Recursion

by Tony Ballantyne

  “Can you think of anything we’ve forgotten?” Robert asked, his gaze still traveling from viewing field to viewing field.

  “No,” said Herb. He wished he could think of something.

  “Okay, here we go, then.”

  When he was younger, Herb had thought he knew all about superluminal travel. He was now just old enough to admit that he didn’t. The AIs insisted that the methods used were beyond human intelligence, and no human had yet been able to contradict them. Herb did understand the basic principles, however.

  He knew that special relativity dictated that it was impossible to travel faster than light in an area of flat space-time; however, he also knew that general relativity placed no restrictions on two regions of flat space-time moving apart at greater than light speed. The equations describing a warp field that could move a region of flat space-time faster than light had been derived long ago, at the end of the twentieth century, before even the first AIs had appeared. Human intelligence had shown that exotic matter was required in order for the fields to exist.

  It was fair to say that contemporary AIs insisted that the superluminal travel they provided was far removed from those “trivial” equations, but they did agree on two particulars.

  First, the warp drive required exotic matter.

  Second, it involved moving a region of flat space-time around the universe.

  Herb was in such a region now. And the ship’s velocity within that flat region must be considerable.

  Herb wondered why.

  They inserted themselves back into regular space-time. The forward-viewing areas lit up with brilliant white light. Those to the rear of the cabin darkened.

  “Atomic explosion,” Robert said in some surprise. “Their detection systems are better than I expected, as are their reactions. If we were at rest relative to the warp, we’d have been right at the heart of that. As it is, we’ve probably got the length of this sentence before they get a lock on us again. Ah! Got it!”

  “Got what?” called Herb.

  “The security web monitoring this system. I’ve altered our status flag to “friendly object.” See what I mean when I talk about superior intelligence? It’s not about having a stronger hull or more powerful weaponry. The battles of the twenty-third century aren’t fought by AIs. They’re fought inside AIs.”

  “Wha—?”

  The viewing screens glared brightly again. This time the ceiling darkened.

  “What was that?” Herb shouted.

  “Another atomic. There is a second web watching the first, monitoring its integrity. It noted our changes and launched another attack. I jumped us forward a couple of light seconds to escape the blast. Don’t worry, I’ve also tackled the second web.”

  “Does that mean we’re safe now?”

  “We’ve always been safe. If, however, you mean, ‘Will we be attacked again?’ then I’m afraid the answer is yes. We can’t stay hidden forever. The surveillance systems will take counter-countermeasures against our countermeasures.”

  Johnston reached into his breast pocket and pulled out his white handkerchief. He flapped it twice in the air and then spread it flat on the sofa next to him.

  “Okay, Herb. Now to replenish this ship’s mass. The planet below has been converted by saliva nanotechs. Are you aware of the term?”

  “Yes.”

  Robert felt in a pocket and pulled out a silver cigar-shaped machine which Herb recognized as one of his own VNMs, placing it on the white handkerchief.

  “The term ‘saliva nanotech’ was coined by Katie Kirkham,” he explained.

  “I know,” said Herb.

  “It describes a simple VNM, the principal use of which is to convert matter into suitable building material for other VNMs. It obviates the need for a stomach or other such device being built into the principal VNMs in an area, thus speeding up the rate of replication, and hence construction.”

  “I know,” said Herb. “I said I’d heard the term before.”

  “Drop a few saliva nanotechs in a suitable area, leave them for a while, and when you return you have ready-processed material for other VNMs to use.”

  “I know.” Herb was becoming quite angry. “I also know that you use them with caution. You don’t want them getting away and converting everything around. And that you have to tailor them to the prevailing conditions. Those set to find and reclaim silicon would be no good in water.”

  Robert ignored him. He waved a hand at the VNM he had taken from Herb’s accidentally destroyed planet.

  “This machine that you built does its own conversion. Its silvery color is due to the prevailing mineral content of the area of the planet where it was released. If someone were to travel over your converted planet, I imagine the color of the machines and makeup of the machines they saw would vary according to the former local geology.”

  “That’s right. I know. I designed it.”

  Robert looked a little surprised.

  “Surely you mean, you purchased the design for a type six self-replicating machine and made the appropriate modifications?”

  Realization flashed through Herb. It finally hit him. He finally understood.

  “You’re doing this deliberately, aren’t you? Every time things get tense. You do your best to get me annoyed, just to take my mind off things.”

  Johnston smiled. “That’s right, Herb.”

  The smile widened. Herb counted ten teeth, gleaming against the pink flesh behind Robert Johnston’s dark lips.

  “I didn’t want you concentrating too hard on the fact that we were about to descend onto an Enemy planet to steal some of its building blocks for our ship, or that this region of space has been seeded with security nanotechs, several of which have attached themselves to our ship and are currently at work converting our hull into more security nanotechs. I’d guess we have about ten minutes before this lounge dissolves before our eyes.”

  “Don’t they think we’re on their side like everything else in here?”

  “No. Too small. They’re not part of the security web. They’re just here as another line of defense in case the web doesn’t work. It’s a very effective passive defense, too: they’ll eat anything that isn’t labeled as inedible.”

  “Well, label us inedible.”

  “I’m doing that even as we speak. They’re transmitting a code using a public key system. Obviously they inherit the key from each other when they replicate. If I can figure out the key and send back a message encoded using the private key, they should trust us.” He closed his eyes.

  “Come on,” said Herb, squirming nervously on the sofa. “They’ll be through any minute now.”

  Robert opened his eyes in puzzlement.

  “Oh, sorry. I solved that problem while I was explaining it to you.” He tapped his head and rolled his eyes. “I must remember to keep you informed. No. I was just working out the coordinates for the transition to the planet’s surface. Okay. We’re jumping now.”

  Herb clenched his left fist in frustration. His right hand was too sore from clutching Robert’s machine.

  “What is the point of me being here?” he complained. “I can’t think fast enough to beat the Enemy. I don’t know what to do, anyway.”

  “I need you to press the button that makes that VNM reproduce, remember?” Johnston replied, pointing to Herb’s right hand.

  Herb looked at him in disbelief. “Is that it? Couldn’t you place it on a timer or something?”

  Johnston shook his head slowly and sighed. “Oh, Herb. Why won’t you trust me? There are some aspects to this mission that only a human can accomplish. If you will just be patient, you’ll see what they are. Okay. Let’s jump.”

  There was a sudden discontinuity and then they were hovering above the surface of the destination planet.

  “Nighttime,” said Herb.

  “No,” muttered Robert, distantly. “We’re in interstellar space. This planet has no star. It wanders alone.” He nodded thoughtfully. “There are more of
these planets than you might expect; they’re just incredibly difficult to find. Hold it. I’ll adjust the view so you can see better.”

  Virtual daylight filled the ship as he adjusted the viewing field’s output, pushing everything into the visible spectrum. The ship was floating over a silver sea studded with rocky columns and promontories that trailed away from a row of cliffs. Everything had a spongy, desiccated look.

  “They’ve gone for the metals first,” Robert murmured. “The sea below is a nickel iron alloy. This planet must have been mostly metal. Come on, let’s feed the ship.”

  They began to descend, the metallic sea appearing to expand as they sank toward it.

  “How long does it take this ship to absorb matter?” Robert asked. He glanced up and backward at a viewing field located just behind his right shoulder.

  “It depends,” answered Herb. “Usually it takes it on board and plates it in a layer just inside the hull. It’s gradually transported from there to the necessary locations as part of the ongoing maintenance and repair procedure.”

  Johnston nodded. “I guessed as much. And how long to take the necessary material on board?”

  “A couple of minutes, if that.”

  “Good. We’ve got just about enough time, then.”

  “Just about enough time for what?” Herb asked. Something about the way Robert spoke brought the never too distant feeling of fear in his stomach back to the fore.

  The robot did something to one of the fields. The view focused on something, pulled back and refocused, pulled back again and refocused once more.

  “Just enough time to get away from that,” he murmured.

  Herb gazed at the viewing field in horror. From the high vantage point of the virtual camera he could finally make out what was going on. The sea over which they floated was crystallizing in a circle around them. It was as if a rime of white frost was settling on the surface of the gently moving liquid metal and freezing it into a rapidly tightening noose of ice. Herb could see their ship, clearly marked as occupying the center position. The bullseye.

  He became aware of something else. A slow, deliberate movement around the edges of the sea. A second viewing field focused in on one particular section, and Herb was momentarily thrown by the contrast within his range of vision, between the quiet calm of his lounge—the polished wood sculpture and the white vase with the gentle pattern of flowers embossed around the rim, the parquet floor and the cool eggshell finish of the ceiling—and the frantic battle outside. In the midst of the calm of his lounge, there on the viewing field, he could see the little machines outside forming themselves from the sea of metal, sucking its material as they bulged and then split into two.

  “Reproducing once every eight point two seconds,” said Robert. “Pretty impressive really. Well, when you consider the limitations of the intelligence we’re up against.”

  “They’re going to surround us,” whispered Herb. “We’ll be trapped.”

  It seemed inevitable. He could see the thickening cloud of the tiny machines as they rose into the air, an angry cloud of insects that seemed to pull a silver curtain up from the surface, such was their density—a silver curtain that promised to engulf them. It was as if a sack was being lifted up and around and over the ship.

  “Shouldn’t we run now?” asked Herb.

  Robert shook his head. “Don’t worry. I’ve worked out their rate of reproduction. We’ll get away with fourteen seconds to spare.”

  Herb said nothing to that. There was nothing to say. All he could do was sit and stare at the rising cloud of little machines, each about the size and shape of a saucer. They spun and shimmered in the virtual light. Their underside was darker than the top and scored with a series of concentric circular grooves. When they fissioned, it was into two saucers joined along their tops, grooved undersides facing outward.

  “How do they know we’re here?” asked Herb. “I thought we were masquerading as friends?”

  Robert grinned. “Oh Herb. I keep telling you: the intelligence behind the Enemy Domain is convinced of its own superiority. It is in the nature of such individuals to trust no one else. How could they trust an inferior? This is a paranoid region we have wandered into. It has security systems piled upon security systems. We will never deceive all of them. We can only hope to fool a few of them for just long enough.”

  He glanced at his wristwatch. “One minute until we leave.”

  One minute. It seemed an eternity to Herb. He was sure that would be too long. The cloud of machines rising from the circumference of the sea was now diminishing. Those machines closest to the planet’s surface began to change shape, their circular edges flattening off as the saucers became octagonal. The machines began merging together along these flat edges. As they did so, the gaps left between the shapes began to widen, the body of the plates narrowed and thickened.

  “They’re forming a mesh. We’ll be trapped in the cage.”

  Herb licked his lips and wished he hadn’t spoken. His voice sounded high-pitched and cracked.

  “We’ll be fine,” said Robert, rising to his feet. “Thirty seconds and we’ll be gone. There’s nothing to worry about here.”

  He picked up the silver machine, the modified VNM he had taken from Herb’s planet. Its legs waved gently as Robert carried it across the room to the hatchway.

  “The real problems will emerge the deeper we travel into the Enemy Domain. You see, the Enemy isn’t stupid; it will learn from its mistakes. We won’t be able to defeat it the same way twice.”

  The hatch slid open. Robert held the silver machine over the space in the floor for a moment. Its legs began to wave a little faster as it sensed the vast pool of raw materials beneath it.

  Robert glanced across to Herb.

  “You should be pleased with yourself, Herb. If you should die, think this of yourself. There is a planet, in some distant sky, that will be forever a part of your creation.”

  He let go of the machine and it tumbled through the hatch, its legs flickering up and down like the needles on a sewing machine.

  Above them, a viewing field showed what would become the roof of their cage now closing over them as a faint mist of silver saucers. The hatch slid shut. A gentle note sounded in the cabin.

  “Okay, we’re full. Off we go.”

  Herb let out a huge sigh. How long had he been holding his breath? The silver sea below them began to recede; the thin misty roof above them approached closer and closer. They burst through the insubstantial cloud of silver saucers without any difficulty and began to accelerate into space.

  Herb felt a wave of relief that was quickly overtaken by anxiety again. They had escaped this trap, only to have Robert jump them deeper into the Enemy Domain.

  “I don’t think I can take much more of this,” muttered Herb, seriously.

  Robert eyed him closely. “Of course you can,” he replied. “I’m monitoring all your vital signs. Your stress levels are well within acceptable limits.” He raised his eyebrows just a little. “All right, your blood pressure is a touch too high, but if you were to reduce your salt consumption, you’d be okay.”

  He sat back down on the sofa. “Warp jump in twenty seconds. We’re going to try and lead them off on a false trail. We don’t want them waiting for us with any nasty surprises when we break back into normal space.”

  “I thought it was impossible to track someone through warp space.”

  “It is,” said Robert. “Come on, Herb, think laterally. There are ways and means.”

  “Is this another one of your ways to keep me calm? Take my mind off things?”

  “That’s right. Here’s something else to think about, too. Why did I drop that machine of yours on the planet?”

  Herb gave a puzzled frown. “To reproduce, of course. I would have thought that was obvious.”

  “Of course, Herb. Silly me for thinking I could tell you anything.”

  The ship was accelerating again, building up tremendous speed.

&nb
sp; “Do you think they’ll try to nuke us when we arrive again?” asked Herb nervously.

  “Of course,” replied Robert. “Okay. Jump in five seconds. Four, three, two, one…”

  They jumped.

  eva 4: 2051

  “Heads we walk down the drive, tails we try to cut through the woods.”

  Eva wrapped her arms about herself and shivered as Alison tossed the coin. The night wasn’t that cold, she told herself. A low layer of cloud brooded above, pushing the dampness back down into the stretch of grass between the sleeping Center and the silent woods.

  “Tails,” said Alison, peering at the coin with the faint light of her phone’s screen. “Through the woods.”

  “Are you sure the positioning chip in that thing is disabled?” Nicolas asked suspiciously.

  “Positive,” said Katie. “Anyway, they’re top of the range stealth phones. Even the military can’t track them.”

  “I still don’t think it was a good idea bringing them.”

  “It would look suspicious if we didn’t have them with us,” said Alison. “Who doesn’t carry a phone nowadays? Now come on. Into the woods. Eva, get the trees to help us.”

  Eva strode across the wet grass, her sneakers slipping on the slick surface, and she wondered again if she should have put her boots on.

  The woods looked impossibly dark, the sky above them lit with a faint orange glow from the vast Northwest conurbation.

  “Are you there?” she muttered to the night in general.

  “I’m here,” said her brother. “Keep going in a straight line. It looks okay.”

  “Good. We need to keep going in a straight line.” Eva whispered the instruction to the others and they walked on in silence. Nicolas kept glancing nervously back toward the dark outline of the Center. Katie gazed at the sky; Alison walked on with an expression of grim determination. She didn’t seem happy.

  “Something’s up with her. Watch her, Eva. Whoah! Stop. Just ahead of you. Can you see it?”

  “Stop!” called Eva. The group froze. Ahead of them a faint ghost hung on the night air. Almost invisibly thin lines criss-crossed the space at the edge of the tree line.