BEYOND DISCOVERY

THE PATH FROM RESEARCH TO HUMAN BENIFIT™

This article was adapted by Gary Taubes from an article written by MIT scientist Daniel Kleppner for Beyond Discovery: The Path from Research to Human Benefit, a project of the National Academy of Sciences. The Academy, located in Washington, D.C., is a society of distinguished scholars engaged in scientific and engineering research and dedicated to the use of science and technology for the public welfare. For over a century, it has provided independent, objective scientific advice to the nation. Our web site is accessible at http://www2.nas.edu/bsi

©1996 by the National Academy of Sciences

August 1996

bsi@nas.edu (202) 334-1575

THE GLOBAL POSITIONING SYSTEM

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 is made possible by 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 from an account by physicist Daniel Kleppner, describes how the GPS was conceived and developed. 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.

Where Is He?

It was 2:08 in the morning of June 6, 1995, when a U.S. Air Force pilot flying an F-16 fighter over Serbian-held positions in Bosnia-Herzegovina first heard “Basher 52” coming over his radio. “Basher 52” was the call signal of American pilot Captain Scott O'Grady, whose own F-16 had been shot down by Serbian forces in that area 4 days earlier. The pilot would say later that hearing O'Grady 's call signal was like hearing a voice from beyond the grave. O'Grady's F-16 had been hit by a Serbian ground-to-air missile and had exploded immediately. Although the 29-year-old pilot had managed to eject safely, his wingman had seen no parachute come out of the flaming debris.

Now O'Grady had been on the ground behind enemy lines for 4 days, surviving on grass and insects, sleeping by day under camouflage netting, and moving by night. He had finally risked radio contact with fliers, who verified his position and



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BEYOND DISCOVERY: THE PATH FROM RESEARCH TO HUMAN BENIFIT™ BEYOND DISCOVERY THE PATH FROM RESEARCH TO HUMAN BENIFIT™ This article was adapted by Gary Taubes from an article written by MIT scientist Daniel Kleppner for Beyond Discovery: The Path from Research to Human Benefit™, a project of the National Academy of Sciences. The Academy, located in Washington, D.C., is a society of distinguished scholars engaged in scientific and engineering research and dedicated to the use of science and technology for the public welfare. For over a century, it has provided independent, objective scientific advice to the nation. Our web site is accessible at http://www2.nas.edu/bsi ©1996 by the National Academy of Sciences August 1996 bsi@nas.edu (202) 334-1575 THE GLOBAL POSITIONING SYSTEM 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 is made possible by 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 from an account by physicist Daniel Kleppner, describes how the GPS was conceived and developed. 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. Where Is He? It was 2:08 in the morning of June 6, 1995, when a U.S. Air Force pilot flying an F-16 fighter over Serbian-held positions in Bosnia-Herzegovina first heard “Basher 52” coming over his radio. “Basher 52” was the call signal of American pilot Captain Scott O'Grady, whose own F-16 had been shot down by Serbian forces in that area 4 days earlier. The pilot would say later that hearing O'Grady 's call signal was like hearing a voice from beyond the grave. O'Grady's F-16 had been hit by a Serbian ground-to-air missile and had exploded immediately. Although the 29-year-old pilot had managed to eject safely, his wingman had seen no parachute come out of the flaming debris. Now O'Grady had been on the ground behind enemy lines for 4 days, surviving on grass and insects, sleeping by day under camouflage netting, and moving by night. He had finally risked radio contact with fliers, who verified his position and