Plaque marks NPL as birthplace of atomic timekeeping

13 February 2014

The National Physical Laboratory (NPL) was officially recognised as the European birthplace of atomic timekeeping by the European Physical Society (EPS) on 31 January.

A plaque to commemorate the occasion was unveiled there by the IOP’s immediate past president, Prof. Sir Peter Knight, (pictured left) and Prof. John Dudley, president of the EPS (right).

Prof. Paul Hardaker, chief executive of the IOP, was also at the event in Teddington, where guests heard how Louis Essen designed the world’s first caesium atomic clock and worked with John Parry to construct it at NPL in 1955. This led to a new definition of the second, based on the fundamental properties of atoms rather than the Earth’s period of rotation. A new form of clock, the caesium fountain, is now in use and is 500,000 times faster than Essen’s clock.

The event to celebrate the award of EPS Historic Site status to NPL included lectures and laboratory tours. The award commemorates places in Europe that are important for the development and history of physics through their association with an event, discovery, research or body of work that has made an exceptional contribution to physics.