History of atomic clocks
The first thoughts of an atomic clock
In 1930 a physics professor named Isidor Rabi does work on a technique called atomic beam magnetic resonance. 15 years later he has an idea on how that technique could be used to build a very accurate clock. Four years later the first atomic clocks based on the vibrations of ammonia molecules were built.Atomic clocks become more accurate
In 1952 the first cesium atomic clocks were built. The first clock was called NBS-1 and it became the calibration source for all other clocks. Six years after that the first commercial cesium atomic clocks were made. These atomic clocks could be bought for only $20,000 each. In 1960 the atomic clock NBS-2 is built. That clock is able to run for longer periods of time. In 1963 NBS-3 was built and in 1968 NBS-4 was built. Both of those atomic clocks improves the accuracy at which we could measure a second.Atomic clocks with even greater accuracy
In 1972 NBS-5 was built and in 1975 the atomic clock NBS-6 was built. NBS-6 becomes the most accurate atomic clock built. It neither gains nor loses a second in 300,000 years. By 1991 NIST-F1 is built. This atomic clock is still used today and is accurate to 1 second every 20 million years.Back to atomic clocks
Back to main clocks page at Clock Types