A time ball or timeball or ball time is an obsolete 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 chronometers. Accurate timekeeping is essential to the determination of longitude at sea.
Time ball stations set their clocks according to transit observations of the positions of the sun and stars. Originally they either had to be stationed at the observatory itself, or had to keep a very accurate clock at the station which was set manually to observatory time. Following the introduction of the electric telegraph around 1850, time balls could be located at a distance from their source of mean time and operated remotely.
The first time ball was erected at Portsmouth, England, in 1829 by its inventor Robert Wauchope, a captain in the Royal Navy. Others followed in the major ports of the United Kingdom (including Liverpool) and around the maritime world. One was installed in 1833 at the Greenwich Observatory by the Astronomer Royal, John Pond, and the time ball has dropped at 1 p.m. every day since then. Wauchope submitted his scheme to American and French ambassadors when they visited England. The US Naval Observatory was established in Washington, D.C., and the first American time ball went into service in 1845.
Time balls were usually dropped at 1 p.m. (although in the United States they were dropped at noon). They were raised half way about 5 minutes earlier to alert the ships, then with 2–3 minutes to go they were raised the whole way. The time was recorded when the ball began descending, not when it reached the bottom.
A variation of the concept has been used since 31 December 1907 at New York City's Times Square as part of its New Year's Eve celebrations, in which a lit ball—inspired by an organizer having seen the time ball on the Western Union Building in operation, is lowered down a pole atop One Times Square to signal midnight and the arrival of the new year. Rather than the ball being dropped rapidly with its release used as the time signal, it descends slowly over the course of 60 seconds from 11:59 p.m. until midnight. For 31 December 1987, the event's organizers acknowledged the addition of a leap second by extending the drop to 61 seconds (although in fact the leap second was five hours earlier, as they occur worldwide at midnight UTC).
Lyttelton Timeball Station
The Lyttelton Timeball Station in Lyttelton, New Zealand, was operational until it was damaged in the 2010 Canterbury earthquake. Further severe damage occurred in the February 2011 Christchurch earthquake, and a decision was made in March 2011 to dismantle the building, a danger to the public, but the tower collapsed during the major aftershock that hit the Lyttelton area on 13 June 2011. In November 2012, a large financial donation  was made available to contribute towards rebuilding the tower, a project the community considered. On 25 May 2013, it was announced that the tower and ball would be restored, and that funds were to be sought from the community to rebuild the rest of the station.
Around the world
Today there are over sixty time balls standing, though many of these are no longer operational. The existing stations include those at:
- National Maritime Museum, Valparaiso, Chile
- Deal, Kent
- Margate Clock Tower, Kent
- The Old Windmill, Brisbane, Australia
- Fremantle, Western Australia
- Gdańsk, Poland (The time ball was installed in 1876, moved to the Danzig (now Gdańsk) lighthouse in 1894, and removed in 1929. In 2008 it was reconstructed from original plans)
- Greenwich Observatory
- Clock Tower, Brighton, East Sussex (originally operated hourly, but was later stopped as it was too noisy)
- Nelson's Monument on Calton Hill, Edinburgh
- Sydney Observatory, Australia
- Newcastle Customs House, Australia
- Victoria & Alfred Waterfront, Cape Town
- United States Naval Observatory
- Titanic Memorial, New York
- Citadelle of Quebec, Quebec City
- Semaphore, South Australia
- Williamstown Lighthouse, Victoria
- Blackhead Point, in Hong Kong, where a time ball was operated from 1908 to 1933
- History of longitude
- Shepherd gate clock
- Time signal
- Weather ball
- Greenwich Mean Time (GMT)
- Aubin, David (2010). The Heavens on Earth: Observatories and Astronomy in Nineteenth-Century Science and Culture. Durham, N.C.: Duke University Press. p. 164. ISBN 978-0-8223-4640-1.
- Greenwich Time Ball Retrieved 27 December 2010
- "Deal Timeball Tower: The Ball Drop". Retrieved 4 January 2009.
- "The Gdańsk Nowy Port Lighthouse and Time Ball". Archived from the original on 2013-04-01. Retrieved 4 January 2009.
- McFadden, Robert D. (1987-12-31). "'88 Countdown: 3, 2, 1, Leap Second, 0". New York Times. Retrieved 2 January 2009.
- "NYC ball drop goes 'green' on 100th anniversary". CNN. 31 December 2007. Retrieved 2007-12-31.
- "Lyttelton Timeball Station, Christchurch". Yahoo! Travel.
- "New Zealand quake: The epicentre town". BBC News. 25 February 2011.
- Gates, Charlie (4 March 2010). "Timeball Station to be demolished". stuff.co.nz. Retrieved 15 June 2011.
- Greenhill, Marc (14 June 2011-updated). "Workmen unscathed as Timeball Station collapses". stuff.co.nz. Retrieved 15 June 2011. Check date values in:
- Greenhill, Marc (28 November 2012). "Donor fronts to save Lyttelton Timeball Station". Stuff. stuff.co.nz. Retrieved 2012-11-28.
- Lee, Francesca (25 May 2013). "Million dollar donation to rebuild Lyttelton Timeball". Stuff. stuff.co.nz. Retrieved 2013-05-25.
- "$1m donation to rebuild timeball". Radio New Zealand. radionz.co.nz. 25 May 2013. Retrieved 2013-05-25.
- "Heritage Gateway Listed Buildings Online — Clock Tower and Attached Railings, North Street (north side), Brighton, Brighton and Hove, East Sussex". Heritage Gateway website. Heritage Gateway (English Heritage, Institute of Historic Building Conservation and ALGAO:England). 2006. Retrieved 2 June 2010.
- "List of Timeballs". Index to the House Documents, Otherwise Publ. as Executive Documents. U.S. Congress. 1876–1877. pp. 305–308. List of time balls worldwide in 1876.
- Time ball/cannon hobbyist
- Time ball and cannon Association
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