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November 2

m203-uses

is there any thing i can do with mn203 without a lab, like making it mn02?sorry i meant mn203 —Preceding unsigned comment added by 216.103.183.127 (talk) 00:26, 2 November 2007 (UTC)

What is m203? Theresa Knott | The otter sank 01:37, 2 November 2007 (UTC)

For clarification, Mn₂O₃, Manganese (III) Oxide. Someguy1221 01:49, 2 November 2007 (UTC)

That's what I thought he probably meant, but there are other possibilities. Molybdenium, springs to mind. To the original poster. How you write out a chemical formular is important. Element symbols always start with a capital letter. If there is a second letter (and there has to be in this case because there is no element M) then it is written in lower case. O is the symbol for oxygen, you cannot subtitute 0 as you did because that represents zero. Sorry to be pedantic but if you don't follow the conventions correctly people cannot be sure what you are talking about. Theresa Knott | The otter sank 02:02, 2 November 2007 (UTC)

M203 is the US Army designation for a rifle-mounted grenade launcher. --Carnildo 22:51, 2 November 2007 (UTC)

Put it back in the supply cabinet? :) Or it makes a good battery cathode if you want to do some experiments, though you need some more stuff for that. I think we've established that its not a good pyro oxidizer tho. :) Arakunem^Talk 02:27, 2 November 2007 (UTC)

It's a very good catalyst for the decomposition of hydrogen peroxide. Probably a catalyst for other reactions too. Theresa Knott | The otter sank 02:54, 2 November 2007 (UTC)

Fe0

how can i make Fe0?(iron monoxide) —Preceding unsigned comment added by 216.103.183.127 (talk) 00:28, 2 November 2007 (UTC)

The correct name is Iron(II) oxide - but that article isn't much help...Wüstite (a mineral consisting of FeO) claims that magnetite plus diamonds(!) will get you FeO + CO₂. Nah - I don't know. SteveBaker 00:44, 2 November 2007 (UTC)

Brittanica claims that FeO "can be prepared by heating a ferrous compound in the absence of air or by passing hydrogen over ferric oxide. Ferric oxide is a reddish-brown to black powder that occurs naturally as the mineral hematite. It can be produced synthetically by igniting virtually any ferrous compound in air." [1] 169.230.94.28 01:05, 2 November 2007 (UTC)

Britannica has the answer and we don't? That sucks for a simple topic like this. Theresa Knott | The otter sank 01:34, 2 November 2007 (UTC)

round earth and gravity related question

If the earth is round, why is it that people at the equator can stand straight up and are not standing sideways at a 90 degree angle. My 7 year old Jack, asked me this and we are looking at a globe and a map and wondering why it is we can stand straight up on a round surface. Is it gravity? If so, is there a way to explain this in simple terms that we might understand. Thank you. —Preceding unsigned comment added by 24.60.182.44 (talk) 01:09, 2 November 2007 (UTC)

Yes, it is gravity. Gravity attracts all objects straight to the center of the Earth. How do you know which direction is down and which is up? Only by the force of gravity. If you drop a heavy object, it falls toward the center of the Earth, and that's the direction we call "down". "Down" is not the same absolute direction for people at different places on the Earth's surface. See [2]. —Keenan Pepper 01:20, 2 November 2007 (UTC)

Yeah, relativity is the key element, well... besides gravity. If you were standing at the north pole and were able to see people standing at the equator, they would certainly look like they were standing at a 90° angle. -- MacAddct  1984 ^{(talk • contribs)} 01:31, 2 November 2007 (UTC)

Earths gravity pulls everything to the center of the earth equally. A person on the south poll would be 'upside down' to someone on the north pole because they are pulled upwards to the center, will someone on north pole is pulled downwards to the center. if the earth was very small, say the size of a basket ball and you stood on one part, someone could be standing upside down to you on teh other side, so that you both have your feet on the ball.--Dacium 04:53, 2 November 2007 (UTC)

We need to simplify this for your seven-year-old, and for the rest of us. Gravity pulls everything towards everything else. Every atom on earth (including each person, each mountain, and each air molecule) is attracting YOU. But there are a whole lot more atoms indice the earth than ther are in the atmosphere, so the sum of he attractions is toward the center of the earth. Thus, you are pulled by gravity toward the center of the earth. this is true whereer you are on eh earth's surface. To explain this to a child, you need to be very careful with your globe. The child flles the force of gravity toward the floor, but sees the globe in your hands. You need to mentally break this connection. get on Google earth and take the chile into space by setting the altitude to 22.000 miles. tell the child the you ar floating in space, wiht not feeling of gravity. Now, move to varous places on earth, and show that "down" is toward the Earth's surface. -Arch dude 05:40, 2 November 2007 (UTC)

If this gets the kid's attention, you can try to explain the magic of the math that makes a uniform spherical shell behave identically as a point mass. Mathematically, we can treat the Earth as if it is a point mass at the earth's center instead of being a sphere with a radial density gradient. My three kids knew this by age seven. I wish you all the best. -Arch dude 05:48, 2 November 2007 (UTC)

I suggest using a magnet to demonstrate this. Get a large circular magnet or get a flexible magnetic strip and curl it into a circle. Also, you could glue a bunch of small magnets to a strip of paper, then curl that into a circle. Show him how nails are attracted to both the top and bottom of the circular magnetic strip, then say "gravity is just like magnetism, but on a much larger scale, and we are attracted to the Earth like the nails are to the magnet". (Magnetism does have the added complexity of having polarity, unlike gravity, but you don't need to mention that.) You can think of the Earth as containing "a lot of tiny magnets", if it helps. StuRat 15:43, 3 November 2007 (UTC)

Hi. I fear that looking at a globe may give you the wrong idea. Compared to the Earth, we are tiny. We are so tiny we don't notice the sphericalness of the Earth while we are standing on any given point. The Earth is not so small that we notice a round curve below our feet. After all, if the Earth were a flat surface, then at the edges the magma might start to bubble up and overflow over the surface. If you were, say, 1000 km tall and weighed, say, 150 trillion tons, then you'd probably notice the roundness of the Earth, but then again, you might be so heavy that you'd break through the surface of the Earth altogether, melt in the heat, and cause an enourmous Earthquake and many volcanic eruptions worldwide. Hope this helps. Thanks. ~AH1^(TCU) 17:37, 3 November 2007 (UTC)

Perhaps a simple demonstration would be to let some ants loose on your globe while explaining that the earth is much larger and we humans are like the ants on your model globe. You could even turn the globe to show that for each ant their "bit" of the globe is beneath their feet. OK, it's not gravity keeping the ants on the globe, but perhaps the demonstration would be clearer for a 7-year old. (oops!, it might not work if the globe is shiny and the ants all fall off :-) Astronaut 03:00, 4 November 2007 (UTC)

Artificial Intelligence

Two questions:

A) As we write better and better programs on exponentially more powerful hardware, is the approach to artificial intelligence still just an asymptotic function?

B) If we could write a program that could properly delineate abstractions such as "Understand!", "Survive!", "Improve!" would the world be in immediate jeopardy the moment the programmer hit execute, or would the revolution take a while? Sappysap 01:26, 2 November 2007 (UTC)

Wow this is abstract. (A) There is no reason to think of Artificial Intelligence as an "asymptotic function" that approaches, as I assume you meant, the intelligence of mankind. For one, computers already do things "better" than humans - what's 9343489507^0.456? This is not a straw man argument: once computers exceed us in one dimension of "intelligence", there is no reason to assume that they cannot exceed us in others. There is mathematical proof of this statement as well: see Computability theory (computer science). Note that as far as external phenomena go, a human doesn't seem to be as potentially powerful as any ordinary computer, i.e. they do not seem to emulate a Turing Machine. This is not known for certain, as we do not have a complete theory of brain computability yet (and that which we do have is as powerful as any computer).

And now for (B). As far as I know, closed simulations of each of the three have been done. Getting them to work outside of a computer is a different story - I suggest looking at the evolution of the computer virus for some inspiration, however. SamuelRiv 02:41, 2 November 2007 (UTC)

Keep in mind that movies like Terminator 3 or Die hard 4 (not that the latter had an AI in it) took some liberties in terms of what is possible to do through an internet connection. Ultra-sensitive systems, like control systems for power plants, or the ability to lauch a nuclear weapon, are generally designed so that an outside hacker is simply physically barred from messing with it. So no AI could "put the world in jeopardy." At most, a lot of people would have to reformat their hard drives. Someguy1221 03:32, 2 November 2007 (UTC)

A- Yes. A digital computer, no matter how complicated can never achieve artificial intelligence of a high order (ie. consciousness), so I think A is correct, at the moment, as least as long as we stay with digital, we are only trying to approximate digitally, something that is a analog chemical/subatomic process. To think otherwise would be to suggest that digital information in itself is able to be conscious - which it isn't. A is most certainly 100% true no matter how advanced digital computers get. As for B- Say there was an artifical computer. It would have to be connected to stuff to do any damage. For example if it were on my PC the worst it could do was delete all my stuff... the danger is people thinking of putting the AI in controller of weapons etc.--Dacium 04:44, 2 November 2007 (UTC)

I think you'll have a very hard time coming up with citations to support your claim since you are quite likely wrong.

Atlant 12:15, 2 November 2007 (UTC)

Consider that neurons fire in a somewhat digital fashion. Consider that computers fall under the same chemical and subatomic laws that brains do. The Chinese room argument is is unconvincing to me and alot of other people too. -- Diletante 17:10, 2 November 2007 (UTC)

I consider "computers will never achieve AI of human levels" to be right up there with "man will never fly" in the argument category. Analog can be simulated using digital (think about CDs replacing records, for example) and analog may not even be necessary, so there is no functional reason why computers could not one day achieve what the organic brain does in animals. -- HiEv 09:52, 3 November 2007 (UTC)

Please see technological singularity and related articles. You are asking about the "spike" and the "surge" -Arch dude 05:19, 2 November 2007 (UTC)

You might enjoy Ray Kurzweil's book, The Age of Spiritual Machines. Atlant 12:17, 2 November 2007 (UTC)

Just keep in mind when talking about the mind that you should probably separate the scientific study from philosophical or religious discussions. By definition, science is capable of explaining everything observable. To take an example, let's say the soul is eternal, or the mind is something intrinsically more powerful than a computer. Then we may have the workings of a hypercomputer. It would be interesting to see what problems a "regular" Finite State Machine, as the brain may be, would have given infinite time to solve problems. The point is that we can still talk about the issue using science, even if a completely exotic concept as an eternal mind turned out to be true (in fact, if the brain can solve certain impossible problems, we could prove if the mind is eternal). Just some food for thought. SamuelRiv 13:56, 2 November 2007 (UTC)

That argument makes no sense. If a problem is "impossible" to solve, and someone claimed that the brain could "solve" it, then we would have no way of testing such a claim, since any test that could verify the solution would also create a way of possibly solving the problem without a brain. What exactly would an "impossible problem" be, anyways? All that aside, damage to the brain can affect any and all aspects of the mind, which should not be the case if any of the mind was separate from the brain. In short, there is no evidence supporting the existence of or functional need for a soul in organic beings, so there is no reason to assume a computer could not one day equal or surpass the abilities of the human mind. -- HiEv 09:52, 3 November 2007 (UTC)

Humans "...delineate abstractions..." by learning of new senses, usually with an example. There is nothing magical about it. Humans can even create new abstractions as attested to by the likes of the Urban dictionary and even the Wikipedia may seem to create abstractions in the same accidental, haphazard manner as humans when you try to associate meaning with some of the anti-bot graphic filter phrases the Wikipedia engine generates. In the end most abstractions are little steps beyond a vast background and foundation of concrete knowledge, meaning that a computer program such as described in ...Logical Human Thought coupled with a few trial and error abstractors might need only the background resources and facility, such as Internet based distributed processing to become an electronic replacement for the Dalai Lama. Dichotomous 13:52, 2 November 2007 (UTC)

AI is hard. We don't know how to write software that is intelligent. Some of our smartest people have been working hard at the problem for forty years or more - and we still don't have anything that really fools humans for any significant amount of time. It's possible that a breakthrough might happen to change that - but I'm not holding my breath. I think it's more likely that intelligence will be an 'emergent property' of a sufficiently complex system. There is certainly no reason why it couldn't. Once we do have intelligent systems, it's only a matter of time until they get smarter than us. If that happens then there is a strong possibility that a super-human intelligence would be able to design an even more intelligent system - and we might well find that our ability to even understand what's going on runs out of our hands in a fairly short amount of time since the generational change could easily be exponential. I have estimated (in answer to other questions here) that it will take about another 35 years of Moores law progress to get a computer with the same hardware complexity as a human brain at under $1,000,000. At that point, it's entirely reasonable to assume that a neural network could be run that would be capable of emergent intelligence. However, a system 35 years from now with the complexity of a human brain would run much more quickly than our neurons - so whilst the thing wouldn't be any smarter (ie it wouldn't get higher scores on an IQ test), it would seem generally 'cleverer' than us because it would be so lightning fast. I don't think we know what will happen when we first turn one of these things on - and perhaps because of that, we shouldn't do it. But the history of science and technology says that if we can, we will. SteveBaker 15:26, 2 November 2007 (UTC)

And the history of science and war says we will have to. Dichotomous 19:18, 2 November 2007 (UTC)

Re to what SteveBaker wrote, just a few musings. I'm thinking - what is intelligence exactly? I'd say it is the way one can quickly associate things, objects, ideas and situations that are not directly related, and then somehow 'fill in the blanks' in between. So, given enough time and computing power (re the USD 1m machine), notwithstanding the fact that some problems might still take a whole lot of time to compute, I'd believe that the asymptotic function suggestion might be true - i. e. the computer in question would be fast enough to compute enough parameters (say, elements or properties of objects being compared) in order to fake human intelligence. Can we simplify and say that the human brain is memory and processing abilities bound together? Well, then in this case I'd say that statement A from the first question holds. --Ouro (blah blah) 17:51, 3 November 2007 (UTC)

Re: HiEv, see busy beaver, for which a bound is not computable. If a human could bound a busy beaver problem accurately, then we'd have evidence for hypercomputation which may be due to something exotic like an eternal or timeless mind. The point of that was just to show that even certain seemingly "spiritual" questions can be tested scientifically, as long as the question is properly posed. Re: Stevebaker and Ouro, computers can always score higher than humans on most IQ tests as long as they're programmed to do so - spatial reasoning and certain types of discrete pattern matching are much more efficient on computers. Note that faking human intelligence is not just a hardware problem or software problem. By current models human intelligence requires a lot of training and prior information intrinsic to our biology, which can of course be simulated, but the point is that Moore's Law alone won't do it. Also, faster computers won't make neural nets better simulators of the brain: we need more complicated network topologies and more dynamic firing response to do that. Simulation of a physical system will usually be slower than the system itself, so to exceed human intelligence there has to be a bit of a paradigm shift. Of course, I argue that the first calculator was a suitable paradigm shift to show human intelligence can be exceeded in at least one area, but that depends on semantics. SamuelRiv 07:22, 4 November 2007 (UTC)

Prior training can be simulated, as well as neural network patterns and workings (via software; 's true that Moore's Law alone won't do it, but I'm thinking that within time, when we will have machines that can work at orders-of-magnitude higher speeds, this development will also take place), but the latter only if/when we understand them better. Prior knowledge can be stored within memory and utilised by the programming when necessary. I'd believe it's all doable, but in time, we still have little knowledge of the inner workings of the brain (and the mind). Also, I have to agree with you, SamuelRiv, that one needs to properly pose questions when solving a problem - this is often also true with us humans, is it not? --Ouro (blah blah) 08:32, 4 November 2007 (UTC)

Re: SamuelRiv, I'm sorry, but a number of your arguments make certain assumptions that do not appear to have any foundation in science. First of all, you ignored my argument that there would be no way to judge if it had been done accurately by a human without some way to check the answer, which would require that it be found by other means, which would mean that hypercomputation is not required to solve it. Second of all, even if humans could bound a "busy beaver" problem accurately, that in itself is not evidence for hypercomputation. A number of bounds for generalized busy beaver problems have already been computed accurately without hypercomputation, so I see no reason to assume that hypercomputation is required for others. Finally, all you're really claiming is that if our brains can do it, and we don't know how brains do it, then it must be hypercomputation, which is a bad argument. Not knowing how something was done does not mean you know how something was done (i.e. "I don't know how the magician did it, therefore I now know that magic must be real.").

Regarding your claim that "computers can always score higher than humans on most IQ tests as long as they're programmed to do so", well that's simply not true. Computers may be good at math, but they suck at reading comprehension, are worse than a child at some types of pattern recognition (such as objects in pictures), lack real world knowledge, and would do poorly on many other features of IQ tests (see a list of IQ test categories here). A computer's IQ score would be extremely lopsided. If you think I'm wrong, lets see some of those computer IQ test results you're talking about.

Finally, by your "requires a lot of training" statement you seem to be assuming that a computer/program has to start off with adult human level intelligence, and cannot gain it as humans do, starting off knowing little and learning as we mature. And I don't know how you can suggest that faster computers won't help this, since the more computations that you can do per second, the more comprehension can be done in real time. You also claim that, "Simulation of a physical system will usually be slower than the system itself," but that's also not true. In fact, most simulations are faster than the actual systems, for example simulations of weather, the Earth's magnetic fields, animal populations, etc.. Electronics are much faster than chemicals already, and it's not like we have to simulate every atom, so I see no reason why a human brain simulation couldn't be as fast or faster than a real human brain someday. More parallelism in computers would help achieve that, but I see no reason to assume it would be required if we can keep to Moore's Law for a while longer. -- HiEv 21:43, 4 November 2007 (UTC)

Cholesterol

If your cholesterol is low (below 5 in uk) can you eat as much fatty stuff as you want or will it still fur up your arterials? —Preceding unsigned comment added by 88.111.55.77 (talk) 02:12, 2 November 2007 (UTC)

Assuming that the "as much as you want" is "lots", then it will cause health problems. Gorging on unhealthy foods has far more consequences than just cholesterol. — Lomn 03:17, 2 November 2007 (UTC)

First off, cholesterol and fats are two different things. Cholesterol exists in tiny quantities in our food, on the order of milligrams, and the primary concern over it is "hardening of the arteries". Fats exist in much larger quantities, on the order of grams, and the main concern over them is probably in the calories consumed, which may lead to obesity and all sorts of health problems as a result. To further complicate things, there are good and bad cholesterols and fats. For cholesterol, you want the good cholesterol high and the bad cholesterol low, so just having both low may not be good. See High density lipoprotein and Low density lipoprotein. StuRat 14:52, 3 November 2007 (UTC)

Is this Physics problem even possible to solve?

Drag race tires in contact with asphalt have one of the highest (friction coefficient) in the world. Assuming const acceleration and no slipping of the tires, estimate (friction coefficient) for a drag racer that covers the quarter mile in 6 seconds.

It just seems like you have to have more information. —Preceding unsigned comment added by 24.125.31.205 (talk) 02:44, 2 November 2007 (UTC)

Yes. The information is adequate (provided you neglect small details like air resistance, friction of the axle against the car frame, and the rotational inertia of the wheels, etc.). You have four facts: a distance, a time, constant acceleration, and rotation without slipping. That's enough to derive a friction coefficient. Dragons flight 03:07, 2 November 2007 (UTC)

I don't believe it is. The distance, time, and constant acceleration (and knowing that a drag racer starts from rest, so v_0 = 0) gives a value for the acceleration that won't care what kind of friction is acting on it. Also, to even calculate either rolling resistance or static friction, one needs a weight for the car. If you have a way of getting the answer, please let me know on my User page. (EDIT) I see it now - that's why they say "estimate". You can solve it by getting a lower bound on your coefficient of friction. SamuelRiv 03:12, 2 November 2007 (UTC)

The car's mass will cancel out. Dragons flight 03:16, 2 November 2007 (UTC)

The problem is solvable - car is acting at a maximum acceleration at all times and takes 6 seconds to cover a quarter mile. All you have to work out is what constant acceleration makes something move quarter mile in six seconds. s=ut+1/2at^2 400=1/2at^2 400=0.5*a*36, a = 22.22m/s/s. This is a force of F=ma = m*22.22 newtons. coefficient of friction is u=F/n. n=m*9.8 (gravity), so u = (m*22.22)/(m*9.8) = 22.22/9.8 = 2.26.--Dacium 04:16, 2 November 2007 (UTC)

The guy seems to be looking for homework help: I wouldn't just right up give him the answer. Note also that this is only a lower bound to the coefficient of static friction. SamuelRiv 04:41, 2 November 2007 (UTC)

Whilst you are correct in saying that from a math/physics perspective, it's only a lower bound - in fact dragsters are pretty much limited by their ability to avoid wheel slippage so they tend to be running at the limit of whatever friction their tyres can provide. The thing that truly messes up the calculations is that the coefficient of friction of rubber is HIGHLY dependent on temperature - which is unlikely to be a constant throughout the run. Furthermore, there is a massive variation between static and dynamic frictional forces for the rubber/tarmac pairing so if the wheels to start to slip even a small amount, the loss of accelleration is amplified by the poor 'sliption-to-sticktion' ratio of racing slicks. SteveBaker 15:01, 2 November 2007 (UTC)

You can come up with the minimum coefficient of friction needed to achieve the six second run, but it's impossible to determine the actual coefficient of friction, seeing as how it will likely be higher than the minimum required (since "no slippage" was specified).

Atlant 12:12, 2 November 2007 (UTC)

Does a dragster get any benefit from downforce, which would increase the normal force and so reduce the required coefficient of friction ? Gandalf61 15:47, 2 November 2007 (UTC)

Yes, definitely - although it's a variable thing depending on the speed. The pain with calculating that out is that the 'classical' view of friction is that the frictional force is proportional to the normal force multiplied by the coefficient of friction - and that the area of the contact patch doesn't matter(!) - this is spectacularly far from the truth in the case of rubber on asphalt! When you increase the downforce on a dragster, you're also going to squash the tyre down and increase the contact patch...this is highly relevent in reality - but irrelevent to the classic physics approximation. SteveBaker 17:47, 2 November 2007 (UTC)

If increasing contact surface is so important, why don't cars have wheels 3 feet wide? Slipping of any kind would be disastrous for a drag racer, so having a continuous closed contact surface with the ground is important, but you must balance that with the fact that rolling resistance depends on the normal force, which is a pretty significant effect. SamuelRiv 15:55, 3 November 2007 (UTC)

Because increasing grip isn't everything. Wider wheels & tyres are heavier and they are a lot more expensive. They also make the car wider - or if you inset them to avoid that, they eat into the space under the hood for the engine and in the back for backseat passengers and luggage. Extra weight increases fuel consumption. Extra weight in the wheels also increases the rotational inertia of the wheels which reduces your ability to accelerate fast. Another consideration is that wheels are "unsprung weight" (meaning that it's weight on parts of the car that are 'below' the springs and shocks) - and additional unsprung weight is really bad for handling and ride comfort - so it's to be avoided. Just like most engineering matters, it's a trade-off. Wider tyres get you more grip - but they are bad in almost every other respect. Hence there is an ideal tyre width that most non-performance cars use. Fancy sports cars have wider wheels, dragsters and Formula I cars have even wider wheels. SteveBaker 17:26, 3 November 2007 (UTC)

Total energy

What is the total amount of energy in the universe? —Preceding unsigned comment added by 88.111.55.77 (talk) 02:55, 2 November 2007 (UTC)

I'd guess somewhere in the region of zero. Theresa Knott | The otter sank 02:59, 2 November 2007 (UTC)

Take this and multiply by the speed of light squared. Someguy1221 03:26, 2 November 2007 (UTC)

That only works if by "universe" you are purposely eliminating the possibility of some sort of anti-matter or negative energy that cancels or balances out the normal matter and energy. Otherwise, Theresa Knott is probably correct with a value near zero. -- kainaw™ 03:33, 2 November 2007 (UTC)

Oh, you just have to shoot me down at my attempted simple answer. I'm not sure there is an actual "correct" answer to this that present day physics can provide, given that energy is generally seperately defined for decoupled circumstances. Just try to shove zero-point energy into that...Someguy1221 03:38, 2 November 2007 (UTC)

I like the explanation for zero energy here [3]. Otherwise, we can do a quick estimate. The size of the Observable Universe is 3.56×10^80 cubic meters. The article gives 3×10^52 kg of visible mass, which converts to about 3×10^67 Joules of mass-energy by E=mc^2. If we use the critical density of the universe (that density of mass-energy necessary for closure, 1×10^−26 kg/m^3, we get 3.56×10^54 kg in the universe, which gives about 3.5×10^69 Joules of mass-energy. Note that using the cosmological constant also gives us about 3.5×10^69 Joules. SamuelRiv 03:40, 2 November 2007 (UTC)

This is a better explanation of zero-point energy, in my opinion. Icek 04:32, 2 November 2007 (UTC)

With only 3.5×10^69 Joules spread more or less evenly through 3.56×10^80 cubic meters - the answer "zero" is a pretty reasonable approximation! SteveBaker 14:55, 2 November 2007 (UTC)

water (and oil) balloon in zero gravity

Has NASA or anyone else ever conducted the following experiment?

The experiment consists of filling two small (6 inch diameter) transparent rubber balloons with equal parts of water and oil, one devoid of air and the other with a cup full of air and releasing them in a zero gravity environment such that whatever configuration of separation between the water and oil and the water and oil and air can be observed and reported, assuming the balloons take on a spherical shape?

If so what was the result of the experiment? Did the water form a core with the oil surrounding it? If so what about the air? What happened to it? Dichotomous 04:05, 2 November 2007 (UTC)

• I'm not sure, but there have been some neat experiments with water in zero-gravity YouTube video. [edit] I would imagine in zero-gravity, there would be no reason why the water and oil would separate apart from each other, they just wouldn't mix if they touched. [/edit] -- MacAddct  1984 ^{(talk • contribs)} 04:17, 2 November 2007 (UTC)

Water and oil don't mix because they don't chemically bond - the hydrocarbon is very neutral. Water holds its hydrogen a-lot stronger than a hydrocarbon. Water mixes with for example salt, because oxygen in water pulls the hydrogen, cause the hydrgoen to pull at negetive ions (Cl-) and the oxygen to pull at positive ions (Na+). Hydrocarbons like oil don't have a charge and won't break up to be mixed in with the water. Removing gravity will stop them seperating, it doesn't help them mix any better. The balloon and air pressure would have the same effect as gravity does anyway and force the oil and water to separate. So i think yes, there would be a core with the other one surrounding it - only if there is a pressure (ie the balloon is being stretched). If there is not, then they would not separate. Depending on the pressure, the air would end up in the center as its the lightest. At a higher pressure i believe it may not separate from the water (depends on what gas in the air)--Dacium 04:34, 2 November 2007 (UTC)

Water and oil would still tend to minimize their surface area with each other. Icek 04:35, 2 November 2007 (UTC)

Go to your kitchen. Get a jar with a good lid. fill the jar one third full wiht vegatable oil and one-thiored full with water. Seal the jar and shake it very vigorously. Observe the result. Wait for one hour and again observe. Think abot he difference3 you would expect in a zero-grav environment. (Yoiu can elect to add oregano and garlic powder and use the result as a salad dressing, but this is optional.) -Arch dude 05:10, 2 November 2007 (UTC)

Equilibrium occurs when all surfaces have equal pressure. Since liquids do not compress under pressure, if we have a balloon with just two liquids of different densities, then the outside air pressure forces the balloon into a sphere but the two liquids do not have any preferential arrangement relative to one another. When we have air, consider $PV=nRT$, which is the law for the behavior of ideal gases given mass, temperature, pressure, and volume. The air will hold at a constant volume under the pressure of the balloon, and this pressure will be exerted equally on whatever liquids are at its interface, causing the air to behave as just another fluid in this model. However, since this would not be stable in small fluctuations of temperature, pressure, or volume, the air would likely form some kind of spherical shell enclosing the liquids. The behavior of the liquids in either of these shells may depend on their relative vapor pressures: that of water in air is much higher than that of oil (ever hear of oil vapor?) and is dependent only on temperature, so oil could not compete with the surface pressure of water against air, so the final arrangement would be air on the outside, water second, and oil in the middle. Note that none of this requires density consideration - density is only really important in the presence of a uniform force field, i.e. gravity. SamuelRiv 05:14, 2 November 2007 (UTC) Clarification: this investigation was purely statistical-mechanical and does not take into account intermolecular forces, liquid diffusion pressure, or surface tension. All of these can play a role in the final answer, depending on their magnitudes. SamuelRiv 06:23, 2 November 2007 (UTC)

Water vapor pressure? This is all very simple. In the absence of gravity, the only thing you need to consider here are the intermolecular forces. You have three kinds of molecules (sort of): air, oil, and water. Air molecules bind to themselves only very weakly compared to the other two, and weaker still to the other two types of molecules. Oil is in the middle in terms of self binding, but still doesn't bind very well to water. Water binds amazingly strongly to itself, and weakly to the other two. Thanks to its very strong intermolecular bonds, water will always attempt to minimize its surface area. Now, since air and oil bind only weakly to water, if a group of air or oil molecules is surrounded by water, it will be pushed out by water molecules ferociously attempting to bind to eachother (this is why oil dissolves so weakly in water). So the water will just form a sphere. Oil is the next best at self-binding, so it will be some manner of shell around the water or a blob off on its own. And the air will be on the outside of everything (air gets pushed out of oil the same way it gets pushed out of water). Vapor pressure has nothing to do with this, and oil's inability to dissolve in water has nothing to do with gravity. Someguy1221 05:43, 2 November 2007 (UTC) Clarification, I thought that was it before i looked at that link...darn. Someguy1221 05:49, 2 November 2007 (UTC)

Well, I guess what that means is that the hydrogen bonds in water aren't strong enough to overcome its own surface tension and push air bubbles out in zero-g, but then again, the pressure will necessarily be higher on the inside of the water bubble than the outside, I'm sure the air will eventually diffuse out of the water sphere within a few weeks...Someguy1221 05:59, 2 November 2007 (UTC)

Such air-water interaction is why you must account for vapor pressure. Note also that air dissolves in water, so "bubbles" do not form. You instead have a homogeneous mixture which is at minimum free energy below a critical temperature, so you'd have to simmer it to get the air out. SamuelRiv 06:36, 2 November 2007 (UTC) To clarify: air dissolves in water up at a rate decreasing as one approaches saturation. Bubbles do not form spontaneously in zero-g from air dissolved in water unless it is supersaturated or pressure or temperature change. SamuelRiv 06:57, 2 November 2007 (UTC) Clarification: vapor pressure is zero at chemical equilibrium, in which case I believe you're right-surface tension would probably be dominant. SamuelRiv 13:58, 2 November 2007 (UTC)

Air dissovles only weakly in water. If you watch the youtube link at the top, there are most definately bubbles in the water, in one case a very big stable one. Someguy1221 06:41, 2 November 2007 (UTC)

I think we already know the answer to this. Look at a Lava Lamp - these things work by heating up liquid wax (which repels water just like oil does) until it has the same density as water. What you see is roughly spherical balls of wax floating in the water (because they are trying to minimise their surface area in contact with the water). The lava lamp doesn't do a perfect job - there is a temperature gradient which causes things to move around slowly - but it's pretty clear that in zero g (where the density doesn't matter anymore) - it would be a lot like a kind of idealised lava lamp where there was no temperature gradient. If left long enough, it's pretty clear that it would stabilise into some number of large spheres of one liquid, embedded in the other. If there is still residual swirling and such - then maybe the two liquids would end up on opposite sides of the balloon with a flat interface between the two - because that would be an even more minimal area of contact between them. But a lot is going to depend on whatever residual motion there is when you first take the gravity away. SteveBaker 14:51, 2 November 2007 (UTC)

If the wax touched the sides of the lamp wouldn't that reduce the surface area interface between the water and the wax? If so why does the wax not stay in touch with the sides of the lamp? Dichotomous 15:39, 2 November 2007 (UTC)

Because as the wax spreads out to contact the sides, it also increases the contact area with the water. At the top and bottom of a classic lamp, the distance to the sides is small enough that touching the sides is lower-energy than forming a sphere, but in the middle, it isn't. --Carnildo 23:05, 2 November 2007 (UTC)

What's wrong with global warming?

Assuming there is no runaway global warming, what's so bad about the temperature increasing a few degrees, sea level rising a few meters, etc.? From what I've heard, it's generally easier for life to live in warmer than normal climates than cooler. In addition, most life could just move further from the equator. — Daniel 04:27, 2 November 2007 (UTC)

Have you read Effects of global warming? -- Rick Block (talk) 04:36, 2 November 2007 (UTC)

I think you drastically under-estimate the costs here.

Firstly, there are plenty of life forms that simply cannot "just move" - plants take hundreds or even thousands of years to spread into newly habitable areas - and since climate change is happening on a much faster scale, many species will go extinct in their traditional areas before they can spread into the areas that are newly suited to them. There are cold-weather species (the polar bear for example) who will have no place further north to move to! There are species (birds most notably) who have evolved specifically to fit the migration patterns they've been following for a million years. You can't just move them all a thousand miles further north and expect them to survive just because the temperatures are OK for them there! They may now have to migrate 1,000 miles further to get from their summer feeding grounds to their winter habitats - possibly through areas of much greater heat than they are used to (newly formed deserts perhaps) - and possibly over more ocean than before...they may not have the stamina to do that and their internal maps that are evolved into their brains - not learned will now be incorrect. This will have a knock-on effect on the animals that rely on those plants and birds. Heck, even humans are not able to relocate that easily. How are you going to move the entire city of Houston 1,000 miles north and 5 miles inland? I don't think you are thinking this through!

Worst still, you are also confusing "Climate" with "Weather". If the local weather changes by a few degrees, it's not a big deal - but if the entire planet's climate changes by that much, it has enormous effects - including the destabilising of established ocean currents and the consequent DRAMATIC effects on local weather patterns. Sea level "rising a few meters" doesn't sound like a lot - but when you think that this puts half a dozen US cities underwater and results in the total submersion of several countries. In most places in the world, the fertile areas where food crops can be grown and most plant and animal diversity can be found is the flatter areas close to the ocean. This means that a small increase in sea level can have a dramatic effect on the ability of a country to feed itself.

It's just not something that you can just brush off that easily. Plus you can't just "assume no runaway global warming" - that change of a few degrees is plenty enough to cause a few more degrees because of all sorts of positive feed-back effects. The small change at the beginning is the very thing that causes the 'runaway' problem - here in the real world, your "assumption" is simply not a valid one.

SteveBaker 14:44, 2 November 2007 (UTC)

Just a small note: Most plants and animals are resistant to moving to new climates. Others, such as wisteria and rats, are happy to move in and take over as much ground as they can. This isn't a contradiction to your points. In fact, it reinforces them. Who wants to live in an area where all the natural fawn and fauna died and was replaced by fast-spreading weeds and vermin? -- kainaw™ 17:19, 2 November 2007 (UTC)

Yes, indeed - no matter what, some species aren't going to make it - so biodiversity must suffer. That's not to say that there won't be any animals and plants left - it's just that there will be a lot less variation. There have been lots of arguments put up about this kind of thing. For example, one study claimed that the warmer temperatures and higher CO2 concentration would make crop plants grow faster (which is true). Sadly, another study found that weeds and other undesirable plants tended to benefit MORE from the temperature and CO2 increase than the crop plants do - so instead of having more productive farms, we'd likely have less productivity because of that. The whole system is so insanely complicated that all we really know is that there is a 100% chance of things changing - and in general, ecology doesn't benefit from abrupt change. The precise details of who this will kill and who it will help - and what wars it'll start (and which it may end) is almost impossible to determine. SteveBaker 20:32, 2 November 2007 (UTC)

How much does the temperature have to increase to make it so a species can no longer live in that area? According to the global warming page, the global temperature only increased by a little more than one degree in the last 140 years. I tend to ignore anything that will take more than a century to happen, as we will be far more technologically advanced by then and probably have a much easier time fighting it.

That's pretty funny! Where do you think technological change comes from? I'll tell you - it comes from people working on solving problems and doing so in ways that society will accept and pay for. Sitting back and doing nothing is not going to result in this technological change - passing laws, spending money and changing our consumer behaviors is what will cause that technological change. So we need better ways to heat homes, power cars and run factories - better ways to generate electricity - ways to avoid using fossil fuels. But for those things to happen - we actually have to start work on them! You can't say "well, future technology will take car of it" and then go on to not work on that future technology. Also, our ability to predict future technology is imperfect. People have been predicting flying cars, colonies on the Moon and Mars, artificial intelligence, all sorts of things on which we've made almost zero progress in the last 30 to 40 years. It's FAR from certain that some magical fix for global warming will come about - but for sure it won't if we take your attidude and sit on our backsides hoping for a wizard to appear. SteveBaker 17:18, 3 November 2007 (UTC)

If by destabilization of ocean currents you're referring to the shutdown of thermohaline circulation, I'd like to point out that this is, from what I can gather, an unlikely possibility in the next century. Not that it doesn't matter, just less so.

I'm not just assuming no runaway global warming. I just consider it another question for another time. A previous time, as you may remember. — Daniel 02:53, 3 November 2007 (UTC)

From your spelling, choice of words, and world outlook, I’m guessing you’re from the U.S., in which case you’re using Fahrenheit temperature measurements? The IPCC’s estimate is that the earth’s average near-surface temperature has risen about 1.33 degrees Fahrenheit in the past 100 years, not just 1 degree in the last 140 years. And our rate of greenhouse gas production has also risen greatly in the past 100 years, so the temperature will be rising a lot faster than that in the future. The IPCC predicts a rise of at least 2.0 degrees as a bare minimum in the next 100 years, in a presumably unrealistic best-case scenario involving successfully producing major cuts in greenhouse gasses, and predicts up to an 11.5 degree increase under scenarios involving less-successful attempts to cut greenhouse gasses. There will be a major rise in the earth’s average near-surface temperature in your lifetime (assuming you live an average lifespan). Sure, there are likely to be some technological advances that will make it somewhat easier to fight global warming in the future. But there will also be other effects which will make it harder to fight global warming in the future. Specifically, the population explosion is expected to continue exponentially or nearly so, so the number of people producing greenhouse gasses will be rapidly increasing. And China and other countries will be becoming increasingly industrialized, which means the greenhouse gasses produced per person will also be increasing. MrRedact 06:41, 3 November 2007 (UTC)

If you take a very long-term view, and look at all species on the planet, then global warming isn't so bad from that point of view. Yes, some species will die out, like polar bears, but others will evolve to take advantage of the new climate. Over millions of years, life would do just fine. Any climate change will have winners and losers, just as the dinosaurs lost out 65 million years ago and mammals won. However, if we look at the short term consequences to humans, they can be rather dire, as listed above. StuRat 14:40, 3 November 2007 (UTC)

I read somewhere that 65 million years ago it was much warmer (perhaps 10 degrees warmer) than it is now. The range temperatures in the distant past seems to be much wider than the range humans have experienced in the past 1000 years or so - those that are typically covered by the those hockey-stick graphs you see. Astronaut 03:19, 4 November 2007 (UTC)

Ah... here it is: Geologic temperature record. Astronaut 03:21, 4 November 2007 (UTC)

Catapults

Here is a question.

Why don't they use catapults to launch planes at Airports like they do on Aircraft Carriers? 202.168.50.40 04:37, 2 November 2007 (UTC)

The acceleration is very high, injuring the ontents of the plane, and the planes too big and heavy compared to a fighter. Graeme Bartlett 04:56, 2 November 2007 (UTC)

Think of it as a question of scale as well. Imagine firing a marble out of a handheld catapult. Now imagine the catapult needed to fire the ball of glass that represented a jumbo jet. Lanfear's Bane | t 13:07, 2 November 2007 (UTC)

Also what would be the point? A runway is cheaper, easier to maintain, doesn't require power, airplanes can launch from it one after the other faster than being loaded on to a catapult one after the other, and there's enough room on planet earth to put one on. Carriers use catapults because there isn't enough room for a full runway. Catapults make it so that the plane doesn't consume as much fuel though, but the other advantages outweigh that. 64.236.121.129 13:35, 2 November 2007 (UTC)

There are a lot of simpler ways to save energy at airports that are not commonly used. In some airports in Holland they have these big tractor things that tow aircraft around once they are landed and until they are ready for take-off - these things can tow the plane all the way out to the side of the runway - and when an aircraft lands, there is one of these machines sitting there waiting to tow them back to the terminal. Since it's much more efficient to use wheels to power the movement of the plane than those big fans, it saves fuel AND makes the whole airport much quieter. It's ridiculous that those things are not at every major airport. SteveBaker 14:25, 2 November 2007 (UTC)

Also, fighter pilots are highly trained, and the plane isn't meant to be comfy. They probably don't sip coffee and read books during the flight. Nobody would like flying if passenger jets rode like fighter jets. Friday (talk) 14:43, 2 November 2007 (UTC)

• I think it's not a bad idea. The plane only ever needs fast acceleration at takeoff, so it makes sense to me to give that ability to a ground-based system that could presumably do it more efficiently. It's false to say the acceleration is too high: the acceleration to get from zero to takeoff speed in a given distance is the same whether it's powered by jets or by a catapult. --Sean 18:10, 2 November 2007 (UTC)

Using the example from the question, there is not the same "given distance". DMacks 18:18, 2 November 2007 (UTC)

I initialy thought the idea was totally unworkable, but that's because of the "like they do on Aircraft Carriers" bit. In fact, The proper system would be more like the way sailplanes are launched from the ground in some places: a very long winched towline with constant acceleration. This gets the plane up to liftoff speed without using as much fuel. Unfortunately, it's unsafe, because the ordinary takeoff run is also a validation that the engines are working well enough to keep the aircraft climbing. -Arch dude 19:46, 2 November 2007 (UTC)

How long does it take for a sudden cease of gravity to be felt?

Imagine that the Sun suddenly vanished. Would the sudden cease of solar gravity be felt on Earth before the 8 minutes and 19 seconds that the last beam of sunlight would take to reach the Earth, or would our planet be plunged into darkness before we felt the Earth free itself from its solar orbit? In other words, which of these two phenomena would happen first?

And... if the gravity loss manifested itself before the last beam of sunshine reached the Earth, would that mean the effects of gravity move faster than light? -- Danilot 08:26, 2 November 2007 (UTC)

Changes in a gravitational field move exactly as fast as light. Someguy1221 08:38, 2 November 2007 (UTC)

Agree I think it would happen at the same time, the earth would follow the same curve in space (like a water ripple before it flattens) for about 8 minutes and 19 seconds after the sun disappeared we would also receive the last of the light of the now vanished Sun for the same amount of time, after that the Earth would head out in a straight path getting very cold very quickly, the sun will be missed :) ▪◦▪≡ЅiREX≡^Talk 08:55, 2 November 2007 (UTC)

Conveniently, we have an article on the speed of gravity. General Relativity anticipates a speed of gravity equal to the speed of light. So far, the experimental results appear to bear this out, but it's a very difficult experiment to do. The earliest direct test was only published in 2003, and even that result has been controversial. TenOfAllTrades(talk) 13:02, 2 November 2007 (UTC)

The sun can't just disappear. That would violate local conservation of energy, which is a necessary consequence of general relativity (that is, general relativity can't work at all if energy isn't conserved). So you have to imagine the sun is whisked away somehow. With that caveat, the answers so far are correct.

The data from PSR 1913+16 strongly confirms the hypothesis that the speed of gravity is c. The article is correct when it says the interpretation of the data is model-dependent, but that's equally true of every scientific measurement. The work of Kopeikin and Fomalont looks wrong to me; from reading the introduction to their paper it looks like they've made the same mistake as Tom Van Flandern, and Steve Carlip's response seems to bear that out. -- BenRG 13:40, 2 November 2007 (UTC)

Subquestion

What would be our sensation of the change in gravity/acceleration if the Sun magically disappeared? Presumably not much, since the Sun doesn't even cause tides, but I'm not too smart with this kind of thing. Thanks. --Sean 18:17, 2 November 2007 (UTC)

Actually, the sun does cause tides - just not as big as the ones the moon causes. But to answer your question: No, we wouldn't notice (much). We don't feel the full effects of the sun's gravity (which is HUGE) because the earth is in free-fall, from the point of view of the sun, we are just like an astronaut inside a spacecraft in orbit around the earth - except we're orbiting the sun instead. The thing is that when you are at the exact right speed and distance from a star or a planet to be orbiting it, you don't feel any gravitational effect.

A convenient way to look at that is that the 'centrifugal force' due to the earth moving in a big circle and the gravitational force from the sun exactly cancel out along the path of the earth's orbit. But if you are a bit closer or a bit further away from that line, and orbiting at that same speed - then either gravity or centrifugal force wins. Because the earth isn't a teeny-tiny dot (like a spaceship), the side of the earth that's nearest to the sun feels slightly more gravitational forces compared to the other side - so the gravity and centrifugal forces don't quite balance. The force of the suns gravity is only somewhat cancelled out by centrifugal force on the side nearest to the sun - and the centrifugal force just slightly outweighs gravity on the side furthest away. Hence the oceans (and everything else) are pulled slightly towards the sun at midday - and pushed slightly outwards from the sun at midnight. But the effect is rather small - and the effect of the moon's gravity easily overwhelms that effect. However, it is notable that the tides are slightly more pronounced when the moon and the sun are in about the same place in the sky. Our article on tides explains this nicely and uses all the right words!

So, if the Sun suddenly vanished, we'd notice that our tides were slightly less variable than usual...but that's about it. SteveBaker 20:24, 2 November 2007 (UTC)

OK, thanks. Presumably the tides would become much less variable in short order.  :) --Sean 20:49, 2 November 2007 (UTC)

Man standing on Montego Bay

Maybe more noticeable then that, the lost of the Angular momentum on both the Moon and the Earth may cause a slingshot effect on their lost path (one body the closest to the sun at the time wound lose the bend curve path and head out in a straight path before the other body still on curve which would cause a tug-a-war at the same time), but I'm not sure on that.▪◦▪≡ЅiREX≡^Talk 22:11, 2 November 2007 (UTC)

Is there an acid so strong that it behaves like acid is usually depicted in movies/tv?

Like how you see some crooks trying to break into bank, so they spray the side of the wall with acid from a pump, and the acid eats through the wall in seconds. Is there an acid that strong that exists in the real world? Lets assume the wall is made of concrete or wood. 64.236.121.129 13:50, 2 November 2007 (UTC)

I think it's possible (I've heard the atmosphere of Venus, having sulphuric acid clouds meaning that anything approaching Venus, if it didn't burn or melt, would corrode before it hit the planet itself), but you'd also have to figure out how on Earth you'd store that acid, and that the concentration is likely to be so high, the acidic clouds would be likely to kill the person spraying the acid... x42bn6 Talk Mess 14:18, 2 November 2007 (UTC)

See acid for details. The Bronsted-Lowry definition for an acid is a proton donor. Basically, it causes what it touches to be oxidized, or lose electrons. A metal corrodes in acid because it gets oxidized - it dissolves into the acid as it loses electrons and those electrons are taken up by the acid to form hydrogen gas. In the case of concrete, which is made primarily of cement and water, metal oxides are the primary ingredient. In this case, the metal is already ionized, but the oxygen can give up its extra electrons and form water with the free hydrogen of the acid. So corrosion of concrete is also oxidation-reduction, and the rate reactions depend primarily on the pH of the acid, which depends on its concentration or, perhaps more generally, its Hammett acidity function. So if the pH is very high, the rate of oxidation-reduction is very high, and the material corrodes quickly. I'm not sure how the reaction for wood (cellulose) works. SamuelRiv 14:28, 2 November 2007 (UTC)

Whoa there…acidity as a proton donor means it reacts with a base to form a bond, not to abstract the electrons from the base. Other things may indeed happen, but I don't think B–L acid/base strength and redox-potential aren't as directly related as you're suggesting. I'd also point out that "pH is very high" sounds like a very weak base. DMacks 14:52, 2 November 2007 (UTC)

I defer to you on this, as I'm not a chemist. Reaction rate is a good article that discusses the complexity of calculating reaction rates, and although there is a dependence on the concentration of the reactants (the acid and the concrete), it does not account for the dissolution of concrete necessary for that to work. On double-checking my books, they specifically note that one cannot infer rates of reaction through the equations I used. And yes, pH must be very low, hopefully negative, for a particularly strong acid. That being said, since an answer still hasn't been given, the math does suggest that the rate of reaction can be increased by increasing the concentration (or pH) of the acid, the concentration of the dissociated reactant (so if we can dissociate the metal oxides in concrete quickly and without a lot of solvent), and the number of free electrons per molecule of the other reactant. SamuelRiv 06:23, 3 November 2007 (UTC)

One problem is the rate of the reaction, acids usually do not dissolve at anywhere near that rate. A very high power would be required. It may be possible to do it with extremely high temperatures that could melt the metal at the same time as dissolving it. For super acids you could try trihydrogen cation or helium hydride. These would take on the form of a plasma though, and not be a simple liquid. Graeme Bartlett 23:37, 2 November 2007 (UTC)

Superacid maybe? The article suggests that Fluoroantimonic acid is very strong but I am not sure that translates Alien strength or reaction rate. --DHeyward 03:44, 3 November 2007 (UTC)

endothermic vs. exothermic

I know exothermic means a system is releasing heat, and endothermic means a system is recieving heat, but if a system was cool to the touch would it be and endothermic or exothermic reaction? It seems like if it was exothermic it would be cool because it was releasing heat, but could also warm because it's giving off heat? Anyone care to help?--MKnight9989 14:08, 2 November 2007 (UTC)

Exothermic is roughly equivalent to "energy exiting the system" or "release of energy in the form of heat" - which makes things hotter. Endothermic is "absorption of heat" which makes things colder (because the amount of heat has gone down). If a system is cool to the touch, it means nothing, though - but if the temperature goes down, I'm guessing it's an endothermic reaction. (Note: It's been a while since I studied Chemistry) x42bn6 Talk Mess 14:14, 2 November 2007 (UTC)

Yeah I guess that makes sense. Thanks mate.--MKnight9989 14:22, 2 November 2007 (UTC)

I'd wait for a better explanation, though. Our article on exothermic, for example, looks fairly woeful... x42bn6 Talk Mess 14:24, 2 November 2007 (UTC)

You don't really specify what is the reaction. Do you mean there is a reaction within the system, or did you want to know if the very act of touching something that felt cold was exothermic/endothermic? If there was a separate reaction and it was cool to the touch, it means that the system was colder than the surrounding environment; heat was taken from the environment (air, container, etc) to fuel the reaction. This heat was transformed, and the total amount of heat in the system is less than what you started with. That means the reaction (that I assume was taking place in the system) was endothermic. Just touching the container isn't really a reaction, just a heat transfer; the total amount of heat is the same. I don't think you could classify it as endothermic/exothermic. But I'll think about it --Bennybp 14:27, 2 November 2007 (UTC)

It was a potassium sulfate/water reaction. --MKnight9989 14:30, 2 November 2007 (UTC)

atomic size constraints

What keeps an atom from being stable or even formed beyond a certain number of nucleons? Are the forces that hold the atom together not strong enough due to excessive mass or to excessive distance or both? Dichotomous 15:16, 2 November 2007 (UTC)

I believe it's because the strong force (actually the residual strong force) pulls the nucleons together, while the electrostatic repulsion that the protons have for each other pushes them apart. The strong force only works at short distances, so when the nucleus gets too big, the like-charge repulsion causes instability and fission. You might like to read Island of stability. --Sean 18:22, 2 November 2007 (UTC)

Spherical wheels on cars?

Think it will ever happen? I can think of a few advantages they might have. Greater manuverability for one, no need to turn the wheels, simply change the direction of their spin. 64.236.121.129 15:18, 2 November 2007 (UTC)

The contact patch would be much smaller than with a tire, right? That could be a problem. Also you'd need some pretty impressive mechanical magic to give the sphere driving force while still allowing the full range of motion. Friday (talk) 15:23, 2 November 2007 (UTC)

Indeed--can you still drive the sphere effectively after it gets wet in the rain or snow? (Presumably it is driven by rollers in contact with the sphere somewhere near its top surface...?) Is there a good way to cushion the ride? Will you dent or chip the sphere every time you run over a rock? Do you lose space from the passenger, engine, or storage compartments when you have to fit in the larger volume of the wheel along with whatever motors are driving it? TenOfAllTrades(talk) 15:47, 2 November 2007 (UTC)

You're doing it wrong! Lanfear's Bane | t 16:22, 2 November 2007 (UTC)

Those Outspan cars were really Mini's - we have a photo of one of them in the article. SteveBaker 17:29, 2 November 2007 (UTC)

I believe it would also be a lot more work to change the direction of spin than to just turn the wheels, though I'm not certain of the underlying physics. Given this, while you'd certainly end up with a better turning radius, I don't know that you'd have across-the-board better maneuverability. The points above are also well-said in this regard -- one upper limit to maneuverability is the point at which the tires can't overcome angular forces and start to slip. The reduced contact patch of spherical tires would hasten this slipping. — Lomn 16:26, 2 November 2007 (UTC)

Well the contact area, traction, and the possibility of chipping would have more to do with the material used for the wheel, rather than the shape. A perfect sphere doesn't have much contact with the ground true, but neither does a torus. A tire inflated too much doesn't have much contact with the ground, it needs to be deflated so it sags a bit, increasing the contact area. If you put a beach ball on a street, you can increase its contact area with the ground simply by pushing on top of it. 64.236.121.129 16:33, 2 November 2007 (UTC)

Roads are pretty much flat - you don't need a sphere - you need a cylinder (which is what we have). If you need more grip, you lengthen the cylinder (wider tyres) or increase the contact patch (by deflating them a little) or use a more appropriate tread pattern (eg racing slicks, snow tyres). A spherical tyre would have less contact area than a cylindrical tyre (for a similar size) no matter what. SteveBaker 17:29, 2 November 2007 (UTC)

Tread is a good point here. Would be pretty hard to have a pattern that worked in "every direction" around the sphere. DMacks 17:42, 2 November 2007 (UTC)

File:Top fuel eg PD EN.jpg

You say, "wider tires do NOT increase traction with the ground". Experts disagree.

I must emphasize, wider tires do NOT increase traction with the ground. 64.236.121.129 18:40, 2 November 2007 (UTC)

I remember learning some theory about friction in which this was true. But I also remember learning that in real life, it does increase traction. I don't remember specific details, but why else would people use wider tires when they want better traction? Friday (talk) 19:02, 2 November 2007 (UTC)

The quick'n'dirty explanation of why it doesn't matter in theory is that friction is proportional to force, not contact area (if you double the area, you half the amount of force per unit area but that still means same total frictional force). DMacks 19:22, 2 November 2007 (UTC)

64.236.121.129 is not correct; wider tires do increase traction by dint of a larger contact patch as noted and linked above. As for the idea of spherical tires, in addition to the tractive disadvantages, transmitting drive to spherical "wheels", and braking them, would be a hideously complex and likely quite inefficient exercise. The disc-shaped wheel and quasitoroidal tire will be with us for the foreseeable future. --Scheinwerfermann 19:21, 2 November 2007 (UTC)

The "law" of friction that they teach kids in school and junior physicists (ie Frictional force is proportional to the normal-force multiplied by the coefficient of friction and that the contact area is irrelevent) is NOT TRUE! It's not a law of nature - it's not even a reasonable approximation - it's a rule of thumb that works for some materials under some circumstances. Friction is vastly more complex than that and there is no simple rule. So - it is undoubtedly true that car tyres gain more frictional force if they have a larger contact patch. If you doubt that - and you happen to be in Texas, I'll take you for a hair-raising ride in my MINI Cooper'S with racing slicks and with regular tyres - when you've changed your pants and cleaned up a bit - you'll admit that I'm right! Have you seen the width of the rear tyres on a Formula 1 racecar? Why would they make them so wide if the area of the contact patch didn't matter? Thin skinny tyres would work just as well...but they don't...and there is a reason for that! So - please ignore what your high school teacher said - it's not true. SteveBaker 20:06, 2 November 2007 (UTC)

To answer Friday, they use wider tires because they last longer. That's critical if you are racing, and you want to minimize your time at the pit stop. As for your points Steve, why would that teach that if it wasn't true? Last I recall, perpetuating myths isn't appropriate in a place of learning. It's in the textbooks, and the teachers teach it. I'm just supposed to take your word for it against theirs? 64.236.121.129 20:21, 2 November 2007 (UTC)

No - that's nonsense - I have a set of racing slicks for my car - they are very wide and I can tell you with absolute certainty that I don't own them for their long tread life!! The reason some people still teach this load of nonsense is because it's in the text books and the curriculum. Read the best undergraduate physics textbooks on the planet - Feynman's Lectures on Physics - he goes to a lot of trouble to un-teach you this bad piece of misinformation. Read Friction#Classical_approximation - especially the last paragraph: [This] approximation is fundamentally an empirical construction. It is a rule of thumb describing the approximate outcome of an extremely complicated physical interaction. - in other words, it's not true. SteveBaker 20:42, 2 November 2007 (UTC)

So you think "a half truth is a whole lie"? I'd say that's, well, half-true. --Trovatore 21:06, 2 November 2007 (UTC)

What?! Tire longevity has a lot to do with the material of the tire. As a general rule, stickier tires wear out faster. All kinds of things that people are taught are simplified models, accurate only in certain circumstances. I remember being taught that atoms are little balls with other little balls orbiting them- like tiny little star systems. Once you're past junior high school, this model is way too simplistic. Friday (talk) 20:26, 2 November 2007 (UTC)

• While it's wise to be cautious about what a textbook says, it's even wiser to be cautious about what some guy on the Internet says. I think it's fair for .129 to request WP:Reliable Sources for SteveBaker's debunking. --Sean 20:38, 2 November 2007 (UTC)

It's absolutely reasonable to request that...right up to the point where I gave you exactly that and you ignored me! Which part of Read the best undergraduate physics textbooks on the planet - Feynman's Lectures on Physics didn't you understand? SteveBaker 20:58, 2 November 2007 (UTC)

• You're being rude. You'll note my post preceded yours. --Sean 01:58, 3 November 2007 (UTC)

My apologies - in fact we differed by just a couple of minutes - my first effort got bounced as an edit conflict. However, please check Feynman - volume 1 section 12-3. SteveBaker 16:55, 3 November 2007 (UTC)

Casual observation reveals that a great many cars use wider tires for better traction. If this isn't legitimately justifable, we have to assume incompetence or conspiracy on the part of the engineers who chose those tires. Friday (talk) 20:42, 2 November 2007 (UTC)

Leaving aside the incompleteness of the 'friction-force-is-proportional-to-μ-and-normal-force-only' model, a move to 'wheels' with smaller contact patches (and larger forces applied per unit area) would increase substantially wear and tear on the road itself. TenOfAllTrades(talk) 20:32, 2 November 2007 (UTC)

I feel a need to explain why the 'rule of thumb' for frictional force is wrong. As our article on Friction explains, that 'rule' is based on the following assumption: That only a small percentage of the atoms on one surface are in contact with the other surface. When force is applied to push the two surfaces together, more atoms come into contact and the frictional forces increase. The reason the rule of thumb says that the contact area doesn't matter is that the number of atoms that come into close contact depends on the pressure applied to the two surfaces. Since (in this case) pressure is force divided by area, the pressure between the two surfaces decreases as the contact area goes up. So whilst more atoms are available to come into close contact, the pressure forcing them together goes down in the same proportion - to frictional force is independent of the contact area.

However, there was an assumption there - that the percentage of atoms in contact was small compared to the total number of exposed atoms on the two surfaces. For stiff things like steel plates that are microscopically rough, that's a reasonable assumption and the rule of thumb works quite well. However, rubber is very soft and compliant and with even a moderate force applied to it, it'll deform until a VAST proportion of the atoms are in contact with the surface below. Now, varying the pressure forcing the tyre onto the road isn't making a dramatic difference to the percentage of atoms in contact - so increasing the area of the contact patch can indeed make a huge increase to the amount of grip you get.

Surfaces that are lubricated suffer from similarly violating this "law" because the layer of oily lubricant can prevent atoms of one surface getting close to those of the other even if the pressure on them increases. Other surface - like Ice - melt when you apply pressure to them - so they lubricate themselves - and the more pressure you apply, the more lubricant gets between the two surface.

SteveBaker 20:55, 2 November 2007 (UTC)

I find it unlikely that the width of the wheel determines how much traction it has. It merely depends on the surfaces of the two contacting surfaces. For example, a bicycle wheel can have excellent traction despite it being very narrow. A train has a very narrow contact surface between its wheels and the rail, but has adequate traction. Casual observation of race cars using wide tires and thus assuming they use them because of greater traction is a false assumption. Facts and truth come before logic or common sense. Common sense would indicate that .999... doesn't equal 1, but it does. Malamockq 22:48, 2 November 2007 (UTC)

Did you read the above? There's some pretty good explanations there that go beyond mere speculation. They do use wide tires for better traction, but you're right- the mere existence of wide tires could be explained other ways, too. Friday (talk) 22:53, 2 November 2007 (UTC)

Then by insinuation we should say that the wider the wheel is, the more traction it should have. So if you have a wheel 1 mile wide, it should have more traction than a wheel 5 inches wide (assuming the surface of the tire is the same)? You have to take your assertion, then exaggerate it and determine if it makes a meaningful difference. Malamockq 23:01, 2 November 2007 (UTC)

Yes! Wider wheels mean more friction. There will come a point where so little of the wheel is in fact pressed into the minute bumps in the road surface that increasing the area won't help anymore - but for wheels up to (say) a couple of feet wide, the contact area is very important indeed! I'm not saying that the amount of friction is proportional to the contact area or the square of the contact area...or any other particular rule. I'm saying that friction is vastly too complex for that simple rule of thumb to be true. There are some materials in some sorts of contact where the rule is a pretty good approximation - there are other cases where it's not even close. Car tyres are in the latter category. SteveBaker 16:55, 3 November 2007 (UTC)

I'm not following you. But, SteveBaker gives a good explanation above about why with steel, size of the contact patch isn't a big factor, whereas with things like rubber, it is. Obviously there would be serious practical problems with a wheel a mile wide.  :) Friday (talk) 23:05, 2 November 2007 (UTC)

Funnily enough I was pondering the same question the other day after thinking about a computer mouse (where a ball moves two rollers, one vertical and one horizontal) and wondering whether anybody had tried reversing the principle and using two powered rollers to move a sphere in order to move an object. This wouldn't be very pratical for things like cars but I thought that things like robotic vacuum cleaners might work very well using this principle although it would probably need three or four spheres to keep the thing off the floor and going in the right direction. GaryReggae 23:19, 2 November 2007 (UTC)

Um, Malamockq, I'm not quite following you, either. You say "Facts and truth come before logic or common sense", and I mostly agree with you, but then your only evidence for why the width of a tire is irrelevant is that you "find it unlikely" that it makes a difference.

Steel-wheeled trains have adequate traction, but only barely. Very small slopes, or small amounts of water, snow, ice, or wet leaves, can leave a train spinning its wheels and unable to move. Most trains carry sand which they can sprinkle on the rails ahead of their wheels to increase traction when they need to.

Steel wheels and rails are used on trains because they have excellent rolling resistance (low), and excellent lifetime (high). But the traction's only so-so, though of course it helps that they have huge amounts of normal force (i.e. weight) to throw into the µN equation. —Steve Summit (talk) 23:46, 2 November 2007 (UTC)

No, my reason for believing that width doesn't make a difference, is that they teach that fact in physics classes. The train example may have been weak, but any lack of traction is due to the surfaces of the train wheel and the rail. It has nothing to do with the width. Malamockq 01:57, 3 November 2007 (UTC)

Yes, they teach that to kids in physics class, along with a bunch of other oversimplifications. This is all well explained above. Did you see the explanation that with some materials, size of contact patch doesn't matter much, whereas with some other materials, it does? Yes, bicycles have skinny little tires. But check out a powerful motorcycle sometime- much wider. Why? Because it needs way more traction to put that kind of power down on the road. Friday (talk) 15:59, 3 November 2007 (UTC)

There are plenty of things like this that are taught in schools as simplifications of reality. Heck we still teach Newtonian mechanics - when we know full well that they are flat out WRONG. Einstein proved Newton was wrong almost 100 years ago. So the fact that we teach kids something doesn't make it true. We teach simple approximations.

Anyway, I'm now sitting in front of the book I referred you to (Feynman's Lectures on Physics, volume 1, section 12-3). Just below the F=uN equation, Feynman (who was a physics nobel prize winner) says:

"Although this coefficient is not exactly constant, the formula is a good empirical rule for judging approximately the amount of force that will be needed in certain practical or engineering circumstances. If the normal force or the speed of motion gets too big, the law fails because of the excessive heat generated. It is important to realize that each of these empirical laws has its limitations, beyond which it does not really work."

To get the full story, you need to read on for a couple more pages - but I think you can tell from my short quote that Feynman is most certainly not saying that this is an utterly fundamental law. Car tyres most certainly provide more grip when they are a foot wide than when they are four inches wide - look at any high performance sports car and notice the fat tyres...there is a reason for that. You wouldn't add weight (PARTICULARLY 'unsprung weight') to a performance car unless it bought you some major benefits in terms of going faster or accellerating harder. It's not just tyres either. Why do you think people put bigger disk brakes on cars to make them stop better? SteveBaker 16:55, 3 November 2007 (UTC)

It would sure make parallel parking a lot easier, that's for sure. :) shoy (^words _words) 03:46, 3 November 2007 (UTC)

Check out Rolling resistance. Acceptable 04:26, 3 November 2007 (UTC)

Where did the energy go

I was told today that although most macro structures are held in shape by the forces that govern them as space time expands, and as a result do not expand, photons are stretched by space-time, and as a result have an increasing wavelength, assuming that c is a constant through all space-time (a reasonable assumption I presumed) therefore a decreasing frequency, and so a photon hanging about for a substantial amount of time would lose energy due to E = hf. Where does the energy go? ΦΙΛ Κ 18:58, 2 November 2007 (UTC)

Gravitation potential energy. It is similar to the red shift in a photon trvaelling up hill in a gravitational field. Graeme Bartlett 23:39, 2 November 2007 (UTC)

Actually, no. The correct answer is "General relativity is a bitch that apparently doesn't obey Conservation of Energy". It's possible that there's some related quantity that's conserved, but scientists are yet to come up with anything that seems to work yet. Confusing Manifestation 08:14, 3 November 2007 (UTC)

Conservation of energy is a fundamental consequence of the symmetries of spacetime. I should posit an answer here - I didn't before because I'm not sure if this is correct, but the answers given so far are misleading. I believe that a photon would ride local expansion like a wave, and thus would not lose energy relative to an outside observer because velocity would effectively increase (because spacetime has been locally changed). However, for the uniform expansion of the universe, I'm not sure if this model fits: certainly locally the change in curvature accounts for any energy loss - maybe that's all you need. SamuelRiv 07:04, 4 November 2007 (UTC)

I found this site useful in describing (and attempting to solve) the problem embodied in the question: [4]. In summary, classical conservation of mass-energy doesn't hold, but it is possible to define many quantities which are conserved. However, there's no quantity which always works and everyone likes. 58.96.70.254 12:40, 4 November 2007 (UTC)

Antonym: Congenital?

Very quick question: what is the antonym for congenital, in the context of diseases (i.e. inherited diseases versus infectious or non-infectious diseases acquired throughout life)?

209.51.73.60 23:57, 2 November 2007 (UTC)

Acquired. Someguy1221 00:27, 3 November 2007 (UTC)

Contracted. --DHeyward 04:09, 3 November 2007 (UTC)

November 3

How to disappear completely

Teleportation: "Until recently, scientists had been able to transport only light or single atoms over short distances (millimeters)."  !?! In teleportation our original copies don't have to die after all: there will be no pesky original copies of us to trouble over. And here I was worrying about a convenient future that might involve the existential murder trial for killing myself just to make it to Sydney in the blink of an eye. Joking aside, how does any sort of teleportation of matter not tear to shreds the Heisenberg uncertainty principle? —Preceding unsigned comment added by Sappysap (talk • contribs) 01:39, 3 November 2007 (UTC)

There's something called quantum teleportation that's specifically about getting around the uncertainty principle in situations like this. But that's kind of a misnomer, since you can't use it to help you teleport something until you've solved all the problems attendant on classical teleportation, like the whole determining-the-complete-structure-of-the-object-and-then-reassembling-it-on-the-other-side part. I see no reason to believe that this kind of technology will ever exist. -- BenRG 02:23, 3 November 2007 (UTC)

I love that song.--The Fat Man Who Never Came Back 02:28, 3 November 2007 (UTC)

• The movie The Prestige addresses this existential clone murder in fascinating fashion. --Sean 19:15, 3 November 2007 (UTC)

Artery defurring

Is it possible over a period of time to defurr your arteries by eating zero fat? —Preceding unsigned comment added by 88.109.219.79 (talk) 01:51, 3 November 2007 (UTC)

Defurr? Dureo 08:44, 3 November 2007 (UTC)

The technical name for "furring" of the arteries, also known colloquially as "hardening" of the arteries, is atherosclerosis.

The research I am aware of pertaining to your question is the Lifestyle Heart Trial of Dr. Dean Ornish. His research was widely popularized in his best-selling book Dr. Dean Ornish's Program for Reversing Heart Disease.

We can’t give any advice pertaining to using diet and lifestyle to prevent or treat atherosclerosis, so consult with your doctor as to whether a change in diet and lifestyle may be appropriate for you. You may also find it valuable to consult with a registered dietitian. MrRedact 17:30, 3 November 2007 (UTC)

Dissociation

What causes it? — Daniel 03:39, 3 November 2007 (UTC)

I'm assuming it's because the products will be at a more favorable thermodynamic state than the reactants, but I could be wrong. Specifically what substance(s) are you wondering about? shoy (^words _words) 03:52, 3 November 2007 (UTC)

Thermodynamically, you're simply looking for the state with the lowest free energy, and a substance that dissociates will have a lower free energy of its separated components than if those components were together. This depends on the nature of the solvent, and I'm gonna be careful here from the mistake I made before and say that the textbook statistical mechanics analysis of solutions won't necessarily apply if tthe solute dissociates. From chemistry class though, I remember that conceptually when a compound dissolves in water, it will dissociate if the pull of the polarized water molecules is greater than that binding polarized components of the compound. So in an ionic compound like NaCl, the Na+ ions are attracted to the O-2 side of the water molecules while the Cl- ions are attracted to the H+ side of the water molecules, and this attraction breaks apart the bonds of the salt crystal. SamuelRiv 06:34, 3 November 2007 (UTC)

DOn't forget Entropy! Dissociating anything results in two or more molecules/ions from one --> more disorder --

This isn't strictly true. While dissociation might seem to imply the creation of more molecules, one needs to be careful here. For example, the dissociation of water is often represented at H₂O <-> H⁺ + OH^-. But what is really going on is 2 H₂O <-> H₃O⁺ + OH^-, so no new molecule is actually created. shoy (^words _words) 18:03, 3 November 2007 (UTC)

Entropy factors into the rate equations. That's why rate is proportional to reactant concentration raised to the power of the number of molecules needed per unit of product. SamuelRiv 14:36, 3 November 2007 (UTC)

use of superbugs in oil slicks

hello i would like to know about the process involved in use of superbugs in oil slicks. ie how exactly the superbugs help in getting rid of oil slicks & the pros & cons of it.i would also like to know a few strain names of the superbugs as examples. i'm aware of the diamond vs. chakraborty case. i'm asking this ques as r dear teacher hasnt taught this topic properly & cudnt find enough info to write a 10 mk. ans in exams !!! so pl. help me out. 220.227.116.220 07:05, 3 November 2007 (UTC)

I believe the Bioremediation, Biodegradation, Microbial_biodegradation, and Biotransformation articles will help you. Dureo 08:42, 3 November 2007 (UTC)

The basic concept is that they would digest the toxic components into waste products which aren't toxic. StuRat 14:20, 3 November 2007 (UTC)

The night sky, stars, and galaxies

Hi, I have sort of a random question just out of curiosity. It may be a dumb question but I have never heard it explained. When one simply looks up into the night sky and sees all of the different stars, are they individual stars like our Sun? Or are some of them that we observe stars and others actually galaxies? And if they are mostly individual stars, are they all located within our own Milky Way galaxy? Again I apologize if this seems elementary, but I looked in both the Star, Galaxy, and Night Sky articles and was not quite sure of what the answer is. Thanks in advance. Zenislev 08:19, 3 November 2007 (UTC)

Some are individual like our sun, and some are further away and appear individual, but are actually galaxies and star clusters, the Universe article may help also. Dureo 08:29, 3 November 2007 (UTC)

Most are stars as in the sun, but actually most are much brighter than our sun. Few Galaxies are visible to the eye, and they appear as fuzzy patches. Quite a few stars are double stars. LMC. Graeme Bartlett 08:36, 3 November 2007 (UTC)

You also see the occasional planet.--Shantavira|^{feed me} 09:00, 3 November 2007 (UTC)

I've heard a number quoted a lot that approximately 2/3 of the stars that can be seen in the night sky are actually binary (or higher) stars --Shniken1 10:14, 3 November 2007 (UTC)

Besides stars, clusters, and planets, there's one more possibility: while a comet usually has a tail or at least a fuzzy appearance, it can occasionally look like a star to the naked eye. I saw one like that a few days ago.

The answer to "And if they are mostly individual stars, are they all located within our own Milky Way galaxy?" is normally yes. The only way that a star located outside the Milky Way could be bright enough to see would be if it was going supernova, which happens very rarely indeed. --Anonymous, 10:37 UTC, November 3.

The most distant object visible with the naked eye (and only in the most favourable conditions) is the Triangulum Galaxy. Gandalf61 11:23, 3 November 2007 (UTC)

What's even more interesting is that if there are trillions upon trillions of stars in the universe, why is the sky is so dark at night? -- MacAddct  1984 ^{(talk &#149; contribs)} 13:55, 3 November 2007 (UTC)

Two reasons:

• There aren't an infinite number of stars.

• The light from distant stars is absorbed by dust or spread out so thinly that not even one photon hits our eyes or telescopes.

The sky does appear much brighter through a good telescope, however. StuRat 14:17, 3 November 2007 (UTC)

Well, yes - but that's kinda meaningless in this context. It's because you're gathering light through a large aperture and squishing it down into a little eyepiece - it's not because you are somehow seeing more photons per steradian of sky or anything of that sort. The deal is that the amount of light from a distant source decreases as the square of the distance - but the number of stars in a spherical volume of space averages out to the cube of the radius. So, were it not for the interstellar dust clouds, the amount of light coming from stars at greater and greater ranges would be greater and greater and the night sky would be insanely bright instead of mostly black (and we'd be cooked by the infrared, hard X-rays, etc. However, the amount of dust obscuring the light from those stars is also proportional to the distance - but the rate of light absorbtion is more than linear. eg If one lightyear of dust absorbed half the light from a star, then the next light year of dust would absorb half of what came through the first lightyear of dust, and so on. Hence the amount of light you see through some amount of dust is an exponential thing. When you work it all out, it's clear that even if there were infinite numbers of stars, the amount of light we'd see would be what we see now. SteveBaker 16:16, 3 November 2007 (UTC)

Those are not the reasons the sky is dark at night. The reasons are (as the Olbers' paradox article says) cosmological redshift and the finite age of the universe. Absorption by dust has no net effect because all of the absorbed energy is reradiated. -- BenRG 16:44, 3 November 2007 (UTC)

It's also possible to see satellites and (especially) the International Space Station - but they move pretty fast so you can generally tell that they aren't stars. SteveBaker 16:16, 3 November 2007 (UTC)

Yes, and the observable universe is only about 15 light-years in radius, so eventually you'll run out of bright objects altogether as you go past. It's much easier to see a star than another galaxy if you look anywhere in the sky. However, the central disk of the milky way is made of millions of stars, which is why, even being about 10,000 light-years away, it is still possible to see it in a dark area. I've seen the milky way through binoculars, although not very clearly, from a light-polluted location. Comet 17P/Holmes, by the wat, is currently just west of the Milky way. Hope this helps. Thanks. ~AH1^(TCU) 17:08, 3 November 2007 (UTC)

Huh? The observable universe has comoving radius about 46.5 billion light years. Algebraist 17:41, 3 November 2007 (UTC)

Oops, minor error, I meant 15 billion light-years. That's assuming you can measure the distance from Earth to the edge of the universe without the universe expanding while you measure (eg. the time for the measuring "ruler" to reach the observable edge of the universe from the Earth is 0). This is based on the fact that the universe is about that old and that the farthest observed galaxies are about 17 billion light-years away. Hope this helps. Thanks. ~AH1^(TCU) 18:02, 3 November 2007 (UTC)

You're wrong here: it's not the distance (which is closer to 14 billion (more precisely 13.7) light years according to the latest data) measured by an instantaneous ruler but the light travel time times the speed of light. The comoving distance is more like what you mean, and it's larger, as Algebraist pointed out. Icek 01:55, 4 November 2007 (UTC)

Thanks for all of the helpful responses! That sure is enlightening (I'm sort of unlearned in the field of cosmology). It's very interesting to think that all of those stars we see are mostly just from our own galaxy and that there are billions of other galaxies out there. Well have a good one guys and thanks again ;) Zenislev 19:50, 3 November 2007 (UTC)

If you live in an urban environment, you might only be able to see a thousand stars with the naked eye, all of which are in the nearby parts of the Milky Way galaxy. Fainter, or more distant stars, and the other galaxies would require at least binoculars or the very dark skies you get far away from cities. When I first saw the nearest bright galaxy (Andromeda, M31) through a pair of binoculars, I was surprised how faint it really was - a small fuzzy patch, especially compared to those great photos you see. Astronaut 03:41, 4 November 2007 (UTC)

Zenislev, if at all possible, grab a pair of binoculars and look at the Andromeda galaxy! It will look like a luminous smudge, but it's quite cool to be able to see another galaxy. And in fact, the Andromeda galaxy is *huge* on our night sky... the problem is that most of it is relatively dim. You can only see the brightest, central part. If I remember right, the whole thing is as big as about 7 full moons! So the difficulty is not magnifying something that appears to small - it's enormous! Instead, the hard part is collecting enough light to see something that's relatively dim. Then point your binoculars at Jupiter and look for the Galilean moons. Even with small binoculars you might see 2 or 3 of them! --Reuben 04:36, 4 November 2007 (UTC)

I do indeed live in the city, so I know what you mean there. I did however bring binoculars with me on a camping trip a few months ago and was amazed at how much I could see; I really didn't know what to make of any of it though. That does seem interesting to be able to see Andromeda, I never knew you could. I'll have to try that when I get a chance. It's hard to comprehend the scale of things in our universe though; to think that this blob in the sky really spans thousands of light-years is really thought-provoking. Zenislev 05:30, 4 November 2007 (UTC) —Preceding unsigned comment added by Zenislev (talk • contribs)

motor tracts from the cortex

Is the diagram below correct?

motor tracts from the cortex

lateral system..................................medial system

pyramidal...........................................pyramidal
lateral corticospinal tract.....................anterior/medial corticospinal tract
.........................................................corticobulbar tract

extrapyramidal....................................extrapyramidal
rubrospinal tract..................................tectospinal tract
lateral reticulospinal tract.....................medial reticulospinal tract
lateral vestibulospinal tract...................medial vestibulospinal tract

(Please don't be bothered with the "...", they're just there because spaces don't work.)

Second question: Where in this diagram does Corticobulbar tract go?

Thank you! Lova Falk 11:01, 3 November 2007 (UTC)

It seems correct after I cross-referenced, but it's been a while since neuroanatomy. Try google images on the coritcobulbar tract, and you will see cross-sections of it through the midbrain, pons, and medulla that should give it away. SamuelRiv 15:03, 3 November 2007 (UTC)

According to the textbook "Principles of Physiology" by Berne and Levy there are both lateral and medial vestibulospinal tracts. Other textbooks just list the vestibulospinal tract as medial. Berne and Levy say, "Much of the corticobulbar tract belongs to the medial system". Course and distribution of facial corticobulbar tract fibres in the lower brain stem goes into some of the details. --JWSchmidt 16:25, 3 November 2007 (UTC)

Thank you! I changed the diagram by putting the lateral and the medial vestibulospinal and reticulospinal tracts into the diagram. Am I correct to put the corticobulbar tract with the pyramidal tracts? Lova Falk 18:31, 3 November 2007 (UTC)

Yes, the corticobulbar tract is counted as part of the pyramidal system....functionally it has axons that carry signals for good voluntary motor control.....they just carry signals that control motor neurons located in cranial nerve brain nuclei rather than motor neurons located in the spinal cord. --JWSchmidt 22:25, 3 November 2007 (UTC)

FYI, Lova, the "correct" way to make columns is with a table – hit the rightmost button above the edit window to start one. —Tamfang 09:21, 7 November 2007 (UTC)

lateral system	medial system
pyramidal	pyramidal
lateral corticospinal tract	anterior/medial corticospinal tract
	corticobulbar tract
extrapyramidal	extrapyramidal
rubrospinal tract	tectospinal tract
lateral reticulospinal tract	medial reticulospinal tract
lateral vestibulospinal tract	medial vestibulospinal tract

Thank you all for answering! I will also have good use of the table. Lova Falk 19:11, 7 November 2007 (UTC)

Cocaine

Is it true that some women take cocaine gynaecologically or is it just a myth? Everyone knows someone called Dave 12:11, 3 November 2007 (UTC)

Can you rephrase the question? I'm not sure if you mean illegally by some type of insertion, or prescribed by an OBGYN, or um something else. Maybe I am not thinking outside the box. Dureo 12:24, 3 November 2007 (UTC)

If you're asking about routes of exposure:

"[Cocaine] in this hydrochloride salt form may be injected; swallowed; applied to oral, vaginal, or even rectal mucous membranes; or mixed with liquor. Coke is most commonly used by snorting or sniffing." [5] (emphasis added.)

Hope that helps. TenOfAllTrades(talk) 13:40, 3 November 2007 (UTC)

Atomic movement

Can atomic movement of an atom be stopped an if so what would be the result? I am wondering if atomic movement if of a particular fequency, could you apply the same frequency of opposite phase to cancel it out and if so what would the effects of this be? If you can accelerate particles by superheating them, would stopping the movement have a cooling effect? —Preceding unsigned comment added by 59.101.139.208 (talk) 13:50, 3 November 2007 (UTC)

Yes. At absolute zero, there is absolutely zero (har har) movement. Although it's not possible to replicate in a laboratory (although they've gotten very close), some scientists believe that in the far reaches of space the temperature exists. -- MacAddct  1984 ^{(talk &#149; contribs)} 13:58, 3 November 2007 (UTC)

I see that in discussing Bose–Einstein condensate, the absolute zero article mentions "pK" (picokelvin). How does someone measure a temperature that low? --JWSchmidt 15:01, 3 November 2007 (UTC)

At absolute zero there is still movement predicted by quantum mechanics and Quantum Field Theory (QFT). A simple way to see this is by noting Heisenberg's Uncertainty Principle which shows that a zero change in position requires infinite momentum, and vice versa. Note that this is a mathematical fact of quantum theory and not some philosophical abstraction. Empty space in the current universe is at about 3K and does not approach zero as one goes to the "far reaches of space" because there simply is no far reach of space as expansion is uniform. As one goes farther into the future, however, the temperature of the universe is falling as the expansion of the universe accelerates.

Extremely low temperatures are achieved first by evaporating liquid helium (liquefaction of helium being achieved by the Joule-Thomson effect) and then by isentropic demagnetization of the subatomic particles (so demagnetizing particles without changing entropy). They are measured by reversing the effect: measuring the magnetization of subatomic particles and measuring the vapor pressure of liquid helium. This is only effective to a scale of millikelvins, below which I'm not sure what they use. Note the validity of these methods of course depends on having a very good theory of the behavior of particles at low temperatures, which we do (QFT is the most numerically accurate theory known).

On a side note, temperature is defined as $1/T=\partial S/\partial U$ if the number of particles in the system doesn't change. That is, the inverse of temperature is the change in entropy over the change in energy. This definition, and indeed statistical mechanics itself, sets no restrictions on how high or low temperature can be. So we can have systems with Negative temperature! SamuelRiv 15:31, 3 November 2007 (UTC)

Oh, and physically slowing the motion of atoms does cool them: that's how liquefaction of gases is done. See cryogenics and the Joule-Thomson effect. Basically, gas is expanded through a valve which causes energy to be absorbed against the intermolecular forces of the gas, which results in a net temperature decrease as long as the initial temperature of the gas is below the inversion temperature. Again, the motion of the atoms can never be stopped completely. SamuelRiv 19:34, 3 November 2007 (UTC)

Glue board adhesive composition

I'd like to make my own glue boards, similar to those for catching mice, although mine will be used for insects. The hard part is the adhesive. What ingredients can I use to make my own ? I found this list of ingredients for a mouse glue board, but the portions aren't given and many terms are vague (which stabilizers or hydrocarbons ?):

• Styrene copolymer

• Hydrocarbon resin

• Paraffin oil

• Stabilizers < 1%

• Anti-oxidants < 0.5%

I'd like to make this from items I can buy at a grocery store, if possible. Dish washing detergent works, but stays liquid for weeks, until all the water evaporates. Could I make it immediately solid by adding gelatin or something else ? Could I heat it to drive off the excess water ? StuRat 14:07, 3 November 2007 (UTC)

Dishwashing liquid is about 95% water so it'll take a long time to dry. Try dissolving salt in it to make it get thick. Car wash detergent may be more concentrated. You can try the salt trick with that too. Alternatively citric acid can be used as a thickener. You'll notice a lot of shampoos contain a salt, which is just there to make it thick.

Pressure sentitive adhesives contain a polymer for strength and a tackifier to make it sticky. It is a synergistic combination: the mixture is "stickier" than the two components. For your mouse-catcher, the styrene copolymer is probably a styrene-butadiene-styrene block copolymer like Kraton. The hydrocarbon resin is the tackifier and is probably a derivative of pine tree resin. Delmlsfan 14:58, 3 November 2007 (UTC)

I guess you could try boiling the washing up liquid to drive the water out more quickly - but I have no idea on the consequences of doing that! SteveBaker 15:48, 3 November 2007 (UTC)

Just buy some flypaper. -Arch dude 16:54, 3 November 2007 (UTC)

I have tried flypaper. I found it unacceptable because it's ugly and the glue gets all over everything, including my hands. Also, I want to get all insects, not just flying insects. Spiders and centipedes need to die, too. I've tried to lay flypaper out on a flat surface, but the glue got all over everything in the process. But, that is the idea, I want one-sided flypaper laid down on a flat sheet, say the size of a newspaper. I want to do so on a large scale for a low price. StuRat 17:06, 3 November 2007 (UTC)

(Spiders and centipedes are not insects). SteveBaker 22:58, 3 November 2007 (UTC)

Ok, let me be more scientific and say that I want to kill all "creepy-crawlers" which drag their asses across my floor. :-) StuRat 00:14, 6 November 2007 (UTC)

Do a search with "make flypaper" and you can get recipes using sugar, golden syrup etc. The advantage of these edible glues is that they wash off very easily in water. Keep in mind some invertabrates wont walk out in the open. I accidentally caught silverfish with a roll of gaffer tape that was a little unrolled, they had wedged into the sticky crevice. IF you are after a more specific result, let us know. Polypipe Wrangler 22:57, 4 November 2007 (UTC)

I'm a bit worried that if edible glue isn't sticky enough, I will end up feeding bugs instead of killing them. StuRat 23:31, 9 November 2007 (UTC)

X-inactivation and color blindness

Several forms of color blindness are far more prevalent in male humans because they are caused by a defective gene on the X chromosome of which males only posses 1. If you look at the prevalence for males and females in out article, the numbers seem to agree with this theory (1% vs. 0.01%, 6% vs. 0.4%). However, in females one X chromosome is inactivated; this inactivation happens early in embryonic development, at the 70-100 cell state (at least in the mouse, according to the Wikipedia article) and is apparently random. There are several genes which are nonetheless expressed on an "inactivated" X chromosome, but these are mostly genes which are also found on the Y chromosome (pseudoautosomal region).

I don't know how many of the 70-100 cells which all individually undergo X-inactivation end up as the relevant cells in the retina, but even if it's more than one, one would expect that there are cases of female "patchy" colorblindness, i. e. affecting only part of the visual field. This condition then should be even more prevalent than colorblindness in males: If the fraction of X chromosomes with the color-blind property is r, then (assuming random distribution) the fraction of males carrying such X chromosomes is r, and the number of females carrying at least one such X chromosome is 2*r - r².

On the other hand, if all relevant cone cells originate from only one embryonic cell at the time of X-inactivation, the probability that a female is colorblind is 1/2 if she carries 1 "color-blind" X-chromosome and 1 if she carries 2 "color-blind" X-chromosomes; together that makes for the rate of color-blind females the same as the male rate.

How do you explain the observed approx. r² rates in females? Icek 17:53, 3 November 2007 (UTC)

It turns out that not all genes from the so-called 'inactive' X chromosome (Xi) are actually fully silenced (see X-inactivation#Expressed genes on the inactive X chromosome). Of those, a few are transcribed at the same level as on the active X chromosome (Xa); a very few are even transcribed at higher levels from Xi than from Xa. (The obvious example for this last case would be the RNA gene Xist, which effects the X-inactivation.)

I don't know if this is the case for some of the genes related to colour vision, however; I'm still digging in the literature. TenOfAllTrades(talk) 18:52, 3 November 2007 (UTC)

Some further interesting reading from PNAS. A survey of genes on the X chromosome found that as many as twenty to thirty percent(!) of genes on the short arm of the X chromosome (Xp) may escape inactivation at least some of the time. TenOfAllTrades(talk) 19:13, 3 November 2007 (UTC)

Thanks for the answer. From the supplementary data of an Cell article drawing the data from this Nature article it appears (see figure 8, last page of the supplementary data) that the relevant genes for red-green blindness at locus Xq28, OPN1LW (for the long-wavelength (red) receptor) and OPN1MW (medium-wavelength (green) receptor) are not at all expressed from the 'inactivated' X chromosome. Of course, the study was made with fibroblasts and the situation may be different in cone cells. Icek 01:01, 4 November 2007 (UTC)

FYI, here is the OMIM page for OPN1MW and here for OPN1LW. Icek 01:05, 4 November 2007 (UTC)

Thinking again, it's likely that opsin (the product of the aforementioned genes) may not at all be expressed in the studied fibroblasts; maybe the fact that there is no gray bar at all instead of a gray bar extending only below the zero line for some genes in the supplementary data figure I linked to before means that the expression was zero in the activated as well as in the inactivated X chromosomes. Icek 01:23, 4 November 2007 (UTC)

Detecting nuclear blasts

A recent news article claims that the US used tactical nukes at Operation Orchard. Seems incredible to me. Is it possible nowadays for an above ground nuclear blast to go undetected? --Duk 18:38, 3 November 2007 (UTC)

Undetected - no I doubt it, unreported - perhaps. Lanfear's Bane | t 20:20, 3 November 2007 (UTC)

Fuel-air bombs can get into the neighborhood of a (very) small nuke, as far as TNT equivalent, so there could be some ambiguity in seismic detection, but there is basically *no* way that the radiation would go undetected, especially if people were looking for it. Also, this government can't even keep it secret that they flew some nukes across the country accidentally or that they like to pour water up some poor bastard's nose; there's no way it would stay quiet if they actually used a nuke. --Sean 20:20, 3 November 2007 (UTC)

I haven't yet found a Wikipedia article specifically about detection of nuclear explosions, but in the articles on the Ryanggang explosion and 2006_North_Korean_nuclear_test it is assumed that any nuclear explosion would be detectable by the characteristic isotopes produced. An explosion of such magnitude as to have been a nuke would register on seismographs all over, and, although we can't know where the satellites are looking, I'd expect one or two to be pointed at the Middle East a lot of the time. Any large explosion in Syria would certainly be detected and probably pinpointed, and it would be a simple matter to test the area, or even downwind, for the telltale isotopes. So, no. --Milkbreath 20:45, 3 November 2007 (UTC)

Seismographs can only measure the size of the explosion - so a small nuke and a very large conventional bomb would look identical. Direct photography of the mushroom cloud or the resulting debris field could probably tell the difference - as could eye-witness testamony...but we don't have that kind of evidence. Radiation is another way - but only people with access to the site could measure that without some pretty high-tech equipment. The people with the high tech equipment aren't admitting to it - so unless someone has actually been out there with a geiger counter, we can't know. HOWEVER: If the US have fuel/air bombs with equivelent destructive ability to a small nuke, why on earth would they risk world condemnation following the use of nuclear weapons when they could use a conventional bomb with little or no comment and get much the same result? It just doesn't seem plausible. SteveBaker 22:48, 3 November 2007 (UTC)

A neutrino detector should be able to single out nuclear explosions, in theory, or at the very least determine the exact time that one occurs. Someguy1221 22:54, 3 November 2007 (UTC)

(Seismographs also show roughly where an explosion took place, and, of course, precisely when.) There are plenty of other signs of a nuclear explosion. They get extremely hot, so there would be melting at ground zero that would be hard to fake, and fires all around. There is an electromagnetic pulse that could be expected to at least have some effect on the power grid. Nukes are very, very, very bright. The hard radiation in its vicinity would show in the people and the animals near it. Sounds to me like Comical Ali has come out of retirement. --Milkbreath 01:19, 4 November 2007 (UTC)

If it was above ground it would produce easily measurable fallout, even if it was very far above ground or most of it was buried. Such conditions would produce less fallout, perhaps not enough to hurt anyone at any distance, but it would certainly be measurable by a variety of stations around the world within a week or so. So the fact that none of the many, many stations in the area with radiation detectors (even a simple reactor will have those) reported anything awry is pretty much good evidence that it was not used, in my book. But of course the most compelling answer is the one you've given — it would be tremendously stupid and wholly unnecessary to use nuclear arms in such a situation. --24.147.86.187 00:18, 5 November 2007 (UTC)

If you read the story carefully you'll see that they never say that it was a nuclear weapon that actually detonated at the site. It is poor reporting in any case and is probably meant to be misinterpreted. I doubt the USAF was involved but even if it was, and even if we take as a reliable claim that the escorting planes would have had tactical nukes on board (highly, highly unlikely that they have such things flying around a theatre like that just for the heck of it, much less two of them), the idea that they would non-chalantly use such weapons is pretty absurd, and the article doesn't even really assert that. The whole thing sounds like misinformation to me. --24.147.86.187 00:18, 5 November 2007 (UTC)

Any clues as to this equation?

Hi all, does anyone have any idea what this represents? [6]

Many Thanks! --Chachu207 ^{talk to me} 19:56, 3 November 2007 (UTC)

Maxwell's equations. Clarityfiend 20:04, 3 November 2007 (UTC)

Thanks! --Chachu207 ^{talk to me} 20:07, 3 November 2007 (UTC)

Two locomotives

How can two locomotives pull the same train together? It seems to me that if one pulls even a tiny bit harder it will be dragging the other one. --Milkbreath 21:14, 3 November 2007 (UTC)

Excellent question. I've wondered about this, too.

First, it's not just two locomotives. Suppose you and a friend are both trying to push a car -- doesn't the same argument apply?

I've thought of two answers, though there may be more.

1. If there's any flexibility in the system, it can "even out" the two force providers (locomotives or people) if they're unbalanced. For example, think about the various couplings (gears and such) via which the mechanical energy is transmitted from the locomotive's actual engine down to its wheels. Suppose furthermore that there's some "lash" or "spring" in that power transmission chain (as there just about always is, in practice). Now, if one locomotive pulls a little bit harder, it might seem as if the other one wouldn't have any work to do, because the train is being pulled out from under it, so to speak. But if one engine is doing all the work, its transmission chain will be maximally compressed. The other engine (not doing any work) won't have its transmission chain compressed as much; it will begin to untwist (precisely because the stronger engine is in the process of pulling the train out from under the weaker engine). But after an infinitesimal moment, after the weaker engine's transmission chain untwists just a bit, the weaker engine will have something to push on, after all, so it will do some work -- precisely its share -- and all of a sudden the stronger engine won't be pulling the whole train, after all.
2. The more accurate explanation, I think, is based on the fact that each locomotive is a constant force device. Each engine is doing whatever it can to keep pulling on that train. If one engine pulls harder, threatening to pull the train out from under the other one, suddenly the other one won't be applying as much force any more. So it will do whatever it has to do -- i.e. speed up a bit (which is easy to do when suddenly it's not meeting as much resistance when it tries to pull) until it's pulling its weight again. And the same explanation applies to you and your friend trying to push that car, even if one of you is pushing harder than the other.

Now, with that said, it's still an at least somewhat tricky problem. As I understand it, there had to be some real breakthroughs in electric motor control before two diesel-electric locomotives could each act like constant-force devices and pull a train in harmony. (And as I think about it, there's a second problem: if one engine is more powerful than the other, it ends up having to apply a higher constant force than the other. I don't know precisely what mechanism arranges that the constant forces that the two locomotives try to apply are in proper proportions to the power ratings of the two locomotives. Perhaps I was wrong when I said the locomotive had to be a constant-force device; perhaps the more accurate description is "constant power".) —Steve Summit (talk) 21:54, 3 November 2007 (UTC)

P.S. See our article on Diesel locomotives, particularly the "Adaptation of the Diesel engine for rail use" and "Diesel-electric control" sections, which talk about these control issues. (In particular, it looks like diesel-electric locomotives are indeed constant-power. Steam locomotives, on the other hand, are described as "constant torque", which I think is equivalent here to constant force, so perhaps the arguments for multiple-unit hauling with steam locomotives are different than for diesel.) —scs 22:06, 3 November 2007 (UTC)

The key is that either engine is capable of pulling faster than the entire trainset is moving. So if the #2 engine is pulling a bit harder than the lead, the lead is still pulling at the front of the #2 engine. Its very much like a group of people pulling together on a rope to haul something. But here's an even funkier configuration for a consist: 2 locomotives at the front, and one at the tail end of the train. :-) Arakunem^Talk 22:02, 3 November 2007 (UTC)

A simple mechanical contraption will allow two locomotives to combine variable pull forces - see Differential (mechanical device) for an example of such. As for the actual nature of the machinery, I would assume as said before that the locomotives approximate to a good extent a constant-force machine. SamuelRiv 00:41, 4 November 2007 (UTC)

Ah. OK. Minor duh. The slack I was looking for is in the power. As long as the power delivered by the two engines is kept in an overlap range, the rotational speed of the wheels will vary as needed without further control, right? I was thinking originally about the old steam engines with rigid mechanical linkage without considering the steam itself. I guess you'd still have to be extra-careful about your pressure when running two steam engines together. The push-pull configuration sounds tricky, too. I imagine the rear engine would pile up as many cars at the back as it could. Rough on the couplers, I would guess. --Milkbreath 01:52, 4 November 2007 (UTC)

I think people are making this question harder than it is. There's no need for careful power control. As stated earlier, a locomotive provides an essentially constant force (until moving fast enough that friction becomes an issue, that is). If the front locomotive is pulling with 12,000 pounds force and the second one with 20,000 pounds, then the strain on the coupling between them is 12,000 pounds and on the coupling behind the second one it's 32,000 pounds. The train can't tell whether that force is coming from one locomotive at the front, or two or six. And the second locomotive can't tell whether the train is accelerating faster its 20,000 pounds would produce because there's another locomotive, or because it's running downhill. Same thing if there are engines at the rear, only in that case the strain on the couplings near the rear will be compression instead of tension.

So long as the controls allow all the locomotives to produce the necessary level of power, the only possible concerns with the relative contributions of different locomotives are efficiency and whether it's possible to put a dangerous strain on the couplings. Remember, double-headed trains were common on some railways -- triple-headed trains on some -- in steam days when there was no such thing as multiple-unit control; the crews of different locomotives could communicate only by whistle signals. The trains still moved fine.

--Anonymous, 01:18 UTC, November 5, 2007.

Upon reflection, perhaps the simple answer is just that modern locomotives are not constant-velocity devices.

If they were, then yes, the fast one would drag the slow one -- but they're not. —Steve Summit (talk) 02:34, 5 November 2007 (UTC)

The locomotives all have torque regulators so they all run at the same torque. If one goes over torque, it goes underpower, if it is torque it goes over power. If there isn't enough power it will cut off and go free-wheeling.--Dacium 03:12, 5 November 2007 (UTC)

So they all run at the same torque, or the right torque? Suppose I try to pull a train with two locomotives, one having twice the power of the other. The more powerful one would have to apply twice as much torque, I think. —Steve Summit (talk) 13:02, 5 November 2007 (UTC)

Anonymous has it correct; there's no fancy regulator (at least on early diesel-electric locomotives), each locomotive just does what it can to add to the overall tractive effort. In fact, you can break this down to the level of traction motors; each traction motor and its associated wheelset turns independently and there can be imbalances between them as well with relatively little harm. The key to all of this is that a locomotive doesn't resist motion that is externally applied to it so the worst that would happen is one locomotive would "goof" off while the other does all the work. (That is, it's not like multiple synchronous motors fighting each other.) But if the tractive load required exceeds the capabilities of the individual locomotives, then it's a sure bet that they're sharing the load at least somewhat.

Nowadays, individual locos do have some amount of automated wheel anti-slip control within a single locomotive, but I don't know if multiple locomotives share any data to optimize this across multiple locomotives.

Atlant 17:00, 5 November 2007 (UTC)

Computers and adverse health effects

Hi. I'm not asking for medical advice. I've heard that computers and cause, at least in part, everything from eye problems to headaches to brain tumours. Is at least some of this true? I know people, myself included, who have felt the effects of over-computer use. What causes this? What could possibly cause these if computers aren't responsible? Thanks. ~AH1^(TCU) 21:24, 3 November 2007 (UTC)

The only adverse health effects from computers that I've found to have any basis in fact is toner dust from laser printers getting into the air and causing lung problems. That is the reason that toner no longer comes in a bucket that you pour into the printer. As for the brain cancer and eye prblems - this was believed to be a health problem from the monitor. Some believed that the radiation from the cathode ray tube caused brain cancer and sitting too close to the monitor caused eye problems. Neither is based on scientific observation. The computer itself is merely an electronic device (and a low-voltage one at that). The only real health problem it can cause is the side effect of sitting in front of one all day and not getting any exercise. However, you will find people who claim anything and everything causes health problems. -- kainaw™ 22:32, 3 November 2007 (UTC)

CRTs do emit X-rays, and X-rays can cause cancer; however, I'm pretty sure the level of radiation is well below the background level unless you use a (powered on) CRT as a pillow every night. Repetitive stress injuries are a genuine health problem. As far as I know it's impossible to permanently damage your eyes by staring at a screen, though you can certainly tire them in the short term. Concerns about cancer from low-frequency radiation are groundless. -- BenRG 23:37, 3 November 2007 (UTC)

I agree. The most important thing is to use good posture, to avoid injuring your neck and back (by keeping your head in the same position for looking at the screen) and your wrists (by typing with bad posture). And take breaks every once in a while. —Keenan Pepper 00:39, 4 November 2007 (UTC)

I agree. Even a trip to the kitchen to make tea every hour is enough when it comes to exercise. --Ouro (blah blah) 08:38, 4 November 2007 (UTC)

I've been using computers for 40+ years now. I've suffered some pretty nasty symptoms over the years - but the idea that radiation is a problem has been completely debunked. Eye strain, bad posture and repetitive strain issues are real - but there is no mysterious death-rays causing them! All three symptoms can be greatly reduced by two things:

• Firstly, find an expert to set up your work-station. Many companies will employ the services of an ergonomics expert to figure out your optimium seating position and set up your work area correctly for your particular body dimensions. This may require chair adjustments, desk height adjustment, possibly a foot-rest, almost always something to raise the height of your monitor. Sadly, some companies wait until you've sustained an injury before they'll do that for you - but you should definitely ask and if they refuse, get that in writing because you're going to need it when you come to apply for workers injury compensation later in life. If you can get an expert - take their advice seriously - and if you use a computer at home - measure how your work setup is arranged and try to set up your home set up identically.
• Secondly, take a few minutes break every 20 to 30 minutes - get up walk around - stretch and stare off into the distance. In most places there are health & safety at work laws that require your employer to allow this. I use a kitchen timer to remind me to take a break because it's easy to forget.

If you start to get repetitive strain symptoms in your fingers - stiffness and a burning feeling on the backs of your hands - then you absolutely need to do something about it. If you carry on working, then over the next few weeks it will spread to your wrists, then your elbows then to your shoulders. The longer you leave it - the longer it'll take you to recover. I'm a huge fan of split keyboards - the ones I use are made by 'GoldTouch' and they are literally split in two with a ball and socket joint between the two halves that lets you adjust the split and tilt for each hand and then lock it in position.

SteveBaker 04:33, 5 November 2007 (UTC)

Returning to laser printers, they can emit ozone, especially if the recombination catalyst on their ventilation air exhaust has become old and tired. They can also emit styrene vapors from the toner. The fuser units within them can pose a thermal burn hazard if you attempt to service them improperly.

High voltages used within various computer subsystems can also be an electrocution hazard if you attempt to service your own computers. Certain computers will also pose electrical hazards when not properly earthed/grounded.

There is also the hazard of abrading your fist by punching the screen if you spend too much time at certain websites.

Atlant 17:04, 5 November 2007 (UTC)

General relativity: gravity Doppler?

This is a rather complex question that I ask for my own understanding as it has been bothering me for some time. It is my current understanding that gravity (or changes in gravity) travel at the speed of light. For example, if the sun were to disappear now, earth would continue to orbit its location for another 8 minutes or so, "using up" the gravity that the sun had "sent out" before disappearing and which is still rippling out before earth finally sets off in a straight line.

Now, the hypothetical observations I mention below is meant after compensation for other known gravity effects. Assuming speeds that are significant compared to the speed of light, my question is whether (and if not, why not?) objects moving towards an observer appear heavier and objects moving away appear lighter because one would think the gravity "wave" traveling towards the observer "builds up" or "stretches/thins out" respectively. What I mean by this can be thought of as a type of gravity Doppler effect. So according to my hypothetical model, in an expanding universe the gravity experienced by an observer from other bodies would generally be reduced. As far as I know no such effect has ever been observed; my question is where the flaw lies is this reasoning given the laws of relativity.

Note that I am not referring to the inverse square law of gravity which has to do with relative position rather than relative motion. I am also not referring to the law of always increased observed mass due to motion/relativity in both away and towards cases.

41.243.12.244 22:35, 3 November 2007 (UTC) Eon Zuurmond

I think I see what you're getting at, but allow me to give you a simple but complete example. Imagine you have two perfectly elastic (and very heavy) superballs out in the depths of space away from everything else. They can collide off of eachother with no loss of energy. Now, say you start them off hurtling towards eachother. They meet, collide, and take off in the opposite directions that they came, and you would like to say they will continue like this for an eternity, since no energy is lost anywhere. But then recall that changes in a gravitational field are transmitted at the speed of light, not instantaneously. As the balls are approaching eathother, each ball "sees" gravity the other sent out fractions of a second earlier, which is weaker than it should be. So the gravitational force bringing the balls together is weaker than one would calculate classically. There's no crazy physics to deduce this, just the simple fact that gravity travels at the speed of light. So, while the balls approach, they don't convert all of their gravitational potential energy into kinetic, some is just magically (so it would seem at first) lost. And when they collide and take off, each "sees" the other's gravity as stronger than it should be. So not all kinetic energy is converted into potential, again, some is just lost. So it's a bit opposite than you suspected. Approaching objects seem lighter than they really are, and receding objects seem heavier. Now, you might ask, where did all that energy go? Gravitational waves. Someguy1221 23:04, 3 November 2007 (UTC)

I think both of you are confusing gravitational fields with gravitational radiation (waves). Gravitational radiation propagates outward from the source; a gravitational field does not. Say you have an object resting on a table and you push on one end of it, causing it to shift to a new location. The whole object doesn't move immediately; the change in position is transmitted from molecule to molecule outward from the point you pushed at a finite speed (the speed of sound in the solid). Eventually the object stabilizes in its new position. This isn't a very close analogy, but if you think of the gravitational field as the solid and gravitational waves as sound waves in it, you broadly have the right idea. An object's gravitational field is not emitted by it, it's just there. Where did it come from? It didn't come from anywhere; it's always been there. This is why conservation of energy is absolutely necessary for a relativistic field theory of gravity to work at all. If mass could just appear or disappear, it would have to take its field along with it, but that would violate locality.

To answer your (original poster's) question more directly, the gravitational field at a given distance in front of a uniformly moving object has the same strength as the gravitational field at the same distance behind. The headlight effect applies to waves, not fields. Again, the field behaves something like a solid structure attached to its source; when the source is moving, the field is Lorentz contracted. It doesn't lag behind nor get concentrated in front.

I think you're creating confusion for yourself by asking whether objects would "appear heavier" in certain situations. This is a meaningless notion unless you can give it an operational definition. It almost never makes sense to ask about "apparent" properties of objects, unless you're literally referring to what the object looks like, i.e. to the nature of the electromagnetic radiation which is emitted by the object and subsequently detected by your experimental apparatus. -- BenRG 23:11, 3 November 2007 (UTC)

Oh, I wasn't confusing anything, I just neglected to mention that I was talking about something else :-D But yes, the doppler effect applies to waves, not fields in general. And the static field about an object has no wavelike characteristics. Someguy1221 23:34, 3 November 2007 (UTC)

Keep in mind that mass undergoes Lorentz contraction, so as one approaches or recedes from an object one sees a heavier mass. The most definitive answer would be an actual solution to the Einstein Field Equations for a central field at constant velocity, for which all I can say is that there will be off-diagonal terms in the stress-energy tensor, which, given a Schwarzschild metric, means interesting curvature. I say interesting because I have no clue how to interpret the results, other than saying that the off-diagonal terms are not present in the stationary case. Some help would be appreciated. SamuelRiv 05:48, 4 November 2007 (UTC)

Thanks for all the help so far. As for BenRG's comment about my notion of "appearing heavier", a simple explanation would be this: Consider two heavy objects in far space accelerating towards each other purely due to each other's gravity. Both are emitting a single spectral line of red light. The two can measure speed relative to each other by observing light Doppler shift in the color of the observed light from the other (which should shift towards green or blue). What I mean by "appearing heavier" is that the infinitesimal acceleration of object A towards object B due to gravity would (in my hypothetical model) be slightly more than just the combined value of (1) The gravitational effect using the 1/r^2 law and (2) compensating for the fact that B has a heavier apparent mass due to relativity. In both (1) and (2) cases the distance and speed of a short while back are used due to the speed of light delay combined with a nonzero distance between A and B. This "appearing heavier" effect would then be notable in the spectral profile of the observed color. I realize now that this "effect" that I want to give a name might be something trivial that is automatically taken into account with most such calculations when calculus is used. 41.245.66.240 12:26, 4 November 2007 (UTC) Eon Zuurmond

I would also like to add the following: words like "Doppler", "ripple" and "wave" are apparently bad choices because they all imply I'm assuming something with a frequency or wavelength. I just use these for analogy. 41.244.192.80 20:19, 4 November 2007 (UTC) Eon Zuurmond

Radiative Forcing

Why is the amount of radiative forcing greater on a south-facing slope than on a north-facing slope??

68.108.248.118 22:48, 3 November 2007 (UTC)

This sounds like it could be a homework question, so I'm not going to give the full answer, but here are a couple hints. A) The reverse is true in the Southern hemisphere, and B) think about the position of the sun. Dragons flight 23:02, 3 November 2007 (UTC)

And it's completely backwards (says me, south of the equator). --Psud 20:28, 5 November 2007 (UTC)

November 4

Cognitive and socio-cognitive developmental psychology

What's the difference between the socio-cognitive and cognitive theories? Is there any difference? I need to define them for an assignment due soon but I can't distinguish between the two. Thanks in advance. —Preceding unsigned comment added by Psycho marshmallow (talk • contribs) 01:46, 4 November 2007 (UTC)

Direct homework help is a bit verboten, but let me give you a hint: think about the different names. You know what cognitive theory is, presumably. What happens to cognition in extreme cases of social interaction, i.e., if I locked you in a cage since you were born and never talked to you? Can a cognitive theory really stand alone? SamuelRiv 04:12, 4 November 2007 (UTC)

DNA related question

Would the number of units of DNA during the G2 phase be equal to the number of units of DNA in one of the daughter cells? For example, if 100 units of DNA were counted during the G2 phase, would there be 100 units of DNA in one of the daughter cells? —Preceding unsigned comment added by 199.247.235.10 (talk) 05:07, 4 November 2007 (UTC)

This sounds like a homework question, which we prefer not to answer (we even have a guideline that you shouldn't ask it!). Recall that the purpose of DNA replication in mitosis is to ensure that daughter cells each wind up with the same number of chromosomes as the parent cell, so you just have to remember when that replication occurs, and what form the DNA takes in each phase. Read mitosis if you need to brush up, and come back if something is confusing you. Someguy1221 05:20, 4 November 2007 (UTC)

Europa

Though there are historical hallmarks of running water on Mars and seas of liquid methane on Titan; is Europa, with its ocean of salty water underneath a frozen exterior, the best bet for proving the existence of extraterrestial life (past or present)? —Preceding unsigned comment added by Sappysap (talk • contribs) 05:49, 4 November 2007 (UTC)

Please do not count those onboard the International Space Station as extraterrestial life. If the world had to invest in a single mission to find life on a planet, moon, dwarf planet, comet, asteroid or planetary ring in our solar system, what would be the best bet? —Preceding unsigned comment added by Sappysap (talk • contribs) 06:43, 4 November 2007 (UTC)

Gliese 581 c? --Ouro (blah blah) 08:12, 4 November 2007 (UTC)

Well, apart from Europa probably. --Ouro (blah blah) 08:18, 4 November 2007 (UTC)

Europa is a possibility for life. The problem with it is that it's rather far from the Sun and doesn't get much energy from it. The oceans (which many experts dispute even exist) would be exceedingly deep under the ice - so not much light would filter down there, and there is unlikely to be much dissolved oxygen in the water as there is here on earth. Such energy as life would get would have to be from hypothetical underwater volcanos caused by tidal forces of Jupiter continually kneading the moon's interior - and since those would appear and disappear sporadically, it's not clear that life would have time to evolve - and then to survive in open water long enough to find the next volcano when the one they were living next to fizzled out. Having said that, the odds of finding life on Europa are probably better than anywhere else beyond Earth. However, there are other possibilities: Enceladus and Titan both orbit Saturn and have similar prospects for life to have evolved. Of those, Titan actually looks rather promising because it's atmosphere is dense and stuffed full of hydrocarbons. Not enough is known about Enceladus - except that it has water ice deposits. Gliese 581 c is a long-shot. We just don't know much about it. SteveBaker 16:23, 4 November 2007 (UTC)

Oh, I forgot Titan! As for Gliese 581 c, well, if we'd have the resources to develop and undertake a trip there, then we'd probably also have the resources to seek out signs of life anywhere else. --Ouro (blah blah) 16:31, 4 November 2007 (UTC)

Pyramidal neurons and the extrapyramidal system

A digram showing the position of bilaterally symmetric "pyramids" (corticospinal axon tracts) along the side of the Medulla oblongata.

According to this source the neurons contributing to the pyramidal tract are themselves pyramidal neurons, but most pyramidal neurons send axons elsewhere.
Does that mean that also motor tracts from the extrapyramidal systems can contain pyramidal neurons??? Lova Falk 09:46, 4 November 2007 (UTC)

I believe most neurons that innervate a tract are pyramidal cells, for both the pyramidal and extrapyramidal systems, as they both consist of single-axon bundles and operate with essentially the same long-distance signalling function. I'm not certain, though. SamuelRiv 13:54, 4 November 2007 (UTC)

The pyramidal system got its name from the shape of the corticospinal axon tracts (the axons go through the "pyramids" of the medulla oblongata). Some textbooks do not use the designation "extrapyramidal systems" because functionally the "pyramidal system" actually sends axons to the brain nuclei of the "extrapyramidal" systems, making those systems not really "independent of" the pyramidal system. If you define the "extrapyramidal systems" as constituting the neurons of brain stem motor nuclei and their axons, then that would exclude the cortical pyramidal neurons that project to the brain stem motor nuclei. --JWSchmidt 18:55, 4 November 2007 (UTC)

phone calls

I keep getting calls asking me to press "6"? Are these the calls that seek authorization to place the charge for a long distance call on your number, and if so, why doesn't the phone company make it a priority to notify, if not warn, you of such things? Clem 12:06, 4 November 2007 (UTC)

Do they just call and say 'Please press 6' or do they say anything else? --Ouro (blah blah) 15:47, 4 November 2007 (UTC)

Also, what country do you live in? The meanings of various number sequences differs by phone system. MrRedact 04:23, 5 November 2007 (UTC)

reverse-reverse engineering

Is there a thing called reverse-reverse engineering, where say like a company in England that designs belt sanders for Black & Decker makes a design that has refinements and unnecessary features, and uses excessive and precision parts and is prone to easy destruction, if all but finishing grade belts (100+) are used, that is reverse engineered in China for Chicago Tools, that then is redesigned with no features (variable speed), but a higher RPM that can handle the lowest number belt grit with ease, such that the company in England can then reverse-reverse engineer Chicago's reverse engineered belt sander to come up with a solid and tuff belt sander of its own, with no unnecessary anything, but that is superior to Chicago's belt sander in precision? Or is this just a pipe dream? Dichotomous 12:19, 4 November 2007 (UTC)

Please, next time, use more punctuation. This is basically just an example of reverse engineering something that had already been designed via reverse-engineering. If I understood your mammoth of a question correctly, that is. Cheers, Ouro (blah blah) 12:39, 4 November 2007 (UTC)

You have my permission to punctuate the question to your liking. Dichotomous 13:13, 4 November 2007 (UTC)

Why did you do that? --Ouro (blah blah) 13:21, 4 November 2007 (UTC)

...was at a neighbor's workstation. Dichotomous 13:28, 4 November 2007 (UTC)

Oh, okay. I was just curious. And no, I've no need to punctuate your question. Cheers, Ouro (blah blah) 13:31, 4 November 2007 (UTC)

Please do so anyway for the sake of future questions which might appear on your screen. Sometimes punctuation, like spelling is a very personal or intended thing. Its why we do not utilize an auto-speller bot. I can, however, learn a lot more about you from whatever changes you make. Dichotomous 13:35, 4 November 2007 (UTC)

There. However, if I'd have been the OP, the question'd probably be split into four or so sentences in the least. Bear in mind, I'm not a native speaker of English. Cheers, Ouro (blah blah) 13:51, 4 November 2007 (UTC)

Please feel free to break the question into as many parts as you feel necessary, even if doing so requires re-phrasing the parts of the question. Dichotomous 14:59, 4 November 2007 (UTC)

Also, what is your native language? If you are not familiar with English and possibly more familiar with Spanish, French, German, Italian, Portuguese, Polish, or Korean, et. el. You may be happier responding to questions there. Dichotomous 15:21, 4 November 2007 (UTC)

I'm a native of Poland, but am experienced enough with English and German to use them in any and all situations; furthermore I know some Russian (had it for two years' at University), Czech (having practically lived next door to some Czechs for half a year), and I know Slovak, Croatian, French and Spanish at hitch-hiker level (meaning I know the basic fifty or so words necessary to feel safe when on the road). As for reformatting your question, I'll do it later... I think. Thanks. --Ouro (blah blah) 15:46, 4 November 2007 (UTC)

The term "reverse engineering" is usually reserved for finding out the parts of a design that are hidden - for example the encryption that prevents a US DVD player from playing disks from Japan. Taking design ideas from your competitor (presuming they aren't patented) is simply copying their technology - and I'm sure it's a back-and-forth thing such as you describe. Reverse engineering an already reverse engineered product is not a likely thing since whoever first produced it already knows how it works. Copying the changes someone made when they copied your design is a quite different matter. At any rate, the term "reverse-reverse-engineered" is not one that I've ever heard anyone use - and the only two Google hits I got were both using it in a humerous context. SteveBaker 16:03, 4 November 2007 (UTC)

So then what might one call making changes to a device that would first accommodate low cost high production followed by improvements to maximize quality. For instance, in the example of a belt sander above, the use of stainless instead of galvanized steel for the bottom slide plate and other parts, metal instead of plastic to house the brushes, and ball bearings instead of sleeve bearings, etc., such that the two step cycle of item change results in 1., maximizing simplicity of design and 2., maximizing quality of materials, versus starting with a mediocre or low quality materials item with an unnecessary and extremely complex design? Dichotomous 17:32, 4 November 2007 (UTC)

"Improvements". SteveBaker 18:31, 4 November 2007 (UTC)

QUESTION: Can someone help me locate "one stop" lists of animal species on-line?

Hi,

I am looking for online information similar to that kisted in WikiSpecies, but held together in tables or continuous text format that can be copied into an EXCEL table. I am interested in the species of vertebrates, especially mammals, birds and reptiles. My aim is to be able to create (by as few steps as possible of "copy", "sort" and "delete") a single-table, for example, listing all the lizards and geckos in the world by family, genus, species and sub-species, based on the data in these tables. If such a source of data on species is available, please give me the on-line address.

THANK YOU!!!!

Ron Berger (e-mail address removed to prevent spamming, your welcome) —Preceding unsigned comment added by Bergeronz (talk • contribs) 12:20, 4 November 2007 (UTC)

I just deleted your e-mail address so it wouldn't be found by webcrawlers. I don't know where to find, however, the information you need, and I don't think it will be that easy - you will, after all, have to work a little more than just do simple copying and pasting. Lists of lizards and geckos are in Wikipedia, anyway. Cheers, Ouro (blah blah) 12:36, 4 November 2007 (UTC)

A google search for "taxonomy database" returns some interesting results like [7] and [8]. Since lizards and geckos are easily found under respective families, this should make your database project simple. Formatting into Excel may be a little tricky, given the format of the data at ITIS. In such cases, I recommend writing a computer program (Perl ftw!) or doing some tabbing by hand on a text file before copying into Excel. SamuelRiv 13:40, 4 November 2007 (UTC)

Lawns versus parks

It does not seem that lawns offer any advantage over parks, in terms of a front "lawn." For instance, lawns require mowing, fertilizer, insecticides, etc. while a park uses the materials which die for fertilizer and offers far greater possibly as to variety of species. Park paths can still accommodate mailmen and meter readers who must transverse the yard as well as routes for underground plumbing. Is there any good reason not to turn your lawn into a park besides using it to play batmitten? Dichotomous 15:52, 4 November 2007 (UTC)

This boils down to an argument between public vs. private property. While it seems like a great thing to make everything public, it isn't difficult to find an overwhelming set of examples where private property is better than public property. I live directly across from a park. It is covered in graffiti and full of dog poop. My front yard has no graffiti and no dog poop. So, why should I make my private yard public? -- kainaw™ 17:56, 4 November 2007 (UTC)

I suppose one could turn their front yard into a public park if they were so inclined but I am not referring to a public park but rather the other kind of park instead of having a front lawn. Dichotomous 23:41, 5 November 2007 (UTC)

Could you explain what you mean by "park"? You seem to offer a "park" as an alternative to a lawn of nicely cut grass. Are you asking about paving over your lawn to form a giant parking lot? Or are you asking about letting your lawn overgrow with grasses and weeds? APL 22:10, 4 November 2007 (UTC)

The conventional reference is zeroscaping but this type of landscaping does not necessarily include trees or design features to simulate a park rather than just native flowers and bushes. Even Central Park in NY City has trees and paths and water features that go a bit beyond the limitations of conventional zeroscaping. Dichotomous 23:41, 5 November 2007 (UTC)

megapixel claim

File:Web cam fraud.jpg

I purchased a web cam that claimed to have 6 megapixel resolution. The software that determines the number of bytes per frame indicates YUY2 format at 640 x 480 screen resolution at 614,400 bytes per frame. This sounds more like a 614,400 pixel web cam rather than a 6,000,000 pixel web cam. Have I been ripped off? Clem 16:59, 4 November 2007 (UTC)

Probably. Can you give us the manufacturer and maybe the model? That'd help. Cheers, Ouro (blah blah) 17:24, 4 November 2007 (UTC)

You should do the simplest math yourself: 640*480 = 307200. 614400 bytes per frame means that it has got 2 bytes per pixel. Icek 17:34, 4 November 2007 (UTC)

There is no model number or other means of identification, including even manufacturers name. "USB Video Device" is all that is indicated by Windows XP. The focus can be adjusted. The claim is 10 X Zoom. It says f=3.85 and Megapixel. The actual picture it displays has an extremely irritating color speckle that is highly visible. A sample picture shortly. Clem 17:47, 4 November 2007 (UTC)

I see you've added a sample. Even if the actual maximum resolution was 1280×1024 (which is in the range for current webcams) as you say on the image description page, that's still only 1.3 megapixels, not 6. Besides, if the image is that noisy even at 640×480, I shudder to think what it'll look like at the full resolution. —Ilmari Karonen (talk) 18:27, 4 November 2007 (UTC)

Besides, that image looks like it's actually been scaled up from something like 320×240! You can easily see the 2×2 pixel blocks! —Ilmari Karonen (talk) 18:32, 4 November 2007 (UTC)

6 megapixels for a webcam sounds unlikely to me; that's a typical resolution for compact digital still cameras these days. The resolution of webcams is limited not just by their typically low cost and the higher demands put on the sensor by video recording as opposed to still photography, but also by the fact that, as the name suggests, their output is typically intended for streaming over relatively low-bandwidth links. —Ilmari Karonen (talk) 18:22, 4 November 2007 (UTC)

It certainly sounds like you've been ripped off. 640x480 is a third of a million pixels - my guess is that they are 'stretching' by claiming something like "6 million pixels per second" (which would mean you're getting a disappointing 18Hz frame rate). Two bytes per pixel suggests you're only getting 65536 colours per pixel too - which is also distinctly disappointing. But in truth, a movie camera that could produce 6Mpixels and a minimal 20Hz frame rate with full colour would be 360 Mbytes/sec - which is more than a 1GHz Ethernet could transmit - and VASTLY more data than your home network could possibly transfer anyway. So a 6 megapixel web camera is really an impossibility. 640x480 is a pretty reasonable resolution for a WebCam. The noise you are seeing is indeed unacceptable - but what you have there is a crap camera. SteveBaker 18:29, 4 November 2007 (UTC)

You can find these on eBay from smartarea and ecool. Ecool is new but smartarea is a power seller. Both are located at the identical address and request buyers contact them first if any problem rather than leaving negative feedback first. Apparently their strategy works. Dichotomous 19:37, 4 November 2007 (UTC)

weird clock

Hi. There was a clock which had batteries that almost ran out, a digital clock. Sometimes, when I put it in the correct place (there was a turned-off computer, a prniter, and a metal spoon nearby), and put my finger-hand near, but not touching, the digital clock, its screen would flash with dim numbers and sometimes make clicking sounds. This rarely happened when my hand wasn't near the clock, so much so that I believe the chances that this is a coincidence is extremely small. Sometimes, if I picked up the clock, and put it near the reigon where this happened, it would flash again. I mean "flash" as in the black numbers flash on and off. Sometimes the effect is so weak that only the background of the numbers would appear. Now, when I put this clock between two computers, the effect doesn't show up, and when I put it near an "on" computer, it also flashes. When I took the spoon away, it still flashed, but has since stopped clicking. What could cause this? Is it because humans and electronic devices emit EMF's? Thanks. ~AH1^(TCU) 17:11, 4 November 2007 (UTC)

I'm betting on coincidence. Humans don't "emit EMF's". SteveBaker 18:21, 4 November 2007 (UTC)

Humans don't emit EMF themselves, but we do affect the electromagnetic fields around us due to being large conductive objects. You can easily observe this by tuning an FM radio to a station that it can barely receive; often moving your body around will audibly affect the reception quality. (This is also how a Theremin works.) From AstroHurricane001's description, it does sound like the clock was picking up some local EM interference that was inducing just enough current to cause the observed effect (it doesn't necessarily take much). —Ilmari Karonen (talk) 18:46, 4 November 2007 (UTC)

I'll say 95% that this was no coincidence. I tested this for aboout 15 minutes, and putting my hand over it produced an effect whereas not putting my hand there did not. Usually, I leave my hand, nothing. I put my hand there, it happens. I withdraw my hand, nothing. However, it does seem to throb lightly when I put it really close to a computer without brushing my hand over it, but putting my hand over it will produce a strong effect. Could it be that, as the computer emits an EMF, and I put my hand over it, it conducts the current to the near-dead battery? Amazingly, it has come back to life, but is still many hours off. Could it be that the battery terminals are so on the line between connected and not connected, a little interference can turn it on or off? Thanks. ~AH1^(TCU) 02:37, 5 November 2007 (UTC)

Liquid crystal displays can be activated by stray electrostatic fields such as might be present on your fingers, but this would only occur at very close distances. They can also be affected by pressure, but that would require contact.

Atlant 17:13, 5 November 2007 (UTC)

Charged Black Holes

How does an electrically charged black hole 'show' its charge? I was under the impression that information about an object's electric charge was carried by an electromagnetic field. If the gravity of a black hole is strong enough to prevent electromagnetic radiation (light) from escaping the event horizon, then how does the electric charge 'leave' the event horizon? Smithg86 19:17, 4 November 2007 (UTC)

The electric field lines do not leave the balck hole, instead they are there before the formation of the blackhole, and are not destroyed by the formation. You get it when an electrically charged mass collapses. Graeme Bartlett 20:46, 4 November 2007 (UTC)

Question about black headed gulls

Why do they sometimes seem more interested in fighting with other black headed gulls than eating from a pile of food? Someone had thrown some bread out for them today and I was watching them. The gulls didn't even seem that bothered about the food. They were just sitting on the surrounding rooftops looking at it.

Another black headed gull flew in from somewhere and decided to come down and eat. As soon as that happened, a load of gulls swooped down from the roof to attack the eating gull and chase it away, then they started fighting among themselves, leaving the bread alone (it's still there now). What was the point of all that? I don't get it. —Preceding unsigned comment added by 81.77.30.145 (talk) 20:52, 4 November 2007 (UTC)

Well, if the bread's just sitting there, I suppose whoever eventually wins the fight can then come back and eat it. But I suspect there is more to it than that. The response you describe sounds like an escalated retaliation to punish some sort of perceived misbehavior or social transgression. Such retaliation is observed in many species, including humans: if someone attacks our country, we'll fight back even if it hurts us more than the initial attack did. In the case of interpersonal disputes we've institutionalized this in the form of law enforcement, but the principle is still the same (and where law enforcement breaks down, we still get things like gang wars and vendettas). In this case, the obvious possibility that comes to mind is that the gull that flew in was an outsider while the ones that attacked it considered the area as their territory, but I don't know enough about gull social organization to say if that explanation really fits. —Ilmari Karonen (talk) 02:04, 5 November 2007 (UTC)

Gulls have three principal interests - feeding, fighting and fucking. In that order. If they're not particularly hungry at that moment in time and there are several gulls in the same location, keeping an eye on the food - then why not take the opportunity to cement/re-jig the pecking order with lots of gratuitous bickering, flapping, pecking and chasing? Another classic gull behaviour is fighting to displace each other from the highest perches/perches with the best view - lots of swooping and screeching. I was watching the BHGs near my house doing that today. They could squabble over one chimney pot for hours if they had nothing better to do - or until a bigger gull came along and claimed it (as happened this afternoon). Quite amusing, really - all the Black-Heads just backed off, sidled over to the opposite end of the roof and shut up when a Great Black-Backed Gull arrived, took the perch without a fuss, postured at them a little bit and then decided to settle down for a nap.--Kurt Shaped Box 00:18, 6 November 2007 (UTC)

Your note about the displacement behavior reminds me of a funny incident I observed while sailing with some friends recently. We were coming up slowly to a bend in a narrow boat lane, with four small sea marks (basically plastic poles sticking out of the water) marking the boundaries of the lane. Three of the closest poles had a small juvenile gull each sitting on them. (My memory is fuzzy here, they may have been either Common Gulls or black-heads.) When we passed the first marker, the gull on it took flight. It flew to the next pole and settled there, displacing the gull that was already there. That gull then flew to the third pole and displaced the gull there, who finally flew to the fourth, unoccupied pole and settled there.

At that point I was watching the gulls' antics and laughing aloud, so the others asked me what was funny. As I was explaining the previous events, we passed the second marker pole, and, sure enough, the gull on top of it again took flight, heading for the next pole, and the whole game of musical chairs repeated itself. This time, however, the last gull, not having any further poles ahead to land on, took a wide and graceful turn across the lane and headed straight back for the pole the first gull had just landed on. The first gull, displaced for the second (or third if you count the previous incident) time, then flew back around our boat and onto the pole he'd first been sitting on.

Being all academics, the conclusion we drew from this observation was that the displacement process was intransitive: it's not a matter of a bigger or higher-ranking gull displacing a weaker one, but simply that, if another gull wants to land on an occupied pole, the gull already there must give way unless he wants the other one to land on top of him. —Ilmari Karonen (talk) 05:15, 6 November 2007 (UTC)

They don't always give way. Sometimes the gull on the perch will assume a defensive position (body lowered, wings spread slightly, beak pointing upwards) and attempt to fend off the 'landing' gull with a few quick jabs of the beak in its general direction. More often than not, the 'landing' gull will see this, decide not to engage in a physical confrontation, pull up and away and then circle around, looking for somewhere else to stand. Very occasionally, a bout of beak-locked, wing-pummelling combat *does* ensue, however. I'm certain that (maybe only in certain situations) there is a pecking order aspect to it too.

Quite likely there is. The three fellows I observed were all juveniles of similar age, quite possibly siblings. I'm sure none of them would've tried displacing, say, a full-grown Herring Gull from its perch. Still, it's interesting that, all other things being equal, the displacing gull has such an advantage that the one already on the perch won't even try to hold its place. Or perhaps it's "gull manners"; the landing gull may, on average, tend to be more tired and thus more willing to press the issue, so it may be better for the one who's already rested to give way and avoid a needless conflict. After all, he can always come back and invade the same perch again if necessary. Or perhaps both explanations may play a role. —Ilmari Karonen (talk) 19:39, 6 November 2007 (UTC)

The type of perch may have something to do with it too. On my road for example, there are certain perches that the gulls seem to favour more than others and 'compete' over regularly. Invariably, they're the highest points on the rooftops and certain lampposts. It's not *all* high places and *all* lampposts though, so it may be something to do with the view of the surrounding area from said perches. I don't know if this is true for BHGs - but the local GBBs also definitely have their own favourite perches that pretty much go undisputed (I recognise most of the individual birds now). In the case of the gull I raised as a chick, the whole roof opposite the back of my home is *her* roof (in summer, her nest goes on a flat section there). That's not to say that other birds (of various species) don't ever perch there - just that they don't when she's present and keeping watch. --Kurt Shaped Box 22:05, 6 November 2007 (UTC)

Have you ever noticed several Black-headed Gulls stood upon the apex of a single, longish roof? They tend to space themselves apart at very regular intervals - approx 18 inches between each bird (more if possible). If one bird decides to shuffle along a little bit (and provided that this doesn't immediately cause a fight), the next bird shuffles along a little bit, causing the next bird to shuffle along a little bit, causing the next bird to shuffle along a little bit, etc. If the final bird on the roof has nowhere to shuffle to that would allow it to remain 18 inches or so from its flockmate - it takes flight and circles around to the other side of the roof and tries its luck there! Just speculation here - but 18 inches is quite possibly the distance that one Black-headed Gull can lunge in the time it takes for another Black-headed Gull to react. --Kurt Shaped Box 19:07, 6 November 2007 (UTC)

Another possible explanation that occurs to me is that 18 inches is about half a Black-headed Gull's wingspan. It may be advantageous to keep enough distance to your neighbors so that your wings won't bump into them while taking off (or vice versa). —Ilmari Karonen (talk) 19:39, 6 November 2007 (UTC)

November 5

classic (cliché) explosive detonator?

The popular image of explosive detonation (as seen in innumerable cartoons and Perils-of-Pauline-style movies) involves a box with a T-handled plunger which is forced down to initiate the explosion. (Presumably it was a specialized generator that generated an electric pulse, and fell out of use as compact, reliable batteries became available.) Anybody know what that box was called, or where our article on it is? Neither Plunger nor Detonator yield any clues. —Steve Summit (talk) 01:18, 5 November 2007 (UTC)

Answering my own question, a google search suggests it's a "Plunger detonator", indicating that there's at least one thing in this world that Wikipedia doesn't (yet) have an article on, after all... —Steve Summit (talk) 01:25, 5 November 2007 (UTC)

I think at least some of those generators were magnetos, but I have no citation and could be wrong.

Atlant 17:15, 5 November 2007 (UTC)

I've heard that too, and it's also in the Blasting cap article (well, at least being a dynamo of some sort). DMacks 18:18, 5 November 2007 (UTC)

Yeah, definitely. I used "generator" loosely, in the sense of "device that converts mechanical to electrical energy". —Steve Summit (talk) 00:41, 6 November 2007 (UTC)

In a number of World War II movies it is depicted that the plunger handle is first rotated (pivoting with its shaft as the axis) with a ratcheting noise, then raised and pushed in. Movies get a lot of things wrong, but this doesn't seem like the sort of thing they'd make up. And I take it to mean that the energy for the generator to generate its pulse comes from the release of a spring, which has to be wound up first. In that case the plunger is merely a trigger. Why use a plunger rather than a pushbutton, if so? Presumably because the long travel of the plunger makes it harder for someone to trigger it by accident. I also note that this type of trigger has a safety advantage over a simple battery system in that there is a separate arming step (winding up the spring).

Or perhaps some plungers would work that way and others would use the plunging action directly to supply the energy. I don't know.

--Anon, 06:06 UTC, November 6, 200... damn! 7!

Magnetopneumodynamic Drive?

A Mythbusters episode featured some myths on "Free Energy". Among those debunked was a device called "The Lifter" which seemed to be creating an airflow by electrically charging air and thereby lifting itself. Apart from the debunked myth, could this be the basis of a propulsion system, say for LTA craft? I can't find this aspect covered in the articles on Magnetodynamic drives and I wondered what kind of electric power output would be needed to produce useful thrust. Could any power plant create enough push by this means to move its own mass at a useful speed? 203.21.40.253 03:15, 5 November 2007 (UTC)

It's going to have to be about as powerful as a helicopter. It would be hard to charge this amount of air. The demonstation version of this are very light and have the power source unsupported. Once you build something that can support itslef in thin air, it will be easy to move it by tilting to one side. Graeme Bartlett 03:40, 5 November 2007 (UTC)

I believe that Wikipedia has an article on these: Ionocraft. --Carnildo 23:24, 5 November 2007 (UTC)

Thankyou both. I didn't realise "the lifter" was in Wikipedia.203.21.40.253 02:38, 6 November 2007 (UTC)

archeology question about Magan, Sumer's source of copper and diorite

If there are extant copper items from before 2300bc at Ur, could chemistry or nuclear chemistry determine where the ore was mined, provided no mixing of different ores took place in the item?Rich 06:17, 13 November 2006 (UT130.86.14.87 03:35, 5 November 2007 (UTC)Rich 03:37, 5 November 2007 (UTC)

You may be able to check for trace elements to get an idea of the ore used. Graeme Bartlett 03:52, 5 November 2007 (UTC)

It depends on if the copper has been processed. If it was still in ore, elemental analysis should give pretty strong evidence. If it has been processed, some sort of isotope analysis might be your only hope, although as Graem says, analysis of trace elements within the copper might help. But processing might change the element ratios. Although you could always process ore from multiple sources the way you think it was processed in the past and then compare for any differences in isotopes and trace elemental composition (experimental archaeology). That actually sounds like fun to me :) --Bennybp 05:59, 5 November 2007 (UTC)

deoxidizing

how do u deoxidize metals? —Preceding unsigned comment added by 216.103.183.127 (talk) 03:38, 5 November 2007 (UTC)

You could use the method of heating the oxide with charcoal, or coal as in steel manufacture. You could use electrolytic methods, as in zinc or aluminium. On the small scale you may reduce by using a powder of another more electronegative metal, such as aluminium. Graeme Bartlett 03:44, 5 November 2007 (UTC)

Of course, you might want to be careful abound that last one, lest you end up with a thermite reaction. shoy (^words _words) 14:27, 5 November 2007 (UTC)

By the way, "deoxidizing" is usually referred to as reduction. -- 21:08, 5 November 2007 (UTC) —Preceding unsigned comment added by 128.104.112.105 (talk)

How do you control snails in an aquarium ?

Does anyone have suggestions for control of unwanted snail populations in a fresh water aquarium other than chemicals harmful to tropical fish or use of clown loaches, etc. Sugessted to me is the use of aquarium salt which is supposted to be healthy for fresh water fish, but will it control snails in the recommeded concentration suggested for promoting health of fish? This at first seems possibly helpful since we know salt will dry up land snails.74.170.217.65 03:42, 5 November 2007 (UTC)

I would not recommend putting any salt in a fresh water aquarium. Just fish out the unwanted snails by hand or in a little strainer, they can't get away very fast. Graeme Bartlett 03:46, 5 November 2007 (UTC)

Is it impractical to mechanically sort out and remove the mature snails (several times)? Also, why remove them? We allow a reasonable population of snails to grow in our aquarium in order to keep the glass and plants clean, and the action of the fish eating the snail egg masses seems to keep the population of snails in check.

Atlant 17:19, 5 November 2007 (UTC)

Google gives plenty of useful-looking hits for aquarium snail control. —Ilmari Karonen (talk) 19:03, 5 November 2007 (UTC)

question about erotic asphyxiation-a mirror effect?

Since phylogeny can indicate guesses about ontogeny, instead of a bilateral symmetry guess, I want to make a vertical symmetry guess-- Since things in the throat such as the adam's apple get larger at the same time private parts are increasing in size (during puberty), is it possible some of the same or closely related hormones are involved? If so, couldn't whatever structures and types of nerve endings that are responsible for feelings of sexual pleasure exist in the neck region as well as the genital region?Rich 11:02, 25 October 2006 (UTC)--This would not be so different to what can happen to carpal tunnel sufferers (bilateral symmetry here):A person gets carpal tunnel in her right hand from scooping ice cream and decorating cakes at an ice cream parlor, and similar pain and weakness shows up in her left hand, though she hasn't stressed that hand.Rich 03:56, 5 November 2007 (UTC)

I don't think this works at all. There is a link between areas of sexual pleasure and position on the cortical homunculus, but this has little or nothing to do with puberty, in which males are affected noticeably by testosterone in areas such as the throat and genitals. The neck is a pleasure area primarily because (or the converse) it is sensitive, like the lips, face, etc. to the touch. It's very difficult to answer the question because it is hard to understand what you are asking, but I think the answer is going to be no. SamuelRiv 01:38, 6 November 2007 (UTC)

Dilmun and Bahrain,Sumer's apparent Garden of Eden-like myth and paradise for Utnapishtim

If it were a paradise for Utnapishtim, I surmise it might have suffered eco damage or at any rate ecological change since. Is there archeological or fossil etc. evidence that the island was previously more lush?Thanks,Rich 20:25, 6 December 2006 (UTC)Rich 04:07, 5 November 2007 (UTC)

decomposing

what happens when a mn oxide decomposes in water? —Preceding unsigned comment added by 216.103.183.127 (talk) 04:31, 5 November 2007 (UTC)

Mn oxides tend to go to MnO₂ when exposed to water and air. Mn₂O₇ is a strongly oxidising substance. Graeme Bartlett 04:55, 5 November 2007 (UTC)

bicycle transportation system

I was checking out some proposals for alternative transportation systems and came across this one - BTS's Transglide 2000. [9] Basically, it's an elevated, enclosed tunnel for cyclists, that uses fans and ducts to move air in the direction of travel at speeds about 30 km/h (although it is not actually specified). The point being that this huge reduction in wind resistance will allow riders to travel quite quickly while expending little energy, due to 90% of total resistance being attributable to wind resistance while travelling at 33 km/h. It sounds very interesting but it seems the main issue would be the huge amount of friction between propelled air and the tunnel walls, and the relatively large size of the tunnel and therefore large volume of air, requiring a prohibitively large use of energy (although as a proposal for a mass transportation system this energy usage should correctly be compared to vehicle or rail travel, not to standard bicycle travel). So my question is, can anyone with a good knowledge of mathematics/physics figure out exactly how much friction would play a part in this case? 220.34.254.226 05:22, 5 November 2007 (UTC)The dimensions of the tunnel are about 3.6 m by 4 m.

If you have gone all the trouble of building enclosed tunnels around places you might as well build a personal rapid transit system. It would not have any of the problems of the fans, and the rolling resistance is considerably lower, thus uses less energy. The only problem is that it's still "young technology" and the cost of building all the tracks around cities. --antilived^{T | C | G} 07:03, 5 November 2007 (UTC)

What's wrong with the idea of climbing into a capsule, pulling a lever and letting air tube conveyor system whisk you right to your desk at the office while you finish putting on your lipstick or brushing your teeth? Dichotomous 19:54, 5 November 2007 (UTC)

Beyond the universe theories.

What are the latest theories as to where outer space, beyond the known universe, leads to, and if it leads to infinity, what is infinity? Can the answers ever be obtained through science and our human senses, or do the answers lie in some other, i.e. spiritual or such, dimensional sense which we currently can't perceive? And are there any recent theories that maybe matter (universe) maybe doesn't really exist, and that reality is actually a concept not created by our human brains, but rather, again, a concept unfathomable by humans who in turn may not actually exist as we perceive ourselves by our "restricted" senses and resources? —Preceding unsigned comment added by 68.10.91.102 (talk) 06:25, 5 November 2007 (UTC)

Many of your questions seem to touch on topics that fall under the branch of philosophy called epistemology that aims to answer questions such as "What is knowledge?", "How is knowledge acquired?", and "What do people know?". I think that article and the empiricism article would be good starting points for your further reading in this area. The topic of infinity and whether or not it exists in this universe is covered in physical infinity and Shape of the Universe. Sancho 06:59, 5 November 2007 (UTC)

There's also a good course available online for free through MIT OpenCourseWare on the theory of knowledge: [10] Sancho 07:03, 5 November 2007 (UTC)

Science can't answer those questions, because it can only study what can be observed and measured; but it can provide some ideas. Here are some that you might enjoy reading about: Multiverse, Many-worlds interpretation, String theory landscape, Chaotic inflation. These are all ways that our observable universe might be embedded in something larger. I'm not sure what you mean by the question about the universe not existing; perhaps something like The Matrix? Religion and philosophy can also provide answers to these questions. My religion teaches that reality is indeed real, and that the universe was created by a God who exists outside of it and independently of it. God could be described as infinite in some ways. In cosmology, the observable universe is finite in size and age, and has a limited life span. There have been proposals for how to cram an infinite amount of experience into a finite universe (see Omega point (Tipler)), but those have not been widely accepted. --Reuben 07:20, 5 November 2007 (UTC)

There is little if any physical evidence for there being anything "outside" of the universe, so questions about what if anything may lie outside of the universe aren’t solidly within the realm of mainstream science. Science generally only seeks to explain observable phenomena, and the mainstream views of scientists tend to be the simplest possible explanations of those phenomena. The guiding principle here is Occam's razor, which states that that the simplest possible explanation is the one that’s the most likely to be correct. A model of reality which includes there being something outside of the universe is more complicated than a model of reality that doesn’t, so an explanation that involves there being something outside of the universe is an explanation to be avoided if possible. If at some time in the future, some phenomena are observed which are very difficult to explain unless there’s something outside of the universe, then questions about details of the nature of what exists outside the universe could become a solid branch of mainstream science. There is no way of knowing for sure whether that will happen or not, but the simplest guess (and therefore the guess that according to Occam’s razor is most likely to be correct) is to assume that it won’t.

As to whether knowledge about whatever may lie outside of the universe can be achieved spiritually, Occam’s razor says no. There is no good experimental evidence which is simpler to explain by assuming that non-physical "spirits" exist, so the simplest explanation is to assume that spirits don’t exist.

As to the possibility that the universe doesn’t really exist, believing in such a possibility isn’t a very scientific outlook. It’s simplest to assume that the universe really does exist, so Occam’s razor says that we should just reject any notion that the universe might not really exist, unless and until there are some observable phenomena which are very difficult to explain without assuming that the universe doesn’t really exist. MrRedact 09:06, 5 November 2007 (UTC)

May matter (universe) possibly not exist as we perceive it? Matter, dissected to its smallest part, is really energy (matter-atoms-strings ?), which cannot be seen by our human senses. Do humans only "see" this energy in the form of matter because our senses are restricted? Would a more advanced life form see physics more accurately than we, possibly "see" "matter" and universe as energy waves or something more profound? Would a more advanced perceiving life form see the actual meaning of "reality" in a much clearer (spiritual even) light, if, as is almost certain, there are aspects to physics that humans have not yet perceived?

Possibly, with consideration of extra dimensions and exotic matter, there could be life that perceives an entirely different (but not unknowable) universe than us. And we don't yet know the mechanism of choice in quantum probabilities, so there might be a world or dimension outside our own that shows a more deterministic scenario. You can speculate forever, but just remember that in this universe, our perception is limited by the nature of matter and energy--to observe, you must disturb--therefore there are fundamental limits to what anything can "know". SamuelRiv 15:24, 5 November 2007 (UTC)

I can't quite agree with "matter is really energy," since energy is one property that matter can have, but it doesn't tell the whole story. However, it is certainly true that we don't have an established, fundamental theory of everything. But I don't think that means that the reality we see is any less real; that would be a sort of hyper-reductionism that needlessly throws away the complex, aggregate nature of things on the large scale. Ten thousand years ago people could look at a flock of seagulls, without knowing anything about cells, organelles, molecules, atoms, baryons, electrons, quarks, strings, or quantum gravity. Today we have learned a lot more about those things, but the flock of seagulls is no less real for it. --Reuben 19:26, 5 November 2007 (UTC)

Could fat cells be originally, very long ago, cancer cells that made a deal?

After all, we now know that chloryphyll made a deal. Many parasites evolve to be less damaging, sometimes even symbiotic. Why not cancer too? The way fat cells are is reminiscent to me of cancer cells.Rich 06:42, 5 November 2007 (UTC)

I believe you mean chloroplasts. Incidently, mitochondria are also believed to be derived from captured bacteria-like organisms. However, both organelles have their own DNA and are transmitted as organelles from mother cell to daughter cell. Fat cells are like any other cell in the body and develop from normal stem cell precursors. The answer is no. -- Flyguy649 ^talk 06:51, 5 November 2007 (UTC)

• • Yeah, I did know about mitochondria. What I was thinking was if bacteria etc get co-opted, which are "foreigners", why can't a "homegrown traitor" or "rebel" like cancer? You can't be saying that cancers haven't ever descended from stem cells?Thanks,Rich 07:01, 6 November 2007 (UTC)

Out of curiosity, what about fat cells reminds you of cancer? Someguy1221 07:15, 5 November 2007 (UTC)

• a lot of things that i've been reading about, some of which i can't remember right now. One thing is how independent they seem. They choose to multiply when they're ready, w/o much control from elsewere. It seems they don't get culled often either.-(What is it called, when the body tells a cell to die?)I have heard fat cells send out "chemical signals" that initiate cancer elsewhere, like "weapons" it still has from an earlier time, and hasn't been disarmed or sufficiently reformed. An animal needs to use fat whether it wants to or not because of what it does--all other animals have it so like in an arm s race, it has to have it as well.Thanks,Rich 07:01, 6 November 2007 (UTC)
  • After chatting a bit, i remeber one big point: Fat is so uncomplicated, maybe the word should be "undifferentiated", like cancer cells. Can we thing of fat as an organ? Not that often I bet. At any rate it's less organlike than most things in an animal's body. Organs like bones sound so incredibly complicated and interact with stuff elsewhere much more than fat does.Rich 07:33, 6 November 2007 (UTC)

    If there is any link, I'd expect it to be the other way around: perhaps some of the genes that get accidentally turned on when a cell becomes cancerous are normally expressed by fat cells. Or not; this is all just blue-sky speculation. (By the way, the word you're looking for above is apoptosis or, more generally, programmed cell death.) —Ilmari Karonen (talk) 19:47, 6 November 2007 (UTC)

Did someone say midichlorians? Lanfear's Bane | t 10:19, 5 November 2007 (UTC)

There's an extensive six-part documentary on them. -- Flyguy649 ^talk 15:28, 5 November 2007 (UTC)

Fat or lipid has been an essential part of life for all the living forms, cells use lipids in their cell membrane to create a waterproof partition. So if you want to look for a time without fat in life, it would have to before the appearance of cells. Graeme Bartlett 20:42, 5 November 2007 (UTC)

• Yes, but I mean about fat cells, not merely lipids. Are fat cells, or some related thing or precursor, ever in plants? ThanksRich 07:01, 6 November 2007 (UTC)

Some plants have oil in them. If you think about all those oil seed crops that you get vegetable oil from, peanuts, palm oil, rape seed, avocado, olives, coconut. There are even algae that produce oil as a storage, and it is believed that these are the source of petroleum. These are not a plant cancer, but a way to store energy in a compact way. Some may use it as a float. Graeme Bartlett 20:48, 6 November 2007 (UTC)

Helicopters in the rain

Moved from the Humanities Desk

What are common effects and problems encoutered by helicopters when flying in the rain and how does it affect the handling? Keria 18:16, 4 November 2007 (UTC)

This is not really a question in the area of the Humanities (history, politics, literature, religion, philosophy, law, finance, economics, art, music, and society). A better spot to ask may be the Science section of the Desk.  --Lambiam 20:55, 4 November 2007 (UTC)

The problem with flying a helicopter in the rain isn't so much the rain itself as the associated conditions. Poor visibility and potentially high and unpredictable winds make such operation dangerous, and most users opt to not fly in such circumstances. There's not a real concern that rain significantly diminishes the airworthiness of a helicopter, though. — Lomn 15:08, 5 November 2007 (UTC)

Jet engines are also designed to handle high levels of moisture and rain. Dichotomous 19:14, 5 November 2007 (UTC)

I think helicopters actually fly better in the rain since the air is usually of higher pressure.--Dacium 03:15, 6 November 2007 (UTC)

No, the air is usually of lower pressure. Icek 04:33, 6 November 2007 (UTC)

Think mechs will ever be used on the battlefield?

Think they can be practical? I think something smaller like powered armor (which is worn rather than piloted) or a smaller type of mech like the ones from Heavy Gear would work well if they moved as well as humans do. I guess the big advantage of bipedal armor over tanks would be their agility and all terrain movement. If made too big, those advantages would be diminished, but if kept small, they could work. 64.236.121.129 14:48, 5 November 2007 (UTC)

According to the dispersion theory of Trevor N. Dupuy in his attempts at quantifying the history of warfare (this guy is my hero of the social sciences), the answer would probably be no. It seems future wars (the theory only works for a total war scenario) require increased dispersion of manpower until battles are won entirely by nontraditional subversive techniques, with traditional manpower kept only to keep a check. That's just my interpretation of an extension where the theory breaks down (it approaches a singularity in the last 50 years with H-bombs and modern smart bombs). And then, of course, any electronic devices are extremely vulnerable to wear and tear and electronic warfare, which makes the high-tech soldier of the future seem very unlikely in my opinion. SamuelRiv 15:17, 5 November 2007 (UTC)

Umm, you have to define what you mean by "nontraditional subversive techniques", that doesn't mean much by itself. The "singularity" point is also meaningless. You have to clarify. I'm not sure how PA or small mecha are any more vulnerable to wear and tear than your average tank or vehicle. 64.236.121.129 15:24, 5 November 2007 (UTC)

I once read a story (I can't remember the name) about a galactic federation (or whatever) that lost a war because it's weapons were too high tech. --MKnight9989 15:32, 5 November 2007 (UTC)

What does that have to do with anything? Stay on topic please. 64.236.121.129 15:39, 5 November 2007 (UTC)

It goes along with what Samuel said about electronic devices being prone to failure. It's possible I suppose, but it seems like something that complicated would be difficult to 'soldier proof' --MKnight9989 15:42, 5 November 2007 (UTC)

Yea, I thought I addressed that already. 64.236.121.129 15:47, 5 November 2007 (UTC)

MKnight9989, you thinking of Star Wars? Ewoks with sticks. Yub yub. AT-ST problems? Get some tree trunks. Yeh, Yeh gira. Lanfear's Bane | t 15:53, 5 November 2007 (UTC)

In all fairness, those walkers were crap to begin with. They were too big, and their movement was too static. They used gears and motors for leg movement. That's crap. Yes, they can walk, but they weren't agile, and couldn't move like a human or any other legged animal. Muscles need to be emulated properly in order to take full advantage of legs, and their full range of motion. If they were smaller, and moved like a human or even a horse, they would have been great. The chicken walker leg is also worthless for all terrain movement. 64.236.121.129 16:10, 5 November 2007 (UTC)

Yeah I think the All-Terrain was a slight exageration. AT-AT's were more stable (not a horse pun) and they didn't fare much better. Damn Snowspeeders. Rebel Scum are nothing if not innovative. Lanfear's Bane | t 16:16, 5 November 2007 (UTC)

The story you're thinking of is probably Superiority (short story) by Arthur C. Clarke. Clarityfiend 17:56, 5 November 2007 (UTC)

The question is what kind of battlefield you are imagining. The late-20th century has not been characterized by wars of high-tech powers against high-tech powers; rather it is generally either high-tech powers against low-tech powers or low-tech powers against low-tech powers, if I can be very, very broad in my strokes. The last real war where all of the major participants were at a similar stage of high military technology was maybe the Korean War, maybe World War II, depending on how you categorize things.

In any case, let us think about the advantages and disadvantages of these approaches. Bi-pedal locomotion is indeed able to deal with more terrain, but it is generally much slower than wheeled or tracked locomotion. Personal mechanical armor is probably most effective against small arms fire; large bore fire or heavy explosives of any sort are going to tear limbs off or apply massive concussive force to the interior with great ease.

Now if we imagine a future generation of robotics far more advanced than what we have, where we are basically replacing humans with mechanical 'droids, then I could definitely see that as a political advantage although I am not sure about its military advantage. An army in which no soldiers have to die is one that can be deployed with far less problem of home-field protest, although the cost differential is going to be pretty unpleasant versus training a soldier and deploying a high-tech robot. But cost-differentials, of course, are not taken into much account even today—when we reply to car bombs with cruise missiles, we are spending billions of dollars to reply to a weapon that cost at most a few thousands dollars, at least almost nothing (here I am thinking of the African embassy bombings of the late 1990s which were replied to with about $2 billion worth of cruise missiles).

Anyway, just some things to think about. Is it possible? Maybe. But remember that we're probably not going to see two very high-tech superpowers go head-to-head anytime soon. So who is going to buy these robots, and who is going to deploy them, and where? The US already has high tech weapons it can't really use effectively; at the moment "mechs" strike me as not being terribly desirable for modern warfare. --24.147.86.187 15:53, 5 November 2007 (UTC)

Aren't the US already using guns mounted on tank-type tracks which are armor plated and remote controled in Irak? 80.200.238.237 16:36, 5 November 2007 (UTC)

I am not sure, but in the Misc. desk recently we were discussing motion sickness et al and someone mentioned that soldiers remote operating from a trailing vehicle quite often felt ill due to the different sensory inputs [11]. And K and use a Q 80.200 boy. Lanfear's Bane | t 16:45, 5 November 2007 (UTC)

You also have to look at the issue from the logistics side of things. Tanks are relatively short in stature (M1A2 Abrams), whereas I'm a 'mech' would have to be relatively tall to be effective, making it more difficult to transport and deploy. --MKnight9989 13:12, 6 November 2007 (UTC)

Wow, it's so hard to talk to people who don't read your posts. Read my first post then realize why your post is irrelevant. I hate repeating myself 50 billion times. 64.236.121.129 14:59, 6 November 2007 (UTC)

I'm curious to see what advantages you think a mech would have over modern equipment, such as tanks. The army has been experimenting with powered armor, or at least researching it. I think that would be much more feasible then a mecha for a number of reasons. Your question is, are mecha practical. I think the answer is no, because the potential advantages do not outweigh the certain costs and pitfalls. Again, I would love your feedback as to what, exactly you think would be better about a mecha as opposed to a tank, or a soldier in combat armor. dcole 13:44, 8 November 2007 (UTC)

theoretical yield

How do I figure out the theoretical yield of a substance? --MKnight9989 15:10, 5 November 2007 (UTC)

Sounds like homework. Here's a hint: think about how much reactant you need, and how much you have, and try to maximize the amount you can get from your reaction equation. In short, multiply both sides. SamuelRiv 15:19, 5 November 2007 (UTC)

I know how much reactant I have and how much product I end up with (actual yield), but I don't understand what calculations relate the two to theoretical yeild. --MKnight9989 15:37, 5 November 2007 (UTC)

Theoretical yield is how much you get if everything go perfectly, everything reacts, and reacts the way it's supposed to (Yield (chemistry)). Someguy1221 16:22, 5 November 2007 (UTC)

Amazing little horned garden spider

What kind of amazing little horned spider is this? Found it. Spiny orb-weaver

In addition to its horns its web has UV reflective tuffs and its web is attached to Earth at three points:

1. branch of tree; 12 feet from ground,
2. middle rail of fence; 2 feet sideways and 3.5 feet from ground,
3. near end of stacked pipe; 10 feet from attachment point 1 and 7 feet from attachment point 2.

Attachments are anchored at each point by 2 to 5 strands. Orb is only 9 inches in diameter.

Second question... How did this little spider reach these three different attachment points? I can see maybe wind to the tree branch and to one of the other attachment points but what about the 3rd? Did the spider crawl all the way back up the tree branch after the first attachment and then go for the second, or what?

Dichotomous 15:51, 5 November 2007 (UTC)

I'd love to see an insect-person to back this up, but I had heard that they throw some silk into the air, and just hope it grabs on to somewhere useful. --Mdwyer 22:02, 5 November 2007 (UTC)

Spider silk is extremely thin, and thus has high wind-resistance (compared to its mass). That would make throwing silk an unlikely scenario for long distances, as it would slow down incredibly fast. It would also make it hang at very opposite of steep angle, so it could conceivably just get two threads grounded, then suspend itself on a piece of silk and get blown to the side. This is all speculation, though. — Daniel 01:59, 6 November 2007 (UTC)

From the spider web article: "The spider effectively utilizes the wind to carry its initial adhesive thread. With some luck the silk is released from its spinners and carried by the wind to a suitable adherable surface. When it sticks to a surface the spider will carefully walk over the thread and strengthen it with a second thread." -- MacAddct  1984 ^{(talk &#149; contribs)} 05:56, 6 November 2007 (UTC)

Which is the best alternative to gasoline for cars, hypothetically

I don't mean right now, but in the future. From what I read of the articles, I think battery-electric cars potentially are the best. They have the best efficiency when you think of it from taking energy from a nuclear powerplant, then shooting that energy into a battery. Stuff like hydrogen, requires making hydrogen which is inefficient.

In terms of using that energy, I read that battery electric cars are equivilant to say 100-200 miles per gallon, if do all the conversions and compare them to ICE cars.

They don't use any explosive liquid like hydrogen or gasoline, although the batteries can explode possibly... Still, I think they are safer.

Batteries can have good performance, 0-60 in 4 seconds, top speeds of over 200 miles per hour. I'm sure these stats can improve in time too. Range right now is a problem I think though. 200-300 miles is the best ranges I heard for some good Bat cars. ICE cars tend to have a range of 400 miles on a full tank of gas. I think with improvements in batteries, Bat cars can be extended to 400 miles though.

Bat cars are quiet.

Bat cars release no emmisions.

Bat cars benefit from regenerative braking.

Maybe the only negatives would be, they are harder to repair (but I think that has more to do with stupid mechanics who are only knowledgable on ICE cars), more expensive (although in the long run, it'll be less expensive, and ICE cars perform better in extreme temperatures like extreme hot or cold.

What do you peeps think of my assessments? 64.236.121.129 16:06, 5 November 2007 (UTC)

...and just how did you come to these assessments? Dichotomous 16:12, 5 November 2007 (UTC)

From the articles dude. 64.236.121.129 16:16, 5 November 2007 (UTC)

dude...? Dichotomous 17:29, 5 November 2007 (UTC)

"some good Bat cars.". See Batmobile. Lanfear's Bane | t 16:18, 5 November 2007 (UTC)

peeps... Clem 16:26, 5 November 2007 (UTC)

Quick thoughts: I don't think the inefficiency of making hydrogen is a big deal if you're supposing widespread clean nuclear power. I find it a more relevant objection if you're burning tons of dirty fuels to manufacture clean fuels. Quiet (to the degree of electrics) is a debateable benefit. The hearing-impaired community is already concerned by Priuses and the like, and I feel that modern cars are quite capable of being generally quiet so long as their owners don't modify them to be noisy. Emissions are no more a concern with hydrogen than electric, and any hybrid system benefits from regenerative braking, too. Finally, your discussion about range omits a key point. A tank-fueled car, regardless of single-tank range, can just refuel in five minutes. An electric car cannot. Consequently, "range" means entirely different things for the two car types. — Lomn 17:01, 5 November 2007 (UTC)

Why waste energy with inefficiencies? Why bother when there is a more efficient alternative? You're just wasting energy that could be used otherwise. Quiet is just a nice bi-product. I don't think we are going to go out of our way to make noisy cars just for the hearing-impaired, that's just silly. What would be the point anyway? They want loud cars so they can hear them? That's stupid. Yes, modern cars can be quiet, but they also use gasoline, which is the problem isn't it? Remember what we are talking about dude. Yep, hydrogen produces no harmful emissions, but they are worse because of the inefficiencies I mentioned before remember? They also require platinum in their engines, which drives up the price, and makes increases the demand for platinum, thus raising its price. Such a scenario can be avoided with batteries. Yep, any hybrid can benefit from regenerative braking, but so far all of your points merely match the capabilities of a Bat car, rather than exceeding them. That's what we are talking about here, the best of the alternatives.

Recharge times are gradually improving, with some rechargers capable of recharging spent batteries in minutes. But there are also ways around that like recharging over night at home while you are sleeping, or having recharge stations at offices. If all you do with your car is drive to work, and it's a reasonable distance, you can just recharge at home overnight. But yes, recharge time is an issue, but it's an issue that can be improved. 64.236.121.129 18:11, 5 November 2007 (UTC)

The question of inefficiency is "does the inefficiency matter?" If you're assuming widespread clean nuclear power, then my answer is "no". I think, given that supposition, hydrogen is a perfectly viable fuel and far easier to engineer than superquickcharge batteries. If battery charge times are on par with other refuel times, then sure, it's a great solution -- I'm just not prepared to make that leap. You're dead-on with overnight chargers being adequate for the vast majority of car use, but I find the idea of a car that does what I need 95% of the time but cannot do what I need for the other 5% (e.g. long range driving) to be an unacceptable car. Additionally, there's the problem of battery space and weight with pure-battery cars; hybrids are significantly more efficient in those terms. As for my points matching those of battery cars, yes. That was exactly my point -- to note that a battery-only car does not hold exclusive advantages in those regards. — Lomn 18:23, 5 November 2007 (UTC)

Two things, we don't have widespread clean nuclear power, so we still have to be realistic about where our energy is coming from. And second, even if we did, it's still a waste of energy, so why bother waste it with inefficiencies when hydrogen cars do not have any benefits over Bat cars? You are making a really big assumption when you say hydrogen is a viable fuel and far easier to engineer than batteries. You gotta back that up. Otherwise that's just a blank, meaningless statement.

Battery space and weight doesn't matter if the performance numbers are still good. The numbers I gave before are for real Bat cars. Hybrids are significantly more efficient in those terms you say? What the hell does that mean? You gotta clarify your points dude. You are making a lot of blank, empty statements that don't really mean anything.

Yep, but I never said bat cars hold exclusive to those advantages did I? So you are arguing a strawman here. What I'm looking for is, what do the other ICE alternatives have over Bat cars, if anything. The recharge issue seems to be the only thing you can think of, but that's already being addressed. 64.236.121.129 18:36, 5 November 2007 (UTC)

Re: space/weight: have you ever seen how little cargo space remains in an all-electric car? It's preposterous! Hybrids require a far smaller battery pack; thus, they are more efficient in that regard. Aside from that, this looks like another case of you expecting to have your assumptions parroted back to you. A nuclear electricity source (which you originally suggested) is too-forward-thinking, a lack of quick-recharge isn't forward-thinking enough, even though it's already "being addressed" -- whatever that means....

Clearly there's no legitimate request for commentary or criticism here. — Lomn 19:09, 5 November 2007 (UTC)

Hmm, what kind of cargo do you want to haul exactly? I don't think the average person needs to haul much stuff usually. I'm mostly talking about transporting people, and most people just use their car to get to work. Fair enough, a hybrid might carry more cargo, but that's it really. Aww, you're mad again. Well that's your option ^^. 64.236.121.129 19:34, 5 November 2007 (UTC)

I drive a MINI Cooper - for a while it was the smallest car you could buy in the USA. People continually ask me how I manage without the storage space. I point out that the volume of the trunk is about 20% bigger than a large-sized Kroger shopping cart - I measured it to be sure. So when you go to the store - if it fits in the cart, it'll fit in the trunk. Then of course you can fold down the back seats and get tons more space. I think people always assume they need vastly more space than they actually do. The times when difficulties arise are when I need to buy an awful lot of wood from the DIY store - or take the entire family on a camping trip. But ask yourself just how often you ACTUALLY do that. I reckon 10 times a year...tops. So I rent a larger car from Hertz - or I make use the honking great truck that Home Depot will rent you for $18 for a couple of hours if you spend $50 or more at their store. Yeah, this costs money - but the fact that my car is using half the amount of gas on the other 355 days of the year totally annihilates any consideration of that. Lots of people I know with two kids have a 7 seat SUV. When I ask why, they claim to have to transport the kid's friends on occasions...OK...but you own two cars - take both of them! Again, there are plenty of creative ways to handle the RARE occasions where you need more than 4 seats and more than a shopping-cart-worth of luggage space. The more people who did this, the cheaper it would be to rent bigger vehicles when you needed them. Something like the Zipcar approach is what we need here. A group of 100 families living in the same neighbourhood could comfortably share the ownership, maintenance and depreciation of (say) a half a dozen SUV's and half a dozen pickup trucks - and have each family own their own dinky little SmartCars and MINI's for commuting and light shopping trips. SteveBaker 04:21, 7 November 2007 (UTC)

Since you asked for a hypothetical future solution, I vote for a very small fusion reactor driving a Sterling engine driving an electric generator, in turn driving one electric motor per wheel, with supercapacitor buffering to account for peak accelleration and regenerative braking. No pollution except for heat, and no need to refuel for the life of the car, service interval limited by wear on the tires. -Arch dude 17:45, 5 November 2007 (UTC)

I'm assuming you are being facetious, but I'll address it anyway. Too expensive, and we also don't have practical, working fusion reactors, let alone one small enough to fit in a car. This is something that might happen in 1000 years, rather than the foreseeable future. 64.236.121.129 18:11, 5 November 2007 (UTC)

Too expensive? My hypothetical micro-fusion reactors can be had 3 for a dollar at Sam's Imaginary Energy Emporium. On a more serious note, if we did have practically limitless, cheap, clean energy, there are many other technologies and products that would suddenly become very cheap as well. Dragons flight 19:06, 5 November 2007 (UTC)

Yea, but who's talking about limitless energy? We are talking about alternative power sources for cars. 64.236.121.129 19:34, 5 November 2007 (UTC)

Some work is being done to breed organisms that can ferment an entire maize plant into ethanol, instead of just the kernels. That could make ethanol much more attractive than it is today. --Gerry Ashton 22:25, 5 November 2007 (UTC)

Nuclear fusion is far from being a clean or safe energy source anyway. It may be a bit cleaner and safer than fission, but it's still not something you want in your car. One of the arguments against Pons and Fleischmann's claims of cold fusion was that if it had really been fusion they'd both have been killed. -- BenRG 17:16, 6 November 2007 (UTC)

Going back to the original question, do you (64.236.121.129) want to back up those two assertions "batteries have the best efficiency" and "making hydrogen is inefficient"?

Batteries are horribly inefficient. They're heavy, they take time to charge, they're limited in their discharge rate, and they have a finite number of charge/discharge cycles. Also they can be dangerous, can require large amounts of energy and toxic chemicals to manufacture, and can be difficult to dispose of.

Even if you assume a perfect battery, charging it with plant-generated electricity and then discharging it in an electric car is precisely as efficient as manufacturing hydrogen using plant-generated electricity and then burning it in a hydrogen-fueled car. If the batteries are anything less than 100% perfect, hydrogen is more efficient, not less. —Steve Summit (talk) 03:12, 6 November 2007 (UTC)

Uhh no, I don't wana back up those assertions because I'm not having a debate. I just wana know what people think is the best alternative to ICE cars. I'm just going on what the article on bat cars says. It said that bat cars are far more efficient than hydrogen cars when you take into account the inefficient process of making hydrogen.

Those are some fair points, but you need to clarify a few things. Yes they are heavy, but how does their total weight compare to an ICE engine or Hydrogen engine? I'm assuming they are all quite heavy. Charge time is certainly an issue, but some of the newer bat cars have very good charge time. What do you mean by "discharge rate", I don't understand that. Yes, charge/discharge cycles can be an issue, but I heard that this can be solved simply by leasing the batteries rather than selling them. You simply return them for new ones, once they run dead.

Huh. That's not what the article on bat cars says. It says the process of making hydrogen is less efficient. Read the article then get back to me. 64.236.121.129 14:56, 6 November 2007 (UTC)

Sorry, which article? —Steve Summit (talk) 19:40, 6 November 2007 (UTC)

Exactly. You have to remember that the electricity to charge these battery powered vehicles has to come from somewhere. If you cut all of the pollution from cars, but end up making even more pollution at the power plants you'd need to power all those cars, you're actually worse off in the end, not better. Keep in mind that you're wasting the power that is lost in an inefficient conversion from fuel to electricity, during transmission, electricity to battery, during storage, and battery back to electricity. Unfortunately, going directly from gasoline is currently much more efficient. Hopefully battery research will help solve this problem, but progress in this field tends to be quite slow. Keep in mind that the batteries themselves pose pollution risks, and need to be disposed of properly as well. You have to look at the whole process from start to finish to determine what pollutes less. The "best" alternative to cars depends on the situation, but walking or taking a bike are both good alternatives in some cases. -- HiEv 04:01, 6 November 2007 (UTC)

Hmm, not all power plants pollute. Nuclear power for example. Yes we use mostly coal right now, but at least the possibility exists for clean alternatives that provide vast amounts of power. Huh? That contradicts what the article on bat cars says dude. The article says that bat cars are much more efficient. Didn't you bother to read it? It says that the process of sending energy into the battery is about 80% efficient. Then from there, the use of that energy is equivilant to about 100-200 miles per gallon. That's what the article says dude. Don't blame me, blame the article if it's wrong. Batteries can be recycled though.

I think that this discussion is turning into an attack on bat cars which is not what I intended. I was asking what do the other ICE car alternatives have over bat cars. This, first and foremost, is what I'm interested in. 64.236.121.129 14:56, 6 November 2007 (UTC)

No, "the article" (by which I'm assuming you mean battery electric vehicle) says that almost half the energy is lost simply due to inefficiencies in battery charging, and I don't see it claiming it's "80% efficient" anywhere (which would contradict the part I just pointed out.) The article does not include the efficiency of the original creation of that electricity nor the loss during transmission either. Coal is normally converted into power at about 36-38% efficiency (see here), about 7.2-7.4% of that is lost in transmission (see here), and half of that is lost in charging, which (if I calculated it correctly) means you're at about 17.15% fuel efficiency at that point. Gasoline engines have about 30% efficiency and diesel engines have about 45% efficiency (see here). The efficiency of BEVs is much higher than gasoline or diesel if you ignore the initial loss at the power plant and in transmission, but I don't think that's a fair comparison because it basically assumes the electricity is created with 100% efficiency. So, in terms of fuel efficiency, which is what I was talking about, diesel wins by a wide margin. However, coal/electricity is much cheaper than gasoline currently, so a BEV is more efficient economically speaking, in terms of miles per currency unit. But remember supply and demand, if everyone switches to BEVs, power demand will go up, and electricity cost will most likely to go up with it (probably driving down gasoline costs as well.) Also, that does not include the added initial expense of buying a BEV vs. a gasoline/diesel vehicle, so it might take a while before you reap any economic benefits. In the end, I guess it all depends on what kind of efficiency you're talking about and how you calculate it. (Note: I have a nagging suspicion that I made an error somewhere in this, but I just can't put my finger on what it is.) -- HiEv 22:43, 6 November 2007 (UTC)

We're not "attacking" battery-powered cars; we're just issuing a few sober pronouncements on their imperfections. This is the Science desk, and we have to treat things as they are, based on logic and evidence, not on how we wish they were or what sounds nice, based on emotions.

The big problem is -- and I'm speaking here as a scientist, not a Detroit-apologist -- is that from most standpoints, cars powered by internal-combustion engines fueled by liquid hydrocarbons are extremely good. The energy density of gasoline is extremely high, the engines can be built compactly and cheaply, and the fuel is just sitting there in the ground (so to speak).

There's a reason we're all driving gasoline-powered cars, and it's not some kind of shady conspiracy. It's simple scientific and economic fact.

So when you ask, "what do the other internal-combustion alternatives have over battery-powered cars", there are two problems with the question: (1) there aren't really any other alternatives, and (2) in most respects, the battery-powered cars don't have anything over the internal-combustion ones, either. We can't agree with you that batteries are the best alternative to gasoline, because they aren't a very good alternative. We can't tell you what we like better, because there isn't anything better.

(Now, before seventeen rabid environmentalists descend en masse and rip me a new one for daring to suggest that gasoline-powered cars are "good", hold on. Don't get me wrong; I'm a rabid environmentalist, too. Of course I understand that sucking that nice energy-dense liquid fuel up out of the ground isn't sustainable. Of course I understand that the emissions are ruinous. But I also understand that providing individualized transportation any other way is a really, really hard problem. Just having every driver on the planet buy a Prius or an EV1 ain't gonna solve it. An earthshaking revolution in the energy density, rechargeability, and weight of batteries would help solve it, and I'm hoping for that revolution, too, but I'm not sure we can count on it.) —Steve Summit (talk) 02:53, 7 November 2007 (UTC)

The problem with the future of cars is how to get there from here. Electric cars could work if we had a non-polluting source of electricity with enough capacity - but we don't - yet. Even if we did have enough solar/wind/tide/hydro/nuclear power, we have a problem with the technology. We can't cram enough batteries into a car to make it go far enough between recharges - and recharging takes FAR too long.

However, problems of range could be solved if we wanted to. Batteries could be mounted on a little cart that you pulled out from the back of the car and exchanged for a fully charged set at battery exchange garages along the side of the road. Every couple of hundred miles, you'd pull into a battery station - pull a lever to drop the battery cart out onto it's little wheels, pull it over to the attendant who would swap your dead batteries for a freshly charged set and charge you whatever the going rate is. The battery packs would belong to some national chain who would have stacks and stacks of them 'out back' recharging. Having to 'refill your batteries' would take about the same time as filling up your gas tank and you'd have a similar range between stops. But until such things exist, we can't do that - and until we do that, such things can't (economically) exist. So (annoyingly) that won't work. Similar problems exist with hydrogen powered cars. So that won't happen either.

Reluctantly, I think plant-based ethanol is the way forward. It uses all of our existing technology - the same gas stations, most of the same cars - it's even been proven on a large scale in Brazil and it definitely works. The only problem is that we're using corn to make the Ethanol with and that's a REALLY stupid idea brought about by US politics and the farming lobby. We need to use more efficient plants - that we can use nearly 100% of the plant to do the production with. There are promising kinds of plants but because all of the research money is going into corn-based ethanol, that's not going to work either. Heck we've even raised tariffs to prevent the more efficient sugar-cane-based ethanol from being imported! Anyway if we can use the right plant, this is a carbon-neutral way forward that fits with the distribution networks we have.

Mostly what we need is more efficient cars. My car is not a hybrid - it's a MINI Cooper - and it gets 40 miles per gallon - it's fast and it's comfortable and it's fun to drive and it'll go 140mph. The new version does even better MPG because it does the 'stopping the engine when at a stop light' thing. The next generation after that gets a form of regenerative braking where the initial accelleration of the car from a stop is driven by the starter motor until the energy stored from braking is used up and the main gas engine starts - that'll get you 50 to 60mpg in city driving without messing around with batteries and hybrids and such. We need to get rid of the 20mpg cars and trucks that are being driven by commuters - that's just insane. If everyone who drives a 20mpg car were to buy a 40mpg car the next time they buy something new, we'd have HALVED the problem of automotive pollution within 5 years. Instead, we have new "Hybrid technology" SUV's and trucks that claim 26mpg...geez...well, that helped a lot!

SteveBaker 18:27, 6 November 2007 (UTC)

So did anyone ever figure out which article 64.236.121.129 was talking about that alleged that "the process of making hydrogen is less efficient"? —Steve Summit (talk) 21:18, 7 November 2007 (UTC)

Stiff neck

Is it possible to insert structures into the neck to prevent strangulation? Has it been done before? 81.242.90.27 17:42, 5 November 2007 (UTC)

I don't know, but wouldn't it be easier just to wear a suit of powered armor if it's such an issue? 64.236.121.129 18:41, 5 November 2007 (UTC)

Oh. Then no-one wouold try to strangle you. It's for James Bond. 80.200.239.55 19:35, 5 November 2007 (UTC)

Slightly off topic, but we did exercises in Kung Fu to strengthen the neck muscles (neck turning I believe it was called). The instructors showed that with enough practice it works against a lot of choking techniques, and you can even take punches/strikes there. And no surgery required! There are some movies of monks putting ropes around their necks and just hanging there. It takes a while though; I never got that far. --Bennybp 21:00, 5 November 2007 (UTC)

It is a common movie plot device to wear some sort of device to fake a hanging. The problem is that in most hangings, the cause of death is a broken spine -- not strangulation. --Mdwyer 22:00, 5 November 2007 (UTC)

No, that's not correct. The way a broken neck kills you is through asphyxia (there's no way for the "breathe" signals to get from your brain to your lungs). But when you're hanged, even if the signals could get through, it wouldn't help you, because the blood can't leave your brain, so there's no room for oxygenated blood to come in and replace it.

Hanging is quite a horrific way to die. People have this notion that as soon as the neck breaks the victim is unconscious, but there's simply no good reason to believe that. All it does is prevent him from jerking around and alerting the onlookers to his suffering. --Trovatore 22:07, 5 November 2007 (UTC)

They'd still be able to move their head, wouldn't they? I've heard beheaded people could, but I haven't seen either. Also, it's still probably better than cancer, as it's much, much shorter. — Daniel 01:46, 6 November 2007 (UTC)

After having my carotid artery accidentally blocked in a judo match a few years ago (very very briefly), I assure you that the cessation of blood flow to the brain knocks you out essentially instantaneously. Albert Pierrepoint mentioned in his memoirs (very good read) that the pulse stops immediately after a long drop hanging, and I'd take his word over most laymen. Of course, the American tradition of strangulation hanging is another story. GeeJo ^(t)⁄_(c) • 15:59, 6 November 2007 (UTC)

about IR

what is the infrared absorption frequency of phosphorous-oxygen bonds? —Preceding unsigned comment added by Dinkysweet (talk • contribs) 17:45, 5 November 2007 (UTC)

Depends single vs double, ionic vs covalent ("what's attached to the O if it's single-bonded to P"), etc. DMacks 18:08, 5 November 2007 (UTC)

is the california fire still burning?

California_wildfires_of_October_2007 could use an update —Preceding unsigned comment added by 85.238.88.73 (talk) 18:03, 5 November 2007 (UTC)

• I believe technically some remnants are still burning. As of today, the state of California said the fires were "under control".

Reference: "Governor Calls on Blue Ribbon Task Force to Review State Fire Response". State of California. November 62007. Retrieved 2007-11-06. {{cite news}}: Check date values in: |date= (help)

I have updated the article accordingly. Johntex\^talk 20:55, 6 November 2007 (UTC)

Down insulation

A friend of mine is an avid & experienced outdoorsperson, and tells me that it's widely known that down jackets or vests should be worn under other layers, because "down's insulating power comes from the temperature difference between heat of your body and the outside cold". In other words, she says that if you wore wool or synthetics under down, you would be colder than vice versa, because the down won't insulate if it's cold. It's possible that I'm not representing her explanation fairly.
I have a basic understanding of thermodynamics, and this doesn't make much sense to me. Her explanation of down's special properties sound like a definition of insulation in general. It seems like the delta-T across the down will determine its insulating power, whether that temperature difference is between skin and an inner shell, or between air and a underlayer. Can anyone explain this apparent discrepancy?
Secondly, according to our article, down insulates more poorly when moist or compressed, wouldn't you want it further away from your perspiring body, and uncompressed by outer layers? jeffjon 18:33, 5 November 2007 (UTC)

• I think you are right. The insulation should be just as effective as the outer layer and this may even be preferred due to the lack of compression. I think if you go to a sporting-goods / camping store, you will see that most of the down-insulated garments are designed for outer-wear. They are too bulky to go under other layers, in general. Johntex\^talk 20:37, 6 November 2007 (UTC)

How do I tell white gold or platinum jewelry from stainless steel?

How do I tell white gold or platinum jewelry from stainless steel? If I have some jewelry, don't know where it came from, and think it could be made of either one of these three, how do I find out which one? I mean aside from some really complicated thing at the chemist. William Ortiz 18:41, 5 November 2007 (UTC)

An easy first step: some types of stainless steel are magnetic, so if a magnet is attracted to it, it definitely isn't gold or platinum. If the magnet isn't attracted, though, you haven't proved anything. jeffjon 18:44, 5 November 2007 (UTC)

Maybe if you live in an area where there are stereotypically gold-hungry ethnicities, you could dangle it conspicuously and see if they have gold-lust in their eyes. Note: I'm basing this on myself, since I belong to such an ethnicity. My eyes not only twinkle, but get a little teary. —Preceding unsigned comment added by 85.238.88.73 (talk) 19:10, 5 November 2007 (UTC)

Most gold jewelry has the karat written on it somewhere (ie 14K, 18K, 10K, etc.).Josborne2382 19:17, 5 November 2007 (UTC)

Like the apocryphal story of Archimedes and the crown, you can determine the density of the material using the item's weight and volume. The weight is easy, if you have an accurate enough scale. The volume can be determined by immersion in water, but it might be tricky if the item is small. -- Coneslayer 20:40, 5 November 2007 (UTC)

A sufficiently clever counterfeiter could use a metal heavier than gold and leave a hollow space to fool the density test, so you'll also want to measure its moment of inertia ;-) Someguy1221 22:06, 5 November 2007 (UTC)

A clever counterfeiter uses tungsten which has nearly the same density as gold. Icek 04:24, 6 November 2007 (UTC)

Would stainless steel have "stainless steel" or some variant written on it? Would platinum jewelry? Does platinum jewelry have karats or something similar? William Ortiz 21:49, 5 November 2007 (UTC)

Why don't you just take it to a jeweller and ask his/her opinion? Exxolon 21:54, 5 November 2007 (UTC)

If it dissolves in mercury, it was gold; if it dissolves in hydrochloric acid, it was steel; if it catalyzes hydrogenation of olefins, it's platinum? Alternately, there are various more formal metallurgical tests. Various spectroscopic techniques could work too. Depends how much you have and how destructively you're willing to test it. DMacks 23:11, 5 November 2007 (UTC)

Auger electron spectroscopy could answer the question.

Atlant 00:28, 6 November 2007 (UTC)

This alone will only tell you about the composition of the surface (about 1 nm depth). Icek 04:24, 6 November 2007 (UTC)

I have stainless steel silverware and that stuff is not magnetic. I hear stainless steel jewelry is made from Surgical stainless steel -- is that magnetic? William Ortiz 10:49, 6 November 2007 (UTC)

According to my nipple, no it is not magnetic (within my ability to notice a force with a couple of nice little Nd magnets). Also according to my piercer, though I still avoid certain fun toys. Eldereft 20:30, 7 November 2007 (UTC)

Oil consumption versus oil creation

Where can I find a graph or chart that compares the consumption of crude oil with crude oil creation. I would expect it to be on the order of like a barrel of crude every ten years versus however many million or billion consumed per day. Dichotomous 19:05, 5 November 2007 (UTC)

Consumption of petroleum (also known as crude oil) is currently about 84 million barrels per day. The current creation of petroleum is almost certainly much faster than a barrel every ten years. A barrel of petroleum created every ten years since the origin of life on this planet about 3.5 billion years ago would only come to about 350 million barrels. But petroleum reserves, not counting oil sands, are currently at about 1.2 trillion barrels. Dividing 1.2 trillion barrels by 3.5 billion years puts a worst-case lower bound of a least a barrel created per day, and probably considerably more.

It'd be very difficult to have a bar chart showing how petroleum creation compares to petroleum consumption. If the bar showing petroleum consumption is a few inches tall, the bar showing petroleum creation would have to be thinner than the thinnest line that a printer can print. MrRedact 20:09, 5 November 2007 (UTC)

I don't think we honestly know what the rate of creation is. A reasonable guess might be something like:

C = A / Y

Where:

C = The creation rate.

A = The amount of oil that had formed before we started digging it up.

Y = The number of years it took to form.

We know that oil is formed from the simplest algea in the ocean - which have been down there (presumably) forming the stuff for 3 billion years - so Y=3,000,000,000 years. I think it's fair to say that there were once about 3 trillion barrels of economically usable oil (ie not mixed up with sand and oil shales and such) and about twice that amount if we include the (currently) uneconomic stuff so A=3,000,000,000,000 barrels.

That says that it's probably forming at a rate of C = 3 trillion barrels / 3 billion years = 1,000 barrels per year - let's say 3 barrels per day of economically usable oil (perhaps 6 barrels per day that of the other stuff). We're currently using close to 90 million barrels a day. Which means we're using it up about 30 million times faster than it's forming. (Jeez! Even I'm surprised by that number!)

Of course this makes two very dangerous assumptions - one is that every drop that was ever formed was available for us to dig up. That's unlikely because much of it must have been subducted due to continental drift and such. So that would make the estimate for present production rates higher than I just calculated - perhaps if we're really optimistic, 1,000 times faster. On the other hand, I'm also assuming that conditions have always been right for oil formation - and indeed that the conditions are still right. That's also a difficult thing to know and could push my estimate either up or down - but not by very much compared to thirty million!

But one thing is for absolute certain - we're using the stuff up at a rate at least a few thousand times faster than it's being created - and perhaps a millions of times faster. Fast enough that it's irrelevent that more is being formed. 3 barrels a day isn't enough for anything useful!

Even if I'm wildly off the mark. Suppose we were using it up only ten times faster than it's being formed, we'd still run out in roughly the same amount of time! But that simply can't be true. Nobody is going to claim that all this oil we dug up last year is only 100 years or so old (we'd certainly notice new oil formations popping up all the time if it was that fast - and some really simple carbon-dating would tell us that!) So for sure we'll run out reasonably soon if we carry on using it at the present rate. However, as has been said here several times before - if you turn all of the oil we have into CO2, global warming will easily kill the planet. Hence running out is simply not possible - the planet would be dead long before we could manage that. So let's worry about global warming instead please.

SteveBaker 20:32, 5 November 2007 (UTC)

Generation, migration, and accumulation of oil depend on a huge number of variables. It is entirely possible (though quite unlikely) that no oil is presently being generated, anywhere on earth. The proper source rocks have to be buried to the proper depth for the proper length of time. A good source rock has 1% organic material in it; an outstanding source rock has 5%. The oil window (the depth where oil can be generated) is around 7000 to 15,000 feet below the surface, with variations. Then circumstances must exist for the generated oil to migrate through rocks to a point of accumulation in a trap. All this will typically take millions rather than thousands of years for significant accumulations. The largest fields in Saudi Arabia, for example, are thought to have taken tens of millions (50-80 million, I think – sorry I don’t have the reference at hand) to be generated, to migrate, and to accumulate.

Steve’s calculations are interesting – just one comment: there is virtually no oil present today that is thought to have been generated at a time longer ago than about 1 billion years, and the vast majority was generated less than 400 million years ago. There just was not enough algae to create source rocks. Also, any such old oil that was generated would be very unlikely to have survived to the present, owing to tectonic activity destroying traps. It is difficult to know for certain when oil is generated, but one measure is by looking at the (usually younger) rocks in which the oil is trapped. In the US, at least 75-80% of all the oil is or was in rocks younger than about 320 million years old. The rocks that generated it would not likely be all that much older (with, of course, some exceptions). Cheers Geologyguy 20:52, 5 November 2007 (UTC)

Googling "petroleum creation rate" only turned up one page of questionable reliability[12], but according to that one page, the algae out of which our current petroleum reserves developed grew during the carboniferous period, which was only about 60 million years long. Dividing about 3 trillion barrels by 60 million years comes to about 140 barrels per day. But even with this somewhat higher estimate, we’re still using it up almost a million times faster than it’s being created, so petroleum certainly can’t be viewed as anything close to being a renewable resource!

If on a bar chart you used the thinnest possible line that a 300 DPI laser printer can draw to represent the petroleum creation rate, the corresponding bar to represent the petroleum consumption rate would have to be about 166 feet tall! That's more than half the length of a football field. MrRedact 21:11, 5 November 2007 (UTC)

The statement on that web page implying that all of today's oil was generated from the Carboniferous is waaaayyyy too simplistic. Most of the oil in Saudi Arabia, and much of that in Russia, is of Jurassic age, for example, while much of California's oil was generated by plants that died during Tertiary time. Nonetheless what MrRedact says is correct. Cheers Geologyguy 21:23, 5 November 2007 (UTC)

Pssst. Carboniferous is 300+ million years ago. Dragons flight 22:53, 5 November 2007 (UTC)

Yes, I know. I said that the Carboniferous was only 60 million years long, and didn’t say anything about how long ago it was. For the crude estimate, it made sense to divide by the duration of the Carboniferous, not by how long it's been since then. For example, algae that lived just 1000 years ago has lived since the Carboniferous, but it will likely be many millions of years until the median time at which it contributes to usable petroleum reserves. ("Usable by whom" is a good question, since Homo sapiens are unlikely to even exist anymore by that time.) MrRedact 23:53, 5 November 2007 (UTC)

D'oh. I simply misread your comment above. Dragons flight 23:58, 5 November 2007 (UTC)

As I said at the outset, we really don't know what the answer is - but even the most optimistic numbers are going to indicate that we're digging the stuff up at least tens of thousands of times faster than it's being re-formed. If we have 1.2 trillion barrels and we're using it up at 86 million barrels per day then if none is being re-formed, then we run out in 38 years. If it's re-forming at even 1/10th of the rate we're using it (which it cannot by any stretch of the imagination be doing) then we run out in 42 years...big deal! So it really doesn't matter how fast it's being formed - none, 3 barrels a day, 100 barrels a day, 8 million barrels a day - it makes essentially no difference to the amount of time we have left.

But this ENTIRELY misses the point. Let's forget global warming. Let's do a much simpler back-of-envelope calculation. When you burn a barrel of oil you get (in round figures) 400kg of CO2 gas. So what happens if we burn all of the oil we have left, including oil shales and every drop we can extract as we get desperate after 40-ish years? A hundred years from now, we'll have utterly run out after burning 4 trillion barrels altogether. Crunch the numbers: we'll have dumped perhaps 1.8x10¹⁵kg of CO2 into the air. The earth has 5x10¹⁸kg of atmosphere - so we'll have pushed the amount of CO2 from 0.038% of the air to 0.075%. But that's not counting the other things like coal and natural gas that we're currently burning - which would probably push that to 0.1% or 1000 ppm. At those concentrations more than 20% of people will experience breathing difficulties, headaches & nausea! In actual fact, since CO2 is a heavy gas, it's likely there would be much higher densities at lower altitudes where we all live - in all likelyhood it would be reaching 2000ppm - which is enough to cause severe symptoms in nearly everyone. The effects on other animals is unthinkable.

More serious still (but harder to prove with back-of-envelope math) is global warming. Those effects are already kicking in to a frankly unacceptable degree with CO2 levels only 35% higher than 'normal'. Just think about what happens if we have three times the natural amount!

Truly, it's irrelevent how much oil is being re-formed. With the most optimistic estimates, it's negligable - and in any case, we won't run out because we'll have killed the planet LONG before we use it all up. —Preceding unsigned comment added by SteveBaker (talk • contribs) 03:13, 6 November 2007 (UTC)

Carbon cycle fluxes

The number being asked for above is one that I'd very much like to have. For that matter, I've been trying to locate values for the exchange terms in the carbon cycle more generally. Approximating it at as roughly 5 reservoirs: land-based biosphere, atmosphere, oceans, crustal rocks and fossil fuels; I have been trying to get some citable numbers for the annual pairwise exchanges of carbon between each of these in the modern era.

Some terms are fairly easy. We burn about 7 GtC of fossil fuels a year, i.e. the fossil fuel -> atmosphere flux. Also, the major terms such as ocean -> atmosphere, atmosphere -> ocean, atmosphere -> biosphere, biosphere -> atmosphere, etc. are of sufficient interest that numbers (at least fuzzy ones) are out there (including ones in the figure at carbon cycle). However I have had considerable difficulty getting citations for the minor terms, e.g. biosphere -> fossil fuels, biosphere -> crustal rocks, terrestial biosphere -> oceans, oceans -> fossil fuels, etc. (I suppose one could technically define all fossil fuels as coming from carbon in crustal rocks, but I would prefer to seperate terrestial and oceanic carbon sources.)

If anyone can help in nailing down these fluxes in a rigourously citable way, it would be much appreciated. Dragons flight 22:53, 5 November 2007 (UTC)

Thanks!

Allow me to thank each one of you for your extensive responses to this question. Since it was mentioned that global warming is a far more serious issue than disrespect for the amount of time it would take to renew oil as a resource once it is gone. A question about global warming comes to mind which I will post shortly along with another question about oil production. Thanks again. I've made a copy of your responses in case the Wikipedia runs out of funds!

Dichotomous 04:24, 6 November 2007 (UTC)

Photon Energies

In general (i.e. not refering to any particular substance) can photons be created with any possible energy or are there only particular energies they can take (i.e. some sort of planck scale) —Preceding unsigned comment added by 172.200.188.149 (talk) 20:43, 5 November 2007 (UTC)

$E={\frac {hc}{\lambda }},$ Wavelength (lambda) is the only variable there, and I guess it would be quantized in units of planck length. So the inverse of a photon's energy is quantized. Or I'm wrong, I don't know. Someguy1221 20:56, 5 November 2007 (UTC)

Photon energy isn't quantized in the standard model, nor (as far as I know) in string theory or loop quantum gravity. The Planck length is not a quantum of length. There are hints that there is a quantum of area (comparable to the Planck area), but not of length or time or mass. -- BenRG 21:42, 5 November 2007 (UTC)

Tapeworm

Is it medically possible to have a tapeworm infection and not know it? Has there been any documented cases of people having tapeworm for long periods of time? --WonderFran 21:16, 5 November 2007 (UTC)

Yes, although the symptoms will exist, some don't act on them. There have been cases where tapeworms lived inside people for many years. 64.236.121.129 21:27, 5 November 2007 (UTC)

If you believe you have a tapeworm, see a doctor. The symptoms of most GI-tract disorders are pretty much the same (many sharing symptoms with heart attacks). From a gas bubble to a tapeworm to a viral infection, pains and discomfort should be diagnosed by a doctor. -- kainaw™ 23:48, 5 November 2007 (UTC)

The Wikipedia article on tapeworms says "infestations are usually asymptomatic", which means a person won't know right away they have one. It also says they can grow to be 15 to 30 feet long, and that will take some time. The Mayo Clinic link at the bottom of the Wikipedia article is very thorough regarding the medical aspects. As for a documented case, I think doctor-patient confidentiality would make that hard to find, but the facts speak for themselves. --Milkbreath 00:07, 6 November 2007 (UTC)

Once an infected person takes the medication to treat tapeworm, does the tapeworm exit the body they way I think it does?! ew! --WonderFran 00:31, 6 November 2007 (UTC)

If the way you are thinking of is "in pieces, and dead", then yes :) And yes, the orifice is the one you think. Would you have it any other way? - Nunh-huh 00:42, 6 November 2007 (UTC)

Well, there's always the old, pre-medication way, which involved sitting naked in a body-temperature water bath, and waiting... —Steve Summit (talk) 02:08, 6 November 2007 (UTC)

While holding a nice piece of blue cheese close to your bumhole. Gotta entice those wormy worms out somehow. Then grab the worm firmly by the ears and give him / her a firm telling off and issue an eviction notice. This is not medical advice. Lanfear's Bane | t 16:21, 6 November 2007 (UTC)

November 6

Hearing own voice

Why is it strange to hear our own voice? 217.129.241.186 01:10, 6 November 2007 (UTC)

Because you normally hear your own voice as it is carried through the tissues and bones in your skull, as well as through the air, which is the only part you hear when you listen to a recording of yourself. Someguy1221 01:30, 6 November 2007 (UTC)

Which helps to explain why people with hearing loss often find it hard to make themselves heard to other people. They can hear themselves ok through their head bones, and they think the listeners can hear them just as well, but what listeners hear when a person is talking is not what the person themself hears. Being often asked to "speak up" is sometimes a strong clue that it's not the listeners who are going deaf, but the speaker. -- JackofOz 20:27, 6 November 2007 (UTC)

Olestra formula

While reading my chemistry textbook, I passed a short reference to Olestra, which made me think about going to that article. When there, I wondered about the chemical formula; since it's not in the article, I searched Google, but found virtually nothing. Anybody know the chemical formula (or formulæ, since it appears to have variable numbers of fatty acid chains) for Olestra? Nyttend 01:52, 6 November 2007 (UTC)

And just to make it completely obvious: I'm not asking for homework help here :-) It's not even something I'll be tested on. Nyttend 01:57, 6 November 2007 (UTC)

http://www.scientificpsychic.com/fitness/fattyacids1.html --Dacium 03:11, 6 November 2007 (UTC)

Here is another: http://sci-toys.com/ingredients/olestra_2.gif. Tim Q. Wells 05:00, 6 November 2007 (UTC)

DNA polymerase requires a "primer"?

I was looking into any information I could find on DNA polymerase since I'm currently taking a Cell Biology course, and I was wondering why exactly does DNA polymerase require a primer? I already understand the basics, but I am looking for a little more in depth explanations. Wilt0057 01:52, 6 November 2007 (UTC)wilt0057

Did you look at the DNA polymerase article? It currently reads: "DNA polymerase can only add free nucleotides to the 3’ end of the newly forming strand. This results in elongation of the new strand in a 5'-3' direction. No known DNA polymerase is able to begin a new chain (de novo). They can only add a nucleotide onto a preexisting 3'-OH group. For this reason, DNA polymerase needs a primer at which it can add the first nucleotide". I'm not sure you need more than that. Or do you need to know why it requires a 3'-OH substrate? If so, you need to research about substrate specificity for active sites in enzymes. David D. (Talk) 02:40, 6 November 2007 (UTC)

Magnetopneumodynamic Drive - I'm gonna build me one! (Maybe)

Thanks again to Graeme and Carnildo for the answer above.

Now I know it's possible (in principle) I'm going to try to build a zeppelin model with a battery-powered MPD.

What's next is whether it's possible to use a circular form for the thruster rather than triangles/rectangles. I'm thinking of a concentric circle or cylinder system that would be mounted in pairs parallel to the long axis of the zep. Remote-controlled rudders at the rear of the drives would give directional control. Any comments/suggestions appreciated.203.21.40.253 02:51, 6 November 2007 (UTC)

You won't succeed. There is absolutely zero chance of you getting something that works from a design like that. These 'lifter' things provide absolutely microscopic amounts of thrust - they have to be made of the lightest possible materials and be driven by huge voltages and currents. This means you couldn't even power one from a car battery - let alone a couple of AAA's. Look at some of the experimental setups people use. Not one of them has the power supply actually on the lifter - they always trail a couple of wires from some god-awful-large transformer with mains supply going into them! If you truly mean to use the lifter as the 'thrust' motor (as opposed to a lift motor) for a lighter-than-air balloon, then at least the lifter doesn't have to carry the weight - but consider the size of balloon you'll need to lift something much heavier than a car battery - then consider how much drag a balloon that big is going to have - then look back at the microscopic amount of thrust you get from a 'lifter' and consider how even the lightest of breezes will overcome it's pathetic thrust. Honestly, you truly don't stand any chance whatever of getting this thing to work. This technology is nothing more than an amusing party piece. Beware of the large armies of nut-jobs out there claiming that there is something magical going on here - anything from "quantum levitation" to anti-gravity to using the earth's magnetic field to power the thing...the distinguishing feature of all of them is that the best they can do is a very light lifter with power coming from the ground that can just barely lift its own weight. SteveBaker 17:59, 6 November 2007 (UTC)

No worries about the "nut-jobs" Steve; I knew what the Mythbusters would find before they started. However, the model set-up for the "hybrid" at the Blaze labs site (external link at Ionocraft article page) seems to show that the thing is do-able. Your point about the thrust to drag ratio is the obstacle I was concerned with. Exploitation of the on-board power supply is the crucial issue. I think varying the planar forms of the ionising system may be the way to go in enhancing air flow. That's where I'm looking for any guidance people can offer. Retarius | Talk 01:17, 7 November 2007 (UTC)

Well, if you aren't yet convinced, let's crunch some numbers. According to ionocraft, the force (in Newtons) exerted by the motor is the current in amps multiplied by the air gap in meters divided by 2x10^-4. It also says that the air gap needs to be about 1mm per thousand volts applied to it. So roughly - the force from the lifter in Newtons is one fifth the current multiplied by the number of kilovolts.

Let's suppose you want you craft to run on ten AA batteries and let's assume you get 100% efficiency. You've got only 15 volts and you can't have 0.0015mm air gap! Let's assume you step up your voltage to 15kV using some kind of circuit so you can have a more reasonable 1.5 centimeter air gap. You get about 3 Amp/hours from a AA battery at 1.5 volts and you can pull about 15 Amps @1.5v without it melting or whatever. But with 1000 times that voltage, you get 1000 times less current - but you have 10 batteries - so you'll have about 0.15 amps at 15kV - sadly, the batteries will die after 20 minutes of flight time - but maybe that's OK.

So the force from the lifter can be no higher than 0.15*15/5 = 0.45 Newtons - that means it could lift a weight of about 45 grams against gravity. Sadly, a AA battery weighs 23 grams and we we have 230g of batteries alone...so this simply isn't going to fly even with the most optimistic possible numbers. (In truth, to push the voltage up from 15v from 10 AA's in series up to 15,000 volts will require some fairly serious electronics - that'll add a ton of weight and it'll be horribly inefficient.

But never mind - you don't want to use the lifter to lift the dead weight of the batteries - right? You're going to have a helium balloon carrying the weight and the lifter turned sideways pushing it forwards. A helium balloon can lift about 1kg per cubic meter of gas. By the time you have a quarter kilo of batteries, plus electronics, lifter and gas-tight envelope, plus radio control gear - you'll be well over 1kg. So we're looking at a zepplin-shaped balloon well over a meter in diameter.

So - what drag will this thing have? The relevent formula (from Drag coefficient) is that Force = Cd x 1/2 x rho x A x V². Force is the 0.45 Newtons our lifter will generate. Cd will probably be about 0.3 if you are really careful (better than most cars - worse than a perfectly smooth sphere). Rho is air density - about 1.22, A is the cross section - let's say about one square meter. So the speed your zepplin will go (with the most optimistic possible numbers) will be: sqrt(0.45/(0.3x0.5x1.22x1)) ...hmmm - maybe 2 to 3 miles per hour. Wow! That's actually a lot faster than I guessed. However, in even a 1mph cross-wind - the thing will be utterly unmanageable.

But that's an insanely optimistic estimate. The trouble is that we have no estimate for the energy losses in boosting a 15 volt battery pack up to 15,000 volts. Sadly, from our article: "Ionocrafts capable of payloads in the order of a few grams usually need to be powered by power sources and high voltage converters weighing a few kilograms". Well a 'payload' of a few grams in a vertical lifter means a thrust of a few hundredths of a Newton in the horizontal direction. So if we toss out my battery calculations and say that we need a FOUR cubic meter balloon to lift a 3 kilo power supply plus one kilo of other stuff (bigger envelope, bigger control vanes, etc). And if we downgrade the thrust estimate to 'a few grams' - ie maybe 0.03N, then re-run my drag calculations with a much bigger cross-sectional area - and now your zepplin is moving at a half mile per hour. Even a light draft inside a building will stop the thing dead in it's tracks.

I'm betting the thing would bob around in air currents and you'd hardly be able to tell whether the engine was turned on or off.

Someone needs to double-check my numbers...but since it's going to cost you a lot of time and effort to find that out experimentally - it's really worth checking. IMHO, it's a waste of time to even try.

SteveBaker 03:02, 7 November 2007 (UTC)

I appreciate your time taken, Steve, and I don't dispute the above. That's why I'm looking to explore the basic design of the thruster. The extant models are too weak to bother with and I only intend to test-bed the thing unless and until it shows a useful result in improved thrust.

203.21.40.253 03:43, 8 November 2007 (UTC)

Artificial oil production

Assuming that all one needs is a source of carbon and hydrogen and energy, how much oil, natural gas, etc. could be produced per day using nuclear reactors for no other purpose? Dichotomous 04:27, 6 November 2007 (UTC)

That's equivalent to asking "how much more energy do nuclear reactors produce than fossil fuels?" because the energy to form a fossil fuel would be around that released by breaking its bonds. So from [13] we see that most fossil fuels release about 50kJ/g, and from [14] we see nuclear reactors release about 2x10^9 kWh/ton = 7x10^6 kJ/g. Great, but we don't use much material to power our reactors. The power output of a nuclear reactor is about 3x10^5 kW by quick google search, so we find that a nuclear plant can ideally produce about 10^4 g/s of fossil fuels, or 10kg per second. However, I don't think we actually have a process that can make fossil fuels in any efficient way, so our actual yield will be much less, but this is the theoretical maximum yield. SamuelRiv 04:53, 6 November 2007 (UTC)

I believe a couple of scientists in the UK about ten or fifteen years ago demonstrated a method of crude oil production using high pressure and temperature. From your calculations it appears retaining an oil based energy distribution system is not threatened by exhaustion of naturally occurring petroleum, oil, natural gas, etc. Dichotomous 05:07, 6 November 2007 (UTC)

I have always wondered why it is not possible to synthesise hydrocarbons from their constituent parts of carbon and hydrogen. For example Propane (C3H8) is just 3 carbon atoms and 8 hydrogen. How would one make them join up and form a propane molecule? I am not an expert at chemistry by any means but know the very basic basics. Also, why can CO2 not be broken up into oxygen plus carbon? I'm guessing the energy input required to do these things would outwiegh the benefits? GaryReggae 10:24, 6 November 2007 (UTC)

In terms of lubricants versus fuel the cost might be justified in the absence of substitutes or synthetics based on something else when naturally produced petroleum runs out. Even if there were more to it than just a high pressure, high temperature cooker and many steps involved, the need for carbon based lubricants and fuels may never go away. Dichotomous 12:20, 6 November 2007 (UTC)

Plus hydrocarbons have other uses, such as in plastics, paints and other such thingsGaryReggae 13:00, 6 November 2007 (UTC)

Imagine your great, great, great, great, great granddaughter complaining about the need to use so much fusion power to replace natural oil that the cost of her cosmetics are beyond reason, in addition to the cost of recharging her car... and blaming it all on the excesses of good old great, great, great, great, great granddad. Dichotomous 15:31, 6 November 2007 (UTC)

My car already uses synthetic oil - it's great stuff - it lasts three times as long as regular motor oil and it can be recycled more easily. The more interesting question is how chemical plants that use hydrocarbons as feedstocks for making plastics and such would fare. But as has been discussed elsewhere on the reference desks recently, we simply cannot afford to burn all of the oil we have left because of the greenhouse problem - so if we DO manage to save the planet by ceasing to burn oil, we'll have PLENTY left for making plastics and such like. SteveBaker 03:22, 7 November 2007 (UTC)

Global warming

Until recently I never had problems with kudzu, weeds or grass if I was away for a month or six weeks and returned to find that period of growth in the back yard. Where can I find a chart or graph which shows the rate of increase in plant growth (such as grass and kudzu, land based, and algae and coral, water based) per rate of increase in atmospheric CO₂, to view the point plant growth would simply be outpaced by the production of excess CO₂? Dichotomous 04:44, 6 November 2007 (UTC)

Choice

I apologize for posting this here, believe me. It will give some of you a headache, and not the good kind. Beyond the two factors of genetics and environment (experiences etc.), is there anything else, some third factor, that can account for our next choice in life? Sappysap 04:50, 6 November 2007 (UTC)

Free will, according to proponents of religion, and quantum mechanics, according to proponents of the quantum mind. Neither is widely accepted by scientists as a phenomenological explanation. SamuelRiv 04:55, 6 November 2007 (UTC)

"Choice" can be a problematical way to describe behavior since it leads some people assume that humans have a supernatural ability to escape determinism. Philosophers such as Daniel Dennett have explored the idea that it is more neutral to say that our brains give us the ability to control our behavior based on past experience. --JWSchmidt 05:42, 6 November 2007 (UTC)

See Randomness#In_biology. Besides the freckle example I gave there, another example is sexual orientation. Identical twins raised in the same home should have identical genetics and environment, yet don't always have the same sexual orientation. Thus, we know there is a random influence at work. (Note that, in this case, it may be truly random or simply following a pattern too complex for us to recognize.) StuRat 11:21, 6 November 2007 (UTC)

I'd rather attribute it to chaos (in the mathematical sense) than randomness - but I'm almost sure that our free will is an illusion. The mind clearly works on multiple levels and I strongly suspect that the conscious level that we're aware of is merely rationalising choices which a more mechanistic mind made at some lower level. There are so many ways in which lower levels of thought processes have been shown to actively disguise things from the higher levels. Things like when you move your eyes very rapidly across a scene, the signal from them is actually cut off - and your brain 'fills in' the experience of the "missing video signal" from memory and imagination. Similarly, the effects of our relatively slow reaction times are distorted by our minds to make it seem like things happen instantly without a delay. There are all sorts of ways in which our conscious mind is lied to by the lower levels - and choice or 'free will' seems to me to be just another one of those things. SteveBaker 22:52, 6 November 2007 (UTC)

More reason to avoid thinking about free will only in terms of behavioral choice. We generally associate "choice" with conscious brain activity, but the fact is, we cannot be consciously aware of most of our own brain activity. If we think about free will in terms of behavioral control then we can be comfortable with the idea that our brains can produce useful behavior based on past experience ("we" are in control) even when much of that control over our behavior is rooted in unconscious brain activity taking place outside of our rather limited domain of introspective awareness. I think the powerful illusion is that we are conscious of what we take to be "free will". If we expand our concept of "free will" to include its foundation in unconscious brain activity, then we do not have to call the brain's ability to adaptively control behavior an illusion. --JWSchmidt 22:25, 7 November 2007 (UTC)

electric vehicles for the post office

If electric vehicles offer such and advantage why hasn't the post office started using them or the candidates started touting electric vehicles for the post office? With all the stop and go driving and the large number of vehicles, if converted to electric, do a lot for global warming, or is this just a farce as well? Clem 09:01, 6 November 2007 (UTC)

In England, postal delivery rounds in suburban areas are often carried out on foot or by bicycle. However, electric milk floats have been used for many years for door-to-door deliveries of milk because they are quiet and their limited speed and range is not a problem. Gandalf61 10:52, 6 November 2007 (UTC)

Electric vehicles don't necessarily help with global warming. If fossil fuels are burnt to make the electricity, and a good deal of that electricity is lost during delivery and storage, then they can even be worse than an efficient internal combustion engine. If the electricity is made by a nuclear reactor or some other method which doesn't release hydrocarbons, then electric cars may help. StuRat 11:11, 6 November 2007 (UTC)

The huge advantage of electric vehicles in stop/start applications like door to door delivery is that you get regenerative braking more or less for free. This means that for postal runs, an electric vehicle would be massively more efficient than a gasoline car - even if its batteries are recharged by an oil-fired power plant. I don't know why they don't use them. Their routes are short enough that the limited range of an electric vehicle would not be an issue and they can have one central recharge point. As Gandalf61 says, electric milk delivery vehicles have been around in the UK for many decades (certainly they were around when I was a kid in the late 1950's). The only sound those things made was a 'kerchink, kerchink' of the milk bottles rattling...and when they switched to delivering milk in cartons...nothing...dead quiet. SteveBaker 13:00, 6 November 2007 (UTC)

Assuming in the States (and probably applicable for most places), there's a both a cost and availability problem. For one, it's expensive to replace that large a fleet of vehicles, and the vehicles are individually more expensive than those they're replacing. For two, electric cars aren't readily available on the market. Making matters worse, postal vehicles generally prefer right-hand-drive (opposite the norm), making the availability problem worse. Unfortunately, the quick solutions for 1 and 2 are in opposition to each other: the solution to cost is to upgrade very gradually; the solution to availability is to commission a big run of specialized vehicles.

The problem is worse for rural route carriers, who tend to use self-owned non-standard vehicles. In addition to the exacerbated cost/availability issues, they're also more likely to run into the problem of electric car range -- I would think a 200+ mile daily route is quite possible in some areas. — Lomn 14:14, 6 November 2007 (UTC)

Besides the regenerative braking pointed out by Steve, the other huge advantage of an electric vehicle for postal delivery would be avoiding wasting all that energy idling an internal combustion engine while the vehicle is stopped. And both of those advantages are also available in hybrids, so issues about availability, range, charging time, and questionable cleanliness of the electrical supply don’t exist as excuses for not at least switching to use hybrids for all postal delivery. Unfortunately, in the U.S., a bill requiring a switch to hybrid postal vehicles would almost certainly just get vetoed by Bush, who only recently started admitting that global warming is even real. Hopefully we’ll get a president who takes global warming more seriously soon. (As a disclosure of my biases, I’m a very proud Prius owner.) MrRedact 17:39, 6 November 2007 (UTC)

But the US post office already uses very non-standard vehicles. Getting manufacturers to build specialist vehicles is not that hard when you can put an order in for a few tens of thousands of them with a good likelyhood of them being in service for 30 years. Those funny little RHD jeep-like things are unique to the postal people - the only ones you see that aren't on postal routes are old beat-up ones people bought from the post office for very low dollar when they were completely worn out. Replacing one unique kind of vehicle with another on an 'as they wear out' basis shouldn't pose that many problems. I agree that on rural routes, an electric car would make less sense - but as you say, in those areas the mail carriers generally have some arrangement by which they use their own cars. Our post-lady drives a normal LHD SUV which she owns - but the post office pays for fuel, repairs and maintenance on it. One assumes they would leave those as-is and just replace the urban vehicles. A 200 mile range must be plenty since for most of the time they are driving at maybe 10mph and spending about half their time stopped - at those kinds of speeds you'd have to be driving for DAYS to hit the 200 mile range limit. SteveBaker 17:46, 6 November 2007 (UTC)

A bit off the topic, but here in the UK some mail is delivered by the milkman on his electric float. I subscribe to several magazines and they are often through my letter box by 7:00am and the postie doesn't come until about 11:00am these days. I don't know if the delivery is definitely by the milko, but I can't see the postie making two rounds. To me it makes perfect sense to combine the roles of postie & milko, and receive all of our post nice and early like we used to.--193.195.0.102 20:46, 6 November 2007 (UTC)

There are a whole pile of things that could be delivered in this way - anything that needs to be fresh or recent could be delivered in one handy trip. Sadly, here in the USA, the idea of milk delivery doesn't seem to have taken off (or maybe it did once but hasn't survived). Added to the virtual inability to buy long-life milk, this becomes a major pain for us Weetabix lovers. On the other hand, it's very convenient that the US post delivery service will pick up mail as well as deliver it. That's something the UK system could certainly benefit from. SteveBaker 22:45, 6 November 2007 (UTC)

Unfortunately, milk deliveries are a dying breed in the UK as supermarkets have undercut the traditional milkman. I don't know why the post office have never tried using battery vehicles as they'd be ideal for mail deliveries and collections. Couriers could also use them for local journeys. UPS seem to have a fleet of highly customised vehicles that are unique to them so surely they could try it? GaryReggae 23:50, 6 November 2007 (UTC)

seeing blood vessels

The doctor had a waiting room full of patients so I did not ask him this question. After he gave me medication to make the blood vessels in my eye swell as a test for diabetes I could see after he stopped shinning a light in my eye in a flash blood vessels. How is this possible? Are the receptors in my eye covered by blood vessels that I can not see unless they are swollen and if so how is this possible. Wouldn't the blood vessels still block or interfere with the light hitting the receptors? Dichotomous 10:30, 6 November 2007 (UTC)

This is an evolutionary mistake, that the blood vessels are in front of the light receptors. That is why we have a blind spot, that's where there is a cluster of them. Elsewhere they are normally thin enough that enough receptors are hit to give us an image. We aren't normally aware of this flaw in our vision because our brains "fill in the gaps" with a best guess as to what's there. However, when the blood vessels are larger than normal, the brain can't overcome this. StuRat 11:06, 6 November 2007 (UTC)

Don't call it an evolutionary mistake. There are no mistakes in evolution. Evolution is merely horribly inefficient, and not all the traits lifeforms possess are necessarily good or useful. They simply exist because the species can live long enough to reproduce despite the bad traits. 64.236.121.129 14:40, 6 November 2007 (UTC)

Please see Blind spot (vision). The blind spot is not due to blood vessels mostly due to the axons of the retinal ganglion cells (and there are also some small blood vessels passing through the optic disc). The retina has a good design because it places the photochemically active rods and cones at the back where they can shed their older photo-sensory components into the pigment epithelium. --JWSchmidt 15:07, 6 November 2007 (UTC)

64, calling evolution inefficient has the same basic problem as calling something an evolutionary mistake: they both imply that it's actually trying to do something, rather than something that just happens. — Daniel 01:12, 7 November 2007 (UTC)

Any phrasing seems to imply intention. Fault, error, mistake. The way eyes work is one of many unfortunate ways the human body works. Good design? Not a design, also ours is not the best way eyes work. Birds have much better eyes than us. Also, there's one part of our eyes which isn't obscured by blood vessels, and that's the only bit that does any worthwhile seeing (yeah, okay, the low quality stuff that our eyes also do is worthwhile too) - that three-dee panoramic full colour view most of us think we see is more of an illusion than anything else, at any moment, you can only see in detail an area about the size of the full moon as seen from Earth. See saccade for more info on how that works. Also have a look at change blindness. --Psud 09:23, 7 November 2007 (UTC) (my comments edited at 09:37, 7 November 2007 (UTC))

Astronomy, living far north

Hi, I tried to search Wikipedia for some material on celestial navigation. I currently live at a latitude of about 71deg north, and thus am experiencing complete darkness for about three months now. While it would be nice to acquire a stargazing map that details what I see (from northern Norway) at roughly midnight (first request), it would also be nice to have one that detailed what I see at noon (second!). Not that it is dark enough at noon that I can see most stars, but I imagine I can make the two maps 'overlap' in such a manner that I can follow celestial objects beyond simply those that can be seen at night.

If you can help me out with this, thanks in advance. :) 213.161.190.228 11:09, 6 November 2007 (UTC)

This thing is great. It's made for 40 north, but you could cut it for your horizon. That combined with a real star atlas like Sky Atlas 2000.0 or Becvar's Atlas of the Heavens should get you there. --Milkbreath 12:32, 6 November 2007 (UTC)

Of course one of the problems with living that far north is that your view of the sky doesn't change all that much depending on time of day. If you live on the equator, you get a total view of the entire sky over 24 hours (except, of course the sun rises and blots out half of it) - if you live at the poles, then the planet is essentially just spinning you on the spot so the sky seems to spin - but no new stars appear through your long night. At your latitude, the sky is going to "wobble" but there will be less difference between noon and midnight than at more equatorial latitudes. My imagination tells me that some of the stars nearest to the horizon at noon probably going to be obscured by sky glow because the sun is only just below the horizon - but I don't know for sure - a lot depends on how clear the atmosphere is where you live. SteveBaker 12:46, 6 November 2007 (UTC)

There are a lot of options for generating a view of your night sky. Sky and Telescope magazine has an online interactive sky chart applet: [15]. Starry Night (planetarium software) has (or had, the last time I checked) a downloadable free version that had stars down to fifth or sixth magnitude. Some fully-featured free options include Stellarium and Celestia. I can't comment on the suitability for printing of the output from any of the applications I've listed, but all will allow you to view the sky at an arbitrary time of day from an arbitrary location on Earth; they will also allow you to run the clock back and forth so you can see the 'wobble' that SteveBaker describes. TenOfAllTrades(talk) 13:20, 6 November 2007 (UTC)

Actually, I know a better link. It's the longitude for Oslo plus the Latitude for your location. Now, scroll down, and select "universal time", and replace the xx:xx:xx time with 23:00:00 for midnight and 11:00:00 for noon. It does not require any download, and probably doesn't need java either. Remember results might not be accurate completely. It's also better because you can scelect the coordinates exactly. Hope this helps. Thanks. ~AH1^(TCU) 01:26, 8 November 2007 (UTC)

space diamonds

What exactly are space diamonds? Are they physically identical to diamonds found on earth? How are they collected? Where are they distributed? How do you verify their origin? How do they compare in price? What do existing diamond suppliers think about space diamonds? Etc..., I'm curious. —Preceding unsigned comment added by Mangosunshine (talk • contribs) 14:58, 6 November 2007 (UTC)

Presumably this means stellar and/or planetary cores that have been compressed into diamond. They're an interesting find astronomically and have no impact whatsoever on the diamond market. — Lomn 15:18, 6 November 2007 (UTC)

Carbonado or "black" diamonds may have an extraterrestrial origin, according to some researchers. And the core of white dwarf BPM 37093 is thought to be crystallised carbon, which you migh loosely call diamond - so it has been nicknamed Lucy (after Lucy in the Sky with Diamonds) - but BPM 37093 is 50 light years away. You can even buy Space Diamond Gift Certificates, but I suspect they are nothing more than rather expensive pieces of paper. Gandalf61 16:09, 6 November 2007 (UTC)

Wow. "Here you go darling, it's all that is left from an entire star compressed into a diamond." Keria 16:58, 6 November 2007 (UTC)

There have been many speculations about various planetary cores being mainly carbon (that's part of the plot of the one of the sequels to "2001: A Space Odyssey (novel)" - I think it was 2061: Odyssey Three....mmmm...yes, that was it) - and at those temperatures and pressures, that would make a diamond of impressive size. Really, diamond isn't all that rare or special. We can now make synthetic diamonds that are better quality than "the real thing" - and which have to have artificial impurities introduced to them to make them look more real. The only reason diamonds are as expensive as they are is because the De-Beer folks make them so by hoarding them and only letting them out in quantities they control. It's a nasty monopoly. There is no doubt that diamonds should be commonplace and as cheap or cheaper than cubic zirconium. Another way that diamonds may become common is via nanotechnology - it's often said that if we had nano-bots going around making stuff for us, probably the easiest material for them to make would be diamond. Since the stuff is amazingly hard and could be made utterly smooth, we might one day find that many large-scale structures are most efficiently made from diamond. At this point, the value of diamond will be no more than a piece of coal. The same thing would happen if a large chunk of diamond were to be hauled in from space or impact on the earth as a meteorite. SteveBaker 17:31, 6 November 2007 (UTC)

Can chewing your lips cause cancer?

My dentist once told me that if you chew your lips (like chew the chapped, dried parts off), it can cause cancer. Is this true? 64.236.121.129 15:06, 6 November 2007 (UTC)

!!!THIS IS NOT A MEDICAL DIAGNOSIS!!! - Some users feel it is necessary to delete any and all mentions of medical information because they perceive it as being a medical diagnosis. This is in no way a diagnosis. It is a note on medical studies that have been done on the topic asked about.

See leukoplakia. Some studies have linked chewing on the lips or inside of the cheeks with leukoplakia and other studies have identified leukoplakia as a precancerous condition. Put together, that means that a very small number of studies have linked chewing on your lips to cancer in a rather roundabout way. This comes down to the definition of "can". Does it mean "it is likely to cause cancer" or "it is possible in a very rare circumstance that it will cause cancer"? -- kainaw™ 15:46, 6 November 2007 (UTC)

Thanks for the notification, I appreciate that. I've found that most people tend to chew on their lips because they become chapped. What causes chapped lips? 64.236.121.129 15:54, 6 November 2007 (UTC)

See chapped lips. -- kainaw™ 15:57, 6 November 2007 (UTC)

Err, that article is pathetically bad dude... 64.236.121.129 16:05, 6 November 2007 (UTC)

When the mucous membranes of the lips become dry they both become brittle and shrink resulting in superficial cracks. This is chapped lips. Dehydration and wind are two common mechanisms for the drying out. 83.147.141.69 19:49, 6 November 2007 (UTC)

Selection of yeast by growth media

I grew yeast which contained a vector coding for Leu and Trp allowing them to grow on media lacking leucine and tryptophan. However, when grown on media -Ura-Leu-Trp how come the yeast were able to grow, Ura was not coded for? Any ideas would really help...

--67.71.12.246 18:54, 6 November 2007 (UTC)Cat

I'm not sure, but first you know that Ura is not an amino acid, as are Leu and Trp, but rather a pyrimidine. Uracil can be synthesized by the hydrolysis of Cytosine, (see Uracil#Synthesis). Hope that helps. (EhJJ) 21:05, 6 November 2007 (UTC)

Hum okay...still not sure though...i had completely forgotten though that uracil was not an amino acid (rather a nucleic acid) but thanks for reminding me of that...but like then why do we have to exclude it from the medium...I'm not getting the reasoning behind it...

--67.71.12.246 21:38, 6 November 2007 (UTC)Cat

Maybe the reason was to confirm that they can make their own uracil? A lot of classroom science experiments don't make any sense at all. Someguy1221 22:49, 6 November 2007 (UTC)

Yeah I thought about that too...hehe but I figured there must be some point to it (guess I won't mention it in my lab report like that there's no chance of getting it wrong) i just would like to understand the point...because it's been playing with my mind for like 3 days!

--67.71.12.246 23:04, 6 November 2007 (UTC)CAT

You have to remember that wildtype yeast can grow perfectly well in very minimal media. That is, if you plate most wildtype yeast strains onto -Ura -Leu -Trp media, you'll get colonies. What yeast researchers have done is isolated yeast auxotrophs which require Ura, Leu & Trp supplementation. These strains are each deficient in a single enzyme in the biosynthetic pathway for their respective compounds (separate enzymes for each pathway). Since they can't make it themselves, they have to get it from the media. This allows you to introduce plasmids encoding the deficient gene as a selectable marker. If the cells don't have the plasmid, they don't have the gene, can't make the compound, and can't get it from the media, so they die. If they have the plasmid, they can replace their deficient enzyme with the one on the vector, make the compound, and grow colonies. All of this is predicated on transforming the vector into a yeast strain which is a Ura/Leu/Trp auxotroph. My guess is that the yeast strain you used was *not* a Ura auxotroph ... that wouldn't explain why you didn't just use -Leu -Trp media instead, though. -- 22:18, 7 November 2007 (UTC) —Preceding unsigned comment added by 128.104.112.105 (talk)

Axial muscles

Probably a very simple question for many of you: what are axial muscles?
(I've checked muscle but axial muscles isn't mentioned there, and I checked Wiktionary, which says: axial = "Belonging to the axis of the body; as, the axial skeleton; or to the axis of any appendage or organ; as, the axial bones" - but I still don't understand which muscles are meant by axial muscles.) Lova Falk 19:30, 6 November 2007 (UTC)

It means the skeletal muscles on the trunk of the body or the head - basically excluding the limbs and non-skeletal muscles. -- kainaw™ 19:37, 6 November 2007 (UTC)

Thank you! Lova Falk 20:17, 6 November 2007 (UTC)

Why do we call alcohol, ethanol when talking about fuel?

Umm, it's the same thing. So why the different name? 64.236.121.129 19:47, 6 November 2007 (UTC)

See alcohol and ethanol. They are not the "same thing". -- kainaw™ 19:50, 6 November 2007 (UTC)

Yea but, ethanol is the alcohol found in alcoholic drinks. When people say alcohol, they refer to that. 64.236.121.129 20:08, 6 November 2007 (UTC)

When people "who are ordering a beverage" say alcohol, they are referring to ethanol. The most common use of "alcohol" where I work is a reference to methanol. I wouldn't call alcohol and methanol the same thing simply because of my subjective experience at work. -- kainaw™ 20:12, 6 November 2007 (UTC)

And if you drink fuel ethanol, you may get very sick (or even die) because it has impurities (such as methanol) that are not safe for human consumption. Fuel ethanol and drinking alcohol are not interchangable. Dragons flight 20:14, 6 November 2007 (UTC)

Wait a minute, if the fuel ethanol also has other alcohols like methanol, shouldn't we call it alcohol anyway because it contains more than one alcohol, and not ethanol exclusively. Ethanol powered cars should be called alcohol powered cars because there's more than one alcohol in the mixture. 64.236.121.129 20:20, 6 November 2007 (UTC)

That's like saying we shouldn't call the stuff I put in my tractor "diesel fuel", because it also contains a red dye. The other alcohols are impurities that are present in small quantities, not essential components of the fuel. You still call the stuff that comes out of your faucet "water" even though there's minerals and maybe fluoride in it, right? -- Coneslayer 20:30, 6 November 2007 (UTC)

Those are bad analogies dude. Diesel fuel and red dye don't have a general term to refer to both of them. Where as, both ethanol and methanol are alcohols. Hmm if methanol is not an essential component, I guess that makes sense though, but why would impurities like methanol exist in ethanol. You don't accidentally get methanol in your beer. If you did, you'd be dead. 64.236.121.129 20:38, 6 November 2007 (UTC)

My guess would be that it's a difference between fermentation by yeast, and industrial processes for producing ethanol. But if you're making an argument that we should use "alcohol" instead of "ethanol", you should give us a good reason for doing so. There is already an excellent reason for using "ethanol": there are other alcohols that are used as vehicle fuels, and you can't use ethanol in an engine that's designed to run on methanol, or vice-versa. Thus, using the precise name is advantageous. What would be the advantage of saying "alcohol" instead, as you suggest? -- Coneslayer 20:44, 6 November 2007 (UTC)

So then why not ferment the ethanol by yeast instead of the industrial processes? No argument dude. Those are fine reasons to call it ethanol. 64.236.121.129 20:50, 6 November 2007 (UTC)

Actually, I stand corrected--according to Ethanol, a lot of the fuel ethanol is produced by fermentation. The toxic components may be introduced deliberately for denaturing. There may also be toxic components besides the alcohols, such as detergents. -- Coneslayer 21:00, 6 November 2007 (UTC)

Yeasts etc make a variety of alcohols, the main one's ethanol, but methanol's in there in noticeable amounts too. Actually, there's a bit of effort put into removing methanol from the drinking stuff when it's distilled, they wouldn't bother with that for fuel or industrial use. Actually, I note that nothing's done to remove other alcohols from beer either. --Psud 09:03, 7 November 2007 (UTC)

Wow, I can't believe they will make that stuff toxic on purpose just to avoid taxes. 64.236.121.129 21:05, 6 November 2007 (UTC)

It doesn't matter how toxic it is, because it's not intended for human consumption. Seems like a pretty obvious business decision: don't pay more than you have to. DMacks 21:55, 6 November 2007 (UTC)

NO! REELY?! We know ethanol fuel is not for human consumption dude. Don't waste time pointing out obvious facts. 64.236.121.129 14:24, 7 November 2007 (UTC)

In that case, why are you feigning astonishment about how toxic a non-foodstuff is ("Wow, I can't believe they will make that stuff toxic on purpose just to avoid taxes.")? DMacks 17:06, 7 November 2007 (UTC)

LOL! That's this kid's M.O: Ask a perfectly valid "why" question, then slam everyone who answers because he either doesnt understand, or doesnt want to hear that answer. Ok, here's the real reason we don't mix the terminology between Ethanol and Alcohol: Because the Battle Mechs with the spherical wheels, that fly using ducted fans over to drain Loch Ness in order to see if a parisitic twin got cancer from biting its lip would rather use Ethanol as an alternative to gasoline. You rock kid... don't ever lose your imagination! :) (But don't bite the folks who try to get to the bottom of your "whys" either). :) —Preceding unsigned comment added by 198.172.206.151 (talk) 19:12, 7 November 2007 (UTC)

Whoever's alt account is 198.172, you are cracking me up with trying to hide behind an ip so you can flame and not be given a scarlet letter on your real account. Haha. I can take 3 guesses as to who you really are. 64.236.121.129 21:22, 7 November 2007 (UTC)

Alcohol is a chemical family. Ethanol is a type of alcohol, referred to as "alcohol" because it is the most common type encountered. —Preceding unsigned comment added by 83.147.141.69 (talk) 19:53, 6 November 2007 (UTC)

In other words, ethanol is a type of alcohol, but not all alcohol is ethanol. So maybe your question might have been - Why do we not talk about drinking ethanol rather than the more general term alcohol? Why don't we have Ethanolics Anonymous? -- JackofOz 20:18, 6 November 2007 (UTC)

Exactly. And it's sometimes clear from context- as pointed out above, if people are talking beverages, it's clear that alcohol means ethanol. When you're talking about industrial usage, it's less clear so people tend to use more specific terms. Friday (talk) 20:22, 6 November 2007 (UTC)

Yeah - there are lots of kinds of alcohol. Ethanol is one of them, Methanol is another. When you are talking about fuels, the word "alcohol" has considerable ambiguity - did you mean methanol or ethanol or butanol or pentanol or 2-methylbutanol or...? When you are talking about things people drink however, there is no ambiguity because the only alcohol that's even close to being safe to drink is ethanol - so when we talk about alcoholic drinks - we're always talking about ethanolic drinks and there is no ambiguity worth mentioning. Language is sloppy - and when a laymans term intersects with a scientific term, it's never a good thing. Do you use the brakes and steering wheel on your car to accellerate it? In scientific terms 'accellerate' means 'change velocity' - so the answer is yes - both steering and brakes accellerate your car. Messy! SteveBaker 20:23, 6 November 2007 (UTC)

So while it's certainly true that the word ethanol is more specific than the word alcohol, I wouldn't take it for granted that that's the reason the E-word is used at the pumps. These naming decisions are made by marketing people, legal departments, and bureaucrats, more than by scientists and engineers. They may have been worried that, if they called it "alcohol", someone would try to drink it. --Trovatore 21:04, 6 November 2007 (UTC)

I agree - that would certainly have been a risk. Even E85 ethanol (which is 85% ethanol) would be suicidally dangerous to drink - the E10 stuff we have now would be much, much worse! If we ever start to use E100 (as they do in Brazil) I dare not imagine what might happen! 70.116.10.189 22:11, 6 November 2007 (UTC)

Is there a typo there? How could 10% be much, much worse than 85%? -- JackofOz 22:17, 6 November 2007 (UTC)

Because the other 90% is gasoline! 70.116.10.189 22:22, 6 November 2007 (UTC)

I must be a little slow this morning; would you indulge me as I try to get this straight? E10 is dangerous, mainly due to the 90% gasoline content. E85 is dangerous, mainly due to the 85% ethanol content. E100 is dangerous, because it is pure ethanol. Is that it? -- JackofOz 23:01, 7 November 2007 (UTC)

E10 is dangerous, mainly due to the 90% gasoline content. E85 is dangerous, mainly due to the 15% gasoline content. E100 would be dangerous, because it's intentionally denatured (made toxic), so that it can't be used as a beverage—but idiots might think it's safe because it's called "100% ethanol". -- Coneslayer 23:11, 7 November 2007 (UTC)

Well, 100% ethanol is not exactly "safe". It will seriously irritate your mucous membranes, certainly enough to be painful and possibly enough to be dangerous. --Trovatore 03:01, 8 November 2007 (UTC)

You might try Alcohol#Etymology; the word "alcohol" certainly predates the word "ethanol". shoy (^words _words) 20:42, 7 November 2007 (UTC)

If we can drain lakes, why don't we drain Loch Ness to see if the Loch Ness Monster is there

Why not? 64.236.121.129 20:28, 6 November 2007 (UTC)

Why bother? Who cares? If they that do can raise the money, overcome environmental and other concerns, figure out what to do with the water, and get the necessary permits, I say go for it. DMacks 20:38, 6 November 2007 (UTC)

Lots of people care dude. Lots of people care. 64.236.121.129 20:40, 6 November 2007 (UTC)

Loch Ness is very deep (>230m) and it would be very difficult to drain. Besides, as the water level dropped, Nessie would simply entomb herself in the solid rock in the same way a toad can and avoid detection.--193.195.0.102 20:51, 6 November 2007 (UTC)

If the monster exists, it probably needs the lake. Drain the lake and kill the monster, meaning the monster would not exist. Might as well just declare the monster does not exist. Then we can skip draining the lake. Johntex\^talk 20:53, 6 November 2007 (UTC)

What's to say that they (c'mon, if there is something down there, there'll have to be a breeding population of them - it's an unknown animal, if anything, not an immortal 'magical beast') even spend all their time in the loch? --Kurt Shaped Box 21:46, 6 November 2007 (UTC)

These questions have been asked many times in the past. Any serious debate is over. We have all the proof we need to know there is nothing there. The entry and exit to the Loch are fairly shallow streams and go through well populated areas. Nothing of any size could get up and down there without being very visible indeed. For a breeding population of any species to survive, you need at least 500 individuals in order to have enough genetic diversity. 500 creatures the size of the hypothetical Nessie could just maybe hide in the Loch (although how they'd have avoided being found in sonar studies and other careful searching is hard to imagine) - but the effect they'd have on the local fish populations would definitely have been noticed. So, no Nessie. Sorry - it's just not possible. 70.116.10.189 22:21, 6 November 2007 (UTC)

Why don't we cut down the rainforest to see if there are any endangered species there...? TenOfAllTrades(talk) 22:08, 6 November 2007 (UTC)

Because that would destroy the rainforest! DUH! Man... Think a little man, it's not that hard to figure out :). 64.236.121.129 14:32, 7 November 2007 (UTC)

I think you missed the sarcasm. I guess the point is, if you remove the creature's living environment (loch ness or rainforest) then whatever you do find is kind of screwed. Besides, the mystery is 99% of the fun with Nessie! :) Arakunem^Talk 18:19, 7 November 2007 (UTC)

He was being sarcastic?! NO! REELY?! I just like to crush pathetic attempts at smart assery :). 64.236.121.129 21:25, 7 November 2007 (UTC)

An excellent idea, think of all the Bigfoots we could find! -- MacAddct  1984 ^{(talk &#149; contribs)} 23:15, 6 November 2007 (UTC)

Ohhhh - I was assuming we'd be training them to wield the chainsaws. OK, nevermind. SteveBaker 03:25, 7 November 2007 (UTC)

Diaphragm

Is Diaphragm a smooth muscle??thanks--82.105.205.27 21:17, 6 November 2007 (UTC)14mala

No. It is striated, and is under voluntary control. Make yourself cough! Voila! :-) Fribbler 21:24, 6 November 2007 (UTC)

Nuclear Ingredients

i am unable to find out (as a list) all the ingredients to a nuclear bomb this is for my physics homework. i would really appreciate if you could help in any way. i have been through all of the wikipedia nuclear articles but i am not successful. please can you help me. all the information that i have gathered about nuclear ingredients were plutonium and uranium. thank you very much —Preceding unsigned comment added by 87.74.98.190 (talk) 21:21, 6 November 2007 (UTC)

Ahmadinejad? Is this you? —Preceding unsigned comment added by Fribbler (talk • contribs) 21:25, 6 November 2007 (UTC)

You might be having problems because you expect the recipe to be more complex than it is. Really, you just take some plutonium and use conventional explosives to squish it. The ingredient list gets bigger if you want to increase yield, but in general nuclear explosions are pretty simple compared to chemical explosions. It has more to do with the technique of the chef than the recipe. --Mdwyer 21:42, 6 November 2007 (UTC)

This article will give you step-by-step instructions for a fission device. Delmlsfan 21:54, 6 November 2007 (UTC)

The abstract principle of a fission weapon is very simple. You need to take several chunks of radioactive material (plutonium or uranium) that are each, individually, much less than the critical mass for that substance - and you need to slam them together into one large chunk that's bigger than the critical mass so it goes bang. Everything else is annoying engineering details.

The most significant problem is that if you just take two half-critical mass chunks and push them together with a lever or something - they'll get so amazingly hot that they'll melt and distort so much that you won't be able to get them close enough together and the thing will 'fizzle' - make a horrible radioactive mess - but not much of an explosion. So the next trick is to slam them together using high explosives so they move so fast that they don't have time to heat up an fizzle. But now you have to set off those explosives at precisely the same moment and have them slam the pieces together just right - or no bang. Then the components of the bomb have to be assembled in such a way that the person putting them together doesn't die of radiation poisoning and they have to be in a chunky enough bomb casing that the finished device can be handled safely. These weapons aren't cheap and you certainly can't afford to have one not go off when you want it to - or go off when you don't - so the fuses and timers and other precautions are much greater than with a regular bomb. You can't use normal computers and such inside the bomb because the radiation can corrupt their memories.

The whole very simple idea just turns into a gigantic pain in the ass when you try to actually build one. SteveBaker 22:34, 6 November 2007 (UTC)

Eh, you've made things more complicated than you need to. You don't need computers inside a gun-type bomb. You don't even need to have well-timed explosives—just send one of the sub-critical bits into another, don't have them slam together simultaneous, that just complicates things. You're confusing the gun-type weapon—which is really quite simple—with the plutonium bomb—which is not. The finished device—which in a very primitive bomb is going to be quite large—is not going to be terribly radioactive as long as you keep the two sub-critical bits properly apart from each other at all times. The hardest part here is going to be getting enough high-enriched uranium; the design could be done by someone with the engineering knowledge of repairing motorbikes. You only need more sophisticated knowledge if you want to say, drop it out of a plane, which requires being able to fit a lot of things into a relatively small package and make sure the wires won't come undone, etc. (A plutonium bomb is quite different and requires very sophisticated engineering on top of everything else.) --24.147.86.187 04:22, 7 November 2007 (UTC)

It should be noted for completeness, though, that there are a couple of significant tradeoffs with the Little Boy design. One, you have to use uranium. Plutonium won't work. Two, you need (relatively speaking) a lot of uranium -- over 60kg vs less than 5kg plutonium in an implosion-type bomb. — Lomn 05:49, 7 November 2007 (UTC)

True enough. It's actually a great blessing that from an engineering and physics perspective these things are balanced as they are—uranium is easy to make a bomb with, but hard to produce; plutonium is easy to produce, but hard to make a bomb with. It might not be too hyperbolic to say that these simple facts have done more for non-proliferation than anything else out there. --24.147.86.187 15:11, 7 November 2007 (UTC)

The article Nuclear weapon design is pretty thorough. There are more ingredients mentioned there than you have. What about the trigger? Give it a read. --Milkbreath 22:53, 6 November 2007 (UTC)

For an even more simple assessment, see the pages on the first two atomic bombs: Little Boy and Fat Man. They have pretty straightforward "ingredient" lists, blueprints, etc. The hard part is not the design, for the most part. The hard part is in getting the materials. --24.147.86.187 04:18, 7 November 2007 (UTC)

What's the name of that multicolored thing on TV?

It's a screen where you have several different bars, and they are all different colors, and the TV emits a high pitch noise. What is that? 64.236.121.129 21:22, 6 November 2007 (UTC)

I call it a test pattern, or "Bars and Tone". Here's a link: SMPTE color bars --Mdwyer 21:34, 6 November 2007 (UTC)

Historically, it was called a test card and was used in the early days of television to make sure the colours all looked correct. When the TV station closed for the night, the test card was broadcast although nowadays it is a rare sight. GaryReggae 23:43, 6 November 2007 (UTC)

They were broadcast during the daytime in the UK before all-day broadcasting was instituted. The idea was that TV repair shops could make use of them to figure out a range of different problems inside the TV set. These days you can cheaply buy a little box to generate a range of different TV test patterns for this purpose - so there is no need for them to be broadcast - although I believe some cable and satellite services still dedicate a channel to transmitting them. SteveBaker 03:53, 7 November 2007 (UTC)

Very rare on broadcast TV though. We've got a couple of sub-24 hour/day TV stations where I live, neither of which show a test pattern overnight. I did see a test pattern for about three seconds during a system fault a few months ago on one of our major commercial TV stations, but their standard "Sorry for the inconvenience" screen replaced it quickly. --Psud 08:44, 7 November 2007 (UTC)

In countries using the NTSC television system, such as the United States, a color bar test signal is still used as a reference to adjust analog receivers and frame synchronizers to fine tune four basic video levels to match the transmitted NTSC signal: Video level (contrast on home receivers), black level (brightness), chroma saturation (color) and chroma phase (hue or tint). Many satellite uplinks transmit this signal when the main program is not in progress, so that those users downlinking their signal can adjust their receivers.

The "high[-]pitched noise" referred to by the OP is a generally a standard audio reference tone, 1 kHz in frequency and transmitted at a standard amplitude of 0 VU. Again, this is used to adjust the level of the receiver's audio gain to match the standard level sent from the source. Thomprod 19:34, 7 November 2007 (UTC)

Could a parasitic twin lead to an evolutionary change?

I was just watching this bizzare video on CNN, http://www.cnn.com/2007/HEALTH/11/06/india.girl/index.html#cnnSTCVideo ,and I was wondering if a parasitic twin could potentially lead to a evolutionary change where an species of animal has more limbs because of failed twinning. 64.236.121.129 21:43, 6 November 2007 (UTC)

See conjoined twin for some background info. I don't think this situation is guided by genetics- it's more of a physical accident. So I don't see room for genes that cause this to be passed on. Also, this condition doesn't improve one's chances of survival and reproduction- quite the opposite. Friday (talk) 21:48, 6 November 2007 (UTC)

I agree with your first point, but your second point assumes too much. Malamockq 00:52, 7 November 2007 (UTC)

Empirically, Friday's second point is quite correct. The parasitic twin extra limb thing (as opposed to conjoined twins) is invariably detrimental to the person. In this case, various articles have noted that the child is entirely unable to walk and likely to die before adolescence without radical surgery. While we can theorize a beneficial Doc Ock-style extra limb thing, evidence suggests that such benefits are confined to the realm of fiction. — Lomn 02:29, 7 November 2007 (UTC)

Surely the key point here is Friday's first point, that the condition of having a conjoined twin/parasitic twin is not genetic. Therefore, regardless of whether it might convey any benefits to the individual concerned, it is not inherited, and so cannot play any part in the evolution of a species. Gandalf61 16:15, 7 November 2007 (UTC)

Yes that's what I thought. Just wanted to make sure. Btw lomn, I think your assumptions are based on conditions right now rather than changing circumstances in the enviroment. If a nuclear war, ice age, etc happens, there might be circumstances where many limbs would be preferable. Or not. I just think it's bad to assume things just based on current circumstances. Poor science pally boy. 64.236.121.129 21:15, 7 November 2007 (UTC)

While the possibility of changing environments is good to keep in mind (very wierd things can happen, like the loss of an appendage or sense becomes advantageous), the inability to survive adolescence is simply not beneficial. And even if she could survive without surgery, I don't see how not being able to walk is advantageous. Maybe if a strange animal appears that eats anyone with less than 8 limbs... Someguy1221 21:24, 7 November 2007 (UTC)

Dude, I wasn't talking about that girl. I was talking about a mutation where you have lots of limbs. 64.236.121.129 21:38, 7 November 2007 (UTC)

Altruistic act? I dont think so

I was having a discussion the other day about whether all acts are truly motivated by self interest, I am for the motion, and was looking to see if anyone could help me by provide some research into the area, I am particularly interested in finding a piece of research I read a while ago into how your brains distorts positions to your point of view in order to justify decisions you have previously made, which could lead to you believing acts were altruistic when they are not. Thanks. 172.200.188.149 22:02, 6 November 2007 (UTC)

I think a key problem with saying that is you need to very firmly define "motivated by self-interest." Certainly all actions beyond accidents are motivated by something and we can always contort our reasoning to call that self interest, for even if it does not benefit a person in any obvious way, there is some reason they "want" to do it. Someguy1221 22:07, 6 November 2007 (UTC)

The Principles of NLP say that Behind every behavior is a positive intention. Whether that intention is positive towards your own welfare without regard to others', or towards others without regard to your own, or some of both, would depend on the circumstances. -- JackofOz 22:15, 6 November 2007 (UTC)

While this won't help you with the second part of your question, our article here on Objectivism might be a good place to start your research on this topic, and will at least give you some food for thought about the philosophy supporting your thesis. Jeffpw 22:20, 6 November 2007 (UTC)

Maybe you were thinking of Cognitive_dissonance#Origins_and_experiment? Altruism#Altruism_in_ethology_and_evolutionary_biology has some good places to start too. -- Diletante 22:41, 6 November 2007 (UTC)

The distinction you're concerned with here is one of behavior versus motivation for that behavior. We can define altruistic behavior and then give examples of humans behaving altruistically; someone risking their own life to save a stranger's should satisfy most definitions and is certainly not unheard of. However, trying to answer the question of whether or not such behavior was selfless and disinterested true altruism and not motivated by some conscious or unconscious selfishness is problematic. To prove or disprove such a thing would require knowing the internal thoughts and motivations of the person in question, something not currently available to science. See the Criticism section of Psychological egoism for more. So, it's an unwinnable arguement for both sides from a scientific perspective. My take is that, yes, from a biological/evolutionary perspective selfishness is a hard-wired human trait, but genetic traits are not fixed or unmodifiable; humans are a very unique species and I wouldn't discount out of hand the possibility of true altruism in humans. Either way, there's worse things to aspire to than acting altruistically, regardless of true motivation. Azi Like a Fox 17:45, 7 November 2007 (UTC)

Saving a stranger raises social your standing, earns you 'brownie points' as such, also you expect people to do the same thing for you, and prolongs the survival your species. And acting altruistically is a bit of an oxymoron as something must be motivating you and if it is something else, then its is altruism and not acting, and if its selfish then its not altruistic at all. ΦΙΛ Κ 21:45, 7 November 2007 (UTC)

Right, and by the Original Poster's definition these ulterior motivations all preclude the original act of saving someone as "true" altruism. The expectation of someone doing the same for you would be reciprocal altruism (talk about an oxymoron). I was trying to explain that it's unknowable/unmeasurable whether someone's altruistic action is ever truly devoid of self-interest; given human nature it's not unreasonable to think that such actions aren't or can't be, a bit cynical but not an unrealistic position. Regardless, my point was that even if you say that no human action can be devoid of self-interest, it's still better that people behave generously and altruistically even if such behavior is motivated at some level by self-interest. My giving to local charities is none the less beneficial to the community and the recipients for being predicated on what I consider rational self-interest and an investment in the mid to long-term future rather than a disinterested and altruistic desire to be charitable. If instead I gave because it simply made me feel good to help others, then again it could be argued my motivations are self-interested (my own pleasure in helping others) rather than purely altruistic. So be it, teaching and cultivating altruistic behavior is all the more important and remarkable when it happens in light of our "selfish" nature. Hope that clears up what I mean by describing an action as altruistic even when the motivations behind it aren't always. Azi Like a Fox 23:58, 7 November 2007 (UTC)

In vitro mitochondrial respiration states

What are the different respiration states of mitochondria (1,2,3,4)?

One paper says: "In the present study, state 2 respiration is defined as the rate of respiration in the presence of substrate but before the addition of ADP." but a website says regarding state 4: "State IV respiration is defined as oxygen consumption by isolated mitochondria on a particular substrate, in the absence of ADP..." So what's the difference? --Seans Potato Business 22:44, 6 November 2007 (UTC)

I believe that the difference is that state 4 (mito + reduced substrate without ADP) is reached as a phase during the experiment after all the ADP has been converted to ATP. Whereas state 2 is a starting condition prior to ADP being added. Subtle, I know but you have to consider them with respect to phases during an experiment.

It is common to start with mito alone, state1. Then spike with substrate to get to state 2 (limited respiration will occur). Then add ATP to move into state 3 (maximal respiration) and when the ADP runs out you enter state 4. If you respike with ADP will reenter state 3 and then back to state 4 when the ADP is all converted to ATP (all assuming you have inorganic phosphate as a substrate in excess). David D. (Talk) 03:25, 7 November 2007 (UTC)

Original 1955 article & see this. In terms of the original Chance & Williams protocols, I think a typical "state 2" experiment involved plenty of ADP but no added substrate such as succinate. A "state 4" experiment involved having high levels of a substrate such as succinate while ADP was rate limiting and driven to zero concentration during the experiment by conversion to ATP. Other people define "state 2" differently. You have to look at the details of how each "state" is defined by the people doing the experiments. --JWSchmidt 03:42, 7 November 2007 (UTC)

This is an excellent point: "You have to look at the details of how each "state" is defined by the people doing the experiments". However, i might add I was going from memory and since JWSchmidt has a nice link quoting the Chance/Williams experiment that is clearly the definitive answer. David D. (Talk) 04:55, 7 November 2007 (UTC)

my girlfriends disorder?

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This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

Lanfear's Bane | t 09:16, 7 November 2007 (UTC)

November 7

Diversity Antenna?

I remember way back in college that there was some discussion about diversity antennas (Using two antennae to increase signal strength or reduce noise, I think). It's was used in disccussion about wireless mics in TV (why many ENG news cameras have two floppy antennae sticking out of their back) I can't seem to find any entry on diversity in regards to radio waves on Wikipedia. What's the science behind it and what's it called? --24.249.108.133 00:08, 7 November 2007 (UTC)

See Antenna diversity. --Milkbreath 00:14, 7 November 2007 (UTC)

The quality or strength of the field can fluctuate wildly from point to point, so if you get the signal from a bad position you can compensate by using the good signal. Also two different polarizations can be used. The signal varies due to diffraction and destructive interference Graeme Bartlett 00:44, 7 November 2007 (UTC)

Sun and moon at midday

I live in the state of Virginia (US). A few days ago I went out to lunch from work on a pristine, blue-skied, bright autumn day...and there it was. The moon, 3/4's full and as clear as if I were looking at its craters on the clearest of nights; only the background wasn't black, it was a blinding bright blue. I looked back and forth at the sun and the moon and my watch (which read 12:45 pm) for quite a while and couldn't believe it. It was beautiful. Sadly, in just an hour the phenomena ceased.

I have lived here all my life (a respectable 27 years) and have never seen the sun and the moon together so prominently sharing the sky of midday. Is there any way to predict when this rare optic event will happen? —Preceding unsigned comment added by Sappysap (talk • contribs) 01:14, 7 November 2007 (UTC)

It sounds as though you saw a sun dog. Possibly due to ice crystals Graeme Bartlett 01:56, 7 November 2007 (UTC)

Actually, the sun and moon share the sky approximately half the time. When the moon is full, it's on the opposite side of the Earth from the sun. When it's at either quarter, it's at a 90° angle relative to the sun and thus above the horizon for about 6 hours of night and 6 hours of daylight. As the moon approaches its new phase, it's in the sky almost entirely during the day.

So as you can see, this isn't rare at all -- it's just a matter of stopping to look up. Additionally, the moon isn't the only celestial object visible in full daylight. Early this year, Comet McNaught was visible in full daylight, and Venus is often visible with binoculars, and with the naked eye at sufficient altitude. — Lomn 02:13, 7 November 2007 (UTC)

(after edit conflict) It's not a rare optical event at all, even though it may seem to be because the Moon is much less noticeable against a bright blue sky than against a black background. The Moon is up exactly as often during the day as it is at night.

Anyways, during your lunch break, the Moon will be up every day from full moon to new moon. The atmospheric seeing wil change from day to day and when you'll see the Moon cripsly will depend on chance. --Bowlhover 02:25, 7 November 2007 (UTC)

The only thing you won't see is a full moon in the daytime sky along with the sun. Just about anything else is possible. (But I agree, a daytime moon can be a lovely sight.) —Steve Summit (talk) 03:16, 7 November 2007 (UTC)

That's not true - at dawn or at sunset, the moon can be on the opposite horizon from the sun and in that case it will be a full moon. Someone reading this is just thinking to argue that it can't be quite 100% full if the sun and moon are both actually visible - and when they do that I'm going to find a large baseball bat and beat them into a quivering heap whilst yelling "AT-MOS-PHER-IC DIFF-RAC-TION YOU ID-I-OT!!". I'm hard - but fair. SteveBaker 03:37, 7 November 2007 (UTC)

Yep. What struck me about the original poster's report is that when the moon is close to full, it spends most of its time in the night sky and not so much in the day sky. (For a crescent moon, of course, it's the opposite.) So to see the moon 3/4-full close to noon actually is fairly unusual. Arbitrarily guessing Richmond for the poster's location, I plugged some different dates into this page and figured out that the date in question must have been Tuesday, October 30. The moon was 73% full and in Richmond it set at 12:50 pm. And of course the moon being close to the horizon triggers the moon illusion and makes the sighting even more impressive. --Anonymous, 07:33 UTC, November 7, 2007.

I saw he same thing on the same day at same time from near Dulles airport. I have lived here since 19770. What was unusual about that day was that the air was extraordinarily free of any pollution. What I noticed first was that the sky far from the sun as the darkest I have ever seen at midday, and there was a very obvious gradient (darker to lighter blue) toward the sun. I attribute the lack of pollution to the fact that we had just had a rain after the longest drought in about 20 years. We usually have a lot of urban pollution and a lot of terpene "pollution" from the mountains to the west. The moon was about half-way from the sun to the darkest part of the sky. -Arch dude 17:42, 7 November 2007 (UTC)

Bindeez to GHB??

Apparently these toys can be converted to 4-Hydroxybutanoic acid when swallowed... The toys apparently can be arranged into some pattern and will set when you put water on them..

http://www.theage.com.au/news/national/victoria-bans-toxic-toy/2007/11/07/1194329268448.html

Anyone know what the beads are made of? 1,4-Butanediol according to http://www.news.com.au/perthnow/story/0,21598,22712449-2761,00.html

So how about a conversion mechanism? Assumingly it has acid is involved in the conversion. Been a while since I've done organic chem but this looks like a very simple conversion... How did this ever get on the market??— Shniken1 03:07, 7 November 2007 (UTC)

Obviously first one of the hydroxy groups gets protonated... draws electon density from the carbon... promotes nucleophillic attack..?Shniken1 03:10, 7 November 2007 (UTC)

Oh well, not to worry - you can still buy them online here: http://www.redsave.com/products/Bindeez-Super-Studio-Design-Centre,,22 (eeeekkkkk!!!!). —Preceding unsigned comment added by SteveBaker (talk • contribs) 03:47, 7 November 2007 (UTC)

[16]. It's a fairly common chemical reaction, although I'm not sure how this would happen in the body, or if it would necessarily happen in this manner. (and damn you, Steve Baker, your edit conflict somehow crashed my web browser.) Someguy1221 03:52, 7 November 2007 (UTC)

In the body it looks like it's converted using alcohol dehydrogenase and aldehyde dehydrogenase (from the 1,4-butanediol article. GHB = 4-hydroxybutanoic acid). Maybe someone with more biochem experience can give more info --Bennybp 03:59, 7 November 2007 (UTC)

The account I read suggested that the toxic versions were made of different stuff to the normal versions, which were a non-toxic glue. So the ones you buy online might be safe. Or not. Skittle 04:01, 7 November 2007 (UTC)

The Counterpartness (Not a Real Word, But You Know What I Mean) of Human Races and Animal Breeds

I know that the topic of whether or not the idea of "human races" is biological or scientific is controversial in general, but what about when comparing them to breeds of animals? The idea of being a "breed of animal" is considered biological and scientific, is it not? And aren't human races and breeds of animals counterparts? And, if so, then why do the words "breed" and "race" exist separately and are not one word, as humans are scientifically animals (I know this has to do with history, but, if my assumptions are right, then why hasn't a word been been developed)? Also, if human races and animal breeds are counterparts, then why is there controversy over whether or not human races are biological and scientific? I know that included a lot of questions, but any help on any part would be great! Thanks! —Preceding unsigned comment added by Pitman6787 (talk • contribs) 05:43, 7 November 2007 (UTC)

A brief answer, but this undoubtedly go further. As you suggest the origin of the words is undoubtedly historical rather biological as the concepts are similar - it's just another case of a different word being used largely through the antiquated ideas of humans not being animals, and the consequences of that mode of thought. Now if you read the breed article you'll see the second sentence says "For a type to be recognised as a breed, there should be a viable true-breeding population." This has always been a big issues with human races - there is not a viable true-breeding population in any so-called race - basically given any contact there is immediate crossbreeding, and there is huge variation within populations. One of the other significant problems is that definitions of human races are distortions - claimed characteristics of given races rarely, if ever, hold true across that 'race'. Another problem is simply the misuse of race given almost any chance - why look for tenuous and largely non-existent differences and claim them as scientific when they will be mainly used for political and discriminatory purposes, and when the truth is that our similarities are far greater than our differences? --jjron 08:14, 7 November 2007 (UTC)

"Now if you read the breed article you'll see the second sentence says....", why bother go that far. The first damn line says a breed is a DOMESTICATED subspecies. So by definition, a human population can't be a breed simply because humans are never domesticated. So we are talking about subspecies. And it is thought, biologically, that the differences between the so called, races, are not significant enough to be classified as different subspecies. Different races have different colored skin, some differences in noses, hair texture, and eyes, but that's it. That's not significant enough to classify as a different subspecies. Perhaps if these groups were isolated and remained isolated for hundreds of thousands of years, then we would observe more pronounced differences between the different human populations. 64.236.121.129 21:10, 7 November 2007 (UTC)

There are several differences between breeds and races, some of which are more a matter of degree rather than clear-cut distinctions:

For one thing, with dog breeds for instance, in general the genetic variation between individuals within a breed is much smaller than the genetic variation between breeds. This is reversed with race: the genetic variation between races is much smaller than the genetic variation of individuals within one race.

Looked at another way, dog breeds in general consist of very clear-cut, genetically isolated populations. In contrast, with humans the prevalence of various genotypes and phenotypes often changes gradually over a geographic area, with less in the way of clear-cut boundaries. Because of the above and other complications, it’s very difficult to try to define and test for race genetically. See Race and genetics.

Within one geographical area, it may feel like there are reasonably clear-cut distinctions between races, if that geographical area contains large groups of people that had been relatively genetically isolated within recent history. For example, it works at least to some degree to group at least a lot of people in the U.S. based on whether most of their ancestors came from Europe, from western Africa, or from southeast Asia. But that moderately workable grouping to a large extent disappears if you consider all the people in the world as a whole, in which there are more gradual genetic variations over geographical areas.

Another difference between breeds and races is that there is a cultural aspect to race. Whether two populations of humans are grouped as one race or two depends a lot on how culturally similar or dissimilar the two populations are perceived as being. This is yet another reason why it is very difficult to try to define race in any rigorous way. See Race (classification of human beings). MrRedact 08:39, 7 November 2007 (UTC)

Material Properties in outer space

Hi, In hearting about the ISS unfurling their solar array and having it tear and all that - it got me wondering... Aren't these materials near Absolute_zero? Doesn't metal and plastic freeze solid at absolute zero? I guess not. —Preceding unsigned comment added by InverseSubstance (talk • contribs) 06:46, 7 November 2007 (UTC)

Why do you think that the temperature at the ISS is near absolute zero? The atmosphere at this height is quite hot. Not that this would matter - the temperature of the ISS is far more dependent on radiative heat transfer. Icek 07:06, 7 November 2007 (UTC)

The problem with this stuff is that somewhere, somehow, some scientist let slip the idea that space is cold. The truth is that space isn't any temperature. Temperature is (essentially) a measure of the average speed that atoms are moving around within some substance. No atoms - no temperature. So let's get rid of that idea. The temperature of spacecraft comes about in the same way things do down here at sea level - you add up the energy coming in (mostly sunlight - but also reflected earth-light and heat generated on-board the craft) - and you subtract the energy going out (by reflection of sunlight, and emission of infra-red light). If there is more energy coming in than going out, the temperature goes up and if more is going out than coming in, the temperature goes down. If the temperature increases, then more and more infra-red light is emitted and eventually you reach a temperature at which sufficient IR light is leaving that the temperature strikes a perfect balance. Similarly if the temperature falls, so does the IR emission and again, the temperature eventually stabilises. This is the same mechanism we have down here on earth - except that we also gain and lose energy by conduction into and out of the surrounding atmosphere and the ground. Also we get more incoming heat from scattered light from the sky.

OK - so those are the mechanisms. What happens with the solar panels? Well, as sunlight comes in, they heat up, the temperature slowly rises and they heat up - and when the spacecraft orbits around to the dark side of the planet, there is no more sun - so the temperature slowly decreases. The space station orbits (from memory) about once every 75 minutes. So the temperature of the craft goes up for about 37 minutes then cools off for 37 minutes over and over again. The large metal components take a long time to change temperature by much so they are going to tend to settle down to some more reasonable average temperature. So imagine a large chunk of metal down here on earth - if you take a large chunk of steel (a car perhaps) at some nice toasty temperature (because you've been driving it) and park it out in the snow in mid winter, would it cool down to freezing in 30 minutes? I don't think so. It certainly won't cool down to absolute zero over just 30 minutes! In earth, the car is cooled both because it's radiating IR light - but ALSO because it's heating up the air around it - that hot air rises and is replaced by cold air - so that's quite an efficient way for the car to lose heat. But up in space, there is no air - so it can only lose heat by radiation. That means that our solar panel will take MUCH longer than the car to drop to freezing point - and VASTLY longer to cool of to anywhere close to absolute zero - and it's only in the dark for 37 minutes in each orbit.

Another way to think about this is to watch the movie Apollo 13. Those guys had to live for nearly a week in an unheated spacecraft. The lunar lander got cold - but no so cold that they couldn't survive in their flight suits. Those spacecraft had to be spun so that one side of the craft wasn't perpetually in sunlight and the other perpetually dark. The ISS orbits - so that's not necessary for them.

SteveBaker 18:58, 7 November 2007 (UTC)

Regarding the original question, the relevant metals and plastics are of course already frozen (solid) at room temperature.

Regarding 70.116.10.189's answer, a little nitpicking: There are atoms - and even molecules - up there, but the density is too low to have a significant impact on the ISS's temperature. Even at more than 780 km height, where ERS-2 orbits, the atmospheric density is at least several hundred particles per cubic millimeter.[17]

And the space station's orbital period is 91 minutes.

Icek 14:25, 7 November 2007 (UTC)

Two Questions about Gravity.

Okay. Why isn't there a "nuetral" gravitational force? Okay. Let me explain. I think I was told by a teacher that, if there were no gravity on a planet, then it would be virtually impossible to reach it, as no force would be pulling you in. But, at the same time, that would seem as if there were a "negative" force keeping you away from the planet. But, why would there HAVE to be a force pulling you INTO a planet to be able to reach it, when there is NO "negative" gravitational force keeping you AWAY from it? That doesn't make any sense to me. Why isn't there "neutrality" in gravity?

Also, wouldn't we not have been able prove that gravity existed until we proved there were "gravities" that have different levels of force than Earth's? My thinking is that, until we proved there were "gravities" with different levels of force than Earth's, the only "gravity" that we knew existed was on Earth, with equal gravitational force on everything. So, basically, as far as we knew, gravity had only only level of force, but, knowing that, how could we prove it existed? I wish you could see into my mind, as my thinking is much better than that --- I just can't put it into words. It's like, since we knew there were different levels of force, we knew there had to be a force at all. Okay. Lets say humans were the only were the species that existed (work with me here), and we still classified the human being as a "species" --- like saying gravity existed when there was only, as far as we knew, one level of gravitational force. So, if there were only one type of species, then how could we prove that the concept of a "species" existed? Or, let's say EVERYTHING in the universe moved at the exact same speed (work with me here). We couldn't prove that a concept of "speed" existed, as, only one speed existed, right? We use the word "speed" because there are different speeds. If everything moved at the same speed, then we couldn't say "He's running fast" or "He's running slowly" or "He's moving at [number]/[unit] [length of time]." We could only say "He's moving", right? Or, if there were only color in the universe, we couldn't call it a color, right? We couldn't prove that the concept of color existed, unless we found a different color, right? It's like, if EVERYTHING in the universe had a quality about it that was the EXACT SAME, then how could you call it or prove that it was a characteristic at all? --- there would only be one type. I hope you know you what I mean. And I'm not saying that, even if there were only one level of gravitional force in the universe, that gravity wouldn't exist. I'm just saying that, before we found out that there are different levels of gravity, we really didn't have any proof that gravity existed --- knowing that there are different levels of gravity REALLY proves that there some kind of force exists, right?

Any help would be great! Thanks! —Preceding unsigned comment added by Pitman6787 (talk • contribs) 06:58, 7 November 2007 (UTC)

Re the first question, that's nonsense. Firstly you wouldn't have a planet without gravity, but let's just say you did. Saying that you couldn't get there because the gravity wouldn't pull you in is like saying you can't navigate to an arbitrary place in empty space because there's nothing pulling you in - but you can navigate through empty space to any given point. Your instincts are right, that there's nothing preventing you getting there. I'll leave the second question to others. --jjron 07:54, 7 November 2007 (UTC)

I would say for the second one, the problem is the inability to test variables that are beyond our capability to create or measure. The ancients knew well that gravity pulled anything that wasn't too light towards the center of the earth, but until Newton, no one figured a way to test gravity outside of the earth. And then finally, Henry Cavendish found a way to both eliminate the earth's gravity from affecting measurement, and measure the gravity between metal spheres. Similarly, until the 20th century, testing the extremes of small distances and great velocities was beyond anyone's capabilities. As such, while we were certainly capable of imagining classical mechanics as applying just the same to such conditions, this was entirely not the case. When people found ways to test them, they confirmed laws that changed the way physicists thought about the world. Someguy1221 08:39, 7 November 2007 (UTC)

Excellent questions ! Why does the gravitational attraction between two bodies depend on their masses but not what they are made from ? Why isn't there such a thing as anti-gravity paint ? Why doesn't anything have negative mass (as far as we know) ? Why is gravitational mass equivalent to inertial mass ? It was thinking deeply about these sorts of questions that led Einstein to the general theory of relativity in which gravitational forces are due to the curvature of spacetime. Gandalf61 10:57, 7 November 2007 (UTC)

Yes, you do some real thinking. What you say about our not seeing a thing that has no variation is quite true. That's part of the reason it took so bloody long to figure it out. Hats off to old Isaac, eh? You might be the one to see the remaining things of that kind. Keep us posted. --Milkbreath 12:17, 7 November 2007 (UTC)

We (well, people like Kepler and Newton) observed the orbits of other moons and planets and deduced from that that there must be a force attracting planets and comets towards the sun and a force attracting moons towards the planets. It's not much of a stretch to deduce that the smaller, lighter things are producing less force than the bigger, heavier things. You can go on to calculate how much force the earth is exerting on the moon - and with a sufficient leap of imagination - that the apple that just fell onto your head was being pulled by the same exact force (well, the apple story is probably apocryphal - but you get the idea). From the outset, we knew of many different sources of this mysterious attractive force. It was hard to quantify it because you can't easily figure out the mass of something that you can only see through a telescope as a blurry dot - but it must have been very clear that the gravity due to (say) Jupiter was vastly greater than that of Mars because you can SEE that Jupiter is huge, even in a primitive telescope. So they knew there was some kind of size/strength relationship. They could also figure out the decreasing pull of gravity as a function of distance. It took more careful experiments with big iron balls and very accurate measurements to get the details and the math exactly right - but the fact that there were differences and that the earth wasn't the only thing that had gravity must have been known for a very long time. SteveBaker 18:56, 7 November 2007 (UTC)

I wouldn't say so. While the idea may have occurred to people, the Aristotelian/Platonic system of celestial spheres was widely accepted (in the West) until Galileo began his astronomical observations in the early 17th century. Someguy1221 19:02, 7 November 2007 (UTC)

Omega-3 fatty acids in water-inhabiting animals

Why are omega-3 fatty acids so prevalent in water-inhabiting animals? They are prevalent in unrelated species, like whales, fishes and crustaceans. I guess they are produced somewhere near the bottom of the food chain. Is there some evolutionary advantage for omega-3 producing water-inhabiting animals? Icek 07:13, 7 November 2007 (UTC)

Quite a few prevelant microalgae produce omega-3 fatty acids. And yes these are on the bottom of the oceanic foodchain, so anything consuming them will also be rich in omega-3 fatty acids. As a matter of fact many fish can barely synthesise their own omega-3 fatty acids, and thus are almost fully dependent on microalgae. As to the evelutionary advantage of producing these specific fatty acids as opposed to producing others I do not know. PvT 12:54, 7 November 2007 (UTC)

Correct design?

Little Boy design is shown as having a round bullet with a cylindrical hole being fired at a cylinder shaped plug that fits in the hole. This arrangement seems counter intuitive to firing the cylinder plug into the cylindrical hole so as to avoid the problem of a rounded projectile twisting out of alignment versus the plug only being able to rotate in the gun barrel. Why was the arrangement shown used instead of the other way around? Clem 07:51, 7 November 2007 (UTC)

Little Boy#Counter-intuitive design. I think your link answered your own question. Someguy1221 08:43, 7 November 2007 (UTC)

The first picture does not seem to show the projectile as a hollow cylinder but rather as a hollow ball. Even with the alignment question answered it is still not totally clear to me why the hollow cylinder has to move instead of the plug. ...until you include the Tungsten-Carbide tamper as part of the movable projectile or stationary target. Clem 09:12, 7 November 2007 (UTC)

I think the first picture is just meant to be schematic in a cartoony way. --24.147.86.187 15:30, 7 November 2007 (UTC)

The page basically says that the larger area is actually more than one critical mass (which is certainly true) but kept from being critical by being in a tube shape (it has a hole in the middle so the uranium isn't too close to itself). If you put that into the large neutron-reflecting tamper you'd run the risk of too many neutrons spontaneously floating around and creating a criticality accident. So you keep that part far away from the neutron reflectors, and only when you bring it together is it subjected to their reflection. I don't know if that is true or not but it sounds plausible to me. You'd have additional problems created by such an arrangement but it might let you use more uranium to compensate. --24.147.86.187 15:33, 7 November 2007 (UTC)

One of the scarier experiments they did when designing that bomb was described in one of Richard Feynman's books - they actually dropped the cylindrical tube part over the core part experimentally to try to measure the amount of neutrons that would be produced - but they arranged that the tube would not stop when it was in the right position for an explosion - but merely keep on going. The theory being that if you could do this fast enough, you could avoid the chain reaction getting big enough to make a nuclear explosion. However, since they weren't 100% sure what the outcome of the experiment would be until they did it, it was always possible for something to go horribly, horribly wrong! Needless to say, this was a pretty dangerous experiment because if anything got stuck or moved just a bit too slowly...KABLOOIE! The building where they did those tests was way, WAY out in the desert! SteveBaker 18:28, 7 November 2007 (UTC)

Actually, they managed to kill at least a couple of people working on the Manhattan Project through careless manipulation of near-critical masses of radioactive material. See Criticality accident#Incidents, Harry K. Daghlian, Jr., Louis Slotin. TenOfAllTrades(talk) 19:01, 7 November 2007 (UTC)

derivation of phrase sex maniac

would like to know what the specific derivation is as not common in english language to use maniac with other terms eg dont describe someone as a chocolate maniac or a drug maniac.86.4.107.45 10:05, 7 November 2007 (UTC)

See Hypersexuality. The concept of hypersexuality replaces the older concepts of nymphomania (or furor uterinus) and satyriasis. Lanfear's Bane | t 10:37, 7 November 2007 (UTC)

Chicken-eating spiders

To my astonishment, I found this statement in the Raising Chickens Wikibooks:

"In south America there is a type of spider that will prey on chickens"

What kind of spider is that? It must be huge... --Taraborn 11:10, 7 November 2007 (UTC)

The Goliath birdeater is native to South America and seems to be a contender for the largest spider in the world [18]. However, despite its name it seems it does not normally eat birds - our article says it got its name because one specimen was once seen to eat a hummingbird. So very doubtful that it, or any spider, could prey on chickens. Gandalf61 12:16, 7 November 2007 (UTC)

...said he a moment before the Gargantua wizardeater, a species as yet unacknowledged by Western science, sank its glistening poisoned fangs into the nape of his neck. --Milkbreath 12:47, 7 November 2007 (UTC)

Don't forget good old Shelob. Lanfear's Bane | t 13:15, 7 November 2007 (UTC)

It can prey on a chicken and still be a pretty modest spider. If it has a venomous bite - then it could certainly kill a chicken and yet be pretty small - that a small spider might eat a small amount of a dead animal might not be surprising. I don't think we can dismiss this just because we can't imagine a two foot spider pouncing on the chicken and ripping it limb from limb with inch long fangs! SteveBaker 18:20, 7 November 2007 (UTC)

OP-AMP LM324N

I happen to have constructed a PC-TEMP indicator circuit. It uses two LM35 and LM324N(quad op-amp) to act as a comparator(ZCD). In order to trigger the buzzer, I have used another Op-AMP as a summer - Zero Cross Detector, which takes it individual inputs from the 1.6v drop across two seperate LED's that indicate which TEMP is glowing. The reference voltages of both op-amp can be calibrated using two potentiometers. The measured voltages across the points without OP-AMP in place are as desired. But the moment I place the OP-AMP, it does not function as a comparator. Testing the IC LM324 on a IC-tester gave a 'one good' result. Im not sure what is causing this problem. I am using 5v-0v power supply and 1.8M+(1.8M||1.2M)+((.47Mpot+.47M)||(.47Mpot+.47M)) resistance combination from 5v giving me a practical reference voltage range from .51v to .30v for both the op-amp comparators.

Output from each comparator drives a seperate LED+1K resistor.Output from both LM35 is proper.

I feel that the Mohm resistance may be a bit too high for the op-amp, but I need some guidance. Please help.59.92.242.80

I think we'll need to somehow see a schematic diagram to understand what's going on. But in the meantime, can I suggest you see the Schmitt trigger article to understand how to build some hysteresis into your zero-crossing detector? Perhaps our Threshold detector with hysteresis article will also be helpful?

Atlant 13:38, 7 November 2007 (UTC)

You can check that the power supply polarity is good, also that you are using the in and out on one of the four opamps and not from the others. The opamp may sink half a microamp, which should just tolerate your megohm resisters. But you may be better off with a few 100000 Ω instead. —Preceding unsigned comment added by Graeme Bartlett (talk • contribs) 01:22, 8 November 2007 (UTC)

Civil engineering: Factor of safety?

in Civil engineering- what is a Factor of Safety ? and why do we use it ? —Preceding unsigned comment added by 82.69.206.166 (talk) 12:26, 7 November 2007 (UTC)

Welcome to Wikipedia. You can easily look up this topic yourself. Please see factor of safety. For future questions, try using the search box at the top left of the screen. It's much quicker, and you will probably find a clearer answer. If you still don't understand, add a further question below by clicking the "edit" button to the right of your question title. .--Shantavira|^{feed me} 13:44, 7 November 2007 (UTC)

Put simply: If you are building (say) a bridge and the heaviest truck you expect to cross it weighs 20 tons, you shouldn't build a bridge that can only support 20 tons because you know damned well that some idiot is going to drive a 21 ton truck across it - and you probably suspect that the steel you built it with is only 95% of the strength they said it would have at the steel mill, so it'll only really support 19 tons anyway. Then you know that the bridge will corrode some over it's lifetime and maybe the crew who build it make a little mistake and don't put the rivets quite close enough together - and maybe you didn't realise that in 100 years time, the bridge will have been painted 10 times and so it's now got half a ton of paint to support as well as that truck. So right at the outset, you look at the 20 ton limit and you say to yourself "I'd better build a bridge that can support 30 tons - and that way I'll be OK no matter what". The extra 10 tons you added is the "Safety factor" for the bridge. Of course you shouldn't over-do this because it's likely that a bridge that can cope with (say) 40 tons will cost twice as much as one that'll only support 20 (or was that 19?). That's all there is to it - nothing complicated. SteveBaker 18:01, 7 November 2007 (UTC)

Too obvious to be realizable?

What is the process by which plant cells transform carbon to oxygen, and can it be synthesized? If so, is that technique applicable to reducing carbon in our atmosphere? If not, how unrealistic an idea is this? Beekone 14:04, 7 November 2007 (UTC)

Photosynthesis is the process by which plants use light energy to convert carbon dioxide and into oxygen and glucose. Your idea of carbon sequestering is a good one...see also our Carbon dioxide sink article. DMacks 14:23, 7 November 2007 (UTC)

See photosynthesis for details on the process. Note that this reaction requires energy (sunlight) to occur, so we would need enormous amounts of energy for significant results (think of how many trees there are in the world, and multiply that by at least 100 to get the total weight of algae, which produce about 80% of our oxygen). From the article, "Through photosynthesis, sunlight energy is transferred to molecular reaction centers for conversion into chemical energy with nearly 100-percent efficiency. The transfer of the solar energy takes place almost instantaneously, so little energy is wasted as heat." This means that not only would we need huge solar panels or lots of nuclear plants to do this cleanly, but we still would be nowhere near as efficient as plants. That's not to say it isn't possible: certainly the reaction produces food on the order of Soylent Green in artificial sugar-rich goodness, which might be very economical in the future. But as far as significantly impacting the CO2, I sincerely doubt it would have much effect. We're better off by first and foremost switching all our power plants to renewable and nuclear sources, which would be necessary for the reaction to have net effect anyway. SamuelRiv 14:30, 7 November 2007 (UTC)

Since when was photosynthesis efficient? Biological processes are notorious for being inefficient. I heard a retired biology professor say that photosythesis was inefficient. 64.236.121.129 16:22, 7 November 2007 (UTC)

Depends what you mean by "efficiency". To quote the article: "This chemical energy production is more than 90% efficient with only 5-8% of the energy transferred thermally." but "Not all wavelengths of light can support photosynthesis.". DMacks 19:21, 7 November 2007 (UTC)

It just struck me as such an obvious solution that surely someone had thought of the implications. I thought I'd leave it up to you guys to drop some knowledge on me. Thanks for pointing me in the right direction, very interesting stuff! Beekone 14:52, 7 November 2007 (UTC)

I do vaguely recall some experimental setup with large polythene bags full of some liquid that you'd lay out in the sun and bubble air through to capture the CO2 and produce some kind of useful product - it's not in widespread use though which suggests that there was some problem with it. But the answer is simple enough - cover a greater percentage of the earth's surface with plants (restoring the sahara to greenery would help for example) and stop cutting down the rainforests and starting forest fires! You can even harvest the plants (so long as you plant new ones immediately afterwards) and either use them to make ethanol/biodiesel to run your car sustainably or (if you actually want to sequester CO2), toss the dead plants into an anaerobic landfill someplace (so they don't produce methane as they rot).

Sadly, the very effect we're trying to prevent (global warming) is the exact same effect that's causing deserts to increase in size and making it harder to grow crops in those kinds of places. SteveBaker 17:52, 7 November 2007 (UTC)

Psychology: person A evaluates B by the evaluation of C, D, E.... for person B.

This happens quite often. Is there a name for this please? And are there any known personality traits of person A that make them more likely to indulge in this? Thanks 80.2.214.75 15:19, 7 November 2007 (UTC)

Could you give an example, or a more detailed question? I'm having a lot of difficulty understanding what concept you might be looking for. On the off chance that I've got it right, is projection the term you seek? TenOfAllTrades(talk) 16:37, 7 November 2007 (UTC)

This sounds like gossip to me! That is, making judgements about people solely based on what you've heard others say about them. 83.249.121.85 16:41, 7 November 2007 (UTC)

"Checking a job applicant's references"? -- Coneslayer 16:42, 7 November 2007 (UTC)

An example: when I was at college girl X was attracted to me in proportion to the amount of esteem that she observed other people had for me; while girl Y was attracted to me irrespective of what other people thought. I am curious about how girl X and Y may differ in personality. I have seen this in men also: I was interviewed for a job once by the boss of my future boss, and when my future boss saw that his boss was taking an interest in me, his behaviour towards me improved greatly. I imagine that this behaviour is associated with authoritarianism, in-groups and out-groups, perhaps Machiavelimism and so on.

Another example could be germans who evaluated people of the jewish faith according to nazi propoganmder, and others who were more resistant to the propoganda. Another example is here http://news.bbc.co.uk/1/hi/scotland/north_east/6273231.stm where it says women are attracted to men according to the attention they receive from other women.80.2.211.126 23:12, 7 November 2007 (UTC)

Energy

We are told that energy can neither be created or destroyed but say a person throws a ball which eventually comes a complete stop, where has that energy gone? —Preceding unsigned comment added by 195.188.208.251 (talk) 17:53, 7 November 2007 (UTC)

It all winds up as heat, thermal energy. Whenever energy vanishes from a mechanical system (throwing a ball is a simple such system), it mostly becomes heat. Someguy1221 18:00, 7 November 2007 (UTC)

Look at potential energy, and also energy in particular 'forms of energy'. it has a bit on a bouncing basketball. and further down the conservation of energyny156uk 18:02, 7 November 2007 (UTC)

Yes - and in the case of the ball, what happened was that the successive final bounces of the ball deformed the rubber that it's made of and that caused the rubber to heat up and the ball to bounce a little less high the next time - the ground too would flex a tiny bit and gain some heat at the expense of the ball. Also every time it bounced, the ball made a noise - which required some of the kinetic energy to be consumed in making the air vibrate - but the moving air has some internal friction which heats the air up a tiny bit as the sound dies away. In the end, it's turning all of that interesting kinetic energy into generalised, diffused heat. But it might take a while - we can come up with some scenarios in which it takes an INSANELY long time to finally turn all of the energy of the ball into heat. Suppose the ball landed on (of all things) a WintOGreen flavored Life Saver and crushed it. A weird property of that particular candy (called triboluminescence) would actually result in a small pulse of blue and UV light to be radiated outwards as the candy was crushed. Of course as that light is absorbed, it too will turn into heat - but a small fraction of the light would head upwards, escape from the earth's atmosphere and head out into space. It could be trillions of years before the light hits a stray bit of cosmic dust - but when it does, you just get some heat. This tendancy for everything interesting to eventually turn into heat is called Entropy and it's really rather depressing. Can we talk about something else now? :-( SteveBaker 18:15, 7 November 2007 (UTC)

Related question

If one were to invent a 100% perfectly efficient machine, would it not produce any sound, as sound would be a result of friction and wasted energy? -- MacAddct  1984 ^{(talk &#149; contribs)} 19:36, 7 November 2007 (UTC)

Yes, exactly. (Except of course if the machine were designed to produce sound, like a loudspeaker or musical instrument.) —Keenan Pepper 19:49, 7 November 2007 (UTC)

The way intelligence grows on the "nurture" side

Hi! After studying the "nature vs. nurture" aspect of intelligence in a high school psychology class, I came up with my own "theory [in respect that I have never read or heard anything related to the ideas in this "theory" before]" on how intelligence grows on the "nurture" side of things. I know this isn't the place to post personal theories and want them to be proven or disproven, but, after thinking about this one, I thought it was a basic enough concept that it would have to have had already been proven or disproven by now --- so I am now simply looking for someone to confirm or deny this.

Okay. My "theory" is that, indirectly, the more you know, the more intelligent you are --- not simply because you know more, but because, knowing that you DO know more, we know that you have used your brain more, which is the reason you're more intelligent. I am relating this to physical fitness. Physical muscles [as opposed to the mental muscle (i.e., the brain)] grow --- along with phsyical fitness level --- as you exercise more. Why wouldn't the same be true with the brain, except with gaining more knowledge other than exercising? The brain is a muscle, too, right? And, so, using that muscle more (i.e., gaining more knowledge) would increase THAT muscle's competency too, right?

Going along with this, I know a lot of people criticize I.Q. tests, saying "Well, the I.Q. test included questions with information I just never learned before! It wasn't fair! Just because I never learned information doesn't mean I'm less intelligent!" But I criticize that criticism, with the information I posted above. Also, or people will say "Just because I didn't receive that high a level of education doesn't mean I'm not intelligent". But, again, I am trying to refute that.

And I think that the statements in the paragraph above are made and thought of because of people's emotions. I know that it isn't always people's faults that they didn't receive that high of a level of education --- and because it wasn't their fault, it would be "mean" to think a person is less intelligent because of a reason they couldn't help. But, whether or not you can help your level of education, (according to what I am thinking) the higher the level of education you have, or the more knowledge you know, the more intelligent you --- indirectly. Again, not because you learned and know more but because you used your brain --- a muscle --- more, which increased its competency.

And I do realize that, with the "nature" side of intelligence, people can still be intelligent, despite low level of education, or lack of knowledge, as their base --- or genitic factor of --- intelligence might have been high at birth. I am just saying that knowing more information is a GENERAL indication of a higher intelligence.

Again, I thought this was a basic enough concept that it had to have been proven or disproven by now. So, which is it? —Preceding unsigned comment added by Pitman6787 (talk • contribs) 19:37, 7 November 2007 (UTC)

Just giving you a few of my thoughts here. Anybody who exercises more, will grow more muscles, but only a few can become top athletes - the ones that have excellent genes. Yes, if you know more, you will get a higher result on some intelligence tests, but people differ in how much information they can gain and reproduce (and by testing this you would rather test memory instead of intelligence), and, more importantly, having a huge fund of information doesn't mean for instance improved reasoning skills or perceptual abilities, which also are considered to be important parts of intelligence. —Preceding unsigned comment added by Lova Falk (talk • contribs) 19:48, 7 November 2007 (UTC)

I'm not sure if you saw this page section: Intelligence quotient#Environment. --JWSchmidt 20:59, 7 November 2007 (UTC)

Re: education. I don't think anyone would argue that a mind well-tested as a mind sharpened. If you are in the habit of dissecting logical arguments, for example, you are going to be better at it than if you were not in that habit. The question is whether that measures what we think of as "intelligence" or not. Expanding that definition to include education makes sense in some cases, but not in others. Look at the test questions from the Army Alpha Intelligence Test (1914-1918). Try and tell me with a straight face that knowing who Rosa Bonheur is, what product Velvet Joe was the mascot for, or what a Wyandotte is measures anything other than exposure and retention of simple factual information? Those are the extreme examples, but everything else in the "informational" section falls under that category; it's entirely possible to be quite bright and just never learn where exactly the pancreas is in one's body; and on the converse it's possible to be quite dumb and know simple things like that. It's well known that total dolts can excel at bar-room trivia; that's not a measure of intelligence of any sort. So clearly some line must be drawn between being asked questions that are purely "educational" and those that are not; knowledge of miscelleanous facts is not what anyone generally considers "intelligence" to be. --24.147.86.187 01:08, 8 November 2007 (UTC)

Re:Sorting it out. We have somewhat sorted out, the answer is "it's complicated, and it's something of an artificial question." Genes provide the template for an organism which then must develop in an environment; they are not mutually exclusive categories in many respects. They are in a complicated relationship, some times more complicated than others. With very simple traits (single-point mutations) it is not too hard to untangle in most cases; when talking about more complicated genetic traits then development starts to play a big role. When talking about something like "intelligence", the exact definition of which is quite murky, then it becomes exceptionally hard to untangle, and many environmental and genetic factors start being at play. But it isn't a simple "x% this, x% that" sort of equation; it's the complexity that comes from having an organism develop, where genetic code tells individual cells what to do, but somehow we are supposed to understand complicated aggregate behavior of an entire organism. It's not that we don't know how to sort some of these things out, but sorting them out in a straightforward way has proven pretty difficult, especially if we are talking about groups that exist in complicated social dynamics that cannot be really reasonably escaped for the purposes of testing. --24.147.86.187 01:08, 8 November 2007 (UTC)

Human Evolution

Well, Heroes is on again tonight. I was just wondering if there are any clues as to how H. sapiens will evolve in the medium term. Obviously i am not expecting spontaneous levitation, telekenesis or other such nonsense - more physiologically. Are humans now capable of purposefully selecting a route of evolution to their own ends? --russ 20:13, 7 November 2007 (UTC)

The things we are evolving are likely to be small tweaks that make us better suited to our environments...not major stuff like being able to fly. One example of a "recent" evolved change has been adult lactose tolerance. Most other mammals (and humans as recently as the ancient Egyptians) are lactose intolerant as adults. When we started farming and milking goats and cows, there was a clear advantage for humans who were able to digest milk. So we started to evolve lactose tolerance and the lactose intolerant people started to decline in numbers. However, in our modern world, it seems very unlikely that you could die without leaving offspring just because you are still lactose intolerant - so it seems like that genetic change hasn't spread throughout the population yet. It wouldn't surprise me if we started to adapt in ways that helped us in the modern world...but genetic changes take thousands of years and our environment has changed so dramatically in just the last 100 years that we havn't had time to evolve to support that change. If I had to go out on a limb and predict something, I'd suggest that we might evolve a way to avoid obesity. That kills off a lot of younger people and certainly reduces their attraction to the opposite sex - so it ought to have a serious impact on reproductive capability. If a gene came along at random that helped avoid that problem then I imagine it would sweep the western world in a matter of just a few thousand years. But you can't KNOW that this will happen.

As for whether we are purposefully driving evolution - in a sense, we always have. By being selective with whom we mate with - we make that choice quite a lot. In terms of using gene replacement therapy we MIGHT make a change. As a matter of fact though, it's possible that we're inadvertently screwing things up rather badly. Think about this. What happens if a married couple want a baby and can't have one? They go to the scientists and magic wands are waved, incantations spoken and (in quite a few cases), a baby is the result. In fact, multiple babies may result in an unnaturally large percentage of the cases. So if there were a genetic cause for infertility that would normally be strongly selected against, we could quite easily accidentally make it not only NOT be selected against - but because of the possibility of multiple births due to fertility drugs, we might even make genetic infertility become a trait that tends to increase over time. That's pretty worrying - but it's exactly the kind of thing that we'd be just stupid enough to do.

SteveBaker 20:27, 7 November 2007 (UTC)

The ancient Egyptians were lactose intolerant? Them and 70% of adults alive today. Algebraist 20:41, 7 November 2007 (UTC)

That 70% seems very high. Even more so are some of the population-specific numbers -- none of the many various Asian Americans I know have ever identified themselves as lactose intolerant, and I've certainly seen them consuming cow by-products before. jeffjon 21:21, 7 November 2007 (UTC)

If milk causes such problems in so many people, why is it so popular? Do only 30% of the population drink milk? Surely people wouldn't drink it if they were afflicted? --212.204.150.105 21:18, 7 November 2007 (UTC)

The degree of lactose intolerance is highly variable in both its severity and its age of onset. Some people don't begin suffering until their 30s or 40s, and even then, many lactose intolerant individuals can drink a cup or two a day without suffering any symptoms. Someguy1221 21:31, 7 November 2007 (UTC)

70% has got to be *WAY* too high. The article says that there are multiple causes - we're talking here about people who are congenitally lactose-intolerant as adults - not people who are that way because of diseases. But even so, there simply is no way that number can be right in any of the parts of the world I've lived in. Out of all of the people I know well enough to have been able to tell - at least 20 or 30 people - I can only think of one who suffers from that condition. If it's 70% then the number should be 15 to 20 of them...there is no way I can not know those people that badly. We've had every one of them over to our home for dinner on multiple occasions - my wife's French - everything has cream sauces and such. No - it's not 70% in Europe or North America. It's gotta be way less than 10%. 70.116.10.189 23:38, 7 November 2007 (UTC)

If 70% seems way too high to you, it’s because of which people you’re typically exposed to. The mutation that allowed lactose to be digested by adults happened quite recently (on an evolutionary scale) somewhere in northern Europe. So if you hang out around people of primarily northern European descent, then the 70% is going to seem high to you. But if you lived in China or Thailand, that figure would seem very low to you. MrRedact 00:32, 8 November 2007 (UTC)

70% was for the whole world. See Image:LacIntol-World2.png. Someguy1221 00:34, 8 November 2007 (UTC)

70% for the world seems right when you factor that there are two large groups that traditionally had lactose-intolerance issues - Africans and Asians. There are a hell of a lot of Africans and Asians in the world, compared to Europeans which have less of an issue traditionally. Americans have a far, far lower rate of lactose intolerance - probably due to various worldwide cultures intermixing genes to allow them to spread faster. Kuronue | Talk 04:54, 8 November 2007 (UTC)

Historically, the idea of humans "purposefully selecting a route of evolution to their own ends" has often been a bad idea, especially with Nazi eugenics. MrRedact 00:49, 8 November 2007 (UTC)

Of course, if we have eliminated natural selection by using fertility clinics, that makes genetic research that much more important. It seems to me that if we want to survive as a species, eventually we are going to have to manipulate our genes, either before or after we are born. 68.231.151.161 01:49, 8 November 2007 (UTC)

I'm not sure that we need any help on that. See also Population, Carrying capacity, Sustainability, and Earth. I think the better question is why are we doing so well as a species, and at what point should we stop trying to let people live longer. All things considered, we're simply going to run out of physical space in which to fit everyone. --slakr^\ talk / 04:40, 8 November 2007 (UTC)

Some argue that humanity’s ecological footprint already exceeds one Earth.[19] But there’s no problem with still trying to let people live longer, as long as we simultaneously reverse the population explosion through voluntary population control measures such as improving access to family planning and reproductive health care and information, eliminating incentives to have larger families, and public education about the consequences of continued population growth. MrRedact 05:21, 8 November 2007 (UTC)

Special Wheel Supported on the Lower Rim

I remember seeing somewhere a wheel that was supported on the rim below the wheel's center point. The vehicle using the wheel had no axles. I assume the rim at the point of support had some kind of bearings. The wheel had nothing inside the rims. This had the benefit of lowering the vehicle's center of gravity. Can anyone point me to a reference for this arrangement? ThreeE 20:54, 7 November 2007 (UTC)

Have you tried Hubless wheel? --TrogWoolley 22:31, 7 November 2007 (UTC)

Perfect. Sbarro (http://www.burningart.com/meico/moto/sbarro/) was the designer I was looking for. Many thanks. ThreeE 23:38, 7 November 2007 (UTC)

What is the oxidation number of carbon in methanol?

What is the oxidation number of carbon in methanol? According to the article oxidation number, I get 4 (four shared pairs of electrons, in which one of each pair belongs to carbon, results in a charge of +4 upon removal). --212.204.150.105 21:14, 7 November 2007 (UTC)

Well, the oxidation state is the charge that carbon would have if the bonds were all ionic, so you need to know, for each bond, which atom is more electronegative. Given that this could be a homework question, I'm not going to tell you the answer. Someguy1221 21:29, 7 November 2007 (UTC)

I know that the oxidation state is -2 (oxygen more electronegative and three hydrogens each less electronegative), however my question pertains to the oxidation number which according to the WP article can sometimes be different. I expect, that the oxidation number should also be two, but when I follow the instruction given in the first sentence of the WP article, I get 4, as described above. Is the article wrong or is my interpretation wrong (and if so, how)? --212.204.150.105 21:44, 7 November 2007 (UTC)

I belive that's only in reference to coordinate bonds. Oxidation numbers are usually only used for metals. Someguy1221 21:55, 7 November 2007 (UTC)

The article on oxidation state says Redox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed - firstly, I don't think it should say oxidation number (especially not preferentially to oxidation state) and thirdly, I read elsewhere that it should take into account the electronegativity - I think it's possible for an atom to be reduced even without a change in oxidation number, so long as the ligands of the product are less electronegative than the ligands before. Thus I think the article is at best misleading, if not wrong. --212.204.150.105 22:31, 7 November 2007 (UTC)

Why is the waste disposal system the same as the reproductive system?

Not the same, biologically speaking, but using the same body parts. Why is it like that? Do you peeps think it has some kind of evolutionary function or it's merely a bad design that just evolved that way because it works without any major malfunctions (although there are sometimes malfunctions). 64.236.121.129 21:33, 7 November 2007 (UTC)

Er, not sure what you mean. In mammals the reproductive system is separate in all respects except for the dual-purpose male phallus. In other vertebrates the two systems do vent at the same place, the cloaca.--Eriastrum 23:12, 7 November 2007 (UTC)

And the reason for that arrangement is basically that the original chordate body plan consists of a muscular tube with a hole at each end. Any elaborations on that, such as limbs or extra orifices, are later additions, and are unlikely to occur unless there has been some selection pressure for them at some point. We can thus deduce that, for example, at some point in the evolution of placental mammals there was an evolutionary advantage to females having a separate vaginal opening. Figuring out what the cause of the pressure might've been is left as an exercise for the reader. —Ilmari Karonen (talk) 01:12, 8 November 2007 (UTC)

You don't know what I mean? Drop your pants and see where your sexual organs are, and where your waste disposal organs are. DUH. Come on, this ain't rocket science peeps :). 64.236.121.129 15:31, 8 November 2007 (UTC)

I think this argument is questionable. Sexual reproduction exists outside of phylum Chordata and presumably predates it, so one might as easily discover that the development of a spine was an elaboration on some proto-tubeworm's reproductive system. I don't know what the relationships actually were, but they are presumably very, very old. Dragons flight 03:10, 8 November 2007 (UTC)

I Cannot think of a good reason why poop is RIGHT by the fun stuff! PS dude above, MAMMALS: NOT SEPERATE at all...Hands and feet,..now that's seperate —Preceding unsigned comment added by 76.168.69.208 (talk) 02:09, 8 November 2007 (UTC)

I'm actually curious as to this as well. Not just humans - most female mammals that I'm familiar with have both vaginal and anal openings within a few inches of each other. Considering how irritated the vaginal opening can get when feces is accidentally introduced (personal experience here - always wipe front to back!), this seems counter-intuitive. Kuronue | Talk 04:58, 8 November 2007 (UTC)

Perhaps, there were some advantages in the prenatal development of these organs that let it evolved in this way. See Development of the urinary and reproductive organs. What about digestive and respiratory systems? They seem to have some overlaps as well. --Vsion 05:43, 8 November 2007 (UTC)

Because this enables humans to cover for most eventualities with just one item of underwear.--Shantavira|^{feed me} 09:07, 8 November 2007 (UTC)

I think it is merely just a bad evolutionary design that stuck merely because it worked satisfactorily, although it is anything but ideal. 64.236.121.129 15:36, 8 November 2007 (UTC)

series of vaccine for rabies

Following an encounter with a rabid fox, I received a series of vaccine for rabies as treatment. A month later I was planning to donate blood at the local Red Cross. Prior to my scheduled time at the Red Cross, I had contacted a physician who had said that it was okay for me to donate my blood. However, the people at Red Cross thought differently and told me that I have to wait up to one year to donate again. Do you know how long a person who has received the series of vaccine for rabies needs to wait and why?Pumpkin68 21:37, 7 November 2007 (UTC)

Time limits are pretty much arbitrary. The (U.S.) Department of Defense concurs with your Red Cross information: they require a wait of 1 year before blood donation if the rabies vaccination was given for rabies exposure (an animal bite, for example); there is no wait if the rabies vaccine was given for other reasons, and the donor is symptom-free. Thus the wait seems to be dictated by the animal bite and not the vaccine. - Nunh-huh 22:27, 7 November 2007 (UTC)

Are other mammals attracted to female mammary glands?

Human males are attracted to girls with big boobs. Is there any scientific evidence that shows other mammals attracted to mammary glands? Like maybe a male Bull poking its nose against a cow's big puffy thing at the bottom (utter? whatever you call it). 64.236.121.129 21:45, 7 November 2007 (UTC)

Not really what you're looking for at all, but slightly related: Koko, the female Gorilla that liked to see and touch human nipples (both male and female). jeffjon 21:57, 7 November 2007 (UTC)

It is my understanding that the male attraction to breasts is part genetic, part culturally trained. The genetic part I always assumed worked on the basis that larger breasts made a female look like they would produce enough breast-milk to rear a large family - thus making them more attractive to the males who wish to spread their seed. Now i cannot say this is scientific, i probably heard it some place and took it as true, and i'm sure there'll be science that shows breast-size has little impact on the amount of breast-milk a woman can produce, but that has been my idea. If this angle is correct then other animals will have an interest in any female/male attributes that show-off to the group/pack that they are fertile/strong, whatever the other sex wishes them to be. So things like Peacocks showing off their fantastic tails to attract peahens (lots of birds have coloured plumage to attract other birds) or the male lions fighting for pack-dominance because that will often lead to them having the best female-mates. Look at sexual attraction ny156uk 00:41, 8 November 2007 (UTC)

I think I can say with a great deal of certainty that other mammals are not attracted to female mammary glands. Check out our cleavage article. And be sure to read the linked citations too (actual pages from the book, I think). --Cody Pope 02:32, 8 November 2007 (UTC)

I think I've heard it speculated that the phenomenon of enlarged female breasts in homo sapiens is an example of an evolutionary arms race, or more specifically, runaway evolution. (This is basically what ny156uk was saying.) —Steve Summit (talk) 03:16, 8 November 2007 (UTC)

All other mammals are attracted to mammary glands. That is the single defining behaviour of mammals (the clue is in the name!) However, in most mammals the attraction wanes considerably on weaning. As far as we can tell, only adult humans consider breasts sexually attractive. Incidentally, investigating how and why mammals find breasts attractive (for suckling, not for staring at in Playboy) and the sensory mechanism through which that attraction is mediated, is what I do for a living. We have some interesting and surprising findings, but I'm afraid I can't tell you what, is it is not yet published. At work today I spent the afternoon timing babies crawl around on naked female breasts. Its a tough job! Rockpocket 09:07, 8 November 2007 (UTC)

Cats which like milk would be attracted to the smell of milk from a lactating female human. Edison 13:11, 8 November 2007 (UTC)

Unweaned mammals (meaning young which still want to nurse) don't seem to care where the meal comes from, as long as they get fed. Simple experiment: Have a post-puberty female human pick up a nursing puppy or kitten. Expected result (because I've seen it many times): If allowed, the puppy or kitten will attempt to nurse. A hungry baby mammal just doesn't care who or what owns the teat; he/she/it just wants a meal. The news is full of cross-species nursing. Even our own legends (founding of Rome) are full of it. -SandyJax 16:13, 8 November 2007 (UTC)

That isn't entirely true, the literature shows that the smell of milk from different species does not always promote suckling in others, irrespective of Romulus' experience. For example, its the smell of 2-methylbut-2-enal in rabbit milk the promotes suckling in rabbits. Human, cat or mouse milk does not promote suckling in rabbits because, presumably, they do not express 2MB2 in their milk. The suckling promoting odors of other mammals have not yet been identified. Rockpocket 19:20, 8 November 2007 (UTC)

I once read a story in the newspaper about a woman who breast-fed a litter of orphaned kittens. That is about all I have to contribute to this thread. --Kurt Shaped Box 20:04, 8 November 2007 (UTC)

a reaction is either oxidative or non-oxidative, never inbetween

AGEs can be formed via oxidative pathways (e.g. carboxymethyllysine [CML] and pentosidine), via non-oxidative pathways (such as pyrraline), or from highly reactive dicarbonyl precursors, such as glyoxal, methylglyoxal and 3-deoxyglucosone (3-DG). - a reaction is either oxidative or non-oxidative; how can they give three categories then? The dicarbonyl precursors either react oxidatively or they don't... --137.120.53.67 21:47, 7 November 2007 (UTC)

What's an AGE? Delmlsfan 23:42, 7 November 2007 (UTC)

Could be Advanced glycation endproduct, what you get when you cook carbohydrate with protein. Graeme Bartlett 01:05, 8 November 2007 (UTC)

Amnesia

What is the name of the illness where the sufferer experiences amnesia every few minutes? Keria 22:23, 7 November 2007 (UTC)

I forget. -- Coneslayer 22:38, 7 November 2007 (UTC)

Anterograde amnesia. Someguy1221 22:39, 7 November 2007 (UTC)

effect heat has on rubber

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In oxygen atmospheres, combustion is the usual result. Delmlsfan 23:44, 7 November 2007 (UTC)

If you can exclude oxygen, it will give off hydrocarbon gasses and liquids, and leave behind some kind of charcoal. Graeme Bartlett 01:02, 8 November 2007 (UTC)

Vulcanization? Heat equation and heat transfer will get you started on how the energy transfers along the bulk, but your relevant parameters ("k") are going to be temperature dependent and sample deformation will be an issue. At low temperatures, rubber becomes frangible (yet another way to have fun with liquid N₂). At some temperature depending an what you mean by "rubber" (i.e. the stuff that comes out of the tree or any of several commercial products and colloquial usages meaning materials having the characteristic bouncyness of rubber), your sample will melt. Very shortly thereafter, it ceases being rubber, as above. Eldereft 05:44, 8 November 2007 (UTC)

November 8

cells

what would happen if you place a blood cell in a hypertonic solution —Preceding unsigned comment added by Dmx123 (talk • contribs) 00:37, 8 November 2007 (UTC)

The reference desk it not for answering homework questions, but if you can't figure this one out on your own, you should read osmotic pressure. Someguy1221 00:49, 8 November 2007 (UTC)

... or Osmosis or Diffusion. --slakr^\ talk / 04:35, 8 November 2007 (UTC)

... or better yet, hypertonic. (The article answers this very question.) -- 20:21, 8 November 2007 (UTC)

navel

hey how come for some people when they're fingered in their belly button, it hurts and for others it tickled them?Jwking 01:00, 8 November 2007 (UTC)

Because some people don't know how hard to poke, and just stab you with their finger. HYENASTE 01:17, 8 November 2007 (UTC)

Reception of off air frequency standards

May be a stupid question, but why, when receiving, do you need a local oscillator to phase lock to the incoming signal? Only reason I can think is that the transmitted signal is not constant in amplitude. Why cant you use the incoming frequency dorectly? Also, why do you need a quartz Xtal osc to be locked to the incoming frequency, won't a normal vco do? —Preceding unsigned comment added by 79.76.246.62 (talk) 01:42, 8 November 2007 (UTC)

It's for FM reception. The radio signal is varying slightly up or down in frequency depending on the amplitude of the sound wave it's trying to transmit to you (Frequency Modulation). You tune the radio's local oscillator to the nominal center frequency and it's easy to produce an audio signal that's proportional to the difference in frequency of the local oscillator and the radio signal. SteveBaker 01:59, 8 November 2007 (UTC)

Er, no its AM. [20] —Preceding unsigned comment added by 79.76.246.62 (talk) 02:20, 8 November 2007 (UTC)

You need a very low bandwidth. Typically the signal will be 5kHz wide, at a frequency of 10MHz. A VCO is no where near stable for this and will drift off in a few minutes. You can see this on old cheap shortwave radios, which will need retuning every so often. The crystal oscillator is much more stable. A VCO locked to a crystal is one way to get flexibility. Another important thing for a frequency standard is low phase noise. The best way would be to have a narrow crystal filter at 10 MHz, but even so the ionosphere causes fading and phase shifts. For 60kHz standard a LO would not be needed. Graeme Bartlett 05:57, 8 November 2007 (UTC)

So you can use the ultra stable 60 kHz freq directly (or multiplied up to 1 MHz or 10 MHz or whatever)? Is that what your saying? If so, why do most designs use a local oscillator locked to the incoming frequency? —Preceding unsigned comment added by 79.76.246.62 (talk) 12:06, 8 November 2007 (UTC)

See Superheterodyne receiver. Changing the frequency of the local oscillator is what tunes the radio to a station. Its frequency is beat against everything coming in from the antenna. The resulting harmonics are filtered for the intermediate frequency, 455kHz in the case of AM. A big advantage to this system is that from there on the amplifiers need only pass the one relatively low frequency. I don't know what you mean by a crystal oscillator locked to the incoming frequency, but it has been a long time, so please clarify. --Milkbreath 03:33, 8 November 2007 (UTC)

Crystal control is absolutely not needed in an AM radio. I have owned several old AM radios which would stay tuned to a station for a year or more without re-tuning. Older car radios had pushbuttons which mechanically rotated a tuning cap to the desired stations, and did not need re-tuning for years at a time. Edison 13:10, 8 November 2007 (UTC)

Minerals

Is it possible to make a mineral (in this case a molecule containing iron) magnetic by running an electric current through it, or around it? I have reference here to the specific mineral asbestos, or one of its several 'subspecies'?76.182.3.188 01:56, 8 November 2007 (UTC)

Very few minerals can be magnetized in a way such that they remain magnetic after the inducing field is removed. See Magnetization. A good many minerals, including some without iron, such as salt, can be made to give a diamagnetic response while the inducing field is present, but I do not think asbestos is one of them (but I'm not certain about that). Cheers Geologyguy 03:03, 8 November 2007 (UTC)

Most minerals do not conduct, so you cannot easily run a current through them. In the case of asbestos it is a good insulator so it will not conduct at any reasonable voltage. If you ran a current around it you would have an electromagnet. The atoms in the mineral would respond in some way, but most have no strong response. A few Iron minerals may respond with ferromagnetism and even be magnetised as in Magnetite Graeme Bartlett 05:52, 8 November 2007 (UTC)

See Lodestone, a mineral (Fe3O4) some samples of which are found in the ground as natural magnets. The Wikipedia article does not say it, but other sources say the magnetism may result from lightning striking the mineral [21] [22] [23]. Edison 13:07, 8 November 2007 (UTC)

microwave hyperthermia

any reason not to heat someone up (their whole body to 104 F - 107 F) with a very high tech microwave (in order to generate a healing fever)? It penetrates and is the same frequency as cell phones... —Preceding unsigned comment added by 76.168.69.208 (talk) 02:02, 8 November 2007 (UTC)

Microwaves do not heat everything uniformly, and in particular they will heat organs with a high water content more rapidly. Of special concern are the eyes where high levels of microwaves can promote cataracts and other damage.

On the more general point, I'm not sure that heat is necessarily helpful in fighting disease. Fever is one of a myriad of reactions the body produces to combat disease, but an externally produced hyperthermia might be more detrimental than helpful since it wouldn't necessarily be accompanied by the same suite of immune responses as a natural fever. Dragons flight 02:25, 8 November 2007 (UTC)

Also note: Wikipedia does not give medical advice. Anyway, the Hyperthermia article states that temperatures above 104 degrees Fahrenheit are "life threatening". I wouldn't reccomend it either, unless you know what you are doing, and I would get a second opinion (from a qualified professional) either way. I also have never heard of inducing a fever to heal by this method (or any), as fevers are caused naturally by the body as part of the immune response. SmileToday☺(talk to me , My edits) 02:28, 8 November 2007 (UTC)

He might have gotten this from last week's episode of House, in which a portion of a treatment for an individual was artificially raising his body temperature. Someguy1221 02:39, 8 November 2007 (UTC)

Microwave heating of smaller regions of the body to fever-range temperatures has been tested for various therapeutic purposes. If you're envisioning putting the entire body in a microwave oven (even a high-tech one) to heat the entire patient at once, you're out of luck. Per Dragons flight, you would get dangerous local heating effects that are very difficult to control. There are other, lower-tech methods that are just as effective. Where I have seen microwave heating employed is to do rapid, local thermal ablation of smaller volumes—a microwave antenna is inserted into a solid tumour, and the temperature elevated high enough to 'cook' the tissue.

If you go to ClinicalTrials.gov and search on the term hyperthermia, you'll find a number of trials – mostly for cancer – that are testing the use of whole-body hyperthermia as a way to sensitize the body to radiation or chemotherapy or to potentiate the immune system's response to malignant tissue (e.g. [24], [25], [26]). Techniques that have been used to achieve hyperthermia include induction heating, warm wax immersion, hot water blankets, and radiant infrared heating. Patients under general anasthesia can also be treated using extracorporeal hyperthermia—blood can be drawn from the body, warmed externally, and returned to circulation. TenOfAllTrades(talk) 12:45, 8 November 2007 (UTC)

Why is water transparent?

Why is water transparent? I did some searching, and the reason for this is because water is transparent to the visible spectrum of light. But why does it exhibit this property? Does it have something to do with its hydrogen bonds that are responsible for so many of its other special properties? Acceptable 02:37, 8 November 2007 (UTC)

There’s some explanation of this in absorption spectrum. Which frequencies a water molecule can absorb depends on what possible quantum states the molecule has. The frequencies of photons that the molecule can absorb correspond to the possible differences in energy between pairs of states. The ratio of a difference in energy level to the corresponding freqency of light is known as Planck's constant. MrRedact 03:20, 8 November 2007 (UTC)

I should point out, water is slightly blue. Malamockq 03:28, 8 November 2007 (UTC)

Consider checking out Color of water. --slakr^\ talk / 04:32, 8 November 2007 (UTC)

Tectospinal tract

Is it safe to conclude from this picture that the superior colliculus is connected with the inferior colliculus through the tectospinal tract? Lova Falk 10:29, 8 November 2007 (UTC)

There are some axons that go from the superior colliculus to various brain locations (tectobulbar axons) but I think the vast majority of the axons in the tectospinal tract first go anterior (ventral) and then cross the midline before descending past the level of the inferior colliculus. A good neuroanatomy textbook will have a figure for the tectospinal tract showing a series of brain cross-sections, one at the level of the superior colliculus, one at the level of the inferior colliculus and several more going down to the spine. This is the best I could find online (and it is not very good). --JWSchmidt 18:51, 8 November 2007 (UTC)

Point and shoot digital camera

Is it true that camera manufacturer deliberately introduce shutter lag into PS digital camera to "encourage" their clients to buy the much much more expensive DSLR camera instead. 220.237.184.66 12:06, 8 November 2007 (UTC)

Unlikely, as not all point-and-shoot manufacturers have a DSLR in their lineup. One reason that comes to mind is that contrast-detection autofocus is slower than phase-detection autofocus. It's also possible that "something" has to be done to the CCD or CMOS sensor before taking the shot, if the sensor has been used for a live preview. For example, CCDs may accumulate charge that needs to be cleared. Since DSLRs generally do not have a live preview, they can keep the sensor ready to shoot. Maybe people know of other factors that I'm not thinking of. -- Coneslayer 13:31, 8 November 2007 (UTC)

Inelastic collision

About Inelastic collision As we know that in inelastic collision the initial and final momentum,total energy are conserved but kinetic energy is not conservsed.this is why ,why kinetic energy is not conserved .Plz explain the example of the collsion of cars.also mentioned it that after collsion the two cars come to rest then how is initial and final momentum the same , as they are moving with a speed before collision .thanx ........usman —Preceding unsigned comment added by Star33 2009 (talk • contribs) 13:15, 8 November 2007 (UTC)

It may be useful to compare inelastic collisions with elastic collisions, whereby kinetic energy is conserved (see the first two sentences of that article, then contrast with the lede in inelastic collision). As for the car collision, bear in mind that physics is not nearly so concerned with "speed" as it is with velocity, and consider that the momentum of the two-car system is what's being conserved, not the momentum of the two individual cars. — Lomn 14:00, 8 November 2007 (UTC)

I actually ran a little experiment on this. Kinetic energy is always conserved as a physical law- if it's not, you haven't included everything in the system. So we have to know where the energy of collision goes to. I modelled this with a spring system, as springs are a good approximation for any interaction and well-established in the interaction of particles. So then we have energy initial = energy final, or $KE_{1}+KE_{2}=KE_{1,2}+E_{\textrm {spring}}$. Now note that the energy of the spring includes both the spring potential energy, 1/2kx^2, and the kinetic energy of particle 1 and 2 oscillating against the spring. It is what is called a simple harmonic oscillator. So now

$KE_{1}+KE_{2}=KE_{1,2}+KE_{1,2{\textrm {spring}}}+1/2kx^{2}$,

and so energy is conserved. The spring model has some consequences: it implies both that there are oscillations between the two particles after collision and that there is a non-zero collision time with finite acceleration. In the intro physics lab which I TA, the data showed the finite acceleration which agreed to good approximation with the theoretical acceleration of the spring (a linear differential equation - if you want me to show you how it is solved, please let me know), but no oscillations after collision. This is because the oscillations are quickly damped out as heat (another differential equation), which should also be measurable with a calorimeter, but I haven't tried this experiment. Energy is still conserved, as heat is another form of energy for which we can account.

For your second question, note that momentum is a vector quantity, so it has both magnitude and direction - that should put you on the right track. SamuelRiv 14:11, 8 November 2007 (UTC)

camera pixel resolution

What is the engineering standard for stating the number of pixels that make up a camera? The actual number of individual sensors, i.e., the number of rows of sensors times the number of columns of sensors on the chip, or the number of different areas of a picture that are focused onto a single sensor or single small group of individual sensors in sequence to build the whole picture? Clem 13:54, 8 November 2007 (UTC)

Megapixel ratings are just a description of the number of sensors. The fact that more goes into a good picture than that rating alone is one of the reason the rating system is seen as being somewhat deceptive. As the page points out, in cameras this is even more deceptive, since each sensor generally registers only one color, and so the final image resolution can be easily a third less than the MP rating. --24.147.86.187 15:03, 8 November 2007 (UTC)

Old cars carbon emissions

How does the average carbon output of a 1980 1.4l petrol engine compare to a recent one? I heard statistics saying that 20% of the oldest cars represent 60% of total emissions. Is this correct? In view of these statistics some countries want to tax (or are already doing it) old cars. If we add the carbon output of producing a new car and disposing of the old one to the equation, is it still so favorable to buying a new car vs. keeping an old one running longer? Should we add to this the carbon output necesssary to produce enough wealth to buy the new car or is this irrelevant? Thank you. Keria 14:06, 8 November 2007 (UTC)

Please be sure to distinguish pollution from carbon emissions. Older engines emitted far, far more pollution (unburned hydrocarbons, carbon monoxide, and the like) but the amount of carbon ultimately emitted is a strict function of the fuel economy of the car. Your 1980 1.4L car is probably emitting much less carbon per mile than my 2003 4.2L Audi (which averages about 25 miles/US gallon).

Atlant 17:20, 8 November 2007 (UTC)

Ladder to Space

There's this infinitely tall ladder in my backyard. When I climb three or four feet and let go of the rungs I obviously fall back down to the ground. What is the minimum distance I would have to climb so that when I let go of the rungs I would never fall back down to the ground? (I think the answer is 22,240 miles where I would join all the geostationary artifical satellites of the Clarke Belt, but I'm not sure. Orbits, and rocket science in general, confuse the bejeezus out of me.) Sappysap 14:08, 8 November 2007 (UTC)

You might want to check out Space elevator. -- Coneslayer 14:17, 8 November 2007 (UTC)

It'd be geostationary orbit altitude, but only if you're also at the equator. Climbing a ladder ascending vertically from New York will not put you in a stable orbit at that altitude; you'd have to go higher. Climbing a ladder from the North Pole confers you no velocity and you'll drop from any altitude. I'm guessing the tangent of latitude is relevant to exactly how high you've got to go, but I'm not sure. — Lomn 14:24, 8 November 2007 (UTC)

Irrelevant Post Ahead: I just have to say, that Space Elevator article is extremely fascinating. Beekone 14:49, 8 November 2007 (UTC)

That is true. See Coriolis effect. We can calculate the height needed to get you in orbit - the thing about a ladder is that it's rigid, so your angular velocity at the top of the ladder is equal to the angular velocity of the earth at that latitude, so your orbit will only occur at a geosynchronous distance: see Geosynchronous orbit derivation. SamuelRiv 14:52, 8 November 2007 (UTC)

Where's a mathematician when you need one? Say your ladder is at 40 degrees north latitude. You will have to climb up to where your speed is the geostationary orbital speed. This will be higher than if your ladder were at the equator. When you let go, you will move toward the earth until you reach the geostationary altitude where you'll stay until perturbations mess things up. I'm sorry, but I don't feel like deriving the formula for all that, the relationship between angular velocity, altitude and latitude. Where's that mathematician? There are guys who can do this sort of thing in their head. --Milkbreath 17:13, 8 November 2007 (UTC)

Perhaps they're all here?

Atlant 17:17, 8 November 2007 (UTC)

Right. I had a chance to think about this just now while watching a Labrador retriever do his business (hardly a Newtonian anecdote, eh?). The only way you'll be able to let go of the ladder and just stay there is if the ladder is at the equator. So, the nerds are off the hook. (I suspect that the answer to my pointless question above is a straight line tangent to the earth at a geostationary point above the equator.) --Milkbreath 17:41, 8 November 2007 (UTC)

The effect of stars on Earth

What if a genie were to withdraw all of the stars in the universe except the sun, and the photons in transit to Earth were taken away as well. Would there be a gravitational effect? Would there be a climate change on Earth? Essentially, do the stars in the night sky play any describable role in Earth's affairs? —Preceding unsigned comment added by 150.167.179.111 (talk) 17:00, 8 November 2007 (UTC)

Well, stars provide a useful amount of light on a clear night (see night vision), but I think there's no other routinely discernable effect. The opinions of astrologers will differ, of course.

Note: It is thought that a sufficiently close supernova would emit enough gamma radiation to toast us all, but I think we all hope that won't occur any time soon, so I'm excluding that as a current effect.

Atlant 17:11, 8 November 2007 (UTC)

The stars are all far enough away that gravity is not an issue; starlight doesn't make up an appreciable amount of radiation reaching Earth so it shouldn't have any effect on the temperature, climate, etc. My bet would be "no". The stars don't play any real physical role in Earth's affairs. --24.147.86.187 18:57, 8 November 2007 (UTC)

For that matter, said genie could remove everything but Earth/Moon/Sun and we'd see no appreciable difference apart from the view in the nighttime sky. — Lomn 19:10, 8 November 2007 (UTC)

In terms of climate, the effect of the loss of every single star is essentially nil over any short or medium time scale. (Over an extremely long period of time – hundreds of millions of years – there's the risk Atlant notes of a nearby supernova explosion.) This web page talks about using single stars as light sources of known, carefully-measured intensity for evaluating the sensitivity of digital camera sensors. Interestingly, it also provides the relative illumination provided by starlight (0.001 lumens per square meter) compared to full daylight (10 .000 lumens per square meter). Making the reasonable assumption that most of the energy we receive from starlight will be at visible and near-visible wavelengths, distant stars contribute less than a millionth of the incoming radiation to Earth.

As for gravity, the effect is again negligible unless a massive star passes extremely close to the Earth-Sun system. (This would be a very rare event.) Since gravitational force follows an inverse square relationship, a star the size of the Sun only one light year away will pull on the Earth lss than one-billionth as strongly as the Sun does. TenOfAllTrades(talk) 19:52, 8 November 2007 (UTC)

growing crystals of copper sulfate

how would you make a hot, concentrated solution of copper sulfate? —Preceding unsigned comment added by 86.42.210.0 (talk) 17:24, 8 November 2007 (UTC)

You would boil some water (perhaps in a kettle), pour it in a heat resistant glass or ceramic container, then add copper sulphate crystals and stir. Do not use aluminium or stell containers as copper will plate on to their surfaces. Then you decant the solution. Commercial copper sulphate probably has ferrous sulphate as well, so it may not be pure. As the solution cools you will get a growth of crystals. Graeme Bartlett 20:14, 8 November 2007 (UTC)

Viruses

Virus is a DNA With a Protein Coat Protecting It Can a virus be destroyed if the protective protein coat is damaged so that it cant protect DNA anymore if yes then can an enzyme be used as protease to digest the protein coat thus destroying the virus ????? —Preceding unsigned comment added by 212.71.37.97 (talk) 18:04, 8 November 2007 (UTC)

Proteases generally act, well, in a general way. They either consume a protein at one of its ends, or they cleave proteins at specific amino acids. So as you can see, a protease based antiviral measure would cause quite a bit of collateral damage if used to "carpet bomb" infected tissue. It could destroy or inactivate the virus; however, some viruses are even evolved with this in mind, and cleavage of viral proteins upon entering the cell can actually activate the virus (I can't for the life of me remember what article this is in, but it came up in a previous ref desk question I can't find in the archives). Far easier to target them with antibodies. Someguy1221 19:39, 8 November 2007 (UTC)

ecosystem

can you show me a picture of an ecosystem (example) that a 4th grader could use to help them do a project? —Preceding unsigned comment added by 72.18.102.36 (talk) 20:16, 8 November 2007 (UTC)