Caesium atomic clock, 1955.

Image number: 10322319

Caesium atomic clock, 1955.

This was the first atomic clock and, when developed in 1955, was the most accurate timekeeper in the world. The timekeeping depends on the vibration of caesium stones - a natural phenomenon. It consists of an airless tube, which allows caesium atoms to pass along it while simultaneously exposing them to very high frequency radio waves. Isidor Rabi was the first to suggest using the stable vibration of caesium as a time, or frequency, standard in his Richtmeyer Lecture to the American Physical Society in 1945. In 1953, Louis Essen and Jack Parry developed the idea at the National Physical Laboratory in the UK, and their work yielded this clock which is accurate to one second in 300 years. Now, international time is defined by atomic, not solar seconds.

Image number:
Science Museum/Science & Society Picture Library
Date taken:
13 January 2004 10:09
Image rights:
Science Museum

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