_{The Macrocosm:}

The heliocentric hypothesis gained momentum when GalileoGalilei (1564-1642) published his Dialogo in 1632. Long a convinced Copernican, Galileo thought he had proof of the theory when he viewed four satellites of Jupiter through his telescope and saw that they appeared in different positions relative to the planet. Convinced that they were circling Jupiter just as the earth was revolving around the sun, he found himself in trouble with the Church. In 1616 Copernicanism was examined by the Qualifiers of the Holy Office and Galileo was forbidden to teach it. However, in 1623, his good friend, Maffeo Barberini, became Pope Urban VIII and Galileo, who assumed that the intelligent Pope would see things his way, asked the Pope's permission to write a book showing the truth of the Copernican theory. Of course, the Pope refused and Galileo restated his request, asking for permission to argue both sides of the question, the earth-centered and the sun-centered theories. To this the Pope agreed and Galileo produced the Dialogo which was anything but an equal treatment of both theories. Cast in the form of a dialogue between three characters, Salviati (named for a friend of Galileo's and who spoke for Galileo), Sagredo (an intelligent laymen who, while not an astronomer, could recognize the "truth"), and finally Simplicio, whose name tells the story. Poor simple Simplicio thought the earth was the center of the universe! When the book was published, the Pope and his advisors were furious, convinced that Galileo had betrayed them. The book was recalled, and its production resulted in the trial of Galileo.

Galilei, Galileo.
Dialogo di Galileo Galilei Linceo matematico sopraordinario dello stvdio di Pisa. E filosofo e matematico primario del serenissimo gr. Dvca di Toscana. Doue ne i congressi di quattro giornate si discorre sopra i due massimi sistemi del mondo tolemaico e copernicano; proponendo indeterminatamente le ragioni filosofiche, e naturali tanto per l'vna, quanto per l'altra parte.
Fiorenza, Per Gio: Batista Landini, 1632.

The Dialogo was the first book DeGolyer purchased for the Collections when he went to Europe in 1949. The Collections' copy of the Dialogo belonged to Galileo himself, and includes changes and corrections in his own handwriting for the second edition. The handwriting was verified by Galileo expert, Stilman Drake, when he visited the Collections in 1983. This book is one of four of the twelve first editions of Galileo's works in the Collections that contains his own handwriting. Neither Copernicus and Galileo questioned the circularity of planetary orbits.