Are we in danger of being erased from the universe? Here we look at the factors that could doom humanity: natural disasters, human-triggered cataclysms, willful self-destruction, and greater forces directed against us.
We’ve had a good run of it. In the 500,000 years Homo sapiens has roamed the land we’ve built cities, created complex languages, and sent robotic scouts to other planets. It’s difficult to imagine it all coming to an end. Yet 99 percent of all species that ever lived have gone extinct, including every one of our hominid ancestors. In 1983, British cosmologist Brandon Carter framed the “Doomsday argument,” a statistical way to judge when we might join them. If humans were to survive a long time and spread through the galaxy, then the total number of people who will ever live might number in the trillions. By pure odds, it’s unlikely that we would be among the very first hundredth of a percent of all those people. Or turn the argument around: How likely is it that this generation will be the one unlucky one? Something like one fifth of all the people who have ever lived are alive today. The odds of being one of the people to witness doomsday are highest when there is the largest number of witnesses around—so now is not such an improbable time.
1. Global warming
The mother of all apocalyptic fears, climate change is the biggest threat facing the planet, many scientists say. Climate change could make extreme weather more severe, increase droughts in some areas, change the distribution of animals and diseases across the globe, and cause low-lying areas of the planet to be submerged in the wake of rising sea levels. The cascade of changes could lead to political instability, severe drought, famine, ecosystem collapse and other changes that make Earth a decidedly inhospitable place to live.
It’s the mainstay of disaster movies, but scientists are legitimately worried that a space rock could wipe out Earth. A meteor impact probably doomed the dinosaurs, and in the Tunguska event, a massive meteoroid damaged about 770 square miles (2,000 square kilometers) of the Siberian forest in 1908. Even more frightening, perhaps, is that astronomers only know about a fraction of the space rocks lurking in the solar system.
3. Nuclear war
Many scientists are still worried about the classic end-of-the-world threat: global nuclear war. Beyond North Korean leader Kim Jong Un’s saber rattling and Iran’s secretive nuclear efforts, massive stockpiles of nuclear weapons around the globe could wreak destruction if they were to get into the wrong hands. Last year, the Bulletin of the Atomic Scientists, a nontechnical magazine on global security founded in 1945 by former Manhattan project physicists, moved the Doomsday Clock, at five minutes to midnight. The Doomsday Clock shows how close humanity is to destruction via nuclear or biological weapons or global climate change.
4. Robot ascension
“The Terminator” may be science fiction, but killing machines are not far from reality. The United Nations recently called for a ban on killer robots — presumably because experts worried that several countries were developing them.
Many computer scientists think the singularity, the point at which artificial intelligence overtakes human intelligence, is near. Whether those robots will be benevolent helpers or the scourge of humanity is still up for debate. But a lot can go wrong when there are hyperintelligent robots armed with lethal weapons running around.
The fear of an overpopulated globe has been around since the 18th century, when Thomas Malthus predicted that population growth would cause mass starvation and overtax the planet. With the global population at 7 billion and counting, many conservationists think population growth is one of the key threats to the planet. Of course, not everyone agrees: Many think population growth will stabilize in the next 50 years, and that humanity will innovate its way out of the negative consequences of the overcrowding that does occur.
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