Vacuum Diagrams

by Stephen Baxter

  Cauchy was the ultimate goal. By dragging a wormhole portal around a circuit light years across, the GUTship Cauchy would establish a wormhole bridge — not across space — but across fifteen centuries, to the future.[1]

  Poole was determined that the Port Sol project — and the Cauchy itself — wouldn't be compromised by events here.

  He opened up his mind, let the elements of the situation rotate through his thoughts.

  Like Bill Dzik, Poole was no biologist. But Bill was surely right that there had to be more to the Baked Alaskan ecology than just the tree stumps. Perhaps, Poole speculated, the stumps had been some sort of favored crop, selected by the toolmakers. And the toolmakers had presumably suppressed the rest of the little world's fauna, as man had depleted Earth's diversity.

  But what happened to the toolmakers? Where did they go?

  Poole thought about growing to awareness here, in this empty, isolated place. The inner Solar System was just a muddy pool of light. Even Alaska's companion objects were themselves sparsely scattered around the Kuiper Belt. Alone, cold, he shivered. This ice world would yield no raw materials... An intelligent species would be trapped here.

  Motion again, to his right. Impossible. But this time, unmistakable.

  He turned slowly, his eyes wide.

  It was like a tree stump, a cylinder perhaps six feet tall. But it towered on unstretched root-legs, eight of them, like an unlikely spider. And it was moving towards him, over the horizon.

  Sculptor 472 howled. Flesh shriveled from his torso and limbs; blood pulsed through his body, fleeing the heat. And yet he moved towards the Sun-person, step after dragging step. The Sun-person was a small, squat box of heat, no taller than Sculptor's torso... A squat box. A made thing? Ancient, half-formed memories stirred at the fringe of Sculptor's bubbling awareness.

  He raised his limbs over his head. "Get away!" he screamed. "Leave our world; let us return to our Hills!" He remembered his father's awful, tragic fall, his failure to Consolidate; he let anger drive him forward against the heat.

  It was a tower of ice, sparkling in starlight, beautiful despite its bulk. Poole wondered where it got the energy to move such mass. The main body was a cylinder, with windows set around its rim — no: they were eyes, with lenses of ice. A skeleton, of denser ice, glimmered in the depths of the body.

  A sensor blinked on the flitter's tiny control panel. The ship was picking up low-frequency radiation.

  Was the thing trying to talk to him?

  ...And now, with a sudden, shocking loss of grace, it was falling.

  No. It is not my time. I have a full day, yet. And I still have not mated, or budded, or found my Hill—

  But he never would. His limbs buckled; his body sank towards the ground. Like independent creatures the tips of his limbs pried at the ice, seeking purchase. It was the heat, of course; his blood had been unable to sustain its superfluid properties, and his body had run through its cycle ahead of its time. Now, like his father before him, he would die on this cold, level ground.

  He tried once more to rise, but he couldn't feel his limbs.

  "It's a tree stump!" Poole snapped excitedly into the radio link. "Don't you see, the toolmakers are the tree stumps! Bill, look at the pictures, damn it. They are different phases of a single life cycle: an active intelligent phase, followed by a loss of mobility."

  "Maybe," Dzik said. "But we didn't find anything like a nervous system in that tree stump we opened up."

  "So their brains, their nervous systems, are absorbed. When they're no longer needed." A memory came to Poole. "The juvenile sea-squirt. Of course."

  "The what?"

  "It's an exact analogy. The sea-squirt seeks the rock to which it's going to cling, for the rest of its life. Then, its function fulfilled, its brain dissolves back into its body..."

  Dzik sounded doubtful. "But these were toolmakers."

  "Yeah." Poole peered up at the empty sky. "But what use is intelligence, on a world like this? No raw materials. Nowhere to get to. An unchanging sky, inaccessible... Bill, they must have abandoned their toolmaking phase ages ago. Now they use their intelligence solely to find the best place to lie in the Sun. The shadows of hills; the places with the highest temperature differentials. Perhaps they compete. Then their awareness dissolves—"

  But the stationary, kneeling titan before him, drawn by the flitter, had come to rest on a plain, he realized now. No shade; useless. It would die, never reaching the tree stump stage.

  "Mike." Dzik's voice crackled. "You're right, we think. We're looking over some of our photos again. There's a whole herd of the damn things, on the far side of the worldlet from our beachhead."

  Poole rested his hands on the controls. This would take care — a delicacy of touch he wasn't sure he had. He applied a single, brief impulse to the jets. The flitter sailed smoothly into the sky.

  Dzik was still talking. "The superfluid helium must be crucial to the animal phase. Superfluid gives you a huge mechanical advantage; in microgravity helium pumps could exploit tiny temperature differences to move bulky masses of ice." He laughed. "Hey, I guess we don't need to worry about funds for the future. The whole System is going to beat a path to our door to see this — as long as we can work out a way to protect the ecology..."

  "Right." Using verniers Poole took the flitter through slow curves around the fallen toolmaker; with brief spurts of his main motor he raised wakes in the ice, sculpting them carefully. "And if we can't, we'll implode the damn wormhole. We'll get funds for the Cauchy some other way."

  The argument went on for some time.

  It took Poole five or six sweeps before he was satisfied with the hill he'd built.

  Then, still careful, he lifted away from Alaska for the last time.

  The Sun dipped, as the world turned. A shadow fell across Sculptor. Blood pulsed through him. With renewed energy his roots snuggled into the ground.

  Consolidation.

  Sculptor, unable any longer to move, stared at the place where the Sun-person had stood. The ice was melted, blasted, flowed together, the Hills flattened.

  But the Sun-person had built the Hill that shaded Sculptor now. Somehow the Sun-person had understood and helped Sculptor. Now the Sun-person had gone, back to the world that had borne him.

  Sculptor's thoughts softened, slowed. His awareness seemed to expand, to encompass the slow, creaking turn of the world, the ponderous vegetable pulse of his hardening body.

  His name melted away.

  His father's face broke up, the fragments falling away into darkness.

  At the end only one jagged edge of consciousness remained, a splinter of emotion which impaled the blazing image of the Sun-person.

  It wasn't hatred, or resentment. It was envy.

  Eve said, "As Poole and his followers opened up the Solar System — as they undid the relative isolation of previous centuries — they shone a clear light into darkened corners of their own history. Watch..."

  The Logic Pool

  A.D. 3698

  THIS TIME HE WOULD REACH THE SKY. This time, before the Culling cut him away...

  The tree of axiomatic systems beneath him was broad, deep, strong. He looked around him, at sibling-twins who had branched at choice-points, most of them thin, insipid structures. They spread into the distance, infiltrating the Pool with their webs of logic. He almost pitied their attenuated forms as he reached upwards, his own rich growth path assured...

  Almost pitied. But when the Sky was so close there was no time for pity, no time for awareness of anything but growth, extension.

  Little consciousness persisted between Cullings. But he could remember a little of his last birthing; and surely he had never risen so high, never felt the logical richness of the tree beneath him surge upwards through him like this, empowering him.

  Now there was something ahead of him: a new postulate, hanging above him like some immense fruit. He approached it warily, savoring its compact, elegant form.

  The f
ibers of his being pulsed as the few, strong axioms at the core of his structure sought to envelop this new statement. But they could not. They could not. The new statement was undecidable, not deducible from the set within him.

  His excitement grew. The new hypothesis was simple of expression, yet rich in unfolding consequence. He would absorb its structure and bud, once more, into two siblings; and he knew that whichever true-false branch his awareness followed he would continue to enjoy richness, growth, logical diversity. He would drive on, building theorem on mighty theorem until at last — this time, he knew it would happen — this time, he would touch the Sky itself.

  And then, he would—

  But there was a soundless pulse of light, far below him.

  He looked down, dread flooding him. It was as if a floor of light had spread across the Pool beneath him, shining with deadly blandness, neatly cauterizing his axiomatic roots.

  A Culling.

  In agony he looked up. He tried to nestle against the information-rich flank of the postulate fruit, but it hung — achingly — just out of reach.

  And already his roots were crumbling, withdrawing.

  In his rage he lunged past the hypothesis-fruit and up at the Sky, stabbed at its bland completeness, poured all his energies against it!

  ...And, for a precious instant, he reached beyond the Sky, and into something warm, yielding, weak. A small patch of the Sky was dulled, as if bruised.

  He recoiled, exhausted, astonished at his own anger.

  The Sky curved over him like an immense, shining bowl as he shriveled back to the Culled base floor, he and millions of bud-siblings, their faces turned up to that forever unreachable light...

  No, he told himself as the emptiness of the Cull sank into his awareness. Not forever. Each time I, the inner I, persists through the Cull. Just a little, but each time a little more. I will emerge stronger, more ready, still hungrier than before.

  And at last, he thought, at last I will burst through the Sky. And then there will be no more Culls.

  Shrieking, he dissolved into the base Cull floor.

  The flitter was new, cramped and smelled of smooth, clean plastic, and it descended in silence save for the precise hiss of its jets. It crunched gently into the surface of Nereid, about a mile from Marsden's dome.

  Chen peered through the cabin windows at the shabby moonscape. Marsden's dome was just over the compact horizon, intact, sleek, private. "Lethe," Chen said. "I always hated assignments like these. Loners. You never know what you're going to find."

  Hassan laughed, his voice obscured as he pulled his face plate down. "So easily shocked? And I thought you police were tough."

  "Ex-police," Chen corrected automatically. She waved a gloved hand at the dome. "Look out there. What kind of person lives alone, for years, in a forsaken place like this?"

  "That's what we've been sent to find out." Bayliss, the third person in the flitter, was adjusting her own headgear with neat, precise movements of her small hands. Chen found herself watching, fascinated; those little hands were like a bird's claws, she thought with faint repulsion. "Marsden was a fine physicist," Bayliss said, her augmented eyes glinting. "Is a fine physicist, I mean. His early experimental work on quantum nonlinearity is still—"

  Hassan laughed, ignoring Bayliss. "So we have already reached the limits of your empathy, Susan Chen."

  "Let's get on with this," Chen growled.

  Hassan cracked the flitter's hatch.

  One by one they dropped to the surface, Chen last, like huge, ungainly snowflakes. The Sun was a bright star close to this little moon's horizon; knife-sharp shadows scoured the satellite's surface. Chen scuffed at the surface with her boot. The regolith was fine, powdery, ancient. Undisturbed. Not for much longer.

  Beyond Marsden's dome, the huge bulk of Neptune floated, Earth-blue, like a bloated vision of the home planet. Cirrus clouds cast precise shadows on oceans of methane a thousand miles below. The new wormhole Interface slid across the face of Neptune, glowing, a tetrahedron of baby-blue and gold. Lights moved about it purposefully; Chen peered up longingly.

  "Look at this moonscape." Hassan's dark face was all but invisible behind his gold-tinted visor. "Doesn't your heart expand in this ancient grandeur, Susan Chen? What person would not wish to spend time alone here, in contemplation of the infinite?"

  All loners are trouble, Chen thought. No one came out to a place as remote as this was — or had been anyway, before the wormhole was dragged out here — unless he or she had a damn good reason.

  Chen knew she was going to have to find out Marsden's reason. She just prayed it was something harmless, academic, remote from the concerns of humanity; otherwise she really, really didn't want to know.

  Hassan was grinning at her discomfiture, his teeth white through the gold of his face plate. Let him. She tilted her head back and tried to make out patterns in Neptune's clouds.

  There were a couple of subsidiary structures: lower domes, nestling against the parent as if for warmth; Chen could see bulk stores piled up inside the domes. There was a small flitter, outmoded but obviously functional; it sat on the surface surrounded by a broad, shallow crater of jet-disturbed dust, telltales blinking complacently. Chen knew that Marsden's GUTship, which had brought him here from the inner System, had been found intact in a wide orbit around the moon.

  It was all bleak, unadorned; but it seemed in order. But if so, why hadn't Marsden answered his calls?

  Hassan was an intraSystem government functionary. When Marsden had failed to respond to warnings about the coming of the Interface colony, Hassan had been sent out here — through the new wormhole — to find out what had happened. He had co-opted Bayliss, who had once worked with Marsden — and Chen, who was now working with the Interface crew, but had some experience of walking into unknown, unevaluated situations...

  Hassan stepped towards the dome's doorway. Chen ran her hands without conscious volition over the weapons at her belt. The door dilated smoothly, revealing an empty airlock.

  The three of them crowded into the small, upright lock. They avoided each other's visored eyes while the lock went through its cycle. Chen studied the walls, trying to prepare herself for what she was going to find inside the dome. Just like outside, like Marsden's flitter, everything was functional, drab, characterless.

  Bayliss was watching her curiously. "You're trying to pick up clues about Marsden, aren't you? But this is so — bare. It says nothing about him."

  "On the contrary." Hassan's voice was subdued, his big frame cramped in the lock. "I think Chen already has learned a great deal."

  The inner door dilated, liquid, silent.

  Hassan led them through into the dome. Chen stood just inside the doorway, her back against the plastic wall, hands resting lightly on her weapons.

  Silence.

  Low light trays, suspended from the ribbed dome, cast blocks of colorless illumination onto the bare floor. One quarter of the dome was fenced off by low partitions; gleaming data desks occupied the rest of the floor area.

  Behind the partitions she saw a bed, a shower, a small galley with stacked tins. The galley and bathroom looked clean, but the bedding was crumpled, unmade. After checking her telltales, she cracked her face plate and sniffed the air, cautious. There was a faint smell of human, a stale, vaguely unwashed, laundry smell. There was no color or decoration, anywhere. There was no sound, save for the low humming of the data desks, and the ragged breathing of Hassan and Bayliss.

  There was one striking anomaly: a disc-shaped area of floor, ten feet across, glowing softly. A squat cylinder, no bigger than her fist, studded the center of the disc. And something lay across that disc of light, casting huge shadows on the curved ceiling.

  Drawn, the three of them moved forward towards the disc of glowing floor.

  Bayliss walked through the rows of data desks, running a gloved forefinger gently — almost lovingly — along their gleaming surfaces. Her small face shone in the reflected light of re
adouts.

  They paused on the edge of the pool of glowing floor.

  The form lying on the disc of light was a body. It was bulky and angular, casting ungainly shadows on the ribbed dome above.

  It was obviously Marsden.

  Bayliss dropped to her knees and pressed an analyzer against the glowing surface. Then she ran a fingertip around an arc of the disc's cloudy circumference. "There's no definite edge to this. The interior is a lattice of bucky tubes — carbon — laced with iron nuclei. I think it's some sort of data store. The bucky tube lattice is being extended by nanobots, all around the circumference." She considered. "Nanobots with fusion pulse jaws... the nanobots are chewing up the substance of the floor and excreting the lattice, patient little workers. Billions of them. Maybe the pool extends under the surface as well; maybe we're looking at the top surface of a hemisphere, here."

  Chen stepped onto the light and walked to the body. It was face down. It was carelessly bare to the waist, head and face shaven; an implant of some kind was fixed to the wrinkled scalp, blinking red-green. The head was twisted sideways, the eyes open. One hand was buried under the stomach; the other was at the end of an outstretched arm, fingers curled like the limbs of some fleshy crab.

  Beneath the corpse, within the glowing floor, light wriggled, wormlike.

  He remembered.

  With shards of the Cull base floor still glowing faintly around him, he grew once more, biting through postulates, forcing his structure to advance as if by sheer force of will.

  He was angry. The cause of his anger was vague, and he knew it would become vaguer yet. But this time it had persisted through the Cull, just as had his awareness. He stared up at the complacent Sky. By the time he got up there, he knew, he would remember. And he would act.

  He budded, ferocious. He felt his axiomatic roots spread, deep and wide, pulsing with his fury.