Eli5 if the universe is everything but it is constantly expanding, what is it expanding into?

Question

Eli5 if the universe is everything but it is constantly expanding, what is it expanding into?

In: 22

Answer 1

Here’s a good way to think about it:

There is infinite empty space out there. As far as we know, the nothingness outside of the universe goes on forever. The universe is all of the actual STUFF out there. So the nothingness isn’t part of the universe.

But the universe is expanding ever since the big bang, which means it is expanding into that infinite nothingness. You could call it the void if you like. The universe is expanding into the infinite void.