Humanity is doomed. Don’t take it personally, though; everything is ultimately doomed. Just as each individual organism must meet its end and the entire universe appears to be heading towards its own “big freeze” death, Homo sapiens will one day cease to be. The end of days has long been prophesised – by everyone from scientists to religious fanatics and apocalyptic fiction writers – but regardless of the mechanism: it is an inevitability. Although the huge human population makes any complete extinction of the species relatively unlikely in the immediate future, given enough time a terrifying array of possibilities exist. Here are fourteen of the most likely.
This is one of the favoured doomsday scenarios in fiction, but the possibility of it actually occurring is extremely slim. The reasons are numerous, but the most pressing is that any virus is likely to have biological similarities to ones we’ve already encountered, which means some people would inevitably be immune. With the massive population, the number of people that would be statistically immune would be more than sufficient to continue the race. However, if a pathogen lived in an unlikely place (like near deep-sea vents) and proliferated, before being spread around the planet quickly by a natural disaster, it is a possibility. Similarly, the chance of extra-terrestrial diseases being transported to Earth and wreaking havoc cannot be written off.
13: Orbital billiards
A study from 2008 in the Astrophysical Journal looked at the probable gravitational effects of Jupiter (the biggest body in the solar system aside from the Sun) on Mercury’s already elliptical orbit. This could result in the planet crashing into the Sun, but there is also a possibility that it could be thrown out into the solar system, interacting with planets on the way. This could result in anything from Mars being ejected from the solar system (with the gravitational effect acting like a cosmic nightclub bouncer) to Mercury smashing directly into the Earth. It’s very unlikely (around a 1 percent chance in the next five billion years), but a devastating possibility.
12: Rogue black hole
Black holes are what happens when too much stuff hangs out together. It starts to pull in everything – even light – and accumulate more and more mass. Super-massive black holes sit (relatively) peacefully at the centre of galaxies, but they aren’t all so nicely positioned. Some black holes – called “rogue” black holes – are thought to wander through space. Although the closest one would probably be thousands of light years away, in the future it’s entirely possible that one will pass by and engulf huge chunks of our solar system.
Related: The Hubble Telescope: Images in time
11: Alien invasion
This seems like the realms of science fiction, but alien life is actually a probability, not a mere possibility. An astrophysicist named Francis Drake famously created an equation to estimate the number of extra-terrestrial civilisations in our galaxy, with the result being anywhere from 1,000 to 100 million. This is nothing more than an intelligent (yet still flawed) guess, of course, but it does mean that the sci-fi scenario is entirely possible. Stephen Hawking suggests using the model of human colonisation to determine what would happen if aliens did visit, and unfortunately, the picture isn’t a pleasant one. Ask the Native Americans.
Related: The most credible UFO encounters
10: Diatom pollution
According to Joe Kirschvink, a geobiologist at Caltech, a species of miniscule algae could cause human extinction. 2.35 billion years ago, cyanobacteria mutated and started to photosynthesize. This “polluted” the atmosphere with oxygen, killing off many species which evolved to thrive in the carbon dioxide-heavy atmosphere of the time. They were poisoned by the oxygen. If modern diatoms evolved to subsist on salt instead of water, they would flood the planet with chlorine gas in the same way – potentially wiping out all humans.
Super-volcano eruptions are favoured by doomsday-nuts as an apocalypse scenario, but many of their fears are unfounded. Geological timescales far outstrip human ones, and as a result it’s unlikely that one will occur in the near future. However, it’s virtually impossible to say when one will strike – despite claims of volcanoes erupting at regular intervals, they basically erupt when they erupt, not like clockwork. A volcano eruption may have caused the largest mass extinction on record 250 million years ago, by unleashing gases and ash into the atmosphere and causing the food chain to collapse. The same could well happen again, whether from Yellowstone or elsewhere.
Related: History's worst natural disasters
8: Gamma ray bursts
Gamma ray bursts happen every single day. They’re thought to result from massive stars reaching the end of their lifespan collapsing into black holes and releasing gargantuan jets of energy in the process. They’re the most powerful cosmic explosions since the big bang. From the point of view of the Earth, it’s like the universe has gotten drunk on moonshine and started firing an astronomical scale energy weapon wildly in all directions. If one of the gamma ray bursts hits us, it could disrupt photosynthesis and ultimately lead to mass extinction. Currently, the star WR 104 looks like a contender for creating a gamma ray burst, and it could well be pointing for the Earth. However, astronomical timescales mean that it could happen now or up to (and possibly beyond) half a million years from now.
7: Machine super-intelligence
The world could become an all-to-real homage to the Terminator in the distant future, according to Dr. Bostrom of the Future of Humanity Institute at Oxford University. He raises the concerns which have been echoed throughout sci-fi history – the unemotional, hyper-intelligent machines may go to any lengths to fulfil their programming, and would arguably be indifferent to human life. This is mere philosophical speculation, but as technology advances it seems destined to become a very real problem.
Related: Video on how to build a toy robot
6: Dark matter clumps
Dark matter is thought to make up around 20 percent of the universe, but it has eluded both observation and explanation. However, since its gravitational effect can be detected, it’s possible that some stray dark matter could pass through our solar system and cause comets and asteroids to be flung off course and bombard the Earth. Gould’s Belt of stars may have been created by passing dark matter, and the potential effects if some came near the Earth are hard to predict with current scientific understanding.
Related: 6 Candidates for dark matter
5: Biological warfare
One of the primary concerns raised by the Future of Humanity Institute at Oxford University is biological warfare. Our growing ability to manipulate genetic structures means that although natural diseases don’t have much chance of wiping out the species, we could create something that does. One example is the variant of the H5N1 virus which was created by American and Dutch scientists. The mutation made the disease airborne, vastly increasing the potential for mass infection. Although some humans would still be immune, “designer” pathogens like this could also wreak havoc on other animals and potentially cause a collapse in the food chain.
Related: How to survive a zombie outbreak
4: Nuclear winter
Nuclear weapons aren’t cool, but if world leaders ever decide to play with them some people would inevitably survive the blast. The aftermath is another story, which would in no way be as much fun as the Fallout games. The masses of dust, smoke and radioactive particles unleashed into the stratosphere after a series of nuclear blasts could literally block out the Sun. Weather cycles occur in the troposphere (much lower), so the problem would last for several years, basically creating a permanent winter. With no crops growing on the planet (and radioactive particles raining down on us), humanity wouldn’t last much longer.
This is classic doomsday scenario that has happened before. If an asteroid around 10 km (6.2 miles) in diameter struck the planet, it could easily cause a mass extinction and send humanity the way of the dinosaurs. The big “near Earth objects” are being studied and tracked, of course, and there isn’t too much to worry about in the near future. The odds of one in 250,000 for 99942 Apophis hitting the Earth in 2036 aren’t very scary, but there’s a one in 1,000 chance of a big strike in 2182. We can’t run these odds forever.
2: The Sun
In around five billion years, the Sun will run out of hydrogen fuel and start to swell into a red giant. As it loses mass and gains size, Mercury and Venus are virtually certain to be engulfed. The Earth is in less certain peril, but still will probably meet the same fate. Only one exo-planet has been observed to survive its star’s red giant phase at a similar distance, and the resulting surface temperature was around 200 °C. Either way, five billion years looks like the maximum remaining lifespan of the human race, unless we colonise a suitable planet around a mid-phase star before then.
Related: About nuclear fusion in stars
1: The “unknown unknowns”
We do not know everything. This might seem like a null point, but it’s far from it. There is a strong possibility that we’re currently blissfully unaware of the thing that will eventually wipe out the human race. Any speculation about the future is ultimately not known, but we can’t even indulge in logical guess-work about a risk if we don’t know what it is. Our lack of knowledge won’t kill us, but the things we lack knowledge of genuinely could.
- Discovery: 20 ways the world might end
- ABC News: Forget the Mayans. Here are 5 actual apocalyptic possibilities.
- Wired: Scientific doomsday: Ways the world could actually end
- Discover Magazine: 30 ways the world could end
- Physics World: Earth could survive a red giant Sun
- Mental Floss: 5 pop culture apocalypse scenarios and how they might happen
- NASA: FAQs about NEO impacts
- University of Oxford: Studying the possible causes of human extinction
- BBC: How are humans going to become extinct?
- Existential Risk: FAQ