Caesium atomic clock
Reloj atómico de cesio
- Date
- 1955 · confidence high
- Place
- National Physical Laboratory, Teddington, United Kingdom
- Credited to
- Louis Essen and Jack Parry (NPL); an ammonia forerunner at the NBS (Harold Lyons, 1949)
- People
- 👤 Jack Parry1924–2010👤 Louis Essen1908–1997
- Field
- Knowledge & symbols
What it is
A clock that defines the second by the frequency of a transition in the caesium atom, accurate to one second in millions of years. It redefined time in 1967 and synchronises GPS, the internet and finance.
What it led to
- GPS, which is essentially a network of atomic clocks in orbit
- The synchronisation of telecommunications networks and financial markets
- Optical clocks and tests of relativity
Built on
- Caesium1860
- Bohr model of the atom1913
- Space quantization (Stern-Gerlach experiment)1922
- Ammonia atomic clock1949
- Maser1954
- microwave spectroscopy
- quartz oscillator
Made possible
- Satellite navigation (Transit)1960
- Atomic definition of the second1967
- Global Positioning System (GPS)1978-1995
- Caesium fountain atomic clock1989-1999
- Coordinated Universal Time
- optical clocks