This year will be a doozy for doomsayers. Depending on the prophecy, the world is predestined to expire by means of a solar storm, asteroid strike, rogue-planet collision, plague, falling stars, earthquake, debt crisis, or some combination thereof. Of course, nobody seems to be preparing for any of these impending 2012 apocalypses, with the exception of a porn studio reportedly building a clothing-optional underground bunker.
And why should we? Scientifically speaking, the prophecies are strictly ballyhoo. Physicists can do a lot better. When it comes to end-times scenarios, cosmological data-crunchers have at their disposal far more meaningful prognostication tools that can tell us how it’s really going to end—not just Earth, but the whole universe. Best of all, they can tell us how to survive it.
Science, oddly, is a lot better at predicting things like the death of stars than next week’s weather. The same laws of physics that enable scientists to study the Big Bang that occurred 13.7 billion years ago also allow them to gaze into the future with great precision. And few people have peered farther than University of California, Santa Cruz, astronomer Greg Laughlin, science’s leading soothsayer. As a graduate student in 1992, he was plugging away at a simple computer simulation of star formation when he broke for lunch and accidentally left the simulation running. When he returned an hour later, the simulation had advanced 100 million billion years, much further into the future than most scientists ever think (or dare) to explore.
The program itself didn’t reveal anything terribly startling—the simulated star had long since gone cold and died—but Laughlin was intrigued by the concept of using physical simulations to traverse enormous gulfs of time. “It opened my eyes to the fact that things are going to evolve and are still going to be there in timescales that dwarf the current age of the universe,” he says.
Four years later, still fascinated, Laughlin teamed up with Fred Adams, a physics professor at the University of Michigan, to investigate the future of the universe more rigorously. Working in their spare time, the two researchers coauthored a 57-page paper in the journal Reviews of Modern Physics that detailed a succession of future apocalypses: the death of the sun, the end of the stars, and multiple scenarios for the fate of the universe as a whole.
The paper made a surprising splash in the popular press, even grabbing the front page of The New York Times. Soon Laughlin and Adams found themselves in great demand on the lecture circuit, joining like-minded colleagues in discussions about such weighty topics as the physics of eternity and possible survival strategies for unthinkably grim cosmic events. (One future projection calls for a violent rip in the fabric of space-time that annihilates all matter within 30 minutes.) “Nobody makes it his life’s work,” says Glenn Starkman, a theoretical physicist at Case Western Reserve University in Cleveland who has coauthored papers such as “Life and Death in an Ever-Expanding Universe,” among other lighthearted fare. “There are more pressing problems,” he says, “but it is fun stuff to think about.”
Flight from planet Earth
For Starkman and other futurists, the fun begins a billion years from now, a span 5,000 times as long as the era in which Homo sapiens has roamed Earth. Making the generous assumption that humans can survive multiple ice ages and deflect an inevitable asteroid or comet strike (NASA predicts that between now and then, no fewer than 10 the size of the rock that wiped out the dinosaurs will hit), the researchers forecast we will then encounter a much bigger problem: an aging sun.
Stable stars like the sun shine by fusing hydrogen atoms together to produce helium and energy. But as a star grows older, the accumulating helium at the core pushes those energetic hydrogen reactions outward. As a result, the star expands and throws more and more heat into the universe. Today’s sun is already 40 percent brighter than it was when it was born 4.6 billion years ago. According to a 2008 model by astronomers K.-P. Schröder and Robert Connon Smith of the University of Sussex, England, in a billion years the sun will unleash 10 percent more energy than it does now, inducing an irrefutable case of global warming here on Earth. The oceans will boil away and the atmosphere will dry out as water vapor leaks into space, and temperatures will soar past 700 degrees Fahrenheit, all of which will transform our planet into a Venusian hell-scape choked with thick clouds of sulfur and carbon dioxide. Bacteria might temporarily persist in tiny pockets of liquid water deep beneath the surface, but humanity’s run in these parts would be over.
Such a cataclysmic outcome might not matter, though, if proactive Earthlings figure out a way to colonize Mars first. The Red Planet offers a lot of advantages as a safety spot: It is relatively close and appears to contain many of life’s required ingredients. A series of robotic missions, from Viking in the 1970s to the Spirit rover still roaming Mars today, have observed ancient riverbeds and polar ice caps storing enough water to submerge the entire planet in an ocean 40 feet deep. This past August the Mars Reconnaissance Orbiter beamed back time-lapse photos suggesting that salty liquid water still flows on the surface.
The main deterrent to human habitation on Mars is that it is too cold. A brightening sun could solve that—or humans could get the job started without having to wait a billion years. “From what we know, Mars did have life and oceans and a thick atmosphere,” says NASA planetary scientist Christopher McKay. “And we could bring that back.”
McKay is a leading scientist in the study of transforming Mars into an Earth-like world through a process called terraforming. Drawing on lab experiments and climate models, he has demonstrated that manufacturing and releasing more than 3 billion tons of perfluorocarbons and other intense greenhouse gases there would warm the planet. Natural processes on Mars would then take over: Ice caps would melt, releasing water and carbon dioxide and speeding up the warming process until the planet had a thick, sustainable atmosphere. In McKay’s mind, 1 billion years is plenty of time to custom-build a Martian outpost and a spacecraft to take us there. Existing technology, he notes, could theoretically blast astronauts to Mars in three months. One hopes we could improve on that over the next eon.
For now, let’s assume we do, and humanity transitions successfully to Mars. By Laughlin’s calculations, life there could proceed relatively comfortably for another 4.5 billion years after Earth becomes uninhabitable and before the sun’s bloat once again forces a move. According to standard models of stellar evolution, around that time the sun will largely deplete the hydrogen reserves in its core and begin to balloon as its fusion reactions migrate outward. Through their telescopes astronomers have watched this scenario play out with many other stars, so they know with considerable certainty what happens next: In a dramatic growth spurt, the sun will swell to become a red giant star, 250 times as large and 2,700 times as bright as it is now, stretching farther and farther out into the solar system. It will vaporize Mercury, Venus, and Earth and turn Mars into a molten wasteland.