Greg Egan - The Arrows of Time

There was a long silence, followed by a rhythmic squeaking noise that was almost certainly one of the bolts being turned. Agata restrained herself from cheering; Ramiro was asleep.

It took Tarquinia more than a chime to loosen all six bolts and remove the access panel. Agata peered over her shoulder into the exposed cavity, where cooling pipes ran along the back of the rebounders. If one of the banks of rebounders had failed, someone could have squeezed in here to fit a replacement.

‘Anything?’ Agata asked hopefully.

‘Nothing obvious,’ Tarquinia admitted. ‘I thought this was the last place we hadn’t poked around in, but maybe I should sit down with the maintenance logs to confirm that.’

‘Right.’

Tarquinia lingered, lowering her head partway through the hatch and turning her face sideways. ‘There’s a big stone beam that goes right across the top of the engines, from rim to rim.’

‘Could something be attached to it?’ Agata suggested. ‘Out of sight from where you are?’

‘I’m just wondering why it’s there at all,’ Tarquinia replied. ‘The floors of the cabins should provide enough bracing for the engines. And why a beam that runs across one particular diameter of the disc, and not another one at right angles to it? Nothing about the stress from the engines picks out one axis like that.’

‘No.’

Tarquinia said, ‘If I don’t come out in six lapses, send in Azelio with a rope.’

‘Azelio?’

‘No offence to you or Ramiro, but he’s the skinniest. There’s not much point in two people getting stuck.’ Tarquinia climbed head first through the access hatch, slithering deeper and humming softly as the cooling pipes banged against her, until even her feet had disappeared from view.

Agata waited, listening intently for any cries of discovery or distress. She was starting to wonder if she should have kept her inspiration to herself. Tarquinia trapped in the guts of the Surveyor would not be a happy outcome – and if she actually located the mythical device there could be worse to follow.

Worrying silences were punctuated with thuds, pings and echoing curses. Finally, Agata heard Tarquinia returning, her steady advance eliciting a resonant hum from the maze of pipes.

‘That was exhausting,’ she said. ‘Can you give me a hand up?’

Agata jumped down into the shaft and helped her out through the hatch. The flesh of Tarquinia’s torso had become corrugated as she’d forced it between the pipes, giving her the appearance of a decoratively shaped novelty loaf on legs.

‘Any luck?’

Tarquinia said, ‘There’s nothing hidden beside the beam.’

‘Oh.’

‘But the beam itself is hollow.’

‘Really? How can you tell?’

‘You can hear it when you tap,’ Tarquinia explained.

‘Couldn’t that just be to save mass?’

‘In principle it could be. But when I got to the far end I found something peculiar: it looks as if the cooling air is actually routed through the beam. Why do that, except to make life harder on anyone tampering with it?’

‘So if there’s a bomb,’ Agata said, ‘it might be anywhere inside a hardstone beam that spans the diameter of the Surveyor . And the only way we’ll ever know for sure is if we cut the whole thing open – in a place where there’s barely room to move, let alone the space to wield tools safely.’

Tarquinia inclined her head admiringly. ‘Trust Verano to find a civilised solution.’

Agata hummed with distaste. ‘Is there such a thing as a civilised bomb?’

‘Well, no,’ Tarquinia conceded. ‘But the Council would have asked him to fit a booby trap, and at least he made that idea redundant. There’s no way that Ramiro alone – or even the four of us – could have taken that hiding place apart and left the Surveyor functioning. A booby-trapped bomb would probably have been triggered by accident, long ago. We can thank Verano for finding a way to make the thing as good as tamper-proof, without turning it into a death sentence.’

Agata said, ‘I’ll send him flowers when I get back. But if we can’t get the bomb out and leave the Surveyor functioning—’

‘We couldn’t have done it in the void ,’ Tarquinia interjected. ‘But with an external atmosphere, there’s no comparison. I think even the most paranoid Councillor would have reasoned that if Ramiro had proposed the mission merely as a cover for an attack on the Peerless , he would hardly have been willing to spend twelve years actually detouring all the way to Esilio just to remove this thing.’

‘You really think you can go back down there and slice the beam open?’ Agata gestured at the curves still imprinted into Tarquinia’s body.

Tarquinia said, ‘Not just like that. First we take out most of the cooling pipes. Then we drill inspection holes in the beam, to see what we can see. The whole exercise could take a while, but it’s not impossible.’

‘Assuming there are no other problems. Assuming there really is no booby trap.’

Tarquinia said, ‘Yes.’

Agata slumped against the side of the shaft. Before she’d approached Tarquinia, she’d been picturing the bomb hidden behind a false wall at the back of the pantry, requiring nothing more to disarm it than the snip of a cable.

Tarquinia began smoothing out the kinks in her flesh. ‘I’m not going to try something like this without unanimous assent. And just because you raised the idea yourself doesn’t mean that you can’t change your mind.’

As Agata described her plan to blast their own arrow into the Esilian soil, she could see an expression of delight growing on Azelio’s face – as if she’d slipped a drawing of a flourishing garden sprouting from a bomb-shattered hillside into the stack the children had left him. There was scepticism too, but she was sure now that he would understand that it was at least worth trying.

Ramiro, though, remained as dispirited as ever. ‘If we do set off this explosive,’ he reasoned, ‘shouldn’t we be able to see some evidence of that already?’

Agata said, ‘You mean a crater?’

‘Yes.’

‘If we found a site like that, it would be useless to us. It would imply that after we set off the bomb, the crater would be gone and the sand around it would be rock again.’

Ramiro scowled. ‘Esilio doesn’t care what’s useful or useless, or it wouldn’t have killed the plants, would it?’

‘Esilio doesn’t care,’ Agata agreed, ‘but why would we go ahead and set off the bomb there, knowing that it would do us no good?’

‘Because the crater would prove that we did!’ Ramiro replied heatedly.

‘But as far as we know, there is no such crater.’ Agata met his gaze openly, trying to reassure him of her sincerity: she wasn’t playing some verbal game just to annoy him. ‘There is no crater, because if we saw it, we wouldn’t choose to make it. Esilio can’t force our hand; whatever happens has to be consistent with everything, including our motives.’

Ramiro said, ‘It can’t force our hand, but there could still be an accident.’

‘That’s true. But if we saw such a crater, we wouldn’t even go near it with the explosive.’ Agata would have liked to have taken comfort from the fact that there were no signs at the landing site of any future accident, but if the blast was capable of imposing its own arrow that meant nothing.

Ramiro’s hostility wavered. ‘I don’t know how to think about any of this,’ he admitted. He ran a hand over his face. ‘If the plants can’t bring their arrow to Esilio, why should a bomb do any better?’

‘The roots of a plant aren’t entirely passive,’ Azelio replied, ‘but they do rely on the state of the soil. I don’t think the bomb going off will rely on anything like that.’