Diaspora

Apart from contamination with interstellar gas and dust, the surface was pure quartz, silicon dioxide. Silicon-30, oxygen-18, the heaviest stable isotopes of each. The artifact appeared to be in thermal equilibrium with its surroundings, but that didn't prove that it was dead. Waste heat, entropy, could be poured into a hidden internal sink for a finite amount of time.

They landed microprobes on the artifact, and tomographed it with faint seismic waves. It was exactly the same density throughout, uniform solid quartz, but the technique only had a resolution of about a millimeter. Smaller structures would not show up.

Paolo suggested, "It might he a working polis. They could be getting energy in and out through a traversable wormhole."

"If you're right, are they deliberately ignoring us? Or are they oblivious to the outside world?" Even Ashton-Laval's citizens would have known about it, immediately, if someone had stroked their polis hull with a laser. "And if they're ignoring us now, what happens if we do something intrusive enough to get their attention?"

Paolo said, "We could wait a thousand years and see if they deign to make contact."

They sent a small swarm of femtomachines burrowing below the surface. A few meters down, they found structure: a pattern of tiny defects in the quartz. Statistical analysis showed that the defects were not random; the probability of certain spatial correlations arising by chance was infinitesimal. But the whole crystal was static, completely unchanging.

It was not a polis. It was a store of data.

The sheer scale of it was overwhelming. The data was packed almost as densely as their own molecular storage, but the artifact was five hundred trillion times the volume of the polis. They ran pattern-analysis software, trying to make sense of slivers and fragments, but nothing emerged. They rushed for a century while the femtomachines went deeper, and software ground away at the problem.

They rushed for a millennium. The femtomachines found a copy of the old galactic map written in the defects, surrounded by undecipherable material. Taking heart at this, they rushed for another thousand years, but the software could not decode the storage protocol of any other data. And though they'd barely begun to sample it, Yatima suspected that they could read it all and still fail to understand anything more.

Out of the blue, Paolo said numbly, "Orlando will be dead. There'll be nothing left of him but flesher great-great-grandchildren, living on some obscure planet in the second macrosphere."

"Your other selves will have visited him. Met his children. Said goodbye."

Paolo took ancestral form, and wept. Yatima said, "He was a bridger. He created you to touch other cultures. He wanted you to reach as far as you could."

The surface of the artifact was full of long neutrons, hearing the same catalyst as always. And the core-burst map was encoded in the wormhole sequence, too—though the tiniest fluctuation of the vacuum, here, was an unimaginably greater event than any cataclysm devouring the Milky Way.

They took a sample of the neutrons, built a new polis in the seventh macrosphere, and moved through.

There was another artifact floating freely near the singularity, made out of the marker mineral they'd first seen on Poincare.

It was cold and inert, and full of the same kind of microscopic defects as the first. It was impossible to say whether or not the data was identical; they could only compare tiny samples of each. The software found some matching sequences, bit strings that recurred relatively often in both crystals. The storage protocol remained opaque, but it was probably the same.

Yatima said, "We can turn back anytime."

"Stop saying that! You know it's not true." Paolo laughed, more resigned than bitter. "We've burned six thousand years. We've turned our own people into strangers."

"That's a matter of degree. The sooner we return, the easier it will he to fit in again."

Paolo was unswayed. "It's past the point of going back empty-handed. If we cut our losses and give up now, it will mean the search was never worth it in the first place."

There was a third artifact in the eighth macrosphere, and a fourth in the next. The shapes and sizes could be meaningfully compared between the same-dimensional pairs, and, random microcraters aside, the difference was barely measurable. When they sampled the artifacts at matching positions, lining up the femtomachines' paths as best they could then hunting for correlations, they found large tracts of data the same. But not all of it.

The pattern continued in the tenth macrosphere, the eleventh, the twelfth. The artifacts changed shape, slightly. Ten or twenty percent of the bits in all the exabytes they sampled at corresponding positions were different.

Paolo said, "They're like rows of tiles from the Orphean carpets. Only we don't know the dynamics, we don't know the rules to get from frame to frame."