Number 165 (Story #4), February 17, 1994 by Phillip F. Schewe and Ben Stein|
THE GLOBAL POSITIONING SYSTEM (GPS) can determine latitude and longitude for any spot on Earth with an uncertainty of only 10 meters; the distance between two points hundreds of km apart can be determined to within 1 cm. GPS does this by relaying timing signals from a network of satellites, each carrying an atomic clock, to a receiver (sometimes a hand-held device) which calculates the position from the relative time delay of the signals. In an essay in the January 1994 Physics Today, MIT physicist Daniel Kleppner uses GPS as a case study for demonstrating why science is a good investment. He recounts the slow, painstaking march of scientific and technological advances---e.g., hydrogen-maser clocks, microelectronics, high- speed data processing---that culminated in GPS.