The Eternal Flame

last career. But if you really believe you have the patience to carry this through—”

“I’m certain of that,” Carlo insisted.

Tosco looked skeptical, but he was done with arguing. He said, “How can I turn down an agronomist who’s willing to step off his pedestal and rejoin his old friends?”

It was Carlo’s turn to travel down the axis, to meet his co in the new home she’d made for herself. Most of his friends had told him that a partial separation sounded like the worst of both worlds, but he’d studied the numbers from the last census. Total separation was a bad idea: it left women at an elevated risk of spontaneous fission, and no amount of holin could eliminate that entirely. But living together and relying on willpower alone to delay reproduction was even worse; more than half the recorded births in those circumstances had come earlier than planned. The trick was to let your co’s body know that you hadn’t abandoned her—that if it waited, her children would be cared for—while doing all you could to minimize the risk of delivering on that promise prematurely.

Carla wasn’t home when he arrived at the apartment. The moss-light was enough for him to see his way around, so he didn’t light a lamp. He’d brought four loaves for them to share, for the evening meal and breakfast; he packed them away in the empty cupboard.

Passing the entrance to the bedroom, he saw a spare tarpaulin floating in the air, suspended against the weak gravity by a faint updraft from a cooling vent.

When he heard the guide rope twanging in the corridor he went to the doorway and parted the curtains. Carla saw him and chirped excitedly. “Get ready to hear some good news,” she said.

“What—you’ve won a place on the Gnat?”

“That would be something.” She followed him back into the apartment. “But this is better.”

Carlo lit a lamp in the front room, then clung to the rope beside her as she described her tarnishing experiment. She’d had to refresh his hazy memories of Nereo’s force and Yalda’s puzzles countless times before, so he knew she’d forgive him if he didn’t immediately grasp the significance of the results.

“Five to four,” he said. “What’s so special about that?”

“A ratio of small integers isn’t likely to be a coincidence,” Carla replied. “If it was dozens and something to dozens and something else, that would be meaningless, but this suggests very strongly that the numbers in the ratio really are lurking in the physics itself. Four of something, then five of something… the transitions mark a kind of succession.”

Carlo could only understand physics by translating it into geometry; he started raising undulating lines on his chest. “So can I draw it like this, fitting different numbers of cycles into the same amount of time?”

“No, no, no!” Carla chided him. “You’ve got it backward!”

“What’s wrong?” he asked. “Doesn’t that give a five to four frequency ratio?”

“It does,” she conceded. “But I’m working on the assumption that the frequency goes down as the associated integer goes up, and you’ve described the opposite trend. Going your way, there’d be another transition at a higher frequency—‘frequency six’, out in the infrared—beyond which mirrors would start tarnishing at an even greater rate. The trouble with that is, if the pattern in tarnishing rates held up then Marzio’s mirrors would have needed re-polishing after a couple of stints, not a couple of years.”

“All right,” Carlo said. “So how should I picture it?”

“I don’t know yet,” Carla admitted. “All I can say is that light produces a strong tarnishing effect when four times the frequency exceeds a certain number. When the frequency falls so low that you need to multiply it by five to meet the same target, the effect suddenly becomes drastically weaker—and when you need to multiply it by six, it becomes weaker still. It might even vanish entirely at that point; I’d need to do a much longer exposure to be sure.”

Carlo pondered this. “Wouldn’t it be easier to follow the pattern in the other direction? If the effect grows weaker as the magic number goes from four to five to six… what about three? Shouldn’t you get super-fast tarnishing from waves where you can reach the target merely by tripling the frequency?”

“There are no such waves,” Carla replied. “The target is more than three times the maximum frequency of light, so you can never reach it by tripling.”

“Aha.” Carlo had a glimmer of comprehension. “Which is a good thing for mirrorstone, isn’t it? If it was that easy to damage, it probably wouldn’t be around at all.”

“Exactly!” Carla’s eyes widened with pleasure. “Whatever’s going on here, it’s showing us the border of stability. And maybe every mineral, every solid, has its own ‘target number’ like this—but in the case of something like hardstone, it could be so high that even six times the maximum frequency of light doesn’t reach it.”

Carlo said, “The empirical rule sounds simple enough. I suppose the hard part will be making it mesh with the theory—with Nereo’s equation and the luxagen model?”

“Yes.”

“And…?” he prompted her.

“And right now,” she admitted, “I have no idea how to do that.”

Carlo told her about his meeting with Tosco. He’d given her no warning of his plan to return to the animal physiology group—and he offered no justification now, but he watched her face as he spoke. Carla listened politely, in silence, but she almost flinched when he reached the point of describing his new research program. And this was from the subject in its most abstract, impersonal form: comparing biparous and quadraparous fission, hunting for the mechanism that allowed some species to switch between the two.

He understood why it was painful for her to hear. Behind these calm career announcements he was whispering a promise that he had no right to make: I’ll find a way out of the famine—if not for you, for our daughter. He had no right, because people had tried and failed before: countless women driven by hunger, countless men driven by the suffering they’d seen. There was a terrible equilibrium now, and an unspoken consensus that the only real option was to cling to their hard-won resilience and endure what had to be endured.

Carlo couldn’t live like that any more, but he understood that he had to follow this new path quietly, making it as easy as possible for everyone around him to avert their gaze. When he’d said all he needed to say for the sake of honesty, he steered the conversation back to the mysteries of light and matter. Failure there might leave them stranded, doom their whole mission and kill off all their ancestors—but at least they hadn’t been cursed with some wretched half-solution that sapped their resolve and kept them from reaching the real thing.

5

“Lizard skin?” Tamara asked incredulously.

“Lizard skin,” Ivo confirmed. “The jungle has its uses.”

“Is that where you go looking, when nothing else works?”

Ivo said, “That depends on what I’m after. When people think of light they usually think of flowers, but most animal tissues have some kind of optical activity too.”

Tamara managed a murmur of concurrence, as if the first course of action that anyone should consider when faced with the need to find a new chemical would be to pop a lizard in a centrifuge and see what oozed out.

“What kind of wavelengths are we talking about? What kind of sensitivity?”

“Come and see for yourself.” Ivo led her deeper into the chemists’ domain, four hands shuttling him swiftly along the guide rope.

As they moved down the center of the cylindrical chamber, Tamara watched his colleagues at work around them. Most were harnessed to benches fixed to the walls, or were attending to various spinning or vibrating contraptions, but one eight-armed chemist was blithely floating in mid-air as he snatched vials of reagents from a weightless cluster in front of him, mixing the contents in a dizzyingly rapid sequence that Tamara could only assume