Refraction, the speed of light and minimal action: From Descartes to Maupertuis through many more

Abstract

In the 17th and 18th centuries, several natural philosophers studied the phenomenon of refraction and attempted to obtain the Snell law from various assumptions. Lacking experimental data, it was generally believed that light travels faster in a refracting medium than in air. In the present article, I review the contributions to the problem of light refraction by Descartes, Fermat, Huygens, Leibniz, Newton, Clairaut, and finally Maupertuis who established a principle of least action based on his own approach to the problem.