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Maxwell's Demon

  1. Nov 4, 2004 #1
    This came up in another topic, but rather than talk on about it there, I created a new thread as it would be too far off subject for the said other thread.

    I don't see the big deal about "Maxwell's Demon". Assuming the walls and everything in the system are perfect insulators, wouldn't (grossly oversimplifying here) the door, being the size of a molecule, have to be made of at least 1 molecule, and the 'creature' require enough energy to move this 1 molecule back and forth for each molecule/transition that must occur?

    What does everyone think?
  2. jcsd
  3. Nov 6, 2004 #2
    Yes, that is one of the explanations that has been given to this paradox. Anotherone is that the demon would require energy to "measure" the speed of the molecules. The action of measuring would also modify the moleculeĀ“s energy.

    The paradox is based in a completely classical model, and molecules do not behave classically. The paradox has no sense in a modern microscopic description of matter.
    Last edited: Nov 6, 2004
  4. Nov 29, 2004 #3
    Oh, so how do molecules behave?
  5. Nov 30, 2004 #4
    Quantum models describe their behaviour. Molecules are systems of particles, electrons and nuclei. Classical laws failed to describe them a hundred years ago.
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