The mechanization of light in Galilean science / Susanna Gómez.
Abstract:
In 1640, at the end of his life, Galileo admitted having devoted hundreds and hundreds of hours trying to understand the nature of light. This acknowledgment contrasts with the limited pages Galileo devoted explicitly to this issue. However, an attentive reading of some of his writings shows how the question about the nature of light was really underlying through his scientific career and was especially tied to the development of his ideas about the theory of matter. This essay aims to reveal how the question of the nature of light was one of the most crucial keys to better understanding the Galilean development from an atomism of atomi quanti to the atomism of infinite non-quanti atoms set forth in the Discorsi. The definition of light as a sustanza spiritosissima in the letter to Dini in 1615, with clear Neoplatonic echoes, seemed to be not compatible with the strict materialistic and corpuscularian conception of light defended in the correspondence about sunspots two years early. Some years after, in IlSaggiatore, Galileo defined light as a corporeal substance made of authentic indivisibles without extension. Through this article, I propose to interpret this Galilean assertion in Il Saggiatore as a conciliatory strategy of the atomistic conceptions of light with the Neoplatonic interpretations of it. However, this definition of light as a compound of not extensive atoms leaves doubt as to whether light was a material substance and its transmission in tempore. The physical-geometrical atomism defended in the Discorsi finally managed to restore light's materiality and finite velocity thanks to considering it a fluid subjected to the same laws of motions of all material substances.
Galilaeana A. 5 (2008), p. 207-244