Galileo Galilei (Encyclopedia of Science and Religion)
The condemantion of Galileo by the Roman Catholic Church in 1633 is one of the most dramatic incidents in the long history of the relations between science and religion. Galileo claimed in his Dialogue on the Two Chief World Systems, published the year before, that the sun-centered system of Copernicus was not only a convenient mathematical device for calculating the position of the planets but that it was the physical truth. This appeared to many Christians to run counter to statements in the Bible where the sun is described as mobile and the earth as stationary.
The clash between scientific truth and biblical revelation could have been avoided if Galileo, who had no decisive proof that the earth moves, had been more cautious and if theologians, who tended to be dogmatic, had not assumed that the Bible was to be interpreted literally whenever it mentioned natural events.
Galileo Galilei was an Italian astronomer, physicist, and natural philosopher. He was born in Pisa on February 15, 1564, and died in Arcetri on January 8, 1642. Galileo studied at the University of Pisa where he became Professor of Mathematics in 1589. Three years later he moved to the University of Padua where he taught elementary astronomy, mathematics, and physics. Medical students made up the majority of his audience, and he also lectured on fortification and military engineering to young noblemen.
The first indication of Galileo's commitment to the Polish astronomer Nicolaus Copernicus (1473543) appeared in a letter that Galileo wrote to his former colleague at Pisa, Jacopo Mazzoni, in 1597. In August of that year he received a copy of Johannes Kepler's Mysterium Cosmographicum, in which the heliocentric theory of the solar system was vindicated on mathematical and symbolic grounds. After reading the preface, Galileo wrote to Kepler (1571630) to voice his approval of the view that the earth is in motion, but also to express his fear of making his position known to the public at large.
Around 1602, Galileo began making experiments with falling bodies in conjunction with his study of the motion of pendulums. He first expressed the law of freely falling bodies, namely the fact that speed increases as the time squared, in 1604, but claimed to have derived it from the assumption that speed is proportional to distance (whereas, as he later realised, speed is proportional to the square root of the distance). In the autumn of 1604, the appearance of a supernova gave him the opportunity to argue that heavenly matter is not unchangeable.
In July 1609, after hearing that a Dutchman had invented a device to make distant objects appear nearer, Galileo built one himself and gave a demonstration of his telescope from the top of the Campanile of San Marco in Venice. The practical value for sighting ships at a distance impressed the Venetian authorities who confirmed Galileo's appointment for life and raised his salary from 520 to 1,000 florins, an unprecedented sum for a professor of mathematics. Galileo never quite mastered the optics of his combination of a plano-convex objective and a plano-concave eyepiece (an opera glass), but he succeeded in producing a twenty-power telescope, which he turned to the sky in 1610. What he saw is reported in the Sidereus Nuncius (The Starry messenger), which appeared in March 1610. The work was to revolutionize astronomy. The moon was revealed as covered with mountains, new stars appeared as out of nowhere, the Milky Way dissolved into a multitude of starlets and, more spectacular still, four satellites were found orbiting around Jupiter. This was particularly important since, if Jupiter was revolving around a central body with four attendant planets, it could no longer be objected that the earth could not carry the moon around the sun. Jupiter's satellites were not a decisive argument for Copernicanism, but they removed a major obstacle to having it seriously entertained by astronomers.
The Grand Duke of Tuscany, Ferdinand, died in January 1609 and was succeeded by his son, Cosimo II. Galileo had wanted to return to Florence for some time and he realised that his newly-won fame might assist him in effecting a change of residence. He christened the satellites of Jupiter Medicean stars in honour of Cosimo and, in July 1610, he was appointed Mathematician and Philosopher of the Grand Duke of Tuscany. Soon thereafter he discovered that Venus has phases like the moon, and that sunspots move across the surface of the sun.
In December 1613, theological objections were raised at a dinner at the court of the Grand Duke in Pisa. Galileo was absent but his disciple Benedetto Castelli defended his views when questioned by Christina of Lorraine, the Grand Duchess of Tuscany and the mother of the Grand Duke. Galileo felt that the matter was important enough to write a long letter to Castelli, dated December 21, 1613, in which he argued that the heliocentric system was not at variance with the Christian faith. On the fourth Sunday of Advent 1614, a Dominican friar, Tommaso Caccini, inveighed against the Copernican system from the pulpit of the church of Santa Maria Novella in Florence. Another Dominican, Nicolo Lorini, denounced Galileo to the Inquisition. Galileo then wrote a long letter to Christina of Lorraine, where he developed the view that God speaks through the book of nature as well as through the book of Scripture, and that the Bible teaches people how to go to heaven, not how the heavens go. In 1615, Cardinal Robert Bellarmine wrote a letter stating that in the absence of a conclusive proof for the motion of the earth, Galileo and astronomers should content themselves with speaking hypothetically. The Cardinal added that should such a proof become available then the passages in the Bible that seem to say that the earth is at rest would have to be reinterpreted. In 1616, Copernicus's On the Revolutions of the Heavenly Spheres was placed on the list of proscribed books and Galileo was privately, but nonetheless officially, warned not to teach orally or in writing that the earth revolves around the sun.
The debate on the comets and Galileo's trial
In 1618 great excitement was generated over the appearance, in rapid succession, of three comets. Galileo thought that they were merely optical phenomena caused by refraction in the atmosphere and he wrote a Discourse on the Comets to criticise the account of Father Orazio Grassi (1583654), a professor of mathematics at the Collegio Romano, who claimed the comets were real bodies beyond the moon. Grassi published a rejoinder, to which Galileo replied. The result was bitter enmity between himself and the Jesuits.
What changed Galileo's Copernican fortune was the election of Cardinal Maffeo Barberini to the Roman Pontificate in 1623. The following spring Galileo journeyed to Rome, and the new Pope, Urban VIII (1623644), granted him no less than six audiences. Galileo returned to Florence feeling that he could now write about the motion of the earth. In January 1630 his long awaited Dialogue on the Two Chief World Systems was ready for publication and the manuscript was sent to Rome where a friend, Giovanni Ciampoli, played a vital role in securing permission to print the book. Ciampoli exceeded his powers and was largely responsible for Galileo's subsequent trouble.
The Dialogue had gone to press in Florence in June 1631. The publisher had decided to print a thousand copies, a large edition for the time, and the work was not completed until February 1632. Copies did not reach Rome until the end of March or early April. Pope Urban VIII created a commission to investigate the licensing of the Dialogue. In the file on Galileo at the Holy Office the commission found an unsigned memorandum of 1616 stating that he had been enjoined not to teach that the earth moves. The commission concluded that Galileo had disobeyed a formal order of the Holy Office, and Galileo was summoned to Rome, arriving, after much delay, on February 13, 1633. Despite his vigorous denial, Galileo was judged to have contravened the orders of the Church. On the morning of June 22, 1633, he was taken to a hall in the convent of Santa Maria Sopra Minerva in Rome and was made to kneel while the sentence condemning him to imprisonment was read out aloud. Still kneeling, Galileo formally adjured his error. He was allowed to leave for Siena and later, in 1634, to return to Florence, where he was confined to his house in Arcetri.
Later years and modern assessment
Galileo sought comfort in work, and within two years he completed the Discourse on Two New Sciences, the book on which his lasting fame as a scientist rests. In this work Galileo studied the structure of matter and the strength of materials, and explained motion in the light of the timessquared law of falling bodies and the independent composition of velocities. Together these laws enabled him to give an accurate description of the parabolic path of projectiles. When he cast about for a publisher, he came up against a new problem: the Church had issued a general prohibition against printing or reprinting any of his books. Galileo's manuscript was sent to the Protestant Louis Elzevier in Holland, where it appeared in 1638. Galileo became blind in that year, and he remained under house arrest until his death on January 8, 1642, five weeks before his seventy-eighth birthday.
In contemporary times, the Roman Catholic Church has recognized that the trial of Galileo rested on a misunderstanding of the moral authority of the Church. This was clearly expressed by Pope John Paul II in 1983 at a commemoration of the 350th anniversary of the publication of the Dialogue on the Two Chief World Systems. The Pope declared that divine revelation does not involve any particular scientific theory of the universe, and that the Holy Spirit does not guarantee our human explanations of the physical constitution of reality. Galileo had made exactly that point in his letter to Christina of Lorraine.
See also ASTRONOMY; CHRISTIANITY, ROMAN CATHOLIC, ISSUES IN SCIENCE AND RELIGION; COSMOLOGY; GRAVITATION; MATHEMATICS; SCIENCE AND RELIGION, MODELS AND RELATIONS
Blackwell, Richard J. Galileo, Bellarmine, and the Bible. Notre Dame, Ind.: Notre Dame University Press, 1991.
Fantoli, Annibale. Galileo: For Copernicanism and for the Church, 2nd edition. Rome: Vatican Observatory Publications, 1996.
Finocchiaro, Maurice A. The Galileo Affair: A Documentary History. Berkeley: University of California Press, 1989.
Galileo Galilei. Le Opere di Galileo Galilie, ed. Antonio Favaro. Florence: G. Barbèrea, 1890-1909.
Koyré, Alexandre. Galileo Studies. Atlantic Highlands, N.J.: Humanities Press, 1978.
Machamer, Peter. The Cambridge Companion to Galileo. Cambridge, UK: Cambridge University Press, 1998.
Redondi, Pietro. Galileo Heretic. Princeton, N.J.: Princeton University Press, 1987.
Sharratt, Michael. Galileo: Decisive Innovator. Cambridge, UK: Cambridge University Press, 1996.
Shea, William R. Galileo's Intellectual Revolution. New York: Science History Publications, 1972.
Shea, William R. "Galileo and the Church." In God and Nature: Historical Essays on the Encounter Between Christianity and Science, eds. David C. Lindberg and Ron L. Numbers. Berkeley: University of California Press, 1986.
WILLIAM R. SHEA
Galilei, Galileo (1564-1642) (World of Earth Science)
Italian mathematician and astronomer
Galileo Galilei is credited with establishing the modern experimental method. Before Galileo, knowledge of the physical world that was advanced by scientists and thinkers was for the most part a matter of hypothesis and conjecture. In contrast, Galileo introduced the practice of proving or disproving a scientific theory by conducting tests and observing the results. His desire to increase the precision of his observations led him to develop a number of inventions and discovery, particularly in the fields of physics and astronomy.
The son of Vincenzo Galilei (c.1520591), an eminent composer and music theorist, Galileo was born in Pisa. He received his early education at a monastery near Florence, and in 1581, entered the University of Pisa to study medicine. While a student he observed a hanging lamp that was swinging back and forth, and noted that the amount of time it took the lamp to complete an oscillation remained constant, even as the arc of the swing steadily decreased. He later experimented with other suspended objects and discovered that they behaved in the same way, suggesting to him the principle of the pendulum. From this discovery he was able to invent an instrument that measured time, which doctors found to be useful for measuring a patient's pulse rate, and Christiaan Huygens later adapted the principle of a swinging pendulum to build a pendulum clock.
While at the University of Pisa, Galileo listened in on a geometry lesson and afterward abandoned his medical studies to devote himself to mathematics. However, he was unable to complete a degree at the university due to lack of funds. He returned to Florence in 1585, having studied the works of Euclid and Archimedes. He expanded on Archimedes' work in hydrostatics by creating a hydrostatic balance, a device designed to measure the density of objects. The following year, he published an essay describing his new invention, which determined the specific gravity of objects by weighing them in water. With the hydrostatic balance, Galileo gained a scientific reputation throughout Italy.
In 1592, Galileo was appointed professor of mathematics at Padua University in Pisa, where he conducted experiments with falling objects. Aristotle had stated that a heavier object should fall faster than a lighter one. It is said that Galileo tested Aristotle's assertion by climbing the leaning tower of Pisa, dropping objects of various weights, and proving conclusively that all objects, regardless of weight, fall at the same rate.
Some of Galileo's experiments did not turn out as expected. He tried to determine the speed of light by stationing an assistant on a hill while he stood on another hill and timed the flash of a lantern between the hills. He failed because the hilltops were much too close together to make a measurement.
In 1593, Galileo invented one of the first measuring devices to be used in science: the thermometer. Galileo's thermometer employed a bulb of air that expanded or contracted as temperature changed and in so doing caused the level of a column of water to rise or fall. Though this device was inaccurate because it did not account for changes in air pressure, it was the forerunner of improved instruments.
From 1602 to 1609, Galileo studied the motion of pendulums and other objects along arcs and inclines. Using inclined planes that he built, he concluded that falling objects accelerate at a constant rate. This law of uniform acceleration later helped Isaac Newton derive the law of gravity.
Galileo did not make his first contribution to astronomy until 1604, when a supernova abruptly exploded into view. Galileo postulated that this object was farther away than the planets and pointed out that this meant that Aristotle's "perfect and unchanging heavens" were not unchanging after all. Ironically, Galileo's best-known invention, the telescope, was not his creation after all. The telescope was actually invented in 1608 by Hans Lippershey, a Danish spectacle maker. When Galileo learned of the invention in mid-1609, he quickly built one himself and made several improvements. His altered telescope could magnify objects at nine-power, three times the magnification of Lippershey's model. Galileo's telescope proved to be very valuable for maritime applications, and
Galileo was rewarded with a lifetime appointment to the University of Venice.
He continued his work, and by the end of the year he had built a telescope that could magnify at 30-power. The discoveries he made with this instrument revolutionized astronomy. Galileo saw jagged edges on the Moon, which he realized were the tops of mountains. He assumed that the Moon's large dark areas were bodies of water, which he called maria ("seas"), though we now know there is no water on the Moon. When he observed the Milky Way, Galileo was amazed to discover Jupiter, which resulted in his discovery of its four moons; he later called them "satellites," a term suggested by the German astronomer Johannes Kepler. Galileo named the moons of Jupiter, Sidera Medicea ("Medicean stars") in honor of Cosimo de Medici, the Grand Duke of Tuscany, whom Galileo served as "first philosopher and mathematician" after leaving the University of Pisa in 1610. Also, with repeated observation, he was able to watch the moons as they were being eclipsed by Jupiter and from this he was able to correctly estimate the period of rotation of each of the moons.
In 1610, Galileo outlined planetary discoveries in a small book called Siderus Nuncius ("The Sidereal Messenger"). Venus, seen through the telescope, exhibited phases like the Moon, and for the same reasons: Venus did not produce its own light but was illuminated by the Sun.
Saturn was a mystery: Galileo's 30-power telescope was at the limit of its ability to resolve Saturn, and the planet appeared to have three indistinct parts. When Galileo looked at the Sun, he saw dark spots on its disc. The position of the spots changed from day to day, allowing Galileo to determine the rotational rate of the Sun.
In 1613, Galileo published a book in which for the first time he presented evidence for and openly defended the model of the solar system earlier proposed by the Polish astronomer Nicholas Copernicus, who argued that Earth, rather than being positioned at the center of the universe, as in the Ptolemaic design, was only one of several galactic bodies that orbited the Sun. While there was some support even among ecclesiastical authorities for Galileo's proof of the Copernican theory, the Roman Catholic hierarchy ultimately determined that a revision of the long-held astronomical doctrines of the church was unnecessary. Thus, in 1616, a decree was issued by the church declaring the Copernican system "false and erroneous," and Galileo was ordered not to support this system.
Following this run-in with the Catholic Church and the inquisition that forced his adherence to the Copernican theory of the solar system, Galileo focused on the problem of determining longitude at sea, which required a reliable clock. Galileo thought it possible to measure time by observing eclipses of Jupiter's moons. Unfortunately, this idea was not practical for eclipses could not be predicted with enough accuracy and observing celestial bodies from a rocking ship was nearly impossible.
Galileo wanted to have the edict against the Copernican theory revoked, and in 1624, traveled to Rome to make his appeal to the newly elected pope, Urban VIII. The pope would not revoke the edict but did give Galileo permission to write about the Copernican system, with the provision that it would not be given preference to the church-sanctioned Ptolemaic model of the universe.
With Urban's imprimatur, Galileo wrote his Dialogue Concerning the Two Chief World Systemstolemaic and Copernican, which was published in 1632. Despite his agreement not to favor the Copernican view, the objections to it in the Dialogue are made to sound unconvincing and even ridiculous. Summoned to Rome to stand before the Inquisition, Galileo was accused of violating the original proscription of 1616 forbidding him to promote the Copernican theory. Put on trial for heresy, he was found guilty and ordered to recant his errors. At some point during this ordeal Galileo is supposed to have made his famous statement: "And yet it moves," referring to the Copernican doctrine of Earth's rotation on its axis.
While the judgment against Galileo included a term of imprisonment, the pope commuted this sentence to house arrest at Galileo's home near Florence. Although he was forbidden to publish any further works, he devoted himself to his work on motion and parabolic trajectories, arriving at theories that were later refined by others and made an important impact on gunnery. Galileo died blind at the age of 78.
See also Gravity and the gravitational field