Convergent Series

by Larry Niven

  Vatch watched some of them bend over the bodies of those he had injected. They might have been nibbling at the flesh above the hearts. A minute of that, and then they fell over and lay as dead as the ones they had been trying to rescue.

  Good enough, thought Vatch. He flashed the light on his bottle to check the supply of Spectrum Cure.

  It was just short of dead empty.

  Vatch sighed. The horde of dead men had drawn away from the casualties— the dead dead ones— and gone back to trying to climb the rock. Some would make it. Vatch picked up his sword. An afterthought: he injected himself. Even if they got to him, they would not rouse him from death before morning.

  The scrabbling of finger bones against rock became a cricket chorus.

  Vatch stood looking down at them. Most of these had only been dead for hours. Their faces were intact, though slack. Vatch looked for Roy Tanner.

  He circled the edge rapidly, striking occasionally at a reaching arm, but peering down anxiously. Where the blazes was Roy Tanner?

  There, pulling himself over the lip of the crack.

  In fact they were all swarming into the crack and climbing over each other. Their dead brains must be working to some extent. The smell of them was terrific. Vatch breathed through his mouth, closed his imagination tight shut, and waited.

  The nightwalker remains of Roy Tanner pulled itself up on the rock. Vatch sprayed it in the face, turned the body over in haste, and found it: Roy Tanner's medical kit, still intact. He spilled out the contents and snatched up Roy's bottle of Spectrum Cure.

  He sprayed it before him, and then into the crack, like an insecticide. He held his aim until they stopped moving... and then, finally, he could roll away from the choking smell. It was all right now. Roy had fallen early in the battle. His bottle had been nearly full.

  ***

  For something like six hours they had watched each other: Tomas Vatch on the lip of the rock, seven nightwalkers below. They stood in a half circle, well out of range of Vatch's spray gun, and they stared unblinking into Vatch's flashlight.

  Vatch was dreadfully tired. He had circled the rock several times, leaping the crack twice on each pass.

  "Cured" corpses surrounded the base and half filled the crack. He had seen none of them move. By now he was sure. There were only these seven left.

  "I want to sleep," he told them. "Can't you understand? I won. You lost. Go away. I want to sleep." He had been telling them this for some time.

  This time it seemed that they heard.

  One by one they turned and stumbled off in different directions. Vatch watched, amazed, afraid to believe. Each nightwalker seemed to find a patch of level ground it liked. There it fell and did not move.

  Vatch waited. The east was growing bright. It wasn't over yet, but it would be soon. With burning eyes he watched for the obvious dead to move again.

  Red dawn touched the tips of glacier-spilled rocks. The orange dwarf sun made a cool light; he could almost look straight into it. He watched the shadows walk down the sides of the rocks to the ground.

  When the light touched the seven bodies, they had become bright green patches, vaguely man-shaped.

  Vatch watched until each patch had sprouted a bud of yellow in its center. Then he dropped to the ground and started walking north.

  Wrong Way Street

  ***

  "Wrong Way Street" has never been in any of my collections; but it has been in a Galaxy "best" anthology, and an anthology of time-travel stories, and a theme collection of "first man on the Moon" stories. More success than I expected for my second professional sale. Naturally I remember the story with fondness. I sometimes wish I could write more about the critters who built that peculiar base on the Moon... but of course there's no way.

  ***

  Mike Capoferri turned out to be at one time in his life the loneliest man on the Moon. But it was not his first venture into aloneness. He had felt it before, almost twenty years before, when he was twelve and his eight-year-old brother died.

  Young Tony had been riding a Flexy, a kind of bobsled on wheels, down the hill road above Venice Boulevard. At the bottom of the hill he had turned hard right onto Venice. The Flexy had flipped over on its back, and its blunt rubber handle had poked hard into Tony's stomach.

  One of the first things the doctor did was to take Tony's blood pressure. It was low, which meant shock.

  It started to fall almost as soon as the blood pressure cuff was removed, but the doctor didn't know that until it was too late. Tony's spleen was ruptured.

  Mike had loved his younger brother. He sat in his room most of the time, unable to get used to his loss, and not really trying. After four weeks of it his father neglected his own grief long enough to take Mike to a child psychologist.

  Mike was a recent but ardent science fiction fan. "I want to change it, Doctor Stuart," he said earnestly.

  "I want to go back to four weeks ago and take away Tony's Flexy." He meant it, of course.

  Doctor Stuart had worked hard to get Mike to say those words. If he was thinking in terms of sibling rivalries and guilt feelings, it didn't show. "You can't do that, Mike. Time is a one-way street with no parking spaces. You just have to keep going."

  "Until you have an accident," Mike said bitterly.

  Doctor Stuart nodded. "Or run out of gas," he added, because he himself was old enough for the analogy to apply. They talked for almost three hours, with Mike doing most of the talking. Afterward Mike gradually stopped mourning.

  ***

  When Mike Capoferri graduated from high school he had become intensely interested in space travel.

  His first year at Cal Tech was the year Walnikov landed on Mars. Mike was determined to follow.

  In a way he traveled further than Walnikov. He never got to Mars, but he did make it to the Moon. And unlike Mars, the Moon once had intelligent visitors.

  ***

  Mike was one of many. Thirty men and women had come to the alien base, determined to probe all its secrets. By this time Mike was thirty-one years old some and held doctorates in physics, mathematics and philosophy. He was tall, dark, not too homely, a little too earnest. He got over that at the base, where the only defense against strangeness was a sense of humor.

  Besides the base, the aliens had thoughtfully provided one spaceship. It rested on its side near the base, a fat cylinder with conical ends and asymmetrical bulges in unexpected places. Mike began going through the ship before he ever entered the base, and he kept at it through the years. This wasn't unusual.

  The ship was thought to be the real treasure, for its star charts showed (in hard-to-read notations in ultraviolet ink) that it had cruised between widely separated stars. It may have had a faster-than-light drive.

  The base personnel lived in the base itself, with their own air regenerating system and their own air lock built into the open alien airlock. There was plenty of room for them. The aliens had averaged ten feet tall, and there were things which must have been bunks for forty-eight of them.

  Still, the base took getting used to. The alien engineers had put steps and ledges in the floor wherever the ground beneath wasn't exactly level. Newcomers learned not to sit on the "bunks," which looked like pieces of free-form sculpture, felt like foam rubber with a metal core, and changed shape without warning. They were told not to touch mosaic designs which had been marked with paint, for the design might hide a control of some kind.

  ***

  It was four years since Mike had landed on the Moon. In that time the human tenants had made a great deal of progress.

  An emergency repair kit from the ship had yielded a method of creating artificial crystals of almost any shape from almost any solid, by building them up atom by atom. Already ships had lifted on rocket motors built from large diamonds.

  A box which held perfectly preserved sections from non-terrestrial animals, possibly used as food had given them a field which would interrupt any chemical process. The applications were n
umerous and varied. A short-range death ray. A beam to fight forest fires. A new method of inducing suspended animation, very useful In surgery.

  A sculpting implement, used by the aliens as a means of recreation (the base was infested with the statues they had left behind), had become a disintegrator. Turning it on had been heartbreakingly difficult.

  Mike had solved that problem in his second year, but had never been able to turn it off. The alien rec room had to be kept in vacuo, with a separate airlock, because air disappeared into the little ball of nothing at the end of the sculpting tool.

  Enough progress had been made on the alien number system that it was possible to do calculus with it.

  The money system, however, remained a complete mystery.

  Aside from the crystal maker and the airlock controls, the ship was as great and as fascinating an enigma as ever. The rows of "bunks" near the back— suppose a bunk changed shape and dumped its occupant during a 5G maneuver? The controls, in plain sight on a common-sense control board in the bunk section— what did it take to make them work? And what was the purpose of the dull red tetrahedron, seven feet on a side, which was set in the rear wall of the passenger section?

  Mike was taking a coffee break with Terry Holmes, a pretty, cheerful, blonde little Doctor of Languages, the day he first said, "I think I know what the central pyramid is for."

  Many people had said that, of course, but Mike was not addicted to wild guesses. "What is it?" Terry asked eagerly.

  "It's a time machine," he said.

  Terry got mad and left the table. The Halloween before Mike had dressed to imitate an alien statue and had frighteningly "come to life" before her horrified eyes. Since then she had been sensitive about his jokes.

  "No, really," he told her during the afternoon coffee break. "The idea makes a great deal of sense. We can be sure that the aliens had suspended animation, can't we?"

  "Sure." The reaction damping field was perfect for that purpose.

  "Right. So if they had time travel to go with it, it adds up to an FTL drive. They can sleep through a hundred-year journey and then move back a hundred years."

  "You're only guessing," Terry told him. "If the pyramid is an interstellar drive they didn't need time travel.

  If they had suspended animation they could have spent generations on one trip. We'll have to do that ourselves, probably."

  "Sure, but the idea of a time-travel device in the center of a spaceship is at least logical. I've been working on the thing for quite a while, and I think that's what it is. I've made it produce a weak gravitational field, so I know it can distort four-space."

  "Then it's for artificial gravity." She laughed as his face fell. "Mike, I dub thee world's champion rationalizer. And now I've got to get back to work."

  For a month nothing important happened. Carlos found a way to turn on the alien television set and got three-dimensional, technicolor static. Terry made some progress with the alien money; she had a tentative ordering of coins into either ascending or descending value, if in fact they were coins.

  Then one day the ship disappeared.

  ***

  Mike was trying something new. He had set up a magnetic field around the control board and pushed one of the pyramid knobs. There were two of these, the same shape and color as the massive machine behind him. Now he put a block of glass between the poles of his generator and cut the current. The knob lit with an almost invisible blue glow. Suddenly everything was in free fall.

  "Eureka," Mike said absently, meaning: at last I've gotten some action out of the beast. When he turned his head he saw that the big red tetrahedron was base forward. He'd heard no sound of motion.

  A faint purple line grew across the top of the board. There were too many unknowns crawling into his experiment. Mike looked back so that he could see the big pyramid turn around, and switched his generator back on. Results came instantly.

  Mike sat up trying to rub the pain out of his eyes. It was several seconds before he could open them.

  The pyramid was apex-forward again. Mike got up and pulled out the pyramid knob, waited a moment for luck, then turned off the field generator. At last he sat down perspiring on an alien "bunk." What a sight that had been! He couldn't even remember it without his eyes hurting.

  Mike's bunk inconsiderately dropped him on the floor. He promptly got up and made for the airlock, feeling a crying need for coffee, Terry Holmes, conversation and familiar things. The strangeness had suddenly become too much to take.

  His momentary fear of the ship was gone by the time he left the airlock. What had started it, anyway?

  Merely the fact that he'd gotten things to working at last. Now they could make some real progress.

  He moved toward the base in easy four-foot leaping strides which splashed waves of dust when he landed. He was looking straight at the base airlock, but he was preoccupied by the thought of coffee and the familiar, instantly suppressed wish for a cigarette. He was half way there before he noticed...

  The base airlock was closed. The alien airlock!

  Mike stopped short, staring. At first he was only bewildered, not horrified. How could the doors have closed? The bulk of the UN airlock would have stopped them. Or was the alien metal strong enough to—

  Mike made a strangling noise. The human airlock must have been crushed flat!

  He ran.

  ***

  It had taken the base team months to open those doors. Although Mike had arrived a year later, he knew how they had done it. But why had they closed it? Had some fool been meddling with the controls?

  With alien designing, practically anything could be a control. The aliens had cleverly hidden their knobs, buttons, and pressure sensitive surfaces in esthetically pleasing design. The doors could have been closed by somebody accidentally leaning against a wall. Nobody had ever bothered to find out how to open them from the inside.

  Mike began picking pressure points out of the mosaic on the outer door. He stopped to wonder if the base held air, then decided that it didn't matter. Anyone still alive would be wearing a spacesuit under emergency regulations.

  He was taking a breather when he noticed that the UN ship was gone.

  Had they started to evacuate the base? No, the ship only held four people and cargo. They must have gone for help.

  The lock had been designed for use by two ten-footers with fourteen-foot branched tentacles. Mike needed forty minutes and a great deal of ingenuity, but finally the lock swung open.

  There was no wreckage in the lock.

  "Dust," Mike told himself. There was almost no moondust on the worn path between the ship and the base. Yet dust had spurted beneath his boots... and there was no Earth-built ship, and the station was locked.

  "Eureka," he said softly. "They haven't found the base yet. I've traveled in time."

  Yet there were other possibilities. Mike began seeking them out even as he was going to work on the inner door. Maybe he had gone forward in time, to when the base had been restored as a museum. Or, worse yet, to some time after the return of the legitimate owners. (That had once been a favorite joke around the base: "Hey, look, they're coming back!") He might even be in another time track, one in which the base had never been abandoned. After all, he really didn't know much about the machine he'd been running.

  One look through a telescope would have told all. He could see the Earth from where he was standing, huge and full, of course, he could not make out the shapes of the continents.

  He kept working.

  He was rigidly tensed as the doors folded back. Had the station been abandoned yet? Was his the honor, God help him, of meeting the first inhuman intelligence? But nobody came to meet him.

  His air pressure dial read 22.4 pounds/square inch. This must be alien air.

  ***

  He walked through the base, slowly and cautiously; after four and a half years he was used to watching where he stepped. The base was like a haunted house. There was an air of strangeness here t
hat he had never known before, not even when he had first come. Not Commander Link Day of UN Flight Four, but Mike Capoferri, was the first man to set foot in this place.

  Could he get back? Sure he could. The other button must be the one that controlled flight into the future.

  But even then, he might not be able to tell anyone.

  Hey, he told himself proudly, I'm a time traveler! Wait here, he answered solicitously, I'll call the medic.

  No, he protested, I can prove it. Get in the ship and I'll show you. But that could go wrong in a dozen ways. He'd want to know more about what he was doing before he tried this again.

  Kilroy was here, he thought.

  If he left marks of his visit, they would still be here when he returned to his own time. He could scratch his initials— hmm.

  He turned right. When he reached the rec room he went to one of the sculpting machines and began to take it apart.

  The tool itself looked like a big, fat mechanical pencil. It was set in a brace which could be moved to any part of the work. The brace allowed the tool to move freely under pressure and held it steady otherwise.

  The pointed business end of the tool generated a sphere of emptiness into which matter vanished without trace.

  Removing the tool from the brace was almost easy. Turning it on took just under an hour. Once Mike almost gave up the idea, but he kept at it, for he had nothing else which would mar any of the indestructible materials used to build the base.

  He held the device like a pencil, but more carefully. His first thought had been to put a portrait of Commander Link Day on the statue of an alien female in the bunk room. He'd changed his mind. It would be dangerous and stupid to change his own past. He had to do something which would not be discovered before he arrived at the base, in 1985.

  The inner side of the outer door would be a good place to hide a carving, because nobody had ever seen it. It folded against the airlock wall when the lock was open.

  A wind blew toward his hand as he walked. There must,be a way to shut air out of the disintegrator, but he hadn't the time to find it. He couldn't remember whether the team had found air in the base. If they had, he was changing the past right now.