Vacuum Diagrams

by Stephen Baxter

  Then the GUTdrive veered sharply upwards, climbing directly towards Lvov and Cobh at the Interface.

  "Cobh, are you sure this is going to work?"

  Lvov could hear Cobh's breath rasp, shallow. "Look, Lvov, I know you're scared, but pestering me with dumb-ass questions isn't going to help. Once the drive enters the Interface, it will take only seconds for the instability to set in. Seconds, and then we'll be home. In the inner System, at any rate. Or..."

  "Or what?"

  Cobh didn't reply.

  Or not, Lvov finished for her. If Cobh has designed this new instability right, the Alcubierre wave will carry us home. If not —

  The GUTdrive flame approached, becoming dazzling. Lvov tried to regulate her breathing, to keep her limbs hanging loose —

  "Lethe," Cobh whispered.

  "What?" Lvov demanded, alarmed.

  "Take a look at Pluto. At Christy."

  Lvov looked into her face plate.

  Where the warmth and light of the GUTdrive had passed, Christy was a ferment. Nitrogen billowed. And, amid the pale fountains, burrows were opening. Lids folded back. Eggs cracked. Infant flakes soared and sailed, with webs and nets of their silk-analogue hauling at the rising air.

  Lvov caught glimpses of threads, long, sparkling, trailing down to Pluto — and up towards Charon. Already, Lvov saw, some of the baby flakes had hurtled more than a planetary diameter from the surface, towards the moon.

  "It's goose summer," she said.

  "What?"

  "When I was a kid... the young spiders spin bits of webs, and climb to the top of grass stalks, and float off on the breeze. Goose summer — gossamer."

  "Right," Cobh said skeptically. "Well, it looks as if they are making for Charon. They use the evaporation of the atmosphere for lift... Perhaps they follow last year's threads, to the moon. They must fly off every perihelion, rebuilding their web bridge every time. They think the perihelion is here now. The warmth of the drive — it's remarkable. But why go to Charon?"

  Lvov couldn't take her eyes off the flakes. "Because of the water," she said. It all seemed to make sense, now that she saw the flakes in action. "There must be water glass, on Charon's surface. The baby flakes use it to build their bodies. They take other nutrients from Pluto's interior, and the glass from Charon... They need the resources of both worlds to survive — "

  "Lvov!"

  The GUTdrive flared past them, sudden, dazzling, and plunged into the damaged Interface.

  Electric-blue light exploded from the Interface, washing over her.

  There was a ball of light, unearthly, behind her, and an irregular patch of darkness ahead, like a rip in space. Tidal forces plucked gently at her belly and limbs.

  Pluto, Charon and goose summer disappeared. But the stars, the eternal stars, shone down on her, just as they had during her childhood on Earth. She stared at the stars, trusting, and felt no fear.

  Remotely, she heard Cobh whoop, exhilarated.

  The tides faded. The darkness before her healed, to reveal the brilliance and warmth of Sol.

  It was a time of extraordinary ambition and achievement. The anthropic theories of cosmological evolution were somewhere near their paradigmatic peak. Some believed humans were alone in the Universe. Others even believed the Universe had been designed, by some offstage agency, with the sole object of delivering and supporting humans.

  Given time, humans could do anything, go anywhere, achieve whatever they liked.

  Michael Poole was rightly celebrated for his achievements. His wormhole projects had opened up the System much as the great railroads had opened up the American continent, two thousand years earlier.

  But Poole had greater ambitions in mind.

  Poole used wormhole technology to establish a time tunnel: a bridge across fifteen hundred years, to the future. 1

  1 See Timelike Infinity

  Why was Poole's wormhole time link built?

  There were endless justifications — what power could a glimpse of the future afford? — but the truth was that it had been built for little more than the sheer joy of it.

  But Poole's bridge reached an unexpected future.

  The incident that followed the opening of the wormhole was confused, chaotic, difficult to disentangle. But it was a war — brief, spectacular, like no battle fought in Solar space before — but a war nevertheless. It was an invasion from a remote future, in which the Solar System had been occupied by an alien power.

  The incursion was repelled. Michael Poole drove a captured warship into the wormhole, to seal it against further invasion. In the process, Poole himself was lost in time.

  The System, stunned, slowly returned to normal.

  Various bodies combed through the fragments of data from the time bridge incident, trying to answer the unanswerable.

  It was said that before Poole's wormhole path to the future finally closed, some information had been obtained on the far future. And the rumors said that the future — and what it held for mankind — were bleak indeed.

  If the data was anything like accurate, it was clear that there was an agency at large — which must be acting even now — systematically destroying the stars...

  And, as a consequence, humanity.

  In response, an organization called the Holy Superet Church of Light emerged and evolved. Superet believed that humanity was becoming mature, as a species. And it was time to take responsibility for man's long-term survival as a species.

  Eve said, "A fresh starship was launched, called the Great Northern, in an attempt to build a new time bridge. And probes were prepared to investigate the heart of man's own star, the Sun, where a dark cancer was growing..."[2]

  Cilia-of-Gold

  A.D. 3948

  THE PEOPLE — THOUGH EXHAUSTED by the tunnel's cold — had rested long enough, Cilia-of-Gold decided.

  Now it was time to fight.

  She climbed up through the water, her flukes pulsing, and prepared to lead the group further along the Ice-tunnel to the new Chimney cavern.

  But, even as the people rose from their browsing and crowded through the cold, stale water behind her, Cilia-of-Gold's resolve wavered. The Seeker was a heavy presence inside her. She could feel its tendrils wrapped around her stomach, and — she knew — its probes must already have penetrated her brain, her mind, her self.

  With a beat of her flukes, she thrust her body along the tunnel. She couldn't afford to show weakness. Not now.

  "Cilia-of-Gold."

  A broad body, warm through the turbulent water, came pushing out of the crowd to bump against hers: it was Strong-Flukes, one of Cilia-of-Gold's Three-mates. Strong-Flukes' presence was immediately comforting. "Cilia-of-Gold. I know something's wrong."

  Cilia-of-Gold thought of denying it; but she turned away, her depression deepening. "I couldn't expect to keep secrets from you. Do you think the others are aware?"

  The hairlike cilia lining Strong-Flukes' belly barely vibrated as she spoke. "Only Ice-Born suspects something is wrong. And if she didn't, we'd have to tell her." Ice-Born was the third of Cilia-of-Gold's mates.

  "I can't afford to be weak, Strong-Flukes. Not now."

  As they swam together, Strong-Flukes flipped onto her back. Tunnel water filtered between Strong-Flukes' carapace and her body; her cilia flickered as they plucked particles of food from the stream and popped them into the multiple mouths along her belly. "Cilia-of-Gold," she said. "I know what's wrong. You're carrying a Seeker, aren't you?"

  "...Yes. How could you tell?"

  "I love you," Strong-Flukes said. "That's how I could tell."

  The pain of Strong-Flukes' perception was as sharp, and unexpected, as the moment when Cilia-of-Gold had first detected the signs of the infestation in herself... and had realized, with horror, that her life must inevitably end in madness, in a purposeless scrabble into the Ice over the world. "It's still in its early stages, I think. It's like a huge heat, inside me. And I can feel it reaching into my mind. Oh, Strong-Fluk
es..."

  "Fight it."

  "I can't. I—"

  "You can. You must."

  The end of the tunnel was an encroaching disc of darkness; already Cilia-of-Gold could feel the inviting warmth of the Chimney-heated water on the cavern beyond.

  This should have been the climax, the supreme moment of Cilia-of-Gold's life.

  The group's old Chimney, with its fount of warm, rich water, was failing; and so they had to flee, and fight for a place in a new cavern.

  That, or die.

  It was Cilia-of-Gold who had found the new Chimney, as she had explored the endless network of tunnels between the Chimney caverns. Thus, it was she who must lead this war — Seeker or no Seeker.

  She gathered up the fragments of her melting courage.

  "You're the best of us, Cilia-of-Gold," Strong-Flukes said, slowing. "Don't ever forget that."

  Cilia-of-Gold pressed her carapace against Strong-Flukes' in silent gratitude.

  Cilia-of-Gold turned and clacked her mandibles, signaling the rest of the people to halt. They did so, the adults sweeping the smaller children inside their strong carapaces.

  Strong-Flukes lay flat against the floor and pushed a single eye stalk towards the mouth of the tunnel. Her caution was wise; there were species who could home in on even a single sound-pulse from an unwary eye.

  After some moments of silent inspection, Strong-Flukes wriggled back along the Ice surface to Cilia-of-Gold.

  She hesitated. "We've got problems, I think," she said at last.

  The Seeker seemed to pulse inside Cilia-of-Gold, tightening around her gut. "What problems?"

  "This Chimney's inhabited already. By Heads."

  Kevan Scholes stopped the rover a hundred yards short of the wall-mountain's crest.

  Irina Larionova, wrapped in a borrowed environment suit, could tell from the tilt of the cabin that the surface here was inclined upwards at around forty degrees — shallower than a flight of stairs. This "mountain," heavily eroded, was really little more than a dust-clad hill, she thought.

  "The wall of Chao Meng-Fu Crater," Scholes said briskly, his radio-distorted voice tinny. "Come on. We'll walk to the summit from here."

  "Walk?" She studied him, irritated. "Scholes, I've had one hour's sleep in the last thirty-six; I've traveled across ninety million miles to get here, via flitters and wormhole transit links — and you're telling me I have to walk up this damn hill?"

  Scholes grinned through his face plate. He was AS-preserved at around physical-twenty-five, Larionova guessed, and he had a boyishness that grated on her. Damn it, she reminded herself, this "boy" is probably older than me.

  "Trust me," he said. "You'll love the view. And we have to change transports anyway."

  "Why?"

  "You'll see."

  He twisted gracefully to his feet. He reached out a gloved hand to help Larionova pull herself, awkwardly, out of her seat. When she stood on the cabin's tilted deck, her heavy boots hurt her ankles.

  Scholes threw open the rover's lock. Residual air puffed out of the cabin, crystallizing. The glow from the cabin interior was dazzling; beyond the lock, Larionova saw only darkness.

  Scholes climbed out of the lock and down to the planet's invisible surface. Larionova followed him awkwardly; it seemed a long way to the lock's single step.

  Her boots settled to the surface, crunching softly. The lock was situated between the rover's rear wheels: the wheels were constructs of metal strips and webbing, wide and light, each wheel taller than she was.

  Scholes pushed the lock closed, and Larionova was plunged into sudden darkness.

  Scholes loomed before her. He was a shape cut out of blackness. "Are you okay? Your pulse is rapid."

  She could hear the rattle of her own breath, loud and immediate. "Just a little disoriented."

  "We've got all of a third of a gee down here, you know. You'll get used to it. Let your eyes dark-adapt. We don't have to hurry this."

  She looked up.

  In her peripheral vision, the stars were already coming out. She looked for a bright double star, blue and white. There it was: Earth, with Luna.

  And now, with a slow grandeur, the landscape revealed itself to her adjusting eyes. The plain from which the rover had climbed spread out from the foot of the crater wall-mountain. It was a complex patchwork of crowding craters, ridges and scarps — some of which must have been miles high — all revealed as a glimmering tracery in the starlight. The face of the planet seemed wrinkled, she thought, as if shrunk with age.

  "These wall-mountains are over a mile high," Scholes said. "Up here, the surface is firm enough to walk on; the regolith dust layer is only a couple of inches thick. But down on the plain the dust can be ten or fifteen yards deep. Hence the big wheels on the rover. I guess that's what five billion years of thousand-degree temperature range does for a landscape..."

  Just twenty-four hours ago, she reflected, Larionova had been stuck in a boardroom in New York, buried in one of Superet's endless funding battles. And now this... wormhole travel was bewildering. "Lethe's waters," she said. "It's so — desolate."

  Scholes gave an ironic bow. "Welcome to Mercury," he said.

  Cilia-of-Gold and Strong-Flukes peered down into the Chimney cavern.

  Cilia-of-Gold had chosen the cavern well. The Chimney here was a fine young vent, a glowing crater much wider than their old, dying home. The water above the Chimney was turbulent, and richly cloudy; the cavern itself was wide and smooth-walled. Cilia-plants grew in mats around the Chimney's base. Cutters browsed in turn on the cilia-plants, great chains of them, their tough little arms slicing steadily through the plants. Sliding through the plant mats Cilia-of-Gold could make out the supple form of a Crawler, its mindless, tubelike body wider than Cilia-of-Gold's and more than three times as long...

  And, stalking around their little forest, here came the Heads themselves, the rulers of the cavern. Cilia-of-Gold counted four, five, six of the Heads, and no doubt there were many more in the dark recesses of the cavern.

  One Head — close to the tunnel mouth — swiveled its huge, swollen helmet-skull towards her.

  She ducked back into the tunnel, aware that all her cilia were quivering.

  Strong-Flukes drifted to the tunnel floor, landing in a little cloud of food particles. "Heads," she said, her voice soft with despair. "We can't fight Heads."

  The Heads' huge helmet-skulls were sensitive to heat — fantastically so, enabling the Heads to track and kill with almost perfect accuracy. Heads were deadly opponents, Cilia-of-Gold reflected. But the people had nowhere else to go.

  "We've come a long way, to reach this place, Strong-Flukes. If we had to undergo another journey — "through more cold, stagnant tunnels" — many of us couldn't survive. And those who did would be too weakened to fight.

  "No. We have to stay here — to fight here."

  Strong-Flukes groaned, wrapping her carapace close around her. "Then we'll all be killed."

  Cilia-of-Gold tried to ignore the heavy presence of the Seeker within her — and its prompting, growing more insistent now, that she get away from all this, from the crowding presence of people — and she forced herself to think.

  Larionova followed Kevan Scholes up the slope of the wall-mountain. Silicate surface dust compressed under her boots, like fine sand. The climbing was easy — it was no more than a steep walk, really — but she stumbled frequently, clumsy in this reduced gee.

  They reached the crest of the mountain. It wasn't a sharp summit: more a wide, smooth platform, fractured to dust by Mercury's wild temperature range.

  "Chao Meng-Fu Crater," Scholes said. "A hundred miles wide, stretching right across Mercury's South Pole."

  The crater was so large that even from this height its full breadth was hidden by the tight curve of the planet. The wall-mountain was one of a series that swept across the landscape from left to right, like a row of eroded teeth, separated by broad, rubble-strewn valleys. On the far side of the summit,
the flanks of the wall-mountain swept down to the plain of the crater, a full mile below.

  Mercury's angry Sun was hidden beyond the curve of the world, but its corona extended delicate, structured tendrils above the far horizon.

  The plain itself was immersed in darkness. But by the milky, diffuse light of the corona, Larionova could see a peak at the center of the plain, shouldering its way above the horizon. There was a spark of light at the base of the central peak, incongruously bright in the crater's shadows: that must be the Thoth team's camp.

  "This reminds me of the Moon," she said.

  Scholes considered this. "Forgive me, Dr. Larionova. Have you been down to Mercury before?"

  "No," she said, his easy, informed arrogance grating on her. "I'm here to oversee the construction of Thoth, not to sightsee."

  "Well, there's obviously a superficial similarity. After the formation of the main System objects five billion years ago, all the inner planets suffered bombardment by residual planetesimals. That's when Mercury took its biggest strike: the one which created the Caloris feature. But after that, Mercury was massive enough to retain a molten core — unlike the Moon. Later planetesimal strikes punched holes in the crust, so there were lava outflows that drowned some of the older cratering.

  "Thus, on Mercury, you have a mixture of terrains. There's the most ancient landscape, heavily cratered, and the planitia: smooth lava plains, punctured by small, young craters.

  "Later, as the core cooled, the surface actually shrunk inwards. The planet lost a mile or so of radius."

  Like a dried-out tomato. "So the surface is wrinkled."

  "Yes. There are rupes and dorsa: ridges and lobate scarps, cliffs a couple of miles tall and extending for hundreds of miles. Great climbing country. And in some places there are gas vents, chimneys of residual thermal activity." He turned to her, corona light misty in his face plate. "So Mercury isn't really so much like the Moon at all... Look. You can see Thoth."