Cesium Second and Atomic Clocks

Throughout his career, Andrew Kortyna has worked at various educational institutions and laboratories. Andrew Kortyna is also an accomplished researcher, having written and published numerous papers on the properties of cesium atoms. His research in this field helped develop and build better and more accurate atomic clocks.

The United States Naval Observatory (USNO) and England’s National Physical Laboratory (NPL) measured cesium transition frequency in relation to the standard second in 1958. By then, Louis Essen of NPL had already built a reliable atomic clock based on cesium. USNO’s William Markowitz made a moon-position camera that could give access to standard time.

In 1967, the International Committee of Weights and Measures adopted a new definition of the second, based on the measurements by USNO and NPL. According to the new standard, the second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom.

Cesium-133 atoms have to be at absolute zero temperature to achieve the defined frequency. However, that is impossible in real-world applications, and even cesium atomic clocks need corrections. Nowadays, the most accurate atomic clocks lose one second every 1.4 million years.