**Epilog 20th Century Clouds of Physics and Einstein Dammerung**

Translation of Letter by Heisenberg November 28, 1957

Dear Winterberg,

many thanks for your reprint about the possibility to test the relativistic time dilation by artificial satellites. I consider your mentioning this possibility very interesting, however, since I have for many years not done anything in general relativity, I do not wish to voice an opinion on the details of your calculations.

At the end of your letter you raise the question, if the general theory of relativity could be of importance in the theory of the elementary particles. About this point I have à definite opinion. I believe, that one can completely neglect all gravitational effects, as long as one also neglects the weak interaction (which is responsible for the radioactive beta-decay). For the determination of the mass spectrum of the elementary particles, neither the weak nor the gravitational interaction is going to be of importance. However, l suspect that the inclusion of the weak interaction is going to lead also to an understanding of gravitation, and that at this place the ideas underlaying quantum field theory are going to find à connection with those of the general theory of relativity. But quite à few years are going to pass before the quantum field theory has advanced that far.

With many greetings also to Professor Bagge

Yours

(Werner Heisenberg)