GALILEI, GALILEO

Mathematician, astronomer, and natural philosopher, Galileo Galilei (1564–1642), who was born the same year as William Shakespeare in Pisa, Italy, on February 15, contributed fundamentally to the scientific revolution of the sixteenth and seventeenth centuries in which Ptolemaic geocentric cosmology and Aristotelian were successfully challenged by Copernican heliocentric cosmology and a new science of motion. Galileo's participation in the astronomical revolution included the best-known cases of his technological innovation and ethical/religious conflict, namely, his application of the telescope as an astronomical instrument and his engagement with the Roman Catholic Church over matters of biblical interpretation and the Copernican hypothesis. He died on January 8 in Arcetri near Florence where he was living under house arrest that had been imposed following his conflict with the church.

Natural Philosopher and Inventor

Galileo's career as a natural philosopher involved an ongoing study of natural motion, especially inertial motion and that of falling bodies, projectiles, and pendulums. His work helped lay the foundation for the new science of classical mechanics, which found its early modern culmination in the genius of Isaac Newton (1642–1727). In addition to the telescope, which he first turned toward the heavens in 1609, evidence suggests that Galileo contributed to the technological development, improvement, and scientific application of no fewer than eight other scientific instruments. These included the pulsilogium, a device that applied a pendulum to measure the human pulse, in 1583; a hydrostatic balance which he developed for his experiments on floating bodies, in 1586; the thermoscope, an early thermometer, in 1593; a geometrical and military compass, in 1597; a natural magnet called a loadstone used to further the new science of magnetism, in 1601; the microscope, in 1610; the giovilabio, which was an obscure tool developed to compute the distances and periods of revolution of Jupiter's moons, which Galileo had discovered with his telescope in 1612; and finally, a number of vibration-counters, some derived from his study of pendulums, which he applied to the mechanisms of clocks by 1637.

That the majority of Galileo's technical instruments were measuring devices is indicative of his philosophical commitment to a quantitative science. Well-know for his aphorism that mathematics is the language in which the book of Nature has been written, Galileo sought mathematical regularities in his scientific description and placed a premium on the collection of quantitatively accurate data. Indeed it was Galileo's unswerving commitment to an ideal of scientific knowledge grounded in rigorous measurement and observation that fostered his commitment to Copernicanism, which led to his famous struggle with authorities of the Roman Catholic Church.

Galileo did not invent the telescope. He learned in 1609, however, that a Dutch lens grinder had secured a patent the previous year for a device that magnified distant objects by combining two lenses. On the strength of this news, Galileo crafted his own telescope and turned the tool, which had originally been conceived for terrestrial purposes, toward the heavens. He reported his observations, which included details of lunar topography, descriptions of previously unobserved stars and constellations, and an account of Jupiter's four principal moons, the following year in his best-selling book, The Starry Messenger (1610). By this time Galileo was fully convinced of the truth of Copernican (sun-centered) theory. Hence as his book popularized astronomy, it introduced Copernicanism to the common people. This move did not help his reputation among contemporary natural philosophers.

Argument with the Church

Galileo's Copernicanism placed him in opposition to common sense as well as to reigning scientific and theological opinions. During Galileo's lifetime conclusive scientific evidence sufficient to establish the Copernican system as true was not yet available. Galileo believed his theory of the tides provided the needed empirical proof, but he was mistaken. This error made him overconfident. He was originally attracted to Copernicanism by its mathematical elegance and aesthetic superiority, not because he possessed irrefutable evidence. Galileo's principal opponents, Aristotelian natural philosophers (that is, the scientific community), did not believe that such evidence would ever be found. Moreover many of these opponents disliked Galileo for reasons unrelated to the Copernicanism. Galileo had inherited from his father a feisty spirit and taste for intellectual combat. He had engaged anti-Copernican natural philosophers on other scientific questions related to such matters as floating bodies, sunspots, and a new supernova. In each case he had distanced himself from the established scientific authorities and embittered his opponents, many of whom wished to see Galileo silenced, by the Church if necessary.

The Catholic Church, in the absence of conclusive scientific evidence for Copernicanism, followed the lead of natural philosophers in rejecting it. Moreover this seemed to be in accord with a straightforward reading of relevant Biblical texts (Gen. 1; Eccles. 1:4–5; Josh. 10:12; Ps 19:4–6; Ps 93: 1; Ps 104: 5, 19), the interpretation of which rested with church authorities. As a loyal Catholic, Galileo was interested in persuading church leaders to reject geocentrism and thereby be saved from future embarrassment. To do so, however, would require scientific evidence he could not provide. Just as importantly, it would also require expert theological skill in interpreting those biblical texts that seemed to refute Copernicanism. Although a layman, Galileo attempted to provide such advice on biblical interpretation. His "Letter to the Grand Duchess Christina" (1615) was offered as guidance "concerning the use of Biblical quotations in matters of science." It ranks among the classic statements on the relation of the Bible to science. In it Galileo argued that because God is the author of both the book of nature (i.e. the physical world) and the book of revelation (the Bible), it is not possible for genuine conflict between science and scripture. When there appeared to be such a conflict regarding matters of the physical world, the advice of Cardinal Baronius (1538–1607) should be recalled, namely, "That the intention of the Holy Ghost is to teach us how one goes to heaven, not how the heaven goes" (Drake 1957, p. 186). Because, argued Galileo, the Bible is a religious and moral text, not a scientific text, passages that seemed to treat subjects of scientific inquiry should be interpreted with deference to scientific opinion.

Although Galileo had made a compelling argument, two factors counted against him. First the weight of scientific opinion did not yet favor Copernicanism. Second he was a layman presuming to instruct on principles of biblical interpretation. This was an especially dangerous thing to do in the early seventeenth century in the wake of the Protestant Reformation and the Council of Trent (1545–1563). Predictably and defensibly the Catholic Church acted with prudence by upholding both contemporary scientific judgment and received biblical interpretation. Thus in 1616 the Theological Consultors of the Holy Office (advisors to the Pope) declared the Copernican theory foolish and heretical. This opinion was not uniquely Catholic either: Both Martin Luther and John Calvin disapproved of Copernicanism. After the publication of his Dialogue Concerning the Two Chief World Systems: Ptolemaic and Copernican (1632), Galileo was judged by church authorities to be vehemently suspected of heresy and sentenced to house arrest. It is interesting and important to note, however, that despite the opposition of so many church leaders to Galileo's Copernicanism, the Church never formally condemned the Copernican theory ex cathedra. That is, it never formally made rejection of terrestrial motion a matter of ecclesiastical dogma. Galileo had been punished for transgressing a theological boundary by engaging in biblical interpretation as a layman, even though the question was of scientific relevance. Here a key ethical/philosophical dimension of the affair turned on the question of whether or not Copernicanism was a matter of religious faith. Galileo did not believe that it properly was. Church authorities disagreed. Viewed in such a light, the Galileo affair, ultimately, stands as a religious debate between Roman Catholics about biblical interpretation.

Galileo's achievement as a scientist rests not only on the fact that history has vindicated his Copernicanism. His achievements in the fields of dynamics, technical instrumentation, optics, astronomy, and philosophy of science combine to place him among the greatest of scientific minds. His engagement with the Catholic Church was a complicated affair that testifies to the vigor of his scientific ability and to his Christian faith. Although it has often been presented as a clash between modern science and religion, the Galileo affair is not best understood in this way, because all players were committed churchmen. Rather the affair evidences the complicated religious and ethical dimensions that surface when human beings seek to construct a coherent worldview that also does justice to deeply held convictions about matters both scientific and religious.

MARK A. KALTHOFF

SEE ALSO Scientific Revolution;Space Exploration.

BIBLIOGRAPHY

Blackwell, Richard J. (1991). Galileo, Bellarmine, and the Bible. Notre Dame, IN: University of Notre Dame Press.

DeSantillana, Giorgio. (1955). The Crime of Galileo. Chicago: University of Chicago Press.

Drake, Stillman. (1957). Discoveries and Opinions of Galileo. New York: Doubleday Anchor Books. This volume remains the standard English translation of Galileo's Starry Messenger, his letter to the Grand Duchess Christina, and other early works.

Galilei, Galileo. (1997). Galileo on the World Systems: A New Abridged Translation and Guide, trans. Maurice A. Finoc-chiaro. Berkeley: University of California Press. An accessible abridged English translation of Galileo's dialogue with a valuable introduction and notes for the modern student.

Howell, Kenneth J. (2002). God's Two Books: Copernican Cosmology and Biblical Interpretation in Early Modern Science. Notre Dame, IN: University of Notre Dame Press.

Jaki, Stanley L. (2001). Galileo Lessons. Pinckney, MI: Real View Books.

Koyré, Alexandre. (1978). Galileo Studies, trans. John Mepham. Atlantic Highlands, NJ: Humanities Press.

Langford, Jerome J. (1992). Galileo, Science and the Church, 3rd edition. Ann Arbor: University of Michigan Press. This is the best brief introductory volume on the subject of Galileo's encounter with the catholic church.

Lindberg, David C., and Ronald L. Numbers. (1986). God and Nature: Historical Essays on the Encounter between Christianity and Science. Chicago: University of Chicago Press. This classic anthology of scholarly articles includes two important chapters on Copernicanism and Galileo.

Machamer, Peter, ed. (1998). The Cambridge Companion to Galileo. New York: Cambridge University Press.

McMullin, Ernan, ed. (1967). Galileo: Man of Science. New York: Basic Books.

Shea, William R., and Mariano Artigas. (2003). Galileo in Rome: The Rise and Fall of a Troublesome Genius. Oxford, UK: Oxford University Press.