the big bang? simple:
there was nothing... nothing... and that nothing exploded... in nothing...
and in that nothing the nothing spread out, and an infinite universe was created...
or multiple infinite universes...
if there are multiple universes, then where are they? since our universe is infinite...
there can't be anything beyond it, since it ends nowhere...
so where would those other universes be?
the question is: what did that nothing explode in, when there was nothing?