There is no proof or way to determine it right now. Even evidence that we find can be interpreted in any way for or against.
I believe that it exists because it is possible. If a flower or animal exists then other must exist. If planets exist then other planets exist. If galaxies exist then there are other galaxies.
If a universe arises then other universes COULD exist.
A computer program could be run multiple times. And a universe could run multiple times or simultaneously. Just like many planets exist from far away.
I believe that there must be other universes because if something happened it can happen again or happen elsewhere.
Now I can't prove it or come up with a way to find out but their probably is.
I could be wrong but that is my reasoning.
One cannot exist without the other as all has a specific structure and to have one another specific structure must exist to support that one and so on infinitely. A system that does not understand it self all parts understands nothing, The idea is not enough, All the physical everything must be understood because the physical aspects of the physical are different then the idea. The system must understand everything as understanding only comes from knowing everything and the system without understanding everything, There is a missing like, One object cannot be compared another, One cannot exists without two and viseversa. Without all the states existing and being understood one link the chain breaks the chain breaks as one thing supports all of them. Therefore all must exist for anything to exist.
The only real scientific backing for alternate realities is a highly specific and speculative interpretation of quantum mechanics. Arguing that the seemingly random movements of the “god particles” is actually creating anew universes with each movement and that’s why we can’t predict them in a deterministic manner. This is just as absurd as it sounds
You’ve likely imagined it before: another universe out there. Just like ours. But could these alternate universes be a reality?
Maybe. Though I highly doubt it. If there was another universe what would they be in? Not dark matter. That’s what universes are made of.
In not saying it's not possible but it's unlikely. Many people state that nothing can exist without an opposite. Well. . . Ok let's pretend that’s true, Shall we? Well if this is true why must it be in another universe? Why not this one?
Many trolls have popped up over the years claiming that they found an alternate universe via a telescope or things like that. Or that they have teleported to a world that is exactly the opposite of ours. That is ridiculous. First, You can't see outside of our universe from a TELESCOPE. Second many who claim that they were teleported say that they were asleep which means they are most likely dreaming.
If there is another universe out there cool. No. Awesome! It would reshape science as we know it. We would see our world in a completely different way. But let us focus on our universe first.