Parallel Worlds Collide
Eventually, some theorists begin to argue that parallel worlds can and do interact. In his 2005 book Parallel Worlds, theoretical physicist and string theorist Michio Kaku suggests that when parallel worlds—which, according to string theory, exist in parallel dimensional membranes—bump into one another, the impact sets off an astronomical Big Bang that generates a universe-worth of elements in the fiery aftermath. It's possible, Kaku writes, that our own universe started in just this way. Is he right? As with all scientific theories, including Everett's innovative foray into parallel worlds half a century ago, only time—and a lot more work—may tell. In the meantime, science fiction, running in parallel, will no doubt break new ground of its own.