I've always believed the Universe to have existed "forever."
Only the average man has an issue with processing things like 'forever' and 'infinity.' I am an above average man.
Eventually the whole she-bang will collapse into itself once again, and thus it will be recreated once again.
I do disagree with the fact that the "space" utilized is finite, and is determined solely by the fact of matter existing in it... I have never bought into that theory, and never will. The "usable" space stretches out to infinity, IMHO, and I don't believe it corresponds to the fact that matter must be present... This is one thing I disagree upon, and as such I'm not sure "time travel" will ever be a possibility, since that theory isn't one that I believe to be possible, due to my own beliefs of time and space.