ANDREW BROOKES, NATIONAL PHYSICAL LABORATORY / SCIENCE PHOTO LIBRARY ANDREW BROOKES, NATIONAL PHYSICAL LABORATORY / SCIENCE PHOTO LIBRARY
Louis Essen's notes on atomic clocks Louis Essen (1908-1997) was a British physicist who was involved in producing the first atomic clock. The notebook on this desk contains the recordings and calculations written by Louis Essen on 3rd June 1955, which were used to develop his pioneering clock. Essen and his colleague Jack Parry designed a means of precisely timing each second using caesium-133 atoms. This led to the replacement of the astronomical second with the atomic second as a standard of time, as it was the first apparatus to be used reliably as a clock on a long-term basis.
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