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Old 12-02-2005, 04:48 PM
KenProspero KenProspero is offline
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Join Date: Jul 2004
Posts: 123
Default Re: The existence of random

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The laws of physics apply on all the matter in the universe. Therefore it could be resonable to expect that knowing the current state of the universe including all its matter, energi, position etc. etc. would give you (in theory) enough info to foretell how the universe would be in 1 day or 10000 years as all the universe is bound up in the laws of physics.

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In fact, based on our best current understanding, it appears that the laws of physics say the exact opposite.

The view you state is generally attributed to Laplace. "In effect what he said was, that if at one time, we knew the positions and speeds of all the particles in the universe, then we could calculate their behaviour at any other time, in the past or future." (Quoting Stephen Hawking Hawking Lecture

Laplace's view of the Universe was generally accepted throughout the 19th and early 20th centuries. However, the development of Quantum Mechanics by Planck had implications that are inconsistent with Laplace's view. Specifically, Heisenberg demonstrated that if quantum mechanics is correct, it is impossible to measure both position and the speed of a particle precisely. This is called the Heisenberg Uncertainty Principle.

(Again, quoting Hawking)"Laplace's vision, of scientific determinism, involved knowing the positions and speeds of the particles in the universe, at one instant of time. So it was seriously undermined by Heisenberg's Uncertainty principle. How could one predict the future, when one could not measure accurately both the positions, and the speeds, of particles at the present time? No matter how powerful a computer you have, if you put lousy data in, you will get lousy predictions out."

Now, if you want, you can choose to not believe in quantum mechanics as a law of physics. And take heart, if you do so, you're in good company -- Einstein, was unable to accept the implication of the Heisenberg Uncertainty Principle of the randomness of nature. His view is often summarized by his famous quote "G-d does not play dice."

(quoting Hawking)"He seemed to have felt that the uncertainty was only provisional: but that there was an underlying reality, in which particles would have well defined positions and speeds, and would evolve according to deterministic laws, in the spirit of Laplace. This reality might be known to God, but the quantum nature of light would prevent us seeing it, except through a glass darkly."

However, experimental science seems to show that Einstein was wrong on this point. The best scientific evidence to date is that Heisenberg is correct. Based on this evidence, it appears there is a randomness in nature, and G-d does,in fact, play dice.

(Most of this post is a truncation of the Hawking lecture, for which a link has been provided. If you're interested in the subject, I highly recommend the lecture in its entirety.)
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