A. Einstein. Ether and the Principle of Relativity. Translated from the German by A. P. Afanasyev. Petrograd, 1921. Scientific Publishing House.

The brochure is a translation of Einstein’s remarkable address, delivered at a ceremonial meeting of Leiden University on May 5, 1920. Having set forth the physical facts that made the hypothesis of the ether inevitable, Einstein, in a few words, outlines that hopeless—

the difficult position in which this hypothesis found itself, having fallen between the Scylla and Charybdis of the experiments of Fizeau and Michelson. The standpoint adopted by Einstein on this question from 1905 onward in his theory of relativity was the denial of the ether. The address under review is a turning point in this respect. Einstein considers it possible to identify the ether with the physical space of the general theory of relativity: “The ether of the general theory of relativity is a medium which, in itself, is deprived of all mechanical and kinematic properties, but which at the same time determines mechanical (and electromagnetic) events.” Further, the difficulties arising as a consequence of the dual nature of the new ether (a mechanical and an electromagnetic ether) are pointed out. With this indication the brief address ends. In such a view there is nothing essentially new; the possibility of identifying the concepts of the “ether” and of Einstein’s physical space of variable curvature was pointed out, for example, by P. Lenard in 1918. Most remarkable is the “lifting of the ban” from the hypothesis of the world ether by the very author of this “ban,” which had hypnotized1 science for 15 years and had undoubtedly hindered the natural development of a hypothesis valuable for physics.

The brochure is intended for a reader already familiar with the foundations of the theory of relativity.

— S. Vavilov.

1. Cf., for example, A. Sommerfeld, Atombau, p. 380, 1921, where the author apologizes for using the term “ether.” ↩