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.
“In fact, our most advanced computers have a design something like this,” he said. “Perhaps you know it. At the core of the ‘nervous system’ of a greenship is a vat of radiant energy, much of it gamma-ray photons, but some of it more exotic higher-energy particles. Energy is bled off from the ship’s GUT generator, to keep the photon soup at around a billion degrees. Information is stored in the positions and trajectories of the photons, and is processed by collisions between the particles. To read it, you open up a hole in the side of the box and let some of the light out.”
There were limitations with such a design, because the rate at which information could be extracted, limited by lightspeed, was much less than the computer’s storage capacity. “You only get a glimpse of what’s going on in there,” said Nilis. “So our best computers are massively parallel, with subsections working virtually independently.” The input-output rate could be increased if the computer were made smaller, because it took less time for information to be moved around. But as the size was reduced, the energy density would increase. “You encounter more and more exotic high-energy particles,” said Nilis, “until you pass the point at which you can control them. Gamma-ray processing is the limit of our technological capabilities right now. But of course that’s not the
physical
limit. If you keep crushing down your computer, keep increasing its density, you finish up with—”
“A black hole,” said Torec.
“Yes.” He beamed, and plucked at a thread dangling from the sleeve of his battered robe. “And then the physics becomes simple again.”
Pirius began to see it. “And Chandra is a black hole—the biggest in the Galaxy.”
“Exactly,” Nilis whispered. “I thought the Xeelee were using Chandra to power their central computing facility. Now I believe that the Xeelee are using
Chandra itself,
a black hole with the mass of millions of suns, as a computer. The audacity!”
Torec asked, “How can you use a black hole as a computer?”
Nilis said that information could be “fed” to a black-hole computer during the hole’s formation, or by infalling matter later. “The data would be stored on the hole’s event horizon in the form of impressed strings.”
Pirius was becoming baffled. “Strings?”
All of reality could be looked on as an expression of vibrating strings. Invisibly small, these loops and knots shimmered and sang, and their vibration modes, the “notes” they sounded, were the particles of the universe humans could discern. Pirius took in little of this, but he liked the idea that the universe was a kind of symphony of invisible strings in harmony.
“A black hole’s event horizon is a terminus to our universe, though,” Nilis said. “Strings can’t extend beyond it. So they become embedded in the surface—like wet hair plastered over your head. The strings bear information about how the hole was formed, and how it grew.” To get at the information you had to let the hole evaporate, as all black holes did, by emitting a dribble of “Hawking radiation.” The smaller the hole the more rapidly it evaporated.
“You won’t be surprised that the Silver Ghosts once dabbled with this kind of technology,” Nilis said ruefully. “They created microscopic black holes, with information and processing instructions encoded in the formative collapse. Small enough holes evaporate very quickly—they explode, in fact. The computation’s output is encoded in the radiation they emit in the process. You can solve some spectacularly hard problems that way.” He sniffed. “The Ghosts did get it to work. But each micro-hole computer was a one-off; you could only run one program, because it blew itself up in the process! Even the Ghosts couldn’t find a way to make the technology practical.”
“And,” Torec prompted, “this is what the Xeelee are doing?”
“Yes. But
they
don’t restrict themselves to mere microscopic holes.”
He showed them data extracted from Pirius Blue’s jaunt into the Cavity. They still had no good close-up images of Chandra, but somehow the Xeelee were controlling the inflow of matter to the event horizon. And through that control, they were “programming” the monstrous black hole. They allowed the Planck scale dynamics of the event horizon to process the input information, and were “reading” the results by analyzing the Hawking radiation the black hole gave off.
“At least that’s what I think they are doing,” Nilis said. “There is still a great deal we don’t know about black holes. For instance, there must be structure in the deep interior, close to the singularity. There the strings and membranes that underlie subatomic particles must be torn and stretched, perhaps reaching dimensions comparable to the black hole itself. Can this ‘fuzzball’ be used for computing purposes? I don’t know—I can’t rule it out. Or perhaps the Xeelee work on some other principle entirely . . .
“It’s remarkable,” he breathed. “A black hole is a convergence of information and physics, a junction in the structure of our universe. And the Xeelee are using this miracle as a tactical computer!” He grinned. “No wonder they were able to fend us off so easily. But now, thanks to your CTC computer, we’ve changed the rules—eh, Ensigns? Even a black hole computer can’t beat
that.
“
But I don’t think I’ve got to the bottom of it yet.”
“Of what, sir?”
“Of Chandra.”
His proximity to the Galaxy’s center had inspired him to start a whole new line of research, he said. He would go to the Navy’s archives for tactical material from three thousand years’ worth of scouting missions, and perhaps even hunt out scientific data from more innocent times, when Chandra had been thought to be a mere astrophysical marvel, not a military target. “In the quagmites and the Xeelee we have already found two layers of life, from quite different cosmic epochs—and a third, if you include us! I’m beginning to wonder what else is there in Chandra’s nested layers, waiting to be uncovered. Perhaps there is more life to be found in there, still more ancient and strange, perhaps permeating the singularity itself.
“We understand so little,” he said, “even now. If you look back at the theories of the ancients you can see how they groped for understanding. Their physics made them capable of recognizing a black hole, say, and describing its broad features. But their science gave them no real understanding of what it
is.
Some of what we are capable of today would have seemed impossible to the ancients, as if we were defying the laws of physics themselves! But you have to wonder how incomplete our own precious theories may be.”
Pirius kept his face blank. With Torec’s hand curled warmly in his own, he daydreamed of other things.
After a week, Nilis set up his “showdown” with Marshal Kimmer in a conference room in Officer Country. Pirius and Torec were summoned to attend.
The Marshal was thin as a blade and impossibly tall, so tall that outside Officer’s Country he had to stoop or else his bald head would have scraped the ceiling. His cheekbones were so sharp they looked as if they would cut through his flesh, and his mouth was invisibly small. But he had space-hardened eyes implanted in his face, tokens of the battlefield. They masked Kimmer’s expression completely, as was perhaps their intention.
The Marshal didn’t so much as acknowledge Pirius’s presence, as if the ensign didn’t even exist. But officially, Pirius supposed, given his future crime, he didn’t.
Nilis opened with a bumbling presentation on the latest incarnation of his Project Prime Radiant, and how it would be carried out. The operational details were starting to be refined, through work with Darc, Torec, Pirius, and others. Nilis described how a squadron of modified greenships would sail into the Cavity behind a single, carefully selected Rock, known as Orion Rock, which would be used for cover.
Commander Darc sat alongside Nilis. Pila was here, Minister Gramm’s aide, and now his representative at the Core. She sat silently, obviously not wanting to be here; she seemed to regard the Base, the Core, and the whole messy business of the war with utter disdain. And here were Pirius and Torec, sitting awkwardly at the table, hoping nobody would notice them.
Marshal Kimmer sat motionless and expressionless through the presentation. He had brought various aides who sat behind him, whispering to each other.
At last Nilis finished, to everyone’s relief, including his own. He dispersed his last Virtual image with a wave of his hand and sat down, mopping sweat from his brow with his robe’s grimy sleeve. “Marshal, the floor is yours.”
The Marshal remained silent for long heartbeats, his expression thunderous. Pirius didn’t dare so much as breathe.
When the Marshal did speak, his voice was so soft Pirius could barely hear it. “Let me see if I’ve got this straight. You want twenty greenships.”
“A full squadron of ten, yes, plus reserve craft, and others for development and training—”
“
Twenty ships.
And it’s not just the ships you want. There’s the crew as well, plus backups. And the ground crew.
And
all the facilities that will be required to modify these ships with your gadgets, and to train up the crews in their use. You want me to draw away these resources from the front line, for this wild scheme of striking at Chandra itself. Is that what you’re asking me?”
“Marshal—”
“Next, your tactical plan. You will sail into the Cavity behind a Rock. Fine, but not just any Rock. You want Orion Rock itself! Commissary, we have been developing stratagems based on Orion for
a thousand years.
” His voice was rising steadily. “And you want to throw away all that work, all that preparation, on
this
?”
Nilis was sweating harder. “Marshal,
this
could win the war.”
Kimmer stood grandly, and his aides scuttled to their feet. “Every few years we have to put up with one or another of you gadgeteers or armchair strategists who imagine you know how this war should be fought, better than those who have served the Coalition over three thousand years. You may have fooled them on Earth, Commissary. But this is the Front. And you don’t fool me.” He made to stalk out of the room.
Pirius glanced at Torec. He had anticipated Kimmer’s reaction, but even so he felt numb despair. There was none of the brute wisdom he had sensed in Minister Gramm in Kimmer. Gramm was a flawed man, but he had a deep, troubled sense of a responsibility for the conduct of the war. In Kimmer there was nothing but resistance to a challenge to his own power. Pirius could hardly believe that they had come all this way, achieved so much, only to be faced by yet another block.
Unexpectedly, Commander Darc spoke up. “Wait, Marshal.”
Kimmer turned, his expression cold. “Did you speak, Commander?”
“Sir, you’re my superior officer. I apologize for speaking out of turn. But I have to point out you’re wrong. The Commissary isn’t asking you for anything. The Grand Conclave has issued an executive order, and the Commissary is merely passing on its instructions. We have to give Nilis what he needs to do the job.”
Kimmer hissed, “This fat earthworm has fooled you as he fooled the Conclave, Commander.”
“No doubt you’re right, sir. But in the meantime we have our orders.”
Kimmer glared at his aides, who confirmed in whispers that Darc was right. Kimmer’s mouth worked. Pirius knew he would make the Commander pay for what he had said.
“All right, Commissary. As the Commander says, I have my orders. Until I’ve had time to appeal against the executive mandate, you and your stooges can have what you want.” He stabbed a finger at Nilis. “But I do have discretion on how I carry out those orders. I won’t take any usable resources away from our vital struggle. You’ll have your ships. But they will not come from the line: you can have the superannuated, the battle-damaged, the patched-up wrecks. And I won’t let you waste the lives of my best crews either. Do you understand?”
Nilis nodded his head. “Quite clearly.”
“Oh, Nilis—one more thing. If you mean to use Orion Rock you’ll have to be quick about it. It will be in position in ten weeks.”
Nilis gasped. “
Ten weeks?
Oh, Marshal, but this is—we can’t be ready—”
Darc put his soft hand on Nilis’s shoulder. “It’s all right, Commissary. Ten weeks it is, sir.”
Kimmer seemed still more infuriated. He stalked out of the room, followed by his chattering aides.
The Commissary was trembling. “I thought I had blown the whole thing,” he said hoarsely. “My stumbling and fumbling, like a buffoon—how can I deal with a Marshal if I can’t hold myself together for five minutes?”