Part 31 (2/2)
seventeen thousand miles an hour. And no separation from the external tank-two unmanned tankers awaited to top off their nearly empty ET.”Three . . . two . . . one . . . MECO.”Kyle's arms floated free of the armrests. His stomach lurched. His pulse raced. It was suddenly, blissfully quiet; radioed exchanges with ground control were the only sounds. As he tipped his head backward, a bony finger poked him: Speedy reaching across the gap between their seats. ”Welcome to s.p.a.ce, Doc.” In the front seats, Carlisle and McNeilly tended to the details of raising and circularizing their orbit. He could not tear his eyes from the panoramic view of Earth through the overhead cabin windows. He'd dreamed of this moment for forty-some years now, had an image in his mind's eye of sparkling blue and rich brown and lacy white.
The Earth stretched out below him was a cruel caricature of that expectation. Huge, angry whirlpools of cloud dominated the Atlantic. In the black ma.s.ses of cloud masking much of western Europe, lightning sparked and flashed like Thor and Zeus gone to war.
And exactly as if hostile aliens had conspired to wipe Earth clean of all life.
* * * The Big Dim was actually quite simple. The moon, like the Earth, receives solar energy at an average rate of 1345 watts per square meter. To darken the moon, convert incoming sunlight to electricity. To cool the moon, use that electricity to broadcast an electromagnetic signal . . . energy is removed instead of absorbed. Emit half of the incident energy that way, and-the moon being far smaller than the Earth-the transmitted energy is about 3% of the solar energy Earth receives. By way of comparison, the annual change in sunlight that causes Earth's seasons is only plus-or-minus 3.4%.
And if the goal is at the same time to sterilize the Earth? Merely broadcast in a suitable microwave frequency. Pick a frequency to which the Earth's atmosphere is transparent, a frequency strongly absorbed by liquid water-then focus all of that energy on the Earth. A frequency of 2.45 GHz works well . . . the frequency used inside every microwave oven.
Solar energy to electricity? That's easy: solar cells. Electricity to microwave beams? That's also straightforward: masers. Solar cells and masers are readily fabricated from semiconductors, with well understood human technology. The most common semiconductor is silicon. By weight, a fifth of the lunar surface is silicon.
But what could cover the whole surface of the moon with solar cells and masers?
Krulchukor laser cannons had already been grown on the moon, enclaves of solar cells and semiconductor lasers reprogrammed to project the mirage of the mother s.h.i.+p. That which has been reprogrammed can be reprogrammed again.
What humans call light and microwaves are only different regions in the electromagnetic spectrum, so resize and recalibrate new semiconductor structures to emit microwaves. Move the aiming point from a tiny, fast-moving radar buoy to the impossible-to-miss globe of Earth. Delete the code that limited the growth to small regions. Wait until the nanotech-produced texture-no dimension of its surface manifestation larger than inches, impossibly small to see from Earth-infests the entire lunar surface. Then turn out the lights and crank up the heat.
* * * ”Like a freaking ballet outside, only interesting.” Speedy was admiring an ET/unmanned-tanker rendezvous through a flight-deck window. ”Doc. You gotta see this.” Kyle was out of her sight, on the middeck. ”I caught the first act.” The ET had already drained one remote-controlled tanker. The load from the second tanker would bring the ET to about half filled. That would more than get Endeavor where it needed to go. The hard part of s.p.a.ce travel was reaching low Earth orbit.
”You staring dirtside again, Doc?” she persisted.
”Uh-huh.” Doctor Doom was too many syllables for regular use. He'd lucked out-Doom would have gotten old. ”It keeps me focused on why we're up here.”
They were over the eastern Pacific, approaching the Panamanian coast. Two enormous tropical
depressions were converging on the area. By historical standards, it was early in hurricane season, but the National Hurricane Center was already up to Norman on this year's second pa.s.s through the alphabet. Central America was going to get clobbered again. He couldn't help but remember that kid who washed out to sea. It had been one death among thousands in a single storm, and there had been hundreds of hurricanes, typhoons, and cyclones since-and it was the tragedy that still gave Darlene nightmares.
His eyes were glued to the ten-inch window in the side hatch. Logically, the view was no different than what he'd seen often in satellite imagery. Maybe so, but it was more real with only a pane of gla.s.s and vacuum between him and the unfolding catastrophe. As he watched, lightning erupted like popcorn over the cloud-cloaked mountainous spine of the isthmus. More mudslides in the making? d.a.m.n Grelben.
”Doc. Since you're downstairs, check on the MDS, w.i.l.l.ya?””Sure, Craig.” The microwave dump system was one of the postapocalypse retrofits to the orbiter. Endeavor had launched during a waning crescent moon; there was comparatively little Earth-bound microwave energy. Even if the moon had been full, its microwaves were a different sort of hazard than the defeated masersats. Those had focused weapons-grade bursts on small targets. The endless lunar emissions blanketed all of Earth facing the moon. The MDS reradiated the incoming, comparatively diffuse microwaves. ”The panel shows all green.”
”Thanks, Doc.”
”Coming through.” Speedy dove through an interdeck opening, with a grace in micro-G he could only
envy. She retrieved a camera from her locker on the middeck. The storm caught her attention on her return soar. With a tuck, roll, and light kick off a bulkhead, she stopped gracefully in midair. ”Je-sus!”
”I wouldn't want to be wherever that monster comes ash.o.r.e.”
Another well-placed kick propelled her closer. She stared out the hatch's inset window. ”You understand this stuff? Really?”
The implicit admission surprised him, since there was so much he had yet to learn. Maybe he'd feel more at home when the puking stopped. That half of astronauts had a few days of s.p.a.ce adaptation sickness was little comfort. The old hands recommended keeping busy. ” 'This stuff'? You mean how The Big Dim hoses the climate?”
”Right, Doc.” She took a snack bar from a jumpsuit pocket. ”You want half?”His stomach gurgled. ”No thanks. All right, the weather. The moon used to reflect about ten percent of sunlight hitting it, and that was scattered. Now, about half the incident light is reemitted, and it all comes Earth's way. As microwaves. If the microwaves. .h.i.t water-and Earth's surface is seventy-percent water-they increase evaporation. Vast regions of moist, warm air rise, spun up by Coriolis forces.” He pointed at the huge storms forming below. ”Okay?”
”So far, so good.”
”But more energy and more storms are just the start. Greenhouse effect is the kicker.”
She nabbed a crumb that had floated off. ”I don't get it.”
Not her field, not her fault. ”During the day, solar energy soaks into the ground. The heat reradiates to
s.p.a.ce at night, as infrared. But some gases block IR, trapping heat in the atmosphere. The effect is like gla.s.s in a greenhouse.”
”Like carbon dioxide.”At five miles per second, crossing Central America didn't take long; the Endeavor made the traverse while Kyle was in what Dar called pedantic mode. A hurricane was brewing in the Caribbean. ”Right. But not only carbon dioxide. Water vapor is another greenhouse gas.”
”Aha. The microwaves increase evaporation, producing water vapor, which traps heat, which further increases evaporation. A vicious cycle.” She finished the snack bar and carefully zipped the wrapper into a pocket. ”The evaporation leads to more clouds, and so to more rain.”
”Yes, but not indefinitely. Hot air rises. The water vapor-laden air rises. Rain, of course, begins as airborne droplets forming in the cool upper atmosphere, condensing around airborne dust. Condense enough water, and the drop gets heavy and falls. But these microwaves evaporate water from would-be raindrops. So the new vapor rises still higher, into colder and colder parts of the atmosphere. Drive the vapor high enough, and you get permanent upper-atmospheric ice crystals instead of rain.”
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