The Eternal Flame

everyone all right?” she asked. Ada, Carla and Ivo responded in turn, their hesitation sounding more like diligence than a lack of confidence: the answer was too important to be given without a pause or two of mental and physical self-inventory.

Tamara took hold of the guide rope beside her couch and dragged herself toward the center of the cabin, where the three mutually orthogonal ropes, offset slightly, didn’t quite meet. She opened her dark-adapted rear eyes; the view they added was so much crisper than the gray shadows in front of her that it felt as if she had a lantern strapped to the back of her head. She could see her fellow crew members clearly now; Ada had taken off her helmet, and Carla was in the process of doing so. The bright horizon line of the home cluster’s stars shone through the windows, its hoop tilted satisfyingly against the Gnat’s axis. That small geometric hint alone told her that they were not wildly off-course: it was unlikely that any serious mishap with the engines could have left the craft so close to its expected orientation.

“No pain, no dizziness, no hearing problems?” she asked.

“I’m fine,” Ada replied, propelling herself with her legs from the couch. She drifted across the cabin before grabbing one of the transverse guide ropes.

“I am too,” Carla said. Ivo took off his helmet before responding, “My right shoulder’s a bit sore. I think my arm got pinned in an awkward position when the engines fired. It’s not even worth resorbing though; a short rest will fix it.”

Tamara wasn’t too worried; Ivo’s age left him more vulnerable than the rest of them, but this sounded no more serious than the twinges he’d owned up to after the most strenuous of the safety drills. Resorbing and re- extruding a limb was difficult without removing your cooling bag, and though the cabin’s air was cooling them perfectly well, the ideal was to keep the bags on at all times in case there was an unexpected breach.

She said, “Ivo, I want you resting for the next six bells, but when Carla’s checked her own equipment you should talk her through the checks on your own.”

“Right,” Ivo agreed.

Tamara dragged herself away from the center of the cabin and took her place beside one set of theodolites, mounted within the polyhedral dome of a window. Ada, at the opposite window, had her own duplicate instruments, including a separate clock. Tamara began with some star measurements, establishing the Gnat’s orientation precisely, then she aimed the theodolite with the widest field in the direction where she expected to sight the next scheduled flash from a beacon.

“If we had sufficiently accurate clocks,” Carla mused, “we could find our distance from each beacon using the time it takes for the light to reach us.”

Tamara buzzed with mirth. “Accurate to what, a piccolo-pause? While you’re at it, why not use the geometric frequency shift to compute our velocity?”

“Who knows?” Ada interjected. “If people end up shuttling back and forth between the Peerless and the Object, do you think they’ll still be navigating like this after a dozen generations?”

“There’s only so much you can do to make a clock keep better time,” Tamara replied. “We’re already close to the limits of engineering.”

“But nature’s full of systems with their own rapid, regular cycles,” Carla countered. “Light itself, among others.”

“Very practical,” Tamara retorted. “Once you filter out a single pure hue from a lamp, the beam will still be made up of lots of short wave trains: a few cycles at a time, all with random phases compared to each other. Even if you had some way to count the cycles, it would be like listening for the ticking from a vast heap of clocks that started up at random moments, ran for a few pauses and then died.”

“That’s true,” Carla said. “But why not look for better ways to use the same clocks? The light given off by tarnishing mirrorstone as it spits out each luxagen ought to be in phase with the light that stimulated the emission in the first place. If you bounced that emitted light back onto the mirrorstone, looping the whole process around, you might be able to build a source that remained in phase over much longer periods than any kind of natural light.”

“Light that elicits light that elicits still more light?” Ada joked. “That’s starting to sound like the Eternal Flame.”

“Not so eternal,” Carla said ruefully. “The tarnishing would use up the mirrorstone just as surely as any flame consumes its fuel.”

“And you count the cycles… how?” Tamara pressed her.

Carla said, “I’ll have to get back to you on that.”

Tamara felt the dials at her fingertips reach the configuration she’d been waiting for. The beacon’s flash came a moment later—almost certainly from her own clock running slightly fast. But this wasn’t Carla’s brave new world yet, and it was the position of the beacon against the stars that mattered most, not the timing. She recorded the angles on her forearm, then turned the theodolite toward her second target.

“First sighting acquired,” she announced. “Well within the expected region.”

Ivo hummed with pain. “I’m sorry, I’m going to have to take the bag off. Just partly, along the right side.”

Tamara said, “Carla, can you assist him?”

“Of course.”

Tamara watched them without leaving her post. It was a simple enough maneuver, and even if the Gnat chose this moment to split apart and spill them all into the void, Ivo would still have his bag, helmet and two air cylinders with him like the rest of them.

Ivo chirped with relief as he resorbed his right arm, then he spent a lapse rearranging the flesh internally before extruding a new limb. Carla helped him refit it to the bag, running some air through as a test.

“Thank you,” Ivo said. “I think I can check the equipment myself now.”

“There’s no pain at all?” Tamara asked him.

“None. The new arm’s perfect.”

“All right.” With anyone else she wouldn’t have fretted over such a minor injury, but Ivo’s dexterity would soon be crucial.

Tamara turned back to the theodolite in time to catch the flash of another beacon. “Second sighting acquired,” she said. “Within the expected region.” Each flash, observed against the background of the stars, placed the Gnat on a line that passed through the beacon in question. Had the craft been stationary it could have been pinned down at the intersection of two such lines, but even in motion three sightings would be enough to determine its trajectory, and any more would improve the accuracy of the solution. That was assuming that all the errors in the measurements were random, but she and Ada could compare their results as a check against any systematic bias.

“Still nothing?” Tamara asked Ada, puzzled that her co-navigator had yet to report a single sighting. Each beacon only flashed once a bell, but the times were staggered so that one beacon or another was visible every lapse.

“Either my first target’s died, or something on the window obscured it,” Ada explained.

“Why didn’t you tell me?” Tamara was confused. They needed to communicate everything clearly, but Ada knew that perfectly well. In all of the drills, she’d been scrupulous.

“Ivo was telling us about his injuries, I didn’t want to interrupt him.”

“But once he’d stopped—”

“I know,” Ada said. “I apologize.” Her tone was even, with no trace of resentment, but Tamara still felt awkward to be reprimanding her.

There were contingency plans for all the observations to be performed out on the hull if there was serious damage to the windows from an encounter with orthogonal dust, but that was an extreme measure that would make the whole procedure much more arduous. Stray particles from the Gnat’s own exhaust might have left a smattering of subtle defects in the clearstone, but Tamara had never really thought through the proper response to such a minor vitiation.

“Once we’ve finished with the beacons, we should do a systematic check for pitting,” she decided.

“Good idea,” Ada said. A moment later she added, “Ah, first sighting acquired! Within the expected region.”