Beyond the Fringe: Diffraction as seen by Grimaldi, Fabri, Hooke and Newton

Abstract

Beginning his third ‘Account of a Book’ in no.79 of his Philosophical Transactions (22 January 1671/2) Henry Oldenburg wrote: ‘This learned Treatise was not to be altogether omitted in these Philosophical Transactions though an Account of it hath been deferr’d (too long), it being but lately fallen into the Publisher's hands.’ (1) The work in question was Francesco Maria Grimaldi’s Physico-Mathesis de Lumine (Bologna, 1665); Oldenburg accorded it a moderately long review of almost three pages. He noted that Grimaldi had introduced a fourth manner of propagation of light, that is, ‘not only directly, and by refraction , and reflexion , but also by diffraction ’ thus coining a new technical word for the English language. But alas! the account leaves the new phenomenon very obscure, for Oldenburg continues: ‘which last, according to him, is done, when the parts of Light, separated by a manifold dissection, do in the same medium , proceed in different ways.’ The essence of a typical 17th century diffraction experiment - a narrow beam of light partially obstructed by a sharp edge - is not mentioned.