"The universe has always existed; that is, it has existed throughout all time, because time exists only as a constituent of the physical universe.... The only thing that exists in the physical universe is motion. Our theory, as it now stands, defines what motion is, and what it does, but not how it originated, or whether it had an origin. Since time, in a universe of motion, exists only as an aspect of that motion, the universe and time are coeval. On this basis, the universe has existed always-during all time-regardless of whether or not it originated from an act of creation."

- (Chapter 31, The Universe of Motion)