Dominique Raynaud: Is there such a thing as the Snellius-Descartes law of refraction?

If we examine the status of the law of refraction in the texts of Ibn Sahl, Harriot, Snel and Descartes, we find that none of these authors knew the law of refraction as it is taught today. The differences concern the nature of the relationship linking the angle of incidence and the angle of refraction, the role conferred to this relationship in optical texts, and even its recognition as a physical law. In these circumstances, the question of who discovered the law of refraction – Descartes, Snel, Harriot or Ibn Sahl? – makes little sense.

Dominique Raynaud argues that such questions are plagued by ethno-nationalist agendas that have nothing to do with objective historical knowledge. He calls for knowledge about this relationship to be clarified without being influenced by such agendas.

Dominique Raynaud is Associate Professor of History of Science at the University of Grenoble Alpes.

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