Since analyzing the results of the tests on the Xeelee craft, Nilis said, he had hardened his ideas about the nature and origin of the Xeelee. He tried to talk his way through a very complex series of graphics which supported, he said, his hypothesis about the nature of the Xeelee nightfighter: that it was not just a machine.
“Life on Earth is of course built on oxygen-carbon chemistry. But a wide range of such compounds are possible under chemical law. If you analyze the contents of carbon-compound material scraped from a lifeless comet, you get a broad, smooth distribution like this.” A flat, even curve. “An indiscriminate melange of many compounds. Whereas if you analyze a scraping of my skin, for instance, a sample from a living being, you get this.” A spiky distribution showing a heavy concentration of certain compounds, nothing of others. “We call this the building-block principle, and it’s believed to be a universal feature of life. There is a strong selection toward standard building blocks, you see: living things from Earth use the same handful of key components — amino acids, sugars — over and over, out of all the theoretically possible compounds—”
“A Xeelee nightfighter isn’t made of amino acids,” Gramm growled.
“No. But look here.” Nilis showed displays of substructures he had observed in the Xeelee’s design, in its condensate hull, even its spacetime-defect wings. The distributions were spiky. “You see? A characteristic building-block pattern. And that has certain consequences. Of course any life-form must have certain features — notably an information store.”
He began to speculate about how a Xeelee genome might be stored. A genotype of an organism was the internal data store that defined that organism’s growth and structure; Nilis’s own genotype was stored in DNA. The phenotype was the expression of that data, like Nilis’s body. Nilis said that extended quantum structures had been discovered in the “spine” of the craft. So far it had only been possible to hack into the simpler communications loops that controlled the ship’s basic operations. But if he was right, somewhere in there was stored the equivalent of Xeelee DNA.
“They may reproduce through some exotic principle, much more sophisticated than our own molecule-splitting. We know they use quantum entanglement to communicate. Perhaps for a Xeelee, giving birth is more like teleportation, making a copy of oneself outside the body.” He imagined what might be possible if human hackers could break into that genotype, how Xeelee technology could be hijacked…
His listeners took this in with resentment and impatience. Pirius thought it was remarkable how a genius like Nilis could continually misjudge the mood of his audience. Pirius himself was sanguine. He had become a veteran of incomprehensible technical briefings long before he left Arches Base, and he knew how to keep up a show of attentiveness while letting his thoughts wander.
Pirius had picked up some gossip from the locals. An ice-coated ball of rock, Enceladus wasn’t even Saturn’s largest moon — that was called Titan. On Titan, vast factory ships cruised seas of hydrocarbon slush and processed it into nano-food, to feed ever-hungry Earth. Of course, these days all this was controlled by the agencies of the Coalition, but Titan had a racy history. Titan had once been the most populous human world beyond the orbit of Earth itself. Even now — so the locals informed him — in the great ports with their ice-carved harbors, where kilometer-long factory ships put in to offload their stores and hundred-meter-high waves lapped like dreams, there were exotic adventures to be had, if you knew where to look.
But Pirius hadn’t seen Titan. He was stuck here on Ensh, as the locals called it, which was just another Navy base that could have been anywhere from here to the Prime Radiant itself. Once, it wouldn’t even have occurred to him to feel restless. But now he felt as if his curiosity had been opened up by his time in Sol system. What else was out there to be experienced — what else might he already have missed, if not for the strange irruption into his life of Pirius Blue?
He tried to focus on the discussion.
Commander Darc was out of his depth. “Forgive me, Commissary. I’m just a humble tar. Are you saying that the nightfighter is alive? That the Xeelee are their ships?”
“I, I—” Nilis stumbled, wiped his face with the back of his hand. He was overworking, Pirius knew, stretching himself thin across Sol system. “Yes, if you want a short answer. But it isn’t as simple as that. I’m saying there is no distinction between the Xeelee and their technology.”
Luru Parz seemed amused by all this. “But, Commissary, spacetime defects or condensate — neither seems very promising material to make a phenotype out of. Unlike the carbon-compound molecules of which you are made, for instance, there simply isn’t much of it about.”
“Quite true.” Nilis smiled at her. “Most life-forms we have encountered have a certain commonality. Space is full of prebiotic chemicals, the carbon-based chemistry that underlies our kind of life — stuff like simple amino acids, ammonia, and formaldehyde. This stuff is manufactured in interstellar clouds and rains down on the planets. Even today, thousands of tonnes of the stuff fall on Earth, for instance. So carbon-water chemistry is really an obvious resource for making life. Of course there is little in common in the detail between humans and, say, Silver Ghosts. But we derive from the same prebiotic interstellar chemistry; in a deep sense we are indeed cousins.
“But, as you say, Luru Parz, the Xeelee are different. These spacetime defects of which they have been baked aren’t common at all. Or at least, not now… but there was a time in the universe’s complicated history when they were common. The Xeelee — or their progenitors — must surely have arisen in an earlier age of the universe, an epoch when spacetime defects proliferated. But that era was in the first moments after the singularity. If that’s true, the Xeelee have very deep roots in time.”
Gramm made an explosive noise through his plump lips. “You goad me beyond endurance, Commissary. This is supposed to be a military briefing! Will — you — get — to the point?”
Nilis leaned on a desk and glared at Gramm. “The point, Minister, is that we now may understand why the Xeelee cluster around Chandra, the black hole. They need its deep gravity, its wrenching spacetime curvature.”
“Ah.” Luru Parz nodded. “To them, Chandra is like a last fire in a universe grown cold.”
“But there’s more than that,” Nilis said. He started to describe the condensate superstructure of the craft. “Now, condensate matter was common at a certain stage in the early universe — but a different stage from that when the spacetime defects emerged. It was a cosmic age as alien to the first as will our own far future be to us, that age when all the stars have died, and dark energy dominates the swelling of spacetime… But the Xeelee, or their forebears, managed to form a partnership, a symbiosis, with these remote beings. Through that symbiosis they have managed to survive the slow unravelling of the universe — and it persists still, in the fabric of their craft.
“How do we compare, then, with the Xeelee? There are some who argue that there have been ten crucial steps in the evolution of humanity…”
The ten began with the development of a DNA-based genetic code, and continued with steps Pirius understood only a little: the exploitation of oxygen to provide free energy, the use of glucose in energy metabolism, the development of photosynthesis, and the incorporation of mitochondria — like miniature power plants — into complex cells. “The first great triumph of symbiosis,” Nilis said enigmatically. His remaining steps were the formation of a nervous system, the evolution of an eye, the development of an internal skeleton to allow the colonization of dry land, the evolution of the backboned animals.