Wikipedia:Reference desk/Archives/Science/2008 January 29

= January 29 =

Alkaline drinking water
I saw this advertised on TV today: a machine that makes your drinking water more alkaline (to a pH of about 10) so that it supposedly neutralizes the harmful health effects of acidic soft drinks. Is there any scientific basis for this? Wouldn't the alkalinity actually make you sicker? --Anakata (talk) 01:01, 29 January 2008 (UTC)


 * I'd certainly have thought so. If it didn't give you acid burns to your throat on the way down, it would certainly have a good go at neutralising the acid in your stomach. Acidic soft drinks are certainly less acidic than your stomach acid, so if anything they would make your stomach less acidic. -mattbuck 01:23, 29 January 2008 (UTC)


 * Mild alkalinity isn't any worse for you than mild acidity is. Your stomach is already highly acidic, so a little acid or base either way isn't generally going to make any difference at all.
 * The harmful effects of the acidity in soft drinks are, I believe, the way they dissolve your teeth. So unless you took a quick drink of your allegedly-neutralizing tap water immediately after every soft drink you drank, I can't see this claim as having any validity. —Steve Summit (talk) 01:17, 29 January 2008 (UTC)


 * Have a good read of this before you buy anything. There is a heck of a lot of water-related quackery about. --Kurt Shaped Box (talk) 01:29, 29 January 2008 (UTC)


 * What you really want is this stuff. Someguy1221 (talk) 01:33, 29 January 2008 (UTC)


 * Heh. I remember seeing some new-age crackpot selling (expensive) little bottles of 'activated water concentrate' on one of those TV shopping channels a couple of years ago... --Kurt Shaped Box (talk) 01:45, 29 January 2008 (UTC)


 * Read about Phosphoric acid. It's pretty bad for you, and I'm not so sure that neutralizing it in the stomach will be all that effective. Ariel. (talk) 02:27, 29 January 2008 (UTC)


 * Phosphoric acid isn't "pretty bad". It is even an essential molecule for the cell - think of ATP hydrolysis, lots of phosphoric acid is created that way constantly. Nucleotidases hydrolyse phosphoesters in usual food, so, as far as I can see, phosphorus can only get into the body as phosphoric acid (or as some form of phosphate which rapidly attains equilibrium with the acid by taking up protons, and the other way around) in larger amounts. So virtually all the phosphorus that we need, including the phosphorus that ends as bone minerals, enters the body as phosphoric acid. The Wikipedia article mentions some studies which don't seem to contradict my assumption. Icek (talk) 21:06, 29 January 2008 (UTC)
 * Addendum: Nucleotides are not the only phosphoesters; there are also phosphorylated proteins, but I suspect that they're also largely hydrolysed in the stomach (are there digestive proteases which produce phosphorylated single amino acids from phosphorylated peptides?). Icek (talk) 21:11, 29 January 2008 (UTC)

Global Warming/Greenhouse Gases
The Wikipedia article on global warming shows percent ranges for greenhouse gases: 36-70% water vapor, 9-26% CO2, 4-9% methane, and 3-7% ozone. It seems to me the range for water vapor is impossible. If water vapor was under 58% it would be impossible to have 100% of greenhouse gases represented. I understand there are minor greenhouse gases that may be included, but nowhere near enough to make the percents come out to 100%. I would appreciate an explanation as I am using this data in a speech on climate change. Roy Mc (talk) 02:06, 29 January 2008 (UTC)


 * Like everything to do with global warming there are 1 billion sources saying 1 billion different things. It was (almost) universally accepted for a long time that water vapour contributed 95% - 98%. You would need to see check the sources from the article to figure this out.--155.144.251.120 (talk) 02:47, 29 January 2008 (UTC)


 * The problem is one of non-linearity and what does one mean by percentage of greenhouse gases (GHGs). If you remove all GHGs from the atmosphere except water vapor, then ~70% of the greenhouse effect would remain.  In this sense water vapor is 70% of the effect.  However, if you remove the water vapor from the atmosphere and leave the rest, then the remaining GHGs still absorb 64% of the affected radiation.  In this sense the water vapor only contributed 36% of the total.  The problem is that GHGs have overlapping absorption bands, so a portion of the radiation absorbed by water vapor can be absorbed by CO2, etc. and vice versa.  Hence assigning a percentage to any particular gas is rather ill-defined.  Dragons flight (talk) 10:16, 29 January 2008 (UTC)

Are these whales using tools?
See crows using "tools" here and chimps here, I was wondering if humpback whales using bubbles to "net" herring , are also animals that are using tools? Julia Rossi (talk) 02:33, 29 January 2008 (UTC)

There's a species of shrimp which snaps its claws together to create a sound shock that stuns nearby shrimp. Is that a tool? The question here is, what do you define as a tool?18.96.7.80 (talk) 02:46, 29 January 2008 (UTC)


 * Clever little shrimp. I'm wondering what defines a tool and how much consciousness goes into making it for use. If a tool is a device used with conscious intent, technique's in there too... In the article about the apes scientists are excited because it's to do with the human evolution scale. What happens to that when you say more than chimps use tools? Julia Rossi (talk) 03:11, 29 January 2008 (UTC)


 * See sonoluminescence for the shrimp's thing Robinh (talk) 15:48, 29 January 2008 (UTC)
 * Animal cognition.....I've seen people make the distinction between species that just use an available item as a tool and species that take an active role in making a tool or at least modifying a naturally occurring object so as to make it into a more efficient tool. These folks describe the whales as using a tool. --JWSchmidt (talk) 03:21, 29 January 2008 (UTC)


 * And then of course there's the question of what constitutes consciousness. It looks like a certain animal is "using" a "tool", but is it (a) innate/instinctive behavior, (b) accidentally discovered and remembered behavior, (c) learned behavior, or (d) deliberately contrived behavior? —Steve Summit (talk) 03:33, 29 January 2008 (UTC)


 * That makes it interesting – does this mean there's a difference between awareness of self and others, then self and things, and self and things and others? (If) a tool is one thing connecting a creature with another, a task or an outcome, is any animal known to use a "machine", then ? like a simple two-part tool. —Preceding unsigned comment added by Julia Rossi (talk • contribs) 05:04, 29 January 2008 (UTC)


 * Personally I'd say no, that's not tool use. They aren't modifying anything; it's something their bodies can produce. Skunks aren't using tools when they spray someone. If we expand tool use to include physiological products of animals then we've destroyed the meaning of the word. Intentionality is necessary, but not sufficient, for something to be tool use. Whales using bubbles are not even in the running. Something much more on the edge would be a beaver dam, which is clearly a very complicated modification of existing resources for a very purposeful end, though they are not adaptable (it is clearly a very straightforward evolved instinct). --24.147.69.31 (talk) 14:42, 29 January 2008 (UTC)


 * Someone always chimes in with this, so I'll be the one today: whatever answer you arrive at will tell you more about the meaning of the word "tool" than the cognitive abilities of that animal. --Sean 14:48, 29 January 2008 (UTC)
 * Haha. Very enlightening. Thanks, all. Julia Rossi (talk) 02:55, 30 January 2008 (UTC)


 * Here's a recent article on how the brain thinks about tools.   --Sean 14:03, 30 January 2008 (UTC)

Does light have a finite distance it can cover?
My question is about the distance light can travel. Does it go on forever or does it "weaken" over distance eventually coming to a "stop" or "disappearing?" If I was in outter space and shone on of those million candle watt power flashlights toward a nearby star, will the light ever reach there? If not, what happens to it? —Preceding unsigned comment added by 216.154.19.46 (talk) 03:12, 29 January 2008 (UTC)
 * Currently accepted theories do not provide any mechanism for light traveling in a vacuum to weaken, stop, or disappear. (See tired light for a speculative idea that's not currently accepted -- not sure it's been definitively refuted but there's not much evidence for it and no theoretical basis to believe it).
 * However light does spread out, and become less intense that way. Even lasers (see diffraction). So while the photons from your flashlight will eventually get to the distance of the nearest star, I think there won't be enough of them in any reasonable amount of area for anyone to pick up a signal from you that way. --Trovatore (talk) 03:22, 29 January 2008 (UTC)


 * ... and if the light is travelling for a very long distance then it becomes redshifted due to the metric expansion of space - although it has to be travelling for hundreds of millions of years for this to have a significant effect. But we can see light from distant quasars such as 3C 273 which has been travelling for thousands of millions of years. Gandalf61 (talk) 07:20, 29 January 2008 (UTC)


 * See Extinction (astronomy) for a discussion of how far light can go without bumping into too many bits of dust. --Sean 14:50, 29 January 2008 (UTC)


 * It might be werth mentioning that at the speed of light, time stands still, which is why there is no break down. See general relativity.--155.144.251.120 (talk) 22:24, 29 January 2008 (UTC)

I think that in space there probably is a tiny bit of gas, and debris drifting around so it will weaken eventually. My guess is that it will go a lot further than it will on Earth.KarateKid101 (talk) 10:32, 3 February 2008 (UTC)

the mute button
I can always hear things very slightly when it's "muted".. from TVs to my headphones. Is this a psychological phenomenon or real? D\=&lt; (talk) 03:46, 29 January 2008 (UTC)


 * I, too, hear this - indeed, I find that "mute" is louder than turning the volume control all the way to zero. DuncanHill (talk) 03:47, 29 January 2008 (UTC)
 * Yeah I agree. Why do they do this.. is there some property of resistors that when they're considering a rating for the "muted" resistor past a certain point it's too big/expensive/hot to go any more powerful? --D\=&lt; (talk) 03:52, 29 January 2008 (UTC)


 * There's no practical reason (e.g., "resistors") why mute has to be set to any particular volume, zero or not. Me, I tend to like the approach Sony sometime uses where "mute" is 20 dB down from the unmuted volume. But on our current Sony DSP-based receiver, "mute" is absolute; no sound/infinite attenuation. And in that receiver, it's all firmware-determined; no resistors are involved.


 * Atlant (talk) 11:58, 29 January 2008 (UTC)


 * My television has three settings that it toggles through on the mute button: Full Sound, Half Sound, No Sound. I assume they figure that some people want to just make the TV quieter and not get rid of all the sound. --  k a i n a w &trade; 15:12, 29 January 2008 (UTC)


 * You're not hallucinating. Mute is often accomplished by switching on a transistor somewhere in the pre-amplifier that shorts the audio to ground. That transistor, no matter how hard you turn it on, will have some slight resistance to it, and that will leave a tiny amount of audio to pass through to the amplifier. Also, you can get something like crosstalk from the proximity of parts of the circuit with audio on them to parts that are beyond the mute circuit. Power circuits like the final amplifier are made unhappy by having their load instantaneously switched in and out, so they don't just cut the output leads for mute, which would eliminate all sound. --Milkbreath (talk) 12:55, 30 January 2008 (UTC)


 * I seem to notice a similar phenomenon, but with video instead of audio. In some channels that I don't have but almost have, or with channels that I have but are so staticy and mute that they're nearly useless, I seem to notice the image move up and down, but occasionally especially with the ones that aren't just random static, it's possible to notice faint images of people or other images, but only with the channels that I do have is this effect pronouced, with the channels that I don't have the images are so barely noticeable that it's hard to tell if you're actually seeing them or hypnotised by the static, so the images are effectively useless, but with the ones that are pure random static you can't pick up any image at all. Thanks. ~ A H  1 (TCU) 19:20, 1 February 2008 (UTC)


 * "They're heeee-eeere..."


 * Atlant (talk) 18:00, 2 February 2008 (UTC)

Gravity
I hope this question makes sense, since I am rather scientifically illiterate...but how big does something have to be before it has a gravitational pull? Is it relative, by which I mean will something very very small, like a mosquito, be affected by something relatively enormous, like a person? Adam Bishop (talk) 08:55, 29 January 2008 (UTC)
 * Anything with mass has "pull", as Gravitation notes in the intro. If you mean, how big does it have to be before you notice it, that depends on how sensitive your detector is. Clarityfiend (talk) 09:37, 29 January 2008 (UTC)


 * Newton's law of universal gravitation tell us that every object in the universe attracts every other object with a force that is is proportional to the product of their two masses and inversely proportional to the square of the distance between them. Einstein's theory of general relativity provides a more sophisticated and more precise theory of gravity, but in almost all circumstances it gives essentially the same results as Newton's law. So, yes, a person will gravitationally attract a mosquito - and, by Newton's third law, the mosquito attracts the person with the same force. The gravitational attraction between two such relatively small objects is very tiny, but it can be measured with sufficiently sensitive apparatus - see our article on the Cavendish experiment. Gandalf61 (talk) 09:37, 29 January 2008 (UTC)


 * As a follow-up, the reason that you're asking "how big" is that (relative to the other fundamental interactions), gravity is weak. It's 1036 times weaker than electromagnetic force, which is the other fundamental action responsible for most of our day-to-day experience.  As that orders of magnitude article suggests, there's virtually nothing about 1036 for common sense to grasp on (best approximation I found: one atom to the number of atoms in all humans everywhere).  Consequently, the masses in question also have to be far larger than what everyday experience grasps before the gravitational interaction becomes meaningful outside a laboratory environment. &mdash; Lomn 14:01, 29 January 2008 (UTC)

I should also note that size isn't a factor. It's mass. You can have a hot air baloon the size of Venus, but it won't have as much gravity as a neutron star, which is smaller in size. 64.236.121.129 (talk) 15:08, 29 January 2008 (UTC)

Cool, thanks everyone! Adam Bishop (talk) 17:13, 29 January 2008 (UTC)


 * Just to give a specific example, if a mosquito weighing 2 mg (about 1/14,000 ounce) is 1 meter (about 3'3") away from a person weighing 60 kg (132 pounds), then it is attracted to the person with a gravitational force of 8 femtonewtons, or about 1/35,000,000,000,000 of an ounce of force. And the person is attracted to the mosquito by the same force, because gravity works symmetrically.  It really is a very weak force until you get planet-sized masses involved.  --Anonymous, 02:40 UTC, January 30, 2008.


 * Lomn said gravity is 10^36 times weaker than the electromagnetic force. That is incorrect. Finding such a value requires dividing electric charge by mass. — Daniel 04:39, 30 January 2008 (UTC)
 * It's approximately correct; certainly it's correct enough for a discussion of why we don't find gravity to be practically relevant until we get to planet-sized masses. &mdash; Lomn 14:14, 30 January 2008 (UTC)

Expansion and contraction
I have an aluminum rod stuck in a brass pipe by nothing more than slight hand pressure. Now it is impossible to separate them. I've tried usign cold to shrink them and heat to eaxpand them but nothing. Is the cold shrinking the pipe more than the rod or is the heat expanding the rod more than the pipe or what is going on and what is the best way to separate them? —Preceding unsigned comment added by 71.100.3.254 (talk) 09:08, 29 January 2008 (UTC)


 * It's a bit iffy, since brass is an alloy and has a number of variations. Aliminum generally has a linear thermal expansion coefficient about 20% greater than brass at room temperature. So if you cool them down, the aluminum shaft will shrink about 20% faster than the pipe (again, varying depending on the brass alloy). You may need to really cool them down to make it loose enough, however, and I'd certainly suggest applying a lubricant at the same time. Someguy1221 (talk) 09:16, 29 January 2008 (UTC)


 * I did the cooling and the lubricant - but nothing. The rod will not budge and twists without turning whatsoever. Now I'm thinking put a little water in the pipe and cap it and then put the pipe in a fire... this should force both apart but maybe not or maybe the pipe will explode or the rod will become a missile. —Preceding unsigned comment added by 71.100.3.254 (talk) 09:26, 29 January 2008 (UTC)


 * Finally... what worked was a little colder temp and adding silicon spray to the oil. This seemed to free the grip the brass had on the aluminum which prevented turning and the cold and the relative softness of the aluminum seemed to work for axial motion. Eventually turning and pulling got the two apart with lots of scoring on the aluminum. —Preceding unsigned comment added by 71.100.3.254 (talk) 09:58, 29 January 2008 (UTC)

seeing through metal
would it be possible to create a sheet of metal so thin that you can see through it? --86.135.126.195 (talk) 10:27, 29 January 2008 (UTC)
 * Yeah, they coat glass in gold to block UV and you can still see through it sort of. Also just a few days ago I figured out that Pop Tart wrapper foil is so thin that it's transparent when you hold it up to your eye D\=&lt; (talk) 10:58, 29 January 2008 (UTC)


 * The pilots of the SR-71 Blackbird and Lockheed U-2 have helmets that feature a extremely thin layer of Gold on the visor, the visor is still perfectly clear and suitable for use, and the gold coating prevents the visor from freezing and misting up as it conducts heat and warms the visor ever so slightly. The astronauts that landed on the moon also used a similar gold plated visor on their spacesuits. We're still a long way from transparent Aluminium that is mentioned in Star Trek however. Nick (talk) 11:03, 29 January 2008 (UTC)


 * Our transparent aluminum article disagrees with you, but disappointingly provides no citation. Someguy1221 (talk) 11:08, 29 January 2008 (UTC)


 * (I'm pretty sure that the latest info in the transparent aluminum article could be sourced through New Scientist magazine; I think that's where I read about that. Perhaps some diligent Wikipedian could take a look... -- Atlant (talk) 12:03, 29 January 2008 (UTC))


 * :-( Someguy1221 (talk) 12:21, 29 January 2008 (UTC)


 * That's surprising that New Scientist doesn't have 30 blaring articles about how you can make it in your basement. Tempshill (talk) 23:04, 29 January 2008 (UTC)


 * In this context see also Toronto's Royal Bank Plaza. --Anonymous, 02:50 UTC, January 30, 2008.


 * Closer to the idea of "just plain metal" (rather than a metalization layer), gold leaf is normally thin enough to see light through it.


 * Atlant (talk) 12:01, 29 January 2008 (UTC)

Gold is a good reflector for near infrared and longer-wavelength visible light, but not for blue light (hence its color). So it sounds strange that it is a good reflector for UV - are you sure, Froth? Or maybe the absorption of UV is relevant in the thin layers and is much higher than the combined absorption and reflection of visible light (but I doubt that)? Icek (talk) 20:54, 29 January 2008 (UTC)

Detailed info (with pics) how cable internet works
Hey everybody. I've had some trouble with my cable internet connection, and had a technician here today checking things out. Being the (huge) geek that I am, I became quite interested in how these things work, so I'm looking for some detailed info. I've read the articles at HowStuffWorks, but I'm rather looking for a "guided tour" of sorts, preferably with many images. I'm not very interested in the high-level things (i.e. anything above layer 1/2 in the OSI model), such as protocols or modulation, but rather what's beyond the jack in my wall - such as where the cable in the wall goes, what equipment is located there, and so on until we've reached the actual 'net. Thanks in advance :) Aeluwas (talk) 11:32, 29 January 2008 (UTC)
 * DOCSIS would be a good place to start reading and work your way from the various articles provided there. It doesn't have pictures though. - Dammit (talk) 11:37, 29 January 2008 (UTC)


 * I have a book at home (which is titled something creative like Residential Broadband) that goes into this in great detail. If you like, I can probably find the exact title/author or perhaps you can find it on Amazon.


 * Atlant (talk) 12:05, 29 January 2008 (UTC)


 * Thanks guys. A book would be overkill, though (free ebooks aside)! Aeluwas (talk) 19:34, 29 January 2008 (UTC)


 * Well, if you eventually decide that you want a book, the one I was speaking of is titled Residential Broadband, Second Edition by George Abe, published by Cisco Press, ISBN 1-57870-177-5, $US50.00.


 * Atlant (talk) 00:13, 30 January 2008 (UTC)


 * Your library system might have a copy. Worth checking :) 130.88.140.119 (talk) 16:13, 1 February 2008 (UTC)

zero order hold
my question is that is zero orderhold a linear device?explain your answer in detailsSam kshitij (talk) 13:22, 29 January 2008 (UTC)


 * I'm not even going to try to read this, but we apparently have an article on it: Zero-order hold. Feel free to ask more questions if there's something you don't understand. Someguy1221 (talk) 13:29, 29 January 2008 (UTC)


 * Also see Linear system. Hint: the answer isn't simply yes or no. You have to explain what it means to be a linear device and under what assumptions a ZOH satisfies the requirements. —Keenan Pepper 13:38, 29 January 2008 (UTC)

Relation of ohms to watts in speakers
Hello, pretty noobish question here. Yesterday me and my friends bought two speakers from Savers for $3 a piece. They look like they have 8 inch speakers with a couple small tweeters. They have no text on them at all, no brand name or specifications. Using a multimeter, I found out that they are rated at 8 ohms which I understand is the standard for speakers of this size. I have a stereo in my basement (with a quite old Marantz preamp very similar to this one) which reads "185w" on the back. It is hooked up to two very worn out speakers, rated at 8 ohms. What I'm wondering is, does it matter a whole lot what the wattage of the preamp is as long as the resistance is correct? I'm basically wondering if pairing these new speakers with my old preamp will work, considering that they weren't made for each other but they are compatible in the sense of ohms. I don't want to blow these speakers I just got so I don't know if 185 watts is too much or what. Thanks a lot! NIRVANA2764 (talk) 15:30, 29 January 2008 (UTC)
 * Without going into technicalities I don't remember anymore, the amplifiers need something to work against, and they were designed for an 8 ohm load. You have an 8 ohm load.  You're good.  End of question 1.  Question 2 is "Is 185w too much?"  That's the rated power of the final stage power amps, and probably is too much for the old speakers you want to use.  The solution?  Don't run the amp at full power.  In English, that means keep the volume turned down. Try to pump too much power thru those speakers and they will object.  Loudly, if briefly.  -SandyJax (talk) 22:14, 29 January 2008 (UTC)

Divergence of a species (speciation)
After much reading, I'm still not exactly sure on the mechanism of speciation. I understand the ways a population can get divided and be subject to different selective pressures. I also understand that it's populations that evolve, not the individual. However, doesn't it come to a point where individuals (or maybe "generations of families" is more appropriate) must evolve to make themselves incapable of producing fertile offspring? Maybe I just answered my own question... I guess when species don't evolve "together" and become incapable of interbreeding, that's natural selection at work? -- MacAddct &#xF8FF; 1984 (talk &#149; contribs) 15:37, 29 January 2008 (UTC)


 * Mutations are at the heart of evolution, and they do indeed occur in individuals. So in a certain colloquial sense I think you could say that individuals can evolve.  I think when people say that "individuals don't evolve", they mean two things: First, individuals don't transform partway through their lives like on certain Star Trek episodes.  Second, and more importantly, biologists define evolution not as speciation or as mutation but as changes over time in the frequency of given alleles in a population ( I'm pretty sure that's right, even though it isn't quite how our Evolution article defines it [now that I think about it, it's pretty much saying the same thing]).  So by definition evolution occurs in populations rather than in individuals.  As far as speciation goes, I think you're on the right track.  Two parts of one population diverge in their traits until they can't or don't interbreed.  But if a single population changes together over time, that's still evolution (by the formal definition) even if it isn't speciation.  --Allen (talk) 18:12, 29 January 2008 (UTC)


 * Oh, one more thing... evolution, whether it involves speciation or not, can be driven by genetic drift as well as by natural selection. --Allen (talk) 18:15, 29 January 2008 (UTC)


 * I guess my confusion is (although it may be an unintentional straw man) that a group of species must all evolve the same characteristics at the same time that would make them all fertile with each other, but different enough from the old niche. Even I feel like I'm misrepresenting something though... -- MacAddct &#xF8FF; 1984 (talk &#149; contribs) 19:13, 29 January 2008 (UTC)
 * Of course a large population can be split in two over time. The classical example for instance is the slow appearance of either a mountain range or a river which would keep two populations of a species separate. This prevents genetic material being exchanged between these populations.PvT (talk) 21:01, 29 January 2008 (UTC)
 * I recall reading something about two species of insects that only recently split off from each other and are almost genetically identical except that one reproduces at night and the other in the day (or something like that) so that they weren't separated by a physical obstacle but by a mutation that was able to persist. — Æµ§œš¹  [aɪm ˈfɻɛ̃ⁿdˡi]  22:20, 29 January 2008 (UTC)


 * Well, it normally takes a good number of changes before two populations can't interbreed, so we're talking about thousands to hundreds of thousands of generations. That is usually enough time for the changes to be available throughout the population unless one of two things happens.  First, if the two populations are isolated or mostly isolated from each other, then they can't exchange genes, and yes, this will cause speciation.  In fact, that's the most common cause of speciation.  However, in some rare cases, a species living in one area may separate into two groups, and then evolve apart from each other.  For example, a mate selection trait may appear, and one part of the population will select mates with one particular trait, and another part will select mates without that trait, and eventually genetic drift and mutations will cause them to become separate species, despite coexisting (see Sympatric speciation). --  Hi  Ev  04:48, 30 January 2008 (UTC)


 * Bear in mind also that speciation isn't necessarily all-or-nothing (though it usually is). I believe (though I haven't found a WP article on it) that there are cases where variation occurs across a wide geographical range, such that neighbouring varieties are mutually fertile, but the extreme forms are not fertile with each other. --ColinFine (talk) 00:07, 4 February 2008 (UTC)
 * Ring species. --Allen (talk) 03:33, 4 February 2008 (UTC)

Mystery metal
Since there appear to be some metal experts manning the reference desk (going by a few topics above) can anyone tell me what kind of metal that is extremely hard at room temperature - so hard in fact the it requires extra effort to be penetrated by a high speed steel drill bit yet melts into a blob similar to aluminum under an alcohol flame but with no slag. —Preceding unsigned comment added by 71.100.3.254 (talk) 16:50, 29 January 2008 (UTC)


 * Physical properties (like hardness and melting point) are related to chemical properties (strength of alloy crystal bonds, etc). Something that is very hard generally also has a relatively high melting point, because these properties are related.  Do you have an example of this magical material?  Some possibilities include (for some values of "room temperature") normal frozen water, or ice.  Ice is very hard, yet has a pretty low melting point.  I know, it's not a metal.
 * Also, does anyone know the flame temperature for "alcohol"? I assume ethanol is meant, but that's not in Gas burner.  -SandyJax (talk) 20:33, 29 January 2008 (UTC)


 * Most alcohol stoves use Isopropanol, or a mixture of Methanol and Ethanol. The latter is more commonly known as Sterno.  As for metals, you might want to look at Tin and Lead -- specifically, the mixture used in solder.  The melting is about right, but the hardness...not so much.  Also look for Gallium, which melts at skin temperature! --Mdwyer (talk) 22:04, 29 January 2008 (UTC)


 * Any of the fusible alloys should meet your melting requirement, although I'm not sure what any of their strengths are. Someguy1221 (talk) 22:14, 29 January 2008 (UTC)


 * A high speed drill would create temperatures in the vicinity of an alcohol-fueled flame rather rapidly, thus meting it and reducing drill-resistance. I am aware of some materials which become hard (though not very hard) when exposed to certain stresses, and yet are typically fluid at room temperature. Perhaps there is a material that fits the description with respect to physical forces (that is, a material which melts at the specified temp, yet becomes an oobleck-like fluid once it melts), but is not a metal. Tuckerekcut (talk) 22:32, 29 January 2008 (UTC)
 * An extremely hard metal is osmium, however that also has a very high melting point. Hardness and high metling point usually go hand in hand.  But you may be able to have a mixture of say fine emery particles in solder.  The drill will struggle, but the substance will melt.  Safes may be built with metal with hard particles mixed in to make them hard to drill. Graeme Bartlett (talk) 01:54, 30 January 2008 (UTC)

The material reacted to the drill like glass or crystal in a brittle sort of way unlike steal which the high speed steel drill easily cuts through. I do not think there are any particles added but it is possible. The material was used simply to make end caps for threaded household lamp wiring tube. A center punch dented it but the drill required extra ordinary pressure to get it to go through. —Preceding unsigned comment added by 71.100.3.254 (talk) 08:22, 30 January 2008 (UTC)
 * Fascinating - I can't think of such a metal - those that would melt in an alcohol flame include tin/lead ie solder, maybe mercury alloys and possibly zinc (or aluminium) - none of these is very hard at all. Does the stuff break or dent when hit? how easy is it to - produce filings of with a file and how easy to saw through with a fine toothed saw ???87.102.77.153 (talk) 12:03, 30 January 2008 (UTC)
 * (also what is "threaded household lamp wiring tube" - is that an electrically conducting part?)87.102.77.153 (talk) 12:11, 30 January 2008 (UTC)


 * No it resists sawing and filing like it does drilling and dents but does not crack or break when hit with a center punch. Its the relatively low melting point that has me baffled as the threaded household lamp wiring tube is made of steel. The "threaded household lamp wiring tube" is the tubing used hold lamp parts together yet allow electrical wiring to be run through the tubing. The treads are on the outside and the inside is not threaded. All of the other end caps and connectors and threaded fittings used with it are either steel, brass or pot metal. This metal is very shiny and silvery after melting and more like polished aluminum than anything else. Maybe there are other tests I can do with acids and bases that will tell me what it is. —Preceding unsigned comment added by 71.100.162.155 (talk) 06:49, 31 January 2008 (UTC)
 * Right - a hollow tube with a screw thread on the outside I think .. and the material attatches to it. Sorry I can't think of such a hard low melting thing - and it's definately not zinc, lead, tin, solder etc?87.102.33.230 (talk) 08:04, 31 January 2008 (UTC)
 * Bismuth is low melting too, but I don't think as strong as you describe.
 * Questions.. after melting does the shinyness fade slowly to a more grey colour? does it burn in any way in a flame or show any rust/oxidations?87.102.33.230 (talk) 08:18, 31 January 2008 (UTC)
 * Also antimony is used in 'low friction allows' - could a slippery metal account for it;s difficulty to drill ?? a slippery antimony allow is my best guess87.102.33.230 (talk) —Preceding comment was added at 08:23, 31 January 2008 (UTC)

Rotten Coconuts
So I've been craving a coconut for a while now, but the last four I've bought from two different grocery stores have all been rotten. If I had to guess, I'd say it was because it's winter and it's out of season for coconut harvesters. Am I correct or am I just unlucky? (I live in Minnesota if that helps) --Ouzo (talk) 20:23, 29 January 2008 (UTC)


 * Since the coconut palm is a tropical plant, I'm not sure winter is a factor. So far I haven't found any specific references regarding that the coconut "season" might be.  Maybe your grocery stores have had their coconuts lying about for too long.  Is there a way you can ask for a fresh shipment from them?  Or, there are several companies listed on this page which indicate that they deliver.  -- LarryMac  | Talk  21:03, 29 January 2008 (UTC)


 * This coconut is always fresh. DuncanHill (talk) 22:54, 29 January 2008 (UTC)

A few weeks ago, a number of the coconuts found in the shops and markets in Israel were rotten with mould. Could there be some blight today affecting coconuts? Simonschaim (talk) 09:08, 30 January 2008 (UTC)

Commercial aspects using License Plate Identification software
Is there uses now in large shopping centers or business districts or industrical parks of a large city where the use of License Plate Identification software is used to track potential customers or repeat customers or criminal activities within these areas? Wikipedia article? —Preceding unsigned comment added by 66.255.74.101 (talk) 20:28, 29 January 2008 (UTC)
 * Yes, we have an article on Automatic number plate recognition. (EhJJ) 20:47, 29 January 2008 (UTC)

Unknown husk
Excuse me, what is this? It's one half of a egg shaped husk I found outside, made of dry reedy, wickery, balsa-woody material. It is extremely light, seems to have a seed pod inside it, and smells very nice, like the kind of thing you get in those baskets from the shops that sell the fancy soaps... What is it? Thanks SGGH speak! 23:42, 29 January 2008 (UTC)


 * Could be Mace (spice) the covering of a nutmeg. DuncanHill (talk) 00:06, 30 January 2008 (UTC)


 * Nice shirt! ;) Rockpock  e  t  06:34, 30 January 2008 (UTC)
 * It does look like the seedpod in the mace piture SGGH speak! 08:58, 30 January 2008 (UTC)


 * Where did you find it? As in, which geographical region. − Twas Now ( talk • contribs • e-mail ) 02:33, 2 February 2008 (UTC)