"Oh, that's too bad," said Arcot, leaning back comfortably in his chair. "We're sorry you're so busy. We were thinking of going out to see what Antares, Betelguese, or Polaris looked like at close range. And, if we don't get too bored, we might run over to the giant model nebula in Andromeda, or one of the others. Tough about your being busy; you might have helped us by designing the ship and earned your board and passage. Tough." Arcot looked at Fuller sadly. Fuller's eyes narrowed. He knew Arcot was kidding, but he also knew how far Arcot would go when he was kidding--and this sounded like he meant it. Fuller said: "Look, teacher, a man named Einstein said that the velocity of light was tops over two hundred years ago, and nobody's come up with any counter evidence yet. Has the Lord instituted a new speed law?" "Oh, no," said Wade, waving his pipe in a grand gesture of importance. "Arcot just decided he didn't like that law and made a new one himself." "Now _wait_ a minute!" said Fuller. "The velocity of light is a property of space!" Arcot's bantering smile was gone. "Now you've got it, Fuller. The velocity of light, just as Einstein said, is a property of space. What happens if we change space?" Fuller blinked. "Change space? How?" Arcot pointed toward a glass of water sitting nearby. "Why do things look distorted through the water? Because the light rays are bent. Why are they bent? Because as each wave front moves from air to water, _it slows down_. The electromagnetic and gravitational fields between those atoms are strong enough to increase the curvature of the space between them. Now, what happens if we reverse that effect?" "Oh," said Fuller softly. "I get it. By changing the curvature of the space surrounding you, you could get any velocity you wanted. But what about acceleration? It would take years to reach those velocities at any acceleration a man could stand." Arcot shook his head. "Take a look at the glass of water again. What happens when the light comes _out_ of the water? It speeds up again _instantaneously_. By changing the space around a spaceship, you instantaneously change the velocity of the ship to a comparable velocity in that space. And since every particle is accelerated at the same rate, you wouldn't feel it, any more than you'd feel the acceleration due to gravity in free fall." Fuller nodded slowly. Then, suddenly, a light gleamed in his eyes. "I suppose you've figured out where you're going to get the energy to power a ship like that?" "He has," said Morey. "Uncle Arcot isn't the type to forget a little detail like that." "Okay, give," said Fuller. Arcot grinned and lit up his own pipe, joining Wade in an attempt to fill the room with impenetrable fog. "All right," Arcot began, "we needed two things: a tremendous source of power and a way to store it.