Greg Egan - The Clockwork Rocket

In fact, the two planets were so far from the sun that the density of the solar wind in their vicinity was believed to be a tiny fraction of its value around the nearer worlds—and no Hurtlers had ever been seen at such a distance, in accord with the idea that it was friction with that gas that made the pebbles burn up. But the lack of the usual pyrotechnics hadn’t prevented this unheralded impact.

The Hurtlers were everywhere, visible or not—and Ludovico’s absurd explanation for them that blamed the solar wind alone was now completely untenable. Yalda didn’t expect him to recant, but the people who’d voted with him against Eusebio’s offer didn’t have the same degree of pride invested in the matter.

Perhaps the new star was no more exotic than the Hurtlers themselves, but its meaning was far easier to read: the only thing that had spared their own planet so far was luck. Any day, any night, the world could go the same way.

“The good news,” Yalda said, “is that we might just get our flying mountain after all.”

12

“Stay close to me!” Yalda called out to the group as they approached a bend in the tunnel. “Anyone suffering from nausea? Weakness? Dizziness?”

A chorus of weary denials came back at her; they were tired of being asked. She’d been pacing the tour carefully—and the mountain’s interior was maintained at higher pressure than the air outside—but everyone’s metabolism was different, and Yalda had decided that it was better to nag than face a crisis. She certainly didn’t want any of these potential recruits associating the place with sickness.

“All right, we’re now coming to one of the top engine feeds.” For the last few saunters the tunnel had been lit solely by the red moss clinging to its walls, but the illumination from a more variegated garden could already be seen spilling around the bend.

As they took the turn, a vast, vaulted chamber appeared in front of them, a disk almost half a stroll wide and a couple of stretches high. It had been hollowed out of the rock three years before, using jackhammers powered by compressed air; no engines or lamps were employed in the presence of naked sunstone. The usual drab moss and some hardy yellow-blossomed vines covered the arched ceiling, but between the supports the floor was a maze of flower beds luminescing in every hue. Many of the plants were arranged haphazardly, or in small, localized designs, but long strands of cerulean and jade could be seen weaving from garden to garden around the gaping black mouths of the boreholes.

“It wasn’t always so colorful here,” Yalda recalled, “but the construction workers brought in different plants over the years.”

“Will you keep the gardens when the engine’s in use?” Nino asked.

“No—that would interfere with the machinery, and in the long term their roots could even damage the cladding. But these plants won’t be destroyed; they’ll be shifted to the permanent gardens higher up.”

Yalda led her dozen charges to the edge of the nearest borehole and invited them to peer down into the gloom. Far below the chamber, the darkness was relieved by four splotches of green and yellow light; clinging to rope ladders that ran the full height of the shaft, workers wreathed in vines were inspecting the hardstone cladding that lined the surrounding sunstone.

“When the engine is operating,” Yalda explained, “these holes will have been filled-in again, but liberator will be pouring down around the edges. If there are gaps in the cladding, the fuel could start burning in the wrong place.”

“This is the top layer of the rocket, isn’t it?” Doroteo asked.

“Yes.”

“So it won’t be in use for a very long time,” he pointed out.

“That’s true, and I’m sure it will be inspected again before it’s fired,” Yalda said. “But that’s no reason for us to neglect the job now.” Her ideal would have been to prepare every piece of machinery in the Peerless in such a way that the travelers would be able to turn around and come home safely whenever they wished—without requiring any new construction work, let alone any radical innovations. But given the current yield from the sunstone, this top layer of fuel would actually be burned away sometime during the decelerate-and-reverse phase, halfway through the journey. Relying on the status quo would not be an option.

Yalda led the group to a stairwell at the rim of the chamber, and they gazed up into its moss-lit heights. Four taut rope ladders ran down the center—installed early in the construction phase and retained in anticipation of weightlessness—but for now a more convenient mode of ascent involved the helical groove three strides deep that had been carved into the wall, its bottom surface tiered to form a spiral staircase.

“We’ll be climbing up four saunters here,” Yalda warned the group, “so please, take it carefully, and rest whenever you need to.”

Fatima said, “I don’t feel weak, but I’m getting hungry.”

“We’ll have lunch soon,” Yalda promised. Fatima was a solo, barely nine years old; Yalda felt anxious every time she looked at the girl. What kind of father would have let her travel alone across the wilderness, to enlist in a one-way trip into the void? But perhaps she’d lied to him in order to come here; perhaps he thought she was hunting for a co-stead in Zeugma.

The group was evenly split between couples and singles; the singles were all women, except for Nino. Yalda hadn’t interrogated Nino about his background, but she’d formed a hunch that he was that rare and shameful thing, a male runaway.

They began trudging slowly up the stairs; the pitch appeared to have been set to discourage running, should anyone have felt tempted. Their footsteps, and the whispered jokes of Assunta and Assunto up ahead, came back at them in multiple echoes from the underside of the stairs above. Beyond their own presence, Yalda could hear an assortment of odd percussive sounds, creaks and murmurs drifting down from higher levels. The workforce inside the mountain had fallen far below its peak, but it still numbered about a dozen gross, and most of the activity now was in the habitation high above the engines.

“Will the travelers be able to see the stars?” Fatima asked Yalda, trailing her by a couple of steps.

“Of course!” Yalda assured her, trying to dispel any notion that the Peerless would end up feeling like a flying dungeon. “There are observation chambers, with clearstone windows—and it will even be possible to go outside for short periods.”

“To stand in the void?” Fatima sounded skeptical, as if this were as fanciful as walking on the sun.

Yalda said, “I’ve been in a hypobaric chamber, as close to zero pressure as the pumps could produce. It feels a bit… tingly, but it’s not painful, and it’s not harmful if you don’t do it for too long.”

“Hmm.” Fatima was begrudgingly impressed. “And in the sky—will they be our stars, or the other stars?”

“That depends on the stage of the journey. Sometimes both will be visible. But I’ll talk about that with everyone later.” A moss-lit staircase wasn’t the place to start displaying four-space diagrams.

They emerged from the stairwell into a wide horizontal tunnel; this one ran all the way around the mountain, but the nearest junction was just a short walk ahead. Yalda offered no warning as to what lay around the corner; the light gave some clues, but the thing itself always took the uninitiated by surprise.

The chamber was no wider than the one below, but it was six times taller—and the broad stone columns supporting the arched ceiling were all but lost among the trees. High above their heads, but far below the treetops, giant violet flowers draped across a network of vines formed a fragmented canopy that divided the forest vertically. With no sunlight to guide their activity, these flowers had organized themselves into two populations with staggered diurnal rhythms, one group opening while the others were closed. Through the gaps left by the sagging, dormant blossoms, shafts of muted violet reflected back by the stone above revealed swirling dust and swooping insect throngs. Even the air moved differently here, driven by complex temperature gradients arising within the vegetation.