The Arrows of Time

‘Not really,’ she admitted. ‘Maybe what we need is some kind of covered system of barriers. If we can place it on the floor and then reconfigure it without opening the cover, we ought to able to manipulate the dust inside without any more arriving.’

‘That sounds… elaborate.’

Agata put on her corset and tool belt and followed Azelio to the airlock, then waited for him to cycle through. The view through the window showed that the weather was calm, but the Surveyor had become so filthy that Tarquinia now insisted on the protocol, regardless. Agata was beginning to suspect that the only remedy for the dust invasion would be to ascend into the void and flush every room out with clean air – and even that depended on their arrow prevailing and the void not being ready with a conspiracy of pollutants poised to rush in the moment they opened the airlock, in a perfect reversal of the intended purge.

Outside, she caught up with Azelio at the start of the trail. It was Ramiro who’d noticed the regularly spaced indentations in the ground after the last high winds, and decided to fill them with rocks marking the way to each of the four test plots. Agata hadn’t questioned him too closely on the matter, but she suspected that he’d already been contemplating doing something similar. The idea hadn’t come from nowhere, inspired by nothing but the evidence of its own implementation.

‘How are the calculations going?’ Azelio asked her, as they started along the trail.

‘Slowly.’

‘Just as well. If you finish them, what will you do on the journey back?’

‘There’s no risk of that.’ Agata had set aside her efforts to understand the curved vacuum and instead had spent the last two stints attempting to analyse their current situation, using a crude model of a field in which two opposing thermodynamic arrows met. But in the versions that were simple enough to handle, both arrows rapidly decayed away, leading almost immediately to a time-blind equilibrium state. The reality, in which countless slender fingers of opposing time interpenetrated, seemed to depend on details too subtle for her to approximate in any meaningful way.

‘It’s Luisa’s fifth birthday today,’ Azelio announced cheerfully. ‘I’ll show you her drawing for it when we get back.’

‘Happy birthday, Luisa!’ Agata played her coherer’s beam over the grey stones to her left. ‘You never peek, do you? You never riffle through the pile to see what’s coming up?’

Azelio buzzed. ‘Of course not! That would defeat the whole point.’

‘I know. But that wouldn’t be enough to stop me.’

When they reached the first plot the plants were all dormant, their flowers closed. Agata glanced up at the sky; she knew from the positions of the stars that the sun was well above the horizon, but she would have had to forego artificial light for a few lapses to have any chance of picking out the faint disc. ‘I was hoping the petals might synchronise to the Esilian day,’ she said. ‘They give out photons, the sun accepts them: what could be more sensible than that?’

‘Except that eons of evolution has left them with no skill but waiting for an ordinary night, not a time-reversed day.’

‘Maybe the settlers could breed it into them,’ Agata suggested. If detecting the dawn for themselves was too hard, the plants could still be prodded with more conventional signals into following the new cycle. For now, the Esilian sun would be getting its due regardless – from the plants, the ground, and her own skin – but not in any useful way.

‘Can you do the heights and the stalk circumferences?’ Azelio asked her.

‘Sure.’ Agata knelt by the first plant and reached into her tool belt. In a perfect world some clever instrument builder would have added a data recorder directly to the tape measure, but instead she had to aim her coherer so that she could read the tape by eye, raise the figure on her skin, and have her corset record it. ‘Is one soil type racing ahead yet?’ she asked Azelio. He’d started from the other end of the row, making his own inspection to record the number and condition of the flowers.

‘No.’

‘So there’s not much difference? The settlers could farm anywhere?’

Azelio was silent. Agata regretted distracting him; she’d probably made him lose count.

As he stood to move on to the next plant, he said, ‘Actually, they’ve all stopped growing.’

Agata was startled; nothing in Azelio’s demeanour had prepared her for this news. ‘All of them? Every single one?’

‘Yes.’ Azelio spoke calmly. ‘At first it was only a few cases, and I put it down to transplantation shock. But the numbers just kept getting worse, and three days ago the last exceptions succumbed.’

Agata struggled to find the least dismaying interpretation of these facts. ‘Do you think it’s the wind?’ They could always improve the windbreaks, or even relocate the whole experiment.

‘No. They haven’t lost that many petals, or had roots dislodged.’

‘So it’s the soil,’ she concluded. ‘All four kinds are inhospitable.’

‘It’s looking that way.’

‘Have you told Ramiro?’