here are even more questions? does the universe end? if so what would the end look like? I understand what you are talking about but things can't just always be there can they? and how can someone say the Univese is Expanding when we don't know if it even ends?
If you define the universe as the sum of all matter and energy that can be seen/felt/detected, than it could be said that the universe doesn't end, it just changes size. It gets smaller, to the size of a point, which explodes, getting larger. According to our current understanding of time/gravity/physics, etc. there are many possibilities for the ultimate fate of our universe.
As for infinity, there a some "easily" understood things that go on forever in some sense. Numbers, for example, never end in either direction, you can always add or subtract another one from the current number. We all accept this because no matter how large or small a number we choose, we
can always add or subtract. Now, extend that idea to time. We can set some arbitrary time to zero, for ease, let's set it at the change from BC to AD. Now in either direction, we can always add or subtract a second, minute, and/or hour to the time. This means that , theoretically, time is infinite. However, if there is nothing around for the effect of time to influence, i.e. moving particles, time ceases to have meaning. So if we give time an infinite existence, we must allow the fact that there must be something for time to act on for time's entire existence.
This may help to see how a universe could exist for ever by starting with something "understood" and using the principle on more and more abstract concepts. I am aware that this proves nothing, seeing as how time is really nothing more than a human construct, but I hope it helps to show the possibility of an infinite universe, or series of universes.
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Micah
"Of course...we all creat god in our own image" - Willard Decker, Star Trek: The Motion Picture