"The jump band is founded on the basic of the Moebius strip," one student E was saying heatedly. "This little gadget sends out a field in the shape of such a strip, a band with a half twist before rejoined. Its width is as variable as we need it, up to a light-year."

"Only it hasn't any width at all," the other student argued. "That's the whole point. The Moebius strip has only one edge, so it can't have width. We enter that edge, go through a line that doesn't exist, and come out a light-year away, without taking any longer than the time to pass a point."

"But that's what happens, not how," the other shouted angrily. "Everybody knows what happens. Tell me how and maybe I'll listen."

Tom caught his flight engineer's eye and signaled with his head that it might be a good idea to get rid of the students. Any other time it would be all right, a part of their stand-by job, but they'd got word last night to have the ship in readiness from six o'clock on. They might have to wait all day, but then again, some E might get an idea and want to go shooting out to Eden right off.

Frank caught the signal, grinned, and began to herd the two students toward the door. They were in such heated argument now, accusing one another of parrot repetition instead of thinking for himself, that they didn't realize that they were being nudged out of the ship, down its ramp, and out on the field.

"Don't think it hasn't been educational, and all," Frank murmured to them as he got them off the ramp. "You get the how of it figured out, you let me know."

The two looked at him as if he might be an interesting phenomenon, decided he wasn't, and wandered away, back toward the school dormitories, still arguing.

"Sometimes I think a quiet milk run out to Saturn would have its brighter side," Frank muttered to Tom when he came back inside the ship. Tom grinned at him in wordless understanding.

There was no tension between them. They had worked together so long that they had got over all the attraction-repulsion conflicts which operate far beneath the surface mind to cause likes and dislikes. Now they accepted one another in the way a man accepts his own hands—proud of them when they do something with extra skill, making allowances when they fumble; but never considering doing without them.

"Wonder who the E will be this time?" Frank asked, without too much concern. It didn't really matter. An E was an E, for better or for worse.