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-   -   Perpetual Motion (http://www.physicsforums.com/showthread.php?t=660018)

samsara15 Dec20-12 06:11 AM

Perpetual Motion
 
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?

mfb Dec20-12 08:00 AM

Re: Perpetual Motion
 
Quote:

Spin does work.
Not without slowing down.

Quote:

Why isn't the spin of particles considered to be perpetual motion?
The spin of particles is not motion. They are not rotating. Spin is just a quantum number, similar to charge.

Quote:

Doesn't particle spin violate the laws of Thermodynamics?
No.

Khashishi Dec20-12 02:48 PM

Re: Perpetual Motion
 
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.

ModusPwnd Dec20-12 04:48 PM

Re: Perpetual Motion
 
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.

mfb Dec20-12 05:02 PM

Re: Perpetual Motion
 
Both types are called perpetual motion.


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