My shower is theory is that there are infinite universes getting created all the time and we can never know about it because we're restricted in this universe. I love having these talks with my daughter.
That's almost the mainstream position in physics as of 2025 -- that cosmic inflation never stopped, that it produces universes beyond number, and we're in one pinched-off region of it.
The trouble would be that even if we sensed other universes we might not be able to go there unless we can create our own pocket universes. There's no guarantee that an adjacent universe has the same rules of physics.
All of the enzymes in your body might stop working if you stepped into even a slightly different universe. You could just turn into a gas, and not in a good way.
