Wikipedia:Reference desk/Archives/Science/2009 April 1

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April 1

Artificial nectar

constructing a bird feeder is one thing, now I need a recipe for nectar to supply it.Eg. Tui —Preceding unsigned comment added by Mike Penhey (talk • contribs) 03:26, 1 April 2009 (UTC)

Your local pet shop will sell all kinds of bird food. If you want to make it yourself, it would probably help to know what species of bird you are hoping to attract (at least, where you are). --Tango (talk) 03:58, 1 April 2009 (UTC)

He did say "e.g. tui" which would suggest: 1) He's hoping to attract tui (amongst other birds). 2) He's somewhere in New Zealand (at least I hope so since if the OP is in say Australia and hoping to attract tui I don't think we can help) Nil Einne (talk) 05:51, 1 April 2009 (UTC)

Nectar is usually mostly sugar water, so you could just dissolve as much white sugar in water as possible. Some birds are attracted to bright colors, so you might want to add some food dye, too, perhaps red. You might want to add some actual fruit juice to supply some vitamins, too, although that might make it more likely to spoil. StuRat (talk) 13:28, 2 April 2009 (UTC)

No, no, NO!!! There was a big hoo-ha here in Texas (where humming birds are relatively common - and people often put out feeders to attract them). People who are feeding them sugar water and (worse) artificially colored sugar water - were found to be killing off these poor birds in vast numbers because the birds are not getting all of the proteins, minerals and vitamins they needed - and at least one brand of artificial nectar contained a food coloring that's OK for humans - but toxic to humming birds. Most humming birds eat nothing but nectar - and if you provide them with a free supply - that's all they'll eat. So this is a very serious concern. There has even been talk of passing a law banning the sale of of hummingbird feeders and artificial nectar that does not contain everything that real nectar has. SteveBaker (talk) 14:16, 2 April 2009 (UTC)

I hate to disagree with my hero, but I think that Steve is wrong. Here is what one good source says: "The sugar water we use to fill hummingbird feeders is only a supplement to the birds' natural diet. It's not necessary to buy a commercial "nectar" mix that includes additional vitamins, protein, or other substances, because the birds get all they need from the flower nectar and insects they consume. All they want from us is the quick energy they get from ordinary white cane sugar. It's just fuel for chasing bugs, and causes no known health problems in hummingbirds, whose metabolism is significantly different from humans'." (hummingbirds.net)--Eriastrum (talk) 17:51, 2 April 2009 (UTC)

The Cornell Laboratory of Ornithology concurs that a sugar solution is not harmful. -- Coneslayer (talk) 20:00, 2 April 2009 (UTC)

And note that I did suggest adding some actual fruit juice to provide at least some of the missing nutrients. StuRat (talk) 17:37, 3 April 2009 (UTC)

Also, I'd expect that hummingbirds, like other birds and animals, will detect that they are deficient in some nutrient and become hungry for foods which have provided that nutrient in the past (say nectar from real flowers). This type of reaction is extremely important to the survival of the species, so I'd expect just about every species to exhibit it. Do we have an article on this ? StuRat (talk) 17:41, 3 April 2009 (UTC)

Ahem, Stu that doesn't even work for humans. We'll happily consume high calorie foods and run out of vitamins and minerals. Vitamin deficiency can make vegetarians who don't take supplements seriously ill after a couple of decades. If you want an animal model, cats will gorge themselves on cat food and may run out of taurine if their food doesn't contain that. (OR Even outdoor cats don't supplement their diet with sufficient amounts to offset that deficiency.) Survival of the species only has to keep enough individuals in reasonable shape to reproduce until they have done so. Over many generations natural selection will favor individuals most adapted to a certain diet, but it will just as easily wipe out populations when certain foods are unavailable. There are some mechanisms that evolved over time, like many species having a craving for salt. That can however lead to individuals being killed off by consuming too much salt if it becomes available in abundance. 76.97.245.5 (talk) 06:51, 4 April 2009 (UTC)

The mechanism I described certainly doesn't work perfectly, but does work to some extent. I find myself craving protein when I'm protein-starved. I imagine that vegetarians do, as well, but are unfortunately able to suppress that craving. StuRat (talk) 17:30, 5 April 2009 (UTC)

cell division

why division takes place in living cells only. —Preceding unsigned comment added by Muzhu (talk • contribs) 08:29, 1 April 2009 (UTC)

Hmm, as opposed to dead cells? Dead cells (and dead people) in general aren't very active. Please rephrase your question if you meant something else. ;) -- Aeluwas (talk) 08:41, 1 April 2009 (UTC)

(ec) Cell division requires co-ordinated expenditure of chemical energy to drive specific reactions to create specific proteins and nucleic acid chains. This metabolism cannot occur in dead cells. Axl ¤ [Talk] 08:43, 1 April 2009 (UTC)

Actually I was analyzing the Biology papers of 0-levels, i found this question and it asked for an appropriate answer, so I intended to know more appropriately that why only living cells tend to divide? —Preceding unsigned comment added by Muzhu (talk • contribs) 09:06, 1 April 2009 (UTC)

Isn't the reason that the very definition of "death" in a cell is its inability to divide? SteveBaker (talk) 17:55, 1 April 2009 (UTC)

I don't think that's the definition of death in a cell -- otherwise red corpuscles and neurons would be dead. Looie496 (talk) 18:00, 1 April 2009 (UTC)

And so would senescent cells. Algebraist 18:02, 1 April 2009 (UTC)

Damn! I forgot about that. OK - let me put it another way. A cell that can still divide is not considered to be dead PRECISELY BECAUSE it can still divide and hence must still be alive. Hence dead cells cannot by definition divide - and no further explanation of why that is can be made. SteveBaker (talk) 14:08, 2 April 2009 (UTC)

(for Looie or others) Just curious: by what definition are red corpuscles alive? --Scray (talk) 01:59, 2 April 2009 (UTC)

If we use the Conventional definition here, I'd argue that a RBC satisfies (1) homeostasis, (2) organization, and (3) metabolism pretty well - for 120 days or so. They really don't (6) respond to stimuli in a coordinated way, and the other three requirements clearly aren't met. I'd say RBCs are dead, they just don't know it yet. --Scray (talk) 02:07, 2 April 2009 (UTC)

That definition begins "Life is a characteristic of organisms...". Using that definition, anything that is not an organism cannot be alive. Axl ¤ [Talk] 08:32, 2 April 2009 (UTC)

Awesome! Now would you care to define "organism" without using the word "life" anywhere? SteveBaker (talk) 14:08, 2 April 2009 (UTC)

A collection of organelles which together can conduct homeostasis, metabolize, grow, adapt, respond to stimuli and reproduce? Cyclonenim :  Chat  18:06, 2 April 2009 (UTC)

Hehe! Our article begins: "an organism is any living thing...". The second sentence is (perhaps) more helpful: "organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homeostasis as a stable whole". Using this definition, we could argue that a von Neumann probe is an organism. ;-) Axl ¤ [Talk] 18:19, 2 April 2009 (UTC)

You appear to have missed the ability to organise and metabolize which are listed later on in the article, which von Neumann probes cannot do ;) Cyclonenim :  Chat  18:31, 2 April 2009 (UTC)

I respectfully disagree. The (theoretical) von Neumann probe does indeed organize both its own structure and that of its children. It needs to "metabolize" the raw materials that it encounters using chemical reactions to maintain itself and build children. Axl ¤ [Talk] 18:40, 2 April 2009 (UTC)

I respectfully embarrassed myself, then ;) Cyclonenim :  Chat  19:25, 2 April 2009 (UTC)

What came first, the chicken or the egg?

67.184.14.87 (talk) 08:45, 1 April 2009 (UTC)

I guess you could say the egg since the chicken evolved from a prehistoric bird species (actually according to our article two, Red Junglefowl and Grey Junglefowl) which laid eggs but we are unlikely to call chickens. Nil Einne (talk) 08:57, 1 April 2009 (UTC)

As I expected, this question has been discussed lots of times before (with basically the same answer), check the archives. We also have an article chicken or the egg. It gets more complicated if you ask: which came first the chicken or the chicken-egg or which came first, the bird or the egg? But since you didn't we don;t have to worry about that. Nil Einne (talk) 09:01, 1 April 2009 (UTC)

You'd have to make that "bird or bird egg", as many egg-laying creatures lived before birds, such as insects and reptiles. Still, under every possible interpretation of the Q, the answer is still that the egg came first, as the egg is genetically identical to that which hatches from it, but not to that which laid it. StuRat (talk) 13:17, 2 April 2009 (UTC)

You might like to know that for reasons I don't understand but am happy to follow, when you're offering people a question of dilemma, it's usually rendered "Which...?". Can anyone explain why? --Dweller (talk) 09:11, 1 April 2009 (UTC)

Because this is the current meaning of the interrogative adjective 'which', which used to be used as a fairly general interrogative, analogous to 'what', but is now restricted to (OED which 3) 'In limited sense, expressing a request for selection from a definite number: What one (or ones) of a (stated or implied) set of persons, things, or alternatives.' I don't know how these changes came about, but the OED, as ever, has many illustrative quotations. Algebraist 11:35, 1 April 2009 (UTC)

The mother of the egg that became the first chicken was not herself a chicken. So the answer is 'egg'. —Preceding unsigned comment added by 79.75.39.108 (talk) 00:37, 2 April 2009 (UTC)

The Easter Bunny, silly people. --jpgordon^∇∆∇∆ 00:41, 2 April 2009 (UTC)

Squirrel monkey behaviour

Can someone tell me if squirrel monkeys like doughnuts and use them for rituals? Simply south (talk) 11:23, 1 April 2009 (UTC)

Rituals??? (Incidentally, it's generally a bad idea to trust random comments you hear on radio) Nil Einne (talk) 13:09, 1 April 2009 (UTC)

I would not give them donuts. They are not good for people, I doubt they are good for monkeys. And you don't want to start a monkey cult. 65.121.141.34 (talk) 13:42, 1 April 2009 (UTC)

Well we know squirrels like nuts, so all we have to do is find a monkey playing with dough and and there are lots of recipes available for monkey bread, so just do some algebra and we're all set. DMacks (talk) 14:54, 1 April 2009 (UTC) DMacks (talk) 15:47, 1 April 2009 (UTC)

Yes, it is true, the use them for very complicated rituals concerned with choosing a partner. It is fascinating to see and there have been many questions asked about what they used before doughnuts were invented. The really, I mean really, odd thing is that they only carry out this ritual on one day in the year, Hmm? I wonder which date that is??!! —Preceding unsigned comment added by 86.4.190.210 (talk) 18:26, 1 April 2009 (UTC)

I believe that the scientific consensus is that the monkeys actually invented the doughnut 50,000 years ago, and that people adapted the monkey dating tool to a morning energy booster for police officers. 65.121.141.34 (talk) 18:52, 1 April 2009 (UTC)

Solar Eclipse

This is a question asked to me by my little sister and somehow i just couldnt give her a satisfactory answer... the question is... its said that a solar eclipse occours when the moon comes between the sun and the earth. But that happens so many times a year, so why don't we have that many solar eclipses each year??? —Preceding unsigned comment added by Rrkrish (talk • contribs) 13:15, 1 April 2009 (UTC)

Because that doesn't happen many times a year. For our article solar eclipse: 'The Moon's orbit around the Earth is inclined at an angle of just over 5 degrees to the plane of the Earth's orbit around the Sun (the ecliptic). Because of this, at the time of a new moon, the Moon will usually pass above or below the Sun. A solar eclipse can occur only when the new moon occurs close to one of the points (known as nodes) where the Moon's orbit crosses the ecliptic.' Algebraist 13:22, 1 April 2009 (UTC)

The moon may come "Between" the earth and the sun once a month in a rough sense, but in order to have an eclipse they have to be exactly lined up in a straight line. That doesn't happen often, it's usually off a little one way or the other.

This might not be obvious on a flat drawing of the solar system, but if you consider the situation in 3d, it's pretty clear. (ie: if you draw the solar system on paper, you need to understand that not all the heavenly bodies are exactly on the paper, they might be a little above or below it.) APL (talk) 13:37, 1 April 2009 (UTC)

Also check out this illustration showing the relative size and distance of the Earth and Moon to scale. APL (talk) 13:46, 1 April 2009 (UTC)

The other point is that although total eclipses are fairly rare (because the earth/moon/sun system have to be lined up to a spectacularly precise degree) - partial eclipses of various kinds are about three times more common. There are typically around two eclipses per year - although in 2011, there will be four of them! The moon orbits the earth about 13 times per year - so the odds of it causing an eclipse is about one in every six times it passes roughly between earth and sun - which I think we can tell your little sister is actually "pretty common". However, you don't see them all that often because you have to be standing in the shadow of the moon to see them. Since the moon is rather tiny compared to the earth, its shadow is pretty small too - so the odds of you happening to be in the right place to see a partial eclipse is also surprisingly small. If you look at List of solar eclipses in the 21st century - you'll see that the next eclipse (in July) is only going to be total in Central and Northeastern India, Bhutan, Bangladesh, Myanmar, China and the Ryukyu Islands - if you don't live there - you won't see it (although it's also going to be a partial eclipse in Asia, the Philippines, Indonesia, Melanesia and Hawaii). SteveBaker (talk) 17:43, 1 April 2009 (UTC)

evolution or creation

why are we always taught that all the species that we see on the earth today have in some way or the other evolved from the ones that were there before them??? why aren't there any theories being taught today in schools and colleges that also stress on creation of life and different species by God, rather than by plain evolution?? —Preceding unsigned comment added by Rrkrish (talk • contribs) 13:19, 1 April 2009 (UTC)

Assuming that's true, it's probably because there isn't any evidence supporting the creation theories. See Creation and evolution in public education for more. Zain Ebrahim (talk) 13:27, 1 April 2009 (UTC)

Because it is not possible to prove creationism with science as an omnipotent being could reinvent the laws of science in any way to get stuff done, and science is built upon there being a set of rules that are assumed (and so far observed) to be immutable. 65.121.141.34 (talk) 13:41, 1 April 2009 (UTC)

There are lots of theories out there about all sorts of different things. Only the ones that have strong evidence on their side get to be taught in the schools. Theories about the origin of species are no exception. Dauto (talk) 15:05, 1 April 2009 (UTC)

In practice it is a bit more complicated than having strong evidence (see, for example, string theory—evidence is NOT the reason people think it is a good idea and why it gets taught at university levels). I think usually it is safer to just say that what gets taught in schools as "science" is that which the scientific community as a whole considers to be "science". Why they think this or that theory is more scientific than, say, another, can vary from theory to theory, field to field. --140.247.241.244 (talk) 16:47, 1 April 2009 (UTC)

Put more practically (no epistemological assumptions needed), public schools have for a long term determined that "science" needs to be taught in "science" classes. The idea of differently, uniquely created types of species by God is not considered by the courts or the scientists to be "science". There are some who disagree, but they have not been terribly successful in convincing people of that on the whole. "Evolution" is currently the explanation for speciation that is considered to be the most in line with "science". In "religion" classes they do read Genesis though they don't necessarily claim that it is actually "what happened" more so than they would for, say, the Koran, which they'd probably also read. --140.247.241.244 (talk) 16:44, 1 April 2009 (UTC)

You actually can be taught in public school that God created the different species, if you're willing to move to some of the most backward places on Earth. --Sean 16:58, 1 April 2009 (UTC)

Actually - you aren't allowed to teach "God did it" in public schools in Texas - that's still contrary to the US constitution. All you're actually allowed to teach is that evolution isn't necessarily a proven theory...which is still ridiculous...but the US constitution still applies, even in the Texas public school system. SteveBaker (talk) 17:09, 1 April 2009 (UTC)

Of course that is subject to interpretation. The constitution only says "Congress shall make no law respecting an establishment of religion", which according to a an originalist really says nothing about this matter. Sorry, this is getting a little tangential.-RunningOnBrains 17:20, 1 April 2009 (UTC)

Why pick only on evolution? We could be trying to teach students the formula for the period of swing of a pendulum as a function of it's length - and we'd have to keep stopping and saying "Unless God just decided to make up the evidence to make it seem that this is how a pendulum swings in order to test our faith". But then, that's just the christian god and the christian creation myth - in the interests of open-mindedness and skepticism - wouldn't we also have to teach the theories of all of the List of religions and spiritual traditions (check out that list...it's VERY long!). If we opened up the teaching of evolution to include creationism - wouldn't we also have to teach that the universe was farted out of the butt of a camel (or whatever it is that other people believe)?

The problem is that to teach science - you have to teach "The Scientific Method". That method says that all of science is the result of application of the Hypothesis/Experiment/Theory approach. The problem with creationism and intelligent design is that they quite utterly fail to use that approach. Hence they cannot be taught as "Science" because they really aren't at all scientific. But in the end - we teach evolution because it's true. We don't teach the other things because they are clearly a pile of steaming crap that doesn't stand up to the slightest scientific investigation! Frankly - if I were interested in pushing a religious POV - the very last thing I'd want would be to have scientists telling our children about it! They are going to have to teach that the creationism myth has no evidence leading toward it - that no experiments have been done to back it up - that there are a million pieces of rather impressive evidence that it's NOT true - that, far from answering the question of how all of this happened - it just creates another question ("How did God originate?"). Personally - I'd think you'd probably do better to avoid that happening and stick to teaching your poor kids all of this crap in the privacy of your own home/church/mosque!

Another problem: There are a literal infinite number of unprovable things that we could teach (See Russels teapot. If we tried to teach even 0.000001% of them - we'd have no time left to teach students what they actually need to know to become working scientists - to earn money - to make breakthroughs and generally be scientists. If a kid tries to get a job as a working scientist and it comes out in the interview that they don't consider evolution to be true - then they really aren't going to get jobs. That's not a matter of discrimination - it's a matter of survival in a modern science-laden world. There is simply no need to teach this other stuff in order to get the job done. If the religious fanatics out there need to push this stuff - then let them do so - but please - not while we're trying to teach teach kids science. SteveBaker (talk) 17:09, 1 April 2009 (UTC)

Sean, what evidence do you have that creation is commonly/usually taught as science in Iranian schools? While religious education is a compulsary part of education in many Islamic countries, including Iran and I presume the creation idea is taught there, my understanding, supported by our Islamic creationism and Creation–evolution controversy#Islamic countries is that the evolution-creation controversy has largely passed over the Islamic world until recently. The controversy appears to have started to take hold, particularly in Turkey. Our article mentions evolution is taught in Egypt, but banned in Sudan and Saudi Arabia (it doesn't however say that creationism is taught as science in either schools). Iran is not mentioned. Iran is not mentioned. However from [1] and [2] while not entirely clear, it appears to me that evolution is accepted and may in some instances be taught, provided it doesn't get to the point where it's considered in opposition to the Islamic teachings. It's definitely not clear that creationism is taught as science in Iranian schools. (Actually my gut feeling is that potentially nothing is taught). Nil Einne (talk) 10:23, 2 April 2009 (UTC)

Iran was not mentioned twice ? :-) StuRat (talk) 12:32, 2 April 2009 (UTC)

Sorry I striked that Nil Einne (talk) 17:33, 14 December 2009 (UTC)

Steve, you seem to be passionate about your arguments, but the fact that creationism is not scientifically provable does not translate it into being a complete pile of crap. It just means that it can not be proven scientifically. Science does not have all the answers, no matter how much some may wish it did. The key difference is that some think that science CAN get all the answers eventually, and others think that humans are rather arrogant to think that they can eventually understand and explain every phenomenon in the universe, past present and future. 65.121.141.34 (talk) 18:26, 1 April 2009 (UTC)

No - that doesn't really hold water.

Either...

You have to look at:

• All of those neatly arranged fossils - dated and arranged in timewise order, they show a clear progression of gradual change.
• The DNA evidence for common ancestry - all living things share large chunks of DNA in common - and where they differ, that follows the evolutionary chain that the fossils provide (eg Human DNA is more like Chimp DNA than Dog DNA - but all mammal DNA has more in common than all fish DNA).
• The demonstrable evolution of things in modern nature such as antibiotic-resistant bacteria in hospitals or warfarin tolerant rats in big cities - butterflies on remote islands, Darwins finches...you name it.
• The ability to demonstrate evolution in simulation and in laboratory experiment - if you set up a computer program that has creatures with simulated DNA, simulated mutation, simulated survival-of-the-fittest - then your synthetic creatures evolve just like real ones. If you take a bucket of bacteria and sequence their genes - then stress them with some toxin over many generations - then after a week or two, do a gene test on the survivors - then you can find the gene that mutated...the bacteria evolved - right there in front of your eyes.

and then, you must seriously ask: Does your theory have an explanation for ALL of these well-established easily demonstrable facts? (Evolution does - creationism certainly does not) - if it does not - then it's disproved because it doesn't explain the facts. Disproved is a lot stronger than "Not proved". If creationism were true then we would have human fossils of the same age as dinosaur fossils - and we don't...not even close. The efforts creationists take to weasel their way around these problems are flat out laughable in their lack of scientific rigor.

...OR...

You have to resort to the purely religious approach of saying "God put all of these bizarre things like fossils and DNA and warfarin-tolerance into the world in order to make weak-willed people believe in evolution as a test of their faith"...or something like that. In so doing - you are heading down a dark and dangerous path. Every time anyone raises any objection whatever to your theory you are now forced to say "God made it that way to test you - logic doesn't apply here". You can do that - and science certainly can't prove it's not true - but in so doing, you've shed any hope of a logical outcome to the debate - and you head down a road where you can't reason about the universe anymore. You can't build a bridge without having no clue whether it'll fall down or not - because you can't trust your math and materials science anymore...maybe God just put those there to test our faith too? What you have is religion, belief, faith and all that goes along with it...and you can't teach that in US public schools - because it is (quite rightly) illegal. In most school systems around the 'civilised' world, that kind of thing is moved out of science classrooms and into 'religious instruction' classes because parents of non-christian children have a right to NOT have their children indoctrinated by a bunch of raving loonies (as we atheists see you guys...let's be quite clear about that!). In the worst school systems in the world, religion gets taught to the exclusion of science - and I'd like for you to pause and look at the quality of life in those places - and ask yourself whether that's really where you'd like to go.

If you go with the former approach then the failure of creationism and the success of evolution to explain those things - AND have the predictive power that all good scientific theories should have - means that it is (objectively) a far less viable theory than evolution - and it should therefore be shelved and largely ignored...just as we have given up on the steady-state theory of the universe in favor of the Big bang because the former cannot explain the nature of the cosmic microwave background - and just as the big-bang theory may one day have to be shelved when we figure out what 'Dark energy' actually is.

If you go with the latter approach - then you have created for yourself an "unfalsifiable" theory - which means that science MUST ignore it because unfalsifiable theories are as firmly disallowed as dividing by zero in mathematics (and, interestingly, for similar reasons!).

So this is not simply a matter of "not yet having all of the answers" - it's a matter of having two competing theories - one of which fits the facts elegantly and perfectly - and the other of which either contradicts the facts and is therefore false - or is unfalsifiable and therefore not worthy of further consideration. Either way - evolution wins...just as the big bang wins over steady state and the periodic table of elements beat out the earth/air/fire/water theory of matter. When a theory is useless - we put it back on the shelf, stop teaching it to our kids and we move on. And that's PRECISELY what's happened here with creationism - it had a good run of several thousand years - but now it's as obsolete as flat earth theory, heliocentricism, astrology, etc. Of course there are always (and should always be) people who continue to defend the old theory for a while - we need a measure of skepticism. But there comes a point (and we're certainly WELL beyond that with evolutionary theory) where the evidence is so totally overwhelming that it's time to put creationism away along with lysenkoism and the theory that mice are created from bits of cheese and old clothing. Without some kind of evidence of ANY kind - it's simply crazy to keep beating that dead horse.

If you maintain that creationism "can not be proven scientifically" - then you are in the 'non-falsifiable' camp - and science simply doesn't teach non-falsifiable things. SteveBaker (talk) 20:39, 1 April 2009 (UTC)

Thank you Steve, you completely made my point. You can not disprove that which is not scientific, so that is why it is not taught in a science class. As an aside though, creationists don't usually go with God creating fossils and leaving them around fo people to find. Most of them believe that the geological record is not as constant as the majority of scientists believe and that the great flood found in the Bible buried them.65.121.141.34 (talk) 20:54, 1 April 2009 (UTC)

Actually, Steve did an excellent job disproving creationism as it contradicts all the available evidence, unless you want to subscribe to the idea of dishonest god(s) who plant fake fossils, etc. to trick mankind. I guess you can't disprove those god(s). But I'm not aware of any religion that actually subscribes to such a view so I guess one would have to invent one. A Quest For Knowledge (talk) 12:14, 2 April 2009 (UTC)

Yes. My point exactly. You either use logic to argue that creationism is possible - and find that science beats your crappy theory into a small mangled splat on the sidewalk of life...or you loudly assert that God can make fossils if he wants to - and that's that. I have met fundamentalist christians who first start down the "logical argument" path with me - and then when I actually have them cornered and convinced that they've run out of arguments, they ALWAYS fall back on the "Well, God just made it that way" argument. Typically this comes about roughly when you explain precisely WHY the dinosaurs couldn't have died out in the same flood that killed the Neanderthals and floated Noah's clearly impossible boat. Isaac Asimov said that violence is the last refuge of the incompetent. I think he was wrong about that - it's religion. When your brain is too tiny to accept all of the evidence with an open mind - and reason your way through it - it's just easier to sit back and say "God did it" in response to every difficult question. SteveBaker (talk) 14:02, 2 April 2009 (UTC)

Yeah - and that's just typical. They make that statement and then walk away without listening to the scientist's response. Firstly, if these prehistoric creatures all died at the same time and been buried in some amazing flood - then they wouldn't be found in rock strata organised by age. We find all of the early fish in one layer - all of the creatures that just climbed out of the water and onto the land in another layer on top of that - dinosaurs of various kinds in more layers on top of that - larger mammals on top of that. You can find all sorts of mineral deposits that let you see how the layers of compressed silt are separated by things like lava flows. You can see that those lava flows had then been eroded by thousands of years of wind and water - then more fossils in layers on top of that. This doesn't in any way fit with one single mass-extinction event. With more recent species we can do radio-carbon and other radioactivity datings. There are literally DOZENS of ways to disprove that crazy theory. However, the nut-job creationists don't want to hear any of that. As I said - if they submit themselves to the processes of scientific tests, logic and explanation - their theory evaporates - it's a joke. Only if they resort to "Because God did it" - can they escape that conclusion - and at that point, this is religion - and it doesn't belong in science classes. SteveBaker (talk) 00:38, 2 April 2009 (UTC)

There are versions of Creationism which purport to be as "scientific" as the real "science". They purport to have lots of evidence. Institutionally trained scientists almost always disagree with their evidence and disagree with their assertion that they practice the scientific method. Creationists can point quite validly to a large body of literature about scientific practice which has shown for some decades now that 1. scientists are not a "scientific" as they claim to be in such debates, 2. the line between "science" and "non-science" is often in the eye of the beholder, and 3. there really is no consistent "scientific method" that holds true for all fields of what is considered to be "science". Nobody is arguing about teaching everything (there aren't the resources)—the question is, with limited resources, what to teach? The Creationists believe there are good reasons to teach Creationism that go beyond simple careerism (in part because if the educational system changed dramatically the careerist approach would not be relevant—if everyone learned Creationism then it wouldn't be a way to sort it out). Now I'm no Creationist in the slightest but I don't think the debate is helped by appeals to a single Science with its singular Method and its unfailing adherence to Evidence and all of these concepts that are trotted out despite being quite problematic both in practice and in theory. It ends up being an argument against a straw man and a false dilemma when formulated in such terms. I think it's a lot easier to take an almost Wikipedia approach to it: in schools, we generally agree that in "science" classes "science" should be taught. The line between science and non-science should not be mediated by civilian school boards who don't have the necessary training or broad view in order to decide what the long-term consequences of such a decision would be. The most appropriate place for that sort of discussion to take place is probably with the established scientists who have brought us all those good things that we like about science enough to teach it anyway (which we can claim is about a love of knowledge, but in this society the number one reason we want institutionalized science training is because 1. science affects our world in massive ways, and 2. one of the main outgrowths of science is technology). So if you want to teach Creation "science" in schools, you've got the convince the scientists first that it is real science! --140.247.241.244 (talk) 17:21, 1 April 2009 (UTC)

From the scientist point of view the Evolution vs Creation is a very boring debate. The creation side has nothing going for it. No evidence at all. None. Zip. Nill. Zero. That makes the decision wheather to teach creation or not a very trivial matter indeed. Dauto (talk) 01:44, 2 April 2009 (UTC)

Let's consider what happens if Biblical Creationism were to be taught as science. In addition to being taught as an alternative to Evolution, there also would need to be Biblical alternatives to teach plate tectonics and geology, as the current scientific approach requires the Earth to be far older than the Bible would indicate. Similarly, the rate of nuclear decay would need some alternative explanation in chemistry class, to prevent carbon dating, etc., and the speed of light would need to be altered in astronomy class to allow light to reach us from stars very far away in a universe that's not old enough to permit that. Moving on to social studies, we would need to move the first humans from Africa to "Eden", wherever that is, and make all languages form at once (tower of Babel), rather than when they actually did form. And, if only God can create different languages, and does so to confuse mankind, we need an explanation for why languages change over time, or else we need to deny that they do, and insist that Shakespeare was using the exact same words that we use now. If great floods and other natural disasters are also used by God to punish people, we need a class that teaches exactly what sin each natural disaster was created to punish, and how we can therefore prevents disasters by repenting rather than building levies, clearing flammable underbrush, etc. StuRat (talk) 12:58, 2 April 2009 (UTC)

The folks who are writing the new Texas public school science books are here - taking notes - and would like to personally thank StuRat for this comprehensive guide to how they should be updating the 2010 editions. Awesome - excellent - thank you!

There is no doubt that once you start to doubt the findings of mainstream science - it's hard to stop with evolution. As I explained before - you get to a point where no scientific explanation whatever can be considered entirely valid - and at that point, you can't do engineering anymore. If you want to build a bridge - you can't trust materials science - so your calculations on the stresses involved are essentially worthless. But that's OK because when the bridge collapses, you can just say it was "The will of God" - and there was just nothing anyone could do. I always find it amusing that property insurance covers "Acts of God"...I always wonder whether they should take into account my blameless and relatively sin-free life when setting the premiums!

For me, personally, God (and gods in general) are precisely as believable as Santa Claus, the Easter Bunny and the Tooth Fairy. Seriously basing how I teach science on the premise that somewhere there are flying reindeer and a sleigh that can deliver toys to all of the children of the world in one night - is PRECISELY as ludicrous as teaching creationism. There is truly no distinction in the scale of lunacy involved. I'm pretty sure that almost all religious people would be very upset if teachers in public schools started teaching their children that Santa Claus was real and that they WILL be getting free stuff delivered down the chimney on Xmas eve - and that the Tooth Fairy literally does come in the middle of the night and swap out that tooth for a nickel. They should consider my (identical) position when (as an Atheist) I demand that they do not inflict their pile of steaming bullshit on my child. SteveBaker (talk) 13:48, 2 April 2009 (UTC)

I can comprehend your viewpoint without the need for profanity. I request that you strike it from the record and refrain from such comments in the future. There may be children present. 65.121.141.34 (talk) 18:57, 3 April 2009 (UTC)

Two problems with that:

1. As a matter of policy Wikipedia does not censor for the benefit of children or otherwise - and I think children (even quite religious ones) are completely aware of what 'steaming bullshit' is - it comes out of bulls - and it steams. And just in case they don't, I should explain that it's "moo-cow poop" kiddies!
2. The entire concept of "profane language" is meaningless to an atheist. The definition of 'profane' (according to Wiktionary) is:

1. Unclean; ritually impure; unholy, desecrating a holy place or thing.
2. Not sacred or holy, unconsecrated; relating to non-religious matters, secular.
3. Treating sacred things with contempt, disrespect, irreverence, or undue familiarity; blasphemous, impious. Hence, specifically; Irreverent in language; taking the name of God in vain; given to swearing; blasphemous; as, a profane person, word, oath, or tongue.

I'm fully in favor of verbally desecrating things that are complete nonsense. I'm more than happy to be 'non-sacred' and 'un-holy' and I most certainly do intend to continue to treat "sacred things" with contempt, disrespect...etc. I do not intend to give religion of any kind any respect whatever - it's nonsense and I intend to continue saying that because to do otherwise would be dishonest - and I value honesty. Hence profane language is a goal - not something to apologize for. SteveBaker (talk) 21:05, 3 April 2009 (UTC)

Some might claim that the scientific explanation of the origin of the universe is equally ludicrous considering there is no explanation given for where the energy to create the big bang originated, especially considering that some scientific principals Conservation of energy, Conservation of mass state that neither energy nor mass can be created or destroyed. If there is an explanation for the spontaneous generation of energy and mass from nothing using current scientific laws, I would be most interested in reading it. 65.121.141.34 (talk) 16:16, 2 April 2009 (UTC)

If that bothers you - then you don't understand the theory. The big bang created spacetime as well as all of the matter. There is no "before" because time itself starts at the big bang. That's not just a 'theological matter' as you'd say if I asked where God came from - it's actually what the math and the physics say must have happened given the evidence that is everywhere around us. And it's an elegant solution because it answers the entire set of questions that you're asking. May I recommend reading "A brief history of time" - by no less than Stephen Hawkins himself. It's a short and easy read and it covers this exact point rather well in language that the layman can understand. SteveBaker (talk) 20:26, 2 April 2009 (UTC)

But certainly the idea is correct, that neither science nor religion can completely explain everything. We get down to "did God always exist or was he somehow created ?" or "what are strings made of ?". You could always push the question back a bit farther, by creating an earlier race of gods or explaining what strings are made of, but there's always another "then what caused that ?" question to be added. StuRat (talk) 17:30, 3 April 2009 (UTC)

The fact that there are no current scientific explanations for some things does not invalidate the scientific explanations that do currently exist. The one disadvantage that Science has in arguments with Religion is Science's willingness to say "I don't know" in response to the question "Why?"

Of course, that is ultimately to Science's advantage, as it then toddles off to find the answer. - Eron^Talk 16:45, 2 April 2009 (UTC)

It's not even that - certainly, when presented with something we don't know, we say "Hold on while I find out" (which might take an hour or perhaps a century or two). But more importantly, when we do find that one of our theories is proven wrong, the overwhelming response is "OH! COOL!". We love nothing more than to have our world overturned by something freakishly unlikely that has somehow gotten strong evidence for it. This doesn't happen when creationism challenges evolution because it doesn't overturn anything - it just turns out to be wrong. But when (for example) the rate of change of speed of the Voyager probe as it leaves our solar system is not what we expect - we don't try to hush it up because it messes with out theories - we leap out there and excitedly start looking for seemingly bizarre explanations and things that might point to new forces or a new understanding of gravitation. The most exciting moments for most scientists are when experiments don't come out the way we expect - because that's when we learn something new. SteveBaker (talk) 21:16, 2 April 2009 (UTC)

Hot water for drinking

Why don't we like warm water for drinking, whereas it is very pleasurable to use warm water while taking shower and warm food to eat? Is there some role of evolution? - DSachan (talk) 14:26, 1 April 2009 (UTC)

Because we associate warm-water with standing-water. I would expect it is quite cultural rather than evolutionary. We associate ice-cold water with freshness/quality (as in drinking water quality) - we associate tepid water with standing/stale water, and we associate hot-water with hot-drinks, though plenty of people drink hot-water as a drink (at least where i'm from). 194.221.133.226 (talk) 14:56, 1 April 2009 (UTC)

I know a lot of people who drink hot water, in preference, say, to tea or coffee. (And I don't associate warm water with standing water.)--Shantavira|^{feed me} 15:52, 1 April 2009 (UTC)

Mind your "we"; it's totally cultural. In Great Britain, if you ask for "a glass of water", you will most likely get a glass of room-temperature water. You have to ask for ice specifically, and if they have any you'll get it, but it's considered a slightly special request. —Scheinwerfermann ^T·_C16:03, 1 April 2009 (UTC)

Where, here in the US, you typically get water with ice in it - whether you want it or not - and it may be a major struggle to NOT have ice in your Coke when you go to some fast-food place. SteveBaker (talk) 16:45, 1 April 2009 (UTC)

Most of the taste of pure water comes from dissolved oxygen, and warm water has a lot less than cold water. Looie496 (talk) 18:04, 1 April 2009 (UTC)

I'm not sure about Schein's comment - generally if you ask for a glass of water in the UK the host will run the tap until the water is cold (i.e the water in the the house's pipes has been purged and the water is fresh from the main) - while not ice cold it's certainly colder than room temperature. Exxolon (talk) 19:34, 1 April 2009 (UTC)

Are we talking about hot water say 45C which is disgusting, or warm water, say 25C which is fine? Also, I have noticed that if you boil water and then cool it, it still tastes funny. —Preceding unsigned comment added by 65.121.141.34 (talk) 19:11, 1 April 2009 (UTC)

That follows naturally from Looie496's comment - when you boil water, you drive out the dissolved oxygen - so afterwards it tastes 'flat'. SteveBaker (talk) 19:53, 1 April 2009 (UTC)

The concept is likely much more than cultural; clearly people all over the world from various times and places prefer hot or cold water to tepid water. Consider this 2000 year old text; "I wish you were either one or the other! So, because you are lukewarm—neither hot nor cold—I am about to spit you out of my mouth." The original Greek uses the word for "Vomit" in the place of "spit out"... Clearly tepid water as disgusting was a well known concept; otherwise this analogy would have not been so easy... --Jayron32.talk.contribs 21:56, 1 April 2009 (UTC)

Although many Christians would like to believe the bible is universally applicable, I'm not convinced that its use here indicates anything other then it being applicable to the culture of those who wrote it. Also in terms of the cooled hot water, it is common practice and often recommended to boil your tap water before drinking. So I used to drink cooled or cold tap water all the time and to be honest I've never noticed anything odd about the taste. Nil Einne (talk) 09:55, 2 April 2009 (UTC)

I've been told that vigourously shaking water after boiling it will re-oxygenate the water and eliminate the "flat" taste. - Eron^Talk 16:46, 2 April 2009 (UTC)

Maybe cold water (with ice) is less favored in Britain because it has a colder climate? All but the northernmost parts of the US are pretty hot in summer. 128.194.103.37 (talk) 13:27, 5 April 2009 (UTC)

schrodinger's time independent equation

in the relation of time-independent schrodinger's equation

            ∆^2Ψ + 2m/(ħ^2)[E-V]Ψ  = 0                                              -(1)

there appears a "E" in (E-V),which is kinetic energy of the particle. but if we take the kinetic energy of any particle executing some non-uniform motion,how can be the kinetic energy independent of time? since kinetic energy of any particle can be expressed as

                       E=1/2(mv^2);

where,

           m = mass of particle
           v = velocity of particle

if a particle executes non uniform motion its velocity and hence kinetic energy will depend upon time and the the whole equation seems to be dependent on time.

for a particle, its total energy E(total) can be expressed as sum of its kinetic energy as well as potential energy,which is independent of time.

               Et = E + V

where,Et = total energy of the particle

     v= potential energy of the particle

so, E = Et-V -(A)

Making this substitution in the schrodinger's equation, we get

                         ∆^2Ψ + 2m/(ħ^2)[Et-2V]Ψ  = 0

this equation is totally independent of time, making schrodinger's expression independent of time —Preceding unsigned comment added by Sachin nishchal (talk • contribs) 17:15, 1 April 2009 (UTC)

1. If you have seperated the time-dependent Schroedinger equation then the E which appears in the time-independent equation cannot depend on time. So, I'd say this rules out from the start a lot of what you go on to say.
2. E in the time-dependent equation is the total energy. Not the 'kinetic part' as I think you suggest.
3. Due to the subtleties of what can be known simultaneously (a la Heisenberg), it's not true that you can seperate the energy into a kinetic part and a potential part for most systems. (In light of this, how would that affect your definition of E in terms of v?)

I realise I wasn't comprehensive but there are some comments to get you started at least. 86.140.160.93 (talk) 19:56, 1 April 2009 (UTC)

Yes, indeed the 'E' that shows up at Schroedinger's time independent equation is the total energy. Dauto (talk) 02:49, 2 April 2009 (UTC)

Genetics Question

A brown-eyed man whose mother is colorblind and whose father had blue eyes is engaged to marry a woman whose colorblind mother had blue eyes and whose normal visioned father had blue eyes. What is the Genotype of the young man? Of his fiancee? If they marry and have children, what are the chances of having a brown-eyed, normal visioned child? A blue-eyed, colorblind child? A brown-eyed normal visioned daughter? A blue-eyed, colorblind son? —Preceding unsigned comment added by 198.85.212.10 (talk) 17:17, 1 April 2009 (UTC)

I added a section header for you. APL (talk) 17:29, 1 April 2009 (UTC)

Looks like a homework problem, and we don't do those. Looie496 (talk) 18:09, 1 April 2009 (UTC)

Isn't colour-blindness a male trait, so this is an unusual situation to find yourself, likewise eye colour isn't based on a single gene... But nevermind, read the through the question and draw a family tree, although I think you probably need more infomation. —Preceding unsigned comment added by MedicRoo (talk • contribs) 18:32, 1 April 2009 (UTC)

Colorblindness is mostly male because the most common form is X-linked recessive. Looie496 (talk) 18:41, 1 April 2009 (UTC)

(ec) No, color-blindness is (most commonly) a recessive trait on the X chromosome, meaning it is apparent more often in males (since they don't have a second X chromosome to "override" the trait). This question has "homework" written all over it—specifying the mothers are colorblind is a convenient way to fully-indicate their genes ("normal-vision" could mean they have 0 or 1 colorblind gene). To solve it, consider each "trait" (colorblindness, eye color) independently, find the genes of the parents, their children, then prospective offspring. Your book will most likely have example problems similar to this one. If you get stuck, explain where you're at and what you're having problems with and we might be able to help, but we won't do your homework for you. – 74  18:54, 1 April 2009 (UTC)

Briefly, your teacher apparently wants you to assume that eye color is determined by a single gene (not true, but I guess close enough for government work) at which "brown" is dominant and "blue" is recessive, and also wants you to assume that the kind of color-blindness he's talking about is X-linked recessive.

With these assumptions:

A brown eyed person with a blue eyed parent must have inherited a blue allele from that parent, and a brown from the other.

A person with a color-blind mother must have inherited her color-blindness gene, because she must have it on both X chromosomes or she wouldn't be color-blind; a man only has one such gene, so all her sons will necessarily be colorblind. A woman with a color-blind mother inherits a color-blindness gene from her, but also inherits a gene from her father, and in this case, he's not color-blind. So the financee is heterozygous for color-blindness.

A person with blue eyes necessarily is homozygous for "blue" eyes (the information about the fiancee's parent's eye color is unneeded; you know her genotype because you know her phenotype, because only one genotype produced that phenotype. You'd need to know the parent's eye colors if her eyes were brown, because more than one genotype produces that phenotype.)

So, using BLUE/BROWN and CB (for colorblind) and N (for not-color-blind), and - for no gene at all:

groom = BLUE/BROWN; CB/-

bride = BLUE/BLUE; CB/N

	BLUE	BROWN
BLUE	BLUE/BLUE = blue	BLUE/BROWN = brown
BLUE	BLUE/BLUE = blue	BLUE/BROWN = brown

If you make a Punnet square, you will see that you would expect half the couple's children to be blue-eyed, and half to be brown-eyed.

The colorblindness question is probably most easily explained if you consider where a person's X chromosome comes from. Men have one X chromosome, and it comes from their mother. So all sons of this couple will be color-blind. Women have two X chromosomes. One of them is from their father, and the other is a mixture of their mother's X chromosomes. Since one gene is enough for normal color vision, and she is certain to get one of these from her father, all daughters of the couple will have normal color vision.

To work out the chances, you have to realize there are only two independent traits of the three: eye color is independent, color vision is dependent on sex. All daughters will have normal color vision; all sons will be color blind.

So, the chances of any particular child being:

a brown-eyed, normal-visioned child: 50% chance of brown eyes, 50% chance of being female => 25%

a blue-eyed, colorblind child: 50% chance of blue eyes, 50% chance of being male => 25%

a brown-eyed, normal visioned daughter: 50% chance of brown eyes, 50% chance of being female => 25%

a blue-eyed, colorblind son: 50% chance of blue eyes, 50% chance of being male => 25%

The chance of:

a brown-eyed, normal-visioned son: 50% chance of brown eyes, 0% chance of being male with normal vision => 0%

a blue-eyed, colorblind daughter: 50% chance of blue eyes, 0% chance of being female with colorblindness => 0%

- Nunh-huh 11:30, 2 April 2009 (UTC)

I thought we weren't supposed to answer homework questions here... 74 already gave enough information to get the right answer. That being said, I would agree with the genotypes given by Nunh-huh above, and the eye color calculations are correct, but the color-blindedness conclusions are wrong. It was correctly stated that the man in this relationship is heterozygous for blue/brown eye color and hemizygous for the colorblind mutation on the X chromosome (i.e. he's affected, but the questioner wanted you to deduce that from the fact that his mother is colorblind). It was also correctly stated that the female in this relationship is heterozygous for the colorblind mutation because her father was colorblind and she is therefore an obligate carrier.

Here is where the problems start: "Men have one X chromosome, and it comes from their mother. So all sons of this couple will be color-blind" - only if the mother is affected. In the couple we're talking about here, the mother is a carrier and hence has a 50/50 chance of passing the colorblind mutation to each child. Therefore, all male offspring (who inherit their father's Y chromosome) have a 50% chance to inherit the colorblind mutation from their carrier mother and thus be affected and a 50% chance to inherit the normal copy of the gene and thus be unaffected.

"Women have two X chromosomes. One of them is from their father, and the other is a mixture of their mother's X chromosomes. Since one gene is enough for normal color vision, and she is certain to get one of these from her father, all daughters of the couple will have normal color vision" - only if the father has normal vision. In this example, he's colorblind and therefore all of his female offspring MUST inherit the colorblind mutation on his X chromosome. However, since the mother is ALSO a carrier, they have a 50% chance to inherit the colorblind mutation carried by their mother, making them homozygous for the colorblind mutation and thus affected, and a 50% chance to have inherited the normal copy of the gene from their mother and thus be unaffected but carriers of the mutation.

"To work out the chances, you have to realize there are only two independent traits of the three: eye color is independent, color vision is dependent on sex" - well, sort-of... eye color in this example is an autosomal trait and colorblindedness is X-linked. Color vision depends on the number of X chromosomes you have and whether or not you have any normal copies of the color vision gene. It is possible for a female with Turner syndrome (i.e. only one X chromosome) to be colorblind if she inherits a mutation of the colorblind gene from her mother, and it is possible for a male with Klinefelter syndrome (i.e. XXY) to have normal vision if he carries one mutated copy and one normal copy of the gene. Granted, these are extreme examples but they illustrate the point. "All daughters will have normal color vision; all sons will be color blind" Not exactly. The question posed by the OP's presumed homework question is also another extreme example meant to illustrate a point. In this case, the sex of the offspring doesn't matter in terms of the % chance of having an affected child (50%) because both parents have a copy of the colorblind mutation.

I'm sure the OP can multiply the probabilities together to get the correct answers to the last parts of the question. Hopefully working through the problem will help the him/her understand the concepts rather than just spitting back answers provided by strangers on the internet... --- Medical geneticist (talk) —Preceding undated comment added 22:41, 2 April 2009 (UTC).

An extraordinary delusion

Does there exist a delusion in which the sufferer believes himself or herself to be the same person as another specific individual(say, a celebrity), and living a double life? Like the Fregoli delusion except that the delusional person identifies himself as one of the "imposters". 69.224.37.48 (talk) 18:04, 1 April 2009 (UTC)

Do you mean something like Syndrome of subjective doubles? 152.16.16.75 (talk) 02:00, 5 April 2009 (UTC)

Nicotine concentrations of cigars?

Hi all. I am trying to find a page.. somewhere that gives the nicotine concentrations of different cigar brands, but I am not having any luck.. most of my searches lead me to nicotine concentrations of cigarettes, or FAQ's about cigar smoking.

Much help appreciated ! 98.242.86.119 (talk) 18:13, 1 April 2009 (UTC)

(Subscription required to access the article) This study "examined characteristics relating to nicotine delivery of 17 cigar brands..." 152.16.16.75 (talk) 23:36, 5 April 2009 (UTC)

Chemistry and lock?

16:41, 8 April 2009 (UTC)bsm (=bimellahalrahmanalrahim) We must draw a plan for hacking door`s look that relate to chemistry any way, at least a little relation. we saw very ways but there are physically, completely. if there is any way or starting point?80.191.15.10 (talk) 16:41, 8 April 2009 (UTC)

Chlorine gas

Will chlorine gas react with water vapor to create HCl? 65.121.141.34 (talk) 19:28, 1 April 2009 (UTC)

I'm not sure if this applies to gaseous water, but yes in general: [3] Cyclonenim :  Chat  19:53, 1 April 2009 (UTC)

Adding impedances

I'm not sure if this question is in the right category, but there isn't a "tech" category.

I am wanting to build a speaker cabinet for my guitar amp head. The head has an output impedance of 16ohms - but the speakers I am looking at have an 8ohm input impedance. I know I could add an 8ohm resistor in series with the speaker, but I don't want to lose any of the power.

How do I connect two 8ohm speakers together so that they become one input with a 16ohm impedance?

I think that if I wire both "hot" wires from the speakers to the "hot" of the input, this would be them connected in parallel - which I think (only think) will half the overall impedance.

Also, what is the equation to work out what frequency a value of a capacitor will allow an AC signal through? This isn't worded very well, but I am trying to figure out how I could divert the higher frequency signals to a tweeter, mid range to a mid speaker and low frequency to a bass speaker. I know this may screw up the impedance calculations - and if so, I may not bother with it - but could you let me know it anyway.

Any help is appreciated! —Preceding unsigned comment added by 81.153.145.76 (talk) 20:02, 1 April 2009 (UTC)

Resistances and impedances add in series—"cold" on the first speaker connected to the "hot" on the second, with the remaining wires connected to the respective source lines. On the second part, you want a high-pass filter, band-pass filter, and low-pass filter. You could construct them yourself, but they generally aren't all that expensive. – 74  21:58, 1 April 2009 (UTC)

Audio crossover should give some help on the second point —Preceding unsigned comment added by 79.75.13.2 (talk) 22:21, 1 April 2009 (UTC)

Thanks for the tip on connecting the cold on speaker 1 to the hot on speaker 2. I just remembered some stuff I forgot to ask - What could I do to up the impedance with only one 8ohm speaker? Can I use a ferrite toroid(inductor) instead of a resistor? And how do I measure the impedance? Can I use the resistance setting on my multimeter? —Preceding unsigned comment added by 81.153.145.76 (talk) 16:00, 2 April 2009 (UTC)

It would be easier to get a different amplifier, or modify the one you have. With the current technology speakers cost more than amps. If you promise to only go to half power you should be able to run your 8 ohm speaker from your amp with out anything blowing in the amp. An ohm meter will not measure the impedance of your speaker, as it is actually working at audio frequencies. When the speaker is driven to move by the power applied, it gives a back EMF, so that not all the power goes to heating the resistance, but instead goes into moving the cone back and forwards. You will need to measure using an AC source. In practice your meter probably cannot do that, so you may just have to use the meter in AC measurement mode, connect it to an amp and play something with a constant volume (say an electronic organ note), then measure the AC current and the AC voltage. Graeme Bartlett (talk) 20:34, 2 April 2009 (UTC)

I believe you want to use a 2:1 transformer, not an inductor or resistor. 75.62.6.87 (talk) 22:38, 5 April 2009 (UTC)

Ancestry

http://wiki.riteme.site/w/index.php?title=Wikipedia:Reference_desk/Science&action=edit&section=46 What is the approx. percentages that there might be Eqyptian or Mongolian or African ancestors in my family tree if both my parents are the everyday US causasian people? They are not sure but one parent says they have Irish great parents and the other parent says English Canadian great grandparents. I think it's facinating when someone says that they have an exotic ancestor. --Reticuli88 (talk) 20:17, 1 April 2009 (UTC)

Depends from where you start, Human are meant to have originated in Africa about 200,000 years ago, so everyone had 'African' ancestry. From there people have travelled around a bit and as 0.5% of the worlds population are descended from Genghis Khan[4] it is entirely possible if you had any Asian ancestry it is possible you would have a Mongolian blood. In that way everyone has exotic ancestry, probably best to do a bit of research into your family tree. Irish ancestry tends to be a heady mix of Viking, Anglosaxon and Norman, but a lot of migration has occured over the years so that itself doesn't mean that much... MedicRoo (talk) 20:34, 1 April 2009 (UTC)

Irish ancestry would surely suggest predominantly Celtic descent before those other possibilities you mention. --ColinFine (talk) 23:54, 1 April 2009 (UTC)

You might find the Passing (racial identity) article interesting. Grantus4504 (talk) 09:38, 4 April 2009 (UTC)

Strength of human hair

What is the tensile strength of human hair and can it be made higher by using certain hair products? Also, what does the phrase 'stronger feeling hair' mean? Ive seen this on a TV advert. —Preceding unsigned comment added by 79.75.13.2 (talk) 22:14, 1 April 2009 (UTC)

TV cosmetics adverts are amongst the worst examples of poor science you'll see out there in the real world. So "stronger feeling hair" is probably ad-speak for "not stronger at all". But they are more than happy to use excessive precision - to make statements like "57% more shine!" - without saying 57% of what? 57 percent more than filthy, dirty hair is not impressive. 57 percent better than your leading competitor might be. But "shininess" is a vague property. The amount of light reflected isn't the only thing - plastics can reflect a lot of light - but they don't look as shiney as metals because they reflect it over a wide range of angles...so are they talking 57% more 'reflectivity' or a 57% sharper lambert coefficient. As for the strength numbers...first be aware that according to our Hair article, human hair varies in diameter 17 to 181µm. Since strength is likely to be proportional to cross-sectional area - you'll probably find that there is at least a factor of 100 between the weakest human hair and the strongest. Several sources I found suggest that a single human hair can support a weight of about 100 grams. [5] talks about strengthening hair and suggests that it's possible - but also that it's still a research topic. I strongly doubt that existing haircare products have any significant impact on the strength...but it is at least possible. SteveBaker (talk) 23:37, 1 April 2009 (UTC)

Just for comparison, and probably not from a very reliable source, but I read that human hair is "stronger" (in what way?) than aluminum. ~AH1^(TCU) 00:47, 2 April 2009 (UTC)

Of course, there are many kinds of strength. There's compressive strength, tensile strength, shear strength, elasticity, hardness, plasticity, toughness. etc. etc. --Jayron32.talk.contribs 00:55, 2 April 2009 (UTC)

Those ads may not mean tensile strength at all, but rather resistance to being pulled out of the follicle or forming split ends. A scientist wouldn't call this "strength", but they aren't scientists, are they ? The reason I doubt that they mean tensile strength is that this is rarely a problem, in my experience. How many people have hair that breaks in half ? StuRat (talk) 12:09, 2 April 2009 (UTC)

Ah - yes, that makes more sense. A more straightforward: "Our product helps to stop your hair from falling out." would get them into a lot of legal trouble - and wouldn't help sell the product to people with a full head of hair. But as I said - science and clear language is not the strong point of people selling stuff for cosmetic purposes. SteveBaker (talk) 13:26, 2 April 2009 (UTC)

Hair follicle actually has more info on the structure of hair than the hair article does. Hair is made up of 3 layers. The outer cuticle layers are 6 to 10 layers of dead cells arranged in a scaly overlapping pattern like roof shingles. In healthy hair these ce3lls lie flat together. IF you treat hair with an alkaline substance the scales will lift and your hair will become less shiny and will break easier. (People who dye their hair and those with certain health defects or nutritional deficiencies have hair that breaks easily.) Acidic substances make the scales lie flat. The next layer is the inner cortex. It's made up of bundles of lots of keratin fibers. They are interconnected with sulfur bridges and embedded in a keratin matrix that determines the tensile strength and flexibility of the hair. The innermost part, the medulla contains waste materials and fat substances. Healthy follicles will also produce sebum to coat the outer hair. That will protect the hair. You can replace this layer with waxes or silicone substances after it got washed off. Hope this helps. 76.97.245.5 (talk) 04:38, 3 April 2009 (UTC)

I once saw three girls on the subway having a hair contest. Each pulled out one of her own hairs. The brunette's hair broke that of the redhead, and the redhead's hair broke that of the blonde, when the girl held a piece of her hair tightly between fingers and pushed it against the other girl's hair until one hair broke. So "stronger" hair might mean "brunette" hair. (I seem to recall also an old possible unrelated engineering term relating colors of some type of hair and closeness of adjustment. This terminology implied that blond hairs were smaller in diameter than red hairs). Edison (talk) 04:58, 3 April 2009 (UTC)

There is certainly a very large range of hair diameters (our article suggests a 10:1 ratio between the thickest and thinnest). The article I referenced up above says that Asiatic hair tends to be a LOT stronger than European hair. 12:46, 3 April 2009 (UTC)

I've noticed that there seems to be more of a gender difference in Oriental hair. That is, men's hair tends to be much thicker, stiffer, and stronger than women's. I don't believe that this pattern holds, to the same extent, for European hair. StuRat (talk) 17:19, 3 April 2009 (UTC)

Does studying actually improve IQ scores?

Taking a degree makes you more knowledgeable, but does it also raise your score in IQ tests? 89.242.107.39 (talk) 23:18, 1 April 2009 (UTC)

In theory - no. In practice - probably, yes. If nothing else, there is good evidence that doing lots of IQ tests can improve your score significantly. SteveBaker (talk) 00:45, 2 April 2009 (UTC)

Since most IQ tests are written, having good written language comprehension (in the language used on the test) would be important, and you can improve that with study. StuRat (talk) 12:02, 2 April 2009 (UTC)

Are there any research papers available about this? I was waiting for someone to mention of London taxi drivers whose brains develop to allow them to memorise all the streets. Although with Satnav, sadly that tradition may be in danger. 89.243.219.134 (talk) 17:47, 2 April 2009 (UTC)

That would be "The Knowledge". London cab drivers are required to memorize the entire map of London in exquisite detail in order to get their licenses. Some of the things they need to know - such as traffic patterns at various times of day - are not covered by GPS navigation systems - so it's likely that this tradition will stand for a while yet. It's also a way for the established cab drivers to limit the amount of competition they have to face. SteveBaker (talk) 20:17, 2 April 2009 (UTC)

One problem is the reliability of IQ tests. I've seen a lot of self-proclaimed "IQ tests" filled with questions about sports and movie trivia. --79.116.90.132 (talk) 17:32, 3 April 2009 (UTC)

In such cases, it's still a valid IQ test, just one that's used to judge the IQs of the test-makers, rather than the test-takers. :-) StuRat (talk) 17:13, 5 April 2009 (UTC)