With the glider and the catapult blocking her view, Rosalind pictured the scene on the balcony, and judged the time. Too soon, and the act would seem abrupt and alarming, too late and people would start to worry that she’d lost her nerve.
But when the perfect moment came, she didn’t hesitate, she just kicked the release lever. The catapult’s response was too fast for her to analyze; she looked down past her feet and saw the tower below her, a needle of glinting ice that seemed to narrow down to nothing long before it touched the ground—and then even the top of it retreated into invisibility, leaving her with the gray disk of Tvíbura, and beyond its edge nothing but stars.
Above her, the nose of the glider limited her view, but she could see the world’s shadow just beginning to encroach on Tvíburi’s brightness. The progress of the eclipse would give her a sharper sense of time than the slower motion of the arcs of dawn and dusk; the shadow would come and go in slightly less than one seventh of a day, while her journey was predicted to take about one fifth. Until she hit the atmosphere, she would be part of the same majestic gravitational machinery as the twin worlds themselves, and unless the catapult had been egregiously misaligned or mis-calibrated, there would be no real uncertainty in her trajectory until the very end.
She was surprised at how calm she felt now. Once the tower had vanished, she’d had no cues to provide any sense of motion, and it would take a while yet for the tug of Tvíburi to add much to the catapult’s initial impetus. She glanced back down, hopeful for a moment that she might catch a glimpse of whoever had followed her, though she knew that was absurd. If they’d wanted to cheer each other with their presence along the way, they should have contrived some kind of massive, blazing lamp that could burn in the void, turning each traveler into a beacon for the rest.
In the void, the stars were only a little brighter than on the ground, but they were impossibly sharp, and their colors far clearer. Rosalind found it strange that they were all so much bluer than the sun, when they were thought to be suns themselves, perhaps with worlds of their own. But who would ever know that for sure? No telescope could reveal it, and no traveler could endure the journey it would take to find the truth firsthand.
Her mind turned to her mother, but behind the ache of separation she could still find reasons to be content. No one would let her mother starve, and even if a majority of the young people began to leave Tvíbura, having fewer mouths to feed would help make up for the dwindling harvests. The village councils had had generations to plan for the transition, and her mother still had many friends who would be staying behind with her. Tvíbura would not become a wasteland or a graveyard—not in her lifetime, maybe never at all. Let her see her daughter’s farm from afar before she died; that was all that Rosalind could hope to provide for her, but it would be no small thing.
By the time Tvíburi emerged from its twin’s shadow into full daylight, proximity had changed everything. Rosalind had lain beneath the telescope, night after night, sketching maps of this terrain—committing as many features as she could to memory, preparing for the time when she’d lose the luxury of an all-encompassing view. But even those meticulous acts of cartography had never quite made the land real to her, and to see it now with her naked eyes in more detail than the telescope had ever revealed made her feel as if a story that she’d cherished and learned by heart, but never taken to be more than an entertaining myth, was suddenly bursting out from the pages of a book and wrapping itself around her.
The gray mountains were taller, and far more numerous than those of Tvíbura, which suggested that the geysers had always been more active, piling up insanely high deposits of soil fast enough to outpace erosion and allow their own weight, and the passage of time, to solidify them into rock. But even the flatlands rose up from the ice, high enough to prove that they were being constantly replenished. People had argued that if the soil here was the same as Tvíbura’s, then the seeds that must surely have taken a ride on a geyser now and then would have left the twin world covered in grasslands, but Rosalind was not convinced. Even over the eons, the number of chances for a seed to have made the journey and land, undamaged, on anything but ice need not have been so great as to prove that the soil itself was inhospitable.
The storybook world expanded below her, with geysers and mountains retreating into the distance as the ice field commandeered the plot, preparing a thousand-page monologue detailing its every ridge and crack. Rosalind felt a prickling sensation on her skin. The glider itself was steady, but she could feel the panels growing warm around her back.
This was it: she was touching the atmosphere. And she was coming in fast enough for this rarefied upper layer to heat the glider, even before it delivered any perceptible force. She contemplated the gentle heat, refusing to let it alarm her. Joanna had taken her through the calculations: if every scrap of the difference in potential energy between the top of the tower and the surface of Tvíburi was used to raise the temperature of her body, the effect would be about the same as holding her hand a bit too close to a lamp for comfort. To be that hot for too long would be intolerable, then injurious, and eventually unsurvivable—but once there was any kind of wind to cool her, the actual heat she retained would start to fall short of that hypothetical limit. If she could have ensured that all the inflows and outflows of energy were averaged over the descent, she would have had a guarantee that she’d be fine. In reality, it would all be down to details of Tvíburi’s atmosphere that no one had known how to measure in advance.
Rosalind fixed her gaze on the ice, picturing the chilly weather below as the heat shifted from cheerful to unpleasant. The glider began to tremble, then pitch; it oscillated unsteadily, then settled with its nose toward the horizon, leaving her facing straight down. A thin, hot breeze flowed over her body; somehow she’d expected the wind to be cool, as if the air’s two roles were separable, and this merciful intervention would be like an independent bystander coming to her aid. But the truth was good enough: the balance was shifting, and as the hot wind blew more strongly, it also grew less fierce. As the air thickened, and slowed her more and more, it also had the capacity to absorb a greater share of the energy burden itself, and to carry more heat away.
Her view had shrunk to a region much smaller than any of her maps, but she’d retained a sense of the position of the landmarks that had gone out of sight, so she did not feel lost. As the ice field loomed toward her, she picked up lateral speed, flipping through the ever-expanding storybook, glossing over the details of the icy monologue, hoping to reach the end before dark. The air was merely warm now; she opened her throat and took a tentative breath. It was thicker than she’d expected, and carried a strange dusty aftertaste, but it seemed to satisfy her lungs. She waited a few moments, in case there was some delayed adverse reaction—as if her caution really mattered, when in the end she’d have no choice. But when she felt an unambiguous surge of energy spreading to her limbs, she inhaled again, deeply. The warmth and the strange smell made her cough, but the realization that Tvíburi seemed to be welcoming her filled her with equal parts elation, and shock at the stark reminder that the result could easily have been different.
The ice was a blur now, but the glider remained steady; Rosalind couldn’t recall a flight as calm as this. The thicker air could only react more forcefully to her encroachment, but apparently its greater density also helped dampen out turbulence. If the glider broke apart, it wasn’t going to do it in flight. Everything would depend on the landing.