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 07-08-2002, 09:02 AM #16 (permalink) luckyeddie Hall of Fame Member     Join Date: Jun 2002 Location: Derby, England Posts: 17,629 Another answer for Roy. Please note that Quantum Mechanics is not one of my strong suits. If anyone can add to the explanation, please feel free to do so. ... explain the uncertainty principle Heisenberg's Uncertainty Principle states that "The more precisely the POSITION is determined, the less precisely the MOMENTUM is known in this instant, and vice versa". What he is referring to here is subatomic particles, in particular electrons. My first thought is that he could have actually reduced that principle still further, since momentum is mass times velocity. The mass of an electron is known and does not vary, therefore the momentum is directly proportional to its velocity. Consequently, Heisenberg's principle OUGHT to read "The more precisely the POSITION is determined, the less precisely the VELOCITY is known in this instant, and vice versa". That's not an answer, is it? OK, I'll try again. In order to determine anything (position, velocity, momentum) to do with a particle, I have to MEASURE it. Now, each measurement has some error built into it (you can never measure anything precisely). Fine so far? OK. Now, let's assume that our accuracy of measuring things is improving. Eventually, we become so good at measuring that we can say, to all intents and purposes, we are 'spot on'. Now, we take our super-duper ultra-accurate Vernier calipers or atomic clock or whatever, and we introduce it to the system where we have our electron which is whizzing around. We get closer to the flipping electron until, eventually, we bump into it (disturb it really, and move it, so it's no longer where we thought it was). Not only that, we have also disturbed our measuring device too, but that's another story. Maybe Heisenberg can help me find my car keys. Only two brain cells left, now. Heisenberg v Erwin Schrodinger will have to wait. Can't we have questions about biomechanics, so one of our other eggheads can have a go? Why is it always the physics and the momentum and the black holes and the quantum mechanics (Burhey!)? I'm not touching self-replicating DNA with yours. __________________ Nigel Clough's Black and White Army, beating Forest away with 10 men