I think you assume one can measure the time between two events at different locations. I believe Einstein proved you can’t because there’s no way to truly synch

I think you assume one can measure the time between two events at different locations. I believe Einstein proved you can’t because there’s no way to truly synchronize clocks at different locations. Another way to say it is that there’s no instantaneous "now" that all observers can agree on. In special relativity, "now" is meaningless. Or rather, "now" depends on the observer’s inertial frame of reference. There’s a nice diagram one can plot, with 1 dimension of space and 1 dimension of time, that shows lines of simultaneous events based on the velocity of a moving observer in another frame of reference.