"Can it do that?" asked Bliss, sounding rather awe-struck.
"Well, it can't move the Galaxy itself back in time, but it can move the map in its memory banks back in time."
Bliss said, "Will we see anything happen?"
"Watch," said Trevize.
Very slowly, the half-dozen stars crawled over the face of the screen. A new star, not hitherto on the screen, drifted in from the left hand edge, and Pelorat pointed in excitement. "There! There!"
Trevize said, "Sorry. Another red dwarf. They're very common. At least three fourths of all the stars in the Galaxy are red dwarfs."
The screen settled down and stopped moving.
"Well?" said Bliss.
Trevize said, "That's it. That's the view of that portion of the Galaxy as it would have been twenty thousand years ago. At the very center of the screen is a point where the Forbidden World ought to be if it had been drifting at some average velocity."
"Ought to be, but isn't," said Bliss sharply.
"It isn't," agreed Trevize, with remarkably little emotion.
Pelorat released his breath in a long sigh. "Oh, too bad, Golan."
Trevize said, "Wait, don't despair. I wasn't expecting to see the star there."
"You weren't?" said Pelorat, astonished.
"No. I told you that this isn't the Galaxy itself, but the computer's map of the Galaxy. If a real star is not included in the map, we don't see it. If the planet is called 'Forbidden' and has been called so for twenty thousand years, the chances are it wouldn't be included in the map. And it isn't, for we don't see it."
Bliss said, "We might not see it because it doesn't exist. The Comporellian legends may be false, or the co-ordinates may be wrong."
"Very true. The computer, however, can now make an estimate as to what the co-ordinates ought to be at this time, now that it has located the spot where it may have been twenty thousand years ago. Using the co-ordinates corrected for time, a correction I could only have made through use of the star map, we can now switch to the real starfield of the Galaxy itself."
Bliss said, "But you only assumed an average velocity for the Forbidden World. What if its velocity was not average? You would not now have the correct co-ordinates."
"True enough, but a correction, assuming average velocity, is almost certain to be closer to its real position, than if we had made no time correction at all."
"You hope!" said Bliss doubtfully.
"That's exactly what I do," said Trevize. "I hope. And now let's look at the real Galaxy."
The two onlookers watched tensely, while Trevize (perhaps to reduce his own tensions and delay the zero moment) spoke softly, almost as though he were lecturing.
"It's more difficult to observe the real Galaxy," he said. "The map in the computer is an artificial construction, with irrelevancies capable of being eliminated. If there is a nebula obscuring the view, I can remove it. If the angle of view is inconvenient for what I have in mind, I can change the angle, and so on. The real Galaxy, however, I must take as I find it, and if I want a change I must move physically through space, which will take far more time than it would take to adjust a map."
And as he spoke, the screen showed a star cloud so rich in individual stars as to seem an irregular heap of powder.
Trevize said, "That's a large angle view of a section of the Milky Way, and I want the foreground, of course. If I expand the foreground, the background will tend to fade in comparison. The co-ordinate spot is close enough to Comporellon so that I should be able to expand it to about the situation I had on the view of the map. Just let me put in the necessary instructions, if I can hold on to my sanity long enough. Now. "
The starfield expanded with a rush so that thousands of stars pushed off every edge, giving the watchers so real a sensation of moving toward the screen that all three automatically leaned backward as though in response to a forward rush.
The old view returned, not quite as dark as it had been on the map, but with the half-dozen stars shown as they had been in the original view. And there, close to the center, was another star, shining far more brightly than the others.
"There it is," said Pelorat, in an awed whisper.
"It may be. I'll have the computer take its spectrum and analyze it." There was a moderately long pause, then Trevize said, "Spectral class, G-4, which makes it a trifle dimmer and smaller than Terminus's sun, but rather brighter than Comporellon's sun. And no G-class star should be omitted from the computer's Galactic map. Since this one is, that is a strong indication that it may be the sun about which the Forbidden World revolves."
Bliss said, "Is there any chance of its turning out that there is no habitable planet revolving about this star after all?"
"There's a chance, I suppose. In that case, we'll try to find the other two Forbidden Worlds."
Bliss persevered. "And if the other two are false alarms, too?"
"Then we'll try something else."
"Like what?" "I wish I knew," said Trevize grimly.
Part Three Aurora
Chapter 8 Forbidden World
31.
"GOLAN," said Pelorat. "Does it bother you if I watch?"
"Not at all, Janov," said Trevize.
"If I ask questions?"
"Go ahead."
Pelorat said, "What are you doing?"
Trevize took his eyes off the viewscreen. "I've got to measure the distance of each star that seems to be near the Forbidden World on the screen, so that I can determine how near they really are. Their gravitational fields must be known and for that I need mass and distance. Without that knowledge, one can't be sure of a clean Jump."