The base of the lifedome expanded in Mark’s vision until it covered the sky, becoming an immense, complex, semi-transparent roof; guide lights and the outlines of ports — large and small — encrusted the surface with color, and everywhere there was movement, a constant flow of cargo, pods and spacesuited figures through the multiple locks. Again Mark had the impression that this was not so much a ship as a city: immense, busy, occupied with the endless business of maintaining its own fabric.

Suspended beneath the lifedome, cradled in cables, was the dark, wildly incongruous form of the Great Britain. It looked like an immense lifeboat, suspended there, Mark thought; he grinned, relishing this evidence of Louise’s sentimentality.

The pod, working autonomously, made a flawless entry into one of the huge airlocks. After a couple of minutes the lock had completed its cycle.

The four of them emerged, drifting, into the air at the base of the Northern’s lifedome. It seemed to Mark that the base itself — constructed with the universal semisentient transparent plastic — was a wall dividing the Universe into two halves. Before him was the elaborate, sparkling-clean interior of the lifedome; behind him was the tough, angular spine of the GUTship, and the static darkness of transPlutonian space.

Louise led them to a row of zero-gee scooters; the scooters nuzzled against the transparent base, neat and efficient. Mark took a scooter. It was a simple platform, its pneumatic jets controlled by twists of its raised handles.

They formed into pairs — Louise and Uvarov in the lead, with Mark and Milpitas following. With near-silent sighs of scooter air the four moved off in formation, up toward the heart of the lifedome.

The lower fifth of a mile of the lifedome was known as the loading bay: a single, echoing hall, brilliantly lit and free of partitions. The roof of the loading bay — the underside of the first habitable section, called the maintenance bulkhead — was a mist-shrouded tangle of infrastructure, far above. Today, the loading bay was filled with bulky machinery and crates of supplies; huge masses, towed by people on scooters or by ’bots, crossed the air in all directions, emerging from a dozen locks.

Serena Milpitas performed a slow, easy spiral as she rose up through the air beside Mark. “I love these scooter things, don’t you?”

Mark smiled. “Sure. But they’re a lazy way to travel in zero gee. And they won’t be a lot of use when we’re underway.”

“No. A constant one-gee drive for a thousand years. What a drag.”

Mark studied the engineer as she went through her rolls; her expression was calm, almost vacuous, with every sign that she was lost in the simple physical pleasure of the scooter-ride. Mark said, “How did you feel about having to dig up those old techniques — the reliability procedures?”

“How did I feel?” Milpitas stabilized her scooter and studied Mark, a half-smile on her face. “You sound like a Keplerian… They’re dippier than anyone else back home on Mars. Ah, but I guess that’s your job, isn’t it? The social engineer.”

Mark smiled. “Maybe. But I’m off-duty now.”

“Sure you are.” Milpitas thought for a moment. “I guess our work isn’t so dissimilar, Mark. Your job — as I understand it — is to come up with ways for us to live with each other over a thousand years. Mine is to ensure that the ship itself — the external fabric of the mission — can sustain itself. When it came to redesigning Northern, I didn’t like messing up Louise’s nice, clean designs, frankly. But if you’re going to succeed at something like this you have to take no chances. You have to plan.” Her eyes lost their focus, as if she were looking at something far away. “It had to be done. And it was worth it. Anything’s worth it, for the project, of course.” Her expression cleared, and she looked at Mark, appearing confused. “Is that answering your question?”

“I think so.”

Mark hung back a little, and let Milpitas move ahead, up toward the complex maintenance bulkhead. He fell into line with Louise.

“You don’t look so happy,” Louise said.

Mark shrugged. “Just a little spooked by Serena, I guess.”

Louise snorted. “Aren’t we all.”

Many of the original crew of the Northern — who had, after all, seen themselves as potential colonists of the Tau Ceti system, not as time travelers with quasi mystical goals about saving the species — had decided not to stay with the ship after its new flight plan was announced by Louise. Louise had lost, for instance, the genial Sam Gillibrand, her original first assistant. On the other hand, Serena Milpitas — and Uvarov, for that matter — had seemed eager to join the project after its rescoping by Superet.

Both Milpitas and Uvarov seemed natural Superet supporters, to Mark; they’d absorbed with a chilling alacrity the induction programs Superet had offered them all.

Milpitas and Uvarov had become converts. Mark thought uneasily.

“You know, I always liked Sam Gillibrand,” he said wistfully. “Sam wants to go to Tau Ceti and build houses under the light of a new sun; the dark possibilities of five megayears hence couldn’t be of less interest to him. Serena is different, though. Under all that bluff Martian chatter and confident engineering, there’s something darker — more driven. Obsessive, even.”

“Maybe,” Louise said. “But, just as human engineering isn’t yet up to thousand year flights, so the average human head isn’t capable of thinking on thousand year timescales.” She sighed and ran her fingers through her close-cropped hair. “Serena Milpitas can win through for the mission, Mark. Both Milpitas and Uvarov seem able to think in millennia — megayears, even. And as a consequence, or as a cause, they are dark, multilevelled, complex people.” She looked at Mark sadly. “The Superet stuff is spooky, I agree. But I think it comes with the territory, Mark.”

Maybe in the complexities of the future the home-builders like Sam would be obsolete, their simple skills and motivation displaced in a dangerous Universe, Mark thought. Perhaps Superet and its converts represented the human of the future — the next wave of evolution, what the species would have to become to survive on cosmic timescales.

Maybe. But — judging by Milpitas and Uvarov — there wouldn’t be too many laughs.

Anyway, he thought gloomily, he was going to have ten centuries with these people to find out about them… And it was going to be Lethe’s own challenge for him to construct a viable society around them.

“It still surprises me that you agreed to sign up for this,” he said. “I mean, they took away your mission.”

Louise shrugged. “We’ve been over this enough times. Let’s face it, they would have taken Northern away from me anyway. I want to see the ship perform. And — ”

“Yes?”

She grinned. “Besides, after I got over my irritation at the way Superet runs its affairs, I realized no one’s ever tried a thousand-year flight before. Or tried to establish a time bridge across five million years. I can get one over on Michael Poole, wherever he is — ”

“Yes, but look what happened to him.”

Mark could see what was going on inside Louise’s head. With the Superet mission — with this immense stunt — she was going to be able to bypass the intimidating shadow of the future, simply by leaping over it. And she was obviously entranced by the idea of taking her technology to its limits. But he wondered if she really — really — had any idea of the scale of the problems they would face.

He opened his mouth to speak.

Louise, with unusual tenderness, laid a finder over his lips, closing them. “Come on, Mark. We’ve a thousand years to think of all the problems. Time enough. Today, the ship is bright and new; today, it’s enough for me to believe the mission is going to be fun.”