>>11481794>So, nothing to expand into, no expansionWrong. You don't need to have anything to expand into to have expansion. The distances between objects grows over time, like a sheet of graph paper "zooming in" as time passes (so the number of squares between you and any given point grows over time, assuming each square on the graph paper represents the same length at all times. You could also imagine that the graph paper stays the same but the length each square represents increases over time.).
So, you see, you don't need anything external to our universe to have expansion, you just need to have certain values in our universe grow over time.
The argument that the universe is self contained and there cannot therefore be anything external to it is just semantics. If by universe I mean the OBSERVABLE universe then it is not self contained. If I mean the whole universe then it might be self contained, but it could be part of a larger multiverse, and that multiverse is the self contained one, but that's all just a matter of naming conventions, nothing more.
