Greg Egan - Incandescence

"At least," Roi agreed. "Maybe longer."

"So what are we honest workers supposed to do while we're waiting for you to judge the shape of space-time?"

Roi said, "You had plans for a second tunnel, didn't you?"

Bard replied wryly, "On skin, a second tunnel costs nothing. It was on the drawing I made, when I first had the idea. But I spent so long failing to get the first one started that I gave up thinking about anything so ambitious."

"You should build the second one if you can," Roi said. "Then a third, then a fourth. There's every chance we're going to need them. When we go ducking and weaving around the Wanderer, the faster we can move, the better."

Roi's second task on the sardside was to visit Neth, and see if she could persuade her to return to the Null Chamber. The theorists would need all the help they could get, and the battle Neth had come here to fight, to win people over to the cause of the tunnel, had been resoundingly won.

Bard had given her directions to the place where she could find Neth, but nobody could keep track of all the obstructions and detours surrounding the Great Project. The signage teams had probably all gone mad, or disbanded. As Roi passed among a group of workers shifting rubble from the tunnel's construction, she recognized one of them as Jos, the light-maker she'd met when she was traveling with Ruz and Zak.

Jos was happy to see her, but didn't want to stop working, so Roi walked beside her, helping her to carry a heavy piece of stone. Ideally, everyone doing this job would have had wheeled carts for their loads, but there probably weren't that many carts in the whole of the Splinter.

"This must be hard work," Roi said. "Shift after shift." She was struggling beneath the weight of the stone, even with two of them sharing the burden.

"It's not so bad," Jos said. "We're always taking the rubble downhill, sard of the tunnel. Bard told us that every rock we move shifts the Calm a small way sardwards, strengthening the garmside winds."

The darkness descended, but Jos insisted that they keep moving. "I've traveled this route so many times that I know it by touch."

Roi had little choice but to trust her. "What happened to your light machine?"

"It's at one of the rock faces. It's more useful there, where they can leave it in one place for a while. If I tried to carry it with me everywhere, I'd have no room on my back, and no strength for any rock."

"Fair enough." Roi hadn't brought the one that Cot had given her, even though she had little else to carry; this deep into the sardside the weight would have been too much.

"I still think about light all the time," Jos said. "What it is, how we can make it and use it." She added, almost apologetically, "There's nothing else to think about when you're carrying rocks."

Roi was no longer surprised by statements like this. Once, it had gone without saying that work and companionship, loyalty and cooperation, were more than enough to fill anyone's mind. Now the strange urges that had made people like her and Zak such aberrations were infesting half the Splinter. The strangest thing of all was that it had not brought anarchy and chaos, famine and death. People still carried out their work, still made sure that every necessary thing was done. There was a restlessness, though, a fluidity, reshaping the organization of the Splinter, faster than any tunnel builders could reshape its rock.

"What kind of ways could we use light?" Roi asked her. "Apart from the obvious."

"Imagine a flat sheet of metal at one end of a tunnel," Jos said. "An ordinary tunnel, not the one we're building. You could see it clearly from a very long distance: until the bend in the tunnel took it out of sight. Now if someone turned it edgeways to you, you'd notice straight away. In the dark phase you'd need a light machine beside it, but with care you could keep it visible all the time."

"I don't doubt that, but what use would it be?"

"Suppose you needed to get a message to someone on the other side of the Splinter. If we had a team of people positioned in the right locations, watching for changes in each other's sheets of metal, they could pass the message faster than anyone could run. Like couriers for words."

Roi was bemused. "Words need drumming or writing. Where are the words?"

"We agree on a list of simple words," Jos said. "Then we divide the list in half, in half again, and so on, until the last half is a single word. Tilting the metal once can tell us which half of the list the word is in, twice which half of that half-list, and so on."

The light was returning. Roi said, "You've thought about this for a while?"

"It passes the time."

If they needed to change the plugs in Bard's tunnel quickly, a system such as this might help. Roi had been struggling to imagine how they were going to navigate their way safely out to the Wanderer's orbit and beyond, when the one place where they could see into the void and the one place from which they could change the Splinter's motion were so far apart. She'd thought of trying to construct a platform for observations closer to the tunnel, but the directions of the weight made that a daunting prospect. Having to cling upside-down to the Splinter's exterior — when there was nowhere to land if you should fall — was not a situation likely to be conducive to accurate measurements.

Roi explained all of this to Jos.

"So you think it could actually be useful?"

"Absolutely! You need to start work on this immediately," Roi said. "See if you can persuade some of your team-mates to join you. Work out the details, smooth out the problems. Then come and meet me at the Null Line and let me know how things are going." Roi gave her directions to the Null Chamber.

Jos seemed overwhelmed by the sudden turn of events. "I believe you when you say this is important," she said. "But my job here, with the rocks. I came here, I listened to Bard. " She trailed off, confused. The Jolt had changed her enough to bring her here, and enough to make her restless with ideas, but she hadn't entirely lost the sense that the best thing to do was to stick with your team as long as you could.

"When will it end?" she implored Roi. "I want the old way back."

"You'll get it back," Roi said. "But first you have to do this."

Jos signaled to her to halt, and they came to a stop together. With a rasp of reluctant acquiescence she eased the rock down between them.

Roi said, "You're just going to leave that here?"

"It's not my job any more," she replied.

Roi found Neth alone in a chamber, surrounded by template frames. Neth greeted her warmly, and listened to all the news.

"I'm sad to hear of Zak's death," Neth said, "but I expected it long ago."

Roi didn't want to dwell on that. "So how are you spending your time here?"

"I'm trying to understand the wind," Neth said. "Even before we've cut open the mouth of the tunnel, moving all this rock has changed the flow. This whole thing is not as simple as Bard suggests."

"What do you mean?"

"If the Splinter simply wasn't here, the wind would blow straight from rarb to sharq; we can all agree on that. I'm not convinced, though, that cutting a long tunnel through the Splinter will necessarily have the same effect. The surrounding rock will still be diverting and complicating the flow of the rest of the wind. It will all mix together in the tunnel. The result isn't easy to predict."

Roi was dismayed. She had thought the hard part would be persuading people to help build the tunnel; now Neth was suggesting that it might not even work.

"What can we do if the flow isn't strong enough to make a difference? Build more tunnels?"

"That could help," Neth said. "But the important thing will be learning how to shape and control the flow through however many tunnels we have. What you say Bard has planned, with the varying plugs, will make a good start, but we'll need to study the effects of that arrangement, experiment with it, fine-tune it."