Xeelee Redemption

by Baxter, Stephen

  That was, until the strut became visible. A wall itself twenty thousand miles wide. Plummeting into view.

  Forty-one days after reaching the river, they approached the strut base.

  They drove off the river. The strut was a wall that reached from ground to sky, from horizon to horizon. More exploration proved there was indeed another hull-plate ‘stream’ flowing up the face of the strut surface.

  And another day of cautious experimenting proved that getting a ride along the strut, straight up into the sky, would be easier than they had feared. Here, it turned out, the Xeelee had used its inertia-control technology. Somehow the tug of spin gravity was overcome, and a sense of gravity with ‘down’ pointing into the strut wall was established. Once the convoy was on the strut, the vehicles could simply ride the up-flowing central river as easily as they had followed the deck’s own central flow.

  Getting a vehicle onto the strut was a challenge, though. There seemed no obvious transitional equipment, no ramps or slings . . .

  In the end cautious experiments, made by skinsuited people just walking in, showed that the inertial-control system seemed to incorporate a kind of invisible ramp. If you walked forward you were lifted up, through a smooth right-angle curve, until your feet hit the strut face. And there you were, standing at right angles to your crewmates.

  So to get aboard the strut in a truck, you had to just drive forward and hope. It was an interesting experience, Jophiel discovered when he tried it.

  It took two more days of trial and experiment before the convoy had been transferred to the strut.

  Then ten more days to sit tight, and allow the convoy to be borne up the strut – or across it. To the senses the ‘strut’ now felt like a bridge between the upended decks, between two vertical walls. Walls that spanned the sky. The architecture of Heaven, Nicola said.

  On the expedition’s seventieth day, however – over halfway along the strut – they rode through an earthquake.

  That was how it felt to Jophiel, who had been trying to get some sleep at the time. The truck he rode jolted, shuddered, rose a little, before settling back on its suspension.

  Just like before.

  With the trucks still travelling, Michael Poole called a conference, where they made observations, compared notes, and debated the matter. The best idea anybody had was that once again a rogue star, falling out of a Galaxy-centre sky full of rogue stars, had got through whatever defences the Xeelee had set up and slammed into the Wheel – into a strut or a deck.

  Back in the Solar System, Michael Poole had once crashed a GUTship into a Xeelee artefact – and later, a whole minor moon had been hurled at the Xeelee sycamore-seed ship itself. Neither had shown the slightest deflection. It was as if, Highsmith Marsden had speculated, Xeelee technology was anchored to spacetime itself. Evidently that anchoring had limits. ‘Hit it hard enough,’ Poole concluded bleakly, ‘and this thing would ring like a tuning fork.’

  Asher logged the event carefully. This impact had happened seventy days into their odyssey by truck. As they rose up the strut they had very quickly climbed out of the deep time pit, but even so Asher ascribed the event an astounding external date of ad 2,710,000. Whereas the first impact they’d experienced had happened at around ad 220,000.

  Jophiel was flummoxed; he hadn’t tracked the cosmic dates so carefully.

  They were approaching three million years since Cold Earth. And here was Galaxy Core weather. Raining stars.

  He had trouble sleeping.

  On the seventy-fourth day they reached the terminus of the strut. They passed through a peculiarly conventional-seeming tunnel, that led them over anther right-angle bent-gravity curve, to the upper surface of the new Deck, Deck Two.

  Here they spent another interesting day in their transition to the new Deck, a fresh hull-plate river.

  From there, another ninety days.

  And they came to the rim of the cupworld.

  Earth Two. A place glimpsed only in hasty flybys across astronomical distances. And now their best hope of salvation.

  The convoy drove off the river, the trucks were circled, and a camp quickly established.

  Then, after a couple of hours, a single truck dragging a trailer laden with the components of an aircraft cautiously approached the cupworld’s edge.

  49

  Ship elapsed time since launch: 26 years 57 days

  Earth date: c. ad 2,710,000

  The crew emerged from the truck.

  Jophiel deliberately took a step away from the others and looked around.

  The sky was heavily distorted by their motion, but much less so than at the extreme of Deck One: stars, though blue-shifted and red-shifted, were clearly discernible, all around him, above and below this great platform in space. Time dilation was gentler here too. On Deck Two a subjective day corresponded to a mere seventeen months in the outside universe, compared to nearly fourteen thousand years on Deck One.

  Above his head Deck Three, over a thousand astronomical units high, was invisible to the naked eye. Behind him the great flat expanse of Deck Two. Around him his companions, all in their heavy-duty skinsuits, their soles gripping the featureless hull-plate floor: Chinelo, Asher, Nicola, Poole. All looking around with evident curiosity, if not awe.

  And before them a captive world, yet another vast feature on a vaster artefact. As if they stood on the other side of the sky.

  Cautiously, they approached the rim of the pit. The texture of the ground itself changed at the edge, Jophiel saw. On this side, under his feet in the vacuum, hull plate. Beneath the lid, what looked convincingly like rock – a kind of granite, Asher had suggested.

  There was no sense that this was an enclosed pit, no sense of curvature. It was, Jophiel thought, as though he stood at the straight-line edge of some tremendous canyon, as though he looked straight down fifty-kilometre cliffs to a rust-brown ground, where a few splashes of grey-green huddled. Asher had promised there was air down there, with a decent proportion of oxygen, and liquid water, and, evidently, life, though there hadn’t been time yet to examine it up close.

  Directly below him, near the clinging clumps, he could see a dark snake that might be a river. He lifted his head slowly, following the line of the river across an arid plain, as it made for a blue-grey expanse that might be a landlocked sea.

  Then, beyond the sea, more mountains, rounded, eroded.

  Beyond the mountains, a grey plain.

  Beyond the plain, a distant horizon, perfectly flat as far as he could see, with no sense of curvature. This really was a bowl the size of a world.

  All of this was faintly obscured; he was fifty kilometres high, and looking down through an entire atmosphere. He was struck by how few clouds he saw: a few wan layers, spread out below him. And he made out a kind of shading of the landscape, as if cast by banks of cloud – a striping, alternately bright and dark, though the pattern was complex; it swirled and knotted like flow lines. Not cloud shadows, surely . . .

  Standing here, he could see there was something separating him, out here in the vacuum in his simulated skinsuit, from the apparently living world below. A layer over the sky. It was like a flat, almost transparent lid, stretching over the whole of the pit as far as he could tell. Or it was like the surface of a very still pond, Jophiel thought now, occasionally visible in elusive reflections.

  They’d glimpsed this feature on cupworlds from afar, even during the flyby. The cupworlds were covered by some kind of force field, was the best guess so far. It was presumably meant to keep stuff out, such as the unending sleet of Galaxy-centre radiation, rather than keep stuff in; these rock walls were so high that even without this intangible lid the atmospheric loss, from the great puddle of air down there, would have been negligible.

  To go further they would have to penetrate that shield.

  Jophiel glanced around at his companion
s.

  Chinelo stood and stared. Asher grinned widely, as if delighted by all she saw.

  Poole frowned. There was a kind of impatience about Michael Poole, who, Jophiel suspected, saw all this not as an adventure but an obstacle, another hurdle to cross.

  Nicola, in her custom skinsuit, seemed puzzled. ‘Something odd about those oceans,’ she said now. ‘And the mountains, come to that.’

  Jophiel glanced at her. ‘Odd?’

  ‘Odd that they exist at all. This isn’t a world, it’s a – toy. There’s nothing underneath it all but hull plate – as far as we know. So, what about erosion? There has to be weather down there, and where there’s weather there is erosion. What happens when those mountains wear away, and the oceans silt up? On Earth, tectonic cycling – the drifting of the continents, the recycling of material through the crust – would turn all the silt back into mountains.’

  ‘There hasn’t been the time,’ Jophiel said. ‘At this level, Deck Two, while the time dilation is a lot less than down in Deck One . . .’

  It was a strange paradox of the Wheel’s nature that the higher you climbed into its structure, rising up from Deck One, the younger it was – because the higher decks moved more slowly than the lower, and suffered less time dilation.

  As seen from the external universe, the best part of three million years had elapsed since the Xeelee had come here to build this thing. On Deck One, the lowest level, less than a year had elapsed since then, as seen by a witness there. But this second deck was five thousand years old – and the upper deck, subjectively, was more than half a million years old. Such numbers had led to many wild hypotheses among the crew about the sequence in which the Wheel had been constructed.

  Asher put in, ‘She has a point, though. Even if this cupworld is only five thousand years old you’d build for the future, wouldn’t you? A self-sustaining system?’

  Jophiel shrugged. ‘Maybe there are repair mechanisms, Asher. We just haven’t found them yet.’

  But Asher scowled, and Jophiel knew that expression. She didn’t like it when the universe didn’t make sense, and she would keep nagging at the detail until it did. Jophiel felt a spark of admiration. Here was a human dwarfed by her tremendous surroundings, three million years out of her time, staying calm, gathering data, interpreting, thinking.

  ‘So,’ Michael Poole said, ‘we need to go forward. I’m thinking of a planned sequence of tests of that force-field barrier. Starting with a probe, attached to some kind of lanyard.’

  Chinelo stared at him. ‘A lanyard? How long is that going to take? Oh, look—’

  She crumpled up a softscreen and just hurled it at the shield.

  They were in vacuum, and in close to a full gravity; the screen sailed over like a brick, even as it unfolded. It fell, and passed through the shield, that elusive meniscus, without any apparent hindrance, and landed flat on the rocky surface beyond.

  ‘Ha!’ Chinelo walked forward, and peered down. ‘There, I can see the screen is working.’ She tapped at a wrist unit. ‘Picking up and returning data, just fine.’

  Nicola laughed. ‘Well done, kid. I have a feeling that if this barrier was meant to hurt us, we wouldn’t be able to get even this close. But don’t you go marching through it yet, Chinelo. Let’s see if it lets through something as complex as a Virtual first.’

  Which meant Jophiel. ‘Thanks a lot, Nicola.’

  Chinelo scowled. ‘Not fair.’

  Poole said, with the weary tone of an exasperated father, ‘Let’s just get it done. Jophiel—’

  Asher held up her own screen. ‘Ready.’

  So Jophiel, Virtual heart hammering, stepped forward.

  The hull plate dipped down, slightly, so that it passed under the shield surface. Jophiel took one step, two, until his boots were covered by the shining meniscus.

  ‘I feel nothing.’

  ‘It looks like you’re standing in a shallow lake,’ Asher said.

  ‘Stepping off the hull plate and onto the rock . . . I can feel the unevenness; my boot soles are thin enough for that. It’s pretty steep but I think I can walk down it . . .’

  The shield, all but invisible, rose up across his body. He could feel nothing.

  When he was immersed, he looked back up at the others, standing on the hull plate, looking down. ‘Here I am, as intact as I ever was. I can see you, the stars. So.’ He struck a pose. ‘On behalf of all mankind, I name this world—’

  ‘Oh, no, you don’t.’ Chinelo came stumbling down the slope after him.

  They still had some hours of work to get through before moving on.

  The next step was to carry their flyer down through the lid – not an easy chore given the quickening steepness of the rocky rim inside the cupworld. Once through they test-fired the craft’s fusion engine and other systems. They checked too, at Poole’s insistence, that the flyer could be hauled back out of the pit and would still function.

  All this procedure was built on earlier, cautious planning, Jophiel knew. Although the GUTengines in the trucks seemed to have been protected from quagma-phantom attack by improvised shelters of hull plate, Poole had never been happy with similar attempts to rig a GUTengine inside the tight hull of the flyer; there wasn’t the room for shielding. Hence, fusion power only, with various kinds of battery backup.

  Poole ran the fusion engine through one final startup-shutdown cycle. Then, at last, he nodded. ‘Let’s get aboard.’

  50

  With Nicola, inevitably, at the controls, the flyer lifted smoothly off the tilted rock surface of the rim.

  At first, with the air density negligible, the flyer was powered as if for vacuum flight, by high-performance fusion-heat rockets with internal propellant tanks. Nicola tested out the controls, careful not to let the flyer ride up and touch the force-field ‘sky’.

  Then, with an extravagant gesture, she sent the craft on a long sweeping dive, down, down past the rocky face of the peripheral cliffs, down and seeking the thicker air, where the ramjets would cut in: atmospheric air sucked in and superheated to be used as propellant. Deeper yet, when the atmosphere was thick enough, the flyer would become a true aircraft, relying for lift on the thickness of the air flowing over its wings.

  Poole, sitting up front with Nicola, glared out. Asher was intent on her screens and other monitors.

  Chinelo pointed back over her shoulder. ‘The Rim Mountains.’ She pointed up. ‘The Lid. We ought to start naming stuff, if we’re going to live here.’

  Nicola said, ‘There may be people here already, of course. Who already gave stuff names of their own. Kind of disrespectful not to ask, don’t you think?’

  Chinelo scoffed. ‘Look down there. What people? Where?’

  ‘I can’t answer that,’ Asher said. ‘Not yet. But I can tell you that this world not only looks like Earth, it is turning out to be like Earth, in the detail. Oxygen-nitrogen atmosphere, thick enough down there to be breathable for us, and without any nasties – not an excessive carbon dioxide percentage, for instance. A lack of ozone, but maybe that’s insignificant given the shielding effect of the Lid. Earthlike, if not Earth. But the humidity is down, compared to the Earth average.’

  ‘You mean it’s dry,’ Chinelo said. ‘Like a desert.’

  ‘Not quite—’

  ‘I can tell that much. And I never saw a planet before.’

  ‘At forty kilometres now,’ Nicola said. ‘Aero surfaces starting to bite . . .’

  A glance out of the window showed Jophiel how she was still tracking down the face of the Rim Mountains, leading the craft through smooth S-shaped curves as the flyer’s aerosurfaces explored the unfamiliar air.

  Asher said thoughtfully, ‘Well, you’re right, Chinelo. My first estimates say there is about one-third ocean cover here, to two-thirds land. The reverse of the proportions on Earth. And the air is a little thin, and lac
king water vapour – there must be a ferocious dip in temperature at night, even if it’s hot during the day. Like a high desert on Earth.’

  Nicola grunted. ‘You’re missing the fundamentals. What night? This isn’t a planet. It doesn’t spin on its axis, it doesn’t orbit a sun – it can’t have a day-night cycle. I know there are worlds that keep one face to their stars the whole time. But life like ours evolved on worlds that spin.’

  ‘True enough,’ Asher murmured. ‘So, if you were going to build a refuge maybe you’d mimic some kind of day-night cycle. Life from Earth, at least, depends on it.’

  Jophiel nodded, and he leaned forward so he could see the sky, the Lid. ‘Hence, maybe, those stripes of shadow.’

  From underneath, that flow-like effect in the sky was much more marked, a clear diminution of the light in huge, swirling, interlocking bands. And where the bands were at their most opaque, Jophiel saw, significant shadows were cast on the ground below.

  ‘Like zebra stripes,’ Chinelo said. ‘Not that I ever saw a zebra.’

  Asher stared. ‘You’re right, though. That is how it looks, a sort of organic, self-organising pattern. And this must be it – the key to day and night. Over a given spot on the ground, those bands coalesce or scatter, blocking or admitting the light through the Lid. It’s going to take some analysing, starting with a timing of the cycle. I wonder if it’s smart enough to mimic seasonality? Or the effect of latitude – long polar nights?’

  Nicola grinned, not unkindly, as far as Jophiel could read the expression on her silvered face. ‘You’ve got a lot of fun studying to do, that’s for sure.’

  Abruptly, reflected light flared through the pilot’s window.

  Even Jophiel winced, before the windows cut down the incident light. Looking out, he saw they were descending past a brilliant white surface.

  ‘Sorry,’ Nicola said. ‘Got too interested in your fascinating conversation. Flying down smooth and easy. We just ducked down under eight kilometres from the mean surface. We’re no higher than the tallest mountains on Earth, now. And we’re flying parallel to that reflective layer in the rock face.’