Editing Time ball (section)

{{Short description|Time-signalling device}}
{{Use dmy dates|date=February 2018}}
[[File:Royal_observatory_greenwich.jpg|thumb|right|240px|[[Royal Observatory, Greenwich]], London. Installed in 1833, a time ball sits atop the Octagon Room]]

A '''time ball''' or '''timeball''' is a time-signalling device. It consists of a large, painted wooden or metal ball that is dropped at a predetermined time, principally to enable navigators aboard ships offshore to verify the setting of their [[marine chronometer]]s. Accurate timekeeping is essential to the determination of [[longitude]] at sea.<ref name=nyseaport />

Although time balls have since been replaced by electronic [[time signal]]s, some time balls have remained operational as historical [[tourist attraction]]s.