What if we live in just one of many universes. The multiverse theory is very unprovable but possible.
Then there is the “rubberband” theory. Which is an expanding and contracting universe which collapses on itself and begins again, and again...
Fascinating stuff.
What if we live in just one of many universes
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Then you would have to change the very definition of the word “universe” which means “everything” You just can’t have more than one “everything.