Is the Past indeterministic?

Question

Could multiple distinct past states of the universe have lead to the same present? Whether the difference is almost trivial or not is fine, though the greater the difference can be, the more interesting the related answer would be.

I'm aware chaos would make it basically impossible for two universes with macroscopic differences to reach the same state further down the road, but is it impossible from even a theoretical point of view? As in "no amount of luck, no matter how big, would make it possible". If the answer to that is negative, is it still possible for very small differences, at particle scale?

See the discussion here of ill-posed inverse problems. – J.G. Dec 05 '21 at 20:32 — J.G., Dec 05 '21 at 20:32

score 0 · Answer 1 · answered Dec 05 '21 at 20:41

No. Relativity of simultaneity prohibits alternate possible histories: if some event is in your past, there is some reference frame for which that event is in the present. If we can change the past without changing the present, there is some frame for which we can change the present without changing the present, which is a contradiction.

Is the Past indeterministic?

1 Answers1