The theory of relativity is a scientifically proven theory.
Discussion
There are no proven theories, my dear friend.
There are only hypotheses not (yet) disproven.
Relativity does have formidable explanatory power, and has survived numerous attempts on its "life", but it will one day be replaced by a new paradigm, as it replaced Newtonian Mechanics.
Predestination is still be outside that, as we have no way to prove or disprove it.