This is the stuff of great sci-fi and fantasy but it’s also becoming a part of modern science. In fact, Dr. Michio Kaku has become a celebrity on the Discovery Channel as he continues to examine M Theory which is simply the theory of everything. His book, Parallel Worlds is an incredibly stunning look at the possibility that there are not only multiple universes, but an infinite number of them.
In 1995, a television show called Sliders first aired and quickly became one of my favorites. It was tough to get past the acting of Jerry O'Connell but it also starred Gimli (John Rhys-Davies) long before his debut in Lord of the Rings. The premise from Wikipedia is as follows:
The show follows a group of people, called "Sliders", as they travel ("sliding") between different Earths in parallel universes via a wormhole-like "vortex", hoping to return safely to their original Earth Prime. The vortex can only be opened at random but preset intervals on each new world, monitored by a countdown clock on a portable timer that they carry; failure to open the vortex in time would strand the Sliders for 29 years in that universe. While waiting for the timer countdown, the group learns about the differences in the alternate Earth from their own, and often become unwillingly involved in events that they must resolve before they can safely leave via the vortex. As a result of the misuse of the timer in the pilot episode, the travelers have no control over what world they end up in, but continually look for means to repair the timer and find Earth Prime.
Writers from H.G. Wells, to C.S. Lewis, to Neil Gaiman have crafted gorgeous stories around the idea of alternate universes. And now I have as well. Why? The grass is always greener in the other universe. Or something like that.