“A network of ancient machine civilizations. They sent the Watchers.”
“I still don’t understand why the concentration on machines versus us,” Nikka said.
“Partly I’m relying on what the Snark said, and events afterward.”
“Well, Nigel,” Carlotta said diplomatically, “most people think you were, you know, off the deep end back then… .”
“I never claimed to be a conservative Republican. But there’s good reason to believe machines left over from a nuclear Armageddon won’t be friendly as lap dogs.”
“Why?”
“They started off with a genocide. One we caused. They’ll remember that.”
He wrote up his theory and duly gave a seminar for ExoBio and Theory sections. It was politely received.
The Watcher around Epsilon Eridani, he said, was there to be certain that no organic form arose again (or returned from nearby stars—there might be colonies). Something—the Watcher?—had destroyed the native organic civilization. It had incinerated the planet in such a way that the Skyhook remained.
Why leave the Skyhook? Most likely, because the Watcher wanted an economical way to send expeditions to the surface, where remnants could be sought out and exterminated.
He reviewed the observations of the oil haulers of Pro-cyon. At highest magnification the machines looked well-designed, sprouting antennas and hatches. Nigel deduced that they were perhaps a bit further advanced beyond the Wolf 359 ice luggers. Still carrying out mechanical tasks, but not running on instructions left over from a long-dead society. Instead, they seemed to be integrated into some interstellar economic scheme. An ocean of oil was a great boon, of course—but not merely for making energy. Anything that could cross between stars would not be hobbled by a chemical-energy economy. They might well need plentiful lubricants, though.
Isis was harder to explain. The EMs had engineered themselves to use radio as their basic sense. Was this to deceive the two Watchers into considering them a protomachine society?
That would imply a certain rigidity and literal-mindedness in those Watchers. Maybe they were old, decaying? Or else biding their time, studying the EMs. The fact that one Watcher attacked any attempt to inspect it tended to support the second point of view.
Nigel used all the data he could muster. He compared spectra and diagnostics of the various Watchers, estimated their ages (all gave billion-year upper bounds), and correlated as many variables as he could plausibly justify. There was no clean way to show a common origin for the Watchers. On the other hand, he pointed out, there was no reason to believe the Watchers had been constructed at the same place or time.
His theory did not muster much support. He had not expected it to.
The prevailing notion in Theory Section was the simplest—Occam’s razor triumphant. All these worlds, Theory said, were the husks of war-obliterated cultures. They proved that intelligent life was plentiful but suicidal. The Watchers were simply a common form of weapon, reinvented again and again in separately evolving societies. Battle stations. By the time a race developed one, it was close to annihilation.
As for Isis—the specifics of the great war that doomed that world were now mired in the EM legends. And legends were notoriously unreliable sources of hard facts. The EMs had modified their own bodies to survive, pure and simple, in the ruin they had made.
Neither side could explain the Swarmers and Skimmers. Nigel stood before the audience and countered arguments as best he could. He had a vague sense that the Skimmers and the EMs were somehow similar, but knew enough not to venture such an idea without an underpinning of hard explanation.
Someone from ExoBio pointed out that the Swarmers atleast demonstrated the prevalence of violence and warfare in other life-forms. There was applause after this remark. Nigel stood silent, not knowing how to counter it.
He saw the polite, well-concealed disbelief in their faces and accepted it. He merely hammered home again his prediction: Whatever they found ahead at Ross 128, if a world could possibly bring forth organic life—or had—it would have a circling Watcher. Walmsley’s Rule, someone called it.
His point made, he sat down to moderate applause. The seminar turned on to other topics in astrophysics and biology. No one, he noted, brought up the obvious exception to Walmsley’s Rule: Earth.
FIVE
Nigel stayed in their apartment much of the time. Nikka was quite fit, and did a variety of jobs around the ship. He participated in seminars and helped with assembly nets, all done over the apartment flatscreen. He liked the isolation and peace, but in fact it was forced on him by the need to tie into the blood filter four times daily. He and Nikka had put the rig together using gear from ship’s surplus; medical engineering was as easy as auto repair, most of it modular and plug-in. Still, they were tinkering with his life; Nikka checked the flow patterns every day. Of course, bypassing the medmons was a violation of shipregs, but that didn’t cause them any fretting.
He regularly tapped into the ExoBio seminars, mostly to use the interactive data bases and 3-D choice-theory-outcome representations. These last were visualizations of the overall consequences of any theory of extraterrestrial life, tracing the many strands of planetary evolution, biology, and socioeconomics. Earthside’s spotty flow of news on the Swarrners and Skimmers had to be folded into what Lancer and the independent probes found. There were competing schools of thought, led by specialist analysts among the crew. Nigel seldom met these savants. They existed for him as disembodied constellations of theory in the seminar representations, ways of organizing the data. Their command of interconnections was formidable. They could relate the structure of the Marginis wreck to the swim patterns of the Swarmers, fold it into a theory of universal languages, and come up with (a) an estimate of the probability that most galactic lifeforms still lived exclusively in oceans, (b) a best-choice scheme for achieving radio contact through use of gigawatt-level radio beacons, (c) a recalculated optimum-search strategy for probes to stars within a hundred light-years. Nigel recalled Mark Twain’s remark that the wonder of science was how vast a return of speculation you got for such a trifling investment of fact.
The snag was that you had to have some initial premise to fit it all together. Shipboard, the running consensus was that all earlier alien contacts—the Snark craft that Nigel spoke to briefly, and the Marginis wreck—had been feelers. Something, probably the Swarmers and Skimmers themselves, had probed Earth for a long time, sizing up its suitability as a biosphere. The conventional wisdom of the past, that no species would bother to invade another world, seemed no longer true. Lancer had found that most planets were blasted relics. It would be far easier to adapt to an existing biosphere like Earth, than to start at zero with a smashed, barren planet. So the Swarmers had probably been bioengineering themselves to adapt to Earth’s oceans, ever since they discovered it in the expedition that left the Marginis wreck.
The theory even explained Walmsley’s Rule. The Swarmers—or the civilization they represented, the technology that built the starships they came in—made the Watchers, to keep track of other possible life sites, other developing societies. Some Watchers survived the final war that scraped some worlds free of life; others didn’t. Man was coming late upon the galactic stage; he should expect to find some props from earlier acts—most of them tragedies. Thus went the conventional wisdom, new edition.
Nigel’s point of view was duly heard, discussed, footnoted in later work—and then the stream of theories and models and self-consistency cheeks flowed on around it, a consensus river skirting an island. He did not know enough about analysis to integrate his model with the wealth of data. He thought it probable that the Marginis wreck had died while destroying Earth’s Watcher. Over half a million years after its crash, the crumpled eggshell vessel had demonstrated powerful weapons—which was how Moon Operations found it. At full capability, the wreck could have blown apart whole asteroids—and Nigel suspected that was precisely what it was designed to do. Many of the worlds they’d seen by probe—and Isis, too—had been pulverized by bombardment. It was the cheapest way to damage a planetary surface in terms of energy invested. So the Marginis wreck had laid there as man evolved up from apes. The wreck could detect and smash any large asteroid falling toward the biosphere. But its strength ebbed. It had stood up to battering attacks, only to fade slowly as time wore it down.
Now humanity could defend itself against asteroids or even worse weapons. As long, Nigel thought to himself, as we can recognize them as weapons.
SIX
Luyten 789–6 had only one world, circling near one of the two small suns, and it was devoured by fire.
As the probe swung near it, the spectral traces and photometry showed a pall of smoke and sheets of flame. The planet was Earth-size, comfortably warm, 80 percent ocean. Above the seas the oxygen content of the air was 25.4 percent, and over the continents, 23.7 percent.
It did not take much analysis to see what had happened. Warm surface temperatures made sea life abundant. Microorganisms there exhaled large amounts of oxygen. On Earth the same process ran, too, but oxygen was only 21 percent of the air.
The probability of forest fire nearly doubles with each 1 percent rise in oxygen. On the sole world of Luyten 789–6, the sea life poured oxygen into the forever burning tropical forests. Even Arctic tundra ignited. In the planet’s winter season plants grew despite the cold, driven by the high chemical reaction rates, and by processes in the soil. With summer came worldwide fires.
On Earth, methane belched up from mud ponds soaks oxygen from the air, keeping a stable balance. Somehow that mechanism had failed here. There was evidence from the chem sampling that this world was older than Earth; the grow-and-burn cycle had been running for billions of years. No animal life moved on the land; none could survive the fires. Yet a Watcher circled the world—impassive, scarred, and ancient.
“Carlotta!”
She turned. Nigel walked faster with obvious effort and caught up at a Y in the corridors. “Time for some talk?”
She grinned. “Sure. I’ve been wanting to bring something up myself. Just haven’t had an opportunity.”
They made their way to a viewpod that looked out on the base of the ship’s axis. Here the centrifugal gravity was low. Nigel’s face showed relief at the lessened strain. Beyond, they could see a globe of water ejected at the axis. People swam in it as it wobbled and flowed along the axis in free fall. They had thin rubber bands fixed to their ankles, in case they broke the surface tension and fell outward, Few did; they were adept fish, showering droplets and laughter.
“I miss that,” Nigel mused. “Haven’t done it for years.”
“Well, soon you’ll be able to again and we can—”
