Galactic Empires

by Neil Clarke

  They crunched through the possibilities. Wherever the Amalgam had an established presence, the infrastructure already on the ground could convert data into any kind of material object. Transmitting yourself to such a place, along with whatever you needed, was simplicity itself: lightspeed was the only real constraint. Excessive demands on the local resources might be denied, but modest requests were rarely rejected.

  Far more difficult was building something new at a site with raw materials but no existing receiver; in that case, instead of pure data, you needed to send an engineering spore of some kind. If you were in a hurry, not only did you need to spend energy boosting the spore to relativistic velocities—a cost that snowballed due to the mass of protective shield-ing—you then had to waste much of the time you gained on a lengthy braking phase, or the spore would hit its target with enough energy to turn it into plasma. Interactions with the interstellar medium could be used to slow down the spore, avoiding the need to carry yet more mass to act as a propellant for braking, but the whole business was disgustingly inefficient.

  Harder still was getting anything substantial to a given point in the vast empty space between the stars. With no raw materials to hand at the destination, everything had to be moved from somewhere else. The best starting point was usually to send an engineering spore into a cometary cloud, loosely bound gravitationally to its associated star, but not every such cloud was open to plunder, and everything took time, and obscene amounts of energy.

  To arrange for an observatory to be delivered to the most accessible point along the beam’s line of sight, traveling at the correct velocity, would take about fifteen thousand years all told. That assumed that the local cultures who owned the nearest facilities, and who had a right to veto the use of the raw materials, acceded immediately to their request.

  “How long between course corrections?” Leila wondered. If the builders of this hypothetical network were efficient, the nodes could drift for a while in interstellar space without any problems, but in the bulge everything happened faster than in the disk, and the need to counter gravitational effects would come much sooner. There was no way to make a firm prediction, but they could easily have as little as eight or ten thousand years.

  Leila struggled to reconcile herself to the reality. “We’ll try at this location, and if we’re lucky we might still catch something. If not, we’ll try again after the beam shifts.” Sending the first observatory chasing after the beam would be futile; even with the present free-fall motion of the nodes, the observation point would be moving at a substantial fraction of lightspeed relative to the local stars. Magnified by the enormous distances involved, a small change in direction down in the bulge could see the beam lurch thousands of light-years sideways by the time it reached the disk.

  Jasim said, “Wait.” He magnified the region around the projected path of the beam.

  “What are you looking for?”

  He asked the map. “Are there two outposts of the Amalgam lying on a straight line that intersects the beam?”

  The map replied in a tone of mild incredulity. “No.”

  “That was too much to hope for. Are there three lying on a plane that intersects the beam?”

  The map said, “There are about ten-to-the-eighteen triples that meet that condition.”

  Leila suddenly realized what it was he had in mind. She laughed and squeezed his arm. “You are completely insane!”

  Jasim said, “Let me get the numbers right first, then you can mock me.” He rephrased his question to the map. “For how many of those triples would the beam pass between them, intersecting the triangle whose vertices they lie on?”

  “About ten-to-the-sixth.”

  “How close to us is the closest point of intersection of the beam with any of those triangles—if the distance in each case is measured via the worst of the three outposts, the one that makes the total path longest.”

  “Seven thousand four hundred and twenty-six light-years.”

  Leila said, “Collision braking. With three components?”

  “Do you have a better idea?”

  Better than twice as fast as the fastest conventional method? “Nothing comes to mind. Let me think about it.”

  Braking against the flimsy interstellar medium was a slow process. If you wanted to deliver a payload rapidly to a point that fortuitously lay somewhere on a straight line between two existing outposts, you could fire two separate packages from the two locations and let them “collide” when they met—or rather, let them brake against each other magnetically. If you arranged for the packages to have equal and opposite momenta, they would come to a halt without any need to throw away reaction mass or clutch at passing molecules, and some of their kinetic energy could be recovered as electricity and stored for later use.

  The aim and the timing had to be perfect. Relativistic packages did not make inflight course corrections, and the data available at each launch site about the other’s precise location was always a potentially imperfect prediction, not a rock-solid statement of fact. Even with the Amalgam’s prodigious astrometric and computing resources, achieving millimeter alignments at thousand-light-year distances could not be guaranteed.

  Now Jasim wanted to make three of these bullets meet, perform an elaborate electromagnetic dance, and end up with just the right velocity needed to keep tracking the moving target of the beam.

  In the evening, back in the house, they sat together working through simulations. It was easy to find designs that would work if everything went perfectly, but they kept hunting for the most robust variation, the one that was most tolerant of small misalignments. With standard two-body collision braking, the usual solution was to have the first package, shaped like a cylinder, pass right through a hole in the second package. As it emerged from the other side and the two moved apart again, the magnetic fields were switched from repulsive to attractive. Several “bounces” followed, and in the process as much of the kinetic energy as possible was gradually converted into superconducting currents for storage, while the rest was dissipated as electromagnetic radiation. Having three objects meeting at an angle would not only make the timing and positioning more critical, it would destroy the simple, axial symmetry and introduce a greater risk of instability.

  It was dawn before they settled on the optimal design, which effectively split the problem in two. First, package one, a sphere, would meet package two, a torus, threading the gap in the middle, then bouncing back and forth through it seventeen times. The plane of the torus would lie at an angle to its direction of flight, allowing the sphere to approach it head-on. When the two finally came to rest with respect to each other, they would still have a component of their velocity carrying them straight toward package three, a cylinder with an axial borehole.

  Because the electromagnetic interactions were the same as the two-body case—self-centering, intrinsically stable—a small amount of misalignment at each of these encounters would not be fatal. The usual two-body case, though, didn’t require the combined package, after all the bouncing and energy dissipation was completed, to be moving on a path so precisely determined that it could pass through yet another narrow hoop.

  There were no guarantees, and in the end the result would be in other people’s hands. They could send requests to the three outposts, asking for these objects to be launched at the necessary times on the necessary trajectories. The energy needs hovered on the edge of politeness, though, and it was possible that one or more of the requests would simply be refused.

  Jasim waved the models away, and they stretched out on the carpet, side by side.

  He said, “I never thought we’d get this far. Even if this is only a mirage, I never thought we’d find one worth chasing.”

  Leila said, “I don’t know what I expected. Some kind of great folly: some long, exhausting, exhilarating struggle that felt like wandering through a jungle for years and ending up utterly lost.”

  “And then what?”

  “Surrend
er.”

  Jasim was silent for a while. Leila could sense that he was brooding over something, but she didn’t press him.

  He said, “Should we travel to this observatory ourselves, or wait here for the results?”

  “We should go. Definitely! I don’t want to hang around here for fifteen thousand years, waiting. We can leave the Nazdeek observatories hunting for more beam fluorescence and broadcasting the results, so we’ll hear about them wherever we end up.”

  “That makes sense.” Jasim hesitated, then added, “When we go, I don’t want to leave a back-up.”

  “Ah.” They’d traveled from Najib leaving nothing of themselves behind: if their transmission had somehow failed to make it to Nazdeek, no stored copy of the data would ever have woken to resume their truncated lives. Travel within the Amalgam’s established network carried negligible risks, though. If they flung themselves toward the hypothetical location of this yet-to-be-assembled station in the middle of nowhere, it was entirely possible that they’d sail off to infinity without ever being instantiated again.

  Leila said, “Are you tired of what we’re doing? Of what we’ve become?”

  “It’s not that.”

  “This one chance isn’t the be-all and end-all. Now that we know how to hunt for the beams, I’m sure we’ll find this one again after it shifts. We could find a thousand others, if we’re persistent.”

  “I know that,” he said. “I don’t want to stop, I don’t want to end this. But I want to risk ending it. Just once. While that still means something.”

  Leila sat up and rested her head on her knees. She could understand what he was feeling, but it still disturbed her.

  Jasim said, “We’ve already achieved something extraordinary. No one’s found a clue like this in a million years. If we leave that to posterity, it will be pursued to the end, we can be sure of that. But I desperately want to pursue it myself. With you.”

  “And because you want that so badly, you need to face the chance of losing it?”

  “Yes.”

  It was one thing they had never tried. In their youth, they would never have knowingly risked death. They’d been too much in love, too eager for the life they’d yet to live; the stakes would have been unbearably high. In the twilight years, back on Najib, it would have been an easy thing to do, but an utterly insipid pleasure.

  Jasim sat up and took her hand. “Have I hurt you with this?”

  “No, no.” She shook her head pensively, trying to gather her thoughts. She didn’t want to hide her feelings, but she wanted to express them precisely, not blurt them out in a confusing rush. “I always thought we’d reach the end together, though. We’d come to some point in the jungle, look around, exchange a glance, and know that we’d arrived. Without even needing to say it aloud.”

  Jasim drew her to him and held her. “All right, I’m sorry. Forget everything I said.”

  Leila pushed him away, annoyed. “This isn’t something you can take back. If it’s the truth, it’s the truth. Just give me some time to decide what I want.”

  They put it aside, and buried themselves in work: polishing the design for the new observatory, preparing the requests to send to the three outposts. One of the planets they would be petitioning belonged to the Snakes, so Leila and Jasim went to visit the nest for a second time, to seek advice on the best way to beg for this favor. Their neighbors seemed more excited just to see them again than they were at the news that a tiny rent had appeared in the Aloof’s million-year-old cloak of discretion. When Leila gently pushed her on this point, Sarah said, “You’re here, here and now, our guests in flesh and blood. I’m sure I’ll be dead long before the Aloof are willing to do the same.”

  Leila thought: What kind of strange greed is it that I’m suffering from? I can be feted by creatures who rose up from the dust through a completely different molecule than my own ancestors. I can sit among them and discuss the philosophy of life and death. The Amalgam has already joined every willing participant in the galaxy into one vast conversation. And I want to go and eavesdrop on the Aloof? Just because they’ve played hard-to-get for a million years?

  They dispatched requests for the three modules to be built and launched by their three as-yet unwitting collaborators, specifying the final countdown to the nanosecond but providing a ten-year period for the project to be debated. Leila felt optimistic; however blasé the Nazdeek nest had been, she suspected that no space-faring culture really could resist the chance to peek behind the veil.

  They had thirty-six years to wait before they followed in the wake of their petitions; on top of the ten-year delay, the new observatory’s modules would be traveling at a fraction of a percent below lightspeed, so they needed a head start.

  No more telltale gamma ray flashes appeared from the bulge, but Leila hadn’t expected any so soon. They had sent the news of their discovery to other worlds close to the Aloof’s territory, so eventually a thousand other groups with different vantage points would be searching for the same kind of evidence and finding their own ways to interpret and exploit it. It hurt a little, scattering their hard-won revelation to the wind for anyone to use—perhaps even to beat them to some far greater prize—but they’d relied on the generosity of their predecessors from the moment they’d arrived on Nazdeek, and the sheer scale of the overall problem made it utterly perverse to cling selfishly to their own small triumph.

  As the day of their departure finally arrived, Leila came to a decision. She understood Jasim’s need to put everything at risk, and in a sense she shared it. If she had always imagined the two of them ending this together—struggling on, side by side, until the way forward was lost and the undergrowth closed in on them—then that was what she’d risk. She would take the flip side to his own wager.

  When the house took their minds apart and sent them off to chase the beam, Leila left a copy of herself frozen on Nazdeek. If no word of their safe arrival reached it by the expected time, it would wake and carry on the search.

  Alone.

  VI

  “Welcome to Trident. We’re honored by the presence of our most distinguished guest.”

  Jasim stood beside the bed, waving a triangular flag. Red, green and blue in the corners merged to white in the center. “How long have you been up?”

  “About an hour,” he said. Leila frowned, and he added apologetically, “You were sleeping very deeply, I didn’t want to disturb you.”

  “I should be the one giving the welcome,” she said. “You’re the one who might never have woken.”

  The bedroom window looked out into a dazzling field of stars. It was not a view facing the bulge—by now Leila could recognize the distinctive spectra of the region’s stars with ease—but even these disk stars were so crisp and bright that this was like no sky she had ever seen.

  “Have you been downstairs?” she said.

  “Not yet. I wanted us to decide on that together.” The house had no physical wing here; the tiny observatory had no spare mass for such frivolities as embodying them, let alone constructing architectural follies in the middle of interstellar space. “Downstairs” would be nothing but a scape that they were free to design at will.

  “Everything worked,” she said, not quite believing it.

  Jasim spread his arms. “We’re here, aren’t we?”

  They watched a reconstruction of the first two modules coming together. The timing and the trajectories were as near to perfect as they could have hoped for, and the superconducting magnets had been constructed to a standard of purity and homogeneity that made the magnetic embrace look like an idealized simulation. By the time the two had locked together, the third module was just minutes away. Some untraceable discrepancy between reality and prediction in the transfer of momentum to radiation had the composite moving at a tiny angle away from its expected course, but when it met the third module the magnetic fields still meshed in a stable configuration, and there was energy to spare to nudge the final assembly precisely into step wit
h the predicted swinging of the Aloof’s beam.

  The Amalgam had lived up to its promise: three worlds full of beings they had never met, who owed them nothing, who did not even share their molecular ancestry, had each diverted enough energy to light up all their cities for a decade, and followed the instructions of strangers down to the atom, down to the nanosecond, in order to make this work.

  What happened now was entirely in the hands of the Aloof.

  Trident had been functioning for about a month before its designers had arrived to take up occupancy. So far, it had not yet observed any gamma ray signals spilling out of the bulge. The particular pulse that Leila and Jasim had seen triggering fluorescence would be long gone, of course, but the usefulness of their present location was predicated on three assumptions: the Aloof would use the same route for many other bursts of data; some of the radiation carrying that data would slip past the intended receiver; and the two nodes of the network would have continued in free-fall long enough for the spilt data to be arriving here still, along the same predictable path.

  Without those three extra components, delivered by their least reliable partners, Trident would be worthless.

  “Downstairs,” Leila said. “Maybe a kind of porch with glass walls?”

  “Sounds fine to me.”

  She conjured up a plan of the house and sketched some ideas, then they went down to try them out at full scale.

  They had been into orbit around Najib, and they had traveled embodied to its three beautiful, barren sibling worlds, but they had never been in interstellar space before. Or at least, they had never been conscious of it.

  They were still not truly embodied, but you didn’t need flesh and blood to feel the vacuum around you; to be awake and plugged-in to an honest depiction of your surroundings was enough. The nearest of Trident’s contributor worlds was six hundred light-years away. The distance to Najib was unthinkable. Leila paced around the porch, looking out at the stars, vertiginous in her virtual body, unsteady in the phoney gravity.