Share your thoughts on how the world will end at our Science Not Fiction blog. Which of these doomsday scenarios do you find the most likely? Which obvious Armageddon did we miss?
Fashions come and go in all human endeavors—even eschatology, the study of the end of the world.
Back in the 1980s, our planet seemed sure to perish in a nuclear barrage, and songs about atomic apocalypse were at the top of the charts: Cue Prince’s “1999” (“Everybody’s got a bomb/We could all die any day”). By the 1990s, death by asteroid impact was all the rage. After 9/11 and the 2001 anthrax attacks, worries turned to a bioweapon unleashed by a terror group. The latest obsession is plague, delivered in the metaphorical form of vampires and zombies—especially zombies, since vampires have developed an unseemly fondness for chaste romance.
In truth, all these possible ends only scratch the surface, as I learned a decade ago while working on my article "20 Ways the World Could End" for DISCOVER’s 20th-anniversary issue. And I quickly found that I was far from the only one with a fascination for such gloomy things. Soon after came a flurry of similar end-of-days TED lectures, books, and television shows.
We are fascinated by speculation about the end of the world, I think, because it paradoxically makes us feel safe. Global destruction is so grand, so overdramatic, that it doesn’t feel connected to our lives the way more immediate worries like cancer or Alzheimer’s are. We can dabble in morbid fantasies about our demise while believing that we won’t be the ones fated to see them realized. Then again, lots of people bet that they wouldn’t be the ones left holding overpriced Florida homes when the real estate market collapsed. We might lose this bet as well.
For DISCOVER’s 30th anniversary, the time seemed right to revisit the science of doomsday. As with every sequel, this time it delivers more, more, more. So my latest list goes to 30: 10 brand-new possible ends, along with updated odds on the original 20.
30 INFORMATION OVERLOAD Futurist Ray Kurzweil talks expansively about the coming “singularity,” a moment when human and machine intelligence become indistinguishable and the pace of progress accelerates unimaginably. If minds could be transferred to computers, Kurzweil argues, death would become meaningless. And if humans merged with their machines, the world as we know it would no longer exist. In the evolutionary sense, this could represent the emergence of a new species—Homo singularity?—that would be mostly technology driven. (And don’t ask what happens if the power fails.) Linguist Stephen Pinker dismisses this whole vision, likening it to the old predictions of domed cities and nuclear-powered cars. But Kurzweil claims he can provide the date when the singularity will arrive: 2045, just in time for DISCOVER’s 65th anniversary. ODDS: indeterminate, but likely—human-machine merging is starting already.
29 GENETICALLY MODIFIED SUPERHUMANS The debate over human germ-line engineering—reworking genes in the sperm and egg to create inheritable new traits—sputtered out early in the last decade after gene therapy had a series of notable failures. The revival of that research (see page 31) suggests it is time to resume the conversation. Soon it could be possible to design babies whose DNA has been rewritten to give them greater mental and physical abilities. Such “transhumans” might eventually be a true breed apart, able to mate only with others of their kind. In a Hollywood blockbuster, the transhumans would include a cackling villain who turns against his progenitors, but there is no need: If they are truly superior, they might outcompete us by benign means, marking the first synthetic transition from one homi-nid species to the next. Odds: high, since germ-line modification seems nearly inevitable in the long run.
28 SPACE COLONY UPRISING From America to Angola, colonies have a history of rising up against the nations that founded them. If we ever establish self-sustaining colonies on other worlds, the social and political pressures will probably be much the same. (In 1973, the crew of the first American space station, Skylab, went on strike to protest their working conditions.) As with the American Revolution, the separation could be violent without being catastrophic. But an interplanetary conflict opens some grim possibilities. A self-sustaining colony could afford to unleash a planetwide attack, such as an unstoppable bioweapon, since the consequences on Earth would have no effect on the attackers. Odds: high that there will be a political separation; low that it will be catastrophic. England colonized half the world and is still standing.
27 ALIEN PLAGUE A biological attack from space need not be deliberate. British astronomer Fred Hoyle, whose “steady state” cosmology was for years a serious challenger to the Big Bang theory, was convinced that comets are full of viruses that cause flu epidemics when they rain down on Earth. His ideas, once ridiculed, have been partially vindicated by the discovery that pieces of Mars have landed on Earth, and by studies showing that extremely hardy microbes could survive extended voyages through space. NASA takes the idea of alien pathogens seriously enough that it has an elaborate quarantine protocol for any space sample returned here. The possibility that our planet was seeded with microbial life from Mars (or even, per Hoyle, from a comet) means that we cannot be certain that space microbes would be incompatible with our biology. Odds: still low, given the sketchy evidence that space microbes play any role in terrestrial disease.
26 SUPERBOMB The atomic bomb is hardly the ultimate tool of destruction. Matter-antimatter reactions are a much more effective way to tap E = mc2. Splitting a uranium atom converts only about 0.1 percent of its mass into energy, but mixing matter and antimatter is 100 percent efficient. About 100 pounds of antimatter would exceed the yield of all the world’s atomic weapons. Fortunately, we don’t know how to store more than a few atoms’ worth of it at a time. Another possibility if you want to destroy the world: Use a giant particle accelerator to fabricate a mini black hole. If it had more mass than that of a large mountain, it would be stable and would immediately sink through the ground, consuming the planet from within until there was nothing left but an Earth-mass black hole, about one-third of an inch wide. Odds: high for a weapon more destructive than the H-bomb, very low for the black hole in particular.
25 WEATHER-CONTROL MISHAP Efforts to control the weather have a poor track record (China attempted it during the 2008 Olympics, but nobody can tell if the project worked). Still, some researchers are talking seriously about global climate modification as a way to counteract climate change. These "geoengineering" schemes include pumping light-reflecting sulfur compounds into the stratosphere and placing giant sunshades in space. What could go wrong seems more obvious than what could go right. This approach could also lead to another doomsday weapon: Shoot an enormous cloud of chaff into a stable spot between Earth and the sun and you could dim the whole world, possibly triggering an ice age. Odds: very low. Geoengineering schemes would be tested extensively first; a chaff bomb is a slow, cumbersome way to attack.
24 TIME TRAVEL This is one of the favorite tropes in science fiction: Hop into your time machine, visit the past, and you could wipe out the present—intentionally or not (watch out for that butterfly). The current thinking in physics is that time travel might actually be possible. Now the catch: The same theories say that a time machine could go back only to the moment when it was activated. Even if genuine travel to the past is possible, Seth Lloyd of MIT argues that quantum rules would prevent the traveler from doing anything that contradicts what he already knows about the present. Where is the fun in that? Odds: indeterminate, but logic dictates that destructive interference with the past is impossible.
23 STRANGE MATTER Ordinary atoms contain particles called quarks, which come in two varieties: up and down. There are other kinds of quarks that we don’t encounter because they normally form unstable particles. But in 1984 Ed Witten, the godfather of string theory, proposed that there might be a stable state of matter that consisted in part of a third type of quark, called a strange quark. This hypothetical type of matter, called a strangelet, could possibly be created naturally by an extremely energetic cosmic ray, or deliberately in a particle accelerator even more potent than the Large Hadron Collider. Once unleashed, a strangelet could act as a kind of subatomic infection, converting any ordinary matter into strange matter. Eventually it would consume the whole planet, leaving a lump of strangeness in its wake. Odds: very low. Cosmic rays have been striking Earth for billions of years with no such effect.
22 DARK MATTER CLUMP Dark matter is the heavy but invisible (and as yet undetected) stuff believed to hold galaxies together. If a clump passed near our sun, its pull could shake loose comets from the outer solar system, sending some of them crashing into Earth. Australia-based astronomer Kenji Bekki claims that one such passage happened millions of years ago, forming a ring of stars called Gould’s Belt. If a dark cloud headed right into (and through) Earth, that might have dire consequences too. In theory, dark matter particles could interact with each other, giving off gamma radiation. Afsar Abbas, a physicist in India, suggests that the radiation would not only cause a wave of mutations but also heat up Earth’s interior and trigger massive volcanism, leading to a double extinction. Odds: indeterminate. Dark matter is so elusive that an event could be starting right now and we might not know it.
21 SOLAR SHUTDOWN Back in the 1970s, when it seemed that the sun was not emitting the expected number of particles known as neutrinos, some solar physicists proposed that our star might go through million-year stretches of reduced activity, during which time its brightness could drop by perhaps 40 percent. Although the initial evidence for a solar shutdown evaporated, the mechanism remains possible. Such a dip would put our planet in a deep freeze, and in fact paleontologists now find evidence of one such episode of extreme cold (nicknamed "Snowball Earth") about 650 million years ago. If the sun dimmed significantly today, the oceans would gradually freeze solid, and most multicellular life on Earth—humans included—would probably go extinct. Odds: low. There is no evidence that other sunlike stars experience such shutdowns, though there is not much proof that they don’t.
Handicapping the Other 20 Doomsdays
Still not anxious? Here are the original disasters from "20 Ways the World Could End", along with a fresh evaluation of their likelihood.
PLAUSIBLE
For two key natural disasters—asteroid impact and flood-basalt volcanism—it is not a question of whether they will happen again, but when. NASA is now quite sure that no Earth-killer asteroids are on a near-term collision course, but 50-meter asteroids (large enough to flatten a city) strike every few hundred years, and almost all of them are uncharted. Large-scale eruptions happen roughly on 25-million-year timescales; a regional supervolcano could erupt at Yellowstone in the next few thousand. A magnetic field reversal is a near certainty within the next few hundred thousand years, but there is no evidence that reversals actually are deadly. Global epidemics, global warming, and environmental toxins are here now, but it is not clear that any of them have the potential to wipe out humanity. The risks of a biotech disaster are even less established, since nobody has yet designed a deadly pathogen or established a health risk from genetically modified organisms. Another global war seems depressingly likely; the question mark is how deadly the weapons will be next time around. Ecosystem collapse may have helped usher out the dinosaurs. An asteroid and huge eruption also contributed, but we humans are putting a lot of our own stresses on the web of life.
POSSIBLE BUT EXTREMELY UNLIKELY
Gamma-ray bursts happen constantly, but we now know the likely kinds of progenitor stars, and there seems to be none close enough to cause serious trouble. Black holes are a legitimate threat, but the nearest known one is 1,600 light-years away. Solar superflares have been tentatively observed on some sunlike stars, but there is strong evidence the sun has never produced such an outburst, and stars become less active as they age. A particle accelerator mishap is improbable since nature regularly pelts Earth with cosmic rays more energetic than the particles in the Large Hadron Collider. Mass insanity lacks a clear definition or trend, and it is not a recipe for global destruction unless it triggers an all-out war or terror attack.
INDETERMINATE
These have never happened before or rely on mechanisms that lie beyond science. The technology that could allow a robot takeover or a nanotechnology disaster has made only modest progress since 2000. The odds of an alien invasion got a boost from the discovery of vaguely Earth-like planets around other stars, but we still have no idea if alien civilizations exist. Collapse of the vacuum probably happened in the first 10–32 second of the universe’s life. Until we discover another universe or develop a better theory of physics, there is no way to judge its likelihood of happening again. Whether divine intervention will occur is a matter of faith. And is this all a dream? Maybe. I’ll pinch my arm now and see if it goes away…
Share your thoughts on how the world will end at our Science Not Fiction blog. Which of these doomsday scenarios do you find the most likely? Which obvious Armageddon did we miss?
Corey S. Powell is the editor in chief of DISCOVER, where he has worked for the past 13 years. He is the author of God in the Equation: How Einstein Transformed Religion.
