5 2 D O C U M E N T 1 2 J U N E 1 9 2 5 12. From Edwin E. Slosson[1] [Washington, D.C.,] June 26, 1925. Dear Professor Einstein, I am sending you advance proofs of “Science” and National Academy of Sci- ences containing the first complete report of the experiments of Professor Dayton C. Miller of the Case School of Applied Science, Cleveland, Ohio, on ether-drift.[2] He has repeated the experiments of Michelson and Morley[3] with more exact ap- paratus and gets what he regards as positive evidence of ether-drift when he is on the top of the mountain, which is a different result from what he gets at lower levels and what Michelson got in the basement of the Case School.[4] The paper made a deep impression upon the National Academy of Sciences when it was read here.[5] Even those who were most strongly convinced of the validity of the theory of rel- ativity were unable to account for the results, and expressed the opinion that, if con- firmed, they would tend to invalidate that theory, or at least in part. Dr. Ludwik Silberstein[6] regarded the experiments as convincing and gave Science Service a statement to that effect, a copy of which I enclose.[7] I cabled you and Professor Eddington[8] for expressions of opinion the day the paper was given. Professor Eddington responded with a cablegram saying that he would have to await further details before giving an opinion upon results, but he expressed his great gratification with the confirmation of the shift of the lines in the spectrum of the faint companion of Sirius reported by Dr. Hale of Mount Wilson at the same session of the Academy.[9] You were absent, I believe, in South America at the time, so I got no reply to my cable to you. I hope, however, that with this paper of Dr. Miller’s in hand you will be willing to write us your comment and opinion, even if only a few hundred words, either in German or English. It will be of particular interest if you can explain how far Pro- fessor Miller’s experiments, if completely confirmed by subsequent investigations, would invalidate either the general or the special theories of relativity. We will, of course, pay you for the article. I find on asking mathematicians and physicists of my acquaintance that they are in disagreement as to whether proof of the existence of ether and of its partial movement relative to the earth would affect your theories. Any word of comment from you would be of interest to the American public as well as scientific circles. I assume you have Professor Michelson’s report of his recent experiments near Chicago.[10] I understand that while these were in accordance with your theory, they are not incompatible with the older ether theory.