Across a Billion Years

  Dihn Ruuu, faithful to the end, tells us stubbornly that we're going to find High Ones here. For once we're all in agreement that the robot's wrong. It seems pretty clear to us that McBurney IV is another case of machines in perpetual motion: a planet inhabited by robots with an infinite life-span, waiting as Dihn Ruuu waited for the masters to come back. The masters, though, have been extinct for upward of half a billion years, but since the robots haven't been programmed to consider such a possibility, they just go on and on and on about their chores, keeping the place in good trim, waiting, waiting, waiting some more.

  We may be all wrong, naturally. What the zog: we may very well find the High Ones still in business on McBurney IV after all this time. This trip has produced so many surprises already that it isn't safe to rule out any possibility. Nevertheless, I don't really think the Mirt Korp Ahm have survived into our own era. And, as I said many months ago, I'm not sure I'd like to run into them if they did. I don't know what I'd do if I ever found myself face to face with one of the superbeings who built this civilization. Fall flat on my snout and pay homage, I guess. It would be something like meeting a god. My company manners aren't up to meeting gods.

  We'll know soon enough, because Dihn Ruuu is now trying to make radio contact with his fellow robots on the planet below, so that they don't blast us out of the sky as we try to land. If all goes well we'll be going into our entry orbit within the hour.

  * * *

  Dihn Ruuu has obtained landing permission for us. We're on our way down.

  FIFTEEN

  March 10,

  2376 McBurney IV

  We didn't make a powered landing; the robots wouldn't let us. Communicating with Dihn Ruuu via the ship's radio, they ordered us to cut our engines and submit to proxy control from below.

  Mild crisis.

  "Like zog I will," Nick Ludwig shouted. "Turn my ship over to unknown alien forces? Risk everybody's life? Either I land this on my own heat or I'm not landing!"

  Dihn Ruuu said, "They refuse to permit anything else. You must realize that they have no knowledge of your competence as a pilot. All they see is a strange ship."

  Nick blustered some more. Dr. Schein mildly suggested that Nick had better give in. When Nick threatened to turn around and leave, Dr. Schein just as mildly began to talk about breach of contract. He brought up in an oblique way the question of the piece of the mercury mine that we had promised the spaceman, and other likesuch variosities. Nick yielded. He looked like he was ready to go nova, but he yielded.

  Some five thousand meters from planetfall he cut the engines and we slipped back into a parking orbit. Then the robots grabbed us from below. As if yanking on us with a giant magnet, they pulled us out of orbit and guided us down. We were completely inertialess: just floating toward McBurney IV under no means of acceleration, but making a pretty good velocity. Nick Ludwig invited us up front to look at his instruments. I've never seen a man more perplexed. "What are they going to do?" he asked. "Catch us in a net? We're building up speed at what looks like a one-g acceleration, but where's the acceleration? Where are the laws of physics?"

  Repealed, I guess. All the tonnage of our ship was nothing more than a straw on the wind, a sliver of iron in a magnetic field. We went down and down and down in a dreamy way and came to rest, gently, easily, in the precise center of a huge bullseye target where we were surrounded by gaunt, spidery rings of instruments, stretching away for hundreds of meters on every side. Golden loops and coils and towers and cross-hatched antennae hemmed us in: the equipment that had plucked us from the sky and set us down, no doubt. Nick Ludwig, pale and dazed, stared at all this in distress. It was an article of faith for poor Nick that planetary landings were to be made according to the principles of Newton, with thrust balancing pull, de-celeration canceling acceleration. But this landing was pure magic. Inertialess acceleration indeed!

  The atmosphere of McBurney IV tested out as breathable, maybe, but risky on account of a heavy carbon dioxide concentration and some whiffs of something hexafluoride. So we went outside in breathing-suits, with Dihn Ruuu leading the way. The gravity was a bit more than Earthnorm; the weather was hot.

  A dozen robots of Dihn Ruuu's general shape greeted us. Clustered about us, like vast walking statues. Peered at us, sniffed us, touched us. Communicated with one another about us, via an audio channel we could not pick up.

  "What are they saying?" I asked Dihn Ruuu. "Do the Mirt Korp Ahm still occupy this planet?"

  "I have not yet been able to obtain information on that subject," said the robot.

  "Why are they so excited, then?"

  "They have never seen protoplasmic life before," Dihn Ruuu replied. "These are machines that were created by other machines. They are captured by you."

  "Captivated," I corrected.

  Dihn Ruuu didn't acknowledge the correction. Our robot had hooked itself into the conversation and had ceased to take notice of us. For perhaps five minutes the delegation of metal beings conferred earnestly. Pilazinool seemed to be getting more than his share of attention; I realized finally that the High Ones robots thought that he was our robot, since so much of his body was nonorganic, and they were trying to draw him into the discussion. Dihn Ruuu explained, I think.

  Vehicles appeared. Six long, slim aircars made of green plastic came whistling down, and from their bellies descended metal scoops, onto which we moved at the instructions of Dihn Ruuu. Up we went, into the aircars, and away, flying at a height of perhaps a hundred meters. To the city.

  The city was everywhere. Once we were beyond the concentric rings of the spaceport and its intricate landing devices, we were in the city. It resembled in general look the High Ones cities we had seen on our globe, but in actual point of detail there were very few correspondences at all. The buildings did not dangle; each was firmly rooted, although there were so many levels that we had difficulty tracing any one row of buildings through the maze. The design of each building was different from those we had seen earlier; these were sleek pyramid-shaped structures, mostly, whose surfaces glowed with a soft inner light. I saw no windows.

  We were taken to a particularly large pyramid and left by ourselves in a spherical room of colossal size. Little blobs of golden light drifted freely near the ceiling. Abstract decorative patterns, red streaks and purple dots and blue spirals, rotated dizzyingly in panels on the walls. There was nothing to sit on except the floor, which was carpeted in something soft and spongy and seemingly alive, for it wriggled and writhed whenever someone put his weight on it. All the robots left us. Including Dihn Ruuu, our one link to the real universe, our guide, our interpreter.

  Two hours passed, and then two hours more.

  We hardly spoke. We sat or stood or sprawled around the great room, puzzled, ill at ease, off guard, baffled into a state of total spinlessness. This episode had taken on all the qualities of a dream: our floating descent, the jostling and pinching given us by the towering robots, our inability to communicate with anyone, the eerie silence, the strangeness of the city, the unreality of this bare cavernous room in which we now found ourselves . . . prisoners.

  Conversation, such as it was, tended to be made up mostly of phrases like:

  "Where are we?"

  "What does it all mean?"

  "How long will they keep us here?"

  "Where are the High Ones?"

  "Are there any High Ones?"

  "Why doesn't Dihn Ruuu come back?"

  "Whose pocket are we in?"

  "What's the whole giboo about?"

  Since we had no answers to any of these questions, conversations that began with them tended to be rather brief. By the end of the second hour we had exhausted most immediate themes of this sort and had lapsed into silence all around. Mirrik and Kelly, as usual, were fairly cheerful; Dr. Horkkk sat by himself in a kind of black meditation, all his legs tightly crossed; Pilazinool unscrewed limbs; Dr. Schein wore a frown that deepened and deepened, as though he were having a great many second thoug
hts all at once; Leroy Chang skulked; Saul Shahmoon seemed to be asleep, possibly dreaming about the postage stamps of Mc-Burney IV; Nick Ludwig paced like a caged beast; Jan and I sat close together, and occasionally one of us flashed a quick nervous grin at the other. We tried not to show our fear; but, after all, this was no dream.

  In the third hour we began to wonder when, if ever, the robots planned to let us out. Or feed us. We had a couple of days' supply of food tablets, but for all we knew we'd be left here two or three months before anyone considered our needs. We had hardly any supply of water. There weren't any hygienic facilities in here either.

  It was the longest afternoon of my life, I think. Here we were in the midst of an incredible city of an ancient civilization—and unable to see a thing, unsure of what was in store.

  Finally a place in the wall below one of the stripe-and-dot panels began to swell and pucker; it popped open and Dihn Ruuu stepped through. I could see a couple of the other robots lurking just beyond the opening. Dihn Ruuu moved slowly to the center of the room and swiveled to scan us all.

  "The Mirt Korp Ahm," the robot announced solemnly, "no longer inhabit the present planet. I have learned that this outpost was abandoned by them 84,005,675 years ago, and is currently occupied only by the Dihn Ruuu, that is to say, the Machines To Serve."

  The calm words, delivered in that weird metallic imitation of my own voice, hit us with tremendous impact.

  We weren't amazed to find that there were no High Ones here, just a population of self-sufficient, virtually immortal robots. But to learn that the High Ones had abandoned McBurney IV only some eighty-four million years ago—!

  Funny how your perspective changes. On Earth eighty-four million years ago the dinosaurs still went stumbling around, and the only mammals that existed were little ratty things with long noses and sharp teeth. Nor had intelligent life evolved on any of the other planets of our galaxy that currently have it, such as Shilamak, Dinamon, or Thhh. So by any human perspective, eighty-four million years ago is pre-pre-pre-pre-historic.

  Yet I said only eighty-four million years. And I wasn't jesting.

  Up to this point all archaeological evidence had indicated, as I'm sure I've told you, that the High Ones had mysteriously disappeared from our galaxy 850 million years ago. No trace of them more recent than that had ever been found. On that scale, eighty-four million years ago was practically last week. With one brief statement Dihn Ruuu had lopped away 90 percent of the time-span since the vanishing of the High Ones.

  The implications of the robot's statement staggered us. Seemingly we would have to rethink our entire outlook on the High Ones and their place in the sequence of time. A dozen questions jiggled my brain at once, and it must have been the same for everyone else. But before we could get anything out, Dihn Ruuu iced us on all wavelengths with a far more sposhing statement.

  Like a college professor reading off routine announcements at the beginning of class, Dihn Ruuu went on, "It is with great pleasure that I state that the home world of the Mirt Korp Ahm does in fact still exist, and neither it nor its star have been destroyed, despite the impossibility of locating them that I experienced. According to communications received on this planet 13,595,486 years ago, the Mirt Korp Ahm embarked on a project at that time for the transformation of their home system into an enclosed sphere permitting full utilization of the solar energy. An uninhabited planet of the system was used as the source of mass for this project. The enterprise was successfully completed within a period of 150 years after receipt of first notice here. Thereafter, naturally, the home star of the Mirt Korp Ahm ceased to be detectible by conventional optical means."

  I pondered the meaning of that set of cloudy phrases without much immediate success. But to Saul Shah-moon the robot's explanation was lucidity itself. "Of course!" Saul cried. "A Dyson sphere!" Taking no notice of the interruption, Dihn Ruuu sailed serenely onward. "No communications have been received from the home world since the completion of the enclosure project," the robot said. "However, there is every reason to believe that the Mirt Korp Ahm continue to inhabit their original solar system. Inasmuch as my own responsibilities have been terminated, I propose to journey at once to that system and request reassignment. It would please me if you were to accompany me there."

  * * *

  Time out for explanations. I needed some myself, at this point.

  A Dyson sphere, according to Saul, is a concept first put forth by an American physicist, Freeman Dyson, some time in the early years of the Energy Revolution. Dyson lived in the middle of the twentieth century, after the harnessing of atomic energy but before the colonization of Earth's surrounding planets.

  Dyson's main point was that in its natural state a solar system is a terribly wasteful thing. The central sun, surrounded by a handful of planets, sends most of its energy shooting uselessly off into space. The planets are too widely separated to intercept more than a small fraction of the energy the sun generates; and therefore the sun's output speeds away in all directions, radiating so intensely in the visible spectrum alone that its light can be seen thousands of light-years away. This has the esthetic advantage of producing lovely starry nights on distant worlds, but otherwise has little to commend it.

  A really thrifty civilization, Dyson said, would catch all of its sun's energy before it was squandered. One way to do it, he suggested, was to demolish Jupiter and use its mass to build a shell surrounding the sun at approximately the distance of Earth's orbit from the center of the solar system. Smashing up the biggest planet and rearranging its pieces this way would take a fair amount of energy all by itself: roughly as much as the sun's total output for eight hundred years. But once the job was finished, the shell would intercept every photon of energy coming from the sun; this could be put to use as an all-purpose power source.

  Mankind would cease to live on the Earth, which even in his time was a pretty small and crowded place, and unsatisfactory in terms of application of solar energy, since at any given time half of it is receiving no solar radiation at all. Instead we would take up residence on the inner surface of the artificial sphere. Not only would every point on that surface have full access to sunlight at every moment, but the surface area of the sphere would be about one billion times greater than the surface area of the Earth. Splicing in all the plus factors, we'd find that the sphere could comfortably support a human population of 3 x 1023 individuals, which is to say a good many sextillion or septillion people—work out the exponents yourself. Anyway, it would be a gigantic number. Let's see: Earth has thirteen billion people now, which is 13 x 109, and things are pretty crowded, and this would be a population increase of 1014, so ... It gives you the dizzies, eh?

  Dyson thought that any intelligent species would be capable of converting its home world into such a sphere within two or three thousand years after it entered the industrial age. So we ought to be able to do it about 4000 A.D. However, it must be a tougher trick in practice than in theory, if the Mirt Korp Ahm, whom we know were at the stage of galactic travel 1.1 billion years ago, waited until a mere thirteen million years ago to do it. Or did they just not bother to get around to it any earlier?

  A Dyson sphere would not, of course, show up on optical telescopes, since all of the sun's light output is trapped inside the sphere. That explains Dihn Ruuu's failure to see the star when he looked for it in the sky. Nevertheless, even a Dyson-sphere civilization would be unable to make use of all the energy that was available to it, and would have to get rid of some of it in the form of heat, that is to say, infrared radiation. Dyson suggested that the sphere would have a surface temperature of 200° to 300° K., and would be emitting plentiful radiation in the far infrared wavelengths. This, of course, could be detected easily by outside observers. Dihn Ruuu could stop grieving, then. The home star of his creators had neither burned out nor blown up. It was still there—under wraps, so to speak.

  * * *

  Small surprises eclipse big miracles. Old Paradoxian proverb, jus
t invented by your humble servant. Dihn Ruuu had thrown so much astonishing news at us in a dozen sentences that for a moment, in the excitement of the Dyson-sphere discussion, we forgot to get excited over the real orbit-smasher, which was…

  That the High Ones possibly weren't extinct at all….

  And that Dihn Ruuu was inviting us to help him pay a call on them.

  Wonders were multiplying too swiftly.

  Of course, Dihn Ruuu's guess that the High Ones were still alive was only a guess. The McBurney IV robots had heard neither beep nor plink from the Mirt Korp Ahm in thirteen million years, and it's dangerous to think of thirteen million years as anything but a zog of a long time. On the other hand, we were accustomed to thinking of the High Ones as beings buried a billion years in the past; if they had survived until thirteen million years ago, it was a reasonable bet that they still existed. On the third hand—

  We did a lot of talking all at once, shouting out theories, disputations, suppositions, postulates, hypotheses, and even some plain old guesses. Nobody could hear anybody else in the uproar, until suddenly one voice cut across all the rest:

  "Help!"

  We fell silent and looked around.

  "Who called for help?" Dr. Schein asked.

  "I did," Pilazinool said in a small voice. "I finally did it."

  He finally had. During our excited outburst, the Shilamakka had given way to his old nervous habit of unfastening hands and feet and limbs, and this time, in a kind of supreme act of self-mutilation, he had contrived to unscrew everything at once, arms and legs. Don't ask me how. I guess he was simultaneously unscrewing his right arm with his left, and his left with his right; however it happened, he had stripped himself down to a bare torso and was looking piteously at his heap of discarded limbs, unable to start assembling himself again. His expression of bewilderment was so intense that I was afraid something was seriously wrong. But then Dr. Schein began to laugh, and Mirrik snorted, and Kelly picked up one of Pilazinool's arms and put it in place, whereupon Pilazinool began hastily and in huge embarrassment to get the rest of himself attached.