Noroku

Ok I've read many things stating that the size of the Universe is in fact expanding. This concept has has generated a few problems for me to grasp.

First if we start out stating that the Universe is all that exists (including space) how could this increase or decrease in size? I understand that we can sa ythe matter is getting spread out further from a conceptual center (being the point of the big bang in theory).

Now since Space itself is the complete lack of matter, it seems to me that having this included in a definition of the universe makes it impossible for it to expeand or retract, but rather just items in it to move within it's boundries (which are by definition limitless). Thus wouldn't the so called Universe always be the same size and the real issue just be matter moving within it?

Also could we make the arguement that infinity exists in the lack of existence of things in space. Since there is no limit to the amount of nothingness that would be in the Universe? (though I think I've read somewhere about a natural curve to the Universe, which would mean it has boundries, and thus something (even if that something is "Nothing") must exist outside it.

If I haven't confused you yet, as i'm sure i've had difficulty explaining what I mean, please give me your thoughts on the subject.