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Faster than light electron spin

  1. Dec 15, 2012 #1
    I understand that we are not to think of an electron literally spinning on its axis because the equatorial speed would far exceed the speed of light. However, just for fun, I've been trying to find out just what the speed would be to make the numbers come out to agree with the observed angluar momentum. I've seen 100x the speed of light and 10^32 radians/s. But at what polar radius is that? Anyone have more info on this?
  2. jcsd
  3. Dec 15, 2012 #2


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    The theoretical radius of the electron is 0. But people often use the classical electron radius http://en.wikipedia.org/wiki/Classical_electron_radius
    Note that as you get smaller, the problem gets worse because the moment of inertia goes as R^2, and velocity at the edge of a rotating body goes as R.
    Last edited: Dec 15, 2012
  4. Dec 17, 2012 #3
    Your question is "just for fun", so go ahead and do the calculation and do not worry about light speed. Use the reduced Compton wavelength for the radius. What do you get?
  5. Dec 17, 2012 #4
    Just for fun I predict electron 'charge radius' is the same as that of proton, and since proton has smaller magnetic moment I bet it's spinning with less speed than electron.
  6. Dec 17, 2012 #5
    My focus is on the Compton radius (Compton wavelength divided by 2 pi). The radii of electrons and protons will not be the same due to the difference in masses.

    I suspect you will find that the spin velocities are identical.
    Last edited: Dec 17, 2012
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