On February 22, 1632, Ferdinando II de’ Medici, Grand Duke of Tuscany, received the first printed copy of Galileo’s Dialogue Concerning the Two Chief World Systems (Dialogo sopra i Due Massimi Sistemi del Mondo). The Grand Duke was the dedicatee.
Galileo’s Dialogo is a witty and entertaining defense of the Copernican system, where the Sun is at the center of “the universe.” This was opposed to the traditional view — held by Aristotle and Ptolemy — of an Earth-centered armillary sphere.
Only two systems appear in the Dialogo; Galileo pitting what we now call the Ptolemaic system with the Copernican, nowhere mentioning the Tychonic system then favored by most astronomers, one in which the Sun and Moon and stars revolve around Earth, but the planets revolve around the Sun.
Once published, Pope Urban VIII gave orders for the Dialogo to be recalled and summoned Galileo to Rome for trial.