You could push it. You could mount a giant rocket on a spin pole, as had been done on Port Sol, or even a series of rockets around the equator. But you would consume an immense amount of Earth’s own matter in the process, and any instability could cause the planet’s crust to shake itself to pieces. You might end up doing more harm than good.

Alternatively you could use gravity. If the Earth still had its Moon, you could have used that as a tug: push away the Moon as violently as you liked, and let lunar gravity gradually haul the Earth on a slow spiral away from the sun. But the Moon had been detached from the Earth in the course of a long-forgotten war.

Or you could do it piecemeal.

The Ascendents mounted venerable GUTdrive engines on a whole fleet of Kuiper Belt ice moons, including their own base, Port Sol. It took a long time for the slow push of the plasma rockets to make a difference, but at last the moons came swooping out of the dark into the inner system, entering complicated orbits that shuttled between Earth and the greatest planets, Jupiter and Saturn.

And with each moon’s passage Earth’s orbit was deflected, just slightly.

With a long series of slingshots Earth was gradually nudged outward from the sun, while the giants were subtly moved closer. It was as if the Ascendents had linked Earth to its giant cousins with immensely long chains, that drew them slowly together. It was going to take a million encounters with moons the size of Port Sol to move the Earth out to its destination, a new orbit around Saturn. At the rate of two or three encounters a year that would require thousands of centuries. But the undying always had time in abundance, time and patience. And Earth was on its way.

It was a typical undying project, on immense timescales, but low-tech. But you had to keep a sense of perspective, Symat thought. Where the Xeelee had blocked the light of suns across a supercluster of galaxies, all humans could manage was to nudge one little world across Sol system.

And in the end even this monumental exercise in persistence hadn’t been enough. The immortals had saved Earth from the expansion of its sun. Now the Xeelee had come to Sol system, and a new danger loomed.

But again, it seemed, the undying had been preparing.

The three of them continued to walk among the ranks of immortals, each in her station, each with her number.

As they passed the dimly stirring figures, the Curator kept smiling.

Symat asked curiously, ‘Why do you grin like that?’

‘None of them can see well. But many of them respond to simple shapes.’

‘A smiling human face,’ said Mela, wondering. ‘Like a baby. A baby can recognise a smiling face almost as soon as it’s born.’