Free The Arrows of Time: Orthogonal Book Three by Greg Egan Page A

was full of distraught people, torn between celebration and loss.
    Medoro approached and put an arm around her. ‘It’s enough,’ he said. ‘It has to be enough.’
    ‘Of course.’ Agata willed herself to accept that.
    ‘I know you don’t want grandchildren,’ he teased her, ‘but you can always tell your stories to my niece’s kids.’
    Stories of the spin-down, the exotic gravity, the shrunken stars. All her life, she’d ached to live through these tangible signs that the voyage really would have an end. But now that ache
felt worse than ever. When her apartment’s floor was horizontal again, when the giant stairwells were tunnels and the star trails had stretched out into coloured threads that squeezed into
half the sky, what could she look forward to?
    Serena joined them, standing beside her brother. ‘How are you feeling?’ Agata asked her.
    ‘I couldn’t be happier!’ Serena spread her arms. ‘I know, everyone’s emotional, everyone’s confused . . . but what can I say? Octofurcate me:
we’re
headed home!
’
    Agata was ashamed. How many people had kept up the struggle when there’d been no end in sight? She still had her work, she still had her friends, and she’d always have her memories
of this day. What more did she want?
    ‘We’re headed home,’ she agreed. ‘That’s enough.’

 
     
     
     
5
     
     
     
     
    Seated at his console in the main control room, Ramiro watched the image feed from the camera out on the slopes. At his behest, a small tethered engine ran through a series of
moves, tugging on a set of restraining springs and force gauges that allowed its thrust to be measured.
    To his astonishment, the rules that the test rig was obeying remained as simple and intuitive as he could have wished: he could point the engine’s outlet any way he liked, and when he
powered up the engine it generated thrust in the opposite direction. No exceptions, no complications – and no dependence at all on the disposition of distant worlds.
    ‘That’s disturbing,’ he told Tarquinia. An inset showed her in her office near the summit; she’d carried out the tests herself before inviting Ramiro to repeat them.
    ‘What did you expect?’ she asked. She wasn’t mocking him; it was a serious question.
    ‘I don’t know,’ Ramiro replied. ‘Maybe part of me always imagined this outcome, but I shouted it down as naïve.’
    ‘I never knew what to think,’ Tarquinia admitted. ‘My gut feeling – when I was looking at the engine in isolation – was that there’d be thrust in all
directions. But all I had to do to change my mind was picture the consequences of that: all the specks of dust and gas out in the void that would need to conspire to make it happen.’ She sent
Ramiro a sketch via her corset; it appeared in miniature in a second inset. ‘But then all I had to do to change my mind again,’ she added, ‘was to think of the engine magically
“knowing” that it wasn’t meant to work when it was pointed towards the wrong part of the sky. That was just as hard to swallow as the alternative.’
    Ramiro said, ‘Well, now you’ve settled it. Either way, something had to offend our intuition – so we should be grateful that the chosen offence happens far away and out of
sight.’ He enlarged Tarquinia’s sketch, which drove home the point: eerie as it would have been to watch the engine selectively fail, if they could have witnessed the actual results in
every detail that would have been at least as unsettling.
     

    Unless the engine’s outlet was aimed at the
Peerless
itself, every photon it pumped out would eventually strike some distant object: usually just a particle of
gas or dust belonging to one of the clusters. Given the present motion of the
Peerless
, it was easy to arrange the geometry so that the light would be arriving from the dust’s future
– which meant that according to its own arrow of time, the dust would be emitting the light, not receiving