was the big bang actually a white hole?
Maybe...there is some speculation that black holes lead to other universes/Big Bangs...but there's no real evidence there and it's certainly not part of any mainstream theory.
But probably not...black holes/white holes are objects defined within the context of spacetime...not a characteristic of all spacetime (i.e., the universe) itself.
Cosmologists do not know for sure that the Big Bang theory is correct. Even if it were correct, I do not think they would be able to tell if the Big Bang was a white hole.
they're more sure about the big bang theory than they are about the white hole theory, that's for sure.
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