who believes there might be multiple universes out there and why?
My gut feeling is that there aren't, but as I understand it they would explain some tricky features of the universe that we know. It just feels wrong to me.
When we think of matter including energy in the universe as the existence, the rest (space or the void in between) does not exist. Ca?l it anyhing but it really is nothing. Terefore there cannot be more than one universe, my opinion!
They might be but, I do not believe we will ever find out for sure, we may at some point predict their existence mathematically but not anymore than that. it maybe that the Big Bang was in fact the contact point between the membranes of two universes.