The land of the Fweep turned slowly on its axis. The orange sun set and rose again and stared down once more at the meadow where the improbable spaceship rested on its improbable stern. The sixteen Earth hours that the rotation had taken had changed nothing inside the ship, either. Grampa looked up from his pircuit and said, "If I were you, Junior, I would take a good look at the TV repairman when we get back to Earth. _If_ we get back to Earth," he amended. "You can't be Four's father. All over the Universe, gravity is the same, and if it's gravity, the polarizer will polarize it." "That's just supposition," Junior said stubbornly. "The fact is, it isn't because it doesn't. Q.E.D." "Maybe the polarizer is broken," Fred suggested. Grampa snorted. "Broken-shmoken. Nothing to break, Young Fred. Just a few coils of copper wire and they're all right. We checked. We know the power plant is working: the lights are on, the air and water recirculation systems are going, the food resynthesizer is okay. And, anyway, the polarizer could work from the storage battery if it had to." "Then it goes deeper," Junior insisted. "It goes right to the principle of polarization itself. For some reason, it doesn't work here. Why? Before we can discover the answer to that, we'll have to know more about polarization itself. How does it work, Grampa?" Grampa gave him a sarcastic grin. "Now you're curious, eh? Couldn't be bothered with Grampa's invention before. Oh, no! Too busy. Accept without question the blessings that the Good Lord provideth--" "Let's not get up on any pulpits," Fred growled. "Come on, Grampa, what's the theory behind polarization?" Grampa looked at the four faces staring at him hopefully and the jeering grin turned to a smile. "Well," he said, "at last. You know how light is polarized, eh?" The smile faded. "No, I guess you don't." * * * * * He cleared his throat professorially. "Well, now, in ordinary light the vibrations are perpendicular to the ray in all directions. When light is polarized by passing through crystals or by reflection or refraction at non-metallic surfaces, the paths of the vibrations are still perpendicular to the ray, but they're in straight lines, circles or ellipses." The faces were still blank and unillumined. "Gravity is similar to light," he pressed on. "In the absence of matter, gravity is non-polarized. Matter polarizes gravity in a circle around itself. That's how we've always known it until the invention of spaceships and later the polarizer. The polarizer polarizes gravity into a straight line. That makes the ship take off and continue accelerating until the polarizer is shut off or its angle is shifted." The faces looked at him silently. Finally Joyce could endure it no longer. "That's just nonsense! You all know it. Grampa's no genius. He's just a tinkerer. One day he happened to tinker out the polarizer. He doesn't know how it works any more than I do."