They reasoned that the shift in the energy of an atom owing to emission and reabsorption of photons is not really an observable; the only observable is the total energy of the atom, which is calculated by adding this energy shift to the energy calculated in 1928 by Dirac. This total energy depends on the bare mass and bare charge of the electron, the mass and charge that appear in the equations of the theory before we start worrying about photon emissions and reabsorptions. But free electrons as well as electrons in atoms are always emitting and reabsorbing photons that affect the electron’s
...more
