PROBABILITY MOON

by Nancy Kress

  “Negative, Doctor,” Johnson said. “Not without decelerating for shuttle launch, which would be counter to our military mission. If you—” A burst of unintelligble static.

  “What? What was that?” Bazargan said.

  More static. Then nothing.

  Bazargan, Gruber, and Ann looked at each other. David Allen smacked his fist into his hand and stalked off, scowling. Enli looked uncertainly after him, and then at Ann.

  “Something is happening up there,” Gruber said.

  “I think,” Bazargan said quietly, “that we had best assume the worst. Dieter, if the artifact—Tas—emits that wave effect that destabilizes atoms, are we sufficiently protected if we stay right here?”

  “No. Too open. But rock is a good insulator. If we go deeper inside, we will be. Provided we avoid areas of high radioactivity.”

  “Do you know how to get to a safe place from here?”

  Gruber shook his head. “No. I came this far on my first trip, to this basin, then went back the way we came. But we can’t do that. Even if the Worlders have gone away, it’s a long distance outside to the next opening I explored. We would be exposed far too long. To both villagers and the wave effect, if it comes.”

  “So we go on,” Bazargan said. “Are there openings under that overhang?”

  “We will find out,” Gruber said. “Circle around the spring against the wall, Ahmed, to that tunnel there. Stay away from the spring. Ann, you must leave those plants.”

  “I’m taking specimens with me,” she said.

  This time Bazargan went second, behind Gruber, which gave him much more benefit from Gruber’s torch. The comfort of this was balanced by the tunnel’s unknowns. Bazargan discovered that he was walking with every muscle clenched against rockfall or crevice, and consciously made himself relax. Remember Iqbal of Lahore, that zealous reformer: Upon what manner man is bound to manl That tale’s a thread, the end whereof is lostl Beyond unraveling. Bazargan smiled grimly.

  The tunnel turned steeply downward. “No loose rock,” Gruber said, “but we don’t want to go too deep. Still, we will try for a small while.”

  “All right,” said Bazargan, a man bound to man beyond unraveling.

  They moved in silence for what seemed a long time. Occasionally the tunnel narrowed, but not unbearably. Occasionally it widened, so that it was almost a cavern in itself, long and narrow. Frequently Bazargan heard water, although he saw no more of it. Once Gruber stopped to shine his torch on the wall.

  “Look, everyone. See that thin layer of clay there? That’s from the time of the asteroid impact.” The layer wavered along the wall, rising and falling in the patterns of rock uplift, a mute curving testimony to global disaster.

  Longer silent walk, steeper incline. Bazargan began to sweat. How deep were they going? Perhaps they should go back, look for another opening … Gruber had said the rock would shield them from the wave effect that Syree Johnson might let loose on the world. Shielding would do no good if they ended buried alive.

  In front of Bazargan, Gruber abruptly disappeared.

  “Dieter! Are you all right?”

  A long moment, then Gruber’s voice from somewhere below. “Ja. It is all right, just an incline. Not too steep. You can slide down on your asses. There are ways back up from here.”

  He shone the torch back along the slide, and Bazargan saw a fairly smooth incline of perhaps thirty degrees. He sighed, sat on the blanket he carried, and slid down with no more than a single sharp jolt to his tailbone as it went over an unyielding stone. At the bottom he stood and moved away for Enli to follow him.

  He and Gruber stood in a large dark cavern illuminated only by Gruber’s torch, which was pointed the other way. In the gloom Bazargan could see stalactites and stalagmites like large double teeth. Water dripped from the ends of the canines. Sweat dripped from Bazargan, who was unprotected by the temperature-modulating suit.

  “Something is not right here,” Gruber muttered, studying a display strapped to his thick wrist.

  “What isn’t right?” Bazargan asked, but before Gruber could answer, Enli came down the rock slide, an s-suited alien, neckfur flapping, eyes wide and terrified. But the girl made no protest, only picked herself up and moved away from the bottom of the slide as Ann rushed down it.

  “What is not right?” Bazargan repeated. The words came out slowly. Something was wrong with his head; it felt muffled in soggy wool. Fatigue, most likely.

  Allen slid down the rock, graceful and scowling.

  “The geothermal gradient,” Gruber said, and his voice sounded as muffled to Bazargan as his own. A headache was starting just behind Bazargan’s eyes. Fatigue, anxiety, hunger. They had not stopped to eat since last night.

  “What about the … the gradient?”

  Gruber frowned at his wrist display. “It gets hotter as we go deeper, ja. That is normal. Even separating out the effects of magma, naturally occurring radioactivity heats the rocks. Small amounts of radioactivity here—you are not in too much danger, Ahmed—even on Earth. The rock holds the heat, it is an excellent insulator. But as you go deeper, the rate of temperature rise should decrease, since most radioactivity is near the surface. But here, the rate of temperature increase is rising.”

  It was an effort to follow this. From the depths of his headache Bazargan summoned the expected query. “Why?”

  Gruber shrugged. “This is not Earth.”

  “A genius among us,” David Allen said, and for a second anger flared in Gruber’s blue eyes. It died away, replaced by the same lethargy Bazargan felt.

  He made himself speak. “Lead on, Dieter.”

  Gruber shuffled forward, shining his light toward the opposite side of the cave. Multiple openings fringed the distant wall. Gruber started up one.

  “Pek Bazargan,” Enli said, walking behind him, “we should not go this way.”

  It took Bazargan a minute to assimilate what she’d said, or even that she’d spoken at all.

  “Why not? Dieter, wait.”

  Dieter shuffled to a halt, turned ponderously to shine his torch on the people behind him.

  Enli said something in World. After a moment she repeated it in English. Her voice was too quick, too sharp. “The other way goes up. You said it gets too hot deeper. We must go up!”

  Up. Yes, that was right. Enli was right. They must go up; Dieter said they must go up.

  The humans huddled in confusion.

  “Up!” Enli said.

  Up. Yes, that was right. Enli was right. They must go up; Dieter said they must go up.

  His head hurt, Bazargan thought.

  They must go up.

  Someone seized his hand and put in Ann’s. Enli. She forced all their hands together, squeezed past them to the back of the line, and pulled. The train of humans shuffled after her, heading up.

  But then they were back in the caves with stalactites. Bazargan blinked. Wasn’t that down? Weren’t they supposed to go up?

  He couldn’t remember.

  Enli was pulling them along, into a different tunnel. She had the torch, somehow; she was in the lead, somehow. They lurched somnambulently along in the gloom. Bazargan didn’t know how long; perhaps he was asleep. He felt asleep, dreaming, a long dream of stumbling along stone paths, some even and some rough, some wet and some dry, climbing, always climbing …

  Time went by.

  More time went by.

  All at once, something happened.

  His neck snapped … No, his head snapped. Something inside it abruptly gave way and he could think again. It was like the cracking of a shell around his skull.

  “What … what?”

  All four humans looked equally dazed. Enli watched them with anxious eyes. Finally she said, “The soil was very poor. For all of you.”

  “A field of some type,” Dieter said, consulting his displays. “Only it doesn’t register here … except that the rate of geothermal rise is now decreasing!”

  Ann said excitedly, “A field
that affects thought … but Dieter, it has to be electromagnetic!”

  “No. Not according to my displays,” Dieter said. “But, Ahmed, while we were … were like that, you took another seventy rads.”

  Bazargan said, “What’s my total?”

  “One hundred ten.”

  Not good. He would be sick in a day or two, although not fatally, even without medical help. Still, it would be very unpleasant, and it would probably shorten his life in the long run.

  David Allen was stripping off his s-suit. “Here, Doctor, take mine.”

  “I … thank you.” Why not? They had agreed to rotate suits, and Allen was the youngest team member.

  “You are all right here, David,” Gruber said. “Comparatively. Listen, I hear water.”

  “Down that tunnel,” Ann said.

  “Wait here.” Gruber passed out smaller p-torches and disappeared with the big one. The others waited. They stood in a cave the size of a small bedroom, barely large enough to let Bazargan control his breathing, given that the cavern lay under tons of rock. But the floor was dry and reasonably level, and in the light from his torch Bazargan could see an equally smooth, rounded ceiling. One of Dieter’s emptied lava deposits, perhaps. In the gloom Bazargan heard the others breathing: Ann slightly fast, from the climbing. Enli slower. And David Allen, ragged and quick.

  The boy should not be that exhausted from the climb. Bazargan’s muscles all ached, and his stomach grumbled, but his heart wasn’t racing and he had a generation on Allen. So what was bothering David?

  Ann said, “If it wasn’t an electromagnetic field, what the hell was it?” No one answered. Bazargan pulled on Allen’s ssuit and felt it mold itself to his different contours.

  Gruber returned, lugging an expando full of water. Expan-dos folded flat and weighed almost nothing, but at a touch they formed tough, impermeable bags shaped by thin flexible struts almost impossible to break. Every s-suit carried a few.

  “The water’s good,” Gruber said. I suggest we camp here—eat and drink and sleep. It’s as good as anywhere else.”

  The suggestion was welcome. They prepared the tasteless, nutritious food powders with Gruber’s water, drank deeply of more water—it tasted metallic and warm—and arranged themselves to sleep.

  Bazargan lay listening to Gruber and Ann argue softly.

  “Our thinking was affected,” Ann said. “And Enli’s wasn’t. She was the only one functioning normally. That suggests only a few possibilities. An odorless gas that retarded our brain functions but not hers, and I can’t imagine what that could be chemically. A pheromone to which she’s adapted but we’re not—except that the tunnel was too dark and dry for any sort of vegetation. Well, maybe not any. Or an electromagnetic field.”

  “It wasn’t an electromagnetic field,” Gruber said, “or the display would have caught it. There might be dark-adapted fungi emitting pheromones.”

  “For what purpose? Why would they evolve? Surely conscious thought can’t be an evolutionary threat to fungi growing a half kilometer underground!”

  “Not likely,” Gruber said grudgingly. “All right, then, the odorless gas. But Ann, I am more puzzled by the increase in rate of geothermal gradient as we descended and the decrease as we climbed. That is opposite to normal. And if the rate of increase changed at that same constant, it would melt all rock at about thirty kilometers down, and nothing indicates that’s true here.”

  “So what do you think controls the gradient?”

  “I can think of nothing.”

  “Me neither. Only an electromagnetic field.”

  “Ann, I told you …”

  Eventually they stopped arguing and Bazargan heard their breathing grow even and deep. Enli’s was already regular, but she was an alien; impossible to know if she was really asleep. The last thing Bazargan heard as he drifted off, the smell of damp stone earthy in his nostrils, was David Allen’s breathing. Quick, ragged, agitated, as if, for Allen, sleep had been murdered along with poor little Bonnie and Ben Mason.

  SIXTEEN

  EN ROUTE TO SPACE TUNNEL #438

  A conclusion is just the place where you got tired of thinking.

  Syree tried to keep on thinking, even though the towing operation was proceeding without a glitch. She stood on the crowded bridge considering possibilities, contingencies, feasible disasters.

  “Acceleration one gee, speed eight point eight clicks per second,” the helmsman said.

  “Continue acceleration,” Peres answered.

  “Acceleration continuing.”

  Someone behind Syree let out a long low whistle between clenched teeth.

  By now every person on the Zeus knew the ship’s covert mission. It was impossible not to know. The Zeus had dropped from geosynchronous orbit to twenty-three hundred clicks above the planet. Carefully the Zeus had matched the orbit of World’s smallest and fastest “moon,” Orbital Object #7. That moon now stood jammed up against the front of the Zeus, its bulk filling the viewscreen like a huge gray peeled grape. The Zeus wasn’t towing the artifact as much as unceremoniously shoving it out of orbit and into space. That shove took everything the ship had.

  “Acceleration one gee, speed ten point six clicks per second.” The helmsman had been instructed to announce every three minutes.

  “Continue acceleration.”

  “Acceleration continuing.”

  Orbital Object #7 was roughly eighteen times the mass of the Zeus, which was capable of twenty gees at maximum power. Nobody used maximum power for more than a few moments of evasive action, because nobody wanted to crush all the humans aboard into pulpy jelly. But to accelerate an object eighteen times as big as you are at a rate of one gee, you needed eighteen times one-gee power. Syree could feel the Zeus straining around her. She felt it in her bones, in the vibration in her head. How much more, then, must Peres, her commander, feel it.

  Peres said, “Stability report.”

  “Maintaining stability.”

  The Zeus had to target its shove at the artifact’s exact center of mass. Electromagnetic stabilization helped, of course; Syree had induced the field across the surface of the object. Thank God it was a conductor. She couldn’t imagine this operation succeeding if it weren’t.

  “Acceleration one gee, speed twelve point four clicks per second.”

  “Continue acceleration.”

  “Acceleration continuing.”

  The farther the ship shoved the object out of orbit, the easier the shoving would be. The inverse square law was on their side. The Zeus would accelerate all the way to the space tunnel, rather than beginning deceleration halfway. This would cut the transport time to five days, seventeen hours, three minutes. It also meant that when the artifact sailed into the space tunnel, it would be moving at four thousand eight hundred clicks per second. Nothing had ever flown into a space tunnel moving that fast. No one knew what would happen when it did. But then, no one knew a lot of things about this desperate operation.

  Behind Syree, someone coughed, then coughed again.

  “Clear the bridge!” Peres snapped. So he felt the strain, too. Officers left, reluctantly. Syree stayed where she was. An image came to her, from an old training film: a submarine way below its depth, the bolts forced out of its cracking hull by water pressure. One had flown into the head of the helmsman, his crushed skull accidentally caught on film to horrify generations of cadets.

  Her comlink beeped. “Yes?”

  “Zeus, this is Dr. Bazargan. Respond, please.”

  “Colonel Johnson on the Zeus. Yes, Doctor?”

  “We’d like an update on what’s happening out there,” Bazargan said. To Syree his voice sounded uncharacteristically harsh.

  “We are towing the artifact toward Space Tunnel #438,” she said crisply. “No sign of enemy craft. No change in status.”

  The helmsman said, “Acceleration one gee, speed fourteen point one clicks per second.”

  “Continue acceleration.”

  “Acceleration c
ontinuing.”

  “But there has been a change down here,” Bazargan said, even more harshly. “The natives have declared humans unreal and have tried to kill us. They did kill Ben and Bonnie Mason. The rest of us have fled to the Neury Mountains, where we are now. We cannot leave them without being hunted again. Food is limited. We tried to raise you last night to tell you all this, but you didn’t answer. Can you send a shuttle for us?”

  A shuttle? Didn’t these so-called scientists understand the first thing about the physics that governed their lives?

  “Negative, Doctor,” Johnson said. “Not without decelerating for shuttle launch, which would be counter to our military mission. If you—” The ship jolted hard enough to knock the comlink out of her hand.

  “What the hell was that?” Major Canton Lee said, picking himself off the deck.

  The helmsman said shakily, “I don’t know. The … the artifact pushed back!”

  Syree studied the displays. Nothing unusual. She questioned the helmsman, but all he could say was that the displays blinked for a moment and the artifact shuddered. Now it had stopped.

  “Acceleration reading!” Peres snapped.

  “Acceleration one gee, speed fifteen point eight clicks per second.”

  “Continue acceleration.”

  “Acceleration continuing.”

  It did, evenly, as if nothing had happened. Peres said to Syree, “Don’t use your comlink again, Colonel.”

  “Commander, there’s no way the signal from or to the planet could have affected the—”

  “Are you positive about that, Colonel? Do you really understand the physics of this thing so completely that you can say positively what does and does not affect it?”

  Syree was silent.

  “Acceleration one gee, speed sixteen point five clicks per second,” the helmsman said, returning to standard orders.

  “Continue acceleration.”

  “Acceleration continuing.”

  Syree deactivated the comlink and put it in her pocket. On the viewscreen Orbital Object #7, nine hundred thousand tons of featureless gray sphere, moved ponderously from its orbit toward Space Tunnel #438, over a billion klicks away across empty space.