Wikipedia:Reference desk/Archives/Science/2010 January 27

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Science desk
< January 26 << Dec | January | Feb >> January 28 >
Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.


January 27[edit]

What is the meaning, and/or purpose of human life?[edit]

No, I'm not asking for a definitive answer to this question. :) Rather, I'm curious as to *how close* the 'hard' sciences are to providing an definitive answer to the question. Can this question be answered by 'hard' science? Is anyone working on it? Or has the answer already been provided a long time ago, in that the meaning and/or purpose of human life is, simply 'to survive and to reproduce'? --95.148.104.185 (talk) 00:34, 27 January 2010 (UTC)

[[1]] --i am the kwisatz haderach (talk) 00:37, 27 January 2010 (UTC)
I'm not aware of any reason for "hard" sciences to be pursuing an inherently subjective philosophical problem. Philosophers, on the other hand, have produced loads of answers. See meaning of life. — Lomn 00:39, 27 January 2010 (UTC)
The reason I ask about 'hard' sciences is that I was curious as to whether a definitive, demonstrably true 'the purpose of human life is... <x>' answer, with no room for speculation, personal opinions and any other 'grey areas' will ever be devised. I've already read a lot of the philosophical answers. --95.148.104.185 (talk) 00:50, 27 January 2010 (UTC)
To reproduce and maintain human life. --121.54.2.188 (talk) 01:01, 27 January 2010 (UTC)
[citation needed]. Comet Tuttle (talk) 01:06, 27 January 2010 (UTC)
Biological fatalism. 66.65.139.33 (talk) 01:39, 27 January 2010 (UTC)
Purpose implies some form of intelligent design, a theory rejected by science, so science has nothing to say on the subject of the purpose of human existence. --Tango (talk) 01:05, 27 January 2010 (UTC)
Not exactly. It says there is no purpose of human life. Also, the meaning is generally accepted to be a member of homo sapiens with brain activity. — DanielLC 01:07, 27 January 2010 (UTC)
The meaning of life is the avoidance of death. I'm just joking, of course. Bus stop (talk) 01:10, 27 January 2010 (UTC)
One could make the argument that the point of life is to die. But that's pretty depressing. ;-) --Mr.98 (talk) 01:13, 27 January 2010 (UTC)
There is a difference between there not being a purpose and the concept of purpose not applying. Exactly what that difference is and whether it is relevant to this question is a debate best left to philosophers that have nothing better to do, though! --Tango (talk) 01:17, 27 January 2010 (UTC)
The reason no one, including but not limited to scientists, have come up with good answers to this is because it's not a very good question. What people usually mean when they say this is, "why I am conscious, when it seems possible for me not to be?" or "what should I be doing with my time?" Those are better questions, even if science doesn't have a whole lot to say on them. They are at least focused. "What is the meaning of life?" could be anything as vague as pondering why there was a Big Bang, to a request for a strict dictionary definition. Science is not good with vague questions. Narrow the question and maybe science can prove useful. But if you don't know what you are really asking about, science certainly can't help. --Mr.98 (talk) 01:13, 27 January 2010 (UTC)
The answer to the question, "what should I be doing with my time?" is, "as little as possible." I'm just joking, of course. Bus stop (talk) 01:21, 27 January 2010 (UTC)
Indeed, "what is the meaning of life?" can only really be answered by looking up "life" in a dictionary. If you want a less literal interpretation then it could mean anything. "What is the purpose of life?" is a little better, although it does presuppose that there is a purpose, which is why it doesn't have a good answer. --Tango (talk) 01:17, 27 January 2010 (UTC)
Would "the 'purpose'/'raison d'etre' of homo sapiens as a species is to increase the number of homo sapiens" seem like a reasonable statement? --Kurt Shaped Box (talk) 01:20, 27 January 2010 (UTC)
Sure, that's an answer, but if you attempt to apply the scientific method to that, you get nowhere. For example, try: Hypothesis: The purpose is ___." Okay, now how do you go about testing it? What's your control? This is not a scientific hypothesis; it is untestable, it does not make testable or falsifiable claims; therefore, it is out of the purview of (at least the hard) science. Nimur (talk) 01:41, 27 January 2010 (UTC)
What science has discovered is that humans are a human-gene's method to make more human-genes. Every aspect of our being has been tailor made in the forge of evolution to be an optimum copier of human genes. That (as close as we can tell) is basically it.
SteveBaker (talk) 01:22, 27 January 2010 (UTC)
They're not trying to make human-genes. It's just what happens. — DanielLC 01:26, 27 January 2010 (UTC)
When we (humans) build a computer are we trying to build a computer or is it just what happens? Bus stop (talk) 01:34, 27 January 2010 (UTC)
The answer to that, Bus Stop, is very subtle and subjective. See Primum movens, for example - which has both a theological and a secular classical philosophy interpretation. I would go so far as to say, "it's just what happens." In other words, the universe was just so fortunately constructed that physical laws occurred, stars accreted, planets formed, carbon life developed, complex brains evolved, technological society arose, machine tools were invented, and the microelectronics industry accreted - and it just happened because of the laws of the universe. We are sophisticated enough to have the illusion of self-awareness, but we still only act in accordance with physical law. This classifies me as a strong determinist. It doesn't mean I'm right - this is a subjective opinion. To my knowledge, determinism isn't really falsifiable (therefore it's philosophy, not science), although there are some guys who purport that physical nature of quantum mechanics (in particular, the extensions of the disproofs of hidden variable theory) invalidate strong determinism. I'm unconvinced - but that's only because my neurons happen to fire that way. Nimur (talk) 01:48, 27 January 2010 (UTC)
The question presumes an unnecessary assumption about life. Other animals don't need an external to live. Gods of holy texts don't need external reasons to live. Why should we? Just live so you won't have any regrets, assuming you don't get joy from hurting people. 66.65.139.33 (talk) 01:38, 27 January 2010 (UTC)
Well everything is open to interpretation, but if I were to summarize everything I've learned about the 'purpose of life', other than the obvious (there is none, or 'endure suffering', or 'to do glory unto God', or 'have fun') it would be learning to temper yourself into a functional and agreeable human being. I mean everything begins and ends with you and your body, so upgrading the software and hardware is really the first process in anything resembling a good and meaningful life. Vranak (talk) 03:24, 27 January 2010 (UTC)
The OP would do well to read Rocks of Ages by Stephen Jay Gould. Questions of purpose are outside of the remit of science to give the answers to. It would be like asking a question about the plot of Hamlet from your pocket calculator. Yes, calculators give very good answers if asked the right questions, but they are unequipped to give answers about literature! Likewise, science is a tool equipped to give all sorts of really good answers, but not every answer regarding human existance. Where the tool of science falls short, other tools (religion, humanities, art, etc.) must be used. --Jayron32 03:43, 27 January 2010 (UTC)
I deeply disagree with every single part that answer! If some scientist somewhere could figure out an experiment that would determine man's purpose - we'd do it, publish the results and call it a "Theory". It's not something where scientists would say "Well, that's outside our remit so we won't bother." - nothing whatever is beyond the scope of science - there are just some questions that we don't yet know how to answer. A sufficiently advanced calculator could certainly answer questions about the plot of Hamlet - it's a computable problem and a programmable calculator with enough memory could do it. Resorting to religion, art and philosophers to answer the question could never produce an answer with the rigor of a scientific answer. It's a pretty safe bet that no two priests, artists or philosophers would agree anyway! You might just as well guess for all that's worth! SteveBaker (talk) 05:58, 27 January 2010 (UTC)
Science has provided the answers to questions about life and death. Some people just won't accept them, that's all. 66.65.139.33 (talk) 19:40, 27 January 2010 (UTC)
The meaning of life is probably not a question that is answerable by the hard sciences. If the goal was simply to reproduce, then why is this causing us to approach the carrying capacity of the planet and overwhelm sustainability? It may be something more abstract, for example to inspire others and to make a difference in the world. However, that would be bordering on the realm of Religion. Or perhaps it is not meant to be answered at all, but that's the realm of metaphilosophy. There are also some scientific or mathematical theories that offer a glimpse at the picture, for example Oneness. It is also likely, however, that the meaning of life is simply ineffable. ~AH1(TCU) 20:12, 27 January 2010 (UTC)
Evolution has no foresight whatever. Animals and plants will always increase in number until predation and other causes of death balances their maximum reproduction rate - or they hit the limit of the available resources and experience a disasterous population crash as a result. Mankind, having become so efficient at finding and using resources and with no predators and increasingly good health and reproductive care, will obviously grow in numbers until we do indeed run into the limits of the planet and crash horribly in the process. Unless of course, we can use our intelligence to overcome the instincts built into us by evolution and limit our use of resources and reproduction rates in order to meet a sustainable goal. Sadly, there is little sign that enough of us are smart enough to do that. SteveBaker (talk) 01:31, 28 January 2010 (UTC)
The hard sciences are certainly close to making a discovery, all the time, and discoveries are made all the time. The questions asked by the hard sciences however are not so wide in span as to encompass the meanings of things (from what I understand). --Neptunerover (talk) 15:06, 29 January 2010 (UTC)
One should also guard against invalid questions. Garbage in, garbage out. 67.243.7.245 (talk) 15:34, 29 January 2010 (UTC)

Brown lines and sections on house plant leaves[edit]

I remember reading that plant leaves are eaten and digested by tiny things, which leaves trails of the brown stuff. Is that true? Would cutting out the damaged parts with scissors help? I'm guessing it'd hurt the plants, but I'll ask anyway. Thanks. 66.65.139.33 (talk) 01:09, 27 January 2010 (UTC)

Perhaps you are thinking about a Leaf miner which eats the leaf tissue between the upper and lower cuticles of the leaf leaving a visible trail that varies with specie. you could cut out the bits of affected leaf but that would look as bad if not worse than the trails. If it is a minor house plant problem your best bet is to just squeeze the miner between thumb and finger. The miner will be located at the thicker end of the trail. Richard Avery (talk) 08:16, 27 January 2010 (UTC)
I don't see any bugs on my house plants. 66.65.139.33 (talk) 19:38, 27 January 2010 (UTC)
No, you won't, because the miner (bug) is between the two outside layers of the leaf. It stays in there until it has passed through its larval and pupal stage(usually) and then hatches out through the skin of the leaf and goes and lays some more eggs. The only way you can know it is there is by seeing its track as it eats its way across the leaf - but inside the tissue of the leaf. Richard Avery (talk) 07:16, 28 January 2010 (UTC)

Tobacco's body count and total excess deaths of drugs[edit]

Should "Smoking" be "Tobacco" because "Cannabis" is filed under "Drug abuse"?

Recently I came across the statement that "Cigarettes kill more Americans than alcohol, car accidents, suicide, AIDS, homicide, and illegal drugs combined."[2]. Can that be confirmed by reliable sources? The Google search on the question seems confirmatory to me.

Does someone have a chart of the popular drugs sorted by the number of excess deaths? Google is much less helpful for that question. 99.56.138.51 (talk) 02:01, 27 January 2010 (UTC)

We have an article on List_of_preventable_causes_of_death#Leading_causes_in_the_United_States Vespine (talk) 03:04, 27 January 2010 (UTC)
Thanks! That's almost exactly what I need, except "Smoking" needs to be tobacco-specific (by drugs.) 99.56.138.51 (talk) 05:40, 27 January 2010 (UTC)
Yes. In the USA in the year 2000: 432,000 deaths per year due to smoking, 85,000 for alcohol, 43,000 for car accidents, roughly 38,000 for suicide, HIV/AIDS deaths are so small as to be negligable, 29,000 due to firearms ("homicides" would be different - maybe not by much), 17,000 for drugs. So that's 212,000 due to all of those things - 432,000 due to smoking. So - yeah, the statement is true. In fact, smoking kills TWICE AS MANY Americans than all of those other causes combined. The source for that is this paper [3] which is quoting numbers from the Centers for Disease Control and Prevention (CDC) - which is considered to be highly reliable.
Even if you assume that all of the 'drug' deaths were due to smoking drugs (unlikely in the extreme because nobody smokes 30 MJ cigarettes a day - but that's rather common in tobacco smokers!) that hardly makes a dent in the numbers.

SteveBaker (talk) 05:47, 27 January 2010 (UTC)

The World Health Organization predicted that in the 21st century, one billion people will die from tobacco and cigarette smoking. ~AH1(TCU) 20:07, 27 January 2010 (UTC)
At 5 million smoking-related deaths worldwide per year - the number of annual deaths would have to more than double. I'm rather surprised that the rates are still increasing. With all we know, that's rather depressing. SteveBaker (talk) 01:20, 28 January 2010 (UTC)
Unfortunately the "all we know" is quite localized to developed countries. I saw a doco which stated one of the largest "untapped" markets left for the tobacco companies was Chinese women, it is still quite a taboo there for women to smoke. They hire young women "promo girls" there to give out cigarettes and promote that it is empowering and "equal" for women to smoke trying to break down the taboo. The west went through the same thing with the same taboo, only with us it happened in the 20s, except I think they stopped short of giving out free cigarettes, but I could be wrong about that. The dealer giving out the 1st "hit" free comes to mind, and perfectly legal. Sad indeed. Vespine (talk) 02:03, 28 January 2010 (UTC)
They gave out free cigarettes in the Army in the US. It was one of the major reasons for the boom in smoking in the 1940s. But yeah, cigarette companies are now extensively targeting less-developed and newly-developing countries for their new markets, knowing that the US/European market is probably in a state of permanent contraction. Pretty disgusting, if you ask me. (Allan Brandt's The Cigarette Century discusses both of these trends, among others.) --Mr.98 (talk) 14:57, 28 January 2010 (UTC)
Smoking cannabis has never been proven to cause death. There are no confirmed cases. See "Effects_of_cannabis#Toxicity". Axl ¤ [Talk] 18:36, 29 January 2010 (UTC)
Oh yeah? Well then, in this sense of the word, smoking tobacco has never been proven to cause death either. Remember, people who die from tobacco do not die from overdosing on nicotine -- they die from cancer, or emphysema, or other kinds of chronic ailments brought on by inhalation of toxic substances in tobacco smoke. And by the way, the above article says that "cannabis smoke was found to contain higher concentrations of selected polycyclic aromatic hydrocarbons (PAHs) than sidestream tobacco smoke" -- which would make it more carcinogenic than tobacco smoke. 24.23.197.43 (talk) 02:54, 1 February 2010 (UTC)

Capturing a comet inside an asteroid for an aquarium[edit]

How much would it cost to perturb the orbit of an asteroid while excavating it with the goal of colliding it with a comet and capping the resulting ice with a seal to allow for the future possibility of an aquarium, as a function of aquarium size? 99.56.138.51 (talk) 02:04, 27 January 2010 (UTC)

If you collide an asteroid with a comet you will probably just break the two bodies into tiny pieces. A lot (most?) asteroids are just piles of rubble with only a tiny bit of gravity holding them together, they break up very easily. I don't really understand your intention, anyway. However, I can tell you that any elaborate space mission outside Low Earth Orbit that has never been done before is going to cost in the region of billions of dollars at the very least. --Tango (talk) 02:17, 27 January 2010 (UTC)
It's entirely dependent on where the two objects are orbiting and what their relative velocities are - and (I suppose) how soon you need it done. There are so many orders of magnitude of variation involved that there is no meaningful answer. SteveBaker (talk) 05:33, 27 January 2010 (UTC)
Six years. 99.56.138.51 (talk) 05:43, 27 January 2010 (UTC)
Six years from now? I'd say that was pretty much impossible without it being a top priority of most developed nations (which it wouldn't be). It takes longer than that just to plan, design and build such spacecraft, and it would take a very long time to actually create the collision, even if you can find a suitable comet and asteroid. --Tango (talk) 17:02, 27 January 2010 (UTC)

Presumably, the Seal would consider the aquarium to be a Future Love Paradise. --Dweller (talk) 07:59, 27 January 2010 (UTC)

The best order-of-magnitude estimate may be that it would cost about the same as placing a man on the moon, and that the acquarium size would not matter. 92.27.165.25 (talk) 11:50, 27 January 2010 (UTC)
It would probably cost even more then that because your deltaV would probably be larger, and the object which needs to change its velocity is heavier. Googlemeister (talk) 15:49, 27 January 2010 (UTC)

An Aquarium has fish on the inside and observers on the outside. It is filled with liquid water. Has the OP plans to obtain fish, viewers and a way to melt the comet ice? Cuddlyable3 (talk) 19:08, 27 January 2010 (UTC)

Fish need oxygen...where is that coming from? I guess you'd need to use solar panels to make electricity and use that to crack water into H2 and O2...vent the H2 to space and bubble the O2 through the tank. Er...wait a minute...why are we doing this rather crazy thing? SteveBaker (talk) 01:11, 28 January 2010 (UTC)
Like I said, I don't understand what the OP is actually intending to do... --Tango (talk) 01:17, 28 January 2010 (UTC)

Practice perturbing the orbits of asteroids so we are skilled at getting them out of harms way if we ever discover one in harms way, and generation starship building practice. The fish will come later. Melting the ice can be accomplished with solar or nuclear over a longer time frame. Perturbing the asteroid's orbit can be done as part of the excavation process by carefully timed off-shoveling. Six years. Don't try to get it perfect, but design like people's lives depend on it. By the way, explosions are allowed. 99.56.138.51 (talk) 18:57, 29 January 2010 (UTC)

Superball[edit]

I've been given this homework question (I know you're not supposed to answer HQ, but all I need is a little push in the right direction): Suppose a superball (ie a ball such that kinetic energy is conserved during collisions) of mass M is dropped from a height h, with a smaller ball of mass m on top of it (M much greater than m). The question ask, how high will the small ball bounce? Alright, so it's pretty straightforward to calculate the speed of the two balls upon impact with the ground. During the collision, I would think that the kinetic energy both balls had accumulated during the fall are converted into the elastic potential energy. Now, as the balls begin to rebound, there's going to be two forces acting on the superball: the force of the ground pushing up on the superball, and the force of the smaller ball on the superball. The small ball also experiences a force, that of the reaction force to the last mentioned force. Total energy is (m+M)gh, which must be conservered. But I don't know how to combine these facts to get an answer...help! —Preceding unsigned comment added by 173.179.59.66 (talk) 03:01, 27 January 2010 (UTC)

Energy is conserved, so the easiest way to calculate that is to assume that the total energy of the system is that of gravitational potential energy at the top of the drop:
  • E = (m+M)*g*h
Now, at this point the total potential energy is dependent on the sum of the two masses, so (m+M) in this case is the mass of BOTH balls.. When the two balls hit the ground, if the balls are perfectly elastic (which you indicate they are) then 100% of this energy will be transferred to the top ball. So take the E from the first equation and plug it into the kinetic energy equation:
  • E = 1/2*m*v2,

but NOW you only use the mass of the top ball. Solve for v. This is the initial velocity (vi) of the small ball. If we want to know the maximum height, we assume the final velocity is zero. Using the acceleration of gravity and your basic dynamics equation:

  • d = 1/2 (vf2 - vi2)/a
Where vf = 0, vi is the velocity you calculate immediately above, and a = -3.2 m/s2 (the accelration of gravity). Those three steps will get you the right answer. Any questions? oh, and someone else check my algebra here too!--Jayron32 03:37, 27 January 2010 (UTC)
The trouble is, not all of the energy will be transferred to the top ball. Momentum is also conserved. It will be easier to assume that the bottom ball hits the ground and starts to bounce back up before the superball hits it. So first, you'll figure out how fast the bottom ball is when it hits the ground. You can assume (by conservation of energy) that the big ball will be travelling upward when it hits the superball at the same speed that it hit the ground at. Then, you can use both conservation of energy and momentum (the collision is elastic) to find out what happens after the collision (I assume you've been doing collisions in class). The big ball can be assumed to be so massive that it doesn't change velocity at all during the collision. I think that the little ball ends up at three times the height it was dropped from, but you better check that. Buddy431 (talk) 04:00, 27 January 2010 (UTC)
My bad; the superball's speed coming off the bounce is three times what it came in with. That puts it at nine times the initial height. Buddy431 (talk) 04:13, 27 January 2010 (UTC)
It doesn't affect your answer, but momentum isn't conserved since we are assuming the mass of the ground is infinite (ie. it doesn't move) and infinity doesn't follow the usual rules of arithmetic. If you consider the two collisions separately (which I agree is the best approach) then momentum is conserved for the second collision, since it doesn't involve the ground, but not the first. For the first, as you say, the ball is simply reflected. --Tango (talk) 04:16, 27 January 2010 (UTC)
The momentum in the first and second collision are conserved in the same way; we assume the larger body has infinite mass compared to the smaller one. As an aside, our superball article (which is shamefully underdeveloped) says a real life superball keeps something like 70% of it's energy on a bounce. That means after the first bounce you'd be at 84% of the speed you were coming in with, and after you hit the second ball, it only leaves with about 2.4 times the speed it came in with, for a total height of about 5.7 times what you dropped it from. Throw in drag, and the fact that the second ball isn't on infinite mass as compared to the first, and you're looking at 4-5 times the initial height (which is still impressive). I've heard that you can buy sets of three balls meant to be dropped on top of each other, which just seems irresponsible and dangerous. And if 173.179 doesn't like our answers, he can check out this explanation. Buddy431 (talk) 04:38, 27 January 2010 (UTC)
For a look at the demonstration, check out this youtube clip. It doesn't show heights, but provides a good visual of the problem. Buddy431 (talk) 04:45, 27 January 2010 (UTC)
Looking at 173's question again, and Tango's comment, I see that Tango's right, and my answer isn't quite the correct one. The first collision is with the Earth, which does basically have infinite mass, so the large ball bounces off with the same speed it came in with. The second collision isn't the same though; the problem does give two masses m and M for the balls, which I missed. In that case, just use both conservation of momentum and energy to find how fast the small ball leaves. So my answer, assuming that the small ball's mass is negligible compared to the large ball, is a limiting case. The actual answer will be somewhat less than 3 9 times the original height. Buddy431 (talk) 06:03, 27 January 2010 (UTC)
And last time I checked, gravity near the surface of the Earth accelerates objects at 9.81 m/s2. I don't think it will matter in this case (it cancels out), but I'm not sure where the 3.2 number is coming from. Buddy431 (talk) 04:05, 27 January 2010 (UTC)
Like I said, check me. I think I was confusing the foot measurement (32 feet per second per second) with the meter measurement. So sue me. --Jayron32 04:14, 27 January 2010 (UTC)
If it's good enough for NASA, it's good enough for us! --Tango (talk) 04:17, 27 January 2010 (UTC)
Larger ball hits the ground with speed v=\sqrt{2gh}. It rebounds in a perfectly elastic collision, so now has upward speed v. It immediately collides with small ball, which has downward speed v. Collision is again perfectly elastic, so coefficient of restitution is 1, so velocity of small ball relative to big ball after collision must be 2v upwards. Velocities of small and large balls after second collision are \frac{3M-m}{M+m}v and \frac{M-3m}{M+m}v respectively. In the limit, as m/M tends to 0, the velocity of the small ball after the second collision is 3v and it rises to a height of 9h above the collision point.
If we add a third even smaller superball on top of the small ball, with a mass that is much smaller than the small ball, then I think its velocity after colliding with the small ball is an astonishing 7v. Gandalf61 (talk) 10:35, 27 January 2010 (UTC)
And the nth even smaller superball will rebound with a velocity of (2n - 1)v. 124.157.247.221 (talk) 01:05, 31 January 2010 (UTC)

joule thief[edit]

what is a joule thief? what is a torid(on which they coil wire)? how does joule thief works? —Preceding unsigned comment added by Myownid420 (talkcontribs) 03:36, 27 January 2010 (UTC)

See joule thief. --Jayron32 03:38, 27 January 2010 (UTC)
And Toroidal inductors and transformers. SteveBaker (talk) 05:02, 27 January 2010 (UTC)
A great invention. Is there any data on how much extra energy it can squeeze out of a battery? Do any consumer products have this circuity in them? 78.146.106.225 (talk) 13:50, 27 January 2010 (UTC)
The joule thief circuit is a simple relaxation oscillator that converts DC from a battery to an AC or pulsating output. It has two coils wound on a common ferrite core to form a transformer. Current to the collector ("c") of the transistor flows through the primary winding of the transformer. That causes current in the secondary to subtract from the current flowing into the base ("b") of the transistor. (If a winding is connected the wrong way round the secondary current will add to the base current and the circuit will not work.) Recall that the collector current in a Transistor is controlled by the base current. Reducing the base current causes the collector current to reduce which has two consequences: 1) The voltage at the collector rises briefly higher than the battery voltage due to the inductance of the transformer. That is why the LED lights. 2) Both collector and base currents collapse i.e. the transistor turns off. After this the resistor provides base current to start a new cycle. The LED blinks so fast that it seems to be lit continuously.
If you want to make the circuit note that: The number of coil turns is not given but they will be limited by the size of the ferrite bead. Almost any small NPN transistor may work in the circuit. A PNP transistor will also work if the battery and LED are both reversed. The resistor value is critical: if too high the oscillator won't start, if too low the transistor could be damaged.
A similar circuit is used in simple battery powered inverters for fluorescent lamps. It can also be useful for converting the low voltages from a solar cell to a higher voltage e.g. to charge a battery.Cuddlyable3 (talk) 18:58, 27 January 2010 (UTC)
OK, but the 64,000$ question is still how much extra energy it can get out of a battery? 78.149.231.228 (talk) 01:18, 28 January 2010 (UTC)
No that is not the OP's question though it seems important to you 78.149.231.228. If you seek a numerical answer then it must be a percentage of the battery currentxtime rating because "a battery" might be any size. In the case of the joule thief the LED can be lit using a battery that is unable to light the LED directly so the "extra" energy is all the energy. Please do not offer money for answers because our voluntary service here is priceless beyond value reward enough. Cuddlyable3 (talk) 13:22, 28 January 2010 (UTC)
Thanks, although that is a long-winded way of saying "I don't know". 89.242.92.249 (talk) 14:22, 28 January 2010 (UTC)
If you used a Joule Thief with a fresh new battery - for example a 1.5v AAA - would it be likely to burn out the lightbulb or radio or whatever or be damaged? I'm wonder why every torch / flashlight does not have one installed already. 89.242.92.249 (talk) 14:31, 28 January 2010 (UTC)
A normal flashlight contains a lightbulb and a few flat "wires" (two of them slide past each other to make the switch), and is very cheap to produce. Adding a circuit such as a Joule Thief to one would increase the complexity and cost, possibly by an order of magnitude or two. --Carnildo (talk) 01:12, 29 January 2010 (UTC)
That would not apply with a radio, and in any case the extra utility of longer-lasting batteries would make the extra cost worthwhile, and they would probably get lots of free publicity as well. The question asked goes unanswered. 78.149.174.141 (talk) 18:23, 29 January 2010 (UTC)

i want to know, willnot the circuit work without a transistor? also if becoz of joule thief enough current is made , we have to use a resistance- - could not light some another high volt needing battry ?sorry for my english —Preceding unsigned comment added by Myownid420 (talkcontribs) 03:08, 29 January 2010 (UTC)

Heat death of the universe[edit]

This is bordering on philosophical, but I find the Heat Death of the Universe scenario to be extremely depressing. Outside of Asimov, it seems to be a perfect no-win situation - an unhackable Kobayashi Maru. Is there any wiggle room? Or is our universe really condemned to destruction? 218.25.32.210 (talk) 05:00, 27 January 2010 (UTC)

Actually, heat death is an asymptotic condition rather than a finish line. That is, the universe will proceed inexorably towards complete entropy, but will just wind down infinitely without ever reaching it. Perfect entropy is no more attainable than perfect order, we're just moving closer and closer to perfect entropy. However, yes, heat death is unavoidable since the second law of thermodynamics pretty much demands it. As long as hot places keep getting cooler and cold places keep getting warmer, we're just gonna keep moving towards it. --Jayron32 05:07, 27 January 2010 (UTC)
Well, it depends on the nature of the universe...the amount of matter and dark matter. Ultimate fate of the universe describes the most well accepted possibilities and heat death isn't the only one that's possible right now.
The Heat death scenario is kinda depressing - but it's an awful long time away and a sufficiently advanced technology could kinda-sorta escape the worst effects of it.
Suppose we're somehow able to put our minds into computers - it's not an impossible thing. Our brains would run on electricity that we'd extract from the universe in some way or other. Solar panels perhaps. As entropy increases, fewer and fewer photons would come your way. It becomes harder and harder to harvest enough energy to run our brains. But a defense against that is to run our brains more slowly. A computer doesn't have to consume any energy at all until it is 'clocked' - until it does a single step in it's calculation. So what we could do is to extract energy from the universe and charge up a battery - when there is enough charge in the battery, have the computer execute instructions until the battery goes dead again. Then accumulate more energy until you can do it again. As the universe gets more and more uniform, it takes longer and longer to accumulate the energy needed to do a single step in the 'brain' calculation. Our brains would start to slow down. As the universe goes downhill, so our brains go slower.
What would that seem like? Well, it would seem like time was speeding up. So as the universe got more and more boring and uniform, time would seem to speed up for us - so the changes in the universe would seem more rapid. It would be like having the universe on 'fast forward'. Time would become not an absolute thing - but something that became relative to the rate that we could gather energy to think with. The universe will continue to have tiny pockets of slight random variation until the very end, so our brains will continue to operate - but very, very slowly. I think the last time I suggested this, someone pointed out some quantum threshold below which there truly would be no energy to be extracted. So the effect for us would be an exponential speeding up of time followed by a sudden and abrupt end. Not at all the slow depressing decay that you're imagining. The last trillion years could pass us by in a heartbeat as the battery charge for our last thought is accumulated one photon at a time.
Humanity's last wild 'goodbye' party could last for a trillion, trillion years yet seem to pass in a couple of hours.
SteveBaker (talk) 05:27, 27 January 2010 (UTC)
Similar to Dyson's eternal intelligence. APL (talk) 01:02, 28 January 2010 (UTC)
Yep - that's where I heard about it. I merely simplified it to make it easier to explain. Dyson's approach is better. SteveBaker (talk) 03:22, 28 January 2010 (UTC)

<--- Or Asimov's The Last Question. 21:25, 28 January 2010 (UTC)

There's Omega Point (Tipler). This is a fine theory which is unfortunately wrapped in religious overtones, but that wrapping can easily be removed and discarded. 213.122.40.58 (talk) 10:38, 27 January 2010 (UTC)
Yes there is a way out. What people calculate to a nicety on pen and paper and what happens in reality are often worlds apart. And for God, all things are possible. Vranak (talk) 13:52, 27 January 2010 (UTC)
Can he make himself disappear? 66.65.139.33 (talk) 19:36, 27 January 2010 (UTC)
He already did. Vranak (talk) 22:47, 27 January 2010 (UTC)
There's the cyclic universe theory where the heat death thing is just preparation for the next cycle when two branes collide and start the big bang all over again. This is pretty fringe, I think. The book Endless Universe by Turok and Steinhardt was a good read for a layman like myself, and might help with your depression (though, really, we're talking bajillions of years from now...lighten up! :) )Quietmarc (talk) 16:21, 27 January 2010 (UTC)
I've heard of that theory, but I'm not familiar with the details - is there any way to transfer information from one universe to the next? In the original cyclic universe theory (Big Bang->Big Crunch->Big Bang 2->...) there is a singularity between universes which has the affect of wiping the universe clean, so you can't survive from one to the next. --Tango (talk) 17:13, 27 January 2010 (UTC)
My memory's rusty (and I never took even high school physics), but I believe that the expanding universe smooths out the branes almost completely, but that tiny imperfections remain. These imperfections are what cause matter in the new universe to coalesce and lump, so that we get galaxies, etc, so yes, there is some carry-over.Quietmarc (talk) 20:10, 27 January 2010 (UTC)
But where do those imperfections come from? In normal inflationary theory, they come from quantum fluctuations after the big bang. In brane theory can they come from the state of the branes prior to the collision? --Tango (talk) 01:19, 28 January 2010 (UTC)
A more interesting question is why you find it so depressing. The human race will almost surely have died out a long time before that. Intelligence life in general, probably also dead. The lengths of time were are talking about here are ridiculously long. While I'm all for thinking about future generations, trying to worry about something that is trillions of years in the future seems, well, very silly to me. Getting depressed about it seems like human hardwiring gone wrong. --Mr.98 (talk) 15:04, 28 January 2010 (UTC)

Role Directory - Municipal Solid Waste Industry[edit]

can you provide the role directory (Job Designations and roles/responsibilties) in municipal solid waste Industry —Preceding unsigned comment added by Ajaykvssn (talkcontribs) 07:26, 27 January 2010 (UTC)

The US Department of Labor publishes the Occupational Outlook Handbook; its website is here; you can use its Search box to look for jobs in this industry, and it has lengthy job descriptions for each job. Why taxpayers are paying for this, I do not know. Comet Tuttle (talk) 18:24, 27 January 2010 (UTC)

Milk[edit]

Our articles on Milk and Fat content of milk talk about skimmed/homogenized milk only in terms of fat content.

I was curious as to whether there is a significant difference between skimmed and whole milk (homogenized and whatever you call the opposite of homogenized milk) in terms of calcium content?

If this varies from country to country, I'm asking about the UK.

Thanks in advance. --Dweller (talk) 07:45, 27 January 2010 (UTC)

I normally only have lite (i.e. light blue) milk, but as it happens purchased a bottle of standard (i.e. [dark] blue) milk a few weeks ago it was still in my recycling. Pulling it out, I see that standard is 115mg/ml and lite is 125mg/ml. I also have another bottle of a different brand of lite milk which is 125mg/ml so it's probably fairly standard in NZ if the milk isn't calcium enriched. I presume we're talking about fresh milk here not milk powder. In any case, I would guess you have similar dietary labelling in the UK, so why not just have a look the next time you're at a supermarket (or other place that has milk). Maybe even the websites will say Nil Einne (talk) 11:11, 27 January 2010 (UTC)
In fact a quick search comes up with [4] which leads me to [5] which links to this PDF [6] which answers this and probably everything else you want to know about the (average) nutritional details of different dairy products in the UK. Calcium is 118mg per 100g or 122mg per 100ml for whole milk. 125mg per 100g or 129mg per 100ml for skim milk. Nil Einne (talk) 11:15, 27 January 2010 (UTC)

You guys are terrific, thank you. My interpretation (I'm not a scientist) of your responses is:

  1. any difference is really immaterial
  2. if anything, the skimmed milk has more calcium, not less.

Is that accurate? --Dweller (talk) 11:22, 27 January 2010 (UTC)

Yes. Of course, calcium enriched milk (perhaps with added vitamin D) may be a good idea if you want to get more calcium from your milk, however I'm not sure if that's available in the UK (it is here, yellow) Nil Einne (talk) 11:32, 27 January 2010 (UTC)
Since milk is mostly water, you probably want to check the ratio of calcium to calories. (Unless you always consume a set amount of milk and want to know which kind to use.) Ariel. (talk) 20:58, 27 January 2010 (UTC)
Well, skimmed milk takes up less volume than unskimmed milk -- the concentration of calcium has only increased. Skimming doesn't add calcium per se. Ca2+ is just a counterion to negative phosphate and carboxylate anions. John Riemann Soong (talk) 16:52, 28 January 2010 (UTC)
I sort of deduced that since the fat has been removed, but nothing else, that might explain why the calcium level has crept upwards, but why is the Vitamin A content badly lowered by homogenizing/skimming milk? --Dweller (talk) 16:59, 28 January 2010 (UTC)
Vitamin A is fat soluble, so all (most) of it is bound up in the fat that is removed. (Although I would have assumed they would add some back in to make up for it.) Ariel. (talk) 19:20, 28 January 2010 (UTC)
How could you add a fat soluble vitamin to something that's nearly completely fat free? 86.180.52.43 (talk) 22:53, 28 January 2010 (UTC)
Well it's a micronutrient, so it can be suspended in colloidal milk. Also, extensive conjugation improves solvation to a degree. Plus, casein is full of lipohilic protein -- all those lovely proline, glycine, alanine residues, etc. John Riemann Soong (talk) 17:58, 29 January 2010 (UTC)
I had made a similar guess on the calcium and had planned to use a similar example. Except the first vitamin I noticed which changes was Vitamin B12 which is water soluble and it goes down in the skim milk. Not knowing why, I gave up on offering any explaination/guess for the calcium as well :-P Nil Einne (talk) 08:58, 30 January 2010 (UTC)

The sound of a fractal?[edit]

Fractal images have "beauty" presumably because the human mind "likes" organised complexity. But what would a fractal sound like, and would it be pleasing to the ear, like music?Trevor Loughlin (talk) 08:38, 27 January 2010 (UTC)

Search Google for "Fractal Music", quite a bit of work has already been done in this field. Not all of it sounds pleasing to the ear! Zzubnik (talk) —Preceding undated comment added 09:50, 27 January 2010 (UTC).
[7] [8] good examples of the later perhaps. [9] reminds me whale sounds you get in some music however and isn't quite so bad. [10] is also interesting. [11] a better example of using fractals to play notes then the first. [12] also isn't quite so bad. A lot of it depends on how you make your fractal music. Searching is somewhat complicated by the number of people who have fractal music which appears to be real music put to fractals (read the comments or details on the videos) Nil Einne (talk) 11:35, 27 January 2010 (UTC)
I will point out that we do have an article on Algorithmic composition that may be of interest. 10draftsdeep (talk) 13:10, 27 January 2010 (UTC)
The problem is in how you interpret the fractal. If you just built a fractal audio waveform where the voltage sent to your loudspeakers is determined moment by moment by the value of a 1D fractal, the result would sound like the most horrendous noise imaginable. If you use the value of the fractal to pick which notes to play on a piano keyboard then it sounds better. If you use it to pick notes only in a particular key signature - then better still. If you chop every piece of music that Bach ever composed in the key of C into bar-length chunks and pick those out of a table using fractals, better still. If you make a library of jazz 'licks' by a well-known jazz pianist and pick from those using the fractal - still better. Perhaps the fractal determines which tune to download and play from iTunes - and the result is 100% musical. Sadly, none of these things tells you very much about the true nature of the fractal. SteveBaker (talk) 00:55, 28 January 2010 (UTC)

Gray Whales[edit]

Are Gray Whales in the Atlantic Ocean? Were reintrduced the Gray Whale in the Atlantic Ocean? —Preceding unsigned comment added by 92.86.254.236 (talk) 09:34, 27 January 2010 (UTC)

No, not there.--82.59.73.150 (talk) 10:04, 27 January 2010 (UTC)
see Gray Whale--NotedGrant Talk 11:49, 27 January 2010 (UTC)

In 2005, in the news, they said that some gray whales were reintroduced in the Atlantic Ocean. I want to know if that is true. In the article and on the internet there is nothing about this. —Preceding unsigned comment added by 109.96.228.243 (talk) 15:11, 28 January 2010 (UTC)

This page has a copy of a version of the Wikipedia article which states "in July 2005 scientists working at the University of Central Lancashire suggested that some Gray Whales be taken from the Pacific and re-introduced to the Atlantic, specifically, in the Irish Sea. Their idea would create a whale-watching industry in Cumbria in the United Kingdom and bolster the relatively fragile global population of Gray Whales. There is no indication at this time as to whether the idea will actually come to fruition. "
However, those sentences no longer appears in our article. They were added 20 July 2005 with this edit and sourced to this BBC article from 18 July 2005. They were removed with this edit on 15 September 2008, with an edit summary of "It's been three years - no indication this will ever actually happen".
Personally, I think it's an interesting item, and might belong in the article, preferably with more detail about why this has not happened (or if it ever will). --LarryMac | Talk 15:34, 28 January 2010 (UTC)

Thank you for this information LarryMac!

Boxer's Diet[edit]

What is the diet of a professional boxer or other types of fighters? I ask because someone mentioned that they (they - meaning he is training to be a boxer) do not eat salmon because there is not enough (?) to give them the energy they need during matches (I guess something to contribute to endurance). My limited brain thought, salmon is good for the brain but why wouldn't they consider salmon as a good source of energy? --Reticuli88 (talk) 13:46, 27 January 2010 (UTC)

Salmon contains zero carbohydrates, which are the most accessible energy source. The same is true of every type of meat, though. There is no less reason to eat salmon than to eat meat, as far as I know. A boxer certainly needs lots of carbs, but that wouldn't prevent eating salmon in addition. Looie496 (talk) 16:25, 27 January 2010 (UTC)
(ec)Perhaps Carbohydrates as they are the main source of energy from food sources. Salmon would be largely Protein, (along with oils, vitamins, minerals and other nutrients) which is more for building muscles, not endurance. See also Nutrition and Human Nutrition for more detailed information. 220.101.28.25 (talk) 16:25, 27 January 2010 (UTC)
Note that Protein can provide energy, but if I recall correctly, only after all other available bodily stores of energy ie. Carbohydrates & fats have been used, in which case the person is in a state of starvation. Not much use for a boxer. 220.101.28.25 (talk) 17:10, 27 January 2010 (UTC)
Without making any comment on the validity of the premise (whether or not boxers eat salmon), there are two things to consider when discussing the energy from food.
  • There is the raw energy content of the three basic macronutrients, that is how much energy your body can get by digesting them. Carbohydrates and proteins provide 4 food calories per gram, while fats provide 9 food calories per gram of energy. (1 food calorie = 1 kcal = 1000 calories = 4184 joules)
  • There is the rate at which the energy is released into your body, basically "energy" is transported in your blood stream in the form of glucose or blood sugar. Different foods cause different changes to your blood glucose levels, some foods cause a rapid spike in blood glucose, which then drops just as rapidly, while others cause a slow steady stream of energy. The rate at which a food affects your blood glucose is called the glycemic index. GI is actually restricted just to carbohydrate measurements, but a similar concept could be expressed for fats and proteins as well, we just don't have a fancy table to measure it.
So, while the raw amount of energy in food is important, it is also important how your body processes that food, and the effect of that food on things like insulin levels, blood chemistry, etc etc. --Jayron32 18:19, 27 January 2010 (UTC)

chemistry solubility[edit]

The solubility of a compound is 25.0g/100g of water at 50.0 degrees C and 4.00g/100g of water at 25.0 degrees C. what would happen to the solution at the hight temperature if it was suddenly colled to the lower temperature? —Preceding unsigned comment added by Nalapuppers (talkcontribs) 16:18, 27 January 2010 (UTC)

Welcome to Wikipedia. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. --LarryMac | Talk 16:35, 27 January 2010 (UTC)

Are handbooks the Reader's Digest of academia?[edit]

--ProteanEd (talk) 16:26, 27 January 2010 (UTC)

Er, what? Can you be a little more descriptive about what you are calling a "handbook"—give us an example? Using the normal definition, I would say, "no," as Reader's Digest is usually a bunch of abridged-yet-original pieces, whereas handbooks are generally reference works. If you mean something like an anthology (sometimes called "readers"), even those are not usually abridged, though sometimes they are. In any case it is a strained analogy. --Mr.98 (talk) 16:34, 27 January 2010 (UTC)
No. you cannot take an introductory course in say particle physics by reading the particle physics handbook. You would however get good at reciting branching ratios and be the life of the party. EverGreg (talk) 16:44, 27 January 2010 (UTC)
I sure did meet a lot of interesting people when I posted the Navy Research Lab Plasma Physics Formulary on my website... Nimur (talk) 23:23, 27 January 2010 (UTC)

Gadolinium[edit]

Since gadolinium looks just about the same as most other metals, I need to determine if the sample of it that I'm getting for my element collection is genuine. Due to its abnormally low Curie point (292K/19C, slightly below room temperature), one obvious way to test it would be to determine if the sample is paramagnetic, then put it in a bowl of ice water and see if it's ferromagnetic. How can I do this?

Also, is pure gadolinium toxic? --J4\/4 <talk> 16:45, 27 January 2010 (UTC)

I don't have any direct answers, as a non-chemist; but as you're collecting elements, I just wanted to make sure you knew all about the gadolinium sample entry in the fabulous Periodic Table Table. Comet Tuttle (talk) 17:55, 27 January 2010 (UTC)
It's not particularly toxic, but it is an irritant, so avoid touching it[13]. To check the magnetism: at room temperature see if it's (weakly) attracted to both sides of a magnet. Then see if you are able to magnetize it (you should not be able to). Next cool it, and try again, first it should be much more strongly attracted to the magnet, and you should be able to magnetize it, and then repel a magnet.
I'm not sure that the paramagnetism is strong enough for you to feel by hand though. So at best you might be able to detect a change in the magnetic force at different temperatures. Ariel. (talk) 20:54, 27 January 2010 (UTC)
"Handle under an inert atmosphere. Store protected from air. Do not allow contact with water. Keep from contact with moist air and steam."
I had no idea it was so volatile. Does it explode on contact with water/air or something? --75.33.218.77 (talk) 23:09, 27 January 2010 (UTC)
See here Gadolinium#Chemical. In moist air it reacts with oxygen and corrodes, and it reacts with water to form Gadolinium Hydroxide and hydrogen. The hydrogen can burn if it gets hot. I don't know if the reaction releases heat, but it might. So basically in water you might have a fire, and in air you soon won't have pure gadolinium. Ariel. (talk) 01:00, 28 January 2010 (UTC)

Irrational numbers[edit]

I recently saw a book listing e to several thousand decimal places, and it got me wondering. Is there any real-world application for having an irrational number with more than maybe a dozen numbers beyond the decimal point. It seems that all those digits would just be lost in the significant figures, and that pi or e to a thousand digits wouldn't get me a much better answer than to just a few. So, is there an application, or is calculating all those digits just a way to show who's got the biggest ... computer? Tobyc75 (talk) 18:17, 27 January 2010 (UTC)

Numerical approximations of π#Modern algorithms notes "These approximations have so many digits that they are no longer of any practical use, except for testing new supercomputers." DMacks (talk) 18:47, 27 January 2010 (UTC)
See also significant figures. In the real world, we are limited in accuracy and precision to the accuracy and precision of the actual instruments we use to make the actual measurements we need. If our rulers are only accurate to, say, 1 millimeter or so, it makes little sense to use a measurement made with said ruler, and then use a 3000-digit approximation of pi for our calculations. Our approximations of irrational numbers need only be as precise as that of the instruments we use to do our real measurements. Anything more than that is trivial. Interesting for the mathematicians and maybe computer scientists, but for anyone that has to use irrational numbers to actually make something, like a building or a road or a drug, mostly pointless. --Jayron32 20:09, 27 January 2010 (UTC)
So we can find Ellie's circle? (That would be so cool!) SteveBaker (talk) 00:47, 28 January 2010 (UTC)
If pi is normal, which a lot of mathematicians expect it to be (it hasn't been proven yet, though), then it has to be there somewhere. --Tango (talk) 01:22, 28 January 2010 (UTC)
Yes - I agree. I actually downloaded the longest decimal expansion I could find a few years ago, converted it to binary and did a search for approximate circles embedded in square blocks of various sizes - but the nearest I found was a depressingly small number of pixels across (I think it was maybe 5 pixels in diameter - which is hardly recognizable as a circle). But I ignored all of the 'base 11' junk from the book because I stood a much better chance of finding something cool in base 2. Oh well...as you say, we're pretty sure there is a very convincing 512x512 square of 1's with a near perfect circle of 0's inside...it's there somewhere. SteveBaker (talk) 01:54, 28 January 2010 (UTC)
You don't really need to agree - my statement follows directly from the definition of a normal number, so there isn't much to disagree with! I've never read Contact, but our article's description of the whole circle-in-pi thing seems contradictory - it says the length of the sequence is the product of 11 primes, which sounds to me like it probably means distinct primes. That means it is square-free and, in particular, not a perfect square, so how can it be interpreted as a square bitmap image? --Tango (talk) 04:24, 28 January 2010 (UTC)
Arecibo message bw.svg
Yeah - it's a bit of a hazy description. But since I wasn't really looking for a message from the creator of the universe - but something more like "wouldn't it be cool to find a circle inside pi and freak out half the population of the world with my discovery" - I didn't bother looking for rectangular images. Also, I couldn't hope to find a large circle other than by complete flook. I only had a few tens of millions of bits and the probability of finding even a specific 5x5 pixel chunk is the same as finding a specific 25 bit number. The odds of that is something like 64 million to one against at each bit position. If it were not that I had a fairly lax tolerance for what constituted a "circle" at such apallingly low resolution then I'm pretty sure I would find nothing of the sort unless there were some solid mathematical reason for there to be one. But for a couple of hours software work and 48 hours of CPU time on my home PC - it was worth searching. The circle image mentioned in Contact has prime number sized dimensions because that's the standard way we imagine sending SETI type images to distant stars. The image that was actually transmitted by the Aracebo telescope to M13 (see right) is 313 × 938 pixels for precisely that reason...although what the heck an alien civilisation would make from that mess - I have no clue! There is some elementary arithmetic in there - a picture of a human(!) and a drawing of the Aracebo telescope plus a map of the solar system, a picture of a DNA molecule and all sorts of other stuff...but I'd be pretty surprised if an alien could figure out anything past the prime numbers in the top row - it takes a pretty good imagination to guess what the heck it is even when you know! But a circle inside pi! Now that would be something! SteveBaker (talk) 22:35, 28 January 2010 (UTC)
There are some advantages to having "random" number sequences that are known ahead of time, and you could use a normal number (like pi) for that, if you wanted to. (A Million Random Digits with 100,000 Normal Deviates is another such collection.) But there's no real reason to prefer pi or e to a very good set of "random" numbers that I know of. --Mr.98 (talk) 01:33, 28 January 2010 (UTC)
There are much easier ways of making tables of high quality random numbers than generating digits of pi or e...and in many cases the benefit of such a table is that certain bad guys DON'T know it. pi and e are just a bit too public for some applications. SteveBaker (talk) 03:17, 28 January 2010 (UTC)
Right, but there are applications for known sets of random numbers (hence the comparison with the RAND book, which was distributed very widely). Obviously cryptography is not one of them (other than for demonstration purposes, anyway). But I agree that there is really no reason to use pi or e for this, though I have seen (somewhere) suggested that they could be used for this purpose. --Mr.98 (talk) 14:52, 28 January 2010 (UTC)

Near Airports : Blocked Radio Waves[edit]

I believe they block out some radio frequencies somehow for air traffic control reasons. Is there a way to do this for your home/work? --i am the kwisatz haderach (talk) 18:52, 27 January 2010 (UTC)

They don't. Blocking radio waves just isn't practical. You could jam signals, but that floods the frequency band with noise, making it unusable by everyone (and it's heavily frowned on by the FCC). What really happens to keep ATC frequencies clear is that governments allocate frequencies for specific purposes. You can see the US chart here or at frequency allocation. — Lomn 19:16, 27 January 2010 (UTC)
And the government can fine people who are misusing those frequencies. Googlemeister (talk) 20:05, 27 January 2010 (UTC)
Faraday cage? --TammyMoet (talk) 20:06, 27 January 2010 (UTC)
Good point, you can certainly block radio waves in a small enclosed space. Naturally, it won't work for an airport or other open environment. — Lomn 20:23, 27 January 2010 (UTC)
And it would be difficult to do for your home. A small gap somewhere (the door, say) would let the radio waves in. You can have very small gaps (basically a fine mesh) to allow ventilation, but that's about it (if you only want to block long wave radio, that's a little easier - you could get away with gaps of a few meters - but if you want to block mobile phone signals, though, a few millimetres would be too big, I expect). A Faraday cage also doesn't allow you to select specific wavelengths to block - you can block long wavelengths while letting in shorter ones, but that's as selective as it gets. --Tango (talk) 22:14, 27 January 2010 (UTC)
Are you thinking of something similar to mobile phone jammers, that stop them working in a limited area? 220.101.28.25 (talk) 23:57, 27 January 2010 (UTC)

burning hashbrowns[edit]

does the smoke from burning hashbrowns contain monoxide and how much —Preceding unsigned comment added by 67.246.254.35 (talk) 18:58, 27 January 2010 (UTC)

Probably. Carbon monoxide is a product of incomplete combustion, which is difficult (if not impossible) to entirely avoid. As for how much, it'll depend on the precise nature of the burning hashbrowns and their environment. I can't think it would be a significant amount, though, or else we'd see far more warnings about the dangers of cooking. I'd guess it's on par with operating a gas stovetop. Good ventilation is key to avoiding CO poisoning, and good ventilation is also key to getting rid of the smell of burnt hashbrowns, so I'd expect any potential problem to solve itself. — Lomn 19:23, 27 January 2010 (UTC)


how is burning hashbrowns any different than burning coal or wood--67.246.254.35 (talk) 19:54, 27 January 2010 (UTC)

It's not. In any way. --Jayron32 20:04, 27 January 2010 (UTC)
I would guess that hashbrowns have much higher moisture content than your average cord of firewood. By the time they start burning, they're probably pretty dessicated. Nimur (talk) 23:25, 27 January 2010 (UTC)

why not —Preceding unsigned comment added by 67.246.254.35 (talk) 22:04, 27 January 2010 (UTC)

Burned wood=carbon, Burned Hash Brown=carbon, both are carbon based, when burned you get carbon. ps Please sign your posts with four ' tildes' like this. Thanks! ~~~~ --220.101.28.25 (talk) 23:33, 27 January 2010 (UTC)
The basic process of burning is so high energy, that the specific organization of the atoms in the substance makes little difference to the overall process. I can't imagine potato and cordwood burning by any different mechanisms. In the broad picture, potato and wood are almost chemically identical. They contain the same basic elements in roughly the same chemical organization, and the very small difference between wood and potato are unlikely to make much of a difference at all when it comes to an aggressive reaction like burning. --Jayron32 04:34, 28 January 2010 (UTC)
Well I imagine ventilation *into* the hashbrown is pretty important. There'll be in fact be more complete combustion within the hash brown because it's well, thinner and oxygen can get into it easier. John Riemann Soong (talk) 13:55, 28 January 2010 (UTC)

Humane biological warfare - incapacitating the enemy[edit]

Dear Wikipedians.

With some thought paid to guerilla warfare, a concern is raised with regards to the lethality against the oppressor: If many occupant soldiers are killed, this can serve to fuel anger within that army and its leadership. Possibly, one risks systematic vengeance against the civillian populace in which one (as a freedom fighter/guerilla/rebel/terrorist) blends in.

Now, I mean to ask in all seriousness (entirely void of medical advice): What diseases and sicknesses can one reliably inflict upon captured soldiers which will have an incapacitating function, preferably weeks to months? I would range infectious mononucleosis very high, although it seems right on the edge morally (though we should avoid that discussion; I simply make the mention so as to set a benchmark) - the physical capacity is reduced for very long, and it is outrageously taxing on the body.

I would deeply appreciate your educated response to this question. :) Thank you in advance. 77.18.22.117 (talk) 19:18, 27 January 2010 (UTC)

Doing this would violate the 1925 Geneva Protocol, and the 1972 Biological and Toxin weapons convention. Also, if you give your POWs diseases, how will you prevent them from spreading to your own troops? If you want to disable troops very well, give them amoebic dysentery. Googlemeister (talk) 20:02, 27 January 2010 (UTC)
(EC) Thank you for that infection, Googlemeister! This raises a very good candidate for a possible <24 hour incubation disease, which can be used alone, or to taste in a cocktail with one of far greater incubation. Of course, such a cocktail could be fatal. Indeed, I ask on assumptions (if you want me to morally qualify the practise) that these conventions are breached. As they say, the conventions' existence not so much help to constrict the application, but places clear responsibility for the application, on those behind it. It is thought for this scenario that a local militia may not feasibly detain POWs. It is then arguably better for the unfortunate soldiers to have themselves injected with disease and released, than to be shot. It is not so much better if the soldier is made subject to a week of illness followed by death. I do not wish to derail the pursuit for good candidates for the question, be they bacteria, virus or medications of sorts - but I thought it polite to give some motivation. As for spread to one's own forces, I've yet to think much about that subject. 77.18.22.117 (talk) 20:52, 27 January 2010 (UTC)
I'd guess that governments would love to find a highly non-toxic, inexpensive, volatile incapacitating agent, which also has an inexpensive non-toxic antidote / prophylactic. Simply give your soldiers the prophylactic, and spray the incapacitating agent on the city via aircraft, and invasion becomes easy. --Mark PEA (talk) 20:36, 27 January 2010 (UTC)
The article you link deals with chemical warfare, subtly different from the biological. However, I realize there may well be candidates among several sorts of toxins that can have long lasting effects. I shall pursue that path, thank you for mentioning. 77.18.22.117 (talk) 20:52, 27 January 2010 (UTC) (edit: I mislabelled the title "chemical" instead of "biological". Fixed)
The bad news with the idea, would be that after the person who caught your disease recovered, that individual, would now be resistant to your pathogen. Googlemeister (talk) 21:21, 27 January 2010 (UTC)
This is something of an aside, but I think one could make the argument that historically, killing soldiers does not turn a populace against you. Killing civilians does. But just killing a lot of soldiers does not. People seem fairly willing to internalize the "rules of war" in judging such things; only the rampant targeting of noncombatants seems to trigger massive moral outrage. --Mr.98 (talk) 23:13, 27 January 2010 (UTC)
Dear Mr.98, I've made a subtle change in the original text, to help underline what I mean: The guerillas, through killing an occupying force's soldiers, can risk atriocities being performed on the civillians as vengeance and deterrent. 77.18.9.135 (talk) 09:07, 28 January 2010 (UTC)
Not to get off tangent again, but if you can, in some little way, provoke occupying force soldiers into committing atrocities, that will only help your cause and weaken theirs. If you can provoke them to commit atrocities without committing atrocities yourself, you have the obvious moral high ground, and will, in the long term (if history is any indication), win out. --Mr.98 (talk) 23:03, 28 January 2010 (UTC)

A better method would be to produce a genetically engineered virus with the infectivity of a cold and the lethaliy of Ebola targeting only humans with the genes associated with certain traits of human behaviour, such as authoritarianism, misogyny or psychopathy-this would mean the end of the Taliban.Trevor Loughlin (talk) 07:52, 28 January 2010 (UTC)

  • Sorry Trevor, are you standing on a soapbox? ;) 77.18.9.135 (talk) 09:07, 28 January 2010 (UTC)
  • I seriously doubt that these traits have significant genetic components. And if they had them, the Moral Majority would certainly oppose it...for purely moral reasons, of course. --Stephan Schulz (talk) 13:02, 28 January 2010 (UTC)
Genes are absolutely "involved" in human behavior but in nowhere near as selective a way as Trevor would suggest using. There may be genetic variants that predispose a person towards certain behavior types, but we have only a minimal understanding of the combination of genetic and environmental factors that result in the "psychopath". Trevor's misguided suggestion (if at all feasible, which I doubt) would result in the preemptive killing of large numbers of people with genetic "predisposition" to certain types of behavior who themselves never did anything wrong. For all we know, those same genetic variants are also responsible for the types of behaviors that are associated with successful leaders of world nations and large corporations. They are just put to a different use in those whose social/cultural circumstances differ. It's a bad idea all around. --- Medical geneticist (talk) 13:41, 28 January 2010 (UTC)
Even if it worked, I doubt any self-respecting government would use it. If there are two possibilities, one killing a number of people based solely on genetic or behavioral patterns and causing big public outcry, and the other is letting those people prosper, multiply and destroy your nation in the long term, most governments would still choose the later: choosing the first would made them loose their jobs or next elections, and the second choice will only be someone others problem in the future. --131.188.3.21 (talk) 00:55, 29 January 2010 (UTC)

SHM in a RLC circuit[edit]

Can someone please explain to me how from  L\frac{d^2q}{dt^2} + \frac{q}{C} = 0 where L is inductance q is charge and C is capacitance you are supposed to read off angular frequency as \frac{1}{\sqrt{LC}}? Thanks very much --94.193.67.204 (talk) 20:35, 27 January 2010 (UTC)

First you solve this as a differential equation to get a set of formulas for q changing with time. You will find that the solution is a sine equation with arbitrary phase and amplitide, but fixed frequency, and the frequency comes out as \frac{1}{2 \pi \sqrt{LC}}. you can confirm this by calculating  \frac {d^2 \sin{ \omega t } }{dt^2} Graeme Bartlett (talk) 20:49, 27 January 2010 (UTC)
(edit conflict) The standard form differential equation for simple harmonic motion is  \frac{d^2x}{dt^2} = -\omega^2 x, where ω is the angular frequency. Simply put it in that form and it is obvious. Dragons flight (talk) 20:53, 27 January 2010 (UTC)

the chemisty of seating gels[edit]

What is the chemical make-up of seating gel? What are the chemical components and where can I buy them? Who has them for sale and would have directions for a new customer? I'm a garage inventor so to speak and I have a new product idea. Thank you. BlueLoon (talk) 20:41, 27 January 2010 (UTC)

Do you meant the kind of get that you might get in a bicycle seat? Or "setting"? Silicone is a possible substance. Graeme Bartlett (talk) 20:52, 27 January 2010 (UTC)

Yes, nice soft bicycle seats are exactly the type of gel I am looking for info on. I thought of silicone but the silicones I am familiar with from other applications are not so soft aand yielding. I'll try to get confirmation on whether seating like that could be a form of silicone. In the mean time, any other suggestions, anyone? Thanks BlueLoon (talk) 23:04, 27 January 2010 (UTC)

You could try a visco-elastic polyurethane foam. These are often called memory foam. They can be purchased from McMaster-Carr for one place (I am not afiliated with McMaster, but they do ship immediatly after you place the order). I'm sure that many hardware stores carry similar products. CoolMike (talk) 17:40, 28 January 2010 (UTC)
Some patents also mention polyols. However are they actually used for this application? Graeme Bartlett (talk) 20:51, 28 January 2010 (UTC)
AFAIK polymeric polyols are used as intermediates in the manufacture of the aforementioned viscoelastic polyurethane foam. Also polyesters are classified in the "polyol" category. As for the use of polyols other than polyesters as seating gel -- I have no idea. FWIW 24.23.197.43 (talk) 03:10, 1 February 2010 (UTC)

corrosive gun primers[edit]

they form hydroxides, what type thou? also if it corrodes gun metal wouldn't the user get chemical burns from handling the gun or touching the barrel? —Preceding unsigned comment added by 67.246.254.35 (talk) 21:19, 27 January 2010 (UTC)

vicinal halogenated compounds[edit]

Suppose you expose chloroform or carbon tetrachloride to strong base to get something like a carbon with three or four alcohol groups on it, which is of course unstable. The article says chloroform + base converts to phosgene, but I honestly can't see a mechanism. Suppose you react with an alkoxide base to form acetals (which makes it harder to get to something like formic acid or an formate ester)? Would you have say, a stabilised vicinal diacetal? John Riemann Soong (talk) 23:40, 27 January 2010 (UTC)

Where does it say "chloroform + base → phosgene"?
Ben (talk) 18:00, 28 January 2010 (UTC)
Chloroform can react with hydroxide bases by the SN2 reaction to form dichloromethanol, CHCl2OH:

CHCl3 + OH- → CHCl2OH + Cl- The formation of phosgene, though, would require this to be oxidized with the loss of 2 hydrogen atoms. Note also that this reaction only takes place in polar aprotic solvents such as DMSO or DMF. As regards your question about getting a carbon with three or four alcohol groups on it, that is absolutely impossible -- as soon as you get that second OH group on the carbon, you get a gem diol, which immediately dehydrates to formaldehyde (or in this case, chloroformaldehyde CHClO): CHCl2OH + OH- = CHCl(OH)2 → CHClO + H2O 24.23.197.43 (talk) 03:40, 1 February 2010 (UTC)