Free Foundation and Earth by Isaac Asimov Page A

viewscreen, he now saw a fourth, albeit through a computer-controlled telescopic device. The fourth was Comporellon.
    And again, for the fourth time, he was vaguely disappointed. Somehow, he continued to feel that looking down upon a habitable world from space meant seeing an outline of its continents against a surrounding sea; or, if it were a dry world, the outline of its lakes against a surrounding body of land.
    It was never so.
    If a world was habitable, it had an atmosphere as well as a hydrosphere. And if it had both air and water,it had clouds; and if it had clouds, it had an obscured view. Once again, then, Pelorat found himself looking down on white swirls with an occasional glimpse of pale blue or rusty brown.
    He wondered gloomily if anyone could identify a world if a view of it from, say, three hundred thousand kilometers, were cast upon a screen. How does one tell one cloud swirl from another?
    Bliss looked at Pelorat with some concern. “What is it, Pel? You seem to be unhappy.”
    “I find that all planets look alike from space.”
    Trevize said, “What of that, Janov? So does every shoreline on Terminus, when it is on the horizon, unless you know what you’re looking for—a particular mountain peak, or a particular offshore islet of characteristic shape.”
    “I dare say,” said Pelorat, with clear dissatisfaction, “but what do you look for in a mass of shifting clouds? And even if you try, before you can decide, you’re likely to be moving into the dark side.
    “Look a little more carefully, Janov. If you follow the shape of the clouds, you see that they tend to fall into a pattern that circles the planet and that moves about a center. That center is more or less at one of the poles.”
    “Which one?” asked Bliss with interest.
    “Since, relative to ourselves, the planet is rotating in clockwise fashion, we are looking down, by definition, upon the south pole. Since the center seems to be about fifteen degrees from the terminator—the planet’s line of shadow—and the planetary axis is tilted twenty-one degrees to the perpendicular of its plane of revolution, we’re either in mid-spring or mid-summer depending on whether the pole is moving away from the terminator or toward it. The computer can calculate its orbit and tell me in short order if I were to ask it. The capital is on the northern side of the equator so it is either in mid-fall or mid-winter.”
    Pelorat frowned. “You can tell all that?” He lookedat the cloud layer as though he thought it would, or should, speak to him now, but, of course, it didn’t.
    “Not only that,” said Trevize, “but if you’ll look at the polar regions, you’ll see that there are no breaks in the cloud layer as there are away from the poles. Actually, there are breaks, but through the breaks you see ice, so it’s a matter of white on white.”
    “Ah,” said Pelorat. “I suppose you expect that at the poles.”
    “Of habitable planets, certainly. Lifeless planets might be airless or waterless, or might have certain stigmata showing that the clouds are not water clouds, or that the ice is not water ice. This planet lacks those stigmata, so we know we are looking at water clouds and water ice.
    “The next thing we notice is the size of the area of unbroken white on the day side of the terminator, and to the experienced eye it is at once seen as larger than average. Furthermore, you can detect a certain orange glint, a quite faint one, to the reflected light, and that means Comporellon’s sun is rather cooler than Terminus’s sun. Although Comporellon is closer to its sun than Terminus is to hers, it is not sufficiently closer to make up for its star’s lower temperature. Therefore, Comporellon is a cold world as habitable worlds go.”
    “You read it like a film, old chap,” said Pelorat admiringly.
    “Don’t be too impressed,” said Trevize, smiling affectionately. “The computer has given me the applicable statistics of the world,