"Not likely. It's not the human way. Trantor was the capital world of the Galaxy for twelve thousand years - the most populous world for twenty thousand years - yet it did not impose its rotation period of 1.08 Galactic Standard Days on all the Galaxy. And Terminus's rotation period is 0.91 GSD and we don't enforce ours on the planets dominated by us. Every planet makes use of its own private calculations in its own Local Planetary Day system, and for matters of interplanetary importance converts - with the help of computers - back and forth between LPD and GSD. The Galactic Standard Day must come from Earth]"
"Why is it a must?"
"For one thing, Earth was once the only inhabited world, so naturally its day and year would be standard and would very likely remain standard out of social inertia as other worlds were populated. Then, too, the model I produced was that of an Earth that rotated on its axis in just twenty-four Galactic Standard Hours and that revolved about its sun in just one Galactic Standard Year."
"Might that not be coincidence?"
Pelorat laughed. "Now it is you who are talking coincidence. Would you care to lay a wager on such a thing happening by coincidence?"
"Well well," muttered Trevize.
"In fact, there's more to it. There's an archaic measure of time that's called the month..."
"I've heard of it."
"It, apparently, about fits the period of revolution of Earth's satellite about Earth. However - "
"Yes?"
"Well, one rather astonishing factor of the model is that the satellite I just mentioned is huge - over one quarter the diameter of the Earth itself."
"Never heard of such a thing, Janov. There isn't a populated planet in the Galaxy with a satellite like that."
"But that's good," said Pelorat with animation. "If Earth is a unique world in its production of variegated species and the evolution of intelligence, then we want some physical uniqueness."
"But what could a large satellite have to do with variegated species, intelligence, and all that?"
"Well now, there you hit a difficulty. I don't really know. But it's worth examination, don't you think?"
Trevize rose to his feet and folded his arms across his chest. "But what's the problem, then? Look up the statistics on inhabited planets and find one that has a period of rotation and of revolution that are exactly one Galactic Standard Day and one Galactic Standard Year in length, respectively. And if it also has a gigantic satellite, you'd have what you want. I presume, from your statement that you 'have an excellent possibility in mind,' that you've done just this, and that you have your world."
Pelorat looked disconcerted. "Well, now, that's not exactly what happened. I did look through the statistics, or at least I had it done by the astronomy department and - well, to put it bluntly, there's no such world."
Trevize sat down again abruptly. "But that means your whole argument falls to the ground."
"Not quite, it seems to me."
"What do you mean, not quite? You produce a model with all sorts of detailed descriptions and you can't find anything that fits. Your model is useless, then. You must start from the beginning."
"No. It just means that the statistics on populated planets are incomplete. After all, there are tens of millions of them and some are very obscure worlds. For instance, there is no good data on the population of nearly half. And concerning six hundred and forty thousand populated worlds there is almost no information other than their names and sometimes the location. Some galactographers have estimated that there may be up to ten thousand inhabited planets that aren't listed at all. The worlds prefer it that way, presumably. During the Imperial Era, it might have helped them avoid taxation."
"And in the centuries that followed," said Trevize cynically. "It might have helped them serve as home bases for pirates, and that might have, on occasion, proved more enriching than ordinary trade."
"I 'wouldn't know about that," said Pelorat doubtfully.
Trevize said, "Just the same, it seems to me that Earth would have to be on the list of inhabited planets, whatever its own desires. It would be the oldest of them all, by definition, and it could not have been overlooked in the early centuries of Galactic civilization. And once on the list, it would stay on. Surely we could count on social inertia there."
Pelorat hesitated and looked anguished. "Actually, there - there is a planet named Earth on the list of inhabited planets."
Trevize stared. "I'm under the impression that you told me a while ago that Earth was not on the list?"
"As Earth, it is not. There is, however, a planet named Gaia."
"What has that got to do with it? Gahyah?"
"It's spelled G-A-I-A. It means 'Earth.'"
"Why should it mean Earth, Janov, any more than anything else? The name is meaningless to me."
Pelorat's ordinarily expressionless face came close to a grimace. "I'm not sure you'll believe this. - If I go by my analysis of the myths, there were several different, mutually unintelligible, languages on Earth."
"What?"
"Yes. After all, we have a thousand different ways of speaking across the Galaxy..."
"Across the Galaxy, there are certainly dialectical variations, but these are not mutually unintelligible. And even if understanding some of them is a matter of difficulty, we all share Galactic Standard."
"Certainly, but there is constant interstellar travel. What if some world was in isolation for a prolonged period?"
"But you're talking of Earth. A single planet. Where's the isolation?"