# Does the "moving" inertial clock show an earlier or later or the same time compared to the "stationary" clock?

Assume two inertial clocks that were synchronized at the same location to read a certain time one hour ago and moving in opposite directions. At some point during that hour, they instantly reversed direction and did so at the very same moment. Both had undergone precisely the same acceleration resulting in their, then, advancing towards each other at the same speed at which they were originally moving apart from each other (therefore, neglect the effects of acceleration since they would be equal for both clocks). If, one hour later according to our "stationary" clock, we could observe the "moving" clock just as it passes our "stationary" clock, would it show the same time as our "stationary" clock, or earlier time or future time. And the same question except the "moving" clock is advancing towards us (has not yet passed us). And, finally, the same question except the "moving" clock is receding from us (after passing us).

• Are both clocks accelerating to come back together? Is one of them the "stationary" clock? Jan 23, 2023 at 8:14
• @BowlOfRed : Yes to both of your questions.
– user150908
Jan 23, 2023 at 17:42
• Then I don't understand. How is one of the clocks both accelerating and stationary? Jan 23, 2023 at 17:52
• My recent answer to physics.stackexchange.com/questions/746656/… might help. This old one might also help: physics.stackexchange.com/questions/402683/… Jan 23, 2023 at 18:03
• @BowlOfRed : Stationary is only with respect to the observer's own frame which is not absolute. There's another frame where both frames in my example can be observed as moving - and a frame from which they're moving at the same speed. It is in this frame where the speed of each is changed (accelerated by equal amounts). Even from the perspective where one frame (our frame) appears stationary, the change in speed (acceleration) happens subsequently (re-read my example). So this frame would no longer be stationary even though it's still our frame because motion due to acceleration IS absolute.
– user150908
Jan 23, 2023 at 19:34