Greg Egan - The Arrows of Time

Medoro said, ‘Now suppose that we arrange a sequence of occultations – of the slowest detectable light, with the blocking taking place as far from the telescope as possible.’

Agata thought she knew where he was headed. ‘Then the image of the star will blink out before the blocking object is actually in place. But you know, even the slowest detectable infrared is quite hard to outpace. So unless you build some massive engines, these flying shutters of yours would need to be launched long before you see their effect on the star.’

But Medoro wasn’t finished with his thought experiment. ‘Now add a pair of mirrors and fold up the light path, so we can achieve the same effect while manipulating an object that’s much closer.’

Agata raised a quick sketch of the proposal.

‘Depending on the dimensions of the system and the number of bounces before the loss to the mirrors is too great,’ she said, ‘you’ll be able to make observations that reveal the shutter’s position some time into the future. I’m no expert on practical optics, but I’d guess that a realistic time-span would be measured in flickers at most.’

Medoro said, ‘Maybe. But suppose it’s more than twice the response time of an automated signal booster. You might only be able to receive the message from a short way into the future, but so long as you can resend it to a time when the booster will be free to handle it “again” – without any overlap with the later boost – the process can go on indefinitely.’

Agata gazed at the picture on his chest. If there was a flaw in his plan, she couldn’t see it.

‘Greta didn’t mention anything like this?’ she asked.

Medoro scowled. ‘No – but do you really think anyone could commission a camera that detects light from the future , without this sort of thing crossing their mind?’

Agata was ashamed that she’d failed to see the possibilities herself long ago. This was the most beautiful idea she’d ever encountered.

‘You’re right,’ she said. ‘The Council must be working on a messaging system. And if they can boost the signal like this…’ She reached over to Medoro, almost touching the diagram. ‘Then I don’t see why we couldn’t use it to learn about the journey still to come, all the way up to the reunion.’

‘Have you lost your mind?’ Ramiro had come to the interview with high hopes, but within a few lapses his mood had been transformed from anticipation to bemusement to horror. ‘That’s the most deranged thing you’ve ever asked me to do – which is not an easy contest to win.’

Greta motioned with her hand on her tympanum, imploring him to keep his voice down.

Ramiro said, ‘If you’re going to keep raising this subject with people, you might want to think about soundproofing your office.’

He began drawing himself out of the harness facing her desk. ‘Where are you going?’ Greta asked anxiously.

‘Relax,’ he said. ‘I’m not going to tell anyone. Though next time you ask me to keep something between us, I’ll take that as a sign that I should turn and run. And when you put this to a referendum, I promise you I’ll be campaigning very noisily—’ Ramiro caught a flicker of discomfort on her face. ‘There is going to be a vote, before you actually build this?’

‘That’s up to the Council,’ Greta replied. ‘But there’s not much point voting on a system whose feasibility is entirely hypothetical.’

Ramiro slipped back into the harness. ‘So you were thinking of building it first? And then what? Hope you can learn something in advance that will guarantee the outcome of the vote? But how would that work? What if the message from next year’s Council is simply that whatever they tried, failed?’

Greta said stiffly, ‘It’s not about vote rigging . It’s about security. You of all people should appreciate that.’

‘Me of all people?’ Ramiro stared back at her in disgust. ‘If we’re being frank, I blame you for the farce with the gnat just as much as I blame the migrationists.’ As the words emerged he wondered if he was letting his anger get the better of him. But Greta showed no sign that she was wounded, let alone contrite.

‘I don’t understand why you’re so vehemently against this,’ she said. ‘You should take a few days to think it over.’

Ramiro buzzed. ‘What’s funny is that you’ve been planning this for a year – but you still can’t see that your last remark should answer the preceding question.’

Greta spent a pause or two struggling to parse that, but it seemed to be beyond her. Ramiro said, ‘You’re inviting me to take my time to ponder all the pros and cons before reaching a decision – but the answer you want from me would eradicate my ability ever to go through the same process again.’

‘That’s nonsense,’ Greta said amiably. ‘No one’s asking you to surrender your free will.’

‘And that’s not how I’d put it, myself,’ Ramiro replied. ‘But I’m not going to start debating terminology. The simple fact is that anyone who knows their own actions in advance will be living a different kind of life than someone who doesn’t.’

‘What makes you think that you’d be forced to know anything about your own actions? The Council will use this facility for planning and security purposes. Any other applications will be carefully controlled – and exposure to information is hardly going to be compulsory.’

Ramiro said, ‘That’s naïve: information would spread through third parties. You could never come close to promising me that I wouldn’t end up hearing things I didn’t want to hear.’

‘What if we’d known the rogue gnat’s trajectory in advance?’ Greta demanded. ‘Are you honestly telling me that it wouldn’t have been worth it?’

Ramiro wasn’t going to let her use the rogue to bludgeon him into submission. Perfect knowledge of the future might have spared him the dangerous encounter, but the whole mountain shouldn’t have to pay the price for the way the threat had been mishandled from the start. ‘I’m sorry I blamed you for that débâcle,’ he said sarcastically. ‘The fault was mine: I should have just let the gnat hit the Object.’

He struggled out of the harness.

‘Are you going to keep your word?’ Greta asked. ‘I knew I was taking a risk, but I thought I could trust you.’

Ramiro freed himself and clung to the guide rope leading to the doorway. If he said the wrong thing, could she have him imprisoned until the messaging system was complete? They’d set a precedent with the migrationists, and if he vanished from sight he wasn’t sure that anyone would come looking for him.

‘I’ll keep my word,’ he said. ‘I don’t break promises.’ He contemplated adding that he trusted the Council to ensure that the matter was put to a vote, but even Greta was likely to pick up the sarcasm.

Outside the office, Ramiro still felt rattled by the confrontation, but as he set off down the corridor he began to regain his composure. It was never exactly prudent to hurl abuse at potential employers, but Greta had a thick skin and he doubted that he’d be thrown in prison for refusing a job. So long as he kept quiet about the offer he’d be left alone.

He reached an intersection and turned into a busy corridor. People strode by, purposeful, intent on their various plans, shaping the minutiae of the unfolding morning. But every child knew that, to the ancestors, the sequence of events that a traveller perceived as evolving over time was no different from the fixed pattern in a tapestry. From the right perspective, each life was a completed picture from birth to death, there to be taken in at a glance.