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mathematician and physicist who devised the basic law of refraction, known
as Snell's law, in 1621. He also founded the method of determining distances
by triangulation. Snell was born in Leiden, where he studied and eventually became professor. Snell developed the method of triangulation in 1615, starting with his house and the spires of nearby churches as reference points. He used a large quadrant over 2 m/7 ft long to determine angles, and by building up a network of triangles, was able to obtain a value for the distance between two towns on the same meridian. From this, Snell made an accurate determination of the radius of the Earth. The laws describing the reflection of light were well known in antiquity, but the principles governing the refraction of light were little understood. Snell's law was published by French mathematician Descartes in 1637. He expressed the law differently from Snell, but could easily have derived it from Snell's original formulation. Whether Descartes knew of Snell's work or discovered the law independently is not known. |