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Originally Posted by Fortis
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Originally Posted by scourge
But here's where that seems like a dodge to me--we have precisely calculated and utilized the -precession- of the proton magnetic moment, the basis of MRI technology, so why can't we figure out the rate of the inherent spin? If we know the charge on the proton, and the magnitude of its magnetic field, why can't we determine the rate of rotation?
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One way of looking at this is to say that experiments indicated that the electron behaved as if it had an intrinsic angular momentum (and an associated magnetic moment), with a z-component that could be +-hbar/2.
The problem occurs when you try to interpret this in terms of a classical spinning object, such as a sphere. As the electron looks pretty much point-like as far as anyone can determine, this would imply, to use a technical term, a humungous angular velocity. It is simpler to attribute spin angular momentum as being as much of a fundamental property of a particle as mass or charge. This may not be the answer that you were looking for, but hopefully it helps. :) |
Thanks Fortis, but let's set aside the enigmatic electon for a moment, because MRI uses protons, and they have a reasonably well-established dimension. Given that, can't we at least approximate a rate of rotation for it, given its charge and magnetic field strength?
I'd like to know this, because it seems a little weird to me that the wavelength equivalent of a proton's rest energy appears to be quite close to a proton's radius. Does that seem even a little fishy to anyone else?