Editing Sundial (section)

==History==
{{Further|History of sundials}}
[[File:Ancient-egyptian-sundial.jpg|thumb|World's oldest sundial, from Egypt's Valley of the Kings (c. 1500 BC)]]
[[File:Phoenician sun dial - Ernest Renan reconstruction.jpg|thumb|Reconstruction of the 2,000 year old [[Phoenician sundial]] found at [[Umm al-Amad, Lebanon]]]]
The earliest sundials known from the archaeological record are shadow clocks (1500 [[Anno Domini|BC]] or [[Common Era|BCE]]) from ancient [[Egyptian astronomy]] and [[Babylonian astronomy]]. Presumably, humans were telling time from shadow-lengths at an even earlier date, but this is hard to verify. In roughly 700 BC, the [[Old Testament]] describes a sundial—the “dial of [[Ahaz]]” in {{bibleverse||Isaiah|38:8|NKJ}} and {{bibleverse|2 Kings|20:11|NKJ}}. By 240 BC, [[Eratosthenes]] had estimated the [[circumference]] of the world using an obelisk and a water well and a few centuries later, [[Ptolemy]] had charted the latitude of cities using the angle of the sun. The people of [[Kingdom of Kush|Kush]] created sun dials through geometry.<ref>{{cite journal|title=Gnomons at Meroë and Early Trigonometry|first=Leo|last=Depuydt|date=1 January 1998|journal=The Journal of Egyptian Archaeology|volume=84|pages=171–180|doi=10.2307/3822211|jstor=3822211}}</ref><ref>{{cite web|url=http://www.archaeology.org/online/news/nubia.html|title=Neolithic Skywatchers|date=27 May 1998|first=Andrew|last=Slayman|website=Archaeology Magazine Archive|access-date=17 April 2011|archive-url=https://web.archive.org/web/20110605234044/http://www.archaeology.org/online/news/nubia.html|archive-date=5 June 2011|url-status=live}}</ref> The Roman writer [[Vitruvius]] lists dials and shadow clocks known at that time in his ''[[De architectura]]''. The [[Tower of the Winds]] in Athens included both a sundial and a [[water clock]] for telling time. A [[canonical sundial]] is one that indicates the canonical hours of liturgical acts, and these were used from the 7th to the 14th centuries by [[religious order]]s. The Italian astronomer [[Giovanni Padovani]] published a treatise on the sundial in 1570, in which he included instructions for the manufacture and laying out of mural (vertical) and horizontal sundials. [[Giuseppe Biancani]]'s ''Constructio instrumenti ad horologia solaria'' (c. 1620) discusses how to make a perfect sundial. They have been in common use since the 16th century.
[[File:Seoul-Gyeongbokgung-Sundial-02.jpg|right|thumb|300x300px|A Korean sundial (''Angbu-ilgu'') first made by [[Jang Yeong-sil]] in the [[Joseon]] period, displayed in [[Gyeongbokgung]].]]