We're living on a planet with an expiration date. One day, Earth will die or explode — and if we're lucky, some of us won't be there. Science fiction is full of stories where we abandon a dead Earth, including the upcoming films Oblivion and After Earth. Here are all the reasons people leave Earth for dead in science fiction.
Top image: After Earth.
Note: We're not including any of the many cases where the Earth is destroyed and absolutely nobody escapes or survives. That would be a way, way longer list.
That said, here are the various reasons science fiction has given us for wanting to put a fork in the planet:
Aliens have a long and terrible history of invading Earth — and sometimes, people get away. In the animated film Titan A.E., some humans escape from the Drej blowing up Earth, and go on to become the scum of the galaxy. In Greg Bear’s novel The Forge of God, Earth is eventually destroyed by one faction of aliens — but fortunately another faction of more benevolent aliens help evacuate some of humanity off world. In John Varley's Ophiuchi Hotline, humanity is forced off Earth by some aliens seeking to protect the whales and dolphins. Humans only thrive off-world though due to help from an alien radio broadcast. In an interesting twist, the Robotech Expeditionary Force leaves earth to take the Robotech Wars to the Robotech Masters. They aren't necessarily going out to colonize space, but wind up doing so as a byproduct which turned out be useful in later wars. Also, in the story "For White Hill" by Joe Haldeman, most of humanity leaves a burnt-out Earth after a terrible war with aliens.
Killed by a Planet-killer
in the final episode of the Canadian TV show LEXX, the eponymous planet-killing spaceship slices the Earth in, but not before a handful of humans are able to make their escape.
Knocked down to make way for a bypass
In Hitchhiker's Guide to the Galaxy by Douglas Adams, the Earth is basically nuked by your local town council, in the form of the poetry-writing bureaucratic Vogons. But at least two humans, Arthur Dent and Trisha "Trillian" McMillan, survive. (And then of course, later it all comes back. But it's a long story.)
We don't need alien ships to render Earth uninhabitable — we're more than capable of doing it ourselves.
"Sic transit mundus" ("Thus passes the world"), says Brother Joshua as he boards a starship to leave Earth in Walter Miller's Canticle for Leibowitz. In Canticle, humans are lucky, because we'd started colonizing space when the epic war broke out and destroyed Earth. In Philip K. Dicks’s classic “Do Androids Dream of Electric Sheep?,” Earth is dying at a slower rate from nuclear radiation poisoning, and most people have already left the planet. In Battlestar Galactica, the missing 13th colony of Earth is found to be still be a nuclear wasteland, forcing the remaining humans and Cylons to colonize a new “Earth”. Similarly, in Toby Litt's Journey into Space, a generation ship is already on its way when the remaining survivors on a damaged Earth launch a final nuclear war and leave nothing to look back at. In Octavia Butler's Lilith's Brood, we nuke our own planet — but then the survivors are rescued by the friendly Oankali, who want to join with us... and we won't be quite the same afterwards. In Asimov's Pebble in the Sky, the Earth is ravaged by "radioactives." And similarly, in his far-future Foundation's Edge, it's noted that the mythical planet Earth is just a wasteland, due to long-ago nuclear wars.
In the short lived television series Earth 2, humans are forced off Earth into space stations by environmental devastation. Weirdly enough, in the space horror film Jason X, we also live on a place called Earth 2 — because of too much pollution making the Earth unlivable. In Alien: Resurrection, Earth is described as a “shithole,” with the novelization providing more details about the planet as a polluted slum that everyone who was able has already left. In Katharine Kerr’s novel “Polar City Blues,” Earth is abandoned because of ecological collapse and holds a less then prestigious place in the galaxy. Also, in Pamela Sargent's Earthseed, it's a combination of environmental devastation and used up resources that drives the last survivors of humanity to escape in a ship, conveniently named Ship.
Turned into a Garbage Dump
Forget death by pollution, what about death by actual garbage? The Earth is turned into a literal dump in the movie Wall-E, and in the Red Dwarf novel Better Than Life. Poor Earth — in the Red Dwarf universe, it first gets a giant toupee to cover its ozone hole and then literally farts itself out of the system thanks to a giant methane explosion from all the interstellar trash.
Turned into a Graveyard
In Clifford Simak's Cemetery World, the entire planet has been converted into an elite cemetery for trillions of the rich and powerful, run by a corporation called Mother Earth, Inc. Wealthy people who feel sentimental about the planet we all came from can pay through the nose for a funeral plot — but a few barbarians still skulk around the planet, and there are also grave robbers visiting from space.
Stripped of Resources
In Firefly and Serenity, we learn that Earth was used up and humans were forced into colonies. In the Trigun anime, which interestingly enough also has a Western theme, Project SEEDS was a deep space colonization mission to preserve the human race after all of Earth’s resources were used up. The scarce resources help to explain a low tech society existing amidst high tech spaceships. Also, in the novel Exile Waiting by Vonda McIntyre and some of her other books, Earth has been abandoned by humans after its resources were all used up. A few surviving humans live in "Center," a technological oasis on an otherwise devastated planet. The story "Deep End" by J.G. Ballard takes this to its furthest extreme — not only are all the natural resources exhausted, but also humans have performed a process called "oxygen mining" on the oceans to gain enough oxygen to create atmospheres on other worlds — leaving nothing but hydrogen, which rose up and stripped the atmosphere.
Impact by a Space Object
The fear of a random object from space destroying Earth is an old classic and rightfully so — look what happened to the dinosaurs. In the 1933 science fiction novel When Worlds Collide, a rogue planet is discovered to be coming to pulverize Earth and scientists work feverishly to build spaceships for evacuation. Playing into all the ridiculous 2012 doomsday conspiracy theories, National Geographic took the time to make the docudrama Evacuate Earth, which featured a rogue neutron star threatening Earth and humanity building generation ships to escape. Also, in the novel End of the World News by Anthony Burgess, a few lucky humans flee Earth in generation ships just before a rogue planet smacks into us. In the Remnants series of books, a group of humans haphazardly launch themselves into space to escape an Earth-destroying asteroid and get picked up by a passing alien ship.
Artificial Black Hole
In Dan Simmons' Hyperion, poet Martin Selenius is sent away from an Earth that's being devoured by a manmade black hole. To be fair, space flight and colonization already exist — but the devouring of the planet by a black hole lead to a final exodus.
This isn't Earth, but the Quarians in the Mass Effect universe were driven from their home system by the synthetic creatures called the Geth at the end of the Morning War. In most other robot uprisings, like the Terminator movies, humanity lack the ability to just leave.
In Century Rain by Alastair Reynolds, the Earth is rendered uninhabitable due to the "Nanocaust," a technological catastrophe that included "smart weather." Now the Earth is a frozen hulk, overrun by "furies." Everybody who's still alive is a descendant of people who were already living in space when the Nanocaust happened.
In the Doctor Who episode "The Beast Below," the Doctor and Amy arrive on the Starship UK, a ship that was built to house the United Kingdom after it evacuated Earth due to solar flares. In the episode "The Ark in Space," humanity has also evacuated Earth due to solar flares. This time, a small group of humans are placed in suspended animation for five thousand years with the plan to repopulate Earth once it is habitable again. The 1953 science fiction novel One in Three Hundred is about humans attempting to escape to Mars because Earth’s atmosphere will be boiled off by sun flares and other solar activity. In the Nic Cage movie Knowing, solar flares are about to destroy Earth, but benevolent aliens take some children off earth.
In the anime Dragon Ball GT, the villain Baby makes a wish to destroy Earth, using the Black Star Dragon Balls. With only two weeks of advance notice, the Z Fighters are forced to lead an evacuation of Earth to the Tuffle planet, using their teleportation powers and good old-fashioned space ships.
Astral Gate Explosion
In the anime Cowboy Bebop, humanity is on its way to hyperspace travel with the construction of an astral gate orbiting the Moon. The “Gate Accident” causes a massive piece of the Moon to shatter, and lunar debris rains down on Earth causing massive devastation and billions of deaths. This led to the rest of the solar system being colonized in fifty years.
The sun dies or goes nova
Again, this isn't Earth, but in the video game Myst, the D’ni are forced to flee their homeward Garternary due to its dying sun. In Arthur C Clarke's novel Songs of Distant Earth, a colony ship of humans land on an alien world after a supernova is predicted to destroy Earth. Also, in Clarke's story "Rescue Party," aliens arrive when Earth's sun is due to go nova within seven hours — and find that the human race is now all on spaceships out near Pluto, ready to conquer the stars. And in Babylon 5, we learn that the sun will go nova in a million years' time, but not before our descendants escape to New Earth.
Additional writing/reporting by Amanda Yesilbas.