For all our talk on “the future now,” there is one future we’d prefer to delay for the next five billion years, and that’s the inevitability of our planet’s destruction. Mankind’s speculated on the end of the world for thousands of years, but it wasn’t until recent centuries that people began attaching scientific possibilities to doomsday scenarios, instead of blaming the gods for our demise.

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During the first half of the 20th century, we focused our imaginations on cosmological disasters. Billions of years from now, the sun will explode, vaporizing the Earth in a ruthless inferno. Or perhaps a swarm of asteroids would bombard our cities and crash into our oceans, resulting in a series of megatsunamis. Other scenarios included one where the Earth’s surface would shrink so tightly, that its core would explode with the pressure, turning our beloved planet into just another asteroid belt. The most bizarre theory was that a rogue star would cross into our solar system, swallowing our planet within streams of deadly solar rays.

More terrifying, however, than the prospect of getting zapped by cosmic rays is the possibility that mankind will bring about its own destruction. Between the end of World War II and the early 1970s, sections of Popular Science essentially functioned as guides to surviving nuclear fallout. Nowadays, “Doomsday machine” sounds like an antiquated sci-fi myth, but type those terms into our archives and see if you don’t feel unsettled by the paranoia surrounding this hypothetical weapon.

At any rate, we lived through the Cold War, although there’s no telling which impending disaster will scare us quite as badly. In the meantime, click through our gallery for more creepy scenarios for how our world will end.

Death Rays: August 1924

Death-rays were a theoretical electromagnetic weapon popular between the 1920s and 1930s for their supposed ability to remotely power devices and destroy living creatures. Inventors like H. Grindell-Matthews, pictured below, claimed to have invented a “mystery ray apparatus,” capable of paralyzing internal combustion engines of airplanes and automobiles with an invisible beam. Although most experts dismissed the claims of Grindell-Matthews and his counterparts, which included Nikola Tesla, the idea of a death-ray nevertheless captured the imaginations of a public already thrilled by H.G. Wells’ fictional descriptions of extraterrestrials who could zap the world into oblivion. Like many leading scientists, we were skeptical that a “diabolical beam” could exist, let alone that it would be powerful enough to wipe out human civilization. At the same time, we acknowledged a related technology, wireless power transmission, could make life easier without “dealing electric death” and contributing to global warfare. Read the full story in “Man’s Most Terrible Invention”

Cosmological Disaster: January 1928

Dr. Dinsmore Alter, a respected American astronomer and meteorologist, predicted that our planet would end in “a gigantic explosion!” As earth neared the end of its time, its surface would crack open into a “vast abyss, until at last the entire globe will be rent asunder.” The subsequent blast would scatter fragments of our planet into the universe, but not for millions and millions of years, Dr. Alter assured us. In between now and the end of the world, humanity would live to see the moon explode, the tides disappear, and Mars collapse into itself. Unless we relocate to another planet, we’ll die out in the Earth’s last ice age, or perhaps during an asteroid collision. Dr. Alter’s theories, while grim, only reflect what he believed already happened to ancient planets that died long before mankind even evolved. Our solar system can’t guard itself against the ravages of time. As the planet ages, its surface will cool, causing the earth’s crust to shrink and pressurize its hot inner core. As you can imagine, cracks extends thousands of miles into the planet’s center can only lead to a global catastrophe. Read the full story in “How the World Will End”

Return of the Ice Age: June 1929

Earth has been through 12 ice ages, and while we’re currently in an interglacial period, geologists speculate that the planet will experience another one….40,000 years from now. In 1929, however, Dr. V. Nordmann, from Denmark, reasoned that an ice age could arrive as “early” as 20,000 to 25,000 years from now. These “glacial invasions” could occur for any number of reasons. The sun, often classified as a “variable star,” could brighten and dim like a strobe light in slow-motion. If we’re in the bright period now, the waning period could induce a frigid climate on earth. Or, adjustments in our atmosphere’s carbon dioxide levels could alter the climate dramatically, forcing mankind to gather in tropical areas for relative warmth. As the illustration at left shows, New York City probably wouldn’t survive the ice storms. Read the full story in “A New Ice Age May Bury Us”

Death of the Sun: March 1929

Earth isn’t the only thing that could grow cold with time. According to the theory of stellar evolution, our sun’s hydrogen core will eventually fizzle out, prompting the sun’s transformation into a red giant. The sun’s luminosity will increase by about 1000 to 10,000 times, while the outer layers of the sun will expand, meaning that the energy emitted from its core will spread over a much larger area, resulting in a cooler surface temperature. Naturally, such a change in the sun’s composition could spell disaster for life on Earth, but Professor Robert A. Millikan, famed American physicist and a Nobel Prize winner, proposed a more optimistic, albeit far-fetched solution: we could subsist on a second sun. Millikan explained to us that the universe continually repairs itself. When stars and planets die, atoms disintegrate in space, hurtling electrons into the cosmos. Eventually, the electrons find each other and recombine into hydrogen, oxygen, silicon and iron. Over billions of years, these tiny electron clusters will give birth to new suns, so eventually, some distant newborn star will provide our planet with solar energy even as our original sun disintegrates. Before that happens, Millikan surmised, man will have found a way to capture the energy of cosmic rays and to use solar energy, sustaining us even as the sun’s death upheaves our solar system. Read the full story in “When the Sun Grow Cold”

Solar Collision: October 1936

Here’s one more for the death by cosmic catastrophe camp. Eons ago, before our sun had planets orbiting around it, a wandering star passed by, nearly colliding with it. Using their respective tidal forces, the stars drew long, “flaming cigars of incandescent matter” from each other. The wandering star eventually withdrew, leaving the “flaming streamers” to form the planets in our solar system. Billions of years from now, another wandering star could venture toward our solar system, resulting in that same process. As the illustration shows, Earth would be caught between the two streamers, but not before Pluto, Neptune and Jupiter began to change their orbits. By that time, we’ll have noticed that something’s amiss — the poles would shift, and our atmosphere would heat up from the exposure to two suns. Our oceans would turn into steam, day and night would cease existence, and our planet would vaporize like a drop of water within a furnace. Read the full story in “How Will the World End?”

The End of Earth: September 1939

The end of the world might be a scary prospect, but it sure makes for good entertainment. In 1939, the Fels Planetarium of the Franklin Institute at Philadelphia but on a show depicting the number of ways we could go extinct. The sun could heat up, melting our Polar ice caps and causing the ocean to rise up and destroy coastal areas. An asteroid could land in our ocean, resulting in a megatsunami. Hell, it could land in a city, scorching everything around it, and initiating an era of mega-earthquakes and hurricanes. If the moon dipped toward the earth, the gravitational pull would draw up gigantic tides while rupturing our planet’s surface. As grim as these scenarios sound, we figured that by the time they happen, man will have ditched Earth for greener pastures. We have a few billion years to figure out the technology, anyhow. Read the full story in “How Will the World End?”

Doomsday Scenarios: November 1946

The same year the Fels Planetarium put on its show, New York’s Hayden Planetarium jumped aboard the Doomsday train by staging its own apocalyptic sky drama. After going on hiatus for the war in 1941, the “End of the World” show resumed in 1946 with enhanced special effects: twelve projectors with perforated housings gave audiences the impression of being inside a blizzard, while another light source would use six projectors to give the impression of a burning skyline The show covered five possible Doomsday scenarios: 1. The sun explodes, vaporizing the Earth. 2. The sun exhausts its energy, burns out, and ushers Earth into a new Ice Age. Snow piles to the top of the Empire State Building. 3. A rogue star flies into our sun, the whole solar system dies. 4. Although it is unlikely, a comet could crash into the Earth. 5. The Earth’s gravity could draw the moon closer, causing it to explode and bombard us with meteors. Read the full story in “Machines That ‘Destroy’ The Earth”

The Doomsday Device: April 1950

Human extinction won’t necessarily come about through a cosmic disaster — technology, ambition and greed might eventually lead to our demise. The advancement of weaponry during the mid-20th century made self-destruction completely possible, and during the Cold War, the United States and the Soviet Union continually teetered on the brink of a nuclear war. As the era of nuclear weapons unfolded, h-bombs became the primary technology in hypothetical doomsday machines. “Can an h-bomb destroy the world?” we asked. No, scientists said, it wouldn’t annihilate the planet with a single blast, but it would leave lasting consequences that would severely compromise our health. An H-bomb would leave a vast radioactive footprint. If around 40,000 casualties occurred through an A-bomb, imagine the devastation wreaked by an H-Bomb. The illustration at left shows the estimated number of supplies needed for just one victim of such disaster. Read the full story in “What is the H-Bomb?”

PopSci’s Guide to Fallout Shelters: December 1961

As the Cold War wore on, people became increasingly paranoid about the threat of nuclear fallout. The Doomsday Machine, which was supposed to be a computer rigged to a series of H-bombs, hadn’t been invented, but what harm could come from preparing for a nuclear holocaust? Naturally, the bomb shelter business started booming as people headed underground to stock up on supplies. Here’s what you needed to know about a shelter, back in 1961: First, don’t bemoan a public shelter, as a large group of people will likely include a doctor and trained nurses. At the same time, you’ll likely be in your own house when the bombs start raining down, so make sure you’re equipped for the disaster. If you’re in a car or outdoors, don’t despair — any cover is better than none. Hiding out in a hole beneath your car seems crude, but it provides 80 percent protection from fallout. Read the full story in “Plain Facts About Fallout Shelters”

Man’s Last Big Blast: September 1962

The title of this article, “Man’s Last Big Blast,” has an ominous ring to it, no? As information about the Doomsday Bombs began to leak out, we began worrying that nothing, not even the deepest underground fallout shelters, could protect us from the destruction of radioactive fallout. Unlike conventional weapons, Doomsday Bombs wouldn’t give either side an advantage. They’d kill everybody. Sure, you would kill yourself and your people by setting off a Doomsday weapon, but some leaders would rather have everyone die than allow their enemies to win. Herman Kahn, author of On Thermonuclear War, said that the blast would do three things: 1) Significantly alter the climate, 2) Burn everything, and 3) Eradicate all living things with radioactive poisoning. Rumor had it that there were a couple of different Doomsday machines in the works. Country-busters could eliminate whole nations or continents. If that doesn’t sound scary enough, these weapons weren’t even considered “true” Doomsday devices, which would not only eliminate large areas, but would start firestorms in the sky. A “conflagration” storm would travel with the wind, burning everything in its path. Yet another Doomsday machine would be detonated in the sea, resulting in enormous tidal waves capable of bringing down entire cities. We estimated that country-busters could be perfected in five years, and true Doomsday weapons, which could kill all of humanity with just the push of a button, could go into affect within a decade. Read the full story in “Man’s Last Big Blast”