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EPS Historic Sites - UK National Physical Laboratory

The National Physical Laboratory [NPL] has been officially declared by the European Physical Society [EPS] Historic Site as the birthplace of atomic timekeeping. The announcement was made during a dedicated event at NPL in Teddington, United-Kingdom, on 31 January 2014 and a plaque commemorating the historic occasion was unveiled.

The EPS Historic Sites Award recognises places in Europe that have made an exceptional contribution to physics. The award recognises NPL as the place where the first practical atomic clock was built, a landmark which has changed global timekeeping and made modern communications and location services possible.

In the 1950s, Louis Essen constructed the atomic clock, Caesium Mk. 1, with fellow physicist John Parry, at NPL. This new clock kept time more accurately than any other in existence and eventually paved the way for redefining the second in 1967, based on the fundamental properties of caesium atoms, rather than the Earth's rotation.

Professor John Dudley, President of the European Physical Society, said: "Today NPL is justly recognised as a historic site. Essen's work here, as well as that of many other leading scientists, has benefitted the lives of all Europeans by providing the precision of timing required for applications such as advanced telecommunications, navigation and defence systems."

Dr Brian Bowsher, Managing Director of NPL, said: "Being recognised by the EPS is an honour and is testament to the work of our current, as well as our past, scientists. Although invisible, atomic time has impacted the lives of all of us. What's more, ground-breaking developments continue to be made in this field, with a new generation of atomic clocks on the horizon that could provide everything from improved satellite navigation systems to more sensitive tests of fundamental physical theories."

NPL continues to provide a vital role in managing and distributing the UK's time. NPL's caesium fountain, NPL-CsF2, which is the reference for the national timescale UTC(NPL) is one of the most accurate clocks in the world, and is over 300,000 times more precise than Essen's clock from the 1950s.

Atomic time affects us all every day. Each GPS satellite has atomic clocks on board that measure time very accurately in order to calculate global position. Atomic clocks synchronise every mobile phone network to manage the transfer from one cell to the next and atomic time is required to synchronise computer systems (for example, through the Network Time Protocol) to enable emails and other transactions online.


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NPL, the place where the first practical atomic clock was built, a landmark which has changed global timekeeping and made modern communications and location services possible



Louis Essen and J.V.L. Parry standing next to the world's first caesium atomic clock, developed at NPL in 1955.
Louis Essen and J.V.L. Parry standing next to the world's first caesium atomic clock, developed at NPL in 1955.


Professor Sir Peter Knight FRS and Professor John Dudley unveiled the plaque. Professor Sir Peter Knight FRS and Professor John Dudley unveiled the plaque.

© NPL - right-click to enlarge images
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