An atomic clock is a timepiece that keeps time by measuring the resonant frequency at which atoms transition between quantized energy states, a frequency fixed by physics rather than by any mechanical part. The SI second is itself defined this way, as the duration of 9,192,631,770 cycles of the radiation from the unperturbed ground-state transition of the caesium-133 atom, and networks of atomic clocks maintain International Atomic Time, from which Coordinated Universal Time is derived. Their precision underlies satellite navigation systems such as GPS and Galileo, where a timing error of a few nanoseconds can shift a position fix by about thirty centimeters. The first atomic clock was built by Louis Essen with Jack Parry at the National Physical Laboratory in the United Kingdom in 1955, using the caesium resonance later adopted as the definition of the second. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/
Facts
SignificanceAtomic clocks became precise enough to redefine the second itself and now anchor global timekeeping, underpinning systems such as satellite navigation that depend on nanosecond-level synchronization. 1 FAQs
Was the 1955 caesium clock the first attempt at an atomic clock?
No. Earlier ammonia and caesium clocks were still under construction in the United States when the National Physical Laboratory caesium clock first ran in 1955.
No. In the early 1950s Louis Essen visited American laboratories, including the US National Bureau of Standards, where ammonia and caesium clocks were under construction, but the Engineering and Technology History Wiki says they fell far short of the required standard. Back at the National Physical Laboratory, Essen and his colleague Jack Parry designed and built a caesium clock of much greater stability and accuracy. It was operated for the first time on 24 May 1955, and within weeks radio time signals controlled by it were being transmitted within the United Kingdom and then around the world.
Connections
In Field
Source Atomic clock (Wikipedia)
Sources
1. Atomic clock (Wikipedia)
Wikimedia FoundationHistory section, first caesium clock sentence
The first practical atomic clock using caesium atoms was built at the National Physical Laboratory in the United Kingdom in 1955 by Louis Essen in collaboration with Jack Parry.
Lead paragraph, TAI definition sentence
This definition underpins the system of TAI, which is maintained by an ensemble of atomic clocks around the world.
In Field: Electrical Engineering, Introduction
It is based on the fact that atoms have quantised energy levels, and transitions between such levels are driven by very specific frequencies of electromagnetic radiation.
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