Greg Egan - The Eternal Flame

“Not entirely,” Carla agreed. “The bulk of the wave lies in the part of the valley where a particle with the same energy would be rolling back and forth—but at the point where the particle would come to a halt and move back toward the center, the wave doesn’t instantly drop to zero. It just becomes weaker as you follow it out past that point.”

She sketched an illustration, but no one could see it clearly in the starlight so Tamara lit a small lantern and aimed the beam at Carla’s chest.

“And the same is true for a luxagen outside the valley, trying to get in?” Ivo wondered. “The energy ridge around the top of the valley won’t keep out a luxagen wave entirely—even if that ridge would be insurmountable to a particle with the same energy?”

“Right,” Carla said. “Energy barriers aren’t absolute for these waves, the way they are for particles.”

Ivo chewed on his loaf for a while, thinking this over. “Then why are solids stable under pressure?”

“Under pressure?”

“You’ve solved the original stability problem,” Ivo said. “You’ve explained why luxagens in a solid don’t gain energy by radiating, which would blow the whole structure apart. But there’s another problem now: if you squeeze a solid hard enough, why doesn’t it collapse? With the old particle mechanics you could expect the energy ridge between two valleys to keep the neighboring luxagens out. But if a luxagen wave has some probability of getting past that ridge, then over time, under pressure, shouldn’t the luxagens be squeezed together into fewer and fewer valleys? Shouldn’t the rock at the center of every world end up as a tiny, dense core too small to see?”

Carla said, “If you pack more luxagens into each valley, the ridges grow higher, making it harder for the waves to get past them. But the valleys do grow deeper as well, which will help to draw the waves in. I’m not sure if those two effects balance out…”

“And the gravitational pressure grows stronger, as the rock becomes more dense,” Ivo added.

“Yes. So it’s complicated. Let me do some calculations when we get back to the Peerless .”

“Hmm.” Ivo seemed pleased that Carla had no immediate answer to his puzzle. “And in spite of all these new ideas, the power of orthogonal matter to act as a liberator remains as mysterious as ever.”

“It does.” Carla was beginning to sound a bit besieged. “An ordinary, plant-derived liberator must have a distinctive shape that allows it to bind to a particular solid and modify its energy levels—rearranging the rungs on the ladder so a luxagen can climb all the way to freedom, radiating just one photon at a time. A rare fifth- or sixth-order phenomenon becomes a first-order event; a faint trickle of light over eons becomes an instantaneous avalanche.

“But what are the chances that the orthogonal dust that fell on the Peerless before the spin-up had just the right geometry needed to modify the energy levels of calmstone? If you pick some mineral at random, that certainly won’t do the job. If you swap its positive luxagens for negative ones, its structure will be exactly the same as the original. It might interact with ordinary calmstone a bit differently—each will see the other’s energy valleys as peaks, and vice versa, so grains of the two minerals might stick together half a wavelength closer than usual—but that would still be a weak and distant bond. So I don’t see how it could compare to the kind of chemical tricks that plants took eons to learn… and in fact, no plant ever gave us a liberator for calmstone.”

Ada said, “How elusive can the answer be, once we have a mountain of orthogonal matter to play with?”

“We’ve been playing with ordinary matter for generations,” Tamara pointed out. “And we don’t have all the answers there.”

“If the Object turns out to be inert,” Carla argued, “that could mean that we do understand both kinds of matter reasonably well. We’ll just be left with the historical curiosity of the dust that threatened to light up the Peerless … and I suppose that could turn out to have been some kind of freakish bad luck.”

Tamara wasn’t inclined to argue when she had no better ideas herself. But she did not believe in that kind of luck.

Tamara gathered six new beacon sightings, then merged them with Ada’s to sharpen their estimate of the Gnat ’s trajectory. A few brief squirts of air from the attitude-control jets reoriented the craft so the engines could deliver a small push in the required direction. She set the parameters of the burn into the controlling clockwork, then the crew donned their helmets and strapped themselves into their couches again.

The glare from the exhaust through the windows was as bright as it had been at the launch, but Tamara had barely registered her weight against the couch when the burn was over. She’d been worried that using the engines again might exacerbate Ivo’s problem, but he assured her that he was completely unharmed this time.

A bell later, the observations showed their modified trajectory to be as good as they could have wished for. There was no point trying to aim the Gnat down to the last saunter yet, when they still hadn’t pinned down the rock they were aspiring to reach with the same precision. The infrared color trails taken from the Peerless could only tell them so much—but they’d soon be able to make a fresh determination of the Object’s trajectory, with the aid of some decent parallax at last.

Looking out at the familiar stars, Tamara realized that she’d never even searched the sky for the Peerless . It would have been invisible to the naked eye, but she’d felt no urge to hunt for it, no pang of separation at its disappearance. And why should she have felt lost? The light from the beacons and the stars formed a grid of intangible guide ropes, transforming the void around the mountain into a solid, traversable realm.

If they could find a way to hold this ground, building a permanent framework of beacons and observatories, the sky from the Peerless need never be flat again—need never revert to the kind of painted dome that befitted a pre-scientific culture. Whatever triumphs or disappointments the Object had in store, if they could just retain the hard-won benefits of parallax, at least her generation would have that much to its name.

“Four different kinds of rock, at least!” Ada declared excitedly. “Different hues, different textures, different albedos.”

Tamara hung back and let Carla and Ivo take their turns at the telescope first. She didn’t mind waiting, listening to their descriptions before she saw the image; it was like savoring the odor of a seasoned loaf for as long as possible before finally taking a bite.

“The more variegated the better,” Ivo said, squinting through the eyepiece. “Ah… wouldn’t it be perfect if just one of these minerals set calmstone on fire, and the others were inert? Then Silvano could have his new farms out here, alongside the liberator mines.”

He moved aside, and Tamara prepared to take his place. From the Peerless , the best view of the Object had given them its rough dimensions but little else. For two days now, she and Ada had been tracking it through their theodolites, treating successive locations of the blurred ellipse as one more set of navigational data, their sightings building up to a family of lines that would complete the elegant geometrical construction that made the rendezvous possible. But now they were close enough for the Gnat ’s largest telescope—barely the size of Tamara’s own body—to show her the whole point of the exercise.