Wikipedia:Reference desk/Archives/Science/2013 July 9

= July 9 =

Can an echo be reborn?
If the history books I read as a child tell it true, King Midas once grew donkey ears and some gossipy fellow couldn't resist at least telling the reeds. The reeds carried his words and wouldn't let them go, and eventually they got back to the king (or one of his crew).

Now, I know there is considerable evidence to suggest all fables are bullshit, and none showing that reeds (or any crop) do this. But could even one word's worth of sound, after being reflected, absorbed and distorted throughout the world, ever be bounced back together, just by chance? Or are the waves lost forever (like scrambled eggs) if they don't reach a microphone?

If it makes it simpler, could it happen if Earth was encased in a bubble, and nothing reached space?

I'm not asking if it is likely (it's not). And I realize that if it could happen, it would be far too quiet to hear with ears (human or donkey) and in a far away place and time from the speaker or the king. But is it theoretically possible?

Also, where's the "echoiest" place on Earth, in fidelity and/or number of echoes? InedibleHulk (talk) 07:19, 9 July 2013 (UTC)


 * Nevermind. I was thinking of a sound wave as actual particles. Not the case. Stupid question.


 * The second one's still open, though. Google's not helping, but maybe I just can't guess the phrase. InedibleHulk (talk) 09:13, 9 July 2013 (UTC)


 * You may wish to read Whispering gallery, and Hair cell in which things a bit like reeds amplify sound (but much smaller in scale). With modern recording technology this can be done with your phone. Graeme Bartlett (talk) 11:43, 9 July 2013 (UTC)
 * Hadn't thought about the similarities in reeds and hairs. Thanks. Wasn't aware of whispering galleries. Pretty spiffy! InedibleHulk (talk) 22:40, 9 July 2013 (UTC)

If you wait long enough, this is how it would happen. Count Iblis (talk) 14:56, 9 July 2013 (UTC)
 * Might be a long wait before I finish that paper, too. A bit over my head. But from what I did understand in skimming, seems like it might be interesting. InedibleHulk (talk) 22:40, 9 July 2013 (UTC)
 * The problem with the OP's question - and with Count Iblis' piano-in-a-box thought-experiment, is that nobody has specified how similar a newly-created sound (or a piano) need be before we consider it identical to the original. Without a measure of similarity, we can't estimate the probabilities with any confidence, except in the extreme case (exactly-identical thermodynamic state, like in the paper Count Iblis linked).  In the case of a sound wave, an exact waveform match is less probable than a perceptually similar sound wave.  In the case of a piano, there are huge swathes - disjoint and unconnected - scattered throughout the total space of available thermodynamic states, in which we would say "a piano is present," but they are unlike the original piano.
 * My point is, we can't be quantitative about the probabilities unless we constrain the problem better. Nimur (talk) 15:18, 9 July 2013 (UTC)
 * Similar enough that a person could (when amplified) recognize the word (say "swordfish"), but not necessarilly recognize the voice, I guess? InedibleHulk (talk) 22:40, 9 July 2013 (UTC)
 * This strays into the... "science"... of EVPs, that ever-popular hallucination game of popular ghost hunting films. Since you can hear, by random chance, voice-like phenomena in white noise every now and then, it stands to reason that eventually words will "echo back" in a very, very loose sense.  The catch being that they will echo back with no more likelihood than if they had not been spoken the first time.
 * Of course, if the NSA has planted listening devices in the reeds, all bets are off - which points out that we're making some assumptions about the landscape. They're probably very reasonable assumptions, but it would be interesting to hear a physicsey way of expressing what they are. Wnt (talk) 20:42, 9 July 2013 (UTC)
 * Yeah, I suppose that's true. Could sound like the original word, but be made by entirely different vibrations. Sort of how (speaking of ghosts) people can look just like old portraits without containing the exact elements, or what came out of the end of a teleporter (theoretically) wouldn't be you, just an exact copy.


 * And yeah, the US has certainly made reeds and echoes obsolete. The joke about cornfields having ears is creepier than funny now (though it never was exactly funny). InedibleHulk (talk) 22:40, 9 July 2013 (UTC)

Imported Fizzy drink tastes
I've always wondered, can the taste of fizzy drinks change if they're imported by airplane? Can the altitude some how affect the taste? Clover345 (talk) 15:25, 9 July 2013 (UTC)
 * Remember, most of the name brand soft drinks are produced locally with only the concentrate being imported in. So the ingredients used in the final product may not be identical in two different countries. I know this isn't what you asked but I thought it might be relevant. StewieCartman (talk) 15:51, 9 July 2013 (UTC)


 * Carbonated drinks do taste different (as do many other foods and drinks) if you consume them while your at high altitude. However, taking the can up to 40,000 feet, then bringing it back down again can't affect the taste because the can is pressurized by the CO2 inside and the pressure of the contents won't change by any significant amount at altitude.


 * I agree with User:StewieCartman that any taste differences are due to the difference between canning plants and minerals and other impurities in the water that they use. It's also well-known that both Pepsi and Coke change their formulations from one country to the next to cater to local tastes.


 * SteveBaker (talk) 16:54, 9 July 2013 (UTC)


 * Coca-cola points out that "Independent bottlers are allowed to sweeten the drink according to local tastes.". SteveBaker (talk) 17:02, 9 July 2013 (UTC)


 * Yeah, somewhat famously the sweetener used in soft drinks varies by country of production. Such as one place may use corn-based sugar, another sugar cane - some say the latter is quite a bit better. 88.112.41.6 (talk) 19:17, 9 July 2013 (UTC)


 * So, I think we agree: Imported drinks taste different from locally produced versions of the exact same brand - but that's not because they've been imported by plane - they'd taste just as different if brought in by ship or truck or whatever. SteveBaker (talk) 15:11, 10 July 2013 (UTC)

Crustaceans
Do coast-dwelling crustaceans prefer course grained sediments over fine grained sediments?99.146.124.35 (talk) 23:19, 9 July 2013 (UTC)

In particular, I want to know about other crustaceans besides crabs. I have already learned a lot about crabs grain size preferences.--99.146.124.35 (talk) 23:21, 9 July 2013 (UTC)

Metal-free
Over the past 15 years or so, a fringe group has developed that desires things to be "metal-free" to avoid the effects of metal on the human body. Without getting into politics about whether these groups consist of left-wing kooks or holistic visionaries, I'd just like to ask a question about ceramics, which seem to be fine according to such thinking.

For example, while the dental implant has historically been made of titanium, there are now ceramic implants available for those who'd like to avoid metal for one reason or another (holistics, esthetics, etc.). I understand how having a white or pink implant might be beneficial from an esthetic perspective (because zirconia can be colored), but if the point is to avoid metal, isn't ceramic just a metal oxide? I mean, zirconia is zirconium oxide (ZrO2), and zirconium is a metallic element. Conceptually (or, perhaps actually), does the oxide prevent it from leaching out elemental metal into the body? I remember reading about toxic waste being stored in the ground in the Yucca Mountain in ceramic casks because metal casks can rust (oxidize) and allow for leakage, while ceramic (metal oxides) take that many more hundreds of thousands of years to break down because it can't oxidize, already being a metal oxide.

Thanks!  DRosenbach  ( Talk 23:39, 9 July 2013 (UTC)
 * Ceramics are not just "metal oxides". See ceramic for more details.  -- Jayron  32  00:07, 10 July 2013 (UTC)


 * If you wanted to avoid corrosive gasses, would you have to avoid table salt because it contains chlorine? μηδείς (talk) 01:41, 10 July 2013 (UTC)


 * Please tell me, Medeis, you are being facetious, because it is hard to tell, and if I'm going to give a chemistry lesson, I'd hate to waste my time if you really don't need it. -- Jayron  32  02:32, 10 July 2013 (UTC)


 * I think it's clear that Medeis was being facetious. The basic point, which Jayron of course understands perfectly, is that compounds that contain metallic elements generally don't have metallic properties.  For example granite contains substantial amounts of aluminum, but isn't the least bit metallic. Looie496 (talk) 02:38, 10 July 2013 (UTC)


 * I was not being facetious. Metallic oxides and other compounds with metals are not necessarily metallic in their behavior, while certain organic films are, I believe, metallic in their behavior.  Of course the burden of explanation lies on the anti-mettalite.  Do the abjure Iron and Magnesium and Zinc?  If so, they die or live as hypocrites.  If all they abjure are metallic substances they have a liimited life available. μηδείς (talk) 03:15, 10 July 2013 (UTC)
 * You really believe that table salt contains corrosive chlorine gas? -- Jayron  32  03:23, 10 July 2013 (UTC)
 * Without knowing the nature of the original poster's friend's objection, we can't take this chlorine analogy in a relevant direction. Obviously salt doesn't contain chlorine as a "corrosive gas", but it does contain chlorine. Unless we have some idea what is really meant by "metal", we can't tell if salt is a good "look how ridiculous it sounds" demonstration or is off-topic because the concern is really "the presence of the atoms in any form" (and without knowing why that might matter...). Metal-containing compounds without "metallic" properties still could each metal atoms, and pieces of metal can leach metal atoms...once the atoms are out, maybe it doesn't matter what their former form was ("chemicals have no memory"). Or maybe the original forms are so different that they do not leach the same types of ions (or don't leach at all), in which case the salt analogy is relevant. DMacks (talk) 05:30, 10 July 2013 (UTC)
 * Note also that table salt is more direct analogue, since Sodium is a metal. I, for one, found μηδείς response quite appropriate. Putting on my whacko-head, I assume that a "metal" is anything that is highly refined and looks silvery/shiny. Salt is not a metal, but a "crystal", and crystals are, of course, good.  But (science head back on), some ceramics are very resistant to both wear and chemical attacks, and even if some material is lost, it tends to be in a highly reduced, stable, inert form. So the premise is whacko, but the method makes some sense if one buys the premise. --Stephan Schulz (talk) 06:30, 10 July 2013 (UTC)
 * Per Stephan, the OP's fringe acquaintances might be "right" – sort of, in a manner of speaking – albeit by an entirely specious ("wrong") chain of reasoning. The bioavailability and potential toxicity of metals in the body certainly and unquestionably often depends on their oxidation state and the presence and/or type of complexing ligands.  For instance, metallic chromium (Cr(0), as chrome plating, say) is pretty harmless.  Cr(III) may be an essential dietary element in trace amounts.  Cr(VI) is a potent carcinogen.  Organometallic compounds of lead or mercury are often dramatically more toxic than the corresponding pure metals.  On the other hand, while many barium compounds are highly toxic, the barium sulfate suspension used as a radiological contrast agent is largely harmless, because the sulfate salt is so poorly water soluble.
 * It is possible that the solubility (and/or reactivity, and/or bioavailability) of oxidized/complexed metals in the ceramic or polymeric preparations used in medical implants is generally lower than it would be if those same metals were in their native, reduced, metallic form. But at best this might represent a 'rule of thumb' guesstimate, rather than an absolute etched-in-stone "shiny metal is worse for you" principle&mdash;I would be inclined to check against actual published data and known properties of the metals and compounds in question.  And of course the metal used in the metallic implant is seldom the same metal that is used in the ceramic implant (in DRosenbach's example, a zirconium compound is substituted for titanium) so it's very much an apples to oranges comparison.  TenOfAllTrades(talk) 14:44, 10 July 2013 (UTC)


 * As usual, these crazy fringe ideas don't hold muster. Avoiding compounds containing metal is utterly impossible.  Your brain works by maintaining sodium and potassium ions in various states of disequilibrium - and if you eliminate those two metals from your diet, you'll die.  Technically, hydrogen is also a metal - so you'd have to stop drinking water, which would erase these crazies from the gene pool fast enough to warrant a well-deserved Darwin award!


 * So we have to assume that they're really trying to eliminate atomic metals - not compounded with other elements - and thats much more practical. Non-compounded metals would have been pretty rare during early human evolution - and not really necessary to survival...so I suppose that a sufficiently determined bunch of loonies could get together some kind of an off-the-grid society that espoused eschewed un-compounded metals.


 * This is a slightly strange set of beliefs though. There are some pure metals (mercury for example) that are quite toxic and should justifiably be avoided at all costs - and others (such as titanium) which the body not only tolerates but seems to seek to actively join with that are very useful in medicine (artificial joint implants, for example).  Certainly we haven't evolved any particular tolerance or intolerance for pure metals as a whole because such things were not present in our environment through most of our evolution.  What effects pure metal have on us is largely a matter of luck.


 * But to focus on pure metals is weird. Take, for example silver...it's a mild antimicrobial agent, which makes it useful - it's biologically inactive - and even if consumed in huge enough quantities, it only causes argyria (which is an embarrassing, but not dangerous, medical condition that irreversibly turns your skin blue).  On the other hand, many simple compounds of silver are nasty poisons.  On the other hand, look at sodium - which as a pure metal would instantly lethal - but compounded with chlorine (another nasty poison) produces table salt, without which we would die.


 * As a practical matter though, our bodies need metal compounds - our blood contains iron in the haemoglobin that carries oxygen through our tissues - we need to eat iron-containing compounds or we'll die, but swallowing a handful of steel ball-bearings doesn't have a whole lot of effect, except that you'll be shitting ball-bearings for a while afterwards. (WARNING: Don't do this!)


 * So whether you choose elemental metals or compounded metals as a fundamental rule of life just doesn't make sense. Why eliminate the benefits of silver just because mercury is so nasty?


 * SteveBaker (talk) 15:05, 10 July 2013 (UTC)
 * Eschewed, not espoused. But an excellent post, as always. Tevildo (talk) 20:59, 10 July 2013 (UTC)
 * Ooopsie! I corrected it - thanks! SteveBaker (talk) 14:16, 11 July 2013 (UTC)
 * Note that argyria specifies that the silver is converted to the sulfide and other compounds when brought into the body, and converted back to the metal by UV irradiation of the skin. (Though until I see a picture of a modest subject with unpigmented regions where he traditionally wears clothing, I'm not sure I believe it)  The invasion of large particles of metal through the body and their orderly dissemination throughout the skin seems hard to picture, though. Wnt (talk) 21:40, 10 July 2013 (UTC)
 * Yep. But since the silver is in the skin for keeps - eventually, enough UV light arrives to turn the victim blue - although it might take years for the condition to...erm...develop (photography joke!).  So while there may initially be unpigmented regions under clothing, they will eventually turn blue.  It's weird that something so seemingly dramatic and obviously not right could be essentially medicaly harmless and yet completely irreversible.  However, we're getting a bit off-topic here! SteveBaker (talk) 14:16, 11 July 2013 (UTC)
 * something so seemingly dramatic and obviously not right could be essentially medicaly harmless and yet completely irreversible...see also tattoo. The ability to trap and retain insoluble pigments in certain layers of the skin is well-known. TenOfAllTrades(talk) 15:00, 11 July 2013 (UTC)