Vacuum Diagrams

by Stephen Baxter

  Allel returned her mother's fierce stare. "I understand, but..."

  Boyd sneered: "But you want to ask the Shell dwellers what it's like living in a saucer." Her eyes were flat, impervious to the hard cold. Allel wondered how she and her mother had grown so far apart, becoming as symmetrical as opposing poles. The one pragmatic, the other — a visionary? — or a fool? Who was right? Perhaps that was a question without an answer—

  She knew Boyd was trying to force her to grow up. But the Shell arced over them like a roof coated with its own ice. Could she give up all her dreams and become a creature of her mother?

  "Listen," she said desperately. "I've thought of a way we can take the Bridge."

  Her mother whirled and drove her palm against Allel's cheek. Blood pumped into Allel's mouth and strange scents flooded her head.

  "You've learned nothing," Boyd said hoarsely. "I'd rather leave you here." She forced herself forward, fists clenched white.

  Allel mumbled: "I mean it." She felt blood freezing on her lip. She became aware she'd lost her cap. But Boyd was hesitating.

  "How?"

  "If I succeed..." She coughed and spat blood. It was vivid against the snow. "If I succeed, will you help me build a hyperdrive machine to fly to the Shell?"

  Boyd's eyes narrowed. "I don't believe it. You're bargaining with me..." Then she dug a bark handkerchief out of a voluminous pocket. "Here. Clean yourself up."

  The dozen warriors converged on the Bridge. They wielded branches hacked from cow-trees, their miraculous meat buds smashed away. To Allel, watching from above, the crude clubs were symbols of the depressing symmetry of humanity's rise and fall.

  The Bridge was a gleaming parabola plastered with teepees. From the teepees defending warriors emerged, grubby and yelling, brandishing rocks and clubs. Blood splashed over the seamless carriageway. But soon it was hard to separate the two sides, but Allel could see that as before the attackers were being driven away.

  The breeze picked up and the great balloon over her creaked into motion, its stitched bark straining. The canvas sling chafed her armpits, and she tended the alcohol burners clustered like berries just above her head. The balloon wallowed in the air. Soon its load would be lighter, she thought, uncertain of her feelings.

  Her shadow drifted over the melee, touching fighters, men and women alike, who wriggled together like blood-soaked termites. They looked up in fear or anticipation. She took a small alcohol lamp, one of a cluster tied to her belt. She lit the lamp, cut its cord with her stone knife, and dropped the lamp delicately into the defenders' muddled line. The lamp flared into flame; a toy man ran screaming, his shirt a torch. Another lamp, and another. Cries of anger sailed up at her, followed by whirling clubs. No weapons could reach her, and she dropped her lamps. Then the defenders' line broke and the battle surged across the Bridge. Teepees crumpled, and old folk screamed. Allel thought she heard her mother shout in triumph.

  Her lamps gone, Allel dropped the pouch and the balloon rose further. She stared up at the Shell's complex tapestry and waited for a breeze to take her home.

  She found the teepee's air filled with her mother's sweat and dirt. Boyd's left wrist was a stump of torn blood vessels and shattered bone. It had been cauterized; now Lantil bathed it with milk and tears. Boyd took Allel's forearm in a grip that pulsed with pain. "Daughter! Your damn bag of smoke worked..."

  Allel tugged gently, wanting only to be released. "Yes. And now you'll have to help me build a real machine to cross the Gap."

  Lantil pushed at Allel's chest, his liver-spotted hand fluttering like a bird. "You should be ashamed to speak to her that way. Can't you see she's hurt?"

  But Allel kept her gaze locked with her mother's.

  Slowly Boyd grinned. "Won't give up, will you? Determined to prove me wrong. All right. On one condition."

  "What?"

  "Take me, too. I've done my job here; maybe I want to see the Shell people, too... ah..."

  The pain silenced her. Lantil pulled his daughter's blood-spattered head against his chest.

  Allel loosened her mother's grasp, and went to her pallet to start her plans. She lay with her face to the bark wall.

  The whole village turned out for the launch. They nudged each other and pointed out panels on the balloon which they themselves had helped stitch, forgetting Boyd's five years of bullying.

  Impeded by their harnesses, Boyd and Allel labored at the bellows-like fuel pumps. The great bark envelope filled slowly, throwing swollen shadows in the flat morning light. Allel eyed the low Sun warily. They'd timed their flight to avoid a collision — fantastic though such a prospect seemed. But, she had reasoned doggedly, the Shell was behind the Sun. They were going to fly to the Shell. Therefore they could hit the Sun, and had to navigate to avoid it.

  Her harness twitched twice, as if coming awake — and then, with a surprising surge, lifted her. The ground tilted away. People gave a ragged cheer and children chased the balloon's shadow. Boyd roared and waved her good hand at them. Her crippled arm was lashed to the rigging. "We're off, daughter!" she bellowed.

  The landscape opened out and swallowed up the huddled villagers. To the north the Atad river curved into view, and beyond the site of their old home Allel could see the glaciers prowling the horizon.

  She felt she was floating into a great silent box. The balloon's throat occluded the Shell's upside-down clouds. She hoisted herself into the rigging to tend the burners, prizing the stubby wicks from the resin-soaked barrels of alcohol. Gritty sweat soaked her eyes. She'd insisted they both wear quilted coats despite Boyd's protests; she remembered the frozen ice-blue bird she'd found on Hafen's Hill on another summer day, five years ago.

  And sure enough, not many minutes later the dampness at her neck chilled and dried. Her breath caught and soon grew labored. "Even the damn air has a Gap here," growled Boyd. "But you know, this harness isn't chafing so much as it did."

  Allel, too, felt oddly light; she had a sensation of falling. But they rose smoothly into blue silence. Soon they were miles up; clouds dissolved as they passed into them. Their world collapsed to a Shell-like map, shutting them out; above and below became symmetrical and Allel's stomach lurched.

  Their rate of ascent slowed. The breeze in the rigging grew softer. The craft lumbered, unstable.

  "What now?" demanded Boyd uneasily. "Watch the burners."

  "Yes. I wonder if — ah. The burners! Quick!"

  The balloon was collapsing.

  They worked grimly, dragging themselves into the rigging and cutting away the burning wicks. The envelope crumpled over the doused lamps.

  And Boyd was upside down.

  Or Allel was.

  Her harness was slack. The components of their balloon drifted in a jumble. Boyd thrashed in the air as if drowning — but there was no up to kick towards. Fear showed beneath her pale scars.

  But Allel understood.

  "It's the middle of the Gap!" Allel yelled, exhilarated by her mother's discomfiture. "The Shell dwellers live upside down. Up for us is down for them. Did we think we'd fly up and bump against the Shell like a ceiling? This is the place where up and down cross over!" Warm air spilled from the balloon and brushed her face. Ground and Shell were enormous parallel plates that careened identically around her. She laughed and swooped.

  But their equilibrium in the weightless zone was unstable, and soon invisible fingers clutched at them. Wind whistled in the tangled rigging and their harness grew taut again. "We're falling back!" Allel cried in disappointment. Boyd struggled to keep her good arm free.

  Now air resistance roughly righted them. The balloon opened out like a parachute but scarcely slowed their fall.

  Boyd roared above the wind: "We've got to light the burners!"

  They hunted for flints and cupped their hands around the wicks to keep out the snatching breeze. Heat roared up. Boyd thrust at the fuel pumps while Allel scrambled precariously into the tangled rigging to drag at the neck of the envelope, trying to
trap all the warmed air.

  Their descent slowed a little. Allel's arms ached and her hair whipped at her forehead. The ground exploded into unwelcome details, rivers and hills and trees and pebbles—

  She rolled on impossibly hard earth, grass blades clutching at her face. Her blood was loud in her ears. The balloon folded as if wounded.

  In a sunlit meadow, mother and daughter lay amid the ruins of their bark spaceship.

  Sunlight scoured her eyes. Allel sat up, blinking, pushing at the knotted remains of her harness. She was surrounded by cool grass and flowers; a brook led to a stand of cow-trees and the horizon was made up of heather-coated hills.

  And, as it had always done, the Shell curved over it all like a great blue tent.

  Boyd slept peacefully in a tatter of the balloon. Allel hesitated for some minutes, vaguely fearful of her mother's reaction. Then she found a remnant of a shattered burner and woke her mother with a cup of brook water. Boyd sat up clumsily, favoring her bad arm.

  "We failed," Allel said.

  "Huh?"

  Allel pointed at the Shell above them. "Look. We must have fallen back. If we'd reached the Shell we'd see the world up there, a ball of rock, cupped by the Shell. And the land would tilt up at the horizon..."

  Boyd grunted. Sensitive to her daughter's mood, she drank in silence. She probed at her limbs. "At least we're still whole," she rumbled. She looked about. Then — unexpectedly — she grinned. "So we failed, did we? Eh?"

  She dug her good hand into the ground, and then shook it in Allel's face. "Look at that! Look!"

  At the heart of the clump was a bright orange flower. A Shell flower.

  Allel's thoughts swam like fish. "Now I really don't understand..."

  "We made it. We're on the Shell! That's enough for me." Then Boyd followed her daughter's gaze upwards, to the roof over the world. Her eyes narrowed.

  Allel said slowly, "Above us we see Home, not the Shell. Yet it looks as the Shell does. The two worlds are complete in themselves, yet they are — wrapped around each other. Symmetry. You see the same thing — a Shell — from whichever world you're on."

  Boyd nodded shrewdly. "Well, that much I understand. Like us, eh? Two halves of the same whole. No weak center, no protecting Shell. Just the two of us."

  Allel dropped her eyes, hotly embarrassed. She went on doggedly: "But how? If we're on the Shell, why doesn't the land curve up like a saucer? Why don't we see Home floating up there like a ball? How can it look like another Shell?"

  Boyd made a little growling noise, and flung the shard of burner into the grass. A small flock of ice-blue birds clattered off, alarmed. "Well, you're the dreamer. Dream up an answer."

  Allel lay flat. She rested her head on very ordinary loam and stared up through two layers of clouds. She thought of two worlds, each a ball yet each cupping the other like a shell round a nut. How could that be?

  Her vision of her universe was crumbling, like the flaking planet-in-a-box milk painting on that museum wall. She imagined reaching into the box to the truth—

  Boyd said gruffly: "Well, what now?"

  Allel gestured vaguely. "Fix the balloon and get home. We've got to make people understand. Build more balloons and go to the old Cities. Find a way to turn back the glaciers, or fix the Sun..."

  Boyd was staring past her shoulder. Allel turned — then sat up quickly.

  The boy stood at the edge of the stand of cow-trees. He was no better dressed than they were; teeth flashed in a dark face as he jabbered at them, smiling and pointing and cupping his hands.

  Allel watched, baffled. "What's he saying?"

  Boyd bellowed with laughter. "I think he's asking what it's like living in a saucer."

  Boyd stood up and, with some dignity, straightened the shreds of her quilted jacket. Allel got to her feet, stiffly. "Come on," said Boyd. "Let's see if his people can cook as well as your grandfather."

  They walked towards the boy across the meadow of bright orange flowers.

  "Lethe. I can't believe they fell so far. They've become utterly dependent on that artificial biosphere. They're reduced to technologies of stone and wood—"

  "But they survived," Eve said. "Humans survived, even beyond the evacuation of the Xeelee. In a world that cared for them. You could argue this is a Utopian vision..."

  "This world of theirs, with the Shell, is a four-dimensional sphere. No wonder they couldn't figure it out."

  I thought of three-dimensional analogies. Allel's people were like two-dimensional creatures, constrained to crawl over the surface of a three-dimensional globe. Home and Shell, the twin worlds, were like lines of latitude, above and below — each unbroken, each apparently cupping the other. Just as the diagrams in the "City" had tried to show them.

  "But they were capable of understanding," Eve said. "After a million years, humans had adapted in subtle ways. Allel had the capacity to visualize, to think in higher dimensions. She could have understood, if someone had explained it to her. As those diagrams in the place she called the City were meant to. And in time, she would figure out some of it..."

  "They were trapped," I said. "In a prison of folded space-time."

  "Perhaps," said Eve. "Perhaps. But they didn't give up..."

  The Eighth Room

  A.D. 4,101,266

  TEAL SLEPT THROUGH DAWN.

  He woke with a jolt. There was the faintest crack of red around the teepee's leather flap.

  After all his planning... it would be broad daylight by the time he reached the bridge anchor.

  But, he reflected ruefully, there was a certain irony. The dawn had been too feeble to wake him — and that was the heart of the problem.

  The Sun was going out. And today Teal was going to try to fix it.

  With a fluid movement he slid off the pallet and stood in the darkness.

  Erwal's breathing was even and undisturbed. Teal hesitated; then he bent and touched his wife's belly, his fingertips exploring the mummy-cow skin blanket to find the second heartbeat beneath.

  Then he pulled on his clothes and slipped out of the teepee.

  His breath steamed. Dawn was an icy glow; a roof of snow-laden cloud hid all sight of Home, the world in the sky.

  He walked softly through the heart of the little village. The ground was corrugated by mummy-cow hooves. He stepped around piles of bone needles and broken stone tools, past heaps of lichen and moss gathered to feed the cows.

  Frost crackled.

  He glanced about uneasily. Nobody knew what he was planning today, and he didn't want to be spotted by any early risers...

  But all the dozen teepees were silent. Even the one belonging to Damen, Teal's elder brother. If Damen knew what he was up to, he'd knock Teal senseless.

  He found himself tip-toeing away like a naughty child.

  He reached the border of the village and began to lope across the tundra, his breathing easier. His even pace ate up the silent miles and the sky was barely brighter when he came to the bridge anchor.

  The anchor itself was an arch about the height of a man, made of something smooth and milky-white. The structure's original purpose was long forgotten, dating from before the ice. It was unimaginably old.

  Now, though, there was a rope tied to the crosspiece. The rope rose from the arch and pierced the clouds, as if it were tethering the sky... but, Teal knew, the rope looped on past the clouds and crossed space to another world.

  He approached the anchor past tarpaulined bundles of balloon equipment. Huddled around the arch were five mummy-cows. Humming simple songs they picked at the rope's knots with their articulated trunks.

  "Get away from that rope."

  The great soft beasts cowered at his voice. In their agitation they bumped together, trembling. Their ears flapped and their food teats wobbled comically.

  Finally one of the cows broke out of the group and approached nervously. "Pardon, ssir..."

  The cow was a broad fur-covered cylinder supported on stumplike legs. Her rectangu
lar head rotated mournfully around a single ball joint, and plate-sized eyes looked down at Teal. From the center of the blocky face sprouted a bifurcated trunk, and humanlike hands at the ends of the trunk's forks pulled at each other nervously.

  The other mummy-cows giggled and whispered.

  "Well?"

  "Pardon, ssir, but it iss... needed to move the rope today. It is the Su-Sun, ssir..."

  "I know about the Sun. Listen to me: I need your help. What's your name?"

  "Orange, ssir..."

  "Well, Orange, I intend to take up a balloon. Go and fetch the envelope and tackle. You know what that means, don't you?"

  "Yess. I often help with flightss. But the Su-Sun will come t-too close today..." The great floppy mouth worked in agitation.

  "That's the idea," he snapped. "I don't want to avoid the Sun. I'm going up to it. All right?"

  The other mummy-cows, startled, whispered together. He silenced them with a glare, his breath quickening. If they suspected he was here without the knowledge of the rest of the village they wouldn't help him.

  But Orange was looking at him steadily. "The Su-Sun is going out, isn't it, s-ssir?"

  "You know about that?" Teal asked, surprised.

  "We live a long time," said Orange. "Longer than people. Some of us notice things... Today the Su... the Sun is orange. But once it was yellow... in the da-dayss when Allel arrived in the f-first balloon from Home."

  The other mummy-cows nodded hugely, pounds of flesh rippling in their cheeks.

  Teal felt obscurely sorry for the mummy-cows, moved to speak to them, to explain. "Even then the world was growing cold," he said. "My grandmother crossed the Gap to find the answer. After that people were excited enough to build this bridge, so now we can travel between the worlds whenever we like.

  "But in the end Allel failed. The Sun's still cooling, and she found no answer."

  "But you will... fix-x it, ssir?"

  Teal laughed. If only he could find a human with such imagination — "Maybe."

  The dawn stained the sky a little brighter. Soon the village would be stirring; he had to be aloft quickly —