Unveiling the size of the Universe: the first accurate measurement of the Earth-Sun distance by Giovanni Domenico Cassini - SISFA Degree Award 2022

Plenary presentation - SISFA Degree Award 2022 for the master's degree thesis with the title “Unveiling the size of the Universe: the first accurate measurement of the Earth-Sun distance by Giovanni Domenico Cassini”. This work sheds new light on the history of a peculiar scientific expedition: the two-year (1672-73) voyage to Cayenne (French Guiana) supervised by the Italian astronomer Giovanni Domenico Cassini and led by the élève astronome of the Académie Royale des Sciences Jean Richer. The observations carried out simultaneously in Cayenne and in Paris enabled Cassini to obtain the first remarkably accurate measurement of the Earth-Sun distance, but not only that. A careful check and inspection of the original documents kept in the Archives of the Académie in Paris allowed to reconstruct the history of the expedition. This essay highlights the key findings and contributions of the thesis.