Because of what can humanity die? Let's put aside man-made options, such as nuclear war and free laboratory viruses, and consider only the causes of natural origin.
Threat # 1: solar storms
The strongest coronal mass ejection in recent history occurred in 1989. A burnt-out transformer in New Jersey left 6 million people in the Canadian province of Quebec without electricity.
The release, known as the 1859 geomagnetic storm or Carrington event, was 10 times more intense. Then the telegraph cables burst out, causing fires and injuries to operators. Polar lights danced even in Cuba.
Some researchers fear that another event like Carrington's storm will destroy hundreds or thousands of transformers, plunging entire continents into darkness for weeks, months, perhaps even years. And this event can happen during our life with you. The study suggests that storms like the Carrington event occur every few centuries. The latest study found a 12 percent chance of such a storm happening in the next decade.
Threat # 2: Strike from Space
From the impact of a large asteroid or comet, the Earth could suffer even more damage. The only way for humanity to defend itself is to prevent a collision.
It is likely that an asteroid 10 kilometers in diameter killed the dinosaurs. But humanity can die from the impact of a much smaller body. The place of collision of an extraterrestrial object with the Earth will be completely destroyed. Huge earthquakes and tsunamis will spread throughout the planet. But the most devastating will be the residual consequences. Models suggest that depending on the speed and angle of impact, an object one kilometer in diameter will eject enough crushed rock to block the Sun for months. To the veil will be added soot from forest fires, which will flare up due to the red-hot debris of the asteroid, scattered from the place of impact.
Fortunately, asteroids of this size hit the Earth only once every few million years, and such as the "dinosaur killer" - once every 100 million years. The chances of dying from an asteroid impact for an ordinary person are slightly higher than the chances of dying in the mouth of a shark.
Astronomers have noticed 15 thousand objects in the vicinity of the Earth, including hundreds of asteroids more than a kilometer in diameter.
Threat # 3: supervolcanoes
The most ruthless threat to our modern civilization is not in space, but on the surface of the planet. Super-eruptions happen much more often than strong cosmic strikes. Approximately every 100 thousand years, somewhere on Earth, a caldera up to 50 kilometers in diameter collapses and begins to violently eject flows of magma. The supervolcano cannot be stopped, and its destructive forces are cruel. One such monster, the Toba volcano in Indonesia, wiped nearly everyone off the face of the earth 74,000 years ago, causing a bottleneck effect still visible in our DNA.
The most far-reaching consequence will be the impact of the supervolcano on the global climate. Sulfate aerosols "injected" into the stratosphere by a super-eruption can lower the temperature on the Earth by 5-10 degrees Celsius for decades, which will suffer agriculture.
Threat # 4: hunger
Space strikes and super-eruptions can cause plants to not bear fruit or grow at all. But two scientists have already sketched a plan to save the world from hunger. In their book Feed Everyone, No matter how, David Denkenberger and Joshua Pearce proposed several ways to feed billions of people without the help of the sun: people can grow mushrooms on deciduous debris and tree trunks felled during a disaster. Either cultivate methane-digesting bacteria on a natural gas diet, or convert cellulose in plant biomass into sugar.