Experiments in Phenomenological Electrodynamics and the Electromagnetic Energy-momentum Tensor*

The microscopic and the macroscopic (phenomenological) approach to the electromagnetic theory in matter can be looked upon as complementary to each other. In view of the complexity of the deductive microscopic approach it is desirable to use experimental information to test the predictions of the more simple macroscopic theory. The purpose of the present paper is to review and give the theory of experiments and Gedanken experiments in relation to various expressions for the electromagnetic energy-momentum tensor. The paper is divided into three parts. The first part discusses the electrostriction effect, mainly in electrostatic experiments. It turns out that both the Hakim—Higham experiment (1962) and the Goetz—Zahn experiment (1958) agree with the predictions of the Helmholtz theory and disagree with the predictions of the Einstein—Laub theory. The second part of the paper is concerned with quasistationary crossed electric and magnetic fields. The electrostriction effect is here unimportant. Both the experiment of Walker et a!. (1975) and that of James (1968) support the Abraham tensor in contradiction to the Minkowski tensor. The third and most extensive part of the paper discusses optical phenomena, in which case a direct observation of the fluctuating Abraham force cannot be made. Underusual circumstances, it turns out to be simplest to use the divergence-free Minkowski tensor. This tensor describes satisfactorily all existing force or torque experiments in optics that we are aware of. Some attention is given also to the tensor alternative recently introduced by Peierls (1976).