Most accurate mechanical clock with a pendulum swinging in free air
- Who
- Donald Saff , National Maritime Museum
- What
- 1/4 second(s)
- Where
- United Kingdom (Greenwich)
- When
- 16 April 2015
The most accurate mechanical clock with a pendulum swinging in free air is ‘Clock B’, owned by Donald Saff, and adjusted and trialled by the Royal Observatory Greenwich. At the beginning of a 100-day trial, 'Clock B' was ¼ seconds behind Coordinated Universal Time (UTC); it ended the trial 7/8 seconds behind UTC as verified on 16 April 2014.
The building of Clock B was started in 1975 by Martin Burgess, based on a theory by the 18th Century clockmaker John Harrison. The design is quite unlike that of other pendulum clocks. Harrison never completed his own clock in his lifetime, and so Burgess’s construction, made from modern materials including duraluminium and invar, represents the first scientific test of Harrison’s theory.