Greg Egan - The Arrows of Time

‘I’ve got the shears around the cable,’ Tarquinia announced. Agata saw Ramiro’s faced contorted with fear. There was a soft click of the blades meeting.

The wind rose up, pelting the wall of the tent with dust. But one word came clearly through the link.

‘Done.’

As Agata trudged up the rocky incline, the patch of bright ground beside the Surveyor remained visible in her rear gaze. But it looked so out of place against the dark valley floor that a part of her mind began to discount it, treating it as nothing but a flaw in her vision. The first few times she felt it vanish from her mental map of her surroundings she panicked, scanning the view for the comforting beacon until it snapped back into focus, acknowledged again as real. But after a while she stopped worrying and let it fade into the landscape. Tarquinia and Ramiro were not going to turn out the lights and hide from her. When the time came she’d have no trouble finding her way back.

Ahead, above the grey hills, the sky could not have marked the way more clearly. The direction along Esilio’s axis that they’d chosen to call ‘south’ pierced the bowl of stars about a twelfth of a revolution below its bright rim, and from this valley in the southern mid-latitudes that celestial pole remained perpetually in view, with the rim twirling around it like a burning hoop and the stars in between never setting.

Azelio walked beside her, carrying two of his potted seedlings from the final dozen he’d held in reserve. He wasn’t complaining, but she could see him struggling with the weight as the slope increased.

‘I’d be happy to take one,’ she offered.

‘Thanks, but I’d rather you had nothing to distract you from your own load,’ he replied.

Agata raised the bomb effortlessly above her head. ‘It hardly weighs anything. And even if I drop it, it’s not going to go off.’ Tarquinia had assured her that the explosive could only be triggered by a bright pulse of light at a specific wavelength, and the only means of delivering that pulse was strapped securely to her tool belt.

Azelio said, ‘I’m more worried that you might damage the detonator and we won’t be able to set it off at all.’

‘Fair enough.’

Azelio had identified a promising outcrop in the images they’d taken from orbit – a body of rock whose spectral signature suggested that it could give rise to fertile soil. No one had objected when Agata had volunteered to accompany him to the site, but she still felt slightly guilty at having wormed her way out of the tedious business of moving everything back into the Surveyor . Blowing up a hillside would be vastly more enjoyable than reassembling cooling pipes and restocking the pantry.

‘Can we rest for a bit?’ Azelio suggested.

‘Of course.’ Agata placed the bomb gently on the ground, then sat beside it, positioning her body so she’d be blocking its way if it began to slide. Azelio did the same with his plants.

‘Do you think they already know how this ends, back on the Peerless ?’ he asked her.

‘I expect so.’ Unless there’d been an ongoing campaign of sabotage, it was hard to believe that the messaging system would not have been completed by now.

‘In some ways that takes the sting off the separation,’ Azelio mused. ‘If the children are already in contact with me, that’s almost like being there.’

‘This from a man who voted against the system,’ Agata teased him.

Azelio said, ‘If the vote had gone against the system then we wouldn’t have needed to be here at all.’

‘Hmm.’ Agata didn’t want to start arguing with him over the attribution of blame.

‘So long as there’s peace, I don’t care about the system,’ Azelio admitted wearily. ‘People can use it or ignore it as they wish. We managed not to go to war over shedding; we ought to be able to live with anything after that.’

‘We ought to, and we will,’ Agata declared. ‘The fanatics who can’t accept that will be free to leave.’

Azelio buzzed wryly. ‘Fanatics carrying the necessary stocks of explosive?’

‘Maybe we can send all the bombs they’ll need in a separate craft,’ Agata suggested. ‘We could bundle off a whole lot of freight to Esilio in an automated vessel at high acceleration, then let the settlers follow. It’s not an intractable problem; we’ll think of some way to do it safely.’

‘Assuming this works at all.’ Azelio nodded towards their own bomb.

‘It has to work.’ Agata searched the dark valley for the speck of light that marked the landing site. ‘If the soil is right and the arrow is right, the plants will grow. Nothing else would make sense.’

The rim of the star bowl was almost vertical as they came over the rise. Agata wished they could have chosen a landscape with more rock than dust from the start; it would have spared them the worst of the storms, and they could have passed the time just sitting outside, gazing at this glorious celestial clock.

‘There it is,’ Azelio announced, pointing ahead. Agata could barely distinguish the hue of the outcrop from that of its surroundings, but she trusted Azelio. He’d studied the image of the hills for half a day as he’d plotted their route, and he had too much at stake to be careless.

The approach was downhill, but the ground was uneven and strewn with small, loose stones. As Agata advanced the stones began jostling her feet, accelerated from a span or two away by time-reversed friction before coming to a halt against her skin. She glanced at Azelio; he was struggling to keep his footing, distracted by the bizarre bombardment.

‘Can you leave the plants here?’ she asked. Once they’d set the charge they’d be retreating to about this point anyway.

‘Good idea.’ Azelio set the pots down and they continued.

When they reached the hillside Azelio switched on his coherer and played it over the pale brown rocks. ‘This is the target,’ he confirmed. He gestured towards the centre of the outcrop. ‘Anywhere about there should do it.’

Agata handed him the bomb and waited for him to step away to a safe distance, then she started swinging her pick into the rock face. Small chips of stone flew out from the point of impact, stinging her forearms, but the rush of power and freedom she felt at the sight of the growing excavation was more than enough to compensate. In Esilian time, the chips were rising from the ground, propelled into the air by conspiracies of time-reversed thermal diffusion, just to aid her as she rebuilt the rock. What stronger proof could there be that the cosmos had a place for her, with all her plans and choices? One day it would kill her, but until then the contract was clear: hardship and frustration and failure were all possible, but she would never be robbed of her will entirely.

She made the hole as deep as she could without widening it excessively; the idea was to confine the pressure wave within the rock as much as possible. When she stopped swinging, Azelio approached and held the bomb up against the opening. It didn’t quite fit at one corner. She set to work removing the obstruction.

On the next attempt, the bomb’s cubic housing entered the aperture without resistance. Azelio gently pushed it deeper, then Agata aimed her coherer into the hole. There were some small gaps around the edge of the housing, but she didn’t think they’d be enough to dissipate the energy of the blast.

She took the detonator from her tool belt. Ramiro had removed most of the original components and added a timer in place of the remote trigger. She started up the photonics and it ran a self-test; a short summary on the display panel reported that everything was working as expected. She plugged the detonation cable into the bomb, and tapped the switch to start the timer. The countdown showed nine lapses and falling. She rested the detonator in the mouth of the hole, then the two of them walked away.