An interesting video called "Parallel Universes, Alternative Timelines & Multiverse - BBC Horizon (understanding Looper)" covers the theories used in the latest Bruce Willis movie.
The notes for the video (in summary) say that:
Parallel Universes - Scientists now believe that there may be an infinite number of parallel universes - we just happen to live in one of them; and
Greater Dimensions - Superstring theory, hyperspace and dark matter have made physicists realize that 3 dimensions aren't enough and that there are actually 11 dimensions. Our universe is just one bubble among many.
Comments
When looking back at the TV series of Star Trek the Next Generation, we actually see this concept being acted out. There was a rift in the universe that allowed all universes with their third dimension to appear in one area at the same time. According to the Pleadians, a twelve dimension is being formed, which to them is an extraordinary event. They keep repeating that we are multidimensional. This means that we have a part of ourselves in other universes. Really fascinating.