Gnomon

thumb|The gnomon is the triangular blade in this sundial. A gnomon is the part of a sundial that casts a shadow. The term is used for a variety of purposes in mathematics and other fields, typically to measure directions, position, or time. Quotes about Having fixed a pole, on a level piece of ground, and having described a circle by a cord attached to the pole, one should mark the points with pegs, where the shadow of the top of the pole touches the circle. The line joining these pegs is the West to East line. Having increased the length of the cord (which is equal to the distance of the two pegs fixed in the East West line) by itself, one should provide two slings at each end of the cord. Fix the slings on the two pegs (already fixed) stretch the cord with its mid point towards the south and fix a peg at the place, where the mid point of the cord touches the ground. He should similarly proceed towards the North. The line joining these pegs will be the South to North line. समे शङ्कंु निखाय शङ्कुसम््ममितया रज््ज्ववा मण््डलं परिलिख््य यत्रलेखयोः शङ््कक््वग्रच््छछाया निपतति तत्र शङ्कू निहन््तति सा प्राची ॥१.२॥तदन््तर रज््ज्ववाऽभ््यस््य पाशौ कृ त््ववा शङ्कोः पाशौ प्रतिमच्ु ्यदक्षिणायम््य मध््यये शङ्कुमेवमत्तु रतः सोदीची ॥१.३॥ verses in the Katyayana Sulbasutra describe a method to determine the directions with the help of a gnomon’s shadow : quoted in : Bhaskar Kamble, The Imperishable Seed: How Hindu Mathematics Changed the World and why this History was Erased, Garuda Prakashan Private Limited, 2022 ISBN 9798885750189 Ohashi, Yukio. ‘Development of Astronomical Observation in Vedic and Post- Vedic India’. Indian Journal of History of Science, 28(3), 1992. External links Category:Astronomy Category:Inventions Category:Engineering Category:Mathematics