Michio Kaku speaks about multiverse and parallel universes 2005 in BBC. You don’t have to believe what the scientist is talking about, but its interesting to learn the points of view of these scientists who believe of the existence of other universes.

Multiverses have been hypothesized in cosmology, physics, astronomy, philosophy, transpersonal psychology and fiction, particularly in science fiction and fantasy. The specific term “multiverse” was coined in 1895 by psychologist William James.  In these contexts, parallel universes are also called “alternative universes”, “quantum universes”, “interpenetrating dimensions”, “parallel worlds”, “alternative realities”, “alternative timelines”, etc. Source Wikipedia.com