Einstein, Albert

Typed letter, signed ("A. Einstein"), 1 page (11 x 8 1/2 in.; 280 x 216 mm), on California Institute of Technology stationery, in German, to Seymour Kety, defending the constancy of the speed of light; lightly browned, formerly folded, cello tape in upper left and lower right blank corners.

Einstein responds to a popular objection to the principle of the invariance of the speed of light.

The objection was raised here by Seymour Solomon Kety (1915 - 2000), then a senior at Central High School in Philadelphia, who later became a professor of neuroscience at the University of Pennsylvania, and winner of the Lasker Special Achievement Award for his contributions to the study of schizophrenia.

Einstein responds (in translation):"The principle of the constancy of the speed of light is valid chiefly according to the special theory of relativity only in reference to inertial systems, thus not in relation to the rotating earth. According to the general theory of relativity, the principle, in its simple form, only requires validity with relation to local coordinate systems (of infinite small extension), but not in relation to arbitrary Gaussian coordinate systems. Therefore, in the case you indicate there is no contradiction with respect to the theory of relativity. With great respect"

Sotheby's wishes to thank Professor Diane K. Buchwald of the Einstein Papers Project for her help with the translation.