Edri laughed. "One at a time, please. And such simple little questions, too! It took centuries to evolve a technology capable of answering them, and you want me to explain it all in a few words. Well, a few words is all I know about it. I'm a drinker by profession, not a scientist. Anyway, a really functional ship, whether it plies water, air, or space, must get its motive power by reacting against the element it travels in. And so, right now, the big atomic-powered generators in the stern are producing fifth-order rays which react against the fabric of space itself. And space, not wishing to be torn apart, obligingly thrusts us onward. Very simple, I believe, once you know the trick." Trehearne grunted. "As to limiting speeds," said Edri, "the Vardda scientists used to believe in them too--until they got to playing around with cosmotrons. One day a particle they were experimenting with upset them horribly by going much faster than light, and that's how they discovered the fifth-order rays. They found out, as your scientists will find, that the theoretical absolutes you set up from limited knowledge will prove illusory when your knowledge expands. I could explain all that to you if I knew continuum-mechanics better than I do!" "I couldn't understand it anyway," said Trehearne, "so it's just as well." They had reached the forward end of the corridor. There was a narrow circular stairway leading up. Edri stood back and motioned Trehearne to climb it. He did, fighting down another attack of the shakes on the way--you couldn't take it all in, you couldn't get used to it all at once, the strangeness, the utter separation from everything that had been, the headlong plunge into alien horizons, for a long time you were going to get panicky when you thought about it. He emerged into a round observation dome of immensely heavy quartz. He didn't know what he had expected to see, but he was disappointed. There was nothing to be seen at all but darkness, streaked with creeping lines of light. "Those are stars," said Edri, who had come up behind him. "Or rather, the radiation patterns of stars. At our present velocity we're overtaking the lines of luminous energy they have left behind them. Star-tracks, we call them." He closed a switch, and the thick quartzite became suffused with a pallid, milky glow. Edri consulted a master dial, and made adjustments. "Watch the dome," he said. "It's triple thickness, of a special molecular composition, each plane laid at a different oblique angle. I've switched high-frequency electronic current into hair-line grids between the three planes and all sorts of interesting and complicated things are happening in the molecular structure of the quartzite." Trehearne watched. His heart was beating hard. "Behold," said Edri, "the light-impulses of the star-tracks are caught, stepped up, wrenched about, and finally held on the inner lens."