Fascinating interview with Dr Michio Kaku on parallel universes, the matrix and superintelligence. I particularly liked his explanation of the multiverse idea:
Now, this can be compared to sitting in a room, listening to radio. When you listen to radio, you hear many frequencies. They exist simultaneously all around you in the room. However, your radio is only tuned to one frequency. In the same way, in your living room, there is the wave function of dinosaurs. There is the wave function of aliens from outer space. There is the wave function of the Roman Empire, because it never fell, 1500 years ago.
All of this coexists inside your living room. However, just like you can only tune into one radio channel, you can only tune into one reality channel, and that is the channel that you exist in.