A Paradox in the Interaction of the Gravitational and Electromagnetic Fields ?

Abstract

RECENTLY Woodward and Yourgrau¹ put forward the hypothesis that the influence of gravitation on the propagation of electromagnetic waves depends on the frequency of the radiation. Their starting point is that the light deflexion by the Sun's gravitational field, as found from optical determinations at solar eclipses, appears somewhat larger^2,3 than the value predicted by Einstein's theory of gravitation. Lately Muhleman et al.⁴ and Seielstad et al.⁵ succeeded in measuring the light deflexion by the Sun at 2.388 GHz and 9.602 GHz. Their results (1.82″ ± 0.2″ and 1.77″ ± 0.2 ″) are in close agreement with the predictions of general relativity. The uncertainty introduced by our limited knowledge of the coronal plasma amounts to about 10 per cent of the relativistic light deflexion⁴, which, being sufficient to prevent a decision between Einstein's theory and the Brans-Dicke theory, is not enough to make these measurements compatible with the predictions of Woodward and Yourgrau. Their hypothesis (according to formula (2), or (1) and (3))¹ gives at 2.388 GHz and 9.602 GHz the tremendous values of 15′ 39″ and 7′ 45″ respectively for the light deflexion (that is, more than 500 times and 200 times the experimental results).