The Greenwich Time Ball and Its Evolution

The Greenwich time ball is surely the best known time ball, given its success and prominent location, both on, and adjacent to, buildings of architectural and historical importance. It has operated almost continuously since 1833, with only a break during the Second World War and up to 1952. It was designed and erected between June and October 1833 and remained in service with only minor modifications for over 80 years, setting a remarkable standard for later time ball arrangements. This chapter describes the early history and the rebuild in 1914-1919, leading to automation in the 1960s. For the latter the source of time was a pendulum clock controlled by the six-pips from the BBC, eventually being superseded by electronic control. In this case the time was derived from the low frequency radio time service, linked to the time standards in the National Physical Laboratory, and then, in 2017, by time signals from the GPS satellites.