Schild's Ladder

by Greg Egan

  Chapter 9

  “Everyone complains about the laws of physics, but no one does anything about them.”

  Tchicaya turned away from the control panel. He hadn't heard Rasmah entering the Blue Room.

  “It's an old joke they used to tell, back on Maeder,” she explained, crossing the wide, empty floor. “Which just goes to show how much work it takes to send a bad meme off to smallpox heaven.”

  “Don't count on having done that,” Tchicaya warned her. “I believe the original version was ‘Everyone complains about human nature.’ When the second half became patently false, the meme just shifted context. You can tear the meaning right out of these one-liners, and they'll still find a way to keep propagating.”

  “Damn.” She sat beside him. “So what are the laws, right now?”

  “As far as I can tell, we have a macroscopic SO(2,2) symmetry, and E7 as the gauge group.” He gestured at the display. “Nothing we haven't grabbed before, generically, though the details of the Lagrangian are unique.” Tchicaya laughed. “Listen to me. I really am getting blasé about this.”

  “Seen one universe, seen them all.” Rasmah leaned closer to examine the symmetry diagrams that the software had guessed from some partial results, and was now proceeding to test further with the Left Hand.

  She glanced at the endurance clock. “Thirteen minutes? That's close to the record. You think this might—” Tchicaya glowered at her, and she laughed. “Don't tell me: I'm jinxing the result.”

  “Hardly. I'm just growing a little impatient with the idea that we keep grabbing dynamics, over and over, in the hope that one of them will turn out to be stable. It's never going to happen.”

  “You think not?” Rasmah pursed her lips. “Okay. It's no use just complaining, though. What do you want to do about it?”

  Tchicaya made a gesture of helplessness.

  She regarded him with disappointment. “Are you this lazy about everything?”

  She was only teasing, but the accusation stung. Rasmah had been on the Rindler just six months longer than he had, but she'd already contributed substantially to several projects. Having helped to design the spectrometer that had been lost with the Scribe, she'd gone on to improve the design still further for the models used in both the Left and Right Hands. The Scribe's replacement had been planned as a single machine, but when attempts to renegotiate the protocols for its shared use collapsed for the seventh time, even the most ecumenical researchers had lost patience, and agreed to the duplication.

  Tchicaya stretched his arms. “I've certainly had enough of staring at this for one day. Are you here to take over?”

  “Yes.” She smiled and added, “But I'm early, so I'm afraid you can't actually leave yet.”

  The destruction of the Scribe, and the end to cooperation between the factions, had delayed follow-ups to Branco's experiment, but once the two Hands were in place and gathering data, everybody on the Rindler had been riveted by the results. For months, the Blue Room—where the Left Hand's data was displayed, now that trips to the border were considered imprudent—had been packed with people twenty-four hours a day, and it was no secret that the Preservationists had reacted in the same way.

  Branco's technique appeared to have confirmed Sophus's original assertion: the novo-vacuum did not obey any single analog or extension of the Sarumpaet rules. It was possible to correlate a macroscopic portion of the near side of the border with parts of the total far-side state that did obey specific rules, but each time the experiment was repeated, the rules were different. All of Sarumpaet's carefully reasoned arguments about which patterns of nodes in a quantum graph could persist as particles had been revealed as utterly parochial; the larger truth was, the ordinary vacuum that dominated the near side was correlated with sequences of graphs that behaved in that particular fashion, so it hid the fact that they were really just part of a superposition of countless other possibilities. The quantum subtleties that could, in principle, render the whole superposition visible were buried in the sheer number of details that would have had to be tracked in order to observe it.

  The far side lacked the means to conceal its quantum nature in the same fashion, but if the view was less misleading, it remained confusing. Interpreting the new experiments was like trying to make sense of a jungle by watching an endless parade of exotic creatures cling briefly to the windows of a vehicle, stunned by the light, curious, or angry, but always flying off a moment later, never to return.

  At first, every new set of laws had had their fifteen minutes of fame, but since none of them could be pinned to the near side for much longer than that, the novelty had begun to wear thin. Exhilaration at the cornucopia had given way to frustration. The experiments continued, but it had become a struggle to maintain even the symbolic presence of one sentient observer around the clock. Tchicaya supposed that this was fair enough: all the theorists were drowning in data already, and they had better things to do than sit and watch more come pouring in. For a week or two, he'd hoped that patient observation might actually lead him to a worthwhile discovery himself, but that was beginning to sound as crazy as looking for patterns in any other set of random quantum results.

  “Oh, there it goes!” Rasmah wailed, as if she'd seriously expected otherwise. The patch of the border they'd pinned to the latest set of laws had just reverted to the old inscrutable glow. “What do you think would happen,” she mused, “if we scribed some device that could function under the far-side dynamics, before we lost the correlation?”

  Tchicaya said, “Even if it survived, what good would that do us? We've never been able to grab the same dynamics twice.”

  “What if we scribed a Scribe?”

  “Ha! Like that Escher drawing?”

  “Yeah.” Rasmah pulled a face, suddenly aghast. “Though...that's a left hand drawing a right, and vice versa. We can't have that, can we?”

  “Are you serious, though? Do you think we could insert a machine that could signal back to us in some way?”

  Rasmah didn't reply immediately. “I don't know. What does the border look like, from the other side? Does it always look as if our physics is happening behind it? Or is something more symmetrical going on, where someone on the far side would catch glimpses just as varied and transient as the ones we're seeing?”

  “I have no idea,” Tchicaya admitted. “I don't even see how you could pose that question, in Sophus's model. You'd have to describe a specific observer on the far side, on whose terms you wanted to see things. But if the different far-side dynamics don't form decoherent branches—except over the tiny patches where we're forcing them to do so—what exactly are the laws the observer is supposed to obey?” The startled birds and butterflies fluttering against the window weren't even real; it was no use asking what they saw, staring back. The slices of different “universes” pinned against the border were more like the patterns formed by splattered insects. If they hadn't been dead, they would never have been seen side by side in quite the same way.

  It was midnight, by the Rindler's arbitrary clock. The lighting of public spaces changed with the cycle, and though many people happily slept through the daytime and worked all night, Tchicaya had ended up in synch with the light.

  He stood. “That's it, I've had enough.”

  “You could stay and keep me company,” Rasmah suggested.

  “I wouldn't want to distract you.” He smiled and backed away, raising a hand good night. They'd been circling each other at a distance for weeks, and his body had begun to change for her, but Tchicaya had decided that he would not allow anything to happen between them. While it would have been unlikely to end as swiftly, or as comically, as his experiment with Yann, he wanted to keep his life free of complications.

  Tchicaya made his way around the ship, slightly removed from everything around him. The corridors were nearly deserted; maybe the Preservationists were having some kind of conference. The ghost town ambience reminded him of a hundred provincial cities he'd trekked through at
night; on the empty walkways, the blaze of stars was like the view when you left the brightest streets behind, and the sky came suddenly to life.

  He recalled a night he'd spent in a small town on Quine, thirty-six subjective years after he'd left Turaev: the mirror image of his birth in the moment of his departure. Three centuries had passed, in real time. He'd sat in an alley and wept for hours, like an abandoned child. The next day, he'd made half a dozen new friends among the locals, and some of the friendships had lasted three times longer than all the years he'd spent on his home world.

  He still missed those people. He still missed Lesya, and his children and grandchildren on Gleason. And yet, he could never entirely separate that from the realization that part of the joy he'd felt in their presence had come from the sense that they were lifting him out of his state of exile. They had never been substitutes for the home and family he'd left behind; it had never been that crude. But every kind of happiness bore some imprint in the shape of the pain it had assuaged.

  He heard footsteps behind him, outpacing his own. He stopped and turned to face the wall of the walkway, as if admiring the view, wiping his eyes with his forearm, less embarrassed by his tears than the fact that he'd be at a loss to explain them. If he'd still been on Turaev after four thousand years, he would have gone mad. And if he'd traveled and returned in the approved way, to find that nothing had changed in his absence, he would have gone mad even faster. He did not regret leaving.

  Mariama said, “You look like you're about to jump off a bridge.”

  “I didn't realize you were following me.”

  She laughed. “I wasn't following you. What are we meant to do? Walk in opposite directions around the ship? All Preservationists must march clockwise? That would make for some long journeys.”

  “Forget it.” He turned to look at her. It was unjust beyond belief, but right at this moment—having resolved for the thousandth time that he'd made the right decision—he wanted to rant in her face about the price she'd made him pay. After all her talk as a rebel child, after leading by example, after four thousand years as a traveler, she had now decided that her role in life was to fight to keep the planet-bound cultures—all the slaves she'd vowed to liberate, all the drones she'd promised to shake out of their stupor—safely marinating in their own inertia for another twenty thousand years.

  He said, “Where are you heading?”

  Mariama hesitated. “Do you know Kadir?”

  “Only slightly. We didn't exactly hit it off.” Tchicaya was about to add something more acerbic, when he realized that today was the day Kadir's home world, Zapata, would have fallen. That was only true in terms of a reference frame fixed to the local stars, not the Rindler's notion of simultaneity, and in any case no confirmation of the event would reach them for decades, but unless the border had magically altered its speed in distant regions, the planet's loss was a certainty.

  “He's holding a kind of wake. That's where I'm going.”

  “So you and he are close?”

  Mariama said, “Not especially. But he's invited everyone, not just his friends.”

  Tchicaya leaned back against the wall, unfazed by its transparency. He said, “Why did you come here?”

  She shaded her eyes against the borderlight. “I thought you'd decided that we were never going to have this argument.”

  “If you think I've shut you up, now's your chance.”

  “You know why I'm here,” she said. “Don't pretend it's a mystery.” The glare was too much; she turned to stand beside him. “Do you want to come with me, to this thing of Kadir's?”

  “You must be joking. Do you think I'm a provocateur, or just a masochist?”

  “This isn't factional. He's invited everyone.” She frowned. “Or are you afraid to spend ten minutes in the company of people who might disagree with you?”

  “I spent ten years on Pachner.”

  “Keeping your mouth shut.”

  “No. I was honest with everyone I met.”

  “Everyone who asked. If the issue came up.”

  Tcicaya moved away from her angrily. “I wasn't sure of my plans, when I first arrived. And when I was sure, I didn't walk around with a banner that read ‘I'm off to the Rindler, to make certain the same fate befalls as many other worlds as possible.’ Does that make me dishonest? Does that make me a coward?”

  Mariama shook her head. “All right, forget Pachner. But if you're so sure of your position now, why don't you come with me? No one's going to lynch you.”

  “It would be inflammatory. What makes you think Kadir wants the company of people who disagree with him?”

  “There's an open invitation,” she protested. “Check with the ship if you don't believe me.”

  She was right. Tchicaya's Mediator had filtered it out automatically; he'd told it to classify general announcements by known factional allegiances, to keep him from being distracted, and depressed, by news of events where Yielders were unlikely to be welcome.

  “I'm tired,” he said. “It's been a long day.”

  “You're pathetic.” Mariama walked away without another word.

  Tchicaya called after her, “All right! I'll come with you!” She didn't stop. He ran to catch up with her.

  They walked in silence for a while, then Tchicaya said, “This whole iron curtain thing is insane. Within a decade, we'll find a way to pin some state to the border that will freeze it in place. If we worked on it together, it would take half as long.”

  Mariama regarded him coolly. “If we froze it, you think that would be enough?”

  “Enough for what?”

  “Enough to satisfy either side.”

  “Ideally, I still want to cross through,” Tchicaya admitted. “We shouldn't have to flee from this, or annihilate it. We should be able to adapt. If the ocean comes a few meters inshore, you retreat. A few kilometers, you build a dike. A few thousand...you learn to live in boats. But if freezing the border turns out to be possible, and it rules out exploration, I'd just have to accept that.”

  Mariama was skeptical. “And you'd take no risks at all, from that moment on? You'd do absolutely nothing that had a chance of unfreezing it? You'd let it sit there for a hundred thousand years, undisturbed, and you wouldn't be tempted in the least?”

  “Oh, I see. That's the logic that dictates the use of Planck worms? If you don't wipe the whole thing out of existence, some Yielder is certain to come along eventually, and unplug the dike.”

  Mariama didn't reply. They entered the module where the wake was being held, and walked up the stairs.

  On the map Tchicaya consulted, Kadir's cabin had been merged with a dozen of his neighbors', producing a roughly circular room. Ahead of him, the entrance was wide open, and music wafted out into the corridor.

  Mariama's clothes changed as they approached the doorway, forming a pattern of woven bands broken up by ellipses, in earthen colors. “You look good in that,” Tchicaya observed. The comment elicited a reluctant flicker of warmth in her eyes, and she knew him too well to mistake it for insincere flattery, but she walked on into the room without a word. He steeled himself, and followed her.

  There was quite a crowd inside, talking, eating, a few people dancing. Tchicaya could see no other Yielders, but he resisted the urge to ask his Mediator to hunt for friendly signatures.

  Images of Zapata shone from the walls. The planet from space; aerial views of towns, mountains, and rivers. Tchicaya had spent forty years on Zapata, moving from continent to continent, never really settling down long enough to make close friends.

  The life the settlers had unleashed on the sterile planet, though ultimately derived from natural terrestrial genomes, had been a little wilder and stranger than most. There were lithe winged cats in some of the jungles that could tear out your throat. Toward the end of his stay, it had been discovered that in one small, isolated town, deliberate exposure to harm by these creatures had become a “rite of passage” into adulthood—as if adolescence itself was i
nsufficiently traumatic. The partially eaten bodies could generally be repaired, and at worst the Qusp could always be tracked down and recovered from the animal's stomach, so the ritual fell short of local death, but as far as Tchicaya was concerned, that only made it more barbaric. Better to suffer memory loss and discontinuity than the experience of having your jugular gnawed open—and better anything than the company of people who'd decided that this was the definition of maturity.

  Children in the town who declined to participate had been ostracized, but once the practice came to light, the wider society of Zapata had intervened—with a concerted effort to improve transport and communication links. After a few years of heightened exposure to the possibility of simply walking away from the town and its self-appointed cultural guardians, no one was interested in being bullied into conformity anymore.

  It was the kind of behavior that could only occur when people had been trapped for thousands of years, staring at the same sights, fetishizing everything around them, spiraling down toward the full-blown insanity of religion. You didn't need gates and barbed wire to make a prison. Familiarity could pin you to the ground, far more efficiently.

  Mariama waved a small yellow fruit at him, half-bitten. “Try one of these. They're delicious.”

  “Good grief. Where do you think he grew them?”

  “In the garden. Lots of people have set up plots for food. You have to tweak the genomes to get photosynthesis to work in the borderlight, but that's old hat, you just copy those ugly things the original builders put in.”

  “I must have walked past without even noticing.”

  “They're quite far back from the path. Are you going to try one?”

  Tchicaya shook his head. “I've tasted them before. There can't be many; I'm not going to hog them.”

  Mariama turned to address Kadir, who'd appeared before them like a perfect host. She said, “Tchicaya was just telling me that he'd already tasted quetzal-fruit.”