21 Ways the World Could End

The biggest threats are often not what we think they are. The sheep spends its whole life fearing wolves only to be killed by the shepherd. With that in mind, here are some of the many things that could end the human race as we know it...

1. Our universe collides with another universe

Quantum theorists think it's possible that our universe is just one of many bubbles floating in a greater cosmos. What would happen if our universe collided with another? The answer: no one knows. It could be that one or both universes would be destroyed. So are we just one day away from destruction? Probably not. After all, the universe has survived this long.

2. Strong Artificial Intelligence

Within the next 100 years, it's possible, even likely, that the human race will be made obsolete by artificial intelligence. This hypothesized event is known as the The Singularity, so named because it is the point in time when the rate of change becomes so steep that it resembles a straight vertical line. Why would this happen? It's actually pretty simple. If humans are able to build a machine that is smarter than humans, then that machine would be able to build an even smarter machine, etc... Within a few years, a single computer will be able to surpass the collective intelligence of the entire human race.

Once this happens, there is no way to put the genie back in the bottle. Humanity will simply not have the resources to defeat a superintelligent computer, just like a human can't beat a computer in chess today. Confused? Read more about it. In any case, it seems possible that humans will be subordinated by computer intelligence within our lifetimes.

Perhaps our new masters will treat us kindly. Perhaps they won't. Perhaps they'll treat us like we treat ants: mostly ignoring them unless they become a nuisance. Or perhaps humans will merge with computers and become superintelligent ourselves. One thing's for certain: if we create superintelligent A.I., the future of the human race will change forever.

3. An asteroid or comet

This is becoming less and less of a global threat. We have done a very good job of tracking near-Earth objects above 1 km in size. And while smaller asteroids might slip through our sensors, they don't have the potential to cause planetary climate change if they collide with Earth. If you are spending time worrying about asteroid impacts, don't.

4. A high mass, extra-solar object

Worry about this instead! In 2017, astronomers first observed something that had never been seen before: an object passing near Earth which came from outside our solar system. This particular object was not large enough to be an existential threat, but it's possible that there are planets, asteroids, or other large objects hurtling through space on a collision path with Earth. For example, some people think that our current Solar System once had five gas giants instead of four with the fifth being ejected to who knows where. NASA has estimated that the Milky Way has trillions of these rogue planets. Perhaps one is hurtling towards Earth as we speak.

5. Nuclear weapons

Nuclear war is bad. Is it the end of the world? Probably not. We simply don't have the firepower to send the human race back to the stone age. At least that's the conclusion of some people who have criticized the flaws of the "nuclear winter" hypothesis popularized by Carl Sagan.

What percent of the population would die in a full nuclear exchange? I'm not sure. Probably at least 10% of the world's population. Possibly 90% or more. But it won't be 100%. Some countries would not be involved in the nuclear exchange at all and would survive relatively unscathed. As a species, we need more and bigger bombs to commit suicide. No doubt very smart people are working on it right now.

6. Grey goo

Nanobots are extremely small robots (trillions per cubic inch) that currently exist as a hypothetical state of future technology. What if someone made self-replicating nanobots? And what if those nanobots were poorly, or maliciously, programmed. Very bad things could happen. They could, much like locusts, convert any food source they encounter into more nanobots, thus turning the world, and everyone you love into "grey goo".

7. Alien attack

Science fiction author Liu Cixin has conceived of the universe as a "Dark Forest" where alien civilizations keep themselves hidden to avoid being attacked. Why do they do that? Because, just like two wild animals meeting in the jungle, two civilizations meeting in space have no way to communicate with or trust each other. Rather than risk being annihilated, it is safer to annihilate the other. Meanwhile humans, like complete morons, have loudly advertised our presence to the universe since the dawn of the radio age.

When the attack comes, it will not be like the movie Independence Day, with lumbering and easily hackable spaceships hovering over our major cities. Instead it will be in the form of a small object moving at relativistic speeds. An object the size of a baseball, moving at 99.99999999% the speed of light would be enough to destroy the entire planet. We would have no possible way to see it coming. One day, Earth would simply be vaporized and that would be the end.

8. Gamma-ray burst

Did you know that supernovas and stellar collisions can cause a Gamma-ray burst? It's possible, though extremely unlikely, that a gamma ray burst in the Milky Way, beamed directly at Earth, could cause a mass extinction event. Some people think that the Ordovician–Silurian extinction event of 450 million years ago was caused by a gamma ray burst.

9. Supervolcanoes

Supervolcanoes are to regular volcanoes as Superman is to a regular man. They are ridiculously more powerful. A typical supervolcano is 1000 times as powerful as the eruption of Mount St. Helens. The eruption of a supervolcano can change the climate of the world for decades.

So could the eruption of a supervolcano kill all humans? It almost did once. Some people theorize that the eruption of Lake Toba 70,000 years ago reduced humanity to a population of just 10,000 or so.

Fortunately for us, we've progressed a lot in the last 70,000 years. We can do a lot to cope with lower temperatures and sunlight. When the supervolcano under Yellowstone awakens from its slumber, Denver could be buried under a meter of ash. But most of the rest of us will bravely soldier on.

10. The simulation is turned off

What if it were possible to create a computer program that could simulate human consciousness? If that were possible, it would also be possible to create a program to simulate a billion people, or a trillion, a quadrillion, or more. With so many simulated humans out there, the odds are nearly 100% that you are just a simulation. And one day the owner of the simulation might get bored and turn it off.

11. A human-created virus

There's a good chance that Covid-19 escaped from a lab. But, with a survival rate above 99%, Covid is the least of concerns. What if someone were able to create a disease with the mortality rate of Ebola and the rate of spread of measles? It would be very, very bad.

But even that wouldn't be enough to end the human race. Viruses that kill their hosts don't tend to spread very well. They tend to mutate to less deadly forms to ensure their survival. It would probably require multiple simultaneous superviruses to finish us off.

If AI does decide to end the human race, there is a good chance that this is how they will do it. Killer robots are expensive, but engineering a super-virus could be done quite cheaply.

12. Accidentally creating a black hole

I'm not really qualified to comment on this, but I'm going to say that it's not out of the realm of possibility that a high energy physics experiment leads to an unexpected consequence which destroys the world.

13. Climate change

You personally are not going to die from climate change. People vastly overestimate the short-term effects of climate change. By the year 2100, sea levels will have only risen by a couple feet. But the long term effects of climate change could be devastating. It's possible that, over thousands of years, we trigger a runaway greenhouse effect which makes the planet completely uninhabitable.

But even this seems extremely unlikely. The Earth has been much hotter than it is today. 400 million years ago, CO2 levels in the atmosphere were five times what they are today. Climate change is going to cause the extinction of many species. Humans probably won't be one of them.

14. A sexless future

Did you know that fertility rates in the developed world are far below the rate of replacement? Already, several countries have fertility rates near 1 child per woman. This means that each generation will be less than half as big as the one before it. What if the human race ceases to exist because of lack of interest?

I think this is also fairly unlikely. People who don't want children will become extinct. Other people will thrive. The population of Amish, Mormons, Hasidic Jews, and many other traditional religions is growing quickly. There is a Hasidic community in New York state where the average age is just 13 years old, due to an insanely high birth rate. At current rates, religious extremists will form a majority of the world population within a couple centuries.

15. The sun becomes a red giant

In about 5 billion years, the sun will grow into a red giant. It will become so large that it will completely absorb Mercury, Venus, and possibly even Earth.

But it won't take 5 billion years to kill off the human race. The sun is continuously getting brighter. It is estimated that within 1.1 billion years the sun will get so much brighter that the Earth is no longer habitable.

16. Global... cooling?

The Snowball Earth theory suggests that, at least two times in Earth's history, the entire surface of the globe was covered with ice. It's possible that, in the extremely long term, the Earth once again reverts to a total ice age which makes every continent uninhabitable. Unless global warming kills us first...

17. A totalitarian future

For much of history, China had the largest economy and the highest level of technology in the entire world. So why, beginning around 1500 AD, did China stagnate while European civilization grew to eventually dominate the globe?

Some people think China was stymied by central control. In the crucial years between 1500–1900, Europe was a loose patchwork of warring civilizations while China was mostly united under a single emperor. Throughout Chinese history, the central bureaucracy imposed high levels of control, at times burning books, preventing technological innovation, and shutting down the exploration of the seas. Europeans did the same things too, of course. But since no one power exerted too much influence, there was always room for maneuver. Christopher Columbus, for example, was rejected by many royal courts before convincing Spain to fund his voyages.

Today, central governments exert more power than ever. China, once again, takes the lead. Their Social Credit System seeks to score every aspect of a person's life in terms of obedience to the central authority. Lest we feel too smug, freedom in western countries is on the wane as well.

One day, China (or another country) may control the entire world. The entire globe might be stuck in a trap where few are happy, but no one can challenge the central authority. And while this wouldn't be the literal end of humanity, it would mean the death of joy, beauty, and self-determination. We might as well be extinct.

18. Heat death of the universe

The Second Law of Thermodynamics says that entropy always increases. Eventually the stars will die and there will be no source of energy to power a civilization. Even black holes will eventually evaporate due to Hawking radiation.

Perhaps humans will leave Earth and colonize the stars, founding an intergalatic civilization that lasts for trillions of trillions of years. Even so, nothing lasts forever. Eventually, after 10¹⁰⁶ years, even the largest black holes will disappear, leaving the universe a mostly featureless void.

19. A Miyake Event

The Carrington Event was an intense solar storm that happened in 1859. In addition to producing beautiful auroras, aka "northern lights", it took out telegraph systems throughout the world. If it were to happen today, it could disable satellites and power stations. People would die. JetPunk would probably go down.

What's interesting is that the Carrington Event was nothing compared to a Miyake Event a sudden burst of cosmic energy which happens every few thousand years. A Miyake Event would have a good chance of plunging the Earth into a pre-industrial society overnight, toppling power stations worldwide.

Would it be the end of the world? Probably not. Humans can adapt to nearly anything. But if electricity were out for weeks or months, the chaos and death could be horrific.

20. A Doomsday Device

There is no limit to human imagination, and it's possible that one day a government might develop a weapon so powerful it could end life on Earth as we know it.

One example of a potential doomsday weapon is a Cobalt bomb, a nuclear weapon surrounded with ordinary cobalt metal. When it explodes, it would create a radioactive isotope of cobalt that has a half life of about 5 years, much longer than typical nuclear fallout. This could make the affected area uninhabitable for decades.

21. Not with a bang, but with a whimper

Thomas Malthus was an English philosopher who observed that the population grows to meet any growth in the production in food, meaning humans will always be hungry.

Ironically, he made this observation at the cusp of the Industrial Revolution, the start of a period when human prosperity began to grow faster than ever before. Today, the world produces far more food than we can possibly consume. Does this prove Malthus wrong? I don't think so. Like many great thinkers, he wasn't wrong, just early.

The human race gained a temporary reprieve due to the extraordinary gains in productivity that happened after the Industrial Revolution. Today, productivity growth is slowing. Eventually, it will stop and reverse. We will return to the situation which governed humanity through most of its history: a perpetual shortage of food and resources. Over thousands of years, we will exhaust the world's supply of metals, fossil fuels, nitrates, and other substances necessary for human civilization. The population will fall. Ten thousand years from today, all that remains will be small bands of hunter gatherers, completely ignorant of the vast and grand societies which preceded them. And then, something else will happen, and we will be gone.