Esta é " The Long Way Home " de Fred Saberhagen.
... Then the main group will start pulling against number one, as I saw them doing a little while ago, and their ship will begin to move toward Sol. Every day they go through this they move about thirty miles closer to home. "Honey, these people are walking home and pulling their ship with them. It must be a religion with them by now, or something very near it . . ." He put an arm around Laura.
"... how long would it take them?"
"Space is big," he said in a flat voice, as if quoting something he had been required to memorize.
After a few moments he continued. "I said just moving a little faster won't help them. Let's say they've traveled thirty miles a day for two thousand years. That's — somewhere near twenty-two million miles. Almost enough to get from Mars to Earth at their nearest approach.