Diaspora

Ve turned to Orlando. "I don't think they're in hiding. How shy could they be, after giving the atmosphere a spectrum that screams, 'Civilization! Come and visit!' We only noticed it close up, but it wouldn't take a huge technological advance to spot it from thousands of light years away.

Orlando didn't reply; he'd been staring down into the puddle, and he continued to watch a swarm of crimson larvae molting, and eating each other's discarded skins. Yatima understood the stake he had in making contact with the Transmuters. By the end of the Diaspora, when his scattered clones had reconverged, the Earth would be habitable again—but he could never feel secure about returning to the flesh until Lacerta had been explained. Any Coalition theory was likely to remain as suspect as the original belief that Lac G-1's neutron stars would take seven million years to collide. But if the Transmuters had firsthand knowledge of the galaxy's dynamics on a timescale of millions of years—and were beneficent enough to transform this planet's atmosphere, atom by atom, just to save their distant relatives from extinction—surely they wouldn't begrudge an infant civilization a little information and advice on its own long-term survival.

"Okay." Orlando looked up. "Maybe the spectrum was meant to stand out like a beacon. Maybe that's the whole point. They could have preserved the atmosphere in a thousand other ways, but they chose a method that would get them noticed."

"You mean they went out of their way to attract attention? Why?"

"To bring people here."

"Then why are they being so unsociable? Or are they just waiting to ambush us?"

"Very funny." Orlando met vis gaze. "You're right, though: they're not hiding from us, that's absurd. They're gone. But they must have left something behind. Something they wanted us to see."

Yatima gestured at the oasis.

Orlando laughed. "You think they built this as an ornamental pond, and invited the whole galaxy to come and admire it?"

"It doesn't look like much now," Yatima admitted. "But even loaded with deuterium and oxygen-18 it's been drying out slowly. Six billion years ago it might have been spectacular."

Orlando was not persuaded. "Maybe we're both wrong about the biosphere. Maybe there was no life here at all when the Transmuters left; it could have evolved later. The persistence of water vapor might he nothing but a side effect of the method they chose to make Swift stand out to anyone with a decent spectroscope and a glimmering of intelligence."

"And we just haven't searched hard enough for whatever it is we were meant to find? The lure wasn't exactly subtle, so the payoff should be just as hard to miss. Either it's turned to dust, or we're looking at the dregs of it right now."

Orlando was silent for a moment, then he said bitterly, "Then they should have used a beacon that turned to dust, too."

Yatima resisted pointing out the technical problems with choosing isotopes with suitable half-lives. Ve said, "They might have visited other planets, and left something more enduring. The next C-Z to arrive might find some kind of artifact…" Ve trailed off, distracted. Another possibility was hovering on the edge of consciousness; ve waited a few tau, but it wouldn't break through. Keeping vis icon in the Swift scape—along with vis linear input, in case Orlando spoke—ve shifted vis gestalt viewpoint to a map of vis own mind.

The scape portrayed a vast, three-dimensional network of interlinked neuron-like objects, but they were symbols, not junctions in the lowest-level network that dealt with individual pulses of data. Each symbol glowed with an intensity proportional to the reinforcement it was receiving from the others already dominating the network: vis conscious preoccupations. Simple linear cascades were rapidly tried out, then inhibited as stale or vis mind would have been paralyzed by positive feedback loops of hot/cold, wet/dry banality—but novel combinations of symbols were firing all the time, and if they resonated strongly enough with the current activity, their alliance could be reinforced, and even rise to consciousness. Thought was a lot like biochemistry; there were millions of random collisions going on all the time, but it was the need to form a product with the right shape to adhere firmly to an existing template that advanced the process in a coherent way.

The map was a slow-notion replay; Yatima was looking at the firing patterns behind the nagging sensation that hadn't quite gelled, not the real-time firing caused by the act of looking at the map. And, color-coded by the map's software, the relevant alliance was easy to pick out, though by chance it hadn't quite crossed the threshold into self-supporting activity. Symbols had fired for isotope, enduring, obvious… and neutron.