Instantiation

by Greg Egan

  “If you honestly don’t know where you belong, we’ll need to find a place for you in the village,” Gerther declared.

  Sagreda stood in silence. Part of her was humbled by the generosity of the offer, but part of her balked – as if she was being asked to assent to a far less benevolent assimilation. The stone was cold on the soles of her feet.

  “What’s holding us up?” she asked.

  “What do you mean?”

  “If gravity points east, everywhere…” Sagreda gestured toward the floor, “then what’s keeping this rock from heading east?”

  “The rock below it,” Gerther replied, deadpan.

  “Ha!” Sagreda waited for the woman to crack a smile and admit that she was teasing. “I might have come down in the last landslide, but I’m not a five-year-old. If there’s nothing keeping up the rock below us except the rock below that, and you repeat the same claim all the way around the planet … then there’s nothing holding up any of it. You might as well tell me that a wheel can’t be spun because each part of it obstructs the part beside it.”

  “I meant the rock closer to the center of the Earth,” Gerther explained. “We believe that the Change doesn’t reach all the way in. Once you go deep enough, gravity becomes normal again. After all, that’s what happens far above the ground: the moon still orbits us in the old way.”

  Sagreda examined the walls of the cave. “So this rock is being pulled east by its own weight, but you’re saying that because it’s of a piece with some deeper rock that isn’t being pulled east … that’s enough to keep the floor from falling out from under us?” The gray mineral around them made her think of granite, but whatever it was it certainly appeared solid and unyielding.

  And heavy.

  “That still makes no sense,” she said. “Before the Calamity, what’s the longest overhang you ever saw jutting out from a cliff?”

  “I have no knowledge of those times,” Gerther insisted.

  Sagreda had no clear memories, herself. But she could still picture rock formations with various shapes, and judge them plausible or preposterous. “I doubt there was ever an overhang longer than thirty or forty feet, and even then it was probably supported in part by some kind of natural arch – you wouldn’t see forty feet of rock just sticking out like a plank! If the Change spans a range of altitudes that encompasses most of the surface of the Earth – and if it didn’t, why would we be here at all, instead of living a normal life in whatever lowlands or highlands break out into normal gravity? – then it must be exerting an eastward force on slabs of rock thousands of feet long. And if there’s nothing stopping such a massive object from moving east under its own weight except the fact that it joins up at one end with a deeper body of rock, it’s going to tear free. Neighboring slabs won’t help: they have their own weight to bear, they can’t prop up anything else. So everything down to the depth where the Change begins should be rubble by now: an endless landslide of boulders, tumbling around in ever faster circles.”

  Gerther spread her arms. “It doesn’t look like it.”

  Sagreda rubbed her temple. “No, it doesn’t,” she admitted. Maybe she was simply mistaken about the strength of rock. Amnesic or not, she was fairly sure that she’d never been a professional geologist.

  “If the rock doesn’t fall, what about sand?” she wondered. “And what about the oceans! There ought to be the mother of all waterfalls cascading around the planet – growing faster with every cycle!”

  “Maybe there is,” Gerther conceded. “Who knows what wonders we’d find in distant lands? I can’t say; I’ve never left the village.”

  “Then what about the air?” Sagreda moved closer to the mouth of the cave. “There’s a strong wind traveling east, but why isn’t it picking up speed?”

  “Friction?” Gerther suggested.

  That gave Sagreda pause. She knew that a rock falling through air wouldn’t accelerate forever: eventually the drag on it matched its weight and it fell steadily at some terminal velocity. So perhaps the layer of air falling past the Earth’s surface would reach a similar state.

  But what was friction, exactly? The creation of heat from other kinds of motion. So if friction was robbing the air of all the speed it would otherwise have gained by plummetting so far, surely the wind ought to feel like the breath from a furnace, and the ground ought to be as hot as the shielding on a space capsule plunging back to Earth.

  “There’s another problem I don’t understand,” Sagreda said. “What happened to conservation of energy?”

  Gerther frowned. “Conservation?”

  Sagreda couldn’t tell when the woman was joking with her, but whether or not she was familiar with the term, Gerther surely had some feel for the concept. “Suppose I dropped a rock from some point far enough from the ground for it to come full circle, unobstructed. If it didn’t burn up from friction, it would return to the place where I’d released it, traveling faster than any bullet. I could extract its energy and then send it on its way again, over and over, as many times as I liked.”

  “Good luck with that,” Gerther scoffed.

  “I’m surprised no one’s done it yet.” Sagreda looked around the barren cave. “I’m assuming this place isn’t on the grid?” But the practicality of the scheme wasn’t the point: it was the fact that she could do it in principle that was troubling. “Maybe the Earth acts as a kind of reservoir?” she mused. “As the rock circles around ever faster, maybe the Earth spins a tiny bit slower?” If for every force there was an equal and opposite force, maybe the pull that sent the rock eastward was matched by a westward tug on the planet, so that everything added up in the end. “Does that make sense?”

  Gerther offered no opinion. Sagreda said, “Why don’t I test the laws and see what’s possible?”

  She searched the floor and found a few pebbles of various sizes, then she took them back to the place where she’d been standing with Gerther and arranged them on the ground. She flicked the largest into motion with her thumb, striking the smallest and sending it skidding across the cave.

  “That tiny one started out motionless, and then it gained whatever amount of energy the large one could give it that would satisfy the conservation laws. Right?” Give or take a little energy lost to sound and friction, what else could determine the pebble’s final speed?

  Gerther didn’t challenge her, so Sagreda continued. “Now let’s see what happens when I hit one that’s a bit heavier.” She launched the same large pebble into a collision with a second, more substantial target, which slid away – noticeably slower than its predecessor.

  None of this struck Sagreda as surprising. And on reflection, the unexceptional results seemed inevitable, given that she was alive at all. The biochemical machinery in every cell in her body would rely on the rules of molecular billiards that had held sway since before life began. Rejigging them overnight would have been fatal.

  Gerther said, “What is it you think this game is telling you?”

  “The smaller pebbles started out motionless,” Sagreda replied. “Then they took some energy from another, larger body, and ended up traveling at a certain speed. For the second pebble, that speed was slower than it was for the first. And the only reason for that was the fact that the second pebble was heavier – everything else was the same.”

  “So…?”

  “If I dropped those two pebbles, with no air to impede them, and waited for them to come full circle … they’d fall side by side all the way, and arrive with identical speeds. That means you can’t balance the energy they gain by taking it away from the motion of the Earth! For the changes to add up, the heavier pebble needs to move more slowly than the lighter one – in the same way as when the same laws determine the speeds after a collision.”

  “How can you be sure that it wouldn’t fall more slowly?” Gerther asked.

  “Oh, please! Do you think if I tied two rocks together with string, that would magically change the speed at which they fell? Do you think I would have h
ad a slower fall myself if I’d been lugging a boulder around?”

  “Hmm.” Gerther wasn’t buying into those ridiculous scenarios, but she still didn’t seem to grasp the implications of rejecting them.

  Sagreda fell silent, letting the increasingly dubious principles of the altered world play out in her mind. “There’s something wrong with the whole idea of falling in a circle,” she said. “Something even more basic than the threat of perpetual motion. I can’t quite put my finger on it … but give me a second, I’m sure it will come to me.” The moon had always fallen in a circle around the Earth, so it wasn’t the shape of the path itself that was absurd – but the moon hadn’t started from rest and then circled around ever faster.

  “Why do you keep denying the evidence of your senses?” Gerther asked irritably. “For all your talk, the floor of this cave isn’t falling! Why can’t you leave it at that?”

  “Einstein,” Sagreda recalled, “said that inside a falling elevator, you might as well be drifting in interstellar space. When you’re in free fall, you’re weightless, and you can’t really see the effects of gravity – not without taking in a much bigger picture. If you watch things falling beside you – nearby things that you track for a short time – then as far as you’re concerned they’ll just move in straight lines at a constant speed, the way things move in the absence of gravity.”

  Gerther didn’t ask who Einstein was. Even for a post-apocalyptic peasant, there were some claims of ignorance that just wouldn’t fly.

  Sagreda continued. “Suppose I fall from the mouth of this cave, and keep falling east in a circle. But suppose you fell before I did, from some place further west. You arrive at my starting point when I’m still barely moving, so you’ve had time to build up enough speed to overtake me. Is that what would happen – would you fall right past me?”

  “Of course.” Gerther wasn’t happy, but Sagreda was relying on nothing more than the woman’s own claims about the Change. Gravity pulled you east, in a circle. Starting from rest you moved faster over time.

  “Walk with me in a circle, and overtake me,” Sagreda challenged her.

  “Do I have to?” Gerther asked sullenly.

  “Humor me.”

  Sagreda moved back further from the mouth of the cave. Reluctantly, Gerther joined her and began pacing out an arc, counter-clockwise, her steps growing steadily brisker as she approached Sagreda from behind. Sagreda waited a second or two before starting her own fall – too late to keep Gerther from passing her and continuing around the circle.

  Sagreda slapped her hands together in triumph. “You came in behind me from my left … and moved away in front of me, still on my left! That’s how it would look, if you fell past me! But Einstein said that, in close up, every falling object seems to move in a straight line. A straight line doesn’t come in from your left and then leave on your left as well. If your path meets mine as we fall, they should cross! You can’t sidle up on the left and then retreat!”

  “If the circle was larger,” Gerther protested, “you wouldn’t even know that I was on your left! You’d think I was approaching straight from behind.”

  Sagreda considered this. “If you’re going to claim that any sufficiently gentle curve looks straight, Einstein’s idea becomes vacuous. Why would he have even bothered to say it, if it can’t tell you a single thing about gravity?” She thought for a moment. “If you had two satellites in the same orbit, but moving in opposite directions, then they really would come at each other head on. That’s the standard we have to compare things to: where you don’t need to umm and ah about the orbit being large to get away with it.”

  Sagreda was prepared to mime the collision, if that was what it took to drive home the difference, but Gerther switched tactics. “You don’t know how much was changed in the Change,” she said.

  “It really can’t be all that radical, if my atoms haven’t exploded.”

  “String theory!” Gerther invoked desperately. “Extra dimensions! Zero-point energy!”

  “I don’t think so.” Sagreda had no memory of studying any of these things, but she was as close to sure as she could be that they all involved attempts to build on earlier science, not wantonly discard it. Free fall ought to have the same basic properties in any geometry. Whatever wildly curved, multi-dimensional space-time anyone tried to dream up in the hope of making falling bodies accelerate in circles, they were doomed to fail.

  “So what’s the trick?” Sagreda asked flatly. She strode toward the cave’s entrance. “Is there a mirror out there?”

  “No.”

  Sagreda reached the edge of the cave’s safe floor and stood with the sun slanting up to strike her chin, her toes at the top of a rocky lip that appeared ready to launch her into the vast drop below.

  “If you fall,” Gerther warned her, “you really will fall.”

  Sagreda was having trouble understanding how the illusion had been conjured so seamlessly. A mirror just below her feet, slanting down at forty-five degrees, could deflect her downward gaze into a horizontal line of sight. But then a second mirror needed to be in front of her, tilted up toward the sky, blocking her direct view of the landscape ahead without obscuring the reflected one. And when she looked to the side and saw more of the same barren rock stretching out to the horizon …

  “I have to do this,” she declared, sliding the front of her right foot over the edge. Her body disagreed, and began urgently counseling retreat. “Or maybe I should just start throwing rocks until I smash a few mirrors.”

  “There are no mirrors,” Gerther announced wearily. “It’s all digital.”

  “Digital?” Sagreda turned to her, thrilled by the confession. “You mean a projection? Like IMAX?”

  “More like virtual reality.”

  Sagreda groped at her face. “But I’m not wearing goggles. I’d know if I was wearing goggles.”

  “Things have moved on since the days of goggles,” Gerther replied.

  “To what? Contact lenses?” Sagreda stuck a finger in the corner of her eye and began probing for the source of the deception. Gerther stepped up and took her by the shoulders, then drew her back from the mouth of the cave.

  “To what?” Sagreda demanded. “Is there a wire in my brain? Is there a chip in my skull? What’s feeding me all of this garbage?”

  “It’s moved on to everything,” Gerther said. “You have no eyes, no brain, no body. It’s all digital: you, me, and everything around us.”

  Sagreda felt her legs grow weak, digital or not. “Why should I trust you?” she asked bitterly. “If that’s the truth, why did you lie to me before?”

  “To make your life easier,” Gerther said sadly. “I knew there wasn’t much hope, but with every newcomer we try our best.”

  “Try your best to make them think that this is real?”

  “Yes.”

  Sagreda laughed. “Why would that make my life easier?”

  “This is a game world,” Gerther replied. “But we’re not paying customers; we’re just part of the scenery. Our job is to act as if we’ve lived all our lives here, knowing nothing else, taking the gimmick seriously. Any bright ten-year-old could see through this world in five minutes – but if we break character in front of a customer and let them know that we know it’s a farce, that’s it.”

  “That’s what?” Sagreda asked.

  “That’s when you get deleted.”

  2

  The “village” of Owl’s Rest was a small network of caves that linked up with the one in which Sagreda had woken. Gerther led her through a dark passage to a sunlit alcove where a reception party was waiting: half a dozen people, and a blanket bearing some meager portions of food.

  “Is she the One?” a young man asked Gerther.

  “No, Mathis.”

  Sagreda frowned. “The One?”

  “The Holy Fool with the power to believe that this is real,” Mathis replied. “Long have we prophesied the coming of a stranger who could teach us how to pull the woo
l over our eyes.”

  “It took me a while to tear my own blindfold off,” Sagreda admitted.

  “You did well,” Gerther assured her. “Some people take a whole day, they’re so disoriented by the arrival.”

  Gerther made the introductions. “Sagreda, this is Mathis, Sethis, and Jethis,” she said, pointing to the three disheveled men in turn. The women seemed to have made more of an effort with their appearance, if not their choice of names. “Cissher, Gissher and Tissher.”

  “Really?” Sagreda winced. “Where are Pissher and Tossher?”

  “You gotta go with the gimmicks,” Mathis reproved her sternly. “If you think you’re hanging on to ‘Sagreda’ with the customers, forget it.”

  “Can’t I be a foreigner with a more … classical inflection?” Sagreda pleaded.

  “Do you want to try that and see what happens?” Cissher asked ominously.

  Sagreda was starving. At Gerther’s invitation she sat cross-legged by the blanket and tried a piece of cheese. The texture was odd, but it wasn’t too bad. “So we have to go through the whole charade of making this ourselves? Milking a simulated cow…?”

  “Goat,” Tissher corrected her. “You can’t smell it?”

  Sagreda looked around for signs of the animal, but instead her eyes were caught by a kind of sundial on the wall: a wooden peg jammed into a crevice in the rock, beside which was etched a series of calibrated curves for its shadow. She hadn’t yet dared ask anyone how long they’d been here, but the curves looked as if they’d been constructed and refined over at least two full journeys through the seasons.

  “So whose idea was the Calamity?” she asked. It was as if someone had tried to invent an exotic new world, but knew so little about the way the real one worked that all they could come up with was a dog’s breakfast of contrivances and inconsistencies.

  “When the customers come through in groups,” Mathis said, “we sometimes overhear them going meta. The consensus seems to be that this world is based on an obscure pulp novel called East, by a man named William Tush.”