Shafer nodded. “So is Nemesis. And if it’s rock the maser heat will get conducted down quickly. Okay, say a kilowatt gives us half a degree a second on this little stone, and the Beta maser heats a target at five hundred degrees a second.” The Nobel man counted fingers. “Hey, these guys must be beaming one megawatt per square metre at five thousand miles’ range, can you believe that?”
Noordhof radiated happiness. “Nothing could withstand it. And laser beams don’t spread out with distance. We’ll ablate Nemesis clean out of the solar system, punch boulders off it. Hey, who needs the eggheads? I thought of this all by myself.”
Shafer shook his head sorrowfully. “No dice, Mark. Laser beams do spread out. Imagine two mirrors at the ends of a tube, reflecting light back and forth, one of the mirrors with a pinhole. You generate fluorescence inside the tube, and the light reflects and gets pumped up to huge intensity. The only light that makes it out through the hole has travelled the full length of the beam, but there’s still an angular spread. It’s the wavelength of the light divided by the diameter of the gun.”
“Maybe it’s a very big gun,” Noordhof interrupted, “Giving a very small dispersion.”
“You have the Alpha lasers in orbit. They’re hydrogen-fluoride, emitting at 2.7 microns. I guess their peak power can reach ten or twenty megawatts, but they can’t be more than a few metres across.”
Noordhof waved the magazine at Shafer. His tone was a mixture of triumph and desperation. “But this guy is talking about masers, not lasers. Everything is much bigger at radio wavelengths.”
Shafer shook his head again. “No way can you guys be hiding an array more than ten kilometres across, not even in the New Mexico desert. Ergo, if you’re beaming centimetre waves the angular spread is at least one part in a million.”
Noordhof spread his hands. “So? Nothing!”
“Nothing at five thousand miles. But if you catch Nemesis a million kilometres away the centimetre wave beam is spread out over one kilometre, the whole size of the asteroid. With attenuation like that you couldn’t boil an egg. Uncertainties in thermal conductivity or internal temperature will make no difference. I’m sorry Mark, but your top secret, Darth Vader, gigabuck, Space Dominance, missile-zapping Star Wars supermaser is as useful as a peashooter. We’re back to nukes.”
Webb couldn’t resist it: “I told you it wouldn’t work.”
“Where the hell do you think you’re going, Webb? Are you looking for Nemesis in the woods?”
“I’m looking for inspiration, Colonel. From the performance I’ve seen here, I’m more likely to find it with the squirrels.”
Noordhof opened the microwave door angrily. “Well, you might take the friggin’ rock out with you.”
Shafer was still laughing when Webb left the building.
At the far end of the little car park there was a gap in the trees which, on closer examination, turned out to be the beginning of a natural path. It was close to a cluster of garbage bins and Webb suspected that it might be a raiding route for some animals. He took off along it, and found that the path skirted the foot of Eagle Peak, rising gently as it went, with the cliff easily visible to the left through the heavy ponderosa trees. After about twenty minutes, far beyond Noordhof’s hundred-metre limit, he turned off to the base of the cliff, brushed the powdery snow off a broad boulder and sat down on it. There was the merest hint of cable rising above the trees about a mile back; otherwise there were no signs of human artefact. For the first time since he had been snatched from another snow-covered mountain, halfway round the planet, Webb had time to stop and think.
A last-minute asteroid deflection was a crass thing, a hefty punch with a barely controllable outcome. A punch on the nose, slowing Nemesis down long enough for the Earth to slip past, was more effective than a sideways swipe. But as the warning time dwindled so the punch became increasingly desperate, to the point where either you risked breaking the asteroid into a lethal swarm or you could do nothing to ward it off. Just which side of the threshold they were on they wouldn’t know until they had identified Nemesis.
The Russians, however, had had a different problem: that of precision. Probably, Webb thought, they had used a standoff explosion of a few megatons to give a crude impulse of a metre a second or thereabouts. The bigger the bomb the more potential asteroid weapons were available, and the Russians had hundred-megatonners in their arsenal. For every asteroid liable to hit the Earth they would have a hundred or more potential weapons in the form of near-missers.
But after that they would have had to finesse. A hit within a few hundred miles — or even a thousand miles — of Kansas would be adequate to obliterate the States. But a thousand miles is precision! After the initial big explosion, possibly years in the past, they would have required a series of small shepherding explosions, maybe little more than Hiroshimas, to guide the asteroid in.
All of which implied a fair amount of clandestine space activity, maybe using the Phobos or Venera series as a cover. Leclerc’s knowledge of past Russian space trips was the key.
There was a movement in the woods. A couple of crows were cautiously dropping from branch to branch about fifty yards away. And something small was scurrying through the trees. A white fox popped its head up and looked at Webb curiously. In a flash of inspiration, Webb suddenly realized that there was another key. He jumped up and the fox and crows disappeared.
In passing he looked in the kitchen and the common room, and knocked on Leclerc’s door. He threw off the hat and jumper. Back down to the conference room. “Where’s André?” he asked. Judy looked up briefly from a terminal and shrugged.
Webb picked up a pile of blank paper and made his way to the common room. It was empty. Warm afternoon sunlight was streaming in through the panoramic window. A green leather chair had a worn, comfortable look about it. He settled in. The sun was warm on his thighs and a light scented breeze was coming in through the window.
In some anonymous galaxy near the boundaries of space and time, two neutron stars had collided. With collision velocities close to the speed of light, the stars had annihilated their own matter, transforming it into a flash of radiation of incomprehensible intensity. Before even the Sun and Earth had formed, the radiation was spreading out through the Universe as a thin, expanding spherical shell. And then came the Sun and planets, and life evolved in the oceans, and then the reptiles had crawled on to land and the big archosaurs had ruled the Earth until the solar system entered a spiral arm, whence they had died in a massive bombardment of dust and impacts. It was an episode which had left the mammals and the insects, in their turn, to inherit the Earth. By the time the first primates had appeared the gamma rays were invading the Local Supercluster of galaxies; when homo sapiens was learning to carve on rocks the radiation was sweeping through the cave man’s own galaxy; and finally, at the very instant the apes had learned how to throw little metal machines around the Earth, the shell had momentarily rushed through the solar system, on its endless voyage to other stars and other galaxies.
But as the energetic photons swept past, a tiny handful had been picked up by the satellites which the apes had just developed; a millisecond gamma ray burst was duly recorded; theoreticians speculated; papers were written and debated; and arriving from cataclysms scattered through the cosmic wilderness, other gamma ray bursts were being picked up, recorded, discussed and debated, and catalogued.
And this was Webb’s problem. The Universe snaps and crackles across the whole electromagnetic spectrum. Neutron stars collide; massive stars run out of thermonuclear fuel, collapse and then destroy themselves in a gigantic thermonuclear explosion; red dwarfs dump their atmospheres on to white dwarf companions; relativistic jets squirt from the nuclei of galaxies and stars. Somewhere in this tremendous background of noise was a local event. A sprinkling of X-rays, perhaps, from an illegal nuclear explosion; or a brief flash of light in the sky. An explosion on Nemesis would throw hundreds of thousands of tons of debris into space. Maybe ice, maybe boulders, but surely dust. A cone of dust, fanning out into space and sparkling in the sunlight; a beacon in the dark interplanetary void.