My vague qualm about the unlikeliness of Kaku's lifeboat theory was considerably sharpened when I talked to J. Richard Gott III, an astrophysicist at Princeton University. Gott is known for making bold quantitative predictions about the longevity of things—from Broadway shows like Cats to America's space program to intelligent life in the universe. He bases these predictions on what he calls the Copernican Principle, which says, in essence: You're not special. "If life in the universe is going to last a long time, why do we find ourselves living when we do, only 13 billion years after the beginning?" Gott said to me, speaking in an improbable Tennessee accent whose register occasionally leapt up an octave, like Don Knotts'. "And it is a disturbing fact that we as a species have only been around for 200,000 years. If there are going to be many intelligent species descended from us flourishing in epochs far in the future, then why are we so lucky to be the first?" Doing a quick back-of-the-envelope calculation, Gott determined that it was 95 percent likely that humanity would last more than 5,100 years but would die out before 7.8 million years (a longevity that, coincidentally, is quite similar to that of other mammal species, which tend to go extinct around 2 million years after appearing). Gott was not inclined to speculate on what might do us in—biological warfare? asteroid collision? nearby supernova? sheer boredom with existence? But he did leave me feeling that the runaway expansion of our universe, if real, was the least of our worries.
Despite the pessimistic tenor of Gott's line of thought, he was positively chirpy in conversation. In fact, all the cosmologists I had spoken to so far had a certain mirthfulness about them when discussing eschatological matters—even Lawrence Krauss, the one who talked about this being the worst of all possible universes. ("Eschatology—it's a great word," Krauss said. "I had never heard of it until I discovered I was doing it.") Was no one made melancholy or irritable by the prospect of our universe decaying into nothingness? I thought of Steven Weinberg, the Nobel laureate in physics who, in his 1977 book about the birth of the universe, The First Three Minutes, glumly observed, "The more the universe seems comprehensible, the more it also seems pointless." It was Weinberg's pessimistic conclusion in that book—he wrote that civilization faced cosmic extinction from either endless cold or unbearable heat—that had inspired Freeman Dyson to come up with his scenario for eternal life in an expanding cosmos.
I called Weinberg at the University of Texas, where he teaches. "So, you want to hear what old grumpy has to say, eh?" he growled in a deep voice. He began with a dazzling theoretical exposition that led up to a point I had heard before: No one really knows what's causing the current runaway expansion or whether it will continue forever. The most natural assumption, he added, was that it would. But he wasn't really worried about the existential implications. "For me and you and everyone else around today, the universe will be over in less than 10^2 years," he said. In his peculiarly sardonic way, Weinberg seemed as jolly as all the other cosmologists. "The universe will come to an end, and that may be tragic, but it also provides its fill of comedy. Postmodernists and social constructivists, Republicans and socialists and clergymen of all creeds—they're all an endless source of amusement."
It was time to tally up the eschatological results. The cosmos has three possible fates: Big Crunch (eventual collapse), Big Chill (expansion forever at a steady rate), or Big Crackup (expansion forever at an accelerating rate). Humanity, too, has three possible fates: eternal flourishing, endless stagnation, or ultimate extinction. And judging from all the distinguished cosmologists who weighed in with opinions, every combination from Column A and Column B was theoretically open. We could flourish eternally in virtual reality at the Big Crunch or as expanding black clouds in the Big Chill. We could escape the Big Crunch/Chill/Crackup by wormholing our way into a fresh universe. We could face ultimate extinction by being incinerated by the Big Crunch or by being isolated and choked off by the Big Crackup. We could be doomed to endless stagnation—thinking the same patterns of thoughts over and over again, or perhaps sleeping forever because of a faulty alarm clock—in the Big Chill. One distinguished physicist I spoke to, Andrei Linde of Stanford University, even said that we could not rule out the possibility of their being something after the Big Crunch. For all of the fascinating theories and scenarios they spin out, practitioners of cosmic eschatology are in a position very much like that of Hollywood studio heads: Nobody knows anything.
Still, little Alvy Singer is in good company in being soul-sick over the fate of the cosmos, however vaguely it is descried. At the end of the 19th century, figures like Swinburne and Henry Adams expressed similar anguish at what then seemed to be the certain heat-death of the universe from entropy. In 1903 Bertrand Russell described his "unyielding despair" at the thought that "all the labors of the ages, all the devotion, all the inspiration, all the noonday brightness of human genius, are destined to extinction in the vast death of the solar system, and that the whole temple of Man's achievement must inevitably be buried beneath the debris of a universe in ruins." Yet a few decades later, he declared such effusions of cosmic angst to be "nonsense," perhaps an effect of "bad digestion."
Why should we want the universe to last forever, anyway? Look—either the universe has a purpose or it doesn't. If it doesn't, then it is absurd. If it does have a purpose, then there are two possibilities: Either this purpose is eventually achieved, or it is never achieved. If it is never achieved, then the universe is futile. But if it is eventually achieved, then any further existence of the universe is pointless. So, no matter how you slice it, an eternal universe is either a) absurd, b) futile, or c) eventually pointless.
Despite this cast-iron logic, some thinkers believe that the longer the universe goes on, the better it is, ethically speaking. As John Leslie, a cosmological philosopher at the University of Guelph in Canada, told me, "This is true simply on utilitarian grounds: The more intelligent happy beings in the future, the merrier." Philosophers of a more pessimistic kidney, like Schopenhauer, have taken precisely the opposite view: Life is, on the whole, so miserable that a cold and dead universe is preferable to one teeming with conscious beings.
If the current runaway expansion of the cosmos really does portend that our infinitesimal flicker of civilization will be followed by an eternity of bleak emptiness, then that shouldn't make life now any less worth living, should it? It may be true that nothing we do in A.D. 2004 will matter when the burnt-out cinder of our sun is finally swallowed by a galactic black hole in a trillion trillion years. But by the same token, nothing that will happen in a trillion trillion years matters to us now. In particular (as the philosopher Thomas Nagel has observed), it does not matter now that in a trillion trillion years nothing we do now will matter.
Then what is the point of cosmology? It's not going to cure cancer or solve our energy problems or give us a better sex life, obviously enough. Still, it is bracing to realize that we live in the first generation in the history of humanity that might be able to answer the question, How will the universe end? "It amazes me," Lawrence Krauss said, "that, sitting in a place on the edge of nowhere in a not especially interesting time in the history of the universe, we can, on the basis of simple laws of physics, draw conclusions about the future of life and the cosmos," he said. "That's something we should relish, regardless of whether we're here for a long time or not."
So, remember the advice offered by Monty Python in their classic "Galaxy Song." When life gets you down, the song says, and you're feeling very small and insecure, turn your mind to the cosmic sublimity of the ever-expanding universe—"because there's bugger-all down here on Earth."