Henry Cavendish on Gravitational Deflection of Light

Abstract

A recent analysis of two handwritten sheets of paper by Henry Cavendish (1731–1810) reveals the details of his calculation of the deflection of light induced by the gravitational field of isolated celestial bodies. Except for a few lines from one of these pages, where Cavendish communicated the result, the two documents have never been published. This gave rise to speculations about how, if at all, Cavendish derived his formula for the deflection angle by his own calculations. Such doubts are dispelled and it is demonstrated how Cavendish, in these documents, applied Newtonian mechanics to the corpuscles of light.