[baudrunner]

By definition alone there can only be one universe for it is defined as that which encompasses all. However, that is not science, but semantics.

Still, I believe that there is one and only one universe. It is tempting to think of creation in the opposite direction yielding an anti-matter universe, but anti-matter exists only in the one and only universe. We could have been, or could be anti-matter, because all an anti-matter particle is is a particle which has the opposite properties of spin, direction, and orientation to its complementary matter particle.

Before the many Big Bangs that ultimately yielded the matter particles that are compatible for the generation of all the matter in this universe as it now exists there were stereometric equivalents of all the sub-particle configurations that created themselves out of the original spinning strings left behind by the accelerating creation front and they can be construed as anti-matter equivalents. Ultimately, one quantity wins over the other and this universe could just as easily have gone with the stereometric opposites. Or it did. It's academic. But I prefer to believe that there was a generous predominance of the particles that make up matter today. Why? Because creation happened in the one direction only, and the spins of those original strings would have been oriented in a dominant direction, with rare exceptions. Anti-matter particles would have been just as rare then as now.

But leave it not go unrepeated that while mathematical what-ifs can easily propose other universes there aren't any. And the one that exists cannot be observed from the outside because there isn't any outside. It can only be observed from within. Sorry, no bubble universes, no other dimensions, no alternate universes. Just the Universe.

I am a fierce proponent of practical science.