The Clockwork Rocket

face him. “This is excellent work!” she declared. “I’ll want you to give a talk on it to all the researchers, sometime in the next few days. Have you done anything on the theoretical side?”

Sabino produced a sheet of paper from a hold beside the microscope. “So far, only this,” he said.

“These are the energy troughs around a hexagonal array of luxagens,” he explained. “I drew it when I was first thinking about this project, back on the ground. It took about four stints to calculate.”

“I can believe that,” Yalda replied. It was a nice example of the kind of pattern that could persist beyond the edge of a solid—and she could easily picture a second array getting caught in those energy pits, like a truck sinking into another’s wheel ruts. She said, “We’re going to need to find ways to estimate the forces arising from much larger arrays, and to take account of the whole three-dimensional geometry. But don’t worry about that for now; you should concentrate on refining this setup.”

“All right.” Sabino was still a bit dazed, and though Yalda was trying to keep him as grounded as possible, he could not have failed to realize the importance of his discovery. If this experiment could be repeated and elaborated upon, it promised to make the nature of matter the subject of systematic inquiry—ending the days when the differences between a stone and a puff of smoke had no better explanation than the empty incantation that “solid objects occupy space”. Nereo had paved the way, but until now all his beautiful mathematics had remained untested guesswork. It was possible that Sabino and Nereo would be spoken of alongside Vittorio, who had made sense of the orbits of the planets—but Yalda thought it best not to overwhelm the young researcher with florid praise and promises of immortality. What he needed to do now was pursue the work itself.

The three of them talked through some possibilities for the next step; simply measuring the force that had to be applied to pull one grain of calmstone free of another was one obvious goal, but the torques required to twist them out of their preferred alignment might also yield information about the underlying geometry.

They took the discussion to the food hall, where it turned to the question of other minerals: were they all made of the same kind of luxagens, differently arranged? Could geometry alone account for all the differences between hardstone and clearstone, calmstone and firestone? The experiments they’d envisaged so far would only be the start; Yalda could see the chase that Sabino had begun lasting a generation.

But as she finally dragged herself off to her apartment to sleep, she thought: That’s the beauty of it—there is no rush. Time back home had come to a standstill, and any Hurtler that struck the Peerless now would barely leave a mark. The mountain’s resources would not last forever—and they certainly didn’t have enough sunstone to get themselves home by burning it the old way—but at last a tiny crack had opened up in their ignorance as to what a slab of sunstone might actually be.

Yalda climbed into her bed, shrugging at the resin-sticky sand until it covered her body beneath the tarpaulin, more hopeful now than ever that they were following the right course.

Fatima appeared outside Yalda’s office, back from her latest errand. Yalda ushered her in, then asked quietly, “How was Nino?”

“He didn’t look too bad,” Fatima replied. “He said to thank you for the books.”

Yalda was embarrassed. “You’re the one who should be thanked.”

“I don’t mind taking things to him,” Fatima said. “Climbing all those stairs would have been hard work, but now it’s not much different than going anywhere else.”

Yalda did not believe that she was endangering her with these trips—Fatima wouldn’t be blamed merely for following instructions—but she was worried about the effect on the girl of being Nino’s only visitor.

“It doesn’t upset you, having to see him like that?”

“I’d rather he was free,” Fatima said candidly. “He’s been punished enough. But I know you can’t let him out yet. He was kind to me, back when we were both still recruits, so I’m happy to go there and try to cheer him up.”

“All right.” This was the arrangement Nino had wanted, and for now Yalda had no better ideas. “Just promise that you’ll tell me if you start finding it difficult.”

“I will.” Fatima swung back on the ropes as if to depart, but then she stopped herself. “Oh, I checked in on the forest too, on my way back.”

Yalda had almost forgotten that she’d asked her to do that. No one had been officially assigned to monitor the Peerless’s tiny patch of wilderness, and she’d been loath to divert any of the farmers to the task while they were still coming to terms with the onset of weightlessness. “How’s it looking?”

“It’s less dusty there than in the fields and the gardens,” Fatima said. “There were a lot of twigs and petals and dead worms in the air, but nothing larger—the trees haven’t become uprooted, and I didn’t see any arborines flailing around on the ceiling.”

“That’s a relief.”

“I don’t think the wheat’s doing too well there, though,” Fatima added.

“Wheat?”

“There’s a plot of wheat in one of the clearings,” Fatima explained. “It looks as if the stalks were moved there whole—dug up from a field and replanted, not grown there in the plot. But none of their flowers were open when I was there.”

“I see.” Yalda was perplexed; whoever was conducting the experiment hadn’t mentioned it to her.

She sent Fatima to rejoin her physics class, and went looking for Lavinio, the chief agronomist. A note at the entrance to his office said he’d be down in the fields for another two stints. Yalda tried counseling herself to be patient; she didn’t expect to be kept informed about every last scientific activity on the Peerless, and it might attract Lavinio’s resentment if she showed up far from her usual haunts for no other reason than to question him about some trivial experiment.

But how trivial was it? The farmers were far too busy addressing the logistics of weightless harvesting to go and plant wheat in the forest just to test an idle conjecture about the effects of companion species on growth rates. No one would have done this unless it was important.

She couldn’t wait two stints.

Weightlessness had transformed the stairwells from sites of interminable drudgery to the mountain’s smoothest thoroughfares. With a pair of ropes all to herself and no one else in sight, Yalda switched to her high- speed gait: propelling herself forward with all four limbs at once, then releasing the ropes and moving ballistically for as long as possible before brushing them again with whichever hands were necessary to correct any sideways drift and replenish her speed. The moss-lit walls flew by, while the threatening edges of the helical groove that wrapped around her, its jagged steps proclaiming a vertiginous descent guaranteed to end with her head split open, only added to her triumphant sense of control. Once you could survive throwing yourself down a staircase as tall as a mountain, anything seemed possible.

Yalda reached the level of the forest in what felt like less than a bell. When she moved from the stairwell to the access tunnels, her mind insisted on treating all the arborine-proof doors along the way as hatches, and she emerged into the chamber with a strong sense of ascending through a floor. The trees stretched out “above” her did their best to persuade her to realign her sense of the vertical, but all the loose detritus suspended around them rather undermined their case.

The refitting of this chamber had been perfunctory, with just a few unpaired guide ropes suspended between hooks on the wall, so Yalda had to push off from the rock and drift freely through the air to enter the forest itself. Once she was among the trees, though, the branches offered plenty of hand-holds. Tiny dark mites darted past her with exuberant energy, coming and going in a flicker. A green-flecked lizard scampered out of her way, its claws still finding easy purchase in the bark. However ancient and unvarying their instincts, these animals had not been defeated by the change.

She found the clearing Fatima had described—and Lavinio with it. He’d crisscrossed the small treeless space with ropes, the better to access the dying wheat plants. Only now did Yalda feel that the netted soil was below her: she was an aerial spy, sneaking through the canopy like the arborine in her grandfather’s story. She descended with as much creaking of branches as possible, to dispel any appearance of