"Sure. Movin' things take the shortest path."
The astronomer, frankly dubious, said, "But, really! An ellipse could hardly do that because a 'shortest path'—"
"No?" said Hank. "You take a flat piece of paper. The quickest way acrost it is a straight line, ain't it?"
"Naturally."
"You take a globe of the world, though, an' things don't work the same. You want to go from, say, Los Angeles to Japan, you wouldn't follow straight across one of them lines of latitude, would you? You'd sort of hump up by way of Alaska."
A listener nodded eagerly. "That's right. You'd take the arc of a great circle. The Great Circle route."
"Well," said Hank, "same thing in the universe—which has got, near's I can figger out, another right angle in it besides the ones we know an' see."
"You mean another dimension? A fourth dimension?"
"Call it that. Anyhow, in this sort of super-globe which has four dimensions, stands to reason that the shortest distance from one point to another will be a closed figger. A sort of lopsided circle."