“Damn right,” Yugo said.
“The theory fits.”
“Yup. Psychohistory works.”
Hari stared at the flexing colors. “I never thought…”
“It could work so well?” Dors had walked behind his chair and now rubbed his scalp.
“Well, yes.”
“You have spent years including the proper variables. It must work.”
Yugo smiled tolerantly. “If only more people shared your faith in mathists. You’ve forgotten the sparrow effect.”
Dors was transfixed by the shimmering data-solids, now rerun ning all Trantorian history, throbbing with different-colored schemes to show up differences between real history and the equations’ post-dictions. There were very few. What’s more, they did not grow with time.
Not taking her eyes from the display, Dors asked slowly, “Spar row? We have birds as pets, but surely—”
“Suppose a sparrow flaps its wings at the equator, out in the open. That shifts the air circulation a tiny amount. If things break just right, the sparrow could trigger a tornado up at the poles.”
Dors was startled. “Impossible!”
Hari said, “Don’t confuse it with the fabled nail in the shoe of a horse, that a legendary beast of burden. Remember?—its rider lost a battle and then a kingdom. That was failure of a small, critical component. Fundamental, random phenomena are democratic. Tiny differences in every coupled variable can produce staggering changes.”
It took a while to get the point through. Like any other world, Trantor’s meteorology had a daunting sensitivity to initial condi tions. A sparrow’s wing-flutter on one side of Trantor, amplified through fluid equations over weeks, could drive a howling hurricane a continent away. No computer could model all the tiny details of real weather to make exact predictions possible.
Dors pointed at the data-solids. “So—this is all wrong?”
“I hope not,” Hari said. “Weather varies, but climate holds steady.”
“Still…no wonder Trantorians prefer indoors. Outdoors can be dangerous.”
“The fact that the equations describe what happened—well, it means that small effects can smooth out in history,” Hari said.
Yugo added, “Stuff on a human scale can average away.”
She stopped massaging Hari’s scalp. “Then…people don’t mat ter?”
Hari said carefully, “Most biography persuades us that people—that we—are important. Psychohistory teaches that we aren’t.”
“As a historian, I cannot accept—”
“Look at the data,” Yugo put in.
They watched as Yugo brought up detail, showed off features. For ordinary people, history endured through art, myth, and liturgy. They felt it through concrete examples, close up: a building, a cus tom, a historical name. He and Yugo and the others were like sparrows themselves, hovering high over a landscape unguessed by the inhabitants below. They saw the slow surge of terrain, glacial and unstoppable.
“But people have to matter.” Dors’ voice carried a note of forlorn hope. Hari knew that somewhere deep in her lurked the stern dir ectives of the Zeroth Law, but over that lay a deep layer of true human feeling. She was a humanist who believed in the power of the individual—and here she met blunt, uncaring mechanism, in the large.
“They do, actually, but perhaps not in the way you want,” Hari said gently. “We sought out telltale groups, pivots about which events sometimes hinge.”
“The homosexuals, f’instance,” Yugo said.
“They’re about one percent of the population, a consistent minor variant in reproductive strategies,” Hari said.
Socially, though, they were often masters of improvisation, fashioning style to substance, fully at home with the arbitrary. They seemed equipped with an internal compass that pointed them at every social novelty, early on, so that they exerted leverage all out of proportion to their numbers. Often they were sensitive indicators of future turns.
Yugo went on, “So we figured, could they be a crucial indicator? Turns out they are. Helps out the equations.”
Dors said severely, “Why does history smooth out?”
Hari let Yugo carry the ball. “Y’see, that same sparrow effect had a positive side. Chaotic systems could be caught at just the right instant, tilted ever so slightly in a preferred way. A well-timed nudge could drive a system, yielding benefits all out of proportion to the effort expended.”
“You mean control?” She looked doubtful.
“Just a touch,” Yugo said. “Minimal control—the right nudge at the right time—demands that the dynamics be intricately under stood. Maybe that way, you could bias outcomes toward the least damaging of several finely balanced results. At best, they could drive the sys tem into startlingly good outcomes.”
“Who’s controlling?” Dors asked.
Yugo looked embarrassed. “Uh, we…dunno.”
“Don’t know? But this is a theory of all history.”
Hari said quietly, “There are elements, interplays, in the equations that we don’t grasp. Damping forces.”
“How can you not understand?”
Both men looked ill at ease. “We don’t know how the terms in teract. New features,” Hari said, “leading to…emergent order.”
She said primly, “Then you don’t really have a theory, do you?”
Hari nodded ruefully. “Not in the sense of a deep understanding, no.”
Models followed the gritty, experienced world, he reflected. They echoed their times. Clockwork planetary mechanics came after clocks. The idea of the whole universe as a computation came after computers. A worldview of stable change came after nonlinear dy namics…
He had a glimmering of a metamodel, which would look at him and describe how he would then select among models for psycho history. Peering down from above, it could see which was likely to be favored by Hari Seldon…