Exultant

by Stephen Baxter

  They looked so young, he thought, their faces blank, like desks empty of data. They were like children. And what was happening to him was childish, as the factions and cliques of the barracks combined to bully a new victim. It was just as Nilis had said: they might look like adults, and they would have to fight and die for mankind. But they were not long out of childhood, and every now and again it showed.

  Childish it might be, but the pressure was extraordinary.

  He clambered out of bed, made his way to Torec’s bunk, and crawled in beside her. They lay nested together, his belly against her back.

  “We said we wouldn’t do this,” she whispered. “We have to fit in.”

  “I couldn’t stand it anymore,” he replied. “Don’t throw me out.”

  After a time she turned over and kissed his forehead.

  In many ways she was the stronger one. But he sensed that she was as glad he was there, as he was to be there. They clung to each other, innocent as children themselves, until they fell asleep.

  The next morning Captain Seath led them to a flitter. The little ship slid out of port and threaded its cautious way through the crowded sky.

  Seath asked coolly, “Sleep well?”

  “No, sir,” Pirius said honestly.

  Torec said, “Captain, I don’t understand. Why does everybody hate us?”

  “I don’t imagine they hate you.”

  Pirius said, “We’re just the same as we were before.”

  Seath eyed him. “No,” she said, “you’re not. You’ve done extraordinary things. You’ve seen Earth, Ensign. Even I can’t begin to imagine it. And you’ve been close to power, closer than anybody here, closer than me, closer even than the base commanders. You have changed. And you can’t change back.”

  “There’s no place for us on Earth,” Pirius said.

  Seath laughed. “There’s no place for you here.”

  “Where, then?” Torec asked.

  “Why, nowhere.” She shrugged. “It’s not your fault. It’s just the way of things. The only people who understand you are each other—and each other is all you will ever have. You’ll just have to get on with it.”

  As she said that, Pirius felt Torec moving subtly away from him. He sensed a return of her old resentment: they had come all the way back to Arches, and she still couldn’t get away from him.

  The base for Nilis’s pet squadron was just another rock among the hurtling asteroids of Arches. Known only as Rock 492, it was a kilometer-wide lump of debris. On its battered surface was a cluster of buildings of bubble-blown rock, and a few broad pits that had once been landing pads and dry docks. But all this was long abandoned.

  They had to climb out of the flitter in their skinsuits.

  The buildings, long stripped of anything usable, were so old their surviving walls were pocked with micrometeorite craters, and a thin silt of dust had gathered around the bases of their walls. Some of their domes had cracked open altogether.

  Only one of the buildings was airtight to regulation standard. When they clambered inside, through a temporary airlock hastily patched into a hole in the wall, they found themselves in a cavernous hollow. Bots crawled over the floor and roof, patching up defects. But even the bots looked old and worn out, and the engineers who supervised them weren’t much better. There was no gravity in here—or rather, only the microgravity of the asteroid, just a feather touch—and the light, cast by a few hovering globes, was misty, the air a shining silver-gray.

  Pirius cracked his faceplate and took a deep breath. The air was stale, so lacking in oxygen his chest ached, and it stank of oil and metal, and of the burning smell of raw asteroid dust, oxidizing busily. As the irritating dust got to work on his sinuses he started to sneeze.

  “Lethe,” he said. “Is this it?”

  “Nothing works but the inertial deflectors,” Torec said. That had to be true, or else the whole Rock, plummeting through the complicated geometry of Arches, would have been a hazard. She sighed. “Don’t they realize we are trying to save the Galaxy? How are we supposed to do that if the toilets don’t work?”

  But there was nothing to be done about the strange internal politics of Arches, the Navy, the Coalition, and humankind in general. So they got to work.

  For the next few days they wrestled with ancient air and water cyclers, balky nano-food systems, and hovering light globes that wouldn’t stay still. Even the machines didn’t seem to like them: they resisted being fixed, and developed faults and quirks that simply seemed perverse. Their social life didn’t get any better, either. If they had been outsiders in the Barracks Ball, they were definitely not wanted here, by engineers who clearly believed they had better things to do than labor over a lump of shit like Rock 492.

  But in another way it was fun, Pirius thought. Getting immersed in the guts of a broken pump or a clogged air-filter system was dirty, hard work, but it was a job that was finite and understandable and something you could finish, unlike the diffuse politicking of Earth.

  The systems came online one by one. As they heard the laboring of air pumps, and felt the shuddering of water pumping through the pipes, the place started to seem alive. And because they had worked so hard over it, Pirius and Torec thought of it as theirs. Before he had gone to Earth, the only homes Pirius had ever known had been one Barracks Ball after another. Now Rock 492 was starting to feel like home—though he and Torec only dared discuss such thoroughly non-Doctrinal matters in whispers, and they would never have mentioned it to Captain Seath.

  The ensigns were summoned to regular meetings with Nilis.

  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 pow
er 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 Ni
lis. 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.