“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 avalanched 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.
“Nine thousand years, our well-wishing opponents say. Ample time to make ready. Meanwhile, why should we lock ourselves into a program that will transform our civilization?
“People of Earth, through me and my colleagues Terra Central tells you that defense against the nebula calls for resources we dare not spend on anything less.”
Monstrous constructions, thousands of them, in orbits that only machine intelligence can maintain—powered by thermonuclear reactions or often by the mutual destruction of matter and antimatter—and first the antimatter must be manufactured by megatonnes—generating forces to ionize alien atoms and whirl the plasmas away—a citadel around the entire globe, waging a war that lasts a tenth of a million years.
“Sun-mirrors to hold back the glaciers in the near future won’t be compatible with this. Their advocates admit it, but say that come the time, we can make adjustments. Perhaps they are right. What they do not say is whether or not the mirrors will tie up too much material and effort. We’ll have to conduct a very thorough survey of the Solar System before we know. Meanwhile, every year we delay starting to take action, the Ice advances farther and becomes harder to fight.
“But we, people of Earth, we now alive, who must make the decision that all our descendants must live with or die by—we should think beyond the engineering requirements. Let’s ask ourselves a simple and terrible question. In the course of nine thousand years, what can happen?”
And she gave them history to show it was unforeseeable.
The Neolithic Revolution tamed wildernesses, fed suddenly large populations, founded the earliest towns, built the earliest smithies—and turned free hunters into peasant masses with god-kings above them.
Scarcely were the Pharaohs of Egypt laid to their eternal rest than thieves plundered the tombs. When railroads later ran through what had been their domains, for a while the steam engines were stocked with mummies.
The Persian Empire fell into internecine war, then fell to Alexander, whose own empire did not outlast his untimely death. What followed was a prolonged bloodbath.
Within four centuries of Jesus’ entry into Jerusalem, Christians were killing heretic Christians.
The peace and refinement of Heian Japan gave way to incessant struggle between clans and war lords. In China, dynasty after dynasty claimed the Mandate of Heaven and eventually, bloodily, lost it.
The Mongols galloped from end to end of Asia, deep into Europe, until their Khan reigned over half a continent. In a few generations that sovereignty crumbled. Nonetheless a remnant of it turned the nascent democracy of Russia into the Tsardom, and another remnant bore Islam to India.
The mighty Aztec and Inca realms broke before a handful of Spanish invaders. The wealth that flowed thence into Europe energized the trading nations of the North but rotted Spain itself, whose long-term legacy became one of tyranny and corruption.
From the “Liberty, Equality, Fraternity” of the French Revolution sprang Napoleon. From the idealism of Sun Yat-sen sprang Chiang Kai-shek and Mao Zedong.
No one in power understood what such modern weapons as the machine gun portended, nor was able to end the stalemate they brought before it had destroyed four empires, lives in the tens of millions, and the spiritual foundations of Western civilization. A greater war ensued, and then a twilight struggle for half a century more, while on its fringes countries newly established went at each other’s throats.
In an age when science was reaching from the innermost atom to
