I hesitate to ask this but what are electric and magnetic fields? We are told that the electromagnetic force is carried by the photon (which consists of oscillating electric and magnetic fields) but the photon does not cause (?) or interact with external magnetic and electic fields. Presumably quantum mechanics will make things crystal clear! Incidentally isn't the prediction of the existence of electro-magnetic waves by Maxwell one of the most amazing in the history of science – coupled with the calculation of the speed of these postulated waves.