conversation had run out after that and seldon watched the structures of the streeling sector as they passed. some were quite low, while some seemed to brush the "sky." wide crosspassages broke the progression and frequent alleys could be seen.

at one point, it struck him that though the buildings rose upward they also swept downward and that perhaps they were deeper than they were high. as soon as the thought occurred to him, he was convinced it was true. occasionally, he saw patches of green in the background, farther back from the expressway, and even small trees.

he watched for quite a while and then became aware that the light was growing dimmer. he squinted about and turned to hummin, who guessed the question.

"the afternoon is waning," he said, "and night is coming on."

seldons eyebrows raised and the corners of his mouth turned downward. "thats impressive. i have a picture of the entire planet darkening and then, some hours from now, lighting up again."

hummin smiled his small, careful smile. "not quite, seldon. the planet is never turned off altogether--or turned on either. the shadow of twilight sweeps across the planet gradually, followed half a day later by the slow brightening of dawn. in fact, the effect follows the actual day and night above the domes quite closely, so that in higher altitudes day and night change length with the seasons."

seldon shook his head, "but why close in the planet and then mimic what would be in the open?"

"i presume because people like it better that way. trantorians like the advantages of being enclosed, but they dont like to be reminded of it unduly, just the same. you know very little about trantorian psychology, seldon."

seldon flushed slightly. he was only a heliconian and he knew very little about the millions of worlds outside helicon. his ignorance was not confined to trantor. how, then, could he hope to come up with any practical applications for his theory of psychohistory?

how could any number of people--all together--know enough? it reminded seldon of a puzzle that had been presented to him when he was young: can you have a relatively small piece of platinum, with handholds affixed, that could not be lifted by the bare, unaided strength of any number of people, no matter how many?

the answer was yes. a cubic meter of platinum weighs 22,420 kilograms under standard gravitational pull. if it is assumed that each person could heave 120 kilograms up from the ground, then 188 people would suffice to lift the platinum.--but you could not squeeze 188 people around the cubic meter so that each one could get a grip on it. you could perhaps not squeeze more than 9 people around it. and levers or other such devices were not allowed. it had to be "bare, unaided strength."

in the same way, it could be that there was no way of getting enough people to handle the total amount of knowledge required for psychohistory, even if the facts were stored in computers rather than in individual human brains. only so many people could gather round the knowledge, so to speak, and communicate it.

hummin said, "you seem to be in a brown study, seldon."

"im considering my own ignorance."

"a useful task. quadrillions could profitably join you.--but its time to get off."seldon looked up. "how can you tell?"

"just as you could tell when you were on the expressway your first day on trantor. i go by the signs."

seldon caught one just as it went by: streeling university--3 minutes.

"we get off at the next boarding station. watch your step."

seldon followed hummin off the coach, noting that the sky was deep purple now and that the walkways and corridors and buildings were all lighting up, suffused with a yellow glow.

it might have been the gathering of a heliconian night. had he been placed here blindfolded and had the blindfold been removed, he might have been convinced that he was in some particularly well-built-up inner region of one of helicons larger cities.

"how long do you suppose i will remain at streeling university, hummin?" he asked.

hummin said in his usual calm fashion, "that would be hard to say, seldon. perhaps your whole life."

"what!"

"perhaps not. but your life stopped being your own once you gave that paper on psychohistory. the emperor and demerzel recognized your importance at once. so did i. for all i know, so did many others. you see, that means you dont belong to yourself anymore."

library

venabili, dors-- ... historian, born in cinna ... her life might well have continued on its uneventful course were it not for the fact that, after she had spent two years on the faculty of streeling university, she became involved with the young hari seldon during the flight ...

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