Gnomon
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robot Adding: [[is:Gnómon]]
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[[Image:SundialBridgeCA2.jpg|thumb|left|The [[cantilever]] spar of this [[cable-stayed bridge|cable-stay bridge]], the [[Sundial Bridge at Turtle Bay]], forms the gnomon of a large [[garden]] [[sundial]]]]
The '''gnomon''' is the part of a [[sundial]] that casts the [[shadow]]. Gnomon (γνώμων) is an [[ancient Greek]] word meaning "indicator", "one who discerns," or "that which reveals."
[[Image:Sundial Taganrog.jpg|thumb|right|right|The gnomon is the [[triangular]] blade in this sundial]]
In the [[northern hemisphere]], the shadow-casting edge is normally oriented so that it points [[north]] and is parallel to the rotation axis of the [[Earth]]. That is, it is inclined to the horizontal at an [[angle]] that equals the [[latitude]] of the sundial's location. On some sundials, the gnomon is vertical. These were usually used in former times for observing the [[altitude]] of the [[Sun]], especially when on the [[meridian (geography)|meridian]]. The style is the part of the gnomon that casts the shadow. This can change as the sun moves. For example, the upper [[west]] edge of the gnomon might be the style in the morning and the upper east edge might be the style in the afternoon.
The art of constructing a gnomon sundial is sometimes termed gnomonics. One so skilled would be referred to as a gnomonist.
Gnomon may also imply the [[design paradigm]] relationship between an indicator and a dial or other reference, as with a [[speedometer]] and needle. In this case, the needle functions as a gnomon against the incremented speedometer background.
Gnomon is also a [[mathematical]] term that describes the part of a [[parallelogram]] that remains when a similar parallelogram is removed from one of its corners.
Also, gnomon is the name given to an aesthetic process utilized by [[James Joyce]] in his set of short stories ''[[Dubliners]]'', whereby the whole of the character is revealed by a single part.
[[Anaximander]] ([[610 BC|610]]–[[546 BC]]) is credited with introducing this [[Babylonian]] instrument to the [[Greeks]]. The [[China|Chinese]] also used the gnomon, mentioned in the 2nd century ''[[Nine Chapters on the Mathematical Art]]'' as being used much earlier by the [[Duke of Zhou]] (11th century BC).
==Gnomons in Popular Culture==
*In the book "[[The Tower at the End of the World]]", an [[island]] with a giant [[tower]] and thin stairs is found on a [[lake]]. The tower and stairs, along with the odd [[sculpture]]s surrounding it, are later discovered to be a giant sundial, with the tower and stairs being the gnomon. The island the tower is found on is often called "Gnomon Island".
==References==
{{Commonscat|Sundials}}
*[[Midhat J. Gazalé|Gazalé, Midhat J.]] ''Gnomons, from Pharaohs to Fractals'', Princeton University Press, Princeton, 1999. ISBN 0-691-00514-1.
*[[Albert E. Waugh|Waugh, Albert E.]], ''Sundials: Their Theory and Construction'', Dover Publications, Inc., 1973, ISBN 0-486-22947-5.
*[[R. Newton Mayall|Mayall, R. Newton]],[[Margaret W. Mayall|Mayall, Margaret W.]], ''Sundials: Their Construction and Use'', Dover Publications, Inc., 1994, ISBN 048641146X
[[Category:Clocks]]
[[Category:Sundials]]
[[Category:Timekeeping]]
[[Category:Traditional Chinese objects]]
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