Axiomatic

by Greg Egan

  She laughed. ‘No. But I don’t tell myself everything. I like to be surprised now and then. Don’t you?’

  Her casual attitude stung me. Never lets herself be distracted by trivia. I struggled for words; this whole conversation was unknown to me, and I never was much good at improvising anything but small talk.

  I said, ‘Today is important to me. I always thought I’d write the most careful—the most complete—account of it possible. I mean, I’m going to record the time we met, to the second. I can’t imagine sitting down tonight and not even mentioning the first time we kissed.’

  She squeezed my hand, then moved close to me and whispered, mock-conspiratorially: ‘But you will. You know you will. And so will I. You know exactly what you’re going to write, and exactly what you’re going to leave out—and the fact is, that kiss is going to remain our little secret.’

  * * *

  Francis Chen wasn’t the first astronomer to hunt for time-reversed galaxies, but he was the first to do so from space. He swept the sky with a small instrument in a junk-scattered near-Earth orbit, long after all serious work had shifted to the (relatively) unpolluted vacuum on the far side of the moon. For decades, certain—highly speculative—cosmological theories had suggested that it might be possible to catch glimpses of the universe’s future phase of re-contraction, during which—perhaps—all the arrows of time would be reversed.

  Chen charged up a light detector to saturation, and searched for a region of the sky which would unexpose it—discharging the pixels in the form of a recognisable image. The photons from ordinary galaxies, collected by ordinary telescopes, left their mark as patterns of charge on arrays of electro-optical polymer; a time-reversed galaxy would require instead that the detector lose charge, emitting photons which would leave the telescope on a long journey into the future universe, to be absorbed by stars tens of billions of years hence, contributing an infinitesimal nudge to drive their nuclear processes from extinction back towards birth.

  Chen’s announcement of success was met with virtually unanimous scepticism—and rightly so, since he refused to divulge the coordinates of his discovery. I’ve seen the recording of his one and only press conference.

  ‘What would happen if you pointed an uncharged detector at this thing?’ asked one puzzled journalist.

  ‘You can’t.’

  ‘What do you mean, you can’t?’

  ‘Suppose you point a detector at an ordinary light source. Unless the detector’s not working, it will end up charged. It’s no use declaring: I am going to expose this detector to light, and it will end up uncharged. That’s ludicrous; it simply won’t happen.’

  ‘Yes, but—’

  ‘Now time-reverse the whole situation. If you’re going to point a detector at a time-reversed light source, it will be charged beforehand.’

  ‘But if you discharge the whole thing thoroughly, before exposing it, and then…’

  ‘I’m sorry. You won’t. You can’t.’

  Shortly afterwards, Chen retired into self-imposed obscurity—but his work had been government funded, and he’d complied with the rigorous auditing requirements, so copies of all his notes existed in various archives. It was almost five years before anyone bothered to exhume them—new theoretical work having made his claims more fashionable—but once the coordinates were finally made public, it took only days for a dozen groups to confirm the original results.

  Most of the astronomers involved dropped the matter there and then—but three people pressed on, to the logical conclusion:

  Suppose an asteroid, a few hundred billion kilometres away, happened to block the line of sight between Earth and Chen’s galaxy. In the galaxy’s time frame, there’d be a delay of half an hour or so before this occultation could be seen in near-Earth orbit—before the last photons to make it past the asteroid arrived. Our time frame runs the other way, though; for us, the ‘delay’ would be negative. We might think of the detector, not the galaxy, as the source of the photons—but it would still have to stop emitting them half an hour before the asteroid crossed the line of sight, in order to emit them only when they’d have a clear path all the way to their destination. Cause and effect; the detector has to have a reason to lose charge and emit photons—even if that reason lies in the future.

  Replace the uncontrollable—and unlikely—asteroid with a simple electronic shutter. Fold up the line of sight with mirrors, shrinking the experiment down to more manageable dimensions—and allowing you to place the shutter and detector virtually side by side. Flash a torch at yourself in a mirror, and you get a signal from the past; do the same with the light from Chen’s galaxy, and the signal comes from the future.

  Hazzard, Capaldi and Wu arranged a pair of space-borne mirrors, a few thousand kilometres apart. With multiple reflections, they achieved an optical path length of over two light seconds. At one end of this ‘delay’ they placed a telescope, aimed at Chen’s galaxy; at the other end they placed a detector. (‘The other end’ optically speaking—physically, it was housed in the very same satellite as the telescope.) In their first experiments, the telescope was fitted with a shutter triggered by the ‘unpredictable’ decay of a small sample of a radioactive isotope.

  The sequence of the shutter’s opening and closing and the detector’s rate of discharge were logged by a computer. The two sets of data were compared—and the patterns, unsurprisingly, matched. Except, of course, that the detector began discharging two seconds before the shutter opened, and ceased discharging two seconds before it closed.

  So, they replaced the isotope trigger with a manual control, and took turns trying to change the immutable future.

  Hazzard said, in an interview several months later: ‘At first, it seemed like some kind of perverse reaction-time test: instead of having to hit the green button when the green light came on, you had to try to hit the red button, and vice versa. And at first, I really believed I was “obeying” the signal only because I couldn’t discipline my reflexes to do anything so “difficult” as contradicting it. In retrospect, I know that was a rationalisation, but I was quite convinced at the time. So I had the computer swap the conventions—and of course, that didn’t help. Whenever the display said I was going to open the shutter—however it expressed that fact—I opened it.’

  ‘And how did that make you feel? Soulless? Robotic? A prisoner to fate?’

  ‘No. At first, just… clumsy. Uncoordinated. So clumsy I couldn’t hit the wrong button, no matter how hard I tried. And then, after a while, the whole thing began to seem perfectly… normal. I wasn’t being “forced” to open the shutter; I was opening it precisely when I felt like opening it, and observing the consequences—observing them before the event, yes, but that hardly seemed important any more. Wanting to “not open” it when I already knew that I would seemed as absurd as wanting to change something in the past that I already knew had happened. Does not being able to rewrite history make you feel “soulless”?’

  ‘No.’

  ‘This was exactly the same.’

  Extending the device’s range was easy; by having the detector itself trigger the shutter in a feedback loop, two seconds could become four seconds, four hours, or four days. Or four centuries—in theory. The real problem was bandwidth; simply blocking off the view of Chen’s galaxy, or not, coded only a single bit of information, and the shutter couldn’t be strobed at too high a rate, since the detector took almost half a second to lose enough charge to unequivocally signal a future exposure.

  Bandwidth is still a problem, although the current generation of Hazzard Machines have path lengths of a hundred light years, and detectors made up of millions of pixels, each one sensitive enough to be modulated at megabaud rates. Governments and large corporations use most of this vast capacity, for purposes that remain obscure—and still they’re desperate for more.

  As a birthright, though, everyone on the planet is granted one hundred and twenty-eight bytes a day. With the most efficient data-compression sche
mes, this can code about a hundred words of text; not enough to describe the future in microscopic detail, but enough for a summary of the day’s events.

  A hundred words a day; three million words in a lifetime. The last entry in my own diary was received in 2032, eighteen years before my birth, one hundred years before my death. The history of the next millennium is taught in schools: the end of famine and disease, the end of nationalism and genocide, the end of poverty, bigotry and superstition. There are glorious times ahead.

  If our descendants are telling the truth.

  * * *

  The wedding was, mostly, just as I’d known it would be. The best man, Pria, had his arm in a sling from a mugging in the early hours of the morning—we’d laughed over that when we’d first met, in high school, a decade before.

  ‘But what if I stay out of that alley?’ he’d joked.

  ‘Then I’ll have to break it for you, won’t I? You’re not shunting my wedding day!’

  Shunting was a fantasy for children, the subject of juvenile schlock-ROMs. Shunting was what happened when you grimaced and sweated and gritted your teeth and absolutely refused to participate in something unpleasant that you knew was going to happen. In the ROMs, the offending future was magicked away into a parallel universe, by sheer mental discipline and the force of plot convenience. Drinking the right brand of cola also seemed to help.

  In real life, with the advent of the Hazzard Machines, the rates of death and injury through crime, natural disaster, industrial and transport accidents, and many kinds of disease, had certainly plummeted—but such events weren’t forecast and then paradoxically ‘avoided’; they simply, consistently, became increasingly rare in reports from the future—reports which proved to be as reliable as those from the past.

  A residue of ‘seemingly avoidable’ tragedies remains, though, and the people who know that they’re going to be involved react in different ways: some swallow their fate cheerfully; some seek comfort (or anesthesia) in somnambulist religions; a few succumb to the wish-fulfilment fantasies of the ROMs, and go kicking and screaming all the way.

  When I met up with Pria, on schedule, in the Casualty Department of St Vincent’s, he was a bloody, shivering mess. His arm was broken, as expected. He’d also been sodomised with a bottle and slashed on the arms and chest. I stood beside him in a daze, choking on the sour taste of all the stupid jokes I’d made, unable to shake the feeling that I was to blame. I’d lie to him, lie to myself—

  As they pumped him full of painkillers and tranquillisers, he said, ‘Fuck it, James, I’m not letting on. I’m not going to say how bad it was; I’m not frightening that kid to death. And you’d better not, either.’ I nodded earnestly and swore that I wouldn’t; redundantly, of course, but the poor man was delirious.

  And when it was time to write up the day’s events, I dutifully regurgitated the light-hearted treatment of my friend’s assault that I’d memorised long before I even knew him.

  Dutifully? Or simply because the cycle was closed, because I had no choice but to write what I’d already read? Or… both? Ascribing motives is a strange business, but I’m sure it always has been. Knowing the future doesn’t mean we’ve been subtracted out of the equations that shape it. Some philosophers still ramble on about ‘the loss of free will’ (I suppose they can’t help themselves), but I’ve never been able to find a meaningful definition of what they think this magical thing ever was. The future has always been determined. What else could affect human actions, other than each individual’s—unique and complex—inheritance and past experience? Who we are decides what we do—and what greater ‘freedom’ could anyone demand? If ‘choice’ wasn’t grounded absolutely in cause and effect, what would decide its outcome? Meaningless random glitches from quantum noise in the brain? (A popular theory—before quantum indeterminism was shown to be nothing but an artefact of the old time-asymmetric world-view.) Or some mystical invention called the soul… but then what, precisely, would govern its behaviour? Laws of metaphysics every bit as problematical as those of neurophysiology.

  I believe we’ve lost nothing; rather, we’ve gained the only freedom we ever lacked: who we are is now shaped by the future, as well as the past. Our lives resonate like plucked strings, standing waves formed by the collision of information flowing back and forth in time.

  Information—and disinformation.

  Alison looked over my shoulder at what I’d typed. ‘You’ve got to be kidding,’ she said.

  I replied by hitting the check key—a totally unnecessary facility, but that’s never stopped anyone using it. The text I’d just typed matched the received version precisely. (People have talked about automating the whole process—transmitting what must be transmitted, without any human intervention whatsoever—but nobody’s ever done it, so perhaps it’s impossible.)

  I hit save, burning the day’s entry on to the chip that would be transmitted shortly after my death, then said—numbly, idiotically (and inevitably)—‘What if I’d warned him?’

  She shook her head. ‘Then you’d have warned him. It still would have happened.’

  ‘Maybe not. Why couldn’t life turn out better than the diary, not worse? Why couldn’t it turn out that we’d made the whole thing up—that he hadn’t been attacked at all?’

  ‘Because it didn’t.’

  I sat at the desk for a moment longer, staring at the words that I couldn’t take back, that I never could have taken back. But my lies were the lies I’d promised to tell; I’d done the right thing, hadn’t I? I’d known for years exactly what I’d ‘choose’ to write—but that didn’t change the fact that the words had been determined, not by ‘fate’, not by ‘destiny’, but by who I was.

  I switched off the terminal, stood up and began undressing. Alison headed for the bathroom. I called out after her, ‘Do we have sex tonight, or not? I never say.’

  She laughed. ‘Don’t ask me, James. You’re the one who insisted on keeping track of these things.’

  I sat down on the bed, disconcerted. It was our wedding night, after all; surely I could read between the lines.

  But I never was much good at improvising.

  * * *

  The Australian federal election of 2077 was the closest for fifty years, and would remain so for almost another century. A dozen independents—including three members of a new ignorance cult, called God Averts His Gaze—held the balance of power, but deals to ensure stable government had been stitched together well in advance, and would survive the four-year term.

  Consistently, I suppose, the campaign was also among the most heated in recent memory, or short-term anticipation. The soon-to-be Opposition Leader never tired of listing the promises the new Prime Minister would break; she in turn countered with statistics of the mess he’d create as Treasurer, in the mid-eighties. (The causes of that impending recession were still being debated by economists; most claimed it was an ‘essential precursor’ of the prosperity of the nineties, and that The Market, in its infinite, time-spanning wisdom, would choose/had chosen the best of all possible futures. Personally, I suspect it simply proved that even foresight was no cure for incompetence.)

  I often wondered how the politicians felt, mouthing the words they’d known they’d utter ever since their parents first showed them the future-history ROMs, and explained what lay ahead. No ordinary person could afford the bandwidth to send back moving pictures; only the newsworthy were forced to confront such detailed records of their lives, with no room for ambiguity or euphemism. The cameras, of course, could lie—digital video fraud was the easiest thing in the world—but mostly they didn’t. I wasn’t surprised that people made (seemingly) impassioned election speeches which they knew would get them nowhere; I’d read enough past history to realise that that had always been the case. But I’d like to have discovered what went on in their heads as they lip-synched their way through interviews and debates, parliamentary question time and party conferences, all captured in high-resolution holographic perfection f
or anterity. With every syllable, every gesture, known in advance, did they feel like they’d been reduced to twitching puppets? (If so, maybe that, too, had always been the case.) Or was the smooth flow of rationalisation as efficient as ever? After all, when I filled in my diary each night, I was just as tightly constrained, but I could—almost always—find a good reason to write what I knew I’d write.

  Lisa was on the staff of a local candidate who was due to be voted into office. I met her a fortnight before the election, at a fund-raising dinner. To date, I’d had nothing to do with the candidate, but at the turn of the century—by which time, the man’s party would be back in office yet again, with a substantial majority—I’d head an engineering firm which would gain several large contracts from state governments of the same political flavour. I’d be coy in my own description of the antecedents of this good fortune—but my bank statement included transactions six months in advance, and I duly made the generous donation that the records implied. In fact, I’d been a little shocked when I’d first seen the print-out, but I’d had time to accustom myself to the idea, and the de facto bribe no longer seemed so grossly out of character.

  The evening was dull beyond redemption (I’d later describe it as ‘tolerable’), but as the guests dispersed into the night, Lisa appeared beside me and said matter-of-factly, ‘I believe you and I are going to share a taxi.’

  I sat beside her in silence, while the robot vehicle carried us smoothly towards her apartment. Alison was spending the weekend with an old schoolfriend, whose mother would die that night. I knew I wouldn’t be unfaithful. I loved my wife, I always would. Or at least, I’d always claim to. But if that wasn’t proof enough, I couldn’t believe I’d keep such a secret from myself for the rest of my life.

  When the taxi stopped, I said, ‘What now? You ask me in for coffee? And I politely decline?’

  She said, ‘I have no idea. The whole weekend’s a mystery to me.’