Gnomon
Related Category: Astronomy: General
(n´mn): see sundial.
More on Gnomon ...
gnomon: (pron. no-mon) the physical structure of a sundial which casts the shadow (from the Greek for 'indicator').
Gnomon (i) The "pointer" in a sundial. (ii) Vertical stick, rod or pillar, the length and direction of whose shadow indicates the altitude of the Sun and the time of day.
gnomon
The central piece of a sundial which casts the shadow required to determine the time of day.
Gnomon -- The part of a sundial which casts the shadow, usually a rod or fin pointed at the celestial pole.
Gnomon
The gnomon is the part of a sundial that casts the shadow. Gnomon is an ancient Greek word meaning "indicator", "one who discerns," or "that which reveals."...
The "gnomon" was a vertical stick in the ground. It could be used to determine the local noon and the seasons via the summer and winter solstices and the spring and fall equinoxes.
By the time Schmitt had finished the trench, Cernan had finished dusting the TV camera - so that Houston could have a good look - and arrived with the gnomon and a supply of sample bags.
He has also been said to have introduced such astronomical instruments as the sundial and the gnomon to ancient GreeceDiogenes Laertius - Anaximander.
Thus on this circle the shadow of the gnomon moves 7 mm a minute. The time is read by the position of the centre of the shadow of the gnomon on this circle. The sundial is adjusted in two ways.
These are the Book on Numbers and Computation, the Arithmetical Classic of the Gnomon and the Circular Paths of Heaven and the Nine Chapters on the Mathematical Art.
Specially prepared sundials have gnomons to take all these effects into account, so the sundial time is always very close to clock time. However, due to the precession of the equinoxes, the shape of the analemma is changing, very very slowly… ...
A sundial can track the Sun's motion across the sky by the shadow of a rod or fin ("gnomon") pointing to the celestial pole (click here for construction of a folded-paper sundial), allowing the day to be divided into hours and smaller units.
APIN, contains catalogues of stars and constellations as well as schemes for predicting heliacal risings and the settings of the planets, lengths of daylight measured by a water-clock, gnomon, shadows, and intercalations.
 See also: Time, Second, Earth, Sun, Minute
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