Editing Time signal (section)

==Audible and visible time signals==

One sort of public time signal is a [[striking clock]].  These clocks are only as good as the clockwork that activates them, but they have improved substantially since the first clocks from the 14th century.  Until modern times, a public clock such as [[Clock Tower, Palace of Westminster|Big Ben]] was the only time standard the general public needed.

Accurate knowledge of time of day is essential for [[navigation]], and ships carried the most accurate [[marine chronometer]]s available, although they did not keep perfect time. A number of accurate audible or visible time signals were established in many [[seaport]] cities to enable navigators to set their chronometers.

=== Signal guns ===

In [[Vancouver]], [[British Columbia]], a "[[9 O'Clock Gun]]" is still shot every night at 9&nbsp;pm.  (This gun was brought to [[Stanley Park]] in 1894 by the [[Fisheries and Oceans Canada|Department of Fisheries]] originally to warn [[fishermen]] of the 6:00&nbsp;pm Sunday closing of fishing.) The 9:00&nbsp;pm firing was later established as a time signal for the general population. Until a time gun was installed, the nearby [[Brockton Point]] lighthouse keeper detonated a stick of dynamite. Elsewhere in Canada, a "Noon Gun" is fired daily from the citadels in [[Citadel Hill (Fort George)|Halifax]] and [[Citadelle of Quebec|Quebec City]] and from [[Signal Hill, St. John's|Signal Hill]] in [[St. John's, Newfoundland and Labrador]].<ref>{{Cite web|url=https://www.pc.gc.ca/en/lhn-nhs/nl/signalhill/activ/activ-and-exp/Noon-Day-Gun|title=Noon Day Gun - Signal Hill National Historic Site|first=Government of Canada|last=Parks Canada Agency|date=10 April 2019|website=www.pc.gc.ca}}</ref>

In the same manner, a [[Noon Gun]] has been fired in [[Cape Town]], since 1806.<ref>{{cite web|url=http://www.bokaap.co.za/noon-gun/|title=Noon Gun -|website=bokaap.co.za|access-date=8 April 2018}}</ref> The gun is fired daily from the Lion Battery at [[Signal Hill (Cape Town)|Signal Hill]].

The [[Noonday Gun]] serves a similar purpose in [[Hong Kong]]. The tradition, which started in the 1860s under British colonial rule, has become a tourist attraction in recent times. 

A cannon was fired at one o'clock every weekday at [[Liverpool]], at the [[Edinburgh Castle|Castle]] in [[Edinburgh]], and also at [[Perth Observatory|Perth]] to establish the time. The Edinburgh "[[One O'Clock Gun]]" is still in operation. A cannon located at the top of Santa Lucia Hill, in [[Santiago]], is shot every noon.

In [[Rome]], on the [[Janiculum]], a hill west of the [[Tiber]] since 1904 a cannon is fired daily at noon towards the river as a time signal. This was introduced in 1847 by [[Pope Pius IX]] to synchronise all the church bells of Rome. It was situated in [[Castel Sant'Angelo]] until 1903 when it was moved to [[Monte Mario]] for a few months until it was placed in its current position. The cannon was silenced from the start of [[WWII]] for about twenty years until 21 April 1959, the 2712th anniversary of Rome's founding, and has been in use since then.

For many years an old cannon was fired "about noon" from a mountain near [[Kabul]].<ref>{{cite journal|url=https://www.csmonitor.com/1982/0422/042212.html|title=The noon gun|date=22 April 1982|access-date=8 April 2018|journal=Christian Science Monitor}}</ref><ref>{{cite web|url=http://www.digitalsilver.co.uk/TimeGun/kabul_gun.html|title=The Old Noon Day Gun of Kabul - Afghanistan|website=digitalsilver.co.uk|access-date=8 April 2018|archive-date=28 August 2017|archive-url=https://web.archive.org/web/20170828020350/http://www.digitalsilver.co.uk/TimeGun/kabul_gun.html|url-status=dead}}</ref>

=== Sirens, whistles, and other audible signals ===

In many Midwestern US cities where tornadoes are a common hazard, the [[emergency siren]]s are tested regularly at a specified time (say, noon each Saturday); while not primarily intended to mark the time, local people often check their watches when they hear this signal. In many non-seafaring communities, loud factory [[whistle]]s served as public time signals before radio made them obsolete. Sometimes, the tradition of a factory whistle becomes so deeply entrenched in a community that the whistle is maintained long after its original function as a time keeper became obsolete.<ref>{{cite news |last1=Ross |first1=Jenna |title=Midwestern towns with sirens weigh nostalgia against nuisance |url=http://www.startribune.com/towns-with-daily-sirens-balance-nostalgia-nuisance/288938591/ |access-date=21 June 2018 |work=Minneapolis Star Tribune |date=9 April 2015}}</ref> For example, the [[University of Iowa]]'s power plant whistle has been reinstated several times by popular demand after numerous attempts to silence it.<ref>{{cite news |last1=Snee |first1=Tom |title=The enduring exhalations of The Whistle |url=https://fyi.uiowa.edu/04/18/the-whistle/ |access-date=21 June 2018 |work=Iowa Now |date=18 April 2011 |archive-date=22 June 2018 |archive-url=https://web.archive.org/web/20180622005411/https://fyi.uiowa.edu/04/18/the-whistle/ |url-status=dead }}</ref>

=== Visual signals ===
[[File:Royal observatory greenwich.jpg|thumb|right|The [[time ball]] on the roof of [[Greenwich Observatory]], London]]
In 1861 and 1862, the Edinburgh Post Office Directory published time gun [[map]]s relating the number of seconds required for the report of the time gun to reach various locations in the city. Because [[speed of light|light]] travels much faster than [[speed of sound|sound]], visible signals enabled greater precision than audible ones, although audible signals could operate better under conditions of reduced visibility. The first [[time ball]] was erected at [[Portsmouth]], England in 1829 by its inventor [[Robert Wauchope (admiral)|Robert Wauchope]].<ref name=AUB>Aubin, David [https://books.google.com/books?id=9EKzLQL3RQEC&dq=Robert+Wauchope+time+ball&pg=PA164 The Heavens on Earth: Observatories and Astronomy in Nineteenth-Century Science and Culture] p.164. Duke University Press, 2010</ref> One was installed in 1833 on the roof of the [[Royal Greenwich Observatory|Royal Observatory]] in [[Greenwich]], London, and the time ball has dropped at 1:00 pm every day since then.<ref>{{cite web|url=http://wwp.greenwichmeantime.co.uk/info/timeball.htm|title=Greenwich Time Ball|website=greenwichmeantime.co.uk|access-date=8 April 2018|url-status=dead|archive-url=https://web.archive.org/web/20101023194034/http://wwp.greenwichmeantime.co.uk/info/timeball.htm|archive-date=23 October 2010}}</ref> The first American time ball went into service in 1845.<ref name=AUB/> In New York City, the ceremonial [[Times Square Ball]] drop on New Year's Eve in [[Times Square]] is a vestige of a visual time signal.