Galileo Galilei
GALILEO GALILEI (1564–1642) is considered to be the father of modern science. Born at Pisa, Italy, Galileo received some of his early schooling there. He then was sent to the ancient Camaldolese monastery at Vallombroso, where, attracted by the quiet and studious life, he joined the order as a novice. His father, however, wished him to study medicine and took him to Florence, where Galileo continued his studies with the Camaldolese monks until he matriculated at the University of Pisa in 1581. During his student years at Pisa, Galileo is said to have made his celebrated observation of the sanctuary lamp swinging like a pendulum from the cathedral ceiling and to have thereby discovered that the time taken for a swing was independent of the size of the arc, a fact that he used later for measuring time in his astronomical studies.
Finding that his talents for mathematics and philosophy were increasingly being recognized, Galileo gave up his medical studies and left the university in 1585, without a degree, to begin lecturing at the Florentine academy. There he published an account of his invention of the hydrostatic balance (1586) and then an essay on the center of gravity in solid bodies (1588), which won him a lectureship at Pisa. In 1592 he was appointed professor of mathematics at the renowned University of Padua, where he remained for eighteen years. There, in 1604, he published his laws of motion of falling bodies in his book De motu.
In 1597 Galileo wrote to Johannes Kepler that he had been a Copernican "for several years." Having heard in Venice of the newly invented telescope, Galileo immediately constructed one of his own and in 1610 announced many astronomical discoveries. These included his discovery that the Milky Way is made up of innumerable stars and his observation of the satellites of Jupiter. He also made observations of sunspots and of the phases of Venus. Thus he vastly expanded astronomical knowledge and challenged the established natural philosophy, which was based on Aristotelian ideas that had been reconciled with Christian doctrine by Thomas Aquinas. Shortly after the publication of these discoveries, Galileo was appointed philosopher and mathematician to the grand duke of Tuscany.
In 1613, Galileo's Letters on Sunspots was published. Its preface claimed that Galileo had been the first to observe sunspots, an assertion that generated bitter resentment among some Jesuit scholars (who had an arguable claim to priority of observation) and that eventually had serious consequences for Galileo. In this book, he first stated in print his unequivocal acceptance of Copernican astronomy, challenging a basic postulate of the Aristotelian view by insisting that all celestial phenomena should be interpreted in terms of terrestrial analogies. Furthermore, Galileo wished to make science independent of philosophy by his assertions that the essence of things cannot be known and that science should concern itself only with the properties of things and with observed events. It was the philosophers rather than the theologians who were the early opponents of the Copernican system and, insofar as he supported it, of Galileo's work. No doubt they were also put off by Galileo's extremely high opinion of himself, and they exploited personal jealousies and resentments against him and tried to enlist the aid of theologians in condemning both Copernican ideas and Galileo's advocacy of them.
Not until 1616, seventy-three years after the publication of Copernicus's De revolutionibus orbium coelestium (On the revolution of the heavenly spheres), did the Theological Consultors of the Holy Office declare it "false and contrary to Holy Scripture" and recommend that Copernicus's book be "suspended until corrected." Cardinal Roberto Bellarmino had earlier written to Galileo warning him to confine himself to the realm of hypothesis until demonstrative proof could be produced. When Galileo went to Rome to defend his position, he was officially cautioned neither to hold nor to defend the Copernican ideas. And Galileo, good Catholic that he was (and remained), agreed.
Throughout, Galileo maintained that the purpose of scripture is not to teach natural philosophy and that issues of faith and issues of science should be kept separate and should be settled on different grounds. He quoted Tertullian approvingly: "We conclude that God is known first through nature, and then again, more particularly, by doctrine; by nature in his works, and by doctrine in his revealed word." He also cited Cardinal Cesare Baronius, a contemporary, who had quipped, "The Bible tells us how to go to Heaven, not how the heavens go."
The appearance of the great comets in 1618 stirred up much controversy, which Galileo joined by writing his Discourse on Comets, annoying the philosophers still further because of his anti-Aristotelian bias. In 1623, Galileo published The Assayer, which he dedicated to Urban VIII, the new pope, who was much more favorably disposed toward intellectuals and their work than his predecessor had been. In 1624, Galileo visited Rome and had six audiences with the pope. In 1632, Galileo published his Dialogue on the Two Great World Systems. Having intended this book to be "a most ample confirmation" of the Copernican opinion, Galileo in effect had ignored the spirit of the instructions given him by the church in 1616. Nevertheless, during the trial that followed the publication of the Dialogue, Galileo maintained that he had obeyed the instructions to the letter.
Galileo's trial in 1633 marked the beginning of what has since become a cliché—namely, the idea that science and religion must inevitably be in conflict. Also, Galileo is often seen as science's first martyr in the perennial battle between the church and the spirit of free inquiry. There is no question that the church took a wrong position (contrary to its own tradition in such matters as established by Augustine and Thomas Aquinas); this much was acknowledged by a statement made by John Paul II in 1979, and it was underscored by the Vatican's publication, in 1984, of all documents from its archives relating to Galileo's trial. However, a considerable amount of blame for Galileo's persecution must also fall on the philosophers. Indeed, the decree of sentence issued by the Holy Office was signed by only seven of the ten cardinal-judges.
Unlike innumerable martyrs who have accepted torture or even death for the sake of their convictions, Galileo chose, most unheroically, to abjure his beliefs. (The myth that he, on leaving the tribunal, stamped his foot and said, "Yet it [i.e., the earth] does move," was invented by Giuseppe Baretti in 1757 and has no basis in fact.) Galileo's sentence was then commuted; there was no formal imprisonment. He was allowed to move back to his country estate near Florence, where he resumed his writing. His Discourses concerning Two New Sciences, regarded by many as his greatest scientific contribution, was published in 1638.
Bellarmino, Roberto; Copernicus, Nicolaus.
Bibliography
The best scientific biography of Galileo, tracing the historical development of his thought, is Stillman Drake's Galileo at Work (Chicago, 1978). A knowledgeable presentation of Galileo's philosophy is Ludovico Geymonat's Galileo Galilei: A Biography and Inquiry into His Philosophy of Science (New York, 1965). For Galileo's theological views and accounts of his trial, the following three books are indispensable: Giorgio de Santillana's The Crime of Galileo (New York, 1955), Jerome J. Langford's Galileo, Science and the Church (Ann Arbor, Mich., 1971), and Stillman Drake's Galileo (New York, 1980). The play by Bertolt Brecht, Galileo (New York, 1966), is tendentious and historically unreliable. Galileo's own views and remarks concerning the relationship between science and religion are scattered throughout his many letters and other writings. Among these the most important are his Letter to the Grand Duchess Christina (1615) and The Assayer (1623); both of these have been translated by Stillman Drake and are published in his Discoveries and Opinions of Galileo (Garden City, N.Y., 1957). The latest, and perhaps the final, effort made by the Roman Catholic church to repair its wrong decision in the case of Galileo is represented by the publication, by the Pontifical Academy of Sciences, of I documenti del processo di Galileo Galilei (Rome, 1984), which contains transcriptions of documents relating to Galileo's trial that had been held in the Vatican archives.
New Sources
Drake, Stillman. Essays on Galileo and the History and Philosophy of Science. Toronto, 1999.
Feldhay, Rivka. Galileo and the Church: Political Inquisition or Critical Dialogue? Cambridge, U.K., 2003.
Gingerich, Owen. "How Galileo Changed the Rules of Science." Sky and Telescope 85 (March 1993): 32.
Shea, William, and Mariano Artigas. Galileo in Rome: The Rise and Fall of a Troublesome Genius. Oxford, 2003.
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