Page:Relativity (1931).djvu/113



ITHERTO I have purposely refrained from speaking about the physical interpretation of space- and time-data in the case of the general theory of relativity. As a consequence, I am guilty of a certain slovenliness of treatment, which, as we know from the special theory of relativity, is far from being unimportant and pardonable. It is now high time that we remedy this defect; but I would mention at the outset, that this matter lays no small claims on the patience and on the power of abstraction of the reader.

We start off again from quite special cases, which we have frequently used before. Let us consider a space-time domain in which no gravitational field exists relative to a reference-body $$K$$ whose state of motion has been suitably chosen. $$K$$ is then a Galileian reference-body as regards the domain considered, and the results of the special theory of relativity hold relative to $$K$$. Let us suppose the same domain referred to a