A Quora question asks: Is it true that the past still exists and the future is predetermined? Is the ‘’block universe’’ correct, since Special relativity is scientifically proven? – Quora
No. It’s not true that in the context of Special Relativity “the past still exists”.
In fact, according to Special Relativity (which does appear to be correct for situations where the effects of gravity are negligible – though nothing outside of mathematics is ever “scientifically proven”), the whole idea of the (unique) past is meaningless since there are events that you consider past that are not in the past for a remote relatively moving observer who is at an event which you consider simultaneous with your present.
Also, again according to Special (and maybe* General) Relativity, the word “still” is also meaningless as its use at any time refers to events that are simultaneous with the statement, but that criterion will correspond to different sets of events for different observers.
*- I have added the word “maybe” since Viktor Toth# has mentioned that in General (but not Special) Relativity it is possible to identify a preferred set of inertial frames (in which the redshift due to expansion is the same in all directions), and these do share a common concept of simultaneity.
But of course, even in a Galilean universe, there is also the question of what you mean by saying that the past “exists”. Yes it exists as the past (and even in SR the past of my worldline exists as my past) but that does not mean it is happening now. And the same applies to the future. Even in a non-deterministic universe the future “exists”, as what will turn out to have happened, regardless of the fact that we have no way of predicting it.
#PS I am not linking to Viktor Toth’s answer because, despite having some good bits, I feel that it is marred by the inclusion of some very misleading (and quite unnecessary) statements about Quantum Mechanics.