Greg Egan - The Eternal Flame

“Maybe the influence doesn’t bother trying to cross species,” Macaria suggested. “Or maybe it did try early on, when we picked out the cages.”

Amanda said, “Load the recorder again. I’ll go and get a healthy vole.”

She returned a chime later with the bait, almost re-enacting Macaria’s entrance for the lizard experiment. These voles had not been bred apart, though; they’d all been raised together until the sick ones were removed, so any signal they exchanged now would not be due to a lack of familiarity.

When Carlo rewound the tape it was covered in dark bands. His skin crawled. This was it, right in front of him: a disease that could leap through the air from victim to victim as infrared light. The voles had merely been weakened, but there was a chance that the very same kind of pattern had pushed his father to the point of death.

“Why not ignore every code?” he asked. “Why would our bodies risk harming themselves?”

“The trade-off must be worth it,” Macaria said. “There must be beneficial traits circulating as well. The catch is, how do you know which is which without trying them out?”

Carlo said, “So… some traits we pick up don’t get expressed until the next generation. We come across a healthy-looking group of strangers, exchange advice with them in infrared, and try some of it out on our children. If everyone’s being honest, there’s a good chance that everyone benefits.”

“But then the system was hijacked,” Macaria conjectured. “Someone sent out a code that acted immediately on the recipient, forcing them to send out copies of itself. And maybe we developed some defenses against that… but it turned out to be advantageous not to shut off the process completely. We hijacked the hijacked system, at least enough to make it useful sometimes.”

“And all of it by chance.” Amanda buzzed softly. “No malice in it, or beneficence. Just accidental success.”

Carlo wound the tape back further, looking for the start of the sequence. If he could identify the part of the code that made an animal accept that the whole thing was worth trying, then cut that out and splice it onto instructions to the body to give birth to exactly two children… would that work? No one had ever reported an influence like that, but then, even if such a sequence had come into existence there’d be no reason to expect it to persist. What could be found in nature would be a tiny subset of what was biologically possible.

He reached the start, and examined the innocent-looking stripes. Do whatever follows —was it as simple as that? No doubt some voles had learned to ignore this particular directive, but for those who had succumbed it was apparently as hard to resist as the patterns passed down through their own flesh.

Carlo said, “We need to keep studying this process in voles, but their biology is still too distant from our own. We should use them whenever we need a short breeding cycle, but their bodies are so small that the internal signals are always going to be hard to collect.”

Amanda said, “Lizards don’t grow much larger, and we have even less in common with them.”

“I know.” Carlo glanced at the vole she’d brought in; it was already looking subdued as its body followed the instructions imposed on it. “We need to scale things up, and move closer on the family tree. We need to go and capture some arborines.”

30

“Mirror balls,” Tamara told Marzio, unrolling the plans across his desk. “Take a sphere, and cover it with small, planar mirrors. That’s it: no fuel to replace, no moving parts, nothing to align or orient. All we need to do is get enough of these in position while the old beacons are still visible, then we can set up the whole grid using nothing but the Gnat .”

Marzio looked over the sketches. “You do recall that mirrors tarnish faster in the void?”

“We haven’t forgotten,” Ada replied. “But we’ll only be illuminating these things for a tiny fraction of the time they’re out there. When they’re in use we can limit it to periodic flashes—longer than the old sunstone ignitions, so they’re harder to miss, but pulsed, so the total exposure time for the mirrors is less. And when nobody’s flying we’ll just shut down the beams completely.”

“What’s more,” Tamara added, “if Carla gives us a choice of frequencies we can opt for something at the blue end of the spectrum. That will cut the tarnishing rate even more. If we can get the drift speed low enough, these things could be in service for generations.”

“Hmm.” Marzio still didn’t seem happy. Tamara suspected that he found the new design almost insultingly simple; the old beacons had been triumphs of precision engineering, but now she was asking him to supervise the gluing of reflective shards onto a gross of identical spheres.

“The real challenge will be keeping the beams on target,” Tamara reminded him. If the beacons themselves looked like toys, the machinery required to illuminate them would still demand the skills of a master instrument builder. “But we can’t make much progress on that until we have a prototype of the light source.”

“No.” Marzio smoothed the sheet and pointed to the core of the sphere that Tamara had drawn in the dissected view. “The choice of materials here is going to be crucial, if you want the mirrors to survive a couple of generations without air cooling.”

“Right.” Despite their lack of moving parts, the beacons would gradually gain thermal energy from purely optical effects. But it would be better to give the spheres enough heat capacity to slow their rise in temperature than to add the unwelcome complication of an active cooling system.

Marzio said, “Leave this with me, let me think about it.”

Halfway back to the observatory, Ada turned to Tamara. “If you’ve got time, we should make a detour here. There’s someone I’d like you to meet.”

Tamara understood her meaning immediately. “You could have warned me,” she protested.

“And given you the chance to think up an excuse?” Ada teased her. “You didn’t object when my father offered to make enquiries for you. You can’t say this has come as a surprise.”

“I was only being polite to Pio,” Tamara said. “I never thought he’d actually find someone.”

“Your father found Tamaro a co-stead, and they’re both in prison.”

“Tamaro has an entitlement.”

“And Livio has an entitlement,” Ada replied. “Not all widowers give up and sell them.”

“No—the smart ones find widows with entitlements of their own, then they sell the spare one when the children are born.” Ada was already leading them down a side corridor; escape was looking increasingly unlikely. “What does this Livio do?”

“Masonry. Construction and repairs. Actually, he was in the crew that built the airlock for the Gnat .” Ada hesitated, then added jokingly, “So he’s hardly a stranger. You already have that connection.”

Tamara didn’t reply. She and Tamaro had been raised side by side from birth, expecting to remain together to the end. No arrangement of convenience with a co-stead could replace that. Whether or not Tamaro’s betrayal proved that she’d been fooling herself all along about the nature of their bond, she would never feel as close to anyone again.

Ada navigated the way to the masonry workshop, far enough from the axis for gravity to keep the dust under control. Tamara was relieved to find that her suitor hadn’t contrived to meet her on his own; half a dozen people were busy in the workshop, shaping and polishing blocks of calmstone.

Ada approached one of them, a short, robust-looking man. He shut off his grinding wheel and removed his safety visor.