Editing Light (section)

===Descartes===
[[René Descartes]] (1596–1650) held that light was a [[Mechanism (philosophy)|mechanical]] property of the luminous body, rejecting the "forms" of [[Alhazen|Ibn al-Haytham]] and [[Witelo]] as well as the "species" of [[Roger Bacon#Legacy|Roger Bacon]], [[Robert Grosseteste]] and [[Johannes Kepler]].<ref name="Theories of light">''Theories of light, from Descartes to Newton'' A.I. Sabra CUP Archive,1981 p. 48 {{ISBN|978-0-521-28436-3}}</ref> In 1637 he published a theory of the [[refraction]] of light that assumed, incorrectly, that light travelled faster in a denser medium than in a less dense medium. Descartes arrived at this conclusion by analogy with the behaviour of sound waves.{{Citation needed|date=January 2010}} Although Descartes was incorrect about the relative speeds, he was correct in assuming that light behaved like a wave and in concluding that refraction could be explained by the speed of light in different media.

Descartes is not the first to use the mechanical analogies but because he clearly asserts that light is only a mechanical property of the luminous body and the transmitting medium, Descartes's theory of light is regarded as the start of modern physical optics.<ref name="Theories of light" />