Xeelee: Endurance

by Stephen Baxter

  ‘Here it is. Knew you boys would have got hold of a shot of this.’ Tasqer tapped an image, dark, grainy, much less impressive than the rest. But a glimmering tetrahedral form was clearly visible. ‘That,’ he said, ‘is a wormhole mouth. Poole era, a classic design. And this image isn’t fifteen hundred years old but, what, a month?’

  Mara frowned, baffled. ‘A month old? How is that possible?’

  ‘This is Poole’s own design,’ Tasqer said. ‘Poole’s own ship! One of Poole’s last projects was to build a GUTship called the Cauchy, which he sent off on a fifteen-hundred-year loop out into space, towards the galactic centre. Towing a wormhole mouth, not to the planets, but to the stars and back. Fifteen hundred years, you see. The flight plan predicted it should arrive back home about now – we knew that, and looked out for it – and here it is, right on schedule, out on the edge of interstellar space. That’s what inspired you kids to fool around with wormholes, right?’

  Juq grinned. ‘How could we not, sir? An authentic Poole wormhole, returning to the Solar System . . . I suppose I should have told you we have this, Mother. But everybody’s got the image, everybody’s talking about it.’

  Mara pursed her lips. ‘Well, I didn’t know about this. The Poole ship.’

  Tasqer leaned forward. ‘This is obviously why the Qax suddenly want us to build another wormhole ship. Because of this ghost from the past. But to what end, Ambassador?’

  Parz hesitated before replying. ‘It’s complicated. And frankly it’s best you know as little as necessary about this. All of you. I’m afraid that going forward with this you’ll need to be vetted by the security services.’

  Mara didn’t like the sound of that. ‘Vetted? For what?’

  ‘For any links to seditious groups.’ He glanced at Tiel. ‘I know that some in your family, Tiel, have links to a group called the Friends of Wigner. You have a cousin called Shira who is currently—’

  Juq put a protective arm around Tiel’s shoulders. ‘You don’t need to worry about that, Ambassador. Tiel can stay with us from now on – I’ll vouch for him.’

  Tiel looked shocked at this sudden appropriation of his life, as well he might, Mara thought.

  But Parz nodded thoughtfully. ‘Good, good. I’m sure it can all be arranged. But I urge you to be circumspect. Cautious. Well, gentlemen, I can see there’s a long way to go and no assurance of success. But I think we have a commission for you. Though I’m sure that to build a navigable wormhole will take more than scavenged lasers and a tabletop.’

  Tiel nodded. ‘We’ll need to make more exotic matter. A lot of it. More than we can fudge up with scrap optic cables.’

  ‘And what do you think you’ll need to achieve that?’

  Without hesitation Tiel replied, ‘A Squeem hyperdrive unit.’

  The Engineer laughed out loud.

  Parz, showing admirable composure, asked, ‘Is that all?’

  ‘No. Also Xeelee construction material.’

  2

  The flitter rose from Occupied Earth like a stone thrown from a blue bowl.

  Like most Earthborn humans of her era, Mara had only rarely travelled above the atmosphere. Now, as the ship settled into a low check-out orbit, the glowing innocence of the planet took her breath away. Two centuries of Qax Occupation had left few visible scars on Earth’s surface – far fewer, in fact, than the damage wrought by humans themselves during their slow, haphazard rise to technological civilisation. Away from the cities like Mellborn, rewilded Australe was a pale green-brown, the colour of scrubland populated by herds of immense beasts: the colours of life, of nature. But still it was disturbing to see how the Qax-run plankton farms bordered the coast in lurid purple-green. And on the land, scattered and gleaming fields of glass marked mankind’s brief and inglorious struggle against the Qax – at the site of SydCity, for instance, which was still left abandoned.

  Mara sat with the Virtual of Parz, who was politely making this ride into space with her. The louring Engineer Tasqer sat opposite. Chael was riding up front in the cockpit, a backup in this pilotless craft. A month after Parz had initiated the Endurance project they were on their way to the Moon, to inspect the experimental exotic-matter production facility to whose design Tiel and Juq had been contributing.

  But to get to the Moon, first you had to leave Earth. And Parz’s expression, in the bright light of Earth, was complex, she thought.

  He caught her watching, and smiled. ‘You’re wondering what I’m thinking.’

  ‘You must have made this journey many times. In the flesh, I mean—’

  ‘I always meant for the best, you know. I do know what people think of me. Given that the Qax Occupation was imposed on mankind over a century before I was even born, and given that I discovered I had certain diplomatic skills that spanned both communities, human and Qax, I thought I could find a way to do some good through negotiation. Mediation.’

  Tasqer asked, ‘And do you think you succeeded? Look down there. That is not a human landscape.’

  ‘Maybe not,’ Mara felt compelled to put in. ‘But it could surely have been a lot worse. They say the Squeem occupation was more brutal, in some ways. Yes, there was a war; yes, we lost cities. The Qax forced their own food production system on us, as you can see from here. But since the Occupation was imposed, the Qax have allowed us to preserve our cultural treasures – the ancient heart of Mellborn, for instance. And much of this continent remains wild, green.’ Mara was proud of this aspect of her own people’s legacy. ‘The wild is there because humans brought it back, long before the Qax ever came. We reversed extinctions using genetic traces; we reconstructed ecologies lost when humans allowed themselves to overcrowd their world.’

  Tasqer snorted. ‘The Qax only allowed all that to be preserved because they mine it for export. Exotic biochemistries sold to their alien markets, out there among the stars somewhere. They are more sophisticated than the Squeem, I’ll give them that. But they are conquerors just the same.’

  Parz put in, ‘The Qax are essentially traders, you know; that’s their motivation for conquest.’

  The Engineer laughed. ‘They trade in Earth’s riches while humans eat slop from the coastal farms. Once we built starships. Once a kid like Tiel would have been training up on hyperdrive, rather than crawling through sewers sifting garbage.’

  Parz said sharply, ‘Well, Tiel is getting his chance now, isn’t he? And you Engineers seem to have long memories.’

  ‘Should we not? Somebody must remember, now the old ones are dying off . . .’

  Mara had heard that was true. After two centuries, and with their AS treatment long ago curtailed, the last survivors of the pre-Qax era, the last to remember Earth as it had been before the alien Occupation, were being lost one by one.

  ‘We stayed independent,’ Tasqer said now. ‘We Engineers. I myself was born between planets. My ancestors fled Earth at the time of the Occupation war. With no place to land, the refugees ganged together their spacecraft and found ways to live, through trading, piloting, even a little mercenary soldiering.’

  ‘And banditry, when you dare,’ Parz said.

  ‘But you yourself are no longer free,’ Mara pointed out.

  Tasqer shrugged. ‘I dared once too often. After my capture I parlayed imprisonment into service for the Qax. And here I am, building a GUTship for them.’

  ‘Just so,’ Parz said. ‘The Qax can be . . . benign.’

  ‘Maybe you people need to get out of your golden cages more often,’ Tasqer said. ‘To the Qax we are probably more valuable as sacks of exotic chemicals than as thinking beings.’

  Mara shuddered at that.

  ‘Enough,’ snapped Parz. ‘You don’t have a monopoly on conscience, Tasqer. And after all, this is a moment of human triumph, against all the odds: we are travelling to see the great machinery that Mara’s son is assembling on the Moon – and all o
f it prompted by the return of Michael Poole’s starship from the past.’

  Mara said, ‘I admit I don’t understand what the purpose of that flight was, what Poole hoped to achieve – a great circle in interstellar space?’

  Parz smiled. ‘I’m no physicist myself. But as I understand it, Mara, what Poole was aiming for, having spent decades building wormhole bridges between the planets, was to build a bridge to the future . . .’

  Poole’s peculiar time machine was built on a combination of two extraordinary physical phenomena.

  The first was wormholes, flaws in space and time that connected points separated perhaps by light years with near-instantaneous passages of curved space. And the second was time dilation. As a ship accelerated close to the speed of light, its clocks slowed compared to those observed from its planet of origin. Its crew would age more slowly, as would any equipment they carried – such as a wormhole Interface.

  Poole’s GUTship Cauchy had been dispatched on a long, near-light-speed jaunt in the direction of Sagittarius, towards the centre of the Galaxy. It had carried one terminus of a wormhole, whose other end remained in Jupiter orbit. The Cauchy was to return after a subjective century of flight but, thanks to time dilation effects, to a Solar System fifteen centuries older.

  And that was the purpose of the project. When, after a century of subjective time, the Cauchy completed its circular tour, its hundred-year-old wormhole portal, delivered to the fifteen-hundred-years-hence date of AD 5274, would be linked to its hundred-year-old sibling, in Jovian orbit, back in the year AD 3829, a century after the ship’s launch. And then it would be possible, using the wormhole, to step in a few hours across fifteen centuries of time, forward or back.

  Mara was astonished. ‘What audacity.’

  ‘What an experiment!’ Parz said with a grin.

  ‘Well, now the Cauchy is back. Has anybody tried using it yet? Either going back fifteen centuries – or has anybody come forward, from Poole’s era? And I would like to understand why the Qax’s response to this bizarre arrival has been to build another wormhole of their own.’

  The Engineer and the Ambassador exchanged a glance.

  ‘Very well,’ Jasoft Parz said. ‘The immediate cause of the Qax’s action is that it is a response to – well, a rebellion. A minor one, but effective. I can speak openly of this because the event was visible to human observers, suitably equipped—’

  ‘I’ll say,’ the Engineer said with a grin. ‘It was a rogue craft, assembled in secret—’

  ‘Under a cultural monument,’ Parz said disapprovingly.

  Tasqer said, ‘We don’t know who they were. But, yes, somebody managed to reach the Poole wormhole. They got off the Earth and out of the Solar System and through that time bridge, to the past. What do you think of that, lady? If they made it through, if it all worked as Poole designed, what will they be doing now, back there in history? What will they be saying of the Qax, or of you, Ambassador, to an independent mankind? What wave of new history is rolling towards us even now?’

  Parz sniffed. ‘Their belief system struck me as so insane that I doubt they’ll make any difference at all.’

  Mara frowned. ‘If they made it to the past, shouldn’t that show up in the records, in our histories?’

  Parz said hesitantly, ‘There are some mentions of a great disruption at the time, which people called the Emergency. But our knowledge of history has been badly damaged, by the Starfall war, by the Squeem occupation – by the activities of the Qax too, though I’m convinced they aren’t trying to disrupt our knowledge of that era specifically. Anyhow, there’s nothing we can do about that, is there? All we can do—’

  ‘Is carry out the orders of the Qax,’ the Engineer finished sourly.

  Mara said cautiously, ‘And exactly what are those orders? You still haven’t told me it all, have you?’

  Tasqer glanced at Parz, as if for approval. Then he said, ‘The Qax want to do what Michael Poole did, Mara. Just as Poole built a wormhole bridge to his future – our present – so the Qax want to build another bridge, with the wormhole built by your sons and towed by this new ship, the Endurance – a bridge to their own future.’

  The idea astonished Mara, and horrified her. ‘And what then?’

  ‘Well, we cannot know,’ Parz said softly. ‘I suspect even the Qax Governor, who ordered this, does not know, yet. But that is the project we have been given.’

  The flitter swivelled, its main drive cutting in at last to push the craft to the Moon, and Mara watched as Earth fell away. Now she glimpsed huge Spline craft, three, four, five of them, fleshy spheres glistening with sensor bays and weapons pods and armed with starbreaker beams: living ships that bore the Qax overlords, cruising over the planet they dominated. It felt almost a relief as Earth diminished in her view, and the Spline were no longer visible.

  The Mare Serenitatis turned out to be a plain of basaltic dust. Its human history was dominated by two monuments, one the relic of a vast circular particle accelerator some three thousand kilometres long that was thought to date from the Poole era, and the other an even older treasure, set like a jewel in its own preserved park to the eastern edge of the accelerator: the site of a primitive lander from Earth, one of the earliest, although whether robot or human, none of the party could remember.

  There were still many humans living and working on the Moon, as on other colony worlds and moons around the System. Up to now the Qax had been content to let such off-world knots of humanity persist, as long as they did not interfere with the projects of the conquerors; the Earth itself, with its teeming billions and complex ecologies, was the prize, not a few work-shacks on airless moons. And, guided by Tiel and his primitive engineering instincts, the Endurance engineering effort had been brought to Serenitatis because of that huge old accelerator, which, though damaged during the Starfall war, still had powerful installations and infrastructures that could quickly be renovated and adapted for this new purpose.

  Mara, uncomfortable in the low gravity, let her son guide her around the hulks of enormous machines in this cavernous facility, which for her taste was dimly lit by too few light globes. But against this background Juq looked good, as he did almost anywhere. He was wearing a kind of uniform he’d designed himself, a practical coverall with flashes on shoulder and lapels. The project had to have an identity, he said – with, he hadn’t needed to add, himself as the symbolic head. Mara saw how well he filled that role, a natural aristocrat who seemed to inspire by his very presence the workers brought here from across Earth and the lunar colonies. No wonder he had been elevated by Parz, who was nothing if not a wily player. And it seemed to Mara now that Juq was throwing himself into the project with real enthusiasm, for better or worse. Not for her son a consideration of moral ambiguities, she thought wistfully; technological toys were all he was interested in.

  But for all Juq’s charm, it was Tiel who explained the intricacies of what they were doing here.

  ‘The challenges we face constructing wormholes are essentially the same as those faced by Michael Poole. But we have stuff even Michael Poole never had. Squeem hyperdrives, left over from their occupation.’

  Tasqer grunted. ‘No doubt there’s quite a stockpile for you to use. The Qax are still impounding human spacecraft, even after two centuries. I worked on a yard in Korea myself, breaking down vessels, taking out the hyperdrive units.’

  ‘That must have been heartbreaking for you,’ Mara said.

  He just looked back at her.

  Jasoft Parz said, ‘I admit I’m confused as to why you need a hyperdrive unit, a faster-than-light technology, to manufacture exotic matter for another kind of faster-than-light link . . .’

  Tiel was patient. Evidently he’d had to answer such questions many times before. ‘The hyperdrive works by manipulating spacetime – and if you do that, you’re automatically manipulating gravity. With a modified hyperdrive
I’m able to construct a gravitational field optimised to squeeze the quantum vacuum in such a way that the negative-energy components of a given field are extracted far more efficiently than with the optical systems we used earlier. Soon we’ll be able to churn out exotic matter on an industrial scale.’

  ‘He always talks like this now,’ Juq put in with a kind of graceful admiration. It was a way, Mara saw, of making his own lack of ability a charming asset rather than a handicap. She marvelled at her son’s apparently unconscious skill.

  ‘Very well,’ Parz said. ‘And what of the Xeelee construction material you asked for?’

  Tiel said, ‘Construction material is light, easily grown from any energy source, impermeable to most radiation fields, very strong . . . It is ideal for our project, which will require the quick construction of large facilities if we are to meet production targets.’

  Chael rubbed his hands. ‘You hear that, Ambassador? The boy has the brain of a genius but the logistical judgement of a born manager. Well, you’ve seen our full report—’

  ‘I have. And you’ve done remarkably well, boys, you and the other like-minded enthusiasts we gathered here. You’ve even hit the timescale we set you, of just a month to get this proof-of-concept facility up and running. I’m happy to approve the roll-out to full production, here on the Moon and on other suitable off-world sites. And we’ve no time to lose. Michael Poole took forty years at Jupiter to manufacture the exotic matter for his Cauchy project. We have a mere five more months. But we’ll get it done, I have no doubt. Well done, boys.’ He started to clap his hands, and the others joined in. ‘Well done indeed!’