If events A and B are close to each other in space time (light from one can have arrived at the other by then), then the ordering is fixed. If they are far from

If events A and B are close to each other in space time (light from one can have arrived at the other by then), then the ordering is fixed. If they are far from each other (light won't get from one to another by then), then time gets weirder. The notion of what is simultaneous to what gets weird. If you and I are moving relative to each other, we're going to disagree on which distant events happen at the same time. If that happens, then whether something's happening now might change depending on reference frame. The ordering can be t(A) = t(B) or t(A) != t(B). Since no frame is privileged, we can also change the other way around, so t(A) != t(B) can be t(A) < t(B) or t(A) > t(B) depending on reference frame. It's only flexible like that for things that could be simultaneous in some frame, which at least in special relativity means light from one can't have gotten to another yet. I never took general relativity, so who knows how it works in that setting. https://en.wikipedia.org/wiki/Relativity_of_simultaneity#Thought_experiments https://en.wikipedia.org/wiki/Relativity_of_simultaneity#Tho...