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SEP 1 1971, SEP 3 1971; Clock Strapped In For Flight; Midshipman Melvin Barrentine of U.S. Naval Academy adjusts the seat belt around an atomic clock from the U.S. Naval Observatory, Washington, D. C., for a flight aboard a United Air Lines jet from Denver to Washington. The clock, which uses radiation emitted by a cesium atom to provide superaccurate time, had been taken around the world to synchronize other clocks at military bases. This highly accurate clock and others like it are brought to Colorado frequently to check with the national time ; standard at National Bureau of Standards in Boulder.; (Photo By David Cupp/The Denver Post via Getty Images)