Incandescence

was encouraging. Most of what she’d seen in the void remained utterly mysterious to her, but they were moving in the right direction.

“There’s one more thing we need to decide before we call in the calculating team,” Tan said. “How are we going to measure distances from the Hub now?”

In the previous calculation, they’d described each point’s relationship to the Hub by the size of the sphere on which it lay. You didn’t need to worry about the actual, messy curved geometry all the way from the point to the Hub itself; instead you imagined rotating the point around the Hub in all possible directions, sweeping out a sphere whose surface area would increase the further the point was from the Hub.

With the spherical symmetry gone, they could no longer do this. They could replace the spheres with circles —rotating each point around the axis of symmetry and then considering the circumference of the circle it swept out—but away from the plane of the Incandescence it wasn’t clear how those circles would be related to each other.

Ruz appeared at the entrance to the Chamber. He greeted them politely and apologized for interrupting, but Roi could tell from the way he hunched against the wall that he had something he urgently needed to say.

“We’re seeing more flares from the Wanderer,” he announced. “Nine, in the last report I’ve received.” While Roi had been visiting Bard and Neth, Ruz had arranged a group of new recruits to stay at the junub edge, with pairs climbing up through the crack in the wall each time it was safe, to make observations.

“We’ve felt no new Jolt,” Tan said.

“No,” Ruz replied, “we’ve been lucky. But if this continues, it’s only a matter of time before another one strikes us. We’re also seeing the Wanderer’s orbit changing: it’s losing its inclination, coming closer to the plane of the Incandescence.”

Roi felt a crushing sense of hopelessness descend, but she struggled to fight it off. One tunnel was almost complete, and Neth would help Bard sort out any problems with the flow. They were tracking the Wanderer heartbeat by heartbeat. Now it was up to the theorists to find the way forward, to draw the map that showed the way to safety.

She addressed Tan. “We should assemble the calculating team, next shift.”

“All right,” he said. “But what about the question of distance from the Hub?”

Roi thought for a while. “There’s one symmetry that’s always present, that we forgot to mention: the geometry really doesn’t care how we describe it.” You could wrap space-time in numbers in countless different ways, but the underlying shape was oblivious to the packaging. “We don’t know the best way to express distance from the Hub, and even if we make a certain guess now it might turn out to make things harder. So we should give ourselves room to manoeuvre: we should set up the templates so we can choose the easiest scheme at any point in the calculations.”

Tan concurred. He said, “I’ll go and tell the calculating team.”

When he’d left, Ruz said, “I’d better go and send the messengers back to get the next report.”

Roi said, “Remember Jos?”

“Jos?”

“One of the people we met with the light machine?”

Ruz looked tired. “Vaguely. Why?”

“She’s had an idea for something much faster than any messenger. I think you need to talk to her.”

19

Rakesh spooned chillied dhal into his mouth with an urgency that had nothing to do with hunger. The longer he spent among the Arkdwellers, the more he needed to reinforce his sense of presence in his own neglected body, and the familiar taste and aroma brought him back to himself like nothing else did.

“I’m going mad,” he announced. “One more month of this, and you can erase me and break the news to my backup.”

Parantham said, “Don’t expect my sympathy. Just because the Arkdwellers’ culture turned out to be resilient, it doesn’t mean you were right to take a risk with it.”

“Resilient? I think the word you’re looking for is catatonic.” Sweat was pouring down the back of his neck from the spices, but he kept eating without pause, and without diluting the heat with bread or rice.

Each time his Arkdweller colleague Saf slept, Rakesh took his senses out of his avatar, leaving it dormant in a crack in the rock close to the one she’d chosen. Each time Saf stirred, his avatar would notice and summon him back. It was a summons he was beginning to dread.

His job had allowed him to tour the Ark, and at first the experience had been fascinating. The Ark’s biosphere was bottom-heavy in fungi and bacteria, but it had a few niches for larger organisms. A genetic analysis of the five varieties of herd animals the Arkdwellers farmed showed that they’d been created by selective breeding from an earlier inventory of just two species. Whether the Arkmakers had initially stocked the place with more and the others had been lost at some point was unclear; it was also unclear just when the Arkdwellers had lost their ancestors’ ability to engineer the animals’ genomes, and had to revert to patient observation of traits and restrictive mating or manual fertilization. Both the larger animals and the Arkdwellers themselves reproduced in more or less the same way, which involved excruciating pain for all fertile males and more pity than pleasure on the part of the harassed females who put them out of their misery. Rakesh fervently hoped that it was something the ancestors had passed down from their own biology only because it was too technically difficult to change. The possibility that they might have freely devised such a scheme didn’t bear thinking about.

The flow of stellar winds into the neutron star’s accretion disk was a powerful and relatively constant source of energy, and even the tiny portion siphoned off by the Ark was enough to allow a technologically unsophisticated culture to rise above subsistence agriculture. A range of simple goods was manufactured, mainly from animal products, but also from a small amount of scrupulously recycled metal. Services ranged from courier rounds like Saf’s to the curating and restoration of repositories of documents, written on animal skin, bearing recipes for such things as inks and glues, and drawings of useful tools and machines.

It was all very practical, but it seemed a long way removed from the kind of knowledge their ancestors must have possessed. Though born on the surface of an ordinary planet, the Arkmakers had mastered the plasma hydrodynamics of a neutron star’s accretion disk in sufficient detail to construct a whole world that could flourish in this radically new environment. Rakesh couldn’t see the current inhabitants coping with even the mildest disruption to their routine.

Parantham said, “It need not be pathological, to respond to stability with stasis. Perhaps this is what the Arkmakers longed for: after all the turmoil they’d faced, they didn’t want to have to look over their shoulders for the rest of eternity. They didn’t want to be fretting about how they’d escape the next unpredictable disaster.”

“This is the bulge,” Rakesh replied. “You have no choice but to look over your shoulder.”

“In the long run, maybe not, but they’ve managed to survive for fifty million years. Perhaps they calculated the odds, and said, if we burrow down deep into this neutron star’s gravity well, it will be a long, long time before anything else wanders by that’s strong enough to prise us out.” Parantham spread her hands. “Once you make that decision, what’s the point in being outward-looking, or in seeking constant change? Some cultures have thrived on uncertainty, but for some species there’s nothing more stressful than the need for vigilance.”

Rakesh could see her point, but he didn’t like where she was heading. “So when the Arkmakers faced the prospect of the neutron star tearing up their home world, you think they willingly rid themselves of the very traits that allowed them to survive that event? They resented the unpredictable universe so much that they consciously stripped away all their curiosity, all their powers of abstract reasoning, and gave birth to this nest of sleepwalkers?”

“Are they happy?” she asked.

“They’re not miserable,” he replied, begrudgingly. “But only because they don’t know what they’re missing.”

“Are they happier than you were back at the node?” Parantham countered. “Going mad with frustration