Andromedan Dark

by Ian Douglas

  That’s what St. Clair was looking at now.

  “How can those things rotate and not get all tangled up?” Symm asked.

  “On that scale, Excomm,” Senior Lieutenant Nolan said, “curvature would be very, very slight, too small for any kinking to occur. It would be a topological challenge, of course, but if you could build it, you could spin it.”

  “A simpler possibility,” Lieutenant Weiss pointed out, “would be to build it in segments, each independently rotating to provide different gravities, and sealed off from its neighbors to provide different atmospheres, different environments.”

  “Like anything about this could be simple,” Symm said.

  “It seems unlikely,” Newton added, “that this one is now inhabited.”

  “Why do you say that, Newton?” Symm asked.

  A series of magnifications came up on the bridge display. Masses of loosely intertwined threads enlarged to become massive tubules. The long-range imagers focused on one tube that had split wide open, exposing cavernous darkness within.

  “Parts of the structure show extensive areas of damage,” Newton said, “even complete destruction. And the radiation from the structure at all wavelengths is in equilibrium, consistent with what would be expected to come through, unfiltered, from the central star. It is possible that this structure has been destroyed in a deliberate attack.”

  “Another LIO,” St. Clair said softly. “This one big enough to hold a few hundred trillion inhabitants.”

  “A large intelligent object, my lord?” Cameron asked. “Why would it be intelligent?”

  “It would almost have to be,” St. Clair replied. “Something that large, that massive—you would need super-AI just to keep track of all the mass vectors as you brought the thing together. Once you have it built, it takes superhuman brain power to keep the whole thing running. Temperatures balanced, atmospheres intact. Too, there would have to be some sort of thruster system to adjust the positions of different parts of the structure, to keep it from drifting into its star.”

  “The builders almost certainly employed star-lifting techniques,” Christine Nolan pointed out. “Techniques that are well beyond the capabilities of natural organic intelligence.”

  There’s that, too, St. Clair thought. It was possible, he reflected, that the builders of this cosmic spaghetti had started with a star much like Sol, or a slightly smaller, cooler K-class sun, and pulled so much mass from it that it was reduced now to a red dwarf with a very long expected lifetime indeed. The lifted mass would have been transmuted into heavier elements in order to construct the cloud of tubes now surrounding it.

  And Christine had a good point. Such mining and manufacturing techniques were so far beyond human capabilities that almost by definition they would have been carried out by SAI—super AI—able to solve mind-numbingly complex problems, and to do so over a period of thousands, even millions of years.

  And once an SAI like that was up and running, you didn’t just turn it off. It should still be in there, somewhere, possibly within many billions of tons of computronium worked into the very walls of the twisting habitat threads.

  “Subcommander Jablonsky,” he called.

  “Yes, my lord.”

  “Do you have the Roceti program on line?”

  “We do, my lord. Ready at your order.”

  “Okay. Stand by.”

  A copy of the Roceti AI had been left running on board the Tellus module, though the Kroajid, now that they’d tapped into the linguistic and cultural data acquired by Roceti, seemed to be having no trouble communicating with their human guests. The original Roceti torpedo, though, had remained on the Ad Astra. St. Clair wasn’t sure how well its stored data covered systems and civilizations residing within Andromeda, but it might help crack any alien languages they encountered during this scouting expedition.

  “Anything?”

  “I’m broadcasting a variety of greetings and encounter protocols,” Newton replied. “No response so far.”

  Closer still. “Still no sign of a population?” St. Clair asked.

  “Negative,” Newton told him.

  “Another dead artificial world, then. Like the Alderson disk.”

  “So it would seem.”

  “Still,” Symm said, “a structure that huge . . . it might not be completely dead.”

  “What do you mean?”

  “Well, just like the Anderson disk, there would be room enough in something that large for whole Earths to be in hiding. Populations that reverted to primitivism . . . no radio, no industrial waste heat. Nothing going at all but the automated neutrino beacon.”

  “That assumes the disaster didn’t leak the atmosphere into space.”

  “That would be unlikely,” Newton said. “The tube is almost certainly partitioned to prevent such a catastrophe.”

  St. Clair nodded. “Instruments are showing a slight external atmosphere—a few millibars. Probably collected in the structure’s gravity field. Let me see it with the grav filter.”

  The scene dipped into a deep and bloody red register, overlaying the physical structure ahead in a colored indication of local mass. The image revealed a lot of mass within the tangled structure surrounding the star . . . more, he thought, than might be explained by the physical structure itself.

  “Dark matter?” he asked.

  “Possibly a local aggregation of dark matter WIMPs and axions,” Newton replied.

  “Any indication that it’s alive?”

  “Negative. It appears inert.”

  “What are the chances of entering this time, looking for local civilizations, and hitting three duds in a row? Two enormous artificial worlds, both dead . . . and one that’s vanished into its own navel either for jollies or for contemplation of the whichness of the why.”

  “The active Kroajid are still available for interaction,” Symm said. She sounded doubtful, however.

  “Gus and his Guardian pals don’t count, not really,” St. Clair said. “They’re totally wrapped up in their caretaker duties.”

  “I agree,” Lieutenant Gonzalez said. “They’re a subset of the larger culture, which has chosen to withdraw.”

  “If the spaghetti was managed by a SAI,” Jablonsky pointed out, “it must still be running.”

  “That was my thought, too,” St. Clair said.

  “But why would you think that?” Symm said.

  “Because it hasn’t drifted sideways and brushed up against its star,” Jablonsky replied. “A structure like that would be gravitationally unstable. Even a simple ring around a star—a classic ringworld—would be unstable over hundreds of thousands of years, and would need some sort of thruster system to keep it in place. The problem is much more severe with an object like this.”

  “Good point, Subcommander,” St. Clair said.

  “If there is an SAI in there,” Newton said, “I have not yet detected it. However, it might be in hibernation . . . or operating at a temporal level at which detection is difficult.”

  One advantage AI minds had over organics, St. Clair thought, was their ability to shift time frames. They could operate at speeds millions of times faster than a human brain, so that a second passed for them like centuries. Or they could slow themselves down until a single thought took thousands of years . . . or until their sleep was interrupted by an automated warning system.

  “So,” St. Clair said. “Any guesses from anyone as to whether this giant hairball is native to Andromeda or if it represents a colony from our own Galaxy?”

  “A colony, Lord Commander?” Symm said. “How do you figure that?”

  “For billions of years, Andromeda and the Milky Way have been slowly getting closer and closer, right? I would imagine any civilizations interested in exploration or expansion would have been able to make the crossing starting, oh, maybe even a few hundred million years ago. Newton? How long ago did the two galaxies begin their collision?”

  “That is difficult to say without knowledge of the topologies i
nvolved,” Newton replied, “but assuming a closing velocity of one hundred ten kilometers per second, it would be on the order of eighty to ninety million years ago.”

  “A third again longer than the time span separating our world from the dinosaurs,” St. Clair said. “Plenty of time to colonize Andromeda a hundred times over.”

  It was the Fermi’s paradox restated. Any star-faring civilization—in this case one that could travel far faster than the speed of light—could expand through an entire Galaxy, colonizing every world, occupying every niche, within far fewer than a million years or so, the cosmic blink of an optical organ. And if it could, why hadn’t it?

  “Yeah, well, what does it matter, my lord?” Symm said. “If the builders come from the Milky Way, or are native to Andromeda, I mean.”

  “It tells us something about the history,” St. Clair replied. “About what’s been going on. The Kroajid talk about raiders from Andromeda and about something they call the Andromedan Dark. The first sounds like a fairly typical star-faring culture of some sort, maybe a bit on the militant side of things. But the second sounds so weird we can’t even get a mental reference for it, and we end up speculating about dark matter ecologies and invisible invaders. If we’re going to be able to defend ourselves from these beasties, we’re going to have to figure out exactly what we’re up against.”

  “Fair enough,” Symm said. “Just one question.”

  “What’s that, Excomm?”

  She indicated the tangle of threads wrapped around its sullen ember of a central star. “Where the hell’s the front door to that thing?”

  NEWTON WAS less interested in finding a way inside than he was with communicating with his opposite number within the structure—if, indeed, there was one. Ever since Ad Astra had arrived within this volume of space, Newton had been scanning through billions of different channels—microwave, radio, visible light, UV and X-ray, and neutrino—without result. The neutrino beacon continued its steady pulse, but there was no information heterodyned within that steady beat-beat-beat other than the self-evident fact that it was there. Newton even closely examined the ambient gravitational background in case there was a signal there, but found nothing save the presence of the background mass: both matter and dark matter.

  As Ad Astra drifted steadily closer to the object, however, Newton was able to peer more closely into the available spectra, searching for signals so weak they barely rose above the overall level of background radiation.

  Contact!

  FINDING THE front door, as Excomm Symm had phrased it, proved to be relatively simple. Ad Astra carried a number of auxiliary ships—military, exploration, and logistical—and if the massive Ad Astra herself couldn’t be chivied inside one of the rotating tubes, something like an AAT-2440 Marine transport could.

  Jacob Weiss’s suggestion that the habitat threads might be divided into sections, each independently rotating and sealed to enclose its own specific environment, had proven correct. Lieutenant Thom Nakamura, at Ad Astra’s helm, had edged the vessel as close as he dared to one particular segment that had been badly damaged, its power off, its rotation halted, its side ripped open by some unimaginable cataclysm that had emptied it of air and life. As a Marine landing party boarded a pair of AAT-2440s for deployment to the structure, a small fleet of uncrewed observation drones had been deployed, guided by Newton into the gaping hole in the habitat’s side, and into the interior darkness.

  Images transmitted from the drones were displayed on the bridge bulkheads. As the lead drone skimmed above the endless gray plain of the habitat’s exterior, approaching the wound in its side, St. Clair was reminded of riding linked-in with a tourist drone above the surface of Earth’s moon. The habitat’s outer surface was pocked by meteor strikes and sandblasted by eons of micrometeorites. The structure, like the Alderson disk, was old.

  Then, his probe swung over the abyssal gulf and descended into the darkness. He ordered the probe to switch on its external lights, but for a long time he was too far from any surface for it to reflect the illumination. Only slowly did shapes begin to materialize out of the night, eerily twisted—the stuff of nightmares.

  The landscape was surreal, carved from pure crystal. St. Clair had difficulty sorting out what he was seeing . . . shapes that might have been twisted, alien-looking trees . . . or abstract statues . . . or even buildings. The probe’s powerful lights flashed and sparkled through towering forests of crystal, and St. Clair wondered how he would even recognize life here, if it was here to find at all.

  In places, the forests had been shattered, reduced to gleaming piles of broken shards and fragments. Whatever atmosphere had been here had bled away into space; the habitat was filled now by the same trace gasses that had collected around the outside of the entire structure—about ten millibars’ worth. The drone drifted ahead on microjet pulses; with that hab section no longer rotating, the only gravity was that of the small and relatively distant sun, plus the G-force generated by the mass of the structure itself. The spaghetti tangle of the LIO totaled more mass than several thousand Earths, but that mass was spread out across a volume of space half an AU across or more and perhaps a third of that in thickness. The total gravitational force inside the structure worked out to less than a twentieth of a G, and remote fliers and drones had no trouble picking their way through the eldritch landscape.

  Vast shadows cast by the probe’s light shifted and jumped, creating an illusion of life, but the place was dead, as dead as the Alderson disk.

  “Lord Commander!” Senior Lieutenant Nolan called. “Some of our probes have penetrated the next section. It’s still powered.”

  “How?”

  “Solar power, converted to electricity. The next section is rotating, and the airlocks are working.”

  St. Clair mentally changed channels. He was seeing through them electronic imagers of a different probe, now, one moving a few meters above what appeared to be a forest canopy. The airlock joining one section of the cosmic spaghetti to the next included rings rotating at increasing speeds in succession, so that probes emerging in the new section shared that section’s rotational velocity. The probes were fliers, however, which meant they needed to apply continuous thrust; otherwise, their straight-line paths would have carried them into the rapidly rising ground, exactly as if they’d been falling.

  The trees were mushroom-shaped and had bright purple foliage, with leaves like tight little corkscrews. Reddish light spilled down from a central core running down the length of the cylinder, exactly as the sunbeam did in the Tellus modules. The temperature here was a fairly chilly three degrees Celsius; the air was a weakly reducing atmosphere composed of hydrogen, methane, ethane, and nitrogen. Droplets of carbon tetrachloride were floating as a thin mist in the air, and what looked like a broad lake in the distance was probably liquid carbon tet. The rotational artificial gravity was set for about half a G.

  There were cities here: broad, oval patches carved out of jungle, composed of translucent domes and bubbles. They appeared to be made of some sort of tough plastic, and showed no sign of wear or age.

  Then St. Clair saw the bones.

  CHAPTER

  EIGHTEEN

  The creatures had been enormous, and he could only think of land-dwelling whales. Of titans.

  St. Clair guided his probe lower, allowing the onboard AI to handle thrust and attitude. Below, within a hundred-meter clearing in the violet jungle, some dozens of creatures had died, leaving behind tangled piles of dark gray objects that could only be skeletal remains. Judging from the evidence, they’d been huge, four or five times the mass, perhaps, of an extinct African elephant. Six massive legs like tree trunks, bony structures like enormous, hollowed-out eggs at both ends of the body that might have been heads or might have been something else entirely, long and flexible tubes of bone segments that must have looked something like an elephant’s trunk, but branched at the tips, and with six in the front and six in the back.

  Had these, then, be
en the spaghetti’s dominant life form? More likely, St. Clair thought, they were one species of many. As they had discussed, he suspected that the doughnut of tangled threads had been a project shared by hundreds or thousands of species, providing a wide variety of enclosed environments. Perhaps these beings had recreated the environment of their original homeworld here within several segments of the sun-embracing tubules.

  It was just so hard to believe something so big didn’t rule whatever land it inhabited.

  “Interesting,” the voice of Lieutenant Gonzalez said. “They had brain implants Not that different from us, actually.”

  “How can you tell?”

  Gonzalez threw up a pointer visible over the probe’s image channel. Gold-colored wires ran across dark bone and vanished into the interior by way of small holes. “See here? And here? If we assume these oval shapes fore and aft are skulls, protecting the brains—”

  “We can’t make that assumption, Gonzalez,” Subcommander Guo Jiechi said. Guo was head of Ad Astra’s xenobiology section. “Two brains? How would such a being even be able to walk?”

  “These are clearly electrical leads of some sort, sir,” Gonzalez insisted. “They appear to have grown through the bone, so they may have used nanotechnology to implant them, just as we do.”

  “Colonel Shaeffer,” St. Clair called. “Are your Marines on board the structure yet?”

  “They are, Lord Commander.” Colonel Vincent Shaeffer was the CO of the 1st Marine Regiment, 1st MARDIV, and the senior Marine officer currently embarked on board the Ad Astra. St. Clair had not been anticipating needing to carry out a planetary invasion and so he’d brought along only Colonel Shaeffer and two regiments of Marines—about twenty-four hundred Marines, all told. Most of those were still on board Ad Astra; for this preliminary scouting run, Shaeffer had sent in only the second battalion of the 1st Marines, the 2/1.