Time ball

Time ball

A time ball is a large painted wooden or metal ball that drops at a predetermined time, principally to enable sailors to check their marine chronometers. Accurate timekeeping is one way of enabling mariners to determine their 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. Through the use of the electric telegraph (from around 1850), time balls could be located at a distance from their source of Mean Time and operated remotely.

Time balls are usually dropped at 1pm (although in the USA 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. The time ball was not usually dropped at noon as the observatories would be too busy taking readings.

The first time ball was erected at Portsmouth in 1829 by its inventor Robert Wauchope, a Captain in the Royal Navy. Others followed in the major ports of the UK (including Liverpool) and around the maritime world. One was installed in 1833 at the Greenwich Observatory by Astronomer Royal John Pond, and has dropped at 1pm every day since then.

With the commencement of radio time signals (in Britain from 1924), time-balls gradually became obsolete and many were demolished in the 1920s.

Today

Today there are over 60 timeballs standing, including those at:

* United States Naval Observatory
* Greenwich Observatory
* Nelson's Monument on Calton Hill, Edinburgh
* Victoria & Alfred Waterfront, Cape Town
* Deal, Kent
* Fremantle, Western Australia
* Point Gellibrand, Victoria
* Lyttelton, New Zealand
* Sydney Observatory, Australia
* Jubilee Clock Tower, Brighton, Sussex

A modern version of a timeball is the ball drop at the stroke of midnight on December 31, notably in Times Square, New York City.

ee also

* Time signal
* Shepherd gate clock
* Weather ball
* Time Cube

References

* [http://dealtimeball.tripod.com/ Time Ball Tower Museum]
* [http://latarnia.gda.pl/en/index.php?go=kula,czasu The Historic Gdańsk Nowy Port, Poland Lighthouse and Time Ball]


Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Time ball — Time Time, n.; pl. {Times}. [OE. time, AS. t[=i]ma, akin to t[=i]d time, and to Icel. t[=i]mi, Dan. time an hour, Sw. timme. [root]58. See {Tide}, n.] 1. Duration, considered independently of any system of measurement or any employment of terms… …   The Collaborative International Dictionary of English

  • time ball — noun : a large ball on a pole (as at an observatory) that is arranged to drop suddenly to mark a particular hour of day (as noon) * * * time ball noun A ball mounted on a vertical pole, eg on top of a high building, that drops at a regular point… …   Useful english dictionary

  • Time Ball — Boule horaire Pour les articles homonymes, voir boule et horaire. La boule horaire de l Observatoire royal de Gr …   Wikipédia en Français

  • Time ball — Boule horaire Pour les articles homonymes, voir boule et horaire. La boule horaire de l Observatoire royal de Gr …   Wikipédia en Français

  • time-ball — noun a ball that slides down a staff to show a fixed time; especially at an observatory • Hypernyms: ↑ball, ↑globe, ↑orb • Part Holonyms: ↑timepiece, ↑timekeeper, ↑horologe …   Useful english dictionary

  • time ball — noun A large wooden or metal ball that drops at a predetermined time to enable sailors to check their marine chronometers from their boats offshore …   Wiktionary

  • Time — Time, n.; pl. {Times}. [OE. time, AS. t[=i]ma, akin to t[=i]d time, and to Icel. t[=i]mi, Dan. time an hour, Sw. timme. [root]58. See {Tide}, n.] 1. Duration, considered independently of any system of measurement or any employment of terms which… …   The Collaborative International Dictionary of English

  • Time bargain — Time Time, n.; pl. {Times}. [OE. time, AS. t[=i]ma, akin to t[=i]d time, and to Icel. t[=i]mi, Dan. time an hour, Sw. timme. [root]58. See {Tide}, n.] 1. Duration, considered independently of any system of measurement or any employment of terms… …   The Collaborative International Dictionary of English

  • Time bill — Time Time, n.; pl. {Times}. [OE. time, AS. t[=i]ma, akin to t[=i]d time, and to Icel. t[=i]mi, Dan. time an hour, Sw. timme. [root]58. See {Tide}, n.] 1. Duration, considered independently of any system of measurement or any employment of terms… …   The Collaborative International Dictionary of English

  • Time book — Time Time, n.; pl. {Times}. [OE. time, AS. t[=i]ma, akin to t[=i]d time, and to Icel. t[=i]mi, Dan. time an hour, Sw. timme. [root]58. See {Tide}, n.] 1. Duration, considered independently of any system of measurement or any employment of terms… …   The Collaborative International Dictionary of English

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”