|
|
|
 |
 |
Introduction |
Where am I? The question seems simple; the answer, historically, has proved not to be. For centuries, navigators and explorers have searched the heavens for a system that would enable them to locate their position on the globe with the accuracy necessary to avoid tragedy and to reach their intended destinations. On June 26, 1993, however, the answer became as simple as the question. On that date, the U.S. Air Force launched the 24th Navstar satellite into orbit, completing a network of 24 satellites known as the Global Positioning System, or GPS. With a GPS receiver that costs less than a few hundred dollars you can instantly learn your location on the planet--your latitude, longitude, and even altitude--to within a few hundred feet.
This incredible new technology was made possible by a combination of scientific and engineering advances, particularly development of the world's most accurate timepieces: atomic clocks that are precise to within a billionth of a second. The clocks were created by physicists seeking answers to questions about the nature of the universe, with no conception that their technology would some day lead to a global system of navigation. Today, GPS is saving lives, helping society in countless other ways, and generating 100,000 jobs in a multi-billion-dollar industry. The following article, adapted in part from an account by physicist Daniel Kleppner, describes how basic research into the nature of time and ways to measure time accurately contributed to development of GPS. It provides a dramatic example of how science works and how basic research leads to technologies that were virtually unimaginable at the time the research was done. |
|
|
|
|
|
|
