Greg Egan - The Arrows of Time

‘Then let’s go for a ride.’

Silvio drove the three of them out into the desert. Gemma was setting, but four long Hurtlers lit the sky.

‘Why would anyone want to put the sun out?’ Valeria demanded.

‘We’re planning to turn half the surface into an engine.’ Eusebio had had Clara’s hands separated; she gestured as if she were cupping a globe. ‘Moving the sun is the safest way to move the world. There’ll still be some seismic activity as it tugs you along, but not as much as if we put the engines here on the ground.’

‘Tugs us along?’

‘You have heard of gravity?’ Clara joked. ‘And we’ll be bringing Gemma as well, for light. It will end up closer when the new orbits settle, so it will do a better job than it does now.’

‘But where would we be going?’ Valeria was furious that she had to conduct the whole interrogation herself. Eusebio was huddled beside them in silence, apparently too ashamed to speak. He’d wanted to get Clara ensconced in the largest guest room of his father’s mansion immediately, but she’d insisted on making the trip first.

‘This planet needs to match velocities with the Hurtlers,’ Clara explained.

‘Which would just turn everything else around us into Hurtlers!’ Valeria protested. ‘You didn’t research this fraud well enough. The Peerless went into a dust-free corridor, but it doesn’t stretch on for ever. If we followed the mountain’s route, what would we do at the end?’

Clara said, ‘Actually, you could zigzag up and down the corridor on a trajectory that would last for eons, but we settled on a better solution than that. If you shadow a world in the orthogonal cluster, we can read the future density of dust in the region by inspecting its surface. That’s the helpful thing about a time-reversed planet: it gives you a forecast that can’t be wrong.’

Valeria couldn’t fault the woman’s imagination. At the very least, she must have gone to one of Yalda and Eusebio’s recruiting lectures when they were trying to assemble the crew for the Peerless . Maybe she’d even signed up, but then lost her courage at the last moment.

‘Here we are,’ Clara announced.

Valeria had been expecting some kind of conical structure adorned with parachutes, contrived to resemble one of the test rockets that had made short flights and returned, but perhaps Clara hadn’t been close to the real project after all. The object sitting on the sand, a few saunters from the road, looked like a small stone cabin on stilts, with the upper parts of each wall tilted outwards so that the windows they bore faced down at an angle. Just getting the bizarre construction here must have involved quite an investment – but what advantage did the woman hope to garner?

The four of them trudged across the desert together. Silvio looked even more contemptuous of the whole farce than Valeria, but he said nothing.

‘Where are the engines?’ Valeria asked.

‘Underneath, of course.’ Clara gestured to the bottom of the floor, about a stride above the ground. Valeria ducked down between the stilts.

‘There’s nothing here but a kind of… black mirrorstone,’ she reported. It was hard to see much by starlight, but the surface looked utterly smooth and unbroken. ‘Where does the exhaust come out?’

‘There is no exhaust. Just light.’

‘Light? Your rocket runs on light, but no one spotted you descending?’

‘Ultraviolet light,’ Clara persisted. ‘The faster the light a rocket uses, the less heat it generates in the process.’

Valeria emerged and straightened up. ‘Let me guess: your vehicle suffered some damage in the landing, but with sufficient funds you could get it working again. Your backers will be rewarded, of course, with new inventions that will put them so far beyond their rivals—’

Eusebio said angrily, ‘Enough! Whatever you believe, this woman is my guest, and I won’t allow you to talk to her that way.’

Clara said, ‘Scepticism is an admirable trait, and we seem to have confused everyone by arriving early.’ She turned to Valeria. ‘My vehicle suffered no damage. And I promised you a ride.’

Valeria stared at her. ‘You want to… ?’ She pointed upwards.

‘Yes. Eusebio? Will you come with us?’

He said, ‘If you’re sure you’re not too tired.’

‘I’m not a pilot; the photonics – the machines – will do everything for us. Silvio?’

Silvio said, ‘Thanks, but I should watch the truck.’

Clara led Valeria and Eusebio up the short flight of stairs and through the doorway. Valeria’s gut was squirming: she didn’t know what she believed any more, but just letting the woman take charge felt dangerous.

A little starlight entered through the cabin’s thick windows; Valeria could make out four couches and what looked like a tank of compressed air. Clara said, ‘Lights,’ and three large panels in the ceiling immediately began to glow. Valeria reached up and pressed her fingers to the illuminated surfaces; she could feel no heat, and the light was impossibly steady for any kind of lamp.

‘How… ?’ she pleaded.

Clara said, ‘Nothing I say would make any sense to you until you’ve learnt about the energy levels in a solid. But don’t worry, I’m sure I could bring you up to speed in about a stint.’ She gestured at the couches. ‘It shouldn’t be bumpy at all, but the protocol is to strap in during take-off.’

Valeria lay down on one of the couches and Clara helped her with the harness before attending to Eusebio.

‘There should be a reception at the university tomorrow, or the Council chambers,’ he babbled.

‘I’ll be happy to talk to anyone, anywhere,’ Clara assured him. ‘Anyone but jailers.’

She climbed onto her own couch. ‘Pilot?’ A diagram appeared on the wall, as self-luminous as the ceiling panels. After a moment, Valeria thought she recognised it as a topographical map of Zeugma’s environs.

Conjurors could do all kinds of things with lenses and hidden lamps. But they were getting close to the moment of truth, and if this woman had secreted a few hefts of sunstone above the smooth black panel in the floor with the hope of actually making this cabin fly, the only effect it was likely to produce would be to incinerate them all.

‘Pilot: plan a vertical ascent to an altitude of five slogs, followed by a return to our starting point, with a maximum deviation of one part in six from standard gravity.’

The topographical map tilted and became something like an artist’s rendering of the landscape. Then the viewpoint ascended to take in an ever wider portion of the desert, while a dashed red line rose up from the ground, sprouting strange annotations.

Valeria said hurriedly, ‘I believe you! We don’t have to do this!’ In truth she still doubted the woman’s story, but she did not want to be proven right and consumed by flames.

Clara buzzed mischievously. ‘Don’t be a killjoy. Pilot: execute the plan.’

Valeria felt a gentle pressure pushing her into the couch, as if someone had placed a young child on her belly. She looked to the window; they really were ascending, albeit with an impossible grace. No one could have done this but a traveller returned.

Clara dimmed the lights so that they could see out more easily, but once the hills by the roadside had dropped from view there was nothing in sight from their present vantage but the unchanging sky.

‘You can get up now if you like,’ Clara announced, unstrapping herself and rising to her feet. Eusebio did the same, then Valeria joined them by the window. The dark ground was receding rapidly; she could already see the lights of the city. But their motion was so smooth that it felt more like the product of ropes and pulleys than any kind of rocket.