Fatima entered the airlock and began working the pump energetically, bracing herself with three hands against the clearstone walls.
By the time Yalda was through onto the slope, Fatima and the rest of the team were already out of sight. Yalda swung herself between the guide rails and set off down the mountain, moving briskly but always keeping at least two hands on the rails. In the absence of gravity she ought to have been oblivious to the gradient of the slope, but the rim of the inverted bowl of garish color trails above her matched the old horizon perfectly, making it impossible to think of the ground as level.
The new horizon was a dazzling, multicolored circle where the fastest ultraviolet light from the old stars was shifted to visible frequencies before giving way abruptly to blackness. Straight ahead of her—“downhill”—the more modest trails of the orthogonal cluster shone sedately. Away from the guide rails, silhouetted in the starlight, dead trees sprawled at odd angles. Notwithstanding the high altitudes to which they’d been accustomed, their roots had not been enough to keep them cool in the complete absence of air. Patches of red moss had colonized the deadwood, but its faint light suggested that it was struggling.
A few saunters from the airlock, Yalda reached the pit. Lamplight from deep within the tunnel shimmered off the dust emerging from its mouth. At first glance it was easy for a planet-trained eye to see these motes as being borne on some kind of breeze, but then the thumb-sized fragments of rock scattered among the specks—moving more slowly, but just as freely—put an end to that illusion. Nothing was propelling the dust; it was flowing out of the tunnel for no other reason than its own chance collisions, inexorably driving it to occupy more space.
The guide rails, dating from before the launch, ran right past the tunnel’s entrance but couldn’t take her in. Yalda shifted her grip to a pair of ropes anchored to a series of wooden posts that veered off into the light. The floor of the tunnel sloped gently down into the rock; it was another half saunter before the roof was above her.
The haze of dust and grit thickened. When Yalda gripped the rope close to the posts, she could feel the vibration of the jackhammers. When she raised her hand, backlit motes of rock swirled away from it, driven by the air slowly escaping through the fabric. Fatima was right to be dissatisfied; it was a crude business when the only way they could cool themselves was to throw warm air away.
Gradually the rock face came into view, ringed by blazing sunstone lamps. Seven members of the team were working it with jackhammers, braced against the rock within their cages. Three taut guy ropes ran from the top of each cage to the tunnel wall, holding worker and cage in place against the tool’s relentless kick. Yalda had done that bone-shaking job for two stints, and then finally conceded that she was past it.
Four other workers were moving between the cages, clinging to the guy ropes and dragging the open mouths of their rubble sacks over the fragments of broken rock that were bouncing away from the hammers. It was impossible to scoop up all the debris, but their efforts kept the workspace more or less navigable.
Fatima spotted Yalda and waved to her, then turned her attention back to the rubble she was chasing. With the cooling bags covering everyone’s skin, communication was reduced to glances and hand gestures. If you brushed against someone you could exchange a few muffled words, but mostly the shifts were spent in a kind of tacit camaraderie, where the rhythms of the work itself—shifting the hammer cages, re-pinning the guy ropes—had to take the place of friendly banter.
There were already two full sacks waiting to be removed, the drawstrings at the top pulled closed and used to tie them to hooks on a pulley line that ran the full height of the tunnel. Yalda dragged the line around to bring the sacks within reach, slipped their drawstrings over her shoulders, then set off back to the mouth of the tunnel.
The catapult sat on the other side of the guide rails. Yalda put the rubble sacks on holding hooks at the side of the machine, grasped a nearby support post with her two left hands, then started turning the crank that ratcheted the catapult’s launching plate back along its rails, stretching a set of springs below. As the crank began stiffening its resistance, she could feel the support post working itself loose from the ground. Cursing, she shifted her lower hands to the catapult, dug a mallet out of the tool hold, and bashed the support post half a dozen times.
Yalda checked the post; it felt secure now. But as she bent to put the mallet back in the hold, she could feel a tiny rocking motion in the catapult itself: she’d managed to loosen some of the tapered wooden pegs that held its base against the ground.
Never mind; she’d deal with that later. She swung the first sack onto the launching plate, checked that it was properly closed and sitting squarely on the plate, then reached down and released the catch. The plate shot up a full stride before the springs stopped it, leaving the whole machine reverberating. The sack continued on, gliding away smoothly into the void. Yalda had had her qualms about disposing of the rock this way; who knew what demands their descendants might have for even the most mundane materials? But the effort that would have been needed to secure the rubble on the slopes—let alone cycle it all through the airlocks and stash it somewhere inside the mountain—was more than they could spare.
She launched the second sack into oblivion, then headed back down the tunnel.
The haze was growing thicker. Two of the hammers had hit a lode of powderstone, which left no solid pieces to collect and just wafted out like smoke, coating everyone’s faceplates with gray dust.
Four more sacks were waiting on the pulley line. Yalda brought down two of them, then paused to wipe her helmet clean and squint up at the rock face. The crumbling powderstone was a nuisance, but it would speed progress. Once the main excavation was completed, half a dozen small feed chambers would be constructed behind the rock face, accessible through a separate tunnel leading straight up to the surface. Apart from Benedetta’s probes, this would be their first real test of an engine that wasn’t gravity-fed, with the liberator pushed through the fuel by compressed air. Yalda was already feeling anxious about that, but in some ways the test would be forgiving. The geometry of the engine placement would be the most important thing; small variations in the thrust wouldn’t be critical.
She slogged her way back out to the catapult. As she cranked it, the support post she was holding came loose again. She fumbled for the mallet—the simple task of retrieving it made harder by the streaks of gray powder still stubbornly clinging to her faceplate—then she realized that one of the sacks was actually blocking the front of the tool hold, so she shifted it onto the launching plate. Then she gripped the base of the catapult with her lower pair of hands to brace herself, and started bashing the support post.
Yalda was upside-down and two strides above the ground before she felt the tightness around her lower wrist; she dropped the mallet and reached down frantically toward the catapult, but it was already too late to grab any part of it. With her rear gaze she stared up at the sack’s drawstring, twisted around her hand. She must have left the drawstring protruding from the side of the launching plate, and then slipped her arm through its loop.
Her first, idiotic, impulse was simply to disentangle herself from the sack—as if it alone were the cause of all her problems, and if only she were free of it she’d drift gently back to the ground. Her next thought was to pull it closer to her body, which she did. Then she freed her wrist from the string and clutched the coarse fabric of the sack against her chest, but she managed to stop herself from completing the plan: tossing the sack upward in order to propel herself back toward the mountain. Her instinctive sense that this tactic ought to work was almost overpowering; had she been stranded in the middle of a chamber inside the Peerless, it would certainly have done the trick. But even if she’d pushed the sack away with all the strength in her four arms—even if she’d burst the seams of her cooling bag and extruded two more—it would not have been enough. She knew how long she’d labored to turn the crank on the catapult, how much energy she’d put into the springs. A single burst of effort couldn’t match that. And a partial victory that merely slowed her ascent would be completely useless, if in the process she lost the means to do anything more.
Yalda glanced back at the receding light from the tunnel mouth. If she panicked and acted without thinking, she was dead. Her rapidly increasing distance from the ground was terrifying, but it was not her real enemy. It didn’t matter how long it took her to reverse direction; once she was headed back to safety, the length of her trip would be irrelevant. Or very nearly so: the sole criterion was that she needed to return before her air canister ran out—and it held enough for an entire six-bell shift.
Could the canister itself help? She ran a hand over its cool surface, imagining a swift burst of air that would send her hurtling down to safety. But without any tools, she doubted she could break open the valve that limited the outflow—and even if she could, the momentum of the entire contents might not be sufficient for the task. What’s more, a marginal success would make a lie of her indifference to distance; if she ended up drifting slowly back toward the ground, without cooling she could easily die of hyperthermia on the way. There were a dozen replacement canisters in the catapult’s tool hold, but did she really want to smash this one open and gamble on reaching the others in time?
No air rocket, then. All she had for exhaust was the rubble in the sack, and all she had to propel it was her own strength. But the catapult had put her in this plight using nothing but stored muscle power; if she parceled out the rubble in a manner that allowed her to expend more energy on this task than she had on turning the crank, she should be able to reverse the consequences.
Her body’s slow spin had her facing back down toward the light from the tunnel again. Her fellow workers would certainly miss her as the rubble sacks began filling up the pulley line, but they would not be in a rush to come looking for her; she could easily have spent all this time on minor repairs to the catapult. The rock face was where serious accidents happened; what kind of fool managed to shoot herself into the void? But whenever they did start to worry about her absence, she could forget about anyone throwing her a rope; she was already too far away for that.
No matter; if she stayed calm, she could fix this. She identified the point on the star-trail horizon that, as near as she could tell, marked the direction in which she was traveling: precisely opposite the shrinking patch of light on the ground. She loosened the drawstring and opened the sack a little, fearful of spilling the contents with her jostling, then reached in and took out a handful of rubble. She waited for her rotation to bring the target in front of her again; she wasn’t going to try to reconfigure her flesh to give equal strength to a backward throw. Then she brought back her arm and flung the handful of rock away with all her strength.
The effort felt puny and ineffectual—and she suddenly realized that in her haste and agitation she’d been laboring under yet another delusion. If she threw a heavy object, like the whole sack of rubble, the energy she put into it would be limited by the maximum force her muscles could apply. If she divided the sack in two and threw each half separately, the same force would let her throw a half-sack faster than a whole one, transferring as much energy to each half as she would have used on the whole.
Two throws, twice as much energy—hooray! But two throws would still not be enough, so why not four throws, a dozen, a gross, taking her time but increasing the total energy as much as she needed? That was what she’d been thinking: matching the energy she’d put into the catapult would simply be a matter of eking out the rubble with sufficient care.
But the pattern of throwing ever smaller weights ever faster only held true up to a point—for a half-sack, yes, but not for a handful of pebbles. By that point, the limiting factor would be the speed at which her muscles could contract, not the force they could apply. And when the speed was fixed, the energy she could put into a given quantity of rubble became proportional to its mass—which meant that it would add up to the same total, regardless of how many separate throws she made.
It didn’t matter how much strength she still had in her body; it didn’t matter that she could have cranked that catapult ten dozen more times without tiring. Her fate was completely determined by the total mass of rock in the sack, and the speed at which she could throw, not the greatest load, but the smallest.
Yalda looked back at the mountain. She could see three other worksites now, the bright mouths of tunnels further down the slope. But her trajectory was carrying her off to the side, and an expanse of dark rock was now spread out below her. There was an entire second line of worksites a half-turn around the mountain; the full set of engines would consist of a dozen diametrically opposite pairs. But if any of those sites came into view she’d know that something was wrong—that she’d been misdirecting her throws and inadvertently bending her trajectory.
She took another handful of rubble from the sack, waited for the target, then threw it. Her spin provided a rhythm for the process, giving her a chance to rest her arm without delaying the next throw too long. After a dozen cycles, she switched arms. She couldn’t extrude any new limbs without damaging her cooling bag, but although she felt some jarring at the end of each throw it didn’t build up to enough pain or damage to slow her down.
What she could have done with, though, was a good slingshot.
Yalda could see ten of the worksites now, with the remaining two from her side of the mountain probably just hidden behind small outcrops. All these engines would be completed, with or without her. The Peerless would get its spin, the crops would thrive once more. The real purpose of their journey would soon come to the fore again. Sabino had opened up a path that the brightest young students—Fatima, Ausilia and Prospera—would follow. Her death would not mean the end of anything.
And Nino? She cut off the morbid train of thought. The rubble sack was still more than half-full, her situation had not yet been proved unsalvageable.
As she threw another handful of rubble, she saw a flash of light in her rear gaze. She tried to place it exactly, to backtrack from the afterimage, but her spin confused her. Had she glimpsed one of the other worksites, the lights from its tunnel peeking briefly over the edge of the mountain? It had been too bright for that, hadn’t it? The tunnel mouths all faced the same way around the mountain—so those at the other worksites would be pointing away from her. The most she could have seen was the spill of light from the ground near the pit, and the scatter in the dust haze. How could that have outshone the sites where she was facing straight into the tunnels?
A few turns later, she was facing the mountain when she saw a second flash: far from any of the worksites, surrounded by blackness. She wondered if someone might have lit a sunstone lamp inside one of the observation chambers—but why would they do such a thing, let alone light it only for an instant?
The third flash was at a different location, still nowhere near any worksite—and too brief and too bright, Yalda concluded, to be an artificial source at all. Something must have collided with the Peerless—something small that nevertheless carried enough energy to turn the rock white-hot.
The telescopes had shown a corridor devoid of matter, but there’d been a limit to the sensitivity of those observations. Any speck of dust here, drifting along at a leisurely rate relative to the ordinary stars, would now be like a Hurtler to the Peerless. That was the price of taming the Hurtlers by matching their pace: ordinary dust could now do as much damage to the mountain as a Hurtler could do to an ordinary world.
So much for the city of carefree scholars, working in safety and tranquility until the secrets of the cosmos were laid bare to them. Just like the people they’d left behind, they would be living with the constant threat of conflagration. And not for four years: for generations.
Worst of all, Yalda realized, she was probably the sole witness to these events. The dust could have been striking the mountain for days, but most of the surface was invisible from the worksites and observation chambers. She had to get back and organize a fire watch for the Peerless; they had to prepare themselves to reach and douse a wildfire anywhere on the slopes, or risk going the way of Gemma.
Yalda cast another few stones—imagining them heavier in the hope of tricking her body into dispensing a little more force. The sack was a quarter full. She believed she was still heading away from the mountain, but judging tiny changes in the view at this distance was almost impossible.
How could they keep a lookout for fires? From a cage tethered on a rope, high above the surface, stabilized… somehow. Once the mountain was spinning, though, the problem wouldn’t be stability, but the strength of the rope.
And once the mountain was spinning, it would be far harder to move around on the surface. Weightlessness had made it difficult enough, but every part of the slope would be transformed into a ceiling. How did you douse a raging fire on a ceiling?
The sack was empty. Yalda clutched it to her chest, unwilling to presume that she’d have no further use for it. Was she moving toward the mountain, or away from it? For some time now, she hadn’t discerned any change in the angle it occupied in the sky, but she’d been too distracted to give the task much thought. She needed to pick a few distinctive stars close to the edge of the mountain, then wait to see if they crept away from it, or whether its silhouette slowly grew and hid them.
Yet another flash of light came from the mountain, this one very close to one of the worksites. Perhaps someone there, outside the tunnel on catapult duty, would have seen it? Yalda counted the pit-lights down from the summit, and realized that the site was her own.
The light winked again, from exactly the same direction. Not an impact, then. By now, she realized, her team would be out scouring the area for her, their sunstone lamps occasionally turning up into the sky. Yalda pictured them inspecting the catapult, feeling how loose it was, wondering if anyone could possibly have been careless enough—
The same light appeared, brighter than before, crossing her line of sight so slowly that it dazzled her. When she completed a half-turn it struck her rear gaze and stayed—wandering a little, but never fading out completely.
The lamp wasn’t on the surface of the mountain; it was moving straight toward her through the void. And it couldn’t be aiming itself, searching her out itself.
Yalda spread the empty sack out in front of her, hoping to make a larger, more reflective target. The approaching light began wavering oddly, as if seen through a heat haze. Through a burst of air, spreading out through the void. Some beautiful idiot had come after her—launched along the same trajectory by the catapult—and now they were using compressed air to brake. Not from a tiny canister like her own, but from one of the giant cylinders that powered the jackhammers.
The dazzling light overshot her, passing to one side. It rebounded, then overshot in the other direction. It was excruciating, but Yalda could do nothing to meet her rescuer halfway. By trial and error, by eye and airburst alone, the distance and difference in speed that separated them was whittled down to the point where the lamp became superfluous and its owner shut it down. No longer blinded by its glare, by starlight alone Yalda could see the figure before her, clutching an air tank and a coil of rope, wrapped in a familiar cooling bag.