Scientists discovered some time ago that atoms and molecules have 'resonances' and that each chemical element and compound absorbs and emits 'electromagnetic radiation' within its own characteristic 'frequencies'. This we are told is highly accurate even over 'Time and Space'.
The development of radar and the subsequent experimentation with high frequency radio communications during the 1930s and 1940s created a vast amount of knowledge regarding 'electromagnetic waves', also known as 'microwaves', which interact with the atoms. The development of atomic clocks focused firstly on microwave resonances in the chemical Ammonia and its molecules. In 1957, 'NIST', the 'National Institute of Standards and Technology', completed a series of tests using a 'Cesium Atomic Beam' device, followed by a second programme of experiments by NIST in order to have something for comparision when working at the atomic level. By 1960, as the outcome of the programmes, 'Cesium Time Standards' were incorporated as the official time keeping system at NIST.
The 'Natural frequency' recognized currently is the measurement of time, used by all scientists, defines the period of 'one second' as exactly '9,192,631,770 Oscillations' or '9,192,631,770 Cycles of the Cesium Atom's Resonant Frequency'. From the 'Macrocosm', or 'Planetary Alignment', to the 'Microcosm', or 'Atomic Frequency', the cesium now maintains an accuracy with a degree of error to about 'one-millionth of a second per year'.
Much of modern life has come to depend on such precise measurements of time. The day is long past when we could get by with a timepiece accurate to the nearest quarter hour. Transportation, financial markets, communication, manufacturing, electric power and many other technologies have become dependent on super-accurate clocks. Scientific research and the demands of modern technology continue to drive our search for ever more accuracy. The next generation of Cesium Time Standards is presently under development at NIST's 'Boulder Laboratory' and other laboratories around the world.