)

Gosh! 86.169.184.247 (talk) 21:59, 31 January 2014 (UTC)

Err. Were there any magic mushrooms growing close by?--Aspro (talk) 00:43, 2 February 2014 (UTC)

If so you want to stay away from them 'shrooms, as they too can open the door into anther universe, where one realizes that even your worst enemy is a friend – and that is not the American-Way. After all, it would mean there is no one anymore, to go to war with! That would not go down very well with the defence industry, that provides so many of our citizens with employment and health-care insurance.--Aspro (talk) 01:02, 2 February 2014 (UTC)

From a theoretical perspective, your ribbing of Wnt is not necessarily a safe bet. The CIE colour space does show scope for colours along the red-purple-blue trajectory that may stimulate the green receptors less than anything a screen could do (i.e. to have a more saturated colour). In nature, it is also possible to have fluorescence, in which a colour intensity is larger that 100% reflectance of a band of colours, which could lead to a super-intense colour not possible from pure reflectivity. From the graph, I expect that it would not be difficult to find cyans that are markedly more saturated than anything an RGB screen could produce. Colour-additive screens (of which RGB is an example) will have another quirk: they can produce the highest intensities precisely at hues where they cannot produce full saturation, as hinted by the three bright lines that can be seen radiating from the centre. —Quondum 16:29, 2 February 2014 (UTC)

Part of my understanding as to why RGB displays cannot reproduce the entire color space comes from my understanding of violet light. A blue phosphor emits light of a certain wavelength we call blue - it stimulates all cones to a certain degree even the red one. However violet light only stimulates the blue cone because it is beyond the sensitivity of the red and green receptors, while a blue phosphor is not. Please correct me if I'm wrong.  — TimL • talk 09:27, 3 February 2014 (UTC)

Effects of long, long term exposure to radiation on human body/skeleton

Hello dear Wikipedians.

For reasons of fiction, I wish to inquire what might be the effects of 2,000, 5,000 and 10-20,000 years worth of cosmic radiation to a human body. More specifically, a deceased body kept in a glass coffin of sorts, floating idly far away from our solar system. Do I assume correctly that the skeleton does not simply remain, but might alter in certain ways due to the radiation? And what about the rotting process? Anything left as a waste product inside this confined space?

I thank you very much for any educated guesses.

213.104.126.183 (talk) 02:57, 31 January 2014 (UTC)

A dead body in deep space (which is what I assume you mean by "far away from our solar system") would become very, very cold and freeze solid. At that point, most normal decay processes would essentially stop. If the coffin is not air tight and the body is exposed to vacuum, then volatile compounds (like water) would gradually be lost to space. Dragons flight (talk) 04:53, 31 January 2014 (UTC)

Cosmic radiation is a little different, but basically you're asking about food irradiation. There's something about meat being irradiated so that you can keep it at room temperature around 70 kGy, which is a lot compared to figures I'm seeing in radiation carcinogenesis in past space missions of 0.12 mGy/day (though to be honest, I didn't look very closely - why bother, if you want you can make your future space shielding better or worse than the missions). So I think you get that in 550 000 000 days, more than a million years? I also didn't look into whether the flavor of heavily irradiated meat is noticeably different, but it should at least look like a corpse. Wnt (talk) 06:21, 31 January 2014 (UTC)

Unless it happens to drift near a supernova or a pulsar (or, God forbid, a quasar) -- in which case it would be charbroiled before it got to the other side. 67.169.83.209 (talk) 06:39, 31 January 2014 (UTC)

Mmmmmmm. After your first decade or so marooned on floating space junk eating algae recycled from your body waste, you'd be amazed how a charbroiled corpsicle gets your appetite going. :) Wnt (talk) 15:37, 31 January 2014 (UTC)

My back-of-the-envelope estimate shows it only takes about 15 minutes for a room-temperature body to radiate enough heat to reach freezing temperature, so no traditional decomposition should occur. Katie R (talk) 14:57, 31 January 2014 (UTC)

Given the time span mentioned, some type of nuclear transmutation may well occur.--Auric talk 19:39, 31 January 2014 (UTC)

OP here. THank you for your responses. I see the consensus is a quickly frozen body, outwardly largely similar despite radiation. Nothing spectacular happening anywhere, then? Colour of the skin, structure of the eyes? 213.104.126.183 (talk) 02:43, 1 February 2014 (UTC)

Well, there could be other aspects of being in space that would have more dramatic effects. For example, depending on the equilibrium temperature the body reaches, it may be warm enough for ice to sublime, leading to freeze drying. I really have no conception what freeze drying an eye does, but it might be visually interesting. Also, if it is in a coffin that sunlight can penetrate, especially high frequencies, the body would be affected pretty substantially by solar bleaching effects. And if the orbit (including just the coffin rotating slowly in the sun) causes the body's temperature to increase and decrease periodically ... I'm not sure what would happen, I just think about what the seasonal temperature changes and frost heaving do to the roads. Wnt (talk) 05:38, 1 February 2014 (UTC)

Center of mass of the sun-earth system

Which of the following two statements is correct?
1) Earth moves around the center of the sun.
2) Both, earth and sun, moves around their common center of mass. 27.62.119.215 (talk) 06:49, 31 January 2014 (UTC)

Neither. There are other planets in the solar system too. AndyTheGrump (talk) 07:18, 31 January 2014 (UTC)

If we ignore other planets, then the two items orbit about a barycenter. In the case of the Earth-Sun pairing, that barycenter is still within the Sun, but not at it's center (slightly offset towards the Earth). StuRat (talk) 07:21, 31 January 2014 (UTC)

Two astronomical bodies orbiting a barycenter inside one body (not drawn to scale).

I should have used earth-moon system instead of sun-earth system. I think you have got what I was asking. In the article Barycentric coordinates (astronomy), it is given that - "When a moon orbits a planet, or a planet orbits a star, both bodies are actually orbiting around a point that is not at the center of the primary (the larger body). For example, the Moon does not orbit the exact center of the Earth, but a point on a line between the center of the Earth and the Moon, approximately 1,710 km below the surface of the Earth, where their respective masses balance. This is the point about which the Earth and Moon orbit as they travel around the Sun."
Do moon and earth orbit their common center of mass in circular orbits or in elliptical? 182.66.191.224 (talk) 07:45, 31 January 2014 (UTC)

Perfect circles don't really occur in these situations, but in the case of the Moon's orbit the distance from the earth varies roughly between 405,000 and 363,000 km, so the orbit is noticeably non-circular (it has an orbital eccentricity of 0.0549). The same should be true for the Earth's orbit, because the ratio between the Earth's and the Moon's distances to their center of mass is by definition a constant. - Lindert (talk) 09:36, 31 January 2014 (UTC)

According to the classical picture of an atom, an electron orbits the nucleus. In this case also, is it true that both (proton and electron in hydrogen atom) orbit around their common center of mass? 106.216.120.89 (talk) 11:39, 31 January 2014 (UTC)

Yes, the principle is the same. Do note however that in an elliptic orbit the center of mass is not actually located in the center of the ellipse, but in one of the two focal points. - Lindert (talk) 12:11, 31 January 2014 (UTC)

If you mathematically treat an electron like a ball and the nucleus like another ball (i.e. the model of Hantaro Nagaoka), then yes, the same physics equations would apply. However, there's lots of good reasons why an electron should not be treated like a ball orbiting a bigger ball, not the least of which is that the Larmor principle states that any accelerating electric charge always sheds energy in the form of photons. Since a revolution is a form of acceleration, consider an atom where an electron was truly orbiting a nucleus. Said electron would be continuously shedding energy, slowing down and spiraling in towards the nucleus. Since electrons don't do that, the model that says they do "orbit" the nucleus like a planet does must be wrong. That sort of inconsistency is partially what led to the quantum mechanical model of the atom. --Jayron32 03:46, 1 February 2014 (UTC)

Well, there are Rydberg atoms in which an electron can actually be resolved as a particle well separated from the nucleus. I recall asking about them earlier and ironically enough, as I recall, these are actually superpositions of a wide range of quantum states in order to assemble the observed point particle. (Measuring the position scrambles the momentum, and measuring momentum would scramble position, per the Heisenberg uncertainty principle) [5] Still, it should be clear that between discrete emission events and observations, a macroscopically separated electron will orbit by Kepler's laws. Also, note of course both particles do orbit symmetrically about the center of mass, in ellipses; they're just different ellipses. If you have two identical planets orbiting elliptically, one on the left, one on the right, the center of mass is the right focus of the left ellipse and the left focus of the right ellipse. Wnt (talk) 05:28, 1 February 2014 (UTC)

Sort of. The solutions to quantum mechanical stuff always resolves to classical physics in the macroscopic world. That is, you can use quantum mechanics to describe, say, the trajectory of a cannon ball and get results that match observed data for its flight. But classical physics works also for that situation and is simpler. That simple fact means there must be some scale where the transition between "where quantum mechanics applies but classical mechanics doesn't" and "where quantum mechanics and classical mechanics both apply, but where classical mechanics makes more sense to use cuz it's easier" occurs. The Rydberg atom lies just at that point: the electron is so weakly bound to the nucleus that its behavior matches that of a simple "small sphere orbiting a larger sphere" one would predict using simple Kepler physics. But it's basically a situation invented just to explore the physics at that peculiar scale. For normal atoms (i.e. what you and I and everything are made of), classical physics doesn't work well (i.e. the Larmor problem noted above: classically, electrons should spiral into the nucleus). --Jayron32 05:41, 1 February 2014 (UTC)

"ironically enough, as I recall, these are actually superpositions of a wide range of quantum states in order to assemble the observed point particle" – it's a single state, but that state is a sum of a lot of energy eigenstates (states of definite energy). The reason is simply the uncertainty principle: if the electron's position within the orbit is not completely indeterminate then its orbital energy must be at least somewhat indeterminate. This applies to macroscopic objects too, in theory. -- BenRG (talk) 08:47, 1 February 2014 (UTC)

I'd say that what breaks down at atomic scales is the Larmor formula, not the idea that electron orbitals are orbits. I suppose it's just a matter of language. Regardless, the center of mass of a hydrogen atom is about 1/1836 of the way from the nucleus to the electron, or about 1/1836 of an angstrom, which is significantly larger than the proton's radius of around 1 fm (1/10000 of an angstrom), so the "orbital fuzziness" of the nucleus is quite large, larger even than the fuzziness of my estimate. -- BenRG (talk) 08:47, 1 February 2014 (UTC)

Calories in medicinal clay

I have long wondered about Geophagy, and whether medicinal clay has any caloric value. I can't find even a mention of calorie content in either article. Can someone direct me to a method to calculate this? The calorimetry article is too technical.--Auric talk 20:18, 31 January 2014 (UTC)

I don't think the body is realistically going to break down silicates, let alone extract energy from changing their form. There are cases in which bomb calorimetry is wrong: for example, it would measure calories in dietary fiber that you don't actually extract. If your interest is in whether energy can theoretically be extracted from it, we could continue, but if the calorie count in a food sense is what you're after I think you should write it off. (Of course, if the clay is impure or mixed with flavorings, it could have calories; also, its use by parrots in absorbing alkaloids and the medical side effects listed in the medicinal clay article also suggest the potential to have somewhat negative effective calorie count by hindering absorption of other food) Wnt (talk) 21:50, 31 January 2014 (UTC)

Realistically, your body only gets food energy from about 6-7 different classes of compounds. Silicates are not one of them. Other than the "big three" of protein, carbohydrate, and lipids, there's stuff like ethanol, some dietary fiber (which does give some food energy), and a few other classes of compounds. There's really nothing in clay aside from tiny bits of rock, and you can't extract food energy from that. There may be some dietary minerals in there, but that's about it. --Jayron32 03:39, 1 February 2014 (UTC)

Orbitally Rearranged Monatomic Elements

Why is there not even a stub? Seems quite odd to not even have an entry.. — Preceding unsigned comment added by 50.78.98.154 (talk) 22:41, 31 January 2014 (UTC)

In order for a fringe theory to warrant an article, it must be notable, irrespective of whether it is true or untrue. Nimur (talk) 23:02, 31 January 2014 (UTC)

Articles have been created on the topic, but the overwhelming consensus each time has been to delete them. For the discussions about why they were deleted, see WP:Articles for deletion/Orbitally rearranged monoatomic element and WP:Articles for deletion/Orbitally Rearranged Monoatomic Elements. Red Act (talk) 01:24, 1 February 2014 (UTC)

Is this topic really not notable enough for a Wikipedia article? 86.169.184.247 (talk) 04:33, 1 February 2014 (UTC)

Really. See, Wikipedia will cover bullshit, but only when enough people have written about the bullshit as bullshit. See, for example, flat earth, or homeopathy. Those are two examples of well documented bullshit. This bullshit here is not even notable as bullshit. That is, it isn't receiving even notice for being bullshit, at least of the level of coverage we'd expect to support a Wikipedia article. --Jayron32 04:40, 1 February 2014 (UTC)

I understand the difficulty of writing about a topic if reliable sources do not discuss it. However, there seems to be a pretty extensive crackpot literature on this topic, and I, for one, would appreciate a rational Wikipedia article about it. 86.161.61.104 (talk) 20:50, 2 February 2014 (UTC)

It there is only 'crackpot literature' on a subject, it doesn't meet our notability guidelines, and a lack of non-crackpot sources would make writing a policy-compliant article impossible. 'Crackpot' sources are only reliable for the authors' opinions (rarely notable, and in consequence of little relevance to an encyclopaedia), and the lack of non-crackpot sources would oblige us to engage in original research to demonstrate the obvious crackpottery of the idea. AndyTheGrump (talk) 21:09, 2 February 2014 (UTC)

In my opinion crackpot coverage should contribute to notability. 86.161.61.104 (talk) 23:53, 2 February 2014 (UTC)

Hmmm, seems like this takes this guy apart like a frog in a blender. The funny thing is though, the original patent doesn't seem that far-fetched as a concept. I mean, we know that the transition elements have orbitals in different shells at very similar energies, such that the precise electronic configuration of an element is not a trivial thing to guess but had to be determined empirically. Why shouldn't there be low-energy excited states of transition elements that have notably different chemical properties? And could any of them turn out to be stable long enough to be isolatable in a laboratory? Wnt (talk) 05:59, 1 February 2014 (UTC)

@Wnt: – To be of any significance, it should not be purely unsubstantiated conjecture. We know that in any substance in thermodynamic equilibrium, all possible states of a substance are present in abundances according to the respective energy levels, which kind of trashes that idea, unless there is an exceptional mechanism blocking transitions to and from other states so that it takes very long to reach equilibrium under normal conditions. Although some transitions are "forbidden", thus slowing certain modes of decay, to have certain orbital configurations being effectively isolated from excitation to or decay from any other available modes under normal room-temperature conditions in such a complicated system as a transition element would be truly phenomenal. To have these configurations being stable yet to be chemically very distinct takes this even further into the realms of impossibility, since these two properties are pretty much incompatible. —Quondum 22:21, 2 February 2014 (UTC)

Of course - I realize we're talking about fringe science here, not anything remotely supported. But when evaluating fringe science, the mere idea that something might even conceivably not be completely and absolutely impossible is entertaining, because then we get to ask: how do we know for sure? Wnt (talk) 23:27, 2 February 2014 (UTC)

You apply the Russell's teapot variant of Occam's razor, and then you go home and get a good night's sleep. It's not my responsibility to respond to every evidence-free assertion that someone made up. TenOfAllTrades(talk) 00:37, 3 February 2014 (UTC)

At an investigative level, naturally everything should be entertained. But at a reference level, no. Also, answering the question only becomes interesting when we feel there may be some path to a better understanding, and I discern none. In any event, in the original context framed by the OP, that is to say, whether this warrants an article in WP, I think that the WP principles and guidelines give a pretty unambiguous "no". WP is not a secondary source; we are editors, not journalists. —Quondum 00:53, 3 February 2014 (UTC)

February 1

Unregistered SIM cards

Which countries still don't require people to register their prepaid SIM cards? --49.145.78.106 (talk) 04:46, 1 February 2014 (UTC)

Which countries do? HiLo48 (talk) 07:29, 1 February 2014 (UTC)

Certainly not in the UK. We bought a 'disposable' SIM card (with cash) to use while we were on vacation there back in December - it cost 50 UK pounds and had 50 pounds worth of pre-paid minutes & texts on it - and the whole process was completely anonymous. SteveBaker (talk) 14:19, 1 February 2014 (UTC)

@HiLo48: Which countries? Examples: Kenya, Malawi, Zambia, Uganda --49.147.165.12 (talk) 02:31, 3 February 2014 (UTC)

South Africa https://www.mtn.co.za/support/Pages/Rica.aspx 196.214.78.114 (talk) 10:18, 3 February 2014 (UTC)

I wonder whether these cards in the UK, Kenya, Malawi and so on are truly anonymous, or whether they require some form of activation like calling the number to be activated from a landline, which would leave a track to follow in case you decide to use the SIM for harassment, prank calls, drug dealing, or other criminal activity. Indeed, although they might be quite convenient for tourists, checking the ID of someone would just require 1 minute, and can avoid problems down the line. OsmanRF34 (talk) 13:00, 3 February 2014 (UTC)

It is rather unlikely that there is any such requirement for activation with anonymous prepaid systems: you arrive at an airport, and expect immediate activation of your newly purchased card. Even a landline is of little use, because it could be from the lobby of a hotel. And assuming that the telephone infrastructure leaves the sort of trace, and that it is readily accessible, is assuming NSA-like capabilities of third-world countries. It is also a misconception that registering numbers is a direct countermeasure to crime; it is not difficult to get a card that is registered in way way that does not connect it to the user. It seems more likely that the registration process is a way of simplifying traffic analysis where full traffic analysis is still beyond the capability of the authorities. I suspect that in countries with the capability of recording and analysing telephone traffic on an ongoing basis such as the UK and USA, individuals can be tracked far more reliably through analysis of the frequency of specific numbers called, even when they are not from the same phone. —Quondum 16:05, 3 February 2014 (UTC)

The SIM card I bought at a phone store at London Gatwick airport may well have needed some kind of registration - but that was all done by the guy behind the counter at the store - who didn't ask our names or require any sort of ID. Since we paid with cash - any kind of registration process could only have identified the store and/or it's owner. Of course, the airport is stuffed full of security camera - I'm quite sure that if someone in authority wanted to figure it out, they could have timed when the card was sold to the pictures of my wife and I standing at the store counter - then compared those images to people going through passport control and thereby figured out *exactly* who bought the phone card with that phone number associated with it. The incredible power of this kind of security surveillance is not in one single source of information - but in combining multiple sources - each of which is relatively innocuous.

Note also, that every phone has a unique number built into it - aside from the number on the SIM card and the actual phone number. That number can also be read from the cell tower - so just buying a 'disposable' SIM card isn't enough to ensure that you can't be tied to phone calls. You'd really need to buy a 'disposable' phone too. SteveBaker (talk) 19:23, 3 February 2014 (UTC)

store meat in vacuum?

A couple of sections up, I was reminded of a novel set in a city on the Moon. Expecting a large influx of refugees, the city slaughters most of its meat animals, to reduce competition for air and water. They can't eat all the meat right away, and haven't enough freezer space for all of it; but, I thought, what if the carcasses are stored outside? Obviously they'll dry out in a hurry (enough of a hurry to kill all bacteria?), but does that make the protein useless? Could it be used later for soup stock, say? —Tamfang (talk) 07:10, 1 February 2014 (UTC)

Lots of dried meat is eaten around the world see: Dried meat. It's just a case of preparing it properly - usually using salt to kill the bacteria. Richerman (talk) 08:34, 1 February 2014 (UTC)

The freezing would prevent bacterial problems - so you don't need the salt. Wrapping the meat tightly in plastic would certainly help to delay the onset of freezer burn in much the way that vacuum packing does. But in any case, freezer burn mostly only affects the surface of the meat - so entire cow carcasses would probably be unaffected - especially if the hide is left on it. SteveBaker (talk) 14:15, 1 February 2014 (UTC)

Note that anything outdoors on the moon will fluctuate between extremely cold and extremely hot, with a "day" lasting a month. The hot phase will do bad things to meat. Looie496 (talk) 16:31, 1 February 2014 (UTC)

Although some of the craters are in permanent shadow and extremely cold at the bottom [6] Richerman (talk) 17:18, 1 February 2014 (UTC)

Is sea star wasting syndrome the same thing as starfish wasting disease?

I've created an article for sea star wasting syndrome, which is currently in the news. Some searching revealed an already existing article starfish wasting disease. It looks like these might be about the same thing, but I don't know enough about marine biology to make the call. Are these the same? -- The Anome (talk) 11:19, 1 February 2014 (UTC)

They're the same thing. I saw a report on this problem on TV a few weeks ago. The terms "sea star" and "starfish" are synonyms. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:53, 1 February 2014 (UTC)

Thanks. I've added mergefrom/mergeto tags to the articles. -- The Anome (talk) 14:19, 1 February 2014 (UTC)

Dieting too quickly.

When dieting, it's frequently said that if you eat too little, your body will go into "starvation mode" in which your metabolism becomes more efficient - and it'll actually be harder to lose weight.

My question is for how long do you have to eat too little to produce this effect - and how long does the body take to go back to a normal metabolic rate when you resume eating more?

Some diets claim that skipping even a single meal is too much - where others suggest that you need to take a break from dieting every four to six months in order to avoid this effect!

Is there some scientific evidence for the onset, duration and magnitude of this effect? Is it even true?

SteveBaker (talk) 14:40, 1 February 2014 (UTC)

This study shows that fasting for 24 hours actually increases metabolic rate. Also check out this blog post which - using thyroid surrogate markers - suggests that going under 25kcal/kg lean BW/day (in combination with an exercise-induced 1300kcal/day deficit!) could decrease metabolic rate. Markr4 (talk) 17:33, 1 February 2014 (UTC)

Firstly, dieting really means: Latin diaeta, way of living, not food reduction. Simply reducing food intake can also reduce muscle mass as well as fat. The latter is not good. The body is sacrificing itself to make up for the shortfall of real nutrition (starvation mode). Dieting should really be about eating balanced diet where the body feels sated and not hungering for more, with all it needs have been satisfied. The high sugar and fat rich foods (like ice cream) that we like today, were unknown to out ancient ancestors. Modern prepossessed foods are very short on those other stuffs, that stops our bodies hungering for more. The packaging may have little bit printed on the back stating the fibre content etc as the amount recommend as a daily intake but add up the days consumption of all those printed bits and there is a lot missing. So the body is hungering in the hope of some real food to make up for that short full. The Paleolithic diet is odd to try at first, but it doesn't necessitate eating too little. Alas, it is also not a commercially viable wait-loss-plan that can be owned by any company, so it receives no commercial promotion.--Aspro (talk) 18:50, 1 February 2014 (UTC)

Well, to be fair, a real Paleolithic diet probably involved a lot of fasting, need it or not. :0 Wnt (talk) 03:53, 3 February 2014 (UTC)

True. In palaeolithic times and up to quite recently (on the evolution time scale) there were seasonal times of want. The homo-sapient has a metabolism to go into a acute starvation mode but that is different from a 'chronic' starvation mode as in modern dieting protocols . For instance, we can store up several months worth of ascorbic acid to see us over the winter. Swedish mothers used to encourage their children to run around naked in the spring sunshine (even though they did not have a notion about vitamin D) but cultural wisdom that got passed down from mother to daughter was proved right. A true palaeolithic diet in this sense, would harken back to the old wisdom of my grandmother's time, which was only eat foods that are in season. Now that one can buy Californian grown lettuces way up in Alaska in January, makes this true natural diet difficult, for as I admit, do like a good salad at any time of the year. So one has to aim for the median. If one is living up in (say) Caribou, Maine, then eating high fat foods (energy rich) during the winter keeps you warm. Yet for a Hispanic living down in the warm south and consuming high fat/sugar takeaways.... this is a recipe for diabetes, obesity and an early death.--Aspro (talk) 22:04, 3 February 2014 (UTC)

Aspro's claims about "nutrient deficiency" increasing appetite are common, but there isn't actually any evidence for it. It's more likely that foods like ice cream promote overindulgence because they taste nice. Markr4 (talk) 12:20, 3 February 2014 (UTC)

Yeah! Heroin an Smack make you feel nice to. What is your point? Micronutrient-rich diet's? I say you are allowing yourself to baffled by 'his' science. A good diet contains more. An mixture of protein, carbohydrates, fatty acids etc., as well as micronutiants and vitamins. Also, talk to a cattle farmer. He may mention Mineral lick. The cattle partake in them instinctively (cattle can't read health advice articles). If you have ever looked after livestock – you will see they go for what they need first. Cumulatively, that blows your sided Stephan Guyenet argument out of the water. --Aspro (talk) 21:59, 3 February 2014 (UTC)

Macrophages

I'm reading a textbook of mine and came across a claim during a discussion of how the body prevents glycation and cross-linking of proteins, that macrophages "seek out glucose molecules, engulf them, destroy them, and send them to the kidneys for elimination". I have never heard of this function of macrophages and questioned whether it was true, but cannot find any sources supporting this claim. Does anyone know if this actually happens? Brambleclawx 15:47, 1 February 2014 (UTC)

It's true in a sense but weirdly worded. Glucose is the fuel that macrophages primarily burn, so they do "engulf and destroy" them, but the more commonly used terms would be "uptake" and "metabolize". The products of glucose metabolism are CO2 and water -- the water is indeed sent to the kidneys for elimination, but this is again a weird way of putting it. Looie496 (talk) 16:27, 1 February 2014 (UTC)

Yeah, I was wondering if that was what they meant, but in that case, all cells that metabolize should have been mentioned. Brambleclawx 17:26, 1 February 2014 (UTC)

It seems they must have wanted to say "seeks out glycated molecules", otherwise they went to a lot of bother to say macrophages absorb sugar from blood plasma, and there'd be no point of saying anything was sent to the kidneys, unless they meant water. μηδείς (talk) 23:06, 1 February 2014 (UTC)

Yeah, I think they're looking for advanced glycation end-products with both hands and a flashlight. Wnt (talk) 01:54, 3 February 2014 (UTC)

Stiffest Material

Wich materiasl has the highest Bending stiffness? I want to ask cause it is realy interresting which material has the most highest stiffness or bending stiffness. cause you can make great things out of it and you have little weight but you dont have to make complaints out of it.Saludacymbals (talk) 17:49, 1 February 2014 (UTC)

You might want to read articles such as Young's modulus, Stiffness, Graphene and Carbon nanotube. You might not be looking to maximize some specific property, or you might find that many materials exist that surpass your expectations, and that other criteria (other properties and cost) might be significant. —Quondum 19:15, 1 February 2014 (UTC)

From the basic theory of bending, there are 2 important equations relating materials properties, loading, and geometry. The first important property is the Young's modulus. However, the yield strength is also important as the theory is only valid as long as the stress at all points remains below the yield stress. Which one is more important would depend on the geometry of your beam because, as they depend on factors like the second moment of area and how the load is distributed.

It's also only valid for pure bending (there are more complicated theories that can take more complicated loading into account). The geometry can also affect whether it will buckle before it will fail in bending.

And if you're making an actual object out of something, you also have to take brittleness into account. Many stiff materials are also brittle, which means if you do exceed the maximum load, it will shatter rather than bend in plastic deformation.

Many materials also exhibit anisotropic properties (properties that differ depending on direction). Rope is fairly stiff when pulled in tension but has virtually no bending stiffness because it's made up of fibers all oriented in one direction. So how you turn your raw material into a bar will also affect its bending strength.

The highest Young's modulus known is linear acetylenic carbon. However, all the calculations are theoretical based on quantum mechanics no one has actually been able to make more than a few molecules of it and it's not known how, or even if, it could be made into a bulk material.

Diamond is a distant second and could be used to make really small objects.

If you wanted to make something relatively big, the best choice is probably tungsten carbide. It's usually formed as a powder mixed with a softer metal like cobalt. But its melting point is "only" 2870 C, so casting it into a solid piece is difficult, but possible. Osmium has similar properties but at around US$100/gram (where 1 g is a 3.5 mm cube) it probably isn't very practical. Mr.Z-man 21:12, 1 February 2014 (UTC)

Yes. The stiffest materials such as diamond carbon nanotube are too exotic for commonly manufactured things and you may be more interested in materials with high strength-to-weight ratio. Consider the usefulness of balsa wood which weighs little but is used to construct a warplane, wind turbine blades or a sea-going raft because its Specific strength (see article) exceeds metals such as aluminium and brass. You may also be interested in Steel which inexpensive, recyclable and is not one but a wide range of different alloys 1 2 3 that can be selected not only for stiffness but also for their strength, hardness, toughness, wear resistance, corrosion resistance, Weldability, Ductility and hardenability. I don't understand what the OP means about complaints but suspect that Cymbal making may be another article of interest. 84.209.89.214 (talk) 21:18, 1 February 2014 (UTC)thanks for your kind information! but i only thought of the bending stiffness from a material in this case.Saludacymbals (talk) 21:43, 2 February 2014 (UTC)

February 2

Large body flying through the solar system.

Suppose a rogue planet with mass like that of Jupiter went thru the inner solar system at high enough speed to keep going and exit the solar system. Would it be true to say that, the higher the rogue planet's speed, the less disruption to orbits of planets like earth, mars and venus would be caused? Regardless, would orbits be severely deranged? thanks.76.218.104.210 (talk) 05:58, 2 February 2014 (UTC)

If it went perpendicular to the ecliptic and all the planets happened to be on the other side of the Sun, I suspect all it might do would be to permanently disrupt Earth's climate by altering its orbit, and cause mass extinctions by disrupting the asteroid belt, but s.o. would have to do the calculations. — kwami (talk) 06:57, 2 February 2014 (UTC)

Yes, in general, higher speed should mean less disruption. (Providing it doesn't actually hit anything that is!) Gravity is the only significant effect it would have. Gravity imparts an acceleration onto nearby object for as long as it's present - and the longer that acceleration goes on, the more velocities throughout the system are changed - and hence the more kinetic energy is transferred between the various bodies involved. So as a general observation, the amount of energy that it would "rearrange" throughout the system would be in proportion to the amount of time that it was nearby - so the higher the speed, the less time it's transferring energy and the less "disruption" there is. Of course a heck of a lot depends on when, where and in what direction this body was moving...and "disruption" is something of a fuzzy term...if all it did was drastically move the orbits of a few comets - then maybe we'd say that was considerably less "disruption" than (say) an 0.01% change in the Earth's orbital velocity - even if the energies involved were higher for the comets. SteveBaker (talk) 15:53, 2 February 2014 (UTC)

If you are really interested in stuff like this, you can try a gravity simulator like this one and see for yourself what happens. Not sure how easy it would be to set up a scenario like the one you describe, I personally haven’t played with one but I’ve heard it talked about in the context of a game I’ve started playing and it sounds like it should be possible. If not with the software I’ve linked, then with something similar. Vespine (talk) 02:50, 3 February 2014 (UTC)

The orbits may be temporarily disturbed, as the mass of the rogue planet nears the ecliptic (we'll assume the planet passes very close to the sun for simplification) the planets will "feel" more gravity and their orbits briefly contract, ever so slightly, but once the planet is far off, the planets would resume "feeling" the same gravitational force as before and settle back into their original orbits. I imagine the greatest effect would be to change the ellipticity of the planets' orbits.  — TimL • talk 09:10, 3 February 2014 (UTC)

No, that's off, TimL. The perturbed orbits would be under the influence of the original planets as well all the time, the effects of the acceleration they underwent due to the intruder would not simply disappear. There wouldn't be any further disruption by the intruder once it passed, but there are no preferred orbits to snap back to, and once in motion stays in motion. μηδείς (talk) 19:24, 3 February 2014 (UTC)

most ancient arrow poison

Hi,

I am trying to find reliable information on the most ancient arrow poison ever used (maybe from chemical analasys of ancient arrows found?). The article chemical warfare mentiones use of arrow poison by the San people 10000 years ago, but with no reference. I would appreciate any information. Thanks! 2.55.131.28 (talk) 07:15, 2 February 2014 (UTC)

The article on the San people mentions Diamphotoxin as the poison used. --Cookatoo.ergo.ZooM (talk) 10:13, 2 February 2014 (UTC)

yes, but since when? 2.55.127.242 (talk) 12:39, 2 February 2014 (UTC)

If you include biological warfare, dipping arrows in feces might go back much further. The people doing so wouldn't have needed to know about bacteria, or even that it would tend to cause the enemy to become infected. They might have done so just as a way to humiliate the enemy. StuRat (talk) 18:36, 2 February 2014 (UTC)

• I am curious whether there might be a telltale sign on arrowheads like grooving that indicates they've been modified for poison. μηδείς (talk) 20:48, 3 February 2014 (UTC)

• Unfortunately, grooves can also be there to help attach the arrowhead to the arrow. StuRat (talk) 23:25, 3 February 2014 (UTC)

How did Newton derived his law of gravitation?

How did Newton derived his law of gravitation? 182.66.52.106 (talk) 14:02, 2 February 2014 (UTC)

The history of how Newton's law of gravitation came to be is somewhat under dispute. See Newton's law of universal gravitation#History. Red Act (talk) 14:29, 2 February 2014 (UTC)

Newton wrote down exactly how he derived it! It's called Philosophiae Naturalis Principia Mathematica, and it is one of the most important physics books ever written. Fringe historiographers can debate all they like about attribution, or discuss prior work that influenced Newton, but there is no reason to doubt that Newton wrote this book; so to answer the question "how did Newton derive his law of gravitation," there is no better source than Principia.

If you choose to read the Principia (for example, in English translation), you can see exactly how Isaac Newton presents the derivation of universal gravitation. He begins with philosophical assertions. I paraphrase them thusly: natural laws ought to be consistent throughout the universe, and natural law directly corresponds to observable phenomena, and there are no hidden variables (Newton calls these "intensions"). Next, Isaac Newton presents a data table of observations concerning the Galilean moons - the four largest moons of Jupiter that are easily visible from Earth - even using 16th-century optics. Newton writes some mathematics to show that the conclusions of Keplerian motion are consistent with those observations. Finally, Newton writes a mathematical expression that relates the Keplerian motion to a central force law of second order - which he already explored mathematically in Book 1. Over the next few hundred pages, he explores these consequences in greater depth. As Isaac Newton writes in his introduction to Book 3 of the Principia, a commonly-educated man might not have time to read and study all of Principia - there are so many propositions - but anyone sufficiently familiar with the most important principles and definitions - what we today call Newton's laws of motion - can skip directly to Book 3 and study his derivation of the mechanics of gravity. Nimur (talk) 17:11, 2 February 2014 (UTC)

My understanding is that the history is a little more complicated than that. As I understand it, Newton invented calculus and used it to work out the law of gravity and its consequences. But when he wanted to publish it, he felt that people wouldn't believe results obtained using such a newfangled method, so for the book he worked out proofs for everything using classical geometry, and completely avoided any mention of calculus. The result is that the book is much more complicated than it really needs to be. Looie496 (talk) 17:32, 3 February 2014 (UTC)

February 3

How far below the horizon could I see the sun from mount everest?

I've heard the trick of being able to see the sun set twice if you lay down and watch the sun set and then quickly stand up. I also know that due to the earth's refraction we can still see the sun when it is about 1º below the horizon. Now I might be able to figure this out for myself by watching for when the sun's light no longer lights up the tallest of the thunderheads and then looking a smartphone app that shows the current sun elevation, but it's winter here in Florida so no thunderheads to help me out. I looked at the article at horizon but couldn't really wrap my head around which equation would help me out.I think it is basic trigonometry, but my brain is a bit rusty. (the motivation for this question stemmed from wondering about the visibility of partial eclipses at sunrise/sunset when the maximum eclipse is well below the horizon at sea level)  — TimL • talk 08:59, 3 February 2014 (UTC)

You could use an online calculator for calculating the distance to the horizon: [[7]]. I don't believe you need trigonometry for that, the Pythagora's theorem should be enough. OsmanRF34 (talk) 13:34, 3 February 2014 (UTC)

Although the curved hypotenuse (ie, the curvature of the earth) makes it a bit tricky. These calculations were important for battleships in the pre-radar era, as knowing how far away an enemy ship on the horizon was, gave you a clue as to how to aim your guns. Alansplodge (talk) 14:04, 3 February 2014 (UTC)

No, it's not tricky. The hypotenuse is not on the curve. Indeed, there is no curve here. There is a right angle where your view 'touches' the Earth. And you know two sides of these triangle. One of them is the radius of the Earth (one leg of the triangle). The other (the hypotenuse) is the radius of the Earth added to the height your eyes are over the Earth surface. Your are trying to discover the other leg of the triangle. OsmanRF34 (talk) 14:11, 3 February 2014 (UTC)

Let's ignore refraction and assume a spherical Earth with radius R. If you are a height h above sea level then the line of sight to the horizon will be at an angle θ below the horizontal where θ is given by:

$\theta =\cos ^{-1}\left({\frac {R}{R+h}}\right)$

If we take R to be 6371 km and h to be 8.8. km (the approximate height of Mount Everest) then θ is about 3 degrees. The sun takes about 12 minutes to traverse an angle of 3 degrees. Of course, if you are really on Mount Everest your local horizon will be domonated by other nearby mountains, so your effective line of sight to the local horizon will probably be rather less than 3 degrees below the horizontal. Gandalf61 (talk) 14:48, 3 February 2014 (UTC)

Yes, the terrain to the east and west of Mount Everest is very high, and you can't even come close to seeing the sea-level horizon in those directions. There are other places where you'd be able to see a lot farther, even if the peaks are not as high. Looie496 (talk) 17:24, 3 February 2014 (UTC)

That raises an interesting question which the OP's question leads to: What is the highest mountain from which an ocean is visible? ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:32, 3 February 2014 (UTC)

Mauna Kea comes to mind. From the top, at an altitude of about 14,000 feet, you can see ocean in all directions - provided the day is clear. Nimur (talk) 21:11, 3 February 2014 (UTC)

That's about half the height of Everest and the other tallest Himalayan peaks, so it would be a good one to test with. First compute what the answer "should be", and test it by one of you going to the mountaintop and one of you going to the shore, and compare notes via cellphone. As an added bonus to that experiment, you're in Hawaii, which is generally a better climate than the Himalaya range. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:16, 3 February 2014 (UTC)

As I recall, you can see the ocean but not the shore, because the south-eastern coast is obscured by Mauna Loa. Nimur (talk) 23:40, 3 February 2014 (UTC)

The question would be whether the team member who's on top of the mountain can see the ocean's horizon. That assumes the team member near the shore also has a clear view of the ocean's horizon. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:10, 4 February 2014 (UTC)

Is every death by drugs a overdose?

Couldn't it just be some sort of bad reaction, which could happen with any amount of the same drug? Without any trace of a given drug a person wouldn't die of it, so in this sense it's clear that any death by drugs is an overdose. But overdose seems to imply that the quantity was too much, not that an interaction happened. OsmanRF34 (talk) 12:33, 3 February 2014 (UTC)

I'm no expert, but I imagine that you could also be poisoned by something else being mixed in with the drug that you didn't know about, or you could do something fatally dangerous while "under the influence", neither of which could be described as "an overdose". Alansplodge (talk) 14:10, 3 February 2014 (UTC)

Paraquat was one such toxic contaminant, in marijuana. Drug dealers cutting drugs with whatever nasty chemical is at hand is also a problem. During Prohibition in the US, toxic wood alcohol was also a common contaminant in grain alcohol. StuRat (talk) 15:41, 3 February 2014 (UTC)

News reports say they're going to get going on Hoffman's autopsy pronto. That should tell us what specifically killed him. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:32, 3 February 2014 (UTC)

You can get an embolism if you mix air with your heroin. Technically not the drug, but close enough. No idea how common it is, but pretty sure the actual heroin kills more. InedibleHulk (talk) 16:14, February 3, 2014 (UTC)

• NO, people have allergic reactions to certain drugs which are otherwise taken at a small, therapeutic dose. Surely you've heard commercials warn, "If you develop a sudden rash, notice swelling of the tongue, and have trouble breathing, stop taking fratastatin immediately, and make an appointment with your coroner," μηδείς (talk) 16:23, 3 February 2014 (UTC)

I'm trying to figure out what would be the proper dose of heroin. Although it might be that, by definition, an overdose of anything is "just enough to kill you." Like if you're highly allergic to peanuts, maybe you could survive eating a few - but if you ingest an entire container, you might be in major trouble. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:29, 3 February 2014 (UTC)

If you are highly allergic to peanuts you are at risk of anaphylaxis from exposure to trace amounts. Sufferers given oral peanut therapy can only tolerate five peanuts a day after six months increasing exposure. Richerman (talk) 22:52, 3 February 2014 (UTC)

For recreational use, the 'proper' dose is presumably the minimum dose which produces the desired physiological and psychological effects.

Heroin is prescribed to addicts in some countries (generally under fairly restrictive, controlled, specific conditions) as part of a harm reduction strategy and/or to ease withdrawl symptoms.

Heroin is used clinically as a potent analgesic. Taken orally, it is deacetylated and enters the system as morphine. As an injectable, in the UK it is used more often than morphine for treatment of acute pain (in clinical use, the choice between heroin and morphine is down to a combination of history, training, government regulations, and differences in pharmacokinetics and bioavailability in certain circumstances). So yes, there are clearly defined 'proper' doses of heroin for a wide variety of situations. TenOfAllTrades(talk) 16:50, 3 February 2014 (UTC)

The articles on drug overdose and adverse drug reaction suggest that indeed bad things other than overdose can occur. "The term 'overdose' is often misused as a descriptor for adverse drug reactions or negative drug interactions due to mixing multiple drugs simultaneously." More links to related subjects in those articles. 88.112.50.121 (talk) 18:47, 3 February 2014 (UTC)

With some drugs, other substances can dangerously amplify their effects. The most commonly cited example of this is that eating grapefruit will increase the body's sensitivity to a wide range of drugs - resulting in the symptoms of an overdose, even for people taking the correct amounts. SteveBaker (talk) 19:13, 3 February 2014 (UTC)

Pre echo removal

How can I remove pre echo from my audio recordings using a sound editing package?--86.184.57.126 (talk) 16:06, 3 February 2014 (UTC)

I don't know of a tool that does it directly.

The most obvious suggestion is to:

1. Look carefully at the audio wave-form that precedes the start of the recording and try to estimate the delay and the relative amplitude of the pre-echo compared to the true sound.
2. Duplicate the track, shift it in time and reduce it in amplitude to match the delay on the echo. The time shift will need to be very accurate to do this well.
3. Subtract the shifted, quieter version of the track from the original.
4. Play with the delay and the amplitude reduction until you're happy with the results.

I think you can do all of those steps in (for example) Audacity - which is a free/OpenSourced program...but I've never tried it.

The likely problem is that some of the mechanisms that cause pre-echo (such as audio tape print-through and groove distortion in vinyl records) may produce somewhat varying delay and amplitude throughout the recording. That might mean that you can correct this problem for short recordings - but not for long ones.

One problem with this is that if there is noise in the recording that happened AFTER the print-through happened, then you'll be adding pre-echoed noise into the recording by doing it.

Another problem with vinyl record pre-echo on stereo recordings is that the echo will not always be on both sides of the stereo image identically - and one side of the original may have echoed more strongly into the other. So cross-talk maybe a major issue here.

SteveBaker (talk) 19:03, 3 February 2014 (UTC)

How long would it take for a cylinder of ice 2850m high and 2850m in diameter to melt?

First an explanation: This is not a homework assignment! I'm a linguistics major who graduated a long time ago :) I want this question answered for a personal creative writing project. I have attempted to solve this problem on my own but I've reached a brick wall where my knowledge and ability is totally insufficient, and would really appreciate someone who actually knows this stuff to help me out.

The problem is as follows:

The cylinder of ice is 2850m in length and 2850m in diameter. One of its flat surfaces is on rock and it is surrounded by air on all other sides. The ice starts at -45C and the surrounding air temperature is 5C. How long would it take to completely melt?

A back of the envelope calculation is all I really need, just so I can get an idea if it's going to be more in the order of years or centuries. Thanks very much to anyone who can help me with this. --87.82.207.195 (talk) 20:17, 3 February 2014 (UTC)

Whether there's any wind or sunlight on it would make a huge difference, but I think centuries is more what we're talking about. Also notice that even small impurities will tend to concentrate on the outside, after some ice melts, adding a layer of insulation that won't melt away.

The ground temperature under the ice would also play a roll. Of course, unless it had a major source of heat like volcansm or an underground stream, the ground would soon cool down to match the ice's temperature. Also, if the humidity is low, you could get significant sublimation of the ice directly to the air, without melting first.

Something else to consider is that that much ice, over years, will behave more like gelatin than a solid. That is, it will flatten out and flow downhill, just as glaciers do. The flattening out will increase the surface area and thus the melt rate, as will the inevitable fissures which form, and gullies from meltwater. So, if you hope to keep a cylinder of ice that shape for years, it would need to be in space, away from gravity (although it might even deform a bit under it's own gravity).StuRat (talk) 23:11, 3 February 2014 (UTC)

Hmmm, wind speed and rainfall would also play a major role. Anyway, the heat of fusion of water is 79.8 cal/g, the density of ice is something like 0.92 g/cc, and the volume of this thing is 2850 * (2850/2)^2 * pi = 1.82 x 10¹⁰ m^3 = 1.67 x 10¹⁹ g = 1.33 x 10²¹ cal = 5.58 x 10²¹ J. Now the entire surface of the cylinder is 2850 * (2850 * pi) + (2850/2)^2 * pi * 2 = 3.8 x 10⁷ m^2. So the time x the amount of watts per square meter absorbed has to be equal to the 5.6 zettajoules (yeah, I just looked that up), i.e. 5.6 E+21 / 3.8 E+7 = 1.46 E+14. Now sunlight can go up to 120 watts/meter, but that's still E+12 seconds. (3.16 E+7 is a year). I'm not sure how to qualify the wind and rain heating though, which I'd expect to be more substantial. (The close observer will note that this relation doesn't hold as the cylinder gets smaller; it will go from the present volume per surface to zero. Whether that integrates to a net 1/2 or something else, I haven't tried to figure out. Also note a net 1/2 in the other direction since sunlight won't hit any more than half of it.) This still doesn't bring me to a bottom line on account of the weather variables. Hmmm, wait... suppose the area gets 20 inches of rainfall a year. It comes down at 5 C. It takes 80 C worth of energy to melt ice, so the rainfall would melt 20 * 5/80 = 1.2 inches (5 cm) of ice a year (supposing from the top down) and take, oh, 20* 2850 years to get to the bottom. Which is another 10^5 year figure. The wind, well... Wnt (talk) 23:43, 3 February 2014 (UTC)

How dangerous is Everclear?

Is there anything specific about Everclear, other than its strength that would make it extremely dangerous to do straight shots, or chug it freely from the bottle? I realize that the strength is more than twice that of a typical vodka, so you're going to get drunk quicker (twice as fast - is it even a linear thing?) - but aside from that, is there anything else that justifies the 'Everclear will kill you' belief that seems to be around.

The purpose of this question is not so that I may plan my own debauched drinking session. I don't think that you can even buy it, or anything comparable in my country (that I've seen). I've seen people talking about it (slightly fearfully) online, and joking about the crazy guys who shoot Everclear, is all. --Kurt Shaped Box (talk) 21:04, 3 February 2014 (UTC)

No. Alcohol is alcohol. The real danger is people not realizing the strength and drinking too much, too fast. Oftentimes people associate everclear with backyard distilling operations, in which case, contaminants like methanol, etc. can find their way into the everclear. But for the legally produced and regulated everclear, there is no danger. Justin15w (talk) 21:10, 3 February 2014 (UTC)

"Alcohol is alcohol" is not quite correct. Everclear is a very strong but consumable form of Ethanol a.k.a. grain alcohol. Wood alcohol, or Methanol, can be deadly. Of course, even consumable alcohol can be poisonous if too much is ingested. Everclear is typical added to something else, to "spike" it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:14, 3 February 2014 (UTC)

It is my understanding, though I don't have a ref, that if you concentrate ethanol to nearly 100% (absolute alcohol), it actually is more dangerous than the same amount of total ethanol consumed as a larger volume of more dilute liquor. The reason is that, at such high concentrations, it sucks water out of your tissues on its way down, which can severely irritate your throat and esophagus. Whether EverClear is that concentrated, I don't really know.

By the way, there is another danger to lab-grade ethanol even if you dilute it, which is that, in order to get ethanol more concentrated than the ethanol–water azeotrope, it is distilled using benzene, which causes cancer. How much benzene is left, or how dangerous that is, again, I don't really know. But just because the bottle has a liquor tax stamp (in the US at least) doesn't necessarily mean it's safe to spike the punch with it. --Trovatore (talk) 21:23, 3 February 2014 (UTC)

In chemistry lessons at school, they always told us not to even think of drinking the lab ethanol - because it would kill you. I was never sure whether they actually meant it, or it was just something that they said to discourage 14 year olds from stealing it and getting drunk. Later on in life I met someone who worked in a lab, who told me that the stuff goes great with orange juice, so I dunno... --Kurt Shaped Box (talk) 21:36, 3 February 2014 (UTC)

Well, they may both have been right. If the issue is cancer, then it very well might kill you, but not so fast as to keep you from coming to the conclusion that it goes great with OJ. --Trovatore (talk) 21:48, 3 February 2014 (UTC)

School Chemistry Lab alcohol will be Denatured alcohol in most cases. APL (talk) 23:05, 3 February 2014 (UTC)

• Everclear is meant for consumption, so you don't need to worry about contaminants. But it is a wicked desiccant, as Trovatore mentions, and can lead to acute and chronic damage, along the path of Christopher Hitchens. If you leave Everclear open to the air it will absorb water until it reaches a certain weaker proof at equilibrium with the ambient humidity. Lab alcohol is often denatured alcohol, meaning it has been adulterated to make it unpalatable, and thus not subject to the steep tariff on drinking alcohol. But not all lab alcohol is adulterated, since some reaction need pure ethanol. Basically, Everclear is a vanity item. μηδείς (talk) 22:05, 3 February 2014 (UTC)

Note that there is another reason why drinking concentrated alcohol is more dangerous than drinking the same quantity of alcohol, mixed with more filler (mainly water). That is because the filler limits your rate of consumption. If it takes a gallon of beer to reach a fatal level of alcohol poisoning, most people will find it difficult to drink a gallon quickly. They might very well be able to drink a gallon of beer over the course of a night, but their body is metabolizing the alcohol during that period, so it never reaches a fatal level. Also, since the alcohol level builds up more slowly, they are likely to pass out or vomit before they reach a fatal blood alcohol level.

Now, with highly concentrated alcohol, provided they can choke it down, it's relatively easy to receive a fatal dosage quickly. StuRat (talk) 23:05, 3 February 2014 (UTC)

What, in ounces, would be a fatal LD50 of Everclear? μηδείς (talk) 01:11, 4 February 2014 (UTC)

It would, of course, be unethical to kill half your human test subjects to determine the LD50. However, the LD50 for rats, fed a 70% ethanol solution orally, is >90 mL/kg of body weight, according to [8]. From there you can convert from metric and adjust for the percentage of ethanol in Everclear (there are apparently 2 concentrations commonly sold). StuRat (talk) 01:27, 4 February 2014 (UTC)

Is it true that a person can become a stutterer by wilful practice?

Is it true that a person can become a stutterer by wilful practice, or is the speech disorder neurological? (Please note: this question is not to demean stutterers in any way, as I have high respect for these people. I am only asking out of curiosity.) 140.254.227.177 (talk) 21:21, 3 February 2014 (UTC)

Two words: Mel Blanc. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:15, 3 February 2014 (UTC)

joule heating is rii but also vv/r

so.. why using high voltage to distribute power? thanx --80.182.18.25 (talk) 22:13, 3 February 2014 (UTC)--80.182.18.25 (talk) 22:13, 3 February 2014 (UTC)

In the formulas P = I²R and P = V²/R, the value of R is the total resistance in the circuit, including both the resistance of the wires, and the resistance of the load. When one is only interested in finding the power dissipation in the wires, the formulas do not apply. Jc3s5h (talk) 23:05, 3 February 2014 (UTC)

They do apply if you use the right values, where P is the power lost in transmission, R is the resistance of the transmission line, I is the current, and V is the voltage drop only along the transmission lines, not the total voltage. 80...125 was probably confused by thinking of using the total voltage dropped across both the transmission lines and the load in their calculation for power lost. -- ToE 01:25, 4 February 2014 (UTC)

February 4

Load velocity

what is the max velocity of a mans load?--31.55.94.75 (talk) 01:13, 4 February 2014 (UTC)

According to Men's Health magazine, 28 mph. Dismas|^(talk) 01:32, 4 February 2014 (UTC)

Delta Dagger, part 3

Since at least some Delta Daggers that stood alert in the bad old days were armed with the AIM-26 nuclear air-to-air missile, and since that missile was always under the pilot's direct control, this begs the question: What precautions (if any) were in place to prevent an accidental launch? 67.169.83.209 (talk) 03:10, 4 February 2014 (UTC)