Published online by Cambridge University Press: 27 September 2019
Galileo participated in exchanges of encrypted correspondence at key moments in his life. In 1610–11, following the publication of the “Sidereal Messenger,” ciphers helped Galileo to diplomatically reveal what he was observing through his telescope. After his Inquisition trial of 1633, Galileo and his closest allies relied on a substitution code (gergo) to protect the privacy of his conversations and to facilitate the removal of his library and manuscripts at Arcetri. Throughout this article, we position Galileo's use of codes within the rich contemporary literature about communicating securely and reflect on cryptic writing as a strategy of communication and dissimulation.
Many thanks to the reviewers for their very helpful suggestions on an earlier draft; to Nick Wilding, Crystal Hall, and Eileen Reeves who provided valuable advice and Galilean camaraderie at key stages; and to Brian Brege and Rachel Midura for sharing our delight in coded communication. Unless otherwise noted, all translations are our own.