Some physicists theorize that parallel universes exist. Brian Greene, for example, describes nine types. Max Tegmark has defined four levels. Parallel universes remain unproven. But the many ways they may manifest suggests a reasonable probability they’re real. And if they are, there may be an infinite number of them.
Let’s assume even one type of parallel universes exists. For me, the parallel universes suggested by eternal inflation seem convincing. Why is our universe so tuned for life? Because an infinite number of universes have and will always inflate into existence. Some collapse. Some expand but don’t support life. Some, like ours, support life that’s able to comprehend its existence. That’s why our universe is so tuned to life. If it weren’t, we wouldn’t be here to observe that fact.
There is growing evidence that our universe may be one in an infinite, eternal multiverse. And if true, it presents philosophical conundrums.
The one I struggle with currently is consciousness. I’m a materialist. I believe that my consciousness and identity reflect the connectome in my head. I am my neural networks. These comprise biological parts such as neurons. These in turn comprise molecules, which comprise atoms, which comprise subatomic particles.
But here’s the thing. If there are infinite parallel universes, there are infinite versions of me. Some of these would be identical down to the subatomic level. So why is my consciousness rooted in this universe? Wouldn’t it be in any universe where the same configuration of particles and atoms forms my brain? If not, what determines the location of my consciousness? We can say now that consciousness exists within 3 dimensions of space and 1 of time. Do we also need one or more dimensions describing its location in the multiverse?
Of course, the multiverse is an unproven theory. But if it or other parallel universes theories prove true, it will keep philosophers busy. Consciousness is still mysterious. Consciousness amongst infinite universes in an eternal multiverse even more so.