by Bryan Walsh
The Oxford moral philosopher Derek Parfit proposed a thought experiment. Imagine three possible futures. In the first, there is peace. In the second, there is a nuclear war that kills 99 percent of the world’s population, leaving a sliver of survivors to carry on. In the third, a nuclear war kills 100 percent of the world’s population—every man, woman, and child, resulting in the total eradication of the human race. It doesn’t take an Oxford PhD to conclude that the first future is the best of the three, or that the third one—the extinction scenario—is the worst. And most people would instinctively conclude that the difference between peace and a nuclear holocaust that killed all but 1 percent of the world is much greater than the difference between the death of 99 percent of the global population and the death of 100 percent. Certainly that’s what the raw numbers would say. But Parfit disagreed, writing the following in his 1984 book Reasons and Persons: “Civilization began only a few thousand years ago. If we do not destroy mankind, these few thousand years may be only a tiny fraction of the whole of civilized human history. The difference between [possibilities] 2 and 3 may thus be the difference between this tiny fraction and all of the rest of history.”18
Extinction, as the environmental slogan goes, is forever.19 The true horror of the end of the world is measured not by our own deaths, and the deaths of everyone we know and love, not just by the deaths of our children and grandchildren, but by the nullification of all who would come after them, all those who would live and love and carry this species forward. An existential risk realized is the death of the future.
Basic morality calls us to do what we can to save a single life. If the world were in immediate existential peril—if, for example, a very large asteroid were bearing down on Earth—we would do whatever we could, spend whatever we had, to try to save the billions of people who live here. By that same token, shouldn’t we be even more motivated, even more desperate, to protect the future generations who would take their turn on Earth—provided we don’t destroy it all now, or let it be destroyed by inaction? If we include the future—all of the future—the stakes of what we do or don’t do in the present moment become unimaginably enormous. We could have thousands, tens of thousands, even millions of years of civilization ahead of us, but that future depends on those of us alive in the present moment.
That is what I feel now when I look at that photograph of my new family. It is the past and future made tangible in a single moment. I think of the endless chain of events that had to fall into place in the past to make my son a reality. And I think of the events that are unfolding even now to bring the entire human future into being. That chain could have ended at any time, cut short by disease or catastrophe or simple bad luck. And until very recently, if that end had come—if this species had gone extinct like so many others—there would have been little we could have done about it. Our ancestors couldn’t deflect an asteroid, or invent a vaccine to cure a killer disease. But we can. This could be the end of our times—or just the beginning. The choice and the responsibility are ours.
In the pages to come, I’ll offer a tour of existential risk, and plot a path to survival. I’ll survey the threat of asteroids and comets from space, and hunt with astronomers for the near-Earth objects that could extinguish our future on this planet. I’ll explore the underappreciated danger from the supervolcanoes that have disrupted life on this planet over and over again, including one that sits beneath America’s first national park. I’ll travel to the birthplace of man-made existential risk—Trinity Site in New Mexico, where a terrible beauty was born. I’ll tell the inside story of the climate change conferences that have failed to stop the frightening pace of global warming, and ask just what the present owes to the future. I’ll share what it was like to live through the first global disease outbreak of the twenty-first century, and why a simple virus can wreak havoc on an interconnected world. I’ll stand looking over the shoulders of the scientists remaking life with synthetic biology, and I’ll ask whether the rise of superintelligent artificial intelligence (AI) is something to be welcomed, feared, or merely disbelieved. I’ll search for extraterrestrial civilizations, and scour the so far silent cosmos for any clues it might offer for our own fate. And I’ll explain how our species can survive the unsurvivable, should existential catastrophe finally arrive.
Make no mistake—we are in mortal danger. But the existential risks that follow in these pages have called forth dedicated scientists and experts who are doing their part and more to defend our future from the end times. New organizations have been created to study existential threats across disciplines: the Future of Humanity Institute at the University of Oxford, the Centre for the Study of Existential Risk at the University of Cambridge, the Future of Life Institute in Boston. Combatting existential risk isn’t just a matter of devising asteroid deflectors or ensuring our future robot overlords are peaceful. It demands a new kind of scientific method, a willingness to grapple with planetary uncertainties and cosmic numbers. Original thinkers like Nick Bostrom, Anders Sandberg, Milan Ćirković, Olle Häggström, and others have shed fresh light on the ultimate fate of human beings, a subject that, despite its obvious importance, has been less studied than the life of the humble dung beetle.20 Their work inspired this book, and I will return to it again and again through these pages.
To save ourselves we need to think about the unthinkable, and not merely understand the future but feel its gravity. Our greatest existential challenge isn’t technical or political, but conceptual. We have to believe that the end of the world can happen, and at the same time we have to believe that we can do something about it. But our track record is poor.
The Bulletin of the Atomic Scientists is an academic journal founded after World War II by some of the same people who helped develop the atomic bomb. In 1947 the artist Martyl Langsdorf was tasked with creating a cover for its first issue, and she channeled her dread of the new weapon into what would become one of the most iconic symbols of the Cold War: the Doomsday Clock, its hands inching toward midnight.
From 1947 on, the people behind the Bulletin have shifted the hands of the Doomsday Clock to represent, crudely but effectively, just how close our end times might be. In 1949 it was moved to three minutes to midnight in response to the Soviet Union’s first successful test of an atomic bomb, which kick-started the nuclear arms race. After Washington and Moscow signed the 1963 Partial Test Ban Treaty, putting an end to aboveground nuclear bomb tests, the hands were moved back to twelve minutes to midnight. And while the first decades of the Doomsday Clock focused exclusively on the threat of a nuclear holocaust, the clock continued to keep time after the Cold War ended, broadening out to include new dangers from climate change and emerging technologies. The Doomsday Clock is the closest thing we have to a thermometer of existential risk.
Each fall, the science and security board of the Bulletin—a group of top-level scientists and defense experts—meet and ask themselves two questions: Is humankind safer or at greater risk this year than the last? And is humankind safer or at greater risk this year relative to the entire history of the clock? It’s an imprecise symbol—existential risk isn’t divided up into neat sixty-minute intervals—but a grimly effective one nonetheless. It’s why one of the first trips I took for my reporting for End Times was to Washington, D.C., on January 25, 2018, to witness the Bulletin reveal the new time for the Doomsday Clock at the National Press Club. They did not disappoint. “We have come to a grim assessment,” Rachel Bronson, the president and CEO of the Bulletin, announced to the world. “As of today, it is two minutes to midnight.”
Only in 1953, after a year in which both the United States and the Soviet Union exploded their first hydrogen bombs—weapons of mass destruction far more powerful than the atomic bombs dropped on Hiroshima and Nagasaki—had the clock been this close to striking midnight. The construction of the Berlin Wall, the Cuban Missile Crisis, the Vietnam War—none posed as great a threat to the further existence of the human race as the events of 2017
, at least according to the hands of the Doomsday Clock. The Bulletin experts cited an array of factors: North Korea’s atomic breakout, uncertainty over the future of the Iranian nuclear deal, a planned U.S. withdrawal from the Paris climate agreement, the spread of cyberhacking, and of course, an unpredictable President Donald Trump. But what mattered more than the reasons behind the clock’s move—all debatable—was the time itself, and how little might remain for us. “These are dangerous, dangerous times,” Bronson told me after the announcement. “This is not your father’s Cold War.”
In the movie version of this story, Bronson and her Bulletin colleagues would have been delivering their alarm to an overflowing crowd of journalists in the nation’s capital. Cable news shows would have interrupted their regular programming to cover the announcement live, and print newspapers would have broken out their wartime headline font. The Doomsday Clock is about nothing less than the fate of the entire human race, all seven and a half billion of us, and all those who might come after. There should be nothing more important.
Yet only a handful of journalists were with me in the audience that January morning in the National Press Club’s First Amendment Lounge, asking only a handful of desultory follow-up questions. The Doomsday Clock would not go unmentioned by the media—fear makes for good press—but most outlets would treat it as one more data point in a world going madder by the day, to be overtaken almost immediately by the next story, the next scandal.
As I walked out of the National Press Club that morning, I could witness the forgetting already unfolding on cable news playing in the building’s lobby. The breaking stories were about how Trump would perform at the upcoming World Economic Forum summit in Davos, Switzerland, how global demand for iPhones was slowing down, how the midterm elections were shaping up. On one screen ninety-four-year-old Henry Kissinger, a ghost from an earlier doomsday, croaked his testimony to the Senate Armed Services Committee. The clock kept ticking—our clock, our time. And no one seemed to care.
We must care. We can’t give in to apathy, just as we can’t give in to panic or despair. We face enormous challenges, and so many of them are of our own making. But we can overcome them, for our sake and for the sake of generations to come. I know the future that I’m fighting for. I can look in his eyes. And we can begin that fight together, by casting our eyes to the skies above.
ASTEROID
The Universe Is Trying to Kill Us
This is a book about the threat of human extinction, but it’s impossible to begin the subject without considering the eradication of a group of animals that also once seemed secure in its reign over the Earth: the dinosaurs. Dinosaurs existed for more than 180 million years,1 hundreds of times longer than Homo sapiens’s so-far brief stay on the planet—and then they met a sudden and violent end. What matters for us is not merely the fact that the dinosaurs went extinct, however, but how it happened. We might be reading our own future in the chronicle of catastrophe that is the fossil record.
About 66 million years ago, at what we now know as the close of the Cretaceous period, the orbit of a single asteroid intersected that of Earth. Asteroids are hardly rare—hundreds of thousands of these chunks of rock and metal circle the sun, just as our planet does. At more than six miles wide, this leftover piece of the solar system’s birth was unusually large, yet it was still tiny compared to the planet it would impact, the equivalent of a marble colliding with a beach ball. But as the asteroid met the Earth it plunged through the planet’s atmosphere at a steep angle, like a high diver slashing toward the bottom of the pool, speeding toward what is now present-day Mexico at a velocity of 12.4 miles per second—20 times faster than a gunshot.2 Friction ignited the air around the plummeting asteroid into blue-hot plasma.3 It took just twenty seconds for the asteroid to hit the sea below.
The ocean at the impact point was shallow, and as the asteroid reached the water it punched through the surface, the seafloor, and the crust below, burrowing into red-hot streams of underground magma. The energy released by the resulting explosion had the force of 100 million tons of TNT, greater than 6,500 times more powerful than the nuclear bomb dropped on Hiroshima. A mega-tsunami flooded the surrounding coasts. More than a thousand cubic miles of vaporized rock were blown into the sky, punching a hole in the planet’s atmosphere. Some of the debris condensed into sand-sized, solid particles called spherules, and as they fell back to Earth they were so numerous that 10,000 of them were found on every square inch of the planet’s surface. Thermal radiation from the hot air started fires globally and burned much or all of the land biomass. Some four inches of the Earth’s oceans boiled off. “The asteroid hit and everything on the surface burned. It was like being inside an oven with the broiler on,” said Brian Toon, an atmospheric researcher at the University of Colorado, Boulder, I spoke to who has studied the aftermath of the impact. “It would have baked the dinosaurs alive.”
Those dinosaurs were, above all else, victims of catastrophically terrible luck. As we’ll see, objects from space strike the Earth all the time, but the chance of being hit by something the size of the Chicxulub asteroid—named for the modern Mexican town near the underwater impact crater the asteroid left, one of the largest in the planet’s history—is minuscule. That was the first turn of bad fortune. Even an asteroid as large as Chicxulub may not have wiped out the dinosaurs had it not landed precisely where it did. The shallow seabed at the impact point was unusually rich in sulfur, so the debris cloud caused by the asteroid was spiked with sulfur droplets. Sulfur reflects sunlight, and that cloud suffused with sulfur—and massive amounts of soot—blocked much of the sun’s heat from reaching the Earth’s surface. Global temperatures plummeted, perhaps by as much as 50 degrees Fahrenheit over land and 36 degrees over the oceans. For as long as two years following the asteroid strike, the darkness was so total that photosynthesis all but stopped, leaving only whatever food might have been left on the land and below the surface. “Light levels would have fallen below one percent for a couple of years,” said Toon. “When you have something that extreme, animals and plants can’t compensate.”
That was the second turn of bad fortune—and the last one for the dinosaurs. As traumatic as the actual asteroid strike would have been, especially near the impact site, it was the global loss of light and food that ultimately killed the dinosaurs and some three-quarters of the animals and plants living on the Earth at the time. Wrenching environmental change unfolded faster than anything living could adapt, deadly to anything that couldn’t hide in a hole. It’s what would likely kill us if a comparably sized asteroid collided with the Earth today—unless we’re smart enough to save ourselves.
The story of the asteroid that wiped out the dinosaurs has become so ingrained in our imagination as a stand-in for a natural apocalypse that it’s easy to forget how recently the theory was born. The first identification of an asteroid crossing Earth’s orbit didn’t occur until 1932, and even as Neil Armstrong and Buzz Aldrin walked on the moon in 1969, scientists were only beginning to understand that the craters pocking the lunar surface were the result of ancient asteroid impacts.
Here on Earth, geologists were still in the grip of a theory called uniformitarianism. It may sound like a little-known Protestant sect, but uniformitarianism was the idea that the geological features we see today—from oceans to craters to mountains—were all formed by gradual and uniform processes like erosion. That includes extinctions—scientists at the time largely believed that species went extinct gradually, rather than in sudden mass waves. It was only in 1980 that the father-and-son team of physicist Luis Alvarez and geologist Walter Alvarez published research showing that clay from the layer of sedimentary rocks marking the end of the Cretaceous contained an unusual concentration of iridium, an element found in far greater amounts in asteroids than in the Earth’s crust. The iridium was like the fingerprint of a suspect on a murder weapon, and the Alvarezes theorized that the dinosaurs’ extinction had been caused by the impact of a gigantic asteroid or
comet.4
While there are still some dissenters who believe that massive volcanic eruptions were the chief cause of the dinosaurs’ demise—a possibility we’ll examine in the next chapter—the asteroid theory was accepted by most scientists, especially after the underwater site of the Chicxulub crater was discovered in 2001.5 The Alvarezes’ research also helped dispel the theory of uniformitarianism as it became clear to scientists that along with work of slow, everyday geological processes, the Earth had been utterly reshaped by instantaneous catastrophes—hence the name of the new theory, catastrophism. And if such a catastrophe had happened once, it could happen again.
Dinosaurs are the poster species for total extinction, and so their destroyer has come to symbolize a universe that, as the astrophysicist Neil deGrasse Tyson has said, “is trying to kill us.”6 Unlike some of the other natural existential risks we’ll discuss in this book, we’d likely be able to see asteroids coming, which adds to their dreadful power, even as the cataclysmic effects of impact would be felt in an instant. No wonder Hollywood has made asteroids its favorite nonhuman existential villain. They may be chunks of rock and metal, but asteroids are inherently cinematic.
There’s something else that sets asteroids apart. Unlike most other existential risks—especially natural ones—this is one world-ending threat we can potentially eliminate now. Astronomers can find and track asteroids that might intersect with the planet’s orbital path—what are called near-Earth objects (NEOs)—years and even decades in advance of a possible impact. And if an NEO menaces, we have theoretical methods to target and deflect it before it endangers life on Earth. As Tom Jones, a veteran NASA astronaut who has an academic background in asteroid detection, told me, “We are learning how to change the way the solar system works to preserve our species.”
When Chicxulub came for them sixty-six million years ago, there was nothing the dinosaurs could do but die. And if a similar-sized NEO struck again during humanity’s watch on the planet, there would have been nothing we could have done, either—until today. Now we can alter the mechanics of the heavens to keep ourselves and our future safe. We can save the world—from this threat at least—but we’ll need to act soon.