Fleet of Worlds

Humanity has been faithfully serving the Citizens for years, and Kirsten Quinn-Kovacks is among the best and the brightest of the humans. She gratefully serves the race that rescued her ancestors from a dying starship, gave them a home world, and nurtures them still. If only the Citizens knew where Kirsten's people came from.A chain reaction of supernovae at the galaxy's core unleashes a wave of lethal radiation that will sterilize the galaxy. The Citizens flee, taking their planets, the Fleet of Worlds, with them.Someone must scout ahead, and Kirsten and her crew eagerly volunteer. Under the guiding eye of Nessus, their Citizen mentor, they explore for any possible dangers in the Fleet's pathand uncover long-hidden truths that will shake the foundations of worlds. Fleet of Worldsmarks Larry Niven's first novel-length collaboration within his Known Space universe, the playground he created for his bestselling Ringworld series. Teaming up with fellow SF writer Edward M. Lerner,Fleet of Worldstakes a closer look at the Human-Puppeteer (Citizens) relations and the events leading up to Niven's first Ringworld novel.

LARRY NIVEN is the multiple Hugo and Nebula Award-winning author of the Ringworld series, along with many other science fiction masterpieces. His Beowulf's Children, co-authored with Jerry Pournelle and Steven Barnes was a New York Times bestseller. He lives in Chatsworth, California. EDWARD M. LERNER has degrees in physics and computer science, a background that kept him mostly out of trouble until he began writing SF full-time. His books include Probe, Moonstruck, and the collection Creative Destruction. Fleet of Worlds is his first collaboration with Larry Niven. He lives in Virginia with Ruth, his wife of a mere 35 years.

Prologue
Long Pass crossed the sky in a series of shallow curves, because Diego MacMillan willed it so.
Interstellar space is not uniform. The tenuous interstellar medium isn’t just a few atoms of hydrogen per cubic inch, forever. There are pockets of greater density, some thick enough to form strings of stars, given time. Between the dense patches there is nothing. A Bussard ramjet like Long Pass, which eats interstellar hydrogen and accelerates by spitting out fused helium, must coast between the denser clouds.
This is worse than it sounds. At any reasonable fraction of light speed, interstellar muck comes on like cosmic rays. As much as propulsion, a Bussard ramjet’s purpose is to guide that lethal muck away from the life support system.
Every simulation run in Sol system had reached the same inconclusive conclusion: Course tweaking to exploit density fluctuations in the interstellar medium was “likely to be” unproductive. Between Sol and the target star the muck was thick enough. Sure, a course tweak might funnel a bit more hydrogen into the ramscoop here, but was it enough to compensate later? A slight diversion at these velocities took a heavy toll in kinetic energy. And what would you find when you reached the end of a detour? Maybe that was where the law of averages caught up with you, and the near-vacuum of interstellar gas became vacuum indeed.
Of course, flatlanders had built the models. Diego MacMillan had nodded noncommittally at their advice. Technically he was also a flatlander—spacers pinned that label on every Earthborn—but he had traveled across the solar system. Once Long Pass launched, whether he undertook the experiment was beyond their control.
Long Pass had followed its wobbly curves for decades now. Maybe he’d saved a few months’ travel. That was okay. Studying the variations, plotting alternate courses, assessing probabilities—they kept him busy. What had the experts imagined the ship’s navigator would do for decades?
They could never have imagined what, in his obsessive peering ahead, he would find. 
“And to what do we owe this honor?” Captain Nguyen asked.
Meaning that by the current schedule Diego would normally be asleep. It was all he could do not to blurt out the answer. One step at a time, he told himself. “All will be revealed,” he intoned with his best mock pretension.
The ship’s population numbered just above ten thousand. Most were embryos, sharing the freezers with forty-three hibernating adult passengers. The crew numbered only four, between them covering three daily shifts. Together, they filled the ship’s tiny dayroom.
He had arrived early to configure the claustrophobia-denying decor. Undulating, verdant forest, the Andean foothills of his youth, receded into the digital wallpaper. Fluffy clouds scudded across the brilliant blue sky glowing overhead—he had no use for the cave-parks his Belter crewmates thought normal. Leaves rustled and insects droned softly in surround sound. Most of one wall presented a well-remembered mountain lake on which a sleek, two-toned power boat cruised. Its hundred-horsepower inboard motor was throttled down to a barely audible purr.
Nothing, alas, could mask the ubiquitous odor of endlessly recycled air, nor could the rough-hewn planks projected from the dayroom table disguise the plasteel slickness beneath his fingers. He twiddled the cabin controls, tuning chirps and twitters down a notch, while his curious shipmates took coffee and snacks from the synthesizer.
Barbara Nguyen sat first. She had the tall, gangly frame of a Belter, and her head was shaved except for a cockatoo-like Belter crest of thick black hair. She was their captain and the most cautious among them; which was cause and which effect remained stubbornly unclear to Diego. Throughout their hitherto uneventful voyage, she had let decisions emerge by consensus. With luck, consensus-seeking had become a habit.
Sayeed Malloum, their engineer, was taller still but stocky for a Belter. Each of them handled the tedium in his own way. Sayeed’s latest affectation, dating back several weeks, involved dyeing his crest and disposable jumpsuit in matching colors. Today’s hue was chartreuse, shading to deep yellow.
Jaime MacMillan, ship’s doctor and Diego’s wife of fifty years, slid into the last chair. She was built to earthly scale, nearly matching his six feet, but otherwise illustrated the old adage about opposites attracting. She was lithe while he was pot-bellied, blonde where he was dark, and as fair as he was swarthy. Those were shipboard skin tones, of course. Flatlander full-body dye jobs and elaborate skin patterns had been left on far-off Earth.
Jaime slipped a hand beneath the tabletop to give his knee a reassuring pat, although not even she knew what he was about to reveal. With a start, he noticed she had printed her jumpsuit in Clan MacMillan tartan: another silent vote of confidence. How anxious did he seem?
Barbara cleared her throat. “Spill it, Diego. Why did you call everyone together?”
Oh, how the details and analyses, all the terabytes of specifics in his personal journal, yearned to be free. This was not the time. “Have a look.” Above the picnic-table illusion he projected a navigational holo. Amid the scattered pink, orange-white, and yellow-white specks of the nearest stars, a brilliant green asterisk blinked: You are here. As his friends nodded recognition, he superimposed, in tints of faint gray, a delicate 3-D structure. Would they see it? “Density variations in the interstellar gas and dust.”
Sayeed frowned, likely anticipating another pitch for rerouting the ship on one more just-a-bit-off-our-planned-course wrinkle in the void.
“You’ve shared density plots before. It’s never involved much fanfare.” Barbara eyed him shrewdly. “And you’ve never before struggled so hard not to bounce in your chair.”
Words alone would not suffice—not for this, not with Belters. That was not a criticism. Growing up inside little rocks, they lacked the background. Diego said, “Jeeves, give us Boat One.”
“On full throttle, sir, as you had specified.” The virtual speedboat slewed until its stern faced them and the shore. With a roar, the boat’s bow rose. A great vee-shaped wake formed. Diego tracked the boat as it receded, the ripples of its wake dwindling as they spread.
Sayeed’s gaze flicked between the simulated lake and the 3-D graphic that still hung above the table. “There’s a shock wave in the interstellar gas. A . . . a bow wave.”
Barbara narrowed her eyes in concentration. “I concede the resemblance, but we’re comparing two simulations. Diego, are you certain about the underlying data?”
It would be so easy to dive into minutiae about years of observations patiently culled and collated, about converting those observations from the ship’s accelerating frame of reference to a stationary frame, about estimating and correcting for the perturbations of stellar winds. He could have discussed at length vain efforts to match his readings to the sky survey with which they had departed Sol system. He yearned to explain the extrapolation of the full pattern from the mere fraction so far glimpsed, even after so many years and light-years of observations.
He must have had a fanatical glint in his eye, because Jaime shot him the warning look that reminded: There’s a fine line between scary-smart and just scary. Diego kept his response to a confident nod.
Barbara said, “I’ll want to go through it later, step by step. No offense, just captain’s prerogative.”
“What could have made this bow wave?” Sayeed asked.
That was the right question. Diego started another simulation. A more nearly uniform background wash, modeled from a century-old survey, replaced the translucent ripples in the stellar display. “This is what we expected to encounter. And . . . now.”
A new speck, this one bright violet, materialized in the holo. Gathering speed, it recreated the 3-D shock wave.
Jaime stood, squeezing behind his chair to study the image from another perspective. She poked a finger into the image. “Then whatever caused the waves is here?”
“Obviously, the simulation runs faster than real-time. I’ve given you no way to gauge the compression factor. The object producing the wake is moving at one-tenth cee, and we’re nearly a light-year apart. To look at it, we aim”—Diego tweaked a program parameter, and a backward-extrapolated trajectory materialized—“where it was.”
He linked their main telescope to the display. A dark sphere shimmered, faintly aglow in a false-color substitution for IR. Mountain peaks and hints of continental outlines peered out from beneath an all-encompassing blanket of ices.
Sayeed leaned forward to read annotations floating above the globe. “An Earth-sized world. At one point, it was Earthlike, its oceans and atmosphere since frozen. It’s a bit warmer than the interstellar background, which is why we can detect it, perhaps leakage from a radioactive core. And somehow, you say, it’s racing by at one-tenth light speed. How can that be?”
Barbara shook her head, setting her crest to bobbing. “A fair question, but I have a more basic one. Diego, you might have begun by showing us what you’d found. Why didn’t you?”
“Because this isn’t about an out-of-place planet. I need you to accept the years of observation and the model that showed us where to look.” Diego took a deep breath. Would they believe? “They prove that that world has been accelerating steadily at 0.001 gee.
“Someone is moving it—someone who controls technology we can’t even imagine.” 
“Are you awake?”
Diego was reasonably certain he’d been prodded in the ribs to assure a positive response. “Uh-huh,” he answered groggily. “What’s on your mind?”
Propped up on an elbow, long hair looking stirred from tossing and turning, Jaime stared at him. “Are we doing the right thing?”
For days, the four of them had gone around and around on this. Even Nguyen had come over. The big day was tomorrow.
But decisions feel different in the dark. “Jeeves, lights to quarter bright,” he told the onboard computer. It had the good judgment to comply without speaking. “Hon, we’ve all agreed. We can’t let Earth decide! They’re almost fifteen light-years away. Whether they signal the aliens directly—which they wouldn’t, since there’s no guarantee the planet won’t change course in the meanwhile—or they tell us to proceed, that’d be nearly a thirty-year delay. What does that do for us?” Despite himself, a yawn interrupted his response.
Then she surprised him. “That’s not what I meant. Maybe we shouldn’t contact them at all. What if they’re . . . hostile?”
That brought him fully awake. Ascribing violent intent was a good way to get sent for medical help—but aboard this ship, she was the medical help. “Advanced civilizations are peaceful,” he said cautiously.
“I know.” She raked a hand, fingers splayed, through her mussed hair. “War was a societal psychosis. With the resources of a solar system at our disposal, and with Fertility Boards to keep population levels under control, there’s been peace for more than a century. We left behind violence with the era of scarcity that the mentally ill used to excuse it.” The words came out like the secular catechism that they were. “They”—no antecedent was needed—“move entire worlds. How could they possibly covet the resources humans administer?”
She was shivering! Sitting up, he put an arm around her. “Then why are you worried?”
She snuggled against him. “Because aliens must surely be alien. Can we presume to predict their social development?”
“Can we presume to decide for mankind not to try contacting them? We’re almost a light-year apart. We’re moving at thirty percent cee. The ice world is moving at ten percent cee, and accelerating. Contacting them by comm laser already requires extrapolation and faith. Deferring to Earth could mean losing the opportunity.” He kissed the top of her head.
“We’re not making this decision only for ourselves,” she said softly.
He said, “There’s a reason our computers, like every starship’s computers, carry the UN’s standard First Contact protocol. Sending us off with the protocol means the UN recognized we might have to—”
“I mean our children.” She shifted into a sitting position, careful not to dislodge his arm. “Diego, they may be only frozen specks, two among thousands, but the decision we’ve made affects them.”
The children they were permitted only by leaving Sol system behind. “I think companionship in the universe will be a wondrous gift for them.”
For a long while, the omnipresent hum of fans was the only sound. Then she said, “I might be worried about nothing. There may be no answer to our signal. Some unknown natural phenomenon could explain that planet’s movements.” She squeezed his hand. “The first extraterrestrial intelligence or a brand-new cosmic force. Either way, you’ve made one heck of a discovery.”
If its acceleration were constant, the ice world had taken about a century to reach its current velocity. In that time, it would have crossed a bit over five light-years. A red-dwarf star lay more-or-less in its backtracked direction, at about that distance. One of its worlds, a gas giant alongside which Jupiter would seem puny, had a separation in its satellite system, a gap at odds with the accepted theory of planetary formation. “It could be a natural phenomenon,” Diego agreed.
But he didn’t believe that. 
The normal course of shipboard events was that there were none. One could get very bored, even at full cruising speed, between encounters with significantly sized dust motes. Every excuse for a celebration was quickly embraced.
Four birthdays and New Year’s Day (despite Diego’s railing at the pointlessness of commemorating a random spot on the orbit of an increasingly remote planet) left long stretches of mind-dulling routine.
The liquid in Diego’s glass was undeniably of that morning’s vintage. “Jeeves, did you taste this stuff?”
“Harmless,” the Jeeves program said. “Mostly harmless.”
“Good enough,” and Diego raised his glass. Fine wine would significantly overtax the synthesizer’s capabilities. Today the four of them celebrated something real. Ice World, months ago promoted to proper-noun status, should now have received the first-contact greeting lased more than a year earlier. Should . . . for such a simple word, it conveyed a satisfying and very newfound conclusiveness. They had signaled to where they projected the distant, speeding planet would be—if it continued without interruption on its steady course and acceleration.
It had.
A miniature Ice World, unanimous choice for the party’s décor, glittered above the dayroom table. Months of continuous observation had yielded details far beyond the crude holo he had first shown his shipmates.
His shipmates. With a start, and to Jaime’s knowing smile, he returned his attention to the party. “To new friends!” Glasses clinked, contents sloshing a little, and were enthusiastically emptied.
Sayeed shrugged. In the steadfastness of the Ice World’s hurtling trajectory, which three of them saw as evidence of intelligent intervention, he saw a mindless, if unknown, natural force. On one point all agreed: At least one of them was spectacularly wrong. Long after the discovery of pulsars, astronomers still remembered the hasty misattribution of the celestial rhythms to aliens. None of them planned to be forever remembered for announcing imagined aliens—or for failing to recognize real ones.
“In another year-plus. Two if they ponder and muse for a while about how to respond.” Barbara poured another round of the vin très ordinaire. “I wonder what, still assuming someone is there, they will have to say.”
Any alcohol is potable by the third serving. The day was special; they imbibed enough of today’s wine to render it superb. Eventually, they had Jeeves draw virtual straws. Jaime lost. She was taking a very strong stim when the rest of them headed to bed. 
The voice of Jeeves brought Diego instantly awake. “All hands to the bridge!”
He burst through the cabin door shouting, “What happened?”
Barbara beat him onto the bridge, but only because her cabin was closer. He and Sayeed were left to loiter anxiously in the corridor. The bridge couldn’t accommodate them all.
“Radar pulse hit us.” Jaime’s chair spun as she relinquished it to the captain. “There’s nothing on our sensors.”
“Jeeves, alarms off.” The warbling screech mercifully faded. Barbara settled into her seat and triggered a ping. Above a monitoring console, a spherical volume grew and grew: the representation of the space probed by that pulse. “Nothing,” she finally concluded. She downed the stim pills Jaime offered. “That’s as it should be. We must have a flaky sensor.”
Diego nodded jerkily. They couldn’t have reached us.
A new alarm blared. Parallel rows of floor lights blinked, painfully bright, their sudden manic cycling drawing Diego’s attention down the curved corridor. Emergency hatches slammed; the siren and the whooshing stopped. “Hull breach in storage bay D,” Barbara said. “Check that out, Sayeed.”
Diego’s head pounded. He dry-swallowed the pills Jaime now offered him. The alarms resumed, joined by the windstorm of a second breach aft. Something was poking holes in their ship. What, if nothing were nearby, had breached the hull? They were moving at thirty percent of light speed. What could possibly overtake the ship from behind? Light speed! They couldn’t have reached us!
“Jaime! Trade places.”
They squeezed past each other and he dropped into the lone chair beside the captain. Radar, lidar, maser—the instruments reported nothing, regardless of the frequency they sent.
Oh.
“Barbara, let’s just look. No active sensors, just Mark I eyeballs.” She spared him a sideways glance—light-years from the nearest sun, what could he expect to see, and how? But she did as he proposed.
The exterior cameras spun with the hull. Computers compensated for the gravity-simulating rotation, projecting a stationary star field onto the bridge. The stars behind were reddened and dimmed; the stars ahead flared, visibly shifted toward blue. And to one side: a large, circular patch of pitch-blackness. Whatever blocked the starlight was huge, or close, or both. Its immobile appearance meant it was orbiting them, matching the ship’s rotation.
“What the tanj is that?” Barbara focused their radar and lidar on the apparition. “Still no return signals. The echoes are being nulled somehow.”
“They’re—” Jaime bit it off, but Diego could finish it for her. They’re poking holes in our ship! Enemy aliens. She thought they were under attack.
“Sayeed, report.” Diego’s words echoed from speakers across the ship. There was no answer.
Another alarm. More wind rushing from the bridge. More emergency bulkheads slammed shut. “I’m on it.” Jaime’s voice quavered as she dashed off.
There was precious little privacy in the Long Pass; by mutual agreement, the corridor cameras had been powered down early in the mission. Muttering under his breath, Diego hunted for the command sequences to awaken them. The first reactivations came a tantalizing few moments late. Was that shadow disappearing around a corner Sayeed’s? Jaime’s?
One more ear-piercing alarm and again sudden wind tugged at his clothes. This alarm, too, faded as Barbara reset it. What was that scurrying sound?
“Pressure continues to drop throughout the ship. I’m closing all interior hatches,” announced the main bridge computer.
“Thank you, Jeeves. Give us the corridor cameras.”
At last they were all on. Diego cursed as one revealed Sayeed, crumpled and motionless, face down on the deck.
Black, many-limbed figures scuttled past the camera at a nearby corridor intersection, moving too fast for Diego to integrate what he was seeing into a meaningful picture. Aliens, or robots, or alien robots. . . .
Barbara had seen it, too. “We’ve been boarded.”
The bridge hatch burst inward before he could respond. There was a brief glimpse of serpentine limbs, an impression of something pointing at him, and a nearly subsonic vibration.
Then there was only darkness. Copyright © 2007 by Larry Niven and Edward M. Lerner. All rights reserved.