The Arrows of Time

by Greg Egan

  ‘I’m not afraid that we might lose,’ she said. ‘What worries me is that we had to ask the question at all.’

  ‘So we should just be happy cogs in Eusebio’s machine?’ Medoro goaded her. ‘Born into the mountain with no say in anything?’

  ‘You make it sound as if Eusebio had a choice,’ Agata retorted. ‘If there’d been no launch, you wouldn’t have been born anywhere.’

  ‘Of course,’ Medoro agreed. ‘The builders did the right thing, and I’m grateful. But that doesn’t mean we should be enslaved to them. What we owe the ancestors isn’t blind allegiance, it’s constant scrutiny of the actual possibilities. Your brother’s wrong because his arguments are wrong – not because the mere idea of deviating from the plan should be unthinkable.’

  Agata was unimpressed by his euphemism: ‘deviating from the plan’ was a phrase befitting a bold rebellion against pernickety bureaucracy, not a calculated act that amounted to mass murder. But she wasn’t in the mood to pick a fight. ‘Pio’s had his chance to be heard, so maybe that will get it out of his system.’

  Medoro said, ‘Sure – but it’s not just Pio and the people who’ll vote with him who needed this. Every one of us knows that the outcome was always a foregone conclusion . . . but it still matters that it’s only a foregone conclusion because we’ll judge it to be the best choice on offer.’

  ‘Hmm.’

  Medoro headed into the hall. Agata watched as the tally on the screen reached one third of the enrolled population. The ‘yes’ count now outnumbered the ‘no’ by more than a dozen to one. In principle the result remained undecided, but the truth was that her side was heading for an overwhelming victory.

  Medoro emerged, and approached her with a guilty demeanour. ‘Don’t be angry with me,’ he pleaded. ‘But I thought it would only be fair to even things out a little—’

  Agata took a swipe at him; he twisted away. She was almost certain that he was joking, but if he wasn’t she didn’t want to know.

  ‘Come and eat,’ Medoro said. ‘Assuming you’re not turning into a Starver.’

  ‘Hardly.’ Agata followed him down the corridor towards the food hall. ‘I’m not turning into a Shedder, either.’ The idea of giving birth terrified her – whether or not she had to live through the process – but beyond her own fears the last thing she’d wish on any child was to be raised by her idiot brother.

  3

  Greta turned to Ramiro. ‘Start the spin-down,’ she said.

  Unaccountably, Ramiro hesitated. He’d been anxious for days that, at this very moment, some obscure detail that he’d failed to allow for would make itself known by undermining everything – but an unplanned hiatus wouldn’t so much forestall the risk of humiliation as turn his fears into a self-fulfilling prophecy.

  Just as Greta’s expression of controlled anticipation was on the verge of faltering – and revealing to every onlooker that the delay was not just unexpected but incomprehensible – his paralysis ended and he threw the switch. A single tiny coherer in the panel in front of him sent its light into the maze of photonics below, and the system that Ramiro had spent the last six years building, testing and refining began, very slowly, to move the mountain.

  The entire Council had crowded into the control room, and now they turned to watch the main navigation screen mounted high on the wall. At Greta’s insistence, Ramiro had programmed an elaborate animation that made it look as if the sensor readings confirming the successful firing of the counter-rotation engines were only arriving gradually, piece by piece. ‘Not so slowly that they start to get worried,’ she’d suggested, ‘but not so fast that it’s an anticlimax.’

  ‘And if something fails?’ he’d asked. ‘How do you want that paced?’

  Greta had given this careful thought. ‘Delay it long enough that it looks as if things were going perfectly, up to a point. But not so long that anyone could say that we were hiding it.’

  Ramiro’s own unobtrusive display was feeding him news in real time; so far it was all encouraging. Not only were the engines reporting a flawless performance, the accelerometers and the star trackers showed that the Peerless really had begun shedding its spin. If all went well, in less than three days the mountain would be perfectly still.

  For the first time in six generations, chambers at the rim of the Peerless would be as weightless as those on the axis, and for a stint, the farmers and an army of helpers would work to reconfigure the fields, shifting soil from the useless centrifugal floors to surfaces once seen as walls. When they were done, the mountain would be slowly flipped, base over apex, ready for the main event.

  The catalogue of triumphs unfurling on the navigation screen finally reached the same conclusion as the real-time reports. ‘Congratulations!’ Councillor Marina offered effusively. ‘We couldn’t have hoped for a smoother start.’ Ramiro glanced towards her with his rear gaze, but she was addressing herself solely to Greta.

  Greta inclined her head graciously.

  ‘This is promising,’ Councillor Prisca conceded, ‘but the real test is yet to come.’

  ‘Of course,’ Greta concurred, though Ramiro could see her struggling not to add a few words in favour of the present achievement. The mountain had gained its spin from giant slabs of sunstone spewing flame into the void, controlled by compressed air and clockwork. Now it was losing it through nothing but light – light flowing through the switches and sensors as much as the engines themselves. If that didn’t count as a real test, they should all just stay silent and humble until the home world itself had been shifted from its course.

  An inset opened in the navigation screen and Tarquinia spoke from the observatory on the peak. ‘I’ve made sightings of six beacons and estimated the rate of change of the Peerless’s spin. Everything’s within the expected range.’

  Ramiro thanked her and she closed the link. For all the built-in redundancy in his own system, an independent manual check was a welcome proof that the software was faithfully reporting reality.

  The Councillors filed out, with Greta following. Ramiro leant back in his harness and stretched his shoulders, chirping softly with relief. In principle, the program controlling the photonics could do everything now without further intervention: kill the spin, turn the mountain so the giant engines at the base were aimed in the right direction, then start those engines and keep them glowing with exactly the right power and frequency, until they’d fully reversed the travellers’ original velocity with respect to the home world. Ramiro could see himself sitting at his console watching the script playing out day by day. But if it was too much to hope that the Peerless really would drive itself for the next three years, he’d be satisfied if the program managed to detect and describe any problems it was unable to circumvent.

  ‘Ramiro?’

  He looked up; Tarquinia had reappeared on the navigation screen.

  ‘What’s happening?’ he asked, surprised that she’d have anything more to report so soon.

  ‘Don’t panic,’ she said. ‘The spin-down’s going perfectly.’

  ‘But?’

  ‘I just saw the latest snapshot of the halo.’

  Ramiro’s anxiety deepened. The navigators used ultraviolet images of the region around the Object as a way of measuring the density of interstellar gas, traces of which could be seen being annihilated as it struck the orthogonal asteroid’s dust halo.

  Tarquinia read the look on his face and buzzed softly. ‘The gas is as rarefied as ever; the corridor should still be safe to traverse. But there was something unexpected on the image. I think it was a gnat moving away from the Station.’

  Ramiro struggled to make sense of this claim. ‘I heard there was a gnat left behind; the last shift didn’t have enough pilots to fly them all back. It should have been tied up, but I suppose it could have sprouted some kind of air leak that pushed it away—’

  ‘I don’t mean drifting,’ Tarquinia interjected. ‘It was firing its engines. Some of the flare came our way – that’s the only rea
son it showed up on the snapshot.’

  ‘But the Station’s empty. Everyone’s been evacuated.’

  Tarquinia knew what she’d seen. ‘Do you think someone could have automated the gnat?’ she asked. ‘To start flying on its own, after they’d left the Station?’

  ‘It’s possible,’ Ramiro conceded. ‘But why would they?’

  ‘I have no idea. But it’s either that, or someone’s managed to stay behind.’

  ‘What are you suggesting? Some disappointed voters from Pio’s faction have decided that they’re going to get their way after all . . . at the Station?’ Ramiro didn’t know whether he should be amused or horrified. The ambition was comical, but if there really were holdouts who’d concluded that the safest life they could make for their children lay in an abandoned research habitat, there’d be nothing funny when they starved to death.

  ‘This image shows a gnat using its engines,’ Tarquinia replied. ‘I’m not going to try to guess if there are people inside, let alone what their motives could be.’

  ‘Do you want me to chase down the Councillors?’ Ramiro didn’t know whose job it had been to ensure that every last traveller was inside the Peerless before the spin-down commenced, but he was glad it fell entirely outside his own domain.

  Tarquinia said, ‘You’d better do that.’

  Ramiro loosened his harness. ‘If we had cameras in all the corridors,’ he mused, ‘and programs for recognising invariant anatomy . . .’

  ‘We could have done an automated census before starting up the engines?’ Tarquinia suggested.

  ‘Ah, good idea.’ Ramiro hadn’t been thinking on quite that scale. ‘I was just picturing a way of getting messages to people when they were wandering around the mountain.’ But Greta and her guests would not have gone far. ‘Are you certain this isn’t a false alarm?’

  ‘No,’ Tarquinia admitted. ‘But if we fire the main engines and there are people left behind, do you want to be the one who takes responsibility?’

  Ramiro said, ‘I’ll find the Councillors.’

  Ramiro was roused by a discordant clanging of his own design, impossible to mistake for anything else. It was not a pleasant way to wake, but experience had shown him that no gentler sound could penetrate his sleep. He dragged himself out from beneath the tarpaulin of his sand bed and over to the communications link. The walls’ red moss-light had been gentle on his eyes, but when he switched on the display the sudden brightness was painful.

  ‘I’m going to need you to go outside,’ Greta said.

  ‘Why?’ Ramiro asked, baffled. ‘Is someone waiting in the corridor?’

  ‘I’m not talking about your apartment.’

  Ramiro massaged his skull, hoping to conjure up a third interpretation.

  ‘The census results are in,’ Greta said. ‘There’s no one missing from the Peerless.’

  ‘Good! We can fire the main engines with a clear conscience.’

  Greta hummed impatiently. ‘The observatories are tracking the gnat, but we still have no idea what it’s doing.’

  ‘Why should we care?’ Ramiro was mildly curious, but chasing a moving target across the void when no one’s life was at stake, and the environs in which the whole strange prank was playing out would soon be left far behind, struck him as a little disproportionate.

  Greta said, ‘Who understands automation better than you do?’

  ‘Appeals to my vanity will get you nowhere.’

  ‘That wasn’t a rhetorical question,’ she retorted. ‘The gnats aren’t meant to be able to do this. But it looks as if someone else knows your field well enough to make it happen.’

  ‘It’s a trivial modification,’ Ramiro stated flatly. ‘If you want to get me interested you’re going to have to do better than that.’

  Greta fell silent.

  ‘What?’ he pressed her. ‘You can trust me to automate the turnaround, but you can’t tell me the Council’s paranoid theory about a self-driving gnat?’

  ‘We think the intention might be to exploit the Object as some kind of weapon,’ she confessed.

  Ramiro’s skin tingled strangely. He had never even been close to the Object, but since childhood he’d heard stories of Carla and Ivo’s near-fatal first approach, when even the faint wind leaking from their cooling bags had set the rock below them on fire.

  ‘We could always start the main engines ahead of schedule,’ he suggested. ‘Before this gnat can finish doing whatever it’s trying to do.’

  ‘And what about the farms?’

  ‘Some soil spills down the walls, to the place we were moving it anyway.’

  Greta said, ‘It’s only the wheat fields that have been left fallow for the changeover. There are timber plantations, medicinal gardens and a dozen different crops we use for fibres and resins that all need careful transplantation.’

  Ramiro doubted that anyone would have cared about a few upended trees if it had been clear that the whole mountain was at stake. But if the cost to agriculture seemed too great in the face of an undetermined threat, there were other routes to certainty.

  ‘Why not just destroy the gnat?’ he suggested. ‘How hard could that be?’

  ‘The Council wants it intercepted, undamaged,’ Greta insisted. ‘We need to inspect the navigation system and find out exactly what the plan was.’

  ‘Then send your best pilot to bring it back, and I’ll happily dissect the whole system in the comfort of a suitably equipped workshop.’

  ‘That would be ideal,’ Greta conceded. ‘But it might not be possible.’

  Ramiro hummed derisively. ‘This is just a gnat with a modified navigation system. There’s no one inside to defend it. Once your pilot gets on board and cuts a few photonic cables, it will be no different from any other kind of cargo. They can attach a rope to it and tow it back.’

  Greta said, ‘When the Station was vacated there were dozens of samples from the Object left in its workshops. If someone gained access to the gnat at a time when they could move around the Station with next to no scrutiny, who knows what else they might have done besides reprogramming the navigation system?’

  Ramiro stared at her for a moment, then he understood that there really was no squirming out of this. The one thing he couldn’t ask any pilot to bring back to the Peerless was a machine potentially booby-trapped with fragments of antimatter.

  ‘Strap yourself in,’ Tarquinia suggested. ‘It’s going to be a bumpy ride.’

  Ramiro took her advice, fumbling at the harness with hands fitting loosely in the gloves of his cooling bag. While their gnat hung suspended from the outside of the Peerless the long flat couch against his back was vertical, like some kind of recuperative splint to help him stand upright.

  He’d flown in a gnat before, but this was a different design, with space for just the pilot and one passenger and a storage hold between the couches and the cooling system. The clearstone dome that stretched over their heads was close enough to touch. ‘Did they let you talk to your family?’ he asked Tarquinia. Though he didn’t doubt her skills as a pilot, he suspected that one reason she’d been chosen for the job had been to limit the number of people who knew about the situation.

  ‘Greta made the case for secrecy,’ she said. ‘But I told my brother anyway.’

  ‘Good for you.’ Ramiro had resented the pressure to keep quiet, but then welcomed the excuse to say nothing. He wouldn’t have known how to explain the task he was facing without alarming his family, and the last thing he needed right now was a lecture from his uncle about his duty to the children his sister was yet to shed. If everything went well he’d be back long before he was missed.

  He pointed to the navigation console. ‘Have you updated the local maps?’ No one had been expecting to go flying once the spin-down had begun, and apart from the altered velocity of the slopes there was the small matter of steering clear of the beams from the counter-rotation engines.

  ‘No, I just thought I’d leave everything unchanged and see what happened,�
�� Tarquinia replied sarcastically.

  Ramiro was unrepentant. ‘If you’re going to take offence every time I nag you about something that could get us killed—’

  ‘All right!’ Tarquinia’s expression softened. ‘I’m all in favour of some mutual irritation anyway. Better than falling asleep on the job.’

  ‘Don’t tempt me with that.’

  ‘Ready,’ she said. It wasn’t a question. She threw a switch on her panel and the gnat fell away from the mountain.

  Ramiro’s queasiness at the sudden loss of weight soon changed to elation. He’d forgotten how beautiful the outside could be; after six years of moss-light and display screens, the muted shades of starlit rock spreading out above him felt like liberation. As the mountain retreated, he looked down to the bright line of jumbled colours that divided the sky. To his right, the long trails of the home cluster’s stars reached their greatest luminance along this border, then vanished completely. To see any further would have meant seeing these stars’ futures – and they weren’t sending light backwards in time against their own thermodynamic arrows. To his left, the orthogonal cluster had the sky to itself, sprinkling its domain with small, neat colour trails.

  ‘Firing engines,’ Tarquinia warned.

  Ramiro was thrust abruptly back against the couch, ridding him of any notion that he was standing. He’d been expecting the change of vertical, but the pressure on his body was distinctly more uncomfortable than he remembered. After a few pauses wondering whether he was going to be able to hold down his last few meals, he managed to ossify parts of his torso, giving it better support against the unaccustomed weight so that it no longer threatened to squeeze out the contents of his digestive tract.

  As the gnat sped away from the mountain, the sky’s stark asymmetry made it easy to maintain a sense of direction, but Ramiro still needed to check the navigation console to gauge their progress. When he finally looked back towards the Peerless again it was a pale grey triangle, a dwindling near-silhouette against the star trails. The engines labouring to end its spin produced no visible trace at all; even if the sparse dust rising out from the slopes was scattering the beams a little, they were far into the ultraviolet.