Everybody knows about the multiverse, where there are an infinite number of realities that our heroes can visit using the power of their minds or whirly light technology. But then there are the stories that stick close to home, giving us an alternate Earth where our doubles live happier lives despite having no coffee or being under alien attack.
Let's visit ten alternate Earths.
Special explanatory note! An alternate Earth is a parallel world that co-exists with our Earth. It is not an alternate history, or an alternate timeline, that replaces our Earth.
1. Another Earth
Coming out this Friday, the movie Another Earth is probably the first indie flick to explore the idea of a parallel Earth as a backdrop to a story about human relationships and the choices we make. A parallel Earth is discovered in our orbit, on the opposite side of the sun. Our protagonist, a physicist who suffers a horrible tragedy, ponders whether she should visit the other Earth and find out what her life might have been like if things had turned out differently.
2. Alternate Earth in Fringe
When mad scientist Walter opens a door between Earth and its slightly-different, more technologically-advanced counterpart, he can't resist kidnapping Walternate's son Peter after his own version of Peter dies. And thus the antagonism between the two Earths (and the two Walters) begins. By opening the door, Walter has destabilized the fabric of Alternate Earth's reality. Plus, Peter's presence on Earth causes its own problems. Every character and place on Earth seems to have a parallel in Alternate Earth (thus "Manhatan," Fauxlivia, and many characters who lead slightly different lives in Alt.Earth). Many tales of an alternate Earth, like the one in Fringe, include the idea that we all have alternate selves on the mirror planet.
3. Evil Universe Earth in Lexx
In the third and fourth seasons of bizarro Canadian show Lexx, our heroes get sucked through a singularity into an evil version of our universe where — through a series of increasingly meta shenanigans — they wind up on Evil Earth in the 21st century. Evil Earth is controlled by a Satanic bad guy named Prince, whose authoritarian regime involves using shock troops from the Bureau of Alcohol, Tobacco and Firearms. It's a pretty hilarious sendup of American culture, and gets weirder and weirder as the series continues. There are no parallel versions of our main characters, who don't actually come from Earth.
4. His Dark Materials series, by Philip Pullman
This series is set in an alternate version of Earth where magic seems to play the same role that science does in our world. There is an institution that strongly parallels the Catholic Church, which conducts horrible experiments on children in the name of discipline and morality. Our main character Lyra and her friends discover how to enter alternate universes, including our Earth, where it turns out that the study of dark matter is an alternate version of the study of souls and magic in Lyra's world. On our Earth, Lyra meets Will, who becomes her companion and lover. Though they must return to their separate universes to survive, Lyra and Will agree to "meet" at a designated time every year by both sitting on a specific bench on the Oxford campus - a location is mirrored in both their worlds. They never see each other again, but know the other is sitting in the same place just one universe away.
5. "Infinite Earths" in the DC Universe
Both the DC comics and Marvel comics universes are basically multiverses, but DC is perhaps more famous for developing so many parallel Earths that occasionally they have a "crisis" that reverberates across all the Earths and resets the world back to just a few Earths. Of all the DC Earths, the most stable seem to be Earth-One and Earth-Two, where parallel versions of the Justice League of America exist and occasionally team up.
6. Alternate Earths in Stargate-1
The Stargate universe has always toyed with alternate Earths, and indeed the original Stargate movie hinted that the team has found themselves in an alternate Earth where the ancient Egyptian empire never fell. SG-1 was known for exploring alternate Earths where many of the characters chose not to enter the military or the Stargate program. These characters have happier romantic lives but often live on a version of Earth that's about to be attacked by aliens.
7. Super Mario Bros. and The Neanderthal Parallax by Robert Sawyer
In both Super Mario Bros. the movie and Robert Sawyer's Neanderthal Parallax series, there is an alternate version of Earth where evolution has taken a different direction. Super-evolved dinosaurs rule Dinohattan in Super Mario Bros., while in Sawyer's novels the Neanderthals never died out and Homo sapiens isn't in the picture. It's important to contrast these parallel Earth scenarios with alternate evolutionary histories, where evolution has gone another direction but there is no version of "our" Earth's evolution.
An entire TV show about a team of investigators jumping to parallel Earths! Sometimes the results are awesome, and sometimes you get unoriginal stinkers like "this is the world where women dominate men!" But when things aren't upsidown world like that, how do you know you've arrived on an alternate Earth at all? Luckily, two famous alternate world TV episodes have the answer . . .
9. Star Trek's "Mirror, Mirror" and Doctor Who's "Inferno"
These oft-referenced episodes of two classic shows are remembered as much for their silliness as they are for their awesomeness. In "Mirror, Mirror," the Enterprise encounters an evil universe version of itself, and we know the evil Spock because he's got a terrifying goatee! Yes, this is the origin of every "evil goatee" joke you've ever read on the internet. Similarly, when the Doctor finds himself on an alternate Earth where England is fascist, his familiar pal from UNIT is tagged as fascist because he's wearing an eyepatch. So just remember, when in doubt, you're probably on an evil alternate Earth if your friends have goatees or eyepatches.
10. Futurama's "Farnsworth Parabox"
Of course Futurama has a hilarious take on the parallel Earth, where instead of the characters having different personalities or lives they are just a different color than they are in our world. Here we're actually seeing a parallel universe scenario, like in "Mirror, Mirror," so it's not strictly an alternate Earth. But it's close enough that we'll take it.