There's religions based around it, too. In the east it is much more common for people to acknowledge other realms than here. Most of their sanctuaries and temples (goes for the catholic church, too) are modeled after realms and gods, visions.

If you liked Stephen, I strongly recommend you check out Carl Sagan's Cosmos series. The renewed ones aired just recently, with Neil deGrasse Tyson. Both are okay but I prefer the old ones. Also check out Stephen's book The Grand Design. Some of the chapters are 'the mystery of being' 'what is reality' 'alternative histories'.... you can find it online.