World Engine

by Stephen Baxter

  Malenfant goggled. ‘You have a base on Persephone? This Persephone, in this . . . Road?’

  All this was hitting him too quickly. He glanced again to Deirdra, who looked thrilled, if somewhat baffled. This was after all her reality. And here were these odd Brits flying around her Solar System. To her Persephone.

  ‘Certainly we have a Persephone base. Strictly speaking the base is on one of the moons, called Melinoe. We even run a ferry service, of sorts! This ship and a sister vessel take it in turns to cycle out there. But this time we don’t intend to stop there, at Persephone – we of the Harmonia, I mean. Not on this journey. Melinoe is a valuable ice moon where we will refuel again, for the longest leg of the mission.’

  ‘Beyond Persephone?’

  ‘Certainly. Out to a further destination – exploiting that useful planetary alignment, as I say. That alignment is why we have kept on coming back to this Road, having invested in the Persephone base . . .’

  Malenfant caught Deirdra’s eye. As far as he knew there was only one significant object lined up beyond Persephone: just as the Planetary AIs had told him. Shiva, parent of the Destroyer. She looked as electrified as he felt.

  ‘But,’ Lighthill was saying, ‘we have certainly never encountered people wandering around Phobos before, let alone from other Roads than our own.’

  Viktorenko growled, ‘It is interesting. Maybe something about the distribution of worlds, of timelines, is evident here.’ He gestured at Malenfant. ‘We here are survivors of three different . . . Roads. In one, Malenfant crashes his spacecraft; in one, Emma here is stranded at Phobos years earlier; in yet another, war devastates Russia.’

  Malenfant watched the British for their reactions. At that hint of a Russian war they exchanged glances.

  ‘Maybe,’ Viktorenko said now, ‘some of these Roads come close together. In some abstract sense. They occur in tangles, braids. A common background, up to a fairly recent divergence. Commander Lighthill, we come from what my colleagues have called the Nixon Bundle. Maybe there are other bundles. And maybe there are Roads which are more solitary in nature.’

  Lighthill said, ‘Well, perhaps there’s something in that. Devastation of Russia, eh?’

  Viktorenko said bluntly, ‘I come from 2028, or a version of it, where Russia was attacked by a coalition of the West, including Britain and America.’

  The atmosphere was grim after that pronouncement.

  Lighthill, a military man, nodded curtly. ‘Well, sir, I have to tell you that Russia, our Russia, was rather battered long before – 2028, did you say? Certainly by the time Hitler and Joe Stalin had finished lobbing nuclear weapons at each other back in ’46, anyhow.’

  Malenfant and Emma shared a glance of their own at that snippet of news.

  ‘But it does not matter now, in this company,’ Viktorenko said firmly, as if determined to believe it. ‘We are all human beings, taken out of our context. Yes?’

  ‘Yes,’ Lighthill said. ‘I’ll drink to that – or would, if I had a glass. We are being remiss as hosts, to keep you chattering on the doorstep, so to speak – though the talk is fascinating. Bob, why don’t you . . . ?’

  ‘Right away.’

  With good grace, Bob Nash led them to a dining table of what looked like polished oak, set in the middle of the wardroom, more fancy furniture fitted with inset-lidded trays and a variant of Velcro pads, and with practical zero-gravity seats lined up alongside.

  ‘Sit,’ Lighthill said, with a note of jovial command. ‘Please. We have prepared dinner. And you too, Nicola. No, I insist. I suspect you have a lot to talk over with Colonel Malenfant; leave the chores to Nash and me . . .’

  He hustled away, with Nash, to what looked to Malenfant like a galley.

  A dining table. On a spaceship. Well, that was the British for you. ‘I have a head full of clichés and stereotypes,’ Malenfant murmured. ‘Mostly being confirmed.’

  Nicola Mott, at Lighthill’s insistence, was sitting down beside him. ‘What was that?’

  ‘Nothing. Sorry.’

  A moment of awkward silence.

  Then Nicola said hesitantly, ‘Picking up on Vladimir’s idea of resonances between the worlds: maybe it’s so.’ She looked at Malenfant almost shyly. ‘Maybe it’s not just grand events like the fate of nations, but also the – destiny – of individuals. From what you say of the fate of this other Nicola, who flew with you – you and I, perhaps we have been drawn together. Otherwise it seems quite a coincidence, doesn’t it?’

  Her accent definitely was stronger than his Nicola’s, he realised, and she seemed more withdrawn. Maybe coming to America had been good for her counterpart, pilot of the Constitution. For one thing, perhaps she could have been freer about her sexuality. And she was so young.

  Nash emerged now with a bowl of potatoes that he began to dish out, along with an unidentifiable green vegetable mass that stuck to the plates, defying the lack of gravity.

  Nicola said, ‘Tell me about – her. This version of me that you say died.’

  He took a breath. And he gave her a brief summary of the career of the Nicola Mott he had known – though he had to keep backtracking to follow up details – all the way through to the crash of the Constitution.

  The other British had been listening to this with grave interest as they served the food.

  ‘That’s the long and the short of it,’ Malenfant finished. ‘I don’t remember anything myself after that until I woke up here – I mean, in the twenty-fifth century in Deirdra’s, umm, Road.’ But he thought, guiltily, of the flawed Retrieved copy of Nicola he had demanded at the Codex. Something else to tell her later. ‘I’ll happily try to tell you anything else I can of her. You deserve that much.’

  ‘Yes,’ Nicola said. ‘Or she deserved it. I would like that.’

  Some other time, he promised himself, he would tell her about Siobhan Libet.

  ‘Excuse me.’ Lighthill ducked back into the galley, and re-emerged with a heavy pot of what looked like stew, thick, coated in a heavy gravy that, as he dished up, helped it stick to the plates, like Nash’s vegetable slop. ‘Hope you enjoy my signature dish – always my favourite at school . . . Of course it’s field rations for us most of the time, we don’t often get guests – ha! We do have eels, you know, that’s actually our regular feed. Swimming around in our dilute sewage. No worse than the lower Thames, I’m told, and helps with the cleansing of our reused water and so on . . . I digress. There’s one basic thing I don’t understand. Malenfant, in your Road, why wasn’t Nicola flying into space with the RASF?’

  Malenfant shook his head. ‘Because there was no RASF, Lighthill. Just the RAF. Military aircraft, yes. No British space programme – well, none to speak of, a few satellite manufacturers and such. Certainly no crewed programme.’

  Lighthill frowned as he sat down, and began to cut into his own food with cutlery spotted with Velcro, or some allohistorical equivalent. Around mouthfuls he said, ‘I find that hard to believe. Very hard to believe. No British in space at all?’

  ‘Oh, there were some. For example Nicola, or her counterpart, applied to NASA – the American space programme – and worked her way up through the ranks. It helped that she had an American-born mother, even though she grew up in England.’

  ‘Ah,’ Lighthill said. ‘I did know that.’

  ‘Others flew with the Russians, as I recall. But no British spacecraft, Lighthill. No Harmonia. Magnificent as she is.’

  Lighthill grinned and raised his glass. ‘Well, I’ll drink to that. And to all of us. Human companionship, in the middle of cosmic madness.’

  They all raised their glasses, sipped. Malenfant watched Deirdra warily, wondering what her mother would say if she could witness this scene. Not least the wine-drinking. And the smoking.

  Deirdra herself seemed fine, however, and calmer than some of the adults. She said now, ‘The Harmonia is magnificent, sir. But I have some questions too. Real basic ones. Such as, how does she work? I bet Stavros would like to
know that too.’

  Nash smiled. ‘Miss, I would give you a guided tour of the engine room myself, if there’s time. More questions?’

  ‘OK. I’m really muddled up about timings and Roads and bundles and the manifold . . . How did you manage to fly your ship, the Harmonia, from your British-space-programme Road to this one?’

  Lighthill smiled. ‘Excellent question. To answer it, we need to talk about Phobos. Bob?’

  And he cut himself another piece of meat, and chewed busily, while Bob Nash began to speak.

  54

  ‘The first thing you need to understand about Phobos is that it is a machine,’ Nash said.

  ‘I mean, it is a machine built into a moon, but a machine nonetheless. You have all seen the Engine Room – which you call the Sculpture Garden. The arrangement you found deep in an equatorial shaft. Surely it is evident from that alone—’

  ‘We got that much.’ Malenfant spoke awkwardly. He was having trouble chewing through lumps of boiled potato. ‘Machinery. Very advanced, enigmatic, but machinery.’

  Lighthill put in, ‘Very well. And Phobos is a very old machine.’

  Emma said, ‘Can you prove that?’

  Nash nodded. ‘Actually, yes. We think so. Earlier expeditions brought home samples of material – not just surface rocks and so forth, but some of the more exotic materials deep within. The glass-like substance that coats the wall of the deep shafts, for example . . . The thing about that stuff is that it doesn’t wear out.’ He grinned. ‘Ever!’

  Malenfant listened to his highly technical account that followed of what some British lab or other had made of the Phobos samples.

  The glassy stuff was not just very old – it did not age, just as Nash had said. That was due to an odd quantum-mechanics effect, it seemed. A quantum crystal, Nash called it. The ‘glass’ was essentially a diamond, crystalline carbon, though doped with nitrogen. Diamond was a regular lattice of carbon atoms. And in a lattice patterns were repeated in space, over and over again. The odd thing about the Phobos glass seemed to be that such repetition had been pivoted, so that the pattern did not endure just across space, but across time, too . . .

  Lighthill put in, ‘A very small-scale effect that nonetheless, when amplified by repetition and exponential growth – doubling in size, then doubling again and again – can be magnified to the larger scale too.’

  ‘So that’s why the stuff doesn’t wear out,’ said Emma, who seemed to be grasping this faster than Malenfant.

  ‘Precisely,’ Nash said. ‘It is self-repairing, if you like. Self-regenerating. It copies itself, flawlessly, into the future. And such is the scale of the effect, down in the quantum realm, that, paradoxically, no energy is required to fuel this regeneration.’ He shrugged. ‘Marvellous stuff. Once created, once shaped, it just doesn’t wear out. In a sense the structure is its own memory of itself, you see. Phobos, or the asteroid rubble it appears to consist of, seems to be primordial – it is itself probably billions of years old, made of junk left over from the creation of the planets. The crystal stuff may be as old as that, or even older.’

  ‘And so, you see,’ Lighthill said, ‘that’s how long Phobos has sat here – doing what it’s doing. So we believe. Or it sat somewhere. As you know – or I imagine you do – Phobos’s orbit is decaying. I find it hard to believe the whole thing will just smash up in a few million years’ time, after having endured a thousand times as much. There is still plenty we don’t know.’

  Deirdra nodded. ‘I think I understand all that. So Phobos is old. And it is full of machinery. But what does it do?’

  Malenfant had had enough of British bragging. ‘I think we know what, Deirdra. In broad-brush terms. It mixes up histories. Or, Roads. What we don’t have any idea of is how that is achieved.’ He glared at Lighthill, challenging. ‘And I bet you and your boffins in Cambridge don’t know either.’

  ‘Actually it’s Oxford that is leading the way on that stuff, I am galled to admit. I can tell you that the study may be leading us into a theory that could unite, at last, our two post-Einstein pillars of physics, I mean quantum physics and relativity, the small and the large . . .’

  ‘Einstein. Interesting,’ Emma murmured to Malenfant. ‘So wherever the jonbar hinge is between us and these British—’

  ‘Must be a big one.’

  ‘It comes after Einstein anyhow.’

  ‘But,’ Lighthill said now, ‘we have gained some insight into the detail of the mechanism of Phobos. And how to use it, at least.’

  ‘Use it?’ Malenfant asked.

  ‘To cross from one Road into another, a facility which is of value for various reasons – in fact, as I said, we came here ourselves to use that very capability.’

  Malenfant thought back. ‘To exploit this alignment of Persephone.’

  ‘Correct.’ Lighthill had finished his food; he wiped his mouth, and stuck his cutlery to the table with Velcro spots. ‘Look – the, umm, structure of Phobos is complex – but it has a certain logic. For a start there are other access points besides the big equatorial crater, which I understand you call Stickney.’

  ‘We know that much,’ Malenfant said. ‘We found a second route to that Sculpture Garden – a shallow dig down from the pole. Or rather Vladimir and his colleague discovered that.’

  ‘That’s the idea. We are the fourth imperial expedition to come here in fact, and our predecessors have explored some of those access points, and they have made careful surveys of the interior. Mapping as they went. It was a tricky job. Phobos is as riddled with tunnels as an apple infested with worms, and the tunnels do not connect in any simple way. I have a personal theory that, to whatever higher-dimensional mind constructed this thing, it may all seem as simple as the London Underground, say. To us it is a maze, a tangle, and with non-intuitive properties too.’

  ‘Such as?’

  ‘Such as, there are passages which can be traversed one way only. Turn around and you find yourself facing a blank wall of rubble . . . Other anomalies too.’ He smiled, rueful. ‘One learns to accept them, or ignore.’

  Malenfant thought that over. ‘So Phobos is full of – of a trans-dimensional subway system.’

  Lighthill smiled. ‘I did mention the London tube, didn’t I? A very practical way of putting it. Frankly we have no real idea how it works. The boffins speculate it is some kind of quantum tunnelling effect – where, you know, an electron or some such can appear to tunnel through a barrier by spreading out the probability distribution of its existence. It suddenly becomes more likely to be over there rather than here, and hey presto, it comes to pass . . . None of which helps us at all in practical terms. But we have, with time, and great caution, learned how to use the mechanism, at least, if we have yet to understand it. By which I mean, we have learned to navigate through that system.’

  ‘How?’ Emma asked. ‘How exactly?’

  ‘Yes, that’s what I wanted to know,’ Deirdra said. ‘How did you bring this big ship from your, umm, Road, into ours?’

  ‘Well, there are more accessible routes through Phobos than via your Sculpture Garden. You’d expect that, wouldn’t you? I mean, if you designed a transit system you would make it beefy enough to allow the passage of significant cargoes. We’ve found many such routes. Tunnels big enough for the dear old Harmonia, to put it bluntly. And the one that leads here, from there, where we come from, is accessed through a high-latitude crater called Paulis. Named after a member of the first expedition to the Moon . . .’

  Nash went off to produce a paper map of Phobos, a Mercator projection cruder even than the one aboard the Step, Malenfant thought.

  They quickly identified the crater. ‘It’s the one we call Shklovsky,’ Emma said. ‘Well, that’s appropriate enough.’

  ‘So,’ Deirdra pressed, ‘to get here from there you fly into this crater, follow the tunnels and fly out – where?’

  ‘Out of Paulis stroke Shklovksy again,’ Nash said with a grin. ‘It’s nothing if not paradoxical. But that�
�s irrelevant. The point is you can use Phobos purposefully to travel from one Road to another – if you can find your way.’

  Deirdra said softly, ‘So what about the other puzzles? What about the old sunlight?’

  It took a couple of minutes of debate before the group established, in language they had in common, that she meant the odd light, wan, dusty, emerging apparently from the heart of Phobos, seen in elusive glimpses.

  ‘That is indeed sunlight, of an odd sort – our spectrometers established that too,’ Nash told her. ‘It comes from some very deep, very odd passages that seem to lead to – well, to greater depths than we have had the guts to penetrate so far.’

  ‘We call those deep shafts chimneys, actually,’ Lighthill said cheerfully. ‘After a spelunking term from my days in the school caving club. As Bob says – very deep, and apparently leading to an odd place indeed.’

  ‘Deep.’ Deirdra frowned. ‘But in Phobos everything is mixed up. Space and time. “Deep” might mean “old”.’

  Emma raised her eyebrows. ‘That seems pretty insightful to me. And the fact that this inner sunlight seems to fit models of what we believe we know of the early Solar System—’

  ‘All of which,’ Lighthill said sternly, ‘is a little above my pay grade at least. Best left to future, better equipped expeditions than ours – eh? After all, Phobos for us is only a port of call. A stopover, if a necessary one, to get to where we are going. We seek much more distant goals.’

  Deirdra said, ‘I don’t understand. What distant goals?’

  ‘Good question. It’s all to do with chance planetary alignments,’ Nash said earnestly, and he smiled. ‘It’s not just human history that is chaotic, you see. So is the Solar System. Oh, not the big picture, not as far as we have explored: the Sun, the major planets. But details of the minor bodies, the moons, the comets, the asteroids – I suppose that sort of junk is more easily perturbed by minor events, random collisions and so on, that may differ from one Road to the next. And we find divergences in the outer planets too – I mean, the stuff out in the comet cloud beyond Neptune.’