Greg Egan: The Eternal Flame

Marzio’s children, Viviana and Viviano, maneuvered the beacon onto a trolley and began wheeling it toward the airlock. The device was built into a cubical frame of hardstone beams about two strides wide. Cylindrical tanks of powdered sunstone, liberator and compressed air were arranged around an open flare chamber, while all the pipes and clockwork were tucked away neatly behind clearstone panels.

Marzio followed his children, gesturing to Tamara to accompany him. Aside from the wheat fields this workshop had the largest floor in the Peerless —and spread out along its arc a dozen teams of instrument builders were assembling similar beacons. Groups of workers stopped to cheer as the trolley passed, celebrating their common cause.

Marzio said, “Don’t be too dismayed if something goes wrong. We’ll have plenty of opportunity to vary the design if we have to.”

“Unlike the Gnat .”

“Oh, the Gnat will be fine,” he promised her. “It’ll be carrying its own repair crew. The hardest thing to build is a machine that needs to function perfectly without any supervision—without the chance to make a single adjustment once it’s out of your hands.”

They reached the ramp leading down into the airlock. As Viviana and Viviano donned helmets and cooling bags, Tamara hung back, not wanting to interfere with their preparations. She was just a spectator here; the launch could go ahead with or without her.

Viviana raised the airlock door, standing aside to keep it open as her co wheeled the beacon into the chamber. Then she joined him inside, and the spring-loaded door slammed shut. Tamara watched them through the window as they worked the pumps.

“What could still go wrong?” she asked Marzio. “You’ve fixed the nozzle; the rest is just clockwork.”

“Clockwork in the void,” Marzio replied. “You might think it would simplify a machine’s behavior when there’s no air or gravity to contend with—but there’s still heat, there’s still friction, there’s still grit that can hang around to jam moving parts. Odd things can happen to surfaces that turn them unexpectedly sticky, or opaque. In fact a friend of mine has grown very excited over the way mirrorstone tarnishes in the absence of air.”

Tamara had heard about Carla’s discovery, but she didn’t think other physicists were taking it too seriously. “Some people can find patterns in anything,” she replied.

Viviana and Viviano were through the airlock now. Tamara walked down to the rack of cooling bags and selected one for herself. In her rear gaze she saw that Marzio hadn’t followed her.

“You’re not coming out to watch?”

“I’m an old man,” he said. “It makes me queasy.”

“To see the stars below you?”

“No, being in a cooling bag.”

“Oh.” Tamara found the fabric against her skin a bit irritating, but other than that the devices didn’t bother her. She climbed into the one she’d chosen, redistributed some flesh from her shoulders to her chest to accommodate its shape, then asked Marzio to check the fit before she attached the cylinder of air that would carry her body heat off into the void.

Once she was through the airlock, standing at the top of the exterior ramp, she pulled a safety harness from a slot beside her, checked that it was tied securely to the guide rail that ran along the side of the ramp, then stepped into the harness and cinched it tight.

Marzio’s children were further down the ramp, their harnesses tied to opposite rails so they wouldn’t get tangled in each other’s ropes. They had already cranked back the spring-loaded launch plate, and as they slid the beacon off its trolley and moved it into place the scraping sound came faintly through Tamara’s feet, almost overwhelmed by the reassuring susurration of air leaking from her cooling bag. When they’d finished she raised a hand in greeting, and they returned the gesture. The springs would help the beacon clear the ramp safely, but most of its velocity would come from the rotation of the Peerless . In less than a year it would be three gross separations away—by then, Tamara hoped, just one point in a huge, sparse grid of identical devices drifting out across the void, all flashing in a miserly but predictable fashion. Anyone could orient themselves by the stars, but knowing your position was something else entirely. The ancestors had had their sun and their sister worlds to help them navigate, but if the travelers wanted to leave the Peerless without losing their way they would have to create their own guiding lights, on a scale commensurate with their intended journey.

Viviana set the triggering time on the clock beside the launch plate. It was impossible to choose the beacon’s trajectory as precisely as they’d need to know it, but the timing of its launch would be enough to ensure that it was traveling in more or less the right direction. Viviano reached into the beacon and disengaged the safety lever, allowing sunstone and liberator to enter the flare chamber the next time the air valve was opened. Then they both moved back behind the plate, out of harm’s way.

Tamara watched by starlight as the launch clock’s three fastest dials spun toward the chosen alignment. The figures on her skin tingled with recognition just before the faint shudder of the springs reached her through the rock. The beacon shot clear of the ramp and plummeted out of sight. Tamara rushed forward to the edge and peered down, but the machine was already invisible, a speck of darkness lost among the star trails. She glanced back at the clock and pictured Roberto’s fingertips on the same dials spinning beside the observer’s bench: one hand following the time, one on the scope’s coordinate wheels. At the other end of the Peerless another colleague would be doing the same.

When the flash came Tamara raised an arm to cover her eyes, though the light was already fading before she’d moved a muscle. Powdered sunstone burned fast and bright; Roberto would have been using a filter, but the stab of light would have burned the measurements at his fingertips into his brain. Tamara was dazed and half-blinded, but now she could believe that the beacon’s light would be visible across the void, even through the Gnat ’s modest instruments—so long as nothing broke, nothing jammed, and no speck of orthogonal matter turned the machine into a fireball before the Gnat had even been launched.

There was no point waiting for the second flash; the rotation of the Peerless was tipping the ramp up, hiding the beacon behind her. But Roberto and his opposite number would have dozens of chances to repeat their measurements, triangulating a whole series of points along the beacon’s trajectory before the machine switched to its dormant state. After that, the next flash wouldn’t come until a stint before the Gnat ’s launch.

Viviana and Viviano were already headed back to the airlock with the empty trolley. Tamara stayed at the edge of the ramp, one hand around her safety rope, gauging its reassuring tension. She would not be embarking on a fool’s mission; they would not be going blindly into the void. Long before the journey began they would have wrapped the space around them in light, in geometry, in numbers.

The wheat-flowers were opening as Tamara strode along the path that ran down the middle of the farm, the limp gray sacs unfurling until the petals’ red glow filled the whole chamber, overpowering the moss-light from the walls and ceiling. A faint scent of smoke hung over the field but no sign of the burn-off was visible.

Tamara reached out to brush the plants’ yellow stalks with her fingertips. Though the crops rose and fell, the farm itself seemed ageless, unchangeable. But she remembered her grandfather telling her that in his own parents’ life-time the sheer wall of rock on her left had been a soil-covered field. There had been no low ceilings then, no second, third and fourth farms stacked above them; no one had planned for centrifugal gravity when they’d first carved these chambers out of the mountain. Tamara sometimes found herself scandalously wishing that it would be as long as possible before the engines were fired again, sparing any of her immediate descendants the tedious job of reconfiguring the farm for a second and third time. Or perhaps by then some brilliant agronomist would have boosted the crop yield to the point where everyone could live off stored grain for the whole reversal stage, and the farmers could take a three-year holiday.