Xeelee: Endurance

by Stephen Baxter

  ‘No. I am speaking through the – what did you call it? The Mole? I am human, like you.’

  ‘Are you a man or a woman?’

  ‘I am a boy. Coton. What is your name?’

  ‘Lura! My name is Lura! I was born about eighteen thousand shifts ago.’

  ‘Shifts? . . . Please wait. Lura, we think a shift is about a third of a standard day. An old Integrality navy term. Very ancient! So that makes you . . . about sixteen years old.’

  ‘Years?’

  ‘You’re a bit younger than me.’

  ‘Are you talking to other people there? Are you asking them questions?’

  ‘Yes, there are people here. My grandmother, Vala. And we have other machines that help us understand what you say. Actually there are lots of machines, talking to each other in a kind of chain. Your language and mine were once the same, but that was a long time ago.’

  ‘Am I talking to you out of a machine too?’

  ‘No. Yes . . . In a way. Lura, the machine is in my head.’

  ‘How strange. Does it hurt?’

  ‘No. Well, I don’t think so. I don’t like it much.’

  ‘You said your grandmother is there. Where are your parents?’

  ‘Not here. We were moved. My father spent all he had sending me to safety. Not that I feel very safe where I am now . . . An enemy was coming. Well, it still is coming. Everybody had to move. What about your parents, Lura?’

  ‘They both died.’

  ‘Are you with friends? At home?’

  ‘It’s difficult. I can’t talk about it.’

  ‘We’re in such different places. But we don’t have easy lives, do we?’

  ‘Different places? Coton, I don’t understand any of this. I know you’re speaking to me through the Mole. I don’t know where you are.’

  ‘Where do you think I could be?’

  ‘In another of the nebulae that are orbiting the big-star. But there are lots of big-stars orbiting the Core of Cores. Perhaps you’re closer to one of them. Are you on a tree, or in a whale?’

  ‘I don’t understand much of that. No, Lura, I’m not in any of those places.’

  ‘Are you further away, then?’

  ‘Lura, I’m in another universe.’

  ‘A what? Another everything? What does that mean?’

  ‘I think sometimes the translation isn’t very good. Maybe you don’t have the word in your language. I’m in the place people originally came from. Your people. Your ancestors went through a kind of gate, and ended up where you are. They couldn’t get back. Everything is different here. The stars, the stars are bigger than you can imagine—’

  ‘Humans don’t belong here.’

  ‘What?’

  ‘My parents taught me that when I was small. They said it’s the most important thing people should remember. The Brothers would punish you if they caught you saying it. But you can’t do that now, can you, Pesten? Humans don’t belong here! It’s true! Here’s the proof!’

  ‘You haven’t forgotten, then. After all this time. In a way, your Mole never forgot either. It must have been a component of the original ship—’

  ‘The Ship! We have stories about the Ship – some of us. People lived on it for a while, and then they made the Raft out of it, but they had to give that up too.’

  ‘And in the end the Mole called. I managed to hear it . . . It’s complicated.’

  ‘Why did it call?’

  ‘Because it thinks you need help, Lura. All of you, in that universe.’

  ‘I like talking to you, Coton.’

  ‘And I like talking to you. Tell me what you see.’

  ‘The air is red and filled with stars, all falling down . . .’

  8

  Coton lay on his pallet, propped up on pillows, outside Vala’s tetrahedral house. His talks with Lura were draining, and after a half-hour session he always felt as if he hadn’t slept for days.

  Meanwhile Sand and Vala argued over their data, their interpretations, their Virtual reconstructions. They were using facilities loaned by the local Second Coalition authority and imported into this ancient Map Room – and, remarkably, the Marshal herself had invested the time to come here in person.

  What they were discovering was remarkable, inspiring, haunting. Vala had actually found a scrap of a log fired back by the crew of the Integrality’s Constancy of Purpose as the warship, its engine blazing, had fallen through Bolder’s Ring, an immense Xeelee artefact under assault from human fleets – fallen into a new universe . . .

  The ship imploded, and fell into a compact, glowing nebula. Crew members hurried through the corridors of their failing vessel. Smoke filled the passageways as lurid flames singed the air. And then the hull was breached. The raw air of the nebula scoured through the cabins, and through rents in the silver walls the crew saw flying trees and huge, cloudy whales, all utterly unlike anything in their experience . . .

  ‘It’s a miracle anything survives at all,’ Vala said. ‘It’s nearly nine hundred thousand years since this ship was lost! A date, incidentally, we confirmed from the linguistic drift between Lura’s tongue and our own.’

  ‘Perhaps you could skip the self-congratulation, Academician—’

  ‘Gravity!’ Vala said forcefully. ‘That’s the key to universe Beta – which is what the Integrality archivists of the time called it.’

  ‘Our own universe being Alpha, I suppose,’ said Sand drily.

  Vala smiled. ‘Gravity in Beta is a billion times stronger than in Alpha – you understand I mean the fundamental force, the magnitude of the constant of gravity. Other physical constants, the speed of light for instance, are the same.’

  ‘Then everything is different there,’ Sand said, pondering. ‘If Earth was projected into universe Beta—’

  ‘It would have a surface gravity of a billion gees – but it would implode in an instant. Even a mass as small as a human body would have a perceptible gravity field. In Beta, you could make a “star” with the mass of a small comet, say; that would give enough pressure to initiate fusion in the core. Stellar masses scale inversely as the gravity constant raised to the power of three over two . . . Other cosmic objects scale similarly – neutron stars, black holes.

  ‘The cosmology in Beta, reconstructed from what Lura has been able to tell us, is quite unlike our own. Well, you’d expect that.’

  She conjured up a Virtual that looked to Coton like a false-colour sketch of a Solar System, with a dark, brooding sun at the centre, around which orbited bright pinprick ‘planets’, and around these in turn circled glowing clouds of crimson gas, speckled with sparks. A strange orrery, Coton thought. He saw how the light of the Virtual stars reflected from the sheen of the Marshal’s electric-blue jacket.

  Vala said, ‘We don’t think Beta has galaxies of the kind we have here. Primitive gas clouds would implode violently and fragment, and you would quickly end up with massive black holes and an undergrowth of miniature stars. So you get a different sort of clustering, different hierarchies.

  ‘The centre of the system Lura sees is this mass they call the Core of Cores. We suspect this is an extremal black hole – a black hole of the largest possible mass.’

  ‘I didn’t know there was a limit,’ said Sand.

  ‘The larger a hole the more eagerly it consumes infalling matter, crushing it in the process. You reach a point where the resulting radiation blasts away any more infall. That limit’s pretty high, at around fifty billion solar masses in our universe – a good fraction of a galaxy’s mass. In universe Beta you’d expect to find many holes pushing at that limit. Here such a hole would span the Solar System, out to the comets. In Beta, an extremal hole is only a few hundred kilometres across. Lura is pretty far out, on the fringe of the gravity well.

  ‘Star formation probably starts with interstellar birth clou
ds of the same sort of mass and density as here – like the Carina nebula. But instead of Sol-sized stars spaced a few light years apart, such a cloud will collapse into many more comet-mass stars, as close to each other as the planets in the Solar System. We think these are the “big-stars” Lura sees orbiting the Core of Cores.

  ‘Such stars don’t have planetary systems like ours. Instead you have these quite dense gas clouds – nebulae, Lura calls them – orbiting each star, and centred on their own smaller black holes.

  ‘The nebulae are held together by gravity balanced by internal heat, generated by lesser stars inside the nebulae – the ones Lura sees falling through the air. We call them “flare stars”. They seem to be mountain-mass splinters, but with stellar fusion going on in their cores. The flares form at the edge of a nebula and then fall inward, as you see. Whereas the big-stars and the Core are analogues of objects in our universe, scaled according to the gravity constant, the flare stars aren’t like anything we have. Well, you’d expect some exotic objects.

  ‘The nebulae themselves can be full of heavy elements. In Beta, stellar evolution proceeded fast, and churned the primordial hydrogen and helium through fusion processes much more rapidly than here. And the flare stars do more processing in turn. Marshal, those nebulae contain oxygen. You could breathe the air!’

  Marshal Sand seemed unimpressed. ‘Well, of course. Otherwise the crew of the Constancy could not have survived.’

  ‘No indeed. They fell through Bolder’s Ring into air they could breathe, and adapted, and survived, and spread through the nebula . . .

  ‘Marshal, I believe that because of its ferociously strong gravity, Beta’s cosmogony must be accelerated. If the initial Big Bang singularity was like ours, a great spewing of hot hydrogen and helium, gravity would have started to compete with the universal expansion much earlier. Massive stars and huge black holes must have formed quickly, and churned through the raw material of the interstellar medium. And the cosmos itself is ageing much more rapidly too. In Alpha the smallest stars, with a mass of perhaps a tenth of Sol – red dwarfs – are the longest-lived. They may last a hundred trillion years, perhaps ten thousand times longer than a medium mass star like Sol.’

  ‘The photino birds may have something to say about that picture.’

  ‘Oh, the photino birds seem to like red dwarfs . . . The point, Marshal, is that in universe Beta a Sol-mass star’s lifetime would not span five billion years but a mere five years.’

  Sand stared. ‘It’s barely believable.’

  ‘Yes. But it’s simply a matter of proportion. A star’s lifetime scales inversely as the gravitational constant. And even the most parsimonious red dwarf would last only perhaps a million years – which is thus, I believe, roughly the span of Beta’s stelliferous age.’

  ‘A million years, and then the stars die,’ the Marshal pondered. ‘But Lura’s people have already been in there about that expanse of time.’

  ‘Quite. They were lucky, Marshal; their ancestors stumbled into Beta when that universe was very young.’

  ‘You’d think people would know they didn’t belong there,’ Coton blurted. ‘They wouldn’t have to remember by repeating nursery rhymes.’

  ‘How so?’ Sand asked.

  ‘Because they can’t eat the native life, for one thing. Lura told me. And then there’s evolution.’ He glanced at Vala, uncertain, but she nodded encouragement. ‘It took billions of years for complex life to evolve on Earth. But if universe Beta is only a million years old, there hasn’t been enough time for humans to evolve.’ Another thought struck him. ‘Or the trees, or the whales. Where did they come from?’

  Vala smiled. ‘Good thinking, grandson! Of course you’re right. I can only conclude that the whales and the trees and whatnot are refugees like the humans – not from our universe, but from others linked by wormholes to Beta, from universes Gamma and Delta and Epsilon! Beta is a particularly porous place, I suspect. Gravity has surely twisted it up on a cosmological scale, and torn holes in it everywhere . . . Perhaps it’s no surprise that it was Beta that the Constancy crew fell into; in the greater Bulk of universes this sponge-like cosmos must be something of a sink. That’s not to say Beta couldn’t host native life of its own,’ she mused. ‘Fast-living creatures of exotic physics, perhaps, down in the highly stressed spacetime around those big black holes. Lura says there have been observations of something like that. But not biochemical like our own.’

  ‘And still the castaways linger on,’ Sand said. ‘A minor, but remarkable, story of human endurance. Perhaps after all this time we should leave them be. Beta is, by now, their home . . . Ah, but it is dying.’

  ‘I’m afraid so. They have surely had to flee before, within Beta – Lura has told us fragmentary tales of stars dying and nebulae becoming exhausted. But when the last stars go out there will be nowhere left to run.

  ‘And things may get worse yet, and quite quickly. Unlike our universe, which seems destined to endless expansion, Beta, dominated by gravity, will collapse back to a Big Crunch. I don’t know when this will be – we need better data and subtler modelling – but not long! Not compared to our own cosmological timescales.’

  ‘So is it a coincidence that we have made contact with Lura just as her universe is failing?’

  ‘No,’ Vala said. ‘Remember, it was the Mole that called us. A component of the starship. Despite its own “massive sensor dysfunction” it seems to have perceived the problems ahead.’

  ‘And it sent a distress message out of its own universe? That seems quite a conceptual leap.’

  ‘Actually it seems to have sent its messages inwards towards the Core of Cores. That’s where local spacetime is most distorted, and the machine’s message had the best chance of leaking out into the wider Bulk.’ She coughed. ‘There are more speculative possibilities. As I said there may be concentrations of complex matter there, around the Core of Cores. Maybe there is life there – even intelligence—’

  Sand dismissed that. ‘Idle guesswork. The point is this Mole did manage to get its message out, to be picked up by the alien thing in your grandson’s head.’

  Coton thought he felt that phantom ache deep in the core of his brain.

  ‘The question now is how we proceed,’ Vala said.

  Sand frowned. ‘Proceed to do what?’

  ‘Why, to help them, of course. They are humans, Marshal Sand, whose ancestors became castaways following their duty!’

  ‘Their “duty” was to a government that has long vanished, in a long-forgotten war—’

  ‘Against the same enemy,’ Vala said quietly.

  The Marshal stared at her. Then she paced, impatient, one hand slapping her hip. ‘All this is a . . . curiosity. I can see your motivation, Academician. You have spent your life trying to save other relics of dead wars, such as the Starfolk. But what, in the end, can you actually do for these people? They are in another universe – and I have other priorities. I’m under pressure to tidy up here—’

  ‘“Tidy up”?’

  ‘I’m aware of the cultural and historical sensitivities,’ Sand said wearily. ‘But the military priority is to fall back to the Orion-line Wall zone, before the pressure of the Scourge in this region becomes overwhelming. And at the Wall itself, where the demarcation lines are being drawn, there is already some trouble among the displaced, the refugees . . .’ She took off her elaborate peaked cap and rubbed her stubbly hair. ‘Yet I am not without compassion, Academician. And curiosity. You may continue with this, for now. But whatever you intend to do, get it done quickly.’ And she placed her cap back on her head and walked out.

  Vala sighed. She came to sit beside Coton. ‘Well, we’re going to have to get on with it – and so are Lura and her people.’

  ‘Get on with what?’

  Vala smiled and stroked his cheek. ‘To retrace their steps through Bolder’s Ring is out of the question
. . . I suppose teleportation is a possibility. I’ll have to look into it. Go poking around the museums again . . . Do you feel up to talking to the castaways some more? Whatever we do is going to depend on having some kind of anchor at their end. They need to get hold of more high technology, more relics of the ship. There must be some. Perhaps they can find this “Raft” Lura spoke of—’

  He cut through the torrent of words. ‘Grandmother, I don’t understand. Are you going to save the people in Beta?’

  She smiled. ‘Of course I am. What else?’ She stood up. ‘I’ve a lot to do. You rest, and when you feel up to it try to contact Lura again.’ She patted his shoulder and walked off across the floor of the Map Room.

  Wild ideas whirled in his head.

  9

  As the shifts had worn away the whale riders hadn’t disturbed Lura’s lengthy conversations with her machine, and the eerie figures it seemed to speak for. Lura supposed they were kept back by superstition or fear – as she felt only a little less, she suspected. But the riders were becoming increasingly disturbed by the Mole’s pronouncements. They went off towards the whale’s vast inverted face, so they could talk away from their captives.

  But Lura was confused too. In the course of his latest conversation, Coton had told them they needed to find the Raft. It was as if they had been told to chase a fantasy from a child’s bedtime story!

  Lura and Brother Pesten sat side by side, somewhere near the whale’s midriff. They had been left unbound for a few shifts now, and Pesten had been given a coarse, ill-smelling blanket to cover his nakedness. They drank water from sacks made of the skin of sky wolves. The Mole sat on the slippery skin-floor between them, silent for now, its transparent ‘eyes’ gazing out at what they had learned to call universe Beta.

  The whale itself appeared to be feeding. Lura could see a series of ill-defined lumps passing down the huge digestive tract that spanned its diameter, from face to anus, passing above their heads.

  And Lura watched the whale riders. The effective gravity imparted by the whale’s spin was weakest near its axis, and as Anka and Otho and the other half-dozen riders argued, they drifted in the air and spun around, clustering together under their mutual gravity and pushing each other away. They were like squabbling children, she thought.