? In the pre-relativity physics this problem was solved by making unconsciously two hypotheses:—
1. The time is absolute; the time of an event,
', relatively to
' is the same as the time relatively to
. If instantaneous signals could be sent to a distance, and if one knew that the state of motion of a clock had no influence on its rate, then this assumption would be physically established. For then clocks, similar to one another, and regulated alike, could be distributed over the systems