Pick up any science fiction book from the 1960s, and you’ll find parallel dimensions explained through magic portals or mysterious machines that work “just because.” Today’s readers want stories that ...

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

For decades, scientists, philosophers and science fiction writers have been fascinated by the idea of parallel universes — realms that may exist beyond our own, each potentially with its own version ...