A millennium seems like a long time. Not as long as eternity. Woody Allen said, “Eternity is a very long time. Especially the bit towards the end.” Eternity is difficult to define while one thousand years seems clear enough. It is one thousand trips around the sun. One thousand years becomes colossal in terms of a human biological cycle, it is more than one hundred lives and one hundred human generations. It is around thirty billion seconds as measured by a very accurate hypothetical clock. Even if we couldn't build a watch sturdy enough to be trusted for thirty billion seconds, our own earth acts like a mechanism in a giant timepiece, sweeping out entire years on a complex clock with a solar system face. The hands move along the earth's orbit as reliable as Kepler. Instead of seconds or minutes, multiple planetary arms trace Martian years, Jovian years and the many natural periods of the planets' many moons map out lunar cycles. Our solar timepiece will easily execute one thousand more years, even a billion years. And so we think we know what one thousand years adds up to – a very long time.
I know that Longplayer is set to play for this very long time, but I become increasingly unsure of what time is, let alone accumulated units of it. In the history of time, time itself was most secure in Newton’s incarnation as an absolute of nature. Time wasn't mysterious, it just was. Infallible. Lording over change. Tireless. But then Einstein brought us relativity and time was severely demoted from absolute status to a mere relative reading on clocks. Since Einstein, the future of time has become even more precarious. Quantum mechanics may discard time altogether as a mere illusion of perception.
In Newton's world at least we could be reassured that time is one of nature’s unquestioned absolutes. Time is another dimension. I can tell you where I am in three spatial dimensions – the fourth floor in a London studio – but you won’t be able to find me here unless I tell you the location in time – this millennium, or the next. Time churns relentlessly forward, carrying us and the entire universe along in its indomitable current. Only the present exists, the past disappears instantly, evaporates into no more than a memory. A Newtonian absolute time ensures that the universe ages even if there is no one there to take note. Time moves at its steady pace regardless of whether there is anyone or anything to participate in its flow.
Einstein discovered relativity and with it revealed that Newtonian time was a charlatan. Time is not absolute. Time is nothing more than the sequence of events recorded on a mechanical clock or the disintegration of age as recorded by a biological clock. All measures of time are relative, can disagree, and can all be right.
Einstein discovered that time can dilate for observers in relative motion. If I float through empty space, clutching a clock to reassure me that I exist, I can watch time pass, the relentless ticking marking out breath and life. But if someone else races by clutching a clock, a reassurance of his existence, it would appear to me that his clock ran slowly. If he was moving at nearly the speed of light, he would appear to move slowly, talk slowly, even age slowly, like a broken movie projection. But from his perspective, he was the one motionless in space when I whizzed by. To him it would appear that my clock ran slowly, that my motor skills dragged, that I aged slowly. There would be no frame of reference to contradict either of us. We'd both be right. Our measures of time would be completely relative.
A black hole within view would give a frame of reference. We could be certain which one of was motionless relative to the black hole and which one was falling in. The black hole, a dark and dense corpse of a collapsed star, bends space so aggressively that all matter and energy that veer close to its dark horizon are fated to disappear into a massive warp in space. In Einstein’s theory of such curved spaces, General Relativity, the plot in the story of the relativity of time thickens. Time contorts in curved space. We could stay safely far from the black hole where space would almost seem flat and we would feel no funny distortions in space. But the clocks of the lone space walker we saw pass by earlier would dilate more and more as he fell towards the black hole. It would appear to take him an infinite time to reach his dark fate on the other side of the black hole horizon. At least to us the plunge would appear to take an eternity. And in this case it would be true that the bit towards the end was really a very long time. But to him the plunge would happen quickly and he’d meet his end in short order.
The relativity of time begins to erode our faith. If time is malleable, so unreliable, is it conceivable that it does not exist at all? As someone scrawled in a public loo in Texas, “Time is what keeps everything from happening at once”. Is that all?
Even the word watch betrays an intuition that there is no time without the watchers. Floating in empty space, in the absence of watchers, of planets orbiting suns or clocks ticking or bodies aging, there is no time. There is no meaning to the question, how long did an empty universe exist? An instant? An eternity? There is no meaningful difference between an instant and eternity. It is not just that there is no way to ascertain how long an empty, eventless cosmos existed. It is more that time has no meaning in an empty, eventless cosmos. Time is change. It is the relation between two events, a differential, an increase in disorder. Without change there is no time.
And now time’s future is truly endangered. In the wake of a quantum theory of gravitation, time may one day be declared altogether dead. Theorists devising a theory of quantum gravity, the ultimate and evasive fusion of Einstein’s relativity and quantum theory, may come down from their mountain and declare, time is dead, just as Nietzche’s Zarathustra declared, God is dead. Or as Julian Barbour insists, modern physics has precipitated an End of Time. Even the great logician Goedel, who believed that numbers and perfect Platonic shapes had concrete objective existence, doubted the existence of time. Time is under threat because it may just be a consequence of perception and of consciousness.
Consciousness also emerges from changes. There would be no consciousness without thoughts which are ultimately events – the firing of a neuron, the absorption of chemicals. Thoughts, whether or not they can be reduced to biology, are at the least mirrored in changes in brain chemistry. If changes are frozen so that no neurons fire and no chemicals are absorbed, then consciousness will also be frozen. We can only perceive changes and the sequence of changes we perceive creates a sense of time.
We can observe the flow of time demonstrated by a flower blooming, withering, and then rotting. This seems to be an irrefutable physical demonstration that time flows forward independent of consciousness. However what if it was physically possible for a flower to rot, then wither, then bloom, and finally shrink back into a seed? These stages could exist as a sequence of states. The states could be linked by degrees of entropy – a measure of disorder. Suppose the seed is the most ordered and therefore has the lowest entropy. Then as the flower burgeons and finally decays the atoms become more disordered and the entropy increases. Maybe these states exist in a timeless sequence ordered by their degree of disorder. There is no time. Time is dead. But the brain and consciousness, even if it’s a cat’s consciousness, can only perceive changes and therefore can only perceive events as a transition from one state, say a seed, to another state, a flower. Consciousness must take the path of least resistance. Water rolls down hills not up them. The path of least resistance is to flow from one state to a state of nearly the same, but slightly larger entropy. This is just like a rivulet of water flowing one inch at a time down a lumpy hill. It will always move down to a location of lower and lower energy. A stream does not suddenly and unexpectedly charge up a rock face. The entire rock continues to exist, although the trail of water picks out only one line along that hillside. Similarly we can only move through a sequence of events that are ordered so that entropy increases. The entire rock face of possible events always exists, but the trail of consciousness selects only one path along that hillside, so to speak. The past does not evaporate, the future does not just materialize. Present, past and future are mere artefacts of perception.
To be redundant, physical reality could imaginably be an infinite set of possible events, a space of possibilities, and yet we can only perceive a given path through this space. That path is driven tirelessly in the direction of change because change is all that we can perceive.
I can move forwards and backwards in space. Why can’t I move forwards and backwards in time? Why can’t I listen to Longplayer for a few years and then move through time backwards to hear it in reverse? In other words, why can't we perceive change the other way around? We can watch a movie of a boy develop through adulthood and on into old age. But our intuition tells us that if the old man grows young, the movie must be running backwards. Still we are able to watch the movie. If it was physically possible for the old man to grow young, why couldn’t we watch that? The reason may be the same reason that we can't traverse huge regions of space instantaneously. Frighteningly, microscopic quantum particles can traverse extremely small regions of space instantaneously. Quantum particles can be here and simultaneously there. An electron can exist on one side of the nucleus and rematerialize on the other side without ever crossing the space in between. These violations of locality are extremely small quantum leaps and amount to a very small infraction of the energy budget. However, we can’t instantly rematerialize in China if we started in Rome. Although quantum mechanics says it’s possible, it becomes oppressively unlikely if the distance is large and the energy violation is huge. The distance over which quantum particles make their quantum leaps must be small. The two states in question have to be energetically close so as not to be too costly a bending of the world order.
While it might be physically possible for the old man to grow young, maybe it is just formidably improbable. The entropic leap is too vast for consciousness to perceive a connection. We can make minor leaps but not colossal ones across the space of states, that is, the collection of all physically possible events. Why are some things closer in the space of states? Because the space of states is distributed according to entropy and states with nearly the same entropy are in a sense nearby. To instantaneously skip from one entropy state to one with a very much lower entropy would be effectively impossible to perceive. Just as it costs energy for a waterfall to reverse course, it is in a sense costly to go in the wrong entropic direction. Maybe. Anyway, it’s a possible interpretation of the world and it certainly seems an incredibly intriguing story.
Still this space of all possible events admittedly has me a bit confused. In what sense does it really exist? Is it laden with the infinite number of possible physical permutations? Blue flowers, green flowers, plaid flowers. Neither rotting nor growing but co-existing in every possible state of growth and decay. Have we rid the world of determinism that causally links events through time? And if we don’t have determinism any more, what determines which events are or are not physically possible? The old history of time began with a big bang that creates a cosmos in which matter organizes into galaxies, in which stars create carbon, out of which organic material comes to life and dies and more stuff comes to life, some of which feels self-aware and conscious. This whole story of genesis and cosmology and life is based on a causal and determined history throughout time. What happens to this story if time is dead? It makes it even harder to determine why we are here at all. Why this sequence of possibilities? Forget the tree falling in the forest. If there is no one in the cosmos, does it get any older? But my confusion is temporary (`temporal’, an unavoidable reference to time). This is a largely new paradigm to adopt and to formulate. I will allow myself to alternate between feeling resistant and feeling inspired. I am still a bit awed by the potential of the new implications.
I’ll have to learn the rules of this new game. It’s really the rules we’re trying to uncover. For each set of rules we overthrow, we put others in their place. Maybe time is not an absolute of nature and the direction of entropy increase is a better guide. Still we’re not just spinning our wheels. We are making progress in theoretical physics. We never go back to the old ways once the new ways demonstrate their power.
So time might not really exist at all. It is only that the path we can perceive flows in the direction of least resistance and we define the arrow and the duration of this path to be time. Then it gets even more confusing. In quantum theory the observer somehow seems to participate in forming reality. The electron, before it is observed, seems to be in more than one place. It can be on both sides of the nucleus simultaneously and not until it is observed does the electron assume a definite and unambiguous location. Somehow the observer forces one reality to precipitate out of many. Along with this unnerving state of affairs came the many-worlds interpretation. The many-worlds interpretation, an addendum to quantum theory, conjectures that there are many-worlds, that is, many co-existing universes. In one of these universes, for instance, the electron is on one side of the nucleus and in another universe, the electron is on the other side of the nucleus. At the juncture when the observer measures the position of the electron and forces it to occupy one and only one location, a branch off into one universe has been selected instead of a branch of into the other. Maybe in one universe Longplayer plays for one thousand years but in another civilization breaks down along with its machines and Longplayer is silenced. The many-worlds interpretation of quantum mechanics remains the strongest philosophical approach to physics on microscopic scales, though in a sense the interpretation is not necessary. We can use quantum theory to make accurate predictions, build particle accelerators, even design a quantum computer without ever resolving the philosophical issues – in a sense without ever understanding our own theory.
In any case, many-worlds may be the only way to interpret quantum mechanics and interestingly the only way to give at least a plausibility argument for free will. While Newton idealized time, his pure determinism annihilated free will. If there is pure determinism, there can be no free will. We are just pinballs battered about in a confoundingly intricate game that is entirely and completely determined by the initial slap of the paddle. Or quantum mechanics has introduced random chance and chance is not choice. Or there is God and faith and supraphysical souls in which case I am way out of my depth. However, if there is neither chance nor determinism, but merely a set of infinite possibilities and consciousness selects paths through the sequence of events, there may be room for free will. While we can only move forward in time, each conscious entity may be able to choose at each fork in the road at which the many-worlds cross, which road to take. While our choices, poor or rich, will accumulate into the lives we lead, we might find some solace in the possibility that there is another world where our choices, and our lives, are different. I’m not claiming this in any way is a resolved argument for free will, just an argument that free will might at least be plausible.
But what if time machines could be built and we could go back in time? Theoretically, on paper, time machines are possible. In the context of Einstein’s theory of curved spacetime, we could warp both space and time to connect the future smoothly to the past. If you could go back in time and meet yourself at a younger age, you might commit a retrograde suicide, murdering your adolescent self, who you undoubtedly find an embarrassment, and thereby wipe out your entire adulthood which leads to the paradox: if you never reached adulthood, you could never have gone back and committed retrograde suicide. Paradoxes are loathed in theoretical physics. They are hardly a good underpinning for coherence and predictability and indicate the failure of ideas.
You could avoid the paradox and still go back in time as long as you promised not to kill your younger self, and as long as you promised to abstain from a possibly very long list of other actions. This is not just a good-faith agreement with the cosmos. It is physically paradoxical for you to go back in time unless you adhere to these rules – which is confusing since while you might thereby participate in a physically allowed, completely self-contained and self-consistent history you are not a free participant. You are limited in how much free will you could possible demonstrate.
But maybe taking something with that much complexity back in time is too hard. Maybe paths that go backwards, fighting the direction of entropy increase, will not remain organized and ordered into a sentient being, so that only little pieces could go back in time but not a whole person. Since free will requires consciousness which is defined by a certain amount of complexity, maybe a semi-coherent sentient being cannot survive time travel and therefore free will cannot survive time travel.
So where does this leave us? We create time. It does not exist without us. But we can’t fight our own creation. We pick flowers and they decay. We are born and we age and always in that order. Longplayer began at the dawn of the new millennium and will not be heard in 1960 but with our support might be heard in the future, and only in the future.
We cannot resist this illusion of our perception. And so for all intents and purposes we carry on as though time is alive and well. We live and perceive finite intervals of time. Shorter than eternity but longer than never. No thing can exist infinitesimally thin in time. A song so short it has no extension in time defies it's own existence. A song has to have some duration. The notes are written linearly on a page indicating one must follow the other and they are not all to be played at once. But why a minute or an hour? Andy Warhol played with our attention spans and the natural duration of a movie by filming a sleeping friend in real time. Even if you have the patience to tune in to eight hours of peaceful sleep punctuated by an occasional rustle of the toes, maybe if your lucky, a toss or turn, no one could watch a movie that lasted a human lifetime, let alone one that lasted a millennium. A song so long it exceeds the lifetime of the sun has little hope of being heard, or played for that matter. As long as it is, Longplayer falls between the two, between a human lifetime and a solar lifetime. It is longer than one human lifetime but relies on an optimism that it will not be beyond the lifetime of our species. In this way, Longplayer relies on a collective human memory.
None of us will hear Longplayer. Not Jem, not Jem's children. Unless our technology became more advanced and I could travel at 99.995 times the speed of light out of our solar system for a distance of hundreds of light years and return to find Longplayer had played for its one thousand years. Civilizations might have come and gone but I'd be only ten years older. In my spaceship my clocks would run slowly, including my biological clock. My thought processes would slow, but only relative to clocks on earth since there's no absolute meaning or measure of time. In my rocketship, life would pass at its usual pace. There'd be nothing special or peculiar about the ticking of my instruments or the breakdown of my cells. My decade of solitude would have its burdens but it would elapse in concert with one thousand earth years. If Longplayer was designed to send out its song to my spaceship note by note according to its score, I would have heard the entire song by the time I got back to my ancient home. I would have heard in a handful of human years what took one thousand years to beacon into space. But I would receive the song parsed out in unexpected rhythms, modulated by our relative motion, given a cadence Jem did not intend. To hear Longplayer as Jem intended we have to remain here on earth and live and die before it's over. To hear Longplayer as it was composed, we can never hear it. It is a musical score but can never really be a song, like a genetic code that can never be actualised into a person. Music relies on memory to create a sense of how the notes resonate and to allow an impression to emerge from the accumulated sounds and silences. Longplayer exceeds the memory of any one person and probably the memory of any one civilization and possibly the memory of an entire species.
Underlying the hope to maintain Longplayer is the hope to maintain the species. The Clock of the Long Now, designed by Danny Hillis to last ten thousand years, shares a similar implicit hopefulness. A prototype of a mechanical timepiece designed to last many millennia, it requires human involvement and maintenance. It requires human survival. The clock aims to span roughly the same interval of time since the last ice age and thereby force us to think on time scales of civilizations. Encoded with a musical score, a Longplayer machine is also a clock. If a mechanism is built to maintain the music it will be a lighthouse flashing into the future, hopeful someone will see it and hear it in pieces like the capsules that contain little snippets of the last few hundred years that we have naively launched into space with childlike optimism that there could be sentient beings out there somewhere at the same time as us. Instead of a mechanical object, maybe Longplayer should be passed on by word of mouth as a chant, a myth. Then we all become mechanisms in an organic watch. As one mechanism wears down and dies, it is replaced by another. Then as long as Longplayer survives, so do we. As long as we survive, so does time.
© JANNA LEVIN 2003
This essay originally appeared in the book Longplayer (Artangel, London, 2003), available from the bookshop page.
Janna Levin is a Professor of Physics and Astronomy at Barnard College of Columbia University. Her scientific research concerns the Early Universe, Chaos, and Black Holes. Her second book – a novel, A Madman Dreams of Turing Machines (Knopf, 2006) – won the PEN/Bingham Fellowship for Writers that "honors an exceptionally talented fiction writer whose debut work…represents distinguished literary achievement…" It was also a runner-up for the PEN/Hemingway award for "a distinguished book of first fiction". She is the author of the popular science book, How the Universe Got Its Spots: diary of a finite time in a finite space.
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