Atomic Clock
Inventor Louis Essen
Louis Essen
Born6 September 1908
Died24 August 1997 | Age 88

Louis Essen and Jack Parry 1955

In 1955, Louis Essen and Jack Parry built the world's first caesium atomic clock at the National Physical Laboratory in Teddington, Middlesex.

From Quartz

An Atomic clock, is a timekeeping device that is controlled by atomic or molecular oscillations. Essen joined NPL in 1929 to further his ambition to build highly accurate time pieces. He investigated the potential of tuning forks and quartz crystal oscillators for precise time measurement. His research led to his development of the quartz ring clock in 1938, which used the electrically induced vibrations of a quartz crystal to measure time.

The clock soon become the industry standard for time measurement at observatories throughout the world.

Jack Parry & Louis Essen with the first Atomic Clock 1955
Jack Parry & Louis Essen with the first Atomic Clock 1955


Atomic Clock

Essen based his clock on caesium because
  • 'An atom will always have the same transition frequency anywhere in the universe'.
His clock was a 7 foot long horizontal apparatus with a source of caesium atoms on one end, a microwave cavity in the middle probing the atoms frequency and a sensitive detector at the other end. When it was first put in to operation, it was accurate to one second in 300 years.

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