He took the loose end of the tape and reeling off a few feet hooked the end onto the empty spindle. “Watch closely,” he said. “I’m going to show you the number.” He started to wind up the tape on the empty spindle. Tubby stood close beside the strip of tape stretching the space between the two spindles; it passed directly under his face. “Watch closely,” said the professor again. “There comes the first of it.” Tubby saw a row of little digits start on the tape. The first three were 154. Then after the comma began a string of ciphers; after each three ciphers was another comma. The moving tape carried this endless row of little ciphers swiftly under Tubby’s nose. He stared at them fascinated. Faster and faster they flew by as the roll of tape wound up on the spindle the professor was turning. For half an hour he turned briskly. Then the row of ciphers stopped just as the other end of the tape fluttered off the unwinding spindle. The professor leaned against the wall, breathing hard. “That—was—the—number,” he gasped. Tubby blinked. “What—what number was it?” he asked finally. The professor recovered his breath and sat down again in his chair wearily. “It was one hundred and fifty-four zin-tillions,” he answered. “The largest number that has ever been written down. Wrote it down this afternoon.” “Yes,” said Tubby. “It _was_ a big number.” The professor pulled at his side-whiskers thoughtfully. “We must get on,” he said. “Now you understand how far the stars are away. And how fast light travels. That brings us to my Light Machine.” Tubby sat up with interest. “To the Light Machine. Yes, go on.” “As you can see,” the professor continued. “I know all about Light—I am its master. No one in the world knows as much about Light as I do. And only one man in the world thinks he does.” The professor’s eyes gleamed vindictively. “Ah, how I hate him, that man!” “Who?” Tubby asked with interest. “What is his name?” “His name is Einstein,” answered the professor. “I hate him—I loathe him—I despise him.” “Oh,” said Tubby. “I’m sorry.” “But he cannot harm _me_. I’m too clever for him. And _you_ will help me. We still have time—he cannot prove anything yet.” “No—yes,” said Tubby. The professor stood up. “Let us get on with my invention. _Then_ you’ll see what a wonderful man I am. I will be brief.” Tubby joined him beside the telescope in the center of the room. “What you must understand first,” said the professor, “is _my_ theory of Light.” Tubby waited. “No light is ever destroyed,” the professor continued. “It passes beyond our vision, that is all. But it always exists somewhere, in the outer realms of Space.” “That’s where it goes when it goes out,” Tubby put in. “Ain’t I right?” “Yes,” said the professor. “That’s where it goes—out into the realms of Space.