Foundation and Earth

Now the central streak extended beyond the edges of the planet very distinctly and did so in a narrow loop on either side. There was no question of illusion; its nature was apparent. It was a ring of matter, looping about the planet, and hidden on the far side.

"That's enough to give you the idea, I think," said Trevize. "If we were to move over the planet, you would see the ring in its circular form, concentric about the planet, touching it nowhere. You'll probably see that it's not one ring either but several concentric rings."

"I wouldn't have thought it possible," said Pelorat blankly. "What keeps it in space?"

"The same thing that keeps a satellite in space," said Trevize. "The rings consist of tiny particles, every one of which is orbiting the planet. The rings are so close to the planet that tidal effects prevent it from coalescing into a single body."

Pelorat shook his head. "It's horrifying when I think of it, old man. How is it possible that I can have spent my whole life as a scholar and yet know so little about astronomy?"

"And I know nothing at all about the myths of humanity. No one can encompass all of knowledge. The point is that these planetary rings aren't unusual. Almost every single gas giant has them, even if it's only a thin curve of dust. As it happens, the sun of Terminus has no true gas giant in its planetary family, so unless a Terminian is a space traveler, or has taken University instruction in astronomy, he's likely to know nothing about planetary rings. What is unusual is a ring that is sufficiently broad to be bright and noticeable, like that one. It's beautiful. It must be a couple of hundred kilometers wide, at least."

At this point, Pelorat snapped his fingers. "That's what it meant."

Bliss looked startled. "What is it, Pel?"

Pelorat said, "I came across a scrap of poetry once, very ancient, and in an archaic version of Galactic that was hard to make out but that was good evidence of great age. Though I shouldn't complain of the archaism, old chap. My work has made me an expert on various varieties of Old Galactic, which is quite gratifying even if it is of no use to me whatever outside my work. What was I talking about?"

Bliss said, "An old scrap of poetry, Pel dear."

"Thank you, Bliss," he said. And to Trevize, "She keeps close track of what I say in order to pull me back whenever I get off-course, which is most of the time."

"It's part of your charm, Pel," said Bliss, smiling.

"Anyway, this scrap of poetry purported to describe the planetary system of which Earth was part. Why it should do so, I don't know, for the poem as a whole does not survive; at least, I was never able to locate it. Only this one portion survived, perhaps because of its astronomical content. In any case, it spoke of the brilliant triple ring of the sixth planet 'both brade and large, sae the woruld shronk in comparisoun.' I can still quote it, you see. I didn't understand what a planet's ring could be. I remember thinking of three circles on one side of the planet, all in a row. It seemed so nonsensical, I didn't bother to include it in my library. I'm sorry now I didn't inquire." He shook his head. "Being a mythologist in today's Galaxy is so solitary a job, one forgets the good of inquiring."

Trevize said consolingly, "You were probably right to ignore it, Janov. It's a mistake to take poetic chatter literally."

"But that's what was meant," said Pelorat, pointing at the screen. "That's what the poem was speaking of. Three wide rings, concentric, wider than the planet itself."

Trevize said, "I never heard of such a thing. I don't think rings can be that wide. Compared to the planet they circle, they are always very narrow."

Pelorat said, "We never heard of a habitable planet with a giant satellite, either. Or one with a radioactive crust. This is uniqueness number three. If we find a radioactive planet that might be otherwise habitable, with a giant satellite, and with another planet in the system that has a huge ring, there would be no doubt at all that we had encountered Earth."

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.