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Louis Essen (right) and Jack Parry (left) standing next to the world's first caesium-133 atomic clock in 1955, at the National Physical Laboratory in west London.. The Scottish physicist James Clerk Maxwell proposed measuring time with the vibrations of light waves in his 1873 Treatise on Electricity and Magnetism: 'A more universal unit of time might be found by taking the periodic time of ...
Radio clock. A modern LF radio-controlled clock. A radio clock or radio-controlled clock (RCC), and often colloquially (and incorrectly [1]) referred to as an "atomic clock", is a type of quartz clock or watch that is automatically synchronized to a time code transmitted by a radio transmitter connected to a time standard such as an atomic clock.
International Atomic Time. International Atomic Time (abbreviated TAI, from its French name temps atomique international[1]) is a high-precision atomic coordinate time standard based on the notional passage of proper time on Earth's geoid. [2] TAI is a weighted average of the time kept by over 450 atomic clocks in over 80 national laboratories ...
NIST-F1. NIST-F1 is a cesium fountain clock, a type of atomic clock, in the National Institute of Standards and Technology (NIST) in Boulder, Colorado, and serves as the United States' primary time and frequency standard. The clock took less than four years to test and build, and was developed by Steve Jefferts and Dawn Meekhof of the Time and ...
A nuclear clock or nuclear optical clock is a atomic clock being developed that will use the energy of a nuclear isomeric transition as its reference frequency, [1] instead of the atomic electron transition energy used by conventional atomic clocks. Such a clock is expected to be more accurate than the best current atomic clocks by a factor of ...
Caesium standard. 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 ...
Atomichron. The Atomichron was the world's first commercial atomic clock, built by the National Company, Inc. of Malden, Massachusetts. It was also the first self-contained portable atomic clock and was a caesium standard clock. More than 50 clocks with the trademarked Atomichron name were produced. [1][2][3][4]
Department of Defense master clock. United States Naval Observatory. Washington, D.C. United States. 18 cesium atomic clocks and 4 hydrogen maser clocks. Cs, H. National Institute of Information and Communications Technology. Koganei, Japan [ 13 ] Optical lattice clock.