Wikipedia:Reference desk/Archives/Science/2006 November 7

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November 7

Nonalianonactanonacontanonane

I asked a question about hydrocarbons before and I got nonalianonactanonacontanonane (C₉₉₉₉H₂₀₀₀₀) as the answer. I googled it and the only result I got was the wiki page with my question on it. Can someone please tell what this compound would be used for and if it exists (in physical reality not theory). --The Dark Side 00:06, 7 November 2006 (UTC)

It (or at least something longer than it) exists. The longer polymer is called Dyneema which is supposedly millions of monomers long. Did you read the article about Ultra high molecular weight polyethylene after your previous question got answerered? The molecule you mention is somewhere between HDPE and UHMWPE so reading both articles could give you some clous about its applications. - Dammit 00:20, 7 November 2006 (UTC)

Due to the organic chemistry naming standards, just because a chemical has a name doesnt mean it ever been encounters, used, created or even exists, even if larger ones have. Philc _T^E_C^I 18:44, 7 November 2006 (UTC)

Ah, that was me proposing that. :) I was giving the longest (Greek) name possible in accordance with the generally accepted rules. That doesn't necessarily mean that anyone's actually used it - it's pretty unlikely that they would; there are better rules of nomenclature for high-weight polymers. But FWIW, there are about 3 billion base-pairs in your DNA, which means a single chain of 18 billion atoms, in (-C-C-C-O-P-O-) units. And that's just the backbone! --BluePlatypus 19:55, 7 November 2006 (UTC)

Er, that would mean 18 billion atoms among 46 individual chromosome polymer chains. The longest human chromosome has about 245 MBP (thanks, Chromosome#human), so only about 1.5 billion atoms in the backbone. DMacks 20:20, 7 November 2006 (UTC)

Cats

What is the scientific Order for a Tabby Cat?

Thank You Curios Shellbi, 11

Carnivora, see Cat (taxonomic information is given in the infobox at the right side of the article). Great question. --TeaDrinker 00:49, 7 November 2006 (UTC)

Also note that all house cats are of the same genus, species and subspecies, felis silvestris catus. StuRat 03:32, 7 November 2006 (UTC)

Tell that to these guys. Rockpocket 04:48, 7 November 2006 (UTC)

Gulf Stream

How does the gulf stream affect ships traveling from the Caribbean to Europe?

It's easier to go with the current. Check out this sweet lecture from the University of Washington. It's a pdf, so be careful! http://courses.washington.edu/ocean101/Lex/Lecture15.pdf --Cody.Pope 01:35, 7 November 2006 (UTC)

Copeia

The journal Copeia is dedicated to cold-blooded vertebrates. My officemate pointed out that neither she, nor I, knows what the word Copeia actually means, despite both of us working in fisheries or related fields. Any ideas where the word Copeia comes from, or was the word invented as a title without other meaning? --TeaDrinker 01:36, 7 November 2006 (UTC)

According to Copeia, the name came in honor of Edward Drinker Cope, so that explains where "Cope-" comes from. The "-ia" however, probably has something to do with ichthyology. --Wirbelwindヴィルヴェルヴィント (talk) 02:00, 7 November 2006 (UTC)

• smacks head* Ahh yes, right there in the article... Thanks! --TeaDrinker 03:18, 7 November 2006 (UTC)

Anytime. It's often easy to overlook something when you're not expecting it. =P --Wirbelwindヴィルヴェルヴィント (talk) 04:26, 7 November 2006 (UTC)

winterberry

I recently discovered a large group of bushes in the Western Panna woods that I think are Winterberry. The leaf characteristics are different from the reference books. The leaves are opposite and not alternate. They are not shiny like a typical holly and are hairy on the bottom(using a 10X glass) and are light green bottom and darker green on the top. The leaves are more like a dogwood and are smooth edged. They have many red berries approx. 4 to 5 mm. diameter.

Is it a winterberry or what?

Oltim 02:03, 7 November 2006 (UTC)

Is it possible to put up a photo of a leaf etc?--Cody.Pope 02:31, 7 November 2006 (UTC)

Partial pressure Q

hey there! I'm a little stumped on a question on Partial Pressure in Chem. I've got...
V = Volume
n = # of moles
T = Temperature = constant = 298 K
R = Gas Constant (.08206 L atm K^-1 mol^-1)
P = Pressure
Oxygen and Nitrogen are separated in their closed system by a stopper. The stopper is removed and the two gases are combined. Find the Partial pressure of each gas and the Total pressure.
O₂ : P = 4 atm V = 2 L
N₂ : P = 2 atm v = 3 L
Basically what i started out with was with finding the # moles. with P₁=nRT/V in O₂ case 4 atm = n (.08206 L atm K^-1 mol^-1) (298 K) / 2 L and got roughly .3271 mol O₂ and for N₂ 2 atm = n (.08206 L atm K^-1 mol^-1) (298 K) / 3 L and got roughly .2454 mol. With that info I know this next part is definitely wrong and put:
P_x = (n_x/n_t) * (P_t)
(n_t = .5725 mol) for both and ended up getting 4.666 atm for N₂ and about 7.000 atm for O₂. That's where i got stumped basically because my P total is different... Help? --Agester 02:03, 7 November 2006 (UTC)

The first part is correct. From there, answer these questions. 1.) What is the total number of moles of gas in the (combined) chamber? 2.) What is the total volume of the chamber? 3.) What is the TOTAL pressure in that chamber? (Ideal gas law again). From there, the ratio of partial pressures is equal to the ratio of the moles of each compound. Hope this helps and let us know what you get :) --Bennybp 02:39, 7 November 2006 (UTC)

• slaps forehead* CRAP! You're right! I could've did P(5 L) = (.5725 mol) (.08206 L atm K^-1 mol^-1) (298 K) and if i worked it out correctly i could've gotten... 2.800 ATM roughly as P_t and i'm guessing you subsitute the n for each element to get their partial pressure? (therefore O₂ would be .3271 mol)? --Agester 14:20, 7 November 2006 (UTC)

Haha sure. There are a couple different ways. I was thinking taking the combined pressure and calculating the partial pressures using Px = (nx/nt) * (Pt) . Or you can do it your way. Either way it sounds like you got it :) --Bennybp 23:38, 7 November 2006 (UTC)

A Void

I was arguing with a friend, who refuses to believe that there is no such thing as a void, that is a space between matter that has no particles in it. If we were to eliminate electromagnetic radiation and all matter within some space, would there just be *nothing* in that void?--138.29.51.251 04:15, 7 November 2006 (UTC)

Not really "nothing". See Vacuum. Quantum physics predicts that no space is ever void of matter, but has particles zipping in and out of existence. Pretty cool really. --Cody.Pope 04:22, 7 November 2006 (UTC)

Well, there would be gravity from the surrounding matter, if that counts as "something". Also, Neutrinos can penetrate almost anything; it would take a light year of lead to block only half of them. --Bowlhover 04:31, 7 November 2006 (UTC)

Thanks for the replies! I guess my question has pretty much been answered. However, do those quantum particles that zip in and out of existence have mass? What about neutrinos? Gravitrons (the particles that are theorized to make up gravity waves, I think)?--138.29.51.251 13:11, 7 November 2006 (UTC)

The quantum particles are particle-antiparticle pairs, i.e. when an electron is created a positron is also created. You can only say "antiparticle" if it has a charge. All particles that have a charge also have mass, so yes, they do have mass. Neutrinos also have mass (albeit a very small one), but gravitons don't. --Bowlhover 21:33, 7 November 2006 (UTC)

It's a classical philosophical question actually. In a nutshell, it goes back to Parmenides, who didn't believe there was a void, a tradition carried on by Aristotle and Plato. Whereas Democritus and the atomists believed there was a void. Fast forward to the middle-ages and people were still following Aristotle, and the maxim of the day was "Horror vacui" ("nature abhors a vacuum"). So they thought that if you froze a bottle of water, the water would contract (which it doesn't actually), but the bottle would then crack open as to avoid forming a vacuum inside. But once they did understand air pressure, it seemed vacuums might exist after all. At which point Descartes jumped in and proposed there was a "subtle matter" which was still there. Then Newton came along and showed that you didn't seem to need that "subtle matter" filling space anymore, at least not if light travelled as particles. But then they figured that they were waves, and then electromagnetic waves. And since waves needed a medium, the universe got to be filled again, with aether. Then it turned out the aether didn't exist, and that vacuum does exist. Then Quantum physics and QED showed how the electromagnetic field worked through virtual particles. So in summary: From the viewpoint of modern physics, the vacuum does exist. It's just that it's not entirely empty! The reason why it's still considered a vacuum is that the formation of virtual particles is not a property of the vacuum but of space itself. And 'occupying space' is really the only property a vacuum can be said to have. --BluePlatypus 19:33, 7 November 2006 (UTC)

But philsophically that last point is tautologous. "Void" is what's left when you have taken away the things that can be taken away, and left everything else. Rich Farmbrough, 17:06 10 November 2006 (GMT).

Blowing up the moon

As I was watching Mr. Show last night, I had a thought. If we were to drop every nuclear bomb we have on the moon, what impact (if any) would it have for life on earth? --Wyckyd Sceptre 04:35, 7 November 2006 (UTC)

The biggest repercussion is that we've have no more nukes on the planet! Besides, how can one drop a bomb on the moon? -- You have to fly it there first. Chris 00:56, 8 November 2006 (UTC)

We'd be subject to a really bad television show about it. Sorry, couldn't resist. 192.168.1.1 9:04, 6 November 2006 (PST)

What impact would it have on Earth? I can't imagine how it would affect Earth. (The title of this question is "blowing up the moon", but we can't possibly blow up the Moon. The asteroid that caused the Cretaceous-Tertiary extinction event delivered much more energy than the world's nuclear arsenal can possibly deliver, yet relatively little happened to the Earth.) --Bowlhover 05:18, 7 November 2006 (UTC)

My guess is that if the moon was knocked out of orbit, it would change the Earth's orbit, causing temperature changes. IIRC, the moon does cause the Earth to move in a wave-like motion while following the orbit around the sun. It would also affect tides, since tides are related to the moon. But I'm not sure we have enough nuclear bombs to change the orbit of the moon, so probably just a big crater. --Wirbelwindヴィルヴェルヴィント (talk) 05:29, 7 November 2006 (UTC)

My guess is nothing as I suspect every nuclear weapon wouldn't have enough energy to budge it one bit. But just a guess. Remember the Tsunami that affected onle surface water and also earthquakes that are many thousands of nuclear weapons that don't substanitally impact earth except at a very superficial level. --Tbeatty 05:49, 7 November 2006 (UTC)

More drastically, blowing up the moon would cause an instability in the Earth's "wobble". Scary stuff. Check it out No moon!. --Cody.Pope 05:51, 7 November 2006 (UTC)

We're going to lose the moon anyway as it is moving away from the earth (over an inch a year I think) and will eventually not be our moon. --Tbeatty 06:25, 7 November 2006 (UTC)

As that won't happen until after the Sun goes nova, I suspect that it won't matter that much. B00P 07:10, 7 November 2006 (UTC)

Fisrt, the Sun is expected to go red giant, not nova. Second, barring such events or an encounter with an intruding body, the change in the Moon's orbit will never cause it to "not be our moon". The change is caused by tidal friction and the fact that the Earth rotates faster than the Moon moves in its orbit. In the long run the Earth's angular momentum is being transferred to the Moon. This can only go on until the Earth's rotation slows enough so that it always keeps the same face turned towards the moon. Then the day and the lunar month will be the same length (about 40 of our days, I think it works out to). Of course the lengthening day will cause havoc in terms of weather and climate, but the Moon won't be going anywhere. --Anonymous, 00:02 UTC, November 8.

Won't the tidal forces imparted by the sun continue to force the moon away from the earth? --Tbeatty 04:10, 9 November 2006 (UTC)

The only impact I could imagine is that the explosion would be visible from Earth, provided it was on the near side of the Moon and was during night at your location on Earth, and when the Moon is above the horizon. StuRat 06:56, 7 November 2006 (UTC)

Assuming you're old enough, did you feel anything when any of the American or Russian nuclear tests were done? Not even the Tsar Bomba had any noticeable effect outside of the immediate area. Heck, the U.S. army used to blow up bombs near Las Vegas and nobody was disturbed. (Trivia: John Wayne supposedly died of cancer he contracted from filming The Conqueror in the area.) It would take vastly more than the entire nuclear stockpile to budge the Moon, much less blow it up. Clarityfiend 07:22, 7 November 2006 (UTC)

Okay I know very little about the physics of explosions but would it be possible if you carefully organised the explosions? Rather then just dumping all our bombs on the surfaces and exploding them, I'm thinking of tunnelling perhaps to the core in multiple locations (of course, this is probably outside our current level of expertise). Maybe even designing the bombs in such a way to try and blow up the moon rather then flatten a very large area. Nil Einne 10:56, 7 November 2006 (UTC)

OT but looking at the John Wayne article, this might not have been the case. He had a 3 pack a day cigarette habit and contracted lung cancer. The radiation he may or may not have been exposed to may or may not have contributed to his cancer but I wouldn't exactly say he contracted the cancer due to the filming. Indeed given the complexity of cancer, I would be reluctant to ever say someone got cancer from something. More accurate to say it was a major contributing factor. In any case, he actually died from stomach cancer 15 years later when he was 72 (and smoking cigars instead of cigarettes) and the article doesn't explicitly say it was a reoccurance of the lung cancer... Nil Einne 11:01, 7 November 2006 (UTC)

Further OT, but in regards to The Conqueror and cancer, our article mentions that 91 of the people involved with the film had contracted cancer by 1984, three times the number you'd expect in a group that size (220 people). Yeah, they smoked, but that's still a lot of people. Matt Deres 00:33, 8 November 2006 (UTC)

How much energy does the world's nuclear arsenal have? 60 000 megatons? Assuming that all of this energy is converted into kinetic energy, and that all of the kinetic energy goes toward pushing the Moon, the Moon's velocity will change by 8 cm/s. Not exactly enough to "blow up the moon". --Bowlhover 17:16, 7 November 2006 (UTC)

Re

How about expending a few carefully-placed megatons to give 2004 vd17 a moon-impact trajectory? Repeat as often as necessary. In a few hundred years, Earthlings could destroy the moon. Its a real David and Goliath kind of scenario. Lowerarchy 04:03, 8 November 2006 (UTC)

Just reread my own nonsense. Two hundred years isn't enough time to find sufficient movable mass in the near solar system. Are there any Deimos-sized objects floating about loose out there?Lowerarchy 04:09, 8 November 2006 (UTC)

Total world megatonnage is probably a lot less than that. I ran some calculations awhile back and came up with around 2,500 MT for the entire US arsenal at the moment (you can see them at Image:U.S._stockpile_size_2006.svg). If we say that Russia's arsenal is probably comparable to that, and figure that the rest of the world probably doesn't make up more than 1,000 MT at most, we're talking about 6,000 MT max — an order of magnitude less than 60,000 MT. --Fastfission 03:53, 8 November 2006 (UTC)

CHRIST ALL MIGHTY PEOPLE, HAS ANY ONE THOUGHT ABOUT THE TIDES???

Destroying the Moon (or even just slightly modifying its orbit) needs a LOT more energy we currently have. You can find some "useful" data on this page [1], [2]. --V. Szabolcs 16:00, 10 November 2006 (UTC)

Evolution

Could someone refute this for me? I'm pretty sure he's wrong, but I don't know how. [3] Black Carrot 04:54, 7 November 2006 (UTC)

I'll give it a shot. Aquisition of a new antibiotic resistance will probably not lead to a new species. That's a given. The whole bloody point however, is that this is proof that new genes, if advantageous, will spread throughout a population. That's what evolution is, a change in gene frequency over some time. It's not as though we havn't seen evolution occur outside of antibiotic resistance either; ie. we're currently seeing it in Darwin's Finches [4]. His logic is all screwed up. He also seems to claim that no matter how much evolving an E. Coli bacterium does, it's still E. Coli. I can't comprehend what leads him to that conclusion. -- Consumed Crustacean (talk) 05:08, 7 November 2006 (UTC)

At a skim: AFAIK, "species" for bacteria is rather poorly defined. One can call something a new strain while someone else might hypothetically call it a new species. Since now we know about DNA and genes and such (and Darwin didn't have this information), scientists now define "evolution" as a change in gene frequency over time, so it still shows evolution. "Species" is irrelevant.

Also, I find things like "But the whole point of science is that 'almost' isn’t good enough. " totally wrong. Mathematics is "almost isn't good enough". But the whole point of science is "get a theory that works enough to be useful, then when things stop working so well, find a better theory that's even more useful", like Newton's gravity -> Einstein's relativity -> quantum mechanics -> the current search for something unified. —AySz88\^-^ 05:24, 7 November 2006 (UTC)

Very briefly, he’s strawmaning the argument.

Speciation in Prokaryotes:

First off, a species concept for bacteria and other single-cell selfing organisms is not an analogue for a species concept in more complex organisms. Strawman-ing the argument to all speciation processes is wrong. The reason being is that single celled organisms don’t have sex. Generally the ability for two individuals to produce viable offspring together is the “test” necessary for them to be defined as the same species – but not always. This doesn't apply to prokaryotes.

Additionally, given that bacteria don’t readily exchange DNA (though they can see phage), any novel mutation arising in a population can “theoretically” be defined as a speciation event. Generally, scientists don’t do this, but there is some argument that they should. There is a long-standing debate about this in the academic community, but it is one of the main reasons asexual speciation events are different from sexual speciation events.

Also,

No Modern Example of Speciation:

There are, see Vidua for example.

--Cody.Pope 05:31, 7 November 2006 (UTC)

(edit conflict) I know that virus and bacteria are different, but I think this is a good example. A human will obtain antibodies against a flu virus after recovering from the flu, but flu virii keep mutating and continually infect the same human over the course of their lifetime, but it's still a flu virus. --Wirbelwindヴィルヴェルヴィント (talk) 05:34, 7 November 2006 (UTC)

You could logically argue the new flu virus is a new species, if viruses strains were denoted like this. They only reason we don't do it for bacteria is logistical. --Cody.Pope 05:39, 7 November 2006 (UTC)

(very many edit conflicts) Okay, reading this closer, whoever-this-is doesn't even know the right definition of "evolution". His first two major objections (under "novelty" and "mutation" sound as if he thinks "evolution" means speciesization. It doesn't; see before. There is no problem if you use the correct definition of evolution, and there is no claim that it shows speciesization at all.

The third was somewhat addressed before - there is no need for exactness in science. Each new bit of information which agrees with the prediction of a theory adds some support for a theory - it's kinda like "there's a 60% chance that our results are correct and support this logic". For example, if you're trying to get the charge of some really exotic particle, you might hypothesize that its charge is actually zero. So you might do some experiment (or a lot experiments") and get "+0.0001, plus or minus 0.0003". That's not a very certain figure....yet. But other people repeat it, and keep getting values clustered near zero. If you get enough of those together, and they combine to 75% certainty, 90%, 99%, 99.9%, 99.9999%.... Eventually you just accept that it's zero lacking any evidence to the contrary, or maybe zero for all pratical purposes, and move on. —AySz88\^-^ 05:40, 7 November 2006 (UTC)

I didn't bother to read the whole thing. But s/he appears to be using the common BS anti-evolution arguments that are a dime or dozen. E.g. a wing or eye is to complicated to arise from mutation or irreducible complexity. This is rather well refuted throughout the web and if you understand mutation, evolution and a bit of basic biology, you'd probably understand why it's BS P.S. Just checked and our article does appear to describe why the irreducible complexity and the "eye couldn't have evolved" argument is BS Nil Einne 10:49, 7 November 2006 (UTC)

This bit made me laugh. "When such a colony of tuberculosis bacteria is exposed to an antibiotic, it will kill off all the bacteria except those who possess natural resistance, and it is these few who will remain and recolonise." He is using this as an argument against evolution taking place? Skittle 14:03, 7 November 2006 (UTC)

There are so many logical fallacies and misrepresentations (not to mention outright demonstrably false claims) to pick on here, but I'll provide a (rather verbose) response to the overall theme that seems to be presented: established examples of microevolution don't support macroevolution.

Although the author claims that the argument "is more than mere semantics," it's not. The key hang-up is the term "speciation." This is a common argument that ID proponents/anit-evoloutionists use, but doesn't address any real problem in evolutionary theory. Speciation is a human-defined (and rather ambiguous) construct. Usually some combination of differential physical, genetic & behavioral characteristics are cited to claim that two organisms are different species. But the absolutes that some seek are, in the sense of evolutionary biology, rather pointless--lions & tigers are separate species, but (contrary some established "rules" for speciation) female ligers & tigrons are fertile. It seems many opponents of evolution will only be convinced if shown a real-time example of speciation, meeting tight criteria. This belies a general (occasionally willful) ignorance and unreasonable expectations more than any weakness in the theory of evolution.

To wit, speciation is often illustrated by the classic evolutionary tree, with discrete branches departing at distinct times to create new species, and the animals along an unbranched stretch remaining relatively unchanged. A far more accurate view would be to imagine the threads of a rope: a single cord of rope is unbroken from begining to end, but is actually made of of millions of individual fibers that are significantly shorter than the length of the rope. If, in our imaginary rope, each fiber was mostly similar in property to those that immediately preceded it (with small random variation), these fibers are a better representation of evolutionary history--interwoven from beginning to end, they can represent the variability of individuals in a population through their own variations in length, thickness, color & strength. The overall properties of the rope (species) at some point along its length are an integration of the properties of the fibers at and near that point. Rope fibers can conceivably diverge from the main cord, perhaps to again re-integrate with the main cord, or maybe to permanently branch off and form a "separate" rope that may even include fibers from other ropes. It's not hard to imagine in this case that a rope could at one end thin, weak & white and at the other end a branch of thin & red and a branch of thick & white. This model better describes the problem of pointing to a single random individual fiber along the length of rope (a single animal) and trying to determine whether it belongs in the same category as another random fiber.

That long-winded thought exercise was meant to illustrate the short-sightedness of pointing to a microevolutionary change and saying that it's not an example of speciation because the "new version" of the animal is only very slightly different than the old version ("An aardvark that is tuberculosis-resistant is still an aardvark"), not meeting an incredibly strict standard of visibly obviously different. What the author doesn't get, or doesn't ask, is how many events of demonstrated microevolution would it take for a new species to be different enough? (When the length of rope has reached a light shade of pink at some point is it "red enough" to be significantly different from the white end? What about a 5% change in fiber thickness, is that different enough?) Ignored is the preponderance of genetic and fossil data that shows microevolutionary events underlie macroevolutionary changes. If scientists are ever revive an ancient example of a modern species (say by cloning from the blood of mosquitos in amber or thawing out a frozen animal), would, say, a 100,000-year old aardvark (or seagull) be a different species from what we see today?

In conclusion, this brand of ID argument is a classic case of a straw man argument: it oversimplifies the problem of effectively defining speciation and brands simple microevolutionary events as insufficient to explain macroevolution by invoking very complex structures ("feathered wing, the mammalian eye or even the human hand"), without addressing the blindingly obvious point that accumulation of microevolutionary changes can and do result in large-scale physiological differences. -- Scientizzle 22:30, 7 November 2006 (UTC)

Thanks for answering. And don't worry about a long post - I'd rather have a thorough answer. I still don't quite get it, though. How do we know for certain that it's even possible, given a particular genetic code and the known mutations (point mutations, doubled chromosomes, etc), and given the restriction that each mutation must produce a well-adapted organism, that it's even possible to pass through enough of these changes in the necessary space of time? Or within, say, the lifetime of the universe? It seems like both a structure problem, demostrating that such a path exists, and then a statistics problem, demonstrating that it could plausibly occur in time, and I don't see how you could solve that based on what's known. Not that I'm entirely clear on what's known about them, of course, which is why I'm asking. Black Carrot 03:56, 9 November 2006 (UTC)

I'm a little confused by your series of questions (I'm having a hard time lining up the proper subjects & predicates), but I'll try to answer what I think you're getting at: Given the number & type of the mutations that must have taken place to create the complex features indicated, how is it possible that "random" mutations could have resulted in the phenotypes we see, let alone whole organisms? Is that about right?

If so, that's the same kind of argument that William Dembski (Specified complexity) and others have tried to put forward, that the odds of certain combinations of random events happening at the same time are too small to feasibly explain evolution. What Dembski willfully ignores, however, is that the evolution of the eye or wing needn't all happen at once; random mutation is the driving force behind evolution by natural selection, but evolution is a decidedly non-random process--"good" mutations are kept and accumulate. All it takes is that each step in the evolution of trait be generally non-deleterious; mutations that provide a survival advantage will often be selected for in a population, but mutations that lack a phenotype or provide no advantage or disadvantage can also spread (genetic drift), environmental-population dynamics can drastically affect allele frequencies (bottleneck, founder effect), & "deleterious" mutations (which may actually not be such; Heterozygote advantage) can possibly spread if coupled to positive traits (linkage disequilibrium) or other artifically "selected for" via bottleneck--all of these different mechanisms provide pathways for gene variance to exert effects beyond the simplistic model that you seem to be thinking of: "that each mutation must produce a well-adapted organism." In short, while mutation is random, selection is very much not random, does not necessarily require a positively selected phenotype throughout the population, and produces cumulative changes. This, as a math problem, becomes far more complex than the proverbial monkeys typing the complete works of Shakespeare (see Weasel program for more info). Hopefully this is at least a little useful as a response. -- Scientizzle 21:45, 10 November 2006 (UTC)

Skin care ingredients needed

I'm doing research on ingredients in skin care & could only find brand names with the following; Cetyl ethylhexanoate

Specifically I want to know what Cetyl ethylhexanoate is composed of. Thank you, Mary Rushing

Er cetyl ethylhexanoate isn't a brand name. Take a look at Cetyl alcohol. It's been a while since I've done chemistry but cetyl ethylhexanoate is a ethylhexanoate derived from cetyl alcohol I assume... Nil Einne 11:35, 7 November 2006 (UTC)

I think you may have misunderstood the OP. I understood her to mean that she was researching brand name cosmetics and some of them had that ingredient listed. Maybe I'm wrong. :-) Anchoress 16:36, 7 November 2006 (UTC)

Chemically, cetyl ethylhexanoate is an ester formed by the condensation of cetyl alcohol and 2-ethylhexanoic acid. (We don't have an article on that acid, but 2-ethylhexanol is structurally very similar, if you're interested.) Basically, cetyl ethylhexanoate will have much the same physical properties as a fatty alcohol, a mostly inert non-toxic oily substance. It is most likely added to cosmetics as an emollient and skin conditioner. It may be used as a thickening agent, too. --Ed (Edgar181) 13:28, 7 November 2006 (UTC)

bookphobia

what is bookphobia

My guess is bibliophobia --liquidGhoul 12:51, 7 November 2006 (UTC)

It is the fear of books--Manmohan 6:39,7 November 2006

Hyperextension of legs

What are the causes for hyperextension of legs because of which a person fails to walk properly and what can be done to overcome this problem

As it says at the top of this page: If requesting medical or legal advice, please consider asking a doctor or lawyer instead. Any possible remedies, treatments or cures will depend on the causes. How old is the person? Which joints are involved in the hyperextension? What is the person's anamnesis? Any neurological disorders? These and other things are important and should be examined by a qualified expert, that is, a medical doctor. One possibility that comes to mind are weak muscles, but then the next question is: what are the causes for that weakness. And so on.  --Lambiam^Talk`

Weak Ligaments. There are many causes for a person not walking properly and not everything is hyperextension  Doctor Bruno  19:43, 7 November 2006 (UTC)

what keeps cells together?

What is it? How do cells know where they belong?132.231.54.1 13:32, 7 November 2006 (UTC)

cellular differentiation? --Light current 14:05, 7 November 2006 (UTC)

I'd recommend looking at cell adhesion and cell signaling, too. --Ed (Edgar181) 16:13, 7 November 2006 (UTC)

project of pallet calcium chloride

We are one of manufacturers of calcium chlride and we wish to inform you that we are intereseted to put up plant to make Calcium chloride pallets.

we request the suggestion & list ofequipment enable us for further references.

Regards

shanji

Thank you. We wish to inform you that we are an encyclopedia and aim to make encyclopedic knowledge available to humanity. Concrete suggestions for the list of equipment needed to put up a plant for making calcium chloride pellets may be beyond what may be considered encyclopedic knowledge. Best wishes.  --Lambiam^Talk 14:04, 7 November 2006 (UTC)

If it's any help, I know some unemployed chemical engineers. :) --BluePlatypus 19:17, 7 November 2006 (UTC)

Power steering improvement - is it possible?

I have Ford Escort estate with power steering. But Ive just been driving a replacement Megane estate. THesterring on the Megane is very light. I was wondering if my power steering could be adjusted to make it lighter. THe man at the local garage says no. But he says no to most things!--Light current 14:34, 7 November 2006 (UTC)

Without touching the power steering, you may ask for an adjustment to the "toe in" of the front tires. The two front tires are pointed slightly inwards for stability. When you are driving and turn slightly, the toe in pulls the tires back to straight and resists turning (i.e. stable). Reducing the toe in will make the steering more unstable and therefore feel lighter. Mind you, this is just theory. And of course we know the difference between theory and practice is....In theory, nothing. --Tbeatty 04:04, 9 November 2006 (UTC)

I had hoped some car-modifier person would answer, but since that hasn't happened, I'll offer my less-informed opinion. I think your mechanic is basically correct: the "feel" of the steering is set by the combination of the power steering servomechanism design and the pressure developed by the power steering hydraulic pump. For a given car, I doubt there's much you can do about either parameter, at least not without compromising reliability of a critical system (and therefore, your safety).

It's amusing that you're complaining about ths steering on a Ford being too heavy. Here in America, Ford is well-known for designing cars which only require a very light touch on the controls. My father's Galaxy 500 could be steered with just your little finger whirling the steering wheel. It's gotten better; my wife's Taurus had some road feel in the steering wheel (and probably used speed-varying power-steering assist) and the European Fords I've driven were pretty typical for at least a fair balance between assist and road feel. Maybe the American Escort parts are different? Maybe you can adapt some of those to your (presumably) European Escort?

Atlant 13:25, 9 November 2006 (UTC)

Milk allergies

My son is very high allergic to milk and all dairy products. Can he take AC-Zymes which has viable lactobacillus acidophilus? Thank you for any help

Most likely the allergy is caused by milk protein perhaps with lactose intolerance thrown in. It's rather unlikely AFAIK, that lactobacillus acidophilus would be causing the allergy given that only yoguhurt should have this in high concentration anyway. However I can't guarantee your son won't be allergic to lactobacillus acidophilus as well (although from my limited understanding of allergies I don't think it's common to be allergic to certain strains of bacteria) so you might want to consult his GP/doctor or a specialist Nil Einne 15:55, 7 November 2006 (UTC)

The most common cause of problems to digest milk is not an allergy but an intolerance to lactose, the kind of sugar found in milk. The cause of this lactose intolerance (a very common problem) is that after weaning, the body stops producing the enzyme lactase which breaks down lactose and is hence needed to digest dairy products. Read the article on lactose intolerance. At least here, in Austria, all inds of lactose-free dairy products have popped up in the supermarket shelves in the recent two years. It seems that there is some new technology to get the lactose out of dairy products in order to make them suitable for people with lactose intolerance. Anybody knows more about how they do that? Simon A. 19:37, 7 November 2006 (UTC)

Please consult your doctor for such individual problems where a detailed history and examination are needed  Doctor Bruno  19:46, 7 November 2006 (UTC)

Unlike what is stated above, milk allergies are typically milk protein allergies. Lactobacillus is fine and there is no reason to avoid the product. InvictaHOG 20:44, 7 November 2006 (UTC)

Ok, the I use more careful wording: Adverse health reactions to the ingestion of milk are most commonly due to lactose intolerance or due to milk allergy. Which one is more common depends on the race. Symptoms are probably different though I am no expert. But you are right to point out that Lactobacillus is usually not the problem. And Doctor Bruno is right, of course, in advising a visit to a doctor but somehow I imagined that this has already been done. Simon A. 21:48, 7 November 2006 (UTC)

I need more info on the Electro-Chemical Receiving Telephone.

Yeah, I'm in 10th grade and i need to know more about the Electro-Chemical Receiving Telephone. we were talking about edison and our favorite inventions by him, one of the students said something about the Electro-Chemical Receiving Telephone. wondering what it is... i looked on google and ask.com but i couldn't find anything significant. this is not for a report either so....

Thanks, J-

May be something under coherer or barretter Ive seen a page about this somewhere and I cant remember what its called 8-(--Light current 16:36, 7 November 2006 (UTC)

Electrochemical receiving telephone ?? I doubt it, whatever it is. X [Mac Davis] (DESK|How's my driving?) 20:34, 7 November 2006 (UTC)

Someone was doing a series of pages on detectors and Im sure I saw it there. I cant even remeber the name of the editor involved 8-(--Light current 21:45, 7 November 2006 (UTC)

In the Telephone article, it is noted that Bell invented an electromagnetic receiver which reproduced sound well but was a lousy transmitter. Edison invented the carbon button transmitter. To get around the Bell patent, Edison invented the electrochemical receiver, or chalk receiver, or electromotograph. It had a cylinder of moistened chalk about an inch in diameter which was rotated during a phone conversation. The passage of electricity changed the friction with which a contact rubbed against it. The contact was connected to a diaphragm and reproduced voice signals quite loud and audibly: it could be heard 1000 feet away. It was in a sense an amplifier, because a faint electrical current controlled a powerful mechanical force. It is described at [5] where it is called the electromotograph. See also [6] and [7] There is a picture at [8].It should be included in Wikipedia, but I couldn't find it in any article. I believe it is shown in operation in the Spencer Tracy movie "Edison, the Man" (1940). Edison 00:57, 8 November 2006 (UTC)

Physics - Pointlike mass launched from the top of a sphere

Hello all, I've been trying to work out how to solve the following problem, but really don't know how to. Here goes : A pointlike mass (of mass m) is located at the top of a sphere (let's say it's centered at the origin and of radius r). It's launched at an initial velocity v_0 (at any angle) I want to find the trajectory of the mass (no friction whatsoever).

So, I've tried using F = ma, and to get an expression of the normal (reaction) force of the sphere on the mass I tried giving an equation of the sphere (y = sqrt(r² - x²) suffices), differentiating it, then say that at every point IF the mass is still on the sphere, R_n (the normal force) = mg sin(θ) and θ = arctan (dx/dy). But then, I'm sort of stuck. I don't know how to calculate the point at which the masse leaves the sphere, and anyway I don't think I'm really using the good method. Of course, if I calculate the trajectory as if the sphere wasn't there and that that trajectory doesn't intersect the sphere, that gives me a (quite trivial) solution, but I don't know what to do in the general case.

I would also really appreciate a method which I could use 1) If there is friction (any type, but not really expecting a closed form solution in every case) 2) Independently of the object (for example, if the curve was a parabola or an hyperbola) (possibly 1) and 2) at the same time, but well...)

Anyway, any ideas would be appreciated ! Thanks. --Xedi 17:35, 7 November 2006 (UTC)

Is this homework? I certainly remember the no friction version of this problem from A-Level maths. I think what you are missing is the acceleration, V^2/R of something travelling in a circle, you then just need to equate this with the right thing! Hopefully that is enough of a hint.

You should end up with an equation that gives you an angle that the mass leaves the sphere and can work out the velocity at that point from thinking about conservation of energy. You can then use normal ballistics equations for the rest of the trajectory.

In the general case with friction (from sliding, air or whatever) and an arbitrary surface to slide along you have the problem that energy is not conserved so in this case try to come up with a differential equation based on the forces acting on the mass that links the acceleration, velocity and position and then you just need to solve it with the initial conditions that you specify, up to the point when the mass leaves the sphere's surface. JMiall 19:16, 7 November 2006 (UTC)

(edit conflict) Obviously, once the mass leaves the sphere it just follows the usual parabola. So the only question is where it leaves the sphere, and what its velocity looks like until it gets there. If it hasn't left the sphere yet, it's undergoing circular motion and is therefore subject to centripetal acceleration. You can determine the angle at which it leaves the sphere by comparing the centripetal acceleration to the component of the gravitational acceleration directed toward the center (as a function of $\theta$); when they're equal, there's momentarily 0 normal force and then the mass is gone. To calculate the required acceleration you need velocity as a function of $\theta$, which is trivially derived from conservation of energy considerations. You then have everything in terms of $\theta$ for the departure point and can solve. Since we're using $\theta$, why not keep going with it? As long as the mass is on the sphere, it has only a tangential velocity (call it $r{\dot {\theta }}<0$ since we're going down the sphere) and a tangential acceleration provided by gravity. Unfortunately, the result ends up being a non-trivial DE whose solution appears to involve elliptic functions. Hopefully you only want the course the particle follows and not how fast it's following it! --Tardis 19:24, 7 November 2006 (UTC)

Thank you very much, but I still can't solve.

I do the following : mg = mg sin(θ) + mg cos(θ)

Because mg cos(θ) is tangent to the circle, mg sin(θ) + R = F_c (where R is the normal reaction force and F_c is the centripetal force)

F_c = mv²/r

Thus, where the point leaves the sphere, we have mg sin(θ) = mv²/r, or g sin(θ) = v²/r

But v = r dθ/dt : we then have g sin (θ) = r (dθ/dt)²

And here I can't go any further ; I feel I shouldn't be working in terms of time but it seems the only way to get from v to θ.

What should I've done ?

(I'm only really looking for the point at which the mass leaves, and then just having the ODE leading to the solution for v would be nice.)

Thanks (And no, it's not homework, otherwise I would've had at least a vague idea of how to proceed :))

--Xedi 22:14, 7 November 2006 (UTC)

First, your first equation is only true in a vector sense. Second, it's sufficient to determine the condition for $R=0$, as that is when the particle leaves the sphere. Third, look at conservation of energy again. The fact that it's frictionless is critical here. I also discovered that there is a closed-form $\theta (t)$ based on the same $v(\theta )$ relationship. --Tardis 22:54, 7 November 2006 (UTC)

Yes it was meant to be vectors (should've said).

And, oh yes, kinetic and potential energy, don't know how it didn't spring to mind. I'll have a go then ! Thanks again --Xedi 22:58, 7 November 2006 (UTC)

I find $\theta =\arcsin \left({\frac {2}{3}}+{v_{0}^{2} \over 3g}\right)$, is that correct ? --Xedi 23:13, 7 November 2006 (UTC)

That's very close but it can't be quite right (check your units; also, what if ${v_{0} \over r}\rightarrow \infty$?). --Tardis 23:32, 7 November 2006 (UTC)

Hmm well I got ${\frac {v_{0}^{2}-v^{2}}{2}}=g(r-y)$

$v={\sqrt {2g(y-r)+v_{0}^{2}}}\quad y=r\sin(\theta )\quad v={\sqrt {2gr(\sin(\theta )-1)+v_{0}^{2}}}$

Then $g\sin(\theta )=v^{2}/r$ becomes $g\sin(\theta )=2g(\sin(\theta )-1)+{\frac {v_{0}^{2}}{r}}$ and $g\sin(\theta )=2g-{\frac {v_{0}^{2}}{r}}$

Thus $\theta =\arcsin \left(2-{\frac {v_{0}^{2}}{gr}}\right)$

(I forgot an r somewhere, here it's back !)

Thanks --Xedi 23:52, 7 November 2006 (UTC)

Whoops sign error it's v_0² -v² and not v² - v_0² --Xedi 00:18, 8 November 2006 (UTC)

I'm new here, and I don't know how you've set up your angles, but you ought to check the answer again. Currently, for small v_0 your formula tries to take the arcsin of 2, which doesn't fly. Melchoir 09:23, 8 November 2006 (UTC)

Well I did notice that my formula couldn't really be right but I checked everything multiple times and just can't see where the flaw is. I put the centre of the circle at the origin with the point x=0 y=r as the starting point, and θ the angle between the point on the sphere and the x axis. Anyway, any ideas appreciated !

--Xedi (not logged on)

Actually, it appears I did another sign error, I finally get $\theta =\arcsin \left({\frac {2}{3}}+{\frac {v_{0}^{2}}{3gr}}\right)$. Is this correct ? --Xedi

I believe it is. Remember (to correct your above derivation) that $v\geq v_{0}$ and $y\leq r$. --Tardis 18:54, 8 November 2006 (UTC)

Yes, that's the second sign error I made. Well, thank you very much. --Xedi 20:33, 8 November 2006 (UTC)

Cat Allergies

I have three cats. I also enjoy hosting get-togethers. Unfortunately, many of my friends are allergic to cats. Getting rid of the felines isn't really an option at this point.

What can I do to make my house less allergenic when they visit? Assume all the cats are locked away.

I know I need to look into getting a hypo-allergenic filter for the air conditioner, run that for several days prior at least.

Are their sprays or cleaning solutions I can use in the living room and dining areas to help?

Thanks!

TrekBarnes 18:34, 7 November 2006 (UTC)

There are no shortcuts here. All cat dander must be thoroughly removed by thorough vacuum cleaning, preferably with a HEPA bag to remove fine particulates. Even so, some people are sufficiently sensitive to dander that they will suffer allergies despite your best efforts.--Mark Bornfeld DDS 19:17, 7 November 2006 (UTC)

Vacuum thoroughly, keep the windows open, and hand out Claritin at the door. howcheng {chat} 19:50, 7 November 2006 (UTC)

Brush the actual cats as often as you can! Daily isn't unreasonable but every couple of days is better then never, just 5 minutes each, and bonus is most cats love it. Also don't let them sit/sleep on the chairs and couches, it's not inhumane not to let pets on furniture. Depending on how big the rest of your house is, consider not letting the cats into the living room at all. Vespine 22:46, 7 November 2006 (UTC)

Careful where you brush. This puts the dander into the air. Outside is best, but the room they are confined in would be ok too. A good idea for chairs and couches is to put a "cat towel" on them, and then remove it when guests come. Because trust me, your cat sleeps there when you aren't looking. Also, for some reason cats will often sleep right on the towel and nowhere else. It think its related to them sleeping on the newspaper or pieces of paper. Maybe the boundries are attractive. pschemp | talk 23:00, 7 November 2006 (UTC)

If you can bathe your cats once a week, that will remove 90% of the allergens in the environment. Now people laugh, but bathing a cat is possible, though few like it. If you feel brave, put them in the tub (empty!) with one hand holding a fistfull of the scruff of their neck and pour a baby shampoo/water mix all over. (You need something to cut the waterproofing on the coat, plain water will just roll off.) Lather and rinse with a pitcher. Water should be cat skin temp which feels warm to us (approx. 101.5 F). Don't try to hold them under the faucet. Also, only wash from the neck down. It is too easy to get stuff in their eyes and ears and there isn't that much fur there anyway. If they squirm, lift them up partway by the scruff. This kicks in their instinct to calm down and curl their legs under them. Wrap in a towel with only the head showing to absorb the water, then fluff dry with another towel. Be prepared for some dirty looks afterwards. pschemp | talk 22:57, 7 November 2006 (UTC)

I came across a spray in a pet shop (in the UK) the other day that was supposed to reduce allergens, when sprayed directly on the cat regularly. It helped my Mum a bit. Skittle 17:46, 8 November 2006 (UTC)

General Relativity

I would like to know more information about General relativity especially the mathematical equations of the theory. I read the articles about General Relativity, Special Relativity, String theory and M theory but they present only general information not detailed equations. I searched the internet using Google but couldn't find the equations. All websites, like Wikipedia, present only general information.

--Meno25 18:52, 7 November 2006 (UTC)

How about if you look at our article on the mathematics of general relativity, our article einstein field equations or geodesic (general relativity). From there, there should be lots of links to other, related pages. Hope that helps Richard B 19:42, 7 November 2006 (UTC)

How much of a background do you have in mathematics? Before you can really start to learn about GR you'll need to have a solid understanding of tensors. There are sevaral good books about on the subject.

http://math.ucr.edu/home/baez/relativity.html "Relativity on the World Wide Web" --GangofOne 04:27, 8 November 2006 (UTC)

General Relativity is extremely simple and boils down to two equations. One of those two facts is entirely true. (HINT: $G_{\alpha \beta }=8\pi T_{\alpha \beta }$ and ${\frac {d^{2}x^{\gamma }}{d\lambda ^{2}}}+\Gamma _{\alpha \beta }^{\gamma }{\frac {dx^{\alpha }}{d\lambda }}{\frac {dx^{\beta }}{d\lambda }}=0$) Confusing Manifestation 11:26, 8 November 2006 (UTC)

What percentage of DNA do humans share with lesser black-backed gulls?

See subject. --Kurt Shaped Box 19:22, 7 November 2006 (UTC)

No, "Sea subject". DMacks 20:15, 7 November 2006 (UTC)

It's probably much higher than you would think, maybe 80%, because much of our DNA does "behind the scenes" things like building muscle cells, which don't vary much from species to species. StuRat 20:39, 7 November 2006 (UTC)

What % do they share with trolls?Edison 01:03, 8 November 2006 (UTC)

Some humans I've come across share 100%, i'm sure. ;) Vespine 01:15, 8 November 2006 (UTC)

Or at least donate samples of 50% of their own. But I was drunk and I thought all the flapping meant "yes". DMacks 01:34, 8 November 2006 (UTC)

I don't know about gulls, but humans and mice are 85% the same using a letter-by-letter gene comparison. Using that same method, the chimpanzee is 95% the same. So, you can estimate where a bird lies in comparison to the two. --Kainaw ^(talk) 01:59, 8 November 2006 (UTC)

Since, to the best of my knowledge, lesser black-backed gulls are not a candidate for genome sequencing, the best estimate in the foreseeable future will have to come from chicken. So, based on 6.6x coverage, "about 60% of chicken genes correspond to a similar human gene" and these corresponding pairs are "75% identical on average". [9] Its fair to assume gulls will have a similar level of identity to humans. Rockpocket 08:55, 8 November 2006 (UTC)

New H₂/O₂ alloy

How shall we go about incorporating this development[10] into the Wikipedia? The Science Reference Desk is probably the best place for this to be brought up. X [Mac Davis] (DESK|How's my driving?) 20:32, 7 November 2006 (UTC)

It shouldn't be in Wikipedia. Does the Wikipedia reader know how to interpret XRS data? What Ice VI and Ice VII are, and what the difference is? Does the reader know what hexagonal close-packed hydrogen and oxygen are? If not, how are they supposed to interpret this? Because if you go thinking "Woah, a metal alloy made of water!", then you've likely misunderstood more than you've understood. (And there's enough bogosity of this kind on Wikipedia. See, e.g. metallic hydrogen) --BluePlatypus 21:12, 7 November 2006 (UTC)

Turns out the latter article has improved since I last saw it, or perhaps I was looking at something else. But I have seen a definite statement to the effect that metallic H2 exists and is an alkali metal. --BluePlatypus 21:16, 7 November 2006 (UTC)

Maybe you're right. But a reader can know about Ice VI and Ice VII— I believe they are mentioned in the ice articles. There is no need for the reader to interpret any data from the paper. X [Mac Davis] (DESK|How's my driving?) 05:27, 8 November 2006 (UTC)

industrial water pump

I have a constant humming noise in my house. I'm trying to figure out where its coming from. One of the possibilties is a irrigation or sewage water pump. Does a industrial water pump run constantly. My noise is constant but is louder at night. Thank you, I'm desperate to figure this out. Lynette

Hmmm! Do you live near any overhead power lines or a substation perhaps? Is it a low hum or a higher pitched hum?--Light current 21:52, 7 November 2006 (UTC)

The human ear is quite bad at pinpointing from where low-frequency sound comes from, as you might have noticed. Can you be a bit more specific? Where do you live? Why should there be a pump nearby? Also note that electric appliances, especially transformers, may hum. The transformer could either be a big one, transforming down from high voltage and typically mounted outside, or a small one in some electrical device, transforming down to small voltage. In any case, their kind of hum is easily recognizable because the pitch is always the same: 50 cycles per second (60 in the US and other places). Listen to the hum of e.g. the transformer of a halogen lamp to learn which pitch it is and compare. Simon A. 21:57, 7 November 2006 (UTC)

The humming is somewhere from the outside. When I turn off the power it still hums. I have driven around and heard the hum in my area and up to four miles away. I live in the Santa Cruz mountains on the side of a hill. There are golf courses, waste treatment plants. All the places I've checked don't have a generator or pump running 24 hours a day. I have lived in the same house for 20 years. This hum started last august. It also vibrates. It seems to be coming from the walls. I am not near a substation. Thanks for your time

The "louder at night" part may just be perception (since other noises are lower, the hum seems louder in comparison). When you drive around, does it seem stronger in some areas and weaker in others ? I would think a directional (parabolic) microphone that detects that low frequency could be used to locate the sound source direction. Also, high tension power lines can hum like that. StuRat 00:26, 8 November 2006 (UTC)

Several possible lines of approach here.

1. Talk to your local government. Maybe other people have reported this. At least they ought to know if any new industrial facilities opened last August. One obvious candidate would be a power plant. Even talk to other local governments nearby. You said the noise could be heard for miles.
2. Talk to your local newspaper. If they'll do an article on your mystery sound, maybe someone else will see it and provide more information.
3. Try pinning down the direction of the sound by standing immediately outside each side of your house. If if's quietest when you're by the south wall, then the sound is probably coming from the north. Do this at other locations too, where there are buildings you can walk around. But if a building has something like an air-conditioning compressor on one side, be careful that its sound isn't just masking your noise.
4. Try the poor man's version of the directional microphone technique to pin down the direction of the sound: listen to it through a straight cardboard or plastic tube, which you point in different directions. Any of these directional techniques will work best in the open air well away from buildings and cliffs that might create echoes. The best dimensions for the tube will depend on the specific sound but try something you can easily make and carry around. This might not work at all, but if it does, you should hear an obvious difference depending on which way you point the tube.
5. All of the above assumes that other people hear the same sound you do. If not, then this is a medical problem and you need to talk to a doctor. (This does not mean I think you are crazy -- not even if you are the only person who hears it -- so please don't take this the wrong way! But I thought I should mention the possibility that it's your own problem since you didn't mention other people complaining about it.)

--Anonymous, 00:40 UTC, November 3, in a room full of noisy computer fans.

If you complain effectively enough to you power company, they might send out someone with specialized equipment to analyze the intensity and spectral composition of the noise (if indeed it exists outside your head).Edison 01:06, 8 November 2006 (UTC)

Thank you for your suggestions. I have tried some of them, but will need to push harder on the utilities. I'm not the only person who hears it. There are three of us in the house and a few neighbors hear it also. I think the dog is stressed from it too.(hair falling out) The hum hunt continues.

Also, it might not be just audio frequency. Do you get interference on your radio or TV ? Does a magnetic compass behave properly ? StuRat 02:00, 8 November 2006 (UTC)

Absolute Minimum Density

This sort of goes hand in hand with my previous question about voids, but is there some type of absolute minimum density, i.e. a necessary amount of mass that must be in every space? --138.29.51.251 20:56, 7 November 2006 (UTC)

hit alt-2,5,5 on your keyboard to find out Chris

I read somewhere that "space" has a density of (very) roughly one particle per meter cubed. Don't know if that's the minimum. Don't think anyone has managed to make "space" in a controlled environment. Vespine 22:08, 7 November 2006 (UTC)

No, since the discrete nature of particles means that there's a lot of empty (read: nothing) space between them (disregarding virtual particles and the like, of course). At that scale density doesn't really mean a lot.

You might see our article on Vacuum. According to that article, labratory vacuum pumps can achieve pressures down to 10^-13 torr. Conversion of torr to density is left as an excercisee for the reader. -- The Photon 03:11, 8 November 2006 (UTC)

outer space is at ~10^-16 torr. which according to vacuum, equates to a few hydrogen atoms per cm³. Xcomradex 04:27, 8 November 2006 (UTC)

The minimum energy density would have to be the zero point energy. X [Mac Davis] (DESK|How's my driving?) 05:25, 8 November 2006 (UTC)

Well, there's no minimum density of particles— a cubic meter could have no particles in it at all at a particular time, and I suppose there are some between galaxy clusters that do. However, we have reason to believe that there is a minimum energy spready evenly through space called dark energy (which is probably the same stuff Mac Davis mentions). -- SCZenz 21:10, 8 November 2006 (UTC)

Antacid

The article antacid lists side-effects of various possible active ingredients, but which sort of antacid would usually be preferable for occasional acute indigestion in generally healthy individuals (i.e. not suffering from any relevant chronic condition)? I ask because what I have had in the past has contained a mixture of magnesium hydroxide and aluminum hydroxide, but the pharmacy I visited sells instead antacids based on sodium carbonate or calcium carbonate. I queried the pharmacist as to how much of a problem carbon dioxide generation might be, but he didn't sound like he really knew. Thanks. Arbitrary username 22:53, 7 November 2006 (UTC)

I get occasional acute indigestion, like you describe and my favourite antacid is Rennie's, it contains Calcium carbonate 680mg and Magnesium carbonate - heavy 80mg. I don't believe there are many 'side effects' associated with antacids. I have heard that prolonged heavy usage can alter your stomach function, which you probably don't want, but as far as I understand, occasional use is harmless. You can, after all, purchase Rennie's and other antacids off the shelf. Vespine 23:04, 7 November 2006 (UTC)

OTC antacids come in 2 types, generally: bases that counteract the acid in your stomach, and proton pump inhibitors (that decrease the acid production in your stomach). The kind you mention, carbonates and hydroxides both, react with the acidic stomach juice, forming salt and gas or water, respectively. The gas evolved from carbonates, CO2, (which won't necessarily all come out through your mouth), may cause "gas pains", but is otherwise harmless as long as you take the recommended dose. The raise in stomach pH can leave you open to some infections, but this is not generally an issue unless you are immunocompromised or are prone to gastrointestinal ulcers. The hydroxides are actually more likely to cause side-effects than the carbonates. Magnesium salts can interfere with nucleotide anabolism and also cause hypokalemia secondary to diarrhea. Aluminum hydroxide therapy can lead to a sort of rebound-heartburn in some people. In short: the side-effects of carbonates, even those due to CO2 production, are minimal. These OTC drugs are usually effective at treating the disorders they are meant to treat. That said, if you are having chest pain, periodic or not, you should see a physician to rule out cardiac, pulmonary, and more severe gastrointestinal problems before you attempt treatment.Tuckerekcut 23:34, 7 November 2006 (UTC)

Thanks for your help. Arbitrary username 16:40, 8 November 2006 (UTC)

Sorry for interruption, but the proton pump inhibitors youare referring (along with H2 blockers, PG Analogues etc) are not "antacid", but Anti-Ulcer Drugs. All Antacids are anti-ulcer drugs, but not all anti-ulcer drugs are antacids. Rest has been clearly said by Tuckerekcut  Doctor Bruno  02:40, 9 November 2006 (UTC)

Butylated hydroxyanisole

After lengthly research have been unable to locate resource material to answer following questions concerning compound BHA. Please suggest site reference to answer: Who created/invented BHA; Where and when was it created/invented; The density and it's origin.

Lengthy researches should always include Wikipedia! BHA --Zeizmic 02:08, 8 November 2006 (UTC)

Captive bred pet gulls in the UK

Does anyone breed them in captivity for sale to bird enthusiasts in the UK? I asked this before but the only reply I got was someone saying "it's illegal to catch wild gulls to keep as pets" which wasn't even the question. I'd love a tame pet gull. --84.68.216.184 23:38, 7 November 2006 (UTC)

I think you already have your answer: it is illegal. PullToOpen ^talk 00:10, 8 November 2006 (UTC)

It's not illegal if the gulls are captive-bred (people have been breeding native British birds for generations in captivity). I wasn't even considering taking one from the wild. --84.68.216.184 00:16, 8 November 2006 (UTC)

Urrr.... so your just going to magic the egg up then? Philc _T^E_C^I 00:22, 8 November 2006 (UTC)

Did you read my question? I'm looking to buy a captive bred gull from a breeder. --84.68.216.184 00:27, 8 November 2006 (UTC)

It's a pretty geographically specific question that you are asking. Have you considered contacting your local ornithological society? Vespine 01:08, 8 November 2006 (UTC)

I live in the UK and I've never heard of anyone captive-breeding gulls. I've heard of the odd person keeping a crippled gull as a pet or raising orphaned baby gulls (I've done that!) but I'd imagine they'd be an absolute nightmare to breed in aviary conditions. For one thing, they're very long-lived, slow to develop birds. They are also *very* strong-willed. I must admit that I did consider the idea of keeping the baby gull I was raising as a pet - but that only lasted as long as she remained 'babyish' and 'cuddly'. Once her personality started to appear and she didn't 'need' me as such, she made it quite clear that she wanted her wings - and other gulls. I still have some of the scars. --Kurt Shaped Box 13:42, 8 November 2006 (UTC)

I've got to second Kurt Shaped Box's comments. I was reading (can't remember where -- sorry) about someone else who had the exact same experience. They were used to parrots and were expecting a similar "social bird" experience with a gull, and it lasted while the bird was very young, but as soon as the bird reached maturity, the gull became very solitary and strong-willed and could no longer be kept in kaptivity.

Atlant 13:30, 9 November 2006 (UTC)

You've seen how gulls are with other gulls, right? They start acting exactly the same towards a 'non threatening' human when they reach a couple of months old. Anything I was eating, she wanted. If I wouldn't give it to her, she'd try to take it. When she was a baby, she loved me to pick her up and 'snuggle' her (when she was really small, she loved hiding under my shirt or sleeping against my armpit) - then she started to act like I was trying to kill her if I did that. Funnily enough, she actually likes me and still comes to me for food from time to time - she just got sick of being with me 24/7. --Kurt Shaped Box 09:16, 10 November 2006 (UTC)