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An atomic clock is based on a system of atoms which may be in one of two possible energy states. A group of atoms in one state is prepared, then subjected to microwave radiation. If the radiation is of the correct frequency, a number of atoms will transition to the other energy state.
The United States Naval Observatory began the A.1 scale on 13 September 1956, using an Atomichron commercial atomic clock, followed by the NBS-A scale at the National Bureau of Standards, Boulder, Colorado on 9 October 1957. [9] The International Time Bureau (BIH) began a time scale, T m or AM, in July 1955, using both local caesium clocks and ...
Korea Research Institute of Standards and Science. Daejeon, South Korea. Caesium atomic clocks [25] Cs. National Metrology Centre. Queenstown, Singapore. Five caesium clocks, one passive hydrogen maser, two active hydrogen masers.
The first accurate atomic clock, a caesium standard based on a certain transition of the caesium-133 atom, was built by Louis Essen and Jack Parry in 1955 at NPL. [27] [28] Calibration of the caesium standard atomic clock was carried out by the use of the astronomical time scale ephemeris time (ET). [29]
A caesium atomic fountain used as part of an atomic clock. The caesium standard is a primary frequency standard in which the photon absorption by transitions between the two hyperfine ground states of caesium-133 atoms is used to control the output frequency. The first caesium clock was built by Louis Essen in 1955 at the National Physical ...
August 24 – The first accurate atomic clock, a caesium standard based on a certain transition of the caesium-133 atom, is built by Louis Essen with J. V. L. Parry at the National Physical Laboratory (United Kingdom). [20] [43] December 12 – Christopher Cockerell is granted a United Kingdom patent for his design of hovercraft.
The feasibility of measuring time using caesium as an atomic reference had been demonstrated by the US National Bureau of Standards. In 1955, he developed, [ 2 ] in collaboration with Jack Parry, the first practical atomic clock by integrating the caesium atomic standard with conventional quartz crystal oscillators to allow calibration of ...
Although less accurate than existing quartz clocks, it served to prove the concept of an atomic clock. [206] The first accurate atomic clock, a caesium standard based on a certain transition of the caesium-133 atom, was built by the English physicist Louis Essen in 1955 at the National Physical Laboratory in London. [207]