The Universe is 13.7 billion years old. matter-energy creates spacetime via gravitational curvature. So claiming that there is a ‘before’ the Big Bang is as absurd and nonsensical as claiming that there is an ‘outside’ the Universe.

And yet that is exactly what many mainstream physicists propose. They believe our universe is but one of an infinite number of universes, all floating around like bubbles in the bath. They contend that a disturbance or eruption in another existing universe may have been the source of the big bang that created our cosmos.