A very good question Robin, I too would very much like to know the answer! The resource below doesn't really provide one, but it does quantify the (preposterously high, in their opinion) spin rate which would be required if the intrinsic magnetic moment was due to an actual spinning little sphere of charge:
http://hyperphysics.phy-astr.gsu.edu/Hbase/spin.html#c4 <<The term "electron spin" is not to be taken literally in the classical sense as a description of the origin of the magnetic moment described above. To be sure, a spinning sphere of charge can produce a magnetic moment, but the magnitude of the magnetic moment obtained above cannot be reasonably modeled by considering the electron as a spinning sphere. High energy scattering from electrons shows no "size" of the electron down to a resolution of about 10^-3 fermis, and at that size a preposterously high spin rate of some 10^32 radian/s would be required to match the observed angular momentum.>> Why they think it would be preposterous I have no idea, it doesn't look more preposterous to me than electrons going back in time or photons going faster or slower than the speed of light, which have been considered perfectly normal things for many decades. Cheers, Michel 2009/2/25 <mix...@bigpond.com>: > Hi, > > The magnitude of the Bohr magneton is essentially based upon a Bohr orbit. How > is that the intrinsic spin magnetic moment of a point particle electron is so > very close to one Bohr magneton? > > Regards, > > Robin van Spaandonk > > http://rvanspaa.freehostia.com/Project.html > >
