Dialogue Concerning the Two Chief World Systems
![Frontispiece and title page of the Dialogue, 1632](/Images/godic/202502/11/Galileos_Dialogue_Title_Page1034.png")
![A copy of The Dialogo, Florence edition, located at the Tom Slick rare book collection at Southwest Research Institute, in Texas.](/Images/godic/202502/11/Dialogo_Galileo_SWRI1034.jpg")
![Actual path of cannonball B is from C to D](/Images/godic/202502/11/Dialogue-day2-91034.jpg")
![The solar system](/Images/godic/202502/11/Dialogue-day3-11034.png")
The Dialogue Concerning the Two Chief World Systems (Dialogo sopra i due massimi sistemi del mondo) is a 1632 Italian-language book by Galileo Galilei comparing the Copernican system with the traditional Ptolemaic system. It was translated into Latin as Systema cosmicum (English: Cosmic System) in 1635 by Matthias Bernegger. The book was dedicated to Galileo's patron, Ferdinando II de' Medici, Grand Duke of Tuscany, who received the first printed copy on February 22, 1632.