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Atomic clock
Videos
An atomic clock is a clock that measures time by monitoring the resonant frequency of atoms. It is based on the fact that atoms have quantised energy levels, and transitions between such levels are dr
NIST physicists Steve Jefferts (foreground) and Tom Heavner with the NIST-F2 caesium fountain atomic clock, a civilian time standard for the United St
NIST physicists Steve Jefferts (foreground) and Tom Heavner with the NIST-F2 caesium fountain atomic clock, a civilian time standard for the United States
The master atomic clock ensemble at the U.S. Naval Observatory in Washington, D.C., which provides the time standard for the U.S. Department of Defens
The master atomic clock ensemble at the U.S. Naval Observatory in Washington, D.C., which provides the time standard for the U.S. Department of Defense. The rack-mounted units in the background are HP 5071A caesium beam clocks. The black units in the foreground are Sigma-Tau MHM-2010 hydrogen maser standards.
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
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, England.
A caesium atomic clock from 1975 (upper unit) and battery backup (lower unit)
A caesium atomic clock from 1975 (upper unit) and battery backup (lower unit)
Global Positioning System
Videos
The Global Positioning System is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite sy
Atomic clock
…time-keeping capabilities of atomic clocks are also used for navigation by satellite networks such as the EU’s Galileo Programme and the United States’ GPS. The timing accuracy of the atomic clocks matters because even a timing error of 1 nanosecond (10−9 s) corresponds to a positional error of roughly 30…
Artist's impression of GPS Block IIIA satellite in Earth orbit
Artist's impression of GPS Block IIIA satellite in Earth orbit
Late 1990s civilian GPS receiver ("GPS navigation device") in a marine application
Late 1990s civilian GPS receiver ("GPS navigation device") in a marine application
Automotive navigation system in a taxicab, 2000s
Automotive navigation system in a taxicab, 2000s
A United States Space Force officer operates the Global Positioning System in 2022.
A United States Space Force officer operates the Global Positioning System in 2022.