Question

what came before big bang

Answer 1

Stephen Hawking has said that "Since events before the Big Bang have no observational consequences, one may as well cut them out of the theory, and say that time began at the Big Bang. Events before the Big Bang, are simply not defined, because there's no way one could measure what happened at them."

Answer 2

Answer:

Before the big bang, the universe was an infinite stretch of an ultrahot, dense material, persisting in a steady state until, for some reason, the big bang occured. This extra-dense universe may mechanics, the physics of the extremely small scale, Carroll said. The big bang, then, would have represented the moment that classical physics took over as the major driver of the universe's evolution.