Hidden Variables

by Charles Sheffield

  Quite clearly, the earlier survey had landed in only one hemisphere, or had skimped on the detail of their analysis.

  On the second night on the planet, the camp of the Carmel family had been attacked by a large native carnivore, a bipedal reptile that was both quick and ferocious. Elena and Jilli's mother had been killed at once, and their father reached the jump ship with one arm torn off at the shoulder. He had died on the way to Peacock A, after using his last strength to initiate a jump exit. The rescue party had found two small girls, unclear about what had happened to them but with certain memories indelibly rooted.

  Were the Zardalu similar to the carnivores that had killed their parents? It was an irrelevant question. They were similar enough, and there was no doubt—to me and to Rebka—that the Carmel twins had been reliving a terrible period of their childhood when they awoke on Delta Pav Four and found themselves surrounded.

  "But why did they run away?" I asked Rebka. "They must have known they'd made a horrible mistake. There's no way that any Council group would have found them guilty of anything but fear."

  Rebka was moving us cautiously in towards the foot of the umbilical, too busy to look around. "You are asking the question that has pursued me as long as I have pursued them," he said quietly. "Why would innocents flee? I can imagine that they might make one jump, in blind panic. But then they should have known why they had acted as they did. Why did they go on running?"

  It was some consolation to know that not even Sector Moderators, with their combination of native talent, high motivation and specialized training, could explain everything. We climbed out of the car and went on over to the foot of the stalk of the umbilical. The hover-car was small enough to fit into the cargo pod, but I wanted to get one from Midway Station, where they had equipment better suited for work down on the surface of Quake.

  It took us about twenty minutes to get settled into the passenger car that was waiting for us at the foot of the umbilical. Another five minutes, and the drive train took hold to give us a smooth upward acceleration, away from the surface of Egg.

  I had made the trip many times, but Rebka couldn't resist the viewports that showed the scene both ahead and behind the car.

  "How long before we can see the whole umbilical?" he asked.

  I shook my head. "We never will. It looks thick when we're close to it, but it never gets to be more than about fifty meters wide. And there are twelve thousand kilometers of it, remember, between us and Quake. We won't see more than you can see right now."

  In front of us the umbilical stretched away, thinning out to a fine silver thread that at last vanished into invisibility against the purple backdrop of Quake. Rebka was straining his eyes to follow the silver filament, but it would be hours before we could see it meet the surface of Egg's sister planet.

  It was easy to time our progress. Every few minutes there was a vibration and a rumble in the drive train, as a loaded ore car passed us on its trip from Quake to Egg. At this time of year we stopped the transportation of radioactives, even though there were always plenty available on Quake. An accident in the first days of operation of the umbilical had made the use of the transportation system during summertide an activity that always called for caution.

  I looked ahead. Hanging there five thousand kilometers away shone the bright knot of Midway Station, marking our halfway point on the journey along the bar between the two spheres of Egg and Quake—the balanced counterweights of the Dumbbell system. I pointed Midway Station out to Rebka and he spent a long time crouching forward, looking out of the front port.

  "I've seen a fair number of Stalks in different Systems," he said. "But this is the first one between two planets. Why don't they do it like this in other places? Say between Earth and Luna."

  I was fiddling with the scope, trying to get us a better view of Quake's surface. "You need a pair that are in synchronous lock," I said, only half my attention on Rebka—image motion compensation was a problem for the scope at our speed. "Quake and Egg always present the same face to each other. They're so close together, tidal friction has killed off any relative rotation of the two surfaces. In fact, if they were a bit closer together, they'd break apart—they'd be inside the Roche limit."

  I locked in the scope, satisfied that it was as good as I was likely to get. The image was crisp enough to let us see the outward flow of lava from a volcano at the terminator, and clouds of blackish smoke were spreading around the sunward side.

  "Even with the planets in synchronous lock, this was a tricky job," I went on. "There was a lot more to it than the usual cables and drive train that you're used to back on Earth. Wait until we get to Midway—you'll see what I mean."

  Rebka remained silent, staring out of the front screen. I did the same. Quake approaching summer maximum was something I had seen before but never tired of. Tidal forces on the molten interior were steadily mounting and the surface crust was weakening, unable to hold back the heat dragons that would rule the summer land. Already we could see faint blotches of smoke and heat haze, spreading across the purple-grey sphere.

  I should have known better than to sit there, doing nothing. Before I knew it all the old memories were streaming back. I could see Amy's face before me as she nudged me carefully along to her own objectives.

  "You're the expert, aren't you?"

  I was.

  "And you have the whole system under control, don't you? All the tether gear and the movement of the cable?"

  I thought I had it all under control—everything except Amy. "Well, then, why won't you take me with you?"

  "It's dangerous."

  "Not so dangerous that you can't go if you want to. You've been there before."

  "I made one trip. I swore I wouldn't make another."

  Amy was leaning over me as we lay on the open plain. Above our heads, Quake was still ten Days from midsummer. Even with my eyes shut, I could see its strange beauty. The volcanic action near summertide maximum filled all the upper atmosphere with fine dust and smoke, veiling the surface. The sunsets came every seven and a half hours, and they were a riot of purples, reds and gold. There was nothing like them anywhere else in the known universe—nothing that I had read of or heard rumored.

  Amy was watching my expression. She had picked up a piece of fine fern, and was stroking it slowly down my bare chest. She moved in front of my view of Quake, her wide brown eyes unusually serious.

  "So you'll take me with you this time?"

  I shook my head, rolling it from side to side on the soft earth, too lazy to lift it fully.

  "It's not safe there."

  "But it would be if you were there with me." She was working on my resistance like an expert climber, sensing and taking advantage of each tiny niche and fractional fingerhold.

  "Not at summer maximum," I said at last. "We couldn't stay through that. I left before that myself."

  She sensed my weakening resolve even before I knew it myself and moved in on it instantly. I could see a different expression in her face, flushed with a new passion and a gleam of adventure. I was staring into her eyes when a new face appeared before me and a different voice broke into our private world.

  "I wondered if you were having problems. I thought I'd better check."

  I was wrenched back across a four-year gulf. I became aware of Klaus Wethel's anxious face looking in at us over the comscreen, and of Rebka sitting quietly watching me.

  "Everything's fine," I said. "We'll be at Midway Station soon."

  Wethel nodded. "Then I'll go back to Cloudside. Just wanted to check."

  He looked reassured by the fact that the scene in the pod was so peaceful. The comscreen is limited in the amount of information that it will transmit. Klaus Wethel couldn't tell that my shirt was soaked with sweat under the armpits and around the collar—despite the accurate temperature control in the passenger pod.

  I couldn't hold out that hope for Rebka. To someone with his sensitivity I would be radiating like a supernova, a rank blen
d of pheromones: lust, fear, excitement, and anguish.

  I managed to keep my face and voice under firm control as we said our goodbyes to Wethel and he vanished from the screen. Nothing that Rebka had said to Klaus Wethel revealed that anything unusual was happening in the car—perhaps nothing unusual was happening for Rebka. High empaths must be used to a deluge of emotions from those around them.

  After a single, calm look at me, Rebka leaned forward again and set the scope to a higher magnification. Midway Station zoomed towards us.

  "I was about to ask you about this," he said. "Why such a big station? I have seen nothing like that structure on other Stalks from surface to orbit."

  If he was willing to forget what had been happening to me, I was ready to go along with him. I took in a deep breath and tried to hold my attention firmly in the present. No more trips to the past, until we were safely back on Egg and Rebka had gone on his way, with or without the Carmel sisters.

  "That's what I was talking about earlier," I said. "I told you Dumbbell is a tricky system. Midway Station there is four things in one. It's the power center that provides energy all along the umbilical, it's the central maintenance station, plus a very complicated computer system; and it's the Winch, over to the left. Watch as we get closer."

  With the scope magnification that Rebka had set we seemed to be only a few hundred meters from Midway. We could see every detail of the Winch's operation. It looked like a flattened disk almost a kilometer in diameter, from which the load cable of the umbilical protruded on both sides, like a thread through a bead of greenish glass. We could follow the cable for the first few meters inside the Winch, then its outline faded to a delicate branching pattern that baffled the eye. I set the zoom higher and moved our view in to the entry point of the cable.

  "Look at the movement there."

  As we watched, the umbilical on the side facing us was in continuous motion, reeling in meter after meter to the mysterious interior of the Winch. It seemed to be gobbled up endlessly by the dark mouth. Rebka looked at me in alarm.

  "I thought the connection between Ehrenknechter and Castelnuovo-Kryszkoviak was a permanent one? Won't we lose contact at the other end if it keeps in reeling in the load cable like that?"

  "No. Look." I changed the scope setting, so that we had a view of the far end of the umbilical. It was still firmly attached to the surface of Quake, six thousand kilometers ahead of us. "See? We're still connected at both ends. The whole assembly is permanently tied—except for a few hours near midsummer maximum. But the length still has to vary, to allow for changes in the distance between the two planets. Their orbits are almost exactly circular about each other—as near as can be. There are still perturbing forces, though. They depend on the distance of Dumbbell from Eta-Cass A, and on the changes in the tidal forces. And don't forget the wobbles in Egg and Quake. Quake is almost a perfect sphere, but Egg fits its name—we have a two hundred kilometer difference between polar and equatorial radius."

  Rebka was staring hard. "But how does it do it? How do you know how much load cable has to be picked up or let out?"

  "All computer-controlled. I told you we have a fancy set-up at Midway Station. The Winch is programmed to allow for all the perturbing effects—otherwise we could never hold a connection between Quake and Egg for more than a few minutes. We'd break the cable, or have it flopping loose between the planets."

  As we were speaking, we had swept closer and closer to Midway Station. Just before we came to the Winch, our car was detached from the load cable and followed the drive train around the outside of the Winch. After a couple of minutes, we reconnected at the other side, and began the long fall towards Quake, once more securely attached to the drive—which soon had to slow our fall rather than driving us upward away from Egg. Midway Station was set at the mean center of mass of the Dumbbell system. A point of equilibrium, but an unstable one. Only the tension in the umbilical kept the whole assembly in overall balance.

  The complexity of the mechanical structure we had just passed seemed to have quietened Rebka. I felt that he was perhaps beginning to realize that a trip to Quake, for any reason, was not the same as taking a simple air-car flight. The umbilical was as simple as it could be—but that didn't make it simple. We settled into an uneasy silence, and watched the steady approach of the surface of Quake.

  In the two days since Rebka had first looked at it from my office, there had been changes. It was now daytime below us, and the purple-grey-green of our earlier view had dimmed to a general subdued grey. The plants were diving deeper, letting the top foliage die off and dry out. That would be sacrificed to the summer heat and widespread brush-fires.

  As the vegetation retreated from the surface, the scabs of recent wounds were revealed on Quake. I pointed to the long rifts and cuts that marked the planet beneath us.

  "See those? When we get a couple of hundred kilometers closer you'll see more of them."

  "Lava flows?" Rebka's voice was calm. I wondered what he had seen already, in his years as Sector Moderator. Whole planets wasted, and star-going civilizations wiped out? Probably. The Council was reluctant to tell of the worst side of its work. Perhaps Quake at summertide maximum was something he would take in his stride. In that case, I hoped he could teach me the trick. I zoomed the screen in on one of the longer rifts.

  "Lava, and fractures in the rock," I said. "Every year at perihelion, about two percent of Quake's surface gets covered with lava and hot ashes. That may not sound like a lot, but even the parts that don't get covered are affected by the eruptions. What you're looking at is one of last year's, or maybe the year before. The plants haven't had time to grow back yet. They'll do it all right, and they find rich soil there when the lava decomposes, but it takes a few years. Come back in ten years and there'll be a whole new set of scars, in many different places. That's one of the problems with Quake. The eruptions seem to come in different places each year."

  Rebka was looking suitably chastened. "What's the radius of Quake?"

  "About fifty-four hundred kilometers—the Carmel sisters could be anywhere in three hundred and fifty million square kilometers."

  "Yet you are still convinced that you can find them?"

  "We have a good chance. I'm betting that they have stayed within hover-car range of the foot of the umbilical. And they will want to be near water. I think that tells us where to look—if we can look there in time."

  He nodded thoughtfully. "You were quite right. This would be impossible without someone who knows the summer surface of the planet. I would be useless alone."

  So he had considered that option. That proved he was either braver or more foolish than anyone else I knew—perhaps both.

  "Suppose we don't get to them," he went on. "There must still be a chance that they would survive perihelion. How good would that chance be?"

  I had to think hard about that one. Could they survive summertide maximum? I had, in a manner of speaking, but that could be put down to blind fortune.

  I shrugged. "I'd give them maybe five percent. No more, and probably less. What will you do if they get killed there?"

  I should have realized that my question would upset him as much as my answer. Rebka winced at the thought.

  "I will blame myself," he said. "I am the one who has pursued them across four systems. If I had been less clumsy in pursuit—in signalling my approach—perhaps they would not have fled to Dobelle. We must save them, if they cannot save themselves. How do the native animals survive—can you give me any details?"

  No comfort for him there. "Most of them don't," I said. "They all dig deep down, but the biologists who've looked at the fauna here reckon that at least half of the animals are killed off each year. They can breed fast enough to keep up, but overpopulation doesn't ever seem to be a problem on Quake."

  He nodded again and fell silent. He was acting more like the guardian of the Carmel sisters than their pursuer, but it suited me fine if he would keep his mind on them. In a miserable sile
nce, we approached the foot of the umbilical. When we got near enough to see clearly where it joined the surface of Quake, Rebka saw something that brought him out of his introspection.

  "What's going on there?" he said, as we reached the end of the drive train and prepared to descend to the surface.

  He was pointing off to one side, where the first stage of loosening of the tether had begun. The heavy cables had already been deployed around the tether end, as it lay like a broad inverted mushroom on the surface.

  "They're getting the tether loose, ready for midsummer."

  "I thought you said that the connection with the planet was permanent?"

  "It is. It always provides the tension we need to stabilize the load cable. But at midsummer maximum we can't risk a simple mechanical contact, the way we have over on Egg. In a few more Days we'll draw the end of the umbilical up to about three thousand meters from the surface, well away from danger of real damage during the eruptions at tidal maximum. We have to be back here long before that happens."

  "So you are telling me that there is no permanent coupling?"

  I shrugged, and opened the door of the passenger car. We had reached the end of the line, the surface of Quake. So far, everything about us looked peaceful, with no obvious signs of seismic activity. We had to get the hovercar ready and be on our way as soon as possible.

  "It depends what you call a coupling," I replied. "We keep the tension in the cable through midsummer with a magnetic hold. Quake is full of ferromagnetics, and the umbilical has a generator in its tether. We just use Quake as a big lump of iron. The bond is as strong as a mechanical one, and it doesn't need a contact with the surface. You'll see, it works fine."

  "And how do you get off the surface when the umbilical is drawn up?"