Recently I was talking to somebody about the expansion of the Universe and they asked me a very good question,
“If space goes on forever, how can it be expanding?”
This is related to one I’ve been asked quite often,
“What’s the Universe expanding into?”
It seems obvious at first thought that if something is expanding it must be doing so into some sort of surrounding space, some ‘outside’. So something without an edge, like infinite space, has no ‘outside’ to expand into and therefore can’t expand. The problem here is that our personal experiences in the world tell us one thing, but physics and maths tell us another, and to relate these is very tricky.