World Engine

by Stephen Baxter

  And, almost without warning, the Scorpio IV tipped up, leapt from the runway, and hurled itself into the air.

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  The spaceplane, its drive shut down, carried them through a single ninety-minute low orbit of the Earth.

  Malenfant assumed this was to set up a transfer orbit to specialised craft of some kind that would take them to the Moon. And, too, Malenfant supposed, this would allow the plane’s systems a check-out period before going further. Thus the Apollo astronauts had lingered in orbit after launch and before going on to the Moon. He wondered, in fact, how often this plane actually flew. It was itself probably venerable, like most machines he encountered here. Centuries old, even – just not as old as he was, or his Constitution.

  A ninety-minute orbit. Bartholomew and Kaliope, artificial entities each, sat quietly. Deirdra was quiet too, but she gave her attention to the view out of the small cabin windows – the Earth itself – that and the novelty of drinking lukewarm tea in zero gravity.

  Malenfant said little. He just wanted to get on with it.

  When the drive started up again, the push was gentle compared to the rigours of the launch. But the Scorpio soon piled on the velocity.

  And the Earth fell away.

  ‘Oh, Malenfant,’ Deirdra said now, breathless. ‘Come and see.’

  Moving cautiously in the fractional gravity of the thrust, he crossed to her window.

  They had lifted at a Florida noon. Now, after a single orbit, they were over the launch site again, and much of the Americas were visible, bathed in daylight. As the astronauts had always observed, the swirl of cloud in the atmosphere was surprisingly dense, and obscured the surface features, even blurring the boundary between land and sea. Nevertheless, with a little patience, Malenfant began to pick out the familiar school-atlas features – the basic shapes of the continents, at least.

  But much had changed. To the south the Amazon, once a silver thread through the green, had become an inland sea, lapping against the foothills of the Andes. In North America great chunks had been taken out of the coastlines – Florida itself was just a scatter of islands – and Central America had been severed, somewhere in the region of Panama, he guessed. As if the Americas were disintegrating into one vast archipelago.

  And he could clearly make out the new kingdoms of life that had become established down there. Tropical rainforest covered much of South America, a vivid green, and had washed north through Central America, with tongues of it reaching up the old river valleys all the way, it seemed, across the United States to the old Canadian border. North of that was sparser greenery, forest clumps and plains: a savannah that stretched to the edge of the Arctic Ocean.

  In the far north, not a scrap of ice remained. Greenland was a rugged, mountainous island that now was, literally, green.

  Yet what struck Malenfant more than the new green, the lapping forest, more than the vanished ice, was the bare dryness at the heart of North America, and even in patches of what had been Amazonia in the south. Desertification, he supposed, land abandoned by humans and nature alike, in the face of the extreme heat of the Peak Carbon global-warming pulse: a wound life had yet to be able to heal.

  Deirdra touched a window. ‘Just before it gets too far away to see . . .’

  The windows were smart, as Malenfant ought to have guessed. You could tap and swipe to inspect telescopically any part of the view you chose.

  So now Deirdra showed him huge herds crossing new Canadian grasslands.

  ‘They call it the mammoth steppe,’ she said. ‘Even though there are no mammoths.’

  Puzzled by that, Malenfant looked up at Kaliope.

  ‘An ecological experiment,’ she murmured. ‘Which has already endured for centuries. After the Ice Ages, the northern hemisphere was covered by grassland, grazed by big herbivores – mammoth, bison, reindeer – and cave bears and wolves to prey on them. The herbivores’ grazing kept the weeds and trees down, so the grass could flourish.’

  Deirdra said eagerly, ‘I know about this. And the grasslands reflect more sunlight than forests, so the world cools a little bit. All good. So they tried to restore it all, as best they could. I know that the herbivores the biologists put down there are reindeer, sheep, musk oxen, bison. And there are bears and wolves and foxes to prey on them. I really want to go to see it some day.’

  Malenfant smiled. ‘No mammoths? You could gene-splice them out of extinction, couldn’t you?’

  Kaliope actually looked faintly offended. ‘That kind of meddling isn’t done any more, Malenfant. The world is being allowed to heal from the state humanity left it in.’

  Now Deirdra pointed. ‘Malenfant – look at the coasts . . .’

  In the new shallow offshore seas were coral reefs, some of them encrusting the half-drowned ruins of coastal cities. Malenfant looked down on kingdoms of purple and white.

  ‘Of course the oceans themselves have yet to recover from the Anthropocene centuries,’ Kaliope said. ‘Today the ocean’s principal role is to serve as a long-term drawdown reservoir for the excess carbon dioxide in the air. A mechanism that has a timescale of centuries, rather than millennia like the weathering of surface rocks, and so vital to the planet’s near-future prospects . . . Still, the waters are far more fecund than in your day, Malenfant.’

  Kaliope, unlike the Answerers she derived from, had a habit of volunteering information, Malenfant was learning. Interesting. Maybe it was something to do with her embodiment. Look like a human, and you picked up bad human habits.

  Anyhow, it was welcome now.

  He and Deirdra spent many of the hours that followed gazing back at the receding Earth. At an Africa that was a startling green, as if the familiar outline had been coloured in by some giant child. Malenfant remembered Mica’s mention of the ‘Sahara Forest’: well, here it was, evidently. At a thunderstorm over Asia, a huge one, the lightning strikes sparking in clusters between the clouds, like the thoughts of some huge, misty brain.

  Eventually, though, Earth was no more than a ball in the black sky, like a nearly full Moon, its detail becoming tantalisingly hard to make out. Malenfant wondered how far out you would have to get before you could not distinguish this new world from the Earth as it had first been viewed in the round by the Apollo crews. Given the loss of the ice caps, he thought – and given you could see, telescopically, the ice caps of Mars from Earth – maybe a long way indeed.

  Then the craft turned away from the Earth, swivelling on its short axis.

  And a disc in space was revealed, glittering green, hanging like a Christmas tree ornament. It had to be kilometres across.

  ‘What the hell is that?’

  ‘A farm,’ Kaliope said with a smile. ‘Or it was, once. Now it’s your way to the Moon, Malenfant.’

  A farm in space, just as Morrel had once mentioned.

  Malenfant stared, fascinated and amazed, as the Scorpio crept closer.

  At first Malenfant saw the farm as a tipped plate, very thin compared to its diameter, with a lot of surface detail. Around a complex-looking hub, the disc face was divided into six pie-slice sectors, glass-faced, alternately bright or dark. The three dark segments consisted of arcs, concentric bands – dozens of them – with the blackness of space showing beyond, evidently through a transparent floor. The bright segments seemed to be panelled with mirrors; they shone brilliantly in the light of the Sun.

  The whole, six or seven kilometres across, was spinning around its axis, quite rapidly. Malenfant timed it with an amateur astronomer’s count: ‘A thousand and one . . . A thousand and two . . .’ He soon figured the rotation period was around two minutes. Enough for a respectable spin gravity at the perimeter.

  The spaceplane, closing quickly, sailed up and over the face of the disc towards the spin axis. Those illuminated bands swept gracefully beneath. Malenfant glimpsed green, peeking out from beneath the bright mirrored surfaces. Then, nose first, the plane began to descend along the central axis, to a hub that was a logical place for a do
cking port. Malenfant leaned into his window, trying to see the view as the plane headed down.

  Deirdra seemed astounded. She must know more about this structure than Malenfant did, in theory, but she was evidently taken aback. ‘Wow. Look at it sprawling. Kaliope, how wide—’

  ‘The overall diameter is about seven kilometres. Spinning patiently for over three centuries,’ Kaliope said. ‘Skyfarm VII was built when we were still anticipating an expansive population beyond the Earth, on the Moon and Mars, or in deep-space habitats with various functions. Rather than have all those facilities grow their own food, the idea was to have it grown, more efficiently, here. Based on raw materials sent up from Earth.’

  Malenfant frowned. ‘So how would you close the ecological loops? Ship tonnes of human dung back up from the Moon?’

  ‘No, Malenfant. The idea was not to close the loops at all. The skyfarms weren’t independent islands. They were meant to be part of an interconnected space economy, spanning from Earth to the colonies. All those complex carbohydrates the colonists excreted after they ate the sky food were to be used to make soil on the Moon and Mars, under the domes.’

  ‘Ah. So in the very long term, you would get self-sufficient colonies on those worlds. While, in the meantime, keeping the space pioneers fed to perform the tasks they had been sent up there for.’

  ‘There would have been ten thousand people working up here, Malenfant, feeding a putative space-based population of four million.’

  ‘Four million.’

  ‘Of course it never got that far; we never had so many people in space. And, even before the Homeward movement took off, mass protests caused the redirection of the “space food” to starving communities on Earth – though that was symbolic only, and made little difference to the famines. Later, more frugal generations reoccupied the wheels and turned them into cyclers. This one loops endlessly between Earth and Moon.’

  ‘And it’s a garden, Malenfant,’ Bartholomew put in. ‘Not a farm now. A sky garden. And all tended by robots, like me.’

  Malenfant nodded. ‘So all you need to get to the Moon is a spaceplane ride up from Earth, and some kind of shuttle down to the lunar surface, after a free ride on this – fairground wheel. Makes sense.’

  Now they were approaching the hub. Malenfant saw that the central structure, counter-rotating to greet the spaceplane, was an open frame fitted with cradles to take a craft like the Scorpio. There were what looked like cranes and robot arms for unloading cargo, spheres that were probably propellant tanks for refuelling.

  And, under roof panels on the rotating structure all around the hub, he glimpsed more of that dazzling green.

  ‘Not so much Space Station Five as Silent Running, then. O’Neill, eat your heart out.’

  Deirdra turned. ‘Malenfant?’

  ‘He’s just maundering,’ Bartholomew said. ‘Leave him in the past where he belongs.’

  For the first day, they explored.

  The interior of the skyfarm was as fascinating, for Malenfant, as the exterior. From hub to rim there were over thirty floors within the structure, concentric ring-shaped decks along which you could walk or run, like, he thought, Dave Bowman in the Discovery centrifuge. There was Earth-equivalent spin gravity at the rim, and proportionately less at the higher levels, closer to the hub: bands where the gravity was effectively Martian, others where it was lunar . . .

  The disc rotated with its full face to the Sun, whose light, unfiltered by any atmosphere, blasted in. But there were screens and shades, and an ingenious arrangement by which each floor had a shallowly tilting, mirrored roof, so that the sunlight was scattered across the growing area beneath. That reduced the intensity of the raw sunlight incident on the floor; as they wandered it felt no stronger, from what Malenfant remembered, than that of southern California back in his own day. More filters and mirror arrangements adjusted the light levels so that the differing day lengths of higher latitudes could be modelled.

  And, Malenfant wasn’t particularly surprised to find, there was wildlife in here, to eat the foliage and fruit and scatter seeds, and thus, no doubt, help close the ecological loops: birds, rodents like squirrels, even a few shy, miniature deer. Thanks to all this, he learned, the skyfarms preserved samples of biotas that no longer had a place to survive on Earth – some high-latitude evergreen forests, for instance, even tundra.

  In the days that followed, obeying health-awareness recommendations from Bartholomew, they spent equal times in the three main zones. There was the Earth-normal-gravity basement where they could keep their strength up. In Martian gravity, one-third Earth’s strength, games like tree-climbing seemed the most fun, as some optimum was reached between the capability of human muscles and the friendliness of the gravity. And in lunar gravity, where the trees grew stupendously tall – and dwarf deer were learning to leap from branch to branch in the foliage – Malenfant and the others practised bunny-hop Moon walking, like Aldrin alone at Tranquillity.

  Malenfant was fascinated by the technology. Crawling around the greenery, he found a sprinkler system that mimicked rain. And he dug through the rich soil to discover infrastructure decks beneath, within which pumps and fans and filters and humidifiers laboured to maintain the living environment.

  Deirdra, meanwhile, seventeen years old, took to this place like a liberation. She insisted on making up sports and games for the three of them to compete in, herself, Bartholomew and Malenfant – running, throwing, tree-climbing. Bartholomew solemnly encouraged a reluctant Malenfant to join in with this: ‘It will do you the world of good.’

  They were alone here, save for the bots. This was an age after space travel; this skyfarm was a relic of a vanished past, of different customs, like the ruin of a Roman bath-house. But, alone or not, thanks to Deirdra’s youth and energy, they made the empty sky forests echo to their whoops and laughter, as the skyfarm carried them to the Moon.

  Which took three days, just as it had for Armstrong and Aldrin and Collins.

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  The shuttle that would carry them down to the lunar surface was called the Leo IIb.

  As it approached the skyfarm, docking at the counter-spinning port structure at the hub, Malenfant gazed hungrily at this latest bit of advanced technology – advanced for him, a relic to Deirdra. The lander was a blunt design, little more than a habitable sphere fitted with four stout, evidently suspension-loaded legs: four legs for landing on the Moon, just like the Apollo Lunar Modules. The conditions of the Moon had not changed in the centuries since, and neither, evidently, in terms of basic design strategies, had the means of getting there.

  Malenfant thought Deirdra was regretful about leaving the skyfarm, and having to crowd back into the cramped, cluttered interior of the lander. Not a surprise; he thought he had never seen her have so much fun. ‘When I’m rich and famous,’ he said, ‘I’ll get you and your friends up here for a decent vacation.’

  She touched his hand. ‘Malenfant, you already are famous. And everybody is rich. But it’s the thought that counts.’

  ‘Thanks . . . I think.’

  Once they were seated, the Leo neatly decoupled from Skyfarm VII, which fell away into space. The lander, as pilotless as the Scorpio had been, squirted vernier thrusters to back off from the skyfarm.

  Then it turned away, towards the face of the Moon. Malenfant heard Deirdra gasp at the sudden spectacle.

  Just here they seemed to be somewhere over the centre of the sunlit hemisphere. It was a dramatic, startling sight at first glance. Craters like bullet holes punctured an underlying surface of brighter high ground, and darker lowland. Wrinkled chains of mountains were in fact arcs of circles, themselves the remnants of huge, even older craters. All of this was rendered in shades of grey, from charcoal through to almost white.

  Over the next few hours the ride down was cautious, gentle. As it shed the velocity of the Earth-Moon trajectory of the cycler craft, the lander’s engine burned continuously, and it made wide, looping orbits around the Moon, tilte
d at an angle to its equator.

  The passengers were silent, staring out at the changing view.

  Malenfant was fascinated by the relics of the human presence on the Moon, most of them post-dating his own time. In the northern hemisphere he glimpsed a silver dome, huge, nestling in the crater Plato: once the largest optical-light astronomical observatory in the Solar System, he learned, with gaunt open-frame telescopes standing exposed in the lunar vacuum and the forgiving gravity. A splash of green under another dome, this one transparent: the Gardens of Aristarchus. In the south, an altogether grimmer structure in the bright young crater Tycho, a grey dome that, he learned, had for a few decades served as humanity’s toughest maximum-security prison. And a sprawling tangle that spilled out of the crater Clavius, which had once been humanity’s largest single settlement on the Moon. He glimpsed what must have been hydroponic farms – like huge greenhouses, some broken open, presumably by meteorite impacts – and the silver rails of mass-driver electromagnetic launchers. He regretted not seeing Pico, a solitary mountain in the Mare Imbrium which, he remembered, housed the hospital stroke storage facility where he, and other coldsleepers, had passed centuries in dreamless oblivion. Most of these structures were relics, of course, long abandoned since the great Homeward migration. Abandoned by people, if not by the brooding artificial minds he had come to consult.

  He was unreasonably glad that they passed close enough to the Sea of Tranquillity to make out the first landing site, and even glimpse from high above the huge basalt statue of Armstrong saluting the US flag – a gesture he had not survived to make in person, after his landing on 20 July 1969.

  And now, precisely five hundred years later, Reid Malenfant made his own landing on the Moon. Or, more accurately, his second landing. Only this time, he thought with a triumphant grin, he was awake to see it.

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