physics
I was listening to a phycisist's podcast from what I understood he explained that there could be other universes existing out in the unknown outside our universe I think that seems sensible but I don't believe that there are parallel realities of our own reality that is often explained in comic books and scifi movies where copies of ourselves live in so called parallel universes there are are stars, planets and moons in star systems there are many star systems in our galaxy there are many galaxies in our universe so why wouldn't there be many universes in the unknown outside our universe