Wikipedia:Reference desk/Archives/Science/2010 November 14

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November 14

converting doi to acs-style citations

Are there any automated services that will convert doi's to ACS-style citations?

I really really hate tedious, mindless work such as this. John Riemann Soong (talk) 00:09, 14 November 2010 (UTC)

Here on Wikipedia, we have Template:doi and Template:cite doi. I believe "cite doi" will expand to a full citation - though I'm not sure how, I imagine it uses one or more web service APIs either provided by Wikipedia's tool server, or by http://dx.doi.org (the DOI resolving service). You could use the Wikipedia cite-doi tool to generate the citations, and then copy/paste (or screen-scrape, if you need the process to be automated). Note that there seems to be a few minutes of delay when using the cite-doi template while the plain-text is generated and later subst'ed by a bot. Nimur (talk) 04:12, 14 November 2010 (UTC)

Tensor of Inertia

My book says, without proof, that the tensor of inertia remains unchanged to first order for small angular displacements about the principal axes, but I don't think this is true. Don't the products of inertia gain a first-order factor? 76.68.247.201 (talk) 02:11, 14 November 2010 (UTC)

Almost the same question was asked six months ago (Wikipedia:Reference_desk/Archives/Science/2010 May 3#Moment of Inertia), also from a Canadian IP. Was that you? Anyway, the simplest nontrivial case is

${\begin{pmatrix}1&\alpha \\-\alpha &1\end{pmatrix}}{\begin{pmatrix}A&0\\0&B\end{pmatrix}}{\begin{pmatrix}1&-\alpha \\\alpha &1\end{pmatrix}}\approx {\begin{pmatrix}A&\alpha (B-A)\\\alpha (B-A)&B\end{pmatrix}}$

which obviously has first-order terms. What is true, though, is that the tensor of inertia viewed as a geometrical object (the ellipsoid of inertia) is symmetric around the principal axes. So, for example, the moment of inertia around an axis inclined from a principal axis doesn't vary to first order in the angle, since it's an even function of the angle. Probably that's what the book was trying to say (or did say?). -- BenRG (talk) 04:31, 14 November 2010 (UTC)

I'm sorry, but I don't follow :(. I've decided to take a few photos from my book, because I don't think it says what you're trying to say.

http://tinypic.com/r/wbq4k9/7

Here, the question asks to prove that the products of inertia are unchanged to first order...but they clearly aren't! This is important, because the authors use this result to derive Euler's equations.

http://tinypic.com/r/b4g3s9/7

Shouldn't there be another term involving the product of inertia? 76.68.247.201 (talk) 18:47, 14 November 2010 (UTC)

As far as I can tell you're right. Either your textbook is clueless or I am. It may be me. Can anybody else take a look at this? -- BenRG (talk) 10:22, 15 November 2010 (UTC)

I concur, the book looks wrong to me. Just looking at the first page, anyway, I get that, e.g., to first order in α, I_xy=-4mα, so unless I'm missing something, problem 7.11 b appears to be asking you to show something that isn't actually true. Red Act (talk) 11:16, 15 November 2010 (UTC)

So what does that imply about Euler's equations? Is there another reason why we'd ignore the products of inertia when finding how the angular momentum changes when an object deviates from its principal axes? 76.68.247.201 (talk) 14:35, 15 November 2010 (UTC)

In Euler's equations (rigid body dynamics)#Motivation and derivation, the derivation uses a coordinate system that's fixed to the body. In a coordinate system like that, the moment of inertia tensor doesn't change at all when the body rotates. Red Act (talk) 02:59, 16 November 2010 (UTC)

You might want to try also asking this question on the Math Reference desk. Ginger Conspiracy (talk) 06:03, 17 November 2010 (UTC)

Looking for a talk that may have been featured on TED

I'm pretty sure that I saw this on TED talks, but either it's not there anymore, or I am remembering it wrong, but either way, I'm looking for a guy who made a speech about a program (an NGO?) that he was running on (west?) Africa helping to alleviate local desertification by introducing herds of large herbivores into fields periodically to allow their hooves to churn up the soil and their manure to fertilize. He talked about how modern agriculture usually pins overgrazing as a cause for desertification, when in fact historically large herds of herbivores would have periodically grazed small areas completely, allowing the plants to recycle and maintaining the ecosystem. Does this ring bells with anyone? I can't find the specific TED talk but I don't really need it if I could just find out the name of the guy. Thanks! 173.183.68.27 (talk) 03:25, 14 November 2010 (UTC)

Found it, not on TED though. The guy was Allan Savory if anyone is interested. 173.183.68.27 (talk) 04:23, 14 November 2010 (UTC)

Why large herbivores? Wouldn't goats do for this sort of thing? Ginger Conspiracy (talk) 08:07, 17 November 2010 (UTC)

Sounds of jupiter

http://www.youtube.com/watch?v=e3fqE01YYWs

It says that sound can exist as electromagnetic vibrations...but that isn't sound, that's light, no? Am I missing something? 76.68.247.201 (talk) 03:28, 14 November 2010 (UTC)

Sound can be defined two ways:

• Pressure waves of a certain range of frequencies within a fluid medium
• The perception caused by vibrations within the ear or other analogous sense organ.

The second definition is key, if you could generate signals to the ear by means other than pressure waves, perhaps one could define that as sound. However, I suspect that under normal circumstances that's unlikely. Sound information can be transmitted via electromagnetic vibrations (that's what radio is), but the information needs to be decoded and broadcast via a speaker of some sort. --Jayron32 03:33, 14 November 2010 (UTC)

Bear in mind that in the very high atmosphere or in outer space, atoms are typically charged. The solar wind is, for some reason I don't understand, a combination of electrons and protons rather than neutral hydrogen atoms. Thus any pressure wave in the medium is going to be involve variations in charge as well.

I am curious whether the various short sounds in the video represent actual changes over time in the medium, or whether they are spatially localized features that the satellite passes through on its orbit. Wnt (talk) 03:48, 14 November 2010 (UTC)

These "sounds of Jupiter" are electromagnetic signals. They are detected by an instrument (in this case, a VHF/UHF radio that flew on the Voyager probe. Those radio signals are measured at several megahertz - and they are mixed down to audible bands by a very common process known as heterodyning. Then, they are played through a speaker. So, if you could fly past Jupiter like Voyager did, and if you could survive "sticking your head out the window", you would not hear these sounds: first, they are not acoustic waves; and second, they are not in the audible frequency range. Interestingly, here on Earth, the equivalent radio-processes occur, but the relevant parameters of our planet's magnetic field are a bit different than Jupiter - so the very low frequency radio chirps here on Earth are at audible frequencies. (They are still not acoustic waves, though - so you still need a radio to hear them). Nimur (talk) 04:23, 14 November 2010 (UTC)

Also, for the advanced readers: there is such a thing as a magneto-acoustic wave - which is a unique coupling of electromagnetic (radio) wave into a pressure disturbance in a sparse plasma). However, the sounds we are hearing in this Jupiter demo-tape are not due to magneto-acoustic waves - they are actually due mostly to electron gyro frequency noise. Anyway, magneto-acoustic waves only occur in sparse plasmas, and the magnitude of the pressure-waves would be too small to be detected with an acoustic microphone - not to mention what would happen if you tried to put a human ear in that environment!) Nimur (talk) 04:26, 14 November 2010 (UTC)

This isn't my field, but the heterodyning you describe sounds like a cheap cheat, and contrary to what the video says are actual vibrations in the auditory range. I see that Voyager could detect ion acoustic waves with its instruments in the 50 Hz to 12000 Hz range.[1] I didn't look for the provenance of this YouTube recording to figure out exactly what is being measured, but I see no reason to think the video isn't right about them being, essentially, a sort of sound. Wnt (talk) 05:03, 14 November 2010 (UTC)

For further information, Magnetosphere of Jupiter is a very complete article. Yes, there is radio-emission in the VLF (audible base-band) range at Jupiter. I am pretty sure the sounds in the Youtube link are down-mixed UHF - but I may be incorrect. To find out for certain, you can compare to NASA's Jupiter Sounds archive - these recordings are each accompanied by a bit of scientific explanation. And if you're very interested, Imke de Pater (arguably the world expert on Jupiter's radio emissions, and planetary science in general) has a paper on Jupiter’s radio spectrum from 74 MHz up to 8 GHz and a website of her own on Jupiter sounds. Like a false color image, these sounds are "false-frequency" audio - the actual source data is pre-processed and output at a range that humans can hear. I would say that this process has limited scientific utility, but sure does sound cool. Nimur (talk) 05:32, 14 November 2010 (UTC)

I saw the date 1979 mentioned, which is when Voyager 2 passed Jupiter, and that article mentions a NASA "Symphonies of the Planets" 5-disk set, from which this audio should have come. It is possible to find out more about the datasets at [2] which has many records for Voyager 2 fluxgate magnetometer readings. Unfortunately, their information for the magnetometer (also linked from the Voyager 2 article) is now giving an error message. [3] describes "dual low field (LFM) and high field magnetometer (HFM) systems. The dual systems provide greater reliability and, in the case of the LFMs, permit the separation of spacecraft magnetic fields from the ambient fields. Additional reliability is achieved through electronic redundancy. The wide dynamic ranges of +/- 0.5 G for the LFMs and +/- 20 G for the HFMs, low quantization uncertainty of +/- 0.002 nT in the most sensitive +/- 8 nT LFM range, low sensor RMS noise level of 0.006 nT, and use of data compaction schemes to optimize the experiment information rate all combine to permit the study of a broad spectrum of phenomena during the mission. Objectives include the study of planetary fields at Jupiter, Saturn, Uranus and Neptune; satellites of these planets; solar wind and satellite interactions with planetary fields; and the large-scale structure and microscale characteristics of the interplanetary magnetic field. The interstellar field may also be measured." Now from the previous reference I take it that stellar winds do involve vibrations in the range of hearing, and the magnetometer is directly measuring some kind of buffeting at the spaceship itself, rather than at a distance by radio. The exact kind of wave, whether it's compression or transverse, I couldn't say from what I've read so far. Wnt (talk) 06:35, 14 November 2010 (UTC)

Just to clarify one thing: the key difference between acoustic- and magneto-acoustic wave is the mechanism of energy transfer. In the case of acoustic waves, the energy is conveyed by inter-atomic collisions. In space plasmas, the densities are far too low to sustain such aerodynamic/acoustic effects. So, energy is mediated between distant ions via ion/electromagnetic-wave interaction. Most of the time, these result in plasma oscillation. In some situations, this interaction can result in a propagating "pressure-front" in the plasma, but the pressures are still near-vacuum, so it's not quite like an ordinary sound wave in air. The question of measuring "at the spaceship" vs. "at a distance by radio" is moot - you are always measuring at the spacecraft. The question is whether the magnetometer is sensitive to ion pressure or magnetic fields - but from its name, it should be obvious that magnetometers measure magnetic field intensity (and typically, because of geometries, magnetometers are sensitive at ultra low frequency). Comparatively, an ion energy spectrometer would actually measure ion impingement; and a dipole electric field antenna would measure electric fields (because of geometries, a whip antenna will be sensitive at much higher frequencies than a similarly-sized loop magnetometer). The crucial piece of physics is that plasma-interactions describe the relationship between all three types of measurements - ion bulk motion, electric field, and magnetic field. Nimur (talk) 18:50, 15 November 2010 (UTC)

Very informative, thanks everyone. 76.68.247.201 (talk) 20:43, 15 November 2010 (UTC)

Middle-grounders on ID--What, If Any, Spokespeople Exist?

It's understood that the subject of what is called Intelligent Design Theory is dominated by those who assert their having already identified good evidence for external involvement in the origin, development, and/or internal workings of Earth and the life on it. What is the status of their claims in terms of whether they have produced even a single piece of purported evidence that has given the actual scientific community at large pause, and what is the nature of any more abstract debate that may be going on about the future prospects for finding such involvement? As the question of the heading asks, are there any substantially middle-of-the-road players who approach the topic holistically without submitting themselves to being committed to employing Occam's Razor?Julzes (talk) 03:37, 14 November 2010 (UTC)

There really aren't many. Intelligent Design isn't a particularly scientific approach towards working out the manner in which the world came to be. It starts with the premise that the Christian God created the world, assumes that to be true, then seeks to find evidence to support that. That particular approach is not very scientific, and most scientists who work in the fields ID also works in dismiss it offhand because of this. You would find many cosmologists, or evolutionary biologists, or geologists who seriously give it credence. Of course, you likely could find somebody, but the preponderance of respected scientists don't take it seriously in any way. However, please note that this doesn't mean that their aren't religious scientists, or that one must support the idea of Intelligent Design (as a specific theory) in order to be religious. I consider myself a rather devout Christian, but I have no pretense towards needing Intelligent Design in order to reconcile the current scientific understanding of the world, including evolution, the big bang, and anything else the ID people don't want to accept, with my religious view. --Jayron32 03:49, 14 November 2010 (UTC)

Few middle of the road people would want to associate themselves with the strong statements of intelligent design or creationism. There are other discussions which are relevant, but not easily related to the traditional debate. For example, the weakless universe thought-experiment sought to disprove the anthropic principle by showing that a less elaborate physics could produce a world like ours. But which side is which — does the anthropic principle show that humans, by possessing an "awareness" relatable in concept to the soul or to God, have participated in the process of creation? Or does the idea that the universe contains extra complexity and wonder unneeded for us to merely exist prove the fecundity of the divine imagination?

A concept which interests me is whether the slow, cold end of the expanding universe is truly a barren dustbin of history, or whether there could be interesting "chemistry" among the remaining small particles — or new ones — when the tick of the clock is a googol of years. For example, picture two neutrinos of opposing weak isospin slowly orbiting one another in empty space. Could the weak force hold them together, despite the short range^[4] of its carrier particle, if you have 10¹⁰⁰ years to wait for the particle to slip out and cross a vast range of empty space "unnoticed". I always see the Heisenberg principle stated as an approximation, after all. Whether the weak force can apply to them or not, or if simply gravity between these tiny particles keeps them clustered, is the angular momentum of the orbit that they make quantized in terms of $\hbar$? Are there discrete photons or gravitomagnetic particles that might cross between them over vast lengths of time, allowing them to interact? There is something aesthetically appealing to me that our world as we know it is still only one of the first few "moments" of the Big Bang, and that a long succession of interesting worlds of physics and chemistry of ever colder temperatures and smaller particles and larger distances still await their time. If successor regimes of physics exist that are also capable of supporting interesting life and thought, then that would pretty much blow the anthropic principle out of the water, and hint rather strongly at some clever design behind the cosmos. I wouldn't say the absence of it is a disproof, however. Wnt (talk) 04:30, 14 November 2010 (UTC)

(ec):::The term "intelligent design" has come to exclusively mean a pretty narrow subset of religious beliefs that directly contradict scientific fact; these views tend to be pretty radical, so I agree with Jayron that there isn't really a "middle ground" for intelligent design. However, the phrase "intelligent design" can also be interpreted in other, more benign ways. Isaac Newton's description of a "clockwork universe theory" could be branded "intelligent design" - but it does not stipulate certain insane ideas like young earth creationism. There is scholarly debate - mostly in the humanities and philosophy, and not in the scientific community per se, about whether the universe is deterministic or random; and whether there is a role for a deity in our scientific understanding of the world. These could be classified as a "middle ground." But I would be very reluctant to label any theory "intelligent design" because that term has come to mean a very specific set of far-flung, radical Christian-inspired ideas. Nimur (talk) 04:36, 14 November 2010 (UTC)

Not quite the subject matter I was trying to address because of how contaminating the influence of ID on 'intelligent design', I suppose. Since I can expect to run up against an edit conflict if I try to fully present what I'm after, and since new Earth creationism has been singled out already, where is old Earth creationism in the debate (particularly with latitude given to the sense of 'create')? What of so-far unknown but plausible influences? Is there any attempt to comprehensively and coherently address plausible specific holes in scientific ontology, or is it entirely each discipline to its specific purview and each scientist to his or her own expertise (which it seems might leave a gap or gaps in reasoning or evidentiary search)?Julzes (talk) 05:51, 14 November 2010 (UTC)

I cannot see how there can be a "middle ground". Either there is or there isn't an intelligent designer. Pretty binary state of affairs there. And there is no point halfway between zero and one in a binary system. HiLo48 (talk) 05:57, 14 November 2010 (UTC)

I think you misunderstand the question. The poster is asking if there is anyone doing or proposing research into detection of intelligent design who is actually acting in good faith. The answer is none that I know of. No one has yet come up with a proposal for how to detect evidence of intelligent interference in the evolution of life. thx1138 (talk) 06:02, 14 November 2010 (UTC)

To do such research would require the hypothesis that there was an intelligent designer. See my comment above. HiLo48 (talk) 06:07, 14 November 2010 (UTC)

One can present a hypothesis and test it without having an opinion on its veracity. thx1138 (talk) 06:25, 14 November 2010 (UTC)

Unless the hypothesis is inherently untestable. Like say the existence of an omnipotent being who can break the laws of science at will. Googlemeister (talk) 16:08, 15 November 2010 (UTC)

There's an article specifically about old Earth creationism. Oddly, it doesn't address what to me seems like the most obvious way to reconcile religious and scientific ideas, which is to recognize that the time scale used in an author's prologue about the writing of a work is not the same as the time scale of the book itself. Just because Tolkien's works cover thousands of years in Middle-Earth doesn't mean it took thousands of years for him to write them, nor does it mean that the writing was in the same order as the plot. It is entirely reasonable in scientific terms to believe that our universe is a lovely four-dimensional sculpture with a splendid internal consistency of design, but that the author isn't finished with it yet. I would suggest that if you look very closely, some of the chisel-marks are still apparent; and it is not hard for anyone to see that there is still some sculpting to be done before perfection can be attained. But these things are primarily if not entirely visible in social terms, in the minds of men, rather than as aberrations in the fundamental rules of science; the purpose of the plan being, I would speculate, that when those who have suffered and striven have developed deep virtues and appreciation, and the cause of their suffering is scoured away as if it never were, one is left not with a meaningless paradise of opium dreams but a real paradise in which all of the joys are rooted in the free will and essence of the people. Wnt (talk) 06:12, 14 November 2010 (UTC)

The only part of your comment that relates to this discussion is your assertion that the chisel marks are still apparent. The original question was, has anyone proposed a scientific approach to looking for such chisel marks? The answer, so far, is no. thx1138 (talk) 06:25, 14 November 2010 (UTC)

It is hard to say what is relevant in such matters, and harder to decide on proof. I would say, for example, that if you look at the film of the funeral following the 16th Street Baptist Church bombing, you see people grieving, from such injustice, and yet so unified, so free from hatred, so unaccountably dignified, and with our retrospective knowledge that their firm faith was such a fundamental turning point toward the end of racial injustice, there is just some overwhelming sense that more than random chance is at work; that they were allied with the Holy Spirit. You can't test something like that with a multimeter. The real miracles aren't the achievement of a mundane end by impossible means, but the achievement of an impossible end by mundane means. Wnt (talk) 07:00, 14 November 2010 (UTC)

In my opinion, what makes the scientific description of the world so fascinating is the idea that surprisingly complex and beautiful results readily spring from such a deceivingly simple looking set of rules. As a student of math I've gotten a front row seat to examples of beauty popping out seemingly from nothing, so I know that it's possible. And yet some people try to convince me that this sort of miracle is a fantasy. They claim that such complexity could only possibly arise from a set of laws that is equally complex (i.e. some active and unpredictable God). This strikes me as a colossal failure of the imagination. I don't ever want to believe that reality is that dull. It's depressing. Rckrone (talk) 17:35, 14 November 2010 (UTC)

Alright, my opinion: There is nothing wrong with intelligent design as a belief: it's entirely unprovable, and entirely unfalsifiable. basically the question is this: do we assume that the universe (as it is) was designed to be as it is, or do we assume that the universe (as it is) is a product of deterministic/random forces. Either is a belief, and neither belief has any real basis in evidence. The problem with (the dumber) elements of ID is that they start making claims that are contrary to our understanding of the universe in order to support their particular understanding of religious texts. That's just narrow-minded. There is no contradiction between religion and science (in fact someone - I forget who - said that faith transcends and incorporates both evidence and belief), except to the extent that people believe they have to oppose one to advance the other. If you think about it, gravity is such a profound statement of belief that it is surprising that physics doesn't have priests.

end opinion. --Ludwigs2 07:31, 14 November 2010 (UTC)

So, people with faith are really nice people, eh? So are most of my friends, and a bunch of more profound non-believers you'd be hard pressed to find anywhere. And didn't Isaac Newton prove gravity with an apple? That sure didn't need any god. HiLo48 (talk) 10:06, 14 November 2010 (UTC)

There is a set of natural laws that describe the falling of an apple, by which you can link the moment when the apple to falling to a future in which it has fallen further by a specified amount. One can postulate that the same moment could be linked to a different moment in which the apple has stopped, or moved sideways, using a different set of physical laws. This is a different dimension of time, moving forward in a different direction from the same moment in spacetime. The known set of laws makes the most sense, because it is what you remember, what you observe, what the textbooks say that you read, what others you speak to have always known. But what if some other set of laws started to acquire some of the same characteristics? What if you have a choice of whether to move your subjective experience entirely in one dimension of time, or in a combination of the two? What if your action in one timeline influences your ability to take part in another? The reason why I emphasize the need of science and faith to respect one another is that while science is the tool to explore a known universe, there may still be some advantage in looking toward others. Wnt (talk) 15:06, 14 November 2010 (UTC)

LOL'ing at the idea that Newton's argument for gravity did not require belief in a God. Take a look at Isaac Newton's religious views sometime, and the role they played in the formation and expression of his theories. As far as Newton was concerned, gravity was an argument for God, the prime mover who set everything in order, and kept it that way... Newton was a very odd duck and neither atheists nor modern Christians will on the whole find much comfort in his views. --Mr.98 (talk) 19:31, 14 November 2010 (UTC)

Rupert Sheldrake's ideas fall somewhere between a religious ID position and the mainstream understanding of evolution by natural selection. To his supporters he's a respectable, educated scientist who is making some imaginative but scientific leaps; his opponents decry his work as "magic". -- Finlay McWalter ☻ Talk 17:46, 15 November 2010 (UTC)

A lot of the UFO believers think aliens have been artificially selecting human evolution for at least millennia, but there's not even any evidence of breeding husbandry in our genetic drift. It sure seems like we've evolved at about the same rate as all the other mammals. But maybe that's not saying much because of the diversity of such rates. We've evolved much faster than horses and much slower than sheep and cattle. Ginger Conspiracy (talk) 06:01, 17 November 2010 (UTC)

Fuzzball vs. Big Rip

The Big Rip hypothesis supposes all space could be torn apart after cosmic expansion gets off the leash. I would assume that a black hole with a mathematical point singularity at the center should be unaffected by this, since there's no one point to be ripped from another (though I suppose a few things falling in the event horizon at the last minute might discover their status is moot). But a fuzzball (string theory) describes an alternate object, the size and mass of a black hole but filled with strings, that already somehow maintains its structure within highly curved spacetime. What happens if one of these goes up against the Big Rip? Wnt (talk) 05:16, 14 November 2010 (UTC)

Considering we know nothing about about: Black holes, Cosmic Rips, fuzzballs or Dark Energy it's gonna be tough to answer your question! :) I mean all those things have theories and math, but no direct observations. (The observations of black holes could also be super massive objects, there is no direct evidence that they are singularities.) Ariel. (talk) 07:11, 14 November 2010 (UTC)

True, there is a certain Godzilla vs. Megalon quality to the question. ;) But it's funny that modern physics has postulated both the irresistible force and the immovable object... Wnt (talk) 15:09, 14 November 2010 (UTC)

See here. Count Iblis (talk) 17:09, 14 November 2010 (UTC)

Interesting. To summarize here, they say that phantom energy (with a speed of sound squared greater than 0 and less than 1, whatever that means) will accrete into a black hole, dominating over Hawking radiation "until it reaches the Planck mass" at a time "near" the Big Rip. As what I get the impression is typical when you start combining event horizons and negamatter (well, negative energy) you end up with "traversable wormholes", or at least a possibility thereof. (but would infinite phantom energy follow you?) All hands, abandon universe! Wnt (talk) 18:54, 14 November 2010 (UTC)

I have a feeling we were just as close to the truth with the Godzilla vs. Megalon analogy. Ginger Conspiracy (talk) 08:04, 17 November 2010 (UTC)

urine

historically, which has been more effective to make the teeth white; brushing with urine or gargling/rinsing with urine —Preceding unsigned comment added by Kj650 (talk • contribs) 11:32, 14 November 2010 (UTC)

This site under a disclaimer that anything it publishes need be true claims that in ancient times, human urine was used as a tooth whitening product. By modern standards of whitening efficacy the answer to the OP is "Neither." but that need not diminish any excuse for trying. Cuddlyable3 (talk) 14:50, 14 November 2010 (UTC) WARNING of explicit picture!

With as much money as people spend on teeth whitening products these days, swishing with pharmacy grade hydrogen peroxide is very economical. It's usually something like $1/liter and actually makes a very good mouthwash in every other respect, as well. Just don't let your lips touch the mouth of the bottle, because any spittle or foreign matter which gets into a bottle of peroxide can catalyze it into ordinary water in a matter of hours. Ginger Conspiracy (talk) 08:02, 17 November 2010 (UTC)

Burping on command

Is there a scientific explanation of how Drumski89 and I can "burp on command"? 173.49.140.141 (talk) 13:04, 14 November 2010 (UTC)

See Belching. Cuddlyable3 (talk) 14:25, 14 November 2010 (UTC)

As burping involves the expelling of air from the oesophagus it is necessary to have air in the stomach in the first place. Repeated burping will exhaust this supply. You have consciously or unknowingly developed the skill of swallowing air to be able to burp at will. This is a very useful skill if you, for some unthinkable reason, lose your larynx as aerophagia facilitates esophageal speech. Some year ago this was bravely used by the actor Jack Hawkins following a condition that required the removal of his larynx. Oddly it does not mention it in his article but I have very clear memories of hearing him being interviewed and collecting an award using this throat voice as it was called. Caesar's Daddy (talk) 16:29, 14 November 2010 (UTC)

I have this particular ...skill... as well. I don't think the air goes down to the stomach with me. I just swallow some air, restrict the lower part of my larynx for a fraction of a second, and let the air out in a constricted burst that makes a sound in my throat. It's a bit different from proper burping, as swallowed air is momentarily stored in a place that feels higher up, rather than being generated in the stomach. The belching article doesn't really properly describe it... 88.112.56.9 (talk) 18:17, 14 November 2010 (UTC)

I agree. For me, I just force air out of my mouth while it's closed (I just try) and then I feel this little bump in the higher part of my larynx, then I burp. Περσεύς|Talk to me 18:20, 14 November 2010 (UTC)

Oh, and you can add my userbox {{User:Perseus, Son of Zeus/UBX/Burp on command}} to your userpage too. I am the same person as 173.49.140.141. Just logged in. Περσεύς|Talk to me 18:21, 14 November 2010 (UTC)

See this diff. Text:

Those who have a desire to learn how to perform esophageal speech, either for impressing (or disgusting) others or as a real way of communicating (in cases such as larynx removal due to cancer, or similar situations), can attempt the following actions which may or may not induce a belch. A)"Wiggling" the throat. Pressing the tip of the tongue forcefully against the lower front teeth should cause the larynx area to move out, causing air to displace into the esophagus. The throat muscles can then be relaxed, and the belch forced out by contracting the diaphragm muscles, or contracting and relaxing the same throat muscles again. B), Breathing air into the stomach. This can be done by inhaling while keeping the throat muscles tight and glottis closed, so that no air can get into the lungs. If the throat is kept closed while still attempting to breathe in, the air should divert into the stomach, then the normal maneuver can be used to belch out the air. Περσεύς|Talk to me 19:26, 14 November 2010 (UTC)

Burping on command (2)

However, I can burp on command without any preparation. Why? Περσεύς|Talk to me 22:21, 14 November 2010 (UTC)

Try this command: Don't! Cuddlyable3 (talk) 23:15, 14 November 2010 (UTC)

Help me find Einstein-quote!

I found a wiki-quote by Einstein: "It has become appallingly obvious that our technology has exceeded our humanity", but sadly it's unsourced, and googling doesn't help. It's a fascinating quote, and I'd love to read it in context. Does anyone know where I can find it? Thanks, Idunius (talk) 15:16, 14 November 2010 (UTC)

Just search with quotes: "It has become appallingly obvious that our technology has exceeded our humanity" then 350,000 hits. —Preceding unsigned comment added by Perseus, Son of Zeus (talk • contribs) 18:24, 14 November 2010 (UTC)

And which of those 350,000 also-unsourced results contains the quote in context? Which of them lists where the quote is originally from? This is what the poster is obviously asking for, not more unsourced quotations. Einstein is one of these figures that people for whatever reason love to attribute quotes to, often without any evidence that he actually said what was being attributed to him. --Mr.98 (talk) 19:19, 14 November 2010 (UTC)

That's the whole quote. Περσεύς|Talk to me 19:36, 14 November 2010 (UTC)

Er no, that's the whole quote that people keep repeating and saying that he said. I assume it was part of a longer statement about some topic or event, or from a book, or in response to a question from someone else. He probably didn't just walk up to a reporter, say it, and then walk away. I remember the lore surrounding some of his other quotes were about nuclear weapons, my WP:OR is that this sounds like it could be a similar theme. DMacks (talk) 19:43, 14 November 2010 (UTC)

As Mr. 98 says, I was hoping to learn the exact source. (Was the context political? Scientific? Is he referring to any specific event?) Is it certain that it's Einstein? I have, as I said, googled already, and I found a plethora of sites with the quote, but not a single reference except just simple statements that it's Einstein. /--Idunius (talk) 19:50, 14 November 2010 (UTC)

The quotation is indeed listed as "Unsourced" by Wikiquote. Cuddlyable3 (talk) 20:04, 14 November 2010 (UTC)

The OP knows that and has said so. He's asking if we can dig up the original source. (There are some days when I find the Ref Desk to be essentially useless! We've just spent six lines telling the OP what he obviously already knows if anyone had bothered to read his or her question for what it straightforwardly said. Blah.) --Mr.98 (talk) 21:24, 14 November 2010 (UTC)

I poked around quite a bit in Google Books — it's a quote that is thrown around dubiously and unsourced again and again. I doubt he actually said it, to be honest. It is probably one of these half-remembered things that has just been passed around for a decade or two. --Mr.98 (talk) 21:27, 14 November 2010 (UTC)

Same here. I also found a German translation, and searched pretty carefully for the entire quote as well as individual words (using Internet search engines as well as searching a digital library of his works). Over and over again, it's attributed to Einstein, but not to a specific writing or lecture. Would be a nice (possibly fruitless, I'll admit) research project, to thread back in the earliest uses of the quote to try and find its source. Would require a very good library. -- Scray (talk) 00:18, 15 November 2010 (UTC)

Ok. I'd still like to thank you for trying! --Idunius (talk) 07:49, 15 November 2010 (UTC)

Some of the best science questions are those we can't answer. -- Scray (talk) 21:52, 15 November 2010 (UTC)

...though this probably doesn't fall into that category, truth be told. It'd be nice to know where the alleged quote came from, but it's not a real secret of the universe. --Mr.98 (talk) 00:17, 16 November 2010 (UTC)

Proton Gun

In an ancient ZX Spectrum game, The Korth Trilogy, the antagonist aliens used "proton guns" that fired a stream of protons at a target that "simply smash atoms to pieces" on their spaceships and used "proton force fields" force defence that operated on the same principle (they would shred any projectile fired through them). They used ships armed with this technology to blockade Earth, but were unable to invade as the guns couldn't be used in an atmosphere as there would be an explosion as soon as the protons hit the atmospheric molecules and the forcefields would overload when flying through the atmosphere due to the constant impact of the same molecules.

Is this at all realistic, or was this simply dramtic license on the part of the author/programmer? Exxolon (talk) 17:44, 14 November 2010 (UTC)

Protons are just hydrogen nuclei and they don't really have any exceptional ability to smash stuff. They do have a positive charge which lets you accelerate them with magnets, so maybe the proton gun makes some sense, but I'd better leave it to one of the engineers to explain why it's more effective to just shoot bullets. The proton force field is pretty much nonsense though. Rckrone (talk) 18:10, 14 November 2010 (UTC)

You can use a particle accelerator in space, sure; see Particle beam weapon. These were investigated quite heavily as part of the Strategic Defense Initiative. I believe that in general using protons would be problematic since they have a positive charge, and generating a negative charge is pretty easy to do. In particle beams that use hydrogen ions (protons), they usually add an electron to them before sending them out, so they are electrically neutral. Anyway, long story short, you can use these, they have some desirable properties and some less desirable ones, but they aren't too essentially different than using a laser or something like that. They have no magical atom smashing properties. In space such weapons are more desirable than on Earth, as I understand it, because the atmosphere would absorb a lot of the energy and make them far less efficient than, say, a stream of bullets. I doubt they'd "blow up" as described; it's more like your particle beam would just be very weak or require exponentially more energy for the same effect. On the other hand, for very long distances in very short timescales (essentially "instantaneous" by human standards), they could be useful, hence their research for missile defense (which would require shooting things hundreds if not thousands of miles away very quickly, for which projectiles — bullets or rockets or kinetic weapons — are ill-suited). --Mr.98 (talk) 20:04, 14 November 2010 (UTC)

Would not a stream of high energy protons be an kinetic weapon just as a stream of bullets? --Gr8xoz (talk) 21:31, 14 November 2010 (UTC)

Maybe in a very literal sense, but I think one can recognize that there are different properties to a stream of blocks of lead and a stream of protons. That's the distinction I'm indicating. --Mr.98 (talk) 23:04, 14 November 2010 (UTC)

Here on earth, we use neutrons to smash atoms. See nuclear fission Googlemeister (talk) 16:03, 15 November 2010 (UTC)

Which is completely irrelevant to this question. But thanks for contributing it anyway! --Mr.98 (talk) 00:15, 16 November 2010 (UTC)

No, a stream of charged particles would be quickly diffused by air. Even if accelerated to several times the speed of bullets, they would diffuse within a few millimeters of air. And you would need a huge tank of hydrogen to match the mass of a single bullet. The amount of energy it would take to ionize that much hydrogen, let alone accelerate it, would be several thousand times the energy of a bullet's gunpowder. Even in space, the like baryonic charges would quickly diffuse the beam and it would spread out into a harmless cloud no more dangerous than solar wind. Heavier nuclei would be better as a weapon, but a free electron laser is probably more suitable for a beam weapon. Ginger Conspiracy (talk) 05:39, 17 November 2010 (UTC)

Here's a good source that details the effectiveness of particle beam weapons. http://www.projectrho.com/rocket/spacegunconvent.php#Particle_Beams ScienceApe (talk) 04:03, 18 November 2010 (UTC)

Different solvents - which are functionally the same?

Knowledge of solvents would be useful to me, as I often find myself having to do difficult cleaning jobs, where it would be disastrous if the underlying thing was damaged or discoloured. For example, I have a lot of hardened drips of emulsion paint (called latex paint in the US) on the surface of gloss paint (called I think oil-based enamel paint in the US). 1) What commonly available solvents would dissolve or soften the emulsion/latex paint, but not affect the gloss/oil-based-enamel paint underneath?

Some personal research shows that nail polish remover does this. The nail polish remover I used appears to be mostly acetone and water. I've also seen a product on the internet that consists mostly of acetone, toluene, a little methanol, (according to its MSDS sheet) and probably water which claims to do this, but which is not easily available in the UK. A comment in an internet forum suggests that methylated spirits/Denatured alcohol may do the same, in other words ethanol.

There are many different solvents. 2) Is it possible to classify them into groups of similar solvents? 3) Will the ethanol in methylated spirits be functionally equivalent to the acetone and toluene, as solvents?

I have dried paint on some polyester clothing. 4) Would the above solvents dissolve the polyester if I tried to clean it with them, or soaked it in them?

There is another solvent in an expensive specialised cleaner spray that I sometimes use: ethylene glycol. 5) Is there another readily available solvent that is functionally the same as ethylene glycol, in other words dissolves the same things and even more importantly does not dissolve the same things? Thanks 92.15.7.155 (talk) 19:18, 14 November 2010 (UTC)

I don't know nearly enough to speak about what will work on paint, but to get you started, the solvents article has groups of common solvents, and rates them based on how polar they are. (A main property distinguishing toluene from water is how much the positive and negative charge on the molecule is split up; molecules with all C and H tend to be pretty non-polar, whereas water has two protons sticking out to one side) Problem: if you know acetone works, what is easier than that? If you check the charts, ethanol is not that different from acetone in some ways, but it has a terminal -OH that makes it a polar protic solvent and greatly increases its hydrogen bonding potential. Again, I don't know what this means for latex and oil paints. Wnt (talk) 19:36, 14 November 2010 (UTC)

I'm a little surprised that you can't buy acetone in the UK - look in a paint store. They may have toluene as well. Ariel. (talk) 01:37, 15 November 2010 (UTC)

How did you manage to infer that? Not the question asked anyway. 92.29.117.14 (talk) 10:54, 15 November 2010 (UTC)

Is there a chemist in the house? The solvent article refers to the Hansen solubility parameter, but I don't really understand it. Nor do I understand this http://www.solublesolutions.com/solvselect.html 92.29.117.14 (talk) 10:52, 15 November 2010 (UTC)

(1) it depends on the chemical details; try acetone and alcohol together; (2) yes, in many different ways, but none of them will help you as much as trial and error, sadly; (3) no, combinations of solvents are often quite different than combinations of their solvency because of molecular-level interactions; (4) there is only one way to find out. What kind of paint? (5) I doubt it, ethylene glycol is very unique in a few important ways. Basically, if you aren't in a position to be able to try a lot of combinations of solvents on small areas where it won't matter if both of the substances get dissolved, you're probably screwed. If you are, do it under a fume hood or in plenty of ventilation. Ginger Conspiracy (talk) 05:53, 17 November 2010 (UTC)

Thanks, is there anything that a non-chemist could read about this? 92.15.28.182 (talk) 18:19, 17 November 2010 (UTC)

Wave pulse from heavy string to light string

When a wave pulse travels from a heavy string to a light string, what happens? Is its behaviour similar to when a pulse travels from a light string to a heavy string (i.e. it is partially transmitted and partially reflected), or is its behaviour different?--220.253.217.130 (talk) 20:15, 14 November 2010 (UTC)

Yes. If we view the string as a transmission line, a part of the pulse energy gets reflected back to the source at any discontinuity such as a change (up or down) in the string weight. This is a simple animation. Cuddlyable3 (talk) 23:27, 14 November 2010 (UTC)

See Also: Impedance matching#Non-electrical examples Hcobb (talk) 03:50, 15 November 2010 (UTC)

Solving coastline paradox

I still don't understand why we can't fix the coastline length precisely via some software, which thoroughly outlines the upscaled coastline and then calculates it length (like tracking down via some flexible stuff and then straightening it to evaluate)? —Preceding unsigned comment added by 89.77.156.31 (talk) 21:53, 14 November 2010 (UTC)

What we would need to fix precisely would be, not the software, but rather, an agreed-upon smallest scale of wiggle we care about. —Steve Summit (talk) 22:45, 14 November 2010 (UTC)

...or, in other words, the "length of the ruler" as described in the Coastline paradox article and the article Cuddylable linked below. —Steve Summit (talk) 23:26, 14 November 2010 (UTC)

The apparent paradox is explained at How Long Is the Coast of Britain? Statistical Self-Similarity and Fractional Dimension. Cuddlyable3 (talk) 23:19, 14 November 2010 (UTC)

The obvious answer is that the coastline is as long as a ship would take to sail around it. The ship is not going to make minute acrobatic curves just to stay a fixed distance from the caost... This is a better solution than a "length of the ruler" version. Just work with a real ship under real conditions. 91.183.62.45 (talk) 23:52, 14 November 2010 (UTC)

A rowboat or a supertanker? —Steve Summit (talk) 00:06, 15 November 2010 (UTC)

Italy ? Cuddlyable3 (talk) 17:00, 15 November 2010 (UTC)

People make useful and functional measurements of coastlines all the time. The paradox does not preclude this, but instead refers to the notion of well-defined exact measurement in a model system. The apparent paradox is that the observed length depends on the scale of measurement. The method you mention could be used to take such a measurement, but this does not matter at all in terms of `solving' the paradox. SemanticMantis (talk) 00:56, 15 November 2010 (UTC)

There is no paradox here at all. There are two empirical observations, made originally by Lewis Fry Richardson and subsequently put into a wider mathematical context by Mandelbrot:

1. The measured length of a coastline (or any other natural border) depends on the measurement scale (informally, the "ruler length"). This appears strange at first glance, but is actually not that surprising - even the mesaured distance around a perfectly circular island would depend on whether you were sailing round it in a supertanker or a rowing boat.
2. The measured length of a coastline (or any other natural border) does not seem to tend to a finite limit as the measurement scale is made smaller and smaller. This is counterintuitive, and is how coastlines differ from smooth curves such as circles. We can assign a definite length to a smooth curve by finding the limit of the measured length for smaller and smaller measurement scales - in effect, the curve is "straightened" by examining it at smaller and smaller scales. Mandelbrot showed that this limiting process does not work for (most) fractals, and so he interpreted Richardson's research as evidence that coastlines and other natural objects are more closely modelled by fractals than by smooth curves. Gandalf61 (talk) 11:37, 15 November 2010 (UTC)

I still don't fully understand how this applies to real coastlines as opposed to theoretical ones you might find in a math text. Below a certain scale (A few meters) there IS no coastline, fractal or otherwise, there's just a beach. The coastline is a theoretical average of the waterlevels at various times of the day, year, and even minute. That must surely follow a curved line and not a jagged one (Whoever heard of a jagged average?).

It's often implied in these sorts of discussions that the ocean is this frozen, unmoving zone and that individual grains of sand could be definitively assigned to either the ocean or the shore. APL (talk) 22:18, 15 November 2010 (UTC)

Well, not all coastlines are gently curved sandy beaches, of course.

Suppose you've got a coastline that's jagged rock. Which jags are you going to measure, and which not?

And then there are river mouths. Where a river reaches the sea, and gets wider and wider until it forms a bay, how do you measure that? If you "walked along the shore", you could end up walking dozens (perhaps hundreds) of miles inland.

I'm not saying choices couldn't be made about how to answer each of these questions. But the whole point is that that there's clearly no one, single, obvious answer. And every different answer yields a different coastline length. —Steve Summit (talk) 00:43, 16 November 2010 (UTC)

As a practical matter, the length of a coastline is the distance a typical commercial boat needs to navigate safely and conveniently at low tide while staying in sight of the shore. This means there are some granularities of coastal features which measure longer than others with the same geodetic distance from start to finish, as you would expect, but shoals will cause more variation than fjords. Ginger Conspiracy (talk) 07:45, 17 November 2010 (UTC)

FTL communication?

Alice and Bob are 1 ly apart. This should mean that it would take at least 1 yr for Alice to send a message to Bob. However, what if Alice has a pole that's 1 ly long, and she taps on it repeatedly to send Bob a message in binary? Why wouldn't this work? --75.33.217.61 (talk) 22:07, 14 November 2010 (UTC)

Someone asked this a few weeks ago, but I can't find it in the archives. SmartSE (talk) 22:29, 14 November 2010 (UTC)

Wikipedia:Reference_desk/Archives/Science/2010_October_24#Light_speed_and_giant_sticks. APL (talk) 22:25, 15 November 2010 (UTC)

I think we get this question once a month on here? It doesn't work because the pole is not truly rigid — it's a bunch of discrete atoms connected by electron orbits and somesuch, and conveying the "tapping" (or rotating, or whatever) means each atom has to move, turning the atom next to it, at a speed around speed of sound in the material in question. It's not instantaneous. Being perfectly rigid would mean transferring the atoms at infinite speed, which obviously doesn't happen. --Mr.98 (talk) 22:31, 14 November 2010 (UTC)