Multiple Universes..a sound theory? Please comment

Hey all,

I keep reading about parallel universes, the possibility of shadow universes
and "our" universe mixing but never colliding.

But what I never have read is the possibility of multiple universes...for
example, The Big Bang was the creation of OUR universe. But what started the
big bang? This gets into the God/first cause theory, but I am not going to
argue about that...I will say that the "first cause" theory semantically is
quite assuming---I am suggesting that before our Big Bang, or during it, other
entire universes were formed "along side" ours. Ours expands and recedes,
others may be contracting. as we speak If there are universes outside our own,
you can't really speculate what particles and what properties they own, perhaps
they are the same--but "in between" the multiple universes may exist dark
matter, or something else. I don't really want to call these "Shadow"
universes, as that term applies they mingle with us--they may be in a
completely different dimension(s), and hold different properties, some we don't
know exist.

There has got to be something OUTSIDE the universe to have started the big bang
(at least, if we accept the big bang theory). And I again don't have to
interject that God started the universe. That may be so, but if he did or she
did why would they stop with just one universe? I am not one who concedes that
we humans are the only humans --there are many stars which planets like ours
could form around.

I do read a lot about scientists who are so firm about laws of physics and the
nature of the universe, but really, what started it all? Its a good thing in
science you must alter your beliefs with every new experiment*s findings,
because I wouldn't count on today's knowledge too much as again, we don't even
know what went on before the big bang. There could be a whole lotta other
worlds out there!

Let me know if this is old hat or something you would like to comment on....

Regards,

Tom M.