human
Well, he said,
gpt
No? How can you be sure? Steffens grunted.
human
A space-borne race was roaming this part of the Galaxy while men were still pitching spears at each other, _that_ long ago. And this planet is only a parsec from Varius II, a civilization as old as Earth's. Did whoever built these get to Varius? Or did they get to Earth? How can you know?
gpt
And most important, where are they now? A race with several thousand years....
human
Fifteen thousand, Ball said. When Steffens looked up, he added:
gpt
That's what the geology boys say. Fifteen thousand, at the least.
human
But why buildings? Why did they have to build in stone, to last? There's something wrong with that. They shouldn't have had a need to build, unless they were castaways. And castaways would have left _something_ behind. The only reason they would need a camp would be--
gpt
If the ship left and some of them stayed.
human
But then the ship must have come back. Where did it go? He ceased kicking at the sand and looked up into the blue-black midday sky.
gpt
We'll never know.
human
How about the other planets?
gpt
The report was negative. Inner too hot, outer too heavy and cold. The third planet is the only one with a decent temperature range, but _it_ has a CO_{2} atmosphere.
human
How about moons?
gpt
We could try them and find out.