Ranking Fictional Apocalypses on the Plausibility Scale

Entropy (The Dying Earth series, by Jack Vance)
Vance’s Dying Earth novels offer up a perfectly plausible end-of-the-world scenario: time. Taking the long way around, Vance sets his story in the far, far future, when the sun is swelling into a red giant and the planet is soon to be consumed and destroyed. The fact that this is Earth’s eventual, inevitable fate, no matter what else might happen, makes this one the least-ridiculous apocalypse in all of sci-fi.
Plausibility rating: A sure thing.

Ran Out of Humans (The Children of Men, by P.D. James)
The apocalypse James imagines is a slow strangulation of the human race through the simplest manner possible: sterility. While the ultimate cause for the human race’s inability to reproduce isn’t explored in detail, the fact is, fertility rates have been dropping in the real world for some time, so this is one slow, whimpering world’s end that is entirely plausible—as is the horrific societal breakdown surrounding it.
Plausibility rating: Growing likelier by the day.

Nuclear War (On the Beach, by Nevil Shute)
Nuclear war is, sadly, still one of the most likely ways civilization and all human life could end on the planet. Set largely in Australia as the population awaits a huge cloud of deadly radiation stemming from a nuclear war in the Northern Hemisphere, the story remains a gripping and horrifying glimpse of an end of the world that could still happen—at any time.
Plausibility rating: One tweet more likely, anyway.

Weaponized Virus (The Stand, by Stephen King)
The Stand is name-checked any time the idea of a world-ending plague comes up—and for good reason. While King takes the story into a supernatural direction, for much of its immense length, The Stand is one of the most believable stories of a world-ending illness ever written, tracing the breakdown of society in meticulous and realistic detail, from the mistakes that allow the “Superflu” into the wild, to the way people try to deal with the disaster during—and after.
Plausibility rating: Cough, cough.

Asteroid (Lucifer’s Hammer, by Larry Niven and Jerry Pournelle)
Ending the world via asteroid impact is alway a possibility, and Niven and Pournelle pretty much dropped the mic on the concept with the award-winning Lucifer’s Hammer, which explores the possibility in pulse-pounding, stressful—and unfortunately, realistic fashion.
Plausibility rating: Just ask the dinosaurs.

Oops, All Ice (Cat’s Cradle, by Kurt Vonnegut)
Ice-Nine is a specific molecular arrangement of water that is frozen solid at room temperature. Once it touches regular water, it rearranges the other molecules in its image, instantly freezing the water solid. Ice-Nine actually exists, although it doesn’t behave the way Vonnegut writes it—but that’s okay. The idea is plausible enough to be chilling. However, we take points off for the way all the water on the planet is turned to solid ice—ending life as we know it. It’s bonkers, involving a body frozen by suicidal ingestion of Ice-Nine, a plane crash, and a landslide. Although it is perhaps the most Vonnegut of all Vonnegut endings.
Plausibility rating: So it goes.

Intergalactic Red Tape (The Hitchhiker’s Guide to the Galaxy, by Douglas Adams)
At first glance you might think Adams’ hilarious sci-fi satire should be the most ridiculous, since it involves Earth being demolished for to make way for a traffic bypass. In space. By a race of aliens called Vogons, who have all the personality of bureaucrats who write really, really awful poetry. But since this essentially boils down to the Earth got blown up by superior alien firepower, it’s not all that ridiculous. Although it is hilarious.
Plausibility rating: Infinite improbability.

Engineered Supernova (The Force Awakens, by Alan Dean Foster)
Look, the Death Star is cool. Moon-sized weapon that can destroy entire planets? Not only awesome, but theoretically possible, if a bit wasteful. In the new film series (and the novel adaptation that followed), Starkiller Base is essentially the Death Star Writ Bigger—and it becomes infinitely less believable, or even scary. Supposedly powered by a sun in orbit, the complete lack of attention to the physics consequences of such an arrangement is just distracting in a story that is otherwise SF perfection.
Plausibility rating: Insignificant compared to the power of the Force.

Suddenly Bite-Sized (Faller, by Will McIntosh)
We love Faller, a fantastic mystery in which the protagonist wakes up with no memory, a few clues in his pockets, and living on an Earth recently shattered into hundreds of free-floating chunks. It’s a tightly-written story exploring fun but shaky laws of physics, including how everyone still experiences completely normal gravity and climate when the world’s been transformed into planetary gravel. While we don’t think this particular apocalypse is particularly likely, it sure is mind-blowing.
Plausibility rating: We forget.

Not in Fire but in Ice Cream (Lost in a Good Book, by Jasper Fforde)
Dream Topping, for Americans, is essentially Cool Whip. In Jasper Fforde’s second Thursday Next book, Thursday discovers (among many other hilarious and mind-bending literary things) that the world will end in a flood of pink goo that turns out to be strawberry-flavored Dream Topping. This apocalypse is avoided, and the Dream Topping ends up supplying the organic nutrients to kickstart life on Earth instead. And yet somehow, we rank this the least plausible apocalypse ever—although it still ranks pretty high on our must read lists.
Plausibility rating: Deliciously absurd.
What’s the unlikeliest end-of-the-world scenario in fiction?