Universal Concepts of Expansion

I got stuck this morning on a bit of philosophy and science. The universe is expanding and thus bounded rather than infinite. I struggle with the question of into what the universe might be expanding. If nothing lies outside the universe, how can it expand? Where is it going? What is it replacing?

Then in the shower, where insights come, I thought of numbers which go on infinitely. I thought of children topping one another: I bet infinity dollars followed by I bet infinity times infinity dollars, and so on. No number lies outside math. Even the square root of negative-one is inside. There is no outside of math. It's inconceivable.

I still wonder how the universe, a physical space, can expand without going into something else, but I can conceive of math doing it, so maybe someday I'll understand more about the universe.

Even if I can't quite conceive of the universe's expandsion, I can, through the example of numbers, accept it and believe someday I might come to understand.

In this way, my thinking expands. Not into something that it replaces. It just expands.

The universe began from an infintesimally small point, the beginning of the big bang. I began from a very small thing, beginning a much smaller bang. Now here I am, expanding continually and still somehow inside myself.