This is a question about the borders of the Universe (if such a thing actually exists). I got in a discussion with my astronomy professor and inevitably I brought up the question "if the Universe is expanding, and the Universe is contained, what is it expanding into?" He said that it's not actually expanding into anything. I said that doesn't make any sense. He gave me an odd look and said "I know". To me, this would suggest that it's not actually growing larger in size.