These were always held in the Commissary’s room in Officer Country. Even though he had assimilated the experiences of his avatar Virtual who had ridden with Pirius Blue through the Cavity, Nilis seemed as scared of Arches’ daunting sky now as when he had first come here, and he tended to hide in his room. But he had quickly made this faceless little cabin his own, spreading his clutter of data desks, clothes and bric-a-brac over every surface, and filling the air with clustering Virtuals. Torec said he made every place he stayed into a nest, as rats made nests. Pirius thought a little wistfully of what it must mean to have a real home, and to miss it, as Nilis clearly missed his.

Torec complained about the state of Rock 492. Nilis said there was nothing he could do about it for now, they would have to wait for a meeting he had scheduled with Marshal Kimmer, the senior Navy officer on the base. After this “showdown,” as Nilis called it, he was sure their requests would be properly met, as the oversight committee had mandated.

Pirius wasn’t so sure. He knew that officers like Marshal Kimmer tended to regard their bases as their private domains. He wouldn’t take kindly to what he would surely see as interference from out-of-touch bureaucrats on far-off Earth, no matter what their formal authority.

Nilis had continued to analyze the data he had gathered on Chandra, the monstrous, enigmatic black hole at the center of the Galaxy, and hypothesized on its nature and what the Xeelee were doing with it.

He knew now that the Xeelee used Chandra to make nightfighters. Somehow, Nilis had deduced from remote images, they peeled spacetime-defect wings and other structures out of the distorted environment of the black hole. That much had long been suspected by Navy intelligence. But Nilis said he suspected the Xeelee had a more profound use for the black hole.

It was all to do with computing. There were fundamental limits to computing power, he said. The processing speed and memory of any computer were limited by the energy available to it.

He picked up a data desk and waved it around in the air. “This is a sophisticated gadget, the result of twenty-five thousand years of technological progress. But what does it weigh—around a kilogram? From the point of view of the gadget’s purpose, which is computation, almost all of this mass is wasted, just a framework. This desk would be able to achieve a lot more if all of its mass-energy were devoted to computing. In the form of photons, say, this kilogram of stuff could process at the rate of ten to power fifty-one operations per second. That’s a million billion billion billion billion . . .” Similarly, the memory capacity of a computer depended on how many distinguishable states its system could take. If Nilis’s inert kilogram were converted to a liter of light, the capacity would become some ten thousand billion billion billion bits.