Originally Posted By: cashmoney
The size of our universe is otherwise known as the Hubble volume (size of observable universe) and based on how far light can travel since the big bang.
Very likely much more outside the Hubble volume that we will never see including possibly an infinite number of universes including virtually exact duplicates of our own.
Other theories suggest that for every black hole that exists there is an additional universe with possible different physical laws. Our universe could be the direct result of a super large ancient black hole that originally formed and grew to super galactic dimensions in another universe.
Other theories like string theory suggests limited number of other universes in the additional dimensions suggested by string theory.
I believe the accepted size is about 46 billion light years. We can't see beyond it and the universe for us is actually shrinking as everything moves further away from us. Think of it as being a point on a loaf of bread that you bake. As it bakes any point expands further away from another point.
Lots of theories out there, but there's a few generally accepted ones. The outlandish ones have no proof.
The eventual end of the universe seems to be the heat death and the actual end of time as there will not even be any energy left at that stage to even measure time. One of the last things to endure would be black holes as they slowly shrink over time due to Hawking radiation.
https://www.livescience.com/33646-universe-edge.html