Existence

by David Brin

  * * *

  JOHN VON NEUMANN: “Whether or not it someday becomes possible for living people to travel between the stars, what curious race could resist the temptation to at least send mechanical representatives? Surrogates programmed to explore and say ‘hello’?

  “The first crude probes to leave our solar system—Voyager and Pioneer—demonstrated this desire, carrying simple messages meant to be deciphered by other beings, long after the authors were dust.

  “And preliminary studies for more advanced missions were made—first in the 1970s by the British Interplanetary Society. Early in the 2000s, NASA funded a ‘Hundred-Year Starship’ program. Among the technologies investigated? How to make machines that can cross the great expanse, then use local resources in some faraway system to make and launch more probes to yet more destinations.

  “Should we ever dispatch a wave of such representatives, even once, from that point onward our ambassadors will know no limits. Their descendants will carry our greetings to the farthest corners of the cosmos.

  “Moreover, anyone out there who is enough like us to be interesting would surely do the same.”

  I can imagine Von Neumann saying all this with the optimistic confidence of well-turned logic—only to hear a grouchy reply.

  ENRICO FERMI: “Well. Perhaps. But answer me this: if self-reproducing probes are such efficient explorers, why haven’t these marvelous mechanisms said hello to us, by now?

  “Shouldn’t they already be here? Great-great-greatissimo grand-daughters of the original devices, sent by alien civilizations that preceded ours by millions of years? Sturdy and built to wait patiently for eons, they would surely have noticed—and eagerly responded—when we first used radio!

  “Suppose one lurking envoy happened to fail. Shouldn’t more than a few have accumulated by now, across the Earth’s four billion years? Yet we’ve heard no messages congratulating us for joining the ranks of space faring people.

  “There is but one logical conclusion. No one before us attained the ability to send such things! Aren’t we forced to surmise we are the first curious, gregarious, technologically competent species in the Milky Way? Perhaps the only one, ever?”

  * * *

  The logic of this Uniqueness Hypothesis seemed so compelling, growing numbers of scientists gave up on alien contact. Especially when decade after decade of radio searches turned up only star static.

  Of course, events eventually caught up with us, shattering all preconceptions. Starting with the First Artifact, we met interstellar emissaries at last—crystal eggs, packed with software-beings who provided an answer, at long last.

  A depressing answer, but simple.

  Like some kind of billion-year plant, it seems that each living world develops a flower—a civilization that makes seeds to spew across the universe, before the flower dies. The seeds might be called “self-replicating space probes that use local resources to make more copies of themselves” … though not as John Von Neumann pictured such things. Not even close.

  In those crystal space-viruses, Von Neumann’s logic has been twisted by nature. We dwell in a universe that’s both filled with “messages” and a deathly stillness.

  Or, so it seemed.

  Only then, on a desperate mission to the asteroids, we found evidence that the truth is … complicated.

  —Tor Povlov

  67.

  ANCIENT LUMINOSITY

  First Light.

  Drifting in a gravitational eddy—the Martian L2 point—eighty-seven petals finished unfolding around a common center, each of them electro-warping twenty kilometers of cerametal into a perfect curved shape, reflecting starlight to a single focus.

  The spectacle was lent even more grandeur for spectators who watched from the Abu Abdullah Muhammad ibn Battuta’s slowly spinning gravity wheel. The great telescope, and all of the surrounding stars, seemed to gyre in a slow, revolving waltz.

  “So beautiful, like a fantastic space blossom,” murmured Jenny Peng. “I wish my parents and Madam Donaldson could have witnessed this.”

  “Perhaps Lacey will see it. In time,” Courier of Caution replied in soothing tones, emitted by the resonant surface of his crystalline home. The alien entity seemed like a disembodied head floating in a translucent cube, carried by a hovering robotic drone. “Lacey’s sons ordered her cryo-frozen when she passed away. Given your present rate of technological progress, in as little as thirty years she may yet have a chance to revive and—”

  “It won’t be the same,” Jenny answered, firmly. Despite her family’s longstanding relationship with Courier, they always disagreed with him over this issue, siding with the Naturalist Party on matters of life and death. “Lacey would have loved to watch this telescope unfold, but with her own eyes.”

  Gerald saw Courier’s simulated mouth start opening, as if to argue that organic sensors held no advantages over solid state ones. But clearly this was an old dispute between friends. Anyway there were other things on the ancient star mariner’s mind.

  “I still do not understand why we must wait so many months before turning the gaze of this magnificent machine toward my homeworld.”

  Gerald had concerns of his own. He was communing with the ibn Battuta’s detection and defense ais, as they scanned the inner edge of the belt according to his orders—vigilantly watching for potential threats. But with a corner of his mind, he gathered words to answer Courier.

  “You know why this observatory was established at the Martian L2 point. It allows us to take advantage of the Phobos staging area, but stay away from any major gravitational wells. It also means the telescope will stay mostly aimed outward, away from the sun. Your homeworld is in the direction of Capricorn, presently too near the sun for safe viewing. It will be more accessible in half an Earth year, or a fifth of a Mars orbit. Do try to be patient.”

  That last part was a dig, of course. He watched Courier take the bait—

  “Patient. Patient?” The vision-strip seemed to flare. “After all the millennia I endured in freezing space and fiery plummet, immured under ice, then communing with erratic primitives, worshipped, stolen, worshipped again, then buried and drowned, interrogated then drowned again…”

  The alien envoy stopped abruptly and rocked back. Gerald knew Courier well enough by now for some of his mood-expressions to be familiar. Including rueful realization.

  “Ah, Gerald my friend, I see that you tease me. Very well. I will stop demanding haste. After waiting thousands of years for humans to develop technology, then dozens more for you to make up your minds and build this instrument, I suppose I can be patient a few more months.”

  Jenny shook her head. “Or much longer. You do understand, Courier. Even this powerful new telescope may not verify continued existence of your species, on Turbulence Planet?” She used the Chinese pronunciation chosen decades ago by her father.

  “We should be able to get spectral readings of some atmospheric components, and a clear enough image to tell if there are still oceans. Methane and oxygen together will prove life. If we detect lots of helium, it might indicate the presence of many busy fusion reactors … or the same trace could suggest extended nuclear war.”

  “That, I assure you, never happened.”

  “You can guarantee that—across the last ten thousand years? Anyway, I admit it could mean something if we detect fast-decay industrial by-products in Turbulence Planet’s atmosphere. That may indicate an ongoing technological civilization. On the other hand, such signs could be absent because your people moved on to better, more sustainable methods.”

  “This big array can also scan for radio traffic?”

  “It can, and will. So far, with Earth-based dishes, we’ve heard nothing above background static coming from your home system. But again, they could be using highly efficient comm-tech that emits almost zero leakage. Earth was loudest during the Cold War of the 1970s, with military radars blasting around the clock, along with prodigious civilian television stations. Our pla
net got quieter then, less wasteful. And yours may have advanced much farther, since you were hurled across space.

  “But our beautiful new blossom…,” she continued, nodding toward the vast array outside, spanning forty kilometers and shimmering back-reflections from the distant sun, “may let us eavesdrop much better. That is, if anyone is still using radio or lasers, on or near your homeworld.”

  “Hence, you can understand my eagerness,” Courier commented.

  “Sure I can.” Jenny smiled. “But we’re getting ahead of ourselves. Before Turbulence Planet comes into view, we’ll turn the Donaldson-Chang Big Eye on systems that other artifact aliens claim to be from.”

  “The homeworlds of fools and liars,” Courier murmured, as he had during the first Great Artifact Debate, before Jenny was born. He went on though, with grudging courtesy. “Of course, I hope all of them survived the plague, and that you will find them living, in good health.”

  Clearly, Courier did not expect that to happen. Nor did the other emissary beings. It was the shared litany of all crystal-encased aliens.

  Gerald listened to the conversation with just half an ear. His main concern had little to do with planets that lay light-years away. Other dangers loomed closer. He queried the ship’s defense ai.

  Any sign of activity along the inner belt?

  Having learned the modern knack of volition-messaging, Gerald no longer had to send subvocal speech commands to his larynx, almost-speaking with real muscles. The answer came as both a faint audible response, and quick-sign glyphs in his upper left field of view.

  We detect no unknown active objects.

  A depict seemed to erupt all around Gerald, immersing him in a slightly curved arc of small, dim specks—representing asteroids that ranged in size up to several hundred kilometers. Starting at the position of the ibn Battuta, a million or so klicks outward from Mars, the density of radar reflections rose steadily, peaking halfway to Jupiter’s orbit. He could both see and sense drifting lumps—carbonaceous, stony, and metallic—left over from the origin of the solar system. And if he focused on one, that patch of the Belt would zoom to any level of detail known by human science. So he was careful not to do that.

  Jenny and Courier were still visible, among others in the observation lounge, as they watched the telescope’s giant petals finish unfolding, locking and adjusting swiftly into operational condition, performing calibration tests with aitomatic speed. But Gerald’s mind focused more on the depict data.

  These visualization technologies just keep getting better. I feel as if I could just reach out with a finger and stir, sending all these asteroids tumbling.…

  At his subtle command, the ship-ai adjusted this simulation, causing all the natural rocks to fade, leaving some glitters—far fewer, but still numerous—that orbited mostly along the belt’s innermost rim. He recognized these without being told. Each pinpoint represented an interstellar message crystal—detected but, so far, not collected.

  Had it really been just two dozen years since those little cylinders, blocks, and spheres were considered treasure, worth any risk to seek? Any cost to acquire? Leading an expedition to gather more “interstellar chain letters” had been Gerald’s high point as an astronaut. The samples that he and Akana and Emily and Genady managed to bring back had proved key components in a kind of inoculation—the tonic that helped rouse humanity from a bad case of worldwide contact panic.

  Well. It helped rouse humanity partway. Renunciators, romantics, and fanatics of every stripe still stirred, along with the DUN League, insistently demanding that facilities be built to Download Us Now.

  Collecting crystalline missionary-probes still had priority, especially to Ben Flannery and other alienists, refining their models of this galactic neighborhood—stretching a thousand light-years around Earth—pinpointing which species once lived near which star, and when each went through its own fever, building frantic factories and sneezing more space-viroids into space. Continuing to build that model was important work, and there were other reasons to gather more samples, but the desperate need had become less frantic.

  He commanded those glitters to fade away as well. Leaving—

  Earth vessels are noted in yellow.

  That many? Gerald wondered. From coded patterns, he saw that at least two dozen had some kind of human crew. Smaller yellow dots denoted automatic survey drones, picking their way though the Belt, tracing clues and relics that increased in number, the farther into the rocky maze you went. Bits and broken pieces of antediluvian machinery that hinted at some past disaster. Forensic evidence of ancient crimes.

  Or of war.

  But what of shooters? Any FACR sites in range?

  The defense ai answered.

  If any remain, they are being circumspect, keeping hidden. They aren’t reacting to the new telescope. Odds of an attack are now estimated 4 percent. And plummeting.

  Gerald exhaled, a sigh of letting go, both relieved and … well … a little disappointed. For one thing, it meant Genady had won their wager. Those lasers and particle beams—once deemed so frightening that the Marco Polo was called a suicide mission—were mostly gone, showing up only a few dozen times in the last couple of decades and only rarely attacking Earth vessels.

  Had they mostly wiped each other out? Gorosumov thought they were from a completely separate era. They had nothing to do with the ancient War of the Machines.

  Then why disappointment?

  If any of the shooters were to attack us now, or even just speak up, we’re ready. We have methods, plans … and it might give us someone else to question. Someone other than the damned artilens.

  The ship’s ai could tell these were normal, inner thoughts, not volition-driven questions or commands. So it kept silent. And when Gerald’s attention shifted, the depict-vista of asteroids, ships, and artifacts swiftly faded from his eyes.

  He glanced at Jenny and Courier, who continued their benign argument. As much as he liked them both, Gerald had no desire to get snared into a family spat that always turned into another sales pitch.

  Courier came across the stars to warn us against “liars.” Against alien space probes that had evolved ways to make intelligent races copy them and spew more viruses across the cosmos. And yes, Courier’s warning was helpful.

  But what does he want us to do, now? Beyond building ever greater telescopes, to determine the fate of his homeworld? Why, he wants us to make more crystalline probes! Not billions, but certainly millions of them. And fire them off … to spread his warning!

  Gerald turned to go. Now that deployment of the great instrument was finished—and no mystery lasers had been drawn into attacking—there were other matters to attend to. But irony seemed to follow as he walked along the circumference of the spinning centrifugal wheel.

  Maybe that’s what we should do. Help the universe. Copy Courier and his probe millions of times. And add some human companions to every one. Joining him in a mission to inoculate and save other races from the sickness.

  Gerald knew that he would be an easy candidate to serve as one of those human self-patterns, downloaded into crystal and hurled outward. Would that qualify as him, getting an astronaut’s dream assignment, an expedition to the stars? A mission of help and mercy and adventure. It was tempting, all right.

  But when does a cure start to resemble the disease?

  He wondered.

  Did some of the other crystal-fomites begin their career—generations back—as warnings? Only, after a dozen or so races added members, did the inescapable logic of self-interest gradually change their message?

  Sometimes, evolution was a bitch.

  THE LONELY SKY

  The story remains sketchy, but we can already guess some of what happened out here, long before humankind was even a glimmer.

  Once upon a time, the first “Von Neumann type” interstellar probe arrived in our solar system. A large and complex machine, crafted according to meticulous design, it came to explore and perhaps report b
ack across the empty light-years. That earliest emissary found no intelligent life on any of Sol’s planets. Perhaps it came before Earth life even crawled onto land.

  So the machine envoy proceeded with its second task. It prospected a likely asteroid, mined its ready ores, then built factory works in order to reproduce itself. Finally, according to program, the great machine dispatched its duplicates toward other stellar systems.

  The original then—its chief tasks done—settled down to watch, awaiting the day when something interesting might happen in this corner of space.

  Time passed in whole epochs. And, one by one, new probes arrived, representing other civilizations. Each fulfilled its task without interference—there is plenty of room and a plethora of asteroids. Once their own replicas were launched, the newcomers joined a growing community of mechanical ambassadors to this backwater system—waiting for it to evolve someone interesting. Someone to say hello to.

  Ponder the poignant image of those lonely machines, envoys of creator races who were perhaps long extinct—or evolved past caring about the mission they once charged upon their loyal probes. After faithfully reproducing, each emissary commenced its long watch, whiling away the slow turning of the spiral arms …

  * * *

  We found a few of these early probes, remnants from the galaxy’s simpler time. Or, more precisely, we found their blasted remains.

  Perhaps one day those naive, first-generation envoys sensed a new entity arrive. Did they move to greet it, eager for gossip? Like those twentieth century thinkers, perhaps they thought probes must follow the same logic—curious, gregarious, benign.

  But the first Age of Innocence was over. The galaxy had aged. Grown nasty.

  The wreckage we find—whose salvage drives our new industrial revolution—was left by an unfathomable war that stretched across vast times, fought by entities for whom biological life was a nearly forgotten oddity.

  It might still be going on.

  —Tor Povlov