High Quality Content by WIKIPEDIA articles! The Dialogue Concerning the Two Chief World Systems (Dialogo sopra i due massimi sistemi del mondo) was a 1632 Italian language book by Galileo Galilei comparing the Copernican system with the traditional Ptolemaic system. It was translated to Latin as Systema cosmicum (English: cosmic system) in 1635 by Matthias Bernegger. The book, which was dedicated to Galileo`s patron, Ferdinando II de` Medici, Grand Duke of Tuscany and delivered to him on February 22, 1632, was a bestseller.