August 15, 1953

Dear Solovine,

It seems that, under pressure of correspondence, I forgot to answer your letter of June 15. I can answer your first question by saying that, with respect to an accelerated system, the coordinates can not be interpreted in such a way as to make the differences in the coordinates equal the differences in length corresponding to differences in time as measured by rulers and clocks. This becomes clear in the cases where the system of coordinates is uniformly accelerated with respect a system of inertia, or rotates uniformly. That is why, in conformity with the theory of relativity, the field of gravitation is at the same time a term for the metrical structure of space-time.

When Riemann’s condition is “satisfied,” then the equations for gravitation must also be “satisfied.” In other words, the equations for the field of gravitation are a specialization of Riemann’s condition.

You may keep the German manuscript of the Memoir as long as you need it. Naturally, I agree with your proposals concerning revision.

It seems to me that you are not only my only faithful translator, but also my only truly observant reader.

With my cordial greetings
Your         

A. Einstein

P.S. I am glad that the French people have not neglected to show their thick-headed leaders where God sits.