Rallem: "Would the galaxies we see separating further apart every day be enough to base a theory upon if the Universe were infinite as well as the possible galaxies we cannot see? If this Universe were not finite wouldn't a theory or hypothesis of an expanding Universe be sort of like a flat Earth Theory?"

The general assumption is that what's happening in the observable universe is also happening in the unobservable part, and that the known laws of physics also apply beyond that part; but it's not provable. There’s no way can ever know the characteristics of the unobservable universe. Philosophy, reason etc, we can have aplenty, but no proof.

odin1: "The problem I have with this subject is if the universe is expanding what is it expanding in to?"

It's a problem everyone has, I guess. I do. Here's a long answer from Prof David Kornreich:

http://curious.astro.cornell.edu/question.php?number=274

And here's a short answer from Prof Michio Kaku:

"Then it is clear now that the universe is expanding in hyperspace, and that the original Big Bang took place in hyperspace. If we cannot visualize hyperspace, it is only because we spend our time in the third dimension."

odin1: "I said in an earlier post on another thread I really don't believe we know what space is. We explain it in distance and vacuum. I believe there is more to it that that."

People working at the LHC, CERN agree with you, and hope to be able to tell us more in the next few years.