Two particals & time travel
There is no such thing as time travel just as there is no such thing as an inch or foot travel. An inch or foot are units of measure, what you travel is the distance, we use the units of measure to describe the distance traveled. Time and its units of measure are measures of relative motion.
Imagine if all motion in the universe stopped for a billion years then restarted again. There would be no way to tell if the elapsed time had been a billion years or a billionth of a second if nothing moved. The past would be the same as the present and the future. There would be no past, present or future only sameness. Time is only an aspect of motion, a measure of motion. You can’t travel in a measurement only the thing being measured, in this case, motion. Time travel to the past would mean reversing all motion in the universe except you and traveling to the future would mean accelerating all matter in the universe except you. Ain’t gona happen!
Imagine there were only two identical spheres in all the universe. Totally smooth and round. If the two spheres appeared to an observer (disconnected from that universe) to be moving apart there would be no way to tell without a third sphere if both were moving away or only just one or even which one was moving. You couldn’t tell if the motion was curved or straight or zig-zag or it’s relative speed without a third sphere. If one sphere was orbiting the other in a perfect circle it would seem to be standing still. The motion or time of those spheres motion is only possible if compared to the motion of a third sphere’s motion. Time in and of its self doesn’t exist but is only a measure of relative motion of matter. Hins no such thing as ‘time’ as a ‘something’ but only as a measure of a ‘something’, motion.