"In what way?" asked Paul. "We can't set the spotter ship. Not enough time. You'll have to aim the ship visually. It'll make the dispersion-factor somewhat large." "I don't mind." "Good thing you don't," came the glum reply. Both of them knew that the job of aiming a stellar ship was accepted by the public as one of the things that had to be done; few of them knew what went into the job. All stars are but pinpoints in the sky, there is no quick way to tell a close-by star from a distant star by visual inspection. To the untrained, even the solar planets blend with the interstellar reaches. Only the trained eye can tell planets from the stars by the lack of twinkle. The true distances between the stars is too vast to be comprehended. Men speak of light years. Yet even the learned must indulge in quite a bit of cerebration to understand the length of a year, the velocity of light presents figures too extreme for comprehension. Light travels at 328 yards per millionth of a second, 328 yards can be grasped, as a distance of three-football fields, but a millionth of a second cannot be grasped readily; 186,000 miles per second offers only one factor capable of being understood. One can count "Ten-Hundred-One" and realize that a second has passed. But the mind is incapable of grasping the fact that during that time of counting, a beam of light traverses 186,000 miles. Proxima Centauri is four light years away. Using the longest base that the solar system provided, the beginning and the end of the aimed course was like trying to hit a match head at ten thousand yards with a snub-barrelled pistol. A misalignment too minute for the eye to see meant a probable target dispersion as broad as the outer orbits of the solar system. Aim a ship at a target four light years away across aiming points a couple of light hours apart. At a velocity within a couple of percent of precise, multiplied by a number of seconds mounting into five or six figures, you can establish the volume which will contain the spacecraft on its arrival. A volume of probabilities; far, far from the layman's idea of a precise science. Heading as he was for Proxima Centauri, that tiny star would be the focus of his aim. But Proxima is a tiny star, one of a trinary, and the other two magnificent stars overwhelmed the feeble light of Proxima. So the system of Alpha Centauri would lie on the cross-hairs of Paul's telescope. And the cross-hairs of the telescope would be displaced from the axis of drive by a small angle. It was this angle that required the use of the electronic calculator.