The Paradox of the Sets Read online

  “It’s not our crater,” I replied. “It’s Gley’s.”

  CHAPTER ELEVEN

  We found the dead Set on the animal trail that led toward the center of the crater, outside the pitfall trap. It was a pretty sickening sight. Whatever had done it hadn’t been a great believer in waste; the flesh had been torn from the bones and the bones scattered. The head and one of the tibia/fibula sets were gone. A couple of carrion birds flew squawking from the remains as we approached, but they had not had the time to plunder the remains to any great extent. It appeared that they had not been left overmuch to plunder. There was blood all over the grass but there was very little in the way of evidence to indicate what kind of creature had been responsible. The ground was too hard to take tracks of any resolution, and the scuff-marks in the soil were anonymous—they could have been caused by almost anything. There were the occasional imprints of claws, but these were just scratches—no weight had been leaning on them and they were presumably the marks of forepaws which had been busily working at the bones rather than supporting the bulk of the predator. I picked up some gnawed cartilages to look at the tooth marks, and was surprised to find the impressions of quite tiny needle-pointed teeth as well as the marks of grinding teeth.

  “That’s the sixth this summer,” said Gley. “And three donkeys. Year after year it gets worse. Either the thing gets greedier or there’s more than one.”

  “To judge by the teeth,” I murmured, “it’s not actually all that big, Unless, of course, it has a great many teeth.”

  “It has to be big to strip a Set so quickly,” Gley replied. “It’s less than an hour since nightfall—this must have happened soon after dusk.”

  I shone the lantern around carefully, looking at the places where the grass had been temporarily flattened. “Either it changes its position a great deal or it has no great weight,” I opined. “There’s no grass here that’s been crushed through having been sat on for any length of time by something heavy. And I can’t see where it came from. There are plenty of marks just here, but nothing outside a circle a few meters across.”

  “Dropped out of the trees,” said Gley. “My best guess is that it’s some kind of giant snake and that those claw-marks are the mark of some vestigial forelimbs. Sometimes the body-impressions seem to be faintly scaled.”

  “In five summers you’ve never seen it?”

  “No.”

  “Very discreet.”

  “Last year I tried keeping watch over a tethered goat, but it never showed. I scared myself half to death waiting, not knowing whether it might go for me rather than the goat. I might never have seen or heard it before it got me. I keep renewing the pitfall trap, but I don’t hold out any hope for it any more. I only hope that if ever I do see it I can get in one blast of the shotgun before it gets me. The cartridges are big enough to blow a hole in a brick wall, and the shot scatters too.”

  “Just don’t discharge that thing near me,” I said. “I don’t want to be the innocent bystander who gets mown down by accident.”

  He didn’t seem overly impressed by this request, but went on toward the hut.

  I glanced at Linda, and commented, “All this and earthquakes too.”

  “He’s a determined man,” she said.

  “He takes it all very personally,” I agreed, dryly. I couldn’t really think very highly of him for the moment. I had a certain deep-seated prejudice against men who believe that the best answer to a problem is a shotgun that fires big cartridges and scatters the shot so as to preclude any possibility of missing.

  Once we’d eaten we were taken by such a lethargy that there seemed no sense in setting up the apparatus that night—quite apart from the fact that it would entail clearing a space to work amid the hideous mess of Gley’s cabin. Like a true gentleman he abandoned the cabin to us and disappeared to the Sets’ encampment. In the face of such generosity I felt obliged to match the gesture by letting Linda have the bedroom. Once again I found it very uncomfortable sleeping on the wooden floor, and the fact that this time I was stretched across the hearth next to the fire didn’t improve matters any.

  This time, however, Gley’s impatience didn’t allow him to sleep in. I was woken up when he came stamping into the cabin at what seemed to me to be an ungodly hour. I looked at my watch, but I still hadn’t bothered to alter its mechanism, and it was still showing ship’s time. I groaned a little, for form’s sake, and went rummaging in my pack for some pills to resurrect me from my awful state.

  Gley started building up the fire, then went out to fetch water for his kettle. Gradually, I began to feel better, and by the time I’d chewed my way through the dreadful mess that Gley thought of as a healthy breakfast I was almost enthusiastic about the prospect of experiments in impromptu dating.

  We set up the apparatus with some difficulty, and took a few basic readings with a simple meter. There was very little background radiation in the crater’s soil. If there had been a burst of radiation here it had cooled down to practically nothing by now. With much more sensitive apparatus we obtained a count on the amount of carbon-14 in fresh foliage. Plants build their cellulose out of atmospheric CO2 and water and the proportion of radiocarbon in fresh plant material reflects the percentage of C-14 in the air.

  Then we started looking for some very old wood. We went first to Gley’s woodpile, from which he unearthed a great disc which was all that remained of the trunk of a particularly ancient tree.

  “It was dead,” he said. “I burned the rest. I saved this with the intention of looking at the rings under a powerful lens in the hope of finding something anomalous.”

  “And did you?” I asked.

  “I couldn’t see anything with the naked eye. Never did get the lens—not the sort of thing they keep at the farm.”

  We carried it inside and began to take flakes out of rings at varying depths. There were nearly two hundred and fifty rings. It didn’t take us back far beyond the date of the survey, but it was a start. Carbon-14 decays into carbon-12. The carbon-14 count ought to decline along a neat curve as we investigated flakes from ever nearer the heart—that is, it should if the C-14 level in the atmosphere had remained stable over the two hundred and fifty years the tree had lived.

  Four hours later we had a neat hand-drawn graph showing a neat curve exactly as expected. The C-14 level in the atmosphere had been exactly the same two hundred and fifty years ago as it was today.

  “Well,” said Linda, “that’s the easy one out of the way. Now let’s get on to finding out just what’s in the soil and the various rocks.”

  That wasn’t so easy. The general theory was the same but the actual task to hand was more difficult. First we had to identify the minerals in the rock, looking for traces of something radioactive—or traces of something that might well be the product of radioactive decay. Normally you can date rocks by means of estimating radiopotassium, but that particular yardstick is a little coarse. What we were hoping was that we’d find something in the soil that might be debris from a nuclear pile that had gone bang. We already knew that there wouldn’t be much trace of the original fissionables left, but all we needed was a trace and a lot of breakdown product.

  We looked at a lot of bits of rock—Gley had assembled quite a collection—but we found nothing. The rock seemed to have been formed long ago in the geological past, when the volcano last erupted. There were some pretty funny-looking specimens but when it came to analysis they turned out to be mere freaks of nature. He even had some petrified wood that he’d dug up somewhere, but that, too, was millions of years old, and had been quite unperturbed by anything that had happened in the crater over the last several million years.

  I began to suspect that perhaps there was nothing to find.

  “Look,” I said. “You’ve dug at least ten feet into the surface, if only to excavate that bloody pitfall. Didn’t you find anything?”

  At this point I still hadn’t bothered to tell him my hypothesis in all its gory detail in order to
compare it with his own. We had been too busy, and his natural defensiveness didn’t encourage a free exchange of ideas.

  “The pit’s in a natural crack in the rock,” he said. “A cleft, maybe made by a quake with pressure from below. On either side of it the soil’s only a couple of feet deep before it becomes unworkable—practically solid rock.”

  “How did you find the cleft?” I asked. “Happened upon it while you were digging holes in search of the remains, I presume?”

  He looked at me long and hard. It was the fourth or fifth in a series of dark hints but he’d ignored all the others. Now that we were at a particularly low ebb, though, and were all feeling a little frustrated, he took more notice.

  “Maybe,” he said.

  “If you’re holding something back because of some deep-seated reluctance to let go of your last secret,” I said, “forget it. If you’ve got anything else, let’s have it now.”

  “How much have you guessed?” he asked.

  I held up my fingers and ticked them off one by one. “Sets are androids. Two life-systems are competing, one having radiated out from here. The alien base here must have been destroyed. This is probably the relic of an explosion rather than a volcanic crater. You’ve been up here for five summers looking for the remains of what was here before it exploded. Is there more?”

  He seemed resentful, but accepted the situation grudgingly. There was still a little gleam in his eye, though, and it turned out to be more than the reflection of the lamplight.

  “You missed on one count,” he said.

  “What’s that?”

  “It wasn’t an explosion—not the way you mean. There was an explosion, but it was caused by the crash. This is an impact crater. I think a spaceship crashed here—right on top of the base where it was supposed to land. Spaceships have a habit of crashing hereabouts.”

  I appreciated the irony in the last line, but I didn’t really see that it mattered much, and I said so.

  He shook his head.

  “It matters. I don’t know what, they had on top here, but it wasn’t much. It wasn’t built of bricks. Maybe wood, maybe plastic...but something biodegradable. If they could make the Sets they wouldn’t need heavy technology to build a base. These spooks are biological engineers. What they built was consumed—maybe fairly rapidly. It’s not here to be found...because I’d have found it if I could. That’s why nothing will show up on the aerial photographs. Since the base was established—and since it was destroyed—there’ve been wholesale changes in the environment here. Co-adaptation, as you call it, or complementary evolution, or what the hell. There’s been no stable situation to be interfered with in such a way that the record of the interference would be preserved forever. There’s nothing here at the surface or in the shallow soil. That’s all gone.

  “But you can’t biologically engineer a starship. That had to be metal. And any mining they did had to be with heavy technology too. It’s the underground ramifications of the installation that will have been preserved, where they cut their way into the rock itself.

  “Now, if there was an explosion, it wouldn’t be too difficult to get to that underground part of the installation—if there was only an explosion, that is. A lot of the force of an explosion goes upward, and most of the rest sideways. Even a nuclear explosion wouldn’t have pulverized the underground part of the base. But the energy of an impact is straight downward. If a ship came down almost vertically, plummeting in free fall, there’d be one hell of a lot of energy to be dissipated and practically all of that would be absorbed by the mountain. That would smash up any elaborate series of cellars pretty extensively. Enough to leave no trace that anyone could recognize, even after a couple of hundred years, on the surface.”

  “But down there, driven into the rock to a depth we can only guess at, is the remains of the ship. That’s what we have to look for, the only way we can.”

  “You don’t have any evidence at all that your scenario took place,” said Linda quietly. “You only want it to be that way so it will give you an explanation for your failure to find anything on top and an excuse to go on.”

  “It’s the only explanation of my failure to find anything up here,” replied Gley, aggressively.

  “The alternative explanation,” she said, “is that both you and Alex are wrong. Great minds may think alike, but they sometimes think the wrong thing. Consensus is no guarantee of correctness.”

  I felt that she was being a little overpedantic, but the failure to find any evidence of anything with the dating equipment was weighing a little on my self-confidence too.

  “But it could be the way I see it,” insisted Gley.

  “It could be,” she agreed. “But even if it is, what makes you think you can find something down below? Do you think fate owes you the favor—the miracle—of preserving for you a negotiable passage down to the wreck? If there is a little piece of fused metal down there that just could be the remains of a ship, where do you think it’ll be? Encased in a jacket of re-fused magma is where—a jacket that could be hundreds of meters thick.

  “Suppose you do go down. Suppose there’s no limit to the fissures and the caves that they may or may not give access to. Suppose that there’s an underworld down there. And suppose you can’t locate your spaceship wreck, whether it’s there or not. What are you going to do? Spend the next five years wandering about inside the mountain? Just when do you give up?”

  “Not now,” he answered. “It’s too important.”

  “It’s a fool’s game,” she said. “A wild goose chase. Even if you’re right there could be no way of ever proving it. No way at all.”

  “All the rain that falls into the crater goes down those fissures,” said Gley. “Some stays in the pools, but not so much. A little gets expelled as vapor, but very little. The rest must work its way out in a spring probably a hundred miles from here. A lot of water flows through the rock there, and it’s worn away passages. I’ve been a little way into the fissures—I’ve seen them, though I daren’t go down because of the gas. If there ever was an installation here, and there was anything left after the disaster, then the water will have carried it down into the deep caves. I don’t have to find what’s left of the ship. I only have to find something. An artifact of some kind. A metal tool. Anything. And to find it, I have to go down.”

  “It’s a long shot that only a madman would play,” she told him, laying it on the line.

  “Then don’t play,” be said. “It’s my crater, and my game. Just give me the suit. You can stay up here and rot.”

  She glanced sideways, then, away from Gley and straight at me. I realized belatedly that the whole show had been for my benefit. She hadn’t been talking to him at all. She’d been talking at me.

  “Let’s get something to eat,” I said. “Then we can do a little more work. If we find nothing, we can sleep on it. There’s always tomorrow.”

  The look she gave me suggested that she doubted even that.

  CHAPTER TWELVE

  That night, as I tried to go to sleep on the cold wooden floor, the doubts finally collected their scattered forces and began an organized attack.

  If the Sets really were artificial organisms then why was it that their makers had left no trace behind? It was easy, of course, to invent an installation and then invent a spaceship to crash on top of it, scoring a hit so accurate that everything was obliterated. It was easy enough to wave an arm in the air like a conjuror producing a cockatoo and say that most of what they built was constructed out of local materials like wood and biodegradable plastics. But any theory you’re determined to stick to in order to account for a set of facts can be extended infinitely by secondary elaboration to protect it against any conceivable objection. Once you’re determined to construct a particular type of narrative all you have to do is keep twisting the storyline to fit in any awkward point that occurs to you.

  Objection: if there were Set-building aliens, why on Geb would they establish a base here, in the middl
e of the most useless land on the continent?

  Secondary elaboration: they came from a world where the atmospheric pressure was a good deal lower than sea-level pressure on Geb. This was the place they felt initially most comfortable.

  That was easy. It was also plausible, in its fashion. If there really had been aliens, and they really had established their base here for preference, it was the obvious answer. But it added one more twist to the story, one more weak spot that was papered over instead of being filled in.

  I realized all too well that if I were committed to another point of view I could probably build up a story just as comprehensive that made no mention at all of aliens. Maybe I could work something up from the notion of Sets as a decadent species. Maybe I could work out some new evolutionary subtlety to show up yet more of the weird and wondrous ways of natural selection. I’d discarded such accounts because of holes in them that I wasn’t prepared to paper over, but in the cold light of objectivity—or in a savage crossfire of opposed commitments—could my hypothesis hold up any better?

  I had one solid piece of evidence that I still might collect—if, as I’d predicted, the Sets did have a different variety of coding molecules, then that was another half-point in my favor. It was only half a point because coding-molecule variants do occur naturally, though not usually at the metazoan level. But even if it weren’t so, and the variety of coding molecule was identical with the species characteristic of the other metazoan species within the system, it wouldn’t prove that I was wrong. I could get round it by proposing that the Sets had been engineered out of some domestic animal instead of being built from the egg up. As evidence, the investigation might be slightly indicative, but as a crucial test it was useless.

  The main problem was, I decided, that there could be no conceivable piece of hard evidence that would prove me right. How could I turn up a datum that would show conclusively that there never had been any aliens? What would such a datum look like? Any actual substance we found had to support the theory. If we found an artifact, or radioactive material that had leaked from a nuclear pile, or a brick wall or plastic zip-fastener...anything of that order could be conclusive. But in view of the fact that all the hard evidence that might exist supported my case, I had to accept the corollary that the failure to find any such evidence must be taken as cause to abandon it. I could, if I wished, cling to the notion forever, with the desperate tenacity of obsession, and no one could ever put up evidence to demonstrate that I was wrong. But that would make the whole story into an article of faith and not a scientific hypothesis at all. If I wanted to maintain my commitment, then I had to find something solid to rest it on; and I had to give myself a time limit of some kind. I had to specify what constituted doing my utmost to find the proof, and if—when I had done it—no proof had turned up, I had to be prepared to abandon the hypothesis, even if it meant letting the paradox of the Sets lie forever unresolved.