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Gnomon (Sun Dial)

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File:Sundial Taganrog.jpg

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."

It has come to be used for a variety of purposes in mathematics and other fields.

A gnomon as in Euclid book II

Uses of the term

  • Anaximander (610–546 BC) is credited with introducing this Babylonianinstrument to the Greeks.
  • Oenopides used the phrase drawn gnomon-wise to describe a line drawn perpendicular to another.