Time ball
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A time ball is a large, wooden or metal ball that moves up and down a pole, and which is dropped at a predetermined time of day. Because precise timekeeping is essential to the determination of longit
A time ball, installed in 1833, atop the Octagon Room at the Royal Observatory, Greenwich, London
The Boston Time Ball (1881)
Sydney Observatory with time ball
The time ball at Port Lyttelton, New Zealand, started signalling Greenwich Mean Time to ships in the harbour beginning in 1876. The Lyttelton Timeball Station was destroyed by an earthquake in 2011 but was rebuilt and reopened in 2018.
Shepherd Gate Clock
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The Shepherd Gate Clock is mounted on the wall outside the gate of the Royal Observatory, Greenwich building in Greenwich, Greater London. The clock, an early example of an electrically connected cloc
The Shepherd Gate Clock at the entrance to the Royal Observatory, Greenwich. It shows Greenwich Mean Time all year round.
Mechanism of the clock – on display but not in use
Flamsteed House (with its red time ball) overlooks the Gate clock, 1960