"Discourse on the Tides" (Italian: Discorso Sul Flusso E Il Reflusso Del Mare) is an essay written by Galileo Galilei in 1616 as a letter to Alessandro Orsini that attempted to explain the motion of Earth's tides as a consequence of Earth's rotation and revolution around the Sun.[1] The same ideas form an important part of Galileo's Dialogue Concerning the Two Chief World Systems. Galileo's theory was in fact erroneous, as proven by future scientific research and contemporary observations.