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as they raced around the new sun.
    And, out of the collisions, planets grew: rocky worlds in the hot centre, volatile-fat giants further out. A powerful wind blew from the sun, violently ejecting the amniotic remnants of the birth cloud. Planetesimals rained down on the surfaces of the new worlds, leaving scars that would persist for billions of years.
    The gravity of young Jupiter plucked at the belt of planetesimals further in, preventing their coalescence into larger bodies. So, in the gap between Jupiter and Mars, the planetesimals survived as asteroids: rocky chunks closest to the sun, volatile-rich snowballs at the outer rim, moulded by impacts with each other, melted by radioactivity and electrical induction.
    And it was to the asteroids that the starship came: after billions of years drifting like a seed between the stars, still running from the supernova, exhausted, depleted, its ancient machinery cradling the generations that swarmed within, evolving, never understanding their plight.
Scale: Exp 3
    The nanobugs woke him; with reluctance he swam up from dreams of sunlit days with his daughters on the beaches of Galveston.
    He emerged into a gritty, unwelcome reality. Here he was: half a man, with his whole lower body replaced by the gleaming box he called his PMU, pipes and tubes everywhere, still rattling around inside his clumsy old hab module.
    Not that there could be much left of his original home. That old NASA stuff had mostly worn out after a decade, let alone a thousand years. But the Weissmans, or anyhow the robots they’d assigned to keeping him alive, quietly rebuilt this old box around him, just as they rebuilt him continually, nanobugs crawling through his body while he slept away the years.
    Well, the hell with it. He dug out a packet of food – the label reassured him it was chicken soup, and as far as he was concerned that was what it was – and he shoved it into the rehydration drawer of his galley.
    He moved to a window, the little nitrogen reaction-control squirters on his PMU hissing softly. The window gave onto a shaft cut through the regolith, which had a massive lid that would swing down on him in case of a solar flare or some such. It gave him a good view of the surface of Ra-Shalom, and a slice of the night side of Earth, and a handful of stars.
    Water-blue light glared out of Ra.
    When he’d first come here, Ra had been just a lump of dirty carbonaceous stone. Now, the old craters and ravines transformed into a patchwork of windows, roofed over with some kind of smart membrane.
    Greenberg could see into the lens-like surface of one of the crater windows. And right now, a few minutes from the aerobraking of Toutatis, the Weissmans were swimming up from the big spherical ocean they were building in the hollowed-out interior of Ra, swimming up to watch a light show hardly any of them understood, probably.
    The Weissmans came in a variety of shapes. There were even still a few standard-issue four-limbed humans around. But the most common morphology was something like a mermaid, with the legs – useless, heavy distractions in microgravity – replaced by a kind of fish tail, useful for swimming around in the air, or the interior ocean. A lot of them had gills and never came out of the water at all, and some were covered in fur that streamlined and warmed their bodies.
    The Weissmans had done away with every part of the body which wasn’t needed in microgravity. And some had gone further. Some didn’t have hands, or arms. In an age of ubiquitous and one hundred per cent reliable machinery – machinery which could manufacture other machinery – human beings, it seemed, didn’t need to be toolmakers any more.
    To Greenberg, they looked like nothing so much as seals.
    It was their choice, or their progenitors anyhow. But what Greenberg couldn’t figure was what they did all day.
    Greenberg himself still had work to do, in these rare intervals of wakefulness: monitoring Ra’s external