‘Yes. What is worse, my investigation did not advance the goals of the colony.’ She sensed it was studying her. ‘You are shivering. Do you understand why? Your body knows it is losing heat faster than it is being replaced. The shivering reflex exercises many muscles, increasing heat production by burning fuel. It is a short-term tactic, but—’

‘You know a lot about human bodies.’

‘No,’ it said. ‘I know a lot about heat. I am equipped to survive in this heat-sink landscape for extended periods. You, however, are not.’

It was as if cadre-leader Bryn was lecturing her on the endless struggle that was the only future for mankind. We cannot be weak. The Qax found us weak. They enslaved us and almost wiped our minds clean. If we are unfit for this new world, we must make ourselves fit. Whatever it takes. For only the fittest survive. If she let herself die before this enigmatic silver ghost, she would be conceding the new world to an alien race.

Impulsively, she began to stalk into the shallow valley, towards the antique city. Maybe there was something there she could use to signal, or survive.

The silver ghost followed her. It swam over the ground with a smooth, unnatural ease; it was a motion neither biological nor mechanical that she found disturbing.

She pushed through snowed-out air. The cold seemed to be settling in her lungs, and when she spoke her voice quavered from shivering.

‘Why are you here? What do you want on Snowball?’

‘We are’ - a hesitant pause - ‘researchers. This world is like a laboratory to us. This is a rare place, you see, because near-collisions between stars, of the kind that hurled this world into the dark, are rare. We are conducting experiments in low-temperature physics.’

‘You’re talking about absolute zero. Everybody knows you can’t reach absolute zero.’

‘Perhaps not. But the journey is interesting. The universe was hot when it was born,’ the ghost said gently. ‘Very hot. Since then it has expanded and cooled, slowly. But it still retains a little of that primal warmth. In the future, it will grow much colder yet. We want to know what will happen then. For example, it seems that at very low temperatures quantum wave functions - which determine the position of atoms - spread out to many times their normal size. Matter condenses into a new jelly-like form, in which all the atoms are in an identical quantum state, as if lased . . .’

Minda didn’t want to admit she understood none of this.

The ghost said, ‘You see, we seek to study matter and energy in configurations which might, perhaps, never before have occurred in all the universe’s history.’

She clambered over low, shattered walls, favouring hands and feet which ached with the cold. ‘That’s a strange thought.’