5 ms·
> One of the consequences of special relativity is there is no such thing as "simultaneous" events very far apart. No. Special relativity says that simultaneit
by andrewflnr 21d ago
> One of the consequences of special relativity is there is no such thing as "simultaneous" events very far apart.
No. Special relativity says that simultaneity is relative for things moving at different velocities. The classic example is a fast-moving train and a platform disagreeing on simultaneity, even when they're right next to each other. Distance, and light travel time, has nothing to do with it; that's a separate (and mostly less interesting) problem.
Relativity absolutely lets you calculate what was happening simultaneously with a given past event within your own reference frame (i.e. other things moving at roughly the same velocity you are). In fact, you can think of that process, figuring out a consistent version of events after you've gathered all the data, as being exactly what it means to "observe" something in relativity. This is as opposed to "seeing it", which is what happens the exact moment the photons hit your eyes/sensors.