No matter how good life is we always want something better. It may be as simple as wanting nice weekend weather or a traffic-free ride into work, or as sophisticated as wanting to be the Supreme Overlord of the entire universe where every living being grants your every wish without question. (Hey, a guy can dream, can't he?) While it's unlikely that everything you wish for will come to pass, you can at least take some comfort that in another dimension, your dream probably came true.
Let me explain...
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The Many Worlds Theory
There is a field of science called quantum mechanics that deals primarily with things that happen on a minute scale. I'm talking smaller than the size of a single atom. The Many Wolds Theory is an approach to quantum mechanics that says that every time something happens at the quantum level, new universes (co-existing "alongside” our own in another dimension) are created that reflect all the possible outcomes. In these "parallel worlds" there are nearly identical Earths and on these parallel Earths there's another version of you. That means that somewhere there's a version of you that did indulge in the double-chocolate ice cream sundae at dinner last night, though if there is, chances are he or she is carrying around a lot more guilt than you.
Parallel worlds in Science Fiction
The idea of parallel worlds is enticing because if allows us to imagine things that might have been. Science fiction might locate a story in one of these worlds, for example, Philip K. Dick's The Man in the High Castle which posits a world where the Axis powers won World War II. But in addition to such "alternate history" stories, there are books that deal with the multitude of worlds that may co-exist with ours. The thrill of such setups is that characters can move between these worlds at will.
Here are some recent science fiction books that prominently include parallel worlds:
The Broken Universe by Paul Melko continues the story of John Rayburn, an Ohio farm boy who, as depicted in Melko's The Walls of the Universe, obtains a device from an alternate version of himself that allows him to travel between the many alternate Earths. John uses his unique knowledge to gain commercial success by co-opting products and technology from his universe into one that doesn't have it yet. ("Why yes, Virginia, I did invent the Rubik's cube!") Soon, John's trans-dimensional commercial empire, which is run by him, his friends and their doppelgängers from other universes, attracts the attention of other dimensional travelers who stop at nothing to gain control of the powerful tech.
Literary mastermind Ian McDonald plies his craft toward a novel aimed at young adults (but enjoyable by anyone) in Planesrunner, the first book in his Everness series. Planesrunner introduces Everett Singh, a smart young man whose scientist father is suddenly kidnapped, but not before he sends Everett a clue to his amazing scientific discovery. Everett acquires the Infundibulum, a device that lets him travel to alternate Earths. Of even more import is that the device will specifically lead Everett to the alternate Earth where he hopes he might rescue his father.
Genre superstars Stephen Baxter & Terry Pratchett combine forces in The Long Earth, a novel that not only posits that there are multiple Earths, but goes even further and suggests that the human race only exists on our own Earth. This thought-provoking story is told via characters from two different eras. In 1916, a soldier wakes up in an empty field wondering where the war went. And in 2015, a police officer, investigating the burned-out home of a scientist, discovers a device that (surprise!) allows her and the rest on mankind to travel between these many other lifeless dimensions. Is this mankind's do-over?
Another recent source of fantastic fiction featuring parallel worlds is the anthology Other Worlds Than These edited by John Joseph Adams. It offers 30 stories about “other worlds” slightly different than our own. And it offers an spectacular lineup of contributors as well, including Stephen Baxter, Seanan McGuire, Gregory Benford, Paul Melko, Ian McDonald, Alastair Reynolds, Ursula K. Le Guin, Stephen King, Jeff Vandermeer, George R.R. Martin, Carrie Vaughn, Catherynne M. Valente, Orson Scott Card, Christie Yant, Robert Silverberg and more.
If the ides of parallel worlds interests you beyond the pages of fiction, you would do well to check out Parallel Worlds: A Journey Through Creation by Michio Kaku, a theoretical physicist whose no-nonsense explanation of scientific principles make it seem easy to grasp and fun to learn.John DeNardo is the editor of SF Signal, a Hugo-nominated group science-fiction and fantasy blog featuring news, reviews and interviews. He also like bagels.