Then he said, "Yes, sir."

"What was it that awakened you?"

Red saw no harm in it. He said, "I don't know, Dad. It sounded like thunder, sort of, and like a collision, sort of."

"Could you tell where it came from?"

"It _sounded_ like it was out by the hill." That was truthful, and useful as well, since the direction was almost opposite that in which the barn lay.

The Industrialist looked at his guest. "I suppose it would do no harm to walk toward the hill."

The Astronomer said, "I am ready."

Red watched them walk away and when he turned he saw Slim peering cautiously out from among the briars of a hedge.

Red waved at him. "Come on."

Slim stepped out and approached. "Did they say anything about the meat?"

"No. I guess they don't know about that. They went down to the hill."

"What for?"

"Search me. They kept asking about the noise I heard. Listen, did the animals eat the meat?"

"Well," said Slim, cautiously, "they were sort of _looking_ at it and smelling it or something."

"Okay," Red said, "I guess they'll eat it. Holy Smokes, they've got to eat _something_. Let's walk along toward the hill and see what Dad and your father are going to do."

"What about the animals?"

"They'll be all right. A fellow can't spend all his time on them. Did you give them water?"

"Sure. They drank that."

"See. Come on. We'll look at them after lunch. I tell you what. We'll bring them fruit. Anything'll eat fruit."

Together they trotted up the rise, Red, as usual, in the lead.

V

The Astronomer said, "You think the noise was their ship landing?"

"Don't you think it could be?"

"If it were, they may all be dead."

"Perhaps not." The Industrialist frowned.

"If they have landed, and are still alive, where are they?"

"Think about that for a while." He was still frowning.

The Astronomer said, "I don't understand you."

"They may not be friendly."

"Oh, no. I've spoken with them. They've--"

"You've spoken with them. Call that reconnaissance. What would their next step be? Invasion?"

"But they only have one ship, sir."

"You know that only because they say so. They might have a fleet."

"I've told you about their size. They--"

"Their size would not matter, if they have handweapons that may well be superior to our artillery."

"That is not what I meant."

"I had this partly in mind from the first." The Industrialist went on.

"It is for that reason I agreed to see them after I received your letter. Not to agree to an unsettling and impossible trade, but to judge their real purposes. I did not count on their evading the meeting."

He sighed. "I suppose it isn't our fault. You are right in one thing, at any rate. The world has been at peace too long. We are losing a healthy sense of suspicion."

The Astronomer's mild voice rose to an unusual pitch and he said, "I _will_ speak. I tell you that there is no reason to suppose they can possibly be hostile. They are small, yes, but that is only important because it is a reflection of the fact that their native worlds are small. Our world has what is for them a normal gravity, but because of our much higher gravitational potential, our atmosphere is too dense to support them comfortably over sustained periods. For a similar reason the use of the world as a base for interstellar travel, except for trade in certain items, is uneconomical. And there are important differences in chemistry of life due to the basic differences in soils. They couldn't eat our food or we theirs."

"Surely all this can be overcome. They can bring their own food, build domed stations of lowered air pressure, devise specially designed ships."

"They can. And how glibly you can describe feats that are easy to a race in its youth. It is simply that they don't have to do any of that. There are millions of worlds suitable for them in the Galaxy. They don't need this one which isn't."

"How do you know? All this is their information again."

"This I was able to check independently. I am an astronomer, after all."

"That is true. Let me hear what you have to say then, while we walk."

"Then, sir, consider that for a long time our astronomers have believed that two general cla.s.ses of planetary bodies existed. First, the planets which formed at distances far enough from their stellar nucleus to become cool enough to capture hydrogen. These would be large planets rich in hydrogen, ammonia and methane. We have examples of these in the giant outer planets. The second cla.s.s would include those planets formed so near the stellar center that the high temperature would make it impossible to capture much hydrogen. These would be smaller planets, comparatively poorer in hydrogen and richer in oxygen. We know that type very well since we live on one. Ours is the only solar system we know in detail, however, and it has been reasonable for us to a.s.sume that these were the _only_ two planetary cla.s.ses."

"I take it then that there is another."

"Yes. There is a super-dense cla.s.s, still smaller, poorer in hydrogen, than the inner planets of the solar system. The ratio of occurrence of hydrogen-ammonia planets and these super-dense water-oxygen worlds of theirs over the entire Galaxy--and remember that they have actually conducted a survey of significant sample volumes of the Galaxy which we, without interstellar travel, cannot do--is about 3 to 1. This leaves them seven million super-dense worlds for exploration and colonization."

The Industrialist looked at the blue sky and the green-covered trees among which they were making their way. He said, "And worlds like ours?"

The Astronomer said, softly, "Ours is the first solar system they have found which contains them. Apparently the development of our solar system was unique and did not follow the ordinary rules."