Well, as it happens, there are others. Among physicists, it's not controversial. Our universe is but one in an unimaginably massive ocean of universes called the multiverse. If that concept isn't enough to get your head around, physics describes different kinds of multiverse.

How many universes can exist?

The only meaningful answer to the question of how many universes there are is one, only one universe. And a few philosophers and mystics might argue that even our own universe is an illusion.

Can a multiverse exist?

There is not one universe—there is a multiverse. In Scientific American articles and books such as Brian Greene's latest, The Hidden Reality, leading scientists have spoken of a super-Copernican revolution.