Featuring Galileo's Handwriting. This is Galileo’s witty and entertaining dialogue in defense of Copernicus. In the frontispiece, Aristotle and Ptolemy hold an Earth-centered armillary sphere (left). Copernicus holds a Sun-centered model of the universe (right). Just two systems appear in the Dialogo; Galileo nowhere mentions the Tychonic system then favored by most astronomers. Galileo inserted statements about the hypothetical character of the work in the preface and conclusion. Nevertheless, the book as a whole was anything but even-handed, contrary to instructions issued to Galileo in 1616. Once published, Urban VIII gave orders for the Dialogo to be recalled and summoned Galileo to Rome for trial. This copy is one of four first editions of Galileo held by OU which contain Galileo’s own handwriting.