Diaspora

"How? Where?"

"The polis orbiting Yang-Mills can't communicate with the singularity station. The beacon seems to have vanished from the sky."

Yatima's first response was relief. A malfunction in the station's communications hardware wasn't as bad as one of the singularities slipping or decaying. They'd receive no more news from the lower levels, but there was nothing to stop them physically returning, repairing the fallible hardware along the way.

Unless the station had not only lost contact with the distant polis, it had also lost track of the Planck-sized singularity right beside it. The entire second macrosphere could vanish like a fiber in a haystack.

Yatima tried to read Paolo's gestalt. He'd clearly had time to think of the same scenario. "Are you okay?"

Paolo shrugged. "I knew the risks."

"We can turn back anytime you want to."

"If the station's been seriously damaged, we're already too late. The singularity's either been lost by now, or it hasn't; a few thousand years either way before we return won't make the slightest difference."

"Except that we'll know our fate sooner."

Paolo shook his head, with a determined smile.

"What if we go back, and find that everything's working perfectly except for the communications link? We'll feel like complete idiots. We'll have wasted centuries fur nothing."

"We could keep going here, but send clones of our selves back into the third macrosphere, to ride the polis to the station and check it out."

Paolo looked down impatiently at planet Blanca's cratered surface. "I don't want to do that. I don't want to split myself again, just to half turn back. Do you?"

Yatima said, "No."

"Then let's drop the seeds, and move on."

Paolo had spent some time awake in the fourth macrosphere, immersing himself in five-plus-one-dimensional physics, and he'd managed to design a vastly improved spectroscope. With this, they located the Transmuters' marker from the vicinity of the fifth macrosphere's singularity, on the second-closest star, which they dubbed Weyl.

The marker was still covering the rotational pole.

Yatima had vis exoself bring ver out of hibernation at the mid-point of the journey. Ve stood on the 5-space version of Satellite Pinatubo, feeling verself dissolving into the sparse sky. It was meaningless to ask how many universes each handful of vacuum here contained. The Handler's revelations meant that even in the home universe, there were an infinite number of levels below them.

Maybe there was life and civilization, star-farers and long-particle engineers in every universe. But even the Striders, even the Transmuters, could only ascend a finite distance. There could be a Diaspora slowly working its way up from a hundred thousand levels below the home universe, which no one horn in the Milky Way would ever know about.

But their own Diaspora had already overlapped with the Transmuters'. The space around them was infinite, but if they clung to the trail they'd never lose them. It was only a matter of time and persistence before they caught up.

Later, Paolo woke and joined ver. They sat on a girder, pla

In the sixth macrosphere, there was an artifact drifting freely in space, a billion kilometers from the singularity.

It was an irregular shape, roughly spheroidal, two hundred and forty kilometers wide—the size of a large asteroid. It was not greatly pitted, but they were a long way from any star system full of debris. The surface was probably one or two million years old.

It was hard to obtain a spectrum in the faint starlight, and after waiting passively for a megatau for any signs of life, and then as long again for a response to a wide spectrum of radio and infrared signals, they agreed to risk brushing the surface gently with a laser.

They were not incinerated in retaliation.

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 mille

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."