Murray Leinster Read Free

sunlight was close enough, now, for him to reach, but he did not put out his hands. He licked his lips.
    ‘I said the theory’s all right, Limpy! How’d Fellenden do it?’ Limpy said heavily:
    ‘That’s where I’m mixed up. You’ on a train, he says. It’s movin’ through time. Before you can go back you got to slow up. But the train won’t slow. You see a station slidin’ by -Wednesday maybe - an’ you wanna go back. You got on the wrong train Tuesday. Desperate, you start runnin’ for the back of the train. At first you don’t see no difference. But you keep runnin’. Presendy the station ain’t goin’ past you quite so fast. Then you run harder. You hold it even, runnin’ with all you got. An’ all of a sudden you get to the back of the train. The door’s open. You jump down to the tracks, an’ don’t get hurt because you’re runnin’ back as fast as the train runs ahead. An’ then you go high-tailin’ it back along the railroad track to where you got on the wrong train. An’ the right one’s there—’
    ‘It hasn’t left?’ asked Rodney, cynically.
    ‘No,’ said Limpy flatly. ‘I dunno why, but Feilenden said no.’
    Rodney’s pose of cynicism dropped away. Limpy could not possibly have worked out a theory like this. Feilenden must have worked it out, and phrased it carefully in such homely terms for Limpy’s untutored understanding. It was pure logic on a familiar foundation of speculation. You did something, and it had evil consequences. You went back in time, before the event which had the evil consequences. You avoided that event. Then, necessarily, you took a branching time track. You went into another of the innumerable futures which at that point in time were possible for you. The evil consequences of the event you avoided could not be in those other time tracks. And you would cease to exist in the first time track at the point where you turned about and went back.
    Granted the fact of time travel in this way, which was the only possible way in which time travel could take place, it was sound! Limpy could not have imagined it. Someone of the caliber of Feilenden must have devised it. And Feilenden had made that indeterminacy field, which nobody else yet surely understood—
    Rodney licked his lips. It was the answer, if he could get it -and he had one of the four best brains in the country. But it was enraging that he’d had to be instructed by a common criminal like Limpy!
    ‘Tve got it,’ said Rodney curtly. ‘1 see the idea.’
    There was a clanking of the outer doors of the death-cell house. A guard came in. He gave the two prisoners their food. Rodney regarded him with the burning eyes of hatred, in silence. The guard went out.
    Rodney heard the sounds of Limpy, feeding. Himself, he could not eat. He had three days to live - if he did not solve the problem of time travel as Feilenden had solved it. He could believe in the theory, now. If he did not believe, he would go mad! But besides that, there was evidence that it could be done! Feilenden had done it!
    He paced up and down his cell. Time travel. Fellenden had vanished from a death cell in Joliet by traveling back to the time before the killing of his wife. Then he had not killed her. There had been at least two possible futures for him at that point; in one of which he killed her, and in one of which he did not. Rodney lived and moved in the future in which the murder had taken place. In the other - which to Fellenden was now the actual future - Fellenden had not committed a murder, and was doubdess a respected citizen and a prominent physicist instead of an escaped murderer. That other time track was like but not the same as this. It was possible to get into that other time track. Fellenden had done it! Galileo heard that a telescope had been invented, and took thought on the principles of optics, and made a telescope in some ways superior to the original. He, Rodney, now knew that time travel was possible, and he