‘We will always have to combat cultural drift,’ she said. ‘It is the blight of the generation starship. Already we have some pregnancies; soon we will have the first children, who will live and die knowing nothing but this Ship. And in a few generations - well, you can guess the rest. First you forget where you’re going. Then you forget you’re going anywhere. Then you forget you’re on a damn ship, and start to think the vessel is the whole universe. And so forth! Soon nothing is left but a rotten apple full of worms, falling through the void. Even the great engineer Michael Poole suffered this; a fifteen-hundred-year generation starship he designed - the first Great Northern - barely limped home. Oh, every so often you might have a glorious moment as some cannibalistic savage climbs the decks and peers out in awe at the stars, but that’s no consolation for the loss of the mission.

‘Well, not this time. You engineers will know we’re almost at the end of our GUTdrive cruise phase; the propellant ice is almost exhausted. And that means the Ship’s hull is exposed.’ She clapped her hands - and, to more gasps from the crew, the amphitheatre’s floor suddenly turned transparent.

Rusel was seated over a floor of stars; something inside him cringed.

Andres smiled at their reaction. ‘Soon we will leave the plane of the Galaxy, and what a sight that will be. In a transparent hull our crew will never be able to forget they are on a Ship. There will be no conceptual breakthroughs on my watch!’

IV

With the ice exhausted, the Ship’s banks of engines were shut down. From now on a dark matter ramjet would provide a comparatively gentle but enduring thrust.

Dark matter constituted most of the universe’s store of mass, with ‘light matter’ - the stuff of bodies and ships and stars - a mere trace. The key advantage of dark matter for the Ship’s mission planners was that it was found in thick quantities far beyond the visible disc of the Galaxy, and would be a plentiful fuel source throughout the voyage. But dark matter interacted with its light counterpart only through gravity. So now invisible wings of gravitational force unfolded ahead of the Ship. Spanning thousands of kilometres, these acted as a scoop to draw dark matter into the hollow centre of the torus-shaped Ship. There, concentrated, much of it was annihilated and induced to give up its mass-energy, which in turn drove a residuum out of the Ship as reaction mass.

Thus the Ship ploughed on into the dark.