Since the earliest days, humankind has pondered the end of the world. We’ve imagined messianic judgment days, cataclysmic comets, hyperspace bypasses, and Mega Maids. Here are a few apocalyptic scenarios from recent popular culture, how they might happen, and how likely they are to occur.

1. Subterranean Apocalypse

Some existential threats are waiting quietly beneath the surface of the planet, as we learned in Tremors, Gears of War, and the 2002 dragon apocalypse film, Reign of Fire. Is it possible that lurking horrors are underfoot, slumbering or tunneling, waiting for the right moment to strike?

Probably not. But there’s still a lot going on down there. For example, xenophyophores are extremophiles that live at the bottom of the ocean, to include the Mariana Trench, which is 6.6 miles below sea level. While it’s unlikely that these four-inch, single-celled organisms will rise up and enslave humanity, they do have a Wolverine-like resilience. The pressure in the Mariana Trench is eight tons per square inch.

The deepest land creature is 1.23 miles beneath the planet’s surface. Plutomurus ortobalaganensis was discovered eating decaying matter in the Krubera-Voronja cave in Abkhazia, according to Terrestrial Arthropod Reviews, which is an actual publication. But unlike its locust brethren in Gear of War, plutomurus ortobalaganensis is eyeless, giving humans an advantage in the inevitable conflict.

(Lest we become complacent, the Los Angeles Times reported on January 29, 1934, that Lizard People might once have lived in catacombs hundreds of feet beneath the city. It is unclear where they are today.)

2. Alien Apocalypse

If there’s one thing Independence Day taught us, it’s that Bill Pullman can give a pretty stirring speech. If there's a second thing the movie taught us, it’s that when extraterrestrials come, they won’t be looking for Reese’s Pieces. In 1960, astrophysicist Frank Drake estimated the requirements for detecting alien civilizations in the Milky Way. The Drake Equation examines such things as the rate of star formation, the number of planetary systems with life-sustaining worlds, and the number of those worlds that eventually produce life. Although the number is conjecture at best, Drake estimated that there are between 1,000 and 100,000,000 extraterrestrial civilizations in our galaxy.

They can’t all be Vulcans out there. What would happen if aliens found Earth? According to Stephen Hawking, the best model we have for the discovery of Earth is what happened when Europeans discovered the New World. "We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet. I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonize whatever planets they can reach."

Presently, the Voyager 1 space probe is approaching the heliopause, where solar winds give way to interstellar winds. It will be the first manmade object to leave the Solar System and enter interstellar space. (It’s traveled 11.1 billion miles so far; it moves at 38,000 miles per hour. Its battery will allow for data transmission back to Earth until around 2030, but inertia will keep it moving through space until the crack of doom.) The probe will be like a signal flare to the rest of the universe. And considering the mind-boggling technology required for galactic exploration, at best we’re insects to our alien overlords. (Hail Skroob.) At worst, we’re dinner.

3. Zombie Apocalypse

The U.S. Centers for Disease Control has a website devoted to emergency preparedness, with a section for zombie attacks. (“Get a kit. Make a plan. Be prepared.”) The top-selling product by ammunition maker Hornady is a green-tipped bullet called Z-MAX. (Its slogan: “Make dead permanent.”) The Zombie Survival Guide: Complete Protection from the Living Dead, by Max Brooks, remains a bestseller nine years after its debut. Clearly there is some anxiety about “walkers” and the threat they pose.

With good reason. In June 2012, a naked, growling, incoherent woman was arrested in Syracuse, New York, after attacking her family. A woman in Kansas City, Missouri, bit her neighbor, dropped to her knees, and began “digging in the ground, like a dog would.” She then fought against police, kicking wildly, with clods of dirt in her mouth. Only days before, a naked man in Miami was shot dead by police as he chewed the face and eyes off of a homeless man. (The first bullet didn’t stop his gnawing.) In Lafayette Parish, Louisiana, a man was arrested after he “bit a chunk of the victim’s face off.” Each of these grisly incidents, and many others across the United States and around the world, make 28 Days Later seem like a documentary.

A designer drug called “bath salts” has been blamed for each of these zombie attacks. It’s sold at head shops and smoke shops, and is marketed exactly as it’s described: as bath salts. (Don't worry, you won’t accidentally pick up a bag at the local grocery store and turn into a zombie. This stuff isn’t exactly brewed by Proctor & Gamble.) There’s no test for the drug, it’s unknown whether it’s addictive, and according to one former junkie, it makes you feel “like the darkest, evilest thing imaginable.” Like the undead. Praise the Lord and pass the Z-MAX.

4. Asteroid Apocalypse

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1998 was a great (well, terrible) year for Doomsday asteroids in film. Both Armageddon and Deep Impact promised us that if Lucifer’s Hammer came hurling toward us, all it would take are a couple of nukes and a plucky team to save humanity.

Unfortunately, it’s not quite that simple. First, it’s unclear whether we actually could blow up an asteroid that’s large enough to end the world. It’s also unclear whether we would want to. Any asteroid over 6.2 miles in diameter is considered “extinction-class.” The only thing blowing one up would do is turn one giant problem into a bunch of smaller problems. The Earth’s atmosphere would still have to absorb all that kinetic energy, which would probably end human life anyway.

But what are the odds that we might one day live out the video game Rage? There’s a 1-in-1000 chance that asteroid 1999 RQ36 will collide with the Earth in 2182. Those are the same odds as winning the Pick-3, only instead of taking home $600, the world ends. There’s a 1-in-250,000 chance that asteroid 99942 Apophis will impact the planet in 2036, which means you’re more likely to die from an asteroid than you are in a plane crash (1-in-11,000,000). The good news is that the dinosaurs took one for the team 65 million years ago. As Garp might point out, the world has been “pre-disastered.”

5. Thermonuclear Apocalypse

The post-apocalypse might be like the video game Fallout, with great music and the occasional mutant, but it would probably be like the novel The Road, with cannibalism and freezing, sunless days. One cause of such a climate is nuclear winter. (Other causes: impact winter, from an asteroid strike; and volcanic winter, from a super-volcano.) Theoretically, if the world’s nuclear powers decided to let the ICBMs fly, most major metropolitan areas would be targeted. The result would be a lot of smoke. Once the smoke reached the stratosphere it would remain there, as it would be above the clouds, and thus above the rain. This would block the sun, which would almost instantly plunge the planet into a perpetual winter. Without sun or heat, there would be no crops to feed boys or their dogs. This would last for years, though it’s doubtful we’d live long enough to know how many, exactly.

Nuclear winter isn’t the only problem. Contrary to the playground scene in Terminator 2, relatively few people are actually vaporized by the Bomb. (Those who are, though, wouldn’t even know it. They’d simply cease to exist, except for their shadows, which would be imprinted on stones and brick by thermal rays.) Survivors would be treated to searing heat, hurricane winds, and awesome firestorms before things like radiation poisoning or nuclear fallout would even cross their minds. (Essentially, “fallout” is the radioactive dust that’s created and dispersed by the blast. As dust is everywhere and never seems to go away, the resulting problem is self-evident.) Then there would be “black rain,” which is just what it sounds like—dark, radioactive rain.

How likely is this to happen? According to Martin Hellman of Stanford University, there’s at least a ten-percent chance that a child born today will die an early death from nuclear war. But on the plus side, the Mad Max dune buggies are going to be great.

Bonus: Matrix Apocalypse

It’s possible that the apocalypse has already happened, and this is all an elaborate game of The Sims. Dr. Nick Bostrom of Oxford University estimates a 20% chance we're actually living in a computer simulation. As Moore’s Law extends to infinity, it stands to reason that a hundred years from now we could computationally approximate the lives of trillions of people. For all we know, this is a lousy simulation, but it’s beyond our programming to see it. And because it’s hard to imagine things getting much sharper than Apple’s Retina display, maybe the program is coming to an end. As we’ve seen in Sim City, three of the five apocalyptic scenarios listed above are a possibility.

If reality really is just an advanced version of Sid Meier’s Civilization, there is hope yet. A Reddit-user called Lycerius recently posted to the site that he has been playing the same saved game of Civilization II for over a decade. (May our own computer deity have such devotion.) Lycerius reports that the year 3991 A.D. is a “hellish nightmare of suffering and devastation.”

But at least humanity was spared asteroid 1999 RQ36, and the Lizard People never returned.