These time scales relativize my own existence. I find them inspiring and reassuring. As the physicist Freeman Dyson wrote in his book Infinite in All Directions, “Letting our imagination wander among the stars, we too may hear whispers of immortality.” By day, the window on the galaxies is replaced with a grey November sky—a featureless, ashen plain that scrolls from horizon to horizon. This is the season that ends seasons. The bare trees look like abandoned scaffolds left over from a carnival that has yet to be disassembled. But the Austrian pine down the street beside George’s house is as green as it ever is. It has a low, spreading crown and its long needles are set in thick, bushy clumps. When it catches the late-afternoon sun, even on the coldest winter days, it is refulgent with semitropical green that remains steadfast despite the temperature.
In terms of my calendar of life on earth, the seasons have caught up to the present. For me, the first snow marks the beginning of the glacial age and of our own era, the Holocene. There is something aqueous, and a little clinical, about the grey, shadowless light of cloudy November afternoons. Bare branches, the armatures that supported the stage sets of summer foliage, are exposed, and the soil is naked. The glacial ages marked the migration of humans out of Africa northwards into Europe, and they must have huddled in early winter geographies not unlike this one. The deserted November landscape has a post-apocalyptic quiescence. What few remaining islands of green there are, like the Austrian pine, seem to glow. My eyes rest there, slaking their thirst for the colour of life.
On a cool afternoon earlier this week I saw a little cloud of small moths dancing in the air above the table on the patio. It was a mating flight, even though the temperature was only a few degrees above freezing. Still, there they fluttered, a fragile yet hardy species eking out an existence at the final margins of life before winter. November is the month at the end of time—and it is timeless. A photograph of my yard would look the same whether it was taken in in November, December, March or early April. My bedraggled rose bush has one final bud; if we get a few warm days, it may blossom. There is bravery in this evacuated panorama.
GÖTTERDÄMMERUNG
Only a few religions incorporate the idea of Armageddon—most notably Christianity, with its doctrine of the End of Days. But for most of them doomsday is not final—a new order always rises out of the ashes. It seems that true fatalism only existed in early Norse mythology. The Vikings created a belief system that dealt not only with human mortality but also with the mortality of the universe, which they believed would be destroyed in the final battle of the gods. As set forth in the Gylfaginning, their mythology was a precocious forerunner of our current knowledge of the fate of the universe.
You’ll recall that, according to the Gylfaginning, the universe was embodied by a giant ash tree: Yggdrasil, or the world tree. In his book Hammer of the North, the Norse scholar Magnus Magnusson writes, “Yggdrasil holds the fabric of the universe together, a living and sentient being.” Magnusson then goes on to describe the “fearful torments” that the world tree suffered, noting that “Yggdrasil reflected the parlous condition of the world, a world that was flawed and doomed from the start.”
Yggdrasil is fertilized with celestial hydromel, and its three great roots draw nourishment from three sources. One root taps into Urd’s Well, a fountain of youth tended by the three Nornir, the goddesses of fate who rule past, present and future; another root draws water from the Hvergelmir Fountain, the source of all water (in Niflheim); while a third root taps into the Fountain of Mimir in the world of the giants.
It is from Urd’s Well, the fountain of youth, that Yggdrasil derives its longevity. The secret of time, guarded by the Nornir, appears to be the great tree’s elixir. Yet despite being nourished by time itself, Yggdrasil is doomed. At the top of the great tree, a gold cock scans the horizon to warn the gods if it sees the giants mounting an attack that will signal the beginning of the end of the gods. The other lookouts are a giant eagle surveying the entire world from Yggdrasil’s branches and a hawk perched on the eagle’s beak, ready to fly wherever necessary. The agent provocateur in this limited ecology is a mischievous squirrel, who constantly runs up and down the trunk, creating discord between the eagle and the serpent that lives at the roots of the tree.
Our present-day scientific version of the end of everything is on a scale that would be incomprehensible to the Vikings. I think, though, that they would be impressed with both its fatalism and its apocalyptic grandeur. Will there be gods to battle the giants at the end of our universe? Perhaps. Happily, doomsday for the cosmos is a long, long way off, trillions and trillions of years away, and the Anthropic Principle tells us that we have an extraordinary future before us.
Hans Moravec, founder of the world’s largest robotics program, at Carnegie Mellon University, has lingered thoughtfully in the corridors of the future. Tempering his astonishing imagination with scientific rigour, he has painted visions of the future that are as fantastic as they are invidiously plausible. In his seminal book Mind Children, which takes a look at the future of artificial and human intelligence, he chronicles a destiny where inconceivably vast engineering projects and powerful computers combine to reshape planets and the basis of life itself.
One of his more extraordinary scenarios envisages what might happen if a sufficiently large and sophisticated computer were able to simulate the whole surface of our earth—not just at a large scale, but down to the atomic level. Everything—dirt, coral, human consciousness and flies—would be replaced with perfect copies of itself. The total information contained in every cell, every atom, would be extracted and transferred to a computer bank. Human beings in such a simulation would be indistinguishable from you or me.
All this could take place without our even being aware of it. (Of course, if you were a little paranoid, you might think, “How do we know that we aren’t already simulations, imprisoned in a superintel-ligent computer like the pod-bound humans in The Matrix?” But that is an unanswerable question, one about which we could speculate for years without solving its riddle. For now, let’s assume that we’re not.) Moravec knows from his experience with today’s complex simulations, such as planning the trajectory of unmanned space probes to other planets or modelling nuclear explosions, that simulations obey the basic laws of physics, one of which states that time is symmetrical. A simulation can be as easily run backwards as forwards.
So, Moravec asks, once the simulation of earth has reached complete saturation—with every atom, every quark, captured in a replication—why not run the whole planet backwards in time? As each past inhabitant of the earth was resurrected, he or she could be uploaded into a new, immortal body. All the people who ever existed could live again, their infirmities cured and their minds restored. In this way, Moravec claims, even our most distant ancestors would be able to share our fantastic destiny. As he sees it, “Resurrecting one small planet should be child’s play long before our civilization has colonized even its first galaxy.”
Perhaps Judaism has it right: the righteous will be resurrected. Although in Moravec’s vision the not-so-righteous will rise up again as well. The point is, if we survive as a species, if we don’t succumb to our own imperfections, our future literally has no limits. Running time backwards on planet earth, if indeed this ever happens, will be only the first in a series of almost inconceivable scientific and engineering accomplishments—the harnessing of stars, the towing of black holes for use as power—that, given the trillions of years left to us, will inevitably produce superbeings with the powers of gods…or perhaps a single entity stretching from one side of the universe to the other.
The Irish physicist J. D. Bernal had an intimation of how the rise of superbeings might come about. Predicting that humans would transform themselves beyond recognition, he wrote, “Finally, consciousness itself may end or vanish in a humanity that has become completely etherealized, losing the close-knit organism, becoming masses of atoms in space communicating by radiation, and ultimately, perhap
s resolving itself entirely into light.” This adaptation, Bernal said, would allow these post-humans to colonize vast areas of otherwise inhospitable space. He goes on: “As the scene of life would be more the cold emptiness of space than the warm, dense atmosphere of the planets, the advantage of containing no organic material at all, so as to be independent of both these conditions, would be increasingly felt.” Since Bernal published his visions of the future of humanity, other scientists have speculated on what post-humanity may look like. It is certain that it will be nothing we can now imagine. But there are inevitabilities about which we can speculate with some assurance. And Barrow and Tipler make a convincing argument that eventually life will spread to inhabit the entire universe. It will be then, when no other frontier is possible, that the only door locked to these godlike beings will be the one that opens to eternity. For the universe has an expiration date.
The end will come in one of two ways: cosmic “heat death” (which is really more like the “big freeze”) or the “big crunch.” Science can’t tell us which one will win out because the weight of the universe is at the borderline between the two possibilities; it might continue to expand indefinitely, overcoming the contracting effects of gravity, or it might stop expanding and begin to collapse. The first scenario, heat death (or death from lack of heat), sees the stars snuff out one by one, and matter itself disintegrating until the temperature of the empty universe reaches absolute zero in the final darkness. The second, the big crunch, is the reverse of the Big Bang. Here gravity prevails. After expanding for billions of years, the universe starts to contract and ultimately collapses upon itself, imploding in a fiery annihilation that will be the mirror image of its birth.
If, as Thomas Gold proposed, time begins to run backwards in a contracting universe, then for its inhabitants birth will become the final moment of life. But these inhabitants won’t know time is reversed. Their thoughts will flow logically and naturally in the new direction of time as our own do, and the universe will appear to be expanding, just as our own does. But its end will come all the same.
THE ENDGAME
Worlds may freeze, and suns may perish, but there stirs something within us now that can never die again.
—H. G. Wells
Can total annihilation be deferred, or even avoided? How do we snatch eternity from the jaws of a finite universe? Hans Moravec, among others, has wrestled with cosmic mortality and come up with an ingenious solution that just might work. It all hinges on the paradox of Zeno’s Arrow—if you keep halving the distance that the arrow has yet to travel, the arrow will never arrive. This turns out to have practible applications. What if, Moravec asks, the universe is headed for heat death? How could an infinite amount of time be squeezed from a finite amount of matter and energy?
Moravec’s answer is clever. He says that our descendants could build a tremendous battery consisting of two giant mirrors that faced each other. Moravec proposes that a beam of photons be endlessly reflected between the two mirrors to harness the energy of light. The photons would push the mirrors farther apart and the energy from the moving mirrors would power civilization. Moravec writes, “The idea is to use about half the energy in the battery to do T amount of thinking, then wait until the universe is cold enough to permit half the remaining energy to support another T, and so on indefinitely.”
But what if the universe contracted instead? In this case Moravec again proposes mirrors, only now they would surround a stored vacuum. As the universe contracted, the vacuum would yield increasing amounts of energy. He writes, “A subjective infinity of thought might be done in the finite time to collapse by using this growing power to think faster and faster as the end draws nigh. The trick here is to repeatedly do an amount of thinking T in half the remaining time.” Of course, when Moravec refers to “thinking,” he means the complex information-processing that it would take to maintain such advanced beings within their real and virtual worlds.
Freeman Dyson has also contemplated how the endgame might play out is. Dyson is famous for his visions of fantastic engineering projects in the distant future. Perhaps his best-known scheme is the Dyson sphere, where a living star is enclosed within a giant globe and all the star’s energy is harvested for the benefit of a civilization living on the sphere. When first proposed, this idea was so compelling and so logically inevitable that astronomers began looking for Dyson spheres as a method of determining whether there was intelligent life elsewhere in the universe. Occasionally, they argued, stars should sporadically dim and then wink out, evidence that an advanced civilization had reached the Dyson-sphere stage. So far, no such stars have been found.
But even Dyson spheres would not save a dying civilization at the end of the universe—stars will run out of fuel long before that. If heat death is indeed the ultimate fate of the universe, then Freeman Dyson has another trick up his sleeve. He proposes using the cooling temperature as a way to defer mortality. Our descendants, either superbeings or some sort of ultra-intelligences, would have to radically conserve energy in order to carry on. If they could, then they might be able to survive in a “subjective infinity,” as Moravec calls this sleight-of-hand immortality, but only if they were able to speed up their thought processes. Dyson maintains that the cold could be used to dissipate the heat inevitably generated by such vast information processing—thinking generates heat. But as available resources dwindled, these beings would have to ration their energy. He suggests that they might go into long periods of hibernation. Subjectively, they’d never be aware of their downtime, their thoughts would resume without interruption as soon as they reawakened, and the increasingly longer periods of hibernation would go unnoticed.
Frank Tipler, one of the co-authors of The Anthropic Cosmological Principle, has also wrestled with these questions. In his 1994 book The Physics of Immortality, he suggests that a superbeing who had grown to encompass the entire universe would use all available energy to process its thoughts, which would themselves include simulations of all possible worlds. But, appreciating that its own fate was tied to that of the universe, what would the ultra-brain do to survive? As we now know, even it wouldn’t be able to supervene the second law of thermodynamics, no matter how intelligent or omniscient it was.
Tipler’s answer is not unlike Moravec’s: the faster you think, the faster you act, and the more living you can fit into a smaller slice of time. The race does go to the quick, and it is inevitable that the cognitive speed of beings in the future will certainly outpace anything today. Since the longevity of existence is equivalent to the speed of thought (a Femtonian lives a million years during one of our seconds), Tipler argues that as the thinking process of the ultra-brain sped up, it could use the immense energies and unusual physics of a collapsing universe to increase the subjective speed of thought infinitely—the ultimate escape. If time is indeed infinite inwards, and the femtosecond within the nanosecond has an endless series of smaller and smaller divisions within it, then perhaps that inward abyss of time might be the key to our future, and our survival.
Even before the end of the universe, there are other pitfalls along the way that might end it prematurely. There is some speculation that when the first black hole evaporates through Hawking radiation, it might destroy the universe. This is because each black hole contains the end of time. It’s possible that if space-time collapses in the singularity of a black hole that completely evaporates, the collapse will spread outwards and destroy everything else along with it. To forestall such a catastrophe, Barrow and Tipler suggest that future intelligences could simply keep dumping matter into those black holes that were teetering at the brink of complete evaporation. They write, “Thus ultimately life exists in order to prevent the Universe from destroying itself!”
In the end, the interlocked fates of life and the universe hinge on life’s immortality. It is our only hope. But then a new dilemma arises, one that takes me back to my childhood bedroom, where I wrestled with the opposed fates of mortality and immortality
. The idea of existence without end is pretty frightening, so much so that, for some, extinction might seem preferable.
THE DEEP FUTURE
The timeline for our universe, if it keeps expanding and ends in eventual heat death, has been worked out in detail by physicists, astronomers and cosmologists. Regardless of whether or not our progeny expand to fill it, the universe will run down. Tipler and Barrow (who refer to the universe that contains not only our visible universe but also all possible universes with a capitalized “Universe”) predict that in one thousand billion years, new stars will cease to form. Billions of years after that—or ten billion billion years from now—90 percent of the stars in the universe will have evaporated, while the remainder will have been sucked into massive black holes. In ten million, billion, billion, billion years, all carbon-based life forms will become extinct.
You’d think that would pretty much be the end of things, but within the barren, dark emptiness of this future cosmos, inside matter itself, non-carbon-based life would be blazing its own bright future. From now on, the universe’s timeline becomes so staggering that we have to convert to trillions in order to economize on words. In a trillion, trillion, trillion, trillion, trillion, billion years, the massive black holes that once formed the centre of galaxies will evaporate. Yet there will still be plenty of matter and energy available to sustain whatever beings exist.
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