The latest theory - we're a mirror universe
Many cosmologists have theories about the universe and it is rather comical to see these microscopic men insisting their vision of the universe is The Vision. This is rather like bacteria in my gut declaring the universe must certainly be shaped like a gigantic dark and messy tube. But at least cosmologists agree the universe is very, very large, and they themselves are nothing in comparison.
Various theories have included the Steady State universe, in which more matter is somehow created all the time and the universe is static; that the universe is an illusion, but running as a model in a computer; that we are somehow in a black hole (see image); or that we are in an expanding universe, which will lead to a Heat Death, in which over billions of years the stars go out like a used candle and we die of cold. Perhaps there is a multiverse in which all possible universes exist. Some propose even a recycling universe, resulting in a Big Crunch hopefully followed by a Big Bounce. One current theory says we are in an expanding but accelerating universe, resulting in an ultimate Big Rip in which even the nuclear particles are torn apart.
The James Webb Telescope in space is currently finding very young galaxies so big they contradict most of the above models!
A recent and novel model is that the universe is a kind of twin. It has an anti-universe, a kind of mirror universe. In this, at the Big Bang, a normal matter and an antimatter universe were both created and time runs forward for our universe and backwards for the antimatter universe. How strange!
Some of these models will be discarded in the face of evidence; some already have been. If the mirror universe theory accumulates some consensus, we might have to consider that God is in both, perhaps an Alpha in the antiuniverse and an Omega in ours? He would be the Last Word on the subject of universes.