Last Things: Cold Comfort in the Far Future

Published by Gregory Benford on September 24th, 2014

Illustrated by Andrew Probert
. . . the use, however haltingly, of our imaginations upon the possibilities of the future is a valuable spiritual exercise.
—J. B. S. Haldane, 1923

How did it all begin?
This is a very old obsession. Less often fretted over is the symmetric question: How will it all end?
Robert Frost’s famous imagery—fire or ice, take your pick—pretty much sums it up. But lately, largely unnoticed, a revolution has unwound in the thinking about such matters, in the hands of that most rarefied of tribes, the theoretical physicists. Maybe, just maybe, ice isn’t going to be the whole story.
Of course, linking the human prospect to cosmology itself is not at all new. The endings of stories are important, because we believe that how things turn out implies what they ultimately mean. This comes from being pointed toward the future, as any ambitious species must be.
There are three forms of chimpanzees: the common chimp, the bonobo, and us. We are the only chimp who got out of Africa. That experience reflects and probably laid down the deep human urge—indeed, our signature: the urge to restlessly move on, explore, exploit. Natural selection gives us a gut imperative that plays out physically and culturally, in pursuit of our goal: the expansion of human horizons.
On Earth, horizons worked for many millennia. But that time is over, the skies beckon—and it is natural to think in terms of our horizons in time. We have cosmology to aid us now, unlike people only a century ago. Most of us believe that physics can tell us more about our prospects than religion. Still, we do think long, and often with theological implications. The far future matters for very basic reasons.
Our yearning for connection explains many cultures’ ancestor worship: we enter into a sense of progression, expecting to be included eventually in the company. Deep within us lies a need for continuity of the human enterprise, perhaps to offset our own mortality. Deep time in its panoramas, both past and future, redeems this lack of meaning, rendering the human prospect again large and portentous.
We gain stature alongside such enormities. But this flattering perspective sets an ultimate question: will a time come when humanity itself will not be remembered, our works lost and gone for nothing?
Of course, sf has always looked long, from Wells’ dying crab on a red beach, and onward. Freeman Dyson suggested that spheres around stars could be technology’s distant goal, and inspired many sf novels—but such ideas only worked as long as stars burned, which means about 100 billion years. One could look longer, and some did. In this spirit I edited Far Futures in 1995, looking at the long view. Two of the five novella authors therein have died—Poul Anderson and Charles Sheffield; alas, mortality vs. the abyss. There are myriad other literary examples of writers and scientists confronting a truly ultimate question—of Last Things.
* * *
A major change in our ideas of cosmology occurred only ten years ago, with the discovery that the expansion of our universe is accelerating. To reach such an astonishing conclusion demanded new measurements of supernova brightness in far-away galaxies, meanwhile eliminating many possible sources of error, combined with precise calibrations of their distances. Together, these showed that the further away, the faster others were fleeing from us, and us from them, as we share a quickening expansion.
This acceleration overthrows half a century of conventional wisdom. For eighty years, ever since Einstein began modern cosmology, we thought that deceleration held sway. Gravitation would slow the swelling that began with the Big Bang. Around 1950 it even seemed that the universe might cease expanding and implode into a final crunch, and that perhaps this had happened before.
This finding, that space-time is opening ever-faster, relies upon a fairly tricky measurements. It is not easy to study whether the momentary luminosities of supernovas, in very distant galaxies, fit a pattern. It remains to be extensively checked, but for the moment suppose we take it as given.

Ancient Ideas

Acceleration implies an ever-bigger cosmos. Some feel repulsed by the entire notion. Cyclic universes have great appeal, as every public lecturer on cosmology knows from the audience questions. Evolution may have geared us to expect cycles; the seasons deeply embedded this in our ancestors. The ancient Hindu system embraces it especially, holding that we are already uncountably far into the oscillations, and the universe is unknowably old.
Love of cyclic universes may come from a deep unease with linear time, one that predates our modern ideas. At least the periodic supplies some rhythm, a pattern, rolling hills rather than just a flat plain stretching to infinity.
This feeling finds an echo in other common audience questions. Doesn’t all this have a purpose, an end? Does the drama go on forever, really?
But then, genuinely endless repetition also seems to revolt most of the cyclic devotees—they still want to avoid the abyss of infinite time. The Hindu time scale is immeasurably long but not infinite.
Aristotle was an exception. He thought there had been an infinite number of generations, since there had been no beginning. He believed that despite some ups and downs, by and large things stayed on average the same, throughout all time. There were no changes of natural kinds of species or or in nature’s overall arrangement, or of the basic options in life. So even though the universe is eternal, it stays familiar. Aristotle felt that this made studying nature have a point. Nature provides regularities and we can know them, so science is at least possible.
Aristotle was a man of the West. Not all faiths worry about time. Confucian and Taoist beliefs do not comment or care about how the universe began or will end. Chinese thought does spend a lot of energy on history and on the memory of the great ages in the past. There is much concern with social beginnings and endings, golden ages and collapses. But even very long stories have a beginning and end.
For these faiths there is no far-off divine comeuppance, “to which the whole Creation moves,” as Tennyson put it. As the Bhagavad Gita says, “There never was a time when I was not… there will never be a time when I will cease to be.” Since time and space together began creation (as both Saint Augustine and the Big Bang attest) the Bhagavad Gita has a point. The chicken and the egg arrived at the same time.
The Abrahamic faiths “of the book”—Jews, Christians and Islamites alike—envision linear, not cyclic time. This reflects a big conceptual shift from the unchanging atmosphere of the far ancient world, when little changed. Indeed, modern science needs the possibility of change, because Newtonian forces do not have to return everything to the status quo.
Christian scripture says that this is a suffering world, addicted to attachment, to be ultimately transcended. The far future then lies beyond that goal. God’s agenda is then rigorous—creation, fall, incarnation, redemption, final judgment, then the ultimate fate, Last Things. But how far can this sequence go? Forever?
Newton founded his mechanics on the linear flow of time, inventing his “theory of fluxions” (differential calculus). But his cosmology is static, eternal, shadowed by the ever-threatening catastrophe of gravitational collapse. Given enough time, this fate would come through stars colliding and coalescing. This fate prefigures the black hole disaster, when mass colludes to escape our space-time entirely by collapsing to a singular point.
This, Newton thought, could be avoided by occasional divine intervention, as needed—a fixup universe.
As for the beginning, Christian theists seem most comfortable with the Big Bang, since it says Creation is a fact. Saint Augustine’s doctrine that God made both space and time ex nihilo was never supposed to carry great weight as the crucial moment in all time; it was just a beginning, not the whole point of the matter.
When Aristotelian science became widely known, the medievals thought of that first moment as the establishment of the Aristotelian average sameness, as far as nature was concerned. There might be a social linear narrative, but no natural one.
Aristotle does have an argument that time cannot have a beginning or an end. Changes happen for Aristotle when the appropriate items are in the right situation—the pot on the fire, the seed in the ground, and so on. If a purported first change happens, suddenly, in a universe that was previously unchanging, then there had to have been a still earlier change that brought the items for the supposed first change together. Otherwise it would already have happened. But that new first change is subject to the same argument, so there cannot be a true first change. An analogous argument shows that any supposed last change must be followed by a further change, that then disposes things so that they won’t be in a position to change further. But that change needs a later shoring up, etc.
It’s a good argument. But Aquinas then claimed that it doesn’t consider creation, which is not strictly speaking a change, just a beginning, a coming into being of the whole. This allows for a Creation finite in time.
But little rigor got invested in the eventual fate of our universe. That became the domain of modern science. Many are horrified by a universe that lasts only a finite time, ending in cold or heat. Even placing the event in the very far future, long after our personal deaths, carries the heavy freight of making what we do now meaningless, because it does not last. Recall the scene in Annie Hall when young Woody Allen refuses to do his homework because the universe is going to end anyway.
Will Shakespeare endure literally forever? As Bertrand Russell put it in Why I am Not a Christian,
All the labours of the ages, all the devotion, all the inspiration, all the noonday brightness of human genius are destined to extinction in the vast heat death of the solar system, and… the whole temple of man’s achievement must inevitably be buried beneath the debris of a universe in ruins.
So Russell doesn’t believe in God because nothing lasts. At first this seems an odd argument, but it goes to our deep questions. If nothing lasts, what is our purpose?
Some fervent believers attack the second law of thermodynamics (the heat death) for exactly this reason. Ironically, these Christians join company with atheist Friedrich Engels, who disliked entropy because it would destroy historical progress in the long run.
Suppose we could create a heaven on Earth, or at least somewhere. Permanent, unchanging paradise seems boring to many, at least if it means mere joyful indolence. Is perpetual novelty even possible, though? Can we think an infinite variety of thoughts?
Christian theology solved this dilemma by putting God outside time, so that holy eternity was not infinite duration but rather not time at all. This belief is long-standing, but it need not stay in fashion forever. Faiths may arise which long for the heat death, or embrace the (apparently not coming) big crunch—cosmological cheerleaders for cleansing ends.
Theology has responded to cosmology, but the pace of discussion is now quickening so much that the connections between the two need fresh thought. Luckily, this is now coming mostly from the cosmologists themselves.
* * *.
In 1979 the celebrated Princeton physicist Freeman Dyson brought this entire issue to center stage for physicists and astronomers. He already had his prejudices: he wouldn’t countenance the Big Crunch option because it gave him “a feeling of claustrophobia.” Still, must all our revelries end? Science, he thought, might be able to settle whether a Last Day is ever going to arrive.
He knew of the threads in theological thinking. When I discussed these matters with him in the 1970s, he knew that theology faced a paradox. We seem to harbor twin desires—purpose and novelty, progress and eternity alike.
When physicists ask questions, they do a calculation to clarify matters. He discussed the prognosis for intelligent life. Even after stars have died, he asked, can life survive forever without intellectual burn-out?
Energy reserves will be finite, and at first sight this might seem to be a basic restriction. But he showed that this constraint was actually not fatal. He looked beyond times when any stars would have tunnelled into black holes, which would then evaporate in a time that will be, in comparison, almost instantaneous. As J.D. Bernal foresaw in The World, the Flesh, and the Devil (1929):
…consciousness itself may end… becoming masses of atoms in space communicating by radiation, and ultimately resolving itself entirely into light… these beings… each utilizing the bare minimum of energy… spreading themselves over immense areas and periods of time… the scene of life would be… the cold emptiness of space.
Dyson’s answer was positive. He thought that by hibernating, life could endure eternally. But in the decades since Dyson’s article appeared, our perspective has changed in two ways, and both make the outlook more dismal.
First, most physicists now strongly suspect that atoms don’t live forever. The basic building block, the proton, will decay into lesser particles. White dwarfs and neutron stars will erode away in about 1036 years, sputtering into wan energies and small sprays of electrons and positrons. The heat generated by particle decay will make each star glow, but only as dimly as a domestic heater—no real help against the pervasive cold.
Dyson originally assumed matter would last for eternity. Though the proton lifetime remains unmeasured, current particle theory predicts protons should decay in about 1034 years.
Our universe is about 15 billion years old, or a little over 1010 years. In principle, everybody agrees that despite the steady cooling, order could persist even up to 1034 years. Here we speak of unimaginably long times—except that science fiction writers, and now physicists, have imagined them, guided by the gliding calculus of theoretical physics. But writing down numbers is a dry way of gaining what we really mean by imagining, i.e., having a gut feeling. Still, calculation is all we have to go on.
After protons fade away, say 1034 years, our Local Group of galaxies will be just a swarm of dark matter, electrons and positrons. Thoughts and memories could survive beyond the first 1036 years, if downloaded into complicated circuits and magnetic fields in clouds of electrons and positrons—maybe something that would resemble the threatening alien intelligence in The Black Cloud, the first and most imaginative of astronomer Fred Hoyle’s novels, written in the 1950s.
“An austere mode of existence,” Dyson felt. And with classic understatement, “…even if this assumption is wrong, it is certainly good for the next 1034 years, long enough for life to study the situation carefully.”
The second bit of bad news is that the accelerating expansion means the universe cools even faster. There is less time to avert the cold, and less room, too.
Why less? Characteristically, Dyson was optimistic about the potentiality of an expanding universe because there seemed to be no limit to the scale of artifacts that could eventually be built. He envisioned the observable universe getting ever vaster. Many galaxies, whose light hasn’t yet had time to reach us, would eventually come into view, and therefore within range of possible communication and “networking.” Interactions will matter. We could gain knowledge from distant bretheren, for use against the encroaching night.
But an accelerating expansion yields a more constricted long-term future. Galaxies will fade from view ever faster as they get more and more red-shifted—their clocks, as viewed by us, will seem to run slower and slower. Then they will seem to freeze at a definite instant, so that even though they never finally disappear we would see only a finite stretch of their future.
This is analogous to what happens if a cosmologist falls into a black hole: from a vantage point safely outside the hole, we would see our infalling colleague freeze at a particular time. We’ll have only a last snapshot, even though they experience, beyond the horizon, a future that is unobservable to us.
Well before 1034 years, our own Galaxy, its identical twin neighbor Andromeda, and the few dozen small satellite galaxies that are in the gravitational grip of one or other of them, will merge together into a single amorphous system of ageing stars and dark matter. Then the universe will look ever more like an “island system” (the kind of universe originally proposed by Laplace). In an accelerating universe, everything else disappears beyond our horizon. If the acceleration is fixed, this horizon never gets much further away than it is today.
So there’s a firm limit—though of course a colossally large one—to how large any network or artifact can ever become. This translates into a definite limit on how complex anything can get.
Still worse, one important recent development has been to quantify this limit. Space and time cannot be infinitely divided.
The inherent quantum “graininess” of space sets a limit to the intricacy that can be woven into a universe of fixed size. Life has to work within boundaries.
Even if the problem of limited energy reserves could be surmounted—a big order in itself, and the main issue Dyson addressed—there would be a limit to variety and complexity. The best hope of staving off boredom in such a universe would be to construct a time machine and, subjectively at least, exhaust all potentialities by repeatedly traversing a closed time-loop. This appears to be possible, within general relativity, but Dyson and others found it also claustrophobic.
There is other theoretical hope, too. It is a bit abstract, though. Kurt Godel’s famous theorem showed that mathematics contains inexhaustible novelty, i.e., true theorems that can’t be proved with what has come before. Only by expanding the conceptual system can they be shown to be true, in a larger view.
Most people would not turn to mathematics for a message of spiritual hope, but there it is.
* * *
As this darkened universe expands and cools, lower-energy quanta (or, equivalently, radiation at longer and longer wavelengths) can store or transmit information. Just as an infinite series can have a finite sum (for instance, 1 + 1/2 + 1/4 + …….. = 2), there is perhaps, in principle, no limit to the amount of information processing that could be achieved with a finite expenditure of energy. Any conceivable form of life would have to keep ever-cooler, think slowly, and hibernate for ever-longer periods.
But there would be time to think every thought, Dyson believed, even in the face of the heat death. As Woody Allen once said, “Eternity is very long, especially toward the end.”
Life that keeps its temperature fixed will not make it, though. It will eventually exhaust its energy store. The secret of survival will be to cool down as the universe cools. Being frugal means you could dole out in ever-smaller amounts the energy necessary to live and think.
Silicon or even dust could form the physical basis of such enduring life, at least until the protons decay. After that, there is no fundamental reason that information cannot be lodged in electron-positron plasmas, or even atoms made from them. “Positronium” is an “atom” of a positron, an anti-electron, orbiting with an electron, much like a hydrogen atom. In September, 2002, a European group succeeded in producing tens of thousands of them in a magnetic bottle, so they could conceivably be used to build solid structures of a wholly new sort.
No matter what the basis of life is, the crucial distinction for far-future thinkers is their method of storing information. In our computer-saturated world, using information defines life—active flow, not mere passive storage.
Life tends to be defined in terms of the reigning paradigm of the time, so in our computer age we make a crucial distinction. There are two choices: analog or digital.
Old fashioned LPs are analog; CDs are digital. Cosmologist Fred Hoyle’s ominous Black Cloud, imagined in a novel in the 1950s, was analog, storing its memories in magnetic fields and dust particles. A human mind uploaded into a computer would be digital life.
Are our brains analog or digital? We do not know, as yet. But this point became the battleground between Dyson and a bevy of physicists, including Larry Krauss of Case Western University. In The Physics of Star Trek Krauss tried to make sense of the mangled science in Trek. Many of his colleagues suspected his motives were less that of informing the masses than making money, and his challenge to Dyson had the quality of a young buck butting heads with an aging bull. The debate got rarefied right away, including lengthy calculations on the thermodynamics of ultracold, with quantum mechanics for dessert.
Our genetic information carried in DNA is clearly digital, coded in a four-letter alphabet. But the active information in our brains remains mysterious. Memories live in the strengths of synaptic connections between billions of neurons, but we do not fathom how these strengths are laid down or varied. Perhaps memory is partly digital and partly analog; there is no reason the methods cannot blend.
If we are partly analog, then perhaps the hope of the brain-downloading method will be only partly fulfilled, and some of our more fine-grade thoughts and feelings will not make it into a digital representation.
Actually, the analog/digital divide may not be the whole story. Some theorists think the brain may be a quantum computer, keeping information in quantized states of atoms. But since we know little about quantum computers beyond their mere possibility, the argument over in-principle methods has fastened upon analog vs. digital.
Interestingly, the long-term prospects of digital intelligences are not the same as analog forms. Krauss leaned heavily on a digital determinism, which shaded quickly into pessimism. Dyson stood his analog ground.
That there is any contest at all may surprise some, since we are so used to analog tools like slide rules giving way to digital ones like hand calculators. The essential difference is that analog methods deal with continuous variables while digital ones use discrete counting.
Surprisingly, analog wins, digital loses. It turns out that the laws of physics allow a thrifty, energy-hoarding information machine (life) to persist, but not a digital one.
The reasons are fairly arcane, involving the quantum theory of information storage. Still, one can think of a digital system as having rachets that, once kicked forward, cannot go back. As the universe cools, you eventually can’t kick the rachet far enough forward. But a smooth system can inch up as much as you like, storing memories in smaller and smaller increments of energy.
Life can use hibernation to extend its analog form indefinitely. Like bears, it can adapt to falling temperatures by sleeping for progressively longer cosmic naps. Awake, it spends its energy reserves at unsustainable levels. Asleep, it accumulates.
It turns out further that such life can communicate with other minds over the great distances between galaxies, too. Energy reserves can dwindle, but so does the noise background in the universe, as expansion cools the night sky.
Communication depends not on signal strength (energy) but on the ratio of signal to noise. A cold, expanding universe is friendly to the growth of intergalactic networks. Life will have ample time to wait for an answer from, say, the Andromeda galaxy, without worrying about being able to hear the reply.
But not all is well for analog life if the universe continues to accelerate forever. At some distance, the repulsive force that causes this acceleration must win out over gravity’s attraction. So galaxies further away than this critical distance will accelerate beyond view, setting the limit on the size of structures that life can build. This ultimately dooms it.
So to persist forever, life needs to be analog and the universe must not be accelerating forever. The first is an engineering requirement, and presumably savvy life forms will heed it. The second we can do nothing about, unless somehow life can alter the very cosmological nature of our universe—surely a tall order.
We do not yet know (and may not for quite a while) whether the acceleration will slow, because we do not know its cause. This is the biggest riddle in cosmology, and many are pursuing it. The Dyson-Krauss dispute rages still in the hallowed pages of Physical Review. Dyson’s own vaguely optimistic theology clashes with Krauss’s apparent atheism. They are reprising an ancient difference in tastes over the deepest issue: is there any discernible purpose to the universe? And does human action mean anything on this vast stage?
* * *
These long-range projections over zillions of years involve fascinating physics, most of which is quite well understood… but not all of it.
First, we can’t be absolutely sure that the regions beyond our present horizon are like the parts of the universe we see. Just as on the ocean, there could be something amazing just over the horizon.
Physicists John Barrow and Frank Tipler have pointed out that a new source of energy—so-called “shear-energy”—would become available if the universe expanded at different rates in different directions. This shearing of space-time itself could power the diaphanous electron-positron plasmas forever, if the imbalance in directions persists. To harness it, life (whatever its form) would have to build “engines” that worked on the expansion of the universe itself.
Such ideas imply huge structures the size of galaxies, yet thin and able to stretch, as the space-time they are immersed in swells faster along one axis than another. This motor would work like a set of elastic bands that stretch and release, as the universal expansion proceeds. Only very ambitious life that has mastered immense scales could thrive. They would seem like Gods to us.
As well, our universe could eventually be crushed by denser material not yet in view. Or the smoothing out of mass on large scales may not continue indefinitely. There could be a new range of structures, on scales far larger than the part of the universe that we have so far seen.
Physics can tell us nothing of these, as yet. These ideas will probably loom larger as we learn more about the destiny of all visible Creation.
Or… Even more fundamentally, maybe time itself is a hominid illusion, not fundamental at all. It might rather be an emergent property of some deeper structure to be revealed. Our human temporal anxiety would then be a passing fashion, not a feature of the universal destiny. This idea may be more sobering than even the cold comfort awaiting us “way up ahead.”
Finally, what can one infer from physics about theology?
It is tempting to suppose that a God who made such a universe might, as narrative-addicted humans do, think that the end of a story tells its meaning. If all order is to be leached away by eternal cold, what did the building of such structure by intelligence amount to? Put differently, what is the meaning of human action?
Perhaps nothing, if the fate of all order is mere ruin. If it is not, and Dyson proves right, we might turn to another Dyson idea: that the universe has been designed to be the most interesting possible. This means that variations arise and abound, then evolve and finally aspire to greater heights.
So in the end our choice of endings implies a choice of the Designer behind it all.
One wonders if, once the theoretical physics is settled, the outcome will provoke fresh theological thinking. If intelligence can persist forever in principle, will this result be used in a new form of the Argument from Design?
Conversely, if life cannot survive, will atheists make this into an argument for no God, or for a God with a perverse (to us) purpose?
Either way, the debate will be made more interesting by the injection of a new set of physical facts. Science fiction’s role is to explore the human implications. Hot topics like the possibility of other dimensions in which different universes dwell (“branes” for membranes; not a great scientific shorthand) will be experimentally checkable within perhaps five to ten years.
Such exotic notions will provoke much fiction—already has, in my Beyond Infinity. The accelerating expansion might itself accelerate, leading to the “big rip” which shreds atoms, erasing all information—truly a horrifying prospect, if you think Shakespeare’s works should live forever. Surely this is a grand, Wagnerian struggle worthy of life in the far future.
So I end by quoting James Gunn: “Fiction, I think, is humanity’s way of seeking justice in an uncaring universe.”
* * *

Big Universe

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