”Please bear in mind, this will not happen at once. The work must go slowly, piecemeal, in pace with the astronomical cycle, constantly observed and measured, constantly adjusted to hold the giants of climate and weather under control. It will take thousands of years. Then finally, as Earth tilts back sunward, it will be undone, just as gradually and carefully. Most of us will notice little of it in our lifetimes. To our children and children’s children, hundreds of generations, it will be natural, a part of their universe like the moon and stars.”
”That’s the worst,” Omar said. “To them Terra Central will foe what God was to their ancestors. Oh, I don’t suppose they’ll worship it. But they’ll know how utterly dependent on it they are. And meanwhile it will he doing what God never did, evolve itself till it’s beyond all human comprehension. What then, Laurinda?”
Earlier, she had not meant to give his viewpoint as much voice as she now did. However, this might actually be the wisest course. He and his fellows were making their protests widely known. By taking them seriously, she, a designated speaker for the artificial intelligence, could perhaps better show why they were wrong.
”Doubtless most of you have heard that certain people think this whole concept is mistaken.” She left out Omar’s Disastrously mistaken. The more so because it’s millennially slow and all pervading. She smiled. “They are not fools. They have studied the situation and done scientific analyses. Let me discuss their position as I see it. They are right when they say there is an easier, cheaper, and far less disruptive way to stop the Ice.”
Robots in space. Asteroids mined, the stuff of them refined, nanotechnic assemblers forming titanic mirrors to precisions of micrometers, the judicious orbiting of these-no simple task, but well within present-day capabilities. Governed by mathematics and monitors less complex than in the rival scheme, the mirrors’ shine added sunlight onto Earth at the times, places, and intensities needed. The glaciers retreat, climates stabilize, the system stands guard through the necessary era and stands in reserve forever after.
”It would take away the night skies we’ve regained. We would not see many stars, for there would be no full darkness. But simulacra are plentiful; or you can enjoy a holiday in space; and otherwise our world remains much the same.
”Why, then, does Terra Central warn against this?” Again the bright, cold animated diagrams, but expanded first to a galactic scale, then contracted to Sol’s near neighborhood, then down to molecules and force fields.
Space is not empty. Look at the Milky Way on a clear night and you will see bays in its river that are clouds of dust. The dust in such nebulas as Orion’s is luminous from the light of new-born stars, and more are condensing out of it. Hydrogen and helium, the primordial elements, far outmass these quantities of solid material, which are nevertheless colossal. Nowhere do the gas and motes of the interstellar medium reach a density equal to what would count as a hard vacuum on Earth; but taken together, through sevenfold billion cubic light-years, they dominate the visible universe.
Nor are they spread evenly. In some regions they occur more thinly or thickly than elsewhere. Sometimes a knot in the medium grows tight enough to collapse in on itself, and stars and planets form.
Sometimes, swinging around the galactic core on its two hundred million-year path, Sol encounters a dense cloud.
The one immediately ahead was nothing extraordinary. It would never engender worlds. It was merely a few times more compact than the local average and merely a few light-years in extent. Early astronomers had caught no definite sight of it. Even after they were using spaceborne instruments, they were not sure.
”Our interstellar outposts have the baselines to map this shoal with certainty. They have sent us their findings. In about nine thousand years, Sol will enter the region. Yes, it will only transect. A hundred thousand years later, it will be back in clear space. But a hundred thousand years is a long time for living creatures.”
The contact presses on Sol’s wind and magnetic field until the heliosphere and its bow wave, the hydrogen wall, are inside the orbit of Saturn. With the protection they give thus lessened, Earth takes a sleet of cosmic rays, background count tripled or quadrupled. Oh, life has survived comparable events in the past, but species, genera, whole orders died, ecologies to which they had been vital avalanche into ruin, mass extinctions followed. And, in the depths of this encounter, enough hydrogen atoms could reach Earth to deplete her oxygen, enough dust to fill her stratosphere with ice particles and bring on a world of winter like none before.