Incandescence

developed femtomachines sophisticated enough to make transmuting the elements more efficient than scavenging for them.

The second candidate on their list had managed to hold on to even less detritus than the first. The winds from the new-born giants were not as strong here, but if any planets or asteroids worthy of the name had once accompanied this star, they had long ago been dislodged from their orbits by interfering neighbors. Rakesh had learned as a child that life could only thrive out in the disk, and however far the Steelmakers had progressed it was growing ever harder to see them as much of an exception to that parochial rule. Maybe life had flourished in this region, in some as yet undiscovered niche that had nothing to do with planets sitting in stable orbits around stars for billions of years; maybe the Aloof were descended from such creatures. The fact remained, though, that his cousins seemed to have hitched their fortunes to a way of life that simply couldn’t last here.

The third star possessed a substantial asteroid belt, but still no planets. Rakesh thought, This is how it’s going to be: sometimes a few more rocks, sometimes a few less. Each star’s chaotic history of close encounters would sweep a slightly different range of orbits clean, but there’d always be a smattering of junk clinging on.

Parantham said calmly, “The isotope signature of most of these asteroids matches our rock.”

Rakesh viewed the data. Point after point coincided, error bars overlapping. What’s more, the models he ran rejected the notion that these asteroids had been born from the same gas cloud as the star they orbited. It looked as if they’d found the Interloper, and the shattered remnants of the Steelmakers’ world.

Rakesh was shaken, though he knew he had no right to be surprised that the search had ended badly. The Interloper had dragged this world into ever more dangerous territory; the real miracle was that it had enjoyed such a long era of safety and stability around its birth star. “So this is their graveyard,” he said.

“We don’t know that,” Parantham replied. “We know that the Steelmakers built at least one interplanetary probe. At some point they might have built star ships, or engineering spores. They might have left this world behind long before it was broken up.”

Rakesh had his doubts that the Steelmakers—as a species, let alone a technological culture—could have survived their planet’s capture by the Interloper. Still, it was possible that in the intervening hundred million years a second intelligent species had arisen in their place. In any case, he’d honor his promise and sift through the ruins. He owed it to the Steelmakers and whoever might have followed them to do his best to learn their history and bring it back to the Amalgam.

Dynamical models indicated that the Steelmakers’ world had been tidally disrupted, rather than smashed apart by a head-on collision. A compact stellar remnant—most likely a neutron star—had passed through the system fifty million years before, coming close enough for the difference in its gravitational pull from one side of the planet to the other to tear asteroid-sized rocks right out of the mantle and send them fountaining into the sky. Though common sense made that sound like the work of a monstrously powerful force, the models suggested that the tidal stretching had only exceeded the planet’s gravity by a modest amount, perhaps as little as fifty per cent. If there had been any hapless descendants of the Steelmakers around, the tidal force itself would have left them unscathed, but that would have been the least of their problems. Some might have survived the initial quakes, as the pressure bearing down on the planet’s interior was lessened in places and strengthened elsewhere, fracturing the crust like the skin of a squeezed grape. Some would have felt their own weight growing, but not unbearably, and even where the tidal stretch turned gravity skyward, some might have had the presence of mind to grip something anchored securely to the ground and cling to life for a few more minutes as the air around them grew thinner. In the end, though, the ground itself had had nothing to hold it together against its own reversed weight, and the planet had simply disintegrated.

Rakesh worked with Parantham to design a probe swarm to send into the ruins. Each probe would be about a micrometer wide, and would hop from asteroid to asteroid by riding the currents of the stellar wind—not the Interloper’s feeble exhalation, but the overpowering breath of the neighborhood giants. On each rock they visited, the probes would gather energy from sunlight to feed a small band of exploratory nanomachines.

The wind couldn’t carry the probes all the way from Lahl’s Promise into the asteroid belt, so they had the workshop build half a dozen delivery modules, driven by ion thrusters, each carrying a kilogram or so of probes to scatter as they arced along the edge of the belt. These delivery modules would also act as information relays, with instruments to track the probes closely and elicit stored data from them.

The modules filed out of the workshop, flung away from the ship by centrifugal force before their thrusters lit up. Rakesh watched their blue exhaust trails through the cabin window. “Do you regret coming with me now?” he asked Parantham.

“Not at all!” she said. She seemed shocked by the question. “Why would I?”

“If the Steelmakers are dead, with no descendants. “

“Then that’s sad,” she said, “but history is full of sad stories. If there’s no chance of meeting them face to face, I’ll happily settle for archaeology. Archaeology in the disk is finished: every ruin has been tomographed down to the molecular level, every scrap of ancient language and every artefact has been interpreted to death. I was promised nothing but a rock full of microbes when I signed up for this, remember? And you expect me to be having second thoughts just because the sentient species we’ve discovered might have lasted less than one hundred and fifty million years?”

Rakesh couldn’t argue with anything Parantham had said, but his own sentiments were very different. “Maybe at the back of my mind I thought the worst case scenario would be a thousand-year-long slog that ended with nothing but bacteria, while the best case would take us straight to the Planet of the Long Lost Cousins, who I could invite into the Amalgam to live happily ever after. Now that we’ve caught a glimpse of the real story, it seems that it’s bacteria who would have had the best chance of living happily ever after.”

He could easily picture his own village on Shab-e-Noor with a dark pinprick crossing the sky, the ground rumbling, an ominous lightness. Of course, that couldn’t happen in the Age of the Amalgam; there was no conceivable cosmic threat out in the disk that could not be detected and neutralized. Such vulnerability had been relegated to history. Nevertheless, the image haunted him in a way that went beyond mere empathy for its putative victims. There was a chill in his bones at the recognition that, in the broadest sense, he’d stepped out from the shadow of the same kind of ax. His ancestors had been luckier than the Steelmakers, that was all.

The first wave of results from the probes came in while Rakesh was in the kitchen, cooking breakfast.

Dead microbes had been found in more than sixty per cent of the asteroids sampled so far. That figure was surprisingly high; either the biosphere of the Steelmakers’ world had extended deep into the mantle, or the rubble that originated from the depths of the planet had been cross-contaminated by other debris, from closer to the surface.

The genome fragments and general morphology closely matched those of the microbes they’d found in the Aloof’s meteor. Along with the isotope data, this left Rakesh with no doubt that they’d found their target. Half of the Interloper’s asteroid belt consisted of rocks virtually identical to the one that had triggered their search.

“The Aloof should give us a treat and a scratch behind the ears now,” he told Parantham as he filled her plate.

She stared at him as if he’d lost his mind.

“On my home world,” he explained, “we have domestic animals that can find things by scent. You give them a whiff, then they go searching for something that smells the same.”

“You don’t have machines to do that?”

“Of course we do. But these animals enjoy it, it’s part of their ancestry. If they don’t get the chance to exercise their skills, they get sick with boredom.”

“Like the gang back at the node?” Parantham suggested dryly.

“Well, yes.” Rakesh hadn’t intended the comparison to be taken literally, but he felt a momentary frisson of unease. “I suppose that’s one theory we can’t rule out: the Aloof took pity on us and offered us a chance to chase a strange new scent across their paddock.”

“It doesn’t show much pity if they only do it for a couple of people every million years.” Parantham shook her head. “We’re not their pets. They’ve kept a few secrets from us; good for them. It doesn’t make them our superiors.”

“A few secrets?” Rakesh laughed. “We mapped their gamma ray data routes. They get to read our minds, down to the last byte. And you’re the one who told me that the gamma ray network was