Page:Popular Science Monthly Volume 67.djvu/78

72 Galileo's dialogues on the system of the world (1632) have, at the head, a Greek epigraph:

They are dedicated to the Grand Duke of Tuscany. The personages of the Dialogues are Salviati (Galileo himself) who maintains the Copernican doctrines; Sangredo, a man-of-the-world, intelligent, but not a savant; and Simplicius, a convinced Aristotelian, a dull fellow, always worsted in the argument. Galileo's enemies convinced the Pope that Simplicius stood for the Pontiff himself. The subjects discussed are the fall of bodies, the flight of projectiles, the principles of mechanics, the rotation and revolution of the earth and of the planets, the system of Ptolemy—and here Sangredo remarks that he knows many disciples of Ptolemy who have become Copernicans, but not one Copernican converted to the ancient system. The new star of 1572 is shown to have been far more distant than the moon, by long calculations (and it is noteworthy that logarithms are not employed to shorten the work). The preface recites that, some years previously a ‘salutary edict’ had been promulgated at Rome which, to prevent scandals, forbade the teaching of the Pythagorean opinion of the earth's motion, that some hardy spirits had, nevertheless, dared to declare that this edict had been issued without comprehension of the matter and that it was the result of passion, and not of judicial examination. It had been said that advisers entirely ignorant of astronomy ought not to have thus clipped the wings of philosophers.

My zeal, says Galileo, can not support these rash complaints. Well understanding this prudent decree, I wish to do justice to the truth. I was then at Rome; the most distinguished prelates heard and applauded me; the decree would not have been issued without giving me some knowledge of it. I, therefore, wish to show to foreign nations that in Italy, and even at Rome, all that could be advanced in favor of Copernicus was known, before that censure was published. I declared myself the advocate of Copernicus. Proceeding according to a mathematical hypothesis, I endeavored to prove it to be preferable to that which declares the earth at rest, not in an absolute manner preferable, but in the sense in which it is attacked by pretended Aristotelians, who in their philosophizing neglect observations. He will show, he says, certain advantages of the heliocentric system. If Italians have not assented to the mathematical opinion of the motion of the earth, it is not because all of them have been ignorant of the reasons others allege in its support, but because they have other reasons