Xeelee: Vengeance

by Stephen Baxter

  Feeling detached, he walked to the lounge’s huge picture windows.

  And, standing there, with a soft, almost subvocal command, he threw a Virtual projection into the sky.

  Michael Poole rose like a stone thrown from a bowl of ice. And he looked down on Cold Earth .

  From up here, Earth looked spectral in the starlike glint of its distant Sun, pure white, an abstraction of its former self. But it was still possible to discern its geography, the familiar shapes of the continents like plaster sculptures, textured with frozen lakes and mountain chains, and the smoother plains that coated the oceans.

  And those pale landscapes were broken by specks of green. Dots of light in the dark. These were the surviving Towers and other human shelters – heavily reinforced and supported by independent power supplies – and the ecohabs, as they had come to be called, scraps of wilderness preserved by the descendants of the Recovery-era generations who had first restored those ancient landscapes centuries before. In North America, in such shelters, bison and short-faced bears and dire wolves wandered, baffled; in the relics of the north European forests, steppe mammoths and woolly rhinos; in Australia huge wombats and marsupial lions. There were habs even under the oceans, domes of water inside the thickening ice kept liquid by the energies of GUTengines.

  And if Poole watched closely, he could see the slow movement of vehicles across the ice. Lights, crawling bravely through the dark. Even now, fifteen years on from the Displacement, it was still possible to find scattered groups of survivors, living in more or less improvised nests of air and warmth, scraping up frozen oxygen to stay alive. When such caches of people were found and rescued, Poole was always reminded of another fragment of his reading of Anthropocene-era fiction. Pails of air.

  Poole’s initial dramatic gesture, throwing open a wormhole to move the whole Earth and its population of a billion people, had only been the beginning of a struggle for survival that, everyone now suspected, could probably never be regarded as over. By the end of the first week, after the great blizzards had finished, and the skies of Earth cleared, the temperature had started dropping fast – the global average plummeting by three degrees or more per day, after the first month easily breaking pre-Displacement records set here in Antarctica. Meanwhile, out of sight, the freezing-over of the oceans had inflicted an immediate catastrophe on the great, lovingly restored whales and other ocean fauna, which suddenly had no access to air. And with time, as the plankton of the upper waters died off without sunlight, wider food chains collapsed. After a few months or years, the extinctions would have cut to the deepest waters

  People fought to survive. The immediate chill-down was like a slow-burning global war, as swarms of refugees battled over shelter and provisions. In some cases the wars were literal, such as the aggressive conquest of Iceland, rich in geothermal energy, by a band from northern Europe. After five or six weeks the cold had locked down everybody left alive, in whatever scattered shelters they had been able to find. Work parties began the job of retrieving the corpses of the rest.

  Then, almost unbelievably, just two months after the Displacement, the air itself started to rain out. Seas of liquid oxygen pooled over a crust of water ice, itself by now hard as rock. These seas, metres deep in places, froze in their turn.

  And the nitrogen rain began . . .

  On impulse, Poole the Virtual angel threw himself down at the planet – to New York, to Central Park, where, he always remembered, Harry had once gone to witness the effects of the Xeelee’s Atlantic Probe on the American east coast. Now, the surface of the Park itself, swathes of dead grass, was lost under metres of water-ice snow, frozen as hard as basalt. The taller buildings still protruded from the ice, smashed, broken, mostly abandoned – the big old Paradoxa carbon-sequestration dome still stood – and drifts of nitrogen snow metres thick were heaped up against the walls of the dark towers. Exiled Martians laughed that nitrogen and oxygen, this stuff that Earth had been so reluctant to ship to Mars, now lay around for the taking, ready frozen for convenience of mining.

  But the city looked oddly beautiful, as if asleep under an ethereal snowfall. And it was not dead. Walkways had been cast over the banks of frozen air. Even now people moved through the city.

  Through these evolving horrors, blame was heaped on Michael Poole. The inquests were endless. There were demands for trials, and when the authorities refused mock hearings were held anyhow. Effigies were burned or hanged. Harry would give Poole bleak, occasional summaries of how many assassination attempts had been averted lately, along with pleas for Poole to stay out of sight. Sometimes Poole thought it was as if people had forgotten the Xeelee which had impelled him to take this action in the first place.

  None, however, was so critical of Poole as Poole himself. Was there after all something he had missed? Some way of saving the world other than plunging it into this deep-freeze? He felt as if he had grown old. Old and alone, no matter who was with him. He was forty-four years old.

  Meanwhile, fifteen years on, still the temperature fell. The thicker the sea ice, the slower the heat loss, and the more gradual the planet’s overall temperature decline. But the heat leak would not stop until the Earth neared the temperature of interstellar space, a mere few degrees above absolute zero: a temperature set by the faint afterglow of the Big Bang itself.

  Nothing in the universe was colder. Mankind huddled for warmth.

  Poole rose up once more. Suspended in space, he turned away from the planet, and gazed out at the sky of the Oort Cloud. At stars – hard and brilliant and uncomfortable stars, here at the edge of interstellar space.

  He was distracted by a glimmer of light, a flash against the patient, unblinking stars.

  That was probably one of the sun-catcher colonies, strange, remote communities who had moved out here long before the Xeelee had come to the Solar System – isolated, introverted folk living off the resources of comet cores, gathering sunlight so faint you needed a mirrored sail a kilometre wide to reflect enough heat to warm the palm of your hand. Shy they might be, but after the Displacement, cautiously, they had come flocking to a suddenly stranded Earth. Like the Martian refugees already present on Earth, they had known the cold, and how to survive it. All of this fifteen years ago.

  Fifteen years. Any anniversary on Earth was somewhat abstract now, Poole knew. Earth still had its day; it had kept its rotation on its own axis. But the Sun was gone, and a year was a mere abstract interval. Still, people almost obsessively counted the days, and accumulated them into years, and they marked anniversaries, like this one, the fifteenth of the Displacement.

  And on such anniversaries Poole himself took time to reflect. To come out and see, like this.

  He found Sagittarius. That was where the centre of the Galaxy lay, itself hidden by clouds of dust and gas. Poole stared hard, wishing he could see through the galactic murk to that crowded Core. Because, it was believed, according to the best observations, that was the direction the Xeelee had gone.

  With a kind of phobic reluctance, he descended, angelic, to the estate at Antarctica.

  68

  His family acted as if they hadn’t noticed his absence. But he was sure that was just an act. His habit of disappearing was tolerated, barely.

  When Poole had taken his seat, Harry handed him another glass of single malt. ‘Lethe knows we’ve got enough ice these days, though the whisky is an endangered species.’

  ‘No. Thanks.’

  Harry raised a glass to the window. ‘You noticed the sun-catchers out there? Those guys have done what they can for us. But we’ve got to learn a lesson from them. After generations in the dark, most of them have grown up without even a thought of returning to the inner System, where their ancestors came from.’

  Shamiso Emry nodded, her daughter sitting beside her. ‘That’s true. They were already looking outward, long before the Xeelee invaded. That’s a model we can emulate . . .�
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  Poole murmured to Nicola, ‘Not like our families to be so upbeat.’

  ‘Shut up and listen,’ she snapped back. ‘They deserve that, just this once.’

  ‘. . . And there is plenty of room out there.’ Gea, in her ancient avatar as the comical toy robot that had once comforted an elderly and bitterly nostalgic George Poole, rolled silently to and fro on the carpet. ‘This Oort Cloud stretches far out into interstellar space, and is full of places to go. We’ve recently identified a new planet, about twenty-five thousand astronomical units out – a super-Earth, really – which has retained, in the cold, such a thick primordial atmosphere of hydrogen that its surface is actually temperate. Warm enough for liquid water to gather. At least in theory.’

  Harry grunted. ‘We’ve already targeted a few of our scatterships at it. They’re calling it Thule.’

  Shamiso shook her head, as if in wonder. ‘A “few ships”? No less than a couple of hundred thousand people, then. What times we live in!’

  Harry grinned, and poured himself another glass. ‘That is what everybody’s watching,’ he said. ‘I hope. The Scattering. And counting the numbers of successfully despatched evacuees as they stack up.’ Despite his bragging Poole thought he could see strain etched into Harry’s face, despite continued AS treatment; the smoothing of artificial youth, the strain of fifteen years of leadership.

  Poole knew the logic behind the Scattering was elemental. Cold Earth had to be hidden. So, what would make a planet like Earth stand out among a trillion Oort Cloud objects? There were plenty of bodies with a similar mass. Earth had come through the wormhole with a relatively high velocity – a relic of its rapid close-in orbit around the Sun, the planet’s momentum carried through – but even that wasn’t such an anomaly out here.

  Earth’s still-high temperature was, however. Humanity could not afford for the planet to emit more heat energy than naturally leaked from its interior; any more would be an unmistakable sign of a technological civilisation – of people. And that inner energy flow was only one five-thousandth part of the energy that had once poured down on it from the Sun.

  So, even a crude estimate suggested, Earth could not safely support a human population of more than one five-thousandth part of the billion who had been living here, in the warmth of the inner System, before the Xeelee came. A mere few hundred thousand people, who would have to survive on a drizzle of sunlight and the Earth’s own leaked inner heat.

  But to reduce the population to such a thin scraping meant that there needed to be the best part of a billion people less on the planet, within a period of a century or less – such was Harry’s government’s nominal target for the completion of the camouflage of Earth. Some of this could be achieved by a drastically reduced birth rate – but the death rate, on the other hand, was minimal. Most of the billion alive were already supported by AS technology; they were a billion potential immortals.

  So from the beginning Harry and his government had pledged a programme of evacuation. A billion in a century. Ten million a year.

  It was a fantastic challenge. And Michael Poole had got to work. He and his father had kick-started the construction of a whole fleet of mighty new GUTships.

  Cautious raids on Io had extracted dockyard technology from that lost moon. For resources to build the ships, they had quarried a chunk of rock and ice: a nameless inhabitant of the Oort Cloud as old as the Solar System, tethered and cautiously brought into orbit as a new moon for an exiled Earth. The energy for the ships’ GUTdrives was extracted from the collapse of the exotic-matter portal of the wormhole which had brought the Earth here. All to build ships to Poole’s design.

  The ships were all of the class he had tentatively labelled Great Northern, each with a lifedome at least a couple of kilometres wide and fifteen or more decks deep. Once Poole had envisaged these as generation starships, capable of supporting populations of a few thousand people on one-way interstellar migrations lasting millennia, or even longer. Now this design had been upgraded. Each ship would carry, not five thousand active colonists, but an awake crew of fifty or so, and a hundred thousand passengers in deep cryo storage, stacked in banks of cells within the lifedomes. Each lifedome would also shelter a sample of Earth’s ecologies, carefully tended by the active crew. (And, as devised under Jack Grantt’s supervision, two precious ships, full of thin carbon-dioxide air, had already carried away samples of the Lattice which had once embraced Mars: a lengthy working-out of Grantt’s own Plan B to save his Martian mind.)

  A hundred ships a year. Two or three launches a week. On Earth, people actually lived in the lifedomes that were being built to take them to the stars. Even finding the technical crew was a challenge; Poole had set up a kind of cascade system, so that those trained up in Year Two helped bring the Year Three batch up to speed, and so on.

  This was the Scattering: the dispersal of mankind. So far, the job was getting done. Of course there were problems – mostly with the people. Harry’s Operations Division had tried to put together more or less compatible crews. The Division swiftly became the single most hated government department. Some of the ships were more like prison hulks, it was murmured.

  Yet the scatterships were beautiful, as they launched in their mutual-support convoys, their GUTdrive flames bright as stars. In the telescopes they were droplets of Earth green and gleaming light: cities in flight. Dispersing, each was soon locked in a time-dilated deep-freeze, as more were launched, and more, spreading into the sky, heading for new Earths and red dwarf planets and starbirth clouds.

  Publicly, Harry had stayed upbeat throughout. Now he grinned as his display showed the latest members of that fast-growing fleet. He read out their names: ‘Magellan. Mayflower II. Valley Forge. A third of a million people in this flotilla alone.’

  Muriel reached out to him and made one of her odd, tentative reality-defying gestures; perhaps she meant to hold Harry’s hand. She never had got used to being a Virtual, Poole thought.

  She said, ‘In the end the Xeelee underestimated us. It underestimated you, Harry. Flawed you have always been—’

  ‘Well, you married me.’

  ‘But nobody can deny you rose to the occasion.’

  Shamiso smiled. ‘As for me, I choose to stay on Earth. One of Harry’s caretakers. Because of the even longer term.’ She regarded Poole. ‘Michael, it may be that a titanic effort still remains, to save mankind in your mighty scatterships. But you have already saved the Earth. Even without the Sun – even without human intervention – Earth life will survive. Ultimately the oceans will freeze to their beds, but even then there should be islands of life around the black smokers, vents in the ocean-floor crust whose heat will hold the ice back. And the deeper biosphere too: the very rocks of the crust are a vast reservoir of bacteria, leaching minerals, reproducing slowly, slowly . . . Those bugs will barely stir from their aeons-long slumber, whether we live or die. And they preserve in them the DNA mechanisms that are the result of billions of years of evolution and selection. The central hardware of life. This isn’t a trivial legacy, Michael. Even if humanity were to die out completely, the planet lives.’

  Now Gea rolled forward. ‘One day, in fact, the Earth may grow warm again . . . It’s pure chance, Michael, but when you created the Displacement it was early winter, in the northern hemisphere at least. And at that point in its orbit, Earth happened to be heading for the stars in the constellation Leo. Well, now, released from the Sun’s gravity, Earth still is heading for Leo, and always will be. And now we think that in about eighty thousand years’ time, we will be nearing the star Wolf 359. Perhaps our descendants will choose to deflect their course a little, and slow down – how, we don’t know yet. Of course 359 is a variable star, so that will present fresh challenges . . .’

  Poole absorbed all this in silence.

  Harry was studying Poole. ‘Look, son, we’re trying to help you, in our clumsy way. So if we’re all prai
sing your efforts, if humanity is coming out of this long cold tunnel you had to push us into – why the long face?’

  Poole said abruptly, ‘Because this could be the last time we meet like this.’

  Harry and Muriel shared a sharp glance. Poole recognised that look from his boyhood: wary parents.

  Harry snapped, ‘Is there something you two aren’t telling us?’

  Poole glanced at Nicola. She shrugged. ‘Get it over.’

  ‘We’re leaving,’ he said.

  Muriel frowned. ‘Leaving?’

  ‘Nicola and me. That’s why we asked you here, to get you together. To tell you—’

  ‘Are you joining one of the scatterships?’

  ‘Not that. Mother, we’ve been fitting out the Cauchy. You know she’s the prototype of a class of small-crew ships meant for exploration. Interstellar or even extragalactic. That was back in the day when we still thought in terms of such goals as exploration. Well, now we have a different destination. We’ll need some reaction mass. A kilometre-wide block of rock and ice should do it.’

  ‘Do the sums for me, Michael,’ Muriel said gently. ‘How far will that take you?’

  ‘To the centre of the Galaxy,’ he said bluntly.

  Even Gea seemed shocked. ‘That would take a few decades of your lives. But twenty-five thousand years in the external universe. Another twenty-five millennia to come home . . .’

  ‘Coming home isn’t the point.’

  ‘Then what is?’ Muriel asked.

  ‘The Xeelee,’ Harry said. ‘That’s the point. Isn’t it, Michael? That’s where the Xeelee went. It limped away wounded maybe, after we shot it up with monopoles, and left its clients and machines to finish us off. And so you’re going after it. For you it’s not enough to wait until mankind can recover from this low point, grow strong enough to take on the Xeelee. For you it’s personal.’

  ‘Wouldn’t you feel the same?’