The Arrows of Time

Agata buzzed. ‘I don’t mean rocks flying into the air and hitting you in the face for no reason. When individual particles are moving randomly, that makes large assemblies of them more predictable, not less. Most of the time, air will just be air, stone will just be stone, acting the way our instincts expect.’

‘And the rest of the time?’

Agata said, ‘We’ll just have to be prepared for the exceptions.’

Ramiro was on watch, so he stayed in the front cabin monitoring the probe’s data feed long after everyone else had gone to bed. Sitting meekly on the surface of Esilio sending back images of the surrounding landscape, the probe encountered no conspiracies of air, or rock, or heat to impair it. Its temperature remained stable – despite the heat that its photonics would be generating in the normal course of things – which seemed to imply that it was exchanging thermal energy with its surroundings in the usual way. Agata appeared to have been right about that much: the earlier, unanticipated heating had taken place for a perfectly good reason, and there was no risk of it happening again while the probe was motionless on the ground.

Tarquinia had put the Surveyor into a new orbit, so high that it matched Esilio’s rotational period, keeping the probe permanently in their line of sight and allowing the link to remain open. Through the window, the planet itself had shrunk to an enigmatic grey disc, but as Ramiro swept the distant cameras back and forth across the starlit plain, the new world appeared as innocent and tranquil as he could have hoped it to be.

‘I’m happy with the site,’ Azelio announced. ‘The probe can’t verify every detail, but nothing it’s shown us makes me think we were wrong about the geology of the area.’

Tarquinia turned to Agata. ‘Any problems?’

‘No,’ she replied. ‘If we’re careful, I think we can do this safely.’

‘Ramiro?’

Ramiro had no objection to the site, but they could at least try to deal with the one unsettling phenomenon they’d already witnessed. ‘What if we lower ourselves through the atmosphere more slowly than the probe?’ he proposed. ‘That should keep frictional heating to a minimum, whether you look at it as an ascent or a descent.’

‘It would mean more heat from the engines,’ Tarquinia pointed out.

‘We’ve had no problem with that for a year at a time,’ he replied. ‘I know: venting cooling air into Esilio’s atmosphere might not be the same as doing it in the void. But wouldn’t it be the most cautious approach: moving slowly, trying to keep our temperature constant?’

Tarquinia looked to Agata.

Agata said, ‘I think Ramiro’s instincts are sound. The closer we can stay to thermal equilibrium, the more predictable things should be.’

‘All right then. A slow descent it is.’

Tarquinia turned to her console and began plotting their course down from orbit.

In the sunlit view through the time-reversed camera, Ramiro could see the broken ring of hills directly beneath the Surveyor, their eroded peaks casting long shadows to the east. Azelio had been ecstatic when he’d found this site, with the strange confluence of ancient dust flows that its peculiar topography had allowed. Ramiro didn’t pretend to understand the details, but over time the central valley appeared to have trapped wind-borne detritus from at least four different sources. From on high, the variety in the soils was impossible to miss, with great splotches of competing hues laid over each other like a mess of dyes spilt from a child’s paintbox. But though the colours were layered they remained distinct, which suggested that the whole arrangement was stable. The Surveyor was a great deal heavier than the probe, but if these deposits were prone to subsidence they ought to have shown more mixing under their own weight.

The temperature in the cabin had barely changed since they’d entered the planet’s atmosphere. Ramiro didn’t want to grow complacent; no one would forget the near-fatal surprise that the Object had held for its first visitors. But if a mismatch in Nereo’s arrow was a guarantee of mutual annihilation, the arrows of time were more pliable. On this world of lifeless dust with its almost timeless landscape, it did not seem too much to hope for that two opposing directions could coexist.

‘There’s the probe!’ Agata announced excitedly, pointing to a dark elliptical splotch. It was hard to distinguish the thing itself from its shadow.

The Surveyor was descending at a constant rate, leaving the cabin subject to Esilio’s full gravity – about a third higher than the home world’s. That standard was usually taken as the limit for prolonged acceleration, on the assumption that the ancestors’ physiology had adapted to it over the eons. But the travellers had coped easily enough with far lower gravity than the ancestral norm, and Ramiro did not believe that the settlers would be troubled by this minor increase.

Azelio said, ‘I can hear the wind.’