Produced by Sankar Viswanathan, Greg Weeks, and the Online Distributed Proofreading Team at http://www.pgdp.net Transcriber's Note: This etext was produced from Analog Science Fact & Fiction December 1963. Extensive research did not uncover any evidence that the U.S. copyright on this publication was renewed. THIN EDGE There are inventions of great value that one type of society can use--and that would, for another society, be most nastily deadly! BY JOHNATHAN BLAKE MAC KENZIE ILLUSTRATED BY JOHN SCHOENHERR * * * * * I "Beep!" said the radio smugly. "_Beep! Beep! Beep!_" "There's one," said the man at the pickup controls of tugship 431. He checked the numbers on the various dials of his instruments. Then he carefully marked down in his log book the facts that the radio finder was radiating its beep on such-and-such a frequency and that that frequency and that rate-of-beep indicated that the asteroid had been found and set with anchor by a Captain Jules St. Simon. The direction and distance were duly noted. That information on direction and distance had already been transmitted to the instruments of the tugship's pilot. "Jazzy-o!" said the pilot. "Got 'im." He swiveled his ship around until the nose was in line with the beep and then jammed down on the forward accelerator for a few seconds. Then he took his foot off it and waited while the ship approached the asteroid. In the darkness of space, only points of light were visible. Off to the left, the sun was a small, glaring spot of whiteness that couldn't be looked at directly. Even out here in the Belt, between the orbits of Mars and Jupiter, that massive stellar engine blasted out enough energy to make it uncomfortable to look at with the naked eye. But it could illuminate matter only; the hard vacuum of space remained dark. The pilot could have located the planets easily, without looking around. He knew where each and every one of them were. He had to. A man can navigate in space by instrument, and he can take the time to figure out where every planet ought to be. But if he does, he won't really be able to navigate in the Asteroid Belt. In the Nineteenth Century, Mark Twain pointed out that a steamboat pilot who navigated a ship up and down the Mississippi had to be able to identify every landmark and every changing sandbar along the river before he would be allowed to take charge of the wheel. He not only had to memorize the whole river, but be able to predict the changes in its course and the variations in its eddies. He had to be able to know exactly where he was at every moment, even in the blackest of moonless nights, simply by glancing around him.