Parallel universe (fiction)

A **parallel universe** is a world or universe that exists outside of our own, but is similar to it in some ways. The trope of parallel universes is often used in fiction.

## Examples 
### In books 
In 1884, Edwin A. Abbott wrote a novel called *Flatland,* about a world of flat, 2D shapes that discover a world of round, 3D shapes.

In 1905, H. G. Wells wrote a book called *A Modern Utopia*. In the book, two people from Earth go to a new world which is a utopia. Each of them has a doppelganger there. Wells also wrote books where time travel changed history and created different worlds.

In 1934, Murray Leinster wrote a science fiction short story called "*Sidewise in Time.*" In it, time changes, so that people from our world switch places with people from other worlds, whose history is different from what they know. Some people, for example, go to a world where the Roman Empire still exists. In another world, the Vikings took over North America. One person ends up in a world where the Confederate States of America won the American Civil War.

In 1961, DC Comics published a comic book called “*Flash of Two Worlds,”* where the Flash runs so fast that he teleports to another world. Because of this, the original version of Flash, named Jay Garrick, and the new version of Flash, named Barry Allen, meet each other. Barry Allen’s world is called Earth-One, and Jay Garrick’s is called Earth-Two. 

### In television 
In 1967, *Star Trek* had an episode called "Mirror, Mirror," in which Captain Kirk switches places with another version of himself from a Mirror Universe where he and all his crew (except Spock) are evil. The 2009 movie Star Trek is about Spock and his enemy going back in time, changing the past, and creating a new universe.  

In the 1970s, a show called “*The Tomorrow People”* involved time travel being used to change history and create new worlds.   

The 1993 movie *Super Mario Bros* features Mario and Luigi travelling to a world where the dinosaurs never went extinct.    

In the television show *Once Upon a Time*, all fairy tales are true, but they happened in their world called the Enchanted Forest. The only people from our world who can go to the Enchanted Forest are people who write stories about what happens in it for people in the real world to read. It later turns out that not only are all fairy tales true, but all fictional stories are true. Thus, if there’s an Italian version of *Snow White* and a French version of Snow White, then each one is real and exists as its world. The TV show featured iconic stories, including *Frankenstein*, *Dr. Jekyll and Mr. Hyde*, *Twenty Thousand Leagues Under the Sea* and *Moby-Dick*. When Emma Swan wishes she were never the Chosen One, she creates a new world where she never existed, called The Wish Realm. Since then, the Arrowverse superhero television shows and the Marvel Cinematic Universe have both used parallel universes as key plot lines.       

In 2023, *Spider-Man Across the Universe* talks about canon events. These events are somewhat linked to parallel universes in when you make a decision in a canon event there can be yous in other parallel universes that made a different decision that caused a different path to be chosen.