1580-1626

Dutch mathematician and physicist who discovered the law of refraction of light rays, which states that the ratio sin i : sin r is a constant, dependent on the medium, where i stands for the angle of the incident ray and r for the angle of the refracted ray. Snell's most sustained work was his determination of the length of the meridian, for which he improved the method of triangulation of Gemma Frisius and measured the distance between Alkmaar and Bergen-op-Zoom (around 80 miles or 129 km) and later extended the network of triangles all the way to Mechelen, Belgium.