Suspension of Disbelief: 6 Real Doomsday Scenarios Humanity Will Face

Science fiction has a plethora of ideas about what happened in the past and what to expect from the future. Unfortunately, not all of those ideas are exactly plausible in reality. In Suspension of Disbelief, we’ll take a look at the best ideas from sci-fi movies, books, comics and videogames to see where (and if) they intersect with the real world.

Humans love to think about a world in which we no longer exist. Whether we’re blowing ourselves up, being eaten by reanimated corpses, succumbing to rampant plagues, or whatever else, we love to imagine how all of society might be wiped out. Post-apocalyptic fiction is easily one of the most popular genres in science-fiction because it forces us to comprehend a world in which life as we know it is obliterated in one fell swoop.

Maybe through reckoning with the apocalypse we find some sort of catharsis with just how fragile we are on our pale blue dot. Though they’re about humanity in its most dire times, apocalyptic and post-apocalyptic fiction are almost always about the ways that we face the end times head-on, either changing our fates through bravery, ingenuity, and sacrifice, or marching on with our lives even though there seems to be no reason left to.

Unfortunately, the harsh reality of science says that eventually humanity will face multiple apocalypses until our chances of survival has reached zero. Click through the gallery to see the real ways humanity could be (and maybe will be) wiped out.

Hailing from upstate New York, Cameron Wade is a freelance writer interested in movies, videogames, comic books and more. You can find his work at protogeektheblog.wordpress.com.

1 of 6 Nuclear war Perhaps the most widely used fictional device for destroying the world is a nuclear war. There are 14,900 nuclear warheads in the world currently, with Russia and the U.S. splitting 13,800 of those just about evenly. If all of those nuclear bombs were detonated, civilization as we know it would be changed forever. Firstly, hundreds of major cities around the world would be obliterated, causing hundreds of millions of deaths. For millions of miles around those blast areas, people would suffer from third-degree burns. Radiation sickness would be rampant, killing hundreds of thousands more people and leaving many more far outside the blast radius with shortened lifespans. Even a regional nuclear war could create gigantic amounts of debris, ash and smoke, which could end up rising into the stratosphere and blocking out part of the Sun's light and heat. A nuclear winter would be devastating, possibly making agricultural production impossible for much of the world for years and maybe even decades. A large enough bomb detonated 300 miles above the U.S. could send out an electromagnetic pulse and wipe out every electric grid and electronic device in the country. All that said, some parts of the Earth could remain habitable in the event of a nuclear winter, but the likely collapse of society would make other existential threats more likely to destroy our species. Image via Keystone/Stringer

2 of 6 Global pandemic In 1918, at the height of World War I, an outbreak of influenza spread around the world infecting 500 million people – one-third of the total population – and killing an estimated 50 to 100 million people. Roughly five percent of the world's population died in a year, more people than were killed by the Black Death in a century. Apart from the occasional news sensation like the Zika virus or Ebola, we don't often think about our vulnerability to infectious diseases, but there are a few factors that make a global pandemic a genuine possibility. Firstly, there's the difficulty of effectively quarantining infected people in an increasingly global society. The Spanish flu outbreak of 1918 was so widespread partly due to the massive amount of people who were traveling between countries due to World War I. Today, traveling long distances to different countries and continents is relatively common and easy. This ease of travel could help a highly infectious disease spread around the globe before it can be detected and quarantined. Secondly, there's the rise of bacteria, viruses, and other microbes that have become resistant to medication that were once used to effectively treat them. Due to the long-term improper prescription and use of drugs like antibiotics, we have been essentially killing off weak microbes and allowing the stronger, more resistant ones to survive. If a disease that we can't properly quarantine and can't properly treat arises, it could become a global catastrophe with little recourse for us to stop it. Image via Slate.com

3 of 6 Asteroid impact Sixty-six million years ago, an asteroid 6-miles wide collided with the Earth, killing three-quarters of all animal species on the planet, including dinosaurs. It seems like something that could never happen again, but asteroids can hit Earth without warning. In February of 2013, an asteroid just 65-feet wide exploded 18 miles above Chelyabinsk, Russia, shattering windows, collapsing some rooftops, and giving off enough heat that it could be felt by people on the ground (pictured is the trail it left in the sky). Over 1,000 people were injured from that asteroid and it didn't even reach the ground. Depending on where it landed, a large enough asteroid, comet, planetoid or any other object could send up enough debris to block out the Sun and change Earth's climate, create massive tsunamis that would wipe out hundreds of miles of coasts, produce firestorms, generate destructive winds, and cause earthquakes, and that's all without mentioning the force of the impact being equivalent to millions of nuclear bombs going off at the same time. Right now, no country on Earth has a spacecraft ready to deflect or destroy an incoming asteroid, and to make one would take roughly five years between deciding on what method to take, designing it, building it, and launching it. Some proposed deterrent plans include using nuclear bombs to vaporize or push an asteroid off its course, ramming it with a heavy spaceship, or positioning a ship next to the asteroid and using gravity to slowly pull the asteroid toward a different trajectory over several years. It's believed that we know of more than 90 percent of major asteroids half a mile wide or more in the Solar System, but there are still dozens of smaller ones that pass by Earth each year completely unnoticed. Considering humanity's population, diversity, and adaptability, it would probably take an asteroid much larger than the one that killed the dinosaurs to make us go extinct, but if we want to avoid that and any relatively minor impact catastrophes, we should probably start working on our defense plan now. Photo by M. Ahmetvaleev

4 of 6 Gamma-ray bursts Gamma-ray bursts are massive explosions caused by two neutron stars colliding or when a high-mass star goes supernova and collapses into a black hole. In both cases, energy and radiation are expelled in two equal and opposite directions. They're the brightest, most energetic electromagnetic phenomenon in the universe, giving off enough light to be seen billions of light years away and more energy in seconds than the Sun will during its entire 10-billion year lifetime. Because they only occur in very specific circumstances, gamma-ray bursts are incredibly rare, with only a few happening in each galaxy every million years. None have ever been observed in the Milky Way galaxy and that's probably for the best. If a gamma-ray burst did hit the Earth, it would hit half the planet's surface with the energy of a couple hundred nuclear bombs (though without the fireball). On top of that, the burst would destroy large sections of the ozone layer, allowing in enough ultraviolet radiation to be lethal for animals that can't shield themselves from it. Our electrical grids would likely be fried as well causing mass panic the world over. It would also create a smog of nitrogen dioxide effectively shutting down flora's ability to photosynthesize and creating a winter that could last years. Thankfully for us, the chances of a gamma-ray burst hitting Earth in any of our lifetimes is functionally none as only a handful have ever hit Earth during its entire life. Image via CXC/M. Weiss/NASA

5 of 6 The Sun Assuming humanity survives the first four entries on this list, there are a few other extinction possibilities that are impossible to avoid. As the Sun turns hydrogen into helium via nuclear fusion, it gets ever so slightly brighter and warmer. In one billion years, the Sun will be 10% brighter than it is now. That extra heat will be enough to start boiling the Earth's oceans. It'll be near impossible for any species to survive as the Earth's evaporated water acts as a greenhouse gas and traps even more of the Sun's heat in the atmosphere. Eventually, the evaporated water will break apart and dissipate into space, leaving behind the scorched remnants of the Earth. Over the next four billion years, the Sun will finish burning the last of its hydrogen growing larger and gradually consuming Mercury, Venus, and finally, the Earth itself. Even if humanity manages to find a way to overcome the deadly heat of the Sun, there is no getting around the Sun's plasma enveloping the planet. The only way for humanity to survive that is to leave Earth behind permanently. Image via io9.com

6 of 6 The heat death of the universe So, humanity has developed interstellar travel and left our solar system, hopping from new star to new star whenever our current one is about to melt our planet. Unfortunately, doing won't keep us alive forever. The universe is expanding, gradually filling the distances between objects with more space. Though relatively slow on a human timescale, this process is accelerating celestial bodies away from one another. For the next hundred trillion years or so, new stars will still be forming across the universe, but eventually the amount of gas and particles needed to ignite a new star will be too distant to begin nuclear fusion. After the last stars burn out a few billion years from then, the only things left will be black holes, which also have a limited, if enormous, lifespan. By emitting radiation, black holes eventually disappear, some taking as long as a googol years (that's a 1 with 100 zeroes next to it). At that point, the average temperature across the universe will have almost reached 0 Kelvin, the lowest temperature physically possible, and the space between objects will be so massive that the chance of any particles hitting each other would be functionally zero. The universe will be in such a low energy state with such incomprehensibly vast distances between particles that it will be impossible for any physical processes to reverse its decline into, essentially, nothingness. No matter the ships we build and the distant places humanity travels, there's no avoiding that at the end of all things, the universe itself will die.