The equivalence principle and an electric charge in a gravitational field

Abstract

It is shown that there is no violation of the strong principle of equivalence in the case of an electric charge either falling freely or supported in a static uniform gravitational field. For a freely falling charge, the global electromagnetic field distribution at any instant is found to be the same as that of a charge which is moving uniformly with respect to an inertial frame with a velocity equal to the instantaneous velocity of the freely falling charge. In the case of a charge supported in the gravitational field, the total electromagnetic field energy, as measured by freely falling observers instantaneously at rest with respect to the charge, is shown to be equal to the Coulomb field energy of a charge permanently stationary in an inertial frame. The conclusion here, that in neither of the two cases does the charge emit electromagnetic radiation, is independent of our choice of the observer's frame of reference.