Trevize smiled. "I agree, Janov. If we find all three, we will certainly have found Earth."
"If!" said Bliss, with a sigh.
30.
THEY WERE beyond the main worlds of the planetary system, plunging outward between the positions of the two outermost planets so that there was now no significant mass within 1.5 billion kilometers. Ahead lay only the vast cometary cloud which, gravitationally, was insignificant.
The Far Star had accelerated to a speed of 0.1 c, one tenth the speed of light. Trevize knew well that, in theory, the ship could be accelerated to nearly the speed of light, but he also knew that, in practice, 0.1 c was the reasonable limit.
At that speed, any object with appreciable mass could be avoided, but there was no way of dodging the innumerable dust particles in space, and, to a far greater extent even, individual atoms and molecules. At very fast speeds, even such small objects could do damage, scouring and scraping the ship's hull. At speeds near the speed of light, each atom smashing into the hull had the properties of a cosmic ray particle. Under that penetrating cosmic radiation, anyone on board ship would not long survive.
The distant stars showed no perceptible motion in the viewscreen, and even though the ship was moving at thirty thousand kilometers per second, there was every appearance of its standing still.
The computer scanned space to great distances for any oncoming object of small but significant size that might be on a collision course, and the ship veered gently to avoid it, in the extremely unlikely case that that would be necessary. Between the small size of any possible oncoming object, the speed with which it was passed, and the lack of inertial effect as the result of the course change, there was no way of telling whether anything ever took place in the nature of what might be termed a "close call."
Trevize, therefore, did not worry about such things, or even give it the most casual thought. He kept his full attention on the three sets of co-ordinates he had been given by Deniador, and, particularly, on the set which indicated the object closest to themselves.
"Is there something wrong with the figures?" asked Pelorat anxiously.
"I can't tell yet," said Trevize. "Co-ordinates in themselves aren't useful, unless you know the zero point and the conventions used in setting them up-the direction in which to mark off the distance, so to speak, what the equivalent of a prime meridian is, and so on."
"How do you find out such things?" said Pelorat blankly.
"I obtained the co-ordinates of Terminus and a few other known points, relative to Comporellon. If I put them into the computer, it will calculate what the conventions must be for such co-ordinates if Terminus and the other points are to be correctly located. I'm only trying to organize things in my mind so that I can properly program the computer for this. Once the conventions are determined, the figures we have for the Forbidden Worlds might possibly have meaning."
"Only possibly?" said Bliss.
"Only possibly, I'm afraid," said Trevize. "These are old figures after all-presumably Comporellian, but not definitely. What if they are based on other conventions?"
"In that case?"
"In that case, we have only meaningless figures. But-we just have to find out."
His hands flickered over the softly glowing keys of the computer, feeding it the necessary information. He then placed his hands on the handmarks on the desk. He waited while the computer worked out the conventions of the known co-ordinates, paused a moment, then interpreted the co-ordinates of the nearest Forbidden World by the same conventions, and finally located those co-ordinates on the Galactic map in its memory.
A starfield appeared on the screen and moved rapidly as it adjusted itself. When it reached stasis, it expanded with stars bleeding off the edges in all directions until they were almost all gone. At no point could the eye follow the rapid change; it was all a speckled blur. Until finally, a space one tenth of a parsec on each side (according to the index figures below the screen) " all that remained. There was no further change, and only half a dozen dial sparks relieved the darkness of the screen.
"Which one is the Forbidden World?" asked Pelorat softly.
"None of them," said Trevize. "Four of them are red dwarfs, one a near-red dwarf, and the last a white dwarf. None of them can possibly have a habitable world in orbit about them."
"How do you know they're red dwarfs just by looking at them?"
Trevize said, "We're not looking at real stars; we're looking at a section of the Galactic map stored in the computer's memory. Each one is labeled. You can't see it and ordinarily I couldn't see it either, but as long as my hands are making contact, as they are, I am aware of a considerable amount of data on any star on which my eyes concentrate."
Pelorat said in a woebegone tone, "Then the co-ordinates are useless."
Trevize looked up at him, "No, Janov. I'm not finished. There's still the matter of time. The co-ordinates for the Forbidden World are those of twenty thousand years ago. In that time, both it and Comporellon have been revolving about the Galactic Center, and they may well be revolving at different speeds and in orbits of different inclinations and eccentricities. With time, therefore, the two worlds may be drifting closer together or farther apart and, in twenty thousand years, the Forbidden World may have drifted anywhere from one-half to five parsecs off the mark. It certainly wouldn't be included in that tenth-parsec square."
"What do we do, then?"
"We have the computer move the Galaxy twenty thousand years back in time relative to Comporellon."