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Perpetual Motion

  1. Dec 20, 2012 #1

    samsara15

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    Elementary particles spin. So does the Earth. Spin does work. The spin of electrons and other elementary partlces never stops, or slows down. Why isn't the spin of particles considered to be perpetual motion? Doesn't particle spin violate the laws of Thermodynamics?
     
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  3. Dec 20, 2012 #2

    mfb

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    Not without slowing down.

    The spin of particles is not motion. They are not rotating. Spin is just a quantum number, similar to charge.

    No.
     
  4. Dec 20, 2012 #3
    There's nothing unphysical about perpetual motion unless you try to extract energy from it. Throw a ball in space and it will keep moving until something stops it.

    The spin merely stores energy; it doesn't generate it. If you have a spin lattice, you might be able to extract some energy by aligning all the spins, but then you are done. You can't extract anymore energy until you unalign the spins, which takes all the energy you got out. Same basic story is true for all "perpetual motion" scenarios.
     
  5. Dec 20, 2012 #4
    The buzz phrase "perpetual motion" means an over unity, more energy out than in type device. It may not seem technically correct, but that is what it means.
     
  6. Dec 20, 2012 #5

    mfb

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    Both types are called perpetual motion.
     
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