Foundation's Edge by Isaac Asimov

never seen it like this. I never dreamed it had so much detail.”
    “How could you? You can’t see the outer half when Terminus’s atmosphere is between you and it. You can hardly see the nucleus from Terminus’s surface.”
    “What a pity we’re seeing it so nearly head-on.”
    “We don’t have to. The computer can show it in any orientation. I just have to express the wish-and not even aloud.”
    Shift co-ordinates!
    This exercise of will was by no means a precise command. Yet as the image of Galaxy began to undergo a slow change, his mind guided the computer and had it do what he wished.
    Slowly the Galaxy was turning so that it could be seen at right angles to the Galactic plane. It spread out like a gigantic, glowing whirlpool, with curves of darkness, and knots of brightness, and a central all-but-featureless blaze.
    Pelorat asked, “How can the computer see it from a position in space that must be more than fifty thousand parsecs from this place?” Then he added, in a choked whisper, “Please forgive me that I ask. I know nothing about all this.”
    Trevize said, “I know almost as little about this computer as you do. Even a simple computer, however, can adjust co-ordinates and show the Galaxy in any position, starting with what it can sense in the natural position, the one, that is, that would appear from the computer’s local position in space. Of course, it makes use only of the information it can sense to begin with, so when it changes to the broadside view we would find gaps and blurs in what it would show. In this case, though-“
    “Yes?”
    “We have an excellent view. I suspect that the computer is outfitted with a complete map of the Galaxy and can therefore view it from any angle with equal ease.”
    “How do you mean, a complete map?”
    “The spatial co-ordinates of every star in it must be in the computer’s memory banks.”
    “Every star?” Pelorat seemed awed.
    “Well, perhaps not all three hundred billion. It would include the stars shining down on populated planets, certainly, and probably every star of spectral class K and brighter. That means about seventy-five billion, at least.”
    “Every star of a populated system?”
    “I wouldn’t want to be pinned down; perhaps not all. There were, after all, twenty-five million inhabited systems in the time of Hari Seldon-which sounds like a lot but is only one star out of every twelve thousand. And then, in the five centuries since Seldon, the general breakup of the Empire didn’t prevent further colonization. I should think it would have encouraged it. There are still plenty of habitable planets to expand into, so there may be thirty million now. It’s possible that not all the new ones are in the Foundation’s records.”
    “But the old ones? Surely they must all be there without exception.”
    “I imagine so. I can’t guarantee it, of course, but I would be surprised if any long-established inhabited system were missing from the records. Let me show you something-if my ability to control the computer will go far enough.”
    Trevize’s hands stiffened a bit with the effort and they seemed to sink further into the clasp of the computer. That might not have been necessary; he might only have had to think quietly and casually: Terminus!
    He did think that and there was, in response, a sparkling red diamond at the very edge of the whirlpool.
    “There’s our sun,” he said with excitement. “That’s the star that Terminus circles.”
    “Ah,” said Pelorat with a low, tremulous sigh.
    A bright yellow dot of light sprang into life in a rich cluster of stars deep in the heart of the Galaxy but well to one side of the central haze. It was rather closer to the Terminus edge of the Galaxy than to the other side.
    “And that,” said Trevize, “is Trantor’s sun.”
    Another sigh, then Pelorat said, “Are you sure? They always speak of Trantor as being located in the center of the Galaxy.”
    “It is, in a way. it’s as