Time is perpetual motion. In a Universe that expands, in an accelerating manner, time is the cause of all physics. Cause before effect of all things. And the cause of all things is overlap. That is the first thing that happens, followed by a whole chain of events. It's up to you if you want to say that overlap is time, or all of the events following that overlap. The events following overlap are entropy, bump, energy, move apart. This is like an animation. It is a loop. The particles that move apart have nowhere to go but to overlap some more particles, so as you can gather, it is a closed loop. Only the very outside particles have anywhere to go, and this is expansion.