Diaspora

But the Transmuters had not stayed. They'd entered this universe after the Star Striders, spoken with them briefly, then moved on.

When Paolo heard of Yatima's plan, he went straight to Elena. Her current homescape was a verdant jungle on a tide-locked moon of an imaginary gas giant. The banded planet filled a third of the sky.

She said, "Why? Why follow them? There are people with the same technology here. People with as long a history. Out of six thousand cultures, what's so special about the Transmuters?"

"They weren't just fleeing the core burst. They wanted to do more than escape."

Elena gave him a try-harder look. "Most of the people here have nothing to do with the core burst. There are more than a thousand cultures native to this galaxy."

"And they'll all be here when I get back. Will you come with me?" Paolo met her eyes, imploringly.

She laughed. "Why should I go with you? You don't even know why you're going yourself."

They argued for kilotau. They made love, but it changed nothing. Paolo felt her tolerant bemusement firsthand, and she understood his restlessness. But it did not draw them closer.

Paolo brushed the dew from his skin. "Can I hold you in my mind? Just below sentience? Just to keep me sane?"

Elena sighed with mock wistfulness. "Of course, my love! Take a lock of my mind on your journey, and I'll carry a lock of yours on mine."

"Your journey?"

"There are six thousand cultures here, Paolo. I'm not going to hang around the singularity for five hundred years, waiting for the rest of the Diaspora to catch up."

"Then be careful."

Six thousand cultures. And he wouldn't have to lose her. For an instant, Paolo almost changed his mind.

Elena replied placidly, self-contained. "I will."

20

INVARIANCE

Yatima-Venetti polis, UN*

Yatima found the sight of the sky in the second macrosphere disturbing; ve kept wondering which combinations of stars were the images of different individual Striders. If the Handler was to he believed, the local computing nodes in each star system were only millimeters wide, and they communicated with the others, light years away, with pulses so weak, so tightly aimed, so unpredictable in wavelength, and so ingeniously encoded that a thousand interstellar civilizations had come and gone without noticing their presence. The Handler had refused to disclose the nature of its own physical infrastructure, but it must have been operating below the femtomachine level to have penetrated the polis defenses. One line of speculation had it that the Striders had woven a computing device into the virtual wormholes of the vacuum throughout the galaxy, and the Contingency Handlers ran on empty space, permeating everything.

Paolo said, "I'm dropping the seeds."

"Okay."

He braced himself between two girders of the satellite, and pitched a handful of entry capsules in a counterorbital direction. Yatima smiled. It was very theatrical. The real capsules were launched in response to the mime, and Yatima couldn't tell when the scape stopped showing Paolo's fictitious ones and switched to the genuine external image.

Kozuch, the planet beneath them, was Mercury-sized and almost as hot. Like Swift, it stood out for hundreds of light years, branded by heavy isotopes; this step of the route, at least, was clear. The capsules' nanomachines would build a neutron-manipulation system, and then construct a polis in the third macrosphere. The whole procedure was simpler than interstellar flight, once you knew what to do.

Yatima said, "I hope they repeat the marker they used on Poincare. If we have to find someone in every six-dimensional universe who remembers them passing, this could be a very slow process."

Paolo replied with studied nonchalance, "I'll bridge with anyone. I'm willing to do that."

"That's nice to know."

He said, "We can't be sure that the Transmuters came from our universe. They left a map of the core burst for the locals to find, but they might have been passing through from a lower level, not fleeing it themselves."

"So they could be more at home in six dimensions?"

Paolo shrugged. "I'm just saying we shouldn't make any assumptions."

"No."

A point on the surface of planet Kozuch beneath them was begi

Ve stared down into the expanding well. "I'm doing this because of some badly-chosen fields in my mind seed. What's your excuse?"

Paolo didn't reply.

Yatima looked up. "Well, you should be good company."

Ve tugged symbolically downward on a girder of the satellite, and it went plummeting toward the gate.

The nearest star to the singularity in the third macrosphere held more life than Poincare, but there was no marker, and no obviously intelligent species to ask for directions.

The next was barren, or at least too hot and too turbulent for life to have evolved on its thin, fleetingly solid continents. If anything lived in the magma oceans, it was beyond their powers to identify.

The third star was much older and cooler, with a completely solid crust. It was girded by a system of giant causeways, easily visible from orbit. This hypersurface crisscrossed with roads was like some galactic Roman empire out of ancient fantasy, with all the intervening vacuum removed.

Yatima said, "This is it. The Transmuters."

As they approached, there was no signal from the ground. No imitations of long-lost friends appeared in their scapes to welcome them; no invisible defenses woven into the vacuum burned them from the sky.

The second wave of probes revealed that whatever cities or structures the causeways had linked were buried deep beneath an almost uniform, star-wide layer of rubble. It looked as if the crust had suddenly contracted, as some nuclear/chemical pathway had switched on or off deep within the star. That the causeways were visible at all was astounding. Nothing else had survived.

The fourth star showed traces of primitive life, but they didn't stop to examine the evidence closely. There was a marker slab, the same pure mineral as Poincare, and this time it was much closer to the polar sphere.

They named the fourth star Yang-Mills. The Diaspora's rule in the past had been one person only per astronomical body, but it didn't seem right to split the famous pair between universes, or to give one the gateway star and the other a less significant memorial.

Waiting for the long-nucleon facility to he completed, Yatima viewed images, relayed through two singularities, of the first wave of core-burst refugees arriving in U-star C-Z. Blanca was there, and Gabriel twice; some versions of him must have declined to merge. Yatima searched for Inoshiro, but the refugees were all from the Diaspora. No one had yet arrived from Earth.

In the fourth macrosphere, they carried out remote spectroscopy on the hundred nearest star systems. There was a planet labeled with heavy isotopes, 270 light years away. They named it Blanca. By the time they reached it, the core burst would have a

Yatima had vis exoself freeze ver for the journey.

When ve woke, and jumped from vis homescape Satellite Pinatubo, Paolo said flatly, "We've lost contact."