Notable milestones in precision timing
| Year | Achievement |
|---|---|
| 1949 | World’s first atomic clock is built by NIST (then the NBS)—it used ammonia absorption |
| 1951 | Cesium atomic beam device is completed at NBS with Office of Naval Research funding |
| 1952 | First atomic clock using cesium atoms for frequency is built by NIST, named NBS-1, although not accurate enough to be a time standard |
| 1955 | • Louis Essen at the UK’s National Physical Laboratory built the first atomic clock accurate enough to be a time standard •ONR contracts the National Company, Malden, Massachusetts, to produce a military atomic clock based on that of Jerrold R. Zacharias of MIT, with engineering characteristics set forward by the Navy Bureaus of Ships and Aeronautics and the Naval Research Laboratory |
| 1956 | The National Company produces Atomichron, the first commercial cesium atomic beam clock |
| 1958 | Commercial cesium clocks become available, costing $20,000 each, developed by The National Company |
| 1959 | NBS-1 becomes NIST’s primary frequency standard |
| 1960 | First atomic hydrogen maser (or frequency standard) was built at Harvard. NBS-2 is developed at NIST’s laboratories in Boulder, Colorado |
| 1963 | NBS-3 is developed and offers improved accuracy and stability |
| 1964 | Cesium atomic beam tubes are developed by Varian Associates for Hewlett Packard |
| 1967 | The 13th General Conference on Weights and Measures defines the second as the vibrations of the cesium atom, which replaced astronomical timekeeping |
| 1968 | NBS-4 is developed as the world’s most stable clock, used into the 1990s as part of the NIST time system |
| 1972 | NBS-5 is developed and serves as the new primary standard |
| 1975 | NBS-6 is developed; it is accurate to within 1 second in 300,000 years |
| 1993 | NIST-7 is developed and is 20 times more accurate than NBS-6 |
| 1999 | NIST-F1 begins operation—it is accurate to 1 second in 20 million years |
| 2014 | NIST launched NIST-F2, an atomic clock accurate to 1 second in 300 million years |
| Year | Achievement |
|---|---|
| 1949 | World’s first atomic clock is built by |
| 1951 | Cesium atomic beam device is completed at |
| 1952 | First atomic clock using cesium atoms for frequency is built by NIST, named NBS-1, although not accurate enough to be a time standard |
| 1955 | • Louis Essen at the UK’s National Physical Laboratory built the first atomic clock accurate enough to be a time standard •ONR contracts the National Company, Malden, Massachusetts, to produce a military atomic clock based on that of Jerrold R. Zacharias of MIT, with engineering characteristics set forward by the Navy Bureaus of Ships and Aeronautics and the Naval Research Laboratory |
| 1956 | The National Company produces Atomichron, the first commercial cesium atomic beam clock |
| 1958 | Commercial cesium clocks become available, costing $20,000 each, developed by The National Company |
| 1959 | NBS-1 becomes NIST’s primary frequency standard |
| 1960 | First atomic hydrogen maser (or frequency standard) was built at Harvard. NBS-2 is developed at NIST’s laboratories in Boulder, Colorado |
| 1963 | NBS-3 is developed and offers improved accuracy and stability |
| 1964 | Cesium atomic beam tubes are developed by Varian Associates for Hewlett Packard |
| 1967 | The 13th General Conference on Weights and Measures defines the second as the vibrations of the cesium atom, which replaced astronomical timekeeping |
| 1968 | NBS-4 is developed as the world’s most stable clock, used into the 1990s as part of the |
| 1972 | NBS-5 is developed and serves as the new primary standard |
| 1975 | NBS-6 is developed; it is accurate to within 1 second in 300,000 years |
| 1993 | NIST-7 is developed and is 20 times more accurate than NBS-6 |
| 1999 | NIST-F1 begins operation—it is accurate to 1 second in 20 million years |
| 2014 |
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