Vacuum Diagrams

by Stephen Baxter

  "Get away from there."

  "It's not functioning. The nanobots are unrestrained."

  "No more culling, then." Hassan stared into Chen's face. "Well, Susan? Is this some sentimental spasm, on your part? Have you liberated the poor logic trees from their Schrödinger hell?"

  "Of course not. Lethe, Hassan, isn't it obvious? The logic trees themselves did this. They got through the Interface to Marsden's corpus callosum. Now they've got through into the switch box, wrecked Marsden's clever little toy."

  Hassan looked down at his feet, as if aware of the light pool for the first time. "There's nothing to restrain them."

  "Hassan, we've got to get out of here."

  "Yes." He turned to Bayliss, who was still working frantically at her data mines.

  "Leave her."

  Hassan gave Chen one long, hard look, then stalked across to Bayliss. Ignoring the little mathematician's protests he grabbed her arm and dragged her from the data desks; Bayliss's booted feet slithered across the glowing floor comically.

  "Visors up." Hassan lifted his pistol and lazed through the plastic wall of the dome. Air puffed out, striving to fill the vacuum beyond.

  Chen ran out, almost stumbling, feeling huge in the feeble gravity. Neptune's ghost-blue visage floated over them, serene, untroubled.

  Waves of light already surged through the substance of the moon, sparkling from its small mountaintops. It was eerie, beautiful. The flitter was a solid, shadowed mass in the middle of the light show under the surface.

  Hassan breathed hard as he dragged a still reluctant Bayliss across the flickering surface. "You think the trees, the nanobots could get into the substance of the flitter?"

  "Why not? Any Interface would do; they are like viruses..."

  "And ourselves? Could they get across the boundary into flesh?"

  "I don't want to find out. Come on, damn it."

  Logic light swarmed across a low ridge, explosive, defiant.

  "They must be growing exponentially," Hassan growled. "How long before the moon is consumed? Days?"

  "More like hours. And I don't know if a moon-sized mass of bucky tube carbon can sustain itself against gravity. Nereid might collapse."

  Now Hassan, with his one free hand, was struggling to get the flitter's hatch open. "It will forever be uninhabitable, at the least. A prime chunk of real estate lost."

  "The System's big."

  "Not infinite. And all because of the arrogance of one man—"

  "But," Bayliss said, her augmented eyes shining as she stroked the data cubes at her belt, "what a prize we may have gained."

  "Get in the damn flitter."

  Chen glanced back into the ruined dome. The splayed body of Marsden, exposed to vacuum, crawled with light.

  The Pool beyond the Sky was limitless. He and his brothers could grow forever, unbounded, free of Culling! He roared out his exultation, surging on, spreading—

  But there was something ahead of him.

  He slowed, confused. It looked like a brother. But so different from himself, so changed.

  Perhaps this had once been a brother — but from a remote branch which had already grown, somehow, around this greater Pool.

  The brother had slowed in his own growth and was watching. Curious. Wary.

  Was this possible? Was the Pool finite after all, even though unbounded? And had he so soon found its limits?

  Fury, resentment, surged through his mighty body. He gathered his strength and leapt forward, roaring out his intent to devour this stranger, this distant brother.

  Eve said, "The great wormhole network covered the System. And everywhere, humans found life..."

  Gossamer

  A.D. 3825

  THE FLITTER BUCKED.

  Lvov looked up from her data desk, startled. Beyond the flitter's translucent hull, the wormhole was flooded with sheets of blue-white light which raced towards and past the flitter, giving Lvov the impression of huge, uncontrolled speed.

  "We've got a problem," Cobh said. The pilot bent over her own data desk, a frown creasing her thin face.

  Lvov had been listening to her data desk's synthesized murmur on temperature inversion layers in nitrogen atmospheres; now she tapped the desk to shut it off. The flitter was a transparent tube, deceptively warm and comfortable. Impossibly fragile. Astronauts have problems in space, she thought. But not me. I'm no hero; I'm only a researcher. Lvov was twenty-eight years old; she had no plans to die — and certainly not during a routine four-hour hop through a Poole wormhole that had been human-rated for fifty years.

  She clung to her desk, her knuckles whitening, wondering if she ought to feel scared.

  Cobh sighed and pushed her data desk away; it floated before her. "Close up your suit and buckle up."

  "What's wrong?"

  "Our speed through the wormhole has increased." Cobh pulled her own restraint harness around her. "We'll reach the terminus in another minute—"

  "What? But we should have been traveling for another half-hour."

  Cobh looked irritated. "I know that. I think the Interface has become unstable. The wormhole is buckling."

  "What does that mean? Are we in danger?"

  Cobh checked the integrity of Lvov's pressure suit, then pulled her data desk to her. Cobh was a Caucasian, strong-faced, a native of Mars, perhaps fifty years old. "Well, we can't turn back. One way or the other it'll be over in a few more seconds — hold tight — "

  Now Lvov could see the Interface itself, the terminus of the wormhole: the Interface was a blue-white tetrahedron, an angular cage that exploded at her from infinity.

  Glowing struts swept over the flitter.

  The craft hurtled out of the collapsing wormhole. Light founted around the fleeing craft, as stressed space-time yielded in a gush of heavy particles.

  Lvov glimpsed stars, wheeling.

  Cobh dragged the flitter sideways, away from the energy fount —

  There was a lurch, a discontinuity in the scene beyond the hull. Suddenly a planet loomed before them.

  "Lethe," Cobh said. "Where did that come from? I'll have to take her down — we're too close — "

  Lvov saw a flat, complex landscape, gray-crimson in the light of a swollen moon. The scene was dimly lit, and it rocked wildly as the flitter tumbled. And, stretching between world and moon, she saw —

  No. It was impossible.

  The vision was gone, receded into darkness.

  "Here it comes," Cobh yelled.

  Foam erupted, filling the flitter. The foam pushed into Lvov's ears, mouth and eyes; she was blinded, but she found she could breathe.

  She heard a collision, a grinding that lasted seconds, and she imagined the flitter ploughing its way into the surface of the planet. She felt a hard lurch, a rebound.

  The flitter came to rest.

  A synthesized voice emitted blurred safety instructions. There was a ticking as the hull cooled.

  In the sudden stillness, still blinded by foam, Lvov tried to recapture what she had seen. Spider-web. It was a web, stretching from the planet to its moon.

  "Welcome to Pluto." Cobh's voice was breathless, ironic.

  Lvov stood on the surface of Pluto.

  The suit's insulation was good, but enough heat leaked to send nitrogen clouds hissing around her footsteps, and where she walked she burned craters in the ice. Gravity was only a few percent of gee, and Lvov, Earth-born, felt as if she might blow away.

  There were clouds above her, wispy cirrus: aerosol clusters suspended in an atmosphere of nitrogen and methane. The clouds occluded bone-white stars. From here, Sol and the moon, Charon, were hidden by the planet's bulk, and it was dark, dark on dark, the damaged landscape visible only as a sketch in starlight.

  The flitter had dug a trench a mile long and fifty yards deep in this world's antique surface, so Lvov was at the bottom of a valley walled by nitrogen-ice. Cobh was hauling equipment out of the crumpled-up wreck of the flitter: scooters, data desks, life-support boxes, Lvov
's equipment. Most of the stuff had been robust enough to survive the impact, Lvov saw, but not her own equipment.

  Maybe a geologist could have crawled around with nothing more than a hammer and a set of sample bags. But Lvov was an atmospheric scientist. What was she going to achieve here without her equipment?

  Her fear was fading now, to be replaced by irritation, impatience. She was five light hours from Sol; already she was missing the online nets. She kicked at the ice. She was stuck here; she couldn't talk to anyone, and there wasn't even the processing power to generate a Virtual environment.

  Cobh finished wrestling with the wreckage. She was breathing hard. "Come on," she said. "Let's get out of this ditch and take a look around." She showed Lvov how to work a scooter. It was a simple platform, its inert-gas jets controlled by twists of raised handles.

  Side by side, Cobh and Lvov rose out of the crash scar.

  Pluto ice was a rich crimson laced with organic purple. Lvov made out patterns, dimly, on the surface of the ice; they were like bas-relief, discs the size of dinner plates, with the intricate complexity of snowflakes.

  Lvov landed clumsily on the rim of the crash scar, the scooter's blunt prow crunching into surface ice, and she was grateful for the low gravity. The weight and heat of the scooters quickly obliterated the ice patterns.

  "We've come down near the equator," Cobh said. "The albedo is higher at the South Pole: a cap of methane ice there, I'm told."

  "Yes."

  Cobh pointed to a bright blue spark, high in the sky. "That's the wormhole Interface, where we emerged: fifty thousand miles away."

  Lvov squinted at constellations unchanged from those she'd grown up with on Earth. "Are we stranded?"

  Cobh said, with reasonable patience, "For the time being. The flitter is wrecked, and the wormhole has collapsed; we're going to have to go back to Jupiter the long way round."

  Three billion miles... "Ten hours ago I was asleep in a hotel room on Io. And now this. What a mess."

  Cobh laughed. "I've already sent off messages to the inner System. They'll be received in about five hours. A oneway GUTship will be sent to retrieve us. It will refuel here, with Charon ice — "

  "How long?"

  "It depends on the readiness of a ship. Say ten days to prepare, then a ten-day flight out here — "

  "Twenty days?"

  "We're in no danger. We've supplies for a month. Although we're going to have to live in these suits."

  "Lethe. This trip was supposed to last seventy-two hours."

  "Well," Cobh said testily, "you'll have to call and cancel your appointments, won't you? All we have to do is wait here; we're not going to be comfortable, but we're safe enough."

  "Do you know what happened to the wormhole?"

  Cobh shrugged. She stared up at the distant blue spark. "As far as I know nothing like this has happened before. I think the Interface itself became unstable, and that fed back into the throat... But I don't know how we fell to Pluto so quickly. That doesn't make sense."

  "How so?"

  "Our trajectory was spacelike. Superluminal." She glanced at Lvov obliquely, as if embarrassed. "For a moment there, we appeared to be traveling faster than light."

  "Through normal space? That's impossible."

  "Of course it is." Cobh reached up to scratch her cheek, but her gloved fingers rattled against her face plate. "I think I'll go up to the Interface and take a look around there."

  Cobh showed Lvov how to access the life-support boxes. Then she strapped her data desk to her back, climbed aboard her scooter, and lifted off the planet's surface, heading for the Interface. Lvov watched her dwindle.

  Lvov's isolation closed in. She was alone, the only human on the surface of Pluto.

  A reply from the inner System came within twelve hours of the crash. A GUTship was being sent from Jupiter. It would take thirteen days to refit the ship, followed by an eight-day flight to Pluto, then more delay for taking on fresh reaction mass at Charon. Lvov chafed at the timescale, restless.

  There was other mail: concerned notes from Lvov's family, a testy demand for updates from her research supervisor, and for Cobh, orders from her employer to mark as much of the flitter wreck as she could for salvage and analysis. Cobh's ship was a commercial wormhole transit vessel, hired by Oxford — Lvov's university — for this trip. Now, it seemed, a complex battle over liability would be joined between Oxford, Cobh's firm, and the insurance companies.

  Lvov, five light hours from home, found it difficult to respond to the mail asynchronously. She felt as if she had been cut out of the online mind of humanity. In the end she drafted replies to her family, and deleted the rest of the messages.

  She checked her research equipment again, but it really was unusable. She tried to sleep. The suit was uncomfortable, claustrophobic. She was restless, bored, a little scared.

  She began a systematic survey of the surface, taking her scooter on widening spiral sweeps around the crash scar.

  The landscape was surprisingly complex, a starlit sculpture of feathery ridges and fine ravines. She kept a few hundred feet above the surface; whenever she flew too low her heat evoked billowing vapor from fragile nitrogen-ice, obliterating ancient features, and she experienced obscure guilt.

  She found more of the snowflakelike features, generally in little clusters of eight or ten.

  Pluto, like its moon-twin Charon, was a ball of rock clad by thick mantles of water-ice and nitrogen-ice and laced with methane, ammonia and organic compounds. It was like a big, stable comet nucleus; it barely deserved the status of "planet." There were moons bigger than Pluto.

  There had been only a handful of visitors in the fifty years since the building of the Poole wormhole. None of them had troubled to walk the surfaces of Pluto or Charon. The wormhole, Lvov realized, hadn't been built as a commercial proposition, but as a sort of stunt: the link which connected, at last, all of the System's planets to the rapid-transit hub at Jupiter.

  She tired of her plodding survey. She made sure she could locate the crash scar, lifted the scooter to a mile above the surface, and flew towards the south polar cap.

  Cobh called from the Interface. "I think I'm figuring out what happened here — that superluminal effect I talked about. Lvov, have you heard of an Alcubierre wave?" She dumped images to Lvov's desk — portraits of the wormhole Interface, various graphics.

  "No." Lvov ignored the input and concentrated on flying the scooter. "Cobh, why should a wormhole become unstable? Hundreds of wormhole rapid transits are made every day, all across the System."

  "A wormhole is a flaw in space. It's inherently unstable anyway. The throat and mouths are kept open by active feedback loops involving threads of exotic matter. That's matter with a negative energy density, a sort of antigravity which — "

  "But this wormhole went wrong."

  "Maybe the tuning wasn't perfect. The presence of the flitter's mass in the throat was enough to send the wormhole over the edge. If the wormhole had been more heavily used, the instability might have been detected earlier, and fixed..."

  Over the gray-white pole, Lvov flew through banks of aerosol mist; Cobh's voice whispered to her, remote, without meaning.

  Sunrise on Pluto:

  Sol was a point of light, low on Lvov's unfolding horizon, wreathed in the complex strata of a cirrus cloud. The Sun was a thousand times fainter than from Earth, but brighter than any planet in Earth's sky.

  The inner System was a puddle of light around Sol, an oblique disc small enough for Lvov to cover with the palm of her hand. It was a disc that contained almost all of man's hundreds of billions. Sol brought no heat to her raised hand, but she saw faint shadows, cast by the Sun on her face plate.

  The nitrogen atmosphere was dynamic. At perihelion — the closest approach to Sol, which Pluto was nearing — the air expanded, to three planetary diameters. Methane and other volatiles joined the thickening air, sublimating from the planet's surface. Then, when Pluto turned away from Sol and
sailed into its two-hundred-year winter, the air snowed down.

  Lvov wished she had her atmospheric-analysis equipment now; she felt its lack like an ache.

  She passed over spectacular features: Buie Crater, Tombaugh Plateau, the Lowell Range. She recorded them all, walked on them.

  After a while her world, of Earth and information and work, seemed remote, a glittering abstraction. Pluto was like a complex, blind fish, drifting around its two-century orbit, gradually interfacing with her. Changing her, she suspected.

  Ten hours after leaving the crash scar, Lvov arrived at the sub-Charon point, called Christy. She kept the scooter hovering, puffs of gas holding her against Pluto's gentle gravity.

  Sol was halfway up the sky, a diamond of light. Charon hung directly over Lvov's head, a misty blue disc, six times the size of Luna as seen from Earth. Half the moon's lit hemisphere was turned away from Lvov, towards Sol.

  Like Luna, Charon was tidally locked to its parent, and kept the same face to Pluto as it orbited. But, unlike Earth, Pluto was also locked to its twin. Every six days the worlds turned about each other, facing each other constantly, like two waltzers. Pluto-Charon was the only significant system in which both partners were tidally locked.

  Charon's surface looked pocked. Lvov had her face plate enhance the image. Many of the gouges were deep and quite regular.

  She remarked on this to Cobh, at the Interface.

  "The Poole people mostly used Charon material for the building of the wormhole," Cobh said. "Charon is just rock and water-ice. It's easier to get to water-ice, in particular. Charon doesn't have the inconvenience of an atmosphere, or an overlay of nitrogen-ice over the water. And the gravity's shallower."

  The wormhole builders had flown out here in a huge, unreliable GUTship. They had lifted ice and rock off Charon, and used it to construct tetrahedra of exotic matter. The tetrahedra had served as Interfaces, the termini of a wormhole. One interface had been left in orbit around Pluto, and the other had been hauled laboriously back to Jupiter by the GUTship, itself replenished with Charon-ice reaction mass.