No two events can ever be said to be simultaneous, because every moving reference frame has its own relative time, and everything in the universe is moving in relation to something else. As Einstein put it, “There is no audible tick-tock everywhere in the world that can be considered as time.” If time is not absolute, then neither is space or distance. Everything is relative to everything else—speed, time, distance, and so on—except for the speed of light, which never changes.
