Xeelee: Endurance

by Stephen Baxter

  ‘The Seer,’ Eve said.

  The Ambassador said, ‘The control of the core of a giant star during a catastrophic explosion is ferociously difficult. Even modelling it was beyond our processing resources. So we devised a new generation of AI.’

  Five said, ‘This box of dust?’

  ‘This box of dust,’ Eve said, ‘is the most advanced AI we’re aware of. For a machine like this, physically you need components that are small enough to be influenced by quantum effects, yet large enough to feel the effects of gravity. A swarm of smart microprobes – dust motes.’

  ‘A machine like what?’

  ‘A quantum gravity AI . . .’

  ‘On the Miriam we have quantum AIs,’ Donn said.

  ‘Right,’ Eve said, nodding. ‘And that gives you an edge in processing speed. A simple switch can only be in one state at a time – on or off. A quantum switch holds information about all possible states of the switch at any one time. And so you can use it to do parallel processing. Many inputs, many outputs. You get a speed advantage, and a significant one.

  ‘But a quantum gravity machine goes one step further. You abandon causality altogether . . .’

  The blurring of position and velocity in quantum mechanics made traditional causality problematical. And in relativity, too, light-speed limits ensured that causality was more an aspiration than an iron law.

  Donn started to see. ‘And if you put quantum mechanics and relativity together—’

  ‘In a quantum gravity computer, cause and effect are thoroughly mixed up. Time loops are commonplace . . . You can guess where this is going. You don’t even need to have input before output, causally.’

  ‘You get the answer before you’ve even asked the question.’

  ‘That’s it. In practice, I think, the Seer is able to glimpse the outline of a solution to a given problem even before it has begun its calculation, and so can guide its processing efficiently to that outcome. Its thinking must feel like guesswork, an unlikely series of inductive leaps. But it’s always right, and very very fast.’

  ‘The Seer really can see the future,’ Five said. ‘Just as the rumours say.’

  ‘But its visions are limited, to the outcomes of computing algorithms a few microseconds ahead – or to the furthest future, millennia or more away.’

  Five glared at the Ambassador. ‘So why the tetrahedron, fatball? Why is this ultimate brain in a box the shape of the symbol of human freedom?’

  ‘A tetrahedron was the most suitable shape for—’

  ‘It’s a totem, that’s what I think,’ Five snapped. ‘Some of the Samples say Ghosts are starting to worship us humans, because we’re becoming so good at killing you. So, the Silvermen, walking human statues. So, the tetrahedral box.’

  The Ambassador said evenly, ‘We Ghosts do have a propensity for worshipping that which destroys us, it is true. But you are not yet a goddess, Sample 5A43.’

  Donn said sharply, ‘Enough. Eve, you said how the Seer’s thinking feels. How can you know that?’

  ‘Ah. Good question. Because, not for the first time, the Ghosts created an artificial AI which ended up not performing quite as specified.’

  ‘Like the Silverman.’

  ‘Well, yes. And, not for the first time, I, or an avatar of myself, was asked to help interpret for it . . .’ She looked at Donn, her grey hair shining in the light of the stellar core. ‘The Seer sees the future, Donn. And it is afraid.’

  Donn watched Eve. Her eyes were unfocused, and he thought her representation was degrading, her skin smoothing from lack of definition, a lock of her grey hair flickering. He wondered how it must be to be her, a representation every bit as sentient as he was, and yet having endured multiple lives already – and now bonded with a consciousness like no other.

  She said, ‘The Seer is sentient, born of dust into a baffling, acausal universe. But it is a Ghost artefact. And so it shares Ghost values, Ghost assumptions. The Ghosts survived the death of their world through symbiosis, dissimilar life forms gathering together as their sun failed. The Ghosts have faith that the life forms of this era of the universe, a transient age of light and water-based chemistry, will similarly use cooperation and symbiosis to survive the transition to the new cold age to come when the last star dies.’

  Five shuddered. ‘How can you think like that?’

  ‘This has happened already, in the universe’s history,’ Eve said. ‘There are life forms extant now, in this age of matter, which are survivors of earlier epochs, the age of radiation and of annihilation and of superforces. But when this age ends, when dark energy comes to predominate and the fabric of spacetime is torn apart – when this happens, and the Seer can see it – there will be no Ghost left alive to witness it, and no symbiotic descendant of the Ghosts.’

  ‘Why not?’

  ‘Because of us,’ said Five savagely. ‘Because of humans. We win. I don’t need a quantum-gravity computer to tell me that. And we drive the Ghosts to extinction.’

  ‘You must understand,’ the Ambassador said. ‘The detonation of this sun – we do this because we, this Ghost enclave, have been cut off from our home range by the forces of your Coalition. Billions of individuals, a whole world, trapped behind the lines. We were desperate. We looked for a way to change the parameters – the rules of the game. That is our way of resolving problems. We were looking for a way out. Now we see we must do more than that; we must take the Seer and its dreadful counsel to our home ranges. We need time to consider what must be done.’

  ‘Such as what?’ Five asked.

  ‘Such as escape.’

  Escape to where? Donn wondered. Where could the Ghosts go to escape a rampant, Coalition-led mankind? Out of the Galaxy? Out of the cosmos altogether?

  He tried to focus on his own situation. ‘Then why have you brought us here? Why tell us this?’

  ‘Because of me,’ said the Silverman. He stepped forward, still cradling the Seer. ‘You made me smart in order to punish me. But I am human enough to guess how you would feel about an exploding star.’

  The Ambassador said, ‘We did not mean to engineer this star as an act of war, only as a means of escape. We understand now that humans might not see it that way.’

  ‘You really don’t get human psychology, do you?’ Donn said.

  ‘No,’ said the Silverman cheerfully. ‘Donn Wyman, you must warn your people. Make them believe, as we could not. Persuade them to flee. And make them believe the Ghosts did not mean war.’

  ‘That’s a tall order.’

  ‘You are our only hope,’ the Ghost said simply. ‘You, who have shown empathy for our kind before, where others have turned away.’

  Donn thought he ought to feel proud. He felt empty. Could it be true that so much was pivoting on this moment? Because if so, he thought, I am not strong enough to deal with it.

  ‘You don’t have much time,’ said the Ambassador. It floated towards the lip of the platform.

  Donn followed, and looked down at the engineered moon. Ghosts swarmed, pinpricks of dazzling light against the worked regolith. ‘How long?’

  ‘The mathematics is uncertain.’

  ‘There are human colonies scattered through the Association,’ Donn said, thinking. ‘Many of them still have hyperdrive, I think. But the main human concentration is the Reef. And we no longer have hyperdrive—’

  ‘Ask your father,’ the Ambassador said.

  ‘What?’

  ‘I too approved of the Silverman’s wish to contact you personally, Donn Wyman. Because I know that your family has resources. We will send you home now, Donn Wyman.’

  They pulled back and stood in a row, the Silverman with the tetrahedral box, the looming Ghost, and the Virtual of Eve, gradually disintegrating.

  Eve raised her hand. ‘There is more,’ she said solemnly. ‘Human and Ghosts must both join the g
reat confluence of mind in the far future, join with the rest. That is the only way the next transition can be survived by either of us.’

  Donn was shocked by this latest bit of bad news. ‘And if humans destroy the Ghosts—’

  ‘Then neither will survive. Remember,’ she said, her voice scratchy. ‘Remember . . .’

  Five ran towards the Silverman, who stood stock-still, slow to react. She raised her fists and slammed them down on the Seer. Her hands passed through its substance, scattering pixels.

  Donn pulled her away.

  ‘Just an avatar,’ she said, breathless. ‘Worth a try. To strike such a blow . . . It would have been magnificent.’

  The Ghost and its companions were surrounded by a cloud of pixels now. The star’s light flickered.

  And Donn was home.

  His mother ran up to him and grabbed him. ‘Oh, Lethe, Donn! I never thought I’d see you again.’ He let her weep on his shoulder. ‘Benj is back too,’ she whispered. ‘He’s back!’

  Here was Samm, his father, grinning hugely, grabbing onto Benj as hard as his mother was to Donn. The Commissary, Elah, was here too. She looked as shocked as any of them at Donn’s sudden appearance, but she was looking up into the sky with some alarm and muttering into the air, evidently communicating with her Coalition colleagues. And Donn saw Five, still in her bloodstained Ghost-hide suit, looking even more scared and bewildered than in the centre of the star.

  Donn found his brother. Benj was wearing a plain white bath robe; all his hair had been shaved off. ‘Benj. What happened to you?’

  ‘I’ve been a stark-naked lab rat for a day. If it really was you who got me out—’

  ‘It was. You owe me.’

  ‘I was afraid of that. Damn.’

  There were twin concussions, soft explosions, and a breeze of displaced air, as Hama Belk and Kanda Fors returned, coalescing under the lifedome. Grubby, scrawny, they both staggered in the sudden change of gravity, and clung to each other in shock. Then they realised where they were, and their clinging turned to a hug of joy. Then Hama spotted Elah, standing apart in her black Commissary’s robe, and he went over to her immediately.

  And Kanda, recovering her composure quickly, came forward to Donn and Rima.

  Donn gently disengaged his mother. ‘Mother – you have guests.’

  Rima turned. ‘Do I know you?’

  ‘Kanda Fors. Food tech, from the Harry Poole. We met a couple of times, I think . . . I’ve been lost for a number of years.’

  ‘It’s a day of shocks for us all.’ Rima stepped forward, and the women clasped hands.

  Amid more soft concussions, more of the ragged rats from Ghostworld started to appear, many naked, bewildered. One woman cradled a baby.

  Five still stood alone, Donn saw, scared, resentful.

  Donn went over, took Five by the hand, and led her to his mother. ‘Mother, this one’s called Five. Long story. I think she’d appreciate some help, her and her people. Some clothes for a start.’ But Five flinched back. ‘She’s been living wild,’ Donn murmured. ‘It will take some time . . .’

  ‘We’ve all the time in the world. Come, child. And, Kanda, you’ll be wanting to tell your family you’re back?’

  ‘I feel nervous about it. Yes, of course . . .’

  ‘And you – Five, was it? What about your family?’

  ‘I don’t remember.’

  ‘I’m sure we can trace them. Come on, we’ll sort it out.’

  Now Donn approached Samm. ‘Father. I need to talk to you. We’re in trouble. The Boss—’

  ‘I know. Look at this.’ He showed Donn an image, returned by faster-than-light inseparability links from a Coalition drone observer close to the giant star. The Boss was spitting, flaring, ejecting knots of plasma large enough to swallow Earth’s sun whole. ‘It’s becoming unstable.’

  ‘It’s worse than that . . .’ As urgently as he could, Donn told his father all he had witnessed, of the Ghost experiments at the heart of the Boss – of the coming supernova. Samm listened gravely.

  ‘You do believe me, Father?’

  ‘Of course I believe you.’

  ‘As do we,’ Elah said, walking over.

  Hama followed in her wake. Though he was just as grimy and underfed, he didn’t seem the same person he had been on the Ghostworld; he had immediately retreated into his Coalition role, like a shadow of the Commissary.

  ‘What you say,’ Elah went on, ‘ties in with the projections we have been making of the star’s instability.’

  Samm folded his arms. ‘You say you’re here to protect us, you of the Coalition. What are you going to do about this?’

  ‘We have already put out a warning to the other human colonies in the Association. Most of them have hyperdrive ships; they will be able to flee in time. Other Coalition centres are arranging refugee facilities—’

  ‘Blankets and hot water. Great. But what about us? You know damn well the Reef contains the largest human population in the Association. You took away our hyperdrives.’

  ‘In order to serve the greater needs of the Third Expansion—’

  ‘That star’s going to expand before long and cook us all. Going to give us back our technology, are you?’

  ‘That isn’t practical,’ Elah said simply. She listened absently to a voice only she could hear. ‘Come,’ she said to Hama. ‘The flitters are lifting Coalition personnel from the Reef in fifteen minutes.’

  ‘And us?’ Samm tried to grab her arm, but she shook him off. ‘What of us? You’re leaving us to die!’

  From nowhere Elah produced a handgun, a starbreaker. ‘This conversation is over, regrettably.’ Backing up, she and Hama made for the door cut into the lifedome.

  Samm made to follow, but Donn stopped him. ‘Father – let me. Wait, Commissary.’ Cautiously he approached Elah and Hama. In a few, rushed words, he tried to tell them more of what the Ghost had told him within the star.

  ‘The Ghosts don’t want this to be seen as an act of war.’

  ‘Then they shouldn’t detonate supernovas in human space,’ Elah said.

  ‘They’re only doing it to escape the cage we put them in.’

  ‘They put humans in cages. Your friend Five, Hama here—’

  ‘They fear we will drive them to extinction. That’s what the Seer foresees. And if that’s so, we may ultimately destroy ourselves in the process.’

  Elah thought that over. ‘Better a Galaxy in ruins,’ she said, ‘than a Galaxy that is not ruled by us. Good luck, Donn Wyman.’ She backed to the door, and left. Hama looked back once, but it was as if he barely recognised Donn any more, and he followed his superior.

  Donn went back to his father. ‘I failed.’

  ‘Well, what did you expect? You aren’t going to overturn an ideology like the Coalition’s with a couple of sentences. But the Commission for Historical Truth records everything that transpires – everything. Maybe they will figure all this out one day, after a couple of thousand years’ study in some library on Earth – maybe you planted a few seeds for the future. In the meantime, we’ve a supernova to deal with.’ Samm eyed his son. ‘So did your new Ghost best buddy give you any advice?’

  ‘It said I should ask you.’

  Samm sighed. ‘Smart of it. OK, son. I guess it’s time you learned a little family history.’ Carrying his data slate he walked off towards the copse at the centre of the dome, chlorophyll green leaves shining under the light of the bourgeoning supernova.

  Donn hurried after him. ‘Where are we going?’

  ‘The engine room.’

  The kilometre-long elevator descent along the ship’s spine was slow, frustrating.

  Donn knew his way around the control room at the heart of the Miriam’s GUTdrive pod. He had come down here as a kid, to play with his brother, and later as a young man to learn about his
mother’s family’s technological legacy. There wasn’t much to see – a couple of seats and couches, a water dispenser, an emergency pressurised locker. The instruments were blank, antique data slates tiling the walls. And, before the Coalition had taken them away, once in this space vast engines had brooded, engines capable of harnessing the energies of cosmic inflation to drive the ship forward.

  Even though the engines were gone, Donn somehow expected his father to boot up the control slates. He didn’t. Instead he took the small portable slate he had carried down from the lifedome, and pressed it against a wall. It lit up with a crowded panel of displays. ‘There you go,’ Samm said. ‘Two hundred years old and it fires up like it was brand new.’

  ‘What does?’

  ‘This.’ He tapped the slate and showed Donn an external view of the Miriam, seen from below, its lifedome embedded in the rough plane of the Reef, its spine and engine compartment dangling like a lantern. Samm zoomed in on the hull of the engine compartment, where a black slab clung like a parasite.

  Donn leaned forward and stared. ‘What is that?’

  ‘The family secret.’ Samm eyed his son. ‘Look, Donn – you aren’t the first Wyman to have run into the Sink Ambassador. Your grandfather a few times removed—’

  Donn’s heart sank as he realised that his father was falling back on the family legend. ‘Joens Wyman.’

  ‘That’s it. Joens got involved in a kind of intergalactic race with the Ghosts. He was an entrepreneur. And he wanted to get his hands on—’

  ‘A cache of quagma,’ Donn said. ‘You’ve been telling me about this since I was a little boy.’

  ‘But it’s the truth, son. Some of it, anyhow. Just listen. The trouble was the quagma cache was somewhere over twelve billion light years away – the figures are uncertain. Too far even for hyperdrive. But Joens Wyman didn’t use hyperdrive. He used an experimental human technology. It was called a Susy drive.’

  ‘Susy? That’s our flitter’s name.’

  ‘The flitter, and a secret space drive. It was kind of risky . . . It’s not like hyperdrive. Look, they taught you at school that the universe has more dimensions than the macroscopic, the three spatial and one of time. Most of the extra dimensions are extremely small. When you hyperdrive you sort of twist smoothly through ninety degrees into an extra dimension, and go skimming over the surface of the universe like a pebble over a pond. Simple. Whereas with supersymmetry you’re getting into the real guts of physics . . .’