GALILEI, GALILEO (b. Pisa, Italy, 15 February 1564; d. Arcetri, Italy, 8 January 1642), physics, astronomy.

    against terrestrial motion, Galileo added two arguments in its favor. One concerned the annual variations in the paths of sunspots, which could not be dynamically reconciled with an absolutely stationary earth. Geometrically, all rotations and revolutions could be assigned to the sun, but their conservation would require very complicated forces. The Copernican distribution of one rotation to the sun and one rotation and one revolution to the earth fitted a very simple dynamics. The second new argument concerned the existence of ocean tides, which Galileo declared, quite correctly, to be incapable of any physical explanation without a motion of the earth. His own explanation happened to be incorrect; he argued that the earth's double motion of rotation and revolution caused a daily maximum and minimum velocity, and a continual change of speed, at every point on the earth. The continual variation of speed of sea basins imparted different speeds to their contained waters. The water, free to move within the basins, underwent periodic disturbances of level, greatest at their coasts; the period depended on sizes of basins, their east-west orientations, depths, and extraneous factors such as prevailing winds. In order to account for monthly and annual variations in the tides, Galileo invoked an uneven speed of the earth-moon system through the ecliptic during each month, caused by the moon's motion with respect to the earth-sun vector; for annual seasonal effects, he noted changes of the composition of rotational and revolutional components in the basic disturbing cause.

The Dialogue was completed early in 1630. Galileo took it to Rome, where it was intended to be published by the Lincean Academy. There he sought to secure a license for its printing. This was not immediately granted, and he returned to Florence without it. While the matter was still pending, Federico Cesi died, depriving the Academy of both effective leadership and funds. Castelli wrote to Galileo, intimating that for other reasons he would never get the Roman imprimatur and advising him to print the book at Florence without delay. Negotiations ensued for permission to print the book at Florence. Ultimately these were successful, and the Dialogue appeared at Florence in March 1632. A few copies were sent to Rome, and for a time no disturbance ensued. Then, quite suddenly, the printer was ordered to halt further sales, and Galileo was instructed to come to Rome and present himself to the Inquisition during the month of October.

The Trial of Galileo.

The background of the action is fairly clear. Several ecclesiastical factions were hostile to the book but at first produced only shallow pretexts to suppress it. More serious charges were lodged against Galileo when Urban was persuaded that his own decisive argument against the literal truth of the earth's motion—that God could produce any effect desired by any means—had been put in the mouth of the simpleminded Aristotelian in the dialogue as a deliberate personal taunt by Galileo. Next, a search of the Inquisition files of 1616 disclosed the questionable document previously mentioned, which contained a specific threat of imprisonment for Galileo if he ever again discussed the Copernican doctrine in any way. Urban, having known nothing of any personal injunction at the time Galileo sought his permission to write the book, assumed that Galileo had deceitfully concealed it from him. The case was thereafter prosecuted with vindictive hostility. Galileo, who had either never received a personal injunction or had been told that it was without force, was unaware of any wrongdoing in this respect.

Confined to bed by serious illness, he at first refused to go to Rome. The grand duke and his Roman ambassador intervened stoutly in his behalf, but the pope was adamant. Despite medical certificates that travel in the winter might be fatal, Galileo was threatened with forcible removal in chains unless he capitulated. The grand duke, feeling that no more could be done, provided a litter for the journey, and Galileo was taken to Rome in February 1633.

The outcome of the trial, which began in April, was inevitable. Although Galileo was able to produce an affidavit of Cardinal Bellarmine to the effect that he had been instructed only according to the general edict that governed all Catholics, he was persuaded in an extrajudicial procedure to acknowledge that in the Dialogue he had gone too far in his arguments for Copernicus. On the basis of that admission, his Dialogue was put on the Index, and Galileo was sentenced to life imprisonment after abjuring the Copernican “heresy.” The terms of imprisonment were immediately commuted to permanent house arrest under surveillance. He was at first sent to Siena, under the charge of its archbishop, Ascanio Piccolomini. Piccolomini, who is said to have been Galileo's former pupil, was very friendly to him. Within a few weeks he had revived Galileo's spirits—so crushed by the sentence that his life had been feared for—and induced him to take up once more his old work in mechanics and bring it to a conclusion. While at Siena, Galileo began the task of putting his lifelong achievements in physics into dialogue form, using the same interlocutors as in the Dialogue.

Piccolomini's treatment of Galileo as an honored guest, rather than as a prisoner of the Inquisition, was duly reported to Rome. To avoid further scandal, Galileo was transferred early in 1634 to his villa at