Main Question or Discussion Point
this is from Omnes' book Understanding QM
Has this problem been resolved or is it still outstanding?There was an older preconception according to which the electron was an electrically charged sphere with a radius of the order of 10^-15 m (for which the electrostatic energy is [itex]m_ec^2[/itex]). If spin means a rotation of that sphere, the velocity at the sphere surface would have to be greater than the velocity of light. So accepting the idea of spin meant giving up the only model of the electron and, perhaps worse, the idea that angular momentum accompanies a rotational motion.