Basically the title – I have a degree in Aerospace Engineering, but I still can’t answer this question posed by my girlfriend. An infinitely expanding universe implies that there’s a “container” the universe is expanding into, kind of like how you can pour a pancake into a pan & it’ll expand to the limits of the pan. But then that also implies that said container existed before the universe / big bang, which is…wild. Anyway, please ELI5!
In: Physics
First, we don’t actually know. Second, there’s no reason to believe that it’s expanding INTO anything. Physics is under no obligation to be intuitive to us. It could be that the universe itself is the container and that container is simply getting bigger.
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