Greg Egan - The Arrows of Time

She leant against the wall, humming and shivering. Sometimes she missed Medoro so badly that she wanted to die, but everyone expected her life to go on as if nothing had happened. And now Lila was inviting her to spend the next few years struggling with some beautiful ideas that for all she knew might have no bearing on reality at all.

Agata stilled herself and stared down into the black dust at her feet. She felt as if she’d been waiting all her life for just one message from the future, telling her that everything would be worth it in the end – but the hungrier she grew for that scrap of comfort the further it receded, and the greater the cost. She would have given up all hope of it to get Medoro back, but no one was offering her that choice.

She couldn’t spend another day sitting in her office juggling equations, with no idea if they were true or false. And she couldn’t bear to be around Medoro’s family if she had nothing useful to contribute to their lives. Everything on the Peerless was ash to her, now. She needed to find another reason to live, or she was finished.

The Surveyor team were still looking for volunteers. At the cost of spending twelve years cooped up in a glorified gnat, the crew would be the first travellers in six generations to set foot on anything like a planet. If they could bring peace to the mountain, all the better, but just making that trip would be extraordinary.

Agata turned away from the entrance and began retracing her steps. She’d very nearly talked herself into it – but if all she had to offer the rest of the crew was her desperation, they’d be better off leaving her behind to go insane on her own time. She could go through the motions with the vacuum energy calculations, then if the messaging system survived the saboteurs she might at least get a verdict from the future as to whether or not Lila’s theory of gravity applied in the real world. There’d be nothing inconsistent with the laws of physics in being told that she’d wasted her life.

She stopped dead, her skin tingling, ashamed of her self-pity but grateful for one detail of her maudlin fantasy. A verdict on Lila’s theory, how? She’d always imagined that such a thing would never come until after the reunion itself, once there’d been a chance for a future generation of astronomers to make observations from the home world. But the home world was no longer the only planet worth imagining.

Ramiro scratched the skin around his fetter; it had been itching horribly for the last three days. Despite his pleas, Greta had insisted that he remain in chains even when they were interviewing candidates. He was beginning to wonder if he’d be kept in restraints even once he was on the Surveyor itself.

‘The planet Esilio is orbiting a massive star,’ Agata enthused. ‘But we’ll be blind to the light of that star; it will appear to us as nothing but a pale grey disc. That combination offers the perfect conditions for the observations I want to carry out.’

Ramiro had no idea what she was talking about, but they hadn’t seen anyone else with pro-messager credentials half as eager to make the journey. ‘Go on,’ he said.

‘If gravity is really just the curvature of four-space,’ Agata continued, ‘then light that passes close to this star will be bent less than it would be under Vittorio’s theory. I know that sounds strange, but in Lila’s theory the curved space around the star makes centrifugal force stronger than it would be in flat space, so it’s harder to bend the light’s trajectory. With no glare to hamper the observations, we could measure the apparent positions of home-cluster star trails as they approach the edge of this star’s disc, and see which predictions turn out to be correct.’

She summoned an illustration of the phenomenon onto her chest.

‘I’ve exaggerated the scale of the effect here,’ Agata admitted, ‘but it would certainly be measurable with a small telescope.’

Ramiro thought this sounded harmless enough. The last applicant who’d claimed to be drawn to the mission by the chance to carry out a scientific project had wanted to experiment with exotic methods of pulverising Esilio’s surface from orbit, in order to impose their own entropic arrow as firmly as possible. Listening to the woman’s wish-list of weapons that she hoped to load onto the Surveyor had been entertaining, but a theodolite or two would probably be easier to sell to the Council than a flying armoury.

Greta, though, was as suspicious as ever. ‘You’d be willing to give up twelve years of your life, just to observe this minor optical effect?’

‘I would,’ Agata replied. ‘The precise angle by which a beam of light is deflected by a star might not sound important, but until we know for sure whether matter and energy really do curve four-space, the answers that we’re struggling to find to much bigger questions – the geometry of the cosmos, the reasons for the entropy gradient – will just be guesswork.’ She paused, then added, ‘I also think the mission’s worthwhile for its own sake. If there are people who can’t live with the majority’s decisions on the Peerless any more, we should let them leave.’

‘I understand that you were close to one of the instrument builders?’ Greta pressed her. ‘To Medoro?’

‘Yes.’

‘So wouldn’t you rather see his killers punished?’

‘Did I miss the news where they were caught and tried?’ Agata replied sarcastically. ‘If it’s a choice between letting them migrate to Esilio and having them around to do the same thing again, I’d rather get rid of them.’

‘So you see this as protecting other travellers?’

‘Other travellers,’ Agata agreed, ‘and the messaging system itself. I debated Ramiro in the campaign – and I still believe every word I said about the benefits of the system.’

‘How old are you?’ Greta asked.

‘A dozen and ten.’

‘You won’t have many years left when you return, and you’ll have aged more than all of your friends. Do you really want to spend the best years of your life inside a vehicle the size of your apartment – in the company of the man who lost that debate, but then turned around and tried to extort us into giving him his way regardless?’

Ramiro had developed a thick skin when it came to Greta’s characterisations; much as she enjoyed it, her main goal seemed to be to spur his would-be travelling companions into venting their hostility now, instead of waiting until they had the opportunity to carve him up and toss the pieces into the void.

Agata gestured towards Ramiro’s chains. ‘I can see that you don’t trust him – and nor do I, completely. But he was an honest opponent in the debate, and I don’t blame him for my friend’s death. This mission needs people from both factions or it isn’t going to fly at all.’

‘That’s a nice sentiment,’ Greta replied condescendingly. ‘But are you sure you’re ready for the cost of putting your own flesh behind it?’

In response, Agata only grew more stubborn. She said, ‘The first travellers left their friends and family behind for ever. Between the chance to learn how gravity works and the chance to make the Peerless safer, I’m willing to put up with a few years of hardship.’

‘It’s coming together nicely,’ Verano said, leading Ramiro and Greta across the echoing space of the workshop. Verano had the gaunt frame of a Starver, but he displayed no lack of energy or enthusiasm. Ahead, slowly descending from the ceiling’s horizon, the fat disc of the Surveyor sat balanced on its rim within a cage of scaffolding, the polished hardstone glinting in the light of three banks of coherers angled up at it from the floor.