Cosmology and quantum physics both offer tantalizing possibilities that we inhabit just one reality among many. But testing ...

In the season 2 episode "Mirror, Mirror," Star Trek perfected the alternate universe trope long before Hollywood's multiverse obsession.

The universe is a strange, beautiful place—rich with possibilities and governed by the odd rules of quantum mechanics. One of the most mind-bending ideas from this realm is the many-worlds ...

"There was a time when ‘universe' meant ‘all there is,' " writes Greene, but soon we may have to redefine that word, along with our own meager understanding of the cosmos. A theoretical physicist and ...