So I'm sure you've all heard people talk about increasing expansion of the universe, the compact nature of the universe at the moment of the big bang, and other comments like this. The idea of an expanding universe immediately suggests to me an "edge" of the universe, which is something often referred to in pop-science (for the record, I know that expansion does not necessarily mean a movement of the boundary of the universe, it means an expansion of the internal volume. I just don't know if this is the only real implication of this). My question is, is the idea of an "edge of the universe" really valid, or is this just a erroneous view perpetuated by pop-sci sources? Is there a real edge of space, is it just like a bubble of energy and mass outside of which there is absolutely nothing, or is this totally incorrect? What do QFT and modern models have to say about this?